Continuous exposure of airway epithelial cells to hydrogen peroxide: Protection by KGF

Reactive oxygen species (ROS) increase permeability in the airway epithelium. Extended periods of oxidant exposure may be experienced by those suffering from chronic inflammation of the lungs, receiving supplemental oxygen, or living in areas with high levels of air pollution. We studied the effects of long-term, continuous exposure to hydrogen peroxide (H₂O₂) on the trans-epithelial electrical resistance (TER) across cultured monolayers of a transformed cell line of human bronchial epithelial cells, 16HBE14o-(16HBE). A TER perfusion system was employed to continuously monitor the TER without disturbing the tissue model. The TER decreased in a dose-dependent manner with increasing concentrations of H₂O₂ (0.1, 0.5, and 1.0 mM), regardless of pre-incubation conditions. Cell cultures pre-treated with 50 ng/ml keratinocyte growth factor (KGF) showed a significant delay in oxidant-induced TER decreases caused by 0.1 mM H₂O₂. Exposure to 0.1 mM H₂O₂ for 350 min led to disruption of tight junction proteins, ZO-1 and occludin, but KGF treatment prevented this damage. The recovery of epithelial barrier function after exposure to oxidants was also studied. Tissue models exposed to 0.5 mM H₂O₂ for 25 min showed complete recovery of TER after 20 h, independent of culture pre-treatment. In contrast, KGF pre-incubation enhanced the recovery of 16HBE cultures exposed for 50 min to 0.5 mM H₂ O₂.