Preconditioning and postconditioning: the essential role of the mitochondrial permeability transition pore.
OBJECTIVE
The opening of the mitochondrial permeability transition pore (mPTP) at the time of myocardial reperfusion is a critical determinant of cell death. Emerging studies suggest that suppression of mPTP opening may underlie the cardioprotection elicited by both ischemic preconditioning (IPC) and postconditioning (IPost). To further evaluate the role of the mPTP in cardioprotection, we hypothesized that hearts deficient in cyclophilin-D (CYP-D-/-), a key component of the mPTP, will be resistant to cardioprotection conferred by ischemic and pharmacological preconditioning and postconditioning.


RESULTS
Male/female wild type or CYP-D-/- mice were subjected to 30 min of ischemia and 120 min of reperfusion. In wild type mice subjected to in vivo myocardial ischemia-reperfusion injury, a significant reduction in myocardial infarct size was observed with the following treatments (n>/=6/group; P<0.05): (1) IPC (28+/-4% vs. 46.2+/-4% in control); (2) Diazoxide (5 mg/kg) pre-treatment (26.4+/-3% vs. 54+/-10% in vehicle control); (3) IPost-1 or IPost-2, three or six 10-s cycles of ischemia-reperfusion (27.2+/-3% and 32+/-4%, respectively vs. 46.2+/-4% in control); (4) Bradykinin (40 mug/kg) (28.3+/-1% vs. 48+/-4% in vehicle control); (5) cyclosporin-A (10 mg/kg) (32.3+/-3% vs. 48+/-4% in vehicle control) (6) sanglifehrin-A (25 mg/kg) (29.3+/-3% vs. 48+/-4% in vehicle control). Interestingly, however, no infarct-limiting effects were demonstrated in CYP-D-/- mice with the same treatment protocols: (27.9+/-5% in control vs. 31.2+/-7% with IPC, 30.2+/-5% with IPost-1, 24.7+/-8% with IPost-2; 30.1+/-4% in vehicle control vs. 26.4+/-7% with diazoxide; 24.6+/-4% in vehicle control vs. 24.9+/-5% with bradykinin, 26.8+/-7% with cyclosporin-A, 32.5+/-6% with sanglifehrin-A: n>/=6/group: P>0.05).


CONCLUSIONS
This study demonstrates that the mPTP plays a critical role in the cardioprotection elicited by ischemic and pharmacological preconditioning and postconditioning.
Lim
Shiang Y
SY
The Hatter Cardiovascular Institute, University College London Hospital and Medical School, 67 Chenies Mews, London WC1E 6HX, UK.
Davidson
Sean M
SM
Hausenloy
Derek J
DJ
Yellon
Derek M
DM
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019157:Ischemic Preconditioning, Myocardial; D007783:Lactones / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins / Q000502:physiology*; D000083162:Mitochondrial Permeability Transition Pore; D023421:Models, Animal; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D013141:Spiro Compounds / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D000081406:Peptidyl-Prolyl Isomerase F; D004791:Enzyme Inhibitors; D007783:Lactones; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C000631446:PPIF protein, mouse; D013141:Spiro Compounds; D014665:Vasodilator Agents; C121329:sanglifehrin A; D016572:Cyclosporine; D021983:Cyclophilins; D003981:Diazoxide; D001920:Bradykinin