Intraocular pressure regulation via ATP-sensitive potassium channels

描述(申请人提供)：这是一份研究通过三磷酸腺苷敏感钾(KATP)通道调节眼压(IOP)的分子事件的申请。高眼压是青光眼的唯一可治疗的危险因素。不幸的是，涉及流出阻力和眼压控制的关键分子尚不清楚。缺乏这方面的知识限制了针对这些过程的药理学试剂的开发。我们最近发现了一种关键的眼压细胞效应因子，它可能会导致高眼压和青光眼的新的药物治疗。我们发现KATP通道开放剂二氮嗪、尼可地尔和P-1075激活KATP通道可降低人眼前段灌注模型的眼压。药物开放剂对KATP通道的这种激活可被KATP通道封闭剂、格列本脲和甲苯磺丁胺阻断。此外，与单独使用KATP通道开放剂二氮卓和前列腺素类似物拉坦前列素相比，使用KATP通道开放剂二氮嗪和前列腺素类似物拉坦前列素可增加眼压流出能力，这表明这些药物使用不同的机制来降低眼压。到目前为止，还没有关于小梁流出通路中涉及KATP通道的研究。KATP通道的开放和关闭被证明改变了细胞的收缩和通透性，提供了对缺血和缺氧的代谢保护，并增强了细胞对非眼组织的应激适应。所有这些细胞事件都直接或间接地与青光眼的原因有关。我们认为，为了开发治疗高眼压的药物，我们必须首先确定与降低眼压有关的关键内在分子和生理机制。我们的中心假设是KATP通道激活引起的细胞事件导致眼压降低。我们的前提是激活KATP通道导致小梁网松弛，从而增加通透性，改善液体流动，增加流出能力，降低眼压。我们建议描述KATP通道亚单位的结构，确定KATP通道开放剂激活的细胞通路，并确定KATP通道开放与增加流出设施和通过小梁流出途径降低眼压的生理功能。此外，我们还将测定KATP通道开放剂对正常眼和原发性开角型青光眼(POAG)患者眼压的影响。在体内，我们将分析KATP通道开放剂及其对C57BL/6野生型和特异性KATP通道亚单位敲除小鼠眼压的影响。这项建议的完成将提供对KATP通道在小梁流出途径中所起作用的完整的描述性和机械性的了解，并将有助于评估使用KATP通道开放剂作为增加POAG流出设施的治疗方式的可行性。 公共卫生相关性：关于KATP通道的拟议研究将产生关于正常眼和POAG眼用于降低眼压的机制的新信息。对KATP通道亚单位结构的分析和受KATP通道开放剂影响的细胞通路的确定将确定未来治疗可以针对的新目标分子。更重要的是，对KATP通道开放剂的分析可能会导致一类新的治疗高眼压和青光眼的药物。

DESCRIPTION (provided by applicant): This is an application to study the molecular events involved in intraocular pressure (IOP) regulation through adenosine-triphosphate-sensitive potassium (KATP) channels. Elevated IOP is the only treatable risk-factor for glaucoma. Unfortunately, the key molecules involved in outflow resistance and IOP control are unknown. Lack of this knowledge has limited the development of pharmacologic agents that would target these processes. We recently identified a key cellular effector of IOP that may lead to new pharmacologic treatment for ocular hypertension and glaucoma. We have found that activation of KATP channels by KATP channel openers diazoxide, nicorandil, and P-1075 lower IOP in a human anterior segment perfusion model. This activation of KATP channels by the pharmacologic openers can be blocked by KATP channel closers, glyburide, and tolbutamide. In addition, treatment with the KATP channel opener diazoxide and the prostaglandin analogue latanoprost increases outflow facility greater than either agent does individually, suggesting that these agents use distinct mechanisms to lower IOP. To date, no studies involving KATP channels have been performed in the trabecular outflow pathway. The opening and closing of KATP channels have been shown to alter cellular contractility and permeability, provide metabolic protection against ischemia and hypoxia, and enhance cellular adaptation to stress in non-ocular tissues. All of these cellular events have been directly or indirectly linked to the cause of glaucoma. We believe that in order to develop pharmacologic agents for the treatment of elevated IOP, we must first identify key intrinsic molecules and physiological mechanisms involved in lowering IOP. Our central hypothesis is that cellular events resulting from KATP channel activation leads to IOP reduction. It is our premise that KATP channel activation leads to a relaxation of the trabecular meshwork resulting in increased permeability, improved fluid flow, augmented outflow facility, and a decrease in IOP. We propose to characterize KATP channel subunit structure, identify cellular pathways activated by KATP channel openers, and determine the physiological function that couples KATP channel opening to increased outflow facility and a lowering of IOP through the trabecular outflow pathway. In addition, we will determine the effect of KATP channel openers on IOP in normal and primary open-angle glaucoma (POAG) eyes. In vivo, we will analyze KATP channel openers and its effect on IOP in C57BL/6 wild-type and specific KATP channel subunit knockout mice. The completion of this proposal will provide a complete descriptive and mechanistic understanding of the role KATP channels have in the trabecular outflow pathway, and will help in evaluating the feasibility of using KATP channel openers as a treatment modality for increasing outflow facility in POAG. PUBLIC HEALTH RELEVANCE: The proposed studies on KATP channels will yield novel information regarding the mechanisms used to lower IOP in normal and POAG eyes. Analysis of KATP channel subunit structure and determination of cellular pathways affected by KATP channel openers will identify novel target molecules to which future therapies can be directed. More importantly, the analysis of KATP channel openers may result in a new class of drugs for the treatment of ocular hypertension and glaucoma.