Induction of the human HSD3B2 promoter by glucocorticoids: implications for intraadrenal regulation of steroidogenesis

Steroidogenesis in the adrenal cortex is regulated by extraadrenal factors as well as by paracrine/autocrine mechanisms. Whether glucocorticoids belong to this class of intraadrenal regulators, i.e. whether the adrenal cortex is itself a glucocorticoid target tissue, is not known at the present time. We previously demonstrated expression of the glucocorticoid receptor (GR) in the human adrenal cortex, thus supporting this newly arising concept. A potential GR target within adrenocortical cells could be the 3β-hydroxysteroid dehydrogenase (HSD3B2) gene, since its promoter contains a putative palindromic glucocorticoid response element (GRE). To test its glucocorticoid responsiveness, a 680 bp region of the human HSD3B2 promoter region was cloned in front of a luciferase reporter gene and transfected into NCI-H295 adrenal carcinoma cells using electroporation. Cells were then stimulated with different concentrations of dexamethasone. After 17h, cells were lysed, and luciferase activity in the cell lysate was determined in a luminometer. Luciferase activity was stimulated in a dose-dependent manner by dexamethasone, indicating that the GR expressed in NCIh295 cells is functionally active and able to activate the HSD3B2 gene. Addition of RU486, a known GR antagonist, blocked this effect, proving its specificity. We conclude that glucocorticoids can activate the human HSD3B2 promoter in cells of adrenal origin. The intraadrenally expressed GR may, thus, participate in the regulation of steroidogenesis, since activation of HSD3B2 would lead to decreased production of DHEA.

Supported by the Deutsche Forschungsgemeinschaft (GRK336) and the Leidenberger-Müller Stiftung.