A study on the relationship between succinate dehydrogenase and mitoKATPC in the mechanism of ischemic postconditioning protecting against MIRI under CPB in adult rats

Abstract

Abstract Objective: To explore the relationship between succinate dehydrogenase and mitoKATPC in the mechanism of ischemic postconditioning (IPO) attenuating myocardial ischemia-reperfusion injury (MIRI) under CPB in adult rats. Methods: 160 adult male SD rats, SPF grade, weighing 300-350g. Established adult rat CPB ischemia-reperfusion and IPO models. Randomly divided into 8 groups with 20 animals in each group: normal group (Nor), SDH competitive inhibitor Dimethyl malonate (dm) control group (dm+ Nor), ischemia-reperfusion group (I// R), dm+ ischemia-reperfusion group (dm+ I/R), ischemia postconditioning group (IPO), dm+ ischemic postconditioning group (dm+ IPO), mitoKATPC specific inhibitor 5-hydroxydecanoic acid (5-HD) + ischemic postconditioning group (5-HD+IPO), dm+5-HD+ischemic postconditioning group (dm+5-HD+IPO). The blood was collected at the end of reperfusion and the rat hearts were harvested for the following tests: 1. Measure the myocardial infarct size (IS); 2. Observing the ultrastructure of the myocardium and calculating the mitochondrial Flameng score of the myocardial cells; 3. Creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) concentrations; 4. Reactive oxygen species (ROS) generation under confocal microscopy; 5. Myocardial determination SDH activity, content of succinic acid (SA) and fumaric acid (FA); 6. Determination of mRNA and protein expression of succinate dehydrogenase flavoprotein (SDHA) in myocardial tissue. Results: Compared with the Nor group, IS, mitochondrial Flameng score, CK-MB, cTnI, ROS content, SDH activity, SA content, SDHA mRNA expression and SDHA protein expression were significantly increased in the I/R group (P<0.05). Compared with the dm+ Nor group, there was no statistical difference (P>0.05); compared with the I/R group, both were decreased in the dm+ I/R group and the IPO group (P<0.05); compared with the IPO group, the dm+ IPO group decreased, and the 5-HD+IPO group increased (P＜0.05); there was no significant difference between the 5-HD+IPO group and the dm+5-HD+IPO group (P＞0.05) . The FA content is the opposite of the above results. Conclusion: The activity of SDH in myocardial ischemia is significantly increased, which leads to a significant increase in the expression of SDHA, which is involved in the mechanism of myocardial ischemia-reperfusion injury and inhibits the activity of SDH, which can effectively reduce MIRI. Ischemic postconditioning can open mitoKATPC and inhibit the activity of SDH to protect MIRI. The inhibitory effect of ischemic postconditioning on SDH activity is achieved by opening mitoKATPC.