The retinal microenvironment in diabetic retinopathy

描述（由申请人提供）：糖尿病视网膜病变是成人视网膜疾病最常见的原因之一。许多分子和组织学的变化已被证明，它是现在认识到，神经以及血管的问题存在。血管功能障碍的最重要因素是血管内皮生长因子（VEGF）的升高，其导致血管渗漏和血管生成。不幸的是，我们仍然不知道VEGF增加的原因。缺氧和酸中毒都是已知的VEGF调节因子，但糖尿病患者视网膜氧和pH变化的幅度和时间过程尚不清楚。关于这些参数的更多信息将有助于更好地了解疾病进展，并最终可能导致对VEGF导致损伤之前可以靶向的途径的理解。我们将在链脲佐菌素（STZ）诱导的糖尿病大鼠和无糖尿病的酸中毒大鼠中进行PO2和pH的视网膜内记录。为了将这些变化置于其他事件的背景下，我们还将测量重要的血管参数（血流、泄漏、分子信号）。具体目标1：糖尿病视网膜病变中的氧。视网膜组织缺氧与视网膜病变的背景期和增殖期发现的VEGF增加有关。有相当多的间接支持缺氧的存在，糖尿病视网膜病变，但非常有限的直接证据。我们将在患有糖尿病长达1年的大鼠中表征视网膜内氧合。我们的假设是，视网膜内的PO2将在这段时间内减少。我们还将研究糖尿病患者视网膜氧调节的变化。我们的假设是，PO2调节的变化将是微环境变化的更敏感的指标，并且比基线PO2的变化更早发生。我们在早期的一项研究中发现糖尿病12周时视网膜中的PO2增加。我们的假设是，这是由于血流量增加，我们现在将调查。具体目标2：糖尿病视网膜病变中的酸中毒。在某些组织中，VEGF受酸中毒的调节，但在成人视网膜中pH在控制VEGF中的作用尚不清楚。我们将描述糖尿病长达1年的大鼠的视网膜pH值。我们的假设是，至少在几个月内，内层视网膜的酸性会比正常情况下更强。我们还假设，分子机制发挥作用，以减少酸中毒，如增加碳酸酐酶和酸清除机制。这些将通过mRNA和蛋白质测量进行评价。特定目的3：视网膜酸中毒是否足以上调VEGF？发现糖尿病视网膜酸中毒将打开它是调节VEGF的因素之一的可能性，但不会告诉我们它是否重要。因此，在没有糖尿病的情况下，我们将通过碳酸酐酶抑制产生酸中毒。我们将首先建立一个治疗方案，产生类似于糖尿病的视网膜内pH值，然后评估VEGF和渗漏的变化。我们的假设是，酸中毒本身就足以增加VEGF，产生渗漏的分子变化，并导致渗漏本身。

DESCRIPTION (provided by applicant): Diabetic retinopathy is one of the most common causes of retinal disease in adults. Many molecular and histological changes have been demonstrated, and it is now recognized that neural as well as vascular problems exist. The most important contributor to vascular dysfunction is the elevation of vascular endothelial growth factor (VEGF), which causes vascular leakage and angiogenesis. Unfortunately, we still do not know what underlies the increase in VEGF. Hypoxia and acidosis are both known regulators of VEGF, but the magnitude and time course of changes in retinal oxygen and pH are not known in diabetes. More information about these parameters will allow a better understanding of disease progression, and ultimately may lead to an understanding of pathways that can be targeted before VEGF causes damage. We will make intraretinal recordings of PO2 and pH in rats with streptozotocin (STZ)-induced diabetes, and in rats with acidosis in the absence of diabetes. To place these changes in the context of other events, we will also measure important vascular parameters (blood flow, leakage, molecular signals). SPECIFIC AIM 1: Oxygen in diabetic retinopathy. Retinal tissue hypoxia has been implicated in the increased VEGF that is found in both the background and proliferative phases of retinopathy. There is considerable indirect support for the existence of hypoxia in diabetic retinopathy, but very limited direct evidence. We will characterize intraretinal oxygenation in rats with up to 1 year of diabetes. Our hypothesis is that inner retinal PO2 will decrease over this time. We will also investigate changes in the regulation of retinal oxygen in diabetics. Our hypothesis is that changes in regulation of PO2 will be a more sensitive indicator of changes in the microenvironment and occur earlier than changes in baseline PO2. We found increased PO2 in the retina in an earlier study at 12 weeks of diabetes. Our hypothesis is that this was due to increased blood flow, which we will now investigate. SPECIFIC AIM 2: Acidosis in diabetic retinopathy. VEGF is regulated by acidosis in some tissues but the role of pH in controlling VEGF in the adult retina is unknown. We will characterize retinal pH in rats with up to 1 year of diabetes. Our hypothesis is that the inner retina will be more acidic than normal for at least a few months. We also hypothesize that molecular mechanisms come into play to reduce acidosis, such as increased carbonic anhydrase and acid removal mechanisms. These will be evaluated with mRNA and protein measurements. SPECIFIC AIM 3: Is retinal acidosis sufficient to upregulate VEGF? Finding that the diabetic retina is acidotic will open the possibility that it is one of the factors that regulates VEGF, but will not tell us whether it is important. Consequently, we will produce acidosis in the absence of diabetes, via carbonic anhydrase inhibition. We will first establish a treatment protocol that yields intraretinal pH values similar to diabetes, and then evaluate changes in VEGF and leakage. Our hypothesis is that acidosis alone will be sufficient to increase VEGF, produce molecular changes that underlie leakage, and cause leakage itself.