Purines and the health of retinal ganglion cells

嘌呤与视网膜神经节细胞的健康

• 批准号: 6929604
• 负责人: CLAIRE H MITCHELL
• 金额: $ 33.91万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6929604
• 关键词: NMDA receptors; adenosine; adenosine triphosphate; biological signal transduction; blindness; cell death; disease /disorder model; enzyme activity; glaucoma; glutamates; intraocular pressure; laboratory rat; laser capture microdissection; membrane permeability; molecular /cellular imaging; neuroprotectants; protein protein interaction; purinergic receptor; purines; receptor expression; retinal ganglion; tissue /cell culture; voltage /patch clamp

DESCRIPTION (provided by applicant): Glaucoma is a major cause of blindness in the world and is characterized by a loss of retinal ganglion cells. The disease is frequently associated with elevated intraocular pressure, but it is unclear how this elevation leads to the death of ganglion cells. The current proposal is based upon the novel hypothesis that elevated intraocular pressure triggers the release of ATP. This released ATP can activate P2X7 ATP receptors on retinal ganglion cells, leading to activation of NMDA receptors and excitotoxic cell death. Alternatively, the released ATP can be converted into adenosine by ecto-enzymes and stimulate the A3 receptor for adenosine and protect ganglion cells. Three approaches will be used to test this hypothesis. First, the neuroprotective capacity of rat A3 receptors will be investigated pharmacologically, as this represents the most straightforward opportunity for treatment. Receptor identity will be confirmed by amplifying mRNA message from fluorescently-labeled retinal ganglion cells isolated using Laser-Capture Microdissection. Secondly, the interaction between P2X7 and NMDA receptor channels will be explored by examining the ability of NMDA antagonists to prevent the cell death caused by P2X7 stimulation. The mechanism underlying this interaction will be examined by measuring the effect of P2X7 stimulation on glutamate efflux, and determining the permeability of the P2X7 channel itself to glutamate. Indirect pathways for interaction will also be explored, investigating whether P2X7 receptor stimulation depolarizes cells sufficiently to open NMDA channels or trigger a vesicular release of glutamate. Finally, the effect of increased pressure on ATP release will be tested using in vitro and in vivo models. The ability of elevated pressure to trigger ATP release from dissociated rat retinal cells will be confirmed, and the effect of changing the magnitude and duration of this pressure will be investigated. The hypothesis will be tested with a rat model of experimental glaucoma by correlating the magnitude and duration of intraocular pressure elevation with levels of ATP and regulating enzymes. Together this research will provide a new explanation for ganglion cell death in glaucoma and suggests several new approaches to prevent this death.

描述（由申请人提供）：青光眼是世界上导致失明的主要原因，其特征是视网膜神经节细胞损失。这种疾病通常与眼内压升高有关，但尚不清楚这种升高如何导致神经节细胞死亡。目前的提议基于眼内压升高会触发 ATP 释放的新假设。这种释放的 ATP 可以激活视网膜神经节细胞上的 P2X7 ATP 受体，导致 NMDA 受体激活和兴奋毒性细胞死亡。或者，释放的 ATP 可以通过胞外酶转化为腺苷，并刺激腺苷的 A3 受体并保护神经节细胞。将使用三种方法来检验这一假设。首先，将从药理学角度研究大鼠 A3 受体的神经保护能力，因为这代表了最直接的治疗机会。通过放大使用激光捕获显微切割分离的荧光标记视网膜神经节细胞的 mRNA 信息来确认受体身份。其次，将通过检查NMDA拮抗剂防止P2X7刺激引起的细胞死亡的能力来探索P2X7和NMDA受体通道之间的相互作用。将通过测量 P2X7 刺激对谷氨酸流出的影响并确定 P2X7 通道本身对谷氨酸的渗透性来检查这种相互作用的机制。还将探索相互作用的间接途径，研究 P2X7 受体刺激是否足以使细胞去极化以打开 NMDA 通道或触发谷氨酸的囊泡释放。最后，将使用体外和体内模型测试增加压力对 ATP 释放的影响。将证实升高的压力触发离解的大鼠视网膜细胞释放 ATP 的能力，并将研究改变该压力的大小和持续时间的影响。该假设将通过实验性青光眼大鼠模型进行检验，将眼压升高的幅度和持续时间与 ATP 和调节酶的水平相关联。这项研究将为青光眼中神经节细胞死亡提供新的解释，并提出几种预防这种死亡的新方法。