MicroRNA-29 regulates high-glucose-induced apoptosis in human retinal pigment epithelial cells through PTEN

Hyperglycemia or high-glucose (HG)-induced apoptosis in human retinal pigment epithelial (RPE) cells is a characteristic process in diabetic retinopathy. In our study, we examined whether microRNA-29 (miR-29) may regulate HG-induced RPE cell apoptosis. Human RPE cell line, ARPE-19 cells, was treated with various high concentration of glucose in vitro. HG-induced RPE cell apoptosis was examined by terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and miR-29 gene expression by quantitative RT-PCR (qRT-PCR). miR-29 was then downregulated in RPE cells, and its effect on HG-induced apoptosis was examined by TUNEL assay and western blot assay on caspase-7 protein. Association of miR-29 on its downstream target, PTEN, in HG-induced RPE cell apoptosis was evaluated by dual-luciferase assay and qRT-PCR. PTEN was silenced in RPE cells. The effects of PTEN downregulation on miR-29-mediated HG-induced RPE cell apoptosis were also examined by TUNEL and western blot assays. HG induced significant apoptosis in RPE cells in a dose-dependent manner. miR-29 was upregulated by HG in RPE cells. miR-29 downregulation protected HG-induced apoptosis and reduced the production of caspase-7 protein in RPE cells. PTEN was shown to be directly downregulated by HG and then upregulated by miR-29 downregulation in RPE cells. Small interfering RNA (siRNA)-mediated PTEN downregulation reversed the protective effect of miR-29 downregulation on HG-induced RPE cell apoptosis. This study demonstrates that miR-29, through inverse association of PTEN, plays an important role in the process of HG-induced apoptosis in RPE cells.