Pathogenesis Of Idiopathic Inflammatory Myopathies Research Articles

A3.29 Micro-RNA molecules are clearly involved in pathogenesis of idiopathic inflammatory myopathy

Background and ObjectivesMicroRNAs can regulate the gene expression and cellular functions such as cell cycle, differentiation, or apoptosis. Emerging evidence has demonstrated that miRNAs play a vital role also in...

Idiopathic inflammatory myopathies – potential role of the immunoexpression of interleukin-35 in muscle biopsy and peripheral blood mononuclear cells

Background Interleukin-35 (IL-35) is a newly described hetero-dimeric cytokine of the IL-12 family. Studies of immunopathogenesis in idiopathic inflammatory myopathies (IIM) are of interest for future biological therapies. Objective To analyze expression of IL-35 in muscle biopsies and to study its effects on peripheral blood mononuclear cells (PBMC) in vitro to assess its pathogenetic and diagnostic value. Materials and methods Immunoexpression of IL-35 subunits (p35, EBI3) was studied immunohistochemically in 23 muscle biopsies of IIM (12 dermatomyositis, 11 polymyositis), 10 noninflammatory myopathies and 10 controls. PBMCs were stimulated with human recombinant IL-35 protein or TNF-α in vitro. Taq-Man RT-PCR was performed to analyze gene expression after 6hours and ELISA assays were used to confirm the protein secretion after 24 hours of stimulation. Results We showed localization of both IL-35 subunits in B-cells, T-cells and macrophages of the inflammatory infiltrates in IIM. No immunoreactivity was observed in controls. We found that gene expression of both IL-35 subunits were dose- and time-dependently induced by TNF-α in PBMCs. Conclusion Our data suggest pro-inflammatory properties of IL-35 and its potential role in the pathogenesis of IIM. The immunohistochemical expression of IL-35 might be also of diagnostic help in muscle biopsy.

The Role of Resistin in Inflammatory Myopathies

Both immune and non-immune mechanisms are involved in muscle damage and dysfunction occurring in idiopathic inflammatory myopathies (IIMs). Crosstalk among inflammatory cells, muscle and endothelial cells is essential in the pathogenesis of IIMs. Resistin, originally described as an adipokine linking obesity and insulin resistance in rodents, has been shown a pro-inflammatory molecule in humans. Besides its direct effect on production of several inflammatory mediators, resistin influences chemotaxis, migration, proliferation, cell survival, endothelial dysfunction and metabolism--all aspects implicated in the pathogenesis of IIMs. Up-regulation of resistin in muscle tissue and elevated serum resistin levels have been recently demonstrated in patients with IIMs. In addition, serum levels of resistin reflected global disease activity, including extramuscular organ involvement, in patients with this disease. However, there are currently not sufficient data to distinguish the features of resistin that cause injury of muscle tissue from those that promote muscle regeneration and repair. The aim of this review is therefore to summarize current knowledge about potential implication of resistin in idiopathic inflammatory myopathies.

Immunoregulation in Idiopathic Inflammatory Myopathies: From Dendritic Cells to Immature Regenerating Muscle Cells

Idiopathic inflammatory myopathies (IIM) are a group of chronic muscle disorders of unknown origin that lead to muscle destruction. The original classification of IIM proposed by Bohan and Peter in 1975 including polymyositis (PM) and dermatomyositis (DM) was recently revised with the development of histopathological approaches and the discovery of myositis-specific and myositis-associated antibodies that led to the characterization of new entities. In addition to PM and adult and juvenile DM, these novel classifications distinguish inclusion-body myositis (IBM), immune-mediated necrotizing myopathy, overlap myositis, and cancer-associated myositis1,2. While distinct immunopathogenic mechanisms may occur in each subset of myositis, all IIM share a common inflammatory background associated with clinical, histological, and serological overlap. Several molecular pathways, such as adaptive and innate immune responses, autoimmunity, and nonimmune mechanisms, could influence the pathogenesis of IIM. However, the exact contribution of each one in the development of distinct phenotypes remains unclear. In this issue of The Journal , Gendek-Kubiak and Gendek highlight the contribution of dendritic cells (DC)3. We summarize here recent insights in myositis immunoregulation from DC that are central in the development of adaptive and innate response to nonimmune mechanisms. ### Dendritic cells DC are crucial for the development of adaptive and innate immune responses. DC, subdivided into myeloid DC (mDC) and plasmacytoid DC (pDC), are present in lymphatic and blood systems and peripheral organs. They are equipped with a range of pattern-recognition receptors (PRR) and serve as sentinels of the immune system. Their activation after stimulation of PRR, such as Toll-like receptors (TLR) or C-type lectin receptors (CLR), by microbial components and/or endogenous ligands leads to their maturation and the development of an effector T cell immune response. In muscle biopsies from IIM, both myeloid and plasmacytoid DC have been detected with differences according to IIM subtypes. The DC … Address correspondence to Dr. A. Tournadre, Department of Rheumatology, Gabriel Montpied Hospital, CHU Clermont-Ferrand, 58 rue Montalembert BP69, 63003 Clermont-Ferrand Cedex 1, France. E-mail: atournadre{at}chu-clermontferrand.fr

BAFF Expression Correlates with Idiopathic Inflammatory Myopathy Disease Activity Measures and Autoantibodies

To investigate B cell survival cytokine messenger RNA (mRNA) levels as biomarkers of idiopathic inflammatory myopathies (IIM). We measured and compared mRNA levels of B cell survival cytokines by quantitative real-time polymerase chain reaction in 98 patients with IIM, 38 patients with systemic lupus erythematosus, and 21 healthy controls. The cytokines were B cell-activating factor belonging to the tumor necrosis factor family (BAFF); ΔBAFF; and a proliferation-inducing ligand (APRIL); and their receptors BAFF-R, transmembrane activator and calcium modulator and cyclophilin ligand interactor, and B cell maturation antigen (BCMA). We also identified autoantibodies, including anti-Sm, anti-RNP, anti-SSA/Ro, anti-SSB/La, anti-topoisomerase 1, anti-hystidyl-tRNA synthetase, anti-ribosomal P, and anti-chromatin. Clinical disease activity was assessed by the International Myositis Assessment and Clinical Studies core set tool. We examined correlation of mRNA with disease activity, medication use, and autoantibodies. We found a positive correlation of BAFF and ΔBAFF expression with 3 disease activity measures, with ΔBAFF having a stronger correlation. Similarly, anti-SSA/Ro-52 and/or anti-SSA/Ro-60 had a strong positive correlation with mRNA levels of BAFF and ΔBAFF, and with relative ratios of BAFF/APRIL and BCMA/BAFF-R. These findings highlight the potential importance of BAFF, ΔBAFF, and BAFF-R in the pathogenesis of IIM, and suggest an important role in the assessment of disease activity.

Update

Establishing diagnoses and distinguishing active disease from chronic injury remain significant clinical challenges in idiopathic inflammatory myopathies (IIM). Recent 'discovery' approaches utilizing novel genomic and proteomic techniques have revealed candidate molecular biomarkers to augment clinical and classical histological data. Whole blood and serum Type 1 interferons (IFN-1) and IFN-1 inducible genes are gaining traction as disease biomarkers in IIM. IFNβ is emerging as a disease activity marker specifically for dermatomyositis. Recently, molecules associated with innate immune-cell function, including TLR-3, high mobility group box (HMGB)-1, B7 Homolog 1, S100A4, and resistin have been detected in tissues of dermatomyositis patients. Serum Interleukin-17 (IL-17) and IL-23 correlate with active disease in early IIM. Antibodies recognizing the Survival Motor Neuron complex have been newly identified in a subset of patients with polymyositis. Protein aggregates are potential disease activity sensors for inclusion body myositis. Skin and lung harbor potential biomarkers for IIM. Recent advances in understanding the pathogenesis of IIM have led to discovery of molecules that are candidate biomarkers of disease activity. Type 1 interferon and myeloid-cell signatures are leading candidate markers for use in IIM activity monitoring.

