Hepatitis C virus core protein inhibits apoptosis via enhanced Bcl-xL expression

Leveraging metformin to combat hepatocellular carcinoma: its therapeutic promise against hepatitis viral infections

Hepatocellular carcinoma (HCC) is categorized among the most common primary malignant liver cancer and a primary global cause of death from cancer. HCC tends to affect males 2-4 times more than females in many nations. The main factors that raise the incidence of HCC are chronic liver diseases, hepatotropic viruses like hepatitis B (HBV) and C (HCV), non-alcoholic fatty liver disease, exposure to toxins like aflatoxin, and non-alcoholic steatohepatitis (NASH). Among these, hepatitis B and C are the most prevalent causes of chronic hepatitis globally. Metformin, which is made from a naturally occurring compound called galegine, derived from the plant Galega officinalis (G. officinalis ), has been found to exhibit antitumor effects in a wide range of malignancies, including HCC. In fact, compared to patients on sulphonylureas or insulin, studies have demonstrated that metformin treatment significantly lowers the risk of HCC in patients with chronic liver disease. This article will first describe the molecular mechanism of hepatitis B and C viruses in the development of HCC. Then, we will provide detailed explanations about metformin, followed by a discussion of the association between metformin and hepatocellular carcinoma caused by the viruses mentioned above.

Unraveling the Molecular Mechanisms Involved in HCV-Induced Carcinogenesis

Cancer induced by a viral infection is among the leading causes of cancer. Hepatitis C Virus (HCV) is a hepatotropic oncogenic positive-sense RNA virus that leads to chronic infection, exposing the liver to a continuous process of damage and regeneration and promoting hepatocarcinogenesis. The virus promotes the development of carcinogenesis through indirect and direct molecular mechanisms such as chronic inflammation, oxidative stress, steatosis, genetic alterations, epithelial-mesenchymal transition, proliferation, and apoptosis, among others. Recently, direct-acting antivirals (DAAs) showed sustained virologic response in 95% of cases. Nevertheless, patients treated with DAAs have reported an unexpected increase in the early incidence of Hepatocellular carcinoma (HCC). Studies suggest that HCV induces epigenetic regulation through non-coding RNAs, DNA methylation, and chromatin remodeling, which modify gene expressions and induce genomic instability related to HCC development that persists with the infection's clearance. The need for a better understanding of the molecular mechanisms associated with the development of carcinogenesis is evident. The aim of this review was to unravel the molecular pathways involved in the development of carcinogenesis before, during, and after the viral infection's resolution, and how these pathways were regulated by the virus, to find control points that can be used as potential therapeutic targets.

Hepatitis C Core Protein Induces a Genotype-Specific Susceptibility of Hepatocytes to TNF-Induced Death In Vitro and In Vivo

Hepatitis C virus (HCV) core protein is a multifunctional protein that is involved in the proliferation, inflammation, and apoptosis mechanism of hepatocytes. HCV core protein genetic variability has been implicated in various outcomes of HCV pathology and treatment. In the present study, we aimed to analyze the role of the HCV core protein in tumor necrosis factor α (TNFα)-induced death under the viewpoint of HCV genetic variability. Immortalized hepatocytes (IHH), and not the Huh 7.5 hepatoma cell line, stably expressing HCV subtype 4a and HCV subtype 4f core proteins showed that only the HCV 4a core protein could increase sensitivity to TNFα-induced death. Development of two transgenic mice expressing the two different core proteins under the liver-specific promoter of transthyretin (TTR) allowed for the in vivo assessment of the role of the core in TNFα-induced death. Using the TNFα-dependent model of lipopolysaccharide/D-galactosamine (LPS/Dgal), we were able to recapitulate the in vitro results in IHH cells in vivo. Transgenic mice expressing the HCV 4a core protein were more susceptible to the LPS/Dgal model, while mice expressing the HCV 4f core protein had the same susceptibility as their littermate controls. Transcriptome analysis in liver biopsies from these transgenic mice gave insights into HCV core molecular pathogenesis while linking HCV core protein genetic variability to differential pathology in vivo.

Impact of Hepatitis C Virus Infection of Peripheral Blood Mononuclear Cells on the Immune System

Hepatitis C is a worldwide liver disease caused by hepatitis C virus (HCV) infection. The virus causes acute and chronic liver inflammation, and it is transmitted mainly by exposure to contaminated blood. HCV is capable of infecting hepatocytes and peripheral blood mononuclear cells, causing complications and disease progression. This mini review provides an overview of HCV infection, including details on the virological aspects, infection of the immune cells, and its impact on the immune system.

Association Between Chronic Hepatitis C Virus Infection and Esophageal Cancer: A Systematic Review and Meta-analysis

BACKGROUND

Chronic hepatitis C virus (HCV) infection is associated with increased risk of hepatobiliary tract cancer. However, whether chronic HCV infection is also associated with elevated risk of other types of cancer is still unknown. This systematic review and meta-analysis was conducted in order to investigate whether chronic HCV infection is positively associated with esophageal cancer.

METHODS

A systematic review was conducted using Embase and MEDLINE databases from inception to November 2019, with a search strategy that comprised the terms for "hepatitis C virus" and "cancer." Eligible studies were cohort studies consisting of patients with chronic HCV infection and comparators without HCV infection, and followed them for incident esophageal cancer. Hazard risk ratio, incidence rate ratio, relative risk or standardized incidence ratio of this association were extracted from each eligible study along with their 95% confidence intervals and were combined to calculate the pooled effect estimate using the random effect, generic inverse variance method.

RESULTS

A total of 20,459 articles were identified using this search strategy. After 2 rounds of independent review, 7 studies satisfied the inclusion criteria and were included in the meta-analysis. Chronic HCV infection was significantly associated with a higher incidence of esophageal cancer with the pooled relative risk of 1.61 (95% confidence interval: 1.19-2.17; I2=39%). The funnel plot was relatively symmetric which was not suggestive of publication bias.

CONCLUSION

This systematic review and meta-analysis demonstrated that there is a modest association between chronic HCV and incident esophageal cancer. However, more studies are needed to investigate the causality of this association.

Association of HCV mutated proteins and host SNPs in the development of hepatocellular carcinoma

Hepatitis C virus plays a significant role in the development of hepatocellular carcinoma (HCC) globally. The pathogenic mechanisms of hepatocellular carcinoma with HCV infection are generally linked with inflammation, cytokines, fibrosis, cellular signaling pathways, and liver cell proliferation modulating pathways. HCV encoded proteins (Core, NS3, NS4, NS5A) interact with a broad range of hepatocytes derived factors to modulate an array of activities such as cell signaling, DNA repair, transcription and translational regulation, cell propagation, apoptosis, membrane topology. These four viral proteins are also implicated to show a strong conversion potential in tissue culture. Furthermore, Core and NS5A also trigger the accretion of the β-catenin pathway as a common target to contribute viral induced transformation. There is a strong association between HCV variants within Core, NS4, and NS5A and host single nucleotide polymorphisms (SNPs) with the HCC pathogenesis. Identification of such viral mutants and host SNPs is very critical to determine the risk of HCC and response to antiviral therapy. In this review, we highlight the association of key variants, mutated proteins, and host SNPs in development of HCV induced HCC. How such viral mutants may modulate the interaction with cellular host machinery is also discussed.

Increased Spontaneous Programmed Cell Death Is Associated with Impaired Cytokine Secretion in Peripheral Blood Mononuclear Cells from Hepatitis C Virus-Positive Patients

Peripheral blood mononuclear cells (PBMCs) play a critical role in clearing hepatitis C virus (HCV). PBMC defects have been linked with HCV infection; however, the underlying mechanisms remain obscure. We hypothesized that PBMCs of HCV-infected patients are more susceptible to programmed cell death (PCD), and are therefore unable to clear HCV. We compared spontaneous PBMC PCD and cytokine [interleukin (IL)-1, -6, -8, -10, and -12] secretion between untreated (naive) HCV⁺ and treated [sustained responder (SR)] patients with HCV, and HCV^- healthy controls. Spontaneous PBMC PCD was assessed by annexin-V fluorescein isothiocyanate/propidium iodide staining, and cytokine levels were measured by cytometric bead array. Differences between groups were analyzed through paired and nonpaired t tests and Mann-Whitney U test. The rate of spontaneous PCD was higher in PBMCs of naive HCV⁺ patients (p < 0.0001) and SR-HCV patients (p < 0.002) than in HCV^- controls. Significantly low levels of IL-8, -6, and -10 were detected in the supernatant of cell cultures of PBMCs from naive HCV⁺ (p < 0.05) and SR-HCV (p < 0.05) patients relative to HCV^- controls. There was no difference between the naive HCV⁺ and SR-HCV groups in terms of PBMC PCD rate or cytokine levels. The present findings indicate that HCV infection is associated with increased PBMC susceptibility to PCD and decreased production of IL-8, -6, and -10.

Hepatitis B and C virus-induced hepatitis: Apoptosis, autophagy, and unfolded protein response

AIM

To investigate the co-incidence of apoptosis, autophagy, and unfolded protein response (UPR) in hepatitis B (HBV) and C (HCV) infected hepatocytes.

METHODS

We performed immunofluorescence confocal microscopy on 10 liver biopsies from HBV and HCV patients and tissue microarrays of HBV positive liver samples. We used specific antibodies for LC3β, cleaved caspase-3, BIP (GRP78), and XBP1 to detect autophagy, apoptosis and UPR, respectively. Anti-HCV NS3 and anti-HBs antibodies were also used to confirm infection. We performed triple blind counting of events to determine the co-incidence of autophagy (LC3β punctuate), apoptosis (cleaved caspase-3), and unfolded protein response (GRP78) with HBV and HCV infection in hepatocytes. All statistical analyses were performed using SPSS software for Windows (Version 16 SPSS Inc, Chicago, IL, United States). P-values < 0.05 were considered statistically significant. Statistical analyses were performed with Mann-Whitney test to compare incidence rates for autophagy, apoptosis, and UPR in HBV- and HCV-infected cells and adjacent non-infected cells.

RESULTS

Our results showed that infection of hepatocytes with either HBV and HCV induces significant increase (P < 0.001) in apoptosis (cleavage of caspase-3), autophagy (LC3β punctate), and UPR (increase in GRP78 expression) in the HCV- and HBV-infected cells, as compared to non-infected cells of the same biopsy sections. Our tissue microarray immunohistochemical expression analysis of LC3β in HBV(Neg) and HBV(Pos) revealed that majority of HBV-infected hepatocytes display strong positive staining for LC3β. Interestingly, although XBP splicing in HBV-infected cells was significantly higher (P < 0.05), our analyses show a slight increase of XBP splicing was in HCV-infected cells (P > 0.05). Furthermore, our evaluation of patients with HBV and HCV infection based on stage and grade of the liver diseases revealed no correlation between these pathological findings and induction of apoptosis, autophagy, and UPR.

CONCLUSION

The results of this study indicate that HCV and HBV infection activates apoptosis, autophagy and UPR, but slightly differently by each virus. Further studies are warranted to elucidate the interconnections between these pathways in relation to pathology of HCV and HBV in the liver tissue.

Apoptosis in liver carcinogenesis and chemotherapy

Hepatocellular carcinoma (HCC) is a major health problem. In human hepatocarcinogenesis, the balance between cell death and proliferation is deregulated, tipping the scales for a situation where antiapoptotic signals are overpowering the death-triggering stimuli. HCC cells harbor a wide variety of mutations that alter the regulation of apoptosis and hence the response to chemotherapeutical drugs, making them resistant to the proapoptotic signals. Considering all these modifications found in HCC cells, therapeutic approaches need to be carefully studied in order to specifically target the antiapoptotic signals. This review deals with the recent relevant contributions reporting molecular alterations for HCC that lead to a deregulation of apoptosis, as well as the challenge of death-inducing chemotherapeutics in current HCC treatment.

Disruption of Bcl-2 and Bcl-xL by viral proteins as a possible cause of cancer

The Bcl proteins play a critical role in apoptosis, as mutations in family members interfere with normal programmed cell death. Such events can cause cell transformation, potentially leading to cancer. Recent discoveries indicate that some viral proteins interfere with Bcl proteins either directly or indirectly; however, these data have not been systematically described. Some viruses encode proteins that reprogramme host cellular signalling pathways controlling cell differentiation, proliferation, genomic integrity, cell death, and immune system recognition. This review analyses and summarises the existing data and discusses how viral proteins interfere with normal pro- and anti-apoptotic functions of Bcl-2 and Bcl-xL. Particularly, this article focuses on how viral proteins, such as Herpesviruses, HTLV-1, HPV and HCV, block apoptosis and how accumulation of such interference predisposes cancer development. Finally, we discuss possible ways to prevent and treat cancers using a combination of traditional therapies and antiviral preparations that are effective against these viruses.

Biochemical/metabolic changes associated with hepatocellular carcinoma development in mice

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality after lung and stomach cancers. This work was undertaken to investigate some of the biochemical mediators/pathways associated with or implicated in the pathogenesis of HCC. Male albino mice were classified into two groups: normal control group and HCC group. Early stage HCC was induced by injection of diethylnitrosamine (DEN) i.p. 200 mg/kg as a single dose, and after 2 weeks, the mice were given i.p. injection of thioacetamide (TAA) 100 mg/kg twice per week for 4 weeks. Mice were left for further 2 weeks without any treatment, after which, mice were sacrificed; blood and liver samples were collected. Serum was used for determination of activities of glucose-6-phosphate dehydrogenase (G6PDH) and aldolase as well as levels of insulin-like growth factor-1 (IGF-1) and epithelial cadherin (E-cadherin). One portion of the liver was used for histopathological examination and immunohistochemical staining of the tumor suppressor p53 protein. Another portion of the liver was used for determination of citrate synthase activity. Induction of HCC in mice resulted in significant increase in G6PDH and aldolase activities, and E-cadherin level, but significant decrease in IGF-1. HCC mice group showed moderate expression of p53 protein. These results suggest that the molecular pathogenesis of HCC in mice involves reduction of serum level of IGF-1 and increased serum level of E-cadherin accompanied by dysregulation of p53 protein expression. HCC was also associated with reprogrammed metabolic profile shifted toward increased glycolysis and lipogenesis.

RNA virus capsid proteins: more than just a shell

Capsid proteins are obligatory components of infectious virions. Their primary structural function is to protect viral genomes during entry and exit from host cells. Evidence suggests that these proteins can also modulate the activity and specificity of viral replication complexes. More recently, it has become apparent that they play critical roles at the virus–host interface. Here, we discuss how capsid proteins of RNA viruses interact with key host cell proteins and pathways to modulate cell physiology in order to benefit virus replication. Capsid–host cell interactions may also have implications for viral disease. Understanding how capsids regulate virus–host interactions may lead to the development of novel antiviral therapies based on targeting the activities of cellular proteins.

