Glyoxylate Reductase and Primary Hyperoxaluria

描述(申请人提供)：原发性高草酸尿症是一种罕见的遗传性疾病，由草酸的过度内源性合成引起。乙醛酸还原酶(GR)是这一生物合成途径中的关键酶，它将草酸的主要前体乙醛转化为乙醇酸，从而限制其转化为草酸。该项目的长期目标是深入了解与GR活性以及乙醛酸和草酸合成相关的途径，确定GR活性缺失的代谢后果，并确定在GR活性缺失时限制草酸合成的治疗策略。为了帮助实现这些目标，我们开发了一种GR活性降低的细胞系，并获得了一种缺乏GR活性的敲除(KO)小鼠。这项提议有三个具体目标。第一个目标是确定KO小鼠的表型，使用离子色谱-质谱仪(IC/MS)测量血液、尿液和组织中的阴离子浓度。第二个目的是验证这样的假设，即抑制羟脯氨酸氧化酶(HPOX)将是一种有效的治疗策略，以减少与GR缺乏相关的草酸合成增加。为了建立原理证据，将利用RNA干扰来抑制HPOX活性和减少草酸合成。KO小鼠将被用作这些研究的模型。在第三个具体目标中，将研究GR在红细胞中的功能作用。与其他细胞相比，这些细胞具有简化的新陈代谢，初步数据表明这些细胞含有乙醇酸、乙醇酸和草酸，以及GR活性。推测GR具有限制草酸合成和合成乙醇酸的功能，乙醇酸是合成磷酸乙醇酸的潜在底物。这些假说将在KO小鼠的细胞和与乙醇酸和乙醛孵育的人类细胞中进行测试。这些研究将增加我们对与草酸合成相关的代谢的了解，并可能确定减少原发性高草酸尿症草酸合成的新治疗策略。

DESCRIPTION (provided by applicant): Primary hyperoxaluria is a rare, genetic disorder that results from an excessive endogenous synthesis of oxalate. Glyoxylate reductase (GR) is a key enzyme in this biosynthetic pathway, converting glyoxylate, the main precursor of oxalate, to glycolate and thereby limiting its conversion to oxalate. The long term goals of this project are to develop an in depth understanding of the pathways associated with GR activity and glyoxylate and oxalate synthesis, to determine the metabolic consequences of an absence of GR activity, and to identify therapeutic strategies that limit oxalate synthesis when the activity is absent. To assist with these goals we have developed a cell line with reduced GR activity and have obtained a knockout (KO) species of mouse lacking GR activity. This proposal has three specific aims. The first aim is to determine the phenotype of the KO mouse, measuring anion concentrations in blood, urine and tissues using ion chromatography coupled to mass detection (IC/MS). The second aim is designed to test the hypothesis that inhibiting hydroxyproline oxidase (HPOX) will be an effective therapeutic strategy for decreasing the increased oxalate synthesis associated with GR deficiency. To establish proof of principle, RNA interference will be utilized to inhibit HPOX activity and decrease oxalate synthesis. The KO mouse will be used as a model for these studies. In the third specific aim, the functional role of GR in red blood cells will be examined. These cells have a simplified metabolism in comparison to other cells and preliminary data indicate that these cells contain glycolate, glyoxylate and oxalate, as well as GR activity. It is hypothesized that GR functions to limit oxalate production and to synthesize glycolate, a potential substrate for phosphoglycolate synthesis. These hypotheses will be tested in cells from KO mice and human cells incubated with glycolate and glyoxylate. These studies will increase our understanding of the metabolism associated with oxalate synthesis and will potentially identify novel therapeutic strategies to decrease oxalate synthesis in primary hyperoxaluria.