Alcohol: Immunomodulatory Effects and Cancer

ABSTRACT Alcohol consumption has been linked to numerous pathologic conditions, including infectious diseases and several types of cancer. Alcohol exerts its modulatory effects on the immune system (IS) in a dose- and time-dependent manner. Numerous studies indicate that these alterations affect responses such as peripheral inflammation or decreased antibody production and promote chronic inflammation, leading to cell death. The molecular mechanisms underlying these effects involve generating an oxidative tissue environment, producing cell damage-associated molecular patterns (DAMPs), and activating pattern recognition receptors. In particular, toll-like receptors and their signaling system emerge as central elements whose activity is altered by alcohol intake. There is also some epidemiological evidence demonstrating the causal role of alcohol in the development of various types of cancer, such as head-and-neck cancer, esophageal cancer, colorectal cancer, liver cancer, and breast cancer. Most recent evidence suggests that factors related to alcohol consumption and cancer include increased levels of acetaldehyde, production of reactive oxygen species, alteration in DNA methylation, and modifications in retinoid metabolism. In addition, changes associated with alcohol use on the IS and intestinal microbiota may favor the growth of some types of tumors.

Interaction between adverse pregnancy history and polycyclic aromatic hydrocarbon-DNA adducts on missed abortion / 环境与职业医学

Background The incidence rate of missed abortion is increasing year by year, but the etiology has not been fully elucidated. Adverse pregnancy history and exposure to polycyclic aromatic hydrocarbons (PAHs) may increase the risk of missed abortion. Objective To investigate the interaction between adverse pregnancy history and PAHs exposure on missed abortion in early pregnancy, and to provide evidence for the etiologic research of missed abortion. Methods A total of 114 pregnant women diagnosed with missed abortion in the Department of Obstetrics of the First Hospital of Shanxi Medical University from March to December 2019 were selected as the case group, and 139 pregnant women who visited the same hospital for voluntary induced abortion in the same period as the control group, to collect basic information and medical information of abortion, stillbirth, intrauterine growth retardation, and other adverse pregnancy history. Abortion villus tissues were collected to detect PAH-DNA adducts levels, stratified by pregnancy and adverse pregnancy history and grouped by quartile method: Q1 (< 404.61 ng·L−1), Q2 (404.61−453.75 ng·L−1), Q3 (453.76−506.72 ng·L−1), and Q4 (≥506.73 ng·L−1). SPSS 25.0 statistical software was used for χ2 test and multiple logistic regression, and additive and multiplicative models were used to investigate the interaction between adverse pregnancy history and PAH-DNA adducts level on missed abortion. The PAH-DNA adducts were grouped by tertiles and quartiles, and P33, P50, P67 and P75 were used as data cut points for sensitivity analysis. Results The proportion of adverse pregnancy history in the case group (32.46%) was higher than that in the control group (12.23%) (P < 0.001). Among 160 subjects with≥2 pregnancies, the proportion of adverse pregnancy history in the case group (57.81%) was higher than that in the control group (17.71%) (P < 0.001). The results of χ2 test stratified by pregnancy for different PAH-DNA adducts levels between the two groups showed that the PAH-DNA adducts level was associated with missed abortion in subjects with≥2 pregnancies (χ2=10.14, P=0.017). Being further stratified by adverse pregnancy history, the PAH-DNA adducts level in subjects with no adverse pregnancy history was associated with missed abortion (χ2=9.70, P=0.021). The results of logistic regression analysis showed that adverse pregnancy history (OR=5.88, 95%CI: 2.79−12.39) and PAH-DNA adducts (OR=3.01, 95%CI: 1.22−7.40) increased the risk of missed abortion, but no interaction between them was found. The relative excess risk of interaction (RERI), the attributable percentage of interaction (AP), and the synergy index (SI) and its 95%CI were 0.60 (95%CI: −0.58−1.77), 0.74 (95%CI: −0.83−2.30), and 0.20 (95%CI: 0.01−5.43), respectively. Conclusions Adverse pregnancy history and PAH-DNA adducts in pregnant women may increase the risk of missed abortion. The effect of the interaction between them on the occurrence of missed abortion is not supported by the current study.

Quantification of aristolochic acids and their DNA adducts in mice kidney and liver by HPLC-MS/MS / 中国中药杂志

This study aims to establish a quantitative method of 4 aristolochic acids-DNA adducts in mice kidney and liver based on high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) for monitoring the content changes of aristolochic acids-DNA adducts. A Shiseido Capcellpak AQ C_(18) column(3 mm×100 mm, 3 μm) was used, with a mixture of 0.2% acetic acid-5 mmol·L~(-1) ammonium acetate as the aqueous phase and methanol as the organic phase for gradient elution. The multiple reaction monitoring(MRM) scanning method under positive mode by electrospray ionization(ESI) was performed for the detection of the aristolochic acids-DNA adducts which formed by combining aristolochic acid Ⅰ/Ⅱ with deoxyadenosine, deoxyguanosine, and deoxycytidine, respectively. Balb/c mice were given Guanmutong extract by gavage, and the relative content of aristolochic acids-DNA adducts in liver and kidney samples were analyzed within 60 days. It was found that the concentration of 4 aristolochic acids-DNA adducts in the kidney was significantly higher than that in the liver, and there were about 15.87 adducts in per 1×10~6 normal deoxynucleosides, which was 4.5-7.5 times than that of the liver. What's more, some adducts can still be detected on the 30 th day after administration. The concentration of the adducts in the liver was highest on the first day after administration, and a second peak appeared during the 7 th to 14 th days. The results indicated that aristolochic acids-DNA adducts are difficult to eliminate in vivo, and it is of great significance to study the mechanism of liver and kidney injury of aristolochic acid.

Formaldehído: revisión bibliográfica sobre biomarcadores de efecto para la medición de la exposición ocupacional / Formaldehyde: A literature review on biomarkers of effect for measuring occupational exposure / Formaldeído: revisão da bibliografia sobre biomarcadores de efeito para medir a exposição ocupacional

Resumen A pesar de las grandes cantidades de formaldehído que se usa en la industria, la vigilancia de los efectos sobre la salud, derivados de la exposición ocupacional, sigue siendo un aspecto por mejorar en los programas de prevención de riesgos laborales. Objetivo: Identificar los diferentes biomarcadores de efecto que han sido propuestos para ser utilizados como indicadores indirectos de exposición a formaldehído y que se encuentran reportados en la literatura científica. Metodología: Se hizo una revisión bibliográfica desde el año 1990 hasta el primer trimestre del año 2018, usando los descriptores: "Formaldehído", "Biomarcador", "Exposición profesional". Se consultaron las bases de datos y se complementó la búsqueda inicial, mediante la consulta de la bibliografía citada por los autores de los artículos seleccionados. Se revisaron los resúmenes de los artículos y se seleccionaron aquellos que, luego de un análisis preliminar, se identificó contenían información relevante para la investigación. Resultados: Se encontraron 57 artículos relevantes para la revisión que contenían información sobre biomarcadores de efecto en poblaciones de trabajadores expuestos a formaldehído, algunos estudios en animales y células in vitro. Se resumieron los biomarcadores usados, listaron los estudios y describieron brevemente los hallazgos de cada uno. Conclusiones: La falta de conocimiento y entendimiento de los mecanismos toxicocinéticos y toxicodinámicos del formaldehído en los seres humanos limita la aplicación de un biomarcador de efecto que mida de manera práctica y sencilla la exposición al formaldehído exógeno.

Abstract Despite the large amounts of formaldehyde used in the industry, monitoring the health effects of occupational exposure remains an aspect of further improvement in occupational risk prevention programs. Objective: To identify the different biomarkers of effect that have been proposed to be used as indirect indicators of formaldehyde exposure and that are reported in the scientific literature. Methodology: A bibliographic review of literature from 1990 to the first quarter of 2018 was made using the descriptors: "Formaldehyde", "Biomarker", "Professional exposure". Databases were consulted and the initial search was supplemented by consulting the bibliography cited by the authors of the selected articles. Abstracts of articles were reviewed and those that, after preliminary analysis, were determined to contain information relevant to the research were selected. Results: The study found 57 articles relevant to the review which contained information on biomarkers of effect in populations of workers exposed to formaldehyde, some animal studies, and in vitro cells. Used biomarkers were summarized, studies were listed, and the findings of each of them were briefly described. Conclusions: The lack of knowledge and understanding of the toxicokinetic and toxicodynamic mechanisms of formaldehyde in humans limits the application of a biomarker of effect that measures in a practical and simple way exposure to exogenous formaldehyde.

Resumo Apesar da grande quantidade de formaldeído usado na indústria, o monitoramento dos efeitos na saúde, derivados da exposição ocupacional, continua sendo um aspecto a ser aprimorado nos programas de prevenção de riscos ocupacionais. Objetivo: Identificar os diferentes biomarcadores de efeito propostos para serem utilizados como indicadores indiretos da exposição ao formaldeído e relatados na bibliografia científica. Metodologia: Foi realizada uma revisão bibliográfica entre 1990 e o primeiro trimestre de 2018, utilizando os descritores: "Formaldeído", "Biomarcador", "Exposição Profissional". As bases de dados foram consultadas e a busca inicial foi complementada consultando a bibliografia citada pelos autores dos artigos selecionados. Os resumos dos artigos foram revisados e aqueles que, após análise preliminar, foram identificados, continham informações relevantes para a investigação. Resultados: Foram encontrados 57 artigos relevantes para a revisão que continham informações sobre biomarcadores de efeito em populações de trabalhadores expostos ao formaldeído, alguns estudos em animais e células in vitro. Os biomarcadores utilizados foram resumidos, os estudos listados e descritos brevemente os achados de cada um. Conclusões: A falta de conhecimento e entendimento dos mecanismos toxicocinéticos e toxicodinâmicos do formaldeído em humanos limita a aplicação de um biomarcador de efeito que mede de maneira prática e simples a exposição ao formaldeído exógeno.

Investigação dos processos biológicos associados à produção endógena de aldeídos reativos / Research on biological processes associated with endogenous production of reactive aldehydes

Os aldeídos são espécies reativas que podem ser produzidos endogenamente por processos como a lipoperoxidação, podendo reagir com lipídios, proteínas e DNA. Diversas evidências apontam para o envolvimento de aldeídos reativos na progressão de patologias como doenças cardiovasculares, arteriosclerose e doenças neurodegenerativas. Uma meta central do CEPIDRedoxoma é estudar a reatividade química de intermediários redox em ambientes biológicos e consequentes mudanças na estrutura e função de biomoléculas, entender como cada intermediário redox reage com biomoléculas específicas e os efeitos resultantes, essenciais para a concepção de biomarcadores e antioxidantes. O nosso grupo estuda os mecanismos de formação, detoxificação e reação com biomoléculas de aldeídos reativos endógenos e exógenos e seu papel em patologias como a esclerose lateral amiotrófica (ALS). Um dos mecanismos de detoxificação desses aldeídos é através da conjugação com a carnosina. Recentemente, foi observado que a suplementação de animais transgênicos ALS SOD G93A com carnosina via oral resultou em retardo da perda de peso e tendência de aumento da sobrevida dos animais. O presente projeto buscou investigar o possível papel da carnosina em animais modelo para ALS. Para isso as modificações em DNA induzidas por aldeídos reativos e a formação de adutos de carnosina-aldeídos foram analisadas através de metodologia HPLC-MS/MS. Assim observamos que ratos suplementados com carnosina apresentaram níveis significativamente menores de proteína carbonilada em músculo e fígado. Em fígadoforam vistos níveis menores de dois adutos de DNA, 8-oxodGuo e1,N2-HO-propanodGuo, em animais suplementados. Em cérebro foram detectados níveis menores de 1, N2-εdGuo. Com relação aos adutos carnosina-aldeídos, foi observado níveis significativamente maiores do aduto CAR-HHE na medula. Com embasamento nos resultados aqui apresentados, sugere-se a utilização de sequestradores de aldeídos como uma estratégia terapêutica em condições fisiopatológicas nas quais ao acúmulo dessas espécies está comprovado

Aldehydes are reactive species that can be produced endogenously by processes such as lipid peroxidation, which can react with lipids, proteins and DNA. Several evidences point to the involvement of reactive aldehydes in the progression of pathologies such as cardiovascular diseases, atherosclerosis and neurodegenerative diseases. A central goal of CEPID-Redoxoma is to study the chemical reactivity of redox intermediates in biological environments and consequent changes in the structure and function of biomolecules, to understand how each redox intermediate reacts with specific biomolecules and the resulting effects, essential for the design of biomarkers and antioxidants. Our group studies the mechanisms of formation, detoxification and reaction with biomolecules of endogenous and exogenous reactive aldehydes and their role in pathologies such as amyotrophic lateral sclerosis (ALS). One of the detoxification mechanisms of these aldehydes is through carnosine conjugation. Recently, we observed that oral carnosine supplementation in transgenic ALS SODG93A animals resulted in delayed weight loss and a tendency to increase the survival of the animals. The present project investigated the potential role of carnosine in animal models for ALS. Thus, reactive aldehydes induced DNA modifications and carnosine aldehyde adducts were analyzed by HPLC-MS/MS. We observed that rats supplemented with carnosine presented significantly lower levels of protein carbonylation in muscle and liver. Lower levels of two DNA adducts, 8-oxodGuo and 1, N2-HO-propanodGuo, were observed in liver of the supplemented animals. Lower levels of 1, N2-εdGuo were detected in the brain. Regarding the carnosine-aldehydeadducts, significantly higher levels of the CAR-HHE adduct were observed in spinal cord. The results presented here suggest the use of aldehyde scavengers as a therapeutic strategy under pathological conditions in which is proven the accumulation of these species

Molecular Pathways for Nasopharyngeal Carcinoma focused on Acetaldehyde, Nitrosamines and Nicotine Exposures

@#Recently, one of the head and neck tumours located at the nasopharynx epithelium known as nasopharyngeal carcinoma (NPC) have been associated with few cancer-promoting compounds that derived from alcohol, salt preserved foods consumptions and tobacco smoking such as acetaldehyde, nitrosamine, nicotine. These cancer-promoting compounds present the ability to damage the genome and disrupt cellular metabolic processes. This review will discuss further on the molecular mechanism of acetaldehyde, nitrosamine, nicotine and NPC risk. Acetaldehyde can exert influence as carcinogen macromolecular adducts to cellular proteins and DNAs whilst nitrosamines that commonly found in preserved salted foods/diets can contribute as a powerful carcinogen via endogenous nitrosation and reactives molecules by CYP2E1. Nicotine present in tobacco could reacts with nitrosamine to form NNN and NNK known as carcinogenic agent. NNK mediates unstable reactive oxygen species that can induce DNA lesion (α -hydroxylation of NNN at positions 2’and 5’) and microenvironment alteration for tumorigenesis. In conclusion, this study suggests acetaldehydes, nitrosamine and nicotine may contribute to NPC tumourigenesis.

Relationship between 7, 8-dihydrodio1-9.10-epoxide benzoapyrene DNA adducts in peripheral blood of pregnant women and gestational diabetes mellitus / 中国医师进修杂志

Objective@#To examine the relationship between 7, 8-dihydrodio1-9.10-epoxide benzo[a] pyrene-DNA adducts (BPDE-DNA adducts) in the blood of pregnant women and gestational diabetes mellitus (GDM) and explore the environmental factors of the formation of GDM.@*Methods@#Forty pregnant women who were diagnosed GDM (case group) and 40 pair-matched normal pregnantwomen who had no complications accordingto age, gravidity, parity and gestational weeks(normal control group) were enrolled in this study. Questionnaire survey was used to obtain personal information, and BPDE-DNA adducts was examined by high performance liquid chromatography. Logistic regression model was used to analyze the relationship between BPDE-DNA adductsand GDM.@*Results@#The concentration of BPDE-DNA adducts in peripheral blood of case group [(6.1 ± 2.9) adducts/108nucleotides] was significantly higher than that of normal control group [(3.0 ± 1.7) adducts/108nucleotides] (P<0.05). After controlled for possible confounding factors, it was found that maternal serum BPDE-DNA adduct was a risk factor for the occurrence of GDM (OR=1.99, 95%CI 1.43-2.79), while household income was a protective factor (OR=0.55, 95%CI 0.31-0.98). Each increased quartile of the BPDE-DNA adducts exposure level was associated with an elevated risk of GDM by 2.62 folds(OR=3.62, 95%CI 2.07-6.35).@*Conclusions@#The high level of BPDE-DNA adducts in the peripheral blood of pregnant women is a risk factor for the occurrence of GDM.

Association of etheno-DNA adduct and DNA methylation level among workers exposed to diesel engine exhaust / 中华预防医学杂志

Objective@#To investigate the association between etheno-DNA adduct and the promoter of DNA methylation levels of cyclin dependent kinase inhibitor 2A (P16), Ras association domain family 1 (RASSF1A) and O-6-methylguanine-DNA methyltransferase (MGMT) in workers with occupational exposure to diesel engine exhaust (DEE).@*Methods@#We recruited 124 diesel engine testing workers as DEE exposure group and 112 water pump operator in the same area as control group in Henan province in 2012 using cluster sampling. The demographic data were obtained by questionnaire survey; urine after work and venous blood samples were collected from each subject. The urinary etheno-DNA adducts were detected using UPLC-MS/MS, including 1,N6-etheno-2'-deoxyadenosine (εdA) and 3,N4-etheno-2'-deoxycytidine(εdC). The DNA methylation levels of P16, RASSF1A, and MGMT were evaluated using bisulfite-pyrosequencing assay. The percentage of methylation was expressed as the 5-methylcytosine (5mC) over the sum of cytosines (%5mC). Spearman correlation and multiple linear regression were applied to analyze the association between etheno-DNA adducts and DNA methylation of P16, RASSF1A, and MGMT.@*Results@#The median (P25-P75) of urinary εdA level was 230.00 (98.04-470.91) pmol/g creatinine in DEE exposure group, and 102.10 (49.95-194.48) creatinine in control group. The level of εdA was higher in DEE exposure group than control group (P<0.001). DNA methylation levels of P16, RASSF1A and MGMT were 2.04±0.41, 2.19 (1.94-2.51), 2.22 (1.94-2.46)%5mC in exposure group, and 2.19±0.40, 2.41 (2.11-2.67), 2.44 (2.15-2.91)%5mC in control group. DNA methylation levels were lower in exposure group (P values were 0.005, 0.002 and 0.001, respectively). Spearman correlation analysis showed that DNA methylation levels of P16, RASSF1A, and MGMT were negative associated with urinary εdA level (r values were -0.155, -0.137, and -0.198, respectively, P<0.05). No significant correlation was observed between the εdC level and any measured DNA methylation levels (P>0.05) . Multiple linear regression confirmed the negative correlation between εdA and DNA methylation levels of P16, RASSF1A, and MGMT in non-smoking group (β (95%CI) was -0.068 (-0.132--0.003), -0.082 (-0.159--0.004) and -0.048 (-0.090--0.007), P values were 0.039, 0.039 and 0.024, respectively). Moreover, εdC was negative associated with DNA methylation level of MGMT in non-smoking group (β (95%CI) was -0.094 (-0.179--0.008), P=0.032).@*Conclusion@#DEE exposure could induce the increased of εdA and decreased of DNA methylation levels of P16, RASSF1A and MGMT.

Efeitos citotóxicos, genotóxicos e epigenéticos do Bisfenol A em células HL-60, MCF-7 e em ratos / Cytotoxic, genotoxic and epigenetics effects of Bisphenol A on HL-60, MCF-7 cells and rats

Bisfenol A (BPA) é um insumo largamente utilizado na produção de plástico policarbonato e amplamente difundido no meio ambiente, levando o ser humano à exposição crônica desde o período intrauterino. A literatura aponta a possibilidade de BPA aumentar o risco de diversos tipos de câncer, mas são necessários estudos que possibilitem o entendimento de mecanismos pelos quais isso pode ocorrer. Neste trabalho foram investigados os efeitos do BPA ou nitro-BPA em células HL-60, MCF-7 e tecidos de ratos. Células HL-60 foram expostas ao BPA ou nitro-BPA nas concentrações de 25, 100 e 250 µM (0,1 % DMSO v/v) por 2, 24 ou 48 horas na presença ou ausência de H2O2 (40 nmol/5 x 104 células). Células MCF-7 foram expostas da mesma forma, sem o uso de H2O2, mas na presença e ausência de agonista (PCB) de receptor Ah. Ratos Sprague-Dawley machos receberam BPA diariamente ao longo de 4 semanas (50 mg/kg de peso corpóreo) por gavagem, na vigência e ausência de diabetes, com subsequente coleta de urina, fígado, rins, medula óssea e sangue. Nos experimentos com as células, a viabilidade, ciclo celular, fragmentação do DNA e a produção intracelular de espécies reativas de oxigênio (ROs) foram avaliadas por citometria de fluxo, a atividade da cadeia respiratória mitocondrial pelo ensaio do XTT, e a atividade de MPO de células HL-60 por ensaio de fluorescência, bem como a produção de •NO. A metilação e hidroximetilação global do DNA e os adutos 8-oxodG, CEdG, 1,N6-εdA, 1,N2-εdG e BPA-Gua no DNA das células, tecidos, meio de cultura e urina foram analisados por HPLC-ESI-MS/MS. O hemograma e mielograma dos animais foram obtidos no Laboratório de Hematologia Experimental da FCF USP. Observou-se que tanto BPA quanto nitro-BPA induziram a geração de ROS em células HL-60 logo após 2h de incubação. BPA levou subsequentemente à perda de atividade da cadeia respiratória mitocondrial, aumento da permeabilidade da membrana plasmática, fragmentação do DNA, parada na fase G2/M do ciclo celular e hipermetilação acompanhada de hipohidroximetilação global do DNA. A citotoxicidade induzida pelas mesmas concentrações de nitro-BPA em células HL-60 foi menos pronunciada, sem perda de atividade da cadeia respiratória mitocondrial, com pouca fragmentação do DNA, mas com parada na fase G0/G1 do ciclo celular e indução de hipohidroximetilação global do DNA na presença de H2O2. Não foi observada a indução de adutos de DNA nas células HL-60 incubadas com BPA, mas sim de CEdG nas células incubadas com nitro-BPA. Os dados obtidos a partir da exposição das células HL-60 a BPA e nitro-BPA nos indicam que as duas moléculas provocam alterações metabólicas distintas nesse tipo celular, independentes da via estrogênica, que levam a alterações predominantemente epigenéticas (BPA) ou genéticas e epigenéticas (nitro-BPA), que podem ter consequências fenotípicas, como progressão maligna, que precisam ser investigadas. Foi observado que as células MCF-7 são mais resistentes que as células HL-60 à citotoxicidade induzida por BPA e nitro-BPA. Como resultado da exposição das células MCF-7 a BPA, houve pequeno aumento da permeabilidade da membrana plasmática (250 µM), indução dos níveis de ROS após 24 h (25 µM) e aumento da população de células em sub G1, ou seja, com DNA fragmentado (100 µM e 250 µM), mas sem alteração do ciclo celular. No caso de nitro-BPA, foi observada parada do ciclo celular em G2/M (25 µM, 100 µM e 250 µM), assim como aumento de permeabilidade da membrana plasmática após 24 h de incubação (25 µM, 250 µM), sem indução de ROS ou aumento de células em sub G1. Entretanto, observou-se aumento dos níveis de CEdG e 8-oxodG no DNA das células incubadas com BPA (100 µM, 250 µM) sem a ativação prévia de receptores Ah. A ativação dos receptores Ah com PCB levou a menor aumento do nível das lesões após as incubações com BPA. A maior resistência das células MCF-7 aos efeitos citotóxicos do BPA está provavelmente relacionada à ação estrogênica desse xenobiótico. A sinalização estrogênica juntamente com o aumento dos níveis de lesões no DNA aumenta a chance de mutações e de transformação maligna. Nas células com ativação do receptor Ah, BPA levou ainda ao aumento da hidroximetilação global, sem alteração da metilação global do DNA. Os animais não diabéticos expostos ao BPA apresentaram quantidades diminuídas de promielócitos, blastos e bastonetes na medula óssea (aplasia medular), sem alteração no hemograma. Houve aumento dos níveis de CEdG no fígado, da metilação e hidroximetilação global do DNA hepático, e não foi observada alteração das marcas epigenéticas e adutos de DNA no rim ou na urina. Os animais diabéticos expostos ao BPA apresentaram aumento do número de eosinófilos e linfócitos na medula óssea, podendo-se sugerir a indução de um estado inflamatório alérgico, e aumento do número total de hemácias circulantes e do hematócrito. Houve aumento dos níveis de CEdG, da metilação e hidroximetilação global do DNA hepático, aumento dos níveis de 8-oxodG no DNA renal, sem alteração das marcas epigenéticas no rim, e não foi observada alteração dos adutos de DNA na urina. Os dados obtidos apontam para a geração de ROS como uma importante via de cito- e genotoxicidade induzidas por BPA. Sua biotransformação para BPA-3,4- quinona nos modelos utilizados parece ter menor importância para os efeitos, uma vez que não foi detectada a lesão BPA-Gua em nenhuma amostra de DNA, meio de cultura das células ou urina dos animais. Alterações metabólicas induzidas por BPA e ROS podem favorecer as alterações das marcas epigenéticas observadas no DNA das células HL-60, MCF-7 e fígado dos animais. Todas essas alterações podem contribuir para a transformação maligna de células expostas ao BPA

Bisphenol A (BPA) is a compound widely used in polycarbonate plastic production and widespread in the environment, humans are chronic exposed to BPA in intrauterine period and entire life. The literature suggests the possibility of BPA increase the risk of developing cancers, but studies are required to enable the understanding of mechanisms by which this can occur. HL -60 cells were exposed to BPA or nitro-BPA at concentrations of 25, 100 and 250 uM (0.1% DMSO v/v) for 2, 24 or 48 hours in presence or absence of H2O2 (40 nmol/5x104 cells), MCF-7 cells followed a similar profile of exposure without the use of H2O2, but in presence or absence of Ah agonist receptor (PCB126). Male Sprague-Dawley rats received BPA daily over 4 weeks (50 mg/kg body weight) by gavage in presence and absence of diabetes, with subsequent collection of urine, liver, kidney, bone marrow and circulating blood. The viability, cell cycle, DNA fragmentation and the intracellular production of reactive oxygen species (ROS) was evaluated by flow cytometry, MPO activity and NO production was evaluated by fluorescence assay for HL- 60 cells, mitochondrial activity by XTT assay, and the global DNA methylation was checked by HPLC-PDA. DNA adducts 8-oxodG, CEdG, 1,N6-εdA, 1,N6-εdG and BPA-Gua were quantified by HPLC- ESI-MS/MS in DNA of cells, culture medium, urine and tissue collected from Sprague-Dawley rats. Blood count and bone marrow examination were obtained in collaboration with Experimental Hematology Laboratory of University of Sao Paulo We observed that both BPA and BPANO2 induced ROS generation in HL- 60 cells after 2 hours of incubation. BPA subsequently led to failure of mitochondrial respiratory chain activity, increased permeability of the plasma membrane, DNA fragmentation, arrest in G2/M phase of cell cycle, DNA hypermethylation with global hipohydroxymethylation. We saw low cytotoxicity in HL-60 cells induced by nitro-bpa n the same concentration, without loss of mitochondrial respiratory chain activity, discrete DNA fragmentation, but leading cell cycle to stopping at G0/G1 phase, and induction of DNA global hypermethylation. No lesions were observed in the DNA of HL-60 cells.The results obtained from the exposure of HL-60 cells to BPA and nitro-BPA indicate that these two molecules induce different metabolic abnormalities in this cell line, independent of estrogen pathway, leading to changes in epigenetic (BPA) or genetic and epigenetic (nitro-BPA) profile, that can induce phenotypic consequences such as malignant progression. It was observed along the study that MCF-7 cells are more resistant than HL-60 cells to cell damage induced by BPA and nitro-BPA. As a result of MCF-7 cells exposure to BPA, we saw a slight increase in membrane permeability (250 mM), ROS generation after 24h (25 mM) and increase in cell population in sub G1, so we had DNA fragmentation (100 uM and 250 uM), but with no effect on cell cycle. However, we observed increased levels of CEdG and 8-oxodG on DNA of cells incubated with BPA (100 uM, 250 mM) without prior activation of Ah receptors. The activation of Ah receptors with PCB took a small increase in the level of DNA lesions after incubations with BPA. MCF-7 cells resistance to the cytotoxic effects of BPA is probably related to estrogen action of this compound. Estrogen signaling in addition with the increased levels of DNA damage increases the chance of mutations and malignant transformation. In cells with Ah receptor activation, BPA also led to increased DNA global hydroxymethylation, without changing the global DNA methylation. Nondiabetic animals exposed to BPA had decreased amounts of promyelocytes, blasts and rods in the bone marrow, with any change in blood count. There were an increase of CEdG levels in liver, methylation and global hydroxymethylation on hepatic DNA, and was observed any alteration on epigenetic markers and DNA adducts in kidney or urine. On the other hand diabetic animals exposed to BPA showed increased numbers of eosinophils and lymphocytes in bone marrow, suggesting the induction of an allergic inflammatory state. There were increased levels of CEdG, methylation and global hydroxymethylation on hepatic DNA, increased 8-oxodG levels on kidney DNA without changing epigenetic markers, was not observed DNA adducts in urine. The data obtained indicate that the generation of ROS could be the major route of cytotoxic and genotoxic induced by BPA exposure. BPA biotransformation to BPA-3,4-quinone used in the models seem to have poor effects, since we was not detected BPA-Gua lesion in any DNA sample, culture medium of cells or urine of the animals. Metabolic changes induced by BPA and ROS can enable changes in epigenetic markers observed in the DNA of HL-60 cells, MCF-7 and liver tissue. All these changes may contribute to malignant transformation of cells that were exposed to BPA

Factors for differentiation affecting of neonatal regulatory T cells / 中华实用儿科临床杂志

Objective To investigate the possible factors for differentiation affecting of neonatal regulatory T cells(Treg). Methods Umbilical cord blood was collected from 200 newborns. Treg number was detected by DNA demethylation in the Foxp3 of Treg - cell - specific demethylatedregion(TSDR)based on high resolution melting anal-ysis(HRMA),concentrations of 7,8 - dihydroxy - 9,10 - epoxy - benzo(a)pyrene(BPDE - DNA)adducts and interleukin - 4( IL - 4)in the supernatants of cord blood by enzyme - linked immunosorbent assay( ELISA),and follow - up questionnaires were carried out till 1. 0 - 1. 5 years,for recurrent wheezing or stubborn eczema in infants and related information on parental history of atopic diseases. Results (1)In wheezing group[(0. 48 ± 0. 05)% ]and ec-zema group[(0. 76 ± 0. 05)% ],the number of Tregs was significantly lower compared with that of the asymptomatic group[(1. 14 ± 0. 08)% ](t = 2. 62,2. 83,all P ﹤ 0. 05);the number of Treg in parental history of atopic group was significantly lower than that of the non - atopic group(P ﹤ 0. 05);but the Treg numbers in the non - atopic group was still lower than that of the asymptomatic group(P ﹤ 0. 05).(2)The concentrations of BPDE - DNA adducts in the wheezing group[(236. 30 ± 6. 59)ng/ L]and the eczema group[(173. 40 ± 7. 38)ng/ L]were higher than those of the asymptomatic group[(111. 01 ± 3. 36)ng/ L](t = 10. 35,6. 53,all P ﹤ 0. 05),while BPDE - DNA adduct concen-trations in the atopic group with parental history of wheezing or eczema in infants were lower than those of the non -atopic group(P ﹤ 0. 05).(3)The concentrations of IL - 4 in the wheezing or eczema group in the supernatants of cord blood was higher than the asymptomatic group(P ﹤ 0. 05). Conclusions Neonatal genetic factors and BPDE - DNA adducts could affect Treg differentiation,which are probably the reasons for the formation of allergic diseases.

