The mechanism behind why patients with primary ciliary dyskinesia (PCD) exhibit low nasal and exhaled nitric oxide (NO) remains unknown. One hypothesis is that reduced NO biosynthesis is caused by a defect in one or more NO synthases (NOSs). In healthy cells, the biosynthesis of NO is increased following exposure to respiratory pathogens. Here, we aimed to investigate whether ciliated epithelial cells from patients with PCD increase NO production following pneumococcal infection.
Human respiratory epithelium was cultured to a basal or ciliated cell phenotype using submerged or air-liquid interface cultures, respectively. Cells were exposed to media or pneumococci until cells became damaged (< 4 h). Apical fluids were collected prior and following infection, and NO production was determined using chemiluminescence. NOS gene expression was determined using real-time quantitative polymerase chain reaction.
Levels of NO and NOS2 gene expression increased significantly following infection of healthy ciliated epithelial cells but not basal cells. No increase in NO was seen in ciliated cell cultures from patients with PCD, and NOS2 gene expression remained unchanged from baseline.
These results suggest that the biosynthesis of NO in ciliated cells from patients with PCD is abnormal following early bacterial challenge, suggesting an abnormality in the function of inducible NOS in PCD.