sanglifehrin-a and Myocardial-Ischemia

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.. 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).. This study demonstrates that the mPTP plays a critical role in the cardioprotection elicited by ischemic and pharmacological preconditioning and postconditioning.

Topics: Animals; Bradykinin; Cyclophilins; Cyclosporine; Diazoxide; Enzyme Inhibitors; Female; Ischemic Preconditioning, Myocardial; Lactones; Male; Mice; Mice, Knockout; Mitochondria, Heart; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Models, Animal; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Peptidyl-Prolyl Isomerase F; Spiro Compounds; Vasodilator Agents

Transient (low-conductance) opening of the mitochondrial permeability transition pore (mPTP) may limit mitochondrial calcium load and mediate mitochondrial reactive oxygen species (ROS) signaling. We hypothesize that transient mPTP opening and ROS mediate the protection associated with myocardial preconditioning and mitochondrial uncoupling.. Isolated perfused rat hearts were subjected to 35 minutes of ischemia/120 minutes of reperfusion, and the infarct-risk-volume ratio was determined by tetrazolium staining. Inhibiting mPTP opening during the preconditioning phase with cyclosporine-A (CsA, 0.2 micromol/L) or sanglifehrin-A (SfA, 1.0 micromol/L) abolished the protection associated with ischemic preconditioning (IPC) (20.2+/-3.6% versus 45.9+/-2.5% with CsA, 49.0+/-7.1% with SfA; P<0.001); and pharmacological preconditioning with diazoxide (Dzx, 30 micromol/L) (22.1+/-2.7% versus 46.3+/-3.0% with CsA, 48.4+/-5.5% with SfA; P<0.001), CCPA (the adenosine A1-receptor agonist, 200 nmol/L) (24.9+/-4.5% versus 54.4+/-6.6% with CsA, 42.6+/-9.0% with SfA; P<0.001), or 2,4-dinitrophenol (DNP, the mitochondrial uncoupler, 50 micromol/L) (15.7+/-2.7% versus 40.8+/-5.5% with CsA, 34.3+/-3.1% with SfA; P<0.001), suggesting that mPTP opening during the preconditioning phase is required to mediate protection in these settings. Inhibiting ROS during the preconditioning protocols with N-mercaptopropionylglycine (MPG, 1 mmol/L) also abolished the protection associated with IPC (20.2+/-3.6% versus 47.1+/-3.8% with MPG; P<0.001), diazoxide (22.1+/-2.7% versus 56.3+/-3.8% with MPG; P<0.001), and DNP (15.7+/-2.7% versus 50.7+/-6.6% with MPG; P<0.001) but not CCPA (24.9+/-4.5% versus 26.5+/-8.4% with MPG; P=NS). Further experiments in adult rat myocytes demonstrated that diazoxide induced CsA-sensitive, low-conductance transient mPTP opening (represented by a 28+/-3% reduction in mitochondrial calcein fluorescence compared with control; P<0.01).. We report that the protection associated with IPC, diazoxide, and mitochondrial uncoupling requires transient mPTP opening and ROS.

Topics: 2,4-Dinitrophenol; Adenosine; Adrenergic alpha-1 Receptor Agonists; Adrenergic alpha-Agonists; Animals; Cardiotonic Agents; Cells, Cultured; Cyclosporine; Diazoxide; Electric Conductivity; Ion Channel Gating; Ion Channels; Ion Transport; Ischemic Preconditioning, Myocardial; Lactones; Macromolecular Substances; Male; Mitochondria, Heart; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Oxidative Phosphorylation; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Signal Transduction; Spiro Compounds; Uncoupling Agents; Vasodilator Agents