Role of MUC5AC Mucins in Airway Disease

描述(申请人提供)：分泌型粘蛋白糖蛋白是肺粘液的主要大分子成分，包裹和保护呼吸道。在急性和慢性肺部疾病中，粘蛋白过度分泌和过度产生，从而导致呼吸道粘液阻塞，并导致哮喘和其他慢性阻塞性肺疾病患者的疾病发病率和死亡率。MUC5AC是一种主要的呼吸道粘蛋白，定位于传导气道上皮中的杯状细胞，在哮喘气道中高表达。我们的长期目标是在分子水平上更好地确定MUC5AC粘蛋白基因表达的激活和抑制之间的联系，以便为开发新的药物来规避粘蛋白过度生产提供更好的基础。在肺细胞中，MUC5AC基因可以在转录上被激活(IL-1)或被抑制(Dex)，在病理和药理学上是相关的。然而，对调节粘蛋白基因顺式抑制的机制知之甚少，这些机制可能涉及染色质的重塑、更高水平的基因调控或粘蛋白基因的染色质修饰。在这一应用中，我们将重点研究Dex介导的染色质重塑对MUC5AC基因表达的顺式抑制作用，以及IL-1β诱导的染色质修饰上调MUC5AC基因表达的作用。我们将从三个方面研究这些事件在肺细胞中的作用机制。它们将在体外分化的NHBE细胞和A549细胞中进行评估，并在过敏性哮喘小鼠模型和人体组织中进行体内评估。在目标1中，我们将在染色质水平上表征GR诱导的MUC5AC顺式抑制，以验证Dex通过染色质重塑顺式抑制MUC5AC基因表达的假说。在目标2中，我们将对IL-1β诱导的MUC5AC基因的激活进行表征，以检验MUC5AC基因属于一类带有启动子的基因，这些启动子具有调节和延迟可及性，例如，启动子需要在染色质结构中进行刺激依赖的修改，以使转录因子位点可被转录。在目标3中，我们将确定炎症介质(IL-1)和抗炎药(Dex)是否介导了暴露于这两种介质的肺细胞中对MUC5AC染色质结构的相反影响。这将最终影响糖皮质激素治疗炎症性肺部疾病期间MUC5AC粘蛋白的产生。与公共卫生相关。在慢性肺部疾病中，粘蛋白过度分泌和过度产生，从而导致呼吸道粘液阻塞，并导致哮喘和其他慢性阻塞性肺疾病患者的疾病发病率和死亡率。MUC5AC是一种主要的肺粘蛋白，在哮喘的呼吸道中过度产生。已证明MUC5AC基因在肺细胞中被转录激活(IL-1)或被抑制(Dex)，这与病理和药物相关。了解糖皮质激素抑制MUC5AC基因表达的机制将有助于理解为什么类固醇维持对于减少严重哮喘患者的恶化次数和严重程度很重要，并对制定粘蛋白过度产生的肺部疾病的治疗干预措施至关重要。

DESCRIPTION (provided by applicant): Secretory mucin glycoproteins are the major macromolecular component of lung mucus, which coats and protects the respiratory tract. Mucins are hypersecreted and overproduced in acute and chronic lung disease, thereby contributing to mucus obstruction in the airways and to disease morbidity and mortality in patients with asthma and other chronic obstructive pulmonary diseases. MUC5AC, one of the major airway mucins, is localized to goblet cells in the conducting airway epithelium, and is overexpressed in asthmatic airways. Our long term objective is to better define the link between activation and repression of MUC5AC mucin gene expression at the molecular level in order to provide a better foundation for developing novel pharmaceutical agents to circumvent mucin overproduction. The MUC5AC gene can be transcriptionally activated (IL-1¿) or repressed (Dex) in lung cells in a pathologically and pharmacologically relevant fashion. However, little is known about mechanisms that regulate mucin gene cis-repression, which likely involve remodeling of chromatin, a higher level of gene regulation, or about chromatin modification of mucin genes. In this application, we will focus on Dex-mediated chromatin remodeling in cis- repression of MUC5AC gene expression and on IL-1¿-induced chromatin modifications in upregulating MUC5AC gene expression. We will investigate mechanisms underlying these events in lung cells in three Aims. They will be evaluated in vitro in differentiated NHBE cells and A549 cells and in vivo in a murine model of allergic asthma and in human tissue. In Aim 1 we will characterize the GR-induced cis-repression of MUC5AC at the chromatin level to test the hypothesis that Dex cis-represses MUC5AC gene expression by chromatin remodeling. In Aim 2 we will characterize the IL-1¿-induced activation of the MUC5AC gene to test the hypothesis that the MUC5AC gene belongs to a class of genes with promoters with regulated and late accessibility, e.g. promoters that require stimulus-dependent modifications in chromatin structure to make transcription factors sites accessible for transcription. In Aim 3 we will determine whether inflammatory mediators (IL-1¿) and anti-inflammatory agents (Dex) mediate opposing effects on MUC5AC chromatin structure in lung cells exposed to both mediators. This would ultimately impact on MUC5AC mucin production during corticosteroid treatment of inflammatory lung disease. PUBLIC HEALTH RELEVANCE. Mucins are hypersecreted and overproduced in chronic lung disease, thereby contributing to mucus obstruction in the airways and to disease morbidity and mortality in patients with asthma and other chronic obstructive pulmonary diseases. MUC5AC is a major lung mucin and is overproduced in asthmatic airways. The MUC5AC gene has been shown to be transcriptionally activated (IL-1¿) or repressed (Dex) in lung cells in a pathologically and pharmacologically relevant fashion. Understanding the mechanisms whereby MUC5AC gene expression is repressed by glucocorticoids will prove useful in understanding why steroid maintenance is important in reducing the number and severity of exacerbations in severe asthmatic patients and is fundamental for formulating therapeutic interventions in lung diseases with mucin overproduction.