Modification of LDL with oxidized 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphorylcholine (oxPAPC) results in a novel form of minimally modified LDL that modulates gene expression in macrophages

Abstract

Oxidized phospholipids (oxPL) have been found in atherosclerotic plaques and have been associated with the development of atherosclerosis. To investigate the LDL modifying effects of oxPL and subsequent consequences for macrophages, murine bone marrow macrophages were treated with LDL modified with the oxidation products of 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphorylcholine, oxPAPC. Effects of oxPAPC-modified LDL (oxPAPC-LDL) on macrophages were compared to native LDL, copper oxidized LDL (Cu-oxLDL) and acetylated LDL (acLDL). LDL treatment with oxPAPC or CuSO 4 induced active oxidation of the LDL particles, resulting in significant increase in F2-isoprostanes, typical for LDL oxidation, compared with native LDL, acLDL or PAPC-LDL. Uptake of oxPAPC-LDL in macrophages was mediated by CD36 pathways as shown by SR-A and CD36 inhibitors. Surprisingly, both Cu-oxLDL and acLDL induced cholesterol ester accumulation in macrophages while oxPAPC-LDL did not. Microarray analysis showed a pronounced similarity between Cu-oxLDL and oxPAPC-LDL gene expression induction, whereas acLDL and oxPAPC-LDL did not overlap. The main feature shared by oxPAPC-LDL and Cu-oxLDL was the induction of the glutathione dependent antioxidant response, indicating an important role in protecting against both types of modified LDL induced stress. Our experiments show that oxPL modifies LDL, resulting in a minimally oxidized particle that shares many features of classically copper oxidized LDL and that may have relevant in vivo properties.