Hepatitis C virus core and nonstructural proteins induce fibrogenic effects in hepatic stellate cells

Immunopathogenesis in hepatitis C virus cirrhosis

HCV (hepatitis C virus) has a high propensity to persist and to cause chronic hepatitis C, eventually leading to cirrhosis. Since HCV itself is not cytopathic, liver damage in chronic hepatitis C is commonly attributed to immune-mediated mechanisms. HCV proteins interact with several pathways in the host's immune response and disrupt pathogen-associated pattern recognition pathways, interfere with cellular immunoregulation via CD81 binding and subvert the activity of NK (natural killer) cells as well as CD4(+) and CD8(+) T-cells. Finally, HCV-specific T-cells become increasingly unresponsive and apparently disappear, owing to several possible mechanisms, such as escape mutations in critical viral epitopes, lack of sufficient help, clonal anergy or expansion of regulatory T-cells. The role of neutralizing antibodies remains uncertain, although it is still possible that humoral immunity contributes to bystander damage of virally coated cells via antibody-dependent cellular cytotoxicity. Cytotoxic lymphocytes kill HCV-infected cells via the perforin/granzyme pathway, but also release Fas ligand and inflammatory cytokines such as IFNgamma (interferon gamma). Release of soluble effector molecules helps to control HCV infection, but may also destroy uninfected liver cells and can attract further lymphocytes without HCV specificity to invade the liver. Bystander damage of these non-specific inflammatory cells will expand the tissue damage triggered by HCV infection and ultimately activate fibrogenesis. A clear understanding of these processes will eventually help to develop novel treatment strategies for HCV liver disease, independent from direct inhibition of HCV replication.

A specific gene-expression signature quantifies the degree of hepatic fibrosis in patients with chronic liver disease

AIM: To study a more accurate quantification of hepatic fibrosis which would provide clinically useful information for monitoring the progression of chronic liver disease.

METHODS: Using a cDNA microarray containing over 22 000 clones, we analyzed the gene-expression profiles of non-cancerous liver in 74 patients who underwent hepatic resection. We calculated the ratio of azan-stained: total area, and determined the morphologic fibrosis index (MFI), as a mean of 9 section-images. We used the MFI as a reference standard to evaluate our method for assessing liver fibrosis.

RESULTS: We identified 39 genes that collectively showed a good correlation (r > 0.50) between gene-expression and the severity of liver fibrosis. Many of the identified genes were involved in immune responses and cell signaling. To quantify the extent of liver fibrosis, we developed a new genetic fibrosis index (GFI) based on gene-expression profiling of 4 clones using a linear support vector regression analysis. This technique, based on a supervised learning analysis, correctly quantified the various degrees of fibrosis in both 74 training samples (r = 0.76, 2.2% vs 2.8%, P < 0.0001) and 12 independent additional test samples (r = 0.75, 9.8% vs 8.6%, P < 0.005). It was far better in assessing liver fibrosis than blood markers such as prothrombin time (r = -0.53), type IV collagen 7s (r = 0.48), hyaluronic acid (r = 0.41), and aspartate aminotransferase to platelets ratio index (APRI) (r = 0.38).

CONCLUSION: Our cDNA microarray-based strategy may help clinicians to precisely and objectively monitor the severity 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.

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.

New therapies in hepatitis C virus and chronic liver disease: antifibrotics

Fibrotic liver disease occurs after any of the various forms of injury to the liver. Fibrosis is a critical factor leading to hepatic dysfunction and portal hypertension and its complications. The fibrogenic cascade is complex but leads to accumulation of extracellular matrix proteins, followed by nodular fibrosis, tissue contraction, and alteration in blood flow. A critical concept emerging is that activation of effector cells, which produce extracellular matrix, underlies the fibrogenic process. The aggregate data has not only helped lead to an understanding of the pathophysiologic basis of hepatic fibrogenesis, but it has also provided an important context with which to base novel antifibrotic therapy.

Hepatitis C virus core protein blocks interferon signaling by interaction with the STAT1 SH2 domain

Emerging data have indicated that hepatitis C virus (HCV) subverts the host antiviral response to ensure its persistence. We previously demonstrated that HCV protein expression suppresses type I interferon (IFN) signaling by leading to the reduction of phosphorylated STAT1 (P-STAT1). We also demonstrated that HCV core protein directly bound to STAT1. However, the detailed mechanisms by which HCV core protein impacts IFN signaling components have not been fully clarified. In this report, we show that the STAT1 interaction domain resides in the N-terminal portion of HCV core (amino acids [aa] 1 to 23). This domain is also required to produce P-STAT1 reduction and inhibit IFN signaling transduction. Conversely, the C-terminal region of STAT1, specifically the SH2 domain (aa 577 to 684), is required for the interaction of HCV core with STAT1. The STAT1 SH2 domain is critical for STAT1 hetero- or homodimerization. We propose a model by which the binding of HCV core to STAT1 results in decreased P-STAT, blocked STAT1 heterodimerization to STAT2, and, therefore, reduced IFN-stimulated gene factor-3 binding to DNA and disrupted IFN-stimulated gene transcription.

