The hepatitis B virus encoded oncoprotein pX amplifies TGF-beta family signaling through direct interaction with Smad4: potential mechanism of hepatitis B virus-induced liver fibrosis

Tanshinone I activates the Nrf2-dependent antioxidant response and protects against As(III)-induced lung inflammation in vitro and in vivo

AIMS

The NF-E2 p45-related factor 2 (Nrf2) signaling pathway regulates the cellular antioxidant response and activation of Nrf2 has recently been shown to limit tissue damage from exposure to environmental toxicants, including As(III). In an attempt to identify improved molecular agents for systemic protection against environmental insults, we have focused on the identification of novel medicinal plant-derived Nrf2 activators.

RESULTS

Tanshinones [tanshinone I (T-I), tanshinone IIA, dihydrotanshinone, cryptotanshinone], phenanthrenequinone-based redox therapeutics derived from the medicinal herb Salvia miltiorrhiza, have been tested as experimental therapeutics for Nrf2-dependent cytoprotection. Using a dual luciferase reporter assay overexpressing wild-type or mutant Kelch-like ECH-associated protein-1 (Keap1), we demonstrate that T-I is a potent Keap1-C151-dependent Nrf2 activator that stabilizes Nrf2 by hindering its ubiquitination. In human bronchial epithelial cells exposed to As(III), T-I displays pronounced cytoprotective activity with upregulation of Nrf2-orchestrated gene expression. In Nrf2 wild-type mice, systemic administration of T-I attenuates As(III) induced inflammatory lung damage, a protective effect not observed in Nrf2 knockout mice.

INNOVATION

Tanshinones have been identified as a novel class of Nrf2-inducers for antioxidant tissue protection in an in vivo As(III) inhalation model, that is relevant to low doses of environmental exposure.

CONCLUSION

T-I represents a prototype Nrf2-activator that displays cytoprotective activity upon systemic administration targeting lung damage originating from environmental insults. T-I based Nrf2-directed systemic intervention may provide therapeutic benefit in protecting other organs against environmental insults.

Unraveling the complexity of hepatitis B virus: from molecular understanding to therapeutic strategy in 50 years

Hepatitis B virus (HBV) is a well-known hepadnavirus with a double-stranded circular DNA genome. Although HBV was first described approximately 50 years ago, the precise mechanisms of HBV infection and effective therapeutic strategies remain unclear. Here, we focus on summarizing the complicated mechanisms of HBV replication and infection, as well as genomic factors and epigenetic regulation. Additionally, we discuss in vivo models of HBV, as well as diagnosis, prevention and therapeutic drugs for HBV. Together, the data in this 50-year review may provide new clues to elucidate molecular mechanisms of HBV pathogenesis and shed new light on the future HBV therapies.

[Effects of hepatitis B virus X protein on chronic hepatitis B pathophysiology]

The infection by hepatitis B virus often promotes chronic liver inflammation which progresses to cirrhosis and hepatocellular carcinoma in a high percentage of patients. The persistent activation of the immune system causes an incessant liver damage, which fosters a disorganized stimulation of tissue repair and remodelling phenomena. In turn, the viral protein X (HBx) is essential for virus replication and therefore for the maintenance of chronic infection. However, the important oncogenic potential of HBx seems to reside, on one hand, in its ability to integrate into cellular DNA and, additionally, in the transactivation of different cellular signaling pathways involved in cell growth regulation, apoptosis and DNA repair. HBx also interacts with proteasome subunits and notably affects mitochondrial electric potential, thus altering cellular calcium homeostasis. Finally, this review discusses the pathogenic role of HBx in the progression of chronic hepatitis B through its effects on angiogenic, fibrogenic and oncogenic processes.

Hepatitis B virus X protein disrupts stress fiber formation and triggers apoptosis

Cytoskeletal proteins are key participants in the cellular progression to apoptosis. In a previous study we injected nude mice with CCL13-HBx cells and identified in contrast to non-HBx transfected cells a differentially phosphorylated myosin light chain (p-MLC) by two-dimensional PAGE and mass spectrometry of the tumor material. To investigate the role of HBx in myosin light chain kinase (MLCK) signaling pathways, we analyzed the key molecules, p-MLC and MLCK, by western blotting. Immunofluorescence staining analysis showed that HBx disrupted stress fiber formation and that focal adhesion kinase (FAK) and integrin-linked kinase (ILK) were regulated by HBx-mediated phosphatase and tensin homolog (PTEN). We also used pharmacological inhibitors to explore the correlation between cytoskeletal rearrangements and HBx-mediated cell apoptosis via an MLCK and a PTEN-dependent pathway. The results showed that both ML9 and bvp restored the effects caused by HBx induction. Our findings suggest that HBx disrupts stress fiber formation and triggers apoptosis via an MLCK and a PTEN-dependent pathway.

Anti-viral CD8 T cells and the cytokines that they love

Viral infections cause an immunological disequilibrium that provokes CD8 T cell responses. These cells play critical roles in purging acute infections, limiting persistent infections, and conferring life-long protective immunity. At every stage of the response anti-viral CD8 T cells are sensitive to signals from cytokines. Initially cytokines operate as immunological warning signs that inform of the presence of an infection, and also influence the developmental choices of the responding cells. Later during the course of the response other sets of cytokines support the survival and maintenance of the differentiated anti-viral CD8 T cells. Although many cytokines promote virus-specific CD8 T cells, other cytokines can suppress their activities and thus favor viral persistence. In this review we discuss how select cytokines act to regulate anti-viral CD8 T cells throughout the response and influence the outcome of viral infections.

Pathogenic mechanisms in HBV- and HCV-associated hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal cancer, with increasing worldwide incidence, that is mainly associated with chronic hepatitis B virus (HBV) and/or hepatitis C virus (HCV) infections. There are few effective treatments partly because the cell- and molecular-based mechanisms that contribute to the pathogenesis of this tumour type are poorly understood. This Review outlines pathogenic mechanisms that seem to be common to both viruses and which suggest innovative approaches to the prevention and treatment of HCC.

Smad4 expression in hepatocellular carcinoma differs by hepatitis status

AIMS

Primary hepatocellular carcinoma (HCC) is a common malignancy often related to hepatitis viral infection. Smad4 is known to mediate the TGF-β pathway to suppress tumorigenesis. However, the function of Smad4 in HCC is still controversial. In this study we compared levels of Smad4 in HCC tissues with or without hepatitis virus infection and adjacent normal-appearing liver.

METHODS

Samples from HCC patients were analyzed for Smad4 protein and mRNA expression by immunohistochemistry (IHC), RT-PCR and Western blotting.

RESULTS

We found that tumor tissues expressed less Smad4 mRNA and protein than the adjacent tissues. Most HCC tumor tissues were negative for Smad4 in IHC staining, while the majority of adjacent tissues were positively stained. Interestingly, protein levels were higher in HCC tissues with viral hepatitis than those without virus infection. Suppression of expression appeared closely related to HCC, so that Smad4 appears to function as a tumor suppressor gene (TSG).

CONCLUSION

Patients with hepatitis viral infection, at higher risk for HCC, exhibited increased Smad4 protein expression suggesting hepatitis virus may modulate Smad4 expression, which is functionally distinct from its putative role as a TSG. Smad4 expression may thus be an applicable marker for diagnosis and/or a target to develop therapeutic agents for HCC.

Hepatitis B virus encoded X protein suppresses apoptosis by inhibition of the caspase-independent pathway

Hepatitis B virus (HBV) encoded X protein (HBx) has been implicated in apoptotic and related pathogenic events during hepatocellular carcinoma. However, the underlying molecular mechanism through which HBx acts is largely unclear. We used tandem affinity purification under mild conditions to gain insight into the HBx interactome in HBV-producing HepG2.2.15 cells and identified 49 proteins by mass spectrometry that are potentially associated with HBx. Two of the key proteins of the caspase-independent apoptosis pathway were newly identified, apoptosis-inducing factor (AIF) and the homologous AMID (AIF-homologue mitochondrion-associated inducer of death). We confirmed the interactions of HBx with AIF and with AMID by reciprocal coimmunoprecipitation experiments, respectively. We observed the expression of HBx-reduced AIF-mediated apoptosis and HBx colocalization with AIF and AMID, principally in the cytoplasm. Furthermore, the elevated cytoplasmic levels of HBx could inhibit mitochondrion-to-nucleus translocation of AIF. Here, we present the first detailed molecular evidence that HBx can repress apoptosis via inhibition of the caspase-independent apoptosis pathway. This inhibition of apoptosis involves the repression of the mitochondrion-to-nucleus translocation of AIF, although tests with AMID were not conclusive. These findings provide important insights into the new mechanism of the apoptosis inhibition by HBV.

Hedgehog signaling blockade delays hepatocarcinogenesis induced by hepatitis B virus X protein

The hepatitis B virus (HBV) encoded X protein (HBx) contributes centrally to the pathogenesis of hepatocellular carcinoma (HCC). Aberrant activation of the Hedgehog (Hh) pathway has been linked to many tumor types including HCC. Thus, experiments were designed to test the hypothesis that HBx promotes HCC via activation of Hh signaling. HBx expression correlated with an upregulation of Hh markers in human liver cancer cell lines, in liver samples from HBV infected patients with HCC, and in the livers of HBx transgenic mice (HBxTg) that develop hepatitis, steatosis, and dysplasia, culminating in the appearance of HCC. The findings in human samples provide clinical validation for the in vitro results and those in the HBxTg. Blockade of Hh signaling inhibited HBx stimulation of cell migration, anchorage-independent growth, tumor development in HBxTg, and xenograft growth in nude mice. Results suggest that the ability of HBx to promote cancer is at least partially dependent upon the activation of the Hh pathway. This study provides biologic evidence for the role of Hh signaling in the pathogenesis of HBV-mediated HCC and suggests cause and effect for the first time. The observation that inhibition of Hh signaling partially blocked the ability of HBx to promote growth and migration in vitro and tumorigenesis in two animal models implies that Hh signaling may represent an "oncogene addiction" pathway for HBV-associated HCC. This work could be central to designing specific treatments that target early development and progression of HBx-mediated HCC.

Increased serum activin-A differentiates alcoholic from cirrhosis of other aetiologies

BACKGROUND

Activin-A is a molecule of the TGF superfamily, implicated in liver fibrosis, regeneration and stem cell differentiation. However, data on activins in liver diseases are few. We therefore studied serum levels of activin-A in chronic liver diseases. To identify the origin of activin-A, levels in the hepatic vein were also estimated.

MATERIALS AND METHODS

Nineteen controls and 162 patients participated in the study: 39 with hepatocellular carcinoma (HCC: 19 viral associated and 20 alcohol associated), 18 with chronic hepatitis C (CHC), 47 with primary biliary cirrhosis (26 PBC stage I-II and 21 stage IV), 22 with alcoholic cirrhosis (AC, hepatic vein blood available in 16), 20 with HCV cirrhosis (hepatic vein blood available in 18) and 16 patients with alcoholic fatty liver with mild to moderate fibrosis but no cirrhosis.

RESULTS

Activin-A levels were significantly increased (P < 0·001) in serum of patients with AC (median 673 pg/mL, range 449-3279), compared with either controls (149 pg/mL, 91-193) or patients with viral cirrhosis (189 pg/mL, 81-480), CHC (142 pg/mL, 65-559) PBC stage I-II (100 pg/mL, 59-597) and PBC stage IV (104 pg/mL, 81-579). Only patients with AC-associated HCC had significantly increased levels of activin-A (2403 pg/mL, 1561-7220 pg/mL). Activin-A serum levels could accurately discriminate AC from cirrhosis of other aetiologies and noncirrhotic alcoholic fatty liver with fibrosis.

CONCLUSIONS

Increased serum levels of activin-A only in patients with alcohol-related cirrhosis or HCC suggest a possible role of this molecule in the pathophysiology of AC. Further research is warranted to elucidate its role during the profibrotic process and its possible clinical applications.

TGF-β1 down-regulation of NKG2D/DAP10 and 2B4/SAP expression on human NK cells contributes to HBV persistence

The mechanism underlying persistent hepatitis B virus (HBV) infection remains unclear. We investigated the role of innate immune responses to persistent HBV infection in 154 HBV-infected patients and 95 healthy controls. The expression of NKG2D- and 2B4-activating receptors on NK cells was significantly decreased, and moreover, the expression of DAP10 and SAP, the intracellular adaptor proteins of NKG2D and 2B4 (respectively), were lower, which then impaired NK cell-mediated cytotoxic capacity and interferon-γ production. Higher concentrations of transforming growth factor-beta 1 (TGF-β1) were found in sera from persistently infected HBV patients. TGF-β1 down-regulated the expression of NKG2D and 2B4 on NK cells in our in vitro study, leading to an impairment of their effector functions. Anti-TGF-β1 antibodies could restore the expression of NKG2D and 2B4 on NK cells in vitro. Furthermore, TGF-β1 induced cell-cycle arrest in NK cells by up-regulating the expression of p15 and p21 in NK cells from immunotolerant (IT) patients. We conclude that TGF-β1 may reduce the expression of NKG2D/DAP10 and 2B4/SAP, and those IT patients who are deficient in these double-activating signals have impaired NK cell function, which is correlated with persistent HBV infection.

NK cells have been viewed as the most important effectors of the initial antiviral innate immune response. Their activation depends on the integration of signals from “co-activation” receptors, and the cytotoxic effects of NK cells on target cells are tempered by a need for combined signals from multiple activating receptors, such as NKG2D and 2B4. In this study, we showed that NKG2D and 2B4 expression levels were decreased on NK cells from patients in the IT phase of HBV infection. We further demonstrated that lower levels of intracellular adaptor proteins (DAP10 and SAP) were associated with lower surface expression of NKG2D and 2B4. As a result, the synergistically co-activated signalling pathway initiated by NKG2D and 2B4 did not operate properly in IT-phase patients. We demonstrated that high levels of soluble TGF-β1 were associated with the reduction of NKG2D and 2B4 in patients. In addition, we showed that TGF-β1 causes the cell-cycle arrest of NK cells by up-regulating the levels of p15 and p21 in NK cells from IT patients. Collectively, these findings may contribute to our understanding of the immune tolerance mechanism and aid in the development of novel therapeutic methods to clear HBV infection during the initial phase.

Akt augments the oncogenic potential of the HBx protein of hepatitis B virus by phosphorylation

Hepatitis B virus X protein (HBx) is a putative viral oncoprotein that plays an important role in various cellular processes, including modulation of the phosphatidylinositol 3-kinase/Akt signalling pathway. However, the molecular mechanism of Akt activation remains elusive. Here we show that HBx interacts with Akt1 kinase and is phosphorylated at serine 31 as indicated by mutational analysis of the Akt recognition motif (creating the HBxS31A mutant) or immunoblotting of HBx immunoprecipitates using Akt motif-specific antibody. The Akt-dependent phosphorylation of HBx was abrogated in the presence of the phosphatidylinositol 3-kinase inhibitor LY294002 or Akt1 gene silencing by specific siRNA. Co-immunoprecipitation studies provided evidence for HBx-Akt interaction in a cellular environment. This interaction was also confirmed in hepatoma HepG2.2.15 cells in which HBx was expressed at physiological levels from the integrated hepatitis B viral genome. The HBx-Akt interaction was essential for Akt signalling, and involved displacement of the Akt-bound negative regulator 'C-terminal modulator protein' by HBx. HBx-activated Akt phosphorylated its downstream target glycogen synthase kinase 3β, leading to stabilization of β-catenin, while p65 phosphorylation resulted in enhanced promoter recruitment and expression of target genes encoding cyclin D1 and Bcl-XL. Further, the oncogenic potential of HBx was significantly augmented in the presence of Akt in a soft agar colony formation assay. Together, these results suggest that oncogenic co-operation between HBx and Akt may be important for cell proliferation, abrogation of apoptosis and tumorigenic transformation of cells.

Epigenetic repression of E-cadherin expression by hepatitis B virus x antigen in liver cancer

Loss of E-cadherin is associated with acquisition of metastatic capacity. Numerous studies suggest that histone deacetylation and/or hypermethylation of CpG islands in E-cadherin gene (CDH1) are major mechanisms responsible for E-cadherin silencing in different tumors and cancer cell lines. The hepatitis B virus (HBV)-encoded X antigen, HBx, contributes importantly to the development of hepatocellular carcinoma using multiple mechanisms. Experiments were designed to test if in addition to CDH1 hypermethylation HBx promotes epigenetic modulation of E-cadherin transcriptional activity through histone deacetylation and miR-373. The relationships between HBx, E-cadherin, mSin3A, Snail-1 and miR-373 were evaluated in HBx expressing (HepG2X) and control (HepG2CAT) cells by western blotting, immunoprecipitation (IP), chromatin IP as well as by immunohistochemical staining of liver and tumor tissue sections from HBV-infected patients. In HepG2X cells, decreased levels of E-cadherin and elevated levels of mSin3A and Snail-1 were detected. Reciprocal IP with anti-HBx and anti-mSin3A demonstrated mutual binding. Furthermore, HBx-mSin3A colocalization was detected by immunofluorescent staining. HBx downregulated E-cadherin expression by the recruitment of the mSin3A/histone deacetylase complex to the Snail-binding sites in human CDH1. Histone deacetylation inhibition by Trichostatin-A treatment restored E-cadherin expression. Mir-373, a positive regulator of E-cadherin expression, was downregulated by HBx in HepG2X cells and tissue sections from HBV-infected patients. Thus, histone deacetylation of CDH1 and downregulation of miR-373, together with the previously demonstrated hypermethylation of CDH1 by HBx, may be important for the understanding of HBV-related carcinogenesis.

The role of hepatitis B virus X protein is related to its differential intracellular localization

Chronic hepatitis B virus (HBV) infection has been strongly associated with hepatocellular carcinoma. HBV encodes an oncogenic hepatitis B virus X protein (HBx), which is a multifunctional regulator that modulates signal transduction, transcription, cell cycle progress, protein degradation, apoptosis, and genetic stability through direct and indirect interaction with host factors. The subcellular localization of HBx is primarily cytoplasmic, with a small fraction in the nucleus. In addition, high levels of HBx expression lead to an abnormal mitochondrial distribution. The dynamic distribution of HBx could be important to the multiple functions of HBx at different stages of the HBV life cycle. This short review presents an overview of the differential roles of HBx as a function of its intracellular localization.

The molecular and pathophysiological implications of hepatitis B X antigen in chronic hepatitis B virus infection

Hepatitis B virus is considered one of the most significant environmental carcinogens in humans. Because the mechanisms of HBV replication and the development of hepatocellular carcinoma (HCC) are partially known, HBV-associated pathogenesis remains a challenge to increase its understanding. Evidence suggests that the regulatory protein hepatitis B virus X (HBx) mediates the establishment and maintenance of the chronic carrier state. HBx is a multifunctional and potentially oncogenic protein that is conserved among mammalian hepadnaviruses; it is produced very early after infection and throughout the chronic phase. HBx exerts its effects by interacting with cellular proteins and activating various signaling pathways. HBx stimulates the transcription of genes that regulate cell growth, apoptosis, and DNA repair. It also interacts with proteasome subunits and affects mitochondrial stability. Moreover, HBx participates in processes that are associated with the progression of chronic liver disease, including angiogenesis and fibrosis. This review discusses the function of HBx in the life cycle of HBV and its contribution to the pathogenesis of HCC.

HTLV-1 bZIP factor enhances TGF-β signaling through p300 coactivator

Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus that is etiologically associated with adult T-cell leukemia. The HTLV-1 bZIP factor (HBZ), which is encoded by the minus strand of the provirus, is involved in both regulation of viral gene transcription and T-cell proliferation. We showed in this report that HBZ interacted with Smad2/3, and enhanced transforming growth factor-β (TGF-β)/Smad transcriptional responses in a p300-dependent manner. The N-terminal LXXLL motif of HBZ was responsible for HBZ-mediated TGF-β signaling activation. In a serial immunoprecipitation assay, HBZ, Smad3, and p300 formed a ternary complex, and the association between Smad3 and p300 was markedly enhanced in the presence of HBZ. In addition, HBZ could overcome the repression of the TGF-β response by Tax. Finally, HBZ expression resulted in enhanced transcription of Pdgfb, Sox4, Ctgf, Foxp3, Runx1, and Tsc22d1 genes and suppression of the Id2 gene; such effects were similar to those by TGF-β. In particular, HBZ induced Foxp3 expression in naive T cells through Smad3-dependent TGF-β signaling. Our results suggest that HBZ, by enhancing TGF-β signaling and Foxp3 expression, enables HTLV-1 to convert infected T cells into regulatory T cells, which is thought to be a critical strategy for virus persistence.

Proinflammatory cytokine TNF-α increases the stability of hepatitis B virus X protein through NF-κB signaling

Hepatitis B virus (HBV) X protein (HBx) is a key player in HBV-induced hepatocellular carcinoma (HCC). HBx interacts with several cell signaling molecules, leading to activation of various transcription factors including nuclear factor-kappaB (NF-κB). Activated NF-κB signaling is implicated in many human cancers including HCC. Here, we present evidence that the NF-κB signaling activator, tumor necrosis factor (TNF)-α, induces the accumulation of HBx in cells by increasing protein stability due to reduced proteasomal degradation. The effects of TNF-α on HBx protein stability are mediated via activated NF-κB effector kinases IKKα and IKKβ and p65. The non-IKK-phosphorylable p65-S534A mutant did not induce HBx protein stability; hence, phosphorylation of p65 by IKK is a key step in TNF-α-induced stabilization of HBx. Phospho-p65 showed higher affinity to HBx compared with the non-phosphorylable p65 mutant, suggesting that the interaction of phospho-p65 with HBx might be important for HBx stabilization. We also show that the increased level of HBx in cells cooperates with TNF-α toward activation of NF-κB and expression of NF-κB-regulated genes, indicating a positive feedback loop between HBx and NF-κB signaling. Overall, our study provides evidence for interplay between HBx and NF-κB signaling, which may account for HBV-mediated liver carcinogenesis.

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) mediates natural killer cell suppression in chronic hepatitis B

BACKGROUND & AIMS

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) has been shown to influence autoimmune diseases; however, its function in viral infection has not been well-defined. We therefore investigated the expression and regulatory function of Tim-3 in natural killer (NK) cells in chronic Hepatitis B (CHB) infection.

METHODS

Seventy-six CHB patients, 38 healthy controls, and 18 patients with fatty liver disease (FLD) were tested for Tim-3 expression on peripheral blood mononuclear cells (PBMCs) and in the liver tissue by flow cytometry and immunohistochemical stainning. The effects of HBV infection on Tim-3 expression in NK cells and the roles of Tim-3 in regulation of NK-cell function were also studied.

