Endothelin-1 and endothelin-3 in cirrhosis: relations to systemic and splanchnic haemodynamics

Targeting the endothelium by combining endothelin-1 antagonism and SGLT-2 inhibition: better together?

Endothelin A and B receptors, together with sodium-glucose cotransporter-2 (SGLT-2) channels are important targets in improving endothelial function and intervention with inhibitors has been the subject of multiple mechanistic and clinical outcome trials over recent years. Notable successes include the treatment of pulmonary hypertension with endothelin receptor antagonists, and the treatment of heart failure and chronic kidney disease with SGLT-2 inhibitors. With distinct and complementary mechanisms, in this review, we explore the logic of combination therapy for a number of diseases which have endothelial dysfunction at their heart.

Pharmacokinetics and Tolerability of Zibotentan in Patients with Concurrent Moderate Renal and Moderate Hepatic Impairment

BACKGROUND AND OBJECTIVE

Zibotentan, a selective endothelin A receptor antagonist, is in development for chronic liver and kidney disease. The pharmacokinetics (PK) of zibotentan were previously investigated in patients with either renal impairment or hepatic impairment, but the impact of both pathologies on PK was not evaluated. This study evaluated the PK and tolerability of a single oral dose of zibotentan in participants with concurrent moderate renal impairment and moderate hepatic impairment versus control participants.

METHODS

Twelve participants with moderate renal and hepatic impairment and 11 healthy matched control participants with no clinically significant liver or kidney disease were enrolled in an open-label, parallel-group study design. After administration of a single oral dose of zibotentan 5 mg, blood and urine sampling was performed. Pharmacokinetic parameters were determined for each of the two cohorts and compared. Comparisons between the cohorts were based on the geometric least squares mean ratio for the primary endpoints, which were area under the plasma concentration-time curve (AUC) from time zero to infinity (AUC∞) and from time zero to the time of the last measurable concentration (AUClast), and maximum plasma drug concentration (Cmax) on Day 1 through 120 h post-dose. Secondary endpoints included apparent total body clearance (CL/F) on Day 1 through 120 h post-dose. Safety endpoints were assessed up to discharge.

RESULTS

In total, 11 participants with concurrent moderate renal and hepatic impairment, and 11 controls, completed the study. Zibotentan was generally well tolerated, and no new clinically significant safety findings were observed. Total exposure (AUC∞ and AUClast) was approximately 2.10-fold higher in participants with concurrent moderate renal and hepatic impairment versus controls, while Cmax and total nonrenal body clearance were similar among all groups. A regression-based post hoc analysis, comparing exposure and CL/F in patients with concurrent impairment to patients with either renal or hepatic impairment alone, showed that CL/F with concurrent impairment was approximately half of that in controls and was positively correlated with reduction of renal function. Inclusion of the data on concurrent moderate renal and hepatic impairment in the regression analysis led to a narrower confidence interval for the predicted mean CL/F in participants with moderate hepatic impairment.

CONCLUSION

The presented findings advance the understanding of the PK of zibotentan in both renal impairment and hepatic impairment, with and without overlapping pathologies, and will thus increase the confidence of dose selection in future studies, particularly in vulnerable patient populations with concurrent renal and hepatic impairment.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05112419.

Investigational drugs in early clinical development for portal hypertension

INTRODUCTION

Advanced chronic liver disease is considered a reversible condition after removal of the primary aetiological factor. This has led to a paradigm shift in which portal hypertension (PH) is a reversible complication of cirrhosis. The pharmacologic management of PH is centered on finding targets to modify the natural history of cirrhosis and PH.

AREAS COVERED

This paper offers an overview of the use of pharmacological strategies in early clinical development that modify PH. Papers included were selected from searching clinical trials sites and PubMed from the last 10 years.

EXPERT OPINION

A paradigm shift has generated a new concept of PH in cirrhosis as a reversible complication of a potentially curable disease. Decreasing portal pressure to prevent decompensation and further complications of cirrhosis that may lead liver transplantation or death is a goal. Therapeutic strategies also aspire achieve total or partial regression of fibrosis thus eliminating the need for treatment or screening of PH.

Pathophysiology and Management of Variceal Bleeding

Cirrhosis is the fifth leading cause of death in adults. Advanced cirrhosis can cause significant portal hypertension (PH), which is responsible for many of the complications observed in patients with cirrhosis, such as varices. If portal pressure exceeds a certain threshold, the patient is at risk of developing life-threatening bleeding from varices. Variceal bleeding has a high incidence among patients with liver cirrhosis and carries a high risk of mortality and morbidity. The management of variceal bleeding is complex, often requiring a multidisciplinary approach involving pharmacological, endoscopic, and radiologic interventions. In terms of management, three stages can be considered: primary prophylaxis, active bleeding, and secondary prophylaxis. The main goal of primary and secondary prophylaxis is to prevent variceal bleeding. However, active variceal bleeding is a medical emergency that requires swift intervention to stop the bleeding and achieve durable hemostasis. We describe the pathophysiology of cirrhosis and PH to contextualize the formation of gastric and esophageal varices. We also discuss the currently available treatments and compare how they fare in each stage of clinical management, with a special focus on drugs that can prevent bleeding or assist in achieving hemostasis.

Elevated Plasma Big Endothelin-1 at Admission Is Associated With Poor Short-Term Outcomes in Patients With Acute Decompensated Heart Failure

Objective: We aimed to evaluate the association between plasma big endothelin-1 (ET-1) at admission and short-term outcomes in acute decompensated heart failure (ADHF) patients.

Methods: In this single-center, retrospective study, a total of 746 ADHF patients were enrolled and divided into three groups according to baseline plasma big ET-1 levels: tertile 1 (<0.43 pmol/L, n = 250), tertile 2 (between 0.43 and 0.97 pmol/L, n = 252), and tertile 3 (>0.97 pmol/L, n = 244). The primary outcomes were all-cause death, cardiac arrest, or utilization of mechanical support devices during hospitalization. Logistic regression analysis and net reclassification improvement approach were applied to assess the predictive power of big ET-1 on short-term outcomes.

Results: During hospitalization, 92 (12.3%) adverse events occurred. Etiology, arterial pH, lactic acid, total bilirubin, serum creatine, serum uric acid, presence of atrial fibrillation and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels were positively correlated with plasma big ET-1 level, whereas systolic blood pressure, serum sodium, hemoglobin, albumin, and estimated glomerular filtration rate were negatively correlated. In multivariate logistic regression, tertile 3 compared with tertile 1 had a 3.68-fold increased risk of adverse outcomes [odds ratio (OR) = 3.681, 95% confidence interval (CI) 1.410–9.606, p = 0.008]. However, such adverse effect did not exist between tertile 2 and tertile 1 (OR = 0.953, 95% CI 0.314–2.986, p = 0.932). As a continuous variable, big ET-1 level was significantly associated with primary outcome (OR = 1.756, 95% CI 1.413–2.183, p < 0.001). The C statistic of baseline big ET-1 was 0.66 (95% CI 0.601–0.720, p < 0.001). Net reclassification index (NRI) analysis showed that big ET-1 provided additional predictive power when combining it to NT-proBNP (NRI = 0.593, p < 0.001).

Conclusion: Elevated baseline big ET-1 is an independent predictor of short-term adverse events in ADHF patients and may provide valuable information for risk stratification.

Effect of ET-A blockade on portal pressure and hepatic arterial perfusion in patients with cirrhosis: A proof of concept study

BACKGROUND/AIM

Endothelin causes vasoconstriction via the endothelin-A receptor (ET-A) in the intrahepatic circulation in cirrhosis and its increase leads to portal hypertension. The aim of the study was to investigate the acute effect of a selective ET-A antagonist in patients with portal hypertension and cirrhosis.

