Activation of G protein-coupled estrogen receptor induces endothelium-independent relaxation of coronary artery smooth muscle.
ABSTRACT Estrogens can either relax or contract arteries via rapid, nongenomic mechanisms involving classic estrogen receptors (ER). In addition to ERα and ERβ, estrogen may also stimulate G protein-coupled estrogen receptor 1 (GPER) in nonvascular tissue; however, a potential role for GPER in coronary arteries is unclear. The purpose of this study was to determine how GPER activity influenced coronary artery reactivity. In vitro isometric force recordings were performed on endothelium-denuded porcine arteries. These studies were augmented by RT-PCR and single-cell patch-clamp experiments. RT-PCR and immunoblot studies confirmed expression of GPER mRNA and protein, respectively, in smooth muscle from either porcine or human coronary arteries. G-1, a selective GPER agonist, produced a concentration-dependent relaxation of endothelium-denuded porcine coronary arteries in vitro. This response was attenuated by G15, a GPER-selective antagonist, or by inhibiting large-conductance calcium-activated potassium (BK(Ca)) channels with iberiotoxin, but not by inhibiting NO signaling. Last, single-channel patch-clamp studies demonstrated that G-1 stimulates BK(Ca) channel activity in intact smooth muscle cells from either porcine or human coronary arteries but had no effect on channels isolated in excised membrane patches. In summary, GPER activation relaxes coronary artery smooth muscle by increasing potassium efflux via BK(Ca) channels and requires an intact cellular signaling mechanism. This novel action of estrogen-like compounds may help clarify some of the controversy surrounding the vascular effects of estrogens.
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ABSTRACT: The presence of circulating plasma 17β-estradiol (E2) is beneficial in women against abnormal vascular tone development, such as coronary arterial vasospasms. Several vascular diseases have demonstrated that an increased expression of the sarcoplasmic reticulum Ca2+-ATPase pump (SERCA2b) serves to limit the excessive accumulation of intracellular Ca2+. Therefore, the hypothesis of this study was that E2 would increase SERCA2b expression in the coronary vasculature. Coronary arteries were dissected from hearts obtained from mature female pigs. Artery segments were cultured for 24 hrs in E2 (1 pM or 1 nM) and homogenized for Western blot analysis. E2 (1 nM) induced a ~ 50% increase in the immunoreactivity for SERCA2b. E2 also increased the protein expression of the known SERCA regulatory proteins, protein kinase A (PKA) and protein kinase G (PKG). The E2-induced increase in SERCA2b was attenuated when the culture media was supplemented with the α/β estrogen receptor antagonist, ICI 182,780, and the PKG antagonist, KT5823. The PKA antagonist (KT5720) had no effect on SERCA2b expression. Removal of the endothelium (using a wooden toothpick) decreased the E2-mediated increase in SERCA2b and PKG expression by 45% and 47%, respectively. Overall, these findings suggest that one of the potential cardiovascular benefits of E2 in women is the upregulation of SERCA2b, via the activation of the classical α and β estrogen receptor pathway.This article is protected by copyright. All rights reserved.Clinical and Experimental Pharmacology and Physiology 03/2014; · 2.41 Impact Factor
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ABSTRACT: Our previous work showed that chronic activation of the membrane-bound estrogen receptor GPR30/GPER significantly lowers blood pressure in ovariectomized hypertensive mRen2.Lewis female rats which may, in part, reflect direct vasodilatory actions. The current study assessed the hypothesis that cyclic adenosine monophosphate (cAMP) signaling contributes to GPER-mediated vasorelaxation. In mesenteric resistance arteries from intact Lewis females, relaxation to 17-β-estradiol (E2; 47±3% of phenylephrine contraction vs. vehicle 89±2%, P<0.001) or G-1 (44±8%, P<0.001) was blunted to a similar extent by denuding (P<0.001) or the nitric oxide synthase inhibitor L-NAME (P<0.001). In contrast, the cyclooxygenase inhibitor indomethacin did not alter vasodilation (P>0.05). The cAMP analogue Rp-cAMPS partially attenuated vasodilation (65±7%, P<0.001), while the combination of L-NAME and Rp-cAMPS exhibited additive effects to effectively abolish vasorelaxation (P>0.05 vs. vehicle). Pretreatment of endothelium-intact vessels with the adenylyl cyclase inhibitor SQ (63±6%) or the guanylyl cyclase inhibitor ODQ (62±9%) both partially inhibited the response to G-1 (P<0.01), while pretreatment with the both inhibitors completely abolished vasorelaxation (P>0.05 vs. vehicle). In denuded vessels only SQ reduced the response (88±3%, P<0.001). Moreover, G-1 significantly increased intracellular cAMP levels in cultured mesenteric smooth muscle cells (P<0.05). We conclude that GPER-dependent vasorelaxation apparently involves both endothelial release of nitric oxide which activates guanylyl cyclase and smooth muscle cell activation of adenylyl cyclase. Downstream production of cyclic nucleotides and stimulation of protein kinases may phosphorylate proteins to promote vascular smooth muscle cell relaxation. The ability of GPER to initiate these signaling pathways may contribute to the beneficial vascular effects of estrogen.Steroids 11/2013; · 2.80 Impact Factor
Article: Estrogen and the Female Heart.[Show abstract] [Hide abstract]
ABSTRACT: Estrogen has a plethora of effects in the cardiovascular system. Studies of estrogen and the heart span human clinical trials and basic cell and molecular investigations. Greater understanding of cell and molecular responses to estrogens can provide further insights into the findings of clinical studies. Differences in expression and cellular/intracellular distribution of the two main receptors, estrogen receptor (ER) α and β, are thought to account for the specificity and differences in responses to estrogen. Much remains to be learned in this area, but cellular distribution within the cardiovascular system is becoming clearer. Identification of GPER as a third ER has introduced further complexity to the system. 17β-estradiol (E2), the most potent human estrogen, clearly has protective properties activating a signaling cascade leading to cellular protection and also influencing expression of the protective heat shock proteins (HSP). E2 protects the heart from ischemic injury in basic studies, but the picture is more involved in the whole organism and clinical studies. Here the complexity of E2's widespread effects comes into play and makes interpretation of findings more challenging. Estrogen loss occurs primarily with aging, but few studies have used aged models despite clear evidence of differences between the response to E2 deficiency in adult and aged animals. Thus more work is needed focusing on the effects of aging vs. estrogen loss on the cardiovascular system.Molecular and Cellular Endocrinology 01/2014; · 4.04 Impact Factor