Salt-sensitive hypertension: Role of renal superoxide

说明(申请人提供)：在促进肾脏盐分和水分滞留的因素和那些有利于排泄的因素之间存在平衡。不适当的含盐量可能会导致高血压。这个项目的重点是超氧化物(O2-)，它有利于盐分和水分的保持。肾脏O2-是肾功能的重要调节因子，与盐敏感型高血压有关。Henle环的粗大升支是导致盐敏感型高血压患者NaCI不适当滞留的肾单位段之一，也是环状利尿剂的作用部位。在上一次资助期间，我们发现O2-通过增强管腔Na/K/2CI共转运蛋白的活性来增加粗大的上肢转运。这一作用是由于蛋白激酶C(PKC)的激活和一氧化氮(NO)的清除所致。然而，很少有研究直接讨论O2-是如何沿肾单位调节的。通过粗大的上肢的尿流并不是静止的，但由于乳头的蠕动，尿流的变化很大，从超过25NL/分钟到低至0NL/分钟(实际上停止了)。我们的初步数据显示，通过粗大的升支的管腔血流(Thal-flow)的增加刺激了O2的产生。我们的一般假设是，增加尿流量从而增加粗大上肢的伸展、压力或剪应力的因素会增加O2-的产生，进而促进NaCI的吸收，从而促进Na的滞留。粗大的升肢中O2-增多导致的钠滞留增加，可能在高血压和其他与钠滞留相关的疾病的发病机制中起重要作用。目的1将测试急剧增加Thal-flow是否导致NADPH氧化酶的组装和激活，从而促进O2-的产生和NaCI的吸收。AIMS 2和AIMS 3将研究流刺激产生O2-的信号级联反应，重点是蛋白激酶C和小G蛋白rac1。目的4研究流动诱导的NO如何调节NADPH氧化酶活性及其对NaCI吸收的影响。我们将使用最先进的技术来解决这些目标，除了标准的生理、生化和药理学技术外，还包括荧光能量转移和体内病毒转导。这个项目的成功完成将使我们对肾脏中O2-是如何产生的以及它在盐保留中的作用有了新的见解，并预测了治疗高血压的新靶点。

DESCRIPTION (provided by applicant): There is a balance between factors promoting renal salt and water retention and those favoring excretion. Inappropriate salt retention may lead to hypertension. This project focuses on superoxide (O2-), which favors salt and water retention. Renal O2- is an important regulator of kidney function and has been implicated in salt-sensitive hypertension. The thick ascending limb of the loop of Henle is one of the nephron segments responsible for inappropriate NaCI retention in salt-sensitive hypertension and is the site of action of loop diuretics. In the last funding period we showed that O2- increased thick ascending limb transport by enhancing the activity of the luminal Na/K/2CI cotransporter. This effect was due to both activation of protein kinase C (PKC) and scavenging of nitric oxide (NO). However, few studies have directly addressed how O2- production is regulated along the nephron. Urine flow through thick ascending limbs is not static, but acutely varies from more than 25 nl/min to as little as 0 nl/min (actually stopping) due to peristalsis of the papilla. Our preliminary data show that increasing luminal flow through the thick ascending limb (THAL-flow) stimulates O2- generation. Our general hypothesis is that factors that increase urine flow and therefore augment stretch, pressure or shear stress in the thick ascending limb enhance O2- production, which in turn promotes NaCI absorption and therefore Na retention. The increase in Na retention caused by enhanced O2- in the thick ascending limb may be important in the pathogenesis of hypertension and other diseases associated with Na retention. Aim 1 will test whether acutely increasing THAL-flow causes the assembly and activation of NADPH oxidase, thereby enhancing O2- generation and NaCI absorption. Aims 2 and 3 will study the signaling cascades responsible for flow-stimulated O2- production focusing on protein kinase C and the small G-protein Rac1. Aim 4 will investigate how flow-induced NO regulates NADPH oxidase activity and its impact on NaCI absorption. We will employ state of the art techniques to address these aims, including fluorescence energy transfer and in vivo viral transduction in addition to standard physiological, biochemical and pharmacological techniques. Successful completion of this project will give us new insights into how O2- is generated in the kidney as well as its role in salt retention, and predict new targets for treatment of hypertension.