Ebselen, a seleno-organic antioxidant, as an electrophile

Chem Res Toxicol. 2006 Sep;19(9):1196-204. doi: 10.1021/tx0601105.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / chemistry*
  • Azoles / chemistry*
  • Cell Line
  • Electrophoresis, Gel, Two-Dimensional
  • Flow Cytometry
  • Organoselenium Compounds / chemistry*
  • Plasmids
  • Reactive Oxygen Species / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection


  • Antioxidants
  • Azoles
  • Organoselenium Compounds
  • Reactive Oxygen Species
  • ebselen