Metabolism Is Required for the Expression of Ecstasy-Induced Cardiotoxicity in Vitro

Abstract

Cardiovascular complications associated with 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse have increasingly been reported. The indirect effect of MDMA mediated by a sustained high level of circulating biogenic amines may contribute to the cardiotoxic effects, but other factors, like the direct toxic effects of MDMA and its metabolites in cardiac cells, remain to be investigated. Thus, the objective of the present in vitro study was to evaluate the potential cardiotoxic effects of MDMA and its major metabolites 3,4-methylenedioxyamphetamine (MDA), N-methyl-alpha-methyldopamine (N-Me-alpha-MeDA), and alpha-methyldopamine (alpha-MeDA) using freshly isolated adult rat cardiomyocytes. The cell suspensions were incubated with these compounds in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 4 h. alpha-MeDA, N-Me-alpha-MeDA, and their respective aminochromes (oxidation products) were quantified in cell suspensions by HPLC-DAD. The toxic effects were evaluated at hourly intervals for 4 h by measuring the percentage of cells with normal morphology, glutathione (GSH), and glutathione disulfide (GSSG); intracellular Ca(2+), ATP, and ADP; and the cellular activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. No toxic effects were found after exposure of rat cardiomyocytes to MDMA or MDA at any of the tested concentrations for 4 h. In contrast, their catechol metabolites N-Me-alpha-MeDA and alpha-MeDA induced significant toxicity in rat cardiomyocytes. The toxic effects were characterized by a loss of normal cell morphology, which was preceded by a loss of GSH homeostasis due to conjugation of GSH with N-Me-alpha-MeDA and alpha-MeDA, sustained increase of intracellular Ca(2+) levels, ATP depletion, and decreases in the antioxidant enzyme activities. The oxidation of N-Me-alpha-MeDA and alpha-MeDA into the toxic compounds N-methyl-alpha-methyldopaminochrome and alpha-methyldopaminochrome, respectively, was also verified in cell suspensions incubated with these MDMA metabolites. The results obtained in this study provide evidence that the metabolism of MDMA into N-Me-alpha-MeDA and alpha-MeDA is required for the expression of MDMA-induced cardiotoxicity in vitro, being N-Me-alpha-MeDA the most toxic of the studied metabolites.

Electrochemical and spectroscopic characterisation of amphetamine-like drugs: Application to the screening of 3,4-methylenedioxymethamphetamine (MDMA) and its synthetic precursors

“…For instance, N-methylated metabolites of amphetamine-like drugs of abuse (e.g. 3,4-dihydroxymethamphetamine) were found to be important to understand the toxicological profile of "ecstasy", at a molecular level [54,55].…”

Synthesis and Cyclic Voltammetry Studies of 3,4-Methylenedioxymethamphetamine (MDMA) Human Metabolites

“…We have also previously demonstrated that the metabolism is important for MDMA-induced toxicity to peripheral organs. [18][19][20] The underlying mechanisms of MDMA and MDA-induced neurotoxicity, namely the toxic effects mediated by its metabolite(s), remain to be completely elucidated. Herein we present cyclic voltammetry studies that provide evidence for a correlation between the toxicity of MDMA and MDAmetabolites and their redox potential.…”

Neurotoxicity of Ecstasy Metabolites in Rat Cortical Neurons, and Influence of Hyperthermia

“…Alternatively, since the reactive o-quinone intermediates are Michael acceptors, cellular damage can occur through alkylation of crucial cellular proteins and/or DNA. In the presence of GSH, o-quinone may be conjugated with GSH to form a glutathionyl adduct, 5-(glu- matsu et al, 1990;Carvalho et al, 2004c). This GSH conjugate remains redox-active, being readily oxidized to the quinone thioether, which, after the reductive addition of a second molecule of GSH, yields a 2,5-bis-glutathionyl conjugate (for detailed insights on MDMA metabolism, see Fig.…”