J.C. Garcia-Pagan

Relation between portal pressure response to pharmacotherapy and risk of recurrent variceal haemorrhage in patients with cirrhosis

In patients with variceal bleeding as a complication of hepatic cirrhosis, propranolol therapy reduces the risk of recurrent variceal haemorrhage. However, the relation between portal pressure response to pharmacological treatment and clinical events has not been well defined. This relation was prospectively investigated in 69 cirrhotic patients receiving continued propranolol therapy after an episode of variceal bleeding. Hepatic venous pressure gradient (HVPG) was measured before and at 3 months of continued drug therapy. At 3 months HVPG had fallen by 20% or more in 25 patients. During follow-up of 28 (SD 17) months rebleeding occurred in 2 of these 25 patients compared with 23 of 44 who had lesser reductions in HVPG. Cumulative probability of rebleeding at 1, 2, and 3 years was 4%, 9%, and 9% in patients with a decrease in HVPG > or = 20%, and 28%, 39%, and 66% in patients with a decrease in HVPG < 20% (p < 0.001, log-rank test). On multivariate analysis, a decrease in HVPG > or = 20% was the only independent predictor of rebleeding (relative risk 0.09, 95% CI 0.02-0.41. Of the 8 patients in whom the HVPG fell to 12 mm Hg or less, none rebled. This study suggests that measurement of the HVPG response to pharmacotherapy will provide useful prognostic information on the long-term risk of variceal rebleeding.

Increased oxidative stress in cirrhotic rat livers: A potential mechanism contributing to reduced nitric oxide bioavailability.

In cirrhotic livers, decreased nitric oxide (NO) bioavailability is a major factor increasing intrahepatic vascular tone. In several vascular disorders, an increase in superoxide (O2−) has been shown to contribute to reduced NO bioavailability through its reaction with NO to form peroxynitrite. This study was aimed to test the hypothesis that, in cirrhotic livers, increased O2−, by reacting with NO, reduces NO bioavailability. In control and cirrhotic rat livers, NO bioavailability was evaluated by the measurement of cyclic guanosine monophosphate in liver tissue and by 4‐amino‐5‐methylamino‐2′,7′‐difluorofluorescein diacetate (DAF‐FM‐DA) fluorescence in isolated sinusoidal endothelial cells (SEC); the O2− content was determined by dihydroethidium staining in fresh liver sections. In addition, the role of endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), and cyclooxygenase (COX) as possible sources of O2− and the role of superoxide dismutase (SOD) enzymatic activity as an O2− scavenger were determined in liver homogenates. Protein‐nitrotyrosination, a marker of the NO‐O2− reaction, was evaluated in liver homogenates. Furthermore, in control SEC and bovine aortic endothelial cells, NO modulation by O2− was evaluated. Cirrhotic livers exhibited increased O2− levels. This was due, at least in part, to increased production by COX and XO but not eNOS and to reduced scavenging by SOD. Increased O2− was associated with a significant reduction in NO bioavailability and increased nitrotyrosinated proteins. In endothelial cells, an inverse relationship between O2− levels and NO bioavailability was observed. Conclusion: Our data show that oxidative stress may contribute to reduced NO bioavailability in cirrhotic livers, supporting the evaluation of O2− reduction as a potential mechanism to restore NO content. (HEPATOLOGY 2008.)

Effects of Ethanol Consumption on Hepatic Hemodynamics in Patients With Alcoholic Cirrhosis

BACKGROUND & AIMS Increased portal blood flow represents a compensatory mechanism preventing hepatic hypoxia after ethanol consumption. In addition, alcohol increases hepatic vascular resistance. Thus, ethanol consumption, by increasing hepatic vascular resistance and portal flow, may worsen portal hypertension in patients with cirrhosis. The aim of this study was to investigate the effects of ethanol consumption on hepatic hemodynamics in patients with alcohol-induced cirrhosis. METHODS Measurements of hepatic venous pressure gradient (HVPG), azygos blood flow, hepatic blood flow, heart rate, and arterial pressure were obtained in 16 patients with alcohol-induced cirrhosis and portal hypertension before and after random administration of a noncaloric fruit drink (250 mL, n = 7) or of an identical beverage plus 0.5 g/kg of ethanol (n = 9). RESULTS Vehicle caused no effects. By contrast, ethanol increased HVPG (P < 0.0001). The increase in HVPG was maximum at 15 minutes and remained significant at 45 minutes (P < 0.05 vs. vehicle). Ethanol increased azygos blood flow (P < 0.05) without changes in hepatic blood flow. Heart rate and arterial pressure slightly increased. CONCLUSIONS Oral ethanol consumption increases portal pressure and portocollateral blood flow in patients with alcohol-induced cirrhosis. These findings suggest that even moderate alcohol consumption worsens the portal-hypertensive syndrome and, therefore, may increase the risk of variceal bleeding in patients with alcohol-induced cirrhosis.

Cyclooxygenase-1 inhibition corrects endothelial dysfunction in cirrhotic rat livers

BACKGROUND/AIMS Cirrhotic livers exhibit endothelial dysfunction that contributes to the increased hepatic vascular resistance. The present study evaluates the role of cyclooxygenase (COX)-derived prostanoids, implicated in the pathogenesis of endothelial dysfunction in other settings, in the pathogenesis of endothelial dysfunction in cirrhotic livers. METHODS Endothelial dysfunction was evaluated by performing concentration-effect curves to acetylcholine after precontracting the liver with methoxamine in groups of control and CCl(4)-cirrhotic rat livers preincubated either with vehicle, indomethacin, the COX-1 selective inhibitor, SC-560, the COX-2 selective inhibitor, SC-236, the thromboxane A(2) receptor antagonist, SQ 29,548 or the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine. Thromboxane A(2) (TXA(2)) production was determined in samples of the perfusate. RESULTS Cirrhotic livers exhibited endothelial dysfunction, as shown by the significantly lower relaxation to acetylcholine than control livers, that was totally corrected by indomethacin. COX-1 inhibition and TXA(2) blockade, but not COX-2 inhibition, also corrected endothelial dysfunction. Acetylcholine significantly increased TXA(2) production in cirrhotic but not in control livers. Indomethacin and COX-1 inhibition, but not COX-2 or NO inhibition, prevented the increased production of TXA(2). CONCLUSIONS An increased production of TXA(2) is involved in the pathogenesis of endothelial dysfunction in cirrhotic rat livers. This is mainly mediated by COX-1, but not by COX-2.

Three-day tetrahydrobiopterin therapy increases in vivo hepatic NOS activity and reduces portal pressure in CCl4 cirrhotic rats

BACKGROUND/AIMS Tetrahydrobiopterin is an essential cofactor for NOS enzymes to synthesize NO. It has been suggested that reduced intrahepatic tetrahydrobiopterin decreases intrahepatic NO and contributes to increase hepatic vascular resistance and portal pressure in cirrhosis. The main aim of the study was to evaluate the effect of tetrahydrobiopterin supplementation in portal pressure in CCl4 cirrhotic rats. METHODS Cirrhotic rats received vehicle or tetrahydrobiopterin (10mg/kg/day i.p.) for 3 days. Hepatic and systemic hemodynamics and hepatic tetrahydrobiopterin, NOS activity and cGMP levels were measured. In addition, hepatic and systemic hemodynamics were evaluated in normal rats in which tetrahydrobiopterin deficiency was induced by administrating 2,4-diamino-6-hydroxy-pyrimidine (DAHP) for 8h. RESULTS In cirrhotic rats, tetrahydrobiopterin administration increased liver NOS activity and cGMP levels and markedly and significantly reduced portal pressure. Amelioration of portal hypertension was associated with a normalization of arterial pressure. In normal rats DAHP decreased hepatic tetrahydrobiopterin and NOS activity and increased hepatic vascular tone. These effects of DAHP administration were corrected by tetrahydrobiopterin supplementation. CONCLUSIONS The present study shows that tetrahydrobiopterin markedly reduces portal hypertension and improves systemic hemodynamics in cirrhotic rats. These data support the concept that tetrahydrobiopterin supplementation may represent a new therapeutic strategy for portal hypertension.

Tempol administration, a superoxide dismutase mimetic, reduces hepatic vascular resistance and portal pressure in cirrhotic rats

