气道上皮是与环境的广泛界面,需要精心策划的反应来正确调节炎症。传统上,自噬是响应外部细胞应激而触发的稳态途径,并且在慢性气道疾病中升高。最近的研究结果强调了自噬在囊泡运输和蛋白质分泌中的额外作用,暗示自噬途径在疾病中复杂的细胞反应中。Th2 细胞因子、IL-13 和 IL-4 在哮喘和其他导致慢性炎症的气道疾病中增加。此前,我们观察到 IL-13 以自噬依赖性方式增加气道上皮细胞中的活性氧 (ROS)。在这里,我们测试了我们的假设,即通过NADPH 氧化酶 DUOX1,自噬是 IL-13 介导的超氧化物产生所必需的。使用 OVA 过敏原诱导的 Th2 介导的炎症小鼠模型,我们观察到肺中 IL-13 和 IL-4 含量升高,并伴有自噬体水平升高(通过 LC3BII 蛋白水平和免疫染色测定)。在 OVA 攻击的肺中,ROS 水平升高,DUOX1 表达增加 70 倍。为了研究自噬和 ROS 在气道上皮中的作用,我们用 IL-13 或 IL-4 处理原代人气管支气管上皮细胞。长时间的 7 天治疗会增加自噬体的形成和降解,而短暂的激活则没有效果。在平行培养条件下,通过电子顺磁共振 (EPR) 光谱测定,IL-13 和 IL-4 增加了细胞内超氧化物水平。IL-13 激活时间延长会增加位于顶膜的 DUOX1。通过 siRNA 沉默 DUOX1 可减弱 IL-13 介导的超氧化物增加,但不会降低自噬活性。值得注意的是,自噬调节蛋白 ATG5 的消耗显着减少了超氧化物,而不会降低 DUOX1 总水平。然而,ATG5 的耗尽会减少 DUOX1 在顶膜的定位。研究结果表明,非典型自噬活性调节 Th2 炎症期间细胞内超氧化物产生所需的 DUOX1 依赖性定位。因此,在慢性 Th2 炎症性气道疾病中,自噬蛋白可能是细胞内持续产生超氧化物的原因。
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Autophagy regulates DUOX1 localization and superoxide production in airway epithelial cells during chronic IL-13 stimulation
The airway epithelium is a broad interface with the environment, mandating well-orchestrated responses to properly modulate inflammation. Classically, autophagy is a homeostatic pathway triggered in response to external cellular stresses, and is elevated in chronic airway diseases. Recent findings highlight the additional role of autophagy in vesicle trafficking and protein secretion, implicating autophagy pathways in complex cellular responses in disease. Th2 cytokines, IL-13 and IL-4, are increased in asthma and other airway diseases contributing to chronic inflammation. Previously, we observed that IL-13 increases reactive oxygen species (ROS) in airway epithelial cells in an autophagy-dependent fashion. Here, we tested our hypothesis that autophagy is required for IL-13-mediated superoxide production via the NADPH oxidase DUOX1. Using a mouse model of Th2-mediated inflammation induced by OVA-allergen, we observed elevated lung amounts of IL-13 and IL-4 accompanied by increased autophagosome levels, determined by LC3BII protein levels and immunostaining. ROS levels were elevated and DUOX1 expression was increased 70-fold in OVA-challenged lungs. To address the role of autophagy and ROS in the airway epithelium, we treated primary human tracheobronchial epithelial cells with IL-13 or IL-4. Prolonged, 7-day treatment increased autophagosome formation and degradation, while brief activation had no effect. Under parallel culture conditions, IL-13 and IL-4 increased intracellular superoxide levels as determined by electron paramagnetic resonance (EPR) spectroscopy. Prolonged IL-13 activation increased DUOX1, localized at the apical membrane. Silencing DUOX1 by siRNA attenuated IL-13-mediated increases in superoxide, but did not reduce autophagy activities. Notably, depletion of autophagy regulatory protein ATG5 significantly reduced superoxide without diminishing total DUOX1 levels. Depletion of ATG5, however, diminished DUOX1 localization at the apical membrane. The findings suggest non-canonical autophagy activity regulates DUOX1-dependent localization required for intracellular superoxide production during Th2 inflammation. Thus, in chronic Th2 inflammatory airway disease, autophagy proteins may be responsible for persistent intracellular superoxide production.