Endothelial dysfunction in a man with disruptive mutation in oestrogen-receptor gene

Estrogen Receptor and Vascular Aging

Cardiovascular diseases remain an age-related pathology in both men and women. These pathologies are 3-fold more frequent in men than in women before menopause, although this difference progressively decreases after menopause. The vasculoprotective role of estrogens are well established before menopause, but the consequences of their abrupt decline on the cardiovascular risk at menopause remain debated. In this review, we will attempt to summarize the main clinical and experimental studies reporting the protective effects of estrogens against cardiovascular diseases, with a particular focus on atherosclerosis, and the impact of aging and estrogen deprivation on their endothelial actions. The arterial actions of estrogens, but also part of that of androgens through their aromatization into estrogens, are mediated by the estrogen receptor (ER)α and ERβ. ERs belong to the nuclear receptor family and act by transcriptional regulation in the nucleus, but also exert non-genomic/extranuclear actions. Beside the decline of estrogens at menopause, abnormalities in the expression and/or function of ERs in the tissues, and particularly in arteries, could contribute to the failure of classic estrogens to protect arteries during aging. Finally, we will discuss how recent insights in the mechanisms of action of ERα could contribute to optimize the hormonal treatment of the menopause.

Androgenic steroids dysregulation and the risk of coronary artery disease

INTRODUCTION

Endogenous testosterone deficiency or excess anabolic-androgenic steroids (AAS) have been linked to alter the physiology of different organs in the body, more specifically, the vasculature of coronary arteries. Despite the health-related concerns of using synthetic testosterone derivatives, such as AAS, there has been a tremendous increase in the use of AAS among athletes and bodybuilders.

AREAS COVERED

We have highlighted the three main mechanisms that AAS increase the risk of coronary artery disease (CAD): altering the homeostasis of lipid metabolism which results in dyslipidemia and subsequently atherosclerosis, disturbing the function of platelet which results in platelet aggregation and subsequent thrombosis, and increasing the risk of coronary vasospasm by affecting the physiological function of vascular bed.

EXPERT OPINION

Despite the restriction of AAS in specific clinical conditions such as testosterone deficiency and cancer therapy, many amateurs' athletes misuse the AAS. Although there has been a strong association between the AAS misuse and risk of developing CAD, the more valued approach would be a randomized clinical double-blind trial. The suggested primary endpoint would be an occurrence of adverse cardiovascular events, such as myocardial infarction, cerebrovascular accidents, and death. Increasing awareness of the risk of missing AAS among high-risk groups is imperative.

Early Inactivation of Membrane Estrogen Receptor Alpha (ERα) Recapitulates the Endothelial Dysfunction of Aged Mouse Resistance Arteries

Flow-mediated dilation (FMD) of resistance arteries is essential for tissue perfusion but it decreases with ageing. As estrogen receptor alpha (Erα encoded by Esr1), and more precisely membrane ERα, plays an important role in FMD in young mice in a ligand-independent fashion, we evaluated its influence on this arteriolar function in ageing. We first confirmed that in young (6-month-old) mice, FMD of mesenteric resistance arteries was reduced in Esr1−/− (lacking ERα) and C451A-ERα (lacking membrane ERα). In old (24-month-old) mice, FMD was reduced in WT mice compared to young mice, whereas it was not further decreased in Esr1−/− and C451A-ERα mice. Markers of oxidative stress were similarly increased in old WT and C451A-ERα mice. Reduction in oxidative stress with superoxide dismutase plus catalase or Mito-tempo, which reduces mitochondrial superoxide restored FMD to a normal control level in young C451A-ERα mice as well as in old WT mice and old C451A-ERα mice. Estradiol-mediated dilation was absent in old WT mice. We conclude that oxidative stress is a key event in the decline of FMD, and that an early defect in membrane ERα recapitulates phenotypically and functionally ageing of these resistance arteries. The loss of this function could take part in vascular ageing.

Obesity, Body Composition, and Sex Hormones: Implications for Cardiovascular Risk

Cardiovascular disease (CVD) continues to be the leading cause of death in adults, highlighting the need to develop novel strategies to mitigate cardiovascular risk. The advancing obesity epidemic is now threatening the gains in CVD risk reduction brought about by contemporary pharmaceutical and surgical interventions. There are sex differences in the development and outcomes of CVD; premenopausal women have significantly lower CVD risk than men of the same age, but women lose this advantage as they transition to menopause, an observation suggesting potential role of sex hormones in determining CVD risk. Clear differences in obesity and regional fat distribution among men and women also exist. While men have relatively high fat in the abdominal area, women tend to distribute a larger proportion of their fat in the lower body. Considering that regional body fat distribution is an important CVD risk factor, differences in how men and women store their body fat may partly contribute to sex-based alterations in CVD risk as well. This article presents findings related to the role of obesity and sex hormones in determining CVD risk. Evidence for the role of sex hormones in determining body composition in men and women is also presented. Lastly, the clinical potential for using sex hormones to alter body composition and reduce CVD risk is outlined. © 2022 American Physiological Society. Compr Physiol 12:1-45, 2022.

The Role of Estrogens and Vitamin D in Cardiomyocyte Protection: A Female Perspective

Women experience a dramatical raise in cardiovascular events after menopause. The decline in estrogens is pointed to as the major responsible trigger for the increased risk of cardiovascular disease (CVD). Indeed, the menopausal transition associates with heart macro-remodeling, which results from a fine-tuned cell micro-remodeling. The remodeling of cardiomyocytes is a biomolecular response to several physiologic and pathologic stimuli, allowing healthy adaptation in normal conditions or maladaptation in an unfavorable environment, ending in organ architecture disarray. Estrogens largely impinge on cardiomyocyte remodeling, but they cannot fully explain the sex-dimorphism of CVD risk. Albeit cell remodeling and adaptation are under multifactorial regulation, vitamin D emerges to exert significant protective effects, controlling some intracellular paths, often shared with estrogen signaling. In post-menopause, the unfavorable association of hypoestrogenism-D hypovitaminosis may converge towards maladaptive remodeling and contribute to increased CVD risk. The aim of this review is to overview the role of estrogens and vitamin D in female cardiac health, speculating on their potential synergistic effect in cardiomyocyte remodeling, an issue that is not yet fully explored. Further learning the crosstalk between these two steroids in the biomolecular orchestration of cardiac cell fate during adaptation may help the translational approach to future cardioprotective strategies for women health.

Membrane estrogen receptor alpha (ERα) participates in flow-mediated dilation in a ligand-independent manner

Estrogen receptor alpha (ERα) activation by estrogens prevents atheroma through its nuclear action, whereas plasma membrane-located ERα accelerates endothelial healing. The genetic deficiency of ERα was associated with a reduction in flow-mediated dilation (FMD) in one man. Here, we evaluated ex vivo the role of ERα on FMD of resistance arteries. FMD, but not agonist (acetylcholine, insulin)-mediated dilation, was reduced in male and female mice lacking ERα (Esr1-/- mice) compared to wild-type mice and was not dependent on the presence of estrogens. In C451A-ERα mice lacking membrane ERα, not in mice lacking AF2-dependent nuclear ERα actions, FMD was reduced, and restored by antioxidant treatments. Compared to wild-type mice, isolated perfused kidneys of C451A-ERα mice revealed a decreased flow-mediated nitrate production and an increased H₂O₂ production. Thus, endothelial membrane ERα promotes NO bioavailability through inhibition of oxidative stress and thereby participates in FMD in a ligand-independent manner.

Sex differences in acute cardiovascular care: a review and needs assessment

Despite significant progress in the care of patients suffering from cardiovascular disease, there remains a persistent sex disparity in the diagnosis, management, and outcomes of these patients. These sex disparities are seen across the spectrum of cardiovascular care, but, are especially pronounced in acute cardiovascular care. The spectrum of acute cardiovascular care encompasses critically ill or tenuous patients with cardiovascular conditions that require urgent or emergent decision-making and interventions. In this narrative review, the disparities in the clinical course, management, and outcomes of six commonly encountered acute cardiovascular conditions, some with a known sex-predilection will be discussed within the basis of underlying sex differences in physiology, anatomy, and pharmacology with the goal of identifying areas where improvement in clinical approaches are needed.

Association Between 17β-Estradiol Receptors and Nitric Oxide Signaling Augments High-Altitude Adaptation of Ladakhi Highlanders

Pooja, Vandana Sharma, Manish Sharma, Rajeev Varshney, Bhuvnesh Kumar, and Niroj Kumar Sethy. Association between 17β-estradiol receptors and nitric oxide signaling augments high-altitude adaptation of Ladakhi highlanders. High Alt Med Biol. 22: 174-183, 2021. Background: Genomic studies have identified positive natural selection of plasma membrane estrogen receptor signaling pathway for Himalayan highlanders. We sought to investigate significance of this pathway for high-altitude adaptation by studying Ladakhi highlanders. Materials and Methods: We recruited 25 healthy Ladakhi males (age range: 19-37, height: 164 ± 6 cm, and weight 59 ± 4 kg) at Leh (altitude 3,520 m) and age matched sea level volunteers at Delhi (altitude 215 m), India. We evaluated circulatory levels of 17β-estradiol (E2) and testosterone (T) and levels of E2 biosynthesis pathway proteins. In addition, we analyzed mRNA levels of E2 pathway genes and their association with nitric oxide (NO) availability. Results: We observed higher circulatory E2 and lower testosterone (T) in Ladakhi highlanders compared to lowlanders. Studying E2 pathway genes, we identified higher transcript levels of E2 receptors ESR1 (2.02-fold) and ESR2 (3.87-fold) in Ladakhi highlanders. Higher NOS3 mRNA, plasma level of endothelial NO synthase (eNOS), p-eNOS ^Ser1177, NOx (nitrate and nitrite), and cGMP were observed for Ladakhi highlanders. In addition, we observed a positive correlation between E2 with plasma NOx (r = 0.52, p = 0.002) and cGMP (r = 0.72, p = 0.007) for Ladakhi highlanders. Conclusion: Our results demonstrate higher circulatory E2 and lower T levels in Ladakhi highlanders. Higher levels of E2 and its receptors (ESR1 and ESR2) are positively associated with observed higher levels of eNOS signaling pathway metabolites. These results highlight the functional importance of E2 and its receptors for Himalayan pattern of high-altitude adaptation.

Influence of hormonal contraceptives on peripheral vascular function and structure in premenopausal females: a review

Hormonal contraceptives are one of the most widely used prescriptions for premenopausal women worldwide. Although the risk of venous and arterial cardiovascular events (e.g., deep vein thrombosis, arterial clotting) with hormonal contraceptives, specifically oral contraceptive pills, has been established, the literature on early risk indicators, such as peripheral vascular structure and function has yet to be consolidated. The purpose of this review is to summarize literature examining the impact of different hormonal contraceptives on vascular function and structure, including consideration of phasic differences within a contraceptive cycle, and to propose future directions for research. It is evident that hormonal contraceptive use appears to impact both macrovascular and microvascular endothelial function, with phasic differences in some contraceptive types dependent on progestin type, the ratio of ethinyl estradiol-to-progestin, and route of administration. However, hormonal contraceptives do not appear to impact smooth muscle function in the macrovasculature or microvasculature, arterial stiffness, or vascular structure. Underlying mechanisms for observed impacts and areas of future research are discussed. This review provides timely consolidation of research examining hormonal contraceptives and peripheral vascular function and structure and provides guidance on considerations for hormonal contraceptive use in study design.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

The Role of 17β-Estradiol and Estrogen Receptors in Regulation of Ca2+ Channels and Mitochondrial Function in Cardiomyocytes

Numerous epidemiological, clinical, and animal studies showed that cardiac function and manifestation of cardiovascular diseases (CVDs) are different between males and females. The underlying reasons for these sex differences are definitely multifactorial, but major evidence points to a causal role of the sex steroid hormone 17β-estradiol (E2) and its receptors (ER) in the physiology and pathophysiology of the heart. Interestingly, it has been shown that cardiac calcium (Ca²⁺) ion channels and mitochondrial function are regulated in a sex-specific manner. Accurate mitochondrial function and Ca²⁺ signaling are of utmost importance for adequate heart function and crucial to maintaining the cardiovascular health. Due to the highly sensitive nature of these processes in the heart, this review article highlights the current knowledge regarding sex dimorphisms in the heart implicating the importance of E2 and ERs in the regulation of cardiac mitochondrial function and Ca²⁺ ion channels, thus the contractility. In particular, we provide an overview of in-vitro and in-vivo studies using either E2 deficiency; ER deficiency or selective ER activation, which suggest that E2 and ERs are strongly involved in these processes. In this context, this review also discusses the divergent E2-responses resulting from the activation of different ER subtypes in these processes. Detailed understanding of the E2 and ER-mediated molecular and cellular mechanisms in the heart under physiological and pathological conditions may help to design more specifically targeted drugs for the management of CVDs in men and women.

