二肽肽酶I通过激活丝氨酸蛋白酶参与多发性硬化神经炎症的分子机制及功能角色

Multiple sclerosis (MS) is characterized pathologically by inflammation, demyelination, gliosis and axonal injury. Even though MS may be a disease with heterogeneous pathogenetic mechanisms, neuroinflammation, which is characterized by activated microglia and leukocyte invasion at sites of demyelination, is a key player in disease development and a prime therapeutic target for MS. Cysteine protease dipeptidyl peptidase I (DPPI, also known as cathepsin C) plays an important and nonredundant role in the processing and activation of many serine proteases(SP), which are enzymes that modulate inflammation. DPPI has been demonstrated that it is involved in the regulation of cytokine production at sites of inflammation by activating SP in peripheral system. However, there is no report on DPPI expression or functional role in the neuroinflammation of the CNS. In our previous work, we found that LPS and inflammatory factors, like IL-1β and IL-6, induced elevated expression and release of DPPI in neurons and microglial cells in neuroinflammation process in LPS intraperitoneal injection moedel and also in MS animal models. These data suggested that DPPI is involved in the process of neuroinflammation, however, the significance of its expression, inducing factor and its effect on the injury of myelin sheeth and axons in MS are still unknown. In this project, DPPI null mice are going to be used to create MS animal models which are induced by different mechanisms, and the cerebrospinal fluid and blood samples from MS patients are going to be collected. Then by using neuropathological, molecular biological and cytobiological methods combining with in vivo and in vitro experiments, DPPI expression pattern, inducing factors and functional role will be clarified by using these MS animal models and clinical samples. Furthermore, the mechanisms that DPPI invoved in neuroinflammation of MS are going to be investigated starting from SP which in the downstream of DPPI function. By these researches, we propose to grasp the upstream factor which invoved in the occurrence and development of neuroinflammation in MS and to provide a potential therapeutic target and research basis for MS treatment.

虽然多发性硬化（MS）病因不同，但是神经炎症是导致髓鞘脱失和轴突损伤的病理基础，是MS发生、发展的关键。二肽肽酶I（DPPI）在外周系统可通过激活免疫细胞中的丝氨酸蛋白酶（SP）参与多种炎症反应，然而其在中枢神经系统中的作用至今未见报道。我们前期工作表明，LPS和炎性因子可以诱导DPPI在神经元和小胶质细胞内高表达和释放，MS动物模型亦有相似结果，证明DPPI参与中枢神经系统炎症过程。然而诱导DPPI表达的因子以及其表达对MS炎症进程和对髓鞘及轴突损害的影响至今不清。本项目拟利用DPPI基因敲除结合MS动物模型及临床MS患者标本，采用神经病理、分子生物学和细胞生物学手段结合体内和体外实验，对不同致病因子导致的MS动物模型和临床标本中DPPI的表达、诱导因子和功能角色进行阐述，并从其下游SP出发确定DPPI参与MS神经炎症的机制，掌握调控神经炎症发生发展的上游因素，为MS治疗提供理论基础。

虽然多发性硬化（MS）病因不同，但是神经炎症是导致髓鞘脱失和轴突损伤的病理基础，是MS发生、发展的关键。二肽肽酶I（DPPI），也称为cathepsin C在外周系统可通过激活免疫细胞中的丝氨酸蛋白酶（SP）参与多种炎症反应，然而其在中枢神经系统中的作用至今未见报道。本研究根据MS不同病理类型建立了MOG诱导的EAE模型和cuprizone诱导的脱髓鞘模型，发现DPPI在两种模型中均有高表达，并且根据细胞定位研究发现，DPPI在急性EAE模型脑和脊髓的小胶质细胞和中性粒细胞均有表达，在慢性期则主要由中性粒细胞表达。在cuprizone诱导的脱髓鞘模型中，DPPI表达则主要为小胶质细胞。同时，我们对临床MS患者脑脊液中DPPI的表达水平进行了研究发现，其表达水平显著高于非MS患者脑脊液中DPPI的含量。以上结果说明DPPI参与MS的神经炎症过程，并可以被释放于脑脊液中。为了解DPPI参与MS神经炎症的机制，我们构建了FAST(Flexible Accelerated STOP TetO-knockin)系统小鼠，通过操纵DPPI基因沉默和过表达用于对DPPI的功能角色进行阐述，确定DPPI参与MS神经炎症的机制。

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