Molecular mechanisms involved in podocyte EMT and concomitant diabetic kidney diseases: an update

(+)-Catechins Play a Protective Role in Diabetic Kidney Disease by Alleviating EMT through Multiple Pathways

SCOPE

Diabetic nephropathy (DN), a complication of diabetes mellitus, is becoming a significant global health concern, with no complete cure currently available. Tea is regarded as an essential component of a balanced diet and contains (+)-Catechin (CE), which exert a range of pharmacological effects. Consequently, CE may be a potential treatment for DN. The objective of this study is to examine the protective effects and underlying mechanisms of CE on DN, with a particular focus on the epithelial-mesenchymal transition (EMT) process, which plays a pivotal role in regulating DN.

METHODS AND RESULTS

In this study db/db mice are treated with catechins. The results demonstrate that CE reduces obesity and hyperglycemia, improves renal dysfunction and morphological changes in diabetic mice, and inhibits the development of DN through the RAGE/NF-κB signaling pathway. Among them differentially expressed messenger RNA (mRNA) results, those related to EMT, including Cav1, grem2, macrod2, and kap, are identified. To further validate the results, the same experiments are performed on HK-2 cells.

CONCLUSIONS

The research results offer novel perspectives by emphasizing the anti-inflammatory properties of CE and their potential role in mitigating DN through the regulation of EMT-related genes such as RAGE, Cav1, grem2, macrod2, and kap.

Role of Extracellular Vesicle-Derived Noncoding RNAs in Diabetic Kidney Disease

Background

Diabetic kidney disease (DKD), a metabolism-related syndrome characterized by abnormal glomerular filtration rate, proteinuria, and renal microangiopathy, is one of the most common forms of chronic kidney disease, whereas extracellular vesicles (EVs) have been recently evidenced as a novel cell communication player in DKD occurrence and progress via releasing various bioactive molecules, including proteins, lipids, and especially RNA, among which noncoding RNAs (including miRNAs, lncRNAs, and circRNAs) are the major regulators. However, the functional relevance of EV-derived ncRNAs in DKD is to be elucidated.

Summary

Studies have reported that EV-derived ncRNAs regulate gene expression via a diverse range of regulatory mechanisms, contributing to diverse phenotypes related to DKD progression. Furthermore, there are already many potential clinical diagnostic and therapeutic studies based on these ncRNAs, which can be expected to have potential applications in clinical practice for EV-derived ncRNAs.

Key Messages

In the current review, we summarized the mechanistic role of EVs in DKD according to biological function classifications, including inflammation and oxidative stress, epithelial-mesenchymal transition, cell death, and extracellular matrix deposition. In addition, we comprehensively discussed the potential applications of EV-derived ncRNAs as diagnostic biomarkers and therapeutic targets in DKD.

Obesity-related glomerulopathy is associated with elevated WT1 expression in podocytes

BACKGROUND

The prevalence of obesity is increasing worldwide at an alarming rate. In addition to the increased incidence of cardiovascular and metabolic diseases, obesity is the most potent risk factor for developing chronic kidney disease (CKD). Although systemic events such as hemodynamic factors, metabolic effects, and lipotoxicity were implicated in the pathophysiology of obesity-related glomerulopathy (ORG) and kidney dysfunction, the precise mechanisms underlying the association between obesity and CKD remain unexplored.

METHODS

In this study, we employed spontaneous WNIN/Ob rats to investigate the molecular events that promote ORG. Further, we fed a high-fat diet to mice and analyzed the incidence of ORG. Kidney functional parameters, micro-anatomical manifestations, and podocyte morphology were investigated in both experimental animal models. Gene expression analysis in the rodents was compared with human subjects by data mining using Nephroseq and Kidney Precision Medicine Project database.

RESULTS

WNIN/Ob rats were presented with proteinuria and several glomerular deformities, such as adaptive glomerulosclerosis, decreased expression of podocyte-specific markers, and effacement of podocyte foot process. Similarly, high-fat-fed mice also showed glomerular injury and proteinuria. Both experimental animal models showed increased expression of podocyte-specific transcription factor WT1. The altered expression of putative targets of WT1 such as E-cadherin, podocin (reduced), and α-SMA (increased) suggests elevated expression of WT1 in podocytes elicits mesenchymal phenotype. Curated data from CKD patients revealed increased expression of WT1 in the podocytes and its precursors, parietal epithelial cells.

CONCLUSION

WT1 is crucial during nephron development and has minimal expression in adult podocytes. Our study discovered elevated expression of WT1 in podocytes in obesity settings. Our analysis suggests a novel function for WT1 in the pathogenesis of ORG; however, the precise mechanism of WT1 induction and its involvement in podocyte pathobiology needs further investigation.

Activation of TAS2R4 signaling attenuates podocyte injury induced by high glucose

Bitter taste receptors (TAS2Rs) Tas2r108 gene possesses a high abundance in mouse kidney; however, the biological functions of Tas2r108 encoded receptor TAS2Rs member 4 (TAS2R4) are still unknown. In the present study, we found that mouse TAS2R4 (mTAS2R4) signaling was inactivated in chronic high glucose-stimulated mouse podocyte cell line MPC, evidenced by the decreased protein expressions of mTAS2R4 and phospholipase C β2 (PLCβ2), a key downstream molecule of mTAS2R4 signaling. Nonetheless, agonism of mTAS2R4 by quinine recovered mTAS2R4 and PLCβ2 levels, and increased podocyte cell viability as well as protein expressions of ZO-1 and nephrin, biomarkers of podocyte slit diaphragm, in high glucose-cultured MPC cells. However, blockage of mTAS2R4 signaling with mTAS2R4 blockers γ-aminobutyric acid and abscisic acid, a Gβγ inhibitor Gallein, or a PLCβ2 inhibitor U73122 all abolished the effects of quinine on NLRP3 inflammasome and p-NF-κB p65 as well as the functional podocyte proteins in MPC cells in a high glucose condition. Furthermore, knockdown of mTAS2R4 with lentivirus-carrying Tas2r108 shRNA also ablated the effect of quinine on the key molecules of the above inflammatory signalings and podocyte functions in high glucose-cultured MPC cells. In summary, we demonstrated that activation of TAS2R4 signaling alleviated the podocyte injury caused by chronic high glucose, and inhibition of NF-κB p65 and NLRP3 inflammasome mediated the protective effects of TAS2R4 activation on podocytes. Moreover, activation of TAS2R4 signaling could be an important strategy for prevention and treatment of diabetic kidney disease.

Bioflavonoid combination attenuates diabetes-induced nephropathy in rats via modulation of MMP-9/TIMP-1, TGF-β, and GLUT-4-associated pathways

Background

Diabetic nephropathy represents a significant microvascular complication of diabetes, characterized by extracellular matrix accumulation, loss of cell-cell junctions, microalbuminuria, and diminished creatinine clearance. Despite its prevalence, therapeutic options dedicated to this condition are currently lacking. Natural products like bioflavonoids have garnered attention for their potential therapeutic benefits. The present study aimed to evaluate the efficacy of a bioflavonoid combination, including ginger extract, soy extract, and hesperetin, in a diabetic rat model.

Methods

Diabetes was initiated in the rat pups via intraperitoneal injection of streptozotocin on the fifth postnatal day. After six weeks, rats exhibiting blood sugar levels exceeding 160 mg/dL were allocated into diabetic control and treatment groups, with eight animals each. A subset of rats received citrate buffer as a control. The treatment group received the bioflavonoid combination orally for twenty-four weeks. Various parameters, including glycemic levels, urinary parameters, antioxidant status, mRNA expression via Western blot, gel zymography, and immunohistochemistry, were assessed at the study's conclusion.

Results

The bioflavonoid combination demonstrated significant reductions in hyperglycemia and various urinary parameters compared to controls. Notably, it modulated MMP-9/TIMP-1 expression, upregulated GLUT-4, and downregulated TGF-β. Additionally, the combination enhanced total antioxidant capacity, indicating potential antioxidative benefits.

Conclusions

This study highlights the therapeutic potential of a bioflavonoid combination (ginger extract, soy extract, and hesperetin) in improving renal function in diabetic nephropathy. By modulating key factors such as MMP-9/TIMP-1, TGF-β, and GLUT-4, this combination presents a promising avenue for further exploration in managing diabetic nephropathy. These findings underscore the importance of natural products as potential therapeutic agents in addressing diabetic complications.

Acupuncture improve proteinuria in diabetic kidney disease rats by inhibiting ferroptosis and epithelial-mesenchymal transition

Objective

To explore the mechanism of acupuncture to relieve diabetic proteinuria in Diabetic Kidney Disease (DKD).

