Megalin-mediated albumin endocytosis in renal proximal tubules is involved in the antiproteinuric effect of angiotensin II type 1 receptor blocker in a subclinical acute kidney injury animal model

BackgroundTubule-interstitial injury (TII) is one of the mechanisms involved in the progression of renal diseases with progressive proteinuria. Angiotensin II (Ang II) type 1 receptor blockers (ARBs) have been successfully used to treat renal diseases. However, the mechanism correlating treatment with ARBs and proteinuria is not completely understood. The hypothesis that the anti-proteinuric effect of losartan is associated with the modulation of albumin endocytosis in PT epithelial cells (PTECs) was assessed.MethodsWe used a subclinical acute kidney injury animal model (subAKI) and LLC-PK1 cells, a model of PTECs.ResultsIn subAKI, PT albumin overload induced TII development, measured by: (1) increase in urinary lactate dehydrogenase and γ-glutamyltranspeptidase activity; (2) proteinuria associated with impairment in megalin-mediated albumin reabsorption; (3) increase in luminal and interstitial space in tubular cortical segments. These effects were avoided by treating the animals with losartan, an ARB. Using LLC-PK1 cells, we observed that: (1) 20 mg/mL albumin increased the secretion of Ang II and decreased megalin-mediated albumin endocytosis; (2) the effects of Ang II and albumin were abolished by 10^?8 M losartan; (3) MEK/ERK pathway is the molecular mechanism underlying the Ang II-mediated inhibitory effect of albumin on PT albumin endocytosis.ConclusionOur results show that PT megalin-mediated albumin endocytosis is a possible target during the treatment of renal diseases patients with ARB.General significanceThe findings obtained in the present work represents a step forward to the current knowledge on about the role of ARBs in the treatment of renal disease.     

A high salt diet induces tubular damage associated with a pro-inflammatory and pro-fibrotic response in a hypertension-independent manner

High salt diet (HSD), considered a public health problem worldwide, is associated with chronic degenerative diseases including renal diseases. However, little is known about the effects of HSD on renal function independently of the development of hypertension. To address the hypothesis that HSD induces renal injuries even without changes in blood pressure, BALB/c mice were fed for 7 days with chow with a high salt content (0.3–8%). Blood pressure did not change and there was a decrease in cortical (Na⁺ + K⁺)ATPase and NHE3 exchanger and an increase in renal fractional excretion of sodium. Positive correlations between Na⁺ intake or urinary sodium excretion with proteinuria were found. HSD did not change glomerular function and structure, but induced tubule-interstitial injury measured by an increase in collagen deposition, interstitial space and γ-GT activity, a marker of tubular injury. These effects were associated with a decrease in cortical albumin reabsorption and megalin expression. Similarly, the addition of NaCl 20 mM to the incubation medium of LLC-PK1 cells reduced megalin expression and albumin endocytosis indicating that HSD could have a direct effect on proximal tubule cells. Furthermore, tubule-interstitial injury was associated with pro-inflammatory and pro-fibrotic phenotypes with an increase in Th1 and Th17 phenotypes and a decrease in Tregs followed by increases in IL-6, -17, -10, TNF-α, IFN-γ and TGF-β. Our results reveal a complex network involved in renal injuries induced by HSD independently of changes in blood pressure. These findings strengthen the importance of restriction of salt intake for the general population even for salt-resistant individuals.     

Dynamics of Urinary Calprotectin after Renal Ischaemia

Background: Urinary calprotectin has been identified as a promising biomarker for acute kidney injury. To date, however, the time-dependent changes of this parameter during acute kidney injury remain elusive. The aim of the present work was to define the time-course of urinary calprotectin secretion after ischaemia/reperfusion-induced kidney injury in comparison to neutrophil gelatinase—associated lipocalin, thereby monitoring the extent of tubular damage in nephron sparing surgery for kidney tumours. Methods: The study population consisted of 42 patients. Thirty-two patients underwent either open or endoscopic nephron sparing surgery for kidney tumours. During the surgery, the renal arterial pedicle was clamped with a median ischaemic time of 13 minutes (interquartile range, 4.5–20.3 minutes) in 26 patients. Ten retro-peritoneoscopic living donor nephrectomy patients and 6 nephron sparing surgery patients in whom the renal artery was not clamped served as controls. Urinary calprotectin and neutrophil gelatinase—associated lipocalin concentrations were repeatedly measured by enzyme-linked immunosorbent assay and assessed according to renal function parameters. Results: Urinary concentrations of calprotectin and neutrophil gelatinase—associated lipocalin increased significantly after ischaemia/reperfusion injury, whereas concentrations remained unchanged after nephron sparing surgery without ischaemia/reperfusion injury and after kidney donation. Calprotectin and neutrophil gelatinase—associated lipocalin levels were significantly increased 2 and 8 hours, respectively, post-ischaemia. Both proteins reached maximal concentrations after 48 hours, followed by a subsequent persistent decrease. Maximal neutrophil gelatinase—associated lipocalin and calprotectin concentrations were 9-fold and 69-fold higher than their respective baseline values. The glomerular filtration rate was only transiently impaired at the first post-operative day after ischaemia/reperfusion injury (p = 0.049). Conclusion: Calprotectin and neutrophil gelatinase—associated lipocalin can be used to monitor clinical and sub-clinical tubular damage after nephron sparing surgery for kidney tumours. Urinary calprotectin concentrations start rising within 2 hours after ischaemia/reperfusion-induced kidney injury.     

Renal epithelial injury and fibrosis

Chronic kidney disease at a certain advanced stage inevitably progresses to end stage renal failure characterized by the progressing loss of nephrons accompanied by the increasing appearance of fibrotic tissue, called renal fibrosis. The urgent question is whether renal fibrosis is a response to injury or if fibrosis acquires a self-sustaining progressive potential that actively contributes to the deterioration of the kidney. The present review distinguishes between renal fibrosis subsequent to a glomerular injury and fibrosis subsequent to a primary tubular injury. Glomerular diseases enter a progressing course after encroaching onto the tubule leading to what is generally called “tubulointerstitial fibrosis”. The progression of the injury at the level of the tubulointerstitium appears to be fully dependent on the progression of the disease in the corresponding glomerulus. Primary tubular injuries have a very good chance of recovery. If they develop a local fibrotic process, this seems to be supportive for recovery. Cases in which recovery fails appear to secondarily initiate a glomerular disease accounting for a glomerulus-dependent vicious cycle to progression. Even if most researchers think of renal fibrosis as a process promoting the progression of the disease this review points out that the available structural evidence speaks in favour of a protective role of fibrosis supporting recovery after acute tubular injury or, under progressing circumstances, providing a firm three-dimensional framework that permits still intact or partially damaged nephrons to survive. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.     

PKB/Akt partners with Dab2 in albumin endocytosis

Albumin in the glomerular filtrate is normally retrieved by concerted efforts of clathrin, LDL-type receptor megalin- and clathrin-associated sorting proteins. In glomerular diseases, albumin overload triggers a proapoptotic and inflammatory response contributing to tubulointerstitial fibrosis and tubular atrophy. The relationship between albumin overload-induced proximal tubule injury and albumin endocytosis remains to be discovered. We investigated presence of a possible overlap between endocytosis and cell survival. We showed a novel interaction between prosurvival protein, protein kinase B (PKB/Akt), and adaptor protein, disabled 2 (Dab2), with coimmunoprecipitation. Further delineation of this interaction by GST pull-down experiments utilizing different Dab2 constructs identified proline-rich domain as the interacting partner. Expression of Dab2 and PKB/Akt was downregulated at high concentrations of albumin associated with apoptosis. We then examined the physiological relevance of this interaction with functional studies. Overexpression of PKB/Akt increased albumin uptake in human proximal tubule cells. Conversely, inhibition of PKB/Akt with a nonselective Akt/PKB signaling inhibitor-2 and a dominant negative construct of PKB/Akt resulted in a decrease in albumin uptake. Inhibition of Dab2 by silencing RNA abolished PKB/Akt-induced albumin uptake demonstrating the physiological importance of this novel interaction. We concluded that PKB/Akt is part of an endocytic machinery and it mediates albumin uptake through its interaction with Dab2. The role that PKB/Akt plays in the endocytic cascade may dictate its decreased expression in proteinuric states in an attempt to limit albumin endocytosis that may tilt the balance between cell survival and apoptosis toward cell death.     

Reversal of anemia with allogenic RBC transfusion prevents post-cardiopulmonary bypass acute kidney injury in swine

Anemia during cardiopulmonary bypass (CPB) is strongly associated with acute kidney injury in clinical studies; however, reversal of anemia with red blood cell (RBC) transfusions is associated with further renal injury. To understand this paradox, we evaluated the effects of reversal of anemia during CPB with allogenic RBC transfusion in a novel large-animal model of post-cardiac surgery acute kidney injury with significant homology to that observed in cardiac surgery patients. Adult pigs undergoing general anesthesia were allocated to a Sham procedure, CPB alone, Sham+RBC transfusion, or CPB+RBC transfusion, with recovery and reassessment at 24 h. CPB was associated with dilutional anemia and caused acute kidney injury in swine characterized by renal endothelial dysfunction, loss of nitric oxide (NO) bioavailability, vasoconstriction, medullary hypoxia, cortical ATP depletion, glomerular sequestration of activated platelets and inflammatory cells, and proximal tubule epithelial cell stress. RBC transfusion in the absence of CPB also resulted in renal injury. This was characterized by endothelial injury, microvascular endothelial dysfunction, platelet activation, and equivalent cortical tubular epithelial phenotypic changes to those observed in CPB pigs, but occurred in the absence of severe intrarenal vasoconstriction, ATP depletion, or reductions in creatinine clearance. In contrast, reversal of anemia during CPB with RBC transfusion prevented the reductions in creatinine clearance, loss of NO bioavailability, platelet activation, inflammation, and epithelial cell injury attributable to CPB although it did not prevent the development of significant intrarenal vasoconstriction and endothelial dysfunction. In conclusion, contrary to the findings of observational studies in cardiac surgery, RBC transfusion during CPB protects pigs against acute kidney injury. Our study underlines the need for translational research into indications for transfusion and prevention strategies for acute kidney injury.     

Distribution and excretion of a phosphorothioate oligonucleotide in rats with experimentally induced renal injury

The effects of renal injury on the urinary excretion and tissue distribution of a 20-mer phosphorothioate oligonucleotide were investigated in male Sprague-Dawley rats. Renal injury was produced by treating the rats with either 5.0 mg/kg cisplatin or 2.5 mg/kg of a monoclonal antibody (mAb) directed toward Thy1.1. Controls received saline. Three days after cisplatin treatment or 2 days after anti- Thy1.1 treatment, the rats received 10 mg/kg ISIS 3521. Blood was collected at various times to assess the plasma concentrations of ISIS 3521, and rats were killed at various times from 6 to 48 hours after intravenous (i.v.) infusion of oligonucleotide to assess tissue concentrations by capillary gel electrophoresis (CGE). Cisplatin and anti-Thy1.1 antibody produced histologic and biochemical changes consistent with proximal tubular damage and glomerular damage, respectively. Urinary excretion of oligonucleotides was increased 2- to 4-fold of control; however, this amount accounted for only 1% to 2% of dose compared to 0.5% in controls. Proximal tubular damage reduced renal accumulations of ISIS 3521 and other oligonucleotide metabolites, but there were no obvious compensatory increases in concentrations in other organs except for a slight increase in spleen levels of total oligonucleotide. Glomerular damage was not associated with any change in oligonucleotide disposition. Immunohistochemical studies showed no evidence of alterations in the pattern of distribution within the injured kidney. The data suggest that acute renal dysfunction, either renal tubular or glomerular, does not markedly alter the urinary elimination and tissue deposition of a phosphorothioate oligonucleotide.     

