Klaus W. Frommer

Update on the profile of the EUSTAR cohort: an analysis of the EULAR Scleroderma Trials and Research group database

Objectives Systemic sclerosis (SSc) is a rare disease requiring multicentre collaboration to reveal comprehensive details of disease-related causes for morbidity and mortality. Methods The European League Against Rheumatism (EULAR) Scleroderma Trials and Research (EUSTAR) group initiated a database to prospectively gather key data of patients with SSc using a minimal essential dataset that was reorganised in 2008 introducing new items. Baseline visit data of patients who were registered between 2004 and 2011 were analysed using descriptive statistics. Results In June 2011, 7655 patients (2838 with diffuse cutaneous (dc) and 4481 with limited cutaneous (lc) SSc who fulfilled the American College of Rheumatology diagnostic criteria had been registered in 174 centres, mainly European. The most prominent hallmarks of disease were Raynauds phenomenon (96.3%), antinuclear antibodies (93.4%) and a typical capillaroscopic pattern (90.9%). Scleroderma was more common on fingers and hands than on any other part of the skin. Proton pump inhibitors (65.2%), calcium channel blockers (52.7%), and corticosteroids (45.3%) were most often prescribed. Among the immunosuppressant agents, cyclophosphamide was used more often in dcSSc than in lcSSc. Conclusions The EUSTAR database provides an abundance of information on the true clinical face of SSc that will be helpful in improving the classification of SSc and its subsets and for developing more specific therapeutic recommendations.

Adiponectin-mediated changes in effector cells involved in the pathophysiology of rheumatoid arthritis

OBJECTIVE Rheumatoid arthritis (RA) is associated with increased production of adipokines, which are cytokine-like mediators that are produced mainly in adipose tissue but also in synovial cells. Since RA synovial fibroblasts (RASFs), lymphocytes, endothelial cells, and chondrocytes are key players in the pathophysiology of RA, this study was undertaken to analyze the effects of the key adipokine adiponectin on proinflammatory and prodestructive synovial effector cells. METHODS Lymphocytes were activated in part prior to stimulation. All cells were stimulated with adiponectin, and changes in gene and protein expression were determined by Affymetrix and protein arrays. Messenger RNA and protein levels were confirmed using semiquantitative reverse transcription-polymerase chain reaction (PCR), real-time PCR, and immunoassays. Intracellular signal transduction was evaluated using chemical signaling inhibitors. RESULTS Adiponectin stimulation of human RASFs predominantly induced the secretion of chemokines, as well as proinflammatory cytokines, prostaglandin synthases, growth factors, and factors of bone metabolism and matrix remodeling. Lymphocytes, endothelial cells, and chondrocytes responded to adiponectin stimulation with enhanced synthesis of cytokines and various chemokines. Additionally, chondrocytes released increased amounts of matrix metalloproteinases. In RASFs, adiponectin-mediated effects were p38 MAPK and protein kinase C dependent. CONCLUSION Our previous findings indicated that adiponectin was present in inflamed synovium, at sites of cartilage invasion, in lymphocyte infiltrates, and in perivascular areas. The findings of the present study indicate that adiponectin induces gene expression and protein synthesis in human RASFs, lymphocytes, endothelial cells, and chondrocytes, supporting the concept of adiponectin being involved in the pathophysiologic modulation of RA effector cells. Adiponectin promotes inflammation through cytokine synthesis, attraction of inflammatory cells to the synovium, and recruitment of prodestructive cells via chemokines, thus promoting matrix destruction at sites of cartilage invasion.

Adipocytokines as Driving Forces in Rheumatoid Arthritis and Related Inflammatory Diseases

Adipose tissue is ubiquitously present in the human organism. It is a structural component of many organs including the skin, the intestinal tract, and the joints. Besides its central function in energy metabolism, adipose tissue usually serves as a bolster in gaps or intersections between tissues. The dominant cell type, adipocytes, secretes highly bioactive substances, the socalled adipokines or adipocytokines (Table 1). Adipokines include a growing number of pluripotent factors such as adiponectin, resistin, leptin, and visfatin/pre–B cell colony-enhancing factor (PBEF) (1,2). Table 2 provides an overview of several characteristics of these adipokines, and their respective functional aspects are discussed below. There is also increasing evidence that adipocytes actively secrete additional proinflammatory factors operative in the pathophysiology of inflamed joints, such as tumor necrosis factor (TNF ), interleukin-6 (IL-6), factors of the complement system, growth factors, and adhesion molecules (2–4). Moreover, adipokines are able to actively modulate inflammation and the innate immune system (1,5). In this review, the current knowledge about the influence of central adipokines in rheumatic diseases, highlighting several aspects of the role of adipokines in chronic inflammation, is summarized.

Adiponectin isoforms: a potential therapeutic target in rheumatoid arthritis?

Objectives Several clinical studies have suggested the adipocytokine adiponectin is involved in the progression of rheumatoid arthritis (RA). From this point of view, adiponectin might present a new therapeutic target. However, as adiponectin also exerts beneficial effects in the human organism, a strategy that would allow its detrimental effects to be abolished while maintaining the positive effects would be highly favourable. To elucidate such a strategy, the authors analysed whether the different adiponectin isoforms induce diverging effects, especially with regard to rheumatoid arthritis synovial fibroblasts (RASF), a central cell type in RA pathogenesis capable of invading into and destroying cartilage. Methods Affymetrix microarrays were used to screen for changes in gene expression of RASF. Messenger RNA levels were quantified by real-time PCR, protein levels by immunoassay. The migration of RASF and primary human lymphocytes was analysed using a two-chamber migration assay. Results In RASF, the individual adiponectin isoforms induced numerous genes/proteins relevant in RA pathogenesis to clearly different extents. In general, the most potent isoforms were the high molecular weight/middle molecular weight isoforms and the globular isoform, while the least potent isoform was the adiponectin trimer. The chemokines secreted by RASF upon adiponectin stimulation resulted in an increased migration of RASF and lymphocytes. Conclusion The results clearly suggest a pro-inflammatory and joint-destructive role of all adiponectin isoforms in RA pathophysiology, indicating that in chronic inflammatory joint diseases the detrimental effects outweigh the beneficial effects of adiponectin.

Chemerin induces CCL2 and TLR4 in synovial fibroblasts of patients with rheumatoid arthritis and osteoarthritis.

INTRODUCTION Chemerin stimulates migration of leukocytes to sites of inflammation and also increases inflammatory signaling in chondrocytes suggesting a function of chemerin in joint inflammation. Synovial fibroblasts (SF) are critically involved in synovitis and subsequent cartilage destruction. Here, we analyzed whether synovial fibroblasts express chemerin and its receptor CMKLR1. Further, the role of chemerin in synovial fibroblast chemotaxis, proliferation, insulin response and release of inflammatory proteins was studied. METHODS Synovial tissue sections were labeled with chemerin antibody and chemerin was measured in synovial fluid by ELISA. Chemerin mRNA and protein as well as CMKLR1 expression were determined in SFs from patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Effects of chemerin on cytokines, chemokines and matrix metalloproteinases (MMP), and on proliferation, migration and insulin signaling were analyzed appropriately. RESULTS SFs expressed CMKLR1 and chemerin mRNA, and chemerin protein was found in cell supernatants of synovial fibroblasts. Immunohistochemistry detected chemerin in synovial tissue predominantly localized within the lining layer. Chemerin was present in synovial fluids of RA, OA and psoriatic arthritis patients in similar concentrations. Chemerin neither increased IL-6 levels nor MMP-2 or -9 activity in SFs. Also, it did not act as a chemoattractant for these cells. With respect to intracellular signaling, neither basal nor insulin-mediated phosphorylation of Akt was affected. However, chemerin significantly increased TLR4 mRNA and synthesis of CCL2 in SFs while CCL4 and -5 were not altered. Cell proliferation of SFs, however, was modestly reduced by chemerin. CONCLUSIONS These data show that human SFs express both chemerin and its receptor. As chemerin enhanced expression of TLR4 and induced release of CCL2 in SFs, a role of this protein in innate immune system-associated joint inflammation is proposed.

Free fatty acids: potential proinflammatory mediators in rheumatic diseases

OBJECTIVES Due to their role in inflammatory metabolic diseases, we hypothesised that free fatty acids (FFA) are also involved in inflammatory joint diseases. To test this hypothesis, we analysed the effect of FFA on synovial fibroblasts (SF), human chondrocytes and endothelial cells. We also investigated whether the toll-like receptor 4 (TLR4), which can contribute to driving arthritis, is involved in FFA signalling. METHODS Rheumatoid arthritis SF, osteoarthritis SF, psoriatic arthritis SF, human chondrocytes and endothelial cells were stimulated in vitro with different FFA. Immunoassays were used to quantify FFA-induced protein secretion. TLR4 signalling was inhibited extracellularly and intracellularly. Fatty acid translocase (CD36), responsible for transporting long-chain FFA into the cell, was also inhibited. RESULTS In rheumatoid arthritis synovial fibroblasts (RASF), FFA dose-dependently enhanced the secretion of the proinflammatory cytokine IL-6, the chemokines IL-8 and MCP-1, as well as the matrix-degrading enzymes pro-MMP1 and MMP3. The intensity of the response was mainly dependent on the patient rather than on the type of disease. Both saturated and unsaturated FFA showed similar effects on RASF, while responses to the different FFA varied for human chondrocytes and endothelial cells. Extracellular and intracellular TLR4 inhibition as well as fatty acid transport inhibition blocked the palmitic acid-induced IL-6 secretion of RASF. CONCLUSIONS The data show that FFA are not only metabolic substrates but may also directly contribute to articular inflammation and degradation in inflammatory joint diseases. Moreover, the data suggest that, in RASF, FFA exert their effects via TLR4 and require extracellular and intracellular access to the TLR4 receptor complex.

