Mechanisms of Chronic Intermittent Hypoxia Induced Airflow Obstruction during Allergic Lower Airway Inflammation

 描述(由申请人提供)： 知识/工作完成的差距：阻塞性睡眠呼吸暂停(OSA)在哮喘患者中非常常见，并加剧呼吸道疾病，但机制尚不清楚。慢性间歇性低氧(CIH)是阻塞性睡眠呼吸暂停低氧(OSA)的一个显著特征，可能是OSA的一个重要因素。在我们最近发表的前期工作中，致敏原诱导的大鼠气道炎症过程中的CIH暴露：1)引起气流受限；2)使近端气道内胶原沉积增加并导致远端气道和实质的基质降解；3)放大变应原诱导的气道单核细胞增加，这种增加可能是非经典的激活并极化为更有利于纤维化的M2巨噬细胞表型；4)与过敏原协同作用，使支气管肺泡灌洗液(BAL)中纤溶酶原激活物抑制物-1(PAI-1)的表达和活性增加。有趣的是，这些特征都不会对吸入皮质类固醇产生反应。这些新的发现强调了OSA并存可能加重哮喘并对肺功能造成不可逆转的损害。然而，这些发现提出了以下问题：i)中心气道阻力、小气道塌陷和肺实质弹性降低在CIH诱导的气流阻塞中的作用以及这些生理缺陷的可逆性；ii)我们的模型中单核细胞和巨噬细胞的表型、激活状态和ROE；以及iii)PAI-1在CIH诱导的肺重塑和气流阻塞中的作用。缺乏对这些过程及其分子基础的了解，阻碍了为大部分患有OSA相互作用的哮喘患者开发更有效的治疗方法。假设/目的：长期目标是通过针对哮喘与OSA的相互作用来开发治疗哮喘的有效策略。本研究的目的是在室内粉尘螨(HDM)诱导的大鼠炎症过程中，检测CIH引起的气流阻塞和肺重塑的生理、细胞和分子机制。我们的数据使我们得出了一个中心假设，即CIH在过敏原攻击期间引起的气流阻塞是由于近端和远端气道阻力增加以及实质组织弹性降低所致，这是由于单核细胞来源的M2巨噬细胞PAI-1活性增加所致。针对这一假说，我们拟从以下几个方面进行研究：1)在HDM气道炎症过程中，CIH诱导下呼吸道阻塞的生理机制；2)CIH对肺单核细胞活化和巨噬细胞极化的影响；3)PAI-1在CIH诱导的气流阻塞中的作用。设计：棕色-挪威大鼠4组(n=10/组)，用HDM或生理盐水(SAL)致敏，置于CIH和常氧(NORMAL)下6周，每周HDM或SAL刺激。在最后一次挑战的两天后，对于目标1，将在支气管扩张剂前后测量中央和远端气道以及肺弹性属性(弹性和顺应性)。在组织学方面，我们将对支气管胶原蛋白和平滑肌进行定量。对于目标2，单核细胞和巨噬细胞(M1和M2)将通过BAL和/或肺组织中的流式细胞术、定量(Q)聚合酶链式反应和免疫组织化学进行定量。另一项单独的研究将测试氯屈膦酸盐去除骨髓来源巨噬细胞的生理和组织学效应。对于AIM 3，将用ELISA法测定BAL和肺组织匀浆中的总PAI-1和活性PAI-1。另一项实验将测量PAI-1抑制对HDM挑战大鼠的生理和组织学影响，这些大鼠暴露在CIH和正常对照组中，并喂食常规食物或替普拉菌素。项目意义和创新：我们的项目是创新的，因为这是第一次深入研究临床上常见的CIH导致呼吸道阻塞和重塑的机制。这项研究将为患有阻塞性睡眠呼吸暂停综合征和哮喘的退伍军人提供有针对性的治疗。结果将与退伍军人高度重要的其他肺部疾病相关，如肺气肿和肺纤维化，这些疾病也与OSA相互作用，与死亡率增加有关。

 DESCRIPTION (provided by applicant): The Gap in Knowledge/ Work Accomplished: Obstructive sleep apnea (OSA) is highly common among patients with asthma and exacerbates the airways disease, but mechanisms are unknown. Chronic intermittent hypoxia (CIH), a hallmark feature of OSA, may be one important contributor. In our recently published and preliminary work, CIH exposure during allergen-induced airway inflammation in rats: 1) caused airflow limitation; 2) increased peribronchial collagen deposition in the proximal airways and led to matrix degradation of distal airways and parenchyma; 3) amplified the allergen-induced increase in airway monocytes, which may be non- classically activated and polarize into more pro-fibrotic M2 macrophage phenotype; 4) synergistically with the allergen, increased expression and activity of Plasminogen Activator Inhibitor - 1 (PAI-1) in bronchoalveolar lavage (BAL). Interestingly, none of these features would be responsive to inhaled corticosteroids. These novel findings underscore the potential of comorbid OSA to worsen asthma and cause irreversible detriments to lung function. However, these findings raise questions regarding: i) contributions of central airway resistance, small airway collapse and decreased elastance of lung parenchyma to CIH-induced airflow obstruction and reversibility of these physiologic deficits; ii) phenotype, activation state and roe of the monocytes and macrophages in our model; and iii) the role of PAI-1 in CIH-induced lung remodeling and airflow obstruction. Lack of understanding of these processes and their molecular underpinnings prevents development of more effective therapies for the large fraction of asthma patients suffering from the interaction with OSA. Hypothesis/ Aims: The long term goal is to develop effective strategies for treating asthma by targeting its interaction with OSA. The objective of this proposal is to test the physiological, cellular and molecular mechanisms underlying CIH-induced airflow obstruction and lung remodeling during House Dust Mites (HDM)-induced inflammation in rats. Our data led us to the central hypothesis that CIH-induced airflow obstruction during allergen challenge arises from increased resistance in proximal and distal airways along with reduced parenchymal tissue elastance, which result from increased monocyte-derived M2 macrophages with increased activity of PAI-1. To address this hypothesis, we propose to test the following Aims: 1) the physiologic mechanisms of CIH-induced lower airway obstruction during HDM airway inflammation; 2) the effect of CIH on lung monocyte activation and macrophage polarization; 3) the role of PAI-1 in CIH-induced airflow obstruction. Design: Four groups (n=10/group) of Brown-Norway rats will be sensitized with HDM or saline (SAL) and placed under CIH vs. normoxia (NORM) for 6 weeks, with weekly HDM or SAL challenges. Two days after last challenge, for Aim 1, central and distal airway, and lung elastic properties (elastance & compliance) will be measured pre & post bronchodilator. On histology, we will quantify the bronchial collagen and smooth muscle. For Aim 2, monocyte and macrophage (M1 vs. M2) will be quantified by flow cytometry, quantitative (q)PCR, and immunohistochemistry in BAL and/or lung. A separate study will test physiologic and histologic effects of marrow derived - macrophage depletion with clodronate. For Aim 3, total and active PAI-1 will be measured in BAL and lung homogenate by ELISA. An additional experiment will measure physiologic & histologic effects of PAI-1 inhibition in HDM-challenged rats exposed to CIH vs. NORM and fed regular chow or tiplaxtinin. Project Significance and Innovation: Our project is innovative, as it is the first in-depth investigation of the mechanisms whereby a commonly encountered clinical exposure, CIH, induces airway obstruction and remodeling. The study will lead to targeted therapies for Veterans afflicted with comorbid OSA and asthma. Results will be relevant to other lung diseases of high importance to Veterans, such as emphysema and pulmonary fibrosis, which also feature an interaction with OSA that relates with increased mortality.