Effect of Inhaled Histamine on Airway Epithelial Cell Swelling in Ozone-Exposed Guinea Pigs

Abstract

Background: It has been reported that histamine stimulates ion channels on airway epithelial cells and induces changes in osmolarity and the ion composition of the periciliary field of airway epithelia. Objective:To investigate the effect of inhaled histamine on epithelial cell swelling, we studied the role of airway epithelial cells under histamine inhalation challenge in an animal model of airway inflammation using ozone exposure. Method: After exposure to 3.0 ppm ozone for 2 h, guinea pigs were anesthetized and tracheostomized, and then, lung resistance (R_L) was measured. Histamine inhalation challenge and histological examination were performed. Result:The values of R_L before histamine inhalation in the control group and the ozone-exposed group were 0.26 ± 0.11 and 0.45 ± 0.34 cm H₂O/s, respectively. R_L increased significantly after histamine inhalation both in the control and the ozone-exposed groups. The threshold of histamine (PC₂₀₀) in the ozone-exposed group was significantly lower than that in the control group. A significant swelling of the epithelial cells after histamine inhalation was observed both in the control and the ozone-exposed groups, with a greater increase in the ozone-exposed group compared with the control group. However, no change in wall thickness was observed in the histamine/antihistamine or the ozone/histamine/antihistamine group. Conclusion: Our results suggest the possibility that the airway epithelial cell swelling plays a role in the increase in R_L after histamine inhalation, especially in the presence of airway inflammation.