Epigenetic Effects of Particles and Metals on Cardiac Health of an Aging Cohort

描述(由申请人提供)： 心血管疾病(CVD)是美国老年人的主要死亡原因。由于75岁以上的美国人的比例预计将从2000年的6%增加到2050年的11%，因此死于心血管疾病的人数在未来几年可能会大幅上升。在之前的工作中，这组研究人员证明，急性和慢性颗粒物空气污染暴露与特定的心血管结果相关，如心率变异性降低、动脉僵硬和ST段压低，从而导致心血管疾病死亡率增加。 DNA甲基化改变已被发现与炎症、内皮功能和动脉粥样硬化有关。在实验模型和人体中的初步观察表明，空气颗粒和金属是颗粒物污染的组成部分，会改变DNA甲基化状态。在暴露于空气颗粒物和有毒金属(如砷、镉和铅)的受试者中观察到的心血管疾病风险增加是否由DNA甲基化模式的改变介导，目前尚不清楚。这项建议的目标是确定暴露在空气颗粒物和有毒金属(砷、镉和铅)中是否会随着时间的推移改变老年受试者的全局和/或基因特异性甲基化，从而增加心血管疾病的风险。具体地说，这项建议将评估：1)暴露于AlU和LINE-1序列的全球DNA甲基化，以及与涉及内皮功能和动脉粥样硬化的特定基因(ICAM-1、干扰素-伽马、p16)的高甲基化或低甲基化之间的关联；以及2)上述全球和基因特定DNA甲基化变化与心血管相关结果(心率变异性、动脉粥样硬化的脉冲多普勒测量、ST段抬高/压低、炎症/内皮功能的生物标记物)之间的关联。作为次要目标，该倡议将探讨：1)全球或基因特有的甲基化状态是否会改变空气颗粒物和有毒金属(铅、砷、镉)与心血管疾病相关终点的关联；以及2)暴露与甲基化状态之间的关联是否会因饮食因素(叶酸、维生素B6和B12)、血浆同型半胱氨酸水平和DNA甲基化基因中的SNP(MTHFR、cSHMT)的水平或摄入量而改变。这项研究设计基于马萨诸塞州东部现有的700名老年受试者，将允许对空气颗粒物、金属生物标记物、DNA甲基化模式和心血管疾病表型进行基线和纵向分析，因此所有假设都将进行横向和纵向测试。定量DNA甲基化分析是基于对亚硫酸盐处理过的DNA的PCR扩增和焦磷酸测序，将对每个研究对象在很长一段时间内收集的三个血液DNA样本进行。

DESCRIPTION (provided by applicant): Cardiovascular disease (CVD) is the leading cause of death among the elderly in the United States. Since the percentage of Americans over the age of 75 years is expected to increase from 6% in 2000 to 11 % in 2050, the number of persons dying from CVD will likely rise dramatically in the coming years. In previous work, this team of investigators demonstrated that acute and chronic particulate air pollution exposures are associated with specific cardiovascular outcomes, such as decreased heart rate variability, arterial stiffness, and ST-segment depression, resulting in increased death rates for CVD. DNA-methylation changes have been found to be involved in inflammation, endothelial function, and atherosclerosis. Initial observations in experimental models and humans have shown that air particles and metals, which are constituents of particulate pollution, alter DNA methylation status. Whether the increased risk of CVD observed in subjects exposed to air particles and toxic metals (such as arsenic, cadmium and lead) is mediated by alterations of DNA-methylation patterns is unresolved. The goal of this proposal is to determine whether exposure to air particles and toxic metals (arsenic, cadmium and lead) increases CVD risk by altering global and/or gene specific methylation in elderly subjects over time. Specifically, this proposal will evaluate: 1) the association of the exposure with global DNA methylation in Alu and LINE-1 sequences, and with hypermethylation or hypomethylation in specific genes (ICAM-1, IFN-gamma, p16) involved endothelial function and atherosclerosis; and 2) the association between the above global and gene specific DNA-methylation changes and CVD-related outcomes (Heart-rate variability, Pulse Doppler measurements of atherosclerosis, ST segment elevation/depression, biological markers of inflammation/endothelial function). As a secondary aim, this initiative will explore whether: 1) global or gene-specific methylation status modifies the association of air particles and toxic metals (Pb, As, Cd) with CVD-related endpoints; and 2) the association between exposure and methylation status is modified by plasma levels or intakes of dietary factors (folate, Vitamin B6 & B12), plasma homocysteine levels, and SNPs in DNA methylation genes (MTHFR, cSHMT). The study design, based on an existing cohort of 700 elderly subjects in Eastern Massachusetts, will allow for baseline and longitudinal analysis of air particles, metal biomarkers, DNA methylation patterns and CVD phenotypes, therefore all hypotheses will be tested cross-sectionally and longitudinally. Quantitative DNA methylation analysis, based on PCR amplification and pyrosequencing of bisulphite-treated DNA, will be performed for each study subject on three blood DNA samples collected over a long time span.