Endothelial sodium channels trigger endothelial salt sensitivity with aging

Endothelial cell serum and glucocorticoid regulated kinase 1 (SGK1) mediates vascular stiffening

BACKGROUND

Excessive dietary salt intake increases vascular stiffness in humans, especially in salt-sensitive populations. While we recently suggested that the endothelial sodium channel (EnNaC) contributes to salt-sensitivity related endothelial cell (EC) and arterial stiffening, mechanistic understanding remains incomplete. This study therefore aimed to explore the role of EC-serum and glucocorticoid regulated kinase 1 (SGK1), as a reported regulator of sodium channels, in EC and arterial stiffening.

METHODS AND RESULTS

A mouse model of salt sensitivity-associated vascular stiffening was produced by subcutaneous implantation of slow-release deoxycorticosterone acetate (DOCA) pellets, with salt (1 % NaCl, 0.2 % KCl) administered via drinking water. Preliminary data showed that global SGK1 deletion caused significantly decreased blood pressure (BP), EnNaC activity and aortic endothelium stiffness as compared to control mice following DOCA-salt treatment. To probe EC signaling pathways, selective deletion of EC-SGK1 was performed by cross-breeding cadherin 5-Cre mice with sgk1flox/flox mice. DOCA-salt treated control mice had significantly increased BP, EC and aortic stiffness in vivo and ex vivo, which were attenuated by EC-SGK1 deficiency. To demonstrate relevance to humans, human aortic ECs were cultured in the absence or presence of aldosterone and high salt with or without the SGK1 inhibitor, EMD638683 (10uM or 25uM). Treatment with aldosterone and high salt increased intrinsic stiffness of ECs, which was prevented by SGK1 inhibition. Further, the SGK1 inhibitor prevented aldosterone and high salt induced actin polymerization, a key mechanism in cellular stiffening.

CONCLUSION

EC-SGK1 contributes to salt-sensitivity related EC and aortic stiffening by mechanisms appearing to involve regulation of actin polymerization.

Cellular Senescence as a Targetable Risk Factor for Cardiovascular Diseases: Therapeutic Implications: JACC Family Series

The prevalence of cardiovascular diseases markedly rises with age. Cellular senescence, a hallmark of aging, is characterized by irreversible cell cycle arrest and the manifestation of a senescence-associated secretory phenotype, which has emerged as a significant contributor to aging, mortality, and a spectrum of chronic ailments. An increasing body of preclinical and clinical research has established connections between senescence, senescence-associated secretory phenotype, and age-related cardiac and vascular pathologies. This review comprehensively outlines studies delving into the detrimental impact of senescence on various cardiovascular diseases, encompassing systemic atherosclerosis (including coronary artery disease, stroke, and peripheral arterial disease), as well as conditions such as hypertension, congestive heart failure, arrhythmias, and valvular heart diseases. In addition, we have preclinical studies demonstrating the beneficial effects of senolytics-a class of drugs designed to eliminate senescent cells selectively across diverse cardiovascular disease scenarios. Finally, we address knowledge gaps on the influence of senescence on cardiovascular systems and discuss the future trajectory of strategies targeting senescence for cardiovascular diseases.

Salt Sensitivity of Blood Pressure in Black People: The Need to Sort Out Ancestry Versus Epigenetic Versus Social Determinants of Its Causation

Race is a social construct, but self-identified Black people are known to have higher prevalence and worse outcomes of hypertension than White people. This may be partly due to the disproportionate incidence of salt sensitivity of blood pressure in Black people, a cardiovascular risk factor that is independent of blood pressure and has no proven therapy. We review the multiple physiological systems involved in regulation of blood pressure, discuss what, if anything is known about the differences between Black and White people in these systems and how they affect salt sensitivity of blood pressure. The contributions of genetics, epigenetics, environment, and social determinants of health are briefly touched on, with the hope of stimulating further work in the field.

