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 1β (IL-1β) on miR-146a expression were analyzed in orbital fibroblasts by qPCR. To investigate the molecular mechanism underlying IL-1β-induced miR-146a expression, the effects of inhibitors of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), 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-1β-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 1β induced a time- and concentration-dependent increase in miR-146a expression. Interleukin 1β (10 ng/mL, 16 hours) induced an approximately 17.5-fold increase in miR-146 expression. The increase in miR-146a expression by IL-1β was significantly inhibited by NF-κB, 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-1β-induced miR-146 expression, independent t-test). Interleukin 1β-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.