Myeloid Mineralocorticoid Receptor Activation Contributes to Progressive Kidney Disease
01 Oct 2014-Journal of The American Society of Nephrology (American Society of Nephrology)-Vol. 25, Iss: 10, pp 2231-2240
TL;DR: Myeloid deficiency of MR provides protection similar to eplerenone in this disease, and MR signaling in myeloid cells, but not podocytes, contributes to the progression of renal injury in mouse GN.
Abstract: Clinical and experimental studies have shown that mineralocorticoid receptor (MR) antagonists substantially reduce kidney injury. However, the specific cellular targets and mechanisms by which MR antagonists protect against kidney injury must be identified. We used conditional gene deletion of MR signaling in myeloid cells (MR flox/flox LysM Cre mice; MyMRKO) or podocytes (MR flox/flox Pod Cre mice; PodMRKO) to establish the role of MR in these cell types in the development of mouse GN. Accelerated anti–glomerular basement membrane GN was examined in groups of mice: MyMRKO, PodMRKO, wild-type (WT) littermates, and WT mice receiving eplerenone (100 mg/kg twice a day; EPL-treated). At day 15 of disease, WT mice had glomerular crescents (37%±5%), severe proteinuria, and a 6-fold increase in serum cystatin-C. MyMRKO, PodMRKO, and EPL-treated mice with GN displayed proteinuria similar to that in these disease controls. However, MyMRKO and EPL-treated groups had a 35% reduction in serum cystatin-C levels and reduced crescent numbers compared with WT mice, whereas PodMRKO mice were not protected. The protection observed in MyMRKO mice appeared to result predominantly from reduced recruitment of macrophages and neutrophils into the inflamed kidney. Suppression of kidney leukocyte accumulation in MyMRKO mice correlated with reductions in gene expression of proinflammatory molecules (TNF- α , inducible nitric oxide synthase, chemokine (C-C motif) ligand 2, matrix metalloproteinase - 12), tubular damage, and renal fibrosis and was similar in EPL-treated mice. In conclusion, MR signaling in myeloid cells, but not podocytes, contributes to the progression of renal injury in mouse GN, and myeloid deficiency of MR provides protection similar to eplerenone in this disease.
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TL;DR: The induction of MMT, via the Src-centric regulatory network mediated by transforming growth factor-β1 (TGFβ1)–Smad3, serves as a key checkpoint in the progression of chronic inflammation to renal fibrosis.
Abstract: Macrophages have important roles in immune surveillance and in the maintenance of kidney homeostasis; their response to renal injury varies enormously depending on the nature and duration of the insult. Macrophages can adopt a variety of phenotypes: at one extreme, M1 pro-inflammatory cells contribute to infection clearance but can also promote renal injury; at the other extreme, M2 anti-inflammatory cells have a reparative phenotype and can contribute to the resolution phase of the response to injury. In addition, bone marrow monocytes can differentiate into myeloid-derived suppressor cells that can regulate T cell immunity in the kidney. However, macrophages can also promote renal fibrosis, a major driver of progression to end-stage renal disease, and the CD206+ subset of M2 macrophages is strongly associated with renal fibrosis in both human and experimental diseases. Myofibroblasts are important contributors to renal fibrosis and recent studies provide evidence that macrophages recruited from the bone marrow can transition directly into myofibroblasts within the injured kidney. This process is termed macrophage-to-myofibroblast transition (MMT) and is driven by transforming growth factor-β1 (TGFβ1)-Smad3 signalling via a Src-centric regulatory network. MMT may serve as a key checkpoint for the progression of chronic inflammation into pathogenic fibrosis.
212 citations
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TL;DR: Excess mineralocorticoid signaling now appears deleterious in the progression of pathologies that may lead to end-stage organ failure and could therefore benefit from the repositioning of pharmacological MR antagonists.
