Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The expression of individual xenobiotic-metabolizing cytochrome P450 (CYP) genes in human placenta was studied at the mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR). mRNAs of CYP1A1, CYP2E1, CYP2F1, CYP3A3/4, CYP3A5, and CYP4B1 were detected by RT-PCR, and CYP1A2, CYP2A6/7, CYP2B6/7, CYp2C8-19, CYP2D6, and CYp3A7 were not detected. Several enzyme activity assays and immunoblasts were used to further characterize expression of forms producing detectable mRNA transcripts. The catalytic activities of 7-ethoxycoumarin O-deethylase (ECOD), 7-ethoxyresorufin O-deethylase (EROD) and aryl hydrocarbon hydroxylase (AHH) were substantially increased in response to maternal cigarette smoking, and paralleled the amount of CYP1A1 mRNA and protein. Aromatase activities were slightly lower in placentas exposed to cigarette smoke compared with nonexposed placentas. These data show that several xenobiotic-metabolizing CYP genes are expressed in human placenta at a low level. The significant of such low-level expression is unknown, but it may have local physiological or toxic consequences.
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PMID:Expression of xenobiotic-metabolizing cytochrome P450 forms in human full-term placenta. 861 84

Human first-trimester placentas were screened for the expression of xenobiotic-metabolizing cytochrome P450 (CYP) genes. mRNAs of CYP1A1, CYP1A2, CYP2C, CYP2D6, CYP2E1, CYP2F1, CYP3A4, CYP3A5, CYP3A7, and CYP4B1 were identified by reverse transcriptase-polymearse chain reaction (RT-PCR) in at least some of the six placental samples studied. CYP2A and CYP2B message were absent in all samples. The level of all of these CYP mRNAs was lower compared to the corresponding levels in liver or lung. the catalytic activity marker (7-ethoxyresorufin O-deethylase) was inducible in the placentas by maternal cigarette smoking. Thus, the regulatory system of placental CYP1A1, mediated by the Ah-receptor, appears to be developed as early as the first trimester of pregnancy. Three immunoreactive bands from placental microsomes were detected by an antihuman CYP3A4 antibody, but no functional activity of CYP3A enzymes could be detected. These results show that placental tissue during the first trimester of pregnancy has the potential of expressing several CYP genes, and forms a basis for subsequent analysis of these forms at the protein and functional level.
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PMID:Detection of cytochrome P450 gene expression in human placenta in first trimester of pregnancy. 869 64

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.
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PMID:Xenobiotic metabolism enzyme gene expression in human bronchial epithelial and alveolar macrophage cells. 884 77

Human pulmonary tissue are known to contain enzymes mediating procarcinogen activation. Peripheral blood lymphocytes and bronchoalveolar macrophages (BAMs) have been used as surrogates for the lung in studies involving cytochrome P450 (CYP) parameters, including CYP1A1 inducibility in relation to susceptibility to lung cancer. In this study, a comprehensive view of the expression patterns of xenobiotic-metabolizing CYP forms in human BAMs and peripheral blood lymphocytes was obtained by using gene-specific reverse transcriptase-polymerase chain reaction analysis. These patterns were compared with that in the whole lung. mRNAs of CYP2B6/7, CYP2C, CYP2E1, CYP2F1, CYP3A5, and CYP4B1 were detected in all seven BAM samples studied; however, only the mRNA of CYP2E1 was found consistently in all eight lymphocyte samples. The amounts of amplification products of CYP2B6/7, CYP2C, CYP3A5, and CYP4B1 were low and inconsistent, indicating low levels of expression in lymphocytes. Consistent with previous knowledge, mRNAs of CYP1A1, CYP2B6/7, CYP2E1, CYP2F1, CYP3A5, and CYP4B1 were detected in whole-lung tissue. These results give an overall picture of the expression of CYP genes in the xenobiotic-metabolizing families CYP1, CYP2, and CYP3 in BAMs, peripheral blood lymphocytes, and whole-lung tissue and will aid in directing future studies on the respective protein products. The differences in the CYP gene expression patterns between lung and lymphocytes cast additional doubt on the use of lymphocytes as a surrogate for the lung.
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PMID:Detection of mRNA encoding xenobiotic-metabolizing cytochrome P450s in human bronchoalveolar macrophages and peripheral blood lymphocytes. 936 12

Long-term tamoxifen therapy is associated with increased risk of uterine endometrial cancer and benign alterations. Tamoxifen is metabolized to reactive intermediates by endometrial tissue, and tamoxifen therapy-induced DNA adducts have been found in human endometrium. Since metabolic activation is often catalyzed by cytochrome P450 (CYP) enzymes, the expression profile of individual xenobiotic-metabolizing CYP genes was studied in human uterine endometrium by reverse transcriptase-polymerase chain reaction. The following CYP mRNAs were detected: CYP2B6, CYP2C, CYP2E1, CYP3A4, CYP3A5, CYP4B1, and CYP11A. Amplification of CYP1A1, CYP1A2, CYP2A6, CYP2D6, CYP2F1, CYP3A7, and CYP19 was not found. CYP3A5 and CYP4B1 transcripts were found only in samples from premenopausal women. These data suggest that the human endometrial epithelium has the potential of producing CYP enzymes known to generate genotoxic intermediates from tamoxifen and metabolites that affect oestrogen receptors.
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PMID:Expression of cytochrome P450 genes encoding enzymes active in the metabolism of tamoxifen in human uterine endometrium. 949 38

