Integrated control of collecting duct function and endothelin synthesis

 描述（由申请人提供）：集合管（CD）内皮素-1（ET-1）系统在调节血压（BP）和尿Na+排泄中起关键作用。ET-1直接抑制CD Na+和水重吸收; CD特异性敲除ET-1导致盐敏感性高血压。ET受体拮抗剂诱导的液体潴留是限制这些药物在临床试验中成功的主要因素，主要是由于CD ET-1作用的阻断。鉴于CD ET-1调节体液容量（BFV）稳态，重要的是要确定如何通过BFV状态的变化来调节该系统。尿ET-1排泄增加响应盐或水负荷;由于尿ET-1主要来自CD，这些研究结果表明，BFV调节CD ET-1的生产。BFV扩增增强CD ET-1合成的机制尚不完全清楚。我们已经发现，流量通过激活Ca 2+依赖性信号增强了内皮素-1的产生，可能需要初级纤毛和多囊蛋白-1和-2;这些发现提出了令人兴奋的可能性初级纤毛和多囊蛋白在调节CD ET-1和CD盐和水重吸收中的作用。此外，我们发现，嘌呤能受体P2 Y2和P2 X7可能是重要的IMCD ET-1流量响应，表明急性（ATP）和慢性（ET-1）之间的联系，在CD的利尿钠和利尿因子。我们还发现，一氧化氮（NO），可能通过NO合酶3，是必要的流动刺激IMCD ET-1，因为NO从未被证明增加ET-1，这代表了一个新的和重要的研究领域。总之，这些新发现形成了我们关键假设的基础：1）流动通过纤毛、多囊蛋白-1和-2、P2 Y2和P2 X7受体、NO和Ca 2+依赖性信号传导之间的相互作用增加IMCD ET-1产生;和2）纤毛、多囊蛋白-1和-2、P2 Y2和P2 X7受体以及CD ET-1的NO调节影响CD盐和水处理以及BP。本研究的具体目的如下：1）评价纤毛和多囊蛋白对CD、ET-1合成和肾功能的调节作用。这涉及确定CD中的纤毛和多囊蛋白-1和-2是否在生理条件下调节BP和盐和水的排泄，ET-1是否在这种调节中起作用，以及CD中的纤毛和多囊蛋白-1和-2如何调节ET-1的产生。2)评价CD ET-1合成和肾功能的嘌呤能调节。这涉及确定P2 Y2和P2 X7是否在生理条件下调节BP和尿盐和水排泄，CD ET-1是否在这种调节中起作用，以及CD中的P2 Y2和P2 X7如何调节ET-1产生。3)评价NO调节CD、ET-1合成及肾功能。这涉及鉴定CD中特定NOS同种型在生理条件下调节BP和尿盐和水排泄中的作用，如果CD ET-1在这种调节中起作用，以及CD中NOS同种型如何调节ET-1产生。总之，这项研究将大大提高了解小管液流如何调节CD盐和水的重吸收和ET-1在这一过程中的作用。

 DESCRIPTION (provided by applicant): The collecting duct (CD) endothelin-1 (ET-1) system plays a key role in regulating blood pressure (BP) and urinary Na+ excretion. ET-1 directly inhibits CD Na+ and water reabsorption; CD-specific knockout of ET-1 causes salt-sensitive hypertension. ET receptor antagonist-induced fluid retention, a major factor limiting the success of these agents in clinical trials, is largely due to blockade of CD ET-1 actions. Given that CD ET-1 modulates body fluid volume (BFV) homeostasis, it is important to define how this system is regulated by changes in BFV status. Urinary ET-1 excretion is increased in response to salt or water loading; since urinary ET-1 largely derives from the CD, these findings suggest that BFV regulates CD ET-1 production. The mechanism(s) by which BFV expansion enhances CD ET-1 synthesis are incompletely understood. We have found that flow enhances ET-1 production by the inner medullary CD (IMCD) through activation of Ca2+- depending signaling and may require primary cilia and polycystins-1 and -2; these findings raise exciting possibilities about te role of primary cilia and polycystins in the regulation of CD ET-1 and CD salt and water reabsorption. In addition, we found that the purinergic receptors P2Y2 and P2X7 may be important in the IMCD ET-1 flow response, suggesting a link between acutely (ATP) and chronically (ET-1) acting natriuretic and diuretic factors in the CD. We have also found that nitri oxide (NO), likely via NO synthase 3, is necessary for flow stimulation of IMCD ET-1; since NO has never been shown to increase ET-1, this represents a novel and important area of investigation. Taken together, these new findings form the basis for our key hypotheses: 1) Flow increases IMCD ET-1 production through an interplay between cilia, polycystins-1 and -2, P2Y2 and P2X7 receptors, NO and Ca2+-depending signaling; and 2) Cilia, polycystins-1 and -2, P2Y2 and P2X7 receptors, and NO modulation of CD ET-1 affects CD salt and water handling and BP. The following specific aims will be addressed: 1) Evaluate cilia and polycystin regulation of CD ET-1 synthesis and renal function. This involves determining if cilia and polycystins-1 and -2 in the CD regulate BP and salt and water excretion under physiological conditions, if ET-1 plays a role in such regulation, and how cilia and polycystins-1 and -2 in the CD modulate ET-1 production. 2) Evaluate purinergic regulation of CD ET-1 synthesis and renal function. This involves determining if P2Y2 and P2X7 modulate BP and urinary salt and water excretion under physiological conditions, if CD ET-1 plays a role in such regulation, and how P2Y2 and P2X7 in the CD modulate ET-1 production. 3) Evaluate NO regulation CD ET-1 synthesis and renal function. This involves identification of the role of specific NOS isoforms in the CD in modulating BP and urinary salt and water excretion under physiological conditions, if CD ET-1 plays a role in such regulation, and how NOS isoforms in the CD modulate ET-1 production. Taken together, this studies will greatly enhance understanding of how tubule fluid flow regulates CD salt and water reabsorption and the role of ET-1 in this process.