Augmentation of allergic inflammation in the airways of cyclooxygenase‐2‐deficient mice

Abstract

OBJECTIVE: Airway cyclooxygenase-2 (COX-2) is induced by cytokine-mediated inflammation such as occurs in asthma. However, the role of COX-2 in the pathophysiology of asthma is not fully understood. METHODS: Allergic inflammation, airway responsiveness to methacholine and mucous cell metaplasia after ovalbumin sensitization in the airways of COX-2 deficient (-/-) mice, COX-2 (+/+) mice and C57BL/6J mice treated with a selective COX-2 inhibitor, nimesulide were assessed. Histology, cell analysis, measurements of arachidonic acid metabolites and Th2 cytokine levels in bronchoalveolar lavage fluid (BALF), and measurement of serum IgE were performed. RESULTS: Eosinophil infiltration into the airway wall, and the number of eosinophils in BALF were greater in sensitized COX-2 (-/-) mice than in sensitized COX-2 (+/+) mice. The levels of cysteinyl leukotrienes (LTC4/D4/E4), prostaglandin E2 (PGE2) and interleukin (IL)-13 as well as airway responsiveness did not differ in COX-2 (-/-) mice and COX-2 (+/+) mice. However, sensitized COX-2 (-/-) mice had higher LTC4/D4/E4 and lower PGE2 concentrations compared with non-sensitized COX-2 (-/-) mice. The number of PAS/alcian blue-positive airway epithelial cells and serum IgE were elevated in COX-2 (-/-) mice. Nimesulide-treated mice showed augmented eosinophilic inflammation, LTC4/D4/E4 concentrations and mucous cell metaplasia. CONCLUSION: These data indicate that COX-2 deficiency augments allergic inflammation and mucous cell metaplasia.