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Query: UMLS:C0027121 (myositis)
 4,538 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The major new advances in seeking the pathogenic mechanisms of sporadic inclusion-body myositis and hereditary inclusion-body myopathy are discussed. Hypotheses are presented regarding the possible causes and significance of amyloid deposits in sporadic inclusion-body myositis and the roles of abnormally accumulated ubiquitin, beta-amyloid protein, beta-amyloid precursor protein, alpha 1-antichymotrypsin, hyperphosphorylated tau, and prion protein in the vacuolated muscle fibers in both sporadic inclusion-body myositis and hereditary inclusion-body myopathy. Because hereditary inclusion-body myopathy is virtually free of Congophilic amyloid deposits but, like sporadic inclusion-body myositis, contains large accumulations of beta-amyloid protein, it is possible that the lesions in hereditary inclusion-body myopathy may represent "early" changes. There are striking similarities between the pathology of inclusion-body myositis muscle and brains affected by Alzheimer's disease in regard to accumulation of ubiquitin, beta-amyloid protein and its precursor protein, alpha 1-antichymotrypsin, and hyperphosphorylated tau.
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PMID:New advances in inclusion-body myositis. 811 35

We review the newest advances related to seeking the pathogenic mechanism(s) of sporadic inclusion-body myositis (s-IBM) and present the pathologic diagnostic criteria of s-IBM. We discuss the possible pathogenic role of several themes, such as 1) increased amyloid-beta precursor protein (AbetaPP) and of its fragment Abeta; 2) phosphorylation of tau protein; 3) oxidative stress; 4) abnormal a) signal-transduction, b) transcription, and c) RNA accumulation; 5) "junctionalization" and myogenous" denervation; and 6) lymphocytic inflammation. Evidence is provided supporting our hypothesis that overexpression of AbetaPP within the aging muscle fibers is an early upstream event causing the subsequent pathogenic cascade. The remarkable pathologic similarities between s-IBM muscle and Alzheimer disease (AD) brain are discussed, and the possible cause and significance are addressed.
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PMID:Inclusion-body myositis: newest concepts of pathogenesis and relation to aging and Alzheimer disease. 1120 70

Sporadic inclusion-body myositis (IBM) is the most common, progressive muscle disease of older individuals. We investigated the presence of BACE1 and BACE2-two beta secretases that cleave amyloid-beta-precursor protein-in muscle-biopsy samples from patients with IBM and from controls. On immunofluorescence, BACE1 and BACE2 co-localised with amyloid beta in IBM vacuolated muscle fibres, but were not found in controls. Immunoblotting showed increased BACE2 but not BACE1 in patients with IBM compared with controls. Our study suggests that both of these proteases might participate in processing of amyloid-beta-precursor protein in IBM muscle fibres.
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PMID:Presence of BACE1 and BACE2 in muscle fibres of patients with sporadic inclusion-body myositis. 1174 23

This report summarizes clinical features and diagnostic criteria, and the newest advances related to seeking the pathogenic mechanism(s) of sporadic inclusion-body myositis. On the basis of the authors' research, several processes seem to be important in relation to the still-speculative pathogenesis: increased transcription and accumulation of amyloid-b precursor protein and accumulation of its proteolytic fragment amyloid-b; abnormal accumulation of components related to lipid metabolism (eg, low-density lipoprotein receptors and cholesterol; accumulation of cholesterol is possibly caused by its abnormal trafficking); oxidative stress; accumulations of other Alzheimer-related proteins including phosphorylated tau; a milieu of muscle cellular aging in which these changes occur. The authors' basic hypothesis is that overexpression of amyloid-b precursor protein within the aging muscle fibers is an early upstream event causing the subsequent pathogenic cascade. The remarkable pathologic similarities between inclusion-body myositis muscle and Alzheimer's disease brain are discussed.
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PMID:Newest pathogenetic considerations in inclusion-body myositis: possible role of amyloid-beta, cholesterol, relation to aging and to Alzheimer's disease. 1221 48

Sporadic inclusion-body myositis and hereditary inclusion-body myopathies are progressive muscle diseases leading to severe disability. We briefly summarize their clinical pictures and pathologic diagnostic criteria and discuss the latest advances in illuminating their pathogenic mechanism(s). We emphasize how different etiologies might lead to the strikingly similar pathology and possibly similar pathogenic cascade. On the basis of our research, several processes seem to be important in relation to the still speculative pathogenesis, including (a) increased transcription and accumulation of amyloid-beta precursor protein and accumulation of its proteolytic fragment amyloid-beta; (b) abnormal accumulation of components related to lipid metabolism, for example, cholesterol, accumulation of which is possibly owing to its abnormal trafficking; (c) oxidative stress; (d) accumulations of other Alzheimer's disease-related proteins; and (e) a milieu of muscle cellular aging in which these changes occur. We discuss a potentially very important role of unfolded and/or misfolded proteins as a possible mechanism in the formations of the inclusion bodies and other abnormalities.
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PMID:Unfolding story of inclusion-body myositis and myopathies: role of misfolded proteins, amyloid-beta, cholesterol, and aging. 1273 44

Cystatin C (CC), an endogenous cysteine protease inhibitor, is accumulated within amyloid-beta (A beta) amyloid deposits in Alzheimer's disease (AD) brain and was proposed to play a role in the AD pathogenesis. Because the chemo-morphologic muscle phenotype of sporadic inclusion-body myositis (s-IBM) has several similarities with the phenotype of AD brain, including abnormal accumulation of A beta deposits, we studied expression and localization of CC in muscle biopsies of 10 s-IBM, and 16 disease- and five normal-control muscle biopsies. Physical interaction of CC with amyloid-beta precursor protein (A beta PP) was studied by a combined immunoprecipitation/immunoblotting technique in the s-IBM muscle biopsies and in A beta PP-overexpressing cultured human muscle fibers. In all s-IBM muscle biopsies, CC-immunoreactivity either colocalized with, or was adjacent to, the A beta-immunoreactive inclusions in 80-90% of the vacuolated muscle fibers, mostly in non-vacuolated regions of their cytoplasm. Ultrastructurally, CC immunoreactivity-colocalized with A beta on 6-10 nm amyloid-like fibrils and floccular material. By immunoblotting, CC expression was strongly increased in IBM muscle as compared to the controls. By immunoprecipitation/immunoblotting experiments, CC coimmunoprecipitated with A beta PP, both in s-IBM muscle and in A beta PP-overexpressing cultured normal human muscle fibers. Our studies (i) demonstrate for the first time that CC physically associates with A beta PP, and (ii) suggest that CC may play a novel role in the s-IBM pathogenesis, possibly by influencing A beta PP processing and A beta deposition.
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PMID:Cystatin C colocalizes with amyloid-beta and coimmunoprecipitates with amyloid-beta precursor protein in sporadic inclusion-body myositis muscles. 1278 72

Cultured muscle fibers (CMF) from a patient with inclusion-body myositis (IBM) and cardiac amyloidosis associated with the transthyretin (TTR) Val122Ile mutation contained aspects of the IBM phenotype: vacuolation, congophilic inclusions, and clusters of immunocolocalizing amyloid beta-peptide (Abeta) and TTR accumulations. These abnormalities are never present in normal human CMF. These perturbations were greatly increased after Abeta precursor protein gene transfer. The TTR mutation may be a genetic predisposition factor for the patient's IBM.
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PMID:Transthyretin Val122Ile, accumulated Abeta, and inclusion-body myositis aspects in cultured muscle. 1287 14

The 26S proteasome system is involved in eliminating various proteins, including ubiquitinated misfolded/unfolded proteins, and its inhibition results in cellular accumulation of protein aggregates. Intramuscle-fiber ubiquitinated multiprotein-aggregates are characteristic of sporadic inclusion-body myositis (s-IBM) muscle fibers. Two major types of aggregates exist, containing either amyloid-beta (Abeta) or phosphorylated tau (p-tau). We have now asked whether abnormalities of the 26S proteasome contribute to s-IBM pathogenesis and whether the multiprotein aggregates have features of aggresomes. Using cultured human muscle fibers we also studied the effect of amyloid-beta precursor protein (AbetaPP) overexpression on proteasome function and the influence of proteasome inhibition on aggresome formation. We report that in s-IBM muscle biopsies 26S proteasome subunits were immunodetected in the gamma-tubulin-associated aggresomes, which also contained Abeta, p-tau, ubiquitin, and HSP70. In addition, a) expression of proteasome subunits was greatly increased, b) the 20Salpha proteasome subunit co-immunoprecipitated with AbetaPP/Abeta, and c) the three major proteasomal proteolytic activities were reduced. In cultured muscle fibers, AbetaPP-overexpressing fibers displayed diminished proteasomal proteolytic activities, and addition of proteasome inhibitor strikingly increased aggresome formation. Accordingly, proteasome dysfunction in s-IBM muscle fibers may play a role in accumulation of misfolded, potentially cytotoxic proteins and may be induced by increased intracellular AbetaPP/Abeta.
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PMID:Proteasome inhibition and aggresome formation in sporadic inclusion-body myositis and in amyloid-beta precursor protein-overexpressing cultured human muscle fibers. 1604 36

We summarize the molecular phenotype, diagnostic criteria, and the newest advances related to seeking the pathogenic mechanism(s) of sporadic inclusion-body myositis (s-IBM), a muscle disease usually of persons over age 50. On the basis of our research, several processes seem to be important in relation to the still-speculative pathogenesis: 1) increased transcription and accumulation of amyloid-beta precursor protein (AbetaPP), and accumulation of its proteolytic fragment Abeta; 2) abnormal accumulation of cholesterol, caveolin-1, and apolipoprotein E; 3) oxidative stress; 4) accumulations of intramuscle fiber multiprotein aggregates; and 5) evidence that unfolded/misfolded proteins participate in s-IBM pathogenesis. Our basic hypothesis is that overexpression of AbetaPP within the aging muscle fibers is an early upstream event causing a subsequent pathogenic cascade.
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PMID:Molecular pathology and pathogenesis of inclusion-body myositis. 1610

Sporadic inclusion-body myositis (s-IBM), the most common muscle disease of older persons, is of unknown cause and there is no successful treatment. We summarize our most recent findings, which provide a better understanding of the steps in the pathogenetic cascade. We suggest that s-IBM is primarily a myodegenerative disease. Intriguing are the phenotypic similarities between s-IBM muscle fibers and the brains of Alzheimer disease, the most common neurodegenerative disease of older persons. In s-IBM, abnormal accumulation of the amyloid-beta (Abeta) precursor protein and its proteolytic fragment, Abeta, associated with the aging intracellular milieu of the muscle fiber, appear to be key upstream pathogenic events. We propose that the identified abnormal accumulation, misfolding, and aggregation of proteins, perhaps provoked by the aging milieu and aggravated by the oxidative stress, lead to the s-IBM-specific vacuolar degeneration and atrophy of muscle fibers.
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PMID:Inclusion-body myositis: a myodegenerative conformational disorder associated with Abeta, protein misfolding, and proteasome inhibition. 1643 44


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