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，其特征是免疫系统的异质性。 表现，起伏的过程，并显着升高的风险过早心血管疾病。 血小板作为SLE患者过早动脉粥样硬化的相关因素尚未得到充分研究。然而这些 细胞含有转录本和进行翻译所必需的分子机制， 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。血小板表达 低亲和力2型受体（FcγRIIA），其配体为IgG的Fc部分。单个氨基酸取代， H131 R，在细胞外配体结合结构域中增加对IgG的亲和力，并且可以解释个体免疫应答。 血小板活化的变化，特别是功能的获得。利用特征良好的SLE队列，我们 在携带至少一个变异体拷贝的患者中， 与祖先基因的纯合子相比。在第二个SLE队列中， 单核细胞-血小板聚集体（MPA）的患者携带的变体与祖先的基因进行了观察。 虽然尚未评估基因型，但SLE血小板相对于健康人表现出高反应性表型， 捐助者。因此，假设血小板活性测量和血小板衍生的编码以及 FcγRIIA基因型对非编码RNA表达有显著影响。两个目标提供了补充研究， 评估SLE患者血小板活性增加的潜在机制。具体目标1： 在FcγRIIA基因型背景下，SLE血小板表型和转录组之间的关系将 研究了为了检测FcγRIIA基因型对血小板的影响， 将测量代表不同病理生理机制的活动标志物，包括： 透射式聚集测定法（LTA）;白细胞和单核细胞-血小板聚集体;网织血小板;血小板 PAC-1、CD 40配体、P-选择素的受体表达;血小板大小;和血小板转录组。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。在特定目标2中，目标是从分子水平评估血小板反应性， Fc ε RIIA连接和基因型对血管靶点内皮细胞表型的影响 (ECs)和巨噬细胞。与特定目标1相反，该方法利用来自健康对照的血小板 （H/H、R/H和RR），因为SLE患者的血小板可能固有地包被有免疫复合物（IC） 考虑到基线反应性。血小板与抗CD 9的共同治疗将作为IC的替代， 使用封闭抗体接近FcγRIIA依赖性。与抗CD 9共培养的EC和巨噬细胞 评估血小板的促炎和保护性信号级联。小说的鉴定 生物标志物，以衡量对治疗的反应，和/或用于识别过早死亡风险增加的患者。 心血管疾病和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.