title: Tumour necrosis factor-alpha enhances cAMP-induced programmed cell death in mouse thymocytes.
abstract: During T-lymphocyte differentiation in the thymus, the majority of thymocytes die by apoptosis in situ. This process is characterized by internucleosomal DNA fragmentation and is induced by a number of stimuli including glucocorticoids, calcium ionophore, cAMP and 12-o-tetradecanoylphorbol 13-acetate (TPA). In this study, the effect of cytokines tumour necrosis factor-alpha (TNF-alpha) and interferon gamma (IFN-gamma) on the programmed cell death of thymocytes was examined by measuring DNA fragmentation and LDH release. TNF-alpha and IFN-gamma had no effect on DNA fragmentation in control and TPA, or A23187-treated thymocytes. Both human and murine rTNF-alpha enhanced cAMP-induced programmed cell death dose-dependently, but IFN-gamma had no effect on the process. TNF-alpha did not stimulate cAMP accumulation in control or 2-chloroadenosine-treated thymocytes. TPA markedly stimulated cAMP-induced DNA fragmentation as a result of 6 h incubation, whereas TNF-alpha did not. Thus TNF-alpha did not appear to activate protein kinase C directly. The effect of TNF-alpha was observed in the cell preparations from which adherent cells had been removed, suggesting that cytokines secreted by adherent cells in response to TNF-alpha are not involved in the process. The enhancement of cAMP-induced DNA fragmentation was observed in CD4+CD(8+)-double positive cells, but not in CD4+CD(8-)-single positive cells. The results of the present study indicate that a physiological cytokine, TNF-alpha, may modulate programmed cell death in immature thymocytes in concert with cAMP.
authors.affiliation: Department of Biochemistry, Tokyo Dental College, Chiba, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kizaki
authors.forename: S
authors.initials: S
authors.lastname: Nakada
authors.forename: Y
authors.initials: Y
authors.lastname: Ohnishi
authors.forename: Y
authors.initials: Y
authors.lastname: Azuma
authors.forename: Y
authors.initials: Y
authors.lastname: Mizuno
authors.forename: T
authors.initials: T
authors.lastname: Tadakuma
mesh_terms: D015762:2-Chloroadenosine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D000001:Calcimycin / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects; D015232:Dinoprostone / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009707:Nucleosomes / Q000187:drug effects; D011994:Recombinant Proteins / Q000494:pharmacology; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D009707:Nucleosomes; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D015762:2-Chloroadenosine; D000001:Calcimycin; D007371:Interferon-gamma; D000242:Cyclic AMP; D007770:L-Lactate Dehydrogenase; D015232:Dinoprostone; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate