title: Ebselen, a seleno-organic antioxidant, as an electrophile.
abstract: Ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], a seleno-organic compound showing glutathione peroxidase-like activity, is one of the promising synthetic antioxidants. In the present study, we investigated the electrophilic potential of this antioxidant and established the mechanism of the cysteine-targeted oxidation of protein. In addition, using ebselen as an electrophilic probe, we characterized the cysteine residues required for posttranslational modification into an electrophile sensor protein in the phase 2 detoxification response. Ebselen showed a potent antioxidant effect against the spontaneous and 4-hydroxy-2-nonenal-stimulated production of intracellular reactive oxygen species in rat liver epithelial RL34 cells. Meanwhile, upon in vitro incubation with a redox-active sulfhydryl protein (thioredoxin), ebselen showed a strong electrophilic potential of mediating the formation of selenenylsulfide and intra- and intermolecular disulfide linkages within the protein. By taking advantage of this antioxidant and electrophilic property of ebselen, we characterized posttranslational modification of Kelch-like ECH-associated protein 1 (Keap1), an electrophile sensor protein, which represses the ability of the transcription factor NF-E2-related factor 2 (Nrf2) upon induction of the phase 2 detoxification response. Ebselen potently induced the gene expression of a series of phase 2 enzymes in rat liver epithelial RL34 cells, which was associated with the formation of a high molecular weight complex of Keap1. Furthermore, a cysteine residue in Keap1, C151, was found to be uniquely required not only for the formation of the complex but also for the induction of the phase 2 response by ebselen. Thus, this unique antioxidant and electrophilic property of ebselen giving rise to the cysteine-targeted oxidation enabled us to evaluate the role of sensor cysteines in redox regulation of protein function under electrophile stress.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Toyo
authors.initials: T
authors.lastname: Sakurai
authors.forename: Masaya
authors.initials: M
authors.lastname: Kanayama
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shibata
authors.forename: Ken
authors.initials: K
authors.lastname: Itoh
authors.forename: Akira
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001393:Azoles / Q000737:chemistry*; D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D005434:Flow Cytometry; D054833:Isoindoles; D016566:Organoselenium Compounds / Q000737:chemistry*; D010957:Plasmids; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D000975:Antioxidants; D001393:Azoles; D054833:Isoindoles; D016566:Organoselenium Compounds; D017382:Reactive Oxygen Species; C042986:ebselen