RESULTS

There was a significant increase of Tim-3 expression in PBMCs, circulating NK cells and liver infiltrating lymphocytes (LILs) from CHB patients compared to that of healthy controls and FLD patients. Increased Tim-3 expression was also detected in NK92 cells that had been transfected with a HBV expression vector and NK cells isolated from the liver of HBV transgenic mice. Importantly, blockage of Tim-3 signaling with anti-Tim-3 antibodies or Tim-3-Fc fusion proteins resulted in an increased cytotoxicity for NK92 cells compared to HepG2 and HepG2.2.15 cells, as well as an elevated interferon-gamma (IFN-gamma) production. Similarly, enhanced cytotoxicity was also observed in PBMCs or NK cells from CHB patients treated with the Tim-3 blockade ex vivo.

CONCLUSION

HBV infection can up-regulate Tim-3 expression in NK cells, which may in turn suppress NK-cell functions in CHB patients.

The etiology of liver damage imparts cytokines transforming growth factor beta1 or interleukin-13 as driving forces in fibrogenesis

It is unknown whether transforming growth factor beta1 (TGF-beta1) signaling uniformly participates in fibrogenic chronic liver diseases, irrespective of the underlying origin, or if other cytokines such as interleukin (IL)-13 share in fibrogenesis (e.g., due to regulatory effects on type I pro-collagen expression). TGF-beta1 signaling events were scored in 396 liver tissue samples from patients with diverse chronic liver diseases, including hepatitis B virus (HBV), hepatitis C virus (HCV), Schistosoma japonicum infection, and steatosis/steatohepatitis. Phospho-Smad2 staining correlated significantly with fibrotic stage in patients with HBV infection (n = 112, P < 0.001) and steatosis/steatohepatitis (n = 120, P < 0.01), but not in patients with HCV infection (n = 77, P > 0.05). In tissue with HBx protein expression, phospho-Smad2 was detectable, suggesting a functional link between viral protein expression and TGF-beta1 signaling. For IL-13, immunostaining correlated with fibrotic stage in patients with HCV infection and steatosis/steatohepatitis. IL-13 protein was more abundant in liver tissue lysates from three HCV patients compared with controls, as were IL-13 serum levels in 68 patients with chronic HCV infection compared with 20 healthy volunteers (72.87 +/- 26.38 versus 45.41 +/- 3.73, P < 0.001). Immunohistochemistry results suggest that IL-13-mediated liver fibrogenesis may take place in the absence of phospho-signal transducer and activator of transcription protein 6 signaling. In a subgroup of patients with advanced liver fibrosis (stage > or =3), neither TGF-beta nor IL-13 signaling was detectable.

CONCLUSION

Depending on the cause of liver damage, a predominance of TGF-beta or IL-13 signaling is found. TGF-beta1 predominance is detected in HBV-related liver fibrogenesis and IL-13 predominance in chronic HCV infection. In some instances, the underlying fibrogenic mediator remains enigmatic.

Genetic profile of Egyptian hepatocellular-carcinoma associated with hepatitis C virus Genotype 4 by 15 K cDNA microarray: preliminary study

Background

Hepatocellular carcinoma (HCC) is a preventable disease rather than a curable one, since there is no well-documented effective treatment modality until now, making the molecular study of this disease mandatory.

Findings

We studied gene expression profile of 17 Egyptian HCC patients associated with HCV genotype-4 infection by c-DNA microarray. Out of the 15,660 studied genes, 446 were differentially expressed; 180 of them were up regulated and 134 were down regulated. Seventeen genes out of the 180 up-regulated genes are involved in 28 different pathways. Protein phosphatase 3 (PPP3R1) is involved in 10 different pathways followed by fibroblast growth factor receptor 1 (FGFR1), Cas-Br-M ecotropic retroviral transforming sequence b (CBLB), spleen tyrosine kinase (SYK) involved in three pathways; bone morphogenetic protein 8a (BMP8A), laminin alpha 3 (LAMA3), cell division cycle 23 (CDC23) involved in 2 pathways and NOTCH4 which regulate Notch signaling pathway. On the other hand, 25 out of the 134 down-regulated genes are involved in 20 different pathways. Integrin alpha V alpha polypeptide antigen CD51 (ITGVA) is involved in 4 pathways followed by lymphotoxin alpha (TNF superfamily, member 1) (LTA) involved in 3 pathways and alpha-2-macroglobulin (A2M), phosphorylase kinase alpha 2-liver (PHKA2) and MAGI1 membrane associated guanylate kinase 1 (MAGI1) involved in 2 pathways. In addition, 22 genes showed significantly differential expression between HCC cases with cirrhosis and without cirrhosis. Confirmation analysis was performed on subsets of these genes by RT-PCR, including some up-regulated genes such as CDK4, Bax, NOTCH4 and some down-regulated genes such as ISGF3G, TNF, and VISA.

Conclusion

This is the first preliminary study on gene expression profile in Egyptian HCC patients associated with HCV-Genotype-4 using the cDNA microarray. The identified genes could provide a new gate for prognostic and diagnostic markers for HCC associated with HCV. They could also be used to identify candidate genes for molecular target therapy.

Hepatitis B virus HBx protein localizes to mitochondria in primary rat hepatocytes and modulates mitochondrial membrane potential

Over 350 million people are chronically infected with hepatitis B virus (HBV), and a significant number of chronically infected individuals develop primary liver cancer. HBV encodes seven viral proteins, including the nonstructural X (HBx) protein. The results of studies with immortalized or transformed cells and with HBx-transgenic mice demonstrated that HBx can interact with mitochondria. However, no studies with normal hepatocytes have characterized the precise mitochondrial localization of HBx or the effect of HBx on mitochondrial physiology. We have used cultured primary rat hepatocytes as a model system to characterize the mitochondrial localization of HBx and the effect of HBx expression on mitochondrial physiology. We now show that a fraction of HBx colocalizes with density-gradient-purified mitochondria and associates with the outer mitochondrial membrane. We also demonstrate that HBx regulates mitochondrial membrane potential in hepatocytes and that this function of HBx varies depending on the status of NF-kappaB activity. In primary rat hepatocytes, HBx activation of NF-kappaB prevented mitochondrial membrane depolarization; however, when NF-kappaB activity was inhibited, HBx induced membrane depolarization through modulation of the mitochondrial permeability transition pore. Collectively, these results define potential pathways through which HBx may act in order to modulate mitochondrial physiology, thereby altering many cellular activities and ultimately contributing to the development of HBV-associated liver cancer.

Transforming growth factor-beta gene expression signature in mouse hepatocytes predicts clinical outcome in human cancer

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. The clinical heterogeneity of HCC, and the lack of good diagnostic markers and treatment strategies, has rendered the disease a major challenge. Patients with HCC have a highly variable clinical course, indicating that HCC comprises several biologically distinctive subgroups reflecting a molecular heterogeneity of the tumors. Transforming growth factor beta (TGF-beta) is known to exhibit tumor stage dependent suppressive (that is, growth inhibition) and oncogenic (that is, invasiveness) properties. Here, we asked if a TGF-beta specific gene expression signature could refine the classification and prognostic predictions for HCC patients. Applying a comparative functional genomics approach we demonstrated that a temporal TGF-beta gene expression signature established in mouse primary hepatocytes successfully discriminated distinct subgroups of HCC. The TGF-beta positive cluster included two novel homogeneous groups of HCC associated with early and late TGF-beta signatures. Kaplan-Meier plots and log-rank statistics indicated that the patients with a late TGF-beta signature showed significantly (P < 0.005) shortened mean survival time (16.2 +/- 5.3 months) compared to the patients with an early (60.7 +/- 16.1 months) TGF-beta signature. Also, tumors expressing late TGF-beta-responsive genes displayed invasive phenotype and increased tumor recurrence. We also showed that the late TGF-beta signature accurately predicted liver metastasis and discriminated HCC cell lines by degree of invasiveness. Finally, we established that the TGF-beta gene expression signature possessed a predictive value for tumors other than HCC.

