Extracellular redox status regulates Nrf2 activation through mitochondrial reactive oxygen species.
The redox status of the extracellular compartment has only just been elucidated as a mechanism controlling intracellular signal transduction and correlates with aging, diabetes, heart disease and lung fibrosis. In the present paper, we describe a mechanism by which oxidizing extracellular environments, as maintained by the cysteine/cystine (Cys/CySS) redox couple, induce mitochondria-derived ROS (reactive oxygen species) generation and cause the activation of Nrf2 (nuclear factor-erythroid 2-related factor 2), inducing an antioxidant response. NIH 3T3 cells were cultured in medium with extracellular Cys/CySS redox potentials (Eh), ranging from 0 to -150 mV. Cellular and mitochondrial ROS production significantly increased in cells incubated under more oxidizing extracellular conditions (0 and -46 mV). Trx2 (thioredoxin-2) is a mitochondrial-specific oxidoreductase and antioxidant and became oxidized in cells incubated at 0 or -46 mV. MEFs (mouse embryonic fibroblasts) from Trx2-overexpressing transgenic (Trx2 Tg) mice produced less intracellular ROS compared with WT (wild-type) MEFs at the more oxidizing extracellular conditions. Nrf2 activity was increased in WT MEFs at the 0 or -46 mV conditions, but was inhibited in Trx2 Tg MEFs under the same conditions. Furthermore, Nrf2-regulated gene expression was significantly increased in the WT MEFs, but not in the Trx2 Tg MEFs. These results show that the Cys/CySS redox status in the extracellular compartment regulates intracellular ROS generated primarily in the mitochondria, which play an important role in the activation of Nrf2 and up-regulation of antioxidant and detoxification systems.
Imhoff
Barry R
BR
Division of Pulmonary, Allergy/Immunology, Cystic Fibrosis and Sleep, Department of Pediatrics, Emory School of Medicine, Emory University, Atlanta, GA 30322, USA.
Hansen
Jason M
JM
D021581:Active Transport, Cell Nucleus; D000818:Animals; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D003545:Cysteine / Q000378:metabolism; D003553:Cystine / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017879:Isothiocyanates; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D010084:Oxidation-Reduction; D021381:Protein Transport; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
D017879:Isothiocyanates; D051267:NF-E2-Related Factor 2; D017382:Reactive Oxygen Species; D013454:Sulfoxides; D013861:Thiocyanates; D003553:Cystine; D013879:Thioredoxins; D001973:Bromodeoxyuridine; C016766:sulforaphane; D003545:Cysteine