Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human bronchial epithelial cells (BEC), a primary defense against inhaled materials, are the progenitor cells for bronchogenic carcinomas and have important metabolic capabilities. We used reverse transcriptase-polymerase chain reaction (RT-PCR) to identify xenobiotic metabolism enzymes expressed in primary BEC and alveolar macrophages (AM) of non-smoking volunteers. Cytochromes P450 (CYP) 1A1, 1B1, 2B7, 2E1, and 4B1 and microsomal epoxide hydrolase (mEH) were expressed in BEC but not AM. CYP2F1 was expressed in BEC, but it was expressed at barely detectable levels or not at all in AM. NADPH oxidoreductase (NADPH OR), microsomal glutathione transferase (GST 12), glutathione transferase mu, phenol sulfotransferase (PST), thermolabile phenol sulfotransferase (TL PST), and the clara cell-specific gene, CC10 were expressed in both BEC and AM. CYP3A4 and glucuronosyl transferases-1 and 2 were not expressed in either BEC or AM. In contrast to primary BEC, of the genes evaluated, the immortalized human bronchial epithelial cell line BEP2D constitutively expressed only CYP1A1, CYP2E1, NADPH OR, glucuronosyl transferase 1, GST 12, GST mu, PST, TL PST, and CC10. The loss of xenobiotic metabolism enzyme gene expression in the BEP2D cell line may result from either reduced exposure to inducing agents, or loss of differentiative characteristics in culture. It is clear from the data comparing BEC and AM that there are important intertissue differences in expression of xenobiotic metabolism enzymes.
Am J Respir Cell Mol Biol 1996 Mar
PMID:Xenobiotic metabolism enzyme gene expression in human bronchial epithelial and alveolar macrophage cells. 884 77

Hepatic cytochromes P450 are known to be down-regulated by cytokines, lipopolysaccharide, Gram-positive bacteria, and viruses. Little is known, however, about the regulation by inflammation of cytochromes P450 in other tissues. We have found that lipopolysaccharide and interleukin-1 beta stimulate the expression of catalytically active CYP2E1 (but not CYP1A1 or CYP2B) up to 7-fold in rat brain primary cortical glial cultures. The induction reached a maximum after 24 hr and was accompanied by an increase in CYP2E1 mRNA. Chlormethiazole, a specific inhibitor of hepatic CYP2E1 transcription, completely inhibited the induction of CYP2E1 at the mRNA and enzyme levels. Immunofluorescence studies showed CYP2E1 to be expressed in a subset of astrocytes in the lipopolysaccharide-stimulated cortical glial cultures. Using a model of global ischemic injury in the gerbil, we found CYP2E1 to be induced in vivo in astrocytes in the inflammatory phase, 1-3 weeks after the lesion. Likewise, CYP2E1 was induced in the rat cortex 1 week after a focal ischemic injury. Our results suggest tissue-specific regulation of CYP2E1 by inflammatory factors and that CYP2E1 may play a role in astrocytes during inflammation in the brain.
Mol Pharmacol 1996 Nov
PMID:Induction of cytochrome P450 2E1 expression in rat and gerbil astrocytes by inflammatory factors and ischemic injury. 891 36

The mRNA expression of members of two cytochrome P450 (CYP) gene subfamilies involved in carcinogen activation, the CYP1A1/2 and CYP2B1 forms, was determined in primary rat hepatocyte cultures in response to metyrapone and to the inducer phenobarbital or 5,6-benzoflavone (BNF), respectively. Incubation of cells with 0.5 mM metyrapone resulted in accumulation of CYP1A1 and CYP1A2 mRNA and in a marked increase in CYP1A-associated enzymatic activity as determined by deethylation of ethoxyresorufin. Metyrapone and phenobarbital in combination acted synergistically in elevation of ethoxyresorufin O-deethylase activity. In hepatocytes treated with metyrapone or with phenobarbital, accumulation of CYP2B1 mRNA levels preceded an increase in CYP2B-associated, pentoxyresorufin O-depentylase activity. However, CYP2B1 mRNA levels were first detectable after 24 hours of treatment with phenobarbital, whereas metyrapone elicited a substantial increase in mRNA levels within 14 hours, suggesting differing mechanisms leading to accumulation of CYP2B1 mRNA under the two inducers.
Res Commun Mol Pathol Pharmacol 1996 Oct
PMID:Differential induction of mRNA expression of cytochromes P450 (CYP2B1 and CYP1A1/2) by metyrapone in primary rat hepatocyte cultures. 894 14

