151
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Autophagy: a primer for the gastroenterologist/hepatologist. CANADIAN JOURNAL OF GASTROENTEROLOGY = JOURNAL CANADIEN DE GASTROENTEROLOGIE 2012; 25:667-74. [PMID: 22175057 DOI: 10.1155/2011/581264] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophagy is a conserved cellular pathway that maintains intracellular homeostasis by degrading proteins and cytosolic contents of eukaryotic cells. Autophagy clears misfolded and long-lived proteins, damaged organelles and invading microorganisms from cells, and provides nutrients and energy in response to exposure to cell stressors such as starvation. Defective autophagy has recently been linked to a diverse range of disease processes of relevance to gastroenterologists and hepatologists including Crohn's disease, pancreatitis, hepatitis and cancer. The present article provides an overview of the autophagy pathway and discusses gastrointestinal disease processes in which alterations in autophagy have been implicated. The clinical significance of autophagy as a potential therapeutic option is also discussed.
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152
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Minor T, Koetting M, Koetting M, Kaiser G, Efferz P, Lüer B, Paul A. Hypothermic reconditioning by gaseous oxygen improves survival after liver transplantation in the pig. Am J Transplant 2011; 11:2627-34. [PMID: 21906256 DOI: 10.1111/j.1600-6143.2011.03731.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The quality of cold-stored livers declines with the extension of ischemic time and the risk of primary dys- or nonfunction increases. Here, we provide in vivo evidence for the efficacy of the previously developed end-ischemic gaseous oxygen persufflation technique to resuscitate liver grafts after extended storage times. Porcine livers were recovered according to standard multiorgan procurement protocol. Control livers were cold stored in histidine tryptophan ketoglutarate solution for 10 h (cold storage [CS]; n = 6) at 4°C. In the treatment group (n = 6), livers were additionally subjected to hypothermic reconditioning (HR) by gaseous oxygen persufflation via the caval vein for 2 h before transplantation. Viability was assessed by orthotopic liver transplantation and 1 week follow-up. HR significantly improved pretransplant energy charge and initial graft function after transplantation. One week survival after CS was 0% whereas five of six pigs (83%) survived in the HR group. At that time, coagulation parameters were in the normal range and histological analysis disclosed healthy liver tissue with normal trabecular architecture in the treated grafts. Molecular analyses identify the prevention of ischemia-induced decline of cellular autophagy and mitigation of innate immune machinery (high-mobility group protein B1, interferon-β) as operative mechanisms among the protective effects provided by HR.
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Affiliation(s)
- T Minor
- Surgical Research Division, University Clinic of Surgery, Bonn, Germany.
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153
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Raychoudhuri A, Shrivastava S, Steele R, Kim H, Ray R, Ray RB. ISG56 and IFITM1 proteins inhibit hepatitis C virus replication. J Virol 2011; 85:12881-9. [PMID: 21976647 PMCID: PMC3233139 DOI: 10.1128/jvi.05633-11] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 09/28/2011] [Indexed: 12/11/2022] Open
Abstract
Hepatitis C virus (HCV) often leads to persistent infection. Interferon (IFN) and IFN-stimulated genes (ISGs) are amplified during HCV infection but fail to eliminate virus from the liver in a large number of infected patients. We have observed previously that HCV infection induces IFN-β production in immortalized human hepatocytes (IHH) as early as 24 h after infection, although virus replication is not inhibited. To gain insights on possible countermeasures of virus for the suppression of host antiviral response, the cellular transcriptional profiles of ISGs were examined after various treatments of IHH. The majority of ISGs were upregulated in IFN-treated IHH from the level for mock-treated cells. However, the comparison of ISG expression in IFN-treated IHH and IFN-pretreated, HCV genotype 2a-infected IHH indicated that virus infection suppresses the upregulation of a subset of effector molecules, including ISG56 and IFITM1. Similar results were observed for HCV-infected Huh7 cells. Subsequent study suggested that the exogenous expression of ISG56 or IFITM1 inhibits HCV replication in IHH or Huh7 cells, and the knockdown of these genes enhanced HCV replication. Further characterization revealed that the overexpression of these ISGs does not block HCV pseudotype entry into Huh7 cells. Taken together, our results demonstrated that ISG56 and IFITM1 serve as important molecules to restrict HCV infection, and they may have implications in the development of therapeutic modalities.
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Affiliation(s)
| | | | | | - Hangeun Kim
- Internal Medicine, Saint Louis University, St. Louis, Missouri
| | - Ranjit Ray
- Internal Medicine, Saint Louis University, St. Louis, Missouri
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154
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Alavian SM, Ande SR, Coombs KM, Yeganeh B, Davoodpour P, Hashemi M, Los M, Ghavami S. Virus-triggered autophagy in viral hepatitis - possible novel strategies for drug development. J Viral Hepat 2011; 18:821-30. [PMID: 22093031 DOI: 10.1111/j.1365-2893.2011.01530.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Autophagy is a very tightly regulated process that is important in many cellular processes including development, differentiation, survival and homoeostasis. The importance of this process has already been proven in numerous common diseases such as cancer and neurodegenerative disorders. Emerging data indicate that autophagy plays an important role in some liver diseases including liver injury induced by ischaemia reperfusion and alpha-1 antitrypsin Z allele-dependent liver disease. Autophagy may also occur in viral infection, and it may play a crucial role in antimicrobial host defence against pathogens, while supporting cellular homoeostasis processes. Here, the latest findings on the role of autophagy in viral hepatitis B and C infection, which are both serious health threats, will be reviewed.
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Affiliation(s)
- S M Alavian
- Baqiyatallah Research Center for Gastroenterology and Liver Diseases, Tehran, Iran
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155
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Chen Q, Fang L, Wang D, Wang S, Li P, Li M, Luo R, Chen H, Xiao S. Induction of autophagy enhances porcine reproductive and respiratory syndrome virus replication. Virus Res 2011; 163:650-5. [PMID: 22119900 PMCID: PMC7114478 DOI: 10.1016/j.virusres.2011.11.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 11/06/2011] [Accepted: 11/11/2011] [Indexed: 11/20/2022]
Abstract
Autophagy is an evolutionarily conserved lysosome-dependent degradation pathway that acts in the maintenance of cellular homeostasis and plays important functions in viral replication and pathogenesis. In this study, we investigated the role of autophagy in the replication of porcine reproductive and respiratory syndrome virus (PRRSV), an agent that has caused devastating losses in the international swine industry since the late 1980s. Using protein quantification and microscopy, we observed that PRRSV infection results in LC3-I/II conversion, an increased accumulation of punctate GFP-LC3-expressing cells, and a higher number of autophagosome-like double-membrane vesicles in the cytoplasm of host cells. Inhibition of autophagy using 3-methyladenine (3-MA) or small interfering RNAs targeting ATG7 and Beclin-1 led to a significant reduction in PRRSV titers and protein expression. Conversely, induction of autophagy by rapamycin resulted in increased viral replication. These results demonstrate that PRRSV infection induces autophagy which, in turn, enhances viral replication efficiency.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Shaobo Xiao
- Corresponding author. Mailing address: Laboratory of Animal Virology, College of Veterinary Medicine, Huazhong Agricultural University, 1 Shi-zi-shan Street, Wuhan 430070, PR China. Tel.: +86 27 8728 6884; fax: +86 27 8728 2608.
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156
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Yang JA, Park K, Jung H, Kim H, Hong SW, Yoon SK, Hahn SK. Target specific hyaluronic acid–interferon alpha conjugate for the treatment of hepatitis C virus infection. Biomaterials 2011; 32:8722-9. [DOI: 10.1016/j.biomaterials.2011.07.088] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 07/30/2011] [Indexed: 11/27/2022]
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157
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Estrabaud E, De Muynck S, Asselah T. Activation of unfolded protein response and autophagy during HCV infection modulates innate immune response. J Hepatol 2011; 55:1150-3. [PMID: 21723841 DOI: 10.1016/j.jhep.2011.04.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 04/20/2011] [Accepted: 04/21/2011] [Indexed: 01/07/2023]
Abstract
Autophagy, a process for catabolizing cytoplasmic components, has been implicated in the modulation of interactions between RNA viruses and their host. However, the mechanism underlying the functional role of autophagy in the viral life cycle still remains unclear. Hepatitis C virus (HCV) is a single-stranded, positive-sense, membrane-enveloped RNA virus that can cause chronic liver disease. Here we report that HCV induces the unfolded protein response (UPR), which in turn activates the autophagic pathway to promote HCV RNA replication in human hepatoma cells. Further analysis revealed that the entire autophagic process through to complete autolysosome maturation was required to promote HCV RNA replication and that it did so by suppressing innate antiviral immunity. Gene silencing or activation of the UPR-autophagy pathway activated or repressed, respectively, IFN-β activation mediated by an HCV-derived pathogen-associated molecular pattern (PAMP). Similar results were achieved with a PAMP derived from Dengue virus (DEV), indicating that HCV and DEV may both exploit the UPR-autophagy pathway to escape the innate immune response. Taken together, these results not only define the physiological significance of HCV-induced autophagy, but also shed light on the knowledge of host cellular responses upon HCV infection as well as on exploration of therapeutic targets for controlling HCV infection.
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Affiliation(s)
- Emilie Estrabaud
- Service d'Hépatologie and INSERM U773 CRB3, Beaujon Hospital, University Paris VII, France
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158
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Manipulation or capitulation: virus interactions with autophagy. Microbes Infect 2011; 14:126-39. [PMID: 22051604 PMCID: PMC3264745 DOI: 10.1016/j.micinf.2011.09.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 09/26/2011] [Accepted: 09/27/2011] [Indexed: 12/11/2022]
Abstract
Autophagy is a homeostatic process that functions to balance cellular metabolism and promote cell survival during stressful conditions by delivering cytoplasmic components for lysosomal degradation and subsequent recycling. During viral infection, autophagy can act as a surveillance mechanism that delivers viral antigens to the endosomal/lysosomal compartments that are enriched in immune sensors. Additionally, activated immune sensors can signal to activate autophagy. To evade this antiviral activity, many viruses elaborate functions to block the autophagy pathway at a variety of steps. Alternatively, some viruses actively subvert autophagy for their own benefit. Manipulated autophagy has been proposed to facilitate nearly every stage of the viral lifecycle in direct and indirect ways. In this review, we synthesize the extensive literature on virus–autophagy interactions, emphasizing the role of autophagy in antiviral immunity and the mechanisms by which viruses subvert autophagy for their own benefit.
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159
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Harris J. Autophagy and cytokines. Cytokine 2011; 56:140-4. [PMID: 21889357 DOI: 10.1016/j.cyto.2011.08.022] [Citation(s) in RCA: 287] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 07/28/2011] [Accepted: 08/07/2011] [Indexed: 12/21/2022]
Abstract
Autophagy is a highly conserved homoeostatic mechanism for the lysosomal degradation of cytosolic constituents, including long-lived macromolecules, organelles and intracellular pathogens. Autophagosomes are formed in response to a number of environmental stimuli, including amino acid deprivation, but also by both host- and pathogen-derived molecules, including toll-like receptor ligands and cytokines. In particular, IFN-γ, TNF-α, IL-1, IL-2, IL-6 and TGF-β have been shown to induce autophagy, while IL-4, IL-10 and IL-13 are inhibitory. Moreover, autophagy can itself regulate the production and secretion of cytokines, including IL-1, IL-18, TNF-α, and Type I IFN. This review discusses the potentially pivotal roles of autophagy in the regulation of inflammation and the coordination of innate and adaptive immune responses.
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Affiliation(s)
- James Harris
- Immunology Research Centre, School of Biochemistry & Immunology, Trinity College Dublin, College Green, Dublin 2, Ireland.
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160
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Dreux M, Chisari FV. Impact of the autophagy machinery on hepatitis C virus infection. Viruses 2011; 3:1342-57. [PMID: 21994783 PMCID: PMC3185811 DOI: 10.3390/v3081342] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 07/20/2011] [Accepted: 07/21/2011] [Indexed: 12/16/2022] Open
Abstract
Autophagy is a cellular process that catabolizes cytoplasmic components and maintains energy homeostasis. As a stress response, the autophagy machinery interconnects a wide range of cellular pathways, enhancing the spread of certain pathogens while limiting others, and has become a highly active research area over the past several years. Independent laboratories have recently reported that autophagy vesicles accumulate in hepatitis C virus (HCV) infected cells and that autophagy proteins can function as proviral factors required for HCV replication. In this review, we summarize what is currently known about the interplay between autophagy and HCV and the possible mechanisms whereby autophagy proteins might favor HCV propagation.
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Affiliation(s)
- Marlène Dreux
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, Lyon, F-69007, France
- INSERM, U758, Lyon, F-69007, France
- Authors to whom correspondence should be addressed; E-Mails: (M.D.), (F.V.C.); Tel.: +33-426-233834 (M.D.); +1-858-784-8228 (F.V.C.); Fax: +33-472-728137 (M.D.); +1-858-784-2160 (F.V.C.)
| | - Francis V. Chisari
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
- Authors to whom correspondence should be addressed; E-Mails: (M.D.), (F.V.C.); Tel.: +33-426-233834 (M.D.); +1-858-784-8228 (F.V.C.); Fax: +33-472-728137 (M.D.); +1-858-784-2160 (F.V.C.)
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161
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Hepatitis C virus infection is blocked by HMGB1 released from virus-infected cells. J Virol 2011; 85:9359-68. [PMID: 21752923 DOI: 10.1128/jvi.00682-11] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
High-mobility group box 1 (HMGB1), an abundant nuclear protein that triggers host immune responses, is an endogenous danger signal involved in the pathogenesis of various infectious agents. However, its role in hepatitis C virus (HCV) infection is not known. Here, we show that HMGB1 protein is translocated from the nucleus to cytoplasm and subsequently is released into the extracellular milieu by HCV infection. Secreted HMGB1 triggers antiviral responses and blocks HCV infection, a mechanism that may limit HCV propagation in HCV patients. Secreted HMGB1 also may have a role in liver cirrhosis, which is a common comorbidity in HCV patients. Further investigations into the roles of HMGB1 in the diseases caused by HCV infection will shed light on and potentially help prevent these serious and prevalent HCV-related diseases.
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162
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Zhou X, Zhou J, Li X, Guo C, Fang T, Chen Z. GSK-3β inhibitors suppressed neuroinflammation in rat cortex by activating autophagy in ischemic brain injury. Biochem Biophys Res Commun 2011; 411:271-5. [PMID: 21723251 DOI: 10.1016/j.bbrc.2011.06.117] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 06/17/2011] [Indexed: 10/18/2022]
Abstract
Previous studies have shown that GSK-3β inhibitor could reduce infarct volume after ischemia brain injury. However, the underlying mechanisms of GSK-3β inhibitor involving neuroprotection remain poorly understood. In the present study, we demonstrated that GSK-3β inhibitor suppressed insult-induced neuroinflammation in rat cortex by increasing autophagy activation in ischemic injury. Male rats were subjected to pMCAO (permanent middle cerebral artery occlusion) followed by treating with SB216763, a GSK-3β inhibitor. We found that insult-induced inflammatory response was significantly decreased by intraperitoneal infusion of SB216763 in rat cortex. A higher level of autophagy was also detected after SB216763 treatment. In the cultured primary microglia, SB216763 activated autophagy and suppressed inflammatory response. Importantly, inhibition of autophagy by Beclin1-siRNA increased inflammatory response in the SB216763-treated microglia. These data suggest that GSK-3β inhibitor suppressed neuroinflammation by activating autophagy after ischemic brain injury, thus offering a new target for prevention of ischemic brain injury.
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Affiliation(s)
- Xiaogang Zhou
- Department of Orthopaedics Surgery, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai 200032, China
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163
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Czaja MJ. Functions of autophagy in hepatic and pancreatic physiology and disease. Gastroenterology 2011; 140:1895-908. [PMID: 21530520 PMCID: PMC3690365 DOI: 10.1053/j.gastro.2011.04.038] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Accepted: 03/18/2011] [Indexed: 12/13/2022]
Abstract
Autophagy is a lysosomal pathway that degrades and recycles intracellular organelles and proteins to maintain energy homeostasis during times of nutrient deprivation and to remove damaged cell components. Recent studies have identified new functions for autophagy under basal and stressed conditions. In the liver and pancreas, autophagy performs the standard functions of degrading mitochondria and aggregated proteins and regulating cell death. In addition, autophagy functions in these organs to regulate lipid accumulation in hepatic steatosis, trypsinogen activation in pancreatitis, and hepatitis virus replication. This review discusses the effects of autophagy on hepatic and pancreatic physiology and the contribution of this degradative process to diseases of these organs. The discovery of novel functions for this lysosomal pathway has increased our understanding of the pathophysiology of diseases in the liver and pancreas and suggested new possibilities for their treatment.
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Affiliation(s)
- Mark J Czaja
- Department of Medicine and Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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164
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Raglow Z, Thoma-Perry C, Gilroy R, Wan YJY. The interaction between HCV and nuclear receptor-mediated pathways. Pharmacol Ther 2011; 132:30-8. [PMID: 21620888 DOI: 10.1016/j.pharmthera.2011.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 05/03/2011] [Indexed: 12/15/2022]
Abstract
Hepatitis C virus (HCV) is presently the leading indication for liver transplantation in Western countries. Treatment for HCV infection includes a combination of pegylated interferon and ribavirin, which produces highly variable response rates. This reflects the lack of information regarding the roles of host and viral components during viral pathogenesis. Vital processes regulated by the liver, including metabolism, lipid homeostasis, cellular proliferation, and the immune response, are known to be systematically dysregulated as a result of persistent HCV infection. Nuclear receptors and their ligands are recognized as indispensable regulators of liver homeostasis. Pathways mediated by the nuclear receptor superfamily have been shown to be profoundly disrupted during HCV infection, leading to an increased importance in elucidating the exact nature of this complex relationship. Expanded understanding of the role of nuclear receptors in HCV infection may therefore be an essential step in the search for a more universally effective treatment.
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Affiliation(s)
- Zoe Raglow
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
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