Douwe de Boer

Publications (7)22.85 Total impact

• Source

  Available from: Fernando Remião

  Article: CYP2D6 increases toxicity of the designer drug 4-methylthioamphetamine (4-MTA).

  Helena Carmo, Marc Brulport, Matthias Hermes, Franz Oesch, Douwe de Boer, Fernando Remião, Félix Carvalho, Michael R Schön, Niels Krebsfaenger, Johannes Doehmer, Maria de Lourdes Bastos, Jan G Hengstler
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  ABSTRACT: 4-Methylthioamphetamine (4-MTA) belongs to a group of new amphetamine derivatives that is usually sold as "ecstasy" or "flatliners" on the illicit drug market. Large interindividual differences in 4-MTA mediated toxicity have been reported in humans. Therefore, we tested whether CYP2D6 or its variant alleles as well as CYP3A4 influence the susceptibility to 4-MTA. For this purpose, we used the colony formation assay with Chinese hamster lung fibroblast V79 cells expressing human wild-type CYP2D6 (CYP2D6*1), the low activity alleles CYP2D6*2, CYP2D6*9, as well as human CYP3A4. The obtained results showed that the expression of wild type CYP2D6*1 clearly enhanced the susceptibility to the cytotoxic effects of 4-MTA compared with the parental cells devoid of CYP-dependent enzymatic activity. Toxicity in V79 CYP2D6*1 was also higher compared to the V79 cell lines expressing the low activity alleles CYP2D6*2 and CYP2D6*9. In contrast to CYP2D6, the CYP3A4 isoenzyme did not enhance 4-MTA toxicity. In conclusion, our results suggest that CYP2D6 rapid metabolizers may be more susceptible to 4-MTA toxicity than CYP2D6 poor metabolizers.
  Toxicology 02/2007; 229(3):236-44. · 3.68 Impact Factor
• Article: Influence of CYP2D6 polymorphism on 3,4-methylenedioxymethamphetamine ('Ecstasy') cytotoxicity.

  Helena Carmo, Marc Brulport, Matthias Hermes, Franz Oesch, Renata Silva, Luísa M Ferreira, Paula S Branco, Douwe de Boer, Fernando Remião, Félix Carvalho, Michael R Schön, Niels Krebsfaenger, Johannes Doehmer, Maria de Lourdes Bastos, Jan G Hengstler
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  ABSTRACT: Remarkable interindividual differences in 3,4-methylenedioxymethamphetamine ('Ecstasy')-mediated toxicity have been reported in humans. Therefore, we tested whether CYP2D6 or its variant alleles as well as CYP3A4 influence the susceptibility to 3,4-methylenedioxymethamphetamine. 3,4-Methylenedioxymethamphetamine cytotoxicity was determined in V79 cells expressing human wild-type CYP2D6 (CYP2D6*1), the low-activity alleles CYP2D6*2, *9, *10, and *17, as well as human CYP3A4. Metabolites of 3,4-methylenedioxymethamphetamine formed by the different cell lines were quantified by high-performance liquid chromatography/electrochemical detector. Toxicity of 3,4-methylenedioxymethamphetamine was clearly increased in cells expressing CYP2D6*1 compared with the parental cells devoid of CYP-dependent enzymatic activity. Toxicity in V79 CYP2D6*1 cells was also higher than in V79 cell lines expressing the low-activity alleles CYP2D6*2, *9, *10, or *17. In contrast to CYP2D6, the CYP3A4 isoenzyme did not enhance 3,4-methylenedioxymethamphetamine toxicity. Formation of the oxidative 3,4-methylenedioxymethamphetamine metabolite N-methyl-alpha-methyldopamine was greatly enhanced in V79 cell line transfected with CYP2D6*1 compared to all other cell lines. The increase in the cytotoxic effects of 3,4-methylenedioxymethamphetamine observed in this cell line was therefore suspected to be a consequence of the production of this metabolite. This was further investigated by testing the cytotoxicity of N-methyl-alpha-methyldopamine to the control cell line. The results confirmed our hypothesis as the metabolite proved to be more than 100-fold more toxic than the parent compound 3,4-methylenedioxymethamphetamine. CYP2D6*1 mediates 3,4-methylenedioxymethamphetamine toxicity via formation of N-methyl-alpha-methyldopamine. Therefore, it will be important to investigate whether CYP2D6 ultrarapid metabolizers are overrepresented in the cases of 3,4-methylenedioxymethamphetamine intoxications.
  Pharmacogenetics and Genomics 12/2006; 16(11):789-99. · 3.48 Impact Factor
• Article: Metabolic pathways of 4-bromo-2,5-dimethoxyphenethylamine (2C-B): analysis of phase I metabolism with hepatocytes of six species including human.

