Mineralocorticoid Receptor Blocker Research Articles

Hypertension

Blockers of the renin-angiotensin-aldosterone system (RAAS), that is, renin inhibitors, angiotensin (Ang)-converting enzyme (ACE) inhibitors, Ang II type 1 receptor antagonists, and mineralocorticoid receptor antagonists, are a cornerstone in the treatment of hypertension. How exactly they exert their effect, in particular in patients with low circulating RAAS activity, also taking into consideration the so-called Ang II/aldosterone escape that often occurs after initial blockade, is still incompletely understood. Multiple studies have tried to find parameters that predict the response to RAAS blockade, allowing a personalized treatment approach. Consequently, the question should now be answered on what basis (eg, sex, ethnicity, age, salt intake, baseline renin, ACE or aldosterone, and genetic variance) a RAAS blocker can be chosen to treat an individual patient. Are all blockers equal? Does optimal blockade imply maximum RAAS blockade, for example, by combining ≥2 RAAS blockers or by simply increasing the dose of 1 blocker? Exciting recent investigations reveal a range of unanticipated extrarenal effects of aldosterone, as well as a detailed insight in the genetic causes of primary aldosteronism, and mineralocorticoid receptor blockers have now become an important treatment option for resistant hypertension. Finally, apart from the deleterious ACE-Ang II-Ang II type 1 receptor arm, animal studies support the existence of protective aminopeptidase A-Ang III-Ang II type 2 receptor and ACE2-Ang-(1 to 7)-Mas receptor arms, paving the way for multiple new treatment options. This review provides an update about all these aspects, critically discussing the many controversies and allowing the reader to obtain a full understanding of what we currently know about RAAS alterations in hypertension.

Experimental Rat Model of Diabetic Nephropathy : Rage Detection and Effect of Spironolactone Monotherapy

Background: The glycation process results in formation of advanced glycation end products (AGEs), which accumulate in different organs at an accelerated rate in diabetes, resulting in alteration of both structure and function. This effect is via the receptor for AGES (RAGE), which is a signaling receptor leading to profibrotic reactions. The renin angiotensin aldosterone system (RAAS) is activated in diabetic nephropathy (DN) and leads to more renal damage. This is inhibited by angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) and mineralocorticoid receptor blockers (MRBs).Aim of the study: to show the monotherapeutic effect of spironolactone in diabetic nephropathy and to detect RAGE. Method: Diabetes was induced in rats by streptozotocin. Three weeks after,spironolactone (SPL) was given for 4 weeks. Then, control, diabetic and treated rats were sacrificed. Results: The results of blood chemistry at the end of 4 weeks showed statistical increase in serum sodium, potassium and urea with no effect on serum creatinine or blood glucose. Kidney pathological injuries were attenuated by SPL also, RAGE deposition compared to the diabetics. The study showed RAGE deposition in the experimental DN and confirmed the beneficial effects of MRB in DN.

Circulating Aldosterone Levels and Disease Severity in Pulmonary Arterial Hypertension.

It is not known whether aldosterone levels are associated with increased mortality in patients with pulmonary arterial hypertension (PAH). The primary goal of this study was to determine whether circulating aldosterone levels predict severity of PAH in terms of hemodynamic characteristics and mortality. Patients with stable PAH were enrolled at the Baylor PH program. The plasma levels of aldosterone and BNP were measured. Clinical, hemodynamic, and outcome data was collected by chart review. Mean follow up time from study enrollment was 39 ± 102 months. Cox proportional hazards model was used to assess time to death. There were 125 PAH patients with plasma aldosterone levels. Median aldosterone level was 9.9 pg/ml (25th-75th percentile: 4.1 pg/ml, 27.1 pg/ml) and median brain natriuretic peptide (BNP) level was 67.5 pg/ml (25th-75th percentile: 31 pg/ml, 225 pg/ml). Aldosterone levels were not significantly associated with BNP levels, six-minute walk distance, Borg dyspnea score, right ventricular systolic pressure, cardiac output and cardiac index. However, the association between aldosterone and right atrial pressure was dependent on mineralocorticoid receptor blocker treatment (Coef. =2.88, 95CI: 1.19, 4.56, p=0.001). By log-rank statistic there was no statistical difference between the survival of patients divided by median aldosterone level (p=0.914). However, there was a significant difference in patient survival between the BNP categories (p<0.001) such that those with high BNP level (>180 pg/mL) had a shorter survival time. The aldosterone level was not associated with increased mortality in PAH but was a marker of disease severity.

Effects of Add-on Therapy Consisting of a Selective Mineralocorticoid Receptor Blocker on Arterial Stiffness in Patients with Uncontrolled Hypertension.

Aldosterone plays an important role in the pathogenesis of atherosclerosis; however, the significance of mineralocorticoid receptor blockade for atherosclerosis has not been fully elucidated. In this study, the effect of add-on eplerenone on the degree of arterial stiffness was examined in patients with uncontrolled hypertension. Forty-seven uncontrolled hypertensive patients who had previously been treated with anti-hypertensive drugs were examined retrospectively. Thirty-two patients received add-on therapy consisting of eplerenone (Group E) and 15 patients received add-on therapy with a Calcium channel blocker (CCB) or an increased dose of CCB (Group C) in addition to their baseline medications. Both the systolic blood pressure (SBP) and diastolic blood pressure (DBP) values were significantly decreased at two and 12 months in Group C. In contrast, neither the SBP nor DBP values were significantly changed at two months and eventually decreased at 12 months in Group E. The degree of arterial stiffness, as evaluated according to the cardio-ankle vascular index (CAVI), did not improve at either two or 12 months in Group C, whereas the CAVI values improved as early as at two months and the improvement was sustained at 12 months in Group E. The extent of change in the CAVI was not associated with the level of changes in the SBP or DBP values in Group E. Treatment with eplerenone added to the patient's baseline medications improves the degree of arterial stiffness as early as at two months after the beginning of treatment, independent of the blood pressure-lowering actions of these drugs in patients with uncontrolled hypertension.

Role of Mineralocorticoid Receptor Antagonists in Cardiovascular Disease

Aldosterone exerts its best known sodium homeostasis actions by controlling sodium excretion at the level of the distal tubules via activation of the apical epithelial sodium channel and the basolateral Na(+)/K(+)ATPase pump. Recently, this mineralocorticoid hormone has been demonstrated to act on the heart and blood vessels. Excess release of aldosterone in relation to the salt status induces both genomic and nongenomic effects that by promoting endothelial dysfunction, and vascular and cardiorenal adverse remodeling, contribute to the target organ damage found in hypertension, heart failure, myocardial infarction, and chronic renal failure. Mineralocorticoid receptor blockers have been shown to be highly effective in resistant hypertension and to slow down heart failure progression, and in experimental animals, the development of atherosclerosis. Blockade of the action of aldosterone and potentially other mineralocorticoid steroids has been increasingly demonstrated to be an extremely beneficial therapy in different forms of cardiovascular disease. This review provides a summary of the knowledge that exists on aldosterone actions in the cardiovascular system and, in providing the translational impact of this knowledge to the clinical arena, illustrates how much more needs to be achieved in exploring the use of mineralocorticoid receptor blockers in less advanced stages of heart, renal, and vascular disease.

Oxidative DNA damage in kidneys and heart of hypertensive mice is prevented by blocking angiotensin II and aldosterone receptors.

IntroductionRecently, we could show that angiotensin II, the reactive peptide of the blood pressure-regulating renin-angiotensin-aldosterone-system, causes the formation of reactive oxygen species and DNA damage in kidneys and hearts of hypertensive mice. To further investigate on the one hand the mechanism of DNA damage caused by angiotensin II, and on the other hand possible intervention strategies against end-organ damage, the effects of substances interfering with the renin-angiotensin-aldosterone-system on angiotensin II-induced genomic damage were studied.MethodsIn C57BL/6-mice, hypertension was induced by infusion of 600 ng/kg • min angiotensin II. The animals were additionally treated with the angiotensin II type 1 receptor blocker candesartan, the mineralocorticoid receptor blocker eplerenone and the antioxidant tempol. DNA damage and the activation of transcription factors were studied by immunohistochemistry and protein expression analysis.ResultsAdministration of angiotensin II led to a significant increase of blood pressure, decreased only by candesartan. In kidneys and hearts of angiotensin II-treated animals, significant oxidative stress could be detected (1.5-fold over control). The redox-sensitive transcription factors Nrf2 and NF-κB were activated in the kidney by angiotensin II-treatment (4- and 3-fold over control, respectively) and reduced by all interventions. In kidneys and hearts an increase of DNA damage (3- and 2-fold over control, respectively) and of DNA repair (3-fold over control) was found. These effects were ameliorated by all interventions in both organs. Consistently, candesartan and tempol were more effective than eplerenone.ConclusionAngiotensin II-induced DNA damage is caused by angiotensin II type 1 receptor-mediated formation of oxidative stress in vivo. The angiotensin II-mediated physiological increase of aldosterone adds to the DNA-damaging effects. Blocking angiotensin II and mineralocorticoid receptors therefore has beneficial effects on end-organ damage independent of blood pressure normalization.

Biomarkers of activation of renin-angiotensin-aldosterone system in heart failure: how useful, how feasible?

Renin-angiotensin-aldosterone system (RAAS), participated by kidney, liver, vascular endothelium, and adrenal cortex, and counter-regulated by cardiac endocrine function, is a complex endocrine system regulating systemic functions, such as body salt and water homeostasis and vasomotion, in order to allow the accomplishment of physiological tasks, such as orthostasis, physical and emotional stimuli, and to react towards the hemorrhagic insult, in tight conjunction with other neurohormonal axes, namely the sympathetic nervous system, the endothelin and vasopressin systems. The systemic as well as the tissue RAAS are also dedicated to promote tissue remodeling, particularly relevant after damage, when chronic activation may configure as a maladaptive response, leading to fibrosis, hypertrophy and apoptosis, and organ dysfunction. RAAS activation is a fingerprint of systemic arterial hypertension, kidney dysfunction, vascular atherosclerotic disease, and is definitely an hallmark of heart failure, which rapidly shifts from organ disease to a disorder of neurohormonal regulatory systems. Chronic RAAS activation is an indirect or direct target of most effective pharmacological treatments in heart failure, such as beta-blockers, inhibitors of angiotensin converting enzyme, angiotensin receptor blockers, direct renin inhibitors, and mineralocorticoid receptor blockers. Biomarkers of RAAS activation are available, with different feasibility and accuracy, such as plasma renin activity, renin, angiotensin II, and aldosterone, which all accompany the increasing clinical severity of heart failure disease, and are well recognized prognostic factors, even in patients with optimal therapy. Polymorphisms influencing the expression and activity of RAAS pathways have been recognized as clinically relevant biomarkers, likely influencing either the individual clinical phenotype, or the response to drugs. This solid, growing evidence strongly suggests the rationale for the use of biomarkers of the RAAS activation, as a guide to tailor individual therapy in the current practice, and their implementation as a rule-in marker for future trials on novel drugs in the heart failure setting.

Neuroendocrine humoral and vascular components in the pressor pathway for brain angiotensin II: a new axis in long term blood pressure control.

Central nervous system (CNS) administration of angiotensin II (Ang II) raises blood pressure (BP). The rise in BP reflects increased sympathetic outflow and a slower neuromodulatory pressor mechanism mediated by CNS mineralocorticoid receptors (MR). We investigated the hypothesis that the sustained phase of hypertension is associated also with elevated circulating levels of endogenous ouabain (EO), and chronic stimulation of arterial calcium transport proteins including the sodium-calcium exchanger (NCX1), the type 6 canonical transient receptor potential protein (TRPC6), and the sarcoplasmic reticulum calcium ATPase (SERCA2). Wistar rats received a chronic intra-cerebroventricular infusion of vehicle (C) or Ang II (A, 2.5 ng/min, for 14 days) alone or combined with the MR blocker, eplerenone (A+E, 5 µg/day), or the aldosterone synthase inhibitor, FAD286 (A+F, 25 µg/day). Conscious mean BP increased (P<0.05) in A (123±4 mm Hg) vs all other groups. Blood, pituitary and adrenal samples were taken for EO radioimmunoassay (RIA), and aortas for NCX1, TRPC6 and SERCA2 immunoblotting. Central infusion of Ang II raised plasma EO (0.58±0.08 vs C 0.34±0.07 nM (P<0.05), but not in A + E and A + F groups as confirmed by off-line liquid chromatography (LC)-RIA and LC-multistage mass spectrometry. Two novel isomers of EO were elevated by Ang II; the second less polar isomer increased >50-fold in the A+F group. Central Ang II increased arterial expression of NCX1, TRPC6 and SERCA2 (2.6, 1.75 and 3.7-fold, respectively; P<0.01)) but not when co-infused with E or F. Adrenal and pituitary EO were unchanged. We conclude that brain Ang II activates a CNS-humoral axis involving plasma EO. The elevated EO reprograms peripheral ion transport pathways known to control arterial Na+ and Ca2+ homeostasis; this increases contractility and augments sympathetic effects. The new axis likely contributes to the chronic pressor effect of brain Ang II.

