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Neuropsychopharmacologia Hungarica : a... Sep 2010"Ecstasy", 3,4-methylenedioxymethamphetamine (MDMA), an amphetamine analogue is one of the most widely used recreational drugs. In spite of the fact that neurotoxic...
"Ecstasy", 3,4-methylenedioxymethamphetamine (MDMA), an amphetamine analogue is one of the most widely used recreational drugs. In spite of the fact that neurotoxic effects of MDMA has been found in several species from rodents to non-human primates, and results increasingly point to damage also in human MDMA users, data about the sensitivity of different brain areas and the recovery after neuronal damage are scarce. Serotonin transporter (5-HTT) mRNA in the raphe nuclei also has not been examined. Humans with genetic predisposition for the slow metabolism of MDMA, the so-called "poor metabolizers" of debrisoquin are at higher risk. Five- 9% of the Caucasian population is considered to carry this phenotype. These studies were carried out in Dark Agouti rats, a special strain that show decreased microsomal CYP2D1 isoenzyme activity, and thus may serve as a model of vulnerable human users. These works were designed to characterize MDMA-induced damage and recovery of the serotonergic system including sleep and morphological changes within 180 days. In our experiments we investigated the 5-HTT mRNA expression in the brainstem and medullary raphe nuclei, 5-HTT immunoreactive (IR) fibre densities in several brain areas, and 16 functional measures of sleep in response to a single dose of +/- MDMA (15mg\kg). Furthermore, behavioural experiments were performed 21 days after MDMA treatment. We found similar changes in 5-HTT mRNA expression in the examined raphe nuclei, namely transient increases 7 days after MDMA treatment followed by transient decreases at 21 days. Significant (20-40%), widespread reductions in 5-HTT-IR fibre density were detected in most brain areas at 7 and 21 days after MDMA administration. All cortical, but only some brainstem areas were damaged. Parallel to the neuronal damage we observed significant reductions in rapid eye movement (REM) sleep latency, increased fragmentation of sleep and increases in delta power spectra in non-REM sleep. At 180 days almost all functional changes in sleep were normalized together with 5-HTT mRNA expression in the examined raphe nuclei and the recovery of 5-HTT-IR fibre density in most brain areas. Our results also suggest that the acute MDMA administration abolished aggressive behaviour but MDMA pretreatment and the consequent depletion of serotonergic terminals did not affect aggression. Our findings concerning the changes detected in 5-HTT mRNA expression and fibre density indicate lasting impairment of the serotonergic system and suggest that a single use of MDMA may be associated with long-lasting cognitive, learning, memory and mood deficits and sleep disturbances particularly when a constellation of genetic vulnerability and certain environmental factors are present. Our data provide further evidence for the connection between altered serotonergic functions and sleep disturbance.
Topics: Aggression; Animals; Basal Metabolism; Brain; Gene Expression Regulation; Genetic Predisposition to Disease; Humans; Immunohistochemistry; In Situ Hybridization; Male; N-Methyl-3,4-methylenedioxyamphetamine; Neurons; RNA, Messenger; Raphe Nuclei; Rats; Risk Factors; Serotonin; Serotonin Plasma Membrane Transport Proteins; Sleep; Substance-Related Disorders; Time Factors; Wakefulness
PubMed: 20962361
DOI: No ID Found -
British Medical Journal Aug 1973A study was designed to investigate the effect on morbidity and mortality of lowering diastolic blood pressure levels of between 100 and 120 mm Hg to below 100 mm Hg.... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
A study was designed to investigate the effect on morbidity and mortality of lowering diastolic blood pressure levels of between 100 and 120 mm Hg to below 100 mm Hg. Fifty-eight men and women, aged from 45-69 years, with blood pressure levels between 100 and 120 mm Hg were matched for age, sex, and blood pressure levels with 58 control patients. The maintenance of diastolic blood pressures at levels below 100 mm Hg was successfully carried out without serious drug side effects. Treatment effectively maintained diastolic pressures below 100 mm Hg, but no effect was shown on other terminating events. Few problems were found in the management of patients with minimally raised blood pressure, most of whom were symptom-free. The treatment and control groups became less comparable as increasing numbers of patients in the control group were withdrawn from the trial as diastolic pressures rose above 130 mm Hg.
Topics: Aged; Antihypertensive Agents; Bendroflumethiazide; Blood Pressure; Cardiovascular Diseases; Clinical Trials as Topic; Debrisoquin; Female; Humans; Hypertension; Male; Methyldopa; Middle Aged; Placebos; Potassium; Prospective Studies
PubMed: 4580022
DOI: No ID Found -
British Journal of Clinical Pharmacology Mar 19791 The synthesis of [14C]-debrisoquine hydrochloride and 4-hydroxy-debrisoquine sulphate is described. 2 The metabolic fate and excretion profile in both urine and faeces...
1 The synthesis of [14C]-debrisoquine hydrochloride and 4-hydroxy-debrisoquine sulphate is described. 2 The metabolic fate and excretion profile in both urine and faeces of 14C-labelled debrisoquine was studied in five healthy human subjects. 3 Investigations showed that the drug is well-absorbed after a single oral dose of 32 mg and quantitatively eliminated from the body within three days. 4 4-Hydroxy-debrisoquine is the major metabolite of debrisoquine, although significant amounts of 5-,6-, 7- and 8-hydroxy-debrisoquine are also formed. 5 Electron-capture gas chromatography is a useful method for measuring debrisoquine and its five hydroxylated metabolites in urine at the pg level.
Topics: Adult; Biotransformation; Chromatography, Gas; Debrisoquin; Feces; Flame Ionization; Humans; Isoquinolines; Male; Mass Spectrometry; Radioisotope Dilution Technique
PubMed: 371651
DOI: 10.1111/j.1365-2125.1979.tb00930.x -
The Biochemical Journal Feb 2000Homology models of cytochrome P450 2D6 (CYP2D6) have identified serine 304 as an active-site residue and implicated a putative role for this residue in substrate...
Homology models of cytochrome P450 2D6 (CYP2D6) have identified serine 304 as an active-site residue and implicated a putative role for this residue in substrate enantioselectivity and the differential inhibition of enzyme activity by the diastereoisomers quinine and quinidine. The role of serine 304 in selectivity is thought to be achieved through a preferential hydrogen-bond interaction between the hydroxyl group of the residue and one of the stereoisomers of each ligand. We have tested this hypothesis by substituting serine 304 with alanine, a non-hydrogen-bonding residue, and compared the properties of the wild-type and mutant enzymes in microsomes prepared from yeast cells expressing the appropriate cDNA-derived enzyme. The Ser(304)Ala substitution did not alter the enantioselective oxidation of metoprolol; the O-demethylation reaction remained R-(+)-enantioselective (wild-type, R/S, 1.7; mutant, R/S, 1.6), whereas alpha-hydroxylation remained S-(-)-enantioselective (wild-type and mutant, R/S, 0.7). Similarly, the selective oxidation of the R-(+) and S-(-) enantiomers of propranolol to the major 4-hydroxy metabolite was identical with both wild-type and mutant forms of the enzyme (R/S 0.9), although the formation of minor metabolites (5-hydroxy and deisopropylpropranolol) did show some slight alteration in enantioselectivity. The differential inhibition of enzyme activity by quinine and quinidine was also identical with both forms of CYP2D6, the IC(50) values for each enzyme being approx. 10 microM and 0.1 microM for quinine and quinidine, respectively. The kinetics of formation of alpha-hydroxymetoprolol and 4-hydroxydebrisoquine by wild-type and the Ser(304)Ala mutant was also very similar. However, modest changes in the regioselective oxidation of metoprolol and debrisoquine were observed with the Ser(304)Ala mutant. The regio- and enantioselective oxidation of an analogue of metoprolol, in which the hydroxyl group attached to the chiral carbon was replaced by a methyl moiety, was again identical with both wild-type and Ser(304)Ala mutant. However, the observed selectivity was the reverse of that observed with metoprolol. Collectively, these data indicate that Ser(304) is unlikely to be a key ligand-binding residue, although the residue may indeed be located in the active-site cavity. The reversal of selectivity with the methyl analogue of metoprolol indicates that the hydroxyl group attached to the chiral centre of ligands, such as metoprolol, is important in defining the enzyme's selective properties, and that a hydrogen-bonding residue, other than Ser(304), may be involved in this interaction. Current homology models of the active site of CYP2D6 that predict a hydrogen-bond interaction between Ser(304) and specific ligands will need to be re-evaluated, and other candidate residues capable of such an interaction nominated and tested by site-directed mutagenesis studies.
Topics: Alanine; Amino Acid Substitution; Aspartic Acid; Binding Sites; Catalytic Domain; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP2D6 Inhibitors; Debrisoquin; Enzyme Inhibitors; Kinetics; Ligands; Metoprolol; Mutagenesis, Site-Directed; Oxidation-Reduction; Propranolol; Quinidine; Quinine; Serine; Substrate Specificity; Yeasts
PubMed: 10642515
DOI: No ID Found -
Drug Metabolism and Disposition: the... Sep 2006Considerable unexplained intersubject variability in the debrisoquine metabolic ratio (urinary debrisoquine/4-hydroxydebrisoquine) exists within individual CYP2D6... (Clinical Trial)
Clinical Trial
Considerable unexplained intersubject variability in the debrisoquine metabolic ratio (urinary debrisoquine/4-hydroxydebrisoquine) exists within individual CYP2D6 genotypes. We speculated that debrisoquine was converted to as yet undisclosed metabolites. Thirteen healthy young volunteers, nine CYP2D6*1 homozygotes [extensive metabolizers (EMs)] and four CYP2D6*4 homozygotes [poor metabolizers (PMs)] took 12.8 mg of debrisoquine hemisulfate by mouth and collected 0- to 8- and 8- to 24-h urines, which were analyzed by gas chromatography-mass spectrometry (GCMS) before and after treatment with beta-glucuronidase. Authentic 3,4-dehydrodebrisoquine was synthesized and characterized by GCMS, liquid chromatography-tandem mass spectrometry, and (1)H NMR. 3,4-Dehydrodebrisoquine is a novel metabolite of debrisoquine excreted variably in 0- to 24-h urine, both in EMs (3.1-27.6% of dose) and PMs (0-2.1% of dose). This metabolite is produced from 4-hydroxydebrisoquine in vitro by human and rat liver microsomes. A previously unstudied CYP2D6*1 homozygote was administered 10.2 mg of 4-hydroxydebrisoquine orally and also excreted 3,4-dehydrodebrisoquine. EMs excreted 6-hydroxydebrisoquine (0-4.8%) and 8-hydroxydebrisoquine (0-1.3%), but these phenolic metabolites were not detected in PM urine. Debrisoquine and 4-hydroxydebrisoquine glucuronides were excreted in a highly genotype-dependent manner. A microsomal activity that probably does not involve cytochrome P450 participates in the further metabolism of 4-hydroxydebrisoquine, which we speculate may also lead to the formation of 1- and 3-hydroxydebrisoquine and their ring-opened products. In conclusion, this study suggests that the traditional metabolic ratio is not a true measure of the debrisoquine 4-hydroxylation capacity of an individual and thus may, in part, explain the wide intragenotype variation in metabolic ratio.
Topics: Adult; Animals; Antihypertensive Agents; Biotransformation; Cytochrome P-450 CYP2D6; Debrisoquin; Female; Gas Chromatography-Mass Spectrometry; Genetic Variation; Genotype; Glucuronides; Humans; Hydro-Lyases; Hydroxylation; Male; Microsomes, Liver; Phenotype
PubMed: 16782768
DOI: 10.1124/dmd.105.008920 -
Genes and Environment : the Official... 2017Genetic and environmental risk factors play an important role for the susceptibility to sporadic Parkinson's disease (PD). It was hypothesized that a splice variant of...
BACKGROUND
Genetic and environmental risk factors play an important role for the susceptibility to sporadic Parkinson's disease (PD). It was hypothesized that a splice variant of the gene ( allele) is associated with PD because it alters the ability to metabolize toxins and in particular neurotoxins. codes for the drug metabolizing enzyme debrisoquine 4-hydroxylase. The CYP2D6*4 variant results in an undetectable enzyme activity and consequently in a reduction in metabolism of some toxins.
METHODS
Some of agricultural chemicals have neurotoxic potential and CYP2D6 is involved in their detoxification. Thus, we conducted a case control study to investigate the association of the CYP2D6*4 with PD in a Pakistani subpopulation that is known to be exposed to high levels of some agricultural pesticides, insecticides and herbicides.
RESULTS
We found a significantly higher allele and genotype frequency of the variant in 174 sporadic PD patients when compared to 200 controls. In addition, there was a trend to an earlier age of PD onset and a tremor dominant phenotype in variant carriers.
CONCLUSION
Our data provide further evidence that a poor metabolizer status may increase the risk to develop PD especially in populations that are exposed to environmental toxins.
PubMed: 28680508
DOI: 10.1186/s41021-017-0078-8 -
British Journal of Clinical Pharmacology Sep 19921. The aromatic 2-hydroxylation of imipramine was studied in microsomes from three human livers. The kinetics were best described by a biphasic enzyme model. The...
1. The aromatic 2-hydroxylation of imipramine was studied in microsomes from three human livers. The kinetics were best described by a biphasic enzyme model. The estimated values of Vmax and Km for the high affinity site ranged from 3.2 to 5.7 nmol mg-1 h-1 and from 25 to 31 microM, respectively. 2. Quinidine was a potent inhibitor of the high affinity site for the 2-hydroxylation of imipramine in microsomes from all three human livers, with apparent Ki-values ranging from 9 to 92 nM. This finding strongly suggests that the high affinity enzyme is CYP2D6, the source of the sparteine/debrisoquine oxidation polymorphism. 3. The selective serotonin reuptake inhibitors (SSRI), paroxetine, fluoxetine and norfluoxetine were potent inhibitors of the high affinity site having apparent Ki-values of 0.36, 0.92 and 0.33 microM, respectively. Three other SSRIs, citalopram, desmethylcitalopram and fluvoxamine, were less potent inhibitors of CYP2D6, with apparent Ki-values of 19, 1.3 and 3.9 microM, respectively. 4. Among 20 drugs screened, fluvoxamine was the only potent inhibitor of the N-demethylation of imipramine, with a Ki-value of 0.14 microM. 5. Neither mephenytoin, citalopram, diazepam, omeprazole or proguanil showed any inhibition of the N-demethylation of imipramine and the role of the S-mephenytoin hydroxylase for this oxidative pathway could not be confirmed.
Topics: Cytochrome P-450 CYP2D6; Cytochrome P-450 Enzyme Inhibitors; Fluvoxamine; Humans; Hydroxylation; Imipramine; In Vitro Techniques; Kinetics; Microsomes, Liver; Mixed Function Oxygenases; Polymorphism, Genetic; Quinidine; Selective Serotonin Reuptake Inhibitors
PubMed: 1389950
DOI: 10.1111/j.1365-2125.1992.tb04133.x -
Anesthesiology Sep 1992There is considerable variability in the elimination clearance of the opioid analgesic alfentanil. It has been shown previously that alfentanil clearance is independent... (Review)
Review
There is considerable variability in the elimination clearance of the opioid analgesic alfentanil. It has been shown previously that alfentanil clearance is independent of the polymorphic debrisoquine hydroxylase (P-450 2D6), and it is therefore of interest to identify the human cytochrome P-450 enzymes involved in noralfentanil formation, the primary reaction involved in the oxidative N-dealkylation at the piperidine nitrogen. Purified human P-450 3A4 showed appreciable catalytic activity, and yeast recombinant P-450 3A4 also showed alfentanil oxidation activity. When microsomes prepared from different human liver samples were compared, noralfentanil formation activity was well correlated (r = 0.95,P less than 0.005) with nifedipine oxidation (a P-450 3A4 marker) but not with markers of other P-450s, including phenacetin O-deethylation (P-450 1A2), chlorzoxazone 6-hydroxylation (P-450 2E1), and (S)-mephenytoin 4'-hydroxylation (a P-450 2C enzyme). Using antibodies that recognize specific human P-450 enzymes (immunoinhibition techniques), it was possible to demonstrate that anti-P-450 3A4 nearly completely inhibited alfentanil oxidation activity in the human liver microsomes, but no other antibodies showed a measurable inhibitory effect. Selective chemical inhibitors of P-450 3A4, gestodene and troleandomycin, inhibited as much as 90% of the microsomal noralfentanil formation activity, but other chemical inhibitors did not show a detectable inhibitory effect. 7,8-Benzoflavone inhibited as much as 90% of the alfentanil oxidation activity of the microsomal or reconstituted P-450 3A4 system. This work indicates that P-450 3A4 contributes significantly to human liver microsomal alfentanil oxidation, whereas P-450 2D6 does not contribute.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Alfentanil; Benzoflavones; Cytochrome P-450 Enzyme System; Drug Interactions; Fentanyl; Humans; Microsomes, Liver
PubMed: 1519785
DOI: 10.1097/00000542-199209000-00011 -
PloS One 2012The CYP2D family members are instrumental in the metabolism of 20-25% of commonly prescribed drugs. Although many CYP2D isoforms have been well characterized in other...