  Helena Carmo, Jan G Hengstler, Douwe de Boer, Michael Ringel, Fernando Remião, Félix Carvalho, Eduarda Fernandes, Lesseps A dos Reys, Franz Oesch, Maria de Lourdes Bastos
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  ABSTRACT: 4-Bromo-2,5-dimethoxyphenethylamine (2C-B) is a psychoactive designer drug of abuse that is sold under the street names "Venus", "Bromo", "Erox", "XTC" or "Nexus". Concern has been raised because only little is known about its toxicity and metabolism in humans. In the present study we incubated 2C-B with human, monkey, dog, rabbit, rat and mouse hepatocytes to identify the metabolites formed and to determine possible toxic effects as evidenced by an ATP assay. Our data allow construction of the main metabolic pathways of 2C-B. Oxidative deamination results in the 2-(4-bromo-2,5-dimethoxyphenyl)-ethanol (BDMPE) and 4-bromo-2,5-dimethoxyphenylacetic acid (BDMPAA) metabolites. Additionally, 4-bromo-2,5-dimethoxybenzoic acid (BDMBA) can be produced also by oxidative deamination. Further metabolism of BDMPE and BDMPAA may occur by demethylation. Alternatively, the later metabolites can be generated by demethylation of 2C-B followed by oxidative deamination. Two remarkable interspecies differences in metabolism of 2C-B were observed (i) a hitherto unknown metabolite, 4-bromo-2,5-dimethoxy-phenol (BDMP), was identified after incubation only with mouse hepatocytes; (ii) 2-(4-bromo-2-hydroxy-5-methoxyphenyl)-ethanol (B-2-HMPE) was produced by hepatocytes from human, monkey and rabbit but not by dog, rat and mouse. Comparing the toxic effects of 2C-B between hepatocytes of the six examined species we observed only minor interspecies differences. However, large inter-individual differences in susceptibility of hepatocytes from three human donors were observed.
  Toxicology 02/2005; 206(1):75-89. · 3.68 Impact Factor
• Article: Metabolism of the designer drug 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in mice, after acute administration.

  Helena Carmo, Douwe de Boer, Fernando Remião, Félix Carvalho, Lesseps A dos Reys, Maria de Lourdes Bastos
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  ABSTRACT: 4-Bromo-2,5-dimethoxyphenethylamine (2C-B) is a psychoactive drug of abuse often sold under the general street name "Ecstasy". Recent reports on the abuse of 2C-B and analogues denote the lack of knowledge on this drug metabolism. In the present study, we investigated the metabolic profile of 2C-B in the mouse and found unchanged 2C-B and several metabolites, which could be identified by GC/MS in the mice urine. The identification of 2C-B metabolites may give important clues for the biological and toxicological effects of this drug of abuse and provides new important data for forensic analysis on samples taken from 2C-B abusers.
  Journal of Chromatography B 12/2004; 811(2):143-52. · 2.89 Impact Factor
• Article: Comparative metabolism of the designer drug 4-methylthioamphetamine by hepatocytes from man, monkey, dog, rabbit, rat and mouse.

