Effects of a panel of nanoparticles on mutagenicity, DNA damage, ROS levels and the cell cycle in the Muta™mouse lung epithelial

Speaker:

Nicklas Raun Jacobsen , National Research Centre for the Working Environment

Co-Author(s):

Nicklas Raun Jacobsen1, Peter Møller2, Anne Thoustrup Saber1, Corey Cohn1, Paul White3, Ulla Vogel1, Steffen Loft2, and Håkan Wallin1*
1National Research Centre for the Working Environment, Copenhagen, Denmark. 2University of Copenhagen, Copenhagen, Denmark. 3Health Canada, Ottawa, Canada..

Carbon black (CB), diesel exhaust particles (DEP), quartz, single-walled carbon nanotubes (SWCNT) and C60 fullerenes (C60) were investigated for cytotoxicity, genotoxicity, ROS production, proliferation effects and mutagenicity in the FE1-Muta™Mouse lung cell line. Mutagenicity was studied using a parallel continuous sub-culture setup. Cells were incubated for 72 h with either pure media or a test substances (100 ug/ml quartz, SWCNT or C60)(75 ug/ml of CB or DEP)(37.5 ug/ml DEP) through eight subsequent exposure rounds. The cells were incubated with or without the test particle a total of eight exposure rounds, making the total exposure time 576 h. The cumulative dose was 8 mg (quartz, SWCNT and C60), 6 mg (CB and DEP) or 3 mg (DEP). None of the materials were cytotoxic. However, cell proliferation was markedly slower with SWCNT with a larger fraction of cells in the G1 phase. This effect was evident throughout the treatment but disappeared after withdrawal. CB and DEP (75 ug/ml) significantly increased the mutant frequency. The other particles did not significantly affect the mutant frequency (MF). Results were as follows: CB 1.40-fold (p=0.0002), DEP75 1.55-fold (p=0.003), Quartz 1.30-fold (p= 0.14), DEP37.5 1.28-fold (p=0.06), SWCNT 0.95-fold (p=0.64) and C60 0.92-fold (p=0.43). Genotoxicity measured by DNA strand breaks and FPG sites was greatest with CB was the most potent particle. It significantly increased the level of strand breaks (2-fold) and FPG sites (2.1-fold). SWCNT and C60 did not induce strand breaks, but increased the level of FPG sites by 1.5-fold and 1.2-fold, respectively. Quartz gave no effects in the comet assay. ROS production was measured within cells and in cell free experiments following 3 h of exposure at varying low particle concentrations. CB produced the greatest ROS signal both within cells and without cells. SWCNT produced similar levels at the lowest concentrations whereas the other particles only resulted in weak ROS production. In conclusion it appears that genotoxicity determined by comet assay are closely related to the increase in MF. Since the SWCNT exposure did produce FPG lesions, the lack of mutations following this exposure may be due to the reduced proliferation.