Pathogenesis of mucous cell metaplasia in ozone-exposed airways

摘要：环境臭氧水平升高与呼吸系统疾病引起的住院人数增加有关 儿童、老年人和既往存在的粘液阻塞性呼吸道疾病患者的问题。患有疾病的患者 黏膜阻塞性呼吸道疾病经常遇到臭氧污染引起的加重，明显 粘液分泌过多和粘液阻塞。这些特征会导致临床症状的恶化和 肺功能进一步下降。然而，对疾病发生和发展的机械论理解 臭氧应激呼吸道上皮中的粘液细胞化生(MCM)仍未被研究。缺乏这样的能力 知识是制定有效的治疗策略对抗臭氧加剧的主要障碍 粘液阻塞性呼吸道疾病。我们公布的和初步的数据揭示了有趣的关系 臭氧和MCM。首先，反复接触臭氧会导致健康小鼠的MCM。第二，重复臭氧 暴露夸大慢性支气管炎样肺小鼠的MCM和粘膜阻塞性表型 疾病。这些发现提示臭氧诱导的黏膜阻塞性肺症状加重。 患者的部分原因是MCM的夸大和相关的功能缺陷 粘液纤毛自动扶梯。我们的初步数据表明，虽然IL4ra受体和IL4ra受体的mRNA表达 其配体IL-13的分泌水平在亚慢性(3周)大鼠的呼吸道中显著上调 在臭氧暴露的小鼠中，EGFR及其配体Tgfa的mRNA表达显著下调。 这些数据表明，在臭氧诱导的巨噬细胞瘤中，表皮生长因子受体和白细胞介素4受体信号通路的不同调控。 因此，重要的是要从机械上测试eGFR和IL4R调节的通路在臭氧- 裸露的MCM模型。因此，我们的中心假设是臭氧诱导的MCM独立于EGFR 信号转导，但依赖于调节呼吸道上皮细胞转分化的IL4R信号 粘液细胞。具体目标是：目标1：MCM转分化途径的勾画和表达 臭氧暴露小鼠呼吸道中与MCM相关的分子和细胞变化。为了实现这一目标，我们将 臭氧暴露下鼻腔和下呼吸道MCM相关的细胞和分子变化 老鼠。目的2：确定基底细胞和上皮细胞特异性的表皮生长因子受体和白细胞介素4受体在巨噬细胞增生性心肌病中的作用。基底细胞- 呼吸道上皮细胞特异性表皮生长因子受体和白介素4R缺陷小鼠将被用来研究它们的配体的作用 在臭氧诱导的MCM中。我们的研究结果将加强我们对 参与MCM的分子途径。最终，这些发现可能会应用于 治疗空气污染引起的MCM。

Summary: Elevated ambient ozone levels are associated with increased hospitalizations due to respiratory problems in children, the elderly, and patients with pre-existing muco-obstructive airway diseases. Patients with muco-obstructive airway diseases frequently encounter ozone pollution-induced exacerbations with marked overproduction of mucus and mucoobstruction. These features lead to the worsening of clinical symptoms and further decline in lung functions. However, the mechanistic understanding of the initiation and progression of mucous cell metaplasia (MCM) in ozone-stressed respiratory epithelium remains unexplored. Lack of such knowledge is a major obstacle in the development of effective therapeutic strategies against ozone-exacerbated muco-obstructive airway diseases. Our published and preliminary data reveal interesting relationship between ozone and MCM. First, repetitive ozone exposure results in MCM in healthy mice. Second, repetitive ozone exposure exaggerates MCM and mucoobstructive phenotype in mice with ongoing chronic bronchitis-like lung disease. These findings suggest that ozone-induced exacerbations of pulmonary symptoms in muco-obstructive patients are contributed, in part, by exaggerated MCM and associated defects in the functioning of the mucociliary escalator. Our preliminary data demonstrate that while the mRNA expression of Il4ra receptor and the secretory levels of its ligand, IL-13, were significantly upregulated in the airways of sub-chronically (3-week) ozone-exposed mice, the mRNA expression of Egfr and its ligands, i.e., Tgfa, were significantly downregulated. These data indicate differential regulation of EGFR and IL4R signaling pathways in ozone-induced MCM. Therefore, it is important to mechanistically test the role of EGFR- versus IL4R-regulated pathways in ozone- exposed model of MCM. Accordingly, our central hypothesis is that ozone-induced MCM is independent of EGFR signaling but dependent upon IL4R signaling that regulates the transdifferentiation of airway epithelial cells to mucous cells. The specific aims are: Aim 1: To delineate MCM transdifferentiation pathway and to profile molecular and cellular changes associated with MCM in ozone-exposed murine airways. In this aim, we will profile cellular and molecular changes associated with MCM in the nasal and lower airways of ozone-exposed mice. Aim 2: Determine the role of basal- versus epithelial cell-specific EGFR and IL4R in MCM. Basal cell- and airway epithelial cell-specific EGFR- and IL4R-deficient mice will be used to study the role of their ligands in ozone-induced MCM. The findings from our studies will enhance our mechanistic understanding of the molecular pathways involved in MCM. Eventually, these findings may be applied towards the development of therapeutics against air pollution-induced MCM.