Caveolae and the Aged Myocardium

描述（由申请人提供）： 随着美国人口的老龄化，预计到2035年，老年人（>65岁）将从13-14%增加到25%。如果这一趋势继续下去，未来50年内，超过50%的美国人口和超过20亿的全球人口将“老龄化”。老年人的健康面临着巨大的挑战，因为衰老与无数疾病有关。心血管疾病是美国发病率和死亡率的主要原因，其中>50%的死亡归因于冠状动脉疾病，并且>80%的这些死亡发生在65岁及以上的人中。老年心脏比年轻心脏对缺血性损伤更敏感，对心脏保护策略的反应较低。人们提出了许多理论来解释这种老化缺陷。这些理论要么援引遗传学（即，在有丝分裂后细胞中存在随年龄下降或加速的基因表达的程序性调节），生物化学（即，改变的代谢导致能量利用/产生的不匹配，降低的线粒体功能导致产生毒性物质如自由基和蛋白质修饰以降低功能），分解代谢（即，不能在细胞和细胞器水平再循环细胞物质以及改变的线粒体周转），或生理（即，缺血耐受性下降）组分。虽然缺血耐受性中与年龄相关的缺陷的机制尚不清楚，但它们可能涉及细胞信号传导和线粒体的异常，这些异常是遗传、生化、分解代谢和生理缺陷的综合结果。针对这些机制的治疗有可能挽救老年心肌。 我们的初步研究表明，小窝蛋白是本地化的motoprotea和可以调节线粒体功能/动力学。我们提出了以下假设：1）小窝蛋白的靶向细胞运输到关键的调控接头（即，肌膜和线粒体）是对缺血应激的关键反应; 2）由于膜定位的小窝蛋白的损失，在衰老心肌中小窝蛋白向线粒体的细胞运输被破坏; 3）在衰老动物中通过膜和线粒体靶向在不同细胞区室中恢复小窝蛋白可以提供恢复对心肌缺血耐受性的手段。具体目的1：确定膜定位的小窝蛋白的丧失是否导致小窝蛋白表达/小窝形成的丧失，从而限制小窝蛋白向线粒体的运输，以及老化心肌中小窝蛋白的膜靶向表达是否恢复向线粒体的运输。具体目标2：确定衰老是否导致线粒体定位的小窝蛋白减少以改变线粒体功能（即，活性氧物质的产生和mPTP的调节）和线粒体动力学（即，融合-分裂以调节线粒体周转和线粒体自噬），并且如果靶向线粒体的小窝蛋白表达对于恢复线粒体功能/动力学是必要的和足够的。具体目标3：确定在膜或线粒体中靶向表达小窝蛋白是否是恢复老年心脏缺血耐受的必要和充分条件。 公共卫生相关性： 心血管疾病在老年人口中已达到流行病的程度。目前的建议旨在阐明心脏损伤的分子机制，并利用再表达策略来恢复老年心脏的缺血耐受。我们将评估小窝蛋白在线粒体功能障碍中的作用。如果小窝蛋白通过维持线粒体功能来保持细胞“年轻”，那么小窝蛋白疗法可能是保护衰老心肌的可行方法。拟议的研究将进一步允许解剖负责适应压力的分子和亚细胞事件。了解caveolins如何促进正常心脏功能，以及如何因衰老而失去表达而受到干扰，可以深入了解心肌内源性耐受的机制。本提案中描述的工作重点在于阐明支持使用小窝蛋白作为缺血风险患者的新型治疗靶点的机制，并且与VA患者护理使命相关。）

DESCRIPTION (provided by applicant): With the aging of the United States population, it is estimated that the elderly (>65 years of age) will increase from 13-14% to 25% by 2035. If this trend continues, >50% of the United States population and >2 billion people worldwide will be "aged" in the next 50 years. Aged individuals face formidable challenges to their health, as aging is associated with a myriad of diseases. Cardiovascular disease is the leading cause of morbidity and mortality in the United States with >50% of mortality attributed to coronary artery disease and >80% of these deaths occurring in those age 65 and older. Aged hearts are more sensitive than young hearts to ischemic insults and less responsive to cardiac protective strategies. A number of theories have been proposed to account for this aging deficit. These theories either invoke a genetic (i.e., there is a programmed regulation of gene expression that declines or accelerates with age in post-mitotic cells), a biochemical (i.e., altered metabolism leading to a mismatch of energy utilization/generation, diminished mitochondrial function leading to generation of toxic species such as free radicals and protein modification to reduce function), a catabolic (i.e., an inability to recycle cellular material at the cellular and organelle level and altered mitochondrial turnover), or a physiologic (i.e., declining ischemic tolerance) component. Though the mechanisms that underlie an age-related deficit in ischemic tolerance are not clear, they likely involve abnormalities in cellular signaling and mitochondria that are a combined result of genetic, biochemical, catabolic, and physiologic deficiencies. Therapeutics that target these mechanisms have potential to rescue the aged myocardium. Our preliminary studies show that caveolin is localized to motochondria and can modulate mitochondrial function/dynamics. We propose the following hypotheses: 1) targeted cellular trafficking of caveolin to key regulatory junctions (i.e., sarcolemmal membrane and mitochondria) is a critical response to ischemic stress; 2) cellular trafficking of caveolin to mitochondria is disrupted in the aged myocardium due to loss of membrane-localized caveolin; 3) restoration of caveolin in distinct cellular compartments via membrane and mitochondrial targeting in aged animals may provide a means to restore tolerance to myocardial ischemia. The following specific objectives will be addressed: Specific Objective 1: Determine if loss of membrane-localized caveolin leads to loss of caveolin expression/caveolae formation thus limiting trafficking of caveolin to mitochondria and if membrane- targeted expression of caveolin in aged myocardium restores trafficking to mitochondria. Specific Objective 2: Determine if aging results in reduced mitochondria-localized caveolin to alter mitochondrial function (i.e., reactive oxygen species generation and regulation of mPTP) and mitochondrial dynamics (i.e., fusion-fission to regulate mitochondrial turnover and mitophagy) and if mitochondria-targeted caveolin expression is necessary and sufficient to restore mitochondrial function/dynamics. Specific Objective 3: Determine if targeted expression of caveolin in membrane or mitochondria is necessary and sufficient to restore ischemic tolerance in aged hearts. PUBLIC HEALTH RELEVANCE: Cardiovascular disease is reaching epidemic proportions in the aged population. The current proposal aims to unravel the molecular mechanism of cardiac injury and utilize re-expression strategies to restore ischemic tolerance in the aged heart. We will assess the role of caveolins in mitochondria dysfunction. If caveolin serves to keep the cell "young" by maintaining mitochondrial function then caveolin therapy may be a viable means to protect the aged myocardium. The proposed research would further allow for the dissection of molecular and sub-cellular events that are responsible for adaptation to stress. An understanding of how caveolins contribute to normal heart function and how this is perturbed with loss of expression due to aging can shed critical insights into the mechanisms that are at play in endogenous tolerance of the myocardium. The work described in this proposal focuses on elucidating mechanisms to support the use of caveolin proteins as novel therapeutic targets for patients at risk of ischemia and is of relevance to the VA patient care mission.)