Methods

A total of 10 male Sprague-Dawley rats were randomly selected as the negative control group (NC), and a further 30 rats were fed a high-fat diet (HFD) and intraperitoneal streptozotocin (STZ). The DKD model rats in the model group (DKD) and the acupuncture group (DKD + Acu) were randomly assigned. After 4 weeks of intervention, collected urine, peripheral blood, and renal tissues from all rats, and assessed blood urea nitrogen, serum creatinine, triglyceride, 24-h urine protein quantification, and blood glucose, left kidney weight, kidney body ratio index, then observe changes in renal histology in the rats. The renal cortex tissues of three rats from each group were sent for transcriptomic analysis. According to the results of transcriptomic analysis, various kits were used to detect SOD, MDA, GSH, GSH-px, and iron concentration. The expression levels of GPX4 and System Xc-, members of the antioxidative stress pathway, and TfR 1, SLC39A14, FTH 1, and SLC40A1, involved in iron metabolism, in the kidney tissues were measured by western blotting and reverse transcription-quantitative PCR. The expression of mesenchymal phenotype markers and podocyte-specific markers were evaluated by immunofluorescence.

Results

Acupuncture promoted the levels of GSH, GSH-px, and SOD, decreased the level of MDA (P < 0.05), promoted the expression of GPX4 and System Xc- (P < 0.05), decreased the expression of TfR1 and SLC39A14 (P < 0.01), and increased the expression of FTH 1 and SLC40A1 (P < 0.05), inhibited the expression of TGF-β1, desmin, FSP-1, and α-SMA (P < 0.05), promoted the expression of Nephrin, Podocin, and CD2AP (P < 0.05).

Conclusion

Improving the ability of podocytes to prevent oxidative stress and restoring iron ion homeostasis, can improve Ferroptosis and block epithelial-mesenchymal transition, improve podocyte injury, restore filtration function, and reduce proteinuria in DKD rats.

Exosomes derived from mesenchymal stem cells in diabetes and diabetic complications

Diabetes, a group of metabolic disorders, constitutes an important global health problem. Diabetes and its complications place a heavy financial strain on both patients and the global healthcare establishment. The lack of effective treatments contributes to this pessimistic situation and negative outlook. Exosomes released from mesenchymal stromal cells (MSCs) have emerged as the most likely new breakthrough and advancement in treating of diabetes and diabetes-associated complication due to its capacity of intercellular communication, modulating the local microenvironment, and regulating cellular processes. In the present review, we briefly outlined the properties of MSCs-derived exosomes, provided a thorough summary of their biological functions and potential uses in diabetes and its related complications.

Therapeutic role of miR-26a on cardiaorenal injury in mice model of angiotensin-II induced chronic kidney disease through inhibition of LIMS1/ILK pathway

BACKGROUND

Chronic kidney disease (CKD) is associated with common pathophysiological processes, such as inflammation and fibrosis, in both the heart and the kidney. However, the underlying molecular mechanisms that drive these processes are not yet fully understood. Therefore, this study focused on the molecular mechanism of heart and kidney injury in CKD.

METHODS

We generated a microRNA (miR)-26a knockout (KO) mouse model to investigate the role of miR-26a in angiotensin (Ang)-II-induced cardiac and renal injury. We performed Ang-II modeling in wild type (WT) mice and miR-26a KO mice, with six mice in each group. In addition, Ang-II-treated AC16 cells and HK2 cells were used as in vitro models of cardiac and renal injury in the context of CKD. Histological staining, immunohistochemistry, quantitative real-time polymerase chain reaction (PCR), and Western blotting were applied to study the regulation of miR-26a on Ang-II-induced cardiac and renal injury. Immunofluorescence reporter assays were used to detect downstream genes of miR-26a, and immunoprecipitation was employed to identify the interacting protein of LIM and senescent cell antigen-like domain 1 (LIMS1). We also used an adeno-associated virus (AAV) to supplement LIMS1 and explored the specific regulatory mechanism of miR-26a on Ang-II-induced cardiac and renal injury. Dunnett's multiple comparison and t-test were used to analyze the data.

RESULTS

Compared with the control mice, miR-26a expression was significantly downregulated in both the kidney and the heart after Ang-II infusion. Our study identified LIMS1 as a novel target gene of miR-26a in both heart and kidney tissues. Downregulation of miR-26a activated the LIMS1/integrin-linked kinase (ILK) signaling pathway in the heart and kidney, which represents a common molecular mechanism underlying inflammation and fibrosis in heart and kidney tissues during CKD. Furthermore, knockout of miR-26a worsened inflammation and fibrosis in the heart and kidney by inhibiting the LIMS1/ILK signaling pathway; on the contrary, supplementation with exogenous miR-26a reversed all these changes.

CONCLUSIONS

Our findings suggest that miR-26a could be a promising therapeutic target for the treatment of cardiorenal injury in CKD. This is attributed to its ability to regulate the LIMS1/ILK signaling pathway, which represents a common molecular mechanism in both heart and kidney tissues.

Epithelial-mesenchymal plasticity in kidney fibrosis

Epithelial-mesenchymal transition (EMT) is an important biological process contributing to kidney fibrosis and chronic kidney disease. This process is characterized by decreased epithelial phenotypes/markers and increased mesenchymal phenotypes/markers. Tubular epithelial cells (TECs) are commonly susceptible to EMT by various stimuli, for example, transforming growth factor-β (TGF-β), cellular communication network factor 2, angiotensin-II, fibroblast growth factor-2, oncostatin M, matrix metalloproteinase-2, tissue plasminogen activator (t-PA), plasmin, interleukin-1β, and reactive oxygen species. Similarly, glomerular podocytes can undergo EMT via these stimuli and by high glucose condition in diabetic kidney disease. EMT of TECs and podocytes leads to tubulointerstitial fibrosis and glomerulosclerosis, respectively. Signaling pathways involved in EMT-mediated kidney fibrosis are diverse and complex. TGF-β1/Smad and Wnt/β-catenin pathways are the major venues triggering EMT in TECs and podocytes. These two pathways thus serve as the major therapeutic targets against EMT-mediated kidney fibrosis. To date, a number of EMT inhibitors have been identified and characterized. As expected, the majority of these EMT inhibitors affect TGF-β1/Smad and Wnt/β-catenin pathways. In addition to kidney fibrosis, these EMT-targeted antifibrotic inhibitors are expected to be effective for treatment against fibrosis in other organs/tissues.

Dexmedetomidine ameliorates high glucose-induced epithelial-mesenchymal transformation in HK-2 cells through the Cdk5/Drp1/ROS pathway

Epithelial-mesenchymal transformation (EMT) plays an important role in the progression of diabetic nephropathy. Dexmedetomidine (DEX) has shown renoprotective effects against ischemic reperfusion injury; however, whether and how DEX prevents high glucose-induced EMT in renal tubular epithelial cells is incompletely known. Here, we conduct in vitro experiments using HK-2 cells, a human tubular epithelial cell line. Our results demonstrate that high glucose increases the expressions of EMT-related proteins, including Vimentin, Slug, Snail and Twist, while decreasing the expression of E-cadherin and increasing Cdk5 expression in HK-2 cells. Both Cdk5 knockdown and inhibition by roscovitine increase the expressions of E-cadherin while decreasing the expressions of other EMT-related markers. DEX inhibits Cdk5 expression without affecting cell viability and changes the expressions of EMT-related markers, similar to effects of Cdk5 inhibition. Furthermore, Cdk5 is found to interact with Drp1 at the protein level and mediate the phosphorylation of Drp1. In addition, Drp1 inhibition with mdivi-1 could also restrain the high glucose-induced EMT process in HK-2 cells. Immunofluorescence results show that roscovitine, Mdivi-1 and DEX inhibit high glucose-induced intracellular ROS accumulation, while the oxidant H 2O 2 eliminates the protective effect of DEX on the EMT process. These results indicate that DEX mitigates high glucose-induced EMT progression in HK-2 cells via inhibition of the Cdk5/Drp1/ROS pathway.

Metformin inhibits high glucose-induced apoptosis of renal podocyte through regulating miR-34a/SIRT1 axis

BACKGROUND

Previous studies have reported SIRT1 was inversely modulated by miR-34a, However, mechanism of metformin (MFN)'s renal podocyte protection under high glucose (HG) conditions and the connection between miR-34a and SIRT1 expression in diabetic nephropathy (DN) remain unclear.

METHOD

We aimed to further elucidate the role of miR-34a in HG-treated podocytes in DN. A conditionally immortalized human podocyte cell line was cultivated in d-glucose (30 mM).

RESULTS

Microarray and RT-qPCR revealed that miR-34a was downregulated in HG-treated podocytes. Additionally, miR-34a levels increased in MFN-treated HG-induced podocytes. CCK-8 assay, colony formation assay, flow cytometry, and Western blot detection showed that HG treatment reduced cell viability and promoted via HG treatment, and MFN treatment reversed this phenotypic change. MiR-34a upregulation caused restored cell viability and suppressed cell apoptosis in HG-treated podocytes, and miR-34a downregulation led to damaged cell survival and induced apoptosis in MFN-administered and HG-treated podocytes. The dual luciferase reporter assay showed that SIRT1 3'-UTR was a direct miR-34a target. Further studies demonstrated an elevation in SIRT1 levels in HG-exposed podocytes, whereas MFN treatment decreased SIRT1 levels. In addition, miR-34a upregulation led to reduced SIRT1 expression, whereas miR-34a inhibition increased SIRT1 levels in cells. MFN-induced miR-34a suppresses podocyte apoptosis under HG conditions by acting on SIRT1.

