Murine Model Of Chronic Kidney Disease Research Articles

Cognitive impairment and the blood-brain barrier in chronic kidney disease: role of the uremic toxins

Patients with chronic kidney disease (CKD) have an increased risk of cognitive disorders, presenting as vascular dementia, compared with the general population. These cognitive disorders occur early during the course of the kidney disease and evolve in parallel with the decline in glomerular filtration rate. They affect 30 to 80% of patients with stage 5 CKD. Kidney transplantation only partially improves cognitive impairment. In this narrative review, we summarize the epidemiology and recent clinical and experimental data on cognitive impairment in CKD and discuss the potential specific mechanisms. Among the factors associated with cognitive impairment, the accumulation of uremic toxins such as indoxyl sulfate appears to be a specific risk factor for cognitive decline. These toxins have an endothelial toxicity that can disrupt the cerebral endothelium. The rupture of the blood-brain barrier (BBB) is a mechanism implicated in several neurodegenerative pathologies and systemic diseases with cerebral tropism. Recent experimental findings in CKD indicate that disruption of the BBB appears to be an important mechanism behind cognitive impairment in CKD. In murine models of CKD, increased BBB permeability is linked to memory impairment and aryl hydrocarbon receptor activation following accumulation of circulating indoxyl sulfate. This disruption of the BBB could also have harmful consequences for stroke susceptibility and drug neurotoxicity in CKD patients.

Phosphate induces inflammation and exacerbates injury from cigarette smoke in the bronchial epithelium

An elevation in serum phosphate—also called hyperphosphatemia—is associated with reduced kidney function in chronic kidney disease (CKD). Reports show CKD patients are more likely to develop lung disease and have poorer kidney function that positively correlates with pulmonary obstruction. However, the underlying mechanisms are not well understood. Here, we report that two murine models of CKD, which both exhibit increased serum levels of phosphate and fibroblast growth factor (FGF) 23, a regulator of phosphate homeostasis, develop concomitant airway inflammation. Our in vitro studies point towards a similar increase of phosphate-induced inflammatory markers in human bronchial epithelial cells. FGF23 stimulation alone does not induce a proinflammatory response in the non-COPD bronchial epithelium and phosphate does not cause endogenous FGF23 release. Upregulation of the phosphate-induced proinflammatory cytokines is accompanied by activation of the extracellular-signal regulated kinase (ERK) pathway. Moreover, the addition of cigarette smoke extract (CSE) during phosphate treatments exacerbates inflammation as well as ERK activation, whereas co-treatment with FGF23 attenuates both the phosphate as well as the combined phosphate- and CS-induced inflammatory response, independent of ERK activation. Together, these data demonstrate a novel pathway that potentially explains pathological kidney-lung crosstalk with phosphate as a key mediator.

Catalpol Attenuates Oxidative Stress and Inflammation via Mechanisms Involving Sirtuin-1 Activation and NF-κB Inhibition in Experimentally-Induced Chronic Kidney Disease.

Chronic kidney disease (CKD) is a stealthy disease, and its development is linked to mechanisms including inflammation and oxidative stress. Catalpol (CAT), an iridoid glucoside from the root of Rehmannia glutinosa, is reported to manifest anti-inflammatory, antioxidant, antiapoptotic and antifibrotic properties. Hence, we studied the possible nephroprotective effects of CAT and its mechanisms in an adenine-induced (0.2% w/w in feed for 4 weeks) murine model of CKD by administering 5 mg/kg CAT to BALB/c mice for the duration of 4 weeks except during weekends. Upon sacrifice, the kidney, plasma and urine were collected and various physiological, biochemical and histological endpoints were assessed. CAT significantly ameliorated the adenine-induced altered body and kidney weight, water intake, urine volume, and concentrations of urea and creatinine in plasma, as well as the creatinine clearance and the albumin and creatinine ratio. Moreover, CAT significantly ameliorated the effect of adenine-induced kidney injury by reducing the kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, cystatin C and adiponectin. Similarly, the augmented concentrations of markers of inflammation and oxidative stress in the adenine-treated group were markedly reduced with CAT pretreatment. Furthermore, CAT prevented adenine-induced deoxyribonucleic acid damage and apoptotic activity in the kidneys. Histologically, CAT significantly reduced the formation of tubular necrosis and dilation, as well as interstitial fibrosis in the kidney. In addition to that, CAT significantly decreased the adenine-induced increase in the phosphorylated NF-κB and reversed the reduced expression of sirtuin-1 in the kidney. In conclusion, CAT exhibits salutary effects against adenine-induced CKD in mice by mitigating inflammation, oxidative stress and fibrosis via mechanisms involving sirtuin-1 activation and NF-κB inhibition. Confirmatory studies are warranted in order to consider CAT as a potent nephroprotective agent against CKD.

Chronic Kidney Disease Induces Proarrhythmic Remodeling.

Patients with chronic kidney disease (CKD) are at increased risk of developing cardiac arrhythmogenesis and sudden cardiac death; however, the basis for this association is incompletely known. Here, using murine models of CKD, we examined interactions between kidney disease progression and structural, electrophysiological, and molecular cardiac remodeling. C57BL/6 mice with adenine supplemented in their diet developed progressive CKD. Electrocardiographically, CKD mice developed significant QT prolongation and episodes of bradycardia. Optical mapping of isolated-perfused hearts using voltage-sensitive dyes revealed significant prolongation of action potential duration with no change in epicardial conduction velocity. Patch-clamp studies of isolated ventricular cardiomyocytes revealed changes in sodium and potassium currents consistent with action potential duration prolongation. Global transcriptional profiling identified dysregulated expression of cellular stress response proteins RBM3 (RNA-binding motif protein 3) and CIRP (cold-inducible RNA-binding protein) that may underlay the ion channel remodeling. Unexpectedly, we found that female sex is a protective factor in the progression of CKD and its cardiac sequelae. Our data provide novel insights into the association between CKD and pathologic proarrhythmic cardiac remodeling. Cardiac cellular stress response pathways represent potential targets for pharmacologic intervention for CKD-induced heart rhythm disorders.

Gut-Kidney Axis Investigations in Animal Models of Chronic Kidney Disease.

Chronic kidney disease (CKD) is an incurable disease in which renal function gradually declines, resulting in no noticeable symptoms during the early stages and a life-threatening disorder in the latest stage. The changes that accompany renal failure are likely to influence the gut microbiota, or the ecosystem of micro-organisms resident in the intestine. Altered gut microbiota can display metabolic changes and become harmful to the host. To study the gut–kidney axis in vivo, animal models should ideally reproduce the disorders affecting both the host and the gut microbiota. Murine models of CKD, but not dog, manifest slowed gut transit, similarly to patient. Animal models of CKD also reproduce altered intestinal barrier function, as well as the resulting leaky gut syndrome and bacterial translocation. CKD animal models replicate metabolic but not compositional changes in the gut microbiota. Researchers investigating the gut–kidney axis should pay attention to the selection of the animal model (disease induction method, species) and the setting of the experimental design (control group, sterilization method, individually ventilated cages) that have been shown to influence gut microbiota.

Metabolomics analysis of human plasma reveals decreased production of trimethylamine N-oxide retards the progression of chronic kidney disease.

Chronic kidney disease (CKD) is a global public health problem and one of the leading causes of all-cause mortality. However, the pathogenic mechanisms and intervention methods for CKD progression are not fully understood. Plasma from patients with uraemia and from healthy controls (n = 30 per group) was analysed with LC-MS/MS-based non-targeted metabolomics to identify potential markers of uraemia. These potential markers were validated in the same cohort and a second cohort (n = 195) by quantitative analysis of the markers, using LC-MS/MS. The most promising marker was identified by correlation analysis and further validated using HK-2 cells and mouse models. Trimethylamine N-oxide (TMAO) was identified as a promising marker among the 18 potential markers found in the first cohort, and it was optimally correlated with renal function of CKD patients in the second cohort. Treatment of HK-2 cells with TMAO decreased cell viability and up-regulated expression of α-smooth muscle actin. In mice, a TMAO-containing diet decreased kidney mass and increased protein expression of α-smooth muscle actin. Also, control of TMAO production by inhibiting its biosynthetic pathway with 3,3-dimethyl-1-butanol or disrupting gut microbiota function with an antibiotic cocktail, attenuated renal injury in a murine model of CKD. Our data show that decreased TMAO production could be a new strategy to attenuate the progression of renal injury in CKD.

