A New Target for Kidney Stone Prevention: Calcium-Sensitive Transport of Citrate

预防肾结石的新目标：柠檬酸盐的钙敏感转运

• 批准号: 8345192
• 负责人: Kathleen S Hering-Smith
• 金额: $ 30.1万
• 依托单位: TULANE UNIVERSITY OF LOUISIANA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8345192
• 关键词: Accounting; Acidosis; Affinity; Anatomy; Animals; Apical; Calcium; Calculi; Cell Line; Cells; Citrates; Data; Development; Didelphidae; Disease; Excretory function; Genes; Goals; Health Care Costs; Human; In Vitro; Intestinal Absorption; Intestines; Investigation; Ions; Kidney; Kidney Calculi; Knockout Mice; Knowledge; Lead; Magnesium; Medical; Methods; Molecular; Morbidity - disease rate; Mus; Nephrolithiasis; Outcome; Phenotype; Physiological; Physiological Processes; Prevention; Prevention strategy; Process; Proximal Kidney Tubules; Publishing; Regulation; Relative (related person); Research; Residual state; Role; Side; Succinates; Surface; Testing; Transport Process; Urine; Work; absorption; apical membrane; base; citrate carrier; cost; dicarboxylate-binding protein; extracellular; hypercalciuria; improved; in vivo; inhibitor/antagonist; kidney cell; novel; prevent; treatment strategy; tricarboxylate; urinary

DESCRIPTION (provided by applicant): Kidney stones are a common & serious illness. Urinary citrate is the most important inhibitor of calcium stones by keeping calcium soluble. The regulation of citrate transport in the kidney has received inadequate investigation & remains poorly understood. A single transporter NaDC1 has been assumed to be responsible for intestinal & renal citrate reabsorption. However we have recently identified a novel calcium-sensitive citrate transport process. The overall objective of this application is to determine the mechanisms & regulation of kidney proximal tubule apical citrate transport via a novel apical calcium-sensitive transporter, & the relative roles of NaDC1 & NaDC3. Our central hypothesis is that the novel citrate reabsorptive process functions to limit citrate transport in the proximal tubule when calcium is increased. Elucidation of previously unidentified citrate transporters can potentially lead to new treatments to increase urinary citrate. Aims are: 1) Define the novel calcium-sensitive citrate transporter & its role in the proximal tubule. Our working hypothesis, based on data in three proximal tubule cell lines, is that in addition to NaDC1, a novel calcium- sensitive dicarboxylate transporter is present on the apical side of the proximal tubule. We will use knockdown of NaDC1 in these cell lines to demonstrate this. Also we will determine citrate transport rates & the extracellular calcium-sensitivity for the remaining citrate transport process found in proximal tubule cells grown from dissected proximal tubule segments from knockout mice. 2) Determine the role of NaDC3 in proximal tubule reabsorption of citrate. Based on our surprising preliminary data, we will determine if NaDC3 is expressed on the apical membrane & accounts for calcium- sensitive citrate reabsorption. We will determine the localization of NaDC3 in the proximal tubule & determine the calcium sensitivity on the apical surface. We will also determine the role of basolateral NaDC3. 3) Determine the role of NaDC1 in renal reabsorption & intestinal absorption of citrate. Our working hypothesis is that NaDC1 is not the exclusive mechanism of citrate transport in the kidney & intestine. Other apical mechanisms may both be important in conditions such as acidosis & hypercalciuria. We will use NaDC1 knockout mice & compare renal citrate reabsorption in the -/- to +/+ mice both under baseline & conditions of acidosis & hypercalciuria. We will also determine intestinal citrate absorption in NaDC1 knockout mice.. These studies will establish new paradigms in understanding citrate reabsorption in both the kidney proximal tubule & the intestine, & how these paradigms are impacted in acidosis & hypercalciuria. These outcomes are expected to have an important impact since understanding the regulation of citrate transport in the proximal tubule will dramatically improve strategies in the prevention of calcium stones. PUBLIC HEALTH RELEVANCE: Kidney stones are a common and serious medical disorder, causing significant medical costs. Urinary citrate is the most important inhibitor of calcium stones and low urinary citrate is a common contributor to many stone types. The proposed research is expected to identify new mechanisms of regulation of urinary citrate excretion. This contribution will be significant because it will transform our understanding of urinary citrate excretion and would be expected to lead to new treatment paradigms.

描述（由申请人提供）：肾结石是一种常见且严重的疾病。柠檬酸尿液是通过保持钙可溶性的最重要的钙结石抑制剂。肾脏中柠檬酸盐运输的调节已经不充分的调查，并且对尚不理解。已经假定单个转运蛋白NADC1负责肠道和柠檬酸肾酸盐的重吸收。但是，我们最近确定了一种新型的钙敏感柠檬酸盐传输过程。该应用的总体目的是确定通过新型的顶钙敏感转运蛋白和NADC1和NADC3的相对作用来确定肾近端小管顶端柠檬酸酯转运的机理和调节。我们的中心假设是，新颖的柠檬酸盐可吸收过程功能，以限制钙升高时近端小管中的转运。阐明先前未鉴定的柠檬酸盐转运蛋白可以潜在地导致新的治疗方法增加柠檬酸盐。目的是：1）定义新型钙敏感的柠檬酸盐转运蛋白及其在近端小管中的作用。我们的工作假设基于三个近端小管细胞系中的数据，除了NADC1外，近端小管的顶端还存在一种新型的钙敏感二羧酸二羧酸酯转运蛋白。我们将在这些细胞系中使用NADC1的敲低来证明这一点。我们还将确定其余柠檬酸盐运输过程的柠檬酸盐传输速率和细胞外钙敏感性 从敲除小鼠近端小管片段生长的近端小管细胞中发现。 2）确定NADC3在柠檬酸近端重吸收中的作用。基于我们令人惊讶的初步数据，我们将确定NADC3是否在根尖膜上表达，并解释了钙敏感的柠檬酸盐重吸附。我们将确定NADC3在近端小管中的定位，并确定顶部表面上的钙敏感性。我们还将确定基底外侧NADC3的作用。 3）确定NADC1在柠檬酸盐的肾脏吸收和肠道吸收中的作用。我们的工作假设是，NADC1不是肾脏和肠道中柠檬酸盐运输的独特机制。在酸中毒和高钙尿等条件下，其他顶端机制都可能很重要。我们将使用NADC1敲除小鼠，并比较 - / - 与酸中毒和高钙化条件下的 - / - 与 +/ +小鼠相比。我们还将确定NADC1敲除小鼠的肠道柠檬酸盐的吸收。这些研究将在理解肾脏近端小管和肠中柠檬酸盐重吸收方面建立新的范式，以及如何在酸中毒和高钙尿中影响这些范例。这些结果有望产生重要的影响，因为了解近端小管中柠檬酸盐转运的调节将显着改善预防钙石的策略。 公共卫生相关性：肾结石是一种常见且严重的医学障碍，导致了巨大的医疗费用。泌尿柠檬酸盐是钙结石中最重要的抑制剂，低泌尿柠檬酸盐是许多石材类型的常见贡献者。拟议的研究预计将确定柠檬酸尿液排泄调节的新机制。这项贡献将是重要的，因为它将改变我们对柠檬酸尿液排泄的理解，并有望导致新的治疗范例。