Neurokinin-1 receptor mediates stress-exacerbated allergic airway inflammation and airway hyperresponsiveness in mice

Background: A wealth of clinical observation has suggested that stress and asthma morbidity are associated. We have previously established a mouse model of stress-exacerbated allergic airway inflammation, which reflects major clinical findings. Objective: The aim of the current study was to investigate the role of the neurokinin- (NK-)1 receptor in the mediation of stress effects in allergic airway inflammation. Methods: BALB/c mice were systemically sensitized with ovalbumin (OVA) on assay days 1, 14, and 21 and repeatedly challenged with OVA aerosol on days 26 and 27. Sound stress was applied to the animals for 24 hours, starting with the first airway challenge. Additionally, one group of stressed and one group of nonstressed mice received the highly specific NK-1 receptor antagonist RP 67580. Bronchoalveolar lavage fluid was obtained, and cell numbers and differentiation were determined. Airway hyperreactivity was measured in vitro by electrical field stimulation of tracheal smooth-muscle elements. Results: Application of stress in sensitized and challenged animals resulted in a significant increase in leukocyte number in the bronchoalveolar lavage fluid. Furthermore, stressed animals showed enhanced airway reactivity. The increase of inflammatory cells and airway reactivity was blocked by treatment of animals with the NK-1 receptor antagonist. Conclusion: These data indicate that the NK-1 receptor plays an important role in mediating stress effects in allergen-induced airway inflammation.