Neuroprotective Effect And Mechanism Of Sevoflurane Postconditioning On Global Cerebral Ischemic Injury After Cardiopulmonary Resuscitation Following Asphyxial Cardiac Arrest In Rats

Cardiac arrest is a major cause for death in the world, which would cause severe hypoxic and ischemic damage in the brain. Although the improvement of cardiopulmonary resuscitation technology and the emergency medical system could recover the spontaneous breathing and circulation to improve the early survival rate, the survival rate and quality of life in the late was frustrating. Research showed that only less than 50% of the patients had long-term survival after cardiac arrest, but most of these patients had different degree of cognitive and behavioral disorders. So far there was still no effective or ideal drug for cerebral protection, although people devote themselves to a large amount of basic research and clinical practice. This has become a worldwide clinical medical problem for prompt solution. In recent years, studies have shown that sevoflurane postconditioning could significantly improve the neurological function in focal brain injury, but the protection for the global brain injury after cardiopulmonary resuscitation(CPR) was rarely studied.Phosphatidyl inositol 3-kinase / protein kinase B(PI3K/Akt) pathway is an important signaling pathway, involved in cell survival, growth, apoptosis and metabolism, which plays an important role on neuroprotection of drugs in cerebral local and global ischemic injury model of animals. Glycogen synthase kinase-3β(GSK-3β), as an important downstream factor of PI3K/Akt pathway, can phosphorylate a variety of endogenous substrates, such as many proteins and transcription factors involved in the metabolism. So, GSK-3β plays an important role on the process of tumorigenesis, glucose homeostasis and so on. Studies have shown that GSK-3β not only played a protective role in the global cerebral ischemic damage in four blood vessels occlusion model, but also participated in glucose metabolic regulation in the body in many aspects, such as function of β cells, glycogen synthesis and so on.Therefore, the study aimed to use an asphyxial cardiac arrest model in rats through giving different concentration of sevoflurane on the immediate recovery, to observe glucose and NSE in blood, expression of protein P53, histopathological injury in hippocampus CA1 area, and the change of the whole cognitive behavior ability at 72 h after resuscitation, to research the protection of sevoflurane postconditioning on cerebral injury after asphyxial cardiac arrest. Moreover, the rats were given the specific antagonist of PI3 K in vein on the basis of the experiment above, in order to evaluate its influence on neuroprotective effect of sevoflurane postconditioning, to reveal the role of PI3K/Akt pathway on the cerebral protection, to explore the relationship of neuroprotection, antiapoptosis and the regulation of glycometabolism. These would offer a new idea and method for treatment of cerebral injury after cardiopulmonary resuscitation.Experiment Ⅰ Neuroprotective effect of different concentration of sevoflurane postconditioning on global cerebral ischemic injury after cardiopulmonary resuscitation following asphyxial cardiac arrest in rats Objective Studies have shown that sevoflurane postconditioning can significantly improve the nerve defect in some focal brain injury models, but the research on its protection of the global cerebral ischemic injury after cardiopulmonary resuscitation was less. This experiment was designed to evaluate the protection of different concentration of sevoflurane postconditioning on cerebral ischemic injury following asphyxial cardiac arrest in rats.Methods 80 adult male SD rats were randomly divided into five groups: sham group(sham), control group(control), 0.5 MAC, 1.0 MAC and 1.5 MAC sevoflurane postconditioning groups(0.5 SP, 1.0 SP and 1.5 SP). Control, 0.5 SP, 1.0 SP and 1.5 SP groups were induced by 8-min asphyxiation and cardiopulmonary resuscitation. Sevoflurane was inhaled through the breathing machine respectively two times for 5 min each at an interval of 10 min at the onset of resuscitation to achieve postconditioning, to conform its concentration 1.3%, 2.5% and 3.8% respectively in 0.5 SP, 1.0 SP and 1.5 SP groups, but the rats in control group were inhaled 100% oxygen. Record the early rate of recovery, the glucose and Neuron Specific Enolase(NSE) in blood, morphological change of neurons in hippocampus CA1 area, and expression of protein P53 in hippocampus area at 72 h after resuscitation, Neurological Deficit Scores(NDS) at 24 h, 72 h, 7 d respectively and spatial learning and memory ability from 7 d to 11 d after resuscitation. Results There was no statistical difference on recovery rats in all the groups. The levels of glucose and NSE in blood in 1.0 SP and 1.5 SP groups were lower than those of control group significantly(P<0.05). There were more survival neurons, less expression of apoptosis protein P53 in hippocampus area(P<0.05), higher NDS and better ability of spatial learning and memory in groups 1.0SP and 1.5SP than those of control group(P<0.05). Conclusion Postconditioning with 1.0 MAC and 1.5 MAC sevoflurane can significantly reduce global cerebral injury after cardiopulmonary resuscitation following asphyxial cardiac arrest in rats.Experiment Ⅱ The research on the role of PI3K/Akt in the process of sevoflurane postconditioning reducing the cerebral injury following asphyxial cardiac arrest.Objective PI3K/Akt pathway, as an important signaling pathway, takes part in cell survival, growth, apoptosis and metabolism in the body. GSK-3β, as an important downstream factor, could be involved in the regulation of glucose metabolism through glycogen synthesis and other aspects. The experiment was designed to explore the relationship of the neuroprotection of sevoflurane, antiapoptotic effect mediated by PI3K/Akt pathway and regulation of glucose metabolism mediated by GSK-3β. Methods 80 healthy male SD rats were divided into five groups randomly: sham group(sham), control group(control), 1.0 MAC sevoflurane postconditioning group(SP) and PI3 K inhibitor Wortmannin + sevoflurane postconditioning group(W+SP) and only Wortmannin group(W). The rats in sham, control and SP groups were treated as the method of experimentalⅠ; the rats in W+SP group were given Wortmannin in femoral vein 30 min before asphyxiation, established cardiac arrest and cardiopulmonary resuscitation, and inhaled sevoflurane to conform 2.5% concentration twice according to 1.0 SP group in the experimentⅠ; the animals in W group were only given Wortmannin. Record the early rate of recovery, glucose and NSE in blood, morphological change of neurons in hippocampus CA1 area and the various protein expression, such as the apoptosis related proteins--Bcl-2 and Bax, and pathway related protein--p Akt/Akt and p GSK-3β/GSK-3β at 72 h after recovery.Results There was no significantly statistical difference on the rate of recovery among the groups. Compared with the control group at 72 h after recovery, rats in the SP had a lower blood glucose(P<0.05), more survival neurons in hippocampal CA1 area(P<0.05), more anti-apoptosis protein Bcl-2 and less apoptosis protein Bax(P<0.05), along with raising phosphorylated proteins in the downstream of pathway--p Akt and p GSK--3β, but no significant effect on these total proteins. However, compared with the SP group, results in W+SP group were offset partly, such as blood glucose increasing slightly(P<0.05), survival neurons decreasing(P<0.05) and expression of apoptosis related proteins significantly changing(P<0.05), and the expression of phosphorylated proteins in the downstream of pathway-- p Akt and p GSK-3β decreasing(P<0.05).Conclusion Protective mechanism of sevoflurane postconditioning on global cerebral ischemic injury after cardiopulmonary resuscitation following asphyxial cardiac arrest is not only related to the inhibition of apoptosis mediated by PI3K/Akt, but also to the regulation of glucose metabolism involved by GSK-3β.