The immunology of fibrosis.

Fibrosis is the production of excessive amounts of connective tissue, i.e., scar formation, in the course of reactive and reparative processes. Fibrosis develops as a consequence of various underlying diseases and presents a major diagnostically and therapeutically unsolved problem. In this review, we postulate that fibrosis is always a sequela of inflammatory processes and that the many different causes of fibrosis all channel into the same final stereotypical pathways. During the inflammatory phase, both innate and adaptive immune mechanisms are operative. This concept is exemplified by fibrotic diseases that develop as a consequence of tissue damage, primary inflammatory diseases, fibrotic alterations induced by foreign body implants, "spontaneous" fibrosis, and tumor-associated fibrotic changes.

Effects of adalimumab treatment on endothelial cell activation markers in the skeletal muscle of patients with rheumatoid arthritis.

OBJECTIVES: Patients with rheumatoid arthritis (RA), particularly those with severe disease, have increased risk of cardiovascular disease (CVD). Previous studies suggest that endothelial cell activation may contribute to this co-morbidity, and that treatment with tumour necrosis factor (TNF) inhibitors could reduce the risk of CVD in these patients. The aim of this study was to investigate endothelial cell activation markers in muscle tissue of patients after adalimumab treatment. METHODS: Patients with active RA who started treatment with adalimumab 40 mg every two weeks were included. Muscle biopsies taken before and 3 months after start of treatment were available from 11 patients (9 females, mean age 54.2 years, median disease duration 6.5 years, 91% anti-CCP positive, 7 on methotrexate [median dose 20 mg/week]). None of the patients had clinical signs of myopathy. IL-1α and HLA-DQ were investigated by immunohistochemistry. Quantification was performed by computer assisted image analysis. RESULTS: Disease activity, measured by DAS28 decreased (mean 5.5 vs. 4.1; p=0018). A good or moderate EULAR response was seen in 6/11 patients. HLA-DQ was mainly expressed in endothelial cells in capillaries, whereas IL-1α was mainly seen in larger vessels. HLA-DQ expression decreased significantly after treatment (p=0.041). There was a similar trend for IL-1α, in particlar in EULAR good/moderate responders. CONCLUSIONS: Adalimumab treatment was associated with decreased expression of endothelial markers previously associated with severe systemic inflammation in RA. Our findings indicate a reduced endothelial activation in patients treated with anti-TNF drugs, which might contribute to a lower risk of cardiovascular co-morbidity.

TLR4 as receptor for HMGB1 induced muscle dysfunction in myositis.

OBJECTIVES: Polymyositis and dermatomyositis are characterised by muscle weakness and fatigue even in patients with normal muscle histology via unresolved pathogenic mechanisms. In this study, we investigated the mechanisms by which high mobility group box protein 1 (HMGB1) acts to accelerate muscle fatigue development. METHODS: Intact single fibres were dissociated from flexor digitorum brevis (FDB) of wild type, receptor for advanced glycation endproduct (RAGE) knockout and toll like receptor 4 (TLR4) knockout mice and cultured in the absence or presence of recombinant HMGB1. A decrease in sarcoplasmic reticulum Ca(2+) release during a series of 300 tetanic contractions, which reflects the development of muscle fatigue, was determined by measuring myoplasmic free tetanic Ca(2+). TLR4 and major histocompatibility complex (MHC)-class I expression in mouse FDB fibres were investigated by immunofluorescence and confocal microscopy. Immunohistochemistry was used to investigate TLR4, MHC-class I and myosin heavy chain expression in muscle fibres of patients. RESULTS: Our results demonstrate that TLR4 is expressed in human and mouse skeletal muscle fibres, and coexpressed with MHC-class I in muscle fibres of patients with myositis. Furthermore, we show that HMGB1 acts via TLR4 but not RAGE to accelerate muscle fatigue and to induce MHC-class I expression in vitro. In order to bind and signal via TLR4, HMGB1 must have a reduced cysteine 106 and a disulphide linkage between cysteine 23 and 45. CONCLUSIONS: The HMGB1-TLR4 pathway may play an important role in causing muscle fatigue in patients with polymyositis or dermatomyositis and thus is a potential novel target for future therapy.

