Mitochondrial cyclophilin-D as a critical mediator of ischaemic preconditioning.
OBJECTIVE
It has been suggested that mitochondrial reactive oxygen species (ROS), Akt and Erk1/2 and more recently the mitochondrial permeability transition pore (mPTP) may act as mediators of ischaemic preconditioning (IPC), although the actual interplay between these mediators is unclear. The aim of the present study is to determine whether the cyclophilin-D (CYPD) component of the mPTP is required by IPC to generate mitochondrial ROS and subsequently activate Akt and Erk1/2.


RESULTS
Mice lacking CYPD (CYPD-/-) and B6Sv129 wild-type (WT) mice were used throughout. We have demonstrated that under basal conditions, non-pathological mPTP opening occurs (indicated by the percent reduction in mitochondrial calcein fluorescence). This effect was greater in WT cardiomyocytes compared with CYPD-/- ones (53 ± 2% WT vs. 17 ± 3% CYPD-/-; P < 0.01) and was augmented by hypoxic preconditioning (HPC) (70 ± 9% WT vs. 56 ± 1% CYPD-/-; P < 0.01). HPC reduced cell death following simulated ischaemia-reperfusion injury in WT (23.2 ± 3.5% HPC vs. 43.7 ± 3.2% WT; P < 0.05) but not CYPD-/- cardiomyocytes (19.6 ± 1.4% HPC vs. 24.4 ± 2.6% control; P > 0.05). HPC generated mitochondrial ROS in WT (four-fold increase; P < 0.05) but not CYPD-/- cardiomyocytes. HPC induced significant Akt phosphorylation in WT cardiomyocytes (two-fold increase; P < 0.05), an effect which was abrogated by ciclosporin-A (a CYPD inhibitor) and N-2-mercaptopropionyl glycine (a ROS scavenger). Finally, in vivo IPC of adult murine hearts resulted in significant phosphorylation of Akt and Erk1/2 in WT but not CYPD-/- hearts.


CONCLUSIONS
The CYPD component of the mPTP is required by IPC to generate mitochondrial ROS and phosphorylate Akt and Erk1/2, major steps in the IPC signalling pathway.
Hausenloy
Derek J
DJ
The Hatter Cardiovascular Institute, University College London Hospital and Medical School, London WC1E 6HX, UK. d.hausenloy@ucl.ac.uk
Lim
Shiang Y
SY
Ong
Sang-Ging
SG
Davidson
Sean M
SM
Yellon
Derek M
DM
D000818:Animals; D016923:Cell Death; D015687:Cell Hypoxia; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D004195:Disease Models, Animal; D004789:Enzyme Activation; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
D000081406:Peptidyl-Prolyl Isomerase F; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C000631446:PPIF protein, mouse; D017382:Reactive Oxygen Species; D016572:Cyclosporine; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D021983:Cyclophilins
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