Non-coding and intergenic genetic variants of human arylamine N-acetyltransferase 2 (NAT2) gene are associated with differential plasma lipid and cholesterol levels and cardiometabolic disorders.

Arylamine N-acetyltransferase 2 (NAT2) is a phase II metabolic enzyme, best known for metabolism of aromatic amines and hydrazines. Genetic variants occurring in the NAT2 coding region have been well-defined and are known to affect the enzyme activity or protein stability. Individuals can be categorized into rapid, intermediate, and slow acetylator phenotypes that significantly alter their ability to metabolize arylamines, including drugs (e.g., isoniazid) and carcinogens (e.g., 4-aminobiphenyl). However, functional studies on non-coding or intergenic variants of NAT2 are lacking. Multiple, independent genome wide association studies (GWAS) have reported that non-coding or intergenic variants of NAT2 are associated with elevated plasma lipid and cholesterol levels, as well as cardiometabolic disorders, suggesting a novel cellular role of NAT2 in lipid and cholesterol homeostasis. The current review highlights and summarizes GWAS reports that are relevant to this association. We also present a new finding that seven, non-coding, intergenic NAT2 variants (i.e., rs4921913, rs4921914, rs4921915, rs146812806, rs35246381, rs35570672, and rs1495741), which have been associated with plasma lipid and cholesterol levels, are in linkage disequilibrium with one another, and thus form a novel haplotype. The dyslipidemia risk alleles of non-coding NAT2 variants are associated with rapid NAT2 acetylator phenotype, suggesting that differential systemic NAT2 activity might be a risk factor for developing dyslipidemia. The current review also discusses the findings of recent reports that are supportive of the role of NAT2 in lipid or cholesterol synthesis and transport. In summary, we review data suggesting that human NAT2 is a novel genetic factor that influences plasma lipid and cholesterol levels and alters the risk of cardiometabolic disorders. The proposed novel role of NAT2 merits further investigations.

Enhanced cytotoxicity of a novel family of ATPase inhibitors in colorectal cancer cells with high NAT2 activity.

Loss of heterozygosity (LOH) is a hallmark feature of cancer genomes that reduces allelic variation, thereby creating tumor specific vulnerabilities which could be exploited for therapeutic purposes. We previously reported that loss of drug metabolic arylamine N-acetyltransferase 2 (NAT2) activity following LOH at 8p22 could be targeted for collateral lethality anticancer therapy in colorectal cancer (CRC). Here, we report a novel compound CBK034026C that exhibits specific toxicity towards CRC cells with high NAT2 activity. Connectivity Map analysis revealed that CBK034026C elicited a response pattern related to ATPase inhibitors. Similar to ouabain, a potent inhibitor of the Na+/K+-ATPase, CBK034026C activated the Nf-kB pathway. Further metabolomic profiling revealed downregulation of pathways associated with antioxidant defense and mitochondrial metabolism in CRC cells with high NAT2 activity, thereby weakening the protective response to oxidative stress induced by CBK034026C. The identification of a small molecule targeting metabolic vulnerabilities caused by NAT2 activity provides novel avenues for development of anticancer agents.

Expression of arylamine N-acetyltransferase 2 activity in immortalized human bronchial epithelial cells.

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 ß-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 KM 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.

Human N-Acetyltransferase 1 and 2 Differ in Affinity Towards Acetyl-Coenzyme A Cofactor and N-Hydroxy-Arylamine Carcinogens.

Arylamine N-acetyltransferases catalyze the transfer of acetyl groups from the endogenous cofactor acetyl coenzyme A (AcCoA) to arylamine (N-acetylation) and N-hydroxy-arylamine (O-acetylation) acceptors. Humans express two arylamine N-acetyltransferase isozymes (NAT1 and NAT2) which catalyze both N- and O-acetylation but differ in genetic regulation, substrate selectivity, and expression in human tissues. We investigated recombinant human NAT1 and NAT2 expressed in an Escherichia coli JM105 and Schizosaccharomyces pombe expression systems as well as in Chinese hamster ovary (CHO) cells to assess the relative affinity of AcCoA for human NAT1 and NAT2. NAT1 and NAT2 affinity for AcCoA was higher for recombinant human NAT1 than NAT2 when catalyzing N-acetylation of aromatic amine carcinogens 2-aminofluroene (AF), 4-aminobiphenyl (ABP), and ß-naphthylamine (BNA) and the metabolic activation of N-hydroxy-2-aminofluorene (N-OH-AF) and N-hydroxy-4-aminobiphenyl (N-OH-ABP) via O-acetylation. These results suggest that AcCoA level may influence differential rates of arylamine carcinogen metabolism catalyzed by NAT1 and NAT2 in human tissues. Affinity was higher for NAT2 than for NAT1 using N-OH-AF and N-OH-ABP as substrate consistent with a larger active site for NAT2. In conclusion, following recombinant expression in bacteria, yeast, and CHO cells, we report significant differences in affinity between human NAT1 and NAT2 for its required co-factor AcCoA, as well as for N-hydroxy-arylamines activated via O-acetylation. The findings provide important information to understand the relative contribution of human NAT1 vs NAT2 towards N-acetylation and O-acetylation reactions in human hepatic and extrahepatic tissues.