Transcatheter embolization for the management of acute active inferior epigastric artery hemorrhages.

PURPOSE: To report a retrospective review of all patients who were admitted to the interventional radiology unit at our hospital for transcatheter arterial embolization (TAE) of an acute active hemorrhage of the inferior epigastric artery. METHODS: From 1996 to 2012, 52 consecutive patients (26 men; mean age 63±15 years) with hemodynamically relevant active abdominal wall hematoma were admitted for TAE of the inferior epigastric artery. Of these, 19 patients had spontaneous hemorrhage due to use of anticoagulants, 18 due to abdominal trauma, and 15 due to an iatrogenic complication. All superselective embolizations were performed using a coaxial catheter technique with a 0.018-inch microcatheter introduced through the diagnostic macrocatheter. Various embolization methods, alone or in combination, were applied, including primarily microcoils and polyvinyl alcohol particles. RESULTS: Primary technical success was achieved in 47/52 (90%) patients; the remainder needed a second embolization session (secondary success 100%). The mean puncture-to-hemostasis time was 65.4±35 minutes. No patient developed a large hematoma or pseudoaneurysm at the puncture site. The 30-day mortality was 19% (n=10) and the total cumulative mortality rate was 23% (n=12). Over a mean 67-month follow-up of 39/40 survivors (1 lost to follow-up), no complications from the embolization procedure, such as abdominal wall ischemia, were observed. There were no differences in outcomes based on etiology of the hemorrhage. CONCLUSION: In selected patients with acute active hemorrhage of the IEA in the anterior abdominal wall, TAE is a fast, safe, minimally invasive, and reliable method with a high technical success rate and no long-term complications.

The pattern of acute injuries in patients from alpine skiing accidents has changed during 2000-2011: analysis of clinical and radiological data at a level I trauma center.

OBJECTIVES: During the last decade, many educational efforts and technological improvements have been made to protect skiing athletes from injuries. Whether these efforts have changed the pattern of acute injuries from skiing casualties has not yet been shown on a medical basis, which this longitudinal study examines. METHODS: All patients transferred to the Department of Radiology of our level I trauma center for acute emergency computed tomography (CT) after alpine skiing accidents from 2000 to 2011 were included. We hypothesized that only patients with clinical suspicion for injuries were admitted for acute CT. RESULTS: Of all acute patients after skiing accidents, 2,252 could be included. From 2000 to 2011, all cerebral injuries and vascular arterial injuries statistically significantly decreased (p < 0.05, respectively). However, extremity fractures, facial fractures, and vertebral fractures increased (p < 0.04, respectively). The number of cerebral hemorrhages, thoracic injuries, and abdominal injuries remained unchanged (p = NS). The mean (SD) number of all initial radiological examinations per victim statistically significantly decreased from 2.3 (0.7) in 2000 to 1.5 (0.6) in 2011, whereas the admissions for acute CT have significantly increased (p < 0.02; respectively). CONCLUSIONS: Acute radiological evaluation in skiing accidents has changed during the last decade. The decrease in overall cerebral injuries might be a function of the increasing use of skiing helmets. A protection of the extremities, trunk, spine, and face, however, needs further improvements and their radiological assessment with CT warrants attention in skiing casualties.

Autoreactive HSP60 epitope-specific T-cells in early human atherosclerotic lesions.

Atherosclerosis is a multifactorial chronic inflammatory disease characterized by the presence of T-cells, macrophages, and dendritic cells in the arterial intima. Classical risk factors lead to over-expression of stress proteins, especially heat shock protein 60 (HSP60). HSP60 on the surface of arterial endothelial cells (ECs) then becomes a target for pre-existing adaptive anti-HSP60 immunity resulting in infiltration of the intima by mononuclear cells. In the present study, T-cells derived from early, clinically still inapparent human atherosclerotic lesions were analyzed phenotypically and for their reactivity against HSP60 and HSP60-derived peptides. HSP60 was detected in ECs and CD40- and HLA Class II-positive cells within the intima. Effector memory CD4(+) T-cells producing high amounts of interferon-γ and low levels of interleukin-4 were the dominant subpopulation. T-cells derived from late lesions displayed a more restricted T-cell receptor repertoire to HSP60-derived peptides than those isolated from early lesions. Increased levels of soluble HSP60 and circulating anti-human HSP60 autoantibodies were found in donors with late but not early lesions. This is the first functional study of T-cells derived from early human atherosclerotic lesions that supports the previously proposed concept that HSP60-reactive T-cells initiate atherosclerosis by recognition of atherogenic HSP60 epitopes.

