Effect of rapid human N-acetyltransferase 2 haplotype on DNA damage and mutagenesis induced by 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ) and 2-amino-3,8-dimethylimidazo-[4,5-f]quinoxaline (MeIQx)

Abstract

Heterocyclic amines such as 2-amino-3-methylimidazo [4,5-f] quinoline (IQ) and 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx) are dietary carcinogens generated when meats are cooked well-done. Bioactivation includes N-hydroxylation catalyzed by cytochrome P4501A2 (CYP1A2) followed by O-acetylation catalyzed by N-acetyltransferase 2 (NAT2). Nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human CYP1A2 and either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles were treated with IQ or MeIQx to examine the effect of NAT2 genetic polymorphism on IQ- or MeIQx-induced DNA adducts and mutagenesis. MeIQx and IQ both induced decreases in cell survival and significantly (p<0.001) greater number of endogenous hypoxanthine phosphoribosyl transferase (hprt) mutants in the CYP1A2/NAT2*4 than the CYP1A2/NAT2*5B cell line. IQ- and MeIQx- induced hprt mutant cDNAs were sequenced and over 85% of the mutations were single base substitutions with the remainder exon deletions likely caused by splice-site mutations. For the single-base substitutions, over 85% were at G:C base pairs. Deoxyguanosine (dG) -C8-IQ and dG-C8-MeIQx adducts were significantly (p < 0.001) greater in the CYP1A2/NAT2*4 than the CYP1A2/NAT2*5B cell line. DNA adduct levels correlated very highly with hprt mutants for both IQ and MeIQx. These results suggest substantially increased risk for IQ- and MeIQx-induced DNA damage and mutagenesis in rapid NAT2 acetylators.

Role of Human N‐Acetyltransferase 2 Genetic Polymorphism on Aromatic Amine Carcinogen‐Induced DNA Damage and Mutagenicity in a Chinese Hamster Ovary Cell Mutation Assay

“…Similar findings have been reported following administration of heterocyclic amines MeIQx and IQ (Metry et al 2010) but not PhIP (Metry et al 2007). Bioactivation includes N-hydroxylation catalyzed by CYP1A2 followed by O-acetylation catalyzed by NAT2.…”

“…Furthermore, when adding previously published heterocyclic amine-induced mutations (Metry et al 2010), positions 134-135 (GpG), 208-209 (string of G's), 418-419 (GpG), and 589 were frequent mutation locations. The majority of induced mutations for both aromatic amines were missense/nonsense single-base substitutions, in which over 80% were at G:C base pairs.…”

“…The results differed with the heterocyclic amine carcinogen tested, as rapid acetylator NAT2*4 did not affect levels of mutagenesis and DNA adduct formation following incubation with PhIP (Metry et al 2007) whereas both mutagenesis and DNA adduct formation were markedly higher in CHO cells possessing rapid acetylator NAT2*4 following incubation with IQ or MeIQx (Metry et al 2010). The results differed with the heterocyclic amine carcinogen tested, as rapid acetylator NAT2*4 did not affect levels of mutagenesis and DNA adduct formation following incubation with PhIP (Metry et al 2007) whereas both mutagenesis and DNA adduct formation were markedly higher in CHO cells possessing rapid acetylator NAT2*4 following incubation with IQ or MeIQx (Metry et al 2010).…”

Codominant Expression ofN-Acetylation andO-Acetylation Activities Catalyzed byN-Acetyltransferase 2 in Human Hepatocytes

“…dG-C8-ABP, dG-C8-PhIP, and dG-C8-MeIQx adducts have been identified in human tissues and cells (Talaska et al, 1991;Totsuka et al, 1996;Gorlewska-Roberts et al, 2002). Recent results in genetically engineered Chinese hamster ovary cells documented a much greater role for human NAT2 acetylation polymorphism in DNA adduct formation and mutagenesis after exposure to ABP (Bendaly et al, 2009a) and MeIQx (Bendaly et al, 2007;Metry et al, 2010) than PhIP Bendaly et al, 2009b).…”

Present status of quinoxaline motifs: Excellent pathfinders in therapeutic medicine

“…For instance, DNA photocleaving ability of quinoxalinecarbohydrate hybrids 171 has been investigated [160]. DNA damage and mutagenesis was also induced by action of quinoxaline, 172 [161]. Aggarwal and coworkers reported triazolo quionoxaline 173 to be useful tool for probing DNA structure and for photodynamic chemotherapy [162].…”