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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

ABSTRACT Diffuse bronchiectasis is a common problem in respiratory clinics. We hypothesized that mutations in the solute carrier 26A9 ( SLC26 A9) 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 SLC26 A9 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 SLC26 A9-mediated Cl− conductance without decreasing protein membrane expression. Coexpression of CFTR with SLC26 A9-p.Val486Ile resulted in a significant increase in the Cl− current induced by PKA stimulation, similar to that obtained in oocytes expressing CFTR and SLC26 A9- WT. In contrast, coexpression of CFTR with SLC26 A9-p.Arg575Trp inhibited SLC26 A9-enhanced CFTR activation upon PKA. Further structure-function analyses led us to propose a site encompassing Arg575 in the SLC26 A9- STAS domain for CFTR- SLC26 A9 interaction. We hypothesize that SLC26 A9-p.Arg575Trp prevented SLC26 A9-mediated functional activation of CFTR by altering SLC26 A9- 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. [ABSTRACT FROM AUTHOR]

We have previously shown that the eye is a mineralocorticoid-sensitive organ and we now question the role of mineralocorticoid receptor (MR) in ocular inflammation. The endotoxin-induced uveitis (EIU), a rat model of human intraocular inflammation, was induced by systemic administration of lipopolysaccharide (LPS). Evaluations were made 6 and 24 hours after intraocular injection of aldosterone (simultaneous to LPS injection). Three hours after onset of EIU, the MR and the glucocorticoid metabolizing enzyme 11-beta hydroxysteroid dehydrogenase type 2 (11 β-HSD2) expression were down-regulated in iris/ciliary body and the corticosterone concentration was increased in aqueous humor, altering the normal MR/glucocorticoid receptor (GR) balance. At 24 hours, the GR expression was also decreased. In EIU, aldosterone reduced the intensity of clinical inflammation in a dose-dependent manner. The clinical benefit of aldosterone was abrogated in the presence of the MR antagonist (RU26752) and only partially with the GR antagonist (RU38486). Aldosterone reduced the release of inflammatory mediators (6 and 24 hours: TNF-α, IFN-γ, MIP-1 α) in aqueous humor and the number of activated microglia/macrophages. Aldosterone partly prevented the uveitis-induced MR down-regulation. These results suggest that MR expression and activation in iris/ciliary body could protect the ocular structures against damages induced by EIU. [ABSTRACT FROM AUTHOR]

Experimental and clinical studies have shown that aldosterone/mineralocorticoid receptor (MR) activation has deleterious effects in the cardiovascular system; however, the signalling pathways involved in the pathophysiological effects of aldosterone/MR in vivo are not fully understood. Several in vitro studies suggest that Epidermal Growth Factor Receptor (EGFR) plays a role in the cardiovascular effects of aldosterone. This hypothesis remains to be demonstrated in vivo. To investigate this question, we analyzed the molecular and functional consequences of aldosterone exposure in a transgenic mouse model with constitutive cardiomyocyte-specific overexpression of a mutant EGFR acting as a dominant negative protein (DN-EGFR). As previously reported, Angiotensin II-mediated cardiac remodelling was prevented in DN-EGFR mice. However, when chronic MR activation was induced by aldosterone-salt-uninephrectomy, cardiac hypertrophy was similar between control littermates and DN-EGFR. In the same way, mRNA expression of markers of cardiac remodelling such as ANF, BNF or b-Myosin Heavy Chain as well as Collagen 1a and 3a was similarly induced in DN-EGFR mice and their CT littermates. Our findings confirm the role of EGFR in AngII mediated cardiac hypertrophy, and highlight that EGFR is not involved in vivo in the damaging effects of aldosterone on cardiac function and remodelling. [ABSTRACT FROM AUTHOR]

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 A2 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. [ABSTRACT FROM AUTHOR]

Please cite this paper as: The mineralocorticoid receptor as a novel player in skin biology: beyond the renal horizon? Experimental Dermatology 2010; 19: 100–107. 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. [ABSTRACT FROM AUTHOR]

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 antiinflammatory 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. [ABSTRACT FROM AUTHOR]

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 alteratious. 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 INa, Ito, and IKslow activity and changes in cell calcium homeostasis (increase in Cal, 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. [ABSTRACT FROM AUTHOR]

Androgens are known to regulate gene expression in the renal proximal tubule. Whether the distal parts of the nephron, in particular the cortical collecting duct (CCD), where sodium reabsorption is controlled tightly by aldosterone, are also targets for these hormones is unknown. Real-time PCR on rat isolated renal tubules showed that androgen receptor mRNA is not only, as expected, expressed in the proximal tubule, but also in the CCD. We examined the effects of adrenalectomy (ADX) plus castration and in-vivo administration of the active metabolite of testosterone, dihydrotestosterone (DHT), on the intrarenal expression of N-myc downstream regulated gene 2 ( NDRG2), an early aldosterone-induced gene located specifically in the CCD. NDRG2 belongs to a newly identified family of differentiation-related genes; although the function of these genes remains elusive, regulation of NDRG1 by androgens has been suggested. Castration plus ADX increased NDRG2 expression (RNase protection assay) significantly in the whole kidney, and a single i.p. injection of DHT caused a significant decrease in NDRG2 expression 4 h afterwards (up to 24 h). Furthermore, real-time PCR on microdissected tubules revealed that the decrease in NDRG2 expression caused by DHT is restricted to the CCD. Thus, aldosterone and androgens have opposite effects on NDRG2 expression in the renal CCD. These results are the first demonstration of androgen-dependent gene regulation in the rat renal CCD. [ABSTRACT FROM AUTHOR]

The renal collecting duct plays a key role in control of ion and fluid homeostasis. Genes encoding for ion transporters, hormone receptors, or regulatory proteins specifically expressed in the collecting duct are mutated in several genetic diseases with altered blood pressure. Suitable cellular models expressing genes in a conditional way should represent attractive systems for structure-function analyses and generation of appropriate physiopathological models of related diseases. However, generation of such systems remains laborious and quite inefficient. We adapted and improved a conditional Cre-lox-inducible system in the highly differentiated aldosterone-sensitive rat cortical collecting duct (RCCD2) cell line. The inducible MerCreMer recombinase allowed tight control and high levels of transgene expression, whereas flanking a selection marker with two loxP sites strongly improved the selection procedure. We have used this system to conditionally express an enhanced green fluorescent protein-tagged human mineralocorticoid receptor. In the future, this will allow structure-function analyses as well as mineralocorticoid receptor trafficking studies in these epithelial cells, which retain the features of the native collecting duct. Improvements in the conditional Cre-lox expression system have potentially wide applications in other epithelial or nonepithelial cell lines. [ABSTRACT FROM AUTHOR]

Ubiquitination of proteins such as ion transporters appears to be an important process in the regulation of their membrane expression. Recently, using two-hybrid screening, we have selected a potential partner for the α-subunit of the amiloride-sensitive epithelial sodium channel (ENaC): the WWP1 protein, a ubiquitin ligase belonging to the Nedd4 family. To establish whether WWP1 is co-expressed with ENaC, we employed in situ hybridisation, immunohistochemistry and Western blotting to determine the expression of WWP1 in various tissues and cell lines, including those known to express ENaC. As expected, WWP1 was expressed, like ENaC, in the bronchiolar epithelium. However it was also present in the proximal colon and the proximal part of the nephron (where ENaC is not expressed) and absent in the distal parts of the nephron (where ENaC is expressed abundantly). These results suggest that other channels or transport proteins, containing specific domains, such as PY motifs, could be the targets for regulation by WWP1. [ABSTRACT FROM AUTHOR]

Like the γ-subunit of Na-K-ATPase, the corticosteroid hormone-induced factor (CHIF) is a member of the FXYD family of one-transmembrane-segment proteins. Both CHIF and two splice variants of γ, γ[sub a] and ≈[sub b], are expressed in the kidney. Immunolocalization experiments demonstrate mutually exclusive expression of CHIF and γ in different nephron segments. Specific coimmunoprecipitation experiments demonstrate the existence in kidney membranes of the complexes α/β/γ[sub a], α/β/γ[sub b], and α/β/CHIF and exclude mixed complexes such as α/β/γ[sub a]/γ[sub b] and α/β/γ/CHIF. CHIF has been expressed in HeLa cells harboring the rat α[sub 1]-subunit of Na-K-ATPase. [sup 86]Rb flux experiments demonstrate that CHIF induces a twoto threefold increase in apparent affinity for cytoplasmic Na (K'[sub Na]) but does not affect affinity for extracellular K (Rb) ions (K'[sub K]) or V[sub max]. Measurements of Na-K-ATPase using isolated membranes show similar but smaller effects of CHIF on K'[sub Na], whereas K'[sub K] and K'[sub ATP] are unaffected. The functional effects of CHIF differ from those of γ. An implication of these findings is that other FXYD proteins could act as tissuespecific modulators of Na-K-ATPase. [ABSTRACT FROM AUTHOR]

Determines the conditional expression of an antisense messenger RNA of the mineralocorticoid receptor (MR) in cardiomyocytes. Role of renin-angiotensin-aldosterone system in cardiac failure; Link between cardiac failure and fibrosis; Pathogenesis of the cardiomyopathy.

Examines the tetracycline-inducible gene expression in renal collecting duct (CD) cells from transgenic mice. Role of renal CD in the control of ion and fluid homeostasis; Description of genetic diseases involving gene mutations for ion transport or hormone receptors expressed in CD; Development of a CD cell line using a tetracycline-inducible system.

Presents information on a study which examined the multiple aspects of mineralocorticoid selectivity in renal sodium reabsorptiopn. Background on corticosteroid hormones; Physiological responses of aldosterone and glucocorticoid hormones; Role of mineralocorticoid and glucocorticoid receptors in hormonal selectivity; Dimerization of steroid receptors.

Intracortical distribution of blood flow was studied in the rabbit kidney with 15 μm labelled microspheres (M) injected into the left ventricule. M injection did not alter renal function. Thanks to arterial filling of left kidney with silicone rubber, efferent vascular patterns of the glomeruli could be precisely identified. Glomeruli of different populations were sampled by microdissection and their radioactivity measured. Assuming that intracortical distribution of M reflected distribution of flow to the glomeruli, individual glomerular blood flows (GBF) were determined. In hydropenic rabbits, GBF was higher in deep glomeruli providing vasa recta (G4) (193±14 nl·min) than in most other superficial (G1 and G2) and deep glomeruli (G3) (190±27, 113±10 and 127±9 nl·min respectively; $$\bar m \pm SEM, n = 6)$$ . The exact significance of GBF found in superficial glomeruli with straight ascending efferent arterioles supplying aglomerular suscapsular cortex (G1) was questioned because of the possible axial streaming of spheres. Afferent medulary blood flow was calculated to represent 9.0±0.9% of total renal blood flow. [ABSTRACT FROM AUTHOR]

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. Current treatments for age-related neovascular macular degeneration (nAMD) suffer from limited efficacy. Here, Zhao et al. show that pharmacological inhibition or genetic deletion of the mineralocorticoid receptor (MR) limits choroidal neovascularisation in rodents, and show in a pilot clinical study that targeting the MR pathway may provide clinical benefits in nAMD patiens. [ABSTRACT FROM AUTHOR]

The authors discuss aspects of skin biology and the role of mineralocorticoid receptor in dermatology. They think that glucocorticoids (GR) have beneficial effects but may also have deleterious side effects like skin atrophy and delayed wound healing. The authors believe that mineralocorticoid receptor (MR) is a nuclear receptor that share structural and functional similarities with GR.