title: Hydrogen peroxide induces protection against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) effects in Escherichia coli.
abstract: Cross-adaptive response is defined as the capacity of cells to become resistant to a lethal agent when pretreated with a different lethal substance. In the present paper, the cross-adaptive response between hydrogen peroxide and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in Escherichia coli repair mutants. Our results suggest that high doses of H2O2 induces protection against the lethal effects of MNNG in wild-type strain, ada, ogt, ada-ogt, aidB and alkA mutants. On the other hand, the MNNG induced mutagenesis is reduced by H2O2 pretreatment in wild-type and ogt mutant strains, but not in ada mutant. Furthermore, the protecting effect induced by H2O2 is time dependent: it decreases 15 min after the pretreatment and, after 30 min, is almost abolished. This reduction in the protecting effect is followed by an augmentation in the mutation frequency when MNNG is added 30 min after H2O2 pretreatment. This cross-adaptive response may be due to a modification of the MNNG alkylation pattern in the oxidized DNA.
authors.affiliation: Laboratório de Radiobiologia Molecular, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Asad
authors.forename: N R
authors.initials: NR
authors.lastname: Asad
authors.forename: A B
authors.initials: AB
authors.lastname: Silva
authors.forename: I
authors.initials: I
authors.lastname: Felzenszwalb
authors.forename: A C
authors.initials: AC
authors.lastname: Leitão
mesh_terms: D016587:Antimutagenic Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D008780:Methyltransferases; D009153:Mutagens / Q000633:toxicity*; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics; D019853:O(6)-Methylguanine-DNA Methyltransferase; D016877:Oxidants / Q000494:pharmacology*; D013997:Time Factors; D014157:Transcription Factors
chemical_list: C090096:AidB protein, E coli; D016587:Antimutagenic Agents; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D009153:Mutagens; D016877:Oxidants; D014157:Transcription Factors; D008769:Methylnitronitrosoguanidine; D006861:Hydrogen Peroxide; C023091:rubredoxin-NAD+ reductase; D009247:NADH, NADPH Oxidoreductases; D008780:Methyltransferases; C045675:Ada protein, E coli; D019853:O(6)-Methylguanine-DNA Methyltransferase; C067511:Ogt protein, E coli