The CYP2D family members are instrumental in the metabolism of 20-25% of commonly prescribed drugs. Although many CYP2D isoforms have been well characterized in other animal models, research concerning the chicken CYP2Ds is limited. In this study, a cDNA encoding a novel CYP2D enzyme (CYP2D49) was cloned from the chicken liver for the first time. The CYP2D49 cDNA contained an open reading frame of 502 amino acids that shared 52%-57% identities with other CYP2Ds. The gene structure and neighboring genes of CYP2D49 are conserved and similar to those of human CYP2D6. Additionally, similar to human CYP2D6, CYP2D49 is un-inducible in the liver and expressed predominantly in the liver, kidney and small intestine, with detectable levels in several other tissues. Metabolic assays of the CYP2D49 protein heterologously expressed in E. coli and Hela cells indicated that CYP2D49 metabolized the human CYP2D6 substrate, bufuralol, but not debrisoquine. Moreover, quinidine, a potent inhibitor of human CYP2D6, only inhibited the bufuralol 1'-hydroxylation activity of CYP2D49 to a negligible degree. All these results indicated that CYP2D49 had functional characteristics similar to those of human CYP2D6 but measurably differed in the debrisoquine 4'-hydroxylation and quinidine inhibitory profile. Further structure-function investigations that employed site-directed mutagenesis and circular dichroism spectroscopy identified the importance of Val-126, Glu-222, Asp-306, Phe-486 and Phe-488 in keeping the enzymatic activity of CYP2D49 toward bufuralol as well as the importance of Asp-306, Phe-486 and Phe-488 in maintaining the conformation of CYP2D49 protein. The current study is only the first step in characterizing the metabolic mechanism of CYP2D49; further studies are still required.
Topics: Amino Acid Sequence; Animals; Antibody Specificity; Chickens; Circular Dichroism; Cytochrome P-450 CYP2D6; Cytochrome P-450 Enzyme System; Ethanolamines; Female; HeLa Cells; Humans; Immune Sera; Isoenzymes; Liver; Male; Molecular Sequence Data; Multigene Family; Phylogeny; Recombinant Proteins; Sequence Homology, Amino Acid
PubMed: 22675558
DOI: 10.1371/journal.pone.0038395 -
The Korean Journal of Internal Medicine Jan 1990This is an attempt to investigate the effect of gamma-aminobutyric acid (GABA), a well-known major inhibitory neurotransmitter in the central nervous system, on the...
This is an attempt to investigate the effect of gamma-aminobutyric acid (GABA), a well-known major inhibitory neurotransmitter in the central nervous system, on the blood pressure response in rats and to elucidate the mechanism of its action. GABA injected into a femoral vein of the rat produced a dose-related fall in blood pressure followed by a secondary pressor response. The depressor response evoked by GABA was clearly blocked by pretreatment with chlorisondamine, diazepam and picrotoxin but was unaffected by atropine, prazosin and debrisoquin. GABA-induced pressor responses were significantly attenuated by pretreatment with prazosin or picrotoxin, while not affected by atropine, diazepam, debrisoquin and chlorisondamine. These experimental data suggest that GABA causes biphasically depressor and pressor responses in rats, and that the hypotensive activity evoked by GABA may be exerted through activation of GABAergic receptors and hypertensive activity due to stimulation of the adrenergic alpha-receptors, which appears to be associated with GABAergic receptors.
Topics: Animals; Atropine; Blood Pressure; Chlorisondamine; Debrisoquin; Diazepam; Female; Male; Picrotoxin; Prazosin; Rats; Rats, Inbred Strains; gamma-Aminobutyric Acid
PubMed: 2271508
DOI: 10.3904/kjim.1990.5.1.23