Involvement of peroxynitrite in pollen-induced nasal blockage in guinea pigs

Nitric oxide (NO) has been implicated in early and late phase nasal blockage in a Japanese cedar pollen-induced experimental allergic rhinitis guinea pig model. In this study, we investigated the role of peroxynitrite, which is formed by a rapid reaction of NO with superoxide anion, in the antigen-induced biphasic nasal blockage. Sensitized guinea pigs were repeatedly challenged by pollen inhalation once every week. The peroxynitrite scavenger, ebselen (30 mg/kg), or the xanthine oxidase inhibitor, allopurinol (50 mg/kg), was intraperitoneally administered 30 min before the antigen challenge. The late phase nasal blockage induced 4 h after the challenge was largely suppressed by ebselen (57% inhibition; P < 0.05) and allopurinol (47% inhibition; P < 0.05), but neither ebselen nor allopurinol influenced the early phase response. On the other hand, the intranasal instillation of peroxynitrite (10− 3 and 10− 2 M, 10 μl/nostril) caused a remarkable dose-dependent nasal blockage in the sensitized guinea pig. These results suggest that peroxynitrite plays a major role in the late phase nasal blockage induced by the antigen challenge in sensitized guinea pigs.