Translational Studies Examining Soluble EPO Receptor and EPO Resistance in Dialys

描述（由申请人提供）：促红细胞生成素是一种生长因子，它彻底改变了终末期肾病（ESRD）患者贫血的治疗。在一些患者中仍然存在的显著临床挑战是对促红细胞生成素的相对抗性，这导致使用连续更高的促红细胞生成素剂量和增加的不良结果风险。慢性炎症是促红细胞生成素抵抗的一个重要因素，但介导这种表型的分子途径尚不清楚。促红细胞生成素通过存在于成红细胞中的促红细胞生成素受体（EpoR）起作用。重要的是，选择性mRNA剪接产生存在于人类血液中的可溶性形式的EpoR（sEpoR）。虽然sEpoR的功能是未知的，sEpoR可以调节促红细胞生成素信号，提高了这种可溶性受体的生理作用的可能性。没有研究系统地检查ESRD中的sEpoR水平。使用从ESRD受试者获得的存档血清样品，我们已经生成了初步数据，表明sEpoR在其血清中可检测为27 kDa蛋白，并且较高的血清sEpoR水平与增加的促红细胞生成素需求相关。此外，我们有初步的数据表明，sEpoR抑制促红细胞生成素介导的信号转导和转录激活因子5（Stat-5）磷酸化的细胞系中表达EpoR。我们还证明，血清中的sEpoR水平升高的患者阻断这种磷酸化在离体研究。本申请的目的是证实具有高水平sEpoR的血清可以通过用外源性促红细胞生成素拯救和抑制血清中sEpoR免疫吸附后的作用来体外阻断促红细胞生成素介导的细胞内信号传导。我们还将研究sEpoR分泌的调节，以响应已知在ESRD中升高的炎症介质。最后，我们将使用来自大型透析队列（ArMORR，美国; 4D，德国）的存档样本进行两项临床研究，以检验透析开始时sEpoR水平升高独立预测后续促红细胞生成素剂量的假设。我们相信这种探索性的R21机制将允许基础科学家和临床研究人员的合作团队解决ESRD患者面临的最常见和最棘手的问题之一。这种应用有可能导致红细胞生成素抵抗患者的诊断和管理发生变化。 公共卫生相关性：慢性肾衰竭患者的促红细胞生成素抵抗是一个常见的问题，目前仍无法解释。过量的促红细胞生成素与发病率和死亡率增加有关。我们将检验这一假设，即在肾功能衰竭患者中循环的可溶性促红细胞生成素受体可能导致该人群中的促红细胞生成素抵抗。

DESCRIPTION (provided by applicant): Erythropoietin is a growth factor that has revolutionized the management of anemia in patients with end-stage renal disease (ESRD). A significant clinical challenge that remains in some patients is the relative resistance to erythropoietin, which leads to use of successively higher erythropoietin doses and increased risk of adverse outcomes. Chronic inflammation is an important factor contributing to erythropoietin resistance, yet the molecular pathways mediating this phenotype are unclear. Erythropoietin acts through the erythropoietin receptor (EpoR) present in erythroblasts. Importantly, alternative mRNA splicing produces a soluble form of EpoR (sEpoR) that is present in human blood. While the function of sEpoR is unknown, sEpoR may modulate erythropoietin signaling, raising the possibility of a physiologic role for this soluble receptor. No studies have systematically examined sEpoR levels in ESRD. Using archived serum samples obtained from subjects with ESRD, we have generated preliminary data to show that sEpoR is detectable as a 27kDa protein in their serum, and that higher serum sEpoR levels correlate with increased erythropoietin requirements. In addition we have preliminary data suggesting that sEpoR inhibits erythropoietin mediated signal transducer and activator of transcription 5 (Stat-5) phosphorylation in cell lines expressing EpoR. We also demonstrate that serum from patients with elevated sEpoR levels blocks this phosphorylation in ex vivo studies. The intent of this application is to confirm that serum with high levels of sEpoR can block erythropoietin mediated intracellular signaling in vitro by rescue with exogenous erythropoietin and inhibition of the effect after immunoadsorption of sEpoR from the serum. We will also examine the regulation of sEpoR secretion in response to inflammatory mediators known to be elevated in ESRD. Finally, we will perform two clinical studies using archived samples from large dialysis cohorts (ArMORR, US; 4D, Germany) to test the hypothesis that elevated sEpoR levels at the start of dialysis independently predict subsequent erythropoietin dose. We believe this exploratory R21 mechanism will permit a collaborative team of basic scientists and clinical investigators to address one of the most common and vexing problems faced by ESRD patients. This application has the potential to lead to changes in the diagnosis and management of patients with erythropoietin resistance. PUBLIC HEALTH RELEVANCE: Erythropoietin Resistance in Chronic Renal Failure is a common problem that remains unexplained. Excessive doses of Erythropoietin are linked with increased morbidity and mortality. We will test the hypothesis that Soluble Erythropoietin Receptor circulating in patients with renal failure may contribute to Erythropoietin Resistance in this population.