METHODS

Proof-of-concept study with two different substudies: (a) local intrahepatic administration of the ET-A antagonist BQ 123 and (b) systemic oral administration of the ET-A antagonist Ambrisentan. Portal pressure was determined by hepatic venous pressure gradient (HVPG, both substudies) and hepatic arterial blood flow (HABF) by intra-arterial Doppler measurements (substudy 1) before and under the ET-A antagonist. Systemic haemodynamic parameters were measured in substudy 2.

RESULTS

Twelve patients (Child-Pugh [CP] B/C n = 7/5) were included in substudy 1 and 14 patients (CP A/B/C n = 4/6/4) in substudy 2. The relative decrease in HVPG was -12.5% (IQR: -40% to 0%; P = .05) in substudy 1 and -5.0% (IQR: -11.5% to 0%; P = .01) in substudy 2. Substudy 1 revealed higher decrease in HVPG in CP B patients. HABF increased significantly and patients without portal pressure decrease showed a higher increase of HABF. Substudy 2 showed a slight decrease in the mean arterial pressure without changes of other systemic haemodynamic parameters.

CONCLUSION

Administration of a selective ET-A antagonist decreases the portal pressure in cirrhotic patients. This decrease was higher in CP B patients and the non-responders showed a higher increase in hepatic arterial flow. Selective ET-A antagonists might be a future treatment option in patients with portal hypertension.

Hepatic lipocalin 2 promotes liver fibrosis and portal hypertension

Advanced fibrosis and portal hypertension influence short-term mortality. Lipocalin 2 (LCN2) regulates infection response and increases in liver injury. We explored the role of intrahepatic LCN2 in human alcoholic hepatitis (AH) with advanced fibrosis and portal hypertension and in experimental mouse fibrosis. We found hepatic LCN2 expression and serum LCN2 level markedly increased and correlated with disease severity and portal hypertension in patients with AH. In control human livers, LCN2 expressed exclusively in mononuclear cells, while its expression was markedly induced in AH livers, not only in mononuclear cells but also notably in hepatocytes. Lcn2-/- mice were protected from liver fibrosis caused by either ethanol or CCl4 exposure. Microarray analysis revealed downregulation of matrisome, cell cycle and immune related gene sets in Lcn2-/- mice exposed to CCl4, along with decrease in Timp1 and Edn1 expression. Hepatic expression of COL1A1, TIMP1 and key EDN1 system components were elevated in AH patients and correlated with hepatic LCN2 expression. In vitro, recombinant LCN2 induced COL1A1 expression. Overexpression of LCN2 increased HIF1A that in turn mediated EDN1 upregulation. LCN2 contributes to liver fibrosis and portal hypertension in AH and could represent a new therapeutic target.

Hepatic and Plasma Endothelin-1 in Dogs with Chronic Hepatitis

BACKGROUND

Endothelin (ET)-1 is a 21-amino-acid peptide with potent vasoactive properties, which increases intrahepatic resistance in patients with chronic hepatitis (CH) or cirrhosis. ET-1 concentrations have not been investigated in dogs with CH.

HYPOTHESIS/OBJECTIVES

This study compared hepatic and plasma ET-1 levels in healthy dogs and in dogs with CH, and examined the relationship between the plasma ET-1 level and portal vein pressure in dogs with CH.

ANIMALS

Fourteen healthy dogs and twenty dogs with CH were used in this study.

METHODS

Prospective case-control study. Hepatic ET-1 mRNA expression was determined by real-time reverse transcription polymerase chain reaction, and hepatic and plasma ET-1 levels were assessed using ELISA. Splenic pulp pressure (SPP), as an indicator of portal vein pressure, was measured laparoscopically.

RESULTS

Hepatic ET-1 mRNA levels were 3.7 times higher in dogs with CH than in healthy dogs (P = .008). The median hepatic and plasma ET-1 protein levels were significantly higher in dogs with CH than in healthy dogs (13.20 pg/mg wet liver vs. 3.42 pg/mg wet liver, P = .004, and 0.99 pg/mL vs. 0.71 pg/mL, P = .013, respectively). Moreover, there was a weak but significant correlation between plasma ET-1 level and SPP in dogs with CH (P = .036; r_s = 0.53).

CONCLUSIONS AND CLINICAL IMPORTANCE

The results indicate that ET-1 might play an important role in the pathogenesis of portal hypertension caused by CH.

Hepatic erythropoietin response in cirrhosis. A contemporary review

The main function of erythropoietin (EPO) is to maintain red blood cell mass, but in recent years, increasing evidence has suggested a wider biological role not solely related to erythropoiesis, e.g. angiogenesis and tissue protection. EPO is produced in the liver during fetal life, but the main production shifts to the kidney after birth. The liver maintains a production capacity of up to 10% of the total EPO synthesis in healthy controls, but can be up-regulated to 90-100%. However, the hepatic EPO synthesis has been shown not to be adequate for correction of anemia in the absence of renal-derived EPO. Elevated circulating EPO has been reported in a number of diseases, but data from cirrhotic patients are sparse and the level of plasma EPO in patients with cirrhosis is controversial. Cirrhosis is characterized by liver fibrosis, hepatic dysfunction and the release of proinflammatory cytokines, which lead to arterial hypotension, hepatic nephropathy and anemia. An increase in EPO due to renal hypoperfusion, hypoxia and anemia or an EPO-mediated hepato-protective and regenerative mechanism is plausible. However, poor hepatic synthesis capacity, a decreasing co-factor level and inflammatory feedback mechanisms may explain a potential insufficient EPO response in end-stage cirrhosis. Finally, the question remains as to whether a potential increase in EPO production in certain stages of cirrhosis originates from the kidney or liver. This paper aims to review contemporary aspects of EPO relating to chronic liver disease.

Post-paracentesis circulatory derangements are related to monocyte activation

BACKGROUND & AIMS

Post-paracentesis circulatory dysfunction is associated with development of hepatorenal syndrome and increased mortality. The impact of large volume paracentesis (LVP) on the 24-h blood pressure (BP) profile is unknown, and the relationship to Na+-retentive and pro-inflammatory cytokines also remains unknown. The aims of this study were to (i) define the effects of LVP with albumin administration on 24-h BP profiles, and (ii) relate changes in BP over time to changes in Na+-retentive hormones, clinical factors and inflammatory cytokines.

METHODS

Ten patients undergoing LVP had 24-h ambulatory BP monitoring performed pre- and post-paracentesis. Markers of the innate immune system, bacterial translocation and Na+-retentive hormones were drawn pre- and post-LVP.

RESULTS

Mean arterial pressure (MAP) dropped in nine of the 10 patients in the 24 h following a paracentesis compared to 24 h preceding the procedure (mean drop of 5.5 mmHg, P<0.005). A mixed effects model was used to define time-covariate interactions in predicting changes in BP profile. Monocyte chemotactic protein-1 (MCP1) was associated with Δsystolic BP (β=-0.011, P<0.05), Δdiastolic BP (β=-0.012, P<0.05) and ΔMAP (β=-0.012, P<0.05). Plasma renin activity was also significantly associated with Δsystolic BP (β=-0.21, P<0.05). Renal function was also significantly reduced following LVP.

CONCLUSIONS

Systolic, diastolic and MAP decreased over 24 h after LVP compared to the 24 h pre-LVP. This drop is related to increases in MCP-1 after LVP. Increased MCP-1, a marker of monocyte activation, was strongly related to changes in BP.

New vasoactive peptides in cirrhosis: organ extraction and relation to the vasodilatory state

BACKGROUND

Patients with cirrhosis have substantial circulatory imbalance between vasoconstrictive and vasodilating forces. The study of circulatory vasoactive peptides may provide important pathophysiological information. This study aimed to assess concentrations, organ extraction and relations to haemodynamic changes in the pro-peptides copeptin, proadrenomedullin and pro-atrial natriuretic peptide (proANP) in patients with cirrhosis.

MATERIALS AND METHODS

Fifty-four cirrhotic patients and 15 controls were characterized haemodynamically during a liver vein catheterization. Copeptin, proadrenomedullin and proANP were measured in hepatic and renal veins and the femoral artery.

RESULTS

We found no differences in concentrations of copeptin and proadrenomedullin between patients and controls. ProANPs were higher in cirrhotic patients, median 138 pm (25/75 percentiles 101-194) compared with controls, median 91 pm (25/75 percentiles 82-153) P=0·02. ProANPs were higher in the femoral artery and renal vein, median 140 pm and 116 pm (25/75 percentiles 109-191 and 92-164, respectively), compared with controls, median 99 and 81 (25/75 percentiles 85-146 and 66-123) P=0·02 and P=0·007, respectively. We found no extraction of copeptin, proadrenomedullin or proANP over the liver. Copeptin correlated with portal pressure (R=0·50, P<0·001). Proadrenomedullin correlated with portal pressure (R=0·48, P<0·001) and heart rate (R=0·36, P<0·01). ProANP correlated with cardiac output (R=0·46, P<0·002) and portal pressure (R=0·32, P<0·02). All propeptides correlated with Child score (R>0·31, P<0·03).

CONCLUSIONS

Pro-atrial natriuretic peptide is elevated in cirrhosis. Copeptin, proadrenomedullin and proANP are related to portal pressure and seem associated with systemic haemodynamics. These propeptides may participate in development and perpetuation of vasodilatation and hyperdynamic circulation in cirrhosis.

Clinical aspects of portopulmonary hypertension

Portopulmonary hypertension (PoPH) is an often neglected form of pulmonary hypertension where pulmonary hypertension occurs in the presence of portal hypertension. PoPH is important to diagnose and treat as it may improve the patient's quality of life and improve the outcome after liver transplantation. In this review, we discuss the clinical aspects of PoPH including its pathophysiology, diagnosis, treatment, and prognosis.

Pathophysiology of portal hypertension and esophageal varices

Esophageal varices are the major complication of portal hypertension. It is detected in about 50% of cirrhosis patients, and approximately 5-15% of cirrhosis patients show newly formed varices or worsening of varices each year. The major therapeutic strategy of esophageal varices consists of primary prevention, treatment for bleeding varices, and secondary prevention, which are provided by pharmacological, endoscopic, interventional and surgical treatments. Optimal management of esophageal varices requires a clear understanding of the pathophysiology and natural history. In this paper, we outline the current knowledge and future prospect in the pathophysiology of esophageal varices and portal hypertension.

Hemodynamics and pharmacokinetics of tezosentan, a dual endothelin receptor antagonist, in patients with cirrhosis

PURPOSE

To assess the effect of tezosentan, a parenteral dual ET receptor antagonist, on splanchnic and systemic hemodynamics in patients with cirrhosis. In addition, the safety, pharmacokinetics, and pharmacodynamics of tezosentan were evaluated.

METHODS

The population consisted of patients with cirrhosis with clinically significant portal hypertension. This was a randomized, double-blind, multicenter study. The patients were randomized 3:1 to tezosentan (3 mg/h for 2-3 h) or placebo. HVPG, hepatic blood flow (HBF, ICG method), and systemic arterial pressures were measured before and after tezosentan administration. Plasma concentrations of tezosentan and ET-1 were determined peripherally and in the hepatic vein.

RESULTS

Eighteen patients received tezosentan and six placebo. Baseline clinical, biochemical, and hemodynamic characteristics were balanced between the two groups. There was no significant treatment effect on HVPG. The extraction ratio (0.31), the plasma clearance of ICG (280 ml/min), and the HBF (1,430 ml/min) did not show any relevant changes during the infusion of tezosentan, and there were no differences between placebo- and tezosentan-treated patients. A linear relationship was observed between the maximum-fold increase in ET-1 concentration and the steady-state tezosentan plasma concentration (r = 0.82). There was a strong correlation (r = 0.88) between plasma clearance of ICG and that of tezosentan (10.2 l/h). Arterial pressure and heart rate did not significantly change in either group.

CONCLUSION

In patients with cirrhosis, a 2- to 3-h tezosentan infusion was safe and well tolerated but did not change the HVPG. Tezosentan infusion had no influence on the extraction ratio and plasma clearance of ICG and did not change HBF.

Hemodynamics and pharmacokinetics of tezosentan, a dual endothelin receptor antagonist, in patients with cirrhosis

PURPOSE

To assess the effect of tezosentan, a parenteral dual ET receptor antagonist, on splanchnic and systemic hemodynamics in patients with cirrhosis. In addition, the safety, pharmacokinetics, and pharmacodynamics of tezosentan were evaluated.

METHODS

The population consisted of patients with cirrhosis with clinically significant portal hypertension. This was a randomized, double-blind, multicenter study. The patients were randomized 3:1 to tezosentan (3 mg/h for 2-3 h) or placebo. HVPG, hepatic blood flow (HBF, ICG method), and systemic arterial pressures were measured before and after tezosentan administration. Plasma concentrations of tezosentan and ET-1 were determined peripherally and in the hepatic vein.

RESULTS

Eighteen patients received tezosentan and six placebo. Baseline clinical, biochemical, and hemodynamic characteristics were balanced between the two groups. There was no significant treatment effect on HVPG. The extraction ratio (0.31), the plasma clearance of ICG (280 ml/min), and the HBF (1,430 ml/min) did not show any relevant changes during the infusion of tezosentan, and there were no differences between placebo- and tezosentan-treated patients. A linear relationship was observed between the maximum-fold increase in ET-1 concentration and the steady-state tezosentan plasma concentration (r = 0.82). There was a strong correlation (r = 0.88) between plasma clearance of ICG and that of tezosentan (10.2 l/h). Arterial pressure and heart rate did not significantly change in either group.

CONCLUSION

In patients with cirrhosis, a 2- to 3-h tezosentan infusion was safe and well tolerated but did not change the HVPG. Tezosentan infusion had no influence on the extraction ratio and plasma clearance of ICG and did not change HBF.

Relationship of 24-hour ambulatory blood pressure and heart rate with markers of hepatic function in cirrhotic patients

Background

There is evidence that in cirrhotic patients, certain hemodynamic parameters, such as blood pressure and heart rate, are related to the severity of liver disease. This study investigated whether non-invasive 24-hour ambulatory blood pressure and heart rate are more closely associated with markers of liver disease severity than conventional office measurements.

Methods

Ambulatory patients with cirrhosis underwent office blood pressure and heart rate measurements, 24-hour ambulatory blood pressure monitoring and blood laboratory tests.

Results

Fifty-one patients (32 men, mean age 57.4 ± 11.3 years) completed the study. Twenty six patients had compensated liver cirrhosis (group A) and 25 patients had more advanced liver disease (group B). Group A and B patients differed significantly both in ambulatory asleep diastolic blood pressure (p < 0.05) and office diastolic blood pressure (p < 0.01), which were lower in more advanced liver disease. Office blood pressure and heart rate correlations were similar to or even stronger than ambulatory ones. Ambulatory blood pressure and heart rate awake-asleep variation (dipping) showed a relatively flat pattern as markers of liver dysfunction were deteriorating. The strongest correlations were found with both ambulatory and office heart rate, which increased as indicators of severity of liver disease were worsening.

Conclusions

Heart rate seems to be a more reliable marker of ongoing liver dysfunction than blood pressure. Evaluation of blood pressure and heart rate with 24-hour ambulatory measurement does not seem to offer more information than conventional office measurements.