Abstract: The mineralocorticoid receptor (MR) and its ligand aldosterone are the principal modulators of hormone-regulated renal sodium reabsorption. In addition to the kidney, there are several other cells and organs expressing MR, in which its activation mediates pathologic changes, indicating potential therapeutic applications of pharmacological MR antagonism. Steroidal MR antagonists have been used for decades to fight hypertension and more recently heart failure. New therapeutic indications are now arising, and nonsteroidal MR antagonists are currently under development. This review is focused on nonclassic MR targets in cardiac, vascular, renal, metabolic, ocular, and cutaneous diseases. The MR, associated with other risk factors, is involved in organ fibrosis, inflammation, oxidative stress, and aging; for example, in the kidney and heart MR mediates hormonal tissue-specific ion channel regulation. Genetic and epigenetic modifications of MR expression/activity that have been documented in hypertension may also present significant risk factors in other diseases and be susceptible to MR antagonism. Excess mineralocorticoid signaling, mediated by aldosterone or glucocorticoids binding, now appears deleterious in the progression of pathologies that may lead to end-stage organ failure and could therefore benefit from the repositioning of pharmacological MR antagonists.
183 citations
Cites background from "Myeloid Mineralocorticoid Receptor ..."
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TL;DR: The available preclinical and clinical data support a benefit of using MRAs in CKD, an approach that should be further explored in future clinical trials.
Abstract: Chronic kidney disease (CKD) represents a global health concern, and its prevalence is increasing. The ultimate therapeutic option for CKD is kidney transplantation. However, the use of drugs that target specific pathways to delay or halt CKD progression, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and sodium-glucose co-transporter-2 (SGLT-2) inhibitors is limited in clinical practice. Mineralocorticoid receptor activation in nonclassical tissues, such as the endothelium, smooth muscle cells, inflammatory cells, podocytes, and fibroblasts may have deleterious effects on kidney structure and function. Several preclinical studies have shown that mineralocorticoid receptor antagonists (MRAs) ameliorate or cure kidney injury and dysfunction in different models of kidney disease. In this review, we present the preclinical evidence showing a benefit of MRAs in acute kidney injury, the transition from acute kidney injury to CKD, hypertensive and diabetic nephropathy, glomerulonephritis, and kidney toxicity induced by calcineurin inhibitors. We also discuss the molecular mechanisms responsible for renoprotection related to MRAs that lead to reduced oxidative stress, inflammation, fibrosis, and hemodynamic alterations. The available clinical data support a benefit of MRA in reducing proteinuria in diabetic kidney disease and improving cardiovascular outcomes in CKD patients. Moreover, a benefit of MRAs in kidney transplantation has also been observed. The past and present clinical trials describing the effect of MRAs on kidney injury are presented, and the risk of hyperkalemia and use of other options, such as potassium binding agents or nonsteroidal MRAs, are also addressed. Altogether, the available preclinical and clinical data support a benefit of using MRAs in CKD, an approach that should be further explored in future clinical trials.
64 citations
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TL;DR: In this article, the role of aldosterone in podocyte injury has been explored in diabetic nephropathy (DN) and showed that mineralocorticoid receptor (MCR) blocker reduces proteinuria.
Abstract: Previous studies have shown that mineralocorticoid receptor (MCR) blocker reduces proteinuria in diabetic nephropathy (DN), but the role of aldosterone in podocyte injury has never been explored in...
58 citations
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TL;DR: Novel, potent, and selective non-steroidal MRAs (third generation) were identified in drug discovery campaigns and a few entered clinical development recently, one of these is finerenone with different physicochemical, pharmacokinetics, and pharmacological properties in comparison with the steroidal MRAs.
Abstract: Characterization of mice with cell-specific deletion or overexpression of the mineralocorticoid receptor (MR) shed a new light on its role in health and disease. Pathophysiological MR activation contributes to a plethora of deleterious molecular mechanisms in the development of cardiorenal diseases like chronic kidney disease (CKD) and heart failure (HF). Accordingly, the available steroidal MR antagonists (MRAs) spironolactone (first generation MRA) and eplerenone (second generation MRA) have been shown to be effective in reducing cardiovascular (CV) mortality and morbidity in patients with chronic HF and a reduced left ventricular ejection fraction (HFrEF). However, they remain underutilized, in large part owing to the risk inducing severe adverse events including hyperkalemia and worsening of kidney function, particularly when given on top of inhibitors of the renin angiotensin system (RAS) to patients with concomitant kidney dysfunction. Novel, potent, and selective non-steroidal MRAs (third generation) were identified in drug discovery campaigns and a few entered clinical development recently. One of these is finerenone with different physicochemical, pharmacokinetics, and pharmacological properties in comparison with the steroidal MRAs. Available data from five clinical phase II trials with finerenone in more than 2,000 patients with HF and additional CKD and/or diabetes as well as in patients with diabetic kidney disease demonstrated that neither hyperkalemia nor reductions in kidney function were limiting factors to its use. Moreover, finerenone demonstrated a nominally improved outcome compared to eplerenone in a phase IIb trial with 1,066 patients with HFrEF and concomitant type 2 diabetes mellitus (T2DM) and/or CKD.
53 citations
References
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TL;DR: The method was applicable also to newborn mice, which allows for the isolation of immature developmental stage glomeruli and makes feasible transcript profiling and proteomic analysis of the developing, healthy and diseased mouse glomerulus.
Abstract: Here we report a new isolation method for mouse glomeruli. The method is fast and simple and allows for the isolation of virtually all glomeruli present in the adult mouse kidney with minimal contamination of nonglomerular cells. Mice were perfused through the heart with magnetic 4.5- micro m diameter Dynabeads. Kidneys were minced into small pieces, digested by collagenase, filtered, and collected using a magnet. The number of glomeruli retrieved from one adult mouse was 20,131 +/- 4699 (mean +/- SD, n = 14) with a purity of 97.5 +/- 1.7%. The isolated glomeruli retained intact morphology, as confirmed by light and electron microscopy, as well as intact mRNA integrity, as confirmed by Northern blot analysis. The method was applicable also to newborn mice, which allows for the isolation of immature developmental stage glomeruli. This method makes feasible transcript profiling and proteomic analysis of the developing, healthy and diseased mouse glomerulus.
473 citations
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TL;DR: In this article, the effects of aldosterone on podocyte, a key player of the glomerular filtration barrier, were investigated in uninephrectomized rats and fed a high-salt diet, where the podocyte injury was accompanied by renal reduced nicotinamide-adenine dinucleotide phosphate oxidase activation, increased oxidative stress, and enhanced expression of Sgk1.
Abstract: Accumulating evidence suggests that mineralocorticoid receptor blockade effectively reduces proteinuria in hypertensive patients. However, the mechanism of the antiproteinuric effect remains elusive. In this study, we investigated the effects of aldosterone on podocyte, a key player of the glomerular filtration barrier. Uninephrectomized rats were continuously infused with aldosterone and fed a high-salt diet. Aldosterone induced proteinuria progressively, associated with blood pressure elevation. Notably, gene expressions of podocyte-associated molecules nephrin and podocin were markedly decreased in aldosterone-infused rats at 2 weeks, with a gradual decrease thereafter. Immunohistochemical studies and electron microscopy confirmed the podocyte damage. Podocyte injury was accompanied by renal reduced nicotinamide-adenine dinucleotide phosphate oxidase activation, increased oxidative stress, and enhanced expression of aldosterone effector kinase Sgk1. Treatment with eplerenone, a selective aldosterone receptor blocker, almost completely prevented podocyte damage and proteinuria, with normalization of elevated reduced nicotinamide-adenine dinucleotide phosphate oxidase activity. In addition, proteinuria, podocyte damage, and Sgk1 upregulation were significantly alleviated by tempol, a membrane-permeable superoxide dismutase, suggesting the pathogenic role of oxidative stress. Although hydralazine treatment almost normalized blood pressure, it failed to improve proteinuria and podocyte damage. In cultured podocytes with consistent expression of mineralocorticoid receptor, aldosterone stimulated membrane translocation of reduced nicotinamide-adenine dinucleotide phosphate oxidase cytosolic components and oxidative stress generation in podocytes. Furthermore, aldosterone enhanced the expression of Sgk1, which was inhibited by mineralocorticoid receptor antagonist and tempol. In conclusion, podocytes are injured at the early stage in aldosterone-infused rats, resulting in the occurrence of proteinuria. Aldosterone can directly modulate podocyte function, possibly through the induction of oxidative stress and Sgk1.
307 citations
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TL;DR: It is shown that myeloid MR is an important control point in macrophage polarization and that the function of MR on myeloids cells likely represents a conserved ancestral MR function that is integrated in a transcriptional network with PPARgamma and glucocorticoid receptor.
