Effects of sodium ferulate on the caspase cascade apoptosis pathway in rat osteoarthritis chondrocytes. Effects of sodium ferulate (SF) on the TNF/TNF receptor (TNFR)-mediated caspase cascade apoptosis pathway of rat osteoarthritis (OA) chondrocytes induced by IL-1β. (a) Effects of SF on expression of TNFα in rat OA chondrocytes. Chondrocytes were incubated with SF alone for 24 hours, and then co-treated with IL-1β and SF for 48 hours. Supernatants were collected after 72 hours. Release of TNFα was analyzed by ELISA. (b) Effects of SF on protein expression of TNFR-1, TNF receptor-associated death domain (TRADD), caspase-8, caspase-3 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in rat OA chondrocytes. Expression of proteins determined by western blotting. (c) Effects of SF on activity of caspase-8 and caspase-3 in rat OA chondrocytes. An activity unit was defined as the amount of enzyme that will cleave 1.0 nmol colorimetric substrate (acetyl-Asp-Glu-Val-Asp p-nitroanilide or acetyl-Ile-Glu-Thr-Asp p-nitroanilide) per hour at 37°C under saturated substrate concentrations. Caspase activity was expressed as activity units compared with total protein content (unit/μg pro). (d, e, f, g) Relative level of TNFR-1, TRADD, caspase-8 and caspase-3 normalized to GAPDH and compared with normal control, quantitatively analyzed by Kodak Digital Science 1D software (Eastman Kodak, Rochester, NY, USA) and expressed as mean optical density. Values represent mean ± standard error of the mean of three different simples. **P < 0.01 versus normal control. #P < 0.05, ##P < 0.01 versus OA model control.