title: Neuroprotective effect of guanosine against glutamate-induced cell death in rat hippocampal slices is mediated by the phosphatidylinositol-3 kinase/Akt/ glycogen synthase kinase 3β pathway activation and inducible nitric oxide synthase inhibition.
abstract: Excitotoxicity and cell death induced by glutamate are involved in many neurodegenerative disorders. We have previously demonstrated that excitotoxicity induced by millimolar concentrations of glutamate in hippocampal slices involves apoptotic features and glutamate-induced glutamate release. Guanosine, an endogenous guanine nucleoside, prevents excitotoxicity by its ability to modulate glutamate transport. In this study, we have evaluated the neuroprotective effect of guanosine against glutamate-induced toxicity in hippocampal slices and the mechanism involved in such an effect. We have found that guanosine (100 μM) was neuroprotective against 1 mM glutamate-induced cell death through the inhibition of glutamate release induced by glutamate. Guanosine also induced the phosphorylation and, thus, activation of protein kinase B (PKB/Akt), a downstream target of phosphatidylinositol-3 kinase (PI3K), as well as phosphorylation of glycogen synthase kinase 3β, which has been reported to be inactivated by Akt after phosphorylation at Ser9. Glutamate treated hippocampal slices showed increased inducible nitric oxide synthase (iNOS) expression that was prevented by guanosine. Slices preincubated with SNAP (an NO donor), inhibited the protective effect of guanosine. LY294002 (30 μM), a PI3K inhibitor, attenuated guanosine-induced neuroprotection, guanosine prevention of glutamate release, and guanosine-induced GSK3β(Ser9) phosphorylation but not guanosine reduction of glutamate-induced iNOS expression. Taken together, the results of this study show that guanosine protects hippocampal slices by a mechanism that involves the PI3K/Akt/GSK3β(Ser9) pathway and prevention of glutamate-induced glutamate release. Furthermore, guanosine also reduces glutamate-induced iNOS by a PI3K/Akt-independent mechanism.
authors.affiliation: Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, Brasil. molz.s @hotmail.com
authors.forename: Simone
authors.initials: S
authors.lastname: Molz
authors.forename: Tharine
authors.initials: T
authors.lastname: Dal-Cim
authors.forename: Josiane
authors.initials: J
authors.lastname: Budni
authors.forename: M D
authors.initials: MD
authors.lastname: Martín-de-Saavedra
authors.forename: Javier
authors.initials: J
authors.lastname: Egea
authors.forename: Alejandro
authors.initials: A
authors.lastname: Romero
authors.forename: Laura
authors.initials: L
authors.lastname: del Barrio
authors.forename: Ana L S
authors.initials: AL
authors.lastname: Rodrigues
authors.forename: Manuela G
authors.initials: MG
authors.lastname: López
authors.forename: Carla I
authors.initials: CI
authors.lastname: Tasca
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D018698:Glutamic Acid / Q000009:adverse effects*; D038341:Glycogen Synthase Kinases / Q000187:drug effects / Q000502:physiology; D006151:Guanosine / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D066298:In Vitro Techniques; D008297:Male; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000009:adverse effects*; D052247:Nitric Oxide Synthase Type II / Q000187:drug effects / Q000502:physiology; D058539:Phosphatidylinositol 3-Kinase / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D018709:Statistics, Nonparametric
chemical_list: D018696:Neuroprotective Agents; D009498:Neurotoxins; D006151:Guanosine; D018698:Glutamic Acid; D052247:Nitric Oxide Synthase Type II; D058539:Phosphatidylinositol 3-Kinase; D038341:Glycogen Synthase Kinases; D051057:Proto-Oncogene Proteins c-akt