Estrogen induces nitric oxide-mediated vasodilation of human mammary arteries in vitro

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

R, Rath A. Efficacy of Estradiol Cream for Venipuncture Pain in Obese Female Patients: A Pilot Study

Introduction: Venipuncture is often a painful procedure causing significant anxiety, distress, and psychological consequences. We evaluated the efficacy of estradiol cream and compared it with a eutectic mixture of local anesthetics (EMLA) cream for alleviation of venipuncture pain and to make cannulation easy in female obese patients.

Materials and methods: The clearance from the Institutional Ethical Committee as well as prior written and informed consent were obtained from the participants. A total of 105 obese female adult patients aged between 25 and 64 years belonging to the American Society of Anesthesiologists (ASA) physical status I and II with body mass index (BMI) > 30 kg/m² were included in our study. The study participants were randomly allocated into three groups: In group I, a placebo cream was applied; in group II, estradiol cream was applied, and in group III, EMLA cream was applied. Any abnormal sensation at the site of application of the cream was noted and followed up at 0, 2, and 6 hours for the same. The primary outcome was the measurement of the severity of the pain experienced during venipuncture using the visual analog scale (VAS). Ease of cannulation was our secondary outcome. VAS was compared with the Z test. Statistical Package for the Social Sciences (SPSS) v16.0 software (SPSS Inc., Chicago) was used for statistical analysis. A p-value of <0.05 was considered statistically significant.

Result: The final analysis was carried out on 25 patients in group I, 27 patients in group II, and 33 patients in group III. There was no significant improvement in the ease of cannulation in group II when compared to group I. The mean VAS was similar in group I and group II, whereas it was significantly reduced in group III (p < 0.05).

Conclusion: EMLA cream was found to significantly reduce the pain of venipuncture in comparison to placebo and estradiol cream. There is no beneficial effect of estradiol cream in reducing the pain from venipuncture or in ease of cannulation compared to placebo.

Rapid estrogen receptor-α signaling mediated by ERK activation regulates vascular tone in male and ovary-intact female mice

Estrogen has been shown to affect vascular reactivity. Here, we assessed the estrogen receptor-α (ERα) dependency of estrogenic effects on vasorelaxation via a rapid nongenomic pathway in both male and ovary-intact female mice. We compared the effect of a primary estrogen, 17β-estradiol (E₂) or 4,4',4″-(4-propyl-[1H]pyrazole-1,3,5-triyl)tris-phenol (PPT; selective ERα agonist). We found that E₂ and PPT induced greater aortic relaxation in female mice than in male mice, indicating ERα mediation, which was further validated by using ERα antagonism. Treatment with 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride (MPP dihydrochloride; ERα antagonist) attenuated PPT-mediated vessel relaxation in both sexes. ERα-mediated vessel relaxation was further validated by the absence of significant PPT-mediated relaxation in aortas isolated from ERα knockout mice. Treatment with a specific ERK inhibitor, PD-98059, reduced E₂-induced vessel relaxation in both sexes but to a lesser extent in female mice. Furthermore, PD-98059 prevented PPT-induced vessel relaxation in both sexes. Both E₂ and PPT treatment activated ERK as early as 5-10 min, which was attenuated by PD-98059 in aortic tissue, cultured primary vascular smooth muscle cells (VSMCs), and endothelial cells (ECs). Aortic rings denuded of endothelium showed no differences in vessel relaxation after E₂ or PPT treatment, implicating a role of ECs in the observed sex differences. Here, our results are unique to show estrogen-stimulated rapid ERα signaling mediated by ERK activation in aortic tissue, as well as VSMCs and ECs in vitro, in regulating vascular function by using side-by-side comparisons in male and ovary-intact female mice in response to E₂ or PPT. NEW & NOTEWORTHY Here, we assessed the estrogen receptor-α dependency of estrogenic effects in vasorelaxation of both male and ovary-intact female mice by performing side-by-side comparisons. Also, we describe the connection between estrogen-stimulated rapid estrogen receptor-α signaling and downstream ERK activation in regulating vascular function in male and ovary-intact female mice.

Estrogens and Coronary Artery Disease: New Clinical Perspectives

In premenopausal women, endogenous estrogens are associated with reduced prevalence of arterial hypertension, coronary artery disease, myocardial infarction, and stroke. Clinical trials conducted in the 1990s such as HERS, WHI, and WISDOM have shown that postmenopausal treatment with horse hormone mixtures (so-called conjugated equine estrogens) and synthetic progestins adversely affects female cardiovascular health. Our understanding of rapid (nongenomic) and chronic (genomic) estrogen signaling has since advanced considerably, including identification of a new G protein-coupled estrogen receptor (GPER), which like the "classical" receptors ERα and ERβ is highly abundant in the cardiovascular system. Here, we discuss the role of estrogen receptors in the pathogenesis of coronary artery disease and review natural and synthetic ligands of estrogen receptors as well as their effects in physiology, on cardiovascular risk factors, and atherosclerotic vascular disease. Data from preclinical and clinical studies using nonselective compounds activating GPER, which include selective estrogen receptor modulators such as tamoxifen or raloxifene, selective estrogen receptor downregulators such as Faslodex™ (fulvestrant/ICI 182,780), vitamin B3 (niacin), green tea catechins, and soy flavonoids such as genistein or resveratrol, strongly suggest that activation of GPER may afford therapeutic benefit for primary and secondary prevention in patients with or at risk for coronary artery disease. Evidence from preclinical studies suggest similar efficacy profiles for selective small molecule GPER agonists such as G-1 which are devoid of uterotrophic activity. Further clinical research in this area is warranted to provide opportunities for future cardiovascular drug development.

Female sex hormones protect against salt-sensitive hypertension but not essential hypertension

Initial studies found that female Dahl salt-sensitive (DS) rats exhibit greater blood pressure (BP) salt sensitivity than female spontaneously hypertensive rats (SHR). On the basis of the central role played by NO in sodium excretion and BP control, we further tested the hypothesis that blunted increases in BP in female SHR will be accompanied by greater increases in renal inner medullary nitric oxide synthase (NOS) activity and expression in response to a high-salt (HS) diet compared with DS rats. Gonad-intact and ovariectomized (OVX) female SHR and DS rats were placed on normal salt (NS; 0.4% salt) or HS (4% salt) diet for 2 wk. OVX did not alter BP in SHR, and HS diet produced a modest increase in BP. OVX significantly increased BP in DS rats on NS; HS further increased BP in all DS rats, although OVX had a greater increase in BP. Renal inner medullary NOS activity, total NOS3 protein, and NOS3 phosphorylated on serine residue 1177 were not altered by salt or OVX in either strain. NOS1 protein expression, however, significantly increased with HS only in SHR, and this corresponded to an increase in urinary nitrate/nitrite excretion. SHR also exhibit greater NOS1 and NOS3 protein expression than DS rats. These data indicate that female sex hormones offer protection against HS-mediated elevations in BP in DS rats but not SHR. We propose that the relative resistance to HS-mediated increases in BP in SHR is related to greater NOS expression and the ability to increase NOS1 protein expression compared with DS rats.

Estrogen dependence of the renal vasodilatory effect of nicotine in rats: role of α7 nicotinic cholinergic receptor/eNOS signaling

AIMS

We recently reported that acute exposure to nicotine vasodilates the renal vasculature of male rats via facilitation of endothelial nitric oxide synthase (eNOS). In this study, we investigated whether this effect of nicotine is sexually dimorphic and the role of estrogen in modulating the nicotine effect.

MAIN METHODS

Nicotine-evoked vasodilation was evaluated in phenylephrine-preconstricted perfused kidneys obtained from male, proestrus female, ovariectomized (OVX) and estrogen-replaced OVX (OVXE(2)) rats.

KEY FINDINGS

Nicotine infusion (5×10(-5), 1×10(-4), and 5×10(-4) M) produced greater concentration-dependent reductions in the renal perfusion pressure (RPP) in an isolated kidney from proestrus females than from males. Inhibition of NOS by N(G)-nitro-L-arginine abolished the nicotine-evoked reduction in RPP and abolished the gender difference in the nicotine effect. Nicotine vasodilation was also attenuated in kidneys isolated from OVX and diestrus rats, models characterized by reduced estrogen levels. Further, estrogen or L-arginine supplementation in OVX rats largely restored the renal vasodilatory response to nicotine. Estrogen receptor blockade by tamoxifen abrogated the enhanced nicotine-evoked vasodilation elicited by E(2) in OVX rats. The nitrite/nitrate levels and protein expressions of eNOS and α(7) nicotinic cholinergic receptor (α(7) nAChRs) were significantly higher in renal tissues of OVXE(2) compared with OVX rats, suggesting a facilitatory effect for E(2) on α(7) nAChRs/eNOS signaling.

SIGNIFICANCE

Estrogen-dependent facilitation of NOS signaling mediates the enhanced vasodilator capacity of nicotine in the renal vasculature of female rats. Preliminary evidence also suggests a potential role for α(7) nAChRs in this estrogen-dependent phenomenon.

Age-related changes in dorsal root ganglia, circulating and vascular calcitonin gene-related peptide (CGRP) concentrations in female rats: effect of female sex steroid hormones

The aim of the present study is to investigate whether immunoreactive (I) calcitonin gene-related peptide (CGRP) content is decreased in plasma and mesenteric arteries (resistance arteries) in middle-aged rats and if so, whether sex steroid hormones enhance I-CGRP in middle-aged female rats. We also examined whether vascular CGRP receptor components, calcitonin receptor like receptor (CRLR) and receptor activity modifying protein 1 (RAMP1) are elevated by sex steroid hormones treatment in middle-aged female rats. Young adult (3 months old) and middle-aged (10-12 months old) ovariectomized rats were treated subcutaneously with estradiol-17beta (E2; 2 mg), progesterone (P4; 5 mg), E2+P4 (2 mg+20 mg) or placebo (control). Radioimmunoassay and Western blot analysis were performed to measure I-CGRP content and CGRP receptor components in dorsal root ganglia (DRG), in resistance arteries and in plasma. Immunofluorescent staining methods were employed to determine cellular localization of CRLR, RAMP1 in resistance arteries. Our data demonstrated that I-CGRP content was significantly (p<0.05) lower in the plasma and resistance arteries of middle-aged female rats compared to young controls. Both RAMP1 and CRLR were concentrated in vascular endothelium and the underlying smooth muscle cells. RAMP1 but not CRLR appeared to be decreased in middle-aged rat vasculature. Chronic perfusion of sex steroid hormones to ovariectomized rats: 1 significantly (p<0.05) elevated I-CGRP in the DRG and in the plasma, and (2) significantly elevated RAMP1 (p<0.05) but did not alter CRLR in resistance arteries. These data suggest that female sex steroid treatment enhances I-CGRP and its receptors, and thus regulate the blood pressure in aged female rats.

Dilatory responses to estrogenic compounds in small femoral arteries of male and female estrogen receptor-β knockout mice

