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Abstract

Objective

Adipokines may influence inflammatory and/or immune responses. This study was undertaken to examine whether adiponectin affects the production of prostaglandin E2 (PGE2) by rheumatoid arthritis synovial fibroblasts (RASFs).

Methods

Synovial tissue was obtained from patients with RA who were undergoing joint replacement surgery. Fibroblast-like cells from the third or fourth passage were used as RASFs. Expression of adiponectin receptor messenger RNA (mRNA) and protein was detected. PGE2 (converted from arachidonic acid) was measured by enzyme-linked immunosorbent assay (ELISA). Expression of mRNA and protein for cyclooxygenase 2 (COX-2) and membrane-associated PGE synthase 1 (mPGES-1), key enzymes involved in PGE2 synthesis, was detected in RASFs. The effects of RNA interference (RNAi) targeting the adiponectin receptor genes and the receptor signal inhibitors were examined. The influence of adiponectin on NF-κB activation in RASFs was measured with an ELISA kit.

Results

Adiponectin receptors were detected in RASFs. Adiponectin increased both COX-2 and mPGES-1 mRNA and protein expression by RASFs in a time- and concentration-dependent manner. PGE2 production by RASFs was also increased by the addition of adiponectin, and this increase was inhibited by RNAi for the adiponectin receptor gene, or coincubation with the receptor signal inhibitors. Enhancement of NF-κB activation by adiponectin as well as by interleukin-1β was observed in RASFs.

Conclusion

Our findings indicate that adiponectin induces COX-2 and mPGES-1 expression, resulting in the enhancement of PGE2 production by RASFs. Thus, adiponectin may play a role in the pathogenesis of synovitis in RA patients.