Role of miR-146a in the Regulation of Inflammation in an In Vitro Model of Graves' Orbitopathy

Abstract

PURPOSE. To investigate the role of microRNA 146a (miR-146a) in the regulation of inflammation in an in vitro model of Graves' orbitopathy (GO). METHODS. The level of miR-146a expression in orbital adipose tissue was compared between GO and non-GO by quantitative real-time PCR (qPCR). The effects of interleukin 1 beta (IL-1 beta) on miR-146a expression were analyzed in orbital fibroblasts by qPCR. To investigate the molecular mechanism underlying IL-1 beta-induced miR-146a expression, the effects of inhibitors of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappa B), mitogen-activated protein kinase/extracellular signal-regulated kinases (MEK)-1/2, c-Jun N-terminal kinases (JNK)-1/2, p38 MAP kinase, and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) were analyzed. The effects of miR-146a mimics and inhibitors on IL-1 beta-induced IL-6 release were examined by ELISA and Western blotting. RESULTS. The level of miR-146a expression was significantly higher in GO orbital adipose tissue than in non-GO (P = 0.032). Interleukin 1 beta induced a time-and concentration-dependent increase in miR-146a expression. Interleukin 1 beta (10 ng/mL, 16 hours) induced an approximately 17.5-fold increase in miR-146 expression. The increase in miR-146a expression by IL-1 beta was significantly inhibited by NF-kappa B, JNK-1/2, and PI3K inhibitors (1.94 +/- 0.25, 5.28 +/- 0.34 and 9.73 +/- 2.32-fold, respectively, P < 0.05 compared with IL-1 beta-induced miR146 expression, independent t-test). Interleukin 1 beta-induced IL-6 protein production was further decreased by miR-146a mimics, but not by inhibitors of miR-146a. CONCLUSIONS. MicroRNA 146a was upregulated by inflammatory stress in orbital fibroblasts. Our results indicated that miR-146a had a positive effect on the anti-inflammatory process. MicroRNA 146a may play a role in the regulation of inflammation in orbital fibroblasts, and may participate in the pathogenesis of GO.