补体H因子和VWF系统的交互作用在狼疮性肾炎继发血栓性微血管病发病机制中的研究

Thrombotic microangiopathy (TMA) secondary to lupus nephritis is an acute and severe clinical syndrome with extremely poor outcome, although its pathogenesis remained unclear. Recent studies elucidated that the dysfunction of von Willebrand factor (VWF)-related coagulation system or complement factor H (CFH)-related over-activation of complement system was the major mechanism of thrombotic thrombocytopenic purpura or atypical haemolytic uraemic syndrome, respectively, which are the typical types of TMA, and there was close association between the two systems. Our previous work had several findings as below: (1) CFH-related over-activation of complement system was found in lupus nephritis associated TMA; (2) the plasma VWF level was increased and its cleaving protease activity was decreased significantly, and the latter was negatively associated with pathological renal vascular scores in some proliferative lupus nephritis patients; (3) more importantly, the VWF cleaving protease activity was positively associated with plasma CFH level, and the elevated complement activation product C5a level was found in lupus nephritis patients with certain genotype of newly found SNP of VWF cleaving protease. Herein, we propose that the crosstalk between CFH and VWF system could contribute to the pathogenesis of TMA secondary to lupus nephritis. In this study, we will target on the patients with TMA secondary to lupus nephritis, investigate the gene background of CFH, VWF, VWF cleaving protease and their autoantibodies, study the interactions between CFH and VWF and the consequent functions. Meanwhile, we will use the lupus nephritis mouse model to mimic the development of secondary TMA to further elucidate this hypothesis.

狼疮性肾炎(LN)继发血栓性微血管病(TMA)临床起病凶险，预后较差，但发病机制不明。既往研究发现，血管性血友病因子(VWF)相关的凝血系统异常或H因子相关的补体系统过度活化分别是经典型TMA中血栓性血小板减少性紫癜或不典型溶血尿毒综合征的主要发病机制，且两系统间存在密切交互作用。申请者前期工作发现，LN继发TMA患者存在H因子功能异常相关的补体过度活化；部分增殖性LN患者血浆中VWF水平升高，其剪切酶活性下降，后者与肾血管病变评分负相关；特别是，VWF剪切酶活性还与H因子水平正相关，新发现的VWF剪切酶的SNP特定基因型患者循环中补体活化产物C5a水平显著升高。故推测，VWF与H因子的交互作用可能参与了LN继发TMA的发病。本研究以LN继发TMA为对象，检测其体内H因子、VWF及其剪切酶的基因背景及抗体；研究H因子与VWF的结合及其功能；并利用LN鼠模型模拟TMA发生，深入阐明上述假说。

狼疮性肾炎继发血栓性微血管病临床起病凶险，发病机制尚不清楚。申请者团队旨在阐明补体H因子和血管性血友病因子（VWF）系统的交互作用在狼疮性肾炎继发血栓性微血管病患者发病机制中的作用。申请者所在的课题组通过对92名狼疮性肾炎继发血栓性微血管病患者的血浆、尿液和肾脏组织H因子及VWF水平检测发现，狼疮性肾炎继发血栓性微血管病患者较正常健康对照尿液和肾脏H因子水平也显著升高，血浆、尿液及肾脏VWF均显著升高，而血浆H因子水平降低。与单纯V型狼疮性肾炎患者相比，狼疮性肾炎继发血栓性微血管病患者有更高的尿液H因子水平，肾脏H因子水平，尿液VWF水平，肾脏VWF水平。与单纯IV型狼疮性肾炎患者相比，狼疮性肾炎继发血栓性微血管病患者有更高的肾脏H因子水平。上述结果提示H因子及VWF可能在狼疮性肾炎继发血栓性微血管病的发病机制中发挥作用。进一步结合实验和功能学研究发现，循环水平上VWF与H因子在体外的结合并可以VWF可以辅助I因子裂解C3b。内皮细胞上野生型的VWF蛋白与H因子并不存在共定位的现象，但内皮细胞内和细胞上清中存在大量可与VWF结合的配体，提示VWF可能与多种配体结合，间接与补体H因子发生相互作用。动物实验中，由于MRL-lpr狼疮鼠与H因子突变的小鼠无法相互受孕，导致目前尚未成功建立狼疮性肾炎继发血栓性微血管病的动物模型。而本课题组前期已成功建立H因子敲除模型，我们尝试在该模型基础上敲除VWF，以期从侧面反映H因子与VWF的相互作用。综上所述，申请者所在的课题组通过在临床、分子和动物水平对补体H因子和VWF系统的研究，发现补体H因子和VWF系统的交互作用在狼疮性肾炎继发血栓性微血管病患者发病机制中发挥重要作用。