5-羟色胺通过HSCs调控Treg细胞参与免疫性肝损伤的机制研究

Regulates T cell (Treg) plays a key role in immunological liver injury, while specific cytokines like TGF-β are needed in the polarization process of Treg. Recent data showed that 5-hydroxytryptamine (5-HT) could activate hepatic stellate cell (HSCs), and activated HSCs would produce large amounts of inflammatory cytokines to regulate immune function. We previously found that 5-HT was involved in the progress of immunological liver injury. We speculated that 5-HT could activate HSCs and some cytokines like TGF-β released from activated HSCs would induce Treg polarization, regulate the function of Treg cells, accentuate inflammation, and ultimately aggravate immunologic injury in the liver. Based on the above ideas, this project aims: ①By TPH1-/- knockout mice based animal model, we further determine the relationship between 5-HT and immunological liver injury; ②By altering the levels of 5-HT receptor or downstream pathways through in-vitro cells experiment, we determine the specific 5-HT receptor(s) that could activate HSCs, and determine the specific cytokines that regulate the function of Treg; ③By clinical cases, we further explore the correlation between 5-HT and patients with immunological liver injury. The accomplishment of this project will help to establish a new theoretical foundation for immunological liver injury, and will provide a new idea for the target therapy.

调节性T细胞（Treg）在免疫性肝损伤中发挥着关键作用，其极化过程需要特定细胞因子如TGF-β的参与。最新研究表明，5-羟色胺（5-HT）可激活肝星状细胞（HSCs），而活化的HSCs可产生大量炎症因子发挥免疫调节功能。我们前期研究提示5-HT参与了免疫性肝损伤的进展。我们推测，5-HT极有可能通过激活HSCs并促使其释放TGF-β等细胞因子诱导Treg细胞极化、调节Treg细胞功能、促进炎症反应等，最终加重免疫性肝损伤。基于上述设想，本项目拟：①通过建立基因敲除小鼠模型，明确5-HT与免疫性肝损伤的关系；②通过体外细胞实验调节5-HT受体及下游通路水平，研究5-HT通过何种受体激活HSCs，活化的HSCs通过分泌哪些细胞因子调控Treg的哪些特性；③通过收集临床病例，探讨5-HT与免疫性肝损伤患者的相关性。本项目的完成将为免疫性肝损伤的病理机制奠定新的理论，亦为寻找新的治疗方案提供思路。

首次发现了血小板源性5-羟色胺与免疫性肝损伤、肝纤维化的关系及其潜在机制。利用野生型及TPH1敲除小鼠（体内5-羟色胺缺失）制造了刀豆蛋白A诱导的免疫性肝损伤及肝纤维化模型，发现TPH1敲除小鼠肝脏损伤及纤维化程度明显减轻；而利用药物干预补足TPH1敲除小鼠缺失的5-羟色胺后，肝脏损伤及纤维化程度加重。进一步研究发现5-羟色胺对免疫性肝损伤及纤维化的损害作用可能是通过调控肝星状细胞、调节性T细胞，促进多种炎症因子的释放、加重肝脏氧化应激损伤、促进肝细胞的凋亡、激活TLRs信号通路等过程实现的。通过体外细胞实验和临床病例，进一步验证了5-HT与免疫性肝损伤的关系及潜在机制。发现刀豆蛋白A造模后小鼠肝组织内5-HT2A受体表达显著增加，而酮色林可通过抑制炎症反应、肝脏氧化应激损伤、肝细胞的凋亡、TLRs信号通路等途径减轻肝脏损伤及纤维化。