Endothelin, sex and hypertension

Astrocytic-derived vascular remodeling factors are independently associated with blood brain barrier permeability in Alzheimer's disease

Astrocytes in Alzheimer's disease (AD) exert a pivotal role in the maintenance of blood-brain barrier (BBB) integrity essentially through structural support and release of soluble factors. This study provides new insights into the vascular remodeling processes occurring in AD, and reveals, in vivo, a pathological profile of astrocytic secretion involving Vascular Endothelial Growth Factor (VEGF), Matrix Metalloproteinases (MMP)-9, MMP-2 and Endothelin-1 (ET-1). Cerebrospinal fluid (CSF) levels of VEGF, MMP-2/-9 were lower in patients belonging to the AD continuum, compared to aged-matched controls. CSF levels of VEGF and ET-1 positively correlated with MMP-9 but negatively with MMP-2, suggesting a complex vascular remodeling process occurring in AD. Only MMP-2 levels were significantly associated with CSF AD biomarkers. Conversely, higher MMP-2 (β = 0.411, p < 0.001), ET-1 levels (β = 0.344, p < 0.001) and VEGF (β = 0.221, p = 0.022), were associated with higher BBB permeability. Astrocytic-derived vascular remodeling factors are altered in AD, disclosing the failure of important protective mechanisms which proceed independently alongside AD pathology.

Sex and stroke risk factors: A review of differences and impact

OBJECTIVES

There is an increase in stroke incidence risk over the lifetime of women, given their longer life expectancy. However, an alarming trend for sex disparities, particularly in certain stroke risk factors, shows a concerning need for focus on sex differences in stroke prevention and treatment for women. In this article, we are addressing sex differences in both traditional and sex-specific stroke risk factors.

METHODS

We searched PubMed from inception to December 2022 for articles related to sex differences and risk factors for stroke. We reviewed full-text articles for relevance and ultimately included 152 articles for this focused review.

RESULTS

Women are at increased risk for stroke from both traditional and non-traditional stroke risk factors. As women age, they have a higher disease burden of atrial fibrillation, increased risk of stroke related to diabetes, worsening lipid profiles, and higher prevalence of hypertension and obesity compared to men. Further, women carry sex hormone-specific risk factors for stroke, including the age of menarche, menopause, pregnancy, and its complications, as well as hormonal therapy. Men have a higher prevalence of tobacco use and atrial fibrillation, as well as an increased risk for stroke related to hyperlipidemia. Additionally, men have sex-specific risks related to low testosterone levels.

CONCLUSIONS

By identifying biological sex-specific risk factors for stroke, developing robust collaborations, researching, and applying the knowledge for risk reduction strategies, we can begin to tailor prevention and reduce the global burden of stroke morbidity and mortality.

Endothelin blockade prevents the long-term cardiovascular and renal sequelae of acute kidney injury in mice

Acute kidney injury (AKI) is common and associated with increased risks of cardiovascular and chronic kidney disease. Causative molecular/physiological pathways are poorly defined. There are no therapies to improve long-term outcomes. An activated endothelin system promotes cardiovascular and kidney disease progression. We hypothesized a causal role for this in the transition of AKI to chronic disease. Plasma endothelin-1 was threefold higher; urine endothelin-1 was twofold higher; and kidney preproendothelin-1, endothelin-A, and endothelin-B receptor message up-regulated in patients with AKI. To show causality, AKI was induced in mice by prolonged ischemia with a 4-week follow-up. Ischemic injury resulted in hypertension, endothelium-dependent and endothelium-independent macrovascular and microvascular dysfunction, and an increase in circulating inflammatory Ly6C^high monocytes. In the kidney, we observed fibrosis, microvascular rarefaction, and inflammation. Administration of endothelin-A antagonist, but not dual endothelin-A/B antagonist, normalized blood pressure, improved macrovascular and microvascular function, and prevented the transition of AKI to CKD. Endothelin-A blockade reduced circulating and renal proinflammatory Ly6C^high monocytes and B cells, and promoted recruitment of anti-inflammatory Ly6C^low monocytes to the kidney. Blood pressure reduction alone provided no benefits; blood pressure reduction alongside blockade of the endothelin system was as effective as endothelin-A antagonism in mitigating the long-term sequelae of AKI in mice. Our studies suggest up-regulation of the endothelin system in patients with AKI and show in mice that existing drugs that block the endothelin system, particularly those coupling vascular support and anti-inflammatory action, can prevent the transition of AKI to chronic kidney and cardiovascular disease.

Role of endothelin in the pathophysiology of migraine: A new view on an old player

There is cumulating evidence that endothelin-1 (ET-1) may play a role in migraine, however controversial findings still impede a conclusion to be drawn. Herein we tested the hypothesis that endothelin ETB receptors are major contributors to migraine-like responses. ET-1, IRL-1620 (selective ETB receptor agonist) or CGRP were injected into the trigeminal ganglion (TG) of female Wistar rats, and the development of periorbital mechanical allodynia was assessed hourly with von Frey hairs. Twenty-four hours later, rats were exposed to an aversive light for 1 h, after which the reactivation of periorbital mechanical allodynia (indicating photic sensitivity) was assessed up to 4 h. Moreover, the effect of systemic Bosentan (ETA/ETB receptors antagonist) or the selective antagonists of ETA (BQ-123) and ETB (BQ-788) receptors injected into the TG were evaluated against CGRP-induced responses. ET-1 and IRL-1620 injection into the TG induced periorbital mechanical allodynia and photic sensitivity. Bosentan attenuated periorbital mechanical allodynia but failed to affect photic sensitivity induced by CGRP. Selective blockade of ETB receptors in the TG fully prevented the development of periorbital mechanical allodynia and photic sensitivity induced by CGRP, but ETA receptor blockade caused only a slight reduction of periorbital mechanical allodynia without affecting photic sensitivity. ETB receptor-operated mechanisms in the TG may contribute to migraine-like responses in female rats.

Impact of gender on outcomes following single-level anterior lumbar interbody fusion

Background

There have been a multitude of studies attempting to identify the relationship between gender and postoperative outcomes; however, few studies have examined how this relationship may affect outcomes after anterior lumbar interbody fusion (ALIF) surgery. We aim to better characterize the impact that self-reported gender may have on patient reported outcome measures (PROMs) and achievement rates of minimum clinically important difference (MCID) after ALIF.

Methods

A retrospective database of a single spine surgeon was searched for patients who had undergone single-level ALIF. Indications for surgery including acute trauma, infection, or malignancy were excluded. The population was separated into cohorts by self-reported gender, female or male. PROMs were recorded and compared within groups to their preoperative baselines and between groups. MCID achievement rate was compared between groups.

Results

140 patients were identified for this study, with 68 patients self-identifying as female gender. The male gender cohort was found to have a significantly greater prevalence of hypertension (p = 0.018). Both cohorts showed significant improvement during at least one or more postoperative time points for each evaluated outcome measure (p ≤ 0.048, all). No significant difference in mean PROM scores was noted between cohorts at any time point for any measured outcome. The female gender cohort had significantly greater MCID achievement rates for visual acuity scale (VAS) back pain overall and at the 6-month time point (p ≤ 0.043, both). The female gender cohort also had significantly greater achievement of MCID at the 1-year time point for VAS leg pain (p = 0.017).

Conclusion

Both female and male gender cohorts demonstrated significant improvement in all outcomes measured at one or more postoperative time points. Postoperative outcomes did not differ by gender. MCID achievement was more common in female patients. Female patients may experience more tangible clinical improvement after ALIF compared to male patients.

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.

Acclimation to a High-Salt Diet Is Sex Dependent

Background Premenopausal women are less likely to develop hypertension and salt-related complications than are men, yet the impact of sex on mechanisms regulating Na+ homeostasis during dietary salt challenges is poorly defined. Here, we determined whether female rats have a more efficient capacity to acclimate to increased dietary salt intake challenge. Methods and Results Age-matched male and female Sprague Dawley rats maintained on a normal-salt (NS) diet (0.49% NaCl) were challenged with a 5-day high-salt diet (4.0% NaCl). We assessed serum, urinary, skin, and muscle electrolytes; total body water; and kidney Na+ transporters during the NS and high-salt diet phases. During the 5-day high-salt challenge, natriuresis increased more rapidly in females, whereas serum Na+ and body water concentration increased only in males. To determine if females are primed to handle changes in dietary salt, we asked the question whether the renal endothelin-1 natriuretic system is more active in female rats, compared with males. During the NS diet, female rats had a higher urinary endothelin-1 excretion rate than males. Moreover, Ingenuity Pathway Analysis of RNA sequencing data identified the enrichment of endothelin signaling pathway transcripts in the inner medulla of kidneys from NS-fed female rats compared with male counterparts. Notably, in human subjects who consumed an Na+-controlled diet (3314-3668 mg/day) for 3 days, women had a higher urinary endothelin-1 excretion rate than men, consistent with our findings in NS-fed rats. Conclusions These results suggest that female sex confers a greater ability to maintain Na+ homeostasis during acclimation to dietary Na+ challenges and indicate that the intrarenal endothelin-1 natriuretic pathway is enhanced in women.

Biomediators in Polycystic Ovary Syndrome and Cardiovascular Risk

Polycystic ovary syndrome (PCOS) is extremely heterogeneous in terms of clinical manifestations. The variability of the syndrome's phenotype is derived from the genetic and molecular heterogeneity, with a great deal of environmental factors that may have long-term health consequences, such as metabolic and cardiovascular (CV) diseases. There is no doubt that women with PCOS suffer from metabolic complications more than their age-matched counterparts in the general population and at an earlier age. Obesity, low steroid hormone-binding globulin (SHBG), hyperandrogenemia, insulin resistance, and compensatory hyperinsulinemia are biomediators and early predictors of metabolic complications in PCOS. Doubts remain about the real risk of CV diseases in PCOS and the molecular mechanisms at the basis of CV complications. Based on that assumption, this review will present the available evidence on the potential implications of some biomediators, in particular, hyperandrogenism, estrogen-progesterone imbalance, insulin resistance, and low SHBG, in the processes leading to CV disease in PCOS, with the final aim to propose a more accurate CV risk assessment.

Endothelin-1 axes in the framework of predictive, preventive and personalised (3P) medicine

Endothelin-1 (ET-1) is involved in the regulation of a myriad of processes highly relevant for physical and mental well-being; female and male health; in the modulation of senses, pain, stress reactions and drug sensitivity as well as healing processes, amongst others. Shifted ET-1 homeostasis may influence and predict the development and progression of suboptimal health conditions, metabolic impairments with cascading complications, ageing and related pathologies, cardiovascular diseases, neurodegenerative pathologies, aggressive malignancies, modulating, therefore, individual outcomes of both non-communicable and infectious diseases such as COVID-19. This article provides an in-depth analysis of the involvement of ET-1 and related regulatory pathways in physiological and pathophysiological processes and estimates its capacity as a predictor of ageing and related pathologies,a sensor of lifestyle quality and progression of suboptimal health conditions to diseases for their targeted preventionand as a potent target for cost-effective treatments tailored to the person.

Association of waist-to-height ratio with estimated glomerular filtration rate in middle-aged and elderly Chinese

OBJECTIVE

This study aimed to assess the relationship between waist-to-height (WHtR) and estimated glomerular filtration rate (eGFR) in men, non-menopausal, and postmenopausal women among middle-aged and elderly Chinese.

METHODS

This study analyzed the data of 7,807 participants in a cross-sectional survey, ie, the third wave of the China Health and Retirement Longitudinal Study. Restrictive cubic-spline regression with three knots was used to assess the dose-response association of WHtR with eGFR. Piecewise linear regression models were further established to calculate the slope of each segment and their 95% confidence interval (CI).

RESULTS

After adjusting for potential confounders, an inverse L-shaped dose-response relationship was found between WHtR and eGFR among men (Pnonlinear = 0.024, threshold = 0.513) and postmenopausal women (Pnonlinear = 0.009, threshold = 0.503). The slopes on the right sides of the threshold were statistically significant among men (β2 = -33.77, 95% CI: -53.23 to -14.31) and postmenopausal women (β2 = -36.53, 95% CI: -49.71 to -23.35), respectively. A weak negative linear relationship existed between WHtR and eGFR in non-menopausal women.

CONCLUSIONS

The relationship between WHtR and eGFR tended to be inverse-L-shaped in men and postmenopausal women, but may vary with postmenopausal status in women.

Twenty years of progress in angiotensin converting enzyme 2 and its link to SARS-CoV-2 disease

The virulence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the aggressive nature of the disease has transformed the universal pace of research in the desperate attempt to seek effective therapies to halt the morbidity and mortality of this pandemic. The rapid sequencing of the SARS-CoV-2 virus facilitated identification of the receptor for angiotensin converting enzyme 2 (ACE2) as the high affinity binding site that allows virus endocytosis. Parallel evidence that coronavirus disease 2019 (COVID-19) disease evolution shows greater lethality in patients with antecedent cardiovascular disease, diabetes, or even obesity questioned the potential unfavorable contribution of angiotensin converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor blockers as facilitators of adverse outcomes due to the ability of these therapies to augment the transcription of Ace2 with consequent increase in protein formation and enzymatic activity. We review, here, the specific studies that support a role of these agents in altering the expression and activity of ACE2 and underscore that the robustness of the experimental data is associated with weak clinical long-term studies of the existence of a similar regulation of tissue or plasma ACE2 in human subjects.

Sex differences in stroke co-morbidities

Males and females possess distinct biological differences that manifest in diverse risk profiles for acute and chronic diseases. A well-documented example of this is ischemic stroke. It has been demonstrated that older females have greater prevalence of, and worse outcome after, ischemic stroke than do males and younger females. Loss of estrogen after menopause is heavily implicated as a contributing factor for this phenomenon; however, there is mounting evidence to suggest that certain risk factors tend to occur more often in older females, such as hypertension and atrial fibrillation, while others more adversely affect females than they do males, such as diabetes and smoking. Sex-specific risk factors, such as oral contraceptive use and menopause, could also contribute to the discrepancy in stroke prevalence and outcome. Additionally, there is evidence to suggest that females tend to present with more nontraditional symptoms of acute stroke than do males, making it more difficult for clinicians to correctly identify the occurrence of a stroke, which may delay the administration of thrombolytic intervention. Finally, certain sociodemographic factors, such as the fact that females were more likely to live alone prior to stroke, may contribute to poorer recovery in females. This review will explore the various co-morbidities and sociodemographic factors that contribute to the greater prevalence of and poorer outcome after stroke in older females and will highlight the critical need for considering sex as a predisposing biological variable in stroke studies.

Evidence for G-Protein-Coupled Estrogen Receptor as a Pronatriuretic Factor

Background The novel estrogen receptor, G-protein-coupled estrogen receptor (GPER), is responsible for rapid estrogen signaling. GPER activation elicits cardiovascular and nephroprotective effects against salt-induced complications, yet there is no direct evidence for GPER control of renal Na+ handling. We hypothesized that GPER activation in the renal medulla facilitates Na+ excretion. Methods and Results Herein, we show that infusion of the GPER agonist, G1, to the renal medulla increased Na+ excretion in female Sprague Dawley rats, but not male rats. We found that GPER mRNA expression and protein abundance were markedly higher in outer medullary tissues from females relative to males. Blockade of GPER in the renal medulla attenuated Na+ excretion in females. Given that medullary endothelin 1 is a well-established natriuretic factor that is regulated by sex and sex steroids, we hypothesized that GPER activation promotes natriuresis via an endothelin 1-dependent pathway. To test this mechanism, we determined the effect of medullary infusion of G1 after blockade of endothelin receptors. Dual endothelin receptor subtype A and endothelin receptor subtype B antagonism attenuated G1-induced natriuresis in females. Unlike males, female mice with genetic deletion of GPER had reduced endothelin 1, endothelin receptor subtype A, and endothelin receptor subtype B mRNA expression compared with wild-type controls. More important, we found that systemic GPER activation ameliorates the increase in mean arterial pressure induced by ovariectomy. Conclusions Our data uncover a novel role for renal medullary GPER in promoting Na+ excretion via an endothelin 1-dependent pathway in female rats, but not in males. These results highlight GPER as a potential therapeutic target for salt-sensitive hypertension in postmenopausal women.

Association of ECE1 gene polymorphisms and essential hypertension risk in the Northern Han Chinese: A case-control study

Background

The ECE1 gene polymorphisms have been studied as a candidate gene in essential hypertension, but no consensus has been reached. To systematically explore their possible association, a case‒control study was conducted.

Methods

This study included 398 hypertensive subjects and 596 healthy volunteers as control subjects in the Northern Han Chinese. A total of 10 tag SNPs of ECE1 gene were genotyped successfully by TaqMan assay.

Results

A total of 10 SNPs (rs212544, rs2076280, rs115071, rs2076283, rs9426748, rs11590928, rs212515, rs2236847, rs2282715, and rs2774028) were identified as the tag SNPs for ECE1 gene. Although no positive connection has been found in general population, several SNPs have been found to be related to EH risk in gender‐stratified subgroup analysis. In males, rs115071 T allele influenced EH risk in a protective manner, with dominant model (TT+TC vs. CC: p = .032, OR = 0.655, 95% CI = 0.445–0.965), additive model (TT vs. TC vs. CC: p = .019, OR = 0.616, 95% CI = 0.411–0.924), as well as allele comparison (T vs. C: p = .045, OR = 0.702, 95% CI = 0.496–0.992). While, in females, rs212544 AA genotype would increase the onset risk of EH (recessive model: AA vs. GA+GG, p = .024, OR = 1.847, 95% CI = 1.086–3.142). In the three haplotype blocks identified, rs2076283‐rs2236847 C‐T haplotype was associated with a decreased risk of EH (OR = 0.558, p = .046).

Conclusion

The current case‒control study suggested that several SNPs and related haplotypes on ECE1 gene might be associated with the susceptibility of EH in certain gender subgroups in the Northern Han Chinese population.

Sex hormones and their influence on chronic kidney disease

PURPOSE OF REVIEW

The majority of end-stage renal disease including dialysis and kidney transplant patients are men. In contrast, the incidence of chronic kidney disease (CKD) is higher in women compared with men. In this review, we dissect the sex hormone levels and its effects on experimental models and patients with CKD.

RECENT FINDINGS

Sex hormones are clearly involved in CKD progression to end-stage renal disease (ESRD). A significant reduction in lipid peroxidation as a mechanism of renoprotection has been observed in kidneys of streptozotocin (STZ)-diabetic ovariectomized rats after estradiol administration. Furthermore, a G-protein-coupled estrogen receptor inhibits podocyte oxidative stress maintaining the integrity of the mitochondrial membrane. Sex hormone depletion has been shown to modulate RAS system and protect against kidney injury in the male STZ-diabetic model. In human primary proximal tubular epithelial cells, a proteomic study showed that dihydrotestosterone dysregulated metabolic, suggesting that the deleterious effect of androgens within the kidney maybe related to altered energy metabolism in renal tubules.

SUMMARY

Male gender is associated with worse CKD progression and this fact may be ascribed to sex hormone. Although male hormones exert a deleterious effect in terms of increasing oxidative stress, activating RAS system, and worsening fibrosis within the damaged kidney, female hormones exert a renoprotective effect.

Gender Differences in Hypertension

Hypertension is the leading risk factor for global mortality and morbidity and remains the major preventable cause of cardiovascular diseases. Gender differences in risk factors and awareness, treatment, and control of hypertension have been well established in humans. There are significant differences in epidemiology and clinical characteristic of hypertension between men and women. Moreover, gender differences are linked with several specific types of hypertension, including postmenopausal hypertension, white coat hypertension, masked hypertension, and hypertensive disorders of pregnancy. Gender differences have been implicated in the prevalence and determinants of hypertension and prehypertension whereas the control rate is similar between men and women taking antihypertensive medication. Importantly, distinct roles of the angiotensin-converting enzyme 2/Apelin signaling, sex hormone, endothelin-1, and sympathetic nervous activity contribute to sex differences in blood pressure control. This review summarizes gender differences in clinical features and determinants of hypertension and the underlying mechanisms responsible for hypertension.

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.

Regulation of blood pressure is influenced by gender: A study in obese Zucker rats

AIM

The present study determined the role of renin-angiotensin system (RAS), endothelin system, and eicosanoid system in the blood pressure (BP) regulation in male and female Zucker rats, and whether the pressor response change similarly in lean and obese animals.

MATERIAL AND METHODS

In female (f) and male (m), lean (L) and obese (O) Zucker rats (ZR) at 22 weeks old, we evaluated the role of the 3 mentioned systems using the following treatments: 1) enalapril (angiotensin I converting enzyme inhibitor), 2) the ABT-627 (endothelin receptor A (ET_A) antagonist), and 3) the 1-aminobenzotriazol (1-ABT: eicosanoid synthesis inhibitor).

KEY FINDINGS

MAP by radiotelemetry was similar and significantly higher in mOZR (120 ± 2 mm Hg) and fOZR (116 ± 4 mm Hg) (p < 0.05 vs. m-, fLZR), than mLZR (105 ± 3 mm Hg) and fLZR (106 ± 1 mm Hg), that were also similar. Enalapril reduced MAP more in mOZR (23%) and mLZR (26%), than fLZR (20%, p < 0.905 vs. mLZR) or fOZR (9%; p < 0.05 vs. other groups). After 10 days of drug-free and recovery period, ABT-627 reduced MAP in fLZR and mLZR by similar amounts (102 ± 4 to 92 ± 3 mm Hg, n = 6; p < 0.05 and 105 ± 2 vs. 92 ± 3 mm Hg, n = 6; p < 0.05, respectively), but did not affect either fOZR or mOZR. After another 10 days of drug-free and recovery period, 1-ABT reduced MAP in fOZR (116 ± 4 to 95 ± 2, n = 6; p < 0.05), and did not affect all other groups.

SIGNIFICANCE

We show that the mechanisms responsible for elevated BP in male and female OZR and LZR are different, and suggest that obesity may cause an increase in BP via different mechanisms in men and women as well.

Sex-specific differences in hypertension and associated cardiovascular disease

Although intrinsic mechanisms that regulate arterial blood pressure (BP) are similar in men and women, marked variations exist at the molecular, cellular and tissue levels. These physiological disparities between the sexes likely contribute to differences in disease onset, susceptibility, prevalence and treatment responses. Key systems that are important in the development of hypertension and cardiovascular disease (CVD), including the sympathetic nervous system, the renin-angiotensin-aldosterone system and the immune system, are differentially activated in males and females. Biological age also contributes to sexual dimorphism, as premenopausal women experience a higher degree of cardioprotection than men of similar age. Furthermore, sex hormones such as oestrogen and testosterone as well as sex chromosome complement likely contribute to sex differences in BP and CVD. At the cellular level, differences in cell senescence pathways may contribute to increased longevity in women and may also limit organ damage caused by hypertension. In addition, many lifestyle and environmental factors - such as smoking, alcohol consumption and diet - may influence BP and CVD in a sex-specific manner. Evidence suggests that cardioprotection in women is lost under conditions of obesity and type 2 diabetes mellitus. Treatment strategies for hypertension and CVD that are tailored according to sex could lead to improved outcomes for affected patients.

Sex-Specific Characteristics of the Microcirculation

The requirements of metabolizing tissue are both continuous and variable; accordingly, the microvasculature serving that tissue must be similarly dynamic. Just as it is recognized that males and females of the same species have differing metabolic requirements, is it not likely that the microvasculature serving these tissues will differ by sex? This section focusing on the constituents of the microcirculation identifies what is known presently about the role sex plays in matching metabolic demand with microvascular function and areas requiring additional study. Many of the identified sex differences are subtle and easily ignored. In the aggregate, though, they can profoundly alter phenotype, especially under stressful conditions including pregnancy, exercise, and disease states ranging from diabetes to heart failure. Although the features presently identified to "have sex" range from differences in growth, morphology, protein expression, and intracellular signaling, males and females alike achieve homeostasis, likely by different means. Studies of microvascular sexual dimorphism are also identifying age as an independent but interacting factor requiring additional attention. Overall, attempting to ignore either sex and/or age is inappropriate and will prevent the design and implementation of appropriate interventions to present, ameliorate, or correct microvascular dysfunction.

Favorable Vascular Actions of Angiotensin-(1-7) in Human Obesity

Obese patients have vascular dysfunction related to impaired insulin-stimulated vasodilation and increased endothelin-1-mediated vasoconstriction. In contrast to the harmful vascular actions of angiotensin (Ang) II, the angiotensin-converting enzyme 2 product Ang-(1-7) has shown to exert cardiovascular and metabolic benefits in experimental models through stimulation of the Mas receptor. We, therefore, examined the effects of exogenous Ang-(1-7) on vasodilator tone and endothelin-1-dependent vasoconstriction in obese patients. Intra-arterial infusion of Ang-(1-7) (10 nmol/min) resulted in significant increase in unstimulated forearm flow (P=0.03), an effect that was not affected by the Mas receptor antagonist A779 (10 nmol/min; P>0.05). In the absence of hyperinsulinemia, however, forearm flow responses to graded doses of acetylcholine and sodium nitroprusside were not different during Ang-(1-7) administration compared with saline (both P>0.05). During infusion of regular insulin (0.15 mU/kg per minute), by contrast, endothelium-dependent vasodilator response to acetylcholine was significantly enhanced by Ang-(1-7) (P=0.04 versus saline), whereas endothelium-independent response to sodium nitroprusside was not modified (P=0.91). Finally, Ang-(1-7) decreased the vasodilator response to endothelin A receptor blockade (BQ-123; 10 nmol/min) compared with saline (6±1% versus 93±17%; P<0.001); nitric oxide inhibition by l-N-monomethylarginine (4 µmol/min) during concurrent endothelin A antagonism resulted in similar vasoconstriction in the absence or presence of Ang-(1-7 Ang-(1-7) (P=0.69). Our findings indicate that in obese patients Ang-(1-7) has favorable effects not only to improve insulin-stimulated endothelium-dependent vasodilation but also to blunt endothelin-1-dependent vasoconstrictor tone. These findings provide support for targeting Ang-(1-7) to counteract the hemodynamic abnormalities of human obesity.

Role of Kidneys in Sex Differences in Angiotensin II-Induced Hypertension

The significance of kidneys in regulation of sodium and water balance and hemodynamics has been demonstrated both in patients and animal models. In the present study, we tested our hypothesis that kidneys play an essential role in control of sex differences in angiotensin II (Ang II)-dependent hypertension. Kidney transplantations (KTXs) were performed between male (M) and female (F) C57BL/6 mice (donor→recipient: F→F, M→M, F→M, and M→F). Radiotelemetry transmitters were implanted for measurement of mean arterial pressure during the infusion of Ang II (600 ng·kg^-1·min^-1). Gene expressions and inflammatory responses in the transplanted grafts were assessed. We found that same-sex-KTX mice still exhibited sex differences in Ang II-dependent hypertension (31.3±0.8 mm Hg in M→M versus 12.2±0.6 mm Hg in F→F), which were reduced between males and females when they received kidneys of the opposite sex (32.9±1 mm Hg in M→F versus 22.3±0.7 mm Hg in F→M). The sex differences in gene expressions, including AT₁R (angiotensin II receptor, type 1), AT₁R/AT₂R, ET-1 (endothelin-1), ETA (endothelin receptor type A), NHE3 (sodium-hydrogen exchanger 3), α-ENaC (α-epithelial sodium channel), and γ-ENaC, were unaltered in same-sex KTXs and much lessened in cross-sex KTXs. In addition, the cross-sex KTXs exhibited more robust inflammatory responses reflected by higher expression of IL-6 (interleukin 6), TNFα (tumor necrosis factor α), and KC (keratinocyte-derived chemokine) than same-sex KTX. Our results indicate that kidneys play an essential role in sex differences of Ang II-dependent hypertension. KTX of male kidneys to females augmented the blood pressure response, whereas KTX of female kidneys to males attenuated the blood pressure response. The host's extrarenal systems modulate expressions of many genes and inflammatory response, which may also contribute to the sex differences in blood pressure regulation.

Ovariectomy uncovers purinergic receptor activation of endothelin-dependent natriuresis

We recently reported that natriuresis produced by renal medullary salt loading is dependent on endothelin (ET)-1 and purinergic (P2) receptors in male rats. Because sex differences in ET-1 and P2 signaling have been reported, we decided to test whether ovarian sex hormones regulate renal medullary ET-1 and P2-dependent natriuresis. The effect of medullary NaCl loading on Na⁺ excretion was determined in intact and ovariectomized (OVX) female Sprague-Dawley rats with and without ET-1 or P2 receptor antagonism. Isosmotic saline (284 mosmol/kgH₂O) was infused in the renal medullary interstitium of anesthetized rats during a baseline urine collection period, followed by isosmotic or hyperosmotic saline (1,800 mosmol/kgH₂O) infusion. Medullary NaCl loading significantly enhanced Na⁺ excretion in intact and OVX female rats. ET_A+B or P2 receptor blockade did not attenuate the natriuretic effect of medullary NaCl loading in intact females, whereas ET_A+B or P2 receptor blockade attenuated the natriuretic response to NaCl loading in OVX rats. Activation of medullary P2Y₂ and P2Y₄ receptors by UTP infusion had no significant effect in intact females but enhanced Na⁺ excretion in OVX rats. Combined ET_A+B receptor blockade significantly inhibited the natriuretic response to UTP observed in OVX rats. These data demonstrate that medullary NaCl loading induces ET-1 and P2-independent natriuresis in intact females. In OVX, activation of medullary P2 receptors promotes ET-dependent natriuresis, suggesting that ovarian hormones may regulate the interplay between the renal ET-1 and P2 signaling systems to facilitate Na⁺ excretion.

Vascular Effects of Obestatin in Lean and Obese Subjects

Obese patients have impaired vasodilator reactivity and increased endothelin 1 (ET-1)-mediated vasoconstriction, two abnormalities contributing to vascular dysfunction. Obestatin, a product of the ghrelin gene, in addition to favorable effects on glucose and lipid metabolism, has shown nitric oxide (NO)-dependent vasodilator properties in experimental models. Given these premises, we compared the effects of exogenous obestatin on forearm flow in lean and obese subjects and assessed its influence on ET-1-dependent vasoconstrictor tone in obesity. In both lean and obese participants, infusion of escalating doses of obestatin resulted in a progressive increase in blood flow from baseline (both P < 0.001). This vasodilation was predominantly mediated by enhanced NO activity, because N^G-monomethyl-l-arginine markedly blunted the flow response to obestatin in both groups (both P < 0.05 vs. saline). In obese subjects, antagonism of ET_A receptors by BQ-123 increased forearm flow during saline (P < 0.001) but did not induce additional vasodilation (P > 0.05) during obestatin. Circulating obestatin levels were not different between lean and obese participants (P = 0.41). Our findings indicate that obestatin causes NO-dependent vasodilation in the human circulation. This effect is preserved in obesity, where it is accompanied by reduced ET-1-mediated vasoconstriction. These latter observations make obestatin a promising target for vascular prevention in obesity and diabetes.

Influence of Normo- and Hypogonadal Condition, Hyperuricemia, and High-Fructose Diet on Renal Changes in Male Rats

Background. There is a gender disparity in the incidence, prevalence, and progression of renal disease. The object of this paper is to evaluate the presence and type of renal lesion in normogonadic and hypogonadic male rats in a mild hyperuricemia induced condition and exposed to a high-fructose diet. Methods. 56 adult male Wistar rats were used. Animals were divided into two groups, one normogonadic (NGN) and one hypogonadic (HGN), and each group was divided into four subgroups in accordance with the treatment: control with only water (C), fructose (F), oxonic acid (OA), and fructose + oxonic acid (FOA). Renal changes were evaluated by measuring glomerulosclerosis, fibrosis, and arteriolar media/lumen (M/L) ratio. Results. The OA and FOA groups presented significantly hypertension (p < 0.001). The OA group significantly increased (p < 0.05) the percentage of glomerulosclerosis as well as the FOA group (p < 0.001). When comparing NGN versus HGN, we observed a trend to a lower glomerulosclerosis in the latter. A higher arteriolar M/L ratio was observed in the OA (p < 0.05) and FOA (p < 0.001). Conclusion. Hyperuricemia conditions and a high-fructose diet favor blood pressure increase together with changes in the arteriolar media/lumen ratio and renal glomerular damage. These changes were more apparent in normogonadic animals.

Relaxation Induced by Atrial Natriuretic Peptide Is Impaired in Carotid but Not Renal Arteries from Spontaneously Hypertensive Rats Due to Reduced BKCa Channel Activity

Atrial natriuretic peptide (ANP) plays an important role in vascular functions such as blood pressure regulation and relaxant activity. Individual vascular beds exhibit differences in vascular reactivity to various ligands, however, the difference in responsiveness to ANP between carotid and renal arteries and the molecular mechanisms of its vasorelaxant activity in a pathophysiological state, including hypertension, remain unclear. We therefore investigated this issue by exposing carotid and renal artery rings obtained from spontaneously hypertensive rats (SHR) to ANP. In the SHR artery (vs. control WKY artery), the ANP-induced relaxations were reduced in carotid artery but not renal artery. Acetylcholine-induced relaxations were reduced in both arteries in SHR (vs. WKY). Sodium nitroprusside-induced relaxation was similar in both arteries between the groups. In carotid arteries, the ANP-induced relaxation was not affected by endothelial denudation or by treatment with inhibitors of nitric oxide synthase, cyclooxygenase, the voltage-dependent potassium channel, or ATP-sensitive potassium channel in arteries from both SHR and WKY. In the carotid artery from WKY but not SHR, the ANP-induced relaxation was significantly reduced by inhibition of the large-conductance calcium-activated potassium channel (BKCa). The BKCa activator-induced relaxation was reduced in the SHR artery (vs. WKY). These results suggest that ANP-induced relaxation is impaired in the carotid artery from SHR and this impairment may be at least in part due to the reduction of BKCa activity rather than endothelial components.

Serum Concentrations of Endothelin-1 and Matrix Metalloproteinases-2, -9 in Pre-Hypertensive and Hypertensive Patients with Type 2 Diabetes

Endothelin-1 (ET-1) is one of the most potent vasoconstrictors known to date. While its plasma or serum concentrations are elevated in some forms of experimental and human hypertension, this is not a consistent finding in all forms of hypertension. Matrix metalloproteinases -2 and -9 (MMP-2 and MMP-9), which degrade collagen type IV of the vascular basement membrane, are responsible for vascular remodeling, inflammation, and atherosclerotic complications, including in type 2 diabetes (T2D). In our study, we compared concentrations of ET-1, MMP-2, and MMP-9 in pre-hypertensive (PHTN) and hypertensive (HTN) T2D patients with those of healthy normotensive controls (N). ET-1, MMP-2, and MMP-9 were measured by ELISA. Concentrations of ET-1 in PHTN and N were very similar, while those in HTN were significantly higher. Concentrations of MMP-2 and MMP-9 in PHTN and HTN were also significantly higher compared to N. An interesting result in our study is that concentrations of MMP-2 and MMP-9 in HTN were lower compared to PHTN. In conclusion, we showed that increased production of ET-1 in patients with T2D can lead to long-lasting increases in blood pressure (BP) and clinical manifestation of hypertension. We also demonstrated that increased levels of MMP-2 and MMP-9 in pre-hypertensive and hypertensive patients with T2D mainly reflect the early vascular changes in extracellular matrix (ECM) turnover.

Novel relationships of markers of monocyte activation and endothelial dysfunction with pulmonary dysfunction in HIV-infected persons

OBJECTIVE

Chronic obstructive pulmonary disease is a common comorbidity in HIV, with prevalence and severity of disease incompletely explained by risk factors such as smoking and age. Unique HIV-associated factors, including microbial translocation, monocyte activation, and endothelial dysfunction, have been described in other comorbidities, but have not been investigated in relation to pulmonary abnormalities in HIV. This study assessed the relationship of these pathologic processes to pulmonary function in HIV-infected and uninfected individuals and determined if relationships were unique to HIV.

DESIGN

Longitudinal observational study.

METHODS

Total 274 participants completed pulmonary function testing. Markers of inflammation (IL-6, IL-8, and TNFα), microbial translocation (lipopolysaccharide, sCD14), monocyte activation (sCD163, sCD14, and IL-2 receptor), and endothelial dysfunction (endothelin-1) were measured at baseline. Cross-sectional and longitudinal analyses were performed, adjusting for pertinent covariates.

RESULTS

In HIV-infected individuals, higher IL-6 and endothelin-1 associated with worse forced expiratory volume in one second (FEV1) percentage-predicted, and higher sCD163 associated with worse FEV1/forced vital capacity. IL-6, TNFα, lipopolysaccharide, sCD163, IL-2 receptor, and endothelin-1 associated with diffusing impairment. sCD163 and endothelin-1 interacted with HIV status in relationship to pulmonary function. In HIV-infected individuals only, baseline endothelin-1 was associated with lower FEV1, and sCD163 and endothelin-1 were associated with lower diffusing capacity during follow-up.

CONCLUSION

Circulating markers of HIV-associated humoral abnormalities are associated with airflow obstruction and diffusing impairment and baseline measures of monocyte activation and endothelial dysfunction associate with lower pulmonary function over time in HIV-infected persons. These findings suggest mechanisms of the disproportionate burden of chronic obstructive pulmonary disease in HIV-infected persons.

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.

Endothelin, sex, and pregnancy: unique considerations for blood pressure control in females

Endothelin-1 (ET-1) is a potent vasoconstrictor, and dysregulation of the endothelin (ET) system has been implicated in the development of hypertension. Sex differences in the ET system have been identified in ET receptor expression and activation, levels of ET-1, and downstream mediators of the ET system. More specifically, males have greater ET-1/ETA receptor activation, whereas females exhibit greater ETB receptor activation. These differences have been suggested to contribute to the sex differences observed in blood pressure control, with greater ETB receptor activation in females potentially acting as an important pathway contributing to the lower prevalence of hypertension in young females compared with age-matched males. This hypothesis is further supported by studies in pregnancy; the role of the ET system is enhanced during pregnancy, with dysregulation of the ET system resulting in preeclampsia. Further research is necessary to elucidate the relative roles of the ET system in blood pressure control in both sexes and to further explore the potential benefits of pharmacological ET blockade in women.

