Transforming growth factor beta 1(TGF-β1) down-regulates TNFα-induced RANTES production in rheumatoid synovial fibroblasts through NF-κB-mediated transcriptional repression

Transforming growth factor (TGF)-β1 is a pleiotropic cytokine with many functions, including those related to growth modulation, immunosuppression, and pro-inflammation, in a wide variety of cell types. In this study, we investigated the ability of TGF-β1 to regulate RANTES production by activated rheumatoid synovial fibroblasts. Fibroblast-like synoviocytes (FLS) were cultured in the presence of TGF-β1 and IL-1β, IL-15, TNFα, or IL-17, and the secretion of RANTES into culture supernatants was measured by enzyme-linked immunosorbent assay (ELISA). Expression of RANTES encoded mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR), and NF-κB binding activity for RANTES transcription was determined by electrophoretic mobility shift assay (EMSA). We found that the concentrations of RANTES in synovial fluid (SF) from rheumatoid arthritis (RA) patients were lower than in SF from osteoarthritis (OA) patients, whereas the concentrations of TGF-β1 were higher in RA SF than in OA SF. TGF-β1 dose-dependently inhibited TNFα-induced production of RANTES protein and mRNA from RA FLS. Addition of RA SF with high-level TGF-β1 mimicked the effect of TGF-β1 on TNFα-induced RANTES production, which was inhibited by treatment with anti-TGF-β1 neutralizing antibody. TGF-β1 blocked the degradation of cytosolic IκB-α and the translocation of activated NF-κB to the nucleus. EMSA showed that the inhibitory effect of TGF-β1 was associated with decreased binding of NF-κB to the RANTES promoter. These results suggest that elevated TGF-β1 in rheumatoid synovial tissue may suppress joint inflammation by inhibiting RANTES secretion from synovial fibroblasts, thus blocking the infiltration of immune cells. These findings may provide an explanation for the mechanism by which TGF-β1 regulates immune function in RA.