Expression of nitric oxide synthases in primary ciliary dyskinesia

Nitric oxide is believed to play a central role in nonspecific defense of upper airways. Patients with primary ciliary dyskinesia have very low concentration of nasal nitric oxide, which may contribute to the chronic upper airway diseases encountered by these patients. The mechanisms underlying this drop of nasal nitric oxide in primary ciliary dyskinesia are still unknown. The goal of the present work was to study nitric oxide synthases expression in upper airway tissues from patients with primary ciliary dyskinesia. For this purpose, 5 patients with primary ciliary dyskinesia and 10 nonallergic age-matched patients without primary ciliary dyskinesia undergoing nasal polypectomy were included. Nasal nitric oxide concentration was measured before polypectomy, and nitric oxide synthase expression and function were studied in nasal polyps. The nasal nitric oxide in patients with primary ciliary dyskinesia was lower than that in patients without primary ciliary dyskinesia (13 [9-16] ppb versus 210 [167-254] ppb, P < .0001). Nitric oxide synthase 2 immunostaining was prominent at the apical part of the ciliated epithelial cells and was similar in both groups. Nitric oxide synthase 3 staining was restricted to endothelial cells in both groups. In addition, reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was superimposable to nitric oxide synthases 2 and 3 immunostaining, suggesting a preserved NADPH-activity of nitric oxide synthase. We therefore conclude that the drop in nasal nitric oxide in patients with primary ciliary dyskinesia is not secondary to the loss of nitric oxide synthase expression.