The relationship between interleukin-8 and airway hyperresponsiveness in guinea pigs

OBJECTIVE: To explore the relationship between interleukin-8 (IL-8) and airway hyper-responsiveness (AHR) of asthma in guinea pigs. METHODS: IL-8 at a dose of 0.5 microgram/kg or 5.0 micrograms/kg was administered intranasally to guinea pigs twice a week for 3 weeks. 24 hours after the last administration, airway responsiveness was measured as an overall index of airway response to the increasing concentrations of histamine inhaled (25, 50, 100 and 200 micrograms/ml), and the numbers of different inflammatory cells in bronchoalveolar lavage fluid (BALF) were counted. RESULTS: The IL-8 treatment significantly enhanced airway responsiveness to histamine in a dose-dependent manner (P < 0.05 or P < 0.01) and induced a significant influx of neutrophils in BALF (P < 0.01), and a great number of neutrophils were seen within the airway wall, but not within the control animals treated with phosphate buffered saline (PBS). CONCLUSION: The IL-8 could produce neutrophil inflammation of the airways and induce AHR, which suggested that IL-8 may play an important role in asthma, especially in the development of AHR.