Serum adipokine levels in patients with ankylosing spondylitis and their relationship to clinical parameters and radiographic spinal progression.

Adipokines have metabolic and inflammatory functions but can also affect bone metabolism. The purpose of this study was to determine the relationship between serum levels of adiponectin, resistin, and visfatin and markers of inflammation, disease activity, and radiographic spinal progression in patients with ankylosing spondylitis (AS).

Visfatin/Pre-B-cell Colony-enhancing Factor (PBEF), a Proinflammatory and Cell Motility-changing Factor in Rheumatoid Arthritis

Background: The adipokine visfatin exerts proinflammatory effects in synovial fibroblasts of patients with rheumatoid arthritis (RA). Results: Visfatin induces high amounts of chemokines, creating a microenvironment of enhanced fibroblast motility. Conclusion: Visfatin is therefore very capable of contributing to the inflammatory state of RA. Significance: Enlightening visfatin pathophysiology may lead to possible therapeutic targeting in the future. Adipokines such as adiponectin and visfatin/pre-B-cell colony-enhancing factor (PBEF) have been recently shown to contribute to synovial inflammation in rheumatoid arthritis (RA). In this study, we evaluated the pathophysiological implication of visfatin/PBEF in the molecular patterns of RA synovial tissue, focusing on RA synovial fibroblasts (RASFs), key players in RA synovium. Expression of visfatin/PBEF in synovial fluid and tissue of RA patients was detected by immunoassays and immunohistochemistry. RASFs were stimulated with different concentrations of visfatin/PBEF over varying time intervals, and changes in gene expression were evaluated at the RNA and protein levels using Affymetrix array, real-time PCR, and immunoassays. The signaling pathways involved were identified. The influence of visfatin/PBEF on fibroblast motility and migration was analyzed. In RA synovium, visfatin/PBEF was predominantly expressed in the lining layer, lymphoid aggregates, and interstitial vessels. In RASFs, visfatin/PBEF induced high amounts of chemokines such as IL-8 and MCP-1, proinflammatory cytokines such as IL-6, and matrix metalloproteinases such as MMP-3. Phosphorylation of p38 MAPK was observed after visfatin/PBEF stimulation, and inhibition of p38 MAPK showed strong reduction of visfatin-induced effects. Directed as well as general fibroblast motility was increased by visfatin/PBEF-induced factors. The results of this study indicate that visfatin/PBEF is involved in synovial fibroblast activation by triggering fibroblast motility and promoting cytokine synthesis at central sites in RA synovium.

Adipokines in bone disease

Adipose tissue secretes highly bioactive factors, the adipokines. Systemic levels of adipokines are often altered in the presence of inflammation. In turn, adipokines affect different tissues and cells systemically as well as locally, contributing to immunomodulatory and bone remodelling mechanisms. The role of adipokines has been evaluated in chronic inflammatory diseases, such as rheumatoid arthritis, as well as in primarily degenerative joint diseases, such as osteoarthritis, particularly with regard to their levels of expression and their effects on joint tissues including synovial membrane, cartilage and bone. Distinct adipokines have been found to modulate matrix remodelling as well as inflammatory responses. In this Review, we summarize current knowledge relating to adipokines in rheumatic diseases, with a particular focus on the effects of adipokines on bone remodelling.

Expression of adipokines in osteoarthritis osteophytes and their effect on osteoblasts.

OBJECTIVE Osteophyte formation in osteoarthritis (OA) is mediated by increased osteoblast activity, which is -in turn- regulated by the Wnt signaling pathway. Obesity is regarded a risk factor in OA, yet little is known about the interaction between adipose tissue-derived factors, the adipokines, and bone formation, although adipokines are associated with the pathogenesis of OA. Therefore, the effect of adipokines on bone and cartilage forming cells and osteophyte development was analyzed. METHODS Human OA osteophytes were histologically characterized and adipokine expression was evaluated by immunohistochemistry. Osteoblasts and chondrocytes were isolated from OA tissue and stimulated with adiponectin, resistin, or visfatin. Cytokine and osteoblast/chondrocyte markers were quantified and activation of Wnt and p38 MAPK signaling was analyzed. RESULTS Adiponectin, resistin, and visfatin were expressed in OA osteophytes by various articular cell types. Stimulation of OA osteoblasts with adiponectin and of OA chondrocytes with visfatin led to an increased release of proinflammatory mediators but not to osteoblast differentiation or activation. Additionally, visfatin increased matrix degrading factors in chondrocytes. Wnt signaling was not altered by adipokines, but adiponectin induced p38 MAPK signaling in osteoblasts. CONCLUSION Adipokines are present in OA osteophytes, and adiponectin and visfatin increase the release of proinflammatory mediators by osteoblasts and chondrocytes. The effects of adiponectin were mediated by p38 MAPK but not Wnt signaling in osteoblasts. Therefore, the results support the idea that adipokines do not directly influence osteophyte development but the proinflammatory conditions in OA.