Mitochondria-mediated Apoptosis in Human Lung Type Ⅱ Alveolar Epithelial-like A549 Cells by Paraquat / 中国医科大学学报

ABSTRACT

Objective To investigate the apoptosis mechanism induced by paraquat (PQ) in human type Ⅱ alveolar epithelial-like A549 cells.Methods A549 cells were cultured in vitro.The cells in the experimental group were exposed to various concentrations of PQ (50,100,150,and 200 μmol/L),while those in the control group were cultured in RPMI1640 medium.After treatment for 24 and 48 h,the cell survival rate was assessed by MTT assay.Morphological changes in the nuclei were observed by Hoechst 33258 fluorescence staining.Cellular apoptosis and mitochondrial transmembrane potential were assayed by flow cytometry.The activities of caspase-3 and caspase-9 were assayed by spectrophotometry.Western blotting was used to analyze the expression of proteins in the Bcl-2 family,such as Bcl-2,Bcl-xL,Bax,and Bak.Results PQ exhibited significant anti-proliferative activity in A549 cells.PQ-treated A549 cells were subjected to Hoechst 33258 staining.The hallmarks of apoptosis were detected,and the degree of apoptosis increased.Mitochondrial membrane potential was decreased,the levels of active caspase-3 and caspase-9 increased,the expression of Bcl-2 and Bcl-xL was decreased,and the expression of Bax and Bak was increased.These effects occurred in concentration-and time-dependent manners.Conclusion PQ efficiently induced intracellular apoptosis through the mitochondrial pathway in A549 cells.