Protein nitration in chronic sinusitis and nasal polyposis: Role of eosinophils

OBJECTIVES: To investigate the possible role of eosinophil peroxidase (EPO) in 3-nitrotyrosine (3NT) formation. STUDY DESIGN AND SETTING: Observational study employing immunocytochemistry to assess the presence of 3NT, inducible nitric oxide synthase (NOS), eosinophils, mast cells, neutrophils, and lymphocytes in ethmoid sinus mucosal biopsies from normal controls and subjects with allergic and nonallergic chronic sinusitis and nasal polyposis. RESULTS: 3NT was more evident in biopsies from sinusitis patients (2.67 +/- 0.14, n = 21) than in healthy mucosa (0.43 +/- 0.2, n = 7, P < 0.01), but scores in atopic and nonatopic subjects were similar. Colocalization studies confirmed that 3NT was largely confined to eosinophils. No relationship was found between 3NT and other immune cells. 31NT detection was not correlated with the amount of immunostaining for iNOS. SIGNIFICANCE., Chronic sinusitis is accompanied by 3NT formation, which is largely restricted to the eosinophils, and likely driven by the action of eosinophil peroxidase, rather than by nitric oxide levels.