The environmental carcinogen 3-nitrobenzanthrone and its main metabolite 3-aminobenzanthrone enhance formation of reactive oxygen intermediates in human A549 lung epithelial cells.
The environmental contaminant 3-nitrobenzanthrone (3-NBA) is highly mutagenic and a suspected human carcinogen. We aimed to evaluate whether 3-NBA is able to deregulate critical steps in cell cycle control and apoptosis in human lung epithelial A549 cells. Increased intracellular Ca(2+) and caspase activities were detected upon 3-NBA exposure. As shown by cell cycle analysis, an increased number of S-phase cells was observed after 24 h of treatment with 3-NBA. Furthermore, 3-NBA was shown to inhibit cell proliferation when added to subconfluent cell cultures. The main metabolite of 3-NBA, 3-ABA, induced statistically significant increases in tail moment as judged by alkaline comet assay. The potential of 3-NBA and 3-ABA to enhance the production of reactive oxygen species (ROS) was demonstrated by flow cytometry using 2',7'-dichlorofluorescein-diacetate (DCFH-DA). The enzyme inhibitors allopurinol, dicumarol, resveratrol and SKF525A were used to assess the impact of metabolic conversion on 3-NBA-mediated ROS production. Resveratrol decreased dichlorofluorescein (DCF) fluorescence by 50%, suggesting a role for CYP1A1 in 3-NBA-mediated ROS production. Mitochondrial ROS production was significantly attenuated (20% reduction) by addition of rotenone (complex I inhibition) and thenoyltrifluoroacetone (TTFA, complex II inhibition). Taken together, the results of the present study provide evidence for a genotoxic potential of 3-ABA in human epithelial lung cells. Moreover, both compounds lead to increased intracellular ROS and create an environment favorable to DNA damage and the promotion of cancer.
Hansen
Tanja
T
Fraunhofer Institute of Toxicology and Experimental Medicine, Hannover, Germany. tanja.hansen@item.fraunhofer.de
Seidel
Albrecht
A
Borlak
Jürgen
J
D017209:Apoptosis / Q000187:drug effects; D001551:Benz(a)Anthracenes / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D004249:DNA Damage; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*
C475568:3-aminobenzanthrone; D001551:Benz(a)Anthracenes; D002273:Carcinogens; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D019363:Cytochrome P-450 CYP1A1; C117220:3-nitrobenzanthrone