Selenium, Glutathione Peroxidase-1, and Homocysteine-induced Cardiac Remodeling

描述(由申请人提供)：高同型半胱氨酸血症(HHE)是收缩期和舒张期心力衰竭的独立危险因素。我们实验室的数据表明，HHE会导致心肌纤维化和舒张期功能障碍。在快速增长的老年人口中，舒张期功能障碍和HHE更为普遍。因此，了解HHE对心肌影响的机制是至关重要的，这样才有可能设计出适当的预防和治疗策略来对抗心力衰竭的流行。我们的初步数据有力地表明，HHE通过增加心脏成纤维细胞的氧化应激而导致心肌纤维化和舒张期功能障碍。膳食硒是HHE诱导的心肌纤维化的潜在主要调节因子，因为对抗氧化应激的主要细胞防御是需要硒的酶谷胱甘肽过氧化物酶-1(GPX-1)。根据我们的初步观察，同型半胱氨酸降低了培养的心脏成纤维细胞中GPX-1的活性，增加了氧化应激和胶原分泌，而硒可以阻止这些作用。这项拟议的项目将检验这一中心假设，即硒通过改变GPX-1的活性来调节HHE诱导的心肌氧化应激和纤维化。我们将通过三个具体目标来解决这一中心假设。首先，我们将确定GPX-1对HHE诱导的心肌纤维化的调节程度，利用证明GPX-1表达显著减少、正常和增加的雄性和雌性小鼠模型，并用我们特征良好的HHE饮食模型进行治疗。测定血浆和心肌氧化应激标志物、GPX-1和其他参与氧化剂水平调节的酶的表达和活性、心肌胶原蛋白的表达以及心肌细胞、肥大细胞、血管平滑肌细胞和内皮的变化。基于我们的初步数据，我们还将检测p38丝裂原活化蛋白激酶(MAPK)系统的激活情况，该系统是连接HHE诱导的氧化应激与心肌纤维化的主要信号转导途径。其次，我们将确定硒通过改变GPX-1活性来调节HHE诱导的心肌纤维化的程度。在第一个目标中使用的相同的小鼠模型将用将产生HHE的饮食与缺乏或过量的饮食硒结合起来进行治疗。第三，我们将确定硒是否通过改变心脏成纤维细胞中的GPX-1活性来调节同型半胱氨酸的促纤维化作用。我们将从上述不同表达GPX-1的小鼠模型中分离心脏成纤维细胞，然后研究不同水平的同型半胱氨酸和硒暴露后，氧化应激，GPX-1和其他氧化和抗氧化酶的表达和活性，p38MAPK的激活，以及胶原代谢。申请者在HHE诱导的心肌纤维化和功能障碍方面的专业知识，再加上世界著名的HHE、氧化应激和心血管疾病专家Joseph Loscalzo博士和Se和GPX-1生物化学专家Diane Handy博士的实验室的大力支持，使我们能够进行拟议的研究。 研究背景：高同型半胱氨酸水平在普通人群中广泛流行，是美国心力衰竭流行的潜在主要因素。我们的建议检验了一种假设，即饮食中的硒摄入量通过增强心脏的抗氧化保护机制，可能是高同型半胱氨酸水平引起的心力衰竭的强大调节器。这些调查的结果可能导致新的预防和治疗策略，以减轻美国心力衰竭的负担。

DESCRIPTION (provided by applicant): Hyperhomocysteinemia (Hhe) is an independent risk factor for both systolic and diastolic heart failure. Data from our laboratory demonstrate that Hhe leads to myocardial fibrosis and diastolic dysfunction. Diastolic dysfunction and Hhe are more prevalent in the rapidly increasing older population. Hence, it is crucial to understand the mechanisms involved in Hhe's effects on the myocardium, so that it will be possible to devise appropriate preventive and treatment strategies to combat the epidemic of heart failure. Our preliminary data strongly suggest that Hhe acts via increased oxidant stress in cardiac fibroblasts to cause myocardial fibrosis and diastolic dysfunction. Dietary selenium is a potential major modulator of Hhe-induced myocardial fibrosis, since a major cellular defense against oxidant stress is the selenium requiring enzyme glutathione peroxidase- 1 (GPx-1). Based on our preliminary observations, homocysteine decreases GPx-1 activity and increases oxidant stress and collagen secretion in cultured cardiac fibroblasts, and selenium prevents these effects. The proposed project will test the central hypothesis that selenium modulates Hhe-induced myocardial oxidant stress and fibrosis by altering GPx-1 activity. We will address this central hypothesis through three Specific Aims. First, we will determine the extent to which Hhe-induced myocardial fibrosis is modulated by GPx-1, utilizing male and female mouse models that demonstrate markedly reduced, normal and increased expression of GPx-1 and treated with our well characterized dietary model of Hhe. Plasma and myocardial markers of oxidant stress, expression and activity of GPx-1 and other enzymes involved in the regulation of oxidant levels, myocardial collagen expression, as well as changes in cardiomyocytes, mast cells, vascular smooth muscle cells and endothelium will be measured. Based on our preliminary data, we will also examine for activation of the p38 mitogen activated protein kinase (MAPK) system as the main signal transduction pathway linking Hhe-induced oxidant stress to myocardial fibrosis. Second, we will determine the extent to which selenium modulates Hhe-induced myocardial fibrosis via altered GPx-1 activity. The same mouse models utilized in the first aim will be treated with diets that will create Hhe combined with deficient or excess dietary selenium. Third, we will determine if selenium modulates homocysteine's profibrotic effects by altering GPx-1 activity in cardiac fibroblasts. We will isolate cardiac fibroblasts from the mouse models with varying GPx-1 expression described above and will then study oxidant stress, expression and activity of GPx-1 and other pro- and anti-oxidant enzymes, activation of p38MAPK, and collagen metabolism, after exposure to varying levels of homocysteine and selenium. The applicant's expertise with Hhe-induced myocardial fibrosis and dysfunction, coupled with strong support from the laboratories of Dr. Joseph Loscalzo, a world renowned expert on Hhe, oxidant stress and cardiovascular disease, and Dr. Diane Handy, an expert on the biochemistry of selenium and GPx-1, positions us uniquely to conduct the proposed research. RELEVENCE: A high blood homocysteine level is widely prevalent in the general population and is a potential major contributor to the heart failure epidemic in the United States. Our proposal examines the hypothesis that dietary selenium intake, by enhancing anti- oxidant protective mechanisms in the heart, could be a powerful modulator of heart failure induced by high homocysteine levels. The results of these investigations could lead to novel preventive and treatment strategies to reduce the burden of heart failure in the Unites States.