The Regulatory Effects Of Estrogen Receptor And Retinoic Acid Receptor On The Corticotropin-releasing Gene Expression

A hyperfunction of the hypothalamus-pituitary-adrenal (HPA) axis and the hyperactivity of the corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus are the important neurophysiology symptoms of depression. Several members of steroid/thyroid receptor family have been suggested in the regulation of CRH gene expression. We mainly investigated the regulatory effects of the estrogen receptor and retinoic acid receptor on the CRH gene expression.1 . The regulatory effect of estrogen receptor-αand -βon the human corticotropin-releasing hormone geneCorticotropin-releasing hormone (CRH) plays a central role in controlling stress response. In this study, we aimed to identify the regulatory effect of estrogen receptor (ER) on CRH and the underlying mechanism. We investigated the regulation of CRH mRNA in the BE(2)-C cell line, a human neuroblastoma cell line which express endogenous CRH. Quantitative reverse transcriptase-polymerase chain reactions showed that in the presence of estradiol overexpressing ERαor ERβin BE(2)-C cells increased the transcription of CRH. Chromatin immunoprecipitation assays in this cell line also showed that both ERαand ERβcan be recruited to the CRH promoter with the treatment of estradiol. However, electrophoretic mobility shift assays did not show direct binding between estrogen receptors and two estrogen response elements (ERE) half sites in the CRH promoter. To clarify the regulatory mechanism, site-directed mutagenesis and reporter gene assay in the CHO cell line were used. When the ERE half sites and the cAMP regulatory element (CRE) in the CRH promoter were disrupted, ER-mediated up-regulation of CRH promoter activity reduced. Between the two ERE half sites studied, the ?316 ERE half site contributed more to the constitutive CRH expression induced by ER. In summary, our results confirm the stimulation of ERαand ERβon CRH expression and demonstrate the important roles of the ERE half sites and CRE for the action of ERαand ERβ.2 . The involvement of retinoic acid receptor-αin corticotropin-releasing hormone gene expression and affective disorders Corticotropin-releasing hormone (CRH) is considered the central driving force in the stress response and plays a key role in the pathogenesis of depression. Retinoic acid (RA) has been suggested by clinical studies to be associated with affective disorders. First, hypothalamic tissues of 12 patients with affective disorders and 12 matched control subjects were studied by double-label immunofluorescence to analyze the expression of CRH and retinoic acid receptor-α(RAR-α). Second, critical genes involved in the RA signaling pathways were analyzed in a rat model of depression. Finally, the regulatory effect of RAR-αon CRH gene expression was studied in vitro. We found that the expression of RAR-αwas colocalized with CRH neurons in human hypothalamic paraventricular nucleus (PVN). The density of RAR-α-immunoreactive neurons and CRH-RAR-αdouble-staining neurons was significantly increased in the PVN of patients with affective disorders. The ratio of the CRH-RAR-αdouble-staining neurons to the CRH-immunoreactive neurons in affective disorder patients was also increased. Recruitment of RAR-αby the CRH promoter was observed in the rat hypothalamus. A dysregulated RA metabolism and signaling was also found in the hypothalamus of a rat model for depression. Finally, in vitro studies demonstrated that RAR-αmediated an upregulation of CRH gene expression. These results suggest that RAR-αmight contribute to regulating the activity of CRH neurons in vivo, and the vulnerable character of the critical proteins in RA signaling pathways might provide novel targets for therapeutic strategies for depression.