17Beta-estradiol attenuates PDGF signaling in vascular smooth muscle cells at the postreceptor level

Systems genetics and bioinformatics analyses using ESR1-correlated genes identify potential candidates underlying female bone development

Estrogen receptor α (ESR1) is involved in E2 signaling and plays a major role in postmenopausal bone loss. However, the molecular network underlying ESR1 has not been explored. We used systems genetics and bioinformatics to identify important genes associated with Esr1 in postmenopausal bone loss. We identified ~2300 Esr1-coexpressed genes in female BXD bone femur, functional analysis of which revealed 'osteoblast signaling' as the most enriched pathway. PPI network led to the identification of 25 'female bone candidates'. The gene-regulatory analysis revealed RUNX2 as a key TF. ANKRD1 and RUNX2 were significantly different between osteoporosis patients and healthy controls. Sp7, Col1a1 and Pth1r correlated with multiple femur bone phenotypes in BXD mice. miR-3121-3p targeted Csf1, Ankrd1, Sp7 and Runx2. β-estradiol treatment markedly increased the expression of these candidates in mouse osteoblast. Our study revealed that Esr1-correlated genes Ankrd1, Runx2, Csf1 and Sp7 may play important roles in female bone development.

Gender differences in GRK2 in cardiovascular diseases and its interactions with estrogen

G protein-coupled receptor kinase 2 (GRK2) is a multifunctional protein involved in regulating G protein-coupled receptor (GPCR) and non-GPCR signaling in the body. In the cardiovascular system, increased expression of GRK2 has been implicated in the occurrence and development of several cardiovascular diseases (CVDs). Recent studies have found gender differences in GRK2 in the cardiovascular system under physiological and pathological conditions, where GRK2's expression and activity are increased in males than in females. The incidence of CVDs in premenopausal women is lower than in men of the same age, which is related to estrogen levels. Given the shared location of GRK2 and estrogen receptors, estrogen may interact with GRK2 by modulating vital molecules such as calmodulin (CaM), caveolin, RhoA, nitrate oxide (NO), and mouse double minute 2 homolog (Mdm2), via signaling pathways mediated by estrogen's genomic (ERα and ERβ), and non-genomic (GPER) receptors, conferring cardiovascular protection in females. Highlighting the gender differences in GRK2 and understanding its interaction with estrogen in the cardiovascular system is pertinent in treating gender-related CVDs. As a result, this article explores the gender differences of GRK2 in the cardiovascular system and its relationship with estrogen during disease conditions. Estrogen's protective and therapeutic effects and its mechanism on GRK2-related cardiovascular diseases have also been discussed.

Women-specific factors to consider in risk, diagnosis and treatment of cardiovascular disease

In the era of individualized medicine, gaps in knowledge remain about sex-specific risk factors, diagnostic and treatment options that might reduce mortality from cardiovascular disease (CVD) and improve outcomes for both women and men. In this review, contributions of biological mechanisms involving the sex chromosomes and the sex hormones on the cardiovascular system will be discussed in relationship to the female-specific risk factors for CVD: hypertensive disorders of pregnancy, menopause and use of hormonal therapies for contraception and menopausal symptoms. Additionally, sex-specific factors to consider in the differential diagnosis and treatment of four prevalent CVDs (hypertension, stroke, coronary artery disease and congestive heart failure) will be reviewed with emphasis on areas where additional research is needed.

STAT5a/b contribute to sex bias in vascular disease: A neuroendocrine perspective

Previous studies have elucidated a neuroendocrine mechanism consisting of the hypothalamus (growth hormone releasing hormone, GHRH) - pituitary (growth hormone, GH) - STAT5a/b axis that underlies sex-biased gene expression in the liver. It is now established that male vs female patterned secretion of GHRH, and thus of circulating GH levels ("pulsatile" vs "more continuous" respectively), leading to differently patterned activation of PY-STAT5a/b in hepatocytes results in sex-biased gene expression of cohorts of hundreds of downstream genes. This review outlines new data in support of a STAT5a/b-based mechanism of sex bias in the vascular disease pulmonary hypertension (PH). Puzzling observations in PH include its 2-4-fold higher prevalence in women but a male-dominance in many rodent models, and, paradoxically, inhibition of PH development by estrogens in such models. We observed that conditional deletion of STAT5a/b in vascular smooth muscle cells (SMC) in mice converted the male-dominant model of chronic hypoxia-induced PH into a female-dominant phenotype. In human idiopathic PH, there was reduced STAT5a/b and PY-STAT5 in cells in late-stage obliterative pulmonary arterial lesions in both men and women. A juxtaposition of the prior liver data with the newer PH-related data drew attention to the hypothalamus-GH-STAT5 axis, which is the major target of estrogens at the level of the hypothalamus. This hypothesis explains many of the puzzling aspects of sex bias in PH in humans and rodent models. The extension of STAT5-anchored mechanisms of sex bias to vascular disease emphasizes the contribution of central neuroendocrine processes in generating sexual dimorphism in different tissues and cell types.

