GPER deficiency in male mice results in insulin resistance, dyslipidemia, and a proinflammatory state

GPER is required for the age-dependent upregulation of the myocardial endothelin system

AIMS

Cardiac aging is associated with progressive structural changes and functional impairment, such as left ventricular hypertrophy, fibrosis and diastolic dysfunction. Aging also increases myocardial activity of endothelin-1 (ET-1), a multifunctional peptide with growth-promoting and pro-fibrotic activity. Because the G protein-coupled estrogen receptor (GPER) regulates vascular responsiveness to ET-1, we investigated whether GPER also plays a role in the regulation of the myocardial endothelin system with aging.

MAIN METHODS

Young (4month-old) and aged (24month-old) wild-type and Gper-deficient (Gper(-/-)) mice were studied. Gene expression levels of prepro-ET-1, endothelin converting enzymes ECE-1 and ECE-2, and endothelin ETA and ETB receptors were determined by qPCR in left ventricular myocardium.

KEY FINDINGS

Aging markedly increased steady-state mRNA expression levels of ECE-1, ECE-2, ETA and ETB receptors (each p<0.001 vs. young mice). Deletion of Gper inhibited the age-dependent increase in ECE-2 and ETB receptor mRNA levels (57% and 40% reduction, respectively, each p<0.01 vs. wild-type mice), whereas gene expression of prepro-ET-1, ECE-1, and the ETA receptor was unaffected in Gper(-/-) mice.

SIGNIFICANCE

We identified a novel regulatory mechanism through which the endogenous Gper facilitates the age-dependent increase in myocardial expression of ECE-2 and the ETB receptor, which is compatible with an activating role of GPER for the local endothelin system with aging. Targeting GPER signaling by selective antagonists may therefore be considered a new therapeutic approach to reduce age-dependent increased ET-1 activity and the associated development of left ventricular hypertrophy, fibrosis and heart failure.

The G protein-coupled estrogen receptor as a modulator of neoplastic transformation

Estrogens play a crucial role in the regulation of physiological and pathophysiological processes. These hormones act through specific receptors, most notably the canonical estrogen receptors α and β (ERα and ERβ) and their truncated forms as well as the G protein-coupled estrogen receptor (GPER). Several studies have shown that GPER is expressed in many normal and cancer cells, including those of the breast, endometrium, ovary, testis and lung. Hormonal imbalance is one possible cause of cancer development. An accumulating body of evidence indicates that GPER is involved in the regulation of cancer cell proliferation, migration and invasion, it may act as a mediator of microRNA, and is believed to modulate the inflammation associated with neoplastic transformation. Furthermore, used in various treatment regimens anti-estrogens such as tamoxifen, raloxifen and fulvestrant (ICI 182.780), antagonists/modulators of canonical estrogen receptors, were found to be GPER agonists. This review presents the current knowledge about the potential role of GPER in neoplastic transformation.

Neuroendocrine Regulation of Metabolism

Given the current environment in most developed countries, it is a challenge to maintain a good balance between calories consumed and calories burned, although maintenance of metabolic balance is key to good health. Therefore, understanding how metabolic regulation is achieved and how the dysregulation of metabolism affects health is an area of intense research. Most studies focus on the hypothalamus, which is a brain area that acts as a key regulator of metabolism. Among the nuclei that comprise the hypothalamus, the arcuate nucleus is one of the major mediators in the regulation of food intake. The regulation of energy balance is also a key factor ensuring the maintenance of any species as a result of the dependence of reproduction on energy stores. Adequate levels of energy reserves are necessary for the proper functioning of the hypothalamic-pituitary-gonadal axis. This review discusses valuable data presented in the 2015 edition of the International Workshop of Neuroendocrinology concerning the fundamental nature of the hormonal regulation of the hypothalamus and the impact on energy balance and reproduction.

Not lost in translation: Emerging clinical importance of the G protein-coupled estrogen receptor GPER

It has been 20years that the G protein-coupled estrogen receptor (GPER) was cloned as the orphan receptor GPR30 from multiple cellular sources, including vascular endothelial cells. Here, I will provide an overview of estrogen biology and the historical background leading to the discovery of rapid vascular estrogen signaling. I will also review the recent advances in the understanding of the mechanisms underlying GPER function, its role in physiology and disease, some of the currently available GPER-targeting drugs approved for clinical use such as SERMs (selective estrogen receptor modulators) and SERDs (selective estrogen receptor downregulators). Many of currently used drugs such as tamoxifen, raloxifene, or faslodex™/fulvestrant were discovered targeting GPER many years after they had been introduced to the clinics for entirely different purposes. This has important implications for the clinical use of these drugs and their modes of action, which I have termed 'reverse translational medicine'. In addition, environmental pollutants known as 'endocrine disruptors' have been found to bind to GPER. This article also discusses recent evidence in these areas as well as opportunities in translational clinical medicine and GPER research, including medical genetics, personalized medicine, prevention, and its theranostic use.

Estrogens and Coronary Artery Disease: New Clinical Perspectives

In premenopausal women, endogenous estrogens are associated with reduced prevalence of arterial hypertension, coronary artery disease, myocardial infarction, and stroke. Clinical trials conducted in the 1990s such as HERS, WHI, and WISDOM have shown that postmenopausal treatment with horse hormone mixtures (so-called conjugated equine estrogens) and synthetic progestins adversely affects female cardiovascular health. Our understanding of rapid (nongenomic) and chronic (genomic) estrogen signaling has since advanced considerably, including identification of a new G protein-coupled estrogen receptor (GPER), which like the "classical" receptors ERα and ERβ is highly abundant in the cardiovascular system. Here, we discuss the role of estrogen receptors in the pathogenesis of coronary artery disease and review natural and synthetic ligands of estrogen receptors as well as their effects in physiology, on cardiovascular risk factors, and atherosclerotic vascular disease. Data from preclinical and clinical studies using nonselective compounds activating GPER, which include selective estrogen receptor modulators such as tamoxifen or raloxifene, selective estrogen receptor downregulators such as Faslodex™ (fulvestrant/ICI 182,780), vitamin B3 (niacin), green tea catechins, and soy flavonoids such as genistein or resveratrol, strongly suggest that activation of GPER may afford therapeutic benefit for primary and secondary prevention in patients with or at risk for coronary artery disease. Evidence from preclinical studies suggest similar efficacy profiles for selective small molecule GPER agonists such as G-1 which are devoid of uterotrophic activity. Further clinical research in this area is warranted to provide opportunities for future cardiovascular drug development.

