Molecular mechanisms of increased intrahepatic resistance in portal hypertension

Portal hypertension in patients with nonalcoholic fatty liver disease: Current knowledge and challenges

Portal hypertension (PH) has traditionally been observed as a consequence of significant fibrosis and cirrhosis in advanced non-alcoholic fatty liver disease (NAFLD). However, recent studies have provided evidence that PH may develop in earlier stages of NAFLD, suggesting that there are additional pathogenetic mechanisms at work in addition to liver fibrosis. The early development of PH in NAFLD is associated with hepatocellular lipid accumulation and ballooning, leading to the compression of liver sinusoids. External compression and intra-luminal obstacles cause mechanical forces such as strain, shear stress and elevated hydrostatic pressure that in turn activate mechanotransduction pathways, resulting in endothelial dysfunction and the development of fibrosis. The spatial distribution of histological and functional changes in the periportal and perisinusoidal areas of the liver lobule are considered responsible for the pre-sinusoidal component of PH in patients with NAFLD. Thus, current diagnostic methods such as hepatic venous pressure gradient (HVPG) measurement tend to underestimate portal pressure (PP) in NAFLD patients, who might decompensate below the HVPG threshold of 10 mmHg, which is traditionally considered the most relevant indicator of clinically significant portal hypertension (CSPH). This creates further challenges in finding a reliable diagnostic method to stratify the prognostic risk in this population of patients. In theory, the measurement of the portal pressure gradient guided by endoscopic ultrasound might overcome the limitations of HVPG measurement by avoiding the influence of the pre-sinusoidal component, but more investigations are needed to test its clinical utility for this indication. Liver and spleen stiffness measurement in combination with platelet count is currently the best-validated non-invasive approach for diagnosing CSPH and varices needing treatment. Lifestyle change remains the cornerstone of the treatment of PH in NAFLD, together with correcting the components of metabolic syndrome, using nonselective beta blockers, whereas emerging candidate drugs require more robust confirmation from clinical trials.

Portal Hypertension in Nonalcoholic Fatty Liver Disease: Challenges and Paradigms

Portal hypertension in cirrhosis is defined as an increase in the portal pressure gradient (PPG) between the portal and hepatic veins and is traditionally estimated by the hepatic venous pressure gradient (HVPG), which is the difference in pressure between the free-floating and wedged positions of a balloon catheter in the hepatic vein. By convention, HVPG≥10 mmHg indicates clinically significant portal hypertension, which is associated with adverse clinical outcomes. Nonalcoholic fatty liver disease (NAFLD) is a common disorder with a heterogeneous clinical course, which includes the development of portal hypertension. There is increasing evidence that portal hypertension in NAFLD deserves special considerations. First, elevated PPG often precedes fibrosis in NAFLD, suggesting a bidirectional relationship between these pathological processes. Second, HVPG underestimates PPG in NAFLD, suggesting that portal hypertension is more prevalent in this condition than currently believed. Third, cellular mechanoresponses generated early in the pathogenesis of NAFLD provide a mechanistic explanation for the pressure-fibrosis paradigm. Finally, a better understanding of liver mechanobiology in NAFLD may aid in the development of novel pharmaceutical targets for prevention and management of this disease.

Selective gene expression profiling contributes to a better understanding of the molecular pathways underlying the histological changes observed after RHMVL

Background

In previous studies, five vasoactive drugs were investigated for their effect on the recovery process after extended liver resection without observing relevant improvements. We hypothesized that an analysis of gene expression could help to identify potentially druggable pathways and could support the selection of promising drug candidates.

Methods

Liver samples obtained from rats after combined 70% partial hepatectomy and right median hepatic vein ligation (n = 6/group) sacrificed at 0 h, 24 h, 48 h, and 7days were selected for this study. Liver samples were collected from differentially perfused regions of the median lobe (obstruction-zone, border-zone, normal-zone). Gene expression profiling of marker genes regulating hepatic hemodynamics, vascular remodeling, and liver regeneration was performed with microfluidic chips. We used 3 technical replicates from each sample. Raw data were normalized using LEMming and differentially expressed genes were identified using LIMMA.

Results

The strongest differences were found in obstruction-zone at 24 h and 48 h postoperatively compared to all other groups. mRNA expression of marker genes from hepatic hemodynamics pathways (iNOS,Ptgs2,Edn1) was most upregulated.

Conclusion

These upregulated genes suggest a strong vasoconstrictive effect promoting arterial hypoperfusion in the obstruction-zone. Reducing iNOS expression using selective iNOS inhibitors seems to be a promising approach to promote vasodilation and liver regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01364-z.

Microbiota transplantation in portal hypertension: promises and pitfalls

In this commentary, we discuss new findings indicating that microbiota transplantation has favorable impact on portal hypertension (PH) in the experimental model of cirrhosis induced by bile duct ligation (BDL) (Huang et al.; Clin Sci (Lond) (2021) 135(24): 2709-2728, doi: 10.1042/CS20210602). Sinusoidal PH is an ominous outcome of advanced chronic liver disease, characterized by increased intrahepatic vascular resistance (IHVR), splanchnic hyperemia, and the development of portosystemic collaterals. In the work of Huang et al., microbiota transplantation not only alleviated splanchnic hyperdynamic circulation by improving vascular responsiveness and decreasing mesenteric angiogenesis, but also reduced blood flow in portosystemic collaterals. Surprisingly, however, microbiota transplantation had no effect on intrahepatic vasoconstriction in this experimental model. We discuss these observations in the context of recent literature showing that manipulation of the gut microbiota (either by transplantation or through the use of probiotics) may improve IHVR, which is one of the earliest abnormalities in the pathogenesis of sinusoidal PH. Further research is needed to explore the specific molecular and cellular targets associated with the correction of dysbiosis in liver disease.

Acute Portal Vein Thrombosis Predicts Concomitant Diagnosis of Hepatocellular Carcinoma in Cirrhotic Patients

PURPOSE

Portal vein thrombosis (PVT) is a common condition in cirrhotic patients and mostly attributed to portal hypertension. The objective of our study was to examine the association of PVT with hepatocellular carcinoma (HCC) in cirrhotic patients.

METHODS

A retrospective study was performed to identify cirrhotic patients with thrombosis of the portal system. Clinical and laboratory characteristics were collected and analyzed.

RESULTS

Thirty-nine patients were identified. Twenty-four out of 39 patients with PVT did not develop HCC (group A) after follow-up time of 38.5 months from the diagnosis of PVT. Eight patients (20.5%) were diagnosed with HCC within two weeks following diagnosis of PVT (group B). Seven patients (17.9%) were diagnosed with tumor thrombus (group C) at time of PVT diagnosis. The average age was 53.5, 66.5, and 69 years for groups A, B, and C respectively. Most patients (75 and 87.5% for groups B and C respectively) diagnosed with PVT and HCC were males. The most common cause of cirrhosis in groups B and C was chronic hepatitis B virus infection (HBV) in 62.5% and 50% respectively. The most common clinical presentation of PVT in group A was abdominal pain in 55.5% compared to new/worsening ascites in 43% and 37.5% for groups B and C respectively. The platelet count in groups B and C was higher as compared to that in group A (126 and 125 vs. 107 thousand, P = NS).

CONCLUSION

In 38.4% of cases, new diagnosis of PVT was associated with concomitant diagnosis of HCC. Identifiable risk factors were chronic HBV infection and higher platelet count.

Clinical Impact and Safety of Anticoagulants for Portal Vein Thrombosis in Cirrhosis

OBJECTIVES

Portal vein thrombosis (PVT) is a frequent complication of cirrhosis. Benefit, safety, and duration of anticoagulant treatment in this setting are controversial issues. The aim of this study was to analyze the course of PVT in a large cohort of cirrhotic patients undergoing or not anticoagulation therapy.

METHODS

The data of 182 patients who presented between January 2008 and March 2016 with cirrhosis and PVT with at least 3 months of follow-up after the first PVT detection were analyzed. Eighty-one patients received anticoagulants and 101 were untreated per physician discretion.

RESULTS

The extension of the thrombosis decreased by >50% in 46 (56.8%, with complete recanalization in 31/46) patients under anticoagulation and in 26 (25.7%) untreated patients. Of the 46 patients who underwent recanalization, 17 (36%) suffered recurrent thrombosis after stopping anticoagulation therapy. Kaplan-Meier analysis showed a higher survival rate in the treated group (p = 0.010). At multivariate analysis, anticoagulation was an independent factor associated with longer survival (HR:0.30, CI:0.10-0.91, p = 0.014). The Child-Turcotte-Pugh classes B/C negatively influenced survival (hazard ratio, (HR):3.09, confidence interval (CI):1.14-8.36, p = 0.027 for Child-Turcotte-Pugh B and HR:9.27, CI:2.67-32.23, p < 0.001 for Child-Turcotte-Pugh C). Bleeding complications occurred in 22 (21.8%) untreated and 16 (19.7%) treated patients, but in only four cases was it judged to be related to the anticoagulant treatment. No death was reported as a consequence of the bleeding events.

CONCLUSIONS

Anticoagulant treatment is a safe and effective treatment leading to partial or complete recanalization of the portal venous system in 56.8% of cases, improving the survival of patients with cirrhosis and PVT. Discontinuation of the therapy is associated with a high rate of PVT recurrence.

Portal vein thrombosis in patients with liver cirrhosis and its impact on early and long-term outcomes after liver transplantation

AIM

Portal vein thrombosis (PVT) is a common complication amongst patients with liver cirrhosis. The PVT risk factors and its impact on post liver transplant outcome has not been well defined, yet. This study aimed to investigate PVT prevalence, its risk factors and influence on early and long-term outcomes after liver transplantation.

METHODS

Adult (>18 years) patients with liver cirrhosis undergoing liver transplantation between March 2013 to March 2015 were included. Presence or absence of PVT was recorded at transplant. PVT risk factors in patients with liver cirrhosis and its impact on early and long-term outcomes were analysed.

RESULTS

Portal vein thrombosis was diagnosed in 174 patients (17.3%). Large oesophageal varices (grade II and III vs grade I) (OR: 2.5; 95% CI: 1.46-4.26; P = 0.001), diabetes mellitus before transplantation (OR: 2.03; 95% CI: 1.13-3.64; P = 0.017) and cryptogenic-NASH (OR: 1.36; 95% CI: 1.08-1.72; P = 0.008) as a cause of underlying liver disease were the independent risk factors for PVT. PVT (OR: 2.05; 95% CI: 1.10-3.81; P = 0.023) was an independent predictor of early (within 90 days) posttransplant mortality, but did not influence long-term survival.

CONCLUSION

Portal vein thrombosis prevalence is high in pretransplant period. NASH related cirrhosis and diabetes mellitus might be risk factors for PVT. More intense screening of these patients for PVT is warranted.

Portal Vein Thrombosis in Patients With Cirrhosis Undergoing Elective Transjugular Intrahepatic Portosystemic Shunt: Risk Factors, Warfarin Efficacy, and Clinical Outcomes

Portal vein thrombosis (PVT) is a common complication in cirrhosis. The aim of this study was to determine risk factors for PVT, assess the efficacy of anticoagulant therapy, and evaluate the effects of PVT on patients with cirrhosis undergoing elective transjugular intrahepatic portosystemic shunt (TIPSS). A total of 101 patients with cirrhosis undergoing elective TIPSS were prospectively studied. After TIPSS, all patients received preventive therapy for PVT and were followed up at 3, 6, 12, and 24 months. Clinical outcomes were compared between patients who developed PVT after TIPSS and those who did not. Multivariate analysis showed that white blood cell count (relative risk [RR]: 0.377; 95% confidence interval [CI]: 0.132-0.579; P = .001), Child-Turcotte-Pugh score (RR: 1.547; 95% CI: 1.029-2.365; P = .032), and ascites (RR: 1.264; 95% CI: 1.019-1.742; P = .040) were independent predictors for PVT. Warfarin treatment within 12 months achieved significantly higher rates of complete recanalization than aspirin or clopidogrel in patients with PVT (54.5% vs 31.3%; P = .013), although adverse events were similar between the 2 groups ( P > .05). Patients without PVT had significantly lower 2-year cumulative rates of variceal rebleeding (15.9% vs 36.6%; P = .023), shunt dysfunction (27.0% vs 46.8%; P = .039), hepatic encephalopathy (24.1% vs 42.6%; P = .045), and hepatocellular carcinoma (11.4% vs 31.2%; P = .024) and markedly higher 2-year cumulative survival rates (89.8% vs 72.9%; P = .041) than those with PVT. The PVT is associated with poorer clinical outcomes in TIPSS-treated patients, and warfarin is both safe and more effective in recanalizing PVT than aspirin or clopidogrel.

Treatment for cirrhotic ascites

Common complications of decompensated liver cirrhosis are esophageal varices, hepatic encephalopathy and ascites. After the onset of complications, the prognosis worsens. In patients with ascites, the 5-year mortality rate is 44%. Furthermore, hyponatremia, spontaneous bacterial translocation and hepatorenal syndrome also greatly worsen the prognosis. Effective treatment of cirrhotic ascites improves the quality of life and survival rate. Recently, the newly produced diuretic, tolvaptan (vasopressin V2 receptor antagonist), was reported to be effective in the treatment of refractory ascites in liver cirrhosis; however, there has not been an associated positive effect on the prognosis. There are various types of treatment for ascites, such as large-volume paracenteses, a cell-free and concentrated ascites reinfusion therapy, a transjugular intrahepatic portosystemic shunt, and a peritoneo-venous shunt. Although they improve the prognosis, liver transplantation remains the ultimate form of treatment. The present article discusses the therapeutic management of cirrhotic ascites.

Hepatic Infarction Caused by Portal Vein Thrombophlebitis Misdiagnosed as Infiltrative Hepatic Malignancy with Neoplastic Thrombus

Portal vein thrombosis (PVT) is a form of venous thrombosis that usually presents in chronic form without any sequalae in patients with hepatocellular carcinoma (HCC) or liver cirrhosis. Accurate differential diagnosis of bland PVT from neoplastic PVT is an important step for planning treatment options, but the acute form can be challenging. Here we present a case of acute hepatic infarction caused by acute bland PVT combined with pylephlebitis, which was misdiagnosed as infiltrative hepatic malignancy with neoplastic PVT owing to the perplexing imaging results and elevated tumor markers.

Angiocrine signaling in the hepatic sinusoids in health and disease

The capillary network irrigating the liver is important not only for nutrient and oxygen delivery, but also for the signals distributed to other hepatic cell types necessary to maintain liver homeostasis. During development, endothelial cells are a key component in liver zonation. In adulthood, they maintain hepatic stellate cells and hepatocytes in quiescence. Their importance in pathobiology is highlighted in liver regeneration and chronic liver diseases, where they coordinate paracrine cell behavior. During regeneration, liver sinusoidal endothelial cells induce hepatocyte proliferation and angiogenesis. During fibrogenesis, they undergo morphological and functional changes, which are reflected by their role in hepatic stellate cell activation, inflammation, and distorted sinusoidal structure. Therapeutic strategies to target angiocrine signaling are in progress but are in the early stages. Here, we offer a short synthesis of recent studies on angiocrine signaling in liver homeostasis, regeneration, and fibrogenesis.

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

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

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

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

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

Portal vein thrombosis in cirrhosis: Controversies and latest developments

Portal vein thrombosis (PVT) is encountered in liver cirrhosis, particularly in advanced disease. It has been a feared complication of cirrhosis, attributed to significant worsening of liver disease, poorer clinical outcomes and potential inoperability at liver transplantation; also catastrophic events such as acute intestinal ischaemia. Optimal management of PVT has not yet been addressed in any consensus publication. We review current literature on PVT in cirrhosis; its prevalence, pathophysiology, diagnosis, impact on the natural history of cirrhosis and liver transplantation, and management. Studies were identified by a search strategy using MEDLINE and Google Scholar. The incidence of PVT increases with increasing severity of liver disease: less than 1% in well-compensated cirrhosis, 7.4%-16% in advanced cirrhosis. Prevalence in patients undergoing liver transplantation is 5%-16%. PVT frequently regresses instead of uniform thrombus progression. PVT is not associated with increased risk of mortality. Optimal management has not been addressed in any consensus publication. We propose areas for future research to address unresolved clinical questions.

Portal vein thrombosis in cirrhosis

Portal vein thrombosis (PVT) is being increasingly recognized in patients with advanced cirrhosis and in those undergoing liver transplantation. Reduced flow in the portal vein is probably responsible for clotting in the spleno-porto-mesenteric venous system. There is also increasing evidence that hypercoagulability occurs in advanced liver disease and contributes to the risk of PVT. Ultrasound based studies have reported a prevalence of PVT in 10-25% of cirrhotic patients without hepatocellular carcinoma. Partial thrombosis of the portal vein is more common and may not have pathophysiological consequences. However, there is high risk of progression of partial PVT to complete PVT that may cause exacerbation of portal hypertension and progression of liver insufficiency. It is thus, essential to accurately diagnose and stage PVT in patients waiting for transplantation and consider anticoagulation therapy. Therapy with low molecular weight heparin and vitamin K antagonists has been shown to achieve complete and partial recanalization in 33-45% and 15-35% of cases respectively. There are however, no guidelines to help determine the dose and therapeutic efficacy of anticoagulation in patients with cirrhosis. Anticoagulation therapy related bleeding is the most feared complication but it appears that the risk of variceal bleeding is more likely to be dependent on portal pressure rather than solely related to coagulation status. TIPS has also been reported to restore patency of the portal vein. Patients with complete PVT currently do not form an absolute contraindication for liver transplantation. Thrombectomy or thromboendovenectomy is possible in more than 75% of patients followed by anatomical end-to-end portal anastomosis. When patency of the portal vein and/or superior mesenteric vein is not achieved, only non-anatomical techniques (reno-portal anastomosis or cavo-portal hemitransposition) can be performed. These techniques, which do not fully reverse portal hypertension, are associated with higher morbidity and mortality risks in the short term.

Portal vein thrombosis, cirrhosis, and liver transplantation

Portal vein thrombosis is not uncommon in candidates for transplantation. Partial thrombosis is more common than complete thrombosis. Despite careful screening at evaluation, a number of patients are still found with previously unrecognized thrombosis per-operatively. The objective is to recanalize the portal vein or, if recanalization is not achievable, to prevent the extension of the thrombus so that a splanchnic vein can be used as the inflow vessel to restore physiological blood flow to the allograft. Anticoagulation during waiting time and transjugular intrahepatic portosystemic shunt (TIPS) are two options to achieve these goals. TIPS may achieve recanalization in patients with complete portal vein thrombosis. However, a marked impairment in liver function, which is a characteristic feature of most candidates for transplantation, may be a contraindication for TIPS. Importantly, the MELD score is artificially increased by the administration of vitamin K antagonists due to prolonged INR. When patency of the portal vein and/or superior mesenteric vein is not achieved, only non-anatomical techniques (renoportal anastomosis or cavoportal hemitransposition) can be performed. These techniques, which do not fully reverse portal hypertension, are associated with higher morbidity and mortality risks. Multivisceral transplantation including the liver and small bowel needs to be evaluated. In the absence of prothrombotic states that may persist after transplantation, there is no evidence that pre-transplant portal vein thrombosis justifies long term anticoagulation post-transplantation, provided portal flow has been restored through conventional end-to-end portal anastomosis.

Hyponatremia in cirrhosis

Hyponatremia is common in patients with cirrhosis. Portal hypertension, diuretics, large volume paracentesis without albumin, infection, and multiple medications are connected with the development or worsening of hyponatremia. Hyponatremia in cirrhosis, particularly advanced cirrhosis, is a common development.(1) In a population survey of 997 patients with cirrhosis, 486 (49.4%) and 211 (21.6%) had a serum sodium concentration ([Na(+)]) <135 mEq/L and ≤ 130 mEq/L, respectively.(2) Hyponatremia and its severity correlate with the presence of severe complications of cirrhosis such as hepatorenal syndrome, encephalopathy, and spontaneous bacterial peritonitis. The presence of hyponatremia frequently complicates the management of the cirrhotic patient.

Antiangiogenic therapies in portal hypertension: a breakthrough in hepatology

Portal hypertension is the most important complication that develops in patients with cirrhosis. Several studies have shown that angiogenesis (i.e. splanchnic neovascularization) driven by VEGF and other proangiogenic molecules, like PDGF, may be a major mechanism involved in portal hypertension, hyperdynamic splanchnic circulation and portosystemic collateralization. According with this, antiangiogenic therapies, like sorafenib or sunitinib, have been recently shown to reduce portosystemic collateral circulation, improve splanchnic hyperdynamics and decrease portal pressure in experimental model of portal hypertension. This effect was associated to a decrease in VEGF, PDGF expression and splanchnic neovascularization. In addition, these therapies were associated with a decrease in both splanchnic and intrahepatic inflammatory infiltrates, in hepatic stellate cell activation and in intrahepatic fibrosis. These data suggest that antiangiogenic therapies may therefore, by limiting liver fibrosis and inflammation in cirrhosis, prevent the occurrence of severe complications, such as portal hypertension and potentially liver cancer.

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.

Histological and histomorphometric evaluation of the retina of mice infected with Schistosoma mansoni in its hepatosplenic form

PURPOSE: To evaluate retinal manifestations of Schistosomiasis mansoni in its hepatosplenic form in mice. METHODS: It was performed a study with two groups of mice; one of them was infected with 40 cercariae of Schistosoma mansoni. After 120 days of the infection, the eyes underwent a retinal microscopy study. The histology findings were reported. Histomorphometric analysis was also performed, including: thickness measurement of the retinal layer and the number of the ganglion layer cells. RESULTS: In one case a retinal granuloma was found. The analysis of the other histological sections demonstrated normal architecture of the retina. The mean thickness of the retinal layer between the two groups were similar (41.81±6.09µm versus 38.48±8.58µm - p=0.279); as well as the mean number of the ganglion layer cells (20.93±4.88 versus 20.64±4.10 - p=0.864). Disorganization of the retinal layers was not identified and the histomorphometric analysis revealed no significant difference between the two groups. CONCLUSION: The absence of findings in this study does not exclude that hemodynamic and autoregulation changes associated with hepatosplenic schistosomiasis could be correlated to retinal manifestations. It is necessary that other methods with a high parasite infection should be performed.

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.

Bile-acid-activated farnesoid X receptor regulates hydrogen sulfide production and hepatic microcirculation

AIM: To investigate whether the farnesoid X receptor (FXR) regulates expression of liver cystathionase (CSE), a gene involved in hydrogen sulfide (H₂S) generation.

METHODS: The regulation of CSE expression in response to FXR ligands was evaluated in HepG2 cells and in wild-type and FXR null mice treated with 6-ethyl chenodeoxycholic acid (6E-CDCA), a synthetic FXR ligand. The analysis demonstrated an FXR responsive element in the 5’-flanking region of the human CSE gene. The function of this site was investigated by luciferase reporter assays, chromatin immunoprecipitation and electrophoretic mobility shift assays. Livers obtained from rats treated with carbon tetrachloride alone, or in combination with 6-ethyl chenodeoxycholic acid, were studied for hydrogen sulphide generation and portal pressure measurement.

RESULTS: Liver expression of CSE is regulated by bile acids by means of an FXR-mediated mechanism. Western blotting, qualitative and quantitative polymerase chain reaction, as well as immunohistochemical analysis, showed that expression of CSE in HepG2 cells and in mice is induced by treatment with an FXR ligand. Administration of 6E-CDCA to carbon tetrachloride treated rats protected against the down-regulation of CSE expression, increased H₂S generation, reduced portal pressure and attenuated the endothelial dysfunction of isolated and perfused cirrhotic rat livers.

CONCLUSION: These results demonstrate that CSE is an FXR-regulated gene and provide a new molecular explanation for the pathophysiology of portal hypertension.