Spironolactone improves endothelial dysfunction in streptozotocin-induced diabetic rats.

Endothelial dysfunction is a critical initiator for developing diabetic vascular complications. Substantial clinical and experimental evidence suggests that aldosterone plays a crucial role in its pathogenesis. The present study aimed to investigate the effect of the mineralocorticoid receptor (MR) blocker, spironolactone, on diabetes-associated endothelial dysfunction and address the underlying mechanism(s) involved in this setting. Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ) to rats and spironolactone was orally administered (50mg/kg/day). Our results showed a marked increase in aortic malondialdehyde (MDA) level and upregulation of the catalytic NADPH oxidase subunit, NOX2 gene expression alongside reducing catalase enzyme capacity, and the serum nitric oxide (NO) bioavailability in diabetic rats. This was associated with a significant reduction in endothelial nitric oxide synthase (eNOS) immunoreactivity and gene expression in diabetic aorta. The transforming growth factor-β (TGF-β) protein and the MR gene expression levels were significantly increased in the diabetic rat aorta. Moreover, the diabetic aorta showed a marked impairment in acetylcholine-mediated endothelium-dependent relaxation. Additionally, spironolactone significantly inhibited the elevated MDA, TGF-β, NOX2, and MR levels alongside correcting the dysregulated eNOS expression and the defective antioxidant function as well as NO bioavailability. Spironolactone markedly reversed the impaired endothelial function in the diabetic aorta. Collectively, our study demonstrates that spironolactone ameliorated the vascular dysfunction of diabetic aorta, at least partially via its anti-inflammatory and anti-oxidative effects alongside correcting the dysregulated eNOS and TGF-β expression. Thus, blockade of MR may represent a useful therapeutic approach against diabetic vasculopathy.

Aldosterone induces fibrosis, oxidative stress and DNA damage in livers of male rats independent of blood pressure changes

Mineralocorticoid receptor blockers show antifibrotic potential in hepatic fibrosis. The mechanism of this protective effect is not known yet, although reactive oxygen species seem to play an important role. Here, we investigated the effects of elevated levels of aldosterone (Ald), the primary ligand of the mineralocorticoid receptor, on livers of rats in a hyperaldosteronism model: aldosterone-induced hypertension.Male Sprague–Dawley rats were treated for 4weeks with aldosterone. To distinguish if damage caused in the liver depended on increased blood pressure or on increased Ald levels, the mineralocorticoid receptor antagonist spironolactone was given in a subtherapeutic dose, not normalizing blood pressure. To investigate the impact of oxidative stress, the antioxidant tempol was administered.Aldosterone induced fibrosis, detected histopathologically, and by expression analysis of the fibrosis marker, α-smooth muscle actin. Further, the mRNA amount of the profibrotic cytokine TGF-β was increased significantly. Fibrosis could be reduced by scavenging reactive oxygen species, and also by blocking the mineralocorticoid receptor. Furthermore, aldosterone treatment caused oxidative stress and DNA double strand breaks in livers, as well as the elevation of DNA repair activity. An increase of the transcription factor Nrf2, the main regulator of the antioxidative response could be observed, and of its target genes heme oxygenase-1 and γ-glutamylcysteine synthetase. All these effects of aldosterone were prevented by spironolactone and tempol.Already after 4weeks of treatment, aldosteroneinfusion induced fibrosis in the liver. This effect was independent of elevated blood pressure. DNA damage caused by aldosterone might contribute to fibrosis progression when aldosterone is chronically increased.

Blocking the mineralocorticoid receptor improves effectiveness of steroid treatment for low back pain in rats.

Localized inflammation of lumbar dorsal root ganglia (DRG) may contribute to low back pain. Local injections of corticosteroids used for low back pain are sometimes ineffective. Many corticosteroids activate not only the target glucocorticoid receptor (GR) but also the mineralocorticoid receptor (MR), which may have proinflammatory effects countering the effects of GR activation. A low back pain model was implemented in rats (n = 6 to 10 per group) by locally inflaming the L5 DRG. Sensory neuron excitability and mechanical hypersensitivity of the hind paws were measured. Tested steroids were applied locally to the inflamed DRG or orally. The selective MR blocker eplerenone reduced pain behaviors when given orally starting at the time of surgery, or starting 7 days later. The highly GR-selective agonist fluticasone, applied locally to the inflamed DRG, was much more effective in reducing mechanical hypersensitivity. The MR/GR agonist 6-α methylprednisolone, commonly injected for low back pain, reduced mechanical hypersensitivity when applied locally to the DRG but was less effective than fluticasone. Its effectiveness was improved by combining it with local eplerenone. All tested steroids reduced hyperexcitability of myelinated sensory neurons (n = 71 to 220 cells per group) after inflammation, particularly abnormal spontaneous activity. This preclinical study indicates the MR may play an important role in low back pain involving inflammation. Some MR effects may occur at the level of the sensory neuron. It may be useful to consider the action of clinically used steroids at the MR as well as at the GR.

Mineralocorticoid and AT1 receptors in the paraventricular nucleus contribute to sympathetic hyperactivity and cardiac dysfunction in rats post myocardial infarct.

Intracerebroventricular infusion of a mineralocorticoid receptor (MR) or angiotensinII type1 receptor (AT1R) blocker in rats attenuates sympathetic hyperactivity and progressive left ventricular (LV) dysfunction post myocardial infarction (MI). The present study examined whether knockdown of MRs or AT1Rs specifically in the paraventricular nucleus (PVN) contributes to these effects, and compared cardiac effects with those of systemic treatment with the β1-adrenergic receptor blocker metoprolol. The PVN of rats was infused with adeno-associated virus carrying small interfering RNA against either MR (AAV-MR-siRNA) or AT1R (AAV-AT1R-siRNA), or as control scrambled siRNA. At 4weeks post MI, AT1R but not MR expression was increased in the PVN, excitatory renal sympathetic nerve activity and pressor responses to air stress were enhanced, and arterial baroreflex function was impaired; LV end-diastolic pressure (LVEDP) was increased and LV peak systolic pressure (LVPSP), ejection fraction (EF) and dP/dtmax decreased. AAV-MR-siRNA and AAV-AT1R-siRNA both normalized AT1R expression in the PVN, similarly ameliorated sympathetic and pressor responses to air stress, largely prevented baroreflex desensitization, and improved LVEDP, EF and dP/dtmax as well as cardiac interstitial (but not perivascular) fibrosis. In a second set of rats, metoprolol at 70 or 250mgkg(-1)day(-1) in the drinking water for 4weeks post MI did not improve LV function except for a decrease in LVEDP at the lower dose. These results suggest that in rats MR-dependent upregulation of AT1Rs in the PVN contributes to sympathetic hyperactivity, and LV dysfunction and remodelling post MI. In rats, normalizing MR-AT1R signalling in the PVN is a more effective strategy to improve LV dysfunction post MI than systemic β1 blockade.

Aldosterone blockade as an alternative renin-angiotensin-aldosterone system blocking agent in cases of treatment associated anemia

Blockade of the renin-angiotensin-aldosterone system (RAAS) is a mainstay of therapy for proteinuric kidney disease due to effects on blood pressure, proteinuria, and overall cardiovascular risk. In this case series, we highlight one of the rare but serious side effects of the most commonly used RAAS blocking drugs, angiotensin converting enzyme inhibitors (ACE-Is) and angiotensin receptor blockers (ARBs): a severe anemia due to impaired erythropoiesis. The four patients presented here were switched to a mineralocorticoid receptor blocker (MRB) that targets aldosterone without any inhibition of angiotensin II, and resulting in significant rebounds back to baseline hemoglobin levels. Furthermore, all patients had optimal blood pressure control and proteinuria reductions. These data support the use of aldosterone blocking agents in kidney disease patients with anemia secondary to ACE-Is or ARB. Presumably, any patient - regardless of kidney status - for whom RAAS blockade is indicated (e.g., diabetic patients or patients with congestive heart failure) should be switched to MRB therapy if significant anemia develops after starting an ACE-Is or ARB.

Pretreatment with mineralocorticoid receptor blocker reduces intestinal injury induced by ischemia and reperfusion: involvement of inhibition of inflammatory response, oxidative stress, nuclear factor κB, and inducible nitric oxide synthase

BackgroundSpironolactone (Sp), a mineralocorticoid receptor antagonist, protects against the ischemia reperfusion (IR) injury of retina, kidney, heart, and brain. We aimed to investigate the effects of Sp on intestinal IR injury. MethodsMale Wistar rats were randomly divided into: (1) a sham control group; (2) an IR control group, subjected to 30 min ischemia and 3 h reperfusion; (3) a group treated with Sp (20 mg/kg) for 3 d before the IR; and (4) a sham-operated control group treated with Sp (20 mg/kg). After the reperfusion, blood and intestinal tissue samples were collected to evaluate histopathologic state, neutrophil infiltration (by measuring myeloperoxidase activity), levels of the cytokines (tumor necrosis factor α, interleukin 1α [IL-1α], interferon γ, monocyte chemotactic protein-1, granulocyte macrophage-colony stimulating factor, and IL-4), malondialdehyde (MDA) and reduced glutathione contents, and immunohistochemical expressions of nuclear factor κB, inducible nitric oxide synthase (iNOS), and caspase-3. ResultsMDA content, myeloperoxidase activity, and plasma levels of tumor necrosis factor α, IL-1α, and monocyte chemotactic protein-1 were all elevated in IR, indicating the oxidative stress and local and systemic inflammatory response. Sp administration markedly reduced the MDA content and the cytokine levels. The pretreatment alleviated intestinal injury, neutrophil infiltration, and the expressions of caspase-3, iNOS, and NFκB. ConclusionsThe results implicate that Sp may have a strong protective effect against the intestinal IR injury. The effect can be mediated via suppression of both systemic inflammatory response and apoptosis through amelioration of oxidative stress and generation of proinflammatory cytokines, iNOS, caspase-3, and nuclear factor κB. Therefore, mineralocorticoid receptor antagonism might be of potential therapeutic benefit in cases of intestinal IR damage.

Low-dose spironolactone reduces plasma fibulin-1 levels in patients with type 2 diabetes and resistant hypertension.

Diabetic patients with hypertension are at particularly high risk of vascular damage and consequently cardiovascular and renal disease. Fibulin-1, an extracellular matrix glycoprotein, is increased in arterial tissue and plasma from individuals with type 2 diabetes. This study aimed to evaluate whether antihypertensive treatment with spironolactone changes plasma fibulin-1 levels. In a multicenter, double-blind, randomized, placebo-controlled study, 119 patients with type 2 diabetes and resistant hypertension were included. A dose of spironolactone 25 mg or matching placebo was added to previous treatment at randomization. Blood pressure (BP) and plasma fibulin-1 were measured at baseline and at 16 weeks follow-up. Overall, 112 patients completed the study. All measures of BP were reduced in the spironolactone group at follow-up. Plasma fibulin-1 was significantly reduced after spironolactone treatment (P=0.009), but increased after placebo (P=0.017). Baseline plasma fibulin-1 correlated with BP and estimated glomerular filtration rate. Increased levels of plasma fibulin-1 (P=0.004) were observed in diabetic participants reporting erectile dysfunction as compared with participants who did not. Treatment with low-dose spironolactone reduced plasma fibulin-1 levels in patients with type 2 diabetes and resistant hypertension. This supports the hypothesis that the antihypertensive effect of the mineralocorticoid receptor blocker in part may be due to regression of vascular remodeling.

Actions of circulating angiotensin II and aldosterone in the brain contributing to hypertension.

In the past 1-2 decades, it has become apparent that the brain renin-angiotensin-aldosterone system (RAAS) plays a crucial role in the regulation of blood pressure (BP) by the circulating RAAS. In the brain, angiotensinergic sympatho-excitatory pathways do not contribute to acute, second-to-second regulation but play a major role in the more chronic regulation of the setpoint for sympathetic tone and BP. Increases in plasma angiotensin II (Ang II) or aldosterone and in cerebrospinal fluid [Na(+)] can directly activate these pathways and chronically further activate/maintain enhanced activity by a slow neuromodulatory pathway involving local aldosterone, mineralocorticoid receptors (MRs), epithelial sodium channels, and endogenous ouabain. Blockade of any step in this slow pathway prevents Ang II-, aldosterone-, or salt and renal injury-induced forms of hypertension. It appears that the renal and arterial actions of circulating aldosterone and Ang II act as amplifiers but are not sufficient to cause chronic hypertension if their central actions are prevented, except perhaps at high concentrations. From a clinical perspective, oral treatment with an angiotensin type 1 (AT1)-receptor blocker at high doses can cause central AT1-receptor blockade and, in humans, lower sympathetic nerve activity. Low doses of the MR blocker spironolactone appear sufficient to cause central MR blockade and a decrease in sympathetic nerve activity. Integrating the brain actions of the circulating RAAS with its direct renal and arterial actions provides a better framework to understand the role of the circulating RAAS in the pathophysiology of hypertension and heart failure and to direct therapeutic strategies.

0346: Aldosterone promotes cardiac endothelial cells proliferation and angiogenesis

The mineralocorticoid receptor (MR) and its ligand, aldosterone (aldo), are involved in cardiac diseases. However, the cardiomyocyte-MR regulated processes leading to these injuries are still unclear. To identify new aldosterone-regulated functions involved in cardiac diseases. Double transgenic mice overexpressing MR in cardiomyocytes (DT) and their controls (CT) were treated for 7 days with aldosterone (60 μg/kg/day; n = 6-9 / group) and a genome microarray analysis was performed. In CT mice, aldo regulated 70 genes. In DT mice, aldo induced much more genes (343). To identify the biological processes modulated by aldo, a gene ontology analysis was performed. The majority of aldosteroneregulated genes were involved in cell division, as shown by the relative expression of Cycline B1 and Cdk1 (Cycline; CT untreated 1 ± 0.02, CT aldotreated 2.1 ± 0.5; Cdk1; CT untreated 1 ± 0.05, CT aldo-treated 2.2 ± 0.4). Moreover, the Ki-67 index of aldo-treated mice (CT and DT) was higher than in non-treated ones (% of positive Ki-67 nuclei vs total nuclei; CT untreated 15±4, CT aldo-treated 51±12%; DT untreated 29 ± 5, DT aldo-treated 61 ± 19%). Co-staining of Ki-67 with caveolin 1 revealed that the cycling cells were endothelial cells. Ki-67 index was increased in an experimental model of heart failure (transverse aortic constriction: TAC) in rats. Eplerenone (eple), a MR blocker, prevented this increase (% of positive Ki-67 nuclei vs total nuclei; sham 26 ± 3, TAC 42 ± 5, TAC+eple 23 ± 6%). Aldosterone induces cardiac endothelial cells proliferation in vivo and underlines the role of cardiomyocyte-MR activation in this process. Favre and collaborators (AJP 2011) reported that cardiomyocyte- MR activation is involved in coronary endothelial dysfunction, via pathways of oxidative stress. It appears interesting to study if the cardiac endothelial cells proliferation induced by aldo is oxidative stress dependent.

Mineralocorticoid receptor blockade in addition to angiotensin converting enzyme inhibitor or angiotensin II receptor blocker treatment: An emerging paradigm in diabetic nephropathy: A systematic review

