基于TLR2/4-ROS-PI3K-Akt信号通路探讨厌氧消化链球菌在幽门螺杆菌致病中的作用

Gastrointestinal microbiota plays an important role in the pathogenesis of Helicobacter pylori (Hp). Recent studies have indicated that Peptostreptococcus anaerobius (Pa) as the major component of gastrointestinal flora has been revealed to induce ROS production via Toll-like receptor (TLR) 2/4, which contributes to malignant transformation of intestinal mucosa. Our previous work has shown a significant accumulation of Peptostreptococcus species including Pa in the gastric mucosa of Hp-infected mice, and an increase in relative abundance of Pa in the cascade of events from gastric inflammation to carcinoma, and these findings suggest that Pa is involved in the pathogenesis of Hp. Futhermore, Pa has been found to promote the PI3K/Akt signaling pathway in gastric epithelial cells. However, it remains unclear whether Pa could act in synergy with Hp in gastric carcinogenesis and this synergic effect is dependent on ROS-PI3K-Akt signaling pathway. Based on previous studies and our preliminary findings, we will: (1) investigate the effect of Pa in the pathogenesis of Hp in human samples, cell lines, and INS-GAS transgenic mice; (2) explore if TLR2/4-induced ROS-PI3K-Akt pathway is responsible for Pa in synergy with Hp in the gastric tumorigenesis using inhibitors (siRNAs) of TLR2/4 or ROS scavenger. Completion of this study could contribute to understanding the effect of imbalance of gastric flora in the pathogenesis and provide a new insight for prevention and management of Hp infection.

胃肠菌群在幽门螺杆菌（Hp）感染引起的胃黏膜病变过程中发挥重要作用。新近研究表明厌氧消化链球菌（Pa）作为胃肠菌群的组成部分，可作用于Toll样受体（TLR）2/4诱导活性氧（ROS）产生，促进肠黏膜恶性转化。我们的前期研究显示Hp感染小鼠胃黏膜Pa所在菌属丰度增加，且胃黏膜炎-癌转化过程中Pa丰度逐渐升高，提示Pa参与了Hp感染导致的胃黏膜癌变；进一步发现Pa感染胃上皮细胞后可激活ROS下游PI3K/Akt通路。然而，Pa能否协同Hp致病及TLR2/4介导的ROS-PI3K-Akt通路在其中的作用尚不清楚。本课题拟在人体、细胞及INS-GAS转基因小鼠多层面研究Pa对Hp致病的影响，并通过调控ROS、TLR2/4表达，明确Pa协同Hp致病是否通过TLR2/4-ROS-PI3K-Akt信号这一机制。研究结果将有望阐明胃内微生态失衡对Hp致病的影响，为Hp感染相关疾病的防治研究提供新思路。

胃肠菌群在幽门螺杆菌（H. pylori）感染引起的胃黏膜病变过程中发挥重要作用。新近研究表明厌氧消化链球菌（P. anaerobius）作为胃肠菌群的组成部分，可作用于Toll样受体（TLR）2/4，促进肠黏膜恶性转化。我们的研究显示胃黏膜癌变过程P. anaerobius丰度逐渐升高，提示P. anaerobius参与了H. pylori感染导致的胃黏膜癌变；进一步发现P. anaerobius感染胃上皮细胞后可引起细胞增殖、侵袭、迁移等行为能力增强，且介导显著的炎症反应。机制层面，通过转录组学分析，我们发现P. anaerobius菌感染细胞后，NF-κB信号通路显著富集。我们推测P. anaerobius菌可通过激活NF-κB信号通路促进胃黏膜炎症。实验结果证实P. anaerobius菌通过可显著上调细胞p-P65（Ser536）、p-IKK（Ser176/180）表达，显著下调IκBα表达，促进P65入核。且这一过程依赖TLR4/TRIF的活化，抑制TLR4可明显减轻P. anaerobius菌介导的NF-κB信号通路活化及细胞炎症。最终，我们通过P. anaerobius菌感染的动物模型进一步验证了细胞实验的结果。总而言之，我们的实验发现P. anaerobius感染可介导胃上皮细胞生物学行为改变，引起INS-GAS小鼠胃黏膜病变，促进体内外炎症反应; P. anaerobius感染通过TLR4/TRIF/NF-κB信号通路促进胃黏膜炎症，抑制TLR4及TRIF可明显减轻P. anaerobius感染介导的炎症反应。以上结果可为菌群参与胃癌发生提供新证据，为通过微生态干预预防胃癌提供新思路。