title: Differential effects of proinflammatory cytokines on cell death and ER stress in insulin-secreting INS1E cells and the involvement of nitric oxide.
abstract: Proinflammatory cytokines produced by immune cells destroy pancreatic beta cells in type 1 diabetes. The aim of this study was to investigate the cytokine network and its effects in insulin-secreting cells. INS1E cells were exposed to different combinations of proinflammatory cytokines. Cytokine toxicity was estimated by MTT assay and caspase activation measurements. The NFκB-iNOS pathway was analyzed by a SEAP reporter gene assay, Western-blotting and nitrite measurements. Gene expression analyses of ER stress markers, Chop and Bip, were performed by real-time RT-PCR. Cytokines tested in this study, namely IL-1β, TNFα and IFNγ, had deleterious effects on beta cell viability. The most potent toxicity exhibited IL-1β and its combinations with other cytokines. The toxic effects of IL-1β towards cell viability, caspase activation and iNOS activity were dependent on nitric oxide and abolished by an iNOS blocker. IL-1β was the strongest inducer of the NFκB activation. An iNOS blocker inhibited IL-1β-mediated NFκB activation in the first, initial phase of cytokine action, but did not affect significantly NFκB activation after prolonged incubation. Interestingly iNOS protein expression was induced predominantly by IL-1β and decreased in the presence of an iNOS blocker in the case of a short time exposure. The changes in the expression of ER stress markers were also almost exclusively dependent on the IL-1β presence and counteracted by iNOS blockade. Thus cytokine-induced beta cell death is primarily IL-1β mediated with a NO-independent enhancement by TNFα and IFNγ. The deleterious effects on cell viability and function are crucially dependent on IL-1β-induced nitric oxide formation.
authors.affiliation: Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Str.1, 30625 Hannover, Germany.
authors.forename: Stella
authors.initials: S
authors.lastname: Kacheva
authors.forename: Sigurd
authors.initials: S
authors.lastname: Lenzen
authors.forename: Ewa
authors.initials: E
authors.lastname: Gurgul-Convey
mesh_terms: D000818:Animals; D053454:Caspase 12 / Q000378:metabolism; D016923:Cell Death / Q000502:physiology*; D002460:Cell Line; D016207:Cytokines / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004789:Enzyme Activation; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013312:Stress, Physiological
chemical_list: D016207:Cytokines; D053583:Interleukin-1beta; D016328:NF-kappa B; D009573:Nitrites; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D053454:Caspase 12