title: Genetic or pharmacologic activation of Nrf2 signaling fails to protect against aflatoxin genotoxicity in hypersensitive GSTA3 knockout mice.
abstract: Mice are resistant to aflatoxin hepatotoxicity, primarily due to high expression of glutathione S-transferases (GSTs), and in particular the GSTA3 subunit. Nuclear factor erythroid 2 related factor 2 (Nrf2) signaling, which controls a broad-based cytoprotective response, was activated either genetically or pharmacologically in an attempt to rescue GSTA3 knockout mice from aflatoxin genotoxicity. Genetic activation of Nrf2 signaling was attained in a GSTA3: hepatocyte-specific Keap1 double knockout (DKO) mouse whereas pharmacologic activation of Nrf2 was achieved through pretreatment of mice with the triterpenoid 1-[2-cyano-3-,12-dioxoleana-1,9(11)-dien-28-oyl] imidazole (CDDO-Im) prior to aflatoxin B1 exposure. Following oral treatment with aflatoxin, urine was collected from mice for 24 h and hepatic and urinary aflatoxin metabolites then quantified using isotope dilution-mass spectrometry. Although Nrf2 was successfully activated genetically and pharmacologically, neither means affected the response of GSTA3 knockout mice to chemical insult with aflatoxin. Hepatic aflatoxin B1-N(7)-guanine levels were elevated 120-fold in GSTA3 knockout mice compared with wild-type and levels were not attenuated by the interventions. This lack of effect was mirrored in the urinary excretion of aflatoxin B1-N(7)-guanine. By contrast, urinary excretion of aflatoxin B1-N-acetylcysteine was >200-fold higher in wild-type mice compared with the single GSTA3 knockout or DKO mouse. The inability to rescue GSTA3 knockout mice from aflatoxin genotoxicity through the Nrf2 transcriptional program indicates that Gsta3 is unilaterally responsible for the detoxication of aflatoxin in mice.
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, Maryland 21205.
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Kensler
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Slocum
authors.forename: Dionysios V
authors.initials: DV
authors.lastname: Chartoumpekis
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Dolan
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Johnson
authors.forename: Zoran
authors.initials: Z
authors.lastname: Ilic
authors.forename: Dana R
authors.initials: DR
authors.lastname: Crawford
authors.forename: Stewart
authors.initials: S
authors.lastname: Sell
authors.forename: John D
authors.initials: JD
authors.lastname: Groopman
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Kensler
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Egner
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D016604:Aflatoxin B1 / Q000493:pharmacokinetics / Q000633:toxicity* / Q000652:urine; D000818:Animals; D003598:Cytoskeletal Proteins / Q000235:genetics; D005982:Glutathione Transferase / Q000235:genetics*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006973:Hypertension / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology*; D000072019:Kelch-Like ECH-Associated Protein 1; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009153:Mutagens / Q000493:pharmacokinetics / Q000633:toxicity*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics
chemical_list: C472829:1-(2-cyano-3,12-dioxooleana-1,9-dien-28-oyl) imidazole; D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D007093:Imidazoles; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D009153:Mutagens; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D009828:Oleanolic Acid; D016604:Aflatoxin B1; C000594000:GSTA3 protein, mouse; D005982:Glutathione Transferase
keywords: DNA adducts; Keap1; Nrf2; aflatoxin; glutathione S-transferases