The covalent binding of cyclosporin a to rat liver macromolecules in vivo and in vitro: The role of cytochrome P-450

We report the analysis of DNA adducts formed from aristolactams I and II, which are the final metabolites derived from carcinogenic aristolochic acids in vivo, after their oxidation by microsomal cytochrome P-450 and horseradish peroxidase in vitro. DNA adducts were detected and quantified using the nuclease P1-enhanced variation of the 32P-postlabeling assay. Quantitative analysis revelead that the extent of modification of DNA by aristolactams activated by peroxidase was more than one order of magnitude higher than for activation by microsomal cytochrome P-450. Peroxidase catalyzes the formation of active oxygen in the presence of NADH, H2O2 and aristolactams. Aristolactams are also oxidized by mammalian peroxidase prostaglandin H synthase. The possible role of aristolactams in carcinogenesis induced by aristolochic acid is discussed.

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Cytochrome P-450-dependent covalent binding of carbon disulfide to rat liver microsomal protein in vitro and its prevention by reduced glutathione

Archives of Toxicology ◽

10.1007/bf00661375 ◽

1987 ◽

Vol 61 (2) ◽

pp. 155-157 ◽

Cited By ~ 3

Author(s):

R. R. Dalvi

Keyword(s):

Rat Liver ◽

Carbon Disulfide ◽

Reduced Glutathione ◽

Covalent Binding ◽

Microsomal Protein ◽

Cytochrome P 450

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In vivo and in vitro effects of a new macrolide antibiotic roxithromycin on rat liver cytochrome P-450: Comparison with troleandomycin and erythromycin

Chemico-Biological Interactions ◽

10.1016/0009-2797(88)90015-4 ◽

1988 ◽

Vol 68 (3-4) ◽

pp. 179-188 ◽

Cited By ~ 26

Author(s):

Marcel Delaforge ◽

Eric Sartori ◽

Daniel Mansuy

Keyword(s):

Rat Liver ◽

Macrolide Antibiotic ◽

Liver Cytochrome ◽

In Vitro Effects ◽

Cytochrome P 450

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The role of cytochrome P-450 in cholesterol biogenesis and catabolism

Biochemical Journal ◽

10.1042/bj1280237 ◽

1972 ◽

Vol 128 (2) ◽

pp. 237-242 ◽

Cited By ~ 30

Author(s):

Sandra D. Atkin ◽

Eileen D. Palmer ◽

P. D. English ◽

B. Morgan ◽

M. A. Cawthorne ◽

...

Keyword(s):

Cholesterol Metabolism ◽

Carbon Disulphide ◽

Normal Serum ◽

Liver Cholesterol ◽

Drug Metabolizing Enzyme ◽

Metabolizing Enzyme ◽

Cytochrome P 450

1. Adjuvant-induced arthritis in rats is accompanied by a loss of activity of the drug-metabolizing enzyme system and a decrease in hepatic cytochrome P-450. 2. Arthritic rats have normal serum and liver cholesterol concentrations. 3. The rate of biogenesis of cholesterol in vivo and in vitro from either [14C]acetate or [14C]mevalonate in arthritic rats was the same as or greater than that found in control rats. 4. Treatment of rats with carbon disulphide (1ml/kg) resulted in a loss of drug-metabolizing-enzyme activity and increased cholesterol biogenesis. 5. The activity of cholesterol 7α-hydroxylase in adjuvant-induced arthritic rats did not differ significantly from that in control rats. 6. Rats fed with cholestyramine had an elevated hepatic cholesterol 7α-hydroxylase activity, but neither the concentration of cytochrome P-450 nor the activity of the drug-hydroxylating enzyme, aminopyrine demethylase, was affected. 7. The relationships between drug hydroxylation and cholesterol metabolism are discussed.

