Fas/Fas ligand-mediated death pathway is involved in oxLDL-induced apoptosis in vascular smooth muscle cells

Oxidized low-density lipoprotein (oxLDL) is a potent inducer of apoptosis for vascular cells. In the present study, we demonstrate that the expression of death mediators, including p53, Fas, and Fas ligand (FasL) was substantially upregulated by oxLDL in cultured vascular smooth muscle cells (SMCs). The induction of these death mediators was time dependent and was accompanied by an increase in apoptotic death of SMCs following oxLDL treatment. Two oxysterols, 7β-hydroxycholesterol and 25-hydroxycholesterol, were also effective to induce the expression of death mediators and apoptosis. α-Tocopherol and deferoxamine significantly attenuated the induction of death mediators and cell death induced by oxLDL and oxysterols, suggesting that reactive oxygen species are involved in triggering the apoptotic event. Incubation of cells with FasL-neutralizing antibody inhibited the oxLDL-induced cell death up to 50%. Furthermore, caspase 8 and caspase 3 activities were induced time dependently in SMCs following oxLDL treatment. Collectively, these data suggest that the Fas/FasL death pathway is activated and responsible for, at least in part, the apoptotic death in vascular SMCs upon exposure to oxLDL.