title: H2O2- or l-DOPA-injured dopaminergic neurons trigger the release of soluble mediators that up-regulate striatal GDNF through different signalling pathways.
abstract: Glial cell line-derived neurotrophic factor (GDNF) is a potent neuroprotective molecule for dopaminergic neurons of the nigrostriatal pathway that degenerate in Parkinson's disease. We have previously shown that H2O2- or l-3,4-dihydroxyphenylalanine (l-DOPA)-challenged dopaminergic neurons trigger the release of soluble factors that signal ventral midbrain astrocytes to increase GDNF expression. In the present work, we evaluated whether the factors released by ventral midbrain-challenged cells were able to alter GDNF expression in striatal cells, the targets of dopaminergic neurons projecting from the substantia nigra, and investigated the signalling pathways involved. Our data showed that soluble mediators released upon H2O2- or l-DOPA-induced dopaminergic injury up-regulated GDNF in striatal cells, with different temporal patterns depending on the oxidative agent used. Conditioned media from H2O2- or l-DOPA-challenged midbrain astrocyte cultures failed to up-regulate GDNF in striatal cultures. Likewise, there was no direct effect of H2O2 or l-DOPA on striatal GDNF levels suggesting that GDNF up-regulation was mediated by soluble factors released in the presence of failing dopaminergic neurons. Both phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways were involved in striatal GDNF up-regulation triggered by H2O2-induced dopaminergic injury, while diffusible factors released in the presence of l-DOPA-challenged dopaminergic neurons induced GDNF expression in striatal cells through the activation of the MAPK pathway. These soluble mediators may constitute, in the future, important targets for the control of endogenous GDNF expression enabling the development of new and, hopefully, more efficient neuroprotective/neurorestorative strategies for the treatment of Parkinson's disease.
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6200-506 Covilhã, Portugal. Electronic address: carla@fcsaude.ubi.pt.
authors.forename: Carla Pais
authors.initials: CP
authors.lastname: Fonseca
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6200-506 Covilhã, Portugal. Electronic address: susana_martgama@hotmail.com.
authors.forename: Susana
authors.initials: S
authors.lastname: Gama
authors.affiliation: Department of Cell Biology, Immunology and Neurosciences, Faculty of Medicine, University of Barcelona, 08036 Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain; Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED), Spain. Electronic address: anasaavedra@ub.edu.
authors.forename: Ana
authors.initials: A
authors.lastname: Saavedra
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6200-506 Covilhã, Portugal. Electronic address: gbaltazar@fcsaude.ubi.pt.
authors.forename: Graça
authors.initials: G
authors.lastname: Baltazar
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001930:Brain Injuries / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004298:Dopamine / Q000235:genetics / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000235:genetics* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity*; D007980:Levodopa / Q000633:toxicity*; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D014793:Visual Cortex / Q000187:drug effects / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; D051100:Glial Cell Line-Derived Neurotrophic Factor; D007980:Levodopa; D006861:Hydrogen Peroxide; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D004298:Dopamine
keywords: Dopaminergic neuron; GDNF; Neuroprotection; Parkinson's disease; Signalling pathway; Striatum