Resveratrol retards progression of diabetic nephropathy through modulations of oxidative stress, proinflammatory cytokines, and AMP-activated protein kinase

Background

Diabetic nephropathy (DN) has been recognized as the leading cause of end-stage renal disease. Resveratrol (RSV), a polyphenolic compound, has been indicated to possess an insulin-like property in diabetes. In the present study, we aimed to investigate the renoprotective effects of RSV and delineate its underlying mechanism in early-stage DN.

Methods

The protective effects of RSV on DN were evaluated in streptozotocin (STZ)-induced diabetic rats.

Results

The plasma glucose, creatinine, and blood urea nitrogen were significantly elevated in STZ-induced diabetic rats. RSV treatment markedly ameliorated hyperglycemia and renal dysfunction in STZ-induced diabetic rats. The diabetes-induced superoxide anion and protein carbonyl levels were also significantly attenuated in RSV-treated diabetic kidney. The AMPK protein phosphorylation and expression levels were remarkably reduced in diabetic renal tissues. In contrast, RSV treatment significantly rescued the AMPK protein expression and phosphorylation compared to non-treated diabetic group. Additionally, hyperglycemia markedly enhanced renal production of proinflammatory cytokine IL-1β. RSV reduced IL-1β but increased TNF-α and IL-6 levels in the diabetic kidneys.

Conclusions

Our findings suggest that RSV protects against oxidative stress, exhibits concurrent proinflammation and anti-inflammation, and up-regulates AMPK expression and activation, which may contribute to its beneficial effects on the early stage of DN.     

Establishment of a Model of Renal Impairment with Mild Renal Insufficiency Associated with Atrial Fibrillation in Canines

Background

Chronic kidney disease and occurrence of atrial fibrillation (AF) are closely related. No studies have examined whether renal impairment (RI) without severe renal dysfunction is associated with the occurrence of AF.

Methods

Unilateral RI with mild renal insufficiency was induced in beagles by embolization of small branches of the renal artery in the left kidney for 2 weeks using gelatin sponge granules in the model group (n = 5). The sham group (n = 5) underwent the same procedure, except for embolization. Parameters associated with RI and renal function were tested, cardiac electrophysiological parameters, blood pressure, left ventricular pressure, and AF vulnerability were investigated. The activity of the sympathetic nervous system, renin-angiotensin-aldosterone system, inflammation, and oxidative stress were measured. Histological studies associated with atrial interstitial fibrosis were performed.

Results

Embolization of small branches of the renal artery in the left kidney led to ischemic RI with mild renal insufficiency. The following changes occurred after embolization. Heart rate and P wave duration were increased. Blood pressure and left ventricular systolic pressure were elevated. The atrial effective refractory period and antegrade Wenckebach point were shortened. Episodes and duration of AF, as well as atrial and ventricular rate during AF were increased in the model group. Plasma levels of norepinephrine, renin, and aldosterone were increased, angiotensin II and aldosterone levels in atrial tissue were elevated, and atrial interstitial fibrosis was enhanced after 2 weeks of embolization in the model group.

Conclusions

We successfully established a model of RI with mild renal insufficiency in a large animal. We found that RI with mild renal insufficiency was associated with AF in this model.     

The Prevention of Diabetic Cardiomyopathy by Non-Mitogenic Acidic Fibroblast Growth Factor Is Probably Mediated by the Suppression of Oxidative Stress and Damage

Background

Emerging evidence showed the beneficial effect of acidic fibroblast growth factor (aFGF) on heart diseases. The present study investigated whether non-mitogenic aFGF (nm-aFGF) can prevent diabetic cardiomyopathy and the underlying mechanisms, if any.

Methodology/Principal Findings

Type 1 diabetes was induced in mice by multiple intraperitoneal injections of low-dose streptozotocin. Hyperglycemic and age-matched control mice were treated with or without nm-aFGF at 10 µg/kg daily for 1 and 6 months. Blood pressure and cardiac function were assessed. Cardiac H9c2 cell, human microvascular endothelial cells, and rat cardiomyocytes were exposed to high glucose (25 mM) for mimicking an in vitro diabetic condition for mechanistic studies. Oxidative stress, DNA damage, cardiac hypertrophy and fibrosis were assessed by real-time qPCR, immunofluorescent staining, Western blotting, and pathological examination. Nm-aFGF significantly prevented diabetes-induced hypertension and cardiac dysfunction at 6 months. Mechanistic studies demonstrated that nm-aFGF showed the similar preventive effect as the native aFGF on high glucose-induced oxidative stress (increase generation of reactive oxygen species) and damage (cellular DNA oxidation), cell hypertrophy, and fibrotic response (increased mRNA expression of fibronectin) in three kinds of cells. These in vitro findings were recaptured by examining the heart of the diabetic mice with and without nm-aFGF.

Conclusions

These results suggest that nm-aFGF can prevent diabetic cardiomyopathy, probably through attenuation of cardiac oxidative stress, hypertrophy, and fibrosis.     

A Blueberry-Enriched Diet Improves Renal Function and Reduces Oxidative Stress in Metabolic Syndrome Animals: Potential Mechanism of TLR4-MAPK Signaling Pathway

Background

Metabolic syndrome (MetS) is characterized by a cluster of health factors that indicate a higher risk for cardio-renal diseases. Recent evidence indicates that antioxidants from berries are alternative to attenuate oxidative stress and inflammation. We tested the hypothesis that inflammation-induced renal damage is triggered by the activation of TLR4, and subsequent modulation of redox-sensitive molecules and mitogen-activated protein kinase (MAPK) pathway.

Methods

Five-week old lean and obese Zucker rats (LZR and OZR) were fed a blueberry-enriched diet or an isocaloric control diet for 15 weeks. A glucose tolerance test and acute renal clearance experiments were performed. Gene and protein expression levels for TLR4, cytokines and phosphorylation of ERK and p38MAPK were measured. Kidney redox status and urinary albumin levels were quantified. Renal pathology was evaluated histologically.

Results

Control OZR exhibited lower glucose tolerance; exacerbated renal function parameters; increased oxidative stress. Gene and protein expression levels of TLR4 were higher and this was accompanied by increased renal pathology with extensive albuminuria and deterioration in antioxidant levels in OZR. In addition, OZR had increased phosphorylation of ERK and p38MAPK. Blueberry-fed OZR exhibited significant improvements in all these parameters compared to OZR.

Conclusion

TLR4-MAPK signaling pathway is a key to the renal structural injury and dysfunction in MetS and blueberry (BB) protect against this damage by inhibiting TLR4.

Significance

This is the first study to put forth a potential mechanism of TLR4-induced kidney damage in a model of MetS and to elucidate a downstream mechanism by which blueberry exert their reno-protective effects.     

Preconditioning with physiological levels of ethanol protect kidney against ischemia/reperfusion injury by modulating oxidative stress

Background

Oxidative stress due to excessive production of reactive oxygen species (ROS) and subsequent lipid peroxidation plays a critical role in renal ischemia/reperfusion (IR) injury. The purpose of current study is to demonstrate the effect of antecedent ethanol exposure on IR-induced renal injury by modulation of oxidative stress.

Materials and Methods

Bilateral renal warm IR was induced in male C57BL/6 mice after ethanol or saline administration. Blood ethanol concentration, kidney function, histological damage, inflammatory infiltration, cytokine production, oxidative stress, antioxidant capacity and Aldehyde dehydrogenase (ALDH) enzymatic activity were assessed to evaluate the impact of antecedent ethanol exposure on IR-induced renal injury.

Results

After bilateral kidney ischemia, mice preconditioned with physiological levels of ethanol displayed significantly preserved renal function along with less histological tubular damage as manifested by the reduced inflammatory infiltration and cytokine production. Mechanistic studies revealed that precondition of mice with physiological levels of ethanol 3 h before IR induction enhanced antioxidant capacity characterized by significantly higher superoxidase dismutase (SOD) activities. Our studies further demonstrated that ethanol pretreatment specifically increased ALDH2 activity, which then suppressed lipid peroxidation by promoting the detoxification of Malondialdehyde (MDA) and 4-hydroxynonenal (HNE).

Conclusions

Our results provide first line of evidence indicating that antecedent ethanol exposure can provide protection for kidneys against IR-induced injury by enhancing antioxidant capacity and preventing lipid peroxidation. Therefore, ethanol precondition and ectopic ALDH2 activation could be potential therapeutic approaches to prevent renal IR injury relevant to various clinical conditions.     

Circulating FGF21 levels are progressively increased from the early to end stages of chronic kidney diseases and are associated with renal function in Chinese

Background

Fibroblast growth factor 21 (FGF21) is a hepatic hormone involved in the regulation of lipid and carbohydrate metabolism. This study aims to test the hypothesis that elevated FGF21 concentrations are associated with the change of renal function and the presence of left ventricular hypertrophy (LVH) in the different stages of chronic kidney disease (CKD) progression.

Methodology/Principal Findings

240 subjects including 200 CKD patients (146 outpatients and 54 long-term hemodialytic patients) and 40 healthy control subjects were recruited. All CKD subjects underwent echocardiograms to assess left ventricular mass index. Plasma FGF21 levels and other clinical and biochemical parameters in all subjects were obtained based on standard clinical examination methods. Plasma FGF21 levels were significantly increased with the development of CKD from early- and end-stage (P<0.001 for trend), and significantly higher in CKD subjects than those in healthy subjects (P<0.001). Plasma FGF21 levels in CKD patients with LVH were higher than those in patients without LVH (P = 0.001). Furthermore, plasma FGF21 level correlated positively with creatinine, blood urea nitrogen (BUN), β2 microglobulin, systolic pressure, adiponectin, phosphate, proteinuria, CRP and triglyceride, but negatively with creatinine clearance rate (CCR), estimated glomerular filtrate rate (eGFR), HDL-c, LDL-c, albumin and LVH after adjusting for BMI, gender, age and the presence of diabetes mellitus. Multiple stepwise regression analyses indicated that FGF21 was independently associated with BUN, Phosphate, LVMI and β2 microglobulin (all P<0.05).

Conclusion

Plasma FGF21 levels are significantly increased with the development of early- to end-stage CKD and are independently associated with renal function and adverse lipid profiles in Chinese population. Understanding whether increased FGF21 is associated with myocardial hypertrophy in CKD requires further study.     

Increased Expression of Intranuclear Matrix Metalloproteinase 9 in Atrophic Renal Tubules Is Associated with Renal Fibrosis

Background

Reduced turnover of extracellular matrix has a role in renal fibrosis. Matrix metalloproteinases (MMPs) is associated with many glomerular diseases, but the histological association of MMPs and human renal fibrosis is unclear.

Methods

This is a retrospective study. Institutional Review Board approval was obtained for the review of patients’ medical records, data analysis and pathological specimens staining with waiver of informed consents. Specimens of forty-six patients were examined by immunohistochemical stain of MMP-9 in nephrectomized kidneys, and the association of renal expression of MMP-9 and renal fibrosis was determined. MMP-9 expression in individual renal components and fibrosis was graded as high or low based on MMP-9 staining and fibrotic scores.

Results

Patients with high interstitial fibrosis scores (IFS) and glomerular fibrosis scores (GFS) had significantly higher serum creatinine, lower estimated glomerular filtration rate (eGFR), and were more likely to have chronic kidney disease (CKD) and urothelial cell carcinoma. Univariate analysis showed that IFS and GFS were negatively associated with normal and atrophic tubular cytoplasmic MMP-9 expression and IFS was positively correlated with atrophic tubular nuclear MMP-9 expression. Multivariate stepwise regression indicated that MMP-9 expression in atrophic tubular nuclei (r = 0.4, p = 0.002) was an independent predictor of IFS, and that MMP-9 expression in normal tubular cytoplasm (r = −0.465, p<0.001) was an independent predictor of GFS.

Conclusions

Interstitial fibrosis correlated with MMP-9 expression in the atrophic tubular nuclei. Our results indicate that renal fibrosis is associated with a decline of MMP-9 expression in the cytoplasm of normal tubular cells and increased expression of MMP-9 in the nuclei of tubular atrophic renal tubules.     

Rhubarb Enema Attenuates Renal Tubulointerstitial Fibrosis in 5/6 Nephrectomized Rats by Alleviating Indoxyl Sulfate Overload

Aim

To investigate the effects of rhubarb enema treatment using a 5/6 nephrectomized rat model and study its mechanisms.

Methods

Twenty-eight Sprague Dawley rats were divided into three groups: sham operation group (n = 8), 5/6 nephrectomized (5/6Nx) (n = 10), and 5/6Nx with rhubarb enema treatment (n = 10). The rhubarb enema was continuous for 1.0 month. Serum creatinine, serum indoxyl sulfate (IS) level, renal pathology, tubulointerstitial fibrosis, and renal oxidative stress were assessed.

Results

5/6Nx rats showed increasing levels of serum creatinine and severe pathological lesions. Their serum creatinine levels obviously decreased after rhubarb enema treatment (P < 0.05 vs 5/6Nx group). The administration of rhubarb enema attenuated the histopathological changes in 5/6Nx rats. In addition, 5/6Nx rats showed an enhanced extent of tubulointerstitial fibrosis compared with sham rats, and administration of rhubarb enema to 5/6Nx rats ameliorated tubulointerstitial fibrosis. 5/6Nx rats showed increased serum levels of IS, renal oxidative stress, and NF-κB compared with sham rats, whereas administration of rhubarb enema to 5/6Nx rats decreased serum levels of IS, renal oxidative stress, and NF-κB levels.

Conclusion

Rhubarb enema treatment ameliorates tubulointerstitial fibrosis in the kidneys of 5/6Nx rats, most likely by alleviating IS overload and reducing kidney oxidative stress and inflammatory injury.     

Role of Moesin in Renal Fibrosis

Background

Renal fibrosis is the final common pathway of chronic kidney disease (CKD). Moesin is a member of Ezrin/Radixin/Moesin (ERM) protein family but its role in renal fibrosis is not clear.

Method

Human proximal tubular cells (HK-2) were stimulated with or without TGF-β1. Moesin and downstream target genes were examined by real-time PCR and western blot. Phosphorylation of moesin and related signaling pathway was investigated as well. Rat model of unilateral ureteral obstruction (UUO) was established and renal moesin was examined by immunohistochemistry. Moesin in HK-2 cells were knocked down by siRNA and change of downstream genes in transfected HK-2 cells was studied. All animal experiments were reviewed and approved by the Ethics Committee for animal care of Ruijin Hospital.

Result

HK-2 cells stimulated with TGF-β1 showed up-regulated level of α-SMA and down-regulated level of E-Cadherin as well as elevated mRNA and protein level of moesin. In rat model of UUO, renal moesin expression increased in accordance with severity of tubulointerestital fibrosis in the kidneys with ureteral ligation while the contralateral kidneys were normal. Further study showed that TGF-β1 could induce phosphorylation of moesin which depended on Erk signaling pathway and Erk inhibitor PD98059 could block moesin phosphorylation. Effects of TGF-β1 on moesin phosphorylation was prior to its activation to total moesin. RNA silencing studies showed that knocking down of moesin could attenuate decrease of E-Cadherin induced by TGF-β1.

Conclusion

We find that moesin might be involved in renal fibrosis and its effects could be related to interacting with E-Cadherin.     

Serum Metabonomic Analysis of Protective Effects of Curcuma aromatica Oil on Renal Fibrosis Rats

Background

Curcuma aromatica oil is a traditional herbal medicine demonstrating protective and anti-fibrosis activities in renal fibrosis patients. However, study of its mechanism of action is challenged by its multiple components and multiple targets that its active agent acts on.

Methodology/Principal Findings

Nuclear magnetic resonance (NMR)-based metabonomics combined with clinical chemistry and histopathology examination were performed to evaluate intervening effects of Curcuma aromatica oil on renal interstitial fibrosis rats induced by unilateral ureteral obstruction. The metabolite levels were compared based on integral values of serum ¹H NMR spectra from rats on 3, 7, 14, and 28 days after the medicine administration. Time trajectory analysis demonstrated that metabolic profiles of the agent-treated rats were restored to control levels after 7 days of dosage. The results confirmed that the agent would be an effective anti-fibrosis medicine in a time-dependent manner, especially in early renal fibrosis stage. Targeted metabolite analysis showed that the medicine could lower levels of lipid, acetoacetate, glucose, phosphorylcholine/choline, trimethylamine oxide and raise levels of pyruvate, glycine in the serum of the rats. Serum clinical chemistry and kidney histopathology examination dovetailed well with the metabonomics data.

Conclusions/Significances

The results substantiated that Curcuma aromatica oil administration can ameliorate renal fibrosis symptoms by inhibiting some metabolic pathways, including lipids metabolism, glycolysis and methylamine metabolism, which are dominating targets of the agent working in vivo. This study further strengthens the novel analytical approach for evaluating the effect of traditional herbal medicine and elucidating its molecular mechanism.     

The Renal Arterial Resistive Index and Stage of Chronic Kidney Disease in Patients with Renal Allograft

Objective

The study investigated the optimal threshold value of renal arterial resistive index as assessed by Doppler ultrasonography determining chronic kidney disease stage 4 or higher in patients with renal allograft.

Methods

In a cross-sectional study the renal arterial resistive index were obtained in interlobar arteries by Doppler ultrasonography in 78 patients with renal allograft. The stage of chronic kidney disease was determined by the estimated glomerular filtration rate equation.

Results

The median renal arterial resistive index was 0.61 (interquartile range, 0.56 to 0.66). We observed a significant association between renal arterial resistive index above the upper quartile and chronic kidney disease stage 4 or higher (relative risk, 4.64; 95% confidence interval, 1.71 to 12.55; p = 0.003 by Fisher’s exact test). Multivariate logistic regression analysis showed that renal arterial resistive indices (p = 0.02) and time since transplantation (p = 0.04), but not age, gender, or blood pressure were significantly associated with chronic kidney disease stage 4 or higher.

Conclusion

A renal arterial resistive index higher than 0.66 may determine the threshold value of chronic kidney disease stage 4 or higher in patients with renal allograft.     

Altered Retinoic Acid Metabolism in Diabetic Mouse Kidney Identified by 18O Isotopic Labeling and 2D Mass Spectrometry

Background

Numerous metabolic pathways have been implicated in diabetes-induced renal injury, yet few studies have utilized unbiased systems biology approaches for mapping the interconnectivity of diabetes-dysregulated proteins that are involved. We utilized a global, quantitative, differential proteomic approach to identify a novel retinoic acid hub in renal cortical protein networks dysregulated by type 2 diabetes.

Methodology/Principal Findings

Total proteins were extracted from renal cortex of control and db/db mice at 20 weeks of age (after 12 weeks of hyperglycemia in the diabetic mice). Following trypsinization, ¹⁸O- and ¹⁶O-labeled control and diabetic peptides, respectively, were pooled and separated by two dimensional liquid chromatography (strong cation exchange creating 60 fractions further separated by nano-HPLC), followed by peptide identification and quantification using mass spectrometry. Proteomic analysis identified 53 proteins with fold change ≥1.5 and p≤0.05 after Benjamini-Hochberg adjustment (out of 1,806 proteins identified), including alcohol dehydrogenase (ADH) and retinaldehyde dehydrogenase (RALDH1/ALDH1A1). Ingenuity Pathway Analysis identified altered retinoic acid as a key signaling hub that was altered in the diabetic renal cortical proteome. Western blotting and real-time PCR confirmed diabetes-induced upregulation of RALDH1, which was localized by immunofluorescence predominantly to the proximal tubule in the diabetic renal cortex, while PCR confirmed the downregulation of ADH identified with mass spectrometry. Despite increased renal cortical tissue levels of retinol and RALDH1 in db/db versus control mice, all-trans-retinoic acid was significantly decreased in association with a significant decrease in PPARβ/δ mRNA.

Conclusions/Significance

Our results indicate that retinoic acid metabolism is significantly dysregulated in diabetic kidneys, and suggest that a shift in all-trans-retinoic acid metabolism is a novel feature in type 2 diabetic renal disease. Our observations provide novel insights into potential links between altered lipid metabolism and other gene networks controlled by retinoic acid in the diabetic kidney, and demonstrate the utility of using systems biology to gain new insights into diabetic nephropathy.     

Circulating fibroblast growth factor 21 levels are closely associated with hepatic fat content: a cross-sectional study

Background and Aims

Fibroblasts growth factor 21 (FGF21), a liver-secreted endocrine factor involved in regulating glucose and lipid metabolism, has been shown to be elevated in patients with non-alcoholic fatty liver disease (NAFLD). This study aimed to evaluate the quantitative correlation between serum FGF21 level and hepatic fat content.

Methods

A total of 138 subjects (72 male and 66 female) aged from 18 to 65 years with abnormal glucose metabolism and B-ultrasonography diagnosed fatty liver were enrolled in the study. Serum FGF21 levels were determined by an in-house chemiluminescence immunoassay and hepatic fat contents were measured by proton magnetic resonance spectroscopy.

Results

Serum FGF21 increased progressively with the increase of hepatic fat content, but when hepatic fat content increased to the fourth quartile, FGF21 tended to decline. Serum FGF21 concentrations were positively correlated with hepatic fat content especially in subjects with mild/moderate hepatic steatosis (r = 0.276, p = 0.009). Within the range of hepatic steatosis from the first to third quartile, FGF21 was superior to any other traditional clinical markers including ALT to reflect hepatic fat content. When the patients with severe hepatic steatosis (the fourth quartile) were included, the quantitative correlation between FGF21 and hepatic fat content was weakened.

Conclusions

Serum FGF21 was a potential biomarker to reflect the hepatic fat content in patients with mild or moderate NAFLD. In severe NAFLD patients, FGF21 concentration might decrease due to liver inflammation or injury.     

Mitochondrial Autophagy Involving Renal Injury and Aging Is Modulated by Caloric Intake in Aged Rat Kidneys

Background

A high-calorie (HC) diet induces renal injury and promotes aging, and calorie restriction (CR) may ameliorate these responses. However, the effects of long-term HC and CR on renal damage and aging have been not fully determined. Autophagy plays a crucial role in removing protein aggregates and damaged organelles to maintain intracellular homeostasis and function. The role of autophagy in HC-induced renal damage is unknown.

Methods

We evaluated the expression of LC3/Atg8 as a marker of the autophagosome; p62/SQSTM1; polyubiquitin aggregates as markers of autophagy flux; Ambra1, PINK1, Parkin and Bnip3 as markers of mitophagy; 8-hydroxydeoxyguanosine (8-OHdG) as a marker of DNA oxidative damage; and p16 as a marker of organ aging by western blot and immunohistochemical staining in the kidneys of 24-month-old Fischer 344 rats. We also observed mitochondrial structure and autolysosomes by transmission electron microscopy.

Results

Expression of the autophagosome formation marker LC3/Atg8 and markers of mitochondrial autophagy (mitophagy) were markedly decreased in the kidneys of the HC group, and markedly increased in CR kidneys. p62/SQSTM1 and polyubiquitin aggregates increased in HC kidneys, and decreased in CR kidneys. Transmission electron microscopy demonstrated that HC kidneys showed severe abnormal mitochondrial morphology with fewer autolysosomes, while CR kidneys exhibited normal mitochondrial morphology with numerous autolysosomes. The level of 8-hydroxydeoxyguanosine was increased in HC kidneys and decreased in CR kidneys. Markers of aging, such as p16 and senescence-associated-galactosidase, were increased significantly in the HC group and decreased significantly in the CR group.

Conclusion

The study firstly suggests that HC diet inhibits renal autophagy and aggravates renal oxidative damage and aging, while CR enhances renal autophagy and ameliorates oxidative damage and aging in the kidneys.     

Delayed mTOR inhibition with low dose of everolimus reduces TGFβ expression, attenuates proteinuria and renal damage in the renal mass reduction model

Background

The immunosuppressive mammalian target of rapamycin (mTOR) inhibitors are widely used in solid organ transplantation, but their effect on kidney disease progression is controversial. mTOR has emerged as one of the main pathways regulating cell growth, proliferation, differentiation, migration, and survival.The aim of this study was to analyze the effects of delayed inhibition of mTOR pathway with low dose of everolimus on progression of renal disease and TGFβ expression in the 5/6 nephrectomy model in Wistar rats.

Methods

This study evaluated the effects of everolimus (0.3 mg/k/day) introduced 15 days after surgical procedure on renal function, proteinuria, renal histology and mechanisms of fibrosis and proliferation.

Results

Everolimus treated group (EveG) showed significantly less proteinuria and albuminuria, less glomerular and tubulointerstitial damage and fibrosis, fibroblast activation cell proliferation, when compared with control group (CG), even though the EveG remained with high blood pressure. Treatment with everolimus also diminished glomerular hypertrophy.Everolimus effectively inhibited the increase of mTOR developed in 5/6 nephrectomy animals, without changes in AKT mRNA or protein abundance, but with an increase in the pAKT/AKT ratio. Associated with this inhibition, everolimus blunted the increased expression of TGFβ observed in the remnant kidney model.

Conclusion

Delayed mTOR inhibition with low dose of everolimus significantly prevented progressive renal damage and protected the remnant kidney. mTOR and TGFβ mRNA reduction can partially explain this anti fibrotic effect. mTOR can be a new target to attenuate the progression of chronic kidney disease even in those nephropathies of non-immunologic origin.     

Urinary Exosomes: A Novel Means to Non-Invasively Assess Changes in Renal Gene and Protein Expression

Background

In clinical practice, there is a lack of markers for the non-invasive diagnosis and follow-up of kidney disease. Exosomes are membrane vesicles, which are secreted from their cells of origin into surrounding body fluids and contain proteins and mRNA which are protected from digestive enzymes by a cell membrane.

Methods

Toxic podocyte damage was induced by puromycin aminonucleoside in rats (PAN). Urinary exosomes were isolated by ultracentrifugation at different time points during the disease. Exosomal mRNA was isolated, amplified, and the mRNA species were globally assessed by gene array analysis. Tissue-specific gene and protein expression was assessed by RT-qPCR analysis and immunohistochemistry.

Results

Gene array analysis of mRNA isolated from urinary exosomes revealed cystatin C mRNA as one of the most highly regulated genes. Its gene expression increased 7.5-fold by day 5 and remained high with a 1.9-fold increase until day 10. This was paralleled by a 2-fold increase in cystatin C mRNA expression in the renal cortex. Protein expression in the kidneys also dramatically increased with de novo expression of cystatin C in glomerular podocytes in parts of the proximal tubule and the renal medulla. Urinary excretion of cystatin C increased approximately 2-fold.

Conclusion

In this proof-of-concept study, we could demonstrate that changes in urinary exosomal cystatin C mRNA expression are representative of changes in renal mRNA and protein expression. Because cells lining the urinary tract produce urinary exosomal cystatin C mRNA, it might be a more specific marker of renal damage than glomerular-filtered free cystatin C.     

Optimal conditions of LDR to protect the kidney from diabetes: Exposure to 12.5 mGy X-rays for 8 weeks efficiently protects the kidney from diabetes

Aims

We reported the attenuation of diabetes-induced renal dysfunction by exposure to multiple low-dose radiation (LDR) at 25 mGy every other day by suppressing renal oxidative damage. We here explored the optimal conditions of LDR to protect the kidney from diabetes.

Main methods

Male C57BL/6J mice with type 1 diabetes were induced with multiple injections of low-dose streptozotocin. Diabetic mice received whole body X-irradiation at a dose of 12.5, 25 or 50 mGy every other day for either 4 or 8 weeks. Age-matched normal mice were similarly irradiated at the dose of 25 mGy for 4 or 8 weeks. The renal function and histopathological changes were examined at the 4th and 8th weeks of the study.

Key findings

Diabetes induced renal dysfunction is shown by the decreased creatinine and increased microalbumin in the urine. Renal oxidative damage, detected by protein nitration and lipid oxidation, and remodeling, reflected by increased expression of connective tissue growth factor, collagen IV and fibronectin, were significantly increased in diabetic mice. All these renal pathological and function changes in diabetic mice were significantly attenuated by exposure to LDR at all regimens, among which, however, exposure to LDR at 12.5 mGy for 8 weeks provided the best protective effect on the kidney of diabetic mice.

Significance

Our results suggest that whole-body LDR at 12.5 mGy every other day for 8 weeks is the optimal condition of LDR to protect the kidney from diabetes.     

Sodium Thiosulfate Ameliorates Oxidative Stress and Preserves Renal Function in Hyperoxaluric Rats

Background

Hyperoxaluria causes crystal deposition in the kidney, which leads to oxidative stress and to injury and damage of the renal epithelium. Sodium thiosulfate (STS, Na₂S₂O₃) is an anti-oxidant, which has been used in human medicine for decades. The effect of STS on hyperoxaluria-induced renal damage is not known.

Methods

Hyperoxaluria and renal injury were induced in healthy male Wistar rats by chronic exposure to ethylene glycol (EG, 0.75%) in the drinking water for 4 weeks. The treatment effects of STS, NaCl or Na₂SO₄ were compared. Furthermore, the effects of STS on oxalate-induced oxidative stress were investigated in vitro in renal LLC-PK1 cells.

Results

Chronic EG exposure led to hyperoxaluria, oxidative stress, calcium oxalate crystalluria and crystal deposition in the kidneys. Whereas all tested compounds significantly reduced crystal load, only STS-treatment maintained tissue superoxide dismutase activity and urine 8-isoprostaglandin levels in vivo and preserved renal function. In in vitro studies, STS showed the ability to scavenge oxalate-induced ROS accumulation dose dependently, reduced cell-released hydrogen peroxide and preserved superoxide dismutase activity. As a mechanism explaining this finding, STS was able to directly inactivate hydrogen peroxide in cell-free experiments.

Conclusions

STS is an antioxidant, which preserves renal function in a chronic EG rat model. Its therapeutic use in oxidative-stress induced renal-failure should be considered.     

Renal Involvement in Non-Hodgkin Lymphoma: Proven by Renal Biopsy

Aims

To determine the spectrum of renal lesions in patients with kidney involvement in non-Hodgkin''s lymphoma (NHL) by renal biopsy.

Methods

The clinical features and histological findings at the time of the renal biopsy were assessed for each patient.

Results

We identified 20 patients with NHL and renal involvement, and the diagnosis of NHL was established following the kidney biopsy in 18 (90%) patients. The types of NHL include the following: chronic lymphocytic leukemia/small lymphocytic lymphoma (n = 8), diffuse large B-cell lymphoma (n = 4), T/NK cell lymphoma (n = 3), lymphoplasmacytic lymphoma (n = 2), cutaneous T-cell lymphoma (n = 1), mucosa-associated lymphoid tissue lymphoma (n = 1) and mantle cell lymphoma (n = 1). All presented with proteinuria, and 15 patients had impaired renal function. The pathological findings included (1) membranoproliferative glomerulonephritis-like pattern in seven patients; (2) crescent glomerulonephritis in four; (3) minimal-change disease in three, and glomeruli without specific pathological abnormalities in three; (4) intraglomerular large B-cell lymphoma in one; (5) intracapillary monoclonal IgM deposits in one; (6) primary diffuse large B-cell lymphoma of the kidneys in one; and (7) lymphoma infiltration of the kidney in eight patients.

Conclusion

A wide spectrum of renal lesions can be observed in patients with NHL, and NHL may be first proven by renal biopsies for evaluation of kidney injury or proteinuria. Renal biopsy is necessary to establish the underlying cause of renal involvement in NHL.