Notch signaling in diabetic nephropathy

Therapeutic approaches and novel antifibrotic agents in renal fibrosis: A comprehensive review

Renal fibrosis (RF) is one of the underlying pathological conditions leading to progressive loss of renal function and end-stage renal disease (ESRD). Over the years, various therapeutic approaches have been explored to combat RF and prevent ESRD. Despite significant advances in understanding the underlying molecular mechanism(s), effective therapeutic interventions for RF are limited. Current therapeutic strategies primarily target these underlying mechanisms to halt or reverse fibrotic progression. Inhibition of transforming growth factor-β (TGF-β) signaling, a pivotal mediator of RF has emerged as a central strategy to manage RF. Small molecules, peptides, and monoclonal antibodies that target TGF-β receptors or downstream effectors have demonstrated potential in preclinical models. Modulating the renin-angiotensin system and targeting the endothelin system also provide established approaches for controlling fibrosis-related hemodynamic changes. Complementary to pharmacological strategies, lifestyle modifications, and dietary interventions contribute to holistic management. This comprehensive review aims to summarize the underlying mechanisms of RF and provide an overview of the therapeutic strategies and novel antifibrotic agents that hold promise in its treatment.

ASH2L-mediated H3K4me3 drives diabetic nephropathy through HIPK2 and Notch1 pathway

Diabetic nephropathy (DN) is one of the complications of diabetes. Long-term hyperglycemia in the kidney results in renal insufficiency, and eventually leads to end-stage renal disease. Epigenetic factor ASH2L has long been identified as a transcriptional activator, and we previously indicated that ASH2L aggravated fibrosis and inflammation in high glucose-induced glomerular mesangial cells, but the pathophysiological relevance and the mechanism of ASH2L-mediated H3K4me3 in DN is not well understood. Here we demonstrated that ASH2L is upregulated in glomeruli isolated from db/db mice. Loss of ASH2L protected glomerular injury caused by hyperglycemia, as evidenced by reduced albuminuria, preserved structure, decreased glomerular extracellular matrix deposition, and lowered renal glomerular expression of proinflammatory and profibrotic markers in db/db mice. Furthermore, we demonstrated that enrichment of ASH2L-mediated H3K4me3 on the promoter regions of ADAM17 and HIPK2 triggered their transcription, leading to aberrant activation of Notch1 signaling pathway, thereby contributing to fibrosis and inflammation in DN. The findings of this study provide compelling evidence for targeting ASH2L as a potential therapeutic strategy to prevent or slow down the progression of DN.

Circ_0068087 knockdown attenuates high-glucose-induced human tubular epithelial cell injury in a microribonucleic acid/progestin and adipoQ receptor 3-dependent manner in diabetic nephropathy

AIMS/INTRODUCTION

Previous studies have shown that circular ribonucleic acid mediates the occurrence of diabetic nephropathy. This study aimed to analyze the effects of circ_0068087 on high-glucose (HG)-induced human kidney 2 (HK2) cell dysfunction.

MATERIALS AND METHODS

Circ_0068087, miR-580-3p, and progestin and adipoQ receptor 3 (PAQR3) expression were detected by quantitative reverse transcription polymerase chain reaction. Cell viability and proliferation were investigated by Cell Counting Kit-8 and EdU assays, respectively. The cell apoptotic rate was assessed by flow cytometry. Inflammatory response was assessed by enzyme-linked immunoassays. Oxidative stress was evaluated by a superoxide dismutase activity assay kit and lipid peroxidation malondialdehyde assay kit. Molecular interaction was identified by dual-luciferase reporter assay.

RESULTS

Circ_0068087 and PAQR3 expression were significantly upregulated in diabetic nephropathy patients. HG treatment inhibited HK2 cell proliferation, but induced cell apoptosis, inflammation, oxidative stress and epithelial-mesenchymal transition by regulating circ_0068087. Circ_0068087 acted as a microribonucleic acid-580-3p (miR-580-3p) sponge, and miR-580-3p targeted PAQR3. Furthermore, circ_0068087 depletion repressed PAQR3 expression through miR-580-3p. MiR-580-3p inhibitors or PAQR3 introduction attenuated circ_0068087 silencing mediated-effects in HG-treated HK2 cells.

CONCLUSION

Circ_0068087 promoted HG-induced HK2 cell injuries by the regulation of the miR-580-3p/PAQR3 pathway.

Natural products in traditional Chinese medicine: molecular mechanisms and therapeutic targets of renal fibrosis and state-of-the-art drug delivery systems

Renal fibrosis (RF) is the end stage of several chronic kidney diseases. Its series of changes include excessive accumulation of extracellular matrix, epithelial-mesenchymal transition (EMT) of renal tubular cells, fibroblast activation, immune cell infiltration, and renal cell apoptosis. RF can eventually lead to renal dysfunction or even renal failure. A large body of evidence suggests that natural products in traditional Chinese medicine (TCM) have great potential for treating RF. In this article, we first describe the recent advances in RF treatment by several natural products and clarify their mechanisms of action. They can ameliorate the RF disease phenotype, which includes apoptosis, endoplasmic reticulum stress, and EMT, by affecting relevant signaling pathways and molecular targets, thereby delaying or reversing fibrosis. We also present the roles of nanodrug delivery systems, which have been explored to address the drawback of low oral bioavailability of natural products. This may provide new ideas for using natural products for RF treatment. Finally, we provide new insights into the clinical prospects of herbal natural products.

Dysregulated coagulation system links to inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) is a significant contributor to end-stage renal disease worldwide. Despite extensive research, the exact mechanisms responsible for its development remain incompletely understood. Notably, patients with diabetes and impaired kidney function exhibit a hypercoagulable state characterized by elevated levels of coagulation molecules in their plasma. Recent studies propose that coagulation molecules such as thrombin, fibrinogen, and platelets are interconnected with the complement system, giving rise to an inflammatory response that potentially accelerates the progression of DKD. Remarkably, investigations have shown that inhibiting the coagulation system may protect the kidneys in various animal models and clinical trials, suggesting that these systems could serve as promising therapeutic targets for DKD. This review aims to shed light on the underlying connections between coagulation and complement systems and their involvement in the advancement of DKD.

Epsin1-mediated exosomal sorting of Dll4 modulates the tubular-macrophage crosstalk in diabetic nephropathy

Tubular epithelial cells (TECs) play critical roles in the development of diabetic nephropathy (DN), and can activate macrophages through the secretion of exosomes. However, the mechanism(s) of TEC-exosomes in macrophage activation under DN remains unknown. By mass spectrometry, 1,644 differentially expressed proteins, especially Dll4, were detected in the urine exosomes of DN patients compared with controls, which was confirmed by western blot assay. Elevated Epsin1 and Dll4/N1ICD expression was observed in kidney tissues in both DN patients and db/db mice and was positively associated with tubulointerstitial damage. Exosomes from high glucose (HG)-treated tubular cells (HK-2) with Epsin1 knockdown (KD) ameliorated macrophage activation, TNF-α, and IL-6 expression, and tubulointerstitial damage in C57BL/6 mice in vivo. In an in vitro study, enriched Dll4 was confirmed in HK-2 cells stimulated with HG, which was captured by THP-1 cells and promoted M1 macrophage activation. In addition, Epsin1 modulated the content of Dll4 in TEC-exosomes stimulated with HG. TEC-exosomes with Epsin1-KD significantly inhibited N1ICD activation and iNOS expression in THP-1 cells compared with incubation with HG alone. These findings suggested that Epsin1 could modulate tubular-macrophage crosstalk in DN by mediating exosomal sorting of Dll4 and Notch1 activation.

Molecular programs associated with glomerular hyperfiltration in early diabetic kidney disease

Hyperfiltration is a state of high glomerular filtration rate (GFR) observed in early diabetes that damages glomeruli, resulting in an iterative process of increasing filtration load on fewer and fewer remaining functional glomeruli. To delineate underlying cellular mechanisms of damage associated with hyperfiltration, transcriptional profiles of kidney biopsies from Pima Indians with type 2 diabetes with or without early-stage diabetic kidney disease were grouped into two hyperfiltration categories based on annual iothalamate GFR measurements. Twenty-six participants with a peak GFR measurement within two years of biopsy were categorized as the hyperfiltration group, and 26 in whom biopsy preceded peak GFR by over two years were considered pre-hyperfiltration. The hyperfiltration group had higher hemoglobin A1c, higher urine albumin-to-creatinine ratio, increased glomerular basement membrane width and lower podocyte density compared to the pre-hyperfiltration group. A glomerular 1240-gene transcriptional signature identified in the hyperfiltration group was enriched for endothelial stress response signaling genes, including endothelin-1, tec-kinase and transforming growth factor-β1 pathways, with the majority of the transcripts mapped to endothelial and inflammatory cell clusters in kidney single cell transcriptional data. Thus, our analysis reveals molecular pathomechanisms associated with hyperfiltration in early diabetic kidney disease involving putative ligand-receptor pairs with downstream intracellular targets linked to cellular crosstalk between endothelial and mesangial cells.

Notch signaling: A possible therapeutic target and its role in diabetic foot ulcers

BACKGROUND & AIM

Diabetic foot ulcers are major cause of lower limb amputations in the diabetic population. The major factors that play a role in causing the delay of the process of healing in diabetic foot ulcers broadly are decreased angiogenesis, reduced proliferation and migration of keratinocytes/fibroblasts. The typical wound healing process has four phases which are overlapping with each other thus making the healing even more complex. Hence it is essential to identify a therapeutic target that involves the regulation of the cellular factors involved in healing and helps to increase angiogenesis and can regulate all four phases accordingly.

METHOD

Literature review involved a search of the databases namely, PubMed, Cochrane, EMBASE, and Web of Science database. Articles were identified and retrieved that specifically dealt with Notch as a target in healing of wounds and its mechanism of action on various cells and phases of healing.

RESULTS

Notch is a cell surface receptor which interacts with transmembrane ligands of the nearby cells and is involved in cell proliferation, differentiation, cell fate and death. It is also involved in cell-to-cell communication, cell signaling, and various phases of development. There exist four known notch genes and five ligands which interact with notch proteins. Hyperglycemia plays a role in the activation of the notch receptor thus causing the release of inflammatory mediators via macrophages. As notch can regulate macrophage-mediated inflammation it can serve as a therapeutic target for diabetic foot ulcers.

CONCLUSION

This review focuses on the effect of notch on various cell mediators and phases of diabetic wound healing and deals with how notch activation or inhibition can serve as a potential therapeutic target for healing diabetic foot ulcers.

Ombuin ameliorates diabetic nephropathy in rats by anti-inflammation and antifibrosis involving Notch 1 and PPAR γ signaling pathways

Diabetic nephropathy (DN) is a common complication of diabetes and it is urgent to develop effective therapies for DN. In this study, high-sucrose and high-fat diet combined with streptozotocin was used to induce DN in rats to observe the effects of natural flavonoid ombuin on renal function, inflammation, and interstitial fibrosis. Immunohistochemistry and western blotting analysis were used to detect protein expression levels. Results showed that ombuin significantly improved renal function and pathological injury, inhibited accumulation of advanced glycation end-products, suppressed the release of inflammatory cytokines, and improved renal interstitial fibrosis in DN rats. Ombuin also significantly downregulated the expressions of transforming growth factor beta1 (TGF-β1), connective tissue growth factor (CTGF), fibronectin (FN), p65, phosphorylated (p)-p65, Cleaved-Notch 1, and hairy and enhancer of split 1 (Hes 1), and upregulated the expression of peroxisome proliferator-activated receptor γ (PPAR γ). When PPAR γ activity was inhibited by T0070907, the effects of ombuin on improving DN were significantly reversed, and the expressions of TGF-β1, FN, CTGF, p-p65, and p65 increased, while the expressions of Cleaved-Notch 1 and Hes 1 were not significantly affected. These results suggest that ombuin may activate PPAR γ to exert anti-inflammatory and antifibrotic effects by inhibiting Notch 1 activity in DN. It is also possible that ombuin acts on these two independent signal pathways synchronously.

Vitamin D/vitamin D receptor/Atg16L1 axis maintains podocyte autophagy and survival in diabetic kidney disease

OBJECTIVE

To investigate the effect of vitamin D/vitamin D receptor (VDR)/Atg16L1 signaling on podocyte autophagy and survival in diabetic nephropathy.

METHODS

Diabetic rat models were induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg) and treated with and without gavage of 0.1 μg/kg/d active vitamin D3 (aVitD3; 1,25- OH vitamin D3) and kidney tissues assessed by histopathology and immunohistochemistry. The murine podocyte cell line MPC-5 was cultured under hyperglycemic conditions in the absence or presence of 100 nmol/L calcitriol to investigate podocyte injury and autophagy. Cell survival rates were analyzed using Cell Counting Kit-8 (CCK-8) assays and the numbers of autophagosomes were determined after transduction with the mRFP-GFP-LC3 autophagy reporter construct. The expression of autophagy-related proteins (LC3-II, beclin-1, Atg16L1) and podocyte-related proteins (nephrin, podocin, synaptopodin, and desmin) was determined by Western blotting.

RESULTS

VDR expression and autophagy were decreased in diabetic nephropathy. Calcitriol treatment repressed renal injury in rat diabetic kidneys and reduced high glucose-induced damage to cultured podocytes. Mechanistically, Atg16L1 was identified as a functional target of VDR, and siRNA-mediated knockdown of VDR and Atg16L1 blocked the protective effects of aVitD3 against podocyte damage.

CONCLUSION

Autophagy protects podocytes from damage in DN and is modulated by VitD3/VDR signaling and downstream regulation of Atg16L1 expression.

Maresin 1 Alleviates Diabetic Kidney Disease via LGR6-Mediated cAMP-SOD2-ROS Pathway

Background. Chronic hyperglycemia-induced inflammation is recognized as the most important pathophysiological process in diabetic kidney disease (DKD). As maresin 1 (MaR1) is an extensive anti-inflammatory lipid mediator, the present study investigated the protective role of MaR1 in the pathogenesis of DKD and its clinical relevance. Methods. Serum MaR1 concentrations were analyzed in 104 subjects with normal glucose tolerant, type 2 diabetes (T2DM), or DKD. Streptozotocin (STZ) together with high fat diet was used to induce male C57BL/6 J mice into diabetic mice which were treated with MaR1. Human renal tubule epithelial cells (HK-2 cells) were treated by high glucose for glucotoxicity cell model and transfected with LGR6 siRNA for knockdown with MaR1 added，and detected oxidative stress and inflammatory related factors. Results. Serum MaR1 concentrations were significant decreased in T2DM with or without kidney disease compared with normal participant and were lowest in patients with DKD. Serum MaR1 concentrations were negatively correlated with hemoglobin A1c (HbA1c), duration of diabetes, urinary albumin to creatinine ratio (UACR), neutrophil, and neutrophil-lymphocyte ratio and were positively correlated with high-density lipoprotein-cholesterol (HDL-C) and estimated glomerular filtration rate (eGFR). In mouse model, MaR1 injection alleviated hyperglycemia, UACR and the pathological progression of DKD. Interestingly, the renal expression of LGR6 was down-regulated in DKD and high glucose treated HK-2 cells but up-regulated by MaR1 treatment. Mechanistically, MaR1 alleviated inflammation via LGR6-mediated cAMP-SOD2 antioxidant pathway in DKD mice and high glucose treated HK-2 cells. Conclusions. Our study demonstrates that decreased serum MaR1 levels were correlated with the development of DKD. MaR1 could alleviate DKD and glucotoxicity-induced inflammation via LGR6-mediated cAMP-SOD2 antioxidant pathway. Thus, our present findings identify MaR1 as a predictor and a potential therapeutic target for DKD.

Integrated analysis of potential gene crosstalk between non-alcoholic fatty liver disease and diabetic nephropathy

BACKGROUND

Growing evidence indicates that non-alcoholic fatty liver disease (NAFLD) is related to the occurrence and development of diabetic nephropathy (DN). This bioinformatics study aimed to explore optimal crosstalk genes and related pathways between NAFLD and DN.

METHODS

Gene expression profiles were downloaded from Gene Expression Omnibus. CIBERSORT algorithm was employed to analyze the similarity of infiltrating immunocytes between the two diseases. Protein-protein interaction (PPI) co-expression network and functional enrichment analysis were conducted based on the identification of common differentially expressed genes (DEGs). Least absolute shrinkage and selection operator (LASSO) regression and Boruta algorithm were implemented to initially screen crosstalk genes. Machine learning models, including support vector machine, random forest model, and generalized linear model, were utilized to further identify the optimal crosstalk genes between DN and NAFLD. An integrated network containing crosstalk genes, transcription factors, and associated pathways was developed.

RESULTS

Four gene expression datasets, including GSE66676 and GSE48452 for NAFLD and GSE30122 and GSE1009 for DN, were involved in this study. There were 80 common DEGs between the two diseases in total. The PPI network built with the 80 common genes included 77 nodes and 83 edges. Ten optimal crosstalk genes were selected by LASSO regression and Boruta algorithm, including CD36, WIPI1, CBX7, FCN1, SLC35D2, CP, ZDHHC3, PTPN3, LPL, and SPP1. Among these genes, LPL and SPP1 were the most significant according to NAFLD-transcription factor network. Five hundred twenty-nine nodes and 1,113 edges comprised the PPI network of activated pathway-gene. In addition, 14 common pathways of these two diseases were recognized using Gene Ontology (GO) analysis; among them, regulation of the lipid metabolic process is closely related to both two diseases.

CONCLUSIONS

This study offers hints that NAFLD and DN have a common pathogenesis, and LPL and SPP1 are the most relevant crosstalk genes. Based on the common pathways and optimal crosstalk genes, our proposal carried out further research to disclose the etiology and pathology between the two diseases.

Application of weighted gene co-expression network analysis to identify novel key genes in diabetic nephropathy

AIMS/INTRODUCTION

Diabetic nephropathy (DN) is among the leading causes of end-stage renal disease worldwide. DN pathogenesis remains largely unknown. Weighted gene co-expression network analysis is a powerful bioinformatic tool for identifying key genes in diseases.

MATERIALS AND METHODS

The datasets GSE30122, GSE104948, GSE37463 and GSE47185 containing 23 DN and 23 normal glomeruli samples were obtained from the National Center for Biotechnology Information Gene Expression Omnibus database. After data pre-processing, weighted gene co-expression network analysis was carried out to cluster significant modules. Then, Gene Set Enrichment Analysis-based Gene Ontology analysis and visualization of network were carried out to screen the key genes in the most significant modules. The connectivity map analysis was carried out to find the significant chemical compounds. Finally, some key genes were validated in in vivo and in vitro experiments.

RESULTS

A total of 454 upregulated and 392 downregulated genes were identified. A total of 16 modules were clustered, and the most significant modules (green, red and yellow modules) were determined. The green module was associated with extracellular matrix organization, the red module was associated with immunity reaction and the yellow module was associated with kidney development. We found several key genes in these three modules separately, and part of them were validated in vivo and in vitro successfully. We found the top 15 chemical compounds that could perturb the overall expression of key genes in DN.

CONCLUSION

Weighted gene co-expression network analysis was applied to DN expression profiling in combination with connectivity map analysis. Several novel key genes and chemical compounds were screened out, providing new molecular targets for DN.

Systems biology and machine learning approaches identify drug targets in diabetic nephropathy

Diabetic nephropathy (DN), the leading cause of end-stage renal disease, has become a massive global health burden. Despite considerable efforts, the underlying mechanisms have not yet been comprehensively understood. In this study, a systematic approach was utilized to identify the microRNA signature in DN and to introduce novel drug targets (DTs) in DN. Using microarray profiling followed by qPCR confirmation, 13 and 6 differentially expressed (DE) microRNAs were identified in the kidney cortex and medulla, respectively. The microRNA-target interaction networks for each anatomical compartment were constructed and central nodes were identified. Moreover, enrichment analysis was performed to identify key signaling pathways. To develop a strategy for DT prediction, the human proteome was annotated with 65 biochemical characteristics and 23 network topology parameters. Furthermore, all proteins targeted by at least one FDA-approved drug were identified. Next, mGMDH-AFS, a high-performance machine learning algorithm capable of tolerating massive imbalanced size of the classes, was developed to classify DT and non-DT proteins. The sensitivity, specificity, accuracy, and precision of the proposed method were 90%, 86%, 88%, and 89%, respectively. Moreover, it significantly outperformed the state-of-the-art (P-value ≤ 0.05) and showed very good diagnostic accuracy and high agreement between predicted and observed class labels. The cortex and medulla networks were then analyzed with this validated machine to identify potential DTs. Among the high-rank DT candidates are Egfr, Prkce, clic5, Kit, and Agtr1a which is a current well-known target in DN. In conclusion, a combination of experimental and computational approaches was exploited to provide a holistic insight into the disorder for introducing novel therapeutic targets.

kTWAS: integrating kernel machine with transcriptome-wide association studies improves statistical power and reveals novel genes

The power of genotype-phenotype association mapping studies increases greatly when contributions from multiple variants in a focal region are meaningfully aggregated. Currently, there are two popular categories of variant aggregation methods. Transcriptome-wide association studies (TWAS) represent a set of emerging methods that select variants based on their effect on gene expressions, providing pretrained linear combinations of variants for downstream association mapping. In contrast to this, kernel methods such as sequence kernel association test (SKAT) model genotypic and phenotypic variance use various kernel functions that capture genetic similarity between subjects, allowing nonlinear effects to be included. From the perspective of machine learning, these two methods cover two complementary aspects of feature engineering: feature selection/pruning and feature aggregation. Thus far, no thorough comparison has been made between these categories, and no methods exist which incorporate the advantages of TWAS- and kernel-based methods. In this work, we developed a novel method called kernel-based TWAS (kTWAS) that applies TWAS-like feature selection to a SKAT-like kernel association test, combining the strengths of both approaches. Through extensive simulations, we demonstrate that kTWAS has higher power than TWAS and multiple SKAT-based protocols, and we identify novel disease-associated genes in Wellcome Trust Case Control Consortium genotyping array data and MSSNG (Autism) sequence data. The source code for kTWAS and our simulations are available in our GitHub repository (https://github.com/theLongLab/kTWAS).

Signaling Pathways Involved in Diabetic Renal Fibrosis

Diabetic kidney disease (DKD), as the most common complication of diabetes mellitus (DM), is the major cause of end-stage renal disease (ESRD). Renal interstitial fibrosis is a crucial metabolic change in the late stage of DKD, which is always considered to be complex and irreversible. In this review, we discuss the pathological mechanisms of diabetic renal fibrosis and discussed some signaling pathways that are closely related to it, such as the TGF-β, MAPK, Wnt/β-catenin, PI3K/Akt, JAK/STAT, and Notch pathways. The cross-talks among these pathways were then discussed to elucidate the complicated cascade behind the tubulointerstitial fibrosis. Finally, we summarized the new drugs with potential therapeutic effects on renal fibrosis and listed related clinical trials. The purpose of this review is to elucidate the mechanisms and related pathways of renal fibrosis in DKD and to provide novel therapeutic intervention insights for clinical research to delay the progression of renal fibrosis.

PPAR-α Agonist Fenofibrate Prevented Diabetic Nephropathy by Inhibiting M1 Macrophages via Improving Endothelial Cell Function in db/db Mice

Background: Diabetic nephropathy (DN) is one of the major diabetic microvascular complications, and macrophage polarization plays a key role in the development of DN. Endothelial cells regulate macrophage polarization. Peroxisome proliferator-activated receptor (PPAR)-α agonists were demonstrated to prevent DN and improve endothelial function. In this study, we aimed to investigate whether PPAR-α agonists prevented DN through regulating macrophage phenotype via improving endothelial cell function.

Methods: Eight-week-old male C57BLKS/J db/m and db/db mice were given fenofibrate or 1% sodium carboxyl methylcellulose by gavage for 12 weeks.

Results: Db/db mice presented higher urinary albumin-to-creatinine ratio (UACR) than db/m mice, and fenofibrate decreased UACR in db/db mice. Fibrosis and collagen I were elevated in db/db mouse kidneys compared with db/m mouse kidneys; however, they were decreased after fenofibrate treatment in db/db mouse kidneys. Apoptosis and cleaved caspase-3 were enhanced in db/db mouse kidneys compared to db/m mouse kidneys, while fenofibrate decreased them in db/db mouse kidneys. Db/db mice had a suppression of p-endothelial nitric oxide synthase (eNOS)/t-eNOS and nitric oxide (NO), and an increase of angiopoietin-2 and reactive oxygen species (ROS) in kidneys compared with db/m mice, and fenofibrate increased p-eNOS/t-eNOS and NO, and decreased angiopoietin-2 and ROS in db/db mouse kidneys. Hypoxia-inducible factor (HIF)-1α and Notch1 were promoted in db/db mouse kidneys compared with db/m mouse kidneys, and were reduced after fenofibrate treatment in db/db mouse kidneys. Furthermore, the immunofluorescence staining indicated that M1 macrophage recruitment was enhanced in db/db mouse kidneys compared to db/m mouse kidneys, and this was accompanied by a significant increase of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in kidneys and in serum of db/db mice compared with db/m mice. However, fenofibrate inhibited the renal M1 macrophage recruitment and cytokines associated with M1 macrophages in db/db mice.

Conclusions: Our study indicated that M1 macrophage recruitment due to the upregulated HIF-1α/Notch1 pathway induced by endothelial cell dysfunction involved in type 2 diabetic mouse renal injury, and PPAR-α agonist fenofibrate prevented DN by reducing M1 macrophage recruitment via inhibiting HIF-1α/Notch1 pathway regulated by endothelial cell function in type 2 diabetic mouse kidneys.

Deletion of delta-like 1 homologue accelerates renal inflammation by modulating the Th17 immune response

Preclinical studies have demonstrated that activation of the NOTCH pathway plays a key role in the pathogenesis of kidney damage. There is currently no information on the role of the Delta-like homologue 1 (DLK1), a NOTCH inhibitor, in the regulation of renal damage. Here, we investigated the contribution of DLK1 to experimental renal damage and the underlying molecular mechanisms. Using a Dlk1-null mouse model in the experimental renal damage of unilateral ureteral obstruction, we found activation of NOTCH, as shown by increased nuclear translocation of the NOTCH1 intracellular domain, and upregulation of Dlk2/hey-1 expression compared to wild-type (WT) littermates. NOTCH1 over-activation in Dlk1-null injured kidneys was associated with a higher inflammatory response, characterized by infiltration of inflammatory cells, mainly CD4/IL17A + lymphocytes, and activation of the Th17 immune response. Furthermore, pharmacological NOTCH blockade inhibited the transcription factors controlling Th17 differentiation and gene expression of the Th17 effector cytokine IL-17A and other related-inflammatory factors, linked to a diminution of inflammation in the injured kidneys. We propose that the non-canonical NOTCH ligand DLK1 acts as a NOTCH antagonist in renal injury regulating the Th17-mediated inflammatory response.

Aberrant Activation of Notch1 Signaling in Glomerular Endothelium Induces Albuminuria

RATIONALE

Glomerular capillaries are lined with a highly specialized fenestrated endothelium and contribute to the glomerular filtration barrier. The Notch signaling pathway is involved in regulation of glomerular filtration barrier, but its role in glomerular endothelium has not been investigated due to the embryonic lethality of animal models with genetic modification of Notch pathway components in the endothelium.

OBJECTIVE

To determine the effects of aberrant activation of the Notch signaling in glomerular endothelium and the underlying molecular mechanisms.

