Cyclooxygenase-2 expression in inflammatory lung lesions of nonhuman primates

Mammalian cells contain two related but unique isoforms of cyclooxygenase ( COX-1 and COX-2). COX-1 is expressed constitutively in a majority of tissue s and is involved in the production of prostaglandins (PGs) that modulate n ormal physiologic functions. COX-2 is inducible by various stimuli and is i nvolved in the production of PGs that modulate physiologic events in develo pment, cell growth, and inflammation. With the exception of peribronchial g lands and chondrocytes of peribronchial cartilage, COX-2 is not detectable in the normal lung of nonhuman primates. We evaluated COX-2 expression by i mmunohistochemical methods in the inflammatory lesions of two cynomolgus mo nkeys (Macaca fascicularis) with acute severe pneumonia. Both monkeys exhib ited acute severe bronchopneumonia; histologically, lung lesions were chara cterized by infiltration of large numbers of neutrophils and fewer macropha ges, mild bronchial epithelial hyperplasia, and slight type-2 pneumocyte hy perplasia. In both monkeys, mild to marked COX-2 immunoreactivity was detec ted within the cytoplasm of macrophages, bronchial epithelial cells, type-2 pneumocytes, and endothelial cells of blood vessels. No COX-2 immunoreacti vity was detectable in the neutrophils that constituted >90% of the inflamm atory cells. These observations suggest that in acute inflammatory lung les ions in nonhuman primates 1) COX-2 is induced in the bronchial and alveolar epithelial cells, 2) macrophages are the primary inflammatory cells that e xhibit COX-2, and 3) neutrophils do not express COX-2.