Regulatory Network Analysis in Estradiol-Treated Human Endothelial Cells.

BACKGROUND/AIMS: Estrogen has been reported to have beneficial effects on vascular biology through direct actions on endothelium. Together with transcription factors, miRNAs are the major drivers of gene expression and signaling networks. The objective of this study was to identify a comprehensive regulatory network (miRNA-transcription factor-downstream genes) that controls the transcriptomic changes observed in endothelial cells exposed to estradiol. METHODS: miRNA/mRNA interactions were assembled using our previous microarray data of human umbilical vein endothelial cells (HUVEC) treated with 17ß-estradiol (E2) (1 nmol/L, 24 h). miRNA-mRNA pairings and their associated canonical pathways were determined using Ingenuity Pathway Analysis software. Transcription factors were identified among the miRNA-regulated genes. Transcription factor downstream target genes were predicted by consensus transcription factor binding sites in the promoter region of E2-regulated genes by using JASPAR and TRANSFAC tools in Enrichr software. RESULTS: miRNA-target pairings were filtered by using differentially expressed miRNAs and mRNAs characterized by a regulatory relationship according to miRNA target prediction databases. The analysis identified 588 miRNA-target interactions between 102 miRNAs and 588 targets. Specifically, 63 upregulated miRNAs interacted with 295 downregulated targets, while 39 downregulated miRNAs were paired with 293 upregulated mRNA targets. Functional characterization of miRNA/mRNA association analysis highlighted hypoxia signaling, integrin, ephrin receptor signaling and regulation of actin-based motility by Rho among the canonical pathways regulated by E2 in HUVEC. Transcription factors and downstream genes analysis revealed eight networks, including those mediated by JUN and REPIN1, which are associated with cadherin binding and cell adhesion molecule binding pathways. CONCLUSION: This study identifies regulatory networks obtained by integrative microarray analysis and provides additional insights into the way estradiol could regulate endothelial function in human endothelial cells.

Approaching Sex Differences in Cardiovascular Non-Coding RNA Research.

Cardiovascular disease (CVD) is the biggest cause of sickness and mortality worldwide in both males and females. Clinical statistics demonstrate clear sex differences in risk, prevalence, mortality rates, and response to treatment for different entities of CVD. The reason for this remains poorly understood. Non-coding RNAs (ncRNAs) are emerging as key mediators and biomarkers of CVD. Similarly, current knowledge on differential regulation, expression, and pathology-associated function of ncRNAs between sexes is minimal. Here, we provide a state-of-the-art overview of what is known on sex differences in ncRNA research in CVD as well as discussing the contributing biological factors to this sex dimorphism including genetic and epigenetic factors and sex hormone regulation of transcription. We then focus on the experimental models of CVD and their use in translational ncRNA research in the cardiovascular field. In particular, we want to highlight the importance of considering sex of the cellular and pre-clinical models in clinical studies in ncRNA research and to carefully consider the appropriate experimental models most applicable to human patient populations. Moreover, we aim to identify sex-specific targets for treatment and diagnosis for the biggest socioeconomic health problem globally.

Mechanisms underlying the influence of oestrogen on cardiovascular physiology in women.

Women show a lower incidence of cardiovascular diseases than age-matched men, but this benefit disappears after menopause. Oestrogen-mediated vascular actions are mainly attributed to oestradiol and exerted by oestrogen receptors (ERα, ERß and G protein-coupled oestrogen receptor), through rapid and/or genomic mechanisms, but these effects depend on ageing and inflammation. A cardiovascular approach in women's health has arisen due to controversy regarding oestrogen's beneficial impact as reported in experimental and observational studies and large randomized trials. These can be explained, in part, by two mutually non-exclusive hypotheses. On the one hand, the timing hypothesis, which states that oestrogen-mediated benefits occur before the detrimental effects of ageing are established in the vasculature; on the other hand, ageing and/or hormonal-associated changes in ER expression that could lead to a deleterious imbalance in favour of ERß over ERα, generally associated with higher inflammation and endothelial dysfunction. In experimental studies, oestradiol acting on ERα promotes the release of vasoactive compounds such as nitric oxide (NO) and prostacyclin, and shifts the angiotensin axis towards angiotensin 1-7 production. Mechanisms underlying oestradiol vascular function also include anti-inflammatory and epigenetic modifications. 17ß-Oestradiol changes the transcriptomic profile of endothelial cells, and the involvement of miRNA in the regulatory pathways of vascular function reinforces assumptions regarding the vascular actions of oestrogen. Thus, the present Symposium Review aims to postulate the role of ERα in oestrogen modulation of endothelium-derived mediators and vascular physiology, as well as its relationship with miRNA and inflammation, and elucidate how physiological changes in postmenopausal women counteract the observed effects.

Microparticles harbouring Sonic hedgehog morphogen improve the vasculogenesis capacity of endothelial progenitor cells derived from myocardial infarction patients.

Aims: Endothelial progenitor cells (EPC) play a role in endothelium integrity maintenance and regeneration. Decreased numbers of EPC or their impaired function correlates with an increase in cardiovascular events. Thus, EPC are important predictors of cardiovascular mortality and morbidity. Microparticles carrying Sonic hedgehog (Shh) morphogen (MPShh+) trigger pro-angiogenic responses, both in endothelial cells and in ischaemic rodent models. Here, we propose that MPShh+ regulates EPC function, thus enhancing vasculogenesis, and correcting the defects in dysfunctional EPC obtained from acute myocardial infarction (AMI) patients. Methods and results: The mechanisms underlying Shh pathway function and nitric oxide (NO) production in EPC were evaluated. MPShh+ increased both the in vitro and in vivo vasculogenic capacity of EPC isolated from adult human peripheral blood samples. MPShh+ treatment significantly increased the expression of Shh signalling pathway genes (PTCH1, SMO, and GLI1) and masters of pro-angiogenic genes (NOS3, VEGFA, KDR, and KLF2) in EPC. Moreover, MPShh+ increased both the protein expression and activity of eNOS, resulting in increased NO production. Most importantly, MPShh+ improved the vasculogenic capacity of EPC from AMI patients to levels similar to that of EPC from healthy patients. All these effects were due to the activation of Shh pathway. Conclusion: MPShh+ increase both the vasculogenesis of EPC and their capacity to produce NO, including EPC from patients who have recently suffered an AMI. This study emphasizes MPShh+ and EPC as potential therapeutic tools for improving vascular regeneration as a treatment for cardiovascular ischaemic disease.

Extracellular histones activate autophagy and apoptosis via mTOR signaling in human endothelial cells.

Circulating histones have been proposed as targets for therapy in sepsis and hyperinflammatory symptoms. However, the proposed strategies have failed in clinical trials. Although different mechanisms for histone-related cytotoxicity are being explored, those mediated by circulating histones are not fully understood. Extracellular histones induce endothelial cell death, thereby contributing to the pathogenesis of complex diseases such as sepsis and septic shock. Therefore, the comprehension of cellular responses triggered by histones is capital to design effective therapeutic strategies. Here we report how extracellular histones induce autophagy and apoptosis in a dose-dependent manner in cultured human endothelial cells. In addition, we describe how histones regulate these pathways via Sestrin2/AMPK/ULK1-mTOR and AKT/mTOR. Furthermore, we evaluate the effect of Toll-like receptors in mediating autophagy and apoptosis demonstrating how TLR inhibitors do not prevent apoptosis and/or autophagy induced by histones. Our results confirm that histones and autophagic pathways can be considered as novel targets to design therapeutic strategies in endothelial damage.

MicroRNA as Crucial Regulators of Gene Expression in Estradiol-Treated Human Endothelial Cells.

BACKGROUND/AIMS: Estrogen signalling plays an important role in vascular biology as it modulates vasoactive and metabolic pathways in endothelial cells. Growing evidence has also established microRNA (miRNA) as key regulators of endothelial function. Nonetheless, the role of estrogen regulation on miRNA profile in endothelial cells is poorly understood. In this study, we aimed to determine how estrogen modulates miRNA profile in human endothelial cells and to explore the role of the different estrogen receptors (ERα, ERß and GPER) in the regulation of miRNA expression by estrogen. METHODS: We used miRNA microarrays to determine global miRNA expression in human umbilical vein endothelial cells (HUVEC) exposed to a physiological concentration of estradiol (E2; 1 nmol/L) for 24 hours. miRNA-gene interactions were computationally predicted using Ingenuity Pathway Analysis and changes in miRNA levels were validated by qRT-PCR. Role of ER in the E2-induced miRNA was additionally confirmed by using specific ER agonists and antagonists. RESULTS: miRNA array revealed that expression of 114 miRNA were significantly modified after E2 exposition. Further biological pathway analysis revealed cell death and survival, lipid metabolism, reproductive system function, as the top functions regulated by E2. We validated changes in the most significantly increased (miR-30b-5p, miR-487a-5p, miR-4710, miR-501-3p) and decreased (miR-378h and miR-1244) miRNA and the role of ER in these E2-induced miRNA was determined. Results showed that both classical, ERα and ERß, and membrane-bound ER, GPER, differentially regulated specific miRNA. In silico analysis of validated miRNA promoters identified specific ER binding sites. CONCLUSION: Our findings identify differentially expressed miRNA pathways linked to E2 in human endothelial cells through ER, and provide new insights by which estrogen can modulate endothelial function.

