Liver fibrosis

A novel lipid-based drug carrier targeted to the non-parenchymal cells, including hepatic stellate cells, in the fibrotic livers of bile duct ligated rats

In fibrotic livers, collagen producing hepatic stellate cells (HSC) represent a major target for antifibrotic therapies. We designed liposomes with surface-coupled mannose 6-phosphate (M6P) modified human serum albumin (HSA) to target HSC via the M6P receptor. In this study we determined the pharmacokinetics and target specificity of M6P-HSA-liposomes in a rat model of liver fibrosis. Ten minutes after injection of [(3)H]-M6P-HSA-liposomes 90% of the dose has cleared the circulation. The blood elimination of these liposomes was counteracted by free M6P-HSA and polyinosinic acid, a competitive inhibitor of scavenger receptors. The M6P-HSA-liposomes accumulated in HSC. However, also Kupffer cells and endothelial cells contributed to the uptake of M6P-HSA-liposomes in the fibrotic livers. Polyinosinic acid inhibited the accumulation of the liposomes in Kupffer cells and liver endothelial cells, but not in HSC. PCR analysis revealed that cultured HSC express scavenger receptors. This was confirmed by Western blotting, although activation of HSC diminishes scavenger receptor protein expression. In conclusion, in a rat model for liver fibrosis M6P-HSA-liposomes can be efficiently targeted to non-parenchymal cells, including HSC. M6P receptors and scavenger receptors are involved in the cellular recognition of these liposomes, allowing multiple pharmacological interference in different pathways involved in the fibrosis.

Diabetes-induced alterations of adenosine receptors expression level in rat liver

Diabetes mellitus is associated with metabolic, functional, and structural changes in the liver. Adenosine has been demonstrated to play an important regulatory role in the liver, and its action has been associated with all four adenosine receptors (ARs) subtypes. The goal of this study was to evaluate the impact of streptozotocin-induced diabetes on expression level of ARs in rat liver. Performed analyses (real-time PCR, Western blots) revealed detectable levels of mRNA and protein of A(1)-AR, A(2A)-AR, A(2B)-AR, and A(3)-AR in the rat liver. Development of diabetes resulted in a significant increase of A(2A)-AR and A(3)-AR mRNA levels. This was associated with elevated ARs protein content. The level of A(2B)-AR mRNA in diabetic liver decreased approximately 40% and was accompanied by 60% drop in A(2B)-AR protein in liver membranes. Diabetes did not affect the expression level of A(1)-AR in the liver. Administration of insulin for four days to diabetic rats resulted in returning of the ARs expression to the levels observed in liver of normal rat. The changes in ARs genes expression and receptors protein content could be related to some pathological changes taking place in diabetic liver. This might suggest involvement of ARs in pathogenesis of liver disease.

Myocardin-related transcription factor B is required for normal mouse vascular development and smooth muscle gene expression

Smooth muscle gene expression is required for the proper development and function of multiple organ systems. Expression of smooth muscle genes is critical for contractile function and tissue architectural integrity. One critical transcription factor for smooth muscle gene expression is the Serum Response Factor (SRF). SRF is expressed ubiquitously, but tissue-specific transcriptional regulation is conferred by its binding to cofactors such as myocardin. Myocardin-related transcription factor B (MRTF-B) is a member of a family of genes (Myocardin(Myocd),Myocardin-related transcription factor A(MRTF-A),MRTF-B) that provides tissue-specificity and potentiate SRF-dependent transcription. Unlike myocardin, which is expressed specifically in smooth and cardiac muscle, MRTF-B is expressed in a wide variety of tissues. To examine the function of MRTF-B, we generated mice containing an insertional mutation of MRTF-B. MRTF-B homozygous mutants die in late gestation with vascular defects and liver hemorrhage. At E9.5, MRTF-B is expressed strongly in the septum transversum mesoderm critical for development of the vitelline system that produces the liver sinusoids and portal venous system. MRTF-B deficiency results in defective smooth muscle gene expression in the liver sinusoids, vitelline veins, and yolk sac, which contributes significantly to the lethal phenotype. These data support our hypothesis that MRTF-B has a unique role in regulating smooth muscle genes important for liver, yolk sac, and portal vascular development.

Reversal of liver cirrhosis: a desirable clinical outcome and its pathogenic background

Cirrhosis is the final stage of chronic liver damage of various etiologies. It used to be considered an irreversible lesion, but enormous advances in our understanding of hepatic cellular and molecular biology in the past 2 decades have challenged this view. There is now substantial evidence that cirrhosis can be a reversible process. This concept is supported by an increasing number of clinical reports showing the disappearance of cirrhotic lesions from liver biopsies taken from patients cured of their liver disease. The reversal of cirrhosis usually occurs in patients with short-lived liver disease, after the successful treatment of the underlying liver damage. Recently, however, we observed the spontaneous reversal of cirrhosis after the loss of hepatitis B viremia in 2 men, 21 and 28 years old, who had developed cirrhosis as young children. Several questions and controversial issues concerning the definition of advanced cirrhosis, the limitations of liver biopsy (eg, sampling, interpretation error), and the applicability of noninvasive methods to the assessment of fibrosis, are being addressed. Future prospects include the possibility of antifibrotic therapy to prevent fibrosis or favor its degradation.

Progression of fibrosis in advanced chronic hepatitis C: evaluation by morphometric image analysis

Fibrosis progression in chronic liver disease has usually been evaluated by liver biopsy using insensitive semiquantitative numerical scores. An alternative to this is to measure fibrous tissue quantitatively using morphometric image analysis. The aim of this study was to quantify fibrosis progression in a cohort of patients with treatment-refractory chronic hepatitis C enrolled in a placebo-controlled clinical trial of interferon gamma-1b (IFN-gamma 1b) for the treatment of advanced hepatic fibrosis. We used morphometry to quantify the amount of fibrous tissue in liver biopsies performed at baseline and after 48 weeks in 245 patients who had paired unfragmented, adequate-sized specimens and correlated the results with clinical and laboratory parameters. Eighty-seven patients were treated with placebo and 158 with IFN-gamma 1b. No effect of the drug on fibrosis was found in the trial, and so data from all 245 patients were combined for analysis. At baseline, 78% had cirrhosis; 22%, bridging fibrosis. The mean morphometrically determined collagen content increased by 58% between baseline and 48 weeks. There were statistically significant but weak correlations of fibrosis with platelet count, albumin, bilirubin, INR, and hyaluronic acid; however, changes in these did not correlate with or predict changes in fibrosis in the liver biopsy.

CONCLUSION

In advanced chronic hepatitis C, fibrosis increases at a rapid pace that can only be detected by morphometry. This technique can be used in future therapeutic trials of agents to inhibit fibrosis progression.

Expression of large tenascin-C splice variants by hepatic stellate cells/myofibroblasts in chronic hepatitis C

BACKGROUND/AIMS

Earlier studies have suggested involvement of tenascin-C (TN-C) in liver fibrosis. Here, we examined expression of TN-C variants and types of alternatively spliced fibronectin-type III (FNIII) repeats in chronic hepatitis.

METHODS

Using three monoclonal antibodies against TN-C variants, immunohistochemical staining was performed and the correlation with histological parameters of chronic hepatitis C was examined. The cellular source was also determined and variant expression and their types were tested using isolated rat hepatic stellate cells (HSCs), liver myofibroblasts, and/or LI90 cells.

RESULTS

Large variants were not expressed in normal liver, but were up-regulated in chronic hepatitis, especially at sites of interface hepatitis and confluent necrosis, showing stronger correlations between staining intensity and these than with other parameters or fibrosis. TN-C deposition was closely correlated with increase in the number of alpha-smooth muscle actin-positive cells, i.e. activated HSCs/myofibroblasts, and in situ hybridization showed TN-C mRNA signals in the cells. Activated HSCs and myofibroblasts in culture highly expressed large variants of TN-C. In LI90 cells, sequencing of large variants revealed that the FNIII repeats D and A1/A4, followed by B, were preferentially included.

CONCLUSIONS

TN-C and its variants are produced by HSCs/myofibroblasts, suggesting important roles in liver fibrogenesis.

The renin-angiotensin system in a rat model of hepatic fibrosis: evidence for a protective role of Angiotensin-(1-7)

BACKGROUND/AIMS

The circulating renin-angiotensin system (RAS) [plasma renin activity (PRA), Angiotensin (Ang) I, Ang II and Ang-(1-7)] was evaluated in a model of hepatic fibrosis in rats. To investigate the pathophysiological involvement of Ang-(1-7), animals were treated with the Ang-(1-7) Mas receptor antagonist, A-779.

METHODS

RAS components, liver function and histology were examined in male Wistar rats (220-300 g). Animals were submitted to sham-surgery or ligature of the bile duct and evaluated 1, 2, 4 and 6 weeks later. Blood samples were obtained to determine biochemical parameters and RAS components. A second group was treated with A-779 or vehicle to measure liver hydroxyproline and total transforming growth factor beta-1 (TGFbeta1).

RESULTS

PRA and Ang I were significantly elevated in rats at 4 and 6 weeks compared to sham-operated animals. Ang II and Ang-(1-7) progressively increased over the 6 weeks. Changes in RAS profile correlated with histological signs of fibrosis and deterioration in liver function. Pharmacological blockade of the Ang-(1-7) receptor aggravated liver fibrosis with a significant elevation in hydroxyproline and total TGFbeta(1).

CONCLUSIONS

Hepatic fibrosis was associated with RAS activation in our model. Our data also suggested that Ang-(1-7) played a protective role in hepatic fibrosis.

The forkhead transcription factor FoxO1 regulates proliferation and transdifferentiation of hepatic stellate cells

BACKGROUND & AIMS

The Forkhead box gene, group O (FoxO) family of Forkhead transcription factors is phopsphorylated and inactivated by the phosphatidylinositol 3-kinase (PI3K)/AKT pathway and regulates a variety of cellular functions. Hepatic stellate cells (HSCs) play a crucial role in liver fibrosis. A fibrotic stimulus causes HSCs to transdifferentiate from a quiescent phenotype to a collagen-producing myofibroblast-like phenotype and to proliferate.

METHODS

Mutation/deletion mutants of FoxO1 were introduced into primary rat, mouse, and immortalized human HSCs and assessed for activation, proliferation, and signal transduction. The role of FoxO1 in experimental liver fibrosis was assessed in FoxO1(+/-) and FoxO1(+/+) mice.

RESULTS

Platelet-derived growth factor (PDGF) or insulin phosphorylates FoxO1 and induces FoxO1 translocation from the nuclei to the cytosol via the PI3K/AKT pathway in HSCs. Constitutively active FoxO1 inhibits proliferation via cell cycle arrest at the G1 phase, whereas dominant-negative FoxO1 enhances proliferation of HSCs even in the presence of the PI3K inhibitor LY294002. In addition, the phosphorylation of FoxO1 is increased during transdifferentiation of HSCs. The transdifferentiation is also inhibited by constitutively active FoxO1 and is accelerated by dominant-negative FoxO1. FoxO1 directly induces the expression of p27(kip1) and manganese superoxide dismutase (MnSOD). After bile duct ligation for 3 weeks, FoxO1(+/-) mice are more susceptible to liver fibrosis, consistent with our in vitro results.

CONCLUSIONS

FoxO1 plays a crucial role in the transdifferentiation and proliferation of HSCs in liver fibrosis. Hyperinsulinemia inactivates FoxO1 in HSCs, resulting in HSC activation and may result in the fibrosis in nonalcoholic fatty liver disease.

Prevention of liver cirrhosis in rats by curcumin

BACKGROUND AND AIM

Curcumin, the major polyphenolic compound in turmeric, has been shown to attenuate hepatic damage in several animal models of liver injury. The aim of the present study was to examine the efficacy of curcumin in preventing thioacetamide-induced cirrhosis and to unravel the mechanism of curcumin's effect on hepatic fibrosis in rats.

METHODS

Liver cirrhosis was induced by thioacetamide (TAA; 200 mg/kg, i.p.) twice weekly for 12 weeks. One group of rats concomitantly received curcumin (300 mg/kg/day, by gavage for 12 weeks); the control group received the solvent at identical amounts and duration.

RESULTS

TAA administration induced liver cirrhosis, which was inhibited by curcumin. Liver histopathology, hydroxyproline levels and spleen weights were significantly lower in the rats treated with TAA+curcumin compared with TAA only (P<0.001). Immunohistochemical studies and in situ hybridization demonstrated inhibition of hepatic stellate cell (alpha smooth muscle actin-positive) activation and collagen alpha1 (I) gene expression in the livers of the TAA+curcumin-treated rats. Curcumin reduced oxidative stress as shown by the decreased hepatic nitrotyrosine staining in the curcumin+TAA-treated rats. Curcumin treatment had no effect on pre existing liver cirrhosis. As determined by in vitro studies using the rat HSC-T6 cell line, curcumin had no direct inhibitory effect on collagen alpha1 (I) messenger RNA expression. Further studies in these cells using reverse transcriptase-polymerase chain reaction demonstrated that curcumin had no effect on the expression of PDGF-induced TIMP-1 and TIMP-2, TGFbeta1, TGFbeta2 and MCP-1 but significantly inhibited tumor necrosis factor alpha expression. Curcumin had no effect on hepatic stellate cells proliferation. Zymography showed that curcumin had no effect on matrix metalloproteinase-2 activity.

CONCLUSIONS

Curcumin inhibited the development of TAA-induced liver cirrhosis mainly due to its anti-inflammatory activities and not by a direct anti-fibrotic effect. As curcumin ingestion is safe in humans, it may be reasonable to assess in clinical studies the beneficial effect of curcumin in slowing the development of liver cirrhosis.

Deficiency of tenascin-C attenuates liver fibrosis in immune-mediated chronic hepatitis in mice

Tenascin-C (TNC), an extracellular matrix glycoprotein, is upregulated in chronic liver disease. Here, we investigated the contribution of TNC to liver fibrogenesis by comparing immune-mediated hepatitis in wild-type (WT) and TNC-null (TNKO) mice. Eight-week-old BALB/c mice received weekly intravenous injections of concanavalin A to induce hepatitis, and were sacrificed one week after the 3rd, 6th, 9th, and 12th injections. In WT livers, immunohistochemical staining revealed a gradual increase in TNC deposition. TNC mRNA levels also increased sequentially and peaked after the 9th injection. Collagen deposition, stained with picrosirius red, was significantly less intense in TNKO mice than in WT mice, and procollagen I and III transcripts were significantly upregulated in WT mice compared with TNKO mice. Inflammatory infiltrates were most prominent after the 3rd-6th injections in both groups and were less intense in TNKO mice than in WT mice. Interferon-gamma, tumour necrosis factor-alpha, and interleukin-4 mRNA levels were significantly higher in WT mice than in TNKO mice, while activated hepatic stellate cells (HSCs) and myofibroblasts, a cellular source of TNC and procollagens, were more common in WT livers. Transforming growth factor (TGF)-beta1 mRNA expression was significantly upregulated in WT mice, but not in TNKO mice. In conclusion, TNC can promote liver fibrogenesis through enhancement of inflammatory response with cytokine upregulation, HSC recruitment, and TGF-beta expression during progression of hepatitis to fibrosis.

Effect of angiotensin II on the proliferation and migration of hepatic stellate cells

AIM: To explore the changes of the proliferation and migration ability of hepatic stellate cells (HSCs) induced by angiotensin Ⅱ (ANGⅡ).

METHODS: HSCs were incubated in vitro. The proliferation and migration ability of HSCs induced by ANGⅡ at different concentration were observed with MTT assay and Transwell chamber assay, respectively.

RESULTS: The proliferation of HSCs was significantly increased when ANGⅡ was used at the concentrations of 1、2、4、8 and 10 μmol/L in comparison with that in the control cells (F = 2.305, P < 0.05; F = 4.003, 6.833, 8.855, 21.066, P < 0.01). With the increasing of ANGⅡ concentration, the proliferative activity was increased, showing a positive correlation (r = 0.917, P < 0.01). ANGⅡ at the concentrations of 10, 8 and 4 μmol/L markedly induced the migration of HSCs (F = 22.084, 15.155, 10.392, P < 0.01). The migration ability of HSCs was also positively correlated with the concentrations of ANGⅡ (r = 0.952, P < 0.01).

