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Journal ArticleDOI

Endogenous Superoxide Dismutase Levels Regulate Iron-Dependent Hydroxyl Radical Formation in Escherichia coli Exposed to Hydrogen Peroxide

01 Feb 1998-Journal of Bacteriology (American Society for Microbiology)-Vol. 180, Iss: 3, pp 622-625

TL;DR: 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 is supported.

AbstractAerobic 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 alpha-(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.

Topics: Superoxide dismutase (58%), Reactive oxygen species (56%), Hydroxyl radical (55%), Catalase (52%), Escherichia coli (51%)

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Citations
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Journal ArticleDOI
TL;DR: A review of the regulation, generation and actions of these molecular mediators, as well as their roles in resisting infection, updates the reader on these concepts and the topical questions in the field.
Abstract: Phagocyte-derived reactive oxygen and nitrogen species are of crucial importance for host resistance to microbial pathogens. Decades of research have provided a detailed understanding of the regulation, generation and actions of these molecular mediators, as well as their roles in resisting infection. However, differences of opinion remain with regard to their host specificity, cell biology, sources and interactions with one another or with myeloperoxidase and granule proteases. More than a century after Metchnikoff first described phagocytosis, and more than four decades after the discovery of the burst of oxygen consumption that is associated with microbial killing, the seemingly elementary question of how phagocytes inhibit, kill and degrade microorganisms remains controversial. This review updates the reader on these concepts and the topical questions in the field.

1,341 citations


Cites background from "Endogenous Superoxide Dismutase Lev..."

  • ...DNA damage is dependent on the presence of iron, which indicates that hydroxyl or ferryl radicals are toxic intermediates that are produced by the FENTON REACTION...

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Journal ArticleDOI
TL;DR: The degradation of this compound is currently understood as an enzymatic process mediated by small molecules, therefore, this review will focus on the role of these mediators and radicals working in concert with enzymes.
Abstract: (Received 17 October 2000/Accepted 12 April 2001) The sources of ligninocellulose that occur in various forms in nature are so vast that they can only be compared to those of water. The results of several, more recent experiments showed that laccase probably possesses the big ability for "lignin-barrier" breakdown of ligninocellulose. The degradation of this compound is currently understood as an enzymatic process mediated by small molecules, therefore, this review will focus on the role of these mediators and radicals working in concert with enzymes. The fungi having a versatile machinery of enzymes are able to attack directly the "lignin- barrier" or can use a multienzyme system including "feed-back" type enzymes allowing for simulta- neous transformation of lignin and carbohydrate compounds.

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Journal ArticleDOI
TL;DR: A review is presented related to the biochemistry of lignocellulose transformation that focuses on the roles of small molecular compounds and radicals working in concert with enzymes in wood rotting basidiomycetous fungi.
Abstract: A review is presented related to the biochemistry of lignocellulose transformation The biodegradation of wood constituents is currently understood as a multienzymatic process with the mediation of small molecules; therefore, this review will focus on the roles of these small molecular compounds and radicals working in concert with enzymes Wood rotting basidiomycetous fungi penetrate wood and lead to more easily metabolized, carbohydrate constituents of the complex Having a versatile machinery of enzymes, the white rot fungi are able to attack directly the "lignin barrier" They also use a multienzyme system including so-called "feed back" type enzymes, allowing for simultaneous transformation of both lignin and cellulose These enzymes may function separately or cooperatively

447 citations


Journal ArticleDOI
TL;DR: It is found that regulators of the Escherichia coli responses to oxidative stress, OxyR and SoxRS, activate the expression of Fur, the global repressor of ferric ion uptake, which demonstrates that iron metabolism is coordinately regulated with the oxidative stress defenses.
Abstract: The cytotoxic effects of reactive oxygen species are largely mediated by iron. Hydrogen peroxide reacts with iron to form the extremely reactive and damaging hydroxyl radical via the Fenton reaction. Superoxide anion accelerates this reaction because the dismutation of superoxide leads to increased levels of hydrogen peroxide and because superoxide elevates the intracellular concentration of iron by attacking iron-sulfur proteins. We found that regulators of the Escherichia coli responses to oxidative stress, OxyR and SoxRS, activate the expression of Fur, the global repressor of ferric ion uptake. A transcript encoding Fur was induced by hydrogen peroxide in a wild-type strain but not in a DeltaoxyR strain, and DNase I footprinting assays showed that OxyR binds to the fur promoter. In cells treated with the superoxide-generating compound paraquat, we observed the induction of a longer transcript encompassing both fur and its immediate upstream gene fldA, which encodes a flavodoxin. This polycistronic mRNA is induced by paraquat in a wild-type strain but not in a DeltasoxRS strain, and SoxS was shown to bind to the fldA promoter. These results demonstrate that iron metabolism is coordinately regulated with the oxidative stress defenses.

383 citations


Cites background from "Endogenous Superoxide Dismutase Lev..."

  • ...In addition, recent work has demonstrated that superoxide toxicity is mainly due to its role in accelerating the Fenton reaction (20, 24)....

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Journal ArticleDOI
TL;DR: This review discusses similarities among HD, Friedreich ataxia and xeroderma pigmentosum, which provide insight into shared mechanisms of neuronal death, and focuses on Huntington's disease.
Abstract: In recent years, it has become increasingly clear that mitochondrial dysfunction and oxidative damage are major contributors to neuronal loss. Free radicals, typically generated from mitochondrial respiration, cause oxidative damage of nucleic acids, lipids, carbohydrates and proteins. Despite enormous amount of effort, however, the mechanism by which oxidative damage causes neuronal death is not well understood. Emerging data from a number of neurodegenerative diseases suggest that there may be common features of toxicity that are related to oxidative damage. In this review, while focusing on Huntington's disease (HD), we discuss similarities among HD, Friedreich ataxia and xeroderma pigmentosum, which provide insight into shared mechanisms of neuronal death.

