Role of LRP1 in NF-kB mediated neuroinflammation

 描述(申请人提供)：多发性硬化症(MS)是一种自身免疫性疾病，以中枢神经系统(CNS)髓鞘破坏和继发性神经变性为特征。目前，人们认为MS发作是由自身反应性T细胞启动的，然后由常驻和外周髓系细胞创造的炎症环境进一步加剧。在多发性硬化症炎症发作后，炎症被消除，但促进内稳态恢复的机制仍然难以捉摸。炎症消退的关键事件是细胞碎片的清除和炎症计划的终止。我们的长期目标是阐明控制中枢神经系统炎症消退的机制，这将有助于开发治疗神经炎性疾病的新疗法，如MS。低密度脂蛋白受体相关蛋白-1(Low Density Lipotein Receptor Related Protein-1，LRP1)是一种清道夫受体，在髓系细胞(包括中枢神经系统驻留的小胶质细胞)上高表达。LRP1促进碎片的吞噬，如降解的髓鞘和濒临死亡的细胞，这些存在于MS炎症发作期间。这一建议的基础是我们的发现，LRP1也作为一种炎症抑制因子，因为缺乏LRP1的细胞在刺激后表现出更多和持续的炎症反应。此外，在实验性自身免疫性脑脊髓炎(EAE)的MS小鼠模型中，髓系细胞LRP1缺失的小鼠疾病严重程度增加。LRP1在清除碎片和抑制炎症方面的功能使该受体作为MS炎症消退的潜在调节因子处于中心阶段。我们的假设是，髓系细胞中的LRP1通过促进细胞碎片的清除和关闭炎症反应来限制MS期间的组织损伤。在强有力的初步证据的指导下，这一假说将通过追求三个具体目标来解决：1)测试LRP1是否通过促进组织碎片的吞噬来抑制炎症。2)体内检测髓系LRP1对变性髓鞘吞噬功能的影响。3)在小胶质细胞或髓系细胞条件缺失LRP1的小鼠模型系统中，检测LRP1在EAE中的功能作用。在第一个目标下，我们将利用原代培养的髓系细胞来研究LRP1介导的吞噬作用和炎症之间的相互作用。在第二个目标中，我们将使用LRP1介导的髓鞘吞噬的双光子实时成像。最终，我们将研究小胶质细胞和炎性巨噬细胞LRP1在EAE病理过程中的作用。我们的方法是创新的，因为我们将使用新的动物模型结合中枢神经系统最先进的实时成像技术来研究清道夫受体LRP1在神经炎症后恢复内稳过程中的功能。我们的建议意义重大，因为这些研究将为了解LRP1在MS中的功能提供基础，最终目标是为MS患者开发新的抗炎治疗。

 DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is an autoimmune disease characterized by the destruction of myelin in the central nervous system (CNS) and secondary neurodegeneration. Currently, it is believed that an MS episode is initiated by autoreactive T-cells and then further exacerbated by an inflammatory milieu created by the resident and peripheral myeloid cells. After an MS inflammatory episode, inflammation is resolved, but the mechanisms that promote the return to homeostasis remain elusive. Key events involved in the resolution of inflammation are the removal of cellular debris and the termination of the inflammatory program. Our long-term goal is to shed light on the mechanisms that control the resolution of inflammation in the CNS, which will facilitate the development of novel therapeutics for neuroinflammatory disorders such as MS. Low density lipoprotein receptor-related protein-1 (LRP1) is scavenger receptor that is highly expressed on myeloid cells, including the CNS-resident microglia. LRP1 promotes the phagocytosis of debris such as degraded myelin and dying cells, which are present during MS inflammatory episodes. The foundation of this proposal is our discovery that LRP1 also functions as an inhibitor of inflammation, as cells lacking LRP1 display increased and sustained inflammatory responses following stimulation. Furthermore, mice with the deletion of LRP1 in myeloid cells have increased disease severity in a mouse model of MS, experimental autoimmune encephalomyelitis (EAE). Functions of LRP1 in debris clearance and inhibition of inflammation put this receptor at the center stage as a potential regulator of the resolution of inflammation in MS. Our hypothesis is that LRP1 in myeloid cells limits tissue damage during MS by enhancing the removal of cellular debris and by shutting down the inflammatory response. Guided by strong preliminary evidence, this hypothesis will be addressed by pursuing three specific aims: 1) Test if LRP1 inhibits inflammation by promoting phagocytosis of tissue debris. 2) Test the contribution of myeloid LRP1 to the phagocytosis of degenerated myelin in vivo. 3) Test the functional role of LRP1 during EAE, using mouse model systems with the conditional deletion of LRP1 in microglia or myeloid cells. Under the first aim, we will study the cross-talk between LRP1 mediated phagocytosis and inflammation using primary cultures of myeloid cells. In the second aim, we will use two-photon live imaging of LRP1 mediated myelin phagocytosis. In the final aim, we will study the contribution of microglial and inflammatory macrophage LRP1 during EAE pathology. Our approach is innovative because we will investigate the function of a scavenger receptor, LRP1, during the return to homeostasis after neuroinflammation using new animal models combined with the state of the art live imaging in the CNS. Our proposal is significant because these studies will provide the basis for understanding the function of LRP1 in MS with the ultimate goal of developing novel anti-inflammatory treatments for MS patients.