Ramon Bataller

Alcoholic Liver Disease: Pathogenesis and New Therapeutic Targets

Alcoholic liver disease (ALD) is a major cause of chronic liver disease worldwide and can lead to fibrosis and cirrhosis. The latest surveillance report published by the National Institute on Alcohol Abuse and Alcoholism showed that liver cirrhosis was the 12th leading cause of death in the United States, with a total of 29,925 deaths in 2007, 48% of which were alcohol related. The spectrum of ALD includes simple steatosis, alcoholic hepatitis, fibrosis, cirrhosis, and superimposed hepatocellular carcinoma. Early work on the pathogenesis of the disease focused on ethanol metabolism-associated oxidative stress and glutathione depletion, abnormal methionine metabolism, malnutrition, and production of endotoxins that activate Kupffer cells. We review findings from recent studies that have characterized specific intracellular signaling pathways, transcriptional factors, aspects of innate immunity, chemokines, epigenetic features, microRNAs, and stem cells that are associated with ALD, improving our understanding of its pathogenesis. Despite this progress, no targeted therapies are available. The cornerstone of treatment for alcoholic hepatitis remains as it was 40 years ago: abstinence, nutritional support, and corticosteroids. There is an urgent need to develop new pathophysiology-oriented therapies. Recent translational studies of human samples and animal models have identified promising therapeutic targets.

NADPH oxidase signal transduces angiotensin II in hepatic stellate cells and is critical in hepatic fibrosis

Angiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II-induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen alpha1(I) mRNA expression, and secretion of TGF-beta1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47phox-/- mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47phox-/- mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle alpha-actin and expression of TGF-beta1 were reduced in p47phox-/- mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.

Promotion of Hepatocellular Carcinoma by the Intestinal Microbiota and TLR4

Increased translocation of intestinal bacteria is a hallmark of chronic liver disease and contributes to hepatic inflammation and fibrosis. Here we tested the hypothesis that the intestinal microbiota and Toll-like receptors (TLRs) promote hepatocellular carcinoma (HCC), a long-term consequence of chronic liver injury, inflammation, and fibrosis. Hepatocarcinogenesis in chronically injured livers depended on the intestinal microbiota and TLR4 activation in non-bone-marrow-derived resident liver cells. TLR4 and the intestinal microbiota were not required for HCC initiation but for HCC promotion, mediating increased proliferation, expression of the hepatomitogen epiregulin, and prevention of apoptosis. Gut sterilization restricted to late stages of hepatocarcinogenesis reduced HCC, suggesting that the intestinal microbiota and TLR4 represent therapeutic targets for HCC prevention in advanced liver disease.

Angiotensin II induces contraction and proliferation of human hepatic stellate cells

BACKGROUND & AIMS Circulating levels of angiotensin II (ANGII), a powerful vasoconstrictor factor, are frequently increased in chronic liver diseases. In these conditions, hepatic stellate cells (HSCs) proliferate and acquire contractile properties. This study investigated the presence of receptors for ANGII and the effects of ANGII in human HSCs activated in culture. METHODS The presence of ANGII receptors was assessed by binding studies. The effects of ANGII on intracellular calcium concentration ([Ca(2+)](i)), cell contraction, and cell proliferation were also assessed. RESULTS Binding studies showed the presence of ANGII receptors of the AT1 subtype. ANGII elicited a marked dose-dependent increase in [Ca(2+)](i) and cell contraction. Moreover, ANGII stimulated DNA synthesis and increased cell number. All these effects were totally blocked by losartan and reduced by nitric oxide donors or prostaglandin E(2). The effects of ANGII were barely detectable in quiescent cells (2 days in culture), suggesting that phenotypic transformation of HSCs is associated with a marked increase in the effects of ANGII. CONCLUSIONS ANGII induces contraction and is mitogenic for human-activated HSCs by acting through AT1 receptors. These results suggest that activated HSCs are targets of the vasoconstrictor action of ANGII in the intrahepatic circulation.

Terlipressin plus albumin infusion: an effective and safe therapy of hepatorenal syndrome.

BACKGROUND/AIM Ornipressin, a vasopressin analog with potent splanchnic vasoconstrictor action, has been shown to reverse hepatorenal syndrome. However, its usefulness in clinical practice is limited by frequent ischemic complications. The aim of this study was to assess the efficacy of terlipressin, an analog of vasopressin with a low profile of side effects, plus albumin in this condition. METHODS Nine consecutive patients with cirrhosis and hepatorenal syndrome were included in a pilot study of terlipressin (0.5-2 mg/4 h i.v.) therapy associated with iv albumin. RESULTS Treatment (9 days, range 5-15) was associated with a marked reduction of serum creatinine (3.9+/-0.7 to 1.3+/-0.1 mg/dl, p<0.001, mean+/-SE). Reversal of hepatorenal syndrome (reduction of creatinine below 1.5 mg/dl) was observed in seven of the nine patients. There was a remarkable improvement in circulatory function, with an increase in mean arterial pressure (68+/-2 to 80+/-4 mmHg, p<0.05) and suppression of vasoconstrictor systems activity (plasma renin activity and plasma norepinephrine decreased from 23+/-12 ng/ml x h and 1549+/-373 pg/ml to 3.5+/-2 ng/ml x h and 373+/-98 pg/ml, respectively, p<0.01 for both). No patient developed signs of intestinal, myocardial or distal ischemia. CONCLUSIONS Terlipressin associated with albumin appears to be a safe and effective treatment of hepatorenal syndrome.

