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N-acetyltransferase 1 (NAT1) is a xenobiotic metabolizing enzyme that uses acetyl coenzyme A (AcCoA) as a cofactor for N-acetylation of many carcinogens including aromatic amines and alkylanilines. NAT1 is characterized by single nucleotide polymorphisms (SNPs) that may modulate affinity towards AcCoA. In the current study, we used Chinese hamster ovary (CHO) cells stably transfected with human NAT1*4 (reference allele) or NAT1*14B (variant allele) to measure AcCoA kinetic parameters for N-acetyltransferase activity measurements towards p-aminobenzoic acid (PABA), 4-aminobiphenyl (4-ABP), β-naphthylamine (BNA), benzidine and 3,4-dimethylaniline (3,4-DMA). Our results showed higher N-acetylation rates for each substrate catalyzed by NAT1*4 compared to NAT1*14B. NAT1*4 exhibited higher affinity to AcCoA when catalyzing the N-acetylation of BNA and benzidine compared to NAT1*14B. The results of the current study provide further insights into differences in carcinogen metabolism among individuals possessing the NAT1*14B haplotype.

Human arylamine N-acetyltransferase 1 (NAT1) catalyzes the N-acetylation of arylamine carcinogens such as 4-aminobiphenyl (ABP), and following N-hydroxylation, the O-acetylation of N-hydroxy-arylamine carcinogens such as N-hydroxy-ABP (N-OH-ABP). Genetic polymorphisms in NAT1 are linked to cancer susceptibility following exposures. The effects of individual single nucleotide polymorphisms (SNPs) in the NAT1 coding exon on Michaelis-Menten kinetic constants was assessed for ABP N-acetyltransferase and N-OH-ABP O-acetyltransferase activity following transfection of human NAT1 into COS-1 cells (SV40-transformed African green monkey kidney cells). NAT1 coding region SNPs 97C > T (rs56318881) (R33stop), 190C > T (rs56379106) (R64W), 559C > T (rs5030839) (R187stop) and 752A > T (rs56172717) (D251V) reduced ABP N- acetyltransferase and N-OH-ABP O-acetyltransferase activity below detection. 21T > G (rs4986992) (synonymous), 402T > C (rs146727732) (synonymous), 445G > A (rs4987076) (V149I), 613A > G (rs72554609) (M205V) and 640T > G (rs4986783) (S241A) did not significantly affect Vmax for ABP N-acetyltransferase or N-OH-ABP O-acetyltransferase. 781G > A (rs72554610) (E261K), and 787A > G (rs72554611) (I263V) slightly reduced ABP N-acetyltransferase and N-OH-ABP O-acetyltransferase activities whereas 560G > A (rs4986782) (R187Q) substantially and significantly reduced them. 560G > A (rs4986782) (R187Q) significantly reduced the apparent Km for ABP and N-OH-ABP a finding that was not observed with any of the other NAT1 SNPs tested. These findings suggest that the role of the 560G > A (rs4986782) (R187Q) SNP cancer risk assessment may be modified by exposure level to aromatic amine carcinogens such as ABP. [ABSTRACT FROM AUTHOR]

Human arylamine N-acetyltransferase 1 (NAT1) catalyzes the N-acetylation of arylamine carcinogens such as 4-aminobiphenyl (ABP), and following N-hydroxylation, the O-acetylation of N-hydroxy-arylamine carcinogens such as N-hydroxy-ABP (N-OH-ABP). Genetic polymorphisms in NAT1 are linked to cancer susceptibility following exposures. The effects of individual single nucleotide polymorphisms (SNPs) in the NAT1 coding exon on Michaelis-Menten kinetic constants was assessed for ABP N-acetyltransferase and N-OH-ABP O-acetyltransferase activity following transfection of human NAT1 into COS-1 cells (SV40-transformed African green monkey kidney cells). NAT1 coding region SNPs 97C > T (rs56318881) (R33stop), 190C > T (rs56379106) (R64W), 559C > T (rs5030839) (R187stop) and 752A > T (rs56172717) (D251V) reduced ABP N- acetyltransferase and N-OH-ABP O-acetyltransferase activity below detection. 21T > G (rs4986992) (synonymous), 402T > C (rs146727732) (synonymous), 445G > A (rs4987076) (V149I), 613A > G (rs72554609) (M205V) and 640T > G (rs4986783) (S241A) did not significantly affect Vmax for ABP N-acetyltransferase or N-OH-ABP O-acetyltransferase. 781G > A (rs72554610) (E261K), and 787A > G (rs72554611) (I263V) slightly reduced ABP N-acetyltransferase and N-OH-ABP O-acetyltransferase activities whereas 560G > A (rs4986782) (R187Q) substantially and significantly reduced them. 560G > A (rs4986782) (R187Q) significantly reduced the apparent Km for ABP and N-OH-ABP a finding that was not observed with any of the other NAT1 SNPs tested. These findings suggest that the role of the 560G > A (rs4986782) (R187Q) SNP cancer risk assessment may be modified by exposure level to aromatic amine carcinogens such as ABP.

TP53 harbors somatic mutations in more than half of human tumors with some showing characteristic mutation spectra that have been linked to environmental exposures. In bladder cancer, a unique distribution of mutations amongst several codons of TP53 has been hypothesized to be caused by environmental carcinogens including 4‐aminobiphenyl (4‐ABP). 4‐ABP undergoes metabolic activation to N‐hydroxy‐4‐aminobiphenyl (N‐OH‐4‐ABP) and forms pre‐mutagenic adducts in DNA, of which N‐(deoxyguanosin‐8‐yl)‐4‐ABP (dG‐C8‐4‐ABP) is the major one. Human TP53 knock‐in mouse embryo fibroblasts (HUFs) are a useful model to study the influence of environmental carcinogens on TP53‐mutagenesis. By performing the HUF immortalization assay (HIMA) TP53‐mutant HUFs are generated and mutations can be identified by sequencing. Here we studied the induction of mutations in human TP53 after treatment of primary HUFs with N‐OH‐4‐ABP. In addition, mutagenicity in the bacterial lacZ reporter gene and the formation of dG‐C8‐4‐ABP, measured by 32P‐postlabelling analysis, were determined in N‐OH‐4‐ABP‐treated primary HUFs. A total of 6% TP53‐mutants were identified after treatment with 40 μM N‐OH‐4‐ABP for 24 hr (n = 150) with G>C/C>G transversion being the main mutation type. The mutation spectrum found in the TP53 gene of immortalized N‐OH‐4‐ABP‐treated HUFs was unlike the one found in human bladder cancer. DNA adduct formation (~40 adducts/108 nucleotides) was detected after 24 hr treatment with 40 μM N‐OH‐4‐ABP, but lacZ mutagenicity was not observed. Adduct levels decreased substantially (sixfold) after a 24 hr recovery period indicating that primary HUFs can efficiently repair the dG‐C8‐4‐ABP adduct possibly before mutations are fixed. In conclusion, the observed difference in the N‐OH‐4‐ABP‐induced TP53 mutation spectrum to that observed in human bladder tumors do not support a role of 4‐ABP in human bladder cancer development. [ABSTRACT FROM AUTHOR]

Laraib Ghanghro Dow Medical College, Dow University of Health Sciences, Karachi, PakistanCorrespondence: Laraib GhanghroDow Medical College, Dow University of Health Sciences, Karachi, PakistanEmail lareb.manan19@dmc.duhs.edu.pk View the original paper by Mr Barsouk and colleagues