Heart Disease in Women: Unappreciated Challenges, GPER as a New Target

Heart disease in women remains underappreciated, underdiagnosed and undertreated. Further, although we are starting to understand some of the social and behavioral determinants for this, the biological basis for the increased rate of rise in atherosclerosis risk in women after menopause remains very poorly understand. In this review we will outline the scope of the clinical issues related to heart disease in women, the emerging findings regarding the biological basis underlying the increased prevalence of atherosclerotic risk factors in postmenopausal women (vs. men) and the role of the G protein-coupled estrogen receptor (GPER) and its genetic regulation as a determinant of these sex-specific risks. GPER is a recently appreciated GPCR that mediates the rapid effects of estrogen and aldosterone. Recent studies have identified that GPER activation regulates both blood pressure. We have shown that regulation of GPER function via expression of a hypofunctional GPER genetic variant is an important determinant of blood pressure and risk of hypertension in women. Further, our most recent studies have identified that GPER activation is an important regulator of low density lipoprotein (LDL) receptor metabolism and that expression of the hypofunctional GPER genetic variant is an important contributor to the development of hypercholesterolemia in women. GPER appears to be an important determinant of the two major risk factors for coronary artery disease-blood pressure and LDL cholesterol. Further, the importance of this mechanism appears to be greater in women. Thus, the appreciation of the role of GPER function as a determinant of the progression of atherosclerotic disease may be important both in our understanding of cardiometabolic function but also in opening the way to greater appreciation of the sex-specific regulation of atherosclerotic risk factors.

Bisphenol S- and bisphenol A-induced adipogenesis of murine preadipocytes occurs through direct peroxisome proliferator-activated receptor gamma activation

BACKGROUND/OBJECTIVES

The use of bisphenol A (BPA) in consumer products and food packaging has been associated under certain conditions with a risk of negative health outcomes. This prompted its removal from many products and replacement with structural analogs. Bisphenol S (BPS) is one such analog, but its metabolic effects have not been fully characterized. The objective of our study was to determine whether BPS functions similarly to BPA at inducing adipogenesis.

METHODS

Murine 3T3-L1 preadipocytes were used to evaluate and compare the adipogenic potential of BPS to BPA. Cells were treated with 0.01-50 μM BPS or 0.01-50 μM BPA and adipogenic effects were measured. Further, their ability to activate peroxisome proliferator-activated receptor gamma (PPARγ), an adipogenic transcription factor, was also determined.

RESULTS

Our results indicate that treatment of 3T3-L1 cells with BPS induced lipid accumulation and increased mRNA and protein expression of key adipogenic markers (1-50 μM; P<0.05). BPS treatment resulted in a higher expression of adipogenic markers as well as greater lipid accumulation when compared with BPA treatment. We showed that BPS can upregulate lipoprotein lipase, adipocyte protein 2, PPARγ, perilipin, adipsin and CCAAT/enhancer-binding protein alpha mRNA expression levels. Furthermore, using transcriptional assays, we showed that BPS and BPA can modestly activate PPARγ using a PPRE (PPARγ response element)-dependent luciferase construct by 1.5-fold (P<0.05). However, BPS but not BPA was able to competitively inhibit rosiglitazone (ROSI)-activated PPARγ, suggesting that BPS interacts with PPARγ distinctly from BPA. Co-treatment of cells with the selective PPARγ antagonist GW9662 inhibits BPS-, BPA-, ROSI- but not dexamethasone-dependent adipogenic differentiation.

CONCLUSIONS

Both BPA and BPS can enhance 3T3-L1 adipocyte differentiation in a dose-dependent manner and require PPARγ to induce adipogenesis. Through direct comparison, we show that BPS is a more potent adipogen than BPA.

Are aryl hydrocarbon receptor and G-protein-coupled receptor 30 involved in the regulation of seasonal testis activity in photosensitive rodent-the bank vole (Myodes glareolus)?

Within the reproductive system both aryl hydrocarbon receptor (AHR) and G-protein-coupled receptor 30 (GPR30) contribute to estrogen signaling and controlling of reproductive physiology. The specific question is whether and how AHR and GPR30 are involved in regulation of testis function in seasonally breeding rodents. Bank vole testes were obtained from animals reared under 18 hours light:6 hours dark (LD) and 6 hours light:18 hours dark (SD) conditions. Aryl hydrocarbon receptor and GPR30 expression were analyzed by quantitative reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry and/or immunofluorescent staining. In addition, the activity of enzymes involved in the intracellular signal transduction; extracellular signal-regulated kinase (ERK), protein kinase (PKA), matrix metalloproteinase 9 (MMP 9) and the concentrations of cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), and calcium (Ca(2+)) were examined by immunohistochemical, immunoenzymatic, and colorimetric assays, respectively. Aryl hydrocarbon receptor and GPR30 were expressed in testes of actively reproducing voles and regressed ones although their expression at the messenger RNA and AHR also at protein level appeared to be photoperiod-dependent. A specific cellular localization and expression of AHR and GPR30 correlated with the expression of ERK, PKA, and MMP 9. Moreover, we found robust differences in the levels of cAMP, cGMP, and Ca(2+) in testicular homogenates between LD and SD voles. In the testes of LD voles, the levels of second messengers were always higher compared to SD. In vole testis, AHR and GPR30 can induce signaling pathways that involve ERK, PKA, MMP 9 and cAMP, cGMP, Ca(2+). In addition, in AHR, signaling the engagement of both photoperiod and estrogens, whereas in GPR30, signaling only estrogens is reported. It is likely that in vole, because of a differential activity of signaling molecules, signal transduction via AHR rather than through GPR30 plays a role in regulation of seasonal changes of testis physiology.

GPER/GPR30 Knockout Mice: Effects of GPER on Metabolism

Endogenous estrogens, predominantly 17β-estradiol (E2), mediate various diverse effects throughout the body in both normal physiology and disease. Actions include development (including puberty) and reproduction as well as additional effects throughout life in the metabolic, endocrine, musculoskeletal, nervous, cardiovascular, and immune systems. The actions of E2 have traditionally been attributed to the classical nuclear estrogen receptors (ERα and ERβ) that largely mediate transcriptional/genomic activities. However, more recently the G protein-coupled estrogen receptor GPER/GPR30 has become recognized as an essential mediator of certain, and particularly rapid, signaling events in response to E2. Murine genetic knockout (KO) models represent an important approach to understand the mechanisms of E2 action in physiology and disease. Studies of GPER KO mice over the last years have revealed functions for GPER in the regulation of obesity, insulin resistance and glucose intolerance, among other areas of (patho)physiology. This chapter focuses on methods for the evaluation of metabolic parameters in vivo and ex vivo with an emphasis on glucose homeostasis and metabolism through the use of glucose and insulin tolerance tests, pancreatic islet and adipocyte isolation and characterization.

The G-protein coupled estrogen receptor, GPER: The inside and inside-out story

GPER possesses structural and functional characteristics shared by members of the G-protein-coupled receptor (GPCR) superfamily, the largest class of plasma membrane receptors. This newly appreciated estrogen receptor is localized predominately within intracellular membranes in most, but not all, cell types and its surface expression is modulated by steroid hormones and during tissue injury. An intracellular staining pattern is not unique among GPCRs, which employ a diverse array of molecular mechanisms that restrict cell surface expression and effectively regulating receptor binding and activation. The finding that GPER displays an intracellular predisposition has created some confusion as the estrogen-inducible transcription factors, ERα and ERβ, also reside intracellularly, and has led to complex suggestions of receptor interaction. GPER undergoes constitutive retrograde trafficking from the plasma membrane to the endoplasmic reticulum and recent studies indicate its interaction with PDZ binding proteins that sort transmembrane receptors to synaptosomes and endosomes. Genetic targeting and selective ligand approaches as well as cell models that express GPER in the absence of ERs clearly supports GPER as a bonafide "stand alone" receptor. Here, the molecular details that regulate GPER action, its cell biological activities and its implicated roles in physiological and pathological processes are reviewed.

Estrogen-mediated inactivation of FOXO3a by the G protein-coupled estrogen receptor GPER

Background

Estrogen (17β-estradiol) promotes the survival and proliferation of breast cancer cells and its receptors represent important therapeutic targets. The cellular actions of estrogen are mediated by the nuclear estrogen receptors ERα and ERβ as well as the 7-transmembrane spanning G protein-coupled estrogen receptor (GPER). We previously reported that estrogen activates the phosphoinositide 3-kinase (PI3Kinase) pathway via GPER, resulting in phosphatidylinositol (3,4,5)-trisphosphate (PIP3) production within the nucleus of breast cancer cells; however, the mechanisms and consequences of this activity remained unclear.

Methods

MCF7 breast cancer cells were transfected with GFP-fused Forkhead box O3 (FOXO3) as a reporter to assess localization in response to estrogen stimulation. Inhibitors of PI3Kinases and EGFR were employed to determine the mechanisms of estrogen-mediated FOXO3a inactivation. Receptor knockdown with siRNA and the selective GPER agonist G-1 elucidated the estrogen receptor(s) responsible for estrogen-mediated FOXO3a inactivation. The effects of selective estrogen receptor modulators and downregulators (SERMs and SERDs) on FOXO3a in MCF7 cells were also determined. Cell survival (inhibition of apoptosis) was assessed by caspase activation.

Results

In the estrogen-responsive breast cancer cell line MCF7, FOXO3a inactivation occurs on a rapid time scale as a result of GPER, but not ERα, stimulation by estrogen, established by the GPER-selective agonist G-1 and knockdown of GPER and ERα. GPER-mediated inactivation of FOXO3a is effected by the p110α catalytic subunit of PI3Kinase as a result of transactivation of the EGFR. The SERMs tamoxifen and raloxifene, as well as the SERD ICI182,780, were active in mediating FOXO3a inactivation in a GPER-dependent manner. Additionally, estrogen-and G-1-mediated stimulation of MCF7 cells results in a decrease in caspase activation under proapoptotic conditions.

Conclusions

Our results suggest that non-genomic signaling by GPER contributes, at least in part, to the survival of breast cancer cells, particularly in the presence of ER-targeted therapies involving SERMs and SERDs. Our results further suggest that GPER expression and FOXO3a localization could be utilized as prognostic markers in breast cancer therapy and that GPER antagonists could promote apoptosis in GPER-positive breast cancers, particularly in combination with chemotherapeutic and ER-targeted drugs, by antagonizing estrogen-mediated FOXO3a inactivation.

G protein-coupled estrogen receptor inhibits vascular prostanoid production and activity

Complications of atherosclerotic vascular disease, such as myocardial infarction and stroke, are the most common causes of death in postmenopausal women. Endogenous estrogens inhibit vascular inflammation-driven atherogenesis, a process that involves cyclooxygenase (COX)-derived vasoconstrictor prostanoids such as thromboxane A2. Here, we studied whether the G protein-coupled estrogen receptor (GPER) mediates estrogen-dependent inhibitory effects on prostanoid production and activity under pro-inflammatory conditions. Effects of estrogen on production of thromboxane A(2) were determined in human endothelial cells stimulated by the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-α). Moreover, Gper-deficient (Gper(-/-)) and WT mice were fed a pro-inflammatory diet and underwent ovariectomy or sham surgery to unmask the role of endogenous estrogens. Thereafter, contractions to acetylcholine-stimulated endothelial vasoconstrictor prostanoids and the thromboxane-prostanoid receptor agonist U46619 were recorded in isolated carotid arteries. In endothelial cells, TNF-α-stimulated thromboxane A2 production was inhibited by estrogen, an effect blocked by the GPER-selective antagonist G36. In ovary-intact mice, deletion of Gper increased prostanoid-dependent contractions by twofold. Ovariectomy also augmented prostanoid-dependent contractions by twofold in WT mice but had no additional effect in Gper(-/-) mice. These contractions were blocked by the COX inhibitor meclofenamate and unaffected by the nitric oxide synthase inhibitor l-N(G)-nitroarginine methyl ester. Vasoconstrictor responses to U46619 did not differ between groups, indicating intact signaling downstream of thromboxane-prostanoid receptor activation. In summary, under pro-inflammatory conditions, estrogen inhibits vasoconstrictor prostanoid production in endothelial cells and activity in intact arteries through GPER. Selective activation of GPER may therefore be considered as a novel strategy to treat increased prostanoid-dependent vasomotor tone or vascular disease in postmenopausal women.

What have we learned about GPER function in physiology and disease from knockout mice?

