Abstract 653: Stimulation Of Endothelial Nitric Oxide Production And Dilation By The G Protein-coupled Estrogen Receptor

Abstract

Endogenous estrogens mediate protective effects in the cardiovascular system in part due to rapid activation of endothelial nitric oxide synthase (eNOS), which involves the classical estrogen receptor (ER) α. Estrogen-dependent increases in NO bioactivity may also be mediated by the G protein-coupled estrogen receptor (GPER/GPR30), although the contribution of GPER to the overall response to estrogen and the mechanisms involved remain unclear. We have investigated GPER-mediated NO signaling in telomerase-immortalized human umbilical vein endothelial (TIVE) cells as well as estrogen-dependent, GPER-mediated relaxation in mouse aortae. Similar to the non-selective ER agonist 17β-estradiol (E2), the GPER-selective agonist G-1 stimulated phosphorylation of eNOS (ser1171) at 100 nM vs. 0.01% DMSO vehicle (53 +/-7 vs. 19+/-4, p=0.035, n=4). Colorimetric detection of nitric oxide demonstrated that Acetylcholine (Ach) (536 +/-18), E2 (425+/- 18) and G-1 (308 +/-18) also increased NO production in TIVEs (vs. veh 94.0 +/-5, p= 0.006, n=4-6). Pharmacologic inhibition of GPER (G36) reduced NO production in response to E2 by 57% (407 +/-29 vs. 235 +/- 15, p=0.009, n=6), but not to Ach (543+/-12 vs. 533+/-9, p=0.838, n=5-8). In contrast, inhibition of EGFR signaling with AG1478 did not reduce GPER-mediated (G-1) eNOS phosphorylation or G-1-induced NO production (172 +/-8 and 201 +/-12, p=0.120, n=3). Myography studies of endothelium-intact aorta from GPER KO showed a 46% reduction in the relaxation response to E2 compared to WT (-32.3 +/-8.1% and -59.2 +/-3.2 %, p=0.009, n=4-5). Relaxation responses to Ach were similar in GPER KO and WT (-88.0 +/- 1.2 mg and -90.6 +/-1.4 mg, p=0.204, n=5), and WT aorta showed similar relaxation to both E2 and G-1 (59.2 +/- 3.21% and 62.03 +/-6.24%, p=0.71, n=7). These findings suggest that in addition to ERα, the activity of GPER is likely required for full eNOS activation and vasodilation in response to E2, and thus may contribute to the estrogen-mediated protective effects in the cardiovascular system.