Dexamethasone-induced accumulation of neuropeptide-Y by aggregating fetal brain cells in culture: a process dependent on the developmental age of the aggregates.
Neuropeptide-Y (NPY) and glucocorticoid receptors are coexpressed in many neurons in the brain. We addressed the question: Do glucocorticoids regulate the accumulation and/or secretion of immunoreactive (IR) NPY by fetal rat brain cells in culture, and if so, is the effect developmental stage dependent? Aggregates, formed from dissociated cells obtained from the hypothalamus-olfactory tubercle of 17-day-old fetuses, were cultured in serum-free medium for 23 days. On day 23, the aggregate NPY content was 6 ng/flask, and secretion (last 2 days) was approximately 12 ng/24 h. Exposure to dexamethasone (Dex; 20 nM) between days 0-23 led to a 1.9-fold increase in the aggregate content of NPY, whereas NPY secretion was not altered. When Dex exposure was limited to days 12-23, 16-23, 19-23, or 21-23, only a 12- to 23-day exposure induced NPY accumulation, and it was as effective as a 0- to 23-day exposure. The Dex-induced increase in NPY content was evident after a lag period of 4 days or more. When Dex exposure occurred on days 0-12, the aggregate NPY content on day 12 or 23 was not altered. None of these treatments altered the aggregate/medium content of immunoreactive somatostatin (SRIF) or the response to a 48-h exposure to forskolin (10 microM). Dex induction of NPY accumulation was a saturable function of the Dex concentration (maximal at 20 nM), and it was completely inhibited by RU486, a glucocorticoid/progesterone receptor antagonist; neither progesterone, 17 beta-estradiol, nor testosterone altered aggregate/medium NPY contents. Protein/DNA contents of the aggregates were either unaffected or slightly reduced by Dex. Thus, 1) Dex stimulates the accumulation of immunoreactive NPY, but not SRIF, by cultured fetal brain cells; 2) this effect requires a continuous 8-12 days of exposure to Dex during a late developmental stage in culture; 3) Dex does not potentiate or attenuate forskolin action on the NPY neuron; and 4) Dex action appears to be mediated by the glucocorticoid receptor. These results are consistent with glucocorticoid induction of production and/or decreased intracellular degradation of NPY, and with glucocorticoids regulating the NPY neuron in the perinatal brain in a developmental age-dependent manner.
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Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235.
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Hajibeigi
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D000818:Animals; D001921:Brain / Q000166:cytology / Q000196:embryology*; D002449:Cell Aggregation / Q000187:drug effects*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D007700:Kinetics; D015735:Mifepristone / Q000494:pharmacology; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D009478:Neuropeptide Y / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000502:physiology; D013004:Somatostatin / Q000378:metabolism
D009478:Neuropeptide Y; D011506:Proteins; D011965:Receptors, Glucocorticoid; D005576:Colforsin; D015735:Mifepristone; D013004:Somatostatin; D003907:Dexamethasone; D004247:DNA