nitrogen-dioxide and Eosinophilia

Allergen sensitization and allergic airway disease are likely to come about through the inhalation of Ag with immunostimulatory molecules. However, environmental pollutants, including nitrogen dioxide (NO2), may promote adaptive immune responses to innocuous Ags that are not by themselves immunostimulatory. We tested in C57BL/6 mice whether exposure to NO2, followed by inhalation of the innocuous protein Ag, OVA, would result in allergen sensitization and the subsequent development of allergic airway disease. Following challenge with aerosolized OVA alone, mice previously exposed via inhalation to NO2 and OVA developed eosinophilic inflammation and mucus cell metaplasia in the lungs, as well as OVA-specific IgE and IgG1, and Th2-type cytokine responses. One hour of exposure to 10 parts per million NO2 increased bronchoalveolar lavage fluid levels of total protein, lactate dehydrogenase activity, and heat shock protein 70; promoted the activation of NF-kappaB by airway epithelial cells; and stimulated the subsequent allergic response to Ag challenge. Furthermore, features of allergic airway disease were not induced in allergen-challenged TLR2-/- and MyD88-/- mice exposed to NO2 and aerosolized OVA during sensitization. These findings offer a mechanism whereby allergen sensitization and asthma may result under conditions of high ambient or endogenous NO2 levels.

Topics: Administration, Inhalation; Aerosols; Allergens; Animals; Bronchial Hyperreactivity; Eosinophilia; Immunologic Factors; Lung; Metaplasia; Mice; Mice, Inbred C57BL; Mice, Knockout; Mucus; Myeloid Differentiation Factor 88; Nitrogen Dioxide; Ovalbumin; Respiratory Hypersensitivity; Toll-Like Receptor 2

Previous studies in asthmatic subjects and guinea pigs have demonstrated attenuation of bronchoconstriction in repeated exposures to clean cold dry air. In the present animal study, we have simulated short-lasting human exposures to subfreezing urban air containing sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2)). The anesthetized, paralyzed, and mechanically ventilated guinea pigs had 4 consecutive 10-min exposures either to clean cold dry air or to cold air with graded concentrations of SO(2) (0-5 ppm) or NO(2) (0-4 ppm). Peak expiratory flow (PEF) and tidal volume (V(T)) were continuously measured both during and after highly controlled exposures. Bronchoalveolar lavage fluid (BALF) and histological samples were obtained after finishing the consecutive exposures. Cold air + SO(2) at 1 and 2.5 ppm (n = 12) produced immediate concentration-dependent increases in the lung function responses compared to the preceding single exposure to clean cold dry air in the same animals (DeltaPEF = -32.7 +/- 6.1% and -35.6 +/- 6.5% vs. -27.0 +/- 3.1%; DeltaV(T) = -22.4 +/- 4.4% and -28.3 +/- 4.7% vs. -18.1 +/- 2.9%). In a multivariate analysis, these responses were significantly larger than the attenuated lung function responses to the corresponding second and third clean cold dry air exposures (p <. 05). The fourth exposure to cold air + SO(2) at 5 ppm produced a smaller response (DeltaPEF = -25.3 +/- 4.8% and DeltaV(T) = -17.8 +/- 3.7%) than cold air with the lower SO(2) concentrations. Cold air + NO(2) at 1 and 2.5 ppm (n = 12) produced roughly similar lung function responses to the preceding single exposure to clean cold dry air in the same animals, and there was no significant attenuation of bronchoconstriction as with the consecutive exposures to clean cold dry air. The largest decreases in lung functions (DeltaPEF = -33.8 +/- 6.7% and DeltaV(T) = -26.2 +/- 6.8%) were recorded during the fourth exposure, which was to cold air + NO(2) at 4 ppm. In the cold air + SO(2) group, there was a significantly lower proportion of macrophages in the differential count of BALF white cells compared to the clean cold dry air group. In addition, there was eosinophilic infiltration within and below the tracheal epithelium in all guinea pigs exposed to either clean cold dry air, cold air + SO(2), or cold air + NO(2). In conclusion, the addition of moderate concentrations of SO(2) or NO(2) to clean cold dry air counteracted the attenuation of bronchoconstriction induced by repea

Topics: Air Pollutants; Animals; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Cell Count; Cold Temperature; Dose-Response Relationship, Drug; Eosinophilia; Guinea Pigs; Hemodynamics; Hyperventilation; Inhalation Exposure; Macrophages; Male; Models, Animal; Nitrogen Dioxide; Propranolol; Pulmonary Ventilation; Respiration, Artificial; Sulfur Dioxide; Tidal Volume; Trachea

Nitrogen dioxide exposure-induced mucosal pathology of the guinea pig nose was studied. Guinea pigs were exposed to 3 ppm or 9 ppm of nitrogen dioxide for 6 h a day, 6 times weekly for 2 weeks, and sacrificed 24 h after the final exposure. Exposure to 3 ppm of nitrogen dioxide resulted in decreased ciliary activity and slight eosinophil accumulation on the epithelium and submucosal layer. More serious pathologies were observed in the nose of guinea pigs exposed to 9 ppm of nitrogen dioxide, including a more prominent eosinophil influx to the epithelium and epithelial injury due to activation of eosinophils. Epithelial damage induced by nitrogen dioxide could lead to hyperresponsiveness and may result in a prolonged allergic inflammation. Our study suggests that environmental nitrogen dioxide may contribute to hyperresponsiveness and thus be involved in the increased morbidity of allergic rhinitis.

Topics: Animals; Cilia; Dose-Response Relationship, Drug; Eosinophilia; Female; Guinea Pigs; Microscopy, Electron; Nasal Mucosa; Nitrogen Dioxide; Random Allocation; Time Factors

Nitrogen dioxide exposure-induced mucosal pathology of the guinea pig trachea was studied. Exposure to 3 or 9 ppm of nitrogen dioxide for 6 h a day, 6 times weekly for 2 weeks resulted in decreased ciliary activity as well as a dramatic eosinophil accumulation to the epithelium and submucosal layer. Especially exposure to 9 ppm of nitrogen dioxide induced epithelial injury through the activation of eosinophils accumulated in the tracheal mucosa. The epithelial damage induced by nitrogen dioxide could lead to hyperresponsiveness and prolonged allergic inflammation. Our study suggests that environmental nitrogen dioxide could contribute to the hyperresponsiveness and could most probably be involved in the development and chronicity of airway allergic disorders.

Topics: Animals; Cilia; Ciliary Motility Disorders; Eosinophilia; Epithelium; Female; Guinea Pigs; Microscopy, Electron; Mucous Membrane; Nitrogen Dioxide; Trachea; Tracheal Diseases