Transcriptional control of microRNAs in lipid metabolism and atherosclerosis

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 DESCRIPTION (provided by applicant): Cholesterol imbalance plays a central role in multiple diseases, particularly cardiovascular disease, and the leading cause of death in the United States. Lipid-loaded macrophage foam cells are a critical determining factor in the pathogenesis of atherosclerosis. MicroRNAs are small non-coding RNA molecules that regulate both cholesterol and lipoprotein metabolism, and may significantly contribute to disease progression. We identified miR-144 as a novel regulator of lipid metabolism that is also regulated by the nuclear receptor farnesoid X receptor (FXR). We identified the cholesterol transporter ABCA1 as a miR-144 target gene, and showed that increased hepatic expression of miR-144 decreased ABCA1 protein and plasma cholesterol levels. Consequently, we hypothesized that silencing miR-144 may have therapeutic potential because, first it would increase the levels of atheroprotective HDL particles; and secondly, it may enhance reverse cholesterol transport (RCT) due to increased ABCA1 levels in macrophages. In the current proposal we now demonstrate that silencing miR-144 is atheroprotective. In Specific Aim 1, we show preliminary data where silencing miR- 144 in Ldlr-/- mice is atheroprotective in a regression model by en face analysis. We will now characterize atherosclerotic lesions in multiple vessels in detail, and determine whether prolonged silencing of miR-144 further enhances regression of atherosclerosis. In Specific Aim 2, we show preliminary analysis where silencing miR-144 attenuates progression of atherosclerosis in Ldlr-/- mice. We will now carry out detailed analysis of the lesions, and determine whether silencing miR-144 is also protective in a different model of atherosclerosis disease. Finally, in Specific Aim 3, we will determine the molecular mechanism that underlies the atheroprotective effects of silencing miR-144. We will determine whether miR-144 silencing enhances RCT, alters HDL properties and affects global gene networks in both macrophages within lesions and liver. Thus, our proposal will determine the molecular basis for the atheroprotective effects of silencing miR-144, and establish this pathway as a bona-fide strategy to treat atherosclerosis.