Investigação de potenciais biomarcadores redox - um enfoque em aldeídos e seus produtos / Potential redox biomarkers investigation - focus on aldehydes and their products

As espécies reativas são associadas a processos toxicológicos e fisiopatológicos, agindo como importantes mediadores, por exemplo, na sinalização celular. Diversas classes de compostos têm sido utilizadas como possíveis biomarcadores de estresse redox, destacando-se os aldeídos α,ß-insaturados, capazes de alquilar biomoléculas como o DNA. Para evitar efeitos deletérios, estes aldeídos são detoxificados por glutationilação e posterior metabolização a derivados mercaptúricos. Contudo, avaliar o estado redox em sistemas biológicos ainda é tarefa bastante complexa, sendo a dificuldade em quantificar de forma prática e acurada os efeitos de sinalização e/ou dano molecular o maior problema dos estudos redox. Assim, o objetivo deste trabalho foi desenvolver métodos acurados e sensíveis de análise de potenciais biomarcadores de estresse redox, isto é: nucleosídeos modificados, aldeídos endógenos e exógenos, glutationa e produtos de glutationilação, e avaliá-los em sistemas modelos, celular e animal, e em humanos. A avaliação dos níveis urinários de três nucleosídeos modificados por metodologia de HPLC-MS/MS desenvolvida pelo grupo em moradores da cidade de São Paulo - região com poluição atmosférica - demonstrou aumento significativo de 1,N2-propanodGuo comparado aos moradores de região não poluída. Ademais, comprova-se pela primeira vez que células deficientes em reparo de ligações cruzadas apresentam níveis basais elevados de 1,N2-propanodGuo, em duas linhagens independentes, colocando este aduto como potencial mediador de carcinogênese em pacientes portadores de Anemia de Fanconi. Utilizando cérebro de ratos SOD1G93A (modelo de Esclerose Lateral Amiotrófica - ELA), verificou-se aumento de 50% nos níveis de 1,N2-propanodGuo e de 100% nos de 1,N6-εdAdo em fase sintomática, sugerindo influência do conteúdo lipídico cerebral, levando a comprometimento do metabolismo neuronal e morte celular. O perfil de aldeídos determinado em cérebro de ratos SOD1G93A demonstrou aumento de trans-hexa-2-enal e trans,trans-hexa-2,4-dienal em fase assintomática e de trans,trans-deca-2,4-dienal em fase sintomática, não sendo observada nenhuma alteração na medula. Conhecer estas variações permite direcionar estudos de modificações em biomoléculas, além de a metodologia per se corroborar com as áreas de análises lipidômicas. Técnicas distintas e o preparo de amostras refletiram nos níveis de glutationa reduzida (GSH) e oxidada (GSSG) relatados. A técnica de espectrometria de massas mostrou-se mais precisa que a detecção eletroquímica; e a alquilação do grupo tiol minimizou interferências de matriz. Por análise de HPLC-UV/Vis-ESI-MS/MS, a quantificação de trans-4-hidroxi-2-nonenal (HNE) e crotonaldeido conjugados com GSH demonstrou não haver alterações em cérebro e medula de ratos SOD1G93A. Contudo, há formação esteroespecífica dos adutos de HNE in vivo. Ressalta-se que a metodologia desenvolvida é extremamente sensível e específica e permite análise simultânea de GSH, GSSG, cisteína, cistina e dos adutos supracitados, servindo para análise de outros adutos de glutationilação de aldeídos que possam ser importantes em doenças associadas a estresse redox

Free radicais and oxidant species are associated with toxicological and pathophysiological processes. It has been demonstrated that production of reactive oxygen species may be involved in cell signaling and regulation. Several biomarkers of redox processes have been used, including adducts formed through the reaction of α,ß-unsaturated aldehydes with biomolecules such as DNA. In order to avoid these deleterious effects, aldehydes are detoxified through glutathionylation and further metabolized to mercapturic derivatives. However, assessing the redox status in biological systems is still a very complex task, and the difficulty in practical and accurate quantification of signaling effects and/or molecular damage is a major problem in redox studies. The objective of this work was to develop accurate and sensitive methods for analysis of potential biomarkers of redox stress, i.e., modified nucleosides, endogenous and exogenous aldehydes, glutathione and glutathionylation products, and their evaluation in cell, animal model and humans. Evaluation of urinary levels of 1,N2-propano-2'-deoxyguanosine (1,N2-propanodGuo), 1,N2-etheno-2'-deoxyguanosine and 8-oxo-7,8-dihydro-2'-deoxyguanosine in residents of São Paulo City - polluted region - showed a significant increase (p<0.05) in 1,N2-propanodGuo levels compared to residents of an unpolluted region by a HPLC-MS/MS methodology developed by the group. Moreover, it was proven, for the first time, that repair deficient cells have basal levels of 1,N2-propanodGuo higher than proficient cells in two independent strains, placing 1,N2-propanodGuo as a potential mediator of carcinogenesis in Fanconi Anemia patients. In an Amyotrophic Lateral Sclerosis (ALS) animal model (SOD1G93A rat) , a 50% increase in the levels of 1,N2-propanodGuo and 100% in the 1,N6-etheno-2'-deoxyadenosine in brain tissue in the symptomatic phase was observed, suggesting that the high brain lipid content may play a role, leading to impairment of cell metabolism and neuronal cell death. There is an increase of trans-hex-2-enal and trans,trans-hexa-2,4-dienal in asymptomatic SOD1G93A rats brain and of trans,trans-deca-2,4-dienal in symptomatic ones. However, no alteration was observed in spinal cord. Our approach contributes to a better understanding of the aldehyde status in vivo and allows us to predict biomolecule modifications. The developed methodology can contribute to lipidomic studies. The use of different techniques and sample preparation reflected in the reported levels of reduced (GSH) and oxidized glutathione (GSSG). The mass spectrometry technique proved to be more accurate than the electrochemical one, and the use of thiol alkylating agent minimizes matrix interference. No changes were observed in the levels of the GSH conjugates of trans-4-hydroxy-2-nonenal (HNE) and crotonaldehyde in brain and spinal cord of SOD1G93A rats quantified by HPLC-UV/Vis-ESI-MS/MS compared to controls. However, it was observed stereospecific HNE adducts formation in vivo. Note that this methodology is extremely sensitive and specific and allows simultaneous analysis of GSH, GSSG, Cys, cystine and the aforementioned adducts, serving for analysis of other aldehyde-glutathionylation adducts that may be important in pathologies associated with stress redox

Mecanismos moleculares involucrados en la mutagenicidad inducida por aflatoxina B1 / Molecular mechanism involved in the mutagenicity induced by Aflatoxin B1 / Mecanismos moleculares envolvidos na mutagenicidade induzida pela aflatoxina B1

La aflatoxina B1 (AFB1) es una micotoxina identificada como el más potente hepatocarcinógeno. El metabolito que resulta del proceso de detoxificación de la AFB1 en el hígado tiene la capacidad de reaccionar con el ADN genómico, generando el aducto AFB1-ADN; durante la replicación del ADN este aducto induce la transversión G:C—>T:A. Polimorfismos en los genes que codifican las enzimas encargadas de la activación y detoxificación de la AFB1 y enzimas de reparación del ADN han sido asociados con el riesgo de desarrollar carcinoma hepatocelular (CHC). Adicionalmente, en poblaciones con alta exposición a aflatoxina y alta prevalencia de infección por el virus de la hepatitis B (VHB) se ha demostrado un sinergismo entre estos dos factores de riesgo para el desarrollo de CHC.

The aflatoxin B1 (AFB1) is a mycotoxin that has been identified as the most potent hepatocarcinogen. The metabolite resulting from detoxification process of AFB1 in liver, has the ability to react with the genomic DNA, generating AFB1-DNA adducts; during DNA replication process, this adduct induced the G:C—>T:A transversion. Polymorphism in genes encoding for enzymes involved in the activation and detoxification of AFB1 and DNA repair enzymes has been associated with the risk of hepatocellular carcinoma (HCC) development. Additionally, in populations of high exposure to aflatoxin and high prevalence of hepatitis B virus (HBV) infection, has been demonstrated a synergism between these two risk factors for the development of HCC.

Aflatoxina B1 (AFB1) é uma micotoxina identificado como o hepatocarcinogen mais potente. O metabolito resultante do processo de desintoxicação de AFB1 no fígado, tem a capacidade de reagir com o ADN genómico, gerando AFB1 DNA-aducto; transversão durante a replicação do ADN deste aducto induz G:C—>T:A. Polimorfismos em genes que codificam as enzimas envolvidas na activação e na desintoxicação de AFB1 e enzimas de reparação do ADN têm sido associados com o risco de desenvolvimento de carcinoma hepatocelular (HCC). Além disso, em populações com elevada exposição a aflatoxina e elevada prevalência da infecção com vírus da hepatite B (VHB) tem sido mostrado um sinergismo entre estes dois factores de risco para o desenvolvimento de carcinoma hepatocelular.

Citotoxicidade do corante dinitrofenilazo CI DB291: biotransformação, estresse oxidativo e alteração epigenética em células HepG2 / Cytotoxicity of the CI DB291 dinitrofenilazo dye: biotransformation, oxidative stress and epigenetic change in HepG2 cells

O produto comercial CI Disperse Blue 291 (CI DB291) é amplamente utilizado pela industria têxtil. Estudos mostram que corantes dinitrofenilazo são genotóxicos no ensaio de Ames/Salmonella, mas há poucos estudos sobre seus efeitos em células eucariontes. Este trabalho teve como objetivo investigar a genotoxicidade e citotoxicidade do corante DB291 em células humanas em cultura, bem como vias pelas quais o corante atua levando aos efeitos tóxicos. O corante comercial foi purificado por HPLC-DAD e utilizado para incubação com células HepG2 (5-100 µM por 3-72 h). A citotoxicidade foi avaliada pelos ensaios de XTT, corante cristal violeta, lactato desidrogenase extracelular e consumo de glicose. A geração de ROS intracelular foi verificada pela emissão de fluorescência da 2',7'-diclorofluoresceína. Análises de ciclo celular, fragmentação do DNA, potencial de membrana mitocondrial (Ψ) e cálcio intracelular foram realizadas por citometria de fluxo. A produção de ATP foi mensurada por quimiluminescência. Níveis de 8-oxodG e 5-mdC foram avaliados por HPLC-ESI-MS/MS e HPLC-UV, respectivamente. A expressão da enzima DNMT1 foi avaliada por western blot. Um produto de biotransformação foi identificado e caracterizado estruturalmente por MS/MS e 1H-RMN. A exposição ao corante DB291 diminuiu significativamente a sobrevivência das células em um modo tempo- e dose-dependente (IC50 = 74 µM), com a concomitante formação de um produto de biotransformação reduzido. A morte celular ocorreu sem lise da membrana plasmática. Nas células expostas, foi observado aumento da atividade enzimática mitocondrial, acompanhado por um aumento da taxa de consumo de glicose. Índices elevados de ATP, Ψ e cálcio foram verificados após a incubação das células com concentrações crescentes do corante. Alterações mitocondriais e o processo de biotransformação impeliram a aumento na produção de ROS intracelular, 8-oxodG e fragmentação do DNA. O dano ao DNA induziu a parada no ciclo...

