The transformation of vascular smooth muscle cells (VSMC) into foam cells leading to increased plaque size and decreased stability is a key, yet understudied step in atherogenesis. Our work in the previous funding cycle (HL117724) demonstrated that Interleukin-19 (IL-19), a novel, anti-inflammatory cytokine, attenuates atherosclerosis by multiple anti-inflammatory effects on VSMC as well as by increasing lipid uptake and efflux in macrophage. In published and preliminary studies described here, we show that IL-19 reduces lipid accumulation in VSMC, an atheroprotective event, but without modifying expression of lipid receptors or transporters. IL-19 induces expression of miR133a, a muscle-specific miRNA previously ascribed to regulate VSMC phenotype. Although unrecognized and unreported, we have identified that miR133a can target and reduce expression of Low Density Lipoprotein Receptor Adaptor Protein 1, (LDLRAP1), an adaptor protein which functions to internalize the LDL receptor. Patients with mutations in LDLRAP1 have LDL receptor malfunction leading to hyperlipidemia and Autosomal Recessive Hypercholesterolemia (ARH) disorder. Nothing at all is known about a role for miR133a in regulation of lipid uptake and development of atherosclerosis. Similarly, nothing at all has been published about LDLRAP1 expression, function, and participation in VSMC foam cell formation. We have reported that that both miR133a and LDLRAP1 regulate oxLDL uptake in VSMC. LDLRAP1 is induced in VSMC by oxLDL, is not detectible in normal medial VSMC, but is expressed in plaque and neointimal VSMC of injured arteries. IL-19 can reduce LDLRAP1 expression and oxLDL uptake in VSMC. Both miR133a and LDLRAP1regulate VSMC proliferation, previously unrecognized functions for these molecules. Preliminary studies indicate that the LDLRAP1+/- mouse has increased atherosclerosis, but reduced restenosis. In this competitive renewal application, we hypothesize that LDLRAP1 can be selectively reduced in VSMC because miR133a is muscle specific, and that reduction of lipid uptake by VSMC is atheroprotective and could also attenuate vascular proliferative syndromes. The overall goals of this application are to determine causative roles for miR133a and LDLRAP1 in VSMC lipid uptake, proliferation, atherogenesis, cholesterol-induced phenotype modulation, and vascular restenosis.
VSMC foam cell formation is an integral molecular event in atherosclerotic plaque reduction. Our preliminary and published data indicate two novel regulators of cholesterol uptake and proliferation in vascular smooth muscle cells; miR133a and LDLRAP1. The goals of this application are to clarify a causal effect between these two molecules, cholesterol uptake in VSMC, and development of vascular diseases.
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