Mechanisms of Sex Disparities in Cardiovascular Function and Remodeling

Epidemiological studies demonstrate disparities between men and women in cardiovascular disease prevalence, clinical symptoms, treatments, and outcomes. Enrollment of women in clinical trials is lower than men, and experimental studies investigating molecular mechanisms and efficacy of certain therapeutics in cardiovascular disease have been primarily conducted in male animals. These practices bias data interpretation and limit the implication of research findings in female clinical populations. This review will focus on the biological origins of sex differences in cardiovascular physiology, health, and disease, with an emphasis on the sex hormones, estrogen and testosterone. First, we will briefly discuss epidemiological evidence of sex disparities in cardiovascular disease prevalence and clinical manifestation. Second, we will describe studies suggesting sexual dimorphism in normal cardiovascular function from fetal life to older age. Third, we will summarize and critically discuss the current literature regarding the molecular mechanisms underlying the effects of estrogens and androgens on cardiac and vascular physiology and the contribution of these hormones to sex differences in cardiovascular disease. Fourth, we will present cardiovascular disease risk factors that are positively associated with the female sex, and thus, contributing to increased cardiovascular risk in women. We conclude that inclusion of both men and women in the investigation of the role of estrogens and androgens in cardiovascular physiology will advance our understanding of the mechanisms underlying sex differences in cardiovascular disease. In addition, investigating the role of sex-specific factors in the development of cardiovascular disease will reduce sex and gender disparities in the treatment and diagnosis of cardiovascular disease. © 2019 American Physiological Society. Compr Physiol 9:375-411, 2019.

Influence of SULT1A1 genetic variation on age at menopause, estrogen levels, and response to hormone therapy in recently postmenopausal white women

Objective:

Onset and symptoms of menopause, and response to hormone therapy (HT) show large interindividual variability. SULT1A1 encodes for a highly expressed enzyme that metabolizes estrogens. We evaluated the relationship between genetic variation in SULT1A1, menopause age, symptoms, and response to HT.

Methods:

Women enrolled in the Kronos Early Estrogen Prevention Study at Mayo Clinic were randomized to 48 months of treatment with oral conjugated equine estrogen (n = 34), transdermal 17β-estradiol (E₂) (n = 33), or placebo (n = 35). Linear regression models and ANOVA were used to test for association of SULT1A1 copy number, rs3760091, rs750155, and rs9282861 (SULT1A1^∗2), with age at menopause and symptoms, levels of estrogens (estrone [E₁], estrone sulfate [E₁S], E₂, and estradiol sulfate [E₂S]), before and after HT.

Results:

SULT1A1 gene copy number affected the minor allele frequency for each single nucleotide polymorphisms tested. Before administration of exogenous hormones, increasing number of G alleles at rs9282861 was associated with earlier age at menopause (P = 0.014), lower frequency of night sweats (P = 0.009), and less severe insomnia (P = 0.046). After 48 months of treatment, SULT1A1 genotype was not associated with the presence of menopausal symptoms. In women randomized to oral conjugated equine estrogen, increasing number of the A allele at rs750155 was associated with lower E₁S and E₂S (P = 0.004 and 0.017), whereas increasing number of the C allele at rs3760091 was associated with lower E₂S/E₂ (P = 0.044).

Conclusions:

Interindividual variability in onset of menopause and symptoms before initiation of HT is explained in part by genetic variation in SULT1A1 and may represent a step toward individualizing HT treatment decisions.

Membrane and Nuclear Estrogen Receptor Alpha Actions: From Tissue Specificity to Medical Implications

Estrogen receptor alpha (ERα) has been recognized now for several decades as playing a key role in reproduction and exerting functions in numerous nonreproductive tissues. In this review, we attempt to summarize the in vitro studies that are the basis of our current understanding of the mechanisms of action of ERα as a nuclear receptor and the key roles played by its two activation functions (AFs) in its transcriptional activities. We then depict the consequences of the selective inactivation of these AFs in mouse models, focusing on the prominent roles played by ERα in the reproductive tract and in the vascular system. Evidence has accumulated over the two last decades that ERα is also associated with the plasma membrane and activates non-nuclear signaling from this site. These rapid/nongenomic/membrane-initiated steroid signals (MISS) have been characterized in a variety of cell lines, and in particular in endothelial cells. The development of selective pharmacological tools that specifically activate MISS and the generation of mice expressing an ERα protein impeded for membrane localization have begun to unravel the physiological role of MISS in vivo. Finally, we discuss novel perspectives for the design of tissue-selective ER modulators based on the integration of the physiological and pathophysiological roles of MISS actions of estrogens.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

The molecular actions of oestrogen in the regulation of vascular health

NEW FINDINGS

What is the topic of this review? This review summarizes the beneficial actions of oestrogen on the vasculature, highlighting both molecular mechanisms and functional outcomes. What advances does it highlight? The net effect of oestrogen on the vascular health of women continues to be debated. Recent advances have provided strong evidence for the role of membrane-bound oestrogen receptors in the maintenance of normal endothelial function. On a broader scale, functional outcomes of oestrogen actions on the vasculature may mediate the reduced risk of cardiovascular disease in premenopausal women. The conflicting implications of the large-scale clinical menopausal hormone therapy trials in humans versus the findings of studies on experimental animals underscore the limitations within our understanding of the molecular actions of oestrogen. However, recent research has provided improved insight into the actions of oestrogen on the endothelium and vascular smooth muscle. This review outlines the actions of oestrogen as it contributes to vascular structure, function and health.

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.

Sex and Gender Differences in Risk, Pathophysiology and Complications of Type 2 Diabetes Mellitus

The steep rise of type 2 diabetes mellitus (T2DM) and associated complications go along with mounting evidence of clinically important sex and gender differences. T2DM is more frequently diagnosed at lower age and body mass index in men; however, the most prominent risk factor, which is obesity, is more common in women. Generally, large sex-ratio differences across countries are observed. Diversities in biology, culture, lifestyle, environment, and socioeconomic status impact differences between males and females in predisposition, development, and clinical presentation. Genetic effects and epigenetic mechanisms, nutritional factors and sedentary lifestyle affect risk and complications differently in both sexes. Furthermore, sex hormones have a great impact on energy metabolism, body composition, vascular function, and inflammatory responses. Thus, endocrine imbalances relate to unfavorable cardiometabolic traits, observable in women with androgen excess or men with hypogonadism. Both biological and psychosocial factors are responsible for sex and gender differences in diabetes risk and outcome. Overall, psychosocial stress appears to have greater impact on women rather than on men. In addition, women have greater increases of cardiovascular risk, myocardial infarction, and stroke mortality than men, compared with nondiabetic subjects. However, when dialysis therapy is initiated, mortality is comparable in both males and females. Diabetes appears to attenuate the protective effect of the female sex in the development of cardiac diseases and nephropathy. Endocrine and behavioral factors are involved in gender inequalities and affect the outcome. More research regarding sex-dimorphic pathophysiological mechanisms of T2DM and its complications could contribute to more personalized diabetes care in the future and would thus promote more awareness in terms of sex- and gender-specific risk factors.

Genetics of cardiovascular disease: Importance of sex and ethnicity

Sex differences in incidence and prevalence of and morbidity and mortality from cardiovascular disease are well documented. However, many studies examining the genetic basis for cardiovascular disease fail to consider sex as a variable in the study design, in part, because there is an inherent difficulty in studying the contribution of the sex chromosomes in women due to X chromosome inactivation. This paper will provide general background on the X and Y chromosomes (including gene content, the pseudoautosomal regions, and X chromosome inactivation), discuss how sex chromosomes have been ignored in Genome-wide Association Studies (GWAS) of cardiovascular diseases, and discuss genetics influencing development of cardiovascular risk factors and atherosclerosis with particular attention to carotid intima-medial thickness, and coronary arterial calcification based on sex-specific studies. In addition, a brief discussion of how ethnicity and hormonal status act as confounding variables in sex-based analysis will be considered along with methods for statistical analysis to account for sex in cardiovascular disease.

Determinants of flow-mediated outward remodeling in female rodents: respective roles of age, estrogens, and timing

OBJECTIVE

Flow (shear stress)-mediated outward remodeling (FMR) of resistance arteries is a key adaptive process allowing collateral growth after arterial occlusion but declining with age. 17-β-estradiol (E2) has a key role in this process through activation of estrogen receptor α (ERα). Thus, we investigated the impact of age and timing for estrogen efficacy on FMR.

APPROACH AND RESULTS

Female rats, 3 to 18 months old, were submitted to surgery to increase blood flow locally in 1 mesenteric artery in vivo. High-flow and normal-flow arteries were collected 2 weeks later for in vitro analysis. Diameter increased by 27% in high-flow arteries compared with normal-flow arteries in 3-month-old rats. The amplitude of remodeling declined with age (12% in 18-month-old rats) in parallel with E2 blood level and E2 substitution failed restoring remodeling in 18-month-old rats. Ovariectomy of 3-, 9-, and 12-month-old rats abolished FMR, which was restored by immediate E2 replacement. Nevertheless, this effect of E2 was absent 9 months after ovariectomy. In this latter group, ERα and endothelial nitric oxide synthase expression were reduced by half compared with age-matched rats recently ovariectomized. FMR did not occur in ERα(-/-) mice, whereas it was decreased by 50% in ERα(+/-) mice, emphasizing the importance of gene dosage in high-flow remodeling.

CONCLUSIONS

E2 deprivation, rather than age, leads to decline in FMR, which can be prevented by early exogenous E2. However, delayed E2 replacement was ineffective on FMR, underlining the importance of timing of this estrogen action.

Sex-specific risk of cardiovascular disease and cognitive decline: pregnancy and menopause

Understanding the biology of sex differences is integral to personalized medicine. Cardiovascular disease and cognitive decline are two related conditions, with distinct sex differences in morbidity and clinical manifestations, response to treatments, and mortality. Although mortality from all-cause cardiovascular diseases has declined in women over the past five years, due in part to increased educational campaigns regarding the recognition of symptoms and application of treatment guidelines, the mortality in women still exceeds that of men. The physiological basis for these differences requires further research, with particular attention to two physiological conditions which are unique to women and associated with hormonal changes: pregnancy and menopause. Both conditions have the potential to impact life-long cardiovascular risk, including cerebrovascular function and cognition in women. This review draws on epidemiological, translational, clinical, and basic science studies to assess the impact of hypertensive pregnancy disorders on cardiovascular disease and cognitive function later in life, and examines the effects of post-menopausal hormone treatments on cardiovascular risk and cognition in midlife women. We suggest that hypertensive pregnancy disorders and menopause activate vascular components, i.e., vascular endothelium and blood elements, including platelets and leukocytes, to release cell-membrane derived microvesicles that are potential mediators of changes in cerebral blood flow, and may ultimately affect cognition in women as they age. Research into specific sex differences for these disease processes with attention to an individual's sex chromosomal complement and hormonal status is important and timely.

GPER regulates endothelin-dependent vascular tone and intracellular calcium

AIMS

An increase in intracellular vascular smooth muscle cell calcium concentration (VSMC [Ca(2+)](i)) is essential for endothelin-1 (ET-1)-induced vasoconstriction. Based on previous findings that activation of the G protein-coupled estrogen receptor (GPER) inhibits vasoconstriction in response to ET-1 and regulates [Ca(2+)](i) in cultured VSMC, we investigated whether endogenous GPER regulates ET-1-induced changes in VSMC [Ca(2+)](i) and constriction of intact arteries.

MAIN METHODS

Pressurized carotid arteries of GPER-deficient (GPER(0)) and wildtype (WT) mice were loaded with the calcium indicator fura 2-AM. Arteries were stimulated with the GPER-selective agonist G-1 or solvent followed by exposure to ET-1. Changes in arterial diameter and VSMC [Ca(2+)](i) were recorded simultaneously. Vascular gene expression levels of ET(A) and ET(B) receptors were determined by qPCR.

KEY FINDINGS

ET-1-dependent vasoconstriction was increased in arteries from GPER(0) compared to arteries from WT mice. Despite the more potent vasoconstriction to ET-1, GPER deficiency was associated with a marked reduction in the ET-1-stimulated VSMC [Ca(2+)](i) increase, suggesting an increase in myofilament force sensitivity to [Ca(2+)](i). Activation of GPER by G-1 had no effect on vasoconstriction or VSMC [Ca(2+)](i) responses to ET-1, and expression levels of ET(A) or ET(B) receptor were unaffected by GPER deficiency.

SIGNIFICANCE

These results demonstrate that endogenous GPER inhibits ET-1-induced vasoconstriction, an effect that may be associated with reduced VSMC Ca(2+) sensitivity. This represents a potential mechanism through which GPER could contribute to protective effects of endogenous estrogen in the cardiovascular system.

Deletion of G protein-coupled estrogen receptor increases endothelial vasoconstriction

Endogenous estrogens mediate protective effects in the cardiovascular system, affecting both endothelium-dependent and endothelium-independent mechanisms. Previous studies have suggested that nonselective estrogen receptor agonists such as endogenous estrogens inhibit endothelium-dependent vasoconstriction; however, the role of estrogen receptors in this response has not yet been clarified. This study investigated whether the intracellular transmembrane G protein-coupled estrogen receptor (GPER) regulates vascular reactivity in mice. Effects of chronic deficiency (using mice lacking the GPER gene) and acute inhibition (using the GPER-selective antagonist G15) on endothelium-dependent and endothelium-independent vascular reactivity, and the effects of GPER deficiency on vascular gene expression and structure were investigated. We found that chronic GPER deficiency is associated with increased endothelial prostanoid-mediated vasoconstriction but has no effect on endothelial nitric oxide bioactivity, gene expression of endothelial nitric oxide synthase and thromboxane prostanoid (TP) receptor, or vascular structure. GPER deletion also increases TP receptor-mediated contraction. Acute GPER blockade enhances endothelium-dependent contractions and reduces endothelial nitric oxide bioactivity. Contractions in response to TP receptor activation are unaffected by G15. In conclusion, this study identifies GPER as the first estrogen receptor with inhibitory activity on endothelium-dependent contractility. These findings may be important for understanding and treating diseases associated with increased endothelial vasoconstrictor prostanoid activity such as hypertension and obesity.

Obesity, insulin resistance and diabetes: sex differences and role of oestrogen receptors

Obesity increases the risk of coronary artery disease through insulin resistance, diabetes, arterial hypertension and dyslipidemia. The prevalence of obesity has increased worldwide and is particularly high among middle-aged women and men. After menopause, women are at an increased risk to develop visceral obesity due to the loss of endogenous ovarian hormone production. Effects of oestrogens are classically mediated by the two nuclear oestrogen receptors (ERs) α and β. In addition, more recent research has shown that the intracellular transmembrane G-protein-coupled oestrogen receptor (GPER) originally designated as GPR30 also mediates some of the actions attributed to oestrogens. Oestrogen and its receptors are important regulators of body weight and insulin sensitivity not only in women but also in men as demonstrated by ER mutations in rodents and humans. This article reviews the role of sex hormones and ERs in the context of obesity, insulin sensitivity and diabetes as well as the related clinical issues in women and men.

Gender differences in the cardiovascular effects of sex hormones

Over the last decade, compelling evidence supports the idea that the different impact of cardiovascular disease (CVD) and the differences in vascular biology in men and women may be, at least in part, related to the cardiovascular and metabolic effects of sex steroid hormones. Indeed, androgens and oestrogens influence a multitude of vascular biological processes and their cardiovascular effects are multifaceted. While in women the effects of androgens mainly depend upon oestrogens' levels and, ultimately, upon the estradiol/testosterone ratio, the effects of androgens in men mostly relate to their aromatization into oestrogens. Oestrogens exert potential beneficial effects on the cardiovascular system in both sexes. In women, the effect of oestrogens, alone or in association with progestins, has been widely investigated, but data obtained from older patient populations have lead the medical community and the general public to misleading conclusions. Growing evidence supports the 'timing hypothesis', which suggests that oestrogen/hormone replacement therapy may increase CVD risk if started late after menopause, but produce beneficial cardiovascular effects in younger postmenopausal women. Because in men adequate interventional studies with testosterone are lacking, specific investigations should be performed.

Sex-based differences in vascular function

Cardiovascular disease is the leading cause of morbidity and mortality for both men and women in the USA. However, there are differences between the sexes in age-dependent onset, severity, symptoms and outcomes. Basic research into the causes of sex-dependent differences in cardiovascular disease is ongoing and includes investigation into genetic variation in expression and distribution of receptors for the sex steroids; specificity of natural and synthetic ligands that activate the sex steroid receptors; and intracellular mechanisms that are activated by the receptors in all components of the vessel wall and blood elements, which integrate to regulate vascular tone, vascular repair and remodeling in health and disease. In this era of personalized medicine, basic research into mechanisms of sex differences in vascular function will result in improved prevention, detection and treatment of cardiovascular disease in both men and women.

Endogenous estrogen levels are associated with endothelial function in males independently of lipid levels

Estrogens and androgens may play an important role in vascular health in both sexes. The aim of this study was to examine the relation of endogenous sex hormone levels with early markers of atherosclerosis in a cohort of apparently healthy males. 124 males (age 46.25 ± 9.56) attending a preventive medicine program were examined for unrecognised features of the metabolic syndrome. Flow-mediated dilatation (FMD) and intima-media thickness (IMT) of the common carotid artery were evaluated. Obesity parameters were recorded; estradiol, testosterone, SHBG, free testosterone, insulin, as well as glucose and lipid levels were measured. FMD was positively correlated with estradiol (r = 0.201, P = 0.041) and negatively with total cholesterol (r = -0.205, P = 0.022), low density lipoproteins (r = -0.232, P = 0.009), and triglyceride levels (r = -0.179, P = 0.046). In multivariate analysis, the association of FMD with estrogen was independent of BMI and lipid levels. No significant association between FMD and testosterone levels was found. Subjects with an increased mean IMT (> 0.73 mm, i.e., > 3rd tertile) had lower levels of free (P = 0.021) and bioavailable (P = 0.016) testosterone. In multivariate logistic regression analysis, this association was no longer significant when age or cholesterol levels were considered. Endogenous estrogen levels are associated with FMD, independently of age and lipid levels, showing a protective effect in middle-age male subjects. Circulating androgens are associated, although not independently, with structural changes such as the IMT of carotid artery; this effect is possibly influenced by lipid levels and age.

Hormonal modulation of endothelial NO production

Since the discovery of endothelium-derived relaxing factor and the subsequent identification of nitric oxide (NO) as the primary mediator of endothelium-dependent relaxations, research has focused on chemical and physical stimuli that modulate NO levels. Hormones represent a class of soluble, widely circulating chemical factors that impact production of NO both by rapid effects on the activity of endothelial nitric oxide synthase (eNOS) through phosphorylation of the enzyme and longer term modulation through changes in amount of eNOS protein. Hormones that increase NO production including estrogen, progesterone, insulin, and growth hormone do so through both of these common mechanisms. In contrast, some hormones, including glucocorticoids, progesterone, and prolactin, decrease NO bioavailability. Mechanisms involved include binding to repressor response elements on the eNOS gene, competing for co-regulators common to hormones with positive genomic actions, regulating eNOS co-factors, decreasing substrate for eNOS, and increasing production of oxygen-derived free radicals. Feedback regulation by the hormones themselves as well as the ability of NO to regulate hormonal release provides a second level of complexity that can also contribute to changes in NO levels. These effects on eNOS and changes in NO production may contribute to variability in risk factors, presentation of and treatment for cardiovascular disease associated with aging, pregnancy, stress, and metabolic disorders in men and women.

Association of estrogen receptor-alpha gene polymorphisms with cardiac autonomic nervous activity in healthy young Japanese males

BACKGROUND

Estrogens exert beneficial effects on the cardiovascular system that are mediated by estrogen receptors. We examined the association between the estrogen receptor alpha gene (ESR1) PvuII and XbaI polymorphisms and cardiac autonomic nervous function in Japanese males.

METHODS

We examined 252 young healthy males for association of ESR1 PvuII and XbaI polymorphisms and short-term heart rate variability (HRV) during supine rest and in a standing position. The very low frequency (VLF), low frequency (LF), and high frequency (HF) components of HRV were quantified by frequency domain analysis.

RESULTS

Carriers of the ESR1 PvuII C allele had higher mean blood pressure (BP), while the XbaI GG genotype was significantly associated with higher diastolic and mean BP, but lower HR. In the haplotype analysis, carriers of the ESR1 haplotype 2 (PvuII C and XbaI A) allele had a higher systolic and mean BP, and lower HRV spectral powers (total power, VLF, LF, and HF components) in a supine rest compared with those of non-carriers.

CONCLUSIONS

The ESR1 PvuII and XbaI haplotype is associated with BP variation and the reduction in cardiac autonomic nervous activity in young Japanese males, which may be precursors of future pathological episodes of cardiovascular diseases.

Vascular endothelial estrogen receptor alpha is modulated by estrogen status and related to endothelial function and endothelial nitric oxide synthase in healthy women

CONTEXT AND OBJECTIVE

Estrogen receptor alpha (ER alpha), a potent transcription factor expressed in vascular endothelial cells, plays a key role in regulating vascular function and health. We determined whether vascular endothelial cell expression of ER alpha is influenced by estrogen status and is related to vascular endothelial function in healthy women.

METHODS

ER alpha protein expression was measured (quantitative immunofluorescence) in endothelial cells from peripheral veins of 16 healthy, premenopausal women during the early follicular (EF) and late follicular (LF) phases of the menstrual cycle and 17 estrogen-deficient postmenopausal women. Endothelial-dependent dilation (EDD; brachial artery flow-mediated dilation) and endothelial nitric oxide synthase (eNOS) expression and activation were also measured in a subgroup of women.

RESULTS

In premenopausal women (n = 10), ER alpha expression was 30% lower (P < 0.001) during the EF (low estrogen) compared with the LF (high estrogen) phase of the menstrual cycle. In postmenopausal women, ER alpha expression was 33% lower (P < 0.001) compared with the LF phase of the menstrual cycle in premenopausal women. ER alpha expression was strongly related (r = 0.67; P < 0.001) to EDD, which was reduced in postmenopausal women. ER alpha abundance was positively related to expression of eNOS (r = 0.54; P = 0.009; n = 21) and ser1177 phosphorylated eNOS (r = 0.59; P = 0.006; n = 20).

CONCLUSIONS

These results provide the first evidence that expression of ER alpha in vascular endothelial cells is modulated by estrogen status and may be a key determinant of vascular endothelial function in healthy pre- and postmenopausal women. ER alpha expression may influence vascular endothelial function in women by affecting protein levels and activation of eNOS.

Gender differences in the cardiovascular effect of sex hormones

The higher incidence of cardiovascular disease in men than in women of similar age, and the menopause-associated increase in cardiovascular disease in women, has led to speculation that gender-related differences in sex hormones have a key role in the development and evolution of cardiovascular disease. Compelling data have indicated that sex differences in vascular biology are determined not only by gender-related differences in sex steroid levels, but also by gender-specific tissue and cellular differences that mediate sex-specific responses. In this Review, we describe the sex-specific effects of estrogen and testosterone on cardiovascular risk, direct vascular effects of these sex hormones, and how these effects influence development of atherosclerosis. Cardiovascular effects of exogenous hormone administration are also discussed. Importantly, evidence has indicated that estrogens alone or in combination with progestins in postmenopausal women increase cardiovascular risk if started late after menopause, but that it possibly has beneficial cardiovascular effects in younger postmenopausal women, although data on long-term testosterone therapy are lacking. Hormone therapy should not be considered solely for primary prevention or treatment of cardiovascular disease at this time.

The role of estrogen receptor subtypes for vascular maintenance

Protective role of estrogens (E2) against cardiovascular disease has been appreciated for many years until the equivocal results of cardiovascular outcomes in clinical trials on hormone replacement therapy were reported. Although new ongoing trials aim to resolve these discrepancies, it is obvious that cardiovascular effects of E(2) are complex and diverse. To understand further the cardiovascular effects of E(2), the detailed knowledge on the specific role of both classical estrogen receptor (ER) subtypes and G protein-coupled receptor-30 in the vasculature are of importance. In this article, we review the current knowledge about the pattern of ERalpha and ERbeta expression in human vasculature, the genomic and non-genomic cardiovascular effects of E(2)versus subtype selective ERalpha and ERbeta stimulation on isolated arteries and in different knockout animal models. The results indicate that although ERalpha and ERbeta are expressed in the endothelium and media of human arteries, there is no definite evidence for predominant expression of one over another, the pattern depends on vascular bed, sex and diseased condition. Data from the experiments on isolated arteries and in ER knockout animal models may indicate that activation of specific ER subtypes could provide additional cardiovascular protective effects. However, a clear role for each ERs have to be finalised with focus on mechanisms and by exploring the potential of ERs-selective agonists for clinical utility.

Genetic and pharmacologic strategies to determine the function of estrogen receptor alpha and estrogen receptor beta in cardiovascular system

BACKGROUND

The biological functions of estrogens extend beyond the female and male reproductive tract, affecting the cardiovascular and renal systems. Traditional views on the role of postmenopausal hormone therapy (HT) in protecting against heart disease, which were challenged by clinical end point studies that found adverse effects of combined HT, are now being replaced by more differentiated concepts suggesting a beneficial role of early and unopposed HT that does not include a progestin.

OBJECTIVE

We reviewed recent insights, concepts, and research results on the biology of both estrogen receptor (ER) subtypes, ERalpha and ERbeta, in cardiac and vascular tissues. Knowledge of these ER subtypes is crucial to understanding gender and estrogen effects and to developing novel, exciting strategies that may have a profound clinical impact.

METHODS

This review focuses on in vivo studies and includes data presented at the August 2007 meeting of the American Physiological Society as well as data from a search of the MEDLINE and Ovid databases from January 1986 to November 2007. Search results were restricted to English-language publications, using the following search terms: estrogen, estrogen receptor alpha, estrogen receptor beta, estrogen receptor alpha agonist, estrogen receptor alpha antagonist, estrogen receptor beta agonist, estrogen receptor beta antagonist, PPT, DPN, heart, vasculature, ERKO mice, BERKO mice, transgenic mice, and knockout mice.

