Premium
Differential postreceptor signaling events triggered by excitotoxic stimulation of different ionotropic glutamate receptors in retinal neurons
Author(s) -
Santos Armanda E.,
Carvalho Ana L.,
Lopes Maria C.,
Carvalho Arsélio P.
Publication year - 2001
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.10036
Subject(s) - kainate receptor , glutamate receptor , ionotropic effect , ampa receptor , stimulation , excitotoxicity , kainic acid , microbiology and biotechnology , biology , ionotropic glutamate receptor , long term depression , receptor , neuroscience , biochemistry
The aim of this work was to investigate whether excitotoxicity induced by overstimulation of different ionotropic glutamate receptors could trigger different intracellular signaling cascades. Cultured chick neuronal retina cells, essentially amacrine‐like, were particularly sensitive to the toxicity induced by non‐NMDA glutamate receptor agonists. One hour stimulation with 100 μM kainate induced a reduction of cell viability of about 44%, as assessed by the MTT test 24 hr after stimulation. Kainate‐induced toxicity was mediated through AMPA receptors. Glutamate (100 μM, 1 hr) reduced cell viability by 26%, essentially acting through N‐methyl‐D‐aspartate receptors. Five hours after stimulation, neuronal retina cells had an apoptotic‐like nuclear morphology. In retinal neurons, the excitotoxic stimulation, with either glutamate or kainate, induced a calcium‐dependent enhancement of the DNA‐binding activity of the activating protein‐1 (AP‐1) transcription factor, which was maximal 2 hr after stimulation. Glutamate induced a greater increase in the AP‐1 DNA‐binding activity than did kainate. Supershift assays using antibodies directed against different members of the Fos and Jun protein families showed that the AP‐1 complex in retinal neurons includes proteins of the Fos family, namely, Fra‐2, c‐Jun, and Jun D. The DNA‐binding activity of the nuclear factor‐κB transcription factor was not significantly changed upon excitotoxic stimulation with any agonist. Stimulation of glutamate receptors with 100 μM kainate or 100 μM glutamate for 2 min was sufficient to induce the activation of the extracellular signal‐regulated kinase (ERK). Inhibition of the ERK activation with the MEK inhibitors U 0126 and PD 98059 increased the toxicity induced by kainate but was without effect on the toxicity induced by glutamate. These results indicate that, although stimulation with both glutamate receptor agonists increased ERK phosphorylation, only kainate‐induced ERK activation correlates with the activation of a survival signaling pathway. Our results suggest that, in chick embryo retinal neurons, the signaling pathways that mediate excitotoxic cell death and neuroprotection are stimulus specific. J. Neurosci. Res. 66:643–655, 2001. © 2001 Wiley‐Liss, Inc.