Vascular cell signaling by membrane estrogen receptors

Hormone Replacement Therapy and Cardiovascular Health in Postmenopausal Women

Sex-related differences are found not only in the reproductive system but also across various biological systems, such as the cardiovascular system. Compared with premenopausal women, cardiovascular disease (CVD) tends to occur more frequently in adult men and postmenopausal women (Post-MW). Also, during the reproductive years, sex hormones synthesized and released into the blood stream affect vascular function in a sex-dependent fashion. Estrogen (E2) interacts with estrogen receptors (ERs) in endothelial cells, vascular smooth muscle, and the extracellular matrix, causing both genomic and non-genomic effects, including vasodilation, decreased blood pressure, and cardiovascular protection. These observations have suggested beneficial effects of female sex hormones on cardiovascular function. In addition, the clear advantages of E2 supplementation in alleviating vasomotor symptoms during menopause have led to clinical investigations of the effects of menopausal hormone therapy (MHT) in CVD. However, the findings from these clinical trials have been variable and often contradictory. The lack of benefits of MHT in CVD has been related to the MHT preparation (type, dose, and route), vascular ERs (number, variants, distribution, and sensitivity), menopausal stage (MHT timing, initiation, and duration), hormonal environment (progesterone, testosterone (T), gonadotropins, and sex hormone binding globulin), and preexisting cardiovascular health and other disorders. The vascular effects of sex hormones have also prompted further examination of the use of anabolic drugs among athletes and the long-term effects of E2 and T supplements on cardiovascular health in cis- and transgender individuals seeking gender-affirming therapy. Further analysis of the effects of sex hormones and their receptors on vascular function should enhance our understanding of the sex differences and menopause-related changes in vascular signaling and provide better guidance for the management of CVD in a gender-specific fashion and in Post-MW.

Menopause-related changes in vascular signaling by sex hormones

Cardiovascular disease (CVD), such as hypertension and coronary artery disease, involves pathological changes in vascular signaling, function, and structure. Vascular signaling is regulated by multiple intrinsic and extrinsic factors that influence endothelial cells, vascular smooth muscle, and extracellular matrix. Vascular function is also influenced by environmental factors including diet, exercise, and stress, as well as genetic background, sex differences, and age. CVD is more common in adult men and postmenopausal women than in premenopausal women. Specifically, women during menopausal transition, with declining ovarian function and production of estrogen (E2) and progesterone, show marked increase in the incidence of CVD and associated vascular dysfunction. Mechanistic research suggests that E2 and E2 receptor signaling have beneficial effects on vascular function including vasodilation, decreased blood pressure, and cardiovascular protection. Also, the tangible benefits of E2 supplementation in improving menopausal symptoms have prompted clinical trials of menopausal hormone therapy (MHT) in CVD, but the results have been inconsistent. The inadequate benefits of MHT in CVD could be attributed to the E2 type, dose, formulation, route, timing, and duration as well as menopausal changes in E2/E2 receptor vascular signaling. Other factors that could affect the responsiveness to MHT are the integrated hormonal milieu including gonadotropins, progesterone, and testosterone, vascular health status, preexisting cardiovascular conditions, and menopause-related dysfunction in the renal, gastrointestinal, endocrine, immune, and nervous systems. Further analysis of these factors should enhance our understanding of menopause-related changes in vascular signaling by sex hormones and provide better guidance for management of CVD in postmenopausal women. SIGNIFICANCE STATEMENT: Cardiovascular disease is more common in adult men and postmenopausal women than premenopausal women. Earlier observations of vascular benefits of menopausal hormone therapy did not materialize in randomized clinical trials. Further examination of the cardiovascular effects of sex hormones in different formulations and regimens, and the menopausal changes in vascular signaling would help to adjust the menopausal hormone therapy protocols in order to enhance their effectiveness in reducing the risk and the management of cardiovascular disease in postmenopausal women.

Efficacy of Local N-Acetylcysteine Administration in Mitigating OHSS Parameters: A Comparative Analysis With Dopaminergic Agonist in the OHSS Model

In this study, we evaluated the effects of intrabursal administration of cabergoline and N-acetylcysteine on ovarian hyperstimulation syndrome (OHSS) in an immature rat model. The study assessed body, ovarian, and uterine weights, as well as the concentrations of vascular endothelial growth factor A (VEGF-A). Moreover, levels of MDA, 4-HDA, and nitrites were assessed in ovarian homogenates, and vascular permeability was quantified in the peritoneal cavity. Ovarian morphology was characterized using histology and hematoxylin-eosin staining, determining the count of ovarian follicles and corpus luteum. Our results demonstrated a significant increase in lipoperoxidation, nitrite levels, and VEGF-A concentrations in the OHSS group compared to the control group. These biochemical alterations corroborate the successful induction of OHSS in the experimental model. Direct injection into the ovarian bursa resulted in reduced vascular permeability and VEGF-A levels, suggesting that the effects of cabergoline are predominantly ovarian. Particularly, cabergoline did not significantly alter other parameters such as ovarian weight, lipoperoxidation, nitrite levels, or morphology. Conversely, low concentrations of N-acetylcysteine (25-50 µg/kg) significantly reduced ovarian and uterine weights, VEGF-A levels, and vascular permeability. Interestingly, this dose-response relationship was not observed at higher NAC concentrations (100-200 μg/kg), suggesting a potential threshold beyond which NAC loses efficacy in these specific parameters. Our results suggest that the localized administration of N-acetylcysteine shows promise as a therapeutic strategy for OHSS by modulating key parameters associated with the syndrome. These promising results warrant further investigation into its mechanisms and efficacy, potentially expanding therapeutic options for OHSS management.

Estrogen dysregulation, intraocular pressure, and glaucoma risk

Characterized by optic nerve atrophy due to retinal ganglion cell (RGC) death, glaucoma is the leading cause of irreversible blindness worldwide. Of the major risk factors for glaucoma (age, ocular hypertension, and genetics), only elevated intraocular pressure (IOP) is modifiable, which is largely regulated by aqueous humor outflow through the trabecular meshwork. Glucocorticoids such as dexamethasone have long been known to elevate IOP and lead to glaucoma. However, several recent studies have reported that steroid hormone estrogen levels inversely correlate with glaucoma risk, and that variants in estrogen signaling genes have been associated with glaucoma. As a result, estrogen dysregulation may contribute to glaucoma pathogenesis, and estrogen signaling may protect against glaucoma. The mechanism for estrogen-related protection against glaucoma is not completely understood but likely involves both regulation of IOP homeostasis and neuroprotection of RGCs. Based upon its known activities, estrogen signaling may promote IOP homeostasis by affecting extracellular matrix turnover, focal adhesion assembly, actin stress fiber formation, mechanosensation, and nitric oxide production. In addition, estrogen receptors in the RGCs may mediate neuroprotective functions. As a result, the estrogen signaling pathway may offer a therapeutic target for both IOP control and neuroprotection. This review examines the evidence for a relationship between estrogen and IOP and explores the possible mechanisms by which estrogen maintains IOP homeostasis.

Short-Term Supplementation With Fermented Red Clover Extract Reduces Vascular Inflammation in Early Post-menopausal Women

The decline in estrogen at menopause poses a critical challenge to cardiovascular and metabolic health. Recently, a growing interest in the role of phytoestrogens, with a particular focus on isoflavones, has emerged as they can bind to estrogen receptors and may mimic the roles of endogenous estrogen. Fermented red clover extract (RC) contains isoflavones with superior bioavailability compared to non-fermented isoflavones, however little is known regarding the impact of isoflavones on cardiovascular and metabolic health. We assessed markers of vascular health in plasma and skeletal muscle samples obtained from healthy but sedentary early post-menopausal women (n = 10; 54 ± 4 years) following 2 weeks of twice daily treatment with placebo (PLA) or RC (60 mg isoflavones per day). The two interventions were administered using a randomized, double-blind, crossover design with a two-week washout period. Plasma samples were utilized for assessment of markers of vascular inflammation. There was a statistically significant reduction (~5.4%) in vascular cell adhesion molecule 1 (VCAM-1) following 2 weeks of RC supplementation compared to PLA (p = 0.03). In contrast, there was no effect of RC supplementation compared to PLA on skeletal muscle estrogen receptor content and enzymes related to vascular function, and angiogenesis. Supplementation with RC reduces vascular inflammation in early post-menopausal women and future studies should address the long-term impact of daily supplementation with RC after menopause.

Therapy for Pulmonary Arterial Hypertension: Glance on Nitric Oxide Pathway

Pulmonary arterial hypertension (PAH) is a severe disease with a resultant increase of the mean pulmonary arterial pressure, right ventricular hypertrophy and eventual death. Research in recent years has produced various therapeutic options for its clinical management but the high mortality even under treatment remains a big challenge attributed to the complex pathophysiology. Studies from clinical and non-clinical experiments have revealed that the nitric oxide (NO) pathway is one of the key pathways underlying the pathophysiology of PAH. Many of the essential drugs used in the management of PAH act on this pathway highlighting its significant role in PAH. Meanwhile, several novel compounds targeting on NO pathway exhibits great potential to become future therapy medications. Furthermore, the NO pathway is found to interact with other crucial pathways. Understanding such interactions could be helpful in the discovery of new drug that provide better clinical outcomes.

The effect of heat therapy on blood pressure and peripheral vascular function: A systematic review and meta-analysis

NEW FINDINGS

What is the topic of this review? We have conducted a systematic review and meta-analysis on the current evidence for the effect of heat therapy on blood pressure and vascular function. What advances does it highlight? We found that heat therapy reduced mean arterial, systolic and diastolic blood pressure. We also observed that heat therapy improved vascular function, as assessed via brachial artery flow-mediated dilatation. Our results suggest that heat therapy is a promising therapeutic tool that should be optimized further, via mode and dose, for the prevention and treatment of cardiovascular disease risk factors.

ABSTRACT

Lifelong sauna exposure is associated with reduced cardiovascular disease risk. Recent studies have investigated the effect of heat therapy on markers of cardiovascular health. We aimed to conduct a systematic review with meta-analysis to determine the effects of heat therapy on blood pressure and indices of vascular function in healthy and clinical populations. Four databases were searched up to September 2020 for studies investigating heat therapy on outcomes including blood pressure and vascular function. Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was used to assess the certainty of evidence. A total of 4522 titles were screened, and 15 studies were included. Healthy and clinical populations were included. Heat exposure was for 30-90 min, over 10-36 sessions. Compared with control conditions, heat therapy reduced mean arterial pressure [n = 4 studies; mean difference (MD): -5.86 mmHg, 95% confidence interval (CI): -8.63, -3.10; P < 0.0001], systolic blood pressure (n = 10; MD: -3.94 mmHg, 95% CI: -7.22, -0.67; P = 0.02) and diastolic blood pressure (n = 9; MD: -3.88 mmHg, 95% CI: -6.13, -1.63; P = 0.0007) and improved flow-mediated dilatation (n = 5; MD: 1.95%, 95% CI: 0.14, 3.76; P = 0.03). Resting heart rate was unchanged (n = 10; MD: -1.25 beats/min; 95% CI: -3.20, 0.70; P = 0.21). Early evidence also suggests benefits for arterial stiffness and cutaneous microvascular function. The certainty of evidence was moderate for the effect of heat therapy on systolic and diastolic blood pressure and heart rate and low for the effect of heat therapy on mean arterial pressure and flow-mediated dilatation. Heat therapy is an effective therapeutic tool to reduce blood pressure and improve macrovascular function. Future research should aim to optimize heat therapy, including the mode and dose, for the prevention and management of cardiovascular disease.

Sex-Steroid Signaling in Lung Diseases and Inflammation

Sex/gender difference exists in the physiology of multiple organs. Recent epidemiological reports suggest the influence of sex-steroids in modulating a wide variety of disease conditions. Sex-based discrepancies have been reported in pulmonary physiology and various chronic inflammatory responses associated with lung diseases like asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and rare lung diseases. Notably, emerging clinical evidence suggests that several respiratory diseases affect women to a greater degree, with increased severity and prevalence than men. Although sex-specific differences in various lung diseases are evident, such differences are inherent to sex-steroids, which are major biological variables in men and women who play a central role to control these differences. The focus of this chapter is to comprehend the sex-steroid biology in inflammatory lung diseases and to understand the mechanistic role of sex-steroids signaling in regulating these diseases. Exploring the roles of sex-steroid signaling in the regulation of lung diseases and inflammation is crucial for the development of novel and effective therapy. Overall, we will illustrate the importance of differential sex-steroid signaling in lung diseases and their possible clinical implications for the development of complementary and alternative medicine to treat lung diseases.

Steroid hormones and first trimester vascular remodeling

Successful implantation and placentation require neoangiogenesis and the remodeling of the uterine spiral arteries. Progesterone and estradiol control various of the placental functions, but their role in vascular remodeling remains controversial. Therefore, this chapter aims to summarize the current knowledge regarding the role of steroid hormones in the uteroplacental vascular remodeling during the first trimester of gestation.

Estrogen Receptors and Estrogen-Induced Uterine Vasodilation in Pregnancy

Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ERα and ERβ) and the plasma-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. In this review, we summarize the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H₂S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.

Effects of resveratrol or estradiol on postexercise endothelial function in estrogen-deficient postmenopausal women

Regular exercise enhances endothelial function in older men, but not consistently in estrogen-deficient postmenopausal women. Estradiol treatment improves basal endothelial function and restores improvements in endothelial function (flow-mediated dilation, FMD) to aerobic exercise training in postmenopausal women; however, estradiol treatment is controversial. Resveratrol, an estrogen receptor ligand, enhances exercise training effects on cardiovascular function and nitric oxide (NO) release in animal models, but impairs exercise training effects in men. We conducted a randomized cross-over, double-blinded, placebo-controlled pilot study to determine whether acute (single dose) resveratrol (250-mg tablet) or estradiol (0.05 mg/day transdermal patch) treatment enhances FMD at rest and after a single bout of moderate-intensity aerobic exercise in healthy estrogen-deficient postmenopausal women (n = 15, 58.1 ± 3.2 yr). FMD was measured before and after (30, 60, and 120 min) a 40-min bout of moderate-intensity treadmill exercise (60-75% peak heart rate) under the respective conditions (separated by 1-2 wk). FMD was higher (P < 0.05) before exercise and at all post-exercise time points in the resveratrol and estradiol conditions compared to placebo. FMD was increased from baseline by 120 min postexercise in the estradiol condition (P < 0.001), but not resveratrol or PL conditions. Consistent with our previous findings, estradiol also enhances endothelial function in response to acute endurance exercise. Although resveratrol improved basal FMD, there was no apparent enhancement of FMD to acute exercise and, therefore, may not act as an estradiol mimetic.NEW & NOTEWORTHY The benefits of endurance exercise training on endothelial function are diminished in estrogen-deficient postmenopausal women, but estradiol treatment appears to restore improvements in endothelial function in this group. We show that basal endothelial function is enhanced with both acute estradiol and resveratrol treatments in estrogen-deficient postmenopausal women, but endothelial function is only enhanced following acute endurance exercise with estradiol treatment.

Effect of Marantodes pumilum Blume (Kuntze) var.alata on β-cell function and insulin signaling in ovariectomised diabetic rats

BACKGROUND

Oestrogen deficiency leads to metabolic disturbances such as insulin resistance and impairment of adipose tissue or lipid metabolism. Marantodes pumilum (Blume) Kuntze (Primulaceae) is believed to have phytoestrogenic properties and is claimed to have beneficial effects in the treatment of diabetes mellitus (DM), but the mechanism behind its phytoestrogenic effects on estrogen-deficient diabetic condition have not been fully examined.

PURPOSE

The present study investigated the effects of oral treatment with M. pumilum var. alata (MPA) extracts on the estrogen receptor, metabolic characteristics and insulin signaling pathway in pancreas and liver of ovariectomised nicotidamide streptozotocin-induced diabetes in female rats.