Physiopathology of splanchnic vasodilation in portal hypertension

In liver cirrhosis, the circulatory hemodynamic alterations of portal hypertension significantly contribute to many of the clinical manifestations of the disease. In the physiopathology of this vascular alteration, mesenteric splanchnic vasodilation plays an essential role by initiating the hemodynamic process. Numerous studies performed in cirrhotic patients and animal models have shown that this splanchnic vasodilation is the result of an important increase in local and systemic vasodilators and the presence of a splanchnic vascular hyporesponsiveness to vasoconstrictors. Among the molecules and factors known to be potentially involved in this arterial vasodilation, nitric oxide seems to have a crucial role in the physiopathology of this vascular alteration. However, none of the wide variety of mediators can be described as solely responsible, since this phenomenon is multifactorial in origin. Moreover, angiogenesis and vascular remodeling processes also seem to play a role. Finally, the sympathetic nervous system is thought to be involved in the pathogenesis of the hyperdynamic circulation associated with portal hypertension, although the nature and extent of its role is not completely understood. In this review, we discuss the different mechanisms known to contribute to this complex phenomenon.

Urotensin II modulates hepatic fibrosis and portal hemodynamic alterations in rats

The influence of circulating urotensin II (UII) on liver disease and portal hypertension is unknown. We aimed to evaluate whether UII executes a pathogenetic role in the development of hepatic fibrosis and portal hypertension. UII was administered by continuous infusion over 4 wk in 20 healthy rats divided into three treatment groups, controls (saline, n = 7), low dose (UII, 1 nmol x kg(-1) x h(-1), n = 8), and high dose (UII, 3 nmol x kg(-1) x h(-1), n = 5). Hemodynamic parameters and morphometric quantification of fibrosis were assessed, and profibrotic cytokines and fibrosis markers were assayed in hepatic tissue. UII induced a significant dose-dependent increase in portal venous pressure (5.8 +/- 0.4, 6.4 +/- 0.3, and 7.6 +/- 0.7, respectively, P = 0.03). High-dose UII infusion was associated with an increase in hepatic transcript for transforming growth factor-beta (P < 0.05) and platelet-derived growth factor-beta (P = 0.06). Liver tissue hydroxyproline was elevated in the high-dose group (P < 0.05). No systemic hemodynamic alterations were noted. We concluded that UII infusion elevates portal pressure and induces hepatic fibrosis in normal rats. This response may be mediated via induction of fibrogenic cytokines. These findings have pathophysiological implications in human liver disease where increased plasma UII levels have been observed.

Advances in drug treatment of portal hypertension

Intrahepatic vascular resistance augmentation and portal blood flow increase are main mechanisms of portal hypertension. The former as an initial factor is mainly due to liver structure changes and motivity changes (reversible). It has been demonstrated that this reversible resistance can be reduced by 20%-30% with drugs. Portosystemic shunt or transjugular intrahepatic portosystemic shunt (TIPS) may induce many severe complications such as hepatic encephalopathy and stent re-obstruction. Therefore, researchers have performed plenty of experimental investigations about drug treatment of portal hypertension, and this article introduces their new advances in this field.

Q-T interval (QT(C)) in patients with cirrhosis: relation to vasoactive peptides and heart rate

OBJECTIVE

Prolonged Q-T interval (QT) has been reported in patients with cirrhosis who also exhibit profound abnormalities in vasoactive peptides and often present with elevated heart rate (HR). The aim of this study was to relate QT to the circulating level of endothelins (ET-1 and ET-3) and calcitonin gene-related peptide (CGRP) in patients with cirrhosis. In addition, we studied problems with HR correction of QT.

MATERIAL AND METHODS

Forty-eight patients with cirrhosis and portal hypertension were studied during a haemodynamic investigation. Circulating levels of ETs and CGRP were determined by radioimmunoassays. Correction of QT for HR above 60 beats per min was performed using the methods described by Bazett (QT(C)) and Fridericia (QT(F)).

RESULTS

Prolonged QT(C) (above 440 ms), found in 56% of the patients, was related to the presence of significant portal hypertension and liver dysfunction (p < 0.05 to 0.001), but not to elevated ET-1, ET-3 or CGRP. When corrected according to Bazett, QT(C) showed no significant relation to differences in HR between patients (r = 0.07, ns). QTF showed some undercorrection of HR (r = -0.36; p < 0.02). During HR variation in the individual patient, QT(C) revealed a small but significant overcorrection (2.6 ms per heartbeat per min; p < 0.001). This value was significantly (p < 0.02) smaller with QTF (1.2 ms per heartbeat per min).

CONCLUSIONS

The prolonged QT(C) in cirrhosis is related to liver dysfunction and the presence of portal hypertension, but not to the elevated powerful vasoconstrictor (ET-1) or vasodilator (CGRP, ET-3) peptides. The problems with correction of the QT for elevated HR in cirrhosis are complex, and the lowest HR should be applied for determination of the QT.

Altered alpha adrenergic vasoresponsiveness in a non-cirrhotic portal hypertension model of E. coli injection

BACKGROUND AND AIM

Portal hypertension is associated with decreased vascular responsiveness to vasoconstrictors, which may contribute to the hyperdynamic circulation in cirrhosis. Animal models of cirrhosis and portal vein ligation have helped in our understanding of portal hypertension. The etiopathogenesis of non-cirrhotic portal fibrosis (NCPF), a common cause of portal hypertension, is still poorly understood. The aim of this study was to investigate the pathophysiology of NCPF in a rabbit model.

METHODS

An indwelling cannula was inserted into the gastrosplenic vein of rabbits. Animals were randomly injected with saline (Group I, n = 13) or lipopolysaccharide (Group II, n = 13) from heat killed Escherichia coli at 0, 1, 2, 7, 14 and 28 days. Portal pressure was measured at 3 months and vasoresponsiveness studied in isolated aortic rings in intact and in endothelium-denuded tissues from both groups.

RESULTS

In all group II compared with group I animals, the splenic weight (0.89 +/- 0.16 vs 0.62 +/- 0.1 g, P < 0.05) and the portal pressure (14.99 +/- 0.56 vs 7.04 +/- 0.42 mmHg, P < 0.05) were higher at 3 months. The group II animals showed reduced responsiveness to phenylephrine showing maximal contraction of 1.25 +/- 0.08 at 10(-4) mol/L as compared to 2.85 +/- 0.33 g tension in Group I (P < 0.05). Endothelium denudation of aortic rings had no effect on reduced reactivity in Group II animals. Acetylcholine induced an increase in vasorelaxation at lower concentrations in preconstricted aortic rings in Group II compared to Group I animals, but this decreased in higher concentrations. Nifedipine produced comparable vasodilatation in preconstricted rings in both the groups of animals.

CONCLUSIONS

Repeated injection of lipopolysaccharide into the gastrosplenic vein leads to the development of portal hypertension. This non-cirrhotic model of portal hypertension is characterized by generalized arterial hyporeactivity to vasoconstrictors akin to other models of portal hypertension.

Endothelin and endothelin receptor antagonism in portopulmonary hypertension

Portopulmonary hypertension (PPHT) is a rare but devastating complication in patients with portal hypertension, characterized by pulmonary arterial obliterative disease with a concomitant rise in pulmonary vascular resistance. A broad body of evidence has accumulated, indicating that endothelin (ET) peptides and their cognate receptors are causally involved in the pathophysiology of pulmonary arterial hypertension (PAH) owing to different aetiologies, including PPHT. In addition, the ET system may be involved in hepatic fibrotic remodelling and portal hypertension. Several experimental models have provided evidence that ET receptor antagonism may have therapeutic potential in PPHT. Initial experience has accumulated during the last 2 years, suggesting that targeting the ET system may have beneficial effects in the clinical setting. In these studies, the orally active, dual ET receptor antagonist bosentan improved pulmonary haemodynamics and functional capacity. These effects were sustained and occurred in the absence of adverse events. If these observations can be corroborated by controlled clinical trials, bosentan would offer several advantages over available therapies, which have major drawbacks owing to their invasive and demanding mode of application.

