Effect Of Hypoxic Postconditioning On Alveolar Epithelial Type Ⅱ Cell Death Receptor Apoptotic Pathway

Objective:To investigate the effects of hypoxic postconditioning on apoptosis of type II alveolar epithelial cells death receptor pathway and provide the new experimental evidence in the protection measures of acute lung injury.Methods:The third generations of subculture human type II alveolar epithelial cells (A549cell) were separated into3groups randomly. They were normoxia group, hypoxia-reoxygenation group and hypoxic postconditioning group, respectively.①normoxia group: the cells were cultured to confluence in six6-well culture plates, incubated in normoxic conditions (5%CO2,95%air at37℃) for24hours.②hypoxia-reoxygenation group (H/R group):the cells were cultured to confluence in six6-well culture plates, subjected to stringent hypoxia (5%CO2,95%N2at37℃) for12hours, and returned to normoxic conditions (5%CO2,95%air at37℃) for12hours.③hypoxic postconditioning group (H-PostC group):hypoxic postconditioning (5R/5H, three times) between the end of hypoxic(5%CO2,95%N2at37℃)for12h and the beginning of reoxygenation(5%CO2,95%air at37℃) followed by reoxygenation for12h. Inverted phase contrast microscope, flow cytometry and RT-PCR method were used to observe cell morphological change, apoptosis rate and expressions of caspase8, Fas, FasL genes, respectively.Results:①Cell morphology changes:The normoxia group displayed:the cells were spindle shape and bright, sticked to the bottle firmly, cell suspension could not been found. The hypoxia-reoxygenation group displayed:cells became round, intercellular space became broad, there were cell lysozyme, floating cells and cell debris in the culture medium. The hypoxic postconditioning group displayed:a few of the cells became round and the intercellular space became a little broad.②Cell apoptosis rate:There was significant statistical difference among the three groups (p<0.05). Compared with normoxia group, it significantly increased in H/R group and H-PostC group (p<0.05). And compared with H/R group, that in H-PostC group was significantly decreased (p<0.05).③caspase8gene expression:There was significant statistical difference among the three groups (p<0.05). Compared with normoxia group, it significantly increased in H/R group and H-PostC (p<0.05). And compared with H/R group, H-PostC group significantly decreased (p<0.05).④Fas gene expression:There were significant statistical differences among three groups (p<0.05). Compared with normoxia group, it significantly decreased in H/R group and H-PostC (P<0.05). Compared with H/R group, that in H-PostC group significantly increased (p<0.05).⑤FasL gene expression:There were significant statistical differences among three groups (p<0.05). Compared with normoxia group, it significantly increased in H/R group and H-PostC(p<0.05). And compared with H/R group, that in H-PostC group significantly decreased (p<0.05).Conclusion:Hypoxia can lead to type Ⅱ alveolar epithelial cell apoptosis via death r-ecepto apoptotic pathway. Hypoxic postconditioning can obviously reduce the cell apoptosis that was induced by hypoxia.