Role of MU5AC Mucins in Airway Disease

描述（由申请方提供）：气道粘液阻塞是囊性纤维化（CF）患者发病和死亡的主要原因，主要归因于粘蛋白糖蛋白（粘蛋白）的过度产生和分泌过多。持续的粘蛋白高分泌需要增加编码粘蛋白的蛋白质骨架的粘蛋白（MUC）基因的表达。最近的报道表明，CF气道在细菌感染之前具有促进粘蛋白过度产生的固有的高炎症环境。我们最近发现，IL 8通过增加粘蛋白mRNA的稳定性来增加两种气道粘蛋白基因MUC 5AC和MUC 5 B的体外表达。重要的是，在感染之前和之后CF患者的气道中升高的IL 8水平表明IL 8可以在体内启动和维持增加的粘蛋白基因表达。糖皮质激素通过多因素机制，包括抗炎蛋白或细胞因子表达的改变，在体内减少气道炎症和粘蛋白的产生。GC还在体外降低粘蛋白基因表达。更好地理解促炎和抗炎介质对粘蛋白基因的调节，以及CF肺中炎性介质的个体发生，最终应导致规避CF气道中粘蛋白基因表达增加和粘液阻塞的治疗。为实现这一目标，提出了三个目标。在目的1中，将通过EMSA、突变分析、转染测定和基因表达分析来检验IL 8通过改变识别粘蛋白基因的3'非翻译区中的特异性顺式序列的RNA结合蛋白（RBP）的表达或通过介导调节或编码RBP的基因的表达来增加气道上皮细胞中粘蛋白mRNA稳定性的假设。在目的2中，将研究GC通过下调在MUC 5AC的5 '上游侧翼序列中的GC反应元件处或附近相互作用的转录因子和/或通过改变介导粘蛋白基因表达的抗炎或促炎基因的表达来降低气道上皮细胞中MUC 5AC基因表达的假设。在目标3中，将通过CF和非CF患者的呼吸道组织的基因表达阵列分析来鉴定和评估参与气道粘蛋白过度产生的候选基因，以检验CF患者中的气道粘液阻塞是CF基因缺陷的结果的假设，这导致介导气道稳态（包括粘蛋白产生）的基因的表达改变。

DESCRIPTION (provided by applicant): Airway mucus obstruction, a major cause of morbidity and mortality in cystic fibrosis (CF) patients, is largely attributed to overproduction and hypersecretion of mucin glycoproteins (mucins). Sustained mucin hypersecretion requires increased expression of mucin (MUC) genes that encode the protein backbone of mucins. Recent reports have indicated that CF airways have an intrinsically high inflammatory milieu, prior to bacterial infection, that promotes mucin overproduction. We have recently shown that IL8 increases in vitro expression of two airway mucin genes, MUC5AC and MUC5B, by increasing mucin mRNA stability. Importantly, elevated levels of IL8 in the airways of CF patients prior to and after infection suggest that IL8 can initiate and maintain increased mucin gene expression in vivo. Glucocorticoids decrease airway inflammation and mucin production in vivo by multi-factorial mechanisms, including alterations in expression of anti-inflammatory proteins or cytokines. GC also decreases mucin gene expression in vitro. A better understanding of mucin gene regulation by pro-and anti-inflammatory mediators, as well as the ontogeny of inflammatory mediators in CF lungs, should ultimately result in therapies that circumvent increased mucin gene expression and mucus obstruction in CF airways. Three aims are proposed to address this objective. In Aim 1, the hypothesis that IL8 increases mucin mRNA stability in airway epithelial cells by altering expression of RNA-binding proteins (RBP) that recognize specific cis-sequences in the 3' untranslated region of mucin genes or by mediating expressions of genes that regulate or encode RBP will be tested by EMSA, mutation analysis, transfection assays and gene expression analyses. In Aim 2, the hypothesis that GC decrease MUC5AC gene expression in airway epithelial cells by down-regulating transcriptions factors that interact at or near GC response elements in the 5'-upstream flanking sequences of MUC5AC and/or by altering expression of anti-or pro-inflammatory genes that mediate mucin gene expression will be investigated. In Aim 3, candidate genes involved in airway mucin overproduction will be identified and assessed by gene expression array profiling of respiratory tract tissues from CF and non-CF patients to test the hypothesis that airway mucus obstruction in CF patients is a consequence of the defective CF gene, which results in altered expression of genes that mediate airway homeostasis, including mucin production.