Dengue virus induces expression of CXC chemokine ligand 10/IFN-gamma-inducible protein 10, which competitively inhibits viral binding to cell surface heparan sulfate

Dengue virus is an arthropod-borne flavivirus that causes a mild febrile illness, dengue fever, or a potentially fatal syndrome, dengue hemorrhagic fever/dengue shock syndrome. Chemokines primarily orchestrate leukocyte recruitment to the areas of viral infection, which makes them critical mediators of immune and inflammatory responses. In the present study, we investigated the induction and function of chemokines in mice early after infection with dengue virus in vivo. We found that CXCL10/IFN-gamma-inducible protein 10 (IP-10) expression was rapidly and transiently induced in liver following infection. The expressed CXCL10/IP-10 likely mediates the recruitment of activated NK cells, given that anti-CXCL10/IP-10-treated mice showed diminished NK cell infiltration and reduced hepatic expression of effector molecules in activated NK cells after dengue virus infection. Of particular interest, we found that CXCL10/IP-10 also was able to inhibit viral binding to target cells in vitro. Further investigation revealed that various CXCL10/IP-10 mutants, in which the residues that mediate the interaction between the chemokine and heparan sulfate were substituted, failed to exert the inhibitory effect on dengue binding, which suggests that CXCL10/IP-10 competes with dengue virus for binding to heparan sulfate on the cell surface. Moreover, subsequent plaque assays showed that this inhibition of dengue binding blocked viral uptake and replication. The inhibitory effect of CXCL10/IP-10 on the binding of dengue virus to cells may represent a novel contribution of this chemokine to the host defense against viral infection.

Transcriptional regulation of stellate cell activation

The identification of activated hepatic stellate cells and related cell types as key fibrogenic effectors during liver injury has led to intense evaluation of transcriptional events underlying their behavior. While initial studies focused on characterizing interactions between transcription factors and regulatory regions within gene promoters, epigenetic mechanisms have emerged as major determinants of gene activation and repression, in particular histone acetylation and promoter methylation, as well as other complex conditional interactions that underlie global changes in gene expression. Three examples are provided that illustrate how stellate cell activation may be controlled by widely divergent regulatory pathways, including alternative splicing of a growth inhibitory transcription factor (Kruppel-like factor-6), epigenetic regulation of a factor regulating stellate cell survival (nuclear factor kappaB), and regulation of a transcription factor whose expression maintains stellate cell quiescence (LIM homeobox gene 2 [Lhx2]). These complex cascades illustrate how clarifying the finely tuned interdependent layers of transcriptional, translational, post-translational and epigenetic gene regulation in stellate cells is raising new prospects for therapy of hepatic fibrosis.

Hepatic fibrosis, stellate cells, and portal hypertension

Hepatic fibrogenesis is the common result of injury to the liver. It is believed to be a critical factor that leads to hepatic dysfunction and may be important in portal hypertension. The fibrogenic response is a complex process in which accumulation of extracellular matrix proteins, tissue contraction, and alteration in blood flow are prominent. A critical event in fibrogenesis is activation of resident perisinusoidal cells that are termed "hepatic stellate cells". Stellate cell activation is characterized by many important phenotypes, including enhanced extracellular matrix synthesis and prominent contractility. Given the central role of stellate cell activation in hepatic fibrogenesis (and portal hypertension), effective therapy for hepatic fibrogenesis is most likely will be directed at this event.

Reliability of total overnight salivary caffeine assessment (TOSCA) for liver function evaluation in compensated cirrhotic patients

BACKGROUND AND AIMS

Systemic caffeine clearance is considered the gold standard for phenotyping cytochrome P450 1A2 in epidemiological studies, and has been recommended for the non-invasive assessment of liver function in chronic liver disease. Our aim was to find a valid, simple and reliable alternative to this method, and therefore focused our attention on the measurement of an unique salivary caffeine concentration, without drug exposure.

METHODS

Our evaluation included 36 healthy controls, 47 patients with compensated liver cirrhosis of viral origin, and 48 obese and diabetic patients with cryptogenetic (likely metabolic) cirrhosis. All shared the same caffeine consumption habits (regular daily use of caffeinated beverages, mainly coffee). The total overnight salivary caffeine assessment (TOSCA) was determined by using a single-point concentration of salivary caffeine, after an overnight period of abstinence.

