MicroRNA-558 regulates the expression of cyclooxygenase-2 and IL-1β-induced catabolic effects in human articular chondrocytes

Objective: Cyclooxygenase-2 (COX-2) is a major prostaglandin E-2 (PGE(2)) synthetic enzyme and is involved in the pathogenesis of chronic inflammation and pain in osteoarthritis (OA). The objective of this study was to directly address whether microRNA (miR)-558 can control the interleukin (IL)-1 beta-mediated induction of COX-2 and catabolic effects in human articular chondrocytes. Materials and methods: Total RNA was extracted from the cartilage tissues of normal and OA donors or cultured human articular chondrocytes. The expression of miR-558 was quantified by TaqMan assay. To investigate the repressive effect of miR-558 on COX-2 expression, human chondrocytes and chondrogenic SW1353 cells were transfected with mature miR-558 or an antisense inhibitor (anti-miR-558). The expression of COX-2 protein was determined by Western blot analysis and the involvement of miR-558 in IL-1 beta-induced catabolic effects was examined by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). Direct interaction between miR-558 and the putative site in the 3'-untranslated region (UTR) of COX-2 messenger RNA (mRNA) was validated by luciferase reporter assay. Results: Normal human articular cartilage expressed miR-558, and its expression was significantly lower in OA cartilage. Stimulation with IL-1 beta led to a significant reduction in miR-558 expression in normal and OA chondrocytes. IL-1 beta-induced activation of MAP kinase (MAPK) and nuclear factor-kappa B (NF-kappa B) decreased miR-558 expression and induced COX-2 expression in chondrocytes. The overexpression of miR-558 directly suppressed the luciferase activity of a reporter construct containing the 3'-UTR of human COX-2 mRNA and significantly inhibited IL-1 beta-induced upregulation of COX-2, while treatment with anti-miR-558 enhanced IL-1 beta-induced COX-2 expression and reporter activity in chondrocytes. Interestingly, IL-1 beta-induced activation of NF-kappa B and expression of matrix metalloproteinase (MMP)-1 and MMP-13 was significantly inhibited by miR-558 overexpression. Conclusion: These findings demonstrated that cartilage homeostasis is influenced by miR-558, which directly targets COX-2 and regulates IL-1 beta-stimulated catabolic effects in human chondrocytes. (C) 2013 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.