The objectives of this study were to determine whether acute dilatory responses to estrogen receptor agonists are altered in isolated arteries from estrogen receptor β-deficient mice (β-ERKO) and to gain insight into the role of nitric oxide (NO) in these responses. Femoral arteries (∼250 μm) from male and female β-ERKO mice and wild-type (WT) littermates (26 female, 13 in each group; and 24 male, 12 in each group) were mounted on a Multi-Myograph. Concentration-response curves to 17β-estradiol (17β-E2) and the selective estrogen receptor-α (ER-α) agonist propyl-[1H]-pyrazole-1,3,5-triy-trisphenol (PPT) were obtained before and after NO synthase (NOS) inhibition [ Nω-nitro-l-arginine methyl ester (l-NAME), 0.1 mM] in arteries preconstricted with U-46619 (a thromboxane analog). In WT mice, responses to the potent estrogen receptor-β (ER-β) agonist 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) and the contribution of NO were also assessed. Concentration-response curves to 17β-E2and PPT were similar in arteries from WT and β-ERKO mice of both genders, but NO-mediated relaxation was different, since l-NAME reduced 17β-E2mediated relaxation in arteries from male and female β-ERKO but not WT mice ( P < 0.05). NOS inhibition reduced dilation to PPT in arteries from male and female WT mice, as well as arteries from female β-ERKO mice ( P < 0.05). Responses to DPN in arteries from WT female and male mice did not differ after NOS inhibition. The acute dilatory responses to estrogenic compounds are similar in WT and β-ERKO mice but differ mechanistically. Because NO appeared to contribute to responses to 17β-E2in arteries from β-ERKO but not WT mice, the presence of ER-β apparently inhibits ER-α-mediated NO relaxation.

Identification of estrogen receptor ligands leading to activation of non-genomic signaling pathways while exhibiting only weak transcriptional activity

Estrogen receptors (ERs) stimulate genomic effects by acting as nuclear transcription factors as well as non-genomic effects by activating distinct cytoplasmic protein kinase cascades. Non-genomic effects have been implicated in numerous cellular processes, such as proliferation, differentiation, apoptosis and vasorelaxation. To exploit non-genomic effects mediated by ERalpha for novel hormone replacement regimens, we screened a focused library of steroid receptor ligands to identify compounds exhibiting properties different from estradiol, i.e. substances that selectively stimulate non-genomic signal transduction pathways while exhibiting low genomic activities. Treatment of breast cancer cells and osteosarcoma cells with estradiol, estren, substance A and substance B led to non-genomic activation of Akt (protein kinase B) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling cascades mediated by Src (Rous Sarcoma Virus, non-receptor tyrosine kinase) and phosphatidylinositol-3-kinase (PI3K) stimulation. Such compounds leading to prominent Akt/ERK activation but exhibiting only weak genomic properties were applied in vasorelaxation assays, modeling physiological non-genomic ER responses. As expected from PI3K and Src activation data, substances were as effective as estradiol in mediating vasorelaxation. We assume that these pathway-selective estrogen receptor ligands may serve as potent lead structures for novel hormone replacement strategies exhibiting lesser side effects than the existing treatment paradigms.

Acute effects of toremifene on the vasculature of intact and menopause-induced rats

Clinical studies have shown that cardiovascular performance in postmenopausal women could be modified by treatment with selective estrogen receptor modulators (SERM). However, the mechanisms by which these drugs act on the cardiovascular system have not been elucidated. This work evaluates the effect of toremifene, a new member of the SERM family, on the vasculature of intact and ovariectomized adult Sprague-Dawley rats. The responsiveness of rings from the thoracic aorta to norepinephrine, potassium chloride, acetylcholine and sodium nitroprusside was assessed before and after 15 min of incubation with 1.0-microM toremifene. Toremifene displaced the concentration-response curve for norepinephrine-induced contractions to the right in both groups of animals. Moreover, the EC(50) values for the curves increased from 154+/-31 to 754+/-162 nM (P<.05) in intact rats and from 88+/-11 to 230+/-71 nM (P<.05) in ovariectomized rats. Toremifene also reduced contractile responses to potassium chloride (10-120 mM), displacing the entire curve to the right in both groups of animals without modifying the EC(50) values. The drug shifted the concentration-response curve for the acetylcholine-induced relaxation to the left and significantly increased E(max) values (18% for ovariectomized rats vs. 16% for controls) without affecting EC(50) values in either group tested. In addition, toremifene potentiated the relaxing responses to physiological doses (0.1-1.0 nM) of sodium nitroprusside in both groups, suggesting a direct effect at the level of the vascular smooth muscle. Acute toremifene incubation increased basal relaxation in aortic rings from both intact and ovariectomized rats. These results suggest that toremifene, by improving the functional status of the endothelium-smooth muscle unit, may have a beneficial effect on the cardiovascular status of menopause-induced rats.