RESULTS

Genetic mouse models and pharmacologic studies that employed selective as well as nonselective ER agonists support the concept that both ER subtypes confer protective effects in experimental models of human heart disease, including hypertension, cardiac hypertrophy, and chronic heart failure.

CONCLUSIONS

Genetic models and novel ligands hold the promise of further improving our understanding of estrogen action in multiple tissues and organs. These efforts will ultimately enhance the safety and efficacy of HT and may also result in new applications for synthetic female sex hormone analogues.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.

Human models of aromatase deficiency

Estrogens exert a wide range of biological effects in both sexes also on non-reproductive systems and organs. Human congenital estrogen deficiency, due to an inactivating mutation of the aromatase gene, leads to the lack of the estrogen synthesis, with gonadotropins and circulating testosterone ranging from normal to elevated. The aromatese-deficient females show hyperandrogenism and virilization at birth with ambiguous genitalia. During childhood there are a dysfunction in the LHRH-LH/FSH axis and a progressive delay in bone age. At puberty they show primary amenorrhea, no breast development, worsening of the virilization and the absence of growth spurt. The clinical phenotype in the male affected subjects comprises tall stature, persistent linear growth and delayed bone age, osteopenia/osteoporosis, eunuchoid body proportion, different degrees of glucose-insulin and of fertility impairment. These phenotypes suggest the physiological role of estrogens on the skeleton, on pituitary function, on the reproductive system, on glucose metabolism, being the precise mechanism on each of these functions not yet known in detail. The estradiol replacement treatment leads to a complete epiphyseal closure and to the skeletal maturation. Moreover, the increasing knowledge on the role of estrogen in several metabolic pathways could be important for a better management of several metabolic diseases.

Androgenic/estrogenic balance in the male rat cerebral circulation: metabolic enzymes and sex steroid receptors

Tissues from males can be regulated by a balance of androgenic and estrogenic effects because of local metabolism of testosterone and expression of relevant steroid hormone receptors. As a critical first step to understanding sex hormone influences in the cerebral circulation of males, we investigated the presence of enzymes that metabolize testosterone to active products and their respective receptors. We found that cerebral blood vessels from male rats express 5alpha-reductase type 2 and aromatase, enzymes responsible for conversion of testosterone into dihydrotestosterone (DHT) and 17beta-estradiol, respectively. Protein levels of these enzymes, however, were not modulated by long-term in vivo hormone treatment. We also showed the presence of receptors for both androgens (AR) and estrogens (ER) from male cerebral vessels. Western blot analysis showed bands corresponding to the full-length AR (110 kDa) and ERalpha (66 kDa). Long-term in vivo treatment of orchiectomized rats with testosterone or DHT, but not estrogen, increased AR levels in cerebral vessels. In contrast, ERalpha protein levels were increased after in vivo treatment with estrogen but not testosterone. Fluorescent immunostaining revealed ERalpha, AR, and 5alpha-reductase type 2 in both the endothelial and smooth muscle layers of cerebral arteries, whereas aromatase staining was solely localized to the endothelium. Thus, cerebral vessels from males are target tissues for both androgens and estrogen. Furthermore, local metabolism of testosterone might balance opposing androgenic and estrogenic influences on cerebrovascular as well as brain function in males.

Ageing, oestrogen, platelets and thrombotic risk

1. Adverse thrombotic cardiovascular events increase in women coincident with the onset of menopause. 2. Age past menopause may be an important variable in defining the benefit/risk of hormone treatments. 3. Few studies have examined hormonal status as a variable of ageing using a polygenomic approach of both humoral and cellular components of the coagulation system. 4. Longitudinal studies of a global set of platelet functions that define procoagulant activity (i.e. adhesion, aggregation, secretion and thrombin production) in individuals with documented hormonal status are needed to better understand how hormonal changes associated with ageing impact thrombotic risk.

Contribution of epoxyeicosatrienoic acids to flow-induced dilation in arteries of male ERalpha knockout mice: role of aromatase

We studied the roles of estrogen receptors (ER) and aromatase in the mediation of flow-induced dilation (FID) in isolated arteries of male ERalpha-knockout (ERalpha-KO) and wild-type (WT) mice. FID was comparable between gracilis arteries of WT and ERalpha-KO mice. In WT arteries, inhibition of NO and prostaglandins eliminated FID. In ERalpha-KO arteries, N(omega)-nitro-L-arginine methyl ester (L-NAME) inhibited FID by approximately 26%, whereas indomethacin inhibited dilations by approximately 50%. The remaining portion of the dilation was abolished by additional administration of 6-(2-proparglyoxyphenyl)hexanoic acid (PPOH) or iberiotoxin, inhibitors of epoxyeicosatrienoic acid (EET) synthesis and large-conductance potassium channels, respectively. By using an electrophysiological technique, we found that, in the presence of 10 dyne/cm(2) shear stress, perfusate passing through donor vessels isolated from gracilis muscle of ERalpha-KO mice subjected to L-NAME and indomethacin elicited smooth muscle hyperpolarization and a dilator response of endothelium-denuded detector vessels. These responses were prevented by the presence of iberiotoxin in detector or PPOH in donor vessels. Gas chromatography-mass spectrometry (GC-MS) analysis indicated a significant increase in arterial production of EETs in ERalpha-KO compared with WT mice. Western blot analysis showed a significantly reduced endothelial nitric oxide synthase expression but enhanced expressions of aromatase and ERbeta in ERalpha-KO arteries. Treatment of ERalpha-KO arteries with specific aromatase short-interfering RNA for 72 h, knocked down the aromatase mRNA and protein associated with elimination of EET-mediation of FID. Thus, FID in male ERalpha-KO arteries is maintained via an endothelium-derived hyperpolarizing factor/EET-mediated mechanism compensating for reduced NO mediation due, at least in part, to estrogen aromatized from testosterone.

Ginsenoside Rb1 inhibits tube-like structure formation of endothelial cells by regulating pigment epithelium-derived factor through the oestrogen beta receptor

BACKGROUND AND PURPOSE

Angiogenesis is a crucial step in tumour growth and metastasis. Ginsenoside-Rb1 (Rb1), the major active constituent of ginseng, potently inhibits angiogenesis in vivo and in vitro. However, the underlying mechanism remains unknown. We hypothesized that the potent anti-angiogenic protein, pigment epithelium-derived factor (PEDF), is involved in regulating the anti-angiogenic effects of Rb1.