CONCLUSION

These data demonstrate the clinical significance of the genes embedded in TGF-beta expression signature for the molecular classification of HCC.

The hepatitis B virus X protein induces paracrine activation of human hepatic stellate cells

Chronic hepatitis B virus (HBV) infection is a major cause of liver fibrosis, eventually leading to cirrhosis and hepatocellular carcinoma. Although the involvement of the X protein of HBV (HBx) in viral replication and tumor development has been extensively studied, little is known about its possible role in the development of fibrosis. In this work we show that expression of HBx in hepatocytes results in paracrine activation and proliferation of hepatic stellate cells (HSCs), the main producers of extracellular matrix proteins in the fibrotic liver. Both human primary HSCs and rat HSCs exposed to conditioned medium from HBx-expressing hepatocytes showed increased expression of collagen I, connective tissue growth factor, alpha smooth muscle actin, matrix metalloproteinase-2, and transforming growth factor-beta (TGF-beta), together with an enhanced proliferation rate. We found that HBx induced TGF-beta secretion in hepatocytes and that the activation of HSCs by conditioned medium from HBx-expressing hepatocytes was prevented by a neutralizing anti-TGF-beta antibody, indicating the involvement of this profibrotic factor in the process.

CONCLUSION

Our results propose a direct role for HBx in the development of liver fibrosis by the paracrine activation of stellate cells and reinforce the indication of antiviral treatment in patients with advanced HBV-related chronic liver disease and persistent liver replication.

Severe acute respiratory syndrome-associated coronavirus nucleocapsid protein interacts with Smad3 and modulates transforming growth factor-beta signaling

Severe acute respiratory syndrome (SARS) is an acute infectious disease with significant mortality. A typical clinical feature associated with SARS is pulmonary fibrosis and the associated lung failure. However, the underlying mechanism remains elusive. In this study, we demonstrate that SARS-associated coronavirus (SARS-CoV) nucleocapsid (N) protein potentiates transforming growth factor-β (TGF-β)-induced expression of plasminogen activator inhibitor-1 but attenuates Smad3/Smad4-mediated apoptosis of human peripheral lung epithelial HPL1 cells. The promoting effect of N protein on the transcriptional responses of TGF-β is Smad3-specific. N protein associates with Smad3 and promotes Smad3-p300 complex formation while it interferes with the complex formation between Smad3 and Smad4. These findings provide evidence of a novel mechanism whereby N protein modulates TGF-β signaling to block apoptosis of SARS-CoV-infected host cells and meanwhile promote tissue fibrosis. Our results reveal a novel mode of Smad3 action in a Smad4-independent manner and may lead to successful strategies for SARS treatment by targeting the TGF-β signaling molecules.

Hepatitis B virus X protein overcomes oncogenic RAS-induced senescence in human immortalized cells

Chronic infection with hepatitis B virus (HBV) is a major risk factor for hepatocellular carcinoma. The HBV X protein (HBx) is thought to have oncogenic potential, although the molecular mechanism remains obscure. Pathological roles of HBx in the carcinogenic process have been examined using rodent systems and no report is available on the oncogenic roles of HBx in human cells in vitro. We therefore examined the effect of HBx on immortalization and transformation in human primary cells. We found that HBx could overcome active RAS-induced senescence in human immortalized cells and that these cells could form colonies in soft agar and tumors in nude mice. HBx alone, however, could contribute to neither immortalization nor transformation of these cells. In a population doubling analysis, an N-terminal truncated mutant of HBx, HBx-D1 (amino acids 51-154), which harbors the coactivation domain, could overcome active RAS-induced cellular senescence, but these cells failed to exhibit colonigenic and tumorigenic abilities, probably due to the low expression level of the protein. By scanning a HBx expression library of the clustered-alanine substitution mutants, the N-terminal domain was found to be critical for overcoming active RAS-induced senescence by stabilizing full-length HBx. These results strongly suggest that HBx can contribute to carcinogenesis by overcoming active oncogene-induced senescence.

X protein of hepatitis B virus functions as a transcriptional corepressor on the human telomerase promoter

The X protein of hepatitis B virus (HBx) is essential for transactivation of hepatitis B viral and host cellular genes. It has been specifically implicated in the development of hepatocellular carcinoma; however, the molecular mechanism remains unknown. Telomeres, the DNA-protein complexes at the ends of eukaryotic chromosomes, protect chromosomes from degradation at the terminal regions, fusion with a broken DNA end, and inappropriate recombination. The shortening of telomeres that occurs during hepatocellular carcinogenesis has been well studied. In the present study, we isolated an HBx isoform that resulted in telomere shortening in hepatoma cell lines. We found that this HBx isoform down-regulated the expression of human telomerase by transcriptionally repressing its promoter. To further determine the molecular mechanism, we examined human telomerase promoter and identified myc-associated zinc finger protein (MAZ) as a transcriptional repressor of the promoter. We found that the HBx isoform achieved transcriptional suppression of human telomerase by enhancing MAZ binding to its consensus sequence in the promoter through physical association with MAZ.

CONCLUSION

The data suggest that HBx can induce telomere shortening by acting as a transcriptional corepressor of MAZ on the human telomerase promoter.

Autocrine TGF-beta signaling in the pathogenesis of systemic sclerosis

Excessive extracellular matrix deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). Fibroblasts isolated from sclerotic lesions in patients with SSc and cultured in vitro are characterized by increased synthesis of collagen and other extracellular matrix components, consistent with the disease phenotype. Thus, cultured scleroderma fibroblasts serve as a principal experimental model for studying the mechanisms involved in extracellular matrix overproduction in SSc. The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that transforming growth factor-beta (TGF-beta) is a key mediator of tissue fibrosis as a consequence of extracellular matrix accumulation in the pathology of SSc. TGF-beta regulates diverse biological activities including cell growth, cell death or apoptosis, cell differentiation, and extracellular matrix synthesis. TGF-beta is known to induce the expression of extracellular matrix proteins in mesenchymal cells and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the extracellular matrix. This review focuses on the possible role of autocrine TGF-beta signaling in the pathogenesis of SSc.

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.

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.

Molecular functions and biological roles of hepatitis B virus x protein

Chronic infection of hepatitis B virus (HBV) is one of the major causes of hepatocellular carcinoma (HCC) in the world. Hepatitis B virus X protein (HBx) has been long suspected to be involved in hepatocarcinogenesis, although its oncogenic role remains controversial. HBx is a multifunctional regulator that modulates transcription, signal transduction, cell cycle progress, protein degradation pathways, apoptosis, and genetic stability by directly or indirectly interacting with host factors. This review focuses on the biological roles of HBx in HBV replication and cellular transformation in terms of the molecular functions of HBx. Using the transient HBV replication assay, ectopically expressed HBx could stimulate HBV transcription and replication with the X-defective replicon to the level of those with the wild one. The transcription coactivation is mainly contributing to the stimulatory role of HBx on HBV replication although the other functions may affect HBV replication. Effect of HBx on cellular transformation remains controversial and was never addressed with human primary or immortal cells. Using the human immortalized primary cells, HBx was found to retain the ability to overcome active oncogene RAS-induced senescence that requires full-length HBx. At least two functions of HBx, the coactivation function and the ability to overcome oncogene-induced senescence, may be cooperatively involved in HBV-related hepatocarcinogenesis.

The activin axis in liver biology and disease

Activins are a closely related subgroup within the TGFbeta superfamily of growth and differentiation factors. They consist of two disulfide-linked beta subunits. Four mammalian activin beta subunits termed beta(A), beta(B), beta(C), and beta(E), respectively, have been identified. Activin A, the homodimer of two beta(A) subunits, has important regulatory functions in reproductive biology, embryonic development, inflammation, and tissue repair. Several intra- and extracellular antagonists, including the activin-binding proteins follistatin and follistatin-related protein, serve to fine-tune activin A activity. In the liver there is compelling evidence that activin A is involved in the regulation of cell number by inhibition of hepatocyte replication and induction of apoptosis. In addition, activin A stimulates extracellular matrix production in hepatic stellate cells and tubulogenesis of sinusoidal endothelial cells, and thus contributes to restoration of tissue architecture during liver regeneration. Accumulating evidence from animal models and from patient data suggests that deregulation of activin A signaling contributes to pathologic conditions such as hepatic inflammation and fibrosis, acute liver failure, and development of liver cancer. Increased production of activin A was suggested to be a contributing factor to impaired hepatocyte regeneration in acute liver failure and to overproduction of extracellular matrix in liver fibrosis. Recent evidence suggests that escape of (pre)neoplastic hepatocytes from growth control by activin A through overexpression of follistatin and reduced activin production contributes to hepatocarcinogenesis. The role of the activin subunits beta(C) and beta(E), which are both highly expressed in hepatocytes, is still quite incompletely understood. Down-regulation in liver tumors and a growth inhibitory function similar to that of beta(A) has been shown for beta(E). Contradictory results with regard to cell proliferation have been reported for beta(C). The profound involvement of the activin axis in liver biology and in the pathogenesis of severe hepatic diseases suggests activin as potential target for therapeutic interventions.

The antifibrogenic effect of (-)-epigallocatechin gallate results from the induction of de novo synthesis of glutathione in passaged rat hepatic stellate cells

Hepatic stellate cells (HSC) are the major players during hepatic fibrogenesis. Overproduction of extracellular matrix (ECM) is a characteristic of activated HSC. Transforming growth factor-beta (TGF-beta) is the most potent fibrogenic cytokine while connective tissue growth factor (CTGF) mediates the production of TGF-beta-induced ECM in activated HSC. HSC activation and hepatic fibrogenesis are stimulated by oxidative stress. Glutathione (GSH) is the most important intracellular antioxidant. The aim of this study is to explore the mechanisms of (-)-epigallocatechin-3-gallate (EGCG), the major and most active component in green tea extracts, in the inhibition of ECM gene expression in activated HSC. It is hypothesized that EGCG inhibits ECM gene expression in activated HSC by interrupting TGF-beta signaling through attenuating oxidative stress. It is found that EGCG interrupts TGF-beta signaling in activated HSC by suppressing gene expression of type I and II TGF-beta receptors. EGCG inhibits CTGF gene expression, leading to the reduction in the abundance of ECM, including alphaI(I) procollagen. Exogenous CTGF dose dependently eliminates the antifibrogenic effect. EGCG attenuates oxidative stress in passaged HSC by scavenging reactive oxygen species and reducing lipid peroxidation. De novo synthesis of GSH is a prerequisite for EGCG to interrupt TGF-beta signaling and to reduce the abundance of alphaI(I) procollagen in activated HSC in vitro. Taken together, our results demonstrate that the interruption of TGF-beta signaling by EGCG results in the suppression of gene expression of CTGF and ECM in activated HSC in vitro. In addition, our results, for the first time, demonstrate that the antioxidant property of EGCG derived from de novo synthesis of intracellular GSH plays a critical role in its antifibrogenic effect. These results provide novel insights into the mechanisms of EGCG as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

Hepatitis B virus X protein and the estrogen receptor variant lacking exon 5 inhibit estrogen receptor signaling in hepatoma cells

Hepatitis B virus (HBV) X protein (HBx) is considered to play a role in the development of hepatocellular carcinoma (HCC) during HBV infection. HCC was shown to be more prevalent in men than in women. Estrogen, which exerts its biological function through estrogen receptor (ER), can inhibit HBV replication. ERDelta5, an ERalpha variant lacking exon 5, was found to be preferentially expressed in patients with HCC compared with patients with normal livers. Here, we report the biological role of ERDelta5 and a novel link between HBx and ERalpha signaling in hepatoma cells. ERDelta5 interacts with ERalpha in vitro and in vivo and functions as a dominant negative receptor. Both ERalpha and ERDelta5 associate with HBx. HBx decreases ERalpha-dependent transcriptional activity, and HBx and ERDelta5 have additive effect on suppression of ERalpha transactivation. The HBx deletion mutant that lacks the ERalpha-binding site abolishes the HBx repression of ERalpha. HBx, ERalpha and histone deacetylase 1 (HDAC1) form a ternary complex. Trichostatin A, a specific inhibitor of HDAC enzyme, can restore the transcriptional activity of ERalpha inhibited by HBx. Our data suggest that HBx and ERDelta5 may play a negative role in ERalpha signaling and that ERalpha agonists may be developed for HCC therapy.

Expression and location of Smad2, 4 mRNAs during and after liver fibrogenesis of rats

AIM: To investigate the location alteration of Smad2 and Smad4 mRNAs in the liver during and after fibrogenesis in rats.

METHODS: Eighty male Wistar rats weighing approximately 200 g each were used. The rat models of experimental hepatic fibrosis were established by injection with carbon tetrachloride (CCl₄), normal rats and rats were injected with olive oil and served as control groups. In situ hybridization(ISH) was used to detect the Smad2 and Smad4 mRNA in liver.

RESULTS: In situ hybridization showed Smad2 and Smad4 mRNA expressions in the cytoplasm of hepatic stellate cells (HSC), fibroblasts and myofibroblasts around the central vein and hepatic sinus during and after fibrogenesis. Expression of Smad2, 4 mRNA was higher than that in normal and control rats.

CONCLUSION: In the process of and after hepatic fibrosis formation, HSC, fibroblasts and myofibroblasts are the major cells that express Smad2 and Smad4. The more serious the hepatic fibrosis is in the injured liver, the higher the level of Smad2 and Smad4 gene expression is during and after fibrogenesis respectively.

Modulation of the transforming growth factor-beta signal transduction pathway by hepatitis C virus nonstructural 5A protein

Transforming growth factor-beta (TGF-beta) is implicated in the pathogenesis of liver disease. TGF-beta is involved both in liver regeneration and in the fibrotic and cirrhotic transformation with hepatitis viral infection. Hepatitis C virus (HCV) infection often leads to cirrhosis and hepatocellular carcinoma. HCV nonstructural 5A (NS5A) protein is a multifunctional protein that modulates cytokine-mediated signal transduction pathways. To elucidate the molecular mechanism of HCV pathogenesis, we examined the effect of NS5A protein on TGF-beta-stimulated signaling cascades. We show that NS5A protein inhibited the TGF-beta-mediated signaling pathway in hepatoma cell lines as determined by reporter gene assay. To further investigate the role of NS5A, we examined the protein/protein interaction between NS5A and TGF-beta signal transducers. Both in vitro and in vivo binding data showed that NS5A protein directly interacted with TGF-beta receptor I (TbetaR-I) in hepatoma cell lines. This interaction was mapped to amino acids 148-238 of NS5A. We also found that NS5A protein co-localized with TbetaR-I in the cytoplasm of Huh7 cells and inhibited TGF-beta-mediated nuclear translocation of Smad2. Furthermore, we demonstrate that NS5A protein abrogated the phosphorylation of Smad2 and the heterodimerization of Smad3 and Smad4. To further explore the relevance to viral infection, we examined the effect of the HCV subgenomic replicon on the TGF-beta signaling pathway. We show that the HCV subgenomic replicon also inhibited TGF-beta-induced signaling cascades. These results indicate that HCV NS5A modulates TGF-beta signaling through interaction with TbetaR-I and that NS5A may be an important risk factor in HCV-associated liver pathogenesis.

