Aldosterone as a mediator in cardiovascular injury

NMR-based plasma metabolic profiling in patients with unstable angina

OBJECTIVES

Unstable angina (UA) is a form of the acute coronary syndrome (ACS) that affects more than a third of the population before age 70. Due to the limitations of diagnostic tests, appropriate identification of UA is difficult. In this study, we proceeded to investigate metabolite profiling in UA patients compared with controls to determine potential candidate biomarkers.

MATERIALS AND METHODS

Ninety-four plasma samples from UA and 32 samples from controls were analyzed based on 1H NMR spectroscopy. The raw data were processed, analyzed, and subjected to partial least squares-discrimination analysis (PLS-DA), a supervised classification method with a good separation of control and UA patients was observed. The most important variables (VIP) ≥1 were selected and submitted to MetaboAnalyst pathway enrichment to identify the most important ones.

RESULTS

We identified 17 disturbed metabolites in UA patients in comparison with the controls. These metabolites are involved in various biochemical pathways such as steroid hormone biosynthesis, aminoacyl-tRNA biosynthesis, and lysine degradation. Some of the metabolites were deoxycorticosterone, 17-hydroxyprogesterone, androstenedione, androstanedione, etiocholanolone, estradiol, 2-hydroxyestradiol, 2-hydroxyestrone, 2-methoxyestradiol, and 2-methoxyestrone. In order to determine test applicability in diagnosing UA, a diagnostic model was further created using the receiver operator characteristic (ROC) curve. The areas under the curve (AUC), sensitivity, specificity, and precision were 0.87, 90%, 65%, and 91%, respectively, for diagnosing of UA.

CONCLUSION

These metabolites could not only be useful for the diagnosis of UA patients but also provide more information for further deciphering of the biological processes of UA.

Effects of eplerenone on cerebral aldosterone levels and brain lesions in spontaneously hypertensive rats

Evidence indicates that renin-angiotensin-aldosterone system (RAS) inhibitors can protect the brain in Alzheimer's disease and Parkinson's disease. The current study evaluated the relationship between aldosterone and tissue damage in the brains of spontaneously hypertensive rats (SHRs) and whether the RAS inhibitor eplerenone can mitigate the damage seen in these rats. SHRs were randomly divided into eplerenone (n = 10) and SHR (n = 10) groups, and Wistar-Kyoto (WKY) rats (n = 10) were used as controls. Eplerenone 50 mg/kg/day was administered orally to the eplerenone group. Pathological changes to the hippocampal formation, plasma and encephalic aldosterone, and plasma potassium levels were compared among the groups. After 10 weeks, rats in the eplerenone and SHR groups showed higher systolic BP (p = .01) than the control group. Aldosterone levels in the brain were higher in the SHR group (0.20 ± 0.06 pg/ml) than in the eplerenone (0.14 ± 0.05 pg/ml, p = .044) or control (0.12 ± 0.07 pg/ml, p = .007) groups. Plasma aldosterone levels in the SHR group were 1.7 times higher than those in the control group (p = .006). Cerebral cortex was thinner in the SHR group (225.18 ± 15.43 μm) than in the eplerenone (240.38 ± 12.85 μm, p < .01) or control (244.72 ± 18.92 μm, p < .01) groups. Thickness did not differ between the latter two groups. The SHR group exhibited apoptotic cells in the hippocampal formation, which were rare in the eplerenone and control groups. Plasma potassium levels were higher in the eplerenone group than those in the other two groups (p < .05). Our results showed that eplerenone can alleviate brain damage (thinning of cortex and increased apoptosis) caused by aldosterone in a rat model of hypertension.

Interactions between the Cyclooxygenase Metabolic Pathway and the Renin-Angiotensin-Aldosterone Systems: Their Effect on Cardiovascular Risk, from Theory to the Clinical Practice

Coronary artery disease (CAD) and stroke are the most common and serious long-term complications of hypertension. Acetylsalicylic acid (ASA) significantly reduces their incidence and cardiovascular mortality. The RAAS activation plays an important role in pathogenesis of CVD, resulting in increased vascular resistance, proliferation of vascular-smooth-muscle-cells, and cardiac hypertrophy. Drugs acting on the renin-angiotensin-aldosterone system (RAAS) are demonstrated to reduce cardiovascular events in population with cardiovascular disease (CVD). The cyclooxygenase inhibitors limit the beneficial effect of RAAS-inhibitors, which in turn may be important in subjects with hypertension, CAD, and congestive heart failure. These observations apply to most of nonsteroidal anti-inflammatory drugs and ASA at high doses. Nevertheless, there is no strong evidence confirming presence of similar effects of cardioprotective ASA doses. The benefit of combined therapy with low-doses of ASA is-in some cases-significantly higher than that of monotherapy. So far, the significance of ASA in optimizing the pharmacotherapy remains not fully established. A better understanding of its influence on the particular CVD should contribute to more precise identification of patients in whom benefits of ASA outweigh the complication risk. This brief review summarizes the data regarding usefulness and safety of the ASA combination with drugs acting directly on the RAAS.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with essential hypertension

BACKGROUND

In the development of hypertensive microvascular remodeling, a relevant role may be played by changes in extracellular matrix proteins. Aim of this study was the to evaluate some extracellular matrix components within the tunica media of subcutaneous small arteries in 9 normotensive subjects and 12 essential hypertensive patients, submitted to a biopsy of subcutaneous fat from the gluteal or the anterior abdominal region.

PATIENTS AND METHODS

Subcutaneous small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured. In addition, fibronectin, laminin, transforming growth factor-beta-1 (TGF-β1) and emilin-1 contents within the tunica media were evaluated by immunofluorescence and relative immunomorphometrical analysis (immunopositivity % of area). The total collagen content and collagen subtypes within the tunica media were evaluated using both Sirius red staining (under polarized light) and immunofluorescence assay.

RESULTS

Normotensive controls had less total and type III collagen in respect with hypertensive patients. Fibronectin and TGF-β1 tunica media content was significantly greater in essential hypertensive patients, compared with normotensive controls, while laminin and emilin-1 tunica media content was lesser in essential hypertensive patients, compared with normotensive controls. A significant correlation was observed between fibronectin tunica media content and media to lumen ratio.

CONCLUSIONS

Our results indicate that, in small resistance arteries of patients with essential hypertension, a relevant fibrosis may be detected; fibronectin and TGF-β1 tunica media content is increased, while laminin and emilin-1 content is decreased; these changes might be involved in the development of small resistance artery remodeling in humans.

Principles of endocrinology

The endocrine system plays a major role in human survival. Endocrine glands secrete chemical messengers or hormones that affect every tissue of the body, including the periodontium, during the life of the individual. As the endocrine system influences a broad assortment of biological activities necessary for life, a general understanding of the principal components and functions of this system is essential. A fundamental assessment of hormone structure, mechanism of action and hormone transport, as well as influence on homeostasis is reviewed. A concise evaluation of the functions of the central endocrine glands, the functions of the major peripheral endocrine glands (other than gonadal tissues) and the known relationships of these hormones to the periodontium is examined.

RU28318, an aldosterone antagonist, in combination with an ACE inhibitor and angiotensin receptor blocker attenuates cardiac dysfunction in diabetes

AIMS

We evaluated the effects of RU28318 (RU), a selective mineralocorticoid receptor (MR) antagonist, Captopril (Capt), an angiotensin converting enzyme inhibitor, and Losartan (Los), an angiotensin receptor blocker, alone or in combination with ischemia/reperfusion- (I/R-) induced cardiac dysfunction in hearts obtained from normal and diabetic rats.

METHODS

Isolated hearts were perfused for 30 min and then subjected to 30 min of global ischemia (I) followed by a period of 30 min of reperfusion (R). Drugs were administered for 30 min either before or after ischemia. Drug regimens tested were RU, Capt, Los, RU + Capt, RU + Los, Capt + Los, and RU + Capt + Los (Triple). Recovery of cardiac hemodynamics was evaluated.

RESULTS

Recovery of cardiac function was up to 5-fold worse in hearts obtained from diabetic animals compared to controls. Treatment with RU was generally better in preventing or reversing ischemia-induced cardiac dysfunction in normal hearts compared to treatment with Capt or Los alone. In diabetic hearts, RU was generally similarly effective as Capt or Los treatment.

CONCLUSIONS

RU treatment locally might be considered as an effective therapy or preventative measure in cardiac I/R injury. Importantly, RU was the most effective at improving -dP/dt (a measure of diastolic function) when administered to diabetic hearts after ischemia.

Aldosterone and the mineralocorticoid receptor in the cerebral circulation and stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide. Elevated plasma aldosterone levels are an independent cardiovascular risk factor and are thought to contribute to hypertension, a major risk factor for stroke. Evidence from both experimental and human studies supports a role for aldosterone and/or the mineralocorticoid receptor (MR) in contributing to detrimental effects in the cerebral vasculature and to the incidence and outcome of ischemic stroke. This article reviews the evidence, including the protective effects of MR antagonism. Specifically, the effects of aldosterone and/or MR activation on cerebral vascular structure and on immune cells will be reviewed. The existing evidence suggests that aldosterone and the MR contribute to cerebral vascular pathology and to the incidence and outcome of stroke. We suggest that further research into the signaling mechanisms underlying the effects of aldosterone and MR activation in the brain and its vasculature, especially with regard to cell-specific actions, will provide important insight into causes and potential treatments for cerebrovascular disease and stroke.

Aldosterone and angiotensin: Role in diabetes and cardiovascular diseases

The present review shall familiarize the readers with the role of renin-angiotensin aldosterone system (RAAS), which regulates blood pressure, electrolyte and fluid homeostasis. The local RAAS operates in an autocrine, paracrine and/or intracrine manner and exhibits multiple physiological effects at the cellular level. In addition to local RAAS, there exists a complete pancreatic RAAS which has multi-facet role in diabetes and cardiovascular diseases. Aldosterone is known to mediate hyperinsulinemia, hypertension, cardiac failure and myocardial fibrosis while angiotensin II mediates diabetes, endothelial dysfunction, vascular inflammation, hypertrophy and remodeling. As the understanding of this biology of RAAS increases, it serves to exploit this for the pharmacotherapy of diabetes and cardiovascular diseases.

APEX1 regulation of aldosterone synthase gene transcription is disrupted by a common polymorphism in humans

RATIONALE

The genetic mechanisms underlying hypertension are unclear, but relative aldosterone excess, present in ≈10% of hypertensive patients, is known to be a heritable trait. This phenotype associates with a T/C single nucleotide polymorphism (SNP) at position -344 of the aldosterone synthase gene (CYP11B2). However, deletion of this SNP has no effect on gene transcription. We have identified another T/C SNP at -1651, in tight linkage disequilibrium with the -344 SNP and here investigate its functional effect on CYP11B2 transcription.

OBJECTIVE

We assessed the effect on transcriptional activity of the -1651 T/C SNP in vivo and in vitro and propose the mechanism by which transcriptional activity is altered.

METHODS AND RESULTS

We demonstrated that the SNP at -1651 exerts significant allele-dependent effects on CYP11B2 transcription. We confirm binding of the transcriptional repressor APEX1 to -1651T, which is associated with reduced transcriptional activity in relation to the less strongly bound -1651C. We show that inhibiting APEX1 by small molecule inhibition or small interfering RNA (SiRNA) leads to increased CYP11B2 transcription. In addition, overexpression of APEX1 is associated with reduced transcriptional activity. Finally, we also show that -1651T associates with lower excretion rates of aldosterone metabolites in human subjects.

CONCLUSIONS

We conclude that APEX1 is a novel transcriptional repressor of CYP11B2 and that differential APEX1 binding at -1651 of CYP11B2 results in altered gene expression. This mechanism may contribute to the observed relationship between CYP11B2 genotype and aldosterone phenotype in a subgroup of hypertensive patients.

Activation of the mineralocorticoid receptor increases striatin levels

BACKGROUND

Aldosterone (ALDO), a critical regulator of sodium homeostasis, mediates its effects via activation of the mineralocorticoid receptor (MR) through mechanisms that are not entirely clear. Striatin, a membrane associated protein, interacts with estrogen receptors in endothelial cells.

METHODS

We studied the effects of MR activation in vitro and in vivo on striatin levels in vascular tissue.

RESULTS

We observed that dietary sodium restriction was associated with increased striatin levels in mouse heart and aorta and that striatin and MR are present in the human endothelial cell line, (EA.hy926), and in mouse aortic endothelial cells (MAEC). Further, we show that MR co-precipitates with striatin in vascular tissue. Incubation of EA.hy926 cells with ALDO (10(-8) mol/l for 5-24 h) increases striatin protein and mRNA expression, an effect that was inhibited by canrenoic acid, an MR antagonist. Consistent with these observations, incubation of MAEC with ALDO increased striatin levels that were likewise blocked by canrenoic acid. To test the in vivo relevance of these findings, we studied two previously described mouse models of increased ALDO levels. Intraperitoneal ALDO administration augmented the abundance of striatin protein in mouse heart. We also observed that in a murine model of chronic ALDO-mediated cardiovascular damage following treatment with N(G)-nitro-L-arginine methyl ester plus angiotensin II an increased abundance of striatin protein in heart and kidney tissue.

CONCLUSION

Our results provide evidence that increased striatin levels is a component of MR activation in the vasculature and suggest that regulation of striatin by ALDO may modulate estrogen's nongenomic effects.

Aldosterone as a modulator of immunity: implications in the organ damage

High plasmatic levels of aldosterone cause hypertension and contribute to progressive organ damage to the heart, vasculature, and kidneys. Recent studies have demonstrated a role for the immune system in these pathological processes. Aldosterone promotes an inflammatory state characterized by vascular infiltration of immune cells, reactive oxidative stress, and proinflammatory cytokine production. Further, cells of the adaptive immune system, such as T cells, seem to participate in the genesis of mineralocorticoid hormone-induced hypertension. In addition, the observation that aldosterone can promote CD4⁺ T-cell activation and Th17 polarization suggests that this hormone could contribute to the onset of autoimmunity. Here we discuss recent evidence supporting a significant involvement of the immune system, especially adaptive immunity, in the genesis of hypertension and organ damage induced by primary aldosteronism. In addition, possible new therapeutic approaches consisting of immunomodulator drugs to control exacerbated immune responses triggered by elevated aldosterone concentrations will be described.

Effects of spironolactone and losartan on diabetic nephropathy in a type 2 diabetic rat model

BACKGROUND

While there is an evidence that the anti-inflammatory properties of spironolactone can attenuate proteinuria in type 2 diabetes, its effects on vascular endothelial growth factor (VEGF) expression in diabetic nephropathy have not been clearly defined. In this study, we examined the effects of spironolactone, losartan, and a combination of these two drugs on albuminuria, renal VEGF expression, and inflammatory and oxidative stress markers in a type 2 diabetic rat model.

METHODS

Thirty-three Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats were divided into four groups and treated with different medication regimens from weeks 25 to 50; OLETF diabetic controls (n=5), spironolactone-treated (n=10), losartan-treated (n=9), and combination of spironolactone- and losartan-treated (n=9).

RESULTS

At week 50, the albumin-to-creatinine ratio was significantly decreased in the losartan and combination groups compared to the control OLETF group. No decrease was detected in the spironolactone group. There was a significant reduction in renal VEGF, transforming growth factor (TGF)-β, and type IV collagen mRNA levels in the spironolactone- and combination regimen-treated groups. Twenty-four hour urine monocyte chemotactic protein-1 levels were comparable in all four groups but did show a decreasing trend in the losartan and combination regimen groups. Twenty-four hour urine malondialdehyde levels were significantly decreased in the spironolactone- and combination regimen-treated groups.

CONCLUSION

These results suggest that losartan alone and a combined regimen of spironolactone and losartan could ameliorate albuninuria by reducing renal VEGF expression. Also, simultaneous treatment with spironolactone and losartan may have protective effects against diabetic nephropathy by decreasing TGF-β and type IV collagen expression and by reducing oxidative stress in a type 2 diabetic rat model.

Aldosterone alters the participation of endothelial factors in noradrenaline vasoconstriction differently in resistance arteries from normotensive and hypertensive rats

This study analyzed the effect of aldosterone (0.05mg/kg per day, 3 weeks) on vasoconstriction induced by noradrenaline in mesenteric resistance arteries from WKY rats and SHR. Contraction to noradrenaline was measured in mesenteric resistance arteries from untreated and aldosterone-treatedrats from both strains. Participation of nitric oxide (NO), superoxide anions, thromboxane A(2) (TxA(2)) and prostacyclin in this response was determined. 6-keto-prostaglandin (PG)F1alpha and thromboxane B(2) (TxB(2)) releases were determined by enzyme immunoassay. NO and superoxide anion release were also determined by fluorescence and chemiluminiscence, respectively. Aldosterone did not modify noradrenaline-induced contraction in either strain. In mesenteric resistance arteries from both aldosterone-treated groups, endothelium removal or preincubation with NO synthesis inhibitor L-NAME increased the noradrenaline-induced contraction, while incubation with the superoxide anion scavenger tempol decreased it. Preincubation with either the COX-1/2 or COX-2 inhibitor (indomethacin and NS-398, respectively) decreased the noradrenaline contraction in aldosterone-treated animals, while this response was not modified by COX-1 inhibitor SC-560. TxA(2) synthesis inhibitor (furegrelate), or TxA2 receptor antagonist (SQ 29 548) also decreased the noradrenaline contraction in aldosterone-treated animals. In untreated SHR, but not WKY rats, this response was increased by L-NAME, and reduced by tempol, indomethacin, NS-398 or SQ 29 548. Aldosterone treatment did not modify NO or TxB(2) release, but it did increase superoxide anion and 6-keto-PGF(1alpha) release in mesenteric resistance arteries from both strains. In conclusion, chronic aldosterone treatment reduces smooth muscle contraction to alpha-adrenergic stimuli, producing a new balance in the release of endothelium-derived prostanoids and NO.

Mineralocorticoid receptor blockade improves diastolic function independent of blood pressure reduction in a transgenic model of RAAS overexpression

There is emerging evidence that aldosterone can promote diastolic dysfunction and cardiac fibrosis independent of blood pressure effects, perhaps through increased oxidative stress and inflammation. Accordingly, this investigation was designed to ascertain if mineralocorticoid receptor blockade improves diastolic dysfunction independently of changes in blood pressure through actions on myocardial oxidative stress and fibrosis. We used young transgenic (mRen2)27 [TG(mRen2)27] rats with increases in both tissue ANG II and circulating aldosterone, which manifests age-related increases in hypertension and cardiac dysfunction. Male TG(mRen2)27 and age-matched Sprague-Dawley rats were treated with either a low dose (∼1 mg·kg(-1)·day(-1)) or a vasodilatory, conventional dose (∼30 mg·kg(-1)·day(-1)) of spironolactone or placebo for 3 wk. TG(mRen2)27 rats displayed increases in systolic blood pressure and plasma aldosterone levels as well as impairments in left ventricular diastolic relaxation without changes in systolic function on cine MRI. TG(mRen2)27 hearts also displayed hypertrophy (left ventricular weight, cardiomyoctye hypertrophy, and septal wall thickness) as well as fibrosis (interstitial and perivascular). There were increases in oxidative stress in TG(mRen2)27 hearts, as evidenced by increases in NADPH oxidase activity and subunits as well as ROS formation. Low-dose spironolactone had no effect on systolic blood pressure but improved diastolic dysfunction comparable to a conventional dose. Both doses of spironolactone caused comparable reductions in ROS/3-nitrotryosine immunostaining and perivascular and interstitial fibrosis. These data support the notion mineralocorticoid receptor blockade improves diastolic dysfunction through improvements in oxidative stress and fibrosis independent of changes in systolic blood pressure.

Amlodipine suppressed cardiac gene expression of brain natriuretic peptide, transforming growth factor-β₁ and fibronectin mediated by aldosterone in male stroke-prone spontaneously hypertensive rats

OBJECTIVES

Amlodipine, a calcium channel blocker (CCB), is one of the most common antihypertensive medicines in Japan. We evaluated whether the calcium channel blocker confers cardiac protection through the renin-angiotensin-aldosterone system in male stroke-prone spontaneously hypertensive rats (SHR-SP).

METHODS

Fifteen week-old rats were divided into 2 groups: amlodipine group (3 mg/kg/day, n = 5) and control group (n = 5).

KEY FINDINGS

The CCB lowered systolic blood pressure significantly (P < 0.05). Plasma aldosterone concentration in the amlodipine group was remarkably lower than in the control group (P < 0.05), but plasma renin activity and plasma angiotensin II concentration were not different between the two groups. The CCB also suppressed the mRNA expression of brain natriuretic peptide, transforming growth factor-β₁, and fibronectin extracted from the left ventricle.

CONCLUSIONS

These results suggest that amlodipine attenuates cardiac damage by lowering plasma aldosterone concentration in hypertensive rats with developing arteriosclerosis.

Aldosterone receptor antagonists--how cardiovascular actions may explain their beneficial effects in heart failure

Historically, aldosterone receptor antagonists (ARA) have been classified as 'potassium sparing diuretics'. However, the positive effect of spironolactone, the most extensively studied ARA, on morbidity and mortality observed in humans suffering cardiac insufficiency could not be explained by the renal effect of the drug alone, and a pivotal clinical study has led to extensive research. Many experimental studies have demonstrated that ARA have previously unexpected beneficial effects on the cardiovascular system including reduction in remodelling of the vascular smooth muscle cells and myocytes and improvement of endothelial cell dysfunction in heart failure. These effects improve vascular compliance and slow down the progression of left ventricular dysfunction and end-organ damage. Furthermore, aldosterone receptor blockade also restores the baroreceptor reflex, improving heart rate variability in heart failure in humans. Some of these effects have been demonstrated in dog models of cardiac disease and so justified further investigation of the potential benefit of ARA in dogs with congestive heart failure (CHF). Positive effects of spironolactone on morbidity and mortality appear to have been seen in studies conducted in dogs suffering from naturally occurring CHF. In addition, eplerenone has been shown to have benefits in canine models of heart failure. The precise mechanisms by which ARA produce these beneficial effects in dogs remain to be determined but this group of drugs clearly provide therapeutic actions out-with their diuretic effects.