RESULTS

Daily routine caffeine intake of our population was adequate for studying the TOSCA. This single-point concentration correlated well with caffeine clearance, measured by salivary concentrations of caffeine. Mean TOSCA in cirrhotic patients was significantly higher than in controls (p<0.001; sensitivity (%) 84.2 and specificity (%) 97.2; negative likelihood ratio=0.16 and positive likelihood ratio=30.32). A cut-off set at 4.2 microg/ml (sensitivity (%) 95.8 and specificity (%) 68.1; negative likelihood ratio=0.06 and positive likelihood ratio=3.0) successfully differentiated the type of cirrhosis. Rapid (with higher metabolism of caffeine) metabolizers were more frequent in the group of patients with cirrhosis of metabolic origin (70.8%; p<0.0001), and the opposite was true for the group of patients with cirrhosis of viral origin, which comprised many poor metabolizers (85.1%; p<0.001). Serum transforming growth factor-beta 1 concentration, mirroring ongoing fibrosis, ranked high in poor metabolizers. The association between overnight assessment and homeostasis model assessment in rapid metabolizers could result from similar roles for cytochrome P450 1A2 and insulin resistance in determining metabolic liver cirrhosis.

CONCLUSION

The TOSCA, although differential between the viral and metabolic etiologies, could be considered a good diagnostic use to verify the presence and eventually the type of compensated liver cirrhosis.

Viral hepatitis and liver cancer: the case of hepatitis C

Chronic infection with the hepatitis C virus (HCV) is a major risk factor for the development of hepatocellular carcinoma (HCC) worldwide. The pathogenesis of HCC in HCV infection has extensively been analysed. Hepatitis C virus-induced chronic inflammation and the effects of cytokines in the development of fibrosis and liver cell proliferation are considered as one of the major pathogenic mechanisms. Increasing experimental evidence suggests that HCV contributes to HCC by directly modulating pathways that promote the malignant transformation of hepatocytes. Hepatitis C virus is an RNA virus that does not integrate into the host genome but HCV proteins interact with many host-cell factors well beyond their roles in the viral life cycle and are involved in a wide range of activities, including cell signaling, transcription, cell proliferation, apoptosis, membrane rearrangements, vesicular trafficking and translational regulation. At least four of the HCV gene products, namely HCV core, NS3, NS4B and NS5A, have been shown to exhibit transformation potential in tissue culture and several potentially oncogenic pathways have been shown to be altered by the expression of HCV proteins. Both HCV core and NS5A induce the accumulation of wild-type beta-catenin and the Wnt-beta-catenin pathway emerges as a common target for HCV (and HBV) in human HCCs, also independently from axin/beta-catenin gene mutations. Induction of both endoplasmic reticulum stress and oxidative stress by HCV proteins might also contribute to HCV transformation. Most of the putative transforming functions of the HCV proteins have been defined in artificial cellular systems, which may not be applicable to HCV infection in vivo, and still need to be established in relevant infection and disease models.

Non invasive fibrosis biomarkers reduce but not substitute the need for liver biopsy

Chronic liver diseases are very common worldwide, particularly those linked to viral hepatitis and to alcoholic and non-alcoholic fatty liver. Their natural history is variable and long-term evolution differs in individual patients. Optimised clinical management of compensated chronic liver diseases requires precise definition of the stage of liver fibrosis, the main determinant of prognosis and of most therapeutic decisions. Liver biopsy is the gold standard for assessment of hepatic fibrosis. However, it is invasive with possible complications, costly and prone to sampling errors. Many non-invasive markers of liver fibrosis have been recently proposed and assessed in the clinical setting as surrogates of liver biopsy. Direct markers are based on biochemical parameters directly linked to fibrogenesis while indirect markers use simple or more sophisticated parameters that correlate with liver fibrosis stages. Non-invasive markers of liver fibrosis have been tested in different forms of chronic liver disease and showed variable diagnostic performance, but accuracy rarely was above 75%-80%. Better results were obtained when markers were combined. On this line, we have recently proposed a set of algorithms that combine sequentially indirect non-invasive markers of liver fibrosis, reaching 90%-95% diagnostic accuracy with significant reduction in the need for liver biopsy. Based on available evidence, it can be anticipated that non-invasive markers of liver fibrosis and their combined use will soon become a most useful tool in the clinical management of many forms of chronic liver disease. However, their implementation is expected to reduce, but not to completely eliminate, the need for liver biopsy.

Identification of two gene variants associated with risk of advanced fibrosis in patients with chronic hepatitis C

BACKGROUND & AIMS

Previously identified clinical risk factors such as sex, alcohol consumption, and age at infection do not accurately predict which patients with chronic hepatitis C (CHC) will develop advanced fibrosis (bridging fibrosis and cirrhosis). The aim of this study was to identify genetic polymorphisms that can predict the risk of advanced fibrosis in patients with CHC.

METHODS

A total of 916 subjects with CHC was enrolled from 2 centers. A gene-centric disease association study of 24,832 putative functional, single nucleotide polymorphisms (SNPs) was performed. Of the 1609 SNPs that were significantly associated (P </= .05) with advanced fibrosis in the discovery cohort (University of California San Francisco [UCSF], N = 433), the first batch of 100 SNPs were selected for validation in the replication cohort (Virginia Commonwealth University [VCU], N = 483).

RESULTS

A missense SNP in the DEAD box polypeptide 5 (DDX5) gene was significantly associated with an increased risk of advanced fibrosis in both the UCSF and the VCU cohorts (OR, 1.8 and 2.2, respectively). Two diplotype groups, carrying the haplotypes composed of the DDX5 SNP and 2 neighboring POLG2 SNPs were also significantly associated with an increased risk of advanced fibrosis and had comparable or better risk estimates. In addition, a missense SNP in the carnitine palmitoyltransferase 1A (CPT1A) gene was associated with a decreased risk of advanced fibrosis in both the UCSF and the VCU cohorts (OR, 0.3 and 0.6, respectively).

CONCLUSIONS

Subjects with CHC carrying DDX5 minor allele or DDX5-POLG2 haplotypes are at an increased risk of developing advanced fibrosis, whereas those carrying the CPT1A minor allele are at a decreased risk.

Mechanisms of alcohol-induced hepatic fibrosis: a summary of the Ron Thurman Symposium

This report is a summary of Ron Thurman Symposium on the Mechanisms of Alcohol-Induced Hepatic Fibrosis which was organized by The National Institutes of Health in Santa Barbara, California, June 25, 2005. The Symposium and this report highlight the unique aspects by which drinking alcoholic beverages may result in hepatic fibrosis. Acetaldehyde, the first metabolite of ethanol, can upregulate transcription of collagen I directly as well as indirectly by upregulating the synthesis of transforming growth factor-beta 1 (TGF-beta1). Reactive oxygen species (ROS) generated in hepatocytes by alcohol metabolism can activate collagen production in hepatic stellate cells (HSCs) in a paracrine manner. Alcohol-induced hepatocyte apoptotic bodies can be phagocytosed by HSCs and Kupffer cells and result in increased expression of TGF-beta1 and subsequent HSC activation. Kupffer cells may contribute to the activation of HSCs by releasing ROS and TGF- beta1. Innate immunity may suppress hepatic fibrosis by killing activated HSCs and blocking TGF-beta1 signaling. In patients infected with hepatitis C virus (HCV), alcohol may promote hepatic fibrosis by suppressing innate immunity. HCV core and non-structural proteins contribute to HCV-induced hepatic fibrosis. Alcohol and HCV together may promote hepatic fibrosis through increased oxidative stress and upregulation of fibrogenic cytokines. The inactive aldehyde dehydrogenase (ALDH2) and the super-active alcohol dehydrogenase (ADH2) alleles may promote hepatic fibrosis through increased accumulation of acetaldehyde in the liver. Hepatic fibrosis can be reversed by inducing selective apoptosis or necrosis of activated HSCs, or by reverse trans-differentiation of activated HSCs into the quiescent phenotype.

Construction of eukaryotic expression plasmid containing HCV NS3 segment and protein expression in human HL-7702 hepatocytes

AIM: To construct the eukaryotic expression plasmid containing HCV NS3 segment and to analyze the expression of NS3 protein in normal human hepatocyte HL-7702.

METHODS: We amplified HCV NS3 fragment from plasmid pBRTM/HCV 1-3011 containing the whole length of HCV genome, recombined it with expression vector pcDNA3.1(-) to form the eukaryotic expression vector pcDNA3.1(-)/NS3, and transfected human HL-7702 hepatocytes with the recombined plasmid by cationic polymers. The expressed HCV NS3 protein was detected and analyzed by immunohistochemical method and Western blot.

RESULTS: The amplified NS3 fragments had correct molecule weight and sequence. The successfully constructed eukaryotic expression plasmids were transfected to HL-7702 cells. The expressed NS3 proteins had correct molecular weight 70000.

CONCLUSION: Eukaryotic expression vector pcDNA3.1 (-)/NS3 containing NS3 segment of HCV can be constructed, the sequence of NS3 fragments is consistent with the template. Normal human HL-7702 hepatocytes can efficiently express specific HCV NS3 protein in vitro.

Hepatitis C -- identifying patients with progressive liver injury

Hepatitis C follows a variable course with some patients developing progressive liver fibrosis, cirrhosis and hepatocellular carcinoma, while others have minimal or no significant liver disease after decades of infection. Studies have identified both host and viral factors associated with disease progression. The importance of general factors such as age at infection, gender, immune status and alcohol consumption has long been recognized; however recently, polymorphisms in a wide array of genes have also been shown to be associated with progressive fibrosis. How specific viral proteins may contribute to disease progression has also been studied. This review highlights what is currently known about the factors associated with progressive liver injury in patients with hepatitis C. A greater understanding of the determinants of disease progression will hopefully lead to improved utilization of existing treatments and ultimately may aid in identification of new therapeutic targets.

Effect of pegylated interferon alpha 2b plus ribavirin treatment on plasma transforming growth factor-β1, metalloproteinase-1, and tissue metalloproteinase inhibitor-1 in patients with chronic hepatitis C

AIM: To evaluate the effect of antiviral treatment on plasma levels of transforming growth factor-β1 (TGF-β1), metalloproteinase 1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) in patients with chronic hepatitis C.

