Signal transduction and oxidative processes in sinonasal polyposis

Background Nasal polyposis is characterized by impaired regulation of nasal tissue growth and is associated with chronic inflammation, sinus infections, and low levels of nitric oxide (NO). Based on its critical role in mediating cell growth and antimicrobial function, decrease of NO levels has been implicated in the pathogenesis of nasal polyposis. Objective We sought to evaluate mechanisms for the low NO level in polyposis, including factors regulating NO synthase (NOS) expression and activity and NO consumptive processes in nasal epithelial cells and nasal lavage fluid. Methods Eighteen patients with nasal polyposis and 8 healthy control subjects were studied. Nasal brushings, nasal lavage fluid, and nasal biopsy specimens were collected and analyzed. Results NO metabolite levels (nitrite and nitrate) in nasal lavage fluid from patients with polyps were less than those in control subjects, but activation of signal transduction and inducer of transcription 1, which regulates inducible NOS gene expression and protein expression, was present at higher levels in polyp than in healthy control tissue. Levels of arginine, methylarginine, and endogenous NOS inhibitors were similar between polyp and control tissue. In contrast, superoxide dismutase activity of polyp tissues was lower than that seen in control tissue and associated with increased nitrotyrosine, a biomarker of oxidant consumptive products of NO. Conclusion Taken together, these data suggest that the nasal polyp environment is characterized by abnormalities in NO metabolism that might predispose to altered regulation of tissue growth and infection. Clinical implications Identification of NO metabolic abnormalities might lead to novel treatments for sinonasal polyposis targeted against the pathways identified within this study.