Estrogens, predominantly 17β-estradiol, exert diverse effects throughout the body in both normal and pathophysiology, during development and in reproductive, metabolic, endocrine, cardiovascular, nervous, musculoskeletal and immune systems. Estrogen and its receptors also play important roles in carcinogenesis and therapy, particularly for breast cancer. In addition to the classical nuclear estrogen receptors (ERα and ERβ) that traditionally mediate predominantly genomic signaling, the G protein-coupled estrogen receptor GPER has become recognized as a critical mediator of rapid signaling in response to estrogen. Mouse models, and in particular knockout (KO) mice, represent an important approach to understand the functions of receptors in normal physiology and disease. Whereas ERα KO mice display multiple significant defects in reproduction and mammary gland development, ERβ KO phenotypes are more limited, and GPER KO exhibit no reproductive deficits. However, the study of GPER KO mice over the last six years has revealed that GPER deficiency results in multiple physiological alterations including obesity, cardiovascular dysfunction, insulin resistance and glucose intolerance. In addition, the lack of estrogen-mediated effects in numerous tissues of GPER KO mice, studied in vivo or ex vivo, including those of the cardiovascular, endocrine, nervous and immune systems, reveals GPER as a genuine mediator of estrogen action. Importantly, GPER KO mice have also demonstrated roles for GPER in breast carcinogenesis and metastasis. In combination with the supporting effects of GPER-selective ligands and GPER knockdown approaches, GPER KO mice demonstrate the therapeutic potential of targeting GPER activity in diseases as diverse as obesity, diabetes, multiple sclerosis, hypertension, atherosclerosis, myocardial infarction, stroke and cancer.

Estrogens and the control of energy homeostasis: a brain perspective

Despite their prominent roles in the control of reproduction, estrogens pervade many other bodily functions. Key metabolic pathways display marked sexual differences, and estrogens are potent modulators of energy balance, as evidenced in extreme conditions of estrogen deficiency characterized by hyperphagia and decreased energy expenditure, and leading to obesity. Compelling evidence has recently demonstrated that, in addition to their peripheral effects, the actions of estrogens on energy homeostasis are exerted at central levels, to regulate almost every key aspect of metabolic homeostasis, from feeding to energy expenditure, to glucose and lipid metabolism. We review herein the state-of-the-art of the role of estrogens in the regulation of energy balance, with a focus on their central effects and modes of action.

International Union of Basic and Clinical Pharmacology. XCVII. G Protein-Coupled Estrogen Receptor and Its Pharmacologic Modulators

Estrogens are critical mediators of multiple and diverse physiologic effects throughout the body in both sexes, including the reproductive, cardiovascular, endocrine, nervous, and immune systems. As such, alterations in estrogen function play important roles in many diseases and pathophysiological conditions (including cancer), exemplified by the lower prevalence of many diseases in premenopausal women. Estrogens mediate their effects through multiple cellular receptors, including the nuclear receptor family (ERα and ERβ) and the G protein-coupled receptor (GPCR) family (GPR30/G protein-coupled estrogen receptor [GPER]). Although both receptor families can initiate rapid cell signaling and transcriptional regulation, the nuclear receptors are traditionally associated with regulating gene expression, whereas GPCRs are recognized as mediating rapid cellular signaling. Estrogen-activated pathways are not only the target of multiple therapeutic agents (e.g., tamoxifen, fulvestrant, raloxifene, and aromatase inhibitors) but are also affected by a plethora of phyto- and xeno-estrogens (e.g., genistein, coumestrol, bisphenol A, dichlorodiphenyltrichloroethane). Because of the existence of multiple estrogen receptors with overlapping ligand specificities, expression patterns, and signaling pathways, the roles of the individual receptors with respect to the diverse array of endogenous and exogenous ligands have been challenging to ascertain. The identification of GPER-selective ligands however has led to a much greater understanding of the roles of this receptor in normal physiology and disease as well as its interactions with the classic estrogen receptors ERα and ERβ and their signaling pathways. In this review, we describe the history and characterization of GPER over the past 15 years focusing on the pharmacology of steroidal and nonsteroidal compounds that have been employed to unravel the biology of this most recently recognized estrogen receptor.

Bisphenol A effects on gene expression in adipocytes from children: association with metabolic disorders

Bisphenol A (BPA) is a xenobiotic endocrine-disrupting chemical. In vitro and in vivo studies have indicated that BPA alters endocrine-metabolic pathways in adipose tissue, which increases the risk of metabolic disorders and obesity. BPA can affect adipose tissue and increase fat cell numbers or sizes by regulating the expression of the genes that are directly involved in metabolic homeostasis and obesity. Several studies performed in animal models have accounted for an obesogen role of BPA, but its effects on human adipocytes - especially in children - have been poorly investigated. The aim of this study is to understand the molecular mechanisms by which environmentally relevant doses of BPA can interfere with the canonical endocrine function that regulates metabolism in mature human adipocytes from prepubertal, non-obese children. BPA can act as an estrogen agonist or antagonist depending on the physiological context. To identify the molecular signatures associated with metabolism, transcriptional modifications of mature adipocytes from prepubertal children exposed to estrogen were evaluated by means of microarray analysis. The analysis of deregulated genes associated with metabolic disorders allowed us to identify a small group of genes that are expressed in an opposite manner from that of adipocytes treated with BPA. In particular, we found that BPA increases the expression of pro-inflammatory cytokines and the expression of FABP4 and CD36, two genes involved in lipid metabolism. In addition, BPA decreases the expression of PCSK1, a gene involved in insulin production. These results indicate that exposure to BPA may be an important risk factor for developing metabolic disorders that are involved in childhood metabolism dysregulation.

Progress in the molecular understanding of central regulation of body weight by estrogens

OBJECTIVE

Estrogens can act in the brain to prevent body weight gain. Tremendous research efforts have been focused on estrogen physiology in the brain in the context of body weight control; estrogen receptors and the related signals have been attractive targets for development of new obesity therapies. The objective is to review recent findings on these aspects.

METHODS

Recent studies that used conventional and conditional knockout mouse strains to delineate the cellular and molecular mechanisms for the beneficial effects of estrogens on body weight balance are reviewed. Emerging genetic tools that could further benefit the field of estrogen research and a newly developed estrogen-based regimen that produces body weight-lowering benefits also are discussed.

RESULTS

The body weight-lowering effects of estrogens are mediated by multiple forms of estrogen receptors in different brain regions through distinct but coordinated mechanisms. Both rapid signals and "classic" nuclear receptor actions of estrogen receptors appear to contribute to estrogenic regulation of body weight.

CONCLUSIONS

Estrogen receptors and associated signal networks are potential targets for obesity treatment, and further investigations are warranted.

Emerging roles of GPER in diabetes and atherosclerosis

The G protein-coupled estrogen receptor (GPER) is a 7-transmembrane receptor implicated in rapid estrogen signaling. Originally cloned from vascular endothelial cells, GPER plays a central role in the regulation of vascular tone and cell growth as well as lipid and glucose homeostasis. This review highlights our knowledge of the physiological and pathophysiological functions of GPER in the pancreas, peripheral and immune tissues, and the arterial vasculature. Recent findings on its roles in obesity, diabetes, and atherosclerosis, including GPER-dependent regulation of lipid metabolism and inflammation, are presented. The therapeutic potential of targeting GPER-dependent pathways in chronic diseases such as coronary artery disease and diabetes and in the context of menopause is also discussed.

Sex Hormones and Their Receptors Regulate Liver Energy Homeostasis

The liver is one of the most essential organs involved in the regulation of energy homeostasis. Hepatic steatosis, a major manifestation of metabolic syndrome, is associated with imbalance between lipid formation and breakdown, glucose production and catabolism, and cholesterol synthesis and secretion. Epidemiological studies show sex difference in the prevalence in fatty liver disease and suggest that sex hormones may play vital roles in regulating hepatic steatosis. In this review, we summarize current literature and discuss the role of estrogens and androgens and the mechanisms through which estrogen receptors and androgen receptors regulate lipid and glucose metabolism in the liver. In females, estradiol regulates liver metabolism via estrogen receptors by decreasing lipogenesis, gluconeogenesis, and fatty acid uptake, while enhancing lipolysis, cholesterol secretion, and glucose catabolism. In males, testosterone works via androgen receptors to increase insulin receptor expression and glycogen synthesis, decrease glucose uptake and lipogenesis, and promote cholesterol storage in the liver. These recent integrated concepts suggest that sex hormone receptors could be potential promising targets for the prevention of hepatic steatosis.

Effects of aldosterone on insulin sensitivity and secretion

Dr. Conn originally reported an increased risk of diabetes in patients with hyperaldosteronism in the 1950s, although the mechanism remains unclear. Aldosterone-induced hypokalemia was initially described to impair glucose tolerance by impairing insulin secretion. Correction of hypokalemia by potassium supplementation only partially restored insulin secretion and glucose tolerance, however. Aldosterone also impairs glucose-stimulated insulin secretion in isolated pancreatic islets via reactive oxygen species in a mineralocorticoid receptor-independent manner. Aldosterone-induced mineralocorticoid receptor activation also impairs insulin sensitivity in adipocytes and skeletal muscle. Aldosterone may produce insulin resistance secondarily by altering potassium, increasing inflammatory cytokines, and reducing beneficial adipokines such as adiponectin. Renin-angiotensin system antagonists reduce circulating aldosterone concentrations and also the risk of type 2 diabetes in clinical trials. These data suggest that primary and secondary hyperaldosteronism may contribute to worsening glucose tolerance by impairing insulin sensitivity or insulin secretion in humans. Future studies should define the effects of MR antagonists and aldosterone on insulin secretion and sensitivity in humans.

G-protein estrogen receptor as a regulator of low-density lipoprotein cholesterol metabolism: cellular and population genetic studies

OBJECTIVE

Estrogen deficiency is linked with increased low-density lipoprotein (LDL) cholesterol. The hormone receptor mediating this effect is unknown. G-protein estrogen receptor (GPER) is a recently recognized G-protein-coupled receptor that is activated by estrogens. We recently identified a common hypofunctional missense variant of GPER, namely P16L. However, the role of GPER in LDL metabolism is unknown. Therefore, we examined the association of the P16L genotype with plasma LDL cholesterol level. Furthermore, we studied the role of GPER in regulating expression of the LDL receptor and proprotein convertase subtilisin kexin type 9.

APPROACH AND RESULTS

Our discovery cohort was a genetically isolated population of Northern European descent, and our validation cohort consisted of normal, healthy women aged 18 to 56 years from London, Ontario. In addition, we examined the effect of GPER on the regulation of proprotein convertase subtilisin kexin type 9 and LDL receptor expression by the treatment with the GPER agonist, G1. In the discovery cohort, GPER P16L genotype was associated with a significant increase in LDL cholesterol (mean±SEM): 3.18±0.05, 3.25±0.08, and 4.25±0.33 mmol/L, respectively, in subjects with CC (homozygous for P16), CT (heterozygotes), and TT (homozygous for L16) genotypes (P<0.05). In the validation cohort (n=339), the GPER P16L genotype was associated with a similar increase in LDL cholesterol: 2.17±0.05, 2.34±0.06, and 2.42±0.16 mmol/L, respectively, in subjects with CC, CT, and TT genotypes (P<0.05). In the human hepatic carcinoma cell line, the GPER agonist, G1, mediated a concentration-dependent increase in LDL receptor expression, blocked by either pretreatment with the GPER antagonist G15 or by shRNA-mediated GPER downregulation. G1 also mediated a GPER- and concentration-dependent decrease in proprotein convertase subtilisin kexin type 9 expression.

CONCLUSIONS

GPER activation upregulates LDL receptor expression, probably at least, in part, via proprotein convertase subtilisin kexin type 9 downregulation. Furthermore, humans carrying the hypofunctional P16L genetic variant of GPER have increased plasma LDL cholesterol. In aggregate, these data suggest an important role of GPER in the regulation of LDL receptor expression and consequently LDL metabolism.

GPR30 mediates anorectic estrogen-induced STAT3 signaling in the hypothalamus

OBJECTIVE

Estrogen plays an important role in the control of energy balance in the hypothalamus. Leptin-independent STAT3 activation (i.e., tyrosine(705)-phosphorylation of STAT3, pSTAT3) in the hypothalamus is hypothesized as the primary mechanism of the estrogen-induced anorexic response. However, the type of estrogen receptor that mediates this regulation is unknown. We investigated the role of the G protein-coupled receptor 30 (GPR30) in estradiol (E2)-induced STAT3 activation in the hypothalamus.

MATERIALS/METHODS

Regulation of STAT3 activation by E2, G-1, a specific agonist of GPR30 and G-15, a specific antagonist of GPR30 was analyzed in vitro and in vivo. Effect of GPR30 activation on eating behavior was analyzed in vivo.

RESULTS

E2 stimulated pSTAT3 in cells expressing GPR30, but not expressing estrogen receptor ERα and ERβ. G-1 induced pSTAT3, and G-15 inhibited E2-induced pSTAT3 in primary cultures of hypothalamic neurons. A cerebroventricular injection of G-1 increased pSTAT3 in the arcuate nucleus of mice, which was associated with a decrease in food intake and body weight gain.

CONCLUSIONS

These results suggest that GPR30 is the estrogen receptor that mediates the anorectic effect of estrogen through the STAT3 pathway in the hypothalamus.

Estrogen signaling in metabolic inflammation

There is extensive evidence supporting the interference of inflammatory activation with metabolism. Obesity, mainly visceral obesity, is associated with a low-grade inflammatory state, triggered by metabolic surplus where specialized metabolic cells such as adipocytes activate cellular stress initiating and sustaining the inflammatory program. The increasing prevalence of obesity, resulting in increased cardiometabolic risk and precipitating illness such as cardiovascular disease, type 2 diabetes, fatty liver, cirrhosis, and certain types of cancer, constitutes a good example of this association. The metabolic actions of estrogens have been studied extensively and there is also accumulating evidence that estrogens influence immune processes. However, the connection between these two fields of estrogen actions has been underacknowledged since little attention has been drawn towards the possible action of estrogens on the modulation of metabolism through their anti-inflammatory properties. In the present paper, we summarize knowledge on the modification inflammatory processes by estrogens with impact on metabolism and highlight major research questions on the field. Understanding the regulation of metabolic inflammation by estrogens may provide the basis for the development of therapeutic strategies to the management of metabolic dysfunctions.

GPER1 is regulated by insulin in cancer cells and cancer-associated fibroblasts

Elevated insulin levels have been associated with an increased cancer risk as well as with aggressive and metastatic cancer phenotypes characterized by a poor prognosis. Insulin stimulates the proliferation, migration, and invasiveness of cancer cells through diverse transduction pathways, including estrogen signaling. As G protein estrogen receptor 1 (GPER1) mediates rapid cell responses to estrogens, we evaluated the potential of insulin to regulate GPER1 expression and function in leiomyosarcoma cancer cells (SKUT-1) and breast cancer-associated fibroblasts (CAFs), which were used as a model system. We found that insulin transactivates the GPER1 promoter sequence and increases the mRNA and protein expression of GPER1 through the activation of the PRKCD/MAPK1/c-Fos/AP1 transduction pathway, as ascertained by means of specific pharmacological inhibitors and gene-silencing experiments. Moreover, cell migration triggered by insulin occurred through GPER1 and its main target gene CTGF, whereas the insulin-induced expression of GPER1 boosted cell-cycle progression and the glucose uptake stimulated by estrogens. Notably, a positive correlation between insulin serum levels and GPER1 expression was found in cancer fibroblasts obtained from breast cancer patients. Altogether, our data indicate that GPER1 may be included among the complex network of transduction signaling triggered by insulin that drives cells toward cancer progression.

GPER-targeted, 99mTc-labeled, nonsteroidal ligands demonstrate selective tumor imaging and in vivo estrogen binding

Our understanding of estrogen (17β-estradiol, E2) receptor biology has evolved in recent years with the discovery and characterization of a 7-transmembrane-spanning G protein-coupled estrogen receptor (GPER/GPR30) and the development of GPER-selective functional chemical probes. GPER is highly expressed in certain breast, endometrial, and ovarian cancers, establishing the importance of noninvasive methods to evaluate GPER expression in vivo. Here, we developed (99m)Tc-labeled GPER ligands to demonstrate the in vivo status of GPER as an estrogen receptor (ER) and for GPER visualization in whole animals. A series of (99m)Tc(I)-labeled nonsteroidal tetrahydro-3H-cyclopenta[c]quinolone derivatives was synthesized utilizing pyridin-2-yl hydrazine and picolylamine chelates. Radioligand receptor binding studies revealed binding affinities in the 10 to 30 nmol/L range. Cell signaling assays previously demonstrated that derivatives retaining a ketone functionality displayed agonist properties, whereas those lacking such a hydrogen bond acceptor were antagonists. In vivo biodistribution and imaging studies performed on mice bearing human endometrial and breast cancer cell xenografts yielded significant tumor uptake (0.4-1.1%ID/g). Blocking studies revealed specific uptake in multiple organs (adrenals, uterus, and mammary tissue), as well as tumor uptake with similar levels of competition by E2 and G-1, a GPER-selective agonist. In conclusion, we synthesized and evaluated a series of first-generation (99m)Tc-labeled GPER-specific radioligands, demonstrating GPER as an estrogen-binding receptor for the first time in vivo using competitive binding principles, and establishing the utility of such ligands as tumor imaging agents. These results warrant further investigation into the role of GPER in estrogen-mediated carcinogenesis and as a target for diagnostic/therapeutic/image-guided drug delivery.

IMPLICATIONS

These studies provide a molecular basis to evaluate GPER expression and function as an ER through in vivo imaging.

G protein-coupled estrogen receptor regulates mammary tumorigenesis and metastasis

The role of 17β-estradiol (E2) in breast cancer development and tumor growth has traditionally been attributed exclusively to the activation of estrogen receptor-α (ERα). Although targeted inhibition of ERα is a successful approach for patients with ERα(+) breast cancer, many patients fail to respond or become resistant to anti-estrogen therapy. The discovery of the G protein-coupled estrogen receptor (GPER) suggested an additional mechanism through which E2 could exert its effects in breast cancer. Studies have demonstrated clinical correlations between GPER expression in human breast tumor specimens and increased tumor size, distant metastasis, and recurrence, as well as established a proliferative role for GPER in vitro; however, direct in vivo evidence has been lacking. To this end, a GPER-null mutation [GPER knockout (KO)] was introduced, through interbreeding, into a widely used transgenic mouse model of mammary tumorigenesis [MMTV-PyMT (PyMT)]. Early tumor development, assessed by the extent of hyperplasia and proliferation, was not different between GPER wild-type/PyMT (WT/PyMT) and those mice harboring the GPER-null mutation (KO/PyMT). However, by 12 to 13 weeks of age, tumors from KO/PyMT mice were smaller with decreased proliferation compared with those from WT/PyMT mice. Furthermore, tumors from the KO/PyMT mice were of histologically lower grade compared with tumors from their WT counterparts, suggesting less aggressive tumors in the KO/PyMT mice. Finally, KO/PyMT mice displayed dramatically fewer lung metastases compared with WT/PyMT mice. Combined, these data provide the first in vivo evidence that GPER plays a critical role in breast tumor growth and distant metastasis.