Hepatitis C virus and hepatocellular carcinoma

Hepatitis C virus (HCV), a hepatotropic virus, is a single stranded-positive RNA virus of ~9,600 nt. length belonging to the Flaviviridae family. HCV infection causes acute hepatitis, chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC). It has been reported that HCV-coding proteins interact with host-cell factors that are involved in cell cycle regulation, transcriptional regulation, cell proliferation and apoptosis. Severe inflammation and advanced liver fibrosis in the liver background are also associated with the incidence of HCV-related HCC. In this review, we discuss the mechanism of hepatocarcinogenesis in HCV-related liver diseases.

Altered of apoptotic markers of both extrinsic and intrinsic pathways induced by hepatitis C virus infection in peripheral blood mononuclear cells

Background

Chronic hepatitis C (CHC) has emerged as a leading cause of cirrhosis in the U.S. and across the world. To understand the role of apoptotic pathways in hepatitis C virus (HCV) infection, we studied the mRNA and protein expression patterns of apoptosis-related genes in peripheral blood mononuclear cells (PBMC) obtained from patients with HCV infection.

Methods

The present study included 50 subjects which plasma samples were positive for HCV, but negative for human immunodeficiency virus (HIV) or hepatitis B virus (HBV). These cases were divided into four groups according to METAVIR, a score-based analysis which helps to interpret a liver biopsy according to the degree of inflammation and fibrosis. mRNA expression of the studied genes were analyzed by reverse transcription of quantitative polymerase chain reaction (RT-qPCR) and protein levels, analyzed by ELISA, was also conducted. HCV genotyping was also determined.

Results

HCV infection increased mRNA expression and protein synthesis of caspase 8 in group 1 by 3 fold and 4 fold, respectively (p < 0.05). In group 4 HCV infection increased mRNA expression and protein synthesis of caspase 9 by 2 fold and 1,5 fold, respectively (p < 0.05). Also, caspase 3 mRNA expression and protein synthesis had level augumented by HCV infection in group 1 by 4 fold and 5 fold, respectively, and in group 4 by 6 fold and 7 fold, respectively (p < 0.05).

Conclusions

HCV induces alteration at both genomic and protein levels of apoptosis markers involved with extrinsic and intrinsic pathways.

The expression and effects the CABYR-c transcript of CABYR gene in hepatocellular carcinoma

BACKGROUND AND AIM

CABYR, a calcium-binding tyrosine phosphorylation regulated fibrous sheath protein, was initially reported to be testis-specific and subsequently shown to be present in brain tumors, pancreas cancer and lung cancer. This study aimed to investigate the expression and effects of the CABYR-c transcript of CABYR gene in hepatocellular carcinoma.

METHODS

mRNA and protein expression of CABYR-c was examined in 20 paired hepatocellular carcinoma tissues and adjacent non-cancerous tissues by real-time quantitative RT-polymerase chain reaction (PCR) and western blot analysis respectively. HepG2 cells were treated with the antisense oligodeoxynucleotides targeting CABYR-c mRNA (CABYR-c antisense oligonucleotides [AS ODNs]) for indicated times, the AS ODNs inhibition effect was evaluated by measuring the CABYR-c mRNA expression level of HepG2 cells after treatment using real-time quantitative RT-PCR, then cell proliferation was studied using MTT assay, and cell cycle distribution and apoptosis were detected by flow cytometry as well.

RESULTS

CABYR-c mRNA levels in hepatocellular carcinoma tissues were significantly higher than that in the paired adjacent non-cancerous tissues (27.5 ± 1.2 versus 2.5 ± 0. 9, P < 0.01). CABYR-c protein expression level in hepatocellular carcinoma tissues was also significantly higher than that in adjacent non-cancerous tissues. CABYR-c mRNA expression in HepG2 cells was most effective down-regulated after treatment of 600 nM CABYR-c AS ODNs for 48 h, which was selected for subsequent experiments. Incubation with 600 nM CABYR-c AS ODNs inhibited the cell growth of HepG2 cells in a dose- and time-dependent manner. The maximum inhibitory effect achieved at 600 nM after 72 h treatment (30.92 ± 3.25%, P < 0.01). HepG2 cells treated 600 nM CABYR-c AS ODNs for 48 h exhibited an increasing proportion of cells in G0/G1 phase (P < 0.05) and a decreasing proportion of cells in S phase (P < 0.05), compared with untreated controls. No obvious differences were observed in G2/M phase. The fraction of apoptotic HepG2 cells in CABYR-c AS ODNs treated group was less than that of untreated control group (P < 0.05).

CONCLUSION

CABYR-c is highly expressed in hepatocellular carcinoma tissues and may play an oncogenic role in heptocarcinogenesis as well as its progression.

Dual behavior of HCV Core gene in regulation of apoptosis is important in progression of HCC

Hepatitis C virus (HCV) causes acute and chronic hepatitis which can lead to HCC (Hepatocelluar carcinoma) via oxidative stress, steatosis, insulin resistance, fibrosis and liver cirrhosis. Apoptosis is essential for the control and eradication of viral infections. In acute HCV infection, enhanced hepatocyte apoptosis is significant for elimination of viral pathogen. In case of chronic HCV, down regulation of apoptosis and enhanced cell proliferation not only causes HCV infection persistency in the majority of patients. However, the impact of apoptosis in chronic HCV infection is not well understood. It may be harmful by triggering liver fibrosis, or essential in interferon (IFN) induced HCV elimination. Regulation of apoptosis in hepatocytes by HCV Core is so important in progression of HCC. This review focuses on the dual character of HCV Core on regulation of apoptosis and progression of HCC.

Anti-apoptotic effect of HCV core gene of genotype 3a in Huh-7 cell line

Background

Hepatitis C virus (HCV) Core protein regulates multiple signaling pathways and alters cellular genes expression responsible for HCV induced pathogenesis leading to hepatocellular carcinoma (HCC). Prevalence of HCV genotype 3a associated HCC is higher in Pakistan as compare to the rest of world; however the molecular mechanism behind this is still unclear. This study has been designed to evaluate the effect of HCV core 3a on apoptosis and cell proliferation which are involved in HCC

Methodology

We examined the in vitro effect of HCV Core protein of genotype 3a and 1a on cellular genes involved in apoptosis by Real time PCR in liver cell line (Huh-7). We analyzed the effect of HCV core of genotype 1a and 3a on cell proliferation by MTT assay and on phosphrylation of Akt by western blotting in Huh-7 cells.

Results

The HCV 3a Core down regulates the gene expression of Caspases (3, 8, 9 and 10), Cyto C and p53 which are involved in apoptosis. Moreover, HCV 3a Core gene showed stronger effect in regulating protein level of p-Akt as compared to HCV 1a Core accompanied by enhanced cell proliferation in Huh-7 cell line.

Conclusion

From the current study it has been concluded that reduced expression of cellular genes involved in apoptosis, increased p-Akt (cell survival gene) and enhanced cell proliferation in response to HCV 3a core confirms anti apoptotic effect of HCV 3a Core gene in Huh-7 that may lead to HCC.

Characterization of chronic HCV infection-induced apoptosis

Background

To understand the complex and largely not well-understood apoptotic pathway and immune system evasion mechanisms in hepatitis C virus (HCV)-associated hepatocellular carcinoma (HCC) and HCV associated chronic hepatitis (CH), we studied the expression patterns of a number of pro-apoptotic and anti-apoptotic genes (Fas, FasL, Bcl-2, Bcl-xL and Bak) in HepG2 cell line harboring HCV- genotype-4 replication. For confirmation, we also assessed the expression levels of the same group of genes in clinical samples obtained from 35 HCC and 34 CH patients.

Methods

Viral replication was assessed in the tissue culture medium by RT-PCR, quantitative Real-Time PCR (qRT-PCR); detection of HCV core protein by western blot and inhibition of HCV replication with siRNA. The expression level of Fas, FasL, Bcl-2, Bcl-xL and Bak was assessed by immunohistochemistry and RT-PCR whereas caspases 3, 8 and 9 were assessed by colorimetric assay kits up to 135 days post infection.

Results

There was a consistent increase in apoptotic activity for the first 4 weeks post-CV infection followed by a consistent decrease up to the end of the experiment. The concordance between the changes in the expression levels of Fas, FasL, Bcl-2, Bcl-xL and Bak in vitro and in situ was statistically significant (p < 0.05). Fas was highly expressed at early stages of infection in cell lines and in normal control liver tissues followed by a dramatic reduction post-HCV infection and an increase in the expression level of FasL post HCV infection. The effect of HCV infection on other apoptotic proteins started very early post-infection, suggesting that hepatitis C modulating apoptosis by modulating intracellular pro-apoptotic signals.

Conclusions

Chronic HCV infection differently modulates the apoptotic machinery during the course of infection, where the virus induces apoptosis early in the course of infection, and as the disease progresses apoptosis is modulated. This study could open a new opportunity for understanding the various signaling of apoptosis and in the developing a targeted therapy to inhibit viral persistence and HCC development.

Potential targets for molecular imaging of apoptosis resistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers, which is mainly a concern in Southeast Asia. Apoptosis resistance in HCC is one of the significant factors for hepatocarcinogenesis and tumour progression. Recent advances of apoptosis resistance mechanisms in HCC could serve as potential targets for molecular imaging, which would be of considerable value to explore the molecular processes involved in HCC progression and to evaluate responses of certain anti-HCC therapies. Disruptions in the balance of anti-apoptotic and pro-apoptotic processes have been found to be involved in apoptosis resistance in HCC. Loss of response to death receptors, transformation of growth factor-β induced apoptosis, upregulation of anti-apoptotic Bcl-2 subgroup, as well as downregulation of pro-apoptotic Bax subgroup and BH3-only subgroup, are associated with apoptosis resistance in HCC. Mutation of p53 gene, dysregulation of NF-κB and survivin are also of interest because of their contribution to HCC development. In this review, the aim is to identify potential targets for molecular imaging of apoptosis resistance in HCC.

The let-7 family of microRNAs inhibits Bcl-xL expression and potentiates sorafenib-induced apoptosis in human hepatocellular carcinoma

BACKGROUND & AIMS

Bcl-xL, an anti-apoptotic member of the Bcl-2 family, is over-expressed in human hepatocellular carcinoma, conferring a survival advantage to tumour cells. The mechanisms underlying its dysregulation have not been clarified. In the present study, we explored the involvement of microRNAs that act as endogenous sequence-specific suppressors of gene expression.

METHODS

The expression profiles of microRNAs in Huh7 hepatoma cells and primary human hepatocytes were compared by microarray analysis. The effect of let-7 on Bcl-xL expression was examined by Western blot and a reporter assay. The involvement of let-7 microRNAs in human tissues was analysed by western blot and reverse transcription-PCR.

RESULTS

Microarray analysis, followed by in silico target prediction, identified let-7 microRNAs as being downregulated in Huh7 hepatoma cells in comparison with primary human hepatocytes, as well as possessing a putative target site in the bcl-xl mRNA. Over-expression of let-7c or let-7g led to a clear decrease of Bcl-xL expression in Huh7 and HepG2 cell lines. Reporter assays revealed direct post-transcriptional regulation involving let-7c or let-7g and the 3'-untranslated region of bcl-xl mRNA. Human hepatocellular carcinoma tissues with low expression of let-7c displayed higher expression of Bcl-xL protein than those with high expression of let-7c, suggesting that low let-7 microRNA expression contributes to Bcl-xL over-expression. Finally, expression of let-7c enhanced apoptosis of hepatoma cells upon exposure to sorafenib, which downregulates expression of another anti-apoptotic Bcl-2 protein, Mcl-1.

CONCLUSIONS

let-7 microRNAs negatively regulate Bcl-xL expression in human hepatocellular carcinomas and induce apoptosis in cooperation with an anti-cancer drug targeting Mcl-1.

Characteristic mutations in hepatitis C virus core gene related to the occurrence of hepatocellular carcinoma

Chronic hepatitis C virus (HCV) infection often results in hepatocellular carcinoma (HCC). Previous studies have shown that there might be some characteristic mutations in the core region of HCV related to HCC. Thus, we downloaded and analyzed HCV genotype 1b core gene sequences from HCV databases online to identify them. Based on the information of the sequences, 63 from patients with HCC and 188 from non-HCC were enrolled into our analysis. Then, the nucleotides at each position were compared by chi(2)-test between the two groups, and 24 polymorphisms were found to be associated with HCC. Further analysis of these 24 polymorphisms by logistic regression indicated that eight were significantly related to the increased HCC risk: A028C, G209A, C219U/A, U264C, A271C/U, C378U/A, G435A/C, and G481A. Moreover, U303C/A was associated with the decreased HCC risk. These mutations could bring about four amino acid substitutions: K10Q, R70Q, M91L, and G161S. In conclusion, eight characteristic mutations in the HCV-1b core gene related to the occurrence of HCC were identified. The structural and functional alterations of core protein due to these mutations and the relationship with the occurrence of HCC need to be further studied.

Hepatitis C virus core protein induces apoptosis-like caspase independent cell death

Background

Hepatitis C virus (HCV) associated liver diseases may be related to apoptotic processes. Thus, we investigated the role of different HCV proteins in apoptosis induction as well as their potency to interact with different apoptosis inducing agents.

Methods and Results

The use of a tightly adjustable tetracycline (Tet)-dependent HCV protein expression cell system with the founder osteosarcoma cell line U-2 OS allowed switch-off and on of the endogenous production of HCV proteins. Analyzed were cell lines expressing the HCV polyprotein, the core protein, protein complexes of the core, envelope proteins E1, E2 and p7, and non-structural proteins NS3 and NS4A, NS4B or NS5A and NS5B. Apoptosis was measured mainly by the detection of hypodiploid apoptotic nuclei in the absence or presence of mitomycin C, etoposide, TRAIL and an agonistic anti-CD95 antibody. To further characterize cell death induction, a variety of different methods like fluorescence microscopy, TUNEL (terminal deoxynucleotidyl transferase (TdT)-catalyzed deoxyuridinephosphate (dUTP)-nick end labeling) assay, Annexin V staining, Western blot and caspase activation assays were included into our analysis.

Two cell lines expressing the core protein but not the total polyprotein exerted a strong apoptotic effect, while the other cell lines did not induce any or only a slight effect by measuring the hypodiploid nuclei. Cell death induction was caspase-independent since it could not be blocked by zVAD-fmk. Moreover, caspase activity was absent in Western blot analysis and fluorometric assays while typical apoptosis-associated morphological features like the membrane blebbing and nuclei condensation and fragmentation could be clearly observed by microscopy. None of the HCV proteins influenced the apoptotic effect mediated via the mitochondrial apoptosis pathway while only the core protein enhanced death-receptor-mediated apoptosis.

Conclusion

Our data showed a caspase-independent apoptosis-like effect of the core protein, which seems to be inhibited in the presence of further HCV proteins like the non structural (NS) proteins. This observation could be of relevance for the viral spread since induction of an apoptosis-like cell death by the core protein may have some impact on the release of the HCV particles from the host cell.

The hepatitis C virus core protein contains a BH3 domain that regulates apoptosis through specific interaction with human Mcl-1

The hepatitis C virus (HCV) core protein is known to modulate apoptosis and contribute to viral replication and pathogenesis. In this study, we have identified a Bcl-2 homology 3 (BH3) domain in the core protein that is essential for its proapoptotic property. Coimmunoprecipitation experiments showed that the core protein interacts specifically with the human myeloid cell factor 1 (Mcl-1), a prosurvival member of the Bcl-2 family, but not with other prosurvival members (Bcl-X(L) and Bcl-w). Moreover, the overexpression of Mcl-1 protects against core-induced apoptosis. By using peptide mimetics, core was found to release cytochrome c from isolated mitochondria when complemented with Bad. Thus, core is a bona fide BH3-only protein having properties similar to those of Noxa, a BH3-only member of the Bcl-2 family that binds preferentially to Mcl-1. There are three critical hydrophobic residues in the BH3 domain of the core protein, and they are essential for the proapoptotic property of the core protein. Furthermore, the genotype 1b core protein is more effective than the genotype 2a core protein in inducing apoptosis due to a single-amino-acid difference at one of these hydrophobic residues (residue 119). Replacing this residue in the J6/JFH-1 infectious clone (genotype 2a) with the corresponding amino acid in the genotype 1b core protein produced a mutant virus, J6/JFH-1(V119L), which induced significantly higher levels of apoptosis in the infected cells than the parental J6/JFH-1 virus. Furthermore, the core protein of J6/JFH-1(V119L), but not that of J6/JFH-1, interacted with Mcl-1 in virus-infected cells. Taken together, the core protein is a novel BH3-only viral homologue that contributes to the induction of apoptosis during HCV infection.

Dysregulation of apoptosis in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a major health problem, being the sixth most common cancer world-wide. Dysregulation of the balance between proliferation and cell death represents a pro-tumorigenic principle in human hepatocarcinogenesis. This review updates the recent relevant contributions reporting molecular alterations for HCC that induce an imbalance in the regulation of apoptosis. Alterations in the expression and/or activation of p53 are frequent in HCC cells, which confer on them resistance to chemotherapeutic drugs. Many HCCs are also insensitive to apoptosis induced either by death receptor ligands, such as FasL or TRAIL, or by transforming growth factor-beta (TGF-β). Although the expression of some pro-apoptotic genes is decreased, the balance between death and survival is dysregulated in HCC mainly due to overactivation of anti-apoptotic pathways. Indeed, some molecules involved in counteracting apoptosis, such as Bcl-X_L, Mcl-1, c-IAP1, XIAP or survivin are over-expressed in HCC cells. Furthermore, some growth factors that mediate cell survival are up-regulated in HCC, as well as the molecules involved in the machinery responsible for cleavage of their pro-forms to an active peptide. The expression and/or activation of the JAK/STAT, PI3K/AKT and RAS/ERKs pathways are enhanced in many HCC cells, conferring on them resistance to apoptotic stimuli. Finally, recent evidence indicates that inflammatory processes, as well as the epithelial-mesenchymal transitions that occur in HCC cells to facilitate their dissemination, are related to cell survival. Therefore, therapeutic strategies to selectively inhibit anti-apoptotic signals in liver tumor cells have the potential to provide powerful tools to treat HCC.

Cellular and molecular interactions in coinfection with hepatitis C virus and human immunodeficiency virus

Coinfection with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) is associated with increased HCV replication and a more rapid progression to severe liver disease, including the development of cirrhosis and hepatocellular carcinoma. In this review, we discuss the current understanding of the pathogenesis of HCV/HIV coinfection and the cellular and molecular mechanisms associated with the accelerated course of liver disease. The strength and breadth of HCV-specific T-cell responses are reduced in HCV/HIV-coinfected patients compared with those infected with HCV alone, suggesting that the immunosuppression induced by HIV compromises immune responses to HCV. HCV is not directly cytopathic, but many of the pathological changes observed in the liver of infected patients are a direct result of the intrahepatic antiviral immune responses. Apoptosis also has a role in HCV-mediated liver damage through the induction of apoptotic pathways involving the host immune response and HCV viral proteins. This review summarises the evidence correlating the role of cell-mediated immune responses and apoptosis with liver disease progression in HCV/HIV-coinfected patients.

Specific targeting of hepatitis C virus core protein by an intracellular single-chain antibody of human origin

The hepatitis C virus (HCV) core protein is essential for viral genome encapsidation and plays an important role in steatosis, immune evasion, and hepatocellular carcinoma. It may thus represent a promising therapeutic target to interfere with the HCV life-cycle and related pathogenesis. In this study, we used phage display to generate single-chain variable domain antibody fragments (scFv) to the core protein from bone marrow plasma cells of patients with chronic hepatitis C. An antibody with high-affinity binding (scFv42C) was thus identified, and the binding site was mapped to the PLXG motif (residues 84-87) of the core protein conserved among different genotypes. Whereas scFv42C displayed diffuse cytoplasmic fluorescence when expressed alone in the Huh7 human hepatoma cell line, cotransfection with the core gene shifted its subcellular distribution into that of core protein. The intracellular association of scFv42C with its target core protein was independently demonstrated by the fluorescence resonance energy transfer technique. Interestingly, expression of the single-chain antibody reduced core protein levels intracellularly, particularly in the context of full HCV replication. Moreover, cell proliferation as induced by the core protein could be reversed by scFv4C coexpression. Therefore, scFv42C may represent a novel anti-HCV agent, which acts by sequestering core protein and attenuating core protein-mediated pathogenesis.

Fas / FasL system, IL-1beta expression and apoptosis in chronic HBV and HCV liver disease

The Fas / Fas-ligand (FasL) system is an important death signal pathway in the liver. An enhanced local inflammatory response prompted by FasL expression, which contributes to neutrophil recruitment and interleukin-1 beta (IL-1beta) release, seems to be crucial to chronic liver damage, persistence of viral infections, and probably initiation and / or promotion of HCC. In order to evaluate the expression of Fas, FasL, and IL-1beta in different stages of human liver disease and to determine whether hepatitis B virus (HBV) and hepatitis C virus (HCV) infections modulate their expression, also in relation to apoptosis, we examined 87 liver samples obtained from patients with: chronic hepatitis (CH) (n.42), cirrhosis (n.9) and hepatocellular carcinoma (HCC) (n.16) and corresponding peritumoural tissues (n.16); histologically-normal liver (n.4) as controls. Fas, FasL and IL-1beta mRNA were quantified using reverse transcriptase-polymerase chain reaction. The apoptotic index was evaluated by TUNEL analysis. Our data showed a progressive Fas / FasL increase from CH to cirrhosis followed by a decline from the latter to HCC. In histological sections apoptosis was detected in HCC. A significant difference emerged between HCV and HBV-related disease for IL-1beta expression only in CH. A significant positive correlation between IL-1beta and FasL in HCV-related disease (P = 0.014) and an inverse correlation between IL-1beta and Fas in HBV-related disease (P = 0.021) were observed. The different pattern of IL-1beta, Fas and FasL expression found in HCV- and HBV-mediated liver disease, points to a different modulation of immune response B and C virus induced, while the decline in Fas / FasL expression in HCC may be related to defence mechanisms adopted by HCC cells against the immune system.

Modulation of signaling pathways by RNA virus capsid proteins

Capsid proteins are structural components of virus particles. They are nucleic acid-binding proteins whose main recognized function is to package viral genomes into protective structures called nucleocapsids. Research over the last 10 years indicates that in addition to their role as genome guardians, viral capsid proteins modulate host cell signaling networks. Disruption or alteration of intracellular signaling pathways by viral capsids may benefit replication of the virus by affecting innate immunity and in some cases, may underlie disease progression. In this review, we describe how the capsid proteins from medically relevant RNA viruses interact with host cell signaling pathways.

