eNOS-Dependent Mechanoregulation of Intraocular Pressure

项目摘要 临床试验表明，患有糖尿病的患者持续显著降低眼压 青光眼是一种神经保护性的、减缓或阻止视力丧失的疾病，即使在正常眼压性青光眼患者中也是如此。 虽然青光眼高眼压的病因已知存在于传统的流出途径中， 产生额外流出阻力的细胞机制尚不清楚。然而，看起来 很可能是调节眼压的动态平衡机制，这可能会导致眼睛出现缺陷 高血压类似于调节血压的物质，包括影响血管张力的物质。 一个关键分子是一氧化氮(NO)，这是一种由血管内皮细胞产生的自由基，具有强大的 血管扩张剂和收缩抑制剂。重要的是，内皮细胞产生的NO受剪切力的调节。 在我们的第一个资助期，我们证明了眼压强烈影响内切应力的大小 Schlemm管(SC)，触发SC细胞释放NO。我们还表明，没有松弛的骨小梁 网状电池，以减少流出阻力。因此，剪切诱导的NO释放在动力学中起作用 调节常规流出阻力和眼压的“反馈环”，在某些情况下似乎受到损害 青光眼患者。我们的中心假设是，干细胞释放的NO提供了一个 机械敏感反馈信号，维持眼压稳态，从而起到眼内的作用 以及青光眼流出通路中NO信号的直接治疗性调节 显著降低眼压。在第一个资助期，我们发现更多的“因素”，包括 振荡剪应力和小梁网(TM)硬度，调制作用于SC细胞的剪应力， 并因此影响他们的NO生产。我们还发现了另一个NO靶点(远端血管张力)。 降低总流出阻力的常规管道。 因此，我们扩展了我们对传统流出道中NO信号的研究，以测试 振荡剪应力和TM硬度对NO产量和流出阻力的影响(目标1)。此外，由于 总流出阻力的25%-50%位于SC的下游，其远端血管部分被 NO敏感的平滑肌细胞，我们将确定NO在调节流出阻力中的作用。 AIM中的收集通道和巩膜内静脉血管2.知道NO是不稳定的，需要近距离接触 针对常规流出道中的阻力产生区，目标3旨在开发有针对性的NO-3。 增加邻近组织、SC和/或水平的常规流出的基础疗法 远端血管。这一点至关重要，因为非靶向不向前段投放可能会对眼球运动产生不利影响。 通过增加巩膜上静脉压或放松睫状肌来提高效率，这两者都会增加眼压。我们的 结果将确定NO介导的动态平衡在流出调节中的机制，揭示治疗 青光眼治疗的靶点，并产生调节一氧化氮信号和眼压的新技术。

Project Summary Clinical trials demonstrate that significant, sustained intraocular pressure (IOP) reduction in people with glaucoma is neuroprotective, slowing or halting vision loss, even in patients with normal-tension glaucoma. While the etiology of ocular hypertension in glaucoma is known to reside in the conventional outflow pathway, the cellular mechanisms responsible for generation of extra outflow resistance remain unknown. Yet, it seems likely that the homeostatic mechanisms regulating IOP, which presumably become defective in ocular hypertension, are similar to those involved in regulating blood pressure, including those affecting vascular tone. A key molecule is nitric oxide (NO), a free radical that is produced by vascular endothelia and acts as a potent vasodilator and inhibitor of contractility. Importantly, NO production by endothelia is regulated by shear stress. We demonstrated in our first funding period that IOP strongly influences the magnitude of shear stress within Schlemm's canal (SC), triggering release of NO from SC cells. We also showed that NO relaxes trabecular meshwork cells to decrease outflow resistance. Thus, shear-induced NO release acts within a dynamic “feedback loop” that regulates conventional outflow resistance and IOP and appears compromised in some glaucomatous individuals. Our central hypothesis is that NO released from SC cells provides a mechanosensitive feedback signal that maintains IOP homeostasis, thereby functioning as an intraocular “barostat”; and that directed therapeutic modulation of NO signaling in the glaucomatous outflow pathway significantly lowers IOP. During the first funding period, we discovered that additional "factors", including oscillatory shear stress and trabecular meshwork (TM) stiffness, modulate the shear stress acting on SC cells, and hence influence their NO production. We also identified an additional NO target (distal vascular tone) in the conventional tract that lowers total outflow resistance. As a result, we extend our examination of NO signaling in the conventional outflow tract to test effects of oscillatory shear stress and TM stiffness on NO production and outflow resistance (Aim 1). Moreover, since 25-50% of total outflow resistance resides downstream of SC in distal vessels that are partly surrounded by NO-sensitive smooth muscle cells, we will determine the role of NO in regulating outflow resistance in the collector channels and intrascleral venous vessels in Aim 2. Knowing that NO is labile and needs close access to resistance generating regions in the conventional outflow tract, Aim 3 is designed to develop targeted NO- based therapeutics that increase conventional outflow at the level of the juxtacanalicular tissue, SC and/or distal vessels. This is critical because non-targeted NO delivery to the anterior segment is likely counter- productive by increasing episcleral venous pressure or relaxing ciliary muscle, both of which increase IOP. Our results will define the mechanisms of NO-mediated homeostasis in outflow regulation, uncover therapeutic targets for glaucoma therapy and generate novel technologies to modulate NO signaling and IOP.