Post-Transcriptional and Epigenetic Regulation of Estrogen Signaling.

Post-translational and epigenetic regulation are important mechanisms controlling functions of genes and proteins. Although the "classic" estrogen receptors (ERs) have been acknowledged to function in mediating estrogen effects via transcriptional mechanisms, estrogenic agents modulate the turnover of several proteins via post-transcriptional and post-translational pathways including epigenetics. For instance, the metabolic and angiogenic action of G-protein coupled estrogen receptor (GPER) in vascular endothelial cells has been recently elucidated. By interacting with GPER, 17ß-estradiol and the GPER agonist G1 enhance endothelial stability of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and capillary tube formation by increasing ubiquitin-specific peptidase 19 levels, thereby reducing PFKFB3 ubiquitination and proteasomal degradation. In addition to ligands, the functional expression and trafficking of ERs can be modulated by post-translational modification, including palmitoylation. MicroRNAs (miRNAs), the most abundant form of endogenous small RNAs in humans, regulate multiple target genes and are at the center of the multi-target regulatory network. This review also discusses the emerging evidence of how miRNAs affect glycolytic metabolism in cancer, as well as their regulation by estrogens. Restoring dysregulated miRNA expression represents a promising strategy to counteract the progression of cancer and other disease conditions. Accordingly, estrogen post-transcriptional regulatory and epigenetic mechanisms represent novel targets for pharmacological and nonpharmacological intervention for the treatment and prevention of hormone-sensitive noncommunicable diseases, including estrogen-sensitive cancers of the reproductive system in women. SIGNIFICANCE STATEMENT: The effects of estrogen are mediated by several mechanisms that are not limited to the transcriptional regulation of target genes. Slowing down the turnover of master regulators of metabolism by estrogens allows cells to rapidly adapt to environmental cues. Identification of estrogen-targeted microRNAs may lead to the development of novel RNA therapeutics that disrupt pathological angiogenesis in estrogen-dependent cancers.

Endothelium and endothelin: regulators of arterial stiffness and fibrinolysis in ANCA-associated vasculitis.

In this issue, Farrah et al. report clinical investigations in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). They demonstrate that endothelium-dependent vasodilatation, fibrinolytic capacity, and monocyte-dependent endothelin-1 clearance are reduced in patients with AAV, whereas circulating levels of endothelin-1 and vascular stiffness are increased. Acute infusion of an endothelin ETA receptor antagonist reduced vasoconstriction and arterial stiffness. This Commentary discusses biological insights and clinical implications of this study.

GPER Mediates Functional Endothelial Aging in Renal Arteries.

Aging is associated with impaired renal artery function, which is partly characterized by arterial stiffening and a reduced vasodilatory capacity due to excessive generation of reactive oxygen species by NADPH oxidases (Nox). The abundance and activity of Nox depends on basal activity of the heptahelical transmembrane receptor GPER; however, whether GPER contributes to age-dependent functional changes in renal arteries is unknown. This study investigated the effect of aging and Nox activity on renal artery tone in wild-type and GPER-deficient (Gper-/-) mice (4 and 24 months old). In wild-type mice, aging markedly impaired endothelium-dependent, nitric oxide (NO)-mediated relaxations to acetylcholine, which were largely preserved in renal arteries of aged Gper-/- mice. The Nox inhibitor gp91ds-tat abolished this difference by greatly enhancing relaxations in wild-type mice, while having no effect in Gper-/- mice. Contractions to angiotensin II and phenylephrine in wild-type mice were partly sensitive to gp91ds-tat but unaffected by aging. Again, deletion of GPER abolished effects of Nox inhibition on contractile responses. In conclusion, basal activity of GPER is required for the age-dependent impairment of endothelium-dependent, NO-mediated relaxation in the renal artery. Restoration of relaxation by a Nox inhibitor in aged wild-type but not Gper-/- mice strongly supports a role for Nox-derived reactive oxygen species as the underlying cause. Pharmacological blockers of GPER signaling may thus be suitable to inhibit functional endothelial aging of renal arteries by reducing Nox-derived oxidative stress and, possibly, the associated age-dependent deterioration of kidney function.

Endothelin and endothelin antagonists in chronic kidney disease.

The incidence and prevalence of chronic kidney disease (CKD), with diabetes and hypertension accounting for the majority of cases, is on the rise, with up to 160 million individuals worldwide predicted to be affected by 2020. Given that current treatment options, primarily targeted at the renin-angiotensin system, only modestly slow down progression to end-stage renal disease, the urgent need for additional effective therapeutics is evident. Endothelin-1 (ET-1), largely through activation of endothelin A receptors, has been strongly implicated in renal cell injury, proteinuria, inflammation, and fibrosis leading to CKD. Endothelin receptor antagonists (ERAs) have been demonstrated to ameliorate or even reverse renal injury and/or fibrosis in experimental models of CKD, whereas clinical trials indicate a substantial antiproteinuric effect of ERAs in diabetic and nondiabetic CKD patients even on top of maximal renin-angiotensin system blockade. This review summarizes the role of ET in CKD pathogenesis and discusses the potential therapeutic benefit of targeting the ET system in CKD, with attention to the risks and benefits of such an approach.

Cholesterol and atherosclerosis: modulation by oestrogen.

PURPOSE OF REVIEW: Oestrogens are important modulators of lipid metabolism, inflammation and vascular homeostasis. Endogenous oestrogens contribute to the low prevalence of atherosclerotic vascular disease in premenopausal women with intact ovarian function, and cessation of oestrogen production following menopause increases cardiovascular risk. Orally administered oestrogens such as postmenopausal hormone therapy increase HDL and reduce LDL cholesterol levels, and they increase triglyceride levels. Current guidelines do not recommend postmenopausal hormone therapy for cardiovascular prevention. RECENT FINDINGS: Recent clinical studies have suggested potential benefits of natural oestrogen or selective oestrogen receptor modulators on cardiovascular outcomes, effects that are associated with lipid profile improvements. In contrast to earlier studies such as the Women's Health Initiative, the Heart and Estrogen/Progestin Replacement Study or the Estrogen Replacement and Atherosclerosis trial, in which investigators used hormone mixtures derived from horse urine (misleadingly named 'conjugated oestrogens' with unknown activity on oestrogen receptors), triphasic oestrogen therapy started early after menopause as primary prevention study protocol improved outcome. New studies suggest therapeutic potential of natural oestrogens and certain selective oestrogen receptor modulators to reduce coronary artery disease risk in postmenopausal women. SUMMARY: Endogenous oestrogens are important regulators of lipid metabolism and inhibit inflammation, vascular cell growth and plaque progression in premenopausal women. The recent trials warrant further studies, which should also determine how much of the potential benefits are due to improvements of lipid metabolism.

Sex and sex steroids as determinants of cardiovascular risk.

There are considerable sex differences regarding the risk of cardiovascular disease (CVD), including arterial hypertension, coronary artery disease (CAD) and stroke, as well as chronic renal disease. Women are largely protected from these conditions prior to menopause, and the risk increases following cessation of endogenous estrogen production or after surgical menopause. Cardiovascular diseases in women generally begin to occur at a later age than in men (on average with a delay of 10 years). Cessation of estrogen production also impacts metabolism, increasing the risk of developing obesity and diabetes. In middle-aged individuals, hypertension develops earlier and faster in women than in men, and smoking increases cardiovascular risk to a greater degree in women than it does in men. It is not only estrogen that affects female cardiovascular health and plays a protective role until menopause: other sex hormones such as progesterone and androgen hormones generate a complex balance that differentiates heart and blood vessel function in women compared to men. Estrogens improve vasodilation of epicardial coronary arteries and the coronary microvasculature by augmenting the release of vasodilating factors such as nitric oxide and prostacyclin, which are mechanisms of coronary vasodilatation that are more pronounced in women compared to men. Estrogens are also powerful inhibitors of inflammation, which in part explains their protective effects on CVD and chronic renal disease. Emerging evidence suggests that sex chromosomes also play a significant role in shaping cardiovascular risk. The cardiovascular protection conferred by endogenous estrogens may be extended by hormone therapy, especially using bioidentical hormones and starting treatment early after menopause.

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.

The G protein-coupled oestrogen receptor GPER in health and disease: an update.

