Inflammation and Oxidative Stress in Hyperglycemic Exacerbation of Infarct Size

描述(申请人提供)：在糖尿病和非糖尿病患者中，急性高血糖与较大的心肌梗死(MI)范围和左心功能受损独立相关。然而，急性高血糖加重心肌损伤的机制尚不清楚，尤其是在非糖尿病患者中。急性高血糖与氧化应激增加、内皮功能障碍、凝血功能激活和炎症增强有关。我们的初步研究表明，在非糖尿病小鼠缺血前不久诱导的急性高血糖显著增强了再灌注损伤，并取消了缺血预适应和后适应。此外，我们已经证明，在再灌流前立即用一种特定的激动剂激活腺苷2A受体(A2AR)可以消除心肌损伤的高血糖加重，就像用强大的抗氧化剂MPG治疗一样。这些研究表明，非糖尿病患者的急性高血糖通过阻断内源性心脏保护机制、增加氧化应激和激发先天炎症反应来增加MI的大小。越来越多的证据表明，急性高血糖时晚期糖化终末产物(AGEs)的形成通过与AGE受体(RAGE)的相互作用在加重MI大小中发挥核心作用。我们以前的工作表明，CD4+T细胞上的A2ARs在调节炎症反应中发挥着关键作用，而炎症反应对MI大小有重要影响，再灌注前激活A2ARs可以缩小梗塞面积。我们的初步研究表明，A2ARs的激活也可以防止心肌损伤的高血糖加重。因此，我们假设急性高血糖通过RAGE刺激和增加氧化应激增强了CD4+T细胞介导的先天免疫反应，从而加重了梗塞面积。为了在体内验证这一假说，我们将使用急性高血糖的心肌缺血/再灌注损伤的小鼠模型来解决以下特定目标：1)确定氧化应激、AGE/RAGE轴和胰岛素对血糖正常化在心肌梗死(MI)范围的高血糖加重中的机制作用。为了达到这一目的，将在小鼠MI模型中应用特定的药理探针(有效的抗氧化剂、AGE抑制剂、可溶性RAGE和胰岛素)，然后评估它们对心肌梗死面积和再灌注后炎症反应的影响。2)确定携带AGE、A2A和IL-18受体的细胞类型，这些受体在体内介导和调节脑梗塞面积的高血糖加重。这一目标将使用一组基因敲除的小鼠(CD4-零、RAGE-零、A2AR-零和IL18R-零)来测试这一假设，即这些受体中的每一个在调节/调节高血糖对MI大小的有害影响中起着关键作用。3)应用从AIMS 1和2收集的机制见解，确定能够最小化正常血糖/高血糖小鼠心肌梗死大小的临床相关治疗策略，并利用心脏MRI的尖端技术确认这对左室结构和功能具有持久的积极影响。公共卫生相关性：在美国，缺血性心脏病仍然是唯一的主要死亡原因，足足占死亡人数的五分之一。心肌梗死(心脏病发作)和心脏病发作引起的心力衰竭占与缺血性心脏病有关的死亡和疾病的绝大多数。有些人在心脏病发作时会有高血糖(高血糖)，即使他们以前没有高血糖病史。与非高血糖患者相比，这些患者死于心脏病的几率要高得多。这项研究项目将增加我们对为什么高血糖会恶化心脏病发作患者的临床结果的理解，并将确定新药和现有药物的最佳组合，以减少有(或没有)高血糖患者的心脏病发作规模。

DESCRIPTION (provided by applicant): Acute hyperglycemia is independently associated with larger myocardial infarct (MI) size and impaired LV function in both diabetic and non-diabetic patients. However, the mechanisms underlying the exacerbation of myocardial injury by acute hyperglycemia remain unclear, especially in non-diabetics. Acute hyperglycemia is associated with increased oxidative stress, endothelial dysfunction, activation of coagulation and enhanced inflammation. Our preliminary studies show that acute hyperglycemia, induced shortly before ischemia in non- diabetic mice, significantly enhances reperfusion injury and abolishes both ischemic pre- and post-conditioning. Furthermore, we have shown that activation of Adenosine 2A Receptors (A2AR) with a specific agonist immediately before reperfusion abrogates the hyperglycemic exacerbation of myocardial injury, as does treatment with the potent antioxidant MPG. These studies indicate that acute hyperglycemia in non-diabetics increases the size of MI by interrupting endogenous cardioprotective mechanisms, increasing oxidative stress and provoking innate inflammatory responses. Growing evidence now indicates that the formation of advanced glycated end products (AGEs) during acute hyperglycemia plays a central role in exacerbating MI size through their interaction with the AGE receptor (RAGE). Our previous work showed that A2ARs on CD4+ T cells play a critical role in regulating the inflammatory responses that contribute importantly to MI size, and that infarct size is reduced by activating A2ARs prior to reperfusion. Our preliminary studies show that activation of A2ARs also prevents the hyperglycemic exacerbation of myocardial injury. We therefore hypothesize that acute hyperglycemia exacerbates infarct size by enhancing CD4+ T cell-mediated innate immune responses via RAGE stimulation and increasing oxidative stress. To test the hypothesis in vivo, we will use a mouse model of myocardial ischemia/reperfusion injury with acute hyperglycemia to address the following specific aims: 1) Determine the mechanistic roles of oxidative stress, the AGE/RAGE axis and glucose normalization with insulin in the hyperglycemic exacerbation of myocardial infarct (MI) size. This Aim will be pursued by applying specific pharmacologic probes (potent antioxidants, AGE inhibitors, soluble RAGE and insulin) in the murine model of MI, then assessing their impact on infarct size and post-reperfusion inflammatory responses. 2) Determine the identity of the cell types carrying the AGE, A2A and IL-18 receptors that mediate and regulate the hyperglycemic exacerbation of infarct size in vivo. This aim will employ an array of knockout mice (CD4- null, RAGE-null, A2AR-null & IL18R-null) to test the hypothesis that the presence of each of these receptors on CD4+ T cells plays a critical role in mediating/regulating the deleterious effects of hyperglycemia on MI size. 3) Apply the mechanistic insights gleaned from Aims 1 & 2 to identify a clinically-relevant treatment strategy capable of minimizing MI size in euglycemic/hyperglycemic mice and confirm that this has an enduring, positive impact on LV structure and function using cutting-edge techniques in cardiac MRI. PUBLIC HEALTH RELEVANCE: Ischemic heart disease remains the single leading cause of death in the United States, accounting for fully one out of every five deaths. Myocardial infarction (heart attack) and heart failure resulting from heart attack account for the vast majority of the death and illness associated with ischemic heart disease. Some people have high blood sugar (hyperglycemia) when they experience a heart attack, even if they have no prior history of high blood sugar. These patients die from their heart attack much more often than patients without high blood sugar. This research project will increase our understanding of why high blood sugar worsens clinical outcome in patients with heart attack, and will identify the best combination of new and existing drugs to reduce the size of heart attack in patients with (and without) high blood sugar.