Regulation of apoptosis by miR-122 in pterygium via targeting Bcl-w

Abstract

PURPOSE. To identify the differently expressed micro (mi) RNAs in pterygium compared with normal conjunctiva and investigate the potential role of miRNAs in the pathogenesis of pterygium. METHODS. With microRNA microarray and quantitative RT-PCR, we identified that microRNA- 122 (miR-122) was significantly decreased in pterygium tissue. We detected the expression of Bcl-w, a predicted target of miR-122, in both pterygium and normal conjunctiva, as well as its correlation with the expression of miR-122. Pterygium epithelial cells were isolated and cultured, and transfected with miR-122 mimic or miR-122 inhibitor to change the miR-122 levels. The regulation of Bcl-w expression by miR-122 was examined with luciferase activity assay, quantitative (q) RT-PCR, and Western blot. The effect of the miR-122 on the apoptosis of cultured pterygium epithelial cells was investigated with TUNEL staining and caspase activity assay. RESULTS. We found the expression of Bcl-w, with an inverse correlation with the expression of miR-122, was significantly increased in pterygium, especially in the superficial layer of epithelium. In cultured pterygium epithelial cells, miR-122 could specifically combine with Bcl-w mRNA, and negatively regulated the expression of Bcl-w. Suppression of miR-122 could reduce apoptosis and caspase activity in pterygium epithelial cell treated with TNFa/ cycloheximide (CHX), and this effect was abolished by inhibition of the expression of Bcl-w with specific siRNA. CONCLUSIONS. Decreased expression of miR-122 in pterygium might result in abnormal cell apoptosis via its regulation of the expression of Bcl-w, and subsequently contribute to the development of pterygium.