Transcription factor Nrf2 mediates an adaptive response to sulforaphane that protects fibroblasts in vitro against the cytotoxic effects of electrophiles, peroxides and redox-cycling agents

Larry G. Higgins, Michael O. Kelleher, Ian M. Eggleston, Ken Itoh, Masayuki Yamamoto, John D. Hayes

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    Abstract

    Sulforphane can Stimulate cellular adaptation to redox stressors through transcription factor Nrf2. Using mouse embryonic fibroblasts (MEFs) as a model, we show herein that the normal homeostatic level of glutathione in Nrf2(-/-) MEFs was only 20% of that in their wild-type counterparts. Furthermore, the rate of glutathione synthesis following its acute depletion upon treatment with 3 mu mol/l sulforaphane was very substantially lower in Nrf2(-/-) MEFs than in wild-type cells, and the rebound leading to a similar to 1.9-fold increase in glutathione that Occurred 12-24 h after Nrf2(+/+) MEFs were treated with sulforaphane was not observed in Nrf2(-/-) fibroblasts. Wild-type MEFs that had been pre-treated for 24 h with 3 mu mol/l sulforaphane exhibited between 1.4- and 3.2-fold resistance against thiol-reactive electrophiles, including isothiocyanates, alpha,beta-unsaturated carbonyl compounds (e.g. acrolein), aryl halides and alkene epoxides. Pretreatment of Nrf2(+/+) MEFs With sulforaphane also protected against hydroperoxides (e.g. cumene hydroperoxide, CuOOH), free radical-generating Compounds (e.g. menadione), and genotoxic electrophiles (e.g. chlorambucil). By contrast, Nrf2(-/-) MEFs were typically similar to 50% less tolerant of these agents than wildtype fibroblasts, and sulforaphane pre-treatment did not protect the mutant cells against xenobiotics. To test whether Nrf2-mediated up-regulation of glutathione represents the major cytoprotective mechanism Stimulated by sulforaphane, 5 mu mol/l buthionine sulfoximine (BSO) was used to inhibit glutathione synthesis. In Nrf2(+/+) MEFs pre-treated with sulforaphane, BSO diminished intrinsic resistance and abolished inducible resistance to acrolein, CuOOH and chlorambucil, but not menadione. Thus Nrf2-dependent up-regulation of GSH is the principal mechanism by which sulforaphane pre-treatment induced resistance to acrolein, CuOOH and chlorambucil, but not menadione. (C) 2009 Elsevier Inc. All rights reserved.

    Original languageEnglish
    Pages (from-to)267-280
    Number of pages14
    JournalToxicology and Applied Pharmacology
    Volume237
    Issue number3
    DOIs
    Publication statusPublished - 15 Jun 2009

    Keywords

    • Cancer chemoprevention
    • Glutathione
    • Glutathione S-transferases
    • Acrolein
    • Chlorambucil
    • Menadione
    • GLUTATHIONE S-TRANSFERASES
    • GENE-EXPRESSION
    • ACETAMINOPHEN HEPATOTOXICITY
    • INDUCIBLE EXPRESSION
    • CHEMOPREVENTIVE ISOTHIOCYANATE
    • OLIGONUCLEOTIDE MICROARRAY
    • OXIDATIVE STRESS
    • DRUG-RESISTANCE
    • REACTIVE OXYGEN
    • DEFICIENT MICE

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