title: Inhibition of vesicular monoamine transporter enhances vulnerability of dopaminergic cells: relevance to Parkinson's disease.
abstract: Parkinson's disease is a neurodegenerative disorder associated with progressive loss of dopaminergic cells in the substantia nigra. Oxidative stress has been implicated in the pathogenesis of the disease, and dopamine has been suggested as a contributing factor that generates reactive oxygen species due to its unstable catechol moiety. We have previously shown that tetrahydrobiopterin (BH4), an obligatory cofactor for dopamine synthesis, also contributes to the vulnerability of dopamine-producing cells by generating oxidative stress. This study shows that the presence of dopamine in the cytosol enhances the cell's vulnerability to BH4. Upon exposure to ketanserin, a vesicular monoamine transporter inhibitor, BH4-induced dopaminergic cell death is exacerbated, accompanied by increased lipid peroxidation and protein bound quinone. While intracellular amount of DOPAC is elevated by ketanserin, the monoamine oxidase inhibitor pargyline showed no significant protection. Instead, the thiol agent N-acetylcysteine and quinone reductase inducer dimethyl fumarate abolish BH4/ketanserin-induced cell death, suggesting that quinone production plays an important role. Therefore, it can be concluded that the presence of dopamine in the cytosol seems to contribute to the cells' vulnerability to BH4 and that vesicular monoamine transporter plays a protective role in dopaminergic cells by sequestering dopamine not only from monoamine oxidase but also from BH4-induced oxidative stress.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-ku, Seoul 138-736, South Korea.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Choi
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Lee
authors.forename: Yuri
authors.initials: Y
authors.lastname: Cho
authors.forename: Onyou
authors.initials: O
authors.lastname: Hwang
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D000069462:Dimethyl Fumarate; D004298:Dopamine / Q000096:biosynthesis*; D004351:Drug Resistance / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005650:Fumarates / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010300:Parkinson Disease / Q000378:metabolism* / Q000503:physiopathology; D013378:Substantia Nigra / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins
chemical_list: D016227:Benzoquinones; D004791:Enzyme Inhibitors; D005650:Fumarates; D008562:Membrane Glycoproteins; D049990:Membrane Transport Modulators; D026901:Membrane Transport Proteins; D008996:Monoamine Oxidase Inhibitors; D050492:Vesicular Biogenic Amine Transport Proteins; D050493:Vesicular Monoamine Transport Proteins; D015102:3,4-Dihydroxyphenylacetic Acid; D001708:Biopterins; C004532:quinone; D007650:Ketanserin; C003402:sapropterin; D000069462:Dimethyl Fumarate; D004298:Dopamine; D000111:Acetylcysteine