Epithelial JNK-TGFb1 Signaling Axis in Airway Remodeling

描述（由申请人提供）：上皮下纤维化的发展是哮喘气道重塑的一个重要特征，上皮细胞在其中的关键作用正在显现。促纤维化细胞因子转化生长因子β -1 （TGF-¿1）在纤维化发生中起着重要作用。TGF-¿1信号转导的结果高度依赖于与其他信号通路的配合。我们最近发现了c- jun - n末端激酶1 （JNK1）在增强TGF- 1的促纤维化作用中的关键作用，与气道上皮细胞（EMT）间充质转化的原因有关。具体来说，我们已经证明：1)JNK主要在卵清蛋白致敏和激发小鼠的气道上皮中被激活；2)缺乏JNK1 （JNK1-/-）的小鼠在卵清蛋白、TGF-¿1或博来霉素作用下不能诱导间充质基因或发生纤维化；3) TGF-¿1诱导的EMT需要JNK1，通过JNK1依赖的连接域SMAD3的磷酸化。这些数据表明，气道上皮来源的jnk1依赖性信号在协调气道纤维化中起关键作用。本文提出的假设是，在屋尘螨诱导的气道疾病中，通过促进上皮-间质转化（EMT），气道上皮中JNK1的激活是上皮下纤维化发展所必需的。具体来说，我们假设JNK1通过在连接域磷酸化SMAD3来增强TGF-¿1信号，从而增强SMAD3降低let-7 microRNA （miRNA）表达的能力。let-7 miRNA的减少反过来增强了高迁移率组A2 （HMGA2）基因的表达，HMGA2基因是EMT的近端调节因子，导致上皮下胶原沉积。在Specific Aim 1中，我们将确定连接域中依赖jnk1的SMAD3磷酸化在抑制肺上皮细胞中let-7 microRNA （miRNA）以及随后增强高迁移率组A2 （HMGA2）基因中的重要性。我们还将分析哮喘患者支气管上皮细胞中let-7 miRNA和HMGA2的表达，并与对照组进行比较，确定哮喘和正常上皮细胞对TGF-¿1诱导的EMT的易感性，并阐明JNK和SMAD3在其中的作用。在Specific Aim 2中，我们将阐明气道上皮内JNK1的激活是否在室内尘肺诱导的上皮向间质转化、气道纤维化和体内呼吸机制改变的协调过程中至关重要，并利用全球缺乏JNK1的小鼠，或细支气管上皮内特异性缺乏JNK1的小鼠，进行cre重组酶介导的消融。在Specific Aim 3中，我们将通过创建TetOP-FLAG-SMAD3-EPSM小鼠和tetop - flag -SMAD3野生型（WT）转基因小鼠作为对照，确定SMAD3连接子结构域磷酸化的重要性，以及由此导致的let-7g miRNA减少在促进上皮向间质转化、气道纤维化和体内呼吸机制改变方面的作用。我们将评估let-7g pre-miRNA递送对hdm诱导的重塑的影响。

DESCRIPTION (provided by applicant): The development of subepithelial fibrosis represents an important feature of airway remodeling in asthma, and a critical role for epithelial cells herei is emerging. The pro-fibrotic cytokine, transforming growth factor beta-1 (TGF-¿1) plays a cardinal role in fibrogenesis. The outcome of TGF-¿1 signaling is highly dependent upon cooperation with other signaling pathways. We have recently identified a critical role for c-Jun-N-terminal- kinase 1 (JNK1) in augmenting the pro-fibrotic effects of TGF-¿1, in association with the causation of a mesenchymal transition of airway epithelial cells (EMT). Specifically, we have demonstrated that: 1) JNK is predominantly activated in airway epithelium from ovalbumin-sensitized and challenged mice; 2) mice lacking JNK1 (JNK1-/-) fail to induce mesenchymal genes or develop fibrosis in response to ovalbumin, TGF-¿1, or bleomycin; 3) TGF-¿1-induced EMT requires JNK1, through JNK1-dependent phosphorylation of SMAD3 in the linker domain. These data, suggest a critical role of airway epithelium-derived JNK1-dependent signals in orchestrating airways fibrosis. The hypothesis addressed herein is that activation of JNK1 in the airway epithelium is required for the development of subepithelial fibrosis in house dust mite- induced airways disease by promoting epithelial-mesenchymal transition (EMT). Specifically, we hypothesize that JNK1 enhances TGF-¿1 signaling via phosphorylation of SMAD3 in the linker domain, which enhances the competency of SMAD3 to decrease expression of let-7 microRNA (miRNA). Decreases in let-7 miRNA in turn enhances expression of the high mobility group A2 (HMGA2) gene, a proximal regulator of EMT, events that lead to subepithelial collagen deposition. In Specific Aim 1 we will determine the importance of JNK1-dependent phosphorylation of SMAD3 in the linker domain in repressing let-7 microRNA (miRNA) in lung epithelial cells, and subsequent enhancement of the high mobility group A2 (HMGA2) gene. We will also analyze expression of let-7 miRNA and HMGA2 in bronchial epithelial cells derived from asthmatics, compared to controls, and determine the susceptibility of asthmatic and normal epithelial cells to TGF-¿1-induced EMT, and elucidate the role of JNK and SMAD3 therein. In Specific Aim 2 we will elucidate whether activation of JNK1 within the airway epithelium is critical in the orchestration of house dust mite-induced epithelial to mesenchymal transition, airways fibrosis, and altered respiratory mechanics in vivo, and utilize mice that globally lack JNK1, or specifically within the bronchiolar epithelium, following and CRE-recombinase mediated ablation. In Specific Aim 3 we will determine the importance of SMAD3 linker domain phosphorylation and resultant decreases of let-7g miRNA in promoting epithelial to mesenchymal transition, airways fibrosis, and altered respiratory mechanics in vivo, via the creation of TetOP-FLAG-SMAD3-EPSM mice, which are refractory to phosphorylation by JNK in the linker domain, and TetOP-FLAG-SMAD3-wild type (WT) transgenic mice, as a control. We will assess the impact of delivery of let-7g pre-miRNA on HDM-induced remodeling.