title: Dopamine transporter-mediated cytotoxicity of 6-hydroxydopamine in vitro depends on expression of mutant alpha-synucleins related to Parkinson's disease.
abstract: 6-Hydroxydopamine (6-OHDA) is widely used to produce animal models of Parkinson's disease (PD) by selectively destroying the nigro-striatal dopaminergic systems, but selective toxicity of 6-OHDA towards dopaminergic cells in vitro remains controversial. Mutant (A30P and A53T) alpha-synuclein isoforms cause increased vulnerability of cells towards various toxic insults and enhance dopamine transporter (DAT)-mediated toxicity of the selective dopaminergic neurotoxin and mitochondrial complex I inhibitor MPP(+) in vitro. Here we extend our recent studies on DAT-mediated toxicity to elucidate the mechanisms involved in selective dopaminergic toxicity of 6-OHDA. We studied the cytotoxicity as well as the toxic mechanisms of 6-OHDA in human embryonic kidney HEK-293 cells ectopically co-expressing mutant alpha-synucleins and the human DAT protein. 6-OHDA showed half-maximal toxic concentration (TC(50)) of 88 microM in HEK-hDAT cells without alpha-synuclein expression after 24 h, whereas the TC(50) values significantly decreased to 58 and 39 microM by expression of A30P and A53T alpha-synuclein, respectively. alpha-Synuclein expression did not affect 6-OHDA toxicity in HEK-293 cells not expressing the DAT. Analysis of intracellular parameters of cellular energy metabolism revealed that the co-expression of mutant alpha-synucleins in HEK-hDAT cells accelerates the reduction of intracellular net ATP levels and ATP/ADP ratios induced by 6-OHDA. Uptake function of the DAT was not altered by expression of alpha-synuclein isoforms. Our data suggest a mechanism of 6-OHDA-induced dopaminergic toxicity involving an interaction of mutant alpha-synucleins with the DAT molecule and subsequent acceleration of cellular energy depletion that might be relevant for the pathogenesis of PD.
authors.affiliation: Department of Neurology, University of Ulm, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Lehmensiek
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Tan
authors.forename: Stefan
authors.initials: S
authors.lastname: Liebau
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenk
authors.forename: Heinz
authors.initials: H
authors.lastname: Zettlmeisl
authors.forename: Johannes
authors.initials: J
authors.lastname: Schwarz
authors.forename: Alexander
authors.initials: A
authors.lastname: Storch
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D016627:Oxidopamine / Q000633:toxicity*; D010300:Parkinson Disease / Q000378:metabolism* / Q000503:physiopathology; D020033:Protein Isoforms / Q000187:drug effects / Q000378:metabolism; D013565:Sympatholytics / Q000633:toxicity; D051844:alpha-Synuclein / Q000235:genetics* / Q000378:metabolism*
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D009498:Neurotoxins; D020033:Protein Isoforms; D013565:Sympatholytics; D051844:alpha-Synuclein; D016627:Oxidopamine; D000255:Adenosine Triphosphate; D004298:Dopamine