17β-Estradiol inhibits cyclic strain-induced endothelin-1 gene expression within vascular endothelial cells

17β-Estradiol promotes sex-specific dysfunction in isolated human arterioles

Despite data showing that estrogen is vasculoprotective in large conduit arteries, hormone therapy (HT) during menopause has not proven to mitigate cardiovascular disease (CVD) risk. Estrogen exposure through prolonged oral contraceptive use and gender-affirming therapy can also increase cis- and trans-females' risk for future CVD, respectively. The microvasculature is a unique vascular bed that when dysfunctional can independently predict future adverse cardiac events; however, studies on the influence of estrogen on human microvessels are limited. Here, we show that isolated human arterioles from females across the life span maintain nitric oxide (NO)-mediated dilation to flow, whereas chronic (16-20 h) exposure to exogenous (100 nM) 17β-estradiol promotes microvascular endothelial dysfunction in vessels from adult females of <40 and ≥40 yr of age. The damaging effect of estrogen was more dramatic in arterioles from biological males, as they exhibited both endothelial and smooth muscle dysfunction. Furthermore, females of <40 yr have greater endothelial expression of estrogen receptor-β (ER-β) and G protein-coupled estrogen receptor (GPER) compared with females of ≥40 yr and males. Estrogen receptor-α (ER-α), the prominent receptor associated with protective effects of estrogen, was identified within the adventitia as opposed to the endothelium across all groups. To our knowledge, this is the first study to report the detrimental effects of estrogen on the human microvasculature and highlights differences in estrogen receptor expression.NEW & NOTEWORTHY Microvascular dysfunction is an independent predictor of adverse cardiac events; however, the effect of estrogen on the human microcirculation represents a critical knowledge gap. To our knowledge, this is the first study to report sex-specific detrimental effects of chronic estrogen on human microvascular reactivity. These findings may offer insight into the increased CVD risk associated with estrogen use in both cis- and trans-females.

ET-1 as a Sex-Specific Mechanism Impacting Age-Related Changes in Vascular Function

Aging is a primary risk factor for cardiovascular disease (CVD), which is the leading cause of death in developed countries. Globally, the population of adults over the age of 60 is expected to double by the year 2050. CVD prevalence and mortality rates differ between men and women as they age in part due to sex-specific mechanisms impacting the biological processes of aging. Measures of vascular function offer key insights into cardiovascular health. Changes in vascular function precede changes in CVD prevalence rates in men and women and with aging. A key mechanism underlying these changes in vascular function is the endothelin (ET) system. Studies have demonstrated sex and sex hormone effects on endothelin-1 (ET-1), and its receptors ETA and ETB. However, with aging there is a dysregulation of this system resulting in an imbalance between vasodilation and vasoconstriction. Thus, ET-1 may play a role in the sex differences observed with vascular aging. While most research has been conducted in pre-clinical animal models, we describe more recent translational data in humans showing that the ET system is an important regulator of vascular dysfunction with aging and acts through sex-specific ET receptor mechanisms. In this review, we present translational evidence (cell, tissue, animal, and human) that the ET system is a key mechanism regulating sex-specific changes in vascular function with aging, along with therapeutic interventions to reduce ET-mediated vascular dysfunction associated with aging. More knowledge on the factors responsible for the sex differences with vascular aging allow for optimized therapeutic strategies to attenuate CVD risk in the expanding aging population.

Endothelial Cell Biomechanical Responses are Dependent on Both Fluid Shear Stress and Tensile Strain

Introduction

The goal of this study was to investigate how concurrent shear stress and tensile strain affect endothelial cell biomechanical responses.

Methods

Human coronary artery endothelial cells were exposed to concurrent pulsatile shear stress and cyclic tensile strain in a programmable shearing and stretching device. Three shear stress-tensile strain conditions were used: (1) pulsatile shear stress at 1 Pa and cyclic tensile strain at 7%, simulating normal stress/strain conditions in a healthy coronary artery; (2) shear stress at 3.7 Pa and tensile strain at 3%, simulating pathological stress/strain conditions near a stenosis; (3) shear stress at 0.7 Pa and tensile strain at 5%, simulating pathological stress/strain conditions in a recirculation zone. Cell morphology was quantified using immunofluorescence microscopy. Cell surface PECAM-1 phosphorylation, ICAM-1 expression, ERK1/2 and NF-κB activation were measured using ELISA or Western blot.

Results

Simultaneous stimulation from pulsatile shear stress and cyclic tensile strain induced a significant increase in cell area, compared to that induced by shear stress or tensile strain alone. The combined stimulation caused significant increases in PECAM-1 phosphorylation. The combined stimulation also significantly enhanced EC surface ICAM-1 expression (compared to that under shear stress alone) and transcriptional factor NF-κB activation (compared to that under control conditions).

Conclusion

Pulsatile shear stress and cyclic tensile strain could induce increased but not synergistic effect on endothelial cell morphology or activation. The combined mechanical stimulation can be relayed from cell membrane to nucleus. Therefore, to better understand how mechanical conditions affect endothelial cell mechanotransduction and cardiovascular disease development, both shear stress and tensile strain need to be considered.

Role of Gender in Regulation of Redox Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is one of the diseases with a well-established gender dimorphism. The prevalence of PAH is increased in females with a ratio of 4:1, while poor survival prognosis is associated with the male gender. Nevertheless, the specific contribution of gender in disease development and progression is unclear due to the complex nature of the PAH. Oxidative and nitrosative stresses are important contributors in PAH pathogenesis; however, the role of gender in redox homeostasis has been understudied. This review is aimed to overview the possible sex-specific mechanisms responsible for the regulation of the balance between oxidants and antioxidants in relation to PAH pathobiology.

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.

Sex differences in endothelial function important to vascular health and overall cardiovascular disease risk across the lifespan

Diseases of the cardiovascular system are the leading cause of morbidity and mortality in men and women in developed countries, and cardiovascular disease (CVD) is becoming more prevalent in developing countries. The prevalence of atherosclerotic CVD in men is greater than in women until menopause, when the prevalence of CVD increases in women until it exceeds that of men. Endothelial function is a barometer of vascular health and a predictor of atherosclerosis that may provide insights into sex differences in CVD as well as how and why the CVD risk drastically changes with menopause. Studies of sex differences in endothelial function are conflicting, with some studies showing earlier decrements in endothelial function in men compared with women, whereas others show similar age-related declines between the sexes. Because the increase in CVD risk coincides with menopause, it is generally thought that female hormones, estrogens in particular, are cardioprotective. Moreover, it is often proposed that androgens are detrimental. In truth, the relationships are more complex. This review first addresses female and male sex hormones and their receptors and how these interact with the cardiovascular system, particularly the endothelium, in healthy young women and men. Second, we address sex differences in sex steroid receptor-independent mechanisms controlling endothelial function, focusing on vascular endothelin and the renin-angiotensin systems, in healthy young women and men. Finally, we discuss sex differences in age-associated endothelial dysfunction, focusing on the role of attenuated circulating sex hormones in these effects.

Ovarian hormones modulate endothelin-1 receptor responses in young women

OBJECTIVE

We recently demonstrated ETB_R mediate vasodilation in young but not postmenopausal women; it is unclear if this is related to age or a decline in ovarian hormones. The purpose of this study was to test the hypothesis that ETB_R responses are modulated by ovarian hormones.

METHODS

We measured cutaneous vasodilatory responses in 12 young women (22 ± 1 years, 23 ± 1 kg/m² ) during the ML (days 20-25) and EF (days 2-5) phases of the menstrual cycle. Cutaneous microdialysis perfusions of lactated Ringer (control), ETB_R antagonist (BQ-788, 300 nmol/L), and ETA_R antagonist (BQ-123, 500 nmol/L) were performed, followed by local heating to 42°C.

RESULTS

Serum estradiol (ML: 118 ± 16 vs EF: 44 ± 9 pg/mL, P < 0.05) and progesterone (ML: 8.3 ± 1.0 vs EF: 0.7 ± 0.2 ng/mL, P < 0.05) were higher during ML vs EF phase. ETB_R blockade decreased vasodilation during ML (control: 91 ± 2 vs BQ-788: 83 ± 2%CVCmax, P < 0.05) but not EF (control: 89 ± 2 vs BQ-788: 89 ± 1%CVCmax). ETA_R blockade also decreased vasodilation during ML (control: 91 ± 2 vs BQ-123: 87 ± 2%CVCmax, P < 0.05) but not EF (control: 89 ± 2 vs BQ-123: 92 ± 2%CVCmax).

CONCLUSIONS

These data suggest that fluctuations in ovarian hormones modulate ETB_R and ETA_R responses in young women.

Connexin 43 Plays a Role in Pulmonary Vascular Reactivity in Mice

Pulmonary arterial hypertension (PAH) is a chronic condition characterized by vascular remodeling and increased vaso-reactivity. PAH is more common in females than in males (~3:1). Connexin (Cx)43 has been shown to be involved in cellular communication within the pulmonary vasculature. Therefore, we investigated the role of Cx43 in pulmonary vascular reactivity using Cx43 heterozygous (Cx43+/−) mice and 37,43Gap27, which is a pharmacological inhibitor of Cx37 and Cx43. Contraction and relaxation responses were studied in intra-lobar pulmonary arteries (IPAs) derived from normoxic mice and hypoxic mice using wire myography. IPAs from male Cx43+/− mice displayed a small but significant increase in the contractile response to endothelin-1 (but not 5-hydroxytryptamine) under both normoxic and hypoxic conditions. There was no difference in the contractile response to endothelin-1 (ET-1) or 5-hydroxytryptamine (5-HT) in IPAs derived from female Cx43+/−mice compared to wildtype mice. Relaxation responses to methacholine (MCh) were attenuated in IPAs from male and female Cx43+/− mice or by pre-incubation of IPAs with 37,43Gap27. Nω-Nitro-L-arginine methyl ester (l-NAME) fully inhibited MCh-induced relaxation. In conclusion, Cx43 is involved in nitric oxide (NO)-induced pulmonary vascular relaxation and plays a gender-specific and agonist-specific role in pulmonary vascular contractility. Therefore, reduced Cx43 signaling may contribute to pulmonary vascular dysfunction.

GPER blockers as Nox downregulators: A new drug class to target chronic non-communicable diseases

Oxidative stress is a hallmark of chronic non-communicable diseases such as arterial hypertension, coronary artery disease, diabetes, and chronic renal disease. Cardiovascular diseases are characterized by increased production of reactive oxygen species (ROS) by NAPDH oxidase 1 (Nox1) and additional Nox isoforms among other sources. Activation of the G protein-coupled estrogen receptor (GPER) can mediate multiple salutary effects on the cardiovascular system. However, GPER also has constitutive activity, e.g. in the absence of specific agonists, that was recently shown to promote hypertension and aging-induced tissue damage by promoting Nox1-derived production of ROS. Furthermore, the small molecule GPER blocker (GRB) G36 reduces blood pressure and vascular ROS production by selectively down-regulating Nox1 expression. These unexpected findings revealed GRBs as first in class Nox downregulators capable to selectively reduce the increased expression and activity of Nox1 in disease conditions. Here, we will discuss the paradigm shift from selective GPER activation to ligand-independent, constitutive GPER signaling as a key regulator of Nox-derived oxidative stress, and the surprising identification of GRBs as the first Nox downregulators for the treatment of chronic non-communicable diseases.

Effects of endothelin-related gene polymorphisms and aerobic exercise habit on age-related arterial stiffening: a 10-yr longitudinal study

Increased arterial stiffness has emerged as a strong predictor of future cardiovascular events and all-cause mortality. The aim of this study was to elucidate influences of endothelin (ET)-related genetic polymorphisms and regular physical activity on age-related arterial stiffening through a 10-yr longitudinal study. A decadal change in brachial-ankle pulse wave velocity (baPWV), an index of arterial stiffness, was evaluated retrospectively among 92 volunteers (63 ± 14 yr, 51 men). The targeted single-nucleotide polymorphisms were ET-A receptor SNP rs5333 (ET-A) and ET-B receptor SNP rs5351 (ET-B). Subjects with either ET-A TC or CC genotypes exhibited significantly greater increases in baPWV (+15.3 ± 11.7 and +16.6 ± 15.7%/dec, respectively) than ET-A TT genotype holders (+9.2 ± 9.0%/dec), whereas subjects with the ET-B GG genotype showed a significantly greater increase in baPWV (+17.7 ± 14.1%/dec) than other ET-B genotype holders (AA: +9.5 ± 10.0%/dec; AG: +11.2 ± 9.6%/dec). The combination of these ET-related genetic risks was associated with a 2.4 times greater decadal increase in baPWV compared with no genetic risk (+8.1 ± 8.4 vs. 19.5 ± 16.0%/dec). In contrast, individuals engaging in >15 METs·h/wk of aerobic exercise showed substantially smaller increases in baPWV (+5.0 ± 9.7%/dec) compared with their physically inactive peers (approximately +13%/dec). These differences remained significant after adjusting for confounding factors, including baseline baPWV and ET-related genotype risk. Our current longitudinal study found that ET-related gene polymorphisms contribute to diverse age-related changes in arterial stiffness, and that regular sufficient aerobic exercise attenuates the age-related arterial stiffening independently of ET-related gene polymorphisms. NEW & NOTEWORTHY This 10-yr longitudinal study suggests that endothelin-related gene polymorphisms contribute to divergent increases in arterial stiffness with advancing age, whereas regular sufficient aerobic exercise attenuates age-related arterial stiffening independently of ET-related gene polymorphisms. This notion partly supports prevailing evidence that regular aerobic exercise contributes to a lower incidence of cardiovascular disease.

Role of the endothelin system in sexual dimorphism in cardiovascular and renal diseases

Epidemiological studies of blood pressure in men and women and in experimental animal models point to substantial sex differences in the occurrence of arterial hypertension as well as in the various manifestations of arterial hypertension, including myocardial infarction, stroke, retinopathy, chronic kidney failure, as well as hypertension-associated diseases (e.g. diabetes mellitus). Increasing evidence demonstrates that the endothelin (ET) system is a major player in the genesis of sex differences in cardiovascular and renal physiology and diseases. Sex differences in the ET system have been described in the vasculature, heart and kidney of humans and experimental animals. In the current review, we briefly describe the role of the ET system in the cardiovascular and renal systems. We also update information on sex differences at different levels of the ET system including synthesis, circulating and tissue levels, receptors, signaling pathways, ET actions, and responses to antagonists in different organs that contribute to blood pressure regulation. Knowledge of the mechanisms underlying sex differences in arterial hypertension can impact therapeutic strategies. Sex-targeted and/or sex-tailored approaches may improve treatment of cardiovascular and renal diseases.

Megakaryocytic leukemia 1 (MKL1) ties the epigenetic machinery to hypoxia-induced transactivation of endothelin-1

Increased synthesis of endothelin-1 (ET-1) by human vascular endothelial cells (HVECs) in response to hypoxia underscores persistent vasoconstriction observed in patients with pulmonary hypertension. The molecular mechanism whereby hypoxia stimulates ET-1 gene transcription is not well understood. Here we report that megakaryocytic leukemia 1 (MKL1) potentiated hypoxia-induced ET-1 transactivation in HVECs. Disruption of MKL1 activity by either a dominant negative mutant or small interfering RNA mediated knockdown dampened ET-1 synthesis. MKL1 was recruited to the proximal ET-1 promoter region (−81/+150) in HVECs challenged with hypoxic stress by the sequence-specific transcription factor serum response factor (SRF). Depletion of SRF blocked MKL1 recruitment and blunted ET-1 transactivation by hypoxia. Chromatin immunoprecipitation analysis of the ET-1 promoter revealed that MKL1 loss-of-function erased histone modifications consistent with transcriptional activation. In addition, MKL1 was indispensable for the occupancy of Brg1 and Brm, key components of the chromatin remodeling complex, on the ET-1 promoter. Brg1 and Brm modulated ET-1 transactivation by impacting histone modifications. In conclusion, our data have delineated a MKL1-centered complex that links epigenetic maneuverings to ET-1 transactivation in HVECs under hypoxic conditions.

Sexual dimorphism on cytokines expression in the temporomandibular joint: the role of gonadal steroid hormones

Temporomandibular joint pain-related conditions are generally characterized by local inflammation; however, little studies have focused on the role of gonadal hormones in the expression of inflammatory mediators, such as cytokines. Therefore, we asked whether gonadal steroid hormones affect formalin-induced cytokines expression in the rat temporomcandibular joint. The expression of tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and cytokine-induced neutrophil chemoattractant (CINC)-1 was significantly higher in males than in diestrus and proestrus females and was decreased by orchiectomy and restored by testosterone replacement. The expression of IL-6 was significantly higher in diestrus and proestrus females than in males, and was decreased by ovariectomy and restored by estradiol or progesterone administration. We conclude that testosterone increases the expression of TNF-α, IL-1β and CINC-1, and estradiol and progesterone increase the expression of IL-6. New clinical approaches based on inhibition of pro-inflammatory mediators are starting to supplant traditional immunosuppressive therapies and gonadal hormones may influence their effectiveness or clinical dosage.

Effects of endomorphins on human umbilical vein endothelial cells under high glucose

The endomorphin-1 (EM1) and endomorphin-2 (EM2) are endogenous opioid peptides, which modulate extensive bioactivities such as pain, cardiovascular responses, immunological responses and so on. The present study was undertaken to investigate the effects of EM1/EM2 on the primary cultured human umbilical vein endothelial cells (HUVECs) damaged by high glucose. PI AnnexinV-FITC detection was performed to evaluate the apoptosis rate. Levels of nitric oxide (NO) and nitric oxide synthase (NOS) activity were measured by the Griess reaction and the conversion of 3H-arginine to 3H-citrulline, respectively. Endothelin-1 (ET-1) was evaluated by the enzyme-linked immunosorbent assay (ELISA). Cell proliferation was determined by the MTT viability assay. mRNA expression of endothelial nitric oxide synthase (eNOS) and ET-1 were measured by real-time PCR. Our data showed that EM1/EM2 inhibited cell apoptosis. The high glucose induced increase in expression of NO, NOS and ET-1 were significantly attenuated by pretreatment with EM1/EM2 in a dose dependent manner. In addition, EM1/EM2 suppressed the mRNA eNOS and mRNA ET-1 expression in HUVECs under high glucose conditions. Naloxone, the nonselective opioid receptor antagonist, did not influence the mRNA eNOS expression when it was administrated on its own; but it could significantly antagonize the effects induced by EM1/EM2. Furthermore, in all assay systems, EM1 was more potent than EM2. The results suggest that EM1/EM2 have a beneficial effect in protecting against the endothelial dysfunction by high glucose in vitro, and these effects were mediated by the opioid receptors in HUVECs.

Hormonal modulation of endothelial NO production

Since the discovery of endothelium-derived relaxing factor and the subsequent identification of nitric oxide (NO) as the primary mediator of endothelium-dependent relaxations, research has focused on chemical and physical stimuli that modulate NO levels. Hormones represent a class of soluble, widely circulating chemical factors that impact production of NO both by rapid effects on the activity of endothelial nitric oxide synthase (eNOS) through phosphorylation of the enzyme and longer term modulation through changes in amount of eNOS protein. Hormones that increase NO production including estrogen, progesterone, insulin, and growth hormone do so through both of these common mechanisms. In contrast, some hormones, including glucocorticoids, progesterone, and prolactin, decrease NO bioavailability. Mechanisms involved include binding to repressor response elements on the eNOS gene, competing for co-regulators common to hormones with positive genomic actions, regulating eNOS co-factors, decreasing substrate for eNOS, and increasing production of oxygen-derived free radicals. Feedback regulation by the hormones themselves as well as the ability of NO to regulate hormonal release provides a second level of complexity that can also contribute to changes in NO levels. These effects on eNOS and changes in NO production may contribute to variability in risk factors, presentation of and treatment for cardiovascular disease associated with aging, pregnancy, stress, and metabolic disorders in men and women.

Endothelin in the female vasculature: a role in aging?

Cardiovascular diseases are the leading cause of morbidity and mortality in the world. Aging is associated with an increased incidence of cardiovascular disease. Premenopausal women are relatively protected from vascular alterations compared with age-matched men, likely due to higher levels of the female sex hormones. However, these vasoprotective effects in women are attenuated after menopause. Thus, the vascular system in aging women is affected by both the aging process as well as loss of hormonal protection, positioning women of this age group at a high risk for cardiovascular diseases such as hypertension, myocardial infarction, and stroke. The endothelin system in general and endothelin-1 (ET-1) in particular plays an important role in the pathogenesis of vascular dysfunction associated with aging. Evidence suggests that the female sex steroids can interfere with the vascular expression and actions of ET-1 via several mechanisms, which may further contribute to pathological processes in the vasculature of aging women. In this review, we have summarized hormone-dependent vascular pathways whereby ET-1 may mediate the deleterious effects of aging in postmenopausal females.

Mechanisms of fibrinogen-induced microvascular dysfunction during cardiovascular disease

Fibrinogen (Fg) is a high molecular weight plasma adhesion protein and a biomarker of inflammation. Many cardiovascular and cerebrovascular disorders are accompanied by increased blood content of Fg. Increased levels of Fg result in changes in blood rheological properties such as increases in plasma viscosity, erythrocyte aggregation, platelet thrombogenesis, alterations in vascular reactivity and compromises in endothelial layer integrity. These alterations exacerbate the complications in peripheral blood circulation during cardiovascular diseases such as hypertension, diabetes and stroke. In addition to affecting blood viscosity by altering plasma viscosity and erythrocyte aggregation, growing experimental evidence suggests that Fg alters vascular reactivity and impairs endothelial cell layer integrity by binding to its endothelial cell membrane receptors and activating signalling mechanisms. The purpose of this review is to discuss experimental data, which demonstrate the effects of Fg causing vascular dysfunction and to offer possible mechanisms for these effects, which could exacerbate microcirculatory complications during cardiovascular diseases accompanied by increased Fg content.

Sex differences in endothelin-1-mediated vasoconstrictor tone in middle-aged and older adults

The prevalence of cardiovascular disease is lower in middle-aged and older women than men. Increased endothelin-1-mediated vasoconstriction has been linked to the etiology of a number of cardiovascular diseases, including atherosclerosis, heart failure, and hypertension. It is unknown whether a sex difference in endothelin-1-mediated vasoconstrictor tone exists in middle-aged and older adults. Therefore, we tested the hypothesis that middle-aged and older men would demonstrate greater ET-1-mediated vasoconstrictor tone than age-matched women. Forearm blood flow in response to intra-arterial infusions of endothelin (ET)-1, BQ-123 (a selective ET(A) receptor antagonist), and BQ-788 (a selective ET(B) receptor antagonist) was assessed by venous occlusion plethysmography in 21 women (age: 58 + or - 1 yr; body mass index: 26.0 + or - 1.0 kg/m(2)) and 25 men (age: 57 + or - 2 yr; body mass index: 26.8 + or - 0.7 kg/m(2)). In response to BQ-123, the increase in forearm blood flow from baseline was significantly higher in the men than the women (24 + or - 5% vs. 9 + or - 5%; P < 0.05). In contrast, the increase in forearm blood flow in response to BQ-123 coinfused with BQ-788 was greater in the women than the men, such that the maximum vasodilation to dual endothelin receptor blockade was similar between men and women (approximately 25%). There was no difference in the vasoconstrictor response to ET-1 between the sexes. These results indicate that middle-aged and older men are under greater ET(A) receptor-mediated vasoconstrictor tone than age-matched women. Since the ET(A) receptor is the predominant receptor subtype in the coronary vasculature, this sex difference in vasoconstrictor tone may be a mechanism contributing to the sex difference in the prevalence of coronary heart disease in middle-aged and older adults.

Fibrinogen-induced endothelin-1 production from endothelial cells

We previously demonstrated that fibrinogen (Fg) binding to the vascular endothelial intercellular adhesion molecule-1 (ICAM-1) leads to microvascular constriction in vivo and in vitro. Although a role of endothelin-1 (ET-1) in this Fg-induced vasoconstriction was suggested, the mechanism of action was not clear. In the current study, we tested the hypothesis that Fg-induced vasoconstriction results from ET-1 production by vascular endothelial cells (EC) and is mediated by activation of extracellular signal-regulated kinase -1/2 (ERK-1/2). Confluent, rat heart microvascular endothelial cells (RHMECs) were treated with one of the following: Fg (2 or 4 mg/ml), Fg (4 mg/ml) with ERK-1/2 kinase inhibitors (PD-98059 or U-0126), Fg (4 mg/ml) with an antibody against ICAM-1, or medium alone for 45 min. The amount of ET-1 formed and the concentration of released von Willebrand factor (vWF) in the cell culture medium were measured by ELISAs. Fg-induced exocytosis of Weibel-Palade bodies (WPBs) was assessed by immunocytochemistry. Phosphorylation of ERK-1/2 was detected by Western blot analysis. Fg caused a dose-dependent increase in ET-1 formation and release of vWF from the RHMECs. This Fg-induced increase in ET-1 production was inhibited by specific ERK-1/2 kinase inhibitors and by anti-ICAM-1 antibody. Immunocytochemical staining showed that an increase in Fg concentration enhanced exocytosis of WPBs in ECs. A specific endothelin type B receptor blocker, BQ-788, attenuated the enhanced phosphorylation of ERK-1/2 in ECs caused by increased Fg content in the culture medium. The presence of an endothelin converting enzyme inhibitor, SM-19712, slightly decreased Fg-induced phosphorylation of ERK-1/2, but inhibited production of Fg-induced ET-1 production. These results suggest that Fg-induced vasoconstriction may be mediated, in part, by activation of ERK-1/2 signaling and increased production of ET-1 that further increases EC ERK-1/2 signaling. Thus, an increased content of Fg may enhance vasoconstriction through increased production of ET-1.

Estrogen is a modulator of vascular inflammation

Vascular inflammation underlies the pathogenesis of atherosclerosis. Atherosclerotic changes in the vasculature lead to conditions such as coronary artery disease and stroke, which are the major causes of morbidity and mortality worldwide. Epidemiological studies in premenopausal women suggest a beneficial role for estrogen in preventing vascular inflammation and consequent atherosclerosis. However, the benefits of estrogen areabsent or even reversed in older postmenopausal subjects. The modulation of inflammation by estrogen under different conditions might explain this discrepancy. Estrogen exerts its antiinflammatory effects on the vasculature through different mechanisms such as direct antioxidant effect, generation of nitric oxide, prevention of apoptosis in vascular cells and suppression of cytokines and the renin-angiotensin system. On the other hand, estrogen also elicits proinflammatory changes under certain conditions, which are less completely understood. Some of the mechanisms underlying a possible proinflammatory role for estrogen include increased expression of the proinflammatory receptor for advanced glycation end products, increased tyrosine nitration of cellular proteins, and generation of reactive oxygen species through an uncoupled eNOS. In this review, we have presented evidence for both antiinflammatory and proinflammatory pathways modulated by estrogen and how interactions among such pathways might determine the effects of estrogen on the vascular system.

alpha-Zearalanol attenuates oxLDL-induced ET-1 gene expression, ET-1 secretion and redox-sensitive intracellular signaling activation in human umbilical vein endothelial cells

alpha-Zearalanol (alpha-ZAL), a phytochemical with both antioxidant and estrogen-like properties, has been shown to retard progression of atherosclerosis and regulate cardiovascular function in part through suppression of endothelin-1 (ET-1) secretion. However, the precise nature behind alpha-ZAL-elicited inhibition on ET-1 cascade is not largely known. Oxidized low density lipoprotein (oxLDL) plays a critical role in the expression and secretion of ET-1 as well as the onset and progression of atherosclerosis through accumulation of reactive oxygen species (ROS) and activation of mitogen-activated protein kinase stress signaling cascade. Therefore, this study was designed to examine the effect of alpha-ZAL on oxLDL-induced extracellular signal-regulated kinase (ERK) phosphorylation, ROS generation, activation of the transcriptional factor activator protein-1 (AP-1), expression, secretion and promoter activity of ET-1 in human umbilical vein endothelial cells (HUVEC). ROS generation was monitored using 2,7-dichlorofluorescin fluorescence. ET-1 expression and promoter activity were evaluated by RT-PCR and luciferase assays, respectively. oxLDL (35 microg/ml) significantly enhanced ERK phosphorylation, ROS generation, AP-1 activity, mRNA expression, secretion and promoter activity of ET-1 in HUVECs, all of which were abrogated by alpha-ZAL and the antioxidant N-acetyl-l-cysteine. Collectively, these data favor the notion that alpha-ZAL antagonizes oxLDL-induced upregulation of ET-1 gene expression and secretion via suppression of oxLDL-induced ROS accumulation, ERK phosphorylation, and activation of the endothelial transcriptional factor AP-1.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.

Tetramethylpyrazine inhibits angiotensin II-increased NAD(P)H oxidase activity and subsequent proliferation in rat aortic smooth muscle cells

Tetramethylpyrazine (TMP) is the major component extracted from the Chinese herb, Chuanxiong, which is widely used in China for the treatment of cardiovascular problems. The aims of this study were to examine whether TMP may alter angiotenisn II (Ang II)-induced proliferation and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with TMP and then stimulated with Ang II, [3H]-thymidine incorporation and the ET-1 expression was examined. Ang II increased DNA synthesis which was inhibited by TMP (1-100 microM). TMP inhibited the Ang II-induced ET-1 mRNA levels and ET-1 secretion. TMP also inhibited Ang II-increased NAD(P)H oxidase activity, intracellular reactive oxygen species (ROS) levels, and the ERK phosphorylation. Furthermore, TMP and antioxidants such as Trolox and diphenylene iodonium decreased Ang II-induced ERK phosphorylation, and activator protein-1 reporter activity. In summary, we demonstrate for the first time that TMP inhibits Ang II-induced proliferation and ET-1, partially by interfering with the ERK pathway via attenuation of Ang II-increased NAD(P)H oxidase and ROS generation. Thus, this study delivers important new insight in the molecular pathways that may contribute to the proposed beneficial effects of TMP in cardiovascular disease.