We developed a quantitative competitive reverse transcriptase-polymerase chain reaction (QC RT-PCR) assay to measure mRNA levels of seven human cytochrome P450 (P450, CYP) genes and microsomal epoxide hydrolase (EH) simultaneously. This assay employs an exogenous recombinant RNA (rcRNA) molecule as an internal standard that shares PCR primer and hybridization probe sequences with CYP1A1, CYP1A2, CYP2A6/7, CYP2D6, CYP2E1, CYP2F1, CYP3A4/5/7, and EH mRNA. Because each rcRNA molecule contains several primer sequences, an entire battery of genes that exhibit differential responsiveness to various classes of xenobiotics may be measured simultaneously from one population of cDNA molecules. In this study, we demonstrated the precision and power of the assay using small amounts of human liver total RNA. We also report for the first time quantitative profiles of P450 and EH mRNA abundance in eight human livers. Cytochrome P450 2E1 mRNA maintained the highest abundance (average 6.67 x 10(7) molecules/microg of total RNA) and least variation (13 fold) in all livers examined. Cytochrome P450 1A2, CYP2A6/7, CYP2D6, CYP3A4/5, and EH mRNAs were approximately one order of magnitude less abundant than CYP2E1 transcripts, with CYP2D6 levels exhibiting the greatest variation (220 fold) between individuals. This QC RT-PCR assay should prove valuable for measuring basal and induced mRNAs in different cell types in vitro, as well as in biomonitoring applications where individuals are exposed or hypersusceptible to certain xenobiotic-initiated toxicities.
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PMID:Quantification of multiple human cytochrome P450 mRNA molecules using competitive reverse transcriptase-PCR. 953 3

To examine the character and variability of human cytochrome P450 (CYP) and microsomal epoxide hydrolase (mEH) gene expression in human blood cells, we used a highly sensitive, quantitative, competitive reverse transcriptase-coupled polymerase chain reaction (QC RT-PCR) assay to assess mRNA profiles for a battery of 8 genes, in peripheral lymphocytes isolated from 10 healthy donors. Of the genes profiled, in lymphocytes CYP2D6 was typically expressed at the highest levels (3.8 x 10(5) molecules/microg total RNA), with CYP2E1 and mEH also maintained at relatively high abundance (1.2 x 10(5) and 1.8 x 10(5) molecules/microg total RNA, respectively). CYP1A1 levels were approximately an order of magnitude lower (3.9 x 10(4) molecules/microg total RNA), followed by CYP2F1 and CYP3A levels that were near the detection limit of the assay. CYP1A2 and CYP2A6/7 mRNAs were not detected in any of the lymphocyte samples. Overall, relatively low levels of inter-individual variation (2- to 6-fold) existed among these endpoint parameters in the subjects tested. To test whether established human blood cell lines were suitable models to assess basal expression and chemical induction responsiveness of these genes, we determined that constitutive CYP and mEH mRNA profiles were essentially conserved across 4 established human blood cell lines, and highly analogous to the basal expression patterns identified in freshly isolated peripheral lymphocytes. mEH protein was detected in all of the cell lines using Western immunoblotting and chemiluminescent visualization, whereas CYP1A1, CYP2D6, CYP2E1 or CYP3A proteins were not detected in these analyses. When blood cell-derived cultures were exposed to the prototypical CYP1A and CYP3A inducers, i.e., beta-naphthoflavone (beta-NF), dexamethasone (DEX) or phenobarbital, generally little or no inductive response was manifested. Thus, the data obtained from this investigation indicate that, although human blood cell lines in general exhibit poor responsiveness to prototypical inducer exposures, the constitutive patterns of CYP and mEH expression in peripheral lymphocytes appear to exhibit relatively low levels of variation among individuals. In addition, these in vivo patterns of expression are well maintained in established cultured blood-cell lines.
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PMID:Fingerprinting of cytochrome P450 and microsomal epoxide hydrolase gene expression in human blood cells. 1082 67

Environmental chemicals are one of the risk factors in breast cancer genesis. Cytochrome P450 (CYP) enzymes play a major role in the activation of these chemicals. Using highly specific and sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. the expression profile of all major xenobiotic metabolizing CYP forms was screened in breast tumour and surrounding tumour free (control) breast tissue in a series of 20 sample pairs obtained from females with infiltrating ductal carcinoma. The levels of CYPIAI mRNA were very low in both tumour and normal tissue. CYP1B1, CYP2B6, CYP2C, CYP2D6, CYP2E1, CYP4B1, and CYP11A1 expressions were positive in both tumours and control tissue. CYP2A6, CYP2A7, CYP2A13, CYP2F1, CYP3A4, CYP3A5. and CYP3A7 mRNAs were expressed neither in tumours nor in control tissue. These results show that several CYPs. responsible for the activation of a quite large number of procarcinogens and genotoxic estrogen metabolites. are expressed in breast tissue with a lack of qualitative differences in CYP expression at mRNA level between breast tumours and surrounding normal breast.
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PMID:The expression of cytochrome P450 enzymes in human breast tumours and normal breast tissue. 1176 4