HCN通道在心梗后交感神经重构中的作用及机制研究

Sympathetic nerve remodeling after myocardial infarction (MI) are main cause for clinical malignant arrhythmias and sudden cardiac death, which relates with activations of central and peripheral renin-angiotensin-aldosterone systems. The HCN channel plays an important role in the maintenance of membrane potential and regulation of cardiac rhythm and sympathetic transmitter release. Blocking HCN channel can reduce sympathetic transmitter release and activity, and decrease the mortality and rehospitalization rate among patients with MI. Recently, we found that blocking HCN channel could inhibit neurotransmitter release from cardiac sympathetic nerve in ischemia/reperfusion rats, suggesting that HCN channel may participate in post infarct cardiac sympathetic nerve remodeling. However, the underlying mechanism has not been clarified. Therefore, we proposed a hypothesis: Increased angiotension II at the circulatory or tissue level may upregulate HCN channel in the cardiac sympathetic nerve, and thus result in post infarct cardiac sympathetic nerve remodeling. In this project, we plan to use rat MI model and PC12 cells and a series of techniques including electrophysiology and cellular and molecular biology to investigate the role and mechanism of HCN channel in post infarct cardiac sympathetic nerve remodeling. Results may provide a new target and strategy for the prevention and treatment of post-infarct arrhythmias.

心肌梗死后交感神经重构是临床恶性心律失常和心源性猝死发生的重要原因，与中枢及外周肾素-血管紧张素-醛固酮系统激活有关。HCN通道在稳定细胞膜电位、调节心脏节律和神经递质释放中发挥重要作用。阻断HCN通道可减少心交感神经递质释放、降低交感神经活性，亦可降低临床病人心梗后死亡率和再住院率。我们近来研究显示，阻断HCN通道可抑制缺血/再灌注大鼠心脏交感神经递质释放，提示HCN通道可能参与心梗后交感神经重构，但机制尚未明了。据此，本项目提出假说：心梗后循环或局部的血管紧张素Ⅱ增加，导致心交感神经HCN通道上调，参与心梗后交感神经结构和功能重构的发生。本项目采用心梗大鼠模型和PC12细胞，应用电生理、细胞和分子生物学等技术，从整体、细胞及分子等不同水平探讨HCN通道在心梗后交感神经重构中的作用及其机制。本研究可为心梗后心律失常的防治提供新的靶点和策略，具有重要的理论意义和潜在的应用价值。

交感神经的正常结构和功能是维持心脏正常生理功能的关键环节。心肌梗死后交感神经重构是临床恶性心律失常和心源性猝死发生的重要原因。迄今为止，有关心梗后交感神经重构的机制尚未阐明。本项目拟采用神经生长因子（NGF）诱导PC12细胞分化模拟交感神经重构模型，应用电生理、细胞和分子生物学等技术，探讨HCN通道在心梗后交感神经重构中的作用及其机制。培养来源于大鼠嗜铬细胞瘤的PC12细胞，并通过NGF诱导分化为类交感神经元活性细胞。PC12细胞的交感定向分化显示交感神经相关的分子标志物，如生长相关蛋白43(GAP-43)和酪氨酸羟化酶(TH)发生显著改变，同时形态学观察显示神经突起生长明显增多。mRNA和蛋白水平结果均表明四种HCN亚型(HCN1, HCN2, HCN3, HCN4)均可在PC12细胞表达。电生理研究也显示NGF通过影响HCN通道活性来部分调节PC12细胞的电生理表型。通过HCN特异性抑制剂伊伐布雷定Ivabradine成功阻断PC12细胞靶向交感神经的分化的过程，HCN通道四种亚型和GAP-43表达均受到抑制。同时类交感神经样突起的形态和数量也相应的发生变化。进一步采用小分子干扰siRNA和分子转染过表达技术，研究发现HCN2和HCN4而不是HCN1和HCN3在NGF诱导的PC12细胞向交感神经元分化中起着重要的调控作用。当前研究结论为了解神经元分化和交感神经芽生在心梗后交感神经重构的研究中提供了重要的理论基础。