Expression of angiotensin II type 1 receptor in human cirrhotic livers: Its relation to fibrosis and portal hypertension

Abstract

Angiotensin II (ANG-II) and its receptor (AT1) have been potential targets of therapy for liver cirrhosis. However, AT1 expression in human cirrhotic livers has not been clarified. We studied AT1 and ANG-II generating enzymes in human autopsy (20 cirrhotics and 20 normal controls) and biopsy (10 cirrhotics) livers. AT1 immunoreactivity in tissue sections was quantified by computer-aided morphometry. AT1 protein and mRNA levels were assessed by Western blotting and real-time polymerase chain reaction. Concerning ANG-II generating system, angiotensin-converting enzyme (ACE) and mast cell chymase were examined. AT1 expression was seen not only in vascular smooth muscle cells, but also in activated stellate cells/myofibroblasts and liver parenchymal cells. AT1-positive vessels and myofibroblasts were significantly increased in fibrous septa of cirrhosis, although overall hepatic AT1 expression was reduced in the cirrhotic livers compared with the controls. Augmentation of AT1-positive vessels was related to severity of portal hypertension. Expressions of ACE and chymase were enhanced in the cirrhotic livers. These results suggest that hepatic AT1 expression is shifted to and concentrated in vessels and myofibroblasts in cirrhotic settings, and increased ANG-II generation by ACE and chymase contributes to portal hypertension and liver fibrosis via binding to AT1 expressed on vessels and myofibroblasts.