Genotoxicity of 3-nitrobenzanthrone and 3-aminobenzanthrone in Muta™Mouse and lung epithelial cells derived from Muta™Mouse

Abstract

FE1 lung epithelial cells derived from Muta™Mouse are a new model system to provide in vitro mutagenicity data with the potential to predict the outcome of an in vivo Muta™Mouse test. 3-Nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust and urban air pollution. We investigated the mutagenicity and DNA binding of 3-NBA and its main metabolite 3-aminobenzanthrone (3-ABA) in vitro and in vivo in the Muta™Mouse assay. Mice were treated with 3-NBA or 3-ABA (0, 2 or 5 mg/kg body weight/day) by gavage for 28 days and 28 days later lacZ mutant frequency (MF) was determined in liver, lung and bone marrow. For both compounds, dose-related increases in MF were seen in liver and bone marrow, but not in lung; mutagenic activity was ∼2-fold lower for 3-ABA than for 3-NBA. With 3-NBA, highest DNA adduct levels (measured by 32P-post-labelling) were found in liver (∼230 adducts per 108 nucleotides) with levels 20- to 40-fold lower in bone marrow and lung. With 3-ABA, DNA adduct levels were again highest in the liver, but ∼4-fold lower than for 3-NBA. FE1 cells were exposed to up to 10 μg/ml 3-NBA or 3-ABA for 6 h with or without exogenous activation (S9) and harvested after 3 days. For 3-NBA, there was a dose-related increase in MF both with and without S9 mix, which was >10 times higher than observed in vivo. At the highest concentration of 3-ABA (10 μg/ml), we found only around a 2-fold increase in MF relative to controls. DNA adduct formation in FE1 cells was dose-dependent for both compounds, but 10- to 20-fold higher for 3-NBA compared to 3-ABA. Collectively, our data indicate that Muta™Mouse FE1 cells are well suited for cost-effective testing of suspected mutagens with different metabolic activation pathways as a guide for subsequent in vivo Muta™Mouse testing. © The Author 2008. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved.