Interleukin-10 modulates pro-apoptotic effects of TNF-α in human articular chondrocytes in vitro

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The aim of this study is to determine if there is an antagonistic effect between tumour necrosis factor (TNF)-α and the immunoregulatory interleukin (IL)-10 on chondrocytes survival. Serum-starved primary human articular chondrocytes were stimulated with either 10 ng/ml recombinant TNF-α, IL-10 or a combination of both (at 10 ng/ml each). Chondrocyte apoptosis was determined by measuring caspase-3/7, -8 and -9 activities using caspase assays. Mitochondrial apoptotic inducer bax, and the suppressor bcl-2 were evaluated using western blotting at 48 h. Results indicated that TNF-α increased caspase activities and resulted in a significant (p = 0.001) increase in bax/bcl-2 ratio. Stimulation with IL-10 did not alter caspase activities, while co-treatment with IL-10 and TNF-α inhibited TNF-α induced caspase activities and significantly (p > 0.004) impaired bax/bcl-2 ratio. At 24 h, mRNA levels for collagen type II, TNF-α and IL-10 were determined using real-time RT-PCR. Stimulation with TNF-α or TNF-α and IL-10 significantly inhibited collagen type II and increased IL-10 and TNF-α mRNA expression. IL-10 modulated the pro-apoptotic capacity of TNF-α in chondrocytes as shown by the decrease in caspase activities and bax/bcl-2 ratio compared to TNF-α stimulated chondrocytes, suggesting a mostly antagonistic interplay of IL-10 and TNF-α on mitochondrial apoptotic pathways.

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