miR-221 promotes lens epithelial cells apoptosis through interacting with SIRT1 and E2F3

MicroRNAs (miRNAs) have been regarded as potential modulators in varying ocular diseases, including age-related cataract (ARC). However, the roles of miR-221 in ARC progression and its underlying mechanism remain poorly understood. In this study, human lens epithelial cell line (SRA01/04) was used to investigate the potential function of miR-221 in vitro. The expressions of miR-221, sirtuin-1 (SIRT1) and E2F transcription factor 3 (E2F3) were measured in ARC tissues by quantitative real-time polymerase chain reaction and western blotting, respectively. To investigate the effect of miR-221, SIRT1 and E2F3 on cell apoptosis, SRA01/04 cells were transfected with miR-221 inhibitor, negative control inhibitor, pcDNA3.1-SIRT1 overexpression vector, pcDNA3.1-E2F3 overexpression vector or pcDNA3.1 empty vector. After the transfection, cell viability was detected in SRA01/04 cells at 0, 24, 48 or 72 h by cell counting kit-8 assay. Cell apoptosis was evaluated in transfected SRA01/04 cells by flow cytometry and western blotting at 72 h. The interaction between miR-221 and SIRT1 or E2F3 was probed by luciferase activity and RNA immunoprecipitation assays. Results showed that high expression of miR-221 was exhibited in ARC tissues compared with that in normal samples and associated with Lens Opacities Classification System III grades. Knockdown of miR-221 promoted cell viability and inhibited apoptosis in SRA01/04 cells. Moreover, both of SIRT1 and E2F3 levels were directly targeted by miR-221 and down-regulated in ARC tissues. Besides, overexpression of SIRT1 or E2F3 increased cell viability and suppressed apoptosis in SRA01/04 cells, which was reversed by addition of miR-221. We concluded that miR-221 promoted lens epithelial cells apoptosis through regulating SIRT1 and E2F3, providing a novel biomarker for treatment of ARC.