Bicarbonate Regulation of Aqueous Flow

碳酸氢盐对水流的调节

• 批准号: 8449088
• 负责人: ALAN D MARMORSTEIN
• 金额: $ 5.3万
• 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 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8449088
• 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

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.

青光眼是美国失明的主要原因，影响多达220万 美国人。当前的所有青光眼治疗策略旨在降低眼内压（IOP）。 最近，我们的实验室表征了一小鼠的菌株，其靶向破坏最佳2基因，即 编码蛋白质bestrophin-2（Best2），一个阴离子通道。在眼中，最好的2在 纤毛体的非色素上皮（NPE）。最好的2 - / - 鼠标表现出明显较低的IOP 比他们的野生型litermates。令人惊讶的是，对这些小鼠水性动力学的全面研究 发现水流增加，并且在Best2 - / - 小鼠中观察到的IOP降低是由于A 显着降低了流出阻力。由于Best2在流出组织中未表达，因此 效果必须是由于流入和流出路径之间的直接通信而产生的 独立机制。该应用程序的一个重要目标是了解这一点的基础 沟通。 Bestrophins对碳酸氢盐具有很高的渗透性，我们最近表明 Best2在生理上携带结肠杯状细胞中的碳酸氢盐电导。虽然碳 多年来，已使用赤道酶抑制剂来降低IOP，这是碳酸氢盐的作用 水流尚不清楚。我们的初步数据表明，碳酸氢盐敏感可溶性腺酸 环酶（SAC）在NPE细胞中表达，该囊可以调节流出。但是，SAC喜欢Best2 似乎没有在排水组织中表达。此外，内皮素-1（ET1）水平是 在Best 2 - / - 小鼠的水性幽默中抬高。 ET1已被证明会改变流入和流出 电阻可能解释了最好的2 - / - 小鼠的异常表型。根据这些数据，我们 建议检验以最佳2频道携带的碳酸氢盐是中心参与者的假设 流入和流出的调节，SAC调节流入和流出的通信 通过调节内皮素等可溶性使者的分泌到水性 幽默。这将在3个特定目标中进行测试。在AIM 1中，我们确定Bestrophin 2是否充当 NPE细胞中的碳酸氢盐通道。在AIM 2中，我们确定可溶性腺苷酸环化酶在 调节水流和眼内压。在AIM 3中，我们探测碳酸氢盐在 调节睫状体的生物活性肽（例如内皮素-1）的分泌。总结这一点 工作将为碳酸氢盐在前室生理学中的作用提供全面的模型 眼室，有可能导致我们进入治疗干预的新途径 青光眼。