Effect of eplerenone, a selective aldosterone blocker, on blood pressure, serum and macrophage oxidative stress, and atherosclerosis in apolipoprotein E-deficient mice

Aldosterone inhibits endothelial morphogenesis and angiogenesis through the downregulation of vascular endothelial growth factor receptor-2 expression subsequent to peroxisome proliferator-activated receptor gamma

Angiogenesis plays a pivotal role in cardiovascular diseases such as ischemic heart disease, limb ischemia and heart failure, and has recently been shown to mediate various biological activities related to the pathogenesis of these diseases. In the present study, we evaluated the role of aldosterone in angiogenesis. Tube formation assay on Matrigel using human umbilical vein endothelial cells (HUVEC) revealed that aldosterone inhibited endothelial morphogenesis in a manner sensitive to eplerenone, a selective mineralocorticoid receptor antagonist. The anti-angiogenic effect of aldosterone was further confirmed by an in vivo angiogenesis assay using a Matrigel plug model in mice. Reverse transcription-mediated polymerase chain reaction and immunoblotting demonstrated that aldosterone downregulated the expression levels of vascular endothelial growth factor receptor-2 (VEGFR-2) and peroxisome proliferators-activated receptor gamma (PPAR gamma). VEGFR-2 expression was found to be enhanced in response to PPAR gamma activation by troglitazone, and attenuated by GW9662, a specific antagonist of PPAR gamma. In the tube formation assay, endothelial morphogenesis was stimulated by troglitazone, and inhibited by GW9662, indicating that PPAR gamma activation mediates positive regulation of angiogenesis through enhancement of VEGFR-2 expression. These data suggest that aldosterone inhibits angiogenesis through VEGFR-2 downregulation, subsequent to, at least in part, attenuation of PPAR gamma expression. The present findings provide a new insight into the possible therapeutic application of mineralocorticoid receptor blockade to various cardiovascular diseases.

Mineralocorticoid receptors in vascular function and disease

The mineralocorticoid receptor (MR), a member of the steroid receptor family, regulates blood pressure by mediating the effects of the hormone aldosterone (Aldo) on renal sodium handling. Over the past decade, it has become clear that MR is expressed in the cardiovascular system and interest has grown in understanding the direct role of the MR in regulating vascular function and contributing to cardiovascular disease. This interest stems from multiple clinical studies in which drugs that decrease MR activation also reduce the incidence of heart attacks, strokes, and mortality out of proportion to modest changes in systemic blood pressure. The presence of functional mineralocorticoid receptors in vascular smooth muscle and endothelial cells is now well established and, while still controversial, data supports the vasculature as an Aldo-responsive tissue. This review summarizes recent advances in our understanding of the role of vascular MR in regulating normal vascular function and in promoting vascular disease. In vitro data, in vivo animal studies, and human data are reviewed suggesting a role for MR-activation in promoting vascular oxidative stress, inhibiting vascular relaxation, and contributing to vessel inflammation, fibrosis, and remodeling. These detrimental vascular effects of MR activation appear to be independent of changes in blood pressure and are synergistic with the presence of endothelial dysfunction or damage. Thus, in humans with underlying cardiovascular disease or cardiovascular risk factors, vascular MR activation may promote vascular aging and atherosclerosis thereby contributing to the pathophysiology of heart attack, stroke, and possibly even hypertension. Further exploration of the molecular mechanisms for the detrimental vascular effects of MR activation has the potential to identify novel therapeutic targets to prevent or treat common cardiovascular disorders.

Measuring and targeting aldosterone and renin in atherosclerosis-a review of clinical data

Our understanding of the development and progression of atherosclerosis has increased substantially over the past decades. A significant role for the renin-angiotensin-aldosterone system (RAAS) in this process has gained appreciation in recent years. Preclinical and clinical studies have associated components of the RAAS with various cardiovascular disease conditions. Classically known for its contribution to hypertension, dysregulation of the system is now also believed to promote vascular inflammation, fibrosis, remodeling, and endothelial dysfunction, all intimately related to atherosclerosis. The reduction in cardiovascular mortality and morbidity, as seen with the use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, supports the concept that RAAS is involved in the pathogenesis of atherosclerotic disease. However, the underlying molecular mechanisms of the pathophysiology remain to be completely understood. Evidence points toward additional benefit from therapeutic approaches aiming at more complete inhibition of the system and the possible utility of renin or aldosterone in the prediction of cardiovascular outcome. This review will summarize the current knowledge from clinical studies regarding the presumptive role of renin and aldosterone in the prediction and management of patients with atherosclerosis. For this purpose, a literature search was performed, focusing on available clinical data regarding renin or aldosterone and cardiovascular outcome.

FAD286, an aldosterone synthase inhibitor, reduced atherosclerosis and inflammation in apolipoprotein E-deficient mice

INTRODUCTION

Aldosterone is known to be involved in atherosclerosis and cardiovascular disease and blockade of its receptor was shown to improve cardiovascular function. It was, therefore, hypothesized that inhibition of aldosterone synthesis would also reduce atherosclerosis development.

METHOD

To test this hypothesis, we examined the effect of FAD286 (FAD), an aldosterone synthase inhibitor, on the development of atherosclerosis in spontaneous atherosclerotic apolipoprotein E-deficient mice. Mice were divided into three treatment groups: normal diet, low-salt diet (LSD) and LSD treated with FAD at 30 mg/kg per day (LSD + FAD) for 10 weeks.

RESULTS AND CONCLUSION

Histomorphometry of the aortas obtained from these mice showed that atherosclerotic lesion area increased by three-fold under LSD compared with normal diet and FAD significantly reduced lesion area to values similar to normal diet. Changes in atherosclerosis were paralleled by changes in the expression of the inflammation markers (C-reactive protein, monocyte chemotactic protein-1, interleukin-6, nuclear factor kappa B and intercellular adhesion molecule-1) in peritoneal macrophages obtained from these mice. Surprisingly, whereas LSD increased serum or urine aldosterone levels, FAD did not alter these levels when evaluated at the end of the study. In J774A.1 macrophage-like cell line stimulated with lipopolysaccharide, FAD was shown to have a direct dose-dependent anti-inflammatory effect. In apolipoprotein E-deficient mice, FAD reduces atherosclerosis and inflammation. However, these actions appeared to be dissociated from its effect on inhibition of aldosterone synthesis.

Aldosterone and mineralocorticoid receptors in the cardiovascular system

Aldosterone is currently thought to exert its physiologic effects by activating epithelial mineralocorticoid receptors, and its pathologic effects on the cardiovascular system via mineralocorticoid receptors in the heart and blood vessels. Recent studies have extended this understanding to include a reevaluation of the roles of aldosterone and mineralocorticoid receptor activation in blood pressure control; the rapid, nongenomic effects of aldosterone; the role of cortisol as a mineralocorticoid receptor agonist under conditions of redox change/tissue damage/reactive oxygen species generation; the growing consensus that primary aldosteronism accounts for approximately 10% of all essential hypertension; recent new insights into the cardioprotective role of spironolactone; and the development of third- and fourth-generation mineralocorticoid receptor antagonists for use in cardiovascular and other inflammatory disease. These findings on aldosterone action and mineralocorticoid receptor blockade are analyzed in the context of the prevention and treatment of cardiovascular disease.

Oxidative stress-related proteins in a Conn's adenoma tissue. Relevance for aldosterone's prooxidative and proinflammatory activity

BACKGROUND AND AIM

Angiotensin II (Ang II) induces oxidative stress (OxSt), which is essential for cardiovascular remodeling. Aldosterone also induces fibrosis and remodeling through direct effect on non-classical mineralocorticoid (MR) target tissues. However, studies on the role of aldosterone on OxSt and related factors in humans are lacking.

MATERIALS AND METHODS

We assessed gene and protein expression of p22phox (RT-PCR and Western blot), NAD(P)H oxidase subunit essential for superoxide production and gene expression of transforming growth fator (TGF) beta, plasminogen activator inhibitor (PAI)-1, and heme oxygenase (HO)-1, effectors of OxSt (RT-PCR), in a Conn's adenoma, removed from a patient with primary hyperaldosteronism. Ang II type 1 (AT1R) and MR receptors expression were also evaluated (RT-PCR). The normal adrenal tissue adjacent to the adenoma was used as control.

RESULTS

p22phox gene and protein expression were higher (31% and 53%, respectively) in the adrenal adenoma. TGFbeta, PAI-1, and HO-1 gene expression were also higher (25%, 129%, and 25%, respectively) in the adrenal adenoma while AT1R gene expression was similar (8%). The expression of MR in the adenoma was documented.

CONCLUSIONS

This report demonstrates in a human model that the increased aldosterone production has effects on enzyme systems related to OxSt, enhancing the systemic fibrogenic effects of aldosterone excess through TGFbeta and PAI-1 expression which was previously demonstrated only indirectly in vitro and in animal models. The presence of MR expression in the adenoma may link the hormone with the adenoma growth. Therefore, the results of this study derived from a single case might represent an important working hypothesis for further research in a larger number of cases to clarify the role of aldosterone overproduction on OxSt and its clinical relevance.

Effect of canrenone and amiloride on the prooxidative effect induced by aldosterone in human mononuclear leukocytes in vitro

Clinical studies have demonstrated that aldosterone receptor antagonists do improve the survival of patients with chronic heart diseases and in vitro studies have shown that canrenone blocks the proinflammatory effect of aldosterone in mononucler leukocytes (MNL). The aim of the study was to compare, in the model of human MNL, the effect of potassium-sparing diuretics amiloride and canrenone, on the protein expression of p22phox, a NADPH-oxidase system subunit, that is a principal marker of production of superoxide anions. MNL were isolated from 10 informed healthy volunteers (5 males and 5 females, age range 24-36 yr) and the proteins extracted. p22phox protein expression was evaluated by Western blot and quantified using a densitometric semiquantitative analysis. The experiments showed that aldosterone (10(-8) M) enhances the protein expression of p22phox and that its effect is reversed by co-incubation with canrenone (10(-6) M), while incubation with amiloride (10(-6) M) reduced the prooxidative effect of aldosterone at a significantly lower extent than canrenone. Co-incubation with canrenone, amiloride, and aldosterone together produced the same effect as aldosterone plus canrenone. Incubation with cortisol (40(-8) M) was not effective. These data confirm the prooxidative effect of aldosterone in MNL. The addition of aldosterone-receptor antagonist canrenone produced a higher inhibition than sodium channel blocker amiloride on the effect of aldosterone on p22phox protein expression.

Eplerenone does not attenuate diabetes-associated atherosclerosis

BACKGROUND

It has been suggested that aldosterone, with its known pro-inflammatory and profibrotic actions, may play a key role in the development and progression of atherosclerosis.

METHOD

In this study, the ability of aldosterone antagonism to reduce atherosclerosis in experimental diabetes was assessed. Diabetes was induced in ApoE knockout mice with streptozotocin, and the mice were treated with the specific aldosterone antagonist, eplerenone, in their feed over 20 weeks (approximately 200 mg/kg per day).

RESULT

En face analysis revealed that eplerenone treatment was unable to attenuate atherosclerosis as assessed by percentage lesion area quantitation in the aortae of these mice compared with untreated diabetic mice (diabetic, 10.7 +/- 1.1; diabetic + eplerenone, 8.8 +/- 1.2%). In contrast, we observed a significant, more than 50% decrease in percentage of plaque area in the nondiabetic control groups. Despite this lack of effect in the diabetic mice, eplerenone treatment was associated with reduced cytosolic superoxide production. However, aortic transcript levels of key molecules implicated in diabetes-associated atherogenesis, such as monocyte chemoattractant protein-1 and vascular cell adhesion molecule-1, were not significantly attenuated by eplerenone.

CONCLUSION

These findings suggest that eplerenone treatment may not be as antiatherosclerotic in the diabetic context.

