Progression Of Renal Injury Research Articles

Obesity, kidney dysfunction and hypertension: mechanistic links.

Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal andrenal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.

USP36 protects proximal tubule cells from ischemic injury by stabilizing c-Myc and SOD2

Acute kidney injury (AKI) is a progressive renal injury with high morbidity and mortality, however, the mechanism is far from being clarified and effective clinical interventions are lacking. USP36 is a deubiquitination enzyme involved in a variety of cellular biological processes, but its involvement in renal cell apoptosis and kidney disease is largely unknown. In the present study, we confirmed the decreased expression of USP36 both in vivo in mouse and human AKI samples and in vitro ischemic human renal proximal tubular cells, which are extremely sensitive to the damage of ischemic injury. Importantly, we found that overexpression of USP36 markedly decreased ischemia-induced apoptosis and oxidative stress in HK-2 cells, which was accompanied by elevated c-Myc and SOD2 protein levels with alleviated ischemia-induced ubiquitination of both proteins. Our findings revealed a novel role of USP36 in inhibiting apoptosis of human renal tubular cells induced by ischemia, and provided a potential therapeutic target for AKI treatment.

Prevention of Vascular Congestion Improves Renal Recovery and Function Post Renal Ischemia‐Reperfusion in Male Spontaneous Hypertensive Rats

Acute kidney injury (AKI) due to ischemia‐reperfusion (IR) is a serious and frequent complication in clinical settings and often progresses to kidney failure. The male gender is associated with greater severity and mortality following AKI, and young males have a greater prevalence of hypertension vs. age‐matched females. Despite the widespread prevalence of hypertension as a common co‐morbid condition with AKI, the impact of established hypertension on the progression of renal injury post‐AKI in either sex is poorly understood. Vascular congestion in the outer medulla is an early event occurring after IR, and congestion has been linked to worse renal outcomes following IR. The present study tested the hypothesis that increased vascular congestion in hypertensive males leads to impaired renal recovery compared to hypertensive females following renal IR. 13 wk old male and female normotensive Sprague Dawley rats (SD) and Spontaneous Hypertensive Rats (SHR) were subjected to sham or 25‐minute warm bilateral ischemia followed by reperfusion (n=6). Blood and urine were collected at 24 hrs and 7 days after IR; kidneys were harvested at 7 days for histological analysis. IR increased plasma creatinine (Pcr), BUN and proteinuria in all groups compared to respective sham controls at 24 hrs, with a sex difference in IR‐induced increases in Pcr observed in SD but not in SHR (SD Scr: Psex*IR<0.05; SHR Pcr: Psex*IR=0.4). At 7 days post‐IR, Pcr and BUN remained elevated only in male SHR compared to sham control (Pcr: PIR=0.03; BUN: PIR<0.05); Pcr and BUN returned to sham levels in all other groups. Histological examination of SHR kidneys at 7 days post‐IR showed sustained increases in vascular congestion (PIR=0.01; Psex*IR=0.002), damaged tubules (PIR=0.0003; Psex*IR=0.0019) and tubular cell apoptosis (P IR=0.001; Psex*IR=0.001) compared to sham controls in male SHR but not in females. Further, to study the role of IR induced vascular congestion on impaired recovery and loss of renal function in male SHR, additional SHR were pretreated with heparin (1500U/kg, n=6) prior to IR. Pre‐treatment with heparin prevented IR‐induced vascular congestion (PIR*Heparin=0.04) and tubular damage (PIR*Heparin=0.02) and improved renal function in male SHR 7 days post‐IR (Scr‐PIR*Heparin<0.05; BUN: PIR*Heparin=0.02) compared to heparin treated sham controls. Heparin pretreatment did not alter kidney function in female SHR 7 days post‐IR (Pcr‐PIR*Heparin=0.9; BUN: PIR*Heparin=0.2). In conclusion, our data demonstrated that persistent IR‐induced vascular congestion is a major driving factor to long‐term impaired renal recovery post IR in hypertensive males.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cyclooxygenase‐2 Regulates the Renal Expression of Indoleamine 2,3‐dioxygenase

