Mineralocorticoid Receptor Antagonists Stimulate Human Hair Growth ex vivo.

Whilst topical steroids represent one of the most frequently administered treatments for skin and hair diseases, predominantly based on their glucocorticoid receptor-mediated anti-inflammatory effects, the mineralocorticoid effects of topical steroids have received surprisingly little attention. However, the role of mineralocorticoid receptor (MR) signaling is now known to extend beyond the kidney, with human skin, including the hair follicle (HF), expressing the MR. Using microdissected female HFs treated ex vivo with MR agonists and antagonists, we sought to determine the effects of MR-mediated signaling in the cutaneous context. Indeed, not only did the skin and HF epithelium express the MR at both the gene and protein level, but its expression was hair cycle dependent. Moreover, the selective MR antagonist eplerenone promoted hair shaft elongation and hair matrix keratinocyte proliferation whilst delaying catagen (HF regression). These novel observations suggest that the female human HF is sensitive to the inhibition of MR signaling and provide the first evidence that sustained MR signaling may even be required to maintain the growth phase (anagen) of human scalp HFs. Indeed, these data encourage the systematic evaluation of MR agonists and antagonists in human hair growth control so as to identify much-needed, novel anti-hirsutism and/or hair growth-promoting agents, respectively.

Mineralocorticoid receptor blockade improves glucocorticoid-induced skin atrophy but partially ameliorates anti-inflammatory actions in an irritative model in human skin explants.

We recently demonstrated that blockade of the mineralocorticoid receptor (MR) effectively ameliorated GC-induced skin atrophy in healthy human skin explants and epidermal MR knockout mice. However, whether MR blockade improves the therapeutic index of glucocorticoids (GCs) in skin pathology was not investigated. We assessed the effects of GCs, MR antagonists (MRA) or both, in SDS-treated human skin explants. All treatments restored SDS-augmented epidermal thickness but only GC plus MRA restored the expression of COL1A1. However, MRA alone or in combination with GCs may exert a dual role in regulating inflammatory cytokines. Thus, although combined treatment may be beneficial to improve irritative skin, extensive in vivo testing is required to establish whether the anti-inflammatory effects of GCs are maintained in the presence of MRA.

SPIRONOLACTONE FOR NONRESOLVING CENTRAL SEROUS CHORIORETINOPATHY: A RANDOMIZED CONTROLLED CROSSOVER STUDY.

PURPOSE: To evaluate the effect of spironolactone, a mineralocorticoid receptor antagonist, for nonresolving central serous chorioretinopathy. METHODS: This is a prospective, randomized, double-blinded, placebo-controlled crossover study. Sixteen eyes of 16 patients with central serous chorioretinopathy and persistent subretinal fluid (SRF) for at least 3 months were enrolled. Patients were randomized to receive either spironolactone 50 mg or placebo once a day for 30 days, followed by a washout period of 1 week and then crossed over to either placebo or spironolactone for another 30 days. The primary outcome measure was the changes from baseline in SRF thickness at the apex of the serous retinal detachment. Secondary outcomes included subfoveal choroidal thickness and the ETDRS best-corrected visual acuity. RESULTS: The mean duration of central serous chorioretinopathy before enrollment in study eyes was 10 ± 16.9 months. Crossover data analysis showed a statistically significant reduction in SRF in spironolactone treated eyes as compared with the same eyes under placebo (P = 0.04). Secondary analysis on the first period (Day 0-Day 30) showed a significant reduction in subfoveal choroidal thickness in treated eyes as compared with placebo (P = 0.02). No significant changes were observed in the best-corrected visual acuity. There were no complications related to treatment observed. CONCLUSION: In eyes with persistent SRF due to central serous chorioretinopathy, spironolactone significantly reduced both the SRF and the subfoveal choroidal thickness as compared with placebo.

Characterization of SLC26A9 in patients with CF-like lung disease.

Diffuse bronchiectasis is a common problem in respiratory clinics. We hypothesized that mutations in the solute carrier 26A9 (SLC26A9) gene, encoding for a chloride (Cl(-)) transporter mainly expressed in lungs, may lead to defects in mucociliary clearance. We describe two missense variants in the SLC26A9 gene in heterozygote patients presenting with diffuse idiopathic bronchiectasis : p.Arg575Trp, identified in a patient also heterozygote for p.Phe508del in the CFTR gene; and p.Val486Ile. Expression of both mutants in Xenopus laevis oocytes abolished SLC26A9-mediated Cl(-) conductance without decreasing protein membrane expression. Coexpression of CFTR with SLC26A9-p.Val486Ile resulted in a significant increase in the Cl(-) current induced by PKA stimulation, similar to that obtained in oocytes expressing CFTR and SLC26A9-WT. In contrast, coexpression of CFTR with SLC26A9-p.Arg575Trp inhibited SLC26A9-enhanced CFTR activation upon PKA. Further structure-function analyses led us to propose a site encompassing Arg575 in the SLC26A9-STAS domain for CFTR-SLC26A9 interaction. We hypothesize that SLC26A9-p.Arg575Trp prevented SLC26A9-mediated functional activation of CFTR by altering SLC26A9-CFTR interaction. Although we cannot confirm that these mutations by themselves are deleterious, we propose that they trigger the pathogenic role of a single CFTR mutation and provide insight into a novel mechanism of Cl(-) transport alteration across the respiratory mucosa, based on functional inhibition of CFTR.

The myeloid mineralocorticoid receptor regulates dermal angiogenesis and inflammation in glucocorticoid-induced impaired wound healing.

BACKGROUND AND PURPOSE: Delayed wound healing is among the deleterious consequences of over-activation of the mineralocorticoid receptor (MR) induced by topical dermocorticoids. The role of dermal inflammation and angiogenesis in the benefits of MR blockade is unknown. EXPERIMENTAL APPROACH: Skin wounds were made on C57Bl6 mice after topical pretreatment with the dermocorticoid clobetasol. The impact of topical MR blockade by canrenoate on inflammation, angiogenesis, and the wound macrophage phenotype was analysed 5 days post-wounding. Similar experiments were conducted on mice with genetic deletion of the MR in myeloid cells. KEY RESULTS: Topical inhibition of the MR with canrenoate improved delayed wound healing through the resolution of prolonged inflammation in glucocorticoid-pretreated mouse skin. This effect was associated with a higher ratio of anti-inflammatory macrophages versus pro-inflammatory macrophages in wounds treated by canrenoate. Furthermore, MR blockade led to upregulated expression of pro-angiogenic factors and improved impaired angiogenesis in wounds of glucocorticoid-pretreated skin. Finally, deletion of MR expression by myeloid cells reproduced the benefits of topical pharmacological MR blockade. CONCLUSION AND IMPLICATIONS: Topical MR antagonism facilitates the switching of macrophages towards an anti-inflammatory phenotype, which improves prolonged inflammation and induces angiogenesis to accelerate wound healing delayed by glucocorticoid treatment.

The endothelial mineralocorticoid receptor regulates vasoconstrictor tone and blood pressure.

Pathophysiological aldosterone (aldo)/mineralocorticoid receptor (MR) signaling has significant effects on the cardiovascular system, resulting in hypertension and cardiovascular remodeling; however, the specific contribution of the vascular MR to blood pressure regulation remains to be established. To address this question, we generated a mouse model with conditional overexpression of the MR in endothelial cells (MR-EC). In basal conditions, MR-EC mice developed moderate hypertension that could be reversed by canrenoate, a pharmacological MR antagonist. MR-EC mice presented increased contractile response of resistance arteries to vasoconstrictors (phenylephrine, thromboxane A(2) analog, angiotensin II, and endothelin 1) in the absence of vascular morphological alterations. The acute blood pressure response to angiotensin II or endothelin 1 infusion was increased in MR-EC mice compared with that in littermate controls. These observations demonstrate that enhanced MR activation in the endothelium generates an increase in blood pressure, independent of stimulation of renal tubular Na(+) transport by aldo/MR or direct activation of smooth muscle MR and establish one mechanism by which endothelial MR activation per se may contribute to impaired vascular reactivity.

The neuroretina is a novel mineralocorticoid target: aldosterone up-regulates ion and water channels in Müller glial cells.

