Aldosterone as a mediator in cardiovascular injury

Spironolactone and its main metabolite canrenoic acid block hKv1.5, Kv4.3 and Kv7.1 + minK channels

Both spironolactone (SP) and its main metabolite, canrenoic acid (CA), prolong cardiac action potential duration and decrease the Kv11.1 (HERG) current. We examined the effects of SP and CA on cardiac hKv1.5, Kv4.3 and Kv7.1+minK channels that generate the human I(Kur), I(to1) and I(Ks), which contribute to the control of human cardiac action potential duration.hKv1.5 currents were recorded in stably transfected mouse fibroblasts and Kv4.3 and Kv7.1 + minK in transiently transfected Chinese hamster ovary cells using the whole-cell patch clamp. SP (1 microM) and CA (1 nM) inhibited hKv1.5 currents by 23.2 +/- 3.2 and 18.9 +/- 2.7%, respectively, shifted the midpoint of the activation curve to more negative potentials and delayed the time course of tail deactivation.SP (1 microM) and CA (1 nM) inhibited the total charge crossing the membrane through Kv4.3 channels at +50 mV by 27.1 +/- 6.4 and 27.4 +/- 5.7%, respectively, and accelerated the time course of current decay. CA, but not SP, shifted the inactivation curve to more hyperpolarised potentials (V(h)-37.0 +/- 1.8 vs -40.8 +/- 1.6 mV, n = 10, P < 0.05).SP (10 microM) and CA (1 nM) also inhibited Kv7.1 + minK currents by 38.6 +/- 2.3 and 22.1 +/- 1.4%, respectively, without modifying the voltage dependence of channel activation. SP, but not CA, slowed the time course of tail current decay.CA (1 nM) inhibited the I(Kur) (29.2 +/- 5.5%) and the I(to1) (16.1 +/- 3.9%) recorded in mouse ventricular myocytes and the I(K) (21.8 +/- 6.9%) recorded in guinea-pig ventricular myocytes.A mathematical model of human atrial action potentials demonstrated that K(+) blocking effects of CA resulted in a lengthening of action potential duration, both in normal and atrial fibrillation simulated conditions. The results demonstrated that both SP and CA directly block hKv1.5, Kv4.3 and Kv7.1 + minK channels, CA being more potent for these effects. Since peak free plasma concentrations of CA ranged between 3 and 16 nM, these results indicated that blockade of these human cardiac K(+) channels can be observed after administration of therapeutic doses of SP. Blockade of these cardiac K(+) currents, together with the antagonism of the aldosterone proarrhythmic effects produced by SP, might be highly desirable for the treatment of supraventricular arrhythmias.

Eplerenone Inhibits Atherosclerosis in Nonhuman Primates

Aldosterone may be involved in the pathogenesis of atherosclerosis. We investigated the effect of eplerenone, a selective mineralocorticoid receptor blocker, on atherosclerosis in monkeys fed a high-cholesterol diet. Monkeys fed a high-cholesterol diet for 9 months were divided into 3 groups: those treated with a low dose of eplerenone (30 mg/kg per day); those treated with a high dose of eplerenone (60 mg/kg per day); and the placebo-treated group. The normal group consisted of monkeys fed a normal diet. There were no significant differences in blood pressure and cholesterol levels between the placebo- and eplerenone-treated groups. On the other hand, monocyte chemoattractant protein-1 and malondialdehyde-modified LDL were significantly higher in the placebo-treated group than in the normal group, whereas they were suppressed in the eplerenone-treated groups. The ratio of intimal volume to total volume by intravascular ultrasound analysis imaging of the aortas was dose-dependently lower in the eplerenone-treated groups than in the placebo-treated group. Acetylcholine-induced vasorelaxation was significantly weaker in the placebo-treated group than in the normal group, but the vasorelaxation was strengthened in the eplerenone-treated groups. A significant upregulation of angiotensin-converting enzyme activity was observed in the placebo-treated group, but the activity was suppressed in the eplerenone-treated groups. In conclusion, eplerenone may strengthen the endothelium-dependent relaxation and suppress angiotensin-converting enzyme activity in the vasculature, thus preventing the development of atherosclerosis in nonhuman primates.

Improvement in Blood Pressure With Inhibition of the Epithelial Sodium Channel in Blacks With Hypertension

Hypertension in blacks is more prevalent and less often controlled than the hypertension of other ethnic groups. We sought to explore the benefit of adding inhibitors of the epithelial sodium channel (ENaC), an aldosterone-regulated site of sodium reabsorption in the distal nephron, to the antihypertensive regimen of black hypertensive patients. In a prospective, randomized, placebo-controlled, double-blind clinical trial, we used a 2-by-2 factorial design with 4 treatment groups: amiloride (a direct inhibitor of ENaC), spironolactone (an aldosterone receptor antagonist), the combination of both drugs, and placebo. The subjects (n=98) had an elevated blood pressure despite treatment that included a diuretic and a calcium channel blocker; the level of plasma renin activity was < or =0.56 ng/L per second. The primary end points were changes from baseline in systolic and diastolic blood pressure over a 9-week period of treatment. The reductions in systolic and diastolic blood pressures (mm Hg) were, respectively, 9.8+/-1.6 (SE) and 3.4+/-1.0 for amiloride (P<0.001) and 4.6+/-1.6 (P=0.006) and 1.8+/-1.0 for spironolactone (P=0.07). Treatment with either amiloride or spironolactone or the combination was well tolerated; no patient experienced hyperkalemia. In a substudy, plasma endothelin-1 levels were observed to decrease after 3 weeks of treatment with spironolactone (P<0.001), consistent with a non-ENaC-related potential benefit of spironolactone. In conclusion, treatment with either amiloride or spironolactone can provide an additional reduction in blood pressure in blacks already receiving conventional antihypertensive therapy.

Effects of eplerenone versus losartan in patients with low-renin hypertension

BACKGROUND

Sodium retention and volume expansion, mediated in part by aldosterone, are prominent features in low-renin hypertension. Agents that block aldosterone at its receptor sites, therefore, should have significant clinical benefit in patients with low-renin hypertension.

METHODS

This 16-week, multicenter, double-blind, active-controlled, parallel-group, titration-to-effect trial compared the blood pressure and neurohumoral responses of the selective aldosterone blocker eplerenone (100-200 mg/d; n = 86) with those of the angiotensin receptor blocker losartan (50-100 mg/d; n = 82) in patients with low-renin hypertension (active renin < or = 25 pg/mL [< or = 42.5 mU/L]). Patients with diastolic blood pressure > or = 90 mm Hg after 8 weeks of monotherapy received add-on therapy with hydrochlorothiazide 12.5 to 25 mg daily.

RESULTS

After 8 weeks of therapy, eplerenone reduced blood pressure to a greater extent than losartan (systolic blood pressure -15.8 vs -10.1 mm Hg, P = .017; diastolic blood pressure -9.3 vs -6.7 mm Hg, P = .05). After 16 weeks of therapy, significantly fewer eplerenone-treated patients (32.5%) than losartan-treated patients (55.6%) required add-on hydrochlorothiazide as allowed per protocol for blood pressure control (P = .003). Eplerenone consistently reduced blood pressure regardless of baseline active plasma renin levels whereas losartan reduced blood pressure more effectively in patients with higher baseline active renin levels. There were no differences between treatments in adverse events (reported by 62.8% of eplerenone patients and by 72.0% of losartan patients).

CONCLUSIONS

These data show that eplerenone was more effective than losartan in reducing blood pressure in patients with low-renin hypertension. Further studies evaluating the efficacy of eplerenone in difficult-to-treat or resistant hypertension are needed.

Increased Plasma Aldosterone in Patients with Clinical Depression

BACKGROUND

Clinical depression has been increasingly recognized as an independent risk factor for adverse cardiovascular events, but the biological mechanisms of this association remain unclear. Recent evidence for renin system dysregulation in patients with depression led us to hypothesize that aldosterone--a well-recognized contributor to vascular injury--could be increased in depressed patients. The present study was designed, therefore, to be a cross-sectional investigation of plasma renin and aldosterone levels in depressed patients as compared with healthy controls with no history of psychiatric illness.

METHODS

A total of 65 depressed patients and 65 age- and gender-matched control subjects were enrolled. Following a fixed sodium and potassium diet, venous blood samples were obtained at 9:00 a.m. to avoid the influence of circadian rhythms.

RESULTS

Although there were no significant differences in plasma level of renin among subjects with depression and controls (7.9 +/- 5.8 vs. 6.4 +/- 4.3 pg/mL, respectively; p=0.10), depressed subjects exhibited greater mean aldosterone levels as compared with control subjects (157.2 +/- 67.5 vs. 125.7 +/- 38.1 pg/mL, respectively; p=0.0014). After adjusting for potential confounders, multivariate logistic regression analysis showed that subjects with depression had 2.77 times higher odds of elevated aldosterone levels compared with healthy control subjects (95% confidence interval, 1.30-5.92, p=0.008).

CONCLUSIONS

Our present findings support the hypothesis that hyperaldosteronism could be a common feature among depressed patients, thereby suggesting that increased aldosterone levels may act as a mediator in the pathway linking depression to unfavorable vascular events.

Eplerenone reduces oxidative stress and enhances eNOS in SHR: vascular functional and structural consequences

The aim of the present study was to evaluate the effect of the aldosterone receptor antagonist eplerenone on endothelial function, oxidative stress, and structural alterations present in spontaneously hypertensive rats (SHR). To carry out the study, male SHR (18 weeks old) were treated with two doses of eplerenone (30 and 100 mg/kg/day) for 10 weeks. A group of n = 8 untreated SHR was used as a control-vehicle group, and a group of Wistar Kyoto rats (n = 8) was used as a reference of normotensive conditions. Systolic arterial pressure (SAP) was measured by the tail-cuff method. Endothelium-dependent and -independent relaxations, as well as endothelial nitric oxide synthase (eNOS) and the subunit p22phox of NAD(P)H oxidase mRNA expressions, were studied in aorta from SHR untreated or treated with eplerenone. Media/lumen ratio was also calculated in aortic preparations. In addition, levels of reduced glutathione (GSH), oxidized glutathione (GSSG), and malonyl dialdehyde (MDA) were evaluated in liver homogenates. Treatment with eplerenone reduced (p < 0.05) SAP and normalized aortic media/lumen ratio and acetylcholine relaxations. Both doses of the drug enhanced (p < 0.05) eNOS and reduced p22phox mRNA expressions. Similarly, eplerenone increased (p < 0.05) hepatic GSH/GSSG ratio, and reduced (p < 0.05) hepatic MDA levels in a comparable manner. Consequently, it could be concluded that aldosterone participates in the functional and structural vascular alterations of SHR through the diminution of nitric oxide availability and an enhancement of vascular and systemic oxidative stress.

Participation of prostacyclin in endothelial dysfunction induced by aldosterone in normotensive and hypertensive rats

The aim of the present study was to analyze the possible involvement of vasoconstrictors prostanoids on the reduced endothelium-dependent relaxations produced by chronic administration of aldosterone in Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). For this purpose, acetylcholine (ACh) relaxations in aortic segments from both strains were analyzed in absence and presence of the cyclooxygenase-1 (COX-1) and COX-2 inhibitor indomethacin, the specific COX-2 inhibitor NS-398, the TP receptor antagonist (SQ 29 548), the thromboxane A2 (TXA2) synthase inhibitor furegrelate, and the prostacyclin (PGI2) synthesis inhibitor tranylcypromine (TCP). In addition, COX-2 protein expression was studied by Western blot analysis. Release of prostaglandin E2 (PGE2) and the metabolites of PGF2alpha, TXA2, and PGI2, 13,14-dihydro-15-keto PGF2a, TXB2, and 6-keto-PGF1alpha, respectively, were measured. Treatment with aldosterone did not modify blood pressure levels in any strain. However, aldosterone markedly reduced (P<0.05) ACh-induced relaxations in segments from both strains in a similar extent. Indomethacin, NS-398, SQ 29 548, and TCP enhanced (P<0.05) ACh relaxations in both strains treated with aldosterone. Aortic COX-2 protein expression was higher in both strains of rats treated with aldosterone. In normotensive animals, aldosterone increases the ACh-stimulated aortic production of 13,14-dihydro-15-keto PGF2a, PGE2, and 6-keto-PGF1alpha (P<0.05). In SHR, ACh only increased the 6-keto-PGF1alpha production (P<0.05). It could be concluded that chronic treatment with aldosterone was able to produce endothelial dysfunction through COX-2 activation in normotensive and hypertensive conditions. PGI2 seems to be the main factor accounting for endothelial dysfunction in hypertensive rats, whereas other prostanoids besides PGI2 appear to be involved in endothelial dysfunction under normotensive conditions.

Participation of aldosterone in the vascular inflammatory response of spontaneously hypertensive rats: role of the NFκB/IκB system

OBJECTIVE

To investigate the participation of aldosterone in the vascular inflammatory process associated with hypertension, as well as the possible involvement of the NFkappaB/IkappaB system.

METHODS

Male spontaneously hypertensive rats (SHR; 20-22 weeks old) untreated or treated with either the aldosterone receptor antagonist, eplerenone (100 mg/kg per day) or triple antihypertensive therapy (HHR: hydralazine + hydrochlorothiazide + reserpine; 20 + 7 + 0.15 mg/kg per day) were used in the study. Wistar-Kyoto rats (WKY) were used as a normotensive reference group. Aortic mRNA expression and plasma levels of interleukin (IL)-1beta, IL-6 and tumour necrosis factor alpha (TNFalpha) were measured. Likewise, the aortic expression of the nuclear factor kappaB (NFkappaB) p50 subunit precursor, p105, and its inhibitor (IkappaB) were measured.

RESULTS

SHR showed higher aortic expression of IL-1beta, IL-6 and TNFalpha than WKY (P < 0.05) and higher plasma levels of IL-1beta and IL-6 than WKY (P < 0.05). Moreover, SHR also presented increased aortic expression of nuclear transcription factor NFkappaB p50 subunit precursor (p105), and a reduction of its inhibitor IkappaB. Both eplerenone and HHR decreased blood pressure to a comparable extent (P < 0.05). This effect was accompanied by a reduction in plasma levels of IL-1beta and IL-6 and aortic mRNA expression of IL-1beta, IL-6 and TNFalpha. However, the effect of eplerenone was more marked, since eplerenone-treated rats showed significantly lower inflammatory parameters than SHR receiving HHR. In addition, both antihypertensive treatments increased IkappaB mRNA expression in a similar manner, but only eplerenone reduced NFkappaB mRNA expression.

CONCLUSIONS

Aldosterone, as well as an increase in haemodynamic forces produced by hypertension, participate in the vascular inflammatory process associated with hypertension in SHR. This effect seems to be mediated by enhanced vascular expression of cytokines through a modification of the NFkappaB/IkappaB system.

Aldosterone receptor antagonists: Biology and novel therapeutic applications

A dysregulation of the aldosterone system has been involved in the pathophysiology of cardiovascular diseases, including myocardial failure and, partially, essential hypertension. In humans and in rat models, aldosterone action induces heart remodeling and interstitial and perivascular myocardial fibrosis. Therefore, a rationale for using aldosterone antagonists (ARAs) of the spironolactone family, which have been available for decades for the treatment of aldosterone excess syndromes, has now emerged. The development of compounds such as eplerenone, with a greater selectivity for mineralocorticoid receptors, is promising also in terms of reduction of endocrine side effects. The use of ARAs for the treatment of myocardial failure and selected cases of hypertension, in combination with the current therapy, has been strongly supported by trials such as the Randomized Aldactone Evaluation Study (RALES) and the Eplerenone Neurohormonal Efficacy and Survival Study (EPHESUS). Thus, the addition of ARAs to the conventional therapy appears beneficial, leading to an improved survival rate and a reduced incidence of cardiac complications.

Interactions of High Salt Intake and the Response of the Cardiovascular System to Aldosterone

High salt intake contributes to the risk of hypertension, and this effect is in part mediated by the physiologic action of aldosterone on renal mineralocorticoid receptors. However, the actions of aldosterone are not restricted to the kidneys, because aldosterone can bind to mineralocorticoid receptors in the heart, vasculature, and brain to produce structural and functional changes that lead to target organ damage. Experimental and clinical studies show that, in the setting of high salt intake, blocking aldosterone at the mineralocorticoid receptor reduces progression to target organ damage and preserves vascular function. In many cases, these benefits are independent of changes in blood pressure. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have short-term effects on reducing aldosterone levels, but frequently aldosterone levels return to pretreatment levels during long-term therapy. Aldosterone blockade may be more completely achieved with mineralocorticoid receptor antagonists. Spironolactone has been shown to have substantial and significant benefits in experimental and clinical studies of cardiac dysfunction. Eplerenone is a selective aldosterone blocker with a greater binding affinity for mineralocorticoid receptors than for androgen and progesterone receptors. Eplerenone has similarly demonstrated significant benefits in experimental animals and in patients with left ventricular dysfunction after myocardial infarction. Thus, aldosterone blockade with mineralocorticoid receptor antagonists offers target organ protection and may blunt some of the adverse effects of chronic high salt intake.

Aldosterone makes human endothelium stiff and vulnerable

BACKGROUND

Aldosterone has long been known to control water and electrolyte balance by acting on mineralocorticoid receptors in kidney. However, recent studies identified these classic receptors also in the vascular system. Indeed, aldosterone alters structure and function of human endothelium. We applied nanotechniques to detect these changes.

METHODS

Experiments were performed in cultured monolayers of human umbilical vein endothelial cells (HUVECs). Ten nanomoles per liter aldosterone or solvent (control) was added to the culture medium for 72 hours. Atomic force microscopy (AFM) was used as a nanotool that physically interacts with the cell surface. In the monolayer we measured cell volume, apical cell surface, and cell stiffness.

RESULTS

Volume, apical surface area, and stiffness of individual cells increased in response to aldosterone by 18% (P < 0.05), 64% (P < 0.001), and 78% (P < 0.01), respectively. Imaging of the cell-to-cell contacts disclosed gaps in response to aldosterone. Furthermore, underneath the monolayer we detected an aldosterone-induced increase of protein deposition by 58% (P < 0.001).

CONCLUSION

Aldosterone remodels human endothelium in vitro. Cells increase in size and stiffness. Protein leakage through intercellular gaps could be caused by the increased apical membrane tension. The increase in cell rigidity could trigger endothelial dysfunction observed in hyperaldosteronism.

Angiotensin II, angiotensin II antagonists and spironolactone and their modulation of cardiac repolarization

Angiotensin II and aldosterone produce pro-arrhythmic effects by several mechanisms, including the modulation of voltage-dependent K(+) channels involved in human cardiac repolarization. Drugs that inhibit the renin-angiotensin-aldosterone system exert anti-arrhythmic actions that are related to the blockade of the pro-arrhythmic actions of angiotensin II and aldosterone. These anti-arrhythmic actions include inhibition of electrical and structural cardiac remodeling, inhibition of neurohumoral activation, reduction of blood pressure and stabilization of electrolyte disturbances. In this article, several angiotensin II AT(1) receptor antagonists (candesartan, E3174, eprosartan, irbesartan and losartan) and aldosterone receptor antagonists (canrenoic acid and spironolactone) that directly modulate the activity of the voltage-dependent K(+) channels are reviewed; the effects of these antagonists might be useful in the prevention and treatment of cardiac arrhythmias.

Aldosterone modulates neural vasomotor response in hypertension: role of calcitonin gene-related peptide

OBJECTIVE

We analyse the effect of aldosterone on vasomotor response induced by electrical field stimulation (EFS) in mesenteric arteries from Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR).

RESULTS

Aldosterone (0.001-1 microM) reduced vasoconstrictor response to EFS in a dose- and time-dependent manner only in SHR. Thus, the rest of experiments were performed only in SHR. Aldosterone did not affect either noradrenaline response or release. Effect of aldosterone (1 microM) on EFS response was not affected by NG-nitro-arginine-methyl esther (100 microM), and was abolished by capsaicin (0.5 microM) and the calcitonin gene-related peptide antagonist (CGRP 8-37, 0.5 microM). Calcitonin gene-related peptide (0.1 nM-0.1 microM) induced a concentration-dependent relaxation, which was enhanced by aldosterone (1 microM). Incubation with either spironolactone (1 microM), glibenclamide (10 microM), RU 486 10 microM, ODQ (10 microM) or cycloheximide (10 microM) significantly reduced the enhancement of CGRP-relaxation produced by aldosterone, while remained unmodified by SQ 22,536.

