Heme oxygenase-1 expression in disease states.

Heme oxygenase-1 (HO-1) is an enzyme which catalyzes the rate-limiting step in heme degradation resulting in the formation of iron, carbon monoxide and biliverdin, which is subsequently converted to bilirubin by biliverdin reductase. The biological effects exerted by the products of this enzymatic reaction have gained much attention. The anti-oxidant, anti-inflammatory and cytoprotective functions associated with HO-1 are attributable to one or more of its degradation products. Induction of HO-1 occurs as an adaptive and beneficial response to several injurious stimuli including heme and this inducible nature of HO-1 signifies its importance in several pathophysiological disease states. The beneficial role of HO-1 has been implicated in several clinically relevant disease states involving multiple organ systems as well as significant biological processes such as ischemia-reperfusion injury, inflammation/immune dysfunction and transplantation. HO-1 has thus emerged as a key target molecule with therapeutic implications.