CONCLUSION

This study proposes a promising approach to interpret the mechanisms of action of the MFN-miR-34a axis involved in DN.

CTRP4 attenuates apoptosis and epithelial-mesenchymal transition markers in podocytes through an AMPK/autophagy-dependent pathway

Hyperglycemia, characterized by high blood glucose levels resulting from pancreatic beta cell dysfunction or impaired insulin signaling, is a contributing factor in the development of diabetic nephropathy. This study aimed to investigate the effects of C1q/TNF-related protein 4 (CTRP4), known for its anti-obesity and anti-inflammatory properties in various disease models, on podocyte apoptosis and endoplasmic reticulum (ER) stress in the presence of elevated glucose levels. The expression levels of various proteins in podocytes and adipocytes were evaluated by Western blotting. Autophagosomes in podocytes were stained by MDC. Chromatin condensation in podocytes was examined by Hoechst staining. The research revealed increased expression of CTRP4 in 3T3-L1 adipocytes and CIHP-1 podocytes exposed to high glucose (HG) conditions. Treatment with CTRP4 effectively mitigated HG-induced apoptosis and ER stress and normalized epithelial-to-mesenchymal transition (EMT) markers in CIHP-1 cells. Furthermore, elevated levels of AMPK phosphorylation and autophagy were observed in CIHP-1 cells treated with CTRP4. Silencing of AMPK or the use of 3-methyl adenine (3 MA) reduced the impacts of CTRP4 on apoptosis, EMT markers and ER stress in CIHP-1 cells. In conclusion, these findings suggest that CTRP4 alleviates ER stress in podocytes under hyperglycemic conditions, leading to the suppression of apoptosis and the restoration of EMT through AMPK/autophagy-mediated signaling. These insights provide valuable information for the development of therapeutic strategies for diabetic nephropathy.

Curcumin ameliorates focal segmental glomerulosclerosis by inhibiting apoptosis and oxidative stress in podocytes

Focal segmental glomerulosclerosis (FSGS), a podocyte disease, is the leading cause of end-stage renal disease (ESRD). Nevertheless, the current effective treatment for FSGS is deficient. Curcumin (CUR) is a principal curcuminoid of turmeric, which is a member of the ginger family. Previous studies have shown that CUR has renoprotective effects. However, the mechanism of CUR in anti-FSGS is not clear. This study aimed to explore the mechanism of CUR against FSGS through a combination of network pharmacological methods and verification of experiments. The analysis identified 98 shared targets of CUR against FSGS, and these 98 targets formed a network of protein-protein interactions (PPI). Of these 98 targets, AKT1, TNF, IL-6, VEGFA, STAT3, MAPK3, HIF1A, CASP3, IL1B, and JUN were identified as the hub targets. Molecular docking suggested that the best binding to CUR is MAPK3 and AKT1. Apoptotic process and cell proliferation were identified as the main biological processes of CUR against FSGS by gene ontology (GO) analysis. The most enriched signaling pathway in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was the PI3K-AKT signaling pathway. Western blots and flow cytometry showed that CUR could inhibit adriamycin (ADR) induced apoptosis, oxidative stress damage, and attenuate podocyte epithelial-mesenchymal transition (EMT) by repressing the AKT signaling pathway. Collectively, our study demonstrates that CUR can attenuate apoptosis, oxidative stress damage, and EMT in FSGS in vitro. These results supply a compelling basis for future studies of CUR for the clinical treatment of FSGS.

Kunxian capsule alleviates podocyte injury and proteinuria by inactivating β-catenin in db/db mice

Background

Diabetic kidney disease (DKD) remains the primary cause of end-stage renal disease (ESRD) globally, but treatment options are limited. Kunxian capsule (KXC) has been utilized for the treatment of autoimmune diseases and IgA nephropathy in China. However, its effect on DKD remains poorly investigated. Therefore, this study aimed to explore the protective effect of KXC in db/db mice and elucidate its underlying mechanism.

Methods

The renoprotective effects of KXC were assessed in a DKD mouse model using male BKS db/db diabetic mice. After 8 weeks of treatment, the urinary albumin-to-creatinine ratio (UACR), blood biochemical parameters, renal histopathological manifestation, and podocyte ultrastructural changes were evaluated. Additionally, the expression of podocyte epithelial-to-mesenchymal transition (EMT) markers [WT1, ZO-1, and collogen I (Col1a1)] was quantitatively analyzed. Furthermore, we explored the role of KXC in the β-catenin signaling pathway to elucidate the underlying mechanism of KXC's renoprotective effect.

Results

KXC treatment effectively reduced albuminuria and attenuated renal structural abnormalities in db/db mice. Additionally, KXC restored the protein and mRNA expression of WT1 and ZO-1 while suppressing the expression of Col1a1 in db/db mice, indicating its ability to alleviate podocyte EMT. Mechanistically, KXC exerted a significant suppressive effect on the activation of β-catenin signaling in diabetic kidneys.

Conclusion

KXC has the potential to protect podocytes during DKD by alleviating podocyte EMT through inactivating β-catenin signaling.

Epigenetic modification in diabetic kidney disease

Diabetic kidney disease (DKD) is a common microangiopathy in diabetic patients and the main cause of death in diabetic patients. The main manifestations of DKD are proteinuria and decreased renal filtration capacity. The glomerular filtration rate and urinary albumin level are two of the most important hallmarks of the progression of DKD. The classical treatment of DKD is controlling blood glucose and blood pressure. However, the commonly used clinical therapeutic strategies and the existing biomarkers only partially slow the progression of DKD and roughly predict disease progression. Therefore, novel therapeutic methods, targets and biomarkers are urgently needed to meet clinical requirements. In recent years, increasing attention has been given to the role of epigenetic modification in the pathogenesis of DKD. Epigenetic variation mainly includes DNA methylation, histone modification and changes in the noncoding RNA expression profile, which are deeply involved in DKD-related inflammation, oxidative stress, hemodynamics, and the activation of abnormal signaling pathways. Since DKD is reversible at certain disease stages, it is valuable to identify abnormal epigenetic modifications as early diagnosis and treatment targets to prevent the progression of end-stage renal disease (ESRD). Because the current understanding of the epigenetic mechanism of DKD is not comprehensive, the purpose of this review is to summarize the role of epigenetic modification in the occurrence and development of DKD and evaluate the value of epigenetic therapies in DKD.

Laminaria japonica polysaccharide attenuates podocyte epithelial-mesenchymal transformation via TGF-β1-mediated Smad3 and p38MAPK pathways

In the present work, we explored the interventional effect and potential mechanism of a purified Laminaria japonica polysaccharide (LJP61A) on podocyte epithelial-mesenchymal transition (EMT) in TGF-β1-induced podocytes and adriamycin-treated mice. Results showed that compared to the model groups, LJP61A significantly up-regulated the levels of epithelial markers (Nephrin, WT-1, podocin) and down-regulated the levels of mesenchymal markers (α-SMA, FN1) in vitro and in vivo, thus preventing EMT-like morphological changes of podocytes, proteinuria and kidney injury. Smad3 and p38MAPK are two central pathways mediating podocyte EMT activated by TGF-β1. We found that LJP61A suppressed TGF-β1-induced activation of Smad3, Smad4 and p38MAPK in vitro and in vivo. Moreover, the inhibitory actions of LJP61A on podocyte EMT were synergistically strengthened by Smad3 inhibitor SIS3 and p38MAPK inhibitor SB203580. Taken together, these findings revealed that LJP61A could prevent podocyte EMT, which might be related to the inhibition of TGF-β1-mediated Smad3 and p38MAPK pathways.

Stem cell-derived exosomal MicroRNAs: Potential therapies in diabetic kidney disease

The diabetic kidney disease (DKD) is chronic kidney disease caused by diabetes and one of the most common comorbidities. It is often more difficult to treat end-stage renal disease once it develops because of its complex metabolic disorders, so early prevention and treatment are important. However, currently available DKD therapies are not ideal, and novel therapeutic strategies are urgently needed. The potential of stem cell therapies partly depends on their ability to secrete exosomes. More and more studies have shown that stem cell-derived exosomes take part in the DKD pathophysiological process, which may offer an effective therapy for DKD treatment. Herein, we mainly review potential therapies of stem cell-derived exosomes mainly stem cell-derived exosomal microRNAs in DKD, including their protective effects on mesangial cells, podocytes and renal tubular epithelial cells. Using this secretome as possible therapeutic drugs without potential carcinogenicity should be the focus of further research.

Friend or foe? The dual role of triptolide in the liver, kidney, and heart

Triptolide, a controversial natural compound due to its significant pharmacological activities and multiorgan toxicity, has gained much attention since it was isolated from the traditional Chinese herb Tripterygium wilfordii Hook F. However, in addition to its severe toxicity, triptolide also presents powerful therapeutic potency in the same organs, such as the liver, kidney, and heart, which corresponds to the Chinese medicine theory of You Gu Wu Yun (anti-fire with fire) and deeply interested us. To determine the possible mechanisms involved in the dual role of triptolide, we reviewed related articles about the application of triptolide in both physiological and pathological conditions. Inflammation and oxidative stress are the two main ways triptolide exerts different roles, and the cross-talk between NF-κB and Nrf2 may be one of the mechanisms responsible for the dual role of triptolide and may represent the scientific connotation of You Gu Wu Yun. For the first time, we present a review of the dual role of triptolide in the same organ and propose the possible scientific connotation of the Chinese medicine theory of You Gu Wu Yun, hoping to promote the safe and efficient use of triptolide and other controversial medicines.

