Reduction of Annexin A5 in Antiphospholipid Pregnancy Loss

描述（由申请人提供）：反复妊娠丢失是抗磷脂综合征（APS）的一个标志，APS是一种复杂的严重高凝障碍，没有确定的机制，目前用现象学替代试验诊断。APS与许多血栓性并发症有关，包括复发性流产、中风、深静脉血栓形成和肺栓塞。胎盘抗凝蛋白，膜联蛋白A5 （AnxAS）是一种有效的磷脂（PL）结合蛋白，可在含有阴离子PLs的膜上形成二维抗凝晶体屏障。AnxAS在胎盘合胞滋养细胞的顶膜上高度表达，在解剖位置上促进绒毛间空间的血液流动性。本应用的核心假设是病原性抗磷脂（aPL）抗体结合到（32-糖蛋白I）上的特定结构域，（32-糖蛋白I）是aPL抗体的主要辅助因子。这些结果导致在合胞滋养细胞的顶端表面形成大分子抗体-抗原复合物，在AnxAS抗凝血屏障中产生缺陷，从而促进

DESCRIPTION (provided by applicant): Recurrent pregnancy losses are a hallmark of the antiphospholipid syndrome (APS), a complicated major hypercoagulable disorder without an established mechanism that is currently diagnosed with phenomenologic surrogate tests. APS is associated with a host of thrombotic complications including recurrent pregnancy losses, stroke, deep vein thrombosis and pulmonary embolism. The placental anticoagulant protein, annexin A5 (AnxAS) is a potent phospholipid (PL)-binding protein that forms 2-dimensional anticoagulant crystal shields over membranes containing anionic PLs. AnxAS is highly expressed on the apical membranes of placental syncytiotrophoblasts where it is in an anatomic position to promote blood fluidity in the intervillous space. The core hypothesis of this application is that pathogenic antiphospholipid (aPL) antibodies bind to specific domains on (32-glycoprotein I, the major cofactor for aPL antibodies. These results in formation of macromolecular antibody-antigen complexes on the apical surfaces of syncytiotrophoblasts that create defects in the AnxAS anticoagulant shield and thereby promote coagulation reactions and reduce blood fluidity in the placental circulation. We have provided strong evidence for this hypothesis and have begun to develop innovative treatments that target this disease mechanism and mechanistic tests that identify resistance to AnxAS anticoagulant activity. This grant will extend the above findings with the following specific aims: 1) To investigate the effects of aPL antibodies on the AnxAS anticoagulant shield that is present on the apical membranes of placental trophoblasts. 2) To translate the findings of the first specific aim into innovative treatments targeting this disease mechanism and into mechanistic assays to diagnose the disease. These aims will be accomplished with atomic force microscopy, ellipsometry, binding studies, and coagulation enzyme studies using PL bilayers, cultured placental cells and placental villi and translational tests for AnxAS resistance. This project will be a major contribution toward elucidating a novel mechanism for pregnancy losses in a significant disease which is lacking an established pathophysiology and will open new approaches toward mechanistically-based diagnosis and treatment.