title: Pivotal role of electrophilicity in glutathione S-transferase induction by tert-butylhydroquinone.
abstract: Although the induction of glutathione S-transferase (GST) activity by tert-butylhydroquinone (tBHQ) has been well-documented in several cell culture systems and rodent experiments, the exact mechanism responsible for its inducibility is still not thoroughly understood. To more precisely define the molecular mechanism of GST induction by tBHQ, we examined the one-electron oxidation and glutathione (GSH) reaction potentials of tBHQ as compared to its analogue, 2,5-di-tert-butylhydroquinone (DtBHQ). tBHQ and DtBHQ showed similar one-electron oxidation potentials, including free radical quenching (antioxidant), oxidative conversion of both compounds to a benzoquinone form, and Cu(2+)-dependent superoxide generation. On the other hand, the reduced GSH level was observed by the addition of tBHQ, but not DtBHQ, suggesting that tBHQ acts as an electrophile while DtBHQ does not. The data were consistent with the observation that tBHQ more potently induced the GSTP1 gene expression in RL34 cells than DtBHQ did. Moreover, we indeed detected the GSH-tBHQ conjugates in the cells exposed to tBHQ using an electrochemical detector-high-performance liquid chromatography technique. Thus, we conclude that an electrophilic quinone oxidation product that reacts with intracellular nucleophiles including protein thiol or GSH plays a major role in the GSTP1 gene expression.
authors.affiliation: Laboratory of Food and Biodynamics, Nagoya University Graduate School of Bioagricultural Sciences, Nagoya 464-8601, Japan. yossan@agr.nagoya-u.ac.jp
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kumagai
authors.forename: Chiho
authors.initials: C
authors.lastname: Yoshida
authors.forename: Yuko
authors.initials: Y
authors.lastname: Naito
authors.forename: Masaaki
authors.initials: M
authors.lastname: Miyamoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohigashi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Osawa
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
mesh_terms: D002460:Cell Line; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology*; D010084:Oxidation-Reduction
chemical_list: D006873:Hydroquinones; C018855:2-tert-butylhydroquinone; D005982:Glutathione Transferase