Inhibition of hepatitis B virus production associated with high levels of intracellular viral DNA intermediates in iron-depleted HepG2.2.15 cells

Chronic hepatitis B complicated with secondary hemochromatosis was cured clinically: A case report

Chronic hepatitis B (CHB) often causes iron overload in the liver but rarely causes severe secondary hemochromatosis (SH). A 48-year-old man was infected with CHB via vertical transmission. For 21 years, nonstandard treatment with second-line hepatitis B antiviral drugs has been administered. Repeated abnormalities in the liver transaminase function and continuous low-level replication of the hepatitis B virus (HBV) have been detected. The skin had turned black 5 years back. Biochemical tests and imaging revealed the presence of hemochromatosis. A liver biopsy suggested severe iron overload. Two genetic tests ruled out hereditary hemochromatosis. The patient was diagnosed with SH and treated with 400 ml bloodletting once per week and an iron-chelating agent. After 12 weeks, liver function was normal, and the skin turned white. First, hepatitis B surface antigen (HBsAg) was lost, and HBV DNA was copied at low levels. The patient was diagnosed with an occult hepatitis B infection. HBV DNA was undetectable after 4 weeks of antiviral treatment with tenofovir. Upon reviewing the patient’s medical history, hemochromatosis was believed to be related to CHB with chronic inflammatory damage and no complete virological response. Improvements in hemochromatosis may promote HBsAg disappearance.

RNR-R2 Upregulation by a Short Non-Coding Viral Transcript

DNA viruses require dNTPs for replication and have developed different strategies to increase intracellular dNTP pools. Hepatitis B virus (HBV) infects non-dividing cells in which dNTPs are scarce and the question is how viral replication takes place. Previously we reported that the virus induces the DNA damage response (DDR) pathway culminating in RNR-R2 expression and the generation of an active RNR holoenzyme, the key regulator of dNTP levels, leading to an increase in dNTPs. How the virus induces DDR and RNR-R2 upregulation is not completely known. The viral HBx open reading frame (ORF) was believed to trigger this pathway. Unexpectedly, however, we report here that the production of HBx protein is dispensable. We found that a small conserved region of 125 bases within the HBx ORF is sufficient to upregulate RNR-R2 expression in growth-arrested HepG2 cells and primary human hepatocytes. The observed HBV mRNA embedded regulatory element is named ERE. ERE in isolation is sufficient to activate the ATR-Chk1-E2F1-RNR-R2 DDR pathway. These findings demonstrate a non-coding function of HBV transcripts to support its propagation in non-cycling cells.

HFE inhibits type I IFNs signaling by targeting the SQSTM1-mediated MAVS autophagic degradation

Iron metabolism is involved in numerous physiological processes such as erythropoiesis, oxidative metabolism. However, the in vivo physiological functions of the iron metabolism-related gene Hfe in immune response during viral infection remain poorly understood. Here, we identified 5 iron metabolism-associated genes specifically affected during RNA virus infection by a high-throughput assay and further found that HFE was a key negative regulator of RIG-I-like receptors (RLR)-mediated type I interferons (IFNs) signaling. RNA virus infection inhibited the binding of HFE to MAVS (mitochondrial antiviral signaling protein) and blocked MAVS degradation via selective autophagy. HFE mediated MAVS autophagic degradation by binding to SQSTM1/p62. Depletion of Hfe abrogated the autophagic degradation of MAVS, leading to the stronger antiviral immune response. These findings established a novel regulatory role of selective autophagy in innate antiviral immune response by the iron metabolism-related gene Hfe. These data further provided insights into the crosstalk among iron metabolism, autophagy, and innate immune response.Abbreviations: ATG: autophagy-related; BAL: bronchoalveolar lavage fluid; BMDMs: bone marrow-derived macrophages; CGAS: cyclic GMP-AMP synthase; CQ: chloroquine; Dpi: days post-infection; ELISA: enzyme-linked immunosorbent assay; GFP: green fluorescent protein; HAMP: hepcidin antimicrobial peptide; Hpi: hours post-infection; HJV: hemojuvelin BMP co-receptor; IFNs: interferons; IL6: interleukin 6; IRF3: interferon regulatory factor 3; ISRE: interferon-stimulated response element; Lipo: clodronate liposomes; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAVS: mitochondrial antiviral signaling protein; MEFs: mouse embryonic fibroblasts; SLC40A1/FPN1: solute carrier family 40 (iron-regulated transporter), member 1; flatiron; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; STING1/STING: stimulator of interferon response cGAMP interactor 1; TBK1: TANK-binding kinase 1; TFRC/TfR1: transferrin receptor; TNF/TNFα: tumor necrosis factor; WT: wild type.

A Chimeric Humanized Mouse Model by Engrafting the Human Induced Pluripotent Stem Cell-Derived Hepatocyte-Like Cell for the Chronic Hepatitis B Virus Infection

Humanized mouse model generated by grafting primary human hepatocytes (PHHs) to immunodeficient mouse has contributed invaluably to understanding the pathogenesis of hepatitis B virus (HBV). However, the source of PHHs is limited, which necessitates the search for alternatives. Recently, hepatocyte-like cells (HLCs) generated from human induced pluripotent stem cells (hiPSCs) have been used for in vitro HBV infection. Herein, we developed a robust human liver chimeric animal model to study in vivo HBV infection by engrafting the hiPSC-HLCs to Fah-/-Rag2-/-IL-2Rγc-/-SCID (FRGS) mice. After being optimized by a small molecule, XMU-MP-1, the hiPSC-HLCs engrafted FRGS (hHLC-FRGS) mice displayed approximately 40% liver chimerism at week 6 after engraftment and maintained at this level for at least 14 weeks. Viremia and HBV infection markers include antigens, RNA, DNA, and covalently closed circular DNA were detectable in HBV infected hHLC-FRGS mice. Furthermore, hiPSC-HLCs and hHLC-FRGS mice were successfully used to evaluate different antivirals. Therefore, we established a humanized mouse model for not only investigating HBV pathogenesis but also testing the effects of the anti-HBV drugs. Highlights:    (1) The implanted hiPSC-HLCs established a long-term chimerism in FRGS mice liver.    (2) hHLC-FRGS mice are adequate to support chronic HBV infection with a full viral life cycle.    (3) hiPSC-HLCs and hHLC-FRGS mice are useful tools for evaluation of antivirals against HBV infection in vitro and in vivo. Research in Context  To overcome the disadvantages of using primary human hepatocytes, we induced human pluripotent stem cells to hepatocyte-like cells (hiPSC-HLCs) that developed the capability to express important liver functional markers and critical host factors for HBV infection. The hiPSC-HLCs were permissive for the HBV infection and supported a full HBV replication. The hiPSC-HLCs were then engrafted to immunodeficient mouse to establish a chimeric liver mouse model, which was capable of supporting HBV infection in vivo and evaluating the effects of antiviral drugs. Our results shed light into improving the cellular and animal models for studying HBV and other hepatotropic viruses.

Improvement of chronic hepatitis B by iron chelation therapy in a patient with iron overload: A case report

RATIONALE

This report describes seroconversion of hepatitis B surface antigen (HBsAg) in a patient with marked iron overload caused by chronic hepatitis B (CHB) after receiving iron chelation therapy and discusses the role of iron chelation therapy in CHB.

PATIENT CONCERNS

Increased serum ferritin level for 2 months.

DIAGNOSIS

Secondary iron overload and CHB.

INTERVENTION

To relieve iron load of the body, the patient underwent regular phlebotomy therapy and deferoxamine (DFO) therapy. During the therapy, serum ferritin and hepatitis B virus (HBV) were monitored and the iron concentration of the liver and heart were followed by T2* of magnetic resonance imaging (MRI) scan.

