Moderate hyperoxia plays a protective role in lung bronchial epithelial cells

Purpose: Oxygen therapy is commonly used in clinical settings, but several problems may result from improper use. Oxygen poisoning involves the initiation of a series of inflammatory reactions. In this study, we compared the effects of moderate hyperoxia (40% O-2) and extreme hyperoxia (85% O-2) on pulmonary bronchial epithelial cells. Methods: Normal human tracheobronchial epithelium (NHBE) cells were exposed to hyperoxia (40% and 85%) for 24 hours, and their survival rates were determined by the colorimetic assay, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide). The protein and mRNA levels of RelA, RelB, ASK1, TNF-alpha and secretory component (SC) were detected by immunohistochemical staining, western blot, and real-time polymerase chain reaction. Results: The NHBE cell survival increased in the presence of moderate hyperoxia. RelA, RelB, ASK1, TNF-alpha and SC expressions were significantly higher in the 85% O-2 group in comparison with the control group and the 40% O-2 group. In the 40% O-2 group, RelA, RelB, ASK1 and TNF-alpha were up-regulated, but SC expression was not significantly different than that of the control group. However, compared with the 85% O-2 group, SC expression was significantly lower in the 40% O-2 group. Conclusion: These results suggest that moderate hyperoxia promotesproliferation in NHBE cells and activates TNF-alpha and downstream ASK1. ThenTNF-alpha activates NF-kappa B and SC to play a protective role.