Reduced expression of cyclooxygenase (COX) in idiopathic pulmonary fibrosis and sarcoidosis

Aims: To test the hypothesis that cyclooxygenase ( COX)-1 or COX-2 expression is defective in lungs in idiopathic pulmonary fibrosis (IPF) and to characterize the cellular distribution. IPF is a progressive inflammatory lung disorder with an adverse prognosis. Previous work has shown that prostaglandin E-2 (PGE(2)) regulates collagen deposition and fibroblast proliferation and a defect in COX regulation may contribute to the fibrosis that occurs in IPF. Methods: Immunohistochemistry was utilized to determine COX immunoreactivity in lung sections from 25 IPF, six sarcoidosis and 14 control subjects. Results: COX-1 and COX-2 expression in bronchiolar epithelial cells was significantly lower in IPF and sarcoidosis than in controls. No significant difference was found in COX-2 expression between macrophages in IPF and control sections, but COX-2 was reduced in macrophages in sarcoidosis compared with controls. Conclusions: These studies confirm COX-2 loss in bronchial epithelial cells but not macrophages in IPF, and show for the first time reduced constitutive COX-1 expression in epithelial cells and macrophages. Similar abnormalities were observed in sarcoidosis.