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)

Normal human bronchial epithelial (NHBE) cells are the putative progenitor cells of all types of lung cancer. NHBE cells immortalized by SV40 T-antigen retain many characteristics of the primary cells and are a useful model for investigating the role of oncogenes, tumor suppressor genes, and certain chemical carcinogens in the molecular pathogenesis of lung cancer. In this study, SV40 T-antigen-positive cells (BEAS-2B) were characterized for their metabolic functions and were shown to continue to express epoxide hydrolase, glutathione S-transferase pi, glutathione peroxidase, and catalase. To increase their metabolic activity towards human procarcinogens, human cytochrome P450 1A2 (CYP1A2) was stably expressed by introducing CYP1A2 cDNA into BEAS-2B cells either by infection with a high-titer recombinant retrovirus (pXT-1A2) or by transfection with a CYP1A2 expression vector (pCMV1A2), which produced the cell lines B-1A2 and B-CMV1A2, respectively. Cell lines established with either expression system expressed enzymatically active CYP1A2 protein and were 50- to 400-fold more sensitive to the cytotoxic effect of the carcinogen aflatoxin B1 (AFB1) than the corresponding control cell lines. The cytotoxic effects of AFB1 were paralleled by increased metabolism of AFB1 and enhanced formation of the AFB1-N7 guanine adduct in B-CMV1A2 cells. Cytotoxicity and adduct formation correlated with a significantly higher protein expression of CYP1A2 by the cytomegalovirus promoter-driven plasmid. Since this human epithelial cell line is the precursor cell type of lung cancer, has normal phase II enzymes, and exhibits highly reproducible expression of phase I enzymes, this in vitro model should aid in the evaluation of putative human carcinogens and anticarcinogens.
Mol Carcinog 1994 Oct
PMID:Activation of promutagens in a human bronchial epithelial cell line stably expressing human cytochrome P450 1A2. 791 94

The potent carcinogen benzo[a]pyrene (B[a]P) and its metabolite B[a]P trans-7,8-dihydrodiol (7,8-diol) require metabolic activation by the microsomal cytochrome P450s (P450s) to exert several adverse biological effects, including binding to DNA, toxicity, mutagenicity, and carcinogenicity. In the study reported here, we defined the role of each of 12 individual cDNA-expressed cytochrome P450s in the metabolism of B[a]P and 7,8-diol. Human P450s 1A1 and 1A2 were expressed in the absence or presence of epoxide hydrolase (EH) in a human lymphoblastoid cell line, and six human and five rodent and rabbit P450s were expressed from cDNA with vaccinia virus vectors in the hepatoma cell line Hep G2. B[a]P metabolism resulted in nine metabolites (three diols, three quinones, and three phenols), which were separated, identified, and quantitated by high-pressure liquid chromatography. In the human lymphoblastoid cells, human 1A1 metabolized B[a]P at a rate 4.5 times greater than that for 1A2. EH was shown to be directly involved in B[a]P activation, since increasing the amount of EH resulted in less 7-hydroxybenzo[a]pyrene and more 7,8-diol formation. Of the human P450s expressed with the vaccinia virus vectors in Hep G2 cells, 1A2 and 2C9 showed the highest activity and 2B6 showed moderate activity for B[a]P metabolism. Mouse 1A1 had activity 40 times higher than any human, rabbit, or rodent P450s, indicating the potential pitfalls of extrapolating P450 activity across species. Metabolism of the 7,8-diol resulted in six metabolites (four tetrols and two triols). In the lymphoblastoid cells, human 1A1 was shown to be 4.2 times more active than 1A2 for 7,8-diol metabolism. Among human P450s expressed from vaccinia virus, 1A2, 2E1, and 2C9 gave the highest activity, and 2C8 and 3A4 showed moderate activity for 7,8-diol metabolism to the diol epoxides. Again, mouse 1A1 was much more active than any other P450. These studies, in which we determined the capacity of individual P450 in the metabolism and activation of B[a]P and 7,8-diol, may thus lead to a better understanding of how P450s control the detoxification and activation of polycyclic aromatic hydrocarbons.
Mol Carcinog 1994 Jul
PMID:The role of 12 cDNA-expressed human, rodent, and rabbit cytochromes P450 in the metabolism of benzo[a]pyrene and benzo[a]pyrene trans-7,8-dihydrodiol. 804 97

