Increased heme oxygenase-1 gene expression in the livers of patients with portal hypertension due to severe hepatic cirrhosis

Surgical bleeding associated with splanchnic hyperaemia due to portal hypertension complicates the anaesthetic management of hepatic transplantation. Although the mechanism(s) of portal hypertension are not fully understood, carbon monoxide, a product of the heme oxygenase (HO) reaction, is thought to be one of the endogenous vasodilators in the liver. In this study, the expression of mRNA encoding inducible HO isozyme (HO-1) in the livers of patients with portal hypertension undergoing hepatic transplantation was determined in comparison with those without portal hypertension. HO-1 mRNA levels were significantly greater in the portal hypertension group than in the group without portal hypertension. In contrast with HO-1, the gene expression of non-specific δ-amino-levulinate synthase (ALAS-N), which is down-regulated by heme in the liver, was the same in both groups. These results suggest that HO-1 is up-regulated through heme-independent stimuli according to the development of portal hypertension, and that induced HO-1 plays a pathophysiological role in portal hypertension through carbon monoxide production.