Some considerations about evolution of idiopathic primary aldosteronism

The prevalence of primary aldosteronism has increased since many patients who were previously considered as being affected by low renin essential hypertension are actually satisfying the new diagnostic criteria using plasma aldosterone/ plasma renin activity (PRA) ratio. Many of these cases could be classified as subclinical hyperaldosteronism, having normal aldosterone and low PRA, or in alternative the normal range of aldosterone should be revised. Idiopathic hyperaldosteronism can, in many cases, be considered as an evolutive disease: it can be hypothesized that the biochemical picture can be preceded by essential hypertension and that, after several years, primary aldosteronism can evolve back to essential hypertension due to age-related reduced vascular and adrenal sensitivity to angiotensin II. This effect is also evident after longterm treatment with aldosterone receptors blockers and therefore it possible that aldosterone-receptors blockers are able to normalize the sensitivity of glomerulosa to angiotensin II even after long-term withdrawal. The use of aldosterone receptors blockers prevents cardiovascular complications due to local aldosterone effect at the level of endothelium and mononuclear leukocytes; therefore, these drugs should be also considered for therapy of patients with hypertension. It is not excluded that aldosterone receptor blockers could prevent the onset of idiopathic hyperaldosteronism and its complications in patients with hypertension without primary hyperaldosteronism. From all these considerations it follows that the concept of normal range of aldosterone should be revised and the use of aldosterone receptor blockers should be revisited.

Torcetrapib-induced blood pressure elevation is independent of CETP inhibition and is accompanied by increased circulating levels of aldosterone

BACKGROUND AND PURPOSE

Inhibition of cholesteryl ester transfer protein (CETP) with torcetrapib in humans increases plasma high density lipoprotein (HDL) cholesterol levels but is associated with increased blood pressure. In a phase 3 clinical study, evaluating the effects of torcetrapib in atherosclerosis, there was an excess of deaths and adverse cardiovascular events in patients taking torcetrapib. The studies reported herein sought to evaluate off-target effects of torcetrapib.

EXPERIMENTAL APPROACH

Cardiovascular effects of the CETP inhibitors torcetrapib and anacetrapib were evaluated in animal models.

KEY RESULTS

Torcetrapib evoked an acute increase in blood pressure in all species evaluated whereas no increase was observed with anacetrapib. The pressor effect of torcetrapib was not diminished in the presence of adrenoceptor, angiotensin II or endothelin receptor antagonists. Torcetrapib did not have a contractile effect on vascular smooth muscle suggesting its effects in vivo are via the release of a secondary mediator. Treatment with torcetrapib was associated with an increase in plasma levels of aldosterone and corticosterone and, in vitro, was shown to release aldosterone from adrenocortical cells. Increased adrenal steroid levels were not observed with anacetrapib. Inhibition of adrenal steroid synthesis did not inhibit the pressor response to torcetrapib whereas adrenalectomy prevented the ability of torcetrapib to increase blood pressure in rats.

CONCLUSIONS AND IMPLICATIONS

Torcetrapib evoked an acute increase in blood pressure and an acute increase in plasma adrenal steroids. The acute pressor response to torcetrapib was not mediated by adrenal steroids but was dependent on intact adrenal glands.

Torcetrapib does not reduce atherosclerosis beyond atorvastatin and induces more proinflammatory lesions than atorvastatin

BACKGROUND

Although cholesteryl ester transfer protein (CETP) inhibition is regarded as a promising strategy to reduce atherosclerosis by increasing high-density lipoprotein cholesterol, the CETP inhibitor torcetrapib given in addition to atorvastatin had no effect on atherosclerosis and even increased cardiovascular death in the recent Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events trial. Therefore, we evaluated the antiatherogenic potential and adverse effects of torcetrapib in humanized APOE*3-Leiden.CETP (E3L.CETP) mice.

METHODS AND RESULTS

E3L.CETP mice were fed a cholesterol-rich diet without drugs or with torcetrapib (12 mg x kg(-1) x d(-1)), atorvastatin (2.8 mg x kg(-1) x d(-1)), or both for 14 weeks. Torcetrapib decreased CETP activity in both the absence and presence of atorvastatin (-74% and -73%, respectively; P<0.001). Torcetrapib decreased plasma cholesterol (-20%; P<0.01), albeit to a lesser extent than atorvastatin (-42%; P<0.001) or the combination of torcetrapib and atorvastatin (-40%; P<0.001). Torcetrapib increased high-density lipoprotein cholesterol in the absence (30%) and presence (34%) of atorvastatin. Torcetrapib and atorvastatin alone reduced atherosclerotic lesion size (-43% and -46%; P<0.05), but combination therapy did not reduce atherosclerosis compared with atorvastatin alone. Remarkably, compared with atorvastatin, torcetrapib enhanced monocyte recruitment and expression of monocyte chemoattractant protein-1 and resulted in lesions of a more inflammatory phenotype, as reflected by an increased macrophage content and reduced collagen content.

CONCLUSIONS

CETP inhibition by torcetrapib per se reduces atherosclerotic lesion size but does not enhance the antiatherogenic potential of atorvastatin. However, compared with atorvastatin, torcetrapib introduces lesions of a less stable phenotype.

Glucocorticoids and cardiovascular disease

Chronic excessive activation of glucocorticoid receptors induces obesity, insulin resistance, glucose intolerance, dyslipidaemia and hypertension. Subtle abnormalities of the hypothalamic-pituitary-adrenal axis and/or of tissue sensitivity to glucocorticoids are also associated with these cardiovascular risk factors in patients with the metabolic syndrome. Furthermore, glucocorticoids have direct effects on the heart and blood vessels, mediated by both glucocorticoid and mineralocorticoid receptors and modified by local metabolism of glucocorticoids by the 11beta-hydroxysteroid dehydrogenase enzymes. These effects influence vascular function, atherogenesis and vascular remodelling following intra-vascular injury or ischaemia. This article reviews the systemic and cardiovascular effects of glucocorticoids, and the evidence that glucocorticoids not only promote the incidence and progression of atherogenesis but also modify the recovery from occlusive vascular events and intravascular injury. The conclusion is that manipulation of glucocorticoid action within metabolic and cardiovascular tissues may provide novel therapeutic avenues to combat cardiovascular disease.

