幽门螺杆菌根除后胃肠道微生态的变化及其对胃肠黏膜TLRs介导的免疫应答的影响

Helicobacter pylori (H. pylori) infection disturbs the gastrointestinal microbiota, which plays an important role in pathogenesis of H. pylori-related diseases. H. pylori eradication could rectify the imbalance of gastrointestinal microbiota and reduce the risk of gastric cancer. However, the antibiotics used in the regimen are reported to affect the gastrointestinal microbiota as well, which could not be neglected. As it is unclear whether or when the microbiota will recover, so the implement of H. pylori eradication is affected in large-scale. Our preliminary research indicated that in C57BL/6 mice model, H. pylori infection induced the alteration of the gastrointestinal flora structure, as well as the activation of Toll-like receptors (TLRs) signaling pathway, which mediated the inflammation of mucosa. TLRs constitute the first barrier of the host which protect against pathogens, and participate in maintaining the homeostastis of gastrointestinal mucosa. However, it remains unclear whether the alteration of gastrointestinal microbiota caused by H. pylori could mediate TLRs signaling pathway. Thus, this project plans to explore the effect of H. pylori eradication on gastrointestinal microbiota in human and animals. Moreover, we try to explore the relationships between H. pylori infection and eradication induced alteration of gastrointestinal microbiota and mucosal immune response induced by TLRs using MyD88-/- animal models and fecal microbiota transplantation. The resolution of this issue will provide theoretical and experimental basis for H. pylori eradication in large-scale and the guideline of preventing gastric cancer.

幽门螺杆菌（Hp）感染引起的胃肠道微生态紊乱在Hp致病中发挥重要作用，根除Hp可调节胃肠道微生态异常、降低胃癌发生风险；但Hp根除方案中抗生素等药物可再次引起胃肠道微生态失衡，其失衡程度及能否恢复存在较大争议，从而影响根除Hp的实施。我们前期研究发现Hp感染C57BL/6小鼠可引起胃肠道菌群结构发生变化，并同时观察到Toll样受体（TLRs）信号通路激活及其介导黏膜免疫炎症反应。TLRs构成机体防御病原体感染的第一道屏障，参与了胃肠道黏膜稳态的维持，而Hp感染引起的胃肠道微生态紊乱是否可调节TLRs信号通路尚不明确。因此，本课题拟同时在人体和动物两个层面探讨根除Hp对胃肠道微生态的影响程度及恢复时间；应用MyD88敲除小鼠模型和粪菌移植技术明确Hp感染及根除后胃肠道微生态变化与TLRs信号介导的免疫应答之间的关系。为我国大规模根除Hp，预防胃癌决策的制定提供理论与实验依据。

根除Hp能够有效预防Hp相关疾病，新近研究发现Hp感染能够引起宿主胃肠道菌群结构紊乱，而根除Hp对胃肠道菌群的影响尚不十分清楚。本研究围绕Hp根除对于胃肠道菌群结构的影响及持续时间，益生菌添加对于根除后胃肠道菌群结构紊乱的逆转效应进行系统探讨。首先招募Hp阳性和阴性的无症状年轻志愿者，发现患者接受Hp根除治疗后胃内菌群α多样性显著升高，并随着时间延长而增加。根除后Hp相对丰度从70%下降至0%，而一些潜在的益生功能菌属Lactobacillus和Bifidobacterium相对丰度升高。Hp感染者肠道菌群α多样性显著高于健康对照者。相比于根除前，Hp根除后半年患者肠道菌群中某些具有潜在益生功能的菌属Blautia和Lachnoclostridium显著升高，而致病菌Alistipes相对丰度下降至对照组水平。铋剂四联根除Hp可以恢复胃内菌群的多样性并伴有某些益生细菌增多。Hp根除后的肠道菌群更趋向于健康对照，而非紊乱。在小鼠体内探讨了Hp感染、根除和根除后补充益生菌对胃肠道菌群和肠屏障功能的影响，发现Hp根除可以降低胃肠道菌群多样性，随着时间延长，菌群多样性逐渐升高，添加益生菌可以显著影响根除后小鼠的菌群结构，Hp根除可以降低小鼠肠道屏障指标，而添加益生菌可以促进肠屏障功能指标表达增加。此外，Hp根除可以显著降低小鼠肠道的SCFA，随着时间可恢复。本研究从人体和动物水平探讨了Hp根除对胃肠道菌群的影响，并进一步在动物水平探讨益生菌添加对于Hp根除后的胃肠道菌群的影响，为我国Hp根除策略的实施提供了一定的依据。