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T Cresteil

Publications and source records attributed to T Cresteil.

At least 55 records · Page 3Linked to original sources
PubMed1989

Induction of drug-metabolizing enzymes in Gunn rat liver. Effect of polycyclic aromatic hydrocarbons on cytochrome P-450 regulation.

Response of congenitally jaundiced rats (Gunn rats) to administration of polycyclic aromatic hydrocarbons (PAH) was investigated and compared to that of Wistar rats. Unlike Wistar, Gunn males did not exhibit changes in the overall cytochrome P-450 content of hepatic microsomes. The first step in the induction process (i.e. presence of cytosolic receptors for PAH) was found present and functionally similar (number of sites, Kd) to that of Wistar rats from which the Gunn strain is derived. An increase in monooxygenase activities related to P-450c and P-450d isoenzymes specifically induced by PAH was noticed, whereas no effect could be detected on the glucuronidation rate of either 4-nitrophenol, testosterone or estrone. As determined by immunoquantification after Western blotting, the isoenzymatic profile of P-450 from PAH-treated male Gunn rats showed an increase of P-450c and P-450d accompanied by an equivalent decrease in P-4502c (major male-specific isoenzyme). The balance between increase in P-450c and P-450d and decrease in P-4502c may explain the absence of increase in the total P-450 in PAH-treated male Gunn rats. Such a response was not observed in PAH-treated male Wistar rats or in female rats of both strains. In contrast, the response of male Gunn rats to PB treatment was similar to that observed in Wistar rats, i.e. increase in overall cytochrome P-450 content of hepatic microsomes and of specific isoenzyme P-450b/e. A possible regulation of P-450 isoenzyme synthesis by the intracellular haem pool might be involved.

Animals↗
PubMed1989

Ontogeny and regulation of drug metabolism in humans. Phase I: Monooxygenases.

Most data concerning the development and regulation of cytochrome P-450-dependent monooxygenases were obtained in experimental animals, especially rats, by two successive approaches: first, the assay of total liver cytochrome P-450 and of related monooxygenase activities; then, more recently, the immunoquantification of molecular forms of cytochrome P-450, and the estimation of corresponding mRNAs with nucleic acid probes. Results were compared, before and after birth, in untreated animals, and in animals treated by inducers, mainly phenobarbital and polycyclic aromatic hydrocarbons. For evident ethical reasons, fewer data could be obtained in human liver during development. However, the availability of specific antibodies and nucleic acid probes recently allowed some progress in the comparison of the isoenzyme pattern of cytochromes P-450 in fetal and adult human liver.

Aging↗
PubMed1988

Expression of cytochrome P-450 isozymes in the liver of hypophysectomized rats. Evidence for different regulation mechanisms concerning P450IIB and P450IIIA subfamilies.

1. Monooxygenase activities have been examined in rat liver to determine the effects of castration and hypophysectomy on cytochrome P-450 species. In adult males, hypophysectomy caused a decrease of total P-450 concentration, aniline hydroxylase, benzopyrene hydroxylase, benzphetamine demethylase, testosterone hydroxylase and imipramine hydroxylase and demethylase activities. The treatment of hypophysectomized animals with human growth hormone or testosterone did not restore the full activity. 2. When probed with antibodies, microsomes from hypophysectomized males and females exhibited an intense reaction with a polyclonal anti-(phenobarbital-induced P-450) which was not observed with a monoclonal antibody of anti-(phenobarbital-induced P-450). 3. These microsomal preparations also reacted with an antibody raised against a developmentally regulated P-450. No sex difference could be detected with this antibody. Furthermore, administration of human growth hormone to hypophysectomized males prevented this immunoreaction. 4. Total RNA has been prepared from the same liver; when probed with cDNAs, no changes occurred in the content in P-450 b/e, PB 24 (a constitutive member of the phenobarbital subfamily) and phenobarbital-inducible mRNA for UDP-glucuronosyltransferase. 5. In contrast, P-450 mRNA induced by pregnenolone 16 alpha-carbonitrile was modulated by hormonal manipulations: lower in females and castrated males than in intact males, increased in both sexes after hypophysectomy. Treatment of hypophysectomized males with human growth hormone abolished this rise in pregnenolone-16 alpha-carbonitrile-induced P-450 mRNA accumulation. Data collected in this study support the assumption that hypophysectomy acts differently on the regulation of various P-450 isozymes and that this regulation clearly does not involve the phenobarbital subfamily of P-450s.

Aniline Hydroxylase↗
PubMed1988

Enhancing effect of a phorbol ester and of retinoic acid on glucocorticoid induction of chenodeoxycholate hydroxylation in hepatoma cultures.

In cultures of the differentiated clones Faza 967, Fao and HF, derived from Reuber hepatoma, physiological doses of glucocorticoid induce chenodeoxycholate 6 beta-hydroxylation, a microsomal cytochrome-P-450-mediated activity (enhanced in liver by phenobarbital and not by benzo[a]anthracene). Whereas 12-O-tetradecanoylphorbol 13-acetate (TPA) alone has no effect the tumor promoter, when added to dexamethasone, enhances this induction. This enhancement, half-maximum with 10 ng/ml TPA, is a function of the dose between 1 ng/ml and 50 ng/ml; 50 ng/ml (80 nM) increase 4-7-fold the induction rate (as measured in cultures by the amount of bile acid hydroxylated per 10(6) cells in 24 h, and in homogenates from treated cells) and 2.5-fold the maximum activity attained by the third day of induction. When added to cultures of the dedifferentiated clone H5, treated with benzo[a]anthracene, TPA does not influence benzo[a]pyrene hydroxylase induction, as shown by the total and relative amounts of the various hydrosoluble benzo[a]pyrene metabolites. TPA does not affect tyrosine aminotransferase induction in dexamethasone-treated Fao cultures. The enhancement is not suppressed by indomethacin, an inhibitor of prostaglandin synthesis. After dexamethasone removal from induced Faza 967 cultures, addition of TPA to the medium does not affect the decay rate of the chenodeoxycholate-hydroxylating activity. Retinoic acid similarly enhances the induction by dexamethasone of chenodeoxycholate hydroxylation, both in treated Faza 967 cultures and in homogenates from treated cultures. The effects of TPA and retinoic acid are additive. These results suggest a possible cooperation at the transcriptional level between transactive factors, involving TPA-mediated alterations, retinoic acid and glucocorticoid receptors. The system described might provide a convenient experimental approach in the study of its mechanism.

Animals↗
PubMed1988

Transplacental induction of cytochromes P-450IA1 and P-450IA2 by polycyclic aromatic carcinogens: TCDD-binding protein level as the rate-limiting step.

Induction of cytochromes P-450c and P-450d have been compared in fetal and adult rat liver. A single dose of 3-methylcholanthrene (MC) 16 h before death, resulted in a pronounced accumulation of both mRNAs in adult liver. In contrast, treatment of fetuses with a single dose of MC did not increase the hepatic content in P-450c and P-450d mRNAs, whereas a 3-day treatment gave rise to a considerable accumulation of mRNAs. The fetal rat liver content in 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD)-binding protein was extremely low compared to the adult content. Pretreatment of fetuses with phenobarbital potentiated the inducing effect of MC upon P-450c and P-450d mRNA accumulation in relation to the duration of pretreatment, as well as increasing the hepatic content in TCDD-binding protein. Data strongly suggest that the hepatic TCDD-binding protein level is the rate-limiting step in MC induction of P-450c and P-450d in fetal but not in adult rat liver. In addition, phenobarbital and MC are potent inducers of the TCDD-binding protein in the fetal rat liver.