Oestrogens and their receptors contribute broadly to physiology and diseases. In premenopausal women, endogenous oestrogens protect against cardiovascular, metabolic and neurological diseases and are involved in hormone-sensitive cancers such as breast cancer. Oestrogens and oestrogen mimetics mediate their effects via the cytosolic and nuclear receptors oestrogen receptor-α (ERα) and oestrogen receptor-ß (ERß) and membrane subpopulations as well as the 7-transmembrane G protein-coupled oestrogen receptor (GPER). GPER, which dates back more than 450 million years in evolution, mediates both rapid signalling and transcriptional regulation. Oestrogen mimetics (such as phytooestrogens and xenooestrogens including endocrine disruptors) and licensed drugs such as selective oestrogen receptor modulators (SERMs) and downregulators (SERDs) also modulate oestrogen receptor activity in both health and disease. Following up on our previous Review of 2011, we herein summarize the progress made in the field of GPER research over the past decade. We will review molecular, cellular and pharmacological aspects of GPER signalling and function, its contribution to physiology, health and disease, and the potential of GPER to serve as a therapeutic target and prognostic indicator of numerous diseases. We also discuss the first clinical trial evaluating a GPER-selective drug and the opportunity of repurposing licensed drugs for the targeting of GPER in clinical medicine.

Challenges in the evaluation of endothelial cell dysfunction: a statement from the European Society of Hypertension Working Group on Endothelin and Endothelial Factors.

Endothelial cell function is mediated by different mechanisms in different vascular beds. Moreover, in humans, endothelial cell dysfunction triggers and accelerates the progression of cardiovascular and chronic kidney diseases. Progression of such diseases can be in part mitigated by the control of cardiovascular risk factors and drugs targeting different systems, including endothelin receptor antagonists (ERAs), renin-angiotensin aldosterone antagonists and agents affecting glucose metabolism, all of which were shown to improve endothelial cell function. In recent years, the microRNAs, which are endogenous regulators of gene expression, have been identified as transmitters of information from endothelial cells to vascular smooth muscle cells, suggesting that they can entail tools to assess the endothelial cell dysfunction in arterial hypertension and target for pharmacologic intervention. This article critically reviews current challenges and limitations of available techniques for the invasive and noninvasive assessment of endothelial cell function, and also discusses therapeutic aspects as well as directions for future research in the areas of endothelial cell biology and pathophysiology in humans.

Childhood obesity: a life-long health risk.

Childhood obesity has become major health concern for physicians, parents, and health agencies around the world. Childhood obesity is associated with an increased risk for other diseases not only during youth but also later in life, including diabetes, arterial hypertension, coronary artery disease, and fatty liver disease. Importantly, obesity accelerates atherosclerosis progression already in children and young adults. With regard to pathophysiological changes in the vasculature, the striking similarities between physiological changes related to aging and obesity-related abnormalities are compatible with the concept that obesity causes "premature" vascular aging. This article reviews factors underlying the accelerated vascular disease development due to obesity. It also highlights the importance of recognizing childhood obesity as a disease condition and its permissive role in aggravating the development of other diseases. The importance of childhood obesity for disease susceptibility later in life, and the need for prevention and treatment are also discussed.

Clinical efficacy and safety of angiogenesis inhibitors: sex differences and current challenges.

Vasoactive molecules, such as vascular endothelial growth factor (VEGF) and endothelins, share cytokine-like activities and regulate endothelial cell (EC) growth, migration, and inflammation. Some endothelial mediators and their receptors are targets for currently approved angiogenesis inhibitors, drugs that are either monoclonal antibodies raised towards VEGF, or inhibitors of vascular receptor protein kinases and signalling pathways. Pharmacological interference with the protective functions of ECs results in a similar spectrum of adverse effects. Clinically, the most common side effects of VEGF signalling pathway inhibition include an increase in arterial pressure, left ventricular dysfunction facilitating the development of heart failure, thromboembolic events including pulmonary embolism and stroke, and myocardial infarction. Sex steroids, such as androgens, progestins, and oestrogens and their receptors (ERα, ERß, GPER; PR-A, PR-B; AR) have been identified as important modifiers of angiogenesis, and sex differences have been reported for anti-angiogenic drugs. This review article discusses the current challenges clinicians are facing with regard to angiogenesis inhibitor therapy, including the need to consider sex differences affecting clinical efficacy and safety. We also propose areas for future research taking into account the role of sex hormone receptors and sex chromosomes. Development of new sex-specific drugs with improved target- and cell-type selectivity likely will open the way to personalized medicine in men and women requiring anti-angiogenic therapy to reduce adverse effects and to improve therapeutic efficacy.

Therapeutic potential of endothelin receptor antagonists for chronic proteinuric renal disease in humans.

Diabetes and arterial hypertension continue to be the main causes of chronic renal failure in 2010, with a rising prevalence in part due to the worldwide obesity epidemic. Proteinuria is a main feature of chronic renal disease and mediated by defects in the glomerular filtration barrier and is as a good predictor of cardiovascular events. Indeed, chronic renal disease due to glomerulosclerosis is one of the important risk factors for the development of coronary artery disease and stroke. Glomerulosclerosis develops in response to inflammatory activation and increased growth factor production. Preclinical and first preliminary clinical studies provide strong evidence that endogenous endothelin-1 (ET-1), a 21-amino-acid peptide with strong growth-promoting and vasoconstricting properties, plays a central role in the pathogenesis of proteinuria and glomerulosclerosis via activation of its ET(A) subtype receptor involving podocyte injury. These studies have not only shown that endothelin participates in the disease processes of hypertension and glomerulosclerosis but also that features of chronic renal disease such as proteinuria and glomerulosclerosis are reversible processes. Remarkably, the protective effects of endothelin receptors antagonists (ERAs) are present even on top of concomitant treatments with inhibitors of the renin-angiotensin system. This review discusses current evidence for a role of endothelin for proteinuric renal disease and podocyte injury in diabetes and arterial hypertension and reviews the current status of endothelin receptor antagonists as a potential new treatment option in renal medicine.

Regulatory role of G protein-coupled estrogen receptor for vascular function and obesity.

We found that the selective stimulation of the intracellular, transmembrane G protein-coupled estrogen receptor (GPER), also known as GPR30, acutely lowers blood pressure after infusion in normotensive rats and dilates both rodent and human arterial blood vessels. Stimulation of GPER blocks vasoconstrictor-induced changes in intracellular calcium concentrations and vascular tone, as well as serum-stimulated cell proliferation of human vascular smooth muscle cells. Deletion of the GPER gene in mice abrogates vascular effects of GPER activation and is associated with visceral obesity. These findings suggest novel roles for GPER in protecting from cardiovascular disease and obesity.

The discovery of endothelium-dependent contraction: the legacy of Paul M. Vanhoutte.

This article summarizes the discovery and the development of endothelial biology with a special focus on the role of endothelium-dependent vasoconstriction. The physician-scientist Paul Michel Vanhoutte contributed many of the initial observations that helped to understand and form the main concepts of modern vascular biology involving endothelial regulation. His laboratory was the first to report endothelial cell-derived vasoconstriction in 1981, followed by the characterization of an endothelium-derived constricting factor published by Hickey et al. in 1985, which was later identified as the endothelin peptide by Yanagisawa et al. in 1988. The identification of the receptor subtypes of this endothelial vasocontrictor two years later, which were named ET(A) and ET(B) receptors according to suggestions put forward by Vanhoutte, ultimately resulted in the development of the only new class of drugs that is entirely based on endothelial cell research. More than a quarter century after Vanhoutte's initial description of endothelial vasoconstriction, this first drug class specifically targeting an endothelial vasoconstrictor, the endothelin receptor antagonists, has been firmly established in cardiovascular medicine for the treatment of pulmonary hypertension. This novel therapeutic principle had its beginnings in Vanhoutte's discovery made 30 years ago.

Serum from Patients with Severe Alcoholic Liver Cirrhosis Inhibits Proliferation and Migration of Human Coronary Artery Smooth Muscle Cells.

Liver cirrhosis has been associated with an increased risk of coronary artery disease and clinical complications following percutaneous coronary revascularization. The present study is based on the hypothesis that cirrhosis may influence intimal hyperplasia following PCI. Sera from 10 patients with alcoholic liver cirrhosis and 10 age-matched healthy controls were used to stimulate cultured human coronary artery smooth muscle cells (HCASMC) for 48 h. HCASMC proliferation, migration, gene expression and apoptosis were investigated. Serum concentrations of growth factors and markers of liver function were also determined in patients and healthy controls. Treatment of HCASMC with patient sera reduced cell proliferation and migration (p < 0.05 vs. healthy controls), whereas apoptosis was unaffected (p = 0.160). Expression of genes associated with a synthetic vascular smooth muscle cell phenotype was decreased in cells stimulated with serum from cirrhotic patients (RBP1, p = 0.001; SPP1, p = 0.003; KLF4, p = 0.004). Platelet-derived growth factor-BB serum concentrations were lower in patients (p = 0.001 vs. controls). The results suggest the presence of circulating factors in patients with alcoholic liver cirrhosis affecting coronary smooth muscle cell growth. These findings may have implications for clinical outcomes following percutaneous coronary revascularization in these patients.