Impaired 11β-Hydroxysteroid Dehydrogenase Type 2 in Glucocorticoid Resistant Patients.

Abstract

CONTEXT\nSix patients carrying heterozygous loss-of-function mutations of glucocorticoid receptor (GR) presented with hypercortisolism, associated with low kalemia, low plasma renin and aldosterone levels with or without hypertension, suggesting a pseudohypermineralocorticism whose mechanisms remain unclear. We hypothesize that an impaired activity of the 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2 encoded by HSD11B2 gene), catalyzing cortisol inactivation, may account for an inappropriate activation of renal mineralocorticoid signaling pathway in these glucocorticoid resistant patients.\n\n\nOBJECTIVE\nWe aim at studying the GR-mediated regulation of HSD11B2.\n\n\nDESIGN\nHSD11B2 promoter was subcloned and luciferase reporter assays evaluated GR-dependent HSB11B2 regulation while 11β-HSD2 expression/activity was studied in human breast cancer MCF7 cells, endogenously expressing this enzyme.\n\n\nRESULTS\nTransfection assays revealed that GR transactivated the long (2.1kbp) HSD11B2 promoter construct while a defective 501H GR mutant was unable to stimulate luciferase activity. GR-mediated transactivation of HSD11B2 gene was inhibited by the GR antagonist RU486. A three-fold increase in HSD11B2 mRNA levels was observed after dexamethasone (DXM) treatment of MCF7 cells, inhibited by RU486 or by Actinomycin, supporting a GR-dependent transcription. Chromatin immunoprecipitation further demonstrated a DXM-dependent GR recruitment onto HSB11B2 promoter. 11β-HSD2 activity, evaluated by cortisone/cortisol ratio quantified by LC-MSMS, was 10-fold higher in the supernatant of DXM-treated cells than controls, consistent with a GR-dependent stimulation of 11β-HSD2 catalytic activity.\n\n\nCONCLUSION\nCollectively, we demonstrate that 11β-HSD2 expression and activity is transcriptionally regulated by GR. In the context of GR haploinsufficiency, these findings provide evidence that defective GR signaling may account for apparent mineralocorticoid excess in glucocorticoid resistant patients.