α7 nAChR内源性配体SLURP1介导新生儿大肠杆菌脑膜炎的作用和机制

Recently, the concept of host-directed antimicrobial drugs against pathogens has received widespread attention in the scientific community. Our previous studies have shown that memantine, an α7 nAChR antagonist, could efficiently block neonatal Escherichia coli (E. coli) meningitis. However, the exact mechanisms by which α7 nAChR contribute to the neonatal E. coli meningitis remain unknown. Recently, in our preliminary study, it was shown that E. coli could enhance the expression of SLURP1, an endogenous ligand of a7 nAChR. We also found that SLURP1 could promote E. coli-induced invasion of brain microvascular endothelial cell and polymorphonuclear neutrophil transmigration. Therefore, we hypothesize that enhancement in the expression of SLURP1 could represent the underlying mechanism to explain the contribution of α7 nAChR to neonatal E. coli meningitis. In this proposal, we will dissect this underlying mechanism of SLURP1-α7 nAChR using gene editing technique, cell and animal models, α7 nAChR knockout mice, kinase inhibitors and so on. The completion of this project will provide novel evidence into the development of α7 nAChR antagonists in the prevention and treatment of neonatal E. coli meningitis.

以细菌感染宿主的重要信号通路为靶点是目前抗感染治疗的研究前沿。前期研究中，我们发现以α7 nAChR为靶点能有效防治新生小鼠大肠杆菌（E. coli）脑膜炎，但E. coli如何激活α7 nAChR介导脑膜炎的发生和发展仍未阐明。最近，我们研究发现E. coli可诱导α7 nAChR内源性配体SLURP1的分泌，并初步证明SLURP1可通过α7 nAChR促进E. coli的侵袭和白细胞迁移。据此，我们提出诱导SLURP1分泌是E. coli激活α7 nAChR并介导脑膜炎发生和发展关键环节的研究假说。本项目拟利用过表达和敲除SLURP1等手段，E. coli脑膜炎模型、α7 nAChR敲除小鼠、激酶抑制剂等工具，阐明SLURP1-α 7nAChR在E. coli脑膜炎发生和发展中的关键作用及其分子机制，为明确以α7 nAChR为靶点防治新生儿E. coli K1脑膜炎的机理提供研究基础。

Alpha 7尼古丁乙酰胆碱受体（α7 nAChR）是介导大肠杆菌K1株（E. coli K1）脑膜炎发病的关键因素。但是，E. coli K1如何利用α7 nAChR信号通路来突破血脑屏障引起脑膜炎并不清楚。在本研究中，我们利用体外血脑屏障模型、脑膜炎动物模型和分析公共转录组数据，发现E. coli K1感染可促进α7 nAChR的内源性配体，分泌型哺乳动物Ly-6尿激酶型纤溶酶原激活物受体相关蛋白1（SLURP1）表达。进一步地，我们发现外源性给予SLURP1、过表达或敲低SLURP1表达能显著促进或抑制E. coli K1对脑微血管内皮细胞的入侵，并降低其诱导中性粒细胞迁移的能力。这些结果表明SLURP1是E. coli K1入侵血脑屏障引发脑膜炎所必需的。最后，我们发现敲除α7 nAChR基因能显著阻断SLURP1促进E. coli K1脑膜炎发病的作用。综上所述，我们发现E. coli K1的感染可促进α7 nAChR的内源性配体SLURP1表达，并利用其激活α7 nAChR而介导入侵血脑屏障，最终引起脑膜炎。本研究不仅进一步阐明了E. coli K1入侵血脑屏障的分子机制，同时揭示阻断SLURP1-α7 nAChR相互作用可能成为治疗E. coli K1脑膜炎的新策略。

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