Mechanisms of estrogen receptor action in the myocardium. Rapid gene activation via the ERK1/2 pathway and serum response elements

HDAC5 inhibition attenuates ventricular remodeling and cardiac dysfunction

BACKGROUND

This study aimed to investigate the role of histone deacetylase 5 (HDAC5) in ventricular remodeling and explore the therapeutic potential of the HDAC5 inhibitor LMK235.

METHODS

A transverse aortic constriction (TAC) mouse model and angiotensin II (Ang II)-treated H9C2 cells were used to evaluate the effects of HDAC5 inhibition with LMK235 on ventricular remodeling and cardiac dysfunction. Additionally, the involvement of the extracellular signal-regulated kinase (ERK)/early growth response protein 1 (EGR1) signaling pathway in regulating myocyte enhancer factor 2 A (MEF2A) expression was assessed.

RESULTS

HDAC5 was upregulated in TAC mice and Ang II-treated H9C2 cells, suggesting its involvement in ventricular remodeling and cardiac dysfunction. LMK235 treatment significantly improved cardiac function in TAC mice and attenuated TAC-induced ventricular remodeling and Ang II-induced H9C2 cell hypertrophy. Mechanically, HDAC5 inhibition activated the ERK/EGR1 signaling pathway.

CONCLUSIONS

Our findings demonstrate that HDAC5 may suppress the activation of ERK/EGR1 signaling to regulate MEF2A expression and therefore participate in cardiac pathophysiology.

Sex-specific impact of diabetes mellitus on left ventricular systolic function and prognosis in heart failure

We aimed to investigate the sex differences in associations of diabetes mellitus (DM) with echocardiographic phenotypes and clinical outcomes of heart failure (HF). We studied 4,180 patients admitted for acute HF between 2009 and 2016 (median follow-up, 31.7 months) whose left ventricular global longitudinal strain (LV-GLS) data were available. Patients were compared by sex and DM. Structural equation model (SEM) analysis was performed to evaluate the moderating effects of two causal paths, via ischemic heart disease (IHD) and LV-GLS, linking DM with mortality. Compared to non-diabetic women, diabetic women had significantly lower LV-GLS (11.3% versus 10.1%, p < 0.001), but the difference was attenuated within men (9.7% versus 9.2%, p = 0.014) (p-for-interaction by sex = 0.018). In Cox analyses, DM was an independent predictor for higher mortality in both sexes (women: adjusted hazard ratio [HR] 1.35, 95% confidence interval [CI] 1.15–1.59 versus men: HR 1.24, 95% CI 1.07–1.44, p-for-interaction by sex = 0.699). Restricted cubic spline curves showed that LV-GLS consistently declined, and mortality increased in women with worsening hyperglycemia, but these trends were not evident in men. In SEM analysis, the main driver from DM to mortality differed by sex; men had a stronger effect via IHD than LV-GLS, whereas LV-GLS was the only predominant path in women.

Using 4-vinylcyclohexene diepoxide as a model of menopause for cardiovascular disease

There is a sharp rise in cardiovascular disease (CVD) risk and progression with the onset of menopause. The 4-vinylcyclohexene diepoxide (VCD) model of menopause recapitulates the natural, physiological transition through perimenopause to menopause. We hypothesized that menopausal female mice were more susceptible to CVD than pre- or perimenopausal females. Female mice were treated with VCD or vehicle for 20 consecutive days. Premenopausal, perimenopausal, and menopausal mice were administered angiotensin II (ANG II) or subjected to ischemia-reperfusion (I/R). Menopausal females were more susceptible to pathological ANG II-induced cardiac remodeling and cardiac injury from a myocardial infarction (MI), while perimenopausal, like premenopausal, females remained protected. Specifically, ANG II significantly elevated diastolic (130.9 ± 6.0 vs. 114.7 ± 6.2 mmHg) and systolic (156.9 ± 4.8 vs. 141.7 ± 5.0 mmHg) blood pressure and normalized cardiac mass (15.9 ± 1.0 vs. 7.7 ± 1.5%) to a greater extent in menopausal females compared with controls, whereas perimenopausal females demonstrated a similar elevation of diastolic (93.7 ± 2.9 vs. 100.5 ± 4.1 mmHg) and systolic (155.9 ± 7.3 vs. 152.3 ± 6.5 mmHg) blood pressure and normalized cardiac mass (8.3 ± 2.1 vs. 7.5 ± 1.4%) compared with controls. Similarly, menopausal females demonstrated a threefold increase in fibrosis measured by Picrosirus red staining. Finally, hearts of menopausal females (41 ± 5%) showed larger infarct sizes following I/R injury than perimenopausal (18.0 ± 5.6%) and premenopausal (16.2 ± 3.3, 20.1 ± 4.8%) groups. Using the VCD model of menopause, we provide evidence that menopausal females were more susceptible to pathological cardiac remodeling. We suggest that the VCD model of menopause may be critical to better elucidate cellular and molecular mechanisms underlying the transition to CVD susceptibility in menopausal women.NEW & NOTEWORTHY Before menopause, women are protected against cardiovascular disease (CVD) compared with age-matched men; this protection is gradually lost after menopause. We present the first evidence that demonstrates menopausal females are more susceptible to pathological cardiac remodeling while perimenopausal and cycling females are not. The VCD model permits appropriate examination of how increased susceptibility to the pathological process of cardiac remodeling accelerates from pre- to perimenopause to menopause.

Estradiol Treatment Initiated Early After Ovariectomy Regulates Myocardial Gene Expression and Inhibits Diastolic Dysfunction in Female Cynomolgus Monkeys: Potential Roles for Calcium Homeostasis and Extracellular Matrix Remodeling

Background

Left ventricular (LV) diastolic dysfunction often precedes heart failure with preserved ejection fraction, the dominant form of heart failure in postmenopausal women. The objective of this study was to determine the effect of oral estradiol treatment initiated early after ovariectomy on LV function and myocardial gene expression in female cynomolgus macaques.

Methods and Results

Monkeys were ovariectomized and randomized to receive placebo (control) or oral estradiol at a human‐equivalent dose of 1 mg/day for 8 months. Monkeys then underwent conventional and tissue Doppler imaging to assess cardiac function, followed by transcriptomic and histomorphometric analyses of LV myocardium. Age, body weight, blood pressure, and heart rate were similar between groups. Echocardiographic mitral early and late inflow velocities, mitral annular velocities, and mitral E deceleration slope were higher in estradiol monkeys (all P<0.05), despite similar estimated LV filling pressure. MCP1 (monocyte chemoattractant protein 1) and LV collagen staining were lower in estradiol animals (P<0.05). Microarray analysis revealed differential myocardial expression of 40 genes (>1.2‐fold change; false discovery rate, P<0.05) in estradiol animals relative to controls, which implicated pathways associated with better calcium ion homeostasis and muscle contraction and lower extracellular matrix deposition (P<0.05).

Conclusions

Estradiol treatment initiated soon after ovariectomy resulted in enhanced LV diastolic function, and altered myocardial gene expression towards decreased extracellular matrix deposition, improved myocardial contraction, and calcium homeostasis, suggesting that estradiol directly or indirectly modulates the myocardial transcriptome to preserve cardiovascular function.

Acute neuroestrogen blockade attenuates song-induced immediate early gene expression in auditory regions of male and female zebra finches

Neuron-derived estrogens are synthesized by aromatase and act through membrane receptors to modulate neuronal physiology. In many systems, long-lasting hormone treatments can alter sensory-evoked neuronal activation. However, the significance of acute neuroestrogen production is less understood. Both sexes of zebra finches can synthesize estrogens rapidly in the auditory cortex, yet it is unclear how this modulates neuronal cell signaling. We examined whether acute estrogen synthesis blockade attenuates auditory-induced expression of early growth response 1 (Egr-1) in the auditory cortex of both sexes. cAMP response element-binding protein phosphorylation (pCREB) induction by song stimuli and acute estrogen synthesis was also examined. We administered the aromatase inhibitor fadrozole prior to song exposure and measured Egr-1 across several auditory regions. Fadrozole attenuated Egr-1 in the auditory cortex greater in males than females. Females had greater expression and clustering of aromatase cells than males in high vocal center (HVC) shelf. Auditory-induced Egr-1 expression exhibited a large sex difference following fadrozole treatment. We did not observe changes in pCREB expression with song presentation or aromatase blockade. These findings are consistent with the hypothesis that acute neuroestrogen synthesis can drive downstream transcriptional responses in several cortical auditory regions, and that this mechanism is more prominent in males.