Heat shock protein 60 and immune inflammatory responses in atherosclerosis.

Hallmarks of inflammation in various cardiovascular diseases, notably atherosclerosis, have been observed for a long time. However, evidence for an (auto)antigen-driven process at these sites of inflammation has come forward only recently. Heat shock proteins (HSPs) have been identified as playing either immunologically mediated disease promoting or protective roles. HSP60 has been shown to trigger innate and adaptive immune responses that initiate the earliest still reversible inflammatory stage of atherosclerosis. HSP60 is structurally highly conserved and abundantly expressed by prokaryotic and eukaryotic cells under stressful conditions. Beneficial protective immunity to microbial HSP60 acquired by infection or vaccination and bona fide autoimmunity to biochemically altered autologous HSP60 is present in all humans. In vitro and in vivo experiments have demonstrated that classical atherosclerosis risk factors can act as endothelial stressors that provoke the simultaneous expression of adhesion molecules and of HSP60 in mitochondria, in cytoplasm, and on the cell surface, where it acts as a "danger signal" for cellular and humoral immune reactions. Hence, protective, preexisting anti-HSP60 immunity may have to be "paid for" by harmful (auto)immune cross-reactive attack on arterial endothelial cells maltreated by atherosclerosis risk factors. These experimentally and clinically proven findings are the basis for the autoimmune concept of atherosclerosis.

The autoimmune concept of atherosclerosis.

PURPOSE OF REVIEW: This review summarizes the recent data on the 'Autoimmune Concept of Atherosclerosis', according to which the first stage of this disease is due to an autoimmune reaction against arterial endothelial cells expressing heat shock protein 60 (HSP60) and adhesion molecules when stressed by classical atherosclerosis risk factors. Special emphasis is put on oxidized low-density lipoproteins as early endothelial stressors. RECENT FINDINGS: Plasma cholesterol and LDL levels considered 'normal' by the medical community are possibly too high from an evolutionary viewpoint. The proinflammatory milieu at sites of early atherosclerotic lesions could be conducive to oxidation of LDL in situ. LDL oxidation can also take place at nonvascular sites or in the circulation under general proinflammatory conditions explaining its proatherosclerotic role in 'normocholesterolemic' individuals. SUMMARY: We hypothesize that the plasma cholesterol and LDL levels currently considered normal are evolutionarily too high. Cholesterol and/or oxidized low-density lipoprotein, even as a mild HSP60-inducing endothelial stressor, function as a ubiquitous risk factor. If this hypothesis is true, most members of developed societies might be at risk to develop atherosclerotic plaques at anti-HSP60-immunity-triggered intimal inflammatory foci, irrespective of the primary risk-factor(s).

Effects of HMGB1 on in vitro responses of isolated muscle fibers and functional aspects in skeletal muscles of idiopathic inflammatory myopathies.

