Role of NF-κB in TNF-α-induced COX-2 Expression in Synovial Fibroblasts from Human TMJ

Abstract

In the temporomandibular joint (TMJ) synovium, cyclo-oxygenase-2 (COX-2) expression has been believed to be directly related to joint pain and synovitis. Here we investigated the role of Nuclear Factor κB (NF-κB) in the regulation of COX-2 expression in synovial fibroblasts from human TMJ induced by tumor necrosis factor-α (TNF-α). By reverse-transcriptase/polymerase chain-reaction (RT-PCR) and Western blotting analysis, TNF-α induced a dose- and time-dependent increase in COX-2 expression. Electrophoretic mobility shift assay (EMSA) revealed that transient NF-κB activation in the COX-2 promoter was triggered by TNF-α. In parallel with transient NF-κB activation, the rapid translocation of NF-κB, particularly the p65 subunit, from the cytoplasm into the nucleus was demonstrated. Pre-treatment with pyrolidine dithiocarbamate (PDTC), one of the NF-κB inhibitors, prevented binding to the COX-2 promoter and expression of COX-2 protein in response to TNF-α. These findings indicate that activation of NF-κB is responsible for TNF-α-induced COX-2 expression in synovial fibroblasts from the TMJ.