Chronic kidney disease (CKD) affects approximately 10% of the population. In CKD patients, the majority of metabolic pathways are in disarray, which most likely contributes to the wide variety of comorbidities observed in these patients. However, few studies have focused on the unique regulatory aspects of enzyme systems during CKD development and progression. The cyclooxygenase‐2 (COX‐2)/prostaglandin (PG) system plays a dominant role in the progression of renal injury. Interestingly, it has been shown that the COX‐2/PG system modulates the activity of indoleamine 2,3‐dioxygenase (IDO) in tumors. Catabolism of tryptophan by IDO gives rise to numerous biologically active metabolites implicated in CKD progression. Therefore, the aim of this project is to explore the interplay between the COX‐2 and IDO enzyme systems during renal injury.We studied the gene expression of IDO, COX‐2 as well as several fibrosis and inflammatory markers in human and murine precision‐cut kidney slices (PCKS) and COX‐2 KO mice. Furthermore, we evaluated the gene expression profile after treatment with butaprost, an EP2 receptor agonist, in hPCKS and following treatment with SC‐236, a selective COX‐2 inhibitor, in mPCKS.Our results demonstrated that IDO gene expression was markedly increased in both human and mouse PCKS during the first 24h of culturing, after which levels dropped again. This expression profile was similar to the gene expression of various cytokines (e.g. IL‐6 and CXCL1), suggesting a potential pro‐inflammatory role of IDO. In addition, in COX‐2 KO animals, constitutive gene expression of IDO was increased as compared to wild‐type mice, and the knockout animals appeared to be more prone to renal fibrosis. Moreover, treatment with butaprost suppressed IDO gene expression, while exposure to SC‐236 induced IDO mRNA expression as well as the gene levels of IL‐6 and IL‐8.Taken together, it appears that COX‐2 suppresses IDO gene expression. In addition, our findings suggest a potential pro‐inflammatory role of IDO. However, the precise role of IDO in CDK development and progression requires further study.Support or Funding InformationThis work was kindly supported by Lundbeckfonden, grant number R231‐2016‐2344.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of Gemfibrozil on the Progression of Proteinuria in Obese Dahl Salt‐Sensitive Rats

The prevalence of obesity has increased dramatically within the last decade and is now considered an independent risk factor for chronic kidney disease (CKD). Recently, we reported that obese Dahl salt‐sensitive leptin receptor mutant (SSLepRmutant) rats exhibit dyslipidemia and renal injury independent of hyperglycemia that progresses to CKD. Interestingly, the kidneys from the SSLepRmutant strain displayed increased renal triglycerides and significant glomerular injury including podocyte foot process effacement and lipid droplets. Lipid‐lowering drugs such as fibrates have proven to be renoprotective in various models of kidney disease. Therefore, in the current study, we tested the effects of gemfibrozil, a fibrate, on the progression of renal injury in SSLepRmutant rats. Twelve‐week‐old SSWT and SSLepRmutant rats were separated into four groups (n=4 in each group): (1) SSWT and (2) SSLepRmutant rats treated with vehicle and (3) SSWT and (4) SSLepRmutant rats treated with gemfibrozil (200 mg/kg/day, orally, powdered food) for 4 weeks. Treatment with gemfibrozil had no effect on body weight or blood glucose levels in SSWT and SSLepRmutant rats. We observed greater than a 10‐fold increase in plasma triglyceride levels in the SSLepRmutant strain versus the values measured in SSWT rats (1265±380 and 117±19 mg/day, respectively). Gemfibrozil treatment significantly reduced plasma triglycerides by 64% in SSWT rats (41±20 mg/dL) and 57% in the SSLepRmutant strain (549±108 mg/dL). During the course of the study, proteinuria rose from 89±26 and 416±11 mg/day to 181±46 and 675±47 mg/day in SS and SSLepRmutant rats, respectively. Chronic treatment with gemfibrozil markedly decreased the progression of proteinuria by 52% in SSWT rats (87±17 mg/day) and 43% in the SSLepRmutant strain (385±75 mg/day). The kidneys from vehicle‐treated SSLepRmutant rats displayed significant glomerular injury with mesangial expansion and increased interstitial fibrosis and tubular protein casts compared to SSWT rats. Gemfibrozil treatment markedly decreased these renal abnormalities in both strains. These data indicate that reducing plasma lipid levels with gemfibrozil prevents the progression of proteinuria in both lean SSWT and obese SSLepRmutant rats.Support or Funding InformationThis study was supported by GM104357 and DK109133.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Increased Renal Expression of Adhesion Molecules and Inflammation in Diabetic Nephropathy