Animals↗
PubMed1987

Transcriptional control of human cytochrome P1-450 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin in human tissue culture cell lines.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces aryl hydrocarbon hydroxylase (AHH) activity and human cytochrome P1-450 mRNA in the human breast carcinoma MCF-7 and hepatoblastoma HepG2 tissue culture cell lines. Although AHH activities induced by 100 nM TCDD are comparable in these cell lines, the EC50 values for TCDD differ: EC50 approximately equal to 1 nM for HepG2; EC50 greater than 20 nM for MCF-7. In order to determine the mechanism responsible for this difference in EC50, we have examined putative regulatory factors such as the intracellular TCDD receptor as well as the kinetics of mRNA transcription and accumulation in these cells. TCDD increases transcription of hP(1)450 mRNA in both MCF-7 and HepG2 cells; however, MCF-7 cells require higher concentrations of TCDD to produce transcriptional activation comparable to that observed for HepG2 cells. These data indicate that the difference in EC50 is determined at an early step in the induction of hP(1)450 mRNA. With the use of a sensitive assay based on high-performance anion-exchange liquid chromatography, an intracellular protein which binds TCDD with high affinity was detected in HepG2 cytosolic fractions but not in MCF-7 cells. Thus, the difference in EC50 for TCDD can be correlated to the differences in TCDD binding. We postulate that MCF-7 cells contain a "defective" receptor with decreased affinity for TCDD.

Aryl Hydrocarbon Hydroxylases↗
PubMed1986

Cytochrome P-450 isoenzyme content and monooxygenase activities in rat liver: effect of ontogenesis and pretreatment by phenobarbital and 3-methylcholanthrene.

The overall cytochrome P-450 content and the immunochemically determined concentrations of constitutive isoenzymes UT-A and UT-I and isoenzymes induced by phenobarbital (PB-B), pregnenolone 16 alpha-carbonitrile (PCN-E), beta-naphthoflavone (BNF-B) and isosafrole (ISF-G) were investigated in liver microsomes from developing rats and tentatively correlated with mono-oxygenase activities. In fetuses of untreated rat, although the cytochrome P-450 was easily quantified spectrally, none of the isoenzymes tested could be immunochemically detected. After birth, each isoenzyme develops in untreated animals with its own pattern of evolution. Mono-oxygenase activities exhibited different developmental pictures. Benzphetamine-N-demethylase and lauric acid 11-hydroxylase activities progressively increased up to adult values, aniline hydroxylase activity was maximal in 15-day-old animals and benzopyrene hydroxylase and lauric acid 12-hydroxylation were increased after birth until 15 days of age in both males and females and underwent a second increase in males. Pretreatment with phenobarbital resulted in the precocious onset of PB-B in fetal and neonatal rat liver accompanied by an increase in classically associated monooxygenase activities. The PCN-E concentration was enhanced by phenobarbital pretreatment only at 15 days and in older animals. BNF-B and benzo(a)pyrene hydroxylase activity were significantly increased by 3-methylcholanthrene whatever the age considered, whereas this inductive effect upon ISF-G concentration became effective only after 2 weeks of age. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis, UT-A was faint in early neonates and intensified at 15 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Aniline Compounds↗
PubMed1985

Immunoquantification of epoxide hydrolase and cytochrome P-450 isozymes in fetal and adult human liver microsomes.

Epoxide hydrolase and three cytochrome P-450 isozymes were immunochemically determined in microsomes from adult and fetal human liver and tentatively correlated with some enzyme activities. The P-450 isozymes 5, 8 and 9 present in adult liver could not be positively correlated with the total cytochrome P-450 concentration spectrophotometrically determined. In fetal liver microsomes, isozyme 8 could not be detected by either electrophoretic or immunochemical procedures. Isozyme 5 was the major isozyme present in the fetal liver and its concentration increased in close relation with the total P-450 level. As shown previously, arylhydrocarbon hydroxylase activity was related to the concentration of isozyme 8 in adult liver. In fetal preparations, the absence of isozyme 8 was associated with a very low arylhydrocarbon hydroxylase activity. Aldrin epoxidase and benzphetamine-N-demethylase activities were correlated with isozyme 5 concentration, but with different slopes for adult and fetal microsomes: adult preparations catalyzed these two reactions more efficiently. Conversely, the dehydroepiandrosterone 16 beta-hydroxylase, also associated with isozyme 5 concentration, was more active in fetal than in adult microsomes. Moreover, if acetanilide hydroxylase increased with isozyme 5 concentration in adult samples, no correlation occurred between activity and P-450 isozyme level in fetal microsomes. Hydroxylations of lauric acid in positions 11 and 12 and of dehydroepiandrosterone in position 16 alpha increased with total P-450 concentration but not with isozyme concentrations whatever the age considered. Lastly, epoxide hydrolase activity towards benzopyrene 4,5-oxide was closely associated with its immunochemically determined level. These results clearly suggest that multiple mechanisms are involved in the regulation of different drug-metabolizing enzymes in the human fetus.

Aging↗
PubMed1984

Induction by 9-hydroxyellipticine of aryl hydrocarbon hydroxylase in perinatal rat liver and in primary fetal hepatocytes in culture.

In neonatal and, to a lesser extent, in fetal rat liver, 9-hydroxyellipticine was able to promote the induction of cytochrome P-450, supporting especially aryl hydrocarbon hydroxylase (AHH) but not aldrin epoxidase activity. The examination of benzopyrene metabolites by high performance liquid chromatography (HPLC) or by benzopyrene-DNA adducts formation shown that, as in adult animals, the formation of hydroxylated metabolites in position 9,10 was enhanced. In primary fetal liver cells culture, similar effects were observed. Furthermore, the presence of glucocorticoids in the culture medium was not required for the induction of AHH by 9-hydroxyellipticine (9-OHE).

Alkaloids↗
PubMed1984

A dual assay for the specific screening of 3-methylcholanthrene- and phenobarbital-like chemical inducers of cytochrome P-450 monooxygenases.

We present and evaluate a dual assay, the CYPIA (Cytochrome P-450 induction assay) for the detection and the simultaneous identification of chemicals belonging either to the 3-methylcholanthrene or phenobarbital classes of cytochrome P-450 monooxygenase inducers. These inducers play an important role in the mutagenic activation of chemical compounds as well as in many pharmacological and toxicological events and therefore should be screened by drug and chemical designers. After treatment of male rats or mice by chemicals, the liver preparations (S9) have been used in the Salmonella typhimurium test, to activate either ethidium bromide or cyclophosphamide into mutagenic metabolites. These transformations are specifically catalyzed by cytochrome P-450-dependent monooxygenases induced by 3-methylcholanthrene-like and phenobarbital-like chemical inducers, respectively. The mutagenicity data were strikingly correlated with other methods (production of [3H]benzo[a]pyrene bay-region metabolites, benzphetamine demethylase activity, immunological double-diffusion analysis). Compared to the latter methods, the CYPIA, based on a single and widespread technology, introduces an interesting simplification, and improves the specificity and the sensitivity of the responses.

Animals↗
PubMed1983

Evaluation of isolated human hepatocytes.

This preliminary study reports the functional capacities of freshly isolated human hepatocytes in regard to their energetic metabolism and monooxygenase activities. Incubated for 30 or 60 min, isolated cells maintain their membrane integrity, ATP and reduced glutathione content and redox potential estimated by means of lactate to pyruvate and beta-hydroxypyruvate to acetoacetate ratios. Three monooxygenase activities, supported by different isoenzymes of cytochrome P-450 are determined by the accumulation of unconjugated metabolites: their relative magnitudes are similar to those observed in microsomes, indicating a good preservation of hydroxylase activities during cell isolation and incubation. Although incubations did not exceed 60 min, one can conclude that human hepatocytes maintain their viability and metabolic capacities after isolation and might be considered in transplantation process for the treatment of acute hepatic failure. Isolated human hepatocytes might be also used as a tool for studying biochemical and toxicological effects of a drug.

