Endothelium-dependent relaxation by G protein-coupled receptor 30 agonists in rat carotid arteries

Abstract

Recent studies have identified that the novel membrane estrogen receptor, G protein-coupled receptor 30 (GPR30), is present in blood vessels. However, the signaling mechanisms associated with GPR30 in the vasculature remain unclear. We examined whether putative agonists of GPR30 exert vasorelaxant and/or antioxidant effects similar to those reported for estrogen. Using wire myography, we assessed the role of the endothelium in relaxation responses to the GPR30 agonists, G-1 and 5408-0877 (1 nM-10 microM), in U-46619-precontracted common carotid arteries from Sprague-Dawley rats. Furthermore, using lucigenin (5 microM)-enhanced chemiluminescence, we tested the effect of G-1 (10 microM) on superoxide levels. Specific immunofluorescence was also used to confirm GPR30 expression in the arterial wall. We found that G-1 and 5408-0877 induced a concentration-dependent relaxation in carotid arteries from both male and female rats. Interestingly, G-1- and 5408-0877-induced relaxation was abolished by endothelium removal and abrogated in the presence of the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (100 microM). In addition, G-1 significantly decreased NADPH (100 microM)-stimulated superoxide production by carotid and intracranial (pooled basilar and middle cerebral) arteries but also attenuated the superoxide signal detected in a cell-free xanthine/xanthine oxidase assay. Furthermore, GPR30 immunoreactivity was observed in endothelial and vascular smooth muscle cells of carotid arteries from both genders. These findings indicate that GPR30 is expressed throughout the arterial wall and that GPR30 agonists elicit endothelial-derived nitric oxide-dependent relaxation of the carotid artery in male and female rats. Additionally, G-1 appears to directly scavenge superoxide anion.

Hormonal effects on blood vessels

“…[39][40][41] It has also been reported that stimulation of GPR30 blocks VSMC proliferation. 37,42 The vasodilator action of G-1 may be mediated by NO-independent 40 and NO-dependent 37,39,40 pathways; the latter involves GPR30-induced endothelial NO synthase (eNOS) phosphorylation. 43 Also, G-1 decreases nicotinamide adenine dinucleotide phosphate-stimulated superoxide production by the carotid and intracranial arteries, indicating the scavenging effects of GPR30 on superoxide anions.…”

“…43 Also, G-1 decreases nicotinamide adenine dinucleotide phosphate-stimulated superoxide production by the carotid and intracranial arteries, indicating the scavenging effects of GPR30 on superoxide anions. 39 In the heart, G-1 reduces ischemia/reperfusion injury and preserves cardiac function through the phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase pathways and by eNOS phosphorylation. 44,45 Treatment with G-1 for 2 weeks reduced the expression of angiotensin II type 1 receptor and angiotensin-converting enzyme.…”

Estrogens and atherosclerosis: insights from animal models and cell systems

“…Xing et al (2007) found that E 2 inhibits TNFa-stimulated expression of the neutrophil-specific chemokine cytokine-induced neutrophil chemoattractant (CINC)-2b and suggested that this effect might be responsible for the reduced infiltration of neutrophils, which is observed in animal models after vessel injury. Finally, estrogens are also known to reduce oxidative stress in VSMC by increasing expression of antioxidative enzymes such as superoxide dismutase and reducing expression and/or activity of NADPH oxidase (Strehlow et al 2003, Wassmann et al 2005, Wing et al 2009, Broughton et al 2010, Sivritas et al 2011. The antiproliferatory, pro-apoptotic, anti-migratory, anti-oxidative, and anti-inflammatory in vitro effects of estrogens collectively translate into reduced neointima formation under in vivo conditions.…”

“…More recently, GPR30 was found to be expressed on VSMC and to modulate vascular tone in rats and in isolated human arteries (Haas et al 2009). GPR30 activation was shown to inhibit VSMC proliferation and NADPH oxidase activation, and GPR30 expression was required for the estrogen-mediated VSMC apoptosis (Ding et al 2009, Haas et al 2009, Broughton et al 2010. Hence, GPR30 activation in VSMC may be tentatively added to the list of cellular effects exerted by estrogens, which are considered atheroprotective.…”

Aldosterone mediates its rapid effects in vascular endothelial cells through GPER activation

“…In vivo, GPER activation has been shown to mediate hypotensive effects (15,21), predominantly mediating endothelium-dependent vasorelaxation (2,23), although there is one report of endothelium-independent relaxation (31) and one report of GPER-mediated vasoconstriction (1). Our initial studies demonstrated aldosterone's rapid effects on endothelium-dependent vasodilator mechanisms and endothelial cell MAP kinase regulation.…”