NF-kappaB activation is responsible for the synergistic effect of herpes simplex virus type 2 infection on interferon-gamma-induced nitric oxide production in macrophages.
Nitric oxide (NO), produced in interferon (IFN)-gamma-activated murine macrophages by the enzyme inducible nitric oxide synthase (iNOS), has been found to have antiviral properties. We have previously shown that herpes simplex virus type 2 (HSV-2) infection of macrophages synergistically enhances IFN-gamma-induced NO production, and we now extend these findings by providing evidence that virus-induced tumour necrosis factor (TNF)-alpha mediates activation of the transcription factor nuclear factor (NF)-kappaB, which in turn is responsible for the synergistic effect. HSV-2 infection and IFN-gamma stimulation of macrophages synergistically induced TNF-alpha secretion and nuclear translocation of NF-kappaB, which bound to a sequence corresponding to a kappaB site in the iNOS promoter. The effect of HSV-2 on NF-kappaB and NO production was eliminated when cells were treated with antibodies to TNF-alpha, and direct inhibition of NF-kappaB activation with pyrrolidinedithiocarbamate (PDTC) also blocked the effect of HSV-2 infection on NO production. The effect of the NF-kappaB activation inhibitor was not mediated through inhibition of the production of interferon regulatory factor (IRF)-1 or of TNF-alpha itself, and a possible alternative mechanism of activation of NF-kappaB through virus-induced activation of the kinase PKR was also ruled out. Thus, our data indicate that NF-kappaB activation, through virus-induced autocrine TNF-alpha secretion, is responsible for the synergistic effect of HSV-2 infection on IFN-gamma-induced NO production, and that such activation might constitute a mechanism by which high-output NO production is targeted to infectious foci.
Paludan
S R
SR
Department of Medical Microbiology and Immunology, University of Aarhus, Aarhus C, Denmark.
Ellermann-Eriksen
S
S
Mogensen
S C
SC
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004357:Drug Synergism; D004790:Enzyme Induction; D006558:Herpes Genitalis / Q000378:metabolism* / Q000821:virology*; D018258:Herpesvirus 2, Human / Q000502:physiology*; D007371:Interferon-gamma / Q000096:biosynthesis*; D008264:Macrophages / Q000378:metabolism* / Q000821:virology*; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D014779:Virus Replication
D016328:NF-kappa B; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase