Toxicity and DNA damage induced by 1-nitropyrene and its derivatives in Chinese hamster lung fibroblasts

1-Nitropyrene and its chemically synthesised derivatives were investigated for their cytotoxicity and ability to induce DNA-strand breaks in Chinese hamster lung fibroblasts. Both 1-nitrosopyrene (0.25-60 micrograms/ml) and 1-aminopyrene (0.25-25 micrograms/ml) were cytotoxic, and induced the formation of DNA lesions, which were measured as DNA single-strand breaks after sedimentation in alkaline sucrose-density gradients. Higher doses of 1-aminopyrene (25-60 micrograms/ml) inhibited the formation of DNA single-strand breaks. 1-Nitropyrene was not toxic (0.25-60 micrograms/ml) and induced low levels of detectable DNA strand breaks, whilst N-acetyl-1-aminopyrene was inactive. The post-mitochondrial supernatant fraction of Aroclor-induced rat-liver containing 4 mM NADPH (S9 mix) did not promote the activation of 1-nitropyrene. In fact DNA strand breaks induced by either 1-nitropyrene or 1-nitrosopyrene was abolished in the presence of S9 mix. The 1-nitropyrene reduced intermediate, N-hydroxy-1-aminopyrene was synthesised by the reduction of 1-nitrosopyrene with ascorbic acid. In the presence of ascorbic acid, 1-nitrosopyrene caused a 5-fold increase in the number of DNA single-strand breaks when compared to cells treated with 1-nitrosopyrene alone. The results are discussed in terms of the metabolic activation of 1-nitropyrene and 1-aminopyrene in Chinese hamster lung cells.