Trace Element Dynamics in the Vertebrate Eye

描述（由申请人提供）：铁是正常生理功能的必需元素。然而，过量会引起广泛的组织损伤，并参与许多眼部病变，包括白内障发生和视网膜变性，如年龄相关性黄斑变性。眼铁代谢的研究多年来一直是本实验室的研究重点。我们最近对铁的生理作用作了新的观察。我们发现铁可以调节眼部组织和神经元的神经递质谷氨酸的合成和分泌。这是基本的临床相关性，因为铁和谷氨酸在神经变性中都是失调的。大量的谷氨酸会对中枢神经系统和视网膜产生兴奋毒性。此外，在视网膜色素上皮细胞（RPE）和晶状体上皮细胞（LEC）中，铁调节转录因子、缺氧诱导因子的活性，从而调节数十种蛋白质的合成。我们的初步数据表明缺氧条件刺激谷氨酸释放，这是另一个非常重要的观察结果，因为缺氧条件发生在中风和视网膜缺血中。此外，随着年龄的增长、白内障的发生和分化，晶状体中铁储存蛋白铁蛋白的结构也发生了深刻的变化。我们将继续探索这些变化如何影响铁蛋白中的铁储存以及这种储存提供的防止铁损伤的保护。不幸的是，由于眼部血液屏障（BOB）与体循环隔绝，人们对眼部铁水平的调节机制知之甚少。该提案的假设是，眼内组织具有独特和独立的系统来调节铁的吸收进入和从眼睛流出。它们的极化位置和眼组织内铁调节的数量允许适当控制眼内铁水平。缺氧、出血和炎症显著影响铁的摄取、储存、利用和外排。由此导致的铁代谢失调在眼部病理中起着关键作用。我们将采用一种创新的综合方法来确定BOB如何调节眼内组织中的铁水平。这两个特定目的利用正常和病理人眼以及正常犬眼和形成bob的细胞的组织培养物，例如RPE和CE。此外，该镜头将用于评估铁处理策略如何适应在正常缺氧环境下的生存。我们将利用最先进的活细胞成像定量荧光显微镜，具有全内反射荧光，用于定量质膜上的事件，并允许在活细胞的四维（4D）中测量这些复杂相互作用的动态过程。本研究的目的是确定眼内铁水平是如何被控制的，以及铁在眼部病理中的具体作用，从而为开发预防和治疗眼部疾病所需的治疗模式提供基础。

DESCRIPTION (provided by applicant): Iron is an essential element for normal physiological functions. However, excess it can cause extensive tissue damage and participates in numerous ocular pathologies including cataractogenesis and retinal degenerations such as age-related macular degeneration. The study of ocular iron metabolism has been a focus of this laboratory for many years. We have made recent novel observations about iron's physiological role. We found that iron regulates synthesis and secretion of the neurotransmitter glutamate by ocular tissues and neurons. This is of fundamental clinical relevance since iron and glutamate are both dysregulated in neurodegeneration. In high quantities, glutamate can be excitotoxic in the central nervous system as well as the retina. Additionally, in retinal pigmented epithelial cells (RPE) and lens epithelial cells (LEC) iron regulates the activity of the transcription factor, hypoxia-inducible factor, which in turn regulates the synthesis of dozens of proteins. Our preliminary data indicate that hypoxic conditions stimulate glutamate release, another critically important observation since hypoxic conditions occur in stroke and retinal ischemia. Furthermore, there are profound changes in the structure of the iron storage protein ferritin in lenses that occur with age, cataractogenesis and differentiation. We will continue to explore how these changes affect iron storage in ferritin and the protection against iron damage such storage provides. Unfortunately, little is known about how iron levels are regulated in the eye which is isolated from the systemic circulation by blood ocular barriers (BOB). The proposal's hypothesis is that intraocular tissues have unique and independent systems for regulating iron uptake into and efflux from the eye across the BOBs. Their polarized location and iron-regulated quantity within ocular tissues allows for proper control of intraocular iron levels. Hypoxia, hemorrhage and inflammation significantly impact iron uptake storage, utilization and efflux. The resulting dysregulation of iron metabolism plays a critical role in ocular pathology. We will use an innovative integrated approach to determine how the BOB's regulate iron levels in intraocular tissues. The two specific aims utilize normal and pathological human eyes as well as normal canine eyes and tissue cultures of cells which form the BOBs, e.g., RPE and CE. Additionally, the lens will be used to assess how iron handling strategies adapt for survival in a normally hypoxic environment. We will utilize a state-of-the-art live-cell imaging quantitative fluorescence microscope with total internal reflection fluorescence for quantifying events at the plasma membrane and allow for measurement of dynamic processes underlying these complex interactions in four dimensions (4D) in living cells. It is the goal of this proposal to determine how intraocular iron levels are controlled and the specific role(s) iron has in ocular pathology in order to provide a basis for development of therapeutic modalities needed for prevention and treatment of ocular disease. PUBLIC HEALTH RELEVANCE: Iron is an essential element needed for normal physiological functions. However, in excess, iron can cause extensive tissue damage and has been shown to participate in numerous ocular pathologies including cataractogenesis and retinal degenerations such as age-related macular degeneration. It is the goal of the work proposed here to determine how intraocular iron levels are controlled and the specific role(s) iron has in ocular pathology in order to provide a basis for the development of therapeutic modalities needed for the prevention and treatment of ocular disease.