title: Low oxygen tension enhances hepatitis C virus replication.
abstract: Low oxygen tension exerts a significant effect on the replication of several DNA and RNA viruses in cultured cells. In vitro propagation of hepatitis C virus (HCV) has thus far been studied under atmospheric oxygen levels despite the fact that the liver tissue microenvironment is hypoxic. In this study, we investigated the efficiency of HCV production in actively dividing or differentiating human hepatoma cells cultured under low or atmospheric oxygen tensions. By using both HCV replicons and infection-based assays, low oxygen was found to enhance HCV RNA replication whereas virus entry and RNA translation were not affected. Hypoxia signaling pathway-focused DNA microarray and real-time quantitative reverse transcription-PCR (qRT-PCR) analyses revealed an upregulation of genes related to hypoxic stress, glycolytic metabolism, cell growth, and proliferation when cells were kept under low (3% [vol/vol]) oxygen tension, likely reflecting cell adaptation to anaerobic conditions. Interestingly, hypoxia-mediated enhancement of HCV replication correlated directly with the increase in anaerobic glycolysis and creatine kinase B (CKB) activity that leads to elevated ATP production. Surprisingly, activation of hypoxia-inducible factor alpha (HIF-α) was not involved in the elevation of HCV replication. Instead, a number of oncogenes known to be associated with glycolysis were upregulated and evidence that these oncogenes contribute to hypoxia-mediated enhancement of HCV replication was obtained. Finally, in liver biopsy specimens of HCV-infected patients, the levels of hypoxia and anaerobic metabolism markers correlated with HCV RNA levels. These results provide new insights into the impact of oxygen tension on the intricate HCV-host cell interaction.
authors.affiliation: Molecular Virology, Hellenic Pasteur Institute (HPI), Athens, Greece. nikiv@pasteur.gr
authors.forename: N
authors.initials: N
authors.lastname: Vassilaki
authors.forename: K I
authors.initials: KI
authors.lastname: Kalliampakou
authors.forename: I
authors.initials: I
authors.lastname: Kotta-Loizou
authors.forename: C
authors.initials: C
authors.lastname: Befani
authors.forename: P
authors.initials: P
authors.lastname: Liakos
authors.forename: G
authors.initials: G
authors.lastname: Simos
authors.forename: A F
authors.initials: AF
authors.lastname: Mentis
authors.forename: A
authors.initials: A
authors.lastname: Kalliaropoulos
authors.forename: P P
authors.initials: PP
authors.lastname: Doumba
authors.forename: D
authors.initials: D
authors.lastname: Smirlis
authors.forename: P
authors.initials: P
authors.lastname: Foka
authors.forename: O
authors.initials: O
authors.lastname: Bauhofer
authors.forename: M
authors.initials: M
authors.lastname: Poenisch
authors.forename: M P
authors.initials: MP
authors.lastname: Windisch
authors.forename: M E
authors.initials: ME
authors.lastname: Lee
authors.forename: J
authors.initials: J
authors.lastname: Koskinas
authors.forename: R
authors.initials: R
authors.lastname: Bartenschlager
authors.forename: P
authors.initials: P
authors.lastname: Mavromara
mesh_terms: D015687:Cell Hypoxia; D002460:Cell Line; D049109:Cell Proliferation; D003402:Creatine Kinase / Q000378:metabolism*; D016679:Genome, Viral; D006019:Glycolysis; D016174:Hepacivirus / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics; D016547:Kinesins / Q000235:genetics; D007770:L-Lactate Dehydrogenase / Q000235:genetics; D000080864:Lactate Dehydrogenase 5; D008099:Liver / Q000821:virology; D008113:Liver Neoplasms / Q000821:virology; D010100:Oxygen; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering; D012367:RNA, Viral; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics; D053586:Virus Internalization; D014779:Virus Replication
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007527:Isoenzymes; C509805:KIF2A protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012367:RNA, Viral; D042461:Vascular Endothelial Growth Factor A; D007770:L-Lactate Dehydrogenase; D000080864:Lactate Dehydrogenase 5; D003402:Creatine Kinase; D016547:Kinesins; D010100:Oxygen