The paradox of nitric oxide in cirrhosis and portal hypertension: too much, not enough

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.

Intraperitoneal LPS amplifies portal hypertension in rat liver fibrosis

Recent studies have shown that the risk of variceal bleeding in patients with liver cirrhosis increases with infections such as spontaneous bacterial peritonitis (SBP). In this study, we hypothesized that pretreatment with intraperitoneal LPS may escalate portal hypertension. In fibrotic livers (4 weeks after bile duct ligation, BDL), the activation of Kupffer cells (KCs) by zymosan (150 microg/ml) in the isolated non-recirculating liver perfusion system resulted in a transient increase in portal perfusion pressure. Pretreatment with intraperitoneal LPS (1 mg/kg body weight (b.w.) for 3 h) increased basal portal perfusion pressure, and prolonged the zymosan-induced increase from transient to a long-lasting increase that was sustained until the end of the experiments in BDL but not in sham-operated animals. Pretreatment with gadolinium chloride (10 mg/kg b.w.), MK-886 (0.6 mg/kg b.w.), Ly171883 (20 microM) or BM 13.177 (20 microM) reduced the maximal and long-lasting pressure increase in BDL animals by approximately 50-60%. The change in portal perfusion pressure was paralleled by a long-lasting production of cysteinyl leukotriene (Cys-LT) and thromboxane (TX) after LPS pretreatment. However, the response to vasoconstrictors was not altered by intraperitoneal LPS. Western blot analyses showed an increased Toll-like receptor (TLR)4 and MyD88 expression after LPS pretreatment. In vivo experiments confirmed that intraperitoneal LPS increased basal portal pressure, and extended the portal pressure increase produced by intraportal zymosan or by LPS infusion. In conclusion, upregulation of TLR4 and MyD88 expression in fibrotic livers confers hypersensitivity to LPS. This may lead to escalation of portal hypertension by production of TX and Cys-LT after endotoxin-induced KC activation. Therefore, LT inhibitors may represent a promising treatment option in addition to early administration of antibiotics in SBP.

Optimal management of hepatorenal syndrome in patients with cirrhosis

Hepatorenal syndrome (HRS) is a functional renal failure that often occurs in patients with cirrhosis and ascites. HRS develops as a consequence of a severe reduction of effective circulating volume due to both an extreme splanchnic arterial vasodilatation and a reduction of cardiac output. There are 2 different types of HRS. Type 1 HRS, which is often precipitated by a bacterial infection, especially spontaneous bacterial peritonitis, is characterized by a rapidly progressive impairment of renal function. Despite its functional origin, the prognosis of type 1 HRS is very poor. Type 2 HRS is characterized by a stable or slowly progressive renal failure so that its main clinical consequence is not acute renal failure but refractory ascites and its impact on prognosis is less negative. New treatments (vasoconstrictors plus albumin, transjugular portosystemic shunt, and molecular adsorbent recirculating system), which were introduced in the past 10 years, are effective in improving renal function in patients with HRS. Among these treatments vasoconstrictors plus albumin can also improve survival in patients with type 1 HRS. Thus, this therapeutic approach has changed the management of this severe complication in patients with advanced cirrhosis.

Treatment with the leukotriene inhibitor montelukast for 10 days attenuates portal hypertension in rat liver cirrhosis

The mechanisms underlying intrahepatic vasoconstriction are not fully elucidated. Here we investigated the Kupffer cell (KC)-dependent increase in portal pressure by way of actions of vasoconstrictive cysteinyl leukotrienes (Cys-LTs). Liver cirrhosis was induced in rats by bile duct ligation (BDL for 4 weeks; controls: sham-operation) and thioacetamide application (18 weeks). Infusion of leukotriene (LT) C(4) or LTD(4) in isolated perfused livers (20 nM, BDL and sham) demonstrated that LTC(4) is a more relevant vasoconstrictor. In BDL animals the Cys-LT(1) receptor inhibitor montelukast (1 microM) reduced the maximal portal perfusion pressure following LTC(4) or LTD(4) infusion. The infusion of LTC(4) or D(4) in vivo (15 microg/kg b.w.) confirmed LTC(4) as the more relevant vasoconstrictor. Activation of KCs with zymosan (150 microg/mL) in isolated perfused BDL livers increased the portal perfusion pressure markedly, which was attenuated by LT receptor blockade (Ly171883, 20 microM). Cys-LTs in the effluent perfusate increased with KC activation but less with additional blockade of KCs with gadolinium chloride (10 mg/kg body weight, 48 and 24 hours pretreatment). KCs were isolated from normal rat livers and activated with zymosan or lipopolysaccharide at different timepoints. This resulted in an increase in Cys-LT production that was not influenced by preincubation with montelukast (1 microM). Infusion of LTC(4) (20 nM) and the thromboxane analog U46619 (0.1 microM) further enhanced portal pressure, indicating additive effects. Treatment with montelukast for 10 days resulted in an impressive reduction in the basal portal pressure and an attenuation of the KC-dependent increase in portal pressure.

CONCLUSION

Activation of isolated KCs produced Cys-LTs. Infusion of Cys-LTs increased portal pressure and, vice versa, treatment with montelukast reduced portal pressure in rat liver cirrhosis. Therefore, montelukast may be of therapeutic benefit for patients with portal hypertension.

Efficacy and cytotoxicity of a liver-targeted nitric oxide-releasing drug in the treatment of liver injury in mice

AIM: To evaluate the efficacy and cytotoxicity of NO-040527, a new liver-targeted nitric oxide-releasing drug, in the treatment of liver injury induced with carbon tetrachloride, acetaminophen or D-galactosamine in mice.

METHODS: Liver injury was induced in mice by intraperitoneal injection of carbon tetrachloride, acetaminophen or D-galactosamine. NO-040527 was orally administered to animals 1 h before and 12 h after the induction of liver injury. The animals were killed 24 h after drug delivery, and blood samples were taken to determine serum ALT and AST levels using an automatic biochemical analyzer. The cytotoxicity of the targeted conjugate was determined by methyl thiazol tetrazolium (MTT) assay.

RESULTS: NO-040527 could significantly inhibit carbon tetrachloride-induced elevation of ALT and AST in mice (both P < 0.01) in a dose-dependent manner. At the same dose (55 mg/kg), NO-040527 exhibited better efficacy than control drug NCX-1000 (P < 0.05) in lowering carbon tetrachloride-induced elevation of serum ALT and AST levels. Similarly, NO-040527 could also significantly inhibit acetaminophen-induced elevation of ALT and AST (both P < 0.01) though no dose-dependent effect was noted. At the same dose (55 mg/kg), NO-040527 exhibited similar efficacy to NCX-1000 in lowering acetaminophen-induced elevation of serum ALT and AST levels. NO-040527 showed no protective effects against liver injury induced with D-galactosamine. No significant differences were noted in serum ALT and AST levels between untreated mice with D-galactosamine-induced liver injury and those treated with medium- or low-dose NO-040527. However, the levels of serum ALT and AST in mice with D-galactosamine-induced liver injury treated with high-dose NO-040527 was higher than those in untreated ones. NO-040527 at a dose of 500 μmol/L began to show cytotoxicity (cell viability rate: 45.96% ± 29.46%; P = 0.058). Significant cytotoxicity was noted when the dose of NO-040527 rose to 1000 μmol/L (P < 0.005). NO-040527 at 50 and 100 μmol/L could accelerate cell growth (cell viability rate: 137.67% ± 8.47% and 152.65% ± 10.084%, respectively; both P < 0.05).

CONCLUSION: NO-040527 has good protective effects against carbon tetrachloride- or acetaminophen-induced liver injury in mice. NO-040527 is cytotoxic when used at high dose.

