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

The interactive role of microRNA and other non-coding RNA in hepatitis B (HBV) associated fibrogenesis

One of the outstanding features of chronic hepatitis B infection (CHB) is its strong association with liver fibrosis. CHB induced inflammation and injury trigger multiple biochemical and physical changes that include the promotion of a wide range of cytokines, chemokines and growth factors that activate hepatic stellate cells (HSCs) CHB induced activation of hepatic stellate cells (HSCs) is regarded as a central event in fibrogenesis to directly promote the synthesis of myofibroblasts and the expression of a range of materials to repair injured liver tissue. Fibrogenesis is modulated by the mainstream epigenetic machinery, as well as by non-coding RNA (ncRNA) that are often referred to as an ancillary epigenetic response to fine tune gene expression. Although extensive research has explained the regulatory role of ncRNA in liver fibrogenesis, most of this research relates to non-CHB etiologies. This review paper outlines the complex interactive regulatory role of microRNA (miRNA) and their interaction with long non-coding RNA (lncRNA), circular RNA (circRNA) and the mainstream epigenetic machinery in CHB induced liver fibrosis. The paper also illustrates some of the difficulties involved in translating candidate ncRNA into approved drugs or diagnostic tools. In conclusion, the important regulatory role of ncRNA in CHB induced liver fibrosis warrants further investigation to exploit their undoubted potential as diagnostic and therapeutic agents.

Transient receptor potential channels in viral infectious diseases: Biological characteristics and regulatory mechanisms

BACKGROUND

Viral infectious diseases have long posed a challenge to humanity. In recent decades, transient receptor potential (TRP) channels have emerged as newly investigated cation channels. Increasing evidence suggests that TRP channel-mediated Ca2+ homeostasis disruptions, along with associated pathological changes, are critical factors in the onset and progression of viral infectious diseases. However, the precise roles and mechanisms of TRP channels in these diseases remain to be systematically elucidated.

AIM OF REVIEW

The aim of this review is to systematically summarize recent advances in understanding TRP channels in viral infections, and based on current progress and challenges, propose future directions for research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review summarizes the classification and biological functions of the TRP family, explores the mechanisms by which TRP channels contribute to viral infections, and highlights specific mechanisms at three levels: virus, host, and outcome. These include the direct role in viral biology and replication, the indirect role in host immunity and inflammation, and the resulting pathological changes. Additionally, we discuss the potential applications of the TRP family in the treatment of viral infectious diseases and propose future research directions.

Hemodialysis bilayer bionic blood vessels developed by the mechanical stimulation of hepatitis B viral X(HBX) gene- transfected hepatic stellate cells

Artificial vascular graft (AVG) fistula is widely used for hemodialysis treatment in patients with renal failure. However, it has poor elasticity and compliance, leading to stenosis and thrombosis. The ideal artificial blood vessel for dialysis should replicate the structure and components of a real artery, which is primarily maintained by collagen in the extracellular matrix (ECM) of arterial cells. Studies have revealed that in hepatitis B virus (HBV)-induced liver fibrosis, hepatic stellate cells (HSCs) become hyperactive and produce excessive ECM fibers. Furthermore, mechanical stimulation can encourage ECM secretion and remodeling of a fiber structure. Based on the above factors, we transfected HSCs with the hepatitis B viral X (HBX) gene for simulating the process of HBV infection. Subsequently, these HBX-HSCs were implanted into a polycaprolactone-polyurethane (PCL-PU) bilayer scaffold in which the inner layer is dense and the outer layer consists of pores, which was mechanically stimulated to promote the secretion of collagen nanofiber from the HBX-HSCs and to facilitate crosslinking with the scaffold. We obtained an ECM-PCL-PU composite bionic blood vessel that could act as access for dialysis after decellularization. Then, the vessel scaffold was implanted into a rabbit's neck arteriovenous fistula model. It exhibited strong tensile strength and smooth blood flow and formed autologous blood vessels in the rabbit's body. Our study demonstrates the use of human cells to create biomimetic dialysis blood vessels, providing a novel approach for creating clinical vascular access for dialysis.

Intercellular Transport of Viral Proteins

Viruses are vehicles to exchange genetic information and proteins between cells and organisms by infecting their target cells either cell-free, or depending on cell-cell contacts. Several viruses like certain retroviruses or herpesviruses transmit by both mechanisms. However, viruses have also evolved the properties to exchange proteins between cells independent of viral particle formation. This exchange of viral proteins can be directed to target cells prior to infection to interfere with restriction factors and intrinsic immunity, thus, making the target cell prone to infection. However, also bystander cells, e.g. immune cell populations, can be targeted by viral proteins to dampen antiviral responses. Mechanistically, viruses exploit several routes of cell-cell communication to exchange viral proteins like the formation of extracellular vesicles or the formation of long-distance connections like tunneling nanotubes. Although it is known that viral nucleic acids can be transferred between cells as well, this chapter concentrates on viral proteins of human pathogenic viruses covering all Baltimore classes and summarizes our current knowledge on intercellular transport of viral proteins between cells.

Insights into the impact of hepatitis B virus on hepatic stellate cell activation

During chronic hepatitis B virus (HBV) infection, hepatic fibrosis is a serious pathological condition caused by virus-induced liver damage. The activation of hepatic stellate cells (HSCs) is a central event in the occurrence and progression of liver fibrosis. Although accumulating evidence has shown that HBV directly stimulates HSC activation, whether the virus infects and replicates in HSCs remains controversial. Inflammation is one of the obvious characteristics of chronic HBV infection, and it has been demonstrated that persistent inflammation has a predominant role in triggering and maintaining liver fibrosis. In particular, the regulation of HSC activation by HBV-related hepatocytes via various inflammatory modulators, including TGF-β and CTGF, in a paracrine manner has been reported. In addition to these inflammation-related molecules, several inflammatory cells are essential for the progression of HBV-associated liver fibrosis. Monocytes, macrophages, Th17 cells, NK cells, as well as NKT cells, participate in the modulation of HBV-related liver fibrosis by interacting with HSCs. This review summarizes current findings on the effects of HBV and the relevant molecular mechanisms involved in HSC activation. Because HSC activation is essential for liver fibrosis, targeting HSCs is an attractive therapeutic strategy to prevent and reverse hepatic fibrosis induced by HBV infection. Video abstract.

Physiomimetic In Vitro Human Models for Viral Infection in the Liver

Viral hepatitis is a leading cause of liver morbidity and mortality globally. The mechanisms underlying acute infection and clearance, versus the development of chronic infection, are poorly understood. In vitro models of viral hepatitis circumvent the high costs and ethical considerations of animal models, which also translate poorly to studying the human-specific hepatitis viruses. However, significant challenges are associated with modeling long-term infection in vitro. Differentiated hepatocytes are best able to sustain chronic viral hepatitis infection, but standard two-dimensional models are limited because they fail to mimic the architecture and cellular microenvironment of the liver, and cannot maintain a differentiated hepatocyte phenotype over extended periods. Alternatively, physiomimetic models facilitate important interactions between hepatocytes and their microenvironment by incorporating liver-specific environmental factors such as three-dimensional ECM interactions and co-culture with non-parenchymal cells. These physiologically relevant interactions help maintain a functional hepatocyte phenotype that is critical for sustaining viral hepatitis infection. In this review, we provide an overview of distinct, novel, and innovative in vitro liver models and discuss their functionality and relevance in modeling viral hepatitis. These platforms may provide novel insight into mechanisms that regulate viral clearance versus progression to chronic infections that can drive subsequent liver disease.

Danshensu attenuated lipopolysaccharide-induced LX-2 and T6 cells activation through regulation of ferroptosis

Liver fibrosis and cirrhosis are primarily caused by the activation of hepatic stellate cells (HSCs), regardless of their etiology. Collagen type I (collagen I) and connective tissue growth factor (CTGF) is produced more readily by activated HSCs. Consequently, identifying the molecular and cellular mechanisms responsible for HSCs activation is essential to better understand its mechanism of action and therapeutic potential. Cell death is caused by iron-dependent lipid peroxidation during ferroptosis. Ferroptosis plays an important role in the survival of activated HSCs and could contribute to the development of innovative prevention and treatment strategies for liver fibrosis. Danshensu (Dan) is a pure molecule extracted from the Salvia miltiorrhiza herb that protects against liver damage. However, Dan's effect on attenuating HSCs activation by regulating ferroptosis remains unclear. The results of this study indicated that lipopolysaccharide (LPS)-induced LX-2 and T6 cells activation occurs through the upregulation of collagen I, CTGF, Gpx4, and SLC7A11. Interestingly, Dan attenuated LPS-induced liver fibrosis in those cells by upregulating collagen I, CTGF, Gpx4, and SLC7A11 and by increasing lipid reactive oxygen species accumulation. Furthermore, the results also showed that the ferroptosis inhibitor liproxstatin attenuated the overproduction of lipid reactive oxygen species in LPS-activated LX-2 cells. We conclude that Dan attenuates LPS-induced HSC activation during liver fibrosis by regulating ferroptosis in LX-2 and T6 cells.

Many Ways to Communicate-Crosstalk between the HBV-Infected Cell and Its Environment

Chronic infection with the hepatitis B virus (HBV) affects an estimated 257 million people worldwide and can lead to liver diseases such as cirrhosis and liver cancer. Viral replication is generally considered not to be cytopathic, and although some HBV proteins may have direct carcinogenic effects, the majority of HBV infection-related disease is related to chronic inflammation resulting from disrupted antiviral responses and aberrant innate immune reactions. Like all cells, healthy and HBV-infected cells communicate with each other, as well as with other cell types, such as innate and adaptive immune cells. They do so by both interacting directly and by secreting factors into their environment. Such factors may be small molecules, such as metabolites, single viral proteins or host proteins, but can also be more complex, such as virions, protein complexes, and extracellular vesicles. The latter are small, membrane-enclosed vesicles that are exchanged between cells, and have recently gained a lot of attention for their potential to mediate complex communication and their potential for therapeutic repurposing. Here, we review how HBV infection affects the communication between HBV-infected cells and cells in their environment. We discuss the impact of these interactions on viral persistence in chronic infection, as well as their relation to HBV infection-related pathology.

Hepatitis B x (HBx) as a Component of a Functional Cure for Chronic Hepatitis B

Patients who are carriers of the hepatitis B virus (HBV) are at high risk of chronic liver disease (CLD) which proceeds from hepatitis, to fibrosis, cirrhosis and to hepatocellular carcinoma (HCC). The hepatitis B-encoded X antigen, HBx, promotes virus gene expression and replication, protects infected hepatocytes from immunological destruction, and promotes the development of CLD and HCC. For virus replication, HBx regulates covalently closed circular (ccc) HBV DNA transcription, while for CLD, HBx triggers cellular oxidative stress, in part, by triggering mitochondrial damage that stimulates innate immunity. Constitutive activation of NF-κB by HBx transcriptionally activates pro-inflammatory genes, resulting in hepatocellular destruction, regeneration, and increased integration of the HBx gene into the host genome. NF-κB is also hepatoprotective, which sustains the survival of infected cells. Multiple therapeutic approaches include direct-acting anti-viral compounds and immune-stimulating drugs, but functional cures were not achieved, in part, because none were yet devised to target HBx. In addition, many patients with cirrhosis or HCC have little or no virus replication, but continue to express HBx from integrated templates, suggesting that HBx contributes to the pathogenesis of CLD. Blocking HBx activity will, therefore, impact multiple aspects of the host–virus relationship that are relevant to achieving a functional cure.

Transforming growth factor-β: An early predictor of a functional cure in chronic hepatitis B treated with interferon

BACKGROUND

The relationship between the serum transforming growth factor (TGF)-β level and HBsAg loss has not been clearly elaborated in patients with chronic hepatitis B (CHB).

METHODS

Two cohorts of patients with CHB were studied. Cohort A: A total of 207 hepatitis B e antigen (HBeAg)-negative CHB patients who finished ≥1 year nucleos(t)ide analogue monotherapy and sequentially received PEGylated interferon treatment for less than 96 weeks were included. Cohort B: Forty HBeAg-positive patients who initially received entecavir therapy for at least 96 weeks were included. Their viral markers and serum TGF-β levels were measured at different time points during therapy.

RESULTS

The levels of serum TGF-β and HBsAg (0-24 W) were significantly lower in the patients who had HBsAg< 0.05 IU/mL at 48 weeks than in patients who did not in cohort A. We got the same results when we further divided the patients into subgroups according to the initial HBsAg cut-off values (1000 IU/mL, 100 IU/mL, 50 IU/mL) in cohort A. However, HBeAg seroconversion did not lead to the downregulation of TGF-β levels. The levels of serum TGF-β were significantly correlated with HBsAg quantitation in cohort A (12-24 W) but not in cohort B (0-48 W). The levels of TGF-β at week 12 could be used as an early index to predict a functional cure (AUC=0.818) as well as the levels of HBsAg itself (AUC=0.882) in HBeAg-negative chronic hepatitis B patients treated with PEGylated interferon.

CONCLUSIONS

The levels of serum TGF-β were significantly associated with HBsAg loss but not with HBeAg seroconversion and could be used as an early index to predict a functional cure in CHB patients treated with PEGylated interferon.

Hepatitis B Virus Promotes Hepatocellular Carcinoma Progression Synergistically With Hepatic Stellate Cells via Facilitating the Expression and Secretion of ENPP2

Background: Hepatitis B virus (HBV) infection is a major risk factor causing hepatocellular carcinoma (HCC) development, but the molecular mechanisms are not fully elucidated. It has been reported that virus infection induces ectonucleotide pyrophosphatase-phosphodiesterase 2 (ENPP2) expression, the latter participates in tumor progression. Therefore, the aim of the present study was to investigate whether HBV induced HCC malignancy via ENPP2.

Methods: HCC patient clinical data were collected and prognosis was analyzed. Transient transfection and stable ectopic expression of the HBV genome were established in hepatoma cell lines. Immunohistochemical staining, RT-qPCR, western blot, and ELISA assays were used to detect the expression and secretion of ENPP2. Finally, CCK-8, colony formation, and migration assays as well as a subcutaneous xenograft mouse model were used to investigate the influence of HBV infection, ENPP2 expression, and activated hepatic stellate cells (aHSCs) on HCC progression in vitro and in vivo.

Results: The data from cancer databases indicated that the level of ENPP2 was significant higher in HCC compared within normal liver tissues. Clinical relevance analysis using 158 HCC patients displayed that ENPP2 expression was positively correlated with poor overall survival and disease-free survival. Statistical analysis revealed that compared to HBV-negative HCC tissues, HBV-positive tissues expressed a higher level of ENPP2. In vitro, HBV upregulated ENPP2 expression and secretion in hepatoma cells and promoted hepatoma cell proliferation, colony formation, and migration via enhancement of ENPP2; downregulation of ENPP2 expression or inhibition of its function suppressed HCC progression. In addition, aHSCs strengthened hepatoma cell proliferation, migration in vitro, and promoted tumorigenesis synergistically with HBV in vivo; a loss-function assay further verified that ENPP2 is essential for HBV/aHSC-induced HCC progression.

