title: Overexpression of manganese superoxide dismutase protects against mitochondrial-initiated poly(ADP-ribose) polymerase-mediated cell death.
abstract: Mitochondria have recently been shown to serve a central role in programmed cell death. In addition, reactive oxygen species (ROS) have been implicated in cell death pathways upon treatment with a variety of agents; however, the specific cellular source of the ROS generation is unknown. We hypothesize that mitochondria-derived free radicals play a critical role in apoptotic cell death. To directly test this hypothesis, we treated murine fibrosarcoma cell lines, which expressed a range of mitochondrial manganese superoxide dismutase (MnSOD) activities, with respiratory chain inhibitors. Apoptosis was confirmed by DNA fragmentation analysis and electron microscopy. MnSOD overexpression specifically protected against cell death upon treatment with rotenone or antimycin. We examined bcl-x(L), p53 and poly(ADP-ribose) polymerase (PARP) to identify specific cellular pathways that might contribute to the mitochondrial-initiated ROS-mediated cell death. Cells overexpressing MnSOD contained less bcl-x(L) within the mitochondria compared to control (NEO) cells, therefore excluding the role of bcl-x(L). p53 was undetectable by Western analysis and examination of the proapoptotic protein bax, a p53 target gene, did not increase with treatment. Activation of caspase-3 (CPP-32) occurred in the NEO cells independent of cytochrome c release from the mitochondria. PARP, a target protein of CPP-32 activity, was cleaved to a 64 kDa fragment in the NEO cells prior to generation of nucleosomal fragments. Taken together, these findings suggest that mitochondrial-mediated ROS generation is a key event by which inhibition of respiration causes cell death, and identifies CPP-32 and the PARP-linked pathway as targets of mitochondrial-derived ROS-induced cell death.
authors.affiliation: Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Kiningham
authors.forename: T D
authors.initials: TD
authors.lastname: Oberley
authors.forename: S
authors.initials: S
authors.lastname: Lin
authors.forename: C A
authors.initials: CA
authors.lastname: Mattingly
authors.forename: D K
authors.initials: DK
authors.lastname: St Clair
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D005354:Fibrosarcoma; D005434:Flow Cytometry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000502:physiology*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; D003574:Cytochrome c Group; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C032456:antimycin; D000968:Antimycin A; D013482:Superoxide Dismutase; D011065:Poly(ADP-ribose) Polymerases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases