Sphingosine-1-phosphate in renal microvascular dysfunction of ischemia-reperfusion kidney injury

肾缺血再灌注(IR)是急性肾损伤(IR-AKI)的主要原因之一，也是一个重要的未解决的问题 临床问题。IR-AKI取得进展的一个关键障碍是，我们的科学研究存在差距 了解延髓血流量持续减少的机制是关键 决定IR-AKI预后和进展为慢性肾脏疾病(CKD)的因素。我们的目标是 通过关注鞘氨醇-1-磷酸(S1P)作为潜在信号的作用来解决这一关键障碍 参与IR-AKI肾微血管功能障碍的分子。我们的中心假设是肾脏 缺血再灌流可显著增强延髓旁传入小动脉的敏感性。 控制MBF的血管节段，到S1P介导的血管收缩，这有助于持续性 IR-AKI组MBF下降，肾小球滤过率(GFR)持续下降。我们的目标是 通过(1)确定S1P在控制延髓旁传入中的作用来解决这一中心假设 IR-AKI的微动脉功能和肾血流动力学；(2)建立S1P-1的细胞机制。 IR-AKI中传入小动脉反应性的依赖调节；以及(3)确定其病理生理作用 S1P在IR-AKI肾微血管功能障碍发生中的作用我们将检验这一中心假设 通过三个具体目标。目标1将验证肾缺血-再灌注导致肾功能增强的假设 传入小动脉对S1P的敏感性，S1P参与持续的血管收缩和MBF减少 在IR-AKI中。目的2验证肾缺血-再灌流诱导反应性增加的假设 在IR-AKI中，氧物种的产生有助于增强传入小动脉对S1P的敏感性。目标3将 抑制S1P受体激活阻止S1P介导的传入增强的假设检验 缺血再灌流过程中的小动脉血管收缩和对IR-AKI的保护作用。我们将使用体外培养的 血液灌流延髓旁肾单位技术评价IR对S1P介导的小动脉的影响 在大鼠和S1P2受体敲除小鼠中的反应。我们将确定S1P对总量和 IR-AKI测定肾局部血流量和肾小球滤过率。我们将确定哪些S1P受体有助于增强 S1P介导的血管收缩。我们将测定IR大鼠肾脏和血浆中的鞘磷脂代谢产物。 老鼠。我们的结果将为肾脏IR激活S1P信号通路提供新的机制见解 在肾脏微血管系统中。外源性S1P可引起传入小动脉和 肾血流量和MBF减少，在IR-AKI时会增强。S1P2受体阻断或缺失 将防止IR-AKI。这项研究的结果将提高我们对病理生理学的理解。 IR-AKI中MBF持续减少和GFR持续下降的机制。改进 抑制S1P2R信号通路的MBF可能是治疗IR-AKI和预防的新的治疗靶点 发展到CKD，从而在该领域产生重大影响。

Renal ischemia-reperfusion (IR) is a leading cause of acute kidney injury (IR-AKI), a significant unsolved clinical problem. A critical barrier to progress with IR-AKI is that there are gaps in our scientific understanding of the mechanisms underlying the persistent reduction of medullary blood flow (MBF), a key factor determining the outcome of IR-AKI and the progression to chronic kidney disease (CKD). Our goal is to address this critical barrier by focusing on the role of sphingosine-1-phosphate (S1P) as a potential signaling molecule contributing to renal microvascular dysfunction in IR-AKI. Our central hypothesis is that renal ischemia-reperfusion leads to significantly enhanced sensitivity of juxtamedullary afferent arterioles, the crucial vascular segment that controls MBF, to S1P-mediated vasoconstriction which contributes to a persistent reduction of MBF and a steady decline in glomerular filtration rate (GFR) in IR-AKI. Our objectives are to address this central hypothesis by (1) determining the role of S1P in controlling juxtamedullary afferent arteriolar function and renal hemodynamics in IR-AKI; (2) establishing the cellular mechanisms of S1P- dependent regulation of afferent arteriolar reactivity in IR-AKI; and (3) determining the pathophysiological role of S1P in the development of renal microvascular dysfunction in IR-AKI. We will test this central hypothesis through three specific aims. AIM 1 will test the hypothesis that renal ischemia-reperfusion leads to enhanced sensitivity of afferent arterioles to S1P which contributes to a persistent vasoconstriction and reduction of MBF in IR-AKI. AIM 2 will test the hypothesis that the renal ischemia-reperfusion-induced increase in reactive oxygen species production contributes to enhanced S1P sensitivity of afferent arterioles in IR-AKI. AIM 3 will test the hypothesis that inhibition of S1P receptor activation prevents enhancement of S1P-mediated afferent arteriolar vasoconstriction during ischemia-reperfusion and protects against IR-AKI. We will use the in vitro blood-perfused juxtamedullary nephron technique to assess the impact of IR on S1P-mediated arteriolar response in rats and in S1P2 receptor knockout mice. We will determine the influence of S1P on total and regional renal blood flow and GFR with IR-AKI. We will determine which S1P receptors contribute to enhanced S1P-mediated vasoconstriction. We will measure sphingolipid metabolites in kidney and plasma of IR rats or mice. Our outcomes will provide new mechanistic insights that renal IR activates the S1P signaling pathway in the renal microvasculature. Exogenous S1P causes potent vasoconstriction of afferent arterioles and reduction of renal blood flow and MBF, which will be enhanced in IR-AKI. S1P2 receptor blockade or deletion will protect against IR-AKI. The results of this study will improve our understanding of the pathophysiological mechanisms underlying the persistent reduction of MBF and a steady decline in GFR in IR-AKI. Improving MBF by inhibiting S1P2R signaling may represent a new therapeutic target for treating IR-AKI and preventing progression to CKD, thereby having a major impact in the field.