METHODS AND RESULTS

We established the ZEG-NICD1 (notch1 intracellular domain)/Tie2-tTA/Tet-O-Cre transgenic mouse model to constitutively activate Notch1 signaling in endothelial cells of adult mice. The triple transgenic mice developed severe albuminuria with significantly decreased VE-cadherin (vascular endothelial cadherin) expression in the glomerular endothelium. In vitro studies showed that either NICD1 (Notch1 intracellular domain) lentiviral infection or treatment with Notch ligand DLL4 (delta-like ligand 4) markedly reduced VE-cadherin expression and increased monolayer permeability of human renal glomerular endothelial cells. In addition, Notch1 activation or gene knockdown of VE-cadherin reduced the glomerular endothelial glycocalyx. Further investigation demonstrated that activated Notch1 suppression of VE-cadherin was through the transcription factors SNAI1 (snail family transcriptional repressor 1) and ERG (Ets related gene), which bind to the -373 E-box and the -134/-118 ETS (E26 transformation-specific) element of the VE-cadherin promoter, respectively.

CONCLUSIONS

Our results reveal novel regulatory mechanisms whereby endothelial Notch1 signaling dictates the level of VE-cadherin through the transcription factors SNAI1 and ERG, leading to dysfunction of glomerular filtration barrier and induction of albuminuria. Graphic Abstract: A graphic abstract is available for this article.

Effect of Salinomycin on Expression Pattern of Genes Associated with Apoptosis in Endometrial Cancer Cell Line

Background

Salinomycin is part of a group of ionophore antibiotics characterized by an activity towards tumor cells. To this day, the mechanism through which salinomycin induces their apoptosis is not fully known yet. The goal of this study was to assess the expression pattern of genes and the proteins coded by them connected with the process of programmed cell death in an endometrial cancer cell Ishikawa culture exposed to salinomycin and compared to the control.

Materials and Methods

Analysis of the effect of salinomycin on Ishikawa endometrial cancer cells (ECACC 99040201) included a cytotoxicity MTT test (with a concentration range of 0.1-100 µM), assessment of the induction of apoptosis and necrosis by salinomycin at a concentration of 1 µM as well the assessment of the expression of the genes chosen in the microarray experiment (microarray HG-U 133A_2) and the proteins coded by them connected with apoptosis (RTqPCR, ELISA assay). The statistical significance level for all analyses carried out as part of this study was p<0.05.

Results

It was observed that salinomycin causes the death of about 50% of cells treated by it (50.74±0.80% of all cells) at a concentration of 1µM. The decrease in the number of living cells was determined directly after treatment of the cells with the drug (time 0). The average percent of late apoptotic cells was 1.65±0.24% and 0.57±0.01% for necrotic cells throughout the entire observation period.

Discussion

Microarray analysis indicated the following number of mRNA differentiating the culture depending on the time of incubation with the drug: H_12 vs C = 114 mRNA, H_8 vs C = 84 mRNA, H_48 vs. C = 27 mRNA, whereas 5 mRNAs were expressed differently at all times. During the whole incubation period of the cells with the drug, the following dependence of the expression profile of the analyzed transcripts was observed: Bax>p53>FASL>BIRC5>BCL2L.

Conclusion

The analysis carried out indicated that salinomycin, at a concentration of 1 µM, stopped the proliferation of 50% of endometrial cancer cells, mainly by inducing the apoptotic process of the cells. The molecular exponent of the induction of programmed cell death was an observed increase in the transcriptional activity of pro-apoptotic genes: Bax;p53;FASL and a decrease in the expression of anti-apoptotic genes: BCL2L2; BIRC5.

The Physiology, Pathology, and Therapeutic Interventions for ROCK Isoforms in Diabetic Kidney Disease

Rho-associated coiled-coil-containing protein kinase (ROCK) is a serine/threonine kinase that was originally identified as RhoA interacting protein. A diverse array of cellular functions, including migration, proliferation, and phenotypic modulation, are orchestrated by ROCK through a mechanism involving cytoskeletal rearrangement. Mammalian cells express two ROCK isoforms: ROCK1 (Rho-kinase β/ROKβ) and ROCK2 (Rho-kinase α/ROKα). While both isoforms have structural similarities and are widely expressed across multiple tissues, investigations in gene knockout animals and cell-based studies have revealed distinct functions of ROCK1 and ROCK2. With respect to the kidney, inhibiting ROCK activity has proven effective for the preventing diabetic kidney disease (DKD) in both type 1 and type 2 diabetic rodent models. However, despite significant progress in the understanding of the renal ROCK biology over the past decade, the pathogenic roles of the ROCK isoforms is only beginning to be elucidated. Recent studies have demonstrated the involvement of renal ROCK1 in mitochondrial dynamics and cellular transdifferentiation, whereas ROCK2 activation leads to inflammation, fibrosis, and cell death in the diabetic kidney. This review provides a conceptual framework for dissecting the molecular underpinnings of ROCK-driven renal injury, focusing on the differences between ROCK1 and ROCK2.

ROCK Inhibition May Stop Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease and is strongly associated with cardiovascular mortality. Given the pandemic of obesity and diabetes, the elucidation of the molecular underpinnings of DKD and establishment of effective therapy are urgently required. Studies over the past decade have identified the activated renin-angiotensin system (RAS) and hemodynamic changes as important therapeutic targets. However, given the residual risk observed in patients treated with RAS inhibitors and/or sodium glucose co-transporter 2 inhibitors, the involvement of other molecular machinery is likely, and the elucidation of such pathways represents fertile ground for the development of novel strategies. Rho-kinase (ROCK) is a serine/threonine kinase that is under the control of small GTPase protein Rho. Many fundamental cellular processes, including migration, proliferation, and survival are orchestrated by ROCK through a mechanism involving cytoskeletal reorganization. From a pathological standpoint, several analyses provide compelling evidence supporting the hypothesis that ROCK is an important regulator of DKD that is highly pertinent to cardiovascular disease. In cell-based studies, ROCK is activated in response to a diverse array of external stimuli associated with diabetes, and renal ROCK activity is elevated in the context of type 1 and 2 diabetes. Experimental studies have demonstrated the efficacy of pharmacological or genetic inhibition of ROCK in the prevention of diabetes-related histological and functional abnormalities in the kidney. Through a bird’s eye view of ROCK in renal biology, the present review provides a conceptual framework that may be widely applicable to the pathological processes of multiple organs and illustrate novel therapeutic promise in diabetology.

Notch inhibitor mitigates renal ischemia‑reperfusion injury in diabetic rats

Diabetes mellitus can exacerbate renal ischemia-reperfusion (I/R) injury (RI/RI) in diabetic rats. Previous studies have shown that Notch signaling is involved in renal disorders. The aim of the present study was to evaluate the protective effect of the Notch inhibitor γ-secretase N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) on RI/RI in a streptozocin (STZ)-induced diabetic rat model. STZ-induced diabetic rats were randomly grouped for different treatments. Cisplatin was used to trigger the Notch signaling pathway and the animals were preconditioned with DAPT to block the signaling pathway. Renal function, oxidative stress and inflammatory factors were examined. DAPT-treated diabetic rats demonstrated mitigated renal injury and function, antioxidative activity was significantly improved and HIF-1a was upregulated. Notch inhibitor DAPT is a potential therapeutic target to improve the outcome of RI/RI in STZ-induced diabetic rats in part via the regulation of anti-oxidation and HIF-1a.

p66Shc regulates podocyte autophagy in high glucose environment through the Notch-PTEN-PI3K/Akt/mTOR pathway

BACKGROUND AND AIMS

Autophagy has been found to be involved in podocyte injury, which is a key factor in the progression of diabetic kidney disease (DKD). p66Shc is an important protein adaptor that regulates production of reactive oxygen species (ROS) and induction of apoptosis, and is a novel biomarker for oxidative damage of renal tubules. Our preliminary studies showed that p66Shc expression in podocytes of DKD patients is increased, while autophagic flux and podocyte number is decreased in DKD patients. The mechanism by which p66Shc may regulate podocyte autophagy and injury remains unknown. The present study aimed to investigate the molecular function of p66Shc under high glucose condition and its possible therapeutic utility in DKD.

METHODS

We histologically evaluated kidney injury in a streptozocin (STZ)-induced mouse model of diabetes using HE, PAS, PASM, and Masson staining and assessed glomerular structure by transmission electron microscopy. The apoptosis rate of high glucose-treated podocytes was assessed by TUNEL and Annexin V/PI staining. Markers of podocyte autophagy were measured by immunofluorescence and western blotting. DHE/ET fluorescence quantification was used for ROS detection and quantification.

RESULTS

Urine creatinine, serum creatinine, urinary microalbumin, and p66Shc expression were significantly increased in STZ-induced diabetic mice. Cultured MPC5 podocytes subjected to high glucose showed reduced viability, and p66Shc overexpression further accelerated apoptosis. p66Shc knockdown enhanced HG-induced autophagy, while p66Shc overexpression reduced the expression of PTEN and increased the expression of mTOR and phospho-mTOR. LC3 protein expression was higher in cells with p66Shc knockdown, indicating that activation of p66Shc inhibits podocyte autophagy. DAPT, an inhibitor of the Notch pathway, downregulated the expression of p66Shc.

CONCLUSION

These findings indicate that p66Shc inhibits podocyte autophagy and induces apoptosis through the Notch -PTEN-PI3K/Akt/ mTOR signaling pathway in high glucose environment, providing novel evidence for its potential role in DKD treatment.

