title: Apoptosis in mitotic competent undifferentiated cells is induced by cellular redox imbalance independent of reactive oxygen species production.
abstract: Oxidants are known to induce cell apoptosis. Because oxidants also elicit redox imbalance, it is difficult to distinguish the direct effects of cellular redox from that of oxidants. This study tests the hypothesis that induction of redox imbalance independent of reactive oxygen species (ROS), can induce cell apoptosis in a mitotic competent, undifferentiated cell line, PC-12. Cells grown in standard DMEM containing 25 mM glucose were treated with diamide, a thiol oxidant, at a concentration that did not generate ROS. Diamide caused a rapid increase in oxidized glutathione (GSSG) and a loss of mitochondrial cytochrome c in 15-30 min, caspase-3 activation in 2 h, and apoptosis in 24 h. N-Acetyl cysteine attenuated GSSG elevation and diamide-induced apoptosis. Incubation of cells in 5 mM glucose or inhibition of the pentose phosphate pathway maintained GSSG elevation and accelerated cell apoptosis. Collectively, these results show that loss of redox balance is an upstream event that kinetically preceded mitochondrial apoptotic signaling. A sustained redox change was not critical or necessary for apoptotic progression, but its prolongation exacerbated apoptotic death. The potentiation of apoptosis by sustained redox imbalance was correlated with decreases in NADPH supply for GSSG reduction.
authors.affiliation: Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, USA.
authors.forename: Erin K
authors.initials: EK
authors.lastname: Pias
authors.forename: Tak Yee
authors.initials: TY
authors.lastname: Aw
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D003958:Diamide / Q000494:pharmacology; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D007700:Kinetics; D008938:Mitosis / Q000502:physiology*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D016716:PC12 Cells; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
chemical_list: D003574:Cytochrome c Group; D016166:Free Radical Scavengers; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D003958:Diamide; D003687:Dehydroepiandrosterone; D009249:NADP; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione; D005947:Glucose; D019803:Glutathione Disulfide; D000111:Acetylcysteine