OUTCOMES

Serum ferritin gradually decreased. Approximately 1 year after the therapy, HBsAg turned persistently negative.

LESSONS

Iron chelation therapy may attenuate HBV infection.

Correlation of serum hepcidin levels with disease progression in hepatitis B virus-related disease assessed by nanopore film based assay

Chronic hepatitis B virus (HBV) infection often develop into cirrhosis, and both are major risk factors of hepatocellular carcinoma. However, effective approaches for the monitoring of HBV-related disease progress are still in need. Increased iron storage has an important role in HBV-related diseases. Hepcidin is a key regulator of iron homeostasis whose expression changes are often indicative of abnormal iron metabolism. There are few reports of hepcidin levels in patients with HBV infections, and the available results are inconsistent. In this study, using a recently validated nanopore silica film based method, we measured serum hepcidin levels in 46 HBV-related patients and 20 healthy controls. Patients were divided into three groups: chronic hepatitis B without cirrhosis; HBV-related cirrhosis; and HBV-related cirrhosis with hepatocellular carcinoma. Compared to healthy controls, the mean serum hepcidin level was significantly higher in CHB patients without cirrhosis, and in those with hepatocellular carcinoma, but not in those with cirrhosis. Iron-loading, viral infection and liver dysfunction are determined to be the major regulators of hepcidin in these patients. These observations suggest correlations between serum hepcidin and progression of chronic HBV infection, and may shed a new light on the development of biomarkers for HBV-related disease surveillance.

Restrictive influence of SAMHD1 on Hepatitis B Virus life cycle

Deoxynucleotide triphosphates (dNTPs) are essential for efficient hepatitis B virus (HBV) replication. Here, we investigated the influence of the restriction factor SAMHD1, a dNTP hydrolase (dNTPase) and RNase, on HBV replication. We demonstrated that silencing of SAMHD1 in hepatic cells increased HBV replication, while overexpression had the opposite effect. SAMHD1 significantly affected the levels of extracellular viral DNA as well as intracellular reverse transcription products, without affecting HBV RNAs or cccDNA. SAMHD1 mutations that interfere with the dNTPase activity (D137N) or in the catalytic center of the histidine-aspartate (HD) domain (D311A), and a phospho-mimetic mutation (T592E), abrogated the inhibitory activity. In contrast, a mutation diminishing the potential RNase but not dNTPase activity (Q548A) and a mutation disabling phosphorylation (T592A) did not affect antiviral activity. Moreover, HBV restriction by SAMHD1 was rescued by addition of deoxynucleosides. Although HBV infection did not directly affect protein level or phosphorylation of SAMHD1, the virus upregulated intracellular dATPs. Interestingly, SAMHD1 was dephosphorylated, thus in a potentially antiviral-active state, in primary human hepatocytes. Furthermore, SAMHD1 was upregulated by type I and II interferons in hepatic cells. These results suggest that SAMHD1 is a relevant restriction factor for HBV and restricts reverse transcription through its dNTPase activity.

Inhibition of replication of porcine reproductive and respiratory syndrome virus by hemin is highly dependent on heme oxygenase-1, but independent of iron in MARC-145 cells

Current vaccines against porcine reproductive and respiratory syndrome virus (PRRSV) have failed to provide sustainable disease control, and development of new antiviral strategies is of great importance. The present study investigated the mechanism of the antiviral effect of hemin during PRRSV infection in MARC-145 cells. Hemin, a commercial preparation of heme, is used as an iron donor or heme oxygenase 1 (HO-1) inducer, and has been shown to provide antiviral activity in many studies. In the current study, the anti-PRRSV activity of hemin was identified through suppressing PRRSV propagation. The 50% inhibitory concentration (IC50) of hemin antiviral activity was estimated to be 32μM, and the 50% cytotoxic concentration (CC50) of hemin was found to be higher than 125μM. Further study showed that the antiviral activity of hemin is independent of iron. In addition, after treatment with Protoporphyrin IX zinc (II) (ZnPP) or Sn (IV) Protoporphyrin IX dichloride (SnPP), inhibitors of HO-1, the inhibition of viral replication by hemin was partially reversed. Additionally, it was confirmed that hemin and N-acetyl cysteine were able to significantly reduce reactive oxygen species (ROS) in MARC-145 cells infected with virus. N-acetyl-L-cysteine (NAC), however, did not produce a reduction in viral load or promote expression of HO-1. Taken together, these data indicate that the effect of hemin on the inhibition of PRRSV propagation via HO-1 induction, as well as the antiviral mechanism of HO-1, is not dependent on decreased levels of ROS. In conclusion, these data demonstrate that hemin had antiviral activity against PRRSV and may serve as a useful antiviral agent inhibiting PRRSV replication.

Protein alteration of HepG2.2.15 cells induced by iron overload

Hepatitis B can progress into hepatocellular carcinoma. Body irons may interfere with the clearance of hepatitis B virus (HBV) and contribute to genesis of tumor. To investigate the role of iron played in HBV-related pathogenesis, here we studied the effect of iron with different concentrations and valence states on growth of HepG2.2.15 cells and secretion of virus proteins. A strong tolerance of HepG2.2.15 cells to iron challenge was found. The concentration of hepatitis B surface antigen in cell culture medium was decreased after iron stimulation. Lower concentrations of iron facilitated hepatitis B e-antigen (HBeAg) secretion. Fe(2+) appeared more effective on HBeAg secretion than Fe(3+) did. In parallel, the differential protein profiles in HepG2.2.15 cells were studied by iTRAQ and LC-MS/MS. The differentially expressed proteins were mainly involved in stress response, signal transduction, apoptosis, etc. Four proteins (14-3-3 β/α, VCP, migration inhibitory factor, and Nup153) were verified by Western-blotting and found to be consistent with the iTRAQ data. Interestingly, nuclear import of Nuclear factor kappa B (NFκB) and its activity were found to be affected by the decreased Nup153 in iron stimulated HepG2.2.15 cells. The results may indicate possible molecular mechanism how the synergism of HBV and iron stimulation damages host liver cells.

TGF-β and iron differently alter HBV replication in human hepatocytes through TGF-β/BMP signaling and cellular microRNA expression

The nature of host-virus interactions in hepatitis B virus infection is incompletely understood. Since soluble factors, e.g., cytokines and metals, may exacerbate liver injury in chronic hepatitis, we considered that defining the effects of receptor-mediated signaling upon viral replication will be significant. Consequently, we studied effects of iron or TGF-β-induced TGF-β/BMP signaling in the HepG2 2.2.15 cell model of hepatitis B virus replication. We found iron and TGF-β increased hepcidin mRNA expression or TGF-β receptor kinase activity, respectively, which indicated that 2.2.15 cells responded appropriately to these substances. However, iron increased but TGF-β decreased hepatitis B virus mRNA and DNA expression. TGF-β induced expression at the mRNA level of multiple TGF-β/BMP pathway genes. This change was not observed in iron-treated cells. On the other hand, presence of SMAD proteins in iron or TGF-β-treated cells, including of SMAD4, did confirm convergence of TGF-β/BMP signaling pathways under these conditions. Since transcription factors in TGF-β/BMP signaling pathways could not have directly targeted hepatitis B virus itself, we studied whether iron or TGF-β exerted their effects through alternative mechanisms, such as by involvement of antiviral cellular microRNAs. We discovered cellular microRNA expression profiles were significantly different in iron or TGF-β-treated cells compared with untreated control cells. In many cases, exposure to iron or TGF-β changed microRNA expression in opposite directions. Introduction in cells of sequences representing such differentially expressed microRNAs, e.g., hsa-miR-125a-5p and -151-5p, even reproduced effects on virus replication of iron- or TGF-β. We surmised that TGF-β/BMP pathway members, i.e., SMADs, likely governed iron or TGF-β-induced microRNA expression. Iron may have mediated Drosha/DGCR8/heme-mediated processing of microRNAs. In turn, cellular microRNAs regulated replication of hepatitis B virus in iron or TGF-β-treated cells. This knowledge should advance studies of mechanisms in viral-host interactions, hepatic injury, and therapeutic developments for hepatitis B.

Humanized murine model for HBV and HCV using human induced pluripotent stem cells

Infection of hepatitis B virus (HBV) and hepatitis C virus (HCV) results in heterogeneous outcomes from acute asymptomatic infection to chronic infection leading to cirrhosis and hepatocellular carcinoma (HCC). In vitro models using animal hepatocytes, human HCC cell lines, or in vivo transgenic mouse models have contributed invaluably to understanding the pathogenesis of HBV and HCV. A humanized mouse model made by reconstitution of human primary hepatocytes in the liver of the immunodeficient mouse provides a novel experimental opportunity which mimics the in vivo growth of the human hepatocytes. The limited access to primary human hepatocytes necessitated the search for other cellular sources, such as pluripotent stem cells. Human embryonic stem cells (hESCs) have the features of self-renewal and pluripotency and differentiate into cells of all three germ layers, including hepatocytes. Humaninduced pluripotent stem cells (iPSCs) derived from the patient's or individual's own cells provide a novel opportunity to generate hepatocyte-like cells with the defined genetic composition. Here, we will review the current perspective of the models used for HBV and HCV study, and introduce the personalized mouse model using human iPSCs. This novel mouse model will facilitate the direct investigation of HBV and HCV in human hepatocytes as well as probing the genetic influence on the susceptibility of hepatocytes to HBV and HCV.

Viral infection and iron metabolism

Fundamental cellular operations, including DNA synthesis and the generation of ATP, require iron. Viruses hijack cells in order to replicate, and efficient replication needs an iron-replete host. Some viruses selectively infect iron-acquiring cells by binding to transferrin receptor 1 during cell entry. Other viruses alter the expression of proteins involved in iron homeostasis, such as HFE and hepcidin. In HIV-1 and hepatitis C virus infections, iron overload is associated with poor prognosis and could be partly caused by the viruses themselves. Understanding how iron metabolism and viral infection interact might suggest new methods to control disease.

HBx modulates iron regulatory protein 1-mediated iron metabolism via reactive oxygen species

Hepatitis B virus X protein (HBx) is involved in viral metabolism and progression of liver disease. Iron metabolism plays a significant role in liver disease. In this report, to elucidate the relationship between iron metabolism and HBx, we established the Huh7 cell lines in which HBx was stably expressed (Huh7-HBx). In Huh7-HBx, we observed that transferrin receptor 1 (TfR1) expression decreased and ferritin heavy chain (FtH) expression increased as well as reactive oxygen species (ROS) level increased. We also found that these modulations were caused by the downregulation of iron regulatory protein 1 (IRP1). Furthermore, the levels of total iron and labile iron pool (LIP) were altered in Huh7-HBx. In addition, antioxidant N-acetylcystein (NaC) increased IRP1 expression by depleting HBx-induced ROS. We also confirmed these alterations of TfR1 and FtH in the primary hepatocytes of HBx transgenic mice and in HepG2.2.15 cells that constitutively replicate the intact HBV genome. In conclusion, these results suggest that HBx modulates iron metabolism via ROS leading to pathological status in liver diseases.

Effect of artemisinin/artesunate as inhibitors of hepatitis B virus production in an "in vitro" replicative system

The antiviral effect against hepatitis B virus (HBV) of artemisinin, its derivative artesunate and other compounds highly purified from traditional Chinese medicine remedies, were investigated. HBV production by permanently transfected HepG2 2.2.15 cells was determined by measuring the release of surface protein (HBsAg) and HBV-DNA after drug exposure (0.01-100 microM) for 21 days. The forms of HBV-DNA released were investigated by Southern-blotting. Neutral Red retention test was used to evaluate drug-induced toxicity on host cells. The compounds were classified according to their potential interest as follows: (i) none: they had no effect on viral production (daidzein, daidzin, isonardosinon, nardofuran, nardosinon, tetrahydronardosinon and quercetin); (ii) low: they were able to markedly reduce viral production, but also induced toxicity on host cells (berberine and tannic acid) or they had no toxic effect on host cells but only had a moderate ability to reduce viral production (curcumin, baicalein, baicalin, bufalin, diallyl disulphide, glycyrrhizic acid and puerarin); (iii) high: they induced strong inhibition of viral production at concentrations at which host cell viability was not affected (artemisinin and artesunate). Moreover, artesunate in conjunction with lamivudine had synergic anti-HBV effects, which warrants further evaluation of artemisinin/artesunate as antiviral agents against HBV infection.

Oncostatin M-stimulated apical plasma membrane biogenesis requires p27(Kip1)-regulated cell cycle dynamics

Oncostatin M regulates membrane traffic and stimulates apicalization of the cell surface in hepatoma cells in a protein kinase A-dependent manner. Here, we show that oncostatin M enhances the expression of the cyclin-dependent kinase (cdk)2 inhibitor p27(Kip1), which inhibits G(1)-S phase progression. Forced G(1)-S-phase transition effectively renders presynchronized cells insensitive to the apicalization-stimulating effect of oncostatin M. G(1)-S-phase transition prevents oncostatin M-mediated recruitment of protein kinase A to the centrosomal region and precludes the oncostatin M-mediated activation of a protein kinase A-dependent transport route to the apical surface, which exits the subapical compartment (SAC). This transport route has previously been shown to be crucial for apical plasma membrane biogenesis. Together, our data indicate that oncostatin M-stimulated apicalization of the cell surface is critically dependent on the ability of oncostatin M to control p27(Kip1)/cdk2-mediated G(1)-S-phase progression and suggest that the regulation of apical plasma membrane-directed traffic from SAC is coupled to centrosome-associated signaling pathways.

Evidence for dual effects of DNA-reactive bile acid derivatives (Bamets) on hepatitis B virus life cycle in an in vitro replicative system

A liver targeting strategy to direct antiviral drugs toward hepatitis B virus (HBV) was investigated. As model drugs we used cisplatin-bile acid derivatives (Bamets) to determine the production of virions by HBV-transfected hepatoblastoma cells (HepG2 2.2.15). Drug uptake was determined using flameless atomic absorption spectrometry to measure platinum cell contents. Cytotoxic effect was determined by formazan formation and neutral red uptake tests. The release of viral surface protein was evaluated by ELISA. The abundance of HBV-DNA in the medium was determined by quantitative real-time PCR and its structure by Southern blot analysis. The uptake of Bamets by HepG2 2.2.15 cells was higher than that of cisplatin. At concentrations lower than 10 microM, distinct Bamets have no toxic effect on host cells, whereas cisplatin dramatically reduced cell viability at concentrations higher than 1 microM. All the drugs tested inhibited the release of viral proteins to the medium, but induced a marked and progressive dose-dependent increase in the amount of viral DNA in the medium. This was mainly due to the release of short fragments of HBV-DNA in the case of cisplatin. On the contrary, Bamets induced an enhanced release of circular forms of HBV-DNA. These findings suggest the existence of a dual effect of Bamets on HBV life-cycle by enhancing the production of DNA replicative intermediates but reducing the secretion of complete virions. Altogether these characteristics recommend consideration of these compounds as a useful experimental tool in the investigation of novel liver targeted therapeutic agents based on bile acid derivatives for the treatment of HBV infections, or to carry out further studies on the HBV life cycle.