Regulatory T-cells and GARP expression are decreased in exercise-associated chikungunya viral arthritis flares.

Objective: Chikungunya virus (CHIKV) causes persistent arthritis, and our prior study showed that approximately one third of CHIKV arthritis patients had exacerbated arthritis associated with exercise. The underlying mechanism of exercise-associated chikungunya arthritis flare (EACAF) is unknown, and this analysis aimed to examine the regulatory T-cell immune response related to CHIKV arthritis flares. Methods: In our study, 124 Colombian patients with a history of CHIKV infection four years prior were enrolled and 113 cases with serologically confirmed CHIKV IgG were used in this analysis. Patient information was gathered via questionnaires, and blood samples were taken to identify total live peripheral blood mononuclear cells, CD4+ cells, T regulatory cells, and their immune markers. We compared outcomes in CHIKV patients with (n = 38) vs. without (n = 75) EACAF using t-tests to assess means and the Fisher's exact test, chi-squared to evaluate categorical variables, and Kruskal-Wallis tests in the setting of skewed distributions (SAS 9.3). Results: 33.6% of CHIKV cases reported worsening arthritis with exercise. EACAF patients reported higher global assessments of arthritis disease ranging from 0-100 (71.2 ± 19.7 vs. 59.9 ± 28.0, p=0.03). EACAF patients had lower ratios of T regulatory (Treg)/CD4+ T-cells (1.95 ± 0.73 vs. 2.4 ± 1.29, p = 0.04) and lower percentage of GARP (glycoprotein-A repetitions predominant) expression per Treg (0.13 ± 0.0.33 vs. 0.16 ± 0.24 p= 0.020). Conclusion: These findings suggest relative decreases in GARP expression may indicate a decreased level of immune suppression. Treg populations in patients with CHIKV arthritis may contribute to arthritis flares during exercise, though current research is conflicting.

Lasp1 regulates adherens junction dynamics and fibroblast transformation in destructive arthritis.

The LIM and SH3 domain protein 1 (Lasp1) was originally cloned from metastatic breast cancer and characterised as an adaptor molecule associated with tumourigenesis and cancer cell invasion. However, the regulation of Lasp1 and its function in the aggressive transformation of cells is unclear. Here we use integrative epigenomic profiling of invasive fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) and from mouse models of the disease, to identify Lasp1 as an epigenomically co-modified region in chronic inflammatory arthritis and a functionally important binding partner of the Cadherin-11/ß-Catenin complex in zipper-like cell-to-cell contacts. In vitro, loss or blocking of Lasp1 alters pathological tissue formation, migratory behaviour and platelet-derived growth factor response of arthritic FLS. In arthritic human TNF transgenic mice, deletion of Lasp1 reduces arthritic joint destruction. Therefore, we show a function of Lasp1 in cellular junction formation and inflammatory tissue remodelling and identify Lasp1 as a potential target for treating inflammatory joint disorders associated with aggressive cellular transformation.

Epigenetics of inflammatory arthritis.

PURPOSE OF REVIEW: Aberrant epigenetic changes in DNA methylation, histone marks, and noncoding RNA expression regulate the pathogenesis of many rheumatic diseases. The present article will review the recent advances in the epigenetic profile of inflammatory arthritis and discuss diagnostic biomarkers and potential therapeutic targets. RECENT FINDINGS: Methylation signatures of fibroblast-like synoviocytes not only distinguish rheumatoid arthritis (RA) and osteoarthritis (OA), but also early RA from late RA or juvenile idiopathic arthritis. Methylation patterns are also specific to individual joint locations, which might explain the distribution of joint involvement in some rheumatic diseases. Hypomethylation in systemic lupus erythematosus (SLE) T cells is, in part, because of active demethylation and 5-hydroxymethylation. The methylation status of some genes in SLE is associated with disease severity and has potential as a diagnostic marker. An integrative analysis of OA methylome, transcriptome, and proteome in chondrocytes has identified multiple-evidence genes that might be evaluated for therapeutic potential. Class-specific histone deacetylase inhibitors are being evaluated for therapy in inflammatory arthritis. SUMMARY: Disease pathogenesis is regulated by the interplay of genetics, environment, and epigenetics. Understanding how these mechanisms regulate cell function in health and disease has implications for individualized therapy.

Receptor Protein Tyrosine Phosphatase α-Mediated Enhancement of Rheumatoid Synovial Fibroblast Signaling and Promotion of Arthritis in Mice.

OBJECTIVE: During rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) critically promote disease pathogenesis by aggressively invading the extracellular matrix of the joint. The focal adhesion kinase (FAK) signaling pathway is emerging as a contributor to the anomalous behavior of RA FLS. The receptor protein tyrosine phosphatase α (RPTPα), which is encoded by the PTPRA gene, is a key promoter of FAK signaling. The aim of this study was to investigate whether RPTPα mediates FLS aggressiveness and RA pathogenesis. METHODS: Through RPTPα knockdown, we assessed FLS gene expression by quantitative polymerase chain reaction analysis and enzyme-linked immunosorbent assay, invasion and migration by Transwell assays, survival by annexin V and propidium iodide staining, adhesion and spreading by immunofluorescence microscopy, and activation of signaling pathways by Western blotting of FLS lysates. Arthritis development was examined in RPTPα-knockout (KO) mice using the K/BxN serum-transfer model. The contribution of radiosensitive and radioresistant cells to disease was evaluated by reciprocal bone marrow transplantation. RESULTS: RPTPα was enriched in the RA synovial lining. RPTPα knockdown impaired RA FLS survival, spreading, migration, invasiveness, and responsiveness to platelet-derived growth factor, tumor necrosis factor, and interleukin-1 stimulation. These phenotypes correlated with increased phosphorylation of Src on inhibitory Y(527) and decreased phosphorylation of FAK on stimulatory Y(397) . Treatment of RA FLS with an inhibitor of FAK phenocopied the knockdown of RPTPα. RPTPα-KO mice were protected from arthritis development, which was due to radioresistant cells. CONCLUSION: By regulating the phosphorylation of Src and FAK, RPTPα mediates proinflammatory and proinvasive signaling in RA FLS, correlating with the promotion of disease in an FLS-dependent model of RA.

The JAK inhibitor CP-690,550 (tofacitinib) inhibits TNF-induced chemokine expression in fibroblast-like synoviocytes: autocrine role of type I interferon.

OBJECTIVES: The objective of this study was to investigate the effect of the novel Janus kinase inhibitor CP-690,550 in fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA). METHODS: RA FLSs were isolated from tissue obtained by arthroplasty, cultured and serum-starved 48 h prior to stimulation. Messenger RNA and protein levels were determined by quantitative PCR and ELISA or multiplex bead assay, respectively. Phosphorylation of STAT (signal transducers and activators of transcription) proteins was determined by western blot. RESULTS: Interleukin-6-induced phosphorylation of STAT1 and STAT3 was inhibited by CP-690,550 with IC(50) values of 23 and 77 nM, respectively. Unexpectedly, although tumour necrosis factor (TNF) did not induce immediate phosphorylation of either STAT, CP-690,550 inhibited TNF-induced expression of several chemokines (IP-10, RANTES and MCP1) at the messenger RNA and protein levels. Chemokine expression was inhibited by cycloheximide, implying a need for de novo protein synthesis, and cycloheximide abolished the effect of CP-690,550 (tofacitinib). TNF induced early interferon (IFN) ß expression and STAT1 phosphorylation beginning at 3 h, which was blocked by CP-690,550. The dependence of TNF-induced chemokine expression on type I IFN was confirmed in FLSs from mice lacking type I IFN receptors (IFNARs) and in RA FLSs using an IFNAR blocking antibody. CONCLUSIONS: The Janus kinase/STAT pathway in FLS is indirectly activated by TNF through autocrine expression of type I IFN, resulting in IFNAR engagement and production of T cell chemokines. These findings illuminate a novel role of CP-690,550 in the treatment of RA: the reduction of chemokine synthesis by FLS, thereby limiting recruitment of T cells and other infiltrating leucocytes.

JNK1 controls mast cell degranulation and IL-1{beta} production in inflammatory arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory disease marked by bone and cartilage destruction. Current biologic therapies are beneficial in only a portion of patients; hence small molecules targeting key pathogenic signaling cascades represent alternative therapeutic strategies. Here we show that c-Jun N-terminal kinase (JNK) 1, but not JNK2, is critical for joint swelling and destruction in a serum transfer model of arthritis. The proinflammatory function of JNK1 requires bone marrow-derived cells, particularly mast cells. Without JNK1, mast cells fail to degranulate efficiently and release less IL-1ß after stimulation via Fcγ receptors (FcγRs). Pharmacologic JNK inhibition effectively prevents arthritis onset and abrogates joint swelling in established disease. Hence, JNK1 controls mast cell degranulation and FcγR-triggered IL-1ß production, in addition to regulating cytokine and matrix metalloproteinase biosynthesis, and is an attractive therapeutic target in inflammatory arthritis.

Gadd45beta deficiency in rheumatoid arthritis: enhanced synovitis through JNK signaling.

OBJECTIVE: JNK-mediated cell signaling plays a critical role in matrix metalloproteinase (MMP) expression and joint destruction in rheumatoid arthritis (RA). Gadd45beta, which is an NF-kappaB-regulated gene, was recently identified as an endogenous negative regulator of the JNK pathway, since it could block the upstream kinase MKK-7. This study was carried out to evaluate whether low Gadd45beta expression in RA enhances JNK activation and overproduction of MMPs in RA, and whether Gadd45beta deficiency increases arthritis severity in passive K/BxN murine arthritis. METHODS: Activation of the NF-kappaB and JNK pathways and Gadd45beta expression were analyzed in human synovium and fibroblast-like synoviocytes (FLS) using quantitative polymerase chain reaction, immunoblotting, immunohistochemistry, electrophoretic mobility shift assay, and luciferase reporter constructs. Gadd45beta(-/-) and wild-type mice were evaluated in the K/BxN serum transfer model of inflammatory arthritis, and clinical signs of arthritis, osteoclast formation, and bone erosion were assessed. RESULTS: Expression levels of the Gadd45beta gene and protein were unexpectedly low in human RA synovium despite abundant NF-kappaB activity. Forced Gadd45beta expression in human FLS attenuated tumor necrosis factor-induced signaling through the JNK pathway, reduced the activation of activator protein 1, and decreased the expression of MMP genes. Furthermore, Gadd45beta deficiency exacerbated K/BxN serum-induced arthritis in mice, dramatically increased signaling through the JNK pathway, elevated MMP3 and MMP13 gene expression in the mouse joints, and increased the synovial inflammation and number of osteoclasts. CONCLUSION: Deficient Gadd45beta expression in RA can contribute to activation of JNK, exacerbate clinical arthritis, and augment joint destruction. This process can be mitigated by enhancing Gadd45beta expression or by inhibiting the activity of JNK or its upstream regulator, MKK-7.

Vanadate, an inhibitor of stromelysin and collagenase expression, suppresses collagen induced arthritis.

OBJECTIVE: Collagen induced arthritis (CIA) is a model of chronic inflammatory synovitis with pannus, neovascularization, and joint destruction similar to rheumatoid arthritis (RA). Matrix metalloproteinases (MMP) are involved in degradation of the extracellular matrix and joint destruction in RA. c-fos and c-jun are protooncogenes whose products combine to form activating protein (AP-1), a regulatory protein that is required for cell proliferation and the transcription of a variety of genes, including MMP such as collagenase and stromelysin. Administration of vanadium compounds suppresses c-fos/c-jun expression and AP-1 activity, resulting in inhibition of MMP expression in response to factors such as interleukin 1 (IL-1). We evaluated whether a vanadium AP-1 inhibitor could reduce MMP expression and subsequent joint damage in CIA. METHODS: Vanadate [bis (maltolato) oxovanadium (IV) (BMOV; 10 mg/kg/day)] and the reducing agent N-acetyl cysteine (NAC; 100 mg/kg/day) were given subcutaneously daily in an attempt to suppress established CIA in rats. NAC in combination with vanadate appeared to increase the efficacy of c-fos/c-jun inhibition, while decreasing toxicity. Controls were given NAC alone. Clinical, radiographic, and histologic measures were evaluated as well as synovial MMP and IL-1a expression. RESULTS: BMOV therapy, initiated on the day of onset of clinical arthritis, significantly reduced clinical arthritis within 2 days (p <0.05) compared to controls. Significance was maintained to the termination of the study on Day 18 post-arthritis onset (p < 0.005), with a maximum difference seen on Day 5 (p < 0.00001). Blinded radiographic scores at the completion of the protocols indicated less joint destruction in the experimental group compared to the control group (p < 0.005). Scanning and transmission electron microscopy confirmed the preservation of articular cartilage with therapy. In BMOV-treated rats, synovial mRNA expression of collagenase, stromelysin, and IL-la were reduced by 78%, 58%, and 85%, respectively, compared to controls. CONCLUSION: This is the first study of vanadate as a potential antirheumatic agent. Further study of this AP-1 and MMP inhibitor may lead to new treatment options in RA.

TLR2 signaling in chondrocytes drives calcium pyrophosphate dihydrate and monosodium urate crystal-induced nitric oxide generation.

Microcrystals of calcium pyrophosphate dihydrate (CPPD) and monosodium urate (MSU) deposited in synovium and articular cartilage initiate joint inflammation and cartilage degradation in large part by binding and directly activating resident cells. TLRs trigger innate host defense responses to infectious pathogens, and the expression of certain TLRs by synovial fibroblasts has revealed the potential for innate immune responses to be triggered by mesenchymally derived resident cells in the joint. In this study we tested the hypothesis that chondrocytes also express TLRs and that one or more TLRs centrally mediate chondrocyte responsiveness to CPPD and MSU crystals in vitro. We detected TLR2 expression in normal articular chondrocytes and up-regulation of TLR2 in osteoarthritic cartilage chondrocytes in situ. We demonstrated that transient transfection of TLR2 signaling-negative regulator Toll-interacting protein or treatment with TLR2-blocking Ab suppressed CPPD and MSU crystal-induced chondrocyte release of NO, an inflammatory mediator that promotes cartilage degeneration. Conversely, gain-of-function of TLR2 in normal chondrocytes via transfection was associated with increased CPPD and MSU crystal-induced NO release. Canonical TLR signaling by parallel pathways involving MyD88, IL-1R-associated kinase 1, TNF receptor-associated factor 6, and IkappaB kinase and Rac1, PI3K, and Akt critically mediated NO release in chondrocytes stimulated by both CPPD and MSU crystals. We conclude that CPPD and MSU crystals critically use TLR2-mediated signaling in chondrocytes to trigger NO generation. Our results indicate the potential for innate immunity at the level of the articular chondrocyte to directly contribute to inflammatory and degenerative tissue reactions associated with both gout and pseudogout.

Quantitative biomarker analysis of synovial gene expression by real-time PCR.

Synovial biomarker analysis in rheumatoid arthritis can be used to evaluate drug effect in clinical trials of novel therapeutic agents. Previous studies of synovial gene expression for these studies have mainly relied on histological methods including immunohistochemistry and in situ hybridization. To increase the reliability of mRNA measurements on small synovial tissue samples, we developed and validated real time quantitative PCR (Q-PCR) methods on biopsy specimens. RNA was isolated from synovial tissue and cDNA was prepared. Cell-based standards were prepared from mitogen-stimulated peripheral blood mononuclear cells. Real time PCR was performed using TaqMan chemistry to quantify gene expression relative to the cell-based standard. Application of the cellular standard curve method markedly reduced intra- and inter-assay variability and corrected amplification efficiency errors compared with the C(t) method. The inter-assay coefficient of variation was less than 25% over time. Q-PCR methods were validated by demonstrating increased expression of IL-1beta and IL-6 expression in rheumatoid arthritis synovial samples compared with osteoarthritis synovium. Based on determinations of sampling error and coefficient of variation, twofold differences in gene expression in serial biopsies can be detected by assaying approximately six synovial tissue biopsies from 8 to 10 patients. These data indicate that Q-PCR is a reliable method for determining relative gene expression in small synovial tissue specimens. The technique can potentially be used in serial biopsy studies to provide insights into mechanism of action and therapeutic effect of new anti-inflammatory agents.