Freeman Michelle R, Sathish Venkatachalem, Manlove Logan, Wang Shengyu, Britt Rodney D, Thompson Michael A, Pabelick Christina M, Prakash Y S
Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota.
Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and.
Am J Physiol Lung Cell Mol Physiol. 2017 Aug 1;313(2):L360-L370. doi: 10.1152/ajplung.00580.2016. Epub 2017 May 18.
Airway remodeling in asthma driven by inflammation involves proliferation of epithelial cells and airway smooth muscle (ASM), as well as enhanced extracellular matrix (ECM) generation and deposition, i.e., fibrosis. Accordingly, understanding profibrotic mechanisms is important for developing novel therapeutic strategies in asthma. Recent studies, including our own, have suggested a role for locally produced growth factors such as brain-derived neurotrophic factor (BDNF) in mediating and modulating inflammation effects. In this study, we explored the profibrotic influence of BDNF in the context of asthma by examining expression, activity, and deposition of ECM proteins in primary ASM cells isolated from asthmatic vs. nonasthmatic patients. Basal BDNF expression and secretion, and levels of the high-affinity BDNF receptor TrkB, were higher in asthmatic ASM. Exogenous BDNF significantly increased ECM production and deposition, especially of collagen-1 and collagen-3 (less so fibronectin) and the activity of matrix metalloproteinases (MMP-2, MMP-9). Exposure to the proinflammatory cytokine TNFα significantly increased BDNF secretion, particularly in asthmatic ASM, whereas no significant changes were observed with IL-13. Chelation of BDNF using TrkB-Fc reversed TNFα-induced increase in ECM deposition. Conditioned media from asthmatic ASM enhanced ECM generation in nonasthmatic ASM, which was blunted by BDNF chelation. Inflammation-induced changes in MMP-2, MMP-9, and tissue inhibitor metalloproteinases (TIMP-1, TIMP-2) were reversed in the presence of TrkB-Fc. These novel data suggest ASM as an inflammation-sensitive source of BDNF within human airways, with autocrine effects on fibrosis relevant to asthma.
由炎症驱动的哮喘气道重塑涉及上皮细胞和气道平滑肌（ASM）的增殖，以及细胞外基质（ECM）生成和沉积增加，即纤维化。因此，了解促纤维化机制对于开发哮喘的新型治疗策略很重要。包括我们自己的研究在内的近期研究表明，局部产生的生长因子如脑源性神经营养因子（BDNF）在介导和调节炎症效应中发挥作用。在本研究中，我们通过检查从哮喘患者与非哮喘患者分离的原代ASM细胞中ECM蛋白的表达、活性和沉积，探讨了BDNF在哮喘背景下的促纤维化影响。哮喘ASM中基础BDNF表达和分泌以及高亲和力BDNF受体TrkB的水平更高。外源性BDNF显著增加ECM的产生和沉积，尤其是胶原蛋白-1和胶原蛋白-3（纤连蛋白较少）以及基质金属蛋白酶（MMP-2、MMP-9）的活性。暴露于促炎细胞因子TNFα显著增加BDNF分泌，特别是在哮喘ASM中，而IL-13未观察到显著变化。使用TrkB-Fc螯合BDNF可逆转TNFα诱导的ECM沉积增加。哮喘ASM的条件培养基增强了非哮喘ASM中的ECM生成，而BDNF螯合可减弱这种增强作用。在存在TrkB-Fc的情况下，炎症诱导的MMP-2、MMP-9和组织金属蛋白酶抑制剂（TIMP-1、TIMP-2）的变化被逆转。这些新数据表明ASM是人气道内对炎症敏感的BDNF来源，对与哮喘相关的纤维化具有自分泌作用。
