Mitochondrial Protection Within Chronically Ischemic Myocardium

描述(申请人提供)：心肌组织可以保持存活，尽管血液流量减少的时间较长。被称为“冬眠”的实体是通过实验观察的，对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。在这项提议中，我们将检验解偶联蛋白(UCP)-2的表达是对缺氧具有保护作用的假设，解偶联蛋白-2是线粒体内的一种适应过程，来自冬眠和预适应的心脏组织在第二保护窗口(SWOP)。在AIM#1中，我们假设UCP-2通过减少超氧化物的产生和阻止导致线粒体通透性转换孔形成和细胞色素c丢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和保护之间有重要的关系，因为GDP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的保护程度以及在长期饮食给予吡格列酮的情况下对过氧化体增殖物激活受体(PPAR)的伽马刺激来进一步发展这一概念。我们在这次重新提交的初步数据显示，服用吡格列酮的野生型但不是UCP-2 KO小鼠的心脏UCP-2显著增加，同时来自小鼠心脏的分离线粒体的保护增加。我们的中心问题是，线粒体对反复供需缺血的适应可能抵消作为冬眠心脏线粒体保护性适应的氧化剂损伤，但在高工作状态下导致亚最大能量和功能反应。因此，在AIM#3中，我们将测试大剂量多巴酚丁胺时体内跨壁能量与功能的关系以及UCP-2的体外表达。我们对冬眠猪心脏的初步数据表明，多巴酚丁胺在体外增加UCP-2含量时，磷酸化状态(以磷酸肌酸(PCR)与ATP的比率衡量)成比例地降低。为了建立更直接的关系，我们将测试长期使用吡格列酮刺激PPAR-γ是否会进一步增加UCP-2的线粒体表达，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来测试在猪模型中慢性吡格列酮是否会进一步减少线粒体ATP合成酶，线粒体ATP合成酶是观察到的冬眠组织基础局部血流减少的潜在贡献因素。对医疗保健的潜在影响-线粒体是严重氧化剂损伤的主要来源。它们有可能成为CHF患者的重要治疗靶点。我们建议研究解决线粒体保护的机制，这可能导致新的治疗方法。我们还将研究治疗糖尿病的格列酮的效果，以及它在诱导UCP-2在CHF演变中的潜在作用。公共卫生相关性：冠心病导致的进行性心力衰竭是最常见的死亡原因。血管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，导致衰弱疾病的细胞死亡的进行性过程仍然是流行的比例。这项建议将解决线粒体适应的潜在机制，通过这些机制来防止血流量急剧减少时的细胞凋亡或细胞死亡，但长期限制最大能量产生。我们将重点研究与流向心脏可存活区域的血流量减少相关的心力衰竭猪模型。该提案将测试线粒体产生的能量(通过最先进的核磁共振成像来衡量)是否会在功能持续下降中发挥作用。利用这个模型，我们提出了一类用于糖尿病患者的药物，它与心力衰竭的恶化有关，以类似的方式改变线粒体的能量产生。

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.