Hydrodynamic forces modulate renal tubular function

水动力调节肾小管功能

• 批准号: 7931615
• 负责人: RAJEEV ROHATGI
• 金额: --
• 依托单位: JAMES J PETERS VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7931615
• 关键词: Address; Adenosine; Adult; Affect; Age; Apical; Back; Blood; Blood Pressure; Cells; Cilia; Congestive Heart Failure; Coronary Arteriosclerosis; Development; Diet; Dinoprostone; Disease; Distal; Duct (organ) structure; Epithelial; Epithelial Cells; Epithelium; Equilibrium; Etiology; Excretory function; Extracellular Fluid; Gene Proteins; Genetic Transcription; Homeostasis; Human; Hypertension; In Vitro; Indomethacin; Ingestion; Intercalated Cell; Isotonic Exercise; JUN gene; Kidney; Kidney Diseases; Lead; Link; Lithium; MAPK14 gene; Maintenance; Measurable; Mediating; Mediator of activation protein; Medical; Membrane; Messenger RNA; Metabolism; Mitogen-Activated Protein Kinase Inhibitor; Mitogen-Activated Protein Kinases; Modeling; Molecular; Morbidity - disease rate; Mus; Nephrectomy; Nephrons; Nucleotides; Oryctolagus cuniculus; PTGS2 gene; Pathway interactions; Persons; Phosphotransferases; Physiological; Play; Population; Production; Prostaglandin Antagonists; Prostaglandins; Proteins; Regulation; Research; Research Personnel; Risk; Rodent; Role; Saline; Signal Pathway; Signal Transduction; Sodium Chloride; Stroke; Surface; Testing; Translations; Tubular formation; Urine; Water; absorption; cyclooxygenase 1; cyclooxygenase 2; extracellular; feeding; hypertension treatment; inhibitor/antagonist; mRNA Expression; mortality; mouse PGE synthase 1; novel; paracrine; prevent; prostaglandin E synthase; prostaglandin transporter; response; salt sensitive; shear stress; synthetic enzyme; urinary

DESCRIPTION (provided by applicant): Synthesis of prostaglandins (PGs), local mediators of salt and water transport in the collecting duct (CD) of the distal nephron, is regulated, in part, by extracellular fluid volume. Extracellular volume expansion promoted by a high Na diet induces local increases in PG synthesis, specifically prostaglandin E2 (PGE2), which is measurable in urine and kidney. PGE2 is a potent inhibitor of Na and water reabsorption in the inner medullary collecting duct (IMCD). Inhibition of the PGE2 synthetic pathway is associated with avid renal Na reabsorption and the development of hypertension, suggesting a critical role for PGE2 in the maintenance of Na balance and blood pressure. In addition, salt-sensitive hypertension is associated with and linked to deficiencies in renal PGE2 synthesis and homeostasis. The physiologic and/or cellular triggers regulating PGE2 production in the distal nephron that maintain precise renal Na homeostasis are unknown. High distal flow rates, as occur in response to water or Na loading, are associated with increases in urinary PGE2 concentration in mice, rodents and humans, which in turn, enhance Na and water excretion. In humans and rodents unilateral nephrectomy also induces increases in distal tubular flow rates and PGE2 production in the solitary kidney, albeit without an alteration in volume status. As expected, inhibitors of PG synthesis reduce urinary Na excretion in these models, suggesting that PGs play an important role post- nephrectomy to maintain Na homeostasis. The common theme among these conditions is that distal tubular flow rate is increased, an observation that leads us to speculate that hydrodynamic forces regulate synthesis of PGE2, and in turn contribute to the final renal regulation of Na balance. Renal tubular epithelial cells respond to hydrodynamic forces associated with increases in urine flow rate, such as laminar shear stress (LSS), with increases in intracellular Ca2+ concentration ([Ca2+]i) which are believed to be transduced by the central cilium, found on the luminal surface of all renal tubular cells, except intercalated cells (though this is controversial). Other investigators have shown that increases in LSS/tubular flow rate regulate nucleotide secretion from renal tubular epithelial cells which, in turn, regulates flow- stimulated [Ca2+]i, suggesting another mechanism by which flow regulates [Ca2+]i. In microperfused cortical CD (CCD), intercalated cells (ICs) release a greater concentration of nucleotides than principal cells (PCs), suggesting the apical cilium is not required for flow-induced nucleotide release. In addition paracrine nucleotide signaling is associated with increased PGE2 production in the renal CD. In conditions of high tubular flow that occur with water loading or lithium ingestion, puringeric signaling and PGE2 production is augmented in CD epithelial isolated from these rodents, suggesting that high tubular flow rates regulate renal purinergic signaling and PGE2 production. However, to date the downstream effects of changes in tubular flow rate (and its hydrodynamic consequences) on intracellular signaling, gene transcription, and protein translation in tubular epithelial cells are largely unknown. Thus, we hypothesize that increases in tubular flow rate trigger nucleotide secretion and purinergic signaling, specifically increasing [Ca2+]i and MAPK activation, in renal tubular epithelia, and that activation of these pathways regulate the synthesis of ptgs-2 mRNA and PGE2 production which influences Na balance. This proposal aims to test this hypothesis by addressing the following specific aims (SAs): SA1: To identify the cellular/molecular mechanisms by which increases in LSS associated with increases in tubular flow rate induce downstream PG synthesis (specifically, PGE2) in vitro in CD cells. SA2: To test whether flow-stimulated transepithelial Na absorption (JNa) is regulated by endogenously produced, flow-stimulated PGE2 synthesis in native CDs isolated from normal and volume expanded mice. PUBLIC HEALTH RELEVANCE: Hypertension is a prevalent medical disorder affecting >30% of the adult U.S. population over the age of 40. It increases a person's risk for kidney disease, stroke, coronary artery disease, congestive heart failure and overall mortality. Reducing blood pressure to normal levels decreases the morbidity and mortality associated with hypertension, but does not bring morbidity and mortality back to control levels. The etiology behind the development of hypertension is unknown, but some investigators have demonstrated that abnormal renal prostaglandin metabolism, which affects Na homeostasis, can lead to Na retention and hypertension. In this research application, we identify a novel physiologic mechanism by which prostaglandin synthesis may be regulated by the kidney, and consequently, renal Na homeostasis. By elucidating the mechanisms by which urine flow rate can activate prostaglandin synthesis in the kidney, we can identify mechanisms which regulate renal Na homeostasis as well as target genes and proteins to prevent the development of hypertension.

描述（由申请人提供）： 在远端肾单位的集合管（CD）中，盐和水运输的局部介质-前列腺素（PGs）的合成部分地受细胞外液量的调节。由高钠饮食促进的细胞外体积扩张诱导PG合成的局部增加，特别是前列腺素E2（PGE 2），其在尿液和肾脏中可测量。PGE 2是内髓集合管（IMCD）中Na和水重吸收的有效抑制剂。PGE 2合成途径的抑制与肾钠重吸收和高血压的发展有关，表明PGE 2在维持钠平衡和血压中起关键作用。此外，盐敏感性高血压与肾脏PGE 2合成和体内平衡缺陷有关。调节远端肾单位中PGE 2产生的生理和/或细胞触发因子维持精确的肾Na稳态是未知的。 高远端流速，如响应于水或Na负荷而发生的，与小鼠、啮齿动物和人类中尿PGE 2浓度的增加相关，这反过来又增强Na和水的排泄。在人类和啮齿类动物中，单侧肾切除术也诱导远端肾小管流速和PGE 2在孤立肾中产生增加，尽管没有改变体积状态。正如预期的，PG合成抑制剂减少了这些模型中的尿Na排泄，表明PG在肾切除术后维持Na稳态中起重要作用。这些条件的共同主题是远端肾小管流速增加，这一观察结果使我们推测，水动力调节PGE 2的合成，进而有助于最终的肾脏Na平衡调节。 肾小管上皮细胞响应与尿流速增加相关的流体动力，如层流剪切应力（LSS），细胞内Ca 2+浓度（[Ca 2 +]i）增加，据信由中央纤毛转导，在所有肾小管细胞的管腔表面上发现，除了闰细胞（尽管这是有争议的）。其他研究者已经表明，LSS/肾小管流速的增加调节肾小管上皮细胞的核苷酸分泌，这反过来又调节流量刺激的[Ca 2 +]i，这表明流量调节[Ca 2 +]i的另一种机制。在微灌注皮质CD（CCD），嵌入细胞（IC）释放更大浓度的核苷酸比主细胞（PC），表明顶端纤毛是不需要的流量诱导的核苷酸释放。此外，旁分泌核苷酸信号传导与肾CD中PGE 2产生增加相关。在水负荷或锂摄入发生的高肾小管流量条件下，从这些啮齿动物分离的CD上皮细胞中的嘌呤信号传导和PGE 2产生增加，表明高肾小管流速调节肾嘌呤信号传导和PGE 2产生。 然而，到目前为止，在肾小管上皮细胞的细胞内信号转导，基因转录和蛋白质翻译的小管流速（及其流体动力学后果）的变化的下游影响在很大程度上是未知的。因此，我们假设，在肾小管流速的增加触发核苷酸分泌和嘌呤能信号，特别是增加[Ca 2 +]i和MAPK激活，在肾小管上皮细胞，这些途径的激活调节ptgs-2 mRNA的合成和PGE 2的生产，影响钠平衡。本提案旨在通过解决以下特定目标（SA）来检验这一假设：SA 1：确定与肾小管流速增加相关的LSS增加在体外CD细胞中诱导下游PG合成（特别是PGE 2）的细胞/分子机制。SA2：为了测试是否流量刺激的跨上皮Na吸收（JNa）是由内源性产生的，流量刺激的PGE 2合成的天然CD从正常和体积扩大的小鼠中分离的调节。 公共卫生相关性： 高血压是一种流行的医学疾病，影响超过30%的40岁以上的美国成年人口。它增加了一个人患肾病、中风、冠状动脉疾病、充血性心力衰竭和总死亡率的风险。将血压降至正常水平可降低与高血压相关的发病率和死亡率，但不会使发病率和死亡率回到控制水平。高血压发展背后的病因尚不清楚，但一些研究人员已经证明，影响钠稳态的肾前列腺素代谢异常可导致钠潴留和高血压。在这项研究应用中，我们确定了一种新的生理机制，前列腺素的合成可能是由肾脏调节，因此，肾钠稳态。通过阐明尿流率可以激活肾脏中前列腺素合成的机制，我们可以确定调节肾脏Na稳态的机制以及靶基因和蛋白质，以防止高血压的发展。