Hydrodynamic forces modulate renal tubular function

水动力调节肾小管功能

• 批准号: 8262629
• 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/8262629
• 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）： 前列腺素（PGS）的合成是远端肾单位的收集管道（CD）中盐和水转运的局部介体，部分通过细胞外液体体积调节。高Na饮食促进的细胞外体积扩张会诱导PG合成的局部增加，特别是前列腺素E2（PGE2），这在尿液和肾脏中是可测量的。 PGE2是内部髓质收集管（IMCD）中Na的有效抑制剂和水的吸收。 PGE2合成途径的抑制与狂热的肾脏NA重吸收和高血压的发展有关，这表明PGE2在维持NA平衡和血压方面起着关键作用。此外，盐敏感的高血压与肾脏PGE2合成和稳态的缺陷有关并关联。在远端肾单位中调节PGE2产生的生理和/或细胞触发，以保持精确的肾脏Na稳态。 响应水或NA负载的高远端流速与小鼠，啮齿动物和人类尿中PGE2浓度的增加有关，从而增强了Na和水分。在人类和啮齿动物中，单侧肾切除术还诱导孤立肾脏的远端管状流速和PGE2产生增加，尽管体积状态没有改变。正如预期的那样，PG合成的抑制剂在这些模型中降低了尿NA排泄，这表明PGS在维持NA的稳态后起着重要作用。这些条件之间的共同主题是，远端管状流量增加，这一观察结果使我们推测流体动力调节PGE2的合成，进而有助于NA平衡的最终肾脏调节。 肾小管上皮细胞对与尿液流量增加有关的流体动力作用，例如层状剪切应力（LSS），并且细胞内Ca2+浓度（[Ca2+] i）的增加，据信被认为是由中央砂浆转导的，该中心是在除插入的细胞外，所有肾小管细胞的腔表面（尽管这是有争议的）。其他研究者表明，LSS/管状流量的增加调节肾小管上皮细胞的核苷酸分泌，而肾小管上皮细胞又调节流动刺激的[Ca2+] I，提示流动调节[Ca2+] i的另一种机制。在微植入的皮质CD（CCD）中，插入式细胞（ICS）释放了比主要细胞（PCS）更大的核苷酸浓度，这表明流动诱导的核苷酸释放不需要根尖纤毛。另外，旁分泌核苷酸信号传导与肾脏CD中的PGE2产生增加有关。在水负荷或锂摄入时出现的高管流量的情况下，从这些啮齿动物分离出的CD上皮中，纯净信号传导和PGE2产生的产生被增强，这表明高管状流量调节肾嘌呤能信号传导和PGE2产生。 然而，迄今为止，管状流速（及其流体动力学后果）对细胞内信号传导，基因转录和蛋白质翻译的下游影响在很大程度上是未知的。因此，我们假设在肾小管上皮中，肾小管流速触发核苷酸的分泌和嘌呤能信号转导，特别增加了[Ca2+] I和MAPK激活，这些途径的激活调节了PTGS-2 mRNA和PGE2 MRNA的合成，该途径的合成影响NA平衡。该提案旨在通过解决以下特定目的（SAS）：SA1：确定与管状流量增加相关的LSS增加的细胞/分子机制来检验该假设。 CD细胞。 SA2：为了测试流量刺激的旋转旋转型Na吸收（JNA）是否受到内源产生的，流量刺激的PGE2合成的调节的天然CD，从正常和体积扩展的小鼠中分离出来。 公共卫生相关性： 高血压是一种普遍的医学疾病，影响了40岁以上美国成年人人群的30％。它增加了一个人患肾脏疾病，中风，冠状动脉疾病，充血性心力衰竭和整体死亡的风险。将血压降低到正常水平会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恢复到控制水平。高血压发展背后的病因尚不清楚，但一些研究人员表明，影响NA稳态的异常肾脏前列腺素代谢可以导致NA保留和高血压。在这项研究应用中，我们确定了一种新型的生理机制，通过该机制，前列腺素合成可以受肾脏的调节，因此可以调节肾脏NA稳态。通过阐明尿液流量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，以防止高血压发展。