Activity of disulfiram (bis(diethylthiocarbamoyl)disulphide) and ditiocarb (diethyldithiocarbamate) against metronidazole-sensitive and -resistant Trichomonas vaginalis and Tritrichomonas foetus. (1/242)

Clinical resistance of Trichomonas vaginalis to metronidazole is best correlated with MIC values measured under aerobic conditions. Under these conditions both disulfiram (bis(diethylthiocarbamoyl)disulphide), and its first mammalian metabolite, ditiocarb (diethyldithiocarbamate), showed high levels of activity against metronidazole-sensitive (disulfiram MIC, 0.1-0.7 microM; ditiocarb MIC, 0.3-9 microM) and -resistant (MICs 0.2-1.3 microM and 1.2-9 microM respectively) isolates. Tritrichomonas foetus was also sensitive-the MICs for seven metronidazole-sensitive isolates were 0.1-1.0 microM for disulfiram and 1.0-6.9 microM for ditiocarb; those for two highly metronidazole-resistant strains were 0.3-1.3 microM and 0.6-6 microM respectively. Under anerobic conditions most strains became highly resistant to both compounds. Surprisingly, disulfiram was consistently more active than ditiocarb.  (+info)

Clinical isoflurane metabolism by cytochrome P450 2E1. (2/242)

BACKGROUND: Some evidence suggests that isoflurane metabolism to trifluoroacetic acid and inorganic fluoride by human liver microsomes in vitro is catalyzed by cytochrome P450 2E1 (CYP2E1). This investigation tested the hypothesis that P450 2E1 predominantly catalyzes human isoflurane metabolism in vivo. Disulfiram, which is converted in vivo to a selective inhibitor of P450 2E1, was used as a metabolic probe for P450 2E1. METHODS: Twenty-two elective surgery patients who provided institutionally-approved written informed consent were randomized to receive disulfiram (500 mg orally, N = 12) or nothing (controls, N = 10) the evening before surgery. All patients received a standard isoflurane anesthetic (1.5% end-tidal in oxygen) for 8 hr. Urine and plasma trifluoroacetic acid and fluoride concentrations were quantitated in samples obtained for 4 days postoperatively. RESULTS: Patient groups were similar with respect to age, weight, gender, duration of surgery, blood loss, and delivered isoflurane dose, measured by cumulative end-tidal isoflurane concentrations (9.7-10.2 MAC-hr). Postoperative urine excretion of trifluoroacetic acid (days 1-4) and fluoride (days 1-3) was significantly (P<0.05) diminished in disulfiram-treated patients. Cumulative 0-96 hr excretion of trifluoroacetic acid and fluoride in disulfiram-treated patients was 34+/-72 and 270+/-70 micromoles (mean +/- SD), respectively, compared to 440+/-360 and 1500+/-800 micromoles in controls (P<0.05 for both). Disulfiram also abolished the rise in plasma metabolite concentrations. CONCLUSIONS: Disulfiram, a selective inhibitor of human hepatic P450 2E1, prevented 80-90% of isoflurane metabolism. These results suggest that P450 2E1 is the predominant P450 isoform responsible for human clinical isoflurane metabolism in vivo.  (+info)

A retinoic acid-inducible transgenic marker of sino-atrial development in the mouse heart. (3/242)

To study the specification of inflow structures in the heart we generated transgenic animals harboring the human alkaline phosphatase (HAP) gene driven by the proximal 840 bp of a quail SMyHC3 promoter. In transgenic mice, the SMyHC3-HAP reporter was expressed in posterior heart precursors at 8.25 dpc, in sinus venosa and in the atrium at 8.5 and 9.0 dpc, and in the atria from 10.5 dpc onwards. SMyHC3-HAP transgene expression overlapped synthesis and endogenous response to retinoic acid (RA) in the heart, as determined by antibodies directed against a key RA synthetic enzyme and by staining of RAREhsplacZ transgenic animals. A single pulse of all-trans RA administered to pregnant mice at 7.5, but not after 8.5, dpc induced cardiac dismorphology, ranging from complete absence of outflow tract and ventricles to hearts with reduced ventricles expressing both SMyHC3-HAP and ventricular markers. Blockade of RA synthesis with disulfiram inhibited RA-induced transcription and produced hearts lacking the atrial chamber. This study defines a novel marker for atrial-restricted transcription in the developing mouse heart. It also suggests that atrial-specific gene expression is controlled by localized synthesis of RA, and that exclusion of RA from ventricular precursors is essential for correct specification of the ventricles.  (+info)

Differential regulation of peptide alpha-amidation by dexamethasone and disulfiram. (4/242)

alpha-Amidation is essential for the function of many peptides in intercellular communication. This C-terminal modification is mediated in a two-step process by the hydroxylase and lyase activities of the bifunctional enzyme, peptidylglycine alpha-amidating monooxygenase (PAM). The first step, catalyzed by peptidylglycine-alpha-hydroxylating monooxygenase (PHM; EC 1.14.17. 3), is rate limiting in the process, and therefore subject to regulation. Dexamethasone and disulfiram (tetraethylthiuram disulfide; Antabuse) were used as in vivo treatments to study the regulation of PHM expression and activity in cardiac atrium. Our findings show that both dexamethasone and disulfiram treatment increase the activity of PHM in atrial tissue but that they do so by distinctly different mechanisms. Dexamethasone elevated tissue levels of PAM mRNA and protein concurrently, suggesting that glucocorticoids regulate PAM expression at the level of gene transcription. In contrast, disulfiram treatment, which depletes stores of alpha-amidated peptides, increased the specific activity of PHM without affecting the level of PAM expression. The catalytic efficiency of PHM was enhanced by raising the Vmax of the enzyme. Importantly, this increase in Vmax was retained through purification to homogeneity, indicating that either a covalent modification or a stable conformational change had occurred in the protein. These novel findings demonstrate that the rate-limiting enzyme in the bioactivation of peptide messengers is differentially regulated by transcriptional and post-transcriptional mechanisms in vivo. It is proposed that regulation of PHM's expression and catalytic efficiency serve as coordinated physiologic mechanisms for maintaining appropriate levels of alpha-amidating activity under changing conditions in vivo.  (+info)

Lack of single-dose disulfiram effects on cytochrome P-450 2C9, 2C19, 2D6, and 3A4 activities: evidence for specificity toward P-450 2E1. (5/242)

Disulfiram and its primary metabolite diethyldithiocarbamate are effective mechanism-based inhibitors of cytochrome P-450 2E1 (CYP2E1)1 in vitro. Single-dose disulfiram diminishes CYP2E1 activity in vivo and has been used to identify CYP2E1 participation in human drug metabolism and prevent CYP2E1-mediated toxification. Specificity of single-dose disulfiram toward CYP2E1 in vivo, however, remains unknown. This investigation determined single-dose disulfiram effects on human CYP 2C9, 2C19, 2D6, and 3A4 activities in vivo. In four randomized crossover experiments, volunteers received isoform-selective probes (oral tolbutamide, mephenytoin, dextromethorphan, or i.v. midazolam) on two occasions, 10 h after oral disulfiram or after no pretreatment (controls). Plasma and/or urine parent and/or metabolite concentrations were measured by HPLC or gas chromatography-mass spectrometry. CYP2C9, 2C19, 2D6, and 3A4 activities were determined from the tolbutamide metabolic ratio, 4'-hydroxymephenytoin excretion, and dextromethorphan/dextrorphan ratios in urine and midazolam systemic clearance, respectively. Midazolam clearance (670 +/- 190 versus 700 +/- 240 ml/min, disulfiram versus controls), dextromethorphan/dextrorphan metabolic ratio (0.013 +/- 0.033 versus 0.015 +/- 0.035), 4'-hydroxymephenytoin excretion (122 +/- 22 versus 128 +/- 25 micromol), and tolbutamide metabolite excretion (577 +/- 157 versus 610 +/- 208 micromol) were not significantly altered by disulfiram pretreatment, although the tolbutamide metabolic ratio was slightly diminished after disulfiram (60 +/- 17 versus 81 +/- 40, p <.05). Results show that single-dose disulfiram does not cause clinically significant inhibition of human CYP2C9, 2C19, 2D6, and 3A4 activities in vivo. When single-dose disulfiram is used as an in vivo probe for P-450, inhibition of drug metabolism suggests selective involvement of CYP2E1. Single-dose disulfiram should not cause untoward drug interactions from inhibition of other P-450 isoforms.  (+info)

The ethanol metabolite acetaldehyde inhibits the induction of long-term potentiation in the rat dentate gyrus in vivo. (6/242)

1. Ethanol has been reported to inhibit the induction of long-term potentiation (LTP) in the hippocampus. However, the correlation between the effects of ethanol in vivo and in vitro remained unclear. In addition, previous works have little considered the possibility that the effect of ethanol is mediated by its metabolites. To solve these problems, we investigated the effects of ethanol and acetaldehyde, the first metabolite in the metabolism of ethanol, on the induction of LTP at medial perforant path-granule cell synapses in the dentate gyrus of anaesthetized rats in vivo. 2. Oral administration of 1 g kg-1 ethanol significantly inhibited the induction of LTP, confirming the effectiveness of ethanol in vivo. 3. A lower dose of ethanol (0.5 g kg-1) failed to inhibit the induction of LTP in intact rats, but significantly inhibited LTP in rats treated with disulfiram, an inhibitor of aldehyde dehydrogenase, demonstrating that LTP is inhibited by acetaldehyde accumulation following ethanol administration. 4. Intravenous injection of acetaldehyde (0.06 g kg-1) significantly inhibited the induction of LTP. 5. The inhibitory effect of acetaldehyde on LTP induction was also observed when it was injected into the cerebroventricules, suggesting that acetaldehyde has a direct effect on the brain. The intracerebroventricular dose of acetaldehyde effective in inhibiting LTP induction (0.1 - 0.15 mg brain-1) was approximately 10 fold lower than that of ethanol (1.0 - 1.5 mg brain-1). 6. It is possible that acetaldehyde is partly responsible for memory impairments induced by ethanol intoxication.  (+info)

Duration of cytochrome P-450 2E1 (CYP2E1) inhibition and estimation of functional CYP2E1 enzyme half-life after single-dose disulfiram administration in humans. (7/242)

Disulfiram (DSF) is a mechanism-based inhibitor of cytochrome P-450 2E1 (CYP2E1), resulting in loss of CYP2E1 protein and activity, which may be useful in preventing CYP2E1-mediated xenobiotic toxicity. The duration of inhibition after a single DSF dose is, however, unknown. The purpose of this investigation was to determine this duration, and CYP2E1 formation and degradation rates, in humans. Oral chlorzoxazone (CLZ) was used as the selective in vivo probe for CYP2E1. Healthy subjects received CLZ to determine baseline CYP2E1 activity (CLZ plasma clearance and 6-hydroxychlorzoxazone fractional metabolic clearance). One week later, DSF (500 mg orally) was administered at bedtime, and CLZ administered the following morning and 3, 6, 8, 10, and 13 days after DSF. A terminal DSF metabolite, 2-thiothiazolidine-4 carboxylic acid, was also measured in each 24-h urine sample. The mean CLZ clearance and 6-hydroxychlorzoxazone fractional metabolic clearance on the first day declined to 10.2 and 5.5% of baseline values, indicating rapid and profound CYP2E1 inhibition. CYP2E1 activity returned to half that of control on day 3, and to baseline values on day 8. Assuming zero-order synthesis and first-order degradation, the in vivo CYP2E1 synthesis rate and degradation half-life was estimated to be 11 +/- 5 nmol/h and 50 +/- 19 h, respectively. Significant amounts of 2-thiothiazolidine-4 carboxylic acid were present only on day 1, suggesting that the return of in vivo CYP2E1 activity was not caused by inhibitor washout, but by enzyme resynthesis. Results regarding CYP2E1 disposition may be useful for modeling the effects of CYP2E1 inducers and inhibitors. For prevention of CYP2E1-mediated bioactivation, depending on protoxicant disposition, a second DSF dose might be necessary to completely prevent toxicity.  (+info)

Effect of diclofenac, disulfiram, itraconazole, grapefruit juice and erythromycin on the pharmacokinetics of quinidine. (8/242)

AIMS: In vitro studies suggest that the oxidation of quinidine to 3-hydroxyquinidine is a specific marker reaction for CYP3A4 activity. To assess the possible use of this reaction as an in vivo marker of CYP3A4 activity, we studied the involvement of cytochromes CYP2C9, CYP2E1 and CYP3A4 in the in vivo oxidative metabolism of quinidine. METHODS: An open study of 30 healthy young male volunteers was performed. The pharmacokinetics of a 200 mg single oral dose of quinidine was studied before and during daily administration of 100 mg diclofenac, a CYP2C9 substrate (n=6); 200 mg disulfiram, an inhibitor of CYP2E1 (n=6); 100 mg itraconazole, an inhibitor of CYP3A4 (n=6); 250 ml single strength grapefruit juice twice daily, an inhibitor of CYP3A4 (n=6); 250 mg of erythromycin 4 times daily, an inhibitor of CYP3A4 (n=6). Probes of other enzyme activities, caffeine (CYP1A2), sparteine (CYP2D6), mephenytoin (CYP2C19), tolbutamide (CYP2C9) and cortisol (CYP3A4) were also studied. RESULTS: Concomitant administration of diclofenac reduced the partial clearance of quinidine by N-oxidation by 27%, while no effect was found for other pharmacokinetic parameters of quinidine. Concomitant administration of disulfiram did not alter any of the pharmacokinetic parameters of quinidine. Concomitant administration of itraconazole reduced quinidine total clearance, partial clearance by 3-hydroxylation and partial clearance by N-oxidation by 61, 84 and 73%, respectively. The renal clearance was reduced by 60% and the elimination half-life increased by 35%. Concomitant administration of grapefruit juice reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 15, 19 and 27%, respectively. The elimination half-life of quinidine was increased by 19%. The caffeine metabolic index was reduced by 25%. Concomitant administration of erythromycin reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 34, 50 and 33%, respectively. Cmax was increased by 39%. CONCLUSIONS: The results confirm an important role for CYP3A4 in the oxidation of quinidine in vivo, and this applies particularly to the formation of 3-hydroxyquinidine. While a minor contribution of CYP2C9 to the N-oxidation of quinidine is possible, a major involvement of the CYP2C9 or CYP2E1 enzymes in the oxidation of quinidine in vivo is unlikely.  (+info)