Maternal Autoantibodies: Pathogenesis of Neonatal Lupus

描述(由申请人提供)：在胎儿中发现孤立的先天性心脏传导阻滞(CHB)几乎可以肯定地预测，可能患有风湿病或没有症状的母亲将具有针对SSA/Ro核糖核蛋白的自身抗体(Ab)。ChB是被动获得性自身免疫的病理读数，它提供了一个特殊的机会来检查免疫的效应臂，并确定抗体介导纤维化的机制，而纤维化在胎儿创伤中尤其异常。对慢性乙肝的研究不仅体现了利用临床线索并在实验室中探索它们的转化性研究，而且还体现了试图将关键的临床和基础观察结合在一起的“综合”研究。在之前的资助期间，我们利用几个罕见的胎儿/新生儿尸检样本来询问发病机制的线索。CHB心脏传导系统(在某些情况下，周围心肌)过度凋亡、巨噬细胞/成纤维细胞串扰、TGF2表达和广泛的纤维化，为体外平行研究提供了体内支持。将细胞凋亡定位为抗体与组织损伤之间的初始联系导致了首次观察到健康的心肌细胞能够吞噬凋亡的心肌细胞，而抗Ro/La抗体抑制了这一功能。这种生理性吞噬作用的干扰将摄取转移到专业的Fc3R吞噬细胞，这与正在进行的实验很好地吻合，该实验表明，当巨噬细胞与抗Ro/La Ab结合的凋亡心肌细胞共同孵育时，巨噬细胞分泌促炎和纤维化细胞因子。最近的实验表明，Toll样受体(TLR)通过与靶自身抗原的RNA部分结合而与巨噬细胞结合。怀孕期间相对氧损伤的可能性，以及解释同卵双胞胎中CHB不一致的需要，将注意力引向了低氧作为远端纤维形成成分的放大因素。缺氧性损伤的足迹包括受影响心脏中缺氧诱导因子(HIF)-11的表达和几种CHB脐带血中促红细胞生成素水平的升高。目的1研究抗Ro/La单抗抑制自体人胎心肌细胞胞吐的特异性及其机制。据推测，抗Ro/La抗体与凋亡的心肌细胞结合不仅抑制清除，而且通过调理这些细胞，为专业吞噬细胞随后的摄取提供免疫复合体。在目标2中，Fc3受体(Fc3R)和TLR信号在巨噬细胞摄取调理的凋亡心肌细胞后的关系将在促进炎症和纤维化的介质的释放方面得到解决。支持这一目标的假说是，凋亡的心肌细胞通过Fc3R依赖的途径诱导巨噬细胞摄取，并通过TLR结扎激活，这启动了不可逆转瘢痕的最后一步。Aim 3的实验解决了由抗Ro/La抗体启动的炎性级联导致心脏成纤维细胞持续纤维化表型的机制。假设是巨噬细胞的产物促使成纤维细胞形成疤痕，而宫内应激如缺氧进一步助长了瘢痕的形成。其他方面健康的母亲或患有风湿病但具有SSA/Ro自身抗体的母亲的胎儿有永久心脏损伤的风险，这需要在生命的某个时候永久起搏，或者可能是致命的。了解这些自身抗体导致心脏瘢痕形成的机制对于制定治疗或预防这种被称为先天性心脏传导阻滞的疾病的策略至关重要。

DESCRIPTION (provided by applicant): Identification of isolated congenital heart block (CHB) in a fetus predicts with near certainty that the mother, who may have a rheumatic disease or be asymptomatic, will have autoantibodies (Ab) to SSA/Ro ribonucleoproteins. CHB, a pathologic readout of passively acquired autoimmunity, provides an exceptional opportunity to examine the effector arm of immunity and define the mechanism whereby an Ab mediates fibrosis, which is particularly aberrant in fetal wounding. The study of CHB exemplifies not only translational research, which draws upon clinical clues and explores them in the laboratory, but "integrational" research which attempts to fit key clinical and basic observations together. In the previous funding periods we leveraged several rare fetal/neonatal autopsy specimens to interrogate clues to pathogenesis. Exaggerated apoptosis, macrophage/myfibroblast crosstalk, TGF2 expression, and extensive fibrosis in the conduction system (and, in some, the surrounding myocardium) of CHB-hearts, provided in vivo support for parallel in vitro investigation. Positing apoptosis as the initial link between Ab and tissue injury led to the first-time observation that healthy cardiocytes are capable of phagocytosing apoptotic cardiocytes, and that anti-Ro/La Abs inhibit this function. That this perturbation of physiologic efferocytosis diverts uptake to professional Fc3R-bearing phagocytes fits well with ongoing experiments demonstrating macrophage secretion of pro-inflammatory and fibrosing cytokines when coincubated with apoptotic cardiocytes bound by anti-Ro/La Ab. The macrophage engagement of Toll-like receptors (TLR) via binding to the RNA moiety of the target autoantigen was suggested by recent experiments. The potential for relative oxygen insult during pregnancy, and the need to explain CHB- discordance in monozygotic twins, directed attention to hypoxia as an amplification factor on the distal fibrosing component. Footprints of hypoxic injury comprised expression of hypoxia-inducible factor (HIF)-11 in affected hearts and increased erythropoietin levels in several CHB-cord bloods. In Aim 1, the specificity and mechanism of anti-Ro/La Ab in inhibiting efferocytosis by autologous human fetal cardiocytes will be evaluated. It is hypothesized that binding of anti-Ro/La Ab to apoptotic cardiocytes not only inhibits clearance but, by opsonizing these cells, provides the immune complex for subsequent uptake by professional phagocytes. In Aim 2, the nexus of Fc3 receptor (Fc3R) and TLR signaling following macrophage uptake of opsonized apoptotic cardiocytes will be addressed with regard to release of mediators that promote inflammation and fibrosis. The hypothesis driving this aim is that opsonization of apoptotic cardiocytes induces macrophage uptake by an Fc3R-dependent pathway and activation via TLR ligation, which set in motion the final step to irreversible scar. The experiments of Aim 3 address the mechanism by which the inflammatory cascade initiated by anti-Ro/La Abs induces a persistent fibrosing phenotype in the cardiac fibroblast. The hypothesis is that macrophage products prime the fibroblast toward scar, which is further abetted by an in utero stress such as hypoxia. Fetuses of mothers who are otherwise healthy or who suffer from a rheumatic disease but have autoantibodies to SSA/Ro are at risk for having permanent heart damage, which requires permanent pacing at some point in life or can be fatal. Understanding the mechanism by which these autoantibodies cause cardiac scarring is critical to the development of strategies for treatment or prevention of this condition, known as congenital heart block.