Neurotrophins in the Lung

描述（由申请人提供）：哮喘气道重塑包括纤维化增加、气道平滑肌（ASM）增殖和迁移。炎症驱动重塑，但ASM通过分泌因子积极参与，调节细胞外基质（ECM）组成，增强增殖/迁移。因此，了解炎症产生重塑的机制是制定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增强了ASM [Ca2+]I和收缩性，增强了炎症的作用。我们的研究表明，ASM不仅是BDNF的靶点，也是BDNF的来源。该资助的第一次更新的重点是了解asm衍生的BDNF在哮喘炎症诱导的气道结构和功能改变中的自分泌/旁分泌作用。根据初步数据，我们认为BDNF在重塑中起关键作用。在这里，BDNF可能与基质金属蛋白酶（MMPs） MMP-2和MMP-9有关，考虑到它们在切割分泌的BDNF中的作用，以及BDNF反过来调节MMPs的有限数据。我们认为BDNF和MMPs形成了一个相互作用的前馈回路，由炎症引发，BDNF介导和调节炎症对ECM产生和ASM增殖/迁移的影响。与哮喘相关，初步数据显示，BDNF在哮喘人类气道和变应性哮喘小鼠模型中的表达和对重塑的作用增强。因此，我们的总体假设是，ASM衍生的BDNF是哮喘炎症诱导的气道重塑的核心，影响ECM组成和ASM的增殖和迁移。在拟议的研究中，我们将通过四个具体目标来验证这一主题：目标1：研究炎症增强人体气道表达和释放的机制；目的2：研究人类ASM增强炎症对ECM产生影响的机制；目的3：研究ASM-derived BDNF， ASM-derived BDNF增强炎症对人类ASM增殖和迁移影响的机制；目的4：在混合过敏原小鼠模型中研究BDNF信号改变对气道重塑的体内影响。Aims 1-3将利用轻度或中度哮喘患者与非哮喘患者的人上皮脱落的ASM组织和细胞来检测细胞因子（TNF¿vs. IL-13）对BDNF的增强（Aim 1），重叠与不同的信号机制，通过这些信号机制介导和调节细胞因子对MMP-2和MMP-9、ECM蛋白纤维连接蛋白和胶原蛋白的作用（Aim 2），以及在ECM成分改变的情况下ASM增殖和迁移的增强（Aim 3）。体外数据将在Aim 4的混合过敏原小鼠哮喘模型中整合，其中BDNF受体的激活将在转基因TrkB敲入小鼠中被抑制。我们研究的临床意义在于，有可能针对具有多效重塑作用的“上游”机制来限制哮喘的这一不可逆特征。ASM-derived脑源性神经营养因子

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