Idiopathic inflammatory myopathies (IIMs) are heterogeneous rheumatic disorders of unknown cause characterized by muscle weakness, inflammatory cell infiltrates, and major histocompatibility complex (MHC) class I expression on muscle fibers. The nonhistone nuclear protein alarmin high-mobility group box 1 protein (HMGB1) has been detected extranuclearly in muscle biopsies from patients with IIMs. We hypothesize that HMGB1 has a central role in the cause of muscle weakness, particularly in the early phases of IIMs. Experiments were performed on skeletal muscle fibers isolated from adult mice, which were exposed to recombinant interferon (IFN)-gamma or HMGB1. The myoplasmic free [Ca(2+)] was measured. Stimulation with IFN-gamma resulted in increased HMGB1 expression in muscle nuclei and the myoplasm. Exposure to HMGB1 induced a reversible up-regulation of MHC class I in the muscle fibers. However, HMGB1 exposure caused an irreversible decrease in Ca(2+) release from the sarcoplasmic reticulum during fatigue, induced by repeated tetanic contractions. HMGB1 and MHC class I were frequently colocalized in the myoplasm of muscle fibers in muscle biopsies from patients with early IIMs. However, HMGB1-expressing fibers outnumbered fibers expressing MHC class I. Our data indicate that HMGB1 could be an early inducer of skeletal muscle dysfunction in IIMs.

Cardiovascular disease in patients with inflammatory rheumatic disease is associated with up-regulation of markers of inflammation in cardiac microvessels and cardiomyocytes.

OBJECTIVE: Various inflammatory rheumatic diseases (IRDs) are associated with increased mortality due to cardiovascular disease. The aim of this study was to investigate heart biopsy specimens obtained from patients undergoing coronary artery bypass grafting and compare markers of inflammation and endothelial cell activation in the cardiac and skeletal muscle of patients with and those without IRD. METHODS: Paired biopsy specimens of cardiac and skeletal muscle were obtained from 22 consecutive patients with IRD and 8 patients without IRD, all of whom were undergoing coronary artery bypass grafting. The biopsy specimens were evaluated in a blinded manner by conventional microscopy and digital image analysis for cell markers (CD3, CD4, CD8, CD68, CD163, and CD31), HLA (HLA-ABC, HLA-DR, and HLA-DQ), adhesion molecules (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1), and proinflammatory cytokines (interleukin-1alpha, interleukin-1beta, and tumor necrosis factor). RESULTS: Patients with IRD had significantly higher expression of adhesion molecules, proinflammatory cytokines, and all classes of HLA on cardiomyocytes and endothelial cells but no increase on mononuclear cells in the myocardium compared with patients without IRD. Furthermore, cardiac muscle from patients with IRD displayed significantly higher local expression of inflammation and activation of cardiac microvessels compared with skeletal muscle from the same patients. CONCLUSION: Patients with cardiovascular disease had increased expression of adhesion molecules, HLA, and proinflammatory cytokines in heart tissue, indicating local inflammation involving microvessels and cardiomyocytes that could play a role in the pathogenesis of cardiovascular disease. The more pronounced changes in patients with IRD compared with patients without IRD might contribute to the increased risk of cardiovascular disease and premature death in patients with IRD.

A longitudinal, integrated, clinical, histological and mRNA profiling study of resistance exercise in myositis.

Polymyositis and dermatomyositis are orphan, chronic skeletal muscle disorders characterized by weakness, infiltrations by mononuclear inflammatory cells, and fibrosis. Until recently, patients were advised to refrain from physical activity because of fears of exacerbation of muscle inflammation. However, recent studies have shown that moderate exercise training in combination with immunosuppressive drugs can improve muscle performance. Despite the positive effects of exercise training, the molecular mechanisms underlying the exercise-associated clinical improvements remain poorly understood. The present study was designed to define, at the molecular level, the effects of resistance exercise training on muscle performance and disease progression in myositis patients. We evaluated changes in muscle strength, histology and genome-wide mRNA profiles to determine the beneficial effects of exercise and determine the possible molecular changes associated with improved muscle performance. A total of 8 myositis patients underwent a 7-wk resistance exercise training program that resulted in improved muscle strength and increased maximal oxygen uptake (VO(2max)). Training also resulted in marked reductions in gene expression, reflecting reductions in proinflammatory and profibrotic gene networks, changes that were also accompanied by a reduction in tissue fibrosis. Consistent with the exercise-associated increase in VO(2max), a subset of transcripts was associated with a shift toward oxidative metabolism. The changes in gene expression reported in the present study are in agreement with the performance improvements induced by exercise and suggest that resistance exercise training can induce a reduction in inflammation and fibrosis in skeletal muscle.

Mycobacterial heat shock protein 65 (mbHSP65)-induced atherosclerosis: Preventive oral tolerization and definition of atheroprotective and atherogenic mbHSP65 peptides.

OBJECTIVE: The aim of this study was to identify atherogenic and atheroprotective peptides of bacterial HSP60 [taking mycobacterial HSP65 (mbHSP65) as a potent paradigmatic representative] that could be used as candidates for an orally applied tolerizing vaccine against atherosclerosis. METHODS: ApoE(-/-) mice were immunized with mbHSP65 protein or peptides, given mbHSP65 orally and then kept either on chow or high cholesterol diet. Atherosclerosis was assessed by en face and immunohistological analysis. Anti-HSP autoantibodies were detected by ELISA. The number and in vitro suppressive function of splenic and lymph node regulatory T cells (Tregs) were analyzed by flow cytometry. Specific T cell reactivity against mbHSP65 protein or peptides was assessed by proliferation assay. RESULTS: Decreased lesion size was accompanied by (a) increased splenic Treg numbers; (b) increased interleukin (IL)-10 mRNA levels in the aorta; (c) increased levels of anti-mbHSP65 and anti-mouse HSP60 antibodies pointing to pro-eukaryotic HSP60 humoral crossreaction, not curtailed by oral tolerization; (d) most importantly, we identified and functionally characterized novel atherogenic and atheroprotective mbHSP65 epitopes. CONCLUSION: Atheroprotective mbHSP65 peptides may be considered as potential candidates for the development of a tolerizing vaccine to prevent and treat atherosclerosis, while keeping protective immunity to non-atherogenic domains of mbHSP65 intact.

Corticosteroids--from an idea to clinical use.

Corticosteroids form the basis of treatment in many inflammatory rheumatic diseases, both as systemic treatment and as treatment with local injections to reduce inflammation. In 1948 the first systemic treatment of a patient with a rheumatic disease was given to a woman with severe rheumatoid arthritis (RA); the impressive effect in this patient, and in another 15 patients, was reported by Dr Hench and co-workers in 1949. Systemic corticosteroid treatment was rapidly adopted and used not only for patients with RA but also for those with other rheumatic diseases such as systemic lupus erythematosus-as well as other disorders such as asthma-with a similar positive effect. In the following year, 1950, the Nobel Prize was awarded for the discovery of the structure and biological effects of the adrenal cortex hormones. This open trial was followed by several controlled trials conducted in the UK in which the effects of cortisone were compared with the effects of aspirin in patients with RA-interestingly, without any significant clinical benefit for the cortisone-treated patients. It was not until 1959, in yet another multi-centre trial in Britain, that a significant effect on functional capacity and general well-being was reported after 2 years of treatment with prednisolone, compared to aspirin, in patients with early RA. Despite the dramatic effects that were observed in the severely ill RA patients reported by Hench and co-workers it took 10 years to demonstrate that this effect was superior to the effect of aspirin when the two compounds were compared in controlled trials. Why was this so? One explanation could be in the study designs and the different outcome measures used in the various studies. Perhaps the results in the first comparative studies would have been different if individual response criteria had been used. This is discussed in this chapter.

The role of heat shock proteins in atherosclerosis.

Atherosclerosis is a chronic, multifactorial disease that starts in youth, manifests clinically later in life, and can lead to myocardial infarction, stroke, claudication, and death. Although inflammatory processes have long been known to be involved in atherogenesis, interest in this subject has grown in the past 30-40 years. Animal experiments and human analyses of early atherosclerotic lesions have shown that the first pathogenic event in atherogenesis is the intimal infiltration of T cells at arterial branching points. These T cells recognize heat shock protein (HSP)60, which is expressed together with adhesion molecules by endothelial cells in response to classic risk factors for atherosclerosis. Although these HSP60-reactive T cells initiate atherosclerosis, antibodies to HSP60 accelerate and perpetuate the disease. All healthy humans develop cellular and humoral immunity against microbial HSP60 by infection or vaccination. Given that prokaryotic (bacterial) and eukaryotic (for instance, human) HSP60 display substantial sequence homology, atherosclerosis might be the price we pay for this protective immunity, if risk factors stress the vascular endothelial cells beyond physiological conditions.

The time-averaged inflammatory disease activity estimates the progression of erosions in MRI of the sacroiliac joints in ankylosing spondylitis.

A method to estimate the individual ankylosing spondylitis (AS) patient radiological progression of semi-quantitative magnetic resonance imaging (MRI) changes in the sacroiliac joints has not been described yet, which this study examines. Inflammatory disease activity and MRIs of the sacroiliac joints of 38 patients with recent onset established AS were analyzed at baseline and during follow-up. Sacroiliac MRIs were semi-quantitatively assessed using a modification of the "Spondylarthritis Research Consortium of Canada" (SPARCC) method. In each patient, the annual inflammatory disease activity was estimated by the time-averaged C-reactive protein (CRP; mg/l), calculated as the area under the curve. The mean (SD) CRP decreased from 1.3 (1.8) at baseline to 0.5 (0.6) at follow-up MRI (p < 0.04), which has been performed after a mean (SD) disease course of 2.8 (1.5) years. The mean (SD) annual increase (∆) of SPARCC score from baseline to follow-up MRI was 0.4 (0.4). Baseline individual SPARCC sub-score for bone marrow edema did not statistically significantly correlate with individual ∆SPARCC sub-score for erosions (p = N.S.). The individual AS patient correlation between annual time-averaged inflammatory disease activity and each annual ∆SPARCC sub-scores was only statistically significant for erosions (p < 0.01; r = 0.71). Our results show that bone marrow edema and contrast-medium enhancement at baseline do not relate to the progression of erosions but the calculation of the individual patient annual time-averaged inflammatory disease activity allows to estimate the annual progression of erosions in sacroiliac MRIs of patients with AS.

T regulatory cells and TH17 cells in peri-silicone implant capsular fibrosis.

BACKGROUND: The authors investigated the immunological mechanisms underlying extensive peri-silicone implant capsule formation, one of the most frequent postoperative complications in patients receiving silicone mammary implants. METHODS: The authors studied immune response activation by phenotypic and functional characterization of lymphocytes accumulated within this tissue. Intracapsular lymphoid cells and autologous peripheral blood mononuclear cells were isolated and analyzed by flow cytometry. The proportion of T regulatory cells (CD4+ CD25(high) Foxp3+ CD127), the cytokine profiles, and the T cell receptor repertoire of these cells were examined. Intracapsular T regulatory cells were then further analyzed by immunohistochemistry and functional suppression assays. RESULTS: In comparison with peripheral blood, the cellular composition of intracapsular lymphocytes showed a predominance of CD4+ cells. Intracapsular T cells predominantly produced interleukin-17, interleukin-6, interleukin-8, transforming growth factor-ß1, and interferon-γ, suggesting a TH1/TH17-weighted local immune response. Intracapsular T cells displayed a restricted T cell receptor α/ß repertoire. The intact suppressive potential of T regulatory cells was demonstrated in crossover experiments with activated peripheral T cells. They did not, however, suppress intracapsular T cells. Interestingly, ratios of intracapsular T regulatory cells were inversely proportional to the clinical degree of capsular fibrosis. CONCLUSION: The authors' results indicate that silicone implants trigger a specific, antigen-driven local immune response through activated TH1/TH17 cells, suggesting that ensuing fibrosis is promoted by the production of profibrotic cytokines as a consequence of faltering function of local T regulatory cells.

Vascular involvement in the pathogenesis of idiopathic inflammatory myopathies.

The identification of the exact role of the involvement of the vascular system in the pathogenesis of idiopathic inflammatory myopathies (IIMs) has been the task of several scientific investigations during the recent years. The observations that microcirculatory disturbances might play a major-if not perhaps the primary-role in IIMs have gained wide recognition among the scientific community and led to different experimental and clinical attempts to study the role of microvessels in IIMs. During the past years, the 'Vascular Hypothesis' of the pathogenesis of IIMs has been co-developed in our laboratory supported by experimental and clinical data. This hypothesis is based on assumptions that phenotypically altered microvessels might affect the local circulation of the muscle and hence lead to the development of tissue hypoxia and metabolic alterations. Subsequently, local hypoxia in muscle tissue could lead to muscle weakness and muscle fatigue, which are the most prominent clinical signs in IIM patients. This hypothesis is further supported by the reported benefits of physical exercise and associated molecular alterations in muscle in patients with IIMs. This review will highlight some of the most important findings that elucidate the role of vascular endothelial cell dysfunction and hypoxia in the pathogenesis of IIMs.

