title: Regulation of tumor necrosis factor-alpha expression by CD40 ligation in BV-2 microglial cells.
abstract: Ligation of CD40 has been shown to induce/stimulate the expression of tumor necrosis factor-alpha (TNF-alpha) in microglial cells. This study delineates the mechanism by which CD40 ligation regulates the expression of TNF-alpha in BV-2 microglial cells. There was very little induction of TNF-alpha by ligation of CD40 alone by either cross-linking antibodies against CD40 or recombinant CD40 ligand (CD154). The absence of any increase in TNF-alpha production by CD40 ligation alone even in CD40-overexpressed BV-2 microglial cells suggest that signal transduced by the ligation of CD40 alone is not sufficient for strong induction of TNF-alpha. However, CD40 ligation markedly induced the production of TNF-alpha as well as the expression of TNF-alpha mRNA in interferon-gamma (IFN-gamma)-stimulated BV-2 glial cells. Ligation of CD40 in CD40-overexpressed cells markedly enhanced the expression of TNF-alpha in the presence of IFN-gamma. To understand the mechanism of CD40 ligation-mediated induction/stimulation of TNF-alpha, we investigated the role of nuclear factor-kappaB (NF-kappaB) and C/EBPbeta. IFN-gamma alone was able to induce the activation of NF-kappaB as well as C/EBPbeta. However, CD40 ligation alone in the presence or absence of CD40 overexpression induced the activation of only NF-kappaB and not that of C/EBPbeta, suggesting that the activation of NF-kappaB alone by CD40 ligation is not sufficient to induce the expression of TNF-alpha and that the activation of C/EBPbeta is also necessary for strong induction of TNF-alpha. Consistently, a dominant-negative mutant of p65 (Delta(p65)) and that of C/EBPbeta (DeltaC/EBPbeta) inhibited the expression of TNF-alpha in BV-2 microglial cells stimulated with the combination of IFN-gamma and CD40 ligand. Taken together, these studies suggest that activation of both NF-kappaB and C/EBPbeta is important for strong induction of TNF-alpha and that CD40 ligation regulates the expression of TNF-alpha by modulating the activation of only NF-kappaB but not that of C/EBPbeta.
authors.affiliation: Department of Oral Biology, University of Nebraska Medical Center, Lincoln, Nebraska 68583-0740, USA.
authors.forename: Malabendu
authors.initials: M
authors.lastname: Jana
authors.forename: Subhajit
authors.initials: S
authors.lastname: Dasgupta
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Liu
authors.forename: Kalipada
authors.initials: K
authors.lastname: Pahan
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology; D019013:CD40 Antigens / Q000378:metabolism*; D023201:CD40 Ligand / Q000378:metabolism*; D002460:Cell Line; D007371:Interferon-gamma / Q000494:pharmacology; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D000906:Antibodies; D022782:CCAAT-Enhancer-Binding Protein-beta; D019013:CD40 Antigens; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D023201:CD40 Ligand; D007371:Interferon-gamma