Transplacental Arsenic Induced Hepatic Dysfunction and Vascular Disease

描述(申请人提供)：心血管疾病是美国的主要死亡原因。长期摄入砷会导致动脉粥样硬化，并与心肌梗死和中风的死亡率增加有关。早年接触砷可能在成年生活中动脉粥样硬化的发展中发挥重要作用，这一点从母亲饮用高水平砷水的地区因晚期动脉硬化导致婴儿死于心肌梗死的报告中得出结论。经胎盘砷暴露可破坏肝脏DNA甲基化模式，从而改变肝脏基因表达。潜在的肝病是动脉粥样硬化的独立危险因素。因此，砷暴露引起的肝病可能是动脉粥样硬化的易感因素，而美国饮用水中砷的广泛暴露可能导致动脉粥样硬化和心血管疾病死亡。我们的工作假设是，砷暴露扰乱了对肝脏基因表达的表观遗传控制，使肝脏容易发生炎症，而炎症是导致动脉粥样硬化的触发因素，导致易感动物动脉粥样硬化加速。初步数据表明，易患动脉粥样硬化的载脂蛋白E基因敲除(ApoE-/-)小鼠在没有高脂饮食的情况下，经胎盘暴露于饮用水中的砷，在10周龄时会出现明显的血管疾病，肝脏基因表达提示一种促炎状态。这项探索性拨款申请的目的是1)提炼和优化这一新开发的经胎盘砷诱导的动脉粥样硬化模型，方法是：测定孕妇和胎儿对砷暴露的反应，确定动脉粥样硬化病变形成的暴露/时间依赖性(病变形成的速度和程度)，评估砷暴露对血管反应性变化的反应，并表征动脉损伤(病变细胞、纤维化和炎症)的性质；2)通过表征肝脏病理特征，确定肝脏功能障碍的循环生物标志物，并检验肝脏变化和血管变化之间存在时间相关性的假设，探索经胎盘砷诱导的肝脏变化。将在出生时以及10、16和24周时对组织进行检查，以确定子宫内砷暴露引起的病程和分子变化的稳定性。拟议研究的目的是利用载脂蛋白E模型确定是否存在加速动脉粥样硬化形成所需的砷暴露阈值水平。这一模型与人类动脉粥样硬化的相关性在于，产前暴露于砷的人在以后的生活中可能更容易受到饮食影响。这些研究将为砷诱导动脉粥样硬化的机制以及胎儿砷暴露在疾病进展中所起的作用提供重要信息。该模型也将为未来砷诱导动脉粥样硬化机制的研究提供丰富的资源，包括确定砷效应的关键发展阶段，以及砷暴露引起DNA甲基化、染色质结构、基因表达和遗传印记的分子研究。与公共健康相关：在美国，接触砷饮用水是一个主要问题。早期接触砷对成人疾病进展的影响尚不清楚，但可能非常重要。本项目使用胎儿砷暴露导致血管疾病的小鼠模型来研究胎儿砷暴露对肝脏发育的影响，这些影响可能会导致年轻成年后的血管疾病。

DESCRIPTION (provided by applicant): Cardiovascular disease is the major cause of death in the U.S. Chronic arsenic ingestion causes atherosclerosis and is associated with increased mortality from myocardial infarction and stroke. Early life arsenic exposure may play a significant role in development of atherosclerosis in adult life, as suggested by reports of infant deaths from myocardial infarction caused by advanced arteriosclerosis in regions where mothers consumed water with high levels of arsenic. Transplacental arsenic exposure can disrupt liver DNA methylation patterns and thus alter liver gene expression. Underlying liver disease is an independent risk factor for atherosclerosis. Hence, arsenic exposure induced liver disease may predispose to atherogenesis, and widespread exposure to arsenic in drinking water in the U.S. likely contributes to atherogenesis and death from cardiovascular disease. Our working hypothesis is that arsenic exposure disrupts epigenetic control of hepatic gene expression predisposing the liver to inflammation that is an atherogenic trigger resulting in accelerated atherosclerosis in susceptible animals. Preliminary data indicate that atherosclerosis-prone apolipoprotein E knockout (ApoE -/-) mice transplacentally exposed to arsenic in drinking water develop overt vascular disease by 10 weeks of age without high lipid diet and that liver gene expression suggests a pro-inflammatory state. The aims of this exploratory grant application are 1) to refine and to optimize this newly developed model of transplacental arsenic induced atherogenesis by determining arsenic exposure response of arsenic blood levels in pregnant females and fetuses, determining exposure/time dependence of atherosclerotic lesion formation (rate and extent of lesion formation), assessing arsenic exposure-response of changes in vascular reactivity and characterizing the nature of arterial lesions (lesion cellularity, fibrosis and inflammation) in arsenic exposed mice; 2) explore transplacental arsenic-induced hepatic changes by characterizing liver pathology, determining circulating biomarkers of liver dysfunction and test the hypothesis that there is a temporal correlation between hepatic changes and vascular changes. Tissues will be examined at birth and at 10, 16 and 24 weeks of age to determine the course of disease and stability of molecular changes induced by in utero arsenic exposure. The goal of the proposed studies is to determine whether there is a threshold level of arsenic exposure necessary to accelerate atherogenesis using the ApoE model. The relevance of this model to human atherosclerosis is that people prenatally exposed to arsenic are likely more susceptible to dietary influences later in life. These studies will provide important information on the mechanisms of arsenic induced atherosclerosis and the role that fetal arsenic exposure plays in disease progression. This model also will be a rich resource for future research on the mechanism of arsenic induced atherosclerosis including determination of the critical stages of development for the arsenic effect, and molecular studies of arsenic exposure induced changes in DNA methylation, chromatin structure, gene expression and genetic imprinting. PUBLIC HEALTH RELEVANCE: Exposure to arsenic drinking water is a major concern in the United States. The effect of early life arsenic exposure on adult disease progression is unknown but potentially very important. This project uses a mouse model of fetal arsenic exposure induced vascular disease to investigate effects of fetal arsenic exposure on liver development that likely cause vascular disease by young adulthood.