Glucocorticoids reduce diabetic macular edema, but the mechanisms underlying glucocorticoid effects are imperfectly elucidated. Glucocorticoids may bind to glucocorticoid (GR) and mineralocorticoid (MR) receptors. We hypothesize that MR activation may influence retinal hydration. The effect of the MR agonist aldosterone (24 h) on ion/water channel expression (real-time PCR, Western blot, immunofluorescence) was investigated on cultured retinal Müller glial cells (RMGs, which contribute to fluid homeostasis in the retina), in Lewis rat retinal explants, and in retinas from aldosterone-injected eyes. We evidenced cell-specific expression of MR, GR, and 11-beta-hydroxysteroid dehydrogenase type II. Aldosterone significantly enhances expression of sodium and potassium channels ENaC-alpha (6.5-fold) and Kir4.1 (1.9-fold) through MR and GR occupancy, whereas aquaporin 4 (AQP4, 2.9-fold) up-regulation is MR-selective. Aldosterone intravitreous injection induces retinal swelling (24% increase compared to sham-injected eyes) and activation of RMGs. It promotes additional localization of Kir4.1 and AQP4 toward apical microvilli of RMGs. Our results highlight the mineralocorticoid-sensitivity of the neuroretina and show that aldosterone controls hydration of the healthy retina through regulation of ion/water channels expression in RMGs. These results provide a rationale for future investigations of abnormal MR signaling in the pathological retina.

Regulation of WNK1 expression by miR-192 and aldosterone.

WNK1 and WNK4 encode two members of the WNK serine-threonine kinase subfamily. Greater WNK1 expression associates with higher BP. A combination of promoters, enhancers, repressors, and insulators regulate WNK1 expression, but whether microRNAs also modulate WNK1 expression is unknown. Here, computational analysis revealed the presence of a target sequence for miR-192 and miR-215 at the same site in the 3' untranslated region of the ubiquitous L- and the kidney-specific KS-WNK1. We functionally validated this target sequence by transient transfection and reporter assays. Although we observed expression of both miRs along the distal nephron, only miR-192 regulated endogenous WNK1 ex vivo. Furthermore, a potassium load, sodium depletion, and aldosterone infusion each significantly reduced miR-192 expression in the kidney. Taken together, these results suggest a miR-driven mechanism of gene regulation by aldosterone and a role for miR-192 in the regulation of sodium and potassium balance in the kidney.

Nanostructured Dense Collagen-Polyester Composite Hydrogels as Amphiphilic Platforms for Drug Delivery.

Associating collagen with biodegradable hydrophobic polyesters constitutes a promising method for the design of medicated biomaterials. Current collagen-polyester composite hydrogels consisting of pre-formed polymeric particles encapsulated within a low concentrated collagen hydrogel suffer from poor physical properties and low drug loading. Herein, an amphiphilic composite platform associating dense collagen hydrogels and up to 50 wt% polyesters with different hydrophobicity and chain length is developed. An original method of fabrication is disclosed based on in situ nanoprecipitation of polyesters impregnated in a pre-formed 3D dense collagen network. Composites made of poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) but not polycaprolactone (PCL) exhibit improved mechanical properties compared to those of pure collagen dense hydrogels while keeping a high degree of hydration. Release kinetics of spironolactone, a lipophilic steroid used as a drug model, can be tuned over one month. No cytotoxicity of the composites is observed on fibroblasts and keratinocytes. Unlike the incorporation of pre-formed particles, the new process allows for both improved physical properties of collagen hydrogels and controlled drug delivery. The ease of fabrication, wide range of accessible compositions, and positive preliminary safety evaluations of these collagen-polyesters will favor their translation into clinics in wide areas such as drug delivery and tissue engineering.

The mineralocorticoid receptor as a novel player in skin biology: beyond the renal horizon?

The mineralocorticoid receptor (MR) and its ligand aldosterone regulate renal sodium reabsorption and blood pressure and much knowledge has been accumulated in MR physiopathology, cellular and molecular targets. In contrast, our understanding of this hormonal system in non-classical targets (heart, blood vessels, neurons, keratinocytes...) is limited, particularly in the mammalian skin. We review here the few available data that point on MR in the skin and that document cutaneous MR expression and function, based on mouse models and very limited observations in humans. Mice that overexpress the MR in the basal epidermal keratinocytes display developmental and post-natal abnormalities of the epidermis and hair follicle, raising exciting new questions regarding skin biology. The MR as a transcription factor may be an unexpected novel player in regulating keratinocyte and hair physiology and pathology. Because its activating ligand also includes glucocorticoids, that are widely used in dermatology, we propose that the MR may be also involved in the side-effects of corticoids, opening novel options for therapeutical intervention.

Evaluation of the collaborative network of highly correlating skin proteins and its change following treatment with glucocorticoids.

