OXIDIZED LOW-DENSITY-LIPOPROTEIN INCREASES ENDOTHELIAL INTRACELLULAR CALCIUM AND ALTERS CYTOSKELETAL F-ACTIN DISTRIBUTION

Central to the pathogenesis of atherosclerosis is an abnormally functi oning endothelium and a consequent loss of vascular integrity. These a bnormalities may be induced by haemodynamic factors, biochemical subst ances, and also by oxidatively modified low-density lipoprotein (LDL). To understand the mechanism by which oxidized LDL causes endothelial dysfunction, human umbilical vein endothelial cells (HUVECs) were load ed with FURA-2, and intracellular calcium mobilization was studied in acute (seconds after LDL was injected) or chronic (24 h after LDL was injected) preparations. Our results demonstrate that 100 mu g mL(-1) o xidized LDL increases HUVEC intracellular calcium. In contrast, native LDL at this same concentration had no effect. In addition, chronic ex posure (24 h) of HUVECs to oxidized LDL significantly increases HUVEC intracellular calcium. Fluorescent photomicrographs of HUVECs stained with BODIPY-phalloidin f-actin indicates that oxidized LDL causes a re organization of microfilaments. The results of this study demonstrate that the mechanism by which oxidized LDL causes a loss of vascular int egrity could be through activation of endothelial cells to increase cy tosolic calcium, which alters the endothelial barrier by reorganizing the cytoskeleton.