title: Catechol estrogens mediated activation of Nrf2 through covalent modification of its quinone metabolite to Keap1.
abstract: The catechol metabolites (2-OHE and 4-OHE) of estrogen enter a redox cycle, thereby generating not only reactive oxygen species (ROS) but also electrophilic quinones. It is well recognized that chemicals causing oxidative stress or electrophiles activate a transcription factor Nrf2 that is negatively regulated by Keap1, leading to up-regulation of downstream proteins responsible for detoxification of electrophiles in cells. The purpose of the present study is to explore the roles of oxidative and electrophilic stress in Nrf2 activation caused by redox-active catechol estrogens. Exposure of RAW264.7 cells to 2- and 4-OHE activated Nrf2, resulting in induction of heme oxygenase-1 (HO-1) and glutamate cysteine ligase catalytic subunit (GCLC). Under these conditions, intracellular oxidants were generated; however, subsequent examinations revealed that quinoid metabolites derived from 2- and 4-OHE mainly participate in the Nrf2 activation. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis revealed Keap1 undergoes modification by such quinoid species through multiple reactive thiol groups. These results suggest that Nrf2 activation during redox cycling of catechol estrogens is dominantly attributable to formation of their ortho-quinones that covalently bind to Keap1.
authors: Master's Program in Environmental Sciences, University of Tsukuba, Ibaraki, Japan.
authors: Daigo
authors: D
authors: Sumi
authors: Yumiko
authors: Y
authors: Numasawa
authors: Akiko
authors: A
authors: Endo
authors: Noriko
authors: N
authors: Iwamoto
authors: Yoshito
authors: Y
authors: Kumagai
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism / Q000502:physiology*; D002393:Estrogens, Catechol / Q000502:physiology*; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1; D051379:Mice; D051267:NF-E2-Related Factor 2; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D011485:Protein Binding; D011809:Quinones / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D002393:Estrogens, Catechol; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; D011809:Quinones; D017382:Reactive Oxygen Species; D051547:Heme Oxygenase-1; D005721:Glutamate-Cysteine Ligase; C544143:GCLC protein, rat