胰腺腺泡细胞－树突状细胞转分化及mTOR-TU.1调控与重症急性胰腺炎早期损伤关系

Clinical studies have found, the early blocking progression can significantly reduce the mortality and improve the prognosis of severe acute pancreatitis patient, but there are lack of effective therapeutic targets of the early stages of SAP. Our previous work has found that in the early stage of SAP, pancreatic acinar epithelium cells significant express DC-SIGN and present epithelium-dendritic cell transdifferentiation phenomenon. Meanwhile in the early phase of inflammatory reaction of intestine, stomach and other digestive organs, if DC-SIGN was blocked by Rapamycin, pathological severity significantly decreased. Therefore, we speculate that in the early stage of SAP, as the iconic molecule of epithelium-dendritic cell transdifferentiation phenomenon, DC-SIGN plays an important role in immune regulation at the initial stage of inflammation. Our group intends to investigate the connection between epithelium-dendritic cell transdifferentiation and the early stage of SAP, and to research the mechanism of DC-SIGN activating naïve CD4+ T cell and the mediated role of mTOR-PU.1 pathway of epithelium-dendritic cell transdifferentiation. The research of DC-SIGN and its upstream and downstream pathways, is to provide a new clinical target of blocking initiate stage of SAP, thereby blocking the pathological process and improving the prognosis.

近年来多项临床研究发现：对于重症急性胰腺炎病人，若能早期阻断其病程进展能显著降低死亡率并改善预后，但是目前临床上缺乏针对早期阶段的有效治疗靶点。本课题组前期研究工作发现，在重症急性胰腺炎早期阶段，胰腺腺泡上皮细胞显著表达DC-SIGN并存在“上皮－树突状细胞转分化”现象。同时在大肠、小肠、胃等消化道器官的早期炎症反应中，若用雷帕霉素阻断DC-SIGN，病理严重程度显著下降。因此我们推测在重症急性胰腺炎病程中，DC-SIGN作为“上皮-树突状细胞转分化”现象的标志性分子，在炎症起始阶段起到重要的免疫激活作用。本课题组拟研究“上皮-树突状细胞转分化”和重症急性胰腺炎早期损伤的关系以及DC-SIGN对初始CD4 T细胞的激活作用及其机制，同时探讨mTOR-PU.1途径对“上皮-树突状细胞转分化”现象的介导作用。DC-SIGN及其上、下游通路的研究，将为临床阻断重症急性胰腺炎始动阶段提供新的靶点。

本项目基于前期研究发现，胰腺腺泡细胞在重症急性胰腺炎（SAP）早期可发生“上皮-树突状细胞转分化”，表达树突状细胞（DC）表型分子DC-SIGN，且在后者调控下具有诱导T细胞促炎应答的DC样功能，在SAP炎症启动及免疫损伤中发挥区室化调节作用。在此基础上，本项目进一步从胰腺腺泡细胞DC样转分化及其区室化调节角度，结合干预手段，围绕并进行了炎症状态下SAP局部免疫微环境及其区域免疫特征等研究。首先从DC-SIGN免疫调节角度，验证了胰腺腺泡细胞DC-SIGN表达与SAP炎症损伤及疾病严重程度关系。提示上述DC样转分化现象可能系上皮细胞基于上皮组织区域免疫特征及区室化调节格局，以此调节局部炎症的一种表现形式，并与组织器官炎症损伤及疾病进展密切关联。其次结合DC-SIGN调控胰腺腺泡细胞诱导T细胞分化及促炎应答的DC样功能，从SAP局部免疫微环境及全身免疫紊乱角度，观察探讨了SAP过程中CD4+T细胞分化及促炎应答异常状况。发现伴随疾病进程，SAP局部及全身出现Th1/Th2、Th17/Treg失衡以及Tfh上调，与体外证实的DC-SIGN介导胰腺腺泡细胞调节有关，并与SAP病程中出现机体免疫紊乱或损伤密切关联。继而结合DC-SIGN免疫调节以及与SAP局部免疫微环境紊乱关系，观察探讨了DC-SIGN表达调控因素及机制，发现证实，mTOR-Myc通路参与调控胰腺腺泡细胞表达DC-SIGN，进而调控胰腺腺泡细胞DC样转分化。且发现c-Myc可通过结合于DC-SIGN启动子区域直接调控其表达。干预mTOR-Myc通路，则可抑制DC-SIGN表达，阻抑胰腺腺泡细胞DC样转分化及其诱导的Th1/Th2及Th17/Treg失衡以及SAP免疫紊乱。在此基础上，分别观察了mTOR抑制剂雷帕霉素及人脂肪干细胞来源外泌体（hASCs-exo）对SAP防治效应，以及该效应与CD4+ T细胞分化调节关系。发现证实，雷帕霉素可通过抑制SAP诱发mTOR活化阻抑DC-SIGN表达，相应上调Th1/Th2及Th17/Treg比例，减轻CD4+T细胞促炎应答并缓解SAP炎症损伤。hASCs-exo则可通过上调胰腺组织Naive CD4+ T细胞及Treg比例，改善胰腺组织免疫微环境，促进SAP损伤后组织修复。上述结果有助于进一步阐述SAP病理机制及其重症化因素，并为临床防治提供新的干预靶标和治疗策略。