ABSTRACT
Objective:To evaluate the relationship between the mechanism of protective effect of hydromorphone postconditioning on myocardium and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway-mediated autophagy in rats.Methods:Forty healthy male Sprague-Dawley rats, weighing 220-250 g, were divided into 5 groups ( n=8 each) using a random number table method: sham operation group (Sham group), ischemia-reperfusion (I/R) group (group IR), hydromorphone postconditioning group (group HP), PI3K inhibitor group (group W) and hydromorphone postconditioning+ PI3K inhibitor group (group HP+ W). Myocardial ischemia was induced by 30 min occlusion of left anterior descending branch of coronary artery followed by 120 min reperfusion.In group HP, hydromorphone 0.1 mg/kg was injected via femoral vein at 5 min before reperfusion in group HP.In group HP+ W, hydromorphone 0.1 mg/kg and wortmannin (PI3K inhibitor) 15 μg/kg were injected via femoral vein at 5 min before reperfusion.In group W, wortmannin 15 μg/kg was injected via femoral vein at 5 min before reperfusion.At the end of reperfusion, the myocardial infarct size (IS) was determined by TTC staining, the activities of serum lactate dehydrogenase (LDH) was detected by colorimetry, myocardial specimens were collected for microscopic examination of the ultrastructure (with a electron microscope), the expression of phosphorylated Akt (p-Akt) and microtubule-associated protein 1 light chain 3 (LC3) was determined by Western blot and the ratio of LC3-Ⅱ/Ⅰwas calculated. Results:Compared with Sham group, IS and the activities of serum of LDH were significantly increased, p-Akt expression in myocardial tissues was up-regulated, the ratio of LC3-Ⅱ/Ⅰwas increased ( P<0.05), autophagic vacuoles were increased and the damage of ultrastructure of cardiomyocytes was obvious in group IR.Compared with group IR, IS and the activities of serum of LDH were significantly decreased, p-Akt expression in myocardial tissues was up-regulated, the ratio of LC3-Ⅱ/Ⅰwas decreased ( P<0.05), autophagic vacuoles were decreased and the damage of ultrastructure of cardiomyocytes was attenuated in group HR.Compared with group HR, IS and the activities of serum of LDH were significantly increased, p-Akt expression in myocardial tissues was down-regulated, the ratio of LC3-Ⅱ/Ⅰwas increased ( P<0.05), autophagic vacuoles were increased and the damage of ultrastructure of cardiomyocytes was aggravated in group HR+ W. Conclusion:The mechanism of protective effect of hydromorphone postconditioning on myocardium is related to activation of PI3K/Akt signaling pathway and inhibition of autophagy in rats.
ABSTRACT
Objective:To investigate the role of PI3K/Akt signaling pathway in hydromorphone postconditioning on alleviating myocardial ischemia/reperfusion (I/R)-induced apoptosis in rats.Methods:Forty healthy male SD rats were randomly(random number) divided into five groups, with 8 rats in each group:①sham group;②I/R group;③I/R+hydromorphone group (I/R+H group);④I/R+PI3K inhibitor group (I/R+W group); and⑤I/R+hydromorphone+PI3K inhibitor group (I/R+H+W group). The myocardial ischemia/reperfusion injury model was established by ligating the left anterior descending coronary artery for 30 min and reperfusion for 120 min. After the experiment, the area of myocardial infarction was measured by 2, 3, 5-triphenyl tetrazolium chloride (TTC) staining. The amount of serum lactate dehydrogenase (LDH) leakage was estimated by colorimetry . The cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) assay. The protein expressions of p-Akt, Bcl-2 and Bax were detected by Western blot. Comparisons among groups were carried out by analysis of variance (ANOVA).Results:Compared with the sham group, the area of myocardial infarction, serum LDH leakage and cardiomyocyte apoptosis were significantly increased, p-Akt and Bax expression were upregulated, Bcl-2 expression was downregulated in the I/R group ( P<0.05). Compared with the I/R group, the area of myocardial infarction, serum LDH leakage and cardiomyocyte apoptosis were markedly decreased, p-Akt and Bcl-2 expression were upregulated and Bax expression was downregulated in the I/R+H group ( P<0.05). Compared with the I/R+H group, the area of myocardial infarction, serum LDH leakage and cardiomyocyte apoptosis were significantly increased, p-Akt and Bcl-2 expression were downregulated, and Bax expression was upregulated in the I/R+H+W group ( P<0.05). Conclusions:Hydromorphone postconditioning can alleviate cardiomyocyte apoptosis induced by myocardial ischemia/reperfusion, and its protection mechanism may be related to the activation of PI3K/Akt signaling pathway.