In vitro and in vivo genotoxic effects of straight versus tangled multi-walled carbon nanotubes

Abstract

Some multi-walled carbon nanotubes (MWCNTs) induce mesothelioma in rodents, straight MWCNTs showing a more pronounced effect than tangled MWCNTs. As primary and secondary genotoxicity may play a role in MWCNT carcinogenesis, we used a battery of assays for DNA damage and micronuclei to compare the genotoxicity of straight (MWCNT-S) and tangled MWCNTs (MWCNT-T) in vitro (primary genotoxicity) and in vivo (primary or secondary genotoxicity). C57Bl/6 mice showed a dose-dependent increase in DNA strand breaks, as measured by the comet assay, in lung cells 24 h after a single pharyngeal aspiration of MWCNT-S (1–200 μg/mouse). An increase was also observed for DNA strand breaks in lung and bronchoalveolar lavage (BAL) cells and for micronucleated alveolar type II cells in mice exposed to aerosolized MWCNT-S (8.2–10.8 mg/m³) for 4 d, 4 h/d. No systemic genotoxic effects, assessed by the γ-H2AX assay in blood mononuclear leukocytes or by micronucleated polychromatic erythrocytes (MNPCEs) in bone marrow or blood, were observed for MWCNT-S by either exposure technique. MWCNT-T showed a dose-related decrease in DNA damage in BAL and lung cells of mice after a single pharyngeal aspiration (1–200 μg/mouse) and in MNPCEs after inhalation exposure (17.5 mg/m³). In vitro in human bronchial epithelial BEAS-2B cells, MWCNT-S induced DNA strand breaks at low doses (5 and 10 μg/cm²), while MWCNT-T increased strand breakage only at 200 μg/cm². Neither of the MWCNTs was able to induce micronuclei in vitro. Our findings suggest that both primary and secondary mechanisms may be involved in the genotoxicity of straight MWCNTs.

• Comet assay
• DNA damage
• genotoxicity
• micronuclei
• multi-walled carbon nanotubes

Acknowledgements

The authors would like to thank Dr. Lison at the Université catholique de Louvain (Belgium) for kindly providing us with tungsten carbide–cobalt mixture.

Declaration of interest

The authors report that they have no conflicts of interests. This study was funded by the Finnish Work Environment Fund (Grant nos. 109137 and 112248) and the European Commission under Grant agreement FP7-211464-2 (NANODEVICE). The work for the exposure characterization at NRCWE (K. I. Kling and K. A. Jensen) was conducted under the Danish Centre for Nanosafety (Grant agreement no. 20110092173/3) funded by the Danish Working Environment Research Fund.

Supplementary material available online