BACKGROUND: Glucocorticoids (GC) represent the core treatment modality for many inflammatory diseases. Its mode of action is difficult to grasp, not least because it includes direct modulation of many components of the extracellular matrix as well as complex anti-inflammatory effects. Protein expression profile of skin proteins is being changed with topical application of GC, however, the knowledge about singular markers in this regard is only patchy and collaboration is ill defined. MATERIAL/METHODS: Scar formation was observed under different doses of GC, which were locally applied on the back skin of mice (1 to 3 weeks). After euthanasia we analyzed protein expression of collagen I and III (picrosirius) in scar tissue together with 16 additional protein markers, which are involved in wound healing, with immunhistochemistry. For assessing GC's effect on co-expression we compared our results with a model of random figures to estimate how many significant correlations should be expected by chance. RESULTS: GC altered collagen and protein expression with distinct results in different areas of investigation. Most often we observed a reduced expression after application of low dose GC. In the scar infiltrate a multivariate analysis confirmed the significant impact of both GC concentrations. Calculation of Spearman's correlation coefficient similarly resulted in a significant impact of GC, and furthermore, offered the possibility to grasp the entire interactive profile in between all variables studied. The biological markers, which were connected by significant correlations could be arranged in a highly cross-linked network that involved most of the markers measured. A marker highly cross-linked with more than 3 significant correlations was indicated by a higher variation of all its correlations to the other variables, resulting in a standard deviation of > 0.2. CONCLUSION: In addition to immunohistochemical analysis of single protein markers multivariate analysis of co-expressions by use of correlation coefficients reveals the complexity of biological relationships and identifies complex biological effects of GC on skin scarring. Depiction of collaborative clusters will help to understand functional pathways. The functional importance of highly cross-linked proteins will have to be proven in subsequent studies.

Cutaneous Wound Healing in Diabetic Mice Is Improved by Topical Mineralocorticoid Receptor Blockade.

Skin ulcers resulting from impaired wound healing are a serious complication of diabetes. Unresolved inflammation, associated with the dysregulation of both the phenotype and function of macrophages, is involved in the poor healing of diabetic wounds. Here, we report that topical pharmacological inhibition of the mineralocorticoid receptor (MR) by canrenoate or MR small interfering RNA can resolve inflammation to improve delayed skin wound healing in diabetic mouse models; importantly, wounds from normal mice are unaffected. The beneficial effect of canrenoate is associated with an increased ratio of anti-inflammatory M2 macrophages to proinflammatory M1 macrophages in diabetic wounds. Furthermore, we show that MR blockade leads to downregulation of the MR target, LCN2, which may facilitate macrophage polarization toward the M2 phenotype and improve impaired angiogenesis in diabetic wounds. Indeed, diabetic LCN2-deficient mice showed improved wound healing associated with macrophage M2 polarization and angiogenesis. In addition, recombinant LCN2 protein prevented IL-4-induced macrophage switch from M1 to M2 phenotype. In conclusion, topical MR blockade accelerates skin wound healing in diabetic mice via LCN2 reduction, M2 macrophage polarization, prevention of inflammation, and induction of angiogenesis.

Mineralocorticoid receptor antagonism limits experimental choroidal neovascularization and structural changes associated with neovascular age-related macular degeneration.

Choroidal neovascularization (CNV) is a major cause of visual impairment in patients suffering from wet age-related macular degeneration (AMD), particularly when refractory to intraocular anti-VEGF injections. Here we report that treatment with the oral mineralocorticoid receptor (MR) antagonist spironolactone reduces signs of CNV in patients refractory to anti-VEGF treatment. In animal models of wet AMD, pharmacological inhibition of the MR pathway or endothelial-specific deletion of MR inhibits CNV through VEGF-independent mechanisms, in part through upregulation of the extracellular matrix protein decorin. Intravitreal injections of spironolactone-loaded microspheres and systemic delivery lead to similar reductions in CNV. Together, our work suggests MR inhibition as a novel therapeutic option for wet AMD patients unresponsive to anti-VEGF drugs.

Conditional glucocorticoid receptor expression in the heart induces atrio-ventricular block.

Corticosteroid hormones (aldosterone and glucocorticoids) and their receptors are now recognized as major modulators of cardiovascular pathophysiology, but their specific roles remain elusive. Glucocorticoid hormones (GCs), which are widely used to treat acute and chronic diseases, often have adverse cardiovascular effects such as heart failure, hypertension, atherosclerosis, or metabolic alterations. The direct effects of GC on the heart are difficult to evaluate, as changes in plasma GC concentrations have multiple consequences due to the ubiquitous expression of the glucocorticoid receptor (GR), resulting in secondary effects on cardiac function. We evaluated the effects of GR on the heart in a conditional mouse model in which the GR was overexpressed solely in cardiomyocytes. The transgenic mice displayed electrocardiogram (ECG) abnormalities: a long PQ interval, increased QRS and QTc duration as well as chronic atrio-ventricular block, without cardiac hypertrophy or fibrosis. The ECG alterations were reversible on GR expression shutoff. Isolated ventricular cardiomyocytes showed major ion channel remodeling, with decreases in I(Na), I(to), and I(Kslow) activity and changes in cell calcium homeostasis (increase in C(al), in Ca2+ transients and in sarcoplasmic reticulum Ca2+ load). This phenotype differs from that observed in mice overexpressing the mineralocorticoid receptor in the heart, which displayed ventricular arrhythmia. Our mouse model highlights novel effects of GR activation in the heart indicating that GR has direct and specific cardiac effects in the mouse.

11ß-HSD2 SUMOylation Modulates Cortisol-Induced Mineralocorticoid Receptor Nuclear Translocation Independently of Effects on Transactivation.

The enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) has an essential role in aldosterone target tissues, conferring aldosterone selectivity for the mineralocorticoid receptor (MR) by converting 11ß-hydroxyglucocorticoids to inactive 11-ketosteroids. Congenital deficiency of 11ß-HSD2 causes a form of salt-sensitive hypertension known as the syndrome of apparent mineralocorticoid excess. The disease phenotype, which ranges from mild to severe, correlates well with reduction in enzyme activity. Furthermore, polymorphisms in the 11ß-HSD2 coding gene (HSD11B2) have been linked to high blood pressure and salt sensitivity, major cardiovascular risk factors. 11ß-HSD2 expression is controlled by different factors such as cytokines, sex steroids, or vasopressin, but posttranslational modulation of its activity has not been explored. Analysis of 11ß-HSD2 sequence revealed a consensus site for conjugation of small ubiquitin-related modifier (SUMO) peptide, a major posttranslational regulatory event in several cellular processes. Our results demonstrate that 11ß-HSD2 is SUMOylated at lysine 266. Non-SUMOylatable mutant K266R showed slightly higher substrate affinity and decreased Vmax, but no effects on protein stability or subcellular localization. Despite mild changes in enzyme activity, mutant K266R was unable to prevent cortisol-dependent MR nuclear translocation. The same effect was achieved by coexpression of wild-type 11ß-HSD2 with sentrin-specific protease 1, a protease that catalyzes SUMO deconjugation. In the presence of 11ß-HSD2-K266R, increased nuclear MR localization did not correlate with increased response to cortisol or increased recruitment of transcriptional coregulators. Taken together, our data suggests that SUMOylation of 11ß-HSD2 at residue K266 modulates cortisol-mediated MR nuclear translocation independently of effects on transactivation.

Conditional mineralocorticoid receptor expression in the heart leads to life-threatening arrhythmias.

BACKGROUND: Life-threatening cardiac arrhythmia is a major source of mortality worldwide. Besides rare inherited monogenic diseases such as long-QT or Brugada syndromes, which reflect abnormalities in ion fluxes across cardiac ion channels as a final common pathway, arrhythmias are most frequently acquired and associated with heart disease. The mineralocorticoid hormone aldosterone is an important contributor to morbidity and mortality in heart failure, but its mechanisms of action are incompletely understood. METHODS AND RESULTS: To specifically assess the role of the mineralocorticoid receptor (MR) in the heart, in the absence of changes in aldosteronemia, we generated a transgenic mouse model with conditional cardiac-specific overexpression of the human MR. Mice exhibit a high rate of death prevented by spironolactone, an MR antagonist used in human therapy. Cardiac MR overexpression led to ion channel remodeling, resulting in prolonged ventricular repolarization at both the cellular and integrated levels and in severe ventricular arrhythmias. CONCLUSIONS: Our results indicate that cardiac MR triggers cardiac arrhythmias, suggesting novel opportunities for prevention of arrhythmia-related sudden death.

Histone Deacetylase 6-Controlled Hsp90 Acetylation Significantly Alters Mineralocorticoid Receptor Subcellular Dynamics But Not its Transcriptional Activity.

The mineralocorticoid receptor (MR) is a member of the nuclear receptor superfamily that transduces the biological effects of corticosteroids. Its best-characterized role is to enhance transepithelial sodium reabsorption in response to increased aldosterone levels. In addition, MR participates in other aldosterone- or glucocorticoid-controlled processes such as cardiovascular homeostasis, adipocyte differentiation or neurogenesis, and regulation of neuronal activity in the hippocampus. Like other steroid receptors, MR forms cytosolic heterocomplexes with heat shock protein (Hsp) 90), Hsp70, and other proteins such as immunophilins. Interaction with Hsp90 is thought to maintain MR in a ligand-binding competent conformation and to regulate ligand-dependent and -independent nucleocytoplasmatic shuttling. It has previously been shown that acetylation of residue K295 in Hsp90 regulates its interaction with the androgen receptor and glucocorticoid receptor (GR). In this work we hypothesized that Hsp90 acetylation provides a regulatory step to modulate MR cellular dynamics and activity. We used Hsp90 acetylation mimic mutant K295Q or nonacetylatable mutant K295R to examine whether MR nucleocytoplasmatic shuttling and gene transactivation are affected. Furthermore, we manipulated endogenous Hsp90 acetylation levels by controlling expression or activity of histone deacetylase 6 (HDAC6), the enzyme responsible for deacetylation of Hsp90-K295. Our data demonstrates that HDAC6-mediated Hsp90 acetylation regulates MR cellular dynamics but it does not alter its function. This stands in contrast with the down-regulation of GR by HDAC6, suggesting that Hsp90 acetylation may play a role in balancing relative MR and GR activity when both factors are co-expressed in the same cell.

Re-Epithelialization of Pathological Cutaneous Wounds Is Improved by Local Mineralocorticoid Receptor Antagonism.

Impaired cutaneous wound healing is a social burden. It occurs as a consequence of glucocorticoid treatment in several pathologies. Glucocorticoids (GC) bind not only to the glucocorticoid receptor but also to the mineralocorticoid receptor (MR), both expressed by keratinocytes. In addition to its beneficial effects through the glucocorticoid receptor, GC exposure may lead to inappropriate MR occupancy. We hypothesized that dermatological use of MR antagonists (MRA) might be beneficial by overcoming the negative impact of GC treatment on pathological wounds. The potent GC clobetasol, applied as an ointment to mouse skin, or added to cultured human skin explants, induced delayed wound closure and outgrowth of epidermis with reduced proliferation of keratinocytes. Delayed wound re-epithelialization was rescued by local MRA application. Normal skin was unaffected by MRA. The benefit of MR blockade is explained by the increased expression of MR in clobetasol-treated mouse skin. Blockade of the epithelial sodium channel by phenamil also rescued cultured human skin explants from GC-impaired growth of the epidermis. MRA application over post-biopsy wounds of clobetasol-treated skin zones of healthy volunteers (from the Interest of Topical Spironolactone's Administration to Prevent Corticoid-induced Epidermal Atrophy clinical trial) also accelerated wound closure. In conclusion, we propose repositioning MRA for cutaneous application to improve delayed wound closure occurring in pathology.

Aldosterone promotes cardiac endothelial cell proliferation in vivo.

BACKGROUND: Experimentally, aldosterone in association with NaCl induces cardiac fibrosis, oxidative stress, and inflammation through mineralocorticoid receptor activation; however, the biological processes regulated by aldosterone alone in the heart remain to be identified. METHODS AND RESULTS: Mice were treated for 7 days with aldosterone, and then cardiac transcriptome was analyzed. Aldosterone regulated 60 transcripts (51 upregulated and 9 downregulated) in the heart (fold change ≥1.5, false discovery rate <0.01). To identify the biological processes modulated by aldosterone, a gene ontology analysis was performed. The majority of aldosterone-regulated genes were involved in cell division. The cardiac Ki-67 index (an index of proliferation) of aldosterone-treated mice was higher than that of nontreated mice, confirming microarray predictions. Costaining of Ki-67 with vinculin, CD68, α-smooth muscle actin, CD31, or caveolin 1 revealed that the cycling cells were essentially endothelial cells. Aldosterone-induced mineralocorticoid receptor-dependent proliferation was confirmed ex vivo in human endothelial cells. Moreover, pharmacological-specific blockade of mineralocorticoid receptor by eplerenone inhibited endothelial cell proliferation in a preclinical model of heart failure (transverse aortic constriction). CONCLUSIONS: Aldosterone modulates cardiac gene expression and induces the proliferation of cardiac endothelial cells in vivo.