Cytokines induce both necrosis and apoptosis via a common Bcl-2-inhibitable pathway in rat insulin-producing cells.
The presence of activated macrophages within pancreatic islets in insulin-dependent diabetes mellitus suggests an involvement of beta-cell death by necrosis. The aim of this study was to investigate the frequencies and mechanisms of cytokine-induced beta-cell apoptosis and necrosis and the possible protection mediated by the antiapoptotic gene bcl-2. A combination of interleukin-1beta, interferon-gamma, and tumor necrosis factor-alpha increased both necrosis (17% of cells) and apoptosis (5% of cells) in isolated whole rat islets, as determined by vital staining and fluorescence microscopy. Hyperexpression of Bcl-2, achieved by stable transfection using a multicopy viral vector containing a bcl-2 complementary DNA in rat insulin-producing RINm5F cells, counteracted both apoptosis and necrosis. Cytokine-induced cleavage of the caspase-3 substrate poly(ADP-ribose) polymerase (which, in other cell types, may occur downstream or independently of a Bcl-2-preventable mitochondrial permeability transition) was observed in control- but neither in bcl-2-transfected cells nor in the presence of the iNOS inhibitor N(G)-methyl-L-arginine. Tumor necrosis factor-alpha alone did not clearly induce cell death or poly(ADP-ribose) polymerase-cleavage. These findings suggest that cytokines induce both necrosis and apoptosis in insulin-producing cells via a common Bcl-2-preventable nitric oxide-dependent pathway, which may involve mitochondrial permeability transition. The necrosis:apoptosis ratio might be increased by a relative lack of caspase activity.
Saldeen
J
J
Department of Medical Cell Biology, Uppsala University, Sweden. johan.saldeen@medcellbiol.uu.se
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D015870:Gene Expression; D007328:Insulin / Q000096:biosynthesis*; D007371:Interferon-gamma / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D007515:Islets of Langerhans / Q000378:metabolism / Q000473:pathology*; D008297:Male; D009336:Necrosis; D009569:Nitric Oxide / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D016207:Cytokines; D007328:Insulin; D007376:Interleukin-2; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D011065:Poly(ADP-ribose) Polymerases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases