Objective To evaluate effect of dexmedetomidine on mitochondrion-dependent apoptosis during hypoxia-reoxygenation (H/R) injury to hippocampal neurons of rats.Methods The primarily cultured hippocampal neurons of Sprague-Dawley rats were divided into 4 groups (n =40 each) using a random number table method:control group (C group),vehicle group (V group),H/R group and dexmedetomidine group (D group).Hippocampal neurons were subjected to oxygen-glucose deprivation followed by restoration of oxygen supply to establish the model of H/R injury.Dexmedetomidine 1 μmol/L was added at 6 h of reoxygenation in D group.The viability of neurons was measured by methyl thiazolyl tetrazolium assay at 20 h of reoxygenation.The ultrastructure of mitochondria was observed by transmission electron microscopy.The expression of cytochrome c (Cyt c),caspase-3,Fis1 and Drp1 was detected by Western blot.The neuronal apoptosis was detected by flow cytometry,and apoptosis rate was calculated.Results Compared with C group,no significant change was found in the viability of neurons in group V (P＞0.05),and the viability of neurons was significantly decreased,the apoptosis rate was increased,the expression of Cyt c,caspase-3,Fis1 and Drp1 was up-regulated (P＜0.05),and the damage to mitochondrial ultrastructure was accentuated in H/R and D groups.Compared with H/R group,the viability of neurons was significantly increased,the apoptosis rate was decreased,the expression of Cyt c,caspase-3,Fis1 and Drp1 was down-regulated (P＜0.05),and the damage to mitochondrial ultrastructure was significantly attenuated in D group.Conclusion The nechanism by which dexmedetomidine reduces the H/R injury to hippocampal neurons is related to inhibiting mitochondrion-dependent apoptosis in rats.

Objective:To investigate the role of receptor-interacting protein kinse3 (RIPK3)-mediated necroptosis in diabetic mellitus-caused abolition of cardioprotection induced by sevoflurane postconditioning in rats.Methods:Eighty rats with diabetes mellitus, aged 4-5 weeks, weighing 90-100 g, were divided into 4 groups ( n=20 each) using a random number table method: sham operation group (group Sham), myocardial ischemia-reperfusion (I/R) group (group I/R), sevoflurane postconditioning group (group SP) and sevoflurane postconditiong plus RIPK3 inhibitor GSK-872 group (group GSK). Myocardial I/R was induced by 40 min occlusion of the left anterior descending branch of the coronary artery followed by 120 min reperfusion.In group SP, 2.4% sevoflurane was inhaled for 15 min at the beginning of reperfusion.In group GSK, GSK-872 3.3 mg/kg (dissolved in normal saline) was intraperitoneally injected at 24 and 2 h before surgery, and the other treatments were similar to those previously described in group SP.After 120 min of reperfusion, blood samples from the abdominal aorta were collected for determination of concentrations of serum lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB). Myocardial tissues were taken for determination of percentage of myocardial infarct size (by TTC staining) and expression of RIPK3, phospho-Ca 2+ -calmodulin-dependent protein kinase Ⅱ (p-CaMKⅡ) and phospho-mixed lineage kinase domain-like protein (p-MLKL) (by Western blot), and the ultrastructure of myocardium was observed by transmission electron microscopy. Results:Compared with group Sham, the serum LDH and CK-MB concentrations and percentage of myocardial infarct size were significantly increased, the expression of RIPK3, p-MLKL and p-CaMKⅡ in myocardial tissues was up-regulated ( P<0.05), and the damage to cardiomyocytes was severe in group I/R.Compared with group I/R, no significant change was found in the parameters mentioned above in group SP ( P>0.05). Compared with group SP, the serum LDH and CK-MB concentrations and percentage of myocardial infarct size were significantly decreased, the expression of RIPK3, p-MLKL and p-CaMKⅡ in myocardial tissues was down-regulated ( P<0.05), and the damage to cardiomyocytes was reduced in group GSK. Conclusion:The mechanism of diabetic mellitus-caused abolition of cardioprotection induced by sevoflurane postconditioning is related to excessive activation of RIPK3-mediated necroptosis in rats.