IMPLICATIONS

This is the first description of a role for the novel estrogen receptor GPER in breast tumorigenesis and metastasis, demonstrating that it represents a new target in breast cancer diagnosis, prognosis, and therapy.

Estrogen-mediated renoprotection following cardiac arrest and cardiopulmonary resuscitation is robust to GPR30 gene deletion

Introduction

Acute kidney injury is a serious,sexually dimorphic perioperative complication, primarily attributed to hypoperfusion. We previously found that estradiol is renoprotective after cardiac arrest and cardiopulmonary resuscitation in ovariectomized female mice. Additionally, we found that neither estrogen receptor alpha nor beta mediated this effect. We hypothesized that the G protein estrogen receptor (GPR30) mediates the renoprotective effect of estrogen.

Methods

Ovariectomized female and gonadally intact male wild-type and GPR30 gene-deleted mice were treated with either vehicle or 17β-estradiol for 7 days, then subjected to cardiac arrest and cardiopulmonary resuscitation. Twenty four hours later, serum creatinine and urea nitrogen were measured, and histologic renal injury was evaluated by unbiased stereology.

Results

In both males and females, GPR30 gene deletion was associated with reduced serum creatinine regardless of treatment. Estrogen treatment of GPR30 gene-deleted males and females was associated with increased preprocedural weight. In ovariectomized female mice, estrogen treatment did not alter resuscitation, but was renoprotective regardless of GPR30 gene deletion. In males, estrogen reduced the time-to-resuscitate and epinephrine required. In wild-type male mice, serum creatinine was reduced, but neither serum urea nitrogen nor histologic outcomes were affected by estrogen treatment. In GPR30 gene-deleted males, estrogen did not alter renal outcomes. Similarly, renal injury was not affected by G1 therapy of ovariectomized female wild-type mice.

Conclusion

Treatment with 17β-estradiol is renoprotective after whole-body ischemia-reperfusion in ovariectomized female mice irrespective of GPR30 gene deletion. Treatment with the GPR30 agonist G1 did not alter renal outcome in females. We conclude GPR30 does not mediate the renoprotective effect of estrogen in ovariectomized female mice. In males, estrogen therapy was not renoprotective. Estrogen treatment of GPR30 gene-deleted mice was associated with increased preprocedural weight in both sexes. Of significance to further investigation, GPR30 gene deletion was associated with reduced serum creatinine, regardless of treatment.

Sexually dimorphic role of G protein-coupled estrogen receptor (GPER) in modulating energy homeostasis

This article is part of a Special Issue "Energy Balance". The classical estrogen receptors, estrogen receptor-α and estrogen receptor-β are well established in the regulation of body weight and energy homeostasis in both male and female mice, whereas, the role for G protein-coupled estrogen receptor 1 (GPER) as a modulator of energy homeostasis remains controversial. This study sought to determine whether gene deletion of GPER (GPER KO) alters body weight, body adiposity, food intake, and energy homeostasis in both males and females. Male mice lacking GPER developed moderate obesity and larger adipocyte size beginning at 8 weeks of age, with significant reductions in energy expenditure, but not food intake or adipocyte number. Female GPER KO mice developed increased body weight relative to WT females a full 6 weeks later than the male GPER KO mice. Female GPER KO mice also had reductions in energy expenditure, but no significant increases in body fat content. Consistent with their decrease in energy expenditure, GPER KO males and females showed significant reductions in two brown fat thermogenic proteins. GPER KO females, prior to their divergence in body weight, were less sensitive than WT females to the feeding-inhibitory effects of leptin and CCK. Additionally, body weight was not as modulated by ovariectomy or estradiol replacement in GPER KO mice. Estradiol treatment activated phosphorylated extracellular signal-regulated kinase (pERK) in WT but not GPER KO females. For the first time, GPER expression was found in the adipocyte but not the stromal fraction of adipose tissue. Together, these results provide new information elucidating a sexual dimorphism in GPER function in the development of postpubertal energy balance.

Reprint of "GPR30 mediates estrogen rapid signaling and neuroprotection"

G-protein-coupled estrogen receptor-30 (GPR30), also known as G-protein estrogen receptor-1 (GPER1), is a putative extranuclear estrogen receptor whose precise functions in the brain are poorly understood. Studies using exogenous administration of the GPR30 agonist, G1 suggests that GPR30 may have a neuroprotective role in cerebral ischemia. However, the physiological role of GPR30 in mediating estrogen (E2)-induced neuroprotection in cerebral ischemia remains unclear. Also unclear is whether GPR30 has a role in mediating rapid signaling by E2 after cerebral ischemia, which is thought to underlie its neuroprotective actions. To address these deficits in our knowledge, the current study examined the effect of antisense oligonucleotide (AS) knockdown of GPR30 in the hippocampal CA1 region upon E2-BSA-induced neuroprotection and rapid kinase signaling in a rat model of global cerebral ischemia (GCI). Immunohistochemistry demonstrated that GPR30 is strongly expressed in the hippocampal CA1 region and dentate gyrus, with less expression in the CA3 region. E2-BSA exerted robust neuroprotection of hippocampal CA1 neurons against GCI, an effect abrogated by AS knockdown of GPR30. Missense control oligonucleotides had no effect upon E2-BSA-induced neuroprotection, indicating specificity of the effect. The GPR30 agonist, G1 also exerted significant neuroprotection against GCI. E2-BSA and G1 also rapidly enhanced activation of the prosurvival kinases, Akt and ERK, while decreasing proapototic JNK activation. Importantly, AS knockdown of GPR30 markedly attenuated these rapid kinase signaling effects of E2-BSA. As a whole, the studies provide evidence of an important role of GPR30 in mediating the rapid signaling and neuroprotective actions of E2 in the hippocampus.

Estrogen biology: new insights into GPER function and clinical opportunities

Estrogens play an important role in the regulation of normal physiology, aging and many disease states. Although the nuclear estrogen receptors have classically been described to function as ligand-activated transcription factors mediating genomic effects in hormonally regulated tissues, more recent studies reveal that estrogens also mediate rapid signaling events traditionally associated with G protein-coupled receptors. The G protein-coupled estrogen receptor GPER (formerly GPR30) has now become recognized as a major mediator of estrogen's rapid cellular effects throughout the body. With the discovery of selective synthetic ligands for GPER, both agonists and antagonists, as well as the use of GPER knockout mice, significant advances have been made in our understanding of GPER function at the cellular, tissue and organismal levels. In many instances, the protective/beneficial effects of estrogen are mimicked by selective GPER agonism and are absent or reduced in GPER knockout mice, suggesting an essential or at least parallel role for GPER in the actions of estrogen. In this review, we will discuss recent advances and our current understanding of the role of GPER and the activity of clinically used drugs, such as SERMs and SERDs, in physiology and disease. We will also highlight novel opportunities for clinical development towards GPER-targeted therapeutics, for molecular imaging, as well as for theranostic approaches and personalized medicine.

GPR30 mediates estrogen rapid signaling and neuroprotection

G-protein-coupled estrogen receptor-30 (GPR30), also known as G-protein estrogen receptor-1 (GPER1), is a putative extranuclear estrogen receptor whose precise functions in the brain are poorly understood. Studies using exogenous administration of the GPR30 agonist, G1 suggests that GPR30 may have a neuroprotective role in cerebral ischemia. However, the physiological role of GPR30 in mediating estrogen (E2)-induced neuroprotection in cerebral ischemia remains unclear. Also unclear is whether GPR30 has a role in mediating rapid signaling by E2 after cerebral ischemia, which is thought to underlie its neuroprotective actions. To address these deficits in our knowledge, the current study examined the effect of antisense oligonucleotide (AS) knockdown of GPR30 in the hippocampal CA1 region upon E2-BSA-induced neuroprotection and rapid kinase signaling in a rat model of global cerebral ischemia (GCI). Immunohistochemistry demonstrated that GPR30 is strongly expressed in the hippocampal CA1 region and dentate gyrus, with less expression in the CA3 region. E2-BSA exerted robust neuroprotection of hippocampal CA1 neurons against GCI, an effect abrogated by AS knockdown of GPR30. Missense control oligonucleotides had no effect upon E2-BSA-induced neuroprotection, indicating specificity of the effect. The GPR30 agonist, G1 also exerted significant neuroprotection against GCI. E2-BSA and G1 also rapidly enhanced activation of the prosurvival kinases, Akt and ERK, while decreasing proapototic JNK activation. Importantly, AS knockdown of GPR30 markedly attenuated these rapid kinase signaling effects of E2-BSA. As a whole, the studies provide evidence of an important role of GPR30 in mediating the rapid signaling and neuroprotective actions of E2 in the hippocampus.

Sex- and age-dependent effects of Gpr30 genetic deletion on the metabolic and cardiovascular profiles of diet-induced obese mice

The G protein-coupled receptor 30 (GPR30) has been claimed as an estrogen receptor. However, the literature reports controversial findings and the physiological function of GPR30 is not fully understood yet. Consistent with studies assigning a role of GPR30 in the cardiovascular and metabolic systems, GPR30 expression has been reported in small arterial vessels, pancreas and chief gastric cells of the stomach. Therefore, we hypothesized a role of GPR30 in the onset and progression of cardiovascular and metabolic diseases. In order to test our hypothesis, we investigated the effects of a high-fat diet on the metabolic and cardiovascular profiles of Gpr30-deficient mice (GPR30-lacZ mice). We found that GPR30-lacZ female, rather than male, mice had significant lower levels of HDL along with an increase in fat liver accumulation as compared to control mice. However, two indicators of cardiac performance assessed by echocardiography, ejection fraction and fractional shortening were both decreased in an age-dependent manner only in Gpr30-lacZ male mice. Collectively our results point to a potential role of Gpr30 in preserving lipid metabolism and cardiac function in a sex- and age-dependent fashion.

G protein-coupled estrogen receptor-selective ligands modulate endometrial tumor growth

Endometrial carcinoma is the most common cancer of the female reproductive tract. GPER/GPR30 is a 7-transmembrane spanning G protein-coupled receptor that has been identified as the third estrogen receptor, in addition to ERα and ERβ. High GPER expression is predictive of poor survival in endometrial and ovarian cancer, but despite this, the estrogen-mediated signaling pathways and specific estrogen receptors involved in endometrial cancer remain unclear. Here, employing ERα-negative Hec50 endometrial cancer cells, we demonstrate that GPER mediates estrogen-stimulated activation of ERK and PI3K via matrix metalloproteinase activation and subsequent transactivation of the EGFR and that ER-targeted therapeutic agents (4-hydroxytamoxifen, ICI182,780/fulvestrant, and Raloxifene), the phytoestrogen genistein, and the “ERα-selective” agonist propylpyrazole triol also function as GPER agonists. Furthermore, xenograft tumors of Hec50 cells yield enhanced growth with G-1 and estrogen, the latter being inhibited by GPER-selective pharmacologic antagonism with G36. These results have important implications with respect to the use of putatively ER-selective ligands and particularly for the widespread long-term use of “ER-targeted” therapeutics. Moreover, our findings shed light on the potential mechanisms of SERM/SERD side effects reported in many clinical studies. Finally, our results provide the first demonstration that pharmacological inhibition of GPER activity in vivo prevents estrogen-mediated tumor growth.

Regulation of vascular smooth muscle tone by adipose-derived contracting factor

Obesity and arterial hypertension, important risk factors for atherosclerosis and coronary artery disease, are characterized by an increase in vascular tone. While obesity is known to augment vasoconstrictor prostanoid activity in endothelial cells, less is known about factors released from fat tissue surrounding arteries (perivascular adipose). Using lean controls and mice with either monogenic or diet-induced obesity, we set out to determine whether and through which pathways perivascular adipose affects vascular tone. We unexpectedly found that in the aorta of obese mice, perivascular adipose potentiates vascular contractility to serotonin and phenylephrine, indicating activity of a factor generated by perivascular adipose, which we designated “adipose-derived contracting factor” (ADCF). Inhibition of cyclooxygenase (COX) fully prevented ADCF-mediated contractions, whereas COX-1 or COX-2-selective inhibition was only partially effective. By contrast, inhibition of superoxide anions, NO synthase, or endothelin receptors had no effect on ADCF activity. Perivascular adipose as a source of COX-derived ADCF was further confirmed by detecting increased thromboxane A₂ formation from perivascular adipose-replete aortae from obese mice. Taken together, this study identifies perivascular adipose as a novel regulator of arterial vasoconstriction through the release of COX-derived ADCF. Excessive ADCF activity in perivascular fat under obese conditions likely contributes to increased vascular tone by antagonizing vasodilation. ADCF may thus propagate obesity-dependent hypertension and the associated increased risk in coronary artery disease, potentially representing a novel therapeutic target.