The Role of Human Hepatic Cytochrome P450 Isozymes in the Metabolism of Racemic 3,4-Methylenedioxy-Methamphetamine and Its Enantiomers

Abstract

ABSTRACT:The entactogen, 3,4-methylenedioxy-methamphetamine (MDMA), is a chiral drug that is mainly metabolized by N-demethylation and demethylenation. The involvement of cytochrome P450 (P450) isozymes in these metabolic steps has been studied by inhibition assays with human liver microsomes and, in part, with heterologously expressed human P450 isozymes. However, a comprehensive study on the involvement of all relevant human P450s has not been published yet. In addition, the chirality of this drug was not considered in these in vitro studies. The aim of the present work was to study the contribution of human P450 isozymes in the N-demethylation and demethylenation of racemic MDMA and its single enantiomers. MDMA and its enantiomers were incubated using heterologously expressed human P450s, and the metabolites were quantified by gas chromatography-mass spectrometry after derivatization with S-heptafluorobutyrylprolyl chloride. The highest contribution for the N-demethylation as calculated from the enzyme kinetic data, were obtained for CYP2B6 (R,S-MDMA), CYP1A2 (R-MDMA), and CYP2B6 (S-MDMA). In the case of the demethylenation, the isozyme with the highest contribution to net clearance for R,S-MDMA, R-MDMA, and S-MDMA was CYP2D6. For the first time, marked enantioselectivity was observed for N-demethylation and demethylenation by CYP2C19 with a preference for the S-enantiomers. In addition, CYP2D6 showed preference for S-MDMA in the case of demethylenation. None of the other isozymes showed major preferences for certain enantiomers. In conclusion, therefore, the different pharmacokinetic properties of the MDMA enantiomers may be caused by enantioselective metabolism by CYP2C19 and CYP2D6.

Differential Roles of Phase I and Phase II Enzymes in 3,4-Methylendioxymethamphetamine-Induced Cytotoxicity

“…It has been suggested that CYP2D6 accounts for approximately 30% of MDMA metabolism, but involvement of other hepatic P450 enzymes, such as CYP1A2, CYP3A4, CYP2B6, and CYP2C19, has been reported (Meyer et al, 2008). However, the contribution of CYP3A4 and CYP1A2 to MDMA metabolism and what metabolites are being formed by these enzymes is less clear (Lin et al, 1992;Tucker et al, 1994;Kreth et al, 2000;Maurer et al, 2000).…”

A mechanistic insight into 3,4-methylenedioxymethamphetamine (“ecstasy”)-mediated hepatotoxicity

“…Most studies concerning polymorphism as a risk factor in acute MDMA intoxications refer to the polymorphism associated with the phase I enzyme CYP2D6, which has been reported in vivo (de la ) and in vitro (Tucker et al 1994;Ramamoorthy et al 2002). At present, it is thought to be the major enzyme yielding reactive MDMA catechol-metabolites (Tucker et al 1994;Lin et al 1997;Wu et al 1997;Delaforge et al 1999;Maurer et al 2000;Kreth et al 2000;de la Torre et al 2005;Segura et al 2005;Meyer et al 2008a). CYP2D6 is highly polymorphic, affecting its expression or activity and determining several metabolic groups as poor metabolizers (PMs, 1% Asians and $10% Caucasians), intermediate metabolizers (IMs $10-15% European population), extensive metabolizers (EMs), and ultra rapid metabolizers (UMs, frequent in Ethiopian and Saudi Arabian and $5% Caucasians), which are distributed over the entire population (Ingelman-Sundberg 2005).…”

“…Phase I MDMA metabolism involves two main routes (Figure 1): (1) chain conversion by N-dealkylation to 3,4-methylendioxyamphetamine (MDA) mainly by CYP1A2, CYP2B6, and CYP2C19 or (2) O-demethylenation of the ring leading to 3,4-dihydroxymethamphetamine (HHMA) and 3,4-dihydroxyamphetamine (HHA) mediated by CYP2D6, CYP3A4, and CYP2C19. The cytochromes responsible of catalyzing the O-demethylation of the ring yield the catechol-metabolites (HHMA, HHA), which are more cytotoxic than the parent compound, indicating that MDMA bioactivation occurs after the opening of the ring (Kreth et al 2000;Jones et al 2005;Milhazes et al 2006;Meyer et al 2008b;Antolino-Lobo et al 2010). These metabolites can be oxidized to the corresponding ortho-metabolites, which generates reactive oxygen species (ROS) and reactive nitrogen species (RNS) (Monks and Lau 1997).…”

“…Following CYP2D6 activity, reactive metabolites (HHMA and HHA) can be determined in vitro and in biological samples such as blood and urine (Tucker et al 1994;Wu et al 1997;Lin et al 1997;Delaforge et al 1999;Kreth et al 2000;Maurer et al 2000;Segura et al 2005;de la Torre et al 2005;Meyer et al 2008a). However, metabolic inactivation of CYP2D6 by MDMA itself has been proven and it has been suggested that the contribution of this enzyme does not exceed the 30% in MDMA metabolism (Tucker et al 1994;Heydari et al 2004;Segura et al 2005;Yang et al 2006; Van et al 2007;O'Mathuna et al 2008).…”

Interactions between Over-the-Counter and Illicit Drugs Utilizing Cytochrome P450 Metabolism: Potential for Exacerbation of Pharmacological Response

“…Although CYP2D6 is the major route of metabolism, other P450 isozymes contribute to the overall metabolism of MDMA. 11,12,74,75 A recent study examined the potential drug-drug interactions between MDMA and caffeine. 76 Although, the authors report that there are no drug-drug interactions which significantly alter MDMA metabolism, the authors acknowledge the importance of the investigation into drug-drug interactions.…”