Dose-dependent endothelial cell growth and stiffening by aldosterone: endothelial protection by eplerenone

The Soluble Fms-like Tyrosine Kinase-1 Contributes to Structural and Functional Changes in Endothelial Cells in Chronic Kidney Disease

Endothelial cells are a critical target of the soluble Fms-like tyrosine kinase-1 (sFlt-1), a soluble factor increased in different diseases with varying degrees of renal impairment and endothelial dysfunction, including chronic kidney disease (CKD). Although the mechanisms underlying endothelial dysfunction are multifactorial and complex, herein, we investigated the damaging effects of sFlt-1 on structural and functional changes in endothelial cells. Our results evidenced that sera from patients with CKD stiffen the endothelial cell cortex in vitro, an effect correlated with sFlt-1 levels and prevented by sFlt-1 neutralization. Besides, we could show that recombinant sFlt-1 leads to endothelial stiffening in vitro and in vivo. This was accompanied by cytoskeleton reorganization and changes in the endothelial barrier function, as observed by increased actin polymerization and endothelial cell permeability, respectively. These results depended on the activation of the p38 MAPK and were blocked by the specific inhibitor SB203580. However, sFlt-1 only minimally affected the expression of stiffness-sensitive genes. These findings bring new insight into the mechanism of action of sFlt-1 and its biological effects that cannot be exclusively ascribed to the regulation of angiogenesis.

Mineralocorticoid receptor in cardiovascular diseases-Clinical trials and mechanistic insights

Aldosterone binds to the mineralocorticoid receptor (NR3C2), a transcription factor of the nuclear receptor family, present in the kidney and in various other non-epithelial cells including the heart and the vasculature. Indeed, extra-renal pathophysiological effects of this hormone have been characterized, extending its actions to the cardiovascular system. A growing body of clinical and pre-clinical evidence suggests that mineralocorticoid receptor overactivation plays an important pathophysiological role in cardiovascular remodelling by promoting cardiac hypertrophy, fibrosis, arterial stiffness and in inflammation and oxidative stress. The following review article outlines the role of mineralocorticoid receptor in cardiovascular disease with a focus on myocardial remodelling and heart failure (HF) including clinical trials as well as cellular and animal studies.

Regulation of ion channels in the microcirculation by mineralocorticoid receptor activation

The mineralocorticoid receptor (MR) has classically been studied in the renal epithelium for its role in regulating sodium and water balance and, subsequently, blood pressure. However, the MR also plays a critical role in the microvasculature by regulating ion channel expression and function. Activation of the MR by its endogenous agonist aldosterone results in translocation of the MR into the nucleus, where it can act as a transcription factor. Although most of the actions of the aldosterone can be attributed to its genomic activity though MR activation, it can also act by nongenomic mechanisms. Activation of this ubiquitous receptor increases the expression of epithelial sodium channels (ENaC) in both the endothelium and smooth muscle cells of peripheral and cerebral vessels. MR activation also regulates activity of calcium channels, calcium-activated potassium channels, and various transient receptor potential (TRP) channels. Modification of these ion channels results in a myriad of negative consequences, including impaired endothelium-dependent vasodilation, alterations in generation of myogenic tone, and increased inflammation and oxidative stress. Taken together, these studies demonstrate the importance of studying the impact of the MR on ion channel function in the vasculature. While research in this area has made advances in recent years, there are still many large gaps in knowledge that need to be filled. Crucial future directions of study include defining the molecular mechanisms involved in this interaction, as well as elucidating the potential sex differences that may exist, as these areas of understanding are currently lacking.

Aldosterone up-regulates MMP-9 and MMP-9/NGAL expression in human neutrophils through p38, ERK1/2 and PI3K pathways

Aldosterone and mineralocorticoid receptors are important regulators of inflammation. During this process, chemokines and extracellular matrix degradation by matrix metalloproteases, such as MMP-9, help leukocytes reaching swiftly and infiltrating the injured tissue, two processes essential for tissue repair. Leukocytes, such as neutrophils, are a rich source of MMP-9 and possess mineralocorticoid receptors (MR). The aim of our study was to investigate whether aldosterone was able to regulate proMMP-9, active MMP-9 and MMP-9/NGAL production in human neutrophils. Here we show that aldosterone increased MMP-9 mRNA in a dose- and time-dependent manner. This hormone up-regulated also dose-dependently proMMP-9 and active MMP-9 protein release as well as the MMP-9/NGAL protein complex. PI3K, p38 and ERK1/2 inhibition diminished these aldosterone-induced neutrophil productions. Furthermore, spironolactone, a MR antagonist, counteracted aldosterone-induced increases of proMMP-9, active MMP-9 and MMP-9/NGAL complex. These findings indicate that aldosterone could participate in tissue repair by modulating neutrophil activity and favoring extracellular matrix degradation.

The role of ENaC in vascular endothelium

Once upon a time, the expression of the epithelial sodium channel (ENaC) was mainly assigned to the kidneys, colon and sweat glands where it was considered to be the main determinant of sodium homeostasis. Recent, though indirect, evidence for the possible existence of ENaC in a non-epithelial tissue was derived from the observation that the vascular endothelium is a target for aldosterone. Inhibitory actions of the intracellular aldosterone receptors by spironolactone and, more directly, by ENaC blockers such as amiloride supported this view. Shortly after, direct data on the expression of ENaC in vascular endothelium could be demonstrated. There, endothelial ENaC (EnNaC) could be defined as a major regulator of cellular mechanics which is a critical parameter in differentiating between vascular function and dysfunction. Foremost, the mechanical stiffness of the endothelial cell cortex, a layer 50-200 nm beneath the plasma membrane, has been shown to play a crucial role as it controls the production of the endothelium-derived vasodilator nitric oxide (NO) which directly affects the tone of the vascular smooth muscle cells. In contrast to soft endothelial cells, stiff endothelial cells release reduced amounts of NO, the hallmark of endothelial dysfunction. Thus, the combination of endothelial stiffness and myogenic tone might increase the peripheral vascular resistance. An elevation of arterial blood pressure is supposed to be the consequence of such functional changes. In this review, EnNaC is discussed as an aldosterone-regulated plasma membrane protein of the vascular endothelium that could significantly contribute to maintaining of an appropriate arterial blood pressure but, if overexpressed, could participate in the pathogenesis of arterial hypertension.

Vascular actions of aldosterone

Aldosterone exerts direct effects on the vascular system by inducing oxidative stress, inflammation, hypertrophic remodeling, fibrosis, and endothelial dysfunction. Aldosterone exerts its effects through genomic and nongenomic pathways in a mineralocorticoid receptor (MR)-dependent or independent manner. Other aldosterone receptors such as GPR30 have been identified. A tight relation exists between the aldosterone and angiotensin II pathways, as well as with the endothelin-1 system. There is a correlation between plasma levels of aldosterone and cardiovascular risk. Recently, an increasing body of evidence has underlined the importance of aldosterone in cardiovascular complications associated with the metabolic syndrome, such as arterial remodeling and endothelial dysfunction. Blockade of MR is an increasingly used evidence-based therapy for many forms of cardiovascular disease, including hypertension, heart failure, chronic kidney disease, and diabetes mellitus.

Real-time monitoring of the effects of telmisartan on angiotensin II-induced mechanical changes in live mesangial cells using atomic force microscopy

BACKGROUND/AIMS

Recent studies have shown that angiotensin II (Ang II) type 1 receptor blockers (ARB) may provide renal protection independent of their blood pressure-lowering effect. However, evidence for this comes from indirect methods, such as genetic or protein expression studies. In this study, we hypothesized that telmisartan, a specific ARB, applied to Ang II-stimulated mesangial cell (MC) would exert a renoprotective effect via modulation of MCs' mechanical properties.

METHODS

We investigated the effect of telmisartan on Ang II-induced changes in MCs utilizing real-time atomic force microscopy (AFM) imaging and force-distance curve measurements.

RESULTS

Real-time AFM images of live MCs demonstrated that cells contracted towards the center after Ang II exposure, and telmisartan treatment abolished this change. Cellular spring constants showed that telmisartan prevented Ang II-induced MC stiffening (Ang II: 0.109 ± 0.019 N/m, Ang II + telmisartan: 0.051 ± 0.016 N/m, p < 0.005). Telmisartan-treated MCs had a significantly lower adhesion force than those of the control group (control: 0.49 ± 0.22 nN, telmisartan: 0.22 ± 0.06 nN, Ang II: 0.40 ± 0.25 nN, Ang II + telmisartan: 0.27 ± 0.14 nN, p < 0.005). These results demonstrate that the dynamic contraction and mechanical properties of Ang II-stimulated MCs are restored by telmisartan.

CONCLUSIONS

We report for the first time the use of AFM force-distance curves on live MCs to directly monitor changes in surface adhesion and stiffness of cells after treatment with telmisartan in real time.

Endogenous aldosterone is involved in vascular calcification in rat

Aldosterone (Aldo) is an important active hormone in the renin–angiotensin–aldosterone system and plays a vital role in the development of hypertension, heart failure and other cardiovascular diseases. We aimed to explore the role of endogenous Aldo in aortic calcification in rats. We induced arterial calcification in rats by intramuscular administration of vitamin D3 plus oral nicotine (VDN) and determined calcium content, 45Ca2+ accumulation and activity of alkaline phosphatase (ALP). The mRNA level of osteopontin (OPN) was measured by semi-quantitative reverse transcriptase polymerase chain reaction. Deposition of collagen in the aorta wall was measured by Sirius red staining. The content of angiotensin II (Ang II) and Aldo in plasma and myocardial and vascular tissue was determined by radioimmunoassay. In rats with VDN treatment, von Kossa staining showed calcification in vascular smooth muscle cells and extracellular matrix, and the content of calcium in calcified arteries was 5.8-fold of that in control arteries ( P < 0.01). The accumulation of 45Ca2+ and activity of ALP in calcified aortic tissue was three- and 2.5-fold, respectively, that in control tissue ( P < 0.01). The mRNA expression of OPN was significantly higher, by 58%, in calcified than control tissue ( P < 0.01). Vascular fibrosis was greater in rats with calcified tissue than in control rats. The level of Ang II and Aldo was 58% and 80% higher, respectively, in calcified than control tissue (both P < 0.01). The changes could be significantly improved by treatment with captopril, an angiotensin-converting enzyme inhibitor, and the Aldo receptor antagonist spironolactone. These results suggest that Aldo is an endogenous bioactive factor involved in vascular calcification.

Membrane potential depolarization decreases the stiffness of vascular endothelial cells

The stiffness of vascular endothelial cells is crucial to mechanically withstand blood flow and, at the same time, to control deformation-dependent nitric oxide release. However, the regulation of mechanical stiffness is not yet understood. There is evidence that a possible regulator is the electrical plasma membrane potential difference. Using a novel technique that combines fluorescence-based membrane potential recordings with atomic force microscopy (AFM)-based stiffness measurements, the present study shows that membrane depolarization is associated with a decrease in the stiffness of endothelial cells. Three different depolarization protocols were applied, all of which led to a similar and significant decrease in cell stiffness, independently of changes in cell volume. Moreover, experiments using the actin-destabilizing agent cytochalasin D indicated that depolarization acts by affecting the cortical actin cytoskeleton. A model is proposed whereby a change of the electrical field across the plasma membrane is directly sensed by the submembranous actin network, regulating the actin polymerization:depolymerization ratio and thus cell stiffness. This depolarization-induced decrease in the stiffness of endothelial cells could play a role in flow-mediated nitric-oxide-dependent vasodilation.

C-reactive protein makes human endothelium stiff and tight

Elevation of C-reactive protein (CRP) in human blood accompanies inflammatory processes, including cardiovascular diseases. There is increasing evidence that the acute-phase reactant CRP is not only a passive marker protein for systemic inflammation but also affects the vascular system. Further, CRP is an independent risk factor for atherosclerosis and the development of hypertension. Another crucial player in atherosclerotic processes is the mineralocorticoid hormone aldosterone. Even in low physiological concentrations, it stimulates the expression and membrane insertion of the epithelial sodium channel, thereby increasing the mechanical stiffness of endothelial cells. This contributes to the progression of endothelial dysfunction. In the present study, the hypothesis was tested that the acute application of CRP (25 mg/L), in presence of aldosterone (0.5 nmol/L; 24 hour incubation), modifies the mechanical stiffness and permeability of the endothelium. We found that endothelial cells stiffen in response to CRP. In parallel, endothelial epithelial sodium channel is inserted into the plasma membrane, while, surprisingly, the endothelial permeability decreases. CRP actions are prevented either by the inhibition of the intracellular aldosterone receptors using spironolactone (5 nmol/L) or by the inactivation of epithelial sodium channel using specific blockers. In contrast, inhibition of the release of the vasodilating gas nitric oxide via blockade of the phosphoinositide 3-kinase/Akt pathway has no effect on the CRP-induced stiffening of endothelial cells. The data indicate that CRP enhances the effects of aldosterone on the mechanical properties of the endothelium. Thus, CRP could counteract any decrease in arterial blood pressure that accompanies severe acute inflammatory processes.

Aldosterone: effects on the kidney and cardiovascular system

Aldosterone, a steroid hormone with mineralocorticoid activity, is mainly recognized for its action on sodium reabsorption in the distal nephron of the kidney, which is mediated by the epithelial sodium channel (ENaC). Beyond this well-known action, however, aldosterone exerts other effects on the kidney, blood vessels and the heart, which can have pathophysiological consequences, particularly in the presence of a high salt intake. Aldosterone is implicated in renal inflammatory and fibrotic processes, as well as in podocyte injury and mesangial cell proliferation. In the cardiovascular system, aldosterone has specific hypertrophic and fibrotic effects and can alter endothelial function. Several lines of evidence support the existence of crosstalk between aldosterone and angiotensin II in vascular smooth muscle cells. The deleterious effects of aldosterone on the cardiovascular system require concomitant pathophysiological conditions such as a high salt diet, increased oxidative stress, or inflammation. Large interventional trials have confirmed the benefits of adding mineralocorticoid-receptor antagonists to standard therapy, in particular to angiotensin-converting-enzyme inhibitor and angiotensin II receptor blocker therapy, in patients with heart failure. Small interventional studies in patients with chronic kidney disease have shown promising results, with a significant reduction of proteinuria associated with aldosterone antagonism, but large interventional trials that test the efficacy and safety of mineralocorticoid-receptor antagonists in chronic kidney disease are needed.

Clinical effects of eplerenone, a selective aldosterone blocker, in Japanese patients with essential hypertension

Eplerenone, a selective aldosterone blocker, has become clinically available in Japan since 2007. It has been reported that eplerenone has a potential antihypertensive effect, with a profile slightly different from that of spironolactone, and has fewer adverse reactions, suggesting that it may become a first-line treatment for hypertension. However, clinical data on hypertensive patients in Japan are lacking for eplerenone. In this study, we explored the clinical efficacy of eplerenone when it is added to an angiotensin-converting enzyme (ACE) inhibitor or a long-acting calcium channel blocker (CCB) in 68 (31 males, 37 females) Japanese patients with essential hypertension. After adding 50 mg of eplerenone to their basal treatment, blood pressure was significantly reduced at 4 weeks, and further reduced after 24 weeks of eplerenone treatment. Urinary albumin excretion decreased significantly after 24 weeks. There were no significant differences in general biochemical test values or electrolytes, but fasting serum triglycerides were significantly decreased after eplerenone treatment. The serum potassium level showed no significant change during treatment. There were no significant correlations between plasma renin activity or plasma aldosterone concentration (PAC) before eplerenone treatment and blood pressure after eplerenone treatment, showing that the antihypertensive effect of eplerenone is not affected by the patient's renin profile or pretreatment PAC values. Eplerenone was also effective in hypertensive patients with metabolic syndrome. In conclusion, eplerenone, when coadministered with an ACE inhibitor or a long-acting CCB, caused an extremely beneficial antihypertensive effect in Japanese patients with essential hypertension, without few clinically important adverse events.

Nebivolol decreases endothelial cell stiffness via the estrogen receptor beta: a nano-imaging study

BACKGROUND

Nebivolol (NEB) is a [beta]1-receptor blocker with nitric oxide-dependent vasodilating properties. NEB-induced nitric oxide release is mediated through the estrogen receptor.

METHOD

Here, we tested the hypothesis that NEB decreases endothelial cell stiffness and that these effects can be abolished by both endothelial nitric oxide synthase and estrogen receptor blockade. Human endothelial cells (EAHy-926) were incubated with vehicle, NEB 0.7 nmol/l, metoprolol 200 nmol/l, 17[beta]-estradiol (E2) 15 nmol/l, the estrogen receptor antagonists tamoxifen 100 nmol/l and ICI 182780 (ICI) 100 nmol/l, the nitric oxide synthase inhibitor N[omega]-nitro-L-arginine methyl ester 1 mmol/l and combinations of NEB and E2 with either tamoxifen, ICI or N[omega]-nitro-L-arginine methyl ester as well as metoprolol and ICI. Atomic force microscopy was performed to measure cellular stiffness, cell volume and apical surface. Presence of estrogen receptor protein in EAHy-926 was confirmed by western blot analysis; quantification of ER[alpha] and ER[beta] total RNA was performed by semiquantitative PCR.

