title: Glutamine potentiates TNF-alpha-induced tumor cytotoxicity.
abstract: L-glutamine (Gln) sensitizes tumor cells to tumor necrosis factor (TNF)-alpha-induced cytotoxicity. The type and mechanism of cell death induced by TNF-alpha was studied in Ehrlich ascites tumor (EAT)-bearing mice fed a Gln-enriched diet (GED; where 30% of the total dietary nitrogen was from Gln). A high rate of Gln oxidation promotes a selective depletion of mitochondrial glutathione (mtGSH) content to approximately 58% of the level found in tumor mitochondria of mice fed a nutritionally complete elemental diet (standard diet, SD). The mechanism of mtGSH depletion involves a glutamate-induced inhibition of GSH transport from the cytosol into mitochondria. The increase in reactive oxygen intermediates (ROIs) production induced by TNF-alpha further depletes mtGSH to approximately 35% of control values, which associates with a decrease in the mitochondrial transmembrane potential (MMP), and elicits mitochondrial membrane permeabilization and release of cytochrome c. Mitochondrial membrane permeabilization was also found in intact tumor cells cultured with a Gln-enriched medium under conditions of buthionine sulfoximine (BSO)-induced selective GSH synthesis inhibition. Enforced expression of the bcl-2 gene in tumor cells could not avoid the glutamine- and TNF-alpha-induced cell death under conditions of mtGSH depletion. However, addition of GSH ester, which delivers free intracellular GSH and increases mtGSH levels, preserved cell viability. These findings show that glutamine oxidation and TNF-alpha, by causing a change in the glutathione redox status within tumor mitochondria, activates the molecular mechanism of apoptotic cell death.
authors.affiliation: Departamento de Fisiología, Universidad de Valencia, Valencia, Spain
authors.forename: E
authors.initials: E
authors.lastname: Obrador
authors.forename: J
authors.initials: J
authors.lastname: Carretero
authors.forename: J M
authors.initials: JM
authors.lastname: Esteve
authors.forename: J A
authors.initials: JA
authors.lastname: Pellicer
authors.forename: A
authors.initials: A
authors.lastname: Pascual
authors.forename: I
authors.initials: I
authors.lastname: Petschen
authors.forename: J M
authors.initials: JM
authors.lastname: Estrela
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000502:physiology; D003574:Cytochrome c Group / Q000378:metabolism; D004032:Diet; D004357:Drug Synergism; D005609:Free Radicals / Q000378:metabolism; D005973:Glutamine / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009336:Necrosis; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D003574:Cytochrome c Group; D005609:Free Radicals; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D005973:Glutamine; D013481:Superoxides; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione; D010100:Oxygen