The Protective Effect And Mechanism Of Vagus Nerve Stimulation On Cerebral Stroke

Objective: Ischemic stroke is the key point of death in the world,and has more patients in China than western countries.Cerebral ischemia and reperfusion can cause many adverse prognostic symptoms,which have not yet been effectively solved.Therefore,it is urgent to find new therapeutic methods and molecular mechanisms that can act on stroke.In recent years,foreign studies have found that VNS has a neuroprotective effect on acute cerebral ischemia reperfusion in rats,but the mechanism is not clear.This study intends to further explore the effects of VNS on inflammation and autophagy response mechanisms after acute cerebral ischemia and reperfusion,as well as the possible molecular mechanisms,so as to provide some theoretical basis for its clinical application.Methods: 120 adult female SD rats were randomly divided into 8 groups.Intracranial injection of antagmiR-5a-20 p was used to inhibit endogenous expression of miR-20a-5p.Middle cerebral artery occlusion model was prepared by suture embolism method.VNS intervention was given 30 minutes after cerebral ischemia and infarction,followed by reperfusion 90 minutes later.At 24 h after reperfusion,neurological function score was evaluated on an 18-point scale,and the cerebral infarction volume was measured by TTC.The expression of miR-20a-5p in each group was detected by fluorescence quantitative PCR.TUNEL was used to detect neuronal apoptosis in the ischemic side of the cortex.The expressions of active proteins of Caspase3,BCL2,LC3 and Beclin1 in the ischemic cortex of each group were detected by Western Blot,and the expressions of caspase-3 positive cells in the ischemic cortex of each group were detected by immunohistochemistry.Results:(1)There was no statistically significant difference between VNS and the control group(sham I/R).(2)Neurological deficit scores and TTC staining results showed that compared with sham I/R group,the neurological deficit scores of I/R,I/R + VNS and I/R + AC group lower,improved lackness of neurologic symptoms,increased infarction volume of brain tissue and VNS significantly increased neurological deficit scores in rats,decrease the lackness of neurologic symptoms and infarction volume of brain tissue.By silencing miR-20a-5p,the effect of VNS was partially weakened.(3)RT-PCR showed that compared with the sham I /R group,the expression level of miR-20a-5p mRNA was increased in the I/R,I/R+VNS and I/R+AC group,and VNS significantly increased the expression level of miR-20a-5p mRNA.After miR-20a-5p was silenced,the promoting effect of VNS was partially inhibited.(4)Immunohistochemistry,TUNEL and Western Bolt showed that compared with the sham I /R group,Caspase3 content in the I/R,I/R+A and I/R+AC group was increased,while BCL2 expression was decreased.VNS significantly reduced Caspase3 content in the I/R and I/R+A group,increased BCL2 expression level,and increased the antiapoptotic effect.By silencing miR-20a-5p,the effect of VNS was partially weakened.(5)Compared with the sham I /R group,the expression levels of Beclin1 and LC3 in the I/R,I/R+A and I/R+AC group were increased by Western Blot.VNS significantly reduced the expression levels of Beclin1 and LC3,and the autophagy was inhibited.The effect of VNS was partially suppressed by silencing miR-20a-5p.(6)Under the effect of VNS,miR-20a-5p expression was increased,Beclin1,LC3,Caspase3 contents were decreased,and BCL2 expression was increased,which significantly reduced the apoptosis and autophagy levels of cerebral ischemia reperfusion rats.Conclusions:(1)The functional deficit of brain and the increase of infarction volume caused by cerebral ischemia reperfusion in rats can be alleviated by VNS.(2)After cerebral ischemia reperfusion,the expressions of Beclin1,LC3 and Caspase3 increased and the expression of BCL2 decreased in rats,while the expressions of Beclin1,LC3 and Caspase3 decreased and the expression of BCL2 increased under VNS.These results indicate that VNS plays a neuroprotective role by inhibiting apoptosis and autophagy in rats with cerebral ischemia reperfusion.(3)The mRNA expression of miR-20a-5p increased after cerebral ischemia reperfusion and increased under VNS in rats.However,the expression of miR-20a-5p was reduced after silencing,and the gain effect of VNS was partially weakened.These results suggested that miR-20a-5p was involved in the protective mechanism of VNS against cerebral ischemia reperfusion in rats.