Rapid estrogen receptor-α signaling mediated by ERK activation regulates vascular tone in male and ovary-intact female mice

Estrogen has been shown to affect vascular reactivity. Here, we assessed the estrogen receptor-alpha (ER alpha) dependency of estrogenic effects on vasorelaxation via a rapid non-genomic pathway in both male and ovary-intact female mice. We compared the effect of a primary estrogen, 17 beta-estradiol (E-2) or 4,4',4 ''-(4-propyl-[1H]pyrazole-1,3,5-triyl)tris-phenol (PPT; selective ER alpha agonist). We found that E-2 and PPT induced greater aortic relaxation in female mice than in male mice, indicating ER alpha mediation, which was further validated by using ER alpha antagonism. Treatment with 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride (MPP dihydrochloride; ER alpha antagonist) attenuated PPT-mediated vessel relaxation in both sexes. ER alpha-mediated vessel relaxation was further validated by the absence of significant PPT-mediated relaxation in aortas isolated from ER alpha knockout mice. Treatment with a specific ERK inhibitor, PD-98059, reduced E-2-induced vessel relaxation in both sexes but to a lesser extent in female mice. Furthermore, PD-98059 prevented PPT-induced vessel relaxation in both sexes. Both E2 and PPT treatment activated ERK as early as 5-10 min, which was attenuated by PD-98059 in aortic tissue, cultured primary vascular smooth muscle cells (VSMCs), and endothelial cells (ECs). Aortic rings denuded of endothelium showed no differences in vessel relaxation after E-2 or PPT treatment, implicating a role of ECs in the observed sex differences. Here, our results are unique to show estrogen-stimulated rapid ER alpha signaling mediated by ERK activation in aortic tissue, as well as VSMCs and ECs in vitro, in regulating vascular function by using side-by-side comparisons in male and ovary-intact female mice in response to E-2 or PPT. NEW & NOTEWORTHY Here, we assessed the estrogen receptor-alpha dependency of estrogenic effects in vasorelaxation of both male and ovary-intact female mice by performing side-by-side comparisons. Also, we describe the connection between estrogen-stimulated rapid estrogen receptor-alpha signaling and downstream ERK activation in regulating vascular function in male and ovary-intact female mice.