Adrenergic Receptor Variants and RBC Adhesion in SCD

描述（由申请人提供）：镰状红细胞（SS RBC）的至少两种主要粘附受体（LU和LW）可通过肾上腺素反应性和PKA依赖性信号传导激活。初步证据显示，暴露于增加细胞内cAMP的试剂的SS RBC在将此类细胞输注到无胸腺小鼠中后在体内表现出与毛细血管后血管壁的可见粘附，而未暴露于此类试剂的SS RBC不粘附。这些数据表明，这种信号通路是生理上重要的。此外，不同个体的SS RBC在体外对肾上腺素刺激的反应性不同。这些研究结果表明，这些激动剂的可变反应可能取决于肾上腺素能受体（AR）的多态性，这些可能会影响镰状细胞病（SCD）的严重程度。此外，我们的初步证据表明，β 2 AR参与了粘附受体激活的过程。因此，我们假设β 2 AR多态性影响SS RBC粘附的程度，粘附的变异性导致SCD临床结局的变异性。为了验证这些假设，我们提出了一个试点项目，以确定β 2 AR多态性是否影响SS RBC粘附，并与或多或少严重的临床结果或不同光谱的终末器官损伤SCD。我们将使用一个预先存在的临床数据库和DNA库，以确定多达200名SCD（血红蛋白SS或S β o地中海贫血）患者的β 2 AR基因型。然后我们将使用这些信息和这些患者的额外血液样本（1）确定β 2 AR多态性是否影响SS RBC在体外显示粘附表型的程度，无论是否有肾上腺素刺激;（2）确定β 2 AR抑制剂在体外阻断LW和LU介导的粘附的能力是否依赖于β 2 AR基因型;（3）探讨β 2 AR表型与SCD临床后遗症的关系。我们希望这些研究将有助于更好地理解为什么不同患者的SS RBC表现出粘附活性表型，以及β 2 AR的多态性如何影响SCD患者的RBC粘附和临床结局。这些结果也将帮助我们了解β 2 AR多态性在红细胞生物学和SCD的病理生理学中的作用，并将有助于指导未来的治疗方法，以改善SCD的血管闭塞过程。

DESCRIPTION (provided by applicant): At least two major adhesion receptors (LU and LW) of sickle red cells (SS RBC) can be activated through epinephrine-responsive and PKA-dependent signaling. Preliminary evidence shows that SS RBC exposed to agents that increase intracellular cAMP demonstrate visible adhesion to post-capillary vessel walls in vivo after such cells are transfused into athymic mice, while SS RBC not exposed to such agents do not adhere. These data suggest that this signaling pathway is physiologically important. In addition, SS RBC from different individuals show variable responsiveness to epinephrine stimulation in vitro. These findings suggest that variable responses to such agonists may depend on adrenergic receptor (AR) polymorphisms and that these may influence the severity of sickle cell disease (SCD). Furthermore, our preliminary evidence implicates beta2ARs in the process of adhesion receptor activation. We therefore hypothesize that beta2AR polymorphisms affect the degree to which SS RBC are adhesive, and that variability in adhesion contributes to the variability of clinical outcomes in SCD. To test these hypotheses, we propose a pilot project to determine whether beta2AR polymorphisms affect SS RBC adhesion and are associated with more or less severe clinical outcomes or different spectra of end-organ damage in SCD. We will use a pre-existing clinical database and DNA bank to identify the beta2AR genotypes of up to 200 patients with SCD (hemoglobin SS or S beta o thalassemia). We will then use this information and additional blood samples from these patients (1) To establish whether beta2AR polymorphisms affect the degree to which SS RBC exhibit an adhesive phenotype in vitro, both with and without epinephrine stimulation; (2) To identify whether the ability of beta2AR inhibitors to block LW- and LU-mediated adhesion in vitro is dependent on beta2AR genotype; and (3) To establish whether a relationship exists between beta2AR phenotypes and clinical sequelae in SCD. We expect that these studies will lead to an improved understanding of why SS RBC from different patients exhibit a variably active adhesive phenotype and how polymorphisms of beta2ARs affect both RBC adhesion and clinical outcomes in SCD. These results will also help us understand the role of beta2AR polymorphisms in red cell biology and in the pathophysiology of SCD and will help direct future therapeutic approaches to ameliorating the vasoocclusive process in SCD.