Blockade of the renin–angiotensin–aldosterone system (RAAS) is a standard therapeutic intervention in diabetic patients with chronic kidney disease (CKD). Concomitant mineralocorticoid receptor blockade has been studied as a novel approach to further slow down CKD progression.We used PubMed and EMBASE databases to search for relevant literature. We included in our review eight studies in patients of at least 18years of age, with a diagnosis of type 1 or type 2 diabetes mellitus and diabetic nephropathy, under an angiotensin converting enzyme inhibitor (ACEI) and/or an angiotensin II receptor blocker (ARB) as standard treatment. A subset of patients in each study also received a mineralocorticoid receptor blocker (MRB) (either spironolactone or eplerenone) in addition to standard treatment.Combined treatment with a mineralocorticoid receptor blocker further reduced albuminuria by 23 to 61% compared with standard treatment. Estimated glomerular filtration rate values upon study completion slightly decreased under combined treatment. Blood pressure levels upon study completion were significantly lower with combined treatment in three studies. Hyperkalemia prevalence increased in patients under combined treatment raising dropout rate up to 17%.Therefore, combined treatment by an ACEI/ARB and a MRB may further decrease albuminuria in diabetic nephropathy. This effect may be due to the specific properties of the MRB treatment. Clinicians should regularly check potassium levels because of the increased risk of hyperkalemia. Available evidence should be confirmed by an adequately powered comparative trial of the standard treatment (ACEI or ARB) versus combined treatment by an ACEI/ARB and a MRB.

Eplerenone attenuated cardiac steatosis, apoptosis and diastolic dysfunction in experimental type-II diabetes

BackgroundCardiac steatosis and apoptosis are key processes in diabetic cardiomyopathy, but the underlying mechanisms have not been elucidated, leading to a lack of effective therapy. The mineralocorticoid receptor blocker, eplerenone, has demonstrated anti-fibrotic actions in the diabetic heart. However, its effects on the fatty-acid accumulation and apoptotic responses have not been revealed.MethodsNon-hypertensive Zucker Diabetic Fatty (ZDF) rats received eplerenone (25 mg/kg) or vehicle. Zucker Lean (ZL) rats were used as control (n = 10, each group). After 16 weeks, cardiac structure and function was examined, and plasma and hearts were isolated for biochemical and histological approaches. Cultured cardiomyocytes were used for in vitro assays to determine the direct effects of eplerenone on high fatty acid and high glucose exposed cells.ResultsIn contrast to ZL, ZDF rats exhibited hyperglycemia, hyperlipidemia, insulin-resistance, cardiac steatosis and diastolic dysfunction. The ZDF myocardium also showed increased mitochondrial oxidation and apoptosis. Importantly, eplerenone mitigated these events without altering hyperglycemia. In cultured cardiomyocytes, high-concentrations of palmitate stimulated the fatty-acid uptake (in detriment of glucose assimilation), accumulation of lipid metabolites, mitochondrial dysfunction, and apoptosis. Interestingly, fatty-acid uptake, ceramides formation and apoptosis were also significantly ameliorated by eplerenone.ConclusionsBy blocking mineralocorticoid receptors, eplerenone may attenuate cardiac steatosis and apoptosis, and subsequent remodelling and diastolic dysfunction in obese/type-II diabetic rats.

New drug therapies interfering with the renin–angiotensin–aldosterone system for resistant hypertension

There is a persistent need for the development of new antihypertensive drugs, because the control of blood pressure is still not achievable in a significant proportion of hypertensive patients. Since the approval in 2007 of aliskiren, no other new antihypertensive based on new mechanism(s) of action have been approved. In fact, the development of promising novel drugs has been stopped for safety, efficacy or marketing reasons. Despite these difficulties, the pipeline is not dry and different new antihypertensive strategies targeting the renin-angiotensin-aldosterone pathway, are in clinical development stage. The dual angiotensin II receptor-neprilysin inhibitor LCZ696, a single molecule synthetized by cocrystallisation of valsartan and the neprilysin inhibitor prodrug AHU377 is in development for resistant hypertension and for heart failure. Daglutril is a dual neprylisin-endothelin converting enzyme inhibitor which was shown to decrease BP in patients with type 2 diabetic nephropathy. Aldosterone synthase inhibitors and the third and fourth generation non-steroidal dihydropyridine based mineralocorticoid receptors blockers are new ways to target the multiple noxious effects of aldosterone in the kidney, vessels and heart. Centrally acting aminopeptidase A inhibitors block brain angiotensin III formation, one of the main effector peptides of the brain renin angiotensin system. However, a long time will be still necessary to evaluate extensively the efficacy and safety of these new approaches. In the mean time, using appropriate and personalized daily doses of available drugs, decreasing physician inertia, improving treatment adherence, improving access to healthcare and reducing treatment costs remain major objectives to reduce the incidence of resistant hypertension.