PD1/PD-L1调控中性粒细胞凋亡在重症急性胰腺炎中的作用机制研究

Severe acute pancreatitis (SAP) is a serious disease, the mortality will be high when SAP progresses to systemic inflammatory response syndrome (SIRS) and/or multiple organ dysfunction syndrome (MODS). Abnormal apoptosis of inflammatory cells serves as an important pathogenic mechanism for the excessive inflammatory response of SIRS/MODS. Programmed Death 1/Programmed Death Ligand-l (PD-1/PD-Ll) is a important immune adaptor, and it could negatively regulate immune response of inflammatory diseases by inducing the apoptosis of inflammatory cells. The results from our preliminary study showed: PD-L1 was positively expressed on inflammatory cells which infiltrated in pancreas in SAP ; Flow cytometry analyze showed PD-L1 was upregulated on neutrophils in SAP , and the upregulation of PD-L1 was paralleled with the increased apoptosis rate. Based on these results, we propose that PD-L1 modulated immune response functions in the development AP/SAP. This project will focus on PD-1/PD-L1 regulated neutrophil apoptosis, by using PD-1/PD-L1 gene knockout/knock in mice, co-culture system and peripheral blood analyze of SAP patients, to further explore the exact role and effects of PD-1/PD-L1 regulated inflammation in AP/SAP. The results from this project will provide new insight for SAP pathogenesis, and provide research evidences for further transnational intervention or therapeutic strategy for SAP.

重症急性胰腺炎(SAP)病情凶险，合并全身炎性反应综合征(SIRS)和多器官功能障碍(MODS)时死亡率高。炎性细胞凋亡异常是引起SIRS/MODS过度炎症反应的重要机制。程序性死亡受体1/程序性死亡受体配体1(PD1/PD-L1)是机体免疫重要调控分子,在炎性疾病中主要通过影响炎性细胞凋亡发挥作用。团队前期研究发现:PD-L1在SAP胰腺浸润的炎性细胞中呈阳性表达；外周血细胞类群分析显示PD-L1在SAP中性粒细胞中表达上调,且该上调伴随中性粒细胞凋亡水平升高。这些发现提示：在SAP中,存在PD1/PD-L1相关的炎症免疫调控。本项目拟以PD1/PD-L1调控中性粒细胞凋亡为切入点,通过基因敲除/敲入小鼠、体外共培养体系,结合SAP患者外周血检测分析,进一步探索PD1/PD-L1炎性调控对SAP发生发展的影响及机制,结果将对SAP发病提出新的认识,并为SAP治疗提供转化思路和实验依据。

【背景及目的】.急性胰腺炎（AP）起病急骤，可迅速引起SIRS/MODS等全身并发症，进展为重症急性胰腺炎（SAP），其死亡率可以高达35%。机体的促炎和抑炎系统处于相对平衡状态，而过度的炎性反应是AP重症化的重要原因。这种过度炎症反应可能是由异常的免疫细胞凋亡引起。程序性死亡受体1/程序性死亡受体配体1(PD1/PD-L1)是机体免疫调控的重要靶点，PD-L1与PD1结合后可抑制活化的免疫细胞增殖和促进免疫细胞凋亡。那么PD-L1是否可以通过调节免疫细胞的凋亡影响AP的发生发展目前还没有研究。因此，本研究以PD-L1调控免疫细胞凋亡为切入点，深入探索PD-L1对免疫细胞凋亡规律的影响以及对AP严重程度的影响，拟为临床治疗提供新的思路及实验依据。.【研究内容】.1. 探讨不同严重程度急性胰腺炎（AP）患者外周血免疫细胞的PD-L1表达情况。.2. 探讨不同时间点AP小鼠模型外周血免疫细胞PD-L1表达规律。.3. 探讨PD-L1基因缺失小鼠（PD-L1-/-）AP严重程度改变及外周血免疫细胞凋亡及胰腺免疫细胞浸润情况。.4. 探讨PD-L1抑制剂（泰圣奇）对PD-L1人源化小鼠急性胰腺炎严重程度的影响。.【结果】.AP患者和AP小鼠外周血免疫细胞的PD-L1表达与急性胰腺炎严重程度呈正相关；PD-L1缺失小鼠AP外周血免疫细胞凋亡趋势及胰腺浸润免疫细胞组成改变，急性胰腺炎严重程度降低，病程缩短；泰圣奇可通过抑制PD-L1显著降低人源化小鼠急性胰腺炎的严重程度。.【结论】.PD-L1参与了AP的发生发展，外周血免疫细胞PD-L1表达与AP严重程度呈正相关，PD-L1在急性炎症中发挥促炎作用。敲除PD-L1缓解了AP炎症进程，通过改变外周血多种免疫细胞的凋亡规律，进而影响胰腺浸润免疫细胞组成可能为作用机制之一；泰圣奇可通过抑制PD-L1显著降低人源化小鼠急性胰腺炎的严重程度。降低或抑制PD-L1可成为AP的治疗策略，为临床实践提供借鉴及思路。