RESUMEN
PURPOSE: Folate is essential to DNA methylation and synthesis and may have a complex dualistic role in prostate cancer. Alcohol use may increase risk and epigenetic factors may interact with lifestyle exposures. We aimed to characterize the independent and joint effects of folate intake, alcohol consumption, and the MTHFR C677T gene polymorphism on prostate cancer risk, while accounting for intakes of vitamins B(2), B(6), B(12), methionine, total energy, and confounders. METHODS: A case-control study was conducted at Kingston General Hospital of 80 incident primary prostate cancer cases and 334 urology clinic controls, all with normal age-specific PSA levels (to exclude latent prostate cancers). Participants completed a questionnaire on folate and alcohol intakes and potential confounders prior to knowledge of diagnosis, eliminating recall bias, and blood was drawn for MTHFR genotyping. Joint effects of exposures were assessed using unconditional logistic regression and significance of multiplicative and additive interactions using general linear models. RESULTS: Folate, vitamins B(2), B(6), B(12), methionine, and the CT and TT genotypes were not associated with prostate cancer risk. The highest tertile of lifetime alcohol consumption was associated with increased risk (OR = 2.08; 95% CI: 1.12-3.86). Consumption of >5 alcoholic drinks per week was associated with increased prostate cancer risk among men with low folate intake (OR = 2.38; 95% CI: 1.01-5.57), and higher risk among those with the CC MTHFR genotype (OR = 4.43; 95% CI: 1.15-17.05). Increased risk was also apparent for average weekly alcohol consumption when accounting for the multiplicative interaction between folate intake and MTHFR C677T genotype (OR = 3.22; 95% CI: 1.36-7.59). CONCLUSION: Alcohol consumption is associated with increased prostate cancer risk, and this association is stronger among men with low folate intake, with the CC MTHFR genotype, and when accounting for the joint effect of folate intake and MTHFR C677T genotype.
RESUMEN
We describe herein a novel series of 3-amino-4-hydrazine-cyclobut-3-ene-1,2-diones as potent and selective inhibitors against the CXCR2 chemokine receptor and IL-8-mediated chemotaxis of a CXCR2-expressing cell line. Furthermore, these alkyl-hydrazine series inhibitors such as 5b demonstrated acceptable metabolic stability when incubated in human and rat microsomes.
Asunto(s)
Antiinflamatorios/síntesis química , Hidrazinas/síntesis química , Receptores de Interleucina-8B/antagonistas & inhibidores , Animales , Antiinflamatorios/química , Antiinflamatorios/farmacología , Células CHO , Quimiotaxis/efectos de los fármacos , Cricetinae , Cricetulus , Diseño de Fármacos , Humanos , Hidrazinas/química , Hidrazinas/farmacología , Interleucina-8/metabolismo , Microsomas Hepáticos/metabolismo , Ratas , Receptores de Interleucina-8B/metabolismo , Relación Estructura-ActividadRESUMEN
The tobacco-specific lung carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) forms DNA methylating and pyridyloxobutylating species. In this study, the involvement of nucleotide excision repair (NER) in the repair of pyridyloxobutyl adducts was assessed using an in vitro NER assay with pyridyloxobutylated plasmid DNA. Nuclear extracts from NER-deficient xeroderma pigmentosum (XP) cells, XPA and XPC, were less active at repairing pyridyloxobutyl adducts than were extracts from normal cells, while combining NER-deficient extracts reconstituted activity. Also, NER-deficient cells were more susceptible to NNKOAc-induced cytotoxicity than were normal cells. Results demonstrate a role for NER in the repair of NNK-induced pyridyloxobutylation.
