title: High accumulation of oxidative DNA damage, 8-hydroxyguanine, in Mmh/Ogg1 deficient mice by chronic oxidative stress.
abstract: 8-Hydroxyguanine (8-OH-G) is a major pre-mutagenic lesion generated from reactive oxygen species. The Mmh/Ogg1 gene product plays a major role in maintaining genetic integrity by removing 8-OH-G by way of the base excision repair pathway. To investigate how oxidative stress influences the formation of 8-OH-G in Ogg1 mutant mice, a known oxidative agent, potassium bromate (KBrO(3)), was administered at a dose of 2 g/l in the drinking water to Ogg1(+/+), Ogg1(+/-) and Ogg1(-/-) mice for 12 weeks. Apurinic (AP) site lyase activity, measured by the excision of 8-OH-G from synthetic oligonucleotides, remained unchanged in kidney cell extracts isolated from Ogg1 mutant mice when the mice were pre-treated by KBrO(3). The levels of 8-OH-G in kidney DNA tremendously increased in a time-dependent manner following exposure of Ogg1(-/-) mice to KBrO(3). Of particular note, the amount of 8-OH-G in kidney DNA from Ogg1(-/-) mice treated with KBrO(3) was approximately 70 times that of KBrO(3)-treated Ogg1(+/+) mice. The accumulated 8-OH-G did not decrease 4 weeks after discontinuing treatment with KBrO(3). KBrO(3) treatment for 12 weeks gave rise to increased mutation frequencies at the transgenic gpt gene in Ogg1(+/+) mice kidney. Absence of the Ogg1 gene further enhanced the mutation frequency. Sequence data obtained from gpt mutants showed that the accumulated 8-OH-G caused mainly GC-->TA transversion and deletion. Other mutations including GC-->AT transition also showed a tendency to increase. These results indicate that 8-OH-G, produced by chronic exposure to exogenous oxidative stress agents, is not repaired to any significant extent within the overall genome of Ogg1(-/-) mice kidney.
authors.affiliation: Banyu Tsukuba Research Institute in Collaboration with Merck Research Laboratories, 3 Okubo, Ibaraki 300-2611, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Arai
authors.forename: Vincent P
authors.initials: VP
authors.lastname: Kelly
authors.forename: Osamu
authors.initials: O
authors.lastname: Minowa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Noda
authors.forename: Susumu
authors.initials: S
authors.lastname: Nishimura
mesh_terms: D000818:Animals; D001959:Bromates / Q000494:pharmacology; D019757:Carbon-Oxygen Lyases / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004252:DNA Mutational Analysis; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D005838:Genotype; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics*; D009841:Oligonucleotides / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D013997:Time Factors
chemical_list: D001959:Bromates; D009841:Oligonucleotides; D016877:Oxidants; C019536:potassium bromate; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase