Cardiovascular Research Advance Access [Accepted Manuscript] published online on October 18, 2007
Cardiovascular Research, doi:10.1093/cvr/cvm039
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NHE-1 inhibition-induced cardioprotection against ischemia/reperfusion is associated with attenuation of the mitochondrial permeability transition
NHE-1 inhibition attenuates mitochondrial permeability transition in IR
Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
1 Division of Nephrology, Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
* Address for correspondence: Dr M Karmazyn Department of Physiology and Pharmacology Schulich School of Medicine and Dentistry University of Western Ontario London, Ontario N6A 5C1 Canada Tel: (519) 661-3872 Fax: (519) 661-3827 E-mail: morris.karmazyn{at}schulich.uwo.ca
Aims: 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 ischemia/reperfusion (IR).
Methods: Langendorff-perfused rat hearts were subjected to 40 min of global ischemia and 60 min of reperfusion in the presence or absence of the NHE-1 specific inhibitor AVE-4890 (AVE, 5µM). Mitochondrial PTP opening was determined in the intact heart using 2-deoxy-[3H]-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 analyzed by Western blotting.
Results: 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 postischemic 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.
KEYWORDS heart; ischemia; reperfusion; mitochondria; sodium-hydrogen exchanger; apoptosis
Time for primary review: 23 days
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