MATERIALS AND METHODS

Ovariectomised diabetic (OVXS) Sprague-Dawley rats were orally administered with either aqueous leaf extract and ethanol (50%) stem-root extract of MPA (50 or 100 mg/kg) respectively for 28 days. Metabolic parameters were evaluated by measuring fasting blood glucose, serum insulin, oral glucose and insulin tolerance test. Distribution and expression level of insulin, oxidative stress and inflammatory marker in the pancreatic islets and liver were evaluated by immunohistochemistry and western blot, respectively.

RESULTS

Oral treatment with aqueous leaf and ethanol (50%) stem-root extracts of MPA (100 mg/kg) significantly reversed the elevated fasting blood glucose, impaired glucose and insulin tolerance. The protein expression of insulin, glucose transporter (GLUT-2 and GLUT-4) increased in the pancreatic islets and liver. Furthermore, marked improvement in the tissue morphology following treatment with MPA was observed. Similarly, the western blots analysis denotes improved insulin signaling in the liver and decreased reactive oxygen species producing enzymes, inflammatory and pro-apoptotic molecules with MPA treatment.

CONCLUSIONS

Taken together, this work demonstrate that 100 mg/kg of aqueous leaf extract and ethanol (50%) stem-root extract of MPA improves β-cell function and insulin signaling in postmenopausal diabetes through attenuation of oxidative stress and partially mediated by oestrogen receptor stimulation.

Gold nanoparticle uptake is enhanced by estradiol in MCF-7 breast cancer cells

Purpose: In the present study, we investigated the effects of 17β-estradiol (E₂) on membrane roughness and gold nanoparticle (AuNP) uptake in MCF-7 breast cancer cells. Methods: Estrogen receptor (ER)-positive breast cancer cells (MCF-7) were exposed to bare 20 nm AuNPs in the presence and absence of 1×10^-9 M E₂ for different time intervals for up to 24 hrs. The effects of AuNP incorporation and E₂ incubation on the MCF-7 cell surface roughness were measured using atomic force microscopy (AFM). Endocytic vesicle formation was studied using confocal laser scanning microscopy (CLSM). Finally, the results were confirmed by hyperspectral optical microscopy. Results: High-resolution AFM images of the surfaces of MCF-7 membranes (up to 250 nm²) were obtained. The incubation of cells for 12 hrs with AuNP and E₂ increased the cell membrane roughness by 95% and 30% compared with the groups treated with vehicle (ethanol) or AuNPs only, respectively. This effect was blocked by an ER antagonist (7α,17β-[9-[(4,4,5,5,5-Pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol [ICI] 182,780). Higher amounts of AuNPs were localized inside MCF-7 cells around the nucleus, even after 6 hrs of E₂ incubation, compared with vehicle-treated cells. Endolysosome formation was induced by E₂, which may be associated with an increase in AuNP-uptake. Conclusions: E₂ enhances AuNP incorporation in MCF-7 cells by modulating of plasma membrane roughness and inducing lysosomal endocytosis. These findings provide new insights into combined nanotherapies and hormone therapies for breast cancer.

ESR2 gene G1730A variant is associated with triglycerides level and myocardial infarction in young men but not in women

OBJECTIVES

The aim of the study was to investigate the role of estrogen receptor type 2 gene (ESR2) variant G1730A in myocardial infarction (MI) in young age.

METHODS

Genotyping was performed with restriction fragments length polymorphism method in 158 patients (79.1% men) with MI aged <50 years (studied group) and in control groups: 150 healthy individuals aged <50 years (63.3% men) and 202 patients (64.3% men) with MI aged ≥50 years.

RESULTS

The AA genotype of ESR2 G1730A variant was significantly more frequent in men with MI aged <50 comparing to men with MI aged ≥50 (21.6% vs. 8.4%, P = 0.004) and to healthy young men (21.6% vs. 11.6%, P = 0.048). There was statistically significant difference between AA genotype and GA + GG genotypes male carriers with MI aged <50 in median triglyceride (TG) level (2.0 vs. 1.7 mmol/l respectively, p = 0.023).

CONCLUSIONS

Our findings suggest a possible role of ESR2 G1730A variant as the risk factor of MI in a young age not as an independent but a potential risk factor associated with TG level in men but not in women.

Sex differences influencing micro- and macrovascular endothelial phenotype in vitro

KEY POINTS

Endothelial dysfunction is an early hallmark of multiple disease states that also display sex differences with respect to age of onset, frequency and severity. Results of in vivo studies of basal and stimulated microvascular barrier function revealed sex differences that are difficult to ascribe to specific cells or environmental factors. The present study evaluated endothelial cells (EC) isolated from macro- and/or microvessels of reproductively mature rats under the controlled conditions of low-passage culture aiming to test the assumption that EC phenotype would be sex independent. The primary finding was that EC, regardless of where they are derived, retain a sex-bias in low-passage culture, independent of varying levels of reproductive hormones. The implications of the present study include the fallacy of expecting a universal set of mechanisms derived from study of EC from one sex and/or one vascular origin to apply uniformly to all EC under unstimulated conditions, and no less in disease.

ABSTRACT

Vascular endothelial cells (EC) are heterogeneous with respect to phenotype, reflecting at least the organ of origin, location within the vascular network and physical forces. As an independent influence on EC functions in health or aetiology, susceptibility, and progression of dysfunction in numerous disease states, sex has been largely ignored. The present study focussed on EC isolated from aorta (macrovascular) and skeletal muscle vessels (microvascular) of age-matched male and female rats under identical conditions of short-term (passage 4) culture. We tested the hypothesis that genomic sex would not influence endothelial growth, wound healing, morphology, lactate production, or messenger RNA and protein expression of key proteins (sex hormone receptors for androgen and oestrogens α and β; platelet endothelial cell adhesion molecule-1 and vascular endothelial cadherin mediating barrier function; α_v β₃ and N-cadherin influencing matrix interactions; intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 mediating EC/white cell adhesion). The hypothesis was rejected because the EC origin (macro- vs. microvessel) and sex influenced multiple phenotypic characteristics. Statistical model analysis of EC growth demonstrated an hierarchy of variable importance, recapitulated for other phenotypic characteristics, with predictions assuming EC homogeneity < sex < vessel origin < sex and vessel origin. Furthermore, patterns of EC mRNA expression by vessel origin and by sex did not predict protein expression. Overall, the present study demonstrated that accurate assessment of sex-linked EC dysfunction first requires an understanding of EC function by position in the vascular tree and by sex. The results from a single EC tissue source/species/sex cannot provide universal insight into the mechanisms regulating in vivo endothelial function in health, and no less in disease.

Role of GPER in estrogen-dependent nitric oxide formation and vasodilation

Estrogens are potent regulators of vasomotor tone, yet underlying receptor- and ligand-specific signaling pathways remain poorly characterized. The primary physiological estrogen 17β-estradiol (E2), a non-selective agonist of classical nuclear estrogen receptors (ERα and ERβ) as well as the G protein-coupled estrogen receptor (GPER), stimulates formation of the vasodilator nitric oxide (NO) in endothelial cells. Here, we studied the contribution of GPER signaling in E2-dependent activation of endothelial NO formation and subsequent vasodilation. Employing E2 and the GPER-selective agonist G-1, we investigated eNOS phosphorylation and NO formation in human endothelial cells, and endothelium-dependent vasodilation in the aortae of wild-type and Gper-deficient mice. Both E2 and G-1 induced phosphorylation of eNOS at the activation site Ser1177 to similar extents. Endothelial NO production to E2 was comparable to that of G-1, and was substantially reduced after pharmacological inhibition of GPER. Similarly, the clinically used ER-targeting drugs 4OH-tamoxifen, raloxifene, and ICI182,780 (faslodex, fulvestrant™) induced NO formation in part via GPER. We identified c-Src, EGFR, PI3K and ERK signaling pathways to be involved in GPER-dependent NO formation. In line with activation of NO formation in cells, E2 and G-1 induced equally potent vasodilation in the aorta of wild-type mice. Gper deletion completely abrogated the vasodilator response to G-1, while reducing the response to E2 by ∼50%. These findings indicate that a substantial portion of E2-induced endothelium-dependent vasodilation and NO formation is mediated by GPER. Thus, selective targeting of vascular GPER may be a suitable approach to activate the endothelial NO pathway, possibly leading to reduced vasomotor tone and inhibition of atherosclerotic vascular disease.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

