Basic fibroblast growth factor priming increases the responsiveness of immortalized hypothalamic luteinizing hormone releasing hormone neurones to neurotrophic factors.
The participation of growth factors (GFs) in the regulation of luteinizing hormone releasing hormone (LHRH) neuronal function has recently been proposed, but little is known about the role played by GFs during early LHRH neurone differentiation. In the present study, we have used combined biochemical and morphological approaches to study the ability of a number of GFs normally expressed during brain development, including basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin and insulin-like growth factor I (IGF-I) to induce survival, differentiation, proliferation, and phenotypic expression of immortalized (GT1-1) LHRH neurones in vitro, at early (3-days in vitro, 3-DIV) and late (8-DIV) stages of neuronal differentiation. Comparison of GF-treated vs untreated neurones grown in serum-deprived (SD) medium demonstrated bFGF to be the most potent, and insulin the least active in promoting neuronal differentiation. Thus, at both 3-DIV and 8-DIV, but especially at 8-DIV, bFGF induced the greatest increase in the total length and number of LHRH processes/cell and in growth cone surface area. bFGF was also the most active at 3-DIV, and IGF-I at 8-DIV, in counteracting SD-induced cell death, whereas EGF was the most potent in increasing [3H]thymidine incorporation. All GFs studied decreased the spontaneous release of LHRH from GT1-1 cells when applied at 3-DIV or 8-DIV, except for insulin which was inactive at both time-points and bFGF which was inactive at 8-DIV. Pre-treatment of GT1-1 cells with a suboptimal ('priming') dose of bFGF for 12 h followed by application of the different GFs induced a sharp potentiation of the neurotrophic and proliferative effects of the latter and particularly of those of IGF-I. Moreover, bFGF priming counteracted EGF-induced decrease in LHRH release and significantly stimulated LHRH secretion following IGF-I or insulin application, suggesting that bFGF may sensitize LHRH neurones to differentiating effects of specific GFs during development.
Gallo
F
F
Departments of Pharmacology, Medical School, University of Sassari, Pharmacology and Biochemistry, Medical School, University of Catania, Catania, Italy.
Morale
M C
MC
Tirolo
C
C
Testa
N
N
Farinella
Z
Z
Avola
R
R
Beaudet
A
A
Marchetti
B
B
D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D016922:Cellular Senescence / Q000502:physiology; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D010641:Phenotype; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution
D007328:Insulin; D009414:Nerve Growth Factors; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; D007987:Gonadotropin-Releasing Hormone; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1