NCX-1000, a nitric oxide-releasing derivative of UDCA, does not decrease portal pressure in patients with cirrhosis: results of a randomized, double-blind, dose-escalating study

OBJECTIVES

NCX-1000 (2(acetyloxy) benzoic acid-3(nitrooxymethyl)phenyl ester) is an nitric oxide (NO)-releasing derivative of ursodeoxycholic acid (UDCA), which showed selective vasodilatory effect on intrahepatic circulation in animal models of cirrhosis. This study was aimed at testing the efficacy and tolerability of this compound in patients with cirrhosis and portal hypertension.

METHODS

This was a single-center, phase-2a, randomized (4:1), double-blind, parallel-group, dose-escalating study. Patients received progressive oral doses of NCX-1000 or placebo up to 2 g t.i.d. or maximum tolerated doses for 16 days. Efficacy on fasting and postprandial hepatic venous pressure gradient (HVPG) at baseline and after treatment was assessed. Hepatic blood flow (HBF) and arterial blood pressure were also measured.

RESULTS

Eleven patients (nine NCX-1000 and two placebo) were enrolled and completed the trial. After NCX-1000 treatment, HVPG did not change (16.7+/-3.8 vs. 17.1+/-3.8 mm Hg; P=0.596), and HBF decreased significantly (904+/-310 vs. 1,129+/-506 ml/min; P=0.043). The postprandial increase in portal pressure and HBF was not modified by NCX-1000. There was no significant effect on diastolic blood pressure, but systolic blood pressure was reduced by the treatment in a dose-dependent manner (121+/-11 mm Hg after NCX-1000 vs. 136+/-7 mm Hg at baseline; P=0.003). Seven non-serious adverse events were experienced by four patients (one on placebo).

CONCLUSIONS

In patients with cirrhosis and portal hypertension, NCX-1000 administration was safe, but it was not able to reduce portal pressure. A significant reduction of systolic blood pressure and HBF was observed in the treatment arm, suggesting that the drug had systemic effects and lacked selective release of NO at the intrahepatic circulation.

Role of HSP-90 for increased nNOS-mediated vasodilation in mesenteric arteries in portal hypertension

AIM: To explore the role of heat shock protein-90 (HSP-90) for nitrergic vasorelaxation in the splanchnic circulation in rats with and without portal hypertension.

METHODS: Neuronal nitric oxide synthase (nNOS) and HSP-90 were analyzed by immunofluorescence, western blotting and co-immunoprecipitation in the mesenteric vasculature and isolated nerves of portal-vein-ligated (PVL) rats and sham operated rats. In vitro perfused de-endothelialized mesenteric arterial vasculature was preconstricted with norepinephrine (EC₈₀) and tested for nNOS-mediated vasorelaxation by periarterial nerve stimulation (PNS, 2-12 Hz, 45V) before and after incubation with geldanamycin (specific inhibitor of HSP-90 signalling, 3 μg/mL) or L-NAME (non-specific NOS-blocker, 10^-4 mol/L).

RESULTS: nNOS and HSP-90 expression was significantly increased in mesenteric nerves from PVL as compared to sham rats. Moreover, nNOS and HSP-90 were visualized in mesenteric nerves by immunofluorescence and immunoprecipitation of nNOS co-immunoprecitated HSP-90 in sham and PVL rats. PNS induced a frequency-dependent vasorelaxation which was more pronounced in PVL as compared to sham rats. L-NAME and geldanamycin markedly reduced nNOS-mediated vasorelaxation abrogating differences between the study groups. The effect of L-NAME and geldanamycin on nNOS-mediated vasorelaxation was significantly greater in PVL than in sham animals. However, no difference in magnitude of effect between L-NAME and geldanamycin was noted.

CONCLUSION: HSP-90 acts as a signalling mediator of nNOS-dependent nerve mediated vascular responses in mesenteric arteries, and the increased nitrergic vasorelaxation observed in portal hypertension is mediated largely by HSP-90.

Melatonin prevents increased asymmetric dimethylarginine in young rats with bile duct ligation

Identifying and treating kidney injury in cirrhosis is important. Bile duct ligation (BDL) is a commonly used cholestatic liver disease model. We hypothesized that asymmetric dimethylarginine (ADMA) is involved in BDL-induced oxidative stress and kidney injury, which can be prevented by melatonin. We also intended to elucidate whether increased ADMA is due to increased protein arginine methyltransferase-1 (PRMT1, ADMA-synthesizing enzyme) and/or decreased dimethylarginine dimethylaminohydrolase (DDAH, ADMA-metabolizing enzyme). Three groups of young rats were studied, sham (N = 7), untreated BDL rats (N = 9), and melatonin-treated BDL rats (N = 6, BDL + M). Melatonin-treated BDL rats received daily melatonin 1 mg/kg/day via intraperitoneal injection. One-third of the young BDL rats died compared with none in the BDL + M group. All surviving rats were killed 14 days after surgery. BDL rats had higher plasma aspartate aminotransferase, alanine aminotransferase, direct and total bilirubin, and ammonia levels than shams. They also had kidney injury characterized by increased tubulointerstitial injury scores and plasma creatinine and symmetric dimethylarginine levels, which melatonin prevented. Plasma ADMA levels were elevated in BDL rats, combined with increased hepatic PRMT1 and decreased renal DDAH activity. In addition, melatonin increased hepatic DDAH2 expression, increased DDAH activity and concomitantly decreased ADMA contents in both the liver and kidney. In conclusion, melatonin therapy decreased mortality and prevented kidney injury induced by BDL via reduction of ADMA (by increasing DDAH activity) and oxidative stress.

Protein nitration is associated with increased proteolysis in skeletal muscle of bile duct ligation-induced cirrhotic rats

Cirrhosis is characterized by skeletal muscle wasting. In this study, the effects of nitric oxide production on skeletal muscle protein nitration and degradation in cirrhosis were investigated. Cirrhosis was induced by bile duct ligation (BDL) in Sprague-Dawley rats for 4 weeks. The BDL-induced cirrhotic rats and sham-operated rats were then injected daily with either saline or N(G)-l-nitro-arginine methyl ester (l-NAME) for 7 days from week 4 to week 5, after which nitrite/nitrate, glutathione reduction, as well as protein nitration, ubiquitination, and degradation were assessed in skeletal muscle. Elevated muscular nitrite/nitrate concentrations, protein nitration, total ubiquitin conjugates, and degradation fragments of myosin heavy chain as well as diminished glutathione reduction levels were observed in BDL-induced cirrhotic rats as compared with controls. Administration of l-NAME for 1 week led to reduction of nitrite/nitrate levels; protein nitration was also decreased in the skeletal muscle. In addition, ubiquitination of muscular proteins and degradation of myosin heavy chain were significantly diminished after treatment of l-NAME. In conclusion, nitrosative stress occurred in the skeletal muscle of BDL-induced cirrhotic rats and may lead to increased proteolysis of muscle-specific structural proteins.

Ascites: pathogenesis and therapeutic principles

Ascites is a classic complication of advanced cirrhosis and it often marks the first sign of hepatic decompensation. Ascites occurs in more than 50% of patients with cirrhosis, worsens the course of the disease, and reduces survival substantially. Portal hypertension, splanchnic vasodilatation, liver insufficiency, and cardiovascular dysfunction are major pathophysiological hallmarks. Modern treatment of ascites is based on this recognition and includes modest salt restriction and stepwise diuretic therapy with spironolactone and loop-diuretics. Tense and refractory ascites should be treated with large volume paracentesis followed by plasma volume expansion or transjugular intrahepatic portosystemic shunt. Ascites complicated by spontaneous bacterial peritonitis requires adequate treatment with antibiotics. New potential treatment strategies include the use of vasopressin V(2)-receptor antagonists and vasoconstrictors. Since formation of ascites is associated with a poor prognosis, and treatment of fluid retention does not substantially improve survival, such patients should always be considered for liver transplantation.

Peripheral and portal plasma iNOS activity and hepatic expression of iNOS in patients with chronic hepatitis or liver cirrhosis

AIM: To investigate the role of nitric oxide (NO) in the development and progression of hepatitis and liver cirrhosis.

METHODS: Peripheral and portal plasma inducible nitric oxide synthase (iNOS) activity was measured by the nitric acid reductase method. The expression of iNOS mRNA and protein in the liver was measured by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemisty, respectively.

RESULTS: Peripheral and portal plasma iNOS activity, especially the latter, was significantly higher in patients with chronic hepatitis or liver cirrhosis than in normal controls (F = 102.793 and 25.052, respectively; both P < 0.01). The expression levels of iNOS protein in the liver of patients with chronic hepatitis or liver cirrhosis were enhanced when compared to that in normal controls (F = 46.796, P < 0.05). The expression levels of iNOS mRNA in the liver of patients with chronic hepatitis or hepatic cirrhosis were also higher than that in normal controls (F = 26.832, P < 0.01), showing an increasing trend with the progression of the diseases.

CONCLUSION: The iNOS/NO system plays an important role in the development and progression of chronic hepatitis and hepatic cirrhosis perhaps by dilating blood vessels.

A study of muscle tissue oxygenation and peripheral microcirculatory dysfunction in cirrhosis using near infrared spectroscopy

BACKGROUND

The circulatory dysfunction associated with cirrhosis is well described. Reduced systemic vascular resistance and high cardiac output are the main features of the hyperdynamic state, but involvement of the peripheral microcirculation in this process is poorly understood. Near infrared spectroscopy (NIRS) has been used to assess muscle tissue oxygenation (StO(2)) in haemorrhagic and septic shock. Vascular occlusion testing (VOT) can produce dynamic changes in StO(2) which represent tissue oxygen extraction, delivery, and hence, surrogate markers of microvascular function.

AIMS

We aimed to investigate dynamic StO(2) changes in the peripheral microcirculation of patients with cirrhosis.

METHODS

Thirty-five subjects were examined (25 cirrhosis, 10 healthy volunteers) with an InSpectra 650 StO(2) monitor and 15 mm thenar probe. Brachial VOT was applied at systolic blood pressure +50 mmHg for 3 min, in triplicate. Dynamic StO(2) parameters are reported for baseline, downslope, upslope, area over ischaemic curve, overshoot, area under recovery curve and recovery time.

RESULTS

Patients with cirrhosis demonstrated significantly larger post-occlusive hyperaemic variables compared with volunteers: overshoot (17 vs 15%, P=0.009), area under recovery curve (25.1 vs 16.3 %/min, P<0.001) and recovery time (3.0 vs 2.2 min, P<0.001). Magnitude of change was also seen to increase with disease stage as defined by Child-Pugh score. Serial VOT revealed microcirculatory ischaemic adaptation in volunteers, which was absent in cirrhosis.

CONCLUSIONS

NIRS can identify dynamic changes in muscle tissue oxygenation in cirrhosis which are compatible with microcirculatory vasodilatation. Ischaemic adaptation was seen in controls but not in patients with cirrhosis. NIRS techniques offer a novel approach to the assessment of peripheral vascular dysfunction in cirrhosis.

Hemodynamic effects of albumin dialysis in patients with liver failure: for better or for worse?

Liver failure, irrespective of is cause, is frequently associated with multi-organ dysfunction, including hemodynamic instability, and renal and cerebral insufficiency. As a result of the combined impact of these complications, liver failure carries an exceptionally high risk of mortality. A central role in the etiopathogenesis of different end-organ manifestations, as well as in the aggravation of the underlying liver failure, has been attributed to the hyperdynamic (hypotensive) state, which is characterized by a reduced systemic vascular resistance and mean arterial pressure, as well as an increased cardiac index, heart rate, and total plasma volume. Since the accumulation of toxins due to the decreased detoxification capacity by the failing liver is considered vital herein, the emergence of extracorporeal liver support has provided a rational basis for the potential reversal of these phenomena. The present article critically reviews data with regard to the hemodynamic effects of artificial liver support in the context of liver failure. Although these are scarce for acute liver failure, several uncontrolled series and small randomized trials have clearly documented that artificial liver support is able to improve both portal hypertension and the associated systemic circulatory dysfunction in patients with acute-on-chronic liver failure. The molecular basis for these effects have been related to temporary changes and/or elimination in endogenous vasoactive substances, improved albumin binding capacity, or restoration of oxidative stress-mediated damage to albumin.

Role of beta3-adrenoceptors for intrahepatic resistance and portal hypertension in liver cirrhosis

Increased intrahepatic resistance and splanchnic blood flow cause portal hypertension in liver cirrhosis. Nonselective beta-adrenoceptor (beta-AR) antagonists have beneficial effects on hyperdynamic circulation and are in clinical use. In this context, the role of the beta(3)-AR is undefined. Here we investigated their expression and role in portal hypertension in patients and rats with liver cirrhosis. We analyzed cirrhotic human and rat tissues (liver, splanchnic vessels) and primary rat cells. Protein expression of beta(3)-AR was determined by western blot and messenger RNA (mRNA) levels by reverse-transcription polymerase chain reaction (RT-PCR). Activities of Rho-kinase and the nitric oxide (NO) effector protein kinase G (PKG) were assessed by way of substrate phosphorylation (moesin, vasodilator-stimulated phosphoprotein [VASP]). Cyclic 3',5' adenosine monophosphate (cAMP) accumulation was determined by an enzyme-immunoassay kit. The effects of selective beta(3)-AR agonists (CGP12177A, BRL37344) and antagonist (SR59230A) were investigated by collagen matrix contraction of hepatic stellate cells (HSCs), in situ liver perfusions, and in vivo hemodynamic parameters in bile duct ligation and carbon tetrachloride intoxication in cirrhotic rats. In cirrhosis of humans and rats, beta(3)-AR expression is markedly increased in hepatic and in splanchnic tissues. Stimulation of beta(3)-AR leads to relaxation of HSCs by way of cAMP accumulation, and by inhibition of Rho-kinase activity; any role of NO and its effector PKG was not observed. beta(3)-AR agonists decrease intrahepatic resistance and portal pressure in cirrhotic rats.

CONCLUSION

There is a marked hepatic and mesenteric up-regulation of beta(3)-ARs in human cirrhosis and in two different animal models of cirrhosis. The beta(3)-AR-agonists should be further evaluated for therapy of portal hypertension.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Nitric oxide suppresses transforming growth factor-beta1-induced epithelial-to-mesenchymal transition and apoptosis in mouse hepatocytes

Nitric oxide (NO) is a multifunctional regulator that is implicated in various physiological and pathological processes. Here we report that administration of NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited transforming growth factor-beta1 (TGF-beta1)-induced epithelial-to-mesenchymal transition (EMT) and apoptosis in mouse hepatocytes. Overexpression of inducible NO synthase (iNOS) by transfection of the iNOS-expressing vector, which increased NO production, also inhibited the TGF-beta1-induced EMT and apoptosis in these cells. Treatment of cells with proinflammatory mediators, including tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and interferon (IFN)-gamma, which increased the endogenous NO production, produced the same inhibitory effect. Furthermore, exogenous NO donor SNAP treatment caused a decrease in the intracellular adenosine triphosphate (ATP) levels. Consistently, depletion of intracellular ATP by mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) inhibited the TGF-beta1-induced EMT and apoptosis, suggesting that an NO-induced decrease of ATP involved in the NO-mediated inhibition of TGF-beta1-induced EMT and apoptosis. NO and FCCP also inhibited TGF-beta1-induced STAT3 activation, suggesting that signal transducer and activator of transcription 3 inactivation is involved in the NO-induced effects on TGF-beta1-induced EMT and apoptosis.

CONCLUSION

Our study indicates that NO plays an important role in the inhibition of TGF-beta1-induced EMT and apoptosis in mouse hepatocytes through the downregulation of intracellular ATP levels. The data provide an insight into the in vivo mechanisms on the function of NO during the processes of both EMT and apoptosis.

Major adverse events, pretransplant assessment and outcome prediction

Liver cirrhosis and portal hypertension pose enormous loss of lives and resources throughout the world, especially in endemic areas of chronic viral hepatitis. Although the pathophysiology of cirrhosis is not completely understood, the accumulating evidence has paved the way for better control of the complications, including gastroesophageal variceal bleeding, hepatic encephalopathy, ascites, hepatorenal syndrome, hepatopulmonary syndrome and portopulmonary hypertension. Modern pharmacological and interventional therapies have been designed to treat these complications. However, liver transplantation (LT) is the only definite treatment for patients with preterminal end-stage liver disease. To pursue successful LT, the meticulous evaluation of potential recipients and donors is pivotal, especially for living donor transplantation. The critical shortage of cadaveric donor livers is another concern. In many Asian countries, cultural and religious concerns further limit the number of the donors, which lags far behind that of the recipients. The model for end-stage liver disease (MELD) scoring system has recently become the prevailing criterion for organ allocation. Initial results showed clear benefits of moving from the Child-Turcotte-Pugh-based system toward the MELD-based organ allocation system. In addition to the MELD, serum sodium is another important prognostic predictor in patients with advanced cirrhosis. The incorporation of serum sodium into the MELD could enhance the performance of the MELD and could become an indispensable strategy in refining the priority for LT. However, the feasibility of the MELD in combination with sodium in predicting the outcome for patients on transplant waiting list awaits actual outcome data before this becomes standard practice in the Asia-Pacific region.

Cardiac and systemic haemodynamic complications of liver cirrhosis

Cardiovascular complications of liver cirrhosis include cardiac dysfunction and abnormalities in the central-, splanchnic,- and peripheral circulation. Vasodilatation prevails, but vascular beds with various degrees of reduced and increased haemodynamic resistance are the results of massive activation of powerful homeostatic, regulatory systems. Cirrhotic cardiomyopathy implies systolic and diastolic dysfunction and electrophysiological abnormalities, an entity that is different from alcoholic heart muscle disease. Being often clinical latent, cirrhotic cardiomyopathy can be unmasked by physical and pharmacological strain. Cardiac failure is an important cause of mortality after liver transplantation and stressful procedures as insertions of transjugular intrahepatic portal systemic shunt (TIPS), peritoneal venous shunting, and other types of surgery. Improvement of liver function has been shown to reverse the cardiovascular complications. The clinical significance is an important topic for future research. At present, no specific treatment can be recommended, and the cardiac failure in cirrhosis should be treated as in non-cirrhotic patients with sodium restriction, diuretics, and beta-adrenergic blocking agents. Special care should be taken with the use of ACE-inhibitors and angiotensin antagonist in these patients.

New insights into the pathobiology of portal hypertension

Portal Hypertension is a frequent complication of cirrhosis and causes significant morbidity and mortality. Increased intrahepatic resistance is the primary factor but portal hypertension is also associated with changes in systemic and porto-sytemic collateral circulation. Cirrhosis is a state of vasoregulatory imbalance with excess vasoconstrictors and less vasodilators in hepatic circulation and the reverse is true for systemic circulation. Multiple pathophysiologic mechanisms including endothelial dysfunction, sinusoidal remodeling and angiogenesis are involved in increasing resistance in hepatic vascular bed. Current evidence suggests that these changes in vasoreactivity contribute to a significant proportion of intrahepatic vascular resistance and that they are reversible, providing an attractive target for therapeutic intervention.

Phosphodiesterase-5 inhibitors have distinct effects on the hemodynamics of the liver

Background

The NO - cGMP system plays a key role in the regulation of sinusoidal tonus and liver blood flow with phosphodiesterase-5 (PDE-5) terminating the dilatory action of cGMP. We, therefore, investigated the effects of PDE-5 inhibitors on hepatic and systemic hemodynamics in rats.

Methods

Hemodynamic parameters were monitored for 60 min. after intravenous injection of sildenafil and vardenafil [1, 10 and 100 μg/kg (sil1, sil10, sil100, var1, var10, var100)] in anesthetized rats.

Results

Cardiac output and heart rate remained constant. After a short dip, mean arterial blood pressure again increased. Systemic vascular resistance transiently decreased slightly. Changes in hepatic hemodynamic parameters started after few minutes and continued for at least 60 min. Portal (var10 -31%, sil10 -34%) and hepatic arterial resistance (var10 -30%, sil10 -32%) decreased significantly (p < 0.05). At the same time portal venous (var10 +29%, sil10 +24%), hepatic arterial (var10 +34%, sil10 +48%), and hepatic parenchymal blood flow (var10 +15%, sil10 +15%) increased significantly (p < 0.05). The fractional liver blood flow (total liver flow/cardiac output) increased significantly (var10 26%, sil10 23%). Portal pressure remained constant or tended to decrease. 10 μg/kg was the most effective dose for both PDE-5 inhibitors.

Conclusion

Low doses of phosphodiesterase-5 inhibitors have distinct effects on hepatic hemodynamic parameters. Their therapeutic use in portal hypertension should therefore be evaluated.

PDEs1-5 activity and expression in tissues of cirrhotic rats reveal a role for aortic PDE3 in NO desensitization

Liver cirrhosis is associated with increased nitric oxide (NO) production in the vasculature. We have previously demonstrated that aorta from rats with liver cirrhosis have a reduced relaxant response to NO donors that is corrected by DMPPO, a PDE5-specific inhibitor. Vasodilator responses to DMPPO itself were also reduced in rings from cirrhotic rats. These results supported previous suggestions that upregulation of PDE5 in liver cirrhosis might contribute to renal sodium retention, and consequently modulate vascular reactivity in the context of increased NO production (Tahseldar-Roumieh et al. in Am. J. Physiol. Heart Circ. Physiol. 290, H481-H488, 2006). Here, we investigated the possible alteration in activity and expression of cyclic nucleotide phosphodiesterase PDE1-PDE5 in kidney and vascular tissues in rats 4 weeks after bile duct ligation. The kidney of rats with cirrhosis had increased activity of PDE1 and PDE4 but not PDE5, and increased expression of PDE1A. Unexpectedly and interestingly, there was no change in cirrhotic aorta PDE5, but an increase in PDE3 and PDE4 activity associated with increased expression of PDE3A and PDE3B. Cilostamide, a specific PDE3 inhibitor, corrected the decreased response to an NO donor in isolated aorta from cirrhotic rats, suggesting that the difference in response to NO donors was due to differences in PDE3-induced hydrolysis of cGMP or to cGMP-induced inhibition of PDE3, rather than to differences in PDE5 contribution. In conclusion, these changes in PDE isozymes could greatly contribute to NO desensitization and to the regulation of vascular and renal function in liver cirrhosis.

Lack of effect of norfloxacin on hyperdynamic circulation in bile duct-ligated rats despite reduction of endothelial nitric oxide synthase function: result of unchanged vascular Rho-kinase?

BACKGROUND/AIMS

In cirrhosis, portal hypertension is maintained by splanchnic vasodilation owing to overproduction of the vasodilator nitric oxide (NO) and defective contractile signalling by Rho-kinase. NO overproduction is partially caused by bacterial translocation from the gut to mesenteric lymph nodes. However, the effects of intestinal bacterial decontamination on hyperdynamic circulation or vascular contractility are unknown. We investigated the haemodynamic and vascular effects of norfloxacin in rats with secondary biliary cirrhosis.

METHODS

Cirrhosis was induced by bile duct ligation (BDL). One group was treated with norfloxacin (20 mg/kg/day, 5 days, orally). Bacterial growth in the lymph nodes was determined on blood agar plates. Invasive haemodynamic measurements were combined with coloured microspheres. Aortic contractility was assessed myographically. Protein expression/phosphorylation was examined by Western blot analysis.

RESULTS

Norfloxacin treatment of BDL rats abolished bacterial translocation to mesenteric lymph nodes. BDL rats had hyperdynamic circulation, including portal hypertension and splanchnic vasodilation. None of these parameters was changed by norfloxacin, although norfloxacin reduced endothelial NO synthase expression and phosphorylation. The latter was associated with a diminished activity of protein kinase G (PKG), which mediates NO-induced vasodilation. However, norfloxacin had no effect on aortic contractility to methoxamine or Ca2+, or the aortic expression of RhoA, Rho-kinase and beta-arrestin 2, or the phosphorylation of the Rho-kinase substrate moesin.

CONCLUSIONS

Short-term treatment of BDL rats with norfloxacin does not change hyperdynamic circulation or vascular contractility, despite reduction of PKG activity.

Pathophysiologic basis for the medical management of portal hypertension

BACKGROUND

Portal hypertension is a potentially life-threatening complication of cirrhosis, resulting from increased intrahepatic resistance and portal inflow.

OBJECTIVE

Given the complex nature of this disorder, a more complete understanding of the pathophysiology of portal hypertension is necessary to develop new therapies that target specific pathways that regulate portal pressure.

METHODS

This review is based on a literature search of published articles and abstracts on the pathophysiology of portal hypertension, its complications and its treatment.

RESULTS/CONCLUSION

A number of therapies have been developed or are under investigation for the treatment of portal hypertension and its complications. These agents may reduce mortality and improve quality of life for patients with advanced liver disease.

Simvastatin lowers portal pressure in patients with cirrhosis and portal hypertension: a randomized controlled trial

BACKGROUND & AIMS

Simvastatin improves liver generation of nitric oxide and hepatic endothelial dysfunction in patients with cirrhosis, so it could be an effective therapy for portal hypertension. This randomized controlled trial evaluated the effects of continuous simvastatin administration on the hepatic venous pressure gradient (HVPG) and its safety in patients with cirrhosis and portal hypertension.

METHODS

Fifty-nine patients with cirrhosis and portal hypertension (HVPG > or =12 mm Hg) were randomized to groups that were given simvastatin 20 mg/day for 1 month (increased to 40 mg/day at day 15) or placebo in a double-blind clinical trial. Randomization was stratified according to whether the patient was being treated with beta-adrenergic blockers. We studied splanchnic and systemic hemodynamics and variables of liver function and safety before and after 1 month of treatment.

RESULTS

Simvastatin significantly decreased HVPG (-8.3%) without deleterious effects in systemic hemodynamics. HVPG decreases were observed in patients who were receiving beta-adrenergic blockers (-11.0%; P = .033) and in those who were not (-5.9%; P = .013). Simvastatin improved hepatic, fractional, and intrinsic clearance of indocyanine green, showing an improvement in effective liver perfusion and function. No significant changes in HVPG and liver function were observed in patients receiving placebo. The number of patients with adverse events did not differ significantly between groups. No patient was withdrawn from the study based on adverse events.

CONCLUSIONS

Simvastatin decreased HVPG and improved liver perfusion in patients with cirrhosis. These effects were additive with those of beta-adrenergic blockers. The beneficial effects of simvastatin should be confirmed in long-term clinical trials for portal hypertension.

Possible mechanisms involved in the discrepancy of hepatic and aortic endothelial nitric oxide synthases during the development of cirrhosis in rats

BACKGROUND/AIM

In cirrhosis, systemic nitric oxide (NO) overproduction and hepatic NO hypoproduction lead to arterial vasodilatation and portal hypertension. The mechanisms involved in these alterations in endothelial NO synthase (eNOS)-derived NO production in hepatic and systemic vasculature remain unknown. The aim of this study was to evaluate the regulation of eNOS and its major modulators in the liver and aorta during the development of cirrhosis in rats.

METHODS

Activated eNOS and Akt and expressions, and caveolin-1 (Cav-1) and scavenger receptor class B type I (SR-BI) expressions were measured before and 1, 2, 3 and 4 weeks after bile duct ligation. Plasma high-density lipoprotein (HDL) levels were measured.

RESULTS

Activated aortic eNOS increased at week 1, whereas it began to decrease at week 3 in the liver. Aortic expression of Cav-1 decreased at week 3 while hepatic expression increased by four-fold. Activated aortic Akt increased progressively while in the liver it gradually decreased during the development of cirrhosis. HDL levels decreased during the first week and decreased thereafter. The hepatic expression of SR-BI decreased.

CONCLUSION

This study shows that the modulation of Akt and Cav-1 is inverted in the liver and the aorta during the development of cirrhosis. In addition, decreased HDL levels may play a role in reduced hepatic eNOS activity.

Carbon monoxide produced by intrasinusoidally located haem-oxygenase-1 regulates the vascular tone in cirrhotic rat liver

BACKGROUND/OBJECTIVE

Carbon monoxide (CO) produced by haem-oxygenase isoforms (HO-1 & HO-2) is involved in the regulation of systemic vascular tone. We aimed to elucidate the vasoregulatory role of CO in the microcirculation in normal and thioacetamide cirrhotic rat livers.

METHODS

Haem-oxygenase expression was examined by Western blot. Total HO enzymatic activity was measured spectrophotometrically. Sensitivity of hepatic stellate cells (HSCs) to CO-mediated relaxation was studied by a stress-relaxed-collagen-lattice model. To define the relative role of CO, the CO-releasing molecule CORM-2, the HO-inhibitor zinc protoporphyrin-IX and the HO-1 inducer hemin were added to an in situ liver perfusion set-up. The topography of vasoactive CO production was evaluated by applying different CO- and nitric oxide-trapping reagents in the liver perfusion set-up and by immunohistochemistry.

RESULTS

Western blot showed decreased expression of both HO isoenzymes (P<0.036 for HO-1; P<0.001 for HO-2) in cirrhotic vs normal rat livers, confirmed by the HO-activity assay (P=0.004). HSCs relaxed on exposure to CORM-2 (P=0.013). The increased intrahepatic vascular resistance (IHVR) of cirrhotic rats was attenuated by perfusion with CORM-2 (P=0.016) and pretreatment with hemin (P<0.001). Inhibition of HO caused a dose-related increase in IHVR in normal and cirrhotic liver. In normal liver, the haemodynamically relevant CO production occurred extrasinusoidally, while intrasinusoidally HO-1 predominantly regulated the microcirculation in cirrhotic livers.

CONCLUSION

We demonstrate a role for CO and HO in the regulation of normal and cirrhotic microcirculation. These findings are of importance in the pathophysiology of portal hypertension and establish CO/HO as novel treatment targets.

Beneficial effects of sorafenib on splanchnic, intrahepatic, and portocollateral circulations in portal hypertensive and cirrhotic rats

Portal hypertension, the most important complication in patients with cirrhosis of the liver, is a serious and life-threatening disease for which there are few therapeutic options. Because angiogenesis is a pathological hallmark of portal hypertension, the goal of this study was to determine the effects of sorafenib-a potent inhibitor of proangiogenic vascular endothelial growth factor receptor 2 (VEGFR-2), platelet-derived growth factor receptor beta (PDGFR-beta), and Raf kinases-on splanchnic, intrahepatic, systemic, and portosystemic collateral circulations in two different experimental models of portal hypertension: rats with prehepatic portal hypertension induced by partial portal vein ligation and rats with intrahepatic portal hypertension and secondary biliary cirrhosis induced by bile duct ligation. Such a comprehensive approach is necessary for any translational research directed toward defining the efficacy and potential clinical application of new therapeutic agents. Sorafenib administered orally once a day for 2 weeks in experimental models of portal hypertension and cirrhosis effectively inhibited VEGF, PDGF, and Raf signaling pathways, and produced several protective effects by inducing an approximately 80% decrease in splanchnic neovascularization and a marked attenuation of hyperdynamic splanchnic and systemic circulations, as well as a significant 18% decrease in the extent of portosystemic collaterals. In cirrhotic rats, sorafenib treatment also resulted in a 25% reduction in portal pressure, as well as a remarkable improvement in liver damage and intrahepatic fibrosis, inflammation, and angiogenesis. Notably, beneficial effects of sorafenib against tissue damage and inflammation were also observed in splanchnic organs.

