Serotonergic neurotoxic metabolites of ecstasy identified in rat brain.
The selective serotonergic neurotoxicity of 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) depends on their systemic metabolism. We have recently shown that inhibition of brain endothelial cell gamma-glutamyl transpeptidase (gamma-GT) potentiates the neurotoxicity of both MDMA and MDA, indicating that metabolites that are substrates for this enzyme contribute to the neurotoxicity. Consistent with this view, glutathione (GSH) and N-acetylcysteine conjugates of alpha-methyl dopamine (alpha-MeDA) are selective neurotoxicants. However, neurotoxic metabolites of MDMA or MDA have yet to be identified in brain. Using in vivo microdialysis coupled to liquid chromatography-tandem mass spectroscopy and a high-performance liquid chromatography-coulometric electrode array system, we now show that GSH and N-acetylcysteine conjugates of N-methyl-alpha-MeDA are present in the striatum of rats administered MDMA by subcutaneous injection. Moreover, inhibition of gamma-GT with acivicin increases the concentration of GSH and N-acetylcysteine conjugates of N-methyl-alpha-MeDA in brain dialysate, and there is a direct correlation between the concentrations of metabolites in dialysate and the extent of neurotoxicity, measured by decreases in serotonin (5-HT) and 5-hydroxyindole acetic (5-HIAA) levels. Importantly, the effects of acivicin are independent of MDMA-induced hyperthermia, since acivicin-mediated potentiation of MDMA neurotoxicity occurs in the context of acivicin-mediated decreases in body temperature. Finally, we have synthesized 5-(N-acetylcystein-S-yl)-N-methyl-alpha-MeDA and established that it is a relatively potent serotonergic neurotoxicant. Together, the data support the contention that MDMA-mediated serotonergic neurotoxicity is mediated by the systemic formation of GSH and N-acetylcysteine conjugates of N-methyl-alpha-MeDA (and alpha-MeDA). The mechanisms by which such metabolites access the brain and produce selective serotonergic neurotoxicity remain to be determined.
Jones
Douglas C
DC
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona Health Sciences Center, Tucson, AZ 85721-0207, USA.
Duvauchelle
Christine
C
Ikegami
Aiko
A
Olsen
Christopher M
CM
Lau
Serrine S
SS
de la Torre
Rafael
R
Monks
Terrence J
TJ
D000111:Acetylcysteine / Q000378:metabolism; D000818:Animals; D001711:Biotransformation; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D004567:Electrodes, Implanted; D005978:Glutathione / Q000378:metabolism; D007035:Hypothermia / Q000139:chemically induced / Q000503:physiopathology; D007279:Injections, Subcutaneous; D008297:Male; D013058:Mass Spectrometry; D017551:Microdialysis; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000493:pharmacokinetics* / Q000633:toxicity*; D009498:Neurotoxins / Q000493:pharmacokinetics* / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D018490:Serotonin Agents / Q000493:pharmacokinetics* / Q000633:toxicity*
D009498:Neurotoxins; D018490:Serotonin Agents; D012701:Serotonin; D005978:Glutathione; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D000111:Acetylcysteine