CONCLUSIONS

Aldosterone decreases the vasoconstrictor response to EFS in mesenteric arteries from SHR but not from WKY. This effect is mediated by an increased response to the sensory neurotransmitter CGRP, substantially, through glucocorticoid receptors activation. Furthermore, this effect is mediated by an increase of cGMP synthesis and ATP-dependent potassium channel activation.

Effects of Eplerenone, a Selective Aldosterone Blocker, on the Progression of Left Ventricular Dysfunction and Remodeling in Rats with Dilated Cardiomyopathy

Aldosterone blockade reduces morbidity and mortality in patients with heart failure. We studied the effects of eplerenone, a novel aldosterone blocker, on the progression of left ventricular dysfunction and remodeling in rats with dilated cardiomyopathy after autoimmune myocarditis. Twenty-eight days after immunization, the surviving Lewis rats were randomized to 1 month's oral treatment with low-dose eplerenone (group L), high-dose eplerenone (group H) or vehicle (group V). Five of 15 (33%) rats in group V and 3 of 15 (20%) rats in group L died during the course of treatment. High-dose eplerenone significantly reduced cardiomyocyte hypertrophy, heart weight and heart weight to body weight ratio. Eplerenone improved left ventricular function in a dose-dependent manner. Central venous pressure and left ventricular end-diastolic pressure were lower, and +/-dP/dt and fractional shortening were higher in group H than group V. Eplerenone also attenuated myocardial fibrosis and reduced left ventricular mRNA expressions of TGF-beta(1) and collagen-III. Our results indicate that treatment with eplerenone improved left ventricular dysfunction and attenuated left ventricular remodeling in rats with heart failure.

Effect of Aldosterone and MR Blockade on the Brain and the Kidney

The renin-angiotensin-aldosterone system (RAAS) plays a central role in the development of hypertension and the progression of end-organ damage. Although angiotensin-I converting enzyme (ACE) inhibitors and angiotensin II (Ang II) subtype-1 (AT(1)) receptor antagonists can initially suppress plasma aldosterone, it is now well established that aldosterone escape may occur whereby aldosterone levels return to, or exceed, baseline levels. The classical effects of aldosterone relate mainly to its action on epithelial cells to regulate water and electrolyte balance. However, the presence of mineralocorticoid receptors (MR) at nonepithelial sites in the brain, heart and vasculature, is consonant with the fact that aldosterone also has direct effects in these tissues. Substantial evidence now exists that supports the action of aldosterone at non-epithelial sites which in turn provokes a number of deleterious effects on the cardiovascular system including necrosis and fibrosis of the vasculature and the heart, vascular stiffening and injury, reduced fibrinolysis, endothelial dysfunction, catecholamine release and production of cardiac arrhythmias. Several studies have now shown that vascular and target-organ protective effects of MR antagonism occurs in the absence of significant blood pressure lowering or fluid loss, which is consistent with a major role for endogenous mineralocorticoids as direct mediators of cardiovascular injury. Adverse cardiovascular effects may occur in response to aldosterone alone, activation of the RAAS or aldosterone escape during chronic ACE inhibition or AT(1) receptor antagonism. The specific blockade of aldosterone action should prove to be of great therapeutic value in the prevention of cerebral and renal vascular disease and associated end-organ damage.

New treatment option for heart failure patients: eplerenone

Aldosterone plays an important role in the harmful cardiac remodeling process and pathophysiology of heart failure after a myocardial infarction. Until recently, spironolactone (Aldactone) was the only pharmacologic agent available to directly block the deleterious effects of aldosterone. The use of spironolactone is complicated by its antiprogesterone and antiandrogen side effects, such as gynecomastia and menstrual irregularities. Eplerenone (Inspra), a member of a new class of drugs called selective aldosterone receptor antagonists, was recently approved for the treatment of both hypertension and post-myocardial infarction heart failure and appears to be devoid of the antiprogesterone and antiandrogen effects. In a trial in patients with heart failure following a myocardial infarction, eplerenone treatment significantly reduced mortality and morbidity compared to placebo. Eplerenone may be considered as part of the therapeutic plan in patients who have suffered a myocardial infarction and demonstrate evidence of heart failure.

Eplerenone: Selective Aldosterone Antagonism in Management of Cardiovascular and Renal Disease

OBJECTIVE

To review the pharmacology, safety, and efficacy data, as well as therapeutic use of eplerenone (Inspra-Pfizer) for management of cardiovascular and renal disease.

DATA SOURCES

A Medline search (January 1980-July 2003) was performed using eplerenone, aldosterone, aldosterone antagonist, spironolactone, and other pertinent terms. Additional articles were identified from bibliographies of retrieved articles.

STUDY SELECTION

All retrievable studies and review articles discussing the pharmacology, safety, and efficacy of eplerenone were evaluated.

DATA EXTRACTION

By the authors.

DATA SYNTHESIS

The detrimental role of the renin-angiotensin-aldosterone system (RAAS) in the pathophysiology of cardiovascular and renal disease has been well documented. Until recently, however, the direct injurious effects of aldosterone on nonclassical tissues such as the brain, heart, and vasculature have been overlooked. Although angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) significantly reduce morbidity and mortality associated with heart disease, preliminary data suggest further benefit with additional aldosterone blockade. The nonselective aldosterone antagonist spironolactone has demonstrated profound morbidity and mortality benefit in heart failure patients, but since its adverse event profile makes it unattractive to patients with milder disease, the need for a selective aldosterone receptor antagonist is evident. Preclinical studies with eplerenone, a recently approved selective aldosterone receptor antagonist, demonstrate a protective effect on nonclassical tissues, thus reducing injury associated with long-term unopposed aldosterone exposure. Early clinical trials with eplerenone have demonstrated additional benefit in hypertension, heart failure, and nephropathy, although long-term morbidity and mortality outcome data in patients with various levels of disease severity are necessary to define the role of eplerenone in current cardiovascular pharmacotherapy.

CONCLUSION

Eplerenone offers a new selective approach to optimizing aldosterone blockade. The availability of additional morbidity and mortality outcome data in various cardiovascular conditions will provide further insights into its role in clinical practice.

Additive effects of combined valsartan and spironolactone on cardiac aldosterone escape in spontaneously hypertensive rats

The additive effects of combined valsartan and spironolactone on plasma and cardiac aldosterone escape were evaluated in spontaneously hypertensive rats (SHRs). Twenty-four SHRs were treated with valsartan (30 mg/kg body weight per day), spironolactone (20 mg/kg body weight per day) and a combination of both for 4 months. Blood was collected and plasma aldosterone (PA) was estimated with radioimmunoassay (RIA). Ex vivo heart perfusion was performed, the ex vivo cardiac aldosterone (EXCA) was assessed by RIA after high-performance liquid chromatography separation. PA and EXCA were significantly decreased after one month but increased after 4 months in valsartan administration group. The combined valsartan and spironolactone therapy normalized cardiac aldosterone levels. This study provides the first evidence that the long-term treatment with Angiotensin II type 1 receptor antagonist (AT1A) induces local aldosterone escape in cardiovascular tissue, whereas the combined AT1A and spironolactone therapy inhibits the escape in hypertensive rats.

Human Endothelium: Target for Aldosterone

Aldosterone has long been known to control water and electrolyte balance by acting on mineralocorticoid receptors in kidney. However, recent studies demonstrated the presence of these receptors in nonclassical locations, including the cardiovascular system. We tested the hypothesis whether endothelial cells respond to aldosterone with changes in cell volume, a measure for ion-mediated water movement across the cell membrane. By means of atomic force microscopy in fluid, we measured volume of adherent human umbilical venous endothelial cells exposed for 72 hours to 10 nmol/L aldosterone. Over this period of time, cells swell by ≈18%. Aldosterone-induced swelling is prevented by 100 nmol/L of the mineralocorticoid receptor antagonist spironolactone, added to the primary endothelial cell culture. Aldosterone-treated cells dramatically shrink when 1 μmol/L of the diuretic amiloride is applied. Cells deprived of aldosterone do not respond to amiloride. Our conclusions are: (1) aldosterone leads to sustained cell swelling inhibited by administration of spironolactone or the sodium channel blocker amiloride; (2) cells respond to amiloride after aldosterone exposure; (3) renal diuretics act on endothelial cells; and (4) both amiloride and spironolactone could be useful for medical applications to prevent aldosterone-mediated endothelial dysfunction.

The effect of spironolactone, cilazapril and their combination on albuminuria in patients with hypertension and diabetic nephropathy is independent of blood pressure reduction: a randomized controlled study

OBJECTIVE

The effect of spironolactone, cilazapril and their combination on albuminuria was examined in a randomized prospective study in female patients with diabetes and hypertension.

PATIENTS AND METHODS

Sixty female diabetic patients aged 45-70 years with blood pressure (BP) 140-180/90-110 mmHg, serum creatinine (sCr) < or = 160 micro mol/l, HbA(1c) < or = 10%, and albuminuria were treated by atenolol 12.5-75 mg/d and hydrochlorothiazide 6.25-25 mg/d. Titration-to-target helped to reach BP values < or = 135/85 mmHg in 46 patients after 12 weeks. These patients were randomized to spironolactone 100 mg/d or cilazapril 5 mg/d for 24 weeks. Then both groups received spironolactone 50 mg/d and cilazapril 2.5 mg/d for 24 weeks. BP was stabilized by tapering the dose of the initial agents. Urinary albumin/creatinine ratio (ACR), BP, K(+). sCr and HbA(1c) were assessed at baseline and at weeks 12, 16, 36 and 60.

RESULTS

The average BP at week 12 was 128 +/- 4/81 +/- 3 mmHg and remained constant, in both groups, throughout the study. ACR declined on spironolactone from a median value (range) of 452 (124-1571) to 216 (64-875) mg/g (P = 0.001), and on cilazapril to 302 (90-975) mg/g (P = 0.001). The difference between spironolactone and cilazapril was significant (P = 0.002). Combined treatment resulted in a further modest decline in ACR. Serum creatinine was unaltered by spironolactone and rose slightly (121 to 126 micro mol/l, P = 0.02) on cilazapril.

CONCLUSION

At the doses tested, spironolactone was superior to cilazapril in reducing albuminuria. Combined administration was more effective than either drug alone. These effects were independent of BP values. Hyperkalaemia was the main side-effect.

Effects of Valsartan and Valeryl 4-Hydroxy Valsartan on Human Platelets: A Possible Additional Mechanism for Clinical Benefits

Valsartan selectively blocks angiotensin II binding to the AT1 receptor. ince platelet activation plays a key role in the pathogenesis of vascular disease, and because AT1 receptors are present on the platelet surface, we assessed the in vitro effects of valsartan and its metabolite, valeryl 4-hydroxy valsartan (V4HV), on platelets in 30 subjects with multiple risk factors for cardiovascular disease. Platelet characteristics in blood samples pretreated and incubated with 10 nmol to 100 micromol concentrations of valsartan and V4HV were assessed by aggregometry, rapid platelet analyzers, and by flow cytometry. Pretreatment of blood with valsartan and V4HV resulted in inhibition of conventional plasma (ADP, P = 0.0001, valsartan; epinephrine, P = 0.0001, V4HV) and whole blood collagen-induced (P = 0.01, valsartan; P =.0001, V4HV) platelet aggregation. Closure time was delayed (P = 0.02, valsartan; P = 0.03, 4VHV), indicating platelet inhibition in whole blood under high shear conditions. Expression of many surface platelet receptors, namely GP IIb/IIIa antigen, and activity, vitronectin, p-selectin, and LAMP-1 was significantly reduced compared with autologous baseline activity. Intensity of platelet-leukocyte formation and other platelet activation markers remained unchanged. Platelet inhibition was not dose dependent and was more potent for 4VHV than valsartan in the therapeutic range.Valsartan and 4VHV exhibited significant in vitro inhibition of human platelets. Their antiplatelet properties, especially more potent activity of the metabolite appear to be independent of those of other antiplatelet agents. Whether valsartan reduces vascular ischemic events via additional pathways of platelet inhibition in patients with myocardial infarction and ischemic stroke requires further clinical research.

Evolving role of aldosterone blockers alone and in combination with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers in hypertension management: a review of mechanistic and clinical data

The renin-angiotensin-aldosterone system (RAAS) plays an integral role in blood pressure regulation and has long been a target of pharmacologic approaches to controlling blood pressure. Traditionally, clinical interventions involving the RAAS have focused mainly on inhibiting the action of angiotensin II with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, and limited attention has been devoted to direct inhibition of the action of aldosterone. Recent advances in understanding the role of aldosterone in cardiovascular injury have elevated the importance of direct inhibition of the action of this hormone in the long-term control of blood pressure and have led to the development of the selective aldosterone blocker eplerenone. This article reviews the role of the RAAS in the development of hypertension and discusses the rationale for the use of eplerenone with other medications affecting the RAAS to control blood pressure.

From CONSENSUS to CHARM—how do ACEI and ARB produce clinical benefits in CHF?

Two decades of research from CONSENSUS to CHARM using modulators of the renin-angiotensin-aldosterone system (RAAS) in chronic heart failure (CHF) patients have shown convincing clinical benefits, but the majority of clinicians prescribing these drugs are still unclear about what mechanisms are responsible for the observed benefits. Of the candidate mechanisms hitherto proposed, there emerges a theme that best fits the spectrum of known factors from pathophysiology of heart failure to how the drugs enhance longevity of patients. This concept can be summarised as follows: after the onset of heart failure, neurohormones are activated resulting in raised levels of angiotensin, aldosterone and catecholamines, which are all known cardiotoxic agents. Cumulatively over time, they are responsible for accelerated cardiomyocyte attrition, manifesting as a faster reduction of cardiac pumping reserve, leading to worsening heart failure, more neurohormonal activation, thus propagating a vicious cycle spiralling towards an earlier fatality. The vicious cycle can be interrupted by dampening the excessive neurohormonal activities, thereby minimising cardiomyocyte losses and preserving cardiac functional reserve for longer. This culminates in maintenance of a reasonable quality of life and enhanced longevity. Such a mechanistic understanding would enable clinicians to have a better perspective on how to apply data from various clinical trials involving these drugs into clinical practice, to optimise and tailor therapy to the individual patient so that each patient can gain maximal benefits.

Efficacy and Safety of the Selective Aldosterone Blocker Eplerenone in Japanese Patients With Hypertension: A Randomized, Double-Blind, Placebo-Controlled, Dose-Ranging Study

Approximately 40% of Japanese patients with essential hypertension, including low-renin hypertension, are inadequately managed. Low-renin hypertension generally responds poorly to angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, but may respond more optimally to diuretics, calcium channel blockers, and aldosterone blockers. This multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose-ranging study evaluated the efficacy and safety of the selective aldosterone blocker eplerenone in 193 Japanese patients with essential hypertension. Although not a study inclusion criterion, baseline active plasma renin levels were consistently low (5.7-10.1 mU/L); most patients met the criteria for low-renin hypertension (< or =42.5 mU/L; normal range, 7-76 mU/L). Patients received placebo or eplerenone 50, 100, or 200 mg once daily for 8 weeks. Systolic blood pressure decreased significantly (-6.8 to -10.6 mm Hg vs. -2.1 mm Hg; p< or =0.0022 vs. placebo). Eplerenone offers significant blood pressure reduction with good tolerability in Japanese patients with hypertension, including those with low-renin hypertension.

Unorthodox Sites and Modes of Aldosterone Action

Aldosterone controls electrolyte balance by acting on the renal epithelium. However, there is strong evidence that vascular endothelium is another target for mineralocorticoids. Endothelial cells gain sensitivity to diuretics when exposed to aldosterone. Atomic force microscopy detects such phenomena. It is speculated that endothelium and kidney join forces in the regulation of body fluids.

Aldosterone target organ protection by eplerenone

The classical mineralocorticoid effect of aldosterone on unidirectional transepithelial sodium transport in the kidney was long thought to be the predominant effect of this hormone. However, there is convincing evidence for additional extrarenal actions of aldosterone that are mediated via activation of mineralocorticoid receptors (MRs) in the heart, vasculature and brain. It is now postulated that many of the detrimental effects of aldosterone are mediated through MR activation in these nonclassical target organs. The selective aldosterone blocker, eplerenone (Inspra), is under development for human therapeutic use for treatment of hypertension and heart failure post-myocardial infarction (MI). Clinical and preclinical studies have linked elevated aldosterone to hypertension, left ventricular and vascular remodeling, cardiac, renal, and cerebral vascular inflammation and injury, and increased risk of mortality in heart failure patients. Multiple studies in experimental models of hypertension and heart failure demonstrate that selective blockade of aldosterone by eplerenone effectively preserves cardiac function, attenuates maladaptive left ventricular remodeling and tissue and vascular injury in part by reducing vascular inflammation in aldosterone target organs.

Eplerenone: a selective aldosterone blocker

Recent studies suggest that aldosterone may play a larger role than once appreciated in normal physiologic function and cardiovascular disease. Some of the adverse cardiovascular effects that have been described include cardiac and vascular fibrosis, vascular necrosis and inflammation, impaired endothelial function, reduced fibrinolysis, hypertension, left ventricular hypertrophy (LVH), congestive heart failure, and cardiac arrhythmias. In light of these findings, the ability to block the actions of aldosterone has gained increased therapeutic importance. Eplerenone is a selective aldosterone receptor blocker that displays little interaction with androgen and progesterone receptors. Eplerenone has already been approved for the treatment of systemic hypertension and has been evaluated in numerous hypertension subgroups, including patients with low plasma renin activity; diabetes; LVH; uncontrolled blood pressure while receiving monotherapy with angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, calcium channel blockers, or beta-blockers; and in black patients. Results of these trials indicate that eplerenone lowers blood pressure and reduces end-organ damage. Further proof of the therapeutic importance of mineralocorticoid receptor blockade comes from the eplerenone post acute myocardial infarction survival and efficacy study (EPHESUS). In this large-scale clinical outcome trial, eplerenone was shown to reduce total mortality by 15% as well as the combined endpoint of cardiovascular mortality/cardiovascular hospitalization by 13% when administered at a mean of 7.3 days post myocardial infarction to patients with evidence of systolic left ventricular dysfunction and symptoms of heart failure. Eplerenone is well tolerated, with an adverse effect profile comparable to placebo. The advent of selective aldosterone blockers, such as eplerenone, should prove to be of great therapeutic value in hypertension control and prevention of cardiovascular disease and associated end-organ damage.

Protective effects of dietary potassium chloride on hemodynamics of Dahl salt-sensitive rats in response to chronic administration of sodium chloride

BACKGROUND

Dietary potassium supplementation decreases blood pressure and prevents strokes in humans, and prevents strokes and renal damage in Dahl salt-sensitive (DSS) rats.

OBJECTIVE

To study the effects of various concentrations of dietary potassium chloride (KCl) on the hemodynamics of Dahl salt-resistant (DSR) and DSS rats receiving a 1% sodium chloride (NaCl) diet for 8 months, to determine whether there is an optimal dietary concentration of KCl that minimizes increases in blood pressure and causes least impairment of blood flow in the brain and kidneys.

METHODS AND RESULTS

We found a biphasic effect on hemodynamic parameters as a function of dietary KCl in DSS rats of the Rapp strain fed 1% NaCl with increasing dietary KCl (0.7, 2.6, 4 and 8%). After 8 months receiving a diet containing 1% NaCl and 0.7% KCl, DSS rats had mean arterial pressures (MAP), plasma volumes, cardiac outputs and renal and cerebral vascular resistances that were significantly increased compared with those of DSR rats receiving the same diet. With a 2.6% KCl diet, all these parameters were significantly reduced compared with those in DSS rats fed the 0.7% KCl diet and were similar to those in DSR rats fed 2.6% KCl. Total peripheral resistance in DSR and DSS rats was similar on all diets. When KCl was increased to 4 and 8%, MAP, plasma volume, cardiac output and renal vascular resistance progressively increased in DSR and DSS rats, without changing total peripheral resistance. These changes paralleled increases in plasma aldosterone, which resulted from adrenocortical stimulation by the increasing dietary KCl; however, cerebral vascular resistance of DSR and DSS rats decreased significantly with a 4% KCl diet, despite increased aldosterone and sodium retention. Only DSS rats fed a 2.6% KCl diet had hemodynamics similar to those of DSR control rats fed the same diet, and hyperaldosteronism, sodium retention and increased plasma volume did not occur.

