Abstract 1093: The Novel Apolipoprotein Mimetic Peptide ATI-5261 Induces Preβ-1 HDL Formation in Human Plasma via a Highly Specific Mechanism Involving Distinct α-HDL Subpopulations
Preβ-1 HDL are lipid-poor apoA-I particles that act as potent stimulators of cellular cholesterol efflux, thereby exerting antiatherosclerosis effects to reduce plaque. Despite therapeutic potential of preβ-1 HDL, the mechanisms governing its formation are incompletely known and there is a deficiency of compounds that increase preβ-1 HDL levels. Recently we created a synthetic peptide that stimulates ABCA1 cholesterol efflux with molar potency similar to apoA-I. This peptide (ATI-5261) greatly reduces established atherosclerosis in hyperlipidemic mice fed high-fat western-diet, similar to HDL-like particles (i.e. ETC-216). Presently we evaluated the pharmaco-kinetic and -dynamic properties of ATI-5261 to gain insight into its mechanism-of-action. Single ip injection of lipid-free ATI-5261 (20 mg/kg) with [3H]cholesterol-labeled J774 foam-cells in apoE−/− mice increased (2-fold) reverse cholesterol transport over 8 – 48 h. Mobilization of peripheral lipid was also observed in rats, where iv injection of ATI-5261 transiently increased plasma cholesterol concentrations. The half-life of ATI-5261 was ~10h in rats, suggesting the peptide binds to HDL and assumes its kinetic properties. Incubation of human plasma with ATI-5261 dose-dependently increased preβ-1 HDL, largely from α-1 and α-2 HDL, as judged by 2D-gel electrophoresis and apoA-I western blots. Increases (4-fold) in preβ-1 HDL occurred with peptide:apoA-I mole ratios of 1:10 (20 μg peptide/ml plasma), and near complete conversion of α- to preβ-1 HDL achieved with ratios of 1:1. This conversion was rapid (<30 min), produced at 4° C and, therefore, did not require metabolic events. Thus the formation of preβ-1 HDL occurred via a highly specific mechanism, perhaps involving peptide targeting protein-protein interactions to displace apoA-I from distinct HDL species. ATI-5261 also increased ABCA1 cholesterol efflux activity of plasma ex vivo. In conclusion, ATI-5261 represents a unique apoA-I mimetic peptide with unprecedented ability to interact with HDL in human plasma and generate preβ-1 HDL, thereby expanding the pool of lipid-poor apoA-I to exert antiatherosclerosis effects. The data suggest that ATI-5261 may represent a powerful therapeutic to combat atherosclerosis.