ROLE OF MACROPHAGES IN COMPLICATIONS OF TYPE 2 DIABETES

1. Macrophage accumulation is a feature of Type 2 diabetes and is associated with the development of diabetic complications (nephropathy, atherosclerosis, neuropathy and retinopathy). The present article reviews the current evidence that macrophages contribute to the complications of Type 2 diabetes. 2. Macrophage-depletion studies in rodent models have demonstrated a causal role for macrophages in the development of diabetic complications. 3. Components of the diabetic milieu (high glucose, advanced glycation end-products and oxidized low-density lipoprotein) promote macrophage accumulation (via induction of chemokines and adhesion molecules) and macrophage activation within diabetic tissues. 4. Macrophages mediate diabetic injury through a variety of mechanisms, including production of reactive oxygen species, cytokines and proteases, which result in tissue damage leading to sclerosis. 5. A number of existing and experimental therapies can indirectly reduce macrophage-mediated injury in diabetic complications. The present article discusses the use of these therapies, given alone and in combination, in suppressing macrophage accumulation and activity. 6. In conclusion, current evidence supports a critical role for macrophages in the evolution of diabetic complications. Present therapies are limited in slowing the progression of macrophage-mediated injury. Novel strategies that are more specific at targeting macrophages may provide better protection against the development of Type 2 diabetic complications.

Aldosterone as a cardiovascular risk hormone

The pathophysiological role of aldosterone in the development of cardiovascular disease has long been considered to be due its potent volume expansion/hypertensive effect mainly via mineralocorticoid receptor (MR) expressed in renal tubular epithelial cells. However, recent accumulating lines of evidence from clinical and experimental studies have suggested that direct cardiovascular effect of aldosterone contributes to the development of cardiovascular injury via MRs in non-epithelial tissue. A series of recent clinical studies have revealed that patients with primary aldosteronism have higher incidence of cardiovascular and renal complications than those with essential hypertension, and that aldosterone antagonism has cardiovascular protective effect in patients with heart failure independent from blood pressure. Numerous experimental studies have shown that both inflammation and oxidative stress play an initial and key role in the development of aldosterone-induced cardiovascular injury via non-epithelial MR activation. In this review, we discuss recent research progress in aldosterone and MR effects, with special emphasis on the pathophysiological role of aldosterone in cardiovascular diseases and the possible molecular mechanism(s) of cardiovascular injury by non-epithelial MR activation.

Renal artery stenosis and accelerated atherosclerosis: which comes first?

Renal artery stenosis (RAS) is usually observed in hypertensive patients with extensive atherosclerosis. There is some evidence that in these patients the atherosclerotic process and the consequent target-organ damage is more severe than in hypertensive patients without RAS. In this review we will entertain the hypothesis that some of the humoral factors that are activated by RAS may contribute to accelerate the progression of atherosclerosis. Several studies identified RAS as a predictor of cardiovascular events in high-risk patients, although in most cases the contribution of blood pressure per se to the progression of vascular lesions could not be determined. As a result of experimental RAS, hypertension and increased oxidative stress are stimuli for atherosclerosis as well as cardiac and renal damage. In the presence of RAS, the renin-angiotensin system is stimulated, and it has been shown that angiotensin II exerts proinflammatory, pro-oxidant and procoagulant activities in experimental models and humans. The potential contribution of reactive oxygen species to the prohypertensive and proatherosclerotic effects of RAS is supported by evidence that nicotinamide adenine dinucleotide phosphate, reduced form oxidase is specifically stimulated by angiotensin II, an activity not shared by epinephrine. Moreover, angiotensin II triggers the release of aldosterone, endothelin 1, thromboxane A2 and other derivatives of the arachidonic acid metabolism, all of which can further and independently aggravate cardiovascular damage. Epidemiological and experimental evidence so far available suggests that accelerated atherosclerosis can be both the cause and the consequence of RAS.

The role of aldosterone and mineralocorticoid receptors in cardiovascular disease

The roles of aldosterone and mineralocorticoid receptors in cardiovascular disease have been expanded, refined, and distinguished over the past decade. Primary aldosteronism has been shown to represent 8-13% (rather than <1%) of unselected hypertensive patients, and patients with primary aldosteronism to have higher indices of cardiovascular damage than controls of the same age, sex, and BP status. While this represents a clearly expanded role for aldosterone, it is improbable that the hormone (as opposed to the mineralocorticoid receptor) plays a major role in other instances of essential hypertension, in cardiac failure, or in atherosclerosis. Evidence from studies in these conditions supports a substantial role for mineralocorticoid receptor activation; low baseline aldosterone levels, and evidence from experimental in vivo studies, support a role for normal levels of physiologic glucocorticoids in activating mineralocorticoid receptors (MR) in the context of tissue damage and reactive oxygen species generation. These relatively recent insights suggest the potential therapeutic role for MR antagonists across a spectrum of cardiovascular disease, as vascular protectants even when circulating levels of aldosterone are low.

A mouse model for human atherosclerosis: long-term histopathological study of lesion development in the aortic arch of apolipoprotein E-deficient (E0) mice

Apolipoprotein E-deficient mice, since their introduction in the early 1990s, have proved to be a very popular model for studying spontaneous hypercholesterolemia and the subsequent development of atherosclerotic lesions. The pathogenesis of atherosclerotic lesions in these mice mimics that found in humans on a very short time-scale. Atherosclerotic lesion development is especially prominent in the aortic arch. We have followed the progressive histopathological development of atherosclerotic lesions in the aortic arch of apolipoprotein E-deficient mice aged from 6 weeks to 18 months in 1 microm epoxy-resin sections stained with alkaline toluidine blue, which gives greatly improved resolution over wax sections. During the early stages of lesion formation, lipid-filled macrophages appear in the subendothelium, and accumulate leading to "fatty streaks". Macrophage degeneration and the formation of lipid pools are accompanied by accumulation of cholesterol deposits. Disruptions of elastic laminae of the Tunica media are accompanied by structural changes in the myocytes. More advanced lesions involve fibrous cap development, calcification of the vessel wall and progressive occlusion of the lumen. Unstable plaque may also be found. Various approaches for quantitative determination of lesion size are considered. The study provides a histopathological baseline for spontaneous atherosclerosis associated with hypercholesterolemia, which can be used in connection with experimental interventional studies on the efficacy of drugs or foodstuffs in retardation of atherosclerosis.

