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）可以通过肾上腺素反应性和pka依赖性信号传导激活。初步证据表明，将暴露于增加细胞内cAMP的试剂的SS红细胞输注到胸腺小鼠体内后毛细血管壁上后可见粘附，而未暴露于此类试剂的SS红细胞则不粘附。这些数据表明这种信号通路在生理上是重要的。此外，来自不同个体的SS红细胞在体外对肾上腺素刺激表现出不同的反应性。这些发现表明，对这些激动剂的不同反应可能取决于肾上腺素能受体（AR）多态性，而这些多态性可能影响镰状细胞病（SCD）的严重程度。此外，我们的初步证据表明β 2ars参与了粘附受体的激活过程。因此，我们假设β 2ar多态性影响SS红细胞的粘附程度，并且粘附的变异性导致SCD临床结果的变异性。为了验证这些假设，我们提出了一个试点项目，以确定β 2ar多态性是否影响SS红细胞粘附，是否与SCD中或多或少严重的临床结果或不同谱的终末器官损伤相关。我们将使用已有的临床数据库和DNA库来鉴定多达200名SCD（血红蛋白SS或S β o地中海贫血）患者的β 2ar基因型。然后，我们将使用这些信息和来自这些患者的额外血液样本(1)来确定β 2ar多态性是否会影响SS红细胞在体外表现出粘附表型的程度，无论是否有肾上腺素刺激；(2)确定beta2AR抑制剂体外阻断LW和lu介导的粘附能力是否依赖于beta2AR基因型；(3)确定β 2ar表型与SCD临床后遗症之间是否存在关系。我们期望这些研究将有助于更好地理解为什么来自不同患者的SS红细胞表现出不同的活性粘附表型，以及β 2ars的多态性如何影响SCD的红细胞粘附和临床结果。这些结果也将有助于我们理解β 2ar多态性在红细胞生物学和SCD病理生理学中的作用，并将有助于指导未来改善SCD血管闭塞过程的治疗方法。

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.