Cocaine-and Amphetamine-Regulated Transcript Peptides Protect Ischemic Brain Injury By Antioxidation And Its Machanism

Object:To investigate the antioxidative effects of cocaine-and amphetamine-regulated transcript peptides (CART) on ischemic brain injury and its mechanism.Method:Healthy male mice were randomly divided into four groups:ischemia-reperfusion (I/R) group, cocaine-and amphetamine-regulated transcript peptides (CART) group, normal saline (NS) group and sham-operation group(control group). A middle cerebral artery occlusion (MCAO) model was induced by plug wire preparation for two hours. Before reperfusion, CART injection and equivalent normal saline were injected via tail vein in CART group and NS group respectively, and repeated for every other24h. Brain infarct volume, water content of brain and the expression of HNE,8-OHdG,3-NT were performed and detected by TTC Stain, Dry/Wet method and Enzyme-linked immunesorbent assay respectively at different time points after reperfusion. Flowcytometry was used to assess the content of reactive oxygen species (ROS) and mitochondrial membrane potential of the infarct cortex tissue. The activity of mitochondrial respiratory chain Complex Ⅰ, Ⅱ and Ⅲ and the expression of mitochondrial DNA (mtDNA) mRNA were detected by colorimetry and reverse transcription-polymerase chain reaction (RT-PCR).Result:(1) Compared with I/R group and NS group, CART significantly reduced infarct volume at24h,48h and72h (all P<0.05).(2) Compared with I/R group and NS group, CART decreased water content of the infarct brain tissue at every point(12h,24h,48h,72h)(all P<0.05).(3) Compared with I/R group and NS group, CART could down-regulate the increased HNE,8-OHdG and3-NT level at every point in brain after ischemia. The level of HNE was down-regulated significantly at every point (P<0.01) and8-OHdG was down-regulated significantly only at12h (P <0.05), while3-NT was down-regulated significantly at24h,48h and72h (P<0.05).(4) Compared with I/R group and NS group, CART reduced the expression of ROS in ischemic brain (P<0.05).(5) Compared with I/R group and NS group, CART upregulated the mitochondrial membrane potential (all P<0.01), the activity of mitochondrial respiratory chain complex Ⅱ (all P<0.05) and the expression of mtDNA (all P<0.05). The activity of mitochondrial respiratory chain complex Ⅰ and Ⅲ were not upregulated by CART (all P>0.05).Conclusion:CART protect ischemic brain injury by antioxidation and its mechanism is associated with stabling the mitochondrial membrane potential, the upregulating activity of mitochondrial respiratory chain complex Ⅱ and the expression of mtDNA.