Determinants of the renin-angiotensin-aldosterone system in cirrhosis with special emphasis on the central blood volume

OBJECTIVE

Several studies have shown activation of the renin-angiotensin-aldosterone system (RAAS) in cirrhosis. Although the activated RAAS may have several determinants, the system is often considered a surrogate marker of effective hypovolaemia. In this study we investigated the activity of the RAAS and its potential determinants with special focus on the central and arterial blood volume (CBV).

MATERIAL AND METHODS

Eighty-nine patients (Child class A/B/C: 19/41/29) and 32 controls were included in the study. All were given a haemodynamic examination with measurement of determinants of the RAAS, including the CBV. Circulating plasma renin concentrations were measured using an immunoradiometric assay.

RESULTS

Arterial renin concentrations were significantly higher in the patients than in the controls (p < 0.003). Plasma renin correlated significantly with several indicators of liver dysfunction and splanchnic and systemic haemodynamics (r = - 0.56-0.55), but only weakly with CBV (r = - 0.25, p < 0.02). In a multivariate regression analysis, plasma renin was determined by serum sodium, alkaline phosphatases and systolic blood pressure (p < 0.04 to p < 0.001).

CONCLUSIONS

CBV correlates weakly with circulating renin, and activation of the RAAS can therefore only partly be considered as an indicator of central hypovolaemia. Mechanisms other than central hypovolaemia relating to the liver disease and portal hypertension contribute significantly to the RAAS activation.

Liver cirrhosis and arterial hypertension

Characteristic findings in patients with cirrhosis are vasodilatation with low overall systemic vascular resistance, high arterial compliance, increased cardiac output, secondary activation of counter-regulatory systems (renin-angiotensin-aldosterone system, sympathetic nervous system, release of vasopressin), and resistance to vasopressors. The vasodilatory state is mediated through adrenomedullin, calcitonin gene-related peptide, nitric oxide, and other vasodilators, and is most pronounced in the splanchnic area. This constitutes an effective (although relative) counterbalance to increased arterial blood pressure. This review considers the alterations in systemic hemodynamics in patients with cirrhosis in relation to essential hypertension and arterial hypertension of the renal origin. Subjects with arterial hypertension (essential, secondary) may become normotensive during the development of cirrhosis, and arterial hypertension is rarely manifested in patients with cirrhosis, even in cases with renovascular disease and high circulating renin activity. There is much dispute as to the understanding of homoeostatic regulation in cirrhotic patients with manifest arterial hypertension. This most likely includes the combination of vasodilatation and vasoconstriction in parallel.

Increased hepatic resistance: a new target in the pharmacologic therapy of portal hypertension

Increased resistance to portal blood flow is the primary factor in the pathophysiology of portal hypertension, and is mainly determined by the morphologic changes occurring in chronic liver diseases. This is aggravated by an increased hepatic vascular tone, which results from an insufficient hepatic bioavailability of nitric oxide (NO) and an increased production of circulating and local vasoconstrictors (angiotensin, endothelin, cysteinyl-leukotrienes, and thromboxane, among others). This dynamic and reversible component provides the rationale for the use of therapies aimed at decreasing portal pressure by reducing the vascular tone. Among them, systemic and liver-selective NO donors, statins, and gene therapy with adenovirus encoding NO synthases have been used to increase NO availability with promising results. Other attempts have been the blockade of the effect of vasoconstrictors, using anti alpha-adrenergic agents and renin-angiotensin system blockers. Some of these pharmacologic approaches have already been incorporated into clinical practice while others are still under investigation.

Hypertension and liver disease

Arterial hypertension is a common disorder with a frequency of 10% to 15% in subjects in the 40- to 60-year age group. Yet most reports find the prevalence of arterial hypertension in patients with chronic liver disease (cirrhosis) much lower. In this review, we consider the alterations in systemic hemodynamics in cirrhosis. The most characteristic findings in cirrhotic patients are vasodilatation with low systemic vascular resistance, increased cardiac output, high arterial compliance, secondary activation of counterregulatory systems (sympathetic nervous system, renin-angiotensin-aldosterone system, neuropituitary release of vasopressin), and resistance to vasopressors. The vasodilatory state is mediated through nitric oxide, calcitonin gene-related peptide, adrenomedullin, and other vasodilators, and is most pronounced in the splanchnic area. This constitutes an effective (although relative) counterbalance to increased arterial blood pressure. Subjects with established arterial hypertension (essential, secondary) may become normotensive during the development of cirrhosis, and arterial hypertension is rarely manifested in patients with cirrhosis, even in cases with renovascular disease and high circulating renin activity. There is much dispute as to the understanding of homeostatic regulation in cirrhotic patients with manifest arterial hypertension. This is a topic for future research.

Use of a mixed endothelin receptor antagonist in portopulmonary hypertension: a safe and effective therapy?

BACKGROUND & AIMS

Portopulmonary hypertension (PPHTN), a severe complication of portal hypertension is observed in 3%-6% of patients evaluated for liver transplantation. Endothelin-1, a potent vasoconstrictor, is likely to play a role in the pathogenesis of primary pulmonary hypertension, and, in 2 recent trials, the dual endothelin receptor antagonist bosentan has shown beneficial effects in this disease. A role for endothelins in the development of both pulmonary hypertension and cirrhosis has been suggested. We therefore hypothesized that endothelin receptor blockade may be beneficial in the treatment of PPHTN.

METHODS

We report a case of a 42-year-old patient with PPHTN and alcoholic cirrhosis treated with the mixed endothelin receptor antagonist bosentan.

RESULTS

The patient rapidly improved from NYHA IV to stage II, experienced a remarkable improvement of 6-minute walking distance from 0 to 590 m within 6 months, and resumed working full-time as a locksmith after 7 months of treatment. Improvement of cardiovascular parameters included a reduction of pulmonary vascular resistance by 60%, a decrease of mean pulmonary artery pressure (mPAP) from 55 to 44 mm Hg at 9 months, and a decline of plasma B-type natriuretic peptide (BNP) from 339 pg/mL to 19 pg/mL after 1 year. There were no adverse events except for a transient decrease in systemic blood pressure.

CONCLUSIONS

To our knowledge, this is the first report of a patient with PPHTN treated with an endothelin receptor antagonist. The marked and sustained improvement supports the undertaking of controlled studies of the safety and efficacy of bosentan in PPHTN.

Ursodeoxycholic acid inhibits endothelin-1 production in human vascular endothelial cells

Endothelin-1 is known to be implicated in the pathogenesis of hepatobiliary diseases such as cirrhosis, especially in portal hypertension. This study aimed to investigate the effects of ursodeoxycholic acid on endothelin-1 production in human endothelial cells. The effects of ursodeoxycholic acid and its conjugates (tauroursodeoxycholic and glycoursodeoxycholic acids) on endothelin-1 production as well as nitric oxide (NO) in human umbilical vein endothelial cells (HUVECs) were examined. The production of endothelin-1 and nitric oxide in culture medium was measured using enzyme-linked immunosorbent assay (ELISA) and the Griess method, respectively. Endothelin-1 and endothelial nitric oxide synthase (eNOS) mRNA expression were investigated by real-time quantitative reverse transcriptase/polymerase chain reaction (RT-PCR). Ursodeoxycholic acid (30-1000 microM) inhibited endothelin-1 production in a concentration-dependent manner, and ursodeoxycholic acid at concentrations higher than 300 microM increased nitric oxide production in culture medium. The conjugates of ursodeoxycholic acid also increased nitric oxide production and decreased endothelin-1 production, which was less effective than ursodeoxycholic acid. N-nitro-L-arginine-mythel-ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, suppressed the ursodeoxycholic acid-induced nitric oxide production, but it did not antagonize the inhibitory effects of ursodeoxycholic acid on endothelin-1 production. Ursodeoxycholic acid also induced a concentration-dependent decrease in endothelin-1 mRNA expression without significant changes in eNOS mRNA expression. These results provide novel evidence that ursodeoxycholic acid inhibits endothelin-1 production in human endothelial cells, but nitric oxide is not responsible for the inhibitory effect of ursodeoxycholic acid on endothelin-1. Thus, ursodeoxycholic acid therapy may prevent the development of several pathogenesis such as portal hypertension observed in patients with cirrhosis due to the improvement of endothelial function.

