低强度迷走神经刺激调控心脏自主神经功能治疗心房颤动的机制研究

Atrial fibrillation (AF) is the most common cardiac arrhythmia seen in clinical practice, but The mechanisms responsible for AF are still uncertain.A lot of sutdies had showed the role of the ANS in the initiation, maintenance, and termination of AF.In the past century, the vagal stimulation was known as the facilitated factor for AF. But in the present report, we have describe a nonpharmacologic, nonablative methodology to reverse and prevent the AF. Contrary to the popular notion, low level vagosympathetic stimulation (LL-VNS) may serve as a novel therapeutic modality to treat AF, particularly to prevent AF from progressing to persistent forms of this arrhythmia.Inhibition of the intrinsic cardiac autonomic nerve system (ANS) by LL-VNS may be responsible for these salutary results. LL-VNS may serve as a novel therapeutic modality to treat AF related to acute or chronic atrial remodeling or a hyperactive state of the intrinsic cardiac ANS. We hypothesize that the mechanism responsible for the atrial antifibrillatory effect of LL-VNS may be due to inhibition of the intrinsic cardiac ANS by the extrinsic cardiac ANS. But how do LL-VNS influence neuronal firing within the cardiac autonomic ganglionated plexi? we still know nothing about this process.In the first part of this study, we will build the chronic AF animal model by atrial rapid pacing in vivo.Then we will implant a neurostimulator subcutaneously which is connect to the right cervical vagosympathetic trunks to stimulate the vagus for six months by different intensity. Histo- and cytofluorescence experiments will be done to analysis the tissue from ARGP.In this protocl, we want to know whether different intensity vagal stimualtion can affect the AF burden, AF cycle length and the morphology of neuron cells in ARGP. We also like to know the activity of neuron in GP by the gene and protein expression of NGS and NT-3. In the second part, we will incubate neuron cells from GPs of the rat in the different electric field strengths.It has been shown that the strong electric field can causes neuronal cellular hypertrophy, which is mediated by NGF and boosters cellular function by NT-3-mediated acetylcholine upregulation. We will change the intensity and sequency of electric field, and want to find out whether low level electric field can prevent or reversal the effect of strong elctric field to neuron cell. Further research will be done to help us understand the possible mechanism, including the regulation mechanism of NSG and NT-3.LL-VNS is a potential therapy that is less invasive than catheter or surgical ablation, and may limit the duration of or even prevent AF thereby reducing the risk of thromboembolic events or cardiomyopathy. This study will provide laboratory basis for its clinical practice.

房颤机制研究一直是近年的热点，大量研究结果表明心脏自主神经系统在房颤的发生、维持中扮演重要角色。近一个世纪的研究始终认为迷走神经刺激是致房颤的，而我们既往的实验结果却发现与传统观念不同，低强度迷走神经刺激可以治疗房颤的。这主要是通过对心脏内源性自主神经丛功能的调控来实现的。但是外源性的刺激是如何影响到心脏内源性神经系统的功能，这个在整个作用机制中承前启后的最重要一环尚是未知数。本研究通过在体急、慢性房颤模型中进行不同强度的迷走神经刺激以及离体心脏自主神经元细胞在不同的电场强度中进行培养的方法，观察不同强度的迷走神经电刺激对心脏自主神经丛神经元细胞形态、构成、超微机构、跨膜电流和功能的不同效应，研究神经生长因子与该效应的相关性的，探讨其可能的分子生物学机制，明确低强度迷走神经刺激可否通过调控神经营养因子介导的神经元细胞肥厚和乙酰胆碱释放影响心脏自主神经丛的功能，从而起到治疗和预防房颤的作用。

无论传统医学，还是现代医学，都强调了心与脑的密切联系。自主神经活性的改变不仅影响心率、传导及血流动力学，还从细胞和亚细胞水平上改变了心肌的特性。心脏作为靶器官同时接受交感神经和副交感神经的支配，最终表现为二者功能的协调和平衡，心律失常的发生与心脏自主神经张力改变关系密切。 . 本研究在体和离体的实验研究，不同强度的迷走神经电刺激对心脏自主神经丛神经元细胞中的神经生长因子有明确的调节作用，低强度迷走神经刺激可以抑制多种神经营养因子。从而使其介导的神经元细胞肥厚和乙酰胆碱释放能力使心脏自主神经丛的神经活性下降，从而起到预防和治疗房颤的作用，为临床上进一步推广该技术奠定牢固的实验室基础。. 在上述研究的基础上，我们同时发现心脏自主神经节丛GP中同样存在这PV阳性中间神经元，NRG1- ErbB4信号通路主要作用于PV阳性中间神经元，增加PV阳性神经元活性，研究表明6小时心房快速起搏可以使心脏自主神经节ARGP的神经活性明显增加，C-FOS和神经生长因子蛋白表达均明显上升。如果使用NRG1预处理ARGP，则这种神经活性的改变以及C-FOS和神经生长因子表达上升则不会出现。NRG1预处理+ ErbB4受体拮抗剂则会极大的弱化这种抑制作用。研究探索通过NRG1- ErbB4信号通路干预GP中PV阳性神经元对GP及房颤发生发展的作用；明确通过化学遗传方法激活GP中PV阳性中间神经元对GP及房颤的影响，为房颤的临床防治提供新策略和新思路。. 本研究同时运用了一种新的自主神经干预方式，验证劲动脉窦的低强度刺激（LL-CBS）是否也具有同样的效应。研究结果提示LL-CBS能够降低缺血再灌注损伤所致的室性心律失常，减小心梗面积。其可能的机制是抑制局部的炎症反应，恢复氧化应激平衡，拮抗梗死区域心肌细胞的凋亡，恢复CX43表达水平，为临床应用提供了一种新的治疗手段，有良好的临床应用前景。