PTGS2 and rheumatoid arthritis: It was reported that triptolide inhibited the IL-1α-induced production of PGE2 by selectively suppressing the gene expression and production of COX-2 in human synovial fibroblasts and suppressed the expression of TNF-α in synovia of collagen-induced RA rat and the expression and activity of NF-kappa B in synovium of collagen-induced RA rats [45, 46].