title: Ascorbic acid partly antagonizes resveratrol mediated heme oxygenase-1 but not paraoxonase-1 induction in cultured hepatocytes - role of the redox-regulated transcription factor Nrf2.
abstract: BACKGROUND
  Both resveratrol and vitamin C (ascorbic acid) are frequently used in complementary and alternative medicine. However, little is known about the underlying mechanisms for potential health benefits of resveratrol and its interactions with ascorbic acid.
  
  
  METHODS
  The antioxidant enzymes heme oxygenase-1 and paraoxonase-1 were analysed for their mRNA and protein levels in HUH7 liver cells treated with 10 and 25 μmol/l resveratrol in the absence and presence of 100 and 1000 μmol/l ascorbic acid. Additionally the transactivation of the transcription factor Nrf2 and paraoxonase-1 were determined by reporter gene assays.
  
  
  RESULTS
  Here, we demonstrate that resveratrol induces the antioxidant enzymes heme oxygenase-1 and paraoxonase-1 in cultured hepatocytes. Heme oxygenase-1 induction by resveratrol was accompanied by an increase in Nrf2 transactivation. Resveratrol mediated Nrf2 transactivation as well as heme oxygenase-1 induction were partly antagonized by 1000 μmol/l ascorbic acid.
  
  
  CONCLUSIONS
  Unlike heme oxygenase-1 (which is highly regulated by Nrf2) paraoxonase-1 (which exhibits fewer ARE/Nrf2 binding sites in its promoter) induction by resveratrol was not counteracted by ascorbic acid. Addition of resveratrol to the cell culture medium produced relatively low levels of hydrogen peroxide which may be a positive hormetic redox-signal for Nrf2 dependent gene expression thereby driving heme oxygenase-1 induction. However, high concentrations of ascorbic acid manifold increased hydrogen peroxide production in the cell culture medium which may be a stress signal thereby disrupting the Nrf2 signalling pathway.
authors.affiliation: Institute of Human Nutrition and Food Science, Christian-Albrechts-University of Kiel, Germany.
authors.forename: Anika E
authors.initials: AE
authors.lastname: Wagner
authors.forename: Christine
authors.initials: C
authors.lastname: Boesch-Saadatmandi
authors.forename: Dorothea
authors.initials: D
authors.lastname: Breckwoldt
authors.forename: Charlotte
authors.initials: C
authors.lastname: Schrader
authors.forename: Constance
authors.initials: C
authors.lastname: Schmelzer
authors.forename: Frank
authors.initials: F
authors.lastname: Döring
authors.forename: Koji
authors.initials: K
authors.lastname: Hashida
authors.forename: Osamu
authors.initials: O
authors.lastname: Hori
authors.forename: Seiichi
authors.initials: S
authors.lastname: Matsugo
authors.forename: Gerald
authors.initials: G
authors.lastname: Rimbach
mesh_terms: D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology; D043303:Aryldialkylphosphatase / Q000235:genetics / Q000378:metabolism*; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D004347:Drug Interactions; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D000077185:Resveratrol; D013267:Stilbenes / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; D010936:Plant Extracts; D012333:RNA, Messenger; D013267:Stilbenes; D006861:Hydrogen Peroxide; D051547:Heme Oxygenase-1; D043303:Aryldialkylphosphatase; D001205:Ascorbic Acid; D000077185:Resveratrol