Differential effects of selective estrogen receptor modulators and estrogens on mammary blood flow in the ovine

OBJECTIVE

Hormone replacement therapy has been implicated in the increased incidence of breast cancer, although selective estrogen receptor modulators have been shown to be effective in the prevention of breast cancer. Breast cancers are associated with increased mammary blood flow compared to benign breast lesions. However, few studies have examined the hemodynamic effects of hormonal agents on the mammary circulation that promote or reduce the risk of breast cancers. Although estradiol-17beta has been shown to increase mammary blood flow, the effect of selective estrogen receptor modulators remains undetermined. We therefore compared the vascular effects of selective estrogen receptor modulators and estrogens on mammary blood flow.

STUDY DESIGN

Fourteen nonpregnant ovariectomized ewes were instrumented to measure mean arterial pressure, heart rate, and uterine and mammary blood flows. Compounds were administered intravenously on separate days, and responses were monitored up to 4 hours. Compounds that were studied included estradiol-17beta (1 microg/kg), conjugated equine estrogens (0.625 and 1.25 mg), tibolone (2.5 and 5 mg), raloxifene (10 microg/kg), and tamoxifen (300 microg/kg).

RESULTS

None of these compounds significantly affected mean arterial pressure or heart rate, but all of the compounds significantly increased uterine blood flow. Estradiol-17beta increased mammary blood flow by 98% +/- 25%; conjugated equine estrogen increased mammary blood flow by 46% +/- 6% and 68% +/- 13% at the 0.625 and 1.25 mg doses, respectively. Tibolone increased mammary blood flow by 37% +/- 13% at the 2.5-mg dose and by only 14% +/- 4% at the 5-mg dose. Neither raloxifene nor tamoxifen significantly altered mammary blood flow.

CONCLUSION

Although estrogens and selective estrogen receptor modulators induced similar increases in uterine blood flow, they had differential effects on mammary blood flow.

Estrogen modulation of endothelial nitric oxide synthase

Over the past decade, clinical and basic research has demonstrated that estrogen has a dramatic impact on the response to vascular injury and the development of atherosclerosis. Further work has indicated that this is at least partially mediated by an enhancement in nitric oxide (NO) production by the endothelial isoform of NO synthase (eNOS) due to increases in both eNOS expression and level of activation. The effects on eNOS abundance are primarily mediated at the level of gene transcription, and they are dependent on estrogen receptors (ERs), which classically serve as transcription factors, but they are independent of estrogen response element action. Estrogen also has potent nongenomic effects on eNOS activity mediated by a subpopulation of ERalpha localized to caveolae in endothelial cells, where they are coupled to eNOS in a functional signaling module. These observations, which emphasize dependence on cell surface-associated receptors, provide evidence for the existence of a steroid receptor fast-action complex, or SRFC, in caveolae. Estrogen binding to ERalpha on the SRFC in caveolae leads to G(alphai) activation, which mediates downstream events. The downstream signaling includes activation of tyrosine kinase-MAPK and Akt/protein kinase B signaling, stimulation of heat shock protein 90 binding to eNOS, and perturbation of the local calcium environment, leading to eNOS phosphorylation and calmodulin-mediated eNOS stimulation. These unique genomic and nongenomic processes are critical to the vasoprotective and atheroprotective characteristics of estrogen. In addition, they serve as excellent paradigms for further elucidation of novel mechanisms of steroid hormone action.

