Prevention of heart failure and death by sphingolipids: outcomes and mechanisms.

描述(由申请人提供)： 项目摘要/摘要心肌梗死和由此导致的充血性心力衰竭仍然是美国头号死亡原因，对老年退伍军人的影响尤其严重。我们实验室发表的发现和令人信服的初步结果支持我们的中心假设，即鞘氨醇激酶/鞘氨醇1-磷酸(S1P)通路是一种有效的心脏保护介质，可以减少缺血和再灌注引起的急性组织损伤、慢性病理重塑和死亡率。因此，预防心肌梗死的这些后果直接关系到我们所服务的退伍军人和普通公众的健康。在先前的研究中，我们确定药物激活内源性S1P的产生或给予外源性S1P足以减少缺血再灌注损伤小鼠心脏的梗死并增强其收缩能力。我们还开发了一种快速而准确的神经鞘氨酸激酶活性的放射分析方法，并通过药理学和基因打靶的方法确定了这种酶在预适应诱导的心脏保护中的重要作用。在暴露于低氧-复氧的成年小鼠心肌细胞中，我们发现S1P1受体的功能、Akt的激活以及细胞底物与线粒体的相互作用有助于S1P介导的存活效应。目前的建议旨在探索S1P受体激动剂的新功能及其机制，并在动物模型中进行翻译研究。在具体目标1中，我们将研究选择性S1P1受体激动剂SEW 2871在两种心肌梗死模型中的作用。模型1是B型清道夫受体I缺陷、亚型载脂蛋白ER61(SR-BI KO/ApoeR61h/h)小鼠。这些小鼠迅速发展为闭塞性冠状动脉粥样硬化、心肌梗死、心力衰竭和过早死亡。在第二个模型中，我们将研究SEW 2871对结扎小鼠冠状动脉左前降支所致的心功能障碍的疗效。我们还将验证这样的假设，即抑制S1P裂解酶，催化不可逆S1P分解的酶，通过增加细胞内S1P含量而导致心脏保护。在特定目标2中，我们将使用在特定目标1中研究的模型来重点研究慢性S1P1受体激动化的影响。这些研究将包括使用鞘氨醇激酶-1和-2缺失的小鼠，测量下游信号通路，以及确定介导慢性信号的S1P受体亚型。此外，还将研究S1P1受体在慢性激动剂暴露后在心肌细胞核中的定位和信号转导，以及在生理和应激条件下S1P对心肌细胞缝隙连接运输和功能的调节。 公共卫生相关性： 与退伍军人健康相关冠心病是美国死亡的唯一主要原因，占死亡人数的五分之一(1)。每年有数以千计的退伍军人因冠心病引起的心肌梗死(心脏病发作)而住院。心肌梗塞后存活的患者，心脏的主要泵室--左心室受损是很常见的。这种左心功能不全通常会导致充血性心力衰竭，这在很大程度上是由于心脏努力维持其因肌肉丧失而受损的泵血能力。正如最近的一篇社论所指出的那样，心力衰竭住院流行病正在恶化，“我们不知道如何预防，也不知道如何治疗”(2)。据估计，65岁以上的退伍军人中有27%患有心脏病(3)，其中大部分是冠状动脉阻塞导致心肌梗死的结果。我们先前的工作已经表明，激活一种以前在心脏中没有研究过的分子通路(鞘氨醇激酶/鞘氨醇1-磷酸介导的信号转导)可以拯救急性缺氧的心肌。我们现在建议使用完整的动物模型来研究这一途径预防死亡和充血性心力衰竭的能力，这两种疾病都是心肌梗死的短期和长期后果。我们计划使用药物来模拟自然产生的化学物质1-磷酸鞘氨醇的作用，并在类似人类疾病的小鼠模型中研究它们的影响。我们还计划研究这些药物在慢性心肌梗死情况下保护心脏的新的生化机制。拟议实验的相关性在于，在相关动物模型中了解这些过程可能会为患有这种常见疾病的退伍军人和其他患者带来新的治疗方法，这种常见疾病每年在全国退伍军人医院提供超过40万个床日的护理。1.美国心脏协会。心脏病发作和心绞痛统计。Http://www.americanheart.org/presenter.jhtml?identifier=4591(2008).2.Butler J和Kalogeropoulos A.心力衰竭住院流行恶化。J·阿默尔·科尔·科尔。2008；435-437。3.全国退役军人调查，国家退役军人分析统计中心。Http://www1.va.gov/vetdata/docs/survey_final.htm(2001年)。

DESCRIPTION (provided by applicant): Project Summary/Abstract Myocardial infarction and resulting congestive heart failure remain the number one cause of mortality in the United States and affect the aging veteran population particularly. Published findings from our laboratory and compelling preliminary results support our central hypothesis that the sphingosine kinase/sphingosine 1- phosphate (S1P) pathway is a potent mediator of cardioprotection that can reduce acute tissue injury, chronic pathological remodeling, and mortality caused by ischemia and reperfusion. Thus, prevention of these consequences of myocardial infarction have direct bearing on the health of both the veterans we serve and of the general public. In prior studies, we determined that pharmacological activation of endogenous S1P production or administration of exogenous S1P was sufficient to decrease infarction and enhance contractility in mouse hearts subjected to ischemia-reperfusion injury. We also developed a rapid and accurate radioassay for measurement of sphingosine kinase activity and established an essential role for this enzyme in preconditioning-induced cardioprotection using pharmacological and gene targeting approaches. In adult mouse ventricular myocytes exposed to hypoxia-reoxygenation, we showed that S1P1 receptor function, Akt activation, and cell substrates interacting with mitochondria contribute to S1P-mediated prosurvival effects. The current proposal is designed to explore new functions of S1P receptor agonism and their mechanisms, and to perform translational studies in animal models. In Specific Aim 1, we will study effects of the selective S1P1 receptor agonist SEW 2871 in two models of myocardial infarction. Model 1 is the Scavenger Receptor Class B Type I-deficient, hypomorphic apolipoprotein ER61 (SR-BI KO/ApoeR61h/h) mouse. These