Investigation of human n-acetyltransferases (NAT1 and NAT2) genetic polymorphisms in susceptibility to aromatic amine and alkylaniline genotoxicity.

Arylamine N-acetyltransferases, NAT1 and NAT2, catalyze the detoxification and/or activation of carcinogens. Single nucleotide polymorphisms or SNPs result in different human NAT1 and NAT2 genotypes. We hypothesize that different NATs alleles will impact levels of N-acetylation, HPRT mutations, DNA damage and oxidative stress induced by carcinogens. NER-deficient Chinese hamster ovary (CHO) cells transfected with human CYP1A2 and NAT1*4, NAT1*14B, NAT2*4, NAT2*5B or NAT2*7B have been used to investigate N-acetylation of benzidine, β-naphthylamine (BNA), and 4, 4’-methylene bis (2-chloroaniline) (MOCA) as aromatic amines and 3,4-dimethylaniline (3,4-DMA) as one of alkylanilines and their associated toxicity. Our findings showed that N-acetylation rates of BNA, MOCA in CHO cells expressing NAT2*4 (rapid acetylator) was significantly higher than cells expressing slow alleles NAT2*5B or NAT2*7B. Difference in BNA N-acetylation between NAT2*5B and NAT2*7B suggest genetic heterogeneity within the slow NAT2 phenotype. N-acetylation rates of benzidine and 3,4-DMA were significantly higher in cells expressing NAT1*4 than cells expressing NAT1*14B. Treatment of cells with BNA, MOCA and benzidine resulted in concentration dependent cytotoxicity in CHO cells. CHO cells with NAT2*4 showed higher levels of DNA damage and oxidative stress induced by BNA or MOCA. On the other hand, NAT2*7B cells had higher level of mutations than NAT2*4 or NAT2*5B cells. NAT1*14B cells showed higher level of mutations and DNA damage but lower oxidative stress induced by benzidine than that of cells expressing NAT1*4. Also, NAT1*14B cells showed higher level of mutations induced by 3,4-DMA compared to NAT1*4 cells while there is no difference between both alleles regarding DNA damage and oxidative stress. Use of NAT1 inhibitor (compound 10) decreased DNA damage and oxidative stress induced by benzidine. These data suggest that individual susceptibility to toxicity can be modified by human NAT genotypes. Moreover, heterogeneity within the “slow” NAT2 acetylator phenotype should be incorporated into epidemiological studies. This model provided a tool that can be used to investigate genotoxicity of other carcinogens. Also, we developed HPLC methods and toxicity biomarkers that can be used to monitor the exposed population. Our results are important for future studies to better understand the role of NATs in cancer risk studies