Impact of medical therapy on atheroma volume measured by different cardiovascular imaging modalities

Atherosclerosis is a systemic disease that affects most vascular beds. The gold standard of atherosclerosis imaging has been invasive intravascular ultrasound (IVUS). Newer noninvasive imaging modalities like B-mode ultrasound, cardiac computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) have been used to assess these vascular territories with high accuracy and reproducibility. These imaging modalities have lately been used for the assessment of the atherosclerotic plaque and the response of its volume to several medical therapies used in the treatment of patients with cardiovascular disease. To study the impact of these medications on atheroma volume progression or regression, imaging modalities have been used on a serial basis providing a unique opportunity to monitor the effect these antiatherosclerotic strategies exert on plaque burden. As a result, studies incorporating serial IVUS imaging, quantitative coronary angiography (QCA), B-mode ultrasound, electron beam computed tomography (EBCT), and dynamic contrast-enhanced magnetic resonance imaging have all been used to evaluate the impact of therapeutic strategies that modify cholesterol and blood pressure on the progression/regression of atherosclerotic plaque. In this review, we intend to summarize the impact of different therapies aimed at halting the progression or even result in regression of atherosclerotic cardiovascular disease evaluated by different imaging modalities.

Aldosteronomas--state of the art

Primary aldosteronism (PA) is the most common cause of secondary hypertension in nonsmokers. Widespread screening of unselected hypertensives has identified PA in as many as 15% of patients. With such screening efforts using the PAC/PRA ratio and PAC, the widespread prevalence of the disease has become apparent while the relative percentage of APA has decreased. PA is confirmed by demonstrating lack of aldosterone suppressibility with sodium loading. Subtype evaluation is best achieved with high resolution CT scanning and AVS in the appropriate setting. In patients with PA and a unilateral source of aldosterone excess, laparoscopic adrenalectomy is the treatment of choice with excellent outcomes and low morbidity as compared with older open approaches. Patients with IHA, or those not amenable or agreeable to surgery, are best managed with a MR antagonist.

21st century endocrinology

Recent developments in the field of diabetes and endocrinology have led to greater understanding of the body's complex hormonal axes. This article reviews the latest significant treatments which have the potential to impact greatly on a wide variety of disease states in the not too distant future.

Evaluation of Angiotensin Converting Enzyme (ACE)-Like Activity of Acellular Hemoglobin

Despite the tremendous progress in research on hemoglobin (Hb) cellular and molecular responses, the current understanding of Hb's overall intrinsic toxicity is still limited. The complete mechanism of Hb-induced vasoconstriction has not yet been established, particularly the involvement of the renin-angiotensin system (RAS). Some studies emphasized that Hb may augment the vascular responsiveness to angiotensin (Ang)-II. It was also reported that Hb, as well as Ang-II, influences the synthesis of 8-iso prostaglandin F2 alpha, which has an impact on renal flow and possibly RAS. Hb in the presence of H(2)O(2) gains enzymatic activity. Thus, it is possible that Hb directly and/or indirectly can activate RAS. In this study, we monitored the effect of ferrous- and ferryl-Hb, and H(2)O(2) alone, on conversion of Ang-I to its active metabolites. The structural and immunological identity of the resulting products were evaluated by reversed phase C-18 HPLC and ELISA, respectively. Additionally, ACE-like activity of Hbs was measured spectrophotometrically by determining their ability to react with the ACE substrate, the synthetic tripeptide N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine. Results indicate that while ferrous-Hb can serve as a receptor for Ang-I, its ferryl form possesses ACE-like activity, being able to convert, within minutes, Ang-I to Ang-II, Ang-III, Ang-IV, Ang (1-7) and other unresolved fragments. H(2)O(2) itself had a very limited hydrolyzing effect on Ang-I. Based on this study, it can be concluded that ACE-like activity of Hb with rapid formation of active angiotensins may be a contributor to the still unexplained vasoconstrictive response observed immediately after Hb administration.

Stress, depression and cardiovascular dysregulation: a review of neurobiological mechanisms and the integration of research from preclinical disease models

Bidirectional associations between mood disorders and cardiovascular diseases are extensively documented. However, the precise physiological and biochemical mechanisms that underlie such relationships are not well understood. This review focuses on the neurobiological processes and mediators that are common to both mood and cardiovascular disorders. The discussion places an emphasis on the role of exogenous stressors in addition to: (a) neuroendocrine and neurohumoral changes involving dysfunction of the hypothalamic-pituitary-adrenal axis and the activation of the renin-angiotensin-aldosterone system, (b) immune alterations including activation of pro-inflammatory cytokines, (c) autonomic and cardiovascular dysregulation including increased sympathetic drive, withdrawal of parasympathetic tone, cardiac rate and rhythm disturbances, and altered baroreceptor reflex function, (d) central neurotransmitter system dysfunction involving the dopamine, norepinephrine and serotonin systems, and (e) behavioral changes including fatigue and physical inactivity. The review also discusses experimental investigations using preclinical disease models to elucidate the neurobiological mechanisms underlying the link between mood disorders and cardiovascular disease. These include: (a) the chronic mild stress model of depression, (b) a model of congestive heart failure, (c) a model of cardiovascular deconditioning, (d) pharmacological manipulations of body fluid and sodium balance, and (e) pharmacological manipulations of the central serotonergic system. In combination with an extensive human research literature, the investigation of mechanisms underlying mood and cardiovascular regulation using animal models will enhance understanding the association between depression and cardiovascular disease. This will ultimately promote the development of better treatments and interventions for individuals with co-morbid psychological and somatic pathologies.

Aldosterone induces endothelial dysfunction in resistance arteries from normotensive and hypertensive rats by increasing thromboxane A2 and prostacyclin

BACKGROUND AND PURPOSE

The present study was designed to assess whether cyclooxygenase-2 (COX-2) activation is involved in the effects of chronic aldosterone treatment on endothelial function of mesenteric resistance arteries (MRA) from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Relaxation to acetylcholine was measured in MRA from both untreated and aldosterone-treated strains. Vasomotor responses to prostacyclin and U46619 were also analysed. Release of 6-oxo-prostaglandin (PG)F1alpha and thromboxane B2 (TxB2) was determined by enzyme immunoassay. COX-2 protein expression was measured by western blot.