mice rapidly develop occlusive coronary atherosclerosis, myocardial infarction, heart failure, and premature death in response to high-fat feeding. In the second model, we will study the efficacy of SEW 2871 on ventricular dysfunction caused by ligation of the left anterior descending coronary artery in mice. We shall also test the hypothesis that inhibition of S1P lyase, the enzyme that catalyzes irreversible S1P breakdown, leads to cardioprotection by raising intracellular S1P content. In Specific Aim 2, we shall employ the models studied in Specific Aim 1 to focus on the effects of chronic S1P1 receptor agonism. These studies will include use of sphingosine kinase-1 and -2 null mice, measurements of downstream signaling pathways, and determination of the S1P receptor subtypes that mediate chronic signals. Studies of S1P1 receptor localization and signaling in myocyte nuclear compartments after chronic agonist exposure will also be carried out, as will investigation of the regulation of gap junction trafficking and function by S1P in ventricular myocytes under physiological and stress conditions. PUBLIC HEALTH RELEVANCE: Relevance to Veterans Health Coronary heart disease is the single leading cause of mortality in the United States, accounting for one of every five deaths (1). Thousands of veterans are hospitalized each year with myocardial infarction (heart attack) caused by coronary heart disease. Impairment of the main pumping chamber of the heart, the left ventricle, is common in those who survive infarction. Such left ventricular dysfunction often leads to congestive heart failure which results in substantial part from efforts of the heart to maintain its impaired pumping ability caused by muscle loss. As noted in a recent editorial, there is a worsening heart failure hospitalization epidemic that "We do not know how to prevent and we do not know how to treat" (2). It is estimated that 27% of veterans over the age of 65 suffer from heart disease (3), most of which is the result of coronary artery obstruction that leads to myocardial infarction. Our prior work has shown that activation of a molecular pathway not previously studied in the heart (sphingosine kinase/sphingosine 1-phosphate - mediated signaling) can rescue heart muscle subjected to acute oxygen deprivation. We now propose to use intact animal models to study the ability of this pathway to prevent death and congestive heart failure, which are both short- and long-term consequences of myocardial infarction. We plan to use drugs that mimic the action of the naturally occurring chemical sphingosine 1-phosphate and to study their effects in mouse models that resemble human disease. We also plan to investigate new biochemical mechanisms by which these drugs act to protect the heart in the setting of chronic myocardial infarction. The relevance of the proposed experiments is that an understanding of these processes in pertinent animal models can potentially lead to new therapeutic approaches in veteran and other patients who suffer from this common disorder, which accounts for over 400,000 bed-days of care in VA hospitals annually throughout the nation. 1. American Heart Association. Heart Attack and Angina Statistics. http://www.americanheart.org/presenter.jhtml?identifier=4591(2008). 2. Butler J and Kalogeropoulos A. Worsening heart failure hospitalization epidemic. J Amer Coll Cardiol. 2008; 435-437. 3. National Survey of Veterans, National Center for Veterans Analysis and Statistics. http://www1.va.gov/vetdata/docs/survey_final.htm (2001).