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，目前的治疗方法侧重于改变一个主要的危险因素，即 降低眼压，而不是直接针对视网膜或 导致神经节细胞死亡的视神经。这是因为我们仍然没有完全了解潜在的 这种疾病的机制。在许多情况下，仅降低眼压是不够的，而且 患者继续失去他们的视力。识别介导神经节细胞退变的新机制将 有利于青光眼替代疗法的发展。 青光眼病理生理学的一个主要假说是视神经头内的星形胶质细胞 在神经节细胞退行性变中发挥重要作用，尽管目前还不清楚这个作用是什么。星形胶质细胞是一种 关键是因为(1)它们分布在视神经头，这是早期神经节细胞轴突损伤的地方， 和(2)视神经头中的星形胶质细胞变得高度“反应”，这是一个改变其形态的过程， 功能和分子表型，但在白质的中枢神经系统还不是很清楚。 使用功能丧失的转基因小鼠模型，我们最近证明STAT3信号是一个关键的 青光眼视神经头内星形胶质细胞反应性的调节。敲除STAT3可以减弱 星形胶质细胞反应性增加，神经节细胞变性和视功能丧失。星形胶质细胞反应性 因此，通过某种机制来保护视力，颠覆了长期以来流行的观点，即反应性是 在疾病中是有害的，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研究这种机制 星形胶质细胞的反应性影响神经节细胞的存活。这项研究在识别和识别 研究与青光眼有关的一种新的机制途径(STAT3信号通路)。我们的方法 是使用定向缺失星形胶质细胞中的两个特定基因来产生功能丧失(STAT3 基因敲除小鼠)和功能获得(SOCS3基因敲除小鼠；STAT3负反馈分子) 建立小鼠模型，并确定它们如何影响组织学、功能和分子结果测量 遵循两种不同的青光眼实验模型。在最后一个实验中，我们将使用一种商用的 可用于测试操纵STAT3途径的治疗潜力的现有药理学试剂 星形胶质细胞对有益结果的反应性。我们实现目标的具体目标是测试 以下假设：(1)STAT3基因敲除可减弱星形胶质细胞的反应性，增加病理改变 青光眼视神经中的突起，特别是与炎症/免疫有关的突起，以及(2) 增加STAT3的激活和增强星形胶质细胞的反应性将改善组织学和功能 结果。由于青光眼是全球第二大致盲原因，这项建议将解决一个主要的 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.