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: Syk activation is prominent in infiltrating myeloids cells in human rapidly progressive glomerulonephritis, and functional studies demonstrate that Syk deletion in myeloid cells is protective in mouse nephrotoxic serum nephritis.
Abstract: Antibody-dependent activation of myeloid cells within the glomerulus plays a central role in rapidly progressive forms of glomerulonephritis. The spleen tyrosine kinase (Syk) is expressed by all leukocytes, except mature T cells, and is required for signalling via the B-cell receptor, Fc receptors, and some integrins. Syk has been proposed as a therapeutic target in glomerulonephritis. However, little is known of Syk activation in human kidney disease, while studies in experimental glomerulonephritis using non-selective Syk inhibitors require validation via conditional gene deletion. The current study addressed both of these important points. Syk activation (Tyr(525/526) phosphorylation) was examined in a cohort of 96 patients with different glomerulonephritides. Syk activation was evident in infiltrating leukocytes, mainly neutrophils and macrophages, in 36/40 cases of rapidly progressive glomerulonephritis. In contrast, non-proliferative diseases showed little or no Syk activation. Glomerular and interstitial cells exhibiting Syk activation correlated with renal function and systemic inflammation. Next, we examined mice with conditional Syk gene deletion in myeloid cells (Syk(My) ) versus Syk(f/f) littermate controls in nephrotoxic serum nephritis - a model of rapidly progressive glomerulonephritis. Control Syk(f/f) mice featured a transient neutrophil influx at 3 h and severe disease on day 9 of nephrotoxic serum nephritis, with crescent formation, macrophage infiltration, inflammation, kidney fibrosis, and renal dysfunction. In contrast, Syk(My) mice had significantly reduced neutrophil and macrophage infiltration despite equivalent glomerular deposition of humoral reactants. Syk(My) mice exhibited reduced crescent formation, inflammation, and fibrosis, with improved renal function on day 9 of nephrotoxic serum nephritis. In conclusion, Syk activation is prominent in infiltrating myeloid cells in human rapidly progressive glomerulonephritis, and functional studies demonstrate that Syk deletion in myeloid cells is protective in mouse nephrotoxic serum nephritis.
16 citations
Cites methods from "Myeloid Mineralocorticoid Receptor ..."
...Immunoperoxidase staining of mouse tissues for p-c-Jun (Ser 63), collagen IV, and α-smooth muscle actin used formalin-fixed paraffin sections, whereas staining for CD68, neutrophils, CD4+ T cells, and CD41+ platelets was performed on paraformaldehyde-fixed cryostat sections as described previously [24,25]....
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...Nephrotoxic serum nephritis (NTN) was induced in Sykf/f and littermate control SykMy mice by subcutaneous injection of sheep IgG in Freund’s complete adjuvant, followed 4 days later (day 0) by intravenous injection of sheep anti-mouse GBM serum [24]....
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TL;DR: In this article, the authors showed that endogenous MMP-12 facilitates macrophage accumulation and activation in anti-GBM glomerulonephritis which is required for glomerular crescent formation, Bowman's capsule rupture, tubular damage and renal function decline.
Abstract: Aim
MMP-12 (macrophage elastase) is an enzyme that can cleave various extracellular matrix proteins and is required for macrophage infiltration and pulmonary fibrosis in experimental emphysema. We have shown previously that MMP-12 is highly up-regulated in experimental anti-glomerular basement membrane (GBM) disease. The aim of this study was to determine whether MMP-12 is required for glomerular macrophage infiltration and crescent formation in anti-GBM glomerulonephritis.
Methods
Accelerated anti-GBM disease was induced in groups of MMP-12 gene deficient mice (MMP-12-/-) and wild type C57BL/6 J (WT) controls, which were killed 12 days after injection of anti-GBM serum.
Results
WT and MMP-12-/- mice developed glomerular damage and glomerular tuft adhesions to Bowman's capsule. Both groups developed severe proteinuria. WT mice also developed significant loss of renal function and crescents in 22% of glomeruli, which were associated with macrophage infiltration and Bowman's capsule rupture. In contrast, MMP-12-/- mice were partially protected from renal function decline, crescent formation and Bowman's capsule rupture. This was associated with reduced macrophage infiltration in both glomeruli and the interstitium, and with reduced expression of CCL2, TNF-α and iNOS mRNA in MMP12-/- kidneys. In addition, KIM-1 mRNA levels were reduced in MMP-12-/- mice indicating less tubular damage.
Conclusions
These data demonstrate that endogenous MMP-12 facilitates macrophage accumulation and activation in anti-GBM glomerulonephritis which is required for glomerular crescent formation, Bowman's capsule rupture, tubular damage and renal function decline.
14 citations
TL;DR: In this paper, the authors reviewed K+ pathophysiology and the clinical impact and management of hyperkalemia considering the availability of the novel K+ binders patiromer and sodium zirconium cyclosilicate, recent results from clinical trials targeting metabolic acidosis, and an increasing understanding of the role of the gut microbiota in health and disease.
