title: Inhibition of glycogen synthase kinase-3 reduces L-DOPA-induced neurotoxicity.
abstract: The neurotoxicity of l-3,4-dihydroxyphenylalanine (L-DOPA), used for the treatment of Parkinson's disease, remains controversial. Although there are many reports suggesting that long-term treatment of L-DOPA causes neuronal death, an increasing body of recent evidence has proposed that L-DOPA might be neuroprotective rather than neurotoxic. We investigated the effect of L-DOPA on neuronally differentiated PC12 (nPC12) cells by treating cells with various concentrations of L-DOPA for 24h. We also studied whether glycogen synthase kinase (GSK)-3 activation is related to L-DOPA-induced neurotoxicity by simultaneously treating cells with several concentrations of L-DOPA and a GSK-3 inhibitor for 24h. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, trypan blue staining, cell counting kit-8, and DAPI staining all showed that L-DOPA decreased nPC12 cell viability at high concentrations. In addition, 100 microM L-DOPA treatment significantly increased the activity of GSK-3 and death signals including cytochrome c, activated caspase-3 and cleaved PARP, and decreased survival signals including heat shock transcription factor-1 in a concentration-dependent manner. Treatment with GSK-3 inhibitor VIII or lithium chloride prevented L-DOPA-induced cell death. Together, these results suggest that L-DOPA induces neuronal cell death at high concentrations and that the neurotoxic effect of L-DOPA might be mediated in part by GSK-3 activation.
authors.affiliation: Department of Neurology, Institute of Biomedical Science, College of Medicine, Hanyang University, Seoul, Republic of Korea.
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Koh
authors.forename: Chiwon
authors.initials: C
authors.lastname: Song
authors.forename: Min Young
authors.initials: MY
authors.lastname: Noh
authors.forename: Hyun Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Kyu-Yong
authors.initials: KY
authors.lastname: Lee
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Juhan
authors.initials: J
authors.lastname: Kim
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Hee-Tae
authors.initials: HT
authors.lastname: Kim
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005609:Free Radicals; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors*; D007980:Levodopa / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects*; D016716:PC12 Cells; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D005609:Free Radicals; D007980:Levodopa; D038362:Glycogen Synthase Kinase 3