JNK1/2调控细胞凋亡/自噬平衡对肝脏缺血再灌注损伤的影响及其影响机制

Liver resection and transplantation surgeries are important and effective therapies for liver diseases (cirrhosis, liver cancer and so on). However, the hepatic ischemia-reperfusion injury (HIRI) induced during surgery seriously affects the clinical outcomes. Studies revealed that as a member of mitogen-activated protein kinase (MAPK) family, c-Jun N-terminal kinase (JNK) signaling pathway was an important mediator during HIRI by inducing apoptosis. Recent reports indicated that JNK signaling pathway was also involved in the autophagy of various cells (such as islet cell). Moreover, hepatic ischemia induced the autophagy of hepatocyte, which ameliorated HIRI through reducing the apoptosis of hepatocyte. Therefore, we hypothesize that JNK is implicated in the autophagy of hepatocyte, and may play a pivotal role in HIRI by orchestrating the homeostasis between apoptosis and autophagy. JNK consists of three isoforms JNK1, JNK2 and JNK3 in mammalian cell, with JNK1 and JNK2 expressed ubiquitously, whereas JNK3 selectively expressed in brain and heart. Literatures and our previous work confirmed that the individual role and mechanism of JNK1 and JNK2 in cell were different. This project will investigate the individual role and mechanism of JNK1 and JNK2 in HIRI by orchestrating the homeostasis between apoptosis and autophagy to identify target molecules involved in HIRI, which may offer novel therapeutic strategies for HIRI treatmeat.

肝切除及移植是肝硬化、肝癌等疾病的重要治疗手段，而手术引发的肝缺血再灌注损伤（HIRI）严重制约着临床手术的疗效。研究证实MAPK家族成员c-Jun氨基末端激酶（JNK）参与HIRI过程，且与诱导细胞凋亡有关。另有研究证实，JNK亦参与胰岛细胞等多种细胞的自噬过程。而且最近研究发现肝缺血可诱导肝细胞自噬，进而通过阻止肝细胞凋亡而减轻HIRI。因此我们推测JNK参与肝细胞自噬，而且可能通过调控凋亡和自噬平衡而影响HIRI。哺乳动物中JNK有JNK1、JNK2、JNK3三型，其中JNK1和JNK2在组织中广泛表达，而JNK3仅在脑、心脏中表达。文献和我们的前期工作表明JNK1、JNK2在细胞中的作用及机制各自不同。本项目将重点探究JNK1、JNK2调控细胞凋亡/自噬平衡而影响HIRI及影响机制的异同，寻找引起HIRI的关键靶点，为阐明HIRI发生机制提供帮助，进而为临床HIRI防治开辟新思路。

肝脏切除及移植是临床肝硬化、肝癌等疾病的重要治疗手段，而手术引发的肝缺血再灌注损伤（HIRI）严重制约手术预后。HIRI的发生机制尚不完全清楚。因此，研究HIRI的发生机制，探索干预HIRI的靶点及方法具有重要临床意义。本项目采用JNK基因敲除（JNK1-/-、JNK2-/-）小鼠，建立HIRI模型，研究JNK1、JNK2在HIRI中的特异性调控作用及作用异同。研究结果显示，JNK1或JNK2缺失后，小鼠肝细胞损伤（血清转氨酶ALT、AST水平）、炎症反应（血清中炎性细胞因子TNF-α、IL-6、IL-1β）水平、肝脏组织结构的病理损伤均显著降低，肝细胞坏死程度和凋亡水平明显降低。细胞机制方面，我们发现，JNK1或JNK2缺失后，HIRI过程中肝细胞凋亡水平均降低。值得注意的是，JNK1缺失后，HIRI过程中肝细胞自噬无明显变化，增殖水平有升高；JNK2缺失后，细胞行为最显著的变化是肝细胞自噬明显升高。JNK1或JNK2缺失减轻HIRI 的分子机制方面，我们探索了MAPK与神经鞘脂通路之间是否存在crosstalk。结果显示JNK1缺失减轻HIRI的过程中ERK活化（p-ERK）明显，神经鞘脂通路SK1明显上调，推测JNK1缺失减轻HIRI的机制可能与ERK激活而调控细胞增殖有关； JNK2缺失减轻HIRI的过程存在S1P升高，以及其生成酶SK2下调，JNK2缺失减轻HIRI的机制，推测可能与S1P 增强细胞自噬而提高细胞存活有关。总之，JNK1或JNK2单独缺失皆可有效减轻HIRI，提示JNK1、JNK2二者的调控作用可能存在叠加（或协同）效应，推测机制是JNK1、JNK2与神经鞘脂通路中的SK1、SK2发生 crosstalk，调控不同的细胞行为（自噬、增殖）而实现。相比已有报道研究JNK（不区分JNK1、JNK2）在HIRI中的作用，研究结果有利于HIRI的精准干预。