基于BDNF/TrkB通路探讨电针对脑缺血再灌注损伤大鼠学习记忆功能及突触可塑性的影响

Effects of electroacupuncture on learning-memory function and synaptic plasticity in rats with cerebral ischemia-reperfusion injury based on the BDNF/TrkB pathway

目的:观察电针“百会”“四神聪”对脑缺血再灌注损伤(CIRI)大鼠缺血侧海马脑源性神经营养因子(BDNF)/酪氨酸激酶受体B(TrkB)通路、突触素(SYN)表达及白细胞介素-1β(IL-1β)、白细胞介素-18(IL-18)含量的影响,探究电针改善CIRI后学习记忆功能的作用及机制。方法:将48只SPF级雄性SD大鼠随机分为假手术组、模型组、电针组和非穴组,每组12只。模型组、电针组和非穴组大鼠采用改良Zea Longa线栓法制备CIRI模型。电针组予电针“四神聪”“百会”,疏密波,频率2 Hz/10 Hz,电流强度1 mA;非穴组电针双侧肋下非经非穴点,电针参数同电针组。两组干预均每次30 min,每天1次,持续7 d。干预期间,于每日固定时间测量大鼠体质量;于干预第1、3、7天观察各组大鼠神经功能缺损情况。干预前后采用小动物磁共振成像技术测量大鼠脑梗死体积。干预后,采用Morris水迷宫评价大鼠学习记忆功能;HE染色观察大鼠海马形态;免疫组化法检测大鼠缺血侧海马SYN阳性表达;Western blot法检测大鼠缺血侧海马BDNF、TrkB、SYN蛋白表达;ELISA法检测大鼠缺血侧海马IL-1β、IL-18含量。结果:干预第2~7天,与假手术组比较,模型组大鼠体质量下降(P<0.01);与模型组和非穴组比较,电针组大鼠体质量增加(P<0.01)。干预第1天,与假手术组比较,模型组、电针组和非穴组大鼠神经功能评分升高(P<0.01);干预第3、7天,模型组大鼠神经功能评分高于假手术组(P<0.01);干预第7天,电针组大鼠神经功能评分低于模型组与非穴组(P<0.05)。与假手术组比较,模型组大鼠逃避潜伏期延长(P<0.05),穿越平台次数减少(P<0.01);与模型组和非穴组比较,电针组大鼠逃避潜伏期缩短(P<0.05),穿越平台次数增加(P<0.01)。干预前,模型组、电针组和非穴组大鼠左侧脑室出现明显高信号梗死灶;干预后与模型组和非穴组比较,电针组大鼠脑梗死体积占比下降(P<0.01)。模型组与非穴组大鼠神经元细胞排列疏散且紊乱、胞质深染且胞核固缩;电针组大鼠神经元细胞数目、排列情况趋于假手术组,胞质深染及胞核固缩现象较模型组减轻。与假手术组比较,模型组大鼠缺血侧海马SYN阳性表达及BDNF、TrkB、SYN蛋白表达减少(P<0.01,P<0.05),IL-1β、IL-18含量升高(P<0.01);与模型组和非穴组比较,电针组大鼠缺血侧海马SYN阳性表达及BDNF、TrkB、SYN蛋白表达增加(P<0.01,P<0.05),IL-1β、IL-18含量下降(P<0.01)。结论:电针“百会”“四神聪”可能通过激活BDNF/TrkB信号通路转导,减轻神经炎性反应,促进突触可塑性恢复来改善CIRI大鼠学习记忆功能。

Objective To observe the effects of electroacupuncture(EA)at"Baihui"(GV 20)and"Sishencong"(EX-HN 1)on the expression of brain-derived neurotrophic factor(BDNF)/tyrosine kinase receptor B(TrkB)pathway,synaptophysin(SYN),and the levels of interleukin-1β(IL-1β)and interleukin-18(IL-18)in the hippocampus of the ischemic side in rats with cerebral ischemia-reperfusion injury(CIRI),and to explore the effects and action mechanism of EA on post-CIRI learning-memory function.Methods Forty-eight SPF-grade male SD rats were randomly divided into a sham operation group,a model group,an EA group,and a non-acupoint group,with 12 rats in each group.The CIRI model was established in the model group,the EA group,and the non-acupoint group using the modified ZeaLonga suture method.The rats in the EA group were treated with EA at"Sishencong"(EX-HN 1)and"Baihui"(GV 20),with disperse-dense wave at frequency of 2 Hz/10 Hz and intensity of 1 mA.The rats in the non-acupoint group were treated with EA at non-meridian and non-acupoint points under the ribs bilaterally with the same parameters as the EA group.EA were conducted for 30 min each session,once daily,for 7 days.During the intervention,body weight was measured daily at a fixed time,and neurological deficits were assessed on the 1st,3rd,and 7th days into intervention.Brain infarct volume was measured using small animal magnetic resonance imaging before and after the intervention.After the intervention,learning-memory function were evaluated using the Morris water maze.Hippocampal morphology was observed with HE staining.The positive expression of SYN in the hippocampus of the ischemic side was detected by immunohistochemistry.BDNF,TrkB,and SYN protein expressions in the hippocampus of the ischemic side were detected by Western blot.IL-1βand IL-18 levels in the hippocampus of the ischemic side were measured by ELISA.Results From the 2nd to the 7th day into intervention,compared with the sham operation group,the body weight of rats in the model group was decreased(P<0.01);compared with the model group and the non-acupoint group,the body weight of rats in the EA group was increased(P<0.01).On the 1st day into intervention,compared with the sham operation group,neurological function scores of rats in the model group,the EA group,and the non-acupoint group were increased(P<0.01);on the 3rd and 7th days into intervention,neurological function scores of rats in the model group were higher than those in the sham operation group(P<0.01);on the 7th day,neurological function scores of rats in the EA group were lower than those in the model group and the non-acupoint group(P<0.05).Compared with the sham operation group,escape latency was prolonged(P<0.05),and the number of platform crossings was decreased(P<0.01)in the model group;compared with the model group and the non-acupoint group,escape latency was shortened(P<0.05),and the number of platform crossings was increased(P<0.01)in the EA group.Before intervention,the high signal infarcts were observed in the left ventricles of rats in the model group,the EA group,and the non-acupoint group;after intervention compared with the model group and the non-acupoint group,infarct volume in the EA group was decreased(P<0.01).Neuronal cells in the model group and the non-acupoint group were sparsely and disorderedly arranged,with deep-stained cytoplasm and shrunken nuclei;the number and arrangement of neuronal cells in the EA group were similar to the sham operation group,with less deep-stained cytoplasm and shrunken nuclei compared to the model group.Compared with the sham operation group,the positive expression of SYN,and BDNF TrkB,and SYN protein expressions in the hippocampus of the ischemic side were decreased(P<0.01,P<0.05),while levels of IL-1βand IL-18 were increased(P<0.01)in the model group;compared with the model group and the non-acupoint group,the positive expression of SYN,and BDNF,TrkB and SYN protein expressions in the hippocampus of the ischemic side were increased(P<0.01,P<0.05),while levels of IL-1βand IL-18 were decreased(P<0.01)in the EA group.Conclusion EA at"Baihui"(GV 20)and"Sishencong"(EX-HN 1)may improve learning-memory function in rats with CIRI by activating the BDNF/TrkB signaling pathway,reducing neuroinflammatory response,and promoting the recovery of synaptic plasticity.