Influence of reactive oxygen species on secretory component in the intestinal epithelium during hyperoxia

Redox imbalance is established in various human diseases. Treatment of intestinal epithelial cells with hyperoxia for a prolonged period of time may cause serious effects on redox balance. Secretory component (SC) protein is secreted by intestinal epithelial cells, and has a vital role in mucosal immune systems and intestinal defense. The present study aimed to investigate the influence of reactive oxygen species (ROS) on intestinal epithelial cells and intestinal epithelial SC protein under hyperoxic conditions. Caco-2 cells were treated with increasing concentrations of hydrogen peroxide (H₂O₂) or 85% O₂ (hyperoxia) for 24 h. Flow cytometry, immunohistochemistry staining, western blot analysis and reverse transcription-quantitative polymerase chain reaction were performed to detect the expression levels of SC protein. Significantly increased apoptosis and mortality rates were observed in hyperoxia- and H₂O₂-treated Caco-2 cells, as compared with the untreated control cells (P<0.05). Protein and mRNA expression levels of SC were significantly increased in hyperoxia- and H₂O₂-treated groups, as compared with the control group (P<0.05). During hyperoxia, intestinal epithelial cells were destroyed and ROS levels increased. Therefore, the results of the present study suggested that ROS might have an important role in intestinal injury in hyperoxic environments.