Possible involvement of nitric oxide and peroxynitrite in nasal polyposis

Nitric oxide (NO) is implicated in inflammation. Its role in the pathogenesis of nasal polyposis is not clear. The expression of inducible NO synthase (iNOS), and the production of peroxynitrite represented by the formation of 3-nitrotyrosine (3-NT) were examined by immunohistochemistry in nasal polyps. The contents of superoxide dismutases (SODs) in nasal polyps and nasal mucosa were assessed by Western blot analyses. iNOS expression and 3-NT accumulation were noted in mucosal epithelium, vascular endothelium, and interstitial cells of nasal polyps. In comparison with our previous study on the nasal mucosa from patients with rhinitis, the stromal cells of the nasal polyp had higher labeling intensity for both iNOS and 3-NT. The polyp showed similar levels of CuZnSOD and MnSOD as those of nasal mucosa. The iNOS/NO system may be important in the pathophysiology of nasal polyposis. The increased peroxynitrite may result from increased iNOS expression but is not related to decreased SODs.