Constitutive nuclear factor-kappaB activity in human upper airway tissues and nasal epithelial cells.

Respiratory epithelial cells are actively involved in the host defence and inflammatory reactions of the airways. Nuclear factor-kappaB (NF-kappaB) is a transcription factor that plays a pivotal role in many cellular responses to environmental changes. The inducible nitric oxide synthase (iNOS) isoform has been implicated in airway inflammation as well as in normal airway function. In this study, the hypothesis that NF-kappaB may be associated with iNOS expression in airway epithelium, not only in inflammatory processes but also under physiological conditions was examined. NF-kappaB deoxyribonucleic acid-binding activity was assayed by means of electrophoretic mobility shift assay (EMSA) and iNOS expression examined using immunohistochemical techniques in healthy nasal mucosa and chronically inflamed nasal polyps. Further NF-kappaB activity was assayed; by means of EMSA, in nasal epithelial cells isolated from both tissues. NF-kappaB was activated in nasal polyps, but also to the same extent in healthy nasal mucosa. Uniform iNOS expression was localized within the airway epithelium in both inflamed and noninflamed tissues. Along with iNOS expression, concomitant NF-kappaB activation was found in nasal epithelial cells obtained from both tissues and no differences were observed when nasal mucosa and nasal polyp were compared. These results suggest that constitutive nuclear factor-kappaB and concurrent inducible nitric oxide synthase expression in epithelial cells may play a physiological role in airway function.