Inhibition of high mobility group box 1 (HMGB1) attenuates podocyte apoptosis and epithelial-mesenchymal transition by regulating autophagy flux

BACKGROUND

Podocyte injury, characterized by podocyte hypertrophy, apoptosis, and epithelial-mesenchymal transition (EMT), is the major causative factor of diabetic nephropathy (DN). Autophagy dysfunction is regarded as the major risk factor for podocyte injury including EMT and apoptosis. High mobility group box 1 (HMGB1) is involved in the progression of DN through the induction of autophagy. However, the underlying mechanism remains unknown.

METHODS

Plasma HMGB1 concentrations were determined in DN patients using ELISA. Apoptosis of DN serum-treated podocytes was evaluated by flow cytometry. Podocyte autophagy flux was measured using immunofluorescence. Western blotting analysis was used to investigate HMGB1 expression, EMT, and autophagy-related signaling pathways.

RESULTS

Upregulation of HMGB1 was found in DN patients and DN serum-treated podocytes. Removal of HMGB1 inhibited DN serum-mediated podocyte apoptosis by inhibiting autophagy and activating AKT/mammalian target of rapamycin (mTOR) signaling. In addition, HMGB1 depletion repressed the progression of podocyte EMT by inhibiting transforming growth factor (TGF)-β/smad1 signaling in vitro and in vivo. The combination of HMGB1 short interference (si) RNA and the autophagy activator rapamycin protected against podocyte apoptosis and EMT progression by inhibiting the AKT/mTOR and TGF-β/smad signaling pathway, respectively.

CONCLUSIONS

Although HMGB1 siRNA and rapamycin treatment had opposite effects on autophagy and AKT/mTOR signaling, there was no contradiction about the role of HMGB1 siRNA and rapamycin on AKT/mTOR pathway because autophagy and AKT/mTOR signaling play dual roles in intracellular biological processes. Based on the findings of this study, we may assume that HMGB1-initiated autophagy is harmful, whereas rapamycin is beneficial to podocyte survival. Possibly combined treatment with HMGB1 siRNA and rapamycin improved podocyte damage and EMT by regulating autophagy homeostasis.

Aberrant activation of Notch-1 signaling inhibits podocyte restoration after islet transplantation in a rat model of diabetic nephropathy

Signaling abnormalities play important roles during podocyte injury and have been indicated as crucial events for triggering many glomerular diseases. There is emerging evidence demonstrating significant improvements in preventing renal injury and restoring podocytes after islet transplantation. However, whether signaling abnormalities affect the therapeutic efficacy of islet transplantation remain unclear. This study was established to investigate the impact of Notch-1 signaling activation on renal injury and podocyte restoration after islet transplantation. Experiments were performed in vivo and in vitro under conditions of diabetic nephropathy and high-glucose medium, respectively. Podocyte injury in vitro was induced by high-glucose concentration, and expression levels of genes associated with the Notch-1 pathway were also regulated by Jagged-1/FC and N-[N-(3,5-Difluorophenacetyl)-L-alanyl]- S-phenylglycine t-butyl ester (DAPT). Podocytes were co-cultured with islets to investigate the protective effect of islets in high-glucose conditions. Histopathological staining and transmission electron microscopy were performed to assess pathological changes in podocytes in glomeruli. The results from this study showed that Notch-1 signaling in podocytes was significantly decreased by functional islet cells in vivo and in vitro. Compared with the co-cultured group and transplanted group, highly activated Notch-1 signaling significantly moderated the effect of islets in affecting podocyte restoration and renal injury. Renal damage and podocyte injury were alleviated after DAPT treatment. Furthermore, the balance between apoptosis and autophagy was diverse under different treatments. All the data in this study showed that highly activated Notch-1 signaling could affect the therapeutic efficacy of islet transplantation on renal injury and podocyte restoration in high-glucose conditions. The balance between apoptosis and autophagy was also closely associated with the degree of podocyte restoration. This finding may suggest that the in vivo microenvironment plays a critical role in podocyte restoration after islet transplantation, which provides a promising and individual assessment and targeting treatment for different diabetic nephropathy patients after islet transplantation into the future.

Jagged1/Notch2 controls kidney fibrosis via Tfam-mediated metabolic reprogramming

While Notch signaling has been proposed to play a key role in fibrosis, the direct molecular pathways targeted by Notch signaling and the precise ligand and receptor pair that are responsible for kidney disease remain poorly defined. In this study, we found that JAG1 and NOTCH2 showed the strongest correlation with the degree of interstitial fibrosis in a genome-wide expression analysis of a large cohort of human kidney samples. Transcript analysis of mouse kidney disease models, including folic-acid (FA)-induced nephropathy, unilateral ureteral obstruction (UUO), or apolipoprotein L1 (APOL1)-associated kidney disease, indicated that Jag1 and Notch2 levels were higher in all analyzed kidney fibrosis models. Mice with tubule-specific deletion of Jag1 or Notch2 (Kspcre/Jag1flox/flox and Kspcre/Notch2flox/flox) had no kidney-specific alterations at baseline but showed protection from FA-induced kidney fibrosis. Tubule-specific genetic deletion of Notch1 and global knockout of Notch3 had no effect on fibrosis. In vitro chromatin immunoprecipitation experiments and genome-wide expression studies identified the mitochondrial transcription factor A (Tfam) as a direct Notch target. Re-expression of Tfam in tubule cells prevented Notch-induced metabolic and profibrotic reprogramming. Tubule-specific deletion of Tfam resulted in fibrosis. In summary, Jag1 and Notch2 play a key role in kidney fibrosis development by regulating Tfam expression and metabolic reprogramming.

Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells

Reactivation of Notch signaling in kidneys of animal models and patients with chronic kidney disease (CKD) has been shown to contribute to epithelial injury and fibrosis development. Here, we investigated the mechanisms of Notch-induced injury in renal epithelial cells. We performed genome-wide transcriptome analysis to identify Notch target genes using an in vitro system of cultured tubular epithelial cells expressing the intracellular domain of Notch1. One of the top downregulated genes was Disabled-2 ( Dab2). With the use of Drosophila nephrocytes as a model system, we found that Dab (the Drosophila homolog of Dab2) knockdown resulted in a significant filtration defect, indicating that loss of Dab2 plays a functional role in kidney disease development. We showed that Dab2 expression in cultured tubular epithelial cells is involved in endocytic regulation and that it also protects cells from TGF-β-induced epithelial-to-mesenchymal transition. In vivo correlation studies indicated its additional role in renal ischemia-induced injury. Together, these data suggest that Dab2 plays a versatile role in the kidney and may impact on acute and CKDs.-Schütte-Nütgen, K., Edeling, M., Mendl, G., Krahn, M. P., Edemir, B., Weide, T., Kremerskothen, J., Michgehl, U., Pavenstädt, H. Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells.

Altered expression of WFS1 and NOTCH2 genes associated with diabetic nephropathy in T2DM patients

AIM

The increased incidence of type 2 diabetes mellitus (T2DM) and the importance of early identification and management of its complications, especially diabetic nephropathy (DN), have spotted the light on genetic factors that increase risk of T2DM and its related nephropathy. The present study aimed at investigating expression of (KCNJ11, ABCC8, JAZF1, WFS1, PPARG, NOTCH2 and EXOSC4) genes in peripheral blood of T2DM patients.

METHOD

The study included 30 non-complicated T2DM patients, 30 patients with DN and 40 healthy controls. Quantitative Real Time PCR Array was used to study gene expression.

RESULTS

NOTCH2 showed higher expression while KCNJ11, JAZF1, WFS1 and PPARG genes showed lower expression in DN patients compared to non-complicated patients. KCNJ11, JAZF1, WFS1, PPARG, and EXOSC4 expression showed significant negative correlation with microalbumin, while NOTCH2 expression was significantly positively correlated with microalbumin. AS regard HbA1c and studied genes expression, there was significant negative correlation between WFS1 expression and HbA1c, while NOTCH2, KCNJ11, JAZF1, PPARG, EXOSC4 expression didn't show significant correlation with HbA1c. Risk ratio of studied genes expression showed that WFS1 and NOTCH2 had highest risk ratio (30) and highest sensitivity and specificity, in relation to DN and they were the best predictors in the group of studied genes at cut off value of ≤0.861 for WFS1 and ≥0.678 for NOTCH2.

CONCLUSION

Altered expression of WFS1 and NOTCH2 genes may play a role in pathogenesis and development of DN in patients with T2DM. These results may contribute in early identification and management of DN.

The impact of neuronal Notch-1/JNK pathway on intracerebral hemorrhage-induced neuronal injury of rat model

Notch signaling is a highly conserved pathway that regulates cell fate decisions during embryonic development. Notch activation endangers neurons by modulating NF-κB and HIF-1α pathways, however, the role of Notch signaling in activating JNK/c-Jun following intracerebral hemorrhage (ICH) has not been investigated. In this study, we used rat ICH models and thrombin-induced cell models to investigate the potential role of Notch-1/JNK signals. Our findings revealed that Notch-1 and JNK increased in hematoma-surrounding neurons tissues following ICH during ischemic conditions (all p<0.05). Besides, the expression of active caspase-3 protein was also up-regulated after ICH. According to in-vitro assays, the expression of Notch-1, p-JNK, and active caspase-3 were all up-regulated in cell viability-decreasing ICH cell models (all p<0.05). However, blocking of either Notch-1 or JNK suppressed the phosphorylation of JNK and the expression of active caspase-3, and cell viability was obviously ameliorated. In conclusion, this work suggested Notch-1 activates JNK pathway to induce the active caspase-3, leading to neuronal injury when intracerebral hemorrhage or ischemia occurred. Thus the Notch-1/JNK signal pathway has an important role in ICH process, and may be a therapeutic target to prevent brain injury.

Adipose tissue DNA methylome changes in development of new-onset diabetes after kidney transplantation

AIM

New-onset diabetes after kidney transplant (NODAT) adversely impacts kidney allograft and patient survival. Epigenetic alterations in adipose tissue like DNA methylation may play a contributory role.

METHODS

Adipose tissue DNA of the patients with NODAT and their age, sex and BMI matched controls (nine each) were sequenced by reduced representation bisulfite sequencing. Differentially methylated CpGs (DMCs) and differentially methylated regions (DMRs) were studied.

RESULTS

Adipose tissue from the patients had reduced DNA methylation in intergenic and intronic regions. DMCs were found to be more hypomethylated in repeat regions and hypermethylated in CGIs and promoter region. About 900 DMRs were found and their associated genes were significantly enriched in 32 pathways, the top ones of which were associated with insulin resistance and inflammation. Some DMR or DMC genes have known T2DM associations.

CONCLUSION

Changes in DNA methylation in adipose tissue may be suggestive of future NODAT.

Rho-Kinase Blockade Attenuates Podocyte Apoptosis by Inhibiting the Notch Signaling Pathway in Diabetic Nephropathy

Podocyte apoptosis is a key process in the onset of diabetic nephropathy. A significant body of evidence shows that the Notch signaling pathway plays a central role in this process. We found that Rho-kinase mediates transforming growth factor β (TGF-β)-induced Notch ligand Jag1 expression. Importantly, TGF-β-mediated podocyte apoptosis was attenuated by Rho-kinase inhibition. Mechanistically, Rho-kinase regulated Jag1 induction via the extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK) but not Smad pathways. Consistently, the Rho-kinase inhibitor fasudil prevented albuminuria and the urinary excretion of nephrin in db/db mice and reduced the prevalence of podocyte apoptosis and Jag1 expression. Finally, the expression of Jag1 and apoptosis markers such as Bax and cyclin-dependent kinase inhibitor 1A (CDKN1A) was decreased in podocytes derived from db/db mice treated with fasudil. The present study provides evidence that Rho-kinase plays a key role in podocyte apoptosis. Rho-kinase is an attractive therapeutic target for diabetic nephropathy.

PGC-1α Protects from Notch-Induced Kidney Fibrosis Development

Kidney fibrosis is the histologic manifestation of CKD. Sustained activation of developmental pathways, such as Notch, in tubule epithelial cells has been shown to have a key role in fibrosis development. The molecular mechanism of Notch-induced fibrosis, however, remains poorly understood. Here, we show that, that expression of peroxisomal proliferation g-coactivator (PGC-1α) and fatty acid oxidation-related genes are lower in mice expressing active Notch1 in tubular epithelial cells (Pax8-rtTA/ICN1) compared to littermate controls. Chromatin immunoprecipitation assays revealed that the Notch target gene Hes1 directly binds to the regulatory region of PGC-1α Compared with Pax8-rtTA/ICN1 transgenic animals, Pax8-rtTA/ICN1/Ppargc1a transgenic mice showed improvement of renal structural alterations (on histology) and molecular defect (expression of profibrotic genes). Overexpression of PGC-1α restored mitochondrial content and reversed the fatty acid oxidation defect induced by Notch overexpression in vitro in tubule cells. Furthermore, compared with Pax8-rtTA/ICN1 mice, Pax8-rtTA/ICN1/Ppargc1a mice exhibited improvement in renal fatty acid oxidation gene expression and apoptosis. Our results show that metabolic dysregulation has a key role in kidney fibrosis induced by sustained activation of the Notch developmental pathway and can be ameliorated by PGC-1α.

Expression of JAZF1, ABCC8, KCNJ11and Notch2 genes and vitamin D receptor polymorphisms in type 2 diabetes, and their association with microvascular complications

BACKGROUND

We studied JAZF1, ABCC8, KCNJ11and Notch2 gene expression and vitamin D receptor (VDR) polymorphisms (Fok1 and Bsm1) in patients with type 2 diabetes mellitus (T2DM) and tried to find out their association with microvascular complications in these patients.

METHODS

The study was conducted on 180 patients (93 complicated and 87 noncomplicated) and 150 healthy subjects. Reverse-transcriptase polymerase chain reaction (RT-PCR) was used to assess gene expression and real-time PCR was used to detect VDR genotypes. Serum vitamin D was assessed using Elisa technique.

RESULTS

After adjustment for age, sex, body mass index and glycated hemoglobin, altered Notch2 gene expression was found between patients and controls and between complicated and noncomplicated cases (p = 0.001 and 0.001, respectively) and ABCC8 gene expression showed significant difference between patients and controls only (p = 0.003), while JAZF1and KCNJ11 expression showed no significant difference between the studied groups (p = 0.3 and 0.4, respectively). Serum vitamin D level was decreased in patients compared with controls (p = 0.001), while no difference was detected between complicated and noncomplicated cases (p = 0.1). Our results revealed no significant difference in VDR Fok1 and Bsm1 genotype distributions (p = 0.7 and 0.1, respectively) and allele frequencies (p = 0.4 and 0.1, respectively) between patients and controls. Patients with complications showed increased frequencies of Fok1GG genotype and G allele, while patients without complications showed increased frequencies of AA, then AG Fok1 genotype and A allele (p = 0.001 and 0.001, respectively). In addition, the frequencies of CC Bsm1 genotype and C allele were significantly higher among patients with complications, while frequencies of TT Bsm1 genotype and T allele were significantly higher among patients without complications (p = 0.02 and 0.003, respectively).

CONCLUSION

Altered expression of Notch2 and ABCC8 genes may play a role in the pathogenesis of T2DM. Altered expression of Notch2 and VDR polymorphisms may play a role in the development of microvascular complications in diabetic patients. These results may assist in early identification and management of diabetic complications.

Effect of berberine on the renal tubular epithelial-to-mesenchymal transition by inhibition of the Notch/snail pathway in diabetic nephropathy model KKAy mice

Renal tubular epithelial-to-mesenchymal transition (EMT) and renal tubular interstitial fibrosis are the main pathological changes of diabetic nephropathy (DN), which is a common cause of end-stage renal disease. Previous studies have suggested that berberine (BBR) has antifibrotic effects in the kidney and can reduce apoptosis and inhibit the EMT of podocytes in DN. However, the effect of BBR on the renal tubular EMT in DN and its mechanisms of action are unknown. This study was performed to explore the effects of BBR on the renal tubular EMT and the molecular mechanisms of BBR in DN model KKAy mice and on the high glucose (HG)-induced EMT in mouse renal tubular epithelial cells. Our results showed that, relative to the model mice, the mice in the treatment group had an improved general state and reduced blood glucose and 24-h urinary protein levels. Degradation of renal function was ameliorated by BBR. We also observed the protective effects of BBR on renal structural changes, including normalization of an index of renal interstitial fibrosis and kidney weight/body weight. Moreover, BBR suppressed the activation of the Notch/snail pathway and upregulated the α-SMA and E-cadherin levels in DN model KKAy mice. BBR was further found to prevent HG-induced EMT events and to inhibit the HG-induced expression of Notch pathway members and snail1 in mouse renal tubular epithelial cells. Our findings indicate that BBR has a therapeutic effect on DN, including its inhibition of the renal tubular EMT and renal interstitial fibrosis. Furthermore, the BBR-mediated EMT inhibition occurs through Notch/snail pathway regulation.

Research Progress on Mechanism of Podocyte Depletion in Diabetic Nephropathy

Diabetic nephropathy (DN) together with glomerular hyperfiltration has been implicated in the development of diabetic microangiopathy in the initial stage of diabetic diseases. Increased amounts of urinary protein in DN may be associated with functional and morphological alterations of podocyte, mainly including podocyte hypertrophy, epithelial-mesenchymal transdifferentiation (EMT), podocyte detachment, and podocyte apoptosis. Accumulating studies have revealed that disruption in multiple renal signaling pathways had been critical in the progression of these pathological damages, such as adenosine monophosphate-activated kinase signaling pathways (AMPK), wnt/β-catenin signaling pathways, endoplasmic reticulum stress-related signaling pathways, mammalian target of rapamycin (mTOR)/autophagy pathway, and Rho GTPases. In this review, we highlight new molecular insights underlying podocyte injury in the progression of DN, which offer new therapeutic targets to develop important renoprotective treatments for DN over the next decade.

The Involvement of Notch1-RBP-Jk/Msx2 Signaling Pathway in Aortic Calcification of Diabetic Nephropathy Rats

BACKGROUND

This study explored the changes in expression of vascular smooth muscle cell (VSMC) markers and osteogenic markers, as well as the involvement of Notch1-RBP-Jk/Msx2 pathway in a rat model of diabetic nephropathy (DN) with vascular calcification.

