Effect of endogenous sulfur dioxide on the apoptosis induced by cobalt chloride in the human pulmonary arterial endothelial cells

Abstract

Objective To explore the effect of endogenous sulfur dioxide (SO2) on the apoptosis induced by cobalt chloride (CoCl2) in the human pulmonary arterial endothelial cells (HPAECs). Methods CoCl2 was used in the primary HPAECs to mimize hypoxia-induced cell apoptosis.The aspartate aminotransferase 1(AAT1), and the key enzyme generating endogenous SO2 were over-expressed by transfecting HPAECs with lentivirus containing AAT1 cDNA.HPAECs were divided into 4 groups: vehicle group, vehicle+ CoCl2 group, AAT1 group and AAT1+ CoCl2 group.The expressions of AAT1, B-cell lymphoma-2 (bcl-2), bcl-associated X protein (bax), Caspase-3 and activated Caspase-3 (cleaved Caspase-3) in the HPAECs were measured by Western blot.The AAT activity was assessed with colorimetry method.The SO2 content in the HPAECs was in situ observed by SO2-specific fluorescent probe.The HPAECs apoptosis was investigated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. Results There were significant differences in the endogenous SO2 content, the expre-ssions of AAT1 and bcl-2, and the ratio of cleaved Caspase-3/Caspase-3 among 4 groups of HPAECs were (F=147.364, 23.738, 6.521, 64.884, all P 0.05). Compared with vehicle group, AAT activity [(0.96±0.24) Carmen′s unit/μg vs.(2.21±0.60) Carmen′s unit/μg], endogenous SO2 content (40.71±7.72 vs.105.60±16.20) and bcl-2 expression (0.59±0.19 vs.1.02±0.20) in the HPAECs of vehicle+ CoCl2 group were significantly decreased, while the cell apoptosis assessed by TUNEL and the ratio of cleaved Caspase-3/Caspase-3 (1.56±0.25 vs.0.95±0.13) were significantly increased (all P 0.05). The SO2 content (351.50±42.43 vs.105.60±16.20) and AAT1 expression (1.22±0.33 vs.0.53±0.11) in the HPAECs of AAT1 group were higher than those of vehicle group (all P 0.05). Moreover, no difference was observed in the HPAECs apoptosis assessed by TUNEL and the ratio of cleaved Caspase-3/Caspase-3 (0.51±0.17 vs.0.50±0.11) between the two AAT1-overexpressed groups (all P>0.05). Conclusion Endo-genous SO2 inhibited the hypoxic HPAECs apoptosis stimulated by the treatment of CoCl2. Key words: Sulfur dioxide; Aspartate aminotransferase 1; Cobalt chloride; Human pulmonary arterial endothelial cells; Apoptosis