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.

Protective regulation of the ACE2/ACE gene expression by estrogen in human atrial tissue from elderly men

Data from animal experiments and clinical investigations suggest that components of the renin-angiotensin system are markedly affected by sex hormones. However, whether estrogen affects human atrial myocardium has not been investigated yet. In this study, we determined the effects of estrogen on key components of atrial renin-angiotensin system: angiotensin-converting enzyme, responsible for generation of angiotensin II and angiotensin-converting enzyme 2, counteracting majority of AngII effects, and different renin-angiotensin system receptors, AT1R, AT2R, and MAS. First, the expression levels of estrogen receptors mRNA were determined in right atrial appendages obtained from patients undergoing heart surgery. The amounts of estrogen receptor α and estrogen receptor β mRNA were similar between women ( n = 14) and men ( n = 10). Atrial tissue slices (350 µm) were prepared from male donors which were exposed to estrogen (1-100 nM; n = 21) or stimulated at 4 Hz for 24 h in the presence or absence of 100 nM estrogen ( n = 16), respectively. The administration of estrogen did not change mRNA levels of estrogen receptors, but activated MAP kinases, Erk1/2. Furthermore, estrogen increased the amounts of angiotensin-converting enzyme 2-mRNA (1.89 ± 0.23; P < 0.05) but reduced that of angiotensin-converting enzyme-mRNA (0.78 ± 0.07, P < 0.05). In addition, the transcript levels of AT2R and MAS were upregulated by estrogen. Pacing of tissue slices significantly increased the angiotensin-converting enzyme/angiotensin-converting enzyme 2 ratio at both the mRNA and protein level. During pacing, administration of estrogen substantially lowered the angiotensin-converting enzyme/angiotensin-converting enzyme 2 ratio at the transcript (0.92 ± 0.21 vs. 2.12 ± 0.27 at 4 Hz) and protein level (0.94 ± 0.20 vs. 2.14 ± 0.3 at 4 Hz). Moreover, estrogen elicited anti-inflammatory and anti-oxidative effects on renin-angiotensin system-associated downstream effectors such as pro-oxidative LOX-1 and pro-inflammatory ICAM-1. An antagonist of estrogen receptor α reversed these anti-inflammatory and anti-oxidative effects of estrogen significantly. Overall, our results demonstrated that estrogen modifies the local renin-angiotensin system homeostasis and achieves protective effects in atrial myocardium from elderly men. Impact statement The present study demonstrates that estrogen affects the human atrial myocardium and mediates protective actions through estrogen receptors-(ER) dependent signaling. Estrogen substantially modulates the local RAS via downregulation of ACE and simultaneous upregulation of ACE2, AT2R and MAS expression levels. This is indicative of a shift of the classical RAS/ACE axis to the alternative, protective RAS/ACE2 axis. In support of this view, estrogen attenuated the expression of RAS-associated downstream effectors, LOX-1, and ICAM-1. A specific antagonist of ERα reversed the anti-inflammatory and anti-oxidative effects of estrogen in paced and non-paced atrial tissue slices. In summary, our data demonstrate the existence of protective effects of estrogen in atrial tissue from elderly men which are at least in part, mediated by the regulation of local RAS homeostasis.

Mechanistic Pathways of Sex Differences in Cardiovascular Disease

Major differences between men and women exist in epidemiology, manifestation, pathophysiology, treatment, and outcome of cardiovascular diseases (CVD), such as coronary artery disease, pressure overload, hypertension, cardiomyopathy, and heart failure. Corresponding sex differences have been studied in a number of animal models, and mechanistic investigations have been undertaken to analyze the observed sex differences. We summarize the biological mechanisms of sex differences in CVD focusing on three main areas, i.e., genetic mechanisms, epigenetic mechanisms, as well as sex hormones and their receptors. We discuss relevant subtypes of sex hormone receptors, as well as genomic and nongenomic, activational and organizational effects of sex hormones. We describe the interaction of sex hormones with intracellular signaling relevant for cardiovascular cells and the cardiovascular system. Sex, sex hormones, and their receptors may affect a number of cellular processes by their synergistic action on multiple targets. We discuss in detail sex differences in organelle function and in biological processes. We conclude that there is a need for a more detailed understanding of sex differences and their underlying mechanisms, which holds the potential to design new drugs that target sex-specific cardiovascular mechanisms and affect phenotypes. The comparison of both sexes may lead to the identification of protective or maladaptive mechanisms in one sex that could serve as a novel therapeutic target in one sex or in both.

Targeted basic research to highlight the role of estrogen and estrogen receptors in the cardiovascular system

Epidemiological, clinical and animal studies revealed that sex differences exist in the manifestation and outcome of cardiovascular disease (CVD). The underlying molecular mechanisms implicated in these sex differences are not fully understood. The reasons for sex differences in CVD are definitely multifactorial, but major evidence points to the contribution of sex steroid hormone, 17β-estradiol (E2), and its receptors, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). In this review, we summarize past and present studies that implicate E2 and ER as important determinants of sexual dimorphism in the physiology and pathophysiology of the heart. In particular, we give an overview of studies aimed to reveal the role of E2 and ER in the physiology of the observed sex differences in CVD using ER knock-out mice. Finally, we discuss recent findings from novel transgenic mouse models, which have provided new information on the sexual dimorphic roles of ER specifically in cardiomyocytes under pathological conditions.

Expression, regulation and function of Egr1 during implantation and decidualization in mice

Abstract Early growth response gene 1 (Egr1), a zinc finger transcriptional factor, plays an important role in regulating cell proliferation, differentiation and angiogenesis. Current data have shown that Egr1 is involved in follicular development, ovulation, luteinization and placental angiogenesis. However, the expression, regulation and function of Egr1 in mouse uterus during embryo implantation and decidualization are poorly understood. Here we showed that Egr1 was strongly expressed in the subluminal stroma surrounding the implanting blastocyst on day 5 of pregnancy. Injection of Egr1 siRNA into the mouse uterine horn could obviously reduce the number of implanted embryos and affect the uterine vascular permeability. Further study found that Egr1 played a role through influencing the expression of cyclooxygenase-2 (Cox-2), microsomal prostaglandin E synthase 1 (mPGES-1), vascular endothelial growth factor (Vegf), transformation related protein 53 (Trp53) and matrix metallopeptidase 9 (Mmp9) genes in the process of mouse embryo implantation. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) might direct the expression of Egr1 in the uterine stromal cells. Under in vivo and in vitro artificial decidualization, Egr1 expression was significantly decreased. Overexpression of Egr1 downregulated the expression of decidual marker decidual/trophoblast PRL-related protein (Dtprp) in the uterine stromal cells, while inhibition of Egr1 upregulated the expression of Dtprp under in vitro decidualization. Estrogen and progesterone could regulate the expression of Egr1 in the ovariectomized mouse uterus and uterine stromal cells. These results suggest that Egr1 may be essential for embryo implantation and decidualization.

17β-Estradiol up-regulates Nrf2 via PI3K/AKT and estrogen receptor signaling pathways to suppress light-induced degeneration in rat retina

Human age-related retinal diseases, such as age-related macular degeneration (AMD), are intimately associated with decreased tissue oxygenation and hypoxia. Different antioxidants have been investigated to reverse AMD. In the present study, we describe the antioxidant 17β-estradiol (βE2) and investigate its protective effects on retinal neurons. Fourteen days after ovariectomy, adult Sprague-Dawley rats were exposed to 8000-lux light for 12h to induce retinal degeneration. Reactive oxygen species (ROS) levels were assessed by confocal fluorescence microscopy using 2,7-dichlorofluorescein diacetate. Nuclear factor erythroid 2-related factor 2 (Nrf2) and antioxidant enzyme mRNA expression were detected by real-time PCR. Western blotting was used to evaluate NRF2 activation. NRF2 translocation was determined by immunohistochemistry, with morphological changes monitored by hematoxylin and eosin staining. Following light exposure, βE2 significantly reduced ROS production. βE2 also up-regulated NRF2 mRNA and protein levels, with maximal expression at 4 and 12h post-exposure, respectively. Interestingly, following βE2 administration, NRF2 was translocated from the cytoplasm to the nucleus, primarily in the outer nuclear layer. βE2 also up-regulated NRF2, which triggered phase-2 antioxidant enzyme expression (superoxide dismutases 1 and 2, catalase, glutaredoxins 1 and 2, and thioredoxins 1 and 2), reduced ROS production, and ameliorated retinal damage. However, the beneficial effects of βE2 were markedly suppressed by pretreatment with LY294002 or ICI182780, specific inhibitors of the phosphatidylinositol 3-kinase-Akt (PI3K/AKT), and estrogen receptor (ER) signaling pathways, respectively. Taken together, these observations suggest that βE2 exerts antioxidative effects following light-induced retinal degeneration potentially via NRF2 activation. This protective mechanism may depend on two pathways: a rapid, non-genomic-type PI3K/AKT response, and a genomic-type ER-dependent response. Our data provide evidence that βE2 is a potentially effective in the treatment of retinal degeneration diseases.