EXPERIMENTAL APPROACHES

Rb1-induced PEDF was determined by real-time PCR and western blot analysis. The anti-angiogenic effects of Rb1 were demonstrated using endothelial cell tube formation assay. Competitive ligand-binding and reporter gene assays were employed to indicate the interaction between Rb1 and the oestrogen receptor (ER).

KEY RESULTS

Rb1 significantly increased the transcription, protein expression and secretion of PEDF. Targeted inhibition of PEDF completely prevented Rb1-induced inhibition of endothelial tube formation, suggesting that the anti-angiogenic effect of Rb1 was PEDF specific. Interestingly, the activation of PEDF occurred via a genomic pathway of ERbeta. Competitive ligand-binding assays indicated that Rb1 is a specific agonist of ERbeta, but not ERalpha. Rb1 effectively recruited transcriptional activators and activated an oestrogen-responsive reporter gene. Furthermore, Rb1-mediated PEDF activation and the subsequent inhibition of tube formation were blocked by the ER antagonist ICI 182,780 or transfection of ERbeta siRNA, indicating ERbeta dependence.

CONCLUSIONS AND IMPLICATIONS

Here we show for the first time that the Rb1 suppressed the formation of endothelial tube-like structures through modulation of PEDF via ERbeta. These findings demonstrate a novel mechanism of the action of this ginsenoside that may have value in anti-cancer and anti-angiogenesis therapy.

Why men's hearts break: cardiovascular effects of sex steroids

Coronary artery disease (CAD) mortality differs in men and women, leading to the speculation that differences in sex steroids contribute to risk. Controlled clinical trials have shown that estrogen replacement is not cardioprotective in certain women, and recent cross-sectional studies associate low testosterone with a greater incidence of CAD in men. Testosterone has demonstrated effects on insulin resistance, obesity, myocardium, coagulation, inflammation, vasodilation, and endothelial function. Imbalance of sex steroids contributes to adverse cardiac effects in men.

Structure-function relationship of estrogen receptor alpha and beta: impact on human health

17Beta-estradiol (E2) controls many aspects of human physiology, including development, reproduction and homeostasis, through regulation of the transcriptional activity of its cognate receptors (ERs). The crystal structures of ERs with agonists and antagonists and the use of transgenic animals have revealed much about how hormone binding influences ER conformation(s) and how this conformation(s), in turn, influences the interaction of ERs with co-activators or co-repressors and hence determines ER binding to DNA and cellular outcomes. This information has helped to shed light on the connection between E2 and the development or progression of numerous diseases. Current therapeutic strategy in the treatment of E2-related pathologies relies on the modulation of ER trancriptional activity by anti-estrogens; however, data accumulated during the last five years reveal that ER activities are not only restricted to the nucleus. ERs are very mobile proteins continuously shuttling between protein targets located within various cellular compartments (e.g., membrane, nucleus). This allows E2 to generate different and synergic signal transduction pathways (i.e., non-genomic and genomic) which provide plasticity for cell response to E2. Understanding the structural basis and the molecular mechanisms by which ER transduce E2 signals in target cells will allow to create new pharmacologic therapies aimed at the treatment of a variety of human diseases affecting the cardiovascular system, the reproductive system, the skeletal system, the nervous system, the mammary gland, and many others.

Cellular mechanisms underlying the cardiovascular actions of oestrogens

Although pre-menopausal women enjoy relative cardiovascular protection, hormone (oestrogen±progestin)-replacement therapy has not shown cardiovascular benefits in post-menopausal women, suggesting that the effects of oestrogens on the cardiovascular system are much more complex than previously expected. Endothelial cells, smooth muscle cells, cardiac myocytes and fibroblasts, the cellular components of blood vessels and the heart, play important roles in cardiovascular health and disease. During the development and progression of cardiovascular disease, changes occur both in the structure and function of these cells, resulting in a wide range of abnormalities, which affect growth, death and physiological function. These cells contain functional oestrogen receptors and are targets for oestrogen action. This review focuses on recent studies on the effects of oestrogen on cardiovascular cell function. Oestrogens, particularly 17β-oestradiol, exert multiple effects on cardiovascular cells, and these effects may contribute to the gender-associated protection against cardiovascular diseases.

No replication of association between estrogen receptor alpha gene polymorphisms and susceptibility to myocardial infarction in a large sample of patients of European descent

BACKGROUND

The effects of estrogen on blood vessels are partly due to changes in vascular cell gene expression and protein synthesis that are mediated by estrogen receptors. In previous association studies, the -397T/C (rs2234693) and -351A/G (rs9340799) single nucleotide polymorphisms in the estrogen receptor alpha gene (ESR1) have been implicated in the risk of coronary atherosclerosis and myocardial infarction. To test these findings, we examined the relationship of the polymorphisms to myocardial infarction in a large sample of white patients and control individuals of predominantly European descent.

METHODS AND RESULTS

The case group included 3657 patients with myocardial infarction, and the control group comprised 1211 individuals with angiographically normal coronary arteries and without signs or symptoms of myocardial infarction. TaqMan assays were used for the determination of genotypes. Genotype distributions of the -397T/C and -351A/G polymorphisms were not significantly different between the control and patient groups (P> or =0.85). The frequencies of haplotypes defined by the -397T/C and -351A/G polymorphisms were similar in the control group and the patient group (P=0.42). In addition, the distributions of haplotype-defined genotypes (diplotypes) were not significantly different between the control group and the patient group (P=0.81). Separate analyses in women and men did not reveal sex-related associations of specific genotypes or haplotypes of the polymorphisms with myocardial infarction (P> or =0.25).

CONCLUSIONS

The results indicate that the -397T/C and -351A/G polymorphisms of ESR1 or haplotypes based on these polymorphisms are not associated with myocardial infarction in a white population.

Platelet characteristics change with aging: role of estrogen receptor beta

Estrogen receptor beta (betaER) is the predominant estrogen receptor in platelets. Experiments were designed to define phenotypic changes in platelets with aging following deletion of betaER (betaERKO). Blood was collected from wild-type and betaERKO female mice at 4-7 (young) and 24-25 (aged) months of age. In young animals, total number of platelets, number of platelets containing RNA (reticulated platelets), aggregation, dense body adenosine triphosphate secretion, and alpha granular secretion were the same in both groups. With aging, total number of platelets decreased but reticulated platelets increased in betaERKO mice; aggregation and dense granule adenosine triphosphate secretion decreased whereas basal expression of fibrinogen receptors increased with age in wild-type and betaERKO mice. Basal expression of P-selectin and annexin V binding increased with aging only in betaERKO mice; thrombin did not increase expression in these mice. Therefore, deletion of betaER is associated with specific platelet functions, which are expressed only with age-associated reproductive senescence.