Neurotrophins in the Lung

哮喘气道高反应性（AHR）和气道重塑涉及气道平滑肌（ASM）增加 收缩性、质量和由炎症驱动的细胞外基质（ECM）。ASM积极分泌增长 通过自分泌/旁分泌影响调节气道结构/功能的因素。在以前的周期中，我们 确定脑源性神经营养因子（BDNF）作为一种自分泌增强的ASM衍生因子， ASM收缩、增殖和纤维化。在此范围内，我们发现了胶质源性神经营养因子 （GDNF）和相关成员neurturin（NRTN）作为新的生长因子在气道中， 炎症效应。GDNF和NRTN在神经系统中具有保护作用，但它们在神经系统中的作用微乎其微。 关于GDNF或NRTN在气道生物学或哮喘中的信息，特别是对于ASM。初步研究表明 A）人ASM响应于激动剂表达并分泌GDNF和NRTN， B）GDNF和NRTN受体Ret、GFRα1和GFRα2存在于哮喘ASM中 C）外源性GDNF和NRTN具有多效性， 对ASM的作用，增强[Ca 2 +]cyt和收缩力，促进ECM形成，以及有趣的ER应激， 线粒体分裂、线粒体Ca 2+和呼吸; D）GDNF和NRTN可以通过GFRα1相互作用。体内 在哮喘的混合变应原（MA）小鼠模型中的研究显示1）GDNF增强气道反应性; 2）Ret GDNF抑制或螯合钝化MA对AHR和重塑的影响。基于这些数据，我们提出了一个 总体假设ASM表达和GDNF配体家族的自分泌信号有助于AHR 以及哮喘的重塑。我们将通过四个目标来检验这一概念，特别关注 ASM衍生的GDNF和NRTN。我们的目标是：目标1：研究上游调控机制， GDNF与NRTN在人ASM中的比较;目的2：检查GDNF与NRTN增强ASM的机制。 炎症和哮喘背景下人ASM中的Ca 2 +/收缩性;目的3：研究机制 GDNF vs. NRTN在炎症和哮喘背景下增强人ASM重塑的机制;目的 4：使用混合的免疫组织化学方法在AHR和重塑的背景下检查GDNF与NRTN的体内重要性。 过敏原小鼠哮喘模型。目的1-3利用人上皮剥脱的ASM组织和分离的ASM 细胞从轻度或中度哮喘与非哮喘检查信号机制， 炎症介质通过以下途径增强GDNF/NRTN的产生（Aim 1）、受体和细胞内途径 这些配体影响收缩性（Aim 2）与ER应激、线粒体结构/功能和 增殖/ECM（Aim 3）。目的4将MA模型应用于GDNF相对于NRTN增强或 抑制，特别是在平滑肌中，并探讨气道结构，ECM组成， 力学临床意义在于确定ASM衍生的生长因子如GDNF或 NRTN影响哮喘病理生理学的多个方面，是有吸引力的治疗靶点。

Airway hyperreactivity (AHR) and remodeling in asthma involve increased airway smooth muscle (ASM) contractility, mass, and extracellular matrix (ECM) driven by inflammation. ASM actively secretes growth factors that modulate airway structure/function via autocrine/paracrine influences. In previous cycles, we identified brain-derived neurotrophic factor (BDNF) as an ASM-derived factor with autocrine enhancement of ASM contractility, proliferation and fibrosis. Within this purview, we discovered glial-derived neurotrophic factor (GDNF) and a related member neurturin (NRTN) as novel growth factors in the airway that promote inflammation effects. GDNF and NRTN have protective roles in the nervous system but there is minimal to no information on GDNF or NRTN in airway biology or asthma, particularly for ASM. Preliminary studies show that A) Human ASM expresses and secretes GDNF and NRTN in response to agonist, with increased release by TNFα or TGFβ and in asthmatic ASM; B) GDNF and NRTN receptors Ret, GFRα1 and GFRα2 are present in ASM with increased expression in inflammation/asthma; C) Exogenous GDNF and NRTN have pleiotropic effects on ASM, enhancing [Ca2+]cyt and contractility, promoting ECM formation, and intriguingly ER stress, mitochondrial fission, mitochondrial Ca2+ and respiration; D) GDNF and NRTN can interact via GFRα1. In vivo studies in mixed allergen (MA) mouse models of asthma show 1) GDNF enhances airway reactivity; 2) Ret inhibition or chelation of GDNF blunt MA effects on AHR and remodeling. Based on these data, we propose an overall hypothesis that ASM expression and autocrine signaling by GDNF ligand family contributes to AHR and remodeling in asthma. We will test this concept via four Aims, focusing particularly on the novel role of ASM-derived GDNF and NRTN. Our Aims are: Aim 1: To examine mechanisms of upstream regulation of GDNF vs. NRTN in human ASM; Aim 2: To examine mechanisms by which GDNF vs. NRTN enhance Ca2+/contractility in human ASM in the context of inflammation and asthma; Aim 3: To examine mechanisms by which GDNF vs. NRTN enhance remodeling in human ASM in the context of inflammation and asthma; Aim 4: To examine in vivo importance of GDNF vs. NRTN in the context of AHR and remodeling using a mixed allergen mouse model of asthma. Aims 1-3 utilize human epithelium-denuded ASM tissues and isolated ASM cells from mild or moderate asthmatics vs. non-asthmatics to examine signaling mechanisms by which inflammatory mediators enhance GDNF/NRTN production (Aim 1), the receptor and intracellular pathways by which these ligands influence contractility (Aim 2) vs. ER stress, mitochondrial structure/function and proliferation/ECM (Aim 3). Aim 4 applies the MA model to mice where GDNF vs. NRTN is enhanced or inhibited, particularly in smooth muscle and explores changes in airway structure, ECM composition, and mechanics. Clinical significance lies in establishing the role of ASM-derived growth factors such as GDNF or NRTN that influence multiple aspects of asthma pathophysiology and are appealing therapeutic targets.