Hepatitis C virus infection and apoptosis

Apoptosis is central for the control and elimination of viral infections. In chronic hepatitis C virus (HCV) infection, enhanced hepatocyte apoptosis and upregulation of the death inducing ligands CD95/Fas, TRAIL and TNFα occur. Nevertheless, HCV infection persists in the majority of patients. The impact of apoptosis in chronic HCV infection is not well understood. It may be harmful by triggering liver fibrosis, or essential in interferon (IFN) induced HCV elimination. For virtually all HCV proteins, pro- and anti-apoptotic effects have been described, especially for the core and NS5A protein. To date, it is not known which HCV protein affects apoptosis in vivo and whether the infectious virions act pro- or anti-apoptotic. With the availability of an infectious tissue culture system, we now can address pathophysiologically relevant issues. This review focuses on the effect of HCV infection and different HCV proteins on apoptosis and of the corresponding signaling cascades.

Redox regulation of hepatitis C in nonalcoholic and alcoholic liver

Hepatitis C virus (HCV) is an RNA virus of the Flaviviridae family that is estimated to have infected 170 million people worldwide. HCV can cause serious liver disease in humans, such as cirrhosis, steatosis, and hepatocellular carcinoma. HCV induces a state of oxidative/nitrosative stress in patients through multiple mechanisms, and this redox perturbation has been recognized as a key player in HCV-induced pathogenesis. Studies have shown that alcohol synergizes with HCV in the pathogenesis of liver disease, and part of these effects may be mediated by reactive species that are generated during hepatic metabolism of alcohol. Furthermore, reactive species and alcohol may influence HCV replication and the outcome of interferon therapy. Alcohol consumption has also been associated with increased sequence heterogeneity of the HCV RNA sequences, suggesting multiple modes of interaction between alcohol and HCV. This review summarizes the current understanding of oxidative and nitrosative stress during HCV infection and possible combined effects of HCV, alcohol, and reactive species in the pathogenesis of liver disease.

Expression of Bax, Bcl-xL and Bcl-2 proteins in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C

AIMS

To determine the expression of regulators of apoptosis in chronic hepatitis C.

METHODS AND RESULTS

Expression of Bax, Bcl-xL and Bcl-2 proteins was assessed immunohistochemically in liver biopsy specimens obtained from 89 adults with chronic hepatitis C. Expression of Bax in hepatocytes correlated inversely with grade of inflammation (P < 0.001) and stage of fibrosis (P = 0.011), classified according to the Scheuer score; expression of Bcl-xL in hepatocytes did not correlate with grade of inflammation (P = 0.106) or stage of fibrosis (P = 0.078); maximum Bcl-xL expression was observed in grade 3 inflammation and stage 4 fibrosis. Expression of Bcl-2 protein in hepatocytes was present in only two cases (both with advanced disease); the expression of Bcl-2 protein in interlobular bile duct epithelial cells correlated with the grade of inflammation (P = 0.018), but not with stage of fibrosis (P = 0.154). The expression of Bcl-2 protein in lymphoid cells infiltrating portal zones and lobules did not correlate with grade of inflammation (P = 0.113) or stage of fibrosis (P = 0.815).

CONCLUSION

Major differences in expression of studied proteins were observed in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C.

High-throughput flow cytometry-based assay to identify apoptosis-inducing proteins

After sequencing the human genome, the challenge ahead is to systematically analyze the functions and disease relation of the proteins encoded. Here the authors describe the application of a flow cytometry-based high-throughput assay to screen for apoptosis-activating proteins in transiently transfected cells. The assay is based on the detection of activated caspase-3 with a specific antibody, in cells overexpressing proteins tagged C- or N-terminally with yellow fluorescent protein. Fluorescence intensities are measured using a flow cytometer integrated with a high-throughput autosampler. The applicability of this screen has been tested in a pilot screen with 200 proteins. The candidate proteins were all verified in an independent microscopy-based nuclear fragmentation assay, finally resulting in the identification of 6 apoptosis inducers.

Modulation of apoptosis as a target for liver disease

Apoptosis mediated via extrinsic or intrinsic pathways is essential for maintaining cellular homeostasis in the liver. The extrinsic pathway is triggered from the cell surface by engagement of death receptors as CD95, TRAIL (TNF-related apoptosis inducing ligand) and TNF (tumour necrosis factor) or TGF-beta (transforming growth factor beta) receptors. The intrinsic pathway is initiated from the mitochondria and can be influenced by Bcl-2 family members. Both pathways are intertwined and play a physiological role in the liver. Dysregulation of apoptosis pathways contributes to diseases as hepatocellular carcinoma, viral hepatitis, autoimmune hepatitis, ischaemia-reperfusion injury, iron or copper deposition disorders, toxic liver damage and acute liver failure. The apoptosis defects are often central pathogenetic events; hence molecular mechanisms of apoptosis give not only insight into disease mechanisms but also provide potential corresponding therapeutic candidates in liver disease. The focus of this review is the identification of apoptotic signalling components in the liver as therapeutic targets.

Expression of Ki-67, transforming growth factor beta1, and B-cell lymphoma-leukemia-2 in liver tissue of patients with chronic liver diseases

BACKGROUND

The purpose of the present paper was to assess expression of proliferation, fibrosis and apoptosis markers in different phases of chronic liver diseases.

METHODS

Sixty-six adults with chronic liver diseases (chronic hepatitis C, n = 48; chronic hepatitis B, n = 10; alcohol chronic liver disease, n = 8) treated at the Department of Infectious Diseases and Hepatology from 1999 to 2001, composed the study group. Liver biopsy specimens were used for immunohistochemical assessment of expression of Ki-67, transforming growth factor beta1 (TGF-beta1) and B-cell lymphoma-leukemia-2 (Bcl-2). Grade of liver inflammation and stage of fibrosis were evaluated according to the Scheuer scale.

RESULTS

Expression of Ki-67 in hepatocytes was most intensive in patients with grade 2 and 3 inflammation. The expression in patients with grade 4 inflammation was low. The expression of Ki-67 in lymphocytes was most intensive in patients with grade 2 inflammation. Expression of TGF-beta1 in hepatocytes reached a maximum in patients with grade 2 or 3 inflammation and dropped in patients with grade 4 inflammation. There was a statistically significant correlation between stage of fibrosis and expression of TGF-beta1 in liver stromal cells. A very strong correlation was found between the expression of Bcl-2 in bile ductules epithelium and the grade of inflammation (P = 0.006). The expression of Bcl-2 in hepatocytes was observed only in patients with very intense liver inflammation (grade 3) and in patients with stage 3 or 4 fibrosis.

CONCLUSION

Processes of proliferation, fibrosis and apoptosis are not directly correlated to progression of liver disease. Expression of studied markers can be used for analysis of dynamics of these processes.

L’apoptose hépatique

Apoptosis or programmed cell death occurs in the liver as in other organs. In the normal state it is not a frequent mode of hepatic cell destruction. Morphological and biochemical characteristics of liver cell apoptosis do not differ from what is observed in other cells. The Fas receptor pathway, a frequent hepatic apoptotic pathway among various others, involves intra-cellular signals amplified by mitochondria. Although hepatic apoptosis may occur by following several others pathways, Fas, which is abundantly expressed in the plasma membrane of hepatocytes, is very often involved in hepatocyte demise during B or C viral hepatitis irrespective of their clinical form, alcoholic hepatitis, cholestasis due to accumulation of hepatic biliary salts, or certain types of drug-induced hepatitis. Fas is also probably responsible for the death of biliary cells in primary biliary cirrhosis. In contrast one of the causes of resistance to apoptosis of hepatic cancerous cells could be related to an alteration of the Fas receptor. This is why much experimental work is presently performed to achieve inhibition of the Fas receptor either at the mRNA level or at the level of Fas-inductible proteolytic enzymes called caspases. One perspective is a specific treatment of apoptosis as an adjuvant treatment of liver diseases.