Inhibitory effects of methanol extract of Cyperus rotundus rhizomes on nitric oxide and superoxide productions by murine macrophage cell line, RAW 264.7 cells

The rhizomes of Cyperus rotundus (C. rotundus) have been used in oriental traditional medicines for the treatment of stomach and bowel disorders, and inflammatory diseases. Nitric oxide (NO) and superoxide (O2-) are important mediators in the pathogenesis of inflammatory diseases. This study was undertaken to address whether the metanol (MeOH) extract of rhizomes of C. rotundus could modulate NO and O2- productions by murine macrophage cell line, RAW 264.7 cells. The MeOH extract of rhizomes of C. rotundus showed the inhibition of NO production in a dose-dependent manner by RAW 264.7 cells stimulated with interferon-gamma plus lipopolysaccharide. The inhibition of NO production by the extract was due to the suppression of iNOS protein, as well as iNOS mRNA expression, determined by Western and Northern blotting analyses, respectively. In addition, the MeOH extract suppressed the production of O2- by phorbol ester-stimulated RAW 264.7 cells in dose- and time-dependent manners. Collectively, these results suggest that the MeOH extract of rhizomes of C. rotundus could be developed as anti-inflammatory candidate for the treatment of inflammatory diseases mediated by overproduction of NO and O2-.

Estrogen and cerebrovascular physiology and pathophysiology

Numerous studies have uncovered a wide variety of estrogen effects with apparent cardiovascular benefits, the most recognized ones being vasodilation, anti-atherogenesis, diminished post-ischemic inflammation and anti-oxidant effects. This article provides an overview of the influence of estrogen on the cerebral vasculature, under physiologic and pathophysiologic conditions, and covers both acute and chronic effects. The discussion is primarily focused on the vasodilatory and anti-inflammatory actions of estrogen, since those particular estrogen influences have received the greatest attention in studies published to date. With respect to vasodilation, although some consideration is given to the role of other vasodilating mechanisms and factors, the emphasis is mostly placed on the endothelial isoform of nitric oxide synthase, eNOS, which has emerged as a clear target of estrogen. Some consideration is given to recent findings that suggest that estrogen can stimulate eNOS activity by decreasing the expression of the eNOS inhibitor caveolin-1. With regard to the ability of estrogen to counteract inflammation, potential mechanisms by which estrogen limits the post-ischemic leukocyte adhesion, and the expression of the inducible NOS, are discussed.

Endothelial vasodilator production by uterine and systemic arteries. VII. Estrogen and progesterone effects on eNOS

Uterine blood flow (UBF) and uterine artery endothelial nitric oxide synthase (eNOS) expression are greatest during the follicular vs. luteal phase. 17 beta-Estradiol (E(2)beta) increases UBF and elevates eNOS in ovine uterine but not systemic arteries; progesterone (P(4)) effects on E(2)beta changes of eNOS remain unclear. Nonpregnant ovariectomized sheep received either vehicle (n = 10), P(4) (0.9 g Controlled Internal Drug Release vaginal implants; n = 13), E(2)beta (5 microg/kg bolus + 6 microg x kg(-1) x day(-1); n = 10), or P(4) + E(2)beta (n = 12). Reproductive (uterine/mammary) and nonreproductive (omental/renal) artery endothelial proteins were procured on day 10, and eNOS was measured by Western analysis. P(4) and E(2)beta alone and in combination increased (P < 0.05) eNOS expression in uterine artery endothelium (vehicle = 100 +/- 16%, P(4) = 251 +/- 59%, E(2)beta = 566 +/- 147%, P(4) + E(2)beta = 772 +/- 211% of vehicle). Neither omental, renal, nor mammary artery eNOS was altered, demonstrating the local nature of steroid-induced maintenance of uterine arterial eNOS. In the myometrial microvasculature, eNOS was increased slightly (P = 0.06) with E(2)beta and significantly with P(4) + E(2)beta. Systemic NO(x) was increased with P(4) and P(4) + E(2)beta, but not E(2)beta, suggesting differential regulation of eNOS expression and activity, since P(4) increased eNOS in uterine artery endothelium while E(2)beta and the combination further increased eNOS protein.