Conclusion: HBV enhanced the expression and secretion of ENPP2 in hepatoma cells, combined with aHSCs to promote HCC progression via ENPP2.

Hepatitis B Virus DNA Integration, Chronic Infections and Hepatocellular Carcinoma

Hepatitis B Virus (HBV) is an Old World virus with a high mutation rate, which puts its origins in Africa alongside the origins of Homo sapiens, and is a member of the Hepadnaviridae family that is characterized by a unique viral replication cycle. It targets human hepatocytes and can lead to chronic HBV infection either after acute infection via horizontal transmission usually during infancy or childhood or via maternal-fetal transmission. HBV has been found in ~85% of HBV-related Hepatocellular Carcinomas (HCC), and it can integrate the whole or part of its genome into the host genomic DNA. The molecular mechanisms involved in the HBV DNA integration is not yet clear; thus, multiple models have been described with respect to either the relaxed-circular DNA (rcDNA) or the double-stranded linear DNA (dslDNA) of HBV. Various genes have been found to be affected by HBV DNA integration, including cell-proliferation-related genes, oncogenes and long non-coding RNA genes (lincRNAs). The present review summarizes the advances in the research of HBV DNA integration, focusing on the evolutionary and molecular side of the integration events along with the arising clinical aspects in the light of WHO's commitment to eliminate HBV and viral hepatitis by 2030.

Gene Polymorphism of MUC15, MMP14, BRAF, and COL1A1 Is Associated with Capsule Formation in Hepatocellular Carcinoma

BACKGROUND

The presence of a capsule is an important prognostic factor in hepatocellular carcinoma (HCC). Capsule formation is affected by tumor-host interaction, which may include collagen deposition and extracellular matrix (ECM) degradation.

PURPOSE

This study aimed to examine whether single-nucleotide polymorphisms (SNPs) in the genes for COL1A1 MUC15, MMP14, CD97, SMYD3, BRAF, and transforming growth factor beta 1 (TGF-β) are related to capsule formation.

METHODS

We prospectively recruited and analyzed 185 patients with HCC with or without a capsule between 2019 and 2020. The SNPs involved were analyzed by polymerase chain reaction. Differences in the allele and genotype frequency between the cases and controls were evaluated using the chi-square test. Odds ratios and 95% confidence intervals were calculated by logistic regression analysis with adjustment for age and sex. Stratification analyses were also performed with preselected variables.

RESULTS

The single-locus analysis showed that the presence of a capsule was significantly associated with five SNPs : MUC15 rs17309195 (P=0.01), rs12271124 (P= 0.02), rs10430847 (P=0.04), MMP14 rs17884816 (P=0.01), and BRAF rs74512895 (P=0.03). Adjusted logistic regression revealed that the decreased capsule formation was statistically significantly associated with BRAF rs76603725, COL1A1 rs2269336, and MUC15 rs17309195, while MMP14 rs17884816 and MUC15 rs10430847, rs2063278, and rs967490 were associated with increased capsule formation. The MUC15 block 2 haplotype was associated with increased capsule formation.

CONCLUSIONS

MUC15, MMP14, BRAF, and COL1A1 gene polymorphisms are associated with capsule formation in HCC. Studies involving larger samples are needed to confirm our results.

Is COVID-19-induced liver injury different from other RNA viruses?‎

Coronavirus disease 2019 is a pandemic disease caused by a novel RNA coronavirus, SARS coronavirus 2 (SARS-CoV-2), which is implicated in the respiratory system. SARS-CoV-2 also targets extrapulmonary systems, including the gastrointestinal tract, liver, central nervous system and others. SARS-CoV-2, like other RNA viruses, targets the liver and produces liver injury. This literature review showed that SARS-CoV-2-induced liver injury is different from other RNA viruses by a transient elevation of hepatic enzymes and does not progress to liver fibrosis or other unfavorable events. Moreover, SARS-CoV-2-induced liver injury usually occurs in the presence of risk factors, such as nonalcoholic liver fatty disease. This review highlights the important differences between RNA viruses inducing liver injury taking into consideration the clinical, biochemical, histopathological, postmortem findings and the chronicity of liver injury that ultimately leads to liver fibrosis and hepatocellular carcinoma.

Pathogenesis of Viral Hepatitis-Induced Chronic Liver Disease: Role of Extracellular Vesicles

Extracellular vesicles are encapsulated lipid nanoparticles secreted by a variety of cell types in living organisms. They are known to carry proteins, metabolites, nucleic acids, and lipids as their cargoes and are important mediators of intercellular communication. The role of extracellular vesicles in chronic liver disease has been reported. Chronic liver disease such as viral hepatitis accounts for a significant mortality and morbidity burden worldwide. Hepatic fibrosis has been commonly associated with the chronic form of viral hepatitis, which results in end-stage liver disease, including cirrhosis, liver failure, and carcinoma in some patients. In this review, we discuss the potential role of extracellular vesicles in mediating communication between infectious agents (hepatitis B and C viruses) and host cells, and how these complex cell-cell interactions may facilitate the development of chronic liver disease. We will further discuss how understanding their biological mechanism of action might be beneficial for developing therapeutic strategies to treat chronic liver disease.

Chrysophanol attenuates hepatitis B virus X protein-induced hepatic stellate cell fibrosis by regulating endoplasmic reticulum stress and ferroptosis

Hepatitis B virus X protein (HBx) and hepatic stellate cells (HSCs) are critical for liver fibrosis development. Anti-fibrosis occurs via reversion to quiescent-type HSCs or clearance of HSCs via apoptosis or ferroptosis. We aimed to elucidate the role of chrysophanol in rat HSC-T6 cells expressing HBx and investigate whether chrysophanol (isolated from Rheum palmatum rhizomes) influences cell death via ferroptosis in vitro. Analysis of lipid reactive oxygen species (ROS), Bip, CHOP, p-IRE1α, GPX4, SLC7A11, α-SMA, and CTGF showed that chrysophanol attenuated HBx-repressed cell death. Chrysophanol can impair HBx-induced activation of HSCs via endoplasmic reticulum stress (ER stress) and ferroptosis-dependent and GPX4-independent pathways.

Key Players of Hepatic Fibrosis

Hepatic fibrosis is a complex mechanism defined by the net deposition of the extracellular matrix (ECM) owing to liver injury caused by multiple etiologies such as viral hepatitis and nonalcoholic fatty liver disease. Many cell types are implicated in liver fibrosis development and progression. In general, liver fibrosis starts with the recruitment of inflammatory immune cells to generate cytokines, growth factors, and other activator molecules. Such chemical mediators drive the hepatic stellate cells (HSCs) to activate the production of the ECM component. The activation of HSC is thus a crucial event in the fibrosis initiation, and a significant contributor to collagen deposition (specifically type I). This review explores the causes and mechanisms of hepatic fibrosis and focuses on the roles of key molecules involved in liver fibro genesis, some of which are potential targets for therapeutics to hamper liver fibro genesis.

Hepatitis B virus X protein enhances the development of liver fibrosis and the expression of genes associated with epithelial-mesenchymal transitions and tumor progenitor cells

The hepatitis B virus X protein (HBx) has pleiotropic biological effects, which underlies its potential role in cell transformation. However, its involvement in hepatic fibrosis remains unclear. In this study, we wanted to clarify, in vivo, the role of HBx protein in the development of liver fibrosis. Mice transgenic for the full-length HBx (FL-HBx) were used. To create liver fibrosis, FL-HBx transgenic and control mice were chronically exposed to carbon tetrachloride (CCl4). Modulation of the expression of proteins involved in matrix remodeling, hepatic metabolism and epithelial-mesenchymal transition (EMT) were investigated. In transgenic mice, FL-HBx expression potentiates CCl4-induced liver fibrosis with increased expression of proteins involved in matrix remodeling (Collagen1a, α-Sma, PdgfR-β, MMP-13). In FL-HBx transgenic mice, an increase in EMT was observed with a higher transcription of two inflammatory cytokines (TNF-α and TGF-β) and a decrease of glutamine synthetase expression level. This was associated with a sustained cell cycle and hepatocyte polyploidy alteration consistent with p38 and ERK1/2 overactivation, increase of PLK1 transcription, accumulation of SQSTM1/p62 protein and increase expression of Beclin-1. This correlates with a higher expression of tumor progenitor cell markers (AFP, Ly6D and EpCam), indicating a higher risk of progression from fibrosis to hepatocellular carcinoma (HCC) in the presence of FL-HBx protein. In conclusion, our results show that FL-HBx protein enhances the development of liver fibrosis and contributes to the progression of liver disease from chronic hepatitis to HCC.

HBx induces expression of CTGF in the transfected hepatoma cell line HepG2

Aim: To investigate the effect of HBx on CTGF expression by hepatocytes. Materials & methods: HepG2 cells were transfected with the full-length gene of HBV, HBV protein-expressing plasmids, rhTGFβ1, LY2109761 or Smad2 siRNA, respectively, using Lipofectamine 3000. CTGF expression was detected by real-time PCR, ELISA, respectively. Then the effect of IL-32 on CTGF promoter was assayed by the Dual Luciferase® Reporter Assay System. Results: We found that HBx could induce CTGF expression by HepG2 cells in a concentration-dependent manner. CTGF expression induced by HBx employed the activation of TGFβ1-Smad2 signal pathway. Inhibition of TGFβ1 or Smad2 decreased CTGF expression induced by HBx. Conclusion: HBV might be involved in the pathogenesis of liver fibrosis through the HBx-induced CTGF expression.

The HBx gene of hepatitis B virus can influence hepatic microenvironment via exosomes by transferring its mRNA and protein

The cellular secretory vesicles known as 'exosomes' have emerged as key player in intercellular transport and communication between different eukaryotic in order to maintain body homeostasis. Many pathogenic viruses utilize exosome pathway to efficiently transfer bioactive components from infected cells to naïve cells. Here, we show that HBx can tweak the exosome biogenesis machinery both by enhancing neutral sphingomyelinase2 activity as well as by interacting with exosomal biomarkers such as neutral sphingomyelinase2, CD9 and CD81. The nano particle tracking analysis revealed enhanced secretion of exosomes by the HBx-expressing cells while confocal studies confirmed the co-localization of HBx with CD9 and CD63. Importantly, we observed the encapsulation of HBx mRNA and protein in these exosomes besides some other qualitative changes. The exosomal cargo secreted by HBx-expressing cells had a profound effect on the recipient hepatic cells including creation of a milieu conducive for cellular-transformation. Thus, the present study unfolds a novel role of HBx in intercellular communication by facilitating horizontal transfer of viral gene products and other host factors via exosomes in order to support viral spread and pathogenesis.

The role of T helper 17 cells in the pathogenesis of hepatitis B virus-related liver cirrhosis (Review)

In chronic hepatitis B virus (HBV)-infected patients, T helper 17 (Th17) cells are significantly elevated. Th17 cells initiate immune-mediated pathogenesis and have a critical role in the process of HBV-related liver cirrhosis (HBV-LC). The mechanisms underlying this process are attributed to Th17-secreted cytokines, which include interleukin (IL)-17, IL-21 and IL-22; however, a systemic analysis regarding these mechanisms has yet to be conducted. Therefore, the present study aimed to investigate the role of Th17 cells in the pathogenesis of HBV-LC. All randomized clinical trials, case series, case reports and meta-analyses that contained the aforementioned keywords were included in the review process. In addition, unpublished information from the Food and Drug Administration was included. The findings indicated that Th17-secreted cytokines, including IL-17, IL-21 and IL-22, function by activating or silencing hepatic stellate cells, modulating proinflammatory and pro- or antifibrogenic effectors, regulating extracellular matrix formation, upregulating chemokine expression, and inducing hepatocellular damage or hepatoprotection during the HBV-LC process. In addition, Th17 cells and Th17-secreted cytokines may be considered a potential tool in the diagnosis or treatment of HBV-LC. The present review summarized the role of Th17 cells in the pathogenesis of HBV-LC in order to deepen the clinical understanding of the role of Th17 cells and also to support the development of effective therapies for patients with HBV-LC.

The evaluation of fibrotic effects of the hepatitis B virus pre-core in hepatic stellate cells

The role of the hepatitis B virus (HBV) endogenous pre-core protein in liver fibrosis is controversial. Whether the expression of the pre-core induces the activation of human stellate cells (HSCs) has not yet been reported. Plasmids expressing HBx, or pre-core protein were transfected into LX-2 cells. Subsequently, total RNA extracted and reverse transcription-quantitative polymerase chain reaction was performed to measure the fold change of collagen type I, α1 chain, α-smooth muscle actin and TIMP metalloproteinase inhibitor-1. Moreover, transforming growth factor (TGF)-β in the supernatant of HSCs was evaluated by ELISA assay. In addition, a MTT assay was performed to test the cytotoxicity of the endogenous expression in LX-2 cells. None of the plasmids exhibited cytotoxic nor significant proliferative effects on LX-2 cells by MTT assessment. The gene expression analysis of fibrotic genes in LX-2 cells demonstrated that the pre-core protein presented no significant (P>0.05) fibrotic impact when compared to the empty control plasmid and HBx. The data from the TGF-β ELISA was consistent with the mRNA expression as detected with the control plasmid (P>0.05). The endogenous expression of the HBV pre-core exhibited no fibrotic impression in HSCs when compared to HBx.

Characterization of gene expression profiles in HBV-related liver fibrosis patients and identification of ITGBL1 as a key regulator of fibrogenesis

Although hepatitis B virus (HBV) infection is the leading cause of liver fibrosis (LF), the mechanisms underlying liver fibrotic progression remain unclear. Here, we investigated the gene expression profiles of HBV-related LF patients. Whole genome expression arrays were used to detect gene expression in liver biopsy samples from chronically HBV infected patients. Through integrative data analysis, we identified several pathways and key genes involved in the initiation and exacerbation of liver fibrosis. Weight gene co-expression analysis revealed that integrin subunit β-like 1 (ITGBL1) was a key regulator of fibrogenesis. Functional experiments demonstrated that ITGBL1 was an upstream regulator of LF via interactions with transforming growth factor β1. In summary, we investigated the gene expression profiles of HBV-related LF patients and identified a key regulator ITGBL1. Our findings provide a foundation for future studies of gene functions and promote the development of novel antifibrotic therapies.

