Pegylation of HDL Decreases Plasma Clearance and Enhances Anti-Atherogenic Activity
Rationale: Infusions of apoA-I, mimetic peptides or HDL remain a promising approach to treatment of atherosclerotic coronary disease. However, rapid clearance leads to a requirement for repeated administration of large amounts of material and limits effective plasma concentrations.
Objective: Since pegylation of purified proteins is commonly used as a method to increase their half-life in the circulation, we determined whether pegylation of apoA-I or HDL would increase its plasma half-life and in turn its anti-atherogenic potential.
Methods and Results:Initial pegylation attempts using lipid-poor apoA-I showed a marked tendency to form multi-pegylated (PEG) species with reduced ability to promote cholesterol efflux from macrophage foam cells. However, pegylation of human holo-HDL or reconstituted phospholipid/apoA-I particles (rHDL) led to selective N-terminal mono-pegylation of apoA-I with full preservation of cholesterol efflux activity. The plasma clearance of PEG-rHDL was estimated following injection into hypercholesterolemic Apoe-/- mice; the half-life of pegylated apoA-I following injection of PEG-rHDL was increased about 7-fold compared to apoA-I in non-pegylated rHDL. Compared to non-pegylated rHDL, infusion of PEG-rHDL (40 mg/kg) into hypercholesterolemic APOe-/- mice led to more pronounced suppression of bone marrow myeloid progenitor cell proliferation and monocytosis, as well as reduced atherosclerosis and a stable plaque phenotype.
Conclusions: We describe a novel method for effective mono-pegylation of apoA-I in HDL particles, in which lipid binding appears to protect against pegylation of key functional residues. Pegylation of apoA-I in rHDL markedly increases its plasma half-life and enhances anti-atherogenic properties in vivo.
- Received February 3, 2013.
- Revision received April 21, 2013.
- Accepted April 23, 2013.