Retinal Oxygenation in Diabetic Retinopathy

糖尿病视网膜病变中的视网膜氧合

• 批准号: 6544442
• 负责人: BRUCE A. BERKOWITZ
• 金额: $ 24.22万
• 依托单位: WAYNE STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2005-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6544442
• 关键词: carbon dioxide; diabetic retinopathy; early diagnosis; enzyme inhibitors; eye disorder diagnosis; fluosol; functional magnetic resonance imaging; genetically modified animals; histopathology; hyperglycemia; hypoxia; laboratory mouse; laboratory rat; nitric oxide synthase; oxygen; oxygen tension; protein kinase C; retina

DESCRIPTION (provided by applicant): Current treatments for diabetic retinopathy are not entirely successful. We reason that therapies could be more rapidly developed and evaluated than is currently possible if a patient's risk of developing retinopathy could be predicted early in the course of the disease. We have developed a unique functional magnetic resonance imaging (fMRI) technique that measures the change in partial pressure of oxygen (deltaPO2) in the vitreous humor while the subject breathes carbogen (95% O2: 5% CO2). Using this acute retinal "stress" test, we have shown that carbogen breathing in rats and mice at 3-4 months of diabetes (before the appearance of retinal lesions) produces a significantly reduced retinal deltaPO2 compared to normals. A subnormal deltaPO2 is consistent with the presence of hypoxia but it cannot yet be unambiguously interpreted as a measure of hypoxia. In addition, in 3 month diabetic rats, aminoguanidine (AMG) treatment prevented the decrease in retinal deltaPO2. AMG is known to prevent retinal lesion formation in diabetic rats and inhibit the activity of both the inducible form of nitric oxide synthase (iNOS) and protein kinase C (PKC) (among other actions). Hypothesis: Subnormal retinal deltaPO2 in experimental diabetes is correlated with retinal hypoxia (Aim 1), and increased iNOS and PKC activity (Aims 2 and 3) but precedes the appearance of histopathology. Specific Aim 1) To compare retinal PO2 and deltaPO2 before, and at 2 wks, and 3 and 9 months of diabetes in rats. fMRI and a carbogen challenge will be used to measure the retinal deltaPO2. To measure PO2, a perfluorocarbon droplet will be injected into the preretinal vitreous over superior or inferior retina and 19F magnetic resonance spectroscopy performed. Specific Aim 2) To compare the retinal deltaPO2 (at 3 months) and histology (at 3 and 15 months) in normal and diabetic rats with and without treatment with a selective iNOS inhibitor (L-NIL (L-N(6)-(1-iminoethyl)lysine)), and in normal, diabetic, and diabetic iNOS knockout mice. Specific Aim 3) To compare the retinal deltaPO2 (at 3 months) and histology (at 3 and 15 months) in normal and diabetic rats with and without treatment with a selective PKC inhibitor (LY333531). In addition, we will compare retinal deltaPO2 in normal mice, transgenic mice that overexpress PKC beta II, diabetic mice, and diabetic PKC beta II-knockout mice. The results of the proposed studies will prove whether or not changes in retinal deltaPO2 correlate with the development of retinal hypoxia or multiple biochemical abnormalities that are associated with diabetic retinopathy but cannot be measured in vivo by existing techniques. The results of these studies could lead to the development of a non-invasive real time method for the early evaluation of diabetic retinopathy and its treatment.

描述（由申请人提供）：目前对糖尿病视网膜病变的治疗并不完全成功。我们认为，如果能够在病程早期预测患者发生视网膜病变的风险，那么治疗方法的开发和评估可能会比目前更快。我们开发了一种独特的功能磁共振成像 (fMRI) 技术，可测量受试者呼吸卡波根 (95% O2: 5% CO2) 时玻璃体液中氧分压 (deltaPO2) 的变化。使用这种急性视网膜“压力”测试，我们发现，与正常人相比，糖尿病 3-4 个月（视网膜病变出现之前）的大鼠和小鼠的卡波金呼吸产生的视网膜 deltaPO2 显着降低。低于正常的 deltaPO2 与缺氧的存在一致，但尚不能明确地将其解释为缺氧的衡量标准。此外，在 3 个月的糖尿病大鼠中，氨基胍 (AMG) 治疗可防止视网膜 deltaPO2 下降。众所周知，AMG 可以预防糖尿病大鼠视网膜病变的形成，并抑制诱导型一氧化氮合酶 (iNOS) 和蛋白激酶 C (PKC) 的活性（以及其他作用）。假设：实验性糖尿病中视网膜 deltaPO2 低于正常与视网膜缺氧（目标 1）以及 iNOS 和 PKC 活性增加（目标 2 和 3）相关，但先于组织病理学的出现。具体目标 1) 比较大鼠患糖尿病前、2 周、3 个月和 9 个月时的视网膜 PO2 和 deltaPO2。 fMRI 和卡波金挑战将用于测量视网膜 deltaPO2。为了测量 PO2，将全氟化碳液滴注射到上视网膜或下视网膜上方的视网膜前玻璃体中，并进行 19F 磁共振波谱分析。具体目标 2) 比较接受和不接受选择性 iNOS 抑制剂 (L-NIL (L-N(6)-(1-) 治疗的正常大鼠和糖尿病大鼠的视网膜 deltaPO2（3 个月时）和组织学（3 个月和 15 个月时）亚氨基乙基）赖氨酸）），以及正常、糖尿病和糖尿病 iNOS 敲除小鼠中。具体目标 3) 比较使用和未使用选择性 PKC 抑制剂 (LY333531) 治疗的正常大鼠和糖尿病大鼠的视网膜 deltaPO2（3 个月时）和组织学（3 个月和 15 个月时）。此外，我们还将比较正常小鼠、过度表达 PKC beta II 的转基因小鼠、糖尿病小鼠和糖尿病 PKC beta II 敲除小鼠的视网膜 deltaPO2。拟议研究的结果将证明视网膜 deltaPO2 的变化是否与视网膜缺氧或与糖尿病视网膜病变相关但无法通过现有技术在体内测量的多种生化异常的发展相关。这些研究的结果可能会导致开发一种非侵入性实时方法，用于糖尿病视网膜病变的早期评估及其治疗。