脂质筏中鞘磷脂在B细胞活化功能中的作用及其参与SLE发病的机制

Lipid raft is a membrane microdomain consisting of sphingomyelin (SM) and cholesterol. Sphingomyelin synthase 1(SMS1) is the last critical enzyme that plays an important role in the enzymatic step of SM biosynthesis. After cloning SMS1, our previous studies had indicated that SMS1-SM-lipid raft plays an important role in pathogenesis of Systemic Lupus Erythematosus (SLE) through abnormal CD4+ T cell function. Lipid raft is an important component of immune synapse，which will link T cell and B cell together to act its functions. In SLE, T cells act as helper cells interacting with B cells, resulting in B cells activation and production of abundant autoantibodies and immune complex. However, the role of SMS1-SM-lipid raft in B cell function is ppoorly identified. In this study we are trying to elucidate 1) whether SMS1-SM-lipid raft on B cell and its function are abnormal; 2) After down-regulate SMS1 in B cells from SLE, whether abnormal B cells function could be restored. 3)Investegate the functions of B cells by SMS1 knock out mice in vivo and in vitro.4） The role of SMS1-SM-lipid raft through disfunction of B cells in SLE disease model by SMS1-/- mice. The purpose of our study is to clearify that SM as an important component of lipid raft also palys a critical role in B cell function and pathogenesis of SLE. SMS1-SM-lipid raft would be a new target for clinical treatment of SLE.

脂质筏是细胞膜上富含鞘磷脂（SM）和胆固醇的微区。鞘磷脂合成酶1（SMS1）是合成细胞膜上SM最后一步的关键酶。我们以前的研究表明SMS1-SM-脂质筏调节CD4+T细胞功能，且参与系统性红斑狼疮的发病。脂质筏是T-B细胞免疫突触的主要成分，SLE发病中T细胞作为辅助细胞，其最终的效应是引起B细胞异常活化产生大量抗体，但目前国内外尚无对SMS1-SM-脂质筏在B细胞功能中研究。因此本研究将探讨1）SLE患者B细胞SMS1-SM-脂质筏及其功能是否异常；2）siRNA技术下调SLE患者 B细胞SMS1后对异常B细胞功能的影响；3）体内、外水平研究SMS1-/-小鼠B细胞功能；4）对SMS1-/-小鼠诱导狼疮模型探讨B细胞SM对SLE发病的影响。本研究从SLE病人，细胞培养和动物模型多层次体内外探讨脂质筏中SM在B细胞活化功能中的作用及其参与SLE发病的机制，为临床防治SLE提供科学实验依据。

脂质筏是细胞膜表面富含鞘磷脂（SM）和胆固醇的功能微区，参与细胞活化和信号转导等多种生物学功能。系统性红斑狼疮（SLE）是以自身抗体产生和多器官受累为特点的自身免疫性疾病。本课题主要探讨脂筏中SM缺陷对B细胞活化及SLE疾病进展的影响。本课题发现：1）在pristane诱导的狼疮模型中，鞘磷脂合成酶1敲除小鼠（SMS1-/-）自身抗体及肾小球肾炎等病理改变明显减轻；2）通过SLE模型及体外刺激发现， SM缺陷导致B细胞的活化水平明显减弱，活化指标CD69，CD80 和CD86 表达明显降低；3）SM缺陷导致BCR信号通路上游Fyn和Syk的磷酸化水平明显减弱；4）SMS1-/-B细胞增殖及分化能力减弱，同时分泌IL-6等细胞因子水平下降；5）SLE患者外周PBMC的SMS1的表达水平明显高于正常人群，同时与血清IgA的浓度呈正相关。本课题研究结果初步表明SM在B细胞活化及SLE疾病进展中挥重要作用，也许可能作为SLE的一个新的治疗靶点。