TNF/TNFR signal transduction pathway-mediated anti-apoptosis and anti-inflammatory effects of sodium ferulate on IL-1β-induced rat osteoarthritis chondrocytes in vitro

Introduction: Sodium ferulate (SF) is a natural component of traditional Chinese herbs. Our previous study shows that SF has a protective effect on osteoarthritis (OA). The objective of this study was to investigate the effect of SF on the TNF/TNF receptor (TNFR) signal transduction pathway of rat OA chondrocytes. Methods: Primary rat articular chondrocytes were co-treated with IL-1 beta and SF. Chondrocyte apoptosis was assessed by fluorescein isothiocyanate-annexin V/propidium iodide assay. The PCR array was used to screen the expression of 84 key genes involved in apoptosis. The release of TNF alpha and prostaglandin E-2 were analyzed by ELISA. Expressions of proteins were assessed by western blotting. The activity of NF-kappa B was determined by electrophoretic mobility shift assay (EMSA). Gene expression of inducible nitric oxide synthase (iNOS) was evaluated by real-time quantitative PCR. The nitric oxide content was measured with the Griess method. Results: After treatment with SF, the apoptosis rate of chondrocytes significantly attenuated (P < 0.01). Results of the apoptosis PCR array suggested that mRNA expression of some core proteins in the TNF/TNFR pathway showed valuable regulation. The protein expressions of TNF alpha, TNFR-1, TNF receptor-associated death domain, caspase-8 and caspase-3 were prevented by SF in a concentration-dependent manner. SF also inhibited activities of caspase-8 and caspase-3 compared with the OA model control (P < 0.01). TNF receptor-associated factor-2 expression, phosphorylations of inhibitor of NF-kappa B kinase (IKK) subunits alpha and beta, and NF-kappa B inhibitor, alpha (I kappa B alpha) were all concentration-dependently suppressed by SF treatment. The results of EMSA showed that SF inhibited the activity of NF-kappa B. In addition, the expressions of cycloxygenase-2 and iNOS and the contents of prostaglandin E-2 and NO were attenuated with the treatment of SF (P < 0.01). Conclusion: SF has anti-apoptosis and anti-inflammatory effects on an OA model induced by IL-1 beta in vitro, which were due to inhibitory actions on the caspase-dependent apoptosis pathway and the IKK/NF-kappa B signal transduction pathway of the TNF/TNFR pathway.