Activated human hepatic stellate cells express the renin-angiotensin system and synthesize angiotensin II.

BACKGROUND & AIMS The renin-angiotensin system plays an important role in hepatic fibrogenesis. In other organs, myofibroblasts accumulated in damaged tissues generate angiotensin II, which promotes inflammation and extracellular matrix synthesis. It is unknown whether myofibroblastic hepatic stellate cells, the main hepatic fibrogenic cell type, express the renin-angiotensin system and synthesize angiotensin II. The aim of this study was to investigate whether quiescent and activated human hepatic stellate cells contain the components of the renin-angiotensin system and synthesize angiotensin II. METHODS Hepatic stellate cells were freshly isolated from normal human livers (quiescent hepatic stellate cells) and from human cirrhotic livers (in vivo activated hepatic stellate cells). Culture-activated hepatic stellate cells were used after a second passage of quiescent hepatic stellate cells. Angiotensinogen, renin, and angiotensin-converting enzyme were assessed by quantitative polymerase chain reaction. Angiotensin II production was assessed by enzyme-linked immunosorbent assay and immunohistochemistry. RESULTS Quiescent hepatic stellate cells barely express the renin-angiotensin system components--angiotensinogen, renin, and angiotensin-converting enzyme--and do not secrete angiotensin II. In contrast, both in vivo activated hepatic stellate cells and culture-activated hepatic stellate cells highly express active renin and angiotensin-converting enzyme and secrete angiotensin II to the culture media. Mature angiotensin II protein is also detected in the cytoplasm of in vivo activated and culture-activated hepatic stellate cells. Growth factors (platelet-derived growth factor and epidermal growth factor) and vasoconstrictor substances (endothelin-1 and thrombin) stimulate angiotensin II synthesis, whereas transforming growth factor-beta and proinflammatory cytokines have no effect. Vasodilator substances markedly attenuate the effect of endothelin-1. CONCLUSIONS After activation, human hepatic stellate cells express the components of the renin-angiotensin system and synthesize angiotensin II. These results suggest that locally generated angiotensin II could participate in tissue remodeling in the human liver.

Interleukin-22 treatment ameliorates alcoholic liver injury in a murine model of chronic-binge ethanol feeding: role of signal transducer and activator of transcription 3.

Interleukin‐22 (IL‐22), a recently identified member of the IL‐10 family of cytokines that is produced by Th17 and natural killer cells, plays an important role in controlling bacterial infection, homeostasis, and tissue repair. Here, we tested the effect of IL‐22 on alcohol‐induced liver injury in a murine model of chronic‐binge ethanol feeding. Feeding male C57BL/6 mice with a Lieber‐DeCarli diet containing 5% ethanol for 10 days, followed by a single dose of ethanol (5 g/kg body weight) by gavage, induces significant fatty liver and liver injury with peak serum levels of approximately 250 IU/L alanine aminotransferase and 420 IU/L aspartate aminotransferase 9 hours after gavage. Moreover, chronic‐binge ethanol administration increases expression of hepatic and serum inflammatory cytokines and hepatic oxidative stress. Using this model, we demonstrate that treatment with IL‐22 recombinant protein activates hepatic signal transducer and activator of transcription 3 (STAT3) and ameliorates alcoholic fatty liver, liver injury, and hepatic oxidative stress. Administration with IL‐22 adenovirus also prevents alcohol‐induced steatosis and liver injury. Deletion of STAT3 in hepatocytes abolishes the hepatoprotection provided by IL‐22 in alcoholic liver injury. In addition, IL‐22 treatment down‐regulates the hepatic expression of fatty acid transport protein, but up‐regulates several antioxidant, antiapoptotic, and antimicrobial genes. Finally, expression of IL‐22 receptor 1 is up‐regulated whereas IL‐22 is undetectable in the livers from mice with chronic‐binge ethanol feeding or patients with alcoholic hepatitis. Conclusion: Chronic‐binge ethanol feeding may be a useful model to study the early stages of alcoholic liver injury. IL‐22 treatment could be a potential therapeutic option to ameliorate alcoholic liver disease, due to its antioxidant, antiapoptotic, antisteatotic, proliferative, and antimicrobial effects with the added benefit of potentially few side effects. HEPATOLOGY 2010