CONCLUSION: ANGⅡ can significantly induce the proliferation and migration of HSCs in a dose-dependent manner.

Signal transduction and activation of hepatic stellate cells

Liver fibrosis, which leads to cirrhosis, occurs as a result of various injurious processes and it is the common pathologic basis of all the chronic hepatic diseases. At present, a good many researches demonstrate that the activation of hepatic stellate cells play a critical role in fibrogenesis. Prolonged liver injury results in hepatocyte damages and secretion of many fibrogenic cytokines such as transforming growth factor-beta 1, angiotensin, and leptin, which triggers the activation of hepatic stellate cells through different intracellular signal transduction pathways. In this article, we reviewed the research advancement in the signal transduction pathway of nuclear receptor and membrane receptor during the activation of hepatic stellate cells.

Bakuchiol-induced caspase-3-dependent apoptosis occurs through c-Jun NH2-terminal kinase-mediated mitochondrial translocation of Bax in rat liver myofibroblasts

Liver fibrosis and cirrhosis may be reversible, possibly through the selective clearance of activated hepatic stellate cells/myofibroblasts by apoptosis. Hepatic stellate cells transdifferentiate into myofibroblast-phenotype cells in culture, a process that recapitulates hepatic stellate cell activation in vivo. Bakuchiol, a prenylated phenolic terpene isolated from the seed of Psoralea corylifolia L. (Leguminosae), reduced activated hepatic stellate cells when treated to rats during liver injury recovery period as demonstrated by alpha-smooth muscle actin immunostaining in rat liver and induced apoptosis in activated hepatic stellate cells/myofibroblasts as demonstrated by DNA fragmentation, activation of caspase-3, release of cytochrome c into the cytoplasm, translocation of Bax into mitochondria, and the proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) in vitro. Bakuchiol-induced apoptosis was prevented by z-DEVD-fmk, a specific inhibitor of caspase-3, and z-VAD-fmk, a general caspase inhibitor, suggesting that bakuchiol-induced apoptosis occurs through a caspase-3-dependent pathway in vitro. Bakuchiol treatment stimulated the activation of extracellular signal-regulated kinase 1/2 (ERK), c-Jun NH2-terminal protein kinase (JNK), and p38 mitogen-activated protein kinases (MAPK) in vitro. Pretreatment with SP600125 attenuated the bakuchiol-induced translocation of Bax into mitochondria, cytochrome c release into the cytosol, caspase-3 activation, and PARP cleavage. In contrast, preincubation with SB203580, a p38 MAPK inhibitor, and U0126, an ERK inhibitor, had no effect on bakuchiol-induced cell death and caspase-3 activity. Taken together, these findings indicate that bakuchiol induces caspase-3-dependent apoptosis through the activation of JNK, followed by Bax translocation into mitochondria in rat liver myofibroblasts.

Polymorphisms of interleukin-1beta in Japanese patients with hepatitis B virus infection

BACKGROUND/AIMS

Hepatitis B virus (HBV) induces liver cirrhosis (LC) and hepatocellular carcinoma (HCC) mainly by causing chronic necro-inflammatory hepatic disease. Our aim was to investigate the relationships between the polymorphisms of the interleukin-1B (IL-1B) promoter region and the interleukin-1 receptor antagonist gene (IL-1RN) and disease progression in an HBV-infected Japanese population.

METHODS

Genomic DNA was extracted from the peripheral blood of 237 HBV carriers. Polymorphisms in IL-1B and IL-1RN were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and PCR with confronting two-pair primers (PCR-CTPP) methods. These polymorphic sites include the promoter regions of IL-1B at positions -511 and -31, and IL-1RN variable tandem repeats.

RESULTS

The IL-1B -31 and -511 loci were in complete linkage disequilibrium, and the frequency of the IL-1B -31 T carrier (IL-1B -31 T/T or T/C) was significantly higher in HBV carriers with LC compared to those without LC (LC; 86.1% vs non-LC; 72.1%, P=0.009). There was no difference in the genotype distribution of the IL-1RN polymorphism.

CONCLUSIONS

This is the first report describing the association between IL-1B polymorphism and HBV-related hepatic fibrosis, and our data suggest that IL-1B polymorphisms may be related to disease progression of HBV-related hepatitis in Japan.

Identification and functional characterization of the hepatic stellate cell CD38 cell surface molecule

The activation of hepatic stellate cells (HSCs) is a critical event in hepatic fibrosis, because these cells are the main producers of extracellular matrix proteins in the liver and contribute to the modulation of inflammatory responses via the secretion of several cytokines and the expression of adhesion molecules. The goal of the present study was to characterize cell surface proteins that regulate HSC activation. To this end, a panel of monoclonal antibodies (mAbs) was generated. mAb 14.27 recognized a protein of 45 kd that was highly expressed on HSCs. Affinity purification of this protein followed by sequencing revealed that protein to be CD38. We subsequently demonstrated that CD38 was constitutively expressed by HSCs and that its expression increased after in vitro and in vivo activation. mAb 14.27 induced an increase in cytosolic Ca2+ levels in HSCs, showing that it functions as an agonistic antibody. Moreover, the effects mediated by the CD38 mAb included induction of the proinflammatory cytokine interleukin-6 and up-regulation of the adhesion molecules intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and neural cell adhesion molecule. Collectively, our data suggest that CD38 can act as a regulator of HSC activation and effector functions.

Alcohol, oxidative stress and free radical damage

The involvement of free radical mechanisms in the pathogenesis of alcoholic liver disease (ALD) is demonstrated by the detection of lipid peroxidation markers in the liver and the serum of patients with alcoholism, as well as by experiments in alcohol-feed rodents that show a relationship between alcohol-induced oxidative stress and the development of liver pathology. Ethanol-induced oxidative stress is the result of the combined impairment of antioxidant defences and the production of reactive oxygen species by the mitochondrial electron transport chain, the alcohol-inducible cytochrome P450 (CYP) 2E1 and activated phagocytes. Furthermore, hydroxyethyl free radicals (HER) are also generated during ethanol metabolism by CYP2E1. The mechanisms by which oxidative stress contributes to alcohol toxicity are still not completely understood. The available evidence indicates that, by favouring mitochondrial permeability transition, oxidative stress promotes hepatocyte necrosis and/or apoptosis and is implicated in the alcohol-induced sensitization of hepatocytes to the pro-apoptotic action of TNF-alpha. Moreover, oxidative mechanisms can contribute to liver fibrosis, by triggering the release of pro-fibrotic cytokines and collagen gene expression in hepatic stellate cells. Finally, the reactions of HER and lipid peroxidation products with hepatic proteins stimulate both humoral and cellular immune reactions and favour the breaking of self-tolerance during ALD. Thus, immune responses might represent the mechanism by which alcohol-induced oxidative stress contributes to the perpetuation of chronic hepatic inflammation. Together these observations provide a rationale for the possible clinical application of antioxidants in the therapy for ALD.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Transforming growth factor-beta differentially regulates oval cell and hepatocyte proliferation

Oval cells are hepatocytic precursors that proliferate in late-stage cirrhosis and that give rise to a subset of human hepatocellular carcinomas. Although liver regeneration typically occurs through replication of existing hepatocytes, oval cells proliferate only when hepatocyte proliferation is inhibited. Transforming growth factor-beta (TGF-beta) is a key inhibitory cytokine for hepatocytes, both in vitro and in vivo. Because TGF-beta levels are elevated in chronic liver injury when oval cells arise, we hypothesized that oval cells may be less responsive to the growth inhibitory effects of this cytokine. To examine TGF-beta signaling in vivo in oval cells, we analyzed livers of rats fed a choline-deficient, ethionine-supplemented (CDE) diet for phospho-Smad2. Phospho-Smad2 was detected in more than 80% of hepatocytes, but staining was substantially reduced in oval cells. Ki67 staining, in contrast, was significantly more common in oval cells than hepatocytes. To understand the inverse relationship between TGF-beta signaling and proliferation in oval cells and hepatocytes, we examined TGF-beta signaling in vitro. TGF-beta caused marked growth inhibition in primary hepatocytes and the AML12 hepatocyte cell line. Two oval cell lines, LE/2 and LE/6, were less responsive. The greater sensitivity of the hepatocytes to TGF-beta-induced growth inhibition may result from the absence of Smad6 in these cells.

