Lubamba Bob A, Jones Lisa C, O'Neal Wanda K, Boucher Richard C, Ribeiro Carla M P
1 Marsico Lung Institute/Cystic Fibrosis Research Center.
2 Department of Medicine, and.
Am J Respir Crit Care Med. 2015 Dec 15;192(12):1449-61. doi: 10.1164/rccm.201504-0657OC.
Alveolar macrophages (AMs) play a key role in host defense to inhaled bacterial pathogens, in part by secreting inflammatory mediators. Cystic fibrosis (CF) airways exhibit a persistent, robust inflammatory response that may contribute to the pathophysiology of CF. Recent findings have linked endoplasmic reticulum stress responses mediated by inositol-requiring enzyme 1α-dependent messenger RNA splicing (activation) of X-box-binding protein-1 (XBP-1s) to inflammation in peripheral macrophages. However, the role of XBP-1s in CF AM function is not known.
To evaluate inflammatory responses of AMs from chronically infected/inflamed human CF lungs and test whether XBP-1s is required for AM-mediated inflammation.
Basal and LPS-induced inflammatory responses were evaluated in primary cultures of non-CF versus CF AMs. XBP-1s was measured and its function was evaluated in AMs using 8-formyl-7-hydroxy-4-methylcoumarin (4μ8C), an inhibitor of inositol-requiring enzyme 1α-dependent XBP-1s, and in THP-1 cells stably expressing XBP-1 shRNA, XBP-1s, or a dominant-negative XBP-1.
CF AMs exhibited exaggerated basal and LPS-induced production of tumor necrosis factor-α and IL-6, and these responses were coupled to increased levels of XBP-1s. In non-CF and CF AMs, LPS-induced cytokine production was blunted by 4µ8C. A role for XBP-1s in AM inflammatory responses was further established by data from dTHP-1 cells indicating that expression of XBP-1 shRNA reduced XBP-1s levels and LPS-induced inflammatory responses; and LPS-induced inflammation was up-regulated by expression of XBP-1s and inhibited by dominant-negative XBP-1.
These findings suggest that AMs contribute to the robust inflammation of CF airways via an up-regulation of XBP-1s-mediated cytokine production.
肺泡巨噬细胞（AMs）在宿主抵御吸入性细菌病原体的过程中发挥关键作用，部分原因是通过分泌炎症介质。囊性纤维化（CF）气道表现出持续、强烈的炎症反应，这可能有助于CF的病理生理学发展。最近的研究发现，由肌醇需求酶1α依赖性信使核糖核酸剪接（激活）X盒结合蛋白1（XBP-1s）介导的内质网应激反应与外周巨噬细胞中的炎症有关。然而，XBP-1s在CF AM功能中的作用尚不清楚。
评估来自慢性感染/炎症的人类CF肺部的AMs的炎症反应，并测试XBP-1s是否是AM介导的炎症所必需的。
在非CF与CF AM的原代培养物中评估基础和脂多糖（LPS）诱导的炎症反应。使用8-甲酰基-7-羟基-4-甲基香豆素（4μ8C）（一种肌醇需求酶1α依赖性XBP-1s的抑制剂）在AMs中测量XBP-1s并评估其功能，在稳定表达XBP-1短发夹RNA（shRNA）、XBP-1s或显性负性XBP-1的THP-1细胞中进行评估。
CF AM表现出基础和LPS诱导的肿瘤坏死因子-α和IL-6产生增加，并且这些反应与XBP-1s水平升高相关。在非CF和CF AM中，4μ8C使LPS诱导的细胞因子产生减弱。来自显性负性THP-1细胞的数据进一步证实了XBP-1s在AM炎症反应中的作用，表明XBP-1 shRNA的表达降低了XBP-1s水平和LPS诱导的炎症反应；LPS诱导的炎症通过XBP-1s的表达上调，并被显性负性XBP-1抑制。
这些发现表明，AMs通过上调XBP-1s介导的细胞因子产生，促进了CF气道的强烈炎症反应。
