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Masoud ST, Vecchio LM, Bergeron Y, Hossain MM, Nguyen LT, Bermejo MK, Kile B, Sotnikova TD, Siesser WB, Gainetdinov RR, Wightman RM, Caron MG, Richardson JR, Miller GW, Ramsey AJ, Cyr M, Salahpour A. Increased expression of the dopamine transporter leads to loss of dopamine neurons, oxidative stress and l-DOPA reversible motor deficits. Neurobiol Dis 2014; 74:66-75. [PMID: 25447236 DOI: 10.1016/j.nbd.2014.10.016] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 10/07/2014] [Accepted: 10/22/2014] [Indexed: 01/17/2023] Open
Abstract
The dopamine transporter is a key protein responsible for regulating dopamine homeostasis. Its function is to transport dopamine from the extracellular space into the presynaptic neuron. Studies have suggested that accumulation of dopamine in the cytosol can trigger oxidative stress and neurotoxicity. Previously, ectopic expression of the dopamine transporter was shown to cause damage in non-dopaminergic neurons due to their inability to handle cytosolic dopamine. However, it is unknown whether increasing dopamine transporter activity will be detrimental to dopamine neurons that are inherently capable of storing and degrading dopamine. To address this issue, we characterized transgenic mice that over-express the dopamine transporter selectively in dopamine neurons. We report that dopamine transporter over-expressing (DAT-tg) mice display spontaneous loss of midbrain dopamine neurons that is accompanied by increases in oxidative stress markers, 5-S-cysteinyl-dopamine and 5-S-cysteinyl-DOPAC. In addition, metabolite-to-dopamine ratios are increased and VMAT2 protein expression is decreased in the striatum of these animals. Furthermore, DAT-tg mice also show fine motor deficits on challenging beam traversal that are reversed with l-DOPA treatment. Collectively, our findings demonstrate that even in neurons that routinely handle dopamine, increased uptake of this neurotransmitter through the dopamine transporter results in oxidative damage, neuronal loss and l-DOPA reversible motor deficits. In addition, DAT over-expressing animals are highly sensitive to MPTP-induced neurotoxicity. The effects of increased dopamine uptake in these transgenic mice could shed light on the unique vulnerability of dopamine neurons in Parkinson's disease.
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Affiliation(s)
- S T Masoud
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
| | - L M Vecchio
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
| | - Y Bergeron
- Department of Medical Biology, Université du Québec à Trois-Rivières, QC G9A 5H7 Canada.
| | - M M Hossain
- Environmental and Occupational Health Sciences Institute, Rutgers, 170 Frelinghuysen Road, EOHSI 340, Piscataway, NJ 08854, USA.
| | - L T Nguyen
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
| | - M K Bermejo
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
| | - B Kile
- Department of Chemistry, University of North Carolina at Chapel Hill, NC 27599, USA.
| | - T D Sotnikova
- Neuroscience and Brain Technologies, Italian Institute of Technology, Via Morego 30, Genova 16163, Italy; Faculty of Biology and Soil Science, St. Petersburg State University, St. Petersburg 199034, Russia.
| | - W B Siesser
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
| | - R R Gainetdinov
- Neuroscience and Brain Technologies, Italian Institute of Technology, Via Morego 30, Genova 16163, Italy; Faculty of Biology and Soil Science, St. Petersburg State University, St. Petersburg 199034, Russia; Skolkovo Institute of Science and Technology, Skolkovo, 143025 Moscow Region, Russia.
| | - R M Wightman
- Department of Chemistry, University of North Carolina at Chapel Hill, NC 27599, USA.
| | - M G Caron
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
| | - J R Richardson
- Environmental and Occupational Health Sciences Institute, Rutgers, 170 Frelinghuysen Road, EOHSI 340, Piscataway, NJ 08854, USA.
| | - G W Miller
- Department of Environmental Health, Emory University, Atlanta, GA 30322, USA; Department of Pharmacology, Emory University, Atlanta, GA 30322, USA; Department of Neurology, Emory University, Atlanta, GA 30322, USA.
| | - A J Ramsey
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
| | - M Cyr
- Department of Medical Biology, Université du Québec à Trois-Rivières, QC G9A 5H7 Canada.
| | - A Salahpour
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle - Rm 4302, Toronto, ON M5S 1A8, Canada.
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