Abstract
A decrease in smooth muscle cells is observed in advanced atherosclerotic lesion. To understand this mechanism, we selected oxysterols as candidates for toxic lipid, and examined their cytotoxicity on human cultured vascular smooth muscle cells, together with the manner of cell death. In the presence of 7-ketocholesterol or 7β-hydroxycholesterol (50 μmol/L), the percentage of detached cells increased significantly with dose dependency, and an increase in detached cell number and DNA nick detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling study (TUNEL) preceded an increase in lactate dehydrogenase released into the medium. DNA extracted from smooth muscle cells incubated with 7-ketocholesterol or 7β-hydroxycholesterol showed a laddering pattern on agarose electrophoresis. In the presence of 7-ketocholesterol or 7β-hydroxycholesterol, fragmented DNA quantified by the quantitative sandwich enzyme immunoassay was significantly increased. From these results, it is proposed that 7-ketocholesterol and 7β-hydroxycholesterol are toxic to smooth muscle cells, and that this cytotoxicity is mediated by apoptosis.
