Résumé
Objective To investigate the effect of mild hypothermia combined with mitochondrial divison inhibitor 1 in mitochondrial after cerebral ischemia-reperfusion (IR).Methods Fourty male healthy Sprague-Dawley (SD) rats, weighing 280-320 g, were randomly divided into 5 groups (n=8 each): group Sham, group IR, hypothermia group (group H), Mdivi-1 group (group M) and hypothermia+Mdivi-1 group (group HM).Animal models of global cerebral IR were established by transoesophageal cardiac pacing inducing cardiac arrest followed by cardiopulmonary resuscitation (ischemia 4 min and reperfusion 6 h).The group Sham was similarly treated to group IR except the cardiac arrest and cardiopulmonary resuscitation.In groups H and HM, the core temperature was cooled down to 32-34℃ within 15 min starting from the beginning of reperfusion, and maintained for 6 h.In the other groups, the core temperature was maintained at the normal temperature.In groups M and HM, the animals were given Mdivi-1 (1.2 mg/kg) intravenously at the beginning of the reperfusion and the other groups were given the same Volume of dimethylsnlfone (DMSO).After 6 h of reperfusion, the rats were sacrificed, and bilateral hippocampi were immediately removed for determination the protein level of dynamin-related proten 1 (Drp1) and cytochrome C (Cyt-C) expression by Western blot and obsevation of the mitochondrial structure of pyramidal cell in hippocampal CA1 under electronic microscope.Results Compared with group Sham, the expression of Drp1 and Cyt-C was up-regulated in groups IR, H, M and HM (P＜0.05).Compared with group IR, the expression of Drp1 and Cyt-C was down-regulated in groups H, M and HM (P＜0.05).Compared with groups H and M, the expression of Drp1 and Cyt-C was down-regulated in group HM (P＜0.05).There was no significant difference in the expression of Drp1 and Cyt-C between groups H and M.The mitochondria were rod-shaped with clear and sound structure in group Sham, while mitochondria showed various degree of fission, swollen structures, matrix deposit, vacuoles formation and cristae collapse in other groups.The changes of group HM were relatively slight.Conclusion Mild hypothermia combined with mitochondrial divison inhibitor 1 alleviate mitochondrial damage after global cerebral IR of rats.The combined effect is better than that of any individual application.
Résumé
Objective To investigate the effects of mitochondrial division inhibitor 1 (mdivi-1) in rats after cardiopulmonary resuscitation (CPR) and its mechanism.Methods Fifty Sprague-Dawley (SD) rats were randomly (random number table) divided into sham group (n =8),cardiac arrest (CA) model group (n =14),dimethyl sulfoxide post-treatment control group (DMSO group,n =14),and mdivi-1 post-treatment group (mdivi-1 group,n =14).Asphyxial CA was reproduced in animals,and they were resuscitated by CPR.In the mdivi-1 group or DMSO group,the animals were given mdivi-1 (1.2 mg/kg) or DMSO (0.1％) intravenously after restoration of spontaneous circulation (ROSC).The neurological functions were assessed using neurological deficit score (NDS) determined at 24,48 and 72 hours after CPR.The brain tissues were harvested at 72 hours after CPR.The histopathologic changes were assessed by hematoxylin and eosin (HE) staining,and the normal neuron was counted.The neuronal apoptosis was assessed with terminal dexynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining,and the expressions of cytochrome C (Cyt-C) protein in mitochondria and cytoplasm from hippocampus were determined by Western Blot.Results NDS in all experiment groups was gradually increased after CPR,and they were significantly lower than thoseo.f the sham group at 24,48,and 72 hours (51.5±3.7 vs.80.0±0.0,59.3±3.6 vs.80.0±0.0,66.7±2.6 vs.80.0±0.0,all P ＜ 0.05).The number of normal pyramidal neurons in the hippocampal CA1 region was markedly reduced (cells/HP:4.4± 1.1 vs.23.1 ± 4.0,P ＜ 0,05),the apoptotic index was significantly increased [(86.9 ± 6.9)％ vs.(3.4 ± 0.8)％,P ＜ 0.05],the expressions of Cyt-C in mitochondria were significantly decreased (A value:0.46±0.18 vs.1.00±0.00,P ＜ 0.05),and the expressions of Cyt-C in cytoplasm were significantly up-regulated (A value:6.65±0.21 vs.1.00±0.00,P ＜ 0.05).Compared with the CA group,NDS at 24 hours and 48 hours in mdivi-1 group was slightly increased (55.2 ± 3.3 vs.51.5 ± 3.7,64.7 ± 2.4 vs.59.3 ± 3.6,both P ＞ 0.05),and it was significantly increased at 72 hours (74.5±2.3 vs.66.7 ± 2.6,P ＜ 0.05),the number of normal pyramidal neurons in the hippocampal CA1 region was markedly increased (cells/HP:16.2±2.4 vs.4.4± 1.1,P ＜ 0.05),the apoptotic index was dramatically reduced [(42.3 ± 3.9)％ vs.(86.9 ± 6.9)％,P ＜ 0.05],the expressions of Cyt-C in mitochondria were significantly increased (A value:0.83 ± 0.22 vs.0.46 ± 0.18,P ＜ 0.05),and the expressions of Cyt-C in cytoplasm were significantly decreased (A value:3.84±0.47 vs.6.65±0.21,P ＜ 0.05).There was no statistically significant difference in above indexes between CA group and DMSO group.Conclusion By inhibiting mitochondrial Cyt-C apoptotic pathway to reduce neuronal apoptosis in rats after CA-CPR,mdivi-1 can improve brain function after CPR.