KEY RESULTS

Aldosterone reduced acetylcholine relaxation in MRA from both strains. In MRA from both aldosterone-treated strains the COX-1/2 or COX-2 inhibitor (indomethacin and NS-398, respectively), TxA2 synthesis inhibitor (furegrelate), prostacyclin synthesis inhibitor (tranylcypromine) or TxA2/ PGH2 receptor antagonist (SQ 29 548), but not COX-1 inhibitor SC-560, increased acetylcholine relaxation. In untreated rats this response was increased only in SHR. Prostacyclin elicited a biphasic vasomotor response: lower concentrations elicited relaxation, whereas higher concentrations elicited contraction that was reduced by SQ 29 548. Aldosterone increased the acetylcholine-stimulated production of 6-oxo-PGF(1alpha) and TxB2 in MRA from both strains. COX-2 expression was higher in both strains of rats treated with aldosterone.

CONCLUSIONS AND IMPLICATIONS

Chronic treatment with aldosterone impaired endothelial function in MRA under normotensive and hypertensive conditions by increasing COX-2-derived prostacyclin and thromboxane A2. As endothelial dysfunction participates in the pathogenesis of many cardiovascular disorders we hypothesize that anti-inflammatory drugs, specifically COX-2 inhibitors, could ameliorate vascular damage in patients with elevated aldosterone production.

A possible association between primary aldosteronism and a lower β-cell function

OBJECTIVE

Primary aldosteronism (PA) is the most common secondary cause of hypertension and recently has been implicated as a cause of impaired glucose tolerance. We investigated the glucose insulin sensitivity and insulin secretion in patients with idiopathic primary aldosteronism.

DESIGN

Thirty PA patients and 60 essential hypertensive (EH) patients as controls were included, matched (1: 2) by their body mass index (BMI) (29.9 +/- 4.3 versus 29.8 +/- 5.8 m/kg), age (53.7 +/- 9.4 versus 59.9 +/- 8.6 years old) and gender (male/female: 8/22 versus 17/43). In all patients, we measured insulin, total cholesterol, triglycerides, C-peptide and fasting glucose levels. Homeostasis model assessment for insulin resistance (HOMA-IR) and HOMA of pancreatic beta-cell function (HOMA-betaF) indexes were calculated. We also evaluated the response to spironolactone in 19 PA patients.

RESULTS

PA patients had higher levels of glucose (5.2 +/- 0.7 versus 4.9 +/- 0.7 mmol/l; P = 0.017). Insulin levels (10.7 +/- 6.5 versus 11.5 +/- 5.8 uUI/ml, P = 0.525) and HOMA-IR (2.51 +/- 1.59 versus 2.45 +/- 1.29 uUI/ml x mmol/l, P = 0.854) were similar in both groups. HOMA-betaF index (138.9 +/- 89.8 versus 179.8 +/- 100.2%, P = 0.049) and C-peptide (0.83 +/- 0.63 versus 1.56 +/- 0.84 ng/dl, P = 0.0001) were lower in PA patients. Potassium was normal in both groups. Negative correlations between serum aldosterone/plasma renin activity (SA/PRA) ratio and HOMA-betaF, and between C-peptide and SA levels were found in all patients. After the spironolactone treatment, we found an increase of C-peptide and insulin levels without changes in HOMA-IR or HOMA-betaF.

CONCLUSION

Our results showed differences in glucose metabolism between PA patients and those with hypertension suggesting that these findings could probably be determined by a lower beta-cell function influenced by aldosterone. These findings highlight the importance of aldosterone in glucose metabolism.

17β-Estradiol deficiency reduces potassium excretion in an angiotensin type 1 receptor-dependent manner

This study examined the effects of ovariectomy (OVX) and 17β-estradiol (E2) replacement (OVX + E2) on renal function in Sprague-Dawley rats. OVX caused a 40% decrease in the fractional excretion of potassium (FEK+) that was prevented by E2 replacement [Sham, 24.2 ± 2.9%; OVX, 14.5 ± 2.1% ( P < 0.05 vs. OVX + E2); and OVX + E2, 26.2 ± 2.7%; n = 7–11] and that corresponded to significant increases in plasma potassium [(in mmol/l): Sham, 3.15 ± 0.087; OVX, 3.42 ± 0.048 ( P < 0.05 vs. OVX + E2); and OVX + E2, 3.19 ± 0.11; n = 7–11]. No effects of OVX were detected on plasma levels of sodium and aldosterone. Angiotensin II type 1 receptor (AT1R) densities in ovariectomized rats were 1.4-fold and 1.3-fold higher in glomerular [maximum binding capacity (Bmax; in fmol/mg protein): Sham, 482 ± 21; OVX, 666 ± 20 ( P < 0.05 vs. OVX + E2); and OVX + E2, 504 ± 26; n = 7–11] and proximal tubular [Bmax (in fmol/mg protein): Sham, 721 ± 16; OVX, 741 ± 24 ( P < 0.05 vs. OVX + E2); and OVX + E2, 569 ± 23; n = 7–11] membranes compared with E2 replete animals, respectively. Both the angiotensin-converting enzyme inhibitor captopril and the AT1R antagonist losartan prevented the OVX-induced decrease in the FEK+ and the increase in renal AT1R densities, suggesting that E2 deficiency reduces potassium excretion in an ANG II/AT1R-dependent manner. These findings may have implications for renal function in postmenopausal women as well as contribute to the reasons underlying the age-induced increase in susceptibility to hypertension-associated disease in women.

The Use of Aldosterone Receptor Blockers in the Treatment of Hypertension

The emerging role of aldosterone in hypertension and cardiovascular diseases has prompted a renewal of interest in therapeutic approaches designed to interfere with the action of this mineralocorticoid hormone. While spironolactone has long been used for this purpose, side effects, largely attributable to the interaction of this agent with non-mineralocorticoid steroid receptors, has reduced the enthusiasm for its use. Eplerenone, a specific aldosterone receptor blocker with a lower incidence of the sex hormone-related side effects than spironolactone, has been used in several recent clinical trials in hypertension and congestive heart failure. This review will highlight the major findings from these studies.

Pharmacogenomics and the Yin/Yang actions of ginseng: anti-tumor, angiomodulating and steroid-like activities of ginsenosides

In Chinese medicine, ginseng (Panax ginseng C.A. Meyer) has long been used as a general tonic or an adaptogen to promote longevity and enhance bodily functions. It has also been claimed to be effective in combating stress, fatigue, oxidants, cancer and diabetes mellitus. Most of the pharmacological actions of ginseng are attributed to one type of its constituents, namely the ginsenosides. In this review, we focus on the recent advances in the study of ginsenosides on angiogenesis which is related to many pathological conditions including tumor progression and cardiovascular dysfunctions. Angiogenesis in the human body is regulated by two sets of counteracting factors, angiogenic stimulators and inhibitors. The 'Yin and Yang' action of ginseng on angiomodulation was paralleled by the experimental data showing angiogenesis was indeed related to the compositional ratio between ginsenosides Rg1 and Rb1. Rg1 was later found to stimulate angiogenesis through augmenting the production of nitric oxide (NO) and vascular endothelial growth factor (VEGF). Mechanistic studies revealed that such responses were mediated through the PI3K-->Akt pathway. By means of DNA microarray, a group of genes related to cell adhesion, migration and cytoskeleton were found to be up-regulated in endothelial cells. These gene products may interact in a hierarchical cascade pattern to modulate cell architectural dynamics which is concomitant to the observed phenomena in angiogenesis. By contrast, the anti-tumor and anti-angiogenic effects of ginsenosides (e.g. Rg3 and Rh2) have been demonstrated in various models of tumor and endothelial cells, indicating that ginsenosides with opposing activities are present in ginseng. Ginsenosides and Panax ginseng extracts have been shown to exert protective effects on vascular dysfunctions, such as hypertension, atherosclerotic disorders and ischemic injury. Recent work has demonstrates the target molecules of ginsenosides to be a group of nuclear steroid hormone receptors. These lines of evidence support that the interaction between ginsenosides and various nuclear steroid hormone receptors may explain the diverse pharmacological activities of ginseng. These findings may also lead to development of more efficacious ginseng-derived therapeutics for angiogenesis-related diseases.

Non-selective nonsteroidal anti-inflammatory drugs and cardiovascular events: is aldosterone the silent partner in crime?

Non-selective nonsteroidal anti-inflammatory drugs (NSAIDs) have long been known to cause gastrointestinal and renal toxicity. More recently, adverse cardiovascular effects have been associated with the selective COX-2 inhibitors. However, current studies that show an increased cardiovascular risk with non-selective NSAIDs raise the question of the exclusive contribution of COX-2 to this type of toxicity. Aldosterone, a key cardiovascular hormone, can induce deleterious effects, such as myocardial fibrosis and vascular stiffening. Non-selective NSAIDs inhibit the metabolism of aldosterone in vitro by human renal tissue, predicating an increased plasma aldosterone concentration in vivo. The question remains whether inhibition of aldosterone metabolism by non-selective NSAIDs is a casual or causal factor in NSAID-induced cardiovascular toxicity.

Management of acute decompensated heart failure: treatment, controversy, and future directions

Acute decompensated heart failure is a growing public health care problem worldwide. The goals of treatment are immediate hemodynamic and symptomatic improvement followed by persistent follow-up with adherence to chronic heart failure guidelines. Controversies have centered around the best treatment options and avoidance of serious adverse events. This article highlights our current understanding of acute decompensated heart failure, discusses the controversy surrounding currently available new vasoactive treatments, and details future potential therapies.

Direct Aldosterone Action on Mouse Cardiomyocytes Detected with Atomic Force Microscopy

There is growing evidence that aldosterone acts on heart where it causes cellular remodeling and hypertrophy. Since it is still unclear whether aldosterone directly acts on cardiomyocytes or indirectly, by an altered electrolyte balance in the organism, we applied atomic force microscopy (AFM) in primary cultures of neonatal mouse cardiomyocytes to measure hormone-induced changes in cell volume and plasma membrane surface. AFM measures cell volume and, at the same time, provides quantitative information on cell surface properties. Neonatal mouse cardiomyocytes were cultured for 28 hours in absence or presence of 100 nM aldosterone. Spironolactone was applied as a selective aldosterone receptor antagonist. At the microscopic level, single cell volume and single cell surface were found unchanged by aldosterone. However, nanoscopy of the cell surface, i.e. analysis of the plasma membrane at the nanometer level, revealed a specific increase in plasma membrane nano-enfoldings (roughness). This aldosterone-mediated increase in cell surface roughness was completely prevented by spironolactone. We conclude: (i) Aldosterone directly acts upon cardiomyocytes. (ii) At the microscopic level, no changes of cell volume and cell surface are detectable. (iii) At the nanoscopic level, aldosterone increases plasma membrane roughness. These nanometer changes, detectable only with AFM in cells scanned in fluid after fixation under physiological conditions, indicate plasma membrane remodeling of cardiomyocytes by mineralocorticoids.

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with primary aldosteronism

CONTEXT AND OBJECTIVE

It has been previously demonstrated that aldosterone may possess a strong profibrotic action in vitro and in animal models of genetic or experimental hypertension. Our aim was to evaluate whether such a profibrotic action is present also in the human microcirculation.

DESIGN AND PATIENTS

We investigated 13 patients with primary aldosteronism, seven patients with essential hypertension, and 10 normotensive controls. All subjects were submitted to a biopsy of gluteal sc fat tissue. Small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured.