MO448MICRORNAS IMPLICATED IN CHRONIC KIDNEY DISEASE

Abstract Background and Aims The gene program is controlled at the post-transcriptional level by the action of small non-coding RNAs known as microRNAs (miRNAs), short, single-stranded molecules that control mRNA stability or translational repression via base pairing with regions in the 3' untranslated region of their target mRNAs. Recently, considerable progress has been made to elucidate the roles of miRNAs in vascular pathogenesis and develop the use of miRNAs as biomarkers, and innovative drugs. We demonstrated during the last decade that miRNAs miR-126 and miR-223 are implicated in the course of chronic kidney disease (CKD) and cardiovascular damage. miR-223 expression is enhanced in vascular smooth muscle cells (VSMCs) subjected to an uremic toxin and also in aortas of a murine model of CKD. As restenosis is a common complication of angioplasty, in which neointimal hyperplasia results from migration of VSMCs into the vessel lumen we measured the effect of miR-223 modulation on restenosis in a rat model of carotid artery after balloon injury. We over-expressed and inhibited miR-223 expression using adenoviral vectors, coding a pre-miR-223 sequence or a sponge sequence, used to trap endogenous microRNA, respectively. We demonstrated that inhibiting miR-223 function significantly reduced neointimal hyperplasia by almost half in carotids. Thus down-regulating miR-223 could be a potential therapeutic approach to prevent restenosis after angioplasty. We also correlated miR-126 and miR-223 expression with clinical outcomes in a large cohort of CKD patients, in collaboration with the University Hospital of Ghent (Belgium) and Ambroise Paré Hospital, France. We evaluated both miRNA’s link with all-cause mortality and cardiovascular and renal events over a 6-year follow-up period. The serum levels of miR-126 and miR-223 were decreased as CKD stage advanced, and patients with higher levels of miR-126 and miR-223 had a higher survival rate. Similar results were observed for cardiovascular and renal events. In conclusion, CKD is associated with a decrease in circulating miR-126 and miR-223 levels in CKD patients. We will also present links between several uremic toxin concentrations and miRNA concentration in the patients of this cohort. Finally, anemia is a common feature of CKD that is associated with cardiovascular disease and poor clinical outcomes. A mixture of uremic toxins accumulates in the blood of CKD patients during the course of the disease, and there is good evidence that they modulate erythropoiesis, explaining at least partly anemia. The exact molecular mechanisms implicated are however poorly understood, although recent progresses have been made to identify key components in the CKD process. We will present results on the effect of uremic toxins on erythropoiesis, having an impact on cell metabolism during this process. Taken together, our findings could be of interest to both researchers and clinicians working in the field since they might shed new light on the molecular mechanisms involved in the CKD process. MicroRNAs implicated in Chronic Kidney Disease Pr. Laurent Metzinger, UR-UPJV 4666 HEMATIM, CURS, Université de Picardie Jules Verne, CHU Amiens Sud, Avenue René Laënnec, Salouel, F-80054, Amiens, France. Tel: (+33) 22 82 53 56, Email: laurent.metzinger@u-picardie.fr

Accumulation of natriuretic peptides is associated with protein energy wasting and activation of browning in white adipose tissue in chronic kidney disease

Protein energy wasting is a common feature of patients with chronic kidney disease (CKD) and is associated with poor outcomes. Protein energy wasting and cachexia, a severe form of protein energy wasting, are characterized by increased resting energy expenditure but the underlying mechanisms are unclear. Browning corresponds to the activation of inducible brown adipocytes in white adipose tissue and occurs in states of cachexia associated with hypermetabolic disease such as cancer. Here we tested the hypothesis that CKD-associated protein energy wasting could result from browning activation as a direct effect of the uremic environment on adipocytes. In a murine model of CKD (5/6 nephrectomy), there was increased resting energy expenditure, expression of uncoupling protein 1 (a thermogenic protein uncoupling oxidative phosphorylation in mitochondria) and citrate synthase activity (a proxy of mitochondrial density in white adipose tissue). Mice with CKD also exhibited increased levels of atrial natriuretic peptide, a well known activator of browning. The incubation of primary adipose cells with plasma from patients receiving dialysis treatment and having signs of protein energy wasting led to an increased synthesis of uncoupling protein 1. Similarly, primary adipose cells exposed to atrial natriuretic peptide at concentrations relevant of CKD led to a significant increase of uncoupling protein 1 content. Thus, accumulation of cardiac natriuretic peptides during CKD could contribute to the browning of white adipose tissue and protein energy wasting.

Adipose tissue-derived mesenchymal stromal cells for treating chronic kidney disease: A pilot study assessing safety and clinical feasibility.

BackgroundChronic kidney disease (CKD) is a growing public health concern, and available treatments are insufficient in limiting disease progression. New strategies, including regenerative cell-based therapies, have emerged as therapeutic alternatives. Results from several groups, including our own, have reported evidence of a supportive role for mesenchymal stromal cells (MSCs) in functional recovery and prevention of tissue damage in murine models of CKD. Prompted by these data, an open pilot study was conducted to assess the safety and efficacy of a single injection of autologous adipose tissue-derived MSCs (AT-MSCs) for treatment of CKD.MethodsAT-MSCs were infused intravenously into six CKD patients at a dose of 1 million cells/kg. Patients were stabilized and followed for one year prior to MSC infusion and one year following infusion.ResultsNo patients presented with adverse effects. Statistically significant improvement in urinary protein excretion was observed in AT-MSCs transplanted patients, from a median of 0.75 g/day (range, 0.15–9.57) at baseline to 0.54 g/day (range, 0.01v2.66) at month 12 (P = 0.046). The glomerular filtration rate was not significantly decreased post-infusion of AT-MSCs.ConclusionFindings from this pilot study demonstrate that intravenous infusion of autologous expanded AT-MSCs into CKD patients was not associated with adverse effects and could benefit patients already undergoing standard medical treatment.

Flavonoids in Kidney Health and Disease.

This review summarizes the latest advances in knowledge on the effects of flavonoids on renal function in health and disease. Flavonoids have antihypertensive, antidiabetic, and antiinflammatory effects, among other therapeutic activities. Many of them also exert renoprotective actions that may be of interest in diseases such as glomerulonephritis, diabetic nephropathy, and chemically-induced kidney insufficiency. They affect several renal factors that promote diuresis and natriuresis, which may contribute to their well-known antihypertensive effect. Flavonoids prevent or attenuate the renal injury associated with arterial hypertension, both by decreasing blood pressure and by acting directly on the renal parenchyma. These outcomes derive from their interference with multiple signaling pathways known to produce renal injury and are independent of their blood pressure-lowering effects. Oral administration of flavonoids prevents or ameliorates adverse effects on the kidney of elevated fructose consumption, high fat diet, and types I and 2 diabetes. These compounds attenuate the hyperglycemia-disrupted renal endothelial barrier function, urinary microalbumin excretion, and glomerular hyperfiltration that results from a reduction of podocyte injury, a determinant factor for albuminuria in diabetic nephropathy. Several flavonoids have shown renal protective effects against many nephrotoxic agents that frequently cause acute kidney injury (AKI) or chronic kidney disease (CKD), such as LPS, gentamycin, alcohol, nicotine, lead or cadmium. Flavonoids also improve cisplatin- or methotrexate-induced renal damage, demonstrating important actions in chemotherapy, anticancer and renoprotective effects. A beneficial prophylactic effect of flavonoids has been also observed against AKI induced by surgical procedures such as ischemia/reperfusion (I/R) or cardiopulmonary bypass. In several murine models of CKD, impaired kidney function was significantly improved by the administration of flavonoids from different sources, alone or in combination with stem cells. In humans, cocoa flavanols were found to have vasculoprotective effects in patients on hemodialysis. Moreover, flavonoids develop antitumor activity against renal carcinoma cells with no toxic effects on normal cells, suggesting a potential therapeutic role in patients with renal carcinoma.

Aryl hydrocarbon receptor is activated in patients and mice with chronic kidney disease

Patients with chronic kidney disease (CKD) are exposed to uremic toxins and have an increased risk of cardiovascular disease. Some uremic toxins, like indoxyl sulfate, are agonists of the transcription factor aryl hydrocarbon receptor (AHR). These toxins induce a vascular procoagulant phenotype. Here we investigated AHR activation in patients with CKD and in a murine model of CKD. We performed a prospective study in 116 patients with CKD stage 3 to 5D and measured the AHR-Activating Potential of serum by bioassay. Compared to sera from healthy controls, sera from CKD patients displayed a strong AHR-Activating Potential; strongly correlated with eGFR and with the indoxyl sulfate concentration. The expression of the AHR target genes Cyp1A1 and AHRR was up-regulated in whole blood from patients with CKD. Survival analyses revealed that cardiovascular events were more frequent in CKD patients with an AHR-Activating Potential above the median. In mice with 5/6 nephrectomy, there was an increased serum AHR-Activating Potential, and an induction of Cyp1a1 mRNA in the aorta and heart, absent in AhR-/- CKD mice. After serial indoxyl sulfate injections, we observed an increase in serum AHR-AP and in expression of Cyp1a1 mRNA in aorta and heart in WT mice, but not in AhR-/- mice. Thus, the AHR pathway is activated both in patients and mice with CKD. Hence, AHR activation could be a key mechanism involved in the deleterious cardiovascular effects observed in CKD.

A Novel Distal Enhancer Mediates Inflammation-, PTH-, and Early Onset Murine Kidney Disease-Induced Expression of the Mouse Fgf23 Gene.

ABSTRACTFibroblast growth factor 23 (FGF23) production is regulated by both calciotropic hormones and inflammation. Consistent with this, elevated FGF23 levels are associated with inflammatory markers as well as parathyroid hormone (PTH) in various disease states, including chronic kidney disease (CKD). However, the molecular mechanisms underpinning Fgf23 transcription in response to these regulators are largely unknown. We therefore utilized chromatin immunoprecipitation followed by DNA sequencing (ChIP‐seq) data from an osteocyte cell line to identify potential regulatory regions of the Fgf23 gene. Based on ChIP‐seq analysis of enhancer‐associated histone modifications, including H3K4 methylation and H3K9 acetylation, we discovered several potential enhancers for Fgf23, one of which was located 16kb upstream of the gene's transcriptional start site. Deletion of this putative enhancer from the mouse genome using CRISPR‐Cas9 technology led to lower bone, thymus, and spleen expression of Fgf23 mRNA without altering circulating levels of the intact hormone, although as previously reported, only bone displayed significant basal expression. Nevertheless, lack of the −16kb enhancer blunted FGF23 upregulation in a tissue‐specific manner by the acute inflammatory inducers lipopolysaccharide (LPS), interleukin‐1‐beta (IL‐1β), and tumor necrosis factor‐alpha (TNFα) in bone, non‐osseous tissues, and in circulation. Lack of the −16kb enhancer also inhibited PTH‐induced bone Fgf23 mRNA. Moreover, the absence of this Fgf23 enhancer in an oxalate diet‐induced murine CKD model prevented the early onset induction of osseous, renal, and thymic Fgf23 mRNA levels and led to a significant blunting of elevated circulating intact FGF23 levels. These results suggest that −16kb enhancer mediates the induction of Fgf23 by inflammation and PTH and facilitates the increase in FGF23 expression in a murine model of CKD. As exemplified herein, these Fgf23 enhancer‐deleted mice will provide a unique model in which to study the role of FGF23 expression in inflammatory diseases. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Resveratrol-loaded nanoparticles conjugated with kidney injury molecule-1 as a drug delivery system for potential use in chronic kidney disease.

We used resveratrol (Res)-loaded nanoparticles (Res NPs) as a novel method for improving the pharmacokinetic properties of Res and analyzed the effect of Res NPs in chronic kidney disease (CKD). We coupled anti-kidney injury molecule-1 antibodies to Res NPs and analyzed safety and efficacy. Res NPs had low toxicity and induced autophagy. Res NPs inhibited the NLRP3 inflammasome and IL-1β secretion. Higher NLRP3 expression levels were observed in peripheral blood monocytic cells of CKD patients than healthy individuals. Treatment with kidney injury molecule-1-Res NPs significantly reduced creatinine and protected against tubulointerstitial injury in a murine model of CKD. Res NPs through NLRP3 inflammasome attenuation and autophagy induction may be as a strategy to prevent CKD.

Endoplasmic reticulum stress inhibition attenuates hypertensive chronic kidney disease through reduction in proteinuria

Endoplasmic reticulum (ER) stress is implicated in chronic kidney disease (CKD) development in patients and in animal models. Here we show that ER stress inhibition through 4-phenylbutyric acid (4-PBA) administration decreases blood pressure, albuminuria, and tubular casts in an angiotensin II/deoxycorticosterone acetate/salt murine model of CKD. Lower albuminuria in 4-PBA-treated mice was associated with higher levels of cubilin protein in renal tissue membrane fractions. 4-PBA decreased renal interstitial fibrosis, renal CD3+ T-cell and macrophage infiltration, mRNA expression of TGFβ1, Wnt signaling molecules, and ER stress-induced pro-inflammatory genes. CHOP deficient mice that underwent this model of CKD developed hypertension comparable to wild type mice, but had less albuminuria and tubular casts. CHOP deficiency resulted in higher nephrin levels and decreased glomerulosclerosis compared to wild type mice; this effect was accompanied by lower macrophage infiltration and fibrosis. Our findings portray ER stress inhibition as a means to alleviate hypertensive CKD by preserving glomerular barrier integrity and tubular function. These results demonstrate ER stress modulation as a novel target for preserving renal function in hypertensive CKD.