Hepatitis B virus X protein in liver tumor microenvironment

Encoded by the hepatitis B virus, hepatitis B virus X protein (HBx) is a multifunctional, potentially oncogenic protein that acts primarily during the progression from chronic hepatitis B to cirrhosis and hepatocellular carcinoma (HCC). In recent decades, it has been established that chronic inflammation generates a tumor-supporting microenvironment. HCC is a typical chronic inflammation-related cancer, and inflammation is the main risk factor for HCC progression. The viral transactivator HBx plays a pivotal role in the initiation and maintenance of hepatic inflammatory processes through interactions with components of the tumor microenvironment including tumor cells and the surrounding peritumoral stroma. The complex interactions between HBx and this microenvironment are thought to regulate tumor growth, progression, invasion, metastasis, and angiogenesis. In this review, we have summarized the current evidence evaluating the function of HBx and its contribution to the inflammatory liver tumor microenvironment.

Hepatic SATB1 induces paracrine activation of hepatic stellate cells and is upregulated by HBx

Chronic hepatitis B virus (HBV) infection is a major cause of chronic liver diseases, but its involvement in hepatic fibrogenesis remains unclear. Special AT-rich binding protein 1 (SATB1) has been implicated in reprogramming chromatin organization and transcription profiles in many cancers and non-cancer-related conditions. We found that hepatic SATB1 expression was significantly up-regulated in fibrotic tissues from chronic hepatitis B virus (HBV)-infected patients and HBV transgenic (HBV-Tg) mouse model. Knockdown of SATB1 in the liver significantly alleviated CCl4-induced fibrosis in HBV-Tg mouse model. Moreover, we suggested HBV encoded x protein (HBx) induced SATB1 expression through activation of JNK and ERK pathways. Enforced expression of SATB1 in hepatocytes promoted the activation and proliferation of hepatic stellate cells (HSCs) by secretion of connective tissue growth factor (CTGF), Interleukin-6 (IL-6) and platelet derived growth factor-A (PDGF-AA). Our findings demonstrated that HBx upregulated hepatic SATB1 which exerted pro-fibrotic effects by paracrine activation of stellate cells in HBV-related fibrosis.

Modulation of Bcl-x Alternative Splicing Induces Apoptosis of Human Hepatic Stellate Cells

Liver fibrosis is a major cause of morbidity and mortality worldwide due to chronic viral hepatitis and, more recently, from fatty liver diseases. Activation and proliferation of hepatic stellate cells (HSCs) represent a key aspect of fibrogenesis and are associated with progressive reduction of HSC apoptosis. Bcl-x, an antiapoptotic member of Bcl-2 gene family, plays a role in apoptosis regulation in mammalian cells. Through alternative splicing, the Bcl-x gene yields two major protein isoforms with opposing functions, antiapoptotic Bcl-xL and proapoptotic Bcl-xS. This study aimed to investigate the role of Bcl-x and its alternate splicing in HSC apoptosis. The results indicated that the expression of Bcl-xL was dramatically higher than Bcl-2 in activated human HSCs. The relative expression of Bcl-xL over Bcl-xS increased gradually when HSCs were activated in cell culture, which was consistent with the increase in apoptosis resistance of activated HSCs. Redirection of Bcl-x splicing by an antisense oligonucleotide from the antiapoptotic isoform to the proapoptotic isoform induced death of HSCs without other apoptosis stimuli. We conclude that Bcl-x plays a role in regulation of HSC apoptosis and modulation of Bcl-x alternative splicing may become a novel molecular therapy for liver fibrosis.

New Concepts on Pathogenesis and Diagnosis of Liver Fibrosis; A Review Article

Liver fibrosis is a potentially reversible response to hepatic insults, triggered by different chronic diseases most importantly viral hepatitis, alcoholic, and nonalcoholic fatty liver disease. In the course of the chronic liver disease, hepatic fibrogenesis may develop, which is attributed to various types of cells, molecules, and pathways. Activated hepatic stellate cell (HSC), the primary source of extracellular matrix (ECM), is fundamental in pathophysiology of fibrogenesis, and thus is the most attractable target for reversing liver fibrosis. Although, liver biopsy has long been considered as the gold standard for diagnosis and staging of hepatic fibrosis, assessing progression and regression by biopsy is hampered by its limitations. We provide recent views on noninvasive approaches including serum biomarkers and radiologic techniques.

Pathophysiological implications of hepatitis B X protein in tumor microenvironment of hepatocellular carcinoma

Hepatitis B X protein (HBx), encoded by hepatitis B virus (HBV), is a multifunctional and potentially oncogenic protein that has significant functions during the progression from chronic hepatitis B to cirrhosis and eventually to hepatocellular carcinoma (HCC). Over the past decades, it has been widely established that chronic inflammation orchestrates a tumor-supporting microenvironment. HCC is a typical chronic inflammation-related cancer and inflammation is the main risk factor for the progression of HCC. As a major viral transactivator, HBx is thought to play a pivotal role in the activation and maintenance of hepatic inflammatory process through interaction with various components of the tumor microenvironment including tumor cell and surrounding peritumoral stroma. Complex interactions between HBx and these cell types in this microenvironment will regulate tumor growth, progression, metastasis, and angiogenesis. In this review, we mainly summarize the current understanding of HBx and its contribution to the inflammatory tumor microenvironment of HBV-related HCC.

CCN: core regulatory proteins in the microenvironment that affect the metastasis of hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) results from an underlying chronic liver inflammatory disease, such as chronic hepatitis B or C virus infections, and the general prognosis of patients with HCC still remains extremely dismal because of the high frequency of HCC metastases. Throughout the process of tumor metastasis, tumor cells constantly communicate with the surrounding microenvironment and improve their malignant phenotype. Therefore, there is a strong rationale for targeting the tumor microenvironment as primary treatment of HCC therapies. Recently, CCN family proteins have emerged as localized multitasking signal integrators in the inflammatory microenvironment. In this review, we summarize the current knowledge of CCN family proteins in inflammation and the tumor. We also propose that the CCN family proteins may play a central role in signaling the tumor microenvironment and regulating the metastasis of HCC.

Wild type HBx and truncated HBx: Pleiotropic regulators driving sequential genetic and epigenetic steps of hepatocarcinogenesis and progression of HBV-associated neoplasms

Hepatitis B virus (HBV) is one of the causative agents of hepatocellular carcinoma. The molecular mechanisms of tumorigenesis are complex. One of the host factors involved is apparently the long-lasting inflammatory reaction which accompanies chronic HBV infection. Although HBV lacks a typical viral oncogene, the HBx gene encoding a pleiotropic regulatory protein emerged as a major player in liver carcinogenesis. Here we review the tumorigenic functions of HBx with an emphasis on wild type and truncated HBx variants, and their role in the transcriptional dysregulation and epigenetic reprogramming of the host cell genome. We suggest that HBx acquired by the HBV genome during evolution acts like a cellular proto-onc gene that is activated by deletion during hepatocarcinogenesis. The resulting viral oncogene (v-onc gene) codes for a truncated HBx protein that facilitates tumor progression. Copyright © 2015 John Wiley & Sons, Ltd.

