Altered endothelial ETB receptor expression in postmenopausal women

Maternal Microvascular Dysfunction During and After Preeclamptic Pregnancy

Preeclampsia, a pregnancy disorder characterized by de novo hypertension and maternal multisystem organ dysfunction, is the leading cause of maternal mortality worldwide and is associated with a fourfold greater risk of cardiovascular disease throughout the lifespan. Current understanding of the etiology of preeclampsia remains unclear, due in part to the varying phenotypical presentations of the disease, which has hindered the development of effective and mechanism-specific treatment or prevention strategies both during and after the affected pregnancy. These maternal sequelae of preeclampsia are symptoms of systemic vascular dysfunction in the maternal nonreproductive microvascular beds that drives the development and progression of adverse cardiovascular outcomes during preeclampsia. Despite normalization of vascular disturbances after delivery, subclinical dysfunction persists in the nonreproductive microvascular beds, contributing to an increased lifetime risk of cardiovascular and metabolic diseases and all-cause mortality. Given that women with a history of preeclampsia demonstrate vascular dysfunction despite an absence of traditional CVD risk factors, an understanding of the underlying mechanisms of microvascular dysfunction during and after preeclampsia is essential to identify potential therapeutic avenues to mitigate or reverse the development of overt disease. This article aims to provide a summary of the existing literature on the pathophysiology of maternal microvascular dysfunction during preeclampsia, the mechanisms underlying the residual dysfunction that remains after delivery, and current and potential treatments both during and after the affected pregnancy that may reduce microvascular dysfunction in these high-risk women. © 2024 American Physiological Society. Compr Physiol 14:5703-5727, 2024.

Comprehensive analysis of the endothelin system in the kidneys of mice, rats, and humans

The intrarenal endothelin (ET) system is an established moderator of kidney physiology and mechanistic contributor to the pathophysiology and progression of chronic kidney disease in humans and rodents. The aim of the present study was to characterize ET system by combining single cell RNA sequencing (scRNA-seq) data with immunolocalization in human and rodent kidneys of both sexes. Using publicly available scRNA-seq data, we assessed sex and kidney disease status (human), age and sex (rats), and diurnal expression (mice) on the kidney ET system expression. In normal human biopsies of both sexes and in rodent kidney samples, the endothelin-converting enzyme-1 (ECE1) and ET-1 were prominent in the glomeruli and endothelium. These data agreed with the scRNA-seq data from these three species, with ECE1/Ece1 mRNA enriched in the endothelium. However, the EDN1/Edn1 gene (encodes ET-1) was rarely detected, even though it was immunolocalized within the kidneys, and plasma and urinary ET-1 excretion are easily measured. Within each species, there were some sex-specific differences. For example, in kidney biopsies from living donors, men had a greater glomerular endothelial cell endothelin receptor B (Ednrb) compared with women. In mice, females had greater kidney endothelial cell Ednrb than male mice. As commercially available antibodies did not work in all species, and RNA expression did not always correlate with protein levels, multiple approaches should be considered to maintain required rigor and reproducibility of the pre- and clinical studies evaluating the intrarenal ET system.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Antecubital venous endothelial ETB receptor protein expression is preserved with aging in men

Changes in endothelial function precede the development of cardiovascular disease (CVD). We have previously shown that age-related declines in endothelial function in women are due in part to a reduction in endothelial cell endothelin-B receptor (ETBR) protein expression. However, it is not known if ETBR protein expression changes with aging in men. The purpose of this study was to test the hypothesis that ETBR protein expression is attenuated in older men (OM) compared with younger men (YM). Primary endothelial cells were harvested from the antecubital vein of 14 OM (60 ± 6 yr; 26 ± 3 kg/m2) and 17 YM (24 ± 5 yr; 24 ± 2 kg/m2). Cells were stained with 4',6-diamidino-2-phenylindole, vascular endothelial cadherin, and ETBR. Images were quantified using immunocytochemistry. Endothelial function was assessed using brachial artery flow-mediated dilation (FMD). Systolic BP was similar (OM, 123 ± 11 vs. YM, 122 ± 10 mmHg) whereas diastolic BP was higher in OM (OM, 77 ± 7 vs. YM, 70 ± 6 mmHg; P < 0.01). Total testosterone was lower in OM (OM, 6.28 ± 4.21 vs. YM, 9.10 ± 2.68 ng/mL; P = 0.03). As expected, FMD was lower in OM (OM, 3.85 ± 1.51 vs. YM, 6.40 ± 2.68%; P < 0.01). However, ETBR protein expression was similar between OM and YM (OM, 0.39 ± 0.17 vs. YM, 0.42 ± 0.17 AU; P = 0.66). These data suggest that ETBR protein expression is not altered with age in men. These findings contrast with our previous data in women and further support sex differences in the endothelin system.NEW & NOTEWORTHY Our laboratory has previously shown that age-related declines in endothelial function are associated with a reduction in endothelial cell ETBR protein expression in women. However, it is unclear if endothelial cell ETBR protein expression is reduced with aging in men. This study demonstrates that endothelial cell ETBR protein expression is preserved with aging in men, and provides additional evidence for sex differences in the endothelin system.

Endothelin mediates sex-differences in acclimation to high salt diet in rats

INTRODUCTION

Current understanding of sodium (Na+) handling is based on studies done primarily in males. Contrary to the gradual increase in high salt (HS) induced natriuresis over 3-5 days in males, female Sprague Dawley (SD) rats have a robust natriuresis after 1 day of HS. Renal endothelin-1 (ET-1) signaling, through ET receptor A and B, is an important natriuretic pathway and was implicated in our previous dietary salt acclimation studies, however, the contribution of ET receptors to sex-differences in acclimation to dietary Na+ challenges has yet to be clarified. We hypothesized that ET receptors mediate the augmented natriuretic capacity of female rats in response to a HS diet.

METHODS

To test our hypothesis, male and female SD rats were implanted with telemeters and randomly assigned to treatment with A-182086, a dual ETA and ETB receptor antagonist, or control. 24-h urine samples were collected and assessed for electrolytes and ET-1. Studies were performed on a normal salt (NS, 0.3% NaCl) diet and after challenging rats with HS (4% NaCl) diet for 1 day.

RESULTS

We found that A-182086 increased blood pressure in male and female SD rats fed either diet. Importantly, A-182086 eliminated sex-differences in natriuresis on NS and HS. In particular, A-182086 promotes HS-induced natriuresis in male rats rather than attenuating the natriuretic capacity of females. Further, the sex-difference in urinary ET-1 excretion in NS-fed rats was eliminated by A-182086.

CONCLUSION

In conclusion, ET receptors are crucial for mediating sex-difference in the natriuretic capacity primarily through their actions in male rats.

Association between serum Klotho concentration and hypertension in postmenopausal women, a cross-sectional study from NHANES 2013-2016

BACKGROUND

The objective of this study was to examine the correlation between serum Klotho protein concentration and postmenopausal hypertension.

METHODS

A cross-sectional study design was used, in which 1713 postmenopausal women who participated in the National Health and Nutrition Examination Survey (NHANES) 2013-2016 were included. Multivariate logistic regression models were applied to assess the association between serum Klotho concentration and postmenopausal hypertension.

RESULTS

A weighted analysis was executed, revealing a noteworthy hypertension prevalence rate of 53.44% among the study participants. Participants with lower quartile of serum Klotho concentration had a higher prevalence of hypertension than those in higher quartiles (Q1:62.29% vs. Q2: 48.52% vs. Q3: 47.33% vs. Q4: 55.02%, p < 0.001). Furthermore, a multivariate logistic regression analysis confirmed that participants with higher quartiles of serum Klotho concentration had a significantly reduced risk of postmenopausal hypertension compared to those in the lowest quartile. Subgroup analysis displayed consistent findings in those following subgroups: aged ≥ 65 years, obesity, nonsmokers, individuals without diabetes and coronary heart disease, and those with higher levels of estradiol and estimated glomerular filtration rate. Based on the results, we concluded that there is a significant association between serum Klotho concentration and postmenopausal hypertension.

CONCLUSION

The findings of this study revealed a significant inverse association between serum Klotho concentration and hypertension among postmenopausal women. Serum Klotho concentration may serve as a valuable biomarker for risk stratification in postmenopausal women who are at risk of developing hypertension.

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.

Endothelin receptor blockade blunts the pressor response to acute stress in men and women with obesity

Obesity is associated with dysregulation of the endothelin system. In individuals with obesity, an exaggerated pressor response to acute stress is accompanied by increased circulating endothelin-1 (ET-1). The impact of combined endothelin A/B receptor (ET_A/B) antagonism on the stress-induced pressor response in overweight/obese (OB) individuals is unknown. The objective of this study is to test the hypothesis that treatment with an ET_A/B antagonist (bosentan) would reduce the stress-induced pressor response and arterial stiffness in overweight/obese compared with normal weight (NW) individuals. Forty participants [normal weight (NW): n = 20, body mass index (BMI): 21.7 ± 2.4 kg/m² and overweight/obese (OB): n = 20, BMI: 33.8 ± 8.2 kg/m²] were randomized to placebo or 125 mg of bosentan twice a day (250 mg total) for 3 days. Hemodynamics were assessed before, during, and after a cold pressor test (CPT). Endothelin-1 was assessed at baseline and immediately after CPT. Following a washout period, the same protocol was repeated with the opposite treatment. The change from baseline in mean arterial pressure (MAP) during CPT following bosentan was significantly lower (P = 0.039) in the OB group than in the NW group (OB: 28 ± 12 vs. NW: 34 ± 15 mmHg). These results suggest that ET_A/B antagonism favorably blunts the pressor response to acute stress in overweight/obese individuals.NEW & NOTEWORTHY Findings from our current translational investigation demonstrate that dual endothelin A/B receptor antagonism blunts the pressor response to acute stress in overweight/obese individuals. These results suggest that modulation of the endothelin system may represent a novel therapeutic target to reduce cardiovascular disease (CVD) risk by blunting the stress response in overweight/obese individuals.

Vascular Ageing and Aerobic Exercise

Impairment of vascular function, in particular endothelial dysfunction and large elastic artery stiffening, represents a major link between ageing and cardiovascular risk. Clinical and experimental studies identified numerous mechanisms responsible for age-related decline of endothelial function and arterial compliance. Since most of these mechanisms are related to oxidative stress or low-grade inflammation, strategies that suppress oxidative stress and inflammation could be effective for preventing age-related changes in arterial function. Indeed, aerobic physical activity, which has been shown to improve intracellular redox balance and mitochondrial health and reduce levels of systemic inflammatory markers, also improves endothelial function and arterial distensibility and reduces risk of cardiovascular diseases. The present paper provides a brief overview of processes underlying age-related changes in arterial function, as well as the mechanisms through which aerobic exercise might prevent or interrupt these processes, and thus attenuate vascular ageing.

ETB receptor-mediated vasodilation is regulated by estradiol in young women

The endothelin-B (ET_B) receptor is a key regulator of vascular endothelial function in women. We have previously shown that the ET_B receptor mediates vasodilation in young women, an effect that is lost after menopause. However, the direct impact of changes in estradiol (E₂) on ET_B receptor function in women remains unclear. Therefore, the purpose of this study was to test the hypothesis that E₂ exposure modulates ET_B receptor-mediated dilation in young women. Fifteen young women (24 ± 4 yr, 24 ± 3 kg/m²) completed the study. Endogenous sex hormone production was suppressed with daily administration of a gonadotropin-releasing hormone antagonist (GnRHant; Ganirelix) for 10 days; E₂ (0.1 mg/day, Vivelle-Dot patch) was added back on days 4-10. We measured vasodilation in the cutaneous microcirculation (microvascular endothelial function) via local heating (42°C) on day 4 (GnRHant) and day 10 (GnRHant + E₂) using laser Doppler flowmetry coupled with intradermal microdialysis during perfusions of lactated Ringer's (control) and ET_B receptor antagonist (BQ-788, 300 nM). During GnRHant, vasodilatory responses to local heating were enhanced with ET_B receptor blockade (control: 83 ± 9 vs. BQ-788: 90 ± 5%CVC_max, P = 0.004). E₂ administration improved vasodilation in the control site (GnRHant: 83 ± 9 vs. GnRHant + E₂: 89 ± 8%CVC_max, P = 0.036). Furthermore, cutaneous vasodilatory responses during ET_B receptor blockade were blunted after E₂ administration (control: 89 ± 8 vs. BQ-788: 84 ± 8%CVC_max, P = 0.047). These data demonstrate that ovarian hormones, specifically E₂, modulate ET_B receptor function and contribute to the regulation of microvascular endothelial function in young women.NEW & NOTEWORTHY The endothelin-B (ETB) receptor mediates vasodilation in young women, an effect lost following menopause. It is unclear whether these alterations are due to aging or changes in estradiol (E2). During endogenous hormone suppression (GnRH antagonist), blockade of ETB receptors enhanced cutaneous microvascular vasodilation. However, during E2 administration, blockade of ETB receptors attenuated vasodilation, indicating that the ETB receptor mediates dilation in the presence of E2. In young women, ETB receptors mediate vasodilation in the presence of E2, an effect that is lost when E2 is suppressed.

Sex Differences in Cardiovascular Aging and Heart Failure

PURPOSE OF THE REVIEW

This review summarizes sex-related changes in the heart and vasculature that occur with aging, both in the presence and absence of cardiovascular disease (CVD).

RECENT FINDINGS

In the presence of CVD risk factors and/or overt CVD, sex-specific changes in the number of cardiomyocytes, extent of the myocardial extracellular matrix, and myocellular hypertrophy promote unique patterns of LV remodeling in men and women. In addition, age- and sex-specific vascular stiffening is also well established, driven by changes in endothelial dysfunction, elastin-collagen content, microvascular dysfunction, and neurohormonal signaling. Together, these changes in LV chamber geometry and morphology, coupled with heightened vascular stiffness, appear to drive both age-related increases in systolic function and declines in diastolic function, particularly in postmenopausal women. Accordingly, estrogen has been implicated as a key mediator, given its direct vasodilating properties, association with nitric oxide excretion, and involvement in myocellular Ca2+ handling, mitochondrial energy production, and oxidative stress. The culmination of the abovementioned sex-specific cardiac and vascular changes across the lifespan provides important insight into heart failure development, particularly of the preserved ejection fraction variety, while offering promise for future preventive strategies and therapeutic approaches.