细菌信号分子c-di-AMP通过STING信号通路调节牙周固有免疫的实验研究

Cyclic dimeric adenosine monophosphate (c-di-AMP) is a newly discovered second messenger in bacteria and archaea. Although many details of the c-di-AMP signaling network remain to be discovered, this nucleotide has been linked to the regulation of fatty acid synthesis, to the sensing of DNA integrity, to cell wall homeostasis in mutiple bacterial species,and to trigger the cytosolic host response.Cytosolic detection of pathogen-derived nucleic acids is critical for the initiation of innate immune defense against diverse bacterial, viral and eukaryotic pathogens. Conversely, inappropriate responses to cytosolic nucleic acids can produce severe autoimmune pathology. The host protein STING has been identified as a central signaling molecule in the innate immune response to cytosolic nucleic acids. STING seems to be especially critical for responses to cytosolic DNA and the unique bacterial nucleic acids called ‘cyclic dinucleotides’..Periodontitis is a common dental disease which results in irreversible alveolar bone loss around teeth, and subsequent tooth loss. Previous studies have focused on bacteria that damage the host and the roles of commensals to facilitate their colonization. Recent studies show that particular host defense responses to oral bacteria can induce alveolar bone loss. Host-damaging and immunostimulatory oral bacteria cooperatively induce bone loss by inducing gingival damage followed by immunostimulation. We have detected c-di-AMP in the extracts of P.gingivalis cells, suggesting that P.gingivalis can produce c-di-AMP, and found the the expression of DDX41and cGAS, the cytosolic DNA sensors, were higher in inflammantal gingival tissues than in normal gingival tissues. According to the published research results and our investigation, we hypothesized that c-di-AMP may play a important role in innate immunity of periodontal tissues through STING /IFN-β pathway. To prove the hypothesis, cell and animal models will be used to investagate the role of c-di-AMP in innate immunity of periodontal tissues and explore the signaling pathway.

c-di-AMP是细菌中广泛存在的环二核苷酸（CDNs）信号分子，作为新发现的病原相关分子模式（PAMPs），c-di-AMP可激活宿主固有免疫反应。目前有关CDNs类PAMPs在牙周组织固有免疫应答中的调节作用及其信号途径尚未阐明。项目组根据文献和预实验结果假设：牙周微生物产生的c-di-AMP可被牙周组织细胞内的CDNs受体所识别，并通过STING信号通路激活牙周固有免疫应答反应，刺激I型干扰素和前炎性细胞因子的产生。为进一步证实该假说，项目将通过细胞和动物模型深入研究c-di-AMP通过STING信号通路对牙周组织I型干扰素反应的调节作用；确定其信号途径中c-di-AMP的胞内受体、信号传递和活化的基因，以及STING信号通路在牙周炎组织损伤中的作用。本项目旨在深入了解口腔微生物所产生的环二核苷酸组分在牙周病发病机制中的信号传导调节，为探索牙周病的有效治疗方法奠定理论基础。

c-di-AMP是细菌中广泛存在的环二核苷酸（CDNs）信号分子，作为新发现的病原相关分子模式（PAMPs），c-di-AMP可激活宿主固有免疫反应。目前有关CDNs类PAMPs在牙周组织固有免疫应答中的调节作用及其信号途径尚未阐明。项目组根据文献和预实验结果假设：牙周微生物产生的c-di-AMP可被牙周组织细胞内的CDNs受体所识别，并通过STING信号通路激活牙周固有免疫应答反应，刺激I型干扰素和前炎性细胞因子的产生。但我们的研究结果显示，虽然牙周致病菌p.gingivalis可以合成并分泌c-di-AMP。但进入牙周膜细胞内的c-di-AMP，并不能激活细胞内的候选PRRs：STING、DDX41和cGAS。其所诱导产生的I型干扰素反应是十分微弱的。而p.gingivalis的活菌侵入牙周膜细胞不仅能显著上调STING、DDX41和cGAS的表达，并且可以促发较强烈的I型干扰素反应。这些研究结果说明，细菌所产生的CDNs作为PAPMs在不同的细胞中其结合的PRRs可能存在着差异，其所促发的I型干扰素反应也主要在免疫细胞中。p.gingivalis作为牙周炎的主要致病菌，其菌体中的其他成分或许可以和STING、DDX41或cGAS结合，并促发I型干扰素反应。但究竟是何种菌体成分，仍需要后续研究。.本项目研究了革兰氏阴性细菌所产生的CDNs类信号分子c-di-AMP，随细菌进入牙周膜细胞，对牙周固有免疫的影响及其可能的信号通路。本课题的研究结果可以帮助我们深入了解口腔微生物所产生的不同组分在牙周病发病机制中的信号传导调节，为探索牙周病的有效治疗方法奠定理论基础。