Calcineurin's role in circadian regulation of cardiac function and remodeling

描述(由申请人提供)： 昼夜节律是分子、生化和行为参数的自我维持的24小时循环，帮助生物体为生理需求的预期变化做好准备。许多重要的心血管因素，包括新陈代谢、心率、血压和激素释放，都会在24小时内振荡。在人类中，心肌梗死、室性心动过速和缺血性心脏病死亡等不良心脏事件的发生率因一天中的不同时间而异，而昼夜节律的强制改变与心力衰竭风险的增加有关。心血管疾病是美国的主要死亡原因，其发病率正在全球范围内达到流行病的水平。尽管有大量证据表明昼夜节律在心血管健康中的重要性，但对控制心脏功能和重塑的细胞内信号通路的昼夜节律调节知之甚少。我们最近发现的证据表明，在正常、健康的心脏中，钙激活蛋白磷酸酶钙调神经磷酸酶的活性有很大的昼夜波动。这一发现值得注意，因为钙调神经磷酸酶的激活主要被认为是导致心肌肥大和衰竭的病理过程。我们假设，钙调神经磷酸酶活动的每日振荡与其他细胞过程形成相互依赖的反馈环，有助于协调心功能的变化和预期生理需求变化的重塑。此外，我们推测，钙调神经磷酸酶活动的正常时间关系的中断会增加心脏应激，并导致心功能恶化。这项资助的目标是确定钙调神经磷酸酶活性昼夜变化的原因，并确定钙调神经磷酸酶依赖的振荡在心脏健康和疾病中的作用。具体目标1：确定钙调神经磷酸酶活性昼夜节律的潜在因素。我们将测试外在因素，如体力活动，还是内在因素，如心肌细胞自主钙振荡，是导致钙调神经磷酸酶昼夜节律激活的主要原因。具体目标2：确定钙调神经磷酸酶依赖活动的昼夜节律变化影响心功能的机制。我们将研究调节蛋白的磷酸化和钙调神经磷酸酶/NFAT途径的直接转录靶标的变化。具体目标3：测试正常昼夜节律的中断是否会促进心脏的病理性重构。改变的光疗法和具有改变的钙调神经磷酸酶活性的转基因品系将被用来扰乱正常的昼夜节律。当动物承受压力超负荷时，心功能和存活率的变化将被评估，以及目标1和2中探索的分子机制的变化。

DESCRIPTION (provided by applicant): Circadian rhythms are self-sustaining, 24-hour cycles in molecular, biochemical, and behavioral parameters that help an organism prepare for anticipated changes in physiological demand. Many important cardiovascular factors, including metabolism, heart rate, blood pressure, and hormone release, oscillate over a 24-hour period. In humans, the incidence of adverse cardiac events, such as myocardial infarction, ventricular tachycardia, and death from ischemic heart disease, vary according to the time of day, and forced changes in circadian rhythm are associated with increased risk for heart failure. Cardiovascular disease is the major cause of death in the United States and its incidence is reaching epidemic proportions worldwide. Despite overwhelming evidence of the importance of circadian rhythms in cardiovascular health, little is known regarding the circadian regulation of intracellular signaling pathways controlling cardiac function and remodeling. We have recently found evidence of large circadian oscillations in the activity of the calcium-activated protein phosphatase calcineurin in normal, healthy hearts. This finding is remarkable because activation of calcineurin has primarily been thought of as a pathological process driving cardiac hypertrophy and failure. We hypothesize that daily oscillations in calcineurin activity form interdependent feedback loops with other cellular processes helping to coordinate changes in cardiac function and remodeling in anticipation of changes in physiological demand. Furthermore, we postulate that disruption of the normal temporal relationship of calcineurin activity increases cardiac stress and contributes to deterioration of cardiac function. The goal of this grant is to identify the cause of circadian changes in calcineurin activity and to determine the role of calcineurin-dependent oscillations in cardiac health and disease. Specific Aim 1: To identify factors underlying the circadian rhythm in calcineurin activity. We will test whether extrinsic factors, such as physical activity, or intrinsic factors, such as cardiomyocyte- autonomous calcium oscillations are the primary cause underlying circadian activation of calcineurin. Specific Aim 2: To determine mechanisms through which circadian changes in calcineurin- dependent activities impact cardiac function. We will examine both changes in phosphorylation of regulatory proteins and direct transcriptional targets of the calcineurin/NFAT pathway. Specific Aim 3: To test whether disruption of normal circadian rhythms promotes pathological remodeling of the heart. Altered light regimens and transgenic lines with altered calcineurin activity will be used to disrupt normal circadian rhythmicity. Changes in cardiac function and survival when the animals are subjected to pressure overload will be assed as well as changes in the molecular mechanisms explored in Aims 1 and 2. (End of Abstract)