Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human small intestine epithelial cells (enterocytes) provide the first site for cytochrome P-450 (CYP)-catalyzed metabolism of orally ingested xenobiotics. The CYP composition of enterocytes could thus affect the potential toxicity or therapeutic efficacy of xenobiotics by modifying systemic uptake. We have characterized human enterocyte CYP composition to enable assessment of its functional roles. An isolation method for enterocytes from human small intestine was developed using EDTA buffer-mediated elution. Villous enterocytes were isolated in high yield, separated from crypt cells. Reverse transcriptase-polymerase chain reaction of total RNA from enterocytes revealed that CYP1A1, 1B1, 2C, 2D6, 2E1, 3A4, and 3A5 mRNA were expressed, but only CYP2C and 3A4 were detectable by Western immunoblotting in enterocyte microsomes from 10 human small intestines, whereas CYP1A1 was weakly detectable in two of eight intestines tested. Microsomal protein content decreased markedly along the small intestine from the duodenum to the ileum, whereas total CYP content and CYP3A4 erythromycin N-demethylase activity increased slightly in progressing from the duodenum to the jejunum and then decreased markedly toward the ileum. Levels of CYP3A4 and 2C protein did not decrease in concert as a function of length along the intestine distally. Maximal CYP content for the 10 intestines varied from 0.06 to 0.18 nmol/mg microsomal protein and maximal CYP3A4 erythromycin N-demethylase activity varied from 0.30 to 0.76 nmol/min/mg microsomal protein. In conclusion, CYP3A4 is the major form of CYP expressed in human small intestine enterocytes, CYP3A5 expression was not detected, CYP2C and, in some intestines, CYP1A1 were expressed. The highest metabolic activity occurred in the proximal intestine.
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PMID:Characterization of human small intestinal cytochromes P-450. 1038 24

The expression of mRNA for five cytochrome P450s (CYP1A1, 2A6/7, 2D6, 2E1 and 3A4) was studied in human bone marrow, bone-marrow-derived macrophages and blood monocyte-derived macrophages. Reverse transcriptase polymerase chain reaction (RT-PCR) detected expression of all five CYPs in each of these cell populations. All five CYPs were also expressed in the haemopoietic cell lines HL-60 and HEL and in Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines. The data suggest that bone marrow macrophages and probably other bone marrow cell types are capable of metabolizing xenobiotics. This metabolic potential may play a role in the bone marrow damage induced by some drugs and chemicals.
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PMID:Demonstration of mRNA for five species of cytochrome P450 in human bone marrow, bone marrow-derived macrophages and human haemopoietic cell lines. 1065 38

Natural resistance-associated macrophage protein (Nramp) genes in rainbow trout, Oncorhynchus mykiss, were identified and characterized. The greatest mRNA level encoding these genes was in the developing ovary of rainbow trout. We evaluated the response of these genes to a certain aromatic hydrocarbon receptor (AHR) agonist. Adult rainbow trout were treated with beta-naphthoflavone (BNF) (50 and 100 mg/kg) for 48 h. Using reverse-transcriptase polymerase chain reaction with ovary and head kidney RNA and specific alpha and beta Nramp primers, a 400 bp Nramp-alpha- and a 400 bp Nramp-beta-specific cDNA were obtained. There were no changes in the alpha and beta Nramp mRNA levels in the ovary following BNF administration. CYP1A1 mRNA was increased in the ovary and kidney, suggesting the presence of AHR in rainbow trout ovary, while the AHR agonist produced no effect on Nramp mRNAs.
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PMID:Lack of effect of beta-naphthoflavone on induction of Nramp genes in adult rainbow trout Oncorhynchus mykiss. 1146 Jun 81

Cytochrome p4501A induction and subsequent enzyme expression is used as a biomarker for exposure to aryl hydrocarbon receptor active contaminants in fish and other species. In the present study, CYP1A cDNA (1912 bp, GenBank accession number AF364076) was cloned, sequenced and characterized from the liver of a beta-naphthoflavone (betaNF)-treated teleost, Atlantic salmon (Salmo salar), by reverse-transcriptase polymerase chain reaction (RT-PCR). The salmon CYP1A sequence contained a 5'-flanking region of 99 bp, an open reading frame of 1566 bp that encodes a 521 amino acid protein, a stop codon, and a 3'-untranslated region of 346 bp, and a single polyadenylated signal. The theoretical molecular mass and isoelectric point was 58.6 kDa and 6.17, respectively. Comparison of the deduced amino acid sequence of salmon cDNA with reported CYP1A genes showed identities of 73-88% with fish CYP1A, 51-54% with mammalian CYP1A1, 47-51% with mammalian CYP1A2 and 54% with frog p450. Phylogenetic analysis showed that salmon CYP1A clustered in the tree with rainbow trout CYP1A1 and eel CYP1A sequences. CYP1A mRNA induction in beta-naphthoflavone-treated salmon showed differential organ expression with a distinct single transcript pattern. A new specific molecular tool has been developed for the monitoring of environmental pollution using CYP1A mRNA from salmon as a biomarker.
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PMID:Complementary DNA cloning, sequence analysis and differential organ expression of beta-naphthoflavone-inducible cytochrome P4501A in Atlantic salmon (Salmo salar). 1245 89

Oltipraz, a promising cancer chemopreventive agent, has been recognized as a monofunctional inducer selectively activating phase II carcinogen-detoxifying enzymes via the antioxidant responsive element (ARE). However, we report here that oltipraz also induces rat glutathione S-transferase A5 (GSTA5), a potent phase II detoxifying enzyme, by means of the xenobiotic responsive element (XRE). Although an ARE sequence exists in the 5' upstream of the rGSTA5 gene, this cis-acting regulatory element loses its responsiveness to oltipraz treatment because of extensive mutations in its distal-half site. Our data indicate that a XRE sequence, located downstream of the transcription initiation site of the gene, is another oltipraz-responsive element. Electrophoretic mobility shift assay showed that oltipraz steadily induces XRE-aryl hydrocarbon receptor (AhR) binding, which can be blocked specifically by excess XRE oligonucleotides or by AhR antibody. By cloning different XREs into the pGL3-promoter vector, we found that oltipraz can activate XRE enhancers from several phase II drug metabolism enzymes, including rGSTA5, rGSTA2, NAD(P)H:quinone reductase, and it also activates XRE from the phase I metabolism enzyme CYP1A1. Oltipraz's effect on XRE is AhR-dependent and is independent of the presence of active CYP1A1. Reverse transcriptase-polymerase chain reaction experiments revealed that oltipraz induces gene expression of both phase I and II drug-metabolizing enzymes in rat hepatoma cells. Thus, we conclude that, like ARE, the XRE pathway constitutes an important part of the molecular mechanism contributing to oltipraz-induced expression of the phase II metabolism enzymes. Oltipraz is a bifunctional inducer, modulating both phase I and II drug-metabolizing enzymes to enhance carcinogen detoxification.
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PMID:Oltipraz is a bifunctional inducer activating both phase I and phase II drug-metabolizing enzymes via the xenobiotic responsive element. 1286 39

The mycotoxin, patulin (PAT), which is frequently found in apples, grapes, oranges, pear, peaches, and in apple juices, has previously been shown to be cytotoxic, genotoxic, and mutagenic. In this study, we have investigated the effect of PAT on mRNA level of pregnane X receptor (PXR), constitutive androstane receptor (CAR), aryl hydrocarbon receptor (AhR), and their corresponding target cytochrome P450s. Using primary cultures of adult human hepatocytes, we evaluated PAT cytotoxicity on hepatocytes after 24 hours of treatment. Real time reverse-transcriptase polymerase chain reaction procedure was employed to determine the effect of PAT on receptors (PXR, CAR, and AhR) and cytochrome (CYP3A4, 2B6, 3A5, 2C9, 1A1, and 1A2) genes. Our results showed that PAT reduced hepatocyte viability. At a noncytotoxic range of PAT concentrations, PAT induced an upregulation of the PXR gene in the three treated hepatocytes cultures, whereas CAR was overexpressed in only 1 treated liver. PXR gene induction was accompanied by the enhancement of CYP2B6, 3A5, 2C9, and 3A4 expression. PAT was also found to induce an overexpression of AhR and CYP1A1 and CYP1A2 mRNA expression. These findings suggested that PAT may activate PXR and/or CAR and AhR. However, further investigations are needed to confirm nuclear receptor activation by PAT and to elucidate the molecular mechanism of PAT action.
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PMID:The mycotoxin, patulin, increases the expression of PXR and AhR and their target cytochrome P450s in primary cultured human hepatocytes. 2193 62