Adolescent↗
PubMed1983

Immunological and enzymatic comparison of hepatic cytochrome P-450 fractions from phenobarbital-, 3-methylcholanthrene-, beta-naphthoflavone- and 2,3,7,8- tetrachlorodibenzo-p-dioxin-treated rats.

A comparison of the cytochrome P-450 forms induced in rat liver microsomes by phenobarbital on the one hand, and 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin on the other hand, was performed using specific antibodies: anti-P-450 B2 PB IG (against the phenobarbital-induced cytochrome P-450) and anti-P-450 B2 BNF IG (against the beta-naphthoflavone-induced cytochrome P-450). On DEAE-cellulose chromatography, four cytochrome P-450 fractions were separated, called P-450 A (non-adsorbed), P-450 Ba, P-450 Bb and P-450 Bc, from control, phenobarbital-, 3-methylcholanthrene, beta-naphthoflavone- and 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated rats. Cytochrome P-450 A fractions appeared to be unmodified by the inducers, whereas the specifically induced cytochrome P-450 forms were always recovered in Bb fractions. The P-450 Bb fractions induced by 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin exhibited common antigenic determinants, comparable catalytic activities (benzphetamine N-demethylase, benzo[a]pyrene hydroxylase) and similar mol. wts. Moreover, the inhibition patterns by the two antibodies of benzphetamine N-demethylase and benzo[a]pyrene hydroxylase activities catalysed by 3-methylcholanthrene, beta-naphthoflavone and 2,3,7,8-tetrachlorodibenzo-p-dioxin microsomes or by the corresponding P-450 Bb fractions in a reconstituted system were quite identical. By these different criteria, beta-naphthoflavone, 3-methylcholanthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin seem to induce a common cytochrome P-450 species in rat liver.

Animals↗
PubMed1983

Enhancement of DNA binding, mutagenicity and carcinogenicity of polycyclic aromatic hydrocarbons after induction of cytochrome P-450 by ellipticines in rats and mice.

Pretreatment of rats by ellipticines enhanced the microsomal concentration of cytochrome P-450, benzo[alpha]pyrene (BP) metabolism and activation and, a smaller extent, ethoxycoumarin deethylation, but not acetanilide hydroxylation. This increased BP biotransformation was essentially due to the formation of bay-region metabolites, BP 9,10-diol, BP 7,8-diol and 9-hydroxy-BP, or to the formation of BP 7,8-diol-9,10-epoxide- and of 9-hydroxy-BP 4,5-oxide-DNA adducts. In the ellipticine series, 9-fluoroellipticine (9-FE) presents a slight inducing potency compared with the parent and 9-hydroxy molecules. Pretreatment of mice with 9-hydroxyellipticine (9-OHE) led also to an increased mutagenicity of BP and to an augmentation of skin carcinogenesis by 7,12-dimethylbenz[alpha]anthracene (DMBA). These results clearly show that 9-OHE induces the biosynthesis of cytochrome P-450 which markedly stimulates the mutagenic and carcinogenic potentialities of polycyclic aromatic hydrocarbons (PAH).

Alkaloids↗
PubMed1983

Induction of drug-metabolizing enzymes by tricyclic antidepressants in human liver: characterization and partial resolution of cytochromes P-450.

Drug-metabolizing enzyme activities were determined in liver microsomes from six kidney-transplant donors, one tricyclic antidepressant-treated and five untreated donors. The tricyclic antidepressant treatment modifies neither the overall cytochrome P-450 content of the liver, nor enzymatic activities of 4-nitroanisole demethylase, aniline hydroxylase, epoxide hydrolase and glutathione S-transferase. Only benzphetamine and ketotifen demethylation and conjugation of bilirubin with UDP-glucuronic acid are markedly augmented (more than two-fold). Separation of the different cytochrome P-450 fractions on a DEAE cellulose column indicates a modification of the elution pattern: the fraction increased by tricyclic antidepressants is responsible for the enhanced monooxygenase activity towards benzopyrene and benzphetamine.

Adult↗