title: Oxidation of mitochondrial deoxynucleotide pools by exposure to sodium nitroprusside induces cell death.
abstract: Human MutT homolog (hMTH1) hydrolyzes oxidized purine nucleoside triphosphates to monophosphates, thereby avoiding incorporation of such oxidized purines into DNA or RNA. We examined whether hMTH1 prevents cellular dysfunction induced by sodium nitroprusside, a spontaneous NO donor. Exposure to sodium nitroprusside caused an 8-oxoguanine (8-oxoG) buildup in DNA of proliferating MTH1-null cells which underwent mitochondrial degeneration and subsequently died. Quiescent MTH1-null cells also died with 8-oxoG buildup but only when the buildup affected mitochondrial and not nuclear DNA. In both proliferative and quiescent conditions, the accumulation of 8-oxoG in DNA and cell death was effectively prevented by hMTH1. Knockdown of MUTYH in quiescent MTH1-null cells significantly prevented the cell death, suggesting that 8-oxoG incorporated into mitochondrial DNA is a main cause of this form of cell death. To verify this possibility, an artificially modified hMTH1, namely mTP-EGFP-hMTH1, which localizes exclusively in mitochondria, was expressed in MTH1-null cells. mTP-EGFP-hMTH1 selectively prevented buildup of 8-oxoG in mitochondrial but not nuclear DNA after exposure of proliferating cells to sodium nitroprusside, and also efficiently prevented cell death. We thus concluded that exposure of cells to sodium nitroprusside causes oxidation of mitochondrial deoxynucleotide pools, and that buildup of oxidized bases in mitochondrial DNA initiates cell death.
authors.affiliation: Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, 812-8582, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Ichikawa
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsuchimoto
authors.forename: Sugako
authors.initials: S
authors.lastname: Oka
authors.forename: Mizuki
authors.initials: M
authors.lastname: Ohno
authors.forename: Masato
authors.initials: M
authors.lastname: Furuichi
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Sakumi
authors.forename: Yusaku
authors.initials: Y
authors.lastname: Nakabeppu
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D016923:Cell Death / Q000187:drug effects*; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D045647:DNA Glycosylases / Q000037:antagonists & inhibitors; D045643:DNA Repair Enzymes / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism / Q000502:physiology
chemical_list: D020030:Nitric Oxide Donors; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D009599:Nitroprusside; D009569:Nitric Oxide; D000080242:8-Hydroxy-2'-Deoxyguanosine; D010744:Phosphoric Monoester Hydrolases; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; C078207:8-oxodGTPase; C509779:Nudt1 protein, mouse; D045643:DNA Repair Enzymes; D003849:Deoxyguanosine