Effects of endothelin-1 on hepatic stellate cell proliferation, collagen synthesis and secretion, intracellular free calcium concentration

AIM: To explore the effects of endothelin-1 (ET-1) on hepatic stellate cells (HSCs) DNA uptake, DNA synthesis, collagen synthesis and secretion, inward whole-cell calcium concentration ([Ca²⁺]_i) as well as the blocking effect of verapamil on ET-1-stimulated release of inward calcium (Ca²⁺) of HSC in vitro.

METHODS: Rat hepatic stellate cells (HSCs) were isolated and cultivated. ³H-TdR and ³H-proline incorporation used for testing DNA uptake and synthesis, collagen synthesis and secretion of HSCs cultured in vitro; Fluorescent calcium indicator Fura-2/AM was used to measure [Ca²⁺]_i inward HSCs.

RESULTS: ET-1 at the concentration of 5 × 10^-8 mol/L, caused significant increase both in HSC DNA synthesis (2247 ± 344 cpm, P < 0.05) and DNA uptake (P < 0.05) when compared with the control group. ET-1 could also increase collagen synthesis (P < 0.05 vs control group) and collagen secretion (P < 0.05 vs control group). Besides, inward HSC [Ca²⁺] _i reached a peak concentration (422 ± 98 mol/L, P < 0.001) at 2 min and then went down slowly to165 ± 51 mol/L (P < 0.01) at 25 min from resting state (39 ± 4 mol/L) after treated with ET-1. Verapamil (5 mol/L) blocked ET-1-activated [Ca²⁺]_i inward HSCs compared with control group (P < 0.05). Fura-2/AM loaded HSC was suspended in no Ca²⁺ buffer containing 1 mol/L EGTA, 5 min later, 10^-8 mol/L of ET-1 was added, [Ca²⁺]_i inward HSCs rose from resting state to peak 399 ± 123 mol/L, then began to come down by the time of 20 min. It could also raise [Ca²⁺]_i inward HSCs even without Ca²⁺ in extracellular fluid, and had a remarkable dose-effect relationship (P < 0.05). Meanwhile, verapamil could restrain the action of ET-1 (P < 0.05).

CONCLUSION: Actions of ET-1 on collagen metabolism of HSCs may depend on the transportation of inward whole-cell calcium.

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.

Plasma endothelin-1 levels in patients with biliary atresia: possible role in development of portal hypertension

BACKGROUND

Biliary atresia (BA) is a severe neonatal liver disease characterized by progressive extrahepatic biliary tract and intrahepatic inflammatory process. Hepatic fibrosis and portal hypertension (PH) still occur despite the disappearance of jaundice following successful hepatic portoenterostomy. Endothelin-1 (ET-1) is a potent vasoconstrictor and has been reported to stimulate hepatic collagen synthesis. The aim of this study was to demonstrate the potential role of ET-1 in the pathogenesis of the progressive inflammation, fibrosis and PH in BA.

METHODS

Thirty pediatric patients with biliary atresia post-hepatic portoenterostomy and 12 healthy children were examined. The ET-1 level was determined by commercially available enzyme-linked immunosorbent assay kits.

RESULTS

Endothelin-1 levels were elevated in the patients compared with those of the controls (5.45+/-3.34 vs. 2.74+/-2.17 pg/ml, P = 0.01). Moreover, patients with PH also had greater levels of ET-1 than those without PH (6.73+/-3.27 vs. 3.26+/-2.2 pg/ml, P = 0.004). Patients with abnormal transaminase enzymes had significantly higher ET-1 levels than those with normal enzymes (6.43+/-3.33 vs. 3.17+/-2.1 pg/ml, P = 0.01). In the jaundice-free group, endothelin-1 levels were elevated in the patients with PH compared with those without PH (5.93+/-2.15 vs. 2.88+/-2.1 pg/ml, P = 0.02).

CONCLUSIONS

Our findings showed elevation of plasma ET-1 levels in patients with BA, especially in those with PH. ET-1 levels were also higher in patients with elevated transminase enzymes as well as in the jaundice-free group with PH. ET-1 might play a role in the pathogenesis of the progressive inflammation, fibrosis and PH in BA.

Effects of the neutral endopeptidase inhibitor thiorphan on cardiovascular and renal function in cirrhotic rats

1. Cirrhosis is associated with cardiovascular and renal dysfunction including sodium retention. Many vasoactive peptides such as atrial natriuretic peptide (ANP) and endothelin-1 (ET-1) are degraded by neutral endopeptidase 24.11 (NEP). We investigated the hemodynamic and renal effects of thiorphan, a NEP inhibitor, in a rat cirrhosis model. 2. Cirrhosis was induced by chronic bile duct ligation, and controls had sham operation. Systemic and renal hemodynamics in conscious, restrained animals were determined using radiolabeled microspheres, and glomerular filtration rate (GFR) was measured by (3)H-inulin clearance. Plasma ANP and ET-1, and renal cGMP and Na(+) - K(+) ATPase activity were assayed. These variables were measured at baseline and after intravenous infusion of thiorphan (0.5 mg kg(-1) loading dose followed by 0.1 mg kg(-1) min(-1) x 30 min). 3. Thiorphan significantly decreased cardiac output, and increased systemic vascular resistance in controls, whereas in cirrhotic rats these variables were unchanged. 4. Compared to the controls, cirrhotic rats showed a decreased baseline GFR and urine sodium excretion, and the latter was significantly increased by thiorphan. 5. Thiorphan increased plasma ET-1 levels in controls, but not cirrhotic rats. ANP levels were not significantly increased in either group by thiorphan. 6. Thiorphan significantly increased cGMP concentrations and decreased Na(+) - K(+) ATPase activity of renal medulla but not cortex in cirrhotic rats; no effect was observed in the control rats. 7. We conclude that thiorphan induces natriuresis in cirrhotic rats by a direct renal medullary mechanism via cGMP and Na(+) - K(+) ATPase, without affecting systemic hemodynamics. This may potentially be useful in patients with ascites.

Systemic and regional changes in plasma endothelin following transient increase in portal pressure

An acute increase in portal pressure or reduction in portal inflow has been shown to decrease renal plasma flow (RPF). The aim of the study was to evaluate regional and systemic hemodynamics after acute occlusion of a transjugular intrahepatic portosystemic stent-shunt (TIPSS) and study the effect of the same on plasma endothelin (ET-1) levels in the systemic circulation, renal vein, and hepatic vein. Sixteen patients attending for portography after previous TIPSS placement were studied. The shunt was acutely occluded with an angioplasty balloon for 12 minutes. Changes in portal pressure gradient (PPG), hepatic plasma flow (HPF), RPF, cardiac output (CO), and systemic vascular resistance (SVR) were measured before and after shunt occlusion. Blood was collected from the femoral artery and hepatic and renal veins for ET-1 measurement. At T = 0, SVR correlated with circulating arterial ET-1 level (r = 0.74; P <.05). After shunt occlusion (T = 12 minutes), heart rate, CO, and mean arterial pressure decreased (P <.05), whereas PPG increased (P <.05). RPF decreased from 485 +/- 55 to 282 +/- 47 mL/min (P <.01), whereas HPF increased from 700 +/- 39 to 779 +/- 33 mL/min (P <.001). There was a significant increase in arterial concentration and renal production, and decrease in hepatic production of ET-1. Veno-arterial (V-A) concentration difference in ET-1 level in the renal vein, as well as renal flux of ET-1, increased significantly, whereas hepatic vein V-A concentration difference and hepatic flux of ET-1 decreased significantly. At T = 12 minutes, ET-1 renal output correlated negatively with RPF (r = 0.72; P <.05). Results of this study show that an acute increase in portal pressure and reduction in portal inflow brought about by occlusion of a TIPSS shunt decreases RPF and increases HPF. These hemodynamic changes are accompanied by increases in arterial, renal vein, and hepatic vein ET-1 concentrations, which may possibly mediate the observed findings.

Cyclooxygenase-derived products modulate the increased intrahepatic resistance of cirrhotic rat livers

In cirrhotic livers, increased resistance to portal flow, in part due to an exaggerated response to vasoconstrictors, is the primary factor in the pathophysiology of portal hypertension. Our aim was to evaluate the response of the intrahepatic circulation of cirrhotic rat livers to the alpha(1)-adrenergic vasoconstrictor methoxamine and the mechanisms involved in its regulation. A portal perfusion pressure dose-response curve to methoxamine was performed in control and cirrhotic rat livers preincubated with vehicle, the nitric oxide synthase blocker N(G)-nitro-L-arginine (L-NNA), indomethacin cyclooxygenase (COX) inhibitor, L-NNA + indomethacin, or the thromboxane (TX) A(2) receptor blocker SQ 29,548. TXA(2) production, COX-1 and COX-2 mRNA expression, and immunostaining for TXA(2) synthase were evaluated. Cirrhotic livers exhibited a hyperresponse to methoxamine associated with overexpression of COX-2 and TXA(2) synthase as well as with increased production of TXA(2). The hyperresponse to methoxamine of cirrhotic livers disappeared by COX inhibition with indomethacin but not after NO inhibition. SQ 29,548 also corrected the hyperresponse of cirrhotic livers to methoxamine. In conclusion, COX-derived prostanoids, mainly TXA(2), play a major role in regulating the response of cirrhotic livers to methoxamine.

Nitric oxide and portal hypertension

In liver cirrhosis, an increase in hepatic resistance is the initial phenomenon leading to portal hypertension. This is primarily due to the structural distortion of the intrahepatic microcirculation caused by cirrhosis. However, similar to other vascular conditions, architectural changes in the liver are associated with a deficient nitric oxide (NO) production, which results in an increased vascular tone with a further increase in hepatic resistance and portal pressure. New therapeutic strategies are being developed to selectively provide the liver with NO, overcoming the deleterious effects of systemic vasodilators. On the other hand, a strikingly opposite process occurs in splanchnic arterial circulation, where NO production is increased. This results in splanchnic vasodilatation and subsequent increase in portal inflow, which contributes to portal hypertension. Systemic blockade of NO in portal hypertension attenuates the hyperdynamic circulation, but its effects increasing hepatic resistance may offset the benefit of reducing portal inflow, thus preventing an effective reduction of portal pressure. Moreover, it cannot be ruled out that NO blockade may have a deleterious action on cirrhosis progression, which raises caution about their use in patients with cirrhosis.

5-lipoxygenase inhibition reduces intrahepatic vascular resistance of cirrhotic rat livers: a possible role of cysteinyl-leukotrienes

BACKGROUND & AIMS

Cysteinyl-leukotrienes (Cys-LTs) increase intrahepatic vascular resistance in normal rat livers. CCl4 cirrhotic rat livers have increased Cys-LT production and 5-lipoxygenase messenger RNA (mRNA) expression. The aim of this study was to investigate the role of 5-lipoxygenase-derived eicosanoids regulating intrahepatic vascular tone in control and CCl4-induced cirrhotic rat livers.

METHODS

In different groups of portally perfused control and cirrhotic rat livers, the following were analyzed: a portal perfusion pressure (PP) dose-response curve to LTD4; the effects on PP caused by either vehicle, the selective 5-lipoxygenase inhibitor AA-861, the selective Cys-LT1 receptor antagonist MK-571, or the dual Cys-LT1 and Cys-LT2 receptor antagonist BAY u9773; and immunohistochemistry for 5-lipoxygenase in liver sections of cirrhotic and control livers.

RESULTS

Cirrhotic livers have a hyperesponse to LTD4. In control livers, AA-861 and MK-571 produced a moderate and similar reduction in PP. In cirrhotic livers, 5-lipoxygenase inhibition produced a marked and significantly greater reduction in PP than in controls. However, no effect on PP was observed after MK-571 or BAY u9773. 5-Lipoxygenase-positive cells were markedly increased in cirrhotic livers.

CONCLUSIONS

Our results suggest that 5-lipoxygenase-derived eicosanoids may contribute to the increased intrahepatic vascular resistance of cirrhotic rat livers and therefore the pathogenesis of portal hypertension.

Endothelin-1 and big-endothelin concentrations are elevated in liver graft tissue during cold storage and reperfusion

Endothelin (ET) and its precursor big-ET were synchronously analyzed by RIA in liver biopsies and systemic plasma during porcine orthotopic liver transplantation (OLT) before graft harvesting (phase A), after cold storage (phase B), and early (phase C) and late reperfusion (phase D). Tissue and plasma concentrations were correlated with length of survival and reperfusion. Increased tissue ET/big-ET levels were already detected during phase B (ET: 46 +/- 20; big-ET: 245 +/- 119 pg/mg cytosolic protein) and remained elevated in phase C (ET: 49 +/- 16; big-ET: 306 +/- 144 pg/mg) compared to baseline (ET: 32 +/- 13; big-ET: 185 +/- 164 pg/mg; p < 0.05). In phase D, a rapid concentration decline was detected (ET: 36 +/- 26; big-ET: 163 +/- 138 pg/mg). Systemic ET levels were elevated in phase B (3.4 +/- 3.0 pg/ml), C, (2.8 +/- 1.2 pg/ml) and D (2.6 +/- 2.0 pg/ml), compared to baseline (1.7 +/- 1.1 pg/ml; p < 0.05). ET/big-ET kinetics in liver tissue and systemic plasma showed analogous characteristics. Intrahepatic ET accumulation during storage and early reperfusion could be of relevance for harvest-related disturbances of hepatic microcirculation.

Levels of circulating endothelin-1 and nitrates/nitrites in patients with virus-related hepatocellular carcinoma

A balance between endothelins (ET) and nitric oxide (NO) might interfere with liver haemodynamics and disease progression in various liver diseases. Increased levels of endothelin 1 (ET-1) and nitrites and nitrates (NOx, the end products of NO metabolism) have been reported in hepatocellular carcinoma (HCC), but the balance has not been studied. The purpose of this study was to assess the ratio of NOx to ET-1 in patients with virus-related hepatocellular carcinoma and to investigate its correlation with the extent of the disease. Eighteen patients with virus-related HCC (six Okuda stage I, six Okuda stage II and six Okuda stage III) were included in the study and were compared with 22 patients with viral cirrhosis (14 decompensated, eight compensated) and seven normal controls. ET-1 was measured with an ELISA assay and NOx with a modification of the Griess reaction. Patients with virus-related HCC had the highest levels of circulating ET-1 and NOx (13.24 +/- 0.82 pg/ml and 112.28 +/- 18.56 micromol/l) compared to compensated cirrhosis (9.47 +/- 0.50 pg/ml, P < 0.004 and 54.47 +/- 2.36 micromol/l, P < 0.01), decompensated cirrhosis (9.57 +/- 0.32 pg/ml, P < 0.001 and 90.20 +/- 11.23 micromol/l, NS) and normal controls (8.84 +/- 0.61 pg/ml, P < 0.001 and 51.17 +/- 6.18 micromol/l, P < 0.01). There was a significant increase of ET-1 and NOx at HCC stage III compared to HCC stages I and II, cirhotics and controls. HCC stage III patients also had a NOx/ET-1 ratio that was higher than HCC stages I and II patients, normal controls and patients with compensated cirrhosis. Virus-related HCC patients have high levels of circulating ET-1, compared to compensated or decompensated cirrhosis. Highest levels of ET-1 are produced in Okuda III tumours. NOx are also increased but only in Okuda stage III tumours. The NOx/ET-1 ratio is increased in virus-related HCC and DC. This increase may account for the known increase in tumour blood flow.

