Control by Oxygen of Lens Metabolism and Cataract Formation

描述：白内障（眼球晶状体混浊）是全球致盲的主要原因，每年花费美国医疗保险计划近50亿美元。核性白内障（晶状体中心混浊）是最常见的老年性白内障。然而，这种疾病的病因尚不清楚。先前的研究表明，人体暴露于增加的氧气是人类核性白内障的一个危险因素。晶状体通常存在于严重缺氧的环境中。我们发现眼睛中氧气水平的变化会影响晶状体基因和蛋白质的表达。我们还发现，玻璃体凝胶结构的丧失是核性白内障的一个重要危险因素，并增加晶状体周围的氧含量。基于这些观察结果，我们认为晶状体暴露于分子氧是年龄相关性核性白内障和晶状体核随着年龄的增长而逐渐混浊的主要原因。我们将在两个具体目标中检验这一假设的预测。首先，我们将确定氧气调节晶状体基因表达的机制，以及氧气水平是否直接导致核性白内障的形成。野生型或表达稳定形式转录因子HIF1alpha的小鼠晶状体将在体内暴露于不同水平的氧气中，然后使用微阵列分析和qPCR来记录基因表达的变化。这将揭示氧气改变晶状体基因表达的分子途径，使晶状体在缺氧环境中存活。我们还将确定减少晶状体周围的氧含量是否可以防止核性白内障的形成。这将通过将6个月大开始发生核性白内障的转基因小鼠维持在较低水平的环境氧气中来实现，这将使晶状体周围的氧气水平降低约50%。如果分子氧导致晶状体氧化损伤，这种处理将延缓晶状体氧化损伤和混浊的形成。通过测量接受视网膜手术的患者眼睛中的氧水平，我们发现玻璃体切除术后晶状体周围的氧升高，而糖尿病视网膜病变患者的氧降低。基于这些数据，我们将验证以下预测：糖尿病患者（玻璃体含氧量较低）玻璃体切除术后白内障的进展速度比非缺血性视网膜病变患者慢。我们还观察到，长期单侧视网膜缺氧的患者在其受影响（缺氧）的眼睛中有较少的核混浊。我们将比较长期单侧视网膜缺血患者双眼核不透明的情况。这项研究将验证我们的预测，即来自视网膜的氧气是“正常的”与年龄相关的晶状体核混浊的原因。

DESCRIPTION: Cataract (opacification of the lens of the eye) is the primary cause of blindness in the world and costs the US Medicare program nearly $5 billion annually. Nuclear cataract (opacification of the center of the lens) is the most common form of age-related cataract. However, the causes of this disease are not well understood. Previous studies showed that exposure of the body to increased oxygen is a risk factor for nuclear cataracts in humans. The lens normally exists in a severely hypoxic environment. We found that changes in oxygen levels in the eye influence lens gene and protein expression. We also found that loss of the gel structure of the vitreous body is an important risk factor for nuclear cataracts and increases oxygen levels around the lens. Based on these and other observations described in this proposal, we propose that exposure of the lens to molecular oxygen is the primary cause of age-related nuclear cataracts and the gradual opacification of the lens nucleus that occurs with age. We will test the predictions of this hypothesis in two specific aims. In the first, we will identify the mechanisms by which oxygen regulates lens gene expression and whether oxygen levels directly contribute to the formation of nuclear cataracts. Mouse lenses that are wild type or that express stable forms of the transcription factor HIF1alpha will be exposed to different levels of oxygen in vivo and then microarray analysis and qPCR will be used to document changes in gene expression. This will reveal the molecular pathways by which oxygen alters lens gene expression, allowing the lens to survive in a hypoxic environment. We will also determine whether reducing the oxygen levels around the lens protects against nuclear cataract formation. This will be done by maintaining genetically modified mice that develop nuclear cataracts beginning at 6 months of age in lower levels of ambient oxygen, which lowers the oxygen levels around the lens by approximately 50%. If molecular oxygen contributes to lens oxidative damage, this treatment will delay the formation of lens oxidative damage and opacification. By measuring oxygen levels in the eyes of patients undergoing retinal surgery we found that oxygen around the lens is elevated after vitrectomy and decreased in patients with diabetic retinopathy. Based on these data, we will test the prediction that, in patients with diabetes (lower oxygen in the vitreous body), post- vitrectomy cataracts will progress more slowly than in patients with non-ischemic retinopathy. We also observed that patients with long-standing, unilateral retinal hypoxia have less nuclear opacity in their affected (hypoxic) eye. We will compare nuclear opacity in both eyes of patients with long-standing, unilateral retinal ischemia. This study will test our prediction that oxygen from the retina is responsible for the "normal," age- related opacification of the lens nucleus.