Hepatitis C virus core protein inhibits deoxycholic acid-mediated apoptosis despite generating mitochondrial reactive oxygen species

BACKGROUND

Hepatitis C virus (HCV) core protein is known to cause oxidative stress and alter apoptosis pathways. However, the apoptosis results are inconsistent, and the real significance of oxidative stress is not well known. The aim of this study was twofold. First, we wanted to confirm whether core-induced oxidative stress was really significant enough to cause DNA damage, and whether it induced cellular antioxidant responses. Second, we wanted to evaluate whether this core-induced oxidative stress and the antioxidant response to it was responsible for apoptosis changes.

METHODS

HCV core protein was expressed under control of the Tet-Off promoter in Huh-7 cells and HeLa cells. We chose to use deoxycholic acid (DCA) as a model because it is known to produce both reactive oxygen species (ROS) and apoptosis.

RESULTS

Core expression uniformly increased ROS and 8-hydroxy-2'-deoxyguanosine (8-OHdG) under basal and DCA-stimulated conditions. Core protein expression also increased manganese superoxide dismutase levels. Core protein inhibited DCA-mediated mitochondrial membrane depolarization and DCA-mediated activation of caspase-9 and caspase-3, despite the increase in ROS by DCA. Core protein inhibited DCA-mediated apoptosis by increasing Bcl-x(L) protein and decreasing Bax protein, without affecting the proportion of Bax between mitochondria and cytosol, resulting in suppression of cytochrome c release from mitochondria into cytoplasm.

CONCLUSIONS

HCV core protein induces oxidative DNA damage, whereas it inhibits apoptosis that is accompanied by enhancement of ROS production. Thus, oxidative stress and apoptosis modulation by core protein are independent of each other.

Hepatitis C virus core protein inhibits mitochondrial electron transport and increases reactive oxygen species (ROS) production

Hepatitis C infection causes a state of chronic oxidative stress, which may contribute to fibrosis and carcinogenesis in the liver. Previous studies have shown that expression of the HCV core protein in hepatoma cells depolarized mitochondria and increased reactive oxygen species (ROS) production, but the mechanisms of these effects are unknown. In this study we examined the properties of liver mitochondria from transgenic mice expressing HCV core protein, and from normal liver mitochondria incubated with recombinant core protein. Liver mitochondria from transgenic mice expressing the HCV proteins core, E1 and E2 demonstrated oxidation of the glutathione pool and a decrease in NADPH content. In addition, there was reduced activity of electron transport complex I, and increased ROS production from complex I substrates. There were no abnormalities observed in complex II or complex III function. Incubation of control mitochondria in vitro with recombinant core protein also caused glutathione oxidation, selective complex I inhibition, and increased ROS production. Proteinase K digestion of either transgenic mitochondria or control mitochondria incubated with core protein showed that core protein associates strongly with mitochondria, remains associated with the outer membrane, and is not taken up across the outer membrane. Core protein also increased Ca(2+) uptake into isolated mitochondria. These results suggest that interaction of core protein with mitochondria and subsequent oxidation of the glutathione pool and complex I inhibition may be an important cause of the oxidative stress seen in chronic hepatitis C.

Proapoptotic and pronecrosis effect of different truncated hepatitis C virus core proteins

OBJECTIVE

To study the roles of different truncated hepatitis C virus (HCV) core proteins (CORE) in the pathogenesis of HCV persistent infection and hepatocellular carcinoma (HCC) and to assess intracellular localization in transiently transfected cells.

METHODS

Seven truncated GFP (green fluorescent protein)-CORE fusion protein expression plasmids were constructed, which contained HCV CORE sequences derived from tumor tissues (BT) and non-tumor tissues (BNT) from one patient infected with HCV. Amino acid (aa) lengths were BT: 1-172 aa, 1-126 aa, 1-58 aa, 59-126 aa, 127-172 aa; BNT: 1-172 aa and C191: 1-172 aa respectively. Subcellular localization of CORE-GFP was analyzed by con-focal laser scanning microscope. Apoptosis and necrosis were quantified by flow cytometry.

RESULTS

Different truncated CORE-GFP localized mainly in the cytoplasm, but nuclear staining was also observed. HCV CORE could induce apoptosis and necrosis, and different truncated COREs could induce cell apoptosis and necrosis at different levels. Among the same length 1-172 aa of BT, BNT and C191, the cell apoptosis and necrosis percentage of BT is highest, and C191 is the lowest (BT>BNT>C191). To the different fragment COREs of BT, N-terminal of CORE induced apoptosis and necrosis higher, compared with that of C-terminal (1-172 aa>1-126 aa>1-58 aa>127-172 aa>59-126 aa).

CONCLUSION

These results suggest HCV CORE could induce apoptosis and necrosis of cells, which might play an important role in the pathogenesis of HCV persistent infection and HCC and the different CORE domains of different HCV quasi-species might have some difference in their pathogenesis.

Hepatitis B virus X protein induces apoptosis in hepatoma cells through inhibiting Bcl-xL expression

The X protein of hepatitis B virus (HBx) exhibits numerous activities affecting gene transcription, intracellular signal transduction, cell proliferation and apoptosis. Recent studies showed that HBx induced apoptosis by causing loss of mitochondrial membrane potential, suggesting that HBx-mediated apoptosis is mitochondria-dependent. However, the molecular mechanism of the gene in this pathway is still far from understood. In this study, we demonstrated that introduction of HBx into a hepatocellular carcinoma cell line, Hep3B, caused apoptosis and sensitized the cell to TNFalpha-induced cell killing. Over-expression of Bcl-xL, an anti-apoptotic Bcl-2 family protein, prevented cell death dragged by HBx. Importantly, expression of HBx in Hep3B cells reduced Bcl-xL mRNA and protein levels, but did not regulate other Bcl-2 family members. Although, HBx itself did not affect intracellular distribution of cytochrome c, an enhanced release of cytochrome c from mitochondria was observed when TNFalpha was applied. Thus, the introduction of HBx into Hep3B cells induces apoptosis and sensitizes Hep3B cells to TNFalpha-mediated cell killing, and these processes may accomplish through inhibiting Bcl-xL expression and subsequently promoting cytochrome c release from mitochondria.

Interferon sensitivity-determining region of nonstructural region 5A of hepatitis C virus genotype 1b correlates with serum alanine aminotransferase levels in chronic infection

The mutations in the interferon (IFN) sensitivity-determining region (ISDR) of nonstructural region 5A (NS5A) of hepatitis C virus (HCV) have been correlated with response to IFN therapy. NS5A appears to disrupt a host antiviral pathway that plays a role in suppressing virus replication and protects hepatocytes from apoptosis. We assessed whether ISDR correlates with viral load and serum alanine aminotransferase (ALT) levels. Serum viral load and ALT levels were prospectively measured bimonthly by HCV core protein assay and monthly, respectively, for 22 months in 87 patients chronically infected with HCV genotype 1b. ISDR of HCV was directly sequenced from the products of reverse transcription and polymerase chain reaction of HCV RNA. Five patients had four or more substitutions (mutant type), 33 had 1-3 (intermediate type), and 49 had no substitutions (wild type) in ISDR. The numbers of substitutions in ISDR were inversely correlated with mean viral load over a 22-month period (r = 0.292, P = 0.0060) and directly with mean serum ALT levels (r = 0.360, P = 0.0006). The numbers of substitutions in ISDR was significantly larger in the patients with changes of viral load more than fivefold during the 22 months (1.4 +/- 2.4) than in those without changes (0.6 +/- 0.8) (P = 0.0188). The present study demonstrates that the patients with more substitutions in ISDR had significantly higher serum ALT levels and smaller viral load. These results suggest that NS5A with more substitutions in ISDR may lose the ability to block host antiviral pathways and to protect hepatocytes from apoptosis.