CONCLUSION

Our results indicate that oval cells, both in vivo and in vitro, are less sensitive to TGF-beta-induced growth inhibition than hepatocytes. These findings further suggest an underlying mechanism for the proliferation of oval cells in an environment inhibitory to hepatocytic proliferation.

Large hepatitis delta antigen modulates transforming growth factor-beta signaling cascades: implication of hepatitis delta virus-induced liver fibrosis

BACKGROUND & AIMS

Transforming growth factor-beta (TGF-beta) has been implicated in the pathogenesis of liver disease. TGF-beta is involved in liver regeneration and in the fibrotic and cirrhotic transformation with hepatitis viral infection. Hepatitis delta virus (HDV) infection causes fulminant hepatitis and liver cirrhosis. To elucidate the molecular mechanism of HDV pathogenesis, we examined the effects of HDV-encoded-only protein, the small hepatitis delta antigen (SHDAg), and the large hepatitis delta antigen (LHDAg), on TGF-beta- and c-Jun-induced signaling cascades.

METHODS

The effects of either SHDAg or LHDAg on TGF-beta- and c-Jun-induced signaling cascades in Huh7 and Cos7 cells were investigated by luciferase reporter gene assay, immunoprecipitation assay, electrophoretic mobility shift assay, Western blot analysis, and confocal microscopy analysis.

RESULTS

The LHDAg, but not the SHDAg, potentiated TGF-beta- and c-Jun-induced signal activation, and the isoprenylation of LHDAg played a major role in signaling cascades. LHDAg synergistically activated hepatitis B virus X protein-mediated TGF-beta and AP-1 signaling cascades. In addition, LHDAg enhanced the protein expression level of TGF-beta-induced plasminogen activator inhibitor-1.

CONCLUSIONS

LHDAg may induce liver fibrosis through the regulation of TGF-beta-induced signal transductions. This regulation of TGF-beta-mediated signaling is accomplished by the isoprenylation of LHDAg, which is a novel mechanism involved in HDV pathogenesis.

Adult stem cells in progression and therapy of hepatocellular carcinoma

Hepatocellular carcinoma is one of the most aggressive solid tumours associated with poor prognosis. Despite its significance, there is only an elemental understanding of the mechanisms that drive disease pathogenesis, and there are just limited therapy options. The medical community is currently experiencing a wave of enthusiasm for clinical trials, in which adult stem/progenitor cells are used for liver regeneration. This is based on promising results in animal models and encouraging reports from some initial clinical studies. On the other hand, several essential precautions are not being fully addressed. Stem cells may contribute to fibrosis or give rise to hepatic cancer stem cells as a source of hepatocellular carcinoma. This review outlines the current state of knowledge in progression of liver disease and highlights the function of adult stem cells in disease and therapy.

Large hepatitis delta antigen modulates transforming growth factor-beta signaling cascades: implication of hepatitis delta virus-induced liver fibrosis

BACKGROUND & AIMS

Transforming growth factor-beta (TGF-beta) has been implicated in the pathogenesis of liver disease. TGF-beta is involved in liver regeneration and in the fibrotic and cirrhotic transformation with hepatitis viral infection. Hepatitis delta virus (HDV) infection causes fulminant hepatitis and liver cirrhosis. To elucidate the molecular mechanism of HDV pathogenesis, we examined the effects of HDV-encoded-only protein, the small hepatitis delta antigen (SHDAg), and the large hepatitis delta antigen (LHDAg), on TGF-beta- and c-Jun-induced signaling cascades.

METHODS

The effects of either SHDAg or LHDAg on TGF-beta- and c-Jun-induced signaling cascades in Huh7 and Cos7 cells were investigated by luciferase reporter gene assay, immunoprecipitation assay, electrophoretic mobility shift assay, Western blot analysis, and confocal microscopy analysis.

RESULTS

The LHDAg, but not the SHDAg, potentiated TGF-beta- and c-Jun-induced signal activation, and the isoprenylation of LHDAg played a major role in signaling cascades. LHDAg synergistically activated hepatitis B virus X protein-mediated TGF-beta and AP-1 signaling cascades. In addition, LHDAg enhanced the protein expression level of TGF-beta-induced plasminogen activator inhibitor-1.

CONCLUSIONS

LHDAg may induce liver fibrosis through the regulation of TGF-beta-induced signal transductions. This regulation of TGF-beta-mediated signaling is accomplished by the isoprenylation of LHDAg, which is a novel mechanism involved in HDV pathogenesis.

Vitamin E in chronic liver diseases and liver fibrosis

Liver fibrosis may be considered as a dynamic and integrated cellular response to chronic liver injury. The activation of hepatic stellate cells and the consequent deposition of large amounts of extracellular matrix play a major role in the fibrogenic process, but it has been shown that other cellular components of the liver are also involved. Although the pathogenesis of liver damage usually depends on the underlying disease, oxidative damage of biologically relevant molecules might represent a common link between different forms of chronic liver injury and hepatic fibrosis. In fact, oxidative stress-related molecules may act as mediators able to modulate all the events involved in the progression of liver fibrosis. In addition, chronic liver diseases are often associated with decreased antioxidant defenses. Although vitamin E levels have been shown to be decreased in chronic liver diseases of different etiology, the role of vitamin E supplementation in these clinical conditions is still controversial. In fact, the increased serum levels of alpha-tocopherol following vitamin E supplementation not always result in a protective effect on liver damage. In addition, clinical trials have usually been performed in small cohorts of patients, thus making definitive conclusions impossible. At present, treatment with vitamin E or other antioxidant compounds could be proposed for nonalcoholic fatty liver disease (NAFLD), the most frequent hepatic lesion in western countries which can progress to nonalcoholic steatohepatitis and cirrhosis due to the production of large amounts of oxidative stress products. However, although some studies have shown encouraging results, multicentric and long-term clinical trials are needed.

Insulin resistance accelerates a dietary rat model of nonalcoholic steatohepatitis

BACKGROUND & AIMS

The increasing prevalence of nonalcoholic steatohepatitis (NASH) is due to the epidemic of obesity and type 2 diabetes, both of which are associated with insulin resistance.

METHODS

To clarify the causal relationship between insulin resistance and the development of NASH, steatohepatitis was induced in obese diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) and nondiabetic control Long-Evans Tokushima Otsuka (LETO) rats by feeding them a methionine and choline-deficient (MCD) diet. Insulin sensitivity of the rats was altered by adding a high-fat (HF) diet or the peroxisomal-proliferator activated receptor-gamma agonist pioglitazone to the MCD diet.

RESULTS

The MCD diet-induced steatohepatitis was accelerated in OLETF rats after 8 weeks. Steatosis preceded inflammation, which led to fibrosis and the development of steatohepatitis. The hepatic gene expression for transforming growth factor-beta, alpha1 procollagen and plasminogen activator inhibitor-1 was up-regulated in OLETF rats compared with LETO rats. The MCD + HF diet further enhanced insulin resistance and led to rapid development of pre-cirrhosis in OLETF rats by increasing the triglyceride pool, activating stellate cells, and up-regulating gene expression for sterol regulatory element-binding protein-1c and fatty acid synthase in the liver. In contrast, pioglitazone attenuated the MCD diet-induced steatohepatitis in OLETF rats but not in LETO rats by reversing the underlying pathogenesis involved in this model through improvement of insulin resistance. These results confirm a link between insulin resistance and the development/progression of steatohepatitis, at least partly via up-regulation of genes for lipogenesis, inflammation, and fibrogenesis, in animal models.

CONCLUSIONS

Insulin resistance and/or diabetes may accelerate the entire pathologic spectrum of NASH.

Hepatic viscoelastic parameters measured with MR elastography: Correlations with quantitative analysis of liver fibrosis in the rat

PURPOSE

To determine the correlations between the viscoelastic parameters of the liver measured with in vivo MR elastography and quantitative analysis of liver fibrosis.

MATERIALS AND METHODS

MR elastography of the liver was performed in 10 rats with hepatic fibrosis induced by intraperitoneal carbon tetrachloride (CCl(4)) injections and five normal rats. Longitudinal waves of 200 MHz were transmitted into the liver with a mechanical transducer. Wave propagation into the liver was analyzed with a phase-locked spin-echo sequence at 1.5 T. The viscoelastic parameters, obtained with the Voigt model, were correlated with automatic image analysis of the fibrotic areas and with analysis of the hydroxyproline content of the liver.

