Vasoactive factors and hemodynamic mechanisms in the pathophysiology of portal hypertension in cirrhosis

Emerging Therapeutic Targets for Portal Hypertension

Purpose of Review

Portal hypertension is responsible of the main complications of cirrhosis, which carries a high mortality. Recent treatments have improved prognosis, but this is still far from ideal. This paper reviews new potential therapeutic targets unveiled by advances of key pathophysiologic processes.

Recent Findings

Recent research highlighted the importance of suppressing etiologic factors and a safe lifestyle and outlined new mechanisms modulating portal pressure. These include intrahepatic abnormalities linked to inflammation, fibrogenesis, vascular occlusion, parenchymal extinction, and angiogenesis; impaired regeneration; increased hepatic vascular tone due to sinusoidal endothelial dysfunction with insufficient NO availability; and paracrine liver cell crosstalk. Moreover, pathways such as the gut-liver axis modulate splanchnic vasodilatation and systemic inflammation, exacerbate liver fibrosis, and are being targeted by therapy. We have summarized studies of new agents addressing these targets.

Summary

New agents, alone or in combination, allow acting in complementary mechanisms offering a more profound effect on portal hypertension while simultaneously limiting disease progression and favoring regression of fibrosis and of cirrhosis. Major changes in treatment paradigms are anticipated.

The Role of the Spleen in Portal Hypertension

As liver disease progresses, intrahepatic vascular resistance increases (backward flow theory of portal hypertension) and collateral veins develop. Adequate portal hypertension is required to maintain portal flow into the liver through an increase in blood flow into the portal venous system (forward flow theory of portal hypertension). The splenic artery resistance index is significantly and selectively elevated in cirrhotic patients. In portal hypertension, a local hyperdynamic state occurs around the spleen. Splenomegaly is associated with a poor prognosis in cirrhosis and is caused by spleen congestion and by enlargement and hyperactivation of splenic lymphoid tissue. Hypersplenism can lead to thrombocytopenia caused by increased sequestering and breakdown of platelets in the spleen. The close relationship between the spleen and liver is reflected in the concept of the hepatosplenic axis. The spleen is a regulatory organ that maintains portal flow into the liver and is the key organ in the forward flow theory of portal hypertension. This review summarizes the literature on the role of the spleen in portal hypertension.

Splenic Volume, an Easy-To-Use Predictor of HCC Late Recurrence for HCC Patients After Hepatectomy

Purpose

The high recurrence rate of hepatocellular carcinoma (HCC) has a poor impact on the quality of life and survival time of patients. Especially for late recurrence, poor data are available in analysis. We aim to evaluate whether the splenic volume (SV) measured from preoperative CT images could predict late recurrence in HCC patients after hepatectomy.

Patients and Methods

A cohort of 300 HCC patients hospitalized at Xiangya Hospital of Central South University between January 2015 and June 2018 was retrospectively analyzed. The SV was calculated by using automated volumetry software from preoperative CT images. A total of 300 HCC patients were separated into the early recurrence cohort (n=167), the late recurrence cohort (n=39), and the no recurrence cohort (n=94) according to whether there is a recurrence and the recurrence time. Univariate and multivariate Cox analyses were performed to identify the independent risk factors of both early and late recurrence.

Results

AFP, Microvascular invasion (MVI), satellitosis, and BCLC staging were independent risk factors of HCC early recurrence. Splenic volume (HR=1.003, 95%CI:1.001-1.005, P<0.001) was the only predictor of HCC late recurrence. Based on X-tile software, 133 non-early recurrence patients were divided into two groups according to SV: low SV (<165ml, n=45) and high SV (≥165ml, n= 88). The low SV group had a significantly better RFS compared with the high SV group (P=0.015). Nomogram was built on the base of SV to get the probability of 3-year RFS, 4-year RFS, and 5-year RFS.

Conclusion

In our study, we drew a conclusion that splenic volume was the only predictor of HCC late recurrence because of its association with portal hypertension and liver cirrhosis. High splenic volume often indicated a worse recurrence.

Management of portal hypertension based on portal hemodynamics

Portal hypertension is most commonly caused by chronic liver disease. As liver damage progresses, portal pressure gradually elevates and hemodynamics of the portal system gradually change. In normal liver, venous returns from visceral organs join the portal trunk and flow into the liver (hepatopetal blood flow). As portal pressure increases due to liver damage, congestion of some veins of the visceral organ occurs (blood flow to and from). Finally, the direction of some veins (the left gastric vein in particular) of the visceral organ change (hepatofugal blood flow) and develop as collateral veins (portosystemic shunt) to reduce portal pressure. Therefore, esophagogastric varices serve as drainage veins for the portal venous system to reduce the portal pressure. In chronic liver disease, as intrahepatic vascular resistance is increased (backward flow theory) and collateral veins develop, adequate portal hypertension is required to maintain portal flow into the liver through an increase of blood flow into the portal venous system (forward flow theory). Splanchnic and systemic arterial vasodilatations increase the blood flow into the portal venous system (hyperdynamic state) and lead to portal hypertension and collateral formation. Hyperdynamic state, especially around the spleen, is detected in patients with portal hypertension. The spleen is a regulatory organ that maintains portal flow into the liver. In this review, surgical treatment, interventional radiology, endoscopic treatment, and pharmacotherapy for portal hypertension (esophagogastric varices in particular) are described based on the portal hemodynamics using schema.

Hepatic Encephalopathy-Associated Cerebral Vasculopathy in Acute-on-Chronic Liver Failure: Alterations on Endothelial Factor Release and Influence on Cerebrovascular Function

The acute-on-chronic liver failure (ACLF) is a syndrome characterized by liver decompensation, hepatic encephalopathy (HE) and high mortality. We aimed to determine the mechanisms implicated in the development of HE-associated cerebral vasculopathy in a microsurgical liver cholestasis (MHC) model of ACLF. Microsurgical liver cholestasis was induced by ligating and extracting the common bile duct and four bile ducts. Sham-operated and MHC rats were maintained for eight postoperative weeks Bradykinin-induced vasodilation was greater in middle cerebral arteries from MHC rats. Both Nω-Nitro-L-arginine methyl ester and indomethacin diminished bradykinin-induced vasodilation largely in arteries from MHC rats. Nitrite and prostaglandin (PG) F_1α releases were increased, whereas thromboxane (TX) B₂ was not modified in arteries from MHC. Expressions of endothelial nitric oxide synthase (eNOS), inducible NOS, and cyclooxygenase (COX) 2 were augmented, and neuronal NOS (nNOS), COX-1, PGI₂ synthase, and TXA₂S were unmodified. Phosphorylation was augmented for eNOS and unmodified for nNOS. Altogether, these endothelial alterations might collaborate to increase brain blood flow in HE.

Association between spleen volume and the post-hepatectomy liver failure and overall survival of patients with hepatocellular carcinoma after resection

OBJECTIVES

Post-hepatectomy liver failure (PHLF) can occur as a major complication after hepatic resection (HR) in patients with hepatocellular carcinoma (HCC) and negatively affects the prognosis. We aimed to retrospectively assess whether the spleen volume (SV) measured from preoperative CT images would be associated with the development of PHLF and overall survival (OS) after HR in patients with HCC.

METHODS

We enrolled 317 consecutive patients with very early/early stage HCC who underwent a preoperative CT and HR between January 2010 and December 2016. The SV was obtained from preoperative CT images using semi-automated volumetric software and was divided by body surface area to yield SV_BSA. Receiver operating characteristic (ROC) curves and logistic regression analyses were performed to identify factors affecting the development of PHLF. The Cox proportional hazard model was used to identify prognostic factors for OS.

RESULTS

PHLF was observed in 72 patients (22.7% [72/317]). SV_BSA was associated with the development of PHLF (odds ratio, 2.321; 95% CI, 1.347-4.001; p = 0.002) with the area under the ROC curve of 0.663 using the cutoff value of 107.5 cm³ (p < 0.001). SV_BSA was also an influencing factor for OS (hazard ratio, 3.935; 95% CI 1.520-10.184; p = 0.005), with the optimal cutoff of 146 cm³. The 5-year OS rate was higher in 245 patients with a SV_BSA ≤ 146 cm³ than in 72 patients with a SV_BSA > 146 cm³ (95.0% vs. 78.7%, p < 0.001).

CONCLUSIONS

In patients with HCC, a larger SV_BSA was associated with a higher rate of PHLF and worse OS after HR. The SV_BSA may be useful in selecting good surgical candidates.

KEY POINTS

• A significantly higher spleen volume divided by body surface area was observed in patients who experienced post-hepatectomy liver failure than in patients who did not (148 cm³ vs. 112 cm³, p < 0.001). • The area under the receiver operating characteristic curve of spleen volume divided by body surface area to predict the development of post-hepatectomy liver failure was 0.663 (p < 0.001). • Spleen volume divided by body surface area was a significant influencing factor for overall survival (hazard ratio, 3.935; 95% CI, 1.520-10.184; p < 0.001), with the optimal cutoff of 146 cm³.

Mechanisms in fluid retention - towards a mutual concept

Fluid retention is a common and challenging condition in daily clinical practice. The normal fluid homoeostasis in the human body is based on accurately counter-balanced physiological mechanisms. When compromised fluid retention occurs and is seen in pathophysiologically different conditions such as liver cirrhosis, heart and kidney failure, and in preeclampsia. These conditions may share pathophysiological mechanisms such as functional arterial underfilling, which seems to be a mutual element in cirrhosis, cardiac failure, cardiorenal and hepatorenal syndromes, and in pregnancy. However, there are also distinct differences and it is still unclear whether kidney dysfunction or arterial underfilling is the initiating factor of fluid retention or if they happen simultaneously. This review focuses on similarities and differences in water retaining conditions and points to areas where important knowledge is still needed.

Gender differences in vascular reactivity of mesenteric arterioles in portal hypertensive and non-portal hypertensive rats

BACKGROUND

Portal hypertension (PHT) is primarily caused by an increase in resistance to portal outflow and secondarily by an increase in splanchnic blood flow. Vascular hyporeactivity both in systemic circulation and in the mesenteric artery plays a role in the hyperdynamic circulatory syndrome.

AIM

To explore gender differences and the role of endogenous sex hormones in PHT and vascular reactivity of mesenteric arterioles in rats.

METHODS

Cirrhosis and PHT were established by subcutaneous injection of carbon tetrachloride (CCl₄) in both male and female integral and castrated rats (ovariectomized [OVX] in female rats, orchiectomy [ORX] in male rats). The third-order branch of the mensenteric artery was divided and used to measure vascular reactivity to vasoconstrictors.

RESULTS

No significant difference in portal pressure was observed between integral and castrated male PHT rats (15.2 ± 2.1 mmHg vs 16.7 ± 2.7 mmHg, P > 0.05). The portal pressure in integral female PHT rats was lower than that in OVX female PHT rats (12.7 ± 2.7 mmHg vs 16.5 ± 2.4 mmHg, P < 0.05). In PHT rats, the concentration response curves of the mesenteric arterioles to norepinephrine were shifted to the right, and the maximal responses (E_max) values were decreased and effective concentrations causing half maximum responses (EC₅₀) values were increased, compared to those of non-PHT rats, both in male and female rats. Compared to non-PHT integral male rats, the sensitivity of the mesenteric arterioles of non-PHT ORX male rats to norepinephrine was decreased (P > 0.05). However, there was no difference between integral and ORX male rats with PHT. In integral female PHT rats, the concentration response curves were shifted to the left (P < 0.05), and the E_max values were increased and EC₅₀ values were decreased compared to OVX female PHT rats.

CONCLUSION

Clear gender differences were observed in mesenteric vascular reactivity in CCl₄-induced cirrhotic and PHT rats. Conservation of estrogen can retain the sensitivity of the mesenteric arterioles to vasoconstrictors and has a protective effect on splanchnic vascular function in PHT.

Vascular syndromes in liver cirrhosis

Liver cirrhosis is associated with multiple vascular syndromes affecting almost all body systems. Many of these syndromes are directly related to impaired liver function and sometimes reversible after liver transplantation while others arise secondary to portal hypertension and ascites. Altered expression of angiogenic and vasoactive compounds (most importantly nitric oxide), endothelial dysfunction, dysregulated neurohormonal control, and systemic inflammatory state play differential roles in mediating homeostatic instability and abnormal vasogenic response. Important vascular features encountered in liver disease include portal hypertension, splanchnic overflow, abnormal angiogenesis and shunts, portopulmonary syndrome, hepatopulmonary syndrome, and systemic hyperdynamic circulation. Redistribution of effective circulatory volume deviating from vital organs and pooling in splanchnic circulation is also encountered in liver patients which may lead to devastating outcomes as hepatorenal syndrome. Etiologically, vascular syndromes are not isolated phenomena and vascular dysfunction in one system may lead to the development of another in a different system. This review focuses on understanding the pathophysiological factors underlying vascular syndromes related to chronic liver disease and the potential links among them. Many of these syndromes are associated with high mortality, thus it is crucial to look for early biomarkers for these syndromes and develop novel preventive and therapeutic strategies.

Management of refractory ascites in cirrhosis: Are we out of date?

Cirrhosis is a major cause of morbidity and mortality worldwide with liver transplantations as it only possible cure. In the face of a significant organ shortage many patients die waiting. A major complication of cirrhosis is the development of portal hypertension and ascites. The management of ascites has barely evolved over the last hundred years and includes only a few milestones in our treatment approach, but has overall significantly improved patient morbidity and survival. Our mainstay to ascites management includes changes in diet, diuretics, shunt procedures, and large volume paracentesis. The understanding of the pathophysiology of cirrhosis and portal hypertension has significantly improved in the last couple of decades but the changes in ascites management have not seemed to mirror this newer knowledge. We herein review the history of ascites management and discuss some its current limitations.

Decompensated liver cirrhosis and neural regulation of mesenteric vascular tone in rats: role of sympathetic, nitrergic and sensory innervations

We evaluated the possible alterations produced by liver cholestasis (LC), a model of decompensated liver cirrhosis in sympathetic, sensory and nitrergic nerve function in rat superior mesenteric arteries (SMA). The vasoconstrictor response to electrical field stimulation (EFS) was greater in LC animals. Alpha-adrenoceptor antagonist phentolamine and P2 purinoceptor antagonist suramin decreased this response in LC animals more than in control animals. Both non-specific nitric oxide synthase (NOS) L-NAME and calcitonin gene related peptide (CGRP) (8-37) increased the vasoconstrictor response to EFS more strongly in LC than in control segments. Vasomotor responses to noradrenaline (NA) or CGRP were greater in LC segments, while NO analogue DEA-NO induced a similar vasodilation in both experimental groups. The release of NA was not modified, while those of ATP, nitrite and CGRP were increased in segments from LC. Alpha 1 adrenoceptor, Rho kinase (ROCK) 1 and 2 and total myosin phosphatase (MYPT) expressions were not modified, while alpha 2B adrenoceptor, nNOS expression and nNOS and MYPT phosphorylation were increased by LC. Together, these alterations might counteract the increased splanchnic vasodilation observed in the last phases of decompensated liver cirrhosis.

Role of estrogen receptor β selective agonist in ameliorating portal hypertension in rats with CCl4-induced liver cirrhosis

AIM: To investigate the role of diarylpropionitrile (DPN), a selective agonist of estrogen receptor β (ERβ), in liver cirrhosis with portal hypertension (PHT) and isolated hepatic stellate cells (HSCs).

METHODS: Female Sprague-Dawley rats were ovariectomized (OVX), and liver cirrhosis with PHT was induced by CCl₄ injection. DPN and PHTPP, the selective ERβ agonist and antagonist, were used as drug interventions. Liver fibrosis was assessed by hematoxylin and eosin (HE) and Masson’s trichrome staining and by analyzing smooth muscle actin expression. Hemodynamic parameters were determined in vivo using colored microspheres technique. Protein expression and phosphorylation were determined by immunohistochemical staining and Western blot analysis. Messenger RNA levels were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Collagen gel contraction assay was performed using gel lattices containing HSCs treated with DPN, PHTPP, or Y-27632 prior to ET-1 addition.

RESULTS: Treatment with DPN in vivo greatly lowered portal pressure and improved hemodynamic parameters without affecting mean arterial pressure, which was associated with the attenuation of liver fibrosis and intrahepatic vascular resistance (IHVR). In CCl₄-treated rat livers, DPN significantly decreased the expression of RhoA and ROCK II, and even suppressed ROCK II activity. Moreover, DPN remarkedly increased the levels of endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS, and promoted the activities of protein kinase G (PKG), which is an NO effector in the liver. Furthermore, DPN reduced the contractility of activated HSCs in the 3-dimensional stress-relaxed collagen lattices, and decreased the ROCK II activity in activated HSCs. Finally, in vivo/in vitro experiments demonstrated that MLC activity was inhibited by DPN.

CONCLUSION: For OVX rats with liver cirrhosis, DPN suppressed liver RhoA/ROCK signal, facilitated NO/PKG pathways, and decreased IHVR, giving rise to reduced portal pressure. Therefore, DPN represents a relevant treatment choice against PHT in cirrhotic patients, especially postmenopausal women.

Effect of TIPS placement on portal and splanchnic arterial blood flow in 4-dimensional flow MRI

OBJECTIVES

To assess changes in portal and splanchnic arterial haemodynamics in patients undergoing transjugular intrahepatic portosystemic shunt (TIPS) using four-dimensional (4D) flow MRI, a non-invasive, non-contrast imaging technique.

METHODS

Eleven patients undergoing TIPS implantation were enrolled. K-t GRAPPA accelerated non-contrast 4D flow MRI of the liver vasculature was applied with acceleration factor R = 5 at 3Tesla. Flow analysis included three-dimensional (3D) blood flow visualization using time-resolved 3D particle traces and semi-quantitative flow pattern grading. Quantitative evaluation entailed peak velocities and net flows throughout the arterial and portal venous (PV) systems. MRI measurements were taken within 24 h before and 4 weeks after TIPS placement.

RESULTS

Three-dimensional flow visualization with 4D flow MRI revealed good image quality with minor limitations in PV flow. Quantitative analysis revealed a significant increase in PV flow (562 ± 373 ml/min before vs. 1831 ± 965 ml/min after TIPS), in the hepatic artery (176 ± 132 ml/min vs. 354 ± 140 ml/min) and combined flow in splenic and superior mesenteric arteries (770 ml/min vs. 1064 ml/min). Shunt-flow assessment demonstrated stenoses in two patients confirmed and treated at TIPS revision.

CONCLUSIONS

Four-dimensional flow MRI might have the potential to give new information about the effect of TIPS placement on hepatic perfusion. It may explain some unexpected findings in clinical observation studies.

KEY POINTS

• 4D flow MRI, a non-invasive, non-contrast imaging technique, is feasible after TIPS. • Provides visualization and quantification of hepatic arterial, portal venous, collateral and TIPS haemodynamics. • Better understanding of liver blood flow changes after TIPS and patient management.

Protective effect of omeprazole on gastric mucosal of cirrhotic portal hypertension rats

OBJECTIVE

To observe the protective effect of omeprazole on gastric mucosal of cirrhotic portal hypertension rats.

METHODS

All rats were randomly divided into normal control group, cirrhosis and treatment group. Thioacetamide was used to establish rat model of cirrhotic portal hypertension. The necrotic tissue of gastric mucosa ulcer focus, degree of neutrophils infiltration at the ulcer margin, portal pressure, portal venous flow, abdominal aortic pressure, abdominal aortic blood flow at front end, gastric mucosal blood flow (GMBF), glycoprotein (GP) of gastric mucosa, basal acid secretion, H(+)back -diffusion, gastric mucosal damage index, NO, prostaglandin E2(PGE2) and tumor necrosis factor-α (TNF-α) were determined respectively, and the pathological changes of gastric mucosa were also observed by microscope.

RESULTS

Compared with cirrhosis group and the control group, the ulcer bottom necrotic material, gastric neutrophil infiltration and UI of the treatment group were all decreased significantly (P<0.01), GMBF value, GP values, serum NO, PGE2, TNF-α were all significantly increased.

CONCLUSIONS

Omeprazole has an important protective effect on gastric mucosal and it can increase gastric mucosal blood flow and related to many factors.

Prostacyclin decreases splanchnic vascular contractility in cirrhotic rats

BACKGROUND

Prostacyclin has been shown to increase portal hypertension, but the mechanism is unclear. This study aimed to investigate whether the overproduction of prostacyclin (PGI2) in cirrhosis participates in the splanchnic vascular hyporesponsiveness to vasoconstrictors in cirrhotic rats.

METHODS

Cirrhotic model was created by subcutaneous injection of 60% carbon tetrachloride (CCl4) corn oil solution combined with intermittent drinking of 5% alcohol, and age-matched rats served as controls. The isolated third-generation mesenteric arterioles were used to examine the contractile response to norepinephrine. The changes in vascular diameter were observed under a microscope imaging device. The plasma concentration of 6-ketone-prostaglandin F1alpha (6-keto-PGF1alpha, a stable metabolite of PGI2) was tested via enzyme immunoassays and the expression of cyclooxygenase (COX) in mesenteric arteries was detected by Western blotting.

RESULTS

In parallel with the increase of plasma 6-keto-PGF1alpha, the contractile response of arterioles from cirrhotic rats to norepinephrine was significantly impaired compared with that from controls. Inhibition of PGI2 or protein kinase A with indomethacin or Rp-adenosine 3', 5'-cyclic monophosphothioate (Rp-cAMPS) partially reversed the vascular hypo-contractile response to norepinephrine in arterioles from cirrhotic rats. Indomethacin significantly decreased the plasma 6-keto-PGF1alpha. Furthermore, indomethacin significantly attenuated the effect of Rp-cAMPS on arterioles from cirrhotic rats. COX-1 expression was up-regulated in mesenteric arteries from cirrhotic rats, whereas COX-2 was not detectable in the mesenteric arteries from both cirrhotic and control rats.

CONCLUSION

Enhanced COX-1 expression in cirrhotic rats resulted in elevated PGI2 production which partially contributed to the splanchnic vascular hyporesponsiveness to a vasoconstrictor via the protein kinase A pathway.

Splanchnic vasodilation and hyperdynamic circulatory syndrome in cirrhosis

Portal hypertension is a clinical syndrome which leads to several clinical complications, such as the formation and rupture of esophageal and/or gastric varices, ascites, hepatic encephalopathy and hepato-renal syndrome. In cirrhosis, the primary cause of the increase in portal pressure is the enhanced resistance to portal outflow. However, also an increase in splanchnic blood flow worsens and maintains portal hypertension. The vasodilatation of arterial splanchnic vessels and the opening of collateral circulation are the determinants of the increased splanchnic blood flow. Several vasoactive systems/substances, such as nitric oxide, cyclooxygenase-derivatives, carbon monoxide and endogenous cannabinoids are activated in portal hypertension and are responsible for the marked splanchnic vasodilatation. Moreover, an impaired reactivity to vasoconstrictor systems, such as the sympathetic nervous system, vasopressin, angiotensin II and endothelin-1, plays a role in this process. The opening of collateral circulation occurs through the reperfusion and dilatation of preexisting vessels, but also through the generation of new vessels. Splanchnic vasodilatation leads to the onset of the hyperdynamic circulatory syndrome, a syndrome which occurs in patients with portal hypertension and is characterized by increased cardiac output and heart rate, and decreased systemic vascular resistance with low arterial blood pressure. Understanding the pathophysiology of splanchnic vasodilatation and hyperdynamic circulatory syndrome is mandatory for the prevention and treatment of portal hypertension and its severe complications.

H2 S inhibits the activation of hepatic stellate cells and downregulates the expression of urotensin II

AIM

H2 S, a newly discovered signaling gasotransmitter, has been found involved in the pathogenesis of portal hypertension through the H2 S/CSE system. Studies also showed that urotensin II (UII), a recently discovered most potent vasoconstrictor, played an important role in cirrhotic portal hypertension. Therefore, studies were conducted to explore the relationship between H2 S and UII in cirrhosis.

METHODS

In the present study, the changes in the expression levels of cystathionine-γ-lyase (CSE), UII, urotensin II receptor (UT), collagen I, collagen III, tissue inhibitor of metalloproteinase-1 (TIMP-1) and α-smooth muscle actin (α-SMA) were determined by fluorescence quantitative polymerase chain reaction after exposure of hepatic stellate cells to H2 S. The influence of H2 S on UII was examined by western blotting, and the relationship between H2 S and UII was further confirmed by detection of cell proliferation and apoptosis.

RESULTS

Studies have shown that increase in H2 S concentration could reduce the expression of UII, UT, collagen I, collagen III, TIMP-1 and α-SMA without involvement of CSE. Moreover, the results of western blotting further proved that H2 S inhibited the expression of UII. The examination of cell proliferation by 5-ethynyl-2'-deoxyuridine assay suggests that H2 S significantly inhibited the proliferation of LX-2 cells and the proliferation-promoting effect of UII. Similarly, the examination of cell apoptosis revealed that H2 S could promote LX-2 cell apoptosis and inhibit the apoptosis-inhibiting effect of UII.

CONCLUSION

H2 S suppresses fibrosis by inhibiting the activation of hepatic stellate cells and reducing the expression of UII.

Role of urotensin-Ⅱ in the pathogenesis of liver cirrhosis and portal hypertension and collateral circulation

Urotensin-Ⅱ (U-Ⅱ) is a somatostatin-like cyclic peptide which has a potent vasoactive effect and can promote vascular reconstruction and hyperplasia. Research shows that UⅡ plays an important role in the development of liver cirrhosis and portal hypertension. UⅡ influences intrahepatic resistance and splanchnic hemodynamics through a variety of pathways, causing portal hypertension and participating in the formation of esophageal and gastric varices. UⅡ receptor antagonists can reduce portal pressure in cirrhotic rats, but this finding need to be confirmed clinically.

Mesenteric arteries responsiveness to acute variations of wall shear stress is impaired in rats with liver cirrhosis

OBJECTIVE

In liver cirrhosis, excessive splanchnic vasodilation is due to abnormal synthesis of endogenous vasodilators and to decreased sensitivity to vasoconstrictors. The role of mechanical stimuli such as wall shear stress (WSS) on splanchnic circulation remains unclear. The aim of this study was to assess the vasodilation induced by wall shear stress (WSS) and acute changes in blood flow in the mesenteric arteries in an experimental model of liver cirrhosis.

MATERIALS AND METHODS

The effect of acute changes in intraluminal flow (0, 10, and 20 μl/min) and WSS on the diameter of the mesenteric arteries (diameters <500 μm) of control and cirrhotic rats was assessed, at baseline and after the inhibition of nitric oxide synthase, cyclooxygenase and hemeoxygenase. Concentration-response curves to phenylephrine were also obtained.

RESULTS

In controls, the increase in intraluminal flow led to a significant increase in arterial diameter (p < 0.05), while WSS remained stable; the effect was maintained in vessels pre-constricted with phenylephrine, blocked by the exposure to indomethacin and L-NAME and restored by the subsequent addition of chromium mesoporphyrin (p < 0.05). In cirrhotic arteries, arterial diameters did not change in response to acute increase in flow, neither at baseline nor after exposure to indomethacin and L-NAME, while WSS increased (p < 0.01). Responsiveness to flow was partially restored (p < 0.05) after exposure of the arteries to chromium mesoporphyrin in addition to indomethacin and L-NAME.

CONCLUSIONS

Arteries from cirrhotic rats showed an abolished responsiveness to acute variations in flow, which exposes the mesenteric endothelium to sudden variations in WSS.

Non-selective β-blockers improve the correlation of liver stiffness and portal pressure in advanced cirrhosis

BACKGROUND

Liver stiffness (LS) correlates with portal pressure (hepatic venous pressure gradient, HVPG). However, the dynamic components of portal hypertension (PHT) in advanced cirrhosis may not be adequately assessed by TE. The influence of treatment with non-selective β-blockers (NSBB) on the correlation of HVPG and LS has not been investigated.

METHODS

One hundred and twenty-two patients with esophageal varices were included. LS, hemodynamic parameters, and HVPG were recorded at baseline (BL) and after 6 weeks of treatment with NSBB (FU). The correlation of LS and HVPG was compared to control patients with HVPG ≤ 12 mmHg.

RESULTS

Patients with higher Child-Pugh stages (A:88/B:25/C:9) had higher levels of liver stiffness (47.4 ± 16.5 vs. 70.3 ± 7.9 vs. 73.7 ± 2.1 kPa) and HVPG (21 ± 5 vs. 26 ± 5 vs. 26 ± 4 mmHg). The correlation of LS and HVPG was stronger in controls with HVPG ≤ 12 mmHg (R = 0.951; P < 0.0001) than in patients with HVPG > 12 mmHg (R = 0.538; P = 0.0004). The association of HVPG with LS became stronger under treatment with NSBB, which finally restored the linear correlation of HVPG and LS (R = 0.930; P < 0.0001). Forty-three percent (53/122) of patients were hemodynamic responders to NSBB. The improvement in the correlation of LS and HVPG under NSBB was mainly noted in hemodynamic responders (R = 0.864), but not in nonresponders (R = 0.535), whereas changes in LS, heart rate, and MAP were similar in responders and nonresponders.

CONCLUSIONS

Targeting the hyperdynamic circulation and the increased splanchnic blood inflow by treatment with NSBB unmasks the linear (mechanical) correlation of HVPG and LS in patients with HVPG > 12 mmHg. Measurement of LS by TE is not a feasible method to assess the dynamic components of PHT.

Effect of short- and long-term portal hypertension on adrenergic, nitrergic and sensory functioning in rat mesenteric artery

In the present study, we analysed possible alterations in adrenergic, nitrergic and sensory functioning in mesenteric arteries from rats at 1 and 21 months after partial portal vein ligation, and the mechanisms involved in these alterations, if any. For this purpose, we analysed the vasoconstrictor response to EFS (electrical field stimulation) and the effect of the α-antagonist phentolamine, the NOS (nitric oxide synthase) inhibitor L-NAME (N(G)-nitro-L-arginine methyl ester) and the CGRP (calcitonin gene-related peptide) receptor antagonist CGRP-(8-37) in mesenteric segments from ST (short-term; 1 month) and LT (long-term; 21 months) SO (sham-operated) and pre-hepatic PH (portal hypertensive) rats. The vasomotor responses to NA (noradrenaline), the NO donor DEA-NO (diethylamine NONOate) and CGRP were analysed. NA, NO and CGRP releases were measured. Phospho-nNOS (neuronal NOS) expression was studied. The vasoconstrictor response to EFS was decreased in STPH animals. Phentolamine decreased this vasoconstrictor response more strongly in SO animals. Both L-NAME and CGRP-(8-37) increased vasoconstrictor response to EFS more strongly in PH than SO segments. PH did not modify vasomotor responses to NA, DEA-NO or CGRP, but it decreased NA release while increasing those of NO and CGRP. Phospho-nNOS expression was increased by PH. In LTPH, no differences were observed in vasoconstrictor response to EFS, vasomotor responses or neurotransmitter release when compared with age-matched SO animals. In conclusion, the mesenteric innervation may participate in the development of the characteristic hyperdynamic circulation observed in STPH through the joint action of decreased adrenergic influence, and increased nitrergic and sensory innervations influences. The participation of each innervation normalizes under conditions of LTPH.

The use of terlipressin in cirrhotic patients with refractory ascites and normal renal function: a multicentric study

Ascites is a common complication of liver cirrhosis, occurring in more than 50-60% of the patients within 10 years of the diagnosis. In 5-10% of patients, ascites cannot be mobilized, or its early recurrence cannot be prevented by medical treatment. This condition is known as "refractory ascites". The use of terlipressin in cirrhotic patients with refractory ascites and normal renal function has not been evaluated. This prospective study was aimed at evaluating whether terlipressin in addition to standard therapy (diuretics plus albumin) might improve the outcome of refractory ascites in cirrhotic patients without HRS.

PATIENTS

26 cirrhotic patients with refractory ascites were prospectively enrolled in this study. All the patients had tense (grade 3) ascites, and 10/26 showed also massive peripheral edema. Patients received maximum diuretic treatment plus albumin and terlipressin.

RESULTS

Complete response was seen in 16/26 patients. The higher response to therapy was seen during the 2nd week of treatment. 6 patients showed a decrease of at least two points in the ascites score. No differences in clinical response to treatment were seen according to the etiology of the disease.

CONCLUSIONS

In conclusion, our study shows a synergistic effect of terlipressin vs treatment with albumin plus diuretics in patients with refractory ascites. One could speculate that albumin might enhance the vasoconstrictive response to terlipressin, thus contributing to counterbalance the negative effects of systemic vasodilation, which characterizes the hyperdynamic circulation of cirrhotic patients.

Oesophageal varices in cirrhotic patients: from variceal screening to primary prophylaxis of the first oesophageal variceal bleeding

Bleeding from oesophageal varices is still a lethal complication in cirrhotic patients with portal hypertension. Approximately 5-10% of patients with cirrhosis will develop oesophageal varices per year, and about 25-30% of cirrhotic patients with oesophageal varices and without previous variceal haemorrhage will bleed from ruptured varices. To date, data on preventing the formation/growth of oesophageal varices (preprimary prophylaxis) are conflicting, with insufficient evidence to use β-blockers. There is evidence for the need for primary prophylaxis, and both β-blockers and endoscopic variceal ligation have shown the same efficacy in preventing first bleeding, but which one to prefer is still controversial. The present article reviews the established and potential therapeutic strategies for preventing the development and rupture of oesophageal varices.

Cirrhosis decreases vasoconstrictor response to electrical field stimulation in rat mesenteric artery: role of calcitonin gene-related peptide

Our study determines alterations in the vasoconstrictor response elicited by electric field stimulation (EFS) in mesenteric arteries from cirrhotic rats treated with CCl(4), and how calcitonin gene-related peptide (CGRP) participates in this response. Vasoconstriction induced by EFS was analysed in the absence and presence of the CGRP receptor antagonist CGRP(8-37) in arterial segments from control and cirrhotic rats. The vasodilator response to exogenous CGRP was tested in both groups of rats, and the interference of the guanylate cyclase inhibitor ODQ or the K(ATP) channel blocker glibenclamide was analysed only in segments from cirrhotic rats. The vasodilator response to the K(ATP) channel opener pinacidil and to 8-bromo-cyclic GMP was tested. The K(ATP) currents were recorded using the patch-clamp technique. Expression of receptor activity-modifying protein 1 (RAMP1), calcitonin receptor-like receptor, Kir 6.1 and sulfonylurea receptor 2B (SUR2B) was also analysed. Release of CGRP and cGMP was measured. The EFS-elicited vasoconstriction was less in segments from cirrhotic rats. The presence of CGRP(8-37) increased the EFS-induced response only in segments from cirrhotic rats. The CGRP-induced vasodilatation was greater in segments from cirrhotic rats, and was inhibited by ODQ or glibenclamide. Both pinacidil and 8-bromo-cyclic GMP induced a stronger vasodilator response in segments from cirrhotic rats. Pinacidil induced greater K(ATP) currents in cirrhotic myocytes. Expression of RAMP1, calcitonin receptor-like receptor, Kir 6.1 and SUR2B was not modified by liver cirrhosis. Liver cirrhosis increased CGRP release, but did not modify cGMP formation. The decreased vasoconstrictor response to EFS in cirrhosis is mediated by increased vasodilator response to CGRP, as well as increased K(ATP) channel gating. This effect of CGRP may play a role in the splanchnic vasodilatation present in liver cirrhosis.

Vasopressin deficiency and vasodilatory state in end-stage liver disease

OBJECTIVES

Relative vasopressin deficiency, a contributor to vasodilatory septic shock, also may be a cause of the vasodilatory state in liver disease. This study assessed endogenous vasopressin levels in patients with liver disease and their hemodynamic response to exogenous vasopressin.

DESIGN

A prospective, observational study.

SETTING

A single-center, tertiary hospital.

PARTICIPANTS

Human subjects undergoing liver transplantation or major surgery.

INTERVENTIONS

Vasopressin levels were measured in 28 patients with liver disease undergoing liver transplantation and 7 control patients with normal liver function. Additionally, intravenous vasopressin was administered to 20 liver transplant recipients, and the hemodynamic response was observed.

MEASUREMENTS AND MAIN RESULTS

Patients with liver disease had significantly lower baseline vasopressin levels than controls (19.3 ± 27.1 pg/mL v 50.9 ± 36.7 pg/mL, p = 0.015). Patients with low vasopressin levels (≤20 pg/mL) were more likely to have lower baseline mean blood pressure (≤80 mmHg) than patients with high vasopressin levels (11/16 v 0/4, p = 0.013). Systemic vascular resistance increased by 33% 3 minutes after intravenous vasopressin. Thirteen of 16 patients with low vasopressin levels compared with 1 of 4 patients with high vasopressin levels responded to exogenous vasopressin, with an increase of mean blood pressure by more than 20% (p = 0.028).

CONCLUSIONS

Patients with liver disease have lower vasopressin levels than controls and respond with a brisk vasoconstrictor response to exogenous vasopressin. Therefore, relative endogenous vasopressin deficiency may contribute to vasodilatory shock in liver disease similar to what has been observed in septic shock.

Comparison of the effects of femoral versus portal vein administration of vasodilators on portal hemodynamics in cirrhotic rats with portal hypertension

AIM: To compare the effects of femoral versus portal vein administration of vasodilators on portal hemodynamics in rats with liver cirrhosis.

METHODS: Forty-two male Wistar rats with liver cirrhosis induced with carbon tetrachloride and alcohol were divided randomly and equally into six groups, which underwent femoral or portal vein injection of nitroglycerol (NG), prostaglandin E₁(PGE₁) or isotonic sodium chloride (NaCl), respectively. Hemodynamic parameters, including portal vein diameter (PVD), portal flow rate (PFR) and portal vein inflow (PVF), were measured after drug injection.

RESULTS: There were no significant differences in PVD, PVF and PFR between rats undergoing femoral and portal vein injection of NaCl (P = 0.1742, 0.2372 and 0.6566). PVD was increased significantly in cirrhotic rats that were given vasodilator agents, however, there were no significant differences in PVD changes between rats undergoing portal and femoral vein administration (P = 0.0516 and 0.1225). PVF was less increased in rats undergoing portal vein administration of NG and PGE₁than in those undergoing femoral vein administration of NG and PGE₁ (P < 0.0001). Comparing with pre-injection, PFR increased in rats undergoing femoral vein administration of NG and PGE₁, but decreased in rats undergoing portal vein administration NG and PGE₁ after dosed 10, 20 min [NG_f: 4.98 mm/(s•100 g) ± 0.62 mm/(s•100 g), 4.31 mm/(s•100 g) ± 0.46 mm/(s•100 g) vs 3.62 mm/(s•100 g) ± 0.38 mm/(s•100 g); PGE_1f: 3.96 mm/(s•100 g) ± 0.56 mm/(s•100 g), 4.18 mm/(s•100 g) ± 0.50 mm/(s•100 g) vs 3.63 mm/(s•100 g) ± 0.47 mm/(s•100 g) P < 0.0001; NG_p: 2.93 mm/(s•100 g) ± 0.22 mm/(s•100 g), 3.13 mm/(s•100 g) ± 0.21 mm/(s•100 g) vs 3.70 mm/(s•100 g) ± 0.48 mm/(s•100 g); PGE_1p: 3.65 mm mm/(s•100 g) ± 0.22 mm/(s•100 g), 3.36 mm/(s•100 g) ± 0.21 mm/(s•100 g) vs 3.84 mm/(s•100 g) ± 0.19 mm/(s•100 g), P< 0.001].

