Role of the permeability transition pore in cytochrome C release from mitochondria during ischemia-reperfusion in rat liver.
Ischemia and reperfusion cause mitochondrial dysfunctions that initiate the mitochondrial apoptosis pathway. They involve the release of cytochrome C and the activation of the caspase cascade but the mechanism(s) leading to cytochrome C release is(are) poorly understood. The aim of this study was to analyse the relation between cytochrome C release and the opening of the permeability transition pore (PTP) during in situ liver ischemia and reperfusion. Liver ischemia was induced for 30, 60 and 120 min and blood re-flow was subsequently restored for 30 and 180 min. Ischemia hugely altered mitochondrial functions, i.e., oxidative phosphorylation and membrane potential, and was accompanied by a time-dependent mitochondrial release of cytochrome C into the cytosol and by activations of caspases-3 and -9. PTP opening was not observed during ischemia, as demonstrated by the absence of effect of an in vivo pre-treatment of rats with cyclosporin A (CsA), a potent PTP inhibitor. Cytochrome C release was due neither to a direct effect of caspases onto mitochondria nor to an interaction of Bax or Bid with the mitochondrial membrane but could be related to a direct effect of oxygen deprivation. In contrast, during reperfusion, CsA pre-treatment inhibits cytochrome C release, PTP opening and caspase activation. At this step, cytochrome C release is likely to occur as a consequence of PTP opening. In conclusion, our study reveals that cytochrome C release, and thus the induction of the mitochondrial cell death pathway, occur successively independently and dependent on PTP opening during liver ischemia and reperfusion, respectively.
Département de Pharmacologie, Faculté de Médecine de Paris XII, 8 rue du Général Sarrail, F-94010 Créteil, France. morin@univ-paris12.fr
Didier
D
Morin
Felipe
F
Pires
Catherine
C
Plin
Jean-Paul
JP
Tillement
D000818:Animals; D020169:Caspases / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism*; D004347:Drug Interactions; D000860:Hypoxia / Q000378:metabolism; D007511:Ischemia / Q000201:enzymology*; D008107:Liver Diseases / Q000201:enzymology*; D008928:Mitochondria; D008930:Mitochondria, Liver / Q000201:enzymology*; D010539:Permeability; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015424:Reperfusion
D019253:Proto-Oncogene Proteins c-bcl-2; D016572:Cyclosporine; D045304:Cytochromes c; D020169:Caspases