Resveratrol inhibits TNF-α-induced IL-1β, MMP-3 production in human rheumatoid arthritis fibroblast-like synoviocytes via modulation of PI3kinase/Akt pathway

miR-375 regulates the canonical Wnt pathway through FZD8 silencing in arthritis synovial fibroblasts

Whether the rheumatoid arthritis (RA) pathogenesis is regulated by microRNA (miRNA) is not entirely clear. In this study, we found that miR-375 was down-regulated significantly in fibroblast-like synoviocytes (FLS) in adjuvant-induced arthritis (AIA) rat model compared with control. Because the web-based software TargetScan and PicTar predict Frizzled 8 (FZD8) as the target of miR-375, we investigated whether up-regulated miR-375 plays a role in the activation of the canonical Wnt signaling by targeting the FZD8. Furthermore, the purpose of the present experiments was also to determine the role of miR-375 in the pathogenesis of AIA rat model and to ascertain the effects of FZD8 in this process. Real time qPCR, Western blotting, ELISA and ChIP assay were used to assess the inhibited role of miR-375 in the pathogenesis of AIA rat model and the canonical Wnt signaling. RNA interference was also used to detect the role of knockdown of dephosphorylated β-catenin. Luciferase reporter gene and related methods were performed to determine the FZD8 as the target of miR-375. The increased miR-375 inhibited the pathogenesis of AIA rat model as indicated by decreases in the several disease markers, such as MMP3 and fibronectin. Interestingly, miR-375 also inhibited the canonical Wnt signaling, and the stabilized form of β-catenin blocked the miR-375 effects. FZD8 was identified as the target of miR-375 in AIA rat model by the firefly luciferase reporter gene. In summary, our results demonstrate that miR-375 regulates the pathogenesis of AIA rat model through the canonical Wnt signaling pathway. This discovery may provide new targets for therapeutic intervention to benefit RA patients.

MicroRNA-152 modulates the canonical Wnt pathway activation by targeting DNA methyltransferase 1 in arthritic rat model

Rheumatoid arthritis (RA) is an autoimmune and progressive systemic disease of unknown etiology. Research shows that fibroblast-like synoviocytes (FLS) participate in the cartilage erosion, synovial hyperplasia, inflammatory cytokine secretion and suggests that fibroblast-like synoviocytes (FLS) display a crucial role in RA pathogenesis. Recent studies have suggested the role of the Wnt signaling pathway in the pathogenesis of RA. In previous study, we identified that increased methyl-CpG-binding protein 2 (MeCP2) reduced the secreted frizzled-related protein 4 (SFRP4) expression in FLS in Arthritic rat model and the DNA methyltransferase (DNMT) inhibitor 5-Aza-2'-deoxycytidine (5-azadC) could induce the SFRP4 expression, indicating that DNMT has a key role in the differential expression of SFRP4. MicroRNAs (MiRNAs), which are small non-coding RNAs, are involved in diverse biological functions, regulation of gene expression, pathogenesis of autoimmune disease and carcinogenesis. In light of the directly down-regulation of miR-152 on DNMT1 expression by targeting the 3' untranslated regions of its transcript in nickel sulfide (NiS)-transformed human bronchial epithelial cells, we investigated whether miR-152 is aberrantly expressed and targets DNMT1 in FLS in Arthritic rat model. Our results demonstrated that the expression of miR-152 was specifically down-regulated in Arthritic rat model, whereas up-regulation of miR-152 in FLS resulted in a marked reduction of DNMT1 expression. Further experiments revealed that increased miR-152 indirectly up-regulated the SFRP4 expression, a negative regulator of WNT signaling pathway, by targeting the DNMT1. Moreover, activation of miR-152 expression in FLS could inhibit the canonical Wnt pathway activation and result in a significant decrease of FLS proliferation. MiR-152 and DNA methylation may provide molecular mechanisms for the activation of canonical Wnt pathway in RA. Combination of miR-152 and DNMT1 may be a promising treatment strategy for RA patients in which SFRP4 is inactivated.

Epigenetic-based immune intervention for rheumatic diseases

Rheumatic disease is a large spectrum of heterogeneous conditions affecting the loco-motor system including joints, muscles, connective tissues, and soft tissues around the joints and bones. Many rheumatic diseases have an element of autoimmunity including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Aberrant epigenetic regulation of gene expression is emerging as a major factor within rheumatic disease, and indicates potential new therapeutic avenues of approach to these debilitating conditions. Understanding the precise role of epigenetics in the development and treatment of rheumatic diseases particularly those which have an associated autoimmune element may be important for the long-term management of such conditions.

Anti-inflammatory effect of resveratrol on adjuvant arthritis rats with abnormal immunological function via the reduction of cyclooxygenase-2 and prostaglandin E2

Rheumatoid arthritis (RA) is a chronic inflammatory disease with unknown etiology. The present study investigated the anti-inflammatory effect of resveratrol on rats with adjuvant arthritis (AA) with abnormal immunological function via the reduction of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). AA model rats were established by injection of complete Freund's adjuvant and alterations in the rats secondary paw swelling and the polyarthritic scores were observed. Pathological examination of joint tissues was observed by hematoxylin and eosin staining. The proliferation of spleen cells was examined using a 3-(4,5-dimethylthiazol-2‑yl)-2,5-diphenyltetrazolium bromide assay in vitro. The protein expression of COX-2 in the synovial tissues was detected by western blotting. The level of PGE2 in the serum was assayed using an ELISA kit. The results demonstrated that resveratrol (10 or 50 mg/kg) was able to significantly reduce paw swelling and decrease the arthritis scores. Compared with the AA model rats, a significant reduction in the proliferation of concanavalin A-stimulated spleen cells was observed, articular cartilage degeneration with synovial hyperplasia and inflammatory cell infiltration was suppressed and the production of COX-2 and PGE2 in AA rats was reduced by treatment with resveratrol. These results suggest that resveratrol has significant anti-inflammatory effects on AA rats, which may be associated with the reduction of COX-2 and PGE2 inflammatory mediators.

Infliximab reverses suppression of cholesterol efflux proteins by TNF-α: a possible mechanism for modulation of atherogenesis

Tumor necrosis factor- (TNF-) α is a proinflammatory proatherogenic cytokine. Infliximab, an anti-TNF-α monoclonal antibody, is effective in treating rheumatoid arthritis. However, its impact on cardiovascular burden and lipid transport is unclear. The present study investigates the effect of TNF-α and infliximab on reverse cholesterol transport (RCT) proteins. Uptake of modified lipoproteins by macrophages in the vasculature leads to atherogenic foam cell formation. RCT is mediated by proteins including ATP binding cassette transporters A1 (ABCA1), G1 (ABCG1), liver X receptor- (LXR-) α, and 27-hydroxylase. RCT counteracts lipid overload by ridding cells of excess cholesterol. THP-1 human monocytes were incubated with either TNF-α alone or TNF-α with infliximab. Expression of proteins involved in cholesterol efflux was analyzed. TNF-α significantly reduced both ABCA1 and LXR-α mRNA (to 68.5 ± 1.59%, P < 0.05, and 41.2 ± 0.25%, P < 0.01, versus control set as 100%, resp.). Infliximab nullified the TNF-α effect. Results were confirmed by Western blot. Infliximab abolished the increase in foam cells induced by TNF-α. TNF-α treatment significantly reduces ABCA1 and LXR-α expression in monocytes, thus bringing about a proatherogenic state. The anti-TNF drug infliximab, commonly used in rheumatology, restored RCT proteins. This is the first report of an atheroprotective effect of infliximab on RCT in monocytes.

Cytosolic phospholipase A2 regulates TNF-induced production of joint destructive effectors in synoviocytes

INTRODUCTION

Rheumatoid arthritis (RA) is an inflammatory disease of the joint characterized by chronic synovitis causing pain, swelling and loss of function due to destruction of cartilage and bone. The complex series of pathological events occurring in RA is largely regulated via excessive production of pro-inflammatory cytokines, the most prominent being tumor necrosis factor (TNF). The objective of this work was to elucidate possible involvement of group IVA cytosolic phospholipase A2 (cPLA2α) in TNF-induced regulation of synovitis and joint destructive effectors in RA, to evaluate the potential of cPLA2α as a future therapeutic target.

METHODS

The involvement of cPLA2α in tumor necrosis factor (TNF)-induced intracellular signaling cascades in synoviocytes (synovial fibroblast-like cells) was analyzed by arachidonic acid (AA) release assay, synoviocyte enzyme activity assay, gene expression analysis by real-time PCR and ELISA immunoassay for the detection of prostaglandin E2 (PGE2), interleukin 8 (IL8) and stromelysin-1 (MMP3), respectively.

RESULTS

Inhibitors of cPLA2α enzyme activity (AVX002, ATK) significantly reduced TNF-induced cellular release of AA, PGE2, IL8 and MMP3. This reduction was evident both at transcriptional, protein or metabolite levels. Interestingly, cPLA2α inhibition affected several key points of the arachidonyl cascade; AA-release, cyclooxygenase-2 (COX2) expression and PGE2 production. Furthermore, the results suggest that cPLA2α is subject to transcriptional auto-regulation as inhibition of cPLA2α resulted in reduced PLA2G4A gene expression in TNF-stimulated synoviocytes.

CONCLUSIONS

cPLA2α appears to be an important regulator of central effectors of inflammation and joint destruction, namely MMP3, IL8, COX2, and PGE2. Decreased transcription of the PLA2G4A and COX2 genes in response to cPLA2α enzyme inhibition further suggest a self-reinforcing effect of cPLA2α inhibition in response to TNF. Collectively, these results support that cPLA2α is an attractive therapeutic target candidate as its inhibition reduces the production of multiple key pro-inflammatory factors involved in RA pathogenesis.