RESULTS

Both NEB as well as E2 decreased cellular stiffness to a similar extent (NEB: 0.83 +/- 0.03 pN/nm, E2: 0.87 +/- 0.03 pN/nm, vehicle: 2.19 +/- 0.07 pN/nm), whereas metoprolol had no effect on endothelial stiffness (2.07 +/- 0.04 pN/nm, all n = 60, P < 0.01). The decrease in stiffness occurred as soon as 5 min after starting NEB incubation. The effects are mediated through nongenomic ER[beta] pathways, as ER[alpha] is not translated into measurable protein levels in EAHy-926. Furthermore, NEB increased cell volume by 48 +/- 4% and apical surface by 34 +/- 3%. E2 had comparable effects. Tamoxifen, ICI and N[omega]-nitro-L-arginine methyl ester substantially diminished the effects of NEB and E2.

CONCLUSION

NEB decreases cellular stiffness and causes endothelial cell growth. These effects are nitric oxide-dependent and mediated through nongenomic ER[beta] pathways. The morphological and functional alterations observed in endothelial cells may explain improved endothelial function with NEB treatment.

Spironolactone ameliorates transplant vasculopathy in renal chronic transplant dysfunction in rats

Chronic transplant dysfunction (CTD) is the leading cause of long-term renal allograft loss and is characterized by specific histological lesions including transplant vasculopathy, interstitial fibrosis, and focal glomerulosclerosis. Increasing evidence indicates that aldosterone is a direct mediator of renal damage via the mineralocorticoid receptor (MR). The MR antagonist spironolactone is renoprotective in native chronic kidney disease, but its effects on CTD are unknown. We studied the effects of spironolactone treatment on CTD development in the Dark Agouti-to-Wistar-Furth renal allograft transplant model, by treatment with 20 mg/kg spironolactone or vehicle daily by oral gavage from 2 days before transplantation (donors and recipients) throughout the experiment (12 wk, recipients). Dark Agouti-to-Dark Agouti isografts served as negative controls. Spironolactone significantly ameliorated the development of transplant vasculopathy in allografts by reducing the number of affected intrarenal arteries. In addition, spironolactone treatment showed a trend toward reduced proteinuria and focal glomerulosclerosis, and significantly reduced glomerular macrophage influx. However, spironolactone treatment did not affect interstitial fibrosis, interstitial macrophage influx, creatinine clearance, and systolic blood pressure. We conclude that spironolactone selectively ameliorates transplant vasculopathy and glomerular lesions in renal CTD in rats. These results suggest that spironolactone may have renoprotective potential as an adjunct treatment in renal transplantation to ameliorate CTD.

Potassium softens vascular endothelium and increases nitric oxide release

In the presence of aldosterone, plasma sodium in the high physiological range stiffens endothelial cells and reduces the release of nitric oxide. We now demonstrate effects of extracellular potassium on stiffness of individual cultured bovine aortic endothelial cells by using the tip of an atomic force microscope as a mechanical nanosensor. An acute increase of potassium in the physiological range swells and softens the endothelial cell and increases the release of nitric oxide. A high physiological sodium concentration, in the presence of aldosterone, prevents these changes. We propose that the potassium effects are caused by submembranous cortical fluidization because cortical actin depolymerization induced by cytochalasin D mimics the effect of high potassium. In contrast, a low dose of trypsin, known to activate sodium influx through epithelial sodium channels, stiffens the submembranous cell cortex. Obviously, the cortical actin cytoskeleton switches from gelation to solation depending on the ambient sodium and potassium concentrations, whereas the center of the cell is not involved. Such a mechanism would control endothelial deformability and nitric oxide release, and thus influence systemic blood pressure.

Assessment of arterial stiffness, a translational medicine biomarker system for evaluation of vascular risk

AIMS

Stiffening of the large arteries is a common feature of aging and is exacerbated by a number of disorders such as hypertension, diabetes, and renal disease. Arterial stiffening is recognized as an important and independent risk factor for cardiovascular events. This article will provide a comprehensive review of the recent advance on assessment of arterial stiffness as a translational medicine biomarker for cardiovascular risk.

DISCUSSIONS

The key topics related to the mechanisms of arterial stiffness, the methodologies commonly used to measure arterial stiffness, and the potential therapeutic strategies are discussed. A number of factors are associated with arterial stiffness and may even contribute to it, including endothelial dysfunction, altered vascular smooth muscle cell (SMC) function, vascular inflammation, and genetic determinants, which overlap in a large degree with atherosclerosis. Arterial stiffness is represented by biomarkers that can be measured noninvasively in large populations. The most commonly used methodologies include pulse wave velocity (PWV), relating change in vessel diameter (or area) to distending pressure, arterial pulse waveform analysis, and ambulatory arterial stiffness index (AASI). The advantages and limitations of these key methodologies for monitoring arterial stiffness are reviewed in this article. In addition, the potential utility of arterial stiffness as a translational medicine surrogate biomarker for evaluation of new potentially vascular protective drugs is evaluated.

CONCLUSIONS

Assessment of arterial stiffness is a sensitive and useful biomarker of cardiovascular risk because of its underlying pathophysiological mechanisms. PWV is an emerging biomarker useful for reflecting risk stratification of patients and for assessing pharmacodynamic effects and efficacy in clinical studies.

Hemodynamic effects of propranolol with spironolactone in patients with variceal bleeds: A randomized controlled trial

AIM: To study the hemodynamic effects of spironolactone with propranolol vs propranolol alone in the secondary prophylaxis of variceal bleeding.

METHODS: Thirty-five cirrhotics with variceal bleeding randomly received propranolol (n = 17: Group A) or spironolactone plus propranolol (n = 18: Group B). Hemodynamic assessment was performed at baseline and on the eighth day.

RESULTS: Spironolactone with propranolol caused a greater reduction in the hepatic venous pressure gradient than propranolol alone (26.94% vs 10.2%; P < 0.01). Fourteen out of eighteen patients on the combination treatment had a reduction in hepatic venous pressure gradient to ≤ 12 mmHg or a 20% reduction from baseline in contrast to only six out of seventeen (6/17) on propranolol alone (P < 0.05).

CONCLUSION: Spironolactone with propranolol results in a better response with a greater reduction in hepatic venous pressure gradient in the secondary prophylaxis of variceal bleeding. A greater number of patients may be protected by this combination therapy than by propranolol alone. Hence, this combination may be recommended for secondary prophylaxis in patients with variceal bleeding.

Evaluation of the aldosterone-blocking agent eplerenone in hypertension and heart failure

Aldosterone blockade is now seen as a crucial therapeutic strategy in the management of cardiovascular disease progression. There is increasing evidence that blocking the rennin-angiotensin-aldosterone system results in a reduction in overall cardiovascular risk. For 40 years, the only agent in this class was spironolactone. Despite its efficacy, the sexual side effects of spironolactone have resulted in poor compliance at best and discontinuation of therapy at worst. A newer agent, eplerenone, has been recently licensed for the treatment of heart failure and in the US also for hypertension. This article reviews the pathophysiology of aldosterone and critically reviews the present evidence for the efficacy and potential role for the new selective aldosterone-receptor antagonist, eplerenone.

Aldosterone and amiloride alter ENaC abundance in vascular endothelium

The amiloride-sensitive epithelial sodium channel (ENaC) is usually found in the apical membrane of epithelial cells but has also recently been described in vascular endothelium. Because little is known about the regulation and cell surface density of ENaC, we studied the influence of aldosterone, spironolactone, and amiloride on its abundance in the plasma membrane of human endothelial cells. Three different methods were applied, single ENaC molecule detection in the plasma membrane, quantification by Western blotting, and cell surface imaging using atomic force microscopy. We found that aldosterone increases the surface expression of ENaC molecules by 36% and the total cellular amount by 91%. The aldosterone receptor antagonist spironolactone prevents these effects completely. Acute application of amiloride to aldosterone-pretreated cells led to a decline of intracellular ENaC by 84%. We conclude that, in vascular endothelium, aldosterone induces ENaC expression and insertion into the plasma membrane. Upon functional blocking with amiloride, the channel disappears from the cell surface and from intracellular pools, indicating either rapid degradation and/or membrane pinch-off. This opens new perspectives in the regulation of ENaC expressed in the vascular endothelium.

Is the vascular endothelium under the control of aldosterone? Facts and hypothesis

Fluid and electrolyte balance in the human organism is controlled by aldosterone, a mineralocorticoid hormone of the suprarenal glands. The major target cells are localized in the kidney where the hormone controls transepithelial salt transport. Over the past few years, evidence has been accumulated that cells of the cardiovascular system are also targeted by the hormone. As an example, endothelial cells resemble similar mechanisms triggered by aldosterone as shown for the kidney. Although the pathological alterations induced by aldosterone excess are obvious, the physiological changes are largely unknown. On the basis of recent experiments, using atomic force microscopy as an imaging tool and a mechanical sensor, I present a hypothesis on the physiological role of aldosterone in endothelial function and its potential implications in the control of blood pressure.