Mineralocorticoids, hypertension, and cardiac fibrosis

Activated mineralocorticoid receptor regulates micro-RNA-29b in vascular smooth muscle cells

Inappropriately activated mineralocorticoid receptor (MR) is a risk factor for vascular remodeling with unclear molecular mechanism. Recent findings suggest that post-transcriptional regulation by micro-RNAs (miRs) may be involved. Our aim was to search for MR-dependent miRs in vascular smooth muscle cells (VSMCs) and to explore the underlying molecular mechanism and the pathologic relevance. We detected that aldosteroneviathe MR reduces miR-29bin vivoin murine aorta and in human primary and cultured VSMCs (ED50= 0.07 nM) but not in endothelial cells [quantitative PCR (qPCR), luciferase assays]. This effect was mediated by an increased decay of miR-29b in the cytoplasm with unchanged miR-29 family member or primary-miR levels. Decreased miR-29b led to an increase in extracellular matrix measured by ELISA and qPCR and enhanced VSMC migration in single cell-tracking experiments. Additionally, cell proliferation and the apoptosis/necrosis ratio (caspase/lactate dehydrogenase assay) was modulated by miR-29b. Enhanced VSMC migration by aldosterone required miR-29b regulation. Control experiments were performed with scrambled RNA and empty plasmids, by comparing aldosterone-stimulated with vehicle-incubated cells. Overall, our findings provide novel insights into the molecular mechanism of aldosterone-mediated vascular pathogenesis by identifying miR-29b as a pathophysiologic relevant target of activated MR in VSMCs and by highlighting the importance of miR processing for miR regulation.-Bretschneider, M., Busch, B., Mueller, D., Nolze, A., Schreier, B., Gekle, M., Grossmann, C. Activated mineralocorticoid receptor regulates micro-RNA-29b in vascular smooth muscle cells.

Update on RAAS Modulation for the Treatment of Diabetic Cardiovascular Disease

Since the advent of insulin, the improvements in diabetes detection and the therapies to treat hyperglycemia have reduced the mortality of acute metabolic emergencies, such that today chronic complications are the major cause of morbidity and mortality among diabetic patients. More than half of the mortality that is seen in the diabetic population can be ascribed to cardiovascular disease (CVD), which includes not only myocardial infarction due to premature atherosclerosis but also diabetic cardiomyopathy. The importance of renin-angiotensin-aldosterone system (RAAS) antagonism in the prevention of diabetic CVD has demonstrated the key role that the RAAS plays in diabetic CVD onset and development. Today, ACE inhibitors and angiotensin II receptor blockers represent the first line therapy for primary and secondary CVD prevention in patients with diabetes. Recent research has uncovered new dimensions of the RAAS and, therefore, new potential therapeutic targets against diabetic CVD. Here we describe the timeline of paradigm shifts in RAAS understanding, how diabetes modifies the RAAS, and what new parts of the RAAS pathway could be targeted in order to achieve RAAS modulation against diabetic CVD.

Aldosterone-induced cardiomyocyte growth, and fibroblast migration and proliferation are mediated by TRAF3IP2

Sustained activation of the Renin-Angiotensin-Aldosterone System (RAAS) contributes to the pathogenesis of heart failure. Aldosterone (Aldo) is known to induce both myocardial hypertrophy and fibrosis through oxidative stress and proinflammatory pathways. Here we have investigated whether Aldo-mediated cardiomycocyte hypertrophy is dependent on TRAF3IP2, an upstream regulator of IKK and JNK. We also investigated whether the pro-mitogenic and pro-migratory effects of Aldo on cardiac fibroblasts are also mediated by TRAF3IP2. Aldo induced both superoxide and hydrogen peroxide in isolated adult mouse cardiomyocytes (CM), and upregulated TRAF3IP2 expression in part via the mineralocorticoid receptor and oxidative stress. Silencing TRAF3IP2 blunted Aldo-induced IKKβ, p65, JNK, and c-Jun activation, IL-18, IL-6 and CT-1 upregulation, and cardiomyocyte hypertrophy. In isolated adult mouse cardiac fibroblasts (CF), Aldo stimulated TRAF3IP2-dependent IL-18 and IL-6 production, CTGF, collagen I and III expression, MMP2 activation, and proliferation and migration. These in vitro results suggest that TRAF3IP2 may play a causal role in Aldo-induced adverse cardiac remodeling in vivo, and identify TRAF3IP2 as a potential therapeutic target in hypertensive heart disease.

Role of Nongenomic Signaling Pathways Activated by Aldosterone During Cardiac Reperfusion Injury

Aldosterone (Aldo) activates both genomic and nongenomic signaling pathways in the cardiovascular system. Activation of genomic signaling pathways contributes to the adverse cardiac actions of Aldo during reperfusion injury; however, the extent nongenomic signaling pathways contribute has been difficult to identify due to lack of a specific ligand that activates only nongenomic signaling pathways. Using a pegylated aldosterone analog, aldosterone-3-carboxymethoxylamine-TFP ester conjugated to methoxypegylated amine (Aldo-PEG), we are able for the first time to distinguish between nongenomic and genomic cardiac actions of Aldo. We confirm Aldo-PEG activates phosphorylation of ERK1/2 in rat cardiomyocyte H9c2 cells similar to Aldo and G protein-coupled receptor 30 (GPR30 or GPER) agonist G1. GPER antagonist, G36, but not mineralocorticoid receptor (MR) antagonist spironolactone, prevented ERK1/2 phosphorylation by Aldo, Aldo-PEG, and G1. The selective nongenomic actions of Aldo-PEG are confirmed, with Aldo-PEG increasing superoxide production in H9c2 cells to similar levels as Aldo but having no effect on subcellular localization of MR. Striatin serves as a scaffold for GPER and MR, with GPER antagonist G36, but not spironolactone, restoring MR-striatin complexes. Aldo-PEG had no effect on MR-dependent transcriptional activation, whereas Aldo increased transcript levels of serum-regulated kinase 1 and plasminogen activator inhibitor-1. Using our ex vivo experimental rat model of myocardial infarction, we found aggravated infarct size and apoptosis by Aldo but not Aldo-PEG. Our studies confirm that in the heart, activation of nongenomic signaling pathways alone are not sufficient to trigger the deleterious effects of aldosterone during myocardial reperfusion injury.

CD47 Promotes Protective Innate and Adaptive Immunity in a Mouse Model of Disseminated Candidiasis

CD47 is a widely expressed receptor that regulates immunity by engaging its counter-receptor SIRPα on phagocytes and its secreted ligand thrombospondin-1. Mice lacking CD47 can exhibit enhanced or impaired host responses to bacterial pathogens, but its role in fungal immunity has not been examined. cd47-/- mice on a C57BL/6 background showed significantly increased morbidity and mortality following Candida albicans infection when compared with wild-type mice. Despite normal fungal colonization at earlier times, cd47-/- mice at four days post-infection had increased colonization of brain and kidneys accompanied by stronger inflammatory reactions. Neutrophil and macrophage numbers were significantly elevated in kidneys and neutrophils in the brains of infected cd47-/- mice. However, no defect in phagocytic activity towards C. albicans was observed in cd47-/- bone-marrow-derived macrophages, and neutrophil and macrophage killing of C. albicans was not impaired. CD47-deficiency did not alter the early humoral immune response to C. albicans. Th1, Th2, and Th17 population of CD4+ T cells were expanded in the spleen, and gene expression profiles of spleen and kidney showed stronger pro-inflammatory signaling in infected cd47-/- mice. The chemoattractant chemokines MIP-2α and MIP-2β were highly expressed in infected spleens of cd47-/- mice. G-CSF, GM-CSF, and the inflammasome component NLRP3 were more highly expressed in infected cd47-/- kidneys than in infected wild-type controls. Circulating pro- (TNF-α, IL-6) and anti-inflammatory cytokines (IL-10) were significantly elevated, but IL-17 was decreased. These data indicate that CD47 plays protective roles against disseminated candidiasis and alters pro-inflammatory and immunosuppressive pathways known to regulate innate and T cell immunity.

Cardiac effects of aldosterone: does gender matter?

Ischemic heart disease (IHD) continues to be the most common cause of death globally, although mortality rates are decreasing with significant advances in treatment. Higher prevalence of co-morbidities in women only partly explains the lack of decrease in mortality rates in younger women due to. Until recently there has been gender bias in pre-clinical studies and many clinical trials, resulting in a significant gap in knowledge whether there are differential responses to therapy for women, particularly younger women. There is increasing evidence that there are significant gender-specific differences in the outcome of post-infarction remodelling, prevalence of hypertension and sudden cardiac death. These differences indicate that cardiac tissue in females displays significant physiological and biochemical differences compared to males. However, the mechanisms mediating these differences, and how they change with age, are poorly understood. Circulating levels and physiological effects of aldosterone vary across the menstrual cycle suggesting female steroid sex hormones may not only regulate production of, but also responses to, aldosterone in pre-menopausal women. This modified tissue response may foster a homeostatic environment where higher levels of aldosterone are tolerated without adverse cardiac effect. Moreover, there is limited data on the direct regulation of this signalling axis by androgens in female animals/subjects. This review explores the relationship between gender and the effects of aldosterone in cardiovascular disease (CVD), an issue of significant need that may lead to changes in best practice to optimise clinical care and improve outcomes for females with CVD.

Aldosterone blockade in chronic kidney disease

Although blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers has become standard therapy for chronic kidney disease (CKD), renewed interest in the role of aldosterone in mediating the injuries and progressive insults of CKD has highlighted the potential role of treatments targeting the mineralocorticoid receptor (MR). Although salt restriction is an important component of mitigating the profibrotic effects of MR activation, a growing body of literature has shown that MR antagonists, spironolactone and eplerenone, can reduce proteinuria and blood pressure in patients at all stages of CKD. These agents carry a risk of hyperkalemia, but this risk likely can be predicted based on baseline renal function and mitigated using dietary modifications and adjustments of concomitant medications. Data on hard outcomes, such as progression to end-stage renal disease and overall mortality, still are lacking in patients with CKD.

Endothelial cell mineralocorticoid receptors regulate deoxycorticosterone/salt-mediated cardiac remodeling and vascular reactivity but not blood pressure

Recent studies have identified novel pathological roles for mineralocorticoid receptors (MR) in specific cell types in cardiovascular disease. The mechanisms by which MR promotes inflammation and fibrosis involve multiple cell-specific events. To identify the role of MR in endothelial cells (EC-MR), the current study explored the vascular responses to aldosterone in wild-type (WT) and EC-null mice (EC-MRKO). Nitric oxide function was impaired in the thoracic aorta and mesenteric arteries of aldosterone-treated WT mice. Although endothelial nitric oxide function was equivalently impaired in the mesenteric arteries of aldosterone-treated EC-MRKO mice, endothelial function was unaffected in the aorta, suggesting a differential role for EC-MR depending on the vascular bed. Second, the contribution of EC-MR to cardiovascular inflammation, fibrosis, and hypertension was determined in WT and EC-MRKO treated with deoxycorticosterone/salt for 8 days or 8 weeks. At 8 days, loss of EC-MR prevented macrophage infiltration and the expression of proinflammatory genes in the myocardium. Increased cardiac fibrosis was not detected in either genotype at this time, mRNA levels of profibrotic genes were significantly lower in EC-MRKO mice versus WT. At 8 weeks, deoxycorticosterone/salt treatment increased macrophage recruitment and proinflammatory gene expression in WT but not in EC-MRKO. Collagen deposition and connective tissue growth factor expression were significantly reduced in EC-MRKO versus WT. Interestingly, systolic blood pressure was equivalently elevated in deoxycorticosterone/salt treated WT and EC-MRKO. Our data demonstrate that (1) EC-MR signaling contributes to vascular nitric oxide function in large conduit arteries but not in resistance vessels and (2) an independent role for EC-MR in the inflammatory and profibrotic response to deoxycorticosterone/salt.

The mineralocorticoid receptor promotes fibrotic remodeling in atrial fibrillation

We studied the role of the mineralocorticoid receptor (MR) in the signaling that promotes atrial fibrosis. Left atrial myocardium of patients with atrial fibrillation (AF) exhibited 4-fold increased hydroxyproline content compared with patients in sinus rhythm. Expression of MR was similar, as was 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which also increased. 11β-HSD2 converts cortisol to receptor-inactive metabolites allowing aldosterone occupancy of MR. 11β-HSD2 was up-regulated by arrhythmic pacing in cultured cardiomyocytes and in a mouse model of spontaneous AF (RacET). In cardiomyocytes, aldosterone induced connective tissue growth factor (CTGF) in the absence but not in the presence of cortisol. Hydroxyproline expression was increased in cardiac fibroblasts exposed to conditioned medium from aldosterone-treated cardiomyocytes but not from cardiomyocytes treated with both cortisol and aldosterone. Aldosterone increased connective tissue growth factor and hydroxyproline expression in cardiac fibroblasts, which were prevented by BR-4628, a dihydropyridine-derived selective MR antagonist, and by spironolactone. Aldosterone activated RhoA GTPase. Rho kinase inhibition by Y-27632 prevented CTGF and hydroxyproline, whereas the RhoA activator CN03 increased CTGF expression. Aldosterone and CTGF increased lysyl oxidase, and aldosterone enhanced miR-21 expression. MR antagonists reduced the aldosterone but not the CTGF effect. In conclusion, MR signaling promoted fibrotic remodeling. Increased expression of 11β-HSD2 during AF leads to up-regulation of collagen and pro-fibrotic mediators by aldosterone, specifically RhoA activity as well as CTGF, lysyl oxidase, and microRNA-21 expression. The MR antagonists BR-4628 and spironolactone prevent these alterations. MR inhibition may, therefore, represent a potential pharmacologic target for the prevention of fibrotic remodeling of the atrial myocardium.

Gene mutations that promote adrenal aldosterone production, sodium retention, and hypertension

Primary aldosteronism (PA) is the most common form of secondary hypertension, found in about 5% of all hypertension cases, and up to 20% of resistant hypertension cases. The most common forms of PA are an aldosterone-producing adenoma and idiopathic (bilateral) hyperaldosteronism. Rare genetic forms of PA exist and, until recently, the only condition with a known genetic mechanism was familial hyperaldosteronism type 1, also known as glucocorticoid-remediable aldosteronism (FHA1/GRA). FHA type 3 has now been shown to derive from germline mutations in the KCNJ5 gene, which encodes a potassium channel found on the adrenal cells. Remarkably, somatic mutations in KCNJ5 are found in about one-third of aldosterone-producing adenomas, and these mutations are likely to be involved in their pathogenesis. Finally, mutations in the genes encoding an L-type calcium channel (CACNA1D) and in genes encoding a sodium–potassium adenosine triphosphatase (ATP1A1) or a calcium adenosine triphosphatase (ATP2B3) are found in other aldosterone-producing adenomas. These findings provide a working model, in which adenoma formation and/or aldosterone production in many cases derives from increased calcium entry, which drives the pathogenesis of primary aldosteronism.

Mineralocorticoid receptor antagonists: emerging roles in cardiovascular medicine

Spironolactone was first developed over 50 years ago as a potent mineralocorticoid receptor (MR) antagonist with undesirable side effects; it was followed a decade ago by eplerenone, which is less potent but much more MR-specific. From a marginal role as a potassium-sparing diuretic, spironolactone was shown to be an extraordinarily effective adjunctive agent in the treatment of progressive heart failure, as was eplerenone in subsequent heart failure trials. Neither acts as an aldosterone antagonist in the heart as the cardiac MR are occupied by cortisol, which becomes an aldosterone mimic in conditions of tissue damage. The accepted term "MR antagonist", (as opposed to "aldosterone antagonist" or, worse, "aldosterone blocker"), should be retained, despite the demonstration that they act not to deny agonist access but as inverse agonists. The prevalence of primary aldosteronism is now recognized as accounting for about 10% of hypertension, with recent evidence suggesting that this figure may be considerably higher: in over two thirds of cases of primary aldosteronism therapy including MR antagonists is standard of care. MR antagonists are safe and vasoprotective in uncomplicated essential hypertension, even in diabetics, and at low doses they also specifically lower blood pressure in patients with so-called resistant hypertension. Nowhere are more than 1% of patients with primary aldosteronism ever diagnosed and specifically treated. Given the higher risk profile in patients with primary aldosteronism than that of age, sex, and blood pressure matched essential hypertension, on public health grounds alone the guidelines for first-line treatment of all hypertension should mandate inclusion of a low-dose MR antagonist.

Effect of Renal Denervation on Neurohumoral Activation Triggering Atrial Fibrillation in Obstructive Sleep Apnea

Obstructive sleep apnea is characterized by repetitive collapses of the upper airway, negative thoracic pressure periods, and intermittent hypoxia, stimulating the autonomic nervous system. The increased sympathetic drive during obstructive sleep apnea results in postapneic blood pressure rises and neurohumoral activation potentially involved in the initiation and progression to permanent atrial fibrillation (AF). In a pig model mimicking obstructive sleep apnea, we studied the effects of repetitive obstructive respiratory events for 4 hours on the occurrence of spontaneous AF episodes, postapneic blood pressure rises, and neurohumoral activation. In addition, renal sympathetic denervation was performed to investigate the impact of the sympathetic nervous system. Repetitive obstructive respiratory events caused pronounced postapneic blood pressure rises, prolonged duration of spontaneous AF episodes triggered by spontaneous atrial beats, and increased plasma renin activity and aldosterone concentrations. This was associated with increased nicotinamide adenine dinucleotide phosphate-oxidase activity, reduced antioxidative capacity, and elevated expression of connective tissue growth factor, a redox-sensitive mediator of fibrosis. Renal sympathetic denervation inhibited postapneic blood pressure rises and decreased plasma renin activity and aldosterone concentrations. The occurrence and duration of spontaneous AF were reduced comparable with a combined pharmacological blockade of angiotensin receptor and β-adrenoceptor. Increased atrial oxidative stress, together with the activation of profibrotic pathways and intermittent hypoxia, was not attenuated after renal sympathetic denervation. Repetitive obstructive respiratory events triggered spontaneous AF, increased atrial oxidative stress, and activated profibrotic pathways in the atrium. Renal sympathetic denervation reduced spontaneous AF and postapneic blood pressure rises by combined reduction of sympathetic drive and components of the circulating renin–angiotensin system. However, the generation of atrial oxidative stress was not modulated.

Mineralocorticoid receptors and the heart, multiple cell types and multiple mechanisms: a focus on the cardiomyocyte

MR (mineralocorticoid receptor) activation in the heart plays a central role in the development of cardiovascular disease, including heart failure. The MR is present in many cell types within the myocardium, including cardiomyocytes, macrophages and the coronary vasculature. The specific role of the MR in each of these cell types in the initiation and progression of cardiac pathophysiology is not fully understood. Cardiomyocyte MRs are increasingly recognized to play a role in regulating cardiac function, electrical conduction and fibrosis, through direct signal mediation and through paracrine MR-dependent activity. Although MR blockade in the heart is an attractive therapeutic option for the treatment of heart failure and other forms of heart disease, current antagonists are limited by side effects owing to MR inactivation in other tissues (including renal targets). This has led to increased efforts to develop therapeutics that are more selective for cardiac MRs and which may have reduced the occurrence of side effects in non-cardiac tissues. A major clinical consideration in the treatment of cardiovascular disease is of the differences between males and females in the incidence and outcomes of cardiac events. There is clinical evidence that female sensitivity to endogenous MRs is more pronounced, and experimentally that MR-targeted interventions may be more efficacious in females. Given that sex differences have been described in MR signalling in a range of experimental settings and that the MR and oestrogen receptor pathways share some common signalling intermediates, it is becoming increasingly apparent that the mechanisms of MRs need to be evaluated in a sex-selective manner. Further research targeted to identify sex differences in cardiomyocyte MR activation and signalling processes has the potential to provide the basis for the development of cardiac-specific MR therapies that may also be sex-specific.

Mineralocorticoid receptor interaction with SP1 generates a new response element for pathophysiologically relevant gene expression

The mineralocorticoid receptor (MR) is a ligand-induced transcription factor belonging to the steroid receptor family and involved in water-electrolyte homeostasis, blood pressure regulation, inflammation and fibrosis in the renocardiovascular system. The MR shares a common hormone-response-element with the glucocorticoid receptor but nevertheless elicits MR-specific effects including enhanced epidermal growth factor receptor (EGFR) expression via unknown mechanisms. The EGFR is a receptor tyrosine kinase that leads to activation of MAP kinases, but that can also function as a signal transducer for other signaling pathways. In the present study, we mechanistically investigate the interaction between a newly discovered MR- but not glucocorticoid receptor- responsive-element (=MRE1) of the EGFR promoter, specificity protein 1 (SP1) and MR to gain general insights into MR-specificity. Biological relevance of the interaction for EGFR expression and consequently for different signaling pathways in general is demonstrated in human, rat and murine vascular smooth muscle cells and cells of EGFR knockout mice. A genome-wide promoter search for identical binding regions followed by quantitative PCR validation suggests that the identified MR-SP1-MRE1 interaction might be applicable to other genes. Overall, a novel principle of MR-specific gene expression is explored that applies to the pathophysiologically relevant expression of the EGFR and potentially also to other genes.

The ubiquitous mineralocorticoid receptor: clinical implications

Mineralocorticoid receptors (MR) exist in many tissues, in which they mediate diverse functions crucial to normal physiology, including tissue repair and electrolyte and fluid homeostasis. However, inappropriate activation of MR within these tissues, and especially in the brain, causes hypertension and pathological vascular, cardiac, and renal remodeling. MR binds aldosterone, cortisol and corticosterone with equal affinity. In aldosterone-target cells, co-expression with the 11β-hydroxysteroid dehydrogenase 2 (HSD2) allows aldosterone specifically to activate MR. Aldosterone levels are excessive in primary aldosteronism, but in conditions with increased oxidative stress, like CHF, obesity and diabetes, MR may also be inappropriately activated by glucocorticoids. Unlike thiazide diuretics, MR antagonists are diuretics that do not cause insulin resistance. Addition of MR antagonists to standard treatment for hypertension and cardiac or renal disease decreases end-organ pathology and sympathetic nerve activation (SNA), and increases quality of life indices.

Adrenalectomy amplifies aldosterone induced injury in cardiovascular tissue: an effect attenuated by adrenally derived steroids

Aldosterone induces fibrotic changes in cardiovascular tissues but its effects have usually been demonstrated in models of pre-existing renal injury and/or hypertension. This study tests the hypothesis that aldosterone can directly induce vascular fibrotic changes in the absence of prior renal injury or hypertension. Experiments were conducted in intact or adrenalectomized (ADX) mice. Mice were divided into groups and treated for 1 week with vehicle or aldosterone (8 μg/kg/day)± inhibitor (800 μg/kg/day): CONTROLS, mice treated with aldosterone, ADX-CONTROLS, ADX+corticosterone (CORT 8 μg/kg/day), ADX with aldosterone, ADX with aldosterone plus the mineralocorticoid receptor (MR) antagonist RU-318, ADX with aldosterone+CORT (CORT inhibitor dose), and ADX with aldosterone+11-dehydro-CORT. Aortic smooth muscle to collagen ratio, aorta intimal thickness (μm), heart weight/body weight ratio (mg/gm), and left ventricular collagen (%) were measured. Prior to sacrifice, blood pressures were normal in all animals. Lower dose CORT alone had no effect on any of the variables examined. Aldosterone exposure was associated with extra-cellular matrix accumulation in cardiovascular tissues in intact mice and adrenalectomy exacerbated these effects. RU-318, CORT (inhibitor dose), and 11-deydro-CORT each attenuated the early fibrotic changes induced by aldosterone. In the heart, aldosterone exposure affected all the parameters measured and caused intimal hypercellularity with monocytes adhering to endothelial cells lining coronary vessels. Cultured endothelial cells exposed to aldosterone (10nM) released E-selectin, produced collagen, and promoted monocyte adhesion. These effects were inhibited by RU-318 and 11-deydro-CORT but not by CORT. Thus, adrenalectomy enhances aldosterone induced early fibrotic changes in heart and aorta. Aldosterone initially targets vascular endothelial cells. MR antagonists and 11-dehydro-CORT, an 11β-HSD dehydrogenase end-product, directly attenuate these effects.

Activation of an apoptotic signal transduction pathway involved in the upregulation of calpain and apoptosis-inducing factor in aldosterone-induced primary cultured cardiomyocytes

In this study, aldosterone (ALD)-induced apoptosis of cardiomyocyte was evaluated based on the previous studies, and the roles of calpain signaling were clarified. Primary cultured rat cardiomyocytes were injured by ALD (0.01-10 μM) for varying time periods. Then, the effects of ethylene glycol tetraacetic acid (EGTA) (0.5 mM), calpeptin (2.5 μM), and spironoclactone (10 μM) were evaluated on cardiomyocytes activated by ALD. Cardiomyocytes that were injured by ALD were assayed by the MTT and LDH leakage ratio. Apoptosis was evaluated by a TUNEL assay, annexin V/PI staining, and caspase-3 activity. The expression of cleavage of Bid (tBid), calpain and apoptosis-inducing factor (AIF) was evaluated by western blot analysis. ALD increased calpain expression and caspase-3 activity and promoted Bid cleavage. It also induced the release of AIF from mitochondria into the cytosol. The upregulation of calpain, tBid and caspase-3 activity were further inhibited by treatment with EGTA in the presence of ALD. Additionally, AIF levels in the cytosol decreased due to EGTA but not due to calpeptin. This was also accompanied by a significant decrease in apoptosis. Furthermore, treatment with spironoclactone not only attenuated the pro-apoptotic effect of ALD but reversed the ALD-induced increase of calpain and AIF levels.

Impact of aldosterone-producing adenoma on cardiac structures in echocardiography

Background

Primary aldosteronism (PA) is a most common cause of secondary hypertension. In PA, left ventricular hypertrophy (LVH) is more progressive than in any other cause of hypertension. Aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA) are major subtypes of PA. However there is little information concerned with differences of cardiac structures between these two subtypes.

Methods

We reviewed echocardiographic findings in 46 patients with PA. All patients had a positive screen test and subtypes of PA were confirmed by adrenal vein sampling. Subjects consisted of 20 patients with APA (APA group, 52.4 ± 10.8 years) and 26 patients with IHA (IHA group, 56.2 ± 9.5 years). We investigated differences of cardiac structures and functions in the left atrium and ventricle between the APA group and IHA group.

Results

In terms of clinical characteristics, the height and duration of hypertension were greater and serum potassium concentration and BMI were lower in the APA group than in the IHA group. Plasma aldosterone concentration (PAC) and PAC to plasma renin activity ratio were higher in the APA group than in the IHA group. In echocardiographic assessment, the left atrial volume, left ventricular end-diastolic and end-systolic diameters, left ventricular mass (LVM), and prevalence of LVH were greater in the APA group than in the IHA group. Multiple linear regression analysis revealed that the diagnosis of APA independently correlated with left atrial volume, left ventricular end-diastolic diameter, and LVM.

Conclusions

We demonstrated that differences of cardiac structures between the APA group and IHA group existed. In APA, left atrial enlargement and LVH were more prominent than in IHA.

Role of mitogen-activated protein kinase pathways in multifactorial adverse cardiac remodeling associated with metabolic syndrome

Metabolic syndrome has been widely associated with an increased risk for acute cardiovascular events. Emerging evidence supports metabolic syndrome as a condition favoring an adverse cardiac remodeling, which might evolve towards heart dysfunction and failure. This pathological remodeling has been described to result from the cardiac adaptive response to clinical mechanical conditions (such as hypertension, dyslipidemia, and hyperglycemia), soluble inflammatory molecules (such as cytokines and chemokines), as well as hormones (such as insulin), characterizing the pathophysiology of metabolic syndrome. Moreover, these cardiac processes (resulting in cardiac hypertrophy and fibrosis) are also associated with the modulation of intracellular signalling pathways within cardiomyocytes. Amongst the different intracellular kinases, mitogen-activated protein kinases (MAPKs) were shown to be involved in heart damage in metabolic syndrome. However, their role remains controversial. In this paper, we will discuss and update evidence on MAPK-mediated mechanisms underlying cardiac adverse remodeling associated with metabolic syndrome.

Demonstration of Blood Pressure-Independent Noninfarct Myocardial Fibrosis in Primary Aldosteronism

Background—

Primary aldosteronism (PA) is common and associates with excess cardiovascular morbidity independent of blood pressure. Exposure to aldosterone and sodium leads to cardiac fibrosis and hypertrophy in humans and animals possibly mediated by inflammation and oxidative stress. We aimed to clarify the effects of aldosterone excess on myocardial structure and composition in human subjects with PA and essential hypertension using contrast-enhanced cardiac magnetic resonance imaging as well as explore the mechanistic basis for any observed differences.

Methods and Results—

Twenty-seven subjects with recently diagnosed PA and 54 essential hypertension controls were recruited. Subjects underwent gadolinium-enhanced cardiac magnetic resonance; noninfarct related myocardial fibrosis was identified by a diffuse pattern of late gadolinium enhancement. Patients also underwent assessment of pulse wave velocity, measurement of circulating superoxide anion and C-reactive protein, as well as blood pressure and biochemical assessment. Subjects were well matched with no difference in severity or duration of hypertension. There was a significant increase in the frequency of noninfarct late gadolinium enhancement in PA (70%) when compared with essential hypertension subjects (13%; P <0.0001) with no difference in left ventricular mass. Pulse wave velocity, superoxide, and C-reactive protein were significantly higher in subjects with PA.

Conclusions—

These data illustrate that patients with PA exhibit frequent myocardial fibrosis as demonstrated by late gadolinium enhancement using cardiac magnetic resonance imaging; this finding is independent of blood pressure. This may be mediated partly through inflammation and oxidative stress. This study highlights the importance of specific targeting of aldosterone excess as well as blood pressure reduction to minimize cardiac morbidity in PA.

Cardiomyocyte mineralocorticoid receptors are essential for deoxycorticosterone/salt-mediated inflammation and cardiac fibrosis

Because the role of mineralocorticoid receptors in specific cell types in cardiac remodeling remains unknown, we have compared cardiac responses with deoxycorticosterone/salt in cardiomyocyte mineralocorticoid receptor-null (MyoMRKO) and wild-type (WT) mice at 8 days and 8 weeks. No differences in cardiac function between untreated WT and MyoMRKO mice were found, whereas profibrotic markers were reduced in MyoMRKO hearts at baseline. At 8 days, MyoMRKO showed monocyte/macrophage recruitment equivalent to WT mice in response to deoxycorticosterone/salt but a suppression of markers of fibrosis compared with WT. At 8 weeks, MyoMRKO mice showed no deoxycorticosterone/salt-induced increase in inflammatory cell infiltration and collagen deposition or in proinflammatory gene expression. Although some profibrotic markers were equivalently increased in both genotypes, MyoMRKO mice also showed increased baseline levels of mRNA and protein for the transforming growth factor-β/connective tissue growth factor inhibitor decorin compared with WT that was accompanied by higher levels of matrix metalloproteinase 2/matrix metalloproteinase 9 activity. These data point to a direct role for cardiomyocyte mineralocorticoid receptor in both deoxycorticosterone/salt-induced tissue inflammation and remodeling and suggest potential mechanisms for the cardioprotective effects of selective mineralocorticoid receptor blockade in cardiomyocytes that may involve regulation of matrix metalloproteinase 2/matrix metalloproteinase 9 activity and the transforming growth factor-β-connective tissue growth factor profibrotic pathway.

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.

Mineralocorticoid receptor antagonists for heart failure with reduced ejection fraction: integrating evidence into clinical practice

Mineralocorticoid receptor antagonists (MRAs) improve survival and reduce morbidity in patients with heart failure, reduced ejection fraction (HF-REF), and mild-to-severe symptoms, and in patients with left ventricular systolic dysfunction and heart failure after acute myocardial infarction. These clinical benefits are observed in addition to those of angiotensin converting enzyme inhibitors or angiotensin receptor blockers and beta-blockers. The morbidity and mortality benefits of MRAs may be mediated by several proposed actions, including antifibrotic mechanisms that slow heart failure progression, prevent or reverse cardiac remodelling, or reduce arrhythmogenesis. Both eplerenone and spironolactone have demonstrated survival benefits in individual clinical trials. Pharmacologic differences exist between the drugs, which may be relevant for therapeutic decision making in individual patients. Although serious hyperkalaemia events were reported in the major MRA clinical trials, these risks can be mitigated through appropriate patient selection, dose selection, patient education, monitoring, and follow-up. When used appropriately, MRAs significantly improve outcomes across the spectrum of patients with HF-REF.

Aldosterone in heart disease

Numerous studies have now shown that sustained elevation of aldosterone levels induces cardiovascular damage independent from its effects on regulation of renal sodium and blood pressure. Increased aldosterone and cortisol levels in patients with heart failure independently predict the risk of mortality. Over the past decade, there has been increased interest in identifying the role of the receptor for aldosterone, the mineralocorticoid receptor (MR), following the results from the large clinical heart failure trials that showed low doses of MR antagonists reduced morbidity and mortality in heart failure and myocardial infarction, even though plasma levels of aldosterone were in the physiologic range. The mechanism for this cardioprotective action remains to be defined, although changes in the redox state have been shown to play a key role in MR-mediated cardiac damage. This review will highlight some of these studies and provide an update on the action of aldosterone in heart disease.

Macrophage mineralocorticoid receptor signaling plays a key role in aldosterone-independent cardiac fibrosis

Mineralocorticoid receptor (MR) activation promotes the development of cardiac fibrosis and heart failure. Clinical evidence demonstrates that MR antagonism is protective even when plasma aldosterone levels are not increased. We hypothesize that MR activation in macrophages drives the profibrotic phenotype in the heart even when aldosterone levels are not elevated. The aim of the present study was to establish the role of macrophage MR signaling in mediating cardiac tissue remodeling caused by nitric oxide (NO) deficiency, a mineralocorticoid-independent insult. Male wild-type (MRflox/flox) and macrophage MR-knockout (MRflox/flox/LysMCre/+; mac-MRKO) mice were uninephrectomized, maintained on 0.9% NaCl drinking solution, with either vehicle (control) or the nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (L-NAME; 150 mg/kg/d) for 8 wk. NO deficiency increased systolic blood pressure at 4 wk in wild-type L-NAME/salt-treated mice compared with all other groups. At 8 wk, systolic blood pressure was increased above control in both L-NAME/salt treated wild-type and mac-MRKO mice by approximately 28 mm Hg by L-NAME/salt. Recruitment of macrophages was increased 2- to 3-fold in both L-NAME/salt treated wild-type and mac-MRKO. Inducible NOS positive macrophage infiltration and TNFα mRNA expression was greater in wild-type L-NAME/salt-treated mice compared with mac-MRKO, demonstrating that loss of MR reduces M1 phenotype. mRNA levels for markers of vascular inflammation and oxidative stress (NADPH oxidase 2, p22phox, intercellular adhesion molecule-1, G protein-coupled chemokine receptor 5) were similar in treated wild-type and mac-MRKO mice compared with control groups. In contrast, L-NAME/salt treatment increased interstitial collagen deposition in wild-type by about 33% but not in mac-MRKO mice. mRNA levels for connective tissue growth factor and collagen III were also increased above control treatment in wild-type (1.931 ± 0.215 vs. 1 ± 0.073) but not mac-MRKO mice (1.403 ± 0.150 vs. 1.286 ± 0.255). These data demonstrate that macrophage MR are necessary for the translation of inflammation and oxidative stress into interstitial and perivascular fibrosis after NO deficiency, even when plasma aldosterone is not elevated.

A new transgenic rat model overexpressing the angiotensin II type 2 receptor provides evidence for inhibition of cell proliferation in the outer adrenal cortex

This study aimed to elucidate the role of the AT(2) receptor (AT(2)R), which is expressed and upregulated in the adrenal zona glomerulosa (ZG) under conditions of increased aldosterone production. We developed a novel transgenic rat (TGR; TGRCXmAT(2)R) that overexpresses the AT(2)R in the adrenal gland, heart, kidney, brain, skeletal muscle, testes, lung, spleen, aorta, and vein. As a consequence the total angiotensin II (Ang II) binding sites increased 7.8-fold in the kidney, 25-fold in the heart, and twofold in the adrenals. The AT(2)R number amounted to 82-98% of total Ang II binding sites. In the ZG of TGRCXmAT(2)R, the AT(2)R density was elevated threefold relative to wild-type (WT) littermates, whereas AT(1)R density remained unchanged. TGRCXmAT(2)R rats were viable and exhibited normal reproduction, blood pressure, and kidney function. Notably, a slightly but significantly reduced body weight and a moderate increase in plasma urea were observed. With respect to adrenal function, 24-h urinary and plasma aldosterone concentrations were unaffected in TGRCXmAT(2)R at baseline. Three and 14 days of Ang II infusion (300 ng·min(-1)·kg(-1)) increased plasma aldosterone levels in WT and in TGR. These changes were completely abolished by the AT(1)R blocker losartan. Of note, glomerulosa cell proliferation, as indicated by the number of Ki-67-positive glomerulosa cells, was stimulated by Ang II in TGR and WT rats; however, this increase was significantly attenuated in TGR overexpressing the AT(2)R. In conclusion, AT(2)R in the adrenal ZG inhibits Ang II-induced cell proliferation but has no obvious lasting effect on the regulation of the aldosterone production at the investigated stages.

Impact of salt on cardiac differential gene expression and coronary lesion in normotensive mineralocorticoid-treated mice

We previously reported that excess of deoxycorticosterone-acetate (DOCA)/salt-induced cardiac hypertrophy in the absence of hypertension in one-renin gene mice. This model allows us to study molecular mechanisms of high-salt intake in the development of cardiovascular remodeling, independently of blood pressure in a high mineralocorticoid state. In this study, we compared the effect of 5-wk low- and high-salt intake on cardiovascular remodeling and cardiac differential gene expression in mice receiving the same amount of DOCA. Differential gene and protein expression was measured by high-density cDNA microarray assays, real-time PCR and Western blot analysis in DOCA-high salt (HS) vs. DOCA-low salt (LS) mice. DOCA-HS mice developed cardiac hypertrophy, coronary perivascular fibrosis, and left ventricular dysfunction. Differential gene and protein expression demonstrated that high-salt intake upregulated a subset of genes encoding for proteins involved in inflammation and extracellular matrix remodeling (e.g., Col3a1, Col1a2, Hmox1, and Lcn2). A major subset of downregulated genes encoded for transcription factors, including myeloid differentiation primary response (MyD) genes. Our data provide some evidence that vascular remodeling, fibrosis, and inflammation are important consequences of a high-salt intake in DOCA mice. Our study suggests that among the different pathogenic factors of cardiac and vascular remodeling, such as hypertension and mineralocorticoid excess and sodium intake, the latter is critical for the development of the profibrotic and proinflammatory phenotype observed in the heart of normotensive DOCA-treated mice.

Mechanisms of mineralocorticoid salt-induced hypertension and cardiac fibrosis

For 50 years aldosterone has been thought to act primarily on epithelia to regulate fluid and electrolyte homeostasis. Mineralocorticoid receptors (MR), however, are also expressed in nonepithelial tissues such as the heart and vascular smooth muscle. Recently pathophysiologic effects of nonepithelial MR activation by aldosterone have been demonstrated, in the context of inappropriate mineralocorticoid for salt status, including coronary vascular inflammation and cardiac fibrosis. Consistent with experimental studies, clinical trials (RALES, EPHESUS), have demonstrated a reduced mortality and morbidity when MR antagonists are included in the treatment of moderate-severe heart failure. The pathogenesis of MR-mediated cardiovascular disease is a complex, multifactorial process that involves loss of vascular reactivity, hypertension, inflammation of the vasculature and end organs (heart and kidney), oxidative stress and tissue fibrosis (cardiac and renal). This review will discuss the mechanisms by which MR, located in the various cell types that comprise the heart, plays a central role in the development of cardiomyocyte failure, tissue inflammation, remodelling and hypertension.

Tissue-specific modulation of mineralocorticoid receptor function by 11β-hydroxysteroid dehydrogenases: an overview

In the last decade significant progress has been made in the understanding of mineralocorticoid receptor (MR) function and its implications for physiology and disease. The knowledge on the essential role of MR in the regulation of electrolyte concentrations and blood pressure has been significantly extended, and the relevance of excessive MR activation in promoting inflammation, fibrosis and heart disease as well as its role in modulating neuronal cell viability and brain function is now widely recognized. Despite considerable progress, the mechanisms of MR function in various cell-types are still poorly understood. Key modulators of MR function include the glucocorticoid receptor (GR), which may affect MR function by formation of heterodimers and by differential genomic and non-genomic responses on gene expression, and 11β-hydroxysteroid dehydrogenases (11β-HSDs), which determine the availability of intracellular concentrations of active glucocorticoids. In this review we attempted to provide an overview of the knowledge on MR expression with regard to the presence or absence of GR, 11β-HSD2 and 11β-HSD1/hexose-6-phosphate dehydrogenase (H6PDH) in various tissues and cell types. The consequences of cell-specific differences in the coexpression of MR with these proteins need to be further investigated in order to understand the role of this receptor in a given tissue as well as its systemic impact.

Aldosterone, mineralocorticoid receptor, and heart failure

Several large clinical studies have demonstrated the important benefit of mineralocorticoid receptor (MR) antagonists in patients with heart failure, left ventricular dysfunction after myocardial infarction, hypertension or diabetic nephropathy. Aldosterone adjusts the hydro-mineral balance in the body, and thus participates decisively to the control of blood pressure. This traditional view of the action of aldosterone restricted to sodium reabsorption in epithelial tissues must be revisited. Clinical and experimental studies indicated that chronic activation of the MR in target tissues induces structural and functional changes in the heart, kidneys and blood vessels. These deleterious effects include cardiac and renal fibrosis, inflammation and vascular remodeling. It is important to underscore that these effects are due to elevated MR activation that is inadequate for the body salt requirements. Aldosterone is generally considered as the main ligand of MR. However, this is a matter of debate especially in heart. Complexity arises from the glucocorticoids with circulating concentrations much higher than those of aldosterone, and the fact that the MR has a high affinity for 11β-hydroxyglucocorticoids. Nevertheless, the beneficial effects of MR inhibition in patients with heart failure emphasize the importance of this receptor in cardiovascular tissue. Diverse experimental models and strains of transgenic mice have allowed to dissect the effects of aldosterone and the MR in the heart. Taken together experimental and clinical data clearly highlight the deleterious cardiovascular effects of MR stimulation.

Mineralocorticoid receptor and embryonic stem cell models: molecular insights and pathophysiological relevance

Mineralocorticoid receptor (MR) signaling is pivotal for numerous physiological processes and implicated in various pathological conditions concerning among others, tight epithelia, central nervous and cardiovascular systems. For decades, the pleiotropic actions of MR have been investigated using animal and cellular models as well as by clinical studies. Here is reviewed and contextualized the utilization of a strategy that recently emerged to analyze the complexity of MR signaling: the derivation and differentiation of mouse embryonic stem (ES) cell models. ES cells were derived from wild-type or transgenic MR overexpressing animals. Undifferentiated ES cells were differentiated into cardiomyocytes, neurons and adipocytes, these cell types being important pathophysiological targets of MR. These approaches have already brought new insights concerning MR effect on cardiomyocyte contractility and ionic channel remodeling, in the regulation of neuronal MR expression and its positive role on neuron survival. Differentiated ES cell models thus constitute powerful and promising tools to further decipher the molecular mechanisms of cell-specific MR actions.

The DOCA-Salt Hypertensive Rat as a Model of Cardiovascular Oxidative and Inflammatory Stress

Oxidative stress and inflammation are two sides of the same coin that are intricately combined to elicit a chronic pathophysiological stress state, especially as seen in cardiovascular remodelling. In this review, we argue that administration of deoxycorticosterone acetate (DOCA) and sodium chloride to uninephrectomised rats, defined as DOCA-salt hypertensive rats, provides a reliable animal model of oxidative and inflammatory stress in the cardiovascular system. The supporting evidence includes pathophysiological and biochemical changes together with pharmacological responses to synthetic and natural compounds that lower the concentrations of reactive free radical species and that curtail inflammatory responses in the cardiovascular system.

Cardiac dimensions are largely determined by dietary salt in patients with primary aldosteronism: results of a case-control study

CONTEXT

Animal studies have demonstrated that dietary sodium intake is a major influence in the pathogenesis of aldosterone-induced effects in the heart such as left ventricular (LV) hypertrophy and fibrosis. LV hypertrophy is an important predictor for cardiovascular morbidity and mortality.

OBJECTIVE

We aimed to investigate the relationships between aldosterone and dietary salt and LV dimensions in patients with primary aldosteronism (PA).

DESIGN AND PARTICIPANTS

This case-control study included 21 patients with confirmed PA and 21 control patients with essential hypertension matched for age, gender, duration of hypertension, and 24-h systolic and diastolic blood pressure.

MAIN OUTCOME MEASURES

Patients were evaluated by echocardiography and 24-h urinary sodium (UNa) excretion while consuming their usual diets.

RESULTS

Patients with PA had significantly greater mean LV end-diastolic diameter, interventricular septum and posterior wall thicknesses, LV mass (LVM) and LV mass index, and end systolic and diastolic volumes than control patients. UNa significantly positively correlated with interventricular septum, posterior wall thicknesses, and LVM in the patients with PA but not in control patients. In a multivariate analysis, UNa was an independent predictor for LV wall thickness and LV mass among the patients with PA but not in patients with essential hypertension.

CONCLUSIONS

These findings emphasize the importance of dietary sodium in determining the degree of cardiac damage in those patients with PA, and we suggest that aldosterone excess may play a permissive role. In patients with PA, because a high-salt diet is associated with greater LVM, dietary salt restriction might reduce cardiovascular risk.

The role of aldosterone in the metabolic syndrome

The metabolic syndrome associates metabolic abnormalities such as insulin resistance and dyslipidemia with increased waist circumference and hypertension. It is a major public health concern, as its prevalence could soon reach 30% to 50% in developed countries. Aldosterone, a mineralocorticoid hormone classically involved in sodium balance regulation, is increased in patients with metabolic syndrome. Besides its classic actions, aldosterone and mineralocorticoid receptor (MR) activation affect glucose metabolism, inducing insulin resistance through various mechanisms that involve oxidative stress, inflammation, and downregulation of proteins involved in insulin signaling pathways. Aldosterone and MR signaling exert deleterious effects on the cardiovascular system and the kidney that influence the cardiovascular risk associated with metabolic syndrome. Salt load plays a major role in cardiovascular injury induced by aldosterone and MR signaling. Large multicenter, randomized clinical trials testing the beneficial effects of MR antagonists on cardiovascular events and mortality in patients with metabolic syndrome are needed.

Aldosterone and aldosterone receptor antagonists in patients with chronic heart failure

Aldosterone is a mineralocorticoid hormone synthesized by the adrenal glands that has several regulatory functions to help the body maintain normal volume status and electrolyte balance. Studies have shown significantly higher levels of aldosterone secretion in patients with congestive heart failure compared with normal patients. Elevated levels of aldosterone have been shown to elevate blood pressure, cause left ventricular hypertrophy, and promote cardiac fibrosis. An appreciation of the true role of aldosterone in patients with chronic heart failure did not become apparent until the publication of the Randomized Aldactone Evaluation Study. Until recently, the use of aldosterone receptor antagonists has been limited to patients with severe heart failure and patients with heart failure following myocardial infarction. The Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure (EMPHASIS-HF) study added additional evidence to support the expanded use of aldosterone receptor antagonists in heart failure patients. The results of the EMPHASIS-HF trial showed that patients with mild-to-moderate (New York Heart Association Class II) heart failure had reductions in mortality and hospitalizations from the addition of eplerenone to optimal medical therapy. Evidence remains elusive about the exact mechanism by which aldosterone receptor antagonists improve heart failure morbidity and mortality. The benefits of aldosterone receptor antagonist use in heart failure must be weighed against the potential risk of complications, ie, hyperkalemia and, in the case of spironolactone, possible endocrine abnormalities, in particular gynecomastia. With appropriate monitoring, these risks can be minimized. We now have evidence that patients with mild-to-severe symptoms associated with systolic heart failure will benefit from the addition of an aldosterone receptor antagonist to the standard therapies of angiotensin-converting enzyme inhibitors and beta-blockers. This review will address the pharmacologic basis of aldosterone receptor antagonists in patients with heart failure and the clinical impact of this therapy.

Proinflammatory protein CARD9 is essential for infiltration of monocytic fibroblast precursors and cardiac fibrosis caused by Angiotensin II infusion

Background

Angiotensin II (Ang II)–induced cardiac remodeling with the underlying mechanisms involving inflammation and fibrosis has been well documented. Cytosolic adaptor caspase recruitment domain 9 (CARD9) has been implicated in the innate immune response. We aimed to examine the role of CARD9 in inflammation and cardiac fibrosis induced by Ang II.

Methods

Two-month-old CARD9-deficient (CARD9^−/−) and wild-type (WT) male mice were infused with Ang II (1,500 ng/kg/min) or saline for 7 days. Heart sections were stained with hematoxylin and eosin and Masson trichrome and examined by immunohistochemistry; and activity and protein levels were measured in macrophages obtained from mice.

Results

WT mice with Ang II infusion showed a marked increase in CARD9⁺ macrophages in the heart, but CARD9^−/− mice showed significantly suppressed macrophage infiltration and expression of proinflammatory cytokines, including interleukin-1β (IL-1β) and connective tissue growth factor (CTGF). Importantly, Ang II–induced cardiac fibrosis (extracellular matrix and collagen I deposition) was diminished in CARD9^−/− hearts, as was the expression of transforming growth factor-β (TGF-β) and level of myofibroblasts positive for α-smooth muscle actin (α-SMA). Furthermore, Ang II activation of nuclear factor-κB (NF-κB), JNK and p38 mitogen-activated protein kinases (MAPKs) in WT macrophages was reduced in CARD9^−/− macrophages.

Conclusion

CARD9 plays an important role in regulating cardiac inflammation and fibrosis in response to elevated Ang II.

Rapid quantification of myocardial fibrosis: a new macro-based automated analysis

Background

Fibrosis is associated with various cardiac pathologies and dysfunction. Current quantification methods are time-consuming and laborious. We describe a semi-automated quantification technique for myocardial fibrosis and validated this using traditional methods.

Methods

Pulmonary Hypertension (PH) was induced in adult Wistar rats by subcutaneous monocrotaline (MCT) injection(40 mg/kg). Cryosections of myocardial tissue (5 μm) of PH rats (n = 9) and controls (n = 9) were stained using Picrosirius red and scanned with a digital microscopic MIRAX slide scanner. From these sections 21 images were taken randomly of each heart. Using ImageJ software a macro for automated image analysis of the amount of fibrosis was developed. For comparison, fibrosis was quantified using traditional polarisation microscopy. Both methods were correlated and validated against stereology as the gold standard. Furthermore, the method was tested in paraffin-embedded human tissues.

Results

Automated analysis showed a significant increase of fibrosis in PH hearts vs. control. Automated analysis correlated with traditional polarisation and stereology analysis (r² = 0.92 and r² = 0.95 respectively). In human heart, lungs, kidney, and liver, a similar correlation with stereology (r² = 0.91) was observed. Time required for automated analysis was 22% and 33% of the time needed for stereology and polarisation analysis respectively.

Conclusion

Automated quantification of fibrosis is feasible, objective, and time-efficient.

Electronic supplementary material

The online version of this article (doi:10.1007/s13402-011-0035-7) contains supplementary material, which is available to authorized users.

Angiotensin III stimulates aldosterone secretion from adrenal gland partially via angiotensin II type 2 receptor but not angiotensin II type 1 receptor

Angiotensin II (Ang II) and Ang III stimulate aldosterone secretion by adrenal glomerulosa, but the angiotensin receptor subtypes involved and the effects of Ang IV and Ang (1-7) are not clear. In vitro, different angiotensins were added to rat adrenal glomerulosa, and aldosterone concentration in the medium was measured. Ang II-induced aldosterone release was blocked (30.3 ± 7.1%) by an Ang II type 2 receptor (AT2R) antagonist, PD123319. Candesartan, an Ang II type 1 receptor (AT1R) antagonist, also blocked Ang II-induced aldosterone release (42.9 ± 4.8%). Coadministration of candesartan and PD123319 almost abolished the Ang II-induced aldosterone release. A selective AT2R agonist, CGP42112, was used to confirm the effects of AT2R. CGP42112 increased aldosterone secretion, which was almost completely inhibited by PD123319. In addition to Ang II, Ang III also induced aldosterone release, which was not blocked by candesartan. However, PD123319 blocked 22.4 ± 10.5% of the Ang III-induced aldosterone secretion. Ang IV and Ang (1-7) did not induce adrenal aldosterone secretion. In vivo, both Ang II and Ang III infusion increased plasma aldosterone concentration, but only Ang II elevated blood pressure. Ang IV and Ang (1-7) infusion did not affect blood pressure or aldosterone concentration. In conclusion, this report showed for the first time that AT2R partially mediates Ang III-induced aldosterone release, but not AT1R. Also, over 60% of Ang III-induced aldosterone release may be independent of both AT1R and AT2R. Ang III and AT2R signaling may have a role in the pathophysiology of aldosterone breakthrough.

Increased levels of oxidative stress, subclinical inflammation, and myocardial fibrosis markers in primary aldosteronism patients

BACKGROUND

Patients with primary aldosteronism experience greater left ventricular hypertrophy and a higher frequency of cardiovascular events than do essential hypertensive patients with comparable blood pressure levels. Aldosterone has been correlated with increased oxidative stress, endothelial inflammation, and fibrosis, particularly in patients with heart disease.

AIM

To evaluate oxidative stress, subclinical endothelial inflammation, and myocardial fibrosis markers in patients with primary aldosteronism and essential hypertension. DESIGN AND INDIVIDUALS: We studied 30 primary aldosteronism patients and 70 control essential hypertensive patients, matched by age, sex and median blood pressure. For all patients, we measured the serum levels of aldosterone, plasma renin activity, malondialdehyde (MDA), xanthine oxidase, metalloproteinase-9, ultrasensitive C-reactive protein and amino terminal propeptides of type I (PINP), and type III procollagen. We also evaluated the effect of PA treatment in 19 PA individuals.

RESULTS

PA patients showed elevated levels of MDA (1.70 ± 0.53 versus 0.94 ± 0.65 μmol/l, P <0.001) and PINP (81.7 ± 50.6 versus 49.7 ± 27 mg/l, P = 0.002) compared with essential hypertensive controls. We found a positive correlation between MDA, PINP, and the serum aldosterone/plasma renin activity ratio in primary aldosteronism patients. Clinically, treating primary aldosteronism patients decreased MDA and PINP levels.

CONCLUSION

We detected higher levels of MDA and PINP in primary aldosteronism patients, suggesting increased oxidative stress and myocardial fibrosis in these individuals. Treating primary aldosteronism patients reduced MDA and PINP levels, which may reflect the direct effect of aldosterone greater than endothelial oxidative stress and myocardial fibrosis, possibly mediated by a mineralocorticoid receptor.

Cellular and molecular pathways to myocardial necrosis and replacement fibrosis

Fibrosis is a fundamental component of the adverse structural remodeling of myocardium present in the failing heart. Replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium, but not without adverse functional consequences. The extensive nature of this microscopic scarring suggests cardiomyocyte necrosis is widespread and the loss of these contractile elements, combined with fibrous tissue deposition in the form of a stiff in-series and in-parallel elastic elements, contributes to the progressive failure of this normally efficient muscular pump. Cellular and molecular studies into the signal-transducer-effector pathway involved in cardiomyocyte necrosis have identified the crucial pathogenic role of intracellular Ca2+ overloading and subsequent induction of oxidative stress, predominantly confined within its mitochondria, to be followed by the opening of the mitochondrial permeability transition pore that leads to the destruction of these organelles and cells. It is now further recognized that Ca2+ overloading of cardiac myocytes and mitochondria serves as a prooxidant and which is counterbalanced by an intrinsically coupled Zn2+ entry serving as antioxidant. The prospect of raising antioxidant defenses by increasing intracellular Zn2+ with adjuvant nutriceuticals can, therefore, be preferentially exploited to uncouple this intrinsically coupled Ca2+ - Zn2+ dyshomeostasis. Hence, novel yet simple cardioprotective strategies may be at hand that deserve to be further explored.