CONCLUSION

Taking into account the limitations of translating animal study results into humans, we believe that our findings will stimulate consideration of sorafenib as an effective therapeutic agent in patients suffering from advanced portal hypertension.

Hepatocyte expression of angiotensin II type 1 receptor is downregulated in advanced human liver fibrosis

BACKGROUND

The renin-angiotensin system plays an important role in fibrosis. Angiotensin II regulates key steps in tissue remodelling processes through angiotensin II type 1 receptor (AT1R). In bile duct-occluded rats, AT1R expression is significantly decreased in advanced liver fibrosis. Therefore, we studied the AT1R expression in human liver tissue during different stages of fibrosis caused by chronic hepatitis C.

METHODS

Liver biopsy specimens from 85 patients were analysed. Real-time reverse transcription polymerase chain reaction was used to quantify AT1R mRNA. Immunohistochemical labelling of AT1R and double staining for AT1R, CD31, CD68, CD3 and fibulin-2 were performed.

RESULTS

AT1R mRNA was significantly reduced in human liver tissue with end-stage cirrhosis compared with early fibrosis. In liver cirrhosis, immunohistochemistry revealed a decreased expression of AT1R on hepatocytes, together with an increased staining intensity on myofibroblasts, vascular endothelium and bile duct epithelium.

CONCLUSION

In conclusion, AT1R expression is downregulated in human liver cirrhosis specimens because of the reduced expression levels on hepatocytes. Therefore, antifibrogenic therapy with AT1R blockers may be most promising if initiated during early stages of fibrosis.

Superimposed coagulopathic conditions in cirrhosis: infection and endogenous heparinoids, renal failure, and endothelial dysfunction

In this article, the authors discuss three pathophysiologic mechanisms that influence the coagulation system in patients who have liver disease. First, bacterial infections may play an important role in the cause of variceal bleeding in patients who have liver cirrhosis, affecting coagulation through multiple pathways. One of the pathways through which this occurs is dependent on endogenous heparinoids, on which the authors focus in this article. Secondly, the authors discuss renal failure, a condition that is frequently encountered in patients who have liver cirrhosis. Finally, they review dysfunction of the endothelial system. The role of markers of endothelial function in cirrhotic patients, such as von Willebrand factor and endothelin-1, is discussed.

The role of the endocannabinoid system in liver diseases

Endogenous cannabinoids (ECs) are ubiquitous lipid signaling molecules provided by a number of central and peripheral effects, which are mediated mainly by the specific receptors CB1 and CB2. In the last decade a considerable number of studies has shown that ECs and their receptors play an important role in the pathophysiology of liver diseases. The EC system is strongly up-regulated during chronic liver diseases. Until now it has been implicated in the pathogenesis of fatty liver disease associated with obesity, alcohol abuse, and hepatitis C, in the progression of fibrosis to cirrhosis, and in the development of portal hypertension, hyperdynamic circulatory syndrome and its complications, and cirrhotic cardiomyopathy. Furthermore, the EC system can participate in the pathogenesis of acute liver injury by modulating the mechanisms responsible for cell injury and inflammatory response. Thus, targeting the CB1 and CB2 receptors represents a potential therapeutic goal for the treatment of liver diseases.

Apelin signaling modulates splanchnic angiogenesis and portosystemic collateral vessel formation in rats with portal hypertension

BACKGROUND/AIMS

Angiogenesis is a pathological hallmark of portal hypertension. Although VEGF is considered to be the most important proangiogenic factor in neoangiogenesis, this process requires the coordinated action of a variety of factors. Identification of novel molecules involved in angiogenesis is highly relevant, since they may represent potential new targets to suppress pathological neovascularization in angiogenesis-related diseases like portal hypertension. The apelin/APJ signaling pathway plays a crucial role in angiogenesis. Therefore, we determined whether the apelin system modulates angiogenesis-driven processes in portal hypertension.

METHODS

Partial portal vein-ligated rats were treated with the APJ antagonist F13A for seven days. Splanchnic neovascularization and expression of angiogenesis mediators (Western blotting) was determined. Portosystemic collateral formation (microspheres), and hemodynamic parameters (flowmetry) were also assessed.

RESULTS

Apelin and its receptor APJ were overexpressed in the splanchnic vasculature of portal hypertensive rats. F13A effectively decreased, by 52%, splanchnic neovascularization and expression of proangiogenic factors VEGF, PDGF and angiopoietin-2 in portal hypertensive rats. F13A also reduced, by 35%, the formation of portosystemic collateral vessels.

CONCLUSIONS

This study provides the first experimental evidence showing that the apelin/APJ system contributes to portosystemic collateralization and splanchnic neovascularization in portal hypertensive rats, presenting a potential novel therapeutic target for portal hypertension.

[Usefulness of liver stiffness measurement for predicting the presence of esophageal varices in patients with liver cirrhosis]

BACKGROUND/AIMS

Bleeding from esophageal varices (EV) is a major cause of death in patients with liver cirrhosis. Endoscopic screening is recommended for diagnosing EV, but various noninvasive parameters can also be used to predict EV. The liver stiffness measurement (LSM), a noninvasive technique for estimating liver fibrosis, was recently reported to be strongly correlated with the hepatic venous pressure gradient. This study evaluated the usefulness of LSM for predicting the presence and size of EV in patients with cirrhosis.

METHODS

The relationships of LSM with the presence and size of EV were analyzed in 112 patients with liver cirrhosis. Liver cirrhosis was diagnosed histologically or clinically. The presence and size of EV were assessed by endoscopy, and LSM was determined by the Fibroscan technique.

RESULTS

LSM was strongly correlated with the presence of EV (P<0.0001): the LSM value was 42.7+/-21.9 kPa (mean+/-standard deviation) in patients with EV (n=82) and 19.1+/-12.6 kPa in patients without EV (n=30). The area under the receiver operating characteristic curve was 0.818 (95% CI, 0.732-0.904) for predicting the presence of EV, and an LSM value of 19.7 kPa was predictive of the presence of EV with a sensitivity of 87%, a specificity of 70%, a PPV of 89%, and a NPV of 66%. However, there was a weak correlation between LSM and the size of EV.

CONCLUSIONS

LSM is useful for predicting the presence of EV in patients with cirrhosis but not their size.

Transjugular intrahepatic portosystemic shunt-placement increases arginine/asymmetric dimethylarginine ratio in cirrhotic patients

AIM: To analyze the change of dimethylarginine plasma levels in cirrhotic patients receiving transjugular intrahepatic portosystemic shunt (TIPS).

METHODS: To determine arginine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and nitric oxide (NO) plasma levels, blood samples were collected from the superior cava, hepatic, and portal vein just before, directly after, and 3 mo after TIPS-placement.

RESULTS: A significant increase in the arginine/ADMA ratio after TIPS placement was shown. Moreover, TIPS placement enhanced renal function and thereby decreased systemic SDMA levels. In patients with renal dysfunction before TIPS placement, both the arginine/ADMA ratio and creatinine clearance rate increased significantly, while this was not the case in patients with normal renal function before TIPS placement. Hepatic function did not change significantly after TIPS placement and no significant decline in ADMA plasma levels was measured.

CONCLUSION: The increase of the arginine/ADMA ratio after TIPS placement suggests an increase in intracellular NO bioavailability. In addition, this study suggests that TIPS placement does not alter dimethylarginine dimethylaminohydrolase (DDAH) activity and confirms the major role of the liver as an ADMA clearing organ.

