MicroRNA-19b promotes macrophage cholesterol accumulation and aortic atherosclerosis by targeting ATP-binding cassette transporter A1.

Rationale: Macrophage accumulation of cholesterol leads to foam cell formation which is a major pathological event of atherosclerosis. Recent studies have shown that microRNA (miR)-19b might play an important role in cholesterol metabolism and atherosclerotic diseases. Here, we have identified miR-19b binding to the 3'UTR of ATP-binding cassette transporter A1 (ABCA1) transporters, and further determined the potential roles of this novel interaction in atherogenesis.

Objective: To investigate the molecular mechanisms involved in a miR-19b promotion of macrophage cholesterol accumulation and the development of aortic atherosclerosis.

Methods And Results: We performed bioinformatics analysis using online websites, and found that miR-19b was highly conserved during evolution and directly bound to ABCA1 mRNA with very low binding free energy. Luciferase reporter assay confirmed that miR-19b bound to 3110-3116 sites within ABCA1 3'UTR. MiR-19b directly regulated the expression levels of endogenous ABCA1 in foam cells derived from human THP-1 macrophages and mouse peritoneal macrophages (MPMs) as determined by qRT-PCR and western blot. Cholesterol transport assays revealed that miR-19b dramatically suppressed apolipoprotein AI-mediated ABCA1-dependent cholesterol efflux, resulting in the increased levels of total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) as revealed by HPLC. The excretion of (3)H-cholesterol originating from cholesterol-laden MPMs into feces was decreased in mice overexpressing miR-19b. Finally, we evaluated the proatherosclerotic role of miR-19b in apolipoprotein E deficient (apoE(-/-)) mice. Treatment with miR-19b precursor reduced plasma high-density lipoprotein (HDL) levels, but increased plasma low-density lipoprotein (LDL) levels. Consistently, miR-19b precursor treatment increased aortic plaque size and lipid content, but reduced collagen content and ABCA1 expression. In contrast, treatment with the inhibitory miR-19b antisense oligonucleotides (ASO) prevented or reversed these effects.

Conclusion: MiR-19b promotes macrophage cholesterol accumulation, foam cell formation and aortic atherosclerotic development by targeting ABCA1.