Autophagy Attenuates MnCl2-induced Apoptosis in Human Bronchial Epithelial Cells

Objective To investigate the role of autophagy in MnC l2-induced apoptosis in human bronchial epithelial 16 HBE cells.Methods Cell proliferation was measured by MTT assay.Mitochondrial membrane potential（MMP） and apoptosis were measured by flow cytometry.Autophagic vacuoles were detected by fluorescence microscopy.Cellular levels of apoptosis and autophagy-related proteins were measured by western blotting.Results 16 HBE cell proliferation was inhibited by Mn Cl2 in a dose-and time-dependent manner.Mn Cl2-induced 16 HBE cell growth inhibition was related to MMP depolarization prior to the induction of apoptosis.Our data revealed that Mn Cl2-induced apoptosis in 16 HBE cells was mediated by decreased expression of Bcl-2 and increased levels of cleaved caspase-3.It was observed that when we exposed 16 HBE cells to MnCl2 in a dose-dependent manner,the formation of autophagic vacuoles and the levels of LC-3B-II were elevated.RNA interference of LC3 B in these Mn Cl2-exposed cells demonstrated that MMP loss and apoptosis were enhanced.Additionally,the pan-caspase inhibitor Z-VAD-FMK increased the cellular levels of Bcl-2 and decreased apoptosis,but did not affect the cellular levels of LC3 B in Mn Cl2-treated 16 HBE cells.Conclusion Mn Cl2 dose-and time-dependently inhibits 16 HBE cell proliferation and induces MMP loss and apoptosis.Autophagy acts in a protective role against Mn Cl2-induced apoptosis in 16 HBE cells.

S Phase Cell Percentage Normalized BrdU Incorporation Rate, a New Parameter for Determining S Arrest

In this study, a new parameter, S phase cell percentage （S fraction） normalized BrdU （SFN-BrdU） incorporation rate, was introduced to detect $ arrest. The results showed a positive linear correlation between the BrdU incorporation rate and the S fraction in unperturbed 16HBE cells. Theoretical analysis indicated that only S arrest could result in a decrease in the SFN-BrdU incorporation rate. Additionally, the decrease in SFN-BrdU incorporation rate and the activation of DNA damage checkpoints further demonstrated that S arrest was induced by diethyl sulfate treatment of 16HBE cells. In conclusion, $FN-BrdU incorporation rate can be used to detecting S arrest.