Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), one of the most abundant of the heterocyclic aromatic amines formed during the cooking of meat, is genotoxic and carcinogenic in rodents. MeIQx requires metabolic activation by P450 before it can exert these effects. Whilst there is indirect evidence that the mutagenic product is N-hydroxy-MeIQx (N-OHMeIQx), we have now identified this unequivocally following incubation of the amine with human hepatic microsomal fraction. A mixture of unlabelled MeIQx, [13C,15N2]MeIQx and [14C]MeIQx was used as substrate and the products analysed by HPLC-thermospray mass spectrometry. Characteristic doublet ions, 3 mass units apart, were found at m/z 214/217 ([M+H]+) from the parent compound, MeIQx and at 230/233 ([M+H]+) from N-OHMeIQx. The presence of a doublet ion at m/z 214/217 with the doublet at 230/233 [M+H+] provided additional evidence that this was N-OHMeIQx, as facile loss of 'O' is characteristic of N-hydroxylamines. Further evidence for the identity of the major metabolite, which accounted for approximately 90% of all microsomal metabolism, was obtained by comparing the mutagenicity of the HPLC eluate using Salmonella typhimurium YG1024, which is particularly sensitive to N-hydroxylamines, and TA98/1,8-DNP6 which is resistant to most N-hydroxylamines. Ninety-five per cent of direct-acting mutagenicity present in the reaction mixture was associated with a single peak, which co-eluted with N-OHMeIQx, as indicated by mass spectrometry. In the presence of a metabolic activation system, only one additional mutagenic peak, corresponding to unchanged MeIQx, could be detected. MeIQx (5 microM) was N-hydroxylated at a rate of 77 +/- 11 pmol/mg/min (mean +/- SEM, n = 4) by human liver microsomes. The specific inhibitor of human CYP1A2, furafylline (5 microM) inhibited the N-hydroxylation of MeIQx by > 90%. These data show that N-OHMeIQx is both the major oxidation product and the major genotoxic product of MeIQx generated by microsomal fractions of human liver and that the reaction is catalysed almost exclusively by CYP1A2.
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PMID:N-hydroxy-MeIQx is the major microsomal oxidation product of the dietary carcinogen MeIQx with human liver. 147 28

Dapsone toxicity is putatively initiated by formation of a hydroxylamine metabolite by cytochromes P450. In human liver microsomes, the kinetics of P450-catalyzed N-oxidation of dapsone were biphasic, with the Michaelis-Menten constants of 0.14 +/- 0.05 and 0.004 +/- 0.003 mmol/L and the respective maximum velocities of 1.3 +/- 0.1 and 0.13 +/- 0.04 nmol/mg protein/min (mean +/- SEM). Troleandomycin (40 mumol/L) inhibited hydroxylamine formation at 100 mumol/L dapsone by 50%; diethyldithiocarbamate (150 mumol/L) and tolbutamide (400 mumol/L) inhibited at 5 mumol/L dapsone by 50% and 20%, respectively, suggesting that the low-affinity isozyme is CYP3A4 and the high-affinity isozymes are 2E1 and 2C. Disulfiram, 500 mg, 18 hours before a 100 mg oral dose of dapsone in healthy volunteers, diminished area under the hydroxylamine plasma concentration-time curve by 65%, apparent formation clearance of the hydroxylamine by 71%, and clearance of dapsone by 26%. Disulfiram produced a 78% lower concentration of methemoglobin 8 hours after dapsone.
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PMID:Metabolism of dapsone to its hydroxylamine by CYP2E1 in vitro and in vivo. 758 50

Metabolic activity of a gel-entrapment, hollow fiber, bioartificial liver was evaluated in vitro and during extracorporeal hemoperfusion in an anhepatic rabbit model. The bioartificial liver contained either 100 million rat hepatocytes (n = 12), fibroblasts (n = 3), or no cells (n = 7) during hemoperfusion of anhepatic rabbits. Eight other anhepatic rabbits were studied without hemoperfusion as anhepatic controls, and three sham rabbits served as normal controls. Albumin production rates (mean +/- SEM) were similar during in vitro (17.0 +/- 2.8 micrograms/h) and extracorporeal (18.0 +/- 4.0 micrograms/h) application of the hepatocyte bioartificial liver. Exogenous glucose requirements were reduced (p < 0.01) and euglycemia was prolonged (p < 0.001) in anhepatic rabbits treated with the hepatocyte bioartificial liver. The maximum rate of glucose production by the hepatocyte bioartificial liver ranged from 50-80 micrograms/h. Plasma concentrations of aromatic amino acids, proline, alanine, and ammonia were normalized in anhepatic rabbits during hepatocyte hemoperfusion. Gel-entrapped hepatocytes in the bioartifical liver performed sulfation and glucuronidation of 4-methylumbelliferone. P450 activity was demonstrated during both in vitro and extracorporeal application of the BAL device by the formation of 3-hydroxy-lidocaine, the major metabolite of lidocaine biotransformation by gel-entrapped rat hepatocytes. In summary, a gel-entrapment, bioartificial liver performed multiple hepatocyte-specific functions without adverse side effects during extracorporeal application in an anhepatic, small animal model. With its potential for short term support of acute liver failure, scale-up of the current bioartificial liver device is indicated for further investigations in large animal, preclinical trials.
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PMID:Extracorporeal application of a gel-entrapment, bioartificial liver: demonstration of drug metabolism and other biochemical functions. 816 29

Omeprazole, a proton pump inhibitor, is used in the treatment of gastrointestinal diseases associated with hyperacidity. It binds to, and inhibits, some of the activities of hepatic cytochrome P450 resulting in increased half-lives of certain pharmacologic and endogenous compounds. It may also increase the activity of cytochrome P450 under certain conditions. Oxidative metabolism of endogenous estrogens, particularly the 2-hydroxylation pathway, is P450-dependent, and is highly sensitive to a variety of dietary and pharmacologic agents. We therefore studied the extent of estradiol 2-hydroxylation in 7 normal male volunteers before and during oral treatment with omeprazole 20 mg twice daily. Using a specific in vivo radiometric assay, the mean extent (+/- SEM) of estradiol 2-hydroxylation was found to be unchanged before and after omeprazole treatment (27.3 +/- 3.0 vs. 27.5 +/- 3.4%, respectively). The excretion of the endogenous urinary estrogen metabolites, 2-hydroxyestrone, estriol, and estrone was also unaltered by omeprazole. These results show that omeprazole, in contradistinction to other medications used in the treatment of peptic ulcer disease, is without effect on estradiol metabolism in men.
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PMID:Omeprazole fails to alter the cytochrome P450-dependent 2-hydroxylation of estradiol in male volunteers. 833 35

Big Blue (BB) and generic B6C3F1 mice were given one to three i.p. injections of 50 mg/kg benzo[a]pyrene (B[a]P) in DMSO every other day to achieve cumulative doses of 50 to 150 mg/kg. Three weeks after treatment, the mutation frequency at the endogenous hprt gene and lacI transgene was measured in splenic T cells. Generic mice given 50, 100, and 150 mg/kg B[a]P displayed induced hprt frequencies (observed hprt frequency minus control frequency) of 5.5 +/- 1.0, 11 +/- 2.0, and 19 +/- 2.6 x 10(-6), respectively (average +/- SEM). In contrast, BB mice given 50 and 150 mg/kg B[a]P displayed induced hprt frequencies of 0.9 +/- 0.6 and 9.1 +/- 1.5 x 10(-6). 32P postlabelling revealed that the lower hprt response in BB mice correlated with lower amounts of BP-DNA adducts in spleen, liver, and lung 24 hours after B[a]P exposure. Western blot analysis of liver samples from B[a]P-treated mice suggests that the reduced adduct load in turn may be due to lower P450 1A1 levels in BB mice. The frequency of induced, nonsectored blue plaques (observed blue plaque frequency minus control frequency) in BB mice receiving 50 and 150 mg/kg B[a]P was 41 +/- 9 and 134 +/- 10 x 10(-6) (15- to 40-fold higher than the induced hprt frequency in the same treated animals). Sectored plaques were observed in both control and B[a]P groups but their frequency showed no relationship to dose (sectored frequency in all groups was approximately 20 x 10(-6)). To test whether persistent DNA adducts in the packaged lambda vector were contributing to the observed blue plaque frequency, purified lambda-LIZ DNA was treated in vitro with B[a]P diol epoxide (BPDE), packaged, and plated on E. coli lawn cells. Treatment with BPDE did not produce significant increases in homogeneous blue plaques, suggesting that the majority of mutants obtained from B[a]P-treated BB mice occurred in vivo. These results indicate that B[a]P exposure produces many more mutations at the lacI transgene than at the endogenous hprt locus.
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PMID:Mutagenic response of the endogenous hprt gene and lacI transgene in benzo[a]pyrene-treated Big Blue B6C3F1 mice. 899 Oct 66

The objective of this study was to investigate changes in expression of mRNAs encoding FSH receptor (FSHr), LH receptor (LHr), cytochrome P450 side-chain cleavage (P450(scc)), cytochrome P450 17alpha-hydroxylase (P450(c17)), and cytochrome P450 aromatase (P450(arom)) during recruitment and selection of bovine ovarian follicles. Dairy heifers (4-5 per group) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, or 96 h after initiation of the first follicular wave following estrus as determined by ultrasonography (Time 0 = initiation of follicular wave; mean +/- SEM = 42.0 +/- 2.6 h after estrus). Expression of mRNAs encoding FSHr, LHr, P450(scc), P450(c17), and P450(arom) was detected by in situ hybridization and quantified by image analysis. Antral follicles were classified as healthy or atretic. Healthy follicles expressed higher (p < 0.01) amounts of mRNAs for gonadotropin receptors and steroidogenic enzymes than did atretic follicles, and expression of LHr, FSHr, P450(scc), P450(c17), and P450(arom) increased (p < 0.01) with follicular size and stage of the follicular wave. Expression of mRNAs for P450(scc), P450(arom), and LHr was time- and size-dependent during recruitment and selection. During recruitment, expression of mRNAs for P450(scc) and P450(arom) was first detected in granulosa cells of 16 of 21 of the follicles 4-6 mm in diameter at 12 h. At 24 and 36 h, almost all follicles 6-9 mm in diameter, but not those 4-5 mm in diameter, expressed both P450(scc) and P450(arom) mRNA in the granulosa cells. At 48 h and thereafter, P450(scc) and P450(arom) mRNA were expressed predominantly in one healthy large follicle per cow with a few exceptions. Expression of LHr mRNA was first detected in granulosa cells at 36 h and was always found in granulosa cells of one follicle > or = 8 mm per cow with exception of one cow at 36 h (no expression) and another two cows, one each at 36 and at 84 h (expression in 2 follicles). In addition, LHr mRNA expression in the granulosa cell layer was limited to follicles that also expressed mRNAs for P450(scc) and P450(arom) in the granulosa cells. In summary, follicular recruitment in cattle was associated with expression of P450(scc) and P450(arom) mRNA within granulosa cells, and the process of follicular selection was associated with initiation of LHr mRNA expression in granulosa cells.
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PMID:Changes in messenger ribonucleic acid encoding luteinizing hormone receptor, cytochrome P450-side chain cleavage, and aromatase are associated with recruitment and selection of bovine ovarian follicles. 916 Jul 14

Historically, catecholamine-producing chromaffin cells and steroid-producing adrenocortical cells have been regarded as two independent endocrine systems that are united under a common capsule to form the adrenal gland. There is increasing evidence for bidirectional interactions, with regulatory influences of adrenocortical secretory products on adrenomedullary functions and vice versa. However, the direct involvement of chromaffin cells on the regulation and maintenance of cortical function has not yet been demonstrated. Therefore, we analyzed glucocorticoid secretion and P450 messenger RNA (mRNA) expression in bovine adrenocortical cells in cocultures with chromaffin cells compared with those in pure cortical cell cultures. Cortisol release from cortical cells in coculture with chromaffin cells was 10 times as high (mean +/- SEM, 1035 +/- 119%) as that from the same number of isolated cortical cells (100 +/- 11%). By a [3H]thymidine incorporation assay, it was demonstrated that this effect was not due to a higher proliferation rate. Northern analysis revealed an increasing expression of P450(17alpha) mRNA in the coculture from days 1-5, whereas in isolated cortical cells, P450(17alpha) mRNA decreased, leading to a 6-fold difference on day 5. Inhibitors of protein (cycloheximide) or RNA (actinomycin D) synthesis completely annulled the observed increase in cortisol release, indicating that de novo protein synthesis is required for this activation of adrenocortical steroidogenesis. Addition of the cyclooxygenase inhibitor indomethacin reduced the stimulatory effect, suggesting that this stimulation is in part mediated by PGs. Locally produced ACTH, catecholamines, and interleukin-1 accounted for 43% of the effect. Secretory products of chromaffin cells that act in concert are believed to be responsible for the stimulation of steroidogenesis in the coculture. The coculture system is an in vitro model that corresponds to the in vivo situation in the intact adrenal gland, where both endocrine cell systems are in close contact. Our data demonstrate the requirement of intraadrenal cellular communication for the full strength of the adrenocortical hormonal response.
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PMID:Basal steroidogenic activity of adrenocortical cells is increased 10-fold by coculture with chromaffin cells. 944 52

A culture system has been designed in which enzymatically isolated oocyte-granulosa cell complexes from fresh and frozen-thawed ovine ovarian tissue can be grown to antral size in vitro. Oocyte-granulosa complexes ranging from 100 to 240 microns in diameter were dissected from stromal tissue and grown individually in serum-free medium for 30 days. Complexes < 190 microns generally excluded their oocytes or lost three-dimensional structure early in the culture period. In contrast, complexes isolated from fresh or frozen-thawed tissue and measuring 190-240 microns on the day of isolation formed antral cavities in 25 +/- 9% and 18 +/- 6% (mean +/- SEM) of cases, respectively. The effect of gonadotrophin supplementation to the culture medium was tested on frozen-thawed oocyte-granulosa cell complexes only. In cultures supplemented with both FSH and LH or FSH alone, there was no significant difference in the number of oocyte-granulosa cell complexes that formed antral cavities (18 +/- 7%). However, antrum formation was significantly less frequent in cultures lacking gonadotrophin stimulation (7 +/- 4%). All oocyte-granulosa cell complexes maintained a three-dimensional structure throughout culture and developed a functional P450 aromatase enzyme complex, as revealed by the induction of oestradiol production during 8 days of culture after antrum formation in serum-free medium containing testosterone. Oocytes recovered after 30 days of culture were viable and had increased in diameter from 78 +/- 2 microns on the day of isolation, to 131 +/- 3 microns at the end of culture. These results show that oocyte-granulosa cell complexes isolated from cryopreserved ovarian tissue can be grown to antral size in vitro with similar efficiency to those isolated from fresh tissue.
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PMID:In vitro growth of oocyte-granulosa cell complexes isolated from cryopreserved ovine tissue. 1034 32

The distinct gender-specific patterns of fat distribution in men and women (android and gynoid) suggest a role for sex steroids. In keeping with these observations, it has been suggested that estrogens can promote preadipocyte cell proliferation and/or differentiation. The enzyme aromatase P450 is responsible for the conversion of androgen precursor steroids to estrogens and may, therefore, have a role in regulating adipose tissue mass and its distribution. We have investigated the glucocorticoid regulation of aromatase expression in human adipose tissue, specifically to define any site- and gender-specific differences. Abdominal subcutaneous (Sc) and omental (Om) adipose tissue was obtained from male and female patients undergoing elective surgery. After collagenase digestion, preadipocytes were cultured in serum-free medium, for 6-10 d, until confluent with either cortisol (10(-6) M, 10(-7) M) or insulin (500 nM) or a combination of both treatments. Adipocytes were studied in suspension cultures. Aromatase activity was assessed using tritiated [1 beta-(3)H]-androstenedione as substrate. In Sc preadipocytes, basal aromatase activity increased in females from 11.5 +/- 1.4 (mean plus minus SEM) to 28.0 +/- 1.8 pmol/mg x h (n = 17, P < 0.05) with 10(-6) M cortisol. By contrast, in males, aromatase activity was inhibited by 10(-6) M cortisol (19.4 +/- 2.4 pmol/mg x h vs. 7.5 +/- 1.3, n = 9, P < 0.01; men vs. women, P < 0.005). These data were endorsed through Western blot analysis using an in-house antihuman aromatase antibody, which recognized a specific 55-kDa species. Aromatase activity was less at Om sites in preadipocytes, increasing in females from 1.1 +/- 0.2 to 3.2 +/- 0.7 pmol/mg x h with 10(-6) M cortisol (P < 0.05) and in males from 2.6 +/- 0.1 pmol/mg x h to 7.8 +/- 0.3 pmol/mg x h after cortisol (men vs. women, P < 0.001). Cortisol-induced aromatase activity in Om adipocytes from postmenopausal females was higher than that in premenopausal females (P < 0.001). Insulin had no independent effect on aromatase expression, but coincubation of preadipocytes with cortisol and insulin eliminated both gender- and site-specific differences. In conclusion, in women, but not men, cortisol increased aromatase activity at Sc sites, and this may facilitate predilection for Sc adiposity in females. The observed site-, gender-, and menopausal-specific differences in the glucocorticoid regulation of this enzyme may contribute to the gender- and menopausal-specific patterns of fat distribution.
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PMID:Glucocorticoid regulation of p450 aromatase activity in human adipose tissue: gender and site differences. 1188 5

Modulation of drug metabolizing enzymes, leading to facilitated elimination of carcinogens represents a successful strategy for cancer chemoprevention. Nitric oxide-donating aspirin (NO-ASA) is a promising agent for the prevention of colon and other cancers. We studied the effect of NO-ASA on drug metabolizing enzymes in HT-29 human colon adenocarcinoma and Hepa 1c1c7 mouse liver adenocarcinoma cells and in Min mice treated with NO-ASA for 3 weeks. In these cell lines, NO-ASA induced the activity and expression of NAD(P)H:quinone oxireductase (NQO) and glutathione S-transferase (GST). Compared with untreated Min mice, NO-ASA increased in the liver the activity (nmol/min/mg; mean+/-SEM for all) of NQO (85+/-6 versus 128+/-11, P<0.05) and GST (2560+/-233 versus 4254+/-608, P<0.005) and also in the intestine but not in the kidney; the expression of NQO1 and GST P1-1 was also increased. NO-ASA had only a marginal effect on P450 1A1 and P450 2E1, two phase I enzymes. The release of NO from NO-ASA, determined with a selective microelectrode was paralleled by the induction of NQO1 and abrogated by NO scavengers; an exogenous NO donor also induced the expression of NQO1. NO-ASA induced concentration-dependently the translocation of Nrf2 into the nucleus as documented by immunofluorescence and immunoblotting; this paralleled the induction of NQO1 and GST P1-1. Thus NO-ASA induces phase II enzymes, at least in part, through the action of NO that it releases and by modulating the Keap1-Nrf2 pathway; this effect may be part of its mechanism of action against colon and other cancers.
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PMID:NO-donating aspirin induces phase II enzymes in vitro and in vivo. 1626 95


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