title: Increased glutathione biosynthesis by Nrf2 activation in astrocytes prevents p75NTR-dependent motor neuron apoptosis.
abstract: Astrocytes may modulate the survival of motor neurons in amyotrophic lateral sclerosis (ALS). We have previously shown that fibroblast growth factor-1 (FGF-1) activates astrocytes to increase secretion of nerve growth factor (NGF). NGF in turn induces apoptosis in co-cultured motor neurons expressing the p75 neurotrophin receptor (p75NTR) by a mechanism involving nitric oxide (NO) and peroxynitrite formation. We show here that FGF-1 increased the expression of inducible nitric oxide synthase and NO production in astrocytes, making adjacent motor neurons vulnerable to NGF-induced apoptosis. Spinal cord astrocytes isolated from transgenic SOD1G93A rats displayed increased NO production and spontaneously induced apoptosis of co-cultured motor neurons. FGF-1 also activates the redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) in astrocytes. Because Nrf2 increases glutathione (GSH) biosynthesis, we investigated the role of GSH production by astrocytes on p75NTR-dependent motor neuron apoptosis. The combined treatment of astrocytes with FGF-1 and t-butylhydroquinone (tBHQ) increased GSH production and secretion, preventing motor neuron apoptosis. Moreover, Nrf2 activation in SOD1G93A astrocytes abolished their apoptotic activity. The protection exerted by increased Nrf2 activity was overcome by adding the NO donor DETA-NONOate to the co-cultures or by inhibiting GSH synthesis and release from astrocytes. These results suggest that activation of Nrf2 in astrocytes can reduce NO-dependent toxicity to motor neurons by increasing GSH biosynthesis.
authors.affiliation: Departamento de Neurobiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
authors.forename: Marcelo R
authors.initials: MR
authors.lastname: Vargas
authors.forename: Mariana
authors.initials: M
authors.lastname: Pehar
authors.forename: Patricia
authors.initials: P
authors.lastname: Cassina
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Beckman
authors.forename: Luis
authors.initials: L
authors.lastname: Barbeito
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D000831:Animals, Newborn; D000975:Antioxidants / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western / Q000379:methods; D002452:Cell Count / Q000379:methods; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D016220:Fibroblast Growth Factor 1 / Q000494:pharmacology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005978:Glutathione / Q000096:biosynthesis* / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology; D008715:Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D009046:Motor Neurons / Q000502:physiology*; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D011422:Propionates / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013116:Spinal Cord / Q000166:cytology; D013482:Superoxide Dismutase; D014162:Transfection / Q000379:methods; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D005904:Glial Fibrillary Acidic Protein; D006873:Hydroquinones; D051267:NF-E2-Related Factor 2; D009566:Nitrates; D009573:Nitrites; D011422:Propionates; D011743:Pyrimidines; D011804:Quinolines; D012333:RNA, Messenger; D020800:Receptor, Nerve Growth Factor; D016220:Fibroblast Growth Factor 1; C042415:buthionine; C059141:verlukast; D014508:Urea; D020932:Nerve Growth Factor; D008715:Methionine; D052247:Nitric Oxide Synthase Type II; C109415:SOD1 G93A protein; D013482:Superoxide Dismutase; D005978:Glutathione; C113399:PD 166866; C031927:hydroquinone