鞘内远端阿片预处理通过抑制脊髓NGF-TRPV1敏化调控心肌缺血伤害感受信号的心肌保护机制

The vanilloid receptor (TRPV1) distributed on the cardiac sensory nerve is activated by cardiac ischemia, transmitting the nociceptive signal from heart to spinal cord. It is known that preconditioning induced TRPV1 activation could reduce myocardial ischemia reperfusion injury (IRI), while its overactivation may also exacerbate myocardial injury. Nerve growth factor (NGF) was reported upregulated after cardiac ischemia, which in turn resulted in TRPV1 sensitization. However, it is unclear whether NGF-induced TRPV1 sensitization contributes to myocardial IRI. We had demonstrated that central remote opioid preconditioning(ROPC) reduced myocardial IRI in rat via activating the three opioid receptors in spinal cord. In view of that opioids could negatively regulate TRPV1 or NGF signaling, we therefore presume that intrathecal ROPC might exert cardioprotective effects via inhibiting spinal NGF-TRPV1 sensitization. This study proposes to investigate the effects of intrathecal ROPC on spinal NGF-TRPV1 sensitization and subsequent nociceptive signal transduction following cardiac ischemia, as well as the molecular mechanism of ROPC regulating NGF-TRPV1 sensitization. The neuronal activity in spine cord following cardiac ischemic will be detected by using 9.4T high field MRI system; In addition, shRNA interference, whole cell patch clamp and other molecular biological techniques will also be used in the experiments. This study will clarify the neuronal signaling mechanisms of ROPC exerting cardioprotective effects, and provide a theoretical basis for its clinical application.

心肌缺血诱导心脏感觉神经上的辣椒素受体（TRPV1）活化将伤害感受信号传至脊髓，已知预处理介导的TRPV1活化可减轻心肌缺血再灌注损伤（IRI），但其过度活化也可能加重心肌损伤，其机制尚待阐明；心肌缺血后神经生长因子（NGF）表达增加，其可致敏TRPV1，NGF-TRPV1敏化在心肌IRI中发挥何种作用，仍不清楚。我们前期研究发现中枢远端阿片预处理（ROPC）通过激活脊髓阿片受体减轻心肌IRI，鉴于阿片类可抑制TRPV1或NGF信号，我们推测：鞘内ROPC可能通过抑制脊髓NGF-TRPV1敏化发挥心肌保护作用。本课题利用9.4T MRI扫描心肌缺血后脊髓神经信号，并应用RNA干扰、膜片钳等方法，研究鞘内ROPC对心肌缺血后脊髓NGF-TRPV1敏化及伤害感受信号传导的影响，并探讨其调控NGF-TRPV1敏化的机制。本课题将阐明ROPC发挥心肌保护作用的神经信号机制，为其临床应用提供依据。

心肌缺血诱导的心脏感觉神经上的辣椒素受体（TRPV1）活化可以传导伤害感受信号，而心肌缺血后神经生长因子（NGF）表达增加，可致敏TRPV1。鉴于阿片类可抑制TRPV1或NGF信号，并且我们前期研究发现中枢远端阿片预处理（ROPC）通过激活脊髓阿片受体减轻心肌缺血再灌注损伤，推测：鞘内ROPC可能通过抑制脊髓NGF-TRPV1 敏化发挥心肌保护作用。故本课题利用9.4T 超高场功能磁共振成像，实时、准确检测心肌缺血刺激后脊髓内神经信号变化；利用形态学和分子生物学技术研究心肌缺血诱导脊髓NGF-TRPV1 敏化在心肌缺血再灌注损伤中的作用；通过RNA干扰技术证明鞘内远端吗啡预处理通过抑制脊髓NGF-TRPV1 敏化，调控心肌缺血后伤害感受信号传导而发挥心肌保护作用；使用细胞膜片钳技术研究NGF诱导DRG神经元TRPV1敏化的信号机制以及吗啡预处理对NGF-TRPV1敏化的调控作用。研究发现鞘内吗啡预处理的心肌保护作用可能是通过降低心肌缺血后大鼠脊髓 SG 神经元的兴奋性，以及抑制心肌缺血后脊髓 SP 和 CGRP 等神经递质的过度释放，减轻心脏伤害感受反应及降低神经元兴奋性，从而发挥心肌保护作用；通过激活中枢阿片受体，降低 NGF 及 TRPV1 的表达，继而抑制 NGF-TRPV1 的敏化，减轻伤害性刺激反应，从而对抗心肌缺血再灌注损伤。本课题阐明ROPC 发挥心肌保护作用的神经信号机制，为其临床应用提供依据。