Isoflurane protects cardiomyocytes and mitochondria by immediate and cytosol‐independent action at reperfusion

Abstract

Background and purpose:The volatile anaesthetic isoflurane protects the heart from ischaemia and reperfusion (I/R) injury when applied at the onset of reperfusion [anaesthetic postconditioning (APoC)]. However, the mechanism of APoC-mediated protection is unknown. In this study, we examined the effect of APoC on mitochondrial bioenergetics, mitochondrial matrix pH (pHm) and cytosolic pH (pHi), and intracellular Ca 2+ . Experimental approach: Cardiac mitochondria from Wistar rats were isolated after in vivo I/R with or without APoC (1.4%-vol isoflurane, 1 minimum alveolar concentration), and mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential (DYm), and oxygen consumption were assessed. In isolated cardiomyocytes and isolated mitochondria I/R injury was produced in vitro, with or without APoC (0.5 mM isoflurane). Intracellular Ca 2+ , pHm, pHi and DYm were monitored with SNARF-1, TMRE and fluo-4, respectively. Myocyte survival was assessed when APoC was induced at pH 7.4 and 7.8. In isolated mitochondria oxygen consumption and ATP synthesis were measured. Key results: In vivo APoC protected against mPTP opening, slowed mitochondrial respiration and depolarized mitochondria. APoC decreased the number of hypercontracted cardiomyocytes at pH 7.4, but not at pH 7.8. APoC attenuated intracellular Ca 2+ accumulation, maintained lower pHm, and preserved DYm during reoxygenation. Isoflurane did not affect the regulation of cytosolic pH. In mitochondria, APoC preserved ATP production rate and respiration. Conclusions and implications: At reperfusion, APoC inhibited mitochondrial respiration, depolarized mitochondria and acidified pHm. These events may lead to inhibition of mPTP opening and, consequently, to preserved DYm and ATP synthesis. This reduces intracellular Ca 2+ overload and cell death.

Enhanced charge-independent mitochondrial free Ca2+ and attenuated ADP-induced NADH oxidation by isoflurane: Implications for cardioprotection

“…This notion is substantiated by the measured time-courses of matrix pH with BCECF-AM dye that showed no change in matrix pH at different concentrations of isoflurane compared to the control and DMSO groups (data not shown). This appears to rule out the possibility that isoflurane has a protonophoric effect to allow H + leak through the IMM [35], which would itself enhance the respiratory rate, but which is the opposite of what was observed.…”

Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes

“…Mitochondria are primary mediators of cardiac ischemia-reperfusion (IR) injury [1–4]; they are also important targets for volatile anesthetic (VA)-induced cardioprotection against IR injury [3, 5–12]. Cardioprotection by a VA can be instituted either before the onset of ischemia (anesthetic pre-conditioning: APC) or at the onset of reperfusion (anesthetic post-conditioning: APOC) [13, 14].…”

Effects of isoflurane postconditioning on chronic phase of ischemia–reperfusion heart injury in rats

“…In the current study (the rats sacrificed on day 14 after reperfusion), we observed an additional 10% reduction of infarct size in isoflurane-treated animals in comparison to the control group (comparing both absolute infarct size in square millimeters and proportion of infarcted area related to the left ventricular surface area). We suggest that this was caused by the influence of isoflurane on the formation of highly vascularized granulation tissue and that this effect was additive to the one proven in numerous short-term studies caused by a decrease of apoptotic cell numbers [27,28].…”