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. Methods and Findings: 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. Conclusion: 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. © 2009 Du et al.