miRNA as a New Regulatory Mechanism of Estrogen Vascular Action.

The beneficial effects of estrogen on the cardiovascular system have been reported extensively. In fact, the incidence of cardiovascular diseases in women is lower than in age-matched men during their fertile stage of life, a benefit that disappears after menopause. These sex-related differences point to sexual hormones, mainly estrogen, as possible cardiovascular protective factors. The regulation of vascular function by estrogen is mainly related to the maintenance of normal endothelial function and is mediated by both direct and indirect gene transcription through the activity of specific estrogen receptors. Some of these mechanisms are known, but many remain to be elucidated. In recent years, microRNAs have been established as non-coding RNAs that regulate the expression of a high percentage of protein-coding genes in mammals and are related to the correct function of human physiology. Moreover, within the cardiovascular system, miRNAs have been related to physiological and pathological conditions. In this review, we address what is known about the role of estrogen-regulated miRNAs and their emerging involvement in vascular biology.

Role of miRNA in the Regulatory Mechanisms of Estrogens in Cardiovascular Ageing.

Cardiovascular diseases are a worldwide health problem and are the leading cause of mortality in developed countries. Together with experimental data, the lower incidence of cardiovascular diseases in women than in men of reproductive age points to the influence of sex hormones at the cardiovascular level and suggests that estrogens play a protective role against cardiovascular disease and that this role is also modified by ageing. Estrogens affect cardiovascular function via their specific estrogen receptors to trigger gene expression changes at the transcriptional level. In addition, emerging studies have proposed a role for microRNAs in the vascular effects mediated by estrogens. miRNAs regulate gene expression by repressing translational processes and have been estimated to be involved in the regulation of approximately 30% of all protein-coding genes in mammals. In this review, we highlight the current knowledge of the role of estrogen-sensitive miRNAs, and their influence in regulating vascular ageing.

Mas receptor is involved in the estrogen-receptor induced nitric oxide-dependent vasorelaxation.

The Mas receptor is involved in the angiotensin (Ang)-(1-7) vasodilatory actions by increasing nitric oxide production (NO). We have previously demonstrated an increased production of Ang-(1-7) in human umbilical vein endothelial cells (HUVEC) exposed to estradiol (E2), suggesting a potential cross-talk between E2 and the Ang-(1-7)/Mas receptor axis. Here, we explored whether the vasoactive response and NO-related signalling exerted by E2 are influenced by Mas. HUVEC were exposed to 10nM E2 for 24h in the presence or absence of the selective Mas receptor antagonist A779, and the estrogen receptor (ER) antagonist ICI182780 (ICI). E2 increased Akt and endothelial nitric oxide synthase (eNOS) mRNA and protein expression, measured by RT-PCR and Western blot, respectively. Furthermore, E2 increased Akt activity (determined by the levels of phospho-Ser473) and eNOS activity (by the enhanced phosphorylation of Ser1177, the activated form), resulting in increased NO production, which was measured by the fluorescence probe DAF-2-FM. These signalling events were dependent on ER and Mas receptor activation, since they were abolished in the presence of ICI or A779. In ex-vivo functional experiments performed with a small-vessel myograph in isolated mesenteric vessels from wild-type mice pre-contracted with noradrenaline, the relaxant response to physiological concentrations of E2 was blocked by ICI and A779, to the same extent to that obtained in the vessels isolated from Mas-deficient. In conclusion, E2 induces NO production and vasodilation through mechanisms that require Mas receptor activation.

Decreased bioavailability of nitric oxide in aorta from ovariectomized senescent mice. Role of cyclooxygenase.

This study investigates the effects of aging and/or ovariectomy on vascular reactivity to thromboxane A2 (TXA2) receptor stimulation with U46619, and the modulation by nitric oxide (NO) and cyclooxygenase (COX) in aorta from female senescence-accelerated mice (SAMP8) and from senescence resistant mice (SAMR1). Five-month-old female SAMR1 and SAMP8 were divided into three groups: sham-operated, ovariectomized and ovariectomized plus estradiol. Twenty-eight days after surgery, thoracic aortic rings were mounted for isometric recording of tension and concentration-response curves for U46619 (10(-10)-3 × 10(-7) M) were performed in the absence and in the presence of the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) and/or COX inhibitor indomethacin (10(-5)M). Vascular superoxide production was detected by dihydroethidium staining on sections of thoracic aorta. NO bioavailability in response to U46619 was suppressed by estrogen withdrawn in young and senescent mice and was restored by the administration of estradiol. In the presence of indomethacin, contractions to U46619 decreased in all groups indicating an aging- and estrogen-dependent modulation of contractile prostanoids. The simultaneous incubation of L-NAME and indomethacin did not change the maximal responses and sensitivities to TXA2 in any group in comparison with untreated aortic segments. The superoxide generation induced by TXA2 was greater in aorta from SAMP8 than in SAMR1. Moreover, in ovariectomized groups superoxide production was further increased and treatment with 17ß-estradiol reverted the effects of the ovariectomy. Inhibition of COX with indomethacin prevented the U46619-induced increase in superoxide formation. Our results indicate that NO bioavailability in response to TP receptor activation is both estrogen- and aging-dependent. TXA2 induced contractions are partially mediated by COX activation. Both aging and ovariectomy enhanced COX-dependent component of the TXA2-induced contraction. It is noteworthy that in the absence of estrogen, COX inhibition induces an increase of NO bioavailability. Therefore, in senescent female mice with an experimental menopause, TP-receptor stimulation is responsible for COX activation and enhanced superoxide generation, which may result in reduced NO bioavailability. These effects were reversed by estrogen administration.

Estradiol, acting through ERα, induces endothelial non-classic renin-angiotensin system increasing angiotensin 1-7 production.

Intracellular renin-angiotensin system (RAS) can operate independently of the circulating RAS. Estrogens provide protective effects by modulating the RAS. Our aim was to investigate the effect of estradiol (E2) on angiotensin converting enzymes (ACE) 1 and ACE2 expression and activities in human endothelial cells (HUVEC), and the role of estrogen receptors (ER). The results confirmed the presence of active intracellular RAS in HUVEC. Physiological concentrations of E2 induced a concentration-dependent increase of ACE1 and ACE2 mRNA expression and ACE1, but not ACE2, protein levels. ACE1 and ACE2 enzymatic activities were also induced with E2. These effects were mediated through ERα activation, since ER antagonists ICI 182780 and MPP completely abolished the effect of E2. Moreover, the ERα agonist PPT mirrored the E2 effects on ACE1 and ACE2 protein expression and activity. Exposure of endothelial cells to E2 significantly increased Ang-(1-7) production. In conclusion, E2 increases Ang-(1-7) production, through ERα, involving increased ACE1 and ACE2 mRNA expression and activity and ACE1 protein levels.

Mobilization of endothelial progenitor cells in acute cardiovascular events in the PROCELL study: time-course after acute myocardial infarction and stroke.

