ROS generation is involved in titanium dioxide nanoparticle‐induced AP‐1 activation through p38 MAPK and ERK pathways in JB6 cells

• Published in: Environmental toxicology 2022-02, Vol.37 (2), p.237-244
• Main Authors: Kong, Lu, Barber, Tabatha, Aldinger, Joni, Bowman, Linda, Leonard, Stephen, Zhao, Jinshun, Ding, Min
• Format: Article
• Language: English
• Subjects: activator protein‐1 (AP‐1); Animal models; Animals; Cell proliferation; Cells; Electron paramagnetic resonance; Electron spin; Electron spin resonance; Extracellular; Extracellular signal-regulated kinase; Extracellular Signal-Regulated MAP Kinases; Genes; Genetic transformation; Hydroxyl radicals; Inflammation; JB6 cells; JNK Mitogen-Activated Protein Kinases; JNK protein; Kinases; MAP kinase; MAP Kinase Signaling System; Metabolic pathways; Mice; mitogen‐activated protein kinases (MAPKs); Nanoparticles; Nanoparticles - toxicity; Neoplasms; p38 Mitogen-Activated Protein Kinases - metabolism; Proliferation; Protein kinase; Proteins; Rats; Reactive Oxygen Species; reactive oxygen species (ROS); Signal transduction; Spin resonance; Sun screens; Titanium; Titanium dioxide; titanium dioxide nanoparticles (TiO2 NPs); Transcription Factor AP-1 - genetics; Transcription Factor AP-1 - metabolism; Transgenic mice; Tumors; Western blotting
• ISSN: 1520-4081; 1522-7278
• DOI: 10.1002/tox.23393

Titanium dioxide (TiO2) is generally regarded as a nontoxic and nongenotoxic white mineral, which is mainly applied in the manufacture of paper, paint, plastic, sunscreen lotion and other products. Recently, TiO2 nanoparticles (TiO2 NPs) have been demonstrated to cause chronic inflammation and lung tumor formation in rats, which may be associated with the particle size of TiO2. Considering the important role of activator protein‐1 (AP‐1) in regulating multiple genes involved in the cell proliferation and inflammation and the induction of neoplastic transformation, we aimed to evaluate the potency of TiO2 NPs (≤ 20 nm) on the activation of AP‐1 signaling pathway and the generation of reactive oxygen species (ROS) in a mouse epidermal cell line, JB6 cells. MTT, electron spin resonance (ESR), AP‐1 luciferase activity assay in vitro and in vivo, and Western blotting assay were used to clarify this problem. Our results indicated that TiO2 NPs dose‐dependently caused the hydroxyl radical (·OH) generation and sequentially increased the AP‐1 activity in JB6 cells. Using AP‐1‐luciferase reporter transgenic mice models, an obvious increased AP‐1 activity was detected in dermal tissue after exposure to TiO2 NPs for 24 h. Interestingly, TiO2 NPs increased the AP‐1 activity via stimulating the expression of mitogen‐activated protein kinases (MAPKs) family members, including extracellular signal‐regulated protein kinases (ERKs), p38 kinase, and C‐Jun N‐terminal kinases (JNKs). Of note, the AP‐1 activation induced by TiO2 NPs could be blocked by specific inhibitors (SB203580, PD98059, and SP 600125, respectively) that inhibit ERKs and p38 kinase but not JNKs. These findings indicate that ROS generation is involved in TiO2 NPs‐induced AP‐1 activation mediated by MAPKs signal pathway.