Diabetic nephropathy: Focusing on pathological signals, clinical treatment, and dietary regulation

Diabetic nephropathy (DN) is one of the most severe complications of diabetes. However, due to its complex pathological mechanisms, no effective therapeutic methods (other than ACEIs and ARBs) have been applied, which have been used for many years in clinical practice. Recent studies have shown that emerging therapeutics, including novel target-based pharmacotherapy, cell therapies, and dietary regulation, are leading to new hopes for DN management. This review aims to shed new light on the treatment of DN by describing the important pathological mechanisms of DN and by analysing recent advances in clinical treatment, including drug therapy, cell therapy, and dietary regulation. In pathological mechanisms, RAAS activation, AGE accumulation, and EMT are involved in inflammation, cellular stress, apoptosis, pyroptosis, and autophagy. In pharmacotherapy, several new therapeutics, including SGLT2 inhibitors, GLP-1 agonists, and MRAs, are receiving public attention. In addition, stem cell therapies and dietary regulation are also being emphasized. Herein, we highlight the importance of combining therapy and dietary regulation in the treatment of DN and anticipate more basic research or clinical trials to verify novel strategies.

Growth hormone induces transforming growth factor-β1 in podocytes: Implications in podocytopathy and proteinuria

Pituitary growth hormone (GH) is essential for growth, metabolism, and renal function. Overactive GH signaling is associated with impaired kidney function. Glomerular podocytes, a key kidney cell type, play an indispensable role in the renal filtration and express GH receptors (GHR), suggesting the direct action of GH on these cells. However, the precise mechanism and the downstream signaling events by which GH leads to diabetic nephropathy remain to be elucidated. Here we performed proteome analysis of the condition media from human podocytes and confirmed that GH-induces TGF-β1. Inhibition of GH/GHR stimulated-JAK2 signaling abrogates GH-induced TGF-β1 secretion. Mice administered with GH showed glomerular manifestations concomitant with proteinuria. Pharmacological inhibition of TGF-βR1 in mice prevented GH-induced TGF-β dependent SMAD signaling and proteinuria. Conditional deletion of GHR in podocytes protected mice from streptozotocin-induced diabetic nephropathy. GH and TGF-β1 signaling components expression was elevated in the kidneys of human diabetic nephropathy patients. Our study identifies that GH induces TGF-β1 in podocytes, contributing to diabetic nephropathy.

QiHuangYiShen Granules Modulate the Expression of LncRNA MALAT1 and Attenuate Epithelial-Mesenchymal Transition in Kidney of Diabetic Nephropathy Rats

Background

QiHuangYiShen granules (QHYS), a traditional Chinese herbal medicine formula, have been used in clinical practice for treating diabetic kidney disease for several years by our team. The efficacy of reducing proteinuria and delaying the decline of renal function of QHYS has been proved by our previous studies. However, the exact mechanism by which QHYS exerts its renoprotection remains largely unknown. Emerging evidence suggests that lncRNA MALAT1 is abnormally expressed in diabetic nephropathy (DN) and can attenuate renal fibrosis by modulating podocyte epithelial-mesenchymal transition (EMT).

Objective

In the present study, we aimed to explore whether QHYS could modulate lncRNA MALAT1 expression and attenuate the podocyte EMT as well as the potential mechanism related to the Wnt/β-catenin signal pathway.

Methods

SD rats were fed with the high-fat-high-sucrose diet for 8 weeks and thereafter administered with 30 mg/kg streptozotocin intraperitoneally to replicate the DN model. Quality control of QHYS was performed using high-performance liquid chromatography. QHYS were orally administered at 1.25, 2.5, and 5 g/kg doses, respectively, to the DN model rats for 12 weeks. Body weight, glycated haemoglobin, blood urea nitrogen, serum creatinine, 24-h proteinuria, and kidney index were measured. The morphologic pathology of the kidney was evaluated by Hematoxylin-eosin and Masson's trichrome staining. The expression level of lncRNA MALAT1 was determined by quantitative real-time polymerase chain reaction. In addition, the expression levels of podocyte EMT protein markers and Wnt/β-catenin pathway proteins in renal tissues were evaluated by Western blotting and immunohistochemistry.

Results

The results showed that QHYS significantly reduced 24-h proteinuria, blood urea nitrogen, kidney index, and ameliorated glomerular hypertrophy and collagen fiber deposition in the kidney of DN rats. Importantly, QHYS significantly downregulated the expression level of lncRNA MALAT1, upregulated the expression of nephrin, the podocyte marker protein, downregulated the expression of desmin and FSP-1, and mesenchymal cell markers. Furthermore, QHYS significantly downregulated the expression levels of Wnt1, β-catenin, and active β-catenin.

Conclusion

Conclusively, our study revealed that QHYS significantly reduced proteinuria, alleviated renal fibrosis, and attenuated the podocyte EMT in DN rats, which may be associated with the downregulation of lncRNA MALAT1 expression and inhibition of the Wnt/β-catenin pathway.

Endothelial-to-mesenchymal transition: An underappreciated mediator of diabetic complications

Diabetes and its complications represent a great burden on the global healthcare system. Diabetic complications are fundamentally diseases of the vasculature, with endothelial cells being the centerpiece of early hyperglycemia-induced changes. Endothelial-to-mesenchymal transition is a tightly regulated process that results in endothelial cells losing endothelial characteristics and developing mesenchymal traits. Although endothelial-to-mesenchymal transition has been found to occur within most of the major complications of diabetes, it has not been a major focus of study or a common target in the treatment or prevention of diabetic complications. In this review we summarize the importance of endothelial-to-mesenchymal transition in each major diabetic complication, examine specific mechanisms at play, and highlight potential mechanisms to prevent endothelial-to-mesenchymal transition in each of the major chronic complications of diabetes.

A natural products solution to diabetic nephropathy therapy

Diabetic nephropathy is one of the most common complications in diabetes. It has been shown to be the leading cause of end-stage renal disease. However, due to their complex pathological mechanisms, effective therapeutic drugs other than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which have been used for 20 years, have not been developed so far. Recent studies have shown that diabetic nephropathy is characterized by multiple signalling pathways and multiple targets, including inflammation, apoptosis, pyroptosis, autophagy, oxidative stress, endoplasmic reticulum stress and their interactions. It definitely exacerbates the difficulty of therapy, but at the same time it also brings out the chance for natural products treatment. In the most recent two decades, a large number of natural products have displayed their potential in preclinical studies and a few compounds are under invetigation in clinical trials. Hence, many compounds targeting these singals have been emerged as a comprehensive blueprint for treating strategy of diabetic nephropathy. This review focuses on the cellular and molecular mechanisms of natural prouducts that alleviate this condition, including preclinical studies and clinical trials, which will provide new insights into the treatment of diabetic nephropathy and suggest novel ideas for new drug development.

Store-operated Ca2+ channel signaling: Novel mechanism for podocyte injury in kidney disease

Studies over the last decade have markedly broadened our understanding of store-operated Ca2+ channels (SOCs) and their roles in kidney diseases and podocyte dysfunction. Podocytes are terminally differentiated glomerular visceral epithelial cells which are tightly attached to the glomerular capillary basement membrane. Podocytes and their unique foot processes (pedicels) constitute the outer layer of the glomerular filtration membrane and the final barrier preventing filtration of albumin and other plasma proteins. Diabetic nephropathy and other renal diseases are associated with podocyte injury and proteinuria. Recent evidence demonstrates a pivotal role of store-operated Ca2+ entry (SOCE) in maintaining structural and functional integrity of podocytes. This article reviews the current knowledge of SOCE and its contributions to podocyte physiology. Recent studies of the contributions of SOC dysfunction to podocyte injury in both cell culture and animal models are discussed, including work in our laboratory. Several downstream signaling pathways mediating SOC function in podocytes also are examined. Understanding the pivotal roles of SOC in podocyte health and disease is essential, as SOCE-activated signaling pathways are potential treatment targets for podocyte injury-related kidney diseases.

Histone modification in podocyte injury of diabetic nephropathy

Diabetic nephropathy (DN), an important complication of diabetic microvascular disease, is one of the leading causes of end-stage renal disease (ESRD), which brings heavy burdens to the whole society. Podocytes are terminally differentiated glomerular cells, which act as a pivotal component of glomerular filtration barrier. When podocytes are injured, glomerular filtration barrier is damaged, and proteinuria would occur. Dysfunction of podocytes contributes to DN. And degrees of podocyte injury influence prognosis of DN. Growing evidences have shown that epigenetics does a lot in the evolvement of podocyte injury. Epigenetics includes DNA methylation, histone modification, and non-coding RNA. Among them, histone modification plays an indelible role. Histone modification includes histone methylation, histone acetylation, and other modifications such as histone phosphorylation, histone ubiquitination, histone ADP-ribosylation, histone crotonylation, and histone β-hydroxybutyrylation. It can affect chromatin structure and regulate gene transcription to exert its function. This review is to summarize documents about pathogenesis of podocyte injury, most importantly, histone modification of podocyte injury in DN recently to provide new ideas for further molecular research, diagnosis, and treatment.

