title: Intracellular signaling pathways involved in post-mitotic dopaminergic PC12 cell death induced by 6-hydroxydopamine.
abstract: Oxidative stress has been shown to mediate neuron damage in Parkinson's disease (PD). In the present report, we intend to clarify the intracellular pathways mediating dopaminergic neuron death after oxidative stress production using post-mitotic PC12 cells treated with the neurotoxin 6-hydroxydopamine (6-OHDA). The use of post-mitotic cells is crucial, because one of the suggested intracellular pathways implicated in neuron death relates to the re-entry of neurons (post-mitotic cells) in the cell cycle. We find that 6-OHDA sequentially increases intracellular oxidants, functional cell damage and caspase-3 activation, leading to cell death after 12 h of incubation. Prevention of cell damage by different antioxidants supports the implication of oxidative stress in the observed neurotoxicity. Oxidative stress-dependent phosphorylation of the MAPK JNK and oxidative stress-independent PKB/Akt dephosphorylation are involved in 6-OHDA neurotoxicity. Decrease in p21(WAF1/CIP1) and cyclin-D1 expression, disappearance of the non-phosphorylated band of retinoblastoma protein (pRb), and expression of proliferating cell nuclear antigen, not present in PC12 post-mitotic cells, suggest a re-entry of differentiated cells into cell cycle. Our results indicate that such a re-entry is mediated by oxidative stress and is involved in 6-OHDA-induced cell death. We conclude that at least three intracellular pathways are involved in 6-OHDA-induced cell death in differentiated PC12 cells: JNK activation, cell cycle progression (both oxidative stress-dependent), and Akt dephosphorylation (not related to the increase of oxidants); the three pathways are necessary for the cells to die, since blocking one of them is sufficient to keep the cells alive.
authors.affiliation: Departamento de Morfología y Biología Celular, University of Oviedo. c/Julian Clavería, Oviedo, Spain.
authors.forename: Jezabel
authors.initials: J
authors.lastname: Rodriguez-Blanco
authors.forename: Vanesa
authors.initials: V
authors.lastname: Martín
authors.forename: Federico
authors.initials: F
authors.lastname: Herrera
authors.forename: Guillermo
authors.initials: G
authors.lastname: García-Santos
authors.forename: Isaac
authors.initials: I
authors.lastname: Antolín
authors.forename: Carmen
authors.initials: C
authors.lastname: Rodriguez
mesh_terms: D000818:Animals; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D019938:Cyclin D1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D018816:Genes, cdc / Q000187:drug effects / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008938:Mitosis / Q000502:physiology; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009498:Neurotoxins; D018384:Oxidative Stress / Q000502:physiology*; D016627:Oxidopamine / Q000633:toxicity*; D016716:PC12 Cells; D010300:Parkinson Disease / Q000378:metabolism / Q000503:physiopathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013378:Substantia Nigra / Q000378:metabolism / Q000503:physiopathology; D013565:Sympatholytics
chemical_list: C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009498:Neurotoxins; D016160:Retinoblastoma Protein; D013565:Sympatholytics; D019938:Cyclin D1; D016627:Oxidopamine; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases; D004298:Dopamine