Endothelial Progenitor Cells and Particulate Air Pollution

描述(申请人提供)：多项流行病学和实验研究报告称，急性或长期暴露在空气污染中与不良心血管事件有关，包括心肌缺血、中风、心律失常、心力衰竭、心脏骤停和动脉粥样硬化。空气污染的这些影响与细颗粒物和超细颗粒物(PM)组分密切相关，这些颗粒物是化石燃料燃烧直接产生的，存在于汽车尾气、木材或煤炭烟雾以及冶炼厂、造纸厂、钢厂或水泥厂的工业排放中。PM相关心血管疾病的一个共同特征是内皮功能障碍的建立和维持。由于内皮功能障碍是心血管疾病的早期症状，也是动脉粥样硬化急性血栓形成并发症的重要因素，如稳定性心绞痛和不稳定型心绞痛、心肌梗死和缺血性中风，因此它可能是PM暴露相关心血管毒性的关键介质。成人内皮细胞是一个分化的细胞层，在实质细胞和外周血之间提供了一个非血栓界面。由于这一层的正常“磨损”造成的损伤可以通过动员和归巢骨髓驻留的多能细胞或内皮祖细胞(EPC)来修复，这也促进了血管生成和伤口愈合。我们最近发现PM暴露与循环EPC水平呈负相关。这里，我们假设EPC动员或功能缺陷是PM诱导的氧化应激诱导的全身性炎症的结果。我们将在三个目标上检验这一假设。首先，我们将研究PM对暴露在浓缩环境空气颗粒物(CAPS)或过滤空气中的小鼠外周血和骨髓中内皮祖细胞数量的影响。我们将确定这些影响的时间进程，是否本身存在动员缺陷，特定的EPC群体和位置是否受到影响，以及这种反应是否对EPC或其他干细胞(如造血干细胞和间充质干细胞)具有选择性。此外，我们将测量EPC衍生微粒的循环水平，以测试暴露在PM中是否会增加EPC的激活或细胞死亡。第二个目标是描述PM暴露影响EPC功能的机制。为此，我们将评估接触CAPS如何影响内皮祖细胞的生长、分化、迁移和促进伤口愈合的能力。我们将研究EPC的这些变化是否伴随着全身炎症和氧化应激的增加，以及抗氧化干预或增加NO可获得性的策略是否可以防止PM诱导的EPC数量和功能缺陷。最后，目标3是检查PM引起的人类外周血内皮祖细胞数量和功能的变化是否伴随着全身炎症、氧化应激和微粒子或miRNA生物标志物的增加，以及抗氧化干预是否可以逆转这些变化。该项目的成功完成将为PM的心血管毒性以及它如何影响干细胞的丰度和修复能力提供新的见解。该项目的发现也可能成为开发PM暴露的新生物标记物或减轻PM毒性的新策略的基础。

DESCRIPTION (provided by applicant): Multiple epidemiological and experimental studies report that acute or chronic exposure to air pollution is associated with adverse cardiovascular events including myocardial ischemia, stroke, arrhythmias, heart failure, sudden cardiac arrest and atherogenesis. These effects of air pollution are most strongly correlated with fine and ultrafine particulate matter (PM) fractions which are generated directly from the combustion of fossil fuels and are found in automobile exhaust, wood or coal smoke and industrial emission from smelters, paper or steel mills or cement plants. A common feature of PM-associated cardiovascular disorders is the establishment and maintenance of a dysfunctional endothelium. Because endothelial dysfunction is an early symptom of cardiovascular disease and an important factor in acute thrombotic complications of atherosclerosis such as stable and unstable angina, myocardial infarction, and ischemic stroke, it could be a key mediator of the cardiovascular toxicity associated with PM exposure. The adult endothelium is a differentiated cell layer that provides a non-thrombotic interface between parenchymal cells and peripheral blood. Damages due to normal "wear-and-tear" in this layer are repaired by the mobilization and homing of bone-marrow resident pluripotent cells or endothelial progenitor cells (EPCs), which also promote angiogenesis and wound healing. We have recently identified a negative correlation between PM exposure and circulating EPC level. Here, we hypothesize that defects in EPC mobilization or function are a consequence of PM-induced systemic inflammation induced by oxidative stress. We will test this hypothesis in three aims. First we will examine PM-induced changes in EPC populations in the peripheral blood and bone marrow of mice exposed to concentrated ambient air particles (CAPS) or filtered air. We will determine the time course of these effects, whether there is a mobilization defect per se, whether specific populations and locations of EPC are affected and whether this response is selective to EPCs or other stem cells such as the hematopoietic stem cells and mesenchymal stem cells are affected as well. In addition we will measure circulating levels of EPC-derived microparticles to test whether exposure to PM increases EPC activation or cell death. The second aim is to delineate the mechanisms by which PM exposure affects EPC function. For this, we will assess how exposure to CAPs affects the ability of EPCs to grow, differentiate, migrate and promote wound healing. We will examine whether these changes in EPC are accompanied by an increase in systemic inflammation and oxidative stress and whether antioxidant interventions or strategies to increase NO availability would prevent PM-induced deficits in EPC number and function. Finally, Aim 3 is to examine whether PM-induced changes in human peripheral blood EPC number and function are accompanied by an increase in systemic inflammation, oxidative stress, and microparticle or miRNA biomarkers and whether anti-oxidant intervention could reverse such changes. Successful completion of this project will provide novel insights into the cardiovascular toxicity of PM and how it affects the abundance and the reparative capacity of stem cells. Findings of this project could also form the basis for the development of new biomarkers of PM exposure or new strategies to mitigate PM toxicity.