Abstract

Acute coronary syndrome (ACS) is characterized by atherosclerotic plaque rupture with a high incidence of recurrent ischemic events. Several microRNAs are found to be aberrantly expressed in atherosclerotic plaques. This study aims to investigate the effects of microRNA-9 (miR-9) on vulnerable atherosclerotic plaque and vascular remodeling in ACS and underlying mechanisms. Microarray-based gene expression profiling was used to identify differentially expressed genes related to ACS and regulatory miRNAs. Oxidized low-density lipoprotein (lectin-like) receptor 1 (OLR1) was identified to be aberrantly activated in ACS and regulated by miR-9. OLR1 was verified as a target gene of miR-9 by bioinformatics prediction and dual luciferase reporter gene assay. The atherosclerotic models were induced in ApoE −/− mice, in which the agomir or antagomir of miR-9, or small interfering RNA (siRNA) against OLR1 were separately introduced. Serum lipid levels and expression of vascular remodeling and inflammatory response-related factors were determined, respectively. On the basis of the obtained results, in the atherosclerosis mice treated with the agomir of miR-9 and siRNA against OLR1, the p38-mitogen-activated protein kinase (p38MAPK) pathway was inhibited; levels of triglyceride, total cholesterol, low-density lipoprotein cholesterol, tumor necrosis factor-α, interleukin-6, and vascular endothelial growth factor were reduced, but the high-density lipoprotein cholesterol level was increased, along with decreased vulnerable atherosclerotic plaque area and enhanced vascular remodeling. Taken together, these findings suggested an inhibitory role miR-9 acts in the formation of vulnerable atherosclerotic plaques in ACS mice, along with a promoted vascular remodeling, via a negative feedback regulation of OLR1-mediated p38MAPK pathway.