epidermal-growth-factor and 1-amino-1-3-dicarboxycyclopentane

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.

Topics: Animals; Antimetabolites, Antineoplastic; Benzoates; Cell Division; Cell Survival; Cells, Cultured; Cellular Senescence; Cycloleucine; Cytarabine; Epidermal Growth Factor; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Fetus; Fibroblast Growth Factor 2; Glutamic Acid; Glycine; Hippocampus; Inositol Phosphates; Neuroglia; Neurons; Neuroprotective Agents; Quinoxalines; Quisqualic Acid; Rats; Receptors, AMPA; Receptors, Kainic Acid; Type C Phospholipases

Glial cells normally do not proliferate in the adult retina despite the presence of glial mitogens. In this study, we examined the hypothesis that endogenous antiproliferative molecules inhibit the effects of glial mitogens. Using cultures of glial cells obtained from the adult human retina, we found that transforming growth factor beta 2 (TGF beta 2) and a metabotrophic glutamate agonist (t-ACPD) inhibit the mitogenic effects of basic fibroblast growth factor, platelet-derived growth factor, epidermal growth factor and insulin-like growth factor-1. These antiproliferative effects may involve activation of protein kinase C (PKC) since chelerythine, a specific PKC inhibitor, blocks the antiproliferative effects of TGF beta 2 and t-ACPD. Furthermore, exposure of the glia to a phorbol ester mimics the inhibitory effects of TGF beta 2 or t-ACPD. Although TGF beta 2 and t-ACPD markedly inhibit a number of mitogens, they do not alter the mitogenic response of retinal glia to thrombin and glutamate. A common characteristic of the mitogens sensitive to TGF beta 2 or t-ACPD is activation of tyrosine kinase-linked receptors. In contrast, thrombin acts at a G-protein-linked receptor, and glutamate stimulates retinal glial proliferation via activation of an NMDA receptor. It appears that TGF beta 2 and t-ACPD may selectively inhibit retinal glial mitogenesis mediated by activation of tyrosine kinase-linked receptors. Our experiments support the idea that endogenous antiproliferative molecules play a role in preventing glial proliferation in the retina.

Topics: Alkaloids; Benzophenanthridines; Cell Division; Cells, Cultured; Cycloleucine; Epidermal Growth Factor; Fibroblast Growth Factor 2; Humans; Insulin-Like Growth Factor I; Neuroglia; Phenanthridines; Platelet-Derived Growth Factor; Protein Kinase C; Retina; Transforming Growth Factor beta