Magnesium and Sickle Cell Disease

描述（由申请人提供）：镰状细胞脱水在镰状细胞病的发病机制中起重要作用。由于Hb S聚合动力学对Hb S浓度的显著依赖性，脱水红细胞中Hb S聚合和镰状反应明显增加。Gardos通道和K-Cl共转运在镰状细胞脱水中的突出作用的确定，使得开发特异性治疗来防止体内脱水（例如增加红细胞Mg）成为可能。然而，关于K-Cl共转运的调控特性，无论是体外还是体内，特别是与镰状细胞病的缺氧和促氧化环境特征和镁补充治疗有关，仍有许多未知之处。我们建议：1)表征激酶和磷酸酶对人和小鼠K-Cl共转运的调节：我们建议在正常红细胞和镰状细胞（小鼠和人）的体外实验中研究蛋白激酶和磷酸酶在调节K-Cl共转运功能中的作用，并确定镰状细胞病中K-Cl共转运上调的机制。2)表征细胞Mg、尿素、缺氧和/或氧化损伤之间的相互作用如何影响红细胞K-Cl共转运的功能特性：将在体外研究红细胞Mg对缺氧、尿素和氧化损伤对K-Cl共转运活性的调节作用。我们将在转基因镰状小鼠中评估补充镁如何调节慢性缺氧和新型抗氧化剂的作用。3)评估补充Mg对镰状细胞病患者的影响：我们建议对10名镰状细胞病患者进行有限的试点研究，以验证在美国用于镰状细胞病患者临床研究的口服碘化镁制剂。这是进行大型多中心临床研究补充镁对镰状细胞病临床益处的必要的初步步骤。这些研究将系统地描述Mg、尿素、缺氧、氧化和抗氧化剂之间的相互作用对调节人和小鼠红细胞K-Cl共转运系统的分子机制的影响。这些目标与申请人的长期目标一致，申请人专注于膜转运和体积调节的研究以及镰状细胞病新疗法的持续开发。

DESCRIPTION (provided by applicant): Sickle cell dehydration plays an important role in the pathogenesis of sickle cell disease. Due to the marked dependence of Hb S polymerization kinetic on Hb S concentration, Hb S polymerization and sickling are markedly increased in dehydrated erythrocytes. Identification of the prominent role of Gardos channel and K-Cl cotransport in sickle cell dehydration has made possible the development of specific therapies to prevent dehydration in vivo (e.g. increasing red cell Mg). However, much remains unknown concerning the regulatory properties of the K-Cl cotransport, both in vitro and in vivo, especially in relation to the hypoxic and pro-oxidant environment characteristic of sickle cell disease and Mg supplementation therapy. We propose to: 1) Characterize the regulation of human and mouse K-Cl cotransport by kinases and phosphatases: We propose in vitro experiments on normal and sickle (mouse and human) erythrocytes to study the role played by protein kinases and phosphatases in regulating K-Cl cotransport function, and determine the mechanism(s) responsible for K-Cl cotransport up-regulation in sickle cell disease. 2) Characterize how the interactions between cell Mg, urea, hypoxia and/or oxidative damage affect the functional properties of erythroid K-Cl cotransport: The effects of erythrocyte Mg on the modulation of K-Cl cotransport activity by hypoxia, urea, and oxidative damage will be studied in vitro. We will assess in transgenic sickle mice how Mg supplementation may modulate the effects of chronic hypoxia and of novel anti-oxidative agents. 3) Assess the effects of Mg supplementation on patients with SS disease: We propose a limited pilot study on 10 patients with SS disease to validate an oral formulation of Mg pidolate to be used for clinical studies in patients with sickle cell disease in the USA. This is a necessary preliminary step for moving to a large multi-center clinical study on the clinical benefits of Mg supplementation in sickle cell disease. These studies will provide a systematic characterization of the interactions between Mg, urea, hypoxia,oxidation and antioxidants on the molecular mechanisms regulating the K-Cl cotransport system of human and mouse erythrocytes. These aims are consistent with the long-term goals of the applicant, who is focused on the study on membrane transport and volume regulation and the continued development of new therapies for sickle cell disease.