A vital role for voltage-dependent potassium channels in dopamine transporter-mediated 6-hydroxydopamine neurotoxicity.
6-Hydroxydopamine (6-OHDA), a neurotoxic substrate of the dopamine transporter (DAT), is widely used in Parkinson's disease models. However, the molecular mechanisms underlying 6-OHDA's selectivity for dopamine neurons and the injurious sequelae that it triggers are not well understood. We tested whether ectopic expression of DAT induces sensitivity to 6-OHDA in non-dopaminergic rat cortical neurons and evaluated the contribution of voltage-dependent potassium channel (Kv)-dependent apoptosis to the toxicity of this compound in rat cortical and midbrain dopamine neurons. Cortical neurons expressing DAT accumulated dopamine and were highly vulnerable to 6-OHDA. Pharmacological inhibition of DAT completely blocked this toxicity. We also observed a p38-dependent Kv current surge in DAT-expressing cortical neurons exposed to 6-OHDA, and p38 antagonists and Kv channel blockers were neuroprotective in this model. Thus, DAT-mediated uptake of 6-OHDA recruited the oxidant-induced Kv channel dependent cell death pathway present in cortical neurons. Finally, we report that 6-OHDA also increased Kv currents in cultured midbrain dopamine neurons and this toxicity was blocked with Kv channel antagonists. We conclude that native DAT expression accounts for the dopamine neuron specific toxicity of 6-OHDA. Following uptake, 6-OHDA triggers the oxidant-associated Kv channel-dependent cell death pathway that is conserved in non-dopaminergic cortical neurons and midbrain dopamine neurons.
Redman
P T
PT
Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, Pittsburgh, PA 15261, USA.
Jefferson
B S
BS
Ziegler
C B
CB
Mortensen
O V
OV
Torres
G E
GE
Levitan
E S
ES
Aizenman
E
E
D018663:Adrenergic Agents / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D016627:Oxidopamine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051381:Rats; D019789:Tetraethylammonium / Q000494:pharmacology; D014162:Transfection / Q000379:methods
D018663:Adrenergic Agents; D050483:Dopamine Plasma Membrane Transport Proteins; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D049452:Green Fluorescent Proteins; D019789:Tetraethylammonium; D016627:Oxidopamine; D004298:Dopamine