MicroRNA-155 modulates the proliferation of vascular smooth muscle cells by targeting endothelial nitric oxide synthase.

A variety of microRNAs (miRNAs) have been reported to be significantly be involved in the regulation of vascular smooth muscle cell (VSMC) proliferation, which is an essential process for the formation of atherosclerotic plaque. The objective of the present study was to explore the role of microRNA-155 (miR-155) in the regulation of VSMC growth and migration. A total of 12 atherosclerotic plaque samples and 9 control samples were collected, and the expression levels of miR-155/endothelial nitric oxide synthase (eNOS) were determined in those samples by RT-qPCR and western blot analysis. The results revealed that the relative expression levels of miR-155 in the atherosclerotic plaque samples were significantly upregulated compared with those in the normal control samples. We further found eNOS to be an effective target of miR-155 in the VSMCs by luciferase assay, which was confirmed by the observation that VSMCs transfected with miR-155 mimics exhibited a significantly lower protein expression level of eNOS. We also demonstrated that the exogenous overexpression of miR-155 significantly enhanced cell proliferation by inhibiting apoptosis in human aortic SMCs (HASMCs), and it also promoted the migratory ability of the cells. In conclusion, our data demonstrate that miR-155 is significantly upregulated in atherosclerotic plaque, functioning to accelerate the proliferation and migration of VSMCs by targeting eNOS.