title: Ajoene, an experimental anti-leukemic drug: mechanism of cell death.
abstract: The organosulfur compound ajoene, a constitutent of garlic, has been shown to induce apoptosis in a leukemic cell line as well as in blood cells of a leukemic patient. The mechanisms of action of ajoene, however, are unknown. The present study aims to characterize the molecular events leading to ajoene-triggered apoptosis. We show here that ajoene (20 microM) leads to a time-dependent activation of caspase-3-like activity as well as to the proteolytic processing of procaspase-3 and -8. Activation of caspases was necessary for ajoene-induced apoptosis since the broad-range caspase inhibitor zVAD-fmk completely abrogated ajoene-mediated DNA fragmentation. Although the initiator caspase-8 was activated, the CD95 death receptor was not involved in death signaling since the HL-60 clone used was shown to express a functionally inactive CD95 receptor. Furthermore, ajoene induced the release of cytochrome c, which was not inhibited by zVAD-fmk indicating that cytochrome c release precedes caspase activation. Ajoene also led to a dissipation of the mitochondrial transmembrane potential. Overexpression of Bcl-x(L) clearly diminished ajoene-induced caspase activation as well as apoptosis. These results indicate that apoptosis in leukemia cells triggered by ajoene is based on the activation of a mitochondria-dependent caspase cascade which includes also the activation of the initiator caspase-8.
authors.affiliation: Department of Pharmacy, Center of Drug Research, University of Munich, Munich, Germany.
authors.forename: V M
authors.initials: VM
authors.lastname: Dirsch
authors.forename: D S M
authors.initials: DS
authors.lastname: Antlsperger
authors.forename: H
authors.initials: H
authors.lastname: Hentze
authors.forename: A M
authors.initials: AM
authors.lastname: Vollmar
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000032:analysis; D053938:DNA Fragmentation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects; D004220:Disulfides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000378:metabolism; D053222:Fas Ligand Protein; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D018922:HL-60 Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects; D019169:Jurkat Cells / Q000187:drug effects / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D010539:Permeability / Q000187:drug effects; D010936:Plant Extracts / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D017382:Reactive Oxygen Species; D013454:Sulfoxides; D051020:bcl-X Protein; D019014:fas Receptor / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000972:Antineoplastic Agents, Phytogenic; C494811:BCL2L1 protein, human; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D004273:DNA, Neoplasm; D004220:Disulfides; D004792:Enzyme Precursors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D010936:Plant Extracts; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013454:Sulfoxides; D051020:bcl-X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; C048980:ajoene; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases