Initiation of Cardiac Hypertrophy

描述(申请人提供)：在美国，心脏肥大和心力衰竭是主要的死亡原因。然而，心脏病发病机制的分子过程还没有被彻底了解。在几年的研究中，我们在自发性高血压大鼠中鉴定并分析了一种12 kDa的蛋白质，肌营养素(Myo)，它可以刺激心肌细胞的生长。过去的资助期已经产生了这些新的观察结果：(1)Myo过表达导致心肌肥大，继而演变为心力衰竭，相关细胞因子/生长因子的分子图谱在早期和晚期疾病中不同；(2)NFkappaB通路的激活对于Myo诱导的心肌肥厚的进展是必要的；(3)在慢性肥厚变成心力衰竭时，心肌细胞的分裂和凋亡并行发生；(4)Myo过表达诱导显著的、强劲的P53过表达，突显了P53在这一过程中的可能作用。每一项发现都将为更多的研究提供肥沃的土壤，但我们在这项更新建议中选择专注于开启和关闭Myo基因表达的影响，并确定p53在肥大过程中的作用。我们假设在心肌肥厚开始时，Myo直接作用于心肌细胞，而在向心力衰竭过渡的时间点，Myo与P53和其他细胞因子/生长因子协同作用。为了验证这一假设，我们提出了一种多学科的方法来评估Myo基因的表达或不表达的效果，方法是：(A)使用LET控制开关；(B)使用siRNA技术沉默Myo基因；或(C)实施传统上给予患有心力衰竭的人类的药物治疗。我们的具体目标是(1)研究通过(A)使用四环素反式激活系统或(B)使用siRNA沉默Myo基因来改变Myo基因表达的影响；(2)研究单独或联合使用药物对与分子变化相关的进展为心力衰竭的肥厚程度的影响；(3)确定P53与Myo在肥厚中以及何时恶化为衰竭的关系；(4)用透射电子显微镜评价肥厚开始/进展到心力衰竭过程中观察到的结构变化；(5)用超声心动图确定心功能，将观察到的形态变化与分子变化联系起来。这些发现对人类心脏病的治疗至关重要。再加上对心肌肥厚发展为心力衰竭的其他分子机制的研究，这些发现将有助于更有效的干预，不仅是在决定干预的时机，而且还在设计适当的基于分子的治疗方法。

DESCRIPTION (provided by applicant): Cardiac hypertrophy and heart failure are leading causes of death in the United States. However, the molecular processes underlying the pathogenesis of heart disease have not been thoroughly understood. During investigations spanning several years we identified and profiled in spontaneously hypertensive rats a 12-kDa protein, myotrophin (Myo), that stimulates myocyte growth. The past funding period has yielded these novel observations: (1) Myo overexpression causes cardiac hypertrophy that devolves to heart failure, and the molecular profiles of associated cytokines/growth factors differ in early- vs. late-stage disease; (2) activation of the NFkappaB pathway is necessary for the progression of Myo-induced cardiac hypertrophy; (3) at the point when chronic hypertrophy becomes heart failure, cell division and apoptosis of cardiac myocytes occur in parallel; and (4) Myo overexpression elicits significant, robust overexpression of p53, highlighting a possible role of p53 in this process. Each finding would provide fertile ground for more investigation, but we chose in this renewal proposal to focus on the effects of turning Myo gene expression on and off and defining the role of p53 in the hypertrophic process. We hypothesize that Myo acts directly on myocyte during initiation of cardiac hypertrophy, whereas it acts in synergy with p53 and other cytokines/growth factors at the point of transition to heart failure. To test this hypothesis, we propose a multidisciplinary approach to evaluating the effects of the expression or nonexpression of the Myo gene by (a) using a let-control switch; (b) silencing the Myo gene using siRNA technology; or (c) administering pharmacological treatment conventionally given to humans with heart failure. Our specific aims are (1) to study the effects of altering Myo gene expression by either (a) using a tetracycline transactivation system or (b) silencing the Myo gene using siRNA; (2) to study the effects of individual pharmacologic agents, alone or in combination, on the degree of hypertrophy as it progresses to heart failure, associated with molecular changes; (3) to define what relationship p53 has to Myo in hypertrophy and when it worsens to failure; (4) to evaluate structural changes observed during initiation/progression of hypertrophy to heart failure by transmission electron microscopy and (5) to determine cardiac function by echocardiogram to correlate observed morphological and molecular changes. These findings bear crucially upon the treatment of heart disease in humans. Together with investigations into additional molecular mechanisms that underlie the progression of cardiac hypertrophy to heart failure, the findings will facilitate more effective intervention, not only in decisions regarding the timing of intervention, but also in the design of appropriate molecularly based therapies.