Atorvastatin lowers portal pressure in cirrhotic rats by inhibition of RhoA/Rho-kinase and activation of endothelial nitric oxide synthase

Abstract

In cirrhosis, increased RhoA/Rho‐kinase signaling and decreased nitric oxide (NO) availability contribute to increased intrahepatic resistance and portal hypertension. Hepatic stellate cells (HSCs) regulate intrahepatic resistance. 3‐Hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitors (statins) inhibit synthesis of isoprenoids, which are necessary for membrane translocation and activation of small GTPases like RhoA and Ras. Activated RhoA leads to Rho‐kinase activation and NO synthase inhibition. We therefore investigated the effects of atorvastatin in cirrhotic rats and isolated HSCs. Rats with secondary biliary cirrhosis (bile duct ligation, BDL) were treated with atorvastatin (15 mg/kg per day for 7 days) or remained untreated. Hemodynamic parameters were determined in vivo (colored microspheres). Intrahepatic resistance was investigated in in situ perfused livers. Expression and phosphorylation of proteins were analyzed by RT‐PCR and immunoblots. Three‐dimensional stress‐relaxed collagen lattice contractions of HSCs were performed after incubation with atorvastatin. Atorvastatin reduced portal pressure without affecting mean arterial pressure in vivo. This was associated with a reduction in intrahepatic resistance and reduced responsiveness of in situ–perfused cirrhotic livers to methoxamine. Furthermore, atorvastatin reduced the contraction of activated HSCs in a 3‐dimensional stress‐relaxed collagen lattice. In cirrhotic livers, atorvastatin significantly decreased Rho‐kinase activity (moesin phosphorylation) without affecting expression of RhoA, Rho‐kinase and Ras. In activated HSCs, atorvastatin inhibited the membrane association of RhoA and Ras. Furthermore, in BDL rats, atorvastatin significantly increased hepatic endothelial nitric oxide synthase (eNOS) mRNA and protein levels, phospho‐eNOS, nitrite/nitrate, and the activity of the NO effector protein kinase G (PKG). Conclusion: In cirrhotic rats, atorvastatin inhibits hepatic RhoA/Rho‐kinase signaling and activates the NO/PKG‐pathway. This lowers intrahepatic resistance, resulting in decreased portal pressure. Statins might represent a therapeutic option for portal hypertension in cirrhosis. (HEPATOLOGY 2007;46:242–253.)