Differential Expression of Estrogen Receptor Variants in Response to Inflammation Signals in Human Airway Smooth Muscle

The prevalence of asthma is higher in pre-pubescent and aging males, and in post-pubertal females, strongly indicating that sex steroids (especially estrogen) may be an important modulator in lung disease. We recently demonstrated that airway smooth muscle (ASM) expresses both alpha and beta forms of the estrogen receptor (ERα and ERβ) in males and females, and that these receptors regulate intracellular [Ca²⁺ ] and ASM contractility. Although both ERα and ERβ have multiple splice variants, it is unclear if and how the expression of these variants is modulated under conditions such as chronic inflammation/asthma. In order to test the hypothesis that the differential expression of ERα and ERβ variants contributes to the pathogenesis of asthma, we profiled the expression of various ERα and ERβ genes in asthmatic and inflamed (TNFα- or IL-13-treated) ASM. Gene expression was assessed at both the mRNA and protein levels in asthmatic ASM cells or non-asthmatic cells treated with TNFα (20 ng/ml) or IL-13 (50 ng/ml). We observed marked variation in the expression of ER isoforms in response to inflammatory stimuli, and in non-asthmatic versus asthmatic ASM. Changes in protein levels of ERα and ERβ corresponded with the observed differential mRNA patterns. Pharmacological studies implicate cytosolic (p42/44 MAPK and PI3 K) and nuclear (NFκB, STAT6, and AP-1) signaling pathways as putative mechanisms that mediate and/or regulate effects of inflammation on ER expression. We conclude that variations in ASM ER expression profiles occur with inflammation and that ER variants could contribute to estrogen signaling in airway diseases such as asthma. J. Cell. Physiol. 232: 1754-1760, 2017. © 2016 Wiley Periodicals, Inc.

Estrogen Receptor Signaling and the PI3K/Akt Pathway Are Involved in Betulinic Acid-Induced eNOS Activation

Betulinic acid (BA) is a naturally occurring pentacyclic triterpenoid with anti-inflammatory, antiviral and anti-cancer properties. Beneficial cardiovascular effects such as increased nitric oxide (NO) production through enhancement of endothelial NO synthase (eNOS) activity and upregulation of eNOS expression have been demonstrated for this compound. In the present study, immortalized human EA.hy 926 endothelial cells were incubated for up to 1 h with 1–100 µM BA and with the phosphatidylinositol-3-kinase (PI3K) inhibitors LY294002 and wortmannin, or the estrogen receptor (ER) antagonist ICI 182,780. Phosphorylation status of eNOS and total eNOS protein were analyzed by Western blotting using a serine 1177 phosphosite-specific antibody. Bioactive NO production was assessed by determination of cGMP content in rat lung fibroblasts (RFL-6) reporter cells. Short-term incubation of EA.hy 926 cells with BA resulted in eNOS phosphorylation at the serine 1177 residue in a concentration- and time-dependent manner with a half-maximal effective concentration of 0.57 µM. This was associated with an enhanced production of NO. BA-induced eNOS phosphorylation and NO production was completely blocked by pretreatment with ICI 182,780, and was attenuated by pretreatment with the PI3K inhibitors wortmannin and LY294002. These results indicate that fast non-genomic effects of ER with downstream signaling through the PI3K/Akt pathway and consecutive eNOS phosphorylation at serine 1177 are involved in BA-induced eNOS activation.

Peripheral Microvascular Vasodilatory Response to Estradiol and Genistein in Women with Insulin Resistance

OBJECTIVE

E2 enhances vasodilation in healthy women, but vascular effects of the phytoestrogen GEN are still under investigation. IR compromises microvascular function. We therefore examined the interaction of E2 , GEN, and IR on microvascular vasodilatory responsiveness.

METHODS

We hypothesized that E2 and GEN increase microvascular vasodilation in healthy women (control, n = 8, 23 ± 2 year, BMI: 25.9 ± 2.9 kg/m2) but not in women with IR (n = 7, 20 ± 1 year, BMI: 27.3 ± 3.0 kg/m2). We used the cutaneous circulation as a model of microvascular vasodilatory function. We determined CVC with laser Doppler flowmetry and beat-to-beat blood pressure during local cutaneous heating (42 °C) with E2 or GEN microdialysis perfusions. Because heat-induced vasodilation is primarily an NO-mediated response, we examined microvascular vasodilation with and without L-NMMA.

RESULTS

In C, E2 enhanced CVC (94.4 ± 2.6% vs. saline 81.6 ± 4.2% CVCmax , p < 0.05), which was reversed with L-NMMA (80.9 ± 7.8% CVCmax , p < 0.05), but GEN did not affect vasodilation. Neither E2 nor GEN altered CVC in IR, although L-NMMA attenuated CVC during GEN.

CONCLUSIONS

Our study does not support improved microvascular responsiveness during GEN exposure in healthy young women, and demonstrates that neither E2 nor GEN improves microvascular vasodilatory responsiveness in women with IR.

Pterostilbene carboxaldehyde thiosemicarbazone, a resveratrol derivative inhibits 17β-Estradiol induced cell migration and proliferation in HUVECs

Angiogenesis plays important roles in tumor growth and metastasis, thus development of a novel angiogenesis inhibitor is essential for the improvement of therapeutics against cancer. Thrombospondins-1 (TSP-1) is a potent endogenous inhibitor of angiogenesis that acts through direct effects on endothelial cell migration, proliferation, survival, and activating apoptotic pathways. TSP-1 has been shown to disrupt estrogen-induced endothelial cell proliferation and migration. Here we investigated the potential of pterostilbene carboxaldehyde thiosemicarbazone (PTERC-T), a novel resveratrol (RESV) derivative, to inhibit angiogenesis induced by female sex steroids, particularly 17β-Estradiol (E2), on Human umbilical vein endothelial cells (HUVECs) and to elucidate the involvement of TSP-1 in PTERC-T action. Our results showed that PTERC-T significantly inhibited 17β-E2-stimulated proliferation of HUVECs and induced apoptosis as determined by annexin V/propidium iodide staining and cleaved caspase-3 expression. Furthermore, PTERC-T also inhibited endothelial cell migration, and invasion in chick chorioallantoic membrane (CAM) assay. In contrast, RESV failed to inhibit 17β-E2 induced HUVECs proliferation and invasion at similar dose. PTERC-T was also found to increase TSP-1 protein expression levels in a dose-dependent manner which, however, was counteracted by co-incubation with p38MAPK or JNK inhibitors, suggesting involvement of these pathways in PTERC-T action. These results suggest that the inhibitory effect of PTERC-T on 17β-E2 induced angiogenesis is associated, at least in part, with its induction of endothelial cell apoptosis and inhibition of cell migration through targeting TSP-1. Thus, PTERC-T could be considered as a potential lead compound for developing a class of new drugs targeting angiogenesis-related diseases.

