哮喘时ET-1/EDNRB通路在脑干胶质细胞变应性激活及其所诱导的气道迷走神经活动增强中的作用

气道迷走神经活动增强是哮喘—尤其重症哮喘发病机制中的重要环节。我们前期发现:哮喘大鼠气道迷走中枢小胶质细胞(microglia,MG)被激活。活化的MG一方面通过BDNF-TrkB-NKCC1/KCC2通路使气道迷走节前神经元胞内氯离子浓度升高,使其对抑制性递质的反应减弱甚至反转为兴奋;同时使气道迷走中枢外核苷酸酶CD73表达和活性下降,ATP-腺苷介导的兴奋-抑制机制失衡。因此,探索哮喘时包括MG在内的胶质细胞的内在激活机制及特异性抑制方法,是抑制气道迷走神经高张性的可行策略。文献表明:外周过敏性疾病时,脊髓内MG-星形胶质细胞被内皮素-1通过其B型受体激活。本项目假设这一机制也存在于哮喘时的气道迷走中枢,拟用膜片钳电生理、肺功能体积描记、western-blot、免疫荧光、RT-PCR、原位杂交等方法进行验证。执行本项目有助于进一步阐明哮喘时气道迷走神经活动增强的机制并促进其防治。

Airway vagal hypertonia is an important link in the pathogenesis of asthma, especially in the pathogenesis of severe asthma attacks. In our previous studies, we have proved that microglia in airway vagal centers are activated in rat model of asthma. Via subsequent activation of BDNF-TrkB-NKCC1/KCC2 pathway in airway vagal preganglionic neurons (AVPNs), microglia activation increases the concentration of neuronal intracellular chloride, leading to reduced or even converted response of AVPNs to inhibitory neurotransmitters. Meanwhile, microglia activation in airway vagal centers decreases the expression and activity of ecto-5’-nucleotidases (CD73, the rate-limiting enzyme in the conversion of extracellular ATP to adenosine), and alters the balance between the ATP-mediated excitation and adenosine-mediated inhibition of AVPNs. Therefore, for the prevention and treatment of asthmatic airway vagal hypertonia, it is an important strategy to investigate the endogenous activating mechanisms of brainstem glial cells including microglia, and to develop specific inhibitors of glial activation. There has been evidence that in peripheral allergic diseases, microglia-astrocytes in the spinal cord are activated by endothelin-1 through activation of endothelin receptor type B. We hypothesize that similar mechanisms might also exist in airway vagal centers in asthma. In this proposal, we aim to test this hypothesis using patch-clamp electrophysiology, plethysmographic evaluation of airway vagal tone, western-blot, immunofluorescent staining, RT-PCR and in situ hybridization. Execution of this proposal will further elucidate the mechanisms involved in the pathogenesis of asthmatic airway vagal hypertonia, and will promote the search for new anti-asthma drugs or therapy.