METHODS: TGF-β1, MMP-1, and TIMP-1 plasma concentrations were measured by an enzyme immunoassay in 28 patients, during 48 wk of treatment with pegylated interferon-alpha 2b (PEG-IFN-α2b) plus ribavirin (RBV) and after 24 wk of follow-up. Patients were divided into two groups: responders (R) and non-responders (NR) related to achieved sustained virologic response. Normal values were evaluated in plasma samples of 13 healthy volunteers.

RESULTS: Baseline plasma concentrations of TGF-β1 and TIMP-1 (30.9±3.7 and 1 506±61 ng/mL respectively) measured in all subjects significantly exceeded the normal values (TGF-β1: 18.3±1.6 ng/mL and TIMP-1: 1 102±67 ng/mL). In contrast, pretreatment MMP-1 mean level (6.5±0.9 ng/mL) was significantly lower than normal values (11.9±0.9 ng/mL). Response to the treatment was observed in 12 patients (43%). TGF-β1 mean concentration measured during the treatment phase decreased to the control level in both groups. However at wk 72, values of NR patients increased and became significantly higher than in R group. TIMP-1 concentrations in R group decreased during the treatment to the level similar to normal. In NR group, TIMP-1 remained significantly elevated during treatment and follow-up phase and significant difference between both groups was demonstrated at wk 48 and 72. MMP-1 levels were significantly decreased in both groups at baseline. Treatment caused rise of its concentration only in the R group, whereas values in NR group remained on the level similar to baseline. Statistically significant difference between groups was noted at wk 48 and 72.

CONCLUSION: These findings support the usefulness of TGF-β1, TIMP-1, and MMP-1 in the management of chronic hepatitis C. Elevated TIMP-1 and low MMP-1 plasma concentrations during antiviral therapy may indicate medication failure.

Cu-Zn super oxide dismutase as a potential antifibrotic drug for hepatitis C related fibrosis

Liver fibrosis plays a pivotal role in liver function impairment and is a feature of chronic infection by hepatitis C virus (HCV). Ten to 20% of patients progress to cirrhosis leading to an increased risk of liver failure or hepatocellular carcinoma (HCC). Recent advances have culminated in clear evidence that fibrosis can be reversible, and in expectation that effective anti-fibrotic therapy will improve the prognosis. Among the different cellular pathways involved in fibrosis, the transforming growth factor-beta1 (TGF-beta1) signaling plays a major role. Increases of TGF-beta1 expression is associated with fibrotic diseases and this cytokine could be a target for an antifibrotic drug. Clinical results on radiation-induced fibrosis have brought some evidences that Cu-Zn SOD (SOD1) could be an anti-fibrotic drug. Its therapeutic effect could be related to a down-regulation of TGF-beta1 as proved in a well characterized pig model of radiation induced fibrosis, where the efficacy of Cu-Zn SOD has been shown in reversing fibrosis. Using 3-D skin co-culture of fibroblasts from this pig model, it was showed that SOD significantly reduces the expression of the TGFbeta1, both at the mRNA and protein level. An experimental work could be undertaken to validate the Cu-Zn SOD as an anti-fibrotic drug, using HCV core protein expressing transgenic mice. As the current anti-HCV therapy with pegylated interferon combined with ribavirin can eradicate virus and stop the progression of fibrosis, but near 50% of HCV infected patients are non responders, a controlled trial is planned for HCV infected patients non responders to this therapy with a Metavir fibrosis score reaching F = 2 or >2.

Hepatitis C virus core variants isolated from liver tumor but not from adjacent non-tumor tissue interact with Smad3 and inhibit the TGF-beta pathway

Hepatitis C virus (HCV) is a major risk factor for human hepatocellular carcinoma (HCC) but the mechanisms underlying HCV-induced carcinogenesis are still poorly understood. We have hypothesized that viral variants, selected during long-term infection, might contribute to cellular transformation. To address this issue, we have investigated the effect of natural HCV core variants isolated from liver tumors (T), or their non-tumor (NT) counterparts, on the tumor growth factor-beta (TGF-beta) pathway, a major regulator of cellular proliferation, differentiation and apoptosis. We have found a significant reduction in TGF-beta reporter gene activity with the expression of core sequences isolated from liver tumors. In contrast, moderate or no effects were observed with non-tumor mutants or a core reference sequence. The molecular mechanisms have been characterized and involved the inhibition, by tumor-derived cores, of the DNA-binding activity of the Smad3/4 transcription factors complex. This inhibition occurs through a direct interaction between the central domain (amino acids 59-126) of tumor-derived core and the MH1 DNA-binding domain of Smad3, thus preventing its binding to DNA. We have therefore identified a new cell-signaling pathway targeted by HCV core and inhibited by tumor-derived core sequences. These results suggest that during chronic infection, there is selection of viral variants that may promote cell transformation by providing, to clonally expanding cells, resistance to TGF-beta antiproliferative effects.

Early hepatic stellate cell activation is associated with advanced fibrosis after liver transplantation in recipients with hepatitis C

Recurrent hepatitis C after liver transplantation is a serious problem faced by liver transplant recipients. Activation of hepatic stellate cells is an early step in hepatic fibrogenesis. The aim of this study was to evaluate hepatic stellate cell activation, early after liver transplantation, as a predictor for the subsequent development of advanced fibrosis. Forty-six patients who underwent liver transplantation for hepatitis C and protocol liver biopsies were divided into rapid fibrosers (n = 21), defined as recipients who developed bridging fibrosis or cirrhosis within 2 years of liver transplantation, and slow fibrosers (n = 25). The protocol liver biopsy obtained 4 months after transplantation was stained and quantitated for hepatic stellate cell activation with antibody to alpha smooth muscle actin. Hepatic stellate cell activity was independently associated with rapid fibrosis (odds ratio: 1.6 [95% CI: 1.1,2.2], P = 0.013). The c-statistics for the receiver operating characteristic curve for stellate cell activity and fibrosis were 0.78 and 0.67, respectively, P = 0.36. The receiver operating characteristic curve for a model including stellate cell activity, histology activity index, and alanine aminotransferase. obtained at month 4 had the best c-statistic (0.88). In recipients with stage 0 or 1 fibrosis on the month 4 liver biopsy who subsequently developed advanced fibrosis, the c-statistic for the receiver operating characteristic curves was significantly better for stellate cell activity than for stage of fibrosis (0.77 and 0.51, respectively; P = 0.004). In conclusion, hepatic stellate cell activation early after liver transplantation complements traditional testing for identifying liver transplant recipients with hepatitis C at greatest risk for developing advanced fibrosis.

Hepatitis C virus RNA and core protein in kidney glomerular and tubular structures isolated with laser capture microdissection

The role of hepatitis C virus (HCV) in the production of renal injury has been extensively investigated, though with conflicting results. Laser capture microdissection (LCM) was performed to isolate and collect glomeruli and tubules from 20 consecutive chronically HCV-infected patients, namely 6 with membranoproliferative glomerulonephritis, 4 with membranous glomerulonephritis, 7 with focal segmental glomerulosclerosis and 3 with IgA-nephropathy. RNA for amplification of specific viral sequences was provided by terminal continuation methodology and compared with the expression profile of HCV core protein. For each case two glomeruli and two tubular structures were microdissected and processed. HCV RNA sequences were demonstrated in 26 (65%) of 40 glomeruli, but in only 4 (10%) of the tubules (P < 0.05). HCV core protein was concomitant with viral sequences in the glomeruli and present in 31 of the 40 tubules. HCV RNA and/or HCV core protein was found in all four disease types. The immunohistochemical picture of HCV core protein was compared with the LCM-based immunoassays of the adjacent tissue sections. Immune deposits were detected in 7 (44%) of 16 biopsy samples shown to be positive by extraction methods. The present study indicates that LCM is a reliable method for measuring both HCV RNA genomic sequences and HCV core protein in kidney functional structures from chronically HCV-infected patients with different glomerulopathies and provides a useful baseline estimate to define the role of HCV in the production of renal injury. The different distribution of HCV RNA and HCV-related proteins may reflect a peculiar 'affinity' of kidney microenvironments for HCV and point to distinct pathways of HCV-related damage in glomeruli and tubules.

Hepatitis C virus-replicating hepatocytes induce fibrogenic activation of hepatic stellate cells

BACKGROUND & AIMS

The mechanism by which hepatitis C virus induces liver fibrosis remains largely obscure. To characterize the profibrogenic potential of hepatitis C virus, we used the hepatitis C virus replicon cell line Huh-7 5-15, which stably expresses the nonstructural hepatitis C virus genes NS3 through NS5B, and hepatic stellate cells as fibrogenic effector cells.

METHODS

Rat and human hepatic stellate cells were incubated with conditioned media from replicon cells, and expression of fibrosis-related genes was quantified by using real-time polymerase chain reaction, protein, and functional assays. Transforming growth factor beta1 activity was determined by bioassay.

RESULTS

Hepatitis C virus replicon cells release factors that differentially modulate hepatic stellate cell expression of key genes involved in liver fibrosis in a clearly profibrogenic way, up-regulating procollagen alpha1(I) and procollagen alpha1(III) and down-regulating fibrolytic matrix metalloproteinases. Transforming growth factor beta1 expression and bioactivity were increased severalfold in hepatitis C virus-replicating vs mock-transfected hepatoma cells. However, transforming growth factor beta1 activity was responsible for only 50% of the profibrogenic activity.

CONCLUSIONS

Hepatitis C virus nonstructural genes induce an increased expression of transforming growth factor beta1 and other profibrogenic factors in infected hepatocytes. The direct induction of profibrogenic mediators by hepatitis C virus in infected hepatocytes explains the frequent observation of progressive liver fibrosis despite a low level of inflammation and suggests novel targets for antifibrotic therapies in chronic hepatitis C.

