Mitochondrial Protection Within Chronically Ischemic Myocardium

描述（由申请人提供）：心肌组织可以保持活力，尽管血流减少的时间较长。被称为“冬眠”的实体是通过实验观察到的，对晚期冠状动脉疾病和缺血性心肌病患者具有重要的临床意义。在这个建议中，我们将测试的假设，解偶联蛋白（UCP）-2，作为一个适应性的过程中的线粒体从冬眠和预处理的心脏组织中的“第二窗口的保护”（SWOP），是保护缺氧。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渗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-再氧化。我们的初步数据表明UCP-2和保护之间的重要关系，因为GDP使UCP-2失活并抑制应激抗性。作为AIM #2的一部分，我们将通过评估基础条件下和吡格列酮长期饮食给药后过氧化物酶体增殖物激活受体（PPAR）γ刺激小鼠心脏中线粒体保护的程度来进一步发展这一概念。我们在此次重新提交中的初步数据显示，野生型小鼠心脏中的UCP-2显著增加，但吡格列酮组UCP-2 KO小鼠心脏中的UCP-2没有显著增加，沿着小鼠心脏分离线粒体的保护作用增加。我们的中心问题是，线粒体适应重复的供应-需求缺血可能会抵消氧化损伤作为一种保护性的线粒体适应冬眠的心脏，但在高工作状态下的次最大能量和功能反应的结果。因此，在AIM#3中，我们将测试在高剂量多巴酚丁胺期间体内透壁能量和功能与UCP-2的离体表达之间的关系。我们从冬眠猪心脏的初步数据表明，磷酸化状态，测量多巴酚丁胺期间的磷酸肌酸（PCr）与ATP的比例减少成比例的增加UCP-2含量离体。为了建立更直接的关系，我们将测试吡格列酮对PPAR-gamma的慢性刺激是否会进一步增加UCP-2的线粒体表达，导致透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来检测线粒体ATP合酶（冬眠组织中观察到的基础区域血流量减少的潜在促成因素）是否会在猪模型中对慢性吡格列酮的反应中进一步减少。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。我们提出了解决线粒体保护机制的研究，这可能会导致新的治疗方法。我们还将研究格列酮（一种治疗糖尿病的药物）的作用及其在UCP-2诱导CHF演变中的潜在作用。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，但在接受这些治疗的大多数患者中，导致衰弱性疾病的细胞死亡的渐进过程仍然是流行病。该提案将解决线粒体适应以防止细胞凋亡或细胞死亡对抗急性血流量减少的潜在机制，但长期限制最大能量产生。我们将重点关注猪心力衰竭模型，该模型与心脏存活区域的血流量减少有关。该提案将测试线粒体产生的能量，如最先进的MRI成像所测量的，是否会在功能的持续降低中发挥作用。使用这个模型，我们提出，糖尿病患者中使用的一类药物与心力衰竭加重有关，以类似的方式改变线粒体能量产生。

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.