Constitutively phosphorylated Smad3 interacts with Sp1 and p300 in scleroderma fibroblasts

OBJECTIVE

To elucidate the role of transforming growth factor-beta (TGF-beta)/Smad signalling in the increased expression of the collagen gene in systemic sclerosis (SSc) fibroblasts.

METHODS

Dermal fibroblasts from seven patients with diffuse SSc of recent onset and from seven healthy individuals were studied. The expression levels of Smad2, Smad3 and Smad4 proteins were determined by immunoblotting. Smad3 phosphorylation and the interaction of Smad3 with Sp1 or p300 were analysed using immunoprecipitation. The effects of overexpression of Smad proteins or Sp1 on the human alpha2(I) collagen gene transcription were investigated with chloramphenicol acetyltransferase (CAT) assays using the -772 COL1A2/CAT construct.

RESULTS

Constitutive increased Smad3 phosphorylation was detected in SSc fibroblasts compared with normal fibroblasts. Increased interaction of Smad3 with Sp1 as well as p300 was also detected in SSc fibroblasts. The overexpression of Smad3 caused an increase of up to 5-fold in COL1A2 promoter activity in normal fibroblasts, while Smad3 caused a small increase in COL1A2 promoter activity in SSc fibroblasts. However, neither Smad2 nor Smad4 caused significant effects in COL1A2 promoter activity in normal fibroblasts or SSc fibroblasts. The overexpression of Sp1 caused further increase in COL1A2 promoter activity stimulated by TGF-beta in normal fibroblasts, but did not change COL1A2 promoter activity in the presence of TGF-beta in SSc fibroblasts. The combined overexpression of Smad3 and Sp1 significantly enhanced TGF-beta response in normal fibroblasts, but less markedly in SSc fibroblasts.

CONCLUSIONS

These results suggested that SSc fibroblasts are less sensitive to exogenous TGF-beta stimulation because they are already activated by the autocrine TGF-beta loop.

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.

Scleroderma, fibroblasts, signaling, and excessive extracellular matrix

Excessive extracellular matrix (ECM) deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that various cytokines such as transforming growth factor (TGF)-beta and their signaling pathways are key mediators of tissue fibrosis as a consequence of ECM accumulation in the pathogenesis of fibrosis such as SSc. TGF-beta regulates diverse biologic activities including cell growth, cell death or apoptosis, cell differentiation, and ECM synthesis. TGF-beta is known to induce the expression of ECM proteins in mesenchymal cells, and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the ECM. This paper focuses on the possible role of ECM, various cytokines, especially TGF-beta signal transduction pathways in the pathogenesis of fibrosis in SSc.

Molecular mechanisms in hepatocellular carcinoma development

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. It usually develops in patients with chronic viral hepatitis, aflatoxin exposure, or excessive alcohol use. Most patients with HCC present with advanced disease and have a poor prognosis. The implementation of antiviral drugs and the availability of a vaccine for hepatitis B should help reduce the incidence of HCC. Considerable effort has now focused on unraveling the molecular pathogenesis of HCC in order to design better treatments, or to prevent the disease altogether. However, so far, the pathogenesis of HCC appears to be quite heterogeneous among patients. In particular, several mechanisms of tumorigenesis seem to be involved, including loss of tumor suppressor gene function, oncogene activation, direct viral effects, DNA methylation, and angiogenesis. It is not clear which events are critical in tumor initiation versus tumor progression. RNA expression arrays and proteomics hold promise to provide further clues about this common and complex cancer.

Hepatitis C viral proteins interact with Smad3 and differentially regulate TGF-beta/Smad3-mediated transcriptional activation

Transforming growth factor-beta (TGF-beta) is a pleiotropic cytokine implicated as a pathogenic mediator in various liver diseases. Enhanced TGF-beta production and lack of TGF-beta responses are often observed during hepatitis C virus (HCV) infection. In this study, we demonstrate that TGF-beta-mediated transactivation is decreased in cells exogenously expressing the intact HCV polyprotein. Among 10 viral products of HCV, only core and nonstructural protein 3 (NS3) physically interact with the MH1 (Mad homology 1) region of the Smad3 and block TGF-beta/Smad3-mediated transcriptional activation through interference with the DNA-binding ability of Smad3, not the nuclear translocation. However, the interactive domain of NS3 extends to the MH2 (Mad homology 2) region of Smad3 and a distinction is found between effects mediated, respectively, by these two viral proteins. HCV core, in the presence or absence of TGF-beta, has a stronger suppressive effect on the DNA-binding and transactivation ability of Smad3 than NS3. Although HCV core, NS3, and the HCV subgenomic replicon all attenuate TGF-beta/Smad3-mediated apoptosis, only HCV core represses TGF-beta-induced G1 phase arrest through downregulation of the TGF-beta-induced p21 promoter activation. Along with this, HCV core, rather than NS3, exhibits a significant inhibitory effect on the binding of Smad3/Sp1 complex to the proximal p21 promoter in response to TGF-beta. In conclusion, HCV viral proteins interact with the TGF-beta signaling mediator Smad3 and differentially impair TGF-beta/Smad3-mediated transactivation and growth inhibition. This functional counteraction of TGF-beta responses provides insights into possible mechanisms, whereby the HCV oncogenic proteins antagonize the host defenses during hepatocarcinogenesis.

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Expression of TGF-b1 and smad4 mRNA in chronic hepatitis, liver cirrhosis, hepatocellular carcinoma and para-cancerous tissues, and their significance

AIM: Transforming growth factor b1 (TGF-b1) signaling pathway is involved in a variety of important cellular regulative functions. including cell growth, differentiation, adhesion migration, extracellular matrix formation and immune regulation. The study was aimed to evaluate the relationship and mechanism of transforming growth factor b1 protein and smad4 mRNA in formation and development of fibrosis by detecting the expression of transforming growth factor b1 protein and smad4 mRNA in liver biopsy of chronic virus hepatitis, hepatocirrhosis and para-cancerous tissues.

METHODS: In situ hybridization and immunohistochemistry were used in 10 cases of normal liver tissue, 17 cases of para-cancerous tissues, 70 cases of chronic virus hepatitis and hepatocirrhosis.

RESULTS: Increased expression of TGF-b1 and smad4 mRNA in the intermediate degree of chronic virus hepatitis and hepatocirrhosis; the positive rates of TGF-b1 and smad4 mRNA were obviously higher in the chronic virus hepatitis and hepatocirrhosis (83.3%, 87.0% and 87.5%, 87.0%) than those in the normal liver (20.0%, 20.0%), the expression of TGF-b1 and smad4 mRNA had a significant relationship between the intermediate degree of chronic virus hepatitis, hepatocirrhosis and the normal liver (^b3P <0.01, χ² = 12.3980; ^b4P <0.01, χ² = 14.0 609; ^b1P <0.01, χ² = 14.6 953; ^b2P <0.01, χ² = 14.0 609); the expression of TGF-b1 and smad4 mRNA in pare-cancerous tissues were significantly lower than that in the chronic virus hepatitis and hepatocirrhosis, as comparied with with the normal liver; the expression of TGF-b1 and smad4 mRNA reached the highest level at the stage S3, and decreased slightly at the stage S4, with positive relevance (χ² = 4.5 064, P = 0.0 336, r = 0.2 668), in which most of the positive cells were distributed surroundings of portal tract, central vein, and the sinus.

