title: Persistent activation of ERK contributes to glutamate-induced oxidative toxicity in a neuronal cell line and primary cortical neuron cultures.
abstract: Oxidative stress can trigger neuronal cell death and has been implicated in several chronic neurological diseases and in acute neurological injury. Oxidative toxicity can be induced by glutamate treatment in cells that lack ionotrophic glutamate receptors, such as the immortalized HT22 hippocampal cell line and immature primary cortical neurons. Previously, we found that neuroprotective effects of geldanamycin, a benzoquinone ansamycin, in HT22 cells were associated with a down-regulation of c-Raf-1, an upstream activator of the extracellular signal-regulated protein kinases (ERKs). ERK activation, although often attributed strictly to neuronal cell survival and proliferation, can also be associated with neuronal cell death that occurs in response to specific insults. In this report we show that delayed and persistent activation of ERKs is associated with glutamate-induced oxidative toxicity in HT22 cells and immature primary cortical neuron cultures. Furthermore, we find that U0126, a specific inhibitor of the ERK-activating kinase, MEK-1/2, protects both HT22 cells and immature primary cortical neuron cultures from glutamate toxicity. Glutamate-induced ERK activation requires the production of specific arachidonic acid metabolites and appears to be downstream of a burst of reactive oxygen species (ROS) accumulation characteristic of oxidative stress in HT22 cells. However, inhibition of ERK activation reduces glutamate-induced intracellular Ca(2+) accumulation. We hypothesize that the precise kinetics and duration of ERK activation may determine whether downstream targets are mobilized to enhance neuronal cell survival or ensure cellular demise.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: M
authors.initials: M
authors.lastname: Stanciu
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: R
authors.initials: R
authors.lastname: Kentor
authors.forename: N
authors.initials: N
authors.lastname: Burke
authors.forename: S
authors.initials: S
authors.lastname: Watkins
authors.forename: G
authors.initials: G
authors.lastname: Kress
authors.forename: I
authors.initials: I
authors.lastname: Reynolds
authors.forename: E
authors.initials: E
authors.lastname: Klann
authors.forename: M R
authors.initials: MR
authors.lastname: Angiolieri
authors.forename: J W
authors.initials: JW
authors.lastname: Johnson
authors.forename: D B
authors.initials: DB
authors.lastname: DeFranco
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D002070:Butadienes / Q000494:pharmacology; D016923:Cell Death; D002460:Cell Line; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects*; D015536:Down-Regulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000633:toxicity*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D018384:Oxidative Stress; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; D018698:Glutamic Acid; D001092:Arachidonate 12-Lipoxygenase; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases