Participation of heme oxygenase-1 in a model of acute inflammation.

In this study, the role of heme oxygenase-1 (HO-1) in the inflammatory response elicited by zymosan in the mouse air pouch model has been examined. This response is characterized by a time-dependent increase in HO-1 expression in the leukocytes migrating into the exudates. At 24-48 h maximal HO-1 expression was accompanied by reduced cyclooxygenase-2 (COX-2) and nitric oxide synthase-2 (NOS-2) expression as well as low levels of inflammatory mediators. Hemin administration into the air pouch caused an elevation of HO-1 protein and bilirubin levels induced by zymosan with inhibition of COX-2 expression. In mouse peritoneal macrophages from hemin-injected mice, we also observed an increased expression of HO-1 with inhibition of COX-2 expression and prostaglandin E(2) (PGE(2)) levels. Our data suggest an anti-inflammatory role for HO-1 in the response induced by this phagocytic stimulus.