Role of innate immunity in a murine model of histidyl–transfer RNA synthetase (Jo‐1)–mediated myositis

Previous studies in humans and in animal models support a key role of histidyl-transfer RNA synthetase (HisRS; also known as Jo-1) in the pathogenesis of idiopathic inflammatory myopathy. While most investigations have focused on the ability of HisRS to trigger adaptive immune responses, in vitro studies clearly indicate that HisRS possesses intrinsic chemokine-like properties capable of activating the innate immune system. The purpose of this study was therefore to examine the ability of HisRS to direct innate immune responses in a murine model of myositis. Following intramuscular immunization with soluble HisRS in the absence of exogenous adjuvant, selected strains of mice were evaluated at different time points for histopathologic evidence of myositis. Enzyme-linked immunosorbent assay-based assessment of autoantibody formation and carboxyfluorescein succinimidyl ester proliferation studies provided complementary measures of B cell and T cell responses triggered by HisRS immunization. Compared to appropriate control proteins, a murine HisRS fusion protein induced robust, statistically significant muscle inflammation in multiple congenic strains of C57BL/6 and NOD mice. Time course experiments revealed that this inflammatory response occurred as early as 7 days postimmunization and persisted for up to 7 weeks. Parallel immunization strategies in DO11.10/RAG-2(-/-) and C3H/HeJ (TLR-4(-/-) ) mice indicated that the ability of murine HisRS to drive muscle inflammation was not dependent on B cell receptor or T cell receptor recognition and did not require Toll-like receptor 4 signaling. Collectively, the findings of these experiments support a model in which HisRS can trigger both innate and adaptive immune responses that culminate in severe muscle inflammation that is the hallmark of idiopathic inflammatory myopathy.

Cutting Edge Issues in Polymyositis

Skeletal muscle is the target tissue of immunoflogistic processes in patients affected with idiopathic inflammatory myopathies (IIM). IIM are classified into three major forms: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis. Recent data suggest that, in the major subsets of myositis, antigens in muscles drive a B-cell antigen-specific immune response. Moreover, some non-immunological mechanisms have been advocated. In this regard, an increased expression of Jo-1 and Mi-2 in muscle biopsies from PM and DM patients compared to normal muscle has been demonstrated; these candidate autoantigens in myositis are expressed at high levels in regenerating muscle cells rather than in mature myotubes. Myositis autoantigen upregulation has also been observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Myositis-specific autoantibodies (MSA) are disease markers and target intracellular proteins involved in key processes such as translocation and nuclear transcription. Myositis target antigens encompass aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, the signal recognition particle ribonucleoprotein, together with novel target antigens including p155/140, CADM-140, and SAE. Despite their high specificity for autoimmune myositis, MSA target non-muscle restricted proteins ubiquitary to all cell types, making the specific muscle involvement difficult to explain. Non-immunological mechanisms also seem to contribute to the pathogenesis of IIM; activation of endoplasmic reticulum stress response due to muscle regeneration and inflammation but independent to MHC-1 up-regulation has been recently reported in patients with myositis.

Immunopathogenesis of juvenile dermatomyositis

There is increasing evidence for involvement of the mechanisms of the innate immune system in the pathogenesis of idiopathic inflammatory myopathies (IIMs), especially in the adult and juvenile forms of dermatomyositis. Juvenile dermatomyositis (JDM) is the most common form of childhood IIM, and this review focuses on recent advances in understanding the actions of the innate immune system in this condition. Over the last few years, great strides have been made in understanding immune dysregulation in IIM, including JDM. Novel autoantibodies have been identified, and new genetic contributions have been described. Among the most striking findings is type I interferon activity in JDM tissue and peripheral blood. This is in conjunction with the description of dysregulation of the major histocompatibility complex (MHC) class I gene and identification of plasmacytoid dendritic infiltrates as the possible cellular source of type I interferons. These findings also point toward the potential prognostic value of muscle biopsies and have helped expand our understanding of the etiopathogenesis of IIM.

Association of the leukocyte immunoglobulin G (Fcγ) receptor IIIa‐158V/F polymorphism with inflammatory myopathies in Dutch patients

Leukocytes are involved in the pathogenesis of idiopathic inflammatory myopathies (IIMs). Immunoglobulin G (IgG) receptors (FcgammaR) link the specificity of IgG to the effector functions of leukocytes. Several FcgammaR subclasses display functional polymorphisms that determine in part the vigour of the inflammatory response. FcgammaRIIIa genotypes were differentially distributed among 100 IIM patients compared with 514 healthy controls with a significant increase of the homozygous FcgammaRIIIa-V-158 genotype (3 x 2 contingency table, chi(2) = 6.3, P = 0.04). Odds ratios (ORs) increased at the addition of each FcgammaRIIIa-V-158 allele, in particular among patients with non-specific myositis and dermatomyositis {OR 2.1 [95% confidence interval (CI) 1.1-4.3] and 2.7 (95% CI 1.1-6.4) for FcgammaRIIIa-V/F158 and FcgammaRIIIa-V/V158 genotypes, respectively, using FcgammaRIIIa-F/F158 as a reference group}. These data suggest that the FcgammaRIIIa-V-158 allele may constitute a genetic risk marker for IIM.

