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）： 前列腺素 (PG) 是远端肾单位集合管 (CD) 中盐和水转运的局部介质，其合成部分受细胞外液体积调节。高钠饮食促进细胞外体积扩张，导致局部 PG 合成增加，特别是前列腺素 E2 (PGE2)，可在尿液和肾脏中测量到。 PGE2 是内髓集合管 (IMCD) 中钠和水重吸收的有效抑制剂。 PGE2 合成途径的抑制与肾脏对 Na 的重吸收和高血压的发生有关，这表明 PGE2 在维持 Na 平衡和血压中发挥着关键作用。此外，盐敏感性高血压与肾脏 PGE2 合成和体内平衡缺陷相关。调节远端肾单位 PGE2 产生以维持精确的肾 Na 稳态的生理和/或细胞触发因素尚不清楚。 水或钠负荷引起的高远端流速与小鼠、啮齿动物和人类尿液中 PGE2 浓度的增加有关，这反过来又会增强钠和水的排泄。在人类和啮齿类动物中，单侧肾切除术也会引起远端肾小管流速和孤立肾中 PGE2 产量的增加，尽管体积状态没有改变。正如预期的那样，PG 合成的抑制剂减少了这些模型中尿 Na 的排泄，表明 PG 在肾切除术后维持 Na 稳态中发挥着重要作用。这些情况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 PGE2 的合成，进而有助于最终肾脏对 Na 平衡的调节。 肾小管上皮细胞对与尿液流速增加相关的水动力做出反应，例如层流剪切应力（LSS），细胞内Ca2+浓度（[Ca2+]i）增加，据信这是由中央纤毛转导的，发现于所有肾小管细胞的管腔表面，除了闰细胞（尽管这是有争议的）。其他研究人员表明，LSS/肾小管流速的增加可调节肾小管上皮细胞的核苷酸分泌，进而调节流量刺激的 [Ca2+]i，这表明流量调节 [Ca2+]i 的另一种机制。在微灌注皮质 CD (CCD) 中，嵌入细胞 (IC) 比主细胞 (PC) 释放更高浓度的核苷酸，这表明顶端纤毛不是流动诱导的核苷酸释放所必需的。此外，旁分泌核苷酸信号传导与肾CD中PGE2产量的增加相关。在水负荷或锂摄入发生的高肾小管流量条件下，从这些啮齿动物中分离出的 CD 上皮中的嘌呤信号传导和 PGE2 产生增强，表明高肾小管流速调节肾脏嘌呤能信号传导和 PGE2 产生。 然而，迄今为止，肾小​​管流速变化（及其流体动力学后果）对肾小管上皮细胞内细胞内信号传导、基因转录和蛋白质翻译的下游影响在很大程度上尚不清楚。因此，我们假设肾小管流速的增加会触发核苷酸分泌和嘌呤能信号传导，特别是增加肾小管上皮中的 [Ca2+]i 和 MAPK 激活，并且这些途径的激活调节 ptgs-2 mRNA 的合成和 PGE2 的产生，从而影响Na平衡。本提案旨在通过解决以下具体目标 (SA) 来检验这一假设： SA1：确定与肾小管流速增加相关的 LSS 增加在体外诱导下游 PG 合成（特别是 PGE2）的细胞/分子机制。 CD细胞。 SA2：测试从正常小鼠和扩容小鼠分离的天然 CD 中，流量刺激的跨上皮 Na 吸收 (JNa) 是否受到内源性、流量刺激的 PGE2 合成的调节。 公共卫生相关性： 高血压是一种普遍存在的疾病，影响超过 30% 的美国 40 岁以上成年人口。它会增加一个人患肾脏疾病、中风、冠状动脉疾病、充血性心力衰竭和总体死亡率的风险。将血压降低至正常水平可以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。高血压发生的病因尚不清楚，但一些研究人员已经证明，肾脏前列腺素代谢异常会影响钠稳态，从而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，通过该机制，肾脏可以调节前列腺素的合成，从而调节肾钠稳态。通过阐明尿流量激活肾脏中前列腺素合成的机制，我们可以确定调节肾钠稳态的机制以及预防高血压发生的靶基因和蛋白质。