A prognostic model for predicting survival in cirrhosis with ascites

BACKGROUND/AIMS Parameters evaluating renal function and systemic hemodynamics are of prognostic significance in cirrhosis with ascites but are rarely used in the evaluation of survival of these patients. The aim of the current study was to develop a prognostic model to estimate survival of patients with cirrhosis and ascites. METHODS 216 Cirrhotic patients admitted to hospital for the treatment of ascites were evaluated. Thirty-two demographic, clinical and laboratory variables, including parameters assessing liver and renal function and systemic hemodynamics, were analyzed as predictive factors of survival by using a Cox regression model. RESULTS Four variables had independent prognostic value: renal water excretion, as assessed by measuring diuresis after water load, mean arterial pressure, Child-Pugh class, and serum creatinine. According to these features a prognostic index was calculated that allows to estimate survival in patients with cirrhosis and ascites. The model accurately predicted survival in an independent series of 84 patients with cirrhosis and ascites. CONCLUSION A prognostic model that uses four easily available variables and predicts prognosis in cirrhotic patients with ascites has been developed. This model may be useful in the evaluation of patients with ascites for liver transplantation.

A dual reporter gene transgenic mouse demonstrates heterogeneity in hepatic fibrogenic cell populations

Activation of hepatic stellate cells (HSCs) and other resident mesenchymal cells into myofibroblasts expressing alpha smooth muscle actin (αSMA) and collagen I is a key event in liver fibrogenesis. However, the temporal expression profiles of αSMA and collagen I genes in these cells is unknown. To address this question, we studied αSMA and collagen α1(I) transcriptional patterns in primary cultures of HSCs, and additionally, in an in vivo model of secondary biliary fibrosis using transgenic mice that express the Discomsoma sp. red fluorescent protein (RFP) and the enhanced green fluorescent protein (EGFP) reporter genes under direction of the mouse αSMA and collagen α1(I) promoter/enhancers, respectively. The αSMA‐RFP mice were crossed with collagen‐EGFP mice to generate double transgenic mice. Reporter gene expression in cultured HSCs demonstrated that both transgenes were induced at day 3 with continued expression through day 14. Interestingly, αSMA and collagen α1(I) transgenes were not coexpressed in all cells. Flow cytometry analysis showed three different patterns of gene expression: αSMA‐RFP positive cells, collagen‐EGFP positive cells, and cells expressing both transgenes. αSMA‐only and αSMA/collagen expressing cells showed higher expression levels of synaptophysin, reelin, MMP13, TIMP1, and ICAM‐1 compared to collagen‐only expressing cells, as assessed by real‐time PCR. Following bile duct ligation, αSMA and collagen α1(I) transgenes were differentially expressed by peribiliary, parenchymal and vascular fibrogenic cells. Peribiliary cells preferentially expressed collagen α1(I), while parenchymal myofibroblasts expressed both αSMA and collagen α1(I). In conclusion, these data demonstrate heterogeneity of gene expression in myofibroblastic cells during active fibrogenesis. These reporter mice provide a useful tool to further characterize fibrogenic cell types and to evaluate antifibrotic drugs. (HEPATOLOGY 2004.)

Human hepatic stellate cells show features of antigen‐presenting cells and stimulate lymphocyte proliferation

Following cell activation, hepatic stellate cells (HSCs) acquire proinflammatory and profibrogenic properties. We investigated whether activated HSCs also display immune properties. Here we show that cultured human HSCs express membrane proteins involved in antigen presentation, including members of the HLA family (HLA-I and HLA-II), lipid-presenting molecules (CD1b and CD1c), and factors involved in T-cell activation (CD40 and CD80). Exposure of HSCs to proinflammatory cytokines markedly up-regulates these molecules. Importantly, cells freshly isolated from human cirrhotic livers (in vivo activated HSCs) highly express HLA-II and CD40, suggesting that HSCs can act as antigen-presenting cells (APCs) in human fibrogenesis. We also explored whether human HSCs can efficiently process exogenous antigens. Activated HSCs internalize low- and high-molecular-weight dextran and transferrin, indicating that they can perform fluid-phase and receptor-mediated endocytosis. Moreover, HSCs can perform phagocytosis of macromolecules because they internalize latex particles as well as bacteria. Interestingly, both culture-activated and in vivo activated HSCs express high levels of CD68, a protein involved in antigen trafficking. Finally, we studied whether HSCs modulate T-lymphocyte proliferation. In basal conditions, coculture of irradiated HSCs barely induces allogeneic T-lymphocyte proliferation. However, cytokine-stimulated HSCs stimulate the allogeneic T-lymphocyte response in an HLA-II-dependent manner. In conclusion, human activated HSCs express molecules for antigen presentation, internalize macromolecules, and modulate T-lymphocyte proliferation. These results suggest that HSCs may play a role in the immune function of the liver.