CONCLUSION

'Optimal' dietary KCl (2.6%) prevents hypertension and preserves cerebral and renal hemodynamics in DSS rats fed a diet containing 1% NaCl for 8 months, which causes hypertension when dietary KCl is limited or excessive.

Mineralocorticoids act centrally to regulate blood-borne tumor necrosis factor-α in normal rats

Excessive mineralocorticoid receptor (MR) stimulation induces neurohumoral excitation and cardiac and vascular fibrosis. In heart failure (HF) rats, with excessive neurohumoral drive, central infusion of the MR antagonist spironolactone (SL) decreases blood-borne TNF-α. This study aimed to determine whether DOCA, a precursor of aldosterone, acts centrally to stimulate TNF-α production in normal rats. DOCA (5 mg sc daily for 8 days) induced a progressive increase in TNF-α beginning on day 3 and increased tissue TNF-α in hypothalamus, pituitary, and heart but not in other brain and peripheral tissues harvested on day 9. A continuous intracerebroventricular infusion of SL (100 ng/h) blocked the plasma TNF-α response. Oral SL (1 mg/kg) blocked the plasma and tissue TNF-α responses. Thus DOCA increases TNF-α in brain, heart, and blood in normal rats. Activation of brain MR appears to account for the increase in plasma TNF-α. These findings have important implications for the understanding of pathophysiological states (e.g., HF, hypertension) characterized by high circulating levels of aldosterone.

Use of nonantiarrhythmic drugs for prevention of sudden cardiac death

It is of interest that the drugs having the most significant impact on total and sudden death mortality are those without direct electrophysiologic actions on myocardial excitable tissue. This observation may provide insight into mechanisms responsible for ventricular tachyarrhythmias causing cardiac arrest. One way to think about ventricular fibrillation is that it is the final common pathway of an electrically unstable heart. After all, the heart can "die" in only three major ways: electromechanical dissociation, asystole and heart block, and ventricular fibrillation, with the latter most common. It is the "upstream" events provoking the electrical instability that these drugs probably act upon (i.e., ischemia, fibrosis). Although we unquestionably need to pursue investigations into the electrophysiology of these ventricular tachyarrhythmias, more studies need to investigate the drugs affecting upstream events, because these agents appear to yield the greatest dividends, at least for the present. This article reviews these drugs and how they may be effective.

Long-term safety and efficacy of the selective aldosterone blocker eplerenone in patients with essential hypertension

BACKGROUND

Even within the normal range, aldosterone levels are linked to end-organ toxicity and mortality in patients with hypertension. Treatment with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers does not sufficiently reduce plasma aldosterone levels.

OBJECTIVE

This study was conducted to assess the long-term safety profile and efficacy of the selective aldosterone blocker eplerenone.

METHODS

This was a multicenter, open-label, uncontrolled trial in patients with mild to moderate essential hypertension. After a 1-week washout of previous antihypertensive medications, eplerenone was initiated at 50 mg once daily; the dose was titrated to a maximum of 200 mg/d to achieve a diastolic blood pressure <90 mm Hg and a systolic blood pressure <140 mm Hg. Thereafter, another antihypertensive agent could be added and titrated once, or another agent could be substituted for eplerenone. Eplerenone treatment was continued for up to 14 months in a subset of patients.

RESULTS

Five hundred eighty-six patients were enrolled in the study. Their adjusted mean blood pressure (BP) at baseline was 150/96 mm Hg. The majority (80.4%) were white; 51.5% were male and 48.5% were female; 62.3% were between the ages of 45 and 64 years and 21.7% were aged >64 years. Three hundred eighty-five patients (65.7%) completed the study; 98 (16.7%) were withdrawn due to treatment failure (only 4.8% of them after month 4), and 40 (6.8%) were withdrawn due to treatment-emergent adverse events. Four hundred thirty-three of 582 (74.4%) patients in the intent-to-treat population achieved BP control during eplerenone treatment: 261 (44.8%) received eplerenone monotherapy and 172 (30.0%) received eplerenone plus another antihypertensive agent.

CONCLUSIONS

Eplerenone therapy was effective in the treatment of mild to moderate hypertension over a 14-month period, either as monotherapy or in combination with another antihypertensive agent. Use of eplerenone was well tolerated in the population studied.

Aldosterone receptor antagonists: biology and novel therapeutical applications

Recent studies suggest that a dysregulation of the aldosterone system is involved in the pathophysiology of different cardiovascular diseases, including myocardial failure and several cases of essential hypertension. In both rat models and in humans, aldosterone action has been shown to induce heart remodeling and interstitial and perivascular fibrosis of the myocardium. For these reasons, a rationale for the use of aldosterone antagonists (ARAs) of the spirolactone family, which have been available for decades in the treatment of aldosterone excess syndromes, has now emerged. Moreover, the recent validation of their use, in combination with the current therapy, for the treatment of these cardiovascular diseases by trials like the RALES Study has further strenghtened this approach. The development of compounds, like eplerenone, with a greater selectivity for mineralocorticoid receptors, seems promising also in terms of reduction of endocrine side effects. The addition of aldosterone antagonists to the conventional therapy of myocardial failure and of selected cases of hypertension thus appears beneficial, resulting in an improved survival rate and a reduced incidence of cardiac complications. This review article, after a brief recall of the physiology of the aldosterone system, addresses the emerging role of aldosterone in cardiovascular diseases, considers the pharmacology of ARAs and the novel therapeutical applications of these compounds in hypertension and heart failure.

Aldosterone plays a pivotal role in the pathogenesis of thrombotic microangiopathy in SHRSP

Angiotensin-converting enzyme inhibitors and aldosterone receptor antagonists ameliorate malignant nephrosclerotic lesions of thrombotic microangiopathy in salt-loaded, stroke-prone, spontaneously hypertensive rats (SHRSP) without controlling hypertension. This suggests that angiotensin II (Ang II) and/or aldosterone (ALDO) plays a critical role in renal injury in this model. For evaluating their relative roles in the pathogenesis of thrombotic microangiopathy, SHRSP were adrenalectomized and infused with vehicle, Ang II, or ALDO or were sham-operated for adrenalectomy (SHAM). Saline-drinking rats were assigned to one of four groups: SHAM, adrenalectomy, adrenalectomy + Ang II (25 ng/min, subcutaneously), or adrenalectomy + ALDO (40 micro g/kg per d, subcutaneously). All SHRSP received dexamethasone (12 micro g/kg per d, subcutaneously). Adrenalectomy did not show changes in body weight, plasma creatinine, sodium and potassium, and daily urinary sodium and potassium excretion; did not prevent hypertension but prevented proteinuria (12 +/- 1 versus 49 +/- 3 mg/d; P < 0.01); and abrogated thrombotic microangiopathy and decreased plasma aldosterone (<16 versus 710 +/- 91 pg/ml; P < 0.001) compared with SHAM. Systolic BP in adrenalectomy + Ang II and adrenalectomy + ALDO (238 +/- 8 and 241 +/- 9 mmHg, respectively) was similar to SHAM. Despite Ang II infusion, proteinuria (17 +/- 9 mg/d) and thrombotic microangiopathy and plasma aldosterone (18 +/- 18 pg/ml) remained low but daily urinary excretion of sodium and potassium were not different from adrenalectomy + ALDO. Adrenalectomy + ALDO showed plasma aldosterone levels of 735 +/- 147 pg/ml; plasma potassium was lower; plasma creatinine and proteinuria (78 +/- 7 mg/d) were greater and thrombotic microangiopathy lesions were comparable to SHAM. These results demonstrate a pivotal role for aldosterone in the development of thrombotic microangiopathy, independent of hypertension.

Primary aldosteronism - treatment options

Diagnosis of primary aldosteronism results in either the surgical cure of hypertension or targeted pharmacotherapy. The two major subtypes of primary aldosteronism are unilateral aldosterone-producing adenoma (APA) and bilateral idiopathic hyperaldosteronism (IHA). Patients with APA usually are treated with unilateral adrenalectomy and patients with IHA are treated medically. The majority of patients with primary aldosteronism have the IHA subtype and require pharmacotherapy. Spironolactone has been the drug of choice to treat primary aldosteronism. However, it is not selective for the aldosterone receptor, and side effects include gynecomastia, erectile dysfunction and menstrual irregularity. Eplerenone is a new competitive and selective aldosterone receptor antagonist recently approved by the United States Food and Drug Administration for the treatment of hypertension. It lacks the side effects associated with spironolactone and will be the superior drug if it is shown to be as effective as spironolactone for the treatment of mineralocorticoid-dependent hypertension.

Minireview: primary aldosteronism--changing concepts in diagnosis and treatment

Primary aldosteronism affects 5-13% of patients with hypertension. Patients with hypertension and hypokalemia and most patients with treatment-resistant hypertension should undergo screening for primary aldosteronism with a plasma aldosterone concentration to plasma renin activity ratio. A high plasma aldosterone concentration to plasma renin activity ratio is a positive screening test result, a finding that warrants confirmatory testing. For those patients that want to pursue a surgical cure, the accurate distinction between the subtypes (unilateral vs. bilateral adrenal disease) of primary aldosteronism is a critical step. The subtype evaluation may require one or more tests, the first of which is imaging the adrenal glands with computed tomography, followed by selective use of adrenal venous sampling. Because of the deleterious cardiovascular effects of aldosterone, normalization of circulating aldosterone or aldosterone receptor blockade should be part of the management plan for all patients with primary aldosteronism. Unilateral laparoscopic adrenalectomy is an excellent treatment option for patients with unilateral aldosterone-producing adenoma. Bilateral idiopathic hyperaldosteronism should be treated medically. In addition, aldosterone-producing adenoma patients may be treated medically if the medical treatment includes mineralocorticoid receptor blockade.

Spironolactone and its main metabolite, canrenoic acid, block human ether-a-go-go-related gene channels

BACKGROUND

It has been demonstrated that spironolactone (SP) decreases the QT dispersion in chronic heart failure. In this study, the effects of SP and its metabolite, canrenoic acid (CA), on human ether-a-go-go-related gene (HERG) currents were analyzed.

METHODS AND RESULTS

HERG currents elicited in stably transfected Chinese hamster ovary cells were measured with the whole-cell patch-clamp technique. SP decreased HERG currents in a concentration-dependent manner (IC50=23.0+/-1.5 micromol/L) and shifted the midpoint of the activation curve to more negative potentials (Vh=-13.1+/-3.4 versus -18.9+/-3.6 mV, P<0.05) without modifying the activation and deactivation kinetics. SP-induced block (1 micromol/L) appeared at the range of membrane potentials coinciding with that of channel activation, and thereafter, it remained constant, reaching 24.7+/-3.8% at +60 mV (n=6, P<0.05). CA (0.01 nmol/L to 500 micromol/L) blocked HERG channels in a voltage- and frequency-independent manner. CA at 1 nmol/L shifted the midpoint of the activation curve to -19.9+/-1.8 mV and accelerated the time course of channel activation (tau=1064+/-125 versus 820+/-93 ms, n=11, P<0.01). The envelope of the tail test demonstrated that at the very beginning of the pulses to +40 mV (25 ms), a certain amount of block was apparent (31.3+/-9.9%). CA did not modify the voltage-dependence of HERG channel inactivation (Vh=-60.8+/-5.6 versus -62.9+/-3.1 mV, n=6, P>0.05) or the kinetics of the reactivation process at any potential tested. CA and aldosterone also blocked the native I(Kr) in guinea-pig ventricular myocytes.

CONCLUSIONS

At concentrations reached after administration of therapeutic doses of SP, CA blocked the HERG channels by binding to both the closed and open states of the channel.

A validated SPE-LC-MS/MS assay for Eplerenone and its hydrolyzed metabolite in human urine

An automated LC-MS/MS assay was validated to quantitate the first selective aldosterone blocker Eplerenone (I) and its hydrolyzed metabolite (II) in human urine. After the addition of the stable isotope labeled internal standards, human urine samples were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The extraction eluates were diluted with 20 mM ammonium acetate aqueous solution and directly injected onto the LC-MS/MS system. The chromatographic separation was performed on a reverse phase Zorbax XDB-C(8) HPLC column (2.1 x 50 mm, 5 microm) with a mobile phase of acetonitrile:water (40:60, v/v) containing 10 mM ammonium acetate (pH 7.4). I and II were ionized using positive and negative ionization mass spectrometry, respectively, to achieve the best sensitivity. The ionization polarity was switched during the run at approximately 2.5 min after the injection. Multiple reaction monitoring (MRM) with a tandem mass spectrometer was used to detect the analytes. The precursor to product ion transitions of m/z 415-->163 and m/z 431-->337 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 50-10000 ng/ml of urine for both of I and II. The lower limit of quantitation (LLOQ) was 50 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. Sample analysis time for each injection was 5 min; a throughput of 100 human urine standards and samples per run was achieved.

Heart failure and the brain: new perspectives

Despite recent therapeutic advances, the prognosis for patients with heart failure remains dismal. Unchecked neurohumoral excitation is a critical element in the progressive clinical deterioration associated with the heart failure syndrome, and its peripheral manifestations have become the principal targets for intervention. The link between peripheral systems activated in heart failure and the central nervous system as a source of neurohumoral drive has therefore come under close scrutiny. In this context, the forebrain and particularly the paraventricular nucleus of the hypothalamus have emerged as sites that sense humoral signals generated peripherally in response to the stresses of heart failure and contribute to the altered volume regulation and augmented sympathetic drive that characterize the heart failure syndrome. This brief review summarizes recent studies from our laboratory supporting the concept that the forebrain plays a critical role in the pathogenesis of ischemia-induced heart failure and suggesting that the forebrain contribution must be considered in designing therapeutic strategies. Forebrain signaling by neuroactive products of the renin-angiotensin system and the immune system are emphasized.