RESUMO
Testosterone has been shown to suppress the acute stress-induced activation of the hypothalamic-pituitary-adrenal axis; however, the mechanisms underlying this response remain unclear. The hypothalamic-pituitary-adrenal axis is regulated by a neuroendocrine subpopulation of medial parvocellular neurons in the paraventricular nucleus of the hypothalamus (PVN). These neurons are devoid of androgen receptors (ARs). Therefore, a possibility is that the PVN target neurons respond to a metabolite in the testosterone catabolic pathway via an AR-independent mechanism. The dihydrotestosterone metabolite, 5α-androstane-3ß,17ß-diol (3ß-diol), binds and activates estrogen receptor-ß (ER-ß), the predominant ER in the PVN. In the PVN, ER-ß is coexpressed with oxytocin (OT). Therefore, we tested the hypothesis that 3ß-diol regulates OT expression through ER-ß activation. Treatment of ovariectomized rats with estradiol benzoate or 3ß-diol for 4 days increased OT mRNA selectively in the midcaudal, but not rostral PVN compared with vehicle-treated controls. 3ß-Diol treatment also increased OT mRNA in the hypothalamic N38 cell line in vitro. The functional interactions between 3ß-diol and ER-ß with the human OT promoter were examined using an OT promoter-luciferase reporter construct (OT-luc). In a dose-dependent manner, 3ß-diol treatment increased OT-luc activity when cells were cotransfected with ER-ß, but not ER-α. The 3ß-diol-induced OT-luc activity was reduced by deletion of the promoter region containing the composite hormone response element (cHRE). Point mutations of the cHRE also prevented OT-luc activation by 3ß-diol. These results indicate that 3ß-diol induces OT promoter activity via ER-ß-cHRE interactions.
