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he导致心肌纤维化和舒张功能障碍。舒张功能不全和he在快速增长的老年人群中更为普遍。因此，了解he对心肌的影响机制是至关重要的，这样就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。我们的初步数据强烈表明he通过增加心脏成纤维细胞的氧化应激导致心肌纤维化和舒张功能障碍。膳食硒是he诱导心肌纤维化的潜在主要调节剂，因为细胞对氧化应激的主要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，在培养的心脏成纤维细胞中，同型半胱氨酸降低GPx-1活性，增加氧化应激和胶原分泌，而硒可以阻止这些作用。该项目将测试硒通过改变GPx-1活性来调节he诱导的心肌氧化应激和纤维化的中心假设。我们将通过三个具体目标来解决这个中心假设。首先，我们将确定GPx-1在多大程度上调节he诱导的心肌纤维化，利用雄性和雌性小鼠模型，这些模型显示GPx-1的表达明显降低、正常和增加，并使用我们的具有良好特征的he饮食模型。测定血浆和心肌氧化应激标志物、GPx-1等参与氧化水平调控的酶的表达和活性、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细胞的变化。基于我们的初步数据，我们还将研究p38丝裂原活化蛋白激酶（MAPK）系统的激活作为连接he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he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使用将产生Hhe的饮食结合缺乏或过量的饮食硒。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GPx-1表达变化的小鼠模型中分离心脏成纤维细胞，然后研究暴露于不同水平的同型半胱氨酸和硒后的氧化应激、GPx-1和其他促氧化酶和抗氧化酶的表达和活性、p38MAPK的激活和胶原代谢。申请人在he诱导心肌纤维化和功能障碍方面的专业知识，加上世界著名he、氧化应激和心血管疾病专家Joseph Loscalzo博士和硒和GPx-1生物化学专家Diane Handy博士的实验室的大力支持，使我们能够独特地进行拟议的研究。

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.