Nicotinamide reduces renal interstitial fibrosis by suppressing tubular injury and inflammation

Renal interstitial fibrosis is a common pathological feature in progressive kidney diseases currently lacking effective treatment. Nicotinamide (NAM), a member of water‐soluble vitamin B family, was recently suggested to have a therapeutic potential for acute kidney injury (AKI) in mice and humans. The effect of NAM on chronic kidney pathologies, including renal fibrosis, is unknown. Here we have tested the effects of NAM on renal interstitial fibrosis using in vivo and in vitro models. In vivo, unilateral urethral obstruction (UUO) induced renal interstitial fibrosis as indicated Masson trichrome staining and expression of pro‐fibrotic proteins, which was inhibited by NAM. In UUO, NAM suppressed tubular atrophy and apoptosis. In addition, NAM suppressed UUO‐associated T cell and macrophage infiltration and induction of pro‐inflammatory cytokines, such as TNF‐α and IL‐1β. In cultured mouse proximal tubule cells, NAM blocked TGF–β‐induced expression of fibrotic proteins, while it marginally suppressed the morphological changes induced by TGF‐β. NAM also suppressed the expression of pro‐inflammatory cytokines (eg MCP‐1 and IL‐1β) during TGF‐β treatment of these cells. Collectively, the results demonstrate an anti‐fibrotic effect of NAM in kidneys, which may involve the suppression of tubular injury and inflammation.     

Capillary rarefaction and altered renal development: the imbalance between pro- and anti-angiogenic factors in response to angiotensin II inhibition in the developing rat kidney

Proper and timely assembly of the kidney vasculature with their respective nephrons is crucial during normal kidney development. In this study, we investigated the effects of enalapril (angiotensin-converting enzyme inhibitor) on angiogenesis-related gene expression and microvascular endothelium related to glomeular and tubular changes in the neonatal rat kidney. Enalapril-treated rats had higher tubular injury scores and lower glomerular maturity grades than those of untreated rats. In the enalapril-treated group, intrarenal angiopoietin-2, Tie-2, and thrombospondin-1 protein expression increased, whereas intrarenal angiopoietin-1 protein expression decreased. JG12-positive glomerular and peritubular capillary staining was reduced in the enalapril-treated rat kidney. The number of JG12-positive capillary endothelial cells was directly correlated with glomerular maturation grade and was inversely related with the tubular injury. Our findings suggest the imbalance between pro- and anti-angiogenic factors may be implicated in the loss of capillaries in associated with impaired nephrogenesis after angiotensin II blockade in the developing rat kidney.     

In Vivo Study of Spherical Gold Nanoparticles: Inflammatory Effects and Distribution in Mice

Objectives

Gold nanoparticles (AuNPs) of 21 nm have been previously well characterized in vitro for their capacity to target macrophages via active uptake. However, the short-term impact of such AuNPs on physiological systems, in particular resident macrophages located in fat tissue in vivo, is largely unknown. This project investigated the distribution, organ toxicity and changes in inflammatory cytokines within the adipose tissue after mice were exposed to AuNPs.

Methods

Male C57BL/6 mice were injected intraperitoneally (IP) with a single dose of AuNPs (7.85 μg AuNPs/g). Body weight and energy intake were recorded daily. Tissues were collected at 1 h, 24 h and 72 h post-injection to test for organ toxicity. AuNP distribution was examined using electron microscopy. Proinflammatory cytokine expression and macrophage number within the abdominal fat pad were determined using real-time PCR.

Results

At 72 hours post AuNP injection, daily energy intake and body weight were found to be similar between Control and AuNP treated mice. However, fat mass was significantly smaller in AuNP-treated mice. Following IP injection, AuNPs rapidly accumulated within the abdominal fat tissue and some were seen in the liver. A reduction in TNFα and IL-6 mRNA levels in the fat were observed from 1 h to 72 h post AuNP injection, with no observable changes in macrophage number. There was no detectable toxicity to vital organs (liver and kidney).

Conclusion

Our 21 nm spherical AuNPs caused no measurable organ or cell toxicity in mice, but were correlated with significant fat loss and inhibition of inflammatory effects. With the growing incidence of obesity and obesity-related diseases, our findings offer a new avenue for the potential development of gold nanoparticles as a therapeutic agent in the treatment of such disorders.     

