title: Induction of lung glutathione and glutamylcysteine ligase by 1,4-phenylenebis(methylene)selenocyanate and its glutathione conjugate: role of nuclear factor-erythroid 2-related factor 2.
abstract: The synthetic organoselenium agent 1,4-phenylenebis(methylene)selenocyanate (p-XSC) and its glutathione (GSH) conjugate (p-XSeSG) are potent chemopreventive agents in several preclinical models. p-XSC is also an effective inducer of GSH in mouse lung. Our objectives were to test the hypothesis that GSH induction by p-XSC occurs through upregulation of the rate-limiting GSH biosynthetic enzyme glutamylcysteine ligase (GCL), through activation of antioxidant response elements (AREs) in GCL genes via activation of nuclear factor-erythroid 2-related factor 2 (Nrf2). p-XSC feeding (10 ppm Se) increased GSH (230%) and upregulated the catalytic subunit of GCL (GCLc) (55%), extracellular-related kinase (220%), and nuclear Nrf2 (610%) in lung but not liver after 14 days in the rat (P<0.05). Similarly, p-XSeSG feeding (10 ppm) induced lung GCLc (88%) and GSH (200%) (P<0.05), whereas the naturally occurring selenomethionine had no effect. Both p-XSC and p-XSeSG activated a luciferase reporter in HepG2 ARE-reporter cells up to threefold for p-XSC and greater than or equal to fivefold for p-XSeSG. Luciferase activation by p-XSeSG was associated with enhanced levels of GSH, GCLc, and nuclear Nrf2, which were significantly reduced by co-incubation with short interfering RNA targeting Nrf2. The dependence of GCL induction on Nrf2 was confirmed in Nrf2-deficient mouse embryonic fibroblasts, in which p-XSeSG induced GCL subunits in wild-type but not in Nrf2-deficient cells (P<0.05). These results indicate that p-XSC may act through the Nrf2 pathway in vivo and that p-XSeSG is the putative metabolite responsible for such activation, thus offering p-XSeSG as a less toxic, yet highly efficacious, inducer of GSH.
authors.affiliation: Graduate Program in Molecular Medicine, Department of Biochemistry and Molecular Biology, Penn State Cancer Institute, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Sans W
authors.initials: SW
authors.lastname: Emmert
authors.forename: Karam
authors.initials: K
authors.lastname: El-Bayoumy
authors.forename: Arunangshu
authors.initials: A
authors.lastname: Das
authors.forename: Yuan-Wan
authors.initials: YW
authors.lastname: Sun
authors.forename: Shantu
authors.initials: S
authors.lastname: Amin
authors.forename: Dhimant
authors.initials: D
authors.lastname: Desai
authors.forename: Cesar
authors.initials: C
authors.lastname: Aliaga
authors.forename: John P
authors.initials: JP
authors.lastname: Richie
mesh_terms: D000818:Animals; D002460:Cell Line; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis*; D005978:Glutathione / Q000096:biosynthesis*; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D016566:Organoselenium Compounds / Q000494:pharmacology*; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats
chemical_list: D051267:NF-E2-Related Factor 2; D016566:Organoselenium Compounds; D034741:RNA, Small Interfering; C074153:1,4-phenylenebis(methylene)selenocyanate; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione