Enzymic- and thiol-mediated activation of halogen-substituted diaziridinylbenzoquinones: Redox transitions of the semiquinone and semiquinone-thioether species

José Goin, Cecilia R Giulivi, John Butler, Enrique Cadenas

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9 Citations (Scopus)

Abstract

Activation of 2,5-diaziridinyl-1,4-benzoquinones bearing halogen (Cl, Br, or F) substituents at C3 and C6 by NADPH-cytochrome P450 reductase and glutathione nucleophilic substitution was examined in terms of free radical production and DNA strand scission. A semiquinone species was observed by direct ESR in aerobic conditions during: (a) NADPH-cytochrome P450 reductase-catalyzed reduction of the above quinones. (b) The interaction of these quinones with GSH entailing primarily reactivity of halogen substituents toward sulfur substitution. (c) NADPH-cytochrome P450 reductase-catalyzed activation of products resulting from the quinone/GSH interaction. The semiquinone ESR signal observed during enzymic catalysis was suppressed by superoxide dismutase and was not affected by catalase. ESR studies in conjunction with the spin trapping technique on the autoxidation of the semiquinones formed by the above reaction pathways indicated the formation of superoxide radicals. In addition, thiyl radicals were formed during the reactions following glutathione nucleophilic substitution of the above quinones. The ESR signals of both superoxide and thiyl radicals were abolished by superoxide dismutase. No hydroxyl radicals were formed in solution during the redox transitions of these halogen-containing diaziridinylbenzoquinones. Bioreductive activation of these compounds via NADPH-cytochrome P450 reductase or sulfur nucleophilic substitution was associated with the formation of DNA strand breaks. This process was substantially inhibited (74-86%) by superoxide dismutase and to a lesser extent (23-31%) by catalase. It is suggested that DNA strand breakage proceeds in a manner entailing a semiquinone-dependent reduction of metal-ligands bound at the DNA surface and leading to site-specific, hydroxyl radical production.

Original languageEnglish (US)
Pages (from-to)525-536
Number of pages12
JournalFree Radical Biology and Medicine
Volume18
Issue number3
DOIs
StatePublished - 1995
Externally publishedYes

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NADPH-Ferrihemoprotein Reductase
Halogens
Sulfides
Sulfhydryl Compounds
Quinones
Oxidation-Reduction
Paramagnetic resonance
Substitution reactions
Chemical activation
Superoxide Dismutase
DNA
Sulfur
Superoxides
Hydroxyl Radical
Catalase
Glutathione
Bearings (structural)
Benzoquinones
Spin Trapping
DNA Breaks

Keywords

  • Aziridinylbenzoquinones
  • AZQ
  • DNA strand breaks
  • ESR
  • Free radicals
  • NADPH-cytochrome P reductase

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)
  • Clinical Biochemistry
  • Medicine(all)
  • Toxicology

Cite this

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title = "Enzymic- and thiol-mediated activation of halogen-substituted diaziridinylbenzoquinones: Redox transitions of the semiquinone and semiquinone-thioether species",
abstract = "Activation of 2,5-diaziridinyl-1,4-benzoquinones bearing halogen (Cl, Br, or F) substituents at C3 and C6 by NADPH-cytochrome P450 reductase and glutathione nucleophilic substitution was examined in terms of free radical production and DNA strand scission. A semiquinone species was observed by direct ESR in aerobic conditions during: (a) NADPH-cytochrome P450 reductase-catalyzed reduction of the above quinones. (b) The interaction of these quinones with GSH entailing primarily reactivity of halogen substituents toward sulfur substitution. (c) NADPH-cytochrome P450 reductase-catalyzed activation of products resulting from the quinone/GSH interaction. The semiquinone ESR signal observed during enzymic catalysis was suppressed by superoxide dismutase and was not affected by catalase. ESR studies in conjunction with the spin trapping technique on the autoxidation of the semiquinones formed by the above reaction pathways indicated the formation of superoxide radicals. In addition, thiyl radicals were formed during the reactions following glutathione nucleophilic substitution of the above quinones. The ESR signals of both superoxide and thiyl radicals were abolished by superoxide dismutase. No hydroxyl radicals were formed in solution during the redox transitions of these halogen-containing diaziridinylbenzoquinones. Bioreductive activation of these compounds via NADPH-cytochrome P450 reductase or sulfur nucleophilic substitution was associated with the formation of DNA strand breaks. This process was substantially inhibited (74-86{\%}) by superoxide dismutase and to a lesser extent (23-31{\%}) by catalase. It is suggested that DNA strand breakage proceeds in a manner entailing a semiquinone-dependent reduction of metal-ligands bound at the DNA surface and leading to site-specific, hydroxyl radical production.",
keywords = "Aziridinylbenzoquinones, AZQ, DNA strand breaks, ESR, Free radicals, NADPH-cytochrome P reductase",
author = "Jos{\'e} Goin and Giulivi, {Cecilia R} and John Butler and Enrique Cadenas",
year = "1995",
doi = "10.1016/0891-5849(94)00175-J",
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volume = "18",
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T1 - Enzymic- and thiol-mediated activation of halogen-substituted diaziridinylbenzoquinones

T2 - Redox transitions of the semiquinone and semiquinone-thioether species

AU - Goin, José

AU - Giulivi, Cecilia R

AU - Butler, John

AU - Cadenas, Enrique

PY - 1995

Y1 - 1995

N2 - Activation of 2,5-diaziridinyl-1,4-benzoquinones bearing halogen (Cl, Br, or F) substituents at C3 and C6 by NADPH-cytochrome P450 reductase and glutathione nucleophilic substitution was examined in terms of free radical production and DNA strand scission. A semiquinone species was observed by direct ESR in aerobic conditions during: (a) NADPH-cytochrome P450 reductase-catalyzed reduction of the above quinones. (b) The interaction of these quinones with GSH entailing primarily reactivity of halogen substituents toward sulfur substitution. (c) NADPH-cytochrome P450 reductase-catalyzed activation of products resulting from the quinone/GSH interaction. The semiquinone ESR signal observed during enzymic catalysis was suppressed by superoxide dismutase and was not affected by catalase. ESR studies in conjunction with the spin trapping technique on the autoxidation of the semiquinones formed by the above reaction pathways indicated the formation of superoxide radicals. In addition, thiyl radicals were formed during the reactions following glutathione nucleophilic substitution of the above quinones. The ESR signals of both superoxide and thiyl radicals were abolished by superoxide dismutase. No hydroxyl radicals were formed in solution during the redox transitions of these halogen-containing diaziridinylbenzoquinones. Bioreductive activation of these compounds via NADPH-cytochrome P450 reductase or sulfur nucleophilic substitution was associated with the formation of DNA strand breaks. This process was substantially inhibited (74-86%) by superoxide dismutase and to a lesser extent (23-31%) by catalase. It is suggested that DNA strand breakage proceeds in a manner entailing a semiquinone-dependent reduction of metal-ligands bound at the DNA surface and leading to site-specific, hydroxyl radical production.

AB - Activation of 2,5-diaziridinyl-1,4-benzoquinones bearing halogen (Cl, Br, or F) substituents at C3 and C6 by NADPH-cytochrome P450 reductase and glutathione nucleophilic substitution was examined in terms of free radical production and DNA strand scission. A semiquinone species was observed by direct ESR in aerobic conditions during: (a) NADPH-cytochrome P450 reductase-catalyzed reduction of the above quinones. (b) The interaction of these quinones with GSH entailing primarily reactivity of halogen substituents toward sulfur substitution. (c) NADPH-cytochrome P450 reductase-catalyzed activation of products resulting from the quinone/GSH interaction. The semiquinone ESR signal observed during enzymic catalysis was suppressed by superoxide dismutase and was not affected by catalase. ESR studies in conjunction with the spin trapping technique on the autoxidation of the semiquinones formed by the above reaction pathways indicated the formation of superoxide radicals. In addition, thiyl radicals were formed during the reactions following glutathione nucleophilic substitution of the above quinones. The ESR signals of both superoxide and thiyl radicals were abolished by superoxide dismutase. No hydroxyl radicals were formed in solution during the redox transitions of these halogen-containing diaziridinylbenzoquinones. Bioreductive activation of these compounds via NADPH-cytochrome P450 reductase or sulfur nucleophilic substitution was associated with the formation of DNA strand breaks. This process was substantially inhibited (74-86%) by superoxide dismutase and to a lesser extent (23-31%) by catalase. It is suggested that DNA strand breakage proceeds in a manner entailing a semiquinone-dependent reduction of metal-ligands bound at the DNA surface and leading to site-specific, hydroxyl radical production.

KW - Aziridinylbenzoquinones

KW - AZQ

KW - DNA strand breaks

KW - ESR

KW - Free radicals

KW - NADPH-cytochrome P reductase

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U2 - 10.1016/0891-5849(94)00175-J

DO - 10.1016/0891-5849(94)00175-J

M3 - Article

C2 - 9101243

AN - SCOPUS:0028966862

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