The Role of Mfge8 and Apoptotic Cell Clearance in Regulating Asthma Severity

描述(申请人提供)：哮喘是一种慢性免疫介导性疾病，其特征是对抗原、炎症和呼吸道阻塞的免疫反应过度。哮喘的发病率在全球范围内都在增加。目前的治疗主要针对呼吸道阻塞的症状性治疗和免疫系统的整体抑制。针对免疫系统的更具体的疗法将会有很大的好处。乳脂球状表皮生长因子8(Mfge8)是一种可溶性糖蛋白，可结合和靶向凋亡细胞进行清除。吞噬细胞通过Mfge8依赖机制吞噬凋亡细胞后，分泌抗炎细胞因子，在哮喘中起关键的免疫抑制作用。在急性哮喘发作期间，炎症细胞被招募到肺内，并经历细胞凋亡和凋亡细胞清除。在哮喘患者中，有效的凋亡细胞清除与不那么严重的疾病和急性发作的恢复有关，这表明凋亡细胞清除的过程促进了哮喘恶化的缓解。这项建议的总体目标是评估Mfge8介导的凋亡细胞清除在调节哮喘严重程度中的关系。我们假设Mfge8介导的炎症细胞的凋亡清除通过诱导抗炎信号抑制哮喘反应。这一假设将通过两个具体目标来探讨。第一个具体目的是确定Mfge8是否在肺变应原攻击后介导了凋亡细胞的清除，以及凋亡细胞清除受损是否加剧了实验性哮喘。第二个具体目的是确定Mfge8是否通过调节适应性免疫反应来调节哮喘的严重程度。我们的实验方法包括评估Mfge8缺陷小鼠对卵白蛋白诱导的实验性哮喘模型的反应。我们将通过多种方法测试Mfge8缺乏是否会导致哮喘诱导后体内凋亡细胞的清除受损，包括定量组织切片上的凋亡细胞数量，定量肺泡巨噬细胞的吞噬能力，以及评估外源性凋亡细胞的加入是否调节对过敏原攻击的反应的严重程度。我们还将评估Mfge8缺乏症患者对过敏原挑战的适应性反应的差异。我们将通过从Mfge8缺陷小鼠和对照组小鼠的支气管肺泡灌洗、肺实质和胸腔淋巴结中分离和表征细胞因子和淋巴细胞图谱来实现这一点。这些研究有可能发现一种新的抑制途径和一种新的候选分子，可能成为治疗过敏性疾病的疾病改良剂。公共卫生相关性：哮喘是一种慢性过敏性/炎症性肺部疾病，患病率不断上升，治疗方案不完整。旨在发现导致哮喘的机制的研究将提供新的治疗选择。该项目的目标是找出Mfge8蛋白调节哮喘严重程度的机制，并确定治疗过敏性疾病的新治疗靶点。

DESCRIPTION (provided by applicant): Asthma is a chronic immunologically mediated disease characterized by an overactive immune response to antigens, inflammation and airway obstruction. The incidence of asthma is increasing globally. Current therapies primarily target symptomatic management of airway obstruction and global suppression of the immune system. More specific therapies targeting the immune system will be of great benefit. Milk fat globule epidermal growth factor like 8 (Mfge8) is a soluble glycoprotein that binds and targets apoptotic cells for removal. Phagocytes secrete anti-inflammatory cytokines with key immune dampening roles in asthma after engulfing apoptotic cells by a Mfge8 dependent mechanism. During an acute asthmatic flare, inflammatory cells are recruited into the lung and undergo apoptosis and apoptotic cell clearance. In asthmatic patients, efficient apoptotic cell clearance is associated with less severe disease and recovery from an acute flare suggesting that the process of apoptotic cell clearance promotes the resolution of asthma exacerbations. The overall objective of this proposal is to evaluate the relationship of Mfge8-mediated apoptotic cell clearance in modulating asthma severity. We hypothesize that Mfge8-mediated apoptotic cell clearance of inflammatory cells dampens the asthmatic response through induction of anti-inflammatory signaling. This hypothesis will be explored through 2 specific aims. The first specific aim is to determine whether Mfge8 mediates apoptotic cell clearance after allergen challenge in the lung and whether impaired apoptotic cell clearance exacerbates experimental asthma. The second specific aim is to determine whether Mfge8 regulates the severity of asthma through modulation of the adaptive immune response. Our experimental approach involves evaluating the response of mice deficient in Mfge8 to an ovalbumin induced model of experimental asthma. We will test whether Mfge8 deficiency leads to impaired apoptotic cell clearance in vivo after asthma induction by multiple methods including quantification of the number of apoptotic cells on tissue sections, quantification of alveolar macrophages phagocytic capacity, and evaluation of whether the addition of exogenous apoptotic cells regulates the severity of the response to allergen challenge. We will also evaluate differences in the adaptive response to allergen challenge with Mfge8 deficiency. We will do this by isolating and characterizing the cytokine and lymphocyte profile from the bronchoalveolar lavage, lung parenchyma, and thoracic lymph nodes of Mfge8 deficient and control mice. These studies have the potential to identify both a novel inhibitory pathway and a new candidate molecule that may be targeted as a disease modifying agents for the treatment of allergic diseases. PUBLIC HEALTH RELEVANCE: Asthma is a chronic allergic/inflammatory disease of the lung with increasing prevalence and incomplete treatment options. Research aimed at discovering the mechanisms that lead to asthma will provide new therapeutic options. The goals of this project are work out the mechanisms by which the protein Mfge8 regulates asthma severity and to identify new therapeutic targets for the treatment of allergic diseases.