Endothelin - Mechanisms in Hypertension and Obesity

 描述（由申请人提供）：指导阶段：导师大卫波洛克博士的长期目标是阐明ET-1在盐敏感性高血压中的作用。最近，它表明，皮肤的钙是一个重要的4水库的Na+，并在这种存储能力的缺陷发生在盐敏感性高血压。虽然机制尚未完全了解，但初步数据表明，血管内皮细胞衍生的ET-1在高盐摄入期间在皮肤Na+储存和清除中起作用。因此，指导阶段的中心假设是肾外血管ET-1的增加通过增加皮肤Na+储存和清除来影响血压，以响应高盐摄入。为了验证这一假设， 将使用特异性ET-1敲除小鼠（VEET KO）。第一个具体目标将确定血管ET-1是否介导调节Na+储存和清除的途径，以响应高盐摄入。这些包括皮肤间质Na+浓度、巨噬细胞和淋巴细胞、张力响应增强子结合蛋白、血管内皮生长因子c和淋巴管增生。预计增加盐摄入量将导致这些因素中的每一个增加，并且这将在VEET KO小鼠中消除。先前的研究表明，这些调节途径中的任何一种的丧失都会导致盐敏感性高血压，然而VEET KO小鼠是肥胖的。据认为，这是由于肾血管系统中缺乏ET-1，这会增加肾功能，会隔离作用， 肾外血管ET-1在血压调节中的作用。问题3将通过将具有完整血管ET-1的对照小鼠的肾脏移植到VEET KO小鼠中来解决这个问题，这种操作预计会引起盐敏感性高血压。独立阶段：一些证据表明，增加ET-1介导与肥胖相关的心血管疾病;然而，初步数据和先前对培养的脂肪细胞的研究表明，脂肪细胞上ETA减少和/或ETB受体活化增加产生了导致肥胖的有利环境。因此，独立阶段的总体假设是脂肪细胞中ETA/ETB受体信号传导之间的不平衡产生了导致肥胖的有利环境。第二个具体目标将确定脂肪细胞中ETA的减少和/或ETB受体表达和功能的增加是否会导致肥胖。这将通过对培养的脂肪细胞以及 特异性敲除小鼠脂肪组织中的ETA受体。具体目标2还将确定肥胖症中是否发生ETA降低和/或ETB受体表达和功能增加。这将通过确定ET-1受体表达、结合和信号传导在瘦和肥胖人类受试者的脂肪组织中是否改变来测试。第三个具体目标将确定代谢和饮食因素，如瘦素和“西方”饮食，是否会导致脂肪组织中ET-1信号的不平衡。将在ob/ob和db/db小鼠和长期喂食高脂肪饮食的动物的脂肪组织中测定ET-1产生以及ET-1受体表达和结合。拟议研究的目标无疑将阐明ET-1影响血压和肥胖的机制途径，这是心血管疾病的两个普遍危险因素。

 DESCRIPTION (provided by applicant): Mentored Phase: A long-term goal of the mentor, Dr. David Pollock, is to elucidate the role of ET-1 in salt sensitive hypertension. Recently, it was demonstrated that the interstitium of the skin is an important 4 reservoir for Na+, and defects in this storage capacity occurs in salt sensitive hypertension. While mechanisms are not fully understood, preliminary data suggest that vascular endothelial cell derived ET-1 plays a role in skin Na+ storage and clearance during a high salt intake. Therefore, the central hypothesis of the mentored phase is that increases in extrarenal vascular ET-1 influences blood pressure by increasing skin Na+ storage and clearance in response to high salt intake. To test this hypothesis, a vascular endothelial cell specific ET-1 knockout mouse (VEET KO) will be utilized. The first specific aim will determine if vascular ET-1 mediates pathways that regulate Na+ storage and clearance in response to a high salt intake. These include skin interstitial Na+ concentration, macrophages and lymphocytes, tonicity-responsive enhancer binding protein, vascular endothelial growth factor c, and lymph vessel hyperplasia. It is expected that increasing salt intake will lead to increases in each of these factors, and this will be abolished n VEET KO mice. Previous studies indicate that loss of any of these regulatory pathways results in salt sensitive hypertension, however VEET KO mice are hypotensive. It is believed that this is due to lack of ET-1 in renal vasculature, which would increase renal function will isolate the role of extrarenal vascular ET-1 in blood pressure regulation. Question 3 will address this question through the transplant of kidneys from control mice with intact vascular ET-1 into VEET KO mice, a manipulation that is expected to cause salt sensitive hypertension. Independent Phase: Several lines of evidence suggest that increased ET-1 mediates cardiovascular disease associated with obesity; however, preliminary data and previous studies on cultured adipocytes suggest that reduced ETA and/or increased ETB receptor activation on adipocytes produce a favorable environment that leads to obesity. Accordingly, the overall hypothesis of the independent phase is that an imbalance between ETA/ETB receptor signaling in adipocytes creates a favorable environment that leads to obesity. The second specific aim will determine if reductions in ETA and/or increases in ETB receptor expression and function in adipocytes can lead to obesity. This will be tested through in vitro experiments on cultured adipocytes as well as knocking out ETA receptors specifically in adipose tissue of mice. Specific aim 2 will also determine if reduced ETA and/or increases in ETB receptor expression and function occurs in obesity. This will be tested by determining if ET-1 receptor expression, binding, and signaling is altered in adipose tissue of lean and obese human subjects. The third specific aim will determine if metabolic and dietary factors, such as leptin and "western" diet, cause an imbalance of ET-1 signaling in adipose tissue. ET-1 production, as well as ET-1 receptor expression and binding will be determined in adipose tissue of ob/ob and db/db mice and animals chronically fed a high fat diet. The goals of the proposed studies will undoubtedly shed light on mechanistic pathways by which ET-1 influences blood pressure and obesity, two prevalent risk factors for cardiovascular disease.