Physiological concentration of 17beta-estradiol on sympathetic reinnervation in ovariectomized infarcted rats

17beta-Estradiol (E2) has been shown to exert antiarrhythmic effect after myocardial infarction; however, the mechanisms remain unclear. This study was performed to determine whether E2 exerts beneficial effects through attenuated sympathetic hyperreinnervation after infarction. Two weeks after ovariectomy, female Wistar rats were assigned to coronary artery ligation or sham operation. Twenty-four hours after coronary ligation, rats underwent one of five treatments: 1) sc vehicle treatment (control), 2) sc E2 treatment, 3) sc E2 treatment + tamoxifen (a potent estrogen receptor antagonist), 4) bosentan (an endothelin receptor blocker), or 5) sc E2 treatment + bosentan and followed for 4 wk. Myocardial endothelin-1 and norepinephrine levels at the remote zone revealed a significant elevation in control infarcted rats, compared with sham-operated rats, which is consistent with sympathetic hyperinnervation after infarction. Sympathetic hyperinnervation was blunted after giving the rats either E2 or bosentan, assessed by immunohistochemical analysis of tyrosine hydroxylase, growth-associated protein 43 and neurofilament, and Western blotting and real-time quantitative RT-PCR of nerve growth factor. Arrhythmic scores during programmed stimulation in E2-treated infarcted rats were significantly lower than in control-infarcted rats. Addition of bosentan did not have additional beneficial effects, compared with rats treated with E2 alone. The beneficial effect of E2 on sympathetic hyperinnervation was abolished by tamoxifen. Our data indicated that E2 has a role for sympathetic hyperinnervation after infarction, probably through an endothelin-1-depedent pathway. Chronic administration of E2 after infarction may attenuate the arrhythmogenic response to programmed electrical stimulation.

Nordihydroguaiaretic acid increases endothelial nitric oxide synthase expression via the transcription factor AP-1

It has been previously reported that the antioxidant compound nordihydroguaiaretic acid (NDGA) increases endothelial nitric oxide synthase (eNOS) expression in cultured bovine aortic endothelial cells. However, the exact mechanism for this effect was unresolved. Thus, the purpose of this study was to further elucidate the effect of NDGA on eNOS protein expression and enzymatic activity in fetal pulmonary arterial endothelial cells (FPAECs), and to identify the transcription factors involved in this regulation. Following overnight exposure to 0-32 microM NDGA, we observed a 2- to 2.5-fold increase in eNOS protein expression in FPAECs, with a similar increase observed in eNOS activity. For eNOS gene promoter analysis, we initially used two promoter-reporter constructs: a 1.6 kb promoter fragment and an 840 bp construct, both of which include an AP-1-specific binding site. NDGA exposure induced a significant increase in eNOS promoter activity in both constructs. However, the NDGA-mediated increase was abolished when we used either a truncated promoter construct lacking the AP-1 element or a construct in which the AP-1 binding site was mutated. AP-1 binding efficiency was also determined by electrophoretic mobility shift assay, where we observed an increase in AP-1 binding in FPAECs treated with NDGA while the binding of AP-1 was found to be decreased when a mutated AP-1 consensus sequence was used. Further, supershift analyses indicated that the AP-1 complex consisted of c-Jun and FosB. We therefore conclude that NDGA antioxidant activity regulates eNOS expression via AP-1 and that antioxidant therapy could potentially be used to increase eNOS expression in diseases, such as persistent pulmonary hypertension of the newborn, where eNOS expression and activity are known to be reduced.

Endothelin, sex and hypertension

The ETs (endothelins) comprise a family of three 21-amino-acid peptides (ET-1, ET-2 and ET-3) and 31-amino-acid ETs (ET-1(1-31), ET-2(1-31) and ET-3(1-31)). ET-1 is synthesized from a biologically inactive precursor, big ET-1, by ECEs (ET-converting enzymes). The actions of ET-1 are mediated through activation of the G-protein-coupled ET(A) and ET(B) receptors, which are found in a variety of cells in the cardiovascular and renal systems. ET-1 has potent vasoconstrictor, mitogenic, pro-inflammatory and antinatriuretic properties, which have been implicated in the pathophysiology of a number of cardiovascular diseases. Overexpression of ET-1 has been consistently described in salt-sensitive models of hypertension and in models of renal failure, and has been associated with disease progression. Sex differences are observed in many aspects of mammalian cardiovascular function and pathology. Hypertension, as well as other cardiovascular diseases, is more common in men than in women of similar age. In experimental models of hypertension, males develop an earlier and more severe form of hypertension than do females. Although the reasons for these differences are not well established, the effects of gonadal hormones on arterial, neural and renal mechanisms that control blood pressure are considered contributing factors. Sex differences in the ET-1 pathway, with males displaying higher ET-1 levels, greater ET-1-mediated vasoconstrictor and enhanced pressor responses in comparison with females, are addressed in the present review. Sex-associated differences in the number and function of ET(B) receptors appear to be particularly important in the specific characteristics of hypertension between females and males. Although the gonadal hormones modulate some of the differences in the ET pathway in the cardiovascular system, a better understanding of the exact mechanisms involved in sex-related differences in this peptidergic system is needed. With further insights into these differences, we may learn that men and women could require different antihypertensive regimens.

Redox features of the cell: a gender perspective

Reactive oxygen and nitrogen species have been implicated in diverse subcellular activities, including cell proliferation,differentiation and, in some instances, cell injury and death. The implications of reactive species inhuman pathology have also been studied in detail. However, although the role of free radicals in the pathogenesis of human diseases has been extensively analyzed in different systems (i.e., in vitro, ex vivo, and in vivo),it is still far from elucidated. In particular, the possible role of gender 4 differences in human pathophysiology associated with reactive species is a promising new field of investigation. Although the complex scenario this presents is still incomplete, important gender-associated "redox features" of cells have already been described in the literature. Here we summarize the different aspects of redox-associated molecules and enzymes in regard to gender differences in terms of the intracellular production and biochemical activity of reactive species. These are often associated with the pathogenetic mechanisms underlying several human morbidities(e.g., degenerative diseases) and can represent a specific target for new pharmacologic strategies. Gender differences may thus pose an important challenge for future studies aimed at the clinical management of diseases characterized by a redox imbalance.

Cyclic strain-mediated matrix metalloproteinase regulation within the vascular endothelium: a force to be reckoned with

The vascular endothelium is a dynamic cellular interface between the vessel wall and the bloodstream, where it regulates the physiological effects of humoral and biomechanical stimuli on vessel tone and remodeling. With respect to the latter hemodynamic stimulus, the endothelium is chronically exposed to mechanical forces in the form of cyclic circumferential strain, resulting from the pulsatile nature of blood flow, and shear stress. Both forces can profoundly modulate endothelial cell (EC) metabolism and function and, under normal physiological conditions, impart an atheroprotective effect that disfavors pathological remodeling of the vessel wall. Moreover, disruption of normal hemodynamic loading can be either causative of or contributory to vascular diseases such as atherosclerosis. EC-matrix interactions are a critical determinant of how the vascular endothelium responds to these forces and unquestionably utilizes matrix metalloproteinases (MMPs), enzymes capable of degrading basement membrane and interstitial matrix molecules, to facilitate force-mediated changes in vascular cell fate. In view of the growing importance of blood flow patterns and mechanotransduction to vascular health and pathophysiology, and considering the potential value of MMPs as therapeutic targets, a timely review of our collective understanding of MMP mechanoregulation and its impact on the vascular endothelium is warranted. More specifically, this review primarily summarizes our current knowledge of how cyclic strain regulates MMP expression and activation within the vascular endothelium and subsequently endeavors to address the direct and indirect consequences of this on vascular EC fate. Possible relevance of these phenomena to vascular endothelial dysfunction and pathological remodeling are also addressed.

