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

J Gen Virol. 2011 Apr;92(Pt 4):807-18. doi: 10.1099/vir.0.028159-0. Epub 2010 Dec 9.

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.

MeSH terms

  • Cell Death*
  • Cells, Cultured
  • Dengue Virus / immunology
  • Dengue Virus / pathogenicity*
  • Epithelial Cells / immunology
  • Epithelial Cells / virology
  • Humans
  • Macrophages / immunology
  • Macrophages / virology
  • NF-kappa B / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Tumor Necrosis Factor-alpha / immunology*
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • NF-kappa B
  • Tumor Necrosis Factor-alpha
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase