Sample records for 3-methylcholanthrene

  1. Effect of interleukin 12 on tumor induction by 3-methylcholanthrene.


    Noguchi, Y; Jungbluth, A; Richards, E C; Old, L J


    Interleukin (IL)-12 has strong antitumor activity in transplantable tumor systems in the mouse. The present study was designed to determine whether tumor induction by 3-methylcholanthrene (3-MC), a carcinogenic hydrocarbon, can be inhibited by IL-12. BALB/cBy mice were injected subcutaneously with 25 micrograms or 100 micrograms of 3-MC and treated with 100 ng, 10 ng, or 1 ng of IL-12 for 5 days a week for 18 weeks, with a schedule of 3 weeks on and 1 week off. In mice injected with 25 microg...

  2. 3-methylcholanthrene induces differential recruitment of aryl hydrocarbon receptor to human promoters

    DEFF Research Database (Denmark)

    Pansoy, Andrea; Ahmed, Shaimaa; Valen, Eivind;


    The aryl hydrocarbon receptor (AHR) is a ligand-activated protein that mediates the toxic actions of polycyclic aromatic and halogenated compounds. Identifying genes directly regulated by AHR is important in understanding the pathways regulated by this receptor. Here we used chromatin immunopreci...... a number of novel AHR-bound promoter regions and target genes that exhibit differential kinetic binding profiles and regulation by AHR.......The aryl hydrocarbon receptor (AHR) is a ligand-activated protein that mediates the toxic actions of polycyclic aromatic and halogenated compounds. Identifying genes directly regulated by AHR is important in understanding the pathways regulated by this receptor. Here we used chromatin...... immunoprecipitation and promoter focused microarrays (ChIP-chip) to detect AHR bound genomic regions after 3-methylcholanthrene (3MC) treatment of T-47D human breast cancer cells. We identified 241 AHR-3MC bound regions and transcription factor binding site analysis revealed a strong over-representation of the AHR...

  3. Regulation of nonmuscle myosin II during 3-methylcholanthrene induced dedifferentiation of C2C12 myotubes

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    Dey, Sumit K.; Saha, Shekhar; Das, Provas; Das, Mahua R.; Jana, Siddhartha S., E-mail:


    3-Methylcholanthrene (3MC) induces tumor formation at the site of injection in the hind leg of mice within 110 days. Recent reports reveal that the transformation of normal muscle cells to atypical cells is one of the causes for tumor formation, however the molecular mechanism behind this process is not well understood. Here, we show in an in vitro study that 3MC induces fragmentation of multinucleate myotubes into viable mononucleates. These mononucleates form colonies when they are seeded into soft agar, indicative of cellular transformation. Immunoblot analysis reveals that phosphorylation of myosin regulatory light chain (RLC{sub 20}) is 5.6±0.5 fold reduced in 3MC treated myotubes in comparison to vehicle treated myotubes during the fragmentation of myotubes. In contrast, levels of myogenic factors such as MyoD, Myogenin and cell cycle regulators such as Cyclin D, Cyclin E1 remain unchanged as assessed by real-time PCR array and reverse transcriptase PCR analysis, respectively. Interestingly, addition of the myosin light chain kinase inhibitor, ML-7, enhances the fragmentation, whereas phosphatase inhibitor perturbs the 3MC induced fragmentation of myotubes. These results suggest that decrease in RLC{sub 20} phosphorylation may be associated with the fragmentation step of dedifferentiation. - Highlights: • 3-Methylcholanthrene induces fragmentation of C2C12-myotubes. • Dedifferentiation can be divided into two steps – fragmentation and proliferation. • Fragmentation is associated with rearrangement of nonmuscle myosin II. • Genes associated with differentiation and proliferation are not altered during fragmentation. • Phosphorylation of myosin regulatory light chain is reduced during fragmentation.

  4. Aflatoxin B1 metabolism by 3-methylcholanthrene-induced hamster hepatic cytochrome P-450s. (United States)

    Lai, T S; Chiang, J Y


    We have studied the activation of aflatoxin B1 by hamster liver microsomes and purified hamster cytochrome P-450 isozymes using a umu mutagen test. The hamster liver microsomes or S-9 fractions were much more active than rat liver microsomes or S-9 fractions in the activation of umu gene expression by aflatoxin B1 metabolites. 3-Methyl-cholanthrene treatment increased aflatoxin B1 activation by hamster liver microsomes. Two major 3-methylcholanthrene-inducible cytochrome P-450 isozymes, P-450 MC1 (IIA) and P-450 MC4 (IA2), were purified from 3-methylcholanthrene-treated hamster liver microsomes, and the metabolism of aflatoxin B1 by these two cytochromes was studied. In the reconstituted enzyme system, both P-450 MC1 and P-450 MC4 were highly active in the activation of aflatoxin B1, and antibodies against these P-450s specifically inhibited these activities. Antibody against P-450 MC1 inhibited the activation of aflatoxin B1 by 20% in the presence of 3-methyl-cholanthrene-treated hamster liver microsomes. In contrast, antibody against P-450 MC4 stimulated the activity by 175%. These results indicated that hamster P-450 MC1 might convert aflatoxin B1 to more toxic metabolite(s), whereas P-450 MC4 might convert aflatoxin B1 to less toxic metabolite(s), than aflatoxin B1 in liver microsomes. The metabolite(s) produced by both hamster cytochrome P-450 MC1 and MC4 were genotoxic in the umu mutagen test. PMID:2126562

  5. The effect of 3-methylcholanthrene and butylated hydroxytoluene on glycogen levels of liver, muscle, testis, and tumor tissues of rats


    POLAT, Fikriye; DERE, Egemen; GÜL, Eylem; YELKUVAN, İzzet; ÖZDEMİR, Öztürk; BİNGÖL, Günsel


    This study examined the effects of separate and combined applications of 3-methylcholanthrene, a polycyclic aromatic hydrocarbon and potent carcinogenic agent, and butylated hydroxytoluene, the antioxidant food additive, on the glycogen levels of liver, muscle, testis, and tumor tissues in rats. Adult male Wistar albino rats weighing 100-110 g at 8 weeks of age were used in this study. This study consisted of a control group (n = 9) and 3 different experiment groups in which rats were chronic...

  6. Analysis of Ki-ras Exon 2 Gene Mutations in 3-Methylcholanthrene and Butylated Hydroxytoluene-Induced Rat Lung Tissues


    POLAT, Fikriye; ÖZDEMİR, Öztürk; ELAGÖZ, Şahende


    3-Methylcholanthrene (MCA) is a polycyclic aromatic hydrocarbon and potent carcinogenic agent that is often used in experimental cancer studies. Butylated hydroxytoluene (BHT) has been widely used for many years as an antioxidant to preserve and stabilize the freshness, nutritional value, flavor, and color of foods. The aim of the present study was to investigate the role of the application of MCA and BHT in the development of lung cancer, and to detect any mutation in the Ki-ras gene exon 2....

  7. Influences of 3-methylcholanthrene, phenobarbital and dexamethasone on xenobiotic metabolizing-related cytochrome P450 enzymes and steroidogenesis in human fetal adrenal cortical cells

    Institute of Scientific and Technical Information of China (English)

    Hui WANG; Min HUANG; Ren-xiu PENG; Jiang LE


    Aim: To explore the influence and possible mechanism of xenobiotics on adrenal steroidogenesis during fetal development. Methods: Primary human fetal adrenal cortical cells were prepared, cultured and treated with 3-methylcholanthrene, phenobarbital and dexamethasone. The activities of 7-ethoxyresorufin 0-dealkylase, benzphetamine, aminopyrine and erythromycin N-demethylases were measured by enzyme assays. At the same time, quantitative analysis of steroid hormones cortisol, aldosterone, testosterone and progesterone were carried out in cultural medium by radioimmunoassays. Results: The activities of benzphetamine and aminopyrine Ar-demethylase were increased in the cultural fetal adrenal cells treated with phenobarbital (0.25-1 mmol/L) for 24 h. Dexamethasone (25-100 μmol/L) also increased the activity of erythromycin W-demethylase. The activity of 7-ethoxyresorufin 0-dealkylase was undetected in the cells treated without and with 3-methylcholanthrene (0.5-2 μmol/L). Meanwhile, the contents of medium cortisol, aldosterone and progesterone were decreased after treatment with 3-methylcholanthrene. Cortisol, aldosterone and progesterone concentrations were also slightly decreased with phenobarbital. Dexamethasone enhanced the productions of cortisol and progesterone remarkably. The trend of testosterone concentration was uncertain after 3-methylcholanthrene, phenobarbital or dexamethasone treatment. Conclusion: 3-Methylcholanthrene, phenobarbital or dexamethasone could interfere with the synthesis of cortisol, aldosterone and progesterone in primary human fetal adrenal cortical cells, which likely act through xenobiotic metabolizing-related cytochrome P450 isoform activation.

  8. CD8+ T cells are crucial for the ability of congenic normal mice to reject highly immunogenic sarcomas induced in nude mice with 3-methylcholanthrene

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    Boesen, M; Svane, I M; Engel, A M;


    An attempt was made to identify the selection pressures put upon a growing tumour by CD8+ T cells. To this end tumours induced with 3-methylcholanthrene in T cell-deficient nude mice and in congenic T cell-competent nu/+ mice were transplanted to nu/+ recipients. The rejection rate of the sarcomas...

  9. Consequences of 3-methylcholanthrene-type induction for the metabolism of 4-aminobiphenyl in isolated rat hepatocytes. (United States)

    Orzechowski, A; Schrenk, D; Schut, H A; Bock, K W


    Carcinogenic aromatic amines such as 4-aminobiphenyl (4-ABP) are extensively metabolized by both oxidative and conjugation reactions. Thus the burden of genotoxic metabolites of 4-ABP in a target organ is probably influenced by the balance of N-hydroxylation and alternative metabolic pathways in the hepatocyte. In freshly isolated rat hepatocytes, 4-ABP (at a substrate concentration of 10 microM) was mainly N-acetylated (54% of total metabolites), while 2% N-hydroxy-4-ABP-N-glucuronide and 21% of unconjugated N-hydroxylated metabolites were detectable. Ring-hydroxylated metabolites and the primary N-glucuronide of 4-ABP accounted for 8% and 4%, respectively. Pretreatment of rats with 3-methylcholanthrene (MC), a dioxin-type inducer of CYP1A isozymes and phenol UDP-glucuronosyltransferase (UGT1A1), led to a dramatic decrease of N-acetylated (2% of total metabolites) and an increase of N-hydroxylated (54% as free and glucuronidated compound) and ring-hydroxylated (35%) metabolites. Essentially similar effects were seen at a substrate concentration of 50 microM. Consistently, MC-type induction with beta-naphthoflavone resulted in a significant increase in the formation of DNA adducts of 4-ABP, detected by 32P-postlabeling of hepatocellular DNA. The results suggest that, similar to a previous study with 2-naphthylamine (2-NA), MC treatment leads to a marked shift from conjugation to N-oxidation. However, N-hydroxy-4-ABP (in contrast to N-hydroxy-2-NA) is mostly released from hepatocytes in the unconjugated form. PMID:8118934

  10. Expression of CYP2A3 mRNA and its regulation by 3-methylcholanthrene, pyrazole, and ß-ionone in rat tissues

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    A.B. Robottom-Ferreira


    Full Text Available Cytochrome P450 (CYP 2A enzymes are involved in the metabolism of numerous drugs and hormones and activate different carcinogens. Human CYP2A6, mouse CYP2A5 and rat CYP2A3 are orthologous enzymes that present high similarity in their amino acid sequence and share substrate specificities. However, different from the human and mouse enzyme, CYP2A3 is not expressed in the rat liver. There are limited data about expression of CYP2A3 in extrahepatic tissues and its regulation by typical CYP inducers. Therefore, the objective of the present study was to analyze CYP2A3 mRNA expression in different rat tissues by RT-PCR, and to study the influence of 3-methylcholanthrene, pyrazole and ß-ionone treatment on its expression. Male Wistar rats were divided into four groups of 5 rats each, and were treated ip for 4 days with 3-methylcholanthrene (25 mg/kg body weight, pyrazole (150 mg/kg body weight, ß-ionone (1 g/kg body weight, or vehicle. Total RNA was extracted from tissues and CYP2A3 mRNA levels were analyzed by semiquantitative RT-PCR. CYP2A3 mRNA was constitutively expressed in the esophagus, lung and nasal epithelium, but not along the intestine, liver, or kidney. CYP2A3 mRNA levels were increased in the esophagus by treatment with 3-methylcholanthrene and pyrazole (17- and 7-fold, respectively, in lung by pyrazole and ß-ionone (3- and 4-fold, respectively, although not statistically significant, in the distal part of the intestine and kidney by 3-methylcholanthrene and pyrazole, and in the proximal part of the intestine by pyrazole. CYP2A3 mRNA was not induced in nasal epithelium, liver or in the middle part of the intestine. These data show that, in the rat, CYP2A3 is constitutively expressed in several extrahepatic tissues and its regulation occurs through a complex mechanism that is essentially tissue specific.

  11. Basal and 3-methylcholanthrene-induced expression of cytochrome P450 1A, 1B and 1C genes in the Brazilian guppy, Poecilia vivipara. (United States)

    Dorrington, Tarquin; Zanette, Juliano; Zacchi, Flávia L; Stegeman, John J; Bainy, Afonso C D


    In fish there are four cytochrome P450 (CYP1) subfamilies: CYP1A, CYP1B, CYP1C, and CYP1D. Here we cloned Poecilia vivipara CYP1A, with an inferred amino acid sequence 91% identical to CYP1A from the killifish Fundulus heteroclitus, another member of the Cypriniformes, and an important model in ecotoxicology. In addition, we examined the expression of CYP1A, CYP1B1, and CYP1C1 by qPCR in liver, gill, and intestine of adult P. vivipara injected with 3-methylcholanthrene (3-MC) or held in clean water (control group) for 24h. All three tissues examined showed basal expression of the three CYP1 genes. CYP1A was most strongly expressed in the liver, while CYP1B1, and CYP1C1 were most strongly expressed in the gill and intestine respectively. 3-MC induced CYP1A, CYP1B1, and CYP1C1 significantly (20-120-fold) in the three organs, consistent with the regulation of CYP1A, CYP1B1 and CYP1C1 via the aryl hydrocarbon receptor. Validation of CYP1 gene biomarkers in fish collected from a contaminated urban mangrove environment was confirmed with significant induction of CYP1A and CYP1C1 in gills (10-15-fold) and CYP1B1 in liver (23-fold), relative to fish from a control site. The responsiveness of these CYP1 genes indicates P. vivipara is suitable as a model for environmental toxicology studies and environmental assessment in Brazil.

  12. Activation of liver X receptor inhibits the development of pulmonary carcinomas induced by 3-methylcholanthrene and butylated hydroxytoluene in BALB/c mice. (United States)

    Wang, Qixue; Sun, Lei; Yang, Xiaoxiao; Ma, Xingzhe; Li, Qi; Chen, Yuanli; Liu, Ying; Zhang, Di; Li, Xiaoju; Xiang, Rong; Wei, Yuquan; Han, Jihong; Duan, Yajun


    We previously reported that LXR ligand, T0901317, inhibited the growth of inoculated Lewis lung carcinoma in C57BL/6 mice by activating IFN-γ production. However, the effects of T0901317 on carcinogen-induced pulmonary carcinomas remain unknown. In this study, we initially conducted a statistical analysis on the data of human lung cancer samples extracted from the TCGA database, and determined that survival rate/time of lung cancer patients and grade of lung adenocarcinoma were positively and negatively related to lung IFN-γ levels, respectively. We then determined the inhibitory effects of T0901317 on mouse pulmonary carcinomas induced by 3-methylcholanthrene (MCA) and butylated hydroxytoluene (BHT) or urethane. We found that T0901317 reduced morbidity and mortality in MCA/BHT-injected BALB/c mice by inhibiting lung adenocarcinoma. T0901317 also protected C57BL/6 mice, but not IFN-γ deficient (IFN-γ(-/-), C57BL/6 background) mice, against MCA/BHT-induced lung hyperplasia/inflammation. In addition, we determined that T0901317 inhibited urethane-induced lung tumors in BABL/c mice. Furthermore, we determined that T0901317 prevented metastasis of 4T1 breast cancer cells in BALB/c mice. Administration of T0901317 substantially increased serum IFN-γ levels and lung IFN-γ expression in BABL/c and C57BL/6 mice. Taken together, our study demonstrates that LXR inhibits MCA/BHT-induced pulmonary carcinomas in BABL/c mice and the inhibition is associated with induction of IFN-γ production. PMID:27250582

  13. Developmental regulation of the 3-methylcholanthrene- and dioxin-inducible CYP1A5 gene in chick embryo liver in vivo. (United States)

    Bentivegna, C S; Ihnat, M A; Baptiste, N S; Hamilton, J W


    The cDNA sequences for two dioxin-inducible cytochrome P450s in chicken, CYP1A4 and CYP1A5, have recently been reported which correspond to two dioxin-inducible forms of P450 previously designated as TCDDAHH and TCDDAA, respectively. The developmental expression of CYP1A4-associated aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH) activity and its association with expression of the Ah receptor had previously been characterized in chick embryo liver. The purpose of this study was to examine the developmental regulation of the second dioxin-inducible P450 gene, CYP1A5, in chick embryo liver. A partial gene sequence for CYP1A5 indicated that the intron/exon organization of this gene was identical to that of the CYP1A1 and CYP1A2 mammalian genes and was present in a single copy in the genome. CYP1A5 mRNA was expressed basally in chick embryo liver and was highly inducible by the Ah receptor ligands, 3-methylcholanthrene, beta-naphthoflavone, and 3,4,3', 4'-tetrachlorobiphenyl (TCB), but not by the phenobarbital analog, glutethimide. CYP1A5 mRNA levels were increased 40- to 50-fold within 5 h after a single TCB treatment, corresponding to a 30- to 40-fold increase in the transcription rate of the CYP1A5 gene at this time point. In contrast to a previous report that CYP1A5 mRNA expression was inducible by estradiol, we observed no effects of estradiol or dexamethasone on CYP1A5 mRNA expression, either alone or in combination with TCB. Basal and TCB-inducible CYP1A5 mRNA expression was maximal in liver at 8 days of development and remained high throughout the remainder of embryonic development. Thus, CYP1A5 appears to be regulated in a very similar manner to CYP1A4 in chick embryo liver. PMID:9705900

  14. 3-Methylcholanthrene, an AhR agonist, caused cell-cycle arrest by histone deacetylation through a RhoA-dependent recruitment of HDAC1 and pRb2 to E2F1 complex.

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    Chih-Cheng Chang

    Full Text Available We previously showed that treating vascular endothelial cells with 3-methylcholanthrene (3MC caused cell-cycle arrest in the Go/G1 phase; this resulted from the induction of p21 and p27 and a decreased level and activity of the cyclin-dependent kinase, Cdk2. We further investigated the molecular mechanisms that modulate cell-cycle regulatory proteins through the aryl-hydrocarbon receptor (AhR/Ras homolog gene family, member A (RhoA dependent epigenetic modification of histone. AhR/RhoA activation mediated by 3MC was essential for the upregulation of retinoblastoma 2 (pRb2 and histone deacetylase 1 (HDAC1, whereas their nuclear translocation was primarily modulated by RhoA activation. The combination of increased phosphatase and tensin homolog (PTEN activity and decreased phosphatidylinositide 3-kinase (PI3K activation by 3MC led to the inactivation of the Ras-cRaf pathway, which contributed to pRb2 hypophosphorylation. Increased HDAC1/pRb2 recruitment to the E2F1 complex decreased E2F1-transactivational activity and H3/H4 deacetylation, resulting in the downregulation of cell-cycle regulatory proteins (Cdk2/4 and Cyclin D3/E. Co-immunoprecipitation and electrophoretic mobility shift assay (EMSA results showed that simvastatin prevented the 3MC-increased binding activities of E2F1 proteins in their promoter regions. Additionally, RhoA inhibitors (statins reversed the effect of 3MC in inhibiting DNA synthesis by decreasing the nuclear translocation of pRb2/HDAC1, leading to a recovery of the levels of cell-cycle regulatory proteins. In summary, 3MC decreased cell proliferation by the epigenetic modification of histone through an AhR/RhoA-dependent mechanism that can be rescued by statins.

  15. Neutrophils Are Required for 3-Methylcholanthrene-Initiated, Butylated Hydroxytoluene-Promoted Lung Carcinogenesis


    Vikis, Haris G.; Gelman, Andrew E.; Franklin, Andrew; Stein, Lauren; Rymaszewski, Amy; Zhu, Jihong; Liu, Pengyuan; Tichelaar, Jay W.; Krupnick, Alexander S.; You, Ming


    Multiple studies have shown a link between chronic inflammation and lung tumorigenesis. Inbred mouse strains vary in their susceptibility to methylcholanthrene (MCA)-initiated butylated hydroxytoluene (BHT)-promoted lung carcinogenesis. In the present study we investigated whether neutrophils play a role in strain dependent differences in susceptibility to lung tumor promotion. We observed a significant elevation in homeostatic levels of neutrophils in the lungs of tumor-susceptible BALB/cByJ...

  16. Protective effect of Ocimum sanctum on 3-methylcholanthrene, 7,12-dimethylbenz(a)anthracene and aflatoxin B1 induced skin tumorigenesis in mice

    International Nuclear Information System (INIS)

    A study on the protective effect of alcoholic extract of the leaves of Ocimum sanctum on 3-mthylcholanthrene (MCA), 7,12-dimethylbenzanthracene (DMBA) and aflatoxin B1 (AFB1) induced skin tumorigenesis in a mouse model has been investigated. The study involved pretreatment of mice with the leaf extract prior to either MCA application or tetradecanoyl phorbol acetate (TPA) treatment in a two-stage tumor protocol viz a viz, DMBA/TPA and AFB1/TPA. The results of the present study indicate that the pretreatment with alcoholic extract of the leaves of O. sanctum decreased the number of tumors in MCA, DMBA/TPA and AFB1/TPA treated mice. The skin tumor induced animals pretreated with alcoholic extract led to a decrease in the expression of cutaneous γ-glutamyl transpeptidase (GGT) and glutathione-S-transferase-P (GST-P) protein. The histopathological examination of skin tumors treated with leaf extract showed increased infiltration of polymorphonuclear, mononuclear and lymphocytic cells, decreased ornithine decarboxylase activity with concomitant enhancement of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the serum, implying the in vivo antiproliferative and immunomodulatory activity of leaf extract. The decrease in cutaneous phase I enzymes and elevation of phase II enzymes in response to topical application of leaf extract prior to MCA, AFB1, DMBA/TPA and AFB1/TPA treatment indicate the possibility of impairment in reactive metabolite(s) formation and thereby reducing skin carcinogenicity. Furthermore, pretreatment of leaf extract in the carcinogen induced animals resulted in elevation of glutathione levels and decrease in lipid peroxidation along with heat shock protein expression, indicating a scavenging or antioxidant potential of the extract during chemical carcinogenesis. Thus it can be concluded that leaf extract of O. sanctum provides protection against chemical carcinogenesis in one or more of the following mechanisms: (i) by acting as an antioxidant; (ii) by modulating phase I and II enzymes; (iii) by exhibiting antiproliferative activity

  17. Activation of liver X receptor inhibits the development of pulmonary carcinomas induced by 3-methylcholanthrene and butylated hydroxytoluene in BALB/c mice


    Qixue Wang; Lei Sun; Xiaoxiao Yang; Xingzhe Ma; Qi Li; Yuanli Chen; Ying Liu; Di Zhang; Xiaoju Li; Rong Xiang; Yuquan Wei; Jihong Han; Yajun Duan


    We previously reported that LXR ligand, T0901317, inhibited the growth of inoculated Lewis lung carcinoma in C57BL/6 mice by activating IFN-γ production. However, the effects of T0901317 on carcinogen-induced pulmonary carcinomas remain unknown. In this study, we initially conducted a statistical analysis on the data of human lung cancer samples extracted from the TCGA database, and determined that survival rate/time of lung cancer patients and grade of lung adenocarcinoma were positively and...

  18. Demethylation of the pesticide methoxychlor in liver and intestine from untreated, methoxychlor-treated, and 3-methylcholanthrene-treated channel catfish (Ictalurus punctatus): evidence for roles of CYP1 and CYP3A family isozymes. (United States)

    Stuchal, Leah D; Kleinow, Kevin M; Stegeman, John J; James, Margaret O


    Exposure to the organochlorine pesticide methoxychlor (MXC) is associated with endocrine disruption in several species through biotransformation to mono-desmethyl-MXC (OH-MXC) and bis-desmethyl-MXC (HPTE), which interact with estrogen receptors. The biotransformation of [14C]methoxychlor was examined in channel catfish (Ictalurus punctatus), a freshwater species found in the southern United States. Hepatic microsomes formed OH-MXC and HPTE, assessed by comigration with authentic standards. The Km for OH-MXC formation by control liver microsomes was 3.8 +/- 1.3 microM (mean +/- S.D., n = 4), and Vmax was 131 +/- 53 pmol/min/mg protein. These values were similar to those of catfish pretreated with 2 mg/kg methoxychlor i.p. for 6 days (Km 3.3 +/- 0.8 microM and Vmax 99 +/- 17 pmol/min/mg) but less (p Methoxychlor pretreatment significantly reduced intestinal metabolite formation from 32 +/- 4 to 15 +/- 6 pmol/min/mg (mean +/- S.D., n = 4), whereas 3-MC treatment significantly increased OH-MXC production to 72 +/- 22 pmol/min/mg. Ketoconazole, clotrimazole, and alpha-naphthoflavone all decreased the production of OH-MXC in liver microsomes, whereas alpha-naphthoflavone stimulated HPTE formation, suggesting that CYP1 and CYP3 family isozymes demethylated methoxychlor. The results suggest that the formation of estrogenic metabolites from methoxychlor would be more rapid in catfish coexposed to CYP1 inducers.

  19. Mesothelioma relative to asbestos, radiation, and methylcholanthrene

    International Nuclear Information System (INIS)

    The carcinogenicity of chrysotile asbestos fibers (Canadian and Rhodesian) for the mesothelium of pleura and peritoneum of NEDH rats was explored by injection of 2 mg of asbestos fibers suspended in saline intratracheally, intrapleurally, or intraperitoneally, with or without ancillary radiation treatment, or alternatively, by injection of asbestos plus 1 mg of 3-methylcholanthrene. A highly significant incidence of mesothelioma (3.8%) was noted in 159 rats treated with asbestos alone, as compared with 0.1% in 1417 control rats. Additional treatment with radiation or 3-methylcholanthrene increased this incidence to 11.8% and 25.5%, respectively

  20. The metabolic activation of 2-naphthylamine to mutagens in the Ames test. (United States)

    Tong, S; Smith, J; Manson, D; Gorrod, J W; Ioannides, C


    The mutagenicity of 2-naphthylamine and its major metabolites in the Ames test was determined in the absence and presence of activation systems derived from rats and hamsters. In the absence of an activation system only N-hydroxy-2-naphthylamine and 2-nitrosonaphthalene were mutagenic. In the presence of activation systems derived from control and 3-methylcholanthrene-treated hamsters and Arochlor 1254-treated rats only 2-naphthylamine exhibited a mutagenic response while its hydroxy-derivatives and 2-acetamidonaphthalene were devoid of mutagenicity. Pretreatment of rats with 3-methylcholanthrene or Arochlor 1254 enhanced the mutagenicity of 2-naphthylamine while treatments with phenobarbitone, safrole and clofibrate had no significant effect. In the hamster treatment with only 3-methylcholanthrene increased the mutagenicity of 2-naphthylamine. It is concluded that the metabolic activation of 2-naphthylamine proceeds via N-hydroxylation which is preferentially catalysed by the 3-methylcholanthrene inducible forms of cytochrome P-450, whereas ring-hydroxylation appears to be a deactivation pathway. PMID:3800318


    Nuclear receptor agonists phenobarbital (PB), 3-methylcholanthrene (3MC), pregnenolone-16a-carbonitrile (PCN), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), and 2,2' ,4,4'-tetrabromodiphenyl ether (BDE 47) decrease serum thyroxine (T4) in rats. This decrease is thought to occur th...


    This study was undertaken to compare the ability of a series of compounds from different chemical classes to induce lung tumors in strain A/J mice after either ip or po administration. 3-Methylcholanthrene, benzo(a)pyrene, urethan, diethylnitrosamine, ethylnitrosourea, and dimeth...

  3. Alterations of cytochrome P450-dependent monooxygenase activities in Eriocheir japonicus in response to water pollution.


    Ishizuka, M; Hoshi, H.; Minamoto, N; Masuda, M; Kazusaka, A; Fujita, S.


    Eriocheir japonicus, fresh-water crabs inhabiting rivers and estuaries in Japan, were investigated for cytochrome P450 (CYP)-dependent drug-metabolizing enzyme activities to see if these activities reflect the river pollution gradient. From the laboratory dose-response experiments, we found that the polycyclic aromatic hydrocarbon (PAH) 3-methylcholanthrene induced total CYP contents, ethoxycoumarin O-deethylase activity, and bunitrolol 4-hydroxylase activity in crab hepatopancreas. In the fi...

  4. Acetaminophen structure-toxicity studies: In vivo covalent binding of a nonhepatotoxic analog, 3-hydroxyacetanilide

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    Roberts, S.A.; Price, V.F.; Jollow, D.J. (Medical Univ. of South Carolina, Charleston (USA))


    High doses of 3-hydroxyacetanilide (3HAA), a structural isomer of acetaminophen, do not produce hepatocellular necrosis in normal male hamsters or in those sensitized to acetaminophen-induced liver damage by pretreatment with a combination of 3-methylcholanthrene, borneol, and diethyl maleate. Although 3HAA was not hepatotoxic, the administration of acetyl-labeled (3H or 14C)3HAA (400 mg/kg, ip) produced levels of covalently bound radiolabel that were similar to those observed after an equimolar, hepatotoxic dose of (G-3H)acetaminophen. The covalent nature of 3HAA binding was demonstrated by retention of the binding after repetitive organic solvent extraction following protease digestion. Hepatic and renal covalent binding after 3HAA was approximately linear with both dose and time. In addition, 3HAA produced only a modest depletion of hepatic glutathione, suggesting the lack of a glutathione threshold. 3-Methylcholanthrene pretreatment increased and pretreatment with cobalt chloride and piperonyl butoxide decreased the hepatic covalent binding of 3HAA, indicating the involvement of cytochrome P450 in the formation of the 3HAA reactive metabolite. The administration of multiple doses or a single dose of (ring-3H)3HAA to hamsters pretreated with a combination of 3-methylcholanthrene, borneol, and diethyl maleate produced hepatic levels of 3HAA covalent binding that were in excess of those observed after a single, hepatotoxic acetaminophen dose. These data suggest that the nature and/or the intracellular processing of the reactive metabolites of acetaminophen and 3HAA are different. These data also demonstrate that absolute levels of covalently bound xenobiotic metabolites cannot be utilized as absolute predictors of cytotoxic potential.

  5. Effect of inducers and inhibitors of glucuronidation on the biliary excretion and choleretic action of valproic acid in the rat. (United States)

    Watkins, J B; Klaassen, C D


    Valproic acid (VPA) induces an immediate choleresis in the rat which may be attributable to the osmotic properties of VPA-glucuronic acid conjugates in bile. The influence of inducers and inhibitors of glucuronidation of VPA on the biliary excretion and choleretic effect of VPA was studied. Hepatic UDP-glucuronyltransferase activity toward VPA was determined in vitro. Pretreatment with phenobarbital (75 mg/kg/day for 4 days) enhanced VPA glucuronidation; borneol (750 mg/kg) decreased VPA conjugation; 3-methylcholanthrene (20 mg/kg/day for 4 days) and galactosamine (600 mg/kg) had no effect on glucuronidation of VPA in vitro. Hepatic UDP-glucuronic acid content was decreased by borneol and galactosamine administration and was enhanced by phenobarbital and 3-methylcholanthrene pretreatment. The enzyme inducers increased the plasma disappearance of VPA in vivo but did not augment its biliary excretion or choleretic effect. Borneol and galactosamine, which inhibited the conjugation and plasma disappearance of VPA, decreased its biliary excretion and inhibited the VPA-induced increase in bile flow. Thus, the bile flow rate after VPA administration is closely related to the excretion of VPA-glucuronic acid. These data support the conclusion that the choleretic effect of VPA is due to the osmotic activity of VPA conjugates in bile.

  6. Inhibition of chemically induced carcinogenesis by drugs used in homeopathic medicine. (United States)

    Kumar, K B Hari; Sunila, E S; Kuttan, Girija; Preethi, K C; Venugopal, C Nimita; Kuttan, Ramadasan


    Homeopathy is considered as one modality for cancer therapy. However, there are only very few clinical reports on the activity of the drugs, as well as in experimental animals. Presently we have evaluated the inhibitory effects of potentized homeopathic preparations against N'-nitrosodiethylamine (NDEA) induced hepatocellular carcinoma in rats as well as 3-methylcholanthrene-induced sarcomas in mice. We have used Ruta, Hydrastis, Lycopodium and Thuja, which are commonly employed in homeopathy for treating cancer. Administration of NDEA in rats resulted in tumor induction in the liver and elevated marker enzymes such as gamma-glutamyl transpeptidase, glutamate pyruvate transaminase, glutamate oxaloacetate transaminase and alkaline phosphatase in the serum and in liver. Concomitant administration of homeopathic drugs retarded the tumor growth and significantly reduced the elevated marker enzymes level as revealed by morphological, biochemical and histopathological evaluation. Out of the four drugs studied, Ruta 200c showed maximum inhibition of liver tumor development. Ruta 200c and phosphorus 1M were found to reduce the incidence of 3-methylcholanthrene-induced sarcomas and also increase the life span of mice harboring the tumours. These studies demonstrate that homeopathic drugs, at ultra low doses, may be able to decrease tumor induction by carcinogen administration. At present we do not know the mechanisms of action of these drugs useful against carcinogenesis. PMID:17477781

  7. Potentiation in the intact rat of the hepatotoxicity of acetaminophen by 1,3-bis(2-chloroethyl)-1-nitrosourea. (United States)

    Nakae, D; Oakes, J W; Farber, J L


    Studies of the killing of cultured hepatocytes by acetaminophen indicate that the cells are injured by an oxidative stress that accompanies the metabolism of the toxin (J. L. Farber et al. (1988) Arch. Biochem. Biophys. 267, 640-650). The present report documents that the essential features of the killing of cultured hepatocytes by acetaminophen are reproduced in the intact animal. Male rats had no evidence of liver necrosis 24 h after administration of up to 1000 mg/kg of acetaminophen. Induction of mixed function oxidase activity by 3-methylcholanthrene increased the hepatotoxicity of acetaminophen. Inhibition of glutathione reductase by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) potentiated the hepatotoxicity of acetaminophen in male rats induced with 3-methylcholanthrene. Whereas the pretreatment with BCNU reduced the GSH content by 40%, a comparable depletion of GSH by diethylmaleate did not potentiate the toxicity of acetaminophen. The antioxidant diphenylphenylenediamine (25 mg/kg) and the ferric iron chelator deferoxamine (1000 mg/kg) prevented the liver necrosis produced by 500 mg/kg acetaminophen in rats pretreated with BCNU. Neither protective agent prevented the fall in GSH produced by acetaminophen. It is concluded the conditions of the irreversible injury of cultured hepatocytes by acetaminophen previously reported are not necessarily different from those that obtain in the intact rat with this toxin. PMID:3214175

  8. Differential effects of chronic alcohol administration to rats on the activation of aromatic amines to mutagens in the Ames test. (United States)

    Steele, C M; Ioannides, C


    Male Wistar albino rats were maintained on alcohol-containing liquid diets for 4 weeks. Hepatic post-mitochondrial preparations derived from these animals were more efficient than control in activating 4-aminobiphenyl and 2-aminofluorene to mutagens in the Ames test. The alcohol-induced enhancement in mutagenicity was not inhibited by dimethylsulphoxide indicating that the generation of hydroxyl radicals is not involved. The activation of 2-naphthylamine was not affected by the treatment with alcohol but the mutagenicities of 2-aminoanthracene, benzo[a]pyrene and 3-methylcholanthrene were inhibited. The same treatment markedly increased hepatic microsomal aniline p-hydroxylase and ethoxyresorufin O-de-ethylase activities and to a lesser extent benzphetamine N-demethylase and microsomal levels of total cytochromes P-450. It is concluded that chronic alcohol administration to rats modulates the metabolic activation of pre-carcinogens to their reactive intermediates presumably by causing the redistribution of cytochrome P-450 isozymes. PMID:3009048

  9. Induction of active melanocytes in mouse skin by carcinogens: a new method for detection of skin carcinogens. (United States)

    Iwata, K; Inui, N; Takeuchi, T


    Application of potent skin carcinogens, such as 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, benzo[a]pyrene and 4-nitroquinoline-1-oxide, induced numerous dihydroxyphenylalanine (dopa)-positive cells in the interfollicular epidermis of C57BL/6 mice in a dose- and time-dependent fashion. Chrysene, a weak skin carcinogen, and croton oil, a tumor promoter, also induced 3--4 times more dopa-positive cells than acetone. Liver carcinogens, such as 3'-methyl-4-dimethylaminoazobenzene and N-2-acetylaminofluorene, and non-carcinogenic aromatic hydrocarbons, such as anthracene, fluoranthene, fluorene and pyrene, did not induce increase in these cells. These results indicate that increase in the number of dopa-positive cells after application of chemicals is well correlated with the abilities of these compounds to induce skin carcinogenesis and suppress sebaceous glands. PMID:7273337

  10. Role of cytochrome P sub 450 in the control of the production of erythropoietin

    Energy Technology Data Exchange (ETDEWEB)

    Fandrey, J.; Seydel, F.P.; Siegers, C.P.; Jelkmann, W. (Medical Univ. of Luebeck (West Germany))


    Effects of agents affecting cytochrome P{sub 450} were studied on the production of erythropoietin (Epo) in cultures of the human hepatoma cell line HepG2. Epo was measured by radioimmunoassay of the culture media after 24 h of incubation. The addition of phenobarbital or 3-methylcholanthrene, which induce cytochrome P{sub 450}, significantly enhanced the formation of Epo. Likewise, the thyroid hormones T{sub 3} and T{sub 4} stimulated the rate of the production of Epo. On the other hand, the formation of Epo was lowered following the addition of diethyl-dithiocarbamate or cysteamine chloride, which inhibit cytochrome P{sub 450}. These findings support the idea that O{sub 2} sensitive hemoproteins of the microsomal mixed-functional oxidases play a role in the control of the synthesis of Epo.

  11. The effects of the continuous administration of N,N-dimethyl-4-phenylazoaniline (DAB) on the activities and the inducibilities of some drug-metabolizing enzymes in rat liver

    DEFF Research Database (Denmark)


    of dye feeding on some of the enzyme activities in the two major liver lobes and differences were found. (3) The effect of phenobarbital (PB) pretreatment on the DAB-fed rats was studied at 4-week intervals. The activities of DAB-azoreductase and of nitroreductase increased throughout the whole period......-glucuronidase and arylsulphatase A were studied. Rapid decreases occurred in the activities of the first six enzymes, reaching minimal values at between 4 and 8 weeks. Activities then increased in all cases to control or nearly control levels. This rate of increase was least for cytochrome P-450. At 4 weeks azoreductase activity......, while the activities of the lysosomal enzymes were decreased. (4) After feeding DAB for 4 weeks the effect of PB and 3-methylcholanthrene (MC) on the activities of DAB-azoreductase, CB10-252-azoreductase and components of the azoreductases-cytochrome P-450, NADPH-cytochrome c reductase, the CO-CB10...

  12. Effects of some tobacco smoke constituents on foreign compound metabolism in the cat and the rat

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D.M.


    The effects of chronic nicotine administration on its own metabolism have been studied in the cat and the rat. Nicotine administration caused an increase in the in vitro metabolism in the liver of both species and in cat kidney. Cotinine production from nicotine was enhanced in both species by pretreatment with nicotine. The magnitude of the increase in enzyme activity was relatively small but of the same order as that produced, in the rat, by phenobarbital treatment. 3-methylcholanthrene pretreatment stimulated rat liver nicotine metabolism but was without effect on cotinine production. Chronic exposure of rats to relatively low levels of carbon monoxide inhibited the in vitro aryl hydrocarbon hydroxylase activity but did not affect nicotine metabolism. The data are discussed in relation to the observed enzyme inductive effects of tobacco smoke.

  13. Enhancement of 5-iododeoxyuridine-induced endogenous C-type virus activation by polycyclic hydrocarbons: apparent lack of parallelism between enhancement and carcinogenicity. (United States)

    Yoshikura, H; Zajdela, F; Perin, F; Perin-Roussel, O; Jacquignon, P; Latarjet, R


    When mouse MLg cells were treated with 3-methylcholanthrene or 7,12-dimethylbenz[alpha]anthracene in the presence of microsomal enzymes and NADPH after 5-iododeoxyuridine (IUDR) treatment, the induction rate of the endogenous C-type virus was increased fivefold to sixfold in comparison with the culture treated with IUDR only. In this reaction, both the microsomal enzymes and NADPH were indispensable. 7,8-Benzoflavone, an inhibitor of the metabolism of hydrocarbons in hamster embryo cultures, inhibited the reaction. For detecting the enhancing activity, the concentration of IUDR for the pretreatment, the concentration of the test products, and the duration of the treatment with the products were important factors. In screening 30 polycyclic hydrocarbons, we were unable to detect a correlation between the in vivo carcinogenicity in the skin and the enhancing activity in the conditions tested.

  14. Development of UDP-glucuronosyltransferase activity toward digitoxigenin-monodigitoxoside in neonatal rats. (United States)

    Watkins, J B; Klaassen, C D


    Glucuronidation is low or undetectable in embryonic and early fetal tissues and changes to adult levels at rates depending on the acceptor, tissue, and species. Because other data indicate there may be a specific UDP-glucuronosyltransferase (GT) in the liver of adult rats that glucuronidates digitoxigenin-monodigitoxoside (DIG), the development of GT activity in neonatal rats toward DIG was compared with that of other acceptors. Conjugation of p-nitrophenol and 1-naphthol was higher at birth and decreased to adult levels by 20 days of age. Glucuronidation of chloramphenicol, morphine, valproic acid, and bilirubin increased from birth to adult activity by 20 days of age. Conjugation of phenolphthalein, estrone, and diethylstilbestrol was low in 1-day-old rats and higher than adult in 20-day-old animals. In contrast, glucuronidation of DIG was barely detectable (9% of adult) in 20-day-old rats. The concentration of UDP-glucuronic acid was 50% of adult levels at birth and increased to adult values by 10 days of age. Administration of 3-methylcholanthrene on days 6 to 9 after birth significantly stimulated GT activity toward 1-naphthol, p-nitrophenol, and morphine, whereas phenobarbital precociously increased conjugation of chloramphenicol, valproic acid, morphine, and diethylstilbestrol. Pregnenolone-16 alpha-carbonitrile enhanced the development of GT activity toward morphine, chloramphenicol, valproic acid, bilirubin, diethylstilbestrol, and estrone. Glucuronidation of DIG was not increased after 3-methylcholanthrene or phenobarbital, but could be induced after pregnenolone-16 alpha-carbonitrile to 7% of adult values in 10-day-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Comparative study on glutathione transferases of rat brain and testis under the stress of phenobarbitol and β-methylcholanthrene

    Institute of Scientific and Technical Information of China (English)



    A comparative study was made on the tissue specific expression of glutathione transferases (GST) in brain and testis after exposure of rat to phenobarbitol (PB) and 3-methylcholanthrene (MC). Glutathione transferases, a family of multifunctional proteins are involved in intracellular transport processes and in detoxication of electrophilic xenobiotics by catalyzing reactions such as conjugation, isomerization, reduction and thiolysis. On purification, the yield of GST proteins by affinity chromatography was 39% in testis and 32% in brain. The affinity purified testis GSTs were resolved by chromatofocusing into six anionic and four cationic isozymes, and in brain glutathione transferases were resolved into four anionic and three cationic isozymes, suggesting the presence of multiple isozymes with Yc, Yb, Y3 and Yδ in both of them. In testis and brain, these isozymes at identical pI values showed variable functions with a battery of substrates and the cationic isozymes of brain and testis showed identical properties in CHP (cumene hydroperoxide) at pH values of above 7.0. Substrate specificity studies and immunoblot analysis of testis and brain proteins revealed that they play a predominant role in the detoxication of phenobarbitol or 3-methylcholanthrene. Expression of the isozymes in testis and brain on exposure to PB and MC indicated elevated subunit variation. In both testis and brain, Yδ ofπclass was expressed on PB treatment and Yc of α class and Y3 of μ class was expressed in MC treated testis and only Yc was predominantly expressed in MC treated brain. Thus these subunits expression is considered as markers for carcinogenesis and specific to chemical toxicity under phenobarbitol and 13-methylcholanthrene stress.

  16. Chemically-induced alteration of UDP-glucuronic acid concentration in rat liver. (United States)

    Watkins, J B; Klaassen, C D


    Since many xenobiotics alter hepatic UDP-glucuronosyltransferase activity, their effect on UDPGA concentration was determined. Rats were pretreated with: 1) microsomal enzyme inducers (7,8-benzoflavone, benzo(a)pyrene, butylated hydroxyanisole, isosafrole, 3-methylcholanthrene, phenobarbital, pregnenolone-16 alpha-carbonitrile (PCN), 2,3,7,8-tetrachlorodibenzo-p-dioxin, trans-stilbene oxide); 2) inhibitors of microsomal enzymes (cobaltous chloride, piperonyl butoxide, SKF 525-A, borneol, galactosamine); 3) hepatotoxins (allyl alcohol, aflatoxin B1, alpha-naphthylisothiocyanate, bromobenzene, cadmium chloride, carbon tetrachloride, 1,1-dichloroethylene), and 4) commonly used anesthetics (pentobarbital, urethane, diethyl ether, halothane, enflurane, methoxyflurane). Rats were decapitated before removal of the liver. All inducers except PCN and isosafrole increased UDPGA 36-85% above control. Mixed-function oxidase inhibitors had no effect whereas borneol and galactosamine reduced UDPGA 85-90%. Aflatoxin B1 and cadmium produced decreases of 59 and 25%, respectively. Hepatic UDPGA content was diminished 70-95% after exposure to the inhalation anesthetics, whereas the other anesthetics reduced UDPGA about 25%. Thus, numerous xenobiotics alter the concentration of UDPGA in rat liver, which may influence the rate of glucoronidation.

  17. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shoko, E-mail: [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Shirakawa, Hitoshi, E-mail: [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Tomita, Shuhei, E-mail: [Division of Molecular Pharmacology, Department of Pathophysiological and Therapeutic Science, Yonago 683-8503 (Japan); Tohkin, Masahiro, E-mail: [Department of Medical Safety Science, Graduate School of Pharmaceutical Science, Nagoya City University, Nagoya 267-8603 (Japan); Gonzalez, Frank J., E-mail: [Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Komai, Michio, E-mail: [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan)


    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.

  18. Qualitative study of three cell culture methods. (United States)

    Wang, Aiguo; Xia, Tao; Ran, Peng; Chen, Xuemin; Nuessler, Andreas K


    Primary rat hepatocytes were cultured using different in vitro models and the enzyme leakage, albumin secretion, and cytochrome P450 1A (CYP 1A) activity were observed. The results showed that the level of LDH was decreased over time in culture. However, on day 5, LDH showed a significant increase in monolayer culture (MC) while after day 8 no LDH was detectable in sandwich culture (SC). The levels of AST and ALT did not change significantly over the investigated time. The CYP 1A activity was gradually decreased in a time-dependent manner in MC and SC. The decline of CYP 1A was faster in MC than in SC. This effect was partially reversed by using cytochrome P450 (CYP450) inducer such as Omeprazol and 3-methylcholanthrene (3-MC) and the CYP 1A induction was always higher in MC than in SC. In bioreactor basic CYP 1A activity was preserved over 2 weeks and the highest albumin production was observed in bioreactor followed by SC and MC. Taken together, it was indicated each investigated model had its advantages and disadvantages. It was also underlined that various in vitro models may address different questions. PMID:12674760

  19. [Effect evaluation of three cell culture models]. (United States)

    Wang, Aiguo; Xia, Tao; Yuan, Jing; Chen, Xuemin


    Primary rat hepatocytes were cultured using three kinds of models in vitro and the enzyme leakage, albumin secretion, and cytochrome P450 1A (CYP 1A) activity were observed. The results showed that the level of LDH in the medium decreased over time in the period of culture. However, on 5 days, LDH showed a significant increase in monolayer culture (MC) while after 8 days LDH was not detected in sandwich culture (SC). The levels of AST and ALT in the medium did not change significantly over the investigated time. The basic CYP 1A activity gradually decreased with time in MC and SC. The decline of CYP 1A in rat hepatocytes was faster in MC than that in SC. This effect was partially reversed by using cytochrome P450 (CYP450) inducers such as omeprazol and 3-methylcholanthrene (3-MC) and the CYP 1A induction was always higher in MC than that in SC. Basic CYP 1A activity in bioreactor was keeped over 2 weeks and the highest albumin production was observed in bioreactor, and next were SC and MC. In conclusion, our results clearly indicated that there have some advantages and disadvantages in each of models in which can address different questions in metabolism of toxicants and drugs. PMID:14963896

  20. Relationship between the radioisotopic footpad assay and other immunological assays in tumor bearing rats

    International Nuclear Information System (INIS)

    KMT-17, a fibrosarcoma induced by 3-methylcholanthrene in a WKA rat, is a sensitive tumor to various kinds of immunological assays and is a suitable model tumor for the study of the immune status in tumor bearing hosts. The antitumor immune response of KMT-17 bearing rats was studied by a radioisotopic footpad assay (FPA) in comparison with other in vivo and in vitro assays. Delayed hypersensitivity to tumor antigens measured by the FPA was observed from the 8th day after transplantation of KMT-17 cells, reached a peak on the 12 - 15th day, and then declined in the late stage on the 17th day. The kinetics of the FPA correlated well with those of an in vivo Winn assay and of an in vitro lymphocyte cytotoxicity assay (51Cr-release assay). The appearance of an antitumor antibody detected by a complement dependent cytotoxicity test also correlated well with the kinetics of the FPA. A growth inhibition assay (GIA) for non-specific cell-mediated immunity also showed similar kinetics to that of the FPA. The delayed hypersensitivity footpad reaction to tumor cell extracts measured by this FPA was tumor-specific. These results suggest that the FPA is a simple and reliable in vivo assay for evaluating antitumor immunity in tumor bearing hosts. (author)

  1. Effect of various chemicals on the aldehyde dehydrogenase activity of the rat liver cytosol. (United States)

    Marselos, M; Vasiliou, V


    The cytosolic activity of aldehyde dehydrogenase (ALDH) was studied in the rat liver, after acute administration of various carcinogenic and chemically related compounds. Male Wistar rats were treated with 27 different chemicals, including polycyclic aromatic hydrocarbons, aromatic amines, nitrosamines, azo dyes, as well as with some known direct-acting carcinogens. The cytosolic ALDH activity of the liver was determined either with propionaldehyde and NAD (P/NAD), or with benzaldehyde and NADP (B/NADP). The activity of ALDH remained unaffected after treatment with 1-naphthylamine, nitrosamines and also with the direct-acting chemical carcinogens tested. On the contrary, polycyclic aromatic hydrocarbons, polychlorinated biphenyls (Arochlor 1254) and 2-naphthylamine produced a remarkable increase of ALDH. In general, the response to the effectors was disproportionate between the two types of enzyme activity, being much in favour for the B/NADP activity. This fact resulted to an inversion of the ratio B/NADP vs. P/NAD, which under constitutive conditions is lower than 1. In this respect, the most potent compounds were found to be polychlorinated biphenyls, 3-methylcholanthrene, benzo(a)pyrene and 1,2,5,6-dibenzoanthracene. Our results suggest that the B/NADP activity of the soluble ALDH is greatly induced after treatment with compounds possessing aromatic ring(s) in their molecule. It is not known, if this response of the hepatocytes is related with the process of chemical carcinogenesis. PMID:2060039

  2. Hepatic microsomal mixed-function oxidase activity in ethanol-treated hamsters and its consequences on the bioactivation of aromatic amines to mutagens. (United States)

    Ioannides, C; Steele, C M


    Male golden Syrian hamsters were maintained on ethanol-containing liquid diets for 4 weeks, corresponding to an average daily intake of 17 g/kg body wt. The p-hydroxylation of aniline was markedly enhanced by this treatment while minimal effects were seen in benzphetamine N-demethylase and ethoxyresorufin O-deethylase activities; there was no change in the microsomal levels of cytochromes P-450. Hepatic microsomal preparations from the ethanol-treated hamsters were more efficient than controls fed isocaloric diets in converting 2-aminofluorene, 4-aminobiphenyl, benzidine and 2-acetylaminofluorene into mutagens in the Salmonella mutagenicity test. The same treatment had no effect on the metabolic activation of 2-naphthylamine and even inhibited the mutagenicity of 2-aminoanthracene. No increase was seen in the activation of the two polycyclic aromatic hydrocarbons, benzo[a]pyrene and 3-methylcholanthrene to mutagens and an inhibitory effect was seen with the former. The ethanol-induced increase in the mutagenicity of 2-aminofluorene was inhibited by 2-butanol but not by the hydroxyl radical scavenger dimethylsulphoxide. It is concluded that chronic ethanol ingestion modulates the bioactivation of aromatic amines and amides to mutagens, the effect being substrate dependent. This effect of ethanol may be catalysed by unique form(s) of cytochrome P-450 whose synthesis is induced by such treatment. PMID:3021347

  3. Effects of Intermediate Metabolites of 37 Xenobiotics on the Catalytic Activities of Reconstituted Cytochrome P—450IIB1 and P—4501A1 Enzyme Systems

    Institute of Scientific and Technical Information of China (English)



    Direct effects of intermediate metabolites of 37 different xenobiotics on the catalytic activities of bothn reconstitute cytochrome P-450ⅡP-45PIA1 enzyme systems were studied by determination of NADPH oxidation at various intervals after initiation of the reaction.The results showed that cytochrome P-4500ⅡB isozyme was much more likely than cytochrome P-450IA1 isozyme to be attacked by the reactive intermediates formed by some xenobiotics with smaller molecular weight and lose its catalytics activities.These xenobiotics were carbon tetrachloride,chloroform,carbon disulfide,benzene,parathion, methylparathion,methyldurshan and dimethylnitrosamine.In contrast,however,steadily increasing metabolic activities were observed toards benzo(a)pyrene,3-methylcholanthrene and polychlorinated biphenyls in reconstituted cytochrome P-450IA1 enzyme system as the reaction time prolonged within 4min.The method discussed in this paper could e be used as a simple and convenient way to observe directly the autocatalytic destruction of P-450 enzymes by soe chemical agents.

  4. Noble metal nanoparticle-induced oxidative stress modulates tumor associated macrophages (TAMs) from an M2 to M1 phenotype: An in vitro approach. (United States)

    Pal, Ramkrishna; Chakraborty, Biswajit; Nath, Anupam; Singh, Leichombam Mohindro; Ali, Mohammed; Rahman, Dewan Shahidur; Ghosh, Sujit Kumar; Basu, Abhishek; Bhattacharya, Sudin; Baral, Rathindranath; Sengupta, Mahuya


    Diagnosis of cancer and photothermal therapy using optoelectronic properties of noble metal nanoparticles (NPs) has established a new therapeutic approach for treating cancer. Here we address the intrinsic properties of noble metal NPs (gold and silver) as well as the mechanism of their potential antitumor activity. For this, the study addresses the functional characterization of tumor associated macrophages (TAMs) isolated from murine fibrosarcoma induced by a chemical carcinogen, 3-methylcholanthrene (MCA). We have previously shown antitumor activity of both gold nanoparticles (AuNPs) and silver nanoparticle (AgNPs) in vivo in a murine fibrosarcoma model. In the present study, it has been seen that AuNPs and AgNPs modulate the reactive oxygen species (ROS) and reactive nitrogen species (RNS) production, suppressing the antioxidant system of cells (TAMs). Moreover, the antioxidant-mimetic action of these NPs maintain the ROS and RNS levels in TAMs which act as second messengers to activate the proinflammatory signaling cascades. Thus, while there is a downregulation of tumor necrosis factor-α (TNF-α) and Interleukin-10 (IL-10) in the TAMs, the proinflammatory cytokine Interleukin-12 (IL-12) is upregulated resulting in a polarization of TAMs from M2 (anti-inflammatory) to M1 (pro-inflammatory) nature. PMID:27344639

  5. Expression of cytochrome P-450 1A1 in human fetal adrenal cells

    Institute of Scientific and Technical Information of China (English)


    Objective: To study the expression and inducibility in vitro ofadrenal cytochrome P-450 (CYP) 1A1 implicated in precarcinogen and premutagen activation in human fetuses. Methods: CYP1A1 mRNA expression and CYP1A1 activity of fetal adrenals were studied and compared with those of fetal liver using the reverse transcriptase-polymerase chain reaction (RT-PCR) and 7-ethoxyresorufin O-deethylase (EROD) assay. Results: 3-methylcholanthrene (3MC, 25 mg/kg ip, qd′ 3), a selective inducer of CYP1A1, could enhance adrenal and liver EROD activities in vivo in adult rat. However, EROD activity was undetected in either adrenal microsomes or 3MC (0.5- 2 m mol.L-1 for 24 h)-treated adrenal cells in vitro in human fetuses. Using RT-PCR method, the expression of CYP1A1 mRNA was detected in fetal adrenal and fetal liver tissues and the expressional percentage was 78% and 73%, respectively. Conclusion: Human fetal adrenals as well as fetal liver had the lower CYP1A1 expression and possessed the potential for risk of carcinogenesis during fetal development.

  6. Methionine restriction inhibits chemically-induced malignant transformation in the BALB/c 3T3 cell transformation assay. (United States)

    Nicken, Petra; Empl, Michael T; Gerhard, Daniel; Hausmann, Julia; Steinberg, Pablo


    High consumption of red meat entails a higher risk of developing colorectal cancer. Methionine, which is more frequently a component of animal proteins, and folic acid are members of the one carbon cycle and as such important players in DNA methylation and cancer development. Therefore, dietary modifications involving altered methionine and folic acid content might inhibit colon cancer development. In the present study, the BALB/c 3T3 cell transformation assay was used to investigate whether methionine and folic acid are able to influence the malignant transformation of mouse fibroblasts after treatment with the known tumour initiator 3-methylcholanthrene. Three different methionine concentrations (representing a -40%, a "normal" and a +40% cell culture medium concentration, respectively) and two different folic acid concentrations (6 and 20 μM) were thereby investigated. Methionine restriction led to a decrease of type III foci, while enhancement of both methionine and folic acid did not significantly increase the cell transformation rate. Interestingly, the focus-lowering effect of methionine was only significant in conjunction with an elevated folic acid concentration. In summary, we conclude that the malignant transformation of mouse fibroblasts is influenced by methionine levels and that methionine restriction could be a possible approach to reduce cancer development.

  7. Caffeic acid phenethyl ester inhibits 3-MC-induced CYP1A1 expression through induction of hypoxia-inducible factor-1α

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung Gyun [Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon (Korea, Republic of); Han, Eun Hee [Division of Life Science, Korea Basic Science Institute, Daejeon (Korea, Republic of); Im, Ji Hye; Lee, Eun Ji; Jin, Sun Woo [Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon (Korea, Republic of); Jeong, Hye Gwang, E-mail: [Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon (Korea, Republic of)


    Caffeic acid phenethyl ester (CAPE), a natural component of propolis, is reported to have anticarcinogenic properties, although its precise chemopreventive mechanism remains unclear. In this study, we examined the effects of CAPE on 3-methylcholanthrene (3-MC)-induced CYP1A1 expression and activities. CAPE reduced the formation of the benzo[a]pyrene-DNA adduct. Moreover, CAPE inhibited 3-MC-induced CYP1A1 activity, mRNA expression, protein level, and promoter activity. CAPE treatment also decreased 3-MC-inducible xenobiotic-response element (XRE)-linked luciferase, aryl hydrocarbons receptor (AhR) transactivation and nuclear localization. CAPE induced hypoxia inducible factor-1α (HIF-1α) protein level and HIF-1α responsible element (HRE) transcriptional activity. CAPE-mediated HIF-1α reduced 3-MC-inducible CYP1A1 protein expression. Taken together, CAPE decreases 3-MC-mediated CYP1A1 expression, and this inhibitory response is associated with inhibition of AhR and HIF-1α induction. - Highlights: • CAPE reduced the formation of the benzo[a]pyrene-DNA adduct. • CAPE inhibited 3-MC-induced CYP1A1 expression. • CAPE induced HIF-1α induction. • CAPE-mediated HIF-1α reduced 3-MC-inducible CYP1A1 expression.

  8. Induction and inhibition of benzo(a)pyrene metabolism in human epidermal keratinocytes and dermal fibroblasts

    International Nuclear Information System (INIS)

    The effects of different growth conditions and various cytochrome P-450 inducers and inhibitors were examined on the benzo(a)pyrene (BP) metabolism of human skin cells in vitro. First, three different populations of neonatal foreskin fibroblasts were treated with 0.98 μM [G-3H]-BP at 9.6 Ci/mmole for 24 hours and the organic-extractable metabolites in the extracellular, the cytoplasmic, and the nuclear fractions were analyzed by high-pressure liquid chromatography (HPLC). Confluent cultures (contact-inhibited cells), which were nontransformable, metabolized BP to a much greater extent than the transformable populations, randomly-proliferating cultures (cells in logarithmic growth) and synchronized cultures (cells treated in S phase). The major extracellular BP metabolites detected were the 9,10-diol, the 7,8-diol, and the phenols, including all four tetrols observed only in the confluent cells. From this data, the state of confluency (i.e. the model for the in vivo state of skin cells) induced enzymes which catalyze primarily the detoxification pathways leading to the formation of metabolites which are readily excreted whereas cells which are actively dividing or synchronized induced the formation of metabolites from activation pathways that led to transformation. Next, the effects of four inducers (3-methylcholanthrene (3-MCA), phenobarbital (PB), isosafrole, and Arochlor 1254) and an inhibitor (butylated hydroxyanisole (BHA)) on the BP metabolism of human epidermal keratinocytes were evaluated

  9. Role of lipid peroxidation in cytochrome P-450 degradation in hepatocytes and lymphocytes and stabilizing effects of antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Kagan, V.; Novikov, K.; Bogdanova, E.; Prilipko, L.


    Incubation of primary culture of hepatocytes was accompanied by spontaneous degradation of cytochrome P-450 (P-450) and by a decrease of its monooxygenase activities. Accumulation of lipid peroxidation (LPO) products also occurred. Addition of LPO inducers (Fe/sup 2 +/-ADP, NADPH) to the medium led to a drastic acceleration of both processes. Synthetic free radical scavengers (butylated hydroxytoluene, 3-hydroxybenzene, alpha-naphthol) prevented LPO activation and protected P-450 against degradation. Phenolic derivatives of 3,4-benzpyrene, formed as a result of its hydroxylation, also had an antioxidant and a protective effect on P-450. Similarly, incubation of human peripheral blood lymphocytes stimulated by PHA resulted in a rapid inhibition of arylhydrocarbon hydroxylase (AHH). In lymphocytes stimulated by PHA and then induced by 3-methylcholanthrene, the sharply increased AHH activity remained unchanged for a long period and no LPO products were accumulated. Exogenous LPO inducers did not either stimulate LPO and were ineffective on the AHH activity. This was due to the presence of 3-methyl cholanthrene phenolic derivatives formed during lymphocytes induction. It is concluded that free radical scavengers could be used as P-450 stabilizers in cell cultures.

  10. Methionine restriction inhibits chemically-induced malignant transformation in the BALB/c 3T3 cell transformation assay. (United States)

    Nicken, Petra; Empl, Michael T; Gerhard, Daniel; Hausmann, Julia; Steinberg, Pablo


    High consumption of red meat entails a higher risk of developing colorectal cancer. Methionine, which is more frequently a component of animal proteins, and folic acid are members of the one carbon cycle and as such important players in DNA methylation and cancer development. Therefore, dietary modifications involving altered methionine and folic acid content might inhibit colon cancer development. In the present study, the BALB/c 3T3 cell transformation assay was used to investigate whether methionine and folic acid are able to influence the malignant transformation of mouse fibroblasts after treatment with the known tumour initiator 3-methylcholanthrene. Three different methionine concentrations (representing a -40%, a "normal" and a +40% cell culture medium concentration, respectively) and two different folic acid concentrations (6 and 20 μM) were thereby investigated. Methionine restriction led to a decrease of type III foci, while enhancement of both methionine and folic acid did not significantly increase the cell transformation rate. Interestingly, the focus-lowering effect of methionine was only significant in conjunction with an elevated folic acid concentration. In summary, we conclude that the malignant transformation of mouse fibroblasts is influenced by methionine levels and that methionine restriction could be a possible approach to reduce cancer development. PMID:27427305

  11. A Microfabricated Platform for Generating Physiologically-Relevant Hepatocyte Zonation (United States)

    McCarty, William J.; Usta, O. Berk; Yarmush, Martin L.


    In vitro liver models have been important tools for more than 40 years for academic research and preclinical toxicity screening by the pharmaceutical industry. Hepatocytes, the highly metabolic parenchymal cells of the liver, are efficient at different metabolic chemistries depending on their relative spatial location along the sinusoid from the portal triad to the central vein. Although replicating hepatocyte metabolic zonation is vitally important for physiologically-relevant in vitro liver tissue and organ models, it is most often completely overlooked. Here, we demonstrate the creation of spatially-controlled zonation across multiple hepatocyte metabolism levels through the application of precise concentration gradients of exogenous hormone (insulin and glucagon) and chemical (3-methylcholanthrene) induction agents in a microfluidic device. Observed gradients in glycogen storage via periodic acid-Schiff staining, urea production via carbamoyl phosphatase synthetase I staining, and cell viability after exposure to allyl alcohol and acetaminophen demonstrated the in vitro creation of hepatocyte carbohydrate, nitrogen, alcohol degradation, and drug conjugation metabolic zonation. This type of advanced control system will be crucial for studies evaluating drug metabolism and toxicology using in vitro constructs.

  12. Radiation carcinogenesis. Comprehensive final report, 16 May 1979-31 December 1980

    International Nuclear Information System (INIS)

    This abstract covers three main areas of investigation: mesothelioma induction by asbestos, radiation tumorigenesis and transplantable tumors. Canadian and Rhodesian asbestos fibers have been administered under anesthesia to rats by intratracheal, intrapleural and intraperitoneal injection. Additional groups were given 3-methylcholanthrene or x-radiation along with asbestos. A large series of mice also treated as above have displayed mesotheliomas. In addition, glass fiber injections and feeding of asbestos were done and have produced negative results to date. The carcinogenic effect of whole-body radiation on hemi-irradiated parabiont partners exposed to a single 1000 R dose of x-ray was evidenced by a significant increase in the incidence of malignant tumors in only six tissues: skin, supporting soft tissue, kidney, bone, pancreatic islets and ovary. In the male adrenal medulla and in the female breast genetic and parabiotic hormonal factors were judged to exert a significant effect. The occurrence of incisional (anastomotic) sarcomas in significant numbers in hemi-irradiated and parabiont control pairs suggests the operation of mechanical factors complicating the healing process, only slightly enhanced by radiation. One of the very valuable but unanticipated developments of the rat radiation program was the isolation of two transplantable endocrine tumors with strong hormonal potentials: an insulinoma of the pancreas and a pheochromocytoma of the adrenal medulla

  13. The product of the cph oncogene is a truncated, nucleotide-binding protein that enhances cellular survival to stress. (United States)

    Velasco, J A; Avila, M A; Notario, V


    Cph was isolated from neoplastic Syrian hamster embryo fibroblasts initiated by 3-methylcholanthrene (MCA), and was shown to be a single copy gene in the hamster genome, conserved from yeast to human cells, expressed in fetal cells and most adult tissues, and acting synergistically with H-ras in the transformation of murine NIH3T3 fibroblasts. We have now isolated Syrian hamster full-length cDNAs for the cph oncogene and proto-oncogene. Nucleotide sequence analysis revealed that cph was activated in MCA-treated cells by a point-mutational deletion at codon 214, which caused a shift in the normal open reading frame (ORF) and brought a translation termination codon 33 amino acids downstream. While proto-cph encodes a protein (pcph) of 469 amino acids, cph encodes a truncated protein (cph) of 246 amino acids with a new, hydrophobic C-terminus. Similar mechanisms activated cph in other MCA-treated Syrian hamster cells. The cph and proto-cph proteins have partial sequence homology with two protein families: GDP/GTP exchange factors and nucleotide phosphohydrolases. In vitro translated, gel-purified cph proteins did not catalyze nucleotide exchange for H-ras, but were able to bind nucleotide phosphates, in particular ribonucleotide diphosphates such as UDP and GDP. Steady-state levels of cph mRNA increased 6.7-fold in hamster neoplastic cells, relative to a 2.2-fold increase in normal cells, when they were subjected to a nutritional stress such as serum deprivation. Moreover, cph-transformed NIH3T3 cells showed increased survival to various forms of stress (serum starvation, hyperthermia, ionizing radiation), strongly suggesting that cph participates in cellular mechanisms of response to stress. PMID:9989819

  14. Induction of UDP-glucuronosyltransferase activities in Gunn, heterozygous, and Wistar rat livers by pregnenolone-16 alpha-carbonitrile. (United States)

    Watkins, J B; Klaassen, C D


    The effect of pregnenolone-16 alpha-carbonitrile (PCN) on UDP-glucuronosyltransferase (UDP-GT) activity was comprehensively examined in Wistar (JJ), heterozygous (Jj) and Gunn (jj) rats with eleven different acceptors for glucuronic acid. UDP-GT activity after 3-methylcholanthrene (3-MC) and phenobarbital (PB) treatment was studied in additional rats for comparative purposes. Conjugation of group-1 aglycones (1-naphthol and p-nitrophenol) was much lower in Gunn than in Wistar rats. PCN did not alter UDP-GT conjugation of these acceptors. UDP-GT activity toward group-1 aglycones was increased by 3-MC in Wistar and heterozygous rats but was not enhanced in Gunn rats by any inducer. Activity toward group-2 aglycones (morphine, chloramphenicol, valproic acid) was similar in control rats of all genotypes. PCN increased chloramphenicol conjugation, whereas PB enhanced the glucuronidation of all group-2 aglycones in Wistar, heterozygous, and Gunn rats. Conjugation of group-3 acceptors (bilirubin and digitoxigenin monodigitoxoside, DIG) was deficient in Gunn rats and was not inducible. PCN increased glucuronidation of bilirubin and DIG in Wistar and heterozygous rats. The concentration of UDP-glucuronic acid (UDPGA) in liver was similar in control animals of all genotypes and was increased in rats treated with 3-MC. The other inducers did not affect hepatic UDPGA levels. Thus, 3-MC, PB, and PCN induce UDP-GT activities toward different groups of acceptors of glucuronic acid. The results support the hypothesis that PCN induces a form of UDP-GT that preferentially conjugates the group-3 acceptors, bilirubin and DIG.

  15. A Novel Antihepatitis Drug, Bicyclol, Prevents Liver Carcinogenesis in Diethylnitrosamine-Initiated and Phenobarbital-Promoted Mice Tumor Model

    Directory of Open Access Journals (Sweden)

    Hua Sun


    Full Text Available Bicyclol, an antihepatitis drug developed by Chinese scientists, has been shown to prevent the malignant transformation induced by 3-methylcholanthrene and 12-O-tetradecanoylphorbol-13-acetate in WB-F344 rat liver epithelial cells. This study provides further evidence on its role as a chemopreventive agent in experimental mice with diethylnitrosamine- (DEN- initiated and phenobarbital- (PB- promoted liver carcinoma. Liver tissue and serum were collected. In the two-stage model of hepatocarcinogenesis in mice, oral administration of bicyclol (100, 200 mg/kg before DEN injection showed significant reduction in the incidence of hepatocellular foci, nodules, or carcinoma. Histopathological examination revealed that there was no hepatocellular carcinoma (HCC and hepatoma formation in the mice pretreated with bicyclol (200 mg/kg at week 20, while the mice treated with DEN/PB developed 33.3% HCC and 55.6% hepatoma. Furthermore, the serum levels of alanine aminotransferase (ALT, alkaline phosphatase (ALP, and α-fetal protein (AFP in serum significantly increased in the DEN/PB model group in comparison with the control group. Pretreatment with bicyclol showed a marked reduction in the above condition. Bicyclol also decreased the expression of AFP and proliferating cell nuclear antigen level in the liver tissue and attenuated the decrease in body weight. In this study, we also found that 10 weeks after stopping the administration of PB and drugs, the control and bicyclol-treated (200 mg/kg animals showed no HCC and hepatoma formation at the time of termination whereas DEN/PB-induced mice developed 100% hepatoma and 50% HCC. These results further indicate that bicyclol has the chemopreventive potential for liver carcinogenesis induced by carcinogens.

  16. Metabolism of 1- and 2-naphthylamine in isolated rat hepatocytes. (United States)

    Orzechowski, A; Schrenk, D; Bock, K W


    The liver probably plays a major role in the metabolic activation of the bladder carcinogen 2-naphthylamine (2-NA) and in the inactivation of the non-carcinogenic isomer 1-naphthylamine (1-NA). However, metabolic profiles of these compounds (including primary metabolites and directly determined conjugates) in hepatocytes are not available. Therefore metabolism of 1- and 2-NA was compared in freshly isolated hepatocytes from 3-methylcholanthrene (MC)-treated and untreated rats. At 10 microM, 2-NA was found to be mainly N-acetylated (66% of total metabolites after 1 h incubation) and N-glucuronidated (19%). Minor pathways led to C-oxidation (7%) and N-oxidation (3%; 2% present as the N-glucuronide). In hepatocytes from MC-treated rats total metabolism was slightly affected (1.5-fold increase). However, C- and N-oxidation were markedly increased (63 and 18% respectively), while N-acetylation and N-glucuronidation were diminished (5 and 2% respectively). Similar experiments were carried out with 1-NA. Its N-glucuronide was the predominant metabolite (68%) followed by the N-acetylated compound (15%) while C-oxidation was low and N-oxidized metabolites could not be detected, even after induction. The results demonstrate that MC treatment markedly shifted 2-NA metabolism from N-acetylation and N-glucuronidation to N- and C-oxidation. In the case of 1-NA metabolism extensive N-glucuronidation together with the lack of N-oxidation may prevent carcinogenesis. PMID:1473229

  17. Embryonic turkey liver: activities of biotransformation enzymes and activation of DNA-reactive carcinogens

    Energy Technology Data Exchange (ETDEWEB)

    Perrone, Carmen E.; Duan, Jian Dong; Jeffrey, Alan M.; Williams, Gary M. [New York Medical College, Department of Pathology, Valhalla (United States); Ahr, Hans-Juergen; Schmidt, Ulrich [Bayer AG, Institute of Toxicology, Wuppertal (Germany); Enzmann, Harald H. [Federal Institute for Drugs and Medical Devices, Bonn (Germany)


    Avian embryos are a potential alternative model for chemical toxicity and carcinogenicity research. Because the toxic and carcinogenic effects of some chemicals depend on bioactivation, activities of biotransformation enzymes and formation of DNA adducts in embryonic turkey liver were examined. Biochemical analyses of 22-day in ovoturkey liver post-mitochondrial fractions revealed activities of the biotransformation enzymes 7-ethoxycoumarin de-ethylase (ECOD), 7-ethoxyresorufin de-ethylase (EROD), aldrin epoxidase (ALD), epoxide hydrolase (EH), glutathione S-transferase (GST), and UDP-glucuronyltransferase (GLUT). Following the administration of phenobarbital (24 mg/egg) on day 21, enzyme activities of ECOD, EROD, ALD, EH and GLUT, but not of GST, were increased by two-fold or higher levels by day 22. In contrast, acute administration of 3-methylcholanthrene (5 mg/egg) induced only ECOD and EROD activities. Bioactivation of structurally diverse pro-carcinogens was also examined using {sup 32}P-postlabeling for DNA adducts. In ovoexposure of turkey embryos on day 20 of gestation to 2-acetylaminofluorene (AAF), 4,4'-methylenebis(2-chloroaniline) (MOCA), benzo[a]pyrene (BaP), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) resulted in the formation of DNA adducts in livers collected by day 21. Some of the DNA adducts had {sup 32}P-postlabeling chromatographic migration patterns similar to DNA adducts found in livers from Fischer F344 rats exposed to the same pro-carcinogens. We conclude that 21-day embryonic turkey liver is capable of chemical biotransformation and activation of genotoxic carcinogens to form DNA adducts. Thus, turkey embryos could be utilized to investigate potential chemical toxicity and carcinogenicity. (orig.)

  18. Metabolism and macromolecular covalent binding of [14C]-1-nitropyrene in isolated perfused and ventilated rat lungs

    International Nuclear Information System (INIS)

    The purpose of this study was to quantitate l-nitropyrene (1-NP) metabolism and macromolecular covalent binding in the isolated perfused rat lung. Rat lungs were perfused with 2, 5, or 24 microM [14C]-1-NP for 90 min. Tidal volume and dynamic lung compliance were monitored throughout the perfusion to document the ventilatory pattern and the decay of tissue elasticity. Perfusate was sampled periodically throughout the experiment and analyzed for 1-NP metabolites with high-performance liquid chromatography. In all experiments, both dynamic lung compliance and tidal volume declined in a nearly linear manner and were approximately 60% of the initial value at the end of 90 min of perfusion. At all concentrations of [14C]-1-NP tested, less than 5 to 6% of the total amount of [14C]-1-NP added was metabolized in lungs from control and phenobarbital (PB)-treated rats. Lungs from control and PB- and 3-methylcholanthrene (3-MC)-treated rats metabolized [14C]-1-NP to oxidized, reduced, and conjugated metabolites. The major metabolites were 3-, 6-, and 8-hydroxynitropyrene. Treatment of rats with PB resulted in a 60% increase in the total metabolism of [14C]-1-NP, whereas treatment of rats with 3-MC resulted in a 10-fold increase in the rate of metabolism of [14C]-1-NP when compared to controls. Conjugate hydrolysis studies indicated that the water-soluble metabolites from lungs of control and PB- and 3-MC-treated rats consisted of hydroxynitropyrene glucuronides and hydroxynitropyrene sulfate conjugates. Quantities of 14C covalently bound to lung macromolecules after 90 min of perfusion from lungs of control and PB-treated rats were 0.06 to 0.21 nmol equivalents/g lung. However, in lungs from 3-MC-treated rats, there was a 20-fold increase in quantities of 14C covalently bound when compared to lungs from either control or PB-treated rats

  19. Studies on the metabolism of l-menthol in rats. (United States)

    Madyastha, K M; Srivatsan, V


    Metabolism of l-menthol in rats was investigated both in vivo and in vitro. Metabolites isolated and characterized from the urine of rats after oral administration (800 mg/kg of body weight/day) of l-menthol were the following: p-menthane-3,8-diol (II), p-menthane-3,9-diol (III), 3,8-oxy-p-menthane-7-carboxylic acid (IV), and 3,8-dihyroxy-p-menthane-7-carboxylic acid (V). In vivo, the major urinary metabolites were compounds II and V. Repeated oral administration (800 mg/kg of body weight/day) of l-menthol to rats for 3 days resulted in the increase of both liver microsomal cytochrome P-450 content and NADPH-cytochrome c reductase activity by nearly 80%. Further treatment (for 7 days total) reduced their levels considerably, although the levels were still higher than the control values. Both cytochrome b5 and NADH-cytochrome c reductase levels were not changed during the 7 days of treatment. Rat liver microsomes readily converted l-menthol to p-menthane-3,8-diol (II) in the presence of NADPH and O2. This activity was significantly higher in microsomes obtained from phenobarbital (PB)-induced rats than from control microsomal preparations, whereas 3-methylcholanthrene (3-MC)-induced microsomes failed to convert l-menthol to compound II in the presence of NADPH and O2. l-Menthol elicited a type I spectrum with control (Ks = 60.6 microM) and PB-induced (Ks = 32.3 microM) microsomes whereas with 3MC-induced microsomes it produced a reverse type I spectrum.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2906604

  20. Leflunomide Induces Pulmonary and Hepatic CYP1A Enzymes via Aryl Hydrocarbon Receptor. (United States)

    Patel, Ananddeep; Zhang, Shaojie; Paramahamsa, Maturu; Jiang, Weiwu; Wang, Lihua; Moorthy, Bhagavatula; Shivanna, Binoy


    Emerging evidence indicates that the aryl hydrocarbon receptor (AhR) plays a crucial role in normal physiologic homeostasis. Additionally, aberrant AhR signaling leads to several pathologic states in the lung and liver. Activation of AhR transcriptionally induces phase I (CYP1A) detoxifying enzymes. Although the effects of the classic AhR ligands such as 3-methylcholanthrene and dioxins on phase 1 enzymes are well studied in rodent lung, liver, and other organs, the toxicity profiles limit their use as therapeutic agents in humans. Hence, there is a need to identify and investigate nontoxic AhR ligands not only to understand the AhR biology but also to develop the AhR as a clinically relevant therapeutic target. Leflunomide is a Food and Drug Administration-approved drug in humans that is known to have AhR agonist activity in vitro. Whether it activates AhR and induces phase 1 enzymes in vivo is unknown. Therefore, we tested the hypothesis that leflunomide will induce pulmonary and hepatic CYP1A enzymes in C57BL/6J wild-type mice, but not in AhR-null mice. We performed real-time reverse-transcription polymerase chain reaction analyses for CYP1A1/2 mRNA expression, western blot assays for CYP1A1/2 protein expression, and ethoxyresorufinO-deethylase assay for CYP1A1 catalytic activity. Leflunomide increased CYP1A1/A2 mRNA, protein, and enzymatic activities in wild-type mice. In contrast, leflunomide failed to increase pulmonary and hepatic CYP1A enzymes in AhR-null mice. In conclusion, we provide evidence that leflunomide induces pulmonary and hepatic CYP1A enzymes via the AhR.

  1. Deletion of Forkhead Box M1 transcription factor from respiratory epithelial cells inhibits pulmonary tumorigenesis.

    Directory of Open Access Journals (Sweden)

    I-Ching Wang

    Full Text Available The Forkhead Box m1 (Foxm1 protein is induced in a majority of human non-small cell lung cancers and its expression is associated with poor prognosis. However, specific requirements for the Foxm1 in each cell type of the cancer lesion remain unknown. The present study provides the first genetic evidence that the Foxm1 expression in respiratory epithelial cells is essential for lung tumorigenesis. Using transgenic mice, we demonstrated that conditional deletion of Foxm1 from lung epithelial cells (epFoxm1(-/- mice prior to tumor initiation caused a striking reduction in the number and size of lung tumors, induced by either urethane or 3-methylcholanthrene (MCA/butylated hydroxytoluene (BHT. Decreased lung tumorigenesis in epFoxm1(-/- mice was associated with diminished proliferation of tumor cells and reduced expression of Topoisomerase-2alpha (TOPO-2alpha, a critical regulator of tumor cell proliferation. Depletion of Foxm1 mRNA in cultured lung adenocarcinoma cells significantly decreased TOPO-2alpha mRNA and protein levels. Moreover, Foxm1 directly bound to and induced transcription of the mouse TOPO-2alpha promoter region, indicating that TOPO-2alpha is a direct target of Foxm1 in lung tumor cells. Finally, we demonstrated that a conditional deletion of Foxm1 in pre-existing lung tumors dramatically reduced tumor growth in the lung. Expression of Foxm1 in respiratory epithelial cells is critical for lung cancer formation and TOPO-2alpha expression in vivo, suggesting that Foxm1 is a promising target for anti-tumor therapy.

  2. Biliary excretion of acetaminophen-glutathione as an index of toxic activation of acetaminophen: effect of chemicals that alter acetaminophen hepatotoxicity

    Energy Technology Data Exchange (ETDEWEB)

    Madhu, C.; Gregus, Z.; Klaassen, C.D.


    Acetaminophen (AA) is converted, presumably by cytochrome P-450, to an electrophile which is conjugated with glutathione (GS). AA-GS is excreted into bile, therefore the biliary excretion rate of AA-GS may reflect the rate of activation of AA in vivo. In order to test this hypothesis, the effect of agents capable of altering the activation of AA including cytochrome P-450 inducers and inhibitors, cobaltous chloride which decreases the amount of P-450, prostaglandin synthetase inhibitors (indomethacin and naproxen), antioxidants (butylated hydroxyanisole, alpha-tocopherol, ascorbic acid and ascorbic acid palmitate) and other chemicals known to decrease AA hepatotoxicity (dimethylsulfoxide and cysteamine), on the biliary excretion of AA-GS was studied in hamsters, the species most sensitive to AA-induced hepatotoxicity. The biliary excretion of AA-GS increased linearly up to 1 mmol/kg of AA i.v., but at higher dosages exhibited saturation kinetics. Dosages above 0.5 mmol/kg lowered hepatic GS concentration. Of the cytochrome P-450 inducers, 3-methylcholanthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin, increased the biliary excretion of AA-GS (2.9- and 3.2-fold, respectively) whereas ethanol and isoniazid did not affect it, and pregnenolone-16 alpha-carbonitrile tended to decrease it (43%). Phenobarbital tended to increase the biliary excretion of AA-GS, but not in a statistically significant manner. Several cytochrome P-450 inhibitors (metyrapone, 8-methoxypsoralen, 2-(4,6-dichloro-biphenyloxy) ethylamine, alpha-naphthoflavone and cimetidine) decreased the biliary excretion of AA-GS, although SKF 525-A and piperonyl butoxide did not. Cobaltous chloride decreased dramatically the biliary excretion of AA-GS.

  3. Aryl hydrocarbon receptors in osteoclast lineage cells are a negative regulator of bone mass.

    Directory of Open Access Journals (Sweden)

    Tai-yong Yu

    Full Text Available Aryl hydrocarbon receptors (AhRs play a critical role in various pathological and physiological processes. Although recent research has identified AhRs as a key contributor to bone metabolism following studies in systemic AhR knockout (KO or transgenic mice, the cellular and molecular mechanism(s in this process remain unclear. In this study, we explored the function of AhR in bone metabolism using AhR(RANKΔOc/ΔOc (RANK(Cre/+;AhR(flox/flox mice. We observed enhanced bone mass together with decreased resorption in both male and female 12 and 24-week-old AhR(RANKΔOc/ΔOc mice. Control mice treated with 3-methylcholanthrene (3MC, an AhR agonist, exhibited decreased bone mass and increased bone resorption, whereas AhR(CtskΔOc/ΔOc (Ctsk(Cre/+;AhR(flox/flox mice injected with 3MC appeared to have a normal bone phenotype. In vitro, bone marrow-derived macrophages (BMDMs from AhR(RANKΔOc/ΔOc mice exhibited impaired osteoclastogenesis and repressed differentiation with downregulated expression of B lymphocyte-induced maturation protein 1 (Blimp1, and cytochrome P450 genes Cyp1b1 and Cyp1a2. Collectively, our results not only demonstrated that AhR in osteoclast lineage cells is a physiologically relevant regulator of bone resorption, but also highlighted the need for further studies on the skeletal actions of AhR inhibitors in osteoclast lineage cells commonly associated with bone diseases, especially diseases linked to environmental pollutants known to induce bone loss.

  4. Caffeine promotes anti-tumor immune response during tumor initiation: Involvement of the adenosine A2A receptor. (United States)

    Eini, Hadar; Frishman, Valeria; Yulzari, Robert; Kachko, Leonid; Lewis, Eli C; Chaimovitz, Cidio; Douvdevani, Amos


    Epidemiologic studies depict a negative correlation between caffeine consumption and incidence of tumors in humans. The main pharmacological effects of caffeine are mediated by antagonism of the adenosine receptor, A2AR. Here, we examine whether the targeting of A2AR by caffeine plays a role in anti-tumor immunity. In particular, the effects of caffeine are studied in wild-type and A2AR knockout (A2AR(-/-)) mice. Tumor induction was achieved using the carcinogen 3-methylcholanthrene (3-MCA). Alternatively, tumor cells, comprised of 3-MCA-induced transformed cells or B16 melanoma cells, were inoculated into animal footpads. Cytokine release was determined in a mixed lymphocyte tumor reaction (MLTR). According to our findings, caffeine-consuming mice (0.1% in water) developed tumors at a lower rate compared to water-consuming mice (14% vs. 53%, respectively, p=0.0286, n=15/group). Within the caffeine-consuming mice, tumor-free mice displayed signs of autoimmune alopecia and pronounced leukocyte recruitment intocarcinogen injection sites. Similarly, A2AR(-/-) mice exhibited reduced rates of 3-MCA-induced tumors. In tumor inoculation studies, caffeine treatment resulted in inhibition of tumor growth and elevation in proinflammatory cytokine release over water-consuming mice, as depicted by MLTR. Addition of the adenosine receptor agonist, NECA, to MLTR resulted in a sharp decrease in IFNγ levels; this was reversed by the highly selective A2AR antagonist, ZM241385. Thus, immune response modulation through either caffeine or genetic deletion of A2AR leads to a Th1 immune profile and suppression of carcinogen-induced tumorigenesis. Taken together, our data suggest that the use of pharmacologic A2AR antagonists may hold therapeutic potential in diminishing the rate of cancer development.

  5. Responsiveness of cerebral and hepatic cytochrome P450s in rat offspring prenatally exposed to lindane

    International Nuclear Information System (INIS)

    ABSTRACT: Prenatal exposure to low doses of lindane has been shown to affect the ontogeny of xenobiotic metabolizing cytochrome P450s (CYPs), involved in the metabolism and neurobehavioral toxicity of lindane. Attempts were made in the present study to investigate the responsiveness of CYPs in offspring prenatally exposed to lindane (0.25 mg/kg b. wt.; 1/350th of LD50; p. o. to mother) when challenged with 3-methylcholanthrene (MC) or phenobarbital (PB), inducers of CYP1A and 2B families or a sub-convulsant dose of lindane (30 mg/kg b. wt., p. o.) later in life. Prenatal exposure to lindane was found to produce an increase in the mRNA and protein expression of CYP1A1, 1A2, 2B1, 2B2 isoforms in brain and liver of the offspring at postnatal day 50. The increased expression of the CYPs in the offspring suggests the sensitivity of the CYPs during postnatal development, possibly, to low levels of lindane, which may partition into mother's milk. A higher increase in expression of CYP1A and 2B isoenzymes and their catalytic activity was observed in animals pretreated prenatally with lindane and challenged with MC (30 mg/kg, i. p. x 5 days) or PB (80 mg/kg, i. p. x 5 days) when young at age (approx. 7 weeks) compared to animals exposed to MC or PB alone. Further, challenge of the control and prenatally exposed offspring with a single sub-convulsant dose of lindane resulted in an earlier onset and increased incidence of convulsions in the offspring prenatally exposed to lindane have demonstrated sensitivity of the CYPs in the prenatally exposed offspring. Our data assume significance as the subtle changes in the expression profiles of hepatic and cerebral CYPs in rat offspring during postnatal development could modify the adult response to a later exposure to xenobiotics

  6. Monocrotophos induces the expression and activity of xenobiotic metabolizing enzymes in pre-sensitized cultured human brain cells.

    Directory of Open Access Journals (Sweden)

    Vinay K Tripathi

    Full Text Available The expression and metabolic profile of cytochrome P450s (CYPs is largely missing in human brain due to non-availability of brain tissue. We attempted to address the issue by using human brain neuronal (SH-SY5Y and glial (U373-MG cells. The expression and activity of CYP1A1, 2B6 and 2E1 were carried out in the cells exposed to CYP inducers viz., 3-methylcholanthrene (3-MC, cyclophosphamide (CPA, ethanol and known neurotoxicant- monocrotophos (MCP, a widely used organophosphorous pesticide. Both the cells show significant induction in the expression and CYP-specific activity against classical inducers and MCP. The induction level of CYPs was comparatively lower in MCP exposed cells than cells exposed to classical inducers. Pre-exposure (12 h of cells to classical inducers significantly added the MCP induced CYPs expression and activity. The findings were concurrent with protein ligand docking studies, which show a significant modulatory capacity of MCP by strong interaction with CYP regulators-CAR, PXR and AHR. Similarly, the known CYP inducers- 3-MC, CPA and ethanol have also shown significantly high docking scores with all the three studied CYP regulators. The expression of CYPs in neuronal and glial cells has suggested their possible association with the endogenous physiology of the brain. The findings also suggest the xenobiotic metabolizing capabilities of these cells against MCP, if received a pre-sensitization to trigger the xenobiotic metabolizing machinery. MCP induced CYP-specific activity in neuronal cells could help in explaining its effect on neurotransmission, as these CYPs are known to involve in the synthesis/transport of the neurotransmitters. The induction of CYPs in glial cells is also of significance as these cells are thought to be involved in protecting the neurons from environmental insults and safeguard them from toxicity. The data provide better understanding of the metabolizing capability of the human brain cells against

  7. Creatine supplementation with methylglyoxal: a potent therapy for cancer in experimental models. (United States)

    Pal, Aparajita; Roy, Anirban; Ray, Manju


    The anti-cancer effect of methylglyoxal (MG) is now well established in the literature. The main aim of this study was to investigate the effect of creatine as a supplement in combination with MG both in vitro and in vivo. In case of the in vitro studies, two different cell lines, namely MCF-7 (human breast cancer cell line) and C2C12 (mouse myoblast cell line) were chosen. MG in combination with creatine showed enhanced apoptosis as well as higher cytotoxicity in the breast cancer MCF-7 cell line, compared to MG alone. Pre-treatment of well-differentiated C2C12 myotubes with cancerogenic 3-methylcholanthrene (3MC) induced a dedifferentiation of these myotubes towards cancerous cells (that mimic the effect of 3MC observed in solid fibro-sarcoma animal models) and subsequent exposure of these induced cancer cells with MG proved to be cytotoxic. Thus, creatine plus ascorbic acid enhanced the anti-cancer effects of MG. In contrast, when normal C2C12 muscle cells or myotubes (mouse normal myoblast cell line) were treated with MG or MG plus creatine and ascorbic acid, no detrimental effects were seen. This indicated that cytotoxic effects of MG are specifically limited towards cancer cells and are further enhanced when MG is used in combination with creatine and ascorbic acid. For the in vivo studies, tumors were induced by injecting Sarcoma-180 cells (2 × 10(6) cells/mouse) in the left hind leg. After 7 days of tumor inoculation, treatments were started with MG (20 mg/kg body wt/day, via the intravenous route), with or without creatine (150 mg/kg body wt/day, fed orally) and ascorbic acid (50 mg/kg body wt/day, fed orally) and continued for 10 consecutive days. Significant regression of tumor size was observed when Sarcoma-180 tumor-bearing mice were treated with MG and even more so with the aforesaid combination. The creatine-supplemented group demonstrated better overall survival in comparison with tumor-bearing mice without creatine. In conclusion, it may be

  8. Microsomal biotransformation of benzo[ghi]perylene, a mutagenic polycyclic aromatic hydrocarbon without a "classic" bay region. (United States)

    Platt, Karl L; Grupe, Stefanie


    Carcinogenic polycyclic aromatic hydrocarbons (PAH), e.g., benzo[a]pyrene (BaP), possess a bay region comprising an ortho-fused benzene ring. Benzo[ghi]perylene (BghiP) represents the group of PAHs lacking such a "classic" bay region and hence cannot be metabolically converted like BaP to bay region dihydrodiol epoxides considered as ultimate mutagenic and carcinogenic metabolites of PAH. BghiP exhibits bacterial mutagenicity in strains TA98 (1.3 his(+)-revertant colonies/nmol) and TA100 (4.3 his(+)-revertant colonies/nmol) of Salmonella typhimurium after metabolic activation by the postmitochondrial hepatic fraction of CD rats treated with 3-methylcholanthrene. Inhibition of microsomal epoxide hydrolase (mEH) with 1,1,1-trichloro-2-propene oxide raised the bacterial mutagenicity of BghiP in TA98 almost 4-fold indicating arene oxides as ultimate mutagens. To confirm this assumption, the biotransformation of BghiP was elucidated. Incubation of BghiP with liver microsomes of CD rats treated with Aroclor 1254 yielded 17 ethyl acetate extractable metabolic products. Twelve metabolites were identified by a combination of chromatographic, spectroscopic, and biochemical methods. The microsomal biotransformation of BghiP proceeds by two pathways: Pathway I starts with the monooxygenase attack at the 7-position leading to the 7-phenol, which is transformed to the 7,8- and 7,10-diphenols followed by oxidation to the 7,8- and 7,10-quinones. On pathway II, the K regions of BghiP are successively converted to arene oxides yielding the indirectly identified 3,4-oxide and the 3,4,11,12-bisoxides. Enzymatic hydrolysis of the 3,4-oxide leads to the trans-3,4-dihydrodiol, which is oxidized to the 3,4-quinone. Similarly, the trans-3,4-trans-11,12-bisdihydrodiols and the trans-3,4-dihydrodiol 11,12-quinone are generated from the 3,4,11,12-bisoxides. The trans-3,4-dihydrodiol and the trans-3,4-trans-11,12-bisdihydrodiols are preferentially formed as R,R and R,R,R,R enantiomers

  9. Transcriptomic analysis of pathways regulated by toll-like receptor 4 in a murine model of chronic pulmonary inflammation and carcinogenesis

    Directory of Open Access Journals (Sweden)

    Grissom Sherry F


    Full Text Available Abstract Background Therapeutic strategies exist for human pulmonary neoplasia, however due to the heterogeneity of the disease, most are not very effective. The innate immunity gene, toll-like receptor 4 (TLR4, protects against chronic pulmonary inflammation and tumorigenesis in mice, but the mechanism is unclear. This study was designed to identify TLR4-mediated gene expression pathways that may be used as prognostic indicators of susceptibility to lung tumorigenesis in mice and provide insight into the mechanism. Methods Whole lung mRNA was isolated from C.C3H-Tlr4Lps-d (BALBLps-d; Tlr4 mutant and BALB/c (Tlr4 normal mice following butylated hydroxytoluene (BHT-treatment (four weekly ip. injections; 150-200 mg/kg/each; "promotion". mRNA from micro-dissected tumors (adenomas and adjacent uninvolved tissue from both strains were also compared 27 wks after a single carcinogen injection (3-methylcholanthrene (MCA, 10 μg/g; "control" or followed by BHT (6 weekly ip. injections; 125-200 mg/kg/each; "progression". Bronchoalveolar lavage fluid was analyzed for inflammatory cell content and total protein determination, a marker of lung hyperpermeability; inflammation was also assessed using immunohistochemical staining for macrophages (F4/80 and lymphocytes (CD3 in mice bearing tumors (progression. Results During promotion, the majority of genes identified in the BALBLps-d compared to BALB/c mice (P Ereg, secreted phosphoprotein 1(Spp1, which can lead to cell growth and eventual tumor development. Inflammation was significantly higher in BALBLps-d compared to BALB/c mice during progression, similar to the observed response during tumor promotion in these strains. Increases in genes involved in signaling through the EGFR pathway (e.g. Ereg, Spp1 were also observed during progression in addition to continued inflammation, chemotactic, and immune response gene expression in the BALBLps-d versus BALB/c mice (P Conclusion This transcriptomic study

  10. Regulation of FoxO transcription factors by environmental NO(x). Influence of metal ions and polycyclic aromatic hydrocarbons; Regulation von FoxO-Transkriptionsfaktoren durch Umweltnoxen. Einfluss von Metallionen und polyzyklischen aromatischen Kohlenwasserstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Eckers, Anna


    FoxO transcription factors are crucial modulators of various cellular processes, controlling the expression of target genes such as those coding for manganese superoxide dismutase (MnSOD) and selenoprotein P (SeP), thereby supporting defense against oxidative stress. Environmental stimuli such as heavy metal ions and polycyclic aromatic hydrocarbons (PAH) modulate signaling pathways both by interaction with proteins or by inducing the generation of reactive oxygen species (ROS). Exposure of hepatoma cells to nickel ions at subcytotoxic doses did not translate into modulation of FoxO activity despite an activation of the Ser/Thr-kinase Akt. The cellular response to nickel ions under these conditions is most likely independent of the formation of ROS, since there were no increased levels of glutathione disulfide detectable. FoxO activity was then found to be modulated in response to exposure of cells to PAH or the tryptophan photoproduct FICZ. Both PAH and FICZ caused an increased activity of a FoxO-responsive promoter construct as well as of glucose 6-phosphatase promoter activity. In contrast, the activities of promoters of genes coding for MnSOD or SeP were decreased in response to exposure to the PAH 3-methylcholanthrene (3-MC). In line with the promoter effects, 3-MC also decreased steady-state levels of SeP mRNA. The response of the SeP promoter to 3-MC was abrogated by point mutations introduced at the two identified FoxO binding elements of the SeP promoter, implying that interaction of FoxO proteins with these sites is essential for the downregulation of promoter activity. In addition to FoxO activity being modulated by xenobiotics, it was then demonstrated that FoxO expression was also modulated by exposure of cells to PAH or FICZ. FoxO4 mRNA levels were downregulated in hepatoma cells exposed to 3-MC or FICZ. Similarly, insulin treatment caused a downregulation of mRNA levels of FoxO 1a, 3a and 4 in hepatoma cells. (orig.)

  11. Metabolism of UV-filter benzophenone-3 by rat and human liver microsomes and its effect on endocrine-disrupting activity

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Yoko, E-mail: [Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553 (Japan); Nihon Pharmaceutical University, Komuro 10281, Ina-machi, Saitama 362-0806 (Japan); Kojima, Hiroyuki; Takeuchi, Shinji [Hokkaido Institute of Public Health, Kita-19, Nishi-12, Kita-ku, Sapporo 060-0819 (Japan); Uramaru, Naoto [Nihon Pharmaceutical University, Komuro 10281, Ina-machi, Saitama 362-0806 (Japan); Sanoh, Seigo [Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553 (Japan); Sugihara, Kazumi [Faculty of Pharmaceutical Science, Hiroshima International University, Koshingai 5-1-1, Kure, Hiroshima 737-0112 (Japan); Kitamura, Shigeyuki [Nihon Pharmaceutical University, Komuro 10281, Ina-machi, Saitama 362-0806 (Japan); Ohta, Shigeru [Graduate School of Biomedical and Health Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8553 (Japan)


    Benzophenone-3 (2-hydroxy-4-methoxybenzophenone; BP-3) is widely used as sunscreen for protection of human skin and hair from damage by ultraviolet (UV) radiation. In this study, we examined the metabolism of BP-3 by rat and human liver microsomes, and the estrogenic and anti-androgenic activities of the metabolites. When BP-3 was incubated with rat liver microsomes in the presence of NADPH, 2,4,5-trihydroxybenzophenone (2,4,5-triOH BP) and 3-hydroxylated BP-3 (3-OH BP-3) were newly identified as metabolites, together with previously detected metabolites 5-hydroxylated BP-3 (5-OH BP-3), a 4-desmethylated metabolite (2,4-diOH BP) and 2,3,4-trihydroxybenzophenone (2,3,4-triOH BP). In studies with recombinant rat cytochrome P450, 3-OH BP-3 and 2,4,5-triOH BP were mainly formed by CYP1A1. BP-3 was also metabolized by human liver microsomes and CYP isoforms. In estrogen reporter (ER) assays using estrogen-responsive CHO cells, 2,4-diOH BP exhibited stronger estrogenic activity, 2,3,4-triOH BP exhibited similar activity, and 5-OH BP-3, 2,4,5-triOH BP and 3-OH BP-3 showed lower activity as compared to BP-3. Structural requirements for activity were investigated in a series of 14 BP-3 derivatives. When BP-3 was incubated with liver microsomes from untreated rats or phenobarbital-, 3-methylcholanthrene-, or acetone-treated rats in the presence of NADPH, estrogenic activity was increased. However, liver microsomes from dexamethasone-treated rats showed decreased estrogenic activity due to formation of inactive 5-OH BP-3 and reduced formation of active 2,4-diOH BP. Anti-androgenic activity of BP-3 was decreased after incubation with liver microsomes. - Highlights: • Metabolic modification of the endocrine-disrupting activity of BP-3 was examined. • 2,4,5-TriOH BP and 3-OH BP-3 were identified as new BP-3 metabolites. • 2,4-DiOH BP and 2,3,4-triOH BP exhibited high or similar estrogenic activities. • Estrogenic activity of BP-3 was enhanced by incubation with rat liver

  12. High hydrostatic pressure influences the in vitro response to xenobiotics in Dicentrarchus labrax liver. (United States)

    Lemaire, Benjamin; Mignolet, Eric; Debier, Cathy; Calderon, Pedro Buc; Thomé, Jean Pierre; Rees, Jean François


    Hydrostatic pressure (HP) increases by about 1 atmosphere (0.1MPa) for each ten-meter depth increase in the water column. This thermodynamical parameter could well influence the response to and effects of xenobiotics in the deep-sea biota, but this possibility remains largely overlooked. To grasp the extent of HP adaptation in deep-sea fish, comparative studies with living cells of surface species exposed to chemicals at high HP are required. We initially conducted experiments with precision-cut liver slices of a deep-sea fish (Coryphaenoides rupestris), co-exposed for 15h to the aryl hydrocarbon receptor (AhR) agonist 3-methylcholanthrene at HP levels representative of the surface (0.1MPa) and deep-sea (5-15MPa; i.e., 500-1500m depth) environments. The transcript levels of a suite of stress-responsive genes, such as the AhR battery CYP1A, were subsequently measured (Lemaire et al., 2012; Environ. Sci. Technol. 46, 10310-10316). Strikingly, the AhR agonist-mediated increase of CYP1A mRNA content was pressure-dependently reduced in C. rupestris. Here, the same co-exposure scenario was applied for 6 or 15h to liver slices of a surface fish, Dicentrarchus labrax, a coastal species presumably not adapted to high HP. Precision-cut liver slices of D. labrax were also used in 1h co-exposure studies with the pro-oxidant tert-butylhydroperoxide (tBHP) as to investigate the pressure-dependence of the oxidative stress response (i.e., reactive oxygen production, glutathione and lipid peroxidation status). Liver cells remained viable in all experiments (adenosine triphosphate content). High HP precluded the AhR agonist-mediated increase of CYP1A mRNA expression in D. labrax, as well as that of glutathione peroxidase, and significantly reduced that of heat shock protein 70. High HP (1h) also tended per se to increase the level of oxidative stress in liver cells of the surface fish. Trends to an increased resistance to tBHP were also noted. Whether the latter observation truly

  13. Metabolism of UV-filter benzophenone-3 by rat and human liver microsomes and its effect on endocrine-disrupting activity

    International Nuclear Information System (INIS)

    Benzophenone-3 (2-hydroxy-4-methoxybenzophenone; BP-3) is widely used as sunscreen for protection of human skin and hair from damage by ultraviolet (UV) radiation. In this study, we examined the metabolism of BP-3 by rat and human liver microsomes, and the estrogenic and anti-androgenic activities of the metabolites. When BP-3 was incubated with rat liver microsomes in the presence of NADPH, 2,4,5-trihydroxybenzophenone (2,4,5-triOH BP) and 3-hydroxylated BP-3 (3-OH BP-3) were newly identified as metabolites, together with previously detected metabolites 5-hydroxylated BP-3 (5-OH BP-3), a 4-desmethylated metabolite (2,4-diOH BP) and 2,3,4-trihydroxybenzophenone (2,3,4-triOH BP). In studies with recombinant rat cytochrome P450, 3-OH BP-3 and 2,4,5-triOH BP were mainly formed by CYP1A1. BP-3 was also metabolized by human liver microsomes and CYP isoforms. In estrogen reporter (ER) assays using estrogen-responsive CHO cells, 2,4-diOH BP exhibited stronger estrogenic activity, 2,3,4-triOH BP exhibited similar activity, and 5-OH BP-3, 2,4,5-triOH BP and 3-OH BP-3 showed lower activity as compared to BP-3. Structural requirements for activity were investigated in a series of 14 BP-3 derivatives. When BP-3 was incubated with liver microsomes from untreated rats or phenobarbital-, 3-methylcholanthrene-, or acetone-treated rats in the presence of NADPH, estrogenic activity was increased. However, liver microsomes from dexamethasone-treated rats showed decreased estrogenic activity due to formation of inactive 5-OH BP-3 and reduced formation of active 2,4-diOH BP. Anti-androgenic activity of BP-3 was decreased after incubation with liver microsomes. - Highlights: • Metabolic modification of the endocrine-disrupting activity of BP-3 was examined. • 2,4,5-TriOH BP and 3-OH BP-3 were identified as new BP-3 metabolites. • 2,4-DiOH BP and 2,3,4-triOH BP exhibited high or similar estrogenic activities. • Estrogenic activity of BP-3 was enhanced by incubation with rat liver

  14. Biological impact of environmental polycyclic aromatic hydrocarbons (ePAHs) as endocrine disruptors. (United States)

    Zhang, Yanyan; Dong, Sijun; Wang, Hongou; Tao, Shu; Kiyama, Ryoiti


    Polycyclic aromatic hydrocarbons (PAHs) are often detected in the environment and are regarded as endocrine disruptors. We here designated mixtures of PAHs in the environment as environmental PAHs (ePAHs) to discuss their effects collectively, which could be different from the sum of the constituent PAHs. We first summarized the biological impact of environmental PAHs (ePAHs) found in the atmosphere, sediments, soils, and water as a result of human activities, accidents, or natural phenomena. ePAHs are characterized by their sources and forms, followed by their biological effects and social impact, and bioassays that are used to investigate their biological effects. The findings of the bioassays have demonstrated that ePAHs have the ability to affect the endocrine systems of humans and animals. The pathways that mediate cell signaling for the endocrine disruptions induced by ePAHs and PAHs have also been summarized in order to obtain a clearer understanding of the mechanisms responsible for these effects without animal tests; they include specific signaling pathways (MAPK and other signaling pathways), regulatory mechanisms (chromatin/epigenetic regulation, cell cycle/DNA damage control, and cytoskeletal/adhesion regulation), and cell functions (apoptosis, autophagy, immune responses/inflammation, neurological responses, and development/differentiation) induced by specific PAHs, such as benz[a]anthracene, benzo[a]pyrene, benz[l]aceanthrylene, cyclopenta[c,d]pyrene, 7,12-dimethylbenz[a]anthracene, fluoranthene, fluorene, 3-methylcholanthrene, perylene, phenanthrene, and pyrene as well as their derivatives. Estrogen signaling is one of the most studied pathways associated with the endocrine-disrupting activities of PAHs, and involves estrogen receptors and aryl hydrocarbon receptors. However, some of the actions of PAHs are contradictory, complex, and unexplainable. Although several possibilities have been suggested, such as direct interactions between PAHs and

  15. UVA Photoirradiation of Oxygenated Benz[a]anthracene and 3-Methylcholanthene - Generation of Singlet Oxygen and Induction of Lipid Peroxidation

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    Diógenes Herreño Sáenz


    Full Text Available Polycyclic aromatic hydrocarbons (PAHs are widespread genotoxic environmental pollutants and potentially pose a health risk to humans. Although the biological and toxicological activities, including metabolism, mutagenicity, and carcinogenicity, of PAHs have been thoroughly studied, their phototoxicity and photo-induced biological activity have not been well examined. We have long been interested in phototoxicity of PAHs and their derivatives induced by irradiation with UV light. In this paper we report the photoirradiation of a series of oxygenated benz[a]anthracene (BA and 3-methylcholanthene (3-MC by UVA light in the presence of a lipid, methyl linoleate. The studied PAHs include 2-hydroxy-BA (2-OH-BA, 3-hydroxy-BA (3-OH-BA, 5-hydroxymethyl-BA (5-CH2OH-BA, 7-hydroxymethyl-BA (7-CH2OH-BA, 12-hydroxymethyl-BA (12-CH2OH-BA, 7-hydroxymethyl-12-methyl-BA (7-CH2OH-12-MBA, 5-formyl-BA (5-CHO-BA, BA 5,6-cis-dihydrodiol (BA 5,6-cis-diol, 1-hydroxy-3- methylcholanthene (1-OH-3-MC, 1-keto-3-methylcholanthene (1-keto-3-MC, and 3-MC 1,2-diol. The results indicate that upon photoirradiation by UVA at 7 and 21 J/cm2, respectively all these compounds induced lipid peroxidation and exhibited a relationship between the dose of the light and the level of lipid peroxidation induced. To determine whether or not photoirradiation of these compounds by UVA light produces ROS, an ESR spin-trap technique was employed to provide direct evidence. Photoirradiation of 3-keto-3-MC by UVA (at 389 nm in the presence of 2,2,6,6-tetramethylpiperidine (TEMP, a specific probe for singlet oxygen, resulted in the formation of TEMPO, indicating that singlet oxygen was generated. These overall results suggest that UVA photoirradiation of oxygenated BA and 3-methylcholanthrene generates singlet oxygen, one of the reactive oxygen species (ROS, which induce lipid peroxidation.

  16. Application of the improved BALB/c 3T3 cell transformation assay to the examination of the initiating and promoting activities of chemicals: the second interlaboratory collaborative study by the non-genotoxic carcinogen study group of Japan. (United States)

    Tsuchiya, Toshiyuki; Umeda, Makoto; Tanaka, Noriho; Sakai, Ayako; Nishiyama, Hiroshi; Yoshimura, Isao; Ajimi, Syozo; Asada, Shin; Asakura, Masumi; Baba, Hiroshi; Dewa, Yasuaki; Ebe, Youji; Fushiwaki, Yuichi; Hagiwara, Yuji; Hamada, Shuichi; Hamamura, Tetsuo; Iwase, Yumiko; Kajiwara, Yoshitsugu; Kasahara, Yasushi; Kato, Yukihiko; Kawabata, Masayoshi; Kitada, Emiko; Kaneko, Kazuko; Kizaki, Yuko; Kubo, Kinya; Miura, Daisaku; Mashiko, Kaori; Mizuhashi, Fukutaro; Muramatsu, Dai; Nakajima, Madoka; Nakamura, Tetsu; Oishi, Hidetoshi; Sasaki, Toshiaki; Shimada, Sawako; Takahashi, Chitose; Takeda, Yuko; Wakuri, Sinobu; Yajima, Nobuhiro; Yajima, Satoshi; Yatsushiro, Tomoko


    The Non-genotoxic Carcinogen Study Group in the Environmental Mutagen Society of Japan organised the second step of the inter-laboratory collaborative study on one-stage and two-stage cell transformation assays employing BALB/c 3T3 cells, with the objective of confirming whether the respective laboratories could independently produce results relevant to initiation or promotion. The method was modified to use a medium consisting of DMEM/F12 supplemented with 2% fetal bovine serum and a mixture of insulin, transferrin, ethanolamine and sodium selenite, at the stationary phase of cell growth. Seventeen laboratories collaborated in this study, and each chemical was tested by three to five laboratories. Comparison between the one-stage and two-stage assays revealed that the latter method would be beneficial in the screening of chemicals. In the test for initiating activity with the two-stage assay (post-treated with 0.1microg/ml 12-O-tetradecanoylphorbol-13-acetate), the relevant test laboratories all obtained positive results for benzo[a]pyrene and methylmethane sulphonate, and negative results for phenanthrene. Of those laboratories assigned phenacetin for the initiation phase, two returned positive results and two returned negative results, where the latter laboratories tested up to one dose lower than the maximum dose used by the former laboratories. In the exploration of promoting activity with the twostage assay (pretreated with 0.2microg/ml 3-methylcholanthrene), the relevant test laboratories obtained positive results for mezerein, sodium orthovanadate and TGF-beta1, and negative results for anthralin, phenacetin and phorbol. Two results returned for phorbol 12,13-didecanoate were positive, but one result was negative - again, the maximum dose to achieve the latter result was lower than that which produced the former results. These results suggest that this modified assay method is relevant, reproducible and transferable, provided that dosing issues, such as the

  17. Novel Functional Association of Serine Palmitoyltransferase Subunit 1-A Peptide in Sphingolipid Metabolism with Cytochrome P4501A1 Transactivation and Proliferative Capacity of the Human Glioma LN18 Brain Tumor Cell Line

    Directory of Open Access Journals (Sweden)

    J. Stewart


    Full Text Available Some chemical modulators of cytochrome P4501A1, Cyp1A1, expression also perturb the activity of serine palmitoyltransferase, SPT, a heterodimeric protein responsible for catalyzing the first reaction in sphingolipid biosynthesis. The effect of altered SPT activity on Cyp1A1 expression has generally been attributed to changes in the composition of bioactive sphingolipids, generated downstream in the SPT metabolic pathway, but the precise mechanism remains poorly defined. A generally accepted model for chemical-induced transactivation of the Cyp1A1 gene involves intracellular signaling mediated by proteins including the arylhydrocarbon receptor, AhR, whose interaction with the 90 kilo Dalton heat shock protein, Hsp90, is essential for maintaining a high affinity ligandbinding receptor conformation. Because ligand-induced Cyp1A1 expression is important in the bioactivation of environmentally relevant compounds to genotoxic derivatives capable of perturbing cellular processes, binding to Hsp90 represents an important regulatory point in the cytotoxicity process. In the present study, based on evidence that indicates subunit 1 of serine palmitoyltransferase, SPT1, interacts with Hsp90, both ligand-induced Cyp1A1 transactivation and capacity for proliferation were evaluated using the wild type Glioma LN18 human brain cancer cell line and its recombinant counterparts expressing green fluorescent SPT1 fusion proteins. Exposure to the prototypical Cyp1A1 inducer, 3-methylcholanthrene, 3-MC, resulted in the translocation of SPT1 from a primarily cytoplasmic domain to sites of focal adhesion complexes. Immunolabel for Hsp90, which was dispersed throughout the cell, became primarily cytoplasmic, while the distribution of AhR remained unaffected. When compared to the wild type, cells transfected with recombinant SPT1-GFP vectors had significantly attenuated levels of 3-MC-induced Cyp1A1 mRNA, as determined by quantitative reverse transcription PCR. Although

  18. Metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in human hepatocytes: 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid is a major detoxification pathway catalyzed by cytochrome P450 1A2. (United States)

    Langouët, S; Welti, D H; Kerriguy, N; Fay, L B; Huynh-Ba, T; Markovic, J; Guengerich, F P; Guillouzo, A; Turesky, R J


    Metabolic pathways of the mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) remain incompletely characterized in humans. In this study, the metabolism of MeIQx was investigated in primary human hepatocytes. Six metabolites were characterized by UV and mass spectroscopy. Novel metabolites were additionally characterized by 1H NMR spectroscopy. The carcinogenic metabolite, 2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline, which is formed by cytochrome P450 1A2 (P450 1A2), was found to be transformed into the N(2)-glucuronide conjugate, N(2)-(beta-1-glucosiduronyl)-2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline. The phase II conjugates N(2)-(3,8-dimethylimidazo[4,5-f]quinoxalin-2-yl)sulfamic acid and N(2)-(beta-1-glucosiduronyl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, as well as the 7-oxo derivatives of MeIQx and N-desmethyl-MeIQx, 2-amino-3,8-dimethyl-6-hydro-7H-imidazo[4,5-f]quinoxalin-7-one (7-oxo-MeIQx), and 2-amino-6-hydro-8-methyl-7H-imidazo[4,5-f]quinoxalin-7-one (N-desmethyl-7-oxo-MeIQx), thought to be formed exclusively by the intestinal flora, were also identified. A novel metabolite was characterized as 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH), and it was the predominant metabolite formed in hepatocytes exposed to MeIQx at levels approaching human exposure. IQx-8-COOH formation is catalyzed by P450 1A2. This metabolite is a detoxication product and does not induce umuC gene expression in Salmonella typhimurium strain NM2009. IQx-8-COOH is also the principal oxidation product of MeIQx excreted in human urine [Turesky, R., et al. (1998) Chem. Res. Toxicol. 11, 217-225]. Thus, P450 1A2 is involved in both the metabolic activation and detoxication of this procarcinogen in humans. Analogous metabolism experiments were conducted with hepatocytes of untreated rats and rats pretreated with the P450 inducer 3-methylcholanthrene. Unlike human hepatocytes, the rat cell preparations did not produce IQx-8