The mobilization pattern and functionality of endothelial progenitor cells after an acute ischemic event remain largely unknown. The aim of our study was to characterize and compare the short- and long-term mobilization of endothelial progenitor cells and circulating endothelial cells after acute myocardial infarction or atherothrombotic stroke, and to determine the relationship between these cell counts and plasma concentrations of vascular cell adhesion molecule (VCAM-1) and Von Willebrand factor (VWF) as surrogate markers of endothelial damage and inflammation. In addition, we assessed whether endothelial progenitor cells behave like functional endothelial cells. We included 150 patients with acute myocardial infarction or atherothrombotic stroke and 145 controls. Endothelial progenitor cells [CD45-, CD34+, KDR+, CD133+], circulating endothelial cells [CD45-, CD146+, CD31+], VWF, and VCAM-1 levels were measured in controls (baseline only) and in patients within 24h (baseline) and at 7, 30, and 180 days after the event. Myocardial infarction patients had higher counts of endothelial progenitor cells and circulating endothelial cells than the controls (201.0/mL vs. 57.0/mL; p<0.01 and 181.0/mL vs. 62.0/mL; p<0.01). Endothelial progenitor cells peaked at 30 days post-infarction (201.0/mL vs. 369.5/mL; p<0.01), as did VCAM-1 (573.7 ng/mL vs. 701.8 ng/mL; p<0.01). At 180 days post-infarction, circulating endothelial cells and VWF decreased, compared to baseline. In stroke patients, the number of endothelial progenitor cells - but not circulating endothelial cells - was higher than in controls (90.0/mL vs. 37.0/mL; p=0.01; 105.0/mL vs. 71.0/mL; p=0.11). At 30 days after stroke, however, VCAM-1 peaked (628.1/mL vs. 869.1/mL; p<0.01) but there was no significant change in endothelial progenitor cells (90/mL vs. 78/mL; p<0.34). At 180 days after stroke, circulating endothelial cells and VWF decreased, compared to baseline. Cultured endothelial progenitor cells from controls and myocardial infarction patients had endothelial phenotype characteristics and exhibited functional differences in adhesion and Ca(2+) influx, but not in proliferation and vasculogenesis. In myocardial infarction patients, VCAM-1 levels and mobilization of endothelial progenitor cells peaked at 30 days after the ischemic event. Although a similar VCAM-1 kinetic was observed in stroke patients, endothelial progenitor cells did not increase. Endothelial progenitor cells had mature endothelial capabilities in vitro.

An affordable method to obtain cultured endothelial cells from peripheral blood.

The culture of endothelial progenitor cells (EPC) provides an excellent tool to research on EPC biology and vascular regeneration and vasculogenesis. The use of different protocols to obtain EPC cultures makes it difficult to obtain comparable results in different groups. This work offers a systematic comparison of the main variables of most commonly used protocols for EPC isolation, culture and functional evaluation. Peripheral blood samples from healthy individuals were recovered and mononuclear cells were cultured. Different recovery and culture conditions were tested: blood volume, blood anticoagulant, coating matrix and percentage of foetal bovine serum (FBS) in culture media. The success of culture procedure, first colonies of endothelial cells appearance time, correlation with number of circulating EPC (cEPC) and functional comparison with human umbilical vein endothelial cells (HUVEC) were studied. The use of heparin, a minimum blood volume of 30 ml, fibronectin as a coating matrix and endothelial growing media-2 supplemented with 20% FBS increased the success of obtaining EPC cultures up to 80% of the processed samples while reducing EPC colony appearance mean time to a minimum of 13 days. Blood samples exhibiting higher cEPC numbers resulted in reduced EPC colony appearance mean time. Cells isolated by using this combination were endothelial cell-like EPCs morphological and phenotypically. Functionally, cultured EPC showed decreased growing and vasculogenic capacity when compared to HUVEC. Thus, above-mentioned conditions allow the isolation and culture of EPC with smaller blood volumes and shorter times than currently used protocols.

Complete blockade of the vasorelaxant effects of angiotensin-(1-7) and bradykinin in murine microvessels by antagonists of the receptor Mas.

The heptapeptide angiotensin-(1-7) is a biologically active metabolite of angiotensin II, the predominant peptide of the renin-angiotensin system. Recently, we have shown that the receptor Mas is associated with angiotensin-(1-7)-induced signalling and mediates, at least in part, the vasodilatory properties of angiotensin-(1-7). However, it remained controversial whether an additional receptor could account for angiotensin-(1-7)-induced vasorelaxation. Here, we used two different angiotensin-(1-7) antagonists, A779 and d-Pro-angiotensin-(1-7), to address this question and also to study their influence on the vasodilatation induced by bradykinin. Isolated mesenteric microvessels from both wild-type and Mas-deficient C57Bl/6 mice were precontracted with noradrenaline, and vascular reactivity to angiotensin-(1-7) and bradykinin was subsequently studied using a small-vessel myograph. Furthermore, mechanisms for Mas effects were investigated in primary human umbilical vein endothelial cells. Both angiotensin-(1-7) and bradykinin triggered a concentration-dependent vasodilatation in wild-type microvessels, which was absent in the presence of a nitric oxide synthase inhibitor. In these vessels, the pre-incubation with the Mas antagonists A779 or d-Pro-angiotensin-(1-7) totally abolished the vasodilatory capacity of both angiotensin-(1-7) and bradykinin, which was nitric oxide mediated. Accordingly, Mas-deficient microvessels lacked the capacity to relax in response to either angiotensin-(1-7) or bradykinin. Pre-incubation of human umbilical vein endothelial cells with A779 prevented bradykinin-mediated NO generation and NO synthase phosphorylation at serine 1177. The angiotensin-(1-7) antagonists A779 and d-Pro-angiotensin-(1-7) equally block Mas, which completely controls the angiotensin-(1-7)-induced vasodilatation in mesenteric microvessels. Importantly, Mas also appears to be a critical player in NO-mediated vasodilatation induced by renin-angiotensin system-independent agonists by altering phosphorylation of NO synthase.

Estradiol, acting through estrogen receptor alpha, restores dimethylarginine dimethylaminohydrolase activity and nitric oxide production in oxLDL-treated human arterial endothelial cells.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. ADMA accumulation, mainly due to a decreased dimethylarginine dimethylaminohydrolase (DDAH) activity, has been related to the development of cardiovascular diseases. We investigate whether estradiol prevents the changes induced by oxidized low density lipoprotein (oxLDL) on the DDAH/ADMA/NO pathway in human umbilical artery endothelial cells (HUAEC). HUAEC were exposed to estradiol, native LDL (nLDL), oxLDL and their combinations for 24 h. In some experiments, cells were also exposed to the unspecific estrogen receptor (ER) antagonist ICI 182780, the specific ERα antagonist MPP or specific agonists for ERα, ERß and GPER. ADMA concentration was measured by HPLC and concentration of NO by amperometry. Protein expression and DDAH activity were measured by immunoblotting and an enzymatic method, respectively. oxLDL, but not nLDL, increased ADMA concentration with a concomitant decrease on DDAH activity. oxLDL reduced eNOS protein and NO production. Estradiol alone had no effects on DDAH/ADMA/NO pathway, but increased the attenuated endothelial NO production induced by oxLDL by reduction in ADMA and preventing loss of eNOS protein levels. ICI 182780 and MPP completely abolished these effects of estradiol on oxLDL-exposed cells. ERα agonist, but not ERß and GPER agonists, mirrored estradiol effects on NO production. In conclusion, estradiol restores (1) DDAH activity, and therefore ADMA levels, and (2) NO production impaired by oxLDL in HUAEC acting through ERα.

Effects of estrogen on vascular inflammation: a matter of timing.

OBJECTIVE: Our study aims to determine the role of time of menopause on vascular inflammation biomarkers and how it affects their modulation by estrogen and raloxifene in postmenopausal women. METHODS AND RESULTS: Uterine arteries from 68 postmenopausal women were divided into 3 segments and cultured for 24 hours in tissue culture media containing 17ß-estradiol (100 nmol/L), raloxifene (100 nmol/L), or vehicle. Assessment of arterial concentration of 13 inflammatory biomarkers was performed by multiplex immunobead-based assay. Aging per se has a positive correlation with the generation of several proinflammatory markers. Although short-term estradiol exposure correlates with lower expression of tumor necrosis factor-α, vascular endothelial growth factor, and interleukin-1ß in all age groups, for most biomarkers aging was associated with a switch from a beneficial anti-inflammatory action by estrogen, at earlier stages of menopause, to a proinflammatory profile after 5 years past its onset. Raloxifene has no significant effect on the expression of all proinflammatory markers. Western blot analysis of estrogen receptor expression (estrogen receptor-α and estrogen receptor-ß) showed that estrogen receptor-ß increases with aging, and this increase has a positive correlation with the generation of several proinflammatory markers. CONCLUSIONS: Aging alters estrogen-mediated effects on the modulation of inflammatory biomarkers in women. How aging affects estrogen responses on vascular inflammation is not clear, but our data show a positive association between increased estrogen receptor-ß expression with aging and proinflammatory effects by estrogen.

Aging negatively affects estrogens-mediated effects on nitric oxide bioavailability by shifting ERα/ERß balance in female mice.