Cytokines are thought to cause the depression of cytochrome P-450 (CYP)-associated drug metabolism in humans during inflammation and infection. We have examined the role of five cytokines, i.e., interleukin-1 beta, interleukin-4, interleukin-6, tumor necrosis factor-alpha, and interferon-gamma, on the expression of CYP1A2, CYP2C, CYP2E1, CYP3A, and epoxide hydrolase in primary human hepatocyte cultures. Steady state P-450 and epoxide hydrolase mRNA levels, as well as ethoxyresorufin-O-deethylase and nifedipine oxidation activities, which are mainly supported by CYP1A1/1A2 and CYP3A, respectively, were measured. Interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha were found to be the most potent depressors of P-450 enzymes. After 3 days of treatment, both mRNA levels and enzyme activities were depressed, typically by at least 40%, whatever the cytokine and the enzyme considered. Interferon-gamma also suppressed CYP1A2 and CYP2E1 mRNA levels and ethoxyresorufin-O-deethylase activity but had no effect on CYP3A and epoxide hydrolase mRNAs. In addition, interleukin-4 had the opposite effect, compared with other cytokines, on CYP2E1 mRNA, which was increased up to 5-fold; ethoxyresorufin-O-deethylase and nifedipine oxidation activities were not significantly affected. These results provide the first demonstration that various cytokines act directly on human hepatocytes to affect expression of major P-450 genes and that a wide range of responses can be observed among the enzymes for a given cytokine, suggesting that different regulatory mechanisms may be involved.
Mol Pharmacol 1993 Oct
PMID:Cytokines down-regulate expression of major cytochrome P-450 enzymes in adult human hepatocytes in primary culture. 823 20

In the present study, we developed a very sensitive, semiquantitative assay based on the reverse transcriptase-coupled polymerase chain reaction to measure, in a region-selective manner, mRNA expression patterns within the brain for microsomal epoxide hydrolase and several cytochrome P-450s (P-450s) known to be induced by prototypic agents in other tissues. The P-450s assessed included the polyaromatic hydrocarbon-inducible CYP1A1 and CYP1A2 systems, together with the phenobarbital-inducible P-450s, CYP2B1, CYP2B2, CYP3A1, which were examined 18 hr after a single intraperitoneal dose of the respective inducing agents. Highly region-specific patterns of expression were evident for P-450 mRNAs within the rat brain. In the control, uninduced brain, CYP1A1 mRNAs were readily detected in the striatum and in the hypothalamus, and to a lesser extent in the other regions examined. The regional pattern of expression was similar for CYP1A2; however, a major difference was noted in the olfactory bulbs, characterized by a relatively high level of CYP1A2 mRNA but correspondingly low levels of CYP1A1. Within the brain regions examined, the highest content of CYP2B1 and CYP2B2 mRNAs were present in the striatum and in the cerebellum, whereas CYP3A1 levels varied only slightly across the respective regions. In contrast to the P-450s, microsomal epoxide hydrolase mRNAs were expressed at relative homogeneous amounts throughout the brain. beta-Naphthoflavone markedly increased the CYP1A1 and CYP1A2 mRNA contents of each brain region investigated, although this agent did not affect levels of epoxide hydrolase. At 18 hr post-treatment with phenobarbital, an optimal time period for hepatic induction, brain expression was characterized by a complex pattern of effects, with increased levels noted for CYP2B1 mRNA content in the medulla oblongata, midbrain, and cortex, but decreased contents measured in the cerebellum, the hypothalamus, and the striatum. In each of these respective regions, CYP2B2 content was profoundly decreased whereas epoxide hydrolase expression was slightly increased by the same treatment. These results establish that the central nervous system actively expresses a number of different biotransformation gene products in a regional specific and inducer-dependent manner, and suggest that for tissues exhibiting low regenerative capacity, like the brain, such reactions are likely to be of critical toxicological significance.
Mol Pharmacol 1993 Nov
PMID:Regional distribution and expression modulation of cytochrome P-450 and epoxide hydrolase mRNAs in the rat brain. 824 22

The herbicide 2,6-dichlorobenzonitrile (DCBN) is known to cause tissue-specific toxicity at very low doses in the olfactory mucosa of rodents. The toxicity of DCBN is reportedly cytochrome P450 (P450) dependent, but the isoforms involved have not been identified, and the effects of this agent on humans are not known. In the present study, DCBN metabolism was examined with microsomes and with purified P450s in a reconstituted system. Rat and rabbit olfactory microsomes act on DCBN to form DCBN-protein adducts as well as two metabolite peaks, designated M1 and M2, identified through high performance liquid chromatography with radiometric detection. The activity of rat olfactory microsomes in DCBN metabolism is much higher than that of liver or lung microsomes. Of seven purified rabbit P450s known to be expressed in the olfactory mucosa, including 1A2, 2A10/11, 2B4, 2E1, 2G1, and 3A6, the 2A10/11 preparation is the most active, producing M2 as well as DCBN-protein adducts; P450 2E1 is the only other active isoform. The addition of purified epoxide hydrolase (EC 4.2.1.63) to the reconstituted enzyme system leads to the formation of M1 and decreased formation of M2. It seems that M1 and M2 are derived from an epoxide intermediate that also forms covalent protein adducts. Gas chromatography- and liquid chromatography-mass spectrometry analyses of nasal microsomal DCBN metabolites and DCBN-glutathione conjugates indicated that the major reactive intermediate may be 2,3-oxo-DCBN and that M1 may be 2,3-dihydroxy-6-chlorobenzonitrile, whereas M2 may correspond to a monohydroxy-DCBN. Interestingly, heterologously expressed human P450s 2A6 and 2E1, but not 1A2, are active in the metabolism of DCBN, forming protein adducts as well as M2. Thus, the preferential expression of P450s of the 2A subfamily in olfactory tissue suggests a molecular basis for the tissue-specific toxicity of the herbicide and may have important implications for risk assessment in humans.
Mol Pharmacol 1996 Jun
PMID:Metabolic activation of 2,6-dichlorobenzonitrile, an olfactory-specific toxicant, by rat, rabbit, and human cytochromes P450. 864 51