RESULTS

Substantial correlations were observed between the shear viscoelastic parameters and the percentage of fibrosis at automatic image analysis (r = 0.7, P = 0.005 for the elasticity, and r = 0.8, P = 0.001 for the viscosity) and moderate correlations were seen between the shear viscoelastic parameters and the hydroxyproline content (r = 0.6, P = 0.016 for the elasticity and r = 0.5, P = 0.041 for the viscosity).

CONCLUSION

The viscoelastic parameters of the liver measured with in vivo MR elastography correlate with quantitative analysis of liver fibrosis. These results suggest that MR elastography is a promising noninvasive method to quantify liver fibrosis.

Fibroblast differentiation in wound healing and fibrosis

The contraction of granulation tissue from skin wounds was first described in the 1960s. Later it was discovered that during tissue repair, fibroblasts undergo a change in phenotype from their normal relatively quiescent state in which they are involved in slow turnover of the extracellular matrix, to a proliferative and contractile phenotype termed myofibroblasts. These cells show some of the phenotypic characteristics of smooth muscle cells and have been shown to contract in vitro. In the 1990s, a number of researchers in different fields showed that myofibroblasts are present during tissue repair or response to injury in a variety of other tissues, including the liver, kidney, and lung. During normal repair processes, the myofibroblastic cells are lost as repair resolves to form a scar. This cell loss is via apoptosis. In pathological fibroses, myofibroblasts persist in the tissue and are responsible for fibrosis via increased matrix synthesis and for contraction of the tissue. In many cases this expansion of the extracellular matrix impedes normal function of the organ. For this reason much interest has centered on the derivation of myofibroblasts and the factors that influence their differentiation, proliferation, extracellular matrix synthesis, and survival. Further understanding of how fibroblast differentiation and myofibroblast phenotype is controlled may provide valuable insights into future therapies that can control fibrosis and scarring.

Gene expression during chemically induced liver fibrosis: effect of halofuginone on TGF-beta signaling

Hepatic fibrosis is associated with the activation of stellate cells (HSCs), the major source of extracellular matrix (ECM) proteins. Transforming growth factor-beta (TGF-beta), signaling via Smad3, is the most profibrogenic cytokine and the major promoter of ECM synthesis. Halofuginone, an inhibitor of liver fibrosis, inhibits TGF-beta-dependent Smad3 phosphorylation in human HSCs in culture. We have used transcriptional profiling to evaluate the effect of halofuginone on gene expression during the progression of thioacetamide (TAA)-induced liver fibrosis in the rat and have focused on genes that are associated with TGF-beta. TAA treatment causes alterations in the expression of 7% of liver genes. Halofuginone treatment prevents the changes in the expression of 41% of these genes and results in the inhibition of HSC activation and collagen synthesis. During the early stages of the disease, halofuginone affects genes involved in alcohol, lipid, protein, and phosphate metabolism and cell adhesion and, at later stages, in the cell cycle (cell development, differentiation, cell proliferation, and apoptosis). The activation of TGF-beta-dependent genes, such as tartrate-resistant acid phosphatase, its putative substrate osteopontin, stellate cell activation-association protein, and fibrillin-1, during chemically induced fibrosis is prevented by halofuginone. This study thus highlights the role of TGF-beta signaling in liver fibrosis and especially its potential for pharmacological intervention. Halofuginone, which has demonstrated efficacy and tolerance in animals and humans, could become an effective and novel therapy for liver fibrosis.

Protective effect of verapamil on multiple hepatotoxic factors-induced liver fibrosis in rats

The purpose of the present work was to investigate the effect of verapamil on liver fibrosis induced by multiple hepatotoxic factors in rats. Male Wistar rats were divided into a normal control group, a liver fibrosis model control group, and verapamil groups with different dosages. Multiple hepatotoxic factors including carbon tetrachloride (CCl(4)), ethanol and high cholesterol were used to make the animal model of liver fibrosis. The parameters of serum l-alanine aminotransferase (ALT), liver malondialdehyde and hydroxyproline contents were measured. Samples of the liver obtained by biopsy were subjected to histological and immunohistochemical studies for the expressions of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta(1) (TGF-beta(1)). Results showed that verapamil induced a dose-dependent decrease of serum ALT, liver malondialdehyde and hydroxyproline compared with liver fibrosis model control. Verapamil reduced hepatocyte degeneration and necrosis, and delayed the formation of liver fibrosis. The levels of expression of alpha-SMA and TGF-beta(1) in the hepatic tissue of three of the verapamil-treated groups were significantly less than those of the liver fibrosis model control group. The results showed that verapamil acts against the formation of liver fibrosis, the mechanism might be due to a protective effect for hepatocytes and through decreasing TGF-beta(1) to block the activation of hepatic stellate cells (HSCs) and collagen gene expression.

Pharmacokinetics of a hepatic stellate cell-targeted doxorubicin construct in bile duct-ligated rats

BACKGROUND/AIMS

Inhibition of hepatic stellate cell (HSC) proliferation is a relevant strategy to inhibit liver fibrosis. Coupling of antiproliferative drugs to the HSC-selective drug carrier mannose-6-phosphate-modified human serum albumin (M6PHSA) may lead to cell-selective inhibition of HSC proliferation. We coupled the antiproliferative drug doxorubicin (DOX) to this drug carrier and investigated the pharmacokinetics of this construct in a rat model of liver fibrosis, as well as in cultured HSC.

METHODS/RESULTS

M6PHSA-DOX was cleared from the plasma in a biphasic manner. Upon i.v. injection of 4 microg kg(-1) (tracer), 2 and 20 mg kg(-1), the clearance in the distribution phase of drug disposition (CL(d)) significantly decreased from 9.7+/-0.7 to 4.7+/-2.3 and 1.0+/-0.1 ml kg(-1)min(-1), respectively. This indicates that saturation of clearance mechanisms occurs in this phase of drug disposition, likely reflecting saturable receptor-mediated uptake in the target cells. Gamma-camera studies revealed that the majority of the conjugate accumulated in the liver within 5 min, and immunohistochemical double-staining of liver sections demonstrated co-localization of the construct with HSC-markers. Simulation of the release of DOX from the carrier, after cellular uptake by HSC, showed that a gradual release of the drug takes place over a 9h period. Studies in cultured HSC illustrated that after 24h incubation with the conjugate, DOX was associated with the cell nucleus.

CONCLUSIONS

The rapid distribution of M6PHSA-DOX from the blood to HSC, in combination with the expected gradual release of DOX within these cells, make this construct a promising tool for achieving sustained and selective inhibition of HSC proliferation.

Hypoxia induces the activation of human hepatic stellate cells LX-2 through TGF-beta signaling pathway

Hypoxia is a common environmental stress factor and is also associated with various physiological and pathological conditions such as fibrogenesis. The activation of hepatic stellate cells (HSCs) is the key event in the liver fibrogenesis. In this study, the behavior of human HSCs LX-2 in low oxygen tension (1% O2) was analyzed. Upon hypoxia, the expression of HIF-1alpha and VEGF gene was induced. The result of Western blotting showed that the expression of alpha-SMA was increased by hypoxic stimulation. Furthermore, the expression of MMP-2 and TIMP-1 genes was increased. Hypoxia also elevated the protein expression of the collagen type I in LX-2 cells. The analysis of TGF-beta/Smad signaling pathway showed that hypoxia potentiated the expression of TGF-beta1 and the phosphorylation status of Smad2. Gene expression profiles of LX-2 cells induced by hypoxia were obtained by using cDNA microarray technique.

