FRI161 An in Vitro Triple Screen Model for Human Mineralocorticoid Receptor Activity

Disclosure: H. Liu: None. S.M. Konzen: None. A. Coy: None. J. Rege: None. C.E. Gomez-Sanchez: None. W.E. Rainey: None. A.F. Turcu: None. Background: The mineralocorticoid receptor (MR, NR3C2) mediates ion and water homeostasis in epithelial cells of the distal nephron. MR is expressed in a variety of other tissues, including gastrointestinal tract, exocrine glands, central nervous system, heart, and adipose tissue. Aldosterone, the prototypical mineralocorticoid, regulates electrolyte and fluid balance. Cortisol binds to MR with equal affinity to aldosterone. In humans, cortisol concentrations far exceed those of aldosterone, but many MR-expressing tissues inactivate cortisol to cortisone via 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2). Dysregulated MR activation contributes to direct cardiovascular tissue insults. Besides aldosterone and cortisol, a variety of MR agonists and/or HSD11B2 inhibitors are putative players in the pathophysiology of low-renin hypertension (LRH), and cardiovascular and metabolic pathology. Objective: To develop an in vitro human MR (hMR) model, to facilitate screening for MR agonists, antagonists, and HSD11B2 inhibitors. Methods: The CV1 monkey kidney cells were transduced with lentivirus to stably express hMR and an MR-responsive gaussian luciferase gene. Clonal populations of MR-expressing cells (CV1-MRluc) were further transduced to express HSD11B2 (CV1-MRluc-HSD11B2). CV1-MRluc and CV1-MRluc-HSD11B2 cells were treated with aldosterone, cortisol, 11-deoxycorticosterone (DOC), 18-hydroxycorticosterone (18OHB), 18-hydroxycortisol (18OHF), 18-oxocortisol (18oxoF), progesterone, or 17-hydroxyprogesterone (17OHP). Cells were also treated with serum from patients with LRH (N=3) or primary hypertension (PH, N=3). Luminescence was measured in conditioned medium using coelenterazine. Results: In CV1-MRLuc cells, aldosterone and DOC displayed similar potency (EC50: 0.45nM and 0.30nM) and maximal response (31- and 23-fold increase from baseline) on hMR; 18oxoF and 18OHB displayed lower potency (19.6nM and 56.0nM, respectively) but similar maximal hMR activation (25- and 27-fold increase, respectively); cortisol and corticosterone exhibited higher maximal responses (73- and 52-fold, respectively); 18OHF showed no MR activation. Progesterone and 17OHP inhibited aldosterone-mediated MR activation. In the MRluc-HSD11B2 model, the EC50 of cortisol for MR activation increased from 20nM (CV1-MRLuc) to 850nM, while the EC50 for aldosterone remained unchanged. Serum from patients with both LRH and PH led to variable degrees of luminescence in the CV1-MRLuc cells, but not in the CV1-MRluc-HSD11B2 cells, suggesting a cortisol-mediated MR activation in these patients, possibly via glycyrrhetinic acid-like factors. Conclusions: Together, these two cell models will facilitate the discovery of novel MR-modulators, informing MR-mediated pathophysiology mechanisms and drug development efforts. Presentation Date: Friday, June 16, 2023