BACKGROUND & AIMS Increased superoxide in cirrhotic livers, by reducing nitric oxide bioavailability, contributes to increase intrahepatic vascular resistance to portal blood flow and as a consequence portal pressure. We aimed to evaluate whether a strategy directed to reduce superoxide using tempol, a small membrane permeable SOD-mimetic, is able to modulate intrahepatic nitric oxide content and reduce portal pressure in cirrhotic rats. METHODS Superoxide and nitric oxide were evaluated in control sinusoidal endothelial cells (SEC) pre-treated with the pro-oxidant diethyldithiocarbamate (DDC) and in CCl(4)-cirrhotic rat livers treated with tempol or vehicle. Mean arterial pressure, portal pressure, and portal blood flow were measured in control and cirrhotic rats treated with tempol (180μmol/kg/h; via ileocholic vein) or vehicle. In a subset of animals, hemodynamic measurements were performed after NO-inhibition with l-NAME. RESULTS Tempol reduced superoxide content and increased NO both in SEC and cirrhotic livers. In cirrhotic rats, but not in controls, tempol significantly reduced portal pressure, and increased portal blood flow, which most likely reflects a reduction in intrahepatic vascular resistance. Tempol significantly reduced mean arterial pressure. l-NAME prevented all these effects. CONCLUSIONS Tempol reduces superoxide, increases nitric oxide, and reduces portal pressure in sinusoidal endothelial cells and in cirrhotic livers. These results confirm that oxidative stress has a role in the pathogenesis of portal hypertension and supports the use of antioxidants in its treatment. However, when considering the use of antioxidants as additional therapy to treat portal hypertension, the potential to produce deleterious effects on systemic hemodynamics needs to be carefully evaluated.

Interaction between NO and COX pathways modulating hepatic endothelial cells from control and cirrhotic rats.

Reduced intrahepatic nitric oxide (NO) bioavailability and increased cyclooxygenase‐1 (COX‐1)‐derived vasoconstrictor prostanoids modulate the hepatic vascular tone in cirrhosis. We aimed at investigating the reciprocal interactions between NO and COX in the hepatic endothelium of control and cirrhotic rats. NO bioavailability (DAF‐FM‐DA staining), superoxide (O2−) content (DHE staining), prostanoid production (PGI2 and TXA2 by enzyme immunoassays) as well as COX expression (Western Blot), were determined in hepatic endothelial cells (HEC) from control and cirrhotic rats submitted to different experimental conditions: COX activation, COX inhibition, NO activation and NO inhibition. In control and cirrhotic HEC, COX activation with arachidonic acid reduced NO bioavailability and increased O2− levels. These effects were abolished by pre‐treating HEC with the COX inhibitor indomethacin. In control, but not in cirrhotic HEC, scavenging of O2− by superoxide dismutase (SOD) incubation partially restored the decrease in NO bioavailability promoted by COX activation. NO supplementation produced a significant and parallel reduction in PGI2 and TXA2 production in control HEC, whereas it only reduced TXA2 production in cirrhotic HEC. By contrast, in control and cirrhotic HEC, NO inhibition did not modify COX expression or activity. Our results demonstrate that NO and COX systems are closely interrelated in HEC. This is especially relevant in cirrhotic HEC where COX inhibition increases NO bioavailability and NO supplementation induces a reduction in TXA2. These strategies may have beneficial effects ameliorating the vasoconstrictor/vasodilator imbalance of the intrahepatic circulation of cirrhotic livers.

Primary prophylaxis of esophageal variceal bleeding in cirrhosis

Variceal bleeding is a common and severe complication of liver cirrhosis. The risk of bleeding increases with the size of varices, red wheal marks and disease severity. Noninvasive tests are not accurate enough for the diagnosis of varices, so all patients with cirrhosis should be screened by endoscopy. Nonselective beta-blockers (propranolol, nadolol) are indicated for primary prophylaxis in patients with medium/large varices, and for those with small varices and red signs or advanced liver failure (Child C). In such patients, beta-blockers have been shown to reduce the risk of bleeding from 25 to 15%. There is no evidence to support using beta-blockers with nitrates or spironolactone. In patients with contraindication or intolerance to beta-blockers, endoscopic band ligations are indicated.

P‐selectin mediates leukocyte rolling in concanavalin‐A‐induced hepatitis

Abstract: Concanavalin‐ A (Con‐A)‐induced hepatitis is an experimental model of human autoimmune hepatitis characterized by leukocyte activation and infiltration of the liver. The aim of the present study was to evaluate the role of P‐selectin on leukocyte–endothelial interactions within the hepatic microvasculature in response to Con‐A.

Measurement of Azygos Blood Flow

Esophageal varices, because of their tendency to cause massive gastrointestinal hemorrhage, represent the more significant part of the portosystemic collateral circulation that develops in response to a chronic increase in portal pressure [1]. In recent years, much interest has been paid to the development of objective techniques allowing the quantification of hemodynamic abnormalities at the varices [2–4]. This has been mainly due to the recognition that, contrary to measurements of portal pressure, the endoscopic assessment of the size and appearance of the varices bear a good correlation with the likelihood of variceal hemorrhage [5–7]. This suggests that direct hemodynamic measurements at the varices may shed more light on the pathophysiology of bleeding and allow a better evaluation of new therapeutic approaches for portal hypertension [1,2,8,9].