title: Activation of mitochondria and release of mitochondrial apoptogenic factors by betulinic acid.
abstract: Different classes of anticancer drugs may trigger apoptosis by acting on different subcellular targets and by activating distinct signaling pathways. Here, we report that betulinic acid (BetA) is a prototype cytotoxic agent that triggers apoptosis by a direct effect on mitochondria. In isolated mitochondria, BetA directly induces loss of transmembrane potential independent of a benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone-inhibitable caspase. This is inhibited by bongkrekic acid, an agent that stabilizes the permeability transition pore complex. Mitochondria undergoing BetA-induced permeability transition mediate cleavage of caspase-8 (FLICE/MACH/Mch5) and caspase-3 (CPP32/Yama) in a cell-free system. Soluble factors such as cytochrome c or apoptosis-inducing factor released from BetA-treated mitochondria are sufficient for cleavage of caspases and nuclear fragmentation. Addition of cytochrome c to cytosolic extracts results in cleavage of caspase-3, but not of caspase-8. However, supernatants of mitochondria, which have undergone permeability transition, and partially purified apoptosis-inducing factor activate both caspase-8 and caspase-3 in cytosolic extracts and suffice to activate recombinant caspase-8. These findings show that induction of mitochondrial permeability transition alone is sufficient to trigger the full apoptosis program and that some cytotoxic drugs such as BetA may induce apoptosis via a direct effect on mitochondria.
authors.affiliation: University Children's Hospital, Prittwitzstrasse 43, D-89075 Ulm, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Fulda
authors.forename: C
authors.initials: C
authors.lastname: Scaffidi
authors.forename: S A
authors.initials: SA
authors.lastname: Susin
authors.forename: P H
authors.initials: PH
authors.lastname: Krammer
authors.forename: G
authors.initials: G
authors.lastname: Kroemer
authors.forename: M E
authors.initials: ME
authors.lastname: Peter
authors.forename: K M
authors.initials: KM
authors.lastname: Debatin
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001865:Bongkrekic Acid / Q000494:pharmacology; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma; D053978:Pentacyclic Triterpenes; D010539:Permeability; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D000094062:Betulinic Acid
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C494811:BCL2L1 protein, human; D003574:Cytochrome c Group; D053978:Pentacyclic Triterpenes; D019253:Proto-Oncogene Proteins c-bcl-2; D014315:Triterpenes; D051020:bcl-X Protein; D001865:Bongkrekic Acid; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D000094062:Betulinic Acid