Systematic review of mediterranean diet interventions in menopausal women

The increasing lifespan of women and their extended time spent in menopause pose significant challenges for health care systems, primarily due to the impacts of postmenopausal estrogen deficiency and aging on health. Menopause's onset is linked to a heightened prevalence of obesity, metabolic syndrome, cardiovascular disease, and osteoporosis. Diet is particularly relevant during menopause given its impact on quality of life and longevity and its modifiability. Because the Mediterranean diet is currently regarded as one of the healthiest dietary models in the world, the aim of this systematic review was to assess current evidence regarding the effectiveness of studies on the Mediterranean diet as an intervention for menopausal women. A systematic review of intervention-based studies involving the Mediterranean diet among menopausal women was performed in Scopus, PubMed, and Web of Science. The results of seven that met the inclusion criteria suggests that adherence to the Mediterranean diet can have beneficial impacts on menopausal women's health, including reductions in weight, blood pressure, blood ω6: ω3 ratio, triglycerides, total cholesterol, and LDL levels. Those results seem to be relevant for public health interventions aimed at improving menopausal women's quality of life.

Life's Essential 8: Optimizing Health in Older Adults

The population worldwide is getting older as a result of advances in public health, medicine, and technology. Older individuals are living longer with a higher prevalence of subclinical and clinical cardiovascular disease (CVD). In 2010, the American Heart Association introduced a list of key prevention targets, known as "Life's Simple 7" to increase CVD-free survival, longevity, and quality of life. In 2022, sleep health was added to expand the recommendations to "Life's Essential 8" (eat better, be more active, stop smoking, get adequate sleep, manage weight, manage cholesterol, manage blood pressure, and manage diabetes). These prevention targets are intended to apply regardless of chronologic age. During this same time, the understanding of aging biology and goals of care for older adults further enhanced the relevance of prevention across the range of functions. From a biological perspective, aging is a complex cellular process characterized by genomic instability, telomere attrition, loss of proteostasis, inflammation, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. These aging hallmarks are triggered by and enhanced by traditional CVD risk factors leading to geriatric syndromes (eg, frailty, sarcopenia, functional limitation, and cognitive impairment) which complicate efforts toward prevention. Therefore, we review Life's Essential 8 through the lens of aging biology, geroscience, and geriatric precepts to guide clinicians taking care of older adults.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Salt as a Trigger for Atrial Tachycardia/Fibrillation

A variety of potential triggers of atrial fibrillation (AF) have been reported, including alcohol consumption, caffeine, exercise, and stress. Vagal AF triggers include gastrointestinal factors such as the amount of food consumed, types of foods, and gas and bloating. In this case report, detailed data of seven dietary and behavioral factors (many vagal) believed to be possible atrial tachycardia (AT) or AF triggers in a single patient with paroxysmal AT/AF were recorded. Episodes of AT and AF were recorded in the patient using a Medtronic loop recorder and analyzed by a cardiac electrophysiologist. To evaluate these potential triggers of AT/AF events, a general linear model with binomial family error distribution was used to fit the data. Then, a stepAIC function from the MASS package in R was used to perform a stepwise model selection using AIC (Akaike information criterion). The analysis only identified the amount of salt intake and the use of polyethylene glycol 3350 as predictors of AT/AF, and high salt intake was the only factor significantly associated with the onset of AT/AF (P < 0.05). Thus, salt intake may trigger AT/AF in ways other than via hypertension.

Effects of amiloride on acetylcholine-dependent arterial vasodilation evolve over time in mice on a high salt diet

The maintenance of endothelial health is required for normal vascular function and blood pressure regulation. The epithelial Na⁺ channel (ENaC) in endothelial cells has emerged as a new molecular player in the regulation of endothelial nitric oxide production and vascular stiffness. While ENaC expression in the kidney is negatively regulated by high [Na⁺ ], ENaC expression in isolated endothelial cells has been shown to increase in response to a high extracellular [Na⁺ ]. In culture, this increased expression leads to cellular stiffening and decreased nitric oxide release. In vivo, the effects of high salt diet on endothelial ENaC expression and activity have varied depending on the animal model utilized. Our aim in the present study was to examine the role of endothelial ENaC in mediating vasorelaxation in the C57Bl/6 mouse strain. We utilized pressure myography to test the responsiveness of thoracodorsal arteries to acetylcholine in mice with increased sodium consumption both in the presence and absence of increased aldosterone. ENaC's contribution was assessed with the use of the specific inhibitor amiloride. We found that while aldosterone had very little effect on ENaC's contribution to acetylcholine sensitivity, a high salt diet led to an amiloride-dependent shift in the acetylcholine response of vessels. However, the direction of this shift was dependent on the length of high salt diet administration. Overall, our studies reveal that ENaC's role in the endothelium may be more complicated than previously thought. The channel does not simply inhibit nitric oxide generation, but instead helps preserve a homeostatic response.

Extracellular Matrix in Aging Aorta

The aging population is booming all over the world and arterial aging causes various age-associated pathologies such as cardiovascular diseases (CVDs). The aorta is the largest elastic artery, and transforms pulsatile flow generated by the left ventricle into steady flow to maintain circulation in distal tissues and organs. Age-associated structural and functional changes in the aortic wall such as dilation, tortuousness, stiffening and losing elasticity hamper stable peripheral circulation, lead to tissue and organ dysfunctions in aged people. The extracellular matrix (ECM) is a three-dimensional network of macromolecules produced by resident cells. The composition and organization of key ECM components determine the structure-function relationships of the aorta and therefore maintaining their homeostasis is critical for a healthy performance. Age-associated remodeling of the ECM structural components, including fragmentation of elastic fibers and excessive deposition and crosslinking of collagens, is a hallmark of aging and leads to functional stiffening of the aorta. In this mini review, we discuss age-associated alterations of the ECM in the aortic wall and shed light on how understanding the mechanisms of aortic aging can lead to the development of efficient strategy for aortic pathologies and CVDs.

Direct Evidence of Endothelial Dysfunction and Glycocalyx Loss in Dermal Biopsies of Patients With Chronic Kidney Disease and Their Association With Markers of Volume Overload

Cardiovascular morbidity is a major problem in patients with chronic kidney disease (CKD) and endothelial dysfunction (ED) is involved in its development. The luminal side of the vascular endothelium is covered by a protective endothelial glycocalyx (eGC) and indirect evidence indicates eGC loss in CKD patients. We aimed to investigate potential eGC loss and ED in skin biopsies of CKD patients and their association with inflammation and volume overload. During living kidney transplantation procedure, abdominal skin biopsies were taken from 11 patients with chronic kidney disease stage 5 of whom 4 were treated with hemodialysis and 7 did not receive dialysis treatment. Nine healthy kidney donors served as controls. Biopsies were stained and quantified for the eGC marker Ulex europaeus agglutinin-1 (UEA1) and the endothelial markers vascular endothelial growth factor-2 (VEGFR2) and von Willebrand factor (vWF) after double staining and normalization for the pan-endothelial marker cluster of differentiation 31. We also studied associations between quantified log-transformed dermal endothelial markers and plasma markers of inflammation and hydration status. Compared to healthy subjects, there was severe loss of the eGC marker UEA1 (P < 0.01) while VEGFR2 was increased in CKD patients, especially in those on dialysis (P = 0.01). For vWF, results were comparable between CKD patients and controls. Skin water content was identical in the three groups, which excluded dermal edema as an underlying cause in patients with CKD. The dermal eGC/ED markers UEA1, VEGFR2, and vWF all associated with plasma levels of NT-proBNP and sodium (all R² > 0.29 and P < 0.01), except for vWF that only associated with plasma NT-proBNP. This study is the first to show direct histopathological evidence of dermal glycocalyx loss and ED in patients with CKD. In line with previous research, our results show that ED associates with markers of volume overload arguing for strict volume control in CKD patients.

Vascular aging, the vascular cytoskeleton and aortic stiffness

Vascular aging, aortic stiffness and hypertension are mechanistically interrelated. The perspective presented here will focus mainly on the molecular mechanisms of age-associated increases in the stiffness of the vascular smooth muscle cell (VSMC). This review will highlight the mechanisms by which the VSMC contributes to disorders of vascular aging. Distinct functional sub-components of the vascular cell and the molecular mechanisms of the protein-protein interactions, signaling mechanisms and intracellular trafficking processes in the setting of the aging aorta will be detailed.

Detrimental or beneficial: Role of endothelial ENaC in vascular function

In the past, it was believed that the expression of the epithelial sodium channel (ENaC) was restricted to epithelial tissues, such as the distal nephron, airway, sweat glands, and colon, where it is critical for sodium homeostasis. Over the past two decades, this paradigm has shifted due to the finding that ENaC is also expressed in various nonepithelial tissues, notably in vascular endothelial cells. In this review, the recent findings of the expression, regulation, and function of the endothelial ENaC (EnNaC) are discussed. The expression of EnNaC subunits is reported in a variety of endothelial cell lines and vasculatures, but this is controversial across different species and vessels and is not a universal finding in all vascular beds. The expression density of EnNaC is very faint compared to ENaC in the epithelium. To date, little is known about the regulatory mechanism of EnNaC. Through it can be regulated by aldosterone, the detailed downstream signaling remains elusive. EnNaC responds to increased extracellular sodium with the feedforward activation mechanism, which is quite different from the Na⁺ self-inhibition mechanism of ENaC. Functionally, EnNaC was shown to be a determinant of cellular mechanics and vascular tone as it can sense shear stress, and its activation or insertion into plasma membrane causes endothelial stiffness and reduced nitric oxide production. However, in some blood vessels, EnNaC is essential for maintaining the integrity of endothelial barrier function. In this context, we discuss the possible reasons for the distinct role of EnNaC in vasculatures.

Evaluation of the Effects of Aging on the Aorta Stiffness in Relation with Mineral and Trace Element Levels: an Optimized Method via Custom-Built Stretcher Device

Aortic stiffness represents the major cause of aging and tightly associated with hypertension, atherosclerosis, cardiovascular diseases, and increased mortality. Mechanical characteristics of the aorta play a vital role in the blood flow, circulation, systolic pressure, and aortic stiffness; however, the correlation of trace element and mineral levels with aortic stiffness has not been studied before. Balance in the trace elements and minerals is vital for the biological functions; however, natural aging may alter this balance. Thus, after measuring aortic stiffness of aged and young rat aortas by a custom-built stretcher device, trace element and mineral levels were evaluated via ICP-MS. Also, biomarkers of aging including blood pressure, arterial pressure glucose, insulin levels, and histochemical parameters were investigated as well. Aortic stiffness, blood glucose, plasma insulin, systolic, diastolic, and mean arterial pressure significantly increased by aging in the aorta of aged rats compared with the young ones. Also, Fe, Al, Co, Ni, Zn, Sr, Na, Mg, and K levels increased in the aged aorta samples compared with the young aorta samples of rats. Increased levels of the indicated elements may be correlated with the development and progression of aortic stiffness and vascular complications. Thus, possible mechanisms correlating aortic stiffness with the imbalance in the trace element and mineral levels should be further investigated.

The importance of the epithelial sodium channel in determining salt sensitivity in people of African origin

Hypertension is highly prevalent in Black Africans and has been found to be associated with worse blood pressure (BP) control and more cardiovascular disease. Black Africans are more salt sensitive with low renin and aldosterone levels. This can be explained in part by variants in the epithelial sodium channel (ENaC) causing an increase in channel activity resulting in sodium and water retention. These variants in the ENaC are increased in the Black African populations presumably due to selective pressure for sodium retention in traditionally low-salt diets. Furthermore, increased endothelial sodium channel activity contributes to the risk of vascular stiffness, which may also result in more difficult to control hypertension. Patients with increased activity of the ENaC are more likely to respond to amiloride (a selective sodium channel antagonist), which has implications for the management of severe and resistant hypertension in Black Africans. A large-scale controlled trial on the use of amiloride compared to usual care is warranted in Blacks with severe or resistant hypertension.

Relationship between saline infusion and blood pressure variability in non-critically patients with hypertension: A retrospective study

Saline is a commonly used intravenous solvent, however, its excessive infusion may increase drug-induced sodium intake. To investigate the effects of saline infusion on blood pressure variability (BPV) in patients with hypertension, a retrospective study was performed in 1010 patients with hypertension. The patients who received saline infusion before surgery for continuous 3 to 5 days were divided into 2 groups according to the saline infusion volume during the hospitalization, which are >500 mL per day group and <500 mL per day group. The overall incidence of abnormal BPV was 11.58%. As for the incidence of abnormal BPV in the <500 mL per day group with 698 patients was 9.17%, while that in the >500 mL per day group with 312 patients was as high as 16.99%. Additionally, >500 mL of daily saline infusion for continuous 3 to 5 days (P for trend = .004, odds ratio [OR] = 1.911, 95% confidence interval [CI] for OR 1.226-2.977), medical history of diabetes mellitus (P < .001, OR = 4.856, 95% CI for OR 3.118-7.563) and cardiovascular diseases (P < .001, OR = 2.498, 95% CI for OR 1.549-4.029) may be risk factors of abnormal BPV; while anti-hypertensive therapy with diuretics (P < .001, OR = 0.055, 95% CI for OR 0.024-0.125) may be the protective factor. Our study suggests that >500 mL of daily saline infusion for continuous 3 to 5 days may have disadvantages in the blood pressure control for hypertensive patients, especially for the patients with diabetes mellitus and cardiovascular diseases.

Sequential nephron blockade with combined diuretics improves diastolic function in patients with resistant hypertension

AIMS

Hypertension is a major contributor to cardiac diastolic dysfunction. Different therapeutics strategies have been proposed to control blood pressure (BP), but their independent impact on cardiac function remains undetermined. In patients with resistant hypertension, we compared the changes in cardiac parameters between two strategies based on sequential nephron blockade (NBD) with a combination of diuretics or sequential renin-angiotensin system blockade (RASB).

METHODS AND RESULTS

After a 4-week period where all patients received Irbesartan 300 mg/day + hydrochlorothiazide 12.5 mg/day + amlodipine 5 mg/day, 140 resistant hypertension patients (54.8 ± 11.1 years, 76% men, mean duration with hypertension: 13.1 ± 10.5 years, no previous history of heart failure or current symptoms of congestive heart failure) were randomized 1:1 to the NBD regimen or to the RASB regimen at week 0 (W0, baseline). Treatment intensity was increased at week 4, 8, or 10 if home BP was ≥135/85 mmHg, by sequentially adding 25 mg spironolactone, 20-40 mg furosemide, and 5 mg amiloride (NBD group) or 5-10 mg ramipril and 5-10 mg bisoprolol (RASB group). No other antihypertensive drug was allowed during the study. BP, BNP levels, and echocardiographic parameters were assessed at weeks 0 and 12. The baseline characteristics, laboratory parameters, and plasma hormones (BNP, renin, and aldosterone) and cardiac echocardiographic parameters did not significantly differ between the NBD and the RASB groups. Over 12 weeks, BNP levels significantly decreased in NBD but increased in RASB (mean [CI 95%] change in log-transformed BNP levels: -43% [-67%; -23%] vs. +55% [46%; 62%] in NBD vs. RASB, respectively, P < 0.0001). Similarly, the proportion of patients presenting ≥2 echocardiographic criteria of diastolic dysfunction decreased between baseline and W12 from 31% to 3% in NBD but increased from 19% to 32% in RASB (P = 0.0048). As compared with RASB, NBD induced greater decrease in ambulatory systolic BP (P < 0.0001), pulse pressure (P < 0.0001), and systemic vascular resistance (P < 0.005). In multivariable linear regression analyses, NBD treatment was significantly associated with decreased BNP levels (adjusted ß: -46.41 ± 6.99, P < 0.0001) independent of age, gender, renal function, and changes in BPs or heart rate.

CONCLUSIONS

In patients with resistant hypertension, nephron blockade with a combination of diuretics significantly improves cardiac markers of diastolic dysfunction independently of BP lowering.

Endothelial factors in the pathogenesis and treatment of chronic kidney disease Part I: General mechanisms: a joint consensus statement from the European Society of Hypertension Working Group on Endothelin and Endothelial Factors and The Japanese Society of Hypertension

: Kidney damage is a common consequence of arterial hypertension, but is also a cause of atherogenesis. Dysfunction and/or harm of the endothelium in glomeruli and tubular interstitium damage the function of these structures and translates into dynamic changes of filtration fraction, with progressive reduction in glomerular filtration rate, expansion of extracellular fluid volume, abnormal ion balance, and hypoxia, ultimately leading to chronic kidney disease. Considering the key role played by endothelial dysfunction in chronic kidney disease, the Working Group on Endothelin and Endothelial Factors of the European Society of Hypertension and the Japanese Society of Hypertension have critically reviewed available knowledge on the mechanisms underlying endothelial cell injury. This resulted into two articles: in the first, we herein examine the mechanisms by which endothelial factors induce vascular remodeling and the role of different players, including endothelin-1, the renin-angiotensin-aldosterone system and their interactions, and of oxidative stress; in the second, we discuss the role of endothelial dysfunction in the major disease conditions that affect the kidney.

Endothelial Nanomechanics in the Context of Endothelial (Dys)function and Inflammation

SIGNIFICANCE

Stiffness of endothelial cells is closely linked to the function of the vasculature as it regulates the release of vasoactive substances such as nitric oxide (NO) and reactive oxygen species. The outer layer of endothelial cells, consisting of the glycocalyx above and the cortical zone beneath the plasma membrane, is a vulnerable compartment able to adapt its nanomechanical properties to any changes of forces exerted by the adjacent blood stream. Sustained stiffening of this layer contributes to the development of endothelial dysfunction and vascular pathologies. Recent Advances: The development of specific techniques to quantify the mechanical properties of cells enables the detailed investigation of the mechanistic link between structure and function of cells.

CRITICAL ISSUES

Challenging the mechanical stiffness of cells, for instance, by inflammatory mediators can lead to the development of endothelial dysfunction. Prevention of sustained stiffening of the outer layer of endothelial cells in turn improves endothelial function.

FUTURE DIRECTIONS

The mechanical properties of cells can be used as critical marker and test system for the proper function of the vascular system. Pharmacological substances, which are able to improve endothelial nanomechanics and function, could take a new importance in the prevention and treatment of vascular diseases. Thus, detailed knowledge acquisition about the structure/function relationship of endothelial cells and the underlying signaling pathways should be promoted.

Mineralocorticoid Receptor and Cardiovascular Disease

Activation of the mineralocorticoid receptor (MR) in the distal nephron by its ligand, aldosterone, plays an important role in sodium reabsorption and blood pressure regulation. However, expression of the MR goes beyond the kidney. It is expressed in a variety of other tissues in which its activation could lead to tissue injury. Indeed, MR activation in the cardiovascular (CV) system has been shown to promote hypertension, fibrosis, and inflammation. Pharmacological blockade of the MR has protective effects in several animal models of CV disease. Furthermore, the use of MR antagonists is beneficial for heart failure patients, preventing mortality and morbidity. A better understanding of the implications of the MR in the setting of CV diseases is critical for refining treatments and improving patient care. The mechanisms involved in the deleterious effects of MR activation are complex and include oxidative stress, inflammation, and fibrosis. This review will discuss the pathological role of the MR in the CV system and the major mechanisms underlying it.

Smooth Muscle Cell-Mineralocorticoid Receptor as a Mediator of Cardiovascular Stiffness With Aging

Stiffening of the vasculature with aging is a strong predictor of adverse cardiovascular events, independent of all other risk factors including blood pressure, yet no therapies target this process. MRs (mineralocorticoid receptors) in smooth muscle cells (SMCs) have been implicated in the regulation of vascular fibrosis but have not been explored in vascular aging. Comparing SMC-MR-deleted male mice to MR-intact littermates at 3, 12, and 18 months of age, we demonstrated that aging-associated vascular stiffening and fibrosis are mitigated by MR deletion in SMCs. Progression of cardiac stiffness and fibrosis and the decline in exercise capacity with aging were also mitigated by MR deletion in SMC. Vascular gene expression profiling analysis revealed that MR deletion in SMC is associated with recruitment of a distinct antifibrotic vascular gene expression program with aging. Moreover, long-term pharmacological inhibition of MR in aged mice prevented the progression of vascular fibrosis and stiffness and induced a similar antifibrotic vascular gene program. Finally, in a small trial in elderly male humans, short-term MR antagonism produced an antifibrotic signature of circulating biomarkers similar to that observed in the vasculature of SMC-MR-deleted mice. These findings suggest that SMC-MR contributes to vascular stiffening with aging and is a potential therapeutic target to prevent the progression of aging-associated vascular fibrosis and stiffness.

Nanomechanics of the endothelial glycocalyx contribute to Na+-induced vascular inflammation

High dietary salt (NaCl) is a known risk factor for cardiovascular pathologies and inflammation. High plasma Na⁺ concentrations (high Na⁺) have been shown to stiffen the endothelial cortex and decrease nitric oxide (NO) release, a hallmark of endothelial dysfunction. Here we report that chronic high Na⁺ damages the endothelial glycocalyx (eGC), induces release of inflammatory cytokines from the endothelium and promotes monocyte adhesion. Single cell force spectroscopy reveals that high Na⁺ enhances vascular adhesion protein-1 (VCAM-1)-dependent adhesion forces between monocytes and endothelial surface, giving rise to increased numbers of adherent monocytes on the endothelial surface. Mineralocorticoid receptor antagonism with spironolactone prevents high Na⁺-induced eGC deterioration, decreases monocyte-endothelium interactions, and restores endothelial function, indicated by increased release of NO. Whereas high Na⁺ decreases NO release, it induces endothelial release of the pro-inflammatory cytokines IL-1ß and TNFα. However, in contrast to chronic salt load (hours), in vivo and in vitro, an acute salt challenge (minutes) does not impair eGC function. This study identifies the eGC as important mediator of inflammatory processes and might further explain how dietary salt contributes to endothelialitis and cardiovascular pathologies by linking endothelial nanomechanics with vascular inflammation.

