Role of endothelin receptors in glaucomatous optic neuropathy

项目摘要 青光眼是一种视神经病变，其特征是视神经变性，视乳头杯状突起， 以及视网膜神经节细胞的凋亡，最终导致失明。眼内压（IOP）升高 是原发性开角型青光眼（POAG）的一个显著危险因素。正常眼压性青光眼 患者也显示出视神经病变的迹象，即使他们具有“正常”的IOP。POAG和NTG 患者的房水中内皮素-1（ET-1）（一种有效的血管活性肽）升高， 循环分别。越来越多的证据表明ET-1参与了视神经的调节 实验性青光眼模型的损害。例如，连续给予小剂量的ET-1 在灵长类动物中，眼球后区域的视神经损伤会导致视神经病变。 然而，ET-1产生这些有害作用的机制尚不清楚。ET-1作用 主要通过两类G蛋白偶联受体，即ETA和ETB受体，它们是 B 主要分别与钙和一氧化氮信号通路相关。 最近的观察表明啮齿动物中内皮素B受体表达上调 青光眼的IOP升高模型。该提案的主要目标是了解内皮素受体是否 在青光眼的动物模型中发挥神经变性作用。待检验的总体假设是， 大鼠中的IOP升高在视网膜中产生增加的ETB受体表达，这有助于视网膜炎症。 B 神经节细胞死亡以下具体目标将针对解决上述假设：1） 用荧光显微镜测量大鼠IOP时间依赖性升高后视网膜中ETBB受体的表达。 结合免疫组织化学和受体结合研究。2)确定视网膜神经节细胞死亡 在IOP升高后，与野生型大鼠相比，ETB-B缺陷型大鼠的IOP降低。这项工作将在 通过在野生型和ETB-B中IOP升高后计数存活的逆行标记的视网膜神经节细胞， 缺乏的老鼠3)了解视网膜病变中ETBB表达增加的分子机制 通过使用启动子-报告基因和电泳迁移率变动分析来鉴定顺式作用的神经节细胞 RGC-5细胞中组成型和诱导型ETBB表达的元件和反式作用因子 线转录因子AP-1、C/EBP和SMAD 3/4的DNA结合活性也将在本研究中进行研究。 视网膜的眼压升高，并与ETBB的表达增加。 这些研究将提供有价值的信息，ETB受体的表达，在青光眼的视神经 B 神经病变和ETBB受体介导的信号传导，其介导视网膜神经节细胞的凋亡性细胞死亡。 从这项研究中获得的信息可能有助于开发内皮素受体拮抗剂， 青光眼治疗中的神经保护剂。

Project Summary Glaucoma is an optic neuropathy characterized by degeneration of the optic nerve, cupping of the optic disc and apoptosis of retinal ganglion cells, ultimately resulting in blindness. Elevated intraocular pressure (IOP) is a prominent risk factor as seen in primary open angle glaucoma (POAG). Normal tension glaucoma (NTG) patients also show sign of optic neuropathy even though they have "normal" IOPs. Both POAG and NTG patients show elevation of endothelin-1 (ET-1), a potent vasoactive peptide, in their aqueous humor and circulation respectively. Increasing evidence points to an involvement of ET-1 in mediating optic nerve damage in experimental models of glaucoma. For instance, continuous administration of small doses of ET-1 to the retrobulbar region of the optic nerve has been shown to produce optic neuropathy in primates. However, the mechanism by which ET-1 produces these deleterious effects are not understood. ET-1 acts through mainly two classes of G-protein coupled receptors, namely, the ETA and ETB receptors, which are B predominantly linked to the calcium and nitric oxide signaling pathways respectively. Recent observations indicate that there is an upregulation of endothelin B receptor expression in a rodent elevated IOP model of glaucoma. The broad goals of the proposal are to understand if endothelin receptors play a neurodegenerative role in an animal model of glaucoma. The overall hypothesis to be tested is that IOP elevation in rats produces increased ETB receptor expression in the retina which contributes to retinal B ganglion cell death. The following specific aims will be directed to addressing the above hypothesis: 1) Measure ETBB receptor expression in rat retinas following a time-dependent elevation of IOP rats using a combination of immunohistochemical and receptor binding studies. 2) Determine if retinal ganglion cell death following IOP elevation, is attenuated in ETB-B deficient rats, compared to wild type rats. This will be carried out by counting viable retrogradely labeled retinal ganglion cells following IOP elevation in wild type and ETB-B deficient rats. 3) Understand molecular mechanisms contributing to increase in ETBB expression in retinal ganglion cells by using promoter-reporter and electrophoretic mobility shift assays to identify cis-acting elements and trans-acting factors contributing to constitutive and inducible ETBB expression in the RGC-5 cell line. The DNA binding activity of transcription factors AP-1, C/EBP and SMAD 3/4 will also be studied in retinas of rats with elevated IOP and correlated with increased ETBB expression. These studies will provide valuable information on expression of the ETB receptor during glaucomatous optic B neuropathy and ETBB receptor mediated signaling that mediates apoptotic cell death of retinal ganglion cells. The information gained from this study could be useful in developing endothelin receptor antagonists as neuroprotective agents in glaucoma treatment.