Abstract 109: Estrogen Receptor Alpha Inhibition Of Mineralocorticoid Receptor In Endothelial Cells As A Mechanism Of Protection From Atherosclerosis Inflammation

Background: Atherosclerosis (athero) inflammation predicts plaque rupture, causing heart attack and stroke. Female protection from heart attack and stroke is lost with age, implicating estrogen, but by unclear mechanism. Our lab showed that the mineralocorticoid receptor (MR) is expressed in endothelial cells (ECs), where it drives plaque inflammation in male mice by inducing the NFkB-regulated adhesion molecule ICAM1. Females had less inflamed plaques, unchanged by EC-MR-knockout (KO). Hypothesis: We hypothesized that EC-estrogen receptor alpha (ER) protects females from plaque inflammation by inhibiting NFkB and EC-MR induction of ICAM1. Methods and Results: Mice with EC specific MR KO (EC-MR-KO), ER KO (EC-ER-KO), or EC KO of both receptors (DKO) were developed and crossed to the LDLR KO background. EC specific gene recombination of MR and/or ER was confirmed by genomic PCR of lung (rich in ECs) and compared to blood, revealing no recombination in leukocytes. Baseline athero risk factors were unchanged by genotype. Male and female mice of all KO lines and floxed Cre- littermate controls were fed high fat diet for 12 weeks resulting in increased body weight and cholesterol with no difference by genotype in athero risk factors. Aortic arches were digested for flow cytometry to quantify plaque inflammation, confirming less inflamed plaques in females versus males. EC-ER-KO increased plaque inflammation, while DKO prevented this increase in both sexes. Compared to controls, ICAM1 protein expression in the descending aorta was decreased by EC-MR-KO only in males. In both sexes, ICAM1 was increased by EC-ER-KO and unchanged by DKO. Females had increased aortic expression of IkB, the inhibitor of NFkB, compared to males and this was prevented by EC-ER-KO. In primary human aortic ECs (HAECs) in vitro , cells from females expressed significantly less ICAM1 protein compared to males. Conclusions: Female atherogenic mice have less inflamed plaques than males and female HAECs express less ICAM1. In vivo , EC-ER protects from plaque inflammation and suppresses ICAM1 in both sexes and IkB in females, and EC-MR is necessary for this atheroprotection. These data support the concept that EC-ER prevents inflammation by inhibiting NFkB and EC-MR-induced ICAM1 expression.