Progesterone Reduces Endothelial Function Without Increasing Endothelial Mineralocorticoid Receptor Expression in Male C57Bl/6 Mice
Authors: Lluch Emily , Kennard Simone , de Chantemele Eric Belin , Faulkner Jessica 
Published: April 2020

Recent work from our lab demonstrated that endothelial cells from women and female mice exhibit higher expression of the mineralocorticoid receptor (ECMR) and identified progesterone as the origin of this sex‐difference in ECMR expression. We also showed that progesterone‐induced increases in ECMR predispose females to obesity‐associated, aldosterone‐mediated endothelial dysfunction and demonstrated that deletion of either progesterone receptor (PR) or endothelial MR protects female mice from aldosterone‐induced endothelial dysfunction. Our preliminary data indicates that endothelial cell PR expression is higher in female mice than in males. However, whether the effects of exogenous progesterone to increase endothelial MR expression is sex‐specific is unknown, a notion that is of clinical importance to the growing population of transgender individuals receiving hormone replacement therapy. We hypothesized that progesterone supplementation increases endothelial MR expression in male mice. We infused male C57bl6 mice with progesterone (0.25mg/day, s.c. osmotic minipump) for 4 weeks. Endothelial and non‐endothelial cells were isolated from aortas to assess MR and PR expression via quantitative real time PCR. Progesterone treatment did not increase ECMR expression (6.37±5.1‐fold from control, Student’s T test, n=9 control, n=7 progesterone) nor in non‐endothelial vascular cells (0.5±0.6‐fold from control). However, a significant increase in PR expression was observed in endothelial cells (6.5±2.6‐fold from control, *p<0.05), that was absent in non‐endothelial vascular cells (0.3±0.4‐fold from control) in response to progesterone. Progesterone supplementation to male mice eliminated the sex discrepancy in endothelial PR expression between male and female mice (5.9±2.4‐fold from male, *p<0.05, n=6) without a correlating change in ECMR expression. Supplementation of human aortic endothelial cells in culture with dihydrotestosterone (10ng/ml) had no effect on ECMR promoter activity (1.2±0.1fold) indicating that testosterone is not the sex specific factor restricting increases in ECMR expression by progesterone in males. We additionally excised thoracic aortas for wire myography. Our results showed that progesterone treatment modestly decreased endothelial mediated relaxation to acetylcholine (2‐way ANOVA with repeated measures, P=0.08) with no significant effect on endothelial independent relaxation to sodium nitroprusside or constriction to phenylephrine compared to control. These data indicate that progesterone‐mediated increases in ECMR expression in females is sex‐specific and does not persist in endothelial cells of male mice, an effect unlikely mediated by testosterone. In addition, endothelial PR expression and endothelial function is sensitive to progesterone treatment in male mice. Therefore, endothelial‐specific PR signaling mechanisms exhibit sex‐specific phenotypes on cardiovascular function, indicating that further study is needed to determine potential risks facing transgender populations on hormone replacement therapies.Support or Funding Information1R01HL130301‐01, 19EIA34760167, Adrenal Center pilot grant, MCG Medical Scholars Program, 1 K99 HL146948‐01A1