CONCLUSION: TGF-b/smad pathway plays a significant role in formation and development of hepatic fibrosis, and the localization of TGF-b1 and smad4mRNA in hepatic tissue section can be used to evaluate accurately situation and tendency of hepatic fibrosis.

Effect of lamivudine treatment on plasma levels of transforming growth factor β1, tissue inhibitor of metalloproteinases-1 and metalloproteinase-1 in patients with chronic hepatitis B

AIM: Transforming growth factor (TGF)-β₁, metalloproteinase (MMP)-1 and its tissue inhibitor (TIMP)-1 are considered predictive biomarkers of chronic hepatitis activity and fibrosis. The aim of this study was to evaluate the effect of lamivudine treatment on the plasma levels of these peptides in patients with chronic hepatitis B.

METHODS: TGF-β₁, MMP-1 and TIMP-1 plasma concentrations were measured with an enzyme immunoassay in 40 patients treated with lamivudine for 48 wk. Elimination of HBV-DNA and HBV antigens was evaluated 24 wk after treatment completion.

RESULTS: Baseline TGF-β₁ (29.6 ± 2.2 ng/mL) and TIMP-1 (1578 ± 93 ng/mL) significantly exceeded normal values (18.3 ± 1.6 ng/mL and 1102 ± 67 ng/mL respectively). Lamivudine treatment resulted in a significant decrease of TGF-β₁ and TIMP-1 during treatment with an increase after 24 wk of treatment. Pretreatment MMP-1 levels (6.7 ± 0.7 ng/mL) were significantly lower than normal values (11.9 ± 0.9 ng/mL) and increased during treatment and follow-up. A significant correlation was noted between TGF-β₁ or TIMP-1 and aminotransferases as well as fibrosis scored in liver biopsy specimens. There were no statistically significant differences of TGF-β₁, TIMP-1 and MMP-1 between four groups at baseline, 24 and 48 wk of treatment. TGF-β₁ and TIMP-1 levels increased significantly in non-responders and normalized in responders at wk 72. MMP-1 also normalized in responders and decreased to values significantly lower than normal in non-responders.

CONCLUSION: These findings support the role of TGF-β₁, TIMP-1 and MMP-1 in the pathogenesis of chronic hepatitis B. Because of their association with hepatic injury and antiviral treatment efficacy, determination of these peptides may be useful in disease management.

Hepatitis C virus NS5A-regulated gene expression and signaling revealed via microarray and comparative promoter analyses

Most individuals exposed to hepatitis C virus (HCV) become chronically infected and are predisposed to liver disease. The mechanisms underlying viral persistence and disease progression are unknown. A role for the HCV NS5A protein in viral replication and interferon resistance has been demonstrated. To identify mechanisms affected by NS5A, we analyzed the gene expression of Huh7 cells expressing NS5A and control cells using oligonucleotide microarrays. A set of 103 genes (43 up-regulated, 60 down-regulated) whose expression was modified by at least twofold was selected. These included genes involved in cell adhesion and motility, calcium homeostasis, lipid transport and metabolism, and genes regulating immune responses. The finding of modulated expression of genes related to the TGF-beta superfamily and liver fibrosis was observed. Interestingly, both the tumor necrosis factor and lymphotoxin beta receptors were down-regulated by NS5A. Similar data were obtained following expression of four NS5A mutants obtained from patients who were not responsive or were sensitive to interferon therapy. Through computational analysis, we determined that 39 of the 43 genes up-regulated by NS5A contained one or more nuclear factor kappaB (NF-kappaB) binding sites within their promoter region. Using the Gibbs sampling method, we also detected enrichment of NF-kappaB consensus binding sites in the upstream regions of the 43 coexpressed genes. Activation of NF-kappaB by NS5A was subsequently demonstrated in luciferase reporter assays. Adenovirus-mediated expression of IkappaBalpha reverted NS5A mediated up-regulation of gene expression. In conclusion, this study suggests a role of NS5A and NF-kappaB in HCV pathogenesis and related liver disease. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).

SMAD5 gene expression, rearrangements, copy number, and amplification at fragile site FRA5C in human hepatocellular carcinoma

Signaling by the transforming growth factor (TGF)-family members is transduced from the cell surface to the nucleus by the Smad group of intracellular proteins. Because we detected alterations on the long arm of chromosome 5, we examined the status of the SMAD5 gene in human hepatocellular carcinoma (HCC) cell lines and primary HCC. In 16 cell lines, chromosome alterations of chromosome 5 were observed in nine cell lines by fluorescence in situ hybridization (FISH), and an increase in SMAD5 gene copy number relative to the ploidy level was found in eight lines. The breakpoints in unbalanced translocations and deletions frequently occurred near the SMAD5 locus, but apparently did not cause loss of SMAD5. In one cell line, where comparative genomic hybridization showed DNA copy number gain confined to the region 5q31, we detected by FISH high-level amplification of the SMAD5 gene located within the fragile site FRA5C. Semiquantitative polymerase chain reaction did not reveal changes in SMAD5 DNA levels in 15 of 17 primary HCC specimens. In 17 HCC cell lines, SMAD5 mRNA levels were either maintained or upregulated by an increase in gene dosage or another mechanism. Collectively, our results show that SMAD5 undergoes copy number gain and increased expression, rather than loss of expression, and therefore suggest that this gene does not act as a tumor-suppressor gene in HCC. The Hep-40 HCC cell line with high-level amplification and significant overexpression of SMAD5 may be useful in studying the interaction of SMAD5 with other genes.

Interaction of the hepatitis B virus X protein (HBx) with heat shock protein 60 enhances HBx-mediated apoptosis

Understanding the function of the hepatitis B virus X protein (HBx) is fundamental to elucidating the underlying mechanisms of hepatitis and hepatocarcinogenesis caused by hepatitis B virus (HBV) infection. We identified heat shock protein 60 (Hsp60) as a novel cellular target of HBx by the combination of affinity purification and mass spectrometry. Physical interaction between HBx and Hsp60 was confirmed by standard immunoprecipitation and immunoblot methods. Analysis of HBx deletion constructs showed that amino acids 88-117 of HBx were responsible for the binding to Hsp60. Confocal laser microscopy demonstrated that HBx and Hsp60 colocalized in mitochondria. Furthermore, terminal deoxynucleotidyl transferase-mediated dUTP end labeling (TUNEL) revealed that the introduction of Hsp60 into cells facilitated HBx-induced apoptosis. These findings suggest the importance of the molecular chaperon protein Hsp60 to the function of HBV viral proteins.

Human S15a expression is upregulated by hepatitis B virus X protein

The hepatitis B virus (HBV)-encoded X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) through the upregulated expression of selected cellular genes. To identify these genes, RNAs isolated from HBxAg-positive and -negative HepG2 cells were compared by PCR select cDNA subtraction. One gene overexpressed in HBxAg-positive cells by Northern and Western blotting is the ribosomal protein S15a. The S15a mRNA is 535 base pairs, encoding a protein 130 amino acids long with a molecular weight of 14.3 kDa. S15a expression was upregulated in HBV-infected livers, where it costained with HBxAg. Overexpression of S15a stimulated cell growth, colony formation in soft agar, and tumor formation in SCID mice. Hence, HBxAg upregulated the expression of S15a, the latter of which participates in the development of HCC, perhaps by altering the integrity of translation.