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Han J, Jang KL. All-trans retinoic acid downregulates HBx levels via E6-associated protein-mediated proteasomal degradation to suppress hepatitis B virus replication. PLoS One 2024; 19:e0305350. [PMID: 38861553 PMCID: PMC11166335 DOI: 10.1371/journal.pone.0305350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 05/28/2024] [Indexed: 06/13/2024] Open
Abstract
All-trans retinoic acid (ATRA), recognized as the principal and most biologically potent metabolite of vitamin A, has been identified for its inhibitory effects on hepatitis B virus (HBV) replication. Nevertheless, the underlying mechanism remains elusive. The present study reveals that ATRA induces E6-associated protein (E6AP)-mediated proteasomal degradation of HBx to suppress HBV replication in human hepatoma cells in a p53-dependent pathway. For this effect, ATRA induced promoter hypomethylation of E6AP in the presence of HBx, which resulted in the upregulation of E6AP levels in HepG2 but not in Hep3B cells, emphasizing the p53-dependent nature of this effect. As a consequence, ATRA augmented the interaction between E6AP and HBx, resulting in substantial ubiquitination of HBx and consequent reduction in HBx protein levels in both the HBx overexpression system and the in vitro HBV replication model. Additionally, the knockdown of E6AP under ATRA treatment reduced the interaction between HBx and E6AP and decreased the ubiquitin-dependent proteasomal degradation of HBx, which prompted a recovery of HBV replication in the presence of ATRA, as confirmed by increased levels of intracellular HBV proteins and secreted HBV levels. This study not only contributes to the understanding of the complex interactions between ATRA, p53, E6AP, and HBx but also provides an academic basis for the clinical employment of ATRA in the treatment of HBV infection.
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Affiliation(s)
- Jiwoo Han
- Department of Integrated Biological Science, The Graduate School, Pusan National University, Busan, Republic of Korea
| | - Kyung Lib Jang
- Department of Integrated Biological Science, The Graduate School, Pusan National University, Busan, Republic of Korea
- Department of Microbiology, College of Natural Science, Pusan National University, Busan, Republic of Korea
- Microbiological Resource Research Institute, Pusan National University, Busan, Republic of Korea
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Gilmore SA, Tam D, Cheung TL, Snyder C, Farand J, Dick R, Matles M, Feng JY, Ramirez R, Li L, Yu H, Xu Y, Barnes D, Czerwieniec G, Brendza KM, Appleby TC, Birkus G, Willkom M, Kobayashi T, Paoli E, Labelle M, Boesen T, Tay CH, Delaney WE, Notte GT, Schmitz U, Feierbach B. Characterization of a KDM5 small molecule inhibitor with antiviral activity against hepatitis B virus. PLoS One 2022; 17:e0271145. [PMID: 36477212 PMCID: PMC9728921 DOI: 10.1371/journal.pone.0271145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 11/14/2022] [Indexed: 12/12/2022] Open
Abstract
Chronic hepatitis B (CHB) is a global health care challenge and a major cause of liver disease. To find new therapeutic avenues with a potential to functionally cure chronic Hepatitis B virus (HBV) infection, we performed a focused screen of epigenetic modifiers to identify potential inhibitors of replication or gene expression. From this work we identified isonicotinic acid inhibitors of the histone lysine demethylase 5 (KDM5) with potent anti-HBV activity. To enhance the cellular permeability and liver accumulation of the most potent KDM5 inhibitor identified (GS-080) an ester prodrug was developed (GS-5801) that resulted in improved bioavailability and liver exposure as well as an increased H3K4me3:H3 ratio on chromatin. GS-5801 treatment of HBV-infected primary human hepatocytes reduced the levels of HBV RNA, DNA and antigen. Evaluation of GS-5801 antiviral activity in a humanized mouse model of HBV infection, however, did not result in antiviral efficacy, despite achieving pharmacodynamic levels of H3K4me3:H3 predicted to be efficacious from the in vitro model. Here we discuss potential reasons for the disconnect between in vitro and in vivo efficacy, which highlight the translational difficulties of epigenetic targets for viral diseases.