The Role of Endothelin System in Renal Structure and Function during the Postnatal Development of the Rat Kidney

Renal development in rodents, unlike in humans, continues during early postnatal period. We aimed to evaluate whether the pharmacological inhibition of Endothelin system during this period affects renal development, both at structural and functional level in male and female rats. Newborn rats were treated orally from postnatal day 1 to 20 with vehicle or bosentan (Actelion, 20 mg/kg/day), a dual endothelin receptor antagonist (ERA). The animals were divided in 4 groups: control males, control females, ERA males and ERA females. At day 21, we evaluated renal function, determined the glomerular number by a maceration method and by morphometric analysis and evaluated possible structural renal alterations by three methods: 〈alpha〉-Smooth muscle actin (α-SMA) immunohistochemistry, Masson's trichrome and Sirius red staining. The pharmacological inhibition of Endothelin system with a dual ERA during the early postnatal period of the rat did not leads to renal damage in the kidneys of male and female rats. However, ERA administration decreased the number of glomeruli, the juxtamedullary filtration surface area and the glomerular filtration rate and increased the proteinuria. These effects could predispose to hypertension or renal diseases in the adulthood. On the other hand, these effects were more pronounced in male rats, suggesting that there are sex differences that could be greater later in life. These results provide evidence that Endothelin has an important role in rat renal postnatal development. However these results do not imply that the same could happen in humans, since human renal development is complete at birth.

Ovarian hormones modulate endothelin A and B receptor expression

AIMS

The study aims to determine the modulatory roles of ovarian hormones, estrogen (E2) and progesterone (P), on the expression of endothelin A (ETA) and B (ETB) receptors in lung, liver and kidney tissues.

MAIN METHODS

Female Sprague-Dawley rats were subjected to bilateral ovariectomy and divided into four groups ovariectomized (OVX), OVX+E2, OVX+P, and OVX+E2+P. A separate group of rats underwent sham surgery and served as a control. Three weeks after OVX or sham surgery, tissues from lungs, liver, renal cortex, and inner medulla were collected, snap-frozen, and kept at -80°C for assessment of ETA and ETB receptor expression using real-time PCR.

KEY FINDINGS

E2-treated OVX animals had significantly lower expression of ETA receptors in the lungs, compared to OVX rats. Pulmonary ETB receptor mRNA was not measurably affected by any of the interventions. Hepatic ETA and ETB were significantly increased in OVX+E2+P rats, compared to sham rats. Renal inner medullary ETA and ETB receptor expressions were significantly elevated in OVX compared to sham, an effect that was prevented by co-supplementation of OVX with E2 and P. Additionally, both ETA and ETB receptor expression in the renal cortex were significantly attenuated by ovariectomy, and this reduction was not evident in OVX+E2 rats.

SIGNIFICANCE

These data suggest that ovarian hormones regulate ET receptor expression and may contribute to sex differences in cardiovascular and renal health.

Constrictor prostanoids and uridine adenosine tetraphosphate: vascular mediators and therapeutic targets in hypertension and diabetes

Vascular dysfunction plays a pivotal role in the development of systemic complications associated with arterial hypertension and diabetes. The endothelium, or more specifically, various factors derived from endothelial cells tightly regulate vascular function, including vascular tone. In physiological conditions, there is a balance between endothelium-derived factors, that is, relaxing factors (endothelium-derived relaxing factors; EDRFs) and contracting factors (endothelium-derived contracting factors; EDCFs), which mediate vascular homeostasis. However, in disease states, such as diabetes and arterial hypertension, there is an imbalance between EDRF and EDCF, with a reduction of EDRF signalling and an increase of EDCF signalling. Among EDCFs, COX-derived vasoconstrictor prostanoids play an important role in the development of vascular dysfunction associated with hypertension and diabetes. Moreover, uridine adenosine tetraphosphate (Up4 A), identified as an EDCF in 2005, also modulates vascular function. However, the role of Up4 A in hypertension- and diabetes-associated vascular dysfunction is unclear. In the present review, we focused on experimental and clinical evidence that implicate these two EDCFs (vasoconstrictor prostanoids and Up4 A) in vascular dysfunction associated with hypertension and diabetes.

Bilateral nephrectomy for uncontrolled hypertension in hemodialysis patient: a forgotten option?

Resistant arterial hypertension in chronic hemodialysis patients is still a therapeutical challenge despite the development of modern antihypertensive drugs and dialysis procedures. Bilateral nephrectomy seems to be a forgotten option, although it has given good results. We present a case of a 39-year-old female chronic hemodialysis patient, in whom the problem of uncontrolled renal parenchymal hypertension remained despite multiple drug therapy and the ultrafiltration intensification. The problem was solved by bilateral nephrectomy. We discuss the role of bilateral nephrectomy for arterial hypertension control in chronic hemodialysis patients and the surgical and non-surgical options of nephrectomy.

Enhanced endothelin receptor type B-mediated vasodilation and underlying [Ca²⁺]i in mesenteric microvessels of pregnant rats

BACKGROUND AND PURPOSE

Normal pregnancy is associated with decreased vascular resistance and increased release of vasodilators. Endothelin-1 (ET-1) causes vasoconstriction via endothelin receptor type A (ET(A)R), but could activate ET(B)R in the endothelium and release vasodilator substances. However, the roles of ET(B)R in the regulation of vascular function during pregnancy and the vascular mediators involved are unclear.

EXPERIMENTAL APPROACH

Pressurized mesenteric microvessels from pregnant and virgin Sprague-Dawley rats were loaded with fura-2/AM for simultaneous measurement of diameter and [Ca²⁺]i.

KEY RESULTS

High KCl (51 mM) and phenylephrine (PHE) caused increases in vasoconstriction and [Ca²⁺]i that were similar in pregnant and virgin rats. ET-1 caused vasoconstriction that was less in pregnant than virgin rats, with small increases in [Ca²⁺]i. Pretreatment with the ET(B)R antagonist BQ-788 caused greater enhancement of ET-1-induced vasoconstriction in pregnant rats. ACh caused endothelium-dependent relaxation and decreased [Ca²⁺]i, and was more potent in pregnant than in virgin rats. ET-1 + ET(A)R antagonist BQ-123, and the ET(B)R agonists sarafotoxin 6c (S6c) and IRL-1620 caused greater vasodilation in pregnant than in virgin rats with no changes in [Ca²⁺]i, suggesting up-regulated ET(B)R-mediated relaxation pathways. ACh-, S6c- and IRL-1620-induced relaxation was reduced by the NO synthase inhibitor Nω-nitro-L-arginine methyl ester, and abolished by tetraethylammonium or endothelium removal. Western blots revealed greater amount of ET(B)R in intact microvessels of pregnant than virgin rats, but reduced levels in endothelium-denuded microvessels, supporting a role of endothelial ET(B)R.

CONCLUSIONS AND IMPLICATIONS

The enhanced ET(B)R-mediated microvascular relaxation may contribute to the decreased vasoconstriction and vascular resistance during pregnancy.

Gender differences in ocular blood flow

Gender medicine has been a major focus of research in recent years. The present review focuses on gender differences in the epidemiology of the most frequent ocular diseases that have been found to be associated with impaired ocular blood flow, such as age-related macular degeneration, glaucoma and diabetic retinopathy. Data have accumulated indicating that hormones have an important role in these diseases, since there are major differences in the prevalence and incidence between men and pre- and post-menopausal women. Whether this is related to vascular factors is, however, not entirely clear. Interestingly, the current knowledge about differences in ocular vascular parameters between men and women is sparse. Although little data is available, estrogen, progesterone and testosterone are most likely important regulators of blood flow in the retina and choroid, because they are key regulators of vascular tone in other organs. Estrogen seems to play a protective role since it decreases vascular resistance in large ocular vessels. Some studies indicate that hormone therapy is beneficial for ocular vascular disease in post-menopausal women. This evidence is, however, not sufficient to give any recommendation. Generally, remarkably few data are available on the role of sex hormones on ocular blood flow regulation, a topic that requires more attention in the future.

Postmenopausal hypertension and sodium sensitivity

It has been well established that women generally have lower incidence rates of hypertension than men at similar ages and these differences may vary with age. It also has been observed in many studies that after menopause, blood pressure (BP) increases in women to levels even higher than in men. The lack of estrogens may not be suggested as the only component involved in the development of postmenopausal hypertension. Thus, in this mini-review, the possible mechanisms by which sex hormones may influence the BP are discussed. This review also examines the renal regulatory mechanisms for gender differences in BP and explores the effects of salt intake on BP (salt-sensitivity) in pre and post-menopausal women.

Estrogen has been shown to stimulate nitric oxide (NO) production, thus female sex hormones have a beneficial effect on BP control. Evidences that angiotensin type 2 receptor (AT₂R) is up-regulated by estrogen support the favorable effects on BPs in women than men. The kidney plays an integral role in the regulation of arterial pressure through the mechanism of pressure-natriuresis, which has been shown to be modulated by the RAS. The prevalence of salt-sensitivity increases with age and low-salt diets has shown to help reduce systolic BP (SBP) and diastolic BP. While oral hormone replacement therapy has yielded only a neutral or minimal effect on the elevation of SBP, both the transdermal route replacement and a novel progestin with anti-aldosterone activity (drospirenone) has also shown to reduce SBP.

Vasoprotective effects of an endothelin receptor antagonist in ovariectomized female rats

AIMS

The effects of hormone replacement therapy with estrogen on cardiovascular disease in postmenopausal women are still controversial. In the present study, we examined the effects of an endothelin (ET) receptor antagonist (ERA) and/or angiotensin receptor blocker (ARB) on neointimal formation following vascular injury in ovariectomized (OVX) female rats.

MAIN METHODS

Female rats were divided into intact female and OVX groups. The right carotid artery was subjected to balloon injury, and harvested 2 weeks later.

KEY FINDINGS

In the intact female groups, treatment with ARB (L-158809; 1 mg/kg/day) for two weeks after the injury significantly decreased neointimal formation, whereas treatment with the ERA (J-104132; 10 mg/kg/day) did not affect neointimal formation. On the other hand, the ERA markedly decreased neointimal formation after the injury in the OVX groups; however, neointimal formation was not significantly improved by the ARB treatment. In addition, the combined treatment with 17β-estradiol (20 μg/kg/day) or the ERA and ARB markedly suppressed neointimal formation after the balloon injury in the OVX groups, whereas no combinational effects were observed due to the combined treatment with 17β-estradiol and the ERA.

SIGNIFICANCE

These results suggest that ERAs have estrogen-like vasoprotective effects on neointimal formation following balloon injury in OVX rats. ERAs may be useful as an alternative therapy to prevent vascular disease in postmenopausal women.

Hypertension: what's sex got to do with it?

Hypertension is a complex and multifaceted disease, and there are well established sex differences in many aspects of blood pressure (BP) control. The intent of this review is to highlight recent work examining sex differences in the molecular mechanisms of BP control in hypertension to assess whether the "one-size-fits-all" approach to BP control is appropriate with regard to sex.

Gender and the prevalence and progression of renal disease

In most experimental models of CKD, male animals progress more rapidly than females. Modulation of the hormonal milieu can replicate the effects of gender on the course of kidney disease. These observations suggest that sex hormones per se may be important determinants of the greater susceptibility of males to progressive kidney injury. The predominance of data in humans suggests that the course of nondiabetic kidney disease is more aggressive in men than women. Male gender is arguably also a risk factor for progression of diabetic nephropathy. Sex hormones directly or indirectly affect many cellular processes by modulating the synthesis of various cytokines, growth factors, and vasoactive agents. In particular, estrogen acts in a receptor-dependent mechanism to regulate genes involved in extracellular matrix metabolism. Estrogen has profound effects on transforming growth factor-β signal transduction and on the renin-angiotensin system. These effects may contribute to alterations in kidney hemodynamics and affect kidney disease progression. Selective estrogen receptor modulators, agents that mimic many of the beneficial effects of estrogen without reproducing estrogen's deleterious effects on reproductive tissue, ameliorate the course of kidney disease in animal models and in postmenopausal women.

ET-1 actions in the kidney: evidence for sex differences

Hypertension and chronic kidney disease are more common in men than in premenopausal women at the same age. In animal models, females are relatively protected against genetic or pharmacological procedures that produce high blood pressure and renal injury. Overactivation or dysfunction of the endothelin (ET) system modulates the progression of hypertension or kidney diseases with the ET(A) receptor primarily mediating vasoconstriction, injury and anti-natriuresis, and ET(B) receptors having opposite effects. The purpose of this review is to examine the role of the ET system in the kidney with a focus on the inequality between the sexes associated with the susceptibility to and progression of hypertension and kidney diseases. In most animal models, males have higher renal ET-1 mRNA expression, greater ET(A) -mediated responses, including renal medullary vasoconstriction, and increased renal injury. These differences are reduced following gonadectomy suggesting a role for sex hormones, mainly testosterone. In contrast, females are relatively protected from high blood pressure and kidney damage via increased ET(B) versus ET(A) receptor function. Furthermore, ET(A) receptors may have a favourable effect on sodium excretion and reducing renal damage in females. In human studies, the genetic polymorphisms of the ET system are more associated with hypertension and renal injury in women. However, the knowledge of sex differences in the efficacy or adverse events of ET(A) antagonists in the treatment of hypertension and kidney disease is poorly described. Increased understanding how the ET system acts differently in the kidneys between sexes, especially with regard to receptor subtype function, could lead to better treatments for hypertension and renal disease. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

Pathological Importance of the Endothelin-1/ET(B) Receptor System on Vascular Diseases

Activation of the endothelin (ET)-1/ET receptor system is involved in the development of vascular diseases such as atherosclerosis, vascular hypertrophy, and restenosis. Some issues still remain unresolved including whether ET receptor antagonists are expected to become the new therapeutic tools for the treatment of vascular diseases. One of the unresolved critical points is the functional role of ET receptor subtypes on each vascular disease, in particular the pathophysiological roles of the ET_B receptor. We recently demonstrated that selective inhibition of the ET_B receptor system showed harmful effects in the development of neointimal formation after vascular injury. However, there was no apparent difference in the therapeutic effects between a nonselective ET_A/ET_B receptor antagonist and selective ET_A receptor antagonist. These findings indicate that antagonism of the ET_A receptor system is essential for suppressing vascular remodeling, irrespective of the presence of ET_B-receptor-mediated actions, although the selective ET_B receptor antagonist worsens vascular remodeling. In addition, we found that ET receptor systems contribute to sex differences in the severity of vascular disease, thereby suggesting that the efficacy of ET receptor antagonists for vascular diseases may differ between sexes. In this paper, we outline the roles of the ET-1/ET_B receptor system on vascular diseases and its sex differences.

Testosterone and vascular function in aging

Androgen receptors are widely distributed in several tissues, including vascular endothelial and smooth muscle cells. Through classic cytosolic androgen receptors or membrane receptors, testosterone induces genomic and non-genomic effects, respectively. Testosterone interferes with the vascular function by increasing the production of pro-inflammatory cytokines and arterial thickness. Experimental evidence indicates that sex steroid hormones, such as testosterone modulate the synthesis and bioavailability of NO and, consequently, endothelial function, which is key for a healthy vasculature. Of interest, aging itself is accompanied by endothelial and vascular smooth muscle dysfunction. Aging-associated decline of testosterone levels is accompanied by age-related diseases, such as metabolic and cardiovascular diseases, indicating that very low levels of androgens may contribute to cardiovascular dysfunction observed in these age-related disorders or, in other words, that testosterone may have beneficial effects in the cardiovascular system. However, testosterone seems to play a negative role in the severity of renal disease. In this mini-review, we briefly comment on the interplay between aging and testosterone levels, the vascular actions of testosterone and its implications for vascular aging. Renal effects of testosterone and the use of testosterone to prevent vascular dysfunction in elderly are also addressed.

STIM1/Orai1 contributes to sex differences in vascular responses to calcium in spontaneously hypertensive rats

Sex differences in Ca2+-dependent signalling and homoeostasis in the vasculature of hypertensive rats are well characterized. However, sex-related differences in SOCE (store-operated Ca2+ entry) have been minimally investigated. We hypothesized that vascular protection in females, compared with males, reflects decreased Ca2+ mobilization due to diminished activation of Orai1/STIM1 (stromal interaction molecule 1). In addition, we investigated whether ovariectomy in females affects the activation of the Orai1/STIM1 pathway. Endothelium-denuded aortic rings from male and female SHRSP (stroke-prone spontaneously hypertensive rats) and WKY (Wistar-Kyoto) rats and from OVX (ovariectomized) or sham female SHRSP and WKY rats were used to functionally evaluate Ca2+ influx-induced contractions. Compared with females, aorta from male SHRSP displayed: (i) increased contraction during the Ca2+-loading period; (ii) similar transient contraction during Ca2+ release from the intracellular stores; (iii) increased activation of STIM1 and Orai1, as shown by the blockade of STIM1 and Orai1 with neutralizing antibodies, which reversed the sex differences in contraction during the Ca2+-loading period; and (iv) increased expression of STIM1 and Orai1. Additionally, we found that aortas from OVX-SHRSP showed increased contraction during the Ca2+-loading period and increased Orai1 expression, but no changes in the SR (sarcoplasmic reticulum)-buffering capacity or STIM1 expression. These findings suggest that augmented activation of STIM1/Orai1 in aortas from male SHRSP represents a mechanism that contributes to sex-related impaired control of intracellular Ca2+ levels. Furthermore, female sex hormones may negatively modulate the STIM/Orai1 pathway, contributing to vascular protection observed in female rats.

The role of uridine adenosine tetraphosphate in the vascular system

The endothelium plays a pivotal role in vascular homeostasis, and endothelial dysfunction is a major feature of cardiovascular diseases, such as arterial hypertension, atherosclerosis, and diabetes. Recently, uridine adenosine tetraphosphate (Up(4)A) has been identified as a novel and potent endothelium-derived contracting factor (EDCF). Up(4)A structurally contains both purine and pyrimidine moieties, which activate purinergic receptors. There is an accumulating body of evidence to show that Up(4)A modulates vascular function by actions on endothelial and smooth muscle cells. In this paper, we discuss the effects of Up(4)A on vascular function and a potential role for Up(4)A in cardiovascular diseases.

Cardiovascular Risk Factors and Estimated 10-Year Risk of Fatal Cardiovascular Events Using Various Equations in Greeks With Metabolic Syndrome

We investigated cardiovascular disease (CVD) risk factors in 1501 Greeks (613 men and 888 women, aged 40-65 years) referred to outpatients with metabolic syndrome (MetS) and without diabetes mellitus or CVD. The 10-year risk of fatal CVD events was calculated using European Society of Cardiology Systematic Coronary Risk Estimation (ESC SCORE), Hellenic-SCORE, and Framingham equations. Raised blood pressure (BP) and hypertriglyceridemia were more common in men (89.6% vs 84.2% and 86.8% vs 74.2%, respectively; P < .001). Low high-density lipoprotein cholesterol (HDL-C) and abdominal obesity were more common in women (58.2% vs 66.2% and 85.8% vs 97.1%, respectively; P < .001). The 10-year risk of fatal CVD events using HellenicSCORE was higher in men (6.3% ± 4.3% vs 2.7% ± 2.1%; P < .001). European Society of Cardiology Systematic Coronary Risk Estimation and Framingham yielded similar results. The risk equations gave similar assessments in a European Mediterranean population except for HellenicSCORE that calculated more MetS women requiring risk modification. This might justify local risk engine evaluation in event-based studies. (Clinical-Trials.gov ID: NCT00416741).

Endothelin receptors: what's new and what do we need to know?

Receptors are at the heart of how a molecule transmits a signal to a cell. Two receptor classes for endothelin (ET) are recognized, the ET(A) and ET(B) receptors. Intriguing questions have arisen in the field of ET receptor pharmacology, physiology, and function. For example, a host of pharmacological studies support the interaction of the ET(A) and ET(B) receptor in tissues (veins, arteries, bronchus, arterioles, esophagus), but yet few have been able to demonstrate direct ET(A)/ET(B) receptor interaction. Have we modeled this interaction wrong? Do we have a truly selective ET(A) receptor agonist such that we could selectively stimulate this important receptor? What can we learn from the recent phylogenic studies of the ET receptor family? Have we adequately addressed the number of biological molecules with which ET can interact to exert a biological effect? Recent mass spectrometry studies in our laboratory suggest that ET-1 interacts with other hereto unrecognized proteins. Biased ligands (ligands at the same receptor that elicit distinct signaling responses) have been discovered for other receptors. Do these exist for ET receptors and can we take advantage of this possibility in drug design? These and other questions will be posed in this minireview on topics on ET receptors.

Extracellular signal-regulated kinase 1/2 activation, via downregulation of mitogen-activated protein kinase phosphatase 1, mediates sex differences in desoxycorticosterone acetate-salt hypertension vascular reactivity

Extracellular signal-regulated kinase (ERK)1/2 has been reported to play a role in vascular dysfunction associated with mineralocorticoid hypertension. We hypothesized that, compared with female rats, an upregulation of ERK1/2 signaling in the vasculature of male rats contributes to augmented contractile responses in mineralocorticoid hypertension. Uninephrectomized male and female Sprague-Dawley rats received desoxycorticosterone acetate (DOCA) pellets (200 mg per animal) and saline to drink for 3 weeks. Control uninephrectomized rats received tap water to drink. Blood pressure, measured by telemetry, was significantly higher in male DOCA rats (191+/-3 mm Hg) compared with female DOCA rats (172+/-7 mm Hg; n=5). DOCA treatment resulted in augmented contractile responses to phenylephrine in aorta (22+/-3 mN; n=6) and small mesenteric arteries (13+/-2 mN; n=6) from male DOCA rats versus uninephrectomized male rats (16+/-3 and 10+/-2 mN, respectively; P<0.05) and female DOCA rats (15+/-1 and 11+/-1 mN, respectively). ERK1/2 inhibition with PD-98059 (10 micromol/L) abrogated increased contraction to phenylephrine in aorta (14+/-2 mN) and small mesenteric arteries (10+/-2 mN) from male DOCA rats, without any effects in arteries from male uninephrectomized or female animals. Compared with the other groups, phosphorylated ERK1/2 levels were increased in the aorta from male DOCA rats, whereas mitogen-activated protein kinase phosphatase 1 expression was decreased. Interleukin-10 plasma levels, which positively regulate mitogen-activated protein kinase phosphatase 1 activity, were reduced in male DOCA-salt rats. We speculate that augmented vascular reactivity in male hypertensive rats is mediated via activation of the ERK1/2 pathway. In addition, mitogen-activated protein kinase phosphatase 1 and interleukin 10 play regulatory roles in this process.