title: Changes in neuronal dopamine homeostasis following 1-methyl-4-phenylpyridinium (MPP+) exposure.
abstract: 1-Methyl-4-phenylpyridinium (MPP(+)), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, selectively kills dopaminergic neurons in vivo and in vitro via a variety of toxic mechanisms, including mitochondrial dysfunction, generation of peroxynitrite, induction of apoptosis, and oxidative stress due to disruption of vesicular dopamine (DA) storage. To investigate the effects of acute MPP(+) exposure on neuronal DA homeostasis, we measured stimulation-dependent DA release and non-exocytotic DA efflux from mouse striatal slices and extracellular, intracellular, and cytosolic DA (DAcyt) levels in cultured mouse ventral midbrain neurons. In acute striatal slices, MPP(+) exposure gradually decreased stimulation-dependent DA release, followed by massive DA efflux that was dependent on MPP(+) concentration, temperature, and DA uptake transporter activity. Similarly, in mouse midbrain neuronal cultures, MPP(+) depleted vesicular DA storage accompanied by an elevation of cytosolic and extracellular DA levels. In neuronal cell bodies, increased DAcyt was not due to transmitter leakage from synaptic vesicles but rather to competitive MPP(+)-dependent inhibition of monoamine oxidase activity. Accordingly, monoamine oxidase blockers pargyline and l-deprenyl had no effect on DAcyt levels in MPP(+)-treated cells and produced only a moderate effect on the survival of dopaminergic neurons treated with the toxin. In contrast, depletion of intracellular DA by blocking neurotransmitter synthesis resulted in ∼30% reduction of MPP(+)-mediated toxicity, whereas overexpression of VMAT2 completely rescued dopaminergic neurons. These results demonstrate the utility of comprehensive analysis of DA metabolism using various electrochemical methods and reveal the complexity of the effects of MPP(+) on neuronal DA homeostasis and neurotoxicity.
authors.affiliation: From the Departments of Neurology.
authors.forename: Se Joon
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: the Institute of Biotechnology, University of Helsinki, 00014 University of Helsinki, Finland.
authors.forename: Anne
authors.initials: A
authors.lastname: Panhelainen
authors.affiliation: From the Departments of Neurology.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Schmitz
authors.affiliation: From the Departments of Neurology.
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Larsen
authors.affiliation: From the Departments of Neurology.
authors.forename: Ellen
authors.initials: E
authors.lastname: Kanter
authors.affiliation: From the Departments of Neurology.
authors.forename: Min
authors.initials: M
authors.lastname: Wu
authors.affiliation: From the Departments of Neurology, Psychiatry, and Pharmacology, Columbia University Medical Center, New York, New York 10032 and.
authors.forename: David
authors.initials: D
authors.lastname: Sulzer
authors.affiliation: From the Departments of Neurology, em706@columbia.edu.
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Mosharov
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity*; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006706:Homeostasis / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009498:Neurotoxins / Q000633:toxicity*
chemical_list: D009498:Neurotoxins; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine
keywords: Dopamine; MPP+; MPTP; Mouse; Neurotoxin; Neurotransmitter; Parkinson Disease; Vesicles