Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme that results in the release of carbon monoxide, iron, and biliverdin (1). The products of this enzymatic reaction play important biological roles in antioxidant, anti-inflammatory and cytoprotective functions (2). Heme oxygenase comprises two isozymes, including the constitutively expressed HO-2 isozyme and the inducible HO-1 isozyme (3). Inducible HO-1 is expressed as an adaptive response to several stimuli, including heme, metals, and hormones (4). The induction of HO-1 has been implicated in numerous disease states, such as transplant rejection, hypertension, atherosclerosis, Alzheimer disease, endotoxic shock, diabetes, inflammation, and neurological disorders (1,5).
