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Background Airway NO synthase (NOS) isoenzymes are responsible for rapid and localised nitric oxide (NO) production and are expressed in airway epithelium. We sought to determine the localisation of neuronal NOS (nNOS) in airway epithelium due to the paucity of evidence. Methods and results Sections of healthy human bronchial tissue in glycol methacrylate resin and human nasal polyps in paraffin wax were immunohistochemically labelled and reproducibly demonstrated nNOS immunoreactivity, particularly at the proximal portion of cilia; this immunoreactivity was blocked by a specific nNOS peptide fragment. Healthy human epithelial cells differentiated at an air–liquid interface (ALI) confirmed the presence of all three NOS isoenzymes by immunofluorescence labelling. Only nNOS immunoreactivity was specific to the ciliary axonemeand co-localised with the cilia marker β-tubulin in the proximal part of the ciliary axoneme. Conclusions We report a novel localisation of nNOS at the proximal portion of cilia in airway epithelium and conclude that its independent and local regulation of NO levels is crucial for normal cilia function.

Primary ciliary dyskinesia (PCD) is an autosomal recessive disease associated with bronchiectasis, chronic rhinosinusitis, infertility and situs inversus. Estimates of prevalence vary widely, but is probably between 1:10,000- 1:40,000 in most populations. A number of observational studies indicate that access to services to diagnose and manage patients with PCD vary both between and within countries. Diagnosis is often delayed and frequently missed completely. The prognosis of patients with PCD is variable, but evidence suggests that it is improved by early diagnosis and specialist care. This article briefly reviews the literature concerning PCD and the evidence that specialist care will improve healthcare outcomes. The article specifically refers to a new national service in the UK.