Defective endothelial nitric oxide synthase signaling is mediated by rho-kinase activation in rats with secondary biliary cirrhosis

Abstract

In liver cirrhosis, down-regulation of endothelial nitric oxide synthase (eNOS) has been implicated as a cause of increased intrahepatic resistance. We investigated whether Rhokinase activation is one of the molecular mechanisms involved in defective eNOS signaling in secondary biliary cirrhosis. Liver cirrhosis was induced by bile duct ligation (BDL). We measured mean arterial pressure (MAP), portal venous pressure (PVP), and hepatic tissue blood flow (HTBF) during intravenous infusion of saline (control), 0.3, 1, or 2 mg/kg/hour fasudil for 60 minutes. In BDL rats, 1 and 2 mg/kg/hour fasudil significantly reduced PVP by 20% compared with controls but had no effect on HTBF. MAP was significantly reduced in response to 2 mg/kg/hour fasudil. In the livers of BDL rats, 1 and 2 mg/kg/hour fasudil significantly suppressed Rho-kinase activity and significantly increased eNOS phosphorylation, compared with controls. P ortal hypertension is a common clinical syndrome associated with liver cirrhosis and characterized by increased intrahepatic resistance and elevated splanchnic blood flow, leading to a pathological increase in portal pressure and the development of portosystemic collaterals such as esophagogastric varices. 1-6 Pharmacological therapy for portal hypertension should be aimed at reducing intrahepatic vascular tone or elevated splanchnic blood flow. However, the only available treatment is a nonselective beta-blocker that reduces portal venous pressure (PVP) by decreasing cardiac output and splanchnic blood flow. 7 Several randomized trials indicate that a nonselective beta-blocker is the first choice for primary and secondary prophylaxis against esophageal variceal bleeding. [8][9][10] However, the mean decrease in PVP in response to beta-blockers is only approximately 15%. Moreover, 15% of patients with cirrhosis are beta-blocker intolerant, whereas another approximately 30% do not respond to betablockers despite adequate blockade. 11 Therefore, there is a pressing need for a more effective pharmacological therapy for portal hypertension.Previous studies have shown that hepatic stellate cells (HSCs) through their contraction play a crucial role in regulating sinusoidal vascular tone. 12 The contractility of HSCs is regulated by the balance of vasoactive agents such as endothelin-1, and vasorelaxing agents such as nitric oxide (NO). 13 Recent studies have shown that the production of NO by endothelial nitric oxide synthase (eNOS) in hepatic sinusoidal endothelial cells (SECs) is Abbreviations: ␣-SMA, alpha-smooth muscle actin;

Diacylglycerol kinase alpha enhances hepatocellular carcinoma progression by activation of Ras–Raf–MEK–ERK pathway

“…Protein extraction and Western blot analysis were performed as described [26]. To measure the relative density of immunoreactive bands, images were scanned and analyzed by Image J software (National Institute of Health., Bethesda, MD).…”

Roles of vascular endothelial growth factor and endothelial nitric oxide synthase during revascularization and regeneration after partial hepatectomy in a rat model

“…Hepatic tissue blood fl ow was measured using a laser Doppler fl ow meter (Omega fl ow type II; Omega Flow, Tokyo, Japan) to measure the surface blood stream of the remaining liver at 0, 24, 72, and 168 h after PHx. [25][26][27] The probe was lightly placed on the surface of the right lobe of the remnant liver, and HTBF was measured three times at each time point.…”

Treatment With the Leukotriene Inhibitor Montelukast for 10 Days Attenuates Portal Hypertension in Rat Liver Cirrhosis

“…This confirmed the particular importance of the Rho kinase pathway in fibrotic livers, as described. 14,15,18 Accordingly in the present study, the maximal portal perfusion pressure increase by infusion of U46619 or LTC 4 or coinfusion of both U46619 and LTC 4 was attenuated by the infusion of Y27632. This result suggests that the effects of these vasoconstrictors are dependent on the function of Rho kinase, which is supposed to act in hepatic stellate cells and myofibroblasts.…”

“…Consequently, intrahepatic vascular resistance can be substantially reduced by Rho kinase inhibitors. 18 In the present study, infusion of the Rho kinase inhibitor Y27632 attenuated the increase in portal perfusion pressure observed following infusion of zymosan for KC activation in BDL animals, but not in sham-operated animals. This confirmed the particular importance of the Rho kinase pathway in fibrotic livers, as described.…”

“…[9][10][11][12][13] One mechanism in addition to the many others for the intrahepatic hyperresponsiveness to vasoconstrictors in the cirrhotic liver is the up-regulation of Rho kinase-mediated contraction. [14][15][16][17][18] Different studies demonstrated a close association between bacterial infections and variceal bleeding. [19][20][21] Indeed, recent studies suggested that Kupffer cell (KC) activation may lead to portal hypertension in cirrhosis by production of intrahepatic vasoconstrictors.…”