S1P Deficiency Prolongs Endothelial Barrier Recovery After Fontan Operation

描述（由申请人提供）：本提案的总体目标是通过研究血管内皮屏障功能来解决Fontan手术后出现的普遍临床问题，即持续性胸腔积液。本建议的基本假设是，单心室生理的儿童在接受Fontan手术后，血管通透性紊乱是继发于体外循环（CPB）的严重炎症效应。因此，确定恢复血管内皮屏障的治疗靶点可能是改善Fontan手术后护理的关键。sphingosin 1-phosphate （S1P）是一种磷脂，可与内皮细胞上的G蛋白偶联受体相互作用，介导内皮屏障功能增强，从而降低血管通透性。S1P在体内调节血管通透性中的关键作用已在动物模型中得到证实。例如，缺乏负责S1P生物合成的两种酶之一鞘氨醇激酶-1的小鼠，在脂多糖（LPS）或PAR-1激活诱导的炎症性损伤下，表现出肺微血管通透性增加和水肿形成水平增加。重要的是，小鼠和狗静脉注射S1P已被证明通过减少肺血管渗漏和肺内分流在急性肺损伤中发挥保护作用。我们对Fontan患者血浆的初步分析显示，术后血浆高密度脂蛋白水平降低，高密度脂蛋白是内皮屏障促进鞘脂的主要载体，鞘脂-1-磷酸（S1P）。基于这些发现，我们假设暴露于CPB后儿童血浆HDL-S1P水平降低，并预测持续胸腔积液和更长的术后恢复时间。此外，我们假设来自持续胸腔积液儿童的血液样本将显示出破坏屏障的倾向或缺乏促进屏障的能力的证据，这两种情况都可以通过外源性给予S1P来克服。为了解决这些相互关联的假设，有两个特定的目的：1)确定血浆中S1P水平是否与Fontan手术后长期术后恢复（即持续胸腔积液）的临床标志物相关；2)确定Fontan手术患者血浆样本诱导的屏障完整性水平，并确定这是否与S1P水平和/或术后胸腔积液的严重程度相关。这些后期的研究还将确定外源性S1P是否可以增加样品的能力，以增强体外屏障，达到术前样品的水平。该应用的目的可能会导致新的基于S1P的策略，用于治疗Fontan患者和其他接受CPB的婴儿和儿童的血管通透性紊乱。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to address a widespread clinical problem occurring after the Fontan operation, persistent pleural effusions, through the investigation of vascular endothelial barrier function. The foundational hypothesis of this proposal is that children with single ventricle physiology who undergo the Fontan operation experience derangements in vascular permeability secondary to the profound inflammatory effects of cardiopulmonary bypass (CPB). Therefore, identifying therapeutic targets that restore vascular endothelial barrier may be critical to improving post-operative care after the Fontan operation. Sphingosine 1-phosphate (S1P) is a phospholipid that interacts with G protein coupled receptors on endothelial cells and mediates enhancement of endothelial barrier function, thus reducing vascular permeability. The critical role of S1P in regulating vascular permeability in vivo has been illustrated in animal models. For example, mice deficient in one of the two enzymes responsible for S1P biosynthesis, sphingosine kinase-1, display increased pulmonary microvessel permeability and greater levels of edema formation in response to an inflammatory insult induced with lipopolysaccharide (LPS) or PAR-1 activation. Importantly, intravenous administration of S1P in mice and dogs has been shown to play a protective role in acute lung injury by reducing pulmonary vascular leakage and intrapulmonary shunting. Our preliminary analysis of plasma from Fontan patients has revealed a reduction in postoperative plasma levels of HDL, the principle carrier of the endothelial barrier- promoting sphingolipid, sphingosine-1-phosphate (S1P). Based on these findings we hypothesize that plasma HDL-S1P levels are lowered in children after exposure to CPB and are predictive of persistent pleural effusions and longer post-operative recovery time. Additionally, we hypothesize that blood samples from children with persistent pleural effusions will display evidence of either propensity to disrupt barrier or a lack of ability to promote barrier either of which can be overcome by exogenous administration of S1P. To address these inter-related hypotheses there are two specific aims: 1) to determine whether plasma levels of S1P correlate with clinical markers of prolonged postoperative recovery (i.e., persistent pleural effusions) after the Fontan operation, and 2) to determine the level of barrier integrity induced by plasma samples from Fontan operation patients and determine if this correlates with S1P levels and/or severity of post-operative pleural effusions. These later studies will also determine whether exogenous administration of S1P can increase the capacity of the samples to enhance barrier in vitro to levels achieved using preoperative samples. The aims of the application may lead to new S1P based strategies for treatment of derangements in vascular permeability in Fontan patients and other infants and children undergoing CPB. PUBLIC HEALTH RELEVANCE: Capillary leakage leading to persistent pleural effusions and multiorgan dysfunction continue to be a significant post-operative problem in children following cardiopulmonary bypass (CPB). Studies to be performed as part of this research program will test the hypothesis that children with persistent pleural effusions have insufficiencies in an HDL-associated lipid, S1P that controls blood vessel barrier maintenance. If plasma levels of S1P are found to be predictive of persistent pleural effusions and prolonged post-operative recovery time after CPB then exogenous administration of S1P may hold promise in improving post-operative recovery after CPB.