CONCLUSION: NG and PGE₁ are able to increase portal vein flow in cirrhotic rats with portal hypertension. Administration of vasodilators via the portal vein is not superior to that via the femoral vein in increasing PVF in cirrhotic rats with portal hypertension.

Advances in understanding the role of the UII/UT system in the pathogenesis of portal hypertension

Urotensin II (UII), a vasoactive peptide with structural similarity to somatostatin, is the most potent vasoconstrictor known in systemic resistance vessels and has multiple biological effects related to a variety of human diseases. Numerous studies have found that UII and its receptor (UT) play an important role in the pathogenesis of portal hypertension. This paper reviews the recent advances in understanding the role of the UII/UT system in the pathogenesis of portal hypertension.

Balancing volume resuscitation and ascites management in cirrhosis

PURPOSE OF REVIEW

Patients with cirrhosis have total extracellular fluid overload but central effective circulating hypovolaemia. The resulting neurohumoral compensatory response favours the accumulation of fluids into the peritoneal cavity (ascites) and may hinder renal perfusion (hepatorenal syndrome). Their deranged systemic haemodynamics (hyperdynamic circulatory syndrome) is characterized by elevated cardiac output with decreased systemic vascular resistance and low blood pressure.

RECENT FINDINGS

Molecular and biological mechanisms determining cirrhosis-induced haemodynamic alterations are progressively being elucidated. The need for a goal-directed assessment of volume resuscitation (especially with volumetric techniques) in patients with cirrhosis is becoming more and more evident. The role of fluid expansion with albumin and the use of splanchnic vasopressors in a variety of cirrhosis-related conditions has recently been investigated.

SUMMARY

The response to fluid loading in patients with advanced cirrhosis is abnormal, primarily resulting in expansion of their noncentral blood volume compartment. Colloid solutions, in particular albumin, are best used in these patients. Albumin may be effective in preventing the haemodynamic derangements associated with large-volume paracentesis (paracentesis-induced circulatory dysfunction), in preventing renal failure during spontaneous bacterial peritonitis and, in association with splanchnic vasopressors, in caring for patients with the hepatorenal syndrome.

Simultaneous inhibition of TXA(2) and PGI(2) synthesis increases NO release in mesenteric resistance arteries from cirrhotic rats

Our present study examines, in mesenteric resistance arteries, possible vasodilation alterations, and the role of NO and COX (cyclo-oxygenase) derivatives, in cirrhosis. The vasodilator response to acetylcholine was analysed in segments from control and cirrhotic rats. The effects of the non-specific COX inhibitor indomethacin, the specific COX-1 inhibitor SC-560 and the specific COX-2 inhibitor NS-398 were analysed in segments from both groups of rats. NO release was measured, and eNOS [endothelial NOS (NO synthase)], phospho-eNOS, iNOS (inducible NOS), COX-1 and COX-2 protein expression was also analysed. The effects of the TP receptor [TXA2 (thromboxane A(2)) receptor] antagonist SQ 29548, the TXA(2) synthesis inhibitor furegrelate, the PGI(2) (prostaglandin I(2)) synthesis inhibitor TCP (tranylcypromine) or TCP+furegrelate were only determined in segments from cirrhotic rats. The vasodilator response to acetylcholine was higher in segments from cirrhotic rats. Indomethacin, SC-560 and NS-398 did not modify the vasodilator response in control rats; however, indomethacin, NS-398 and TCP+furegrelate increased, whereas SC-560 did not modify and SQ 29548, furegrelate or TCP decreased, the vasodilator response to acetylcholine in cirrhotic rats. NO release was higher in cirrhotic rats. Furegrelate decreased, whereas TCP+furegrelate increased, the NO release in segments from cirrhotic rats. eNOS and COX-1 protein expression was not modified, whereas phosho-eNOS, iNOS and COX-2 protein expression was higher in cirrhotic rats. Therefore the increase in iNOS expression and eNOS activity may mediate increases in endothelial NO release. The COX-2 derivatives TXA(2) and PGI(2) may act simultaneously, producing a compensatory effect that reduces NO release and may limit the hyperdynamic circulation.

Long-term portal hypertension increases the vasodilator response to acetylcholine in rat aorta: role of prostaglandin I2

In the present study, we have analysed both the effect of long-term portal hypertension on the vasomotor response to acetylcholine in rat aorta and the mechanism involved in this response. For this purpose, sham-operated rats and rats with pre-hepatic PH (portal hypertension; triple partial portal vein ligation) were used at 21 months after surgery. The participation of NO and COX (cyclo-oxygenase) derivatives in the vasodilator response elicited by acetylcholine after incubation with L-NAME (NG-nitro-L-arginine methyl ester), indomethacin, SC-560, NS-398, tranylcypromine and furegrelate, was analysed. NO, TXB2 (thromboxane B2) and 6-keto PGF1alpha (prostaglandin F1alpha) release were measured. In addition, SNP (sodium nitroprusside), U-46619, PGI2 and forskolin vasomotor responses were analysed. COX-1 and COX-2 expression was also determined. The acetylcholine-induced vasodilating response was higher in rats with PH. TXA2 and NO release, and SNP and U-46619 sensitivity were similar in both groups. PGI2 release was not modified by portal hypertension, but vasodilator responses to this prostanoid and to forskolin were higher in rats with PH. COX-1 and COX-2 expression remained unmodified by surgery. In conclusion, increased vasodilation to acetylcholine is maintained in long-term PH. Although the participation of endothelial NO remained unmodified, the COX-2 derivative PGI2 does participate through an increased vasodilator response.