Antiproliferative effect of salvianolic acid A on rat hepatic stellate cells

Suppression of activation or proliferation, or induction of apoptosis in hepatic stellate cells (HSCs) have been proposed as therapeutic strategies against liver fibrosis. Salvia miltiorrhiza has been reported to exert antifibrotic effects in rats with hepatic fibrosis, but its mechanisms of action remain to be clarified. We have investigated the effects of salvianolic acid A (Sal A), an active principle from S. miltiorrhiza, on the proliferation-related biomarkers in a cell line of rat HSCs (HSC-T6) stimulated with platelet-derived growth factor-BB homodimer (PDGF-BB). DNA synthesis (bromodeoxyuridine (BrdU) incorporation), cell cycle related proteins and apoptosis markers were determined to evaluate the inhibitory effects of Sal A. The results showed that Sal A (1-10 microM) concentration-dependently attenuated PDGF-BB-stimulated proliferation (BrdU incorporation) in HSC-T6 cells. Sal A at 10 microM induced cell apoptosis in PDGF-BB-incubated HSCs, together with a reduction of Bcl-2 protein expression, induction of cell cycle inhibitory proteins p21 and p27, and down-regulation of cyclins D1 and E, suppression of Akt phosphorylation, reduction in PDGF receptor phosphorylation, and an increase in caspase-3 activity. Sal A exerted no direct cytotoxicity on primary hepatocytes and HSC-T6 cells under experimental concentrations. Our results suggested that Sal A inhibited PDGF-BB-activated HSC proliferation, partially through apoptosis induction.

STAT1 inhibits liver fibrosis in mice by inhibiting stellate cell proliferation and stimulating NK cell cytotoxicity

Liver fibrosis, a common scarring response to chronic liver injury, is a precursor to cirrhosis and liver cancer. Here, we identified signal transducer and activator of transcription 1 (STAT1) as an important negative regulator in liver fibrosis. Our findings show that disruption of the STAT1 gene accelerated liver fibrosis and hepatic stellate cell (HSC) proliferation in an in vivo model of carbon tetrachloride (CCl4)-induced liver fibrosis. In vitro treatment with IFN-gamma inhibited proliferation and activation of wild-type HSCs, but not STAT1-/- HSCs. Moreover, compared to wild-type cells, cellular proliferation stimulated by serum or platelet-derived growth factor (PDGF) was enhanced and accelerated in STAT1-/- HSCs, which was partially mediated via elevated PDGF receptor beta expression on such cells. Polyinosinic-polycytidylic acid (poly I:C) or IFN-gamma treatment inhibited liver fibrosis in wild-type mice but not in STAT1-/- mice. Induction of NK cell killing of activated HSCs by poly I:C was attenuated in STAT1-/- mice compared to wild-type mice, which was likely due to reduced NKG2D and TRAIL expression on STAT1-/- NK cells. Finally, activation of TGF-beta/Smad3 signaling pathway was accelerated, whereas induction of Smad7 was diminished in the liver of STAT1-/- mice after CCl4 administration compared to wild-type mice. In conclusion, activation of STAT1 attenuates liver fibrosis through inhibition of HSC proliferation, attenuation of TGF-beta signaling, and stimulation of NK cell killing of activated HSCs. STAT1 could be a new therapeutic target for treating liver fibrosis.

JunD is a profibrogenic transcription factor regulated by Jun N-terminal kinase-independent phosphorylation

JunD is implicated in the regulation of hepatic stellate cell (HSC) activation and liver fibrosis via its transcriptional regulation of the tissue inhibitor of metalloproteinases-1 (TIMP-1) gene. In the present study we found in vivo evidence of a role for JunD in fibrogenesis. Expression of JunD was demonstrated in alpha-SMA-positive activated HSCs of fibrotic rodents and human livers. The junD-/- mice were protected from carbon tetrachloride-induced fibrosis. The livers of injured junD-/- mice displayed significantly reduced formation of fibrotic crosslinked collagen and a smaller number of alpha-SMA-positive HSCs compared with those of wild-type (wt) mice. Hepatic TIMP-1 mRNA expression in injured junD-/- mice was 78% lower and in culture activated junD-/- HSCs was 50%-80% lower than that in wt mice. In examining the signal transduction mechanisms that regulate JunD-dependent TIMP-1 expression, we found a role for phosphorylation of the Ser100 residue of JunD but ruled out JNK as a mediator of this event, suggesting ERK1/2 is utilized. In conclusion, a signaling pathway for the development of fibrosis involves the regulation of TIMP-1 expression by phosphorylated JunD.

Changes of the hepatic proteome in murine models for toxically induced fibrogenesis and sclerosing cholangitis

We investigated the changes in the hepatic proteome in murine models for toxic-induced fibrogenesis and sclerosing cholangitis. A comprehensive comparison of protein changes observed is made and the mechanistical basis of the expression changes is discussed. Hepatic fibrosis was induced by repetitive intraperitoneal CCl4 treatment of BALB/c mice or developed spontaneously in BALB/c-ATP-binding cassette, subfamily B, member 4 (Abcb4) knock out mice. Fibrosis was verified by a morphometric score and assessment of hydroxyproline content of liver tissue, respectively. The innovative difference in-gel electrophoresis (DIGE) technique was used to analyse protein expression levels of the mouse proteome. Results were confirmed by Western blotting and real-time RT-PCR. In CCl4-induced fibrosis 20 out of 40 and in BALB/c-Abcb4(-/-) mice 8 out of 28 differentially expressed proteins were identified utilizing DIGE. Only two proteins, selenium-binding protein (Sbp2) and carbonic anhydrase 3, have been unidirectionally expressed (i.e. down-regulated) in both models. Relevant differences in the pathogenesis of toxically induced liver fibrosis and sclerosing cholangitis exist. The only novel protein with regard to liver fibrosis depicting a unidirectional expression pattern in both animal models was Sbp2. An explicit protein function could not be clarified yet.

Hepatitis B virus promotes angiopoietin-2 expression in liver tissue: role of HBV x protein

The progression of chronic hepatitis B (CHB) is related to fibrosis and to the emergence of intrahepatic anomalous vascular structures. Hepatitis B virus (HBV) X protein transactivator (HBx) may play a significant role in both processes. To analyze how HBV induces vascular growth and remodeling in vivo, we assessed the expression of angiopoietin-2 (Ang2) in liver biopsies from CHB patients by reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry because of the relevant role of Ang2 in vascular development, remodeling, and tumor promotion. In addition, we analyzed the influence of HBx in the expression of Ang2 in HBx-expressing hepatocyte cell lines and in hepatic stellate cells stimulated with conditional medium from HBx-hepatocytes. Ang2 expression was clearly up-regulated at both mRNA and protein levels in the liver of CHB patients, showing an intense staining of inflammatory infiltrates and vascular structures at inflamed portal areas. HBx-expressing hepatocytes and stimulated stellate cells showed a significant induction of Ang2 expression. PI3K inhibitor and antioxidants repressed the 64-kd Ang2 form but further enhanced the inflammation-related 50-kd molecular species. Therefore, HBx could account for the induction of Ang2 observed in CHB, especially the 50-kd form, contributing to pathological angiogenesis and hepatocellular carcinoma progression.

Morphological characterisation of portal myofibroblasts and hepatic stellate cells in the normal dog liver

Background

Hepatic fibrosis is a common outcome of hepatic injury in both man and dog. Activated fibroblasts which develop myofibroblastic characteristics play an essential role in hepatic fibrogenesis, and are comprised of three subpopulations: 1) portal or septal myofibroblasts, 2) interface myofibroblasts and 3) the perisinusoidally located hepatic stellate cells (HSC). The present study was performed to investigate the immunohistochemical characteristics of canine portal myofibroblasts (MF) and HSC in the normal unaffected liver as a basis for further studies on fibrogenesis in canine liver disease.

Results

In the formalin-fixed and paraffin embedded normal canine liver vimentin showed staining of hepatic fibroblasts, probably including MF in portal areas and around hepatic veins; however, HSC were in general negative. Desmin proved to react with both portal MF and HSC. A unique feature of these HSC was the positive immunostaining for alpha-smooth muscle actin (α-SMA) and muscle-specific actin clone HHF35 (HHF35), also portal MF stained positive with these antibodies. Synaptophysin and glial fibrillary acidic protein (GFAP) were consistently negative in the normal canine liver. In a frozen chronic hepatitis case (with expected activated hepatic MF and HSC), HSC were negative to synaptophysin, GFAP and NCAM. Transmission electron microscopy (TEM) immunogold labelling for α-SMA and HHF35 recognized the positive cells as HSC situated in the space of Disse.

