Air exposure causes oxidative stress in cultured bovine tracheal epithelial cells and produces a change in cellular glutathione systems

An air-liquid interface culture system accelerates cell differentiation and growth in airway epithelial cells. In this study, the authors investigated whether glutathione (GSH) affects cell growth in an air-liquid interface culture. Various components of the cellular GSH system were measured and the number of cells was counted after conversion from an immersed feeding to an air-liquid interface. The effect of medium supplementation with cystine, a precursor of GSH, on cell growth was also examined. After conversion to an air-liquid interface, the cellular GSH level increased by 4 to 5-fold. The increase in GSH preceded the rise in cell number. The glutathione disulfide (GSSG)/total GSH ratio (an indicator of oxidative stress) increased initially and reached a plateau (time 0: 0.379%+/-0.054%; day 2: 0.824%+/-0.063%; day 6: 0.806%+/-0.093%). The level of glutathione reductase activity in the cells increased in a time-dependent manner, whereas the glutathione peroxidase activity level declined. When the amount of cystine in the medium was varied after conversion, the cellular GSH level was closely correlated with the rate of cell growth. In conclusion, air exposure causes oxidative stress in cultured cells and produces a change in the cellular glutathione system, resulting in the promotion of cell growth.