儿童肠肝免疫稳态的维持机制研究

Biliary atresia (BA) and paediatric-onset inflammatory bowel disease (PIBD) affect the wellbeing of many infants and children. Poor understanding of disease pathogenesis and limited treatment regimens have prevented the prognosis of children with BA or PIBD. To improve diagnosis and treatment, it is critical to address the following key scientific questions: (1) What are the mechanisms maintaining gut-liver immune homeostasis in paediatric populations? (2) What environmental and genetic factors break gut-liver immune homeostasis? (3) How to restore gut-liver immune homeostasis? To answer these questions, we have previously profiled colonic mucosae of control and PIBD patients, and have uncovered that defects in the cAMP-response pathway promoted a cascade of immune deviation signified by macrophage hyper-inflammation. More importantly, we demonstrated that a pan-phosphodiesterase (PDE) inhibitor dipyridamole was able to restore gut immune homeostasis and alleviate clinical symptoms of children with PIBD (Cell, 2019). Preliminary studies further revealed that: (1) a blockade of enterohepatic circulation of bile acids in patients with BA, or genetic mutations in NLRP3 and RADX, promote colonic macrophage hyper-inflammation. (2) PDE inhibitor dipyridamole was effective in restoring gut-liver immune homeostasis in a mouse model of BA. Based on these results, we hypothesized that genetic predispositions and metabolic disorders promote macrophage hyper-inflammation in the guts of children with BA or PIBD, leading to gut leakiness. Pathogens or microbial-associated molecular patterns transport via the enterohepatic circulation and cause liver immune deviation and fibrosis. To consolidate this hypothesis, we will employ genetic and multi-omics methodology to systemically address the cellular and molecular mechanisms that govern gut-liver immune homeostasis. We will also use animal models and clinical trials to explore feasibility of using PDE inhibitors to treat PIBD and BA.

炎症性肠病和胆道闭锁是由肠-肝免疫稳态失衡所致的、符合指南方向2的重大儿童疾病，防治困难。亟需回答的科学问题有：婴幼儿期肠-肝功能稳态如何维持？遗传环境因素如何破坏肠-肝稳态？稳态能否重建？团队前期发现cAMP第二信使通路缺陷促进巨噬细胞过度炎症，而PDE抑制剂可有效恢复炎症性肠病患儿肠道黏膜稳态（Cell，2019）。进一步研究发现：（1）新生儿肝脏造血及胆汁酸代谢异常促进胆道闭锁患儿肝脏衰竭（Cell待修回），而NLRP3（JACI已修回）、RADX等突变，促进肠道巨噬细胞炎症响应；（2）PDE抑制剂促进疾病模型鼠的肠-肝免疫修复。据此假设：基因突变、代谢紊乱等内外在因素交互促进婴幼儿肠道巨噬细胞过度炎症反应，破坏黏膜屏障，经肠肝循环导致肝脏功能紊乱。本课题拟采用遗传免疫及多组学手段，系统阐述儿童肠-肝免疫稳态的维持机制，验证PDE抑制剂治疗炎症性肠病及胆道闭锁的临床应用前景。

本课题从新生儿和儿童组织器官区域免疫特性与疾病出发，研究炎症性肠病和胆道闭锁的病理机制，回答如下科学问题：婴幼儿肠肝功能稳态建立的细胞学基础是什么？如何利用药物治疗恢复儿童肠肝功能稳态？调节炎症性单核/巨噬细胞激活的分子机制有哪些？在本课题执行过程中，我们建立了儿童肠道免疫和非免疫细胞以及肝脏免疫细胞的单细胞图谱,获得了磷酸二酯酶抑制剂（PDEi）在模型鼠中治疗有效性的数据，并在此基础上产生了炎症性肠病和胆道闭锁患儿治疗后的单细胞转录组学数据。部分研究结果已整理投稿，其中一项研究发现：肠道和嗜肝病毒感染可以导致新生儿发生系统性铁过载和叶酸吸收及代谢障碍，而叶酸治疗则可以抑制肠道和肝脏的脂质过氧化损伤，降低胆道闭锁患儿术后胆管炎的发生率，抑制肝脏纤维化进展（Science Translational Medicine，修回中）。除此之外，我们证实PDEi双嘧达莫可以治疗轮状病毒引起的新生儿腹泻，完成了干混悬儿童制剂开发，即将进入药物临床试验阶段。针对调控炎症性单核巨噬细胞活化的机制，项目团队揭示了基因组损伤修复相关基因RADX突变诱导肠道炎症机制，阐述了固有免疫受体AIM2识别有机污染物诱发炎症机制，描述了抗病毒信号分子TBK1和IRF3的自嗜降解机制，以及蛋白质棕榈酰化促进NOD2活化机制等。综上所述，项目团队认真履行了课题研究计划，获取了独特的新生儿组织器官，疾病特性及药物应答数据，阐述了调控单核/巨噬细胞功能的新机制，并启动了儿童药物制剂研发。这些研究不仅丰富了儿童消化系统疾病的病理机制，也将进一步推动诊疗方式的进步。