title: Extracts of Fruits and Vegetables Activate the Antioxidant Response Element in IMR-32 Cells.
abstract: BACKGROUND
  The biological effects of antioxidant nutrients are mediated in part by activation of antioxidant response elements (AREs) on genes for enzymes involved in endogenous pathways that prevent free radical damage. Traditional approaches for identifying antioxidant molecules in foods, such as total phenolic compound (TP) content or oxygen radical absorption capacity (ORAC), do not measure capacity to activate AREs.
  
  
  OBJECTIVE
  The goal of this study was to develop an assay to assess the ARE activation capacity of fruit and vegetable extracts and determine whether such capacity was predicted by TP content and/or ORAC activity.
  
  
  METHODS
  Fruits and vegetables were homogenized, extracted with acidified ethanol, lyophilized, and resuspended in growth medium. Human IMR-32 neuroblastoma cells, transfected with an ARE-firefly luciferase reporter, were exposed to extracts for 5 h. Firefly luciferase was normalized to constitutively expressed Renilla luciferase with tertiary butylhydroquinone (tBHQ) as a positive control. TP content and ORAC activity were measured for each extract. Relations between TPs and ORAC and ARE activity were determined.
  
  
  RESULTS
  A total of 107 of 134 extracts tested significantly activated the ARE-luciferase reporter from 1.2- to 58-fold above that of the solvent control (P < 0.05) in human IMR-32 cells. ARE activity, TP content, and ORAC ranked higher in peels than in associated flesh. Despite this relation, ARE activity did not correlate with TP content (Spearman ρ = 0.05, P = 0.57) and only modestly but negatively correlated with ORAC (Spearman ρ = -0.24, P < 0.01). Many extracts activated the ARE more than predicted by the TP content or ORAC.
  
  
  CONCLUSIONS
  The ARE reporter assay identified many active fruit and vegetable extracts in human IMR-32 cells. There are components of fruits and vegetables that activate the ARE but are not phenolic compounds and are low in ORAC. The ARE-luciferase reporter assay is likely a better predictor of the antioxidant benefits of fruits and vegetables than TP or ORAC.
authors.affiliation: University of North Carolina at Chapel Hill Nutrition Research Institute, Kannapolis, NC;
authors.forename: Stephen
authors.initials: S
authors.lastname: Orena
authors.affiliation: University of North Carolina at Chapel Hill Nutrition Research Institute, Kannapolis, NC;
authors.forename: Jennifer
authors.initials: J
authors.lastname: Owen
authors.affiliation: Dole Nutrition Research Laboratory, Kannapolis, NC; and.
authors.forename: Fuxia
authors.initials: F
authors.lastname: Jin
authors.affiliation: Dole Nutrition Research Laboratory, Kannapolis, NC; and.
authors.forename: Morgan
authors.initials: M
authors.lastname: Fabian
authors.affiliation: Dole Nutrition Research Laboratory, Kannapolis, NC; and.
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Gillitt
authors.affiliation: University of North Carolina at Chapel Hill Nutrition Research Institute, Kannapolis, NC; Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC steven_zeisel@unc.edu.
authors.forename: Steven H
authors.initials: SH
authors.lastname: Zeisel
mesh_terms: D061745:Antioxidant Response Elements; D045744:Cell Line, Tumor; D005638:Fruit / Q000737:chemistry*; D005786:Gene Expression Regulation; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006873:Hydroquinones / Q000737:chemistry; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry*; D059808:Polyphenols / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000378:metabolism; D014675:Vegetables / Q000737:chemistry*
chemical_list: D006873:Hydroquinones; D010936:Plant Extracts; D059808:Polyphenols; D017382:Reactive Oxygen Species; C018855:2-tert-butylhydroquinone; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; C546365:GCLM protein, human; D005721:Glutamate-Cysteine Ligase
keywords: IMR-32 cells; Nrf2; ORAC; antioxidant response element; polyphenols; total phenolic compounds