L-4F, an Apolipoprotein A-1 Mimetic, Dramatically Improves Vasodilation in Hypercholesterolemia and Sickle Cell Disease

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Abstract
Background— Hypercholesterolemia and sickle cell disease (SCD) impair endothelium-dependent vasodilation by dissimilar mechanisms. Hypercholesterolemia impairs vasodilation by a low-density lipoprotein (LDL)–dependent mechanism. SCD has been characterized as a chronic state of inflammation in which xanthine oxidase (XO) from ischemic tissues increases vascular superoxide anion (O 2 · − ) generation. Recent reports indicate that apolipoprotein (apo) A-1 mimetics inhibit atherosclerosis in LDL receptor–null ( Ldlr −/− ) mice fed Western diets. Here we hypothesize that L-4F, an apoA-1 mimetic, preserves vasodilation in hypercholesterolemia and SCD by decreasing mechanisms that increase O 2 · − generation. Methods and Results— Arterioles were isolated from hypercholesterolemic Ldlr −/− mice and from SCD mice that were treated with either saline or L-4F (1 mg/kg per day). Vasodilation in response to acetylcholine was determined by videomicroscopy. Effects of L-4F on LDL-induced increases in endothelium-dependent O 2 · − generation were determined on arterial segments via the hydroethidine assay and on stimulated endothelial cell cultures via superoxide dismutase–inhibitable ferricytochrome c reduction. Effects of L-4F on XO bound to pulmonary arterioles and content in livers of SCD mice were determined by immunofluorescence. Hypercholesterolemia impaired vasodilation in Ldlr −/− mice, which L-4F dramatically improved. L-4F inhibited LDL-induced increases in O 2 · − in arterial segments and in stimulated cultures. SCD impaired vasodilation, increased XO bound to pulmonary endothelium, and decreased liver XO content. L-4F dramatically improved vasodilation, decreased XO bound to pulmonary endothelium, and increased liver XO content compared with levels in untreated SCD mice. Conclusions— These data show that L-4F protects endothelium-dependent vasodilation in hypercholesterolemia and SCD. Our findings suggest that L-4F restores vascular endothelial function in diverse models of disease and may be applicable to treating a variety of vascular diseases.