EFFECT OF 6-HOUR EXPOSURE TO NITROGEN-DIOXIDE ON EARLY-PHASE NASAL RESPONSE TO ALLERGEN CHALLENGE IN PATIENTS WITH A HISTORY OF SEASONAL ALLERGIC RHINITIS

Background: Recent studies have suggested that exposure to air polluta nts may enhance the airway responsiveness of susceptible individuals t o inhaled allergen. Methods: To investigate the effect of exposure to nitrogen dioxide (NO2) on nasal airways resistance (NAR) and inflammat ory mediators in nasal lavage fluid eight subjects with a history of s easonal allergic rhinitis, who were rested out of season, were exposed in a randomized single-blind, crossover study to either air or 400 pp b NO2 for 6 hours. The charges in NAR and eosinophil cationic protein (ECP), mast cell tryptase (MCT), neutrophil myeloperoxidase (MPO), and interleukin-8 (IL-8) in nasal lavage fluid before and after exposure were evaluated. Another group of eight subjects with a history of seas onal allergic rhinitis were also randomized to exposure to air or 400 ppb NO2 for 6 hours and then challenged with allergen, before evaluati on for changes in NAR and changes in ECP, MCT MPO, and IL-8 in nasal l avage fluid. Results: Exposure to air or NO2 did not alter either NAR or the levels of ECP, MCT, MPO, or IL-8 in nasal lavage fluid. Allerge n challenge after exposure to both air and NO2 significantly (p < 0.05 ) increased levels of MCT, brit not MPO and IL-8, in the nasal lavage fluid. In addition, allergen challenge after exposure to NO2, but not air significantly increased levels of only ECP in nasal lavage fluid ( p < 0.05). Conclusions: These results suggest that acute exposure to N O2, at concentrations found at the curbside in heavy traffic during ep isodes of pollution, may ''prime'' eosinophils for subsequent activati on by allergen in individuals with a history of seasonal allergic rhin itis.