MiR-509-3p promotes oxidized low-density lipoprotein-induced apoptosis in mouse aortic endothelial cells

Abstract

To investigate the effect of microRNA-509-3p (miR-509-3p) on the apoptosis of atherosclerotic vascular endothelial cells. Mouse aortic endothelial cells (MAECs) were divided into normal control group, oxidized low-density lipoprotein (ox-LDL) group, miR-509-3p overexpression group, miR-509-3p overexpression control group, miR-509-3p inhibitor + ox-LDL group, and miR-509-3p inhibitor control + ox-LDL group. MAEC were induced with 100 mg/L ox-LDL for 24 hours, and then transfected with miR-509-3p overexpression/inhibitor and corresponding control for 48 hours. The miR-509-3p expression in MAECs exposed to ox-LDL was detected using real-time fluorescence quantitative polymerase chain reaction (RT-qPCR). Flow cytometry was used to detect the level of apoptosis, and cell counting kit (CCK-8) was used to detect the proliferation activity of MAECs. The direct gene targets of miR-509-3p were predicted using bioinformatics analyses and confirmed using a dual luciferase reporter assay. The expression of Bcl-2 mRNA and protein was detected by RT-qPCR and Western blotting, respectively. Compared with the normal control group, miR-509-3p was significantly upregulated in ox-LDL-stimulated MAECs (1.68±0.85 vs. 1.00±0.30, t = 2.398, P < 0.05). After transfection of MAECs with miR-509-3p overexpression, the luciferase activity of the BCL2 3'UTR WT reporter gene was significantly lower than that of miR-509-3p overexpression control group (0.83±0.06 vs. 1.00±0.07, t = 4.531, P = 0.001). The luciferase activity of the BCL2 3'-UTR mutant (MUT) reporter gene was not significantly different from that of miR-509-3p overexpression control group (0.94±0.05 vs. 1.00±0.08, t = 1.414, P = 0.188). Compared with the normal control group and miR-509-3p mimics control group, the cell proliferation activity was decreased [(0.60±0.06)% vs. (1.00±0.09)%, (0.89±0.04)%, both P < 0.01], the percentage of apoptotic cells were increased [(23.46±2.02)% vs. (7.66±1.52)%, (10.40±0.78)%, both P < 0.05], and the mRNA and protein expression of Bcl-2 were significantly downregulated (Bcl-2 mRNA: 0.52±0.13 vs. 1.00±0.36, 1.10±0.19, Bcl-2 protein: 0.42±0.07 vs. 1.00±0.11, 0.93±0.10, both P < 0.01) in miR-509-3p overexpression group. Compared with the ox-LDL group, inhibition of miR-509-3p expression could increase the proliferation activity of MAECs induced by ox-LDL [(0.64±0.35)% vs. (0.34±0.20%)%, P < 0.05], and reduce the apoptosis rate [(13.59±2.22)% vs. (29.84±5.19)%, P < 0.01], and up-regulated the expression of Bcl-2 mRNA and protein in MAECs induced by ox-LDL (Bcl-2 mRNA relative expression: 0.82±0.09 vs. 0.52±0.10, Bcl-2 protein relative expression: 0.83±0.17 vs. 0.40±0.07, both P < 0.05). Bcl-2 was one of the target genes of miR-509-3p. miR-509-3p can reduce the proliferation activity of endothelial cells, reduce the expression of Bcl-2, and promote cell apoptosis, thereby promoting the occurrence and development of atherosclerosis. Inhibition of miR-509-3p expression may be a potential therapeutic target for atherosclerosis.