Traditional Chinese Medicine in Treating Primary Podocytosis: From Fundamental Science to Clinical Research

Podocytes form a key component of the glomerular filtration barrier. Damage to podocytes is referred to as “podocyte disease.” There are many causes of podocyte injury, including primary injury, secondary injury, and gene mutations. Primary podocytosis mostly manifests as nephrotic syndrome. At present, first-line treatment is based on glucocorticoid administration combined with immunosuppressive therapy, but some patients still progress to end-stage renal disease. In Asia, especially in China, traditional Chinese medicine (TCM) still plays an important role in the treatment of kidney diseases. This study summarizes the potential mechanism of TCM and its active components in protecting podocytes, such as repairing podocyte injury, inhibiting podocyte proliferation, reducing podocyte apoptosis and excretion, maintaining podocyte skeleton structure, and upregulating podocyte-related protein expression. At the same time, the clinical efficacy of TCM in the treatment of primary podocytosis (including idiopathic membranous nephropathy, minimal change disease, and focal segmental glomerulosclerosis) is summarized to support the development of new treatment strategies for primary podocytosis.

An overview of the efficacy and signaling pathways activated by stem cell-derived extracellular vesicles in diabetic kidney disease

Diabetic kidney disease (DKD) is one of complications of diabetes mellitus with severe microvascular lesion and the most common cause of end-stage chronic kidney disease (ESRD). Controlling serum glucose remains the primary approach to preventing and slowing the progression of DKD. Despite considerable efforts to control diabetes, people with diabetes develop not only DKD but also ESRD. The pathogenesis of DKD is very complex, and current studies indicate that mesenchymal stromal cells (MSCs) regulate complex disease processes by promoting pro-regenerative mechanisms and inhibiting multiple pathogenic pathways. Extracellular vesicles (EVs) are products of MSCs. Current data indicate that MSC-EVs-based interventions not only protect renal cells, including renal tubular epithelial cells, podocytes and mesangial cells, but also improve renal function and reduce damage in diabetic animals. As an increasing number of clinical studies have confirmed, MSC-EVs may be an effective way to treat DKD. This review explores the potential efficacy and signaling pathways of MSC-EVs in the treatment of DKD.

Microtubule associated protein 4 phosphorylation-induced epithelial-to-mesenchymal transition of podocyte leads to proteinuria in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) involves various structural and functional changes because of chronic glycemic assault and kidney failure. Proteinuria is an early clinical manifestation of DN, but the associated pathogenesis remains elusive. This study aimed to investigate the role of microtubule associated protein 4 (MAP4) phosphorylation (p-MAP4) in proteinuria in DN and its possible mechanisms.

METHODS

In this study, the urine samples of diabetic patients and kidney tissues of streptozotocin (STZ)-induced diabetic mice were obtained to detect changes of p-MAP4. A murine model of hyperphosphorylated MAP4 was established to examine the effect of MAP4 phosphorylation in DN. Podocyte was applied to explore changes of kidney phenotypes and potential mechanisms with multiple methods.

RESULTS

Our results demonstrated elevated content of p-MAP4 in diabetic patients' urine samples, and increased kidney p-MAP4 in streptozocin (STZ)-induced diabetic mice. Moreover, p-MAP4 triggered proteinuria with aging in mice, and induced epithelial-to-mesenchymal transition (EMT) and apoptosis in podocytes. Additionally, p-MAP4 mice were much more susceptible to STZ treatment and showed robust DN pathology as compared to wild-type mice. In vitro study revealed high glucose (HG) triggered elevation of p-MAP4, rearrangement of microtubules and F-actin filaments with enhanced cell permeability, accompanied with dedifferentiation and apoptosis of podocytes. These effects were significantly reinforced by MAP4 hyperphosphorylation, and were rectified by MAP4 dephosphorylation. Notably, pretreatment of p38/MAPK inhibitor SB203580 reinstated all HG-induced pathological alterations.

CONCLUSIONS

The findings indicated a novel role for p-MAP4 in causing proteinuria in DN. Our results indicated the therapeutic potential of MAP4 in protecting against proteinuria and related diseases. Video Abstract.

CXCL16/ERK1/2 pathway regulates human podocytes growth, migration, apoptosis and epithelial mesenchymal transition

Primary nephrotic syndrome (PNS) is the commonest glomerular disease affecting children. Previous studies have confirmed that CXC motif chemokine ligand 16 (CXCL16) is involved in the pathogenesis of PNS. However, the exact mechanisms underlying the pathogenesis of PNS remain to be elucidated. Thus, the present study aimed to elucidate the role of CXCL16 in PNS. It was found that the expression of CXCL16 and extracellular signal‑regulated kinases 1 and 2 (ERK1/2) were significantly increased in clinical PNS renal tissues using reverse transcription‑quantitative PCR, western blot analysis and immunohistochemistry. Lentivirus overexpression or short hairpin RNA vector was used to induce the overexpression or knockdown of CXCL16 in podocytes, respectively. Overexpression of CXCL16 in podocytes could decrease the cell proliferation and increase the migration and apoptosis, whereas CXCL16 knockdown increased cell proliferation and decreased cell migration and apoptosis. Results of the present study further demonstrated that ERK2 protein expression was regulated by CXCL16. The knockdown of ERK2 expression reversed the effects of CXCL16 on the proliferation, apoptosis, migration and epithelial mesenchymal transition (EMT) of podocytes. Collectively, the findings of the present study highlighted that the CXCL16/ERK1/2 pathway regulates the growth, migration, apoptosis and EMT of human podocytes.

Administration of mesenchymal stem cells in diabetic kidney disease: mechanisms, signaling pathways, and preclinical evidence

Diabetic kidney disease (DKD) is a serious microvascular complication of diabetes. Currently, the prevalence and mortality of DKD are increasing annually. However, with no effective drugs to prevent its occurrence and development, the primary therapeutic option is to control blood sugar and blood pressure. Therefore, new and effective drugs/methods are imperative to prevent the development of DKD in patients with diabetes. Mesenchymal stem cells (MSCs) with multi-differentiation potential and paracrine function have received extensive attention as a new treatment option for DKD. However, their role and mechanism in the treatment of DKD remain unclear, and clinical applications are still being explored. Given this, we here provide an unbiased review of recent advances in MSCs for the treatment of DKD in the last decade from the perspectives of the pathogenesis of DKD, biological characteristics of MSCs, and different molecular and signaling pathways. Furthermore, we summarize information on combination therapy strategies using MSCs. Finally, we discuss the challenges and prospects for clinical application.

Dexmedetomidine Protects Against Kidney Fibrosis in Diabetic Mice by Targeting miR-101-3p-Mediated EndMT

Objective: Our main purpose is to explore the effect and mechanism of Dexmedetomidine (DEX)  in diabetic nephropathy fibrosis.

Methods: Diabetic model was established by intraperitoneal injection of streptozotocin (STZ) treated CD-1 mice and high glucose cultured human dermal microvascular endothelial cells (HMVECs). Immunofluorescence was used to detect renal endothelial-mesenchymal transition (EndMT); Hematoxylin and Eosin (HE) staining and Masson’s Trichrome Staining (MTS) was used to analyze renal fibrosis; CCK-8 was used to evaluate cell viability; Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to assess the expression of miR-101-3p; Western blots were utilized to judge the protein expression levels of EndMT, extracellular matrix and TGF-β1/Smad3 signal pathway.

Results: In this study, we first found that the protective effect of DEX on DN was related to EndMT. DEX alleviated kidney fibrosis by inhibiting EndMT in diabetic CD-1 mice. DEX could also inhibit high glucose-induced HMVECs EndMT. Then, we confirmed that miR-101-3p was the regulatory target of DEX. The expression of miR-101-3p was decreased in diabetic CD-1 mice and high glucose-induced HMVECs. After DEX treatment, the miR-101-3p increased, and the inhibition of miR-101-3p could counteract the protective effect of DEX and aggravate the EndMT. Finally, we found that the TGF- β1/Smad3 signal pathway was involved in the protective effect of DEX on DN. DEX inhibited the activation of TGF-β1/Smad3 signal pathway. On the contrary, inhibiting miR-101-3p promoted the expression of TGF-β1/Smad3.

Conclusion: DEX protects kidney fibrosis in diabetic mice by targeting miR-101-3p-mediated EndMT.

Inhibition of PI3K/AKT/mTOR Signalling Pathway Activates Autophagy and Suppresses Peritoneal Fibrosis in the Process of Peritoneal Dialysis

Peritoneal dialysis (PD) is an important part of replacement therapy for kidney failure. However, long-term PD treatment can cause peritoneal fibrosis. Autophagy may be involved in the pathological mechanism of peritoneal fibrosis (PF). Although autophagy is currently known to be involved in course of PF, its specific effects still lack in-depth research. In this experiment, a high-glucose (HG)-induced peritoneal fibrosis rat model was successfully established via intraperitoneal injection of HG peritoneal dialysate, and the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and the mechanistic target of rapamycin (mTOR) inhibitor rapamycin were used to treat peritoneal fibrosis rats. In addition, in vitro studies of high glucose-induced peritoneal fibrosis were performed using rat peritoneal mesothelial cells (PMCs). In vivo and in vitro experiments showed that LY294002 and rapamycin effectively inhibited the process of PF induced by high glucose. In addition, LY294002 and rapamycin were found to alleviate fibrosis by eliminating intracellular reactive oxygen species (ROS) levels, promoting the expression of the epithelial mesenchymal transdifferentiation proteins zonula occludens-1 (ZO-1) and E-cadherin, and inhibiting the expression of p-PI3K, PI3K, p-mTOR, mTOR, the fibroblast-specific proteins ferroptosis suppressor protein 1 (FSP1), and alpha-smooth muscle actin (α-SMA). Moreover, LY294002 and rapamycin promoted expression of autophagy-related proteins LC3-II/I, p62, and beclin-1. The current data indicated that inhibition of PI3K/AKT/mTOR signalling pathway activated autophagy and suppressed PF in the process of PD. Therefore, intervention in this signalling pathway may become a research goal for the prevention and treatment of PF, which has important clinical significance.

Recent Advances in Traditional Chinese Medicine for Treatment of Podocyte Injury

Podocyte is also called glomerular epithelial cell, which has been considered as the final gatekeeper of glomerular filtration barrier (GFB). As a major contributor to proteinuria, podocyte injury underlies a variety of glomerular diseases and becomes the challenge to patients and their families in general. At present, the therapeutic methods of podocyte injury mainly include angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, steroid and immunosuppressive medications. Nevertheless, the higher cost and side effects seriously disturb patients with podocyte injury. Promisingly, traditional Chinese medicine (TCM) has received an increasing amount of attention from different countries in the treatment of podocyte injury by invigorating spleen and kidney, clearing heat and eliminating dampness, as well enriching qi and activating blood. Therefore, we searched articles published in peer-reviewed English-language journals through Google Scholar, PubMed, Web of Science, and Science Direct. The protective effects of active ingredients, herbs, compound prescriptions, acupuncture and moxibustion for treatment of podocyte injury were further summarized and analyzed. Meanwhile, we discussed feasible directions for future development, and analyzed existing deficiencies and shortcomings of TCM in the treatment of podocyte injury. In conclusion, this paper shows that TCM treatments can serve as promising auxiliary therapeutic methods for the treatment of podocyte injury.

A Neutralizing IL-11 Antibody Improves Renal Function and Increases Lifespan in a Mouse Model of Alport Syndrome

BACKGROUND

Alport syndrome is a genetic disorder characterized by a defective glomerular basement membrane, tubulointerstitial fibrosis, inflammation, and progressive renal failure. IL-11 was recently implicated in fibrotic kidney disease but its role in Alport syndrome is unknown Methods: We determined IL-11 expression by molecular analyses and in an Alport syndrome mouse model. We assessed the effects of a neutralizing IL-11 antibody (X203) versus an IgG control in Col4a3-/- mice (lacking the gene encoding a type IV collagen component) on renal tubule damage, function, fibrosis, and inflammation. Effects on lifespan of X203, the IgG control, an angiotensin-converting enzyme inhibitor (ramipril), or ramipril+X203 were also studied.

RESULTS

In Col4a3 mice, as kidney failure advanced, renal IL-11 levels increased and IL-11 expression localized to tubular epithelial cells. The IL-11 receptor IL11RA is expressed in tubular epithelial cells and podocytes and is upregulated in tubular epithelial cells of Col4a3 mice. Administration of X203 reduced albuminuria, improved renal function, and preserved podocyte numbers and levels of key podocyte proteins that are reduced in Col4a3 mice; these effects were accompanied by reduced fibrosis and inflammation, attenuation of epithelial-tomesenchymal transition, and increased expression of regenerative markers. X203 attenuated pathogenic ERK and STAT3 pathways, which were activated in Col4a3 mice. Median lifespan of Col4a3 mice was prolonged 22% by ramapril, 44% with X203, and 99% with amipril+X203.

CONCLUSIONS

In an Alport syndrome mouse model, renal IL-11 is upregulated, and neutralization of IL-11 reduces epithelial-to-mesenchymal transition, fibrosis, and inflammation, while improving renal function. Anti-IL-11 combined with ACE inhibition synergistically extends lifespan. This suggests that a therapeutic approach targeting IL-11 holds promise for progressive kidney disease in Alport syndrome.

Stem cell-derived and circulating exosomal microRNAs as new potential tools for diabetic nephropathy management

BACKGROUND

Despite major advances in the treatment of diabetic nephropathy (DN) in recent years, it remains the most common cause of end-stage renal disease. An early diagnosis and therapy may slow down the DN progression. Numerous potential biomarkers are currently being researched. Circulating levels of the kidney-released exosomes and biological molecules, which reflect the DN pathology including glomerular and tubular dysfunction as well as mesangial expansion and fibrosis, have shown the potential for predicting the occurrence and progression of DN. Moreover, many experimental therapies are currently being investigated, including stem cell therapy and medications targeting inflammatory, oxidant, or pro-fibrotic pathways activated during the DN progression. The therapeutic potential of stem cells is partly depending on their secretory capacity, particularly exosomal microRNAs (Exo-miRs). In recent years, a growing line of research has shown the participation of Exo-miRs in the pathophysiological processes of DN, which may provide effective therapeutic and biomarker tools for DN treatment.

METHODS

A systematic literature search was performed in MEDLINE, Scopus, and Google Scholar to collect published findings regarding therapeutic stem cell-derived Exo-miRs for DN treatment as well as circulating Exo-miRs as potential DN-associated biomarkers.

FINDINGS

Glomerular mesangial cells and podocytes are the most important culprits in the pathogenesis of DN and, thus, can be considered valuable therapeutic targets. Preclinical investigations have shown that stem cell-derived exosomes can exert beneficial effects in DN by transferring renoprotective miRs to the injured mesangial cells and podocytes. Of note, renoprotective Exo-miR-125a secreted by adipose-derived mesenchymal stem cells can improve the injured mesangial cells, while renoprotective Exo-miRs secreted by adipose-derived stem cells (Exo-miR-486 and Exo-miR-215-5p), human urine-derived stem cells (Exo-miR-16-5p), and bone marrow-derived mesenchymal stem cells (Exo-miR-let-7a) can improve the injured podocytes. On the other hand, clinical investigations have indicated that circulating Exo-miRs isolated from urine or serum hold great potential as promising biomarkers in DN.

Jiangtang Tongmai Prescription Reduced Diabetic Lung Injury Through SnoN and TGF-β1/Smads Signaling Pathway

By establishing a rat diabetes model in rats with intervening treatment by Jiangtang Tongmai Prescription (JTTMP), this study explored the restorative pairing effect of JTTMP on diabetic lung injury. The model of type II diabetes model was used to establish the rat diabetes model, using a high-fat diet and streptozotocin (STZ) induction. Different doses of JTTMP and metformin were administered as a therapeutic to intervene, and blood was collected to assess the blood glucose level of each group of rats. HE (Hematoxylin and eosin (H&E) staining was performed to detect the morphological changes in rat lung tissue and enzyme-linked immunoassay ELISA was used to detect and quantify the expression of interleukin (IL)-6, TNF tumor necrosis factor-ɑa, and IL-1β in serum and the lung tissue of each group of rats. The level expression of TGF-β1 [transforming growth factor (TGF)-β1), SnoN (transcriptional co-repressor Ski-N terminal (SnoN)], Smad2, Smad3, Smad7, and other signaling pathway proteins were assessed by Western blot. In comparison with the normal control (NC) group, rats in the diabetes model (DM) group lost weight and showed significantly increased blood sugar levels. The levels of TGF-β1 and Smad2/3 were increased in the DM group but Smad7 decreased. After 8 weeks of JTTMP intervention, the level of TGF-β1 and Smad2/3 decreased but Smad7 increased, blood sugar decreased significantly and the expression of inflammatory factors in lung tissue decreased. Therefore, JTTMP may activate SnoN and the downstream TGF-β1/Smads signaling pathway to repair diabetic lung injury, which suggests its application has potential for future clinical treatment of diabetes with lung injury.

Astragalus Polysaccharide Reduces Blood Pressure, Renal Damage, and Dysfunction Through the TGF-β1-ILK Pathway

Background:Astragalus polysaccharide extract (APS) has been shown to exhibit antioxidant and anti-inflammatory potential in the treatment of several diseases. However, whether APS could protect against renal damage in hypertensive mice is unknown.

