title: L-DOPA neurotoxicity is prevented by neuroprotective effects of erythropoietin.
abstract: The neurotoxicity of L-3,4-dihydroxyphenylalanine (L-DOPA), one of the most important drugs for the treatment of Parkinson's disease, still remains controversial, although much more data on L-DOPA neurotoxicity have been presented. Considering the well known neuroprotective effects of erythropoietin (EPO), the inhibitory effects of EPO on L-DOPA neurotoxicity need to be evaluated. Neuronally differentiated PC12 (nPC12) cells were treated with different concentrations of L-DOPA and/or EPO for 24h. Cell viability was evaluated using trypan blue, 4',6-diamidino-2-phenylindole (DAPI) and TUNEL staining, and cell counting. Free radicals and intracellular signaling protein levels were measured with 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and Western blotting, respectively. L-DOPA reduced nPC12 cell viability at higher concentrations, but combined treatment with EPO and L-DOPA significantly restored cell viability. Free radicals and hydroxyl radical levels increased by L-DOPA were decreased after combined treatment of L-DOPA and EPO. Levels of survival-related intracellular signaling proteins decreased in nPC12 cells treated with 200 μM L-DOPA but increased significantly in cells treated with 200μM L-DOPA and 5 μM EPO. However, cleaved caspase-3, a death-related protein, increased in nPC12 cells treated with 200 μM L-DOPA but decreased significantly in cells treated with 200 μM L-DOPA and 5 μM EPO. Pretreatment with LY294002, a phosphatidylinositol 3-kinase inhibitor, prior to combined treatment with EPO and L-DOPA almost completely blocked the protective effects of EPO. These results indicate that EPO can prevent L-DOPA neurotoxicity by activating the PI3K pathway as well as reducing oxidative stress.
authors.affiliation: Department of Neurology, Gachon University Gil Hospital, Inchon, Republic of Korea.
authors.forename: Kee Hyung
authors.initials: KH
authors.lastname: Park
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Choi
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Koh
authors.forename: Hyun-Hee
authors.initials: HH
authors.lastname: Park
authors.forename: Young Seo
authors.initials: YS
authors.lastname: Kim
authors.forename: Min-Jung
authors.initials: MJ
authors.lastname: Kim
authors.forename: Su-Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Hyun-Jeung
authors.initials: HJ
authors.lastname: Yu
authors.forename: Kyu-Yong
authors.initials: KY
authors.lastname: Lee
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Hee-Tae
authors.initials: HT
authors.lastname: Kim
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000494:pharmacology*; D006801:Humans; D017665:Hydroxyl Radical / Q000378:metabolism; D007980:Levodopa / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
chemical_list: D000975:Antioxidants; C554270:EPO protein, human; D018696:Neuroprotective Agents; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D004921:Erythropoietin; D017665:Hydroxyl Radical; D007980:Levodopa; D058539:Phosphatidylinositol 3-Kinase; C505410:Casp3 protein, rat; D053148:Caspase 3