title: Contribution of caspase-3 differs by p53 status in apoptosis induced by X-irradiation.
abstract: We investigated the effect of p53 status on involvement of caspase-3 activation in cell death induced by X-irradiation, using rat embryonic fibroblasts (REFs) transduced with a temperature-sensitive mutant (mt) p53 gene. Cells with wild-type (wt) p53 showed greater resistance to X-irradiation than cells with mt p53. In cells with wt p53, X-irradiation-induced apoptosis was not inhibited by the caspase-3 inhibitor acetyl-L-aspartyl-L-methionyl-L-glutaminyl-L-aspartyl-aldehyde (Ac-DMQD-CHO) and caspase-3 activity was not elevated following X-irradiation, although induction of p53 and p21 / WAF-1 protein was observed. In contrast, irradiated cells with mt p53 showed 89% inhibition of cell death with Ac-DMQD-CHO and 98% inhibition with the antioxidant N-acetyl-L-cysteine (NAC). In cells with mt p53, caspase-3 activity was increased approximately 5 times beyond baseline activity at 24 h after irradiation. This increase was almost completely inhibited by NAC. However, inhibition of caspase-3 by Ac-DMQD-CHO failed to decrease production of reactive oxygen species by cells with mt p53. Differential involvement of caspase-3 is a reason for differences in sensitivity to X-irradiation in cells with different p53 status. Caspase-3 activation appears to occur downstream from generation of reactive oxygen species occurring independently of wt p53 during X-irradiation-induced cell death.
authors.affiliation: Department of Clinical Laboratory Medicine, Cancer Research Institute, Sapporo Medical University School of Medicine, Sapporo, Chuo-ku, Sapporo 060-0061, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Tokino
authors.forename: N
authors.initials: N
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D016158:Genes, p53 / Q000235:genetics; D009154:Mutation; D009842:Oligopeptides / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects; D014161:Transduction, Genetic; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D000975:Antioxidants; D061945:Caspase Inhibitors; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; C110922:acetyl-aspartyl-methionyl-glutaminyl-aspartyl-aldehyde; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases