title: Hormesis is induced in the red flour beetle Tribolium castaneum through ingestion of charred toast.
abstract: OBJECTIVE
  Charred foods are generally suspected to exert health threats by providing toxicants, such as acrylamide or polycyclic aromatic hydrocarbons. Using the red flour beetle Tribolium castaneum as a model organism, we tested its survival under heat stress in response to feeding charred toast.
  
  
  METHODS
  Survival of beetles was measured at 42 °C after a pre-feeding phase with flour enriched with increasing concentrations of charred toast. In order to assess the influence of key transcription factors for phase-I and phase-II xenobiotic metabolism, gene homologs for ahr and nrf-2, respectively, were knocked down by the use of RNA interference (RNAi).
  
  
  RESULTS
  Beetles fed only charred toast died off much earlier than control beetles fed on flour, whereas beetles fed flour enriched with 5% charred toast survived significantly longer than the control. Both, ahr and nrf-2 proved essential in order to enable the increase in survival by the feeding of 5% charred toast. Moreover, functional loss of ahr and nrf-2 made the beetles hypersensitive versus the feeding of 100% charred toast. Finally, at the transcriptional level, it was shown that RNAi for ahr blocked the inducing activities of charred toast on nrf-2.
  
  
  CONCLUSIONS
  Our studies suggest a hormetic response of the red flour beetle to feeding of charred toast that causes an increased stress resistance through the activation of ahr and nrf-2. Those adaptations, however, are saturable and accordingly the hormetic effects at increasing concentrations of the toxicants become expended.
authors.affiliation: Molecular Nutrition Research, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Grünwald
authors.forename: Janine
authors.initials: J
authors.lastname: Niedermeier
authors.forename: Uwe
authors.initials: U
authors.lastname: Wenzel
mesh_terms: D020106:Acrylamide / Q000633:toxicity; D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D004435:Eating; D005433:Flour; D059165:Hormesis; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D011084:Polycyclic Aromatic Hydrocarbons / Q000633:toxicity; D034622:RNA Interference; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism; D014231:Tribolium / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D051267:NF-E2-Related Factor 2; D011084:Polycyclic Aromatic Hydrocarbons; D018336:Receptors, Aryl Hydrocarbon; D020106:Acrylamide