Acute administration of 17beta-estradiol reduces endothelin-1 release during pacing-induced ischemia

OBJECTIVES

To assess whether acute administration of 17beta-estradiol reduces pacing-induced cardiac release of endothelin-1 in female menopausal patients with coronary artery disease.

BACKGROUND

Endothelin-1 is a potent vasoactive peptide which plays a pathogenetic role in myocardial ischemia and adverse clinical events in patients with coronary artery disease. Estrogens decrease plasma levels of endothelin-1 and improve stress-induced myocardial ischemia in menopausal women with coronary artery disease.

METHODS

Twenty-two postmenopausal women with angiographically proven coronary artery entered a randomized, double blinded, placebo-controlled study. Patients were sampled into the coronary sinus and aorta for endothelin-1 at baseline and after incremental pacing. After baseline study, patients were randomized to receive either sublingual 17beta-estradiol (1 mg) or placebo and underwent the sampling protocol 20 min thereafter.

RESULTS

17Beta-estradiol but not placebo improved the time of onset of myocardial ischemia during pacing. The coronary sinus plasma levels of endothelin-1 were significantly reduced by estradiol administration but not by placebo, at each step of pacing protocol. The maximum reduction of endothelin-1 was noted at peak pacing (-0.18 ng/l; -0.09, -0.3; 95% CI). No changes in endothelin-1 were noted in patients allocated to placebo (-0.002 ng/l; -0.06, -0.01; 95% CI). Similarly, aorto-coronary sinus difference of endothelin-1 was significantly influenced by 17beta-estradiol administration but not by placebo.

CONCLUSION

Acute administration of 17beta-estradiol reduces pacing-induced cardiac release of endothelin-1 in postmenopausal women with coronary artery disease. This result may be related to the anti-ischemic or to a primary direct effect of the hormone upon myocyte release of the peptide, and may contribute to its anti-ischemic effect.

CONDENSED ABSTRACT

To assess effect of acute 17beta-estradiol administration on pacing-induced cardiac release of endothelin-1, we studied 22 female menopausal patients with coronary artery diseases. In a randomized, double-blinded, placebo-controlled study, patients were randomized to receive either sublingual 17beta-estradiol (1 mg) or placebo. Aortic and coronary sinus plasma endothelin-1 levels were evaluated at baseline, during incremental atrial pacing, and at peak pacing before and after the sublingual administration of either 17beta-estradiol or placebo. The time to the onset of myocardial ischemia during pacing was significantly increased by 17beta-estradiol vs. placebo. Moreover, coronary sinus endothelin-1 levels at peak pacing and aortic-coronary sinus changes were significantly improved by the administration of 17beta-estradiol but not by placebo. Acute administration of 17beta-estradiol reduces pacing-induced cardiac release of endothelin-1 in postmenopausal women with coronary artery disease.

Antiproliferative Effect of Isosteviol on Angiotensin-II-Treated Rat Aortic Smooth Muscle Cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. The aims of this study were to examine whether isosteviol alters angiotensin-II-induced cell proliferation in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with isosteviol, then stimulated with angiotensin II, after which [(3)H]thymidine incorporation and endothelin-1 secretion were examined. Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II on extracellular signal-regulated kinase (ERK) phosphorylation were found reversed with isosteviol and antioxidants such as N-acetylcysteine. In summary, we speculate that isosteviol inhibits angiotensin-II-induced cell proliferation and endothelin-1 secretion via attenuation of reactive oxygen species generation. Thus, this study provides important insights that may contribute to the effects of isosteviol on the cardiovascular system.

Luteolin inhibits endothelin-1 secretion in cultured endothelial cells

We discovered that luteolin, a typical flavonoid contained in various kinds of plants, inhibits the secretion and gene expression of endothelin-1 (ET-1), a potent vasoconstrictor regulating blood pressure, in porcine aortic endothelial cells. Its ED50 was about 10 microM. In addition, the inhibition of ET-1 by a glycoside compound of luteolin (luteolin-6-C-glucoside) was weak.

Inhibitory effect of trilinolein on endothelin-1-induced c-fos gene expression in cultured neonatal rat cardiomyocytes

Trilinolein, isolated from the traditional Chinese herb Sanchi (Panax notoginseng), has been shown to have myocardial protective effects via its antioxidant ability. However, the cellular and molecular mechanisms of the protective effect of trilinolein in the heart remain to be elucidated. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We previously reported that ET-1 induces ROS generation via the ET(A) receptor and ROS modulates c-fos gene expression. We have therefore examined whether trilinolein attenuates ROS production and ET-1-induced c-fos gene expression in cardiomyocytes. Cultured neonatal rat cardiomyocytes were stimulated with ET-1 (10 nM), and c-fos gene expression was examined. Trilinolein (1 and 10 microM) inhibited ET-1-induced c-fos gene expression in cardiomyocytes. We also examined the effects of trilinolein on ET-1-increased NADPH oxidase activity and superoxide formation. Trilinolein inhibited ET-1-increased NADPH oxidase activity and superoxide formation in a concentration-dependent manner. This increase in superoxide production by ET-1 was significantly inhibited by trilinolein, diphenyleneiodonium, or N-acetylcysteine. Trilinolein also decreased ET-1- or H2O2-induced extracellular signal-regulated kinase (ERK) phosphorylation, c-Jun NH2-terminal kinase (JNK) phosphorylation, and activator protein-1 activation. These data indicate that trilinolein inhibits ET-1-induced ERK phosphorylation, JNK phosphorylation, and c-fos gene expression via attenuating superoxide production in cardiomyocytes.

Cyclic mechanical strain increases reactive oxygen species production in pulmonary epithelial cells

Overdistention of lung tissue during mechanical ventilation may be one of the factors that initiates ventilator-induced lung injury (VILI). We hypothesized that cyclic mechanical stretch (CMS) of the lung epithelium is involved in the early events of VILI through the production of reactive oxygen species (ROS). Cultures of an immortalized human airway epithelial cell line (16HBE), a human alveolar type II cell line (A549), and primary cultures of rat alveolar type II cells were cyclically stretched, and the production of superoxide (O2-) was measured by dihydroethidium fluorescence. CMS stimulated increased production of O2- after 2 h in each type of cell. 16HBE cells exhibited no significant stimulation of ROS before 2 h of CMS (20% strain, 30 cycles/min), and ROS production returned to control levels after 24 h. Oxidation of glutathione (GSH), a cellular antioxidant, increased with CMS as measured by a decrease in the ratio of the reduced GSH level to the oxidized GSH level. Strain levels of 10% did not increase O2- production in 16HBE cells, whereas 15, 20, and 30% significantly increased generation of O2-. Rotenone, a mitochondrial complex I inhibitor, partially abrogated the stretch-induced generation of O2- after 2 h CMS in 16HBE cells. NADPH oxidase activity was increased after 2 h of CMS, contributing to the production of O2-. Increased ROS production in lung epithelial cells in response to elevated stretch may contribute to the onset of VILI.

Reactive oxidant and p42/44 MAP kinase signaling is necessary for mechanical strain-induced proliferation in pulmonary epithelial cells

Mechanical strain is necessary for normal lung growth and development. Individuals with respiratory failure are supported with mechanical ventilation, leading to altered lung growth and injury. Understanding signaling pathways initiated by mechanical strain in lung epithelial cells will help guide development of strategies aimed at optimizing strain-induced lung growth while mitigating ventilator-induced lung injury. To study strain-induced proliferative signaling, focusing on the role of reactive oxidant species (ROS) and p42/44 mitogen-activated protein (MAP) kinase, human pulmonary epithelial H441 and MLE15 cells were exposed to equibiaxial cyclic mechanical strain. ROS were increased within 15 min of strain. N-acetylcysteine inactivated strain-induced ROS and inhibited p42/44 MAP kinase phosphorylation and strain-induced proliferation. PD98059 and UO126, p42/44 MAP kinase inhibitors, blocked strain-induced proliferation. To verify the specificity of p42/44 MAP kinase inhibition, cells were transfected with dominant-negative mitogen-activated protein kinase kinase-1 plasmid DNA. Transfected cells did not proliferate in response to mechanical strain. To determine whether strain-induced tyrosine kinase activity is necessary for strain-induced ROS-p42/44 MAP kinase signaling, genistein, a tyrosine kinase inhibitor, was used. Genistein did not block strain-induced ROS production or p42/44 MAP kinase phosphorylation. Gadolinium, a mechanosensitive calcium channel blocker, blocked strain-induced ROS production and p42/44 MAP kinase phosphorylation but not strain-induced tyrosine phosphorylation. These data support ROS production and p42/44 MAP kinase phosphorylation being involved in a common strain-induced signaling pathway, necessary for strain-induced proliferation in pulmonary epithelial cells, with a parallel strain-induced tyrosine kinase pathway.

Gender differences in small intestinal perfusion following trauma hemorrhage: the role of endothelin-1

Although gender differences in intestinal perfusion exist following trauma-hemorrhage (T-H), it remains unknown whether endothelin-1 (ET-1) plays any role in these dimorphic responses. To study this, male, proestrus female (female), and 17 beta-estradiol (E2)-treated male rats underwent midline laparotomy, hemorrhagic shock (blood pressure 40 mmHg, 90 min), and resuscitation (Ringer lactate, 4X shed blood volume, 1 h). Two hours thereafter, intestinal perfusion flow (IPF) was measured using isolated intestinal perfusion. The IPF in sham-operated males was significantly lower than those in other groups and decreased markedly following T-H. In contrast, no significant decrease in IPF was observed in females and E2 males following T-H. The lower IPF in sham-operated males was significantly elevated by ET(A) receptor antagonist (BQ-123) administration and was similar to that seen in sham-operated females. The decreased IPF in males after T-H was also attenuated by BQ-123 administration. The intestinal ET-1 levels in sham-operated males were significantly higher than in other groups. Although plasma and intestinal ET-1 levels increased significantly after T-H in all groups, they were highest in males. Plasma E2 levels in females and E2 males were significantly higher than in males; however, they were not affected by T-H. There was a negative correlation between plasma ET-1 and E2 following T-H. Thus ET-1 appears to play an important role in intestinal perfusion failure following T-H in males. Because E2 can modulate this vasoconstrictor effect of ET-1, these findings may partially explain the previously observed salutary effect of estrogen in improving intestinal perfusion following T-H in males.

Resveratrol inhibits angiotensin II-induced endothelin-1 gene expression and subsequent proliferation in rat aortic smooth muscle cells

Resveratrol is a phytoestrogen naturally found in grapes and is the major constituent of wine thought to have a cardioprotective effect. The aims of this study were to examine whether resveratrol alters angiotenisn II-induced cell proliferation and endothelin-1 gene expression and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with resveratrol then stimulated with angiotensin II, after which [3H]thymidine incorporation and endothelin-1 gene expression were examined. The intracellular mechanism of resveratrol in cellular proliferation and endothelin-1 gene expression was elucidated by examining the phosphorylation level of angiotensin II-induced extracellular signal-regulated kinase (ERK). The inhibitory effects of resveratrol (1-100 microM) on angiotensin II-induced DNA synthesis and endothelin-1 gene expression were demonstrated with Northern blot and promoter activity assays. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-senstive fluorescent dye, showed a resveratrol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II and H2O2 on ERK phosphorylation and activator protein-1-mediated reporter activity were found reversed with resveratrol and antioxidants such as N-acetyl-cysteine. In summary, we speculate that resveratrol inhibits angiotensin II-induced cell proliferation and endothelin-1 gene expression, and does so in a manner which involves the disruption of the ERK pathway via attenuation of reactive oxygen species generation. Thus, this study provides important insight into the molecular pathways that may contribute to the proposed beneficial effects of resveratrol on the cardiovascular system.