title: cFLIP protein prevents tumor necrosis factor-alpha-mediated induction of caspase-8-dependent apoptosis in insulin-secreting betaTc-Tet cells.
abstract: Type 1 diabetes is characterized by the infiltration of activated leukocytes within the pancreatic islets, leading to beta-cell dysfunction and destruction. The exact role played by interferon-gamma, tumor necrosis factor (TNF)-alpha, and interleukin-1beta in this pathogenic process is still only partially understood. To study cytokine action at the cellular level, we are working with the highly differentiated insulin-secreting cell line, betaTc-Tet. We previously reported that it was susceptible to apoptosis induced by TNF-alpha, in combination with interleukin-1beta and interferon-gamma. Here, we report that cytokine-induced apoptosis was correlated with the activation of caspase-8. We show that in betaTc-Tet cells, overexpression of cFLIP, the cellular FLICE (FADD-like IL-1beta-converting enzyme)-inhibitory protein, completely abolished cytokine-dependent activation of caspase-8 and protected the cells against apoptosis. Furthermore, cFLIP overexpression increased the basal and interleukin-1beta-mediated transcriptional activity of nuclear factor (NF)-kappaB, whereas it did not change cytokine-induced inducible nitric oxide synthase gene transcription and nitric oxide secretion. The presence of cFLIP prevented the weak TNF-alpha-induced reduction in cellular insulin content and secretion; however, it did not prevent the decrease in glucose-stimulated insulin secretion induced by the combined cytokines, in agreement with our previous data demonstrating that interferon-gamma alone could induce these beta-cell dysfunctions. Together, our data demonstrate that overexpression of cFLIP protects mouse beta-cells against TNF-alpha-induced caspase-8 activation and apoptosis and is correlated with enhanced NF-kappaB transcriptional activity, suggesting that cFLIP may have an impact on the outcome of death receptor-triggered responses by directing the intracellular signals from beta-cell death to beta-cell survival.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Cottet
authors.forename: Philippe
authors.initials: P
authors.lastname: Dupraz
authors.forename: Fabienne
authors.initials: F
authors.lastname: Hamburger
authors.forename: Wanda
authors.initials: W
authors.lastname: Dolci
authors.forename: Muriel
authors.initials: M
authors.lastname: Jaquet
authors.forename: Bernard
authors.initials: B
authors.lastname: Thorens
mesh_terms: D000818:Animals; D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D011994:Recombinant Proteins; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D007328:Insulin; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D005947:Glucose