Does the maxillary sinus have a triggering role in nasal nitric oxide synthesis?

Objectives: We investigated whether the maxillary sinus plays a stimulatory role in nasal nitric oxide (NO) synthesis. Research on sinusitis and nasal polyps has found low NO levels in exhaled air and linked this to obstruction of the ostium. However, the major source of NO in exhaled air is thought to be the nasal mucosa. In this study, Streptococcus pneumoniae was applied to the maxillary sinus to investigate changes in NO synthesis of the nasal mucosa. Methods: An experimental study was performed with New Zealand white rabbits. Three groups, pneumococcus, control and sham, were created. The maxillary sinus of the pneumococcal group was exposed to Streptococcus pneumoniae suspension. Before and after the exposure, bilateral biopsy specimens were taken from the inferior turbinate. Specimens were examined by RT-PCR for expressions of endothelial nitric oxide synthase (e-NOS) and inducible nitric oxide synthase (i-NOS). Physiological saline solution was administered to the maxillary sinus in the control group and biopsies were obtained. The sham group underwent only biopsy. Results: A significant increase in i-NOS expression of tissue samples from the pneumococcal group on the same and opposite sides were detected. There was no increase in e-NOS expression in this group. The control and sham groups had no significant change in i-NOS or e-NOS expression. Conclusion: In the acute period after the maxillary sinus is exposed to a pathogen, i-NOS expression increases in the nasal mucosa, but endothelial NOS expression is not affected. Consequently, a combined response in the maxillary sinus and the nasal mucosa for nitric oxide synthesis is shown in the present study.