Understanding the mechanism involved in lung epithelial potassium current modulation by ozone

Given that the ionic balance of the pulmonary alveolar lining fluid is essential for correct gas exchange, our previous studies analyzed the effects of ozone (O₃), one of the most harmful pollutants for the respiratory system, on K⁺ current (I_K)in human cultured lung epithelial cells (A549). O₃ exposure significantly alters the flow of K⁺ ions, reducing the outward rectifier current component. O₃ does not act directly, but through its byproducts, among which the main ones are 4-hydroxy-2-nonenal (4HNE) and hydrogen peroxide (H₂O₂). In this study we analyzed the action of 4HNE and H₂O₂ on I_K in human lung cells and verified the protective effect of catalase. MATERIAL: A549 cellular line. 30' exposure: O₃: 0.1 ppm; 4HNE: 5, 10 and 20 μM; H₂O₂: 20 μM. Glucose-oxidase: 10 mU/l, 1.00h exposure, analyzed after 24h. Catalase: 1000 U, 1.30h exposure. METHODS: Western blot, immunofluorescence and patch clamp techniques to study the action of the bio-products on I_K. 4HNE was able to significantly decrease the I_K, but it was less effective than O₃. H₂O₂ produced by the cells after GO administration completely reproduced the O₃ effect. Catalase showed its ability in preserving the outward rectifier component depressed by O₃, bringing back the current to the control level. We can conclude that 4HNE and H₂O₂ are responsible for the O₃ action on potassium channels. The protective role of catalase confirms the ability of O₃ bio-product to modify the cellular redox homeostasis. In perspective it will be interesting to analyze their interaction, and the bio-molecular pathways activated.