Renal Processing of Albumin

白蛋白的肾脏加工

• 批准号: 7531396
• 负责人: OLIVER SMITHIES
• 金额: $ 19.98万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7531396
• 关键词: Aging; Albumins; Albuminuria; Animals; Basement membrane; Chronic; Clinical Medicine; Computer Simulation; Cyclooxygenase Inhibitors; Data; Diabetes Mellitus; Diffusion; Dose; Epithelial; Equation; Excretory function; Filtration; Foot Process; Gel; Glomerular Capillary; Glomerular Filtration Rate; Hypertension; In Vitro; Individual; Kidney; Lead; Mus; Outcome; Pathogenesis; Peptidyl-Dipeptidase A; Process; Proteins; Protocols documentation; Publishing; Radial; Sodium-Restricted Diet; Source; Testing; Therapeutic Intervention; Transmission Electron Microscopy; Urine; Water; design; feeding; glomerular basement membrane; macromolecule; nanoparticle; novel; podocyte; public health relevance; renal artery; research study; slit diaphragm; urinary

DESCRIPTION (provided by applicant): Increased albumin excretion is an indicator of renal damage in a wide variety of conditions, including hypertension, diabetes and aging. Correctly understanding the pathogenesis of albuminuria is prerequisite for interpreting its significance in different conditions, and for designing appropriate therapies. One current view of how the separates small and large molecules assumes that the major physical barrier to macromolecules is the podocyte slit diaphragm (SD) with the glomerular basement membrane (GBM) acting as a coarse pre-filter. Another view ascribes glomerular selectivity to the presence in the GBM of pores of different sizes. In 2003, I proposed a gel permeation/diffusion hypothesis and computer simulation postulating that the GBM is the predominant source of the size selectivity of the kidney, because there is limited space in the GBM (a concentrated gel) into which macro-molecules can permeate. The glomerular filtration rate (GFR) clearly governs all trans-glomerular water transport, but calculations by me and others indicate that diffusion rather than filtration governs Specific Aim (i) will test the primary assumption of the permeation/diffusion hypothesis by directly determining with transmission electron microscopy whether nanoparticles and nanoparticle-tagged proteins of different sizes reach the concentrations in the GBM predicted by a well proven gel permeation equation. Initial experiments will be in vitro with purified GBM; later experiments will be in animals. To test the diffusion postulate we will evaluate the renal distribution of tagged proteins when the renal artery is temporarily clamped following a protocol comparable to that used by Ryan & Karnovsky (1976). Specific Aim (ii) will test the prediction that albuminuria will develop when GFR is substantially decreased. Our preliminary data show that in normal mice angiotensin converting enzyme and/or cyclooxygenase inhibitors in high dose cause temporary reversible albuminuria, exacerbated by a low salt diet. We will carry out experiments to determine the factors leading to this albuminuria, and whether it can be achieved by a decrease in GFR without damaging the GBM, podocytes or tubules. PUBLIC HEALTH RELEVANCE The occurrence of albumin in the urine of an individual (albuminuria) indicates that something is wrong with the kidney. Understanding what changes in the kidney lead to albuminuria is therefore essential for designing proper treatments. We have recently advanced a novel hypothesis that challenges current views on the causes of albuminuria, and are proposing experiments to test this hypothesis.

描述（由申请方提供）：白蛋白排泄增加是多种疾病（包括高血压、糖尿病和衰老）中肾损伤的指标。正确认识蛋白尿的发病机制是阐明其在不同情况下的意义和设计适当治疗方案的前提。目前关于如何分离小分子和大分子的一种观点认为，大分子的主要物理屏障是足细胞狭缝隔膜（SD），肾小球基底膜（GBM）充当粗预过滤器。另一种观点认为肾小球的选择性是由于GBM中存在不同大小的孔。在2003年，我提出了一个凝胶渗透/扩散假说和计算机模拟假设，GBM是肾脏大小选择性的主要来源，因为在GBM（浓缩凝胶）中大分子可以渗透的空间有限。肾小球滤过率（GFR）明显控制所有的跨肾小球水转运，但我和其他人的计算表明，扩散而不是过滤决定了具体目标（i）将通过直接用透射电子显微镜确定纳米颗粒和纳米颗粒是否是渗透/扩散假说的主要假设来测试渗透/扩散假说。不同大小的标记蛋白质达到了通过充分证明的凝胶渗透方程预测的GBM中的浓度。最初的实验将在体外与纯化的GBM;以后的实验将在动物中进行。为了检验扩散假设，我们将按照与Ryan & Karnovsky（1976）所用方案相当的方案，在暂时夹闭肾动脉时评价标记蛋白质的肾分布。具体目标（ii）将检验当GFR显著降低时将发生白蛋白尿的预测。我们的初步数据表明，在正常小鼠中，高剂量的血管紧张素转换酶和/或环氧合酶抑制剂引起暂时性可逆性蛋白尿，低盐饮食加重。我们将进行实验以确定导致这种蛋白尿的因素，以及是否可以通过降低GFR而不损害GBM，足细胞或小管来实现。公共卫生相关性个体尿中出现白蛋白（白蛋白尿）表明肾脏有问题。因此，了解肾脏的哪些变化导致蛋白尿对于设计适当的治疗方案至关重要。我们最近提出了一个新的假设，挑战目前的看法，白蛋白尿的原因，并提出实验来验证这一假设。