Effects of endogenous sulfur dioxide on the oxidative stress induced by cobalt chloride in the rat pulmonary artery smooth muscle cells

Objective To investigate the effects of endogenous sulfur dioxide (SO2) on the oxidative stress induced by cobalt chloride (CoCl2) in the rat pulmonary artery smooth muscle cells (PASMCs). Methods Rat PASMCs were treated with 200 μmol/L CoCl2 to mimic the hypoxia insult.Endogenous SO2 generating enzyme aspartate aminotransferase 1(AAT1) expression was upregulated or downregulated (AAT1sh) by transfection with lentivirus.Rat PASMCs were randomly divided into 8 groups: vehicle group, vehicle + CoCl2 group, AAT1 group, AAT1 + CoCl2 group, scramble group, scramble + SO2 group, AAT1sh group and AAT1sh + SO2 group.SO2 donor Na2SO3/NaHSO3 at concentration of 100 μmol/L were added in scramble + SO2 group and AAT1sh + SO2 group.The expressions of AAT1, superoxide dismutase 1(SOD1) and SOD2 in PASMCs were detected by Western blot method.In situ SO2 content in PASMCs was detected by fluorescent probe.The superoxide anions in PASMCs were labeled by dihydroethidium (DHE) probe under fluorescent microscope. Results Compared with the vehicle group, the levels of SO2 and the expressions of AAT1(0.221±0.002 vs.0.446±0.004), SOD1(0.076±0.028 vs.0.171±0.019)and SOD2(0.080±0.031 vs.0.196±0.018) significantly decreased (all P< 0.01), and superoxide anion increased in rat PASMCs of vehicle + CoCl2 group.Meanwhile, compared with vehicle + CoCl2 group, the levels of SO2 and the expressions of AAT1(0.839±0.056 vs.0.221±0.002), SOD1(0.177±0.020 vs.0.076±0.028)and SOD2(0.195±0.018 vs.0.080±0.031)markedly increased (all P< 0.01), and superoxide anion decreased in rat PASMCs of AAT1 + CoCl2 group.On the contrary, compared with the scramble group, the levels of SO2 and the expressions of AAT1(0.062±0.017 vs.0.354±0.034), SOD1(0.054±0.029 vs.0.157±0.023) and SOD2(0.180±0.100 vs.0.586±0.176)significantly decreased (all P<0.01), and superoxide anion increased in rat PASMCs of AAT1sh group.Furthermore, compared with the AAT1sh group, the levels of SO2 and the expressions of SOD1(0.155±0.022 vs.0.054±0.029) and SOD2(0.578±0.200 vs.0.180±0.100) significantly increased (all P< 0.01), and superoxide anion decreased in rats PASMCs of AAT1sh + SO2 group. Conclusion Endogenous SO2/AAT1 inhibits CoCl2-induced oxidative stress in rat PASMCs. Key words: Sulfur dioxide; Aspartate aminotransferase 1; Endogenous; Pulmonary artery smooth muscle cells; Oxidative stress