title: Diallyl tetrasulfane activates both the eIF2α and Nrf2/HO-1 pathways.
abstract: BACKGROUND
  Diallyl polysulfanes have been shown to exert cell cycle arrest, anti-tumor and anti-inflammatory activities in a variety of in vitro and in vivo models. Although diallyl polysulfanes cause oxidative stress, little is known about the underlying signaling cascades leading to antioxidant defense or apoptosis.
  
  
  METHODS
  Cells were treated with DATTS at different concentrations and for different time periods. Reactive oxygen species and thiol concentrations were determined by commercially available kits. The expression levels of signal molecules were determined by Western Blot analysis. A direct influence of Nrf2 on the promoter of HO-1 gene was determined by a luciferase assay with the StRE promoter element from the HO-1 gene.
  
  
  RESULTS
  We found an immediate increase in the level of the superoxide anion radical O(2)(-) and hydrogen peroxide H(2)O(2) and an overall thiol depletion. DATTS treatment of HCT116 cells also caused an up-regulation of phospho-eIF2α, nuclear Nrf2 and HO-1 protein levels in a time and concentration-dependent manner. Pre-treatment of cells with antioxidants significantly reduced the elevated expression levels of these proteins. A direct contribution of Nrf2 was shown by its interaction with the stress-response element of the HO-1 promoter.
  
  
  CONCLUSIONS
  DATTS activates the ROS-eIF2α/Nrf2 HO-1 signaling cascades leading to the up-regulation of HO-1. However, this antioxidant defense is not sufficient to protect HCT116 cells from apoptosis.
  
  
  CONCLUSIONS
  This study shows for the first time a parallel but not equal activation of signaling pathways by DATTS with a competitive ultimate cellular outcome.
authors.affiliation: Medical Biochemistry and Molecular Biology, University of the Saarland, Homburg, Germany.
authors.forename: Nathaniel Edward Bennett
authors.initials: NE
authors.lastname: Saidu
authors.forename: Rania
authors.initials: R
authors.lastname: Touma
authors.forename: Imad Abu
authors.initials: IA
authors.lastname: Asali
authors.forename: Claus
authors.initials: C
authors.lastname: Jacob
authors.forename: Mathias
authors.initials: M
authors.lastname: Montenarh
mesh_terms: D000498:Allyl Compounds / Q000494:pharmacology*; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology; D051547:Heme Oxygenase-1 / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D013440:Sulfides / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000498:Allyl Compounds; D015852:Eukaryotic Initiation Factor-2; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D013440:Sulfides; D013481:Superoxides; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1