MicroRNA-320b Modulates Cholesterol Efflux and Atherosclerosis

ATP-binding cassette (ABC) transporters and endonuclease-exonuclease-phosphatase family domain containing 1 (EEPD1) are reported to regulate cellular cholesterol efflux in macrophages. Bioinformatics analysis has revealed that ABCG1 and EEPD1 might be potential targets of microRNA (miR)-320b. This study aimed to elucidate the roles of miR-320b in cholesterol efflux from macrophages and the pathogenesis of atherosclerosis.

Microarray was conducted to profile microRNA (miRNA) expression, and quantitative real-time PCR (qPCR) was used to validate the differentially expressed miRNAs in peripheral blood mononuclear cells of coronary artery disease (CAD) patients and healthy controls. Luciferase assay was conducted to evaluate the activity of reporter construct containing the 3´-untranslated region (3´-UTR) of target genes. Besides, NBD-cholesterol efflux induced by high-density lipoprotein (HDL) and lipid-free apolipoprotein A1 (apoA1) was detected using fluorescence intensity, respectively. Apoe^-/- mice were injected with adeno-associated virus (AAV)2-miR-320b or control via tail vein, thereafter fed with 14 week atherogenic diet to study the roles of miR-320b in vivo.

MiR-320b was highly expressed in CAD patients compared with that in the healthy controls in both the microarray analysis and qPCR analysis. In vitro study showed that miR-320b decreased HDL- and apoA1-mediated cholesterol efflux from macrophages partly by directly targeting ABCG1 and EEPD1 genes and partly via suppressing the LXRα-ABCA1/G1 pathway. Consistently, in vivo administration of AAV2-miR-320b into Apoe^-/- mice attenuated cholesterol efflux from peritoneal macrophages, which showed reduced expression of ABCA1/G1 and EEPD1, and increased lipid LDL-C level, with a down-regulation of hepatic LDLR and ABCA1. AAV2-miR-320b treatment also increased atherosclerotic plaque size and lesional macrophage content and enhanced pro-inflammatory cytokines levels through the elevated phosphorylation level of nuclear factor-κB p65 in macrophages.

We identify miR-320b as a novel modulator of macrophage cholesterol efflux and that it might be a promising therapeutic target for atherosclerosis treatment.