Endogenous superoxide dismutase levels regulate iron-dependent hydroxyl radical formation in Escherichia coli exposed to hydrogen peroxide

Michael L. Mccormick, Garry R. Buettner, Bradley E. Britigan

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2- and H2O2. Previous work by others has shown that Escherichia coli mutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD- deficient E. coli cells are exposed to increased levels of hydroxyl radical (OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)-ethanol spin-trapping system, the 4-POBN-CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of OH spin trapped. Exogenous SOD failed to inhibit OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR- detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.

Original languageEnglish (US)
Pages (from-to)622-625
Number of pages4
JournalJournal of bacteriology
Volume180
Issue number3
StatePublished - Feb 1 1998
Externally publishedYes

Fingerprint

Hydroxyl Radical
Hydrogen Peroxide
Superoxide Dismutase
Iron
Escherichia coli
Electron Spin Resonance Spectroscopy
DNA Damage
Spin Trapping
Deferoxamine
Chelating Agents
Catalase
Oxides
Oxidation-Reduction
Reactive Oxygen Species
Spectrum Analysis
Ethanol
Antioxidants
Bacteria
Enzymes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

Cite this

Endogenous superoxide dismutase levels regulate iron-dependent hydroxyl radical formation in Escherichia coli exposed to hydrogen peroxide. / Mccormick, Michael L.; Buettner, Garry R.; Britigan, Bradley E.

In: Journal of bacteriology, Vol. 180, No. 3, 01.02.1998, p. 622-625.

Research output: Contribution to journalArticle

@article{2b56287a5c14495ea6774e39dbd94c6b,
title = "Endogenous superoxide dismutase levels regulate iron-dependent hydroxyl radical formation in Escherichia coli exposed to hydrogen peroxide",
abstract = "Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2- and H2O2. Previous work by others has shown that Escherichia coli mutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD- deficient E. coli cells are exposed to increased levels of hydroxyl radical (OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)-ethanol spin-trapping system, the 4-POBN-CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of OH spin trapped. Exogenous SOD failed to inhibit OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR- detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.",
author = "Mccormick, {Michael L.} and Buettner, {Garry R.} and Britigan, {Bradley E.}",
year = "1998",
month = "2",
day = "1",
language = "English (US)",
volume = "180",
pages = "622--625",
journal = "Journal of Bacteriology",
issn = "0021-9193",
publisher = "American Society for Microbiology",
number = "3",

}

TY - JOUR

T1 - Endogenous superoxide dismutase levels regulate iron-dependent hydroxyl radical formation in Escherichia coli exposed to hydrogen peroxide

AU - Mccormick, Michael L.

AU - Buettner, Garry R.

AU - Britigan, Bradley E.

PY - 1998/2/1

Y1 - 1998/2/1

N2 - Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2- and H2O2. Previous work by others has shown that Escherichia coli mutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD- deficient E. coli cells are exposed to increased levels of hydroxyl radical (OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)-ethanol spin-trapping system, the 4-POBN-CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of OH spin trapped. Exogenous SOD failed to inhibit OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR- detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.

AB - Aerobic organisms contain antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, to protect them from both direct and indirect effects of reactive oxygen species, such as O2- and H2O2. Previous work by others has shown that Escherichia coli mutants lacking SOD not only are more susceptible to DNA damage and killing by H2O2 but also contain larger pools of intracellular free iron. The present study investigated if SOD- deficient E. coli cells are exposed to increased levels of hydroxyl radical (OH) as a consequence of the reaction of H2O2 with this increased iron pool. When the parental E. coli strain AB1157 was exposed to H2O2 in the presence of an α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN)-ethanol spin-trapping system, the 4-POBN-CH(CH3)OH spin adduct was detectable by electron paramagnetic resonance (EPR) spectroscopy, indicating OH production. When the isogenic E. coli mutant JI132, lacking both Fe- and Mn-containing SODs, was exposed to H2O2 in a similar manner, the magnitude of OH spin trapped was significantly greater than with the control strain. Preincubation of the bacteria with the iron chelator deferoxamine markedly inhibited the magnitude of OH spin trapped. Exogenous SOD failed to inhibit OH formation, indicating the need for intracellular SOD. Redox-active iron, defined as EPR- detectable ascorbyl radical, was greater in the SOD-deficient strain than in the control strain. These studies (i) extend recent data from others demonstrating increased levels of iron in E. coli SOD mutants and (ii) support the hypothesis that a resulting increase in OH formation generated by Fenton chemistry is responsible for the observed enhancement of DNA damage and the increased susceptibility to H2O2-mediated killing seen in these mutants lacking SOD.

UR - http://www.scopus.com/inward/record.url?scp=0031935122&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031935122&partnerID=8YFLogxK

M3 - Article

C2 - 9457866

AN - SCOPUS:0031935122

VL - 180

SP - 622

EP - 625

JO - Journal of Bacteriology

JF - Journal of Bacteriology

SN - 0021-9193

IS - 3

ER -