The metastasis-associated protein S100A4 promotes the inflammatory response of mononuclear cells via the TLR4 signalling pathway in rheumatoid arthritis

Objectives. S100A4 has been implicated in cancer and several inflammatory diseases, including RA. The aim of the present study was to determine whether S100A4 can stimulate proinflammatory cytokine production in mononuclear cells. Methods. Peripheral blood mononuclear cells (PBMCs) isolated from patients with RA were stimulated with S100A4, S100A8, S100A9 and S100A12. The production of IL-1β, IL-6 and TNF-α was measured by ELISA. Receptor for advanced glycation end products (RAGEs) and Toll-like receptor 4 (TLR4) signalling were examined. For signalling pathway blocking studies, inhibitors of myeloid differentiation primary response gene 88 (MyD88), nuclear factor kappa B (NF-κB) and the mitogen activated protein (MAP) kinases p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and Jun N-terminal kinase (JNK) were used. MAP kinase activation was evaluated by western blotting. Results. Stimulation of PBMCs with S100A4 significantly up-regulated IL-1β, IL-6 and TNF-α production compared with unstimulated cells (P < 0.001). Importantly, the production of these cytokines was markedly enhanced in response to S100A4 compared with S100A8 and S100A12; however, it was less pronounced compared with S100A9. Furthermore, enhanced production of proinflammatory cytokines in S100A4-stimulated PMBCs was at least partly mediated via TLR4, but not RAGEs, and by activation of the transcription factor NF-κB and the MAP kinases p38 and ERK1/2. Conclusion. This is the first study to demonstrate that S100A4 can induce an inflammatory response mediated by TLR4 and by the activation of NF-κB and the kinases p38 and ERK1/2 in mononuclear cells from patients with RA. Therefore S100A4 may be a potential therapeutic target for immune-mediated disease

The metastasis promoting protein S100A4 is increased in idiopathic inflammatory myopathies

Objectives. The S100A4 protein is known as a metastasis promoting factor; however, its involvement in non-malignant diseases such as RA and psoriasis has been recently described. The aim of this study was to investigate the expression and possible role of S100A4 in idiopathic inflammatory myopathies. Methods. S100A4 protein expression was detected by immunohistochemistry in muscle tissue from control individuals (n = 11) and patients with PM and DM (n = 8/6). IF staining was used to co-localize S100A4 with selected cells. Cytokine expression and protein synthesis in S100A4-treated cells were analysed by RT-PCR and ELISA. Results. S100A4 protein was significantly up-regulated in muscle tissue of patients with inflammatory myopathies compared with control individuals and was associated particularly with the presence of mononuclear infiltrates. Only few regenerating muscle fibres in PM/DM expressed S100A4. Then we analysed the effect of S100A4 on human myocytes and peripheral blood mononuclear cells (PBMCs). Although S100A4 did not affect myocytes, stimulation of PBMCs with S100A4 significantly induced the expression and synthesis of TNF-α, IL-1β and IL-6, but not of IFN-α. We showed that S100A4 is not directly involved in perforin/granzyme B-induced apoptosis and that it does not modulate the expression of Bax and Bcl2 mRNA in myocytes and PBMCs. Conclusion. Increased expression of S100A4 in inflamed muscle tissue highlights its potential role in the pathogenesis of inflammatory myopathies. S100A4 may act as a cytokine-like factor indirectly promoting muscle fibre damage by stimulating mononuclear cells to increase the synthesis of pro-inflammatory cytokine

The role of S100 proteins in the pathogenesis of rheumatic diseases

Introduction: Recent findings and better understanding to the pathogenesis of rheumatic diseases contributed to the development of biological therapies targeting cytokines and immune cells. Several S100 proteins exert cytokine-like effects and participate in the regulation of the inflammatory process. The aim of this work was to study the role of selected S100 proteins in the activity and in the pathogenesis of the rheumatic diseases. Results: Our data show for the first time an association of S100A4 proteinwith RA disease activity and decrease of the bioactive form, but not the total amount of S100A4, after aplication of tumour necrosis factor (TNF) blocking biologic therapy in patients with RA. We demonstrated that in vitro S100A4 acts as a potent pro-inflammatory mediator inducing production of TNFα, interleukin (IL)-1β and IL-6 in PBMCs via Toll-like receptor 4 (TLR-4), transcription factor NFκB and tyrosine kinases erk1/2 and p38. Moreover, S100A4 can play an important role in the pathogenesis of inflammatory myopathies. S100A4 is present in the inflammatory infiltrate of the affected muscles and in the regenerating muscles and may act as a cytokine-like factor indirectly promoting muscle fiber damage by stimulating mononuclear cells to increase the synthesis of pro-inflammatory cytokines. We..

Vaspin and omentin: new adipokines differentially regulated at the site of inflammation in rheumatoid arthritis

Scientific interest in adipose tissue-derived peptides has increased dramatically in recent years (1). Several mediators known as adipo(cyto)kines were first associated with the pathophysiology of obesity-related complications; however a significant role for adipokines such as leptin, adiponectin, resistin and visfatin in regulating immune responses and inflammation has recently been discovered (1, 2). Several reports (3-6) have already demonstrated association of these adipokines with the severity of rheumatoid arthritis (RA). Vaspin, a member of the serine protease inhibitor family, and omentin (also known as intelectin) were recently identified in adipose tissue (7, 8). Vaspin is an adipokine with insulin-sensitizing effects that has been suggested to be a compensatory mediator for abrogating obesity and its inflammatory complications (7). Expression of the omentin gene was demonstrated in omental adipose tissue of patients with Crohn's disease, suggesting that it may be implicated in chronic inflammatory diseases (8). The aim of the present report was to compare local concentrations of vaspin and omentin in synovial fluid of RA patients with those in osteoarthritis (OA) patients and to characterize their potential association with the severity of the disease. Synovial fluid was obtained during therapeutic arthrocentesis from 33 patients with RA and 33 patients with knee OA. The disease activity of RA patients was assessed by DAS28. C-reactive protein (CRP), IgM-rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPA) were routinely analyzed from peripheral blood obtained at the time of arthrocentesis. Characteristics of the patients are given in Table 1. Vaspin (AdipoGen Inc. Korea) and omentin (Apotech Corporation) were analyzed in synovial fluid by ELISA assays. Ethical approval was obtained from the local Ethics Committee and all patients provided informed consent. Statistical analysis was performed using GraphPad Prism 5.0 software. To meet a normal distribution, vaspin and omentin concentrations were naturaly logarithmically (log)-transformed. Differences between two independent parameters were determined by Kruskal-Wallis or T-test. The Spearman test was used for correlation of parameters. As shown in figure 1, the mean (SD) levels of vaspin were significantly higher in the synovial fluid of RA patients than in OA patients (-2.439+/-1.226 vs. -3.366+/-1.318 (log) pg/ml; p=0.003), but interestingly the levels of omentin were significantly lower in the synovial fluid of RA patients compared to OA patients (1.491+/-0.948 vs. 1.964+/-0.902 (log) ng/ml; p=0.045). After log-transformation, synovial fluid vaspin, but not omentin, had a tendency to correlate with DAS28 (r=0.320, p=0.070) in RA patients. However, neither vaspin nor omentin correlated with serum CRP or leukocyte counts in synovial fluid. In addition, levels of synovial fluid omentin, but not vaspin, significantly correlated with serum ACPA (r=0.398, p=0.029) and IgM-RF (r=0.592, p<0.001). The levels of synovial fluid vaspin and omentin were not affected by body mass index (BMI) or age of the patients. The mean concentration of synovial fluid vaspin, but not omentin, was twice as high in female as in male patients, but possibly due to the low number of male patients in this study, it failed to reach statistical significance. Our data shows different levels of the new adipokines vaspin and omentin at the site of local inflammation. We demonstrate here for the first time elevated levels of vaspin and reduced levels of omentin in synovial fluid of patients with RA compared with those with OA

Progranulin Is Associated with Disease Activity in Patients with Rheumatoid Arthritis

Objective. Progranulin (PGRN) is implicated in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to assess the relationship between PGRN and disease activity in RA. Methods. PGRN levels were evaluated in patients with RA (n=47) and OA (n=42) and healthy controls (n=41). Immunohistochemical analysis of PGRN in synovial tissues was performed. The association between PGRN and C-reactive protein (CRP), disease activity score (DAS28-CRP), and health assessment questionnaire (HAQ) was studied. Results. Circulating PGRN was elevated in patients with RA and OA compared to healthy controls (227.1±100.2 and 221.5±102.5 versus 128.1±34.7 ng/mL; P<0.001). Synovial fluid levels of PGRN were higher in patients with RA compared to OA (384.5±275.3 versus 241.4±165.2 ng/mL; P=0.002). PGRN expression was significantly upregulated in the synovial tissue of RA patients particularly in the inflammatory infiltrates. Serum PGRN levels correlated with DAS28 (r=0.327, P=0.049) and HAQ score (r=0.323, P=0.032), while synovial fluid PGRN correlated only with HAQ (r=0.310, P=0.043) in patients with RA. PGRN levels were not associated with CRP or autoantibodies. Conclusions. This study demonstrates increased PGRN expression at local sites of inflammation and association between PGRN levels, disease activity, and functional impairment in patients with RA