Sex differences and rapid estrogen signaling: A look at songbird audition

The actions of estrogens have been associated with brain differentiation and sexual dimorphism in a wide range of vertebrates. Here we consider the actions of brain-derived 'neuroestrogens' in the forebrain and the accompanying differences and similarities observed between males and females in a variety of species. We summarize recent evidence showing that baseline and fluctuating levels of neuroestrogens within the auditory forebrain of male and female zebra finches are largely similar, and that neuroestrogens enhance auditory representations in both sexes. With a comparative perspective we review evidence that non-genomic mechanisms of neuroestrogen actions are sexually differentiated, and we propose a working model for nonclassical estrogen signaling via the MAPK intracellular signaling cascade in the songbird auditory forebrain that is informed by the way sex differences may be compensated. This view may lead to a more comprehensive understanding of how sex influences estradiol-dependent modulation of sensorimotor representations.

The influence of steroid receptor status on the cardiotoxicity risk in HER2-positive breast cancer patients receiving trastuzumab

INTRODUCTION

Expression of steroid receptors and HER2 overexpression in breast cancer cells are predictive and prognostic factors. Overexpression of HER2 allows the use of immunotherapy, in which the most serious side effect is cardiotoxicity. The aim of this study was to evaluate the influence of steroid receptor status on cardiotoxicity risk in HER2 breast cancer patients receiving trastuzumab both in adjuvant treatment and in the case of disease dissemination. This study also assessed well-known cardiac risk factors.

MATERIAL AND METHODS

The study was conducted on 166 patients who received immunotherapy in the Clinical and Experimental Oncology Department, between the years 2006 and 2012.

RESULTS

A predisposition to cardiac side effects (13% vs. 5%) in patients with negative steroid receptor status was observed (p = 0.08). The decrease of left ventricular ejection fraction (LVEF) (12% vs. 0) and cardiac adverse side effects (2% vs. 0) were detected only in ER-/PR- patients but without statistical significance. Discontinuation of therapy because of cardiotoxicity was associated with negative receptor status (33% vs. 7%) (p = 0.019). Irrespective of steroid receptor status, older age of patients (p = 0.009) and previous radiotherapy to the left side of the chest (p = 0.02) were associated with the occurrence of cardiotoxicity and decrease of LVEF. In patients who received previous anthracycline-based chemotherapy, acute cardiac side effects were observed significantly more often (p = 0.01).

CONCLUSIONS

There was no influence of steroid receptor status on the cardiac side effects. Breast cancer type containing Erb-B2 overexpression was associated with predisposition to cardiotoxicity. The results require confirmation in a larger group of patients.

In vivo oestrogenic modulation of Egr1 and Pitx1 gene expression in female rat pituitary gland

EGR1 and PITX1 are transcription factors required for gonadotroph cell Lhb promoter activation. To determine changes in Egr1 and Pitx1 mRNA levels in central and peripheral pituitary stimulations, an in vivo model based on i.c.v. pulsatile (1 pulse/0.5 h over 2 h) GnRH agonist (1.5 nM buserelin) or antagonist (2 nM antide) microinjections was used. The microinjections were given to ovariectomised and 17β-oestradiol (E2) (3×20 μg), ERA (ESR1) agonist propyl pyrazole triol (PPT) (3×0.5 mg), ERB (ESR2) agonist diarylpropionitrile (DPN) (3×0.5 mg) s.c. pre-treated rats 30 min after last pulse anterior pituitaries were excised. Relative mRNA expression was determined by quantitative RT-PCR (qRT-PCR). Results revealed a gene-specific response for GnRH and/or oestrogenic stimulations in vivo. Buserelin pulses enhanced Egr1 expression by 66% in ovariectomised rats, whereas the oestradiol-supplemented+i.c.v. NaCl-microinjected group showed a 50% increase in Egr1 mRNA expression. The oestrogenic signal was transmitted via ERA (ESR1) and ERB (ESR2) activation as administration of PPT and DPN resulted in 97 and 62%, respectively, elevation in Egr1 mRNA expression. A synergistic action of GnRH agonist and 17β-oestradiol (E2) stimulation of the Egr1 gene transcription in vivo were found. GnRHR activity did not affect Pitx1 mRNA expression; regardless of NaCl, buserelin or antide i.c.v. pulses, s.c. oestrogenic supplementation (with E2, PPT or DPN) consistently decreased (by -46, -48 and -41% respectively) the Pitx1 mRNA in the anterior pituitary gland. Orchestrated Egr1 and Pitx1 activities depending on specific central and peripheral regulatory inputs could be responsible for physiologically variable Lhb gene promoter activation in vivo.

cAMP response element-binding protein interacts with and stimulates the proteasomal degradation of the nuclear receptor coactivator GRIP1

The glucocorticoid receptor interacting protein (GRIP1) belongs to the p160 steroid receptor coactivator family that plays essential roles in nuclear receptor-dependent transcriptional regulation. Previously, we reported that the cAMP-dependent protein kinase (PKA) induces ubiquitination leading to degradation of GRIP1. Here we show that the cAMP response element-binding protein (CREB) downregulates GRIP1 and is necessary for the PKA-stimulated degradation of GRIP1, which leads to changes in the expression of a subset of genes regulated by estrogen receptor-α in MCF-7 breast cancer cells. Our data of domain-mapping and ubiquitination analyses suggest that CREB promotes the proteasomal breakdown of ubiquitinated GRIP1 through 2 functionally independent protein domains containing amino acids 347 to 758 and 1121 to 1462. We provide evidence that CREB interacts directly with GRIP1 and that CREB Ser-133 phosphorylation or transcriptional activity is not required for GRIP1 interaction and degradation. The basic leucine zipper domain (bZIP) of CREB is important for the interaction with GRIP1, and deletion of this domain led to an inability to downregulate GRIP1. We propose that CREB mediates the PKA-stimulated degradation of GRIP1 through protein-protein interaction and stimulation of proteasomal degradation of ubiquitinated GRIP1.

Does oestradiol attenuate the damaging effects of a fructose-rich diet on cardiac Akt/endothelial nitric oxide synthase signalling?

Fructose-rich diets (FRD) cause cardiac insulin resistance manifested by impairment of Akt/endothelial NO synthase (eNOS) signalling. In contrast, oestradiol (E2) activates this signalling pathway in the heart. To study the ability of E2 to revert the detrimental effect of fructose on cardiac Akt/eNOS, female rats were subjected to a FRD and ovariectomy followed with or without E2 replacement. We also analysed the effects of the FRD and E2 on cardiac extracellular signal-regulated kinase (Erk 1/2) signalling related to their role in cardiac hypertrophy development. Expression of Akt, eNOS and Erk 1/2, as well as regulatory phosphorylations of these molecules were determined. The protein expression of cardiac Akt and eNOS was not affected by the diet or E2 treatment. However, the FRD was accompanied by a decrease in Akt phosphorylation at Ser(473) and Thr(308), and eNOS at Ser(1177), while the phosphorylation of eNOS at Thr(495) was increased. E2 replacement in ovariectomised fructose-fed rats caused a reversion of the diet effect on Akt and eNOS serine phosphorylation, but mostly had no effect on threonine phosphorylation of the molecules. The FRD and E2 treatment did not influence Erk 1/2 expression and phosphorylation and heart mass as well. The data show that E2 selectively suppress the negative effects of a FRD on Akt/eNOS signalling and probably point to the different effects of E2 on kinase/phosphatase pathways responsible for phosphorylation/dephosphorylation of Akt and eNOS. Furthermore, the results suggest that the heart of females in the reproductive period is partially protected against the damaging effects of increasedfructose intake.