Impaired expression of the peroxisome proliferator-activated receptor alpha during hepatitis C virus infection

BACKGROUND AND AIMS

Liver inflammation, fibrosis, and dyslipidemia are common features in patients with chronic hepatitis C virus (HCV) infection. Because peroxisome proliferator-activated receptor alpha (PPARalpha) is highly expressed in the liver and is involved in the regulation of lipid metabolism and inflammation, we sought to determine whether HCV infection may locally impair PPARalpha expression and activity.

METHODS

PPARalpha expression was investigated in liver biopsy specimens of 86 untreated patients with HCV infection and controls, by using real-time polymerase chain reaction (PCR), Western blot analysis, and immunohistochemistry. PPARalpha activity was assessed by quantification of the key gene target carnitine palmitoyl acyl-CoA transferase 1 (CPT1A) messenger RNA (mRNA). The influence of HCV core protein on PPARalpha mRNA expression was analyzed in vitro by real-time PCR in HCV core-expressing HepG2 cells activated with the PPARalpha ligand fenofibric acid.

RESULTS

Hepatic concentrations of PPARalpha and CPT1A expressed by hepatocytes were impaired profoundly in the livers of untreated patients with HCV infection compared with controls. A mean decrease of 85% in PPARalpha mRNA expression paralleled with a lack of CPT1A mRNA induction also were observed in HCV core-expressing HepG2 cells compared with controls.

CONCLUSIONS

HCV infection is related to altered expression and function of the anti-inflammatory nuclear receptor PPARalpha. These results identify hepatic PPARalpha as one mechanism underlying the pathogenesis of HCV infection, and as a new therapeutic target in traditional treatment of HCV-induced liver injury.

Screening of HCTP4 interacting proteins in leukocytes by yeast-two hybrid technique

AIM: To investigate the biological function of HCTP4, yeast-two hybrid was performed to screen proteins interacting with HCTP4 in leukocytes.

METHODS: The HCTP4 gene was amplified by polymerase chain reaction (PCR) and HCTP4 bait plasmid was constructed by using yeast-two hybrid system 3, then the constructed vector was transformed into yeast AH109. The transformed yeast mated with yeast Y187 containing leukocytes cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x--gal for selecting two times and screening. After extracting and sequencing of plasmid from blue colonies, we underwent analysis by bioinformatics.

RESULTS: Forty-four colonies were sequenced, among which twenty-five colonies were immunoglobulin lambda light chain, six human DNA sequences from clone RP11-189K21, four human DNA sequences from clone RP11-507C10, two homo sapiens 12p BAC RPCI11-75L1, one homo sapiens BAC clone RP11-21M10, one homo sapiens ubiquitin ligase mind bomb (MIB), one homo sapiens genomic DNA, chromosome 11 clone: RP11-867O8, one human DNA sequence from clone RP3-509I19, one homo sapiens small nuclear ribonucleoprotein polypeptide G, one homo sapiens UMP-CMP kinase (UMP-CMPK), and a new gene.

CONCLUSION: Genes of HCTP4 interacting proteins in leukocytes are successfully cloned and the results bring some new clues for studying the biological functions of HCTP4 and associated proteins.

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Proapoptotic effect of hepatitis C virus CORE protein in transiently transfected cells is enhanced by nuclear localization and is dependent on PKR activation

BACKGROUND/AIMS

HCV-CORE protein has been implicated in the regulation of apoptosis of infected cells acting as full-length or C-terminus deleted forms and resulting in both proapoptotic and antiapoptotic effects in different experimental conditions.

METHODS

We have fused full-length and C-terminus deleted CORE with GFP to assess intracellular localization in transiently transfected cell lines and primary hepatocytes. Apoptosis of cells expressing different levels of chimeric proteins was quantified by cytometry.

RESULTS

Full-length CORE localized mainly in the cytoplasm, but nuclear staining was also observed, being more evident in primary human hepatocytes. Nuclear staining only was observed in cells expressing truncated CORE. Full-length CORE induced apoptosis in approximately 15-20% of transfected cells with low expression and in approximately 40-50% of those with high expression of viral protein. Interestingly, 40-50% of cells transfected with truncated CORE underwent apoptosis, independently of protein expression levels. CORE-induced apoptosis was significantly reduced in the presence of a protein kinase R (PKR) inhibiting peptide and truncated CORE was able to enhance translocation of PKR into nucleoli where CORE/PKR colocalization was observed.

CONCLUSIONS

These results suggest that nuclear forms of HCV-CORE are generated in vivo in primary hepatocytes and induce PKR-dependent apoptosis, a mechanism that might have a relevant role during natural infection.

Antiapoptotic regulation by hepatitis C virus core protein through up-regulation of inhibitor of caspase-activated DNase

The hepatitis C virus (HCV) core protein is considered to influence multiple cellular processes. We developed a human hepatoblastoma HepG2-derived inducible cell line, Hep191, which allows tightly regulated expression of the core protein at relatively low but physiological levels under control of the ecdysone-regulated promoter. By transcriptional profiling, we identified differentially expressed genes, some of which are involved in cell growth or apoptosis such as inhibitor of caspase-activated DNase (ICAD), defender against cell death 1, tumor necrosis factor (TNF) receptor 1, and cytochrome c oxidase subunit VIII. Furthermore, we found that core protein expression increases a steady-state level of ICAD protein, possibly through enhancing its promoter activity, and inhibits caspase-3 activity induced by anti-Fas antibody. Since Fas- or TNF-mediated DNA fragmentation is suppressed in the core-induced Hep191 cells, these findings suggest that expression of HCV core at physiological levels confers blocking activity of caspase-activated DNase and consequently inhibiting apoptotic cell death.

Repeated hepatocyte injury promotes hepatic tumorigenesis in hepatitis C virus transgenic mice

Although hepatitis C virus (HCV) is a well-known causative agent of hepatocellular carcinoma (HCC), the mechanism by which HCV induces HCC remains obscure. To elucidate the role of HCV in hepatocarcinogenesis, a model of hepatocyte injury was established using HCV core transgenic mice, which were developed using C57BL/6 mice transfected with the HCV core gene under control of the serum amyloid P component promoter. After 18-24 months, neither steatosis nor hepatic tumors were found in transgenic mice. The extent of hepatocyte injury and tumorigenesis were then examined in transgenic mice following repeated administration of carbon tetrachloride (CCl(4)) using various protocols (20%, 1/week; 10%, 2/week and 20%, 2/week). Serum alanine aminotransferase (ALT) levels did not differ among HCV core transgenic mice and non-transgenic littermates; however, after 40 weeks, hepatic adenomas preferentially developed in transgenic mice receiving 20% CCl(4) once weekly. Moreover, HCC was observed in transgenic mice receiving 2 weekly injections of a 20% solution of CCl(4), and was not observed in the non-transgenic control mice. In conclusion, the HCV core protein did not promote hepatic steatosis or tumor development in the absence of hepatotoxicity. However, the HCV core protein promoted adenoma and HCC development in transgenic mice following repeated CCl(4) administration. These results suggest that hepatotoxicity resulting in an increased rate of hepatocyte regeneration enhances hepatocarcinogenesis in HCV-infected livers. Furthermore, this experimental mouse model provides a valuable method with which to investigate hepatocarcinogenesis.