Bicarbonate Regulation of Aqueous Flow

碳酸氢盐对水流的调节

• 批准号: 8235350
• 负责人: ALAN D MARMORSTEIN
• 金额: $ 37.88万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8235350
• 关键词: Adenylate Cyclase; Adverse effects; Affect; American; Anions; Aqueous Humor; Bicarbonates; Blindness; Carbonic Anhydrase Inhibitors; Cells; Ciliary Body; Colon; Communication; Data; Drainage procedure; Drug usage; Endothelin; Endothelin-1; Epithelium; Exhibits; Eye; Gene Expression; Gene Proteins; Genes; Glaucoma; Goals; Goblet Cells; Knock-out; Laboratories; Lead; Mediating; Mouse Strains; Mus; Operative Surgical Procedures; Pathway interactions; Patients; Peptides; Permeability; Pharmaceutical Preparations; Phenotype; Physiologic Intraocular Pressure; Physiology; Pigment Epithelium; Play; Production; Protein Secretion; Proteins; Regulation; Resistance; Role; Testing; Therapeutic Intervention; Tissues; Transgenic Mice; United States; Vision; Visual impairment; Work; anterior chamber; aqueous; base; gamma-Aminobutyric Acid; inhibitor/antagonist; mouse model; novel; patch clamp; pressure; prevent; promoter; recombinase; role model; treatment strategy

DESCRIPTION (provided by applicant): Glaucoma is a leading cause of blindness in the United States affecting as many as 2.2 million Americans. All current glaucoma treatment strategies aim to reduce intraocular pressure (IOP). Recently our laboratory characterized a strain of mice with a targeted disruption of the Best2 gene, encoding the protein bestrophin-2 (Best2), an anion channel. In the eye, Best2 is expressed uniquely in the Non-Pigmented Epithelium (NPE) of the ciliary body. Best2-/- mice exhibit a significantly lower IOP than their wild type litermates. Surprisingly a comprehensive study of aqueous dynamics in these mice found that aqueous flow was increased and the reduced IOP observed in Best2-/- mice is due to a significantly diminished outflow resistance. Since Best2 is not expressed in outflow tissues, these effects must arise from direct communication between the inflow and outflow pathways via a pressure independent mechanism. An important goal of this application is to understand the basis of this communication. Bestrophins have a high permeability to bicarbonate, and we have recently shown that Best2 physiologically carries a bicarbonate conductance in colon goblet cells. Although carbonic anhydrase inhibitors have been used to lower IOP for many years, the role of bicarbonate in generating aqueous flow is unclear. Our preliminary data establish that a bicarbonate sensitive soluble adenylate cyclase (sAC), is expressed in NPE cells and that this sAC can regulate outflow. Yet, sAC like Best2 does not appear to be expressed in drainage tissues. Furthermore, endothelin-1 (ET1) levels are elevated in the aqueous humor of Best2-/- mice. ET1 has been shown to alter both inflow and outflow resistance potentially explaining the unusual phenotype of the Best2-/- mouse. Based on these data we propose to test the hypothesis that bicarbonate, carried by Best2 channels, is a central player in the regulation of inflow AND outflow, and that sAC mediates communication of the inflow and outflow pathways by regulating the secretion of soluble messengers such as endothelins into the aqueous humor. This will be tested in 3 specific aims. In aim 1 we determine whether bestrophin 2 serves as a bicarbonate channel in NPE cells. In aim 2, we determine the role of soluble adenylyl cyclase in the regulation of aqueous flow and intraocular pressure. In aim 3 we probe the role of bicarbonate in regulating secretion of bioactive peptides such as endothelin-1 by the ciliary body. At its conclusion this work will provide a comprehensive model of the role of bicarbonate in the physiology of the anterior chamber of the eye and could potentially lead us to new avenues for therapeutic intervention in glaucoma. PUBLIC HEALTH RELEVANCE: All current glaucoma treatments seek to reduce intraocular pressure. Deficency of the anion channel bestrophin 2 in mice results in a diminished intraocular pressure despite increased production of aqueous humor, implying the existence of a pressure independent mechanism for regulation of outflow. Understanding how bestrophin 2 functions in the cilliary epithelium and how bicarbonate regulates aqueous production and drainage will lead us to new therapies to prevent or cure vision loss due to glaucoma.

描述（由申请人提供）：青光眼是美国失明的主要原因，影响多达220万美国人。目前所有的青光眼治疗策略都旨在降低眼内压（IOP）。最近，我们的实验室表征了一种小鼠品系，其具有Best 2基因的靶向破坏，该基因编码蛋白质雌激素-2（Best 2），一种阴离子通道。在眼睛中，Best 2在睫状体的非色素上皮（NPE）中唯一表达。Best 2-/-小鼠表现出比它们的野生型小鼠显著更低的IOP。令人惊讶的是，对这些小鼠的房水动力学的综合研究发现，在Best 2-/-小鼠中观察到的房水流量增加和IOP降低是由于流出阻力显著降低。由于Best 2在流出组织中不表达，因此这些效应一定是由流入和流出途径之间通过压力无关机制的直接连通引起的。此应用程序的一个重要目标是了解此通信的基础。Bestrophins对碳酸氢盐具有高渗透性，我们最近发现Best 2在结肠杯状细胞中生理性地携带碳酸氢盐电导。尽管碳酸酐酶抑制剂已被用于降低IOP多年，但碳酸氢盐在产生水流量中的作用尚不清楚。我们的初步数据确定，碳酸氢盐敏感的可溶性腺苷酸环化酶（sAC），在NPE细胞中表达，这种sAC可以调节流出。然而，sAC如Best 2似乎不在引流组织中表达。此外，Best 2-/-小鼠的房水中内皮素-1（ET 1）水平升高。ET 1已被证明可以改变流入和流出阻力，这可能解释了Best 2-/-小鼠的异常表型。基于这些数据，我们提出测试的假设，碳酸氢盐，携带Best 2通道，是一个中央球员在流入和流出的调节，和sAC介导的流入和流出途径的通信，通过调节分泌的可溶性信使，如内皮素进入房水。这将在3个具体目标中进行测试。在目标1中，我们确定是否bestrophin 2作为NPE细胞中的碳酸氢盐通道。在目标2中，我们确定了可溶性腺苷酸环化酶在调节房水流量和眼内压中的作用。在目的3中，我们探索碳酸氢盐在调节睫状体分泌生物活性肽如内皮素-1中的作用。在其结论，这项工作将提供一个全面的模型，碳酸氢盐的作用，前房的眼睛的生理，并可能导致我们的新途径，治疗干预青光眼。 公共卫生相关性：目前所有青光眼治疗都寻求降低眼内压。小鼠中阴离子通道雌激素样肽2的缺乏导致眼内压降低，尽管增加了房水的产生，这意味着存在压力非依赖性机制来调节流出。了解bestrophin 2如何在纤毛上皮中发挥作用，以及碳酸氢盐如何调节水的产生和排出，将使我们找到预防或治疗青光眼所致视力丧失的新疗法。