Bioactivation, Mutagenicity, DNA Damage, and Oxidative Stress Induced by 3,4-Dimethylaniline

3,4-Dimethylaniline (3,4-DMA) is present in cigarette smoke and widely used as an intermediate in dyes, drugs, and pesticides. Nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human CYP1A2 and N-acetyltransferase 1 (NAT1) alleles: <i>NAT1*4</i> (reference allele) or <i>NAT1*14B</i> (the most common variant allele) were utilized to assess 3,4-DMA <i>N</i>-acetylation and hypoxanthine phosphoribosyl transferase (HPRT) mutations, double-strand DNA breaks and reactive oxygen species (ROS). CHO cells expressing <i>NAT1*4</i> exhibited significantly (<i>p</i> < 0.001) higher 3,4-DMA <i>N</i>-acetylation rates than CHO cells expressing <i>NAT1*14B</i> both in vitro and in situ. In CHO cells expressing CYP1A2 and NAT1, 3,4-DMA caused concentration-dependent increases in reactive oxygen species (ROS), double-stranded DNA damage, and HPRT mutations. CHO cells expressing <i>NAT1*4</i> and <i>NAT1*14B</i> exhibited concentration-dependent increases in ROS following treatment with 3,4-DMA (linear trend <i>p</i> < 0.001 and <i>p</i> < 0.0001 for <i>NAT1*4</i> and <i>NAT1*14B</i>, respectively) that were lower than in CHO cells expressing CYP1A2 alone. DNA damage and oxidative stress induced by 3,4-DMA did not differ significantly (<i>p</i> >0.05) between CHO cells expressing <i>NAT1*4</i> and <i>NAT1*14B</i>. CHO cells expressing <i>NAT1*14B</i> showed higher HPRT mutants (<i>p</i> < 0.05) than CHO cells expressing <i>NAT1*4</i>. These findings confirm 3,4-DMA genotoxicity consistent with potential carcinogenicity.