Upregulation of MHC class I in transgenic mice results in reduced force-generating capacity in slow-twitch muscle.

Expression of major histocompatibility complex (MHC) class I in skeletal muscle fibers is an early and consistent finding in inflammatory myopathies. To test if MHC class I has a primary role in muscle impairment, we used transgenic mice with inducible overexpression of MHC class I in their skeletal muscle cells. Contractile function was studied in isolated extensor digitorum longus (EDL, fast-twitch) and soleus (slow-twitch) muscles. We found that EDL was smaller, whereas soleus muscle was slightly larger. Both muscles generated less absolute force in myopathic compared with control mice; however, when force was expressed per cross-sectional area, only soleus muscle generated less force. Inflammation was markedly increased, but no changes were found in the activities of key mitochondrial and glycogenolytic enzymes in myopathic mice. The induction of MHC class I results in muscle atrophy and an intrinsic decrease in force-generation capacity. These observations may have important implications for our understanding of the pathophysiological processes of muscle weakness seen in inflammatory myopathies. Muscle Nerve, 2008.

Impaired myofibrillar function in the soleus muscle of mice with collagen-induced arthritis.

OBJECTIVE: Progressive muscle weakness is a common feature in patients with rheumatoid arthritis (RA). However, little is known about whether the intrinsic contractile properties of muscle fibers are affected in RA. This study was undertaken to investigate muscle contractility and the myoplasmic free Ca2+ concentration ([Ca2+](i)) in the soleus, a major postural muscle, in mice with collagen-induced arthritis (CIA). METHODS: Muscle contractility and [Ca2+](i) were assessed in whole muscle and intact single-fiber preparations, respectively. The underlying mechanisms of contractile dysfunction were assessed by investigating redox modifications using Western blotting and antibodies against nitric oxide synthase (NOS), superoxide dismutase (SOD), 3-nitrotyrosine (3-NT), carbonyl, malondialdehyde (MDA), and S-nitrosocysteine (SNO-Cys). RESULTS: The tetanic force per cross-sectional area was markedly decreased in the soleus muscle of mice with CIA, and the change was not due to a decrease in the amplitude of [Ca2+](i) transients. The reduction in force production was accompanied by slowing of the twitch contraction and relaxation and a decrease in the maximum shortening velocity. Immunoblot analyses showed a marked increase in neuronal NOS expression but not in inducible or endothelial NOS expression, which, together with the observed decrease in SOD2 expression, favors peroxynitrite formation. These changes were accompanied by increased 3-NT, carbonyl, and MDA adducts content in myofibrillar proteins from the muscles of mice with CIA. Moreover, there was a significant increase in SNO-Cys content in myosin heavy-chain and troponin I myofibrillar proteins from the soleus muscle of mice with CIA. CONCLUSION: These findings show impaired contractile function in the soleus muscle of mice with CIA and suggest that this abnormality is due to peroxynitrite-induced modifications in myofibrillar proteins.

Developments in the scientific and clinical understanding of inflammatory myopathies.

The idiopathic inflammatory myopathies are chronic autoimmune disorders sharing the clinical symptom of muscle weakness and, in typical cases, inflammatory cell infiltrates in muscle tissue. During the last decade, novel information has accumulated supporting a role of both the innate and adaptive immune systems in myositis and suggesting that different molecular pathways predominate in different subsets of myositis. The type I interferon activity is one such novel pathway identified in some subsets of myositis. Furthermore, nonimmunological pathways have been identified, suggesting that factors other than direct T cell-mediated muscle fibre necrosis could have a role in the development of muscle weakness.