The commercial CI Disperse Blue 291 (CI DB291) is widely used by textile industry. It is mutagenic in the Ames/S. typhimurium assay, but there are few studies showing its effects in eukaryotic cells. We evaluated here the toxicity of CI DB291 in the human HepG2 cell line. The commercial dye was purified by HPLC-DAD and used for incubation with HepG2 cells (5-100 µM for 3-72 h). Cytotoxicity was assessed by the XTT, crystal violet dye, extracellular lactate dehydrogenase and glucose consumption assays. ROS formation was assessed by 2',7'-dichlorofluorescein fluorescence. Analyses of cell cycle, DNA fragmentation, mitochondrial membrane potential (Ψ) and intracellular calcium were analyzed by flow cytometry. ATP level was measured by chemiluminescence. Levels of 8-oxodG and 5-mdC were evaluated by HPLCESI-MS/MS and HPLC-UV, respectively. DNMT1 expression was assessed by western blot. A biotransformation product was identified and structurally characterized by MS/MS and 1H-NMR. DB291 significantly decreased cell survival in a time- and dose-dependent manner (IC50 = 74 µM), with concomitant formation of a reduced biotransformation product. Plasma membrane lysis did not occur. Increased mitochondrial enzymatic activity, accompanied by increase in glucose consumption rate, was observed in cells incubated with DB291. Elevated ATP, Ψ, and intracellular calcium was verified after cell incubation with increasing dye concentrations. Mitochondrial changes and the biotransformation process accounted for the observed raise in intracellular ROS, 8-oxodG, and DNA fragmentation. DNA damage induced cell cycle arrest and DNMT1 overexpression, followed by DNA hypomethylation in the subsequent cell cycle. Results point for the first time to toxicity of the dye through biotransformation, mitochondrial changes, and oxidative stress.

Relationship between villus BaP-DNA adducts level and blighted ovum in early pregnancy / 中华围产医学杂志

Objective To investigate relations between villus Benzo (a)pyrene (BaP)-DNA adducts and blighted ovum in early pregnancy, and to explore possible environmental factors influencing embryo development. Methods One hundred and two pregnant women with blighted ovum were selected into this study as research group; and 102 normal pregnant women were taken as control group; the age, gravidity, parity and gestational weeks of the two groups were matched. After artificial abortion, villi of the patients were collected and washed by normal saline. Then, the tissue was homogenated and genome DNA was extracted to detect quantity of the tissue. BaP-DNA adducts levels were examined by high-performance liquid chromatography-fluorescence method (HPLC). The personal information of pregnant women was collected by questionnaire. Logistic regression model was used to investigate the association between BaP-DNA adducts and blighted ovum. Results BaP-DNA adducts level in villi of research group [(8. 9±8. 2) adducts/108 nucleotides] was significantly higher than that of control group [(2. 0±1. 4) adducts/108 nucleotides], P＜0.05. The higher the BaP-DNA adducts in villi, the higher risk the blighted ovum; when the BaP-DNA adducts level increased to 6.06 adducts/108 nucleotides, the risk of blighted ovum might increase 59.39 times (95% CI:15.50-227.55). Maternal education level was a protective factor (OR=-0.21, 95%CI:-0. 19--0.03) after controlling potential confounders. Conclusions High level of villi BaP-DNA adducts might increase the risk of blighted ovum in early pregnancy, and could have an adverse effect on embryo development.

Synthesis and electrospray mass spectrometric analysis of aristolochic acid Ⅰ-DNA adduct / 基础医学与临床

Objective To synthesize aristolochic acid Ⅰ(AAⅠ)-DNA adduct in vitro and to develop a method for the characterization of the adduct. Methods Aristolochic acid (AA) was incubated with 2′-Deoxyadenosine 5′-monophosphate in vitro using either enzymatic activation (by xanthine oxidase) or chemical activation (by zinc) to synthesize AAⅠ-DNA adduct. The AAⅠ-DNA adduct was characterized by the liquid chromatography electrospray ionization/tandem mass spectrometry (LC-ESI-MS/MS). Results AAⅠ-DNA adduct was prepared by two activation methods. Full scan spectra were obtained in the negative ion mode and the quasi-molecular ion peak was m/z 621. Analysis by electrospray ionization/tandem mass spectrometry (ESI-MS/MS) provided useful structural information about AAⅠ-DNA adduct. Conclusion AAⅠ can bind covalently to the exocyclic amino group of purine nucleotides to form AAⅠ-DNA adduct. LC/MS/MS is a practical tool to detect AAⅠ-DNA adduct.

Expression of DNA repair gene ERCC1 and its relationship with PAH-DNA adducts in lung cancer tissues / 中国病理生理杂志

AIM: To investigate the expression of nucleotide excision repair gene ERCC1 and its relationship with PAH (polycyclic aromatic hydrocarbons)-DNA adducts in lung cancer tissues. METHODS: ERCC1 mRNA expression and the PAH-induced DNA adducts were detected in 150 lung cancer tissues, 120 adjacent lung tissues without cancer cells, 40 benign lung lesions and 40 normal lung tissues. The effects of some exposure factors on the expression of ERCC1 gene and the connection between ERCC1 and PAH-DNA adduct was analyzed. RESULTS: Reduced expression levels of ERCC1 were observed in 46 of 150 (30.7%) lung cancer specimens and 1 of 40 (2.5%) normal lung tissues. Smoking may suppress the expression of ERCC1 gene. The level of PAH-DNA adduct was negatively correlated with the expression of ERCC1 gene, the Spearman coefficient was -0.648, P

Research Advance on Relationship between PAH-DNA Adducts and Gene Polymorphisms, Prenatal Exposure to Polycyclic Aromatic Hydrocarbons / 环境与健康杂志

The biomarkers can facilitate the evaluation of the factors modulating susceptibility to carcinogens among human populations. As an indicator of DNA damage, carcinogen-DNA adducts represent a critical step on the carcinogenic pathway. Genetic differences in detoxification capabilities and the DNA repair efficiency may modulate PAH-induced DNA damage and carcinogenesis. Experimental animal studies have demonstrated that the fetus and infant are more susceptible to polycyclic aromatic hydrocarbons (PAHs) induced carcinogenesis than adults. Recent years, more and more studies have shown that the prenatal exposure to PAHs not only associated with the increasing risk of cancer, but also related to adverse birth outcomes. This paper reviewed the differential susceptibility to PAHs between the paired maternal and newborn and discussed the relationship between the DNA adducts levels and the gene polymorphisms.

~(32)P-POSTLABELING TEST OF DNA ADDUCTS FORMED IN THE LIVERS OF RATS TREATED WITH CARCINOGEN / 西安交通大学学报(医学版)

DNA in the livers of rats was isolated 24 h af-ter oral administration of benzidine, Congo red andEvan's blue, DNA adducts in the livers of ratswere investigated by a ~(32)P-postlabeling assay. Thelevel of DNA adducts in the livers of rats after oraladministration of benzidine, congo red andEvan'blue were 18. 17, 1. 03 and 1. 74?mol/kgDNA respectively. The results showed that themetabolites of the benzidine derivative azo dyes canform adducts with DNA in the livers of rats.These DNA adducts probably are one of the rea-sons that the incidence of the bladder cancer rosein the people group who are only exposed to benzi-dine derivative azo dyes.