Attenuation of salt-induced cardiac remodeling and diastolic dysfunction by the GPER agonist G-1 in female mRen2.Lewis rats

INTRODUCTION

The G protein-coupled estrogen receptor (GPER) is expressed in various tissues including the heart. Since the mRen2.Lewis strain exhibits salt-dependent hypertension and early diastolic dysfunction, we assessed the effects of the GPER agonist (G-1, 40 nmol/kg/hr for 14 days) or vehicle (VEH, DMSO/EtOH) on cardiac function and structure.

METHODS

Intact female mRen2.Lewis rats were fed a normal salt (0.5% sodium; NS) diet or a high salt (4% sodium; HS) diet for 10 weeks beginning at 5 weeks of age.

RESULTS

Prolonged intake of HS in mRen2.Lewis females resulted in significantly increased blood pressure, mildly reduced systolic function, and left ventricular (LV) diastolic compliance (as signified by a reduced E deceleration time and E deceleration slope), increased relative wall thickness, myocyte size, and mid-myocardial interstitial and perivascular fibrosis. G-1 administration attenuated wall thickness and myocyte hypertrophy, with nominal effects on blood pressure, LV systolic function, LV compliance and cardiac fibrosis in the HS group. G-1 treatment significantly increased LV lusitropy [early mitral annular descent (e')] independent of prevailing salt, and improved the e'/a' ratio in HS versus NS rats (P<0.05) as determined by tissue Doppler.

CONCLUSION

Activation of GPER improved myocardial relaxation in the hypertensive female mRen2.Lewis rat and reduced cardiac myocyte hypertrophy and wall thickness in those rats fed a high salt diet. Moreover, these advantageous effects of the GPER agonist on ventricular lusitropy and remodeling do not appear to be associated with overt changes in blood pressure.

Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies

Cardiac hypertrophy can be defined as an increase in heart mass. Pathological cardiac hypertrophy (heart growth that occurs in settings of disease, e.g. hypertension) is a key risk factor for heart failure. Pathological hypertrophy is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. In contrast, physiological cardiac hypertrophy (heart growth that occurs in response to chronic exercise training, i.e. the 'athlete's heart') is reversible and is characterized by normal cardiac morphology (i.e. no fibrosis or apoptosis) and normal or enhanced cardiac function. Given that there are clear functional, structural, metabolic and molecular differences between pathological and physiological hypertrophy, a key question in cardiovascular medicine is whether mechanisms responsible for enhancing function of the athlete's heart can be exploited to benefit patients with pathological hypertrophy and heart failure. This review summarizes key experimental findings that have contributed to our understanding of pathological and physiological heart growth. In particular, we focus on signaling pathways that play a causal role in the development of pathological and physiological hypertrophy. We discuss molecular mechanisms associated with features of cardiac hypertrophy, including protein synthesis, sarcomeric organization, fibrosis, cell death and energy metabolism and provide a summary of profiling studies that have examined genes, microRNAs and proteins that are differentially expressed in models of pathological and physiological hypertrophy. How gender and sex hormones affect cardiac hypertrophy is also discussed. Finally, we explore how knowledge of molecular mechanisms underlying pathological and physiological hypertrophy may influence therapeutic strategies for the treatment of cardiovascular disease and heart failure.

Melatonin-induced estrogen receptor alpha-mediated calbindin-D9k expression plays a role in H2O2-mediated cell death in rat pituitary GH3 cells

Calbindin-D9k (CaBP-9k) is a 9-kDa polypeptide possessing two calcium-binding sites that is expressed in the mammalian intestine, uterus, and pituitary gland. The factors regulating the expression of the estrogen receptor (ER) and CaBP-9k in the pituitary gland are currently unknown. In this study, we investigated whether the ER and CaBP-9k expression are regulated by melatonin during H(2)O(2)-induced cell death in rat pituitary GH3 cells. Cell survival increased by approximately 27-36% in H(2)O(2) plus melatonin compared to H(2)O(2) alone, and CaBP-9k expression was augmented by treatment with H(2)O(2) plus melatonin. These results suggest that the increase in cell survival and the melatonin-induced CaBP-9k expression may play a role in protecting cells against H(2)O(2)-mediated cell death. This result is also consistent with the increase in CaBP-9k expression leading to rises in p-ERK and p-Bad (S112). Over-expression of CaBP-9k caused an increase in p-ERK. ERalpha expression was higher in H(2)O(2) plus melatonin-treated cells compared to those treated with H(2)O(2) alone, while ERbeta expression was not. Also, ERalpha in the nuclear fraction increased in the presence of melatonin and decreased in the presence of ICI 182 780 or ICI 182 780 plus melatonin. The relative binding affinity of ERalpha for melatonin was higher than that of ERbeta, suggesting that melatonin has the potential to preferentially bind ERalpha. In conclusion, these results indicate that melatonin may increase CaBP-9k expression through ERalpha.

Estrogen receptor alpha interacts with 17beta-hydroxysteroid dehydrogenase type 10 in mitochondria

Estrogen receptor alpha (ERalpha) is present in the nucleus, the cytosol and in mitochondria. The rat ERalpha ligand binding domain was employed as bait in a bacterial two-hybrid screening of a human heart cDNA library to detect novel protein-protein interaction partners of ERalpha in the heart. 17beta-Hydroxysteroid dehydrogenase type 10 (17beta-HSD10), which converts potent (17beta-estradiol) to less potent estrogens (estrone), co-localized with 17beta-HSD10 in the mitochondria of rat cardiac myocytes. GST pull-down experiments confirmed the interaction of ERalpha and 17beta-HSD10. These findings suggest that the ERalpha estrogen receptor might be involved in regulating intracellular estrogen levels by modulating 17beta-HSD10 activity.

Non-nuclear actions of estrogen: new targets for prevention and treatment of cardiovascular disease

Gender-based differences in the incidence of hypertensive and coronary artery disease, the development of atherosclerosis, and myocardial remodeling after infarction are attributable to the indirect effect of estrogen on risk factor profiles, such as cholesterol levels, glucose metabolism, and insulin levels. More recent evidence, however, suggests that activated estrogen receptor (ER) mediates signaling cascades that culminate in direct protective effects such as vasodilation, inhibition of response to vessel injury, limiting myocardial injury after infarction, and attenuating cardiac hypertrophy. Although the ER is usually thought of as a ligand-dependent transcription factor, it can also rapidly mobilize signals at the plasma membrane and in the cytoplasm. Thus, a greater understanding of ER function and regulation may lead to the development of highly specific therapeutics that mediate the prevention and treatment of cardiovascular diseases.

Extranuclear steroid receptors: nature and actions

Rapid effects of steroid hormones result from the actions of specific receptors localized most often to the plasma membrane. Fast-acting membrane-initiated steroid signaling (MISS) leads to the modification of existing proteins and cell behaviors. Rapid steroid-triggered signaling through calcium, amine release, and kinase activation also impacts the regulation of gene expression by steroids, sometimes requiring integration with nuclear steroid receptor function. In this and other ways, the integration of all steroid actions in the cell coordinates outcomes such as cell fate, proliferation, differentiation, and migration. The nature of the receptors is of intense interest, and significant data suggest that extranuclear and nuclear steroid receptor pools are the same proteins. Insights regarding the structural determinants for membrane localization and function, as well as the nature of interactions with G proteins and other signaling molecules in confined areas of the membrane, have led to a fuller understanding of how steroid receptors effect rapid actions. Increasingly, the relevance of rapid signaling for the in vivo functions of steroid hormones has been established. Examples include steroid effects on reproductive organ development and function, cardiovascular responsiveness, and cancer biology. However, although great strides have been made, much remains to be understood concerning the integration of extranuclear and nuclear receptor functions to organ biology. In this review, we highlight the significant progress that has been made in these areas.

Temporal analysis of E2 transcriptional induction of PTP and MKP and downregulation of IGF-I pathway key components in the mouse uterus

17beta-Estradiol (E2) is well known to be associated with uterine cancer, endometriosis, and leiomyomas. Although insulin-like growth factor I (IGF-I) has been identified as a mediator of the uterotrophic effect of E2 in several studies, this mechanism is still not well understood. In the present study, identification of the genes modulated by a physiological dose of E2, in the uterus, has been done in ovariectomized mice using Affymetrix microarrays. The E2-induced genomic profile shows that multiple genes belonging to the IGF-I pathway are affected after exposure to E2. Two phases of regulation could be identified. First, from 0 to 6 h, the expression of genes involved in the cell cycle, growth factors, protein tyrosine phosphatases, and MAPK phosphatases is quickly upregulated by E2, while IGF-I receptor and several genes of the MAPK and phosphatidylinositol 3-kinase pathways are downregulated. Later, i.e., from 6 to 24 h, transporters and peptidases/proteases are stimulated, whereas defense-related genes are differentially regulated by E2. Finally, cytoarchitectural genes are modulated later. The present data show that a physiological dose of E2 induces, within 24 h, a series of transcriptional events that promote the uterotrophic effect. Among these, the E2-mediated activation of the IGF-I pathway seems to play a pivotal role in the uterotrophic effect. Furthermore, the protein tyrosine phosphatases and MAPK phosphatases are likely to modulate the estrogenic uterotrophic action by targeting, at different steps, the IGF-I pathway.

Estrogen-mediated activation of non-genomic pathway improves macrophages cytokine production following trauma-hemorrhage

Although 17beta-estradiol (E2) attenuates the alterations in Kupffer cells and splenic macrophages (MPhi) cytokine production following trauma-hemorrhage, the mechanism by which this occurs remains unknown. Utilizing a cell-impermeable E2 conjugated with BSA (E2-BSA), we examined the non-genomic effects of E2 on the above two cell population cytokine production, MAPK and transcription factors activation following trauma-hemorrhage. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean BP 40 mmHg for 90 min, then resuscitation). E2, E2-BSA (1 mg/kg E2) with or without an estrogen receptor antagonist (ICI 182,780), or vehicle was administrated during resuscitation. Two hrs thereafter, Kupffer cells and SMPhi production of IL-6, TNF-alpha, and IL-10, activation of MAPK (p38, ERK-1/2, and JNK), and transcription factors (NF-kappaB and AP-1) were determined. IL-6, TNF-alpha, and IL-10 productive capacity, MAPK, and transcription factors activation increased in Kupffer cells while they decreased in SMPhi following trauma-hemorrhage. However, E2 administration normalized all of these alterations. Although E2-BSA also attenuated the alterations in cytokine production/transcription factors, the values were higher in Kupffer cells and lower in SMPhi compared to shams. In contrast, E2-BSA prevented trauma-hemorrhage-mediated changes in MAPK activation to the same extent as E2. Co-administration of ICI 182,780 abolished E2-BSA effects. Although some MAPK inhibitors suppressed cytokine production, the inhibitor effectiveness was dependent on cytokine, cell type and animal condition (trauma-hemorrhage or sham). Thus, E2 effects on Kupffer cells and SMPhi cytokine production and transcription factors activation following trauma-hemorrhage are mediated at least in part via non-genomic pathway and these non-genomic effects are likely mediated via MAPK pathways.

Effects of flavonoids genistein and biochanin a on gene expression and their metabolism in human mammary cells

Genistein (GEN) and biochanin A (BCA), dietary isoflavones, possess breast cancer-preventive properties. Our objective was to examine the effect of physiologically relevant concentrations of BCA and GEN on gene expression in normal (HMEC), immortalized but nontumorigenic (MCF12A), and tumorigenic (MCF7) mammary cells and to determine whether the differences in gene expression are related to differences in metabolism in the three types of mammary cells. Using cDNA arrays, we compared the gene expression after a 48-h incubation with 1 microM BCA, GEN, or vehicle. Treatment with GEN or BCA produced the greatest number of significant changes in HMEC compared with MCF12A or MCF7 cells. Unlike GEN, effects of BCA on gene expression were mostly beneficial, involving induction of tumor suppressor genes. Different extents of metabolism were observed in the three mammary cell types; however, GEN concentrations were very low following either GEN or BCA administration in all of the three cell types. Because there were only very low concentrations of GEN, compared with BCA concentrations, in HMEC and MCF12A cells treated with BCA and different gene expression changes were found after BCA and GEN treatment, these findings suggest that BCA has distinct effects compared with GEN. The results suggest that BCA may represent a better breast cancer-preventive agent than GEN.

Estrogen-dependent growth and estrogen receptor (ER)-α concentration in T47D breast cancer cells are inhibited by VACM-1, a cul 5 gene

Vasopressin-activated calcium mobilizing receptor (VACM-1)/cullin 5 (cul 5) inhibits growth when expressed in T47D breast cancer cells by a mechanism that involves a decrease in MAPK phosphorylation and a decrease in the early growth response element (egr-1) concentration in the nucleus. Since both MAPK and egr-1 pathways can be regulated by 17beta-estradiol, we next examined the effects of VACM-1 cDNA expression on estrogen-dependent growth in T47D cells and on estrogen receptor (ER) concentrations. Our results demonstrate that in T47D cells, both basal and 17beta-estradiol-dependent increase in cell growth and MAPK phosphorylation were inhibited in cells transfected with VACM-1 cDNA. Further, Western blot and immunocytochemistry data analyses indicate that ER concentrations and its nuclear localization are significantly lower in cells transfected with VACM-1 cDNA when compared to controls. These data indicate that in the T47D cancer cell line VACM-1 inhibits growth by attenuating estrogen-dependent signaling responses. These findings may have implications in the development of cancer treatments.

The role of MAPKs in B cell receptor-induced down-regulation of Egr-1 in immature B lymphoma cells

Cross-linking of the B cell receptor (BCR) on the immature B lymphoma cell line BKS-2 induces growth inhibition and apoptosis accompanied by rapid down-regulation of the immediate-early gene egr-1. In these lymphoma cells, egr-1 is expressed constitutively and has a prosurvival role, as Egr-1-specific antisense oligonucleotides or expression of a dominant-negative inhibitor of Egr-1 also prevented the growth of BKS-2 cells. Moreover, enhancement of Egr-1 protein with phorbol 12-myristate 13-acetate or an egr-1 expression vector rescued BKS-2 cells from BCR signal-induced growth inhibition. Nuclear run-on and mRNA stability assays indicated that BCR-derived signals act at the transcriptional level to reduce egr-1 expression. Inhibitors of ERK and JNK (but not of p38 MAPK) reduced egr-1 expression at the protein level. Transcriptional regulation appears to have a role because egr-1 promoter-driven luciferase expression was reduced by ERK and JNK inhibitors. Promoter truncation experiments suggested that several serum response elements are required for MAPK-mediated egr-1 expression. Our study suggests that BCR signals reduce egr-1 expression by inhibiting activation of ERK and JNK. Unlike ERK and JNK, p38 MAPK reduces constitutive expression of egr-1. Unlike the immature B lymphoma cells, normal immature B cells did not exhibit constitutive MAPK activation. BCR-induced MAPK activation was modest and transient with a small increase in egr-1 expression in normal immature B cells consistent with their inability to proliferate in response to BCR cross-linking.

Therapeutic implications of the gender-specific aspects of cardiovascular disease

The manifestations of cardiovascular diseases differ between men and women, as do outcomes after therapeutic interventions. It is important that those involved in drug discovery and development, as well as disease treatment, are aware of these differences because such variations are likely to have an increasing role in therapeutic decisions in the future. Here, I review gender differences in the most frequent cardiovascular diseases and their underlying sex-dependent molecular pathophysiology, and discuss gender-specific effects of current cardiovascular drugs and the implications for novel strategies for drug development.

