Effects of ATP release on mucin5AC secretion in airway epithelial cells by mechanical stretching

This study is to determine the effects of ATP and Ca(2+) on mucin5AC (MUC5AC) overexpression in airway epithelial cells in mechanical ventilation. Oxygen was injected into the closed box used in this study to increase the pressure. Gravity-driven draining flow led to formation of a thin liquid film on the upper portion of cell monolayer, exposing cells to the tension forces at the air-liquid interface. The levels of MUC5AC protein and ATP in culture medium were detected by ELISA and high performance liquid chromatography, respectively. Ca(2+) and MUC5AC mRNA in culture cells were detected by flow cytometry and RT-PCR, respectively. Mechanical stretching increased the expression of MUC5AC in cells and the concentration of MUC5AC and ATP in supernatant. BAPTA-AM and EGTA partially reduced the increases in the concentrations of MUC5AC and ATP in supernatant with mechanical ventilation. BAPTA-AM completely inhibited ATP in supernatant with normal breathing conditions. Our results showed that mechanical ventilation increases the secretion of MUC5AC in airway epithelial cells. This is possibly related to Ca(2+)-dependent ATP release and intracellular and external Ca(2+).