title: Cellular titration of apoptosis with steady state concentrations of H(2)O(2): submicromolar levels of H(2)O(2) induce apoptosis through Fenton chemistry independent of the cellular thiol state.
abstract: Apoptosis was studied under conditions that mimic the steady state of H(2)O(2) in vivo. This is at variance with previous studies involving a bolus addition of H(2)O(2), a procedure that disrupts the cellular homeostasis. The results allowed us to define three phases for H(2)O(2)-induced apoptosis in Jurkat T-cells with reference to cytosolic steady state concentrations of H(2)O(2) [(H(2)O(2))(ss)]: (H(2)O(2))(ss) values below 0.7 microM elicited no effects; (H(2)O(2))(ss) approximately 0.7-3 microM induced apoptosis; and (H(2)O(2))(ss) > 3 microM yielded no additional apoptosis and a gradual shift towards necrosis as the mode of cell death were observed. H(2)O(2)-induced apoptosis was not affected by either BCNU, an inhibitor of glutathione reductase, or diamide, a compound that reacts both with low-molecular weight and protein thiols, or selenols. Glutathione depletion, accomplished by incubating cells either with buthionine sulfoximine or in cystine-free medium, rendered cells more sensitive to H(2)O(2)-induced apoptosis, but did not change the threshold and saturating concentrations of H(2)O(2) that induced apoptosis. Two unrelated metal chelators, desferrioxamine and dipyridyl, strongly protected against H(2)O(2)-induced apoptosis. It may be concluded that, under conditions of H(2)O(2) delivery that mimic in vivo situations, the oxidative event that triggers the induction of apoptosis by H(2)O(2) is a Fenton-type reaction and is independent of the thiol or selenium states of the cell.
authors.affiliation: Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, CA, USA. antunes@hsc.usc.edu
authors.forename: F
authors.initials: F
authors.lastname: Antunes
authors.forename: E
authors.initials: E
authors.lastname: Cadenas
mesh_terms: D015082:2,2'-Dipyridyl / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002330:Carmustine / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D003958:Diamide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019169:Jurkat Cells; D009336:Necrosis; D010084:Oxidation-Reduction; D012643:Selenium / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D005609:Free Radicals; D013438:Sulfhydryl Compounds; D003958:Diamide; D015082:2,2'-Dipyridyl; D006861:Hydrogen Peroxide; D005980:Glutathione Reductase; D005978:Glutathione; D012643:Selenium; D003676:Deferoxamine; D002330:Carmustine