.
Articles from the medical literature for 2007.
Greek Letters Used: alpha: a, beta: b,
gamma: g, delta: d
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Thank you.
also see The original meeting poster of this report
Annals of Neurology Vol 62 (suppl 11) page: S60
2007 ANA and CNS Meeting Programs ANA T1-T136
doi:10.1002/ana.11641
Abstract
T-45. Alemtuzumab (CAMPATH 1-H) Therapy in Sporadic Inclusion Body Myositis
(sIBM) Alters Disease Progression and Suppresses Endomysial Inflammation Marinos
C. Dalakas, Goran Rakocevic, Beverly McElroy, Mohammad K. Salajegheh, Jens Schmidt,
Michael Harris-Love, Joseph Shrader, Ellen Levy, and Allen D. Kirk;
Bethesda, MD
In this study we examined the effectiveness of Alemtuzumab in suppressing endomysial inflammation and arresting sIBM progression. Alemtuzumab is a humanized monoclonal antibody against CD52 that causes severe PBL reduction up to 6 months. Thirteen sIBM patients with a 12 month natural history were treated with 0.3 mg/kg/day Alemtuzumab for 4 days. Primary end-points were the disease stabilization or increased strength 6 months after treatment. During a 12 month observation, patients' total strength had declined by a mean of 14.9% on QMT, while six months after therapy, only by 1.9 % (p less than 0.002). Six of 13 patients improved by 15.7% (4 - 35%); the other 7 declined by 6% (-1.5 - 15%). Total MRC scores declined during observation by 13.8% but improved after 6 months by 11.4 % (p less than 0.001). PBL depletion persisted for 6 months after treatment, with naive CD45RA+ CD62L+, but not effector CD45RA+CD62L-, cells affected. Repeated muscle biopsies showed CD3 lymphocyte depletion by a mean of 50 % (p less than 0.008). Only mRNA of Fas, Mipa and alphaB-crystallin, were significantly reduced in muscle. In sIBM, Alemtuzumab causes peripheral and endomysial lymphocyte reduction and halts disease progression up to 6 months.
Cell Death Differ. 2007 Nov;14(11):1916-24. Epub 2007 Aug 3.
Characterization of hereditary inclusion body myopathy myoblasts: possible primary impairment of apoptotic events.
Amsili S, Shlomai Z, Levitzki R, Krause S, Lochmuller H, Ben-Bassat H, Mitrani-Rosenbaum S.
Goldyne Savad Institute for Gene Therapy, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
Hereditary inclusion body myopathy (HIBM) is a unique muscular disorder caused by mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene. GNE encodes a bi-functional enzyme acting in the biosynthetic pathway of sialic acid. Since the underlying myopathological mechanism leading to the disease phenotype is poorly understood, we have established human myoblasts cultures, derived from HIBM satellite cells carrying the homozygous M712T mutation, and identified cellular and molecular characteristics of these cells. HIBM and control myoblasts showed similar heterogeneous patterns of proliferation and differentiation. Upon apoptosis induction, phosphatidylserine externalization was similar in HIBM and controls. In contrast, the active forms of caspase-3 and -9 were strongly enhanced in most HIBM cultures compared to controls, while pAkt, downregulated in controls, remained high in HIBM cells. These results could indicate impaired apoptotic signaling in HIBM cells. Since satellite cells enable partial regeneration of the post-mitotic muscle tissue, these altered processes could contribute to the muscle mass loss seen in patients. The identification of survival defects in HIBM affected muscle cells could disclose new functions for GNE in muscle cells.
Neurosci Lett. 2007 Dec 15 [Epub ahead of print]
Casein kinase 1 alpha associates with the tau-bearing lesions of inclusion body
myositis.
Kannanayakal TJ, Mendell JR, Kuret J.
Center for Molecular Neurobiology, Department of Molecular and Cellular Biochemistry,
College of Medicine, The Ohio State University, 1060 Carmack Road, Columbus,
OH 43210, United States.
Inclusion body myositis and Alzheimer's disease are age-related disorders characterized
in part by the appearance of intracellular lesions composed of filamentous aggregates
of the microtubule-associated protein tau. Abnormal tau phosphorylation accompanies
tau aggregation and may be an upstream pathological event in both diseases.
Enzymes implicated in tau hyperphosphorylation in Alzheimer's disease include
members of the casein kinase 1 family of phosphotransferases, a group of structurally
related protein kinases that frequently function in tandem with the ubiquitin
modification system. To determine whether casein kinase 1 isoforms associate
with degenerating muscle fibers of inclusion body myositis, muscle biopsy sections
isolated from sporadic disease cases were subjected to double-label fluorescence
immunohistochemistry using selective anti-casein kinase 1 and anti-phospho-tau
antibodies. Results showed that the alpha isoform of casein kinase 1 [Ckia],
but not the delta or epsilon isoforms, stained degenerating muscle fibers in
all eight inclusion body myositis cases examined. Staining was almost exclusively
localized to phospho-tau-bearing inclusions. These findings, which extend the
molecular similarities between inclusion body myositis muscle and Alzheimer's
disease brain, implicate casein kinase 1 alpha as one of the phosphotransferases
potentially involved in tau hyperphosphorylation.
Excerpts: Because CK1 isoforms are expressed widely in tissues, including muscle
[26], they may modulate tau phosphorylation
and aggregation state in s-IBM as well as AD.
Immunohistochemical studies indicate that Ckia is positioned to contribute to tau hyperphosphorylation and ubiquitination in both AD [22] and s-IBM (herein).
In summary, these data extend the pathological similarity between the tau-bearing
lesions of AD and IBM to include CK1 colocalization. The results implicate CK1
isoform Ckia in the upstream pathological events that lead to accumulation of
tau phospho-epitopes in both diseases.
Dec 19
Please cite this article in press as:
Needham M, Mastaglia FL,
Sporadic inclusion body myositis: a continuing puzzle,
Neuromuscul Disord (2007), doi:10.1016/j.nmd.2007.11.001
There is now compelling evidence that sporadic inclusion body myositis (sIBM)
is a muscle-specific autoimmune disease in which both T and B-cells play a part
and in which both cytotoxic muscle fibre necrosis and degeneration occur. However
the factors responsible for breakdown of immune tolerance and the nature of the
target antigens expressed by muscle fibres remain unknown. Genetic factors are
known to contribute to susceptibility, in particular MHC haplotyes which may influence
antigenic presentation, and could also operate through genetic variations in muscle
fibre constituents or immune effector mechanisms. Viral infection may act as a
trigger mechanism, as in cases of HIV-associated sIBM. Our understanding of the
mechanisms leading to the degenerative changes in muscle fibres is still incomplete.
Protein misfolding and proteasomal dysfunction rather than defective transcriptional
control is likely to underlie the abnormal accumulation of multiple proteins in
the muscle fibre inclusions. However, aberrant transcription is thought to be
the basis for the accumulation of potentially toxic mutant protein forms (e.g.
UBB(+1)). The origin of the multiple clonally expanded somatic mtDNA mutations
in COX-negative segments of muscle fibres remains uncertain but may be linked
to the effects of oxidative stress. It is proposed that the disproportionate involvement
of certain muscles in sIBM may be due to the existence of muscle group-specific
transcriptomes which are differentially affected by the disease process and that
the male predominance of the disease may indicate the influence of genes preferentially
expressed in males. There is a need to develop better animal models of sIBM in
which the relationship between the inflammatory and degenerative components of
the disease as well as the gender difference in susceptibility and differential
vulnerability of different muscle groups can be more critically investigated.
Pathologically sIBM is characterised by a unique combination of changes comprising
a T-cell predominant inflammatory infiltrate with invasion of MHC-I expressing
muscle fibres, cytotoxic necrosis and the presence of congophilic inclusions and
rimmed vacuoles containing b-amyloid, phosphorylated tau and a variety of other
proteins. In addition, an increased number of fibres show segmental loss of cytochrome
oxidase c (COX) activity, which is associated with the presence of multiple clonally
expanded somatic mitochondrial DNA mutations. A number of pathogenetic theories
have been proposed over the past 40 years, but it is still debated whether sIBM
is primarily a T-cell mediated inflammatory myopathy or a myodegenerative disorder
with abnormal protein aggregation, inclusion body formation and a secondary inflammatory
response in muscle.
Fig. 1. Summary of the major lines of evidence supporting the immunopathogenesis of sIBM.
Fig. 2. Proposed schema for the pathogenesis of sIBM incorporating the known cellular and humoral immune mechanisms, putative factors leading to breakdown of immune tolerance, and downstream events linked to the immune/inflammatory process as discussed in the text of the review. The possible role of mitochondrial dysfunction is not shown but this could contribute to oxidative stress via increased generation of ROS. The interrupted lines indicate steps which are still hypothetical.
related story
Overexcited Neurons Not Good For Cell Health ScienceDaily (Dec. 20, 2007) -
Neurotransmitters have consequences. They initiate events that are critical
to a healthy life, giving us the ability to move, to talk, to breathe, to think.
But that's if the neurotransmitters are getting it right and sending proper
signals downstream to muscle cells, neurons or other cells. Now a Northwestern
University study reports that a mutation in a transcription factor that controls
a neurotransmitter in the nematode C. elegans causes an imbalance in neuronal
signaling that results in protein damage in target cells. Similar results and
consequences on protein folding were found to occur upon exposure to the common
toxins nicotine and lindane (a pesticide). Whether due to genetic mutation or
exposure to small molecules, the neurons become overexcited and fire incorrect
signals too rapidly, resulting in proteins in target muscle cells becoming stressed,
misfolding and becoming non-functional. "To find that small molecules reproduce
our genetic observations -- that both environment and genetics cause a molecular
defect in the ability of proteins to function in muscle cells -- was not expected,"
said Richard I. Morimoto, Bill and Gayle Cook Professor of Biochemistry, Molecular
Biology and Cell Biology in Northwestern's Weinberg College of Arts and Sciences,
who led the research team. This study provides some of the strongest evidence
that nerve cell activity can directly affect the protein folding process in
another cell. (Muscle cells in the case of this study.) Many different diseases
and conditions, such as many neurodegenerative diseases, certain cancers, muscular
dystrophy and the aging process, cause loss of muscle cell function. How that
happens is not well understood. "We may have discovered an unexpected basis
for a number of human diseases," said Morimoto. "Particularly interesting is
the link with the environment. We've shown that pesticides, which are widespread
and have been linked to an increase in Parkinson's disease and other neurodegenerative
diseases among farmers, have profound effects on nerve communication -- even
more than we expected." "Neuronal Signaling Modulates Protein Homeostasis in
Caenorhabditis Elegans Post-synaptic Muscle Cells" is published by the journal
Genes and Development. In addition to Morimoto, the study's co-investigators include
lead author Susana M. Garcia, a former graduate student of Morimoto's and now
a postdoctoral fellow at Harvard University; M. Olivia Casanueva, a postdoctoral
fellow, and M. Catarina Silva, a visiting predoctoral student, both at Northwestern;
and Margarida D. Amaral, University of Lisbon, Portugal. Morimoto and his team
studied presynaptic neurons and postsynaptic muscle cells in C. elegans, a transparent
roundworm whose biochemical environment is similar to that of human beings and
whose genome, or complete genetic sequence, is known. Specifically, the researchers
looked at what happened to polyglutamine proteins in muscle cells that were
at the tipping point: the proteins were at risk of soon aggregating and losing
their function. The scientists wanted to see if they could cause the protein,
which is associated with Huntington's disease, to show its toxicity prematurely.
(If misfolded or damaged proteins accumulate beyond a certain critical point,
they aggregate and disease can result. ) In separate experiments, the researchers
induced two genetic mutations in presynaptic neurons, one that caused the reduction
of the neurotransmitter GABA, which inhibits neuronal firing, and one that increases
the action of a neurotransmitter called acetylcholine, which stimulates neuronal
firing. The result of both mutations was overexcited neurons that disrupted
the way the neurons sent signals to the muscle cells and caused protein aggregation.
The effects were similar when the researchers introduced both nicotine (a neurostimulant)
and lindane (an inhibitor of GABA, causing overstimulated neurons) to neurons
with no mutations. "Neurons integrate information and transfer this information
to surrounding cells, influencing protein homeostasis," said Morimoto, an expert
on Huntington's disease, amyotrophic lateral sclerosis (ALS) and the cellular
and molecular response to damaged proteins. "When a neuron's electrochemistry
is imbalanced every cell downstream is imbalanced. We've revealed that it's
an integrated communications network that determines protein folding." While
Morimoto and his team focused only on postsynaptic muscle cells in this study,
they plan to look at other cells and how neuronal signaling affects their function.
GENES andamp; DEVELOPMENT 21:3006-3016, 2007
Neuronal signaling modulates protein homeostasis in Caenorhabditis elegans post-synaptic
muscle cells
Susana M. Garcia1,2, M. Olivia Casanueva1, M. Catarina Silva1,2, Margarida
D. Amaral2,3, and Richard I. Morimoto1,4
1 Department of Biochemistry, Molecular Biology and Cell Biology, Rice Institute
for Biomedical Research, Northwestern University, Evanston, Illinois 60208,
USA; 2 Department of Chemistry and Biochemistry, Faculdade de Ciandecirc;ncias,
Universidade de Lisboa, 1749-016 Lisboa, Portugal; 3 Centre of Human Genetics/National
Institute of Health, 1649-016 Lisboa, Portugal
Protein homeostasis maintains proper intracellular balance by promoting protein
folding and clearance mechanisms while minimizing the stress caused by the accumulation
of misfolded and damaged proteins. Chronic expression of aggregation-prone proteins
is deleterious to the cell and has been linked to a wide range of conformational
disorders. The molecular response to misfolded proteins is highly conserved
and generally studied as a cell-autonomous process. Here, we provide evidence
that neuronal signaling is an important modulator of protein homeostasis in
post-synaptic muscle cells. In a forward genetic screen in Caenorhabditis elegans
for enhancers of polyglutamine aggregation in muscle cells, we identified unc-30,
a neuron-specific transcription factor that regulates the synthesis of the inhibitory
neurotransmitter -aminobutyric acid (GABA). We used additional sensors of protein
conformational states to show that defective GABA signaling or increased acetylcholine
(ACh) signaling causes a general imbalance in protein homeostasis in post-synaptic
muscle cells. Moreover, exposure to GABA antagonists or ACh agonists has a similar
effect, which reveals that toxins that act at the neuromuscular junction are
potent modifiers of protein conformational disorders. These results demonstrate
the importance of intercellular communication in intracellular homeostasis.
Arthritis Rheum. 2007 Nov;56(11):3784-92. Links
Type I interferon-inducible gene expression in blood is present and reflects disease activity in dermatomyositis and polymyositis.
Walsh RJ, Kong SW, Yao Y, Jallal B, Kiener PA, Pinkus JL, Beggs AH, Amato AA, Greenberg SA.
Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
OBJECTIVE: To apply gene expression profiling to the study of peripheral blood mononuclear cells from patients with inflammatory myopathies, in order to provide insight into disease pathogenesis and identify potential biomarkers associated with disease activity. METHODS: We used Affymetrix whole-genome microarrays to measure the expression of approximately 38,500 genes in 65 blood and 15 muscle samples from 44 patients with dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), myasthenia gravis, or genetically determined myopathies and from 12 healthy volunteers. In 9 patients, 2 samples were obtained at different time points, when disease was either active or improving, and these paired blood samples were also compared. Bioinformatics techniques were used to identify genes with significant differential expression among diagnostic categories and in relation to disease activity. We corroborated the microarray data with quantitative real-time reverse transcriptase-polymerase chain reaction. RESULTS: Most patients with active DM or PM, but not patients with IBM, had significant and high up-regulation of the type I interferon-alpha/beta (IFNalpha/beta)-inducible genes in blood. Furthermore, the up-regulation of these genes correlated with disease activity in DM and PM, with down-regulation occurring when disease was controlled with treatment. CONCLUSION: DM and PM are diseases characterized by the systemic overexpression of IFNalpha/beta-inducible genes. The magnitude of the overexpression of these genes is higher in DM and correlates with disease activity in both disorders. Although PM and IBM have been modeled as having similar immunologic processes occurring within muscle, there are substantial differences in the expression of IFNalpha/beta-inducible genes in blood in these diseases.
J Neuropathol Exp Neurol. 2007 Dec 13 [Epub ahead of print]
Inclusion Body Myositis Associated With Human T-Lymphotropic Virus-Type I Infection:
Eleven Patients From an Endemic Area in Japan.
Matsuura E, Umehara F, Nose H, Higuchi I, Matsuoka E, Izumi K, Kubota R, Saito
M, Izumo S, Arimura K, Osame M.
From the Department of Neurology and Geriatrics (E Matsuura, FU, HN, IH, E Matsuoka,
KI, KA, MO) and Division of Molecular Pathology (RK, SI), Center for Chronic Viral
Diseases, Graduate School of Kagoshima University, Kagoshima; and Department of
Microbiology (MS), Kanazawa Medical University, Ishikawa, Japan.
The objective of this study was to investigate the association of human T-lymphotropic
virus-type I (HTLV-I) infection with sporadic inclusion body myositis in 11 patients
from an endemic area in Japan. The clinical features were consistent with sporadic
inclusion body myositis, and anti-HTLV-I antibodies were present in the sera of
all patients. Their muscle biopsies showed the diagnostic features of inclusion
body myositis, including endomysial T-cell infiltration, rimmed vacuoles, deposits
of phosphorylated tau, and abnormal filaments in the nuclei and cytoplasm of the
myofibers. The fibers expressed major histocompatibility complex class I antigens
and were invaded by CD8 and CD4 cells. In a single human leukocyte antigen-A2-positive
patient, in situ human leukocyte antigen-A*0201 / Tax11-19-pentamer staining showed
pentamer-positive cells surrounding the muscle fibers. Double-immunogold silver
staining and polymerase chain reaction in situ hybridization revealed that HTLV-I
proviral DNA was localized on helper-inducer T cells, but not on muscle fibers.
Human T-lymphotropic virus-type I proviral loads in peripheral blood mononuclear
cells from each patient were similar to those in HTLV-I-associated myelopathy/tropical
spastic paraparesis. This study suggests that HTLV-I infection may be one of
the causes of sporadic inclusion body myositis, as has been reported in human
immunodeficiency virus type-1 infection. PMID: 18091562 [PubMed - as supplied
by publisher]
Hohlfeld, Reinhard MD; Dornmair, Klaus PhD
Revisiting the immunopathogenesis of the inflammatory myopathies.[Editorial]
Comment on Greenberg: Neurology. 2007 Nov 20;69(21):1966-7.
In PM and IBM, CTLs focally surround, invade, and destroy non-necrotic muscle fibers, directing perforin-containing cytotoxic granules vectorially toward the attacked fibers. The target fibers express HLA-class I absent from normal fibers. Thus, an immunologic synapse exists between CTLs expressing T-cell receptors (TCRs) and target fibers expressing HLA-bound peptide antigens. In IBM the CTL-mediated myocytotoxicity might be related to a predisposing degenerative process.
PM and IBM muscle contain mDCs. This observation does not contradict the firmly established role of CD8+ CTL. In fact, it has been known for a long time that the inflammatory infiltrates of PM and IBM contain many monocytes/macrophages, i.e., cells that are functionally and phenotypically closely linked to mDC. The main implication of both the earlier and more recent observations is that all these cells might 1) present local antigens to T cells and B cells, and 2) contribute to muscle fiber damage.
The second new finding is that PM and IBM muscle contains more antibody-producing
B cells than previously appreciated. Again, there is no real conflict with the
established role of CTL. Indeed, experience in other inflammatory and autoimmune
diseases has shown that tissue injury is mediated by a combination of different
effector mechanisms. Thus it would be surprising if PM and IBM were exclusively
mediated by T cells. One possibility is that the locally produced antibodies
bind to muscle-related antigens, thereby earmarking them for antibody-dependent
cytotoxic mechanisms.
Neurology. 2007 Nov 20;69(21):2008-19. Epub 2007 Oct 10.
Proposed immunologic models of the inflammatory myopathies and potential therapeutic
implications.
Greenberg SA.
Department of Neurology, Brigham and Womens Hospital, Harvard Medical School,
Boston, MA 02115, USA. sagreenberg@partners.org
Several immune system cell types and processes have been recently identified
in muscle in inclusion body myositis, dermatomyositis, and polymyositis. Plasmacytoid
dendritic cells, the immune system's professional producer of the type 1 interferons
alpha and beta, are present in dermatomyositis muscle and skin. These tissues
also show high expression of transcripts and proteins from genes that are induced
by interferon alpha and beta. Myeloid dendritic cells, which contribute to an
immunologic synapse responsible for activation of the adaptive immune system,
are abundant within muscle in inclusion body myositis and polymyositis. B cells
and plasma cells, effector cells of the humoral immune system, have been stimulated
by antigen to transcribe immunoglobulins and produce antibodies in muscle in
all three of these diseases. The presence of these immune cells and processes
suggests revisions in models of the pathogenesis of the inflammatory myopathies
and provides rationales for future therapeutic approaches.
The central hypothesis that in IBM and PM muscle is injured by antigen-specific CD8+ cytotoxic T cells invading myofibers may be correct but has not been proven. The presence of muscle T cell clones has been demonstrated by the use of spectratyping and by sequencing of TCR alpha and beta chain transcripts but these studies have not determined whether the clonally related T cells in muscle are CD4+ T helper cells, CD8+ cytotoxic T cells, CD8+ suppressor T cells (which may have clonally restricted TCRs in spectratyping studies and which may invade myofibers, T regulatory cells, or some combination of these, and whether such cells are invading muscle or not.
For IBM and PM, the abundance of T cells and sparseness of B cells have contributed to a model of these as cytotoxic T cell mediated autoimmune diseases. Nevertheless, circulating autoantibodies have been recognized as present in some patients with IBM and PM.
Many other potential immunomodulatory therapies and strategies are being studied for autoimmune disease. The market forces driving development of new drugs have generally led to initial studies in more common autoimmune diseases. Refining models of the inflammatory myopathies may provide rationales for trials of selected agents, particularly FDA-approved drugs, for patients with inflammatory myopathies in the future.
Best Pract Res Clin Rheumatol. 2007 Dec;21(6):1051-70.
Diagnostic uncertainty in the inflammatory myopathies.
Verity MA. David Geffen
School of Medicine, University of California at Los Angeles, 10833 Le Conte Avenue,
Los Angeles, CA 90095, USA.
A group of case histories with appropriate muscle biopsy findings is presented
to demonstrate some atypical presentations of the inflammatory myopathies. Differential
diagnostic possibilities are considered in presentations of idiopathic polymyositis,
statin myotoxicity, the inflammatory component with the dysferlinopathies, treated
dermatomyositis, a necrotizing myopathy with pipe-stem microvascular change, an
inflammatory myopathy with abundant macrophages, inclusion-body myositis, and
the differential diagnosis of problems with eosinophilic infiltration in the muscle
biopsy. Attention is given to the role of membrane attack complex deposition in
the microvasculature and the role of major histiocompatibility complex-1-expressing
muscle fibers indicating activation of the endoplasmic reticulum stress response.
Neuromuscul Disord. 2007 Nov 28 [Epub ahead of print]
Apolipoprotein epsilon alleles in sporadic inclusion body myositis: A reappraisal.
Needham M, Hooper A, James I, van Bockxmeer F, Corbett A, Day T, Garlepp MJ,
Mastaglia FL.
Centre for Neuromuscular and Neurological Disorders, University of Western Australia,
Queen Elizabeth II Medical Centre, Perth, Australia.
Previous studies have differed as to whether APOE epsilon4 is a susceptibility
factor for developing sporadic inclusion body myositis (sIBM), with a positive
association being found only in an Australian cohort of cases. We have now re-examined
this in a larger cohort of 57 sIBM cases and have also carried out a meta-analysis
of all the published studies looking for evidence of a risk association or effect
of APOE alleles on disease expression. Our findings argue against a specific role
for any APOE alleles in conferring susceptibility to sIBM but have demonstrated
a non-significant trend towards an earlier age-of-onset in patients with the epsilon2
allele.
Muscle Nerve. 2007 Oct;36(4):447-54.
Nuclear localization of valosin-containing protein in normal muscle and muscle
affected by inclusion-body myositis.
Greenberg SA, Watts GD, Kimonis VE, Amato AA, Pinkus JL.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's
Hospital, and Harvard Medical School, Boston, MA 02115, USA. sagreenberg@partners.org
Inclusion-body myopathy with Paget's disease and frontotemporal dementia (IBMPFD)
is a disease of muscle, bone, and brain that results from mutations in the gene
encoding valosin-containing protein (VCP). The mechanism of disease resulting
from VCP mutations is unknown. Previous studies of VCP localization in normal
human muscle samples have found a capillary and perinuclear distribution, but
not a nuclear localization. Here we demonstrate that VCP is present in both myonuclei
and endothelial cell nuclei in normal human muscle tissue. The immunodetection
of VCP varies with acetone or paraformaldehyde fixation. Within the nucleus, VCP
associates with the nucleolar protein fibrillarin and Werner syndrome protein
(Wrnp) in normal and IBMPFD muscle. In patients with inclusion-body myositis (IBM),
normal nuclear localization is present and some rimmed vacuoles are lined with
VCP. These findings suggest that impairment in the nuclear function of VCP might
contribute to the muscle pathology occurring in IBMPFD.
J. Clin. Invest. 117:3393-3402 (2007). doi:10.1172/JCI31547.
Valsartan lowers brain beta-amyloid protein levels and improves spatial learning
in a mouse model of Alzheimer disease
Jun Wang1, Lap Ho1,2, Linghong Chen1, Zhong Zhao1, Wei Zhao1, Xianjuan Qian1,
Nelson Humala1, Ilana Seror1, Sadie Bartholomew1, Clive Rosendorff3 and Giulio
Maria Pasinetti1,2,4 1
Department of Psychiatry, Mount Sinai School of Medicine, New York, New York,
USA. 2Geriatric Research Education and Clinical Center, James J. Peters Veterans
Affairs Medical Center, New York, New York, USA. 3Department of Medicine, Mount
Sinai School of Medicine and the James J. Peters Veterans Affairs Medical Center,
New York, New York, USA. 4Department of Neuroscience, Mount Sinai School of Medicine,
New York, New York, USA. Address correspondence to: Giulio Maria Pasinetti, Icahn
Research Institute, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1230,
New York, New York 10029, USA. Phone: (212) 659-8716 or (212) 659-8740; Fax: (212)
876-9042; E-mail: giulio.pasinetti@mssm.edu. Received for publication January
18, 2007, and accepted in revised form August 28, 2007.
Recent epidemiological evidence suggests that some antihypertensive medications
may reduce the risk for Alzheimer disease (AD). We screened 55 clinically prescribed
antihypertensive medications for AD-modifying activity using primary cortico-hippocampal
neuron cultures generated from the Tg2576 AD mouse model. These agents represent
all drug classes used for hypertension pharmacotherapy. We identified 7 candidate
antihypertensive agents that significantly reduced AD-type beta-amyloid protein (Abeta)
accumulation. Through in vitro studies, we found that only 1 of the candidate
drugs, valsartan, was capable of attenuating oligomerization of Abeta peptides into
high-molecular-weight (HMW) oligomeric peptides, known to be involved in cognitive
deterioration. We found that preventive treatment of Tg2576 mice with valsartan
significantly reduced AD-type neuropathology and the content of soluble HMW extracellular
oligomeric Abeta peptides in the brain. Most importantly, valsartan administration
also attenuated the development of Abeta-mediated cognitive deterioration, even when
delivered at a dose about 2-fold lower than that used for hypertension treatment
in humans. These preclinical studies suggest that certain antihypertensive drugs
may have AD-modifying activity and may protect against progressive Abeta-related
memory deficits in subjects with AD or in those at high risk of developing AD.
The Myositis Association's 2007 Annual Conference held in Bellevue, Washington, September 6-9, 2007. A recent issue of The Outlook summarizes some of the important points from the medical panel and some of the sessions related to myositis research, diagnosis and treatment. Please contact TMA for a membership to this very valuable organization. Many of the Conference presentations can be viewed in their entirety on the TMA website at www.myositis.org. Click on 'Updates from Seattle' under 'In the Spotlight.'
Arthritis Res Ther. 2007;9(2):208.
Immune mechanisms in the pathogenesis of idiopathic inflammatory myopathies.
Grundtman C, Malmstrom V, Lundberg IE.
Rheumatology Unit, Department of Medicine, Karolinska University Hospital Solna,
Karolinska Institutet, SE-171 76 Stockholm, Sweden. cecilia.grundtman ki.se
Idiopathic inflammatory myopathies (IIMs), comprising polymyositis, dermatomyositis,
and inclusion-body myositis, are characterized by inflammatory cell infiltrates
in skeletal muscle tissue, muscle weakness, and muscle fatigue. The cellular infiltrates
often consist of T lymphocytes and macrophages but also, in some cases, B lymphocytes.
Emerging data have led to improved phenotypic characterization of the inflammatory
cells, including their effector molecules, in skeletal muscle, peripheral blood,
and other organs that are frequently involved, such as skin and lungs. In this
review we summarize the latest findings concerning the role of T lymphocytes,
B lymphocytes, dendritic cells, and other antigen-presenting cells in the pathophysiology
of IIMs.
A schematic summary of the potential role of different immune cells in the context of chronic muscle inflammation is presented in Figure 3.
Hypothetical involvement of T lymphocytes, B lymphocytes, and dendritic cells (DCs) in idiopathic inflammatory myopathies. (1) An unknown trigger (for example viral infection or ultraviolet radiation) in the respiratory tract or through the skin leads to the cleavage of histidyl-tRNA synthetase by granzyme B through antiviral CD8+ T lymphocytes in the lungs. (2) Immature DCs carry receptors on its surface that recognize common features of many pathogens. When a DC takes up a pathogen in infected tissue it becomes activated and migrates to the lymph node. (3) Upon activation, the DC matures into a highly effective antigen-presenting cell (APC) and undergoes changes that enable it to activate pathogen-specific lymphocytes in the lymph node. T lymphocytes become activated and B lymphocytes, with active help from CD4+ T lymphocytes, proliferate and differentiate into plasma cells. (4) Activated DCs, T lymphocytes, and B lymphocytes could release cytokines into the bloodstream. (5) The activated T lymphocyte, on which the DC-MHC.antigen complex is bound, itself binds to specialized endothelial cells called high endothelial venules (HEV). For this purpose it uses the VLA-4 (very late activation antigen-4) and LFA-1 (lymphocyte function associated antigen-1) molecules on its surface to interact with adhesion molecules (vascular cell-adhesion molecule-1 (VCAM-1) and intercellular cell-adhesion molecule-1 (ICAM-1)) on HEVs, where they can penetrate into peripheral lymphoid tissues. (6,7) Naive T lymphocytes and B lymphocytes that have not yet encountered their specific antigen circulate continuously from the blood into the peripheral lymphoid tissues. (8,9) Various cytokines from the bloodstream or produced locally could affect the muscle tissue or cell in many different ways. However, it is not clear whether the muscle cell itself could produce and release cytokines. (10-12) DCs, macrophages (Mand'Oacute;), and B lymphocytes can interact with T lymphocytes in various ways. T lymphocytes could possibly also bind to muscle cells through inducible co-stimulators (ICOS), CD40 ligand (CD40-L), CD28, and CTLA-4 (CD152) on T lymphocytes to ICOS ligand (ICOS-L), CD40, and BB-1 antigen on the muscle cell. In that fashion, the muscle cell would function as an APC. (13) Plasma cells (CD138+) can be found in the muscle tissue of certain subgroups of patients with idiopathic inflammatory myopathy, but whether these cells could produce autoantibodies locally is not yet known. (14) T lymphocytes have been shown to bind in close contact with muscle cells and to release perforin, granzyme A, and granulysin, which may cause necrosis of muscle tissue or cells.
Clin Neuropathol. 2007 Sep-Oct;26(5):232-40.
Brain imaging and neuropsychology in late-onset dementia due to a novel mutation
(R93C) of valosin-containing protein.
Krause S, Gohringer T, Walter MC, Schoser BG, Reilich P, Linn J, Popperl
GE, Frolich L, Hentschel F, Lochmuller H, Danek A.
Neurologische Klinik, Ludwig-Maximilians-Universitat Munchen, Germany.
Inclusion body myopathy with Paget disease of bone and frontotemporal dementia
(IBMPFD, MIM 167320) is a recently identified autosomal dominant disorder due
to mutations in the valosin-containing protein (VCP) that affects muscle, bone
and brain. Brain involvement and neuropsychological findings of IBMPFD have not
been described in detail. A patient carried a novel heterozygous base pair change,
47832C>T, in the VCP gene that resulted in substitution of an arginine residue
by cysteine at position 93 (R93C). He presented first with myopathy while bone
involvement remained subclinical. The patient developed behavioral abnormalities
in his 60s and showed frank personality change with fluent empty speech at the
age of 74 years. This syndrome was best classified as semantic dementia. Magnetic
resonance imaging disclosed slight but progressive cerebral atrophy with prominent
callosal and frontal white matter loss. Positron emission tomography demonstrated
glucose hypometabolism of the frontal and temporal lobes disproportionate to their
structural involvement. This first comprehensive clinical and neuroimaging study
in IBMPFD may raise the awareness among clinicians as well as basic scientists
for this exemplary genetic model of dementia.
Arthritis Rheum. 2007 Oct 29;56(11):3784-3792 [Epub ahead of print]
Type I interferon-inducible gene expression in blood is present and reflects disease
activity in dermatomyositis and polymyositis.
Walsh RJ, Kong SW, Yao Y, Jallal B, Kiener PA, Pinkus JL, Beggs AH, Amato AA,
Greenberg SA.
Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
OBJECTIVE: To apply gene expression profiling to the study of peripheral blood
mononuclear cells from patients with inflammatory myopathies, in order to provide
insight into disease pathogenesis and identify potential biomarkers associated
with disease activity. METHODS: We used Affymetrix whole-genome microarrays to
measure the expression of approximately 38,500 genes in 65 blood and 15 muscle
samples from 44 patients with dermatomyositis (DM), polymyositis (PM), inclusion
body myositis (IBM), myasthenia gravis, or genetically determined myopathies and
from 12 healthy volunteers. In 9 patients, 2 samples were obtained at different
time points, when disease was either active or improving, and these paired blood
samples were also compared. Bioinformatics techniques were used to identify genes
with significant differential expression among diagnostic categories and in relation
to disease activity. We corroborated the microarray data with quantitative real-time
reverse transcriptase-polymerase chain reaction. RESULTS: Most patients with active
DM or PM, but not patients with IBM, had significant and high up-regulation of
the type I interferon-alpha/beta (IFNalpha/beta)-inducible genes in blood. Furthermore,
the up-regulation of these genes correlated with disease activity in DM and PM,
with down-regulation occurring when disease was controlled with treatment. CONCLUSION:
DM and PM are diseases characterized by the systemic overexpression of IFNalpha/beta-inducible
genes. The magnitude of the overexpression of these genes is higher in DM and
correlates with disease activity in both disorders. Although PM and IBM have
been modeled as having similar immunologic processes occurring within muscle,
there are substantial differences in the expression of IFNalpha/beta-inducible
genes in blood in these diseases.
Ann Rheum Dis. 2007 Oct;66(10):1276-83. Epub 2007 Feb 2.
Limited effects of high-dose intravenous immunoglobulin (IVIG) treatment on
molecular expression in muscle tissue of patients with inflammatory myopathies.
Helmers SB, Dastmalchi M, Alexanderson H, Nennesmo I, Esbjornsson M, Lindvall
B, Lundberg IE.
Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Solna,
Karolinska Institutet, Stockholm, Sweden. Sevim.Barbasso@ki.se
OBJECTIVES: The study was conducted with the aim of achieving an improved understanding
of the molecular mechanisms of high-dose intravenous immunoglobulin (IVIG) in
inflammatory myopathies by investigating the effects on muscle function and
immunological molecules in skeletal muscle of polymyositis (PM), dermatomyositis
(DM) and inclusion body myositis (IBM) patients. METHODS: Thirteen treatment-resistant
patients, 6 PM, 4 DM, 2 IBM and 1 juvenile DM, were treated with 2 g/kg of IVIG,
three times at monthly intervals. Functional Index in Myositis and serum creatinine
kinase (CK) levels were determined, and muscle biopsies were performed before
treatment and after the third IVIG infusion. Immunological molecules were also
studied in biopsies taken 24-48 h after the first infusion. RESULTS: Improved
muscle function was observed in three patients (1 PM, 1 DM and 1 IBM) and CK
levels decreased in five. T cells, macrophages, major histocompatibility complex
(MHC) class I antigen on muscle fibres, intercellular adhesion molecule-1 (ICAM-1)
and vascular cell adhesion molecule-1 (VCAM-1) expression and membranolytic
attack complex (MAC) deposits on capillaries were present to an equal degree
in biopsies before and after IVIG treatment. No correlation between the clinical
response and molecular changes was found. CONCLUSIONS: The clinical effects
of high-dose IVIG on muscle function in patients with refractory inflammatory
active myositis did not correspond to effects on any of the investigated molecules
in our study. T cells, macrophages, phenotypical changes in muscle fibres and
endothelial cell activation were still present after treatment. These observations
question a role for IVIG as an immune-modulating therapy in patients with inflammatory
myopathies.
Neurology. 2007 Oct 23;69(17):1672-9.
T cell receptor profiling in muscle and blood lymphocytes in sporadic inclusion
body myositis.
Salajegheh M, Rakocevic G, Raju R, Shatunov A, Goldfarb LG, Dalakas MC.
Neuromuscular Diseases Section, National Institute of Neurological Disorders and
Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
BACKGROUND: Sporadic IBM (sIBM) is characterized by invasion of non-necrotic MHC-I
class-expressing muscle fibers by clonally expanded CD8+ cells. Whether the endomysial
cells expand in situ or are recruited from the circulation is unclear. METHODS:
We used CDR3 spectratyping of the T cell receptor (TCR) V beta chains to determine
clonal expansion of T cells in simultaneously obtained muscle and peripheral blood
lymphocytes (PBL) from 12 patients with sIBM, and compared the difference between
the two compartments. To determine whether the identified clones belonged to autoinvasive
T cells, we performed immunohistochemistry on the same muscle specimens. Spectratyping
was repeated in four muscle biopsies 1 year after the first. RESULTS: In control
PBL, all 24 TCR V beta subfamilies had a polyclonal or Gaussian distribution.
In sIBM PBL, 5% of the V beta subfamilies demonstrated a single and 16% up to
three peaks. In contrast, in their corresponding muscles, 27% (p = 0.0003) of
the V beta subfamilies demonstrated a single and 71% (p < 0.0001) up to three
peaks. Among the amplified subfamilies, V beta 9, 10, 11, 16, 18, 23, and 24 showed
the highest degree of restriction within muscle. Immunohistochemistry demonstrated
that the clonally expanded CD8+ cells were autoinvasive. In follow-up biopsies
the clonality persisted with an unchanged degree of restriction, but not always
of the same subfamilies, suggesting epitope spreading. CONCLUSION: In sporadic
inclusion body myositis, the endomysial T cells are specifically recruited to
the muscle or expand in situ. The restriction of multiple V beta subfamilies and
their change over time suggests recognition of various local antigens and epitope
spreading.
Proc Natl Acad Sci U S A. 2007 Oct 17; [Epub ahead of print]
Distinctive patterns of microRNA expression in primary muscular disorders.
Eisenberg I, Eran A, Nishino I, Moggio M, Lamperti C, Amato AA, Lidov HG,
Kang PB, North KN, Mitrani-Rosenbaum S, Flanigan KM, Neely LA, Whitney D, Beggs
AH, Kohane IS, Kunkel LM.
Howard Hughes Medical Institute.
The primary muscle disorders are a diverse group of diseases caused by various
defective structural proteins, abnormal signaling molecules, enzymes and proteins
involved in posttranslational modifications, and other mechanisms. Although
there is increasing clarification of the primary aberrant cellular processes
responsible for these conditions, the decisive factors involved in the secondary
pathogenic cascades are still mainly obscure. Given the emerging roles of microRNAs
(miRNAs) in modulation of cellular phenotypes, we searched for miRNAs regulated
during the degenerative process of muscle to gain insight into the specific
regulation of genes that are disrupted in pathological muscle conditions. We
describe 185 miRNAs that are up- or down-regulated in 10 major muscular disorders
in humans [Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, facioscapulohumeral
muscular dystrophy, limb-girdle muscular dystrophies types 2A and 2B, Miyoshi
myopathy, nemaline myopathy, polymyositis, dermatomyositis, and inclusion body
myositis]. Although five miRNAs were found to be consistently regulated in almost
all samples analyzed, pointing to possible involvement of a common regulatory
mechanism, others were dysregulated only in one disease and not at all in the
other disorders. Functional correlation between the predicted targets of these
miRNAs and mRNA expression demonstrated tight posttranscriptional regulation
at the mRNA level in DMD and Miyoshi myopathy. Together with direct mRNA-miRNA
predicted interactions demonstrated in DMD, some of which are involved in known
secondary response functions and others that are involved in muscle regeneration,
these findings suggest an important role of miRNAs in specific physiological
pathways underlying the disease pathology.
3 quotes from article:
1). miRNA expression microarrays containing 428 human miRNAs from the miRBase
database and novel human miRNA (AmbimiRs) were used in this study. In total,
a subset of 185 human miRNAs, corresponding to 43% of human miRNA probes present
on the array, were found to be differentially expressed at a significant level
(Pandlt;0.05, false discovery rateandlt;0.05) in at least one of the 10 muscle conditions
compared with the control panel (SI Table 3). Interestingly, of the differentially
expressed miRNAs, most were up-regulated in the different diseases (39 in DMD,
62 in FSHD, 88 in LGMD2A, 87 in LGMD2B, 69 in MM, 140 in NM, 20 in IBM, 37 in
PM, and 35 in DM) as compared with normal muscle tissue. Whereas a total of
151 different miRNA genes were found to be consistently up-regulated relative
to the control, only 28 miRNAs were down-regulated among the various conditions.
Overlying this broad commonality is the up-regulation of specific miRNAs and
the specific down-regulation of others that allows us to assign a distinctive
signature to each of the 10 conditions (Fig. 1 and SI Table 4). In addition,
a set of six miRNAs (30b, 92, 361, 423, 29a, and 29b)
2). In contrast to many previous studies, mostly in cancer, showing a global reduction of mature miRNA levels compared with normal tissues, an increase in abundance for many miRNAs was observed in the different muscular disorders. In this report, we provide evidence that miRNAs have a potential role in the pathophysiology of primary muscle diseases and present the complete suite of known miRNAs with altered expression in these diseases. These miRNA signatures provide the basis for a list of common target genes whose misregulation may contribute to the pathology of these disorders. Secondary to the genetic defects, necrosis and inflammation play a crucial role in the pathogenesis of the different muscular dystrophies and myopathies, and expression profiling of various diseased muscles revealed distinct patterns of immune or immune modulatory pathways rather than nonspecific processes (11, 30). Although the immunopathology of these disorders is not fully understood, several miRNAs previously described as immune-related were found as commonly dysregulated among the various dystrophies. Together with the different patterns of dysregulated miRNAs unique to each of the different diseases, this pattern offers insights into the complexities of the inflammatory process taking place in the different affected muscle fibers.
3). Conclusion. Considerable advances have been made in understanding the mechanisms, both transcriptional and translational, that lead to altered gene expression under dystrophic conditions. Our results point to an additional dimension of regulation of muscle function mediated by miRNAs.An important aim for the futurewill be to experimentally assess the predicted targets of the miRNAs responsible for adverse skeletal muscle remodeling in the different diseases. The overall discovery of dysregulated miRNAs in the different diseases is expected not only to broaden our biological understanding of these diseases, but more importantly, to identify candidate miRNAs as potential targets for future clinical applications.
Glossary:
= Down regulation is decreasing the rate of gene expression.
= Up regulation is increasing the rate of gene expression.Up-regulation is a
process which occurs within a cell triggered by a signal (originating internal
or external to the cell) which results in increased expression of one or more
genes and as a result the protein(s) encoded by those genes.
= microRNAs (miRNA) are single-stranded RNA molecules of about 21-23 nucleotides
in length, which regulate gene expression. miRNAs are encoded by genes that
are transcribed from DNA but not translated into protein (non-coding RNA); instead
they are processed from primary transcripts known as pri-miRNA to short stem-loop
structures called pre-miRNA and finally to functional miRNA. Mature miRNA molecules
are partially complementary to one or more messenger RNA (mRNA) molecules, and
their main function is to downregulate gene expression. MicroRNAs regulate gene
expression by degrading mRNAs of certain genes or interfering with translational
machinery of mRNAs. MicroRNAs are predicted to regulate expression of as many
as 30% of protein-encoding genes. By measuring activity among genes encoding
miRNA, patterns of gene activity that can distinguish types of disorders can
be discerned. miRNA signatures thus may enable classification of disorders.
= MicroRNAs are now known to regulate genes which make muscle and are likely
also involved in the processes leading to muscle deterioration in the major
muscle disorders.
Press release:
Leads To Muscle Degeneration Uncovered By Massive MicroRNA Scan
18 Oct 2007
Researchers have discovered the first microRNAs -- tiny bits of code that regulate gene activity -- linked to each of 10 major degenerative muscular disorders, opening doors to new treatments and a better biological understanding of these debilitating, poorly understood, often untreatable diseases. The study, to be published online this week by the Proceedings of the National Academy of Sciences, was led by Iris Eisenberg, PhD, of the Program in Genomics at Children's Hospital Boston. Louis Kunkel, PhD, director of the Program in Genomics and an investigator with the Howard Hughes Medical Institute, was senior investigator.
The disorders include the muscular dystrophies (Duchenne muscular dystrophy, Becker muscular dystrophy, limb girdle muscular dystrophies, Miyoshi myopathy, and fascioscapulohumeral muscular dystrophy); the congenital myopathies (nemaline myopathy); and the inflammatory myopathies (polymyositis, dermatomyositis, and inclusion body myositis). While past studies have linked them with an increasing number of genes, it's still largely unknown how these genes cause muscle weakness and wasting, and, more importantly, how to translate the discoveries into treatments.
For instance, most muscular dystrophies begin with a known mutation in a andquot;master gene,andquot; leading to damaged or absent proteins in muscle cells. In Duchenne and Becker muscular dystrophies, the absent protein is dystrophin, as Kunkel himself discovered in 1987. Its absence causes muscle tissue to weaken and rupture, and the tissue becomes progressively nonfunctional through inflammatory attacks and other damaging events that aren't fully understood.
andquot;The initial mutations do not explain why patients are losing their muscle so fast,andquot; says Eisenberg. andquot;There are still many unknown genes involved in these processes, as well as in the inflammatory processes taking place in the damaged muscle tissue.andquot;
She and Kunkel believe microRNAs may help provide the missing genetic links. Their team analyzed muscle tissue from patients with each of the ten muscular disorders, discovering that 185 microRNAs are either too abundant or too scarce in wasting muscle, compared with healthy muscle.
Discovered in humans only in the past decade, microRNAs are already known to regulate major processes in the body. Therefore, Eisenberg believes microRNAs may be involved in orchestrating the tissue death, inflammatory response and other major degenerative processes in the affected muscle tissue. The researchers used bioinformatics to uncover a list of genes the microRNAs may act on, and now plan to find which microRNAs and genes actually underlie these processes.
The findings raise the possibility of slowing muscle loss by targeting the microRNAs that control these andquot;cascadesandquot; of damaging events. This approach is more efficient than targeting individual genes.
The team also defined the abnormal microRNA andquot;signaturesandquot; that correspond to each of the ten wasting diseases. They hope these will shed light on the genes and disease mechanisms involved in the most poorly understood and least treatable of the degenerative disorders, such as inclusion body myositis.
andquot;At this point, it's very theoretical, but it's possible,andquot; says Eisenberg.
The study was funded by the Howard Hughes Medical Institute and also by the National Center for Research Resources, the Associazione Amici del Centro Dino Ferrari, the Telethon Project, the Eurobiobank Project, the Muscular Dystrophy Association, the National Institutes of Health, the Lee and Penny Anderson Family Foundation, and the Joshua Frase Foundation.
Children's Hospital Boston is home to the world's largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 12 members of the Howard Hughes Medical Institute comprise Children's research community. Founded as a 20-bed hospital for children, Children's Hospital Boston today is a 377-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children's also is the primary pediatric teaching affiliate of Harvard Medical School. For more information about the hospital and its research visit: http://www.childrenshospital.org/newsroom.
Source: James Newton
Children's Hospital Boston
Article URL: http://www.medicalnewstoday.com/articles/85951.php
Neurology. 2007 Oct 10; [Epub ahead of print]
Proposed immunologic models of the inflammatory myopathies and potential therapeutic
implications.
Greenberg SA.
From the Department of Neurology, Division of Neuromuscular Disease, Brigham and
Women's Hospital and Harvard Medical School, Boston; and Children's Hospital Informatics
Program and Harvard-MIT Division of Health Sciences and Technology, Boston, MA.
Several immune system cell types and processes have been recently identified in
muscle in inclusion body myositis, dermatomyositis, and polymyositis. Plasmacytoid
dendritic cells, the immune system's professional producer of the type 1 interferons
alpha and beta, are present in dermatomyositis muscle and skin. These tissues
also show high expression of transcripts and proteins from genes that are induced
by interferon alpha and beta. Myeloid dendritic cells, which contribute to an
immunologic synapse responsible for activation of the adaptive immune system,
are abundant within muscle in inclusion body myositis and polymyositis. B cells
and plasma cells, effector cells of the humoral immune system, have been stimulated
by antigen to transcribe immunoglobulins and produce antibodies in muscle in all
three of these diseases. The presence of these immune cells and processes suggests
revisions in models of the pathogenesis of the inflammatory myopathies and provides
rationales for future therapeutic approaches.
Nov
Curr Opin Rheumatol. 2007 Nov;19(6):550-9.
Inclusion-body myositis, a multifactorial muscle disease associated with aging:
current concepts of pathogenesis.
Askanas V, Engel WK.
USC Neuromuscular Center, Department of Neurology, University of Southern California
Keck School of Medicine, Good Samaritan Hospital, Los Angeles, California, USA.
PURPOSE OF REVIEW: Sporadic inclusion-body myositis, the most common muscle
disease of older persons, has no known cause or persistently beneficial treatment.
The unfolding pathogenesis could lead to new treatment strategies and it is
now of growing interest among clinicians and basic scientists. About 100 papers
related to the subject were published in 2006 and the first part of 2007 (we
cite only articles most relevant to this review). RECENT FINDINGS: This review
focuses on the current concepts of the pathogenesis of sporadic inclusion-body
myositis. Both degeneration and mononuclear-cell inflammation are components
of the pathology, but how each relates to the pathogenesis remains unclear.
We suggest that an intramuscle fiber degenerative component is primary, leading
to muscle-fiber destruction, while the lymphocytic inflammatory component may
only slightly contribute to sporadic inclusion-body myositis muscle-fiber damage.
Intracellular accumulation of amyloid-beta precursor protein, amyloid-beta,
and amyloid-beta oligomers in an aging muscle-fiber cellular milieu, and other
abnormalities, appear to be key pathogenic factors. We summarize intracellular
molecular events and their consequences, and correlate findings in sporadic
inclusion-body myositis muscle biopsies with inclusion-body myositis experimental
models in tissue culture and in transgenic mice. SUMMARY: Treatment of sporadic
inclusion-body myositis remains a challenge. Antiinflammatory approaches used
so far are without major or enduring benefit. Possible new treatment avenues
are suggested.
Article here.
Figure 2:
Various detrimental and protective proteins and mechanisms operating within
the s-IBM muscle fiber are diagrammatically illustrated. Ab, amyloid-b;
AbPP, amyloid-b precursor protein; ERS, endoplasmic reticulum stress; p-tau,
phosphorylated tau; HSP, heat shock protein; IGF, insulin-like growth
factor; NMJ, neuromuscular junction.
Figure 3:
(1) Abnormal accumulation of several proteins leads to molecular crowding,
resulting in accumulation of normal and unfolded/misfolded proteins (2),
which evoke endoplasmic reticulum stress (ERS) and unfolded protein response
(UPR) (3). Heat shock proteins (HSPs) (3, 6) can aid proper protein
folding. (4) Oxidative stress contributes to protein misfolding. The 26S/20S
proteasome is inhibited (5) by several factors operating in the aging
environment of the s-IBM muscle, including: oxidative stress, accumulated oligomerized
(unfolded/misfolded) amyloid-b (Ab), other unfolded/misfolded
proteins, and UBB+1. An inhibited proteasome (5) is unable to degrade ubiquitinated
(Ub) proteins, which subsequently (6) are retained within the
muscle fiber. This leads to their accumulation, further unfolding/misfolding,
and binding to important normal proteins, and also forming b-pleated-sheet
amyloid and aggregation into aggresomes (7) and other inclusions (8). Unfolded/misfolded
proteins gradually accumulating within the muscle fibers are
putatively cytotoxic (indicated by *).
Clin Neuropathol. 2007 Sep-Oct;26(5):232-40.
Brain imaging and neuropsychology in late-onset dementia due to a novel mutation
(R93C) of valosin-containing protein.
Krause S, Gohringer T, Walter MC, Schoser BG, Reilich P, Linn J, Popperl GE,
Frolich L, Hentschel F, Lochmuller H, Danek A.
Inclusion body myopathy with Paget disease of bone and frontotemporal dementia
(IBMPFD, MIM 167320) is a recently identified autosomal dominant disorder due
to mutations in the valosin-containing protein (VCP) that affects muscle, bone
and brain. Brain involvement and neuropsychological findings of IBMPFD have not
been described in detail. A patient carried a novel heterozygous base pair change,
47832C>T, in the VCP gene that resulted in substitution of an arginine residue
by cysteine at position 93 (R93C). He presented first with myopathy while bone
involvement remained subclinical. The patient developed behavioral abnormalities
in his 60s and showed frank personality change with fluent empty speech at the
age of 74 years. This syndrome was best classified as semantic dementia. Magnetic
resonance imaging disclosed slight but progressive cerebral atrophy with prominent
callosal and frontal white matter loss. Positron emission tomography demonstrated
glucose hypometabolism of the frontal and temporal lobes disproportionate to their
structural involvement. This first comprehensive clinical and neuroimaging study
in IBMPFD may raise the awareness among clinicians as well as basic scientists
for this exemplary genetic model of dementia.
Sept/Oct
Ann N Y Acad Sci. 2007 Sep;1110:285-96.
Treatment of autoimmune disease with rabbit anti-T lymphocyte globulin: clinical
efficacy and potential mechanisms of action.
Lytton SD, Denton CP, Nutzenberger AM.
M.P.H., SeraDiaLogistics, Hertlingstr 1, 81545 Manduuml;nchen, Germany. simon.lytton@t-online.de.
The rabbit anti-T lymphocyte globulins (rATGs) are immune-suppressive anti-T cell
agents with beneficial effects in solid organ and hematological transplantation.
The present review evaluates the potential mechanisms of rATGs and their impact
on pilot and exploratory studies of diffuse cutaneous systemic sclerosis (scleroderma-SSc),
inclusion body myositis (IBM), vasculitis, and type 1 diabetes mellitus (T1DM).
The rATGs are associated with improvements in well-defined parameters of clinical
autoimmunity: insulin usage, tissue inflammation, and systemic organ functions.
Meta-analysis of a retrospective database of SSc, N = 196 and two prospective
randomized pilot studies; IBM, N = 11 and T1DM, N = 17 shows a two- to ninefold
increase in the relative response to treatments with intravenous infusions of
rATG. The rATGs deplete T cells and are associated with increases in the percentage
of CD25(+) T cell subsets. This may underlie the apparent long-lasting immunomodulation
associated with these agents. The future optimization of rATG adjunct therapy
requires statistically powered-controlled prospective trials of rATG dose-finding
and timing of administration. The potential mechanisms of rATGs:depletion of autoreactive
T cells, generation CDCD25(+)Foxp3(+) regulatory T cells (Tregs), and the acquisition
of regulatory immune cell functions, need to be examined in patients prior to
rATG infusion and at time intervals following rATG treatment to identify those
mechanisms relevant to the improvement of their clinical outcome.
Aug
Ann N Y Acad Sci. 2007 Aug;1109:441-53.
Chemokine profile of different inflammatory myopathies reflects humoral versus
cytotoxic immune responses.
De Paepe B, Creus KK, De Bleecker JL.
The idiopathic inflammatory myopathies (IM) are subdivided into dermatomyositis
(DM), polymyositis (PM), and sporadic inclusion body myositis (IBM). These autoimmune
muscle diseases represent different immunopathological entities. DM is a humoral
endotheliopathy initiated by complement deposition in intramuscular blood vessels,
and characterized by perimysial inflammation and muscle fiber atrophy in perifascicular
regions. In PM and IBM, nonnecrotic muscle fibers are actively invaded by autoaggressive
macrophages and cytotoxic T cells. Chemokines are key mediators of inflammatory
disease as they regulate leukocyte recruitment to tissue target sites. We studied
a large selection of alpha/beta-chemokines and receptors in normal controls
and in the IM using immunohistochemistry, immunofluorescence, in situ hybridization,
and Western blotting. We showed that the chemokine array of normal myocytes
was limited, while the blood vessels in normal skeletal muscle tissue displayed
a broad chemokine profile. The IM were characterized by a general increase of
specific chemokines and chemokine receptors, while chemokine distribution reflected
the two different immune responses represented within these muscle diseases.
In DM, endothelial expression of CCL2 and CXCL12beta was highly increased. In
PM and IBM, macrophages and cytotoxic T cells actively invading nonnecrotic
muscle fibers expressed highest levels of CXCL10 and CCL2. Some chemokines were
selectively expressed by different IM infiltrates: CCL4 was present only in
the perimysial inflammatory foci of a subset of DM biopsies, while CXCL1, CXCL2,
CXCL3, and CCL7-positive cells were exclusively detected in endomysial infiltrates
of a number of PM and IBM samples. The chemokine receptor profile of the IM
indicated the predominance of Th1-mediated immune responses in all three IM.
Our studies identified three ligand-receptor pairs, namely CXCL10/CXCR3, CXCL12/CXCR4,
and CCL2/CCR2, as potential targets for chemokine-based therapy in IM.
Sept
Arthritis Rheum. 2007 Sep;56(9):3112-24.
A possible mechanism for endogenous activation of the type I interferon system
in myositis patients with anti-Jo-1 or anti-Ro 52/anti-Ro 60 autoantibodies.
Eloranta ML, Helmers SB, Ulfgren AK, Randouml;nnblom L, Alm GV, Lundberg IE.
Uppsala University, Uppsala, Sweden.
OBJECTIVE: To investigate type I interferon (IFN) system activation and its
correlation with autoantibodies and organ manifestations in polymyositis (PM),
dermatomyositis (DM), and inclusion body myositis. METHODS: Sera from 30 patients
and 16 healthy controls, or purified IgG, were combined with material released
from necrotized cells to stimulate IFNalpha production by peripheral blood mononuclear
cells (PBMCs) from healthy blood donors. Muscle biopsy specimens from 25 patients
and 7 healthy controls were investigated for blood dendritic cell antigen 2
(BDCA-2)-positive plasmacytoid dendritic cells (PDCs) and IFNalpha/beta-inducible
myxovirus resistance 1 (MX-1) protein. RESULTS: Sera from 13 patients who were
positive for anti-Jo-1 or anti-Ro 52/anti-Ro 60 autoantibodies induced IFNalpha
production in PBMCs when combined with necrotic cell material. In addition,
IgG prepared from anti-Jo-1-positive PM sera induced IFNalpha with necrotic
material, but not when the latter was treated with RNase. BDCA-2 expression
in PDCs in muscle tissue was increased in PM patients with anti-Jo-1 autoantibodies,
while MX-1 staining in capillaries was increased in DM patients, compared with
healthy individuals. IFNalpha-inducing capacity correlated with interstitial
lung disease, while MX-1 expression in the capillaries correlated with DM. CONCLUSION:
Immune complexes containing anti-Jo-1 or anti-Ro 52/anti-Ro 60 autoantibodies
and RNA may act as endogenous IFNalpha inducers that activate IFNalpha production
in PDCs. These PDCs could be of importance for inducing myositis, whereas in
DM patients without autoantibodies the presence of MX-1 protein in capillaries
suggests another cellular IFNalpha source and induction mechanism. Consequently,
the type I IFN system may be of importance in both PM and DM, but via different
pathways.
Sept/
Neuromuscul Disord. 2007 Sep 19; [Epub ahead of print]
Histone H1 is released from myonuclei and present in rimmed vacuoles with DNA
in inclusion body myositis.
Nakano S, Shinde A, Fujita K, Ito H, Kusaka H.
Department of Neurology, Kansai Medical University, Moriguchi 570-8507, Japan.
To investigate myonuclear alterations in sporadic inclusion body myositis (s-IBM),
we immuno-localized histones in muscles in 11 patients. The examination showed
that vacuolar rims were frequently positive for histone H1. In triple-color fluorescence
study, the H1-positive products were found on the inner side of an emerin-positive
circle with DNA. Moreover, H1-positive materials appeared to be released into
the cytoplasm in some vacuoles and myonuclei. The localization of H1 was different
from phosphorylated Elk-1, which is a nuclear protein, but abnormally accumulated
in the cytoplasm in s-IBM. The results strongly support the hypothesis that rimmed
vacuoles are derived from the nucleus. The cytoplasmic H1-release suggests dysfunction
of nuclear membranes in an early phase of the nuclear disintegration. We hypothesize
that, in s-IBM muscles, compromised nuclear envelope may permit release of some
nuclear components such as histone H1 and cannot facilitate the incorporation
of others to the nucleus as in pElk-1.
Sept
Neurology. 2007 Sep 19; [Epub ahead of print]
Correlation of muscle biopsy, clinical course, and outcome in PM and sporadic
IBM.
Chahin N, Engel AG.
From the Department of Neurology, Mayo Clinic, Rochester, MN.
ABSTRACT OBJECTIVE: To correlate muscle biopsy findings with prebiopsy and postbiopsy
clinical course and response to therapy in polymyositis (PM) and sporadic inclusion
body myositis (IBM). BACKGROUND: Existence of pure PM has recently been questioned;
subsequently, the definition and criteria for diagnosing PM were debated. METHODS:
Patient records, follow-up information, and muscle biopsies were analyzed in 107
patients whose biopsies were initially read as PM and IBM. RESULTS: The patients
fell into three groups by combined biopsy and clinical criteria: PM, 27 patients;
IBM, 64 patients; PM/IBM, 16 patients with biopsy diagnosis of PM but clinical
features of IBM. For the three groups, the respective mean periods from disease
onset to end of follow-up were 5.9, 8.5, and 9.6 years. Another autoimmune disease
was present in 4 of 27 PM, 8 of 64 IBM, and 1 of 16 PM/IBM cases. An autoimmune
serologic marker occurred in one-third of each group. Nineteen PM patients had
no associated autoimmune disease or marker. Nonnecrotic fiber invasion by mononuclear
cells appeared in all IBM, 17 of 27 PM, and 13 of 16 PM/IBM patients. The density
of both invaded fibers and cytochrome c oxidase-negative fibers was higher in
IBM and PM/IBM than in PM. Immunotherapy improved 22 of 27 PM patients but had
only transient beneficial effects in 2 of 32 IBM and 1 of 14 PM/IBM patients.
CONCLUSIONS: 1) Sixteen of 43 patients (37%) with biopsy features of polymyositis
(PM) had clinical features of inclusion body myositis (IBM). 2) Absence of canonical
biopsy features of IBM from clinically affected muscles of IBM patients challenges
biopsy criteria for IBM, or the IBM markers appear late in some patients, or their
distribution in muscle is patchy and restricted compared with that of the inflammatory
exudate. 3) The muscle biopsy is a reliable instrument in the diagnosis of PM
and IBM in close to 85% of the patients. Errors of diagnosis in the remaining
15% can be avoided or reduced by combined evaluation of the clinical and pathologic
findings.
Aug
Ann N Y Acad Sci. 2007 Aug;1109:441-53.
Chemokine profile of different inflammatory myopathies reflects humoral versus
cytotoxic immune responses.
De Paepe B, Creus KK, De Bleecker JL.
Department of Neurology, Ghent University Hospital, Belgium.
The idiopathic inflammatory myopathies (IM) are subdivided into dermatomyositis
(DM), polymyositis (PM), and sporadic inclusion body myositis (IBM). These autoimmune
muscle diseases represent different immunopathological entities. DM is a humoral
endotheliopathy initiated by complement deposition in intramuscular blood vessels,
and characterized by perimysial inflammation and muscle fiber atrophy in perifascicular
regions. In PM and IBM, nonnecrotic muscle fibers are actively invaded by autoaggressive
macrophages and cytotoxic T cells. Chemokines are key mediators of inflammatory
disease as they regulate leukocyte recruitment to tissue target sites. We studied
a large selection of alpha/beta-chemokines and receptors in normal controls
and in the IM using immunohistochemistry, immunofluorescence, in situ hybridization,
and Western blotting. We showed that the chemokine array of normal myocytes
was limited, while the blood vessels in normal skeletal muscle tissue displayed
a broad chemokine profile. The IM were characterized by a general increase of
specific chemokines and chemokine receptors, while chemokine distribution reflected
the two different immune responses represented within these muscle diseases.
In DM, endothelial expression of CCL2 and CXCL12beta was highly increased. In
PM and IBM, macrophages and cytotoxic T cells actively invading nonnecrotic
muscle fibers expressed highest levels of CXCL10 and CCL2. Some chemokines were
selectively expressed by different IM infiltrates: CCL4 was present only in
the perimysial inflammatory foci of a subset of DM biopsies, while CXCL1, CXCL2,
CXCL3, and CCL7-positive cells were exclusively detected in endomysial infiltrates
of a number of PM and IBM samples. The chemokine receptor profile of the IM
indicated the predominance of Th1-mediated immune responses in all three IM.
Our studies identified three ligand-receptor pairs, namely CXCL10/CXCR3, CXCL12/CXCR4,
and CCL2/CCR2, as potential targets for chemokine-based therapy in IM.
Sept/Oct
12th International Congress of the World Muscle Society Taormina, Italy, 17-20
October 2007
G.O.2 In sporadic inclusion-body myositis (s-IBM) muscle fibers, Parkinson-disease-associated
DJ-1 is oxidized and might play a novel pathogenic role
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 766-767
C. Terracciano, A. Nogalska, W.K. Engel, S. Wojcik and V. Askanas
2.
G.P.13.01 Prevalence of sporadic inclusion body myositis (s-IBM) in Turkey:
A muscle biopsy based survey
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 849
P. Serdaroglu, F. Deymeer and Y. Parman
3.
G.P.13.03 Familial late-onset inclusion body myositis in a search of a gene
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 849
M. Dunand, J. Lobrinus, P. Richard, R. Bernard, N. Levy and T. Kuntzer
4.
G.P.13.06 Sporadic inclusion body myositis (sIBM): A phenotypic spectrum in
a cohort of 57 cases
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 850
M. Needham, A. Corbett, T. Day and F. Mastaglia
5.
G.P.13.07 Prevalence and diagnosis of sporadic inclusion body myositis (sIBM)
in Western Australia
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 850-851
M. Needham, A. Corbett, T. Day, V. Fabian and F. Mastaglia
6.
G.P.13.09 Proteomic analysis of distal myopathy with rimmed vacuoles (DMRV)
or hereditary inclusion body myopathy (hIBM)
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 851
M. Malicdan, S. Noguchi, G. Kawahara, Y. Hayashi and I. Nishino
7.
G.P.13.10 Proteomic analysis of myotubes from hereditary inclusion body myopathy
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 851-852
S. Mitrani-Rosenbaum, I. Salama, I. Milman, Z. Shlomai, A. Dagan and H. Ben
Bassat
8.
G.P.13.12 Muscle pathology in a mouse model of gelsolin amyloidosis is similar
to human inclusion body myositis
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 852
G. Shelton, L. Page, Y. Jiang, W. Balch, J. Kelly and A. Mizisin
9.
G.P.13.14 Ex vivo treatment with TSA and IGF-1 induces myogenic differentiation
of inclusion-body myositis mesoangioblasts
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 852-853
R. Morosetti, C. Gliubizzi, A. Broccolini, T. Gidaro, C. Sancricca, P. Tonali,
E. Ricci, G. Cossu and M. Mirabella
10.
G.P.13.15 In sporadic inclusion-body myositis muscle-fiber (s-IBM) cytoplasm,
cytochrome C aggregates with a-synuclein and amyloid-andszlig; precursor protein
(Aandszlig;PP), but does not activate caspase-3
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Page 853
S. Wojcik, O. Paciello, W.K. Engel and V. Askanas
11.
G.P.13.17 Recombinant mapping of MHC susceptibility region in sporadic inclusion
body myositis (sIBM)
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 853-854
A. Scott, N. Laing, F. Mastaglia, M. Needham, M. Walter, M. Dalakas and R. Allcock
12.
G.P.17.04 Reduced force generation and atrophy impair overall physical performance
of a mouse model for distal myopathy with rimmed vacuoles (DMRV) or hereditary
inclusion body myopathy (hIBM)
Neuromuscular Disorders, Volume 17, Issues 9-10, October 2007, Pages 884-885
M. Malicdan, S. Noguchi, Y. Hayashi and I. Nishino
Sept/Oct
J Neurol Sci. 2007 Sep 11; [Epub ahead of print]
Non-pathogenic protein aggregates in skeletal muscle in MLF1 transgenic mice.
Li ZF, Wu X, Jiang Y, Liu J, Wu C, Inagaki M, Izawa I, Mizisin AP, Engvall
E, Shelton GD.
Burnham Institute for Medical Research, 10901 N. Torrey Pines Road. La Jolla,
CA 92037, United States.
Protein aggregate formation in muscle is thought to be pathogenic and associated
with clinical weakness. Over-expression of either wild type or a mutant form
of myeloid leukemia factor 1 (MLF1) in transgenic mouse skeletal muscle and
in cultured cells resulted in aggregate formation. Aggregates were detected
in MLF1 transgenic mice at 6 weeks of age, and increased in size with age. However,
histological examination of skeletal muscles of MLF1 transgenic mice revealed
no pathological changes other than the aggregates, and RotaRod testing did not
detect functional deficits. MLF1 has recently been identified as a protein that
could neutralize the toxicity of intracellular protein aggregates in a Drosophila
model of Huntington's disease (HD). We also demonstrate that MLF1 interacts
with MRJ, a heat shock protein, which can independently neutralize the toxicity
of intracellular protein aggregates in the Drosophila HD model. Our data suggest
that over-expression of MLF1 has no significant impact on skeletal muscle function
in mice; that progressive formation of protein aggregates in muscle are not
necessarily pathogenic; and that MLF1 and MRJ may function together to ameliorate
the toxic effects of polyglutamine or mutant proteins in myodegenerative diseases
such as inclusion body myositis and oculopharyngeal muscular dystrophy, as well
as neurodegenerative disease.
4. Discussion
We report here that over-expression of either wild-type MLF1 or MLF1-S34A
mutant resulted in progressive formation of aggregates in skeletal muscle that,
other than the presence of aggregates, caused neither pathological nor functional
abnormalities inmice. Thus, despite the presence of the aggregates in muscle inMLF1
transgenic mice, there were no detectable clinical signs of weakness. These observations
provide evidence that not all protein aggregates in muscle fibers are pathogenic,
and that progressive aggregate formation per se is not harmful to skeletal muscle
in the mouse.
It is apparent from this study that, in addition to brain, mouse skeletal muscle cells can tolerate the progressive formation of protein aggregates formed by overexpression of MLF1. While muscle was not examined for aggregates prior to 6 weeks of age, other than the aggregates, there was no histological evidence of pathogenicity to the muscle fibers or clinical evidence of muscle weakness, and the mice develop normally.
Outlook summer 2007 TMA
Some Kentucky mice will find themselves among the trendy dieters embracing a low-carbohydrate regimen this year. A two-year study at the University of Kentucky begins shortly, designed to find out what happens when animals with the mouse version of inclusion-body myositis are fed a diet that restricts carbohydrates but includes plentiful protein and sufficient healthy fats. The mice will also be made to exercise.
Mouse IBM is similar to the human type in its long-term effects, Paul Murphy, PhD, Assistant Professor, Department of Molecular and Cellular Biochemistry at the University of Kentucky, said. 'The mice develop inclusions in the muscle, and get progressively weaker as the disease progresses. The main difference is that the mouse immune system is a little different, leading to a slightly different type of inflammation.'
The diet, called a 'ketogenic' diet, is closely related to the Atkins diet and other diets based on restricting carbohydrates. 'In addition to being a popular strategy for people to lose weight, this type of diet is already used to help control some forms of epilepsy,' Murphy said.
Murphy says the mice will lose a little bit of weight at first, then stabilize, basically the same as humans on a diet. 'If you were trying to make a comparison to people, it would be roughly equivalent to someone who was a little overweight losing 10- 20 pounds,' Murphy said.
Murphy and his assistant, Christa Studzinski, who was awarded a two-year fellowship
from The Myositis Association, hope the diet will increase the levels of an
enzyme that might clear the inclusion bodies present in the disease. 'There
is already some preliminary evidence from the Alzheimer's disease field
that this may be the case.' Murphy, along with colleagues at the Mayo Clinic,
developed a test to measure the amount of amyloid beta in the mice after treatment
with the special diet and exercise program. 'It's a simple biochemical
test, similar in principle to an HIV test, except we use a small sample of muscle
tissue rather than blood. Since all the mice get the disease, we don't
do a before and after test-we just test them all at the end and compare
the treated mice to the untreated ones. Hopefully, the treated ones get better.'
Murphy was approached by Dr. Frank LaFerla from the University of California at Irvine about the IBM mice LaFerla was studying. 'I was very enthusiastic about the idea. It has always amazed me that for a disease as common as IBM, so few people are involved in studying it,' Murphy said. He believes that the worldwide focus on Alzheimer's disease research has produced a great many ideas that could be treatments for IBM, and these ideas should be examined.
-For instance,- he said, -several potential Alzheimer-s disease therapies are in clinical trial right now, and one or more of these might benefit those suffering from inclusion-body myositis.'
Both Studzinski and Murphy are veterans of Alzheimer's disease research. Murphy-s interest in inclusion-body myositis began when he was struck by the research of TMA Medical Advisor Valerie Askanas. I've been working in the AD field since the early 90s, about the time when Valerie Askanas was reporting key observations that suggested that IBM and AD might be related,- he said.
When studies showed that exercise had a significant benefit for mice with symptoms of Alzheimer-s, Murphy jumped at the chance to investigate its benefits in mice with IBM. He met Studzinski a few years ago when she gave a talk on her dietary studies with dogs, and they both realized that there were also a number of dietary angles that hadn-t been explored in AD.
Since the idea of moderate exercise as a therapy for IBM patients had been around for a while, Murphy thought it might be a good idea to try both approaches, diet and exercise, at the same time. -I-m looking forward to working with a different disease with some of the same features,- Studzinski said. -I-ve been working with Alzheimer-s disease for most of my professional career.- She received her PhD in pharmacology in May from the University of Toronto, and has worked with many animal studies.
One notable study with implications for Alzheimer-s disease was conducted in aging dogs. Studzinski added antioxidants to their food, in the form of fruits and vegetables. -The dogs just loved it,- she said. When this simple dietary change improved their cognition significantly, she was intrigued at the possibility of dietary intervention in chronic and degenerative diseases.
It-s interesting to try to measure the cognition levels of dogs, who have varying degrees of intelligence to begin with. -We used the same type of tests that are used to measure cognitive decline in monkeys,- she said. One such test is presenting animals with covered wells in their food trays. Over time, they-ll go right to the well that really has the food in it. -Dogs seem to love being tested,- she said. One test for cognition in mice is to see how quickly they recognize an escape platform hidden in a small pool, approximately an inch below the surface of the water.
Since the IBM testing measures muscle strength rather than cognition, the mice will be measured on the rotarod, a test Studzinski learned recently from Murphy. -As the name suggests, this is a slowly rotating rod,- said Murphy. -We use it to assess the strength and coordination of their leg muscles.- The same mice who get the ketogenic diet (a kind of readily available mouse chow, Studzinski says) will also be rewarded for exercise on the -rotarod,- an exercise wheel.
The two-year study should provide some clues to possible therapies for IBM that will do no harm and be readily available. -Even though my degree is from the Department of Pharmacology, I am really drawn to these dietary studies,- she said. -From this field, we-re more likely to find ideas that will help large numbers of people, regardless of their tolerance for medications and their ability to pay.-
Aug
Cell Death Differ. 2007 Aug 3; [Epub ahead of print]
Characterization of hereditary inclusion body myopathy myoblasts: possible primary
impairment of apoptotic events.
Amsili S, Shlomai Z, Levitzki R, Krause S, Lochmuller H, Ben-Bassat H, Mitrani-Rosenbaum
S.
Hereditary inclusion body myopathy (HIBM) is a unique muscular disorder caused
by mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase
(GNE) gene. GNE encodes a bi-functional enzyme acting in the biosynthetic pathway
of sialic acid. Since the underlying myopathological mechanism leading to the
disease phenotype is poorly understood, we have established human myoblasts cultures,
derived from HIBM satellite cells carrying the homozygous M712T mutation, and
identified cellular and molecular characteristics of these cells. HIBM and control
myoblasts showed similar heterogeneous patterns of proliferation and differentiation.
Upon apoptosis induction, phosphatidylserine externalization was similar in HIBM
and controls. In contrast, the active forms of caspase-3 and -9 were strongly
enhanced in most HIBM cultures compared to controls, while pAkt, downregulated
in controls, remained high in HIBM cells. These results could indicate impaired
apoptotic signaling in HIBM cells. Since satellite cells enable partial regeneration
of the post-mitotic muscle tissue, these altered processes could contribute to
the muscle mass loss seen in patients. The identification of survival defects
in HIBM affected muscle cells could disclose new functions for GNE in muscle cells.Cell
Death and Differentiation advance online publication, 3 August 2007; doi:10.1038/sj.cdd.4402208.
Aug
Hum Mol Genet. 2007 Aug 18; [Epub ahead of print]
A Gne knockout mouse expressing human GNE D176V mutation develops features similar
to distal myopathy with rimmed vacuoles or hereditary inclusion body myopathy.
Malicdan MC, Noguchi S, Nonaka I, Hayashi YK, Nishino I.
Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion myopathy
(hIBM) is an early adult-onset distal myopathy caused by mutations in the UDP-N-acetylglucosamine
2-epimerase/ N-acetylmannosamine kinase (GNE) gene which encodes for a bifunctional
enzyme involved in sialic acid biosynthesis. It is pathologically characterized
by the presence of rimmed vacuoles especially in atrophic fibers, which also
occasionally contain congophilic materials that are immunoreactive to beta-amyloid,
lysosomal proteins, ubiquitin, and tau proteins. To elucidate the pathomechanism
of this myopathy and to explore treatment options, we generated a mouse model
of DMRV/hIBM. We knocked out the Gne gene in mouse but this resulted to embryonic
lethality. We therefore generated a transgenic mouse that expressed the human
GNE D176V mutation, which is one of the most prevalent mutations among Japanese
DMRV patients, and crossed this with Gne((+/-)) mouse to obtain Gne((-/-))hGNED176V-Tg.
Interestingly, these mice exhibit marked hyposialylation in serum, muscle, and
other organs. Reduction in motor performance in these mice can only be seen
from 30 weeks of age. A compelling finding is the development of beta-amyloid
deposition in myofibers by 32 weeks, which clearly precedes rimmed vacuole formation
at 42 weeks. These results show that the Gne((-/-))hGNED176V-Tg mouse mimics
the clinical, histopathological, and biochemical features of DMRV/hIBM, making
it useful for understanding the pathomechanism of this myopathy and for employing
different strategies for therapy. Our findings underscore the notion that hyposialylation
plays an important role in the pathomechanism of DMRV/hIBM.
Sept
Eur J Neurol. 2007 Sep;14(9):e14-5.
Hereditary inclusion body myopathy with a novel mutation in the GNE gene associated
with proximal leg weakness and necrotizing myopathy.
Motozaki Y, Komai K, Hirohata M, Asaka T, Ono K, Yamada M.
PMID: 17718674 [PubMed - in process]
Aug
Muscle Nerve. 2007 Aug 30; [Epub ahead of print]
An Italian family with inclusion-body myopathy and frontotemporal dementia due
to mutation in the VCP gene.
Gidaro T, Modoni A, Sabatelli M, Tasca G, Broccolini A, Mirabella M.
Mutations of the valosin-containing protein gene (VCP) are responsible for autosomal-dominant
hereditary inclusion-body myopathy associated with frontotemporal dementia and
Paget's disease of bone. We identified the p.R155C missense mutation in the VCP
gene segregating in an Italian family with three affected siblings, two of whom
had a progressive myopathy associated with dementia, whereas one exhibited a progressive
myopathy and preclinical signs of Paget's disease of bone. Our study demonstrates
that VCP mutations are found in patients of Italian background and may lead to
a variable clinical phenotype even within the same kinship. Muscle Nerve, 2007.
Aug
Neurology. 2007 Aug 14;69(7):655-9.
GNE protein expression and subcellular distribution are unaltered in HIBM.
Krause S, Aleo A, Hinderlich S, Merlini L, Tournev I, Walter MC, Argov Z,
Mitrani-Rosenbaum S, Lochmanduuml;ller H.
Friedrich
Mutations in GNE encoding UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine
kinase (GNE) cause hereditary inclusion body myopathy (HIBM). To define the role
of GNE mutations in HIBM pathogenesis, GNE protein expression was analyzed. GNE
protein is expressed at equal levels in HIBM patients and normal control subjects.
Immunofluorescence detection of GNE did not reveal any mislocalization of GNE
in skeletal muscle. We conclude that impaired GNE function, not lack of expression,
may be the key pathogenic factor in HIBM. For diagnostic purposes, direct genetic
analysis of the GNE gene in patients with IBM will remain the mainstay and is
not aided by immunohistochemistry or immunoblotting using antibodies against the
GNE protein.
Aug
Acta Neuropathol (Berl). 2007 Aug 31; [Epub ahead of print]
NOGO is increased and binds to BACE1 in sporadic inclusion-body myositis and
in AbPP-overexpressing cultured human muscle fibers.
Wojcik S, Engel WK, Yan R, McFerrin J, Askanas V.
USC Neuromuscular Center, Department of Neurology, University of Southern California
Keck School of Medicine, Good Samaritan Hospital, 637 S. Lucas Ave, Los Angeles,
CA, 90017-1912, USA, askanas@usc.edu.
Increased amyloid-b precursor protein (AbPP)
and amyloid-beta (Abeta) accumulation appear to be upstream steps in the pathogenesis
of sporadic inclusion-body myositis (s-IBM). BACE1, participating in Ab
production is also increased in s-IBM muscle fibers. Nogo-B and Nogo-A belong
to a family of integral membrane reticulons, and Nogo-B binding to BACE1 blocks
BACE1 access to AbPP, decreasing Abeta production.
We studied Nogo-B and Nogo-A in s-IBM muscle and in our IBM muscle culture models,
based on AbetaPP-overexpression or ER-stress-induction in cultured human muscle
fibers (CHMFs). We report that: (1) in biopsied s-IBM fibers, Nogo-B is increased,
accumulates in aggregates, is immuno-co-localized with BACE1, and binds to BACE1;
Nogo-A is undetectable. (2) In CHMFs, (a) AbPP overexpression
increases Nogo-B, Nogo-A, and BACE1, (b) ER stress increases BACE1 but decreases
Nogo-B and Nogo-A, (c) Nogo-B and Nogo-A associate with BACE1. Accordingly, two
novel mechanisms, AbPP overexpression and ER stress,
are involved in Nogo-B and Nogo-A expression in human muscle. We propose that
in s-IBM muscle the Nogo-B increase may represent an attempt by muscle fiber to
decrease Ab production. However, the increase of Nogo-B
seems insufficient because Ab continues to accumulate
and the disease progresses. We propose that manipulations, which increase Nogo-B
in s-IBM muscle might offer a new therapeutic opportunity.
Jul-Aug
Autophagy. 2007 Jul-Aug;3(4):384-6. Epub 2007 Jul 9.
Comment on: Ann Neurol. 2007 May;61(5):476-83.
Macroautophagy as a pathomechanism in sporadic inclusion body myositis.
Landuuml;nemann JD, Schmidt J, Dalakas MC, Manduuml;nz C.
Laboratory of Viral Immunobiology, Christopher H. Browne Center for Immunology
and Immune Diseases, The Rockefeller University, New York, New York 10021, USA.
Skeletal muscle fibers show a high level of constitutive and starvation-induced macroautophagy. Sporadic Inclusion Body Myositis (sIBM) is the most common acquired skeletal muscle disease in patients above the age of 50 years and is characterized by inflammation and intracellular accumulation of aggregate-prone proteins such as amyloid precursor protein (APP)/beta-amyloid, hyperphosphorylated tau, and presenilin. In a recent study, we found that muscle fibers of sIBM patients show increased frequencies of Atg8/LC3(+) autophagosomes and that intracellular APP/beta-amyloid colocalized with Atg8/LC3 in degenerating fibers. Colocalization of APP/beta-amyloid with LC3(+) autophagosomes was further associated with upregulation of major histocompatibility complex (MHC) class I and class II molecules and T cell infiltration. These findings indicate that APP/beta-amyloid is a substrate for autophagy in skeletal muscle fibers and suggest that degradation of aggregate-prone proteins via macroautophagy can be linked with both immune-mediated and degenerative tissue damage. A better understanding of this pathway in skeletal muscle and in the inflammatory environment of sIBM might provide a rationale for novel therapeutic strategies targeting pathogenic protein aggregation.
From:QUEST MDA USA Sept/Oct 2007.
Research Points to New Directions In Inclusion-Body Myositis Treatment
Inclusion-body myositis (IBM) is a type of muscle disease that-s thought to be part inflammatory (related to immune system activity that causes inflammation) and part degenerative. It-s usually not genetic, but there are genetic forms. The name -inclusion body- comes from clusters of abnormal proteins inside bubble-like spaces in muscle fibers. It doesn-t respond to standard treatments that are effective in other types of myositis.
Caught in the Crossfire? Viruses, specifically a type known as retroviruses,
may underlie at least some cases of nongenetic (-sporadic-) IBM, according
to Marinos Dalakas at the National Institutes of Health and colleagues. This
research group, which published its findings in the May issue of Annals of Neurology,
proposes that a retrovirus may trigger an immune response in the body that-s
then misdirected at muscle tissue. They didn-t find viruses inside muscle
cells, but they did find them in nearby immune system cells. So far, they-ve
seen nine patients with IBM who also have human immunodeficiency virus or human
T-lymphocyte virus 1, and they say they don-t think the association is
just a coincidence. Dalakas- group has found in a separate study that the
drug alemtuzumab (Campath), an immune system suppressant that-s now used
to treat a form of chronic leukemia, may have promise for treating IBM.
Toxic Buildup In another set of findings published in the May issue of Annals
of Neurology, Christian Munz at Rockefeller University and colleagues, including
Dalakas, speculate that a normal cellular system called autophagy (self-digestion)
is overwhelmed in people with IBM, contributing to a buildup of abnormal and
potentially toxic proteins. This process normally breaks down and recycles old
or defective protein molecules, such as beta-amyloid, an abnormally folded molecule
found in excess in IBM-affected muscle cells. Supporting autophagy might be
a treatment avenue, these researchers suggest.
Valerie Askanas at the University of Southern California in Los Angeles has
been studying the role of beta-amyloid in IBM, with MDA support, since the early
1990s. Her recent research, published in Neuropathology and Applied Neurobiology
in April, suggests that theprecursor of a protein called myostatin accumulates
in IBM muscle fibers in association with the precursor of betaamyloid.
Modified Cells to the Rescue Jacques Tremblay, at the University of Laval in Quebec City, says he hopes to launch a clinical trial in which genetically modified muscle stem cells will be used to treat people with a genetic form of IBM. Tremblay, who plans to use inactivated lentiviruses to deliver GNE genes to stem cells taken from patients with hereditary IBM, has applied to the regulatory agency Health Canada for permission to conduct the study. -One of the beauties of this approach is that genetic modification of the cells would be done ex vivo [outside the body],- he says, -so we can verify that they are genetically corrected and not tumor-forming, and so that the patient will not be exposed to the viral vector [transporter].-
JULY
Clin Neurophysiol. 2007 Jul;118(7):1563-8. Epub 2007 May 15.
Single-fiber electromyography in sporadic inclusion body myopathy.
Hatanaka Y, Oh SJ.
Department of Neurology, The University of Alabama at Birmingham, The Veterans
Affair Medical Center, UAB Station, Birmingham, AL 35294, USA.
OBJECTIVE: To report the SFEMG findings in sporadic inclusion body myopathy (S-IBM).
METHODS: We have analyzed the SFEMG data in 25 patients (mean age: 63; 16 males)
with S-IBM which was diagnosed by the presence of classical rimmed vacuoles in
the muscle biopsy together with clinical, laboratory, and electrophysiological
findings. RESULTS: All patients had fibrillations, positive sharp waves, and small-amplitude
short-duration motor unit potentials (MUPs) in the needle EMG. High-amplitude
MUPs were observed in eight (32%) patients, two of whom had long-duration MUPs.
SFEMG was abnormal in 17 (68%) cases: mean andquot;mean consecutive difference (MCD)andquot;
was increased beyond the age-adjusted normal limit in 16 cases, and more than
10% of potential pairs (PP) had MCD longer than the upper normal limit of an individual
MCD in one case. Mean fiber density (FD) was 2.16, with maximum FD being 4.15.
Increased FD was noted in 11 (44%) cases. In four cases, more than 10% of PP had
blocking, but there was no neurogenic blocking in any PP. As expected, MCD increased
linearly (r=0.85) with the percentage of PP beyond the normal upper limit. CONCLUSIONS:
The SFEMG findings in S-IBM are typical of the classical pattern of myopathy.
SIGNIFICANCE: Our findings support the consensus that S-IBM is a myopathy.
JULY
J Neuroimmunol. 2007 Jul;187(1-2):166-74. Epub 2007 Jun 18.
Upregulation of thrombospondin-1(TSP-1) and its binding partners, CD36 and CD47,
in sporadic inclusion body myositis.
Salajegheh M, Raju R, Schmidt J, Dalakas MC.
The Division of Neuromuscular Disease, Department of Neurology, Brigham and
Women's Hospital, 75 Francis Street, Tower 5D, Boston, MA 02115, United States.
The TSP1/CD36/CD47-complex is involved in T cell expansion and inflammatory responses
to beta-amyloid, both relevant to IBM. We report on the mRNA and protein expression
of TSP1/ CD36 /CD47-complex in IBM muscles and in human myoblasts after cytokine
stimulation. The TSP1/CD36 /CD47 was upregulated in IBM. TSP1 immunolocalized
to the connective tissue contiguous to inflammation and CD36/CD47 on the myofibers
and CD8+ cells. Further, TNF-alpha upregulated the production of TSP1 and CD47
by myoblasts. The TSP-complex is another inflammatory mediator associated with
chronic inflammation in IBM that may perpetuate the immune responses to local
antigens in response to TNF-alpha.
JULY
Muscle Nerve. 2007 Jul 11; [Epub ahead of print]
Nuclear localization of valosin-containing protein in normal muscle and muscle
affected by inclusion-body myositis.
Greenberg SA, Watts GD, Kimonis VE, Amato AA, Pinkus JL.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's
Hospital, and Harvard Medical School, 75 Francis Street, Boston, Massachusetts
02115, USA.
Inclusion-body myopathy with Paget's disease and frontotemporal dementia (IBMPFD) is a disease of muscle, bone, and brain that results from mutations in the gene encoding valosin-containing protein (VCP). The mechanism of disease resulting from VCP mutations is unknown. Previous studies of VCP localization in normal human muscle samples have found a capillary and perinuclear distribution, but not a nuclear localization. Here we demonstrate that VCP is present in both myonuclei and endothelial cell nuclei in normal human muscle tissue. The immunodetection of VCP varies with acetone or paraformaldehyde fixation. Within the nucleus, VCP associates with the nucleolar protein fibrillarin and Werner syndrome protein (Wrnp) in normal and IBMPFD muscle. In patients with inclusion-body myositis (IBM), normal nuclear localization is present and some rimmed vacuoles are lined with VCP. These findings suggest that impairment in the nuclear function of VCP might contribute to the muscle pathology occurring in IBMPFD. Muscle Nerve, 2007.
JULY
Arch Pathol Lab Med. 2007 Jul;131(7):1070-6.
Major histocompatibility complex class I and II detection as a diagnostic tool
in idiopathic inflammatory myopathies.
Jain A, Sharma MC, Sarkar C, Bhatia R, Singh S, Handa R.
Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
CONTEXT: Muscle biopsy is at present the gold standard for the diagnosis of idiopathic
inflammatory myopathies (IIMs), which include dermatomyositis, polymyositis, and
inclusion body myositis. Currently, there is no definite diagnostic marker that
helps in the discrimination of different subgroups of IIMs and the discrimination
of IIMs from other clinical and morphologic mimics. Major histocompatibility complex
(MHC) class I and II antigens are not expressed on normal muscle fibers. OBJECTIVE:
To determine the diagnostic utility of MHC class I and II antigen expression on
the muscle biopsies from patients with various neuromuscular disorders and to
validate its addition in the existing diagnostic armamentarium. DESIGN: Expression
of MHC class I and II antigen was studied on 126 muscle biopsies, of which 62
were IIMs and 64 were controls (taken from patients with other neuromuscular disorders).
RESULTS: When compared with controls, the sensitivity of MHC class I expression
for diagnosis of IIMs was 88.7% (100%, 81.6%, and 100% for dermatomyositis,
polymyositis, and inclusion body myositis, respectively), with a specificity of
89.1%. The specificity of MHC class II expression was 100% for all IIMs. CONCLUSION:
Detection of MHC class I and II antigen expression is extremely helpful in the
diagnosis of IIMs and has high sensitivity and specificity, especially in dermatomyositis
[and inclusion body myositis]. This expression can be used as a diagnostic tool
in discriminating IIMs from other muscle diseases in which it is either absent
or weakly expressed.
July
Lancet Neurol. 2007 Jul;6(7):620-31.
Inclusion body myositis: current pathogenetic concepts and diagnostic and therapeutic
approaches.
Needham M, Mastaglia FL.
Centre for Neuromuscular and Neurological Disorders, University of Western Australia,
Queen Elizabeth II Medical Centre, Perth, Australia.
Inclusion body myositis is the most common acquired muscle disease in older individuals, and its prevalence varies among countries and ethnic groups. The aetiology and pathogenesis of sporadic inclusion body myositis are still poorly understood; however genetic factors, ageing, and environmental triggers might all have a role. Unlike other inflammatory myopathies, sporadic inclusion body myositis causes slowly progressing muscular weakness and atrophy, it has a distinctive pattern of muscle involvement, and is unresponsive to conventional forms of immunotherapy. This review covers the clinical presentation, diagnosis, treatment, and the latest information on genetic susceptibility and pathogenesis of sporadic inclusion body myositis.
also see The abstract of this poster subsequently published
May
American Academy of Neurology 59th Annual Meeting, Boston, April 28 - May 5, 2007.
3:45 p.m. S 57.001 Alemtuzumab (CAMPATH 1-H) Therapy in Sporadic Inclusion
Body Myositis (sIBM): A Treatment Trial in Patients with Established Natural
History Data
Marinos Dalakas, Goran Rakocevic, Beverly McElroy, Mohammad Salajegheh, Michael
H. Love, Joseph Shrader, Ellen Levy, Allan D. Kirk
OBJECTIVE: Describe the effect of Alemtuzumab in a cohort of sIBM patients selected
based on natural history data. BACKGROUND: sIBM is characterized by inflammation
and vacuolar degeneration. Even though the endomysial T cells are clonally expanded
and antigen-driven, sIBM is resistant to immunotherapies. Alemtuzumab is a humanized
monoclonal antibody against CD52 that causes an immediate depletion or severe
reduction of peripheral blood lymphocytes (PBL), lasting at least 6 months.
Alemtuzumab is effective in transplantation and appears promising in autoimmune
disorders. DESIGN/METHODS: This is a proof-of-principle study designed to examine
if Alemtuzumab depletes not only PBL but also endomysial T cells and alters
the natural course of sIBM. 13 sIBM patients with 12-month natural history data,
were treated with 0.3 mg kg/day Alemtuzumab for 4 days. The primary end-points
were disease stabilization compared to natural history, or an increase strength,
6 months after treatment initiation. Lymphocytes, cytokines and other autoimmune
markers were serially monitored in the blood and the repeated muscle biopsies.
RESULTS: During a 12-month observation period, the patients total strength had
declined by a mean of 14.3% on QMT measurements. Four months after therapy,
the mean strength of all patients had improved by 8%, and at 6 months by 4%
from baseline. Six of 13 patients had improved by 15.7% ( 4-35%) and reported
increased ADL; the other 7 declined by 6% (-1.5-15%). The MRC data provided
similar information. Depletion of PBL was noted 2 weeks after treatment and
persisted up to 6 months. Repeated muscle biopsies showed lymphocyte depletion,
most prominent in the improved patients. Immunopathologic correlations between
responders and non- responders will be reported. CONCLUSIONS/RELEVANCE: Preliminary
analysis of this proof-of-principle study, concludes that in sIBM an aggressive
lymphocyte depletion, as induced by Alemtuzumab, can improve strength or halt
disease progression up to 6 months after therapy. Supported by: NINDS.
4:00 p.m. S 57.002 Inclusion Body Myositis Functional Rating Scale
Richard J. Barohn, Carlayne Jackson, Shree Pandya, Gary S. Gronseth, Laura
Herbelin, The Muscle Study Group (MSG)
OBJECTIVE: Develop an inclusion body myositis functional rating scale (IBM-FRS).
BACKGROUND: A specific functional rating scale for inclusion body myositis (IBM)
may be useful as an endpoint measurement in clinical trials with IBM patients.
DESIGN/METHODS: We designed a 10 point question survey for IBM patients regarding
their ability to perform activities of daily living administered by a clinical
evaluator. The areas addressed in the questionnaire include swallowing, handwriting,
cutting food and using utensils, fine motor tasks, dressing, hygiene, turning
in bed and adjusting covers, sit to stand, walking, and climbing stairs. Answers
to each item are graded on a 0 to 4 scale (4=normal; 0=unable to perform), maximal
score = 40. The IBM-FRS was utilized in a Muscle Study Group(MSG) sponsored
multicenter clinical trial of clinical safety and tolerability trial of beta-Interferon(Avonex)
in IBM (MSG,2004). 28 IBM patients were enrolled. All received the IBM-FRS at
baseline and monthly for 6 months. Pearsons correlation coefficient determined
how well the IBM-FRS correlated with maximal voluntary isometric contraction
test(MVICT), manual muscle testing(MMT), Amyotrophic Lateral Sclerosis Functional
Rating Scale(ALS-FRS), hand grip dynamometry, Purdue peg board, and DEXA muscle
mass at study entry. RESULTS: 28 patients in the clinical trial underwent IBM-FRS
testing and other endpoint measurements described above. The mean IBM-FRS was
26.8+/-7.1S.D. Pearsons correlation coefficient (and p value) with IBM-FRS and
the other endpoint parameters was as follows: MVICT=0.60(andlt;0.001); MMT=0.73(andlt;0.001);
ALS-FRS=0.86(andlt;0.001); SF36(physical)=0.54(0.002); hand grip dynamometry=0.56(0.001);
Purdue peg board=0.55(0.004); DEXA mass=0.29(0.134). CONCLUSIONS/RELEVANCE:
IBM-FRS correlated well with multiple other endpoint parameters utilized in
a clinical trial. The IBM-FRS is an easily administered survey of symptoms associated
with activities of daily living in IMB patients. The advantages of the IBM-FRS
are that the categories are relevant to IBM, is quickly administered, and does
not require any specialized equipment. The IBM-FRS is a useful endpoint measurement
for therapeutic trials in IBM patients.
4:15 p.m. S 57.003 Using Humoral Immunity for the Identification of Candidate
Antigens in Inclusion Body Myositis
Mohammad Salajegheh, Yin Yin Lin, Kenneth C. Parker, David Sarracino, Annie
P. Moseman, Anthony A. Amato, Steven A. Greenberg
OBJECTIVE: To use immunoglobulins present in the blood and muscle of patients
with inclusion body myositis (IBM) to identify the antigen(s) involved in the
inflammatory process. BACKGROUND: IBM is a common myopathy of the elderly with
no effective therapy. Both degenerative and autoimmune mechanisms are involved
in its pathogenesis, while their relationship remains unclear. Previous studies
have suggested that the cell-mediated and humoral immune responses present in
IBM are antigen-driven, although no antigens have yet been identified. B-cell
based strategies of antigen identification are more likely to succeed than those
using T-cells, since antibodies are easily isolated from tissues and react directly
with targets antigens. Based on the principle of linked-recognition, the same
antigens are likely recognized by both T-cells, B-cells and antibodies produced
by plasma cells. DESIGN/METHODS: We used immunoaffinity techniques to isolate
immunoglobulins from IBM plasma and muscle; immunoblots to assess immunoglobulin
reactivity to muscle proteins; and proteomic techniques and mass-spectrometry
to identify candidate antigens. We are performing targeted experiments including
immunoprecipitation of putative antigens, to further delineate the proteins
of interest, and confirmatory studies with purified proteins to verify their
role as autoantigens. RESULTS: We have isolated higher amounts of immunoglobulin
from IBM muscle compared with controls. Plasma from two IBM patients with serum
monoclonal immunoglobulins demonstrated immunoreactivity of 3 bands in the 14-25KD
and one band in the 100-190KD range against normal muscle, compared with controls.
Mass-spectrometry analysis of these bands identified multiple putative antigens
including alpha-B-crystallin, previously implicated in the degenerative aspects
of IBM, and peroxiredoxin-2, against which elevated levels of antibody have
been reported in autoimmune diseases. CONCLUSIONS/RELEVANCE: Patients with IBM
generate antibodies reactive against muscle antigens. Identification of such
antigen(s) will help us better understand the pathophysiology of the disease,
the relationship between degeneration and inflammation, and determine targets
for drug development. Supported by: MDA, The Sporadic-IBM Research Foundation.
[P05.113] Utility of Needle Muscle Biopsy to Diagnosis Inclusion Body Myositis
Kirsten L. Gruis, James Teener, Mila Blaivas, Ann Arbor, MI
OBJECTIVE: To evaluate the use of percutaneous needle muscle biopsy (NMB) in
the diagnosis of inclusion body myositis (IBM). BACKGROUND: Inclusion body myositis
(IBM) is a common cause of muscle weakness in adults and can mimic motor neuron
disease and other types of myositis. A rapid and reliable muscle biopsy technique
is needed to diagnosis IBM. Many experts contend that only the open muscle biopsy
technique should be performed. However, percutaneous NMB technique has the advantage
of a less invasive and less time consuming procedure given the lack of requirement
for sutures and muscle clamps. DESIGN/METHODS: Muscle biopsy data collected
during routine clinical evaluation of patients with limb weakness and spontaneous
activity in greater than one limb by electromyography (EMG), but without sensory
impairment or upper motor neuron dysfunction, were retrospectively analyzed.
NMB with applied suction through the University College Hospital (UCH, 5 millimeter
diameter) biopsy instrument was performed of the vastus lateralis or proximal
arm muscle. Muscle cores were gently rotated with forceps into one collective
sphere (40-50 mg). Muscle fiber orientation using a dissection microscope was
not performed prior to pathology processing. RESULTS: Thirty patients were identified.
Median age was 67 years; 50% were men. Median symptom duration was 2 years.
NMB provided a diagnosis in 26 (87%) patients who presented with motor weakness.
In combination with clinical and electrodiagnostic findings, NMB resulted in
the diagnosis of IBM in 9 patients, motor neuron disease in 7 patients, inflammatory
myopathy in 5 (all responded to immune modifying treatment), and a non-inflammatory
myopathy in 2 patients (Pompe disease and myotonic muscular dystrophy). It excluded
a myopathic process in 3 patients found to have alternative neurogenic pathology.
CONCLUSIONS/RELEVANCE: The histopathological data from percutaneous needle muscle
biopsy can be used to differentiate the diagnosis of IBM from alternative neuromuscular
diagnoses.
P07.037] Nodular Infiltrates Serving as Sites of B-Cell Maturation in the Muscle
of Patients with Inclusion Body Myositis
Mohammad Salajegheh, Jack L. Pinkus, Remedios Nazareno, Anthony A. Amato,
Steven A. Greenberg, Boston, MA
OBJECTIVE: To determine whether the nodular infiltrates present in inclusion
body myositis (IBM) muscle are involved in local maturation of B-cells. BACKGROUND:
IBM is a myopathy in which a prominent immune process is accompanied by degenerative
changes in muscle fibers. We have recently identified the presence of a highly
active plasma cell antibody response in IBM muscle, at both transcriptional
and protein levels, and determined that this response is antigen-driven. Recent
studies have suggested that the activation and maturation of B-cells could occur
in tertiary lymphoid structures, present as nodular infiltrates in the inflamed
tissue of several autoimmune diseases. These structures, which show similarities
to nodular infiltrates seen in IBM, demonstrate the requisite elements of secondary
lymphoid structures. DESIGN/METHODS: We have used immunohistochemistry to study
the constituents of nodular infiltrates in IBM muscle, and laser capture microdissection
combined with PCR and gene sequencing to determine the precise sequence of rearranged
immunoglobulin genes, in multiple adjacent muscle sections and individual B
and plasma cells from IBM muscle. RESULTS: The nodular infiltrates studied in
IBM muscle contained the requisite elements for lymphoid structures, including
CD3+ T-cells, activated myeloid dendritic cells, B and plasma cells, and follicular
dendritic cells. We have also identified immunoglobulin heavy chain sequences,
in different adjacent sections of IBM muscle, that suggest the presence of related
clones of B and plasma cells which are derived from common precursors. CONCLUSIONS/RELEVANCE:
Our data indicate that the nodular infiltrates present in IBM muscle could act
as tertiary lymphoid structures, and allow local maturation of B-cells stimulated
by antigens present in the muscle. These findings help further elucidate the
pathophysiology of IBM and provide the rationale for studies targeted at better
understanding the humoral immune response in IBM, with the goal of designing
disease specific therapies. Supported by: MDA, The Sporadic-IBM Research Foundation.
June
[related article]
Science 8 June 2007:
Vol. 316. no. 5830, pp. 1416 - 1417
DOI: 10.1126/science.316.5830.1416
[myofibers in s-IBM accumulate amyloid-b (Ab),
phosphorylated tau (p-tau), apolipoprotein E, presenilin-1, the normal cellular
isoform of prion protein (PrPc), and many other characteristic proteins]
News Focus
ALZHEIMER'S DISEASE:
A New Take on Tau
Jean Marx
The search for drugs to combat neuron-destroying diseases is prompting researchers
to take a fresh look at a familiar suspect
When tau goes bad. In a normal neuron (top), tau stabilizes the microtubules
(blue lines) that transport materials to the nerve terminals. But in Alzheimer's
disease, tau loses its ability to bind to the microtubules and forms abnormal
aggregates. The microtubules degenerate, impairing neuronal function.
CREDIT: C. BICKEL/SCIENCE
When it comes to combating Alzheimer's disease, neurobiologists need all the
help they can get. So far, efforts to develop drugs that halt or reverse the
relentless brain degeneration caused by the disorder have met with only modest
success. The few approved therapies slow cognitive decline, but only temporarily,
possibly because they don't target the root cause of the disease.
Drugs that may do that are in the pipeline, however. They're aimed at reducing production of amyloid beta (Ab), a protein fragment thought to be the instigator of the nerve cell death driving Alzheimer's disease (Science, 3 November 2006, p. 781). And now researchers are taking a closer look at another possible target, a protein called tau that is involved in the pathology of a number of neurodegenerative diseases, including Alzheimer's.
Tau has taken a back seat to Ab for the past several years, but recent work with animal models and with cells in lab culture suggests that focusing on tau could pay off. Treatments that reduce the formation within the brain of certain mutant taus, or even of the normal protein itself, can alleviate memory loss and other neurological deficits in mice that have been genetically engineered to develop brain pathology similar to that in human Alzheimer's brains.
Although a lot more work will be needed before any of these early experiments pay off in the clinic, tau researchers are more optimistic than before. The findings andquot;open up a new potential [Alzheimer's] treatment; reducing tau might complement the antiamyloid strategy,andquot; says Lennart Mucke of the University of California, San Francisco, School of Medicine, whose lab is among those doing the work.
And big pharma is taking note as well. For example, Merck andamp; Co. Inc. has just hired Michael Hutton, a tau researcher at the Mayo Clinic in Jacksonville, Florida, to head up a new effort to develop tau-based drugs for Alzheimer's disease. andquot;I'm putting my money where my mouth is,andquot; Hutton says. andquot;I do think tau is a great therapeutic target.andquot;
Tau resurgent
For more than 20 years, neurobiologists have known that both Ab and tau are prominent
in the abnormal structures that stud the brains of Alzheimer's patients: A b is
located in the so-called plaques that form outside dead and dying nerve cells,
whereas tau appears inside neurons in a mesh of proteins called neurofibrillary
tangles (NFTs). For a time, a controversy raged about which protein causes the
brain neurons to degenerate. The tide began to swing in Ab's favor after the
discovery about 16 years ago that mutations in the APP gene, which makes the
larger protein from which Ab is clipped, cause some hereditary Alzheimer's cases.
Indeed, no mutations in the tau gene have ever been linked to the disease, and today even many tau experts concede that Ab-linked abnormalities initiate brain neuron loss. andquot;There's no doubt that Ab [toxicity] is a fairly early event in Alzheimer's disease pathology and that tau is likely downstream,andquot; says Christopher Eckman, also at the Mayo Clinic in Jacksonville.
But tau researchers got a boost about 10 years ago, when several teams found that mutations in the gene for the tau protein cause some cases of a less common but devastating dementia known as FTLD (for frontotemporal lobar degeneration). This discovery showed that abnormal forms of the protein can cause nerve degeneration and as a result, memory loss and other neurological deficits. The work also buttressed the case that counteracting tau's effects might help Alzheimer's patients. andquot;Focusing on tau [for Alzheimer's therapy] makes perfectly good sense,andquot; says Zaven Khachaturian, senior science adviser to the Alzheimer's Association in Chicago, Illinois.
In the past few years, researchers have begun to test the idea of targeting tau, using various mouse models of Alzheimer's disease. The most recent example, described in the 4 May issue of Science (p. 750), comes from Mucke's group. These researchers used a genetically altered mouse strain that carried a mutant human APP gene and varying numbers of the mouse tau gene--either zero, one, or the normal complement of two copies. Because these mice carry the mutant APP gene, all their brains developed structures resembling the amyloid plaques of Alzheimer's brains. But as is commonly seen in such modified mice, none had tangles or neuron loss.
Mucke and his colleagues found that, as the animals aged, those with two tau gene copies became impaired in their ability to learn the Morris water maze, which requires that the animals find an underwater platform. Animals with one copy were less impaired, whereas those with no tau gene learned as readily as normal controls did--results indicating that the absence of tau somehow prevents the behavioral deficits that would otherwise occur in animals with mutant APP.
Yet the tau reduction had no effect on Ab deposition. The animals lacking tau andquot;had brains full of amyloid plaques but could solve the water maze in a snap,andquot; Mucke says. Further work indicated that tau might contribute to neuronal malfunction by making brain neurons hyperexcitable, which can ultimately lead to their death.
Other researchers have also found that reducing tau can alleviate memory loss in mouse models. For their experiments, a team led by Karen Hsiao Ashe of the University of Minnesota Medical School in Minneapolis and the Mayo's Hutton created a strain of mice bearing a mutant human tau gene combined with regulatory sequences that allowed it to be turned off by the antibiotic doxycycline. As the researchers reported about 2 years ago, as these mice age, they accumulate NFTs in brain neurons where the tau gene is active.
Inflammatory link. A mouse brain (bottom) bearing a mutant human tau gene shows
extensive microglial cell activation at 9 months (yellow to red colors). The
brain at top is from a 9-month-old control.
CREDIT: Y. YOSHIYAMA ET AL., NEURON 53, 1 (2007)
What's more, the animals' brains shrink as a result of nerve cell death, and
the mice show a marked deterioration in their ability to learn the water maze.
But suppressing expression of the mutant tau gene with doxycycline improved
the animals' memories and halted the neuronal losses without affecting NFT accumulation
(Science, 15 July 2005, p. 476).
Last year, Frank LaFerla and his team at the University of California, Irvine, reported on a mouse model that they engineered to develop both plaques and tangles. Treatment with two antibodies, one directed at Ab and the other at tau, preserved the animals' ability to learn. Both antibodies were needed. andquot;If we reduce Ab without reducing tau, we don't improve [the animals'] learning and memory behavior,andquot; LaFerla says.
But which tau?
In addition to showing that tau can play a role in cognitive decline, these
studies also shed light on what Hutton calls a andquot;massive uncertaintyandquot;:
What form of tau damages neurons? Identifying the culprit could be important
for guiding efforts to develop therapies; those trying to stop Ab buildup, for
example, continue to wrestle with whether to target soluble or insoluble forms.
For most of the 100 years since Alois Alzheimer described the plaques and tangles in his patients' brains, researchers focused on the tangles with their insoluble tau as the species at fault. But Ashe and her colleagues found that when they turned off tau formation in their animals, NFTs continued to accumulate despite the other improvements. Similarly, the LaFerla team's antibodies were directed at soluble tau as well as soluble Ab and did not reduce plaques or tangles. Some form of tau andquot;before the tangles [develop] is causing the memory problems,andquot; Ashe concludes.
Further evidence that a nontangle form of tau causes neuronal damage comes from Virginia Lee, John Trojanowski, and their colleagues at the University of Pennsylvania School of Medicine in Philadelphia. When these researchers tracked the changes in brain neurons in mice bearing a mutant tau gene, they found that the synapses, which are the connections between neurons, deteriorated at 3 months of age--long before NFTs appeared.
By this same early age, microglial cells, the brain's immune cells, became activated, presumably due to the presence of the mutant tau, the researchers reported in the February issue of Neuron. This suggests that the microglia might be contributing to the neuronal damage by causing inflammation--an idea that got a boost when Lee, Trojanowski, and their colleagues treated the animals with an immunosuppressant. andquot;We delayed everything,andquot; Lee says. andquot;The tangles decreased, the neuronal loss decreased, and the animals lived longer.andquot; These results tie in with other evidence suggesting that inflammation plays a role in Alzheimer's etiology and that anti-inflammatory drugs might help.
Still, tau abnormalities could contribute in other ways to neuronal degeneration and these, too, suggest therapeutic strategies. Normal tau binds to, and stabilizes, the microtubules, which run through the neuronal axon and help transport nutrients, proteins, and other materials back and forth between the cell body and the synapse. For reasons not yet understood, tau becomes excessively phosphorylated in Alzheimer's brains and as a result no longer binds properly to the microtubules. The microtubules in turn deteriorate, ultimately leading to nerve cell death.
Some drugs, including the taxols used to treat breast cancer, stabilize microtubules. About 2 years ago, Lee, Trojanowski, and their colleagues showed that one of these drugs, paclitaxel, improved axonal function and ameliorated the neurological problems of mice carrying a human tau gene. Lee notes, however, that the taxols and other microtubule-stabilizing drugs kill dividing cells and are thus too toxic, especially for long-term use. Her group is currently working to develop less toxic taxol derivatives.
Other researchers are taking a different tack, aiming to inhibit the kinases that add phosphates to tau. Some of these have shown promise in animal models. For example, Hutton's team, working with that of Hanno Roder at Sirenade Pharmaceuticals in Martinsried, Germany, found that an inhibitor of a kinase called ERK2 reduced the excessive tau phosphorylation occurring in mice carrying a human tau gene and also reduced the animals' difficulties in moving.
Similarly, LaFerla and his colleagues have evidence from their mouse model that interventions thought to be protective against Alzheimer's disease, including learning interventions and dietary intake of omega-3 fatty acids, might work partly by decreasing levels of enzymes that phosphorylate tau. But at least in their model, Ab reductions also appear to be necessary for neurological protection.
All of this work in mice raises the obvious question of whether the results are relevant to Alzheimer's disease and other so-called tauopathies such as FTLD. But there is at least one hint that inhibiting tau phosphorylation could help people afflicted by the conditions. The drug memantine is one of the few approved for treating Alzheimer's disease. And although it wasn't designed to inhibit phosphorylation, Khalid Iqbal and his colleagues at the New York State Institute for Basic Research in Developmental Disabilities on New York's Staten Island have evidence from cell studies that the drug decreases tau phosphorylation and inhibits neurofibrillary degeneration. andquot;I don't understand,andquot; Iqbal says, andquot;how anyone can think about Alzheimer's and not think about tau.andquot;
March/April
Clin Exp Rheumatol. 2007 Mar-Apr;25(2):246-51.
Treatment of inclusion body myositis with cyclosporin-A or tacrolimus: successful
long-term management in patients with earlier active disease and concomitant autoimmune
features.
Quartuccio L, De Marchi G, Scott CA, Ferraccioli G, Beltrami CA, De Vita S.
OBJECTIVE:Sporadic inclusion body myositis (s-IBM) is a chronic, progressive,
inflammatory myopathy of unknown aetiology, generally resistant to immunosuppressive
therapy. Given that lymphocyte infiltrates in s-IBM muscle tissue are CD8+ T cells,
targeting these cells may represent a valid approach.PATIENTS AND METHODS:Three
patients with biopsy-proven s-IBM, high creatine kinase levels at diagnosis, two
of whom with associated immune disorders, were treated with either cyclosporin-A
(CyA) or tacrolimus, in combination with high doses of corticosteroids (CS), followed
by rapid CS tapering. Clinical assessment and laboratory evaluation were performed
every three months for the first year and then every six months for the second
year.RESULTS:Based on muscle strength assessment and muscle enzyme serum levels,
a major clinical response was observed at month +3 in two out of the three patients.
A complete clinical response and major clinical response were obtained at month
+6, in two and one patient, respectively. Normalization of serum muscle enzymes
was observed in all. Steroids could be tapered to very low doses in all patients
and were suspended early in one. Laboratory, but not clinical relapse occurred
in one patient and was controlled by increasing the CyA dose. Treatment was well
tolerated, with no serious adverse events occurring. All three patients are maintaining
immunosuppressive therapy.CONCLUSION:Calcineurin inhibitors may represent a useful
option for the long-term management of s-IBM, possibly in a subset characterized
by a short duration with high disease activity or associated autoimmune manifestations.
From: The Outlook, Spring 2007, The Myositis Association.
TMA's Board of Directors approved funding for five new research projects in January,
2007.
= Dr. Valerie Askansas, MD, PhD, Professor of Neurology and Pathology at the University
of Southern California Keck School of Medicine, has published dozens of research
articles on IBM and continues to look for more clues to the disease process. Unlike
polymyositis and dermatomyositis, IBM does not respond to medications that treat
the inflammatory process. Her recent studies have focused instead on the degenerative
mechanisms in IBM muscle fibers. Askanas has demonstrated the similarities between
the Alzheimer's Disease brain and IBM muscle. She now proposes to study a type
of drug that improves cognition in Alzheimer's patients and reduces amyloid-beta
pathology in experimental models to see whether it will also work to reduce the
effects of amyloid-beta in her lab's IBM-experimental human muscle culture model.
= Christa M. Studzinski, a PhD candidate at the University of Kentucky, was awarded
a research fellowship to examine how changes in diet and exercise will affect
transgenic mice. Both diet and exercise, Studzinski notes, have been found to
improve function in animal models of Alzheimer's Disease. Studzinski's mice will
be put on a special low-carbohydrate, high-fat (ketogenic) diet and given a measured
exercise program. The ability of diet and exercise to prevent, halt, or reverse
the disease process of IBM will be tested using a variety of behavioral and laboratory
markers.
= Ingrid Lundberg, MD, PhD, Karolinska University Hospital, Karolinska Institute,
Stockholm, Sweden, was awarded a one-year grant for a project to better classify
the present condition of myositis patients worldwide to determine the most effective
treatments.
= Terry Oh, MD, an assistant professor of physical medicine and rehabilitation
at Mayo Clinic, Rochester, MN, will study whether andquot;Stance Control Orthosisandquot;
is effective for people with IBM and knee instability. This brace may provide
the necessary stability while overcoming the restricted lower leg movement and
tiring effects of traditional braces.
= Drs. Brian Kaspar, PhD, and Jerry Mendell, MD, both of the Columbus Children's
Research Institute, have successfully enlarged and strengthened the quadriceps
muscle in mice by using a common virus to carry a follistatin gene into the quadriceps
muscle. Because follistatin blocks myostatin, which is associated with loss of
muscle mass, Drs. Kaspar and Mendell will test whether such gene therapy might
be used to help humans who have IBM and lose muscle mass and strength.
May [related story]
Source: Weill Cornell Medical College
Date: May 28, 2007
Immune Antibodies Penetrate Neurons To Clear Alzheimer's-linked Amyloid
Science Daily - Researchers at Weill Cornell Medical College have gotten
much closer to understanding how immune-based therapies can treat Alzheimer's
disease - by studying how antibodies go inside brain cells to reduce levels
of Alzheimer's-linked amyloid peptides that form plaques between neurons.
This internalization and activity of the antibody within the cell was a big surprise and something we really haven't appreciated in neurological medicine. It gives us new hope for the use of immunotherapy against Alzheimer's, while casting intriguing new light on other disease processes,andquot; says senior author Dr. Gunnar Gouras, associate professor of neurology and neuroscience at Weill Cornell Medical College and associate attending neurologist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.
There are currently no effective treatments to fight Alzheimer's disease, which now affects over 5 million Americans, according to the Alzheimer's Association. Scientists now project that unless new ways are found to prevent or treat the disease, the total could climb to 16 million by 2050.
For years, the idea of an immune-based vaccine therapy against Alzheimer's has been a Holy Grail of research. In fact, in the past, researchers did have some clinical success with an antibody-directed immune therapy. Those hopes were dampened somewhat after a few subjects came down with a serious, treatment-linked (but nonfatal) meningitis.
andquot;Still, the dream has remained very much alive - especially since we know that antibodies to the beta-amyloid plaques associated with Alzheimer's can cross the blood-brain barrier, gaining access to the brain,andquot; Dr. Gouras explains. He remains one of the leading authorities on beta-amyloid plaques because of earlier work on its deposition and accumulation between neurons.
andquot;One of the things those earlier immunotherapy studies taught us was that antibodies can reduce amyloid plaques, which are a hallmark of the disease,andquot; he said. andquot;The next logical question was - how does it do that?andquot;
Over the past six years, Dr. Gouras' team took advantage of breakthroughs in neuroscience research to help answer that question. They relied on the development of special transgenic mice bred to closely approximate the progress of human Alzheimer's disease.
In their latest study, the researchers exposed amyloid-filled neurons from these mice to immune antibodies similar to those used in clinical trials. They then examined changes in these cells in the lab, using microscopy, immunofluorescence and other high-tech methods.
andquot;What we found astounded us,andquot; Dr. Gouras says. andquot;Instead of working outside the cell, we discovered that these antibodies to beta amyloid bind with a specific part of amyloid precursor protein (APP) - a precursor molecule to beta amyloid - as it lies on the outside of the affected cell. This complex then gets internalized within the cell, where it works to decrease levels of amyloid peptides, the building block of plaques that are found outside and between cells.andquot;
In fact, the antibodies cut down on intracellular amyloid accumulation by about one-third, the researchers found.
How might antibodies working inside neurons decrease exterior plaque levels? The researchers still aren't sure, but they have already ruled out some of the most obvious answers.
andquot;We found no evidence that the antibody somehow inhibits the activity of either of the two cellular enzymes - secretases - that we know help produce beta amyloid,andquot; notes the study's lead author Dr. Davide Tampellini, a researcher in the Weill Cornell Laboratory of Alzheimer's Disease Neurobiology. andquot;In fact, if anything the presence of the antibody appears to boost secretase activity,andquot; Dr. Tampellini says.
According to the researchers, it's possible that the antibody is affecting key trafficking mechanisms within the cell, thereby increasing the degradation of existing beta amyloid before it makes its way to the surface.
andquot;Most of the data we have supports this degradation model rather than an inhibition of beta-amyloid production,andquot; Dr. Gouras says. andquot;More research is needed to clear up that mystery, however.andquot;
What is clear from the study is that immune-based therapy does work to rid brain cells of amyloid - giving new impetus to the search for a safe, effective Alzheimer's vaccine.
andquot;A cure isn't likely as close as we are hoping forandquot; Dr. Gouras cautions, andquot;and new roadblocks to a successful vaccine might arise. But as we better understand how immunotherapy is working, we can better meet those roadblocks head-on.andquot;
And the discovery that antibodies work their magic both inside and outside the cell could have profound implications for the investigation of other disease conditions, especially autoimmune disorders where the immune system mistakenly attacks it own tissues.
"Biologists have long understood that antibodies can affect intracellular processes, but it's been woefully underappreciated in medicine," Dr. Gouras says. "Hopefully this will help to change that."
This work was funded by the Dana Foundation, the Alzheimer's Association, the American Health Assistance Foundation, the U.S. National Institutes of Health, and the Fundacao para a Ciencia e a Tecnologia, Portugal.
His team's study will appear in the Journal of Biological Chemistry, and was published in the May 1 online edition of the journal. Co-authors include Dr. Claudia G. Almeida, Dr. Jordi Magrane, Dr. Reisuke H. Takahashi, Dr. Feng Li and Dr. Michael T. Lin - all of Weill Cornell Medical College. from: http://www.sciencedaily.com/releases/2007/05/070523113732.htm
Ann Neurol. 2007 May;61(5):466-75.
Inclusion body myositis with human immunodeficiency virus infection: four cases
with clonal expansion of viral-specific T cells.
Dalakas MC, Rakocevic G, Shatunov A, Goldfarb L, Raju R, Salajegheh M.
Neuromuscular Diseases Section, National Institute of Neurological Disorders and
Stroke, National Institutes of Health, Bethesda, MD 20892-1382, USA. dalakasm@ninds.nih.gov
OBJECTIVE: Sporadic inclusion body myositis (sIBM), a common adult-onset myositis,
is characterized by an antigen-driven inflammatory response and vacuolar degeneration.
The cause is unknown. We report the association of sIBM with human immunodeficiency
virus (HIV) infection and explore the clonality and viral specificity of the autoinvasive
T cells. METHODS: Clinicopathological studies in four HIV-infected patients with
IBM were performed. The clonal restriction of endomysial T cells, compared with
peripheral blood, was examined by spectratyping. Immunohistochemical studies using
human leukocyte antigen-A* 0201-gag tetramers and the most dominant Vb families
were performed in serial muscle biopsy sections to examine whether clonally expanded
autoinvasive T cells are viral specific and invade muscle fibers expressing the
allele-specific monomorphic major histocompatibility complex class I antigen.
RESULTS: Prominent clonal restriction of certain Vb families was noted among the
endomysial T cells with evidence of in situ expansion. Approximately 10% of the
autoinvasive CD8(+) cells were human leukocyte antigen-A* 0201-HIV-gag specific
and invaded muscle fibers expressing the specific human leukocyte antigen-A* 0201
allele. These cells belonged to restricted Vb families. The HIV gag antigen was
present on several endomysial macrophages but not within the muscle fibers. INTERPRETATION:
sIBM develops in patients who harbor HIV. In HIV-IBM, a subset of CD8(+) T cells
surrounding muscle fibers are viral specific and may play a role in the disease
mechanism by cross-reacting with antigens on the surface of muscle fibers. This
study provides a paradigm that a chronic viral infection in genetically susceptible
individuals can trigger viral specific T cell clones that persist within the muscle
and lead to development of sIBM.
May
Related Article
Immune antibodies penetrate neurons to clear Alzheimer's-linked amyloid
Researchers at Weill Cornell Medical College have gotten much closer to understanding how immune-based therapies can treat Alzheimer's disease -- by studying how antibodies go inside brain cells to reduce levels of Alzheimer's-linked amyloid peptides that form plaques between neurons.
andquot;This internalization and activity of the antibody within the cell was a big surprise and something we really haven't appreciated in neurological medicine. It gives us new hope for the use of immunotherapy against Alzheimer's, while casting intriguing new light on other disease processes,andquot; says senior author Dr. Gunnar Gouras, associate professor of neurology and neuroscience at Weill Cornell Medical College and associate attending neurologist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.
His team's study will appear as a prestigious andquot;paper of the weekandquot; in an upcoming issue of the Journal of Biological Chemistry, and was published in the May 1 online edition of the journal.
There are currently no effective treatments to fight Alzheimer's disease, which now affects over 5 million Americans, according to the Alzheimer's Association. Scientists now project that unless new ways are found to prevent or treat the disease, the total could climb to 16 million by 2050.
For years, the idea of an immune-based vaccine therapy against Alzheimer's has been a Holy Grail of research. In fact, in the past, researchers did have some clinical success with an antibody-directed immune therapy. Those hopes were dampened somewhat after a few subjects came down with a serious, treatment-linked (but nonfatal) meningitis.
andquot;Still, the dream has remained very much alive -- especially since we know that antibodies to the beta-amyloid plaques associated with Alzheimer's can cross the blood-brain barrier, gaining access to the brain,andquot; Dr. Gouras explains. He remains one of the leading authorities on beta-amyloid plaques because of earlier work on its deposition and accumulation between neurons.
andquot;One of the things those earlier immunotherapy studies taught us was that antibodies can reduce amyloid plaques, which are a hallmark of the disease,andquot; he said. andquot;The next logical question was -- how does it do that?andquot;
Over the past six years, Dr. Gouras' team took advantage of breakthroughs in neuroscience research to help answer that question. They relied on the development of special transgenic mice bred to closely approximate the progress of human Alzheimer's disease.
In their latest study, the researchers exposed amyloid-filled neurons from these mice to immune antibodies similar to those used in clinical trials. They then examined changes in these cells in the lab, using microscopy, immunofluorescence and other high-tech methods.
andquot;What we found astounded us,andquot; Dr. Gouras says. andquot;Instead of working outside the cell, we discovered that these antibodies to beta amyloid bind with a specific part of amyloid precursor protein (APP) -- a precursor molecule to beta amyloid -- as it lies on the outside of the affected cell. This complex then gets internalized within the cell, where it works to decrease levels of amyloid peptides, the building block of plaques that are found outside and between cells.andquot;
In fact, the antibodies cut down on intracellular amyloid accumulation by about one-third, the researchers found.
How might antibodies working inside neurons decrease exterior plaque levelsandquot; The researchers still aren't sure, but they have already ruled out some of the most obvious answers.
andquot;We found no evidence that the antibody somehow inhibits the activity of either of the two cellular enzymes -- secretases -- that we know help produce beta amyloid,andquot; notes the study's lead author Dr. Davide Tampellini, a researcher in the Weill Cornell Laboratory of Alzheimer's Disease Neurobiology. andquot;In fact, if anything the presence of the antibody appears to boost secretase activity,andquot; Dr. Tampellini says.
According to the researchers, it's possible that the antibody is affecting key trafficking mechanisms within the cell, thereby increasing the degradation of existing beta amyloid before it makes its way to the surface.
andquot;Most of the data we have supports this degradation model rather than an inhibition of beta-amyloid production,andquot; Dr. Gouras says. andquot;More research is needed to clear up that mystery, however.andquot;
What is clear from the study is that immune-based therapy does work to rid brain cells of amyloid -- giving new impetus to the search for a safe, effective Alzheimer's vaccine.
andquot;A cure isn't likely as close as we are hoping forandquot; Dr. Gouras cautions, andquot;and new roadblocks to a successful vaccine might arise. But as we better understand how immunotherapy is working, we can better meet those roadblocks head-on.andquot;
And the discovery that antibodies work their magic both inside and outside the cell could have profound implications for the investigation of other disease conditions, especially autoimmune disorders where the immune system mistakenly attacks it own tissues.
andquot;Biologists have long understood that antibodies can affect intracellular processes, but it's been woefully underappreciated in medicine,andquot; Dr. Gouras says. andquot;Hopefully this will help to change that.andquot;
Source: Weill Cornell Medical College
http://www.physorg.com/news99143375.html
April
Electromyogr Clin Neurophysiol. 2007 Mar-Apr;47(2):97-104.
Serial quantitative electrophysiologic studies in sporadic inclusion body myositis.
Barkhaus PE, Nandedkar SD.
Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
Sporadic inclusion body myositis (S-IBM) is a progressive, acquired myopathic
process of unknown etiology. No known, successful or proven treatment exists.
Quantitative EMG studies including concentric needle motor unit action potentials,
interference pattern, macro-EMG and fiber density have allowed different measures
to be made of the motor unit. These different measures allow inferences to be
made in how the muscle fibers are distributed within both the normal and diseased
motor unit. The present study is an effort to use multiple quantitative EMG measurements
from the biceps brachii on a serial basis in order to study chronic changes in
the motor unit with disease progression. Twenty-eight studies from 9 patients
over a four-year period are shown. We conclude that while the concentric needle
electrode is most helpful for diagnosing abnormality, the less selective macro-EMG
and surface electrodes are better suited to monitor disease progression, especially
in very weak muscles. These observations have practical applications for monitoring
disease progression, or conversely, response to treatment.
[July]
Autophagy. 2007 Jul 12;3(4) Epub ahead (Published as Autophagy. 2007 Jul-Aug;3(4):396-8.)
Autophagy in a Mouse Model of Distal Myopathy with Rimmed Vacuoles or Hereditary
Inclusion Body Myopathy.
Malicdan MC, Noguchi S, Nishino I. Department of Neuromuscular Research,
National Institute of Neuroscience, National Center of Neurology and Psychiatry,
Kodaira, Tokyo, Japan.
Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion body myopathy
(hIBM) is an autosomal recessive disorder clinically characterized by weakness
that initially involves the distal muscles, although other muscles can be affected
as well. Pathological hallmarks include the presence of rimmed vacuoles (RVs)
and intracellular Congo red-positive depositions in vacuolated or nonvacuolated
fibers. Mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine
kinase (GNE) gene, which encodes the rate-limiting enzyme in sialic acid biosynthesis,
are causative of DMRV/hIBM. Recently, we have generated a mouse model (Gne(-/-)hGNEV572L-Tg)
for this disease, and have shown that these mice exhibit hyposialylation and intracellular
amyloid deposition before the characteristic RVs are detected, indicating that
autophagy is a downstream phenomenon to hyposialylation and amyloid deposition
in DMRV/hIBM.
[April]
Autophagy. 2007 July/August 9;3(4) [Epub ahead of print]
Macroautophagy as a Pathomechanism in Sporadic Inclusion Body Myositis.
Lunemann JD, Schmidt J, Dalakas MC, Munz C.
Laboratory of Viral Immunobiology, Christopher H. Browne Center for Immunology
and Immune Diseases, The Rockefeller University, New York, New York, USA.
Skeletal muscle fibers show a high level of constitutive and starvation-induced
macroautophagy. Sporadic Inclusion Body Myositis (sIBM) is the most common acquired
skeletal muscle disease in patients above the age of 50 years and is characterized
by inflammation and intracellular accumulation of aggregate-prone proteins such
as amyloid precursor protein (APP)/beta-amyloid, hyperphosporylated tau, and
presenilin. In a recent study, we found that muscle fibers of sIBM patients
show increased frequencies of Atg8/LC3(+) autophagosomes and that intracellular
APP/beta-amyloid colocalized with Atg8/LC3 in degenerating fibers. Colocalization
of APP/beta-amyloid with LC3(+) autophagosomes was further associated with upregulation
of major histocompatibility complex (MHC) class I and class II molecules and
T cell infiltration. These findings indicate that APP/beta-amyloid is a substrate
for autophagy in skeletal muscle fibers and suggest that degradation of aggregate-prone
proteins via macroautophagy can be linked with both immune-mediated and degenerative
tissue damage. A better understanding of this pathway in skeletal muscle and
in the inflammatory environment of sIBM might provide a rationale for novel
therapeutic strategies targeting pathogenic protein aggregation.
Eukaryotic cells contain two major protein degradation systems. One is the
ubiquitin-proteasome system, which accounts for the selective degradation of
most short-lived proteins. The other is the lysosomal system. Lysosomal degradation
of exogenous material is mediated by the process of endocytosis/phagocytosis,
whereas degradation of cytoplasmic components occurs after autophagy. During
macroautophagy, the beststudied autophagic pathway, double-membrane vesicles
termed autophagosomes are formed, which sequester cytosolic constituents as
cargo, and then fuse with lysosomes. Basal macroautophagy is ubiquitous in eukaryotes3
and allows for the constitutive removal of cytosolic proteins and organelles.
Discussion
Our study provides evidence supporting the involvement of autophagy in the pathogenesis
of sIBM. In a human muscle cell line, endogenous APP was targeted to Atg8/LC3-positive
autophagosomes. Moreover, in sIBM patients, the frequency of LC3/Atg8-positive
autophagosomes was increased in muscle fibers, often associated with the expression
of inflammation-associated molecules such as MHC classes I and II or invasion
by CD4+ and CD8+ cells. A substantial proportion of intracellular APP fragments,
including b-amyloid, colocalized with forming autophagosomes,
indicating that b-amyloid is targeted for lysosomal
degradation via the autophagic pathway.
In sIBM, aggregations of aberrant proteins such as b-amyloid
in the muscle fibers are a mainstay of the disease pathology.2 Basal autophagy
allows the constitutive removal of cytosolic proteins and organelles in eukaryotic
cells and has recently been shown to be essential in preventing neurodegeneration
in mice. Animals that lack essential autophagy genes in their central nervous
system accumulated diffuse ubiquitinated proteins, as well as inclusion bodies
in neuronal cells, and spontaneously developed neurodegenerative disease phenotypes.6,7
Because the proteasomal function was not altered in these mice, the authors
concluded that autophagy assists in the degradation of accumulated intractable
proteins when the cellular levels of such proteins overwhelm the disposal capacity
of the ubiquitinproteasome system.7 Therefore, similar to the neurodegenerative
disorders of the central nervous system, it is well conceivable that autophagy
is a mechanism operational in sIBM, particularly under conditions of overload
of the proteasome machinery.14 Autophagy-mediated degradation of protein aggregates
may, however, play an even more important role in skeletal muscle cells than
neurons, because muscle fibers already have a high level of constitutive autophagy
and were shown to rapidly increase autophagosome numbers after starvation.3
It is noteworthy in this respect that especially type II (fast-twitching) muscle
fibers, which displayed b-amyloid-associated
degeneration in our samples of sIBM patients, have been shown to be capable
of autophagy upregulation on starvation in GFP-Atg8/LC3 reporter mice.3 This
lends encouraging support for attempts to regulate autophagy in type II muscle
fibers for the degradation of accumulations of b-amyloid
as a potential therapeutic approach in sIBM.
Intracellular accumulation of protein is associated with overload of MHC class
I and endoplasmic reticulum stress, which recently has been demonstrated to
play a crucial role in inflammatory myopathies including sIBM.14,15 Several
studies implicated autophagic pathways in endogenous MHC antigen processing,
and we could recently show that MHC class II loading compartments continuously
receive input from autophagosomes in professional antigen-presenting cells,
as well as in interferon-g activated epithelial cell
lines.12 Although the exact mechanism of this alternative pathway compared with
conventional MHC class II antigen processing remains to be determined,13 the
information is relevant to sIBM where the muscle fibers have the properties
to behave as antigen-presenting cells.16
Atg8/LC3-positive autophagic vacuoles were not specific to sIBM, but also occurred
in the lysosomal storage disease M. Pompe. Expansion of autophagic vesicles
has recently been described in a mouse model of lysosomal acid a-glucosidase
deficiency.17 However, colocalization between b-amyloid/APP
and Atg8/LC3 was not observed in other vacuolated and nonvacuolated myopathies
or nonmyopathic control subjects. This double staining is compatible with the
finding that autophagic compartments, highly enriched for APP and gsecretase
complex components, were found in increased numbers in brain biopsies from patients
with Alzheimer-s disease.18,19 LC3/Atg8-postive autophagosomes and prelysosomal
late autophagic vacuoles accumulated markedly in dystrophic neuronal dendrites
and represented a major reservoir of intracellular b-amyloid.19
Lack of autophagosomal content degradation was actually implicated in accumulation
of intracellular and extracellular b-amyloid plaques,
because inhibition of autophagy decreased b-amyloid
peptide levels.19 Therefore, aberrant autophagic degradation without efficient
breakdown of autophagic cargo in lysosomes might actually exacerbate Alzheimer-s
disease by generating more b-amyloid depositions.
Similar mechanisms may well be crucial events during the pathogenesis of sIBM.
Our data indicate that the autophagic pathway is involved in b-amyloid-associated
degeneration in sIBM muscle and suggest that harnessing the autophagy pathway
could have therapeutic merit. However, in addition to its central role in preventing
intracellular protein accumulation, induction of autophagy has been associated
with various forms of cell death.20 In exploring the therapeutic potential of
autophagy in diseases associated with accumulation of aggregate-prone proteins,
it will be essential to better define the signaling pathways either leading
to protective autophagy or autophagic cell death.
From an Addendum:
This manuscript has been published online, prior to printing for Autophagy,
Volume 3, Issue 4. Definitive page numbers have not been assigned. The current
citation is: Autophagy 2007; 3(4): http://www.landesbioscience.com/journals/autophagy/abstract.php?id=4245
Once the issue is complete and page numbers have been assigned, the citation
will change accordingly.
Figure 1. Increased macroautophagy in degenerating muscle fibers of sporadic inclusion body myositis could enhance b-amyloid deposition (1), degrade b-amyloid aggregates (2), and/or lead to MHC class II presentation of autoantigens (3), thereby initiating or sustaining the inflammatory environment of this muscle disease. Inflammation and especially CD4+ T cells, recognizing intracellular antigen after processing via autophagy, could further stimulate autophagy (4) and the upregulation of antigen presentation via MHC class I and II, as well as maintain the activation of infiltrating CD8+ T cells via cytokine secretion (5). MIIC, MHC class II loading compartments.
Enhanced autophagy might promote or ameliorate degenerative protein aggregation and inflammation in sIBM. Studies that investigate autophagy in skeletal muscle cells and in sIBM in more detail are underway. A better understanding of this pathway in a tissue with high autophagic activity and in the inflammatory environment of sIBM might provide exciting insights into the general regulation of macroautophagy in mammalian cells and could provide a rationale for novel therapeutic strategies targeting pathogenic protein aggregation in sIBM.
[Background]
In cell biology, autophagy, or autophagocytosis, is a catabolic process involving the degradation of a cell's own components through the lysosomal machinery. It is a tightly regulated process which plays a normal part in cell growth, development, and homeostasis, where it helps maintain a balance between the synthesis, degradation, and subsequent recycling of cellular products. It is a major mechanism by which a starving cell reallocates nutrients from unnecessary processes to more essential processes.
A variety of autophagic processes exist, all sharing in common the degradation of intracellular components via the lysosome. The most well known mechanism of autophagy involves the formation of a membrane around a targeted region of the cell, separating the contents from the rest of the cytoplasm. The resultant vesicle then fuses with a lysosome and subsequently degrades the contents.
It was first described in the 1960s[1], however, many questions still remain to be elucidated about the actual processes and mechanisms involved. Its role in disease is not well categorised, it may help to halt the progression of some diseases and plays a protective role against infection by intracellular pathogens; however, in some situations it may actually contribute to the development of a disease.
Macroautophagy involves the formation of a membrane containing target materials moving into the lysosome.
Autophagy. (2007, April 21). See Wikipedia, The Free Encyclopedia.
April
Mayo Clin Proc. 2007 Apr;82(4):441-7.
Dysphagia in inflammatory myopathy: clinical characteristics, treatment strategies,
and outcome in 62 patients.
Oh TH, Brumfield KA, Hoskin TL, Stolp KA, Murray JA, Bassford JR.
Department of Physical Medicine and Rehabilitation, College of Medicine, Mayo
Clinic, 200 First St SW, Rochester, MN 55905 USA. E-mail: oh.terry@mayo.edu.
OBJECTIVE: To assess the clinical characteristics, treatment, and outcome of patients with inflammatory myopathy-associated dysphagia. PATIENTS AND METHODS: We retrospectively reviewed the medical records of all patients with inflammatory myopathy-associated dysphagia seen at the Mayo Clinic in Rochester, Minn, between January 1, 1997, and December 31, 2001. RESULTS: A total of 783 patients were diagnosed as having inflammatory myopathy during the 5-year study period. Of these, 62 patients (41 women and 21 men; mean age, 68.6 years) had inflammatory myopathy-associated dysphagia: 26 with inclusion body myositis (IBM), 18 with dermatomyositis, 9 with polymyositis, and 9 with overlap syndrome. Dysphagia was a presenting symptom in 13 patients (21%), with the highest incidence in the IBM group. Videofluoroscopic examinations revealed pharyngeal pooling and impaired oropharyngeal and cricopharyngeal function. The benefits of swallowing compensation techniques and exercises were difficult to establish. Interventional procedures were performed in 24 patients (39%) and most frequently (62%) in patients with IBM, with cricopharyngeal myotomy being most beneficial. Patients with IBM had the least symptomatic improvement. Overall, 11 patients died during the median follow-up of 38 months, with respiratory failure due to aspiration pneumonia as the most common cause. Mortality was high in patients who required percutaneous endoscopic gastrostomy (7/11, 64%), and 1- year mortality was highest (31%) in those with dermatomyositis. CONCLUSION: Dysphagia is a serious and at times presenting problem in patients with inflammatory myopathy. It occurs most frequently and appears to be most refractory in patients with IBM. The mortality rate was high in patients who required percutaneous endoscopic gastrostomy, and the 1-year mortality rate was the highest in patients with dermatomyositis.
April
PNAS April 17, 2007 vol. 104 no. 16 pps. 6800-6805.
Inducible overexpression of wild-type prion protein in the muscles leads to a
primary myopathy in transgenic mice.
Shenghai Huang, Jingjing Liang, Mengjie Zheng, Xinyi Li, Meiling Wang, Ping
Wang, Difernando Vanegas, Di Wu, Bikram Chakraborty, Arthur P. Hays, Ken Chen,
Shu G. Chen, Stephanie Booth, Mark Cohen, Pierluigi Gambetti, and Qingzhong Kong.
The prion protein (PrP) level in muscle has been reported to be elevated in patients
with inclusion-body myositis, polymyositis, dermatomyositis, and neurogenic muscle
atrophy, but it is not clear whether the elevated PrP accumulation in the muscles
is sufficient to cause muscle diseases. We have generated transgenic mice with
muscle-specific expression of PrP under extremely tight regulation by doxycycline,
and we have demonstrated that doxycyclineinduced overexpression of PrP strictly
limited to muscles leads to a myopathy characterized by increased variation of
myofiber size, centrally located nuclei, and endomysial fibrosis, in the absence
of intracytoplasmic inclusions, rimmed vacuoles, or any evidence of a neurogenic
disorder. The PrP-induced myopathy correlates with accumulation of an N-terminal
truncated PrP fragment in the muscle, and the muscular PrP displayed consistent
mild resistance to protease digestion. Our findings indicate that overexpression
of wild-type PrP in skeletal muscles is sufficient to cause a primary myopathy
with no signs of peripheral neuropathy, possibly due to accumulation of a cytotoxic
truncated form of PrP and/or PrP aggregation.
accumulation of PrP in the muscle fibers (19).
The present study reports that strictly muscle-specific overexpression of wild-type
human PrPC [the normal or cellular prion protein] under tight regulation by doxycycline
in Tg mice leads to a primary myopathy. These data argue that overexpression of
wild-type PrP in the skeletal muscle is in itself sufficient to cause a myopathy.
Our data demonstrate that overexpression of wild-type PrP [PrPC ] in the skeletal
muscles alone is sufficient to cause myopathy. These findings strongly suggest
that the elevated levels of PrP found in the skeletal muscles of human primary
myopathies, such as inclusion body myositis (3-5) and inflammatory myopathies
including polymyositis and dermatomyositis (5), may play an important role in
the pathogenesis.
April
Neuropathol Appl Neurobiol. 2007 Apr;33(2):238-42.
Myostatin precursor protein is increased and associates with amyloid-beta precursor
protein in inclusion-body myositis culture model.
Wojcik S, Nogalska A, McFerrin J, Engel WK, Oledzka G, Askanas V.
USC Neuromuscular Center, Department of Neurology, University of Southern California
Keck School of Medicine, Good Samaritan Hospital, Los Angeles, USA.
The present study provides a novel demonstration in cultured human muscle that
overexpression of AbPP/Ab increases accumulation of MstnPP. Accordingly, this
mechanism might be, at least partially, responsible for the increase of MstnPP
and of mature myostatin in the biopsied s-IBM muscle fibres [9]. Whether lack
of detectable mature myostatin dimer in our model (i) reflects its secretion to
the culture medium, or (ii) is related to the sensitivity of our antibody remains
to be studied.
March
Arthritis Res Ther. 2007 Mar 26;9(2):208
Immune mechanisms in the pathogenesis of idiopathic inflammatory myopathies.
Grundtman C, Malmstrom V, Lundberg IE.
Rheumatology Unit, Department of Medicine, Karolinska University Hospital Solna,
Karolinska Institutet, SE-171 76 Stockholm, Sweden. cecilia.grundtman@ki.se.
ABSTRACT: Idiopathic inflammatory myopathies (IIMs), comprising polymyositis,
dermatomyositis, and inclusion-body myositis, are characterized by inflammatory
cell infiltrates in skeletal muscle tissue, muscle weakness, and muscle fatigue.
The cellular infiltrates often consist of T lymphocytes and macrophages but
also, in some cases, B lymphocytes. Emerging data have led to improved phenotypic
characterization of the inflammatory cells, including their effector molecules,
in skeletal muscle, peripheral blood, and other organs that are frequently involved,
such as skin and lungs. In this review we summarize the latest findings concerning
the role of T lymphocytes, B lymphocytes, dendritic cells, and other antigen-presenting
cells in the pathophysiology of IIMs.
Figure 3 Caption: Hypothetical involvement of T lymphocytes, B lymphocytes,
and dendritic cells (DCs) in idiopathic inflammatory myopathies. (1) An unknown
trigger (for example viral infection or ultraviolet radiation) in the respiratory
tract or through the skin leads to the cleavage of histidyl-tRNA synthetase
by granzyme B through antiviral CD8+ T lymphocytes in the lungs. (2) Immature
DCs carry receptors on its surface that recognize common features of many pathogens.
When a DC takes up a pathogen in infected tissue it becomes activated and migrates
to the lymph node. (3) Upon activation, the DC matures into a highly effective
antigen-presenting cell (APC) and undergoes changes that enable it to activate
pathogen-specific lymphocytes in the lymph node. T lymphocytes become activated
and B lymphocytes, with active help from CD4+ T lymphocytes, proliferate and
differentiate into plasma cells. (4) Activated DCs, T lymphocytes, and B lymphocytes
could release cytokines into the bloodstream. (5) The activated T lymphocyte,
on which the DC-MHC-antigen complex is bound, itself binds to specialized
endothelial cells called high endothelial venules (HEV). For this purpose it
uses the VLA-4 (very late activation antigen-4) and LFA-1 (lymphocyte function
associated antigen-1) molecules on its surface to interact with adhesion molecules
(vascular cell-adhesion molecule-1 (VCAM-1) and intercellular cell-adhesion
molecule-1 (ICAM-1)) on HEVs, where they can penetrate into peripheral lymphoid
tissues. (6,7) Naandiuml;ve T lymphocytes and B lymphocytes that have not yet
encountered their specific antigen circulate continuously from the blood into
the peripheral lymphoid tissues. (8,9) Various cytokines from the bloodstream
or produced locally could affect the muscle tissue or cell in many different
ways. However, it is not clear whether the muscle cell itself could produce
and release cytokines. (10-12) DCs, macrophages (Mf), and B lymphocytes can
interact with T lymphocytes in various ways. T lymphocytes could possibly also
bind to muscle cells through inducible co-stimulators (ICOS), CD40 ligand (CD40-L),
CD28, and CTLA-4 (CD152) on T lymphocytes to ICOS ligand (ICOS-L), CD40, and
BB-1 antigen on the muscle cell. In that fashion, the muscle cell would function
as an APC. (13) Plasma cells (CD138+) can be found in the muscle tissue of certain
subgroups of patients with idiopathic inflammatory myopathy, but whether these
cells could produce autoantibodies locally is not yet known. (14) T lymphocytes
have been shown to bind in close contact with muscle cells and to release perforin,
granzyme A, and granulysin, which may cause necrosis of muscle tissue or cells.
Conclusion
The molecular basis of IIMs in humans, as in many other autoimmune rheumatic
diseases, is heterogeneous, involving several complex cellular components that
probably contribute to differences in disease susceptibility, clinical and histopathological
phenotype, and severity. Although this heterogeneity makes the study of the
pathogenesis of IIMs extraordinarily complex, it might also provide distinct
avenues for novel therapeutic interventions. Controlling the immune response
is as complex as its launching. An essential feature of physiological immune
response is its self-limitation, by which it is attenuated by several mechanisms.
We have only just started to understand the orchestrated life of T lymphocytes,
B lymphocytes, and DCs in IIMs, but there are still many unanswered questions
about how this usually effective system can go awry and result in false immune-mediated
reactions.
On the basis of detailed immunohistochemical studies on muscle biopsies, two
major types of inflammatory infiltrate were observed: endomysial and perivascular/perimysial.
In endomysial infiltrates there was a striking dominance of CD8+ T lymphocytes,
which could even be the predominating infiltrating cell type, followed by macrophages
and CD4+ T lymphocytes. These infiltrates often surrounded nonnecrotic fibers
and sometimes seemed to invade the fibers (Figure 1). This observation suggests
an immune reaction that targets muscle fibers. The perivascular infiltrates,
in contrast, were dominated by CD4+ T lymphocytes and macrophages, and sometimes
the presence of B lymphocytes suggested an immune reaction that targets microvessels
(Figure 2). A role for B lymphocytes as well as one for CD4+ T lymphocytes in
the pathogenesis of IIMs is supported by frequently detected autoantibodies
in polymyositis and dermatomyositis but less often in inclusion-body myositis.
These autoantibodies are both non-specific (frequently also being found in other
autoimmune disease) and myositisspecific [38,39]. A role for CD4+ T lymphocytes
in the disease mechanism is further supported by the genetic association with
HLA-DRB1*0301, DQA1*0501, and DQB1*0201, which was particularly seen for subgroups
of patients with autoantibodies.
The endomysial infiltrates were reported to be characteristic features of polymyositis
and inclusion-body myositis, whereas the perivascular infiltrates were associated
with patients with dermatomyositis. However, there are cases with a less distinct
localization of infiltrates or with combined endomysial and perivascular cellular
infiltrates [3,6]. Moreover, in some cases the inflammatory cell infiltrates
are diffusely spread in the tissue, whereas in other cases the infiltrates are
very small or are not found at all. In addition, the perivascular changes may
be seen in patients without a skin rash, whereas endomysial infiltrates are
occasionally seen in cases with a skin rash.
Taken together, these results indicate that there may be two major pathways:
one leading to cellular infiltrates with predominating endomysial localization,
and another with a predominantly perivascular localization often with microvessel
involvement and capillary loss. The latter is more often seen in patients with
a skin rash and dermatomyositis, but there seems to be an overlap between clinical
phenotypes, histopathology, and immunotypes. These observations suggest that
there might be more than just one factor that determines the histopathological
and clinical phenotypes, for example genes and environment.
March
Muscle Nerve. 2007 Mar 15; [Epub ahead of print] May, 2007, pps. 549-561.
Genetics of inclusion-body myositis.
Needham M, Mastaglia FL, Garlepp MJ.
Centre for Neuromuscular and Neurological Disorders, University of Western Australia,
Level 4, A Block, Queen Elizabeth II Medical Centre, Nedlands, Western Australia
6009.
Sporadic inclusion-body myositis (sIBM) is the most common acquired muscle disease
in Caucasians over the age of 50 years. Pathologically it is marked by inflammatory,
degenerative, and mitochondrial changes that interact in a yet-unknown way to
cause progressive muscle degeneration and weakness. The cause of the disease is
unknown, but it is thought to involve a complex interplay between environmental
factors, genetic susceptibility, and aging. The strongest evidence for genetic
susceptibility comes from studies of the major histocompatibility complex (MHC),
where different combinations of alleles have been associated with sIBM in different
ethnic groups. The rare occurrence of familial cases of inclusion-body myositis
(fIBM) adds additional evidence for genetic susceptibility. Other candidate genes
such as those encoding some of the proteins accumulating in muscle fibers have
been investigated, with negative results. The increased understanding of related
disorders, the hereditary inclusion-body myopathies (hIBM), may also provide clues
to the underlying pathogenesis of sIBM, but to date there is no indication that
the genes responsible for these conditions are involved in sIBM. This review summarizes
current understanding of the contribution of genetic susceptibility factors to
the development of sIBM.
Good overview from article:
Sporadic inclusion-body myositis (sIBM) is the most common acquired muscle disease
associated with aging but may occasionally also occur in younger individuals.
Classically it causes a selective pattern of muscle weakness involving the forearm
flexor and quadriceps femoris muscles, often with later involvement of the distal
leg, proximal arm, and pharyngeal muscles resulting in dysphagia.1,23,40,53,101
Pathologicallyit is characterized by an intramuscular inflammatory component of
variable severity, with a predominance of CD8+ T-cells which are clonally expanded,
89 and upregulation of major histocompatibility complex (MHC) class I antigen
in nonnecrotic muscle fibers.66 There is also evidence of mitochondrial involvement
as evidenced by segmental deficiency of cytochrome c oxidase (COX-deficient fibers)
and ragged-red fibers (RRF),97 as well as a degenerative component with rimmed
vacuole formation, tubulofilamentous inclusions, and eosinophilic inclusions in
muscle fibers.19 The protein inclusions are made up of a number of Alzheimer-type
proteins including b-amyloid and the amyloid precursor
protein (APP), phosphorylated tau, a-1-antichymotrypsin,
(a1ACT), a-synuclein, prion
protein, and apolipoprotein E (ApoE).17
March
Ann Neurol. 2007 Mar 15; [Epub ahead of print]
Inclusion body myositis with human immunodeficiency virus infection: Four cases
with clonal expansion of viral-specific T cells.
Dalakas MC, Rakocevic G, Shatunov A, Goldfarb L, Raju R, Salajegheh M.
Neuromuscular Diseases Section, National Institute of Neurological Disorders and
Stroke, National Institutes of Health, Bethesda, MD.
OBJECTIVE: Sporadic inclusion body myositis (sIBM), a common adult-onset myositis,
is characterized by an antigen-driven inflammatory response and vacuolar degeneration.
The cause is unknown. We report the association of sIBM with human immunodeficiency
virus (HIV) infection and explore the clonality and viral specificity of the autoinvasive
T cells. METHODS: Clinicopathological studies in four HIV-infected patients with
IBM were performed. The clonal restriction of endomysial T cells, compared with
peripheral blood, was examined by spectratyping. Immunohistochemical studies using
human leukocyte antigen-A* 0201-gag tetramers and the most dominant Vb families
were performed in serial muscle biopsy sections to examine whether clonally expanded
autoinvasive T cells are viral specific and invade muscle fibers expressing the
allele-specific monomorphic major histocompatibility complex class I antigen.
RESULTS: Prominent clonal restriction of certain Vb families was noted among the
endomysial T cells with evidence of in situ expansion. Approximately 10% of the
autoinvasive CD8(+) cells were human leukocyte antigen-A* 0201-HIV-gag specific
and invaded muscle fibers expressing the specific human leukocyte antigen-A* 0201
allele. These cells belonged to restricted Vb families. The HIV gag antigen was
present on several endomysial macrophages but not within the muscle fibers. INTERPRETATION:
sIBM develops in patients who harbor HIV. In HIV-IBM, a subset of CD8(+) T cells
surrounding muscle fibers are viral specific and may play a role in the disease
mechanism by cross-reacting with antigens on the surface of muscle fibers. This
study provides a paradigm that a chronic viral infection in genetically susceptible
individuals can trigger viral specific T cell clones that persist within the muscle
and lead to development of sIBM.
March
For the latest from the lab of the The IBM Research Project. see: http://www.s-ibm.org/publications/
A research group dedicated to understanding and finding treatment for sporadic
inclusion body myositis (s-IBM) and other inflammatory myopathies. This is a
multidisciplinary group, part of the Brigham and Women's Hospital, Department
of Neurology, Division of Neuromuscular Disease, Harvard Medical School; the
Children's Hospital Informatics Program; and the Harvard-MIT Division of Health
Sciences and Technology. http://www.s-ibm.org/
March
see January entry on Greenberg (below)
Summary from MDA Quest, March-April, 2007 Volume14 (#2), page, 18.
Recent findings by researchers at Harvard Medical School, Brigham and Women-s
Hospital, and Children-s Hospital, all in Boston, have identified a type
of immune system cell previously undetected in the biopsy samples of people with
inclusion-body myositis (IBM).
MDA grantee Steven A. Greenberg at Harvard and Brigham and Women-s, and colleagues,
who published their findings in the January issue of Muscle andamp; Nerve, say the
results suggest new hypotheses about IBM, as well as new potential treatment possibilities.
The cells, called dendritic cells, haven-t been previously reported in IBM
muscle samples, because their identification requires looking at muscle specimens
using specific markers, Greenberg says. Previous studies have used a more general
type of marker and have misidentified many of the dendritic cells as T-cells,
a better known immune system cell.
-Until the last decade, the study of dendritic cells has been relatively
neglected in immunology and particularly in autoimmune disease,- Greenberg
says, referring to diseases in which the body-s immune system mistakenly
attacks its own tissue. Polymyositis (PM) and dermatomyositis (DM), in which dendritic
cells have previously been noted, have long been classified as autoimmune disorders.
Experts have disagreed about how to classify IBM, although most believe the immune
system is involved in some way.
-These [dendritic] cells are now recognized as central to the initiation
and development of specific immune responses,- Greenberg says. One type,
myeloid dendritic cells, is particularly abundant in IBM muscle tissue.
-Myeloid dendritic cells activate other immune system cells, particularly
T-cells that are believed to be a major cause of muscle damage in IBM and polymyositis.
Their presence in IBM and PM muscle provides a means by which these T-cells become
activated and attack muscle.-
Greenberg says new therapies for autoimmune diseases aimed at disrupting the function
of dendritic cells and their interaction with T-cells could be considered for
future trials in myositis, given these findings. He notes that two drugs -
abatacept (Orencia) and efalizumab (Raptiva), both of which interfere with dendritic
cell-T-cell interactions - are already approved by the Food and Drug Administration
for other conditions.
Feb
February 1, 2007
TMA funds Fifth Cycle of research proposals
TMA-s Board of Directors approved funding for five new research projects in January, 2007. The projects funded this year are very different and are largely focused on therapies:
Two of the proposals selected build on the similarities between IBM and Alzheimer-s Disease: one by exploring medications that have been approved and successful in Alzheimer-s patients; the other will examine the nutritional and exercise interventions that also seem to have benefit in preventing and slowing Alzheimer-s. A third project will test the effectiveness of a high-tech -smart- brace-s potential use for IBM patients; and the fourth proposal funded takes a look at genetic therapy in IBM. The fifth project seeks to better classify the condition of myositis patients worldwide to assist researchers in treating myositis.
The proposals funded were those recommended by TMA-s research committee, and their diversity indicates the coming-of-age of TMA-s young program. -The variety and scope of the projects we have funded are very encouraging, and they indicate that TMA plays an important role in furthering knowledge about myositis,- said Dr. Lawrence Phillips, chairman of TMA-s research committee.
Valerie Askansas, MD, PhD, Professor of Neurology and Pathology at the University of Southern California Keck School of Medicine, has published dozens of research articles on IBM and continues to look for more clues to the disease process. Unlike polymyositis and dermatomyositis, IBM does not respond to medications that treat the inflammatory process. Her recent studies have focused instead on the degenerative mechanisms in IBM muscle fibers. Askanas has demonstrated the similarities between the Alzheimer-s disease brain and IBM muscle.
She now proposes to study a type of drug that improves cognition in Alzheimer-s patients and reduces amyloid-beta pathology in experimental models to see whether it will also work to reduce the effects of amyloid-beta in her lab-s IBM-experimental human muscle culture model.
Christa M. Studzinski, MD, a PhD candidate at the University of Kentucky, was awarded a research fellowship to examine how changes in diet and exercise will affect transgenic mice. Both diet and exercise, Studzinski notes, have been found to improve function in animal models of Alzheimer-s Disease. Studzinski-s mice will be put on a special low-carbohydrate, high-fat (ketogenic) diet and given a measured exercise program. The ability of diet and exercise to prevent, halt, or reverse the disease process of IBM will be tested using a variety of behavioral and laboratory markers.
Ingrid Lundberg, MD, PhD, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden, was awarded a one-year grant for a project to better classify the present condition of myositis patients worldwide to determine most effective treatments.
Terry Oh, MD, an assistant professor of physical medicine and rehabilitation at Mayo Clinic, Rochester, will study whether -Stance Control Orthosis,- is effective for people with IBM and knee instability. This brace may provide the necessary stability while overcoming the restricted lower leg movement and tiring effects of traditional braces.
Drs. Brian Kaspar, PhD, and Jerry Mendell, MD, both of the Columbus Children-s
Research Institute, have successfully enlarged and strengthened the quadriceps
muscle in mice by using a common virus to carry a follistatin gene into the
quadriceps muscle. Because follistatin blocks myostatin, which is associated
with loss of muscle mass. Drs. Kaspar and Mendell will test whether such gene
therapy might be used to help humans who have IBM and lose muscle mass and strength.
http://www.myositis.org/newsroom/index.cfm?id=41andamp;type=P
Research Profile
Conrad Weihl, MD, PhD, Instructor in Department of Neurology and the Division
of Neuromuscular Disorders, Washington University School of Medicine, St. Louis,
MO.
Inclusion body myopathies are a group of disabling skeletal muscle disorders.
The most common form, inclusion body myositis (IBM), affects patients over the
age of 50. There is no effective treatment. IBM muscle tissue contains characteristic
-rimmed vacuoles- and eosinophilic cytoplasmic aggregates. These structures
contain ubiquitin, andszlig;-amyloid, apolipoprotein E, and phosphorylated tau,
the same pathologic proteins present in Alzheimers Disease (AD) brains.
Mutations in the protein p97, also known as VCP (valosin containing protein),
cause a dominantly inherited syndrome with an IBM phenotype. The pathologic consequence
of these mutations has not been studied. p97/VCP belongs to the AAA ATPase (ATPases
associated with other cellular activities) protein family and is implicated protein
degradation via the ubiquitin-proteasome pathway.
My research uses both cellular and animal models of hereditary IBM to explore
the underlying pathogenesis of this disease. These models allow us to understand
mechanisms of protein misfolding and degradation in skeletal muscle and its relation
to other inherited myopathies, muscular dystrophies, cachexia and normal aging.
http://www.neuro.wustl.edu/people/wiehl.html
Mar
Muscle Nerve 35: 322-326, 2007
UNFOLDED PROTEIN RESPONSE AND AGGRESOME FORMATION IN HEREDITARY REDUCING-BODY
MYOPATHY
TEERIN LIEWLUCK, YUKIKO K. HAYASHI, MAKI OHSAWA, RUMI KUROKAWA, MASAKO FUJITA,
SATORU NOGUCHI, IKUYA NONAKA, and ICHIZO NISHINO,
ABSTRACT: Reducing-body myopathy (RBM) is a rare myopathy characterized by the
presence of unique sarcoplasmic inclusions called reducing bodies (RBs). We characterized
the aggresomal features of RBs that contained g tubulin, ubiquitin, and endoplasmic
reticulum (ER) chaperones, together with a set of membrane proteins, in a family
with hereditary RBM. Increased messenger ribonucleic acid and protein levels of
a molecular chaperone, glucose-related protein 78, were also observed. These results
suggest that the unfolded protein response caused by the accumulation of misfolded
proteins in the endoplasmic reticulum plays an important role in the formation
of RBs.
Reducing-body myopathy (RBM) is a rare myopathy characterized pathologically by
the presence of intracytoplasmic inclusion bodies strongly stained by menadione-linked
a-glycerophosphate dehydrogenase (MAG) in the absence
of substrate, a-glycerophosphate. 1 The term -reducing
body (RB)- implies the reducing activity of the inclusions to nitroblue tetrazolium
in the absence of substrate. This condition is also commonly associated with rimmed
vacuoles and cytoplasmic bodies. The clinical features of RBM are variable and
can be classified into three forms, namely (1) severe infantile form,1,8 (2) benign
congenital form,13 and (3) late onset form. Most of the patients have sporadic
disease and only a few familial cases have been reported.4,7 Here we report the
aggresomal features of RBs found in a new family with hereditary RBM (hRBM).
Feb [related topic]
Scientists at the University of Virginia have identified what appears to be a
major missing link in the process that destroys nerve cells in Alzheimer's disease,
an incurable disease that slowly destroys memory and cognitive abilities. The
findings are reported in the Nov. 20, 2006, issue of the Journal of Cell Biology
and could eventually lead to new drugs that target and disrupt specific proteins
that conspire in the brain to cause Alzheimer's.
In Alzheimer's disease, two kinds of abnormal structures accumulate in the brain:
amyloid plaques and neurofibrillary tangles. The plaques contain fibrils that
are made from protein fragments called 'beta-amyloid peptides.' The tangles also
are fibrous, but they are made from a different substance, a protein called 'tau.'
In the new U.Va. study, the researchers found a deadly connection between beta-amyloid
and tau, one that occurs before they form plaques and tangles, respectively.
According to George Bloom, the senior author of the study and a professor of biology
and cell biology at U.Va., this connection causes the swiftest, most sensitive
and most dramatic toxic effect of beta-amyloid found so far. What makes it most
remarkable, though, is that it requires a form of amyloid that represents the
building blocks of plaques, so called 'pre-fibrillar beta-amyloid,' and it only
happens in cells that contain tau. Even though they account for just ~10 percent
of the cells in the brain, nerve cells are the major source of tau, which likely
explains why they are specifically attacked in Alzheimer's disease.
The researchers used cultured mammalian cells that either did or did not make
tau to study how cells respond to beta-amyloid. They found that pre-fibrillar,
but not fibrillar beta-amyloid works together with tau to break apart microtubules
- highways along which 'synapse' replacement parts move rapidly in the nerve cell
from where they are made to where they are needed. Synapses are connections between
nerve cells, and in the brain they are the structural basis of memory and cognition.
When nerve cells in the brain lose their microtubules they also lose the ability
to replace worn out synapse parts, and synapses therefore disappear. The loss
of synapses, and consequent loss of memories and cognitive skills, cannot be reversed,
and can lead directly to nerve cell death.
'We think we've found one of the seminal cell biological events in the pathogenesis
of Alzheimer's and if we can figure out all of the steps in the process and understand
each player at every step, it will represent many potential new drug targets for
Alzheimer's therapy,' Bloom said. 'Our paper defines one of the earliest events
that causes neurons to die in both early-onset familial Alzheimer's and late-onset
Alzheimer's disease. We believe this is the first evidence for the long elusive
'missing link' between amyloid and tau in Alzheimer's disease.'
'This is a very significant finding that greatly improves our understanding of
the mechanisms within the cell that ultimately lead to Alzheimer's disease,' said
Lester Binder, professor of cell and molecular biology at Northwestern University
and a leading researcher on Alzheimer's. Binder said he has already incorporated
the U.Va. study into classes he teaches on the pathogenesis of Alzheimer's disease
and dementia.
The study's first author and lead investigator is Michelle King, a U.Va. research
assistant professor of biology. Other investigators include Bloom, Ho-Man Kan
and Alev Erisir of U.Va., Peter W. Baas of Drexel University and Charles G. Glabe
of the University of California at Irvine.
Feb [related topic] Nature Reviews Neuroscience 8, 87 (February 2007) | doi:10.1038/nrn2083
The accumulation of hyperphosphorylated tau is associated with several neurodegenerative disorders, including Alzheimer's disease, fronto-temporal dementia and Pick's disease, and is suspected to contribute to the pathogenesis of such conditions, although the mechanisms by which it does this are unknown. Feany and colleagues now provide evidence that tau can mediate neurodegeneration through interactions with actin.
Previous in vitro studies have revealed interactions between the microtubule-associated protein tau and actin, and separate studies have suggested that actin aggregation can trigger cell death. Actin-rich inclusions have been found in the brains of patients with various neurodegenerative conditions. However, it is not known whether these interactions can cause neurodegeneration in vivo. To investigate this question, the authors used several strains of transgenic Drosophila melanogaster that expressed wild-type human tau or a mutant form of tau associated with familial fronto-temporal dementia.
Flies in which mutant tau was expressed in all neurons had increased levels of filamentous actin, a proportion of which was associated with tau, demonstrating that neuronal tau and actin interact in this model. The flies' brains also contained rod-shaped, actin-rich inclusions, many of which were positive for phosphorylated tau. Similar results were observed in transgenic mice expressing mutant tau, in which actin-rich inclusions were observed in several brain regions.
To explore further the interactions between tau and actin, double transgenic flies were created, in which expression of a mutant or wild-type tau was targeted to the retina in conjunction with a transgene expressing actin. In flies expressing mutant tau, retinal toxicity was observed; however this was dramatically increased in flies co-expressing actin. Manipulating the actin cytoskeleton, by co-expressing a gene that destabilizes actin filaments, or by knocking out actin completely, reduced tau-induced retinal damage.
These findings indicated that tau and actin can interact to cause neurotoxicity, perhaps through the stabilization and aggregation of actin filaments. When mutant tau and actin were overexpressed in all neurons, there was an increase in filamentous actin and actin-rich inclusions in the brain, which correlated with levels of neurodegeneration. Wild-type tau did not produce these effects, suggesting that mutated tau has a greater capacity to interact with actin to cause neurodegeneration. Modifying actin did not alter tau phosphorylation, suggesting that the stabilization and aggregation of actin filaments is downstream of tau in the pathogenic pathway. Furthermore, when a mutated form of tau that mimics phosphorylation at disease-associated sites was expressed, toxicity was increased, which is associated with increased levels of filamentous actin and actin aggregation.
It is unknown whether the actin-rich inclusions observed in the brain contribute to the disease pathology, or instead represent an attempt by neurons to protect themselves from accumulating potentially toxic actin filaments. Nevertheless, this study provides in vivo evidence for an interaction between hyperphosphorylated tau, modification of the actin cytoskeleton and neurotoxicity. It will be important to test these findings in other in vivo models and further work will be needed to identify the pathogenic events that are downstream of this interaction.
Author: Katherine Whalley
Feb
Ann Rheum Dis. 2007 Feb 2; [Epub ahead of print]
Limited effects of high-dose intravenous immunoglobulin (IVIg) treatment on molecular expression in muscle tissue of patients with inflammatory myopathies.
Barbasso Helmers S, Dastmalchi M, Alexanderson H, Nennesmo I, Esbjornsson M,
Lindvall B, Lundberg IE.
Rheumatology Unit, Karolinska Institutet, Sweden.
OBJECTIVES: To achieve an improved understanding of the molecular mechanisms of high-dose intravenous immune globulin (IVIg) in inflammatory myopathies by investigating the effects on: muscle function and immunological molecules in skeletal muscle of polymyositis (PM)-, dermatomyositis (DM)- and inclusion body myositis (IBM) patients. METHODS: Thirteen treatment resistant patients, 6 PM, 4 DM, 2 IBM, and 1 juvenile DM, were treated with 2g/kg of IVIg, 3 times with a monthly interval. Functional Index in Myositis, serum creatinine kinase (CK)-levels and muscle biopsies were performed before treatment and after the third IVIg infusion. Immunological molecules were also studied in biopsies taken 24-48hrs after first infusion. RESULTS: Improved muscle function was observed in three patients (1PM, 1DM, 1IBM) and CK-levels decreased in five. T cells, macrophages, MHC class I antigen on muscle fibres, ICAM-1 and VCAM-1 expression and MAC- deposits on capillaries were present to an equal degree in biopsies before- and after IVIg treatment. No correlation between the clinical response and molecular changes was found. CONCLUSIONS: The clinical effects of high-dose IVIg on muscle function in patients with refractory inflammatory active myositis did not correspond with effects on any of the investigated molecules in our study. T cells, macrophages, phenotypical changes in muscle fibres and endothelial cell activation were still present after treatment. These observations question the role of IVIG as an immune modulating therapy in patients with inflammatory myopathies.
Jan
Hum Mol Genet. 2007 Jan 15;16(2):115-28. Epub 2006 Dec 12.
A Gne knockout mouse expressing human V572L mutation develops features similar
to distal myopathy with rimmed vacuoles or hereditary inclusion body myopathy.
Malicdan MC, Noguchi S, Nonaka I, Hayashi YK, Nishino I.
Department of Neuromuscular Research, National Institute of Neuroscience, National
Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502,
Japan.
Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion myopathy (h-IBM)
is an early adult-onset distal myopathy caused by mutations in the UDP-N-acetylglucosamine
2-epimerase/N-acetylmannosamine kinase (GNE) gene which encodes for a bifunctional
enzyme involved in sialic acid biosynthesis. It is pathologically characterized
by the presence of rimmed vacuoles especially in atrophic fibers, which also occasionally
contain congophilic materials that are immunoreactive to beta-amyloid, lysosomal
proteins, ubiquitin and tau proteins. To elucidate the pathomechanism of this
myopathy and to explore the treatment options, we generated a mouse model of DMRV/h-IBM.
We knocked out the Gne gene in the mouse, but this resulted in embryonic lethality.
We therefore generated a transgenic mouse that expressed the human GNEV572L mutation,
which is the most prevalent among Japanese DMRV patients, and crossed this with
Gne((+/-)) mouse to obtain Gne((-/-))hGNEV572L-Tg. Interestingly, these mice exhibit
marked hyposialylation in serum, muscle and other organs. Reduction in motor performance
in these mice can only be seen from 30 weeks of age. A compelling finding is the
development of beta-amyloid deposition in myofibers by 32 weeks, which clearly
precedes rimmed vacuole formation at 42 weeks. These results show that the Gne((-/-))
hGNEV572L-Tg mouse mimics the clinical, histopathological and biochemical features
of DMRV/h-IBM, making it useful for understanding the pathomechanism of this myopathy
and for employing different strategies for therapy. Our findings underscore the
notion that hyposialylation plays an important role in the pathomechanism of DMRV/h-IBM.
Jan
Hum Mol Genet. 2007 Jan 15;16(2):115-28. Epub 2006 Dec 12.
A Gne knockout mouse expressing human V572L mutation develops features similar
to distal myopathy with rimmed vacuoles or hereditary inclusion body myopathy.
Malicdan MC, Noguchi S, Nonaka I, Hayashi YK, Nishino I.
Department of Neuromuscular Research, National Institute of Neuroscience, National
Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502,
Japan.
Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion myopathy (h-IBM)
is an early adult-onset distal myopathy caused by mutations in the UDP-N-acetylglucosamine
2-epimerase/N-acetylmannosamine kinase (GNE) gene which encodes for a bifunctional
enzyme involved in sialic acid biosynthesis. It is pathologically characterized
by the presence of rimmed vacuoles especially in atrophic fibers, which also occasionally
contain congophilic materials that are immunoreactive to beta-amyloid, lysosomal
proteins, ubiquitin and tau proteins. To elucidate the pathomechanism of this
myopathy and to explore the treatment options, we generated a mouse model of DMRV/h-IBM.
We knocked out the Gne gene in the mouse, but this resulted in embryonic lethality.
We therefore generated a transgenic mouse that expressed the human GNEV572L mutation,
which is the most prevalent among Japanese DMRV patients, and crossed this with
Gne((+/-)) mouse to obtain Gne((-/-))hGNEV572L-Tg. Interestingly, these mice exhibit
marked hyposialylation in serum, muscle and other organs. Reduction in motor performance
in these mice can only be seen from 30 weeks of age. A compelling finding is the
development of beta-amyloid deposition in myofibers by 32 weeks, which clearly
precedes rimmed vacuole formation at 42 weeks. These results show that the Gne((-/-))
hGNEV572L-Tg mouse mimics the clinical, histopathological and biochemical features
of DMRV/h-IBM, making it useful for understanding the pathomechanism of this myopathy
and for employing different strategies for therapy. Our findings underscore the
notion that hyposialylation plays an important role in the pathomechanism of DMRV/h-IBM.
Jan
BMC Neurol. 2007 Jan 29;7:3.
Intravenous immune globulin in hereditary inclusion body myopathy: a pilot study.
Sparks S, Rakocevic G, Joe G, Manoli I, Shrader J, Harris-Love M, Sonies B,
Ciccone C, Dorward H, Krasnewich D, Huizing M, Dalakas MC, Gahl WA.
BACKGROUND: Hereditary Inclusion Body Myopathy (HIBM) is an autosomal recessive,
adult onset, non-inflammatory neuromuscular disorder with no effective treatment.
The causative gene, GNE, codes for UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine
kinase, which catalyzes the first two reactions in the synthesis of sialic acid.
Reduced sialylation of muscle glycoproteins, such as alpha-dystroglycan and neural
cell adhesion molecule (NCAM), has been reported in HIBM. METHODS: We treated
4 HIBM patients with intravenous immune globulin (IVIG), in order to provide sialic
acid, because IgG contains 8 micromol of sialic acid/g. IVIG was infused as a
loading dose of 1 g/kg on two consecutive days followed by 3 doses of 400 mg/kg
at weekly intervals. RESULTS: For all four patients, mean quadriceps strength
improved from 19.0 kg at baseline to 23.2 kg (+22%) directly after IVIG loading
to 25.6 kg (+35%) at the end of the study. Mean shoulder strength improved from
4.1 kg at baseline to 5.9 kg (+44%) directly after IVIG loading to 6.0 kg (+46%)
at the end of the study. The composite improvement for 8 other muscle groups was
5% after the initial loading and 19% by the end of the study. Esophageal motility
and lingual strength improved in the patients with abnormal barium swallows. Objective
measures of functional improvement gave variable results, but the patients experienced
improvements in daily activities that they considered clinically significant.
Immunohistochemical staining and immunoblotting of muscle biopsies for alpha-dystroglycan
and NCAM did not provide consistent evidence for increased sialylation after IVIG
treatment. Side effects were limited to transient headaches and vomiting. CONCLUSION:
The mild benefits in muscle strength experienced by HIBM patients after IVIG treatment
may be related to the provision of sialic acid supplied by IVIG. Other sources
of sialic acid are being explored as treatment options for HIBM.
Jan
Neuromuscul Disord. 2007 Jan 22; [Epub ahead of print]
Distribution of glucocorticoid receptor alpha and beta subtypes in the idiopathic
inflammatory myopathies.
De Bleecker JL, Paepe BD, Vervaet VL, Arys B, Creus KK, Werbrouck BF, Martin
JJ.
Department of Neurology, Ghent University Hospital, De Pintelaan 185, B-9000 Gent,
Belgium.
In contrast with dermatomyositis and polymyositis, inclusion body myositis is
unresponsive to glucocorticoid treatment. Glucocorticoid action is mediated through
an active glucocorticoid receptor-alpha and negatively regulated by another glucocorticoid
receptor isoform. In several autoimmune diseases glucocorticoid receptor-beta
up-regulation is involved in glucocorticoid resistance. We studied glucocorticoid
receptor distribution in normal and inflammatory myopathy muscle and investigated
whether differences in glucocorticoid receptor-alpha and glucocorticoid receptor-beta
protein expression are involved in the differential glucocorticoid sensitivity
in inclusion body myositis versus polymyositis. Multistep immunofluorescence and
Western blotting on fractionated cytoplasmic or nuclear muscle samples were used.
Glucocorticoid receptor-alpha was the predominant receptor subtype in muscle and
occurred abundantly in myonuclei of control and diseased muscle alike. Glucocorticoid
receptor-beta was constitutively expressed on a subset of endothelial cells. No
differences between dermatomyositis and the other idiopathic inflammatory myopathies
were observed. Increased nuclear glucocorticoid receptor that has dissociated
from heat shock protein 90 was found in glucocorticoid treated subjects. Glucocorticoid
receptor-alpha and -beta isoform levels were unaltered in muscle tissues from
control subjects that had received glucocorticoid treatment prior to biopsy. No
differences in relative glucocorticoid receptor-alpha and glucocorticoid receptor-beta
protein expression were seen in inclusion body myositis versus polymyositis specimens.
Our study indicates that the different glucocorticoid sensitivity in the idiopathic
inflammatory myopathies is not related to up- or down-regulation of a given glucocorticoid
receptor isoform at the protein level.
Jan
Arthritis Rheum. 2007 Jan;56(1):372-83.
Restricted T cell receptor BV gene usage in the lungs and muscles of patients
with idiopathic inflammatory myopathies.
Englund P, Wahlstrom J, Fathi M, Rasmussen E, Grunewald J, Tornling G, Lundberg
IE.
Karolinska University Hospital at Solna, and Karolinska Institutet, Stockholm,
Sweden.
OBJECTIVE: To investigate T cell receptor (TCR) expression in 3 different compartments
that could be involved in patients with myositis: muscle, lung, and peripheral
blood. METHODS: Nine patients with polymyositis (PM), dermatomyositis, or inclusion
body myositis underwent bronchoscopy and bronchoalveolar lavage (BAL) as well
as muscle biopsy and blood sampling. A panel of 19 monoclonal antibodies specific
for TCR V(beta) (BV) and V(alpha) (AV) were used to characterize the TCR profile
in CD4(+) and CD8(+) T cell populations in BAL fluid and peripheral blood by flow
cytometry. Muscle biopsy tissues were analyzed by immunohistochemistry. Patients
were also typed for HLA-DRB1 and DRB3 alleles. RESULTS: A total of 17 T cell expansions
were detected in BAL fluid, 6 in the CD4(+) T cell population and 11 in the CD8(+)
T cell population. Four T cell expansions were detected in peripheral blood. A
selective TCR V usage was found in muscle. Two PM patients, both of whom had BAL
fluid BV3(+) T cell expansions in the CD4 population and in whom BV3 was also
a prominent TCR V segment in muscle tissue, shared the HLA-DRB1*03 allele. These
2 patients were the only ones who were positive for anti-Jo-1 antibody. CONCLUSION:
We found a restricted accumulation of T lymphocytes expressing selected TCR V-gene
segments in the target organ compartments (i.e., lung and muscle). The occurrence
of shared TCR gene segment usage in muscle and lungs could suggest common target
antigens in these organs.
Jan
Muscle Nerve. 2007 Jan;35(1):17-23.
Myeloid dendritic cells in inclusion-body myositis and polymyositis.
Greenberg SA, Pinkus GS, Amato AA, Pinkus JL.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's
Hospital, 75 Francis Street, and Harvard Medical School, Boston, Massachusetts
02115, USA.
Dendritic cells (DCs), immune system cells central to the development of immunity,
have not previously been reported in muscle in inclusion-body myositis (IBM).
We performed immunohistochemical studies on muscle biopsy specimens from 50 patients
using monoclonal antibodies that distinguish two classes of DCs, myeloid DC and
plasmacytoid DC. In 17 of 20 IBM and 9 of 10 polymyositis (PM) specimens, myeloid
DCs were present in substantial numbers, frequently surrounded and sometimes invading
otherwise intact myofibers, and were part of dense collections of cells that included
T cells. Dermatomyositis muscle had more plasmacytoid DCs than myeloid DCs, whereas
IBM and PM had greater numbers of myeloid DCs. The stellate morphology of myeloid
DCs in dense collections of cells that included T cells suggests local intramuscular
antigen presentation in IBM and PM.
Summary from MDA Quest, March-April, 2007 Volume14 (#2), page, 18.
Recent findings by researchers at Harvard Medical School, Brigham and Women-s
Hospital, and Children-s Hospital, all in Boston, have identified a type
of immune system cell previously undetected in the biopsy samples of people with
inclusion-body myositis (IBM).
MDA grantee Steven A. Greenberg at Harvard and Brigham and Women-s, and colleagues,
who published their findings in the January issue of Muscle & Nerve, say the
results suggest new hypotheses about IBM, as well as new potential treatment possibilities.
The cells, called dendritic cells, haven-t been previously reported in IBM
muscle samples, because their identification requires looking at muscle specimens
using specific markers, Greenberg says. Previous studies have used a more general
type of marker and have misidentified many of the dendritic cells as T-cells,
a better known immune system cell.
-Until the last decade, the study of dendritic cells has been relatively
neglected in immunology and particularly in autoimmune disease,- Greenberg
says, referring to diseases in which the body's immune system mistakenly
attacks its own tissue. Polymyositis (PM) and dermatomyositis (DM), in which dendritic
cells have previously been noted, have long been classified as autoimmune disorders.
Experts have disagreed about how to classify IBM, although most believe the immune
system is involved in some way.
-These [dendritic] cells are now recognized as central to the initiation
and development of specific immune responses,- Greenberg says. One type,
myeloid dendritic cells, is particularly abundant in IBM muscle tissue.
-Myeloid dendritic cells activate other immune system cells, particularly
T-cells that are believed to be a major cause of muscle damage in IBM and polymyositis.
Their presence in IBM and PM muscle provides a means by which these T-cells become
activated and attack muscle.-
Greenberg says new therapies for autoimmune diseases aimed at disrupting the function
of dendritic cells and their interaction with T-cells could be considered for
future trials in myositis, given these findings. He notes that two drugs -
abatacept (Orencia) and efalizumab (Raptiva), both of which interfere with dendritic
cell-T-cell interactions - are already approved by the Food and Drug Administration
for other conditions.
Jan
Neurobiol Dis. 2007 Jan 2; [Epub ahead of print]
The cell-specific expression of metalloproteinase-disintegrins (ADAMs) in inflammatory
myopathies.
Dehmel T, Janke A, Hartung HP, Goebel HH, Wiendl H, Kieseier BC.
Department of Neurology, Heinrich-Heine University, Moorenstrasse 5, 40225 Duesseldorf,
Germany.
Inflammatory cell invasion and cytokine activation are important steps in the
pathogenesis of immune-mediated diseases of muscle. Metalloproteinase-disintegrins
(ADAMs) are considered to play a critical role in leukocyte migration by promoting
cellular adhesion, cleavage of molecules of the extracellular matrix and shedding
of membrane bound cytokines. Here, we report the expression patterns of ADAM8,
ADAM9, ADAM10, ADAM12, ADAM17 and ADAM19 in cultured human myoblasts and peripheral
blood mononuclear cells (PBMCs) in vitro, as well as in biopsies from patients
suffering from polymyositis (PM), dermatomyositis (DM), inclusion body myositis
(IBM) and non-inflammatory controls. We observed an in vitro downregulation of
the RNAs of ADAM10, ADAM17 and ADAM19 in myoblasts after stimulation with various
pro- and anti-inflammatory mediators, whereas in PBMCs an RNA upregulation of
ADAM9, ADAM10, ADAM17 and ADAM19 was detectable under identical conditions. In
human muscle biopsies, invading CD3+ T lymphocytes expressed ADAM17 and ADAM19,
whereas macrophages co-localized to ADAM8, as detected by immunohistochemistry.
Transfection of PBMCs with ADAM19 single interfering RNA and incubation with a
metalloproteinase inhibitor suggest proteolytic activity of ADAM19 and involvement
in the shedding of tumor necrosis factor-alpha. No differences in the cellular
expression profiles between PM, DM and IBM were found, whereas the sections from
non-inflammatory controls did not reveal any positive immunoreactivity for ADAMs,
except for ADAM10, which is localized exclusively to muscle fibres. Our results
suggest that certain ADAMs are expressed by specific cell populations during the
genesis of immune-mediated diseases of human muscle.
Jan [related topic]
New gene in Alzheimer's disease
Researchers link gene for a protein involved in amyloid recycling to AD - but
with dozens of genes now associated with the disease, will this one stand out
from the pack?
[Published 15th January 2007 02:50 PM GMT]
A new gene, sortilin-related receptor SORL1, is joining the ranks of other genes
scientists have associated with late-onset Alzheimer's disease, thanks to a
report in this week's Nature Genetics. Many of the two dozen genes already linked
to the disease have disappointed researchers by demonstrating inconsistent correlation
across data sets, sparking debate over the significance of the latest findings.
Still, some scientists are optimistic. "The main difference is the size of the study [linking SORL1 to Alzheimer's], the replication, and the diversity of the sample," Creighton Phelps, director of the Alzheimer's Disease Centers Program at the National Institute on Aging (NIA), told The Scientist. The NIA funded a portion of the study, but Phelps was not involved in the study.
The project, which included teams from Columbia University, the University of Toronto, and Boston University, sampled over 6,000 participants from seven data sets and four ethnic groups. These groups included Caribbean Hispanic and Israeli Arab -- which are known to have an elevated prevalence of Alzheimer's disease -- Northern European, Caucasian, and African American.
The teams searched for single nucleotide polymorphisms (SNPs) among several genes involved in processing amyloid precursor protein (APP), the molecule that generates the toxic amyloid beta peptide (Abeta) involved in Alzheimer's. One gene showed up positive: Six SNPs in two distinct regions of the gene for sorLA/LR11, a receptor that regulates the recycling of APP, were associated with late-onset Alzheimer's disease.
The authors speculate that variants in SORL1 reduce the expression of the gene, sending APP away from the recycling pathway and down the pathway toward Abeta. "It all makes biological sense, it's certainly very plausible," Allen Levey, director of the Center for Neurodegenerative Disease and Alzheimer's Disease Center at Emory University, told The Scientist. In 2004, Levey showed that brains of patients with Alzheimer's disease were about two-fold less abundant in sorLA/LR11. His group is looking into the role sorLA/LR11 might play during mild cognitive impairment, a precursor to Alzheimer's disease.
Lindsay Farrer, chief of the Genetics Program at Boston University and one of the authors on the study, points out that the group has not yet shown that the variants they found result in any reduction in sorLA/LR11 expression. "This is where we hit the limits of the work we've done," Farrer told The Scientist. "As enthusiastic as we are, we have not identified yet any variants that are causally or functionally related to the disease."
This group is not alone: Among other Alzheimer's-associated genes, only one -- APOE -- has yielded evidence of mutants functionally related to the disease, Rudolph Tanzi reported in a meta-analysis in the January issue of Nature Genetics. The analysis, led by Lars Bertram at Massachusetts General Hospital, compiled data from 900 publications on Alzheimer's genetics.
Possessing just one copy of the mutant APOE allele increases the risk of developing Alzheimer's two to three-fold, Tanzi, a Neurology professor at Massachusetts General Hospital, told The Scientist. Relative to APOE, all of the other AD-associated genes described in these publications carry a much smaller risk of developing Alzheimer's, and Tanzi said SORL1 appears no different. The AlzGene Web site developed from the meta-analysis ranks Alzheimer's-associated genes in terms of risk of developing the disease; SORL ranks at around 13th, Tanzi said, giving it a "middle-of-the-pack effect."
Mutations in APOE account for 30% of the genetic risk of Alzheimer's disease, Tanzi said, and the rest he expects results from a combination of risk from many of these other associated variants. "It's still important to discover all of these genes that are associated, because it's all a part of the puzzle. All of them are important, but is [SORL1] more important than any of those that have come before it? No it is not," Tanzi said.
The authors of the SORL1 study say they are eager to see the results of independent analyses on the gene's association with Alzheimer's disease. The next step, Farrer said, is to identify the SORL1 mutations responsible for the elevated risk. He's confident his colleagues will find them. "I believe it's a matter of time, [but] it won't necessarily be easy."
The green arrows track re-entry of APP from the cell surface when SORL1 is present. The red arrows show that, when SORL1 is absent, more APP moves into domains such as the late endosome/lysosome, where the black arrows show how it is subsequently cut by two enzymes, beta-secretase (BACE1) and gamma-secretase (PS1 3-sec), generating the neurotoxic amyloid beta-peptide (A2).
Kerry Grens kgrens the-scientist.com
Links within this article:
E Rogaeva et al., "The neuronal sortilin-related receptor SORL1 is genetically
associated with Alzheimer disease," Nature Genetics, published online January
14, 2007. http://www.nature.com/ng/index.html
National Institute on Aging http://www.nia.nih.gov
MW Anderson, "Amending the amyloid hypothesis," The Scientist, October 25, 2004.
http://www.the-scientist.com/article/display/15006
N Johnston, " Gamma-Secretase makes a splash," The Scientist, July 4, 2005.
http://www.the-scientist.com/article/display/15596
Allen Levey http://neurology.emory.edu/Faculty/Levey.htm
CR Scherzer et al., "Loss of apolipoprotein E receptor LR11 in Alzheimer disease,"
Archives of Neurology 61:1200-1205, 2004. http://archneur.ama-assn.org/cgi/content/abstract/61/8/1200
Lindsay Farrer http://www.bu.edu/alzresearch/team/faculty/farrer.html
R Mahley and Y Huang, "Going beneath the fold," The Scientist, August 1, 2006.
http://www.the-scientist.com/article/display/24105
Rudolph Tanzi http://www.hms.harvard.edu/dms/neuroscience/fac/tanzi.html
L Bertram et al., "Systematic meta-analysis of Alzheimer disease genetic association
studies: the AlzGene database," Nature Genetics 39:17-23. http://www.nature.com/ng/journal/v39/n1/abs/ng1934.html
AlzGene http://www.alzforum.org/res/com/gen/alzgene/default.asp
Jan
J Immunol. 2007 Jan 1;178(1):547-556.
A Local Antigen-Driven Humoral Response Is Present in the Inflammatory Myopathies.
Bradshaw EM, Orihuela A, McArdel SL, Salajegheh M, Amato AA, Hafler DA, Greenberg
SA, O'connor KC.
Department of Neurology, Laboratory of Molecular Immunology, Center for Neurologic
Diseases and Brigham and Women's Hospital;
The inflammatory myopathies are putative autoimmune disorders characterized by
muscle weakness and the presence of intramuscular inflammatory infiltrates. Although
inclusion body myositis and polymyositis have been characterized as cytotoxic
CD8(+) T cell-mediated diseases, we recently demonstrated high frequencies of
CD138(+) plasma cells in the inflamed muscle tissue of patients with these diseases.
To gain a deeper understanding of the role these B cell family members play in
the disease pathology, we examined the molecular characteristics of the H chain
portion of the Ag receptor. Biopsies of muscle tissue were sectioned and tissue
regions and individual cells were isolated through laser capture microdissection.
Ig H chain gene transcripts isolated from the sections, regions, and cells were
used to determine the variable region gene sequences. Analysis of these sequences
revealed clear evidence of affinity maturation in that significant somatic mutation,
isotype switching, receptor revision, codon insertion/deletion, and oligoclonal
expansion had occurred within the B and plasma cell populations. Moreover, analysis
of tissue regions isolated by laser capture microdissection revealed both clonal
expansion and variation, suggesting that local B cell maturation occurs within
muscle. In contrast, sequences from control muscle tissues and peripheral blood
revealed none of these characteristics found in inflammatory myopathy muscle tissue.
Collectively, these data demonstrate that Ag drives a B cell Ag-specific response
in muscle in patients with dermatomyositis, inclusion body myositis, and polymyositis.
These findings highlight the need for a revision of the current paradigm of exclusively
T cell-mediated intramuscular Ag-specific autoimmunity in inclusion body myositis
and polymyositis.
END
Mail Bill: btillier@shaw.ca