title: L-DOPA neurotoxicity is mediated by up-regulation of DMT1-IRE expression.
abstract: BACKGROUND
  The mechanisms underlying neurotoxicity caused by L-DOPA are not yet completely known. Based on recent findings, we speculated that the increased expression of divalent metal transporter 1 without iron-response element (DMT1-IRE) induced by L-DOPA might play a critical role in the development of L-DOPA neurotoxicity. To test this hypothesis, we investigated the effects of astrocyte-conditioned medium (ACM) and siRNA DMT-IRE on L-DOPA neurotoxicity in cortical neurons.
  
  
  RESULTS
  We demonstrated that neurons treated with L-DOPA have a significant dose-dependent decrease in neuronal viability (MTT Assay) and increase in iron content (using a graphite furnace atomic absorption spectrophotometer), DMT1-IRE expression (Western blot analysis) and ferrous iron (55Fe(II)) uptake. Neurons incubated in ACM with or without L-DOPA had no significant differences in their morphology, Hoechst-33342 staining or viability. Also, ACM significantly inhibited the effects of L-DOPA on neuronal iron content as well as DMT1-IRE expression. In addition, we demonstrated that infection of neurons with siRNA DMT-IRE led to a significant decrease in DMT1-IRE expression as well as L-DOPA neurotoxicity.
  
  
  CONCLUSIONS
  The up-regulation of DMT1-IRE and the increase in DMT1-IRE-mediated iron influx play a key role in L-DOPA neurotoxicity in cortical neurons.
authors.affiliation: Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong.
authors.forename: Fang
authors.initials: F
authors.lastname: Du
authors.forename: Zhong-ming
authors.initials: ZM
authors.lastname: Qian
authors.forename: Li
authors.initials: L
authors.lastname: Zhu
authors.forename: Xiao Mei
authors.initials: XM
authors.lastname: Wu
authors.forename: Wing-ho
authors.initials: WH
authors.lastname: Yung
authors.forename: Ting-yuk
authors.initials: TY
authors.lastname: Tsim
authors.forename: Ya
authors.initials: Y
authors.lastname: Ke
mesh_terms: D000818:Animals; D001253:Astrocytes; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D017077:Culture Media, Conditioned; D004305:Dose-Response Relationship, Drug; D007501:Iron / Q000378:metabolism*; D007980:Levodopa / Q000633:toxicity*; D009474:Neurons / Q000473:pathology; D020258:Neurotoxicity Syndromes / Q000209:etiology*; D051381:Rats; D017208:Rats, Wistar; D020218:Response Elements; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D027682:Cation Transport Proteins; D017077:Culture Media, Conditioned; D007501:Iron; D007980:Levodopa; D000099236:Solute Carrier Family 11, Member 2