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Crystalline silica particles cause rapid NLRP3-dependent mitochondrial depolarization and DNA damage in airway epithelial cells

Authors
  • Wu, Rongrong1
  • Högberg, Johan1
  • Adner, Mikael1
  • Ramos-Ramírez, Patricia1
  • Stenius, Ulla1
  • Zheng, Huiyuan1
  • 1 Institute of Environmental Medicine, Karolinska Institutet, Stockholm, SE-17177, Sweden , Stockholm (Sweden)
Type
Published Article
Journal
Particle and Fibre Toxicology
Publisher
BioMed Central
Publication Date
Aug 10, 2020
Volume
17
Issue
1
Identifiers
DOI: 10.1186/s12989-020-00370-2
Source
Springer Nature
Keywords
License
Green

Abstract

BackgroundRespirable crystalline silica causes lung carcinomas and many thousand future cancer cases are expected in e.g. Europe. Critical questions are how silica causes genotoxicity in the respiratory epithelium and if new cases can be avoided by lowered permissible exposure levels. In this study we investigate early DNA damaging effects of low doses of silica particles in respiratory epithelial cells in vitro and in vivo in an effort to understand low-dose carcinogenic effects of silica particles.ResultsWe find DNA damage accumulation already after 5–10 min exposure to low doses (5 μg/cm2) of silica particles (Min-U-Sil 5) in vitro. DNA damage was documented as increased levels of γH2AX, pCHK2, by Comet assay, AIM2 induction, and by increased DNA repair (non-homologous end joining) signaling. The DNA damage response (DDR) was not related to increased ROS levels, but to a NLRP3-dependent mitochondrial depolarization. Particles in contact with the plasma membrane elicited a Ser198 phosphorylation of NLRP3, co-localization of NLRP3 to mitochondria and depolarization. FCCP, a mitochondrial uncoupler, as well as overexpressed NLRP3 mimicked the silica-induced depolarization and the DNA damage response. A single inhalation of 25 μg silica particles gave a similar rapid DDR in mouse lung. Biomarkers (CC10 and GPRC5A) indicated an involvement of respiratory epithelial cells.ConclusionsOur findings demonstrate a novel mode of action (MOA) for silica-induced DNA damage and mutagenic double strand breaks in airway epithelial cells. This MOA seems independent of particle uptake and of an involvement of macrophages. Our study might help defining models for estimating exposure levels without DNA damaging effects.

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