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Affiliation(s)
- Sarah A. Gilmore
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Danny Tam
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Tara L. Cheung
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Chelsea Snyder
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Julie Farand
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Ryan Dick
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Mike Matles
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Joy Y. Feng
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Ricardo Ramirez
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Li Li
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Helen Yu
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Yili Xu
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Dwight Barnes
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Gregg Czerwieniec
- Gilead Sciences, Inc., Foster City, California, United States America
| | | | - Todd C. Appleby
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Gabriel Birkus
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Madeleine Willkom
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Tetsuya Kobayashi
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Eric Paoli
- Gilead Sciences, Inc., Foster City, California, United States America
| | | | - Thomas Boesen
- EpiTherapeutics ApS, Copenhagen, Denmark
- Novo Nordisk A/S, Bagsvaerd, Denmark
| | - Chin H. Tay
- Gilead Sciences, Inc., Foster City, California, United States America
| | | | - Gregory T. Notte
- Gilead Sciences, Inc., Foster City, California, United States America
| | - Uli Schmitz
- Gilead Sciences, Inc., Foster City, California, United States America
- * E-mail:
| | - Becket Feierbach
- Gilead Sciences, Inc., Foster City, California, United States America
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Abstract
PURPOSE OF REVIEW Antiviral therapy for chronic hepatitis B infection is rarely curative, thus research in HBV cure strategies is a priority. Drug development and testing has been hampered by the lack of robust cell culture systems and small animal models. This review summarizes existing models for HBV cure research and focuses on recent developments since 2017 until today. RECENT FINDINGS The field has progressed in the development of cell culture and animal models to study HBV. Although early cell culture systems relied on transfection of HBV genomes in hepatoma cell lines, novel models expressing the entry receptor for HBV are susceptible to infection. Improved culture conditions for primary human hepatocytes, the primary target of HBV, have enabled the screening and validation of novel antivirals. Mouse models grafted with partially humanized livers are suitable for testing viral entry inhibitors or direct acting antivirals, and can be reconstituted with human immune cells to analyze immunotherapies. Other immunocompetent models include mice transduced with HBV genomes or woodchucks infected with their native hepatitis virus. SUMMARY Model systems for HBV research have helped lay the groundwork for the development and optimization of antiviral and immune-based therapeutic approaches that are now moving to clinical trials.
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Qu B, Brown RJP. Strategies to Inhibit Hepatitis B Virus at the Transcript Level. Viruses 2021; 13:v13071327. [PMID: 34372533 PMCID: PMC8310268 DOI: 10.3390/v13071327] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 07/02/2021] [Accepted: 07/06/2021] [Indexed: 12/11/2022] Open
Abstract
Approximately 240 million people are chronically infected with hepatitis B virus (HBV), despite four decades of effective HBV vaccination. During chronic infection, HBV forms two distinct templates responsible for viral transcription: (1) episomal covalently closed circular (ccc)DNA and (2) host genome-integrated viral templates. Multiple ubiquitous and liver-specific transcription factors are recruited onto these templates and modulate viral gene transcription. This review details the latest developments in antivirals that inhibit HBV gene transcription or destabilize viral transcripts. Notably, nuclear receptor agonists exhibit potent inhibition of viral gene transcription from cccDNA. Small molecule inhibitors repress HBV X protein-mediated transcription from cccDNA, while small interfering RNAs and single-stranded oligonucleotides result in transcript degradation from both cccDNA and integrated templates. These antivirals mediate their effects by reducing viral transcripts abundance, some leading to a loss of surface antigen expression, and they can potentially be added to the arsenal of drugs with demonstrable anti-HBV activity. Thus, these candidates deserve special attention for future repurposing or further development as anti-HBV therapeutics.
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Affiliation(s)
- Bingqian Qu
- Division of Veterinary Medicine, Paul Ehrlich Institute, 63225 Langen, Germany
- European Virus Bioinformatics Center, 07743 Jena, Germany
- Correspondence: (B.Q.); (R.J.P.B.)
| | - Richard J. P. Brown
- Division of Veterinary Medicine, Paul Ehrlich Institute, 63225 Langen, Germany
- Correspondence: (B.Q.); (R.J.P.B.)
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Han B, Mo H, Svarovskaia E, Mateo R. A primary human hepatocyte/hepatic stellate cell co-culture system for improved in vitro HBV replication. Virology 2021; 559:40-45. [PMID: 33813211 DOI: 10.1016/j.virol.2021.03.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 11/18/2022]
Abstract
Primary human hepatocytes (PHHs) are considered the gold standard for the in vitro study of HBV replication as they directly reflect the metabolism and functionality of the human liver. However, several limitations of this system include PHH donor-to-donor variability, limited life span and low permissiveness to HBV infection, which precludes long-term infection studies and viral passaging. Here, an easy-to-set-up co-culture platform that combines PHH with hepatic stellate cells (HSCs) was developed. This platform does not rely on chemical supplementation to sustain robust HBV replication and viral antigen secretion making it a more physiologically relevant system for in vitro HBV infection studies compared to the traditional short-lived PHH monocultures.
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Affiliation(s)
- Bin Han
- Gilead Sciences, Inc., Foster City, CA, USA
| | - Hongmei Mo
- Gilead Sciences, Inc., Foster City, CA, USA
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Zeng J, Wu D, Hu H, Young JAT, Yan Z, Gao L. Activation of the Liver X Receptor Pathway Inhibits HBV Replication in Primary Human Hepatocytes. Hepatology 2020; 72:1935-1948. [PMID: 32145089 DOI: 10.1002/hep.31217] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 12/19/2019] [Accepted: 02/19/2020] [Indexed: 12/23/2022]
Abstract
BACKGROUND AND AIMS Hepatitis B virus (HBV) infection is ranked among the top health priorities worldwide. Accumulating evidence suggests that HBV infection and replication are closely associated with liver metabolism. The liver X receptors (LXRs), which belong to the superfamily of nuclear hormone receptors, are important physiological regulators of lipid and cholesterol metabolism. However, the association between the LXR pathway and HBV infection remains largely unclear. APPROACH AND RESULTS In this study, the antiviral activity of LXR agonists was investigated using multiple HBV cellular models. We observed that in HBV-infected primary human hepatocytes (PHHs), synthetic LXR agonists (T0901317, GW3965, and LXR-623), but not an LXR antagonist (SR9238), potently inhibited HBV replication and gene expression, as demonstrated by substantial reductions in viral RNA, DNA, and antigen production following agonist treatment. However, covalently closed circular DNA (cccDNA) levels were not significantly reduced by the agonists. In addition, no rebound in viral replication was observed after treatment withdrawal, indicating a long-lasting inhibitory effect. These results suggest that LXR agonists decrease the transcriptional activity of cccDNA. In contrast, no significant anti-HBV effect was observed in HepG2-derived cell lines. Interestingly, LXR agonist treatment strongly reduced cholesterol 7α-hydroxylase 1 (CYP7A1) mRNA levels. Knockdown of CYP7A1 gene expression with small interfering RNA inhibited HBV activity in PHHs, suggesting CYP7A1 as a potential factor contributing to the antiviral effects of LXR agonists. CONCLUSIONS We found that activation of the LXR pathway with synthetic LXR agonists could elicit potent anti-HBV activity in PHHs, possibly through sustained suppression of cccDNA transcription. Our work highlights the therapeutic potential of targeting the LXR pathway for the treatment of chronic HBV infection.
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Affiliation(s)
- Jing Zeng
- Roche Innovation Center Shanghai, Shanghai, China
| | - Daitze Wu
- Roche Innovation Center Shanghai, Shanghai, China
| | - Hui Hu
- Roche Innovation Center Shanghai, Shanghai, China
| | | | - Zhipeng Yan
- Roche Innovation Center Shanghai, Shanghai, China
| | - Lu Gao
- Roche Innovation Center Shanghai, Shanghai, China
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