Activation of TGF-β1-CD147 positive feedback loop in hepatic stellate cells promotes liver fibrosis

Activation of hepatic stellate cells (HSCs) by transforming growth factor-β1 (TGF-β1) initiates HBV-associated fibrogenesis. The mechanism of TGF-β1 modulating HSC activation is not fully uncovered. We hypothesized a positive feedback signaling loop of TGF-β1-CD147 promoting liver fibrogenesis by activation of HSCs. Human HSC cell line LX-2 and spontaneous liver fibrosis model derived from HBV transgenic mice were used to evaluate the activation of molecules in the signaling loop. Wound healing and cell contraction assay were performed to detect the CD147-overexpressed HSC migration and contraction. The transcriptional regulation of CD147 by TGF-β1/Smad4 was determined using dual-luciferase reporter assay and chromatin immunoprecipitation. We found that a positive reciprocal regulation between TGF-β1 and CD147 mediated HSC activation. CD147 over-expression promoted HSC migration and accelerated TGF-β1-induced cell contraction. Phosphorylation of Smad2 and Smad3 in cooperation with Smad4 mediated the TGF-β1-regulated CD147 expression. Smad4 activated the transcription by direct interaction with CD147 promoter. Meanwhile, CD147 modulated the activated phenotype of HSCs through the ERK1/2 and Sp1 which up-regulated α-SMA, collagen I, and TGF-β1 synthesis. These findings indicate that TGF-β1-CD147 loop plays a key role in regulating the HSC activation and combination of TGF-β receptor inhibitor and anti-CD147 antibody might be promised to reverse fibrogenesis.

Interleukin-8: A critical chemokine in biliary atresia

Biliary atresia (BA) is characterized by periductular inflammation and fibrosis and is associated with the progressive obliteration of the bile ducts. The induction and maintenance of systemic and local inflammatory responses plays a pivotal role in this process. Interleukin-8 (IL-8) is an important mediator of inflammation and the immune response in human disease. IL-8 is overexpressed in BA, and its expression positively correlates with inflammation and liver fibrosis. In this review, we focus on the available evidence, recent insights, and future clinical and preclinical possibilities regarding the role of IL-8 in BA.

Higher proportion of viral basal core promoter mutant increases the risk of liver cirrhosis in hepatitis B carriers

BACKGROUND AND OBJECTIVE

Precore (PC) variant (G1896A) and basal core promoter (BCP) variant (A1762T/G1764A) of HBV are associated with risk of hepatocellular carcinoma in HBV carriers. However, little is known about their impact on the adverse outcomes of hepatitis B e antigen (HBeAg)-negative hepatitis and liver cirrhosis.

METHODS

251 spontaneous HBeAg seroconverters who had genotype B or C infection and received a long-term follow-up were enrolled. PC and BCP mutants were determined qualitatively and quantitatively to correlate with these adverse outcomes. The findings were validated by an independent case-control study, which included 184 patients with biopsy-proven liver fibrosis stages.

RESULTS

In the longitudinal cohort study, BCP mutant and possibly PC wild type were associated with cirrhosis development, but not HBeAg-negative hepatitis. Multivariable analysis showed that only BCP mutant was an independent risk factor for cirrhosis development. Using quantitative analysis of BCP mutant, a higher proportion of BCP mutant, defined as a continuous variable, a dichotomous variable or an ordinal variable, was associated with a higher risk of cirrhosis. If we chose 45% of BCP mutant as the cut-off, the risk of cirrhosis was higher in patients with BCP mutant ≥45% compared to <45% in the longitudinal cohort; this finding was validated by the case-control study (adjusted OR: 2.81, 95% CI 1.40 to 5.67).

CONCLUSIONS

A higher proportion of BCP mutant increases the risk of liver cirrhosis development in HBV carriers with genotype B or C infection.

Diethylcarbamazine reduces chronic inflammation and fibrosis in carbon tetrachloride- (CCl₄-) induced liver injury in mice

This study investigated the anti-inflammatory effects of DEC on the CCl₄-induced hepatotoxicity in C57BL/6 mice. Chronic inflammation was induced by i.p. administration of CCl₄ 0.5 μL/g of body weight through two injections a week for 6 weeks. DEC (50 mg/kg) was administered by gavage for 12 days before finishing the CCl₄ induction. Histological analyses of the DEC-treated group exhibited reduced inflammatory process and prevented liver necrosis and fibrosis. Immunohistochemical and immunofluorescence analyses of the DEC-treated group showed reduced COX-2, IL1β, MDA, TGF-β, and αSMA immunopositivity, besides exhibiting decreased IL1β, COX-2, NFκB, IFNγ, and TGFβ expressions in the western blot analysis. The DEC group enhanced significantly the IL-10 expression. The reduction of hepatic injury in the DEC-treated group was confirmed by the COX-2 and iNOS mRNA expression levels. Based on the results of the present study, DEC can be used as a potential anti-inflammatory drug for chronic hepatic inflammation.

Inhibition of tyrosine kinase receptor Tie2 reverts HCV-induced hepatic stellate cell activation

Background

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease (CLD) and is frequently linked to intrahepatic microvascular disorders. Activation of hepatic stellate cells (HSC) is a central event in liver damage, due to their contribution to hepatic renewal and to the development of fibrosis and hepatocarcinoma. During the progression of CLDs, HSC attempt to restore injured tissue by stimulating repair processes, such as fibrosis and angiogenesis. Because HSC express the key vascular receptor Tie2, among other angiogenic receptors and mediators, we analyzed its involvement in the development of CLD.

Methods

Tie2 expression was monitored in HSC cultures that were exposed to media from HCV-expressing cells (replicons). The effects of Tie2 blockade on HSC activation by either neutralizing antibody or specific signaling inhibitors were also examined.

Results

Media from HCV-replicons enhanced HSC activation and invasion and upregulated Tie2 expression. Notably, the blockade of Tie2 receptor (by a specific neutralizing antibody) or signaling (by selective AKT and MAPK inhibitors) significantly reduced alpha-smooth muscle actin (α-SMA) expression and the invasive potential of HCV-conditioned HSC.

Conclusions

These findings ascribe a novel profibrogenic function to Tie2 receptor in the progression of chronic hepatitis C, highlighting the significance of its dysregulation in the evolution of CLDs and its potential as a novel therapeutic target.

Prediction of fibrosis progression in chronic viral hepatitis

Prediction of liver fibrosis progression has a key role in the management of chronic viral hepatitis, as it will be translated into the future risk of cirrhosis and its various complications including hepatocellular carcinoma. Both hepatitis B and C viruses mainly lead to fibrogenesis induced by chronic inflammation and a continuous wound healing response. At the same time direct and indirect profibrogenic responses are also elicited by the viral infection. There are a handful of well-established risk factors for fibrosis progression including older age, male gender, alcohol use, high viral load and co-infection with other viruses. Metabolic syndrome is an evolving risk factor of fibrosis progression. The new notion of regression of advanced fibrosis or even cirrhosis is now strongly supported various clinical studies. Even liver biopsy retains its important role in the assessment of fibrosis progression, various non-invasive assessments have been adopted widely because of their non-invasiveness, which facilitates serial applications in large cohorts of subjects. Transient elastography is one of the most validated tools which has both diagnostic and prognostic role. As there is no single perfect test for liver fibrosis assessment, algorithms combining the most validated noninvasive methods should be considered as initial screening tools.

Potential mechanisms of hepatitis B virus induced liver injury

Chronic active hepatitis (CAH) is acknowledged as an imperative risk factor for the development of liver injury and hepatocellular carcinoma. The histological end points of CAH are chronic inflammation, fibrosis and cirrhosis which are coupled with increased DNA synthesis in cirrhotic vs healthy normal livers. The potential mechanism involved in CAH includes a combination of processes leading to liver cell necrosis, inflammation and cytokine production and liver scaring (fibrosis). The severity of liver damage is regulated by Hepatitis B virus genotypes and viral components. The viral and cellular factors that contribute to liver injury are discussed in this article. Liver injury caused by the viral infection affects many cellular processes such as cell signaling, apoptosis, transcription, DNA repair which in turn induce radical effects on cell survival, growth, transformation and maintenance. The consequence of such perturbations is resulted in the alteration of bile secretion, gluconeogenesis, glycolysis, detoxification and metabolism of carbohydrates, proteins, fat and balance of nutrients. The identification and elucidation of the molecular pathways perturbed by the viral proteins are important in order to design effective strategy to minimize and/or restore the hepatocytes injury.

