Abstract: Objective To explore the tissue damage and underlying mechanism of hypoxia on human bronchial epithelial cells. Methods Human primary cultured bronchial epithelial cells were divided into three groups: 1)Control group: conventionally cultured in normal environment for 6 hours; 2)Hypoxia group: cultured in 5% O₂ environment for 6 hours; 3)Fumigation group: cultured in 5% cigarette smoke environment for 6 hours. Transmission electron microscopy was used to observe the morphological changes of organelles. Trans-epithelial cell electrical resistance detection was used to evaluate cell permeability, apoptosis was detected by flow cytometry and the expression of atresia band protein 1 (ZO-1) and transmembrane proteins (occludin and claudin-1) was detected by Western blot. Results 1)Compared with control group, the apoptosis rate of cells in the hypoxia group and fumigation group increased while cell resistance decreased and the intercellular permeability increased. 2)The expression of claudin-1 protein decreased in the hypoxia group, the expression of occludin,claudin-1 and ZO-1 proteins in the fumigation group decreased significantly. 3)The nuclear membranes of cells in the hypoxia group and fumigation group shranked and mitochondria were damaged. The autophagosomes and apoptotic bodies were found in cell cytoplasm. Conclusions Hypoxia down-regulates the expression level of tight junction proteins in human bronchial epithelial cells and increases cell permeability, which may lead to impaired epithelial barrier function by demolishing tight junction structures.

Key words: human bronchial epithelial cell, hypoxia, cigarette smoke, tight junction protein