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Phenylhydrazine-mediated induction of haem oxygenase activity in rat liver and kidney and development of hyperbilirubinaemia. Inhibition by zinc-protoporphyrin

Biochemical Journal ◽

10.1042/bj2170409 ◽

1984 ◽

Vol 217 (2) ◽

pp. 409-417 ◽

Cited By ~ 25

Author(s):

M D Maines ◽

J C Veltman

Keyword(s):

Rat Liver ◽

Zinc Protoporphyrin ◽

Serum Total Bilirubin ◽

Potent Inducer ◽

Oxygenase Activity ◽

Liver And Kidney ◽

Haem Oxygenase ◽

Cytochrome P 450

Phenylhydrazine was found to be a potent inducer of microsomal haem oxygenase activity in rat liver and kidney, but not in spleen. The phenylhydrazine-mediated increase in haem oxygenase activity was time-dependent. Maximum activity was attained 12h after treatment in the liver, and 24h after treatment in the kidney. The increases in the activity of haem oxygenase in the liver and the kidney could be inhibited by cycloheximide. Furthermore, the increases could not be elicited by the treatment of microsomal preparations in vitro with phenylhydrazine. In consonance with the increased haem oxygenase activity, a marked increase (16-fold) was observed in the serum total bilirubin concentration in phenylhydrazine-treated rats. The mechanism of haem degradation promoted by phenylhydrazine in vivo appears to differ from that in vitro; only in the former case is bilirubin formed as the end-product of haem degradation. When rats were given zinc-protoporphyrin (40 mumol/kg) 12h before and after phenylhydrazine treatment, the phenylhydrazine-mediated increases in haem oxygenase activity in the liver and the kidney were effectively blocked. Treatment of rats in vivo with the metalloporphyrin also inhibited the activity of splenic haem oxygenase, and promoted a major decrease in the serum bilirubin levels. In phenylhydrazine-treated animals, the microsomal content of cytochrome P-450 was significantly decreased in the absence of a decrease in the microsomal haem concentration. The decrease in cytochrome P-450 content was accompanied by an increased absorption in the 420nm region of the reduced CO-difference spectrum, suggesting the conversion of the cytochrome to an inactive form. The marked depletion of cellular glutathione levels suggests that this conversion may be related to the action of active intermediates and free radicals formed in the course of the interaction of phenylhydrazine with the haem moiety of cytochrome P-450.

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Metabolic activation of acetylenic substituents to derivatives in the rat causing the loss of hepatic cytochrome P-450 and haem

Biochemical Journal ◽

10.1042/bj1740853 ◽

1978 ◽

Vol 174 (3) ◽

pp. 853-861 ◽

Cited By ~ 51

Author(s):

Ian N. H. White

Keyword(s):

Covalent Binding ◽

Metabolic Activation ◽

Microsomal Protein ◽

Significant Loss ◽

Microsomal Cytochrome ◽

Rf Values ◽

Green Pigments ◽

Cytochrome P 450

1. A number of acetylenic-substituted steroidal and non-steroidal compounds, including 2,2-dipropargylacetamide, pregna-2,4-dien-20-yno[2,3-d]isoxazol-17-ol (Danazol) and acetylene gas, when administered to rats in vivo brought about a decrease in the concentrations of hepatic microsomal cytochrome P-450 and haem. Abnormal haem-breakdown products, ‘green pigments’, and porphyrins accumulated in the livers of these animals. 2. For loss of microsomal cytochrome P-450 to occur in vitro, metabolic activation of the acetylenic substituent was necessary. The enzyme system responsible required NADPH and air, and was induced by pretreatment of rats with phenobarbitone; these are characteristics typical of the microsomal mixed-function oxidases. 3. When rats were dosed with 17α-ethynyl-17β-hydroxyandrost-4-en-3-one (ethynyltestosterone, 1mmol/kg) the pattern of green pigments extracted from the liver 4h after dosing and separated by t.l.c. was quite different from that in rats given 17β-hydroxy-17α-vinylandrost-4-en-3-one (vinyltestosterone), suggesting that reduction of the unsaturated triple bond to a double bond is not normally part of the metabolic activation pathway of the acetylenic substituent. 4. The green pigments extracted from the livers of rats 4h after the administration of the acetylenic-substituted compounds (1mmol/kg) when separated by silica-gel t.l.c. had variable RF values. The number and distribution of green pigments was characteristic for each compound examined. There was little correlation between the total loss of hepatic microsomal haem and the apparent intensity of the green pigments seen on the thin-layer chromatograms. 5. After incubation of [14C]acetylene in vitro with microsomal preparations from phenobarbitone-pretreated rats and a NADPH-generating system, no significant covalent binding to microsomal protein was detected over a 30min incubation period, although under similar conditions there was a significant loss of cytochrome P-450.

