Abstract 794: Endothelial Specific Ablation of Estrogen Receptor Alpha Rapid Signaling Revealed Exacerbated Vascular Remodeling Response

Background: Estrogen exerts complex physiological effects via its rapid (non-genomic) and genomic actions. In particular, rapid signaling of estrogen receptor alpha (ERα) has been implicated in the vasculo-protective effects, in which both endothelial and smooth muscle cells might be involved. However, no prior studies have determined the role of ERα rapid signaling in the endothelium. This study aims to clarify the impact of ERα rapid signaling in the vasculo-protection, using a novel mouse model lacking endotheilal-specific ERα rapid signaling. Methods and Results: In immunoblotting, p85α and pGSK3β, non-genomic pathway downstream signals, were reduced in ERα mutants RR259/260AA with estradiol (E2) stimulation at concentrations of 10 -11 and 10 -10 M . ERE-luciferase assay demonstrated E2 induced genomic pathway activity was preserved even in ERα mutants RR259/260AA. We generated a mouse model in which rapid signaling of ERα was ablated in the endothelium by crossing Tie2-Cre transgenic mice with floxed ERα mutants (RR 259/260 AA) in which p85α and ERα interaction was disrupted. In endothelial cells isolated from ERα KI/KI Tie2 cre/+ animals, E2 at a concentration of 10 -8 M failed to induce phosphorylation of Akt, confirming the absence of ERα rapid signaling. Baseline characteristics at 8 to 12 weeks of age were undistinguishable between the genotypes, including body weight (KI:19.2±0.366 g vs WT: 18.9±0.356 g ) systolic blood pressure (KI:106.1±3.336 vs WT: 103.5±2.133 mmHg) and echocardiographic fractional shortening (KI:54.4±0.751 vs WT: 55.19±0.947 %). We then assessed how vascular remodeling process was impacted in a carotid artery wire injury model. Histological analyses with Elastica van Gieson staining two weeks after induction of injury revealed that wall thickness and area of medial layer composed mainly of smooth muscle cells were significantly increased in ERα KI/KI Tie2 cre/+ mouse, as compared to wild types (KI:44.85±1.948 μm vs WT: 29.32±1.753 μm , KI:42,047±1,560 μm 2 vs WT: 32,815±1,211 μm 2 , respectively ). Conclusions: Our results demonstrate that the rapid signaling of ERα in the endothelium critically regulates vascular smooth muscle cell growth after vascular injury, suggesting the essential role to vascular remodeling.