Vitamin E reduces the uptake of oxidized LDL by inhibiting CD36 scavenger receptor expression in cultured aortic smooth muscle cells.

Abstract

Vitamin E is well known as an antioxidant, and numerous studies suggest that it has a preventive role in atherosclerosis, although the mechanism of action still remains unclear. The original aim of this study was to establish whether alpha-tocopherol (the most active form of vitamin E) acts at the earliest events on the cascade of atherosclerosis progression, that of oxidized LDL (oxLDL) uptake and foam-cell formation. We show here that the CD36 scavenger receptor (a specific receptor for oxLDL) is expressed in cultured human aortic smooth muscle cells (SMCs). Treatment of SMCs and HL-60 macrophages with alpha-tocopherol (50 micromol/L, a physiological concentration) downregulates CD36 expression by reducing its promoter activity. Furthermore, we find that alpha-tocopherol treatment of SMCs leads to a reduction of oxLDL uptake. This study indicates that CD36 is expressed in cultured human SMCs. In these cells, CD36 transports oxLDL into the cytosol. alpha-Tocopherol inhibits oxLDL uptake by a mechanism involving downregulation of CD36 mRNA and protein expression. Therefore, the beneficial effect of alpha-tocopherol against atherosclerosis can be explained, at least in part, by its effect of lowering the uptake of oxidized lipoproteins, with consequent reduction of foam cell formation.