Lipid peroxidation of low density lipoprotein by human endothelial cells modifies its metabolism in vitro

Low density lipoprotein (LDL) undergoes qualitative changes when incubated with endothelial cells. Changes in LDL induced by cultured human endothelial cells were associated with release of substances reacting to thiobarbituric acid; they were prevented by addition of EDTA. Modification of LDL by human endothelium, therefore, appears to involve lipid peroxidation. Proneness of LDL to this process was indicated by its occurrence, to a smaller extent, on incubation in the absence of endothelium. Lipid peroxidation of LDL altered its electrophoretic mobility. Modified LDL, but not native LDL, was readily catabolised by human macrophages. Conditioning by human endothelium increased the rate of fractional catabolism of LDL in rabbits. If lipid peroxidation of LDL takes place in vivo it may promote conversion of macrophages to lipid-laden foam cells in the developing atheromatous plaque.