Estrogen down-regulates nicotine-induced adhesion molecule expression via nongenomic signal pathway in endothelial cells

Although gonadal hormone mostly causes genotropic actions through the members of nuclear receptor family, it also can regulate these actions via membrane receptor. To explore the possibility of plasma membrane estrogen receptors (mER) mediating genotropic events, we have investigated estrogen's effect on nicotine-stimulated adhesion molecule expression and evaluated whether this effect depends on calcium, MAPK signal pathway. Fluorescence Spectroscopy analysis of Ca2+ from human umbilical vein endothelial cells (HUVECs) showed through mER, estrogen induced a rapid rise of intracellular free Ca2+ concentration and this rise could not be inhibited by tamoxifen (classic ER inhibitor). In the context of nicotine stimulating, however, estrogen attenuated phosphorylation of mitogen-activated protein kinase (MAPK) family members, extracellular signal regulated kinase 1/2 (ERK1/2), p38 but not c-Jun-N-terminal kinase (JNK) in HUVECs and this effect could not still be prevented by tamoxifen. In the meantime, estrogen also down-regulated surface/soluble vascular cell adhesion molecule (VCAM-1, sVCAM-1) and endothelial selectin (E-selectin, sE-selectin) levels, which was not abolished by tamoxifen either. Moreover, calcium chelator BAPTA, ERK1/2 inhibitor PD98059, p38 inhibitor SB203580 significantly reduced the production of nicotine-activated surface/soluble VCAM-1 and E-selectin and both of the remained levels were no longer regulated by estrogen. Our study here provides the information of decrease effect of mER-mediated estrogen through Ca2+ and ERK1/2, p38 MAPK signaling pathway on nicotine-stimulated expression of surface/soluble VCAM-1 and E-selectin in HUVECs.

Egr-1 is activated by 17beta-estradiol in MCF-7 cells by mitogen-activated protein kinase-dependent phosphorylation of ELK-1

Early growth response-1 (Egr-1) is an immediate-early gene induced by E2 in the rodent uterus and breast cancer cells. E2 induces Egr-1 mRNA and protein levels in MCF-7 human breast cancer cells and reporter gene activity in cells transfected with pEgr-1A, a construct containing the -600 to +12 region of the Egr-1 promoter linked to the firefly luciferase gene. Deletion analysis of the Egr-1 promoter identified a minimal E2-responsive region of the promoter that contained serum response element (SRE)3 (-376 to -350) which bound Elk-1 and serum response factor (SRF) in gel mobility shift assays. Hormone-responsiveness of Egr-1 in MCF-7 cells was specifically inhibited by PD98059, a mitogen-activated protein kinase kinase inhibitor, but not by LY294002, an inhibitor of phosphatidylinositol-3-kinase (PI3-K). These results contrasted with hormone-dependent activation of the SRE in the c-fos promoter, which was inhibited by both PD98059 and LY294002. Differences in activation of the SREs in Egr-1 and c-fos were related to promoter sequence, which defines the affinities of Elk-1 and SRF to their respective binding sites. Thus, Egr-1, like c-fos, is activated through non-genomic (extranuclear) pathways of estrogen action in breast cancer cells.

Cross talk in hormonally regulated gene transcription through induction of estrogen receptor ubiquitylation

Estrogen tightly regulates the levels of circulating gonadotropins, but a direct effect of estrogen receptor alpha (ERalpha) on the mammalian LHbeta gene has remained poorly defined. We demonstrate here that ERalpha can associate with the LHbeta promoter through interactions with Sf-1 and Pitx1 without requiring an estrogen response element (ERE). We show that gonadotropin-releasing hormone (GnRH) promotes ERalpha ubiquitylation and also degradation while stimulating expression of ubc4. GnRH also increases the association and lengthens the cycling time of ERalpha on the LHbeta promoter. The ERalpha association and transactivation of the LHbeta gene, as well as ERalpha degradation, are increased following ubc4 overexpression, while the effects of GnRH are abated following ubc4 knockdown. Our results indicate that ERalpha ubiquitylation and subsequent transactivation of the LHbeta gene can be induced by increasing the levels of the E2 enzyme as a result of signaling by an extracellular hormone, thus providing a new form of cross talk in hormonally stimulated regulation of gene expression.

BDNF function in adult synaptic plasticity: the synaptic consolidation hypothesis

Interest in BDNF as an activity-dependent modulator of neuronal structure and function in the adult brain has intensified in recent years. Localization of BDNF-TrkB to glutamate synapses makes this system attractive as a dynamic, activity-dependent regulator of excitatory transmission and plasticity. Despite individual breakthroughs, an integrated understanding of BDNF function in synaptic plasticity is lacking. Here, we attempt to distill current knowledge of the molecular mechanisms and function of BDNF in LTP. BDNF activates distinct mechanisms to regulate the induction, early maintenance, and late maintenance phases of LTP. Evidence from genetic and pharmacological approaches is reviewed and tabulated. The specific contribution of BDNF depends on the stimulus pattern used to induce LTP, which impacts the duration and perhaps the subcellular site of BDNF release. Particular attention is given to the role of BDNF as a trigger for protein synthesis-dependent late phase LTP--a process referred to as synaptic consolidation. Recent experiments suggest that BDNF activates synaptic consolidation through transcription and rapid dendritic trafficking of mRNA encoded by the immediate early gene, Arc. A model is proposed in which BDNF signaling at glutamate synapses drives the translation of newly transported (Arc) and locally stored (i.e., alphaCaMKII) mRNA in dendrites. In this model BDNF tags synapses for mRNA capture, while Arc translation defines a critical window for synaptic consolidation. The biochemical mechanisms by which BDNF regulates local translation are also discussed. Elucidation of these mechanisms should shed light on a range of adaptive brain responses including memory and mood resilience.

Regulation of signal transduction pathways by estrogen and progesterone

The female sex steroid hormones 17beta-estradiol and progesterone mediate their biological effects on development, differentiation, and maintenance of reproductive tract and other target tissues through gene regulation by nuclear steroid receptors that function as ligand-dependent transcription factors. However, not all effects of 17beta-estradiol and progesterone are mediated by direct control of gene expression. These hormones also have rapid stimulatory effects on the activities of a variety of signal transduction molecules and pathways and, in many cases, these effects appear to be initiated from the plasma cell membrane. There is growing evidence that a subpopulation of the conventional nuclear steroid receptor localized at the cell membrane mediates many of the rapid signaling actions of steroid hormones; however, novel membrane receptors unrelated to conventional steroid receptors have also been implicated. This chapter reviews the nature of the receptors that mediate rapid signaling actions of estrogen and progesterone and describes the signaling molecules and pathways involved, the mechanisms by which receptors couple with components of signaling complexes and trigger responses, and the target tissues and cell functions regulated by this mode of steroid hormone action.

Mechanisms of estrogen receptor signaling: convergence of genomic and nongenomic actions on target genes

Estrogen receptors (ERs) act by regulating transcriptional processes. The classical mechanism of ER action involves estrogen binding to receptors in the nucleus, after which the receptors dimerize and bind to specific response elements known as estrogen response elements (EREs) located in the promoters of target genes. However, ERs can also regulate gene expression without directly binding to DNA. This occurs through protein-protein interactions with other DNA-binding transcription factors in the nucleus. In addition, membrane-associated ERs mediate nongenomic actions of estrogens, which can lead both to altered functions of proteins in the cytoplasm and to regulation of gene expression. The latter two mechanisms of ER action enable a broader range of genes to be regulated than the range that can be regulated by the classical mechanism of ER action alone. This review surveys our knowledge about the molecular mechanism by which ERs regulate the expression of genes that do not contain EREs, and it gives examples of the ways in which the genomic and nongenomic actions of ERs on target genes converge. Genomic and nongenomic actions of ERs that do not depend on EREs influence the physiology of many target tissues, and thus, increasing our understanding of the molecular mechanisms behind these actions is highly relevant for the development of novel drugs that target specific receptor actions.

Estrogen receptor-β mediates male-female differences in the development of pressure overload hypertrophy

The goal of this study was to determine the role of estrogen receptor subtypes in the development of pressure overload hypertrophy in mice. Epidemiological studies have suggested gender differences in the development of hypertrophy and heart disease, but the mechanism and the role of estrogen receptor subtypes are not established. We performed transverse aortic constriction (TAC) and sham operations in male and female wild-type (WT) mice and mice lacking functional estrogen receptor-α [α-estrogen receptor knockout (α-ERKO)] and mice lacking estrogen receptor-β (β-ERKO). Body, heart, and lung weights were measured 2 wk postsurgery. WT male mice subjected to TAC showed a 64% increase in the heart weight-to-body weight ratio (HW/BW) compared with sham, and WT males have increased lung weight at 2 wk. WT female mice subjected to TAC showed a 31% increase in HW/BW compared with sham, which was significantly less than their male counterparts and with no evidence of heart failure. α-ERKO females developed HW/BW nearly identical to that seen in WT littermate females in response to TAC, indicating that estrogen receptor-α is not essential for the attenuation of hypertrophy observed in WT females. In contrast, β-ERKO females responded to TAC with a significantly greater increase in HW/BW than WT littermate females. β-ERKO females have lower expression of lipoprotein lipase at baseline than WT or α-ERKO females. These data suggest an important role for estrogen receptor-β in attenuating the hypertrophic response to pressure overload in females.

