Mitochondrial Protection Within Chronically Ischemic Myocardium

描述（由申请人提供）：尽管血流量长期减少，心肌组织仍然可以保持活力。这种实体被称为“冬眠”，是通过实验观察到的，对于患有晚期冠状动脉疾病和缺血性心肌病的患者具有重要的临床意义。在本提案中，我们将测试以下假设：解偶联蛋白 (UCP)-2 的表达作为“第二保护窗口”(SWOP) 中冬眠和预处理心脏组织的线粒体内的适应性过程，可防止缺氧。在 AIM #1 中，我们假设 UCP-2 通过减少超氧化物的产生并阻止导致线粒体通透性转换孔形成和细胞色素 c 损失的途径来保护线粒体免受缺氧复氧。我们的初步数据表明 UCP-2 与保护之间存在重要关系，因为 GDP 会使 UCP-2 失活并抑制应激抵抗。作为 AIM #2 的一部分，我们将通过评估基础条件下小鼠心脏线粒体保护程度以及通过长期饮食给予吡格列酮进行过氧化物酶体增殖物激活受体 (PPAR) γ 刺激来进一步发展这一概念。我们在这次重新提交中的初步数据显示，使用吡格列酮的野生型心脏中的UCP-2显着增加，但UCP-2 KO小鼠的UCP-2没有显着增加，同时对小鼠心脏中分离的线粒体的保护也有所增加。我们的核心问题是，线粒体针对重复供需缺血的适应可能会抵消氧化损伤，作为冬眠心脏中的保护性线粒体适应，但会导致高工作状态下的次最大能量和功能反应。因此，在 AIM #3 中，我们将测试高剂量多巴酚丁胺期间体内跨壁能和功能之间的关系以及 UCP-2 的离体表达。我们从冬眠猪心脏获得的初步数据表明，磷酸化状态（通过多巴酚丁胺期间磷酸肌酸 (PCr) 与 ATP 的比率测量）随离体 UCP-2 含量的增加而成比例降低。为了建立更直接的关系，我们将测试吡格列酮对 PPAR-γ 的慢性刺激是否会进一步增加 UCP-2 的线粒体表达，从而导致跨壁能量和功能的额外减少。最后，作为 AIM #4 的一部分，我们将使用 iTRAC 来测试线粒体 ATP 合酶（观察到的冬眠组织中基础区域血流量减少的潜在影响因素）是否会因猪模型中的慢性吡格列酮而进一步减少。对医疗保健的潜在影响——线粒体是严重氧化损伤的主要来源。它们有可能成为 CHF 患者的重要治疗靶点。我们提出研究解决线粒体保护机制，这可能会带来新的治疗方法。我们还将研究格列酮（一种糖尿病疗法）的作用，及其在 UCP-2 诱导中对 CHF 演变的潜在作用。公共卫生相关性：冠状动脉疾病引起的进行性心力衰竭是最常见的死亡原因。血运重建疗法和抗心动过速装置可用于预防猝死，但在大多数接受这些治疗的患者中，导致衰弱性疾病的细胞死亡进行性过程仍然是流行病。该提案将解决线粒体适应防止细胞凋亡或细胞死亡以防止血流量急剧减少的潜在机制，但长期限制最大能量产生。我们将重点关注猪的心力衰竭模型，该模型与流向心脏存活区域的血流量减少有关。该提案将测试通过最先进的 MRI 成像测量的线粒体能量产生是否会在功能持续下降中发挥作用。利用这个模型，我们提出，在糖尿病患者中使用的一类与心力衰竭恶化相关的药物，会以类似的方式改变线粒体能量的产生。

DESCRIPTION (provided by applicant): Myocardial tissue can remain viable, despite a prolonged period of reduced blood flow. Referred to as "hibernation", the entity is observed experimentally and has important clinical implications for patients with advanced coronary artery disease and ischemic cardiomyopathy. In this proposal, we will test the hypothesis that expression of uncoupling protein (UCP)-2, as an adaptive process within mitochondria from hibernating and preconditioned heart tissue in the "Second Window of Protection" (SWOP), is protective against anoxia. In AIM #1, we hypothesize that UCP-2 protects mitochondria against anoxia-reoxygenation, by reducing superoxide generation and preventing a pathway that leads to mitochondrial permeability transition pore formation and cytochrome c loss. Our preliminary data suggest an important relationship between UCP-2 and protection, because GDP deactivates UCP-2 and inhibits stress-resistance. As part of AIM #2, we will further develop the concept by assessing the degree of mitochondrial protection in mouse hearts under basal conditions and following peroxisome proliferator activated receptor (PPAR) gamma stimulation with chronic dietary administration of pioglitazone. Our preliminary data in this resubmission show a robust increase in UCP-2 from hearts of wild type but not UCP-2 KO mice with pioglitazone, along with an increase in protection from the isolated mitochondria from the mouse hearts. Our central question is that mitochondrial adaptations against repetitive supply-demand ischemia might offset oxidant damage as a protective mitochondrial adaptation in hibernating hearts, but result in a submaximal energetic and functional response at high work states. Therefore, in AIM #3, we will test the relationship between in vivo transmural energy and function during high dose dobutamine and ex vivo expression of UCP-2. Our preliminary data from hibernating pig hearts show that the phosphorylation state, as measured by the phosphocreatine (PCr) to ATP ratio during dobutamine is reduced proportionate to the increased UCP-2 content ex vivo. To establish a more direct relationship, we will then test whether chronic stimulation of PPAR-gamma with pioglitazone will further increase the mitochondrial expression of UCP-2, leading to an additional decrement in transmural energy and function. Finally, as part of AIM #4, we will use iTRAC, to test whether mitochondrial ATP synthase, a potentially contributing factor to the observed reductions in basal regional blood flow in hibernating tissue, will be further reduced in response to chronic pioglitazone in the pig model. Potential Impact on Health Care- Mitochondria are a major source of severe oxidant damage. They have the potential for being an important therapeutic target for patients with CHF. We propose studies that address mechanisms of mitochondrial protection that may lead to novel treatments. We will also examine the effects of glitazones, a therapy for diabetes, and its potential role in UCP-2 induction on the evolution of CHF. PUBLIC HEALTH RELEVANCE: Progressive heart failure from coronary artery disease is the most common cause of death. Revascularization therapies and anti-tachycardia devices are available to prevent sudden death, but among the majority of patients who have received these treatments, the progressive process of cell death that leads to a debilitating disease remains of epidemic proportion. This proposal will address potential mechanisms by which mitochondria adapt to prevent apoptosis or cell death against acute reductions in blood flow, but limit maximal energy production chronically. We will focus on a pig model of heart failure that is associated with a reduction in blood flow to a viable area of the heart. The proposal will test whether the mitochondrial production of energy, as measured by state-of-the-art MRI imaging, will play a role in the sustained reductions in function. Using this model, we propose that a class of drugs used in diabetic patients that has been associated with heart failure exacerbations, alters the mitochondrial energy production in a similar way.