Rare benzo[a]pyrene-resistant clones were previously isolated from the mouse hepatoma cell line, Hepa-1 (Hepa1c1c7), and shown to be deficient in induction of CYP1A1 mRNA by ligands for the aryl hydrocarbon receptor (AHR). Clones belonging to complementation group B were shown to have reduced levels of ligand binding to AHR. It is shown here that all 15 independently derived B clones analyzed had much reduced levels of AHR mRNA, but in each case, the mRNA was normal in size. Infection of B clones with a retroviral expression vector for AHR restores CYP1A1 inducibility (although viral AHR expression is progressively silenced and CYP1A1 expression progressively diminishes as the cells are maintained in culture). Treatment of the B clones with the histone deacetylase inhibitors sodium butyrate or trichostatin A restores AHR expression and also restores CYP1A1 inducibility to nearly 100% of the cells in the treated cultures. Fusion of a representative B clone with a rat hepatoma cell line restores expression to the mouse AHR gene encoded by the B clone's genome. These results demonstrate that the loss of CYP1A1 inducibility in B clones is probably totally ascribable to their reduced levels of AHR and that the clones are most probably not mutated in the AHR gene but are deficient in its expression. The evidence suggests that the reduction in expression of mRNA encoded by the endogenous AHR gene in the B clones is not due to an epigenetic alteration in chromatin structure but that the clones are probably defective either in a transcription factor for the AHR gene or in a protein required for generating an open chromatin configuration over the gene.
Mol Pharmacol 1996 Dec
PMID:Basis for the loss of aryl hydrocarbon receptor gene expression in clones of a mouse hepatoma cell line. 896 65

Three distinct cytochrome P450 isozymes, P4501A1, P4502B and an unidentified P450 isozyme were separated and isolated from beta-NF-treated gilthead seabream liver microsomes. Cytochrome P4501A1 was partially purified from beta-NF-treated gilthead seabream liver microsomes in the presence of detergents Emulgen 913 and cholate and protease inhibitors using two DEAE-cellulose, Porapak Q and two hydroxylapatite column chromatographies. The overall yield of purified P4501A1 was 1.2% with respect to microsomal total P450 with a specific content of 3 nmol/mg protein. The purified P4501A1 was characterized with respect to spectral, electrophoretic, biocatalytic and immunochemical properties, which are found to be similar to P4501A1s purified from other teleost species such as trout, scup, cod and perch suggesting that the P450 we have purified belongs to CYP1A1.
Biochem Mol Biol Int 1997 Jan
PMID:Separation of three P450 isozymes from liver microsomes of gilthead seabream treated with beta-NF and partial purification of cytochrome P4501A1. 904 42

We have developed a method for the quantitative, exhaustive sequence specificity determination of DNA-binding proteins. The QuESSD method overcomes the limitations inherent in other published in vitro selection methods, not only defining the consensus sequence, but also quantifying the effect on DNA-protein affinity of replacing each base in the recognition domain with every other base. The features distinguishing this method from other in vitro selection approaches are: (1) instead of synthesizing one target oligonucleotide population containing a long randomized domain, we synthesize several oligonucleotide populations, each randomized at two positions. (2) Instead of carrying out several cycles of selection and amplification, we carry out a single cycle. (3) We have developed data collection and analysis procedures that eliminate artifacts and allow generation of quantitative results. The QuESSD method yields accurate measures of: (a) the selectivity of the protein for each base at each position within the recognition domain (normalized relative selectivity), (b) the contributions of individual sites within the recognition domain to the binding affinity (selectivity variance), (c) the relative binding affinity of any given sequence (global selectivity). We confirmed results by (1) tabulating directly the frequency of appearance of individual species in the pool of protein-bound oligonucleotides by cloning and sequencing individual oligonucleotides, and (2) competition EMSA analysis of oligonucleotides designed on the basis of QuESSD data. We have used this method to map the sequence specificity of the nuclear protein XF1 and to distinguish the sequence specificities of XF1 and the AH receptor complex, both of which bind to XRE1, a xenobiotic responsive element (XRE) located upstream of the CYP1A1 gene. Using data obtained by the QuESSD method, we designed oligonucleotides specific for XF1 or for the AH receptor, and prepared CAT reporter gene constructs carrying these oligonucleotides, or wild-type XRE1, upstream of a minimal promoter. Transfection studies using these constructs indicated that XF1 can function as a weak activator of basal transcription, and can, under some circumstances, compete with the AH receptor for binding to XRE1.
J Mol Biol 1997 Feb 28
PMID:Mapping sequence specific DNA-protein interactions: a versatile, quantitative method and its application to transcription factor XF1. 906 5

An inhibitory effect on both constitutive and inducible expression of cytochrome P450 isoenzymes has been shown for different cytokines and growth factors. We previously described an inhibition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 mRNA and enzyme activity by transforming growth factor-beta1 (TGF-beta1) in human lung cancer A549 cells. In the present study, we report that not only TCDD-induced expression of CYP1A1 but also basal mRNA expression of CYP1A1, CYP1B1, and aryl hydrocarbon receptor (AHR) was down-regulated by TGF-beta1 in cells not treated with TCDD. In contrast, mRNA expression of the AHR partner protein Arnt (aryl hydrocarbon receptor nuclear translocator) was not influenced. Furthermore, TCDD-induced expression of CYP1B1 and NMO-1 was inhibited, and the IC50 values of 5-10 pM TGF-beta1 were in the same range as observed for inhibition of CYP1A1 and AHR mRNA expression. Transfection studies with a plasmid containing a luciferase reporter gene under control of two dioxin-responsive elements indicate an effect on AHR protein expression. Results of time-course studies revealed a parallel inhibition of AHR and CYP1 mRNA expression, indicating that TGF-beta1 is a direct negative regulator of transcription of these genes. The treatment of cells with cycloheximide led to a superinduction of TCDD-induced CYP1A1 and CYP1B1 mRNA expression and abolished the inhibitory effect of TGF-beta1 on basal as well as TCDD-induced CYP1 and AHR mRNA expression. TGF-beta1 seems not to influence the stability of AHR mRNA. The results suggest that TGF-beta1 induces rapid transcription and translation of an as-yet-unknown negative regulatory factor or factors that may directly regulate expression of AHR and genes of Ah gene battery.
Mol Pharmacol 1997 May
PMID:Effect of transforming growth factor-beta1 on expression of aryl hydrocarbon receptor and genes of Ah gene battery: clues for independent down-regulation in A549 cells. 914 8

The human colon carcinoma cell line, Caco-2, is widely used as a model for oral absorption of xenobiotics. The usefulness of Caco-2 cells has been limited, however, because they do not express appreciable quantities of CYP3A4, the principle cytochrome P450 present in human small bowel epithelial cells. We report that treatment of Caco-2 cells with 1 alpha,25-dihydroxyvitamin D3, beginning at confluence, results in a dose- and duration-dependent increase in CYP3A4 mRNA and protein, with little apparent effect on the expression of CYP3A5 or CYP3A7. This treatment also results in increases in NADPH cytochrome P450 reductase and P-glycoprotein (the MDR1 gene product) but has no detectable effect on expression of CYP1A1, CYP2D6, cytochrome b5, liver or intestinal fatty acid binding proteins, or villin. Maximal expression of CYP3A4 requires an extracellular matrix on a permeable support and the presence of serum. In the treated cells, the intrinsic formation clearance of 1'-hydroxymidazolam (a reaction characteristically catalyzed by CYP3A enzymes) was estimated to be somewhat lower than that of human jejunal mucosa (1.14 and 3.67 ml/min/g of cells, respectively). The 1'-OH-midazolam/4-OH-midazolam product ratio produced by the cells (approximately 5.3) is comparable to, but somewhat lower than, that observed in human jejunal microsomes (7.4-15.4), which may reflect the presence of CYP3A7 in the Caco-2 cells. 25-Hydroxyvitamin D3 is less efficacious but reproduces the effects of the dihydroxy compound, whereas unhydroxylated vitamin D is without appreciable effect. These observations, together with the time course of response, suggest that the vitamin D receptor may be involved in CYP3A4 regulation. The culture model we describe should prove useful in defining the role of CYP3A4 in limiting the oral bioavailability of many xenobiotics.
Mol Pharmacol 1997 May
PMID:Expression of enzymatically active CYP3A4 by Caco-2 cells grown on extracellular matrix-coated permeable supports in the presence of 1alpha,25-dihydroxyvitamin D3. 914 12

We have studied the transcriptional regulation of the dioxin-inducible mouse CYP1A1 gene in its native chromosomal setting. We analyzed the ability of aromatic hydrocarbon receptor (AhR) mutants and AhR chimeras to restore dioxin responsiveness to the CYP1A1 gene in AhR-defective mouse hepatoma cells. Our data reveal that transactivation domains in AhR's C-terminal half mediate occupancy of the nuclear factor 1 site and TATA box for the CYP1A1 promoter in vivo. Transactivation domains of VP16 and AhR nuclear translocator, but not Sp1, can substitute for AhR's C-terminal half in facilitating protein binding at the promoter. Our data also reveal an apparent linear relationship between promoter occupancy and CYP1A1 gene expression in chromatin. These findings provide new insights into the in vivo mechanism of transcriptional activation for an interesting mammalian gene.
Mol Cell Biol 1997 Jul
PMID:Transactivation domains facilitate promoter occupancy for the dioxin-inducible CYP1A1 gene in vivo. 919 85

Bronchial epithelial cells (BEC) are the progenitors of bronchogenic carcinomas and are exposed to polycyclic aromatic hydrocarbon (PAH) procarcinogens through inhalation of combustion products. PAH are converted to carcinogenic molecules through a combination of monoxygenation by cytochrome p450 (CYP) enzymes in the presence of NADPH oxidoreductase (OR) and hydrolysis by microsomal epoxide hydrolase (mEH). In artificial systems, the relative expression of these genes determines whether carcinogenic or noncarcinogenic species are generated during metabolism. This relationship was explored in humans by using quantitative competitive reverse transcriptase polymerase chain reaction amplification to determine the range of expression of CYP1A1, CYP1B1, mEH, and NADPH OR in BEC recovered from 10 nonsmokers and 9 smokers. CYP2B7 expression was evaluated because, although little is known of its substrate specificity, it is expressed at high levels in human lung tissue. CYP1A1 and CYP1B1 were expressed in BEC at significantly different levels (P < 0.05) in the 9 smokers at 1.4 +/- 2.3 x 10(4) and 2.4 +/- 3.2 x 10(3) molecules/10(6) beta-actin molecules (mean +/- STD), respectively, but each was measurable in only one of the 10 nonsmokers. There was significant inter-individual variation (P < 0.05) in both CYP1A1 and CYP1B1 expression among the subjects for whom sufficient data were obtained. The inducibility of human BEC CYP1A1 gene by PAH exposure was confirmed in vitro by incubating cultured immortalized human BEC with beta-naphthoflavone and observing a > 6-fold induction of CYP1A1 after 24 h. In contrast to BEC, alveolar macrophages expressed CYP1A1 at low (30-70 molecules/10(6) beta-actin molecules) to unmeasurable levels in both smokers and nonsmokers. There was no significant difference in expression of mEH, CYP2B7, or NADPH OR in smokers compared with nonsmokers. The inter-individual variation in absolute and relative expression of PAH metabolism enzymes in BEC reported here supports the hypothesis that inter-individual variation in ability to activate/inactivate inhaled PAH carcinogens accounts for at least some of the inter-individual variation in risk for bronchogenic carcinoma.
Am J Respir Cell Mol Biol 1997 Jul
PMID:Quantitative RT-PCR measurement of cytochromes p450 1A1, 1B1, and 2B7, microsomal epoxide hydrolase, and NADPH oxidoreductase expression in lung cells of smokers and nonsmokers. 922 17


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