Molecular mechanism of hepatitis B virus-induced hepatocarcinogenesis

Hepatitis B virus (HBV) infection is a global public health problem with approximately 2 billion people that have been exposed to the virus. HBV is a member of a family of small, enveloped DNA viruses called hepadnaviruses, and has a preferential tropism for hepatocytes of mammals and birds. Epidemiological studies have proved a strong correlation between chronic hepatitis B virus infection and the development of hepatocellular carcinoma (HCC). HCC is the fifth most common malignancy with about 700000 new cases each year, and more than 50% of them arise in HBV carriers. A large number of studies describe the way in which HBV can contribute to HCC development. Multiple mechanisms have been proposed, including the accumulation of genetic damage due to immune-mediated hepatic inflammation and the induction of oxidative stress. There is evidence of the direct effects of the viral proteins HBx and HBs on the cell biology. Integration of HBV-DNA into the human genome is considered an early event in the carcinogenic process and can induce, through insertional mutagenesis, the alteration of gene expression and chromosomal instability. HBV has also epigenetic effects through the modification of the genomic methylation status. Furthermore, the virus plays an important role in the regulation of microRNA expression. This review will summarize the many mechanisms involved in HBV-related liver carcinogenesis.

Endocytosis of collagen by hepatic stellate cells regulates extracellular matrix dynamics

Hepatic stellate cells (HSCs) generate matrix, which in turn may also regulate HSCs function during liver fibrosis. We hypothesized that HSCs may endocytose matrix proteins to sense and respond to changes in microenvironment. Primary human HSCs, LX2, or mouse embryonic fibroblasts (MEFs) [wild-type; c-abl(-/-); or Yes, Src, and Fyn knockout mice (YSF(-/-))] were incubated with fluorescent-labeled collagen or gelatin. Fluorescence-activated cell sorting analysis and confocal microscopy were used for measuring cellular internalization of matrix proteins. Targeted PCR array and quantitative real-time PCR were used to evaluate gene expression changes. HSCs and LX2 cells endocytose collagens in a concentration- and time-dependent manner. Endocytosed collagen colocalized with Dextran 10K, a marker of macropinocytosis, and 5-ethylisopropyl amiloride, an inhibitor of macropinocytosis, reduced collagen internalization by 46%. Cytochalasin D and ML7 blocked collagen internalization by 47% and 45%, respectively, indicating that actin and myosin are critical for collagen endocytosis. Wortmannin and AKT inhibitor blocked collagen internalization by 70% and 89%, respectively, indicating that matrix macropinocytosis requires phosphoinositide-3-kinase (PI3K)/AKT signaling. Overexpression of dominant-negative dynamin-2 K44A blocked matrix internalization by 77%, indicating a role for dynamin-2 in matrix macropinocytosis. Whereas c-abl(-/-) MEF showed impaired matrix endocytosis, YSF(-/-) MEF surprisingly showed increased matrix endocytosis. It was also associated with complex gene regulations that related with matrix dynamics, including increased matrix metalloproteinase 9 (MMP-9) mRNA levels and zymographic activity. HSCs endocytose matrix proteins through macropinocytosis that requires a signaling network composed of PI3K/AKT, dynamin-2, and c-abl. Interaction with extracellular matrix regulates matrix dynamics through modulating multiple gene expressions including MMP-9.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Molecular mechanism and treatment of viral hepatitis-related liver fibrosis

Hepatic fibrosis is a wound-healing response to various chronic stimuli, including viral hepatitis B or C infection. Activated myofibroblasts, predominantly derived from the hepatic stellate cells (HSCs), regulate the balance between matrix metalloproteinases and their tissue inhibitors to maintain extracellular matrix homeostasis. Transforming growth factor-β and platelet-derived growth factor are classic profibrogenic signals that activate HSC proliferation. In addition, proinflammatory cytokines and chemokines coordinate macrophages, T cells, NK/NKT cells, and liver sinusoidal endothelial cells in complex fibrogenic and regression processes. In addition, fibrogenesis involves angiogenesis, metabolic reprogramming, autophagy, microRNA, and epigenetic regulations. Hepatic inflammation is the driving force behind liver fibrosis; however, host single nucleotide polymorphisms and viral factors, including the genotype, viral load, viral mutation, and viral proteins, have been associated with fibrosis progression. Eliminating the underlying etiology is the most crucial antifibrotic therapy. Growing evidence has indicated that persistent viral suppression with antiviral therapy can result in fibrosis regression, reduced liver disease progression, decreased hepatocellular carcinoma, and improved chances of survival. Preclinical studies and clinical trials are currently examining several investigational agents that target key fibrogenic pathways; the results are promising and shed light on this debilitating illness.

Pathological functions of interleukin-22 in chronic liver inflammation and fibrosis with hepatitis B virus infection by promoting T helper 17 cell recruitment

It is well established that interleukin (IL)-22 has hepatoprotective and antifibrotic functions in acute liver injury models; however, its function in patients with liver fibrosis and liver cirrhosis (LC) remains obscure. In the current study, we demonstrated that expression of numerous IL-22 pathway-associated genes was significantly up-regulated in hepatitis B virus (HBV)-infected liver tissues, compared to normal controls, through microarray analysis. In agreement with these findings, liver-infiltrating IL-22(+) cells were largely increased in HBV-infected patients with LC, compared to those without LC or healthy subjects, and were positively associated with liver fibrosis staging scores. Immunohistochemistry and flow cytometric analyses revealed that IL-22 was produced by multiple intrahepatic immune cells and, preferentially, by T-helper (Th) 17 cells in LC patients. In an HBV transgenic (Tg) mouse model of T-cell-mediated chronic liver inflammation and fibrosis, blockade of IL-22 attenuated hepatic expression of chemokine (C-X-C motif) ligand 10 and chemokine (C-C motif) ligand 20 (CCL20) and subsequently reduced Th17 recruitment and liver inflammation and fibrosis progression. In vitro treatment with IL-22 stimulated hepatic stellate cells (HSCs) to secrete several chemokines and subsequently promoted Th17 cell chemotaxis. Blocking C-X-C chemokine receptor type 3 or CCL20 reduced Th17 cell chemotaxis by IL-22-treated HSCs.

CONCLUSIONS

IL-22 plays a pathological role in exacerbating chronic liver inflammation and fibrosis by recruiting hepatic Th17 cells in HBV-infected patients and HBV Tg mice.

The roles of hepatitis B virus-encoded X protein in virus replication and the pathogenesis of chronic liver disease

INTRODUCTION

Hepatitis B virus (HBV) is a major cause of chronic liver disease (CLD) and hepatocellular carcinoma (HCC) worldwide. More than 350 million people are at risk for HCC, and with few treatment options available, therapeutic approaches to targets other than the virus polymerase will be needed. This review suggests that the HBV-encoded X protein, HBx, would be an outstanding target because it contributes to the biology and pathogenesis of HBV in three fundamental ways.

AREAS COVERED

First, HBx is a trans-activating protein that stimulates virus gene expression and replication, thereby promoting the development and persistence of the carrier state. Second, HBx partially blocks the development of immune responses that would otherwise clear the virus, and protects infected hepatocytes from immune-mediated destruction. Thus, HBx contributes to the development of CLD without virus clearance. Third, HBx alters patterns of host gene expression that make possible the emergence of HCC. The selected literature cited is from the National Library of Medicine (Pubmed and Medline).

EXPERT OPINION

Understanding the mechanisms, whereby HBx supports virus replication and promotes pathogenesis, suggests that HBx will be an important therapeutic target against both virus replication and CLD aimed at the chemoprevention of HCC.

The S protein of hepatitis B virus promotes collagen type I expression in hepatic stellate cells by virtue of hepatocytes

This study was conducted in order to investigate whether hepatitis B surface S protein (HBs) was able to directly or indirectly promote the proliferation and expression of collagen type I (Col I) and α-smooth muscle actin (α-SMA) in hepatic stellate cells (HSCs). The LX-2 human cell line and the HepG2 human hepatocellular carcinoma cell line were employed as HSCs and as hepatocytes, respectively. Recombinant HBs was added to the LX-2 cells for 48 h and the cell proliferation was assessed by the MTT assay. Col I and α-SMA were measured in the supernatant by ELISA, following treatment of the LX-2 and/or HepG2 cells with recombinant HBs. Transforming growth factor-β1 (TGF-β1) was also determined by ELISA in the HepG2 cell supernatants. The data demonstrated that high concentrations of recombinant HBs (10-50 ng/ml) inhibited the proliferation of LX-2 cells, whereas low concentrations (0.5-5 ng/ml) did not affect LX-2 cell proliferation. After treating LX-2 cells alone with recombinant HBs for 48 h, there was no significant increase in the Col I and α-SMA levels. However, Col I was increased ~1.7-fold in co-cultured (LX-2 and HepG2) cell supernatants following treatment with HBs for 24 h (HBs vs. control group: 48.51±3.51 vs. 28.23±2.55 ng/ml, respectively). Furthermore, TGF-β1 was significantly increased in the HepG2 cell supernatants following treatment with recombinant HBs. Therefore, we concluded that HBs directly affected the proliferation of HSCs, but promoted the Col I expression in HSCs possibly by virtue of hepatocytes secreting TGF-β1. This may provide a novel explanation of the fibrogenetic mechanism induced by hepatitis B virus-related proteins.

Using proteomics to identify the HBx interactome in hepatitis B virus: how can this inform the clinic?

Hepatitis B virus (HBV) is a small and enveloped DNA virus, of which chronic infection is the main risk factor of liver cirrhosis and hepatocellular carcinoma. Hepatitis B virus X protein (HBx) is a multifunctional protein encoded by HBV genome, which have significant effects on HBV replication and pathogenesis. Through directly interacting with cellular proteins, HBx is capable to promote HBV replication, regulate transcription of host genes, disrupt protein degradation, modulate signaling pathway, manipulate cell death and deregulate cell cycle. In this review, we briefly discuss the diversified effects of HBx-interactome and their potential clinical significances.

[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 e antigen induces activation of rat hepatic stellate cells

Chronic hepatitis B virus infection is a major cause of hepatic fibrosis, leading to liver cirrhosis and hepatocellular carcinoma. Hepatitis B virus e antigen (HBeAg) is an accessory protein of HBV, not required for viral replication but important for natural infection in vivo. Hepatic stellate cells (HSCs) are the major producers of excessive extracellular matrix during liver fibrogenesis. Therefore, we examined the influence of HBeAg on HSCs. The rat HSC line HSC-T6 was transfected with HBeAg plasmids, and expression of α-smooth muscle actin, collagen I, transforming growth factor-β1 (TGF-β), and tissue inhibitors of metalloproteinase 1 (TIMP-1) was investigated by quantitative real-time PCR. The proliferation of HSCs was determined by MTS analysis. HBeAg transduction induced up-regulation of these fibrogenic genes and proliferation of HSCs. We found that HBeAg induced TGF-β secretion in HSCs, and the activation of HSCs was prevented by a neutralizing anti-TGF-β antibody. Depletion and addition of HBeAg protein in conditioned medium from HSC-T6 cells transduced with HBeAg indicated that HBeAg directly induced the activation and proliferation of rat primary HSCs. Taken together, HBeAg induces the activation and proliferation of HSCs, mainly mediated by TGF-β, and HBeAg protein purified from cell medium can directly activate HSCs.

Morpho-mechanical intestinal remodeling in type 2 diabetic GK rats--is it related to advanced glycation end product formation?

Little is known about the mechanisms for the biomechanical remodeling in diabetes. The histomorphology, passive biomechanical properties and expression of advanced glycation end product (N epsilon-(carboxymethyl) lysine, AGE) and its receptor (RAGE) were studied in jejunal segments from 8 GK diabetic rats (GK group) and 10 age-matched normal rats (Normal group). The mechanical test was done by using a ramp distension of fluid into the jejunal segments in vitro. Circumferential stress and strain were computed from the length, diameter and pressure data and from the zero-stress state geometry. AGE and RAGE were detected by immunohistochemistry staining. Linear regression analysis was done to study association between the glucose level and AGE/RAGE expression with the histomorphometric and biomechanical parameters. The blood glucose level, the jejunal weight per length, wall thickness, wall area and layer thickness significantly increased in the GK group compared with the Normal group (P<0.05, P<0.01 and P<0.001). The opening angle and absolute values of residual strain decreased whereas the circumferential stiffness of the jejunal wall increased in the GK group (P<0.05 and P<0.01). Furthermore, stronger AGE expression in the villi and crypt and RAGE expression in the villi were found in the GK group (P<0.05 and P<0.01). Most histomorphometric and biomechanical changes were associated with blood glucose level and AGE/RAGE expression. In conclusion, histomorphometric and biomechanical remodeling occurred in type 2 diabetic GK rats. The increasing blood glucose level and the increased AGE/RAGE expression were associated with the remodeling, indicating a causal relationship.

A zebrafish model of intrahepatic cholangiocarcinoma by dual expression of hepatitis B virus X and hepatitis C virus core protein in liver

The mechanisms that mediate the initiation and development of intrahepatic cholangiocarcinoma (ICC) associated with hepatitis B and C virus (HBV and HCV, respectively) infection remain largely unclear. In this study we conditionally coexpressed hepatitis B virus X (HBx) and hepatitis C virus core (HCP) proteins in zebrafish livers, which caused fibrosis and consequently contributed to ICC formation at the age of 3 months. Suppressing the transgene expression by doxycycline (Dox) treatment resulted in the loss of ICC formation. The biomarker networks of zebrafish ICC identified by transcriptome sequencing and analysis were also frequently involved in the development of human neoplasms. The profiles of potential biomarker genes of zebrafish ICC were similar to those of human cholangiocarcinoma. Our data also showed that the pSmad3L oncogenic pathway was activated in HBx and HCP-induced ICC and included phosphorylation of p38 mitogen-activated proteinbase (MAPK) and p44/42 mitogen-activated protein kinase (ERK1/2), indicating the association with transforming growth factor beta 1 (TGF-β1) signaling pathway in ICC. Bile duct proliferation, fibrosis, and ICC were markedly reduced by knockdown of TGF-β1 by in vivo morpholinos injections.

CONCLUSION

These results reveal that TGF-β1 plays an important role in HBx- and HCP-induced ICC development. This in vivo model is a potential approach to study the molecular events of fibrosis and ICC occurring in HBV and HCV infection.