Intrahepatic upregulation of RhoA and Rho-kinase signalling contributes to increased hepatic vascular resistance in rats with secondary biliary cirrhosis.
OBJECTIVE
Portal hypertension in cirrhosis is mediated in part by increased intrahepatic resistance, reflecting an increased sensitivity of the hepatic microvasculature to vasoconstrictors. Activation of the RhoA/Rho-kinase pathway is essential for contraction of vascular smooth muscle. The aim of this study was to investigate RhoA/Rho-kinase mediated regulation of the intrahepatic vascular tone in cirrhotic rats.


METHODS
Cirrhosis was induced by bile duct ligation (BDL). Hepatic RhoA and Rho-kinase expressions were studied by real time reverse transcription polymerase chain reaction and western blot analysis. Hepatic Rho-kinase activity in rat and human livers was assessed as phosphorylation of the Rho-kinase substrate moesin. The effect of the Rho-kinase inhibitor Y-27632 on hepatic perfusion pressure was measured in livers perfused at constant flow. The in vivo effect of intravenous application of Y-27632 was studied by haemodynamic measurements.


RESULTS
Hepatic expressions of RhoA and Rho-kinase were increased at mRNA and protein level in BDL rats. Intrahepatic moesin phosphorylation was increased in livers from cirrhotic rats and patients with alcohol induced cirrhosis. Y-27632 reduced the basal perfusion pressure of in situ perfused livers in BDL rats but not in sham operated rats. Y-27632 reduced the sensitivity to methoxamine in isolated perfused livers in sham operated rats more than in BDL rats. In vivo, Y-27632 reduced portal pressure to a greater extent in BDL rats than in sham operated rats. Intrahepatic vascular resistance was decreased in response to bolus injection of Y-27632 in BDL rats but not in sham operated rats.


CONCLUSIONS
Upregulation of RhoA and Rho-kinase contributes to increased intrahepatic resistance in cirrhotic rats and to an increased sensitivity of cirrhotic livers to vasoconstrictors.
Department of Internal Medicine I, University of Bonn, Sigmund-Freud-Str 25, D-53105 Bonn, Germany.
Q
Q
Zhou
M
M
Hennenberg
J
J
Trebicka
K
K
Jochem
L
L
Leifeld
E
E
Biecker
T
T
Sauerbruch
J
J
Heller
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects; D006975:Hypertension, Portal / Q000209:etiology / Q000503:physiopathology; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000378:metabolism; D008102:Liver Circulation; D008105:Liver Cirrhosis, Biliary / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D008840:Microfilament Proteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction; D015854:Up-Regulation; D014655:Vascular Resistance; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000096:biosynthesis* / Q000235:genetics
D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; D014662:Vasoconstrictor Agents; C071058:moesin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D008729:Methoxamine