Inhibiting effect of selenium on oxysterols-induced apoptosis of rat vascular smooth muscle cells

To evaluate the cytoprotection mechanism of selenium against cholestane-3beta,5alpha,6beta-triol (3-triol)-induced vascular smooth muscle cells (VSMCs) damage, cell viability was analyzed by 3-(4,5-dimethylthiazol-2 -yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell count, the percentage release of lactate dehydrogenase (LDH) from the cell was assessed, and apoptosis was detected by DNA laddering and flow cytometric analysis. Meanwhile, the activity of glutathione peroxidase (GPx) of VSMCs was measured. The results showed that 3-triol could inhibit proliferation of VSMCs time-dependently and dose-dependently, increase the percentage release of LDH and induce VSMCs apoptosis. While the cytotoxicity and cells apoptosis induced by 3-triol was attenuated by pretreatment of cells with low concentration of sodium selenite, and the longer the pretreated time was, the stronger the inhibition was. Preincubation of cells with sodium selenite (50 nM) for 12 or 24 h before 1, 5, 10, 25, or 50 microM 3-triol exposure, the cell viabilities increased 28.5% (P<0.05), 18.3%, 197.6% (P<0.01), 66.7%, 50.0% or 35.1% (P<0.05), 62.3% (P<0.05), 329.6% (P<0.01), 221.3% (P<0.05), 74.0% compared with the control cells, respectively. When the cells were preincubated with sodium selenite (50 nM) for 12 or 24 h before exposure to 3-triol (10 microM), the percent of apoptotic cells reduced from 30.47+/-15.34% to 26.88+/-17.32% or 7.41+/-5.46% (P<0.05). With preincubation of sodium selenite (50 nM) for 24 h, the GPx activity of VSMCs increased 18.5% compared with control (P<0.05). In conclusion, the results suggested that incubated VSMCs could absorb and transfer selenite as selenoprotrein, such as GPx, if the time is long enough and VSMCs selenoproteins can protect markedly against apoptosis and damage induced by 3-triol in VSMCs.