肠道菌群靶向卵磷脂代谢激活GPR4炎症信号轴在肝硬化“肠-肝串扰”中的作用及机制研究

The vicious cycle of gut flora imbalance and liver injury, i.e. “gut-liver interaction”, contributes to the progression of cirrhosis, but its mechanism remains unclear. Our previous work demonstrated that cirrhosis increased gut phospholipase A2 bacteria, fecal lysophosphatidylcholine and GPR4 (lysophosphatidylcholine receptor) from ileum tissue. Bioinformatics indicates that gut GPR4 inflammatory signal axis was involved in cirrhosis. This suggest that GPR4 mediated inflammatory signaling axis activated by gut flora targeting phosphatidylcholine metabolism is the key link of “gut-liver interaction” vicious cycle. In this study, we used fecal metagenomics, targeted metabolomics and bioinformatics to construct a gut flora-phosphatidylcholine metabolism association network in liver cirrhosis mice model; and then gut flora inhibition techniques were used to reveal the interaction of gut flora imbalance, gut inflammatory injury and liver injury. Furthermore, we used GPR4 suppression cell and GPR4 knockout cirrhosis mice model to investigate the molecular mechanism of lysophosphatidylcholine-GPR4 mediated inflammatory and its gut and liver injury effects. This study could help to elucidate the pathological mechanism of cirrhosis from the point view of gut flora-phosphatidylcholine metabolism, and provide a new perspective for its prevention and treatment.

肠道菌群失调与肝脏病理改变相互作用（“肠-肝串扰”），是肝硬化进展的恶性循环，但其分子机制不明确。我们前期发现：肝硬化时，肠道产磷脂酶A2细菌、粪便溶血卵磷脂、回肠组织溶血卵磷脂受体GPR4均显著增高；生物信息学提示：肝硬化涉及肠道GPR4炎症信号轴的活化。这提示：肠道菌群靶向卵磷脂代谢介导GPR4炎症信号轴，参与了肝硬化“肠-肝串扰”。为精准揭示这一机制过程，本项目拟对肝硬化小鼠模型行粪便宏基因组学、靶向代谢组学检测，结合生物信息学技术，构建肠道菌群-卵磷脂代谢关联网络；利用肠道菌群抑制技术，解析肝硬化小鼠肠道菌群失调、肠道炎症损伤和肝脏损伤的相互作用。借助GPR4敲降细胞和GPR4基因敲除肝硬化小鼠为研究模型，运用分子生物学技术，阐释溶血卵磷脂-GPR4介导炎症因子释放的分子机制及其肠肝损伤作用。本项目将从肠道菌群-卵磷脂代谢新视角，为肝硬化病理机制的解析及防治提供新思路。

肠道菌群失调与肝脏病理改变相互作用（“肠-肝串扰”），是肝硬化进展的恶性循环，但其分子机制不明确。我们前期发现：肝硬化时，肠道产磷脂酶A2（PLA2）细菌、粪便溶血卵磷脂、回肠组织溶血卵磷脂受体GPR4均显著增高；生物信息学提示：肝硬化涉及肠道GPR4炎症信号轴的活化。为精准揭示这一机制过程，本项目对肝硬化小鼠模型进行了粪便宏基因组学及代谢组学检测并构建了肠道菌群-卵磷脂代谢关联网络；运用分子生物学技术探索了溶血卵磷脂-GPR4介导炎症因子释放的分子机制及其肠肝损伤作用。实验发现：肝硬化小鼠及肝纤维化大鼠肠道产PLA2细菌比例均有升高，粪便PLA2酶活性增强，且肝纤维化大鼠血清IL-6水平较对照组增加，而抑制肠道菌群后，小鼠肝脏纤维化及肠道炎症减轻；此外，我们还发现无论艰难梭菌感染还是其他原因所致腹泻者的粪便代谢物谱和正常对照均有不同，且其粪便中溶血卵磷含量均较正常对照升高2-5倍，提示溶血卵磷脂可能是肠道屏障损伤的通用的致炎物质。同时，分子生物研究表明溶血卵磷脂可诱导脐静脉内皮细胞GPR4表达增加，并激活MAPK（ERK、P38）和NF-κB/P65 等炎症信号通路，促进IL-6等炎症因子的释放。我们的研究表明肠道菌群可靶向卵磷脂代谢介导GPR4炎症信号轴，参与了肝硬化“肠-肝串扰”。另外，我们在研究过程中发现菌群的改变不仅与卵磷脂代谢紊乱有关，亦与嘌呤及嘧啶代谢途径紊乱有关，为下一阶段的研究提供新的靶点，且为肝硬化病理机制的解析及防治提供新思路。