The Androgen Metabolite, 5α-Androstane-3β,17β-Diol (3β-Diol), Activates the Oxytocin Promoter Through an Estrogen Receptor-β Pathway

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, 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol), binds and activates estrogen receptor-beta (ER-beta), the predominant ER in the PVN. In the PVN, ER-beta is coexpressed with oxytocin (OT). Therefore, we tested the hypothesis that 3 beta-diol regulates OT expression through ER-beta activation. Treatment of ovariectomized rats with estradiol benzoate or 3 beta-diol for 4 days increased OT mRNA selectively in the midcaudal, but not rostral PVN compared with vehicle-treated controls. 3 beta-Diol treatment also increased OT mRNA in the hypothalamic N38 cell line in vitro. The functional interactions between 3 beta-diol and ER-beta with the human OT promoter were examined using an OT promoter-luciferase reporter construct (OT-luc). In a dose-dependent manner, 3 beta-diol treatment increased OT-luc activity when cells were cotransfected with ER-beta, but not ER-alpha. The 3 beta-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 3 beta-diol. These results indicate that 3 beta-diol induces OT promoter activity via ER-beta-cHRE interactions. (Endocrinology 154: 1802-1812, 2013)