Passive leg movement-induced vasodilation in women: the impact of age

Passive leg movement (PLM), an assessment of predominantly nitric oxide-dependent vasodilation, is decreased with age and cannot be augmented by posture-induced increases in femoral perfusion pressure in older men. However, this novel method of assessing vascular function has yet to be used to evaluate alterations in nitric oxide-dependent vasodilation with age in females. PLM was performed in 10 young (20 ± 1 yr) and 10 old (73 ± 2 yr) women in both the supine and upright-seated postures, whereas central and peripheral hemodynamic measurements were acquired second by second using noninvasive techniques (finger photoplethysmography and Doppler ultrasound, respectively). The heart rate response to PLM was attenuated in the old compared with the young in both the supine (young, 10 ± 1; and old, 5 ± 1 beats/min; P < 0.05) and upright-seated posture (young, 10 ± 2; and old, 5 ± 1 beats/min; P < 0.05), leading to a blunted cardiac output response in the old in the upright-seated posture (young, 1.0 ± 0.2; and old, 0.3 ± 0.1 l/min; P < 0.05). The PLM-induced peak change in leg vascular conductance was lower in the old compared with the young in both postures (young supine, 5.7 ± 0.5; old supine, 2.6 ± 0.3; young upright, 9.2 ± 0.7; and old upright, 2.2 ± 0.4 ml·min(-1)·mmHg(-1); P < 0.05) and was significantly augmented by the upright-seated posture in the young only, revealing a vasodilatory reserve capacity in the young (3.5 ± 0.6 ml·min(-1)·mmHg(-1), P < 0.05) that was absent in the old (-0.5 ± 0.3 ml·min(-1)·mmHg(-1), P = 0.18). These data support previous literature demonstrating attenuated PLM-induced vasodilation with age and extend these findings to include the female population, thus bolstering the utility of PLM as a novel assessment of vascular function across the life span in humans.

Aurantio-obtusin relaxes systemic arteries through endothelial PI3K/AKT/eNOS-dependent signaling pathway in rats

Aurantio-obtusin is a natural effective compound isolated from Semen Cassiae, which possesses hypotensive and hypolipidemic effects. Although its hypotensive effect have been clarified, mechanisms Aurantio-obtusin relaxes systemic arteries remain unclear. This study was to investigate effects and mechanisms of Aurantio-obtusin on isolated mesenteric arteries (MAs). We examined MAs relaxation induced by Aurantio-obtusin on rat isolated MAs, expression and activity of endothelial nitric oxide synthase (eNOS) and protein kinase B (AKT), and nitric oxide (NO) production in bovine artery endothelial cells (BAECs). Findings showed Aurantio-obtusin elicited dose-dependent vasorelaxation with phenylephrine (PE) precontracted rat MA rings (diameter: 200-300 μm), which can be diminished by denudation of endothelium and inhibition of eNOS activity, while having no effect on rat isolated pulmonary artery (PA) rings. Aurantio-obtusin increased NO production by promoting phosphorylations of eNOS at Ser-1177 and Thr-495 in endothelial cells. Aurantio-obtusin also promoted phosphorylations of Akt at Ser-473. PI3K inhibitor LY290042 could diminish vasorelaxation induced by Aurantio-obtusin. Moreover Aurantio-obtusin also elicited dose-dependent vasorelaxation effect with PE precontracted MA rings (diameter: 100-150 μm). Therefore, vasorelaxation induced by Aurantio-obtusin was dependent on endothelium integrity and NO production, which mediated by endothelial PI3K/Akt/eNOS pathway. Results suggest Aurantio-obtusin may offer therapeutic effects in hypertension, as a new potential vasodilator.

Sex steroid signaling: implications for lung diseases

There is increasing recognition that sex hormones (estrogen, progesterone, and testosterone) have biological and pathophysiological actions in peripheral, non-reproductive organs, including the lung. Clinically, sex differences in the incidence, morbidity and mortality of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, lung cancer and pulmonary hypertension have been noted, although intrinsic sex differences vs. the roles of sex steroids are still not well-understood. Accordingly, it becomes important to ask the following questions: 1) Which sex steroids are involved? 2) How do they affect different components of the lung under normal circumstances? 3) How does sex steroid signaling change in or contribute to lung disease, and in this regard, are sex steroids detrimental or beneficial? As our understanding of sex steroid signaling in the lung improves, it is important to consider whether such information can be used to develop new therapeutic strategies to target lung diseases, perhaps in both sexes or in a sex-specific manner. In this review, we focus on the basics of sex steroid signaling, and the current state of knowledge regarding how they influence structure and function of specific lung components across the life span and in the context of some important lung diseases. We then summarize the potential for sex steroids as useful biomarkers and therapeutic targets in these lung diseases as a basis for future translational research in the area of gender and individualized medicine.

Upregulation of caveolin-1 contributes to aggravated high-salt diet-induced endothelial dysfunction and hypertension in type 1 diabetic rats

AIMS

Endothelial dysfunction and hypertension is more common in individuals with diabetes than in the general population. This study was aimed to investigate the underlying mechanisms responsible for endothelial dysfunction of type 1 diabetic rats fed with high-salt diet.

MAIN METHODS

Type 1 diabetes (DM) was induced by intraperitoneal injection of streptozotocin (70 mg·kg(-1)). Normal or diabetic rats were randomly fed high-salt food (HS, 8% NaCl) or standard food (CON) for 6 weeks.

KEY FINDINGS

Both HS (143±10 mmHg) and DM+HS (169±11 mmHg) groups displayed significantly higher systolic blood pressure than those in the CON group (112±12 mmHg, P<0.01). DM+HS rats exhibited more pronounced impairment of vasorelaxation to acetylcholine and insulin compared with either DM or HS. Akt/endothelial nitric oxide synthase (eNOS) phosphorylation levels and nitric oxide (NO) concentration in DM+HS were significantly lower than in DM. The levels of caveolin-1 (cav-1) in DM+HS were significantly higher than that in DM and HS. Co-immunoprecipitation results showed increased interaction between cav-1 and eNOS in the DM+HS group. In the presence of cav-1 small interfering RNA (siRNA), eNOS phosphorylations in human umbilical vein endothelial cells (HUVEC) were significantly increased compared with control siRNA. Cav-1 was slightly but not significantly lower in HUVEC cultured with high glucose and high-salt buffer solution and pretreated with wortmannin or l-nitro-arginine methyl ester.

SIGNIFICANCE

Impaired endothelial Akt activation and increased cav-1 expression and resultant decreased eNOS activation contributes to aggravated high-salt diet-induced endothelial dysfunction and hypertension in DM rats.

Vascular Aging across the Menopause Transition in Healthy Women

Vascular aging, featuring endothelial dysfunction and large artery stiffening, is a major risk factor for developing cardiovascular disease (CVD). In women, vascular aging appears to be accelerated during the menopause transition, particularly around the late perimenopausal period, presumably related to declines in ovarian function and estrogen levels. The mechanisms underlying endothelial dysfunction and large artery stiffening with the menopause transition are not completely understood. Oxidative stress and the proinflammatory cytokine tumor necrosis factor-α contribute to endothelial dysfunction and large artery stiffening in estrogen-deficient postmenopausal women. Habitual endurance exercise attenuates the age-related increase in large artery stiffness in estrogen-deficient postmenopausal women and can reverse arterial stiffening to premenopausal levels in estrogen-replete postmenopausal women. In contrast, estrogen status appears to play a key permissive role in the adaptive response of the endothelium to habitual endurance exercise in that endothelial improvements are absent in estrogen-deficient women but present in estrogen-replete women. We review here the current state of knowledge on the biological defects underlying vascular aging across the menopause transition, with particular focus on potential mechanisms, the role of habitual exercise in preserving vascular health, and key areas for future research.

Dehydroabietic acid isolated from Commiphora opobalsamum causes endothelium-dependent relaxation of pulmonary artery via PI3K/Akt-eNOS signaling pathway

Commiphora opobalsamum is a Traditional Chinese Medicine used to treat traumatic injury, mainly by relaxing blood vessels. In this study, two diterpenes, dehydroabietic acid (DA) and sandaracopimaric acid (SA) were obtained from it by a bioassay-guided approach using isolated rat pulmonary artery rings. The structures of the two compounds were elucidated by spectroscopic methods (IR, ¹H- and ¹³C-NMR, HR-ESI-MS). Both DA and SA reduced the contraction of phenylephrine-induced pulmonary arteries in a concentration-dependent manner, and endothelium contributed greatly to the vasodilatory effect of DA. This effect of DA was attenuated by N^G-Nitro-L-arginine methyl ester (L-NAME, an eNOS inhibitor). Meanwhile, DA increased nitric oxide (NO) production, along with the increase of phosphorylation level of eNOS and Akt in endothelial cells. LY294002 (a PI3K inhibitor) could reverse this effect, which suggested the endothelial PI3K/Akt pathway involved in the mechanism underlying DA-induced relaxation of pulmonary artery. This work provided evidence of vasorelaxant substances in Commiphora opobalsamum and validated that PI3K/Akt-eNOS pathway was associated with DA-induced pulmonary artery vasodilation.

