Ecstasy metabolites and monoamine neurotransmitters upshift the Na⁺/K⁺ ATPase activity in mouse brain synaptosomes

Abstract

3,4-Methylenedioximethamphetamine (MDMA; “ecstasy”) is a psychotropic drug with well-known neurotoxic effects mediated by hitherto not fully understood mechanisms. The Na⁺- and K⁺-activated adenosine 5′-triphosphatase (Na⁺/K⁺ ATPase), by maintaining the ion gradient across the cell membrane, regulates neuronal excitability. Thus, a perturbation of its function strongly impacts cell homeostasis, ultimately leading to neuronal dysfunction and death. Nevertheless, whether MDMA affects the Na⁺/K⁺ ATPase remains unknown. In this study, we used synaptosomes obtained from whole mouse brain to test the effects of MDMA, three of its major metabolites [α-methyldopamine, N-methyl-α-methyldopamine and 5-(glutathion-S-yl)-α-methyldopamine], serotonin (5-HT), dopamine, 3,4-dihydroxy-l-phenylalanine (l-Dopa) and 3,4-dihydroxyphenylacetic acid (DOPAC) on the Na⁺/K⁺ ATPase function. A concentration-dependent increase of Na⁺/K⁺ ATPase activity was observed in synaptosomes exposed to the tested compounds (concentrations ranging from 0.0625 to 200 µM). These effects were independent of protein kinases A and C activities. Nevertheless, a rescue of the compounds’ effects was observed in synaptosomes pre-incubated with the antioxidant N-acetylcysteine (1 mM), suggesting a role for reactive species-regulated pathways on the Na⁺/K⁺ ATPase effects. In agreement with this hypothesis, a similar increase in the pump activity was found in synaptosomes exposed to the chemical generator of superoxide radicals, phenazine methosulfate (1–250 µM). This study demonstrates the ability of MDMA metabolites, monoamine neurotransmitters, l-Dopa and DOPAC to alter the Na⁺/K⁺ ATPase function. This could represent a yet unknown mechanism of action of MDMA and its metabolites in the brain.