380 citations


References
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Book
13 Jun 1985
TL;DR: 1. Oxygen is a toxic gas - an introduction to oxygen toxicity and reactive species, and the chemistry of free radicals and related 'reactive species'
Abstract: 1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?

21,077 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...rapidly reacts with itself (dismutes) to form H2O2 (7)....

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  • ...Although the aerobic metabolism of bacteria optimally results in the near simultaneous four-electron reduction of O2 to H2O, a variable percentage of O2 reduction occurs initially via either one-electron reduction of O2 to superoxide (O2 ) or divalent reduction to H2O2 (7)....

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Journal ArticleDOI
03 Jun 1988-Science
TL;DR: It is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.
Abstract: A major portion of the toxicity of hydrogen peroxide in Escherichia coli is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.

1,927 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...Pretreatment of the JI132 (SOD-deficient) bacteria with DFO greatly reduced the magnitude of OH generation, confirming that it arose as a consequence of Fenton chemistry, as iron bound to DFO is no longer available for this redox chemistry (10)....

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Journal ArticleDOI
TL;DR: Aerotolerant anaerobes, which survive exposure to air and metabolize oxygen to a limited extent but do not contain cytochrome systems, were found to be devoid of catalase activity but did exhibit superoxide dismutase activity.
Abstract: The distribution of catalase and superoxide dismutase has been examined in various micro-organisms. Strict anaerobes exhibited no superoxide dismutase and, generally, no catalase activity. All aerobic organisms containing cytochrome systems were found to contain both superoxide dismutase and catalase. Aerotolerant anaerobes, which survive exposure to air and metabolize oxygen to a limited extent but do not contain cytochrome systems, were found to be devoid of catalase activity but did exhibit superoxide dismutase activity. This distribution is consistent with the proposal that the prime physiological function of superoxide dismutase is protection of oxygen-metabolizing organisms against the potentially detrimental effects of the superoxide free radical, a biologically produced intermediate resulting from the univalent reduction of molecular oxygen.

949 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...Most bacteria, including Escherichia coli, contain superoxide dismutase (SOD) and catalase as means of eliminating O2 z2 and H2O2, respectively (16, 17)....

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Journal ArticleDOI
TL;DR: This presentation discusses the role of catalytic metals in free radical-mediated oxidations, ascorbate as both a pro-oxidant and an antioxidant, use of asCorbate to determine adventitious catalytic metal concentrations, and uses of ascorBate radical as a marker of oxidative stress.
Abstract: Trace levels of transition metals can participate in the metal-catalyzed Haber-Weiss reaction (superoxide-driven Fenton reaction) as well as catalyze the oxidation of ascorbate. Generally ascorbate is thought of as an excellent reducing agent; it is able to serve as a donor antioxidant in free radical-mediated oxidation processes. However, as a reducing agent it is also able to reduce redox-active metals such as copper and iron, thereby increasing the pro-oxidant chemistry of these metals. Thus ascorbate can serve as both a pro-oxidant and an antioxidant. In general, at low ascorbate concentrations, ascorbate is prone to be a pro-oxidant, and at high concentrations, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the "position" of this crossover effect is a function of the catalytic metal concentration. In this presentation, we discuss: (1) the role of catalytic metals in free radical-mediated oxidations; (2) ascorbate as both a pro-oxidant and an antioxidant; (3) catalytic metal catalysis of ascorbate oxidation; (4) use of ascorbate to determine adventitious catalytic metal concentrations; (5) use of ascorbate radical as a marker of oxidative stress; and (6) use of ascorbate and iron as free radical pro-oxidants in photodynamic therapy of cancer.

801 citations


Journal ArticleDOI
TL;DR: It is concluded that the total absence of SOD in E. coli creates a conditional sensitivity to oxygen.
Abstract: Mu transposons carrying the chloramphenicol resistance marker have been inserted into the cloned Escherichia coli genes sodA and sodB coding for manganese superoxide dismutase (MnSOD) and iron superoxide dismutase (FeSOD) respectively, creating mutations and gene fusions. The mutated sodA or sodB genes were introduced into the bacterial chromosome by allelic exchange. The resulting mutants were shown to lack the corresponding SOD by activity measurements and immunoblot analysis. Aerobically, in rich medium, the absence of FeSOD or MnSOD had no major effect on growth or sensitivity to the superoxide generator, paraquat. In minimal medium aerobic growth was not affected, but the sensitivity to paraquat was increased, especially in the sodA mutant. A sodA sodB double mutant completely devoid of SOD was also obtained. It was able to grow aerobically in rich medium, its catalase level was unaffected and it was highly sensitive to paraquat and hydrogen peroxide; the double mutant was unable to grow aerobically on minimal glucose medium. Growth could be restored by removing oxygen, by providing an SOD-overproducing plasmid or by supplementing the medium with the 20 amino acids. It is concluded that the total absence of SOD in E. coli creates a conditional sensitivity to oxygen.

749 citations


"Endogenous Superoxide Dismutase Lev..." refers background in this paper

  • ...One hypothesis to explain the increased sensitivity of mutants lacking SOD to H2O2-mediated killing is that the absence of SOD results in increased levels of O2 , required for the maintenance of iron in the ferrous form (reaction 1 above) (5, 9)....

    [...]

  • ...Previous studies have proposed that the DNA damage seen following low-dose H2O2 exposure (1 to 3 mM) is a consequence of Fenton chemistry (reaction 2 above) occurring on or near DNA, generating a highly reactive species such as OH, which is then the effector of DNA damage (5, 9)....

    [...]