Search

A relatively fast analytical method for the identification and quantification of the post-transcriptional changes (PTCs) occurring in circulating human serum albumin (HSA) was developed. HSA is the most abundant protein in plasma and it represents the main determinant of plasma oncotic pressure, thus being the main modulator of fluid distribution between body compartments. Cirrhotic patients have low levels of HSA. Moreover, recent studies have demonstrated that during liver cirrhosis HSA presents PTCs affecting its properties. The HSA isoforms derived from these modifications could represent promising biomarkers for liver disease. Human plasma samples were collected from a cirrhotic patient (CH) and from an aged-matched non- cirrhotic subject (CT), purified by reverse-phase chromatography and analysed by an electrospray ionization quadrupole time-of-flight (ESI-Q-ToF) spectrometer. The deconvoluted ESI mass spectra from healthy subjects were all characterized by peaks attributed to mercaptoalbumin, nitrosylated, cysteinylated, glycated and N- terminal truncated HSA isoforms. The relative abundance of each isoform was derived and transformed into a relative per cent amount and the results were compared to those obtained analysing HSA from a CH plasma. The method was validated in terms of intra-day and inter-day reproducibility, both for quantitative results and PTCs molecular weight determination. The optimized method resulted in being effective in disclosing changes in HSA isoforms relative abundance and then it could be used for the systematic screening of cirrhotic patients to identify promising new biomarkers for liver diseases.

Background and Purpose: β(3) -Adrenoceptors participate in the regulation of vascular tone in physiological and pathological conditions. We aimed to assess the effect of pharmacological modulation of β(3) -adrenoceptors on portal pressure (PP) and systemic haemodynamics and their expression in the liver and mesenteric vessels of cirrhotic rats., Experimental Approach: PP, central venous pressure (CVP) and systemic haemodynamics were invasively assessed in control and CCl(4) -treated cirrhotic rats before and during infusion of the selective β(3) -adrenoceptor agonist, SR58611A. Tissue samples were also collected from liver, heart, portal vein and mesenteric artery for immunohistochemistry and molecular biology analysis. The effect of SR58611A on isolated portal vein was assessed., Key Results: At baseline, cirrhotic rats showed portal hypertension, reduced CVP and hyperdynamic circulation. SR58611A induced a significant, dose-dependent decrease in PP in cirrhotic rats, but not in controls. Although both groups manifested a dose-dependent reduction in mean arterial pressure, this effect was associated with decreased cardiac index (CI) and unchanged indicized peripheral vascular resistance (PVRI) in cirrhotic rats and increased CI and decreased PVRI in control animals. Pretreatment with the selective β(3) -adrenoceptor antagonist SR59230 prevented all SR58611A-induced changes in cirrhotic rats. SR58611A concentration-dependently relaxed portal vein in cirrhotic rats to a significantly greater extent than in healthy rats; pretreatment with SR59230A completely prevented SR58611A-induced cirrhotic portal vein relaxation. Finally, β(3) -adrenoceptors were identified in the liver, heart and portal vein of cirrhotic and control animals; their expression was increased in cirrhotic rats., Conclusions and Implications: β(3) -Adrenoceptors are altered in portal hypertension of experimental cirrhosis and may represent a novel therapeutic target., (© 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.)

Unlabelled: MicroRNA-221 (miR-221) is one of the most frequently and consistently up-regulated microRNAs (miRNAs) in human cancer. It has been hypothesized that miR-221 may act as a tumor promoter. To demonstrate this, we developed a transgenic (TG) mouse model that exhibits an inappropriate overexpression of miR-221 in the liver. Immunoblotting and immunostaining confirmed a concomitant down-regulation of miR-221 target proteins. This TG model is characterized by the emergence of spontaneous nodular liver lesions in approximately 50% of male mice and by a strong acceleration of tumor development in 100% of mice treated with diethylnitrosamine. Similarly to human hepatocellular carcinoma, tumors are characterized by a further increase in miR-221 expression and a concomitant inhibition of its target protein-coding genes (i.e., cyclin-dependent kinase inhibitor [Cdkn]1b/p27, Cdkn1c/p57, and B-cell lymphoma 2-modifying factor). To validate the tumor-promoting effect of miR-221, we showed that in vivo delivery of anti-miR-221 oligonucleotides leads to a significant reduction of the number and size of tumor nodules., Conclusions: This study not only establishes that miR-221 can promote liver tumorigenicity, but it also establishes a valuable animal model to perform preclinical investigations for the use of anti-miRNA approaches aimed at liver cancer therapy., (Copyright © 2012 American Association for the Study of Liver Diseases.)

Liver ischemia-reperfusion injury is still an open problem in many clinical circumstances, including surgery and transplantation. This study investigates how mitochondrial structure, mass and oxidative phosphorylation change and may be preserved during a brief period of ischemia followed by a long period of reperfusion, an experimental model that mimics the condition to which a liver is exposed during transplantation. Livers were explanted from rats and exposed for 24 h to three different oxygen availability conditions at 4 °C. Mitochondrial mass, respiration, oxidative phosphorylation (OXPHOS), and levels of OXPHOS complexes were all significantly altered in livers stored under the currently used preservation condition of normoxia. Remarkably, liver perfusion with hyperoxic solutions fully preserved mitochondrial morphology and function, suggesting that perfusion of the graft with hyperoxic solution should be considered in human transplantation.

The endocannabinoids are endogenous mediators implicated in many physiologic and pathophysiologic processes. It has been recently shown that they contribute to the pathogenesis of liver fibrosis and hemodynamic alterations of cirrhosis. The pharmacological modulation of the endocannnabinoid system represents a potential target for the treatment of liver diseases.

Background/aims: Endocannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG). Endocannabinoid-related molecules like oleoyl-ethanolamine (OEA) and palmitoyl-ethanolamine (PEA) have also been identified. AEA contributes to the pathogenesis of cardiovascular alterations in experimental cirrhosis, but data on the endocannabinoid system in human cirrhosis are lacking. Thus, we aimed to assess whether circulating and hepatic endocannabinoids are upregulated in cirrhotic patients and whether their levels correlate with systemic haemodynamics and liver function., Methods: The endocannabinoid levels were measured in peripheral and hepatic veins and liver tissue by isotope-dilution liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. Systemic haemodynamics were assessed by the transthoracic electrical bioimpedance technique. Portal pressure was evaluated by hepatic venous pressure gradient., Results: Circulating AEA and, to a greater extent, PEA and OEA were significantly higher in cirrhotic patients than in controls. PEA and OEA were also increased in the cirrhotic liver tissue. AEA, OEA and PEA levels were significantly higher in peripheral than in the hepatic veins of cirrhotic patients, while the opposite occurred for 2-AG. Finally, circulating AEA, OEA and PEA correlated with parameters of liver function, such as serum bilirubin and international normalized ratio. No correlations were found with systemic haemodynamics., Conclusions: The endocannabinoid system is upregulated in human cirrhosis. Peripheral AEA is increased in patients with a high model of end-stage liver disease score and may reflect the extent of liver dysfunction. In contrast, the 2-AG levels, the other major endocannabinoid, are not affected by cirrhosis. The upregulation of the endocannabinoid-related molecules, OEA and PEA, is even greater than that of AEA, prompting pharmacological studies on these compounds.

Heterotrimeric G proteins transduce the signals of the largest family of membrane receptors (G protein-coupled receptors, GPCRs) hence triggering the activation of a wide variety of physiological responses. G15 is a G protein characterized by a number of functional peculiarities that make its signaling exceptional: 1) it can couple a variety of Gs-, Gi/o-, and Gq-linked receptors to phospholipase C activation; 2) relatively to other G proteins, it is poorly affected by beta-arrestin-dependent desensitization, the general mechanism that regulates GPCR function and 3) at the protein level, its expression is only detected in highly specific cell types (hematopoietic and epithelial cells). G15 alpha-subunit displays unique structural and biochemical properties, and is phylogenetically the most recent and divergent component of the Galphaq/11 subfamily. All these aspects shed a mysterious light on G15 biological role, which remains substantially elusive. Thus, far, G15 signaling has been analyzed in the context of hematopoiesis. Here, we highlight observations supporting the view that G15 functions may extend further beyond the immune system. In addition, we describe puzzling aspects of G15 signaling that offer a novel perspective in the understanding of its physiological role.

