Uncoupling-mediated generation of reactive oxygen by halogenated aromatic hydrocarbons in mouse liver microsomes

Howard G. Shertzer, Corey D. Clay, Mary Beth Genter, Mark C. Chames, Scott N. Schneider, Greg G. Oakley, Daniel W. Nebert, Timothy P. Dalton

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Studying liver microsomes from 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced or vehicle-treated (noninduced) mice, we evaluated the in vitro effects of added chemicals on the production of reactive oxygen due to substrate/P450-mediated uncoupling. The catalase-inhibited NADPH-dependent H2O2 production (luminol assay) was lower in induced than noninduced microsomes. The effects of adding chemicals (2.5 μM) in vitro could be divided into three categories: Group 1, highly halogenated and coplanar compounds that increased H2O2 production at least 5-fold in induced, but not in noninduced, microsomes; Group 2, non-coplanar halogenated biphenyls that did not affect H2O 2 production; Group 3, minimally halogenated biphenyls and benzo[a]pyrene that decreased H2O2 production. Molar consumption of NADPH and O2 and molar H2O2 production (o-dianisidine oxidation) revealed that Group 1 compounds mostly increased, Group 2 had no effect, and Group 3 decreased the H2O 2/O2 and H2O2/NADPH ratios. Microsomal lipid peroxidation (thiobarbituric acid-reactive substances) was proportional to H2O2 production. Although TCDD induction decreased microsomal production of H2O2, addition of Group 1 compounds to TCDD-induced microsomes in vitro stimulated the second-electron reduction of cytochrome P450 and subsequent release of H 2O2 production. This pathway is likely to contribute to the oxidative stress response and associated toxicity produced by many of these environmental chemicals.

Original languageEnglish (US)
Pages (from-to)618-631
Number of pages14
JournalFree Radical Biology and Medicine
Issue number5
StatePublished - Mar 1 2004
Externally publishedYes


  • Cytochrome P450
  • Free radicals
  • Hydrogen peroxide
  • Polyhalogenated aromatic hydrocarbons
  • Superoxide
  • Uncoupling

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


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