Kim Gui Ok, Choi Yoon Seok, Bae Chang Hoon, Song Si-Youn, Kim Yong-Dae
a Graduate School of Health and Welfare, CHA University , Pocheon , Republic of Korea.
b Department of Otorhinolaryngology-Head and Neck Surgery, College of Medicine , Yeungnam University , Daegu , Republic of Korea.
Inhal Toxicol. 2017 Jan;29(1):1-9. doi: 10.1080/08958378.2016.1267282.
Titanium dioxide nanoparticles (TiO NPs) are utilized with growing frequency for a wide variety of industrial applications. Recently, acute and chronic exposures to TiO NPs have been found to induce inflammatory response in the human respiratory tract. However, the effect and mechanism underlying the induction of major airway mucins by TiO NPs have not been elucidated. This study was conducted to characterize the effect of TiO NPs, and the mechanism involved, on the expressions of airway mucins in human airway epithelial cells.
In NCI-H292 cells and primary cultures of normal nasal epithelial cells, the effects of TiO NPs and signaling pathway for airway mucin genes were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassays and immunoblot analysis using several specific inhibitors and small interfering RNAs (siRNAs).
TiO NPs increased MUC5B expression and activated the phosphorylations of extracellular signal-related kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). U0126 (an ERK1/2 MAPK inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited TiO NPs-induced MUC5B expression. And knockdown of ERK1, ERK2 and p38 MAPK using siRNAs significantly blocked TiO NPs-induced MUC5B mRNA expression. Furthermore, Toll-like receptor 4 (TLR4) mRNA expression was increased by TiO NPs, and knockdown by TLR4 siRNA significantly attenuated TiO NPs-induced MUC5B mRNA expression and the TiO NPs-induced phosphorylations of ERK1/2 and p38 MAPK.
These results demonstrate for the first time that TiO NPs induce MUC5B expression via TLR4-dependent ERK1/2 and p38 MAPK signaling pathways in respiratory epithelium.
二氧化钛纳米颗粒（TiO NPs）在各种工业应用中的使用频率日益增加。最近发现，急性和慢性暴露于TiO NPs会在人类呼吸道中引发炎症反应。然而，TiO NPs诱导主要气道粘蛋白的作用及其潜在机制尚未阐明。本研究旨在表征TiO NPs对人气道上皮细胞中气道粘蛋白表达的影响及其相关机制。
在NCI-H292细胞和正常鼻上皮细胞原代培养物中，使用几种特异性抑制剂和小干扰RNA（siRNAs），通过逆转录聚合酶链反应（RT-PCR）、实时PCR、酶免疫测定和免疫印迹分析，研究了TiO NPs对气道粘蛋白基因的影响及其信号通路。
TiO NPs增加了MUC5B的表达，并激活了细胞外信号调节激酶1/2（ERK1/2）和p38丝裂原活化蛋白激酶（MAPK）的磷酸化。U0126（一种ERK1/2 MAPK抑制剂）和SB203580（一种p38 MAPK抑制剂）抑制了TiO NPs诱导的MUC5B表达。使用siRNAs敲低ERK1、ERK2和p38 MAPK可显著阻断TiO NPs诱导的MUC5B mRNA表达。此外，TiO NPs增加了Toll样受体4（TLR4）mRNA的表达，而通过TLR4 siRNA敲低可显著减弱TiO NPs诱导的MUC5B mRNA表达以及TiO NPs诱导的ERK1/2和p38 MAPK的磷酸化。
这些结果首次证明，TiO NPs通过呼吸道上皮细胞中TLR4依赖的ERK1/2和p38 MAPK信号通路诱导MUC5B表达。