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.

Expression of the CD85j (leukocyte Ig‐like receptor 1, Ig‐like transcript 2) receptor for class I major histocompatibility complex molecules in idiopathic inflammatory myopathies

Expression of class I major histocompatibility complex (MHC) molecules on the surface of muscle cells is a biologic feature of idiopathic inflammatory myopathies (IIM). Class I MHC-transgenic mouse models support a causative role for class I MHC expression by muscle cells in the pathogenesis of IIM. The muscle lesions are characterized by leukocyte infiltration. We undertook this study to analyze the expression in muscle lesions of various class I MHC-specific receptors on leukocytes and natural killer (NK) cells. We generated a panel of cell transfectants to control the immunofluorescence analysis of class I MHC receptor expression. We then analyzed the expression of CD158 (killer cell Ig-like receptors [KIRs]) and CD85j (leukocyte Ig-like receptor 1, Ig-like transcript 2) on muscle sections prepared from 14 patients with IIM (5 with dermatomyositis [DM], 5 with polymyositis [PM], and 4 with sporadic inclusion body myositis [IBM]). We could not detect the presence of NK cells in inflammatory lesions. However, the class I MHC receptor CD85j, but no KIRs, was expressed by inflammatory cells infiltrating muscle lesions in IIM. CD85j is expressed in PM and sporadic IBM at the sites of partial invasion and in DM in perivascular inflammation, paving the way for dissecting the role of CD85j in the pathogenesis of inflammatory myopathies.

G.P.17.11 Syrian hamster infected with Leishmania infantum: A new experimental model for inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are inflammatory disorders of unknown origin. On the basis of clinical, histopathlogical and immunological features, they can be differentiated in three major and distinct subsets: dermatomyositis, polymyositis and inclusion-body myositis. The aetiology and pathogenesis of idiopathic inflammatory myopathies remain poorly understood. A few animal models for idiopathic inflammatory myopathies are currently available; however, these models lack of several characteristic aspects of IIMs.

Pathogenesis of myositis in children

There is increasing evidence for involvement of innate immune mechanisms in the pathogenesis of idiopathic inflammatory myopathies. This review focuses on recent advances in understanding these mechanisms in juvenile dermatomyositis, the most common form of childhood inflammatory myopathy. Type I interferon activity in juvenile dermatomyositis has been demonstrated by both global gene expression profiling and immunohistochemical analysis of affected tissues. Most recently, expression of interferon-inducible genes in peripheral blood cells has shown promise as a biomarker for disease activity. The possible pathogenic actions of type I interferons include induction and maintenance of major histocompatibility complex class I expression in affected myofibers, and promotion of local pro-inflammatory cytokine and chemokine production. The cellular source of type I interferons is not clearly defined, though plasmacytoid dendritic cells that constitute a significant component of the inflammatory cell infiltrate are obvious candidates. These cells likely contribute to pathogenesis not only via type I interferon production, but also by regulating other infiltrating inflammatory cells. Type I interferons and plasmacytoid dendritic cells appear to make important contributions to the pathogenesis of juvenile dermatomyositis. Understanding the role of the innate immune system in childhood myositis may lead to novel treatment strategies.

The Expression of Toll-like Receptors in Idiopathic Inflammatory Myopathies

Objective: To investigate the expression of toll-like receptor (TLR)-2, 4 and 9 in idiopathic inflammatory myopathies (IIMs). Methods: The expression of TLR-2, 4 and 9 was measured by real-time RT-PCR and immunohistochemical stain (IHS) from muscle tissues in patients with IIMs and controls. Results: The expression levels of TLR-2, 4 and 9 in IIMs were significantly higher than controls. TLR-2, 4 and 9 were mainly expressed on sarcolemma of muscle fibers, perimysial vascular endothelium and infiltrating inflammatory cells in dermatomyositis, whereas, they were mainly expressed on sarcolemma of muscle fibers, destructed muscle fibers, and enodmysial infiltrating inflammatory cells in polymyositis. Conclusion: TLR-2, 4 and 9 were highly expressed in muscle tissue of IIMs. These results suggest that TLR-2, 4 and 9 play a role in pathogenesis of IIMs.

Immune mechanisms in the pathogenesis of idiopathic inflammatory myopathies

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.

Pathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies, myositis, are characterized by a chronic course with decreased muscle endurance and by infiltrates of T lymphocytes and macrophages in muscle tissue. Treatment with immunosuppressives rarely leads to recovery of muscle function, despite abolishment of inflammatory cell infiltrates in muscle tissue. Therefore, other mechanisms than immune-mediated muscle fiber damage are likely to contribute to the pathogenesis. One such non-immune-mediated muscle dysfunction could be caused by a disturbed microcirculation due to capillary loss or to phenotypically changed endothelial cells in the capillaries. These aberrations may affect the micro-environment of muscle tissue and lead to local tissue hypoxia with development of a secondary metabolic myopathy. Another possible non-immune-mediated mechanism leading to muscle dysfunction is the newly identified endoplasmatic reticulum (ER) stress response in myositis. The ER stress response is thought to be a consequence of the up-regulation of major histocompatibility complex class I in muscle fibers. These newly identified molecular pathways could play a major role in the pathogenesis of myositis and could be important targets in the development of new therapies.

Novel aspects on the contribution of T cells and dendritic cells in the pathogenesis of myositis

This review focuses on recent advances and new hypothesis in the understanding of the T and dendritic cells contribution to the pathogenesis of idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). The new data show that non-specific amplification of muscle inflammation by T lymphocyte and dendritic cells may result from the local production of cytokines and chemokines. Synergistic interactions between these factors explain some of the clinical features. The potent role of these molecules suggests their potential for therapeutic manipulation using specific inhibitors.

Localization of the α-chemokine SDF-1 and its receptor CXCR4 in idiopathic inflammatory myopathies

We studied the distribution of stromal cell-derived factor 1 isoforms α and β, and their receptor CXCR4, in polymyositis, sporadic inclusion body myositis and dermatomyositis using in situ hybridization, immunohistochemistry, immunofluorescence and Western blotting. In control muscle, polymyositis and sporadic inclusion body myositis, stromal cell-derived factor-1α expression was noted in muscle fibers, while stromal cell-derived factor-1β and CXCR4 were predominantly localized to capillaries and arterioles. In dermatomyositis, stromal cell-derived factor-1β immunoreactivity of blood vessels was focally increased. The vast majority of inflammatory cells in idiopathic inflammatory myopathies were CXCR4 positive. A subset of helper T-cells and macrophages expressed stromal cell-derived factor-1α, while only rare inflammatory cells expressed stromal cell-derived factor-1β. A significant increase of stromal cell-derived factor-1α and CXCR4 was observed in protein extracts of idiopathic inflammatory myopathies in comparison with normal controls. The abundance of both CXCR4 and its ligand stromal cell-derived factor-1 implicates their interaction in the pathogenesis of idiopathic inflammatory myopathies and identifies these proteins as possible targets for selective immune therapy.

The role of cytokines, chemokines, and adhesion molecules in the pathogenesis of idiopathic inflammatory myopathies.

Cytokines, chemokines, and adhesion molecules are important mediators in chronic inflammation and in immune regulation. In idiopathic inflammatory myopathies (IIM), increased expression of proinflammatory cytokines particularly interleukin (IL)-1alpha and IL-1beta, tumor necrosis factor (TNF)-alpha and macrophage inflammatory proteins (MIP)-1alpha, as well as of the inhibitory cytokines transforming growth factor (TGF)-beta was observed in muscle. There was no difference in cytokine and chemokine pattern between polymyositis, dermatomyositis, and inclusion body myositis, which could indicate that similar pathogenetic mechanisms are involved in these subsets of myositis. A prominent finding of IL-1alpha expression in endothelial cells, both in patients with active inflammation and in patients with chronic persisting muscle weakness without inflammation, makes this an interesting molecule in understanding the mechanisms for the pathogenesis of muscle weakness. Involvement of the blood vessels in the pathogenesis of myositis was further supported by increased expression of adhesion molecules and by a phenotypical expression of endothelial cells, resembling high endothelium venules in all three subsets of IIM. The molecular studies to date indicate a role of the microvessels in the pathogenesis of IIM not only in DM, as was previously suggested, but also in PM and IBM. The studies also indicate that IL-1alpha could be a target molecule for new therapeutical interventions.