Uncoupling-mediated generation of reactive oxygen by halogenated aromatic hydrocarbons in mouse liver microsomes.
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 H(2)O(2) production (luminol assay) was lower in induced than noninduced microsomes. The effects of adding chemicals (2.5 microM) in vitro could be divided into three categories: Group 1, highly halogenated and coplanar compounds that increased H(2)O(2) production at least 5-fold in induced, but not in noninduced, microsomes; Group 2, non-coplanar halogenated biphenyls that did not affect H(2)O(2) production; Group 3, minimally halogenated biphenyls and benzo[a]pyrene that decreased H(2)O(2) production. Molar consumption of NADPH and O(2) and molar H(2)O(2) production (o-dianisidine oxidation) revealed that Group 1 compounds mostly increased, Group 2 had no effect, and Group 3 decreased the H(2)O(2)/O(2) and H(2)O(2)/NADPH ratios. Microsomal lipid peroxidation (thiobarbituric acid-reactive substances) was proportional to H(2)O(2) production. Although TCDD induction decreased microsomal production of H(2)O(2), addition of Group 1 compounds to TCDD-induced microsomes in vitro stimulated the second-electron reduction of cytochrome P450 and subsequent release of H(2)O(2) production. This pathway is likely to contribute to the oxidative stress response and associated toxicity produced by many of these environmental chemicals.
Shertzer
Howard G
HG
Department of Environmental Health, University of Cincinnati, Medical Center, 123 East Shields Street, Cincinnati, OH 45267-0056, USA. shertzhg@ucmail.uc.edu
Clay
Corey D
CD
Genter
Mary Beth
MB
Chames
Mark C
MC
Schneider
Scott N
SN
Oakley
Greg G
GG
Nebert
Daniel W
DW
Dalton
Timothy P
TP
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects; D051379:Mice; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D017382:Reactive Oxygen Species / Q000378:metabolism*
D006841:Hydrocarbons, Aromatic; D006846:Hydrocarbons, Halogenated; D000072317:Polychlorinated Dibenzodioxins; D017382:Reactive Oxygen Species; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide