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Ayman O S Elkadi - One of the best experts on this subject based on the ideXlab platform.
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down regulation of Cytochrome P450 1A1 by monomethylarsonous acid in human hepg2 cells
Toxicology Letters, 2017Co-Authors: Osama H Elshenawy, Michael S Denison, Anatoly A Soshilov, Ghada Abdelhamid, Ayman O S ElkadiAbstract:Inorganic arsenic is a human toxicant and carcinogen that has been extensively studied over decades; however, no definitive understanding of the underlying mechanisms has been established yet. Arsenic is capable of modulating the expression of aryl hydrocarbon receptor (AhR)-regulated genes, nevertheless, whether its trivalent organic metabolites have similar effects or not need to be investigated. Therefore, in this study we examined the effects of monomethylarsonous acid (MMA(III)) as compared to its parent compound sodium arsenite (As(III)) on the expression of CYP1A1 in HepG2 cells. HepG2 cells were treated with MMA(III) (5μM) or its parents compound, As(III) (5μM), in the absence and presence of the prototypical AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 1nM). Experiments were conducted at 6h for gene expression; 24h for XRE-driven luciferase activity, protein expression, and EROD activity. Our results showed that both MMA(III) and As(III) decreased CYP1A1 mRNA, protein, and catalytic activity levels; and inhibit the TCDD-mediated induction of CYP1A1 mRNA, protein, and catalytic activity levels. MMA(III) and As(III) significantly inhibited XRE-driven luciferase activity and it inhibited the TCDD-mediated induction of XRE-driven luciferase reporter gene expression. Although MMA(III) and As(III) were not shown to be AhR ligands, both compounds showed inhibition of nuclear accumulation of AhR transcription factor as evidenced by immunocytochemical analysis. MMA(III) and As(III) had no effect on CYP1A1 mRNA stability; however MMA(III), but not As(III), decreased the protein stability of CYP1A1. As(III), but not MMA(III), induced HO-1 mRNA levels. Both MMA(III) and As(III) increased ROS production. Our results demonstrate for the first time that, MMA(III) down-regulates CYP1A1 mainly through transcriptional and post-translational mechanisms. This modulation of CYP1A1 proves that trivalent metabolites of arsenic are highly reactive and could participate in arsenic toxicity.
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methylated pentavalent arsenic metabolites are bifunctional inducers as they induce Cytochrome P450 1A1 and nad p h quinone oxidoreductase through ahr and nrf2 dependent mechanisms
Free Radical Biology and Medicine, 2014Co-Authors: Anwar Anwarmohamed, Ayman O S Elkadi, Michael S Denison, Osama H Elshenawy, Anatoly A Soshilov, Larsoliver KlotzAbstract:Activation of the aryl hydrocarbon receptor (AhR) ultimately leads to the induction of the carcinogen-activating enzyme Cytochrome P450 1A1 (CYP1A1), and activation of the nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) in addition to the AhR pathway induces the expression of the NADP(H):quinone oxidoreductase (NQO1). Therefore, the aim of this study was to examine the effect of As(III) pentavalent metabolites, MMA(V), DMA(V), and TMA(V), on AhR and Nrf2 activation and on the expression of their prototypical downstream targets CYP1A1 and NQO1, respectively. Our results showed that treatment of HepG2 cells with MMA(V), DMA(V), or TMA(V) in the absence and presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin or sulforaphane significantly induced both CYP1A1 and NQO1 at the mRNA, protein, and catalytic activity levels. Furthermore, these metabolites increased the AhR-dependent XRE-driven and the Nrf2-dependent ARE-driven luciferase reporter activities, which coincided with increased nuclear accumulation of both transcription factors. However, none of these metabolites were shown to be AhR ligands. The induction of CYP1A1 by these metabolites seems to be ligand-independent, possibly through a decrease in HSP90 protein expression levels. The metabolites also increased ROS production, which was significantly higher than that produced by As(III). Upon knockdown of AhR and Nrf2 the MMA(V)-, DMA(V)-, and TMA(V)-mediated induction of both CYP1A1 and NQO1 proteins was significantly decreased. In conclusion, this study demonstrates for the first time that methylated pentavalent arsenic metabolites are bifunctional inducers, as they increase CYP1A1 by activating the AhR/XRE signaling pathway and they increase NQO1 by activating the Nrf2/ARE signaling pathway in addition to the AhR/XRE pathway.
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sunitinib a tyrosine kinase inhibitor induces Cytochrome P450 1A1 gene in human breast cancer mcf7 cells through ligand independent aryl hydrocarbon receptor activation
Archives of Toxicology, 2013Co-Authors: Zaid H Maayah, Ayman O S Elkadi, Mohamed El A M Gendy, Hesham M KorashyAbstract:Sunitinib (SUN) is a new multi-targeted oral tyrosine kinase inhibitor that has both anti-angiogenic and anti-tumor activities. However, information reported in the literature on the effects of SUN on the constitutive expression of Cytochrome P450 1A1 (CYP1A1) gene in cells from mammalian species remains unclear. Therefore, the main objectives of the current work were to investigate the potentiality of SUN to induce CYP1A1 gene expression in human breast cancer MCF7 cells and to explore the molecular mechanisms involved. Our results showed that SUN induced the CYP1A1 mRNA, protein, and activity levels in a concentration-dependent manner in MCF7 cells. The increase in CYP1A1 mRNA by SUN was completely blocked by the transcriptional inhibitor, actinomycin D; implying that SUN increased de novo RNA synthesis. Furthermore, the ability of SUN to increase luciferase reporter gene expression suggests an aryl hydrocarbon receptor (AhR)-dependent transcriptional control and excludes the possibility of any posttranscriptional mechanisms. In addition, blocking of AhR activation by resveratrol, a well-known AhR antagonist, prevented the SUN-induced CYP1A1 gene expression, further confirms the involvement of AhR. Interestingly, this was associated with the inability of SUN to directly bind to and induce transformation of cytosolic AhR to its DNA-binding form in vitro, suggesting that the effect of SUN does not involve direct binding to AhR. The current manuscript provides the first evidence for the ability of SUN to induce CYP1A1 gene expression in MCF7 cells through AhR ligand-independent mechanisms.
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transcriptional and posttranslational mechanisms modulating the expression of the Cytochrome P450 1A1 gene by lead in hepg2 cells a role of heme oxygenase
Toxicology, 2012Co-Authors: Hesham M Korashy, Ayman O S ElkadiAbstract:Co-contamination with complex mixtures of heavy metals, such as lead (Pb(2+)) and halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may disrupt the coordinated regulation of the carcinogen activating enzyme Cytochrome P450 1A1 (CYP1A1). Therefore, in this study we examined the effects of co-exposure to Pb(2+) and TCDD on the expression of CYP1A1 in human hepatoma HepG2 cells and explored the involvement of transcriptional and posttranscriptional mechanisms. Our results showed that Pb(2+) significantly decreased TCDD-induced CYP1A1 mRNA, protein, and catalytic activity levels in a concentration-dependent manner. Importantly, this inhibition is specific to CYP1A1 and not to other aryl hydrocarbon receptor (AhR)-regulated gene, as Pb(2+) induced NAD(P)H:Quinone oxidoreductase 1 mRNA. Mechanistically, the Pb(2+)-mediated inhibition of CYP1A1 was associated with a significant decrease in the xenobiotic responsive element (XRE)-dependent luciferase activity without affecting the level of AhR protein, suggesting a transcriptional mechanism. On the other hand, the inhibitory effect of Pb(2+) on the induction of CYP1A1 coincided with an increase in heme oxygenase-1 (HO-1) mRNA level and reactive oxygen species production at the posttranslational level. Furthermore, the inhibition of HO-1 activity, by tin mesoporphyrin, or supplementing heme, using hemin, caused a partial restoration of Pb(2+)-mediated inhibition of CYP1A1 induction by TCDD. In addition, transfection of HepG2 cells with siRNA targeting the human HO-1 gene restored the Pb(2+)-mediated inhibition of TCDD-induced CYP1A1. In conclusion, this study demonstrated that Pb(2+) down-regulates the expression of CYP1A1 through transcriptional and posttranslational mechanisms and confirms the role of HO-1 in a Pb(2+)-mediated effect.
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camel urine inhibits the Cytochrome P450 1A1 gene expression through an ahr dependent mechanism in hepa 1c1c7 cell line
Journal of Ethnopharmacology, 2011Co-Authors: Abdulqader A Alhaider, Hesham M Korashy, Mohamed El A M Gendy, Ayman O S ElkadiAbstract:Abstract Aim of the study Drinking camel urine has been used traditionally to treat numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of three different camel urines (virgin, lactating, and pregnant source) to modulate a well-known cancer-activating enzyme, the Cytochrome P450 1A1 (Cyp1A1) in murine hepatoma Hepa 1c1c7 cell line. Materials and methods The effect of different camel urines, compared to bovine urines, on Cyp1A1 mRNA was determined using real-time polymerase chain reaction. Cyp1A1 protein and catalytic activity levels were determined using Western blot analysis and 7-ethoxyresorufin as a substrate, respectively. The role of aryl hydrocarbon receptor (AhR)-dependent mechanism was determined using electrophoretic mobility shift assay (EMSA) and the AhR-dependent luciferase reporter gene. Results All types of camel, but not bovine, urines differentially inhibited the induction of Cyp1A1 gene expression by TCDD, the most potent Cyp1A1 inducer and known carcinogenic chemical. Importantly, virgin camel urine showed the highest degree of inhibition at the activity level, followed by lactating and pregnant camel urines. Furthermore, we have shown that virgin camel urine significantly inhibited the TCDD-mediated induction of Cyp1A1 at the mRNA and protein expression levels. Mechanistically, the ability of virgin camel urine to inhibit Cyp1A1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and DNA binding as determined by EMSA, suggesting that AhR-dependent mechanism is involved. Conclusions The present work provides the first evidence that camel urine but not that of bovine inhibits the TCDD-mediated toxic effect by inhibiting the expression of Cyp1A1, at both transcriptional and post-transcriptional levels through an AhR-dependent mechanism.
Karlwerner Schramm - One of the best experts on this subject based on the ideXlab platform.
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suppressive effects of caraway carum carvi extracts on 2 3 7 8 tetrachloro dibenzo p dioxin dependent gene expression of Cytochrome P450 1A1 in the rat h4iie cells
Toxicology in Vitro, 2005Co-Authors: B Naderikalali, Abdolamir Allameh, Mohammad Javad Rasaee, H J Bach, A Behechti, K Doods, A Kettrup, Karlwerner SchrammAbstract:Abstract Cytochrome P450 1A1 (CYP1A1) is among the Cytochrome P450 classes known to convert xenobiotics and endogenous compounds to toxic and/or carcinogenic metabolites. Suppression of CYP1A1 over expression by certain compounds is implicated in prevention of cancer caused by chemical carcinogens. Chemopreventive agents containing high levels of flavonoids and steroids-like compounds are known to suppress CYP1A1. This study was carried out for assessment of the genomic and proteomic effects of caraway ( Carum carvi ) extracts containing high levels of both flavonoids and steroid-like substances on ethoxy resorufin dealkylation (EROD) activity and CYP1A1 at mRNA levels. Rat hepatoma cells co-treated with a CYP1A1 inducer i.e. TCDD (2, 3, 7, 8-tetrachlorodibenzo- p -dioxin) and different preparations of caraway extracts at concentrations of 0, 0.13, 1.3, and 13 μM in culture medium. After incubation (37 °C and 7% CO 2 for 20 h), changes in EROD specific activity recorded and compared in cells under different treatments. The results show that caraway seed extract prepared in three different organic solvents suppressed the enzyme activity in hepatoma cells in a dose-dependent manner. The extracts added above 0.13 μM could significantly inhibit EROD activity and higher levels of each extract (1.3 and 13 μM) caused approximately 10-fold suppression in the enzyme activity. Accordingly, data obtained from the RT-PCR (TaqMan) clearly showed the suppressive effects of plant extract on CYP1A1-related mRNA expression. These data clearly show that substances in caraway seeds extractable in organic solvents can potentially reverse the TCDD-dependent induction in Cytochrome P450 1A1.
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suppressive effects of caraway carum carvi extracts on 2 3 7 8 tetrachloro dibenzo p dioxin dependent gene expression of Cytochrome P450 1A1 in the rat h4iie cells
Toxicology in Vitro, 2005Co-Authors: B Naderikalali, Abdolamir Allameh, Mohammad Javad Rasaee, H J Bach, A Behechti, K Doods, A Kettrup, Karlwerner SchrammAbstract:Cytochrome P450 1A1 (CYP1A1) is among the Cytochrome P450 classes known to convert xenobiotics and endogenous compounds to toxic and/or carcinogenic metabolites. Suppression of CYP1A1 over expression by certain compounds is implicated in prevention of cancer caused by chemical carcinogens. Chemopreventive agents containing high levels of flavonoids and steroids-like compounds are known to suppress CYP1A1. This study was carried out for assessment of the genomic and proteomic effects of caraway (Carum carvi) extracts containing high levels of both flavonoids and steroid-like substances on ethoxy resorufin dealkylation (EROD) activity and CYP1A1 at mRNA levels. Rat hepatoma cells co-treated with a CYP1A1 inducer i.e. TCDD (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin) and different preparations of caraway extracts at concentrations of 0, 0.13, 1.3, and 13 microM in culture medium. After incubation (37 degrees C and 7% CO2 for 20 h), changes in EROD specific activity recorded and compared in cells under different treatments. The results show that caraway seed extract prepared in three different organic solvents suppressed the enzyme activity in hepatoma cells in a dose-dependent manner. The extracts added above 0.13 microM could significantly inhibit EROD activity and higher levels of each extract (1.3 and 13 microM) caused approximately 10-fold suppression in the enzyme activity. Accordingly, data obtained from the RT-PCR (TaqMan) clearly showed the suppressive effects of plant extract on CYP1A1-related mRNA expression. These data clearly show that substances in caraway seeds extractable in organic solvents can potentially reverse the TCDD-dependent induction in Cytochrome P450 1A1.
Karl T Kelsey - One of the best experts on this subject based on the ideXlab platform.
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polychlorinated biphenyls Cytochrome P450 1A1 and breast cancer risk in the nurses health study
Cancer Epidemiology Biomarkers & Prevention, 2002Co-Authors: Francine Laden, Susan E Hankinson, Naoko Ishibe, Mary S Wolff, Dorota M Gertig, David J Hunter, Karl T KelseyAbstract:There is concern that exposures to the environmental chemicals polychlorinated biphenyls (PCBs) may contribute to breast cancer risk. An individual's susceptibility to the effects of PCBs may be partially determined by polymorphisms in the gene encoding the biotransformation enzyme Cytochrome P450 1A1 (CYP1A1). PCB exposure induces CYP1A1 activity, and PCBs themselves or other xenobiotics can be metabolized to carcinogenic intermediates in the presence of the variant genotype. A previous case-control study provided evidence of an interaction between high exposures to PCBs and the CYP1A1-exon 7 polymorphism (the A to G transition at nucleotide 4889), leading to a significant increase in postmenopausal breast cancer risk. We examined the interaction of PCBs with the CYP1A1-MspI (the T to C transition at nucleotide 6235) and exon 7 polymorphisms among 367 breast cancer case-control pairs (293 postmenopausal pairs) in the Nurses' Health Study. Although there was no independent association of either the CYP1A1 variants or PCBs with breast cancer risk, the relative risk among the postmenopausal women with plasma PCB levels in the highest third of the distribution in the control group and at least one exon 7 variant allele compared with women who were homozygous for the wild-type allele and who had PCB levels in the lowest third was 2.78 (95% confidence interval, 0.99-7.82). The majority of studies have concluded that exposure to PCBs is unlikely to be a major cause of breast cancer, but these findings indicate that further studies of genetically susceptible populations are warranted.
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a prospective study of Cytochrome P450 1A1 polymorphisms and colorectal cancer risk in men
Cancer Epidemiology Biomarkers & Prevention, 2000Co-Authors: Naoko Ishibe, David J Hunter, Meir J Stampfer, Charles H Hennekens, Karl T KelseyAbstract:Positive associations with increased red meat intake and colorectal cancer have been reported consistently [(1)][1] , particularly with the consumption of broiled and grilled meats [(2)][2] . This may be attributable to PAH[4][3] formation. Cigarette smoking is another source of PAH exposure, and an
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cigarette smoking Cytochrome P450 1A1 polymorphisms and breast cancer risk in the nurses health study
Cancer Research, 1998Co-Authors: Naoko Ishibe, Susan E Hankinson, Karl T Kelsey, Graham A Colditz, Donna Spiegelman, Walter C Willett, Frank E Speizer, David J HunterAbstract:Environmental exposure to carcinogens may contribute to increasing breast cancer rates and geographic variation in breast cancer incidence in the United States. One class of chemicals that has received much attention are the polyaromatic hydrocarbons that are ubiquitous in the environment and occur in cigarette smoke. The Cytochrome P450 1A1 ( CYP1A1 ) gene codes for an enzyme that contributes to aryl hydrocarbon hydroxylase activity, which is involved in the metabolism of polyaromatic hydrocarbons. Genotypic variants of CYP1A1 have been associated with increased aryl hydrocarbon hydroxylase activity, and some epidemiological studies suggest that women with the variant genotype(s) are at increased risk for breast cancer. We prospectively evaluated the associations between the CYP1A1 polymorphisms and breast cancer risk, as well as the potential modification of these associations by cigarette smoking, in a case-control study nested within the Nurses' Health Study. We analyzed the T→C transition at nucleotide 6235 ( Msp I) and the A→G transition at nucleotide 4889 ( exon 7 ) in CYP1A1 by PCR-RFLP assays among 466 incident breast cancer cases and 466 matched controls. Relative risks (RRs) and 95% confidence intervals (CIs) were used to quantify the risk of breast cancer among subjects who had at least one variant allele relative to subjects who were homozygous for the wild-type allele, using conditional logistic regression. No overall increase in breast cancer risk with the variant CYP1A1 genotypes was apparent (RR MspI , 1.05; 95% CI, 0.74–1.50 and RR exon 7 , 0.88; 95% CI, 0.58–1.33). However, a suggestive increase in breast cancer risk was observed among women who had commenced smoking before the age of 18 and had the CYP1A1-Msp I variant genotype compared to nonsmokers who were homozygous wild type for the polymorphism (RR, 5.65; 95% CI, 1.50–21.3; percentage of all breast cancer cases attributable to this risk factor, 2.5%). A similar gene-environment association was observed for the exon 7 polymorphism (RR, 3.61; 95% CI, 1.11–11.7; percentage of all breast cancer cases attributable to this risk factor, 2.2%). These data are compatible with the hypothesis that cigarette smoking early in life is a modifiable cause of breast cancer in a subpopulation of genetically susceptible women. However, the proportion of breast cancer attributable to cigarette smoking at a young age among Caucasian women with the variant form of the CYP1A1 polymorphisms is low.
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A case-control study of Cytochrome P450 1A1, glutathione S-transferase M1, cigarette smoking and lung cancer susceptibility (Massachusetts, United States)
Cancer Causes & Control, 1997Co-Authors: Montserrat García-closas, Karl T Kelsey, John K. Wiencke, John C. Wain, David C. ChristianiAbstract:Cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1)genetic polymorphisms are involved in the activation and detoxification ofchemical carcinogens found in tobacco smoke; thus they may influence hostsusceptibility to lung cancer. In this study at Massachusetts GeneralHospital (Boston, MA, USA) of 416 cases and 446 controls (mostly White) weevaluated the association between the CYP1A1 MspI and GSTM1 polymorphisms andlung cancer risk, and their interaction with cigarette smoke. The CYP1A1 MspIheterozygous genotype was present in 18 percent of cases and 16 percent ofcontrols, and one percent of cases and controls were CYP1A1 MspI homozygousvariant. The GSTM1 null genotype was detected in 54 percent of cases and 52percent of controls. After adjusting for age, gender, pack-years of smoking,and years since quitting smoking, while neither the CYP1A1 MspI heterozygousgenotype alone nor the GSTM1 null genotype alone were associated with asignificant increas e in lung cancer risk, having both genetic traits wasassociated with a twofold increase in risk (95 percent confidence interval[CI] = 1.0-3.4). Our data did not provide enough evidence for a substantialmodification of the effect of pack-years on lung cancer risk by the CYP1A1MspI and GSTM1 genotypes. However, limitations of our study preclude aconclusion about this potential interaction.
B Naderikalali - One of the best experts on this subject based on the ideXlab platform.
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suppressive effects of caraway carum carvi extracts on 2 3 7 8 tetrachloro dibenzo p dioxin dependent gene expression of Cytochrome P450 1A1 in the rat h4iie cells
Toxicology in Vitro, 2005Co-Authors: B Naderikalali, Abdolamir Allameh, Mohammad Javad Rasaee, H J Bach, A Behechti, K Doods, A Kettrup, Karlwerner SchrammAbstract:Abstract Cytochrome P450 1A1 (CYP1A1) is among the Cytochrome P450 classes known to convert xenobiotics and endogenous compounds to toxic and/or carcinogenic metabolites. Suppression of CYP1A1 over expression by certain compounds is implicated in prevention of cancer caused by chemical carcinogens. Chemopreventive agents containing high levels of flavonoids and steroids-like compounds are known to suppress CYP1A1. This study was carried out for assessment of the genomic and proteomic effects of caraway ( Carum carvi ) extracts containing high levels of both flavonoids and steroid-like substances on ethoxy resorufin dealkylation (EROD) activity and CYP1A1 at mRNA levels. Rat hepatoma cells co-treated with a CYP1A1 inducer i.e. TCDD (2, 3, 7, 8-tetrachlorodibenzo- p -dioxin) and different preparations of caraway extracts at concentrations of 0, 0.13, 1.3, and 13 μM in culture medium. After incubation (37 °C and 7% CO 2 for 20 h), changes in EROD specific activity recorded and compared in cells under different treatments. The results show that caraway seed extract prepared in three different organic solvents suppressed the enzyme activity in hepatoma cells in a dose-dependent manner. The extracts added above 0.13 μM could significantly inhibit EROD activity and higher levels of each extract (1.3 and 13 μM) caused approximately 10-fold suppression in the enzyme activity. Accordingly, data obtained from the RT-PCR (TaqMan) clearly showed the suppressive effects of plant extract on CYP1A1-related mRNA expression. These data clearly show that substances in caraway seeds extractable in organic solvents can potentially reverse the TCDD-dependent induction in Cytochrome P450 1A1.
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suppressive effects of caraway carum carvi extracts on 2 3 7 8 tetrachloro dibenzo p dioxin dependent gene expression of Cytochrome P450 1A1 in the rat h4iie cells
Toxicology in Vitro, 2005Co-Authors: B Naderikalali, Abdolamir Allameh, Mohammad Javad Rasaee, H J Bach, A Behechti, K Doods, A Kettrup, Karlwerner SchrammAbstract:Cytochrome P450 1A1 (CYP1A1) is among the Cytochrome P450 classes known to convert xenobiotics and endogenous compounds to toxic and/or carcinogenic metabolites. Suppression of CYP1A1 over expression by certain compounds is implicated in prevention of cancer caused by chemical carcinogens. Chemopreventive agents containing high levels of flavonoids and steroids-like compounds are known to suppress CYP1A1. This study was carried out for assessment of the genomic and proteomic effects of caraway (Carum carvi) extracts containing high levels of both flavonoids and steroid-like substances on ethoxy resorufin dealkylation (EROD) activity and CYP1A1 at mRNA levels. Rat hepatoma cells co-treated with a CYP1A1 inducer i.e. TCDD (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin) and different preparations of caraway extracts at concentrations of 0, 0.13, 1.3, and 13 microM in culture medium. After incubation (37 degrees C and 7% CO2 for 20 h), changes in EROD specific activity recorded and compared in cells under different treatments. The results show that caraway seed extract prepared in three different organic solvents suppressed the enzyme activity in hepatoma cells in a dose-dependent manner. The extracts added above 0.13 microM could significantly inhibit EROD activity and higher levels of each extract (1.3 and 13 microM) caused approximately 10-fold suppression in the enzyme activity. Accordingly, data obtained from the RT-PCR (TaqMan) clearly showed the suppressive effects of plant extract on CYP1A1-related mRNA expression. These data clearly show that substances in caraway seeds extractable in organic solvents can potentially reverse the TCDD-dependent induction in Cytochrome P450 1A1.
Hesham M Korashy - One of the best experts on this subject based on the ideXlab platform.
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sunitinib a tyrosine kinase inhibitor induces Cytochrome P450 1A1 gene in human breast cancer mcf7 cells through ligand independent aryl hydrocarbon receptor activation
Archives of Toxicology, 2013Co-Authors: Zaid H Maayah, Ayman O S Elkadi, Mohamed El A M Gendy, Hesham M KorashyAbstract:Sunitinib (SUN) is a new multi-targeted oral tyrosine kinase inhibitor that has both anti-angiogenic and anti-tumor activities. However, information reported in the literature on the effects of SUN on the constitutive expression of Cytochrome P450 1A1 (CYP1A1) gene in cells from mammalian species remains unclear. Therefore, the main objectives of the current work were to investigate the potentiality of SUN to induce CYP1A1 gene expression in human breast cancer MCF7 cells and to explore the molecular mechanisms involved. Our results showed that SUN induced the CYP1A1 mRNA, protein, and activity levels in a concentration-dependent manner in MCF7 cells. The increase in CYP1A1 mRNA by SUN was completely blocked by the transcriptional inhibitor, actinomycin D; implying that SUN increased de novo RNA synthesis. Furthermore, the ability of SUN to increase luciferase reporter gene expression suggests an aryl hydrocarbon receptor (AhR)-dependent transcriptional control and excludes the possibility of any posttranscriptional mechanisms. In addition, blocking of AhR activation by resveratrol, a well-known AhR antagonist, prevented the SUN-induced CYP1A1 gene expression, further confirms the involvement of AhR. Interestingly, this was associated with the inability of SUN to directly bind to and induce transformation of cytosolic AhR to its DNA-binding form in vitro, suggesting that the effect of SUN does not involve direct binding to AhR. The current manuscript provides the first evidence for the ability of SUN to induce CYP1A1 gene expression in MCF7 cells through AhR ligand-independent mechanisms.
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transcriptional and posttranslational mechanisms modulating the expression of the Cytochrome P450 1A1 gene by lead in hepg2 cells a role of heme oxygenase
Toxicology, 2012Co-Authors: Hesham M Korashy, Ayman O S ElkadiAbstract:Co-contamination with complex mixtures of heavy metals, such as lead (Pb(2+)) and halogenated aromatic hydrocarbons (HAHs), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may disrupt the coordinated regulation of the carcinogen activating enzyme Cytochrome P450 1A1 (CYP1A1). Therefore, in this study we examined the effects of co-exposure to Pb(2+) and TCDD on the expression of CYP1A1 in human hepatoma HepG2 cells and explored the involvement of transcriptional and posttranscriptional mechanisms. Our results showed that Pb(2+) significantly decreased TCDD-induced CYP1A1 mRNA, protein, and catalytic activity levels in a concentration-dependent manner. Importantly, this inhibition is specific to CYP1A1 and not to other aryl hydrocarbon receptor (AhR)-regulated gene, as Pb(2+) induced NAD(P)H:Quinone oxidoreductase 1 mRNA. Mechanistically, the Pb(2+)-mediated inhibition of CYP1A1 was associated with a significant decrease in the xenobiotic responsive element (XRE)-dependent luciferase activity without affecting the level of AhR protein, suggesting a transcriptional mechanism. On the other hand, the inhibitory effect of Pb(2+) on the induction of CYP1A1 coincided with an increase in heme oxygenase-1 (HO-1) mRNA level and reactive oxygen species production at the posttranslational level. Furthermore, the inhibition of HO-1 activity, by tin mesoporphyrin, or supplementing heme, using hemin, caused a partial restoration of Pb(2+)-mediated inhibition of CYP1A1 induction by TCDD. In addition, transfection of HepG2 cells with siRNA targeting the human HO-1 gene restored the Pb(2+)-mediated inhibition of TCDD-induced CYP1A1. In conclusion, this study demonstrated that Pb(2+) down-regulates the expression of CYP1A1 through transcriptional and posttranslational mechanisms and confirms the role of HO-1 in a Pb(2+)-mediated effect.
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camel urine inhibits the Cytochrome P450 1A1 gene expression through an ahr dependent mechanism in hepa 1c1c7 cell line
Journal of Ethnopharmacology, 2011Co-Authors: Abdulqader A Alhaider, Hesham M Korashy, Mohamed El A M Gendy, Ayman O S ElkadiAbstract:Abstract Aim of the study Drinking camel urine has been used traditionally to treat numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of three different camel urines (virgin, lactating, and pregnant source) to modulate a well-known cancer-activating enzyme, the Cytochrome P450 1A1 (Cyp1A1) in murine hepatoma Hepa 1c1c7 cell line. Materials and methods The effect of different camel urines, compared to bovine urines, on Cyp1A1 mRNA was determined using real-time polymerase chain reaction. Cyp1A1 protein and catalytic activity levels were determined using Western blot analysis and 7-ethoxyresorufin as a substrate, respectively. The role of aryl hydrocarbon receptor (AhR)-dependent mechanism was determined using electrophoretic mobility shift assay (EMSA) and the AhR-dependent luciferase reporter gene. Results All types of camel, but not bovine, urines differentially inhibited the induction of Cyp1A1 gene expression by TCDD, the most potent Cyp1A1 inducer and known carcinogenic chemical. Importantly, virgin camel urine showed the highest degree of inhibition at the activity level, followed by lactating and pregnant camel urines. Furthermore, we have shown that virgin camel urine significantly inhibited the TCDD-mediated induction of Cyp1A1 at the mRNA and protein expression levels. Mechanistically, the ability of virgin camel urine to inhibit Cyp1A1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and DNA binding as determined by EMSA, suggesting that AhR-dependent mechanism is involved. Conclusions The present work provides the first evidence that camel urine but not that of bovine inhibits the TCDD-mediated toxic effect by inhibiting the expression of Cyp1A1, at both transcriptional and post-transcriptional levels through an AhR-dependent mechanism.
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modulation of tcdd mediated induction of Cytochrome P450 1A1 by mercury lead and copper in human hepg2 cell line
Toxicology in Vitro, 2008Co-Authors: Hesham M Korashy, Ayman O S ElkadiAbstract:Co-contamination with complex mixtures of heavy metals and polycyclic aromatic hydrocarbons (PAHs) is a common environmental problem with multiple biological consequences. In this study, we tested in human hepatoma HepG2 cells the potential effects of three prominent environmental heavy metals, mercury (Hg2+), lead (Pb2+), and copper (Cu2+), on the induction of Cytochrome P450 1A1 (CYP1A1) by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent PAH. Our results show that TCDD in the absence and presence of heavy metals did not significantly affect HepG2 cell viability using MTT and LDH leakage assays. Exposure of HepG2 cells with either Hg2+ or Pb2+ significantly decreased, whereas Cu2+ potentiated the CYP1A1 induction mediated by TCDD at the activity levels. In a manner similar to CYP1A1 activity, both Hg2+ and Pb2+ significantly down-regulated, while Cu2+ up-regulated, the induction of CYP1A1 protein mediated by TCDD, suggesting that the modulations of CYP1A1 by heavy metals are mediated at least in part at the translational level. Based on these results, exposure to metal/PAH mixtures would differentially modulate PAHs-mediated carcinogenicity.
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regulatory mechanisms modulating the expression of Cytochrome P450 1A1 gene by heavy metals
Toxicological Sciences, 2005Co-Authors: Hesham M Korashy, Ayman O S ElkadiAbstract:We recently demonstrated that heavy metals, Hg2+, Pb2+, and Cu2+ induced Cyp1A1 gene expression, yet the mechanisms involved remain unknown. To explore the molecular mechanisms involved in the modulation of Cyp1A1 by heavy metals, Hepa 1c1c7 cells were treated with the metals in the presence and absence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent Cyp1A1 inducer. Time-dependent effect study showed that all metals significantly induced the basal Cyp1A1 mRNA. This was apparent 3 h after treatment, and levels remained elevated for at least 24 h. At the inducible level, Hg2+ and Pb2+ further increased, while Cu2+ decreased, the TCDD-mediated induction of Cyp1A1 mRNA. The RNA synthesis inhibitor, actinomycin D, completely blocked the Cyp1A1 induction by heavy metals. The protein synthesis inhibitor, cycloheximide, and 26S proteasome inhibitor, carbobenzoxy-L-leucyl-L-leucyl-leucinal (MG-132), super-induced the metal-mediated induction of Cyp1A1 mRNA. In addition, all three metals induced aryl hydrocarbon receptor/xenobiotic-responsive element (AhR/XRE) binding, suggesting an AhR-dependent mechanism. Cyp1A1 mRNA and protein decay experiments showed that the three metals did not significantly affect the half-life of mRNA; however, they significantly decreased the degradation rate of its protein, implying a posttranslational regulation of the Cyp1A1 by the heavy metals. A significant decrease in TCDD-mediated induction of Cyp1A1 activity associated with an increase in HO-1 mRNA and a decrease in cellular heme content was observed after all metals treatment. This suggests that heme degradation plays a role in reducing Cyp1A1 activity. This is the first demonstration that heavy metals can directly induce Cyp1A1 gene expression in an AhR-dependent manner through transcriptional and posttranslational mechanisms.
