title: Intracellular glutathione levels determine cell sensitivity to apoptosis induced by the antineoplasic agent N-(4-hydroxyphenyl) retinamide.
abstract: BACKGROUND
  We have previously demonstrated that the synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR) induces the overproduction of reactive oxygen species (ROS) in human leukemia cells, which in turn triggers the intrinsic (mitochondrial) apoptotic pathway. In order to study the role of glutathione in 4-HPR-induced apoptosis, the levels of this antioxidant were analyzed in cell lines which are sensitive and resistant to the effects of 4-HPR, and the effect of the modulation of glutathione levels on 4-HPR cytotoxicity was characterized.
  
  
  METHODS
  Mitochondrial membrane potential (deltaPsim) and the levels of glutathione were measured by flow cytometry. A fluorometric assay was used to measure intracellular ROS generation and Western blot was employed to analyze tissue transglutaminase expression.
  
  
  RESULTS
  4-HPR generated large quantities of ROS in cell lines which expressed low glutathione levels, these cells being the most sensitive to the retinoid. The sensitivity of leukemia cells to 4-HPR could be modulated, either by increasing intracellular glutathione contents using all-trans retinoic acid (ATRA), or by decreasing it using DL-buthionine-S,R-sulfoximine (BSO). ATRA increased the level of expression of tissue transglutaminase, whereas inhibition of this enzyme led to enhanced apoptosis.
  
  
  CONCLUSIONS
  Our findings indicate that the glutathione content contributes to determining the sensitivity of cells to 4-HPR and points to the potential application of glutathione-inhibiting agents as enhancers in 4-HPR-based therapies.
authors.affiliation: Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa- 48940, Bizkaia, Spain.
authors.forename: María-Celia
authors.initials: MC
authors.lastname: Morales
authors.forename: Gorka
authors.initials: G
authors.lastname: Pérez-Yarza
authors.forename: Naiara
authors.initials: N
authors.lastname: Nieto-Rementeria
authors.forename: María-Dolores
authors.initials: MD
authors.lastname: Boyano
authors.forename: Muhialdin
authors.initials: M
authors.lastname: Jangi
authors.forename: Rafael
authors.initials: R
authors.lastname: Atencia
authors.forename: Aintzane
authors.initials: A
authors.lastname: Asumendi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D019328:Buthionine Sulfoximine / Q000008:administration & dosage / Q000494:pharmacology; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017313:Fenretinide / Q000008:administration & dosage / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D015458:Leukemia, T-Cell / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D014212:Tretinoin / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D017313:Fenretinide; D019328:Buthionine Sulfoximine; D014212:Tretinoin; D011503:Transglutaminases; D005978:Glutathione; C008542:monodansylcadaverine; D002103:Cadaverine