The hepatic circulation in health and disease: report of a single-topic symposium

Innovative angiography: a new approach to discover more hepatic vein collaterals in patients with cirrhotic portal hypertension

BACKGROUND

The hemodynamics of patients with cirrhosis and portal hypertension are complex and variable. We aimed to investigate differences in venous pressures determined by innovative angiography and conventional angiography using balloon occlusion of the hepatic veins in patients with alcoholic cirrhosis and portal hypertension.

METHODS

A total of 134 patients with alcoholic cirrhosis who fulfilled the inclusion criteria from June 2017 to June 2020 were included. During transjugular intrahepatic portosystemic shunt, conventional and innovative angiography were performed, and venous pressures were measured. A paired t-test and Pearson's correlation coefficient were used for analysis.

RESULTS

Conventional and innovative hepatic angiography detected lateral branches of the hepatic vein in 26 (19.4%) and 65 (48.5%) cases, respectively (P < 0.001). Innovative angiography detected a total of 65 patients with lateral shunts, of whom 37 (56.9%) had initial shunts. The average wedged hepatic venous pressure and portal venous pressure of the initial lateral branches were 21.27 ± 6.66 and 35.84 ± 7.86 mmHg, respectively, with correlation and determination coefficients of 0.342 (P < 0.05) and 0.117, respectively. The mean hepatic venous pressure gradient and portal pressure gradient were 9.59 ± 7.64 and 26.86 ± 6.78 mmHg, respectively, with correlation and determination coefficients of 0.292 (P = 0.079) and 0.085, respectively.

CONCLUSIONS

Innovative angiography reveals collateral branches of the hepatic veins more effectively than conventional angiography. Hepatic vein collateral branches are the primary factors leading to underestimation of wedged hepatic venous pressures and hepatic venous pressure gradients, with the initial hepatic vein collateral branches resulting in the most severe underestimations.

Therapeutic Potential of Phosphodiesterase Inhibitors for Endothelial Dysfunction- Related Diseases

Cardiovascular diseases (CVD) are considered a major health problem worldwide, being the main cause of mortality in developing and developed countries. Endothelial dysfunction, characterized by a decline in nitric oxide production and/or bioavailability, increased oxidative stress, decreased prostacyclin levels, and a reduction of endothelium-derived hyperpolarizing factor is considered an important prognostic indicator of various CVD. Changes in cyclic nucleotides production and/ or signalling, such as guanosine 3', 5'-monophosphate (cGMP) and adenosine 3', 5'-monophosphate (cAMP), also accompany many vascular disorders that course with altered endothelial function. Phosphodiesterases (PDE) are metallophosphohydrolases that catalyse cAMP and cGMP hydrolysis, thereby terminating the cyclic nucleotide-dependent signalling. The development of drugs that selectively block the activity of specific PDE families remains of great interest to the research, clinical and pharmaceutical industries. In the present review, we will discuss the effects of PDE inhibitors on CVD related to altered endothelial function, such as atherosclerosis, diabetes mellitus, arterial hypertension, stroke, aging and cirrhosis. Multiple evidences suggest that PDEs inhibition represents an attractive medical approach for the treatment of endothelial dysfunction-related diseases. Selective PDE inhibitors, especially PDE3 and PDE5 inhibitors are proposed to increase vascular NO levels by increasing antioxidant status or endothelial nitric oxide synthase expression and activation and to improve the morphological architecture of the endothelial surface. Thereby, selective PDE inhibitors can improve the endothelial function in various CVD, increasing the evidence that these drugs are potential treatment strategies for vascular dysfunction and reinforcing their potential role as an adjuvant in the pharmacotherapy of CVD.

Diagnostic and Prognostic Values of Noninvasive Predictors of Portal Hypertension in Patients with Alcoholic Cirrhosis

Portal hypertension is a direct consequence of hepatic fibrosis, and several hepatic fibrosis markers have been evaluated as a noninvasive alternative to the detection of portal hypertension and esophageal varices. In the present study, we compared the diagnostic and prognostic values of the noninvasive fibrosis markers in patients with alcoholic cirrhosis. A total of 219 consecutive alcoholic cirrhosis patients were included. Biochemical scores and liver stiffness (LS) were compared with hepatic venous pressure gradient (HVPG). For the detection of clinically significant portal hypertension (CSPH; HVPG≥10 mmHg) in compensated patients, LS and LS–spleen diameter to platelet ratio score (LSPS) showed significantly better performance with area under the curves (AUCs) of 0.85 and 0.82, respectively, than aspartate aminotransferase-to-platelet ratio index, FIB-4, Forns’ index, Lok index, (platelet count)²/[monocyte fraction (%) × segmented neutrophil fraction (%)], and platelet count-to-spleen diameter ratio (all P<0.001). However, for the detection of high-risk varices, none of the non-invasive tests showed reliable performance (AUCs of all investigated tests < 0.70). During a median follow-up period of 42.6 months, 46 patients with decompensated cirrhosis died. Lok index (hazard ratio [HR], 1.13; 95% confidence interval [CI], 1.05–1.22; P = 0.001) and FIB-4 (HR, 1.06; 95% CI, 1.01–1.10; P = 0.009) were independently associated with all-cause death in decompensated patients. Among the tested noninvasive markers, only Lok index significantly improved discrimination function of MELD score in predicting overall survival. In conclusion, LS and LSPS most accurately predict CSPH in patients with compensated alcoholic cirrhosis. In the prediction of overall survival in decompensated patients, however, Lok index is an independent prognostic factor and improves the predictive performance of MELD score.

Pathogenesis of Portal Cavernoma Cholangiopathy: Is it Compression by Collaterals or Ischemic Injury to Bile Ducts During Portal Vein Thrombosis?

The pathogenesis of portal cavernoma cholangiopathy (PCC) is important as it can impact the choice of treatment modalities. PCC consists of a reversible component, which resolves by decompression of collaterals as well as a fixed component, which persists despite the decompression of collaterals. The reversible component is due to compression by large collaterals located adjacent to the bile duct as well as possibly intracholedochal varices. The fixed component is likely to be due to ischemia at the time of portal vein thrombosis, local ischemia by compression as well as encasement by a solid tumor-like cavernoma comprising of fibrous hilar mass containing multiple tiny collateral veins rather than markedly enlarged portal collaterals. Although cholangiographic abnormalities in portal hypertension are common, the prevalence of symptomatic PCC is low. This is likely to be related to the cause of portal hypertension, the duration of portal hypertension and possibly the pattern of occlusion of the splenoportal axis. There may possibly be higher prevalence of symptomatic PCC in extension of the thrombosis to the splenomesentric veins.

Adding pulsatile vascular stimulation to venous systemic oxygen persufflation of liver grafts

The effect of adding pulsatility to gaseous oxygen persufflation during liver preservation was studied in an isolated rat liver model. Livers from male Wistar rats were retrieved 30 min after cardiac arrest of the donor and subjected to 18 h of cold storage. Some grafts were subjected to nonpulsatile or pulsatile gaseous oxygen persufflation. Graft viability was assessed thereafter upon warm reperfusion in vitro (n = 5 per group). Pulsatile persufflation significantly improved parenchymal integrity (enzyme release, bile flow) upon reperfusion, with respect to nonpulsatile persufflation or cold storage (CS) (e.g., max. release of alanine aminotransferase: 44 ± 10 vs. 178 ± 29 vs. 345 ± 100 U/L; pulsatile vs. nonpulsatile persufflation vs. CS).The effect was associated with the prevention of the ischemic decline in gene and protein expression of the vasoprotective Krüppel-like factor 2, increased perfusate levels of the endogenous vasodilator nitric oxide, and reduced portal vascular resistance upon reperfusion, while nonpulsatile persufflation was less effective (e.g., vascular resistance: 1235 ± 108 vs. 1607 ± 155 vs. 2215 ± 208 Pa s/mL; pulsatile vs. nonpulsatile persufflation vs. CS). In conclusion, pulsatile mechanostimulation of the hepatovasculature seems a genuine protective mechanism, affecting early graft recovery upon reperfusion.

Prevalence and indicators of portal hypertension in patients with nonalcoholic fatty liver disease

BACKGROUND & AIMS

Little is known about the prevalence and severity of portal hypertension in patients with nonalcoholic fatty liver disease (NAFLD). We investigated the prevalence and noninvasive predictors of portal hypertension in patients with NAFLD.

METHODS

Signs of portal hypertension, including esophageal varices, splenomegaly, portosystemic encephalopathy, and ascites, were investigated in 354 patients with NAFLD.

RESULTS

One hundred patients had portal hypertension at the time of NAFLD diagnosis (28.2%), 88 of these patients had septal fibrosis or cirrhosis (88%). Fibrosis stage correlated with presence (r = 0.41, P < .0001) and number of findings (r = 0.48, P = .006) of portal hypertension. Of the 204 patients with no or mild fibrosis (stages, 0-2), 12 patients had portal hypertension (6%); they had a significantly higher grade of steatosis, based on biopsy analysis, compared with the 192 patients without portal hypertension (94%). Thrombocytopenia, hyperbilirubinemia, cirrhosis, and obesity were associated independently with portal hypertension. Esophageal varices were found in 57 of the 128 patients undergoing endoscopic screening (44.5%) and were associated independently with thrombocytopenia, type 2 diabetes, and splenomegaly.

CONCLUSIONS

Signs of portal hypertension were present in 25% of patients at the time of diagnosis of NAFLD; most had advanced fibrosis or cirrhosis. Portal hypertension can occur in a small proportion of patients with mild or no fibrosis and is associated with the extent of steatosis. Features of advanced liver disease and insulin resistance might identify patients with NAFLD and portal hypertension, and those expected to derive the most benefit from endoscopic screening for esophageal varices.

Prostaglandin E2 induces contraction of liver myofibroblasts by activating EP3 and FP prostanoid receptors

BACKGROUND AND PURPOSE

Increased portal pressure in liver injury results from hypercontraction of perivascular non-parenchymal cells including liver myofibroblasts (MFs). Prostaglandin E2 (PGE2) is the major eicosanoid which is released around the venous system during liver injury, but little is known about their contractile effect on MFs.

EXPERIMENTAL APPROACH

Contraction of primary rat liver MFs was measured by a collagen gel contraction assay. Expression of E prostanoid (EP) receptor subtypes was assessed by reverse transcription-polymerase chain reaction. Fura-2 fluorescence was used to determine intracellular Ca2+ concentration ([Ca2+](i)). Phosphorylation of protein kinase C (PKC) was detected by Western blot analysis.

KEY RESULTS

Liver MFs expressed mRNAs for all four EP receptors. PGE2 induced contraction in a dose- and time-dependent manner, and slightly increased [Ca2+](i) only at high concentrations (10 micromol.L(-1)). An agonist selective for EP(3) receptors, ONO-AE-248, dose-dependently induced MF contraction but did not increase [Ca2+](i). Pretreatment with rottlerin (a specific novel PKC inhibitor) and Ro 31-8425 (a general PKC inhibitor) significantly reduced 1 micromol.L(-1) PGE(2)- or ONO-AE-248-induced contractions. Furthermore, 1 micromol.L(-1) PGE(2) stimulated phosphorylation of PKC isoforms PKCdelta and PKCepsilon. The F prostanoid (FP) receptor antagonist AL8810 abolished the [Ca(2+)](i) elevation and the rapid contraction induced by 10 micromol.L(-1) PGE2.

CONCLUSIONS AND IMPLICATIONS

Lower concentrations up to 1 micromol.L(-1) of PGE2 induce liver MF contraction via a [Ca2+](i)-independent PKC-mediated pathway through the EP(3) receptor, while higher concentrations have an additional pathway leading to Ca(2+)-dependent contraction through activating the FP receptor.

Liposome-mediated gene transfer of endothelial nitric oxide synthase to cirrhotic rat liver decreases intrahepatic vascular resistance

BACKGROUND AND AIMS

Nitric oxide (NO) production by endothelial nitric oxide synthase (eNOS) in sinusoidal endothelial cells is reduced in the injured liver and leads to intrahepatic portal hypertension. The present study evaluates the effects of liposome-mediated gene transfer of eNOS on the intrahepatic vascular resistance and portal venous pressure (PVP) in cirrhotic rats.

METHODS

Hepatic cirrhosis was induced in male Sprague-Dawley rats by intraperitoneal injection of carbon tetrachloride (CCl(4)), whereas the control normal rats were given the same dose of peanut oil. Plasmid eukaryotic expression vector (liposome-pcDNA3/eNOS) was injected into the portal vein of CCl(4) cirrhotic rats, whereas cirrhotic controls received the same dose of naked plasmid (liposome-pcDNA3) or Tris buffer, and control normal rats received the same dose of Tris buffer. Five days after gene transfer, the levels of eNOS mRNA and protein, NO production, PVP and the changes of hepatic intrahepatic vascular resistance were investigated.

RESULTS

Five days after eNOS gene transfer, the levels of eNOS mRNA, eNOS protein and NO production in cirrhotic rats increased remarkably, while hepatic vascular resistance and PVP decreased significantly in cirrhotic rats.

CONCLUSION

Liposome-mediated eNOS gene transfer via intraportal injection is feasible and the increase of intrahepatic eNOS leads to a marked decrease in introhepatic vascular resistance and PVP. These data indicate that intrahepatic eNOS plays an important role in the pathogenesis of portal hypertension and gene transfer of eNOS is a potential and novel therapy for portal hypertension.

Regulation of sinusoidal perfusion in portal hypertension

Portal hypertension, a major complication of cirrhosis, is caused by both increased portal blood flow and augmented intrahepatic vascular resistance. Even though the latter is primarily caused by anatomical changes, it has become clear that dynamic factors contribute to the increased hepatic vascular resistance. The hepatic sinusoid is the narrowest vascular structure within the liver and is the principal site of blood flow regulation. The anatomical location of hepatic stellate cells, which embrace the sinusoids, provides a favorable arrangement for sinusoidal constriction, and for control of sinusoidal vascular tone and blood flow. Hepatic stellate cells possess the essential contractile apparatus for cell contraction and relaxation. Moreover, the mechanisms of stellate cell contraction are better understood, and many substances which influence contractility have been identified, providing a rationale and opportunity for targeting these cells in the treatment of portal hypertension in cirrhosis.

Portal hypertension and variceal hemorrhage

Portal hypertension, a major hallmark of cirrhosis, is defined as a portal pressure gradient exceeding 5 mm Hg. In portal hypertension, porto-systemic collaterals decompress the portal circulation and give rise to varices. Successful management of portal hypertension and its complications requires knowledge of the underlying pathophysiology, the pertinent anatomy, and the natural history of the collateral circulation, particularly the gastroesophageal varices.

The methionine connection: homocysteine and hydrogen sulfide exert opposite effects on hepatic microcirculation in rats

Increased intrahepatic resistance in cirrhotic livers is caused by endothelial dysfunction and impaired formation of two gaseous vasodilators, nitric oxide (NO) and hydrogen sulfide (H(2)S). Homocysteine, a sulfur-containing amino acid and H(2)S precursor, is formed from hepatic methionine metabolism. In the systemic circulation, hyperhomocystenemia impairs vasodilation and NO production from endothelial cells. Increased blood levels of homocysteine are common in patients with liver cirrhosis. In this study, we demonstrate that acute liver perfusion with homocysteine impairs NO formation and intrahepatic vascular relaxation induced by acetylcholine in methoxamine-precontracted normal livers (7.3% +/- 3.0% versus 26% +/- 2.7%; P < 0.0001). In rats with mild, diet-induced hyperhomocystenemia, the vasodilating activity of acetylcholine was markedly attenuated, and incremental increases in flow induced a greater percentage of increases in perfusion pressure than in control livers. Compared with normal rats, animals rendered cirrhotic by 12 weeks' administration of carbon tetrachloride exhibited a greater percentage of increments in perfusion pressure in response to shear stress (P < 0.05), and intrahepatic resistance to incremental increases in flow was further enhanced by homocysteine (P < 0.05). In normal hyperhomocysteinemic and cirrhotic rat livers, endothelial dysfunction caused by homocysteine was reversed by perfusion of the livers with sodium sulfide. Homocysteine reduced NO release from sinusoidal endothelial cells and also caused hepatic stellate cell contraction; this suggests a dual mechanism of action, with the latter effect being counteracted by H(2)S.

CONCLUSION

Impaired vasodilation and hepatic stellate cell contraction caused by homocysteine contribute to the dynamic component of portal hypertension.

Increased sinusoidal resistance is responsible for the basal state and endothelin-induced venoconstriction in perfused cirrhotic rat liver

The localization of increased intrahepatic vascular resistance and the segmental vascular responsiveness to endothelin-1 are not well known in liver cirrhosis. We determined the segmental vascular resistances and their response to endothelin-1 of isolated portally perfused bile duct ligation (BDL)-induced cirrhotic rat livers. The portal occlusion pressure (Ppo) and the hepatic venous occlusion pressure (Phvo) were obtained by analyzing the profiles of the portal (Ppv) and hepatic venous (Phv) pressures during the double occlusion maneuver of simultaneous occlusions of the inflow and outflow perfusion lines. From the pressure gradients among Ppv, Ppo, Phvo, and Phv, the portal-hepatic venous resistance was assigned to three segments of the portal [Rpv = (Ppv - Ppo)/blood flow (Q)], sinusoidal [Rsinus = (Ppo - Phvo)/Q] and hepatic venous [Rhv = (Phvo - Phv)/Q] resistances. Rsinus, but not Rpv or Rhv, was significantly greater in BDL livers than in sham livers. Endothelin-1 (0.1-1 nM) increased Rpv and Rsinus to a similar magnitude, but not Rhv, in both sham and BDL. At 3 nM, the responsiveness of Rpv was smaller in BDL than in sham, but that of Rsinus were similar between in BDL and sham. In conclusion, increased sinusoidal resistance accounts for increased intrahepatic resistance of BDL-induced liver cirrhosis. Endothelin-1 contracts portal veins and sinusoids, but not hepatic veins, in both sham and cirrhotic livers. Sinusoidal contractility to endothelin-1 is not impaired in cirrhotic livers.

Defects in cGMP-PKG pathway contribute to impaired NO-dependent responses in hepatic stellate cells upon activation

NO antagonizes hepatic stellate cell (HSC) contraction, although activated HSC in cirrhosis demonstrate impaired responses to NO. Decreased NO responses in activated HSC and mechanisms by which NO affects activated HSC remain incompletely understood. In normal rat HSC, the NO donor diethylamine NONOate (DEAN) significantly increased cGMP production and reduced serum-induced contraction by 25%. The guanylate cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) abolished 50% of DEAN effects, whereas the cGMP analog 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) reiterated half the observed DEAN response, suggesting both cGMP-dependent protein kinase G (PKG)-dependent and -independent mechanisms of NO-mediated antagonism of normal HSC contraction. However, NO donors did not increase cGMP production from in vivo activated HSC from bile duct-ligated rats and showed alterations in intracellular Ca(2+) accumulation suggesting defective cGMP-dependent effector pathways. The LX-2 cell line also demonstrated lack of cGMP generation in response to NO and a lack of effect of ODQ and 8-BrcGMP in modulating the NO response. However, cGMP-independent effects in response to NO were maintained in LX-2 and were associated with S-nitrosylation of proteins, an effect reiterated in primary HSC. Adenovirus-based overexpression of PKG significantly attenuated contraction of LX-2 by 25% in response to 8-BrcGMP. In summary, these studies demonstrate that NO affects HSC through cGMP-dependent and -independent pathways. The HSC activation process is associated with maintenance of cGMP-independent actions of NO but defects in cGMP-PKG-dependent NO signaling that are improved by PKG gene delivery in LX-2 cells. Activating targets downstream from NO-cGMP in activated HSC may represent a novel therapeutic target for portal hypertension.

Effect of vardenafil, an inhibitor of phosphodiesterase-5, on portal haemodynamics in normal and cirrhotic liver -- results of a pilot study

BACKGROUND

Dysregulation of the cyclic guanosine 3',5' monophosphate-nitric oxide system is in part responsible for portal hypertension in cirrhosis.

AIM

To test the effects of inhibitors of phosphodiesterase-5 on portal haemodynamics.

METHODS

To 18 healthy subjects and 18 patients with Child A liver cirrhosis, 10 mg of vardenafil, an inhibitor of phosphodiesterase-5, were administered orally. Doppler sonographic measurements of hepatic and splanchnic blood flow, systemic blood pressure and heart rate were recorded before, 1 h after, and 48 h after the application. Vardenafil plasma levels were determined after 1 h. In five patients, invasive registration of free and wedged hepatic vein pressure was performed.

RESULTS

Portal venous flow increased in patients from 0.82 +/- 0.30 L/min (mean +/- s.d.) by 26% (CI: 16-37%, P = 0.0004) and in healthy subjects from 0.75 +/- 0.20 L/min (mean +/- s.d.) by 19% (CI: 9-28%; P = 0.0010). Celiac and hepatic artery resistivity indices rose significantly. Systemic blood pressure decreased slightly in patients. The wedged hepatic venous pressure gradient decreased in four of five patients with liver cirrhosis. Vardenafil plasma levels were higher in patients (14 +/- 10 microg/L) than in healthy subjects (9 +/- 6 microg/L; n.s.).

CONCLUSIONS

Inhibition of phosphodiesterase-5 increases portal flow and lowers portal pressure by a decrease in sinusoidal resistance and may be a novel therapeutic strategy for portal hypertension.

Effect of chronic ethanol administration on hepatic eNOS activity and its association with caveolin-1 and calmodulin in female rats

Although chronic and excessive alcohol consumption is associated with liver disease, the mechanism of alcoholic liver injury is still not clear. Whether reduced hepatic production of nitric oxide, which is evident in models of liver injury, is associated with alcohol-induced liver injury has not been investigated. We measured nitric oxide synthase (NOS) activity in the liver of pair-fed rats receiving liquid diet with or without alcohol [3% (vol/vol)] for 12 wk. Compared with control rats, hepatic NOS activity was significantly reduced in alcohol-treated rats along with the evidence of liver injury. Interestingly, there was no difference in the hepatic expression of endothelial NOS (eNOS) between ethanol-fed and pair-fed rats. We then tested the hypothesis that an imbalance between the binding of eNOS with inhibitory and stimulatory proteins may underlie the reduced activity of eNOS because eNOS catalytic activity is regulated partly through dynamic interactions with the inhibitory protein caveolin-1 and the stimulatory protein calmodulin. We found that hepatic caveolin-1 was markedly increased in alcohol-treated rats compared with control rats, whereas calmodulin remained unaltered. The binding of caveolin-1 and calmodulin with eNOS was increased and decreased, respectively, in alcohol-treated rats. Our results suggest that chronic alcohol intake attenuates hepatic eNOS activity by increasing the expression of the inhibitory protein caveolin-1 and enhancing its binding with eNOS.

Non-pulsatile hepatic and portal vein waveforms in patients with liver cirrhosis: concordant and discordant relationships

The relationship between hepatic vein waveform and portal vein waveform (HVW and PVW) was evaluated in 54 healthy subjects and 148 patients with liver cirrhosis and portal hypertension using spectral Doppler ultrasound recordings. In all healthy subjects, the HVW was triphasic and the PVW was slightly pulsatile. 51 of 148 patients (34.5%) had flat non pulsatile HVW with a significantly higher incidence in Child C vs Child A patients (48.9% vs 20.7%, respectively; p<0.01) while 56 of 148 patients (37.8%) had flat PVW, also with significantly higher incidence in Child C vs Child A patients (46.7% vs 25.9%, respectively; p<0.05). Of the 86 patients having flat waves (HVW or PVW), only 21 (24.4%) had concordant flat waves (flat both HVW and PVW) while discordance was detected in the remaining 75.6% patients. Only 22 patients (14.9%) had a triphasic HVW but with broad spectrum and absent window in 20 (90.9%) and significantly lower pre-systolic:systolic (PS) ratio (Vmax of the pre-systolic retrograde wave/Vmax of the systolic antegrade wave) compared with healthy subjects (0.23+/-0.1 vs 0.42+/-0.18, respectively; p<0.001). In conclusion, spectral broadening with window absence and dampening of the retrograde pre-systolic wave mark are the earliest changes in HVW in cirrhotic patients even in the presence of a triphasic pattern. The transmission of hepatic vein pulsatility is not a major factor responsible for portal vein pulsatility.

Management of gastrointestinal bleeding in patients with cirrhosis of the liver

Ruptured gastroesophageal varices are the most severe and frequent cause of gastrointestinal bleeding in cirrhotic patients, leading to death in 5% to 8% of patients during the first 48 hours. In recent times, the 6-week mortality rate has fallen to 20% due to the development of effective treatment strategies. Initial treatment is aimed at achieving hemostasis and preventing bleeding-related complications such as renal failure, infection, and hepatic decompensation. Blood volume replacement is initiated as soon as possible and antibiotic prophylaxis is instituted from admission. Hemostatic treatment for variceal bleeding includes vasoactive drugs to decrease portal pressure, endoscopic procedures, and portosystemic shunts-either a surgical or transjugular intrahepatic portosystemic shunt (TIPS). Treatment of coagulopathy has only been recently assessed in clinical studies, but results to date are promising. This article reviews the current clinical data on management strategies for variceal bleeding and presents the risks and benefits for each type of treatment. Specific sections on gastric varices and portal hypertensive gastropathy are included.

Hyperdynamic circulation and serotonin levels in patients with liver cirrhosis

Patients with liver cirrhosis and portal hypertension develop hyperdynamic state of circulation. Recent studies indicate that nitric oxide, prostaglandin's, endothelin-1 and serotonin are of major importance in the pathogenesis of portal hypertension and other hemodynamic complications. In our study we estimated the levels of serotonin in sera and 24h urine in 20 patients with liver cirrhosis, using original solid phase extraction procedure. Concentration of serotonin in sera was ranged from 18 to 270 nmol/L and in 24h urine ranged from 97 to 238 nmol/L/24h. In comparison with reference values (determined in range from 280 ?1300 nmol/L in sera and determined in the range from 157.8?1035.4 nmol/ L/24h in urine), a significant fall of serotonin concentration in sera, and urine was noted. A statistically significant correlation between serotonin levels in sera and platelet count was found (p = 0.017). Colour Doppler ultrasonography and peroral fiberpanendoscopy was applied in the whole series to evaluate degree of portal hypertension. The average diameter of portal vein was 16 mm (SD=1.36) and mean blood flow velocity in portal vein was 12 cm/s (SD=1.12). Splenomegaly was approved in the whole group and the mean splenic craniocaudal distance was 17.75 mm (SD=1.65). Esophageal varices grade I?II were detected in 8 (40%) of our patients and reamaining 12 (60%) were grade III?IV. In cirrhotic liver, the spleen congestion, result from platelet degradation. Serotonin, release in to spleen sinusoidal spaces, induces strong vasoconstriction response in portal venous circulation, which contributes to maintain portal hypertension. However, we consider that the decrease of serotonin levels in sera lead to development of hyperdynamic state of circulation.

Role of the heme oxygenases in abnormalities of the mesenteric circulation in cirrhotic rats

Carbon monoxide (CO), a product of heme metabolism by heme-oxygenase (HO), has biological actions similar to those of nitric oxide (NO). The role of CO in decreasing vascular responses to constrictor agents produced by experimental cirrhosis induced by carbon tetrachloride was evaluated before and after inhibition of HO with tin-mesoporphyrin (SnMP) in the perfused superior mesenteric vasculature (SMV) of cirrhotic and normal rats and in normal rats transfected with the human HO-1 (HHO-1) gene. Perfusion pressure and vasoconstrictor responses of the SMV to KCl, phenylephrine (PE), and endothelin-1 (ET-1) were decreased in cirrhotic rats. SnMP increased SMV perfusion pressure and restored the constrictor responses of the SMV to KCl, PE, and ET-1 in cirrhotic rats. The relative roles of NO and CO in producing hyporeactivity of the SMV to PE in cirrhotic rats were examined. Vasoconstrictor responses to PE were successively augmented by stepwise inhibition of CO and NO production, suggesting a complementary role for these gases in the regulation of reactivity of the SMV. Expression of constitutive but not of inducible HO (HO-1) was increased in the SMV of cirrhotic rats as was HO activity. Administration of adenovirus containing HHO-1 gene produced detection of HHO-1 RNA and increased HO activity in the SMV within 7 days. Rats transfected with HO-1 demonstrated reduction in both perfusion pressure and vasoconstrictor responses to PE in the SMV. We propose that HO is an essential component in mechanisms that modulate reactivity of the mesenteric circulation in experimental hepatic cirrhosis in rats.

Genetic variants of endothelial nitric oxide synthase in patients with primary biliary cirrhosis: association with disease severity

BACKGROUND AND AIMS

Primary biliary cirrhosis (PBC) presents a wide spectrum of clinical manifestations. In experimental models of liver cirrhosis and cholestasis it has been suggested that altered nitric oxide production is involved in liver injury and portal hypertension development. The present study investigated endothelial nitric oxide synthase (eNOS) genetic polymorphisms (894G/T, -786T/C) in patients with PBC and in controls to verify whether disease susceptibility and progression are associated with a particular genotype.

METHODS

Genomic DNA from 109 Italian PBC patients (65 with advanced disease, i.e. liver transplantation or histological stage III-IV) was obtained and polymorphisms determined by fluorescent probe analysis. Healthy subjects (n = 242) were used as a control group.

RESULTS

The allelic frequencies of both polymorphisms did not differ significantly between PBC patients and controls. When the association between genotypes and disease severity was addressed, both the 894T and the -786T alleles were more frequently found in the 22 patients with progressing disease (894T, frequency 0.455 compared with 0.240; P = 0.032; -786T, frequency 0.682 compared with 0.460; P = 0.038). Patients with 894TT presented higher Mayo score values (6.1 +/- 1.2 compared with 5.4 +/- 1.3 in 894G/G patients; P = 0.030) but similar age and disease duration values.

CONCLUSIONS

The authors suggest that genetic variants of eNOS are not associated with susceptibility to PBC, although the genotypes may lead to differences in disease severity and progression.

Differential expression and localization of nitric oxide synthases in cirrhotic livers of bile duct-ligated rats

Increased vascular nitric oxide (NO) production has been implicated in the pathogenesis of the hyperdynamic circulation in liver cirrhosis. This study investigated the expression of three isoforms of NO synthase (NOS) in rat cirrhotic livers. Cirrhosis was induced by chronic bile duct ligation (BDL). NOS enzyme activity was assessed by L-citrulline generation. Competitive RT-PCR was performed to detect the mRNA levels of NOS. In situ hybridization was done to localize NOS mRNA. Protein expression of NOS was evaluated by Western blotting and immunohistochemistry. The L-citrulline assay showed that constitutive NOS (cNOS) enzymatic activity was decreased, while inducible NOS (iNOS) activity was increased in BDL livers. Both endothelial NOS (eNOS) and neuronal NOS (nNOS) mRNA were detected in BDL and sham rats, but with enhanced expression in BDL rats. eNOS protein was redistributed with less expression in sinusoidal endothelial cells, but the total levels in liver were not changed. nNOS was induced in hepatocytes of BDL rats, in contrast to only a weak signal observed around some blood vessels in sham livers. Intense mRNA and protein expression of iNOS was induced in livers of BDL rats and was localized in hepatocytes, with no or a negligible amount in control livers. In conclusion, iNOS was induced in cirrhotic liver with its activity increased. In contrast, cNOS activity was impaired, regardless of unchanged eNOS protein levels and enhanced nNOS expression. These results suggest that all three types of NOS have a role in cirrhosis, but their expression and regulation are different.

Update on ascites and hepatorenal syndrome

Ascites is the most common complication occurring during liver cirrhosis. Even if a significant decrease in renal clearance may be observed in the first step of chronic active liver disease, renal impairment, at times complicated by the typical signs of hepatorenal syndrome, occurs only in patients with ascites, especially when tense and refractory. Experimental and clinical data seem to suggest a primary sodium and water retention in the pathogenesis of ascites, in the presence of an intrahepatic increase of hydrostatic pressure, which, by itself, physiologically occurs during digestion. Abnormal sodium and water handling leads to plasma volume expansion, followed by decreased peripheral vascular resistance and increased cardiac output. This second step is in agreement with the peripheral arterial vasodilation hypothesis, depicted by an increase in total blood volume, but with a decreased effective arterial blood volume. This discrepancy leads to the activation of the sympathetic nervous and renin-angiotensin-aldosterone systems associated with the progressive activation of the renal autacoid systems, especially, that of the arachidonic acid. During advanced cirrhosis, renal impairment becomes more sustained and renal autacoid vasodilating substances are less available, possibly due to a progressive exhaustion of these systems. At the same time ascites becomes refractory inasmuch as it is no longer responsive to diuretic treatment. Various pathogenetic mechanisms leading to refractory ascites are mentioned. Finally, several treatment approaches to overcome the reduced effectiveness of diuretic therapy are cited. Paracentesis, together with simultaneous administration of human albumin or other plasma expanders is the main common approach to treat refractory ascites and to avoid a further decrease in renal failure. Other effective tools are: administration of terlipressin together with albumin, implantation of the Le Veen shunt, surgical porto-systemic shunting or transjugular intrahepatic portosystemic stent-shunt, or orthotopic liver transplantation, according to the conditions of the individual patient.

Acute and 7-day portal pressure response to carvedilol and propranolol in cirrhotics

BACKGROUND

Carvedilol, a non-selective beta- and alpha-1 blocking agent, has portal hypotensive action. This study evaluates the acute and 7-day response to carvedilol, and compares it to that of propranolol.

METHODS

Thirty-six cirrhotics were randomized into two groups of 18 each, and treated with carvedilol or propranolol. Hepatic venous pressure gradient (HVPG) was measured before and 90 min after either 25 mg carvedilol or 80 mg propranolol was administered orally, and again 7 days after 12.5 mg carvedilol daily or 80 mg propranolol daily, respectively. 'Responders' were defined as those with HVPG reduction of > or = 20%.

RESULTS

With carvedilol, 11/18(61.1%) and 11/17(64.7%) patients responded acutely and after 7 days, respectively, while 9/18(50%) and 10/16(62.5%) did so to propranolol. However, HVPG reduction (percent) by carvedilol was not superior to that by propranolol either acutely (27.67 +/- 31.49 compared to 22.98 +/- 27.40, P = 0.6) or after 7 days (28.2 +/- 29.05 compared to 23.25 +/- 20.15, P = 0.6). With carvedilol, the acute HVPG response (P < 0.001) and responder status (P = 0.018) were good predictors of the response after 7 days, but were weak predictors in the case of propranolol (0.1 > P > 0.05 and P = 0.059, respectively). On carvedilol, only one patient (with ascites) developed symptomatic systemic hypotension with oliguria.

CONCLUSION

Carvedilol is a relatively safe, effective portal hypotensive agent, both acutely and over 7 days, but not superior to propranolol, at least in Indians. The acute hemodynamic response seems promising in predicting long-term response.

Somatostatin suppresses endothelin-1-induced rat hepatic stellate cell contraction via somatostatin receptor subtype 1

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered therapeutic targets to decrease portal hypertension. To elucidate some of the hemodynamic effects of somatostatin (SST) on portal pressure, the presence and function of SST receptors (SSTRs) on HSCs were investigated.

METHODS

SSTR messenger RNA expression, and SSTR presence was investigated using reverse-transcription polymerase chain reaction, real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The function of SSTRs was studied by examining the effects of SST and specific SSTR agonists on endothelin-1(ET-1)-induced HSC contraction.

RESULTS

Specific amplicons for SSTR subtypes 1, 2, and 3 were demonstrated in rat liver and in activated HSCs. The presence of SSTR subtypes 1, 2, and 3 was confirmed by Western blotting. With immunohistochemistry, a strong staining of HSCs was obtained for SSTR subtypes 1, 2, and 3 in CCl4-treated rats, but not in normal rat liver. Incubation of HSCs on collagen gels with buffer, 10(-8) mol/L SST, and 2 x 10(-8) mol/L ET-1 resulted in collagen surface area decreases of 5.5% +/- 3.3%, 6.8% +/- 4.4%, and 49.8% +/- 8.3%, respectively. Relative contraction of gels preincubated with 10(-8) mol/L SST followed by 2 x 10(-8) mol/L ET-1 or vice versa as compared with maximal contraction (100%) with 2 x 10(-8) mol/L ET-1 were 72.6% +/- 17.9% and 76.2% +/- 12.6%, respectively (P < 0.05). SSTR agonist 1, but not SSTR agonist 2 or 3, was able to counteract the contractile effect of ET-1. CONCLUSIONA: Activated rat HSCs bear SSTR subtypes 1, 2, and 3. SST causes significant partial inhibition of ET-1-induced contraction of activated HSCs, mainly by stimulation of SSTR subtype 1.

Cellular and molecular basis of portal hypertension

The molecular basis of the vascular wall abnormalities that contribute to development of portal hypertension are an area of active investigation. Studies to date suggest that diminution in eNOS-derived NO production in liver contributes to this process by causing increased intrahepatic resistance. This process seems to be mediated through inhibitory posttranslational regulatory mechanisms of eNOS. Endothelin-1 signaling is also increased in the intrahepatic vasculature. The mechanisms responsible for increased ET-1 signaling include increased ET-1 production and increased ET-A receptor expression, particularly within hepatic stellate cells, although the stimulus responsible for activation of the ET-1 system remains uncertain. In the splanchnic circulation, increases in eNOS-derived NO contribute to increased portal venous inflow through transcriptional and posttranslational regulation of eNOS. Development of the porto-systemic collateral circulation characteristic of portal hypertension occurs through a combination of NO-dependent dilation of preexisting vessels and through growth factor-mediated angiogenesis and neovascularization (Fig. 3). Further studies in vascular wall biology are continuing to elucidate more clearly the molecular mechanisms of portal hypertension. The [figure: see text] mechanism by which eNOS-derived NO production is increased in the splanchnic arteriolar endothelial cell but decreased in the liver endothelial cell and the role of specific ET receptor subtypes in the mechanism of activation of the ET-1 system and its effect on contractile cells in liver cirrhosis are areas that require further investigation. Further studies are needed to determine the intrahepatic site of pressure and perfusion regulation, be it the hepatic sinusoid and its unique, specialized cell types or the endothelial and smooth muscle cells in the hepatic and portal venules. The role of more recently delineated vasoactive pathways such as urotensin-II/GPR 14 and anandamide/CB1 receptor in portal hypertension must be examined. Most importantly, future studies must focus on novel experimental therapies, using pharmacologic and genetic approaches to modulate these vascular biologic systems and thereby to ameliorate complications and symptoms relating to portal hypertension in patients with cirrhosis.

NCX-1000, a NO-releasing derivative of ursodeoxycholic acid, selectively delivers NO to the liver and protects against development of portal hypertension

Portal hypertension resulting from increased intrahepatic resistance is a common complication of chronic liver diseases and a leading cause of death in patients with liver cirrhosis, a scarring process of the liver that includes components of both increased fibrogenesis and wound contraction. A reduced production of nitric oxide (NO) resulting from an impaired enzymatic function of endothelial NO synthase and an increased contraction of hepatic stellate cells (HSCs) have been demonstrated to contribute to high intrahepatic resistance in the cirrhotic liver. 2-(Acetyloxy) benzoic acid 3-(nitrooxymethyl) phenyl ester (NCX-1000) is a chemical entity obtained by adding an NO-releasing moiety to ursodeoxycholic acid (UDCA), a compound that is selectively metabolized by hepatocytes. In this study we have examined the effect of NCX-1000 and UDCA on liver fibrosis and portal hypertension induced by i.p. injection of carbon tetrachloride in rats. Our results demonstrated that although both treatments reduced liver collagen deposition, NCX-1000, but not UDCA, prevented ascite formation and reduced intrahepatic resistance in carbon tetrachloride-treated rats as measured by assessing portal perfusion pressure. In contrast to UDCA, NCX-1000 inhibited HSC contraction and exerted a relaxing effect similar to the NO donor S-nitroso-N-acetylpenicillamine. HSCs were able to metabolize NCX-1000 and release nitrite/nitrate in cell supernatants. In aggregate these data indicate that NCX-1000, releasing NO into the liver microcirculation, may provide a novel therapy for the treatment of patients with portal hypertension.

Characterisation of portal hypertension models by microspheres in anaesthetised rats: a comparison of liver flow

Several portal hypertensive animal models are available and frequently used for haemodynamic studies. The portal venous inflows, measured with microspheres in pentobarbital anaesthetised rats, are compared here. The partial portal vein ligation model is characterised by a high portal venous inflow, together with extensive portal systemic shunting, at the cost of portal sinusoidal flow. In carbon tetrachloride-induced micronodular cirrhosis, portal sinusoidal flow, which reaches liver parenchyma, is high, and this is more pronounced in the presence of ascites. In bile duct ligation and excision-induced cirrhosis, an increase in liver weight was not equally followed by an increase in portal sinusoidal flow, pointing to a relatively underperfused liver.

Variceal bleeding and portal hypertensive gastropathy

Cirrhosis can be the end stage of any chronic liver disease. At the time of diagnosis of cirrhosis varices are present in about 60% of decompensated and 30% of compensated patients. The risk factors for the first episode of variceal bleeding in cirrhotic patients are the severity of liver dysfunction, large size of varices and the presence of endoscopic red colour signs but only one-third of patients who have variceal haemorrhage have the above risk factors. Recent interest has been directed at identifying haemodynamic factors that may reflect the pathophysiological changes which lead to variceal bleeding, e.g. it has been confirmed that no bleeding occurs if HVPG falls below 12 mmHg and also a hypothesis has been put forward in which bacterial infection is considered a trigger for bleeding. Pharmacological treatment with beta-blockers is safe, effective and is the standard long-term treatment for the prevention of recurrence of variceal bleeding. Combination of beta-blockers with isosorbide-5-mononitrate needs further testing in randomized controlled trials. The use of haemodynamic targets for reduction in HVPG response needs further study, and surrogate markers of pressure response need evaluation. If endoscopic treatment is chosen, variceal ligation is the modality of choice. The combination of simultaneous variceal ligation and sclerotherapy does not offer any benefit. However, the use of additional sclerotherapy for the complete eradication of small varices after variceal ligation needs to be evaluated. The results of current prospective randomized controlled trials comparing variceal ligation with pharmacological treatment are awaited with great interest. Finally, the use of transjugular intrahepatic portosystemic shunt (TIPS) for the secondary prevention of variceal bleeding is not substantiated by current data, as survival is not improved and because of its worse cost-benefit profile compared to other treatments. In contrast, there still is a role for the selective surgical shunts in the modern management of portal hypertension. The ideal patients should be well compensated cirrhotics, who have had troublesome bleeding - either who have failed at least one other modality of therapy (drugs or ligation), have bled from gastric varices despite medical or endoscopic therapy, or live far from suitable medical services. Recently, ligation has been compared to beta-blockers for primary prophylaxis but so far there is no good evidence to recommend banding for primary prophylaxis, if beta-blockers can be given.

Portal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2-type receptors

BACKGROUND

We have shown that the portal hypertensive response to bradykinin in normal rats is mediated by B2 receptors.

METHODS

By using isolated and exsanguinated rat liver perfusion, we studied the portal hypertensive response to bradykinin or des-Arg9-bradykinin (B1 agonist) in inflamed or cirrhotic rat livers. Livers were perfused with bovine serum albumin Krebs-Henseleit buffer (pH 7.4; 37 degrees C) at a constant flow rate, in the absence or presence of des-Arg9[Leu8]-bradykinin or HOE 140 (B1 and B2 receptor antagonists, respectively). Bradykinin (140 nmol) or des-Arg9-bradykinin was injected as a bolus via the afferent route to the liver.

RESULTS

Basal perfusion pressure in liver-cirrhotic rats was higher than in normal rats. In normal, inflamed, or liver-cirrhotic rats, the presence of the B1 antagonist did not change the portal hypertensive response to bradykinin, while the B2 antagonist abolished this response. A 140-nmol dose of des-Arg9-bradykinin did not change the perfusion pressure; 700 nmol of this B1 agonist produced an insignificant perfusion pressure increase. The perfusion pressure increase induced by bradykinin in cirrhotic livers was lower than in normal livers.

CONCLUSIONS

The portal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2 receptors, but not B1 receptors, and there is a contracting hyporeactivity to bradykinin in cirrhotic rat livers.

Gene transfer of recombinant endothelial nitric oxide synthase to liver in vivo and in vitro

Endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) contributes to hepatic vascular homeostasis. The aim of this study was to examine whether delivery of an adenoviral vector encoding eNOS gene to liver affects vasomotor function in vivo and the mechanism of NO production in vitro. Rats were administered adenoviruses encoding beta-galactosidase (AdCMVLacZ) or eNOS (AdCMVeNOS) via tail vein injection and studied 1 wk later. In animals transduced with AdCMVLacZ, beta-galactosidase activity was increased in the liver, most prominently in hepatocytes. In AdCMVeNOS-transduced animals, eNOS protein levels and catalytic activity were significantly increased. Overexpression of eNOS diminished baseline perfusion pressure and constriction in response to the alpha(1)-agonist methoxamine in the perfused liver. Transduction of cultured hepatocytes with AdCMVeNOS resulted in the targeting of recombinant eNOS to a perinuclear distribution and binding with the NOS-activating protein heat shock protein 90. These events were associated with increased ionomycin-stimulated NO release. In summary, this is the first study to demonstrate successful delivery of the recombinant eNOS gene to liver in vivo and in vitro with ensuing NO production.

Drug treatment for bleeding oesophageal varices

At the time of diagnosis of cirrhosis, varices are present in about 60% of decompensated and 30% of compensated patients. The risk factors for the first episode of variceal bleeding in cirrhotic patients are the severity of liver dysfunction, a large size of the varices and the presence of endoscopic red colour signs, but only a third of patients who suffer variceal haemorrhage demonstrate the above risk factors. The only treatment that does not require sophisticated equipment or the skills of a specialist, and is immediately available, is vasoactive drug therapy. Hence, drug therapy should be considered to be the initial treatment of choice and can be administered while the patient is transferred to hospital, as has been done in one recent study. Moreover, drug therapy is no longer considered to be only a 'stop-gap' therapy until definitive endoscopic therapy is performed. Several recent trials have reported an efficacy similar to that of emergency sclerotherapy in the control of variceal bleeding. Furthermore, recent evidence suggests that those patients with high variceal or portal pressure are likely to continue to bleed or re-bleed early, implying that prolonged therapy lowering the portal pressure over several days may be the optimal treatment. Pharmacological treatment with beta-blockers is safe, effective and the standard long-term treatment for the prevention of recurrence of variceal bleeding. The combination of beta-blockers with isosorbide-5-mononitrate needs further testing in randomized controlled trials. The use of haemodynamic targets for the reduction of the HVPG response needs further study, and surrogate markers of the pressure response need evaluation. Ligation has recently been compared with beta-blockers for primary prophylaxis, but there is as yet no good evidence to recommend banding for primary prophylaxis if beta-blockers can be given.

Gene transfer of the neuronal NO synthase isoform to cirrhotic rat liver ameliorates portal hypertension

Reduced production of nitric oxide (NO) in the cirrhotic liver results from a defect in hepatic endothelial cell nitric oxide synthase (ecNOS) and appears to contribute to the high intrahepatic resistance and portal hypertension typical of cirrhosis. Therefore, we postulated that targeting a heterologous NOS isoform to sinusoidal endothelial cells or other perisinusoidal cells, such as hepatic stellate cells, would counter the defect in NO production and reduce resistance to blood flow. Recombinant adenovirus (Ad) carrying the neuronal NOS gene (nNOS) targeted liver sinusoidal endothelial cells, stellate cells, and hepatocytes more efficiently than the corresponding cells in cirrhotic livers, but transduction rates were substantial even in cirrhotic animals. Expression of nNOS in each liver cell type, whether from normal or injured liver, caused increased NO production and inhibited endothelin-1-induced contractility of perisinusoidal stellate cells. Finally, in 2 different in vivo models of cirrhosis and portal hypertension, transduction of livers with recombinant Ad.nNOS significantly reduced intrahepatic resistance and portal pressure. The data highlight the feasibility of gene transfer to diseased liver and hepatic cells and demonstrate the potential of a novel therapy for portal hypertension caused by cirrhosis.

Impaired endothelial nitric oxide synthase activity associated with enhanced caveolin binding in experimental cirrhosis in the rat

BACKGROUND & AIMS

A reduction in nitric oxide (NO) has been implicated as a cause of intrahepatic vasoconstriction in cirrhosis, but the regulatory mechanisms remain undefined. The aim of this study was to examine a contributory role for caveolin-1, a putative negative regulator of endothelial NO synthase, in mediating deficient intrahepatic NO production in the intact cirrhotic liver.

METHODS

Cirrhosis was induced by carbon tetrachloride inhalation. Flow regulation of NO production and perfusion pressure was examined in the perfused rat liver. Protein expression of endothelial NO synthase (eNOS), caveolin, and calmodulin was examined by Western blotting and immunohistochemistry. NOS activity and NO production were assessed by citrulline generation and chemiluminescence, respectively. Protein-protein interactions were examined using whole tissue protein immunoprecipitation.

RESULTS

In response to incremental increases in flow, cirrhotic animals produced significantly less NO(x) than control animals. NOS activity was significantly reduced in liver tissue from cirrhotic animals compared with control animals in the presence of similar eNOS protein levels. Deficient eNOS activity was associated with a severalfold increase in binding of eNOS with caveolin. Protein levels of caveolin-1 were markedly increased in the cirrhotic liver.

CONCLUSIONS

These studies provide evidence that enhanced expression and interaction of caveolin with eNOS contribute to impaired NO production, reduced NOS activity, and vasoconstriction in the intact cirrhotic liver.

Hsp90 regulation of endothelial nitric oxide synthase contributes to vascular control in portal hypertension

The molecular chaperone, heat shock protein 90 (Hsp90), acts as an intermediate in the signaling cascades leading to activation of endothelial nitric oxide synthase (eNOS). In this study, we examine the participation of this pathway in nitric oxide (NO)-dependent vasodilation in the rat mesentery in vitro. In normal animals, immunoprecipitation of eNOS from intact mesentery coimmunoprecipitates Hsp90 and, additionally, both eNOS and Hsp90 colocalize to the endothelial lining of mesenteric vessels. In the perfused mesenteric vasculature of normal animals, geldanamycin (GA), a specific inhibitor of Hsp90 signaling, attenuates ACh-dependent vasodilation but does not affect vasodilation in response to sodium nitroprusside. Next, studies were performed in animals with experimental portal hypertension induced by portal vein ligation (PVL). In PVL animals, NOS catalytic activity is markedly enhanced in mesenteric tissue and the perfused mesentery is hyporesponsive to the vasoconstrictor methoxamine (MTX). GA significantly potentiates MTX-induced vasoconstriction after PVL, thereby partially reversing the hyporeactivity to this agent exhibited in the mesenteric vasculature after PVL. These studies suggest that Hsp90 can act as a signaling mediator of NO-dependent responses in the mesenteric circulation and indicate that the excessive NO production observed in portal hypertension is mediated in part through Hsp90 signaling.

Presence of a nitric oxide synthase inhibitor in the graft efflux during reperfusion in human liver transplantation

Involvement of the nitric oxide (NO) system in complications following human orthotopic liver transplants (OLT) has been reported, but the contribution of the graft to the modulation of the NO system during reperfusion in normal OLT has not been characterized. We have studied the contribution of the graft efflux to the modulation of the NO system in 20 consecutive OLT. We evaluated its effects on isolated vascular reactivity of the rabbit and on rat cultured macrophages stimulated with lipopolysaccharide (LPS). In none of the donor liver biopsies was expression of inducible NO synthase (iNOS) activity by Northern or Western blot analysis found. Graft efflux after the onset of liver reperfusion, but not pre-transplant patient plasma, reversibly inhibited the acetylcholine-induced relaxation of norepinephrine-contracted rabbit aortic rings. Moreover, graft efflux reversibly inhibited NO production in rat macrophages treated with LPS, as evidenced by both a decrease in nitrite plus nitrate formation and a decrease in the production of [14C]citrulline from [14C]arginine. Addition of a 10% dilution of graft efflux to cultured rat macrophages incubated with LPS increased iNOS mRNA levels, suggesting direct inhibition of the enzyme but not of its expression. These results cannot be ascribed to the depletion of arginine the iNOS substrate since they can be reproduced even in the presence of an excess (10 mM) of exogenously added arginine. No correlation was found between the iNOS inhibitory activity in each sample and the corresponding clinical parameters related to either the graft function after the OLT or the existence of post-reperfusion syndrome. Our results indicate the existence of a soluble factor in the graft efflux from human OLT that reversibly and unspecifically inhibits NOS activity. Its involvement in the physiology and/or pathology of human liver diseases deserves further study.

Portal hypertension

Cirrhosis represents the end stage of any chronic liver disease. Two major syndromes result from cirrhosis: portal hypertension and hepatic insufficiency. Additionally, vasodilatation and the hyperdynamic circulation are hemodynamic abnormalities typical of cirrhosis and portal hypertension. Complications of cirrhosis occur as a consequence of a combination of these factors. Gastroesophageal varices result almost solely from portal hypertension, although the hyperdynamic circulation contributes to variceal growth and hemorrhage. Ascites results from sinusoidal hypertension and sodium retention, which is, in turn, secondary to vasodilatation and activation of neurohumoral systems. Hyponatremia and the hepatorenal syndrome result from water retention and renal vasoconstriction, respectively, both of which are also consequences of peripheral vasodilatation. Vasodilatation that occurs in the pulmonary circulation leads to the hepatopulmonary syndrome. Another complication of cirrhosis, portosystemic encephalopathy, is a consequence of both portal hypertension (shunting of blood through portosystemic collaterals) and hepatic insufficiency. This paper reviews the recent advances in the pathophysiology and management of the complications of cirrhosis and portal hypertension.

Pyogenic Liver Abscess

The percutaneous approach-specifically, ultrasound-guided percutaneous catheter drainage-associated with intravenous administration of antibiotics is the therapy of choice in patients with single or multiple pyogenic liver abscesses. The initial empiric antibiotic therapy should be modified based on results of blood and pus cultures. Surgery should be reserved for patients in whom antibiotic therapy and percutaneous drainage is unsuccessful.

Hepatic blood flow and splanchnic oxygen consumption in patients with liver failure. Effect of high-volume plasmapheresis

Liver failure represents a major therapeutic challenge, and yet basic pathophysiological questions about hepatic perfusion and oxygenation in this condition have been poorly investigated. In this study, hepatic blood flow (HBF) and splanchnic oxygen delivery (DO2, sp) and oxygen consumption (VO2,sp) were assessed in patients with liver failure defined as hepatic encephalopathy grade II or more. Measurements were repeated after high-volume plasmapheresis (HVP) with exchange of 8 to 10 L of plasma. HBF was estimated by use of constant infusion of D-sorbitol and calculated according to Fick's principle from peripheral artery and hepatic vein concentrations. In 14 patients with acute liver failure (ALF), HBF (1.78 +/- 0.78 L/min) and VO2,sp (3.9 +/- 0.9 mmol/min) were higher than in 11 patients without liver disease (1.07 +/- 0.19 L/min, P <.01) and (2.3 +/- 0.7 mmol/min, P <.001). In 9 patients with acute on chronic liver disease (AOCLD), HBF (1.96 +/- 1.19 L/min) and VO2,sp (3.9 +/- 2.3 mmol/min) were higher than in 18 patients with stable cirrhosis (1.00 +/- 0.36 L/min, P <.005; and 2.0 +/- 0.6 mmol/min, P <.005). During HVP, HBF increased from 1.67 +/- 0.72 to 2.07 +/- 1.11 L/min (n=11) in ALF, and from 1.89 +/- 1.32 to 2.34 +/- 1.54 L/min (n=7) in AOCLD, P <.05 in both cases. In patients with ALF, cardiac output (thermodilution) was unchanged (6.7 +/- 2.5 vs. 6.6 +/- 2.2 L/min, NS) during HVP. Blood flow was redirected to the liver as the systemic vascular resistance index increased (1,587 +/- 650 vs. 2, 020 +/- 806 Dyne. s. cm-5. m2, P <.01) whereas splanchnic vascular resistance was unchanged. In AOCLD, neither systemic nor splanchnic vascular resistance was affected by HVP, but as cardiac output increased from 9.1 +/- 2.8 to 10.1 +/- 2.9 L/min (P <.01) more blood was directed to the splanchnic region. In all liver failure patients treated with HVP (n=18), DO2,sp increased by 15% (P <.05) whereas VO2,sp was unchanged. Endothelin-1 (ET-1) and ET-3 were determined before and after HVP. Changes of ET-1 were positively correlated with changes in HBF (P <.005) and VO2,sp (P <.05), indicating a role for ET-1 in splanchnic circulation and oxygenation. ET-3 was negatively correlated with systemic vascular resistance index before HVP (P <.05) but changes during HVP did not correlate. Our data suggest that liver failure is associated with increased HBF and VO2, sp. HVP further increased HBF and DO2,sp but VO2,sp was unchanged, indicating that splanchnic hypoxia was not present.

Correlation of endothelium-dependent and -independent vasodilatation with liver function tests during prolonged perfusion of the rat liver

Twelve male Wistar rats were anaesthetized with pentobarbitone (3 mg 100g(-1) i.p.), the livers were excised and perfused in vitro through the hepatic artery and portal vein at constant flow rates of 0.32+/-0.01 (mean+/-S.E.) and 0.98+/-0.03 ml min(-1) g liver(-1), respectively. The tone of the preparation was raised by methoxamine (7.5 x 10(-6) M). Responses to mid-range doses of acetylcholine (-11 log mol) and sodium nitroprusside (-9 log mol) produced submaximal degrees of vasodilatation (-log mol ED50 = 12.18+/-0.08) and (-log mol ED50 = 9.95+/-0.23), respectively, which did not subside until 5.5 h of perfusion. These did not coincide with the increase in activities of lactic acid dehydrogenase (LDH) and aspartate serine transaminase (AST) activity at 2.5 h, which were indicative of hepatocellular mitochondrial and cytoplasmic damage, respectively. Vascular responses suggested that there was little deterioration in endothelial or smooth muscle function in the hepatic artery up to 5 h perfusion. This model can be reliably used to investigate endothelium-dependent and -independent vasodilators in vascular pharmacological studies of the rat liver although some minimal increases may occur in AST and LDH activity before hemodynamic changes appear at 5.5 h.