Suppression of endothelin-converting enzyme-1 during buccal mucosal ulcer healing: effect of chronic alcohol ingestion

Among the factors affecting the efficiency of soft oral tissue healing is endothelin-1 (ET-1), a potent vasoactive peptide produced from a biologically inactive big ET-1 by the action of endothelin-converting enzyme-1 (ECE-1). We investigated the expression of ECE-1 during buccal mucosal ulcer healing in rats maintained for 5 weeks on alcohol containing or control diet. The mucosal activity of ECE-1, characterized by sensitivity to phosphoramidon, was associated with microsomal fraction and showed an elevated (3.1-fold) level in the alcohol diet group. Moreover, the ulcer onset in the alcohol group was reflected in a 39% greater expression of ECE-1 activity, and was accompanied by a 1.4-fold greater increase in TNF-alpha and a 2.5-fold greater enhancement in epithelial cell apoptosis. While in both groups the ulcer healing was associated with a decrease in buccal mucosal expression of ECE-1, as well as a decline in TNF-alpha and apoptosis, the changes were significantly slower in the alcohol diet group and manifested by a 40% delay in healing. Thus, chronic alcohol ingestion leads to up-regulation of ECE-1 expression, induction of TNF-alpha, and triggering apoptotic events that delay the mucosal repair.

The cell and molecular biology of hepatic fibrogenesis. Clinical and therapeutic implications

Much has been learned in the past 2 decades about the cellular and molecular mechanisms underlying hepatic fibrogenesis and about potential therapeutic approaches in patients with liver disease. The central event in fibrogenesis seems to be the activation of hepatic stellate cells. Stellate cell activation is characterized by several important features, including enhanced matrix synthesis and a prominent contractile phenotype, processes that probably contribute to the physical distortion and dysfunction of the liver in advanced disease. It is important to emphasize that the factors controlling activation are multifactorial and complex. The extracellular matrix is a dynamic, active constituent of the fibrogenic response and undergoes active remodeling, including synthesis and degradation. Effective therapy for hepatic fibrogenesis will probably also be multifactorial, based on the basic mechanisms underlying the fibrogenic process. The most effective therapies will probably be directed at the stellate cell. Approaches that address matrix remodeling (i.e., by enhancing matrix degradation or by inhibiting factors that prevent matrix breakdown) may be effective.

Production and release of endothelin-1 from the gut and spleen in portal hypertension due to cirrhosis

This study was aimed to evaluate the source of endothelin-1 (ET-1) in cirrhotic patients. ET-1 is implicated in the pathogenesis of portal hypertension. However, the mechanism and source for increased plasma ET-1 in cirrhotic patients are still obscure. Plasma ET-1 levels in systemic (SV), superior mesenteric (SMV), and splenic venous (SPV) blood were measured in 23 patients with cirrhosis and 8 controls with normal liver. Fourteen removed spleens were immunohistochemically studied for ET-1, CD34, CD68, and CD20. In situ hybridization was done to localize ET-1 messenger RNA (mRNA). In cirrhosis, ET-1 levels in both SMV and SPV were higher than in SV. ET-1 in SV and SPV were significantly higher in cirrhotic patients than in control patients. Three groups of cells in the spleen expressed both protein and mRNA of ET-1: endothelial cells in the sinus, which were also stained for CD34; cells in the germinal center; and cells in the marginal zone of lymphoid sheaths and follicles, which were also stained for CD20 but not for CD34 and CD68. The ET-1 concentration released from the spleen was in parallel with the grade of ET-1 expression in the spleen. The spleen is one of the major sites of ET-1 release in cirrhotic patients. Endothelial cells of the splenic sinus and possibly B lymphocytes in the germinal center and marginal zone of lymphoid sheaths and follicles seem to be the sites of ET-1 production in the spleen.

Up-regulation of endothelin-converting enzyme-1 in gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Endothelin-1 (ET-1) is a vasoactive peptide produced from a biologically inactive big ET-1 by the action of endothelin-converting enzyme-1 (ECE-1). We investigated gastric mucosal expression of ECE-1 during a 10-day course of inflammatory responses associated with acute gastritis elicited by Helicobacter pylori lipopolysaccharide. The ECE-1 activity was associated with microsomal fraction and the level of its expression reflected the extent of mucosal inflammatory involvement. The histologic pattern of inflammation reached a maximum on the 4th day following the lipopolysaccharide and was accompanied by a 4.1-fold enhancement in the expression of ECE-1 activity and a significant elevation in ET-1 (3.1-fold), TNF-alpha (8.8-fold), and apoptosis (11.6-fold). A 41.5% decrease in the severity of mucosal inflammation by the 10th day following the lipopolysaccharide was reflected in a 62.3% reduction in the mucosal expression of ECE-1 and a decline in TNF-alpha, ET-1, and apoptosis. Thus, H. pylori infection causes up-regulation of gastric mucosal ECE-1 expression, which leads to the enhancement of ET-1 production, induction of TNF-alpha, and triggering the apoptotic events that exacerbate the inflammatory process.

Hepatic tissue endothelin-1 levels in chronic liver disease correlate with disease severity and ascites

OBJECTIVES

Plasma endothelin-1 (ET-1) levels are increased in patients with cirrhosis and ET-1 production is increased in the liver itself during experimental injury. These data suggest a possible role for this vasoactive peptide in intrahepatic microcirculatory changes that contribute to the pathogenesis of portal hypertension in cirrhosis. Therefore the aims of this study were to determine whether ET-1 levels were abnormal in the livers of patients with cirrhosis and to investigate possible clinical correlates of altered hepatic ET-1 in cirrhosis.

METHODS

Liver specimens were obtained from explants at the time of liver transplantation in 62 cirrhotic patients; 49 without pretransplantation transjugular intrahepatic portosystemic shunt (TIPS) and 13 with pretransplantation TIPS. The presence of ascites was evaluated by physical examination and ultrasonography. Control specimens consisted of livers with normal morphology obtained from patients who died from nonliver-related causes. Hepatic ET-1 was measured by enzyme immunoassay.

RESULTS

Hepatic ET-1 levels in cirrhotics without (0.17 pg/mg liver tissue) or with TIPS (0.12 pg/mg) were higher than in control patients [0.04 pg/mg (p = 0.02 for ET-1 levels in cirrhotics with or without TIPS vs. control)]. In cirrhotics without ascites who had not had TIPS, ET-1 levels (0.07 pg/mg [0.04-1.00]) were similar to those of the controls. In contrast, ET-1 content was increased in cirrhotics with small (0.11 pg/mg; p = 0.0002) and moderate-to-large (0.69 pg/mg; p = 0.0002) amounts of ascites compared to patients without ascites. There was a modest correlation between ET-1 levels and Child-Pugh score (correlation coefficient 0.32; p = 0.03) and ET-1 levels were significantly higher in patients with Child-Pugh score of 13 or greater (0.88 pg/mg; p = 0.02) than in those with Child-Pugh score of 12 or less (0.16 pg/mg).

CONCLUSIONS

Hepatic tissue ET-1 levels are increased in the liver of patients with cirrhosis. This increase appears to be proportional to the severity of both liver disease and ascites. These data raise a possible role for ET-1 in modulation of intrahepatic resistance in cirrhotic portal hypertension.