Neurotrophins in the Lung

描述(由申请人提供)：哮喘的气道重塑涉及纤维化增加、气道平滑肌(ASM)增殖和迁移。炎症推动重塑，但ASM通过分泌因子、调节细胞外基质(ECM)组成和促进增殖/迁移发挥积极作用。因此，了解炎症导致重塑的机制是新的治疗策略的关键。我们之前的资助周期强调了神经营养因子脑源性神经营养因子(BDNF)的新作用，表明BDNF增强ASM[Ca~(2+)]i和收缩能力，增强炎症的影响。我们的研究表明，ASM不仅是BDNF的靶点，也是BDNF的来源。这项资助的第一次更新的重点是了解ASM来源的BDNF在哮喘背景下炎症诱导的呼吸道结构和功能变化中的自分泌/旁分泌作用。根据初步数据，我们认为BDNF在重塑过程中起着关键作用。在这里，BDNF可能与基质金属蛋白酶(MMPs)的基质金属蛋白酶(MMPs)有关，因为它们在分解分泌的BDNF中发挥作用，而BDNF反过来调节MMPs的数据有限。我们认为BDNF和MMPs在炎症刺激下形成一个相互作用的前馈环路，BDNF介导和调控炎症对ECM的产生和ASM的增殖/迁移的影响。与哮喘相关的初步数据显示，BDNF在哮喘人气道和过敏性哮喘小鼠模型中的表达和重塑作用增强。因此，我们的总体假设是ASM来源的BDNF是炎症诱导的哮喘气道重塑的核心，影响ECM的组成和ASM的增殖和迁移。在拟议的研究中，我们将通过四个特定的目标来测试这一主题：目标1：检测炎症促进人类呼吸道表达和释放的机制；目标2：检测炎症对人ASM产生ECM的炎症影响的机制；目标3：检测ASM衍生的BDNF和ASM衍生的BDNF增强炎症效应对人ASM增殖和迁移的机制；目标4：在体内检测改变的BDNF信号对混合变应原小鼠模型气道重塑的影响。AIMS 1-3将利用来自轻度或中度哮喘患者和非哮喘患者的人去上皮ASM组织和细胞来检测细胞因子(TNF和IL-13)对BDNF的增强(Aim 1)，重叠和不同的信号机制，通过这些机制介导和调节细胞因子对基质金属蛋白酶-2和基质金属蛋白酶-9、细胞外基质蛋白纤维连接蛋白和胶原的影响(目标2)，以及在细胞外基质成分改变的情况下促进血管外基质的增殖和迁移(目标3)。体外数据将在体内整合到AIM 4中的混合变应原小鼠哮喘模型中，其中BDNF受体的激活将在转基因TrkB敲击小鼠中被抑制。我们研究的临床意义在于，一种对重塑具有多效性的“上游”机制可能被靶向地限制哮喘的这一不可逆转的特征。ASM来源的BDNF

DESCRIPTION (provided by applicant): Airway remodeling in asthma involves increased fibrosis, airway smooth muscle (ASM) proliferation and migration. Inflammation drives remodeling, but ASM actively contributes by secreting factors, regulating extracellular matrix (ECM) composition and enhancing proliferation/migration. Accordingly, understanding mechanisms by which inflammation produces remodeling is key to novel therapeutic strategies. Our previous grant cycle highlighted the novel role of the neurotrophin brain-derived neurotrophic factor (BDNF), showing that BDNF enhances ASM [Ca2+]I and contractility, potentiating the effects of inflammation. Our studies now show that ASM is not only a target, but also a source of BDNF. The focus of the first renewal of this grant is to understand the autocrine/paracrine role of ASM-derived BDNF in inflammation-induced changes to airway structure and function in the context of asthma. Based on preliminary data, we believe that BDNF is a key player in remodeling. Here, BDNF may be linked to the matrix metalloproteinases (MMPs) MMP-2 and MMP-9, given their role in cleaving secreted BDNF, and limited data that BDNF conversely regulates MMPs. We propose that BDNF and MMPs form a mutually interactive, feed-forward loop stoked by inflammation, and that BDNF mediates and modulates inflammation effects on ECM production and ASM proliferation/migration. Relevant to asthma, preliminary data show that BDNF expression and effects on remodeling are enhanced in asthmatic human airway, and in a mouse model of allergic asthma. Accordingly, our overall hypothesis is that ASM-derived BDNF is central to inflammation-induced airway remodeling in asthma, affecting ECM composition and ASM proliferation and migration. In the proposed studies, we will test this theme via four Specific Aims: Aim 1: To examine mechanisms by which inflammation enhances expression and release in human airways; Aim 2: To examine the mechanisms by which potentiates inflammation effects on ECM production by human ASM; Aim 3: To examine ASM-derived BDNF ASM-derived BDNF the mechanisms by which ASM-derived BDNF potentiates inflammation effects on human ASM proliferation and migration; Aim 4: To examine in vivo effects of altered BDNF signaling on airway remodeling in a mixed allergen mouse model. Aims 1-3 will utilize human epithelium-denuded ASM tissues and cells from mild or moderate asthmatics vs. non-asthmatics to examine cytokine (TNF¿ vs. IL-13) enhancement of BDNF (Aim 1), overlapping vs. distinct signaling mechanisms by which mediates and modulates cytokine effects on MMP-2 and MMP-9, the ECM proteins fibronectin and collagen (Aim 2), and enhancement of ASM proliferation and migration in the setting of altered ECM composition (Aim 3). In vitro data will be integrated in vivo in Aim 4 in a mixed allergen mouse asthma model where BDNF receptor activation will be inhibited in a transgenic TrkB knockin mouse. The clinical significance of our studies lies in the potential that an "upstream" mechanism with pleiotropic effects on remodeling can be targeted to limit this irreversible feature of asthma. ASM-derived BDNF