Oxidative Modification Reduces HDL-induced Cholesterol Efflux from Cultured Human Arterial Smooth Muscle Cells

To investigate the effects of oxidative modification of high density lipoprotein (HDL) on HDL-mediated cholesterol efflux from human arterial smooth muscle cells(SMC), native HDL (N-HDL) and oxidized HDL(Ox-HDL) induced by copper or hypochlorite were incubated with cultured SMC preloaded with (3)H-cholesterol for 2--24 h. The radioactivities of (3)H-cholesterol of the medium and SMC were measured respectively, and the cholesterol efflux rate (CER) of HDL and Ox-HDL were determined. The result showed that the CER of N-HDL was 43.1% after 24 h incubation, while the CER of Ox-HDL induced by copper or hypochlorite were 28.9% and 23.5% respectively, reduced by 30.0% and 43.1% compared with N-HDL. The speed of 3H-cholesterol efflux of Ox-HDL from SMC were decreased remarkably. Inhibition of oxidation with antioxidants butylated hydroxytoluene(BHT), vitamin C or vitamin E recovered mostly the ability of HDL to stimulate cholesterol efflux. The results suggest that oxidation of HDL may attenuate its effect on cholesterol efflux from arterial SMC, and vitamin C and vitamin E supplementation may protect artery from atherogenesis.