Lipoperoxidative injury to macrophages by oxidatively modified low density lipoprotein may play an important role in foam cell formation

Abstract

Both oxidatively and malondialdehyde modified low density lipoprotein (Ox-LDL and MDA-LDL) could be recognized by the scavenger receptor and induce intracellular cholesteryl ester accumulation of macrophage. The cholesteryl ester accumulation caused by MDA-LDL could be largely cleared by high density lipoprotein (HDL 3), but that caused by Ox-LDL could not be. Further studies showed that Ox-LDL and MDA-LDL all could decrease the binding capacity of HDL 3 and increase intracellular thiobarbituric acid reactive substances (TBARS). When macrophages were first cultured with MDA-LDL and then in medium without LDL, the decreased binding capacity of HDL 3 was somewhat recovered and the intracellular TBARS did not increase any more. However, if macrophages were first cultured with Ox-LDL, the binding capacity of H DL 3 continued to decrease and intracellular TBARS continued to increase. There was a negative correlation ( r = −0.81, P < 0.01) between the decreased binding capacity of HDL 3 and the increased intracellular TBARS caused by Ox-LDL. These results imply that lipid peroxidative injury to macrophages caused by Ox-LDL play an important role in foam cell formation.