Effect of progesterone, testosterone and their 5 alpha-reduced metabolites on GFAP gene expression in type 1 astrocytes.
Astrocytes possess steroid receptors as well as several enzymes typical of steroid target cells, such as 5 alpha-reductase, which converts testosterone (T) and progesterone (P) into their respective 5 alpha-reduced metabolites, and the 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD). Because of this, it was deemed of interest to analyze whether the original hormones P and T, and their 5 alpha-reduced metabolites dihydrotestosterone (DHT), 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol), dihydroprogesterone (DHP) and 5 alpha-pregnan-3 alpha-ol-20-one (THP), might exert some effects on the expression of the most typical astrocytic marker, i.e. the glial fibrillary acidic protein (GFAP). Cultures of rat type 1 astrocytes were exposed to the various steroids for 2, 6, and 24 h, and the variations of GFAP mRNA were measured by Northern blot analysis. A significant elevation of GFAP mRNA levels was observed after exposure to either P or DHP; the effect of DHP appeared more promptly (at 2 h) than that of P (at 6 h). This result suggests that the effect of P might be linked to its conversion into DHP; this hypothesis has been confirmed by showing that the addition of finasteride (a specific blocker of the 5 alpha-reductase) is able to completely abolish the effect of P. After exposure to DHP or THP, a decrease of GFAP gene expression was observed at later intervals (24 h). In the case of androgens, T and 3 alpha-diol did not change GFAP expression at any time of exposure, while DHT produced a significant decrease of GFAP mRNA only after 24 h of exposure. Taken together, the data indicate that the 5 alpha-reduced metabolites of P and T may modulate the expression of GFAP in type 1 rat astrocytes.
Melcangi
R C
RC
Department of Endocrinology, University of Milan, Italy.
Riva
M A
MA
Fumagalli
F
F
Magnaghi
V
V
Racagni
G
G
Martini
L
L
D000818:Animals; D001253:Astrocytes / Q000187:drug effects*; D015152:Blotting, Northern; D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000494:pharmacology*
D005904:Glial Fibrillary Acidic Protein; D013739:Testosterone; D011374:Progesterone