The regulation of JH epoxide hydrolase, JH esterase and 1-naphthyl acetate (NA) esterase activity was studied in ovary, gut, head and carcass after blood feeding in Culex quinquefasciatus. The combined tissues had the greatest JH epoxide hydrolase and JH esterase activity from 24-36 hr after a blood meal. JH epoxide hydrolase activity per female was 2.1-, 1.8- and 1.1-times greater than the JH esterase activity at 24, 36 and 48 hr after blood feeding, respectively. JH epoxide hydrolase activity per until protein was also the major route of primary JH metabolism at most time points examined, and peak JH epoxide hydrolase activity per unit protein in the gut, head and carcass was approximately 2-5 times the highest JH esterase activity per unit protein in corresponding tissues and 4-times the peak JH esterase activity in the ovary. The differential expression of JH epoxide hydrolase versus JH esterase in specific tissues and between tissues suggested that regulation of JH metabolism is tissue specific. Two isoelectric forms of JH esterase were found. The juvenoid, (RS)-methoprene, interfered with the regulation of JH esterase activity, but failed to change the activity levels of JH epoxide hydrolase and 1-NA esterase.
Comp Biochem Physiol B Biochem Mol Biol 1996 Feb
PMID:Juvenile hormone metabolism in the ovary, gut, head and carcass after blood feeding in the southern house mosquito, Culex quinquefasciatus. 865 80

Genes involved in the metabolic activation or detoxification of environmental carcinogens may contribute to breast cancer susceptibility by influencing rates of somatic mutation. To examine this hypothesis, we studied the association between loss of constitutional heterozygosity (LOH) in ductal breast tumors and allelic variability in genes that regulate the metabolism of environmental carcinogens. LOH was measured by typing the tumor and normal tissue of 28 breast cancer cases at 33 chromosomal loci by using highly polymorphic tetranucleotide repeat markers. Genotypes in non-tumor tissue were also measured at the cytochrome P450 1A1 (CYP1A1), cytochrome P450 2D6 (CYP2D6), glutathione-s-transferase mu (GSTM), epoxide hydrolase (EH), and NAD(P)H:quinone oxidoreductase (NQO1) loci. The observed proportion of LOH was 11% overall and ranged from 0% to 37% across loci. LOH greater than 20% was observed on chromosomes 1p, 2p, 10q, 11q, 17p, and 18q. The observed proportion of LOH ranged from 0% to 67% among individuals. An elevated proportion of LOH was observed for genotypes at CYP2D6 (17% for the 1/1 and 1/2 genotypes vs 8% for the 2/ 2 genotype), NQO1 (13% for the 1/2 and 2/2 genotypes vs 8% for the 1/1 genotype), and GSTM (15% for the null genotype vs 7% for the wild-type genotype). No elevated proportion of LOH was observed for genotypes at CYP1A1 (12% for the 1/2 genotype vs 10% for the 1/1 genotype) or EH (11% for the 1/1 genotype vs 10% for the 1/2 genotype). There was no correlation of LOH with any other tumor characteristic such as estrogen- or progesterone-receptor status or number of positive lymph nodes. These results suggest that the proportion of LOH varies substantially across loci and among individuals. Interindividual variability in LOH may thus be explained in part by genes that regulate the metabolism of environmental carcinogens.
Mol Carcinog 1996 Nov
PMID:Variability in loss of constitutional heterozygosity across loci and among individuals: association with candidate genes in ductal breast carcinoma. 894 71

Styrene 7,8-oxide and ethylene oxide are widely used genotoxic bulk chemicals, which have been associated with potential carcinogenic hazard for occupationally exposed workers. Both epoxides alkylate DNA preferentially at the N-7 position of guanine and consequently produce single-strand breaks and alkali labile sites in the DNA of exposed cells. In order to study the role of human microsomal epoxide hydrolase (hmEH) in protecting cells against genotoxicity of styrene 7,8-oxide and ethylene oxide, we expressed the cDNA of hmEH in V79 Chinese hamster cells. We obtained a number of cell clones that expressed functionally active epoxide hydrolase. Among these, the clone 92hmEH-V79 revealed an especially high enzymatic mEH activity toward styrene 7,8-oxide (10 nmol converted per mg of protein per min, measured in the 9,000 x g supernatant of the cell homogenate), that was 100 times higher than that determined in mock-transfected cells and within the range of mEH activity in human liver. Styrene 7,8-oxide-induced DNA single-strand breaks/alkali labile sites (dose range 10 microM to 1 mM styrene 7,8-oxide) measured by the alkaline elution technique were significantly lower in the 92hmEH-V79 cells as compared to the mock-transfected cells. The protection against styrene 7,8-oxide genotoxicity in 92hmEH-V79 cells could be abolished by addition of valpromide, a selective inhibitor of microsomal epoxide hydrolase. These results clearly show that the metabolism of styrene 7,8-oxide by hmEH in 92hmEH-V79 cells was responsible for the protection against styrene 7,8-oxide genotoxicity. On the other hand, no protective effect of epoxide hydrolase expression could be observed on ethylene oxide-induced DNA damage with the recombinant cell line over a dose range of 0.5-2.5 mM ethylene oxide. This selectivity of the protective effect on epoxide genotoxicity thus appears to be an important factor that must be taken into account for the prediction of the genotoxic risk of epoxides themselves or compounds that can be metabolically activated to epoxides.
Environ Mol Mutagen 1997
PMID:Recombinant expression of human microsomal epoxide hydrolase protects V79 Chinese hamster cells from styrene oxide- but not from ethylene oxide-induced DNA strand breaks. 943 84

A full-length cDNA encoding for a microsomal juvenile hormone (JH)-metabolizing epoxide hydrolase (TmEH-1) was isolated from a cDNA library constructed from fat body of last stadium (wandering) cabbage loopers, Trichoplusia ni, at the exact developmental time of maximum JH epoxide hydrolase activity. TmEH-1 was 1887 base pairs in length with a 1389 base pair open reading frame encoding 463 amino acids. Amino acid sequence analysis showed that TmEH-1 was most similar to and contained the exact catalytic triad (Asp-226, Glu-403 and His-430) found in microsomal epoxide hydrolases. TmEH-1-specific message was present along with JH III epoxide hydrolase activity in fat body in feeding (days 1 and 2) and wandering (day 3) larvae with the peak in message level preceding the peak in JH epoxide hydrolase activity by 1 day. When TmEH-1 was expressed in baculovirus-infected Spodoptera frugiperda cells, a 46,000 molecular weight protein appeared on SDS-PAGE which corresponded to the predicted size coded by the TmEH-1 message and which was positively correlated with increases in JH III epoxide hydrolase activity above that of wild-type controls. In subcellular distribution studies, 58% of the juvenile hormone III epoxide hydrolase activity was in the insoluble fractions. Baculovirus expressed TmEH-1 demonstrated a higher specific activity for JH III as compared to the general EH substrates, cis- and trans-stilbene oxide. Southern blot analyses suggested that multiple epoxide hydrolase genes are present in T. ni.
Insect Mol Biol 1999 Feb
PMID:Cloning and expression of a novel juvenile hormone-metabolizing epoxide hydrolase during larval-pupal metamorphosis of the cabbage looper, Trichoplusia ni. 992 77

The Bacillus subtilis sigW gene encodes an extracytoplasmic function (ECF) sigma factor that is expressed in early stationary phase from a sigW-dependent autoregulatory promoter, PW. Using a consensus-based search procedure, we have identified 15 operons preceded by promoters similar in sequence to PW. At least 14 of these promoters are dependent on sigma W both in vivo and in vitro as judged by lacZ reporter fusions, run-off transcription assays and nucleotide resolution start site mapping. We conclude that sigma W controls a regulon of more than 30 genes, many of which encode membrane proteins of unknown function. The sigma W regulon includes a penicillin binding protein (PBP4*) and a co-transcribed amino acid racemase (RacX), homologues of signal peptide peptidase (YteI), flotillin (YuaG), ABC transporters (YknXYZ), non-haem bromoperoxidase (YdjP), epoxide hydrolase (YfhM) and three small peptides with structural similarities to bacteriocin precursor polypeptides. We suggest that sigma W activates a large stationary-phase regulon that functions in detoxification, production of anti-microbial compounds or both.
Mol Microbiol 1999 Jan
PMID:Identification of target promoters for the Bacillus subtilis extracytoplasmic function sigma factor, sigma W. 998 36


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