Inhibiting Succinate Dehydrogenase By Dimethyl Malonate Alleviates Brain Damage In A Rat Model Of Cardiac Arrest

Objective:Brain injury is an important cause of high mortality and high disability in patients with cardiac arrest（CA）.Studies have found that dimethyl malonate（DMM） prevented the ischemia reperfusion injury caused by mitochondrial ROS production.This study investigated the effects of DMM on cardiopulmonary resuscitation（CPR）and brain damage after CA and its mechanisms.Methods:Section ONE:Sprague–Dawley male rats were allocated to three groups:Sham group,all operations except induction of CA were completed in rats;Saline group,rats were subjected to a 6-min CA and CPR was performed,and saline was pumped intravenously immediately after induction of CA;DMM group,rats were subjected to a6-min CA and CPR was performed later,and DMM(6 mg/kg^-1·min^-1)was pumped intravenously immediately after induction of CA.After the return of spontaneous circulation,neurological function of the rats was assessed by a tape removal test for 3 days.The rats were then sacrificed,and serum samples were retained.Their brains were used to assess neuronal apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labelling（TUNEL）assay.Section TWO:（1）The expression of Cleaved Caspase-3 in Hippocampal tissues was detected by Western Blotting analysis.（2）The content of malondialdehyde（MDA）and the activity of superoxide dismutase（SOD）in hippocampus of each group were measured by a biochemical detection.（3）Sprague–Dawley male rats were allocated to four groups:Baseline group,all operations except induction CA were completed in rats;CA group,rats were subjected to a 6-min of CA and their brains were decapitated without CPR;CPR+Saline group,rats were subjected to a 6-min CA and CPR was performed later,and saline was pumped intravenously immediately after induction of CA;CPR+DMM group,rats were subjected to a 6-min CA and CPR was performed later,DMM(6 mg/kg^-1·min^-1)was pumped intravenously immediately after induction of CA.At the end of the 51 min administration of DMM or saline,the rats were decapitated.Hippocampal tissues were separated and tissue mitochondria were extracted immediately.The mitochondrial membrane potential（MMP）was measured using a JC-1 fluorescent probe,and the concentration of cytochrome C in the mitochondrial cytosol was measured by ELISA.（4）The expression of hypoxia-inducible factor-1 alpha（HIF-1α）in hippocampal tissues was detected by Western Blotting analysis.（5）The concentrations of IL-1β,IL-6,IL-10,IFN-γ,and TNF-αin serum samples of all rats were measured by ELISA.Results:（1）DMM improved ROSC in rats after CA,but had no effect on survival rate.（2）DMM attenuated the neurological damage on the third day after CPR in rats.（3）DMM inhibited the apoptosis of hippocampal CA-1 neurons in rats after CPR.（4）DMM inhibited Caspase-3 cleavage at day 3 after CPR.（5）DMM decreased the level of MDA and increased the activity of SOD in the hippocampus of the brain after CPR.（6）DMM inhibited excessive hyperpolarization of MMP and restrained the leakage of cytochrome C after a 45-min CPR.（7）DMM increased the expression of HIF-1αin hippocampus of rats after CPR.（8）DMM had no significant effect on inflammatory factors in serum of rats after cardiopulmonary resuscitation.Conclusion:Inhibiting succinate dehydrogenase by DMM alleviated brain damage afterCA,and the main mechanisms included inhibiting the excessive hyperpolarization of MMP,reducing the generation of mtROS and stabilizing the structure of HIF-1α.