title: Multiple treatments with L-3,4-dihydroxyphenylalanine modulate dopamine biosynthesis and neurotoxicity through the protein kinase A-transient extracellular signal-regulated kinase and exchange protein activation by cyclic AMP-sustained extracellular signal-regulated kinase signaling pathways.
abstract: Multiple treatments with L-3,4-dihydroxyphenylalanine (L-DOPA; 20 µM) induce neurite-like outgrowth and reduce dopamine biosynthesis in rat adrenal pheochromocytoma (PC) 12 cells. We therefore investigated the effects of multiple treatments with L-DOPA (MT-LD) on cell survival and death over a duration of 6 days by using PC12 cells and embryonic rat midbrain primary cell cultures. MT-LD (10 and 20 µM) decreased cell viability, and both types of cells advanced to the differentiation process at 4-6 days. MT-LD induced cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) phosphorylation and exchange protein activation by cAMP (Epac) expression at 1-3 days, which led to transient extracellular signal-regulated kinase (ERK1/2) phosphorylation in both cells. In these states, MT-LD activated cAMP-response element binding protein (CREB; Ser133) and tyrosine hydroxylase (Ser40) phosphorylation in PC12 cells, which led to an increase in intracellular dopamine levels. In contrast, MT-LD induced prolonged Epac expression at 4-5 days in both cells, which led to sustained ERK1/2 phosphorylation. In these states, the dopamine levels were decreased in PC12 cells. In addition, MT-LD induced c-Jun N-terminal kinase1/2 phosphorylation and cleaved caspase-3 expression at 4-6 days in both cells. These results suggest that MT-LD maintains cell survival via PKA-transient ERK1/2 activation, which stimulates dopamine biosynthesis. In contrast, at the later time period, MT-LD induces differentiation via both prolonged Epac and sustained ERK1/2 activation, which subsequently leads to the cell death process. Our data demonstrate that L-DOPA can cause neurotoxicity by modulating the Epac-ERK pathways in neuronal and PC12 cells.
authors.affiliation: College of Pharmacy and Research Center for Bioresource and Health, Chungbuk National University, Cheongju, Republic of Korea.
authors.forename: Keun Hong
authors.initials: KH
authors.lastname: Park
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Park
authors.forename: Keon Sung
authors.initials: KS
authors.lastname: Shin
authors.forename: Myung Koo
authors.initials: MK
authors.lastname: Lee
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D015259:Dopamine Agents / Q000494:pharmacology*; D004622:Embryo, Mammalian; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019922:GAP-43 Protein / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007980:Levodopa / Q000494:pharmacology*; D008636:Mesencephalon / Q000166:cytology; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D015259:Dopamine Agents; D019922:GAP-43 Protein; D020662:Guanine Nucleotide Exchange Factors; C526973:Rapgef3 protein, rat; D007980:Levodopa; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D004298:Dopamine
keywords: ERK1/2; Epac; L-DOPA-induced neurotoxicity; PC12 cells; embryonic rat midbrain primary cell cultures