Specific Interaction of Oxidized Low-Density Lipoprotein With Macrophage-Derived Foam Cells Isolated From Rabbit Atherosclerotic Lesions

Abstract

Interaction of oxidized LDL (OxLDL) with macrophage-derived foam cells is one of the key events in the development and progression of atherosclerosis. To study this interaction, macrophage-derived foam cells were isolated from rabbit atherosclerotic lesions and the expression of scavenger receptors for OxLDL was examined. Atherosclerosis was induced in rabbits by denudation of the large arteries, followed by a hypercholesteremic diet. Macrophage-derived foam cells, characterized by immunostaining with an RAM-11 antibody (a macrophage marker), contained a high content of intracellular lipid. Maximal binding of radiolabeled OxLDL to isolated macrophage-derived foam cells (1652+/-235 ng 125I-OxLDL/mg of cell protein) was 20-fold higher compared with Bmax values of monocytes. Levels of association of OxLDL to macrophage-derived foam cells isolated from atherosclerotic lesions 12 weeks after denudation were >3-fold higher compared with the levels expressed by macrophage-derived foam cells isolated after 6 weeks. Association of 125I-OxLDL could be completely blocked by OxLDL, and partially by acetylated LDL and polyinosinic acid, indicating the presence of a specific binding site for OxLDL on macrophage-derived foam cells. The induction of scavenger receptors for OxLDL on macrophage-derived foam cells during the development of atherosclerosis, as described in this study, may facilitate the lipid accumulation in macrophage-derived foam cells, as observed in advanced atherosclerotic lesions.