METHODS

A rat model of DN with concomitant vascular calcification was created by intraperitoneal injection of streptozotocin followed by administration of vitamin D3 and nicotine. Biochemical analysis and histological examination of aortic tissue were performed. VSMC markers and osteogenic markers as well as target molecules in Notch1-RBP-Jk/Msx2 were determined by quantitative real-time polymerase chain reaction and immunohistochemical analysis.

RESULTS

Serum calcium and phosphorus levels were significantly increased in model rats as compared to that in normal controls. Diabetic rats with vascular calcification exhibited mineral deposits in aortic intima-media accompanied by decreased expression of VSMC markers and increased expression of osteogenic markers. Notch1, RBP-Jk, Msx2, Jagged1, and N1-ICD were barely expressed in the aortic wall of normal rats. In contrast, these were significantly increased in the model group at all time points (8, 12, and 16 weeks), as compared to that in the normal rats.

CONCLUSION

Activation of the Notch1-RBP-Jk/Msx2 signaling pathway may be involved in the development and progression of vascular calcification in DN.

Regulation of podocyte lesions in diabetic nephropathy via miR-34a in the Notch signaling pathway

BACKGROUND

The activation of the Notch signaling pathway has been shown to play an important role in diabetic nephropathy (DN) development. Besides, Notch-1 is a target gene in miR-34a. However, the regulation of the podocyte lesions involved in DN by miR-34a has not been identified.

METHODS

This study utilized miR-34a mimics and small interfering RNA transfection to construct miR-34a overexpression and lower-expression model to investigate the effect of miR-34a on the regulation of the Notch signaling pathway and podocyte lesions in DN. Western blotting and real-time quantitative polymerase chain reaction were applied for the quantitative testing of mRNA and protein expression. Apoptosis of podocyte was detected by TUNEL staining.

RESULTS

In high-glucose (HG) conditions, miR-34a overexpression inhibited the expression of Notch 1, Jagged 1, NICD, Hes 1, and Hey 1 proteins. Further, cleaved caspase-3, Bax, and phosphorylation of p53 (p-p53) were reduced significantly. Therefore, miR-34a overexpression inhibited the Notch signaling pathway and podocyte lesions induced by HG. β-arrestin was slightly reduced in HG conditions. Meanwhile, miR-34a overexpression could remit the inhibition.

CONCLUSION

Results from this study provide evidence that miR-34a may offer a new approach for the treatment of diabetes.

Insights into the Mechanisms Involved in the Expression and Regulation of Extracellular Matrix Proteins in Diabetic Nephropathy

Diabetic Nephropathy (DN) is believed to be a major microvascular complication of diabetes. The hallmark of DN includes deposition of Extracellular Matrix (ECM) proteins, such as, collagen, laminin and fibronectin in the mesangium and renal tubulo-interstitium of the glomerulus and basement membranes. Such an increased expression of ECM leads to glomerular and tubular basement membranes thickening and increase of mesangial matrix, ultimately resulting in glomerulosclerosis and tubulointerstitial fibrosis. The characteristic morphologic glomerular mesangial lesion has been described as Kimmelstiel-Wilson nodule, and the process at times is referred to as diabetic nodular glomerulosclerosis. Thus, the accumulation of ECM proteins plays a critical role in the development of DN. The relevant mechanism(s) involved in the increased ECM expression and their regulation in the kidney in diabetic state has been extensively investigated and documented in the literature. Nevertheless, there are certain other mechanisms that may yet be conclusively defined. Recent studies demonstrated that some of the new signaling pathways or molecules including, Notch, Wnt, mTOR, TLRs and small GTPase may play a pivotal role in the modulation of ECM regulation and expression in DN. Such modulation could be operational for instance Notch through Notch1/Jagged1 signaling, Wnt by Wnt/β- catenin pathway and mTOR via PI3-K/Akt/mTOR signaling pathways. All these pathways may be critical in the modulation of ECM expression and tubulo-interstitial fibrosis. In addition, TLRs, mainly the TLR2 and TLR4, by TLR2- dependent and TGF-β-dependent conduits, may modulate ECM expression and generate a fibrogenic response. Small GTPase like Rho, Ras and Rab family by targeting relevant genes may also influence the accumulation of ECM proteins and renal fibrosis in hyperglycemic states. This review summarizes the recent information about the role and mechanisms by which these molecules and signaling pathways regulate ECM synthesis and its expression in high glucose ambience in vitro and in vivo states. The understanding of such signaling pathways and the molecules that influence expression, secretion and amassing of ECM may aid in developing strategies for the amelioration of diabetic nephropathy.

Valsartan ameliorates podocyte loss in diabetic mice through the Notch pathway

The Notch pathway is known to be linked to diabetic nephropathy (DN); however, its underlying mechanism was poorly understood. In the present study, we examined the effect of Valsartan, an angiotensin II type 1 receptor antagonist, on the Notch pathway and podocyte loss in DN. Diabetes was induced in mice by an intraperitoneal injection of streptozotocin and and this was followed by treatment with Valsartan. Levels of blood glucose, kidney weight and body weight, as well as proteinuria were measured. Samples of the kidneys were also histologically examined. The relative levels of Jagged1, Notch1, Notch intracellular domain 1 (NICD1), Hes family BHLH transcription factor 1 (Hes1) and Hes-related family BHLH transcription factor with YRPW motif 1 expression (Hey1) in the glomeruli were determined by immunohistochemical analysis, western blot analysis and RT-qPCR. The B-Cell CLL/Lymphoma 2 (Bcl-2) and p53 pathways were examined by western blot analysis. Apoptosis and detachment of podocytes from the glomerular basement membrane were examined using a TUNEL assay, flow cytometric analysis and ELISA. The number of podocytes was quantified by measuring Wilms tumor-1 (WT-1) staining. We noted that the expression of Jagged1, Notch1, NICD1, Hes1 and Hey1 was increased in a time-dependent manner in the glomeruli of mice with streptozotocin (STZ)-induced diabetes. Moreover, in diabetic mice, Valsartan significantly reduced kidney weight and proteinuria, and mitigated the pathogenic processes in the kidneys. Valsartan also inhibited the activation of Notch, Bcl-2 and p53 pathways and ameliorated podocyte loss in the glomeruli of mice with STZ-induced diabetes. Taken together, these findings indicated that Valsartan exerted a beneficial effect on reducing podocyte loss, which is associated with inhibition of Notch pathway activation in the glomeruli of diabetic mice.

Notch1 and Notch2 in Podocytes Play Differential Roles During Diabetic Nephropathy Development

Notch pathway activation in podocytes has been shown to play an important role in diabetic kidney disease (DKD) development; however, the receptors and ligands involved in the process have not been identified. Here, we report that conditional deletion of Notch1 in podocytes using NPHS2(cre)Notch1(flox/flox) animals resulted in marked amelioration of DKD. On the contrary, podocyte-specific genetic deletion of Notch2 had no effect on albuminuria and mesangial expansion. Notch1-null podocytes were protected from apoptosis and dedifferentiation in vitro, likely explaining the protective phenotype in vivo. Deletion of Notch1 in podocytes also resulted in an increase in Notch2 expression, indicating an interaction between the receptors. At the same time, transgenic overexpression of Notch2 in podocytes did not induce phenotypic changes, while constitutive expression of Notch1 caused rapid development of albuminuria and glomerulosclerosis. In summary, our studies indicate that Notch1 plays a distinct (nonredundant) role in podocytes during DKD development.

Chrysin inhibits diabetic renal tubulointerstitial fibrosis through blocking epithelial to mesenchymal transition

Renal fibrosis is a crucial event in the pathogenesis of diabetic nephropathy (DN). The process known as epithelial to mesenchymal transition (EMT) contributes to the accumulation of matrix proteins in kidneys, in which renal tubular epithelial cells play an important role in progressive renal fibrosis. The current study investigated that chrysin (5,7-dihydroxyflavone) present in bee propolis and herbs, inhibited renal tubular EMT and tubulointerstitial fibrosis due to chronic hyperglycemia. Human renal proximal tubular epithelial cells (RPTEC) were incubated in media containing 5.5 mM glucose, 27.5 mM mannitol (as an osmotic control), or 33 mM glucose (HG) in the absence and presence of 1-20 μM chrysin for 72 h. Chrysin significantly inhibited high glucose-induced renal EMT through blocking expression of the mesenchymal markers vimentin, α-smooth muscle actin, and fibroblast-specific protein-1 in RPTEC and db/db mice. Chrysin reversed the HG-induced down-regulation of the epithelial marker E-cadherin and the HG-enhanced N-cadherin induction in RPTEC. In addition, chrysin inhibited the production of collagen IV in tubular cells and the deposition of collagen fibers in mouse kidneys. Furthermore, chrysin blocked tubular cell migration concurrent with decreasing matrix metalloproteinase-2 activity, indicating epithelial cell derangement and tubular basement membrane disruption. Chrysin restored the induction of the tight junction proteins Zona occludens protein-1 (ZO-1) and occludin downregulated in diabetic mice. Chrysin inhibited renal tubular EMT-mediated tubulointerstitial fibrosis caused by chronic hyperglycemia. Therefore, chrysin may be a potent renoprotective agent for the treatment of renal fibrosis-associated DN.

KEY MESSAGES

• Glucose increases renal tubular epithelial induction of vimentin, α-SMA and FSP-1. • Glucose enhances renal EMT by blocking tubular epithelial E-cadherin expression. • Chrysin inhibits tubular EMT-mediated tubulointerstitial fibrosis in mouse kidneys. • Chrysin restores renal tubular induction of ZO-1 and occludin downregulated in diabetic mice. • Chrysin blocks glucose-induced renal tubular cell migration with reducing MMP-2 activity.

Overexpression of miR-34c inhibits high glucose-induced apoptosis in podocytes by targeting Notch signaling pathways

Recent findings have shown that microRNAs play critical roles in the pathogenesis of diabetic nephropathy. miR-34c has been found to inhibit fibrosis and the epithelial-mesenchymal transition of kidney cells. However, the role of miR-34c in diabetic nephropathy has not been well studied. The current study was designed to investigate the role and potential underlying mechanism of miR-34c in regulating diabetic nephropathy. After treating podocytes with high glucose (HG) in vitro, we found that miR-34c was downregulated and that overexpression of miR-34c inhibited HG-induced podocyte apoptosis. The direct interaction between miR-34c and the 3'-untranslated region (UTR) of Notch1 and Jagged1 was validated by dual-luciferase reporter assay. Moreover, Notch1 and Jagged1 as putative targets of miR-34c were downregulated by miR-34c overexpression in HG-treated podocytes. Overexpression of miR-34c inhibited HG-induced Notch signaling pathway activation, as indicated by decreased expression of the Notch intracellular domain (NICD) and downstream genes including Hes1 and Hey1. Furthermore, miR-34c overexpression increased the expression of the anti-apoptotic gene Bcl-2, and decreased the expression of the pro-apoptotic protein Bax and cleaved Caspase-3. Additionally, the phosphorylation of p53 was also downregulated by miR-34c overexpression. Taken together, our findings suggest that miR-34c overexpression inhibits the Notch signaling pathway by targeting Notch1 and Jaggged1 in HG-treated podocytes, representing a novel and potential therapeutic target for the treatment of diabetic nephropathy.

Kick it up a notch: Notch signaling and kidney fibrosis

Notch is a critical regulator of kidney development, but the pathway is mostly silenced once kidney maturation is achieved. Recent reports demonstrated increased expression of Notch receptors and ligands both in acute and chronic kidney injury. In vivo studies indicated that Notch activation might contribute to regeneration after acute kidney injury; on the other hand, sustained Notch expression is causally associated with interstitial fibrosis and glomerulosclerosis. This review will summarize the current knowledge on the role of the Notch signaling with special focus on kidney fibrosis.

Renal outcomes in patients with type 1 diabetes and macroalbuminuria

Macroalbuminuria, defined as urine albumin excretion rate (AER)≥300 mg/d, has long been considered a stage of irreversible kidney damage that leads reliably to GFR loss. We examined the long-term renal outcomes of persons with type 1 diabetes who developed incident macroalbuminuria during the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) study. One hundred fifty-nine participants developed incident macroalbuminuria and were subsequently followed for a median duration of 9 years (maximum of 25 years). At the time of macroalbuminuria diagnosis, mean (SD) age was 37 (9) years, mean (SD) duration of diabetes was 17 (5) years, median AER was 524 mg/d, and mean (SD) eGFR was 108 (20) ml/min per 1.73 m(2). Ten years after macroalbuminuria diagnosis, the cumulative incidence of a sustained reduction in AER to <300 mg/d was 52%, mostly but not entirely under treatment with renin-angiotensin system inhibitors. The cumulative incidence of impaired GFR (sustained eGFR<60 ml/min per 1.73 m(2)) 10 years after macroalbuminuria diagnosis was 32%, including 16% who developed ESRD. Lower hemoglobin A1c and BP and regression to AER<300 mg/d were associated with reduced risk of developing impaired GFR. In conclusion, people with type 1 diabetes who develop macroalbuminuria are at high risk of progressive kidney disease. However, through at least 10 years of follow-up, AER could often be controlled, and GFR frequently remained in the normal range.

Ultrasound-mediated microbubble destruction increases renal interstitial capillary permeability in early diabetic nephropathy rats

Diabetic nephropathy (DN) is defined as persistent proteinuria corresponding to a urinary albumin excretion rate >300 μg/mg in the absence of other non-diabetic renal diseases. The aim of this study was to determine if ultrasound (US)-mediated microbubble (MB) destruction could increase renal interstitial capillary permeability in early DN rats. Diabetes was induced with streptozotocin. DN rats presented with mild micro-albuminuria 30 d after onset of diabetes. DN rats (N = 120) were divided into four groups that received Evans blue (EB) followed by: (i) no treatment (control group); (ii) continuous ultrasonic irradiation for 5 min (frequency = 7.00 MHz, mechanical index = 0.9, peak rarefactional pressure = 2.38 MPa: US group); (iii) microbubble injection (0.05 mL/kg: MB group); and (iv) both ultrasound and microbubble injection (US + MB group). Another 8 DN rats were subjected to ultrasound and microbubbles and then injected with EB after 24 h (recovery group). EB content, EB extravasation and E-selectin mRNA and protein expression significantly increased, and interstitial capillary walls became discontinuous in the US + MB group. Neither hemorrhage nor necrosis was observed on renal histology. Urine samples were collected 24 h post-treatment. There was no hematuria, and the urinary albumin excretion rate did not increase after ultrasound-microbubble interaction detected by urinalysis. EB content returned to the control group level after 24 h, as assessed for the recovery group. In conclusion, ultrasound-mediated microbubble destruction locally increased renal interstitial capillary permeability in DN rats, and should be considered a therapy for enhancing drug and gene delivery to the kidney in the future.

Developmental signaling: does it bridge the gap between cilia dysfunction and renal cystogenesis?

For more than a decade, evidence has accumulated linking dysfunction of primary cilia to renal cystogenesis, yet molecular mechanisms remain undefined. The pathogenesis of renal cysts is complex, involving multiple cellular aberrations and signaling pathways. Adding to this complexity, primary cilia exhibit multiple roles in a context-dependent manner. On renal epithelial cells, primary cilia act as mechanosensors and trigger extracellular Ca(2+) influx in response to laminar fluid flow. During mammalian development, primary cilia mediate the Hedgehog (Hh), Wnt, and Notch pathways, which control cell proliferation and differentiation, and tissue morphogenesis. Further, experimental evidence suggests the developmental state of the kidney strongly influences renal cystic disease. Thus, we review evidence for regulation of Ca(2+) and cAMP, key molecules in renal cystogenesis, at the primary cilium, the role of Hh, Wnt, and Notch signaling in renal cystic disease, and the interplay between these developmental pathways and Ca(2+) signaling. Indeed if these developmental pathways influence renal cystogenesis, these may represent novel therapeutic targets that can be integrated into a combination therapy for renal cystic disease.

Renal tubular Notch signaling triggers a prosenescent state after acute kidney injury

The aging kidney has a diminished regenerative potential and an increased tendency to develop tubular atrophy and fibrosis after acute injury. In this study, we found that activation of tubular epithelial Notch1 signaling was prolonged in the aging kidney after ischemia/reperfusion (IR) damage. To analyze the consequences of sustained Notch activation, we generated mice with conditional inducible expression of Notch1 intracellular domain (NICD) in proximal tubules. NICD kidneys were analyzed 1 and 4 wk after renal IR. Conditional NICD expression was associated with aggravated tubular damage, a fibrotic phenotype, and the expression of cellular senescence markers p21 and p16 INK4a. In wild-type mice pharmacological inhibition of Notch using the γ-secretase inhibitor N-[ N-(3,5-difluorophenacetyl)-l-alanyl]- S-phenylglycine t-butyl ester (DAPT) improved tubulo-interstitial damage and antagonized the prosenescent pathway activation after IR. In vitro, activation of Notch signaling with delta-like-ligand-4 caused prosenescent changes in tubular cells while inhibition with DAPT attenuated these changes. In conclusion, our data suggest that sustained epithelial Notch activation after IR might contribute to the inferior outcome of old kidneys after injury. Sustained epithelial activation of Notch is associated with a prosenescent phenotype and maladaptive repair.

Knockdown of glyoxalase 1 mimics diabetic nephropathy in nondiabetic mice

Differences in susceptibility to diabetic nephropathy (DN) between mouse strains with identical levels of hyperglycemia correlate with renal levels of oxidative stress, shown previously to play a central role in the pathogenesis of DN. Susceptibility to DN appears to be genetically determined, but the critical genes have not yet been identified. Overexpression of the enzyme glyoxalase 1 (Glo1), which prevents posttranslational modification of proteins by the glycolysis-derived α-oxoaldehyde, methylglyoxal (MG), prevents hyperglycemia-induced oxidative stress in cultured cells and model organisms. In this study, we show that in nondiabetic mice, knockdown of Glo1 increases to diabetic levels both MG modification of glomerular proteins and oxidative stress, causing alterations in kidney morphology indistinguishable from those caused by diabetes. We also show that in diabetic mice, Glo1 overexpression completely prevents diabetes-induced increases in MG modification of glomerular proteins, increased oxidative stress, and the development of diabetic kidney pathology, despite unchanged levels of diabetic hyperglycemia. Together, these data indicate that Glo1 activity regulates the sensitivity of the kidney to hyperglycemic-induced renal pathology and that alterations in the rate of MG detoxification are sufficient to determine the glycemic set point at which DN occurs.