Immunolocalization of inducible nitric oxide synthase and 3-nitrotyrosine in the nasal mucosa of patients with rhinitis

Since nitric oxide (NO) can be involved in multiple physiological and pathological functions, we evaluated its possible involvement and that of peroxynitrite in the pathogenesis of rhinitis. Inferior nasal turbinates were obtained from allergic rhinitis and nonallergic rhinitis patients during corrective nasal surgery. The expressions of the inducible form of nitric oxide synthase (iNOS) and the production of peroxynitrite and its metabolite 3-nitrotyrosine were examined by immunohistochemistry in consecutive tissue sections. Each section (or tissue compartment) was given a score of 0-4 according to the labeling intensity seen, with the highest number representing the highest labeling intensity. The results showed that iNOS expression was present mainly in the mucosal epithelium, vascular endothelium, and submucosal glands. A significant difference was only observed in the labeling scores of glandular tissues of the allergic group, which had a higher iNOS labeling score. We also found that sections with a higher iNOS level did not necessarily exhibit a higher 3-nitrotyrosine labeling intensity. These data suggest that iNOS-derived NO may have a role in the pathophysiology of rhinitis, especially the glandular function of allergic nasal mucosa. Moreover, our findings suggest that the production of peroxynitrite in rhinitis patients is not dependent on the level of iNOS alone.