Adam Barsouk,1 Krishna Chaitanya Thandra,2 Kalyan Saginala,3 Prashanth Rawla4 1Sidney Kimmel Cancer Center, Jefferson University, Philadelphia, PA, 19107, USA; 2Department of Pulmonary and Critical Care Medicine, Sentara Virginia Beach General Hospital, Virginia Beach, VA, USA; 3Plains Regional Medical Group Internal Medicine, Clovis, NM, 88101, USA; 4Department of Medicine, Sovah Health, Martinsville, VA, 24112, USACorrespondence: Prashanth RawlaDepartment of Internal Medicine/Hospitalist, SOVAH Health, 320 Hospital Dr, Martinsville, VA, 24115, USAEmail rawlap@gmail.com View the original paper by Mr Barsouk and colleagues This is in response to the Letter to the Editor

Abstract Bladder cancer risk is 3‐4 times higher in men than women, but the reason is poorly understood. In mice, male bladder is also more susceptible than female bladder to 4‐aminobiphenyl (ABP), a major human bladder carcinogen; however, female liver is more susceptible than male liver to ABP. We investigated the role of sulfotransferase (Sult) in gender‐related bladder and liver susceptibility to ABP. Sulfation reactions of aromatic amine bladder carcinogens catalyzed by Sult may generate highly unstable and toxic metabolites. Therefore, liver Sult may decrease bladder exposure to carcinogens by promoting their toxic reactions in the liver. Notably, the expression of several liver Sults is suppressed by androgen in male mice. Here, we show that two Sults are critical for gender‐related bladder susceptibility to ABP in mice. We measured tissue level of N‐(deoxyguanosin‐8‐yl)‐4‐aminobiphenyl (dG‐C8‐ABP), a principal ABP‐DNA adduct, as readout of tissue susceptibility to ABP. We identified Sutl1a1 and to a lesser extent Sult1d1 as Sults that promote dG‐C8‐ABP formation in hepatic cells. In mice, gender gap in bladder susceptibility to ABP was narrowed by knocking out Sult1a1 and was almost totally eliminated by knocking out both Sutl1a1 and Sult1d1. This was accompanied by dramatic decrease in ABP genotoxicity in the liver (>97%). These results show the strong impact of the Sults on bladder and liver susceptibility to a human carcinogen. Because liver expression of both Sult1a1 and Sutl1d1 is suppressed by androgen in male mice, our results suggest that androgen renders bladder more exposed to ABP in male mice by suppressing Sult‐mediated ABP metabolism in liver, which increases bladder delivery of carcinogenic metabolites.

Bladder cancer is a significant public health problem, worldwide. In the United States, bladder cancer is the fourth most common cancer in men, and its recurrence rate is the highest among all malignancies. Tobacco smoking is the leading risk factor for bladder cancer. The risk of bladder cancer is directly related to the intensity and duration of smoking, while quitting smoking reduces this risk. The increased risk of smokers for developing bladder cancer is attributable to their exposure to aromatic amines, which constitute a family of known bladder carcinogens present in tobacco smoke. The underlying mechanism of action of aromatic amines in the genesis of bladder cancer is not, however, fully delineated. Research has identified a genotoxic mode of action, specifically DNA adduction and mutagenicity, for aromatic amines, which may account for their carcinogenicity. The present review summarizes our current knowledge on the DNA adduction and mutagenicity of aromatic amines in relation to smoking-associated bladder cancer. For illustrative purposes, representative results from published research on aromatic amine-induced DNA adduction and mutagenesis are discussed. The direction of future research on the underlying mechanisms of tobacco smoke-associated bladder carcinogenesis is also outlined. Understanding the molecular mechanisms of bladder carcinogenesis is essential for improving future strategies for prevention, early detection, treatment, and prognosis of this malignancy.

In this work, a rapid and sensitive thin‐layer chromatography combined with surface‐enhanced Raman spectroscopy method was established for rapid detection of benzidine and 4‐aminobiphenyl in migration from food contact materials based on Au nanoparticle doped metal‐organic framework. Benzidine and 4‐aminobiphenyl were firstly separated by thin‐layer chromatography to solve the limitation of their overlapping Raman peaks. Then the target molecules were monitored by adding AuNPs/MIL‐101(Cr) on the sample spots. Under the optimum conditions, the concentration of benzidine and 4‐aminobiphenyl can be quantitatively measured in the range of 2.0‐20.0 and1.0‐15.0 μg/L, respectively with good linear relationship, and the limits of detection were 0.21 and 0.23 μg/L, respectively. Furthermore, the developed method was applied to analyze benzidine and 4‐aminobiphenyl in migration of different food contact materials. The recoveries of benzidine and 4‐aminobiphenyl for migration of food contact materials, including paper cups, polypropylene food containers, and polyethylene glycol terephthalate bottles, were 80.6‐116.0 and 80.7‐118% with relative standard deviations of 1.1‐9.1 and 3.1‐9.9%, respectively. Surface‐enhanced Raman scattering detection was performed conveniently in the on‐plate mode without additional elution process. The method shows great potential in rapid monitoring of hazardous substances with overlapping characteristic Raman peaks in food contact materials. [ABSTRACT FROM AUTHOR]

Carcinogenic aromatic amines such as 4‐aminobiphenyl (ABP) and 2‐aminofluorene (AF) require metabolic activation to form electrophilic intermediates that mutate DNA leading to carcinogenesis. Bioactivation of these carcinogens includes N‐hydroxylation catalyzed by CYP1A2 followed by O‐acetylation catalyzed by arylamine N‐acetyltransferase 2 (NAT2). To better understand the role of NAT2 genetic polymorphism in ABP‐ and AF‐induced mutagenesis and DNA damage, nucleotide excision repair‐deficient (UV5) Chinese hamster ovary (CHO) cells were stably transfected with human CYP1A2 and either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles. ABP and AF both caused significantly (P < 0.001) greater mutagenesis measured at the hypoxanthine phosphoribosyl transferase (hprt) locus in the UV5/CYP1A2/NAT2*4 acetylator cell line compared to the UV5, UV5/CYP1A2, and UV5/CYP1A2/NAT2*5B cell lines. ABP‐ and AF‐induced hprt mutant cDNAs were sequenced and over 80% of the single‐base substitutions were at G:C base pairs. DNA damage also was quantified by γH2AX in‐cell western assays and by identification and quantification of the two predominant DNA adducts, N‐(deoxyguanosin‐8‐yl)‐4‐aminobiphenyl (dG‐C8‐ABP) and N‐(deoxyguanosin‐8‐yl)‐2‐aminofluorene (dG‐C8‐AF) by liquid chromatography‐mass spectrometry. DNA damage and adduct levels were dose‐dependent, correlated highly with levels of hprt mutants, and were significantly (P < 0.0001) greater in the UV5/CYP1A2/NAT2*4 rapid acetylator cell line following treatment with ABP or AF as compared to all other cell lines. Our findings provide further clarity on the importance of O‐acetylation in CHO mutagenesis assays for aromatic amines. They provide evidence that NAT2 genetic polymorphism modifies aromatic amine‐induced DNA damage and mutagenesis that should be considered in human risk assessments following aromatic amine exposures. Environ. Mol. Mutagen. 61:235–245, 2020. © 2019 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this work, mesoporous silica-based MCM-41 was synthesised, and its adsorptive interaction with carcinogenic aromatic amine 4-aminobiphenyl (4-ABP) was studied. pH, MCM-41 dose, 4-ABP concentration, adsorption time and temperature were selected as process parameters for this purpose. Kinetic experimental data were fitted to pseudo-first-order and pseudo-second-order kinetic models to evaluate the adsorption kinetics. Further, adsorption rate controlling mechanism was investigated using intra-particle diffusion model. Langmuir, Freundlich, Temkin and D-R isotherm (Dubinin-Radushkevich) models were used to represent the adsorption equilibrium data. Gibbs free energy, entropy and enthalpy have also been determined to interpret the adsorption mechanism. MCM-41 exhibited 525 m2 g–1 BET surface area with pore volume of 0.85 cm3 g–1 and pore diameter of 3.21 nm. Kinetic data were best represented by the pseudo-second-order kinetic model. The adsorption equilibrium data were best fitted by Freundlich and Dubinin-Radushkevich (D-R) isotherms. [ABSTRACT FROM AUTHOR]

Occupational and tobacco exposure to aromatic amines (AAs) including 4-aminobiphenyl (4-ABP) and 2-naphthylamine (2-NA) are associated with bladder cancer (BC) risk. Several epidemiological studies have also reported a possible role for structurally related heterocyclic aromatic amines (HAAs) formed in tobacco smoke or cooked meats with BC risk. We had screened for DNA adducts of 4-ABP, 2-NA, and several prominent HAAs formed in tobacco smoke or grilled meats including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-9H-pyrido[2,3-b]indole (AαC) in the bladder DNA of BC patients, using liquid chromatography/mass spectrometry. We detected DNA adducts of 4-ABP, but not adducts of the other carcinogens. In this study, we have examined the capacity of RT4 cells, an epithelial human bladder cell line, to bioactivate AAs and HAAs to DNA damaging agents, which may contribute to BC. 4-ABP and AαC formed DNA adducts, but DNA adducts of 2-NA, PhIP, and MeIQx were not detected. 4-ABP DNA adducts were formed at tenfold higher levels than AαC adducts. Pretreatment of RT4 cells with α-naphthoflavone (1–10 µM), a specific cytochrome P450 1 (CYP1) inhibitor, decreased AαC adduct formation by 50% but did not affect the level of 4-ABP adducts. However, cell pretreatment with 8-methoxypsoralen (0.1–1 µM), a potent inhibitor of CYP2A, resulted in a 90% decrease of 4-ABP DNA adducts levels. These data signify that CYP2A and CYP1A isoforms expressed in the target urothelium bioactivate 4-ABP and AαC, respectively, and may be a critical feature of aromatic amine-induced urinary bladder carcinogenesis. The bioactivation of other tobacco and environmental AAs by bladder CYPs and their ensuing bladder DNA damage warrants further study. [ABSTRACT FROM AUTHOR]

Bladder cancer risk is 3‐4 times higher in men than women, but the reason is poorly understood. In mice, male bladder is also more susceptible than female bladder to 4‐aminobiphenyl (ABP), a major human bladder carcinogen; however, female liver is more susceptible than male liver to ABP. We investigated the role of sulfotransferase (Sult) in gender‐related bladder and liver susceptibility to ABP. Sulfation reactions of aromatic amine bladder carcinogens catalyzed by Sult may generate highly unstable and toxic metabolites. Therefore, liver Sult may decrease bladder exposure to carcinogens by promoting their toxic reactions in the liver. Notably, the expression of several liver Sults is suppressed by androgen in male mice. Here, we show that two Sults are critical for gender‐related bladder susceptibility to ABP in mice. We measured tissue level of N‐(deoxyguanosin‐8‐yl)‐4‐aminobiphenyl (dG‐C8‐ABP), a principal ABP‐DNA adduct, as readout of tissue susceptibility to ABP. We identified Sutl1a1 and to a lesser extent Sult1d1 as Sults that promote dG‐C8‐ABP formation in hepatic cells. In mice, gender gap in bladder susceptibility to ABP was narrowed by knocking out Sult1a1 and was almost totally eliminated by knocking out both Sutl1a1 and Sult1d1. This was accompanied by dramatic decrease in ABP genotoxicity in the liver (>97%). These results show the strong impact of the Sults on bladder and liver susceptibility to a human carcinogen. Because liver expression of both Sult1a1 and Sutl1d1 is suppressed by androgen in male mice, our results suggest that androgen renders bladder more exposed to ABP in male mice by suppressing Sult‐mediated ABP metabolism in liver, which increases bladder delivery of carcinogenic metabolites. Liver sulfotransferases may decrease bladder exposure to carcinogens by generating unstable metabolites that cause toxicity locally. This study shows that sulfotransferases 1a1 and 1d1, whose expression in male mouse liver is suppressed by androgen, promotes 4‐aminobiphenyl (ABP) genotoxicity in hepatic cells, whereas eliminating them in mice greatly protects liver against 4‐aminobiphenyl and decreases excess male bladder susceptibility to 4‐aminobiphenyl. Our results reveal the strong impact of sulfotransferases on bladder and liver susceptibility to a human carcinogen. [ABSTRACT FROM AUTHOR]

4-Aminobiphenyl (4-ABP) which is primarily formed during tobacco combustion and overheated meat is a major carcinogen responsible for various cancers. Its adducted form, N -deoxyguanosine-C8-4-aminobiphenyl (dG-C8-4-ABP), has long been employed as a biomarker for assessment of the risk for cancer. In this review, the metabolism and carcinogenisity of 4-ABP will be discussed, followed by a discussion of the current common approaches of analyzing dG-C8-4-ABP. The major part of this review will be on the history and recent development of key methods for detection and quantitation of dG-C8-4-ABP in complex biological samples and their biological applications, from the traditional 2 P-postlabelling and immunoassay methods to modern liquid chromatography-mass spectrometry (LC-MS) with the latter as the focus. Many vital biological discoveries based on dG-C8-4-ABP have been published by using the nanoLC-MS with column switching platform in our laboratory, which has also been adopted and further improved by many other researchers. We hope this review can provide a perspective of the challenges that had to be addressed in reaching our present goals and possibly bring new ideas for those who are still working on the frontline of DNA adducts area. [ABSTRACT FROM AUTHOR]

Bulky organic carcinogens are activated in vivo and subsequently react with nucleobases of cellular DNA to produce adducts. Some of these DNA adducts exist in multiple conformations that are slowly interconverted to one another. Different conformations have been implicated in different mutagenic and repair outcomes. However, studies on the conformation-specific inhibition of replication, which is more relevant to cell survival, are scarce, presumably due to the structural dynamics of DNA lesions at the replication fork. It is difficult to capture the exact nature of replication inhibition by existing end-point assays, which usually detect either the ensemble of consequences of all the conformers or the culmination of all cellular behaviors, such as mutagenicity or survival rate. We previously reported very unusual sequence-dependent conformational heterogeneities involving FABP-modified DNA under different sequence contexts (TG1*G2T [67%B:33%S] and TG1G2*T [100%B], G*, N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl) (Cai et al. Nucleic Acids Research, 46, 6356–6370 (2018)). In the present study, we attempted to correlate the in vitro inhibition of polymerase activity to different conformations from a single FABP-modified DNA lesion. We utilized a combination of surface plasmon resonance (SPR) and HPLC-based steady-state kinetics to reveal the differences in terms of binding affinity and inhibition with polymerase between these two conformers (67%B:33%S and 100%B).

The rabbit was the initial animal model to investigate the acetylation polymorphism expressed in humans. Use of the rabbit model is compromised by lack of a rapid non-invasive method for determining acetylator phenotype. Slow acetylator phenotype in the rabbit results from deletion of the N-acetyltransferase 2 ( NAT2) gene. A relatively quick and non-invasive method for identifying the gene deletion was developed and acetylator phenotypes confirmed by measurement of N- and O-acetyltransferase activities in hepatic cytosols. Rabbit liver cytosols catalyzed the N-acetylation of sulfamethazine ( p = 0.0014), benzidine ( p = 0.0257), 4-aminobiphenyl ( p = 0.0012), and the O-acetylation of N-hydroxy-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP; p = 0.002) at rates significantly higher in rabbits possessing NAT2 gene than rabbits with NAT2 gene deleted. In contrast, hepatic cytosols catalyzed the N-acetylation of p-aminobenzoic acid (an N-acetyltransferase 1 selective substrate) at rates that did not differ significantly ( p > 0.05) between rabbits positive and negative for NAT2. The new NAT2 genotyping method facilitates use of the rabbit model to investigate the role of acetylator polymorphism in the metabolism of aromatic and heterocyclic amine drugs and carcinogens. [ABSTRACT FROM AUTHOR]

Human N-acetyltransferase 2 (NAT2) catalyzes the N-acetylation of numerous aromatic amine drugs such as sulfamethazine (SMZ) and hydrazine drugs such as isoniazid (INH). NAT2 also catalyzes the N-acetylation of aromatic amine carcinogens such as 2-aminofluorene and the O- and N,O-acetylation of aromatic amine and heterocyclic amine metabolites. Genetic polymorphism in NAT2 modifies drug efficacy and toxicity as well as cancer risk. Acetyltransferase catalytic activities and heat stability associated with six novel NAT2 haplotypes ( NAT2*6C, NAT2*14C, NAT2*14D, NAT2*14E, NAT2*17, and NAT2*18) were compared with that of the reference NAT2*4 haplotype following recombinant expression in Escherichia coli. N-acetyltransferase activities towards SMZ and INH were significantly ( p < 0.0001) lower when catalyzed by the novel recombinant human NAT2 allozymes compared to NAT2 4. SMZ and INH N-acetyltransferase activities catalyzed by NAT2 14C and NAT2 14D were significantly lower ( p < 0.001) than catalyzed by NAT2 6C and NAT2 14E. N-Acetylation catalyzed by recombinant human NAT2 17 was over several hundred-fold lower than by recombinant NAT2 4 precluding measurement of its kinetic or heat inactivation constants. Similar results were observed for the O-acetylation of N-hydroxy-2-aminofluorene and N-hydroxy-2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine and the intramolecular N,O-acetylation of N-hydroxy- N-acetyl-2-aminofluorene. The apparent V of the novel recombinant NAT2 allozymes NAT2 6C, NAT2 14C, NAT2 14D, and NAT2 14E towards AF, 4-aminobiphenyl (ABP), and 3,2′-dimethyl-4-aminobiphenyl (DMABP) were each significantly ( p < 0.001) lower while their apparent K values did not differ significantly ( p > 0.05) from recombinant NAT2 4. The apparent V catalyzed by NAT2 14C and NAT2 14D were significantly lower ( p < 0.05) than the apparent V catalyzed by NAT2 6C and NAT2 14E towards AF, ABP, and DMABP. Heat inactivation rate constants for recombinant human NAT2 14C, 14D, 14E, and 18 were significantly ( p < 0.05) higher than NAT2 4. These results provide further evidence of genetic heterogeneity within the NAT2 slow acetylator phenotype. [ABSTRACT FROM AUTHOR]

Genetic polymorphisms in human N-acetyltransferase 2 (NAT2) modify the metabolism of numerous drugs and carcinogens. These genetic polymorphisms modify both drug efficacy and toxicity and cancer risk associated with carcinogen exposure. Previous studies have suggested phenotypic heterogeneity among different NAT2 slow acetylator genotypes. NAT2 phenotype was investigated in vitro and in situ in samples of human hepatocytes obtained from various NAT2 slow and intermediate NAT2 acetylator genotypes. NAT2 gene dose response ( NAT2*5B/*5B > NAT2*5B/*6A > NAT2*6A/*6A) was observed towards the N-acetylation of the NAT2-specific drug sulfamethazine by human hepatocytes both in vitro and in situ. N-acetylation of 4-aminobiphenyl, an arylamine carcinogen substrate for both N-acetyltransferase 1 and NAT2, showed the same trend both in vitro and in situ although the differences were not significant ( p > 0.05). The N-acetylation of the N-acetyltransferase 1-specific substrate p-aminobenzoic acid did not follow this trend. In comparisons of NAT2 intermediate acetylator genotypes, differences in N-acetylation between NAT2*4/*5B and NAT2*4/*6B hepatocytes were not observed in vitro or in situ towards any of these substrates. These results further support phenotypic heterogeneity among NAT2 slow acetylator genotypes, consistent with differential risks of drug failure or toxicity and cancer associated with carcinogen exposure. [ABSTRACT FROM AUTHOR]

Hair dye products include a range of chemicals, depending on the type and color. A common primary intermediate compound used to achieve the permanent effect of hair dye is para-phenylenediamine (PPD). 4-aminobiphenyl (4-ABP) has reportedly been found as a trace contaminant (presumably from the para-phenylenediamine [PPD] ingredient) in consumer permanent hair dye. While several regulatory agencies have designated 4-ABP as a human bladder carcinogen based on evidence in humans and experimental animals, only the Office of Environmental Health Hazard Assessment (OEHHA) have established a cancer risk value for 4-ABP of 0.03 μg/day based on liver tumors developed in mice. A hypothetical dermal risk assessment was performed to estimate the bladder cancer risk associated with exposure to 4-ABP from personal use of permanent hair dye potentially containing incidental 4-ABP. Previously published laboratory analyses characterizing 4-ABP concentrations in consumer hair dyes indicate the concentrations can range from below the limit of detection to 8120 ppb. Precautionary estimates of human scalp surface area, maximum skin adherence, hair dye retention factor, and percent dermal absorption were used to estimate the daily systemic exposure doses (SEDs) from dermal application of hair dye. The estimated SEDs ranged from 0.05 to 3000 pg/day. A margin of safety (MOS) was calculated as the ratio of the NSRL to the SED and ranged from 10 to 570,000. The results of this study suggest that there is no indication of increased risk of bladder cancer in humans from exposure to 4-ABP in consumer hair dye, especially as it is extremely unlikely that a consumer would use permanent hair dye on a daily basis (as this assessment models). • 4-ABP has reportedly been found as a trace contaminant in permanent hair dye. • Assess whether dermal exposure to 4-ABP in hair dye increases risk of bladder cancer. • Application of contaminated hair dye would not increase the risk of bladder cancer. [ABSTRACT FROM AUTHOR]

The incidence of liver cancer is higher in men than in women. This sex difference is also observed in murine tumor induction models that result in the appearance of liver tumors in adult mice following their exposure on postnatal days 8 and/or 15 to carcinogens such as 4-aminobiphenyl (ABP) or diethylnitrosamine (DEN). Previous studies performed in adult mice showed that acute hepatotoxic and inflammatory responses to high-dose DEN exposure were greater in males than in females, leading to the suggestion that these responses could account for the sex difference in tumor development. We also recently observed that female but not male mice exposed postnatally to ABP had slightly increased expression of the antioxidant defense genes Nqo1 and Ggt1 , which are regulated by the oxidative stress response protein nuclear factor erythroid 2-related factor 2 (NRF2), while expression of Hmox1 was increased in both sexes. The goal of the present study was therefore to compare selected acute hepatotoxic, inflammatory and oxidative stress defense responses to ABP, DEN, or the prototype hepatotoxicant carbon tetrachloride (CCl 4 ), in male and female mice exposed to these chemicals either postnatally or as adults. Exposure of adult mice to ABP, DEN or CCl 4 produced a 2-fold greater acute elevation in serum levels of the hepatotoxicity biomarker alanine aminotransferase (ALT) in males than in females, while levels of the inflammatory biomarker interleukin-6 (IL-6) showed no sex difference. However, treatment of immature mice with either ABP or DEN using standard tumor-inducing postnatal exposure protocols produced no increase in serum ALT or IL-6 levels in either males or females, while CCl 4 produced a 40-fold ALT elevation but with no sex difference. Basal expression of the NRF2-responsive gene Nqo1 was higher in adult females than in males, but there was no sex difference in basal expression of Ggt1 or Hmox1 . Sexually immature animals showed no sex difference in basal expression of any of the three genes. Postnatal DEN exposure modestly increased the expression of Ggt1 only in male mice and Nqo1 in both sexes, while CCl 4 slightly increased expression of Ggt1 in both males and females and Nqo1 only in females. Taken together, our results make it unlikely that acute hepatotoxic, inflammatory or NRF2-activated gene responses account for the male predominance in liver tumor growth following postnatal carcinogen exposure in mice. Our findings also suggest that acute toxicity studies performed in adult mice should be interpreted with caution when extrapolating potential mechanisms to liver carcinogenesis models that commonly use postnatally exposed mice. [ABSTRACT FROM AUTHOR]

Differential pulse voltammetry, cyclic voltammetry, alternating current voltammetry, and chronocoulometry at a hanging mercury drop electrode (HMDE) and DNA modified HMDE were used for the study of the interaction of 4-nitrobiphenyl (4-NBP) with double-stranded DNA and for the detection of DNA damage caused by its interaction with 4-NBP. Moreover, the interaction of DNA with intermediates of the 4-NBP reduction and with 4-aminobiphenyl, a metabolite of 4-NBP, was investigated. The mechanism of the electrochemical reduction of 4-NBP was investigated using CV, too. It was found that the reduction of 4-NBP is controlled by both diffusion and adsorption. The rate constant of the reduction and the diffusion coefficient were calculated as well. [ABSTRACT FROM AUTHOR]

The use of chemicals to obtain semi-processed leather must be consistent with the environmental laws and regulations, which requires evaluation of toxicity in leather goods intended for consumption. The paper proposes to implement and validate an instrumental analytical method to determine azo dyes in leather. The presence of azo dyes was determined on a total of three restricted aromatic amines (4-aminobiphenyl, benzidine, 5-nitro-o-toluidine), which can be found as a result of the split of dyes used in leather dyeing. Validation parameters of gas chromatographic method were: accuracy (trueness and reliability), precision, sensitivity, limit of detection, limit of quantification, working range, linearity. [ABSTRACT FROM AUTHOR]

Humans are exposed to carcinogenic chemicals via occupational and environmental exposures. Common chemicals of concern that can occur in exposures together are aromatic amines (e.g., 4-aminobiphenyl [4-ABP] and β-naphthylamine [BNA]) and hexavalent chromium (Cr[VI]). Arylamine N -acetyltransferases 1 and 2 (NAT1 and NAT2) are key to the metabolism of aromatic amines and their genotoxicity. The effects of Cr(VI) on the metabolism of aromatic amines remains unknown as well as how it may affect their ensuing toxicity. The objective of the research presented here is to investigate the effects of Cr(VI) on the metabolism and genotoxicity of 4-ABP and BNA in immortalized human lung epithelial cells (BEP2D) expressing NAT1 and NAT2. Exposure to Cr(VI) for 48 h increased NAT1 activity (linear regression analysis: P < 0.0001) as measured by N -acetylation of para-aminobenzoic acid (PABA) in BEP2D cells but not NAT2 N -acetylation of sulfamethazine, which are prototypic NAT1 and NAT2 substrates respectively. Cr(VI) also increased the N -acetylation of 4-ABP and BNA. In BEP2D cells the N -acetylation of 4-ABP (1–3 μM) exhibited a dose-dependent increase (linear regression analysis: P < 0.05) following co-incubation with 0–3 μM Cr(VI). In BEP2D cells, incubation with Cr(VI) caused dose-dependent increases (linear regression analysis: P < 0.01) in expression of CYP1A1 protein and catalytic activity. For genotoxicity, BEP2D cells were exposed to 4-ABP or BNA with/without Cr(VI) for 48 h. We observed dose-dependent increases (linear regression analysis: P < 0.01) in phospho-γH2AX protein expression for combined treatment of 4-ABP or BNA with Cr(VI). Further using a CYP1A1 inhibitor (α-naphthoflavone) and NAT1 siRNA, we found that CYP1A1 inhibition did not reduce the increased N -acetylation or genotoxicity of BNA by Cr(VI), while NAT1 inhibition did reduce increases in BNA N -acetylation and genotoxicity by Cr(VI). We conclude that during co-exposure of aromatic amines and Cr(VI) in human lung cells, Cr(VI) increased NAT1 activity contributing to increased 4-ABP and BNA genotoxicity. [Display omitted] • Hexavalent chromium exposure enhances N -acetyltransferase 1 activity in immortalized human lung cells. • Hexavalent chromium exposure increases CYP1A1 activity and protein expression in immortalized human lung cells. • Hexavalent chromium co-exposure enhances the N -acetylation of aromatic amines in immortalized human lung cells. • Hexavalent chromium co-exposure increases the genotoxicity of aromatic amines in immortalized human lung cells. • NAT1 is the driving force for increased aromatic amine genotoxicity in co-exposure with Cr(VI). [ABSTRACT FROM AUTHOR]

4-Aminobiphenyl (ABP) is a trace component of cigarette smoke and hair dyes, a suspected human carcinogen and a potent rodent liver carcinogen. Postnatal exposure of mice to ABP results in a higher incidence of liver tumors in males than in females, paralleling the sex difference in human liver cancer incidence. A traditional model of ABP tumorigenesis involves initial CYP1A2-mediated N-hydroxylation, which eventually leads to production of mutagenic ABP-DNA adducts that initiate tumor growth. However, several studies have found no correlation between sex or CYP1A2 function and the DNAdamaging, mutagenic, or tumorigenic effects of ABP. Oxidative stress may be an important etiological factor for liver cancer, and it has also been linked to ABP exposure. The goals of this study were to identify novel enzyme(s) that contribute to ABP N-oxidation, and to investigate a potential role for oxidative stress in ABP liver tumorigenicity. Isozyme-selective inhibition experiments using liver microsomes from wild-type and genetically modified mice identified CYP2E1 as a major ABP N-hydroxylating enzyme. The N-hydroxylation of ABP by transiently expressed CYP2E1 produced oxidative stress in cultured mouse hepatoma cells. In uiuo postnatal exposure of mice to a tumorigenic dose of ABP also produced oxidative stress in male wild-type mice, but not in male Cyp2el(-/-) mice or in female mice. However, a stronger NRF2-associated antioxidant response was observed in females. Our results identify CYP2E1 as a novel ABP-N-oxidizing enzyme, and suggest that sex differences in CYP2E1-dependent oxidative stress and antioxidant responses to ABP may contribute to the observed sex difference in tumor incidence. [ABSTRACT FROM AUTHOR]

Purpose: Cytochrome b (encoded by CYB5A) and NADH cytochrome b reductase (encoded by CYB5R3) detoxify aromatic and heterocyclic amine mammary carcinogens found in cigarette smoke. We hypothesized that CYB5A and CYB5R3 polymorphisms would be associated with breast cancer risk in women. Methods: We characterized the prevalence of 18 CYB5A and CYB5R3 variants in genomic DNA from African American (AfrAm) and Caucasian (Cauc) women from the Carolina Breast Cancer Study population (1,946 cases and 1,747 controls) and determined their associations with breast cancer risk, with effect modification by smoking. Results: A CYB5R3 variant, I1M+6T (rs8190370), was significantly more common in breast cancer cases (MAF 0.0238) compared with controls (0.0169, p = 0.039); this was attributable to a higher MAF in AfrAm cases (0.0611) compared with AfrAm controls (0.0441, p = 0.046; adjusted OR 1.41, CI 0.98-2.04; p = 0.062). When smoking was considered, I1M+6T was more strongly associated with breast cancer risk in AfrAm smokers (adjusted OR 2.10, 1.08-4.07; p = 0.028) compared with never smokers (OR = 1.21; 0.77-1.88; p for interaction = 0.176). I1M+6T and three additional CYB5R3 variants, -251T, I8-1676C, and *392C, as well as two CYB5A variants, 13G and I2-992T, were significantly more common in AfrAms compared with Caucs. Conclusions: CYB5R3 I1M+6C>T should be considered in future molecular epidemiologic studies of breast cancer risk in AfrAms. Further, variants in CYB5A and CYB5R3 should be considered in the evaluation of other tumors in AfrAms that are associated with aromatic and heterocyclic amine exposures, to include prostate, bladder, and colon cancers. [ABSTRACT FROM AUTHOR]

N-acetyltransferase 1 (NAT1) is a xenobiotic metabolizing enzyme that uses acetyl coenzyme A (AcCoA) as a cofactor for N -acetylation of many carcinogens including aromatic amines and alkylanilines. NAT1 is characterized by single nucleotide polymorphisms (SNPs) that may modulate affinity towards AcCoA. In the current study, we used Chinese hamster ovary (CHO) cells stably transfected with human NAT1*4 (reference allele) or NAT1*14B (variant allele) to measure AcCoA kinetic parameters for N -acetyltransferase activity measurements towards p -aminobenzoic acid (PABA), 4-aminobiphenyl (4-ABP), β-naphthylamine (BNA), benzidine and 3,4-dimethylaniline (3,4-DMA). Our results showed higher N -acetylation rates for each substrate catalyzed by NAT1*4 compared to NAT1*14B . NAT1*4 exhibited higher affinity to AcCoA when catalyzing the N -acetylation of BNA and benzidine compared to NAT1*14B . The results of the current study provide further insights into differences in carcinogen metabolism among individuals possessing the NAT1*14B haplotype., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Habil, Doll and Hein.)

Lung cancer is the leading cause of cancer deaths in the United States with high incidence in tobacco smokers. Arylamine N -acetyltransferase 2 (NAT2) is a xenobiotic enzyme that catalyzes both N - and O -acetylation of carcinogens present in tobacco smoke and contributes towards the genotoxicity of these carcinogens. NAT2 allelic variants result in slow, intermediate, and rapid acetylation phenotypes. A recent meta-analysis reported NAT2 non-rapid (slow and intermediate) phenotypes had a significantly increased risk of lung cancer. NAT2 activity in humans is thought to be restricted to liver and gastrointestinal tract, and no studies to our knowledge have reported the expression of NAT2 activity in immortalized human lung epithelial cells. Given the importance of NAT2 in cancer and inhalation of various carcinogens directly into the lungs, we investigated NAT2 activity in human lung epithelial cells. Both NAT1 and NAT2 protein were detected by "in-cell" Western. Arylamine N -acetyltransferase activity was determined with selective substrates for NAT1 (p-aminobenzoic acid; PABA) and NAT2 (sulfamethazine; SMZ) in the presence and absence of a selective NAT1 inhibitor. PABA N -acetylation (NAT1 activity) in cell protein lysates was abolished in the presence of 25 μM of NAT1 inhibitor whereas SMZ N -acetylation (NAT2) was unaffected. Incubation with the NAT1 inhibitor partially reduced the N -acetylation of β-naphthylamine and the O -acetylation of N -hydroxy-4-aminobiphenyl consistent with catalysis by both NAT1 and NAT2. Immortalized human lung epithelial cells exhibited dose-dependent N -acetylation of 4-ABP with an apparent K M of 24.4 ± 5.1 μM. These data establish that NAT2 is expressed and functional in immortalized human lung epithelial cells and will help us further our understanding of NAT2 in lung cancer. • Immortalized human lung epithelial cells express N -acetyltransferase 2 protein. • Immortalized human lung epithelial cells express N -acetyltransferase 2 activity. • Immortalized human lung epithelial cells express O -acetylation activity catalyzed by N -acetyltransferases 1 and 2. [ABSTRACT FROM AUTHOR]

The urinary metabolites 2-cyanoethylmercapturic acid and 4-aminobiphenyl have been correlated with tobacco smoke exposure. Similarly, 2-cyanoethylvaline and 4-aminobiphenyl haemoglobin adducts have been used as biomarkers of effective dose for the exposure to acrylonitrile and 4-aminobiphenyl, respectively. Each pair of biomarkers is derived from the same parent chemical; however, the correlation between the urinary and the haemoglobin biomarkers has not been investigated. Using clinical study samples, we report a weak correlation between urinary and haemoglobin biomarkers due to different accumulation and elimination rates. Time course analysis showed that a reduction in exposure was paralleled by a delayed reduction in haemoglobin adducts. [ABSTRACT FROM AUTHOR]

4-Aminobiphenyl (4-ABP), an aromatic amine is a major environmental carcinogen found mainly in cigarette smoke. It has been vastly implicated in mutagenesis and cancer development. In this study, commercially available human placental DNA was exposed to 4-ABP (1.3 mM) in presence of sodium nitroprusside (SNP; 8 mM) at 37°C for 3 h. The 4-ABP + SNP-mediated structural changes in human DNA were studied by ultraviolet, circular dichroism and fluorescence spectroscopy, thermal melting profile, agarose gel electrophoresis, and nuclease S1 digestibility assay. Spectroscopical analysis and melting temperature studies suggest structural perturbations in the DNA as a result of modification. This might be due to generation of single-stranded regions and destabilization of hydrogen bonds. Modification was also visualized in agarose gel electrophoresis. Furthermore, nuclease S1 digestibility confirmed the generation of single strand breaks. Rabbits challenged with 4-ABP-SNP-modified human DNA-induced high-titer immunogen-specific antibodies, which showed Cross-reaction with modified/unmodified DNA bases and ss-DNA in competitive inhibition assay. The immunogen specificity of induced antibodies against 4-ABP-SNP-modified human DNA was further confirmed in gel retardation assay. It may be concluded that induction of anti-modified DNA antibodies could be due to perturbation in the DNA structure and its subsequent recognition by immunoregulatory cells as a foreign molecule. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 568-576, 2014. [ABSTRACT FROM AUTHOR]

4-Aminobiphenyl (4-ABP) is a human bladder cancer carcinogen found in the manufacture of azo dyes and the composition of cigarette smoke in the environment. To determine whether low concentrations of 4-ABP induced or promote liver carcinogenesis and investigate the underlying mechanism, we have established the liver cell carcinogenesis model in human liver cell lines and zebrafish to evaluate liver cancer development associated with long-term exposure to low concentrations of 4-ABP. Results show that repeated 4-ABP exposure promoted cellular proliferation and migration via the involvement of ROS in Ras/MEK/ERK pathway in vitro. Also, 4-ABP (1, 10, and 100 nM) induces hepatocellular carcinoma (HCC) formation in HBx, Src (p53 -/- ) transgenic zebrafish at four months of age and in wild-type zebrafish at seven months of age. In addition, we observed a correlation between the Ras-ERK pathway and 4-ABP-induced HCC in vitro and in vivo. Our finding suggests low concentrations of 4-ABP repeated exposure is a potential risk factor for liver cancer. To our knowledge, this is the first report on the promotion of liver carcinogenesis in human liver cells and zebrafish following 4-ABP exposure. [Display omitted] • The tumorigenicity of 4-ABP was first demonstrated. • The low dose of 4-ABP repeated exposure actives Ras-ERK pathway in liver cells. • 4-ABP induces or promotes liver carcinogenesis in liver cell model and zebrafish model. [ABSTRACT FROM AUTHOR]

Schematic diagram for the preparation process of β-NaGdF 4 :Yb3+, Er3+@MIPs responding to 4-aminobiphenyl (4-ABP). Up-conversion nanoparticles (UCNPs) β-NaGdF 4 :Yb3+, Er3+ are used as fluorescent signal component, 4-ABP as template molecules, 3-aminopropyltriethoxysilane (APTES) as functional monomer, tetraethyl orthosilicate (TEOS) as crosslinking agent, and ammonia water (NH 3 ·H 2 O) as initiator. After eluting 4-ABP from β-NaGdF 4 :Yb3+, Er3+@MIPs, the specific three-dimensional imprinted cavities complementary to the size, shape and chemical groups of 4-ABP were obtained. After binding with 4-ABP again, the fluorescence intensity of NaGdF 4 :Yb3+, Er3+@MIPs suffer from decreasing. [Display omitted] • •β-NaGdF 4 :Yb3+, Er3+ is the first time to be used as light-emitting signal component. • •An up-conversion molecularly imprinted nanoprobe is successfully constructed. • •The nanoprobe applies to detecting 4-aminobiphenyl in water environment. • •The detection mechanism is proved to be based on Langmuir adsorption and IFE. • •This developed new method is rapid and straightforward compared to other methods. A new method was developed for selectively and rapidly detecting carcinogen 4-aminobiphenyl, with lower limit of detection and wider linear range. Up-conversion nanoparticles β-NaGdF 4 :Yb3+, Er3+ was the first time to choose as light-emitting signal component. Molecularly imprinted polymers (MIPs) with specific recognition ability were successfully coated on the surface of β-NaGdF 4 :Yb3+, Er3+ to obtain a nano fluorescent probe for detecting 4-aminobiphenyl. The effect of addition amount of β-NaGdF 4 :Yb3+, Er3+ on the detection ability of β-NaGdF 4 :Yb3+, Er3+@MIPs was studied, and composite fluorescence nanoprobe with the best performance was obtained. β-NaGdF 4 :Yb3+, Er3+@MIPs were characterized by transmission electron microscopy, X-ray powder diffractometer, Fourier transform infrared spectroscopy and thermogravimetric analysis. The fluorescence intensity of β-NaGdF 4 :Yb3+, Er3+@MIPs decreased significantly compared with molecularly non-imprinted polymers β-NaGdF 4 :Yb3+, Er3+@NIPs (the maximum emission peak is at 541 nm) in the presence of 4-aminobiphenyl. Adsorption isotherm and adsorption kinetics between UCNP@MIPs and 4-ABP have been investigated and a satisfactory imprinting factor is 2.5. The detection mechanism is proved to be based on Langmuir adsorption and internal filtration effect. Under optimal experimental conditions, the limit of detection and quantification are 0.16 μM and 0.53 μM, respectively. The linear range of response is 1–50 μM, and RSD is less than 6.7%. This method was applied to determining river water samples in order to evaluate the practicability, and the good recovery rate is between 98.89% and 109.7%. These evidences demonstrate that β-NaGdF 4 :Yb3+, Er3+@MIPs is successfully used for the detection of 4-aminobiphenyl. [ABSTRACT FROM AUTHOR]

One model for cancer initiation by 4-aminobiphenyl (ABP) involves N-oxidation by cytochrome P450 CYP1A2 followed by O-conjugation by N-acetyltransferase(s) NAT1 and/or NAT2 and decomposition to a DNA-binding nitrenium ion. We recently observed that neonatal ABP exposure produced liver tumors in male but not in female mice, and that NAT deficiency reduced liver tumor incidence. However, ABP-induced liver tumor incidence did not correlate with liver levels of N-(deoxyguanosin-8-yl)-ABP adducts 24 hr after exposure. In this study, we compared in vivo ABP-induced DNA mutant frequencies and spectra between male and female wild-type and NAT-deficient Muta™Mouse using both the tumor-inducing neonatal exposure protocol and a 28-day repetitive dosing adult exposure protocol. ABP produced an increase in liver DNA mutant frequencies in both neonates and adults. However, we observed no sex or strain differences in mutant frequencies in neonatally exposed mice, and higher frequencies in adult females than males. Neonatal ABP exposure of wild-type mice increased the proportion of G-T transversions in both males and females, while exposure of Nat1/2(-/-) mice produced increased G-T transversions in males and a decrease in females, even though females had higher levels of N-(deoxyguanosin-8-yl)-4-ABP adducts. There was no correlation of mutant frequencies or spectra between mice dosed as neonates or as adults. These results suggest that observed sex- and NAT-dependent differences in ABP-induced liver tumor incidence in mice are not due to differences in either mutation rates or mutational spectra, and that mechanisms independent of carcinogen bioactivation, covalent DNA binding and mutation may be responsible for these differences. Environ. Mol. Mutagen., 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Cytochrome b5 (b5) and NADH cytochrome b5 reductase (b5R) detoxify reactive hydroxylamine (NHOH) metabolites of known arylamine and heterocyclic amine mammary carcinogens. The aim of this study was to determine whether NHOH reduction for the prototypic arylamine 4-aminobiphenyl (4-ABP) was present in human breast and to determine whether variability in activity was associated with single nucleotide polymorphisms (SNPs) in the coding, promoter, and 3′untranslated region (UTR) regions of the genes encoding b5 (CYB5A) and b5R (CYB5R3). 4-ABP-NHOH reduction was readily detected in pooled human breast microsomes, with a Km (280μM) similar to that found with recombinant b5 and b5R, and a Vmax of 1.12 ± 0.19 nmol/min/mg protein 4-ABP-NHOH reduction varied 75-fold across 70 individual breast samples and correlated significantly with both b5 (80-fold variability) and b5R (14-fold) immunoreactive protein. In addition, wide variability in b5 protein expression was significantly associated with variability in CYB5A transcript levels, with a trend toward the same association between b5R and CYB5R3. Although a sample with a novel coding SNP in CYB5A, His22Arg, was found with low reduction and b5 expression, no other SNPs in either gene were associated with outlier activity or protein expression. We conclude that b5 and b5R catalyze the reduction of 4-ABP-NHOH in breast tissue, with very low activity, protein, and messenger RNA expression in some samples, which cannot be attributed to promoter, coding, or 3′UTR SNPs. Further studies are underway to characterize the transcriptional regulation of CYB5A and CYB5R3 and begin to understand the mechanisms of individual variability in this detoxification pathway. [ABSTRACT FROM AUTHOR]

