title: A hepatitis C virus-encoded, nonstructural protein (NS3) triggers dysfunction and apoptosis in lymphocytes: role of NADPH oxidase-derived oxygen radicals.
abstract: The persistent infection caused by hepatitis C virus (HCV) is presumably explained by a deficient immune response to the infection, but the basis for the inefficiency of immune-mediated virus eradication is not known in detail. This study addresses mechanisms of relevance to dysfunction of cytotoxic lymphocytes in HCV infection, with a focus on the role of phagocyte-derived oxygen radicals. We show that NS3, a nonstructural, HCV-encoded protein, induces a prolonged release of oxygen radicals from mononuclear and polymorphnuclear phagocytes by activating a key enzyme in radical formation, the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The NS3-activated phagocytes, in turn, induced dysfunction and/or apoptosis in three major subsets of lymphocytes of relevance to defense against HCV infection: CD3+/56- T cells, CD3-/56+ natural killer (NK) cells, and CD3+/56+ NKT cells. Two inhibitors of the NADPH oxidase, histamine and diphenylene iodonium, suppressed the NS3-induced oxygen radical production and efficiently protected lymphocytes against NS3-induced apoptosis and dysfunction. In conclusion, we propose that NS3, by triggering oxygen radical formation in phagocytes, may contribute to the dysfunction of antiviral lymphocytes in HCV-infected liver tissue and that strategies to circumvent oxidative stress may be useful in preventing HCV-associated carcinogenesis and facilitating lymphocyte-mediated clearance of infected cells.
authors.affiliation: Department of Clinical Virology, Göteborg University, Guldhedsgatan 10b, S-413 46 Göteborg, Sweden. fredrik.thoren@microbio.gu.se
authors.forename: Fredrik
authors.initials: F
authors.lastname: Thorén
authors.forename: Ana
authors.initials: A
authors.lastname: Romero
authors.forename: Magnus
authors.initials: M
authors.lastname: Lindh
authors.forename: Claes
authors.initials: C
authors.lastname: Dahlgren
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Hellstrand
mesh_terms: D017209:Apoptosis / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology; D002469:Cell Separation; D003601:Cytotoxicity Tests, Immunologic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016174:Hepacivirus / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018384:Oxidative Stress / Q000276:immunology; D010586:Phagocytes / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000494:pharmacology*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D004791:Enzyme Inhibitors; D019255:NADPH Oxidases; D017382:Reactive Oxygen Species; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases