Expression and localization of cyclooxigenases (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 Sampter'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.