AIMS: Aging is among the major causes for the lack of cardiovascular protection by estrogen (E2) during postmenopause. Our study aims to determine the mechanisms whereby aging changes E2 effects on nitric oxide (NO) production in a mouse model of accelerated senescence (SAM). METHODS AND RESULTS: Although we found no differences on NO production in females SAM prone (SAMP, aged) compared to SAM resistant (SAMR, young), by either DAF-2 fluorescence or plasmatic nitrite/nitrate (NO2/NO3), in both cases, E2 treatment increased NO production in SAMR but had no effect in SAMP. Those results are in agreement with changes of eNOS protein and gene expression. E2 up-regulated eNOS expression in SAMR but not in SAMP. E2 is also known to increase NO by decreasing its catabolism by superoxide anion (O(2)(-)). Interestingly, E2 treatment decreased O(2)(-) production in young females, while increased O(2)(-) in aged ones. Furthermore, we observed that aging changed expression ratio of estrogen receptors (ERß/ERα) and levels of DNA methylation. Increased ratio ERß/ERα in aged females is associated to a lack of estrogen modulation of NO production and with a reversal in its antioxidant effect to a pro-oxidant profile. CONCLUSIONS: Together, our data suggest that aging has detrimental effects on E2-mediated benefits on NO bioavailability, partially by affecting the ability of E2 to induce up regulation of eNOS and decrease of O(2)(-). These modifications may be associated to aging-mediated modifications on global DNA methylation status, but not to a specific methylation at 5'flanking region of ERα gene.

Estradiol induces endothelial cell migration and proliferation through estrogen receptor-enhanced RhoA/ROCK pathway.

Migration and proliferation of endothelial cells are involved in re-endothelialization and angiogenesis, two important cardiovascular processes that are increased in response to estrogens. RhoA, a small GTPase which controls multiple cellular processes, is involved in the control of cell migration and proliferation. Our aim was to study the role of RhoA on estradiol-induced migration and proliferation and its dependence on estrogen receptors activity. Human umbilical vein endothelial cells were stimulated with estradiol, in the presence or absence of ICI 182780 (estrogen receptors antagonist) and Y-27632 (Rho kinase inhibitor). Estradiol increased Rho GEF-1 gene expression and RhoA (gene and protein expression and activity) in an estrogen receptor-dependent manner. Cell migration, stress fiber formation and cell proliferation were increased in response to estradiol and were also dependent on the estrogen receptors and RhoA activation. Estradiol decreased p27 levels, and significantly raised the expression of cyclins and CDK. These effects were counteracted by the use of either ICI 182780 or Y-27632. In conclusion, estradiol enhances the RhoA/ROCK pathway and increases cell cycle-related protein expression by acting through estrogen receptors. This results in an enhanced migration and proliferation of endothelial cells.

Gathering of aging and estrogen withdrawal in vascular dysfunction of senescent accelerated mice.

The aim of this work was to characterize a mouse model of experimental menopause and cardiovascular aging that closely reflects menopause in women. Senescence accelerated mouse (SAM)-Resistant type 1 (SAMR1, n=30) and SAM-Prone type 8 (SAMP8, n=30) were separated at 5months of age into three groups: 1) sham-operated (Sham); 2) ovariectomized (Ovx); and 3) ovariectomized chronically-treated with estrogen (Ovx+E2). Contractile responses to KCl (60mM) and thromboxane A(2) were greater in aorta from SAMP8 mice compared with SAMR1 in all groups. Neither ovariectomy nor estrogen replacement modified the contractile responses from SAMR1 mice. Conversely, in Ovx SAMP8 the increased maximal contractions were reversed by estrogen treatment. Rings with endothelium from all SAMR1 groups showed a greater relaxation to acetylcholine than SAMP8 groups. In SAMR1, endothelium-dependent relaxation was not altered in Ovx or Ovx+E2 groups. Rings from Ovx SAMP8 showed a decreased maximal response to acetylcholine compared to Sham SAMP8. Estrogen replacement restored the response to acetylcholine altered by ovariectomy. Nitric oxide inhibition by L-NAME markedly reduced acetylcholine responses in all groups, but this effect was less pronounced in SAMP8 and Ovx groups (determined by area under the curve reduction). These results indicate that SAMP8 exhibit a significant decreased endothelium-dependent and NO-mediated relaxation and increased vasoconstrictor responses that are potentiated by the lack of estrogen. Because these responses are closely in agreement with vascular dysfunction observed in menopausal women, we propose SAMP8 Ovx as a new model to concomitantly study the effects of aging and menopause in female mice.