Involvement of superoxide anions in ozone-induced airway hyperresponsiveness in unanesthetized guinea pigs

Abstract

To evaluate the involvement of superoxide in ozone (O 3)-induced airway hyperresponsiveness, we studied the effects of superoxide dismutase (SOD), a scavenger of superoxide anion, and apocynin, an inhibitor of superoxide anion-generating NADPH oxidase in phagocytes, on the airway responses induced by O 3 in unanesthetized guinea pigs. Airway responsiveness was measured by PC 200Mch, the concentration required to produce a doubling in the baseline specific airway resistance to an inhaled methacholine aerosol, in spontaneously breathing animals. Before exposure to 3 ppm O 3 for 30 min, animals inhaled either SOD (5000 U/ml) or vehicle for 5 min. Although SOD did not affect PC 200Mch in the air control group, this agent reduced the O 3-induced airway hyperresponsiveness. Repeated administration of apocynin (12 mg/kg for 4 days) also attenuated the O 3-induced airway hyperresponsiveness. These data suggest that superoxide may be involved in the pathogenesis of O 3-induced airway hyperresponsiveness, possibly through the stimulation of superoxide anions release from bronchoalveolar phagocytes. The data also suggest a potential therapeutic role for antioxidants in oxidant injury by air pollutants.