Adrenergic Receptor Variants and RBC Adhesion in SCD

描述(申请人提供)：至少两个镰状红细胞(SS RBC)的主要黏附受体(LU和LW)可以通过肾上腺素反应和PKA依赖的信号被激活。初步证据表明，在裸鼠体内，经细胞内cAMP增加的SS红细胞与毛细血管后血管壁有明显的黏附，而未接触此类药物的SS RBC则不能黏附。这些数据表明，这一信号通路在生理上是重要的。此外，不同个体的SS RBC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)的多态性，这些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，β2受体参与了黏附受体的激活过程。因此，我们假设β2AR基因多态影响SS RBC的黏附程度，黏附的变异性导致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β2AR基因多态是否影响SS RBC黏附，并与SCD的临床结局或不同的终末器官损害谱相关联。我们将使用现有的临床数据库和DNA库来鉴定多达200名SCD(血红蛋白SS或Sβ地中海贫血)患者的β2AR基因型别。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)确定在有和没有肾上腺素刺激的情况下，β2AR基因多态性是否在体外影响SS RBC表现出黏附表型的程度；(2)确定Beta2AR抑制剂在体外阻断LW和LU介导的黏附的能力是否依赖于Beta2AR基因；以及(3)建立Beta2AR表型与SCD临床后遗症之间是否存在关系。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表现出不同的活性黏附表型，以及Beta2AR基因的多态性如何影响SCD的RBC黏附和临床结果。这些结果还将有助于我们了解β2AR基因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的治疗方法来改善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.