Background/aims: The current approaches to study the molecular mechanisms involved in the pathophysiology of liver diseases often rely on the use of transgenic mice. However, experimental models of decompensated cirrhosis have not been clearly established in mice. Thus, we aimed to set an efficient and well-tolerated protocol to induce cirrhosis in mice able to progress up to the ascitic stage., Methods: C57BL/6N mice received CCl(4) subcutaneously, intraperitoneally or by inhalation. In the latter group, gaseous CCl(4) was administered according to three different schedules: increasing exposure times, twice weekly (traditional protocol; TP), short inhalation cycles, twice or three times weekly., Results: Portal hypertension, sodium retention, and ascites developed in all groups between 11 and 15 weeks. Mortality reached 70% in the TP group, but it was only 0-10% with all other protocols. All the inhalation groups had significantly more ascites at sacrifice than those receiving CCl(4) subcutaneously and intraperitoneally. Extensive abdominal adhesions and evidence of enhanced hepatic inflammation, as suggested by the increased gene expression of pro-inflammatory cytokines in liver tissue, were found in the intraperitoneal group, while large granulomas at the injection site and marked neutrophil infiltration of lungs developed in the subcutaneous group. No extra-hepatic damage could be detected in mice inhaling CCl(4)., Conclusions: The use of short cycles of CCl(4) inhalation represents a novel, safe, and effective method to induce decompensated cirrhosis in mice. Intraperitoneal CCl(4) leads instead to abdominal adhesions precluding a correct evaluation of ascites, while subcutaneous CCl(4) causes an unwanted systemic inflammatory response.

Background/aim: Endotoxaemia can complicate hepatic ischaemia-reperfusion (IR) injury. Endocannabinoids appear to modulate the haemodynamic alterations and cytokine response induced by lipopolysaccharide (LPS). Thus, we aimed to determine the effect of the endocannabinoid CB1-receptor antagonist Rimonabant in a model of hepatic IR injury complicated by endotoxaemia., Methods: Sprague-Dawley rats pre-treated with Rimonabant 3 or 10 mg/kg or vehicle underwent partial hepatic IR and lipopolysaccharide (LPS) injection at reperfusion. Liver injury was evaluated by serum alanine aminotransferase (ALT) and necrotic-cell count. The inflammatory response was investigated by assessing hepatic neutrophil infiltration, tumour necrosis factor alpha (TNFalpha), interferon gamma (IFNgamma), interleukin 6 (IL6), and suppressor of cytokine signalling (SOCS) 1 and SOCS3 gene expression by real-time polymerase chain reaction (RT-PCR). Systolic blood pressure and hepatic blood flow were measured as haemodynamic parameters. Finally, lipid peroxidation, glutathione status, and immunoreactive CB1 receptor expression in the liver were also determined., Results: Liver injury and neutrophil infiltration occurring in the late-phase of LPS-enhanced IR were significantly reduced by CB1-receptor antagonism. Rimonabant-treated rats showed significantly higher gene expression of IFNgamma, IL6, SOCS1 and SOCS3 in "early" reperfusion, while that of TNFalpha was reduced. These findings were associated with increased STAT3 phosphorylation. Furthermore, CB1-receptor antagonism significantly improved the oxidative injury and haemodynamic alterations occurring during reperfusion in untreated rats. Finally, CB1-receptor immunoreactivity was upregulated early after reperfusion., Conclusions: This study demonstrates that CB1-receptor antagonism protects the liver against LPS-enhanced IR injury by interfering with the inflammatory response that causes the late, neutrophil-dependent phase of reperfusion injury, although the prevention of the transient endotoxin-related hypotension occurring early during reperfusion may be also involved.

