Effect of emulsified isoflurane postconditioning on mitophagy during myocardial ischemia-reperfusion in rats

Objective To evaluate the effect of emulsified isoflurane postconditioning on mitophagy during myocardial ischemia-reperfusion(I/R)in rats. Methods Forty-eight pathogen-free healthy male Sprague-Dawley rats, aged 4-5 months, weighing 250-300 g, were divided into 4 groups(n=12 each)using a random number table: sham operation group(group S), group I/R, fat emulsion group(group F)and emulsified isoflurane postconditioning group(group EIP). Myocardial I/R was induced by occlusion of the anterior descending branch of the left coronary artery for 30 min followed by 120 min of reperfusion in pentobarbital sodium-anesthetized rats.Starting from 3 min before reperfusion, 8% emulsified isoflurane 2 ml/kg was intravenously infused over 8 min in group EIP, while 30% fat emulsion 2 ml/kg was intravenously infused over 8 min in group F. Rats were sacrificed at the end of reperfusion, and hearts were removed for measurement of the myocardial infarct size(by 2, 3, 5-triphenyltetrazolium chloride staining), cell apoptosis(by TUNEL), mitochondrial membrane potential and expression of microtubule-associated protein 1 light chain 3(LC3), Beclin1, P62, PINK1 and Parkin in cardiomyocytes(by using Western blot). Apoptosis index(AI)was calculated. Results Compared with group S, the myocardial infarct size and AI were significantly increased, the mitochondrial membrane potential was decreased, the expression of LC3, Beclin1, PINK1 and Parkin was up-regulated, and the expression of P62 was down-regulated in I/R, F and EIP groups(P<0.05). Compared with group I/R, the myocardial infarct size and AI were significantly decreased, the mitochondrial membrane potential was increased, the expression of LC3, Beclin1, PINK1 and Parkin was down-regulated, and the expression of P62 was up-regulated in group EIP(P<0.05). Compared with group F, the myocardial infarct size and AI were significantly decreased, the mitochondrial membrane potential was increased, the expression of LC3, Beclin1, PINK1 and Parkin was down-regulated, and the expression of P62 was up-regulated in group EIP(P<0.05). Conclusion The mechanism by which emulsified isoflurane postconditioning reduces myocardial I/R injury is related to inhibition of mitophagy in rats. Key words: Isoflurane; Fat emulsions, intravenous; Myocardial reperfusion injury; Mitochondria; Autophagy; Ischemic postconditioning