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）与儿童和成人发生哮喘、哮喘更严重和哮喘住院率增加的终生风险相关。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，以响应暴露于包括SHS在内的几种空气污染物。Nadeau和米勒研究小组先前的结果表明，Treg和Teff受到表观遗传学调控，它们的改变影响几种哮喘基因的表达和哮喘相关的临床结果。虽然暴露于SHS已被证明可诱导表观遗传改变，哮喘基因的表观遗传改变可能与哮喘有关，但因果关系尚未得到证实。本研究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暴露与哮喘之间的关系。该提案的关键是在一个表型良好的单卵双胞胎（MZT）队列中进行研究，包括暴露于SHS和哮喘的不一致病例，可以确定SHS诱导的表观遗传标记的关联，以及这种关联的时间，在遗传背景和子宫内和儿童早期环境暴露没有差异的情况下，对哮喘进行研究，既往研究的方法学限制。我们假设暴露于SHS与成人当前的哮喘相关，这种关联是通过Treg和Teff细胞中哮喘基因的DNA甲基化以及随后的下游细胞事件介导的。具体而言，为了了解SHS诱导的哮喘和炎症病理学机制，我们提出：目的1：测试特定遗传位点的CpG甲基化水平是否在吸烟和哮喘不一致的MZT中改变。目标二。确定SHS暴露最小化是否与Teff中Treg中Foxp 3、IL-10和IFNγ甲基化降低以及Teff中IL-4甲基化随时间增加相关。目标3：通过估计主要效应和相互作用并控制哮喘发作时间，确定哮喘和非哮喘双胞胎中Foxp 3、IL-10、IFNγ、IL-4的甲基化水平如何受到从未、既往（仅在子宫内或仅在儿童期）或当前SHS暴露的影响。如果目标得以实现，这一建议将提高我们对暴露于SHS导致哮喘的机制的理解，并确定新的吸烟相关气道疾病的生物标志物，以便更有效地制定环境政策和风险管理，并更早地进行筛查和/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.