Renal sphingosine-1-phosphate receptor 1 in salt-sensitive hypertension

鞘磷脂最初被认为是细胞膜上无声的结构元素。最近， 鞘磷脂代谢物是重要的脂类信号分子。其中，鞘氨醇-1- 已知磷酸(S1P)在各种器官系统的细胞过程中发挥重要作用，包括 心血管系统和肾脏。S1P受体家族(S1P1-S1P5)的五个成员已经被 已确认身份。S1P1-3受体广泛表达，而S1P4在肺和淋巴系统中表达， S1P5主要在脑组织中表达。S1P1-3受体存在于肾脏中。事实证明，S1P 系统在许多疾病的发病机制中起重要作用，包括心血管疾病和肾脏疾病。 疾病。值得注意的是，肾脏中三种S1P受体的功能是不同的。S1P1介导保护性 S1P2和S1P3介导肾脏损伤效应。尽管许多报告显示 S1P途径参与肾脏的生理和病理，对其作用知之甚少 钠排泄系统。我们最近证实，S1P1-3受体显著表达于 肾髓质，主要位于集合管，肾髓质中的S1P1受体介导 通过抑制上皮钠通道(ENaC)起到很强的利钠作用。我们的初步数据显示， 盐的摄入上调了肾髓质中S1P1的水平，有趣的是，醋酸脱氧皮质酮 DOCA治疗显著降低肾髓质中S1P1的水平。有集合管的小鼠 (CD)特异性S1P1基因敲除(KO)，压力性钠尿钝化，高盐摄入促进更多 NA滞留与对照小鼠比较。此外，高盐摄入量会导致盐敏感型高血压。 在CD特异的S1P1KO小鼠中，而在对照组小鼠中，当用降压剂DOCA治疗时不是这样。论 另一方面，将选择性S1P1激动剂BAF312局部注入肾髓质显著减弱 DOCA-盐性高血压。基于这些发现，我们假设肾脏延髓s1p1通路是一个 抑制过多钠重吸收和肾脏抑制的关键平衡机制 延髓S1P1通路参与盐敏感型高血压的发生发展。三个具体目标是 提出用来检验我们的假设。目的1：确定S1P1通路在肾脏中的抑制作用 延髓参与了盐敏感型高血压的发病机制。CD特异性S1P1缺失的小鼠 或者使用CD特异性的S1P1转基因过表达。目的2：确定S1P1通路是否 抑制ENaC活性，从而增加钠排泄，发挥降压作用。膜片钳 将对新分离的收集管道中的ENaC通道活性进行研究。目标3：探索 S1P1激活抑制ENaC活性通过胃肠道发挥降压作用的机制 蛋白质/cAMP偶联信号。拟议的研究将揭示肾脏钠的一种新的分子机制 并为盐敏感型高血压的发病机制提供了新的见解。

Sphingolipids were originally thought to serve as silent structural elements of the cell membrane. Recently, sphingolipid metabolites are emerging as important lipid signaling molecules. Among them, sphingosine-1- phosphate (S1P) is known to play important roles in cellular processes in various organ systems including the cardiovascular system and kidney. Five members of the S1P receptor family (S1P1–S1P5) have been identified. The S1P1-3 receptors are ubiquitously expressed, while S1P4 is in the lung and lymphoid system, and S1P5 mainly in brain tissue. The S1P1-3 receptors are present in the kidneys. It has been shown that S1P system plays a significant role in the pathogenesis of many diseases, including cardiovascular and kidney diseases. Notably, the functions of three S1P receptors in the kidneys are different. S1P1 mediates protective effects, whereas S1P2 and S1P3 mediate injurious effect in the kidneys. Despite many reports showing the involvement of S1P pathway in renal physiology and pathology, little is known about the role of renal S1P system in Na+ excretion. We have recently demonstrated that S1P1-3 receptors are prominently expressed in the renal medulla, mainly located in the collecting ducts, and that S1P1 receptor in the renal medulla mediates a strong natriuretic effect via inhibiting epithelial Na+ channel (ENaC). Our preliminary data showed that high salt intake upregulated the level of S1P1 in the renal medulla, and interestingly, deoxycorticosterone acetate (DOCA) treatment significantly reduced the level of S1P1 in the renal medulla. In mice with collecting duct (CD)-specific S1P1 knockout (KO), the pressure natriuresis was blunted and high salt intake promoted more Na+ retention compared with control mice. Furthermore, high salt intake produced a salt-sensitive hypertension in CD-specific S1P1 KO mice but not in control mice when treated with a subpressor dose of DOCA. On the other hand, infusion of BAF312, a selective S1P1 agonist, locally into the renal medulla remarkably attenuated DOCA-salt hypertension. Based on these findings, we hypothesize that the renal medullary S1P1 pathway is a critical counterbalancing mechanism to inhibit the excessive Na+ reabsorption and that suppression of renal medullary S1P1 pathway contributes to the development of salt-sensitive hypertension. Three specific aims are proposed to test our hypothesis. Aim 1: To determine whether the suppression of S1P1 pathway in the renal medulla contributes to the pathogenesis of salt-sensitive hypertension. Mice with CD-specific deletion of S1P1 or CD-specific overexpression of S1P1 transgene will be used. Aim 2: To determine whether S1P1 pathway inhibits ENaC activity and thereby increases Na+ excretion, exerting the antihypertensive action. Patch clamp studies of ENaC channel activity in freshly isolated collecting ducts will be performed. Aim 3: To explore the mechanism by which S1P1 activation inhibits ENaC activity to exert antihypertensive action via Gi protein/cAMP-coupled signaling. The proposed studies will reveal a novel molecular mechanism in renal Na+ handling and provide new insights into the pathogenesis of salt-sensitive hypertension.