Homozygotes NAT2*5B slow acetylators are highly associated with hepatotoxicity induced by anti-tuberculosis drugs

BACKGROUND Distinct N-acetyltransferase 2 (NAT2) slow acetylators genotypes have been associated with a higher risk to develop anti-tuberculosis drug-induced hepatotoxicity (DIH). However, studies have not pointed the relevance of different acetylation phenotypes presented by homozygotes and compound heterozygotes slow acetylators on a clinical basis. OBJECTIVES This study aimed to investigate the association between NAT2 genotypes and the risk of developing DIH in Brazilian patients undergoing tuberculosis treatment, focusing on the discrimination of homozygotes and compound heterozygotes slow acetylators. METHODS/FINDINGS The frequency of NAT2 genotypes was analysed by DNA sequencing in 162 patients undergoing tuberculosis therapy. The mutation analyses revealed 15 variants, plus two new NAT2 mutations, that computational simulations predicted to cause structural perturbations in the protein. The multivariate statistical analysis revealed that carriers of NAT2*5/*5 slow acetylator genotype presented a higher risk of developing anti-tuberculosis DIH, on a clinical basis, when compared to the compound heterozygotes presenting NAT2*5 and any other slow acetylator haplotype [aOR 4.97, 95% confidence interval (CI) 1.47-16.82, p = 0.01]. CONCLUSION These findings suggest that patients with TB diagnosis who present the NAT2*5B/*5B genotype should be properly identified and more carefully monitored until treatment outcome in order to prevent the occurrence of anti-tuberculosis DIH.

Human Arylamine N-Acetyltransferase 1 (NAT1) Knockout in MDA-MB-231 Breast Cancer Cell Lines Leads to Transcription of NAT2.

Many cancers, including breast cancer, have shown differential expression of human arylamine N-acetyltransferase 1 (NAT1). The exact effect this differential expression has on disease risk and progression remains unclear. While NAT1 is classically defined as a xenobiotic metabolizing enzyme, other functions and roles in endogenous metabolism have recently been described providing additional impetus for investigating the effects of varying levels of NAT1 on global gene expression. Our objective is to further evaluate the role of NAT1 in breast cancer by determining the effect of NAT1 overexpression, knockdown, and knockout on global gene expression in MDA-MB-231 cell lines. RNA-seq was utilized to interrogate differential gene expression (genes correlated with NAT1 activity) across three biological replicates of previously constructed and characterized MDA-MB-231 breast cancer cell lines expressing parental (Scrambled), increased (Up), decreased (Down, CRISPR 2-12), or knockout (CRISPR 2-19, CRISPR 5-50) levels of NAT1. 3,889 genes were significantly associated with the NAT1 N-acetylation activity of the cell lines (adjusted p ≤ 0.05); of those 3,889 genes, 1,756 were positively associated with NAT1 N-acetylation activity and 2,133 were negatively associated with NAT1 N-acetylation activity. An enrichment of genes involved in cell adhesion was observed. Additionally, human arylamine N-acetyltransferase 2 (NAT2) transcripts were observed in the complete NAT1 knockout cell lines (CRISPR 2-19 and CRISPR 5-50). This study provides further evidence that NAT1 functions as more than just a drug metabolizing enzyme given the observation that differences in NAT1 activity have significant impacts on global gene expression. Additionally, our data suggests the knockout of NAT1 results in transcription of its isozyme NAT2.

Acetylation of putative arylamine and alkylaniline carcinogens in immortalized human fibroblasts transfected with rapid and slow acetylator N-acetyltransferase 2 haplotypes.

