NHE-1 inhibition-induced cardioprotection against ischaemia/reperfusion is associated with attenuation of the mitochondrial permeability transition.
OBJECTIVE
The possible contribution of the cardiac mitochondrial permeability transition pore (PTP) towards the cardioprotective effects of Na(+)-H(+) exchanger-1 (NHE-1) inhibition was studied in hearts subjected to ischaemia/reperfusion (IR).


RESULTS
Langendorff-perfused rat hearts were subjected to 40 min of global ischaemia and 60 min of reperfusion in the presence or absence of the NHE-1 specific inhibitor AVE-4890 (AVE, 5 microM). Mitochondrial PTP opening was determined in the intact heart using 2-deoxy-[(3)H]-glucose entrapment and in isolated mitochondria by monitoring the decrease of the calcium-induced light scattering. Mitochondrial respiration was measured with a Clark-type oxygen electrode whereas release of apoptosis-inducing factor (AIF) and endonuclease G (EndoG) and levels of cleaved poly-(ADP-ribose) polymerase (PARP) were analysed by western blotting. IR induced mitochondrial PTP opening, which was inhibited by 28% (P < 0.05) with AVE treatment. Mitochondria isolated from AVE-treated hearts demonstrated significantly less calcium-induced swelling and higher substrate oxidation at complex I and II as well as cytochrome c oxidase and citrate synthase activity. AVE treatment also suppressed IR-induced release of AIF and EndoG from mitochondria, prevented the IR-induced rise in cleaved PARP levels, and was associated with significantly enhanced postischaemic recovery of left ventricular developed pressure and a significant decrease in lactate dehydrogenase release. AVE did not affect PTP opening directly in isolated mitochondria.


CONCLUSIONS
The beneficial effect of NHE-1 inhibition in hearts subjected to IR is associated with attenuation of mitochondrial PTP opening and apoptosis and the resultant mitochondrial dysfunction. The effect of AVE on PTP opening most likely is indirect, as pore opening was not affected by direct administration of AVE to mitochondrial suspensions.
Javadov
Sabzali
S
Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, Medical Sciences Building, London, Ontario, Canada N6A 5C1.
Choi
Angel
A
Rajapurohitam
Venkatesh
V
Zeidan
Asad
A
Basnakian
Alexei G
AG
Karmazyn
Morris
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects*; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors*
D051033:Apoptosis Inducing Factor; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D002950:Citrate (si)-Synthase; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D002118:Calcium