Effects of melatonin and acetylsalicylic acid against hepatic oxidative stress after bile duct ligation in rat

The aim of this study was to assess the effect of melatonin and acetylsalicylic acid (ASA) on hepatic damage induced by bile duct ligation (BDL).

MATERIAL AND METHODS

Male Sprague-Dawley rats were subjected to either sham operation or common BDL before treatment with ASA, melatonin or vehicle. Hepatic superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzyme activities and reduced glutathione (GSH), malondialdehyde (MDA) and nitric oxide (NO) levels were evaluated.

RESULTS

Our results have indicated that BDL caused a significant increase in lipid peroxidation whereas a statistically insignificant decrease in GSH level and some of the antioxidant enzyme activities. Both MEL and ASA administrations, either separately or together, decreased MDA whereas co-administration of MEL with ASA increased GSH levels in BDL rats.

CONCLUSIONS

CAT activity and MEL level decreased in the liver tissues of rats with BDL after administration of either melatonin alone or with ASA. However, melatonin and ASA administration increases liver tissue GSH levels in BDL ligated rats

Nitric oxide and vascular remodeling modulate hepatic arterial vascular resistance in the isolated perfused cirrhotic rat liver

BACKGROUND/AIMS

Hepatic arterial resistance is modulated by the hepatic arterioles but the role of NO and vascular remodeling in hepatic arterial resistance in cirrhosis is unknown.

METHODS

Cirrhosis was induced by CCl(4) or BDL. Using a bivascular liver perfusion dose-responses curves to methoxamine were obtained from the hepatic artery in absence and presence of L-NMMA. Lumen-diameter, wall thickness and number of smooth muscle nuclei were quantitated in the arteries using image analysis.

RESULTS

Hepatic arterial resistance and the response to methoxamine were lower in cirrhosis compared to controls (p< or = 0.04) and lower in BDL compared to CCl(4) (p< or = 0.01). L-NMMA increased the response to methoxamine in CCl(4) (p=0.002) and BDL (p=0.05) but corrected the response only in CCl(4) (p=n.s. vs. control). Wall thickness and the number of smooth muscle nuclei were significantly smaller in cirrhosis compared to controls (p<0.05) and the number of nuclei was also lower in BDL compared to CCl(4) (p=0.005).

CONCLUSIONS

NO is the main modulator of hepatic arterial resistance in CCl(4) but not in BDL. Intrahepatic arterial remodeling is present in both cirrhotic models but is greater in BDL. This indicates a larger role of structural changes in the control of hepatic arterial resistance in BDL.

Pathogenetic background for treatment of ascites and hepatorenal syndrome

Ascites and hepatorenal syndrome (HRS) are the major and challenging complications of cirrhosis and portal hypertension that significantly affect the course of the disease. Liver insufficiency, portal hypertension, arterial vasodilatation, and systemic cardiovascular dysfunction are major pathophysiological hallmarks. Modern treatment of ascites is based on this recognition and includes modest salt restriction and stepwise diuretic therapy with spironolactone and loop diuretics. Tense and refractory ascites should be treated with a large volume paracentesis, followed by volume expansion or transjugular intrahepatic portosystemic shunt. New treatment strategies include the use of vasopressin V(2)-receptor antagonists and vasoconstrictors. The HRS denotes a functional and reversible impairment of renal function in patients with severe cirrhosis with a poor prognosis. Attempts of treatment should seek to improve liver function, ameliorate arterial hypotension and central hypovolemia, and reduce renal vasoconstriction. Ample treatment of ascites and HRS is important to improve the quality of life and prevent further complications, but since treatment of fluid retention does not significantly improve survival, these patients should always be considered for liver transplantation.

2-Arachidonoylglycerol, an endogenous cannabinoid receptor agonist, in various rat tissues during the evolution of experimental cholestatic liver disease

BACKGROUND/AIM

Changes in tissue levels of 2-arachidonoylglycerol (2-AG), an endocannabinoid, during the evolution of bile duct ligation (BDL) may indicate that endocannabinoids have a role in the hemodynamic changes that occur in this condition.

METHODS

2-AG levels, in various organs and vascular beds of BDL rats, 2 and 4 weeks post surgery, were determined. Untouched and sham-operated (SO) rats were used as controls.

RESULTS

2-AG content of a specific organ was not a static finding and depended on the rat's age, the time from the surgical procedure and the type of procedure. The most pronounced changes were observed in BDL rats 4 weeks post surgery. In these rats, hepatic, pulmonary, cardiac and renal medullary and papillary 2-AG levels were highest observed. No changes in splenic, aortic and renal cortical 2-AG levels were observed. In addition a stepwise increase in 2-AG levels from the cortex to the papilla was detected and was followed by a decrease in creatinine clearance.

CONCLUSIONS

2-AG probably has a role in the pathophysiologic changes in the liver, heart, lung and kidney that follows BDL.

The role of hepatic arterial flow on portal venous and hepatic venous wedged pressure in the isolated perfused CCl4-cirrhotic liver

In cirrhosis, hepatic venous pressure gradient is used to measure portal venous and sinusoidal pressures, as well as drug-induced decreases of elevated pressures. The aim of this study was to investigate the influence of hepatic arterial flow (HAF) changes on portal venous perfusion (PVPP) and wedged hepatic venous pressure (WHVP). Normal and CCl4-cirrhotic rats were subjected to a bivascular liver perfusion with continuous measurements of PVPP, WHVP, and hepatic arterial perfusion pressure. Flow-pressure curves were performed with the use of different flows either through the portal vein (PVF: 20-32 ml/min) or HAF (5-15 ml/min). Increases in HAF lead to significant absolute and relative increases in PVPP (P = 0.002) and WHVP (P < 0.001). Absolute changes in HAF correlated to absolute changes in PVPP (cirrhosis: r = 0.64, P < 0.001; control: r = 0.67, P < 0.001) and WHVP (cirrhosis: r = 0.71, P < 0.001; control: r = 0.82, P < 0.001). Changes in PVPP correlated to changes in WHVP due to changes in PVF only in cirrhosis (r = 0.75, P < 0.001), whereas changes in HAF correlated in both cirrhosis (r = 0.92, P < 0.001) and control (r = 0.77, P < 0.001). In conclusion, increases and decreases in HAF lead to respective changes in PVPP and WHVP. This suggests a direct influence of HAF on PVPP and WHVP most likely due to changes in sinusoidal perfusion.

Effects of N-acetylcysteine administration in hepatic microcirculation of rats with biliary cirrhosis

BACKGROUND/AIMS

Increased intrahepatic resistance (IHR) in cirrhosis is due to fibrosis and hepatic endothelial dysfunction (HED). Besides producing fibrosis, increased reactive oxygen species (ROS) promotes ROS-related nitration of anti-oxidative enzymes in cirrhotic livers. Tyrosine nitration (nitrotyrosilation)-related inactivation of anti-oxidative enzymes is increased in cirrhotic livers. This study investigates effects of N-acetylcysteine (NAC) administrations in bile-duct-ligation (BDL) rats.

METHODS

This study measured portal venous pressure (PVP), IHR, hepatic endothelial function, hepatic levels of anti-oxidants and oxidants, type III procollagen (PIIIP), proteins expression of thromboxane synthase (TXS), nitrotyrosine, manganese superoxide dismutase (MnSOD), and hepatic NOx and thromboxane A(2) (TXA(2)) production in perfusates.

RESULTS

The improvement of HED was associated with decreased PVP and IHR, hepatic protein and mRNA levels of PIIIP, protein expression of TXS and nitrotyrosine, oxidants and production of TXA(2) in NAC-treated BDL rat livers. Conversely, hepatic NOx production, anti-oxidants, and protein expression of MnSOD were increased in NAC-treated BDL rat livers.

CONCLUSIONS

In NAC-treated cirrhotic rats, the decrease in IHR was mainly caused by its anti-oxidative effect-related prevention of hepatic fibrogenesis associated with the decrease of oxidants-related nitrotyrosilation and improvement of HED.

Down-regulation of genes related to the adrenergic system may contribute to splanchnic vasodilation in rat portal hypertension

BACKGROUND/AIMS

Splanchnic vasodilation initiates the hyperdynamic syndrome in portal hypertension. We aimed to explore molecular mechanisms involved in the development of mesenteric vasodilation in portal hypertension.

METHODS

Superior mesenteric artery (SMA) samples from portal vein ligated (PVL) and sham rats were compared in a time course experiment using DNA microarrays. Selected genes were quantified by qRT-PCR in PVL and cirrhotic rats. Inmunohistochemistry of tyrosine hydroxylase (Th) and norepinephrine was assessed in SMA sections of PVL and sham rats. Western blot analysis of Th, dopamine beta-hydroxylase (Dbh) and synaptosome-associated protein (Snap-25) was performed in SMA and jejunum samples from the animal models.

RESULTS

Fifty differentially expressed genes implicated in neurotransmission, especially adrenergic, were detected in SMA samples from PVL rats. Sequential analysis showed a profound down-regulation at 14 days in PVL rats. These down-regulated genes were confirmed by RT-PCR in SMA from PVL and cirrhotic rats. Th and NE detection by immunohistochemistry was reduced in PVL compared to sham. Th, Dbh and Snap-25 expression was lower in SMA from 14-day PVL and cirrhotic rats compared to sham and control rats, respectively.

CONCLUSIONS

Genetic down-regulation of genes related to the adrenergic system might have a role in splanchnic vasodilation of portal hypertension.

The management of portal hypertension: rational basis, available treatments and future options

Variceal bleeding is the last step in a chain of events initiated by an increase in portal pressure, followed by the development and progressive dilation of varices until these finally rupture and bleed. This sequence of events might be prevented - and reversed - by achieving a sufficient decrease in portal pressure. A different approach is the use of local endoscopic treatments at the varices. This article reviews the rationale for the management of patients with cirrhosis and portal hypertension, the current recommendations for the prevention and treatment of variceal bleeding, and outlines the unsolved issues and the perspectives for the future opened by new research developments.

Pathogenesis and management of hepatorenal syndrome in patients with cirrhosis

Hepatorenal syndrome is a severe complication of advanced liver cirrhosis, in patients with ascites and marked circulatory dysfunction. It is clearly established that it has a functional nature, and that it is related to intense renal vasoconstriction. Despite its functional origin, the prognosis is very poor. In the present review, the most recent advances in diagnosis, pathophysiology, and treatment are discussed. Recent developments in pathophysiology are the basis of the new therapeutic strategies, which are currently under evaluation in randomised clinical trials.

The endocannabinoid system and liver diseases

Endogenous cannabinoids (EC) are ubiquitous lipid signalling molecules provided by a number of central and peripheral effects, which are mainly mediated by the specific cannabinoid receptors CB(1) and CB(2). Although the expression of these receptors is very low or even absent in the healthy liver, a considerable series of experimental studies and some clinical observations have recognised the EC system as an important player in the pathophysiology of liver diseases. The EC system is highly up-regulated during chronic liver diseases and, to date, it has been implicated in the pathogenesis of non-alcoholic fatty liver disease, progression of fibrosis to cirrhosis and the development of the cardiovascular abnormalities of cirrhosis, such as the hyperdynamic circulatory syndrome and cirrhotic cardiomiopathy. Furthermore, the EC system influences the mechanisms responsible for cell damage and the inflammatory response during acute liver injury, such as that resulting from ischaemia-reperfusion. Thus, molecules targeting the CB(1) and CB(2) receptors may represent potential therapeutic agents for the treatment of liver diseases. At present, the CB(1) antagonists represent the most attractive pharmaceutical tool to resolve fat accumulation in patients with non-alcoholic fatty liver disease and to treat patients with cirrhosis, as they may slow the progression of fibrosis and attenuate the cardiovascular alterations associated with the advanced stage of the disease.

Histological subclassification of cirrhosis based on histological-haemodynamic correlation

BACKGROUND

Determining a relationship between specific histological parameters in cirrhosis and hepatic venous pressure gradient can be used to subclassify cirrhosis.

AIM

To determine the relationship between hepatic venous pressure gradient and specific histological parameters in cirrhosis.

METHODS

Forty-seven patients (mean age: 46.2 +/- 13.6 years; 36 male) with biopsy-proven cirrhosis and hepatic venous pressure gradient measurements within 1 month of biopsy were studied. The following histological parameters were scored semiquantitatively: nodule size, loss of portal tracts and central veins, portal inflammation, periportal inflammation, bile duct proliferation, lobular inflammation, ballooning, fatty change, cholestasis and septal thickness.

RESULTS

On multiple ordinal regression analysis, small nodule size (odds ratio: 21.0; 95% confidence interval: 2.1-208.2, P = 0.009) and thick septa (OR: 42.6; CI: 2.3-783.7, P = 0.011) were significantly associated with the presence of clinically significant portal hypertension. A score was assigned to each of the two parameters (nodule size: large = 1, medium = 2, small = 3 and septal thickness: thin = 1, medium = 2, thick = 3). Two subcategories were devised based on the composite score: category A (n = 12): score 1-3 and category B (n = 35): score 4-6. On ordinal regression, subcategory B (OR: 15.5; CI: 3.3-74.2, P = 0.001) was significantly associated with clinically significant portal hypertension.

CONCLUSION

Small nodularity and thick septa are independent predictors of the presence of clinically significant portal hypertension.

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

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

CONCLUSION

Our data show that oxidative stress may contribute to reduced NO bioavailability in cirrhotic livers, supporting the evaluation of O(2) (-) reduction as a potential mechanism to restore NO content.

Elevated nitric oxide and 3’,5’ cyclic guanosine monophosphate levels in patients with alcoholic cirrhosis

AIM: To evaluate whether serum levels of nitric oxide (NO^•) and plasma levels of cyclic guanosine monophosphate (cGMP) and total glutathione (GSH) are altered in patients with alcoholic cirrhosis and to examine their correlation with the severity of liver disease.

METHODS: Twenty-six patients with alcoholic liver cirrhosis were studied. Serum levels of NO^• and plasma levels of cGMP and GSH were measured in 7 patients with compensated alcoholic cirrhosis (Child-Pugh A) and 19 patients with advanced cirrhosis (Child-Pugh B and C). The model for end-stage liver disease (MELD) score was evaluated. Sixteen healthy volunteers served as controls. Liver enzymes and creatinine levels were also tested.

RESULTS: NO^• and cGMP levels were higher in patients with Child-Pugh B and C cirrhosis than in Child-Pugh A cirrhosis or controls (NO^•: 21.70 ± 8.07 vs 11.70 ± 2.74; 21.70 ± 8.07 vs 7.26 ± 2.47 &mgr;mol/L, respectively; P < 0.001) and (cGMP: 20.12 ± 6.62 vs 10.14 ± 2.78; 20.12 ± 6.62 vs 4.95 ± 1.21 pmol/L, respectively; P < 0.001). Total glutathione levels were lower in patients with Child-Pugh B and C cirrhosis than in patients with Child-Pugh A cirrhosis or controls (16.04 ± 6.06 vs 23.01 ± 4.38 or 16.04 ± 6.06 vs 66.57 ± 26.23 &mgr;mol/L, respectively; P < 0.001). There was a significant correlation between NO^• and cGMP levels in all patients with alcoholic cirrhosis. A significant negative correlation between reduced glutathione/glutathione disulfide and the MELD score was found in all cirrhotic patients.

CONCLUSION: Our results suggest a role for oxidative stress in alcoholic liver cirrhosis, which is more significant in decompensated patients with higher levels of NO^• and cGMP and lower GSH levels than in compensated and control patients. Altered mediator levels in decompensated patients may influence the hemodynamic changes in and progression of liver disease.