Secondhand smoke and asthma: Mechanistic outcomes of DNA methylation in T cells

描述(由申请人提供)：暴露于二手烟(SHS)与患哮喘的终身风险更大、更严重的哮喘以及儿童和成人哮喘住院时间的增加有关。虽然哮喘的免疫发病机制仍不完全清楚，但关键的分子事件包括调节性T细胞(Treg)和效应T细胞(TEff)活性的变化，以应对包括SHS在内的几种空气污染物的暴露。Nadeau和Miller研究小组之前的结果表明，Treg和TJeff是表观遗传调控的，它们的变化影响了几个哮喘基因的表达和哮喘相关的临床结果。虽然暴露于SHS已被证明可诱发表观遗传学改变，哮喘基因的表观遗传学改变可能与哮喘有关，但因果关系尚未得到证实。这项建议将尝试建立一种新的SHS研究方法，通过使用独特的联系机制研究和创新的研究设计来确定SHS暴露和哮喘之间的关系。这一建议的关键是打算在表型良好的同卵双胞胎(MZT)队列中进行研究，包括在暴露于SHS和哮喘方面存在不一致的病例，以确定SHS诱导的表观遗传标记的关联以及这种关联的时机，在没有遗传背景差异的情况下，以及在子宫和儿童早期环境暴露的情况下，与先前研究的方法学限制。我们假设，暴露于SHS与成人当前的哮喘有关，这种联系是通过Treg和TJeff细胞中哮喘基因的DNA甲基化以及相应的下游细胞事件来调节的。具体地说，为了了解SHS诱导哮喘和炎症的病理机制，我们提出：目的1：测试吸烟和哮喘不协调的MZT中特定基因位点的CpG甲基化水平是否发生变化。目的2.确定暴露于自发性高血压病的最小化是否与TEF中FOXP3、IL-10、Treg和干扰素γ甲基化减少以及IL-4甲基化增加有关。目的3.通过评估哮喘和非哮喘双生子的主要作用和相互作用，以及控制哮喘的发病时间，确定从未、以前(仅在宫内或仅在儿童时期)或当前自体激素暴露对哮喘和非哮喘双生子Foxp3、IL-10、干扰素γ、IL-4甲基化水平的影响。如果这些目标得以实现，这项建议将提高我们对暴露于SHS导致哮喘的机制的理解，并确定与吸烟相关的呼吸道疾病的新生物标志物，以便更有效地制定环境政策和风险管理，并可以更早地开展筛查和/或治疗干预。

DESCRIPTION (provided by applicant): Exposure to secondhand smoke (SHS) is associated with a greater lifetime risk of developing asthma, more severe asthma, and increased asthma hospitalizations for both children and adults. While much of the immunopathogenesis of asthma remains incompletely understood, key molecular events include changes in regulatory T cell (Treg) and effector T cell (Teff) activity in response to exposure to several air pollutants including SHS. Previous results from the Nadeau and Miller research groups suggest that Treg and Teff are epigenetically regulated, and their alterations affect the expression of several asthma genes and asthma- related clinical outcomes. While exposure to SHS has been shown to induce epigenetic alterations, and epigenetic changes in asthma genes may be associated with asthma, causal relationships have not been demonstrated. This proposal will try to establish a novel approach of SHS research by determining relationships between SHS exposure and asthma using uniquely linked mechanistic studies and an innovative study design. Key to this proposal is the intent to conduct studies in a well-phenotyped monozygotic twin (MZT) cohort including cases discordant on exposure to SHS and asthma that can determine the association of SHS-induced epigenetic marks, and the timing of this association, on asthma in the absence of differences in genetic backgrounds and in utero and early childhood environmental exposures, methodological limitations from prior studies. We hypothesize that exposure to SHS is associated with current asthma in adults, and this association is mediated through DNA methylation of asthma genes in Treg and Teff cells and the consequential downstream cellular events. Specifically, to understand the mechanisms of SHS-induced pathology in asthma and inflammation, we propose to: Aim 1: Test whether CpG methylation levels of specific genetic loci are altered in MZT discordant for smoking and asthma. Aim 2. Determine if minimization of exposure to SHS is associated with a decrease in methylation of Foxp3, IL-10, in Treg, and IFNγ in Teff and an increase in methylation of IL-4 in Teff over time. Aim 3. Determine how methylation levels of Foxp3, IL-10, IFNγ, IL-4 are influenced by never, prior (only in utero or only childhood), or current SHS exposure in asthmatic and nonasthmatic twins by estimating main effects and interactions and controlling for period of asthma onset. If the aims are achieved, this proposal should improve our understanding of the mechanisms by which exposure to SHS contributes to asthma and identify novel biomarker of smoke-related airway disease so that environmental policy and risk management can be developed more effectively, and screening and/or therapeutic interventions may be instituted earlier.