The Role of Uric Acid in Hypertension of Adolescents, Prehypertension and Salt Sensitivity of Blood Pressure

Uric acid is the end product of purine metabolism. Metabolic disorders of uric acid are associated with many disease states. Substantial evidence suggests the possible role of uric acid as a mediator of high blood pressure. Elevated uric acid is closely associated with new onset essential hypertension in adolescents and prehypertension; and urate-lowering agents can significantly improve these early stages of hypertension. Uric acid also influences salt sensitivity of blood pressure through two phases. Local renin-angiotensin-aldosterone system activation initiates renal damage, arteriolopathy, and endothelium dysfunction, which is followed by the dysregulation of sodium homeostasis, thereby leading to increased salt sensitivity. In this review we summarize the available evidence to contribute to a better understanding of the casual relationship between uric acid and early or intermediate stages of hypertension. We hope our review can contribute to the prevention of hypertension or provide new insights into a treatment that would slow the progression of hypertension.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Vascular effects of dietary salt

PURPOSE OF REVIEW

High dietary salt intake is detrimental in hypertensive and salt-sensitive individuals; however, there are a large number of normotensive salt-resistant individuals for whom dietary salt may also be harmful as a result of the blood pressure-independent effects of salt. This review will focus on the growing evidence that salt has adverse effects on the vasculature, independent of blood pressure.

RECENT FINDINGS

Data from both animal and human studies provide evidence that salt impairs endothelial function and increases arterial stiffness, independent of blood pressure. High dietary salt results in oxidative stress and increased endothelial cell stiffness, which impair endothelial function, whereas transforming growth factor beta promotes increased arterial stiffness in the presence of endothelial dysfunction.

SUMMARY

Health policies and most clinical research are focused on the adverse effects of dietary salt on blood pressure; however, there is an increasing body of evidence to support a deleterious effect of dietary salt on endothelial function and arterial stiffness independent of blood pressure. Endothelial dysfunction and increased arterial stiffness are predictors of cardiovascular disease; therefore, reducing excess dietary salt should be considered important for overall vascular health in addition to blood pressure.

Sodium renders endothelial cells sticky for red blood cells

Negative charges in the glycocalyx of red blood cells (RBC) and vascular endothelial cells (EC) facilitate frictionless blood flow through blood vessels. Na⁺ selectively shields these charges controlling surface electronegativity. The question was addressed whether the ambient Na⁺ concentration controls RBC-EC interaction. Using atomic force microscopy (AFM) adhesion forces between RBC and endothelial glycocalyx were quantified. A single RBC, mounted on an AFM cantilever, was brought in physical contact with the endothelial surface and then pulled off. Adhesion forces were quantified (i) after enzymatic removal of negative charges in the glycocalyx, (ii) under different ambient Na⁺ and (iii) after applying the intracellular aldosterone receptor antagonist spironolactone. Removal of negative surface charges increases RBC-EC interaction forces. A stepwise increase of ambient Na⁺ from 133 to 140 mM does not affect them. However, beyond 140 mM Na⁺ adhesion forces increase sharply (10% increase of adhesion force per 1 mM increase of Na⁺). Spironolactone prevents this response. It is concluded that negative charges reduce adhesion between RBC and EC. Ambient Na⁺ concentration determines the availability of free negative charges. Na⁺ concentrations in the low physiological range (below 140 mM) allow sufficient amounts of vacant negative charges so that adhesion of RBC to the endothelial surface is small. In contrast, Na⁺ in the high physiological range (beyond 140 mM) saturates the remaining negative surface charges thus increasing adhesion. Aldosterone receptor blockade by spironolactone prevents Na⁺ induced RBC adhesion to the endothelial glycocalyx. Extrapolation of in vitro experiments to in vivo conditions leads to the hypothesis that high sodium intake is likely to increase the incidence of thrombotic events.

Downregulation of Endogenous Hydrogen Sulfide Pathway Is Involved in Mitochondrion-Related Endothelial Cell Apoptosis Induced by High Salt

Background. The study aimed to investigate whether endogenous H₂S pathway was involved in high-salt-stimulated mitochondria-related vascular endothelial cell (VEC) apoptosis. Methods. Cultured human umbilical vein endothelial cells (HUVECs) were used in the study. H₂S content in the supernatant was detected. Western blot was used to detect expression of cystathionine gamma-lyase (CSE), cleaved-caspase-3, and mitochondrial and cytosolic cytochrome c (cytc). Fluorescent probes were used to quantitatively detect superoxide anion generation and measure the in situ superoxide anion generation in HUVEC. Mitochondrial membrane pore opening, mitochondrial membrane potential, and caspase-9 activities were measured. The cell apoptosis was detected by cell death ELISA and TdT-mediated dUTP nick end labeling (TUNEL) methods. Results. High-salt treatment downregulated the endogenous VEC H₂S/CSE pathway, in association with increased generation of oxygen free radicals, decreased mitochondrial membrane potential, enhanced the opening of mitochondrial membrane permeability transition pore and leakage of mitochondrial cytc, activated cytoplasmic caspase-9 and caspase-3 and subsequently induced VEC apoptosis. However, supplementation of H₂S donor markedly inhibited VEC oxidative stress and mitochondria-related VEC apoptosis induced by high salt. Conclusion. H₂S/CSE pathway is an important endogenous defensive system in endothelial cells antagonizing high-salt insult. The protective mechanisms for VEC damage might involve inhibiting oxidative stress and protecting mitochondrial injury.

Between Rho(k) and a hard place: the relation between vessel wall stiffness, endothelial contractility, and cardiovascular disease

Vascular stiffness is a mechanical property of the vessel wall that affects blood pressure, permeability, and inflammation. As a result, vascular stiffness is a key driver of (chronic) human disorders, including pulmonary arterial hypertension, kidney disease, and atherosclerosis. Responses of the endothelium to stiffening involve integration of mechanical cues from various sources, including the extracellular matrix, smooth muscle cells, and the forces that derive from shear stress of blood. This response in turn affects endothelial cell contractility, which is an important property that regulates endothelial stiffness, permeability, and leukocyte-vessel wall interactions. Moreover, endothelial stiffening reduces nitric oxide production, which promotes smooth muscle cell contraction and vasoconstriction. In fact, vessel wall stiffening, and microcirculatory endothelial dysfunction, precedes hypertension and thus underlies the development of vascular disease. Here, we review the cross talk among vessel wall stiffening, endothelial contractility, and vascular disease, which is controlled by Rho-driven actomyosin contractility and cellular mechanotransduction. In addition to discussing the various inputs and relevant molecular events in the endothelium, we address which actomyosin-regulated changes at cell adhesion complexes are genetically associated with human cardiovascular disease. Finally, we discuss recent findings that broaden therapeutic options for targeting this important mechanical signaling pathway in vascular pathogenesis.

Vascular biology of ageing-Implications in hypertension

Ageing is associated with functional, structural and mechanical changes in arteries that closely resemble the vascular alterations in hypertension. Characteristic features of large and small arteries that occur with ageing and during the development of hypertension include endothelial dysfunction, vascular remodelling, inflammation, calcification and increased stiffness. Arterial changes in young hypertensive patients mimic those in old normotensive individuals. Hypertension accelerates and augments age-related vascular remodelling and dysfunction, and ageing may impact on the severity of vascular damage in hypertension, indicating close interactions between biological ageing and blood pressure elevation. Molecular and cellular mechanisms underlying vascular alterations in ageing and hypertension are common and include aberrant signal transduction, oxidative stress and activation of pro-inflammatory and pro-fibrotic transcription factors. Strategies to suppress age-associated vascular changes could ameliorate vascular damage associated with hypertension. An overview on the vascular biology of ageing and hypertension is presented and novel molecular mechanisms contributing to these processes are discussed. The complex interaction between biological ageing and blood pressure elevation on the vasculature is highlighted. This article is part of a Special Issue entitled: CV Ageing.