Protective function of STAT3-mediated astrocyte reactivity in experimental glaucoma: mechanism of action

项目摘要 青光眼是一种疾病，目前的治疗集中在修改一个主要的危险因素，即 降低眼内压，而不是直接针对视网膜中的病理生理机制， 导致神经节细胞死亡。这是因为我们还没有完全理解 疾病的机制。在许多情况下，仅仅降低眼内压是不够的， 患者继续失去视力。识别介导神经节细胞变性的新机制将 有利于开发青光眼的替代治疗方法。 青光眼病理生理学中的一个主要假设是视神经乳头内的星形胶质细胞 在神经节细胞变性中发挥重要作用，尽管尚不清楚这种作用是什么。星形胶质细胞是一种 关键焦点是因为（1）它们聚集在视神经头，早期神经节细胞轴突损伤发生的部位， 以及（2）视神经头中的星形胶质细胞变得高度“反应性”，这是改变其形态的过程， 功能和分子表型，但在中枢神经系统的白色物质还没有很好的理解。 最近，我们使用功能丧失的转基因小鼠模型表明，STAT 3信号转导是一个关键的信号转导通路。 星形胶质细胞反应性的调节剂在脑胶质瘤的视神经乳头内。敲除STAT 3减弱 星形胶质细胞反应性，增加神经节细胞变性和视觉功能丧失。星形胶质细胞反应性 因此，通过某种机制来保护视力，推翻了长期流行的信念，即反应性是 这对疾病是有害的，治疗必须预防它。 基于这一初步观察，我们提出的研究的总体目标是调查机制 星形胶质细胞的反应性影响神经节细胞的存活。这项研究是独特的和新颖的， 研究青光眼中涉及的一种新的机制途径（STAT 3信号通路）。我们的方法 是使用从星形胶质细胞中靶向缺失两个特定基因来产生功能丧失（STAT 3 敲除小鼠）和功能获得性（SOCS 3敲除小鼠; STAT 3的负反馈分子） 小鼠模型，并确定这些如何影响组织学，功能和分子结果的措施 采用两种不同的实验性青光眼模型。在最后一个实验中，我们将使用商业上的 可用的药理学试剂来测试操纵STAT 3途径的治疗潜力， 星形胶质细胞的反应性对有益的结果。我们实现目标的具体目标是测试 以下假设：（1）STAT 3敲除，减弱星形胶质细胞的反应性，增加病理性 青光眼视神经中的过程，特别是与炎症/免疫相关的过程，和（2） 增加STAT 3活化和增强星形胶质细胞反应性将改善组织学和功能 结果。由于青光眼是世界范围内第二大致盲原因， 公共卫生问题。

Project Summary Glaucoma is a disease in which current treatments focus on modifying a major risk factor, that is lowering intraocular pressure, rather than directly targeting the pathophysiological mechanisms in the retina or optic nerve that lead to ganglion cell death. This is because we still do not fully understand the underlying mechanisms of the disease. In many cases, lowering the intraocular pressure alone is not sufficient, and patients continue to lose their vision. Identifying new mechanisms that mediate ganglion cell degeneration will benefit the development of alternative treatments for glaucoma. A leading hypothesis in the pathophysiology of glaucoma is that astrocytes within the optic nerve head play an important role in the ganglion cell degeneration, albeit it is not clear what this role is. Astrocytes are a key focus because (1) they populate the optic nerve head, a site where early ganglion cell axon injury occurs, and (2) astrocytes in the optic nerve head become highly “reactive”, a process that changes their morphology, function and molecular phenotype, but in the white matter of the CNS is not well understood. Using a loss-of-function transgenic mouse model, we recently showed that STAT3 signaling is a critical regulator of astrocyte reactivity within the glaucomatous optic nerve head. Knocking out STAT3 attenuates astrocyte reactivity, increasing ganglion cell degeneration and visual function loss. Astrocyte reactivity therefore functions by some mechanism to preserve vision, upturning the long prevailing belief that reactivity is simply detrimental in disease and that treatments must prevent it. Based on this initial observation, the overall goal of our proposed study is to investigate the mechanism by which astrocyte reactivity affects ganglion cell survival. This study is unique and novel in identifying and investigating a novel mechanistic pathway (the STAT3 signaling pathway) involved in glaucoma. Our method is to use targeted deletion of two specific genes from astrocytes to generate a loss-of-function (STAT3 knockout mice) and gain-of-function (SOCS3 knockout mice; the negative feedback molecule of STAT3) mouse model and determine how these affect histological, functional and molecular outcome measures following two different models of experiment glaucoma. In a final experiment, we will use a commercially available pharmacological agent to test the therapeutic potential of manipulating the STAT3 pathway and astrocyte reactivity towards a beneficial outcome. Our specific aims to accomplish our goal are to test the following hypotheses: (1) that STAT3 knockout, which attenuates astrocyte reactivity, increases pathological processes in the glaucomatous optic nerve, particularly processes related to inflammation/immunity, and (2) that increasing STAT3 activation and enhancing astrocyte reactivity will improve histological and functional outcome. As glaucoma is the second leading cause of blindness worldwide, this proposal will address a major public health concern.