Abstract: Inappropriate excess of the steroid hormone aldosterone, which is a mineralocorticoid receptor (MR) agonist, is associated with increased inflammation and risk of cardiovascular disease. MR antagonists are cardioprotective and antiinflammatory in vivo, and evidence suggests that they mediate these effects in part by aldosterone-independent mechanisms. Here we have shown that MR on myeloid cells is necessary for efficient classical macrophage activation by proinflammatory cytokines. Macrophages from mice lacking MR in myeloid cells (referred to herein as MyMRKO mice) exhibited a transcription profile of alternative activation. In vitro, MR deficiency synergized with inducers of alternatively activated macrophages (for example, IL-4 and agonists of PPARgamma and the glucocorticoid receptor) to enhance alternative activation. In vivo, MR deficiency in macrophages mimicked the effects of MR antagonists and protected against cardiac hypertrophy, fibrosis, and vascular damage caused by L-NAME/Ang II. Increased blood pressure and heart rates and decreased circadian variation were observed during treatment of MyMRKO mice with L-NAME/Ang II. We conclude that myeloid MR is an important control point in macrophage polarization and that the function of MR on myeloid cells likely represents a conserved ancestral MR function that is integrated in a transcriptional network with PPARgamma and glucocorticoid receptor. Furthermore, myeloid MR is critical for blood pressure control and for hypertrophic and fibrotic responses in the mouse heart and aorta.
294 citations
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TL;DR: A transgenic mouse line that expresses Cre recombinase exclusively in podocytes is reported, and Histological analysis of the kidneys showed that β‐gal expression was confined to podocytes.
Abstract: We report a transgenic mouse line that expresses Cre recombinase exclusively in podocytes. Twenty- four transgenic founders were generated in which Cre recombinase was placed under the regulation of a 2.5-kb fragment of the human NPHS2 promoter. Previously, this fragment was shown to drive beta-galactosidase (beta-gal) expression exclusively in podocytes of transgenic mice. For analysis, founder mice were bred with ROSA26 mice, a reporter line that expresses beta-gal in cells that undergo Cre recombination. Eight of 24 founder lines were found to express beta-gal exclusively in the kidney. Histological analysis of the kidneys showed that beta-gal expression was confined to podocytes. Cre recombination occurred during the capillary loop stage in glomerular development. No evidence for Cre recombination was detected in any of 14 other tissues examined.
274 citations
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TL;DR: It is suggested that spironolactone safely adds to the reno- and cardiovascular protective benefits of treatment with maximally recommended doses of ACE inhibitor and ARB by reducing albuminuria and blood pressure in type 2 diabetic patients with nephropathy.
Abstract: OBJECTIVE —The objective of this study was to evaluate the safety and short-term effect of adding spironolactone to conventional antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor or an angiotensin II receptor blocker (ARB) on albuminuria and blood pressure in type 2 diabetic patients with nephropathy. RESEARCH DESIGN AND METHODS —Twenty-one type 2 diabetic patients with nephropathy were enrolled in a randomized, double-masked, cross-over study. Patients were treated in random order with spironolactone 25 mg once daily and matched placebo for 8 weeks, respectively, in addition to ongoing antihypertensive treatment including diuretics and maximally recommended doses of an ACE inhibitor and/or an ARB. At the end of each treatment period, albuminuria, 24-h ambulatory blood pressure (ABP), and glomerular filtration rate (GFR) were determined. RESULTS —During the addition of placebo, values were as follows: albuminuria (geometric mean [range]) 1,566 [655–7,762] mg/24 h, ABP (mean ± SE) 138 ± 3/71 ± 1 mmHg, and GFR (mean ± SE) 74 ± 6 ml/min per 1.73 m 2 . During the addition of spironolactone, albuminuria was reduced by 33% (95% CI 25–41) ( P P P r = 0.19, P = 0.42) or diastolic 24-h ABP ( r = 0.01, P = 0.96). Spironolactone treatment induced an insignificant reversible reduction in GFR of 3 ml/min per 1.73 m 2 (−0.3 to 6) ( P = 0.08). One patient was excluded from the study due to hyperkalemia. Otherwise treatment was well tolerated. CONCLUSIONS —Our study suggests that spironolactone safely adds to the reno- and cardiovascular protective benefits of treatment with maximally recommended doses of ACE inhibitor and ARB by reducing albuminuria and blood pressure in type 2 diabetic patients with nephropathy.
264 citations