牙龈卟啉单胞菌通过NLRPs炎症小体途径促进结肠上皮细胞恶性转化的机制研究

Oral microbiome has a tight association with gastrointestinal cancer, but its causal relationship and interaction mechanism are failed to be described in great depth. The researchers have found the presence of Porphyromonas gingivalis(Pg) correlated with colon cancer. Our preliminary experiments showed that Pg detected in the feces of high-sugar diet mice has a relatively high abundance. Moreover, we also established the colon cancer induced by Pg-intestinal infection model, where the expression changes of NLRPs complex related inflammatory molecules can be detected in the tissue microenvironment. Thus, this research hypothesis: intestinal microflora disorders (mainly increased by Pg) could promote colon cancer growth and metastasis through NLRPs inflammation complex pathways, Pg spontaneously induced tumorigenesis can be affected by systemic glucose metabolism. This project adopts the most typical inflammatory carcinoma transformation model of colon cancer, focusing on the molecular mechanisms mediated by inflammation complex both in intestinal epithelial cells and mucosal immune cells, and the regulation mechanism through multi-level study of oral microbial induced intestinal flora imbalance and inflammatory carcinoma transformation. Meanwhile, we use metagenomics analysis to explore the influence of this progress based on the whole body metabolic factors, providing a theoretical basis for the interaction mechanisms of subsequent metabolism. Ultimately, we intended to propose the new ideas for systemic diseases associated clinical transformation strategy by exploring the nutritional metabolism induction and micro-ecology balance.

口腔微生物与消化道肿瘤具有较强的相关性，但前者在肿瘤发生中的演替规律、因果关系及互作机制未能得到深入阐释。本课题组预实验结果显示高糖饮食小鼠粪便中检测到牙龈卟啉单胞菌（Pg）数量增多，而Pg肠道感染模型可诱发结肠癌，该癌变组织微环境中检测到炎症小体NLRPs相关炎性分子表达变化。由此，本研究假设：Pg增多引起的肠道微生态失衡可通过NLRPs炎症小体途径促进结肠上皮恶性转化，且Pg自发诱癌可受全身系统糖代谢影响。本项目以消化道肿瘤中炎癌转换最典型的结肠癌为模型，同时关注肠上皮细胞和黏膜下免疫细胞内炎症小体介导的的分子机制，多层次地研究口腔微生物诱发的肠道微生态失衡与炎癌转化的的调控机制。同时利用元基因组技术探索全身糖代谢因素对此过程的影响，以期为后续代谢互作机制提供理论基础，最终拟为开拓针对营养代谢感应和微生态平衡的全身性重大疾病的临床转化策略提供新思路。

定植于口腔的微生物是人体最复杂的微生物群落之一。口腔作为人体消化道的起始，其微生物不仅促进口腔上皮的恶性转化，还可通过“口-肠轴”影响肠道菌群，引起肠道微生态失衡和免疫微环境的改变，促进结肠上皮的恶性转化。然而，口腔微生物在消化道肿瘤发生中的演替规律、因果关系互作机制未能得到深入阐释。.本项目首先明确了牙龈卟啉单胞菌P.g在口腔黏膜上皮恶性转化中的作用及潜在机制，发现了P.g可侵入口腔上皮并定植，促进口腔上皮黏膜恶性转化，是促进口腔上皮黏膜恶性转化的独立危险因素，其潜在机制可能是通过募集免疫抑制细胞以达到肿瘤免疫逃逸。相关结果发表于口腔医学顶级期刊J Dent Res，2020，JCR一区，且该刊主编同期撰写述评“A New Era for the Oral Microbiome”中引用我们的研究结果，认同我们的研究在为预测、预防或治疗口腔微生物相关疾病提供理论依据做出的贡献。 .同时，本项目探讨了P.g在结直肠癌组织中定植与临床预后之间的相关性，并阐明了P.g在结直肠癌发生发展中的作用。证实了P.g可直接定植于结肠癌组织，且定植与不良预后相关，动物实验明确P.g能够促进结肠癌的发生与发展，机制探究发现P.g感染能够上调结肠癌细胞内质网应激水平，调控自噬相关蛋白表达，促进自噬小体形成，同时阻断自噬溶酶体形成以达到长期定植目的。定植后，P.g通过牙龈蛋白酶（gingipain）激活MAPK/ERK通路促进结直肠癌进展。P.g除了对癌细胞的直接作用，还可通过改变肠道免疫微环境，激活髓系细胞NLRP3炎症小体通路促进结肠癌发生。以上研究结果首次全面地确立了口腔黏膜稳态失衡作为驱动因素促进肠道炎症和炎-癌转化的机制，并提供了一种通过防控口腔从而防控全身疾病的新策略，相关结果已发表在Cancer Res，2021，JCR一区，以及Front Cell Infect Microbiol, 2020, JCR一区。.本项目提出牙周关键致病菌P.g促进口腔癌和结肠癌的发生机制，最终拟为开拓针对微生态平衡的全身性重大疾病的临床转化策略提供新思路。