TRPV4-ATP-P2X受体信号通路对咳嗽高敏感性的作用及机制

Cough hypersensitivity, closely related to TRP family, is a common characteristic of refractory chronic cough. However, clinical evidences of TRPV1 and TRPA1 antagonism for treating cough are insufficient. In animal experiments, we found that ATP was involved in cough hypersensitivity but not related with TRPV1. However, activating TRPV4 may affect cough reflexes though conduction from airway vagal afferent nerves to nodose ganglions. Several studies have confirmed the relationship between ATP-P2X receptors and TRPV4. Thus, we speculated that activating TRPV4 could induce the release of ATP from airway epithelia, stimulate P2X receptors on cough receptors, and then induce cough though conduction from the afferent nerves to nodose ganglions. This study aims to establish a guinea pig model of citric acid induced chronic cough to compare the effects of TRPV4 agonist, TRPV4 antagonist, and P2X1-4, 7 receptor antagonists on cough sensitivity, to test mRNA and protein expressions of P2X and TRPV4 in ganglions, to observe the changes of discharge reactions of single pulmonary C-fiber in vitro and in vivo to the above-mentioned reagents in guinea pigs as well as TRPV4 knock-out mice, to confirm the involvement of TRPV4-ATP-P2X receptor signaling pathway in the formation of cough hypersensitivity, and to explore its mechanism, which can finally lay a foundation of treatments for chronic cough.

咳嗽高敏感性是难治性咳嗽的共同特征，与TRP家族密切相关，但拮抗TRPV1、TRPA1治疗咳嗽的证据不足。我们在动物研究中发现ATP参与咳嗽高敏感性，但与TRPV1无关；激活TRPV4可通过气道传入迷走神经纤维传导至结状神经节，可能影响咳嗽反射；多项研究提示ATP-P2X受体与TRPV4相关。故我们推测，活化TRPV4可导致气道上皮ATP释放，刺激咳嗽感受器上P2X受体，通过传入纤维传导至结状神经节诱发咳嗽。本研究拟建立柠檬酸吸入慢性咳嗽豚鼠模型，比较TRPV4激动剂、拮抗剂和P2X1-4, 7受体拮抗剂对咳嗽反应性的影响，检测神经节等组织P2X及TRPV4的mRNA和蛋白表达，采用在体和离体肺组织记录迷走神经单纤维放电活动的方法，观察豚鼠和TRPV4基因敲除小鼠对上述试剂的放电反应变化，证实TRPV4-ATP-P2X受体信号通路参与咳嗽高敏感性形成，并探讨其机制，为以此治疗咳嗽奠定基础。

咳嗽高敏感性是难治性咳嗽的共同特征，与TRP家族密切相关，但拮抗TRPV1、TRPA1治疗咳嗽的证据不足。我们在动物研究中发现ATP参与咳嗽高敏感性，但与TRPV1无关；激活TRPV4可通过气道传入迷走神经纤维传导至结状神经节，可能影响咳嗽反射；多项研究提示ATP-P2X受体与TRPV4相关。故我们推测，活化TRPV4可导致气道上皮ATP释放，刺激咳嗽感受器上P2X受体，通过传入纤维传导至结状神经节诱发咳嗽。本研究建立了柠檬酸吸入慢性咳嗽豚鼠模型，比较了TRPV4激动剂、拮抗剂和P2X1-4, 7受体拮抗剂对咳嗽反应性的影响，检测了神经节等组织P2X及TRPV4的mRNA和蛋白表达，证实TRPV4-ATP-P2X受体信号通路参与咳嗽高敏感性形成，最终为以此治疗咳嗽奠定了基础。