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Anti-Trypanosoma cruzieffects of cyclosporin A derivatives: possible role of a P-glycoprotein and parasite cyclophilins

Parasitology ◽

10.1017/s003118200700371x ◽

2007 ◽

Vol 135 (2) ◽

pp. 217-228 ◽

Cited By ~ 14

Author(s):

J. BÚA ◽

L. E. FICHERA ◽

A. G. FUCHS ◽

M. POTENZA ◽

M. DUBIN ◽

...

Keyword(s):

Cyclosporin A ◽

Mammalian Cells ◽

Isomerase Activity ◽

P Glycoprotein ◽

Demethylase Activity ◽

Target Molecules ◽

Intracellular Amastigote

SUMMARYCyclophilins are target molecules for cyclosporin A (CsA), an immunosuppressive antimicrobial drug. We have previously reported thein vitroanti-Trypanosoma cruziactivity of H-7-94 and F-7-62 non-immunosuppressive CsA analogues. In this work, we continue the study of the parasiticidal effect of H-7-94 and F-7-62 CsA analoguesin vitroandin vivoand we analyse 3 new CsA derivatives: MeIle-4-CsA (NIM 811), MeVal-4-CsA (MeVal-4) and D-MeAla-3-EtVal-4-CsA, (EtVal-4). The most efficient anti-T. cruzieffect was observed with H-7-94, F-7-62 and MeVal-4 CsA analogues evidenced as inhibition of epimastigote proliferation, trypomastigote penetration, intracellular amastigote development andin vivo T. cruziinfection. This trypanocidal activity could be due to inhibition of the peptidyl prolylcis-transisomerase activity on theT. cruzirecombinant cyclophilins tested. Furthermore, CsA and F-7-62 derivative inhibited the efflux of rhodamine 123 fromT. cruziepimastigotes, suggesting an interference with a P-glycoprotein activity. Moreover, H-7-94 and F-7-62 CsA analogues were not toxic as shown by cell viability and by aminopyrine-N-demethylase activity on mammalian cells. Our results show that H-7-94, F-7-62 and MeVal-4 CsA analogues expressed the highest inhibiting effects onT. cruzi, being promissory parasiticidal drugs worthy of further studies.

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Phenol sulphotransferase and uridine diphosphate glucuronyltransferase from rat liver in vivo and in vitro. 2,6-Dichloro-4-nitrophenol as selective inhibitor of sulphation

Biochemical Journal ◽

10.1042/bj1650553 ◽

1977 ◽

Vol 165 (3) ◽

pp. 553-559 ◽

Cited By ~ 104

Author(s):

Gerard J. Mulder ◽

Egbert Scholtens

Keyword(s):

Rat Liver ◽

Inhibitory Effect ◽

Selective Inhibitor ◽

Biological Processes ◽

Uridine Diphosphate ◽

Duration Of Action ◽

Long Duration

Microsomal UDP-glucuronyltransferase and cytosolic sulphotransferase share many substrates, such as phenols and hydroxamic acids. In a search for a selective inhibitor of sulphation, several phenolic compounds were tested. 2,6-Dichloro-4-nitrophenol is introduced as a selective inhibitor of sulphation in vivo, having no effect on UDP-glucuronyltransferase activity. As substrate for both conjugating enzymes the phenolic drug harmol (7-hydroxy-1-methyl-9H-pyrido[3,4-b]indole) was used. In the rat in vivo 2,6-dichloro-4-nitrophenol caused almost complete inhibition of harmol sulphation after a single intraperitoneal injection (26μmol/kg) for 48h; the percentage of harmol sulphated decreased from 75% in controls to 5% in the treated rats. The percentage of harmol glucuronidated increased from 25 to 95%. Pentachlorophenol was equally effective but also highly toxic. Salicylamide had only a very-short-lasting inhibitory effect on sulphation. In vitro, 2,6-dichloro-4-nitrophenol inhibited sulphation of harmol by a rat liver postmitochondrial supernatant completely at 1μm, whereas even at 100μm it had no effect on glucuronidation of harmol. It is concluded that 2,6-dichloro-4-nitrophenol is a selective inhibitor of sulphation and, further, that its long duration of action makes it suitable for studies on the regulatory role of sulphation in some biological processes.

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