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In this study, we examined the effects of overexpression of SIRT1 on IL-1β-induced gene expression changes in human chondrocytes to explore a protective role of SIRT1 in human chondrocytes. SIRT1 was overexpressed in human chondrocytes by expression plasmid under stimulation with IL-1β. SIRT1 was also inhibited by siRNA under stimulation with IL-1β. Gene expression changes were examined by real-time PCR. The interaction of SIRT1 and p65 (NF-κB) were examined by Western blotting. SIRT1, MMP-13, and ADAMTS-5 expressions in human cartilage were examined by immunohistochemistry. IL-1β stimulation significantly up-regulated MMP-1, 2, 9, and 13 and ADAMTS-5. Overexpression of SIRT1 significantly inhibited the up-regulation of those genes caused by IL-1β while the inhibition of SIRT1 further increased them. In addition, the overexpression of SIRT1 markedly reduced the IL-1β-induced acetylation of p65. SIRT1 expression was clearly detected in the non-OA cartilage while MMP-13 and ADAMTS-5 were undetectable. In contrast, in the OA cartilage, SIRT1 expression was decreased while MMP-13 and ADAMTS-5 were increased. Our observations suggested that SIRT1 can play a protective role by suppressing IL-1β-induced expressions of cartilage-degrading enzymes partially through the modulation of the NF-κB pathway. SIRT1 overexpression might be a new therapeutic approach for OA.
Matsushita et al. (Fri,) studied this question.