Regulation of endothelial nitric oxide synthase and high-density lipoprotein quality by estradiol in cardiovascular pathology

Estrogens have been recognized, in the last 3 decades, as important hormones in direct and indirect modulation of vascular health. In addition to their direct benefit on cardiovascular health, the presence of esterified estrogen in the lipid core of high-density lipoprotein (HDL) particles indirectly contributes to atheroprotection by significantly improving HDL quality and functionality. Estrogens modulate their physiological activity via genomic and nongenomic mechanisms. Genomic mechanisms are thought to be mediated directly by interaction of the hormone receptor complex with the hormone response elements that regulate gene expression. Nongenomic mechanisms are thought to occur via interaction of the estrogen with membrane-bound receptors, which rapidly activate intracellular signaling without binding of the hormone receptor complex to its hormone response elements. Estradiol in particular mediates early and late endothelial nitric oxide synthase (eNOS) activation via interaction with estrogen receptors through both nongenomic and genomic mechanisms. In the vascular system, the primary endogenous source of nitric oxide (NO) generation is eNOS. Nitric oxide primarily influences blood vessel relaxation, the heart rate, and myocyte contractility. The abnormalities in expression and/or functions of eNOS lead to the development of cardiovascular diseases, both in animals and in humans. Although considerable research efforts have been dedicated to understanding the mechanisms of action of estradiol in regulating cardiac eNOS, more research is needed to fully understand the details of such mechanisms. This review focuses on recent findings from animal and human studies on the regulation of eNOS and HDL quality by estradiol in cardiovascular pathology.

Alike but not the same: anatomic heterogeneity of estrogen receptor-mediated vasodilation

In view of recent findings on the anatomic heterogeneity of rapid vasodilation via estrogen receptor (ER)-dependent mechanisms, it is obvious that with regard to human physiology and disease much of it is still unknown, and research in this area is urgently needed. This is also important because chronic drug therapy with estrogens in women systemically affects the circulation and may affect certain arterial beds but not others. It is conceivable that the presence of any vascular disease (as was the case for coronary and carotid atherosclerosis in many of the patients in the large randomized controlled trials HERS and WHI) is likely to affect vascular responses to estrogens as well, and that any beneficial effects may be attenuated or even completely lost. Further work is required to decipher the mechanisms of vasodilation brought about by estrogens in humans and experimental animals, whether anatomic heterogeneity exists with regard to vascular beds and individual estrogen receptors, and how vascular disease (atherosclerosis in particular) affects responsiveness. Also, pharmacologcial tools for newly identified ERs are now available. The hypothesis that disease may modify or even abrogate estrogen-dependent or ER-selective vasodilation should also be tested. Finally, given that certain clinically approved drugs such as SERM or SERDs (thought only to block or downregulate nuclear ERs) actually cause vasodilation through GPER and have been shown in recent clinical studies to provide cardiovascular protection in postmenopausal women, we may have to rethink our current understanding, concepts, and strategies of how to interfere with the increased risk of vascular disease in women with estrogen deficiency or after menopause.

Essential role of estrogen for improvements in vascular endothelial function with endurance exercise in postmenopausal women

OBJECTIVE

In contrast to age-matched men, endurance exercise training is not consistently associated with enhanced endothelial function in estrogen-deficient postmenopausal women. We determined whether endurance exercise training improves endothelial function in postmenopausal women treated with estrogen. In a substudy, we determined if oxidative stress is mechanistically linked to endothelial function adaptations to endurance exercise training.

PARTICIPANTS AND DESIGN

Brachial artery flow-mediated dilation (FMD) was measured in 36 sedentary, estrogen-deficient postmenopausal women (45-65 y) at study entry (baseline), after 12 weeks of either placebo, oral (1 mg/d) estradiol, or transdermal estradiol (0.05 mg/d) (randomized), and after an additional 12 weeks of continued estradiol or placebo treatment with concurrent endurance exercise training. In subgroups of women, FMD also was measured during the infusion of ascorbic acid at baseline and following estradiol/placebo plus endurance exercise training, and in seven habitually endurance-trained estrogen-deficient controls.

RESULTS

FMD increased in the estrogen-treated groups (both P < .01) after 12 weeks and remained unchanged in placebo. FMD further increased following 12 weeks of endurance exercise training in estrogen-treated (both P < .025), but not placebo-treated women (P = .55). In the substudy, baseline FMD was similar between sedentary and endurance-trained controls. Ascorbic acid increased FMD at baseline in sedentary women and endurance-trained controls, and following endurance exercise training in placebo-treated, but not in estrogen-treated women.

CONCLUSIONS

Estrogen status appears to play an important modulatory role in improvements in endothelial function with endurance exercise training in postmenopausal women. The restored endurance exercise training adaptation in estrogen-treated postmenopausal women may be related to mitigation of oxidative stress.

Silymarin improves vascular function of aged ovariectomized rats

Both aging and estrogen depletion lead to endothelial dysfunction, which is the main reason of many cardiovascular diseases. Previous reports have shown that cell protective effect of silymarin (SM) depends on its antioxidant and phytoestrogenic properties. We investigated the effect of SM on vascular stiffness of aged menopausal rats and the involvement of estrogenic activity in this effect. Isolated rat aortas were obtained from 22-month-old rats, after 18 months of ovariectomy (OVX) follow-up. Each ring was incubated in tissue bath either with SM (50 mg/L) and 17β-estradiol (10 μM, E2) or in the presence of SM/fulvestrant (50 mg/L, 10 μM). Endothelium-intact rings were precontracted with phenylephrine (0.001-30 μM) or high potassium (40 mM); endothelium-dependent/independent relaxant responses were obtained using acetylcholine (0.001-30 μM) and sodium nitroprusside (0.0001-3 μM), respectively. While phenylephrine sensitivity was significantly increased in OVX rats, relaxations were significantly less in aged OVX rats compared with young rats. In spite of the presence of estrogen antagonist, immediate SM treatment restored the endothelial function and vascular tone better than estrogen replacement. Additionally, as a complementary and alternative medicine, it does not cause estrogenic side effects when taken acutely.

Increased estrogen receptor alpha in experimental aortic aneurysms in females compared with males

BACKGROUND

Estrogen receptor alpha (ERα) has been identified in the vessel wall, offering vasoprotective effects when upregulated. Estrogens are known to mediate the inflammatory milieu, and inflammation has long been associated with abdominal aortic aneurysm (AAA) formation. Therefore, it is theorized that increased estrogen receptor in females contributes to their relative resistance to AAAs. The objective of this study was to determine gender differences in ERα levels during experimental AAA formation.

METHODS

Infrarenal aortas of male and female C57 mice (n = 18 and n = 16, respectively) were infused with 0.4% elastase. Diameters were measured at days 0 and 14. Aortic messenger RNA expression of ERα was determined on day 3 by reverse transcription-polymerase chain reaction, whereas ERα protein levels were measured via Western blot. Immunohistochemistry using rabbit antibody for ERα was performed on day 14 samples and quantified. Zymography was done for matrix metalloproteinases (MMP)2 and 9 activity levels. Samples of human AAAs were collected and Western blot performed. Data were compared for significance using a student t-test.

