Gene expression and production of TNFα in advanced glycation end product-BSA-stimulated osteoarthritis chondrocytes. (a) Effect of epigallocatechin-3-gallate (EGCG), specific inhibitors for mitogen-activated protein kinases and NF-κB on the gene expression of TNFα in advanced glycation end product (AGE)-BSA-stimulated osteoarthritis (OA) chondrocytes. Primary chondrocytes were pretreated with EGCG (25 to 150 μM) for 2 hours and were stimulated by AGE-BSA (600 μg/ml) for 8 hours. Folds of TNFα mRNA expression, as compared with control and normalized to GAPDH, were determined by quantitative RT-PCR. Concentrations of specific inhibitors of JNK (SP600125), ERK (PD98059), p38 (SB202190) and NF-κB (MG-132) used in these studies were 10 μM, 50 μM, 100 μM and 100 μM, respectively. Native BSA (600 μg/ml) was used as a negative control. (b) Effect of EGCG on the production of TNFα in AGE-BSA-stimulated OA chondrocytes. Primary chondrocytes were pretreated with EGCG (25 to 150 μM) for 2 hours and were stimulated by AGE-BSA (600 μg/ml) for 24 hours. The production level of TNFα was determined by sandwich ELISA. Results are representative (mean ± standard error of the mean) of duplicate experiments with OA chondrocytes obtained from five age-matched and sex-matched OA donors; data without a common letter differ, P < 0.05.