琥珀酸/GPR91信号调控间充质干细胞免疫治疗肝衰竭的作用与机制

Liver failure is characterized with poor prognosis and high mortality; the migration into the injured sites and the immunoregulatory function are required for mesenchymal stem cell (MSC) therapy for liver failure, however, the effects and regulating mechanisms of MSC on liver failure have not been well clarified. The scientific problem of this project is how microenvironment could affect the immunotherapeutic effects of MSC. The liver has the characteristics of metabolic microenvironment. The preliminary experiment showed that succinate, the intermediate product of tricarboxylic acid cycle, increased during liver failure. Succinate, acting on its receptor GPR91, can affect cell migration and immune response. The preliminary experiments also showed that MSC expressed GPR91; succinate/GPR91 promoted the immunotherapeutic effects of MSC on acute liver failure; succinate enhanced the ability of MSC inhibiting T cell proliferation, enhanced the expression of CXCR4 and the key protein of chaperone-mediated autophagy (CMA)- LAMP2A, while inhibited PPAR-γ expression. On the previous results, this project proposed to focus on the metabolic microenvironment of liver failure and the effect of microenvironment on MSC immunoregulatory function, and systematically explored the mechanism of succinate/GPR91 on MSC migration and immunosuppression thereby treating liver failure; investigated the associated mechanism of PPAR-γ and CMA. Therefore, this project would provide theoretical and experimental basis for a novel strategy for optimizing MSC treatment for liver failure by targeting succinate/GPR91.

肝衰竭预后差死亡率高；间充质干细胞（MSC）向损伤部位迁移和发挥免疫调节功能是其治疗肝衰竭的关键，然MSC治疗肝衰竭效应及调控机制尚未阐明。本项目聚焦的科学问题是：疾病微环境对MSC免疫治疗肝衰竭的调控机制。肝脏具有代谢微环境特征，预实验发现肝衰竭中三羧酸循环中间产物琥珀酸升高。琥珀酸作用受体GPR91可影响细胞迁移和免疫反应。预实验发现MSC表达GPR91；琥珀酸/GPR91促进MSC治疗急性肝衰竭，琥珀酸增强MSC抑制T细胞增殖能力、CXCR4与分子伴侣自噬（CMA）蛋白LAMP2A表达，抑制代谢调节因子PPAR-γ表达。因此，本项目拟从肝衰竭代谢微环境及疾病微环境影响MSC免疫调节切入，研究和明确琥珀酸/GPR91调控MSC迁移和免疫抑制功能促进其免疫治疗肝衰竭的作用，解析PPAR-γ和CMA参与的关键机制，为形成干预琥珀酸/GPR91信号为核心的优化MSC治疗肝衰竭新策略提供依据。

肝衰竭预后差死亡率高；间充质干细胞（MSC）发挥免疫调节功能是其治疗肝衰竭的关键，然其治疗的效应及调控机制尚未阐明。本项目研究发现肝衰竭小鼠的肝脏具有代谢微环境特征，表现为三羧酸循环中间产物琥珀酸异常累积；琥珀酸激活对应受体GPR91可上调MSC中免疫抑制因子COX2和iNOS表达，正向调控MSC免疫抑制功能，从而增强其免疫治疗小鼠肝衰竭的作用。此外，炎症因子诱导MSC免疫抑制功能中分子伴侣自噬（CMA）水平受到抑制，发挥负向调控免疫抑制作用，即CMA通过抑制NF-κB及STAT1信号通路导致CXCL10与iNOS表达降低从而影响了MSC免疫抑制及其免疫治疗肝衰竭的作用。而琥珀酸/GPR91信号对MSC的调控作用恰恰与CMA密切相关，GPR91和CMA有望成为优化MSC免疫治疗肝衰竭的重要干预靶点。.同时，我们聚焦肝脏代谢微环境特征对肝脏免疫反应的调控作用，发现激活脂代谢性受体GPR120能够诱导调节性DC生成，抑制T细胞免疫反应，缓解小鼠肝损伤。聚焦表观遗传调控免疫抑制在肝衰竭治疗中的作用，发现：抑制Dot1L可通过增强MDSCs免疫抑制功能，减轻CD4+ T细胞介导的炎症反应，缓解小鼠的肝损伤；Dot1L主要通过介导SOCS1启动子区域的H3K79me2修饰，上调SOCS1的表达，进而抑制STAT1信号通路的活化水平，下调诱导型iNOS的表达，从而调抑MDSCs缓解肝脏及外周炎症反应的免疫抑制功能。.本项目为代谢微环境调控免疫反应拓展了新思路，为MSC等相关免疫治疗肝衰竭等肝脏疾病提供新的策略与潜在靶点。