The method of determination of 4-biphenylamine (4-BA) in workplace air using SPE and HPLC has been presented. The method consists in passing the air that contains 4-BA through a glass fiber filter with sulfuric acid placed on it, washing out the substance settled on the filter, using water and a solution of sodium hydroxide, solid phase extraction (SPE) in order to enrich the analyte, replace the dissolvent with methanol, and analyze the obtained solution using a method of highly efficient liquid chromatography with fluorescent detection (λex = 268 nm, λem = 389 nm). Measuring range for the 100 dm3 air sample was: 0.1-2 μg/m3. Limit of detection (LOD) and limit of quantification (LOQ) were 0.18 ng/m3 and 0.54 ng/m3, respectively. [ABSTRACT FROM AUTHOR]

Background: 4-Aminobiphenyl (4-ABP) and o-toluidine are known human bladder carcinogens, but only 4-ABP-releasing DNA adducts are known. Methods: Determination of 4-ABP and o-toluidine-releasing DNA adducts in epithelial and submucosal bladder tissues of sudden death victims (SDV: n == 46), and bladder tumours ( n == 12) by gas chromatography/mass spectrometry. Results: Above background, 4 and 11 of 12 tumour samples contained adducts of 4-ABP (0.057 ±± 0.125 fmol/µµg DNA) and o-toluidine (8.72 ±± 4.49 fmol/µµg DNA), respectively. Lower adduct levels were present in both epithelial and submucosal bladder tissues of SDV (4-ABP: 0.011 ±± 0.022 and 0.019 ±± 0.047 fmol/µµg DNA; o-toluidine: 0.24 ±± 0.63 and 0.27 ±± 0.70 fmol/µµg DNA). Conclusion: Detection of o-toluidine-releasing DNA adducts support the carcinogenicity of o-toluidine in the human bladder. [ABSTRACT FROM AUTHOR]

Public health authorities worldwide have concluded that exposure to environmental tobacco smoke (ETS) causes diseases, including cancer, in adult nonsmokers. The arylamine, 4-aminobiphenyl (4-ABP), has been identified as a human carcinogen. Some publications have suggested that 4-ABP hemoglobin (4-ABP-Hb) adduct levels in nonsmokers are a result of exposure to ETS, whereas others could not confirm these observations. Toxicokinetic and exposure models proposed in this work are used to estimate the concentration of 4-ABP-Hb adducts resulting from ETS exposure that is based on experimental values for respirable suspended particulates (RSP) concentration. Monte Carlo methods were used to obtain estimates of population distributions of 4-ABP-Hb adduct levels resulting from indoor ETS exposure in homes, workplaces, and hospitality environments. It is found that the mean, median, and 95th percentile 4-ABP-Hb adduct steady-state levels of 0.4–1.4, 0.2–1.0, and 0.97–4.63 pg/g Hb, respectively, are estimated from ETS exposure. These 4-ABP-Hb adduct levels from ETS exposure account for ~1–4% of the median levels reported for nonsmokers, explaining, in part, contradictory literature data on 4-ABP-Hb adduct levels in nonsmokers. No risk assessment of ETS or 4-ABP was conducted in this work, consequently the known health effects of ETS are neither confirmed or challenged and our conclusions are limited to the determination that ETS is not a major source of 4-ABP-Hb adduct levels in non-smokers. [ABSTRACT FROM AUTHOR]

Abstract: Aromatic amines such as 4-aminobiphenyl (ABP) require biotransformation to exert their carcinogenic effects. Genetic polymorphisms in biotransformation enzymes such as N-acetyltransferase 2 (NAT2) may modify cancer risk following exposure. Nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human cytochrome P4501A1 (CYP1A1) and a single copy of either NAT2*4 (rapid acetylator), NAT2*5B (common Caucasian slow acetylator), or NAT2*7B (common Asian slow acetylator) alleles (haplotypes) were treated with ABP to test the effect of NAT2 polymorphisms on DNA adduct formation and mutagenesis. ABP N-acetyltransferase catalytic activities were detectable only in cell lines transfected with NAT2 and were highest in cells transfected with NAT2*4, lower in cells transfected with NAT2*7B, and lowest in cells transfected with NAT2*5B. Following ABP treatment, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP) was the primary adduct formed. Cells transfected with both CYP1A1 and NAT2*4 showed the highest concentration-dependent cytotoxicity, hypoxanthine phosphoribosyl transferase (hprt) mutants, and dG-C8-ABP adducts. Cells transfected with CYP1A1 and NAT2*7B showed lower levels of cytotoxicity, hprt mutagenesis, and dG-C8-ABP adducts. Cells transfected with CYP1A1 only or cells transfected with both CYP1A1 and NAT2*5B did not induce cytotoxicity, hprt mutagenesis or dG-C8-ABP adducts. ABP-DNA adduct levels correlated very highly (r >0.96) with ABP-induced hprt mutant levels following each treatment. The results of the present study suggest that investigations of NAT2 genotype or phenotype associations with disease or toxicity could be more precise and reproducible if heterogeneity within the “slow” NAT2 acetylator phenotype is considered and incorporated into the study design. [Copyright &y& Elsevier]

National surveys of the exposure of non-smokers to secondhand smoke based on serum cotinine analyses have consistently identified certain groups within the population including children, males and non-Hispanic Blacks as having relatively greater exposure. Although these differences in mean serum cotinine concentrations probably represent differences in exposure of individuals in their daily lives, it is also possible that metabolic or other differences in response might influence the results. To better define the nature of those findings, we have examined the response of 40 non-smokers including both men and women and African-Americans and whites to sidestream (SS) cigarette smoke generated by a smoking machine under controlled conditions. In this study, participants were exposed to aged, diluted SS smoke (ADSS) generated in an environmental chamber with a mean air nicotine concentration of 140 μg m-3 and 8.6 ppm CO for 4 h. Salivary cotinine was measured every 30 min, and serum cotinine samples were taken prior to, and 2 h after exposure. Urinary nicotine metabolites and NNAL, a tobacco-specific nitrosamine, and 4-aminobiphenyl (4-AB) haemoglobin adducts were also measured prior to and 2 h following the exposure. Under these uniform, controlled conditions, we found a similar response to ADSS smoke exposure among all the participants. In all cases a significant increase in biomarker concentration was noted following exposure, and the short-term increases in salivary cotinine concentration were quite similar at approximately 12 pg ml-1 min-1 among the groups. In this small study, no significant differences by gender or race were seen in the mean increases observed in cotinine, NNAL or 4-AB adducts following 4 h of exposure. Thus, our results are most consistent with a relatively uniform response in tobacco biomarker concentrations following short-term exposure to ADSS tobacco smoke, and suggest that biomarker measurements are capable of effectively indicating increases in exposure among groups of non-smokers. [ABSTRACT FROM AUTHOR]