Diabetic nephropathy is the main cause of end-stage renal disease. MicroRNAs are powerful regulators of the genome, and global expression profiling revealed miR-21 to be among the most highly regulated microRNAs in kidneys of mice with diabetic nephropathy. In kidney biopsies of diabetic patients, miR-21 correlated with tubulointerstitial injury. In situ PCR analysis showed a specific enrichment of miR-21 in glomerular cells. We identified cell division cycle 25a (Cdc25a) and cyclin-dependent kinase 6 (Cdk6) as novel miR-21 targets in mesangial cells. miR-21-mediated repression of Cdc25a and Cdk6 resulted in impaired cell cycle progression and subsequent mesangial cell hypertrophy. miR-21 increased podocyte motility by regulating phosphatase and tensin homolog (Pten). miR-21 antagonism in vitro and in vivo in streptozotocin-induced diabetic mice decreased mesangial expansion, interstitial fibrosis, macrophage infiltration, podocyte loss, albuminuria, and fibrotic- and inflammatory gene expression. In conclusion, miR-21 antagonism rescued various functional and structural parameters in mice with diabetic nephropathy and, thus, might be a viable option in the treatment of patients with diabetic kidney disease.

Introduction: For the first time in 2012, chronic kidney diseases were added to WHO disease list because of their impact on morbidity/mortality and their substantial impact on the cost to the health care system. Although representing a clear unmet medical need and a huge business case for the pharmaceutical industry, its clinical treatment still mainly relies on drugs invented in the 1980s used for controlling blood pressure.Areas covered: In this review, the authors aim to elucidate why renal drug development is feasible today. The article provides a particular focus on the treatments that target the pathways involved in inflammation, fibrosis and the core mechanisms driving the vicious cycle responsible for disease progression and organ function loss.Expert opinion: Currently, it is plausible to develop effective therapeutics for renal diseases with a plethora of approaches available for their development at a preclinical and clinical level. Furthermore, the relevance of biomarkers and the use of surrogate rare disease indications as proof of mechanism for faster and/or smaller clinical development are now possible; and these developments could revolutionize the way we treat renal disease in the future.

1 injury via TNF alpha dependent inhibition of apoptosis and inflammation 2 3 Song Rong, Katja Hueper, Torsten Kirsch, Robert Greite, Christian Klemann, Michael 4 Mengel, Matthias Meier, Jan Menne, Michael Leitges, Nathan Susnik, Martin Meier, 5 Hermann Haller, Nelli Shushakova, Faikah Gueler 6 7 8 Correspondence to: 9 Prof. Faikah Gueler, 10 Department of Nephrology 11 Medical School Hannover, 12 Carl-Neuberg-Str.1, 30625 Hannover, 13 Tel: 0049-511-532 3722, Fax: 0049-511-552366 14 email: gueler.faikah@mh-hannover.de 15 16 Department of Nephrology, Hannover Medical School, Hannover, Germany 17 Phenos GmbH, Hannover, Germany 18 The Transplantation Center of the affiliated hospital, Zunyi Medical College, China 19 Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, 20 Canada 21 The Biotechnology Centre of Oslo, University of Oslo 22 Institute for Diagnostic and Interventional Radiology, Medical School Hannover, Hannover, 23 Germany 24 Articles in PresS. Am J Physiol Renal Physiol (July 23, 2014). doi:10.1152/ajprenal.00372.2013

Acute kidney injury (AKI) increases the risk of morbidity and mortality after major surgery and transplantation. We investigated the effect of PKC-ε deficiency on AKI and ischemic allograft damage after kidney transplantation. PKC-ε-deficient and wild type (WT) control mice were subjected to 35 min of renal pedicle clamping to induce AKI. PKC-ε deficiency was associated with a marked improvement in survival and an attenuated loss of kidney function. Furthermore, functional MRI experiments revealed better renal perfusion in PKC-ε-deficient mice than in WT mice one day after IRI. Acute tubular necrosis and neutrophil infiltration were markedly reduced in PKC-ε-deficient mice. To determine whether this resistance to ischemia-reperfusion injury resulted from changes in local renal cells or infiltrating leukocytes, we studied a life-supporting renal transplant model of ischemic graft injury. We transplanted kidneys from H(2b) PKC-ε-deficient mice (129/SV) and their corresponding WT littermates into major histocompatibility complex-incompatible H(2d) recipients (BALB/c) and induced ischemic graft injury by prolonged cold ischemia time. Recipients of WT allografts developed severe renal failure and died within 10 days of transplantation. Recipients of PKC-ε-deficient allografts had better renal function and survival; they had less generation of ROS and upregulation of proinflammatory proteins (i.e., ICAM-1, inducible nitric oxide synthase, and TNF-α) and showed less tubular epithelial cell apoptosis and inflammation in their allografts. These data suggest that local renal PKC-ε expression mediates proapoptotic and proinflammatory signaling and that an inhibitor of PKC-ε signaling could be used to prevent hypoxia-induced AKI.

Fibrosis, which affects millions of individuals worldwide, is a leading cause of organ failure. For 40 years myofibroblasts have been recognized to be the key cellular players in fibrosis. Currently, several pharmaceutical targets are under investigation that may contribute to the activation of myofibroblasts. Recent preclinical and clinical evidence suggests that other components in the fibrotic microenvironment can trigger myofibroblast activation, providing new targets for pharmaceutical intervention. Epithelial cells may represent the most promising cellular phenotype that could be exploited in the design of new anti-fibrotic medicines through their paracrine action on myofibroblasts. The present review briefly highlights this hypothesis and discusses some interesting related pharmacological targets.

Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy with proteinuria and peritubular extracellular matrix production. We have previously shown that the PKC isoforms α and β mediate different cellular effects. PKC-β contributes to hyperglycemia-induced renal matrix production, whereby PKC-α is involved in the development of albuminuria. We further tested this hypothesis by deletion of both isoforms and used a PKC inhibitor. We analyzed the phenotype of nondiabetic and streptozotocin (STZ)-induced diabetic homozygous PKC-α/β double-knockout mice (PKC-α/β−/−). After 8 weeks of diabetes mellitus, the high-glucose–induced renal and glomerular hypertrophy as well as transforming growth factor-β1) and extracellular matrix production were diminished in the PKC-α/β−/− mice compared with wild-type controls. Urinary albumin/creatinine ratio also was significantly reduced, however, it was not completely abolished in diabetic PKC-α/β−/− mice. Treatment with CGP41252, which inhibits PKC-α and PKC-β, is able to prevent the development of albuminuria and to reduce existing albuminuria in type 1 (STZ model) or type 2 (db/db model) diabetic mice. These results support our hypothesis that PKC-α and PKC-β contribute to the pathogenesis of diabetic nephropathy, and that dual inhibition of the classical PKC isoforms is a suitable therapeutic strategy in the prevention and treatment of diabetic nephropathy.

Die diabetische Nephropathie ist die wichtigste mikrovaskuläre Spätkomplikation bei langjährigem Diabetes mellitus, da die chronische Niereninsuffizienz durch eine erhöhte kardiovaskuläre Morbidität und Mortalität gekennzeichnet ist. Obwohl es in den letzten Jahrzehnten aufgrund einer frühzeitigen intensivierten Insulintherapie zu einer deutlichen Verminderung der Inzidenz und Prävalenz der terminalen Niereninsuffizienz beim juvenilen Typ 1-Diabetes gekommen ist, nimmt die Zahl chronisch niereninsuffizienter Patienten mit Typ-2-Diabetes aufgrund des wachsenden mittleren Lebensalters und der heute effektiveren Behandlungsmöglichkeiten einer arteriellen Hypertonie und makroangiopathischer Gefäßkomplikationen (koronare Herzkrankheit, periphere arterielle Verschlusskrankheit) weiter kontinuierlich zu. Die erschreckende epidemiologische Dimension der diabetischen Nephropathie hat neben dem persönlichen Schicksal des einzelnen Betroffenen enorme finanzielle Belastungen für die Sozialsysteme zur Folge.

Introduction: The kidneys are vulnerable to injury due to their high filtration capacity and high metabolic activity, and most drugs, especially hydrophilic drugs and their metabolites, are eliminated largely by kidneys in urine, thus increasing the risk of drug-induced nephrotoxicity (DIN). DIN accounts for 18 - 27% of community- and hospital-acquired episodes of acute kidney injury (AKI) and is a serious concern during development of novel therapeutic drugs.Areas covered: This review provides an overview of definitions, classification, risk factors, complications, and outcomes of DIN. In addition, it gives a practical source of information when dealing with nephrotoxicity issues during drug development and provides guidance on renal safety risk evaluation for clinical studies. Lastly, current research focus in the search for novel biomarkers of DIN is also provided.Expert opinion: To enable early detection of DIN and to ensure patients' safety through appropriate risk minimization and mitigation strategies, future research should focus on identification and validation of novel predictive biomarkers of kidney injury and development of DIN-specific classification and staging system. This could help in reducing the current high rate of attrition during drug development, and reduce marketing and post-marketing withdrawals of nephrotoxic drugs.

Observational clinical studies link acute kidney injury to chronic kidney disease (CKD) progression. The pathophysiological mechanisms that underlie this process are currently unknown but recently published papers suggest that tubular epithelial cells and interstitial mesenchymal cells emerge as a single unit, and their integrity alteration as a whole might lead to renal fibrosis and CKD. The present article reviews the biological findings supporting the hypothesis of an altered epithelial/mesenchymal crosstalk in fibrosis development and progression toward CKD.

