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)

In view of the potential role of the cytochrome P450 (CYP) and microsomal epoxide hydrolase (mEH) biotransformation enzymes in the metabolism of protoxicants in the circulatory system, we examined CYP and mEH expression in several primary cultures of human umbilical vein endothelial cells (HUVEC), each established from a different individual. Total RNA was isolated from untreated cells and cells 72 hr after exposure to dimethyl sulfoxide (DMSO), Arochlor 1254 (PCB), and beta-naphthoflavone (beta NF). Specific mRNA transcripts were examined by Northern blotting and reverse transcriptase-coupled polymerase chain reaction (RT/PCR) analyses. CYP2E1, CYP3A, and CYP1A2 mRNAs were not detectable in any of the cultures by Northern blot analysis with radiolabeled oligomer probes; however, CYP1A1 mRNA was detected using this procedure in HUVEC cultures exposed to beta NF for 72 hr. Using RT/PCR, constitutive levels of CYP1A1, CYP1A2, CYP2E1, and CYP3A gene expression in HUVEC cultures were evident; however, constitutive CYP2B6 mRNA was not detected. Constitutive CYP1A2 transcript levels were detected in four of six HUVEC cultures, but levels varied between individual cultures. CYP1A2 mRNA levels were also increased in HUVEC cultures exposed to PCB and beta NF. No increases in the levels of CYP2E1 and CYP3A mRNAs were observed in HUVEC cells subsequent to PCB or beta NF exposures. Constitutive CYP2E1 transcript levels were present in all HUVEC cultures examined and varied among individuals. All HUVEC cultures examined for mEH activity exhibited constitutive levels of mEH which varied 40% between individual cultures and produced on average, 1.51 pmol benzo[a]pyrene 4,5-dihydrodiol per milligram protein per minute of reaction. Thus, these results demonstrate that human endothelial cells express CYP and mEH gene products and suggest that these enzymes may play important roles in determining metabolic fates for circulating protoxicants.
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PMID:Expression of cytochrome P450s and microsomal epoxide hydrolase in primary cultures of human umbilical vein endothelial cells. 750 67

The metabolism of L-696,229, 3-[2-(benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-o ne, a potent human immunodeficiency virus-type 1 reverse transcriptase inhibitor, by rat liver, lung, gut, and kidney microsomes has been studied. L-696,229 was metabolized by rat liver microsomes to several products: the 5 alpha-hydroxyethyl (M1); 5,6-dihydrodiol (M2); 6'-hydroxy (M3); 6-hydroxymethyl (M4); and 5-vinyl (M5) metabolites. For these pathways, liver was the most active metabolizing organ, whereas lung was the major extrahepatic organ in the drug metabolism. In all tissues tested, M1 was the major metabolite. With the exception of M3, gender differences in the hepatic formation of all metabolites were observed. Enzymes responsible for the hepatic metabolism of L-696,229 in rats were also investigated using various enzyme inducers and polyclonal antibodies to rat P-450. Treatment of male rats with dexamethasone (DX) or phenobarbital (PB) caused significant increases in the hepatic formation of the gender-dependent metabolites. Methylcholanthrene (3-MC) greatly enhanced the hepatic formation of M1, M3, and M4. Immunoinhibition studies suggested that CYP2B1/2 and 2E1 were not involved in L-696,229 metabolism, whereas CYP1A was partly responsible for the formation of M1 in untreated rats. CYP3A played an important role in the formation of M1, M2, M4, and M5 in untreated and DX-treated rats. In PB-treated rats, CYP2B1/2 was involved in the increased formation of M1 and M4, whereas CYP3A was partly involved in the enhanced M2 and M4 formation, and primarily responsible for the increased M5 formation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:In vitro metabolism of L-696,229, an HIV-1 reverse transcriptase inhibitor in rats and humans. Hepatic and extrahepatic metabolism and identification of enzymes involved in the hepatic metabolism. 751 54

Troleandomycin (TAO), a selective family 3A cytochromes P450 (CYP3A) inhibitor, decreases enhanced in vivo corticosterone 6 beta-hydroxylation and blood pressure in spontaneously hypertensive rats (SHR). Corticosterone 6 beta-hydroxylation was measured in liver and kidney microsomes, to determine ontogeny and the effect of TAO on CYP3A activity at the organ level. SHR kidney CYP3A activity increased from 4 to 8 weeks, stabilized at 11 and 16 weeks, and was much higher than in control (Wistar-Kyoto, WKY) rats at all ages. Hepatic activity showed less consistency in strain difference. TAO produced a relatively large decrease in renal CYP3A activity compared with liver. Although renal CYP3A mRNA was not present in sufficient quantity for detection by northern blot analysis of total RNA, its presence was demonstrated in SHR by reverse transcriptase-polymerase chain reaction amplification. Correlations between renal CYP3A activity and systolic blood pressure in SHR and WKY rats with variations in age, strain and drug treatment are consistent with the role of the enzyme in the pathogenesis of blood pressure elevation in SHR.
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PMID:Renal and hepatic family 3A cytochromes P450 (CYP3A) in spontaneously hypertensive rats. 760 44

The central nervous system is an important potential target for certain environmental protoxins, but relatively little is known regarding brain-specific expression of biotransformation enzyme systems. We undertook the present study to identify regional and cellular expression patterns of individual cytochrome P-450 genes (CYP) and microsomal epoxide hydrolase (mEH) in human brain. Various regions of normal human brain were isolated and examined with respect to mRNA levels of CYP1A1, CYP1A2, CYP2E1, CPY3A, and mEH, using specific oligomer probes and reverse transcriptase-coupled polymerase chain reaction analysis. We also used immunohistochemical techniques, with antipeptide-derived antibodies, to identify specific cells from various regions of the human brain producing CYP1A1 and mEH protein. Relatively equivalent mRNA expression levels of mEH were detected in the cerebellum (C), frontal (F), occipital (O), pons (P), red nucleus (RN), and substantia nigra (SN) regions of brain. The mRNA expression patterns of CYP2E1 and CYP1A2 were similar; although detected in all brain regions examined, the RN and SN exhibited lower levels of CYP2E1 and CYP1A2 mRNA expression compared to other regions. In addition, regional differences in CYP3A and CYP1A1 mRNA expression also were observed, with the highest level of CYP3A mRNA present in the P region compared to the C, F, O, and RN, while no CYP3A mRNA was detected in the SN. CYP1A1 mRNA expression was evident in all brain regions, but the levels of CYP1A1 mRNA in the P and RN were lower than in the C, F, O, and SN. In all cases, the regional mRNA expression levels of these CYP and mEH mRNAs were less than the corresponding levels detected from the same individual's liver. CYP1A1 and mEH immunoreactivity was present in most neurons of the SN, RN, P, median raphae, locus ceruleus, inferior vestibular nucleus, dorsal motor nucleus of the vagus, and thalamus. Some but not all astrocytes within these regions also demonstrated 1A1 and mEH immunoreactivity. These results indicate that many neurons and astrocytes express mEH and CYP1A1 as well as other CYP genes, and suggest that localized biotransformation events within the certain central nervous system may account for toxicities initiated by exposure to certain environmental chemicals.
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PMID:Regiospecific expression of cytochrome P-450s and microsomal epoxide hydrolase in human brain tissue. 769 60

The cytochromes P450 are a key group of enzymes involved in the metabolism of xenobiotics and several biologically active endogenous compounds. The expression of CYP3A5 has been identified by reverse transcriptase-polymerase chain reaction in human pituitary gland and shown by immunohistochemistry to be localized to growth hormone containing cells of the anterior pituitary gland. This is the first direct identification of an individual P450 subfamily in the pituitary gland and the presence of CYP3A in the pituitary gland may play a role in regulating growth hormone secretion.
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PMID:Cytochrome P450 CYP3A5 in the human anterior pituitary gland. 775 May 48

Epidemiological evidence suggests that the presence of human papillomaviruses (HPV), when combined with smoking behaviors, considerably enhances the risk of developing oral, cervical, vulvar, and/or anal carcinomas. It is well established that the cytochrome P450 (CYP), microsomal epoxide hydrolase (mEH), and other biotransformation enzymes are important modulators of the bioactivation and detoxification of many environmental chemicals, including constituents of tobacco smoke such as certain nitrosamines and polycyclic aromatic hydrocarbons (PAH). Since there is little information regarding oral and cervical epithelial-specific expression of these genes, established primary and HPV-immortalized oral and cervical epithelial cell lines were analyzed for morphology, mRNA and protein expression patterns of specific CYPs and mEH. Primary human oral and cervical epithelial cells were immortalized using retroviral infection with HPV-16 E6/E7 genes. Primary human keratinocyte cells were immortalized by transfection of HPV-18 and made tumorigenic with nitrosomethylurea treatment. Expression profiles for mEH, CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP3A, and CYP2E1 were evaluated in these cultures in the presence or absence of a PAH inducer, using reverse transcriptase-coupled polymerase chain reaction analysis. mEH gene expression was evident in all cultures, while CYP2A6 mRNA was not detected in any of the cell lines, regardless of culture conditions. CYP2E1 mRNA expression was greatest in the oral epithelial cultures and detectable in all other epithelial cultures except for the HPV-18 immortalized keratinocyte cell line. Elevated levels of CYP2D6 mRNA existed in both oral epithelial cell lines and the HPV-16 immortalized cervical epithelial cells when compared to the other cell lines examined. CYP1A1 and CYP1A2 mRNAs were detected in all the cells and several cultures were inducible by PAH exposure. To corroborate the RT/PCR data, Western immunoblotting experiments were conducted on selected samples. Using these methods, CYP1A1 and CYP2E1 proteins were detected in primary and HPV-immortalized oral and cervical epithelial cultures. These data indicate that both primary and HPV immortalized cells appear to express certain biotransformation enzymes necessary for the activation of tobacco-specific nitrosamines and PAHs. Although the overall impact of HPV gene infection on expression of these systems remains to be fully elucidated, as in vitro system is characterized which should prove useful in examining interactive mechanisms of HPV with xenobiotic activation in the etiology of squamous cell carcinomas.
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PMID:Expression of cytochrome P450 and microsomal epoxide hydrolase in cervical and oral epithelial cells immortalized by human papillomavirus type 16 E6/E7 genes. 761 6

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

A method was developed using reverse transcriptase-polymerase chain reaction (RT-PCR) to selectively detect and qualitatively determine the levels of mRNA expression of the major isoenzymes of cytochrome P450 (P450 1A1, 1A2, 2B1/2, 2C11, 2E1, 3A1, 3A2, and 4A1) and fatty acyl-CoA oxidase (FACO) in the rat. Total liver RNA was isolated from male Sprague-Dawley rats treated with various inducers of cytochrome P450 (P450) and analyzed for the presence and relative quantities of each P450 isoenzyme mRNA using this technique. The specificity of the oligonucleotide primers used in the detection of each P450 mRNA was tested and confirmed through the simultaneous analysis of liver microsomal protein preparations for the presence of constitutive or inducible P450 apoprotein and enzyme activities using western immunoblotting and specific enzyme activity measures, respectively. This method of P450 expression analysis is proven to be highly specific and readily applicable for the assessment of P450 enzyme induction and down-regulation in the rat during routine toxicology studies when expression of the gene product is regulated by transcriptional activation and/or mRNA stabilization.
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PMID:Analysis of rat cytochrome P450 isoenzyme expression using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). 876 76

The essential role of cytochrome P450 3A4 (CYP3A4) in human small intestine is well established, and CYP3A5 seems also to be present in most subjects. However, the role of CYP3A7 in the small intestine remains poorly characterized. We have therefore studied the expression of these CYP3A enzymes in the duodenal tissue from 19 patients, using a specific RT-PCR (reverse transcriptase-polymerase chain reaction) method. CYP3A4 and CYP3A5 were present at the mRNA level in the duodenum of 18 and 19 of the 19 patients studied, respectively. In contrast, mRNA for CYP3A7 was not found in the duodenum in any of the patients. These findings strongly suggest that, unlike CYP3A4 and CYP3A5, CYP3A7 is not expressed in human duodenum.
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PMID:Expression of CYP3A4, CYP3A5 and CYP3A7 in human duodenal tissue. 887 31


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