L-DOPA neurotoxicity is mediated by up-regulation of DMT1-IRE expression.
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.
Du
Fang
F
Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong.
Qian
Zhong-ming
ZM
Zhu
Li
L
Wu
Xiao Mei
XM
Yung
Wing-ho
WH
Tsim
Ting-yuk
TY
Ke
Ya
Y
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
D027682:Cation Transport Proteins; D017077:Culture Media, Conditioned; D007501:Iron; D007980:Levodopa; D000099236:Solute Carrier Family 11, Member 2