Résumé
Objective Several studies have indicated that miR-15a,miR-15b and miR-16 may be the important regulators of apoptosis.Since attenuate apoptosis could protect myocardium and reduce infarction size,the present study was aimed to find out whether these miRNAs participate in regulating myocardial ischemia reperfusion (I/R) injury.Methods Apoptosis in mice hearts subjected to I/R was detected by TUNEL assay in vivo,while flow cytometry analysis followed by Annexin V/PI double stain in vitro was used to detect apoptosis in cultured cardiomyocytes which were subjected to hypoxia/reoxygenation (H/R).Taqman real-time quantitative PCR was used to confirm whether miR-15a/15b/16 were involved in the regulation of cardiac I/R and H/R.Results Compared to those of the controls,I/R or H/R induced apoptosis of cardiomyocytes was significantly iucreased both in vivo (24.4％ ± 9.4％ vs.2.2％ ± 1.9％,P ＜ 0.01,n =5) and in vitro (14.12％ ±0.92％ vs.2.22％ ± 0.08％).The expression of miR-15a and miR-15b,but not miR-16,was increased in the mice I/R model,and the results were consistent in the H/R model.Conclusions Our data indicate miR-15 and miR-15b are up-regulated in response to cardiac I/R injury,therefore,down-regulation of miR- 15a/b may be a promising strategy to reduce myocardial apoptosis induced by cardiac I/R injury.
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Objective To investigate the effect of sevoflurane pretreatment on the expression of cystathionine β-synthase(CBS)and heme oxygerase-1(HO-1)during myocardial ischemia-reperfusion(I/R)injury in rats.Methods Thirty adult male SD rats,weighing 180-220 g,were randomly divided into 3 groups(n =10each):sham operation group(group S),I/R group and sevoflurane group(group Sev).Myocardial I/R injury was produced by ligation of the left anterior descending branch of coronary artery for 30 min followed by 2 h reperfusioo.In group Sev,sevoflurane was inhaled before ischemia,the end-tidal concentration was 1.5％-1.7％ and myocardial I/R was produced 60 min later.The rats were sacrificed at 2 h of reperfusion and myocardial tissues were taken for determination of the contents of MDA,GSH,H2S and CO,SOD activity and expression of CBS mRNA and HO-I mRNA.The ultrastructure of myocardium was examined with electron microscope.Results Compared with group S,the contents of MDA,H2S and CO were significantly increased,the expression of CBS mRNA and HO-1 mRNA was up-regulated,and SOD activity and GSH content were significantly decreased in groups I/R and Sev(P ＜ 0.05).Compared with group I/R,the contents of MDA,H2S and CO were significanfly decreased,the expression of CBS mRNA and HO-1 mRNA was down-regulated,SOD activity and GSH content were significantly increased in group Sev.The damage to mitochondrial structure induced by I/R was mitigated by pretreatment with sevoflurane.Conclusion The mechanism by which sevoflurane pretreatment reduces myocardial I/R injury is related to down-regulation of the expression of CBS and HO-1 and decrease in the activities in rats.
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Objective To investigate the effects of phosphocreatine on apoptosis following myocardial ischemia-reperfusion (I/R) in diabetic rats. Methods Male SD rats weighing 150-170 g were used in this study.Diabetes mellitus was induced by high fat diet and intraperitoneal streptozotocin. Twenty-seven rats in which diabetes mellitus was successfully induced were randomly divided into 3 groups ( n = 9 each): sham operation group (group S);myocardial I/R group(group I/R )and phosphocreatine group (group PP). Myocardial I/R was induced by 30 min occlusion of left anterior descending branch of coronary artery followed by 2 h reperfusion in I/R and PP groups. In group PP phosphocreatine 1 g/kg was given intraperitoneally 30 min before myocardial I/R. Blood samples were collected at the end of 2 h reperfusion for determination of plasma concentration of calcium troponin T (cTnT). The animals were then sacrificed and iscbemic myocardial specimens were isolated. The expression of Bcl-2, Bax and Caspase-3 in isehemic myocarcdium was determined and Bcl-2/Bax ratio was calculated. Myocardial apoptosis was detected by TUNEL and apoptotic index was calculated. The ultrastructure of cardiomyocytes was examined with electron microscope. Results Myocardial I/R significantly increased plasma cTnT concentration and Bcl-2, Bax and Caspase-3 expression in myocardium and apoptosis index and decreased Bcl-2/Bax ratio. Phosphocreatine significantly attenuated I/R-induced above-mentioned changes and myocardial damage. Conclusion Phosphocreatine can reduce myocardial I/R injury in diabetic mellitus rats by reducing myocardial apoptosis through up-regulation of Bcl-2 expression and down-regulation of Bax and Caspase-3 expression.
Résumé
Objective To investigate the effect of sevoflurane (Sero) preconditioning (Precon) on cardiomyocyte apoptosis following myocardial ischemia-reperfusion (I/R) in rats. Methods Sixty-four adult male SD rats weighing 270-350 g were randomly divided into 4 groups ( n = 16 each): group Ⅰ sham operation (group S); group Ⅱ myocardial I/R; group Ⅲ Sero and group Ⅳ Sevo-Precon + myocardial I/R. The animals were anesthetized with intraperitoneal pentobarbital 50 mg/kg, intubated and mechanically ventilated. PET CO2 was maintained at 35-45 mm Hg. Myocardial I/R was induced by 30 min occlusion of the left anterior descending branch of coronary artery followed by 2 h reperfusion in group Ⅱ and Ⅳ . In group Ⅲ the animals inhaled 2.5 % sevoflurane for 30 min while in group Ⅳ the animals inhaled 2.5% sevoflurane for 30 min at 15 min before myocardial I/R. Eight animals were killed at the end of 2 h reperfusion in each group. The hearts were removed for determination of myocardial infarct size (IS) as a percentage of area at risk (AAR) (IS/AAR) by triphenyl tetrazolium chloride staining. Myocardial apoptosis was detected using TUNEL and apoptosis index (AI) was calculated. Another 4 animals were killed before ischemia and at the end of 2 h reperfusion for determining the expression of Bcl-2 and caspase-3 protein in myocardium by Western blot. Results Sevoflurane preconditioning significantly decreased infarct size and AI in group Ⅳ as compared with group Ⅱ (group I/R). Bcl-2 protein expression was significantly decreased and caspase-3 protein expression was significantly increased after 2 h reperfusion as compared with the expression before ischemia in group I/R (group Ⅱ ). Sevoflurane preconditioning significantly reversed the I/R-induced changes in Bcl-2 and caspase-3 protein expression. Conclusion Sevoflurane preconditioning can attenuate myocardial I/R injury by decreasing myocardial apoptosis.