FcRIIA, Platelet Activity, and Vasculopathy in Systemic Lupus Erythematosus

摘要 系统性红斑狼疮(SLE)是一种复杂的自身免疫性疾病，其特征是 临床表现不佳，病程起伏不定，患早产儿心血管疾病的风险显著升高。 血小板作为系统性红斑狼疮早期动脉粥样硬化的相关因素尚未得到充分研究。然而，这些 包含转录本和进行翻译所需的分子机制的细胞是细胞间的。 炎症和免疫激活的调节剂，并在动脉粥样硬化血栓形成中发挥关键作用。血小板快递 低亲和力2型受体(FcγRIIA)，其配体是Ig G的Fc部分。一个单一的氨基酸替代， 胞外配体结合域中的H131R增加了对免疫球蛋白的亲和力，并可能解释了个体 血小板活化的变化，特别是功能的增加。利用一个特征良好的SLE队列，我们 发现携带至少一个变异体副本的患者颈动脉斑块显著丰富 与那些祖先基因纯合的人相比。在第二个系统性红斑狼疮队列中， 观察携带该变异基因的患者的单核细胞-血小板聚集物(MPA)。 尽管尚未对SLE患者进行基因分型，但与健康人相比，SLE患者的血小板表现出高反应性。 捐赠者。因此，假设血小板活性测量和血小板衍生编码和 非编码区受FcγRIIA型的影响较大。两个目标为以下方面提供了补充研究 评估系统性红斑狼疮患者血小板活性升高的潜在机制。在具体目标1中， 在Fcγ背景下系统性红斑狼疮血小板表型和转录组之间的RIIA型将是 调查过了。检测Fcγria型对多维血小板--血小板的影响 将测量代表不同病理生理机制的活性标记物，包括：光 传递聚集率(LTA)；白细胞和单核细胞-血小板聚集；网状血小板；血小板 PAC-1、CD40配体、P-选择素受体表达；血小板大小；血小板转录组。读数 将在三组SLE受试者中进行评估和比较：H/H纯合子、R/H杂合子和 R/R纯合子。在特定的目标2中，目标是从分子水平评估依赖于 FcRIIA结扎及基因对血管靶血管内皮细胞表型的影响 (ECS)和巨噬细胞。与特定的目标1不同，该方法使用的是健康对照的血小板 (H/H、R/H和RR)，因为SLE患者的血小板可能本质上包被免疫复合体(IC) 考虑到基线反应性。抗CD9与血小板联合治疗将作为ICs和 使用封闭抗体接近FcγRIIA依赖。抗CD9抗体与内皮细胞和巨噬细胞共培养 将对血小板进行促炎和保护性信号级联的评估。一部小说的鉴定 用于评估治疗反应的生物标记物，和/或用于识别早产风险增加的患者 心血管疾病，并可能受益于抗血小板药物，将是一个进步。

ABSTRACT Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by heterogeneity of presentation, an undulating course, and a remarkably elevated risk for premature cardiovascular disease. Platelets have been understudied as a relevant contributor to premature atherosclerosis in SLE. Yet these cells, which contain transcripts and the necessary molecular machinery to conduct translation, are intercellular regulators of inflammation and immune activation and play a key role in atherothrombosis. Platelets express low affinity type 2 receptor (FcγRIIA) whose ligand is the Fc portion of IgG. A single amino acid substitution, H131R, in the extracellular ligand binding domain increases the affinity for IgG and may account for individual variation in platelet activation, specifically gain of function. Leveraging a well-characterized SLE cohort, we identified a significant enrichment of carotid plaque in patients carrying at least one copy of the variant compared to those homozygotic for the ancestral gene. In a second SLE cohort, a significant increase in monocyte-platelet aggregates (MPA) in patients carrying the variant versus ancestral gene was observed. Although not yet assessed for genotype, SLE platelets exhibited a hyperreactive phenotype relative to healthy donors. Accordingly, it is hypothesized that platelet activity measurements and platelet-derived coding and non-coding RNA are significantly influenced by FcγRIIA genotype. Two aims provide complementary studies to evaluate the underlying mechanism of increased platelet activity in SLE. In Specific Aim 1 the relationship between SLE platelet phenotype and transcriptome in the context of FcγRIIA genotype will be investigated. To test the influence of FcγRIIA genotype on platelets, a multidimensional panel of platelet activity markers representing different pathophysiological mechanisms will be measured, including: light transmission aggregometry (LTA); leukocyte- and monocyte-platelet aggregates; reticulated platelets; platelet receptor expression of PAC-1, CD40 ligand, P-selectin; platelet size; and the platelet transcriptome. Readouts will be assessed and compared in three groups of SLE subjects: H/H homozygotes, R/H heterozygotes, and R/R homozygotes. In Specific Aim 2 the goal is to molecularly assess platelet reactivity dependent on FcRIIA ligation and the impact of genotype on the phenotype of the vascular targets, endothelial cells (ECs) and macrophages. In contrast to Specific Aim 1, the approach utilizes platelets from healthy controls (H/H, R/H, and RR) since platelets from SLE patients may be intrinsically coated with immune complexes (ICs) accounting for baseline reactivity. Co-treatment of platelets with anti-CD9 will serve as a proxy of ICs and FcγRIIA dependency approached using blocking antibodies. ECs and macrophages co-cultured with anti-CD9 platelets will be assessed for both pro-inflammatory and protective signaling cascades. Identification of a novel biomarker to gauge response to therapy, and/or to be used to identify patients at increased risk for premature cardiovascular disease and likely to benefit from anti-platelet agents, would be an advance.