NITROGEN-DIOXIDE INCREASES EOSINOPHIL ACTIVATION IN THE EARLY-PHASE RESPONSE TO NASAL ALLERGEN PROVOCATION

Recent studies have suggested that exposure to air pollutants may sens itise susceptible individuals to allergen. We have investigated the ef fect of exposure for 6 h to 400 ppb NO2 on nasal airways resistance (N AR) and changes in inflammatory mediators (IMs) in nasal lavage in sub jects with a history of seasonal allergic rhinitis. In this single bli nd crossover study, 8 patients were randomised to exposure to either a ir or 400 ppb NO2 in air and evaluated for changes in NAR and IM, befo re and after exposure. Another 8 patients were further challenged with allergen after similar exposure regimes and then evaluated for change s in NAR and IMs. Exposure to air or NO2 did not alter either NAR or t he levels of eosinophil cationic protein (ECP), mast cell tryptase (MC T), myeloperoxidase (MPO) or interleukin (IL)-8 in nasal lavage. MCT w as significantly increased after allergen challenge following exposure to both air and NO2. In contrast, ECP was significantly increased by allergen challenge only after exposure to NO2. Neither MPO nor IL-8 we re altered after allergen challenge. These results suggest that NO2 ma y increase eosinophil activation in the early-phase response to nasal allergen provocation in allergic rhinitis.