Vasomotor Dysfunction of Retinal Arterioles in Diabetes

描述(申请人提供)：视网膜病变是糖尿病的主要并发症，也是美国成年人失明的主要原因。高血糖与早期糖尿病患者视网膜血流量减少有关，提示小动脉功能障碍可能导致视网膜损伤。有趣的是，视网膜血流的非侵入性成像被认为提供了一扇了解心脏健康的“窗口”。虽然糖尿病可以损害冠状动脉血流并促进心肌病，但导致冠状动脉和视网膜小动脉功能障碍的潜在机制可能是不同的，这些机制尚不清楚。此外，还缺乏与人类微循环相关的糖尿病动物模型，用于视网膜和心脏小动脉血管运动功能障碍的机制研究。为了解决这些临床上的重要问题，我们在猪链佐菌素诱导的1型糖尿病动物模型上进行了研究，我们已经证明，这种动物模型在视网膜血管运动调节/调节失调方面与人类相似。我们的初步数据显示，在糖尿病的2周内，内皮依赖的一氧化氮(NO)介导的视网膜和冠状小动脉的扩张明显受损。内皮功能障碍与氧化应激和Rho激酶(ROCK)表达增强有关，在冠状小动脉中可以预防和恢复，但只有在视网膜小动脉中才能通过抗氧化剂和精氨酸酶阻断来预防。在短期糖尿病中，导致血管舒缩功能障碍的信号事件似乎是不同的。急性(3小时)和长期(2-12周)高血糖状态下血管扩张功能障碍的机制差异提示，对精氨酸酶II和SIRT1这两种无生物利用度的调节酶的时间控制可能介导了视网膜小动脉的这种病理生理过程，而c-Jun氨基末端激酶(JNK)和精氨酸酶I的持续激活有助于冠状动脉功能障碍。然而，与氧化应激和精氨酸酶相关的特定ROCK异构体激活的确切作用和信号序列尚未确定。在这里，我们将测试 假设早期糖尿病激活内皮岩依赖的JNK相互作用蛋白-1(JIP1)/JNK信号，从而增强视网膜小动脉下游的NAD(P)H氧化酶和p38依赖的蛋白酶体活性，以及冠状动脉小动脉的黄嘌呤氧化酶活性。氧化应激导致精氨酸酶II和SIRT1的暂时控制，从而减少了NO介导的视网膜小动脉的扩张，而精氨酸酶I的持续升高维持了冠状动脉功能障碍。我们将追求三个具体目标：(1)确定JIP1的ROCK依赖的磷酸化增强是否通过增加氧化应激而导致糖尿病引起的视网膜和冠状动脉功能障碍。(2)确定JNK依赖的氧化酶信号增强是否参与糖尿病所致的视网膜和冠状小动脉功能障碍。(3)确定增强的精氨酸酶活性和p38诱导的蛋白酶体激活是否有助于糖尿病引起的视网膜和冠状动脉功能障碍的时间控制。结果将确定糖尿病早期视网膜和冠状小动脉功能障碍的新靶点。

DESCRIPTION (provided by applicant): Retinopathy is a major complication of diabetes mellitus and a leading cause of blindness in American adults. Hyperglycemia is associated with reduced retinal blood flow in early diabetes, suggesting that dysfunction of arterioles may contribute to retinal damage. Interestingly, noninvasive imaging of retinal blood flow is being regarded as providing a "window" into the health of the heart. Although diabetes can impair coronary blood flow and promote cardiomyopathy, it is possible that underlying mechanisms, which remain unclear, contributing to coronary and retinal arteriolar dysfunction are different. Also, development of a diabetes animal model relevant to human microcirculation for mechanistic study of vasomotor dysfunction of arterioles from the retina and heart is lacking. To address these clinically important issues, we developed streptozocin-induced type 1 diabetes in the pig, an animal model that we have shown resembles human in retinal vasomotor regulation/dysregulation. Our preliminary data show that within 2 wk of diabetes, endothelium-dependent nitric oxide (NO)-mediated dilation of retinal and coronary arterioles is specifically impaired. Endothelial dysfunction correlates with oxidative stress and enhanced Rho kinase (ROCK) expression, and can be prevented and restored in coronary arterioles but only prevented in retinal arterioles by antioxidants and arginase blockade. It appears that signaling events leading to their vasomotor dysfunction in short-term diabetes are different. Mechanistic differences in vasodilator dysfunction under acute (3 hr) vs. prolonged (2 to 12 wk) hyperglycemia suggest that temporal control of arginase II and SIRT1, two regulatory enzymes for NO bioavailability, may mediate this pathophysiology in retinal arterioles, whereas continuous activation of c-Jun N-terminal kinase (JNK) and arginase I contributes to coronary dysfunction. However, the exact role and signaling sequence for specific ROCK isoform activation linking to oxidative stress and arginase have not been defined. Herein, we will test the hypothesis that early diabetes activates endothelial ROCK-dependent JNK-interacting protein-1 (JIP1)/JNK signaling, which enhances downstream NAD(P)H oxidase and p38-dependent proteasome activities in retinal arterioles and xanthine oxidase activity in coronary arterioles. Oxidative stress leads to temporal control of arginase II and SIRT1 with subsequent reduction of NO-mediated dilation in retinal arterioles, whereas prolonged elevation of arginase I sustains coronary dysfunction. We will pursue 3 specific aims: (1) Determine whether enhanced ROCK-dependent phosphorylation of JIP1 contributes to diabetes-induced dysfunction of retinal and coronary arterioles by increasing oxidative stress. (2) Determine whether enhanced JNK-dependent oxidase signaling contributes to diabetes-induced dysfunction of retinal and coronary arterioles. (3) Determine whether enhanced arginase activity and p38-induced activation of proteasomes contribute to temporal control of diabetes-induced dysfunction of retinal and coronary arterioles. Outcomes will identify novel targets involved in retinal and coronary arteriolar dysfunction during early diabetes.