Inhibition of the protein kinase MK-2 protects podocytes from nephrotic syndrome-related injury

While mitogen-activated protein kinase (MAPK) activation has been implicated in the pathogenesis of various glomerular diseases, including nephrotic syndrome (NS), its specific role in podocyte injury is not known. We hypothesized that MK-2, a downstream substrate of p38 MAPK, mediates the adverse effects of this pathway and that inhibition of MK-2 would protect podocytes from NS-related injury. Using cultured podocytes, we analyzed 1) the roles of MK-2 and p38 MAPK in puromycin aminonucleoside (PAN)-induced podocyte injury; 2) the ability of specific MK-2 and p38 MAPK inhibitors to protect podocytes against injury; 3) the role of serum albumin, known to induce podocyte injury, in activating p38 MAPK/MK-2 signaling; and 4) the role of p38 MAPK/MK-2 signaling in the expression of Cox-2, an enzyme associated with podocyte injury. Treatment with protein kinase inhibitors specific for both MK-2 (C23, a pyrrolopyridine-type compound) or p38 MAPK (SB203580) reduced PAN-induced podocyte injury and actin cytoskeletal disruption. Both inhibitors reduced baseline podocyte p38 MAPK/MK-2 signaling, as measured by the degree of phosphorylation of HSPB1, a downstream substrate of MK-2, but exhibited disparate effects on upstream signaling. Serum albumin activated p38 MAPK/MK-2 signaling and induced Cox-2 expression, and these responses were blocked by both inhibitors. Given the critical importance of podocyte injury to both NS and other progressive glomerular diseases, these data suggest an important role for p38 MAPK/MK-2 signaling in podocyte injury and identify MK-2 inhibition as a promising potential therapeutic strategy to protect podocytes in various glomerular diseases.     

Effect of ACE inhibition on glomerular permselectivity and tubular albumin concentration in the renal ablation model

Despite the central role of tubular plasma proteins that characterize progressive kidney diseases, protein concentrations along the nephron in pathological conditions have not been quantified so far. We combined experimental techniques and theoretical analysis to estimate glomerular and tubular levels of albumin in the experimental model of 5/6 nephrectomy (Nx) in the rat, with or without angiotensin-converting enzyme (ACE) inhibition. We measured glomerular permselectivity by clearance of fluorescent Ficoll and albumin and used theoretical analysis to estimate tubular albumin. As expected, 5/6 Nx induced an elevation of the fractional clearance of the largest Ficoll molecules (radii >56 ?, P < 0.05), increasing the importance of the shunt pathway of the glomerular membrane and the albumin excretion rate (119 ± 41 vs. 0.6 ± 0.2 mg/24 h, P < 0.01). ACE inhibition normalized glomerular permselectivity and urinary albumin (0.5 ± 0.3 mg/24 h). Theoretical analysis indicates that with 5/6 Nx, an increased albumin filtration overcomes proximal tubule reabsorption, with a massive increase in average albumin concentration along the tubule, reaching the highest value of >2,500 μg/ml at the end of the collecting duct. ACE inhibition improved glomerular permselectivity, limiting albumin filtration under proximal tubule reabsorption capacity, with low albumin concentration along the entire nephron, averaging <13 μg/ml at the end of the collecting duct. These results reinforce our understanding of the mechanisms of renal disease progression and the effects of angiotensin II antagonism. They also suggest that evaluation of tubular protein concentration levels could help to identify patients at risk of kidney disease progression and to improve clinical management.     

重症蜂螫伤患者的肾脏病理表现

目的:探讨重症蜂螫伤患者的肾脏病理改变,以指导临床针对性的治疗提供参考依据。方法:通过对4例重症蜂螫伤患者的临床表现及肾脏病理做病例报告,初步了解重症蜂螫伤患者的肾脏病理改变。记录所有患者的一般情况、实验室结果、治疗过程及预后,并进行肾穿刺活检以明确病理改变。结果:所有患者均为青壮年,均出现了MODS,包括急性肾衰竭、中毒性心肌炎及急性肝损伤。3例患者的肾组织病理为急性肾小管坏死及急性过敏性间质性肾炎,病理切片中可见少量嗜酸性粒细胞及大量淋巴细胞浸润。1例患者为急性肾小管坏死,未见嗜酸性粒细胞浸润。有急性过敏性间质性肾炎的患者使用小剂量激素反应较好,使用激素后肾功能恢复时间更短。结论:在重症蜂螫伤患者肾脏损伤的过程中,除了常见的急性肾小管坏死、血管内溶血、横纹肌溶解及休克等原因外,急性过敏性间质性肾炎也起着重要的作用,对于此类患者,及时使用激素治疗可能是减轻肾脏损伤、促进肾功能恢复的有效方法。     

Use of mouse hematopoietic stem and progenitor cells to treat acute kidney injury

New and effective treatment for acute kidney injury remains a challenge. Here, we induced mouse hematopoietic stem and progenitor cells (HSPC) to differentiate into cells that partially resemble a renal cell phenotype and tested their therapeutic potential. We sequentially treated HSPC with a combination of protein factors for 1 wk to generate a large number of cells that expressed renal developmentally regulated genes and protein. Cell fate conversion was associated with increased histone acetylation on promoters of renal-related genes. Further treatment of the cells with a histone deacetylase inhibitor improved the efficiency of cell conversion by sixfold. Treated cells formed tubular structures in three-dimensional cultures and were integrated into tubules of embryonic kidney organ cultures. When injected under the renal capsule, they integrated into renal tubules of postischemic kidneys and expressed the epithelial marker E-cadherin. No teratoma formation was detected 2 and 6 mo after cell injection, supporting the safety of using these cells. Furthermore, intravenous injection of the cells into mice with renal ischemic injury improved kidney function and morphology by increasing endogenous renal repair and decreasing tubular cell death. The cells produced biologically effective concentrations of renotrophic factors including VEGF, IGF-1, and HGF to stimulate epithelial proliferation and tubular repair. Our study indicates that hematopoietic stem and progenitor cells can be converted to a large number of renal-like cells within a short period for potential treatment of acute kidney injury.     

Acute treatment with relaxin protects the kidney against ischaemia/reperfusion injury

Although recent preclinical and clinical studies have demonstrated that recombinant human relaxin (rhRLX) may have important therapeutic potential in acute heart failure and chronic kidney diseases, the effects of acute rhRLX administration against renal ischaemia/reperfusion (I/R) injury have never been investigated. Using a rat model of 1‐hr bilateral renal artery occlusion followed by 6‐hr reperfusion, we investigated the effects of rhRLX (5 μg/Kg i.v.) given both at the beginning and after 3 hrs of reperfusion. Acute rhRLX administration attenuated the functional renal injury (increase in serum urea and creatinine), glomerular dysfunction (decrease in creatinine clearance) and tubular dysfunction (increase in urinary excretion of N‐acetyl‐β‐glucosaminidase) evoked by renal I/R. These beneficial effects were accompanied by a significant reduction in local lipid peroxidation, free radical‐induced DNA damage and increase in the expression/activity of the endogenous antioxidant enzymes Mn‐ and CuZn‐superoxide dismutases (SOD). Furthermore, rhRLX administration attenuated the increase in leucocyte activation, as suggested by inhibition of myeloperoxidase activity, intercellular‐adhesion‐molecule‐1 expression, interleukin (IL)‐1β, IL‐18 and tumour necrosis factor‐α production as well as increase in IL‐10 production. Interestingly, the reduced oxidative stress status and neutrophil activation here reported were associated with rhRLX‐induced activation of endothelial nitric oxide synthase and up‐regulation of inducible nitric oxide synthase, possibly secondary to activation of Akt and the extracellular signal‐regulated protein kinase (ERK) 1/2, respectively. Thus, we report herein that rhRLX protects the kidney against I/R injury by a mechanism that involves changes in nitric oxide signalling pathway.     

Inhibition of TLR2 promotes graft function in a murine model of renal transplant ischemia-reperfusion injury

