Potentiation of glutamatergic agonist‐induced inositol phosphate formation by basic fibroblast growth factor is related to developmental features in hippocampal cultures: neuronal survival and glial cell proliferation

Abstract

We investigated the modulation by growth factors of phospholipase C (PLC)-linked glutamate receptors during in vitro development of hippocampal cultures. In defined medium, glial cells represent between 3 and 14% of total cell number. When we added basic fibroblast growth factor (bFGF) 2 h after plating, we found: (i) a neuroprotection from naturally occurring death for up to 5 days; (ii) a proliferation of glial cells from day 3; and (iii) a potentiation of quisqualate (QA)-induced inositol phosphate (IP) formation from 1 to 10 days in vitro (DIV) and 1S, 3R-amino-cyclopentane-1,3-dicarboxylate (ACPD) response from 3 to 10 DIV. The antimitotic cytosine-beta,D-arabinofuranoside (AraC) blocked glial cell proliferation induced by bFGF, but not neuroprotection. Under these conditions, the early potentiation of the QA response (1-3 DIV) was not changed, while the ACPD and late QA response potentiations were prevented (5-10 DIV). Epidermal growth factor was not neuroprotective but it induced both glial cell proliferation and late QA or ACPD potentiation. Surprisingly, the early bFGF-potentiated QA-induced IP response was blocked by 6, 7-dinitro-quinoxaline-2,3-dione (DNQX), suggesting the participation of ionotropic (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate (KA) receptors. The delayed bFGF-potentiated ACPD-induced IP response is inhibited by (S)-alpha-methyl-4-carboxyphenylglycine (MCPG), indicating possible activation of glial metabotropic receptors. These results suggest that, in hippocampal cultures, bFGF modulates AMPA and metabotropic glutamate receptors linked to the IP cascade, possibly in relation to the regulation of neuronal survival and glial cell proliferation, respectively.

Neuroprotection induced by vitamin E against oxidative stress in hippocampal neurons: Involvement of TRPV1 channels

“…Other reports indicate that a-TP is actually able to stimulate de novo protein synthesis in various cell types [13][14][15]. We found that the a-TP pretreatment of hippocampal neurons impairs the intracellular Ca 21 increase elicited by an oxidative insult. Indeed, while Fe 21 ions trigger an intracellular Ca 21 overload leading to cell death, they only moderately enhance intracellular Ca 21 in cells previously treated with low concentration of a-TP [16].…”

“…Beneficial effects of a-TP do not only rely on its antiradical activity but also involve other molecular mechanisms, including some genomic actions [11]. In this respect, we recently demonstrated on cultured hippocampal neurons that an application of a low concentration of a-TP results in an enduring protection against oxidative insults triggered by exposure to Fe 21 ions or hydroperoxides, this protection being lost under the blockade of protein synthesis by cycloheximide [12]. Other reports indicate that a-TP is actually able to stimulate de novo protein synthesis in various cell types [13][14][15].…”

Roles of Ionotropic Glutamate Receptors in Early Developing Neurons Derived from the P19 Mouse Cell Line

“…Furthermore, our results showed that KAmediated neuroprotection in P19 neurons seems to be mediated by phospholipase C signaling. Another study also demonstrated that in cultured developing hippocampal neurons, basic fibroblast growth factor potentiates inositol phosphate formation induced by both AMPA/KA receptors and mGluR activation, but only the potentiation of AMPA/KA receptor signaling resulted in an increased neuronal survival rate [6]. Therefore, it is conceivable that certain dynamic changes in intracellular calcium mediated by ionotropic GluRs play an important role in neuronal survival in the developing nervous system.…”

Potent activation of FGF-2 IRES-dependent mechanism of translation during brain development

“…The protocol was adapted from Blanc et al (1999). Cortex from 16-d-old mouse embryos were dissected and incubated for 12 min in Versene.…”

“…Single labelings were performed directly on plastic wells as described in Blanc et al (1999). Cells were fixed for 20 min with 4% PF in 0.1 M sodium phosphate buffer and then incubated for 5 min in 8 mM sodium borohydride in PBS.…”