Chronic kidney disease (CKD) and end-stage renal disease (ESRD) are currently considered as major health burdens. Notably, CKD can be regarded as an interesting clinical model of accelerated cardiovascular disease (CVD) and ageing, which offers exciting new perspectives and challenges for pharmaceutical drug development. However, during the last decades, therapeutic advances to slow down the progression of CKD and reduce CVD risk have largely failed due to several possible reasons including (i) the lack of profound understanding of the pathophysiology of chronic renal damage and its associated CVD; (ii) an inadequate characterization of molecular mechanisms of currently approved therapies such as renin-angiotensin-aldosterone-system (RAAS) blockade; (iii) the unclear biochemical property needs required for novel therapeutic approaches; (iv) the missing quantity and quality of clinical trials in the nephrology field; and, most importantly, (v) the absence of prognostic renal biomarkers that reflect the severity of the structural organ damage and predict ESRD as well as CVD mortality. There is clearly an insufficient understanding of why a significant proportion of CKD patients progress to ESRD and/or die from CVD whereas others rather remain stable. In this article, we urge renal researchers to develop novel experimental and clinical tools for rational and translational drug discovery. Identification of individualized determinants of CKD progression and/or premature CVD will enable personalized medicine and lead to novel innovative nephro- and/or cardioprotective pharmacological treatment in these high-risk patients.

The incidence of chronic kidney diseases (CKD) is constantly rising, reaching epidemic proportions in the western world and leading to an enormous threat, even to modern health‐care systems, in industrialized countries. Therapies of CKD have greatly improved following the introduction of drugs targeting the renin–angiotensin system (RAAS) but even this refined pharmacological approach has failed to stop progression to end‐stage renal disease (ESRD) in many individuals. In vitro historical data and recent new findings have suggested that progression of renal fibrosis might occur as a result of an altered tubulo–interstitial microenvironment and, more specifically, as a result of an altered epithelial‐mesenchymal crosstalk. Here we the review biological findings that support the hypothesis of an altered cellular crosstalk in an injured local tubulo‐interstitial microenvironment leading to renal disease progression. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BACKGROUND:C57BL/6 and 129/Sv are the 2 most commonly used strains of mice in renal ischemia-reperfusion injury (IRI) studies, yet there are currently no studies that contrast differences in the degree of renal injury after ischemia-reperfusion.METHODS:To evaluate renal IRI in male C57BL/6 and 129/Sv mice, we performed unilateral clamping of the left renal pedicle for 45 minutes and compared the degree of renal tissue damage and function. To measure function and tissue damage we examined: glomerular filtration rate (GFR; by inulin clearance), renal blood flow (RBF; by p-aminohippurate [PAH] clearance), renal morphology, immunohistochemistry for infiltrating leukocytes, and fibrogenic markers by Sirius red staining.RESULTS:After unilateral IRI, 129/sv mice had significantly less GFR and RBF disfunction at both day 14 (d14) and d28. 129/sv mice also had significantly less acute tubular necrosis on d1 and fewer infiltrating leukocytes on d28, as well as less collagen deposition on d28 than C57BL/6 mice.CONCLUSIONS:C57BL/6 mice were much more sensitive to damage caused by renal IRI than are 129/Sv mice.

Background: Progressive loss of podocytes has been documented as an early lesion in the development of glomerular disease. In a variety of glomerular diseases, including diabetic nephropathy the activation of transforming growth factor-beta (TGF-β) has been demonstrated to promote podocyte death and the development of glomerulosclerosis. In this manuscript we analyzed the role of PKC-alpha (PKCα) on TGF-β1 induced apoptosis in podocytes. Methods: To accomplish this we generated stable murine PKCα deficient podocyte cell lines and examined survival- and pro-apoptotic signaling signatures as well as caspase activation after stimulation with TGF-β. Results: After stimulation with TGF-β we can demonstrate an enhanced and prolonged activation of PI3K/AKT and ERK1/2 in PKCα-knockout (PKCα-/-) podocytes compared to PKCα-wildtype (PKCα+/ +) podocytes, whereas proapoptotic signaling via p38MAPK is significantly reduced. Interestingly, activation of the Smad-pathway is also prolonged in the PKCα-/-podocytes. When we analyzed the underlying mechanisms we found a TGF-β inducible interaction of PKCα with the TGF-β-type-I-receptor (TGFβRI). Moreover, endocytosis assays showed that the TGFβRI is less internalized in PKCα-/- podocytes. Conclusion: Since we can demonstrate a key role for PKCα in the signaling response after stimulation with TGF-β we conclude that PKCα might be an interesting target molecule as a “podocyte protective” therapy.

Type 2 diabetes mellitus (T2DM) is associated with a high risk of complications, essentially macrovascular events. Surprisingly, the effect of improved glucose control on coronary and cerebrovascular complications and the target level of glycated hemoglobin (HbA(1c)) in this population remains questionable. We here report the results of 4 recently published randomized controlled trials (ACCORD, ADVANCE, VADT, UKPDS post-trial), which did not demonstrate a significant reduction of cardiovascular events in the intensive group compared to the standard group. On the contrary, in ACCORD, the study with the most ambitious goal (HbA(1c) < 6%), the overall and cardiovascular mortality was greater in the intensive group, although the risk of microangiopathic complications, especially nephropathy, was significantly decreased. VADT suggests that one possibility for the lack of observed effect of intensive therapy could be that the cardiovascular benefit is delayed. This contrasts strongly with the long-term postintervention outcomes of UKPDS, which show a persistent benefit of glycemic control during 10 years of post-trial follow-up (`legacy effect'). Therefore, the best way to protect patients with T2DM against coronary and cerebrovascular disease is to target all cardiovascular risk factors as early as possible by an individualized approach.