Conclusion

In the normal formalin-fixed and paraffin embedded canine liver hepatic portal MF and HSC can be identified by α-SMA, HHF35 and to a lesser extent desmin immunostaining. These antibodies can thus be used in further studies on hepatic fibrosis. Synaptophysin, GFAP and NCAM do not seem suitable for marking of canine HSC. The positivity of HSC for α-SMA and HHF35 in the normal canine liver may eventually reflect a more active regulation of hepatic sinusoidal flow by these HSC compared to other species.

CARMA3/Bcl10/MALT1-dependent NF-kappaB activation mediates angiotensin II-responsive inflammatory signaling in nonimmune cells

Angiotensin II (Ang II) is a peptide hormone that, like many cytokines, acts as a proinflammatory agent and growth factor. After injury to the liver, the hormone assists in tissue repair by stimulating hepatocytes and hepatic stellate cells to synthesize extracellular matrix proteins and secrete secondary cytokines and by stimulating myofibroblasts to proliferate. However, under conditions of chronic liver injury, all of these effects conspire to promote pathologic liver fibrosis. Much of this effect of Ang II results from activation of the proinflammatory NF-kappaB transcription factor in response to stimulation of the type 1 Ang II receptor, a G protein-coupled receptor. Here, we characterize a previously undescribed signaling pathway mediating Ang II-dependent activation of NF-kappaB, which is composed of three principal proteins, CARMA3, Bcl10, and MALT1. Blocking the function of any of these proteins, through the use of either dominant-negative mutants, RNAi, or gene targeting, effectively abolishes Ang II-dependent NF-kappaB activation in hepatocytes. In addition, Bcl10(-/-) mice show defective hepatic cytokine production after Ang II treatment. Evidence also is presented that this pathway activates NF-kappaB through ubiquitination of IKKgamma, the regulatory subunit of the IkappaB kinase complex. These results elucidate a concrete series of molecular events that link ligand activation of the type 1 Ang II receptor to stimulation of the NF-kappaB transcription factor. These findings also uncover a function of the CARMA, Bcl10, and MALT1 proteins in cells outside the immune system.

Protective mechanism of Lygodium flexuosum extract in treating and preventing carbon tetrachloride induced hepatic fibrosis in rats

The protective effect of Lygodium flexuosum extract in preventive and curative treatments of CCl(4) induced fibrosis was quantified. Hepatic fibrosis was induced in male Wistar rats by CCl(4) administration (150 microL/100 gm rat weight, oral) twice a week for 10 weeks. In preventive treatment daily doses of L. flexuosum n-hexane extract (200 mg/kg, p.o) were administered for 10 weeks. In curative treatment L. flexuosum extract (200 mg/kg, p.o) was given for 2 weeks after the establishment of fibrosis for 10 weeks. Treatment with the n-hexane extract (200 mg/kg) reduced the mRNA levels of proinflammatory cytokines, growth factors and other signaling molecules, which are involved in hepatic fibrosis. The expression levels of tumor necrosis factor-alpha, interleukin-1beta, transforming growth factor-beta1, procollagen-I, procollagen-III and tissue inhibitor of metalloproteinase-1 were elevated during carbon tetrachloride administration and reduced the levels to normal by the treatment with the extract treatment. The increased levels of matrix metalloproteinase-13 in extract treated rats were indicative of the protective action of L. flexuosum n-hexane extract. In conclusion, L. flexuosum n-hexane extract functions as a potent fibrosuppresant, effectively reverses carbon tetrachloride-induced hepatic fibrosis in curative treatment and reduces the effects of ongoing toxic liver injury in preventive treatment by promoting extracellular matrix degradation in the fibrotic liver.

Upregulation of the tumor suppressor gene menin in hepatocellular carcinomas and its significance in fibrogenesis

The molecular mechanisms underlying the progression of cirrhosis toward hepatocellular carcinoma were investigated by a combination of DNA microarray analysis and literature data mining. By using a microarray screening of suppression subtractive hybridization cDNA libraries, we first analyzed genes differentially expressed in tumor and nontumor livers with cirrhosis from 15 patients with hepatocellular carcinomas. Seventy-four genes were similarly recovered in tumor (57.8% of differentially expressed genes) and adjacent nontumor tissues (64% of differentially expressed genes) compared with histologically normal livers. Gene ontology analyses revealed that downregulated genes (n = 35) were mostly associated with hepatic functions. Upregulated genes (n = 39) included both known genes associated with extracellular matrix remodeling, cell communication, metabolism, and post-transcriptional regulation gene (e.g., ZFP36L1), as well as the tumor suppressor gene menin (multiple endocrine neoplasia type 1; MEN1). MEN1 was further identified as an important node of a regulatory network graph that integrated array data with array-independent literature mining. Upregulation of MEN1 in tumor was confirmed in an independent set of samples and associated with tumor size (P = .016). In the underlying liver with cirrhosis, increased steady-state MEN1 mRNA levels were correlated with those of collagen alpha2(I) mRNA (P < .01). In addition, MEN1 expression was associated with hepatic stellate cell activation during fibrogenesis and involved in transforming growth factor beta (TGF-beta)-dependent collagen alpha2(I) regulation. In conclusion, menin is a key regulator of gene networks that are activated in fibrogenesis associated with hepatocellular carcinoma through the modulation of TGF-beta response.

Sustained activation of Rac1 in hepatic stellate cells promotes liver injury and fibrosis in mice

Rac, a small, GTP-binding protein in the Rho family, regulates several cellular functions, including the activation of NADPH oxidase, a major intracellular producer of reactive oxygen species (ROS). Hepatic stellate cells (HSCs) isolated from mice that are genetically deficient in NADPH oxidase produce less ROS, and their activation during chronic liver injury is abrogated, resulting in decreased liver fibrosis. Therefore, we hypothesized that HSC ROS production and activation would be enhanced, and fibrosis worsened, by increasing Rac expression in HSCs. To achieve this, we used transgenic mice that express constitutively active human Rac1 under the control of the alpha-smooth muscle actin (alpha-sma) promoter, because alpha-sma expression is induced spontaneously during HSC activation. Transgene expression was upregulated progressively during culture of primary Rac-transgenic HSCs, and this increased HSC ROS production as well as expression of activation markers and collagen. Similarly, Rac mice treated with carbon tetrachloride (CCl(4)) accumulated greater numbers of activated HSCs and had more liver damage, hepatocyte apoptosis, and liver fibrosis-as well as higher mortality-than CCl(4)-treated wild-type mice. In conclusion, sustained activation of Rac in HSCs perpetuates their activation and exacerbates toxin-induced liver injury and fibrosis, prompting speculation that Rac may be a therapeutic target in patients with cirrhosis.

A role for serotonin (5-HT) in hepatic stellate cell function and liver fibrosis

Hepatic stellate cells (HSCs) are key cellular components of hepatic wound healing and fibrosis. There is emerging evidence that the fibrogenic function of HSCs may be influenced by neurochemical and neurotrophic factors. This study addresses the potential for the serotonin (5-HT) system to influence HSC biology. Rat and human HSCs express the 5-HT1B, 5-HT1F 5-HT2A 5-HT2B, and 5-HT7 receptors, with expression of 5-HT1B 5-HT2A and 5-HT2B being induced on HSC activation. Induction of 5-HT2A and 5-HT2B was 106+/-39- and 52+/-8.5-fold that of quiescent cells, respectively. 5-HT2B was strongly associated with fibrotic tissue in diseased rat liver. Treatment of HSCs with 5-HT2 antagonists suppressed proliferation and elevated their rate of apoptosis; by contrast 5-HT was protective against nerve growth factor-induced apoptosis. 5-HT synergized with platelet-derived growth factor to stimulate increased HSC proliferation. HSCs were shown to express a functional serotonin transporter and to participate in both active uptake and release of 5-HT. We conclude that HSCs express key regulatory components of the 5-HT system enabling them to store and release 5-HT and to respond to the neurotransmitter in a profibrogenic manner. Antagonists that selectively target the 5-HT class of receptors may be exploited as antifibrotic drugs.

