颈动脉窦压力感受器电刺激干预慢性心力衰竭犬自主神经重构的机制研究

Mechanisms of carotid baroreceptor stimulation on autonomic remodeling in canine with chronic heart failure

目的 探讨颈动脉窦压力感受器电刺激(CBS)干预慢性心力衰竭(CHF)自主神经重塑的分子机制。方法 将38只雄性比格犬采用单纯随机抽样方法分为正常对照组(CON)、CHF组、CHF伴颈动脉窦压力感受器低水平强度刺激组(LL-CBS)和慢性心衰伴颈动脉压力感器受中等水平强度刺激组(ML-CBS)。所有犬均同时置入心脏起搏器和CBS刺激仪,除正常对照组外,其余三组均开启起搏器制作心衰模型,其中,心力衰竭ML-CBS组和LL-CBS组开启颈动脉窦电刺激,其余两组仅行CBS置入操作,不开启电刺激。持续6周后,记录心电图30 min,取左心室(LV)、颈部迷走神经(CVN)、左星状神经节(LSG)、右侧星状神经节(RSG)组织。采用western blot法检测神经生长因子(NGF)、脑源性神经营养因子(BDNF)、酪氨酸激酶A(TrkA)和P75神经营养因子受体(P75NTR)在上述组织中的蛋白表达水平。对LSG、RSG组织行苏木精-伊红(HE)染色观察神经元细胞大小的变化。结果 与CHF组相比,LL-CBS与ML-CBS均能显著抑制心力衰竭时交感神经活性的增加,迷走神经活性的降低。与CON组相比,CHF组两侧星状神经节神经元体积显著增大,LL-CBS及ML-CBS组相较于CHF组显著减小。CBS可抑制CHF犬CVN中NGF蛋白表达上调,CBS抑制LSG和LV中NGF表达的增加。CHF犬LV、LSG、CVN组织中BDNF、TrkA、P75NTR蛋白表达均下调,CBS可逆转LSG和CVN组织中BDNF、TrkA、P75NTR蛋白表达的降低,但在LV组织未产生明显影响。CHF组RSG中NGF、TrkA、BDNF和P75NTR蛋白表达均升高,CBS对上述蛋白的表达产生的下调作用。结论CBS干预CHF犬自主神经重构与促进NGF-TrkA轴和抑制BDNF-P75NTR轴有关。

Objective To investigate the molecular mechanism by which carotid baroreceptor stimulation(CBS)interferes autonomic remodeling in chronic heart failure(CHF).Methods Thirty-eight male beagles were randomly divided into control(CON),CHF,chronic heart failure with low-level carotid baroreceptor stimulation(LL-CBS)and chronic heart failure with moderate-level carotid baroreceptor stimulation(ML-CBS)groups.All beagles were implanted with cardiac pacemaker and CBS stimulator at the same time.A CHF model was established by 6-week rapid ventricular pacing(RVP)in the CHF,LL-CBS,and ML-CBS groups,whereas the CON group underwent a sham operation of cardiac pacemaker implantation.LL-CBS and ML-CBS were delivered together with RVP in the LL-CBS and ML-CBS groups,respectively,whereas the CON and CHF groups underwent a sham operation of CBS device implantation.After 6 weeks,all beagles underwent a 30-minute electrocardiography(ECG)test.Protein expression levels of nerve growth factor(NGF),Brain‐derived neurotrophic factor(BDNF),tyrosine kinases A(TrkA)and P75 neurotrophin receptor(P75NTR)in the left ventricular(LV),cervical vagus nerve(CVN),left stellate ganglion(LSG)and right stellate ganglion(RSG)tissues were detected by western blot assay.LSG and RSG tissues were stained with hematoxylin-eosin(HE)to observe the changes of neuron size.Results The results of the heart rate variability showed that compared with the CHF group,both the LL-CBS and ML-CBS could significantly inhibit the increase of sympathetic nerve activity and the decrease of vagal nerve activity in CHF group.Neuronal cells in both the LSG and RSG groups were significantly smaller than in the CHF group,which was inhibited by LL-CBS and ML-CBS.In the CHF groug,NGF protein expression increased in CVN and there was a trend of decrease after 6 weeks of CBS.CBS inhibited the increase of NGF expression in LSG and in LV.BDNF,TrkA,P75NTR proteins expression were all decreased in LV,LSG and CVN in the CHF group.CBS reversed the decrease of BDNF,TrkA,P75NTR protein expression in the LSG and CVN tissues but not in LV.In RSG,NGF,TrkA,BDNF and P75NTR proteins expression were increased simultaneously in the CHF group,which were inhibited by CBS.Conclusions CBS reversal of sympathetic neural remodeling in CHF is associated with the activation of NGF-TrkA axis and the inhibition of BDNF-P75NTR axis.