ENaC regulation by biliary factors

胆道因素对 ENaC 的调节

基本信息

批准号：
10220962
负责人：
OSSAMA B KASHLAN
金额：
$ 42.86万
依托单位：
UNIVERSITY OF PITTSBURGH AT PITTSBURGH
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-21 至 2024-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10220962
关键词：
Acute Affect Alcoholic Hepatitis Aldosterone Apical Ascites Bile Acids Biliary Bilirubin Binding Binding Sites Blood Blood Volume Body Fluids Body Water Cell model Cells Charge Chemistry Chronic Colon Data Distal Diuretics Drug usage Duct (organ) structure Ductal Epithelial Cell Ductal Epithelium Edema Electrolytes Epithelial Epithelial Cells Excretory function Exhibits Extracellular Fluid Goals Hormonal Hyperbilirubinemia Hypertension Hypokalemia In Vitro Ion Transport Ions Kidney Lead Learning Liddle syndrome Liquid substance Liver Liver Failure Liver diseases Measurement Measures Mediating Membrane Mineralocorticoids Modeling Molecular Mus Mutation Nephrons Patients Peripheral Plasma Portal Hypertension Potassium Potassium Channel Regulation Renal tubule structure Renin-Angiotensin-Aldosterone System Reporting Role Sampling Serum Side Site Site-Directed Mutagenesis Sodium Spironolactone Taurocholic Acid Testing Tubular formation Urine Vasodilation Weight Xenopus oocyte biophysical properties chemical property chronic liver disease driving force epithelial Na+ channel experience experimental study extracellular gain of function in vivo mutant novel therapeutics prevent response urinary

项目摘要

Patients with advanced liver disease often experience fluid retention and electrolyte disturbances due in part to activation of the renin-angiotensin-aldosterone system. Aldosterone activates the epithelial Na+ channel (ENaC) in the distal nephron, enhancing urinary Na+ retention and K+ excretion. But many liver disease patients experience fluid retention without apparent activation of the renin-angiotensin-aldosterone system. Liver disease patients also frequently exhibit elevated plasma bile acids and hyperbilirubinemia. Preliminary data show that specific bile acids and conjugated bilirubin activate ENaC in vitro and that taurocholic acid activates ENaC in isolated collecting ducts. The central hypothesis of our proposal is that urinary bile acids and possibly conjugated bilirubin directly activate ENaC, promoting Na+ and fluid retention and K+ excretion. The goal of this proposal is to determine whether this regulation occurs in vivo and to determine the molecular mechanism of regulation. Preliminary data suggest that urine from patients with alcoholic hepatitis contains concentrations of activating bile acids and conjugated bilirubin sufficient to activate the channel, and indeed activate the channel. We will determine whether urine from alcoholic hepatitis patients activates ENaC in experimental cells. We further hypothesize that elevated biliary factors activate ENaC in the distal nephron, promoting Na+ retention and K+ excretion. We will test this hypothesis in isolated collecting ducts. We will also test this hypothesis in vivo by chronically administering biliary factors and quantifying changes in weight, blood K+, urinary Na+ and K+, plasma aldosterone, and total body water. Preliminary data suggest that taurocholic acid promotes Na+ retention, K+ loss, and volume expansion. We will determine the contribution of ENaC to observed changes by using drugs to block ENaC, and by using genetic changes to increase the channel's sensitivity to biliary factors or to decrease ENaC's contribution to renal Na+ and K+ handling. Experiments will also investigate the molecular mechanism of ENaC regulation by bile acids. We hypothesize that activating bile acids interact directly with the channel to enhance channel activity. We will use derivatized bile acids to detect direct binding, and key chemical and biophysical properties of the both the channel and bile acids to dissect the interaction. Key experiments will be performed in multiple cell models, including Xenopus oocytes, cultured epithelial cells, and mouse collecting ducts. Direct ENaC activation by biliary factors elevated in liver disease has not been previously investigated, and may contribute to the volume overload, edema, and electrolyte imbalances associated with liver disease.

患有晚期肝病的患者经常经历液体保留和电解质障碍部分原因是肾素 - 血管紧张素 - 醛固酮系统的激活。醛固酮激活远端肾单位中的上皮Na+通道（ENAC），增强了Na+保留和K+ 排泄。但是许多肝病患者在没有明显激活的情况下经历了液体保留率肾素 - 血管紧张素 - 醛固酮系统。肝病患者也经常表现血浆胆酸和高胆红素血症升高。初步数据表明特定的胆汁酸并共轭胆红素在体外激活ENAC，并且牛胆酸激活ENAC中的ENAC 孤立的收集管道。我们提议的中心假设是尿胆酸和可能共轭胆红素直接激活ENAC，促进Na+和流体保留和K+ 排泄。该提案的目的是确定该法规是否发生在体内和确定调节的分子机制。初步数据表明尿液酒精性肝炎的患者含有激活胆汁酸的浓度和共轭胆红素足以激活通道并确实激活了通道。我们将确定酒精性肝炎患者的尿液是否在实验细胞中激活ENAC。我们进一步假设升高的胆道因子激活远端肾单位的ENAC，促进Na+ 保留和K+排泄。我们将在孤立的收集管道中检验这一假设。我们也会通过长期施用胆道因素并量化变化，在体内检验该假设重量，血液K+，尿Na+和K+，血浆醛固酮和全身水。初步数据表明牛胆酸促进Na+保留，K+损耗和体积膨胀。我们将通过使用药物阻止ENAC和通过使用遗传变化来增加通道对胆道因素的敏感性或减少ENAC的敏感性对肾脏NA+和K+处理的贡献。实验还将研究分子胆汁酸调节ENAC的机理。我们假设激活胆汁酸相互作用直接使用通道增强通道活动。我们将使用衍生化的胆汁酸检测直接结合以及通道和胆汁酸的关键化学和生物物理特性剖析相互作用。关键实验将在多个单元模型中进行，包括爪蟾卵母细胞，培养的上皮细胞和小鼠收集管道。直接ENAC激活先前尚未研究肝病升高的胆道因素，并可能有助于与肝病相关的体积过载，水肿和电解质失衡。