RESULTS

Infrarenal aortic diameter increased in elastase-perfused males (ME) by 80% at 14 days after perfusion, whereas females (FE) increased by only 35% (P = 0.0012). FE had ×10 greater ERα messenger RNA expression compared with ME at day 3 (P = 0.003). Similarly, ERα protein levels were 100% higher in FE compared with those in ME on day 14 (P = 0.035). ERα protein levels were 80% higher in female human patients with AAA than those in their male counterparts (P = 0.029). ERα visualized via immunohistochemistry was 1.5 fold higher in FE than ME (P = 0.029). MMP2 and 9 activity levels were decreased in female compared with male aortas.

CONCLUSIONS

This study demonstrates an increase in aortic wall ERα in females compared with males that correlates inversely with MMP activity and AAA formation. These findings, coupled with observations that exogenous estrogen inhibits AAA formation in males, further suggest that estrogen supplementation may be important to prevent AAA formation and growth.

Dexamethasone induces caveolin-1 in vascular endothelial cells: implications for attenuated responses to VEGF

Steroids exert direct actions on cardiovascular cells, although underlying molecular mechanisms remain incompletely understood. We examined if steroids modulate abundance of caveolin-1, a regulatory protein of cell-surface receptor pathways that regulates the magnitudes of endothelial response to vascular endothelial growth factor (VEGF). Dexamethasone, a synthetic glucocorticoid, induces caveolin-1 at both levels of protein and mRNA in a time- and dose-dependent manner in pharmacologically relevant concentrations in cultured bovine aortic endothelial cells. Aldosterone, a mineralocorticoid, but not the sex steroids 17β-estradiol, testosterone, or progesterone, elicits similar caveolin-1 induction. Caveolin-1 induction by dexamethasone and that by aldosterone were abrogated by RU-486, an inhibitor of glucocorticoid receptor, and by spironolactone, a mineralocorticoid receptor inhibitor, respectively. Dexamethasone attenuates VEGF-induced responses at the levels of protein kinases Akt and ERK1/2, small-G protein Rac1, nitric oxide production, and migration. When induction of caveolin-1 by dexamethasone is attenuated either by genetically by transient transfection with small interfering RNA or pharmacologically by RU-486, kinase responses to VEGF are rescued. Dexamethasone also increases expression of caveolin-1 protein in cultured human umbilical vein endothelial cells, associated with attenuated tube formation responses of these cells when cocultured with normal fibroblasts. Immunohistochemical analyses revealed that intraperitoneal injection of dexamethasone induces endothelial caveolin-1 protein in thoracic aorta and in lung artery in healthy male rats. Thus steroids functionally attenuate endothelial responses to VEGF via caveolin-1 induction at the levels of signal transduction, migration, and tube formation, identifying a novel point of cross talk between nuclear and cell-surface receptor signaling pathways.

Osthole relaxes pulmonary arteries through endothelial phosphatidylinositol 3-kinase/Akt-eNOS-NO signaling pathway in rats

Pulmonary arterial hypertension is a life-threatening disease lacking effective therapies. Osthole is a natural coumarin compound isolated from Angelica pubescens Maxim., which possesses hypotensive effect. Although its effects on isolated thoracic aorta (systemic circulating system) are clarified, it remains unclear whether Osthole relaxes isolated pulmonary arteries (PAs) (pulmonary circulating system). The aim of this study was to investigate the effects of Osthole on isolated PAs and the underlying mechanisms. We examined PA relaxation induced by Osthole in isolated human and rat PA rings with force-electricity transducers, the expression and activity of endothelial nitric oxide synthase (eNOS) and protein kinase B (Akt) with western blot, and nitric oxide (NO) production using DAF-FM DA fluorescent indicator. The results showed that Osthole elicited a dose-dependent vasorelaxation activity with phenylephrine-precontracted human and rat PA rings, which can be diminished by endothelium denudation and inhibition of eNOS, while having no effect on rat mesenteric arteries. Osthole increased NO release as well as activation of Akt and eNOS, indicated with increased phosphorylations of Akt at Ser-473 and eNOS at Ser-1177 in endothelial cells. PI3K inhibitor LY294002 also blocked Osthole induced vasodilation. In summary, dilative effect of Osthole was dependent on endothelial integrity and NO production, and was mediated by endothelial PI3K/Akt-eNOS-NO pathway. These may provide a new pulmonary vasodilator for the therapy of pulmonary arterial hypertension.

17ß-estradiol antagonizes the down-regulation of ERα/NOS-3 signaling in vascular endothelial dysfunction of female diabetic rats

Previous studies indicated that estrogen could improve endothelial function. However, whether estrogen protects vascular complications of diabetes has yet to be clarified. The study was designed to investigate the action of 17ß-estradiol on vascular endothelium in streptozotocin (STZ)-induced diabetic rats. Ovariectomized female Sprague-Dawley rats were administered with streptozotocin to produce an ovariectomized-diabetic (OVS) model which manifested as dysfunction of aortic dilation and contraction ability. Meanwhile, OVS animals with 17ß-estradiol supplementation significantly improved aortic function. Accordingly, nitric oxide synthase-3 (NOS-3), Akt, PI3K and estrogen receptor α (ERα) protein expression in aorta declined in the OVS group. Such effects were partially restored by estrogen replacement. The presence of 17ß-estradiol similarly counteracted the reduction of cyclic guanosine monophosphate (cGMP), the enhanced expression of inducible NOS (NOS-2) and NO metabolites (nitrite and nitrate), as well as the increase of matrix metalloproteinase-9/tissue inhibitor of metalloproteinase-1 (MMP-9/TIMP-1), which is an index of arterial compliance. 17ß-estradiol could also decrease ROS production in vascular endothelium. In EA hy 926 cells we found that ER antagonist, wortmannin and Akt inhibitor could block improvement effects of 17ß-estradiol. These results strongly suggest that functional impairment of the ERα/NOS-3 signaling network in OVS animals was partially restored by 17ß-estradiol administration, which provides experimental support for estrogen recruitment to improve vascular outcomes in female diabetes after endogenous hormone depletion.

Vascular effects of estrogenic menopausal hormone therapy

Cardiovascular disease (CVD) is more common in men and postmenopausal women (Post-MW) than premenopausal women (Pre-MW). Despite recent advances in preventive measures, the incidence of CVD in women has shown a rise that matched the increase in the Post-MW population. The increased incidence of CVD in Post-MW has been related to the decline in estrogen levels, and hence suggested vascular benefits of endogenous estrogen. Experimental studies have identified estrogen receptor ERα, ERβ and a novel estrogen binding membrane protein GPR30 (GPER) in blood vessels of humans and experimental animals. The interaction of estrogen with vascular ERs mediates both genomic and non-genomic effects. Estrogen promotes endothelium-dependent relaxation by increasing nitric oxide, prostacyclin, and hyperpolarizing factor. Estrogen also inhibits the mechanisms of vascular smooth muscle (VSM) contraction including [Ca2+]i, protein kinase C and Rho-kinase. Additional effects of estrogen on the vascular cytoskeleton, extracellular matrix, lipid profile and the vascular inflammatory response have been reported. In addition to the experimental evidence in animal models and vascular cells, initial observational studies in women using menopausal hormonal therapy (MHT) have suggested that estrogen may protect against CVD. However, randomized clinical trials (RCTs) such as the Heart and Estrogen/ progestin Replacement Study (HERS) and the Women's Health Initiative (WHI), which examined the effects of conjugated equine estrogens (CEE) in older women with established CVD (HERS) or without overt CVD (WHI), failed to demonstrate protective vascular effects of estrogen treatment. Despite the initial set-back from the results of MHT RCTs, growing evidence now supports the 'timing hypothesis', which suggests that MHT could increase the risk of CVD if started late after menopause, but may produce beneficial cardiovascular effects in younger women during the perimenopausal period. The choice of an appropriate MHT dose, route of administration, and estrogen/progestin combination could maximize the vascular benefits of MHT and minimize other adverse effects, especially if given within a reasonably short time after menopause to women that seek MHT for the relief of menopausal symptoms.

Position paper: The membrane estrogen receptor GPER--Clues and questions

Rapid signaling of estrogen involves membrane estrogen receptors (ERs), including membrane subpopulations of ERα and ERβ. In the mid-1990s, several laboratories independently reported the cloning of an orphan G protein-coupled receptor from vascular and cancer cells that was named GPR30. Research published between 2000 and 2005 provided evidence that GPR30 binds and signals via estrogen indicating that this intracellular receptor is involved in rapid, non-genomic estrogen signaling. The receptor has since been designated as the G protein-coupled estrogen receptor (GPER) by the International Union of Pharmacology. The availability of genetic tools such as different lines of GPER knock-out mice, as well as GPER-selective agonists and antagonists has advanced our understanding, but also added some confusion about the new function of this receptor. GPER not only binds estrogens but also other substances, including SERMs, SERDs, and environmental ER activators (endocrine disruptors; xenoestrogens) and also interacts with other proteins. This article represents a summary of a lecture given at the 7(th) International Meeting on Rapid Responses to Steroid Hormones in September 2011 in Axos, Crete, and reviews the current knowledge and questions about GPER-dependent signaling and function. Controversies that have complicated our understanding of GPER, including interactions with human ERα-36 and aldosterone as a potential ligand, will also be discussed.

Chronic estradiol treatment reduces platelet responses and protects mice from thromboembolism through the hematopoietic estrogen receptor α

Although estrogens are known to have a deleterious effect on the venous thrombosis risk and a preventive action on the development of arterial atheroma, their effect on platelet function in vivo remains unclear. Here, we demonstrate that a chronic high physiologic level of estradiol (E2) in mice leads to a marked decrease in platelet responsiveness ex vivo and in vivo compared with ovariectomized controls. E2 treatment led to increased bleeding time and a resistance to thromboembolism. Hematopoietic chimera mice harboring a selective deletion of estrogen receptors (ERs) α or β were used to demonstrate that the effects of E2 were exclusively because of hematopoietic ERα. Within ERα the activation function-1 domain was not required for resistance to thromboembolism, as was previously shown for atheroprotection. This domain is mandatory for E2-mediated reproductive function and suggests that this role is controlled independently. Differential proteomics indicated that E2 treatment modulated the expression of platelet proteins including β1 tubulin and a few other proteins that may impact platelet production and activation. Overall, these data demonstrate a previously unrecognized role for E2 in regulating the platelet proteome and platelet function, and point to new potential antithrombotic and vasculoprotective therapeutic strategies.

Functions and physiological roles of two types of estrogen receptors, ERα and ERβ, identified by estrogen receptor knockout mouse

Estrogens, a class of steroid hormones, regulate the growth, development, and physiology of the human reproductive system. Estrogens also involve in the neuroendocrine, skeletal, adipogenesis, and cardiovascular systems. Estrogen signaling pathways are selectively stimulated or inhibited depending on a balance between the activities of estrogen receptor (ER) α or ERβ in target organs. ERs belong to the steroid hormone superfamily of nuclear receptors, which act as transcription factors after binding to estrogen. The gene expression regulation by ERs is to modulate biological activities, such as reproductive organ development, bone modeling, cardiovascular system functioning, metabolism, and behavior in both females and males. Understanding of the general physiological roles of ERs has been gained when estrogen levels were ablated by ovariectomy and then replenished by treatment with exogenous estrogen. This technique is not sufficient to fully determine the exact function of estrogen signaling in general processes in living tissues. However, a transgenic mouse model has been useful to study gene-specific functions. ERα and ERβ have different biological functions, and knockout and transgenic animal models have distinct phenotypes. Analysis of ERα and ERβ function using knockout mouse models has identified the roles of estrogen signaling in general physiologic processes. Although transgenic mouse models do not always produce consistent results, they are the useful for studying the functions of these genes under specific pathological conditions.

Current therapeutic strategies to mitigate the eNOS dysfunction in ischaemic stroke

Impairment of endothelial nitric oxide synthase (eNOS) activity is implicated in the pathogenesis of endothelial dysfunction in many diseases including ischaemic stroke. The modulation of eNOS during and/or following ischaemic injury often represents a futile compensatory mechanism due to a significant decrease in nitric oxide (NO) bioavailability coupled with dramatic increases in the levels of reactive oxygen species that further neutralise NO. However, applications of a number of therapeutic agents alone or in combination have been shown to augment eNOS activity under a variety of pathological conditions by potentiating the expression and/or activity of Akt/eNOS/NO pathway components. The list of these therapeutic agents include NO donors, statins, angiotensin-converting enzyme inhibitors, calcium channel blockers, phosphodiesterase-3 inhibitors, aspirin, dipyridamole and ellagic acid. While most of these compounds exhibit anti-platelet properties and are able to up-regulate eNOS expression in endothelial cells and platelets, others suppress eNOS uncoupling and tetrahydrobiopterin (an eNOS stabiliser) oxidation. As the number of therapeutic molecules that modulate the expression and activity of eNOS increases, further detailed research is required to reveal their mode of action in preventing and/or reversing the endothelial dysfunction.

Do the interactions between glucocorticoids and sex hormones regulate the development of the metabolic syndrome?

The metabolic syndrome is basically a maturity-onset disease. Typically, its manifestations begin to flourish years after the initial dietary or environmental aggression began. Since most hormonal, metabolic, or defense responses are practically immediate, the procrastinated response do not seem justified. Only in childhood, the damages of the metabolic syndrome appear with minimal delay. Sex affects the incidence of the metabolic syndrome, but this is more an effect of timing than absolute gender differences, females holding better than males up to menopause, when the differences between sexes tend to disappear. The metabolic syndrome is related to an immune response, countered by a permanent increase in glucocorticoids, which keep the immune system at bay but also induce insulin resistance, alter the lipid metabolism, favor fat deposition, mobilize protein, and decrease androgen synthesis. Androgens limit the operation of glucocorticoids, which is also partly blocked by estrogens, since they decrease inflammation (which enhances glucocorticoid release). These facts suggest that the appearance of the metabolic syndrome symptoms depends on the strength (i.e., levels) of androgens and estrogens. The predominance of glucocorticoids and the full manifestation of the syndrome in men are favored by decreased androgen activity. Low androgens can be found in infancy, maturity, advanced age, or because of their inhibition by glucocorticoids (inflammation, stress, medical treatment). Estrogens decrease inflammation and reduce the glucocorticoid response. Low estrogen (infancy, menopause) again allow the predominance of glucocorticoids and the manifestation of the metabolic syndrome. It is postulated that the equilibrium between sex hormones and glucocorticoids may be a critical element in the timing of the manifestation of metabolic syndrome-related pathologies.

Rapid steroid hormone actions initiated at the cell surface and the receptors that mediate them with an emphasis on recent progress in fish models

In addition to the classic genomic mechanism of steroid action mediated by activation of intracellular nuclear receptors, there is now extensive evidence that steroids also activate receptors on the cell surface to initiate rapid intracellular signaling and biological responses that are often nongenomic. Recent progress in our understanding of rapid, cell surface-initiated actions of estrogens, progestins, androgens and corticosteroids and the identities of the membrane receptors that act as their intermediaries is briefly reviewed with a special emphasis on studies in teleost fish. Two recently discovered novel proteins with seven-transmembrane domains, G protein-coupled receptor 30 (GPR30), and membrane progestin receptors (mPRs) have the ligand binding and signaling characteristics of estrogen and progestin membrane receptors, respectively, but their functional significance is disputed by some researchers. GPR30 is expressed on the cell surface of fish oocytes and mediates estrogen inhibition of oocyte maturation. mPRα is also expressed on the oocyte cell surface and is the intermediary in progestin induction of oocyte maturation in fish. Recent results suggest there is cross-talk between these two hormonal pathways and that there is reciprocal down-regulation of GPR30 and mPRα expression by estrogens and progestins at different phases of oocyte development to regulate the onset of oocyte maturation. There is also evidence in fish that mPRs are involved in progestin induction of sperm hypermotility and anti-apoptotic actions in ovarian follicle cells. Nonclassical androgen and corticosteroid actions have also been described in fish models but the membrane receptors mediating these actions have not been identified.