Department of Respiratory Medicine, The Affiliated Hospital of Qingdao University, Shinan, Qingdao 266071, P.R. China.
Department of Respiratory Medicine, The First Affiliated Hospital, Hainan Medical University, Haikou, Hainan 570102, P.R. China.
Int J Mol Med. 2021 May;47(5). doi: 10.3892/ijmm.2021.4914. Epub 2021 Mar 24.
Endoplasmic reticulum (ER) stress is an important reaction of airway epithelial cells in response to various stimuli, and may also be involved in the mucin secretion process. In the present study, the effect of ER stress on neutrophil elastase (NE)‑induced mucin (MUC)5AC production in human airway epithelial cells was explored. 16HBE14o‑airway epithelial cells were cultured and pre‑treated with the reactive oxygen species (ROS) inhibitor, ‑acetylcysteine (NAC), or the ER stress chemical inhibitor, 4‑phenylbutyric acid (4‑PBA), or the cells were transfected with inositol‑requiring kinase 1α (IRE1α) small interfering RNA (siRNA) or X‑box‑binding protein 1 (XBP1) siRNA, respectively, and subsequently incubated with NE. The results obtained revealed that NE increased ROS production in the 16HBE14o‑cells, with marked increases in the levels of ER stress‑associated proteins, such as glucose‑regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), phosphorylated protein kinase R‑like endoplasmic reticulum kinase (pPERK) and phosphorylated (p)IRE1α. The protein and mRNA levels of spliced XBP1 were also increased, and the level of MUC5AC protein was notably increased. The ROS scavenger NAC and ER stress inhibitor 4‑PBA were found to reduce ER stress‑associated protein expression and MUC5AC production and secretion. Further analyses revealed that MUC5AC secretion was also attenuated by IRE1α and XBP1 siRNAs, accompanied by a decreased mRNA expression of spliced XBP1. Taken together, these results demonstrate that NE induces ER stress by promoting ROS production in 16HBE14o‑airway epithelial cells, leading to increases in MUC5AC protein production and secretion via the IRE1α and XBP1 signaling pathways.
内质网（ER）应激是气道上皮细胞对各种刺激的重要反应，也可能参与黏液素（MUC）5AC 的分泌过程。本研究探讨了 ER 应激对人气道上皮细胞中性粒细胞弹性蛋白酶（NE）诱导的 MUC5AC 产生的影响。培养 16HBE14o-气道上皮细胞，并使用活性氧（ROS）抑制剂乙酰半胱氨酸（NAC）或 ER 应激化学抑制剂 4-苯丁酸（4-PBA）预处理细胞，或转染肌醇需求激酶 1α（IRE1α）小干扰 RNA（siRNA）或 X 盒结合蛋白 1（XBP1）siRNA，然后与 NE 孵育。结果表明，NE 增加了 16HBE14o-细胞中的 ROS 产生，与 ER 应激相关蛋白（如葡萄糖调节蛋白 78（GRP78）、激活转录因子 6（ATF6）、磷酸化蛋白激酶 R 样内质网激酶（pPERK）和磷酸化（p）IRE1α）的水平显著增加。 spliced XBP1 的蛋白和 mRNA 水平也增加，MUC5AC 蛋白水平明显增加。ROS 清除剂 NAC 和 ER 应激抑制剂 4-PBA 可降低 ER 应激相关蛋白表达和 MUC5AC 的产生和分泌。进一步分析表明，IRE1α 和 XBP1 siRNA 也可减弱 MUC5AC 分泌，同时 spliced XBP1 的 mRNA 表达降低。综上所述，这些结果表明，NE 通过促进 16HBE14o-气道上皮细胞中 ROS 的产生诱导 ER 应激，导致 MUC5AC 蛋白的产生和分泌增加，这是通过 IRE1α 和 XBP1 信号通路实现的。
