Polyamines directly induce release of cytochrome c from heart mitochondria.
Cytochrome c release from mitochondria to the cytosol represents a critical step in apoptosis, correlated to the activation of the caspase cascade. In this report, we show that addition of micromolar concentrations of polyamines to isolated rat heart mitochondria induces the release of cytochrome c. Spermine, which is effective at concentrations of 10-100 microM, is more potent than spermidine, whereas putrescine has no effect up to 1 mM. The release of cytochrome c caused by spermine is a rapid, saturable and selective process that is independent of mitochondria damage. Spermine, unlike polylysine, is able to release a discrete amount of cytochrome c from intact, functional mitochondria. The cytochrome c-releasing power of spermine is not affected by cyclosporin A, differently from the effect of permeability transition inducers. In a cardiac cell-free model of apoptosis, the latent caspase activity of cytosolic extracts from cardiomyocytes could be activated by cytochrome c released from spermine-treated heart mitochondria. These data indicate a novel mechanism of cytochrome c release from the mitochondrion, and suggest that prolonged and sustained elevation of polyamines, characteristic of some pathologies such as heart hypertrophy, could be involved in the development of apoptosis.
Stefanelli
C
C
Dipartimento di Biochimica 'G. Moruzzi', Università di Bologna, Via Irnerio, 48. I-40126 Bologna, Italy. cstefan@biocfarm.unibo.it
Stanic'
I
I
Zini
M
M
Bonavita
F
F
Flamigni
F
F
Zambonin
L
L
Landi
L
L
Pignatti
C
C
Guarnieri
C
C
Caldarera
C M
CM
D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002457:Cell Extracts; D002642:Chick Embryo; D016572:Cyclosporine / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology; D010539:Permeability / Q000187:drug effects; D011073:Polyamines / Q000494:pharmacology*; D011107:Polylysine / Q000494:pharmacology; D011700:Putrescine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology
D002457:Cell Extracts; D003574:Cytochrome c Group; D011073:Polyamines; D011107:Polylysine; D013096:Spermine; D016572:Cyclosporine; D020169:Caspases; D013095:Spermidine; D011700:Putrescine