Interleukin-6 and Retinal Ganglion Cell Degeneration in Glaucoma

描述(申请人提供)：青光眼是一种年龄相关的疾病，通过视网膜神经节细胞(RGC)及其视神经轴突的退化而失明。到2020年，将有8000万人患有这种疾病，使其成为导致不可逆转失明的主要原因。虽然年龄是主要的危险因素，但高眼压(IOP)仍然是主要的治疗因素。高眼压直接挑战RGC的存活，但也通过影响其他细胞类型的信号间接地挑战RGC的生存。白介素6是一种由胶质细胞释放的炎性细胞因子，我们已经证明它可以在压力下对分离的视网膜节细胞起到神经保护作用(Sappington等人，2006年)。然而，IL-6作为一种潜在的青光眼治疗干预措施的有效性可能取决于年龄、眼压和RGC的生理状态。本提案的目的是确定IL-6对视网膜神经节细胞在体内受到年龄和高眼压挑战的影响和治疗相关性。利用两种青光眼小鼠模型，我们将确定胶质细胞是否是IL-6的主要来源，以及IL-6的产生如何与1)视网膜节细胞对IL-6的接受性和2)视网膜节细胞的功能和存活有关。为了直接确定IL-6途径对RGC存活的影响，我们将对两种模型中IL-6及其受体IL-6R的表达或活性进行调控。我们将利用DBA/2小鼠，这是一种慢性高眼压模型，以及我们开发的使用微珠阻断房水流动和升高眼压的急性模型。在这些模型中，作为年龄和眼压的函数，我们将量化细胞类型特定的IL-6和IL-6R的表达和定位。我们将把这些数据与RGC功能的衰退和退变的进展联系起来。为了评估RGC变性，我们将使用形态计量学技术来量化视网膜中RGC胞体密度的变化以及视神经中轴突口径和密度的变化。为了评估RGC的功能，我们将使用活性摄取示踪剂和离子活度来量化顺行和逆行轴突运输，并使用锰增强磁共振成像。有关IL-6信号和RGC病理的数据将有助于通过功能丧失和获得研究确定在每个模型中操纵IL-6系统的治疗窗口(S)。对于功能丧失的研究，我们将利用市面上可获得的IL-6基因敲除小鼠和针对IL-6中和的抗体治疗。为了获得功能研究，我们将利用商品化的IL-6高表达小鼠，重组IL-6治疗和针对IL-6R激活的抗体治疗。这些目标的完成将使我们深入了解青光眼中IL-6信号的许多关键组成部分：1)IL-6的表达水平和模式：2)IL-6和IL-6-R的细胞类型特异性表达，以及3)IL-6信号如何在疾病进展过程中影响RGC的生存和功能。 公共卫生相关性：青光眼是全球不可逆性失明的主要原因，涉及视网膜神经节细胞(RGC)的死亡，并与高眼压有关。高眼压直接挑战RGC的存活，但也间接地通过影响来自其他细胞的信号来发挥保护作用。我们提出了一系列研究，以检验炎性细胞因子白介素6作为治疗靶点拯救青光眼视网膜节细胞的潜力。

DESCRIPTION (provided by applicant): Glaucoma is an age-related disease that blinds through the degeneration of retinal ganglion cells (RGCs) and their axons in the optic nerve. By 2020, 80 million people will suffer from the disease, making it the leading cause of irreversible blindness. While age is the leading risk factor, elevated intraocular pressure (IOP) remains the primary treatable factor. Elevated IOP challenges RGC survival directly, but also indirectly by affecting signals from other other cell types. Interleukin-6 is an inflammatory cytokine released by glial cells that we have shown can be neuroprotective for isolated RGCs under pressure (Sappington et al., 2006). However, the effectiveness of IL-6 as a potential therapeutic intervention for glaucoma is likely to depend upon age, IOP and the physiological state of the RGC. The purpose of this proposal is to determine the impact and therapeutic relevance of IL-6 for RGCs challenged by age and elevated IOP in vivo. Using two mouse models of glaucoma, we will determine whether glial cells are a primary source of IL-6 and how production of IL-6 relates to 1) receptivity of RGCs to IL-6 and 2) function and survival of RGCs. To determine directly the influence of the IL-6 pathway on RGC survival, we will manipulate expression or activity of IL-6 and its receptor IL-6R in both models. We will utilize the DBA/2 mouse, a chronic model of ocular hypertension, and an acute model we have developed that uses microbeads to occlude aqueous flow and elevate IOP. As a function of age and IOP in these models, we will quantify cell type-specific expression and localization of IL-6 and IL-6R. We will correlate these data with the decline of RGC function and progression of degeneration. For assessment of RGC degeneration, we will use morphometric techniques to quantify changes in RGC soma density in retina and changes in axon caliber and density in the optic nerve. To assess RGC function, we will quantify anterograde and retrograde axonal transport using active-uptake tracers and ionic activity using and manganese-enhanced magnetic resonance imaging. Data regarding IL-6 signaling and RGC pathology will serve to identify a therapeutic window(s) for manipulation of the IL-6 system in each model using loss and gain of function studies. For loss of function studies, we will utilize a commercially-available IL-6 knockout mouse and antibody therapy directed at neutralization of IL-6. For gain of function studies, we will utilize a commercially-available IL-6 overexpression mouse, recombinant IL-6 therapy and antibody therapy directed at activation of IL-6R. Completion of these aims will provide insight into many key components of IL-6 signaling in glaucoma: 1) the levels and pattern of IL-6 expression: 2) cell type-specific expression of IL-6 and IL6-R, and 3) how IL-6 signaling influences RGC survival and function during disease progression. PUBLIC HEALTH RELEVANCE: Glaucoma is the leading cause of irreversible blindness worldwide, involving the death of retinal ganglion cells (RGCs) and an association with elevated IOP. Elevated IOP challenges RGC survival directly, but also indirectly by affecting signals from other cells that could serve a protective role. We propose a series of studies to examine the potential of the inflammatory cytokine interleukin-6 as a therapeutic target to rescue RGCs in glaucoma.