Tim Costimulation in Liver Transplant Ischemia Injury

 描述（由申请人提供）：与器官获取和冷保存相关的缺血再灌注损伤（IRI）是临床肝移植中最具挑战性但研究不足的问题之一。器官IRI通常导致原发性移植物无功能，可能易发生晚期慢性排斥反应，并导致可用于移植的器官严重短缺。本项目将探讨T细胞免疫球蛋白粘蛋白（TIM）家族的细胞表面蛋白（主要由活化的CD 4 + T细胞和巨噬细胞表达）在临床相关的小鼠模型中肝脏IRI的病理生理学中的新功能，该小鼠模型长期冷藏（4 ℃下20小时），随后进行同基因原位肝移植（奥尔特）。总体假设表明，巨噬细胞TIM-4（先天性臂）和CD 4 + T细胞（适应性臂）上的TIM-1之间的信号传导调节冷储存OLT中IR应激期间的促炎（致病性）和肝细胞细胞保护（稳态）应答。目的1：确定IR应激OLT中CD 4 + T细胞特异性TIM-1信号转导的调节机制。目的1.1：研究TIM-1信号传导是否极化肝脏CD 4 + T细胞功能。假设：TIM- 1阻断通过产生对IL-22-STAT 3/c-Myc信号传导的T细胞偏好来减轻肝脏IRI。我们将研究TIM-1激活如何调节CD 4 + T细胞的致病功能，在一个新的模型，肝脏IRI过继转移RAG KO小鼠，并评估在体内和体外肝细胞保护IL-22的需求。目的1.2：研究TIM-1 - IL-22轴发挥肝保护作用导致稳态的机制。假设：TIM-1阻断增强IL-22介导的肝细胞自噬。我们将采用改良的奥尔特模型和良好控制的体外共培养系统来剖析TIM-1 - IL-22调控下肝保护对自噬途径的需求。目的2：确定IR应激OLT中巨噬细胞特异性TIM-4信号转导的调控机制。目的2.1：探讨TIM-4-TLR 4炎症反应的机制。假设：缺陷的巨噬细胞TIM-4信号转导通过Foxo 1/β-连环蛋白网络对TLR 4活化的自限性反馈调节减轻肝脏IR炎症。我们将在CD 11b-DTR小鼠中利用新开发的肝脏IRI模型，其中过继转移的巨噬细胞群体的条件性消融允许解剖IR炎症中先天和代谢途径之间的TIM-4依赖性交叉调节。目的2.2：分析TIM-4在肝脏吞噬功能中的作用。假设：靶向TIM-4抑制局部吞噬作用，以进一步抑制IR应激肝脏中的TLR 4活化反应。由于TIM-4作为磷脂酰丝氨酸（PS）受体发挥功能，我们将应用新开发的吞噬测定来研究巨噬细胞TIM-4信号传导是否调节PS+肝坏死体的结合/吞噬，并有助于IR-炎症的消退。

 DESCRIPTION (provided by applicant): Ischemia-reperfusion injury (IRI) related to organ procurement and cold preservation represents one of the most challenging yet understudied problems in clinical liver transplantation. Organ IRI often leads to primary graft non-function, may predispose to late chronic rejection, and contributes to acute shortage of organs available for transplantation. This project will explore the emerging function of T cell Immunoglobulin Mucin (TIM) family of cell surface proteins (expressed primarily by activate CD4+ T cells and macrophages) in the pathophysiology of hepatic IRI in a clinically relevant mouse model of extended cold storage (20h at 4C) followed by syngeneic orthotopic liver transplantation (OLT). Overall hypothesis states that signaling between macrophage TIM-4 (innate arm) and TIM-1 on CD4+ T cells (adaptive arm) regulates pro-inflammatory (pathogenic) and hepatocyte cytoprotective (homeostatic) responses during IR-stress in cold-stored OLTs. Aim 1: Define regulatory mechanisms of CD4+ T cell-specific TIM-1 signaling in IR-stressed OLTs. Objective 1.1: To investigate whether TIM-1 signaling polarizes hepatic CD4+ T cell function. Hypothesis: TIM- 1 blockade mitigates liver IRI by producing a T cell bias towards IL-22-STAT3/c-Myc signaling. We will study how TIM-1 activation regulates CD4+ T cell pathogenic functions in a new model of liver IRI in adoptively transferred RAG KO mice; and assess the requirement for IL-22 in hepatic cytoprotection both in vivo and in vitro. Objective 1.2: To study the mechanism by which TIM-1 - IL-22 axis exerts hepatoprotection leading to homeostasis. Hypothesis: TIM-1 blockade enhances IL-22-mediated hepatocyte autophagy. We will employ refined OLT models and well-controlled in vitro co-culture systems to dissect the requirement for autophagy pathway in hepatoprotection under TIM-1 - IL-22 regulation. Aim 2: Define regulatory mechanisms of macrophage-specific TIM-4 signaling in IR-stressed OLTs. Objective 2.1: To assess the mechanism of TIM-4-TLR4 inflammation response. Hypothesis: Defective macrophage TIM-4 signaling mitigates liver IR-inflammation by self-limiting feedback regulation of TLR4 activation via Foxo1/ß-catenin network. We will utilize a newly developed model of liver IRI in CD11b-DTR mice in which conditional ablation of adoptively transferred macrophage populations allows dissecting TIM-4- dependent cross-regulation between innate and metabolic pathways in IR-inflammation. Objective 2.2: To analyze the role of TIM-4 in hepatic phagocytosis. Hypothesis: Targeting TIM-4 inhibits local phagocytosis, to further suppress TLR4-activation response in IR-stressed livers. As TIM-4 functions as a phosphatidylserine (PS) receptor, we will apply a newly developed phagocytosis assays to study whether macrophage TIM-4 signaling regulates binding/engulfment of PS+ hepatic necrotic bodies, and contributes to the resolution of IR- inflammation.