Search

It is well established that 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) causes acute liver damage in animals and humans. The aim of this study was to identify and characterize oxidative modification and inactivation of cytosolic proteins in MDMA-exposed rats. Markedly increased levels of oxidized and nitrated cytosolic proteins were detected 12 h after the second administration of two consecutive MDMA doses (10 mg/kg each). Comparative 2-DE analysis showed markedly increased levels of biotin-N-methylimide-labeled oxidized cytosolic proteins in MDMA-exposed rats compared to vehicle-treated rats. Proteins in the 22 gel spots of strong intensities were identified using MS/MS. The oxidatively modified proteins identified include anti-oxidant defensive enzymes, a calcium-binding protein, and proteins involved in metabolism of lipids, nitrogen, and carbohydrates (glycolysis). Cytosolic superoxide dismutase was oxidized and its activity significantly inhibited following MDMA exposure. Consistent with the oxidative inactivation of peroxiredoxin, MDMA activated c-Jun N-terminal protein kinase and p38 kinase. Since these protein kinases phosphorylate anti-apoptotic Bcl-2 protein, their activation may promote apoptosis in MDMA-exposed tissues. Our results show for the first time that MDMA induces oxidative-modification of many cytosolic proteins accompanied with increased oxidative stress and apoptosis, contributing to hepatic damage., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Despite numerous reports about the acute and sub-chronic toxicities caused by MDMA (3,4-methylenedioxymethamphetamine, ecstasy), the underlying mechanism of organ damage is poorly understood. The aim of this review is to present an update of the mechanistic studies on MDMA-mediated organ damage partly caused by increased oxidative/nitrosative stress. Because of the extensive reviews on MDMA-mediated oxidative stress and tissue damage, we specifically focus on the mechanisms and consequences of oxidative-modifications of mitochondrial proteins, leading to mitochondrial dysfunction. We briefly describe a method to systematically identify oxidatively-modified mitochondrial proteins in control and MDMA-exposed rats by using biotin-N-maleimide (biotin-NM) as a sensitive probe for oxidized proteins. We also describe various applications and advantages of this Cys-targeted proteomics method and alternative approaches to overcome potential limitations of this method in studying oxidized proteins from MDMA-exposed tissues. Finally we discuss the mechanism of synergistic drug-interaction between MDMA and other abused substances including alcohol (ethanol) as well as application of this redox-based proteomics method in translational studies for developing effective preventive and therapeutic agents against MDMA-induced organ damage.

Alcohol (ethanol) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are frequently co-abused, but recent findings indicate a harmful drug interaction between these two agents. In our previous study, we showed that MDMA exposure inhibits the activity of the acetaldehyde (ACH) metabolizing enzyme, aldehyde dehydrogenase2 (ALDH2). Based on this finding, we hypothesized that the co-administration of MDMA and ethanol would reduce the metabolism of ACH and result in increased accumulation of ACH. Rats were treated with MDMA or vehicle and then administered a single dose of ethanol. Liver ALDH2 activity decreased by 35% in the MDMA-treated rats compared to control rats. The peak concentration and the area under the concentration versus time curve of plasma ACH were 31% and 59% higher, respectively, in the MDMA-ethanol group compared to the ethanol-only group. In addition, the MDMA-ethanol group had 80% higher plasma transaminase levels than the ethanol-only group, indicating greater hepatocellular damage. Our results not only support a drug interaction between MDMA and ethanol but a novel underlying mechanism for the interaction.

Despite numerous reports citing the acute hepatotoxicity caused by 3,4-methylenedioxymethamphetamine (MDMA) (ecstasy), the underlying mechanism of organ damage is poorly understood. We hypothesized that key mitochondrial proteins are oxidatively modified and inactivated in MDMA-exposed tissues. The aim of this study was to identify and investigate the mechanism of inactivation of oxidatively modified mitochondrial proteins, prior to the extensive mitochondrial dysfunction and liver damage following MDMA exposure. MDMA-treated rats showed abnormal liver histology with significant elevation in plasma transaminases, nitric oxide synthase, and the level of hydrogen peroxide. Oxidatively modified mitochondrial proteins in control and MDMA-exposed rats were labeled with biotin-N-maleimide (biotin-NM) as a sensitive probe for oxidized proteins, purified with streptavidin-agarose, and resolved using 2-DE. Comparative 2-DE analysis of biotin-NM-labeled proteins revealed markedly increased levels of oxidatively modified proteins following MDMA exposure. Mass spectrometric analysis identified oxidatively modified mitochondrial proteins involved in energy supply, fat metabolism, antioxidant defense, and chaperone activities. Among these, the activities of mitochondrial aldehyde dehydrogenase, 3-ketoacyl-CoA thiolases, and ATP synthase were significantly inhibited following MDMA exposure. Our data show for the first time that MDMA causes the oxidative inactivation of key mitochondrial enzymes which most likely contributes to mitochondrial dysfunction and subsequent liver damage in MDMA-exposed animals.

Fluoxetine has been shown to provide protection from MDMA induced long term neurotoxicity. The purpose of this investigation is to evaluate the pharmacokinetic drug interaction between MDMA and fluoxetine and also to determine the role of P-glycoprotein (P-gp) on mediating drug-drug interactions with MDMA. Bi-directional transport studies were conducted across MDCK-MDR1 and Caco-2 monolayers. MDMA brain and plasma levels were measured in P-gp deficient [mdr1a(-/-)] and normal [mdr1a(+/+)] mice after a 5 mg/kg i.p. dose of MDMA. Sprague-Dawley rats were pretreated with fluoxetine (4 days, 10 mg/kg, i.p.) or saline followed by MDMA (10 mg/kg, p.o.) and brain and plasma samples were collected over 10 h. MDMA and its active metabolite MDA were quantified using a HPLC method with fluorescence detection. In transport studies MDMA exhibited high permeability with essentially unpolarized transport. No significant difference in MDMA and MDA brain levels were seen in P-gp deficient versus normal mice. Pretreatment of rats with fluoxetine resulted in an increase in MDMA (1.4-fold) and MDA (1.5-fold) exposure in both brain and plasma. Elimination half-life was increased for MDMA (2.4 vs. 4.9 h) and MDA (1.8 vs. 8.2 h) with fluoxetine pretreatment. P-gp does not play a physiologically relevant role in absorption and distribution of MDMA, hence this transporter may not have a role in drug-drug interactions with MDMA. Fluoxetine pretreatment to provide protection from MDMA induced long term neurotoxicity decreases elimination of MDMA and MDA and may lead to enhanced risk of MDMA acute toxic effects. Overall, our results indicate that caution need to be practiced when recommending fluoxetine as an agent to provide protection from MDMA induced long term neurotoxicity., (2007 Wiley-Liss, Inc)