Diabetic nephropathy (DN) is the primary risk factor for end‐stage renal disease (ESRD). Previously, we reported that the T2DN rat develops hyperglycemia by 3 months of age, proteinuria by 6 months and progressive renal injury which closely mimics human diabetic nephropathy, including focal glomerular sclerosis, mesangial matrix expansion, thickening of basement membranes, and progressive renal interstitial fibrosis. However, the role of adhesion molecules and renal inflammation in the pathogenesis of DN in this model has not been studied. In the present study, we compared the expression of cytokine and adhesion molecules, as well as the infiltration of inflammatory cells in young (3‐month old), middle‐aged (12‐month old) and elderly (18‐month old) T2DN and SD rats. We found that the expression of the adhesion molecules, ICAM‐1 and E‐selectin, were elevated in elderly T2DN (1.3‐fold and 1.8‐fold, respectively), and E‐selectin level was already higher in young T2DN (2.1‐fold) than in age‐matched SD rats. The number of infiltrating CD45+ leucocytes, CD3+ T cells, CD3−/CD4+ monocytes and CD68+ macrophages per gram of kidney were increased by 2.81±0.45, 2.82±0.44, 3.06±1.05, and 7.86±3.75 times, respectively, in elderly T2DN versus SD control. The rise in infiltrating inflammatory cells was correlated with elevated proteinuria (1144±202 in T2DN vs. 293±47 mg/day in SD) and plasma creatinine level (1.01±0.1 mg/dl in elderly T2DN vs. 0.50±0.02 mg/dl in SD), a greater degree of glomerular sclerosis and a 2‐fold increase in renal fibrosis in elderly T2DN rats versus age‐matched SD rats. These results indicate that the increased expression of adhesion molecules promotes infiltration of inflammatory cells, which is associated with the progression of DN and suggests that immune modulatory drugs may slow the progression of this disease.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Administration of a selective prostaglandin E2 receptor agonist attenuates renal fibrosis in vitro and in vivo

Renal fibrosis plays a pivotal role in the development and progression of chronic kidney disease (CKD), which affects 10% of the adult population. Previously, it has been demonstrated that the cyclooxygenase‐2 (COX‐2)/prostaglandin (PG) system influences the progression of renal injury. PGE2 interacts with four different G‐protein‐coupled PGE2 EP receptors, known as EP1–EP4, and plays a role in several biological functions. Previous studies show that the EP2 receptor is involved in progression of lung fibrosis. In this study, we investigated the effect of an EP2 agonist (butaprost) on renal fibrogenesis on a cellular, renal tissue and organismal level using well‐established in vivo and in vitro models as well as a recently developed human model of renal fibrosis. This model is ideal to study multicellular pathological processes, e.g. fibrosis, directly in human tissue since cellular diversity and organ architecture is maintained in the slices. Butaprost (50 μM) reduced TGF‐β‐induced fibronectin (FN) expression, Smad2/3 phosphorylation and epithelial‐mesenchymal transition in MDCK cells. In addition, treatment with 4 mg/kg butaprost attenuated the development of fibrosis in mice that underwent unilateral ureteral obstruction (UUO) surgery, as illustrated by a significant reduction in the gene and protein expression of α‐smooth muscle actin, FN and collagen 1A1. More importantly, a similar anti‐fibrotic effect of butaprost was observed in human precision‐cut kidney slices exposed to TGF‐β. The mechanism of action of butaprost appeared to be a direct effect on TGF‐β/Smad signaling, which was independent of the cAMP/PKA pathway. In conclusion, this study demonstrates that stimulation of the EP2 receptor effectively mitigates renal fibrogenesis in various fibrosis models. These findings warrant further research into the clinical application of butaprost, or other EP2 agonists, for the inhibition of renal fibrosis.Support or Funding Information Sources of support: This work was kindly supported by Lundbeckfonden, grant number R231‐2016‐2344 as well as the Danish Council for Independent Research, grant number 6110‐00231B, Aarhus University Research Foundation, grant number AUFF‐E‐2015‐FLS‐8‐69 and Hildur and Dagny Jacobsens Foundation grant number 1295716‐1.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Bioengineered VEGF Therapy Following Angioplasty in Renovascular Disease: More and Better Microvessels

Asymmetric dimethylarginine (ADMA) is a pro‐atherogenic marker of endothelial dysfunction and inhibitor of endothelial nitric oxide synthase (eNOS) that may contribute to progression of renal injury. We designed a novel bioengineered fusion of an elastin‐like polypeptide with vascular endothelial growth factor (ELP‐VEGF). We showed that ELP‐VEGF therapy in renovascular disease (RVD) restores renal hemodynamics by improving microvascular (MV) rarefaction in the stenotic kidney. Our preliminary data suggest that co‐adjuvant ELP‐VEGF therapy with renal angioplasty (PTRAs) enhances renal recovery compared to PTRAs alone. We aimed to elucidate underlying mechanisms of renoprotection and test the hypothesis that co‐adjuvant ELP‐VEGF+PTRAs decreases ADMA and thus, its effects on eNOS inhibition, causing augmented renal bioavailability of NO and improvements of MV endothelial function, renal hemodynamics, and reversal of MV rarefaction.RVD was induced by unilateral renal artery stenosis and high cholesterol feeding in 14 pigs. Six weeks later, single‐kidney blood flow (RBF) and filtration (GFR) were quantified in vivo using multi‐detector CT at baseline and during an endothelium‐dependent challenge (with acetylcholine, Ach). Then pigs were randomized to either PTRAs+placebo or PTRAs followed by intra‐renal ELP‐VEGF therapy (RVD+PTRAs+ELP‐VEGF). Pigs were observed for four additional weeks; in vivo CT studies repeated, then pigs were euthanized, and ex vivo renal MV micro‐CT quantification, plasma ADMA concentration, and stenotic kidney eNOS, VEGF, and Flk‐1 expression were measured.Pre‐treatment renal hemodynamics were equally reduced and PTRAs similarly resolved renal artery stenosis in all pigs with RVD. However, PTRAs+ELP‐VEGF led to significantly greater recovery of RBF and GFR and responses to Ach than PTRAs alone. Improvements in renal function were accompanied by decreased plasma ADMA and enhanced stenotic kidney expression of eNOS, VEGF, and its Flk‐1 receptor, and improved MV density and remodeling (Figure).This study extends our previous findings by identifying a potential mechanism of enhanced renal recovery after combined PTRAs+ELP‐VEGF therapy. Reductions in circulating ADMA may have contributed to the improved renal expression of eNOS in tandem with VEGF therapy, resulting in augmented renal bioavailability of NO and ultimately improving functional and structural renal MV rarefaction. Furthermore, decreased ADMA may suggest a slowing down of the atherosclerotic process in the RVD kidney, which may have also helped contribute to the greater improvements in MV density and overall renal function after PTRAs+ELP‐VEGF therapy.Support or Funding InformationR41DK109737, R01HL095638, P01HL51971, P20GM104357, R01HL121527, EIA18490005, IPA34170267, and T32HL105324This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Pentoxifylline for Renal Protection in Diabetic Kidney Disease. A Model of Old Drugs for New Horizons.

Diabetic kidney disease is one of the most relevant complications in diabetes mellitus patients, which constitutes the main cause of end-stage renal disease in the western world. Delaying the progression of this pathology requires new strategies that, in addition to the control of traditional risk factors (glycemia and blood pressure), specifically target the primary pathogenic mechanisms. Nowadays, inflammation is recognized as a critical novel pathogenic factor in the development and progression of renal injury in diabetes mellitus. Pentoxifylline is a nonspecific phosphodiesterase inhibitor with rheologic properties clinically used for more than 30 years in the treatment of peripheral vascular disease. In addition, this compound also exerts anti-inflammatory actions. In the context of diabetic kidney disease, pentoxifylline has shown significant antiproteinuric effects and a delay in the loss of estimated glomerular filtration rate, although at the present time there is no definitive evidence regarding renal outcomes. Moreover, recent studies have reported that this drug can be associated with a positive impact on new factors related to kidney health, such as Klotho. The use of pentoxifylline as renoprotective therapy for patients with diabetic kidney disease represents a new example of drug repositioning.

Renoprotective Effect of the Histone Deacetylase Inhibitor CG200745 in DOCA-Salt Hypertensive Rats

The novel histone deacetylase inhibitor CG200745 was initially developed to treat various hematological and solid cancers. We investigated the molecular mechanisms associated with the renoprotective effects of CG200745 using deoxycorticosterone acetate (DOCA)-salt hypertensive (DSH) rats. DOCA strips (200 mg/kg) were implanted into rats one week after unilateral nephrectomy. Two weeks after DOCA implantation, DSH rats were randomly divided into two groups that received either physiological saline or CG200745 (5 mg/kg/day) for another two weeks. The extent of glomerulosclerosis and tubulointerstitial fibrosis was determined by Masson’s trichrome staining. The renal expression of fibrosis and inflammatory markers was detected by semiquantitative immunoblotting, a polymerase chain reaction, and immunohistochemistry. Pathological signs such as glomerulosclerosis, tubulointerstitial fibrosis, increased systolic blood pressure, decreased creatinine clearance, and increased albumin-to-creatinine ratios in DSH rats were alleviated by CG200745 treatment compared to those manifestations in positive control animals. Furthermore, this treatment counteracted the increased expression of αSMA, TGF-β1, and Bax, and the decreased expression of Bcl-2 in the kidneys of DSH rats. It also attenuated the increase in the number of apoptotic cells in DSH rats. Thus, CG200745 can effectively prevent the progression of renal injury in DSH rats by exerting anti-inflammatory, anti-fibrotic, and anti-apoptotic effects.

Sodium 4-phenylbutyrate treatment protects against renal injury in NZBWF1 mice.

Systemic lupus erythematosus (SLE) is an autoimmune disease predominantly affecting women and often leading to lupus nephritis and kidney damage. Endoplasmic reticulum (ER) stress has been implicated in several forms of kidney disease, but whether ER stress contributes to renal injury in SLE is unknown. To investigate this, a small molecule chaperone, sodium 4-phenylbutyrate (4-PBA), was administered to the New Zealand Black x New Zealand White F1 hybrid (NZBWF1) mouse model of SLE. In a prevention study, treatment with 4-PBA from 20 weeks of age (prior to the development of renal injury) delayed the onset of albuminuria and significantly reduced additional indices of renal injury compared with vehicle-treated NZBWF1 mice at 36 weeks of age, including collagen deposition, tubular casts, renal cell apoptosis, and blood urea nitrogen (BUN) concentration. To test whether ER stress contributes to the progression of renal injury once albuminuria has developed, mice were monitored for the onset of albuminuria (3+ or ≥300 mg/dl by dipstick measurement of 24-h urine sample) and once established, were either killed (onset group), or underwent 4-PBA or vehicle treatment for 4 weeks. Treatment with 4-PBA blocked the worsening of glomerular injury, reduced the number of dilated or cast-filled tubules, and reduced the number of apoptotic cells compared with vehicle-treated mice. BUN and left ventricle to bodyweight ratio (LV:BW) were also reduced by 4-PBA treatment. Renal expression of the endogenous chaperones, protein disulphide isomerase (PDI), and 78 kDa glucose-regulated protein (GRP78, also known as binding Ig protein (BiP)), were increased in 4-PBA-treated mice. Together, these results suggest a therapeutic potential for agents like 4-PBA in combating renal injury in SLE.

Blockade of enhancer of zeste homolog 2 alleviates renal injury associated with hyperuricemia.

Hyperuricemia has been identified as an independent risk factor for chronic kidney disease (CKD) and is associated with the progression of kidney diseases. It remains unknown whether enhancer of zeste homolog 2 (EZH2), a histone H3 lysine 27 methyltransferase, can regulate metabolism of serum uric acid and progression of renal injury induced by hyperuricemia. In this study, we demonstrated that blockade of EZH2 with 3-DZNeP, a selective EZH2 inhibitor, or silencing of EZH2 with siRNA inhibited uric acid-induced renal fibroblast activation and phosphorylation of Smad3, epidermal growth factor receptor (EGFR), and extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in cultured renal fibroblasts. Inhibition of EZH2 also suppressed proliferation of renal fibroblasts and epithelial-mesenchymal transition of tubular cells. In a mouse model of renal injury induced by hyperuricemia, EZH2 and trimethylation of histone H3 at lysine27 expression levels were enhanced, which was coincident with renal damage and increased expression of lipocalin-2 and cleaved caspase-3. Inhibition of EZH2 with 3-DZNeP blocked all these responses. Furthermore, 3-DZNeP treatment decreased the level of serum uric acid and xanthine oxidase activity, alleviated renal interstitial fibrosis, inhibited activation of transforming growth factor-β/Smad3, EGFR/ERK1/2, and nuclear factor-κB signaling pathways, as well as reduced expression of multiple chemokines/cytokines. Collectively, EZH2 inhibition can reduce the level of serum uric acid and alleviate renal injury and fibrosis through a mechanism associated with inhibition of multiple signaling pathways. Targeting EZH2 may be a novel strategy for the treatment of hyperuricemia-induced CKD.

Galectin 3 inhibition attenuates renal injury progression in cisplatin-induced nephrotoxicity.

Nephrotoxicity is a major toxic effect in chemotherapy, which constitutes up to 60% of hospitalized acute kidney injury (AKI). Very few treatment options exist to slow the transition from AKI to subsequent chronic kidney diseases (CKD). Here, we demonstrate that galectin-3 (Gal-3), a β-galactoside binding lectin that plays an important role in kidney fibrosis and renal failure, is one of the key factors for renal injury progression. Ectopic overexpression of Gal-3 significantly decreased the viability of HEK293, simultaneously inducing of cell cycle arrest and apoptosis. However, inhibition of Gal-3, mediated by modified citrus pectin (MCP), predominantly antagonized the pro-apoptotic effects. Mice were pre-treated with normal or 1% MCP-supplemented drinking water 1 week before cisplatin injection. Analyses of serum creatinine and renal tissue damage indicated that MCP-treated mice demonstrated increased renal function and attenuated renal fibrosis after cisplatin-induced injury. MCP-treated mice also demonstrated decreased renal fibrosis and apoptosis, as revealed by masson trichrome staining and Western blot analysis of cleaved caspase-3. Additionally, the protective role of Gal-3 inhibition in the kidney injury was shown to be mediated by protein kinase C α (PKC-α), which promoted cell apoptosis and collagen I synthesis in HEK293 cells. These results demonstrated the potential Gal-3 and PKC-α as therapeutic targets for the treatment of AKI and CKD.

Increased urinary miR-196a level predicts the progression of renal injury in patients with diabetic nephropathy.

Recent data suggest that miR-196a is predominantly expressed in the kidney and plays an inhibitory role in the progress of renal interstitial fibrosis (IF). However, the predictive value of miR-196a in diabetic nephropathy (DN) remains unknown. We validated the role of urinary miR-196a in the progression of renal injury in a cohort of patients with type 2 diabetes mellitus. Our study included 209 patients with biopsy-proven DN. The mean follow-up time was 54.03 ± 32.94 months. Histological lesions were assessed using the pathological classification established by the Renal Pathology Society. Percentages of IF and tubular atrophy were assessed using the Aperio ScanScope system. We measured the correlation of urinary miR-196a with clinical and pathological parameters using the Spearman's correlation test. The influence of urinary miR-196a on renal outcomes was assessed using Cox regression analysis. Urinary miR-196a levels correlated positively with proteinuria (ρ = 0.385, P < 0.001), duration of diabetes mellitus (ρ = 0.255, P < 0.001) and systolic blood pressure (ρ = 0.267, P < 0.001). The baseline estimated glomerular filtration rate (eGFR) and hemoglobin level showed a negative correlation with urinary miR-196a (ρ = -0.247, P < 0.001 and ρ = -0.236, P = 0.001, respectively). Pathologically, urinary miR-196a levels correlated with glomerular sclerosis and IF in patients with DN. Urinary miR-196a was significantly associated with progression to end-stage renal disease [hazard ratio (HR) 2.03, P < 0.001] and a 40% reduction of baseline eGFR (HR 1.75, P = 0.001), independent of age, gender, body mass index, mean arterial pressure and hemoglobinA1c level. However, urinary miR-196a did not improve predictive power to proteinuria and eGFR in DN patients. Increased urinary miR-196a was significantly associated with the progression of renal injury and might be a noninvasive prognostic marker of renal fibrosis in DN patients.

Understanding and managing atherosclerotic renovascular disease: still a work in progress.

Atherosclerotic renovascular disease (ARVD) is an unresolved therapeutic dilemma despite extensive pre-clinical and clinical studies. The pathophysiology of the disease has been widely studied, and many factors that may be involved in progressive renal injury and cardiovascular risk associated with ARVD have been identified. However, therapies and clinical trials have focused largely on attempts to resolve renal artery stenosis without considering the potential need to treat the renal parenchyma beyond the obstruction. The results of these trials show a staggering consistence: although nearly 100% of the patients undergoing renal angioplasty show a resolution of the vascular obstruction, they do not achieve significant improvements in renal function or blood pressure control compared with those patients receiving medical treatment alone. It seems that we may need to take a step back and reconsider the pathophysiology of the disease in order to develop more effective therapeutic strategies. This mini-review discusses potential therapeutic alternatives that focus on the renal parenchyma distal to the vascular obstruction and may provide additional tools to enhance current treatment of ARVD.

Sex Differences in Renal Inflammation and Injury in High-Fat Diet-Fed Dahl Salt-Sensitive Rats.

We examined the impact of sex on high-fat diet (HFD)-induced renal alterations in Dahl salt-sensitive and Sprague Dawley rats. In Dahl rats, HFD (60% kcal from fat for 24-26 weeks starting at weaning) significantly and equally increased blood pressure in males and females when compared with rats fed a control diet (10% kcal from fat). Male Dahl rats on HFD exhibited progressive renal histological injury and moderately increased renal macrophage infiltration at 10 and 24 weeks of feeding when compared with males on control diet. Female Dahl rats had lower grade renal injury and less macrophage infiltration (except at 17 weeks) than males regardless of diet. Male Dahl rats on both diets showed progressively increasing numbers of renal T-cells, a pattern not observed in females. HFD per se did not significantly affect renal T-cell number. Male Dahl rats had lower renal regulatory T-cells cell ratio than females at 24 weeks. Renal macrophage and T-cell infiltrations were highly correlated to final mean arterial pressure levels in males but not in females. Sprague Dawley rats fed HFD were normotensive without significant renal injury/inflammation after 24 weeks of feeding. In summary, HFD feeding fails to increase arterial blood pressure in Sprague Dawley rats but strongly promotes hypertension in both male and female Dahl salt-sensitive rats. Only Dahl males, however, exhibited blood pressure-associated renal inflammation and injury. Maintenance of regulatory T-cells ratio may protect against hypertension-associated renal injury/inflammation but not HFD-induced hypertension.

Urinary Neutrophil Gelatinase-Associated Lipocalin as a Biomarker for Renal Injury in Liver Transplant Recipients Using Calcineurin Inhibitors

BackgroundUrinary neutrophil gelatinase-associated lipocalin (uNGAL) is an early biomarker of renal injury. We examined the feasibility of using uNGAL as an early predictor of renal impairment in patients under calcineurin inhibitors in liver transplant recipients. MethodsFrom urine samples obtained from liver transplant recipients, the glomerular filtration rate (GFR) at the time of urine sampling was compared with that at 5 to 7 months later. Patients were divided into 3 groups according to initial GFR and then divided into 2 groups according to the uNGAL level of 25 ng/mL. Progression of renal injury (PRI) was defined as a decrease in the GFR of more than 5 mL/min/1.73 m2 in the mild or moderate groups, or if a normal group patient shifted to the mild or moderate group. ResultsFifty-one patients were enrolled. The mean uNGAL level was higher in the moderate group than in the normal and mild groups (18.38 ± 14.31 vs 7.74 ± 8.13; P < .01). A proportion of uNGAL-high was also higher in the moderate group than in the mild group (40% vs 5%; P = .03). uNGAL-high was a risk factor for 6-month PRI (odds ratio, 60.375; 95% confidence interval, 1.283–4088.25; P = .037) and 1-year PRI (odds ratio, 21.311; % confidence interval, 0.947–479.578; P = .054). ConclusionsA uNGAL of >25 ng/mg can be a marker for moderate renal impairment (GFR of 30–59 mL/min/1.73 m2) and a predictor of PRI at 6 months in patients using calcineurin inhibitors. Renal protection strategies should be considered in liver transplant recipients with a uNGAL of >25 ng/mg in spot urine sampling.

Renoprotection of dapagliflozin in human renal proximal tubular cells via the inhibition of the high mobility group box 1‑receptor for advanced glycation end products‑nuclear factor‑κB signaling pathway

