Abstract
A consistent clinical finding in patients with major depressive disorder (MDD) is hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the system in the body that facilitates the response to stress. It has been suggested that alterations in glucocorticoid receptor (GR)-mediated feedback prolong activation of the HPA axis, leading to the dysfunction observed in MDD. Additionally, the risk for developing MDD is heightened by several risk factors, namely gender, genetics and early life stress. Previous studies have demonstrated that GR translocation is sexually dimorphic and this difference may be facilitated by differential expression of GR co-regulators. The purpose of this study was to determine the extent to which ovarian hormones alter expression of GR and its co-regulators, Fkbp5 and Ppid, in HT-22 hippocampal neurons. The impact of corticosterone (cort), estradiol (E2), and progesterone (P4) treatments on the expression of the genes Nr3c1, Ppid, and Fkbp5 was assessed in HT-22 hippocampal neurons. Treatment of cells with increasing doses of cort increased the expression of Fkbp5, an effect that was potentiated by E2. Exposure of HT-22 cells to E2 decreased the expression of Ppid and simultaneous exposure to E2 and P4 had combinatory effects on Ppid expression. The effects of E2 on Ppid extend previous work which demonstrated that serum E2 concentrations correlate with hippocampal Ppid expression in female rats. The results presented here illustrate that E2 generates an anti-translocation pattern of GR co-regulators in hippocampal cells.