Methods: Hematoxylin and eosin staining, immunohistochemistry, real-time polymerase chain reaction, and Western blotting were used to investigate the effect of APS on the renal damage in deoxycorticosterone acetate- (DOCA) salt- and angiotensin II- (Ang II-) induced hypertensive mice and to elucidate the underlying mechanisms.

Results: Our data demonstrated that APS significantly reduced blood pressure in DOCA-salt- and Ang II-treated mice. Furthermore, APS reduced the inflammatory response and renal fibrosis, thereby improving renal function. Furthermore, the levels of serum creatinine, urea nitrogen, and uric acid increased in DOCA-salt-treated mice, alleviated by APS administration. At the molecular level, DOCA-salt and Ang II increased the mRNA levels of IL-1β, IL-6, α-SMA, collagen I, and collagen III, while APS significantly inhibited these effects. APS inhibited the TGF-β1/ILK signaling pathway, which was activated in hypertensive mice due to the administration of DOCA-salt.

Conclusion: Our results suggest that APS plays a beneficial role in improving renal dysfunction in hypertensive mice.

EP300/CBP is crucial for cAMP-PKA pathway to alleviate podocyte dedifferentiation via targeting Notch3 signaling

Podocyte injury is the hallmark of proteinuric glomerular diseases. Notch3 is neo-activated simultaneously in damaged podocytes and podocyte's progenitor cells of FSGS, indicating a unique role of Notch3. We previously showed that activation of cAMP-PKA pathway alleviated podocyte injury possibly via inhibiting Notch3 expression. However, the mechanisms are unknown. In the present study, Notch3 signaling was significantly activated in ADR-induced podocytes in vitro and in PAN nephrosis rats and patients with idiopathic FSGS in vivo, concomitantly with podocyte dedifferentiation. In cultured podocytes, pCPT-cAMP, a selective cAMP-PKA activator, dramatically blocked ADR-induced activation of Notch3 signaling as well as inhibition of cAMP-PKA pathway, thus alleviating the decreased cell viability and podocyte dedifferentiation. Bioinformatics analysis revealed EP300/CBP, a transcriptional co-activator, as a central hub for the crosstalk between these two signaling pathways. Additionally, CREB/KLF15 in cAMP-PKA pathway competed with RBP-J the major transcriptional factor of Notch3 signaling for binding to EP300/CBP. EP300/CBP siRNA significantly inhibited these two signaling transduction pathways and disrupted the interactions between the above major transcriptional factors. These data indicate a crucial role of EP300/CBP in regulating the crosstalk between cAMP-PKA pathway and Notch3 signaling and modulating the phenotypic change of podocytes, and enrich the reno-protective mechanisms of cAMP-PKA pathway.

Exploring the Potential Mechanism of Tang-Shen-Ning Decoction against Diabetic Nephropathy Based on the Combination of Network Pharmacology and Experimental Validation

Background

Diabetic nephropathy (DN) has become one of the leading causes of the end-stage renal disease (ESRD). Tang-Shen-Ning (TSN) decoction, an effective Traditional Chinese formula for DN, can improve the renal function and inhibit renal fibrosis in DN. However, its potential mechanism is still unexplored.

Methods

A network pharmacology approach was employed in this study, including screening for differential expressed genes of DN (DN-DEGs), protein-protein interaction (PPI) network analysis, and GO and KEGG enrichment analysis. Besides, a rat model was established to verify the potential effect of TSN in DN.

Results

Twenty-three TSN-related DN-DEGs targets were identified. These genes were associated with decreased glomerular filtration rate (GFR) DN. The enrichment analysis suggested that the inhibition of renal fibrosis and inflammation through growth factors and chemokines is the potential mechanism through which TSN improves DN. TSN reduced renal fibrosis and improved pathological damage in the kidney in vivo through the regulation of GJA1, CTGF, MMP7, and CCL5, which are genes associated with ECM deposition.

Conclusion

This study revealed that TSN improves DN through a multicomponent, multitarget, and multipathway synergy. We provide a scientific basis for potential targets for TSN use to treat DN, yet further experimental validation is needed to investigate these targets and mechanisms.

Deciphering nutritional interventions for podocyte structure and function

Despite increasing awareness and therapeutic options chronic kidney disease (CKD) is still and important health problem and glomerular diseases constitute and important percentage of CKD. Proteinuria/albuminuria is not just a marker; but it also plays a direct pathogenic role in renal disease progression of CKD. Glomerular filtration barrier (GFB) which consists of fenestrated endothelial cells, fused basal membrane and interdigitating podocyte foot process and filtration slits between foot process is the major barrier for proteinuria/albuminuria. Many glomerular diseases are characterized by disruption of GFB podocytes, foot process and slit diaphragm. Many proteinuric diseases are non-specifically targeted by therapeutic agents such as steroids and calcineurin inhibitors with systemic side effects. Thus, there is unmet need for more efficient and less toxic therapeutic options to treat glomerular diseases. In recent years, modification of dietary intake, has been gained to treat pathologic processes introducing the concept of 'food as a medicine'. The effect of various nutritional products on podocyte function and structure is also trending, especially in recent years. In the current review, we summarized the effect of nutritional interventions on podocyte function and structure.

The Aggressive Diabetic Kidney Disease in Youth-Onset Type 2 Diabetes: Pathogenetic Mechanisms and Potential Therapies

Youth-onset Type 2 Diabetes Mellitus (T2DM) represents a major burden worldwide. In the last decades, the prevalence of T2DM became higher than that of Type 1 Diabetes Mellitus (T1DM), helped by the increasing rate of childhood obesity. The highest prevalence rates of youth-onset T2DM are recorded in China (520 cases/100,000) and in the United States (212 cases/100,000), and the numbers are still increasing. T2DM young people present a strong hereditary component, often unmasked by social and environmental risk factors. These patients are affected by multiple coexisting risk factors, including obesity, hyperglycemia, dyslipidemia, insulin resistance, hypertension, and inflammation. Juvenile T2DM nephropathy occurs earlier in life compared to T1DM-related nephropathy in children or T2DM-related nephropathy in adult. Diabetic kidney disease (DKD) is T2DM major long term microvascular complication. This review summarizes the main mechanisms involved in the pathogenesis of the DKD in young population and the recent evolution of treatment, in order to reduce the risk of DKD progression.

C-peptide ameliorates high glucose-induced podocyte dysfunction through the regulation of the Notch and TGF-β signaling pathways

The podocyte is one of the main components of the glomerular filtration barrier in the kidney, and its injury may contribute to proteinuria, glomerulosclerosis and eventually kidney failure. C-peptide, a cleavage product of proinsulin, shows therapeutic potential for treating diabetic nephropathy (DN). The aim of this study was to investigate the effect of C-peptide on high glucose-induced podocyte dysfunction. In the present study, we found that the protective effects of islet transplantation were superior to simple insulin therapy for the treatment of DN in streptozotocin (STZ)-treated rats. And such superiority may due to the function of C-peptide secreted at the implanted site. Based on this background, we determined that the application of C-peptide significantly prevented high glucose-induced podocyte injury by increasing the expression of nephrin and synaptopodin. Meanwhile, C-peptide suppressed high glucose-induced epithelial-mesenchymal transition (EMT) and renal fibrosis via decreasing the expression of snail, vimentin, α-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF). Moreover, the Notch and transforming growth factor-β (TGF-β) signaling pathways were activated by high glucose, and treatment with C-peptide down-regulated the expression of the Notch signaling molecules Notch 1 and Jagged 1 and the TGF-β signaling molecule TGF-β1. These findings suggested that C-peptide might serve as a novel treatment method for DN and podocyte dysfunction.

Total Flavones of Abelmoschus manihot Ameliorates Podocyte Pyroptosis and Injury in High Glucose Conditions by Targeting METTL3-Dependent m6A Modification-Mediated NLRP3-Inflammasome Activation and PTEN/PI3K/Akt Signaling

Background: The total flavones of Abelmoschus manihot (TFA), a compound that is extracted from Abelmoschus manihot, has been widely used in China to reduce podocyte injury in diabetic kidney disease (DKD). However, the mechanisms underlying the therapeutic action of this compound have yet to be elucidated. Podocyte pyroptosis is characterized by activation of the NLRP3 inflammasome and plays an important role in inflammation-mediated diabetic kidneys. Regulation of the PTEN/PI3K/Akt pathway is an effective strategy for improving podocyte damage in DKD. Previous research has also shown that N6-methyladenosine (m6A) modification is involved in DKD and that m6A-modified PTEN regulates the PI3K/Akt pathway. In this study, we investigated whether TFA alleviates podocyte pyroptosis and injury by targeting m6A modification-mediated NLRP3-inflammasome activation and PTEN/PI3K/Akt signaling. Methods: We used MPC-5 cells under high glucose (HG) conditions to investigate the key molecules that are involved in podocyte pyroptosis and injury, including activation of the NLRP3 inflammasome and the PTEN/PI3K/Akt pathway. We detected alterations in the levels of three methyltransferases that are involved in m6A modification. We also investigated changes in the levels of these key molecules in podocytes with the overexpression or knockdown of methyltransferase-like (METTL)3. Results: Analysis showed that TFA and MCC950 protected podocytes against HG-induced pyroptosis and injury by reducing the protein expression levels of gasdermin D, interleukin-1β, and interleukin-18, and by increasing the protein expression levels of nephrin, ZO-1, WT1 and podocalyxin. TFA and 740Y-P inhibited activation of the NLRP3 inflammasome via the PI3K/Akt pathway by inhibiting the protein levels of NIMA-related kinase7, NLRP3, ASC, and caspase-1, and by increasing the protein expression levels of p-PI3K and p-Akt. TFA improved pyroptosis and injury in HG-stimulated podocytes by regulating METTL3-dependent m6A modification. Conclusion: Collectively, our data indicated that TFA could ameliorate pyroptosis and injury in podocytes under HG conditions by adjusting METTL3-dependent m6A modification and regulating NLRP3-inflammasome activation and PTEN/PI3K/Akt signaling. This study provides a better understanding of how TFA can protect podocytes in DKD.