Sodium‑glucose co‑transporter 2 (SGLT2) inhibitors are recently developed oral hypoglycemic agents, which act on renal proximal tubules by reducing the reabsorption of glucose and increasing the excretion of glucose in the urine. However, the mechanism underlying renoprotection has not been fully elucidated. Previous studies have indicated that the expression of high mobility group box 1 (HMGB1) increased in patients with kidney disease, and may result in renal damage through the activation of nuclear factor‑κB (NF‑κB) and an increase in receptor for advanced glycation end products (RAGE) expression. The aim of the present study was to evaluate the effects of the SGLT‑2 inhibitor dapagliflozin on cultured human proximal tubular epithelial cells (HK‑2). HK‑2 cells were grown under high glucose conditions for 48h in the presence or absence of dapagliflozin. The markers of oxidative stress, inflammation and fibrillation levels were then detected by reverse transcription‑quantitative polymerase chain reaction and western blotting. Hyperglycemia increased the mRNA expression and protein levels of malondialdehyde (MDA), superoxide dismutase (SOD), monocyte chemoattractant protein‑1 (MCP‑1), intercellular adhesion molecule‑1 (ICAM‑1), fibronectin (FN), collagenase type 1 (COL‑1), HMGB1, RAGE and NF‑κB, and the effects could be reversed by dapagliflozin in a concentration‑dependent manner. The results of the present study suggested that HMGB1 increased the expression and secretion of markers of inflammation, oxidative stress and fibrillation, including MDA, SOD, MCP‑1, ICAM‑1, FN and COL‑1, in diabetic nephropathy. However, dapagliflozin significantly reduced the levels of inflammatory markers and postponed the progression of renal injury. It was therefore suggested this may be mediated through the inhibition of HMGB1‑RAGE-NF‑κB signaling pathway.

Simultaneous activation of innate and adaptive immunity participates in the development of renal injury in a model of heavy proteinuria.

Protein overload of proximal tubular cells (PTCs) can promote interstitial injury by unclear mechanisms that may involve activation of innate immunity. We investigated whether prolonged exposure of tubular cells to high protein concentrations stimulates innate immunity, triggering progressive interstitial inflammation and renal injury, and whether specific inhibition of innate or adaptive immunity would provide renoprotection in an established model of massive proteinuria, adriamycin nephropathy (ADR). Adult male Munich–Wistar rats received a single dose of ADR (5 mg/kg, iv), being followed for 2, 4, or 20 weeks. Massive albuminuria was associated with early activation of both the NF-κB and NLRP3 innate immunity pathways, whose intensity correlated strongly with the density of lymphocyte infiltration. In addition, ADR rats exhibited clear signs of renal oxidative stress. Twenty weeks after ADR administration, marked interstitial fibrosis, glomerulosclerosis, and renal functional loss were observed. Administration of mycophenolate mofetil (MMF), 10 mg/kg/day, prevented activation of both innate and adaptive immunity, as well as renal oxidative stress and renal fibrosis. Moreover, MMF treatment was associated with shifting of M from the M1 to the M2 phenotype. In cultivated NRK52-E cells, excess albumin increased the protein content of Toll-like receptor (TLR) 4 (TLR4), NLRP3, MCP-1, IL6, IL-1β, Caspase-1, α-actin, and collagen-1. Silencing of TLR4 and/or NLRP3 mRNA abrogated this proinflammatory/profibrotic behavior. Simultaneous activation of innate and adaptive immunity may be key to the development of renal injury in heavy proteinuric disease. Inhibition of specific components of innate and/or adaptive immunity may be the basis for future strategies to prevent chronic kidney disease (CKD) in this setting.

Sodium bicarbonate loading limits tubular cast formation independent of glomerular injury and proteinuria in Dahl salt-sensitive rats.

Sodium bicarbonate (NaHCO3) slows the decline in kidney function in patients with chronic kidney disease (CKD), yet the mechanisms mediating this effect remain unclear. The Dahl salt-sensitive (SS) rat develops hypertension and progressive renal injury when fed a high salt diet; however, the effect of alkali loading on kidney injury has never been investigated in this model. We hypothesized that NaHCO3 protects from the development of renal injury in Dahl salt-sensitive rats via luminal alkalization which limits the formation of tubular casts, which are a prominent pathological feature in this model. To examine this hypothesis, we determined blood pressure and renal injury responses in Dahl SS rats drinking vehicle (0.1 M NaCl) or NaHCO3 (0.1 M) solutions as well as in Dahl SS rats lacking the voltage-gated proton channel (Hv1). We found that oral NaHCO3 reduced tubular NH4+ production, tubular cast formation, and interstitial fibrosis in rats fed a high salt diet for 2 weeks. This effect was independent of changes in blood pressure, glomerular injury, or proteinuria and did not associate with changes in renal inflammatory status. We found that null mutation of Hv1 also limited cast formation in Dahl SS rats independent of proteinuria or glomerular injury. As Hv1 is localized to the luminal membrane of TAL, our data suggest that alkalization of the luminal fluid within this segment limits cast formation in this model. Reduced cast formation, secondary to luminal alkalization within TAL segments may mediate some of the protective effects of alkali loading observed in CKD patients.