THE EFFECT OF PROBUCOL ON HDL-MEDIATED STEROL TRANSLOCATION AND EFFLUX FROM CELLS

It has been suggested that the antioxidant drug probucol can prevent arterial cholesterol accumulation in part by promoting HDL-mediated cholesterol removal from cells. In this study, the effect of probucol in vitro on the interaction of HDL3 with cultured skin fibroblasts, bovine aortic endothelial cells and human monocyte-derived macrophages was tested. Treatment of cholesterol-loaded cells with up to 20-mu-M probucol had no effect on [H-3]cholesterol efflux from plasma membranes. No effect of probucol on HDL3-mediated efflux of labeled sterol was seen after intracellular sterol was labeled either with the biosynthetic precursor [H-3]mevalonolactone or after incubation with lipoprotein-associated [H-3]cholesterol linoleate. Further, no effect of probucol on cell cholesterol mass efflux was observed. Thus these results demonstrate that probucol does not affect movement of sterol from different cellular radiolabeled sterol pools. Within the limitations of cell culture studies, it is suggested that the proposed antiatherogenic effect of probucol in vivo is not likely to be the result of modulation of major cellular pathways for removal of cholesterol.