Ischemic preconditioning preserves proton leakage from mitochondrial membranes but not oxidative phosphorylation during heart reperfusion

Abstract

The aim of this study was to evaluate the role of mitochondria in the recovery of cardiac energetics induced by ischaemic preconditioning at reperfusion. Isolated rat hearts were aerobically perfused (control), subjected to global ischaemia and reperfusion (reperfusion), or subjected to 3 brief cycles of ischaemia/reperfusion and then to the protocol of reperfusion (preconditioning). At the end of the perfusion, antimycin A was delivered to the heart for 25 min, to inhibit mitochondrial respiration and stimulate glycolysis. The increased amount of lactate released in the coronary effluent was correlated with the number of viable cells producing this end-product of glycolysis. Preconditioned hearts released 18% more lactate than reperfused hearts (p < 0.05). This result indicates that preconditioning partially preserved cell viability, as was also evidenced by the MTT assay performed on cardiac biopsies. The difference between antimycin A-stimulated and basal lactate concentration, representing the contribution of mitochondria to the overall energetics of cardiac tissue, was also 18% more elevated in the preconditioned hearts than in the reperfused hearts (p < 0.01). The study of the respiratory function of mitochondria isolated at the end of perfusion, showed that preconditioning did not improve the oxygen-dependent production of ATP (state 3 respiration, ADP/O). On the contrary, state 4 respiration, which is related to proton leakage, was 35.0% lower in the preconditioned group than reperfusion group (p < 0.05). Thus, preconditioning ameliorates cardiac energetics by preserving cell death, but without affecting mitochondrial oxidative phosphorylation. Mitochondria can contribute to cell survival by the attenuation of proton leak from inner membrane.

Priming adult stem cells by hypoxic pretreatments for applications in regenerative medicine

“…Almost conclusive findings demonstrate that mitochondria are the main intracellular orchestrator of IP-induced cytoprotection, following the opening of mitochondrial potassium channels (mitoKATP) that trigger anti-apoptotic responses [60]. Mitochondria primed by IP also contribute to cell survival by attenuating proton leakage from the inner membrane [61]. …”

Nasal vaccination with troponin reduces troponin specific T-cell responses and improves heart function in myocardial ischemia-reperfusion injury

“…Cardiac reductase activity of 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide (MTT) to formazan was determined using an MTT assay (24). Cardiac myocyte cultures were established from newborn C57BL/6 mice.…”

“…Mitochondrial membrane lipids, proteins and nucleic acids are all subject to ROSmediated damage. Measurement of MTT has been used to assess myocyte cell function (24). The MTT assay measures only mitochondrial reductase enzymes, and thus is directly related to the number of viable cells.…”

Renal protection by delayed ischaemic preconditioning is associated with inhibition of the inflammatory response and NF‐κB activation

“…[4][5][6][7] Brief and sublethal prior ischaemia renders an organ more tolerant to subsequent prolonged I/R injury, and this phenomenon is called 'ischaemic preconditioning' (IPC). There are two temporally and mechanistically distinct types of protection afforded by IPC, 4 acute and delayed IPC.…”