title: Neurotrophins rescue cerebellar granule neurons from oxidative stress-mediated apoptotic death: selective involvement of phosphatidylinositol 3-kinase and the mitogen-activated protein kinase pathway.
abstract: Cerebellar granule neurons maintained in medium containing serum and 25 mM K+ reliably undergo an apoptotic death when switched to serum-free medium with 5 mM K+. New mRNA and protein synthesis and formation of reactive oxygen intermediates are required steps in K+ deprivation-induced apoptosis of these neurons. Here we show that neurotrophins, members of the nerve growth factor gene family, protect from K+/serum deprivation-induced apoptotic death of cerebellar granule neurons in a temporally distinct manner. Switching granule neurons, on day in vitro (DIV) 4, 10, 20, 30, or 40, from high-K+ to low-K+/serum-free medium decreased viability by >50% when measured after 30 h. Treatment of low-K+ granule neurons at DIV 4 with nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotrophin-3, or neurotrophin-4/5 (NT-4/5) demonstrated concentration-dependent (1-100 ng/ml) protective effects only for BDNF and NT-4/5. Between DIV 10 and 20, K+-deprived granule neurons showed decreasing sensitivity to BDNF and no response to NT-4/5. Cerebellar granule neuron death induced by K+ withdrawal at DIV 30 and 40 was blocked only by neurotrophin-3. BDNF and NT-4/5 also circumvented glutamate-induced oxidative death in DIV 1-2 granule neurons. Granule neuron death caused by K+ withdrawal or glutamate-triggered oxidative stress was, moreover, limited by free radical scavengers like melatonin. Neurotrophin-protective effects, but not those of antioxidants, were blocked by selective inhibitors of phosphatidylinositol 3-kinase or the mitogen-activated protein kinase pathway, depending on the nature of the oxidant stress. These observations indicate that the survival-promoting effects of neurotrophins for central neurons, whose cellular antioxidant defenses are challenged, require activation of distinct signal transduction pathways.
authors.affiliation: Dipartimento di Farmacologia, CRIBI, Università di Padova, Italy.
authors.forename: S D
authors.initials: SD
authors.lastname: Skaper
authors.forename: M
authors.initials: M
authors.lastname: Floreani
authors.forename: A
authors.initials: A
authors.lastname: Negro
authors.forename: L
authors.initials: L
authors.lastname: Facci
authors.forename: P
authors.initials: P
authors.lastname: Giusti
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D018698:Glutamic Acid / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018384:Oxidative Stress / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011191:Potassium Deficiency / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; C071951:neurotrophin 5; D018698:Glutamic Acid; D019869:Phosphatidylinositol 3-Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C073922:neurotrophin 4