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)的合成在一定程度上受细胞外液容量的调节，PGs是肾单位远端集合管(CD)中盐和水运输的局部中介。高钠饮食促进的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)，可在尿液和肾脏中检测到。前列腺素E_2是内髓集合管(IMCD)钠和水重吸收的有效抑制剂。PGE2合成途径的抑制与肾脏贪婪的钠重吸收和高血压的发生有关，提示PGE2在维持钠平衡和血压方面起着关键作用。此外，盐敏感型高血压与肾脏前列腺素E_2合成和动态平衡缺陷有关。调节远端肾单位PGE2产生的生理和/或细胞触发因素维持精确的肾脏钠平衡尚不清楚。远端流速高，如对水或钠负荷的反应，与小鼠、啮齿动物和人类尿中PGE2浓度的增加有关，这反过来又增加了钠和水的排泄。在人类和啮齿动物中，单侧肾切除也可导致孤立肾远端肾小管流量和PGE2产量的增加，尽管体积状态没有改变。正如预期的那样，在这些模型中，PG合成的抑制剂减少了尿钠的排泄，这表明PGs在肾切除术后维持钠的动态平衡方面发挥了重要作用。这些情况之间的共同主题是远端肾小管流量增加，这一观察结果使我们推测，流体动力调节PGE2的合成，进而有助于最终肾脏对钠平衡的调节。肾小管上皮细胞对与尿流率增加相关的流体动力做出反应，如层流切应力(LSS)，以及细胞内钙离子浓度([Ca2+]i)的增加，据信这些钙离子浓度是由中央纤毛传递的，发现于所有肾小管细胞的管腔表面，但间质细胞除外(尽管这是有争议的)。其他研究人员已经证明，LSS/肾小管流量的增加调节肾小管上皮细胞的核苷酸分泌，进而调节血流刺激的[Ca~(2+)]i，这暗示了Flow调节[Ca~(2+)]i的另一种机制。在微灌流的皮质CD(CD)中，间质细胞(IC)释放的核苷酸浓度高于主细胞(PC)，这表明血流诱导的核苷酸释放不需要纤毛尖部。此外，旁分泌核苷酸信号与肾脏CD中PGE2的产生增加有关。在高肾小管流量的条件下，水负荷或锂摄取时，从这些啮齿动物分离的CD上皮细胞中，精氨酸信号和PGE2的产生增加，这表明高的肾小管流量调节肾脏的嘌呤能信号和PGE2的产生。然而，到目前为止，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信号、基因转录和蛋白质翻译的下游影响尚不清楚。因此，我们推测，肾小管流量的增加触发了肾小管上皮细胞的核苷酸分泌和嘌呤能信号，特别是增加了[Ca2+]i和MAPK的激活，而这些途径的激活调节了ptgs-2mRNA的合成和PGE2的产生，从而影响了钠的平衡。这项建议旨在通过解决以下特定目标(SAS)来验证这一假说：SA1：确定与肾小管流速增加相关的LSS增加在体外诱导CD细胞下游PG合成(特别是PGE2)的细胞/分子机制。SA2：为了测试流动刺激的跨上皮钠吸收(JNA)是否受到内源性产生的、流动刺激的PGE2合成的调节，从正常和容量扩张的小鼠分离的自然CD中。 公共卫生相关性： 高血压是一种流行的疾病，影响着美国30%的40岁以上的成年人口。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恢复到控制水平。高血压发病的原因尚不清楚，但一些研究人员已经证明，影响钠稳态的肾脏前列腺素代谢异常可导致钠滞留和高血压。在这项研究应用中，我们确定了一种新的生理机制，通过这种机制，前列腺素的合成可能受到肾脏的调节，从而调节肾脏的钠稳态。通过阐明尿流率激活肾脏前列腺素合成的机制，我们可以确定调节肾脏钠稳态的机制以及靶基因和蛋白以防止高血压的发展。