Impact of obesity on airway responses to air pollution

描述（由申请人提供）：肥胖是哮喘的危险因素。肥胖受试者对空气污染物臭氧（O3）也有反应，臭氧是哮喘的诱因，其肺功能的下降比瘦人更大。了解肥胖和哮喘之间关系的机制基础是本应用的重点。我们已经确定肥胖小鼠可以作为这类研究的有用模型。肥胖小鼠有先天性气道高反应性（AHR），这是哮喘的一个特征。与瘦老鼠相比，肥胖老鼠对急性臭氧暴露也有更大的反应。我们的初步数据表明，内皮素可能有助于肥胖的先天性AHR：肥胖小鼠肺部内皮素表达增加，内皮素受体拮抗剂减轻肥胖相关的AHR。我们的数据还表明NF-？B的激活可能有助于肥胖对O3的反应增加：在急性O3暴露诱导表达的许多基因中，只有一小部分在肥胖小鼠和瘦小鼠中被诱导到更大程度。这些大部分都是与炎症和免疫有关的基因，大多数是NF-？B依赖。人们越来越认识到，肥胖是脂肪组织和全身氧化应激的一种情况。我们的初步数据表明，肥胖还会增加肺部的氧化应激，导致脂质过氧化增加。值得注意的是，氧化应激和/或脂质过氧化产物已被证明可以诱导内皮素和NF-？B激活。因此，我们的假设是，肺氧化应激通过驱动内皮素表达和加剧O3诱导的NF-？B激活。为了验证这一假设，我们将在室内空气暴露后或急性臭氧暴露后的不同时间测量肺和血液中的脂质过氧化和蛋白质羰基化产物以及抗氧化剂。为了确定内皮素是否通过诱导内皮素表达来促进肥胖相关的AHR，我们将用多种内皮素受体特异性拮抗剂治疗肥胖和瘦小鼠，并测量它们对AHR的影响。我们将研究肥胖对内皮素和内皮素受体表达的影响。我们将确定用抗氧化剂治疗肥胖小鼠是否能减轻与肥胖相关的肺内皮素表达升高并降低与肥胖相关的AHR。我们还将确定是否可以通过限制饮食来逆转肺氧化应激及其后遗症。我们将使用EMSA和Western blotting检测I？B、p50和p65检测o3诱导的NF-？肥胖小鼠的B细胞活化增加。来确定NF-？B，我们将测量NF-？B p50-/-和野生型小鼠饮食诱导肥胖。实验将在表达I？B1突变体抵抗由CC10启动子驱动的降解。这些小鼠对NF-？B在气道上皮细胞中的活化。如果得到证实，这一假设将为已经用于人类其他目的的治疗策略（内皮素受体拮抗剂、抗氧化剂）提供基本原理，并可能因此迅速转化为肥胖哮喘患者。

DESCRIPTION (provided by applicant): Obesity is a risk factor for asthma. Obese subjects also respond to the air pollutant, ozone (O3), an asthma trigger, with greater decrements in lung function than lean individuals. Understanding the mechanistic basis for the relationship between obesity and asthma is the focus of this application. We have established that obese mice obese mice can serve as a useful model for such studies. Obese mice have innate airway hyper- responsiveness (AHR), a characteristic feature of asthma. Compared to lean mice, obese mice also have greater responses to acute O3 exposure. Our preliminary data indicate that endothelin likely contributes to the innate AHR of obesity: endothelin expression is increased in the lungs of obese mice and endothelin receptor antagonists attenuate obesity-related AHR. Our data also indicate that increased NF-?B activation likely contributes to obesity-related increases in the response to O3: of the many genes whose expression is induced by acute O3 exposure, only a fraction are induced to a greater extent in obese versus lean mice. These are, for the most part, genes involved in inflammation and immunity, and most are NF-?B dependent. It is increasingly understood that obesity is a condition of adipose tissue and systemic oxidative stress. Our preliminary data indicate that obesity also increases oxidative stress in the lung, resulting in increased lipid peroxidation. Notably, oxidative stress and/or lipid peroxidation products have been demonstrated to induce to both endothelin expression and NF-?B activation. Hence, our hypothesis is that pulmonary oxidative stress contributes to the effects of obesity in the lung, by driving endothelin expression and by exacerbating O3- induced NF-?B activation. To address this hypothesis, we will measure lipid peroxidation and protein carbonylation products as well as antioxidants in the lungs and blood after room air exposure or at various times after acute O3 exposure. To determine whether endothelin contributes to obesity-related AHR by inducing endothelin expression, we will treat obese and lean mice with a variety of endothelin receptor specific antagonists, and measure their impact on AHR. We will examine the effects of obesity on endothelin and endothelin receptor expression. We will determine whether treatment of obese mice with antioxidants attenuates obesity-related elevations in lung endothelin expression and reduces obesity-related AHR. We will also determine if we can reverse pulmonary oxidative stress and its sequelae with dietary restriction. We will use EMSA and Western blotting for I?B, p50, and p65 to determine O3-induced NF-?B activation is increased in obese mice. To determine the importance of NF-?B, we will measure responses to O3 in NF-?B p50-/- and wildtype mice with diet induced obesity. Experiments will be repeated in transgenic mice expressing an I?B1 mutant that is resistant to degradation driven by a CC10 promoter. These mice are resistant to NF-?B activation in airway epithelial cells. If borne out, this hypothesis would provide the rationale for therapeutic strategies (endothelin receptor antagonists, antioxidants) already in human use for other purposes, and could thus lead to rapid translation to the obese asthmatic. PUBLIC HEALTH RELEVANCE: Obesity is an important risk factor for asthma and also exacerbates the pulmonary effects of the air pollutant, ozone. The goal of this research project is to try and understand how obesity induces these effects. The focus of our research is the inflammation and oxidative stress associated with obesity. Understanding the mechanistic basis for the augmented pulmonary responses to air pollution may lead to new therapeutic strategies for this increasingly at risk population.