Exposure to alkylanilines found in tobacco smoke and indoor air is associated with risk of bladder cancer. Genetic factors significantly influence the metabolism of arylamine carcinogens and the toxicological outcomes that result from exposure. We utilized nucleotide excision repair (NER)-deficient immortalized human fibroblasts to examine the effects of human N-acetyltransferase 1 (NAT1), CYP1A2, and common rapid (NAT2*4) and slow (NAT2*5B or NAT2*7B) acetylator human N-acetyltransferase 2 (NAT2) haplotypes on environmental arylamine and alkylaniline metabolism. We constructed SV40-transformed human fibroblast cells that stably express human NAT2 alleles (NAT2*4, NAT2*5B, or NAT2*7B) and human CYP1A2. Human NAT1 and NAT2 apparent kinetic constants were determined following recombinant expression of human NAT1 and NAT2 in yeast for the arylamines benzidine, 4-aminobiphenyl (ABP), and 2-aminofluorene (2-AF), and the alkylanilines 2,5-dimethylaniline (DMA), 3,4-DMA, 3,5-DMA, 2-6-DMA, and 3-ethylaniline (EA) compared with those of the prototype NAT1-selective substrate p-aminobenzoic acid and NAT2-selective substrate sulfamethazine. Benzidine, 3,4-DMA, and 2-AF were preferential human NAT1 substrates, while 3,5-DMA, 2,5-DMA, 3-EA, and ABP were preferential human NAT2 substrates. Neither recombinant human NAT1 or NAT2 catalyzed the N-acetylation of 2,6-DMA. Among the alkylanilines, N-acetylation of 3,5-DMA was substantially higher in human fibroblasts stably expressing NAT2*4 versus NAT2*5B and NAT2*7B. The results provide important insight into the role of the NAT2 acetylator polymorphism (in the presence of competing NAT1 and CYP1A2-catalyzed N-acetylation and N-hydroxylation) on the metabolism of putative alkyaniline carcinogens. The N-acetylation of two alkylanilines associated with urinary bladder cancer (3-EA and 3,5-DMA) was modified by NAT2 acetylator polymorphism.

Congenic rats with higher arylamine N-acetyltransferase 2 activity exhibit greater carcinogen-induced mammary tumor susceptibility independent of carcinogen metabolism.

BACKGROUND: Recent investigations suggest role(s) of human arylamine N-acetyltransferase 1 (NAT1) in breast cancer. Rat NAT2 is orthologous to human NAT1 and the gene products are functional homologs. We conducted in vivo studies using F344.WKY-Nat2 rapid/slow rats, congenic at rat Nat2 for high (rapid) and low (slow) arylamine N-acetyltransferase activity, to assess a possible role for rat NAT2 in mammary tumor susceptibility. METHODS: Mammary carcinogens, methylnitrosourea (MNU) and 7,12-dimethylbenzanthracene (DMBA) neither of which is metabolized by N-acetyltransferase, were administered to assess mammary tumors. MNU was administered at 3 or 8 weeks of age. DMBA was administered at 8 weeks of age. NAT2 enzymatic activity and endogenous acetyl-coenzyme A (AcCoA) levels were measured in tissue samples and embryonic fibroblasts isolated from the congenic rats. RESULTS: Tumor latency was shorter in rapid NAT2 rats compared to slow NAT2 rats, with statistical significance for MNU administered at 3 and 8 weeks of age (p = 0.009 and 0.050, respectively). Tumor multiplicity and incidence were higher in rapid NAT2 rats compared to slow NAT2 rats administered MNU or DMBA at 8 weeks of age (MNU, p = 0.050 and 0.035; DMBA, p = 0.004 and 0.027, respectively). Recombinant rat rapid-NAT2, as well as tissue samples and embryonic fibroblasts derived from rapid NAT2 rats, catalyzed p-aminobenzoic acid N-acetyl transfer and folate-dependent acetyl-coenzyme A (AcCoA) hydrolysis at higher rates than those derived from rat slow-NAT2. Embryonic fibroblasts isolated from rapid NAT2 rats displayed lower levels of cellular AcCoA than slow NAT2 rats (p < 0.01). CONCLUSIONS: A novel role for rat NAT2 in mammary cancer was discovered unrelated to carcinogen metabolism, suggesting a role for human NAT1 in breast cancer.

Arylamine N-acetyltransferase 2 gene polymorphism in an Algerian population.

BACKGROUND: The arylamine N-acetyltransferase 2 (NAT2) is a key enzyme in the biotransformation of xenobiotics. NAT2 gene polymorphisms have been associated with the risk of isoniazid hepatotoxicity and these polymorphisms change among different populations. AIM: The objective of this study is to investigate NAT2 polymorphisms in order to predict the prevalence of NAT2 phenotype in an Algerian population. SUBJECTS AND METHODS: Genotyping of NAT2 was done using a PCR-RFLP method. Haplotype was analysed using the software package PHASE, version 2.0. RESULTS: The major haplotypes were NAT2*5B (23.72%), NAT2*6 A (18.61%), NAT2*4 (14.60%) and NAT2*5 F (10%). The average of the expected slow acetylator phenotype was 53%. CONCLUSION: Our results suggest that the high frequency of slow acetylator phenotype requires investigation into its possible association with ATDH.

Entrando en la era de la farmacogenética: bases para el uso racional de drogas anti-tuberculosas / Coming in the era of pharmacogenetics: basis for the rational use of anti-tuberculosis drugs

INTRODUCCION: En Argentina se reportan alrededor de 11.000 casos nuevos de tuberculosis (TB) por año. El tratamiento con drogas anti-TB produce daño hepático en una gran proporción de los pacientes, y la isoniacida (INH) es la principal inductora de hepatotoxicidad. Algunos polimorfismos de las enzimas NAT-2 y CYP2E1, involucradas en el metabolismo de INH, estarían directamente asociados con el desarrollo de hepatotoxicidad.OBJETIVO: Analizar la distribución de las variantes alélicas *4, *5, *6, *7 y *14 de NAT-2 y c1/c2 de CYP2E1 en población sana argentina y en pacientes con TB que concurren a hospitales públicos de la ciudad de Buenos Aires y estudiar su asociación con el desarrollo de la hepatotoxicidad.METODOS: Se estudiaron 152 pacientes con TB tratados con drogas anti-TB. La distribución de frecuencias alélicas y genotípicas fue determinada por PCR-RFLP, y los resultados fueron comparados entre pacientes con TB con o sin desarrollo de hepatotoxicidad, usando un análisis de regresión logística binaria.RESULTADOS: El estado acetilador lento resultó la única variable independiente en la predicción de hepatotoxicidad relacionada con las drogas anti-TB (p = 0,019; OR = 2,971).CONCLUSIONES: El presente estudio demuestra que, dada la alta prevalencia del estado acetilador lento en la población argentina y su asociación al riesgo de desarrollar hepatotoxicidad, junto con el aumento en los casos de TB y los costos que conllevan las internaciones por daño hepático asociado a drogas anti-TB, el análisis del estado acetilador previo al tratamiento anti-TB podría ser clave.

INTRODUCTION: In Argentina, about 11.000 new cases of tuberculosis (TB) are reported per year. Treatment with anti-TB drugs produces liver damage in a large proportion of patients, being isoniazid (INH) the main responsible for hepatotoxicity. Some polymorphisms of the enzymes NAT-2 and CYP2E1, which are involved in the metabolism of INH, might be directly associated with the development of hepatotoxicity.OBJECTIVE: To analyze the distribution of NAT-2 variants *4, *5, *6, *7 and *14, and CYP2E1 alleles c1 and c2 in a healthy population from Argentina and in patients with TB who attend public hospitals in Buenos Aires city, and to stude their association with the development of hepatotoxicity.METHODS: The study included 152 patients with TB treated with anti-TB drugs. The allelic and genotypic frequency distribution was determined by PCR-RFLP, and the results were compared between TB patients with or without development of hepatotoxicity using a binary logistic refression analysis.RESULTS: The slow acetylator status was the only independent variable in the prediction of hepatotoxicity associated with anti-TB drugs (p = 0.019; OR = 2.971).CONCLUSIONS: This study shows that, given the high prevalence of slow acetylator status in Argentine population and its association with the risk of hepatotoxicity, together with the increase in TB cases and the hospitalization costs due to liver damage associated with anti-TB drugas, the analysis of acetylator status before anti-TB treatment could be fundamental.

Entrando en la era de la farmacogenética: bases para el uso racional de drogas anti-tuberculosas / Coming in the era of pharmacogenetics: basis for the rational use of anti-tuberculosis drugs

INTRODUCCION: En Argentina se reportan alrededor de 11.000 casos nuevos de tuberculosis (TB) por año. El tratamiento con drogas anti-TB produce daño hepático en una gran proporción de los pacientes, y la isoniacida (INH) es la principal inductora de hepatotoxicidad. Algunos polimorfismos de las enzimas NAT-2 y CYP2E1, involucradas en el metabolismo de INH, estarían directamente asociados con el desarrollo de hepatotoxicidad.OBJETIVO: Analizar la distribución de las variantes alélicas *4, *5, *6, *7 y *14 de NAT-2 y c1/c2 de CYP2E1 en población sana argentina y en pacientes con TB que concurren a hospitales públicos de la ciudad de Buenos Aires y estudiar su asociación con el desarrollo de la hepatotoxicidad.METODOS: Se estudiaron 152 pacientes con TB tratados con drogas anti-TB. La distribución de frecuencias alélicas y genotípicas fue determinada por PCR-RFLP, y los resultados fueron comparados entre pacientes con TB con o sin desarrollo de hepatotoxicidad, usando un análisis de regresión logística binaria.RESULTADOS: El estado acetilador lento resultó la única variable independiente en la predicción de hepatotoxicidad relacionada con las drogas anti-TB (p = 0,019; OR = 2,971).CONCLUSIONES: El presente estudio demuestra que, dada la alta prevalencia del estado acetilador lento en la población argentina y su asociación al riesgo de desarrollar hepatotoxicidad, junto con el aumento en los casos de TB y los costos que conllevan las internaciones por daño hepático asociado a drogas anti-TB, el análisis del estado acetilador previo al tratamiento anti-TB podría ser clave.

INTRODUCTION: In Argentina, about 11.000 new cases of tuberculosis (TB) are reported per year. Treatment with anti-TB drugs produces liver damage in a large proportion of patients, being isoniazid (INH) the main responsible for hepatotoxicity. Some polymorphisms of the enzymes NAT-2 and CYP2E1, which are involved in the metabolism of INH, might be directly associated with the development of hepatotoxicity.OBJECTIVE: To analyze the distribution of NAT-2 variants *4, *5, *6, *7 and *14, and CYP2E1 alleles c1 and c2 in a healthy population from Argentina and in patients with TB who attend public hospitals in Buenos Aires city, and to stude their association with the development of hepatotoxicity.METHODS: The study included 152 patients with TB treated with anti-TB drugs. The allelic and genotypic frequency distribution was determined by PCR-RFLP, and the results were compared between TB patients with or without development of hepatotoxicity using a binary logistic refression analysis.RESULTS: The slow acetylator status was the only independent variable in the prediction of hepatotoxicity associated with anti-TB drugs (p = 0.019; OR = 2.971).CONCLUSIONS: This study shows that, given the high prevalence of slow acetylator status in Argentine population and its association with the risk of hepatotoxicity, together with the increase in TB cases and the hospitalization costs due to liver damage associated with anti-TB drugas, the analysis of acetylator status before anti-TB treatment could be fundamental.

Relationship between polymorphism of arylamine N-acetyltransferase 2 and genetic susceptibility to hair dye dermatitis / 中华医学美学美容杂志

Objective To investigate the relationship between polymorphism of arylamine N-acetyltransferase 2 (NAT2) and hair dye dermatitis in a Chinese population. Methods Polymorphism chain-restriction fragment length polymorphism (PCR-RFLP) was used and the wild-type allele (NAT2 * 4) and three mutant alleles (NAT2 * 5A, 6B and 7A) were determined in 60 patients with hair dye dermatitis and 73 age-matched control subjects in Tianjin region. Results In hair dye dermatitis cases, the frequency of NAT2 * 4, NAT2 * 5A, NAT2 * 6B, NAT2 * 7A was 52. 5 % , 5. 0 % ,26.7 % and 15. 8 %, respectively, and no statistically significant difference of the frequencies was found between the hair dye dermatitis patients and controls (P>0. 05). The frequency of rapid genotype, intermediate genotype and slow genotype was 26. 7 % , 51. 7 % and 21. 7 % in hair dye dermatitis cases, 30. 1 %, 50. 7 % and 19. 2 % in control subjects, respectively, and no statistically significant difference of the frequencies between the two groups (P>0. 05). Conclusions Our study suggests that there might be no relationship between polymorphism of NAT2 and genetic susceptibility to hair dye dermatitis in a Chinese population.