17β-Estradiol inhibits vascular smooth muscle cell migration via up-regulation of striatin protein

Striatin, an estrogen receptor (ER)-interacting protein, plays an important role in estrogen's nongenomic actions in vascular endothelial cells. However, the role of striatin in VSMCs is unknown. Here, we investigated the role of striatin in estrogen-regulated VSMCs migration. 17β-Estradiol (E2) at 10 nM largely inhibited VSMCs migration, which was reversed by the silencing of striatin expression. E2 increased striatin protein expression in a dose- and time-dependent manner. ERα agonist PPT, but not ERβ agonist DPN, mimicked the regulatory effect of E2. The regulatory effect of E2 on striatin protein expression was blocked by the pure ER antagonist ICI 182,780 or the mitogen-activated protein kinase inhibitor PD98059, but not by the phosphatidylinositol-3 kinase inhibitor wortmannin or Src inhibitor PP2, suggesting that E2 increased striatin protein expression via extracellular-signal regulated kinase 1/2 (ERK1/2). E2 resulted in phosphorylation of ERK1/2 in a time-dependent manner. The silencing of ERK1/2 largely abolished E2-enhanced striatin expression. Finally, the inhibitory effect of E2 on VSMC migration was reversed by ICI 182,780 or PD98059. Taken together, our results indicate that E2 inhibits VSMC migration by increasing striatin expression via ERα to ERK1/2 pathway, which maybe helpful to understand estrogen's anti-atherogenic effect in VSMCs.

Endocrine disruptors differently influence estrogen receptor β and androgen receptor in male and female rat VSMC

Sex steroid hormones differently control the major physiological processes in male and female organisms. In particular, their effects on vascular smooth muscle cells (VSMCs) migration are at the root of sex/gender-related differences reported in the cardiovascular system. Several exogenous substances, defined endocrine disruptor chemicals (EDCs), could interfere with these androgen and estrogen effects; however, the sex/gender-related susceptibility of VSMC motility to EDCs is completely unknown. Here, the effect of naturally occurring (naringenin, Nar) and synthetic (bisphenol A, BPA) EDCs on male and female VSMC motility has been evaluated. 17β-estradiol (E2, 0.1 nM-1 µM) induced a dose-dependent inhibition of motility in female-derived VSMC. In contrast, neither dihydrotestosterone (DHT, 0.01-100 nM) nor the common precursor of sex steroid hormones, testosterone (Tes, 0.01-100 nM) modified male-derived VSMC motility. Estrogen receptor (ER) β subtype-dependent activation of p38 was necessary for the E2 effect on cell motility. High BPA concentration prevented E2 effects in female-derived cells being without any effect in male-derived cells. Nar mimicked E2 effects on female-derived cells even in the presence of E2 or BPA. Intriguingly, Nar also inhibited the male-derived VSMC mobility. This latter effect was prevented by ERβ inhibitor, but not by the androgen receptor (AR) inhibitor. As a whole, ERβ-dependent signals in VSMC results more susceptible to the impact of EDCs than AR signals suggesting a possible high and overall susceptibility of female to EDCs. However, several male-derived cells, including VSMC, express ERβ, which could also serve as target of EDC disruption in male organisms.

The Process and Development Mechanism of Age-related Fibrosis in the Pancreatic Islets of Sprague-Dawley Rats: Immunohistochemical Detection of Myofibroblasts and Suppression Effect by Estrogen Treatment

The mechanism of spontaneous islet fibrosis in Sprague-Dawley rats was investigated. Using sections of the pancreas in naive males aged 26 to 102 weeks old and 26-week-old males injected with β-estradiol 3-benzoate (EB), the incidence of lesions and histological scores of fibrosis were examined in conjunction with immunohistochemistry for α-smooth muscle actin (α-SMA), platelet-derived growth factor receptor-α (PDGFRα) and estrogen receptor-α (ERα). The incidence of islet fibrosis increased in 78-week-old animals compared to the 26-week-old animals, and the incidence of atrophy in the fibrotic islet increased in animals over 52 weeks old. α-SMA and PDGFRα were positively stained mainly in fibrotic/inflammatory islets, and the histological score of α-SMA in the fibrotic islet decreased age-dependently. Notably, α-SMA and PDGFRα were co-expressed in inflammatory islets with a high score at all ages. The positive index of ERα in the EB-treated group increased when compared with that of the naive group. However, it was independent of the existence of fibrosis. In contrast, the score of α-SMA and PDGFRα decreased in the EB-treated group. In conclusion, it was clarified that a part of age-related fibrosis in islets became atrophy with age, and α-SMA-positive myofibroblasts were considered to contribute to the development of fibrosis. Strong PDGFRα stainability in fibrotic/inflammatory islets may imply that myofibroblasts were stimulated by PDGF to produce an extracellular matrix. Although estradiol has been known to suppress fibrosis/inflammation in the islet, nuclear-located ER-dependent signaling was considered not to be involved in the suppression mechanism. EB possibly affected the inhibition of the appearance of myofibroblasts.

Estrogens and atherosclerosis: insights from animal models and cell systems

Estrogens not only play a pivotal role in sexual development but are also involved in several physiological processes in various tissues including vasculature. While several epidemiological studies documented an inverse relationship between plasma estrogen levels and the incidence of cardiovascular disease and related it to the inhibition of atherosclerosis, an interventional trial showed an increase in cardiovascular events among postmenopausal women on estrogen treatment. The development of atherosclerotic lesions involves complex interplay between various pro- or anti-atherogenic processes that can be effectively studied only in vivo in appropriate animal models. With the advent of genetic engineering, transgenic mouse models of atherosclerosis have supplemented classical dietary cholesterol-induced disease models such as the cholesterol-fed rabbit. In the last two decades, these models were widely applied along with in vitro cell systems to specifically investigate the influence of estrogens on the development of early and advanced atherosclerotic lesions. The present review summarizes the results of these studies and assesses their contribution toward better understanding of molecular mechanisms underlying anti- and/or pro-atherogenic effects of estrogens in humans.

Cellular and molecular actions displayed by estrone on vascular endothelium

In this work we provide evidence that estrone "per se" modulates cellular endothelial growth and survival, events that play key roles in the development of vascular disease. Moreover, under oxidative stress conditions the hormone prevented apoptosis triggered by hydrogen peroxide. Although estrone did not affect E-selectin and VCAM-1 mRNAs synthesis, the hormone prevented the expression of these adhesion molecules induced by the proinflammatory agent LPS. The steroid partially attenuated leukocyte adhesion not only under basal conditions but also in the presence of LPS. Using ICI182780 compound as estrogen receptor antagonist, and PD98059 as MAPK inhibitor we obtained evidence that the mitogenic action of estrone involved the participation of ER and MAPK transduction pathway activation. The presence of estradiol impaired the effect of estrone on cell proliferation and vasoactive production. These results suggest that estrone exhibits a remarkable biological action on endothelial cells, modulating vasoactive production, proliferation, apoptosis, and cell adhesion events.

The CNS microvascular pericyte: pericyte-astrocyte crosstalk in the regulation of tissue survival

The French scientist Charles Benjamin Rouget identified the pericyte nearly 140 years ago. Since that time the role of the pericyte in vascular function has been difficult to elucidate. It was not until the development of techniques to isolate and culture pericytes that scientists have begun to understand the true impact of this unique cell in the maintenance of tissue homeostasis. In the brain the pericyte is an integral cellular component of the blood-brain barrier and, together with other cells of the neurovascular unit (endothelial cells, astrocytes and neurons) the pericyte makes fine-tuned regulatory adjustments and adaptations to promote tissue survival. These regulatory changes involve trans-cellular communication networks between cells. In this review we consider evidence for cell-to-cell crosstalk between pericytes and astrocytes during development and in adult brain.

Roles of oxidative stress and redox regulation in atherosclerosis

Oxidative stress is believed to be a cause of aging and cardiovascular disorders. In response to inflam-mation or endothelial cell injury, production of reactive oxygen species (ROS) is enhanced in vascular cells. These changes contribute to the initiation of atherosclerosis. Vascular cells possess anti-oxidant systems to protect against oxidative stress, in addition to the redox system. The redox status of pro-tein thiols is important for cellular functions. The Akt signaling pathway exerts effects on survival and apoptosis, and is regulated by the glutathione (GSH)/glutaredoxin (GRX)-dependent redox sys-tem. Sex hormones such as estrogens protect against oxidative stress by protecting the Akt signaling pathway but the physiological role of the extracellular GSH/GRX system has not been clarified, although found an increase in the levels of S-glutathionylated serum proteins in patients with athero-sclerosis obliterans. The results suggested that impaired serum redox potential is a marker of the development vascular dysfunction and estrogen has a possible role in the prevention of atherosclerosis.

17Beta-estradiol increases basal but not bradykinin-stimulated release of active t-PA in young postmenopausal women

Angiotensin-converting enzyme inhibition potentiates basal and bradykinin-stimulated tissue-type plasminogen activator (t-PA) release to a greater extent in women than in men. This study tested the hypothesis that 17beta-estradiol enhances the effect of angiotensin-converting enzyme inhibition on t-PA release in young postmenopausal women. We conducted a double-blind, prospective, crossover study in 14 young postmenopausal women (mean age 48.2+/-2.3 years) who were randomized to receive 17beta-estradiol (1 mg/d) or matching placebo for 4 weeks. At the end of each treatment period, we measured the effect of intraarterial infusion of bradykinin, methacholine, and nitroprusside on forearm blood flow and net t-PA release, before and during intraarterial enalaprilat (0.33 microg/min/100 mL forearm volume). 17Beta-estradiol significantly reduced baseline venous plasminogen activator inhibitor-1 antigen (4.4+/-1.4 versus 10.4+/-2.5 ng/mL, P=0.001) and t-PA antigen (5.5+/-0.6 versus 7.5+/-1.3 ng/mL, P=0.022) compared with placebo. 17Beta-estradiol increased basal forearm vascular release of active t-PA compared with placebo (1.2+/-0.3 IU/mL/min versus 0.4+/-0.1 IU/mL/min respectively, P=0.032), without increasing t-PA antigen release (P=0.761). Enalaprilat significantly increased basal net t-PA antigen release (from -0.8+/-1.0 to 3.2+/-1.2 ng/min/100 mL, P=0.012), but not the release of active t-PA, during either placebo or 17beta-estradiol. Enalaprilat potentiated bradykinin-stimulated vasodilation and t-PA antigen and activity release similarly during placebo and 17beta-estradiol treatment. 17Beta-estradiol treatment does not alter the effect of angiotensin-converting enzyme inhibition on basal t-PA antigen or on bradykinin-stimulated t-PA antigen or activity release. 17Beta-estradiol increases basal release of active t-PA in young postmenopausal women, consistent with enhanced vascular fibrinolytic function.

Decreased capillary filtration but maintained venous compliance in the lower limb of aging women

There are sex-related differences in venous compliance and capillary filtration in the lower limbs, which to some extent can explain the susceptibility to orthostatic intolerance in young women. With age, venous compliance and capacitance are reduced in men. This study was designed to evaluate age-related changes in venous compliance and capillary filtration in the lower limbs of healthy women. Included in this study were 22 young and 12 elderly women (23.1 +/- 0.4 and 66.4 +/- 1.4 yr). Lower body negative pressure (LBNP) of 11, 22, and 44 mmHg created defined transmural pressure gradients in the lower limbs. A plethysmographic technique was used on the calf to assess venous capacitance and net capillary filtration. Venous compliance was calculated with the aid of a quadratic regression equation. No age-related differences in venous compliance and capacitance were found. Net capillary filtration and capillary filtration coefficient (CFC) were lower in elderly women at a LBNP of 11 and 22 mmHg (0.0032 vs. 0.0044 and 0.0030 vs. 0.0041 ml.100 ml(-1).min(-1).mmHg(-1), P < 0.001). At higher transmural pressure (LBNP, 44 mmHg), CFC increased by approximately 1/3 (0.010 ml.100 ml(-1).min(-1).mmHg(-1)) in the elderly (P < 0.001) but remained unchanged in the young women. In conclusion, no age-related decrease in venous compliance and capacitance was seen in women. However, a decreased CFC was found with age, implying reduced capillary function. Increasing transmural pressure increased CFC in the elderly women, indicating an increased capillary susceptibility to transmural pressure load in dependent regions. These findings differ from earlier studies on age-related effects in men, indicating sex-specific vascular aging both in the venous section and microcirculation.