Asunto(s)
Carcinógenos/toxicidad , Núcleo Celular/efectos de los fármacos , Aductos de ADN/metabolismo , Reparación del ADN , Nitrosaminas/toxicidad , Xerodermia Pigmentosa/enzimología , Línea Celular Tumoral , Núcleo Celular/enzimología , Núcleo Celular/efectos de la radiación , Supervivencia Celular/efectos de los fármacos , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Humanos , Piridinas/toxicidad , Factores de Tiempo , Rayos Ultravioleta , Xerodermia Pigmentosa/genética , Xerodermia Pigmentosa/patología , Proteína de la Xerodermia Pigmentosa del Grupo A/genética , Proteína de la Xerodermia Pigmentosa del Grupo A/metabolismoRESUMEN
The objectives of this study were to determine the contributions of CYP2A13 and CYP2A6 to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) metabolism in human peripheral lung microsomes and to determine the influence of the genetic polymorphism, CYP2A13 Arg257Cys, on NNK metabolism. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), the keto-reduced metabolite of NNK, was the major metabolite produced, ranging from 0.28 to 0.9%/mg protein/min. Based on total bioactivation of NNK and NNAL by alpha-carbon hydroxylation, subjects could be classified as either high (17 subjects) or low (12 subjects) bioactivators [(5.26 +/- 1.23) x 10(-2) and (6.49 +/- 5.90) x 10(-3)% total alpha-hydroxylation/mg protein/min, P < 0.05]. Similarly, for detoxification, subjects could be grouped into high (9 subjects) and low (20 subjects) categories [(2.03 +/- 1.65) x 10(-3) and (2.50 +/- 3.04) x 10(-4)% total N-oxidation/mg protein/min, P < 0.05]. When examining data from all individuals, no significant correlations were found between levels of CYP2A mRNA, CYP2A enzyme activity, or CYP2A immunoinhibition and the degree of total NNK bioactivation or detoxification (P > 0.05). However, subgroups of individuals were identified for whom CYP2A13 mRNA correlated with total NNK and NNAL alpha-hydroxylation and NNAL-N-oxide formation (P < 0.05). The degree of NNAL formation and CYP2A13 mRNA was also correlated (P < 0.05). Subjects (n = 84) were genotyped for the CYP2A13 Arg257Cys polymorphism, and NNK metabolism for the one variant (Arg/Cys) was similar to that for other subjects. Although results do not support CYP2A13 or CYP2A6 as predominant contributors to NNK bioactivation and detoxification in peripheral lung of all individuals, CYP2A13 may be important in some.
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Hidrocarburo de Aril Hidroxilasas/metabolismo , Pulmón/enzimología , Microsomas/enzimología , Nitrosaminas/metabolismo , Esteroide Hidroxilasas/metabolismo , Anciano , Hidrocarburo de Aril Hidroxilasas/genética , Biotransformación , Citocromo P-450 CYP2A6 , Femenino , Expresión Génica , Genotipo , Glicoles/metabolismo , Humanos , Hidroxiácidos/metabolismo , Hidroxilación , Cetoácidos/metabolismo , Pulmón/metabolismo , Masculino , Microsomas/metabolismo , Persona de Mediana Edad , Oxigenasas de Función Mixta/genética , Oxigenasas de Función Mixta/metabolismo , Estructura Molecular , Nitrosaminas/química , Nitrosaminas/farmacocinética , Oxidación-Reducción , Polimorfismo de Nucleótido Simple , Piridinas/química , Piridinas/metabolismo , Piridinas/farmacocinética , Fumar/metabolismo , Esteroide Hidroxilasas/genéticaRESUMEN
Aflatoxin B(1) (AFB(1)) is a mycotoxin produced by some strains of Aspergillus and is a recognized pulmonary and hepatic carcinogen. The most widely accepted mechanism of AFB(1) carcinogenicity involves bioactivation to AFB(1)-8,9-exo-epoxide and binding to DNA to form AFB(1)-N(7)-guanine. Another potential cause of DNA damage is AFB(1)-mediated stimulation of reactive oxygen species formation, leading to oxidation of DNA bases. The objective of this study was to determine the ability of AFB(1) to cause oxidative DNA damage in lung cell types of the A/J mouse. The formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in freshly isolated mouse lung alveolar macrophages, alveolar type II cells, and nonciliated bronchial epithelial (Clara) cells was assessed by high-performance liquid chromatography with electrochemical detection. An approximately 3-fold increase in 8-OHdG formation occurred in both alveolar macrophage and Clara cell preparations isolated from A/J mice 2 h following treatment with a single tumorigenic dose of 50 mg/kg AFB(1) ip (n = 3, p < 0.05). Prior treatment with 300 kU/kg polyethylene glycol-conjugated catalase prevented the AFB(1)-induced increase in 8-OHdG levels in all mouse lung cell preparations (n = 3, p < 0.05). These results support the possibility that oxidative DNA damage in mouse lung cells contributes to AFB(1) carcinogenicity.
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Aflatoxina B1/toxicidad , ADN/metabolismo , Desoxiguanosina/análogos & derivados , Pulmón/efectos de los fármacos , Pulmón/metabolismo , Mutágenos/toxicidad , 8-Hidroxi-2'-Desoxicoguanosina , Animales , Catalasa/metabolismo , Separación Celular , Cromatografía Líquida de Alta Presión , Interpretación Estadística de Datos , Desoxiguanosina/metabolismo , Electroquímica , Femenino , Técnicas In Vitro , Pulmón/citología , Ratones , Ratones Endogámicos A , Estrés Oxidativo/efectos de los fármacosRESUMEN
Amiodarone (AM), an antidysrrhythmic drug, can produce serious adverse effects, including potentially fatal AM-induced pulmonary toxicity (AIPT). AM-induced cytotoxicity and pulmonary fibrosis are well recognized, but poorly understood mechanistically. The hypothesis of aryl radical involvement in AM toxicity was tested in non-biological and biological systems. Photolysis of anaerobic aqueous solutions of AM, or N-desethylamiodarone (DEA) resulted in the formation of an aryl radical, as determined by spin-trapping and electron paramagnetic resonance (EPR) spectroscopy experiments. The non-iodinated AM analogue, didesiodoamiodarone (DDIA), did not form aryl radicals under identical conditions. The toxic susceptibility of human lung epithelioid HPL1A cells to AM, DEA, and DDIA showed time- and concentration-dependence. DEA had a more rapid and potent toxic effect (LC(50)=8 microM) than AM (LC(50)=146 microM), whereas DDIA cytotoxicity was intermediate (LC(50)=26 microM) suggesting a minor contribution of the iodine atoms. Incubation of human lung epithelial cells with the spin-trapping nitrones alpha-phenyl-N-t-butylnitrone (PBN, 10 mM) or alpha-(4-pyridyl N-oxide)-N-t-butylnitrone (POBN, 5.0 mM) did not significantly protect against AM, DEA, or DDIA cytotoxicity. Intratracheal administration of AM to hamsters produced pulmonary fibrosis at day 21, which was not prevented by 4 days of treatment with 150 mg/kg/day PBN or 164 mg/kg/day POBN. However, the body weight loss in AM-treated animals was counteracted by PBN. These results suggest that, although AM can generate an aryl radical photochemically, its in vivo formation may not be a major contributor to AM toxicity, and that spin-trapping reagents do not halt the onset of AM toxicity.
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Amiodarona/toxicidad , Antiarrítmicos/toxicidad , Óxidos N-Cíclicos/farmacología , Pulmón/efectos de los fármacos , Piridinas/farmacología , Animales , Cricetinae , Espectroscopía de Resonancia por Spin del Electrón , Radicales Libres , Hidroxiprolina/análisis , Pulmón/química , Pulmón/patología , Masculino , Mesocricetus , FotoquímicaRESUMEN
Aflatoxin B(1) (AFB(1))-N(7)-guanine is the predominant adduct formed upon the reaction of AFB(1)-8,9-exo-epoxide with guanine residues in DNA. AFB(1)-N(7)-guanine can convert to the ring-opened formamidopyrimidine, or the adducted strand can undergo depurination. AFB(1)-N(7)-guanine and AFB(1)-formamidopyrimidine are thought to be predominantly repaired by nucleotide excision repair in bacteria, yeast and mammals. Although AFB(1)-formamidopyrimidine is removed less efficiently than AFB(1)-N(7)-guanine in mammals, both lesions are repaired with equal efficiencies in bacteria, reflecting differences in damage recognition between bacterial and mammalian repair systems. Furthermore, DNA repair activity and modulation of repair by AFB(1) seem to be major determinants of susceptibility to AFB(1)-induced carcinogenesis.
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Aflatoxina B1/farmacología , Daño del ADN/efectos de los fármacos , Reparación del ADN , Animales , HumanosRESUMEN
To investigate the mechanisms responsible for species- and tissue-specific differences in susceptibility to aflatoxin B(1) (AFB(1))-induced carcinogenesis, DNA repair activities of nuclear extracts from whole mouse lung and liver and rat liver were compared, and the ability of in vivo treatment of mice with AFB(1) to alter repair of AFB(1)-DNA damage was determined. Plasmid DNA containing AFB(1)-N(7)-guanine or AFB(1)-formamidopyrimidine adducts were used as substrates for the in vitro determination of DNA repair synthesis activity, detected as incorporation of radiolabeled nucleotides. Liver extracts from CD-1 mice repaired AFB(1)-N(7)-guanine and AFB(1)-formamidopyrimidine adducts 5- and 30-fold more effectively than did mouse lung, and approximately 6- and 4-fold more effectively than did liver extracts from Sprague-Dawley rats. The susceptibility of mouse lung and rat liver to AFB(1)-induced carcinogenesis correlated with lower DNA repair activity of these tissues relative to mouse liver. Lung extracts prepared from mice treated with a single tumorigenic dose of 50 mg/kg AFB(1) i.p. and euthanized 2 hours post-dosing showed minimal incision and repair synthesis activities relative to extracts from vehicle-treated mice. Conversely, repair activity towards AFB(1)-N(7)-guanine damage was approximately 3.5-fold higher in liver of AFB(1)-treated mice relative to control. This is the first study to show that in vivo treatment with AFB(1) can lead to a tissue-specific induction in DNA repair. The results suggest that lower DNA repair activity, sensitivity of mouse lung to inhibition by AFB(1), and selective induction of repair in liver contribute to the susceptibility of mice to AFB(1)-induced lung tumorigenesis relative to hepatocarcinogenesis.
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Aflatoxina B1/análogos & derivados , Aflatoxina B1/toxicidad , Cocarcinogénesis , Reparación del ADN/fisiología , Guanina/análogos & derivados , Neoplasias Hepáticas/inducido químicamente , Neoplasias Hepáticas/genética , Neoplasias Pulmonares/inducido químicamente , Neoplasias Pulmonares/genética , Aflatoxina B1/metabolismo , Animales , Carcinógenos/toxicidad , ADN/efectos de los fármacos , ADN/metabolismo , Femenino , Predisposición Genética a la Enfermedad , Guanina/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Hígado/fisiología , Neoplasias Hepáticas/metabolismo , Pulmón/efectos de los fármacos , Pulmón/metabolismo , Pulmón/fisiología , Neoplasias Pulmonares/metabolismo , Masculino , Ratones , Pirimidinas/metabolismo , Ratas , Ratas Sprague-Dawley , Especificidad de la EspecieRESUMEN
The contributions of different enzymes to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) biotransformation were assessed in human lung microsomes prepared from peripheral lung specimens obtained from seven subjects. Metabolite formation was expressed as a percentage of total recovered radioactivity from [5-3H]NNK and its metabolites per milligram of protein per minute. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol was the major metabolite formed in the presence of an NADPH-generating system, with production ranging from 0.5186 to 1.268%/mg of protein/min, and total NNK bioactivation (represented by the sum of the four alpha-carbon hydroxylation endpoint metabolites) ranged from 0.002100 to 0.005685% alpha-hydroxylation/mg of protein/min. Overall, production of bioactivation metabolites was greater than that of detoxication (i.e., N-oxidation) products. Based on total bioactivation, subjects could be classified as high or low NNK bioactivators. In the presence of an NADPH-generating system, microsomal formation of the endpoint metabolite 1-(3-pyridyl)-1-butanone-4-carboxylic acid (keto acid) was consistently higher than that of all other alpha-carbon hydroxylation endpoint metabolites. Contributions of cytochrome p450 (p450) enzymes to NNK oxidation were demonstrated by NADPH dependence, inhibition by carbon monoxide, and inhibition by the nonselective p450 inhibitors proadifen hydrochloride (SKF-525A) and 1-aminobenzotriazole (ABT), particularly in lung microsomes from high bioactivators. At 5.0 mM, ABT inhibited total NNK bioactivation by 54 to 100%, demonstrating the importance of ABT-sensitive enzyme(s) in human pulmonary NNK bioactivation. Contributions of CYP2A6 and/or CYP2A13, as well as CYP2B6, to NNK bioactivation were also suggested by selective chemical and antibody inhibition in lung microsomes from some subjects. It is likely that multiple p450 enzymes contribute to human pulmonary microsomal NNK bioactivation, and that these contributions vary between individuals.
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Carcinógenos/metabolismo , Pulmón/metabolismo , Microsomas/enzimología , Nitrosaminas/metabolismo , Anciano , Inhibidores Enzimáticos del Citocromo P-450 , Sistema Enzimático del Citocromo P-450/metabolismo , Inhibidores Enzimáticos/farmacología , Femenino , Humanos , Técnicas In Vitro , Pulmón/enzimología , Masculino , Persona de Mediana Edad , Fumar/metabolismoRESUMEN
4-Methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco-specific carcinogen believed to play a role in human lung cancer. Bioactivation of NNK involves alpha-carbon hydroxylation that could be catalyzed by cytochrome P450, hemoglobin, and lipoxygenases (LOX). In the present study, the role of LOX in NNK bioactivation was investigated. Formation of keto acid, the endpoint metabolite of alpha-methylene NNK hydroxylation, was observed in human lung cytosols incubated with 4.2 microM [5-(3)H]NNK (N = 6). Following concanavalin A affinity chromatography to enrich human lung lipoxygenase (HLLO), the fraction containing cytosolic components less LOX (fraction 1) retained the ability to bioactivate NNK. Although enriched HLLO exhibited the characteristic dioxygenase and hydroperoxidase activities, it did not bioactivate NNK. The LOX inhibitor nordihydroguaiaretic acid inhibited dioxygenase activity of HLLO by 83 +/- 19% (P < 0.05, N = 6), but did not inhibit keto acid formation in the crude cytosols (N = 6, P > 0.05). Failure of soybean LOX to catalyze NNK bioactivation supported the results observed in human lung cytosols, and failure of chemically generated alkylperoxyl radicals to bioactivate NNK further suggested that the dioxygenase activity of LOX is not likely to be involved in NNK bioactivation. Horseradish peroxidase and myeloperoxidase catalyzed NNK bioactivation were also nondetectable. Our results demonstrate that, although human lung cytosols can bioactivate NNK to form keto acid, LOX is not involved. We have attributed the ability of crude human lung cytosols to bioactivate NNK to hemoglobin. The inhibitory effect of 1-aminobenzotriazole and arachidonic acid on keto acid formation in the crude cytosols and in fraction 1, respectively (P < 0.05, N = 6), is consistent with hemoglobin-catalyzed NNK bioactivation.