Evaluation of eplerenone in the subgroup of EPHESUS patients with baseline left ventricular ejection fraction ≤30%

AIMS

Because of the prognostic importance of LV dysfunction following an AMI and the increasing use of electrical and/or mechanical interventions in patients with LV systolic dysfunction, this retrospective analysis of EPHESUS patients with LVEF <or=30% at baseline was conducted to determine the value of eplerenone in this setting.

METHODS AND RESULTS

In EPHESUS, 6,632 patients with LVEF <or=40% and clinical heart failure (HF) post-AMI who were receiving standard therapy were randomized to eplerenone 25 mg/day titrated to 50 mg/day or placebo for a mean follow-up of 16 months. Treatment with eplerenone in the subgroup of patients with LVEF <or=30% (N=2106) resulted in relative risk reductions of 21% versus placebo in both all-cause mortality (P=0.012) and cardiovascular (CV) mortality/CV hospitalization (P=0.001), and 23% for CV mortality (P=0.008). The relative risk of sudden cardiac death (SCD) was reduced 33% (P=0.01) and HF mortality/HF hospitalization was reduced 25% (P=0.005) with eplerenone compared with placebo. Within 30 days of randomization, eplerenone resulted in relative risk reductions of 43% for all-cause mortality (P=0.002), 29% for CV mortality/CV hospitalization (P=0.006), and 58% for SCD (P=0.008).

CONCLUSIONS

Treatment with eplerenone plus standard therapy in patients with post-AMI HF and LVEF <or=30% provided significant incremental benefits in reducing both early and late mortality and morbidity.

Aldosterone Impairs Vascular Endothelial Cell Function

Aldosterone is a mineralocorticoid hormone that plays an important role in regulating electrolyte balance and blood pressure and also participates in endothelial dysfunction. We evaluated the direct effect of aldosterone on human umbilical vein cells (HUVEC). Levels of eNOS phosphorylation by vascular endothelial growth factor were diminished, and the amount of NO produced in response to vascular endothelial growth factor measured as NO2+NO3 was significantly decreased in cells previously incubated with aldosterone. Incubation with aldosterone for 24 h dose-dependently increased Nox4 mRNA expression in HUVEC. Although NF-kappaB was not apparently activated by aldosterone, mRNA levels of vascular cell adhesion molecule-1, E-selectin, monocyte chemotactic protein-1, and intercellular adhesion molecule-1 in HUVEC were significantly increased after incubation with aldosterone. Thus, aldosterone directly causes the dysregulation of endothelial cell function, which may be partly responsible for high blood pressure and atherosclerosis.

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.

Mineralocorticoid receptor blocker increases angiotensin-converting enzyme 2 activity in congestive heart failure patients

Aldosterone plays an important role in the pathophysiology of congestive heart failure (CHF), and spironolactone improves cardiovascular function and survival rates in patients with CHF. We hypothesized that the mineralocorticoid receptor blockade (MRB) exerted its beneficial effects by reducing oxidative stress and changing the balance between the counter-acting enzymes angiotensin-converting enzyme (ACE) and ACE2. Monocyte-derived macrophages were obtained from 10 patients with CHF before and after 1 month of treatment with spironolactone (25 mg/d). Spironolactone therapy significantly (P<0.005) reduced oxidative stress, as expressed by reduced lipid peroxide content, superoxide ion release, and low-density lipoprotein oxidation by 28%, 53%, and 70%, respectively. Although spironolactone significantly (P<0.01) reduced macrophage ACE activity by 47% and mRNA expression by 53%, ACE2 activity and mRNA expression increased by 300% and 654%, respectively. In mice treated for 2 weeks with eplerenone (200 mg.kg(-1).d(-1)), cardiac ACE2 activity significantly (P<0.05) increased by 2-fold and was paralleled by increased ACE2 activity in macrophages. The mechanism of aldosterone antagonist action was studied in mouse peritoneal macrophages (MPMs) in vitro. Although ACE activity and mRNA were significantly increased by 250 nmol/L aldosterone, ACE2 was significantly reduced. Cotreatment with eplerenone (2 micromol/L) attenuated these effects. In MPM obtained from p47 knockout mice, where NADPH oxidase is inactive, as well as in control MPMs treated with NADPH oxidase inhibitor, aldosterone did not increase ACE or decrease ACE2. MRB reduced oxidative stress, decreased ACE activity, and increased ACE2 activity, suggesting a protective role for MRB by possibly increasing generation of angiotensin (1-7) and decreasing formation of angiotensin II. These effects are mediated, at least in part, by NADPH oxidase.

Aldosterone stimulates reactive oxygen species production through activation of NADPH oxidase in rat mesangial cells

It has recently been shown that glomerular mesangial injury is associated with increases in renal cortical reactive oxygen species (ROS) levels in rats treated chronically with aldosterone and salt. This study was conducted to determine the mechanisms responsible for aldosterone-induced ROS production in cultured rat mesangial cells (RMC). Oxidative fluorescent dihydroethidium was used to evaluate intracellular production of superoxide anion (O(2)(-)) in intact cells. The lucigenin-derived chemiluminescence assay was used to determine NADPH oxidase activity. The staining of dihydroethidium was increased in a dose-dependent manner by aldosterone (1 to 100 nmol/L) with a peak at 3 h in RMC. Aldosterone (100 nmol/L for 3 h) also significantly increased NADPH oxidase activity from 232 +/- 18 to 346 +/- 30 cpm/5 x 10(4) cells. Immunoblotting data showed that aldosterone (100 nmol/L for 3 h) increased p47phox and p67phox protein levels in the membrane fraction by approximately 2.1- and 2.3-fold, respectively. On the other hand, mRNA expression of NADPH oxidase membrane components, p22phox, Nox-1, and Nox-4, were not altered by aldosterone (for 3 to 12 h) in RMC. Pre-incubation with the selective mineralocorticoid receptor (MR) antagonist, eplerenone (10 micromol/L), significantly attenuated aldosterone-induced O(2)(-) production, NADPH oxidase activation and membranous translocation of p47phox and p67phox. These results suggest that aldosterone-induced ROS generation is associated with NAPDH oxidase activation through MR-mediated membranous translocation of p47phox and p67phox in RMC. These cellular actions of aldosterone may play a role in the pathogenesis of glomerular mesangial injury.

Aldosterone synthase inhibitor ameliorates angiotensin II-induced organ damage

BACKGROUND

Aldosterone and angiotensin (Ang) II both may cause organ damage. Circulating aldosterone is produced in the adrenals; however, local cardiac synthesis has been reported. Aldosterone concentrations depend on the activity of aldosterone synthase (CYP11B2). We tested the hypothesis that reducing aldosterone by inhibiting CYP11B2 or by adrenalectomy (ADX) may ameliorate organ damage. Furthermore, we investigated how much local cardiac aldosterone originates from the adrenal gland.

METHODS AND RESULTS

We investigated the effect of the CYP11B2 inhibitor FAD286, losartan, and the consequences of ADX in transgenic rats overexpressing both the human renin and angiotensinogen genes (dTGR). dTGR-ADX received dexamethasone and 1% salt. Dexamethasone-treated dTGR-salt served as a control group in the ADX protocol. Untreated dTGR developed hypertension and cardiac and renal damage and had a 40% mortality rate (5/13) at 7 weeks. FAD286 reduced mortality to 10% (1/10) and ameliorated cardiac hypertrophy, albuminuria, cell infiltration, and matrix deposition in the heart and kidney. FAD286 had no effect on blood pressure at weeks 5 and 6 but slightly reduced blood pressure at week 7 (177+/-6 mm Hg in dTGR+FAD286 and 200+/-5 mm Hg in dTGR). Losartan normalized blood pressure during the entire study. Circulating and cardiac aldosterone levels were reduced in FAD286 or losartan-treated dTGR. ADX combined with dexamethasone and salt treatment decreased circulating and cardiac aldosterone to barely detectable levels. At week 7, ADX-dTGR-dexamethasone-salt had a 22% mortality rate compared with 73% in dTGR-dexamethasone-salt. Both groups were similarly hypertensive (190+/-9 and 187+/-4 mm Hg). In contrast, cardiac hypertrophy index, albuminuria, cell infiltration, and matrix deposition were significantly reduced after ADX (P<0.05).

CONCLUSIONS

Aldosterone plays a key role in the pathogenesis of Ang II-induced organ damage. Both FAD286 and ADX reduced circulating and cardiac aldosterone levels. The present results show that aldosterone produced in the adrenals is the main source of cardiac aldosterone.

The aldosterone antagonist and facultative diuretic eplerenone: a critical review

Eplerenone is a new aldosterone-receptor blocker that differs from spironolactone by virtue of higher selectivity for the aldosterone receptor. Therefore, eplerenone treatment is associated with comparative and absolute low incidences of gynecomastia, mastodynia, and abnormal vaginal bleeding. Similarly, a lower incidence of sexual impotence than that associated with spironolactone administration may be anticipated. Eplerenone and spironolactone increase natriuresis and cause renal retention of potassium when plasma aldosterone is high, i.e., both agents are facultative diuretics. Eplerenone reduces high blood pressure effectively. The results of a recent large study and an ensuing meta-analysis on antihypertensive treatment suggest that a diuretic should be the first-choice agent in most circumstances. Low-dose eplerenone combinations with a low-dose thiazide-type diuretic appear to be options worth investigating, since the overall cardiovascular benefit brought about by reducing blood pressure with the thiazide would be increased, inter alia, by the antikaliuretic action and by the blockade of extrarenal aldosterone receptors provoked by eplerenone. Eplerenone should replace spironolactone as a natriuretic and antikaliuretic in heart failure and as add-on treatment in severe systolic cardiac insufficiency, and it is indicated after an acute myocardial infarction complicated by left ventricular dysfunction and heart failure. The finding that hypertension control with diuretic-based pharmacotherapy results in better prevention of heart failure than pressure reduction with other drugs makes it pertinent to investigate whether diuretics in general, and eplerenone in particular, should constitute part of the initial pharmacotherapy for heart failure when there is no overt fluid retention and independent of the etiology. Eplerenone may cause hyperkalemia, and it might favor the development of metabolic acidosis or hyponatraemia in some circumstances.

Eplerenone : a review of its use in left ventricular systolic dysfunction and heart failure after acute myocardial infarction

Eplerenone (Inspra) is a selective aldosterone blocker. Oral eplerenone is approved for use in patients with left ventricular (LV) systolic dysfunction and clinical evidence of heart failure following acute myocardial infarction (MI) in the US and in European countries (e.g. the UK and The Netherlands). The addition of eplerenone to standard medical therapy significantly improved mortality and morbidity in patients with LV systolic dysfunction and clinical evidence of heart failure following acute MI in the large, well designed EPHESUS (Eplerenone Post-acute myocardial infarction Heart failure Efficacy and SUrvival Study) trial. The beneficial effects of eplerenone on all-cause mortality and cardiovascular mortality were seen within 30 days of randomisation. Eplerenone was generally well tolerated. Although a higher incidence of hyperkalaemia occurred with eplerenone than with placebo, the incidence of hypokalaemia was significantly lower with eplerenone treatment. Thus, the addition of eplerenone to standard medical therapy is an important new strategy for further improving mortality and morbidity in post-MI patients with LV systolic dysfunction and heart failure.

The Mineralocorticoid Receptor and Oxidative Stress

Reactive oxygen species are profoundly important for many physiologic functions and are also pivotal to numerous disease processes, particularly those involving inflammation. Much evidence has accrued demonstrating that aldosterone acts locally in many cells aside from those in the cortical collecting duct. Peripheral blood monocytes and vascular smooth muscle cells are both influenced by aldosterone to produce reactive oxygen species. This production contributes to nuclear factor kappaB (NF-kappaB) activation and the genes regulated by this transcription factor. Aldosterone thereby plays an important role in atherosclerosis and hypertension-induced vascular injury. Aldosterone interacts with angiotensin (Ang) II-induced signaling. Both aldosterone and Ang II initiate ERK1/2 and JNK signaling; the effects of the two compounds is additive and involves the epidermal growth factor receptor. Recent data suggest that reactive oxygen species, might contribute to aldosterone production in nonadrenal tissues. A novel oxidized derivative of linoleic acid is a prime candidate in this regard. Oxidative stress may impair mineralocorticoid receptor function by inhibiting aldosterone binding. The latter finding has particularly important implications for elderly persons who exhibit increased oxidative stress and who are at risk for diminished aldosterone function in the distal nephron and subsequent hyperkalemia.

Effect of Aldosterone and Mineralocorticoid Receptor Blockade on Vascular Inflammation

Aldosterone, the final product of the renin-angiotensin-aldosterone system, is classically viewed as a regulator of renal sodium and potassium handling, blood volume, and blood pressure. Recent studies suggest that aldosterone can cause microvascular damage, vascular inflammation, oxidative stress and endothelial dysfunction. In animal models, aldosterone-mediated vascular injury in the brain, heart, and kidneys leads to stroke, myocardial injury, and proteinuria. These effects may be modified by dietary salt intake; aldosterone-mediated vascular damage is increased in susceptible animals fed a high-salt diet compared to a low-salt diet despite lower plasma aldosterone levels on the high-salt diet. In humans, there is a growing literature supporting the adverse effects of aldosterone in heart failure, hypertension, left ventricular hypertrophy, and renal disease. Aldosterone receptor antagonists are beneficial even in patients on angiotensin converting enzyme inhibitors and attenuate aldosterone-mediated vascular injury by mechanisms that appear to be independent of changes in systolic blood pressure. This review focuses on the adverse effects of aldosterone on the vascular system and describes our current understanding of the underlying mechanisms for this injury.

Paraoxonases 1, 2, and 3, oxidative stress, and macrophage foam cell formation during atherosclerosis development

Paraoxonases PON1 and PON3, which are both associated in serum with HDL, protect the serum lipids from oxidation, probably as a result of their ability to hydrolyze specific oxidized lipids. The activity of HDL-associated PON1 seems to involve an activity (phospholipase A2-like activity, peroxidase-like activity, lactonase activity) which produces LPC. To study the possible role of PON1 in macrophage foam cell formation and atherogenesis we used macrophages from control mice, from PON1 knockout mice, and from PON1 transgenic mice. Furthermore, we analyzed PON1-treated macrophages and PON1-transfected cells to demonstrate the contribution of PON1 to the attenuation of macrophage cholesterol and oxidized lipid accumulation and foam cell formation. PON1 was shown to inhibit cholesterol influx [by reducing the formation of oxidized LDL (Ox-LDL), increasing the breakdown of specific oxidized lipids in Ox-LDL, and decreasing macrophage uptake of Ox-LDL]. PON1 also inhibits cholesterol biosynthesis and stimulates HDL-mediated cholesterol efflux from macrophages. PON2 and PON3 protect against oxidative stress, with PON2 acting mainly at the cellular level. Whereas serum PON1 and PON3 were inactivated under oxidative stress, macrophage PON2 expression and activity were increased under oxidative stress, probably as a compensatory mechanism against oxidative stress. Intervention to increase the paraoxonases (cellular and humoral) by dietary or pharmacological means can reduce macrophage foam cell formation and attenuate atherosclerosis development.

Eplerenone: Will it have a role in the treatment of acute coronary syndromes?

Aldosterone is known to have multiple adverse cardiovascular effects that are reminiscent of but independent from angiotensin II. These effects include endothelial dysfunction, heightened thrombogenicity, inflammation, and reparative fibrosis, and have been described in experimental and human models of aldosterone excess. Recently a number of clinical investigations have demonstrated that mineralocorticoid receptor (MR) antagonism, even in conditions not traditionally associated with systemic activation of the renin-angiotensin II-aldosterone pathway, may provide additional benefits above and beyond angiotensin-converting enzyme (ACE) inhibition and angiotensin receptor blockade. The Eplerenone Neurohormonal Efficacy and Survival Study (EPHESUS) with eplerenone in patients who were post-myocardial infarction underscores the additive benefit of such a strategy in post-infarction patients that typify an at-risk population for recurrent cardiovascular events. The mechanisms operative in acute coronary syndromes (ACS), including inflammation, altered hemostasis, and endothelial dysfunction, overlap significantly with those seen in the EPHESUS patient population. One may therefore hypothesize that MR antagonism with eplerenone may be beneficial in patients with ACS. Another advantage of using eplerenone is that it offers the advantages of MR antagonism without the side effects due to blockade of other nuclear receptors such as the androgen and progesterone receptors. If MR blockade is found to be beneficial in patients with ACS, the potential reduction in morbidity, mortality, and health care costs are profound.

Aldosterone administration to mice stimulates macrophage NADPH oxidase and increases atherosclerosis development: a possible role for angiotensin-converting enzyme and the receptors for angiotensin II and aldosterone

BACKGROUND

The renin-angiotensin-aldosterone system is involved in the pathogenesis of atherosclerosis, partially because of its pro-oxidative properties. We questioned the effect and mechanisms of action of administration of aldosterone to apolipoprotein E-deficient (E(0)) mice on their macrophages and aorta oxidative status and the ability of pharmacological agents to block this effect.

METHODS AND RESULTS

Aldosterone (0.2 to 6 microg. mouse(-1) x d(-1)) was administered to E(0) mice alone or in combination with eplerenone (200 mg x kg(-1) x d(-1)), ramipril (5 mg x kg(-1) x d(-1)), or losartan (25 mg x kg(-1) x d(-1)). Mouse aortic atherosclerotic lesion area and macrophage and aortic oxidative status were evaluated. Aldosterone administration enhanced the mouse atherosclerotic lesion area by 32%. Mouse peritoneal macrophages and aortic segments from aldosterone-treated mice exhibited increased superoxide anion formation by up to 155% and 69%, respectively, and this effect was probably mediated by NADPH oxidase activation, because increased translocation of its cytosolic component p47phox to the macrophage plasma membrane was observed. THP-1 macrophages incubated in vitro with aldosterone (10 micromol/L) exhibited a higher capacity to release superoxide ions by 110% and increased ability to oxidize LDL by 74% compared with control cells. Aldosterone administration enhanced mouse peritoneal macrophage ACE activity and mRNA expression by 2.3-fold and 2.4-fold, respectively. Only cotreatment of eplerenone with ramipril or losartan completely blocked the oxidative effects of aldosterone.

CONCLUSIONS

Aldosterone administration to E(0) mice increased macrophage oxidative stress and atherosclerotic lesion development. Blocking of the mineralocorticoid receptor and inhibition of tissue ACE and/or the angiotensin receptor-1 reduced aldosterone deleterious pro-oxidative and proatherogenic effects.

Angiotensin in atherosclerosis

PURPOSE OF REVIEW

While it is well established that angiotensin II promotes cardiovascular and renal disorders, recent evidence has indicated a pivotal role in atherosclerotic disease which is distinguished by the central abnormality of lipid accumulation within the vascular wall.

RECENT FINDINGS

Studies published in the last year show that angiotensin II activity is increased in atherosclerosis, but even a transient elevation in angiotensin II potentiates the disease. The downstream hormone, aldosterone, has vasculopathic effects in conjunction with, as well as independently of, angiotensin II. The mechanism for angiotensin II injury includes potentiation of damage by known risk factors such as hypertension, hyperlipidemia, diabetes and insulin resistance, falling estrogens and inflammation. In addition, angiotensin II has direct effects on cellular proliferation, hypertrophy, apoptosis, and synthesis/degradation of matrix proteins and collagen that underlie development and progression of atherosclerosis as well as stability of the plaque. Antagonism of angiotensin II actions, therefore, offers the possibility of interfering with these direct and indirect effects and lessening the progression of atherosclerosis, stabilizing vulnerable plaques, and even reversing the disease.

SUMMARY

Angiotensin is increased in atherosclerosis, and increased angiotensin II amplifies atherosclerosis by modulating individual risk factors as well as by directly affecting lipid metabolism, the vascular response to lipid accumulation, and plaque stability. Antagonism of angiotensin II actions not only lessens the progression of atherosclerosis, but stabilizes the plaque and may even cause regression of the disease.

Possible contributions of reactive oxygen species and mitogen-activated protein kinase to renal injury in aldosterone/salt-induced hypertensive rats

Studies were performed to test the hypothesis that reactive oxygen species (ROS) and mitogen-activated protein kinase (MAPK) contribute to the pathogenesis of aldosterone/salt-induced renal injury. Rats were given 1% NaCl to drink and were treated with one of the following combinations for 6 weeks: vehicle (0.5% ethanol, SC, n=6); aldosterone (0.75 microg/H, SC, n=8); aldosterone plus a selective mineralocorticoid receptor antagonist; eplerenone (0.125% in chow, n=8); aldosterone plus an antioxidant; and tempol (3 mmol/L in drinking solution, n=8). The activities of MAPKs, including extracellular signal-regulated kinases (ERK)1/2, c-Jun-NH2-terminal kinases (JNK), p38MAPK, and big-MAPK-1 (BMK1) in renal cortical tissues were measured by Western blot analysis. Aldosterone-infused rats showed higher systolic blood pressure (165+/-5 mm Hg) and urinary excretion of protein (106+/-24 mg/d) than vehicle-infused rats (118+/-3 mm Hg and 10+/-3 mg/d). Renal cortical mRNA expression of p22phox, Nox-4, and gp91phox, measured by real-time polymerase chain reaction, was increased in aldosterone-infused rats by 2.3, 4.3, and 3.0-fold, respectively. Thiobarbituric acid-reactive substances (TBARS) content in renal cortex was also higher in aldosterone (0.23+/-0.02) than vehicle-infused rats (0.09+/-0.01 nmol/mg protein). ERK1/2, JNK, and BMK1 activities were significantly elevated in aldosterone-infused rats by 3.3, 2.3, and 3.0-fold, respectively, whereas p38MAPK activity was not changed. Concurrent administration of eplerenone or tempol to aldosterone-infused rats prevented the development of hypertension (127+/-2 and 125+/-5 mm Hg), and the elevations of urinary excretion of protein (10+/-2 and 9+/-2 mg/day) or TBARS contents (0.08+/-0.01 and 0.11+/-0.01 nmol/mg protein). Furthermore, eplerenone and tempol treatments normalized the activities of ERK1/2, JNK, and BMK1. These data suggest that ROS and MAPK play a role in the progression of renal injury induced by chronic elevations in aldosterone.

Eplerenone

Aldosterone has been implicated for many years as an important substance in the pathogenesis of heart disease. Elevated aldosterone concentrations have been documented in patients with hypertension and heart failure, leading to the use of aldosterone antagonists for the treatment of these conditions. Spironolactone has been used for nearly 2 decades for the treatment of hypertension, and more recently, has become a standard agent for the treatment of systolic heart failure. Spironolactone, however, is a nonselective antagonist of the aldosterone receptor, binding also to other steroid receptors and causing a significant percentage of patients to have sex hormone-related adverse effects such as gynecomastia. Eplerenone is the first of a new class of drugs known as selective aldosterone receptor antagonists, which selectively block the aldosterone receptor with minimal effect at other steroid receptors, thereby minimizing many of the hormonal side effects seen with spironolactone. Eplerenone has been shown to be beneficial both as monotherapy and combination therapy for lowering elevated blood pressure in patients with hypertension. The antihypertensive efficacy of eplerenone is roughly similar to that of other antihypertensive agents, although in 1 study black patients responded better with eplerenone than losartan. In addition, eplerenone has demonstrated some renoprotective effects in diabetic patients with hypertension. Recently, eplerenone was shown to significantly reduce mortality and cardiovascular morbidity in post-myocardial infarction patients with systolic heart failure currently taking standard heart failure medications. Eplerenone is generally well tolerated, although hyperkalemia with this agent is of some concern. Eplerenone is metabolized by CYP3A4 and administration with potent inhibitors of this enzyme is contraindicated because of the risk of hyperkalemia. In summary, eplerenone has proven to be beneficial in treating hypertension and post-myocardial infarction heart failure. Its exact place in therapy will in large part be determined by its cost and whether or not future studies will be able to demonstrate a clinical benefit of this agent over spironolactone or other currently available treatments.