Genes transactivated by hepatitis C virus core protein, a microarray assay

AIM: To explore the new target genes transactivated by hepatitis C virus (HCV) core protein and to elucidate the pathogenesis of HCV infection.

METHODS: Reverse transcribed cDNA was subjected to microarray assay. The coding gene transactivated by HCV core protein was cloned and analyzed with bioinformatics methods.

RESULTS: The expressive vector of pcDNA3.1(-)-core was constructed and confirmed by restriction enzyme digestion and DNA sequencing and approved correct. mRNA was purified from HepG2 and HepG2 cells transfected with pcDNA3.1(-)-core, respectively. The cDNA derived was subjected to microarray assay. A new gene named HCTP4 was cloned with molecular biological method in combination with bioinformatics method.

CONCLUSION: HCV core is a potential transactivator. Microarray is an efficient and convenient method for analysis of differentially expressed genes.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Insulin resistance impairs sustained response rate to peginterferon plus ribavirin in chronic hepatitis C patients

BACKGROUND & AIMS

We evaluated the effect of insulin resistance and viral factors on sustained virological response in patients with chronic hepatitis C treated with peginterferon plus ribavirin.

METHODS

Patients (n=159; 94 men; age, 41.7 +/- 11.1 years) with chronic hepatitis C (genotype 1, n=113; non-1 genotype, n=46) received treatment with interferon plus ribavirin. Serum levels of leptin and insulin were measured, and the insulin resistance index (HOMA-IR: homeostasis model of assessment) and body mass index were calculated.

RESULTS

A sustained virological response was associated with lower age, insulin resistance index, body mass index, and gamma-glutamyltranspeptidase and serum leptin levels. There was no association with viral load, sex, type of interferon, or cholesterol levels. A sustained virological response was achieved in 43.4% (46/113) of genotype 1 and 89% (32/36) of genotype 2 and 3 (P=.0001) patients. Necroinflammatory activity and steatosis were not associated with the sustained virological response rate. Multivariate regression analysis indicated that the independent variables related to sustained virological response were genotype (odds ratio, 3.57; 95% confidence interval, 1.49-8.3; P=.001), insulin resistance index (odds ratio, 1.82; 95% confidence interval, 1.08-3.06; P=.012), and fibrosis (odds ratio, 1.36; 95% confidence interval, 1.01-1.84; P=.029). A sustained virological response in patients with genotype 1 and insulin resistance (HOMA-IR > 2) occurred in 23 of 70 (32.8%; 95% confidence interval, 21.9%-43.9%) patients, vs. 26 of 43 (60.5%; 95% confidence interval, 45.9%-75.1%) genotype 1 patients without insulin resistance (P=.007; odds ratio, 3.12, 95% confidence interval, 1.42-6.89).

CONCLUSIONS

Insulin resistance, fibrosis, and genotype are independent predictors of the response to antiviral therapy in chronic hepatitis C patients treated with peginterferon plus ribavirin.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

Binding of hepatitis C virus envelope protein E2 to CD81 up-regulates matrix metalloproteinase-2 in human hepatic stellate cells

The hepatitis C virus (HCV) envelope E2 glycoprotein is a key molecule regulating the interaction of HCV with cell surface proteins. E2 binds the major extracellular loop of human CD81, a tetraspanin expressed on various cell types including hepatocytes and B lymphocytes. Regardless, information on the biological functions originating from this interaction are largely unknown. Since human hepatic stellate cells (HSC) express high levels of CD81 at the cell surface, we investigated the E2/CD81 interaction in human HSC and the possible effects arising from this interaction. Matrix metalloproteinase-2 (MMP-2; gelatinase A), a major enzyme involved in the degradation of normal hepatic extracellular matrix, was up-regulated following the interaction between E2 and CD81. In particular, by employing zymography and Western blot, we observed that E2 binding to CD81 induces a time-dependent increase in the synthesis and activity of MMP-2. This effect was abolished by preincubating HSC with an anti-CD81 neutralizing antibody. Similar effects were detected in NIH3T3 mouse fibroblasts transfected with human CD81 with identical time course features. In addition, E2/CD81 interaction in human HSC induced the up-regulation of MMP-2 by increasing activator protein-2/DNA binding activity via ERK/MAPK phosphorylation. Finally, suppression of CD81 by RNA interference in human HSC abolished the described effects of E2 on these cells, indicating that CD81 is essential for the activation of the signaling pathway leading to the up-regulation of MMP-2. These results suggest that HSC may represent a potential target for HCV. The interaction of HCV envelope with CD81 on the surface of human HSC induces an increased expression of MMP-2. Increased degradation of the normal hepatic extracellular matrix in areas where HCV is concentrated may favor inflammatory infiltration and further parenchymal damage.

Mechanisms of Disease: mechanisms of hepatic fibrosis and therapeutic implications

Hepatic fibrosis, or scarring of the liver, is emerging as a treatable complication of advanced liver disease, following significant progress in understanding its underlying mechanisms. Efforts have focused on the hepatic stellate cell, as these cells can undergo 'activation' into proliferative and fibrogenic myofibroblast-like cells during liver injury. Stimuli driving stellate cell activation include hepatocellular necrosis due to oxidant stress, apoptosis, and soluble growth factors. Specific lymphocyte subsets can also stimulate fibrogenesis. A cascade of signaling and transcriptional events in stellate cells underlies the fibrogenic response to liver injury, with each step in the cascade being a potential target for antifibrotic therapy. Disease-specific fibrogenic mechanisms have also been uncovered: in hepatitis C, this may include direct stimulation of stellate cell activation by viral infection; in nonalcoholic steatohepatitis, elevated levels of leptin and increased leptin signaling by stellate cells increase fibrogenesis. Determinants of fibrosis progression include both environmental and genetic factors, with ongoing efforts to define specific polymorphisms correlating with fibrosis progression rates. Human studies now indicate that fibrosis and even cirrhosis could be reversible, especially if the underlying disease is eradicated. A key challenge is to establish noninvasive means of assessing fibrosis stage and progression using either serum tests and/or imaging. In addition, endpoints of antifibrotic clinical trials need to be established so that reliable evidence of benefit can be identified. We are on the cusp of a new era in which antifibrotic therapies could become important in treating chronic fibrosing liver disease.

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Hepatitis C core and nonstructural 3 proteins trigger toll-like receptor 2-mediated pathways and inflammatory activation

BACKGROUND AND AIMS

Recent evidence suggests that toll-like receptors (TLRs) recognize certain viruses. We reported that hepatitis C virus (HCV) core and nonstructural 3 (NS3) proteins activate inflammatory pathways in monocytes. The aim of this study was to investigate the role of TLRs in innate immune cell activation by core and NS3 proteins.

METHODS

Human monocytes, human embryonic kidney cells transfected with TLR2, and peritoneal macrophages from TLR2, MyD88 knockout, and wild-type mice were studied to determine intracellular signaling and proinflammatory cytokine induction by HCV proteins.

RESULTS

HCV core and NS3 proteins triggered inflammatory cell activation via the pattern recognition receptor TLR2 and failed to activate macrophages from TLR2 or MyD88-deficient mice. HCV core and NS3 induced interleukin (IL)-1 receptor-associated kinase (IRAK) activity, phosphorylation of p38, extracellular regulated (ERK), and c-jun N-terminal (JNK) kinases and induced AP-1 activation. Activation of nuclear factor-kappaB by core and NS3 was associated with increased IkappaBalpha phosphorylation. TLR2-mediated cell activation was dependent on the conformation of core and NS3 proteins and required sequences in the regions of aa 2-122 in core and aa 1450-1643 in NS3. Although cellular uptake of core and NS3 proteins was independent of TLR2 expression, cell activation required TLR2. HCV core protein and TLR2 showed intracellular colocalization. The hyper-elevated TNF-alpha induction by TLR2 ligands in monocytes of HCV-infected patients was not due to increased TLR2 expression.

CONCLUSIONS

HCV core and NS3 proteins trigger inflammatory pathways via TLR2 that may affect viral recognition and contribute to activation of the innate immune system.

Influence of interleukin 12B (IL12B) polymorphisms on spontaneous and treatment-induced recovery from hepatitis C virus infection

BACKGROUND/AIMS

Interleukin-12 (IL-12) governs the Th1-type immune response, affecting the spontaneous and treatment-induced recovery from HCV-infection. We investigated whether the IL12B polymorphisms within the promoter region (4 bp insertion/deletion) and the 3'-UTR (1188-A/C), which have been reported to influence IL-12 synthesis, are associated with the outcome of HCV infection.

METHODS

We analyzed 186 individuals with spontaneous HCV clearance, 501 chronically HCV infected patients, and 217 healthy controls. IL12B 3'-UTR and promoter genotyping was performed by Taqman-based assays with allele-specific oligonucleotide probes and PCR-based allele-specific DNA-amplification, respectively.

RESULTS

The proportion of IL12B promoter and 3'-UTR genotypes did not differ significantly between the different cohorts. However, HCV genotype 1-infected patients with high baseline viremia carrying the IL12B 3'-UTR 1188-C-allele showed significantly higher sustained virologic response (SVR) rates (25.3% vs. 46% vs. 54.5% for A/A, A/C and C/C) due to reduced relapse rates (24.2% vs. 12% vs. zero % for A/A, A/C and C/C).

CONCLUSIONS

IL12B 3'-UTR 1188-C-allele carriers appear to be capable of responding more efficiently to antiviral combination therapy as a consequence of a reduced relapse rate. No association of IL12B polymorphisms and self-limited HCV infection could be demonstrated.