Toll-like receptors (TLRs) are important molecules involved in the activation of innate and subsequent development of adaptive immunity. TLRs are ligated by exogenous ligands from pathogens and by endogenous ligands released in inflammatory diseases. Activation of TLR leads to activation of NF-κB and release of proinflammatory cytokines, such as IL-6 and TNF-α. TLRs play an important role in the pathogenesis of renal diseases. Increased expression of TLRs have been associated with ischemic kidney damage, acute kidney injury, end-stage renal failure, acute renal transplant rejection, and delayed allograft function. OPN301 is a mouse anti-human TLR2 antibody that cross-reacts with mouse TLR2. We show that inhibition of TLR2 promotes graft function in an isograft model of renal transplantation. Recipient mice were treated intravenously with OPN301 before reperfusion of the transplanted kidney that had been subjected to 30 min of cold ischemia. After 5 d, the residual native kidney was removed, and renal transplant function was assessed 24 h later by measurement of blood urea nitrogen. Renal function in both saline- and isotype-treated mice was similar, with significant improvement in OPN301-treated mice (isotype-treated vs. OPN301-treated: 33.9±3.2 vs. 19.8±1.9 μM; P<0.01). The histopathological appearance corresponded with renal functional results. In OPN301-treated recipients, renal structure was well preserved, whereas in the saline-treated group, tubular injury was severe, with marked tubular thinning, epithelial shedding, cast formation and necrosis. Inhibition of TLR2 also leads to a decrease in C3d deposition, although it is unclear whether this is due directly to TLR2 inhibition or a decrease in renal inflammation. This study shows that inhibition of TLR2 with a therapeutic agent (OPN301) provides significant protection from ischemia/reperfusion injury in a model of kidney transplantation.     

Potential advantages of acute kidney injury management by mesenchymal stem cells

Mesenchymal stem cells are currently considered as a promising tool for therapeutic application in acute kidney injury (AKI) management. AKI is characterized by acute tubular injury with rapid loss of renal function. After AKI, inflammation, oxidative stress and excessive deposition of extracellular matrix are the molecular events that ultimately cause the end-stage renal disease. Despite numerous improvement of supportive therapy, the mortality and morbidity among patients remain high. Therefore, exploring novel therapeutic options to treat AKI is mandatory. Numerous evidence in animal models has demonstrated the capability of mesenchymal stem cells (MSCs) to restore kidney function after induced kidney injury. After infusion, MSCs engraft in the injured tissue and release soluble factors and microvesicles that promote cell survival and tissue repairing. Indeed, the main mechanism of action of MSCs in tissue regeneration is the paracrine/endocrine secretion of bioactive molecules. MSCs can be isolated from several tissues, including bone marrow, adipose tissue, and blood cord; pre-treatment procedures to improve MSCs homing and their paracrine function have been also described. This review will focus on the application of cell therapy in AKI and it will summarize preclinical studies in animal models and clinical trials currently ongoing about the use of mesenchymal stem cells after AKI.     

A Novel Therapy to Attenuate Acute Kidney Injury and Ischemic Allograft Damage after Allogenic Kidney Transplantation in Mice

Ischemia followed by reperfusion contributes to the initial damage to allografts after kidney transplantation (ktx). In this study we tested the hypothesis that a tetrapeptide EA-230 (AQGV), might improve survival and attenuate loss of kidney function in a mouse model of renal ischemia/reperfusion injury (IRI) and ischemia-induced delayed graft function after allogenic kidney transplantation. IRI was induced in male C57Bl/6N mice by transient bilateral renal pedicle clamping for 35 min. Treatment with EA-230 (20–50mg/kg twice daily i.p. for four consecutive days) was initiated 24 hours after IRI when acute kidney injury (AKI) was already established. The treatment resulted in markedly improved survival in a dose dependent manner. Acute tubular injury two days after IRI was diminished and tubular epithelial cell proliferation was significantly enhanced by EA-230 treatment. Furthermore, CTGF up-regulation, a marker of post-ischemic fibrosis, at four weeks after IRI was significantly less in EA-230 treated renal tissue. To learn more about these effects, we measured renal blood flow (RBF) and glomerular filtration rate (GFR) at 28 hours after IRI. EA-230 improved both GFR and RBF significantly. Next, EA-230 treatment was tested in a model of ischemia-induced delayed graft function after allogenic kidney transplantation. The recipients were treated with EA-230 (50 mg/kg) twice daily i.p. which improved renal function and allograft survival by attenuating ischemic allograft damage. In conclusion, EA-230 is a novel and promising therapeutic agent for treating acute kidney injury and preventing IRI-induced post-transplant ischemic allograft injury. Its beneficial effect is associated with improved renal perfusion after IRI and enhanced regeneration of tubular epithelial cells.