MAIN OUTCOME MEASURES

The total collagen content within the tunica media was detected (Sirius red staining and image analysis), and collagen subtypes were evaluated using polarized light microscopy; under this condition thicker type I collagen fibers appear orange or red, whereas thinner type III collagen fibers are yellow or green.

RESULTS

Tunica media to internal lumen ratio was significantly increased in primary aldosteronism and in essential hypertension compared with normotensive controls. Clinic blood pressure values were similar in primary aldosteronism and in essential hypertension, and greater than in normotensive controls. Normotensive controls had less total and type III collagen (3.23 +/- 0.58 and 1.60 +/- 0.22%, respectively) in respect to the two hypertensive groups (P < 0.001). Total collagen and type III vascular collagen were significantly greater in primary aldosteronism (total collagen, 8.17 +/- 1.38%; type III collagen, 6.06 +/- 0.74%; P < 0.05) than in essential hypertension (total collagen, 6.84 +/- 1.15%; type III collagen, 5.25 +/- 0.80%).

CONCLUSIONS

Our results indicate that, in small resistance arteries of patients with primary aldosteronism, a pronounced fibrosis may be detected, even more evident than in blood-pressure-matched patients with essential hypertension.

Spironolactone preserves cardiac norepinephrine reuptake in salt-sensitive Dahl rats

An impairment of cardiac norepinephrine (NE) reuptake via the neuronal NE transporter (NET) enhances the effects of increased cardiac NE release in heart failure patients. Increasing evidence suggests that aldosterone and endothelins promote sympathetic overstimulation of failing hearts. Salt-sensitive Dahl rats (DS) fed a high-salt diet developed arterial hypertension and diastolic heart failure as well as elevated plasma levels of endothelin-1 and NE. Cardiac NE reuptake and NET-binding sites, as assessed by clearance of bolus-injected [(3)H]NE in isolated perfused rat hearts and [(3)H]mazindol binding, were reduced. Treatment of DS with the mineralocorticoid receptor antagonist spironolactone preserved the plasma levels of endothelin-1 and NE, cardiac NE reuptake, and myocardial NET density. Moreover, the ventricular function and survival of spironolactone-treated DS were significantly improved compared with untreated DS. The alpha(1)-inhibitor prazosin decreased blood pressure in DS similar to spironolactone treatment, but did not normalize the plasma levels of endothelin-1 and NE, NE reuptake, or ventricular function. In a heart failure-independent model, Wistar rats that were infused with aldosterone and fed a high-salt diet developed impaired cardiac NE reuptake. Treatment of these rats with the endothelin A receptor antagonist darusentan attenuated the impairment of NE reuptake. In conclusion, spironolactone preserves NET-dependent cardiac NE reuptake in salt-dependent heart failure. Evidence is provided that aldosterone inhibits NET function through an interaction with the endothelin system. Selective antagonism of the mineralocorticoid and/or the endothelin A receptor might represent therapeutic principles to prevent cardiac sympathetic overactivity in salt-dependent heart failure.

Differential action of steroid hormones on human endothelium

The action of glucocorticoids on vascular permeability is well established. However, little is known about the action of mineralocorticoids on the structure and function of blood vessels. As endothelial cells are targets for both glucocorticoids and mineralocorticoids, we exposed human umbilical vein endothelial cells to both types of steroids. Aldosterone (mineralocorticoid) and dexamethasone (glucocorticoid) were applied for 3 days in culture before measurements of transendothelial ion and macromolecule permeability, apical cell surface and cell stiffness were taken. Transendothelial ion permeability was measured with electrical cell impedance sensing, macromolecule permeability with fluorescence-labeled dextran and apical cell membrane surface by three-dimensional AFM imaging. Cell stiffness was measured using the AFM scanning tip as a mechanical nanosensor. We found that aldosterone increased both apical cell surface and apical cell stiffness significantly, while transendothelial permeability remained unaffected. By contrast, dexamethasone significantly decreased ion and macromolecule permeability, while apical cell surface and cell stiffness did not change. Specific receptor antagonists for dexamethasone (RU486) and aldosterone (spironolactone) prevented the observed responses. We conclude that glucocorticoids strengthen cell-to-cell contacts (`peripheral action'), whereas mineralocorticoids enlarge and stiffen cells (`central action'). This could explain the dexamethasone-mediated retention of fluid in the vascular system, and endothelial dysfunction in states of hyperaldosteronism.

Aldosterone remodels human endothelium

AIM

In response to aldosterone endothelial cells swell and stiffen. Although amiloride-sensitive sodium and water uptake is known to be involved, the underlying mechanisms are yet unclear. We tested the hypothesis whether the intracellular accumulation of water or organic matter is responsible for the structural and functional alterations.

METHODS

Atomic force microscopy was used as an imaging tool and a mechanical nanosensor. Cell water, organic cell matter and cell pressure was measured at single cell level in human umbilical vein endothelial cells (HUVEC). Furthermore, we tested by means of a miniature perfusion chamber in vitro the physical robustness to blood flow of the aldosterone-treated endothelium.

RESULTS

In response to a three-day treatment with 1 nM aldosterone HUVEC swell. To our surprise, cell water decreased from 82+/-6% to 71+/-5% while intracellular organic matter increased from 18+/-1.8% to 29+/-3.0%. These changes were paralleled by a rise in cell pressure of 114%, measured in living HUVEC in vitro. Blood flow across the endothelium was found significantly altered after aldosterone treatment. Imaging the endothelial monolayer after blood perfusion disclosed large gaps between cells treated with aldosterone. The mineralocorticoid receptor blockers, spironolactone and eplerenone could prevent the aldosterone actions.

CONCLUSION

Mild aldosteronism causes intracellular accumulation of organic matter at the cost of cell water. This makes endothelium stiff and vulnerable to shear stress. The measurements could explain clinical observations that high blood pressure combined with high plasma aldosterone concentration may damage the endothelium of blood vessels.

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.