Multidisciplinary Team Care Delays the Initiation of Renal Replacement Therapy in Diabetes: A Five-year Prospective, Single-center Study

Objective Although recent reports have highlighted the benefits of multidisciplinary team care (MTC) for chronic kidney disease (CKD) in slowing the progress of renal insufficiency, its long-term effects have not been evaluated for patients with diabetes mellitus (DM). We compared the renal survival rate between MTC and conservative care (CC). Methods In this five-year, single-center, prospective, observational study, we examined 24 patients (mean age 65.5±12.1 years old, men/women 18/6) with DM-induced CKD stage ≥3 in an MTC clinic. The control group included 24 random patients with DM (mean age 61.0±12.8 years old, men/women 22/2) who received CC. MTC was provided by a nephrologist and medical staff, and CC was provided by a nephrologist. Results In total, 10 MTC and 20 CC patients experienced renal events [creatinine doubling, initiation of renal replacement therapy (RRT), or death due to end-stage CKD]. During the five-year observation period, there were significantly fewer renal events in the MTC group than in the CC group according to the cumulative incidence method (p=0.006). Compared to CC, MTC significantly reduced the need for urgent initiation of hemodialysis (relative risk reduction 0.79, 95% confidence interval [CI] 0.107-0.964). On a multivariate analysis, MTC (hazard ratio [HR], 0.434, 95% CI 0.200-0.939) and the slope of the estimated glomerular filtration rate during the first year (HR, 0.429 per 1 mL/min/m²/year, 95% CI 0.279-0.661) were negatively associated with renal events. Conclusion MTC for DM-induced CKD is an effective strategy for delaying RRT. Long-term MTC can demonstrate reno-protective effects.

Cyanidin-3-O-glucoside attenuates high glucose-induced podocyte dysfunction by inhibiting apoptosis and promoting autophagy via activation of SIRT1/AMPK pathway

Diabetic nephropathy (DN) is a common and complicated chronic kidney disease around the world. To elucidate and find effective therapies of DN is of vital importance. In this paper, we have discovered that cyanidin-3-O-glucoside (C3G), which is one of the anthocyanins, could alleviate high glucose-induced podocyte dysfunction. MTT, flow cytometry assay, and Western blot analysis showed that C3G could reverse the increase of cell apoptosis under high glucose treatment in MPC5 cells by upregulation of Bcl2 and downregulation of Bax and cleaved caspase-3. Moreover, C3G improved the autophagy decrease that was induced by high glucose through regulating the expression level of LC3-II/LC3-I, Beclin1, and p62. In addition, C3G inhibited epithelial-mesenchymal transition (EMT) by increasing E-cadherin and reducing Vimentin. By further study of the mechanisms, we found C3G activated the SIRT1 and AMPK which were inhibited in high glucose condition. Silencing SIRT1 blocked the effect of C3G on regulating cell apoptosis, autophagy, and EMT. In summary, our current findings suggest the protective effect of C3G against high glucose-induced podocyte dysfunction is by improving autophagy and reducing apoptosis and EMT via activating SIRT1/AMPK pathway. It might be a new insight for the treatment of DN.

Mesenchymal stem cell-derived exosomes: a promising vector in treatment for diabetes and its microvascular complications

Mesenchymal stem cell-derived exosomes (MSC-exos) are phospholipid bimolecular vesicles containing various materials, and they mediate crosstalk among cells. MSC-exos can maintain glucose homeostasis and delay the progression of diabetes and its microvascular complications through multiple mechanisms, such as by improving β-cell viability and insulin resistance as well as through multiple signal transduction pathways. However, related knowledge has not yet been systematically summarized. Therefore, we reviewed the applications and relevant mechanisms of MSC-exos in treatments for diabetes and its microvascular complications, particularly treatments for improving islet β-cells viability, insulin resistance, diabetic nephropathy, and retinopathy.

Silencing of miR-150-5p Ameliorates Diabetic Nephropathy by Targeting SIRT1/p53/AMPK Pathway

Diabetic nephropathy (DN) is a common complication of diabetes and an important cause of end-stage renal disease. Increasing evidence suggests that microRNAs (miRNAs) regulate the development of DN. In a preliminary study, high levels of miR-150-5p were detected in the serum and urine of patients with DN. Consequently, we investigated the effect and mechanism of action of miR-150-5p in DN in vitro and in vivo. Our results showed that inhibition of miR-150-5p reversed high glucose-induced podocyte injury and Streptozocin (STZ)-induced diabetic nephropathy in mice. Further analysis revealed that miR-150-5p targeted the 3′ untranslated region (UTR) of sirtuin 1 (SIRT1), consequently decreasing SIRT1 levels in podocytes. Importantly, we found that the silencing of miR-150-5p promoted the interaction between SIRT1 and p53, causing the suppression of p53 acetylation in podocytes and kidney tissue. This resulted in the stimulation of AMP-activated protein kinase (AMPK)-dependent autophagy. In conclusion, our study demonstrated that the silencing of miR-150-5p played a reno-protective role in DN mice through targeting SIRT1.

TET2 mediated demethylation is involved in the protective effect of triptolide on podocytes

The epithelial-mesenchymal transition (EMT) is usually considered the central mechanism of podocyte injury that eventually leads to proteinuria. We used an in vitro TGF-β1 induced podocyte EMT model and an in vivo rat focal segmental glomerulosclerosis (FSGS) model to uncover the mechanism underlying the protective effect of triptolide (TP) on podocytes. We found that TP could reverse the podocyte EMT process and upregulate the expression of TET2 in the TGF-β1-induced podocyte injury model. Bisulfite amplicon sequencing (BSAS) showed TP could alter the methylation status at some specific sites of the medium CpG density region in the promoters of NEPH1 and nephrin, two main markers of the podocyte slit diaphragm. Knockdown of TET2 with shRNA lentivirus (Lv) leads to high methylation of the promoters of NEPH1 and nephrin such that their expression can not return to normal levels, even after treatment with TP. In vivo, we found that TP could protect against podocyte injury in the FSGS rat and increase TET2 expression. These results suggested TET2-mediated DNA demethylation may be partly involved in podocyte injury. We believe these findings can help uncover a novel molecular mechanism of TP in alleviating podocyte-associated glomerular diseases.

Role of SIK1 in the transition of acute kidney injury into chronic kidney disease

Background

Acute kidney injury (AKI), with a high morbidity and mortality, is recognized as a risk factor for chronic kidney disease (CKD). AKI-CKD transition has been regarded as one of the most pressing unmet needs in renal diseases. Recently, studies have showed that salt inducible kinase 1 (SIK1) plays a role in epithelial-mesenchymal transition (EMT) and inflammation, which are the hallmarks of AKI-CKD transition. However, whether SIK1 is involved in AKI-CKD transition and by what mechanism it regulates AKI-CKD transition remains unknown.

Methods

We firstly detected the expression of SIK1 in kidney tissues of AKI patients and AKI mice by immunohistochemistry staining, and then we established Aristolochic acid (AA)-induced AKI-CKD transition model in C57BL/6 mice and HK2 cells. Subsequently, we performed immunohistochemistry staining, ELISA, real-time PCR, Western blot, immunofluorescence staining and Transwell assay to explore the role and underlying mechanism of SIK1 on AKI-CKD transition.

Results

The expression of SIK1 was down-regulated in AKI patients, AKI mice, AA-induced AKI-CKD transition mice, and HK2 cells. Functional analysis revealed that overexpression of SIK1 alleviated AA-induced AKI-CKD transition and HK2 cells injury in vivo and in vitro. Mechanistically, we demonstrated that SIK1 mediated AA-induced AKI-CKD transition by regulating WNT/β-catenin signaling, the canonical pathway involved in EMT, inflammation and renal fibrosis. In addition, we discovered that inhibition of WNT/β-catenin pathway and its downstream transcription factor Twist1 ameliorated HK2 cells injury, delaying the progression of AKI-CKD transition.

Conclusions

Our study demonstrated, for the first time, a protective role of SIK1 in AKI-CKD transition by regulating WNT/β-catenin signaling pathway and its downstream transcription factor Twist1, which will provide novel insights into the prevention and treatment AKI-CKD transition in the future.