Expression and localization of cyclooxygenases (Cox-1 and Cox-2) in nasal respiratory mucosa. Does Cox-2 play a key role in the immunology of nasal polyps?

Introduction: Cyclooxygenases 1 (Cox-1) and 2 (Cox-2) play a key role in arachidonic acid metabolism and in the regulation of eicosanoid production. The balance of prostaglandin and leukotrien release in respiratory mucosa is a crucial factor in the development of Sampler's triad in NSAID (aspirin-) intolerant patients and possibly also relevant in the pathophysiology and immunology of chronic rhinosinusitis (CRS) and nasal polyposis in NSAID tolerant patients. Methods: 36 surgical specimens were immunohistochemically labeled for Cox-1 and Cox-2. Specimens were taken from chronically inflamed mucosa (n=13) and from nasal polyps (n=10) during endonasal sinus surgery. Controls were obtained from healthy nasal respiratory mucosa (n=13), harvested during turbinate surgery in patients with nasal obstruction without inflammatory disease. Results: Analysis revealed that Cox-1 and Cox-2 were labeled in all 23 inflamed / polypoid tissue specimens and in all 13 controls. In chronically inflamed tissue the expression of Cox-1 and Cox-2 was strongly labeled in the respiratory epithelial lining and in mucosal glandular ducts. In nasal polyps the expression pattern of Cox-1 was similar, but Cox-2 was much less intensely labeled in the superficial epithelial cellular lining. Controls showed homogenious labeling of Cox-1 and Cox-2 in both tissues with little intensity. Conclusions: These data suggest that Cox-2 is downregulated in epithelial cells of nasal polyps. Cox-1 and 2 are present in high concentrations in ductal structures of mucosal glands. The significance of these findings has to be discussed with regard to the regulatory function of Cox-2 in eicosanoid release and the role of the latter in the immunology and pathophysiology of nasal polyps.