Paradoxical low nasal nitric oxide in nasal polyposis

Abstract

NO levels are low in nasal polyposis, despite high levels of iNOS, possibly related to blockage of the ostiomeatal complex and failure of NO generated constitutively in the sinuses to reach the nasal airway. A rise in the NO levels is seen with successful polyp treatment, and is proportional to the reduction in endoscopically assessed polyp size, suggesting that with both medical and surgical therapy, the ostiomeatal complex obstruction is decreasing. We propose the following scenario. Nasal NO levels are the result of two processes: inducible NO production by inflamed nasal mucosa plus constitutive sinus mucosal production, detectable in normals. In uncomplicated allergic rhinitis with patent sinus ostia NO levels tend to be elevated, but when inflammation is sufficient to obstruct sinus ostia (as in nasal polyps), NO levels fall because sinus NO makes the major contribution.