High-density lipoproteins protect endothelial cells from apoptosis inducedby oxidized low-density lipoproteins

Endothelial lesion by oxidized low-density liproproteins (LDL) is one of th e first stages in the development of atherosclerosis. The effect of these l ipoproteins can range from a functional lesion of the endothelium to death of the endothelial cells by apoptosis. High-density lipoproteins (HDL) are one of the factors which can have a protective effect against the developme nt of atheromatous plaques. The aim of this study is to establish whether t he death of endothelial cells by apoptosis induced by oxidized LDLs is prev ented by HDLs. ECV304 endothelial cells and bovine aorta endothelial cells were incubated with native LDLs, oxidized LDLs, and a combination of both o xidized LDLs and HDLs. Oxidized LDLs caused a significant increase of morta lity mainly by apoptosis. However, when HDLs were added together with oxidi zed LDLs the percentage of total mortality, the degree of lipoprotein oxida tion in the medium, and the percentage of cells in apoptosis were all signi ficantly decreased. HDLs protect against the cytotoxicity of oxidized LDLs possibly by preventing the propagation of the oxidative chain in these lipo proteins.