Eosinophilic rhinitis accompanies the development of lower airway inflammation and hyper-reactivity in sensitized mice exposed to aerosolized allergen

Background Allergic rhinitis is a risk factor for the development of asthma. About 80% of asthmatic patients also have rhinitis. However, the pattern of induction of allergic rhinitis and asthma remains unclear. Objective The purpose of this study was to investigate the development of upper airway inflammation in mice during the development of an asthma-like disease and after an acute allergen provocation. Methods BALB-c mice were sensitized intraperitoneally (i.p) to ovalbumin (OA, days 1-13) and were challenged with aerosols of either OA or saline on 8 consecutive days (days 33-40). In a second experiment, chronic exposure for 8 days was followed by 10 days of rest and then an acute nebulized allergen provocation was performed (day 50). Inflammatory parameters were investigated at different time-points. Results Upper and lower eosinophilic airway inflammation were simultaneously induced in the course of repeated inhalations of nebulized OA, as shown by analyses of nasal and broncho-alveolar lavage fluids and histological sections of the nose and bronchi. Mice that developed bronchial hyper-responsiveness also had increased thickness of the nasal mucosa on magnetic resonance image (MRI) scans. When chronic exposure was followed by acute allergen provocation, the latter caused a systemic increase in IL-5 levels, with a concomitant rise in blood and airway eosinophils, primarily in the nose. Conclusions Simultaneous induction of eosinophilic inflammation in the nose and lungs was found in a mouse model of respiratory allergy. These findings support the viewpoint that upper and lower airway disease represent a continuum of inflammation involving one common airway and provide evidence for the concept of global airway inflammation after inhalation of allergen.