17 Beta-estradiol and not genistein modulates lacI mutant frequency and types of mutation induced in the heart of ovariectomized big blue rats treated with 7, 12-dimethylbenz[a]anthracene

In industrialized countries, heart disease rates are higher among women after menopause. Recent studies indicate that consumption of phytoestorogens, e.g., isoflavones such as genistein (GE), may have potential cardiovascular health benefits; however, no studies have evaluated the effect of these agents on toxicant-induced damage in the heart. Since estrogen receptors are found in the heart, and GE mimics estrogenic effects, we have examined whether or not dietary GE or 17 beta-estradiol (E2) modulates the lacI mutant frequency (MF) in the heart of ovariectomized (OVX) Big Blue rats exposed to the model carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Groups of female rats were administered 80 mg/kg DMBA or vehicle by gavage and were chronically fed with diets containing 0, 250, or 1,000 microg/g GE or 5 microg/g E2. Sixteen weeks after carcinogen treatment, the animals were sacrificed and the hearts were removed and processed for determining the frequency and types of mutations in the heart tissue. GE and E2 supplementation alone resulted in nonsignificant increases in MF. The DMBA-induced lacI MF in the heart was sevenfold higher than the control (119.8 +/- 18.7 x 10(-6) vs. 17.4 +/- 3.2 x 10(-6); P < 0.001). GE in the diet had no significant effect on DMBA mutagenicity, while feeding E2 to DMBA-treated rats caused a significant reduction in the MF (119.8+/- 18.7 x 10(-6) vs. 61.4 +/- 13.5 x 10(-6); P < 0.017). DNA sequence analysis revealed that the majority of DMBA-induced mutations in rats fed control diet were A:T-->T:A (42%) and G:C-->T:A (19%) transversions, followed by G:C-->A:T (13%) and A:T-->G:C (8%) transitions. Feeding E2 altered the DMBA-induced mutational spectra by decreasing A:T-->T:A (23%) and G:C-->T:A (13%) transversions and increasing G:C-->A:T (24%) and A:T-->G:C (21%) transitions. Taken together, the results suggest that DMBA can induce gene mutations in heart tissue of OVX rats, and while dietary GE had little or no effect on DMBA-induced mutation, dietary E2 reduced the mutagenicity of DMBA.

Morphological effects of estrogen on cholinergic neurons in vitro involves activation of extracellular signal-regulated kinases

In the present study, we examined the ability of estrogen to enhance cholinergic neurite arborization in vitro and identified the signal transduction cascade associated with this effect. Basal forebrain primordia collected from rat pups on postnatal day 1 were cultured for 2 weeks and then treated with 5 nm 17beta-estradiol for 24 hr. Cholinergic neurons were identified immunocytochemically with an antibody against the vesicular acetylcholine transporter and digitally photographed. Morphological analysis indicated that female cultures respond to estrogen treatment with an increase in total neurite length per neuron (4.5-fold over untreated controls) and in total branch segment number per neuron (2.3-fold over controls). In contrast, there was no change in total neurite length per neuron in male cultures, and we also observed a decrease in total branch segment number per neuron (0.5-fold below controls). Detailed histograms indicated that estrogen increases primary and secondary branch length and number and also increases terminal neuritic branches to the seventh order in female cultures. In a second set of experiments, we investigated the signal transduction cascade involved in this response, and found that an upstream extracellular signal-regulated kinase (ERK) inhibitor blocked the ability of estrogen to enhance outgrowth in female cultures. Our study provides strong evidence in support of the fact that the ERK pathway is required for estrogen-induced structural plasticity in the cholinergic system of female rats. Understanding the intracellular processes that underlie the response of cholinergic neurons to estrogen provides a necessary step in elucidating how cholinergic neurons can be particularly susceptible to degeneration in postmenopausal women.

17beta-estradiol antagonizes cardiomyocyte hypertrophy by autocrine/paracrine stimulation of a guanylyl cyclase A receptor-cyclic guanosine monophosphate-dependent protein kinase pathway

BACKGROUND

Significant gender-related differences exist in the development of left ventricular hypertrophy (LVH). In addition, administration of 17beta-estradiol (E2) to ovariectomized female mice attenuates the development of LVH, demonstrating an antagonistic role for E2 in this process, although no molecular mechanism has been proposed for this phenomenon.

METHODS AND RESULTS

E2 attenuated phenylephrine and endothelin-1 induced hypertrophy in neonatal cardiomyocytes, and E2 directly induced atrial natriuretic factor (ANF) expression as assessed by Northern blot, immunocytochemical analyses, and transient transfection assays using ANF promoter deletion fragments. Both the antihypertrophic effects and ANF induction could be blocked by the estrogen receptor antagonist ICI 182,780, which demonstrates a genomic, estrogen receptor-dependent pathway. To mimic E2-induced autocrine/paracrine effects through stimulation of the guanylyl cyclase A receptor (ANF receptor), cardiomyocytes were stimulated with phenylephrine or endothelin-1 in the presence of exogenous ANF or 8-bromo-cyclic guanosine monophosphate (cGMP), both of which attenuated agonist-induced hypertrophy. Both estrogen and ANF increased cGMP activity. The antihypertrophic effect of ANF could be reduced with extracellular ANF antibodies in a dose-dependent manner. cGMP-dependent protein kinase mediates the antihypertrophic effects of E2, so cardiomyocytes were agonist stimulated in the presence of the cGMP-dependent protein kinase blocker KT-5823. KT-5823 not only reversed the antihypertrophic properties of E2, ANF, or 8-bromo-cGMP, but also evoked potentiation of hypertrophy.

CONCLUSIONS

E2-mediated induction of ANF in cardiac hypertrophy contributes to its antagonistic effects in LVH.

Resveratrol modulates the phosphoinositide 3-kinase pathway through an estrogen receptor α-dependent mechanism: Relevance in cell proliferation

Resveratrol (RES), a natural phytoalexin, has antiproliferative activity in human-derived cancer cells and in rodent models of tumor development. We have previously shown that RES induced apoptotic death in estrogen-responsive MCF-7 human breast cancer cells. Recent data have indicated that the estrogen receptor-alpha (ERalpha), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, nonnuclear function of the ERalpha potentially relevant in cell proliferation and apoptosis. In our study, using MCF-7, we have analyzed the ability of RES to modulate the ERalpha-dependent PI3K pathway. Immunoprecipitation and kinase activity assays showed that RES increased the ERalpha-associated PI3K activity with a maximum stimulatory effect at concentrations close to 10 microM; concentrations >50 microM decreased PI3K activity. Stimulation of PI3K activity by RES was ERalpha-dependent since it could be blocked by the antiestrogen ICI 182,780. RES did not affect p85 protein expression but induced the proteasome-dependent degradation of the ERalpha. Nevertheless, the amount of PI3K immunoprecipitated by the ERalpha remained unchanged in presence of RES, indicating that ERalpha availability was not limiting PI3K activity. Phosphoprotein kinase B (pPKB/AKT) followed the pattern of PI3K activity, whereas RES did not affect total PKB/AKT expression. PKB/AKT downstream target glycogen synthase kinase 3 (GSK3) also showed a phosphorylation pattern that followed PI3K activity. We propose a mechanism through which RES could inhibit survival and proliferation of estrogen-responsive cells by interfering with an ERalpha-associated PI3K pathway, following a process that could be independent of the nuclear functions of the ERalpha.

An activator protein 1-like motif mediates 17beta-estradiol repression of gonadotropin-releasing hormone receptor promoter via an estrogen receptor alpha-dependent mechanism in ovarian and breast cancer cells

Although it is recognized that estrogen is one of the most important regulators of GnRH receptor (GnRHR) gene expression, the mechanism underlying the regulation at the transcriptional level is unknown. In the present study, we demonstrated that 17beta-estradiol (E2) repressed human GnRHR promoter via an activator protein 1-like motif and estrogen receptor-alpha, of which the DNA-binding domain and the ligand-binding domain were indispensable for the repression. Interestingly, the same cis-acting motif was also found to be important for both the basal activity and phorbol 12-myristate 13-acetate responsiveness of the GnRHR promoter. EMSAs indicated that multiple transcription factors including c-Jun and c-Fos bound to the activator protein 1-like site and that their DNA binding activity was not significantly affected by E2 treatment. In addition, we demonstrated that the E2 repression could be antagonized by phorbol 12-myristate 13-acetate, which stimulated c-Jun phosphorylation on serine 63, a process that is a prerequisite for recruitment of the transcriptional coactivator cAMP response element binding protein (CREB)-binding protein (CBP). Concomitantly, we found that overexpression of CBP could reverse the suppression in a dose-dependent manner. Taken together, our data indicate that E2-activated estrogen receptor-alpha represses human GnRHR gene transcription via an indirect mechanism involving CBP and possibly other transcriptional regulators.

Regulation of apoA-I gene expression: mechanism of action of estrogen and genistein

We have previously shown that 17-beta-estradiol (E2) and genistein increase the expression of apolipoprotein A-I (apoA-I), the major protein component of HDL, in Hep G2 cells. To elucidate the mechanism mediating the increase in apoA-I gene expression by these compounds, plasmid constructs containing serial deletions of the apoA-I promoter region were generated. The smallest region maintaining response to E2 and genistein spanned the -220 to -148 sequence, and the estrogen antagonist ICI182,780 completely inhibited the E2 and genistein effect. Nuclear extracts from cells treated with E2 and genistein showed increased binding to site B oligonucleotide (-169 to -146), and nuclear extracts from genistein-treated cells showed increased binding to an early growth response factor 1 (Egr-1) oligonucleotide compared to control cells. An increase in the concentrations of Egr-1 and hepatocyte nuclear factor-3beta was observed in nuclear extracts of cells treated with both compounds compared to control cells. Treatment with a specific inhibitor of mitogen-activated protein (MAP) kinase, but not with other inhibitors, abolished the stimulation of apoA-I gene expression by E2 and genistein. These results indicate that the MAP kinase pathway is involved in the regulation of apoA-I gene expression by genistein and E2, possibly through downstream regulation of transcription factors binding to the promoter region.

Kinase-mediated regulation of common transcription factors accounts for the bone-protective effects of sex steroids

It has been found that 4-estren-3alpha,17beta-diol, a synthetic ligand for the estrogen receptor (ER) or androgen receptor (AR), which does not affect classical transcription, reverses bone loss in ovariectomized females or orchidectomized males without affecting the uterus or seminal vesicles, demonstrating that the classical genotropic actions of sex steroid receptors are dispensable for their bone-protective effects, but indispensable for their effects on reproductive organs. We have now investigated the mechanism of action of this compound. We report that, identically to 17beta-estradiol or dihydrotestosterone, but differently from raloxifene, estren alters the activity of Elk-1, CCAAT enhancer binding protein-beta (C/EBPbeta), and cyclic adenosine monophosphate-response element binding protein (CREB), or c-Jun/c-Fos by an extranuclear action of the ER or AR, resulting in activation of the Src/Shc/ERK pathway or downregulation of JNK, respectively. All of these effects are non-sex specific, require only the ligand-binding domain of the receptor, and are indispensable for the antiapoptotic action of these ligands on osteoblastic and HeLa cells. Moreover, administration of 17beta-estradiol or 4-estren-3alpha,17beta-diol to ovariectomized mice induces phosphorylation of ERKs, Elk-1, and C/EBPbeta, downregulates c-Jun, and upregulates the expression of egr-1, an ERK/SRE target gene. Kinase-initiated regulation of commonly used transcription factors offers a molecular explanation for the profound skeletal effects of sex steroid receptor ligands, including synthetic ones that are devoid of classical transcriptional activity.

Nonnuclear actions of estrogen

Estrogen has long been observed to endow cardiovascular protective effects, as evidenced by sex-specific differences in the incidence of hypertensive and coronary artery disease, the development of atherosclerosis, and myocardial remodeling after infarction. To exert its tissue-specific effects, the classic estrogen receptor (ER) functions as a ligand-dependent transcription factor. However, there is growing evidence that in response to 17beta-estradiol and heterologous signals, the ER can also mediate signaling cascades at the membrane and in the cytoplasm via various second messengers, such as receptor-mediated protein kinases. This review summarizes the current understanding of nonnuclear ER signaling and discusses the relevance to eliciting the beneficial cardiovascular effects of estrogen. These include vasodilation, inhibition of response to vessel injury, limiting myocardial injury after infarction, and attenuating cardiac hypertrophy. Defining the full repertoire of ER function promises to expose novel, highly specific targets for pharmacological interventions and may ultimately lead to the primary and secondary prevention of cardiovascular diseases.

Rapid responses to steroid hormones: from frog skin to human colon. A homage to Hans Ussing

Fifty years ago, Hans Ussing described the mechanism by which ions are actively transported across frog skin. Since then, an enormous amount of effort has been invested in determining the cellular and molecular specifics of the transport mechanisms and their regulatory pathways. Ion transport in high-resistance epithelia is regulated by a variety of hormonal and non-hormonal factors. In vertebrates, steroid hormones such as mineralocorticoids, glucocorticoids and estrogens are major regulators of ion and water transport and hence are central to the control of extracellular fluid volume and blood pressure. Steroid hormones act through nuclear receptors to control the transcriptional activity of specific target genes, such as ion channels, ion transporters and ion pumps. These effects are observed after a latency of several hours and can last for days leading to cellular differentiation that allows a higher transport activity. This pathway is the so-called genomic phase. However, in the past 10 years, it has become apparent that steroid hormones can regulate electrolyte and water transport in tight epithelia independently of the transcription of these ion channels and transporters by regulating ion transporter activity in a non-genomic fashion via modulation of various signal transduction pathways. The molecular mechanisms underlying the steroid hormone-induced activation of signal transduction pathways such as protein kinase C (PKC), protein kinase A (PKA), intracellular calcium, intracellular pH and mitogen-activated protein kinases (MAPKs) and how non-genomic activation of these pathways influences epithelial ion transport will be discussed in this review.

Involvement of extracellular signal-regulated kinases 1/2 in cardiac hypertrophy and cell death

In response to pathophysiological stress, the adult heart undergoes hypertrophic enlargement characterized by an increase in the cross-sectional area of individual myofibers. Although cardiac hypertrophy is initially a compensatory response, sustained hypertrophy is a leading predictor for the development of heart failure. At the molecular level, disease-related stimuli invoke endocrine, paracrine, and autocrine regulatory circuits, which directly influence cardiomyocyte hypertrophy, in part, through membrane bound G protein-coupled receptors and receptor tyrosine kinases. These membrane receptors activate intermediate signal transduction pathways within the cytoplasm such as mitogen-activated protein kinases (MAPKs), protein kinase C (PKC), and calcineurin, which directly modify transcriptional regulatory factors promoting alterations in cardiac gene expression. This review will weigh an increasing body of literature implicating the intermediate signaling pathway consisting of MEK1 and extracellular signal-regulated kinases (ERK1/2) as important regulators of cardiac hypertrophy and myocyte survival. The MEK1-ERK1/2 pathway likely occupies a central regulatory position in the signaling hierarchy of a cardiac myocyte given its unique ability to respond to virtually every characterized hypertrophic agonist and stress stimuli examined to date and based on its ability to promote myocyte growth in vitro and in vivo.

Reversal of bone loss in mice by nongenotropic signaling of sex steroids

We show that sex steroids protect the adult murine skeleton through a mechanism that is distinct from that used to preserve the mass and function of reproductive organs. The classical genotropic actions of sex steroid receptors are dispensable for their bone protective effects, but essential for their effects on reproductive tissues. A synthetic ligand (4-estren-3alpha,17beta-diol) that reproduces the nongenotropic effects of sex steroids, without affecting classical transcription, increases bone mass and strength in ovariectomized females above the level of the estrogen-replete state and is at least as effective as dihydrotestosterone in orchidectomized males, without affecting reproductive organs. Such ligands merit investigation as potential therapeutic alternatives to hormone replacement for osteoporosis in both women and men [corrected].