title: Adaptive response to GSH depletion and resistance to L-buthionine-(S,R)-sulfoximine: involvement of Nrf2 activation.
abstract: Pharmacological depletion of L-gamma-glutamyl-L-cysteinyl-glycine (GSH) has been implicated in the sensitization of cancer cells to alkylating agents and apoptosis. However, some types of cells do not induce apoptotic response following chemical depletion of GSH. In the present study, we report that murine embryonic fibroblasts (MEFs) can survive in the presence of GSH inhibitor L-buthionine-(S,R)-sulfoximine (BSO), even though most intracellular GSH was depleted. As a cellular adaptive mechanism, BSO treatment effectively activated the NF-E2-related factor 2 (Nrf2) pathway, which led to up-regulation of antioxidant enzymes in these cells through the extracellular signal-regulated kinase cascade. While nrf2-deficient MEFs lost the inducibility of antioxidant genes, which resulted in higher levels of reactive oxygen species accumulation, caspase-3 activation, and cell death than wild-type cells. Finally, nrf2-deficient cells can be more sensitized to doxorubicin-induced cell death by BSO pre-incubation, while wild-type cells were not. In addition, BSO-mediated cell death was facilitated by administering Nrf2 siRNA to chemoresistant human ovarian cancer cells. These results indicate that Nrf2 is the primary factor inducing the cell survival system under GSH depletion and that the effect of BSO as a chemosensitizer might be enhanced by inhibition of Nrf2.
authors.affiliation: College of Pharmacy, Yeungnam University, 214-1 Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749, South Korea.
authors.forename: Hyang-Rim
authors.initials: HR
authors.lastname: Lee
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Cho
authors.forename: Dong-ha
authors.initials: DH
authors.lastname: Shin
authors.forename: Chul Soon
authors.initials: CS
authors.lastname: Yong
authors.forename: Han-Gon
authors.initials: HG
authors.lastname: Choi
authors.forename: Nobunao
authors.initials: N
authors.lastname: Wakabayashi
authors.forename: Mi-Kyoung
authors.initials: MK
authors.lastname: Kwak
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D019328:Buthionine Sulfoximine / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000166:cytology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D005978:Glutathione / Q000172:deficiency*; D006801:Humans; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; D019328:Buthionine Sulfoximine; D004317:Doxorubicin; D048049:Extracellular Signal-Regulated MAP Kinases; D005978:Glutathione