title: Oxidative stress-responsive transcription factor NRF2 is not indispensable for the human hepatic Flavin-containing monooxygenase-3 (FMO3) gene expression in HepG2 cells.
abstract: The flavin-containing monooxygenases (FMOs) are important for the oxidation of a variety of endogenous compounds and xenobiotics. The hepatic expression of FMO3 is highly variable and until recently, it was thought to be uninducible. In this study, human FMO3 gene regulation by the oxidative stress transcription factor, nuclear factor (erythroid-derived 2)-like 2 (NRF2) was examined. Constitutive FMO3 gene expression is repressed in HepG2 cells, thus this cell can be a good model for FMO3 gene regulation studies. Over-expression of NRF2 in HepG2 cells increased NRF2 target gene expression, heme oxygenase-1 (HMOX1) and
  quinone oxidoreductase-1 (NQO1), but did not alter FMO3 gene expression. Co-transfection studies with NRF2 or its cytosolic regulatory protein, Kelch-like ECH-associated protein 1 (KEAP1), expression vectors, along with FMO3 promoter luciferase reporter constructs of various lengths (5kb or 6kb), did not change FMO3 reporter gene activity significantly. Furthermore, treatment with tert-butyl hydroperoxide (tBHP) and tert-butyl hydroquinone (tBHQ) did not alter FMO3 reporter construct activity. In summary, in vitro results suggest that the transcriptional regulation of FMO3 might not involve the NRF2-KEAP1 regulatory pathway.
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, USA. Electronic address: swetha.rudraiah@uconn.edu.
authors.forename: Swetha
authors.initials: S
authors.lastname: Rudraiah
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, USA. Electronic address: gu.xinsheng@gmail.com.
authors.forename: Xinsheng
authors.initials: X
authors.lastname: Gu
authors.affiliation: US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC, USA. Electronic address: hines.ronald@epa.gov.
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Hines
authors.affiliation: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, USA. Electronic address: jose.manautou@uconn.edu.
authors.forename: José E
authors.initials: JE
authors.lastname: Manautou
mesh_terms: D005786:Gene Expression Regulation; D017930:Genes, Reporter; D056945:Hep G2 Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D000072019:Kelch-Like ECH-Associated Protein 1; D015227:Lipid Peroxidation; D008099:Liver / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics*; D018384:Oxidative Stress / Q000235:genetics; D010105:Oxygenases / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D006873:Hydroquinones; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D020122:tert-Butylhydroperoxide; C018855:2-tert-butylhydroquinone; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming)
keywords: Flavin-containing monoxygenase-3; KEAP1; NRF2; Oxidative stress; Tert-butyl hydroperoxide; Tert-butyl hydroquinone