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Resolving fibrosis in the diseased liver: translating the scientific promise to the clinic

Liver fibrosis and its end-stage disease cirrhosis are a major cause of mortality and morbidity throughout the world. Fibrosis is a response to chronic liver injury or infection that if unabated leads to the replacement of normal functional liver tissue with scar tissue. Basic research over the past decade has generated a vastly improved knowledge of the cell and molecular biology of liver fibrosis that provides a framework on which to design and develop therapeutics. The field has also witnessed a genuine paradigm shift from the original dogma that liver fibrosis is only ever a progressive process, to the new understanding that liver fibrosis even in an advanced stage can be reversible. There is therefore renewed optimism that liver fibrosis may be cured providing that we develop therapies that halt the fibrogenic process and encourage the natural regenerative properties of the liver. The key to the design of effective therapeutics will be to exploit the ongoing discoveries pertaining to the biology and function of fibrogenic hepatic myofibroblasts and their interplay with other liver cells and with the hepatic extracellular matrix. This review provides a critique of those discoveries in basic research that provide the most promise for translation to the clinic. In addition, we review the latest developments in the search for minimal invasive diagnostic tests for fibrosis that will be essential for determining the efficacy of anti-fibrotic drugs.

Liver transduction with a simian virus 40 vector encoding insulin-like growth factor I reduces hepatic damage and the development of liver cirrhosis

Liver transplantation is the only treatment for advanced liver cirrhosis. Therapies halting the progression of the disease are urgently needed. Administration of recombinant insulin-like growth factor-I (rIGF-I) induces hepatoprotective effects in experimental cirrhosis. Therefore, we analyzed the efficacy of a recombinant simian virus 40 vector (rSV40) encoding IGF-I (rSVIGF-I) to prevent cirrhosis progression. First, transgene expression was evaluated in mice injected with rSV40 encoding luciferase, which showed long-term hepatic expression of the transgene. Interestingly, luciferase expression increased significantly in CCl(4)-damaged livers and upon IGF-I administration, thus liver injury and IGF-I expression from rSVIGF-I should favor transgene expression. rSVIGF-I therapeutic efficacy was studied in rats where liver cirrhosis was induced by CCl(4) inhalation during 36 weeks. At the end of the study, the hepatic levels of IGF-I and IGF-binding protein 3 were higher in rSVIGF-I-treated rats than in control cirrhotic animals. Cirrhotic rats treated with rSVIGF-I had reduced serum bilirubin, transaminases and liver fibrosis scores and increased hepatic expression of hepatocyte growth factor and STAT3alpha as compared to cirrhotic animals. Furthermore, cirrhotic animals showed testis atrophy and altered spermatogenesis, whereas testicular size and histology were normal in cirrhotic rats that received rSVIGF-I. Therefore, rSV40-mediated sustained expression of IGF-I in the liver slowed cirrhosis progression.

Four whole-istic aspects of schistosome granuloma biology: fractal arrangement, internal regulation, autopoietic component and closure

This paper centers on some whole-istic organizational and functional aspects of hepatic Schistosoma mansoni granuloma, which is an extremely complex system. First, it structurally develops a collagenic topology, originated bidirectionally from an inward and outward assembly of growth units. Inward growth appears to be originated from myofibroblasts derived from small portal vessel around intravascular entrapped eggs, while outward growth arises from hepatic stellate cells. The auto-assembly of the growth units defines the three-dimensional scaffold of the schistosome granulomas. The granuloma surface irregularity and its border presented fractal dimension equal to 1.58. Second, it is internally regulated by intricate networks of immuneneuroendocrine stimuli orchestrated by leptin and leptin receptors, substance P and Vasoactive intestinal peptide. Third, it can reach the population of +/- 40,000 cells and presents an autopoietic component evidenced by internal proliferation (Ki-67+ Cells), and by expression of c-Kit+ Cells, leptin and leptin receptor (Ob-R), granulocyte-colony stimulating factor (G-CSF-R), and erythropoietin (Epo-R) receptors. Fourth, the granulomas cells are intimately connected by pan-cadherins, occludin and connexin-43, building a state of closing (granuloma closure). In conclusion, the granuloma is characterized by transitory stages in such a way that its organized structure emerges as a global property which is greater than the sum of actions of its individual cells and extracellular matrix components.

Hepatic histology in obese patients undergoing bariatric surgery

BACKGROUND/AIMS

Obesity is one of the most important clinical associations with non-alcoholic steatohepatitis (NASH). Our aim was to assess the prevalence of non-alcoholic fatty liver disease (NAFLD)/NASH in morbidly obese patients and the risk factors to more aggressive liver disease in this population.

METHODS

Review of available studies on prevalence of NAFLD/NASH in severely obese patients submitted to bariatric surgery.

RESULTS

Twelve observational and transversal studies were included, with consecutive recruitment, and prospective evaluation of data, summing 1620 patients with severe obesity. Prevalence of steatosis and NASH was 91% (range: 85-98%) and 37% (24-98%), respectively, with unexpected cirrhosis in 1.7% (1-7%). NASH was not related with age or body mass index, but there was an association between male sex and NASH/hepatic fibrosis. Diabetes mellitus and insulin resistance were the conditions most frequently associated with NASH, and hypertension with advanced hepatic fibrosis.

CONCLUSIONS

There is a very high prevalence of NAFLD in asymptomatic morbidly obese patients, more than one-third presenting histological criteria for NASH. This review underscores the large variations in prevalence of NASH between studies, calling for the need for a better agreement in the use of the histological criteria.

Fibrosis as an end point for clinical trials in liver disease: a report of the international fibrosis group

Deaths due to the consequences of advanced liver fibrosis and cirrhosis remain a significant cause of mortality worldwide. Biologically plausible pathways involved in hepatic fibrogenesis have also led to the identification of numerous preclinical and clinical compounds that have received great interest as potential future therapeutic agents for patients with liver fibrosis. With this in mind, stake holders from academia, regulatory agencies, clinicians, and the pharmaceutical industry met to understand and discuss the many complex issues involved in developing potential therapeutic agents which act primarily through modifying fibrosis and to discuss appropriate end points for clinical trials in these patient populations. In this article, we summarize those discussions and attempt to highlight many of the hurdles and unanswered questions as we attempt to move forward and develop therapies to combat liver fibrosis.

PPARgamma agonists prevent TGFbeta1/Smad3-signaling in human hepatic stellate cells

PPARgamma agonists inhibit liver fibrosis, but the mechanisms involved are uncertain. We hypothesized that PPARgamma agonists inhibit transforming growth factor (TGF)beta1-activation of TGFbeta receptor (TGFbetaR)-1 signaling in quiescent stellate cells, thereby abrogating Smad3-dependent induction of extracellular matrix (ECM) genes, such as PAI-1 and collagen-1alphaI. To test this, human HSC were cultured to induce a quiescent phenotype, characterized by lipid accumulation and PPARgamma expression and transcriptional activity. These adipocytic HSC were then treated with TGFbeta1+/-a TGFbetaR-1 kinase inhibitor (SB431542) or a PPARgamma agonist (GW7845). TGFbeta1 caused dose- and time-dependent increases in Smad3 phosphorylation, followed by induction of collagen and PAI-1 expression. Like the TGFbetaR-1 kinase inhibitor, the PPARgamma agonist caused dose-dependent inhibition of all of these responses without effecting HSC proliferation or viability. Thus, the anti-fibrotic actions of PPARgamma agonists reflect their ability to inhibit TGFbeta1-TGFbetaR1 signaling that initiates ECM gene expression in quiescent HSC.

Integration of technologies for hepatic tissue engineering

The liver is the largest internal organ in the body, responsible for over 500 metabolic, regulatory, and immune functions. Loss of liver function leads to liver failure which causes over 25,000 deaths/year in the United States. Efforts in the field of hepatic tissue engineering include the design of bioartificial liver systems to prolong patient's lives during liver failure, for drug toxicity screening and for the study of liver regeneration, ischemia/reperfusion injury, fibrosis, viral infection, and inflammation. This chapter will overview the current state-of-the-art in hepatology including isolated perfused liver, culture of liver slices and tissue explants, hepatocyte culture on collagen "sandwich" and spheroids, coculture of hepatocytes with non-parenchymal cells, and the integration of these culture techniques with microfluidics and reactor design. This work will discuss the role of oxygen and medium composition in hepatocyte culture and present promising new technologies for hepatocyte proliferation and function. We will also discuss liver development, architecture, and function as they relate to these culture techniques. Finally, we will review current opportunities and major challenges in integrating cell culture, bioreactor design, and microtechnology to develop new systems for novel applications.