Glucocorticoids, ocular hypertension, and glaucoma

描述（由申请人提供）：青光眼是美国和世界范围内视力损害和失明的主要原因。然而，青光眼发生的分子机制尚不清楚。使用抗炎糖皮质激素（GCs）可引起易感个体眼压升高和青光眼。这些“类固醇应答者”发生原发性开角型青光眼（POAG）的风险较高。几乎所有POAG患者都有类固醇反应。GC诱导的高眼压和青光眼在临床上与POAG相似，GC对小梁网（TM）的影响模仿了POAG中发生的许多分子和生化变化。TM是负责调节房水流出（因此IOP）的组织。糖皮质激素受体（GR）的两个主要亚型介导GC的生物反应。GRa是一种配体激活的转录因子，GRb是GC活性的主要负调节因子。我们最近发现，青光眼TM （GTM）细胞与正常TM （NTM）细胞相比，GRb水平非常低，这使得GTM细胞更容易受到GCs的青光眼效应的影响。我们的总体假设是：(a) GR?高表达；在正常TM细胞中导致GC抵抗和低水平GR；在GTM中发现的表达导致青光眼的GC反应性增强和IOP升高，(b) GR？活性和表达受特定剪接蛋白和通过特定进口蛋白转运到细胞核的调控。以下具体目标将解决并验证这一假设：(1)研究剪接蛋白表达和/或活性的改变是否调节GR；青光眼背景下TM的表达；(2)描述GR?的差异转运的作用；和GR ?;(3)评价GC诱导的高眼压是否受GR调节；体外灌注培养前节段及小鼠体内表达。本研究首次探索了选择性剪接和核易位在TM中的作用，将建立两种新的gc性高眼压模型，并为gc性高眼压、类固醇性青光眼和POAG的发病机制提供更好的见解。

DESCRIPTION (provided by applicant): Glaucoma is a leading cause of visual impairment and blindness in the US and worldwide. However, the molecular mechanisms responsible for the development of glaucoma are poorly understood. The use of anti-inflammatory glucocorticoids (GCs) can cause elevated intraocular pressure (IOP) and glaucoma in susceptible individuals. These "steroid responders" are at higher risk for developing primary open-angle glaucoma (POAG). Almost all POAG patients are steroid responders. GC-induced ocular hypertension and glaucoma is clinically similar to POAG, and GC effects on the trabecular meshwork (TM), the tissue responsible for regulating aqueous humor outflow (and therefore IOP), mimic many of the molecular and biochemical changes that occur in POAG. Two major isoforms of the glucocorticoid receptor (GR) mediate GC biological responsiveness. GRa is a ligand activated transcription factor and GRb is a dominant negative regulator of GC activities. We recently found that glaucomatous TM (GTM) cells have very low levels of GRb compared to normal TM (NTM) cells, which makes GTM cells much more susceptible to the glaucomatous effects of GCs. Our overall hypothesis is that: (a) high expression of GR?; in normal TM cells leads to GC resistance, and low levels of GR?; expression, as found in GTM, leads to enhanced GC responsiveness and elevated IOP in glaucoma and (b) GR?; activity and expression are regulated by specific splicesome proteins and by translocation to the nucleus via specific importins. The following specific aims will address and test this hypothesis: (1) to investigate whether altered expression and/or activity of splicesome proteins regulate GR?; expression in the TM in the context of glaucoma, (2) to delineate the role of differential trafficking of GR?; and GR?; in regulating GC sensitivity in the normal and glaucomatous TM, and (3) to evaluate whether GC-induced ocular hypertension is regulated by GR?; expression in ex vivo perfusion cultured anterior segments as well as in vivo in mice. This research explores for the first time the roles of alternative splicing and nuclear translocation in the TM, will develop 2 new models of GC-induced ocular hypertension as well as will provide better insights into the pathogenesis of GC-induced ocular hypertension, steroid glaucoma, and POAG. PUBLIC HEALTH RELEVANCE: Glaucoma is a leading cause of visual impairment and world-wide blindness. The use of anti-inflammatory steroids can cause elevated pressure inside eyes leading to glaucoma in susceptible individuals. This steroid response is found in most glaucoma patients and is an important risk factor in the development of glaucoma. We have discovered a likely mechanism responsible for this steroid responsiveness and are evaluating its role in the development of glaucoma.