  Helena Carmo, Jan G Hengstler, Douwe de Boer, Michael Ringel, Félix Carvalho, Eduarda Fernandes, Fernando Remião, Lesseps A dos Reys, Franz Oesch, Maria de Lourdes Bastos
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  ABSTRACT: Several cases of death associated with 4-methylthioamphetamine (4-MTA) have raised public concern about the abuse of this designer drug that is usually sold as "Ecstasy" or "Flatliners". Since only very little is known about the metabolism of 4-MTA in humans we performed an in vitro study incubating racemic 4-MTA with primary hepatocytes isolated from three male human donors. Additionally, hepatocytes from male monkey (Cynomolgus), dog (Beagle), rabbit (Chinchilla), rat (Sprague-Dawley), and mouse (CD1) were examined for the metabolism of racemic 4-MTA. We observed that 4-MTA was not extensively metabolised by hepatocytes from all species examined. The main metabolite was identified as 4-methylthiobenzoic acid which, for the first time has been described as a human metabolite. In addition to metabolism we also examined 4-MTA-induced toxicity as evidenced by the ATP cellular content. Interestingly, one of the three human donors showed a dramatically increased sensitivity to the reduction in ATP content induced by 4-MTA. Comparing the species examined, the most extensive formation of 4-methylthiobenzoic acid was observed in the rabbit hepatocytes followed by human, monkey, dog and mouse hepatocytes, whereas no formation of 4-methylthiobenzoic acid was seen in the rat hepatocytes. Toxicity data suggest that rabbit hepatocytes are more resistant to 4-MTA than the other species, which may be due to the more extensive metabolism. In conclusion, we have shown that 4-methylthiobenzoic acid is the main metabolite formed from 4-MTA by human hepatocytes and also by the hepatocytes of the other tested species except the rat. Toxicity data suggest only moderate interspecies differences.
  Archiv für Experimentelle Pathologie und Pharmakologie 03/2004; 369(2):198-205. · 2.65 Impact Factor
• Article: 4-Methylthioamphetamine-induced hyperthermia in mice: influence of serotonergic and catecholaminergic pathways.

  Helena Carmo, Fernando Remião, Félix Carvalho, Eduarda Fernandes, Douwe de Boer, Lesseps A dos Reys, Maria de Lourdes Bastos
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  ABSTRACT: 4-Methylthioamphetamine (4-MTA), also known as p-methylthioamphetamine, is a new amphetamine derivative which in humans has been increasingly associated with severe intoxications and several deaths. As hyperthermia is considered to be one of the most life-threatening acute physiological consequences of amphetamine-related intoxications, it was our aim to determine whether 4-MTA induces changes in body temperature in a mouse model. Accordingly, we measured the subcutaneous temperature after acute administration of 4-MTA in CD1 mice. Because hyperthermia seems to result from the central and peripheral actions of catecholamines and serotonin (5-hydroxytriptamine or 5-HT), we also investigated the possible interactions of some catecholaminergic and serotonergic receptor blockers and the inhibition of monoamine oxidase (MAO) with this effect. 4-MTA induced hyperthermia in CD1 mice. Blockade of the 5-HT receptors with methysergide and MAO inhibition with pargyline resulted in the potentiation of the 4-MTA-induced hyperthermic effect. Blockade of the alpha(1)-adrenergic receptors with prazosin completely reverted the 4-MTA-induced hyperthermia while with the beta-adrenergic receptor blocker dl-propranolol this reversal was not complete. Blockade of the alpha(2)-adrenergic receptors with yohimbine had no effect on the hyperthermia induced by 4-MTA. These results suggest that 4-MTA-induced hyperthermia is highly influenced by the catecholaminergic and serotonergic receptor activation and the MAO activity.
  Toxicology and Applied Pharmacology 09/2003; 190(3):262-71. · 4.45 Impact Factor
• Article: Identification of 4-methylthioamphetamine and some of its metabolites in mouse urine by GC-MS after acute administration.

  Helena Carmo, Douwe de Boer, Fernando Remião, Félix Carvalho, Lesseps A dos Reys, Maria de Lourdes Bastos
  Journal of analytical toxicology 26(4):228-32. · 2.02 Impact Factor