374 HSC-DIRECTED RHO-KINASE INHIBITION IS AN EFFECTIVE AND SAVE APPROACH FOR TREATMENT OF PORTAL HYPERTENSION

Abstract

Background: In liver cirrhosis Rho-kinase expression and activation is increased and mediates contraction of activated hepatic stellate cells (HSC) and therefore portal hypertension. Rho-kinase inhibition decreases myosin light chain phosphorylation and contraction of HSC. Consequently inhibition of Rho-kinase decreased portal pressure (PP). However, this was associated with serious side effects on systemic circulation. Mannose-6-phosphate-humanserum- albumin (M6P-HSA) modified compounds bind specifically to activated HSC. The Rho-kinase inhibitor (Y-27632) was coupled to this compound, and was tested with respect to its effect on portal pressure. Methods: CCl4 intoxication and bile-duct ligation (BDL) were used as models of cirrhosis in rats. Injections of an undirected compound or HSA served as controls. Rho-kinase inhibitor was injected i.v. 3 h later invasive measurements of PP and mean arterial pressure (MAP) were performed. Coloured microsphere technique analyzed portal and systemic hemodynamics. Organs were taken for further analyses. Double staining for HSA-carrier and desmin investigated the HSC specifity of the HSC-directed carrier. Rho-kinase activity was measured as the phosphorylation of its substrate moesin using phospho- and site-specific antibodies. Phospho-myosin light chain and collagen was immunohistologically stained in cirrhotic CCl4 rat liver sections to detect the Rho-kinase activity in HSC. Results: The HSC-directed carrier coupled to Rho-kinase inhibitor was localized within the HSC of cirrhotic livers. In contrast to the undirected Rho-kinase inhibition HSC-directed Rho-kinase inhibition decreased the Rho-kinase expression and activity. HSCdirected inhibition of Rho-kinase abolished phosphorylation of myosin light chains in fibrotic septae of cirrhotic rat livers as shown by immunohistology. HSC-directed Rho-kinase inhibitor decreased intrahepatic resistance and PP in vivo in CCL4 and BDL cirrhosis. In other tissues (kidney, heart, femoral muscle) the Rho-kinase expression and activity were not influenced by the HSC-directed Rho-kinase inhibitor. Discussion: The coupling of Rho-kinase inhibitor to M6P-HSA carriers is a save approach to lower portal pressure in portal hypertension. HSC-directed Rho-kinase inhibition should be further considered for a therapy of portal hypertension in cirrhosis.