基于MIF/CD74通路探讨肺泡巨噬细胞极化在肝移植围术期急性肺损伤中的作用

Acute lung injury(ALI) is a major cause of early death after liver transplantation, the mechanism is still not fully elucidated and there's a lack of effective prevention and treatment. Despite that the role of the alveolar macrophages (AM) in the development of ALI is confirmed, the effective intervention has not been found all over the world. Our previous studies have found that the expression of macrophage migration inhibition factor(MIF) is significantly increased in the lung tissue following liver transplantation which is coincident with perioperative acute lung injury, and AM mainly exists as the M1 phenotype having pro-inflammatory activity. The MIF expression quantity and the proportion of M1/M2 are in accordance with the severity of post-operative ALI. The activation of MIF/CD74 pathways promote macrophages to recruit、activate and secret cytokines in inflammatory area, then impact the polarization of macrophages. In view of the above, we put forward the hypothesis that "MIF/CD74 signaling pathway plays a key role in regulating the differentiation of AM toward M1 phenotype and the subsequent perioperative ALI following liver transplantation". This study will illuminate the function and mechanism of the MIF/CD74 pathways regulating AM polarization on the occurrence and development of perioperative acute lung injury following liver transplantation by using the rats liver transplantation model, CD11c-DRT transgenic mice autologous transplantation model which have been excluded M1 macrophages and isolated lung perfusion model,combining with CD74 knockout mice and the drug interventions, such as CD74 agonist/antagonist, through in vivo experiments in animals and in vitro experiments in cultured cells. This study will provide theoretical insights for the prevention of perioperative acute lung injury following liver transplantation.

急性肺损伤(ALI)是肝移植术后早期死亡的主要原因，机制未完全阐明,缺乏有效防治方法。虽肺泡巨噬细胞(AM)在ALI中的作用得到确认，但缺乏干预手段。我们前期研究发现肝移植围术期ALI显著的肺组织中MIF表达上调，AM主要以促炎活性的M1存在,且MIF表达量、M1/M2比例与ALI严重程度一致。MIF/CD74通路激活促进巨噬细胞在炎症局部的聚集、活化和细胞因子分泌，影响巨噬细胞极化。据此，我们提出假设"MIF/CD74调控AM向M1表型分化是肝移植围术期ALI发生的关键所在"。本课题拟用大鼠肝移植模型、CD11c-DRT转基因小鼠剔除M1巨噬细胞后自体肝移植模型、离体肺灌注模型，结合CD74基因敲除鼠及CD74激动剂/拮抗剂等干预，通过在体实验和体外细胞学研究，阐明MIF/CD74通路调控AM极化在移植肝围术期ALI发生、发展中的作用及机制，为防治肝移植围术期ALI提供理论及实验依据。

急性肺损伤(ALI)是肝移植术后早期死亡的主要原因，机制未完全阐明,缺乏有效防治方法。肺泡巨噬细胞(AM)在 ALI 中的作用得到确认，同时我们前期研究发现肝移植围术期 ALI 显著的肺组织中 MIF 表达上调，与 ALI 严重程度一致。在此基础上，我们提出“MIF/CD74 调控 AM 向 M1 表型分化是肝移植围术期 ALI 发生的关键所在”的假设。为证实这个假设，本课题通过四个部分予以论证:1）观察肝移植不同时期 AM 极化特征、MIF 和 CD74 表达、炎症和氧化应激的变化；结果发现肝移植围术期大鼠的肺组织MIF表达升高，同时M1表型的AM增加，伴随炎症介质和炎性细胞募集和浸润；ALI的严重程度与AM的M1表型呈正相关；2）应用野生型及 CD11c-DTR 转基因小鼠的在体实验、离体肺灌注模型及细胞学研究，结果发现肺泡巨噬细胞与肝移植急性肺损伤的严重程度相关；3）通过细胞学研究，探讨 MIF/CD74 对肺泡巨噬细胞极化的调控作用，结果发现MIF/CD74 信号通路对肺泡巨噬细胞极化发挥重要调控作用；4）通过在体动物实验，探讨干预 MIF/CD74 信号通路对肺泡巨噬细胞极化和防治防治肝移植围术期 ALI 的可行性，结果发现MIF20预处理后，加重肝移植围术期急性肺损伤；而MIF98预处理则减轻肝移植围术期急性肺损伤。本研究阐明了肺泡巨噬细胞极化与肝移植围术期 ALI 的关系，明确 MIF/CD74 介导的信号通路介导的肺泡巨噬细胞极化在肝移植围术期 ALI 中的关键性作用，为肝移植围术期急性肺损伤的防治提供潜在的靶点，为防治肝移植围术期 ALI 提供新的理论及实验依据。