Background & Aims: Endocannabinoids contribute to hemodynamic abnormalities of cirrhosis. Whether this favors renal sodium retention and ascites formation is unknown. We determined whether cannabinoid type 1 receptor antagonism prevents sodium retention and ascites formation in preascitic cirrhotic rats., Methods: Once renal sodium handling was impaired, rats with carbon tetrachloride-induced cirrhosis were randomized to receive either vehicle or rimonabant (3 [group 1] or 10 [group 2] mg x kg(-1) x day(-1)) for 2 weeks. Natriuresis, sodium intake, and sodium balance were measured daily. At the end of the protocol, systemic hemodynamics, renal blood flow, ascites volume, and liver fibrosis were assessed., Results: A significant reduction in ascites formation (group 1: 54%; group 2: 10%; vehicle: 90%) and volume (group 1: 1.6 +/- 0.3 mL; group 2: 0.5 mL; vehicle: 5.5 +/- 0.8 mL) occurred in treated rats. Rimonabant significantly improved sodium balance during week 2 (group 1: 0.98 +/- 0.08 mmol; group 2: 0.7 +/- 0.08 mmol; vehicle: 3.05 +/- 0.11 mmol). Both treated groups showed lower cardiac output and higher mean arterial pressure, peripheral vascular resistance, and renal blood flow (P < .05). Liver fibrosis was reduced in group 2 by 30% (P < .05 vs vehicle). Mean arterial pressure inversely correlated with sodium balance (R = -0.61; P = .003), but not with fibrosis score., Conclusions: Rimonabant improves sodium balance and delays decompensation in preascitic cirrhosis. This is achieved though an improvement in systemic and renal hemodynamics, although it cannot be excluded that the antifibrotic effect of the drug may play a role.

G15 is a heterotrimeric G protein of the Gq/11 family. In this study, we describe its exceptional poor sensitivity to the general regulatory mechanism of G protein-coupled receptor (GPCR) desensitization. Enhancing beta2 adrenergic receptor desensitization by arrestin overexpression, did not affect signalling to G15. Similarly, increased levels of arrestin did not affect G15 signalling triggered by the activation of V2 vasopressin and delta opioid receptors. Furthermore, co-immunoprecipitation experiments showed that G15 alpha subunit (as opposed to Galphaq and Galphas) is recruited to a V2 vasopressin receptor mutant that is constitutively desensitized by beta-arrestin. Interestingly, co-expression of Galpha15 partially rescued cell surface localization and signalling capabilities of the same mutant receptor and reduced beta2 adrenergic receptor internalization. Taken together, these findings provide evidence for a novel mechanism whereby GPCR desensitization can be bypassed and G15 can support sustained signalling in cells chronically exposed to hormones or neurotransmitters.

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

Background/aim: Controversial experimental observations suggest that granulocyte colony stimulating-factor may promote hepatic regeneration after hepatectomy and chemical injury either by directly stimulating adult liver cells or facilitating the mobilization of bone marrow cells and their homing to the liver. We investigated whether different schedules of granulocyte colony stimulating-factor administration protect against experimental acute liver injury., Methods: Acute liver injury was induced in Sprague-Dawley fed rats by injecting a single intraperitoneal dose of carbon tetrachloride. Recombinant human granulocyte colony stimulating-factor or vehicle was given daily after intoxication (4 days) or before (7 days) and after carbon tetrachloride administration. Liver injury and regeneration were assessed 2 and 4 days after damage. Bone marrow cells mobilization was evaluated by the white blood cell count and the assessment of circulating clonogenic haematopoietic progenitors (colony forming unit-cells)., Results: In this experimental model, although granulocyte colony stimulating-factor induced the significant mobilization of colony forming unit-cells, the study cytokine had no effect on liver injury (serum alanine amino transaminase level and necrotic index) and liver regeneration (mitotic index and bromodeoxyuridine incorporation), regardless of the administration schedule., Conclusions: This study does not support the conclusion that: (1) granulocyte colony stimulating-factor exerts a protective effect against toxic-induced, non-lethal acute liver injury and (2) promotes hepatocyte regeneration.