Interleukin-17 increases the effects of IL-1 beta on muscle cells: arguments for the role of T cells in the pathogenesis of myositis

Clinical features, pathogenesis and treatment of juvenile and adult dermatomyositis

Juvenile and adult dermatomyositis (DM) have multiple commonalities, yet display differing prevalence of features, outcomes and comorbidities. In general, compared with the disease in adults, children with DM have more vasculopathy and a greater likelihood of calcinosis, periungual and gingival telangiectasias, and ulceration, but have a better long-term prognosis with improved survival. Adults with DM are more likely to have myositis-specific antibodies, develop interstitial lung disease, have amyopathic disease, and have a marked association with malignancy and other comorbidities. Both diseases have similar features on muscle biopsy and interferon gene signature, although subtle differences can exist in pathogenesis and pathology, such as more capillary loss and a greater degree of C5b-9 complement deposition in affected muscle of juvenile patients. Initiatives are underway to improve classification, markers of disease activity and ability to predict outcome of juvenile and adult DM. The purpose of this Review is to compare and contrast the unique features between juvenile and adult disease and to outline new initiatives in the field.

Juvenile dermatomyositis: immunopathogenesis, role of myositis-specific autoantibodies, and review of rituximab use

Juvenile dermatomyositis (JDM) is an autoimmune disease of the skin and muscle that affects children. The etiology is poorly understood, but genetic susceptibility, environmental triggers, and abnormal immune responses are each thought to play a part. T cells have traditionally been implicated in the immunopathogenesis of JDM, but dendritic cells, B cells, and microchimerism are increasingly associated. Additionally, myositis-specific autoantibodies (MSA) can be present in the sera of affected patients and may correlate with distinct clinical phenotypes. Given the role of humoral immunity and MSA, there has been recent interest in the use of rituximab to treat JDM. Early results are mixed, but it is hoped that a prospective clinical trial will shed light on the issue in the near future.

Pathogenic aspects of dermatomyositis, polymyositis and overlap myositis

Inflammatory myopathies (IMs) often have distinct histopathologic features suggesting humorally mediated involvement of the microcirculation in dermatomyositis (DM), including early capillary deposition of the complement C5b-9 membranolytic attack complex (MAC) and secondary ischaemic changes; and CD8 T-cell-mediated and MHC1-restricted autoimmune attack of myofibers in polymyositis (PM) and inclusion body myositis. Novel insights in these specific diseases include emerging evidence that capillary loss involves whole microvascular units in DM, and that regulatory T-cells strongly protect myofibers from experimental autotoxic attack in PM. However, all IMs do not exhibit pathophysiology-relevant histopathologic features of DM or PM. Autoimmune necrotizing myopathies (AINM) occur in the absence of endomysial inflammatory cells and may be specifically associated with anti-SRP autoantibodies. Moreover, IM histopathological features may be scarce, unspecific and overlapping. Therefore, increasing attention is paid to features shared by IMs regardless of their type, relevant to the innate immune response and to non-immune mechanisms. Innate immune responses to myodamage (and/or as yet unknown stimuli), involves release of chemokines, activation of specific Toll-like receptors (TLRs) and complex Th-1, Th-17 and other cytokine interplays; it triggers DC recruitment and maturation, and is associated with type 1 IFN signature (especially in DM where type 1 IFN-producing cells called plasmacytoid DCs are mainly detected). Non-immune mechanisms mainly include endoplasmic reticulum (ER) stress induced in myofibers by up-regulation of MHC-class I antigens (as typically observed in PM with a diffuse pattern and in DM with perifascicular predominance). ER stress may favour autoimmune reactions but may also be associated with myofiber damage and dysfunction in the absence of lymphocytes. Overlap myositis (OM) may be associated with other connective tissue diseases and a variety of autoantibodies, such as those directed against tRNA synthetase. Myositis specific autoantibodies are mainly expressed by regenerating myofibers, that may also express MHC-1 and endogenous ligand-binding TLRs, thus drawing a picture in which the regenerating myofiber plays a central pathophysiologic role.

Physical training effects in renal transplant recipients

INTRODUCTION

Several studies demonstrated the benefits of rehabilitation in uraemic patients. This study evaluates physical and psychosocial effects of exercise on renal transplant recipients (RTRs).

PATIENTS AND METHODS

Eight RTRs were evaluated before and after an exercise training consisting of thirty 40-minute sessions, three times a week, performed with the interval training technique.

RESULTS

Hospital Anxiety and Depression Scale (HADS) significantly decreased (p<0.04 and <0.008, respectively). Quality of life mean scores (SF-36 test) significantly increased (p<0.000). No differences were recorded for muscle and fat mass, maximal explosive power of the lower limbs, alkaline and acid phosphatase, parathormone (PTH), myoglobin, lipoprotein-A, glomerular filtration rate (GFR), at rest heart rate, and cardiac troponin. IL-6 decreased from 2.8±0.6 to 1.7±0.5 pg/mL (p<0.01). Resting MAP fell from 112±4 to 99±3 mmHg (p<0.02). The metabolic threshold rose from 33±4 to 43±5% (p<0.033). The blood lactate level at peak exercise increased from 5.2±0.9 to 6.2±0.7 mmol/L (p<0.012). The maximum oxygen uptake increased from 1200±210 to 1359±202 mL/min (p<0.05), iso-load oxygen uptake decreased from 1110±190 to 1007±187 mL/min (p<0.034). The maximum working capacity increased from 90±14 to 115±15 watts (p<0.000).

CONCLUSION

This study suggests that an appropriate dose of physical training is a useful, safe and non-pharmacologic contribution to RTR treatment.

Interleukin-17 and interleukin-23 in patients with polymyositis and dermatomyositis

OBJECTIVE

To analyse the concentration of interleukin (IL)-17 and IL-23 in serum and ex vivo culture supernatant of peripheral blood mononuclear cells (PBMCs) from patients with polymyositis (PM) and dermatomyositis (DM) compared with healthy controls (HC).

METHODS

Enzyme-linked immunosorbent assay (ELISA) was used to analyse the concentration of IL-17 and IL-23 from 25 patients with PM, 21 patients with DM, and 12 HC in serum or ex vivo culture supernatant of PBMCs following stimulation ex vivo with anti-CD3/CD28 for 72 h.

RESULTS

The levels of IL-23 increased in the serum and culture supernatant of patients with PM and patients with DM compared with HC. By contrast, concentrations of IL-17 in supernatants from patients with PM and DM were not significantly higher than those from HC. We subdivided the group of DM and PM patients into those with early disease versus those with established disease and found that the levels of IL-17 and IL-23 were much higher in early stage compared to established disease.

CONCLUSION

We have demonstrated that stimulated PBMCs from DM and PM patients produce increased levels of IL-23 as compared to HC. IL-17 and IL-23 levels are increased in early as compared to established disease. This provides further evidence that IL-17/IL-23 may play a crucial role in autoimmune diseases.

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.

The inflammatory milieu in idiopathic inflammatory myositis

The idiopathic inflammatory myopathies (IIM) are systemic autoimmune diseases that have predominant mononuclear inflammatory cell infiltrates in the skeletal muscle. The cells that are typically involved in the pathogenesis of disease are B-lymphocytes, T-lymphocytes, macrophages, dendritic cells, and natural killer cells. However, in addition to these immune cells, cells of nonimmunologic origin, such as myocytes, may be directly involved in the immune response. The local milieu also consists of distinct cytokine and chemokine profiles considered related to type 1 interferon stimulation. Tumor necrosis factor and interleukin 1 are also prominent, proinflammatory cytokines involved in the evolution of IIM. Although the pathologic processes involved in IIM have yet to be fully elucidated, we understand the inflammatory milieu is a model of dynamic flux made of diverse cytokine and chemokine expressions leading to alterations in muscle fiber structure and function.

Cytokines in idiopathic inflammatory myopathies

Recent findings suggest cytokines as important key molecules in the pathogenic mechanisms of idiopathic inflammatory myopathies, myositis. In this review, we focus on cytokines with a potential role in disease mechanisms in myositis and present some general information on individual cytokines and an updated summary from the literature concerning cytokines in these disorders. The idiopathic inflammatory myopathies is a heterogeneous group of disorders clinically characterized by symmetric proximal muscle weakness and by certain defined histolopathological findings, including inflammatory infiltrates in muscle tissue. Other prominent findings in the target tissue of these patients are defined molecular changes of blood vessels and muscle fibers, including reformation to high endothelial venule (HEV)-like blood vessels and intensive MHC class I expression in muscle fibers. The predominant clinical symptoms of muscle weakness and decreased muscle endurance are shared by all subsets of inflammatory myopathies and indicate that some pathogenic mechanisms related to muscle function may be shared by the different disease groups. Studies on cytokine gene, RNA and protein expression in muscle tissue from patients with various forms of the disease also indicate similar profiles, despite different phenotypes of the inflammatory cells present in muscle tissue from the different subsets of myositis. There is a pronounced expression of various cytokines in muscle tissue, among which the proinflammatory cytokines TNF-alpha and IL-1 are most widely explored in the inflammatory myopathies, which has made them into potential therapeutic targets. The use of targeted cytokine therapy has been successful in several other chronic inflammatory diseases and although the exact role of cytokines in chronic idiopathic inflammatory myopathies remains to be delineated their potential role as targets for new therapies in this disorder will be discussed in this review.

Diseases that may benefit from manipulating the Th17 pathway

The discovery of IL-17 and of the Th17 pathway has been a step in the classification of human diseases. Th17 targeting appears rather straightforward in diseases associated with inflammation and matrix destruction, such as rheumatoid arthritis, psoriasis, and Crohn's disease. In other conditions where IL-17 is expressed and Th17 activated, it is unclear whether this is a primary or secondary event, making the use of Th17 inhibitors less obvious.

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.

Cytokine response in inflammatory myopathies

After background information about pathologic findings, this review focuses on the cytokine response in the pathogenesis of polymyositis and dermatomyositis. Cytokines are important mediators of the immune response and play a key role in these diseases by acting on inflammatory immune cells, muscle cells, and vessel cells. Various cytokines are found in myositis samples, in particular interleukin-1 and tumor necrosis factor-alpha, which are associated with the migration, differentiation, and maturation of inflammatory cells. Recent advances indicate that the muscle cell itself could participate in the inflammatory process. Cytokines promote changes in muscle metabolism resulting in a self-sustaining inflammatory response. Accordingly, cytokines may represent new targets for therapies.

IL-17A versus IL-17F induced intracellular signal transduction pathways and modulation by IL-17RA and IL-17RC RNA interference in AGS gastric adenocarcinoma cells

Inflammatory processes are implicated in gastric cancer development. In contrast, the role of inflammation and proinflammatory cytokines in established cancer remains to be clarified. We investigated the contribution of IL-17A versus IL-17F-mediated intracellular signalling pathways in human gastric adenocarcinoma AGS cells. IL-8 secretion was evaluated by ELISA, mitogen-activated protein kinase (MAPK)(4) by Western blotting, and activator protein 1(AP-1) and nuclear factor kappa B (NFkappaB) by TransAM transcription factor assay or qRT-PCR. IL-17RA and IL-17RC inhibition were achieved by small interfering RNA (siRNA). IL-17A significantly induced activation of all three MAPK (ERK, p38 and JNK) and downstream transcription factors AP-1 and p65 NFkappaB. IL-17F was less potent but induced a significant activation of p65 NFkappaB. Consistently, IL-17A was more potent to induce IL-8 secretion than IL-17F. Inhibition of either IL-17RA or IL-17RC expression via siRNA led to near complete abrogation of IL-17A-mediated c-Jun and p65 activation. These data suggest that in gastric cancer, absence of either IL-17RA or IL-17RC can inhibit IL-17 responsiveness. Conversely, downstream of IL-17R binding, IL-17A and IL-17F induce key signal transduction pathways implicated in inflammation and carcinogenesis. IL-17A, and possibly IL-17F, may contribute to amplification and persistence of inflammatory processes implicated in inflammation-associated cancer.

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.

Inflammatory disorders of muscle: progress in polymyositis, dermatomyositis and inclusion body myositis

PURPOSE OF REVIEW

To provide an update on the major advances in inflammatory myopathies.

RECENT FINDINGS

Polymyositis is an uncommon disorder that can be misdiagnosed when the old, and never validated, criteria of Bohan and Peter are used. New diagnostic criteria were recently introduced, in which the MHC/CD8 complex is considered a specific immunopathological marker because it distinguishes the antigen-driven inflammatory cells that characterize polymyositis and sporadic inclusion-body myositis from the non-specific, secondary inflammation seen in other disorders, such as dystrophies. In sporadic inclusion-body myositis the inflammatory cells invade non-vacuolated fibers, whereas the vacuolated fibers are not invaded by T cells, implying two independent processes, a primary immune process with antigen-driven T cells identical to polymyositis, and a degenerative process in which beta-amyloid and amyloid-related proteins participate in vacuolar degeneration. In polymyositis and sporadic inclusion-body myositis, antigen-specific and clonally expanded autoinvasive T cells persist for years, even in different muscles, as reconfirmed by proof-of-principle techniques involving CDR3 spectratyping combined with laser microdissected single-cell polymerase chain reaction of the T-cell receptor genes. The formation of immunological synapse between autoinvasive T cells and muscle fibers was recently strengthened by the upregulation of co-stimulatory molecules ICOS/ICOS-L and PD-L1. A new, distinct myopathy characterized by T-cell-triggered macrophage hyperactivation has now been recognized in patients with dermatomyositis-like disease.

SUMMARY

Despite recent progress, the antigen(s) responsible for T-cell activation in polymyositis and sporadic inclusion-body myositis and the cause of vacuolar degeneration in sporadic inclusion-body myositis remain unclear. Newer, more aggressive immunotherapies may be encouraging, but control trials are needed to prove efficacy.

Contribution of tumour necrosis factor alpha and interleukin (IL) 1beta to IL6 production, NF-kappaB nuclear translocation, and class I MHC expression in muscle cells: in vitro regulation with specific cytokine inhibitors

OBJECTIVE

To evaluate the effect of tumour necrosis factor alpha (TNFalpha), interleukin (IL) 1beta, and their respective inhibitors the p75 TNFalpha soluble receptor (sTNFR) and the type II sIL1betaR (sIL1RII) on whole muscle and isolated myoblast activation.

METHODS

Normal muscle samples were stimulated for 7 days with TNFalpha alone or in combination with IL1beta, and myoblasts from these samples for 48 hours. IL6 production was measured by ELISA. Nuclear translocation of NF-kappaB was analysed by immunofluorescent staining and class I MHC expression by FACS.

RESULTS

TNFalpha and IL1beta induced IL6 production by normal muscle samples and myoblasts, the action of TNFalpha being more potent on muscle samples. Their soluble receptors (1 microg/ml) decreased this production. Suboptimal concentrations of TNFalpha and IL1beta induced NF-kappaB translocation. sTNFR markedly down regulated TNFalpha-induced translocation while sIL1RII was less potent on IL1beta-induced activation. NF-kappaB translocation induced by the combination of optimal concentrations of TNFalpha and IL1beta was completely inhibited by their soluble receptors. TNFalpha and to a lesser extent IL1beta induced class I MHC expression by myoblasts and this effect was completely inhibited by their respective soluble receptors.

CONCLUSION

These results suggest that TNFalpha and IL1beta should be targeted for myositis treatment.

Cloning and characterization of Swine interleukin-17, preferentially expressed in the intestines

Interleukin-17 (IL-17), initially reported as CTLA-8, is a proinflammatory cytokine produced mainly by activated T cells. In the present study, the cDNA of a swine IL-17 (PoIL-17) gene was cloned from activated neonatal thymocytes, and the recombinant PoIL-17 (rPoIL-17) was biologically characterized. The complete open reading frame (ORF) of PoIL-17 contains 462-bp coding deduced 153 amino acid residues, with a calculated molecular weight of 17.3 kDa. The amino acid sequence showed 72.9%, 64.9%, 64.7%, 60.1%, and 47.4% similarities with that of human, rat, mouse, Herpesvirus saimiri ORF 13, and chicken, respectively. The six cysteine residues conserved over species including the virus were observed in PoIL-17. We successfully prepared the recombinant mature form of PoIL-17 and analyzed its biologic activities for swine splenocytes. RT-PCR analysis revealed a marked upregulation of expression of IL-1beta, IL-8, tumor necrosis factor-alpha (TNF-alpha), granulocyte colony-stimulating factor (G-CSF), and monocyte chemotactic protein-1 (MCP-1) mRNA expression in splenocytes treated with 100 ng/ml rPoIL-17 for 3 h. Furthermore, a swine chemokine, alveolar macrophage-derived neutrophil chemotactic factor II (AMCF-II), which was classified into the CXC subfamily was also augmented in mRNA level. This evidence indicates that recombinat PoIL-17 expressed in Escherichia coli was biologically active and exerted similar effects to those of a human (HuIL-17) and murine IL-17 (MuIL-17). The PoIL-17 mRNA is strongly expressed in the adult heart, skin, and, interestingly, intestinal tissues, including mesenteric lymph nodes but is restricted in neonatal tissues by using real-time quantitative RT-PCR. The gene sequence and biologically active recombinat protein for PoIL-17 will be useful for elucidation of the role of IL-17 in the regulation of intestinal immune responses.

Mechanical loading and injury induce human myotubes to release neutrophil chemoattractants

The purpose of this study was to 1) test the hypothesis that skeletal muscle cells (myotubes) after mechanical loading and/or injury are a source of soluble factors that promote neutrophil chemotaxis and superoxide anion (O(2)(-).) production and 2) determine whether mechanical loading and/or injury causes myotubes to release cytokines that are known to influence neutrophil responses [tumor necrosis factor-alpha (TNF-alpha), IL-8, and transforming growth factor-beta1 (TGF-beta1)]. Human myotubes were grown in culture and exposed to either a cyclic strain (0, 5, 10, 20, or 30% strain) or a scrape injury protocol. Protocols of 5, 10, and 20% strain did not cause injury, whereas 30% strain and scrape injury caused a modest and a high degree of injury, respectively. Conditioned media from strained myotubes promoted chemotaxis of human blood neutrophils and primed them for O(2)(-). production in a manner that was dependent on a threshold of strain and independent from injury. Neutrophil chemotaxis, but not priming, progressively increased with higher magnitudes of strain. Conditioned media only from scrape-injured myotubes increased O(2)(-). production from neutrophils. Concentrations of IL-8 and total TGF-beta1 in conditioned media were reduced by mechanical loading, whereas TNF-alpha and active TGF-beta1 concentrations were unaffected. In conclusion, skeletal muscle cells after mechanical loading and injury are an important source of soluble factors that differentially influence neutrophil chemotaxis and the stages of neutrophil-derived reactive oxygen species production. Neutrophil responses elicited by mechanical loading, however, did not parallel changes in the release of IL-8, TGF-beta1, or TNF-alpha from skeletal muscle cells.

Increased AP-1 and NF-kappaB activation and recruitment with the combination of the proinflammatory cytokines IL-1beta, tumor necrosis factor alpha and IL-17 in rheumatoid synoviocytes

To determine the contribution of IL-1beta, tumor necrosis factor alpha (TNF-alpha) and IL-17 to AP-1, NF-kappaB and Egr-1 activation in rheumatoid arthritis, the effect of the cytokines used alone or in combination was measured on TF expression in rheumatoid synoviocytes. Effects on mRNA expression were measured by RT-PCR and effects on nuclear translocation were measured by immunocytochemistry. To assess the functional consequences of cytokine induction, osteoprotegerin levels were measured in synoviocyte supernatants.IL-1beta and TNF-alpha alone at optimal concentration (100 pg/ml) induced the nuclear translocation of NF-kappaB and almost all AP-1 members, except JunB and Egr-1 for IL-1beta and except Fra-2 and Egr-1 for TNF-alpha. IL-17 was clearly less potent since no nuclear translocation was observed, except for a weak activation of Fra-1 and NF-kappaB. More importantly, when these cytokines were used at low concentrations, their combination showed a synergistic effect on almost all the TFs, except for Egr-1, with a particular effect on Fra-1 and NF-kappaB. Increased recruitment of additional factors was induced when the three cytokines were combined. IL-1 and TNF-alpha induced mRNA expression of c-jun while IL-17 had no effect. A synergistic effect was seen with their combination. A similar synergistic effect was observed for osteoprotegerin production when these three cytokines were combined at low concentrations.AP-1 and NF-kappaB pathways were highly sensitive to the combination through synergistic mechanisms. These effects observed in rheumatoid arthritis synoviocytes may reflect the conditions found in the rheumatoid arthritis joint and may contribute to the mode of action of cytokine inhibitors.

Inducible nitric oxide synthase activation by interleukin-17

Interleukin-17 (IL-17) is a proinflammatory T cell cytokine presumably involved in physiological responses to infection, but also in immunopathology of autoimmune disorders such as rheumatoid arthritis. The proinflammatory action of IL-17 depends considerably on its ability to trigger the expression of inducible nitric oxide (NO) synthase (iNOS), an enzyme responsible for the generation of cytotoxic and immunoregulatory free radical NO. Here we discuss the role of IL-17 in the cytokine network controlling iNOS expression, and analyze signaling pathways employed by IL-17 for the initiation of iNOS gene transcription. We also propose biological consequences of IL-17-mediated NO release that could be relevant for the mechanisms or therapy of autoimmune and inflammatory disorders.