Abstract: Despite recent therapeutic advances, chronic kidney disease (CKD) is one of the fastest growing global causes of death. This illustrates limitations of current therapeutic approaches and, potentially, unidentified knowledge gaps. For decades, renin-angiotensin-aldosterone system (RAAS) blockers have been the mainstay of therapy for CKD. However, they favor the development of hyperkalemia, which is already common in CKD patients due to the CKD-associated decrease in urinary potassium (K+) excretion and metabolic acidosis. Hyperkalemia may itself be life-threatening as it may trigger potentially lethal arrhythmia, and additionally may limit the prescription of RAAS blockers and lead to low-K+ diets associated to low dietary fiber intake. Indeed, hyperkalemia is associated with adverse kidney, cardiovascular, and survival outcomes. Recently, novel kidney protective therapies, ranging from sodium/glucose cotransporter 2 (SGLT2) inhibitors to new mineralocorticoid receptor antagonists have shown efficacy in clinical trials. Herein, we review K+ pathophysiology and the clinical impact and management of hyperkalemia considering these developments and the availability of the novel K+ binders patiromer and sodium zirconium cyclosilicate, recent results from clinical trials targeting metabolic acidosis (sodium bicarbonate, veverimer), and an increasing understanding of the role of the gut microbiota in health and disease.
13 citations
TL;DR: An improved understanding of the cellular pathophysiological mechanisms leading to kidney injury will hopefully offer improved targeted therapies to prevent and treat the injury in the future.
Abstract: Introduction: Renal ischemia-reperfusion injury (IRI) is a significant clinical challenge faced by clinicians in a broad variety of clinical settings such as perioperative and intensive care. Renal IRI induced acute kidney injury (AKI) is a global public health concern associated with high morbidity, mortality, and health-care costs.
Areas covered: This paper focuses on the pathophysiology of transplantation-related AKI and recent findings on cellular stress responses at the intersection of 1. The Unfolded protein response; 2. Mitochondrial dysfunction; 3. The benefits of mineralocorticoid receptor antagonists. Lastly, perspectives are offered to the readers.
Expert opinion: Renal IRI is caused by a sudden and temporary impairment of blood flow to the organ.
Defining the underlying cellular cascades involved in IRI will assist us in the identification of novel interventional targets to attenuate IRI with the potential to improve transplantation outcomes. Targeting mitochondrial function and cellular bioenergetics upstream of cellular damage may offer several advantages compared to targeting downstream inflammatory and fibrosis processes.
An improved understanding of the cellular pathophysiological mechanisms leading to kidney injury will hopefully offer improved targeted therapies to prevent and treat the injury in the future.
11 citations
TL;DR: A review of recent studies investigating new mechanisms for MR signalling in cardiomyocytes and how their dysfunction contributes to the onset and progression of cardiovascular disease and heart failure.
Abstract: Recent studies have expanded our understanding of the actions of the mineralocorticoid receptor (MR) to a diverse array of tissue types that differ substantially from the epithelial cells of the renal nephron. In these cell types the role of the MR has been largely, but not exclusively, defined in terms of pathogenic signalling pathways leading to tissue injury and remodelling. Macrophages and cardiomyocytes are two cell types in which the MR plays a central role in the cardiac tissue response to injury, renovascular hypertension and oxidative stress for example. Macrophages are critical for resolution of tissue injury and wound healing and their pleiotropic actions are central to the development of many forms of heart, renal and vascular disease. The MR in cardiomyocytes is not only essential for the chronotropic and ionotropic actions of mineralocorticoids in the short and longer term, but also for induction of hypertrophic and proinflammatory signalling programs. The present review discusses recent studies, presented at the Aldosterone and Hypertension Satellite of the 15th Asian-Pacific Congress of Hypertension, investigating new mechanisms for MR signalling in these cells and how their dysfunction contributes to the onset and progression of cardiovascular disease and heart failure.
10 citations
Cites background from "Myeloid Mineralocorticoid Receptor ..."
...evidence that macrophage MR activation is critical for tissue injury, and for remodelling more broadly [36, 37]....
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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.
496 citations
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.
332 citations
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.
324 citations
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.
296 citations
TL;DR: A critical role for the MR in cardiovascular disease has now been demonstrated by the beneficial response to MR blockade in 2 large clinical trials in patients with cardiac failure, needed for the development of antagonists that target the cardiovascular system while avoiding the undesirable side effects of renal MR blockade.
Abstract: Sodium transport in epithelial tissues is regulated by the physiological mineralocorticoid aldosterone. The response to aldosterone is mediated by the mineralocorticoid receptor (MR), for which the crystal structure of the ligand-binding domain has recently been established. The classical mode of action for this receptor involves the regulation of gene transcription. Several genes have now been shown to be regulated by aldosterone in epithelial tissues. Of these, the best characterized is serum- and glucocorticoid-regulated kinase, which increases sodium influx through the epithelial sodium channel. Turnover of these channels in the cell membrane is mediated by Nedd4-2, a ubiquitin protein ligase; serum- and glucocorticoid-regulated kinase interacts with and phosphorylates Nedd4-2, thereby rendering it unable to bind the sodium channels. In nonepithelial tissues, particularly the cardiovascular system, aldosterone also has direct effects, activating an inflammatory cascade, leading to cardiac fibrosis. A critical role for the MR in cardiovascular disease has now been demonstrated by the beneficial response to MR blockade in 2 large clinical trials in patients with cardiac failure. It is these nonepithelial actions of MR activation that need to be exploited for the development of antagonists that target the cardiovascular system while avoiding the undesirable side effects of renal MR blockade.
280 citations