title: Tumour necrosis factor alpha (TNF-alpha) stimulation of cells with established dengue virus type 2 infection induces cell death that is accompanied by a reduced ability of TNF-alpha to activate nuclear factor kappaB and reduced sphingosine kinase-1 activity.
abstract: Tumor necrosis factor alpha (TNF-α) has an antiviral role in some infections but in dengue virus (DENV) infection it is linked to severe pathology. We have previously shown that TNF-α stimulation cannot activate nuclear factor κB (NF-κB) to the fullest extent in DENV-2-infected cells. Here, we investigate further responses of DENV-2-infected cells to TNF-α, focussing particularly on cell death and pro-survival signals. TNF-α stimulation of productively DENV-2-infected monocyte-derived macrophages or HEK-293 cells induced caspase-3-mediated cell death. While TNF-α induced comparable degradation of the inhibitor of NF-κB alpha (IκB-α) and NF-κB activation in mock-infected and DENV-2-infected cells early in infection, later in infection and coinciding with TNF-α-induced cell death, TNF-α-stimulated IκB-α degradation and NF-κB activation was reduced. This was associated with reduced levels of sphingosine kinase-1 (SphK1) activity in DENV-2-infected cells; SphK1 being a known mediator of TNF-α-stimulated survival signals. Transfection experiments demonstrated inhibition of TNF-α-stimulated NF-κB activation by expression of DENV-2 capsid (CA) but enhancement by DENV-2 NS5 protein. DENV-2 CA alone, however, did not induce TNF-α-stimulated cell death or inhibit SphK1 activity. Thus, productively DENV-2-infected cells have compromised TNF-α-stimulated survival pathways and show enhanced susceptibility to TNF-α-stimulated cell death, suggesting a role for TNF-α in the killing of healthy productively DENV-2-infected cells. Additionally, the altered ability of TNF-α to activate NF-κB as infection progresses is reflected by the opposing actions of DENV-2 CA and NS5 proteins on TNF-α-stimulated NF-κB activation and could have important consequences for NF-κB-driven release of inflammatory cytokines.
authors.affiliation: Microbiology and Infectious Diseases, SA Pathology, Adelaide 5000, South Australia.
authors.forename: Satiya
authors.initials: S
authors.lastname: Wati
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rawlinson
authors.forename: Ruby A
authors.initials: RA
authors.lastname: Ivanov
authors.forename: Loretta
authors.initials: L
authors.lastname: Dorstyn
authors.forename: Michael R
authors.initials: MR
authors.lastname: Beard
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Pitson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Burrell
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Carr
mesh_terms: D016923:Cell Death; D002478:Cells, Cultured; D003716:Dengue Virus / Q000276:immunology / Q000472:pathogenicity*; D004847:Epithelial Cells / Q000276:immunology / Q000821:virology; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000821:virology; D016328:NF-kappa B / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D016328:NF-kappa B; D017853:Phosphotransferases (Alcohol Group Acceptor); D014409:Tumor Necrosis Factor-alpha; D000099157:Sphingosine Kinase