The VEGF-A inhibitor sFLT-1 improves renal function by reducing endothelial activation and inflammation in a mouse model of type 1 diabetes

The VEGF decoy receptor soluble Fms-like tyrosine kinase 1 binds to macrophages

BACKGROUND

Soluble Fms-like Tyrosine kinase-1 (sFLT1) is a native inhibitor of VEGF, best known for its antiangiogenic effects in preeclampsia. sFLT1 also reduces chronic inflammation and promotes tissue repair. In experimental diabetic nephropathy, we previously found that sFLT1 ameliorates kidney fibrosis and reduces the infiltration of macrophages. How sFLT1 regulates inflammation is still incompletely understood. Based on the direct association of sFLT1 with various cell types, we here studied whether sFLT1 interacts with macrophages to modulate inflammation.

METHODS

Using various macrophage cell lines, sFLT1 cell surface binding was detected with flow cytometry. Enzyme studies, mass spectrometry and RNAseq were employed to identify potential sFLT1 cell surface interactors and effects of sFLT1 on macrophage signaling.

RESULTS

Soluble FLT1 binds to primary macrophages, THP-1 and RAW264.7 macrophages in vitro. Alternative activation with IL-4 increases sFLT1 binding in THP-1 macrophages, whereas proinflammatory activation with IFN-γ and LPS decreases binding. Binding of sFLT1 depends on heparan sulphates, and colocalizes with the membrane heparin sulfate proteoglycan neuropilin-1. Incubation with sFLT1 reduces the gene expression of chemokine receptors.

CONCLUSION

Our results show that sFLT1, while typically associated with angiogenesis, also directly interacts with macrophages. Alternative activation of macrophages by IL-4 strongly increases binding of sFLT1 to the cell surface membrane, possibly via the VEGF co-receptor neuropilin-1. Considering sFLT1's anti-inflammatory effects in animal studies, our findings indicate a novel function for sFLT1 to directly control anti-inflammatory macrophage function.

Experimental validation of the molecular mechanism of phlorizin in the treatment of diabetic retinopathy

This study conducted an experiment to scrutinize the effect of phlorizin (Phl) on diabetic retinopathy (DR) and to delve into the related molecular mechanisms. Within this investigation, DR was induced in rats with diabetes mellitus (DM) by subjecting them to a regimen involving a high-fat and high-sugar diet, coupled with intraperitoneal administration of streptozotocin (STZ) at a dosage of 45 mg/kg. Retinal damage in DR rats was assessed by means of hematoxylin and eosin (HE) staining. The serum levels of inflammatory and angiogenic factors were also measured. Additionally, the levels of tight junction proteins, angiogenic proteins, and inflammatory proteins in the retinas of DR model rats were assessed using Western blot (WB),immunohistochemistry(IHC) and immunofluorescence(IF). Moreover, bioinformatics and network pharmacology methodologies were utilized to pinpoint intersecting genes linked to DR and to elucidate the mechanism of action of Phl. This involved screening with Venny, conducting Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG)analyses, constructing a Protein-Protein Interaction (PPI) network, and performing molecular docking analysis. The results of this study demonstrated that Phl significantly normalized fasting glucose levels and reduced body weight, thereby alleviating obesity in DR rats after 12 weeks. Furthermore, the serum levels of inflammatory and angiogenic factors were considerably reduced in the drug-treated rats. WB, IHC and IF revealed increased expression of the tight junction proteins zonula occludens-1(ZO-1) and occludin in the retinas of drug-treated DR rats, validating the observed findings. Molecular biology validation experiments based on the predictions by network pharmacology indicated a substantial decrease in the expression levels of vascular endothelial growth factor (VEGF), notch homolog 1 (Notch1), and hypoxia inducible factor-1 (HIF-1α) in the retina upon treatment with Phl. This reduction resulted in the inhibition of neovascularization. Furthermore, Phl exhibited inhibitory effects on inflammatory pathways, leading to a decrease in cytokine release. The overexpression of VEGF was identified as a factor diminishing brain-derived neurotrophic factor(BDNF) expression while increasing the expression levels of inflammatory proteins. Therefore, the results of this research demonstrate that Phl has the potential to protect the retina of DR rats by inhibiting VEGF expression. This protective effect may be associated with the modulation of the VEGF/BDNF/NF-κB signaling pathway.

Exploring the Molecular Modalities in the Pathogenesis of Diabetic Kidney Disease with a Focus on the Potential Therapeutic Implications

Diabetic kidney disease (DKD) is a leading cause of chronic kidney disease (CKD) and end-stage renal disease worldwide, affecting approximately 40% of individuals with type 2 diabetes (T2DM) and 30% of those with type 1 diabetes (T1DM). As the prevalence of diabetes continues to rise, the burden of DKD is expected to grow correspondingly. This review explores the roles of key molecular pathways, including the apelinergic system, vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) axis, and nitric oxide (NO)/nitric oxide synthase (NOS) signaling, in DKD pathogenesis and potential therapeutic applications. The apelinergic system, involving apelin and its receptor (APLNR), influences endothelial function, glucose metabolism, and renal health. Preclinical studies highlight its dual role in renal protection and injury through anti-inflammatory and antioxidant pathways, while other evidence suggests that it may exacerbate DKD through podocyte damage and angiogenesis. Similarly, the VEGF/VEGFR axis demonstrates a complex contribution to DKD, where VEGF-A promotes pathological angiogenesis and glomerular damage, but its inhibition requires careful modulation to prevent adverse effects. The NO/NOS system, integral to vascular and renal homeostasis, also exhibits altered activity in DKD, with reduced bioavailability linked to oxidative stress and inflammation. This review underscores the intricate interplay between these pathways in DKD, revealing both challenges and opportunities in their therapeutic targeting. Further research is essential to refine strategies and develop effective interventions for DKD management.

Is renal dysfunction amplified in an arginine vasopressin induced rat model of preeclampsia?

Renal dysfunction is important in preeclampsia (PE) pathophysiology and has not been fully explored in the arginine vasopressin (AVP) rat model of PE. This study aimed to determine kidney toxicity associated with this model. Female Sprague Dawley rats (n = 24) were subcutaneously infused with AVP or saline for 18 days. Urine samples (GD8, 14 and 18) were used to determine the levels of albumin, VEGF-A, clusterin, NGAL/Lipocalin-2, KIM-1, cystatin C, TIMP-1, β2M and OPN via Multiplex ELISAs. Albumin, and NGAL/lipocalin-2 were significantly elevated in the PAVP vs PS group on GD14 and GD18 (p < 0.001) respectively. VEGF-A significantly decreased in the pregnant vs non-pregnant groups on GD14 and 18 (p < 0.001). Clusterin (p < 0.001) and OPN (p < 0.05) were significantly higher in the PAVP vs PS group on GD18. Cystatin C and KIM-1 are significantly upregulated in the PAVP vs PS groups throughout gestation (p < 0.05). β2M is significantly elevated in the PAVP vs PS group on GD14 and 18 (p < 0.05). AVP elevated the urinary levels of the kidney injury biomarkers and replicated the renal dysfunction associated with PE development. Our findings confirm the potential applications of this model in studying the mechanisms underlying renal damage in PE.

The construction of elastin-like polypeptides and their applications in drug delivery system and tissue repair

Elastin-like polypeptides (ELPs) are thermally responsive biopolymers derived from natural elastin. These peptides have a low critical solution temperature phase behavior and can be used to prepare stimuli-responsive biomaterials. Through genetic engineering, biomaterials prepared from ELPs can have unique and customizable properties. By adjusting the amino acid sequence and length of ELPs, nanostructures, such as micelles and nanofibers, can be formed. Correspondingly, ELPs have been used for improving the stability and prolonging drug-release time. Furthermore, ELPs have widespread use in tissue repair due to their biocompatibility and biodegradability. Here, this review summarizes the basic property composition of ELPs and the methods for modulating their phase transition properties, discusses the application of drug delivery system and tissue repair and clarifies the current challenges and future directions of ELPs in applications.

Renal intrinsic cells remodeling in diabetic kidney disease and the regulatory effects of SGLT2 Inhibitors

Diabetic kidney disease (DKD) is a prevalent complication of diabetes and a major secondary factor leading to end-stage renal disease. The kidney, a vital organ, is composed of a heterogeneous group of intrinsic cells, including glomerular endothelial cells, podocytes, mesangial cells, tubular epithelial cells, and interstitial fibroblasts. In the context of DKD, hyperglycemia elicits direct or indirect injury to these intrinsic cells, leading to their structural and functional changes, such as cell proliferation, apoptosis, and transdifferentiation. The dynamic remodeling of intrinsic cells represents an adaptive response to stimulus during the pathogenesis of diabetic kidney disease. However, the persistent stimulus may trigger an irreversible remodeling, leading to fibrosis and functional deterioration of the kidney. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, a new class of hypoglycemic drugs, exhibit efficacy in reducing blood glucose levels by curtailing renal tubular glucose reabsorption. Furthermore, SGLT2 inhibitors have been shown to modulate intrinsic cell remodeling in the kidney, ameliorate kidney structure and function, and decelerate DKD progression. This review will elaborate on the intrinsic cell remodeling in DKD and the underlying mechanism of SGLT2 inhibitors in modulating it from the perspective of the renal intrinsic cell, providing insights into the pathogenesis of DKD and the renal protective action of SGLT2 inhibitors.

MIF Increases sFLT1 Expression in Early Uncomplicated Pregnancy and Preeclampsia

Insufficient immune tolerance during pregnancy is associated with pathological conditions such as preeclampsia (PE). Soluble fms-like tyrosine kinase-1 (sFLT1), which exerts a role in the late stage of PE, has shown its beneficial anti-inflammatory effects in inflammation-associated diseases. Macrophage migration inhibitory factor (MIF) was reported to upregulate sFLT1 production in experimental congenital diaphragmatic hernia. However, the placental sFLT1 expression in early uncomplicated pregnancy and whether MIF can regulate sFLT1 expression in uncomplicated and preeclamptic pregnancy are unclear. We collected first-trimester placentas and term placentas from uncomplicated and preeclamptic pregnancies to investigate sFLT1 and MIF expression in vivo. Primary cytotrophoblasts (CTBs) and a human trophoblast cell line (Bewo) were used to study the regulation of MIF on sFLT1 expression in vitro. In placentas from first-trimester pregnancy, we observed a high expression of sFLT1, specifically in extravillous trophoblasts (EVTs) and syncytiotrophoblast (STB) cells. MIF mRNA levels strongly correlated with sFLT1 expression in term placentas from preeclamptic pregnancies. In in vitro experiments, sFLT1 and MIF levels increased significantly in CTBs during their differentiation to EVTs and STBs, and MIF inhibitor (ISO-1) significantly reduced sFLT1 expression in a dose-dependent manner during this process. sFLT1 showed significant upregulation with increasing doses of MIF in Bewo cells. Our results show that sFLT1 is highly expressed at the maternal-fetal interface during early pregnancy and that MIF can increase sFLT1 expression in early uncomplicated pregnancy and PE, which suggests that sFLT1 plays an essential role in the modulation of inflammation in pregnancy.

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.

Bioinformatics Analysis of Next Generation Sequencing Data Identifies Molecular Biomarkers Associated With Type 2 Diabetes Mellitus

Background

Type 2 diabetes mellitus (T2DM) is the most common metabolic disorder. The aim of the present investigation was to identify gene signature specific to T2DM.

Methods

The next generation sequencing (NGS) dataset GSE81608 was retrieved from the gene expression omnibus (GEO) database and analyzed to identify the differentially expressed genes (DEGs) between T2DM and normal controls. Then, Gene Ontology (GO) and pathway enrichment analysis, protein-protein interaction (PPI) network, modules, miRNA (micro RNA)-hub gene regulatory network construction and TF (transcription factor)-hub gene regulatory network construction, and topological analysis were performed. Receiver operating characteristic curve (ROC) analysis was also performed to verify the prognostic value of hub genes.

Results

A total of 927 DEGs (461 were up regulated and 466 down regulated genes) were identified in T2DM. GO and REACTOME results showed that DEGs mainly enriched in protein metabolic process, establishment of localization, metabolism of proteins, and metabolism. The top centrality hub genes APP, MYH9, TCTN2, USP7, SYNPO, GRB2, HSP90AB1, UBC, HSPA5, and SQSTM1 were screened out as the critical genes. ROC analysis provides prognostic value of hub genes.

Conclusion

The potential crucial genes, especially APP, MYH9, TCTN2, USP7, SYNPO, GRB2, HSP90AB1, UBC, HSPA5, and SQSTM1, might be linked with risk of T2DM. Our study provided novel insights of T2DM into genetics, molecular pathogenesis, and novel therapeutic targets.

Network pharmacology analysis combined with experimental validation to explore the therapeutic mechanism of Schisandra Chinensis Mixture on diabetic nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic nephropathy (DN) is one of the most common and serious microvascular complications of Diabetes mellitus (DM). The inflammatory response plays a critical role in DN. Schisandra Chinensis Mixture (SM) has shown promising clinical efficacy in the treatment of DN while the pharmacological mechanisms are still unclear.

AIM OF THE STUDY

In this study, a network pharmacology approach and bioinformatic analysis were adopted to predict the pharmacological mechanisms of SM in DN therapy. Based on the predicted results, molecular docking and in vivo experiments were used for verification.

MATERIALS AND METHODS

In this study, the candidate bioactive ingredients of SM were obtained via Traditional Chinese Medicine Systems Pharmacology Database (TCMSP) and supplementing according to the literature. SM putative targets and the verified targets were acquired from TCMSP and SiwssTartgetPrediction Database. DN-related target genes were collected from GeneCards, OMIM, DisGeNET databases, and microarray data analysis. Biological function and pathway analysis were performed to further explore the pharmacological mechanisms of SM in DN therapy. The protein-protein interaction (PPI) network was established to screen the hub gene. The Receiver Operating Characteristic (ROC) analysis and the molecular docking simulations were performed to validate the potential target-drug interactions. The fingerprint spectrum of multi-components of the SM was characterized by UPLC-MS/MS. The signaling pathways associated with inflammation and hub genes were partially validated in SD rats.

RESULTS

A total of 36 bioactive ingredients were contained, and 666 component-related targets were screened from SM, of which 50 intersected with DN targets and were considered potential therapeutic targets. GO analyses revealed that the 50 intersection targets were mainly enriched in the inflammatory response, positive regulation of angiogenesis, and positive regulation of phosphatidylinositol 3-kinase(PI3K) signaling. KEGG analyses indicated that the PI3K-Akt signaling pathway was considered as the most important pathway for SM antagonism to the occurrence and development of DN, with the highest target count enrichment. PPI network results showed that the top 15 protein targets in degree value, VEGFA, JAK2, CSF1R, NOS3, CCR2, CCR5, TLR7, FYN, BTK, LCK, PLAT, NOS2, TEK, MMP1 and MCL1, were identified as hub genes. The results of ROC analysis showed that VEGFA and NOS3 were valuable in the diagnosis of DN. The molecular docking confirmed that the core bioactive ingredients had well-binding affinity for VEGFA and NOS3. The in vivo experiments confirmed that SM significantly inhibited the over-release of inflammatory cytokines such as interleukin (IL)-6 and tumor necrosis factor receptor (TNF)-α in DN rats, while regulating the PI3K-AKT and VEGFA-NOS3 signaling pathways.

CONCLUSION

This study revealed the multi-component, multi-target and multi-pathway characteristics of SM therapeutic DN. SM inhibited the inflammatory response and improved renal pathological damage in DN rats, which was related to the regulation of the PI3K-Akt and VEGFA-NOS3 signaling pathways.

The VEGF Inhibitor Soluble Fms-like Tyrosine Kinase 1 Does Not Promote AKI-to-CKD Transition

(1) Background: Soluble Fms-like tyrosine kinase 1 (sFLT1) is an endogenous VEGF inhibitor. sFLT1 has been described as an anti-inflammatory treatment for diabetic nephropathy and heart fibrosis. However, sFLT1 has also been related to peritubular capillary (PTC) loss, which promotes fibrogenesis. Here, we studied whether transfection with sFlt1 aggravates experimental AKI-to-CKD transition and whether sFLT1 is increased in human kidney fibrosis. (2) Methods: Mice were transfected via electroporation with sFlt1. After confirming transfection efficacy, mice underwent unilateral ischemia/reperfusion injury (IRI) and were sacrificed 28 days later. Kidney histology and RNA were analyzed to study renal fibrosis, PTC damage and inflammation. Renal sFLT1 mRNA expression was measured in CKD biopsies and control kidney tissue. (3) Results: sFlt1 transfection did not aggravate renal fibrosis, PTC loss or macrophage recruitment in IRI mice. In contrast, higher transfection efficiency was correlated with reduced expression of pro-fibrotic and pro-inflammatory markers. In the human samples, sFLT1 mRNA levels were similar in CKD and control kidneys and were not correlated with interstitial fibrosis or PTC loss. (4) Conclusion: As we previously found that sFLT1 has therapeutic potential in diabetic nephropathy, our findings indicate that sFLT1 can be administered at a dose that is therapeutically effective in reducing inflammation, without promoting maladaptive kidney damage.

R-spondin 3 Inhibits High Glucose-Induced Endothelial Activation Through Leucine-Rich G Protein-Coupled Receptor 4/Wnt/β-catenin Pathway

ABSTRACT

High glucose-induced endothelial activation plays critical roles in the development of diabetic vascular complications. R-spondin 3 could inhibit inflammatory damage, and diabetic vascular inflammation is secondary to endothelial activation. In this article, we identify R-spondin 3 as a novel regulator of high glucose-induced endothelial activation. We found that the serum levels of R-spondin 3 were significantly reduced in type 2 diabetic patients and db/db mice. We observed that the increased expressions of vascular cell adhesion molecule-1, intercellular cell adhesion molecule-1, and monocyte chemoattractant protein-1 (endothelial activation makers) in high glucose-stimulated human umbilical vein endothelial cell lines (HUVECs) could be inhibited by overexpressing R-spondin 3 or human R-spondin 3 recombinant protein. Subsequently, high glucose-induced adhesion and migration of human myeloid leukemia mononuclear cells (THP-1 cells) to HUVECs were markedly suppressed by the overexpression of R-spondin 3 in HUVECs. Moreover, the inhibitory effect of R-spondin 3 on the expressions of vascular cell adhesion molecule-1, intercellular cell adhesion molecule-1, and monocyte chemoattractant protein-1 in high glucose-treated HUVECs could be blocked by knockdown of leucine-rich G protein-coupled receptor 4 (R-spondin 3 receptor) or the specific inhibitor of Wnt/β-catenin pathway. Taken together, R-spondin 3 could suppress high glucose-induced endothelial activation through leucine-rich G protein-coupled receptor 4/Wnt/β-catenin pathway.

Pro- and anti-fibrotic effects of vascular endothelial growth factor in chronic kidney diseases

Renal fibrosis is the inevitable common end-point of all progressive chronic kidney diseases. The underlying mechanisms of renal fibrosis are complex, and currently there is no effective therapy against renal fibrosis. Renal microvascular rarefaction contributes to the progression of renal fibrosis; however, an imbalance between proangiogenic and antiangiogenic factors leads to the loss of renal microvasculature. Vascular endothelial growth factor (VEGF) is the most important pro-angiogenic factor. Recent studies have unraveled the involvement of VEGF in the regulation of renal microvascular rarefaction and fibrosis via various mechanisms; however, it is not clear whether it has anti-fibrotic or pro-fibrotic effect. This paper reviews the available evidence pertaining to the function of VEGF in the fibrotic process and explores the associated underlying mechanisms. Our synthesis will help identify the future research priorities for developing specialized treatments for alleviating or preventing renal fibrosis. Abbreviation: VEGF: vascular endothelial growth factor; CKD: chronic kidney disease; ESKD: end-stage kidney disease; ER: endoplasmic reticulum; VEGFR: vascular endothelial growth factor receptor; AKI: acute kidney injury; EMT: epithelial-to-mesenchymal transition; HIF: hypoxia-inducible factor; α-SMA: α smooth muscle actin; UUO: unilateral ureteral obstruction; TGF-β: transforming growth factor-β; PMT: pericyte-myofibroblast transition; NO: nitric oxide; NOS: nitric oxide synthase; nNOS: neuronal nitric oxide synthase; iNOS: inducible nitric oxide synthase; eNOS: endothelial nitric oxide synthase; sGC: soluble guanylate cyclase; PKG: soluble guanylate cyclase dependent protein kinases; UP R: unfolded protein response

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.

Research progress on exosomes/microRNAs in the treatment of diabetic retinopathy

Diabetic retinopathy (DR) is the leakage and obstruction of retinal microvessels caused by chronic progressive diabetes that leads to a series of fundus lesions. If not treated or controlled, it will affect vision and even cause blindness. DR is caused by a variety of factors, and its pathogenesis is complex. Pericyte-related diseases are considered to be an important factor for DR in many pathogeneses, which can lead to DR development through direct or indirect mechanisms, but the specific mechanism remains unclear. Exosomes are small vesicles of 40-100 nm. Most cells can produce exosomes. They mediate intercellular communication by transporting microRNAs (miRNAs), proteins, mRNAs, DNA, or lipids to target cells. In humans, intermittent hypoxia has been reported to alter circulating excretory carriers, increase endothelial cell permeability, and promote dysfunction in vivo. Therefore, we believe that the changes in circulating exocrine secretion caused by hypoxia in DR may be involved in its progress. This article examines the possible roles of miRNAs, proteins, and DNA in DR occurrence and development and discusses their possible mechanisms and therapy. This may help to provide basic proof for the use of exocrine hormones to cure DR.

microRNA-15b-5p shuttled by mesenchymal stem cell-derived extracellular vesicles protects podocytes from diabetic nephropathy via downregulation of VEGF/PDK4 axis

Diabetic nephropathy (DN) is a severe complication of diabetes lethal for end-stage renal disease, with less treatment methodologies and uncertain pathogenesis. In the current study, we determined the role of mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) containing microRNA (miR)-15b-5p in DN. After extraction and identification of MSC-derived EVs, mouse podocyte line MPC5 was selected to establish an in vitro high-glucose (HG) cell model, where expression of miR-15b-5p, pyruvate dehydrogenase kinase 4 (PDK4) and VEGFA expression in tissues and cells were determined. The loss- and gain- function assays were conducted to determine the roles of miR-15b-5p, PDK4 and VEGFA. MPC5 cells were then co-cultured with MSC-derived EVs and their biological behaviors were detected by Western blot, CCK-8 assay, and flow cytometry. The binding relationship between miR-15b-5p and PDK43 by dual luciferase reporter gene assay. The expression of miR-15b-5p was downregulated in podocytes under HG environment, but highly expressed in mouse MSCs-derived EVs. EVs-derived miR-15b-5p could protect MPC5 cell apoptosis and inflammation. miR-15b-5p inhibited the expression of PDK4 by directly bound to the 3'UTR region of PDK4 gene. miR-15b-5p inhibits VEGF expression by binding to PDK4. Inhibition of PDK4 decreased VEGFA expression and reduced apoptosis and inflammation. Collectively, miR-15b-5p shuttled by MSC-derived EV can play protective roles in HG-induced mouse podocyte injury, possibly by targeting PDK4 and decreasing the VEGFA expression.

Circulating Soluble Fms-like Tyrosine Kinase in Renal Diseases Other than Preeclampsia

Soluble Fms-like tyrosine kinase (sFlt-1/sVEGFR1) is a naturally occurring antagonist of vascular endothelial growth factor (VEGF). Despite being a secreted, soluble protein lacking cytoplasmic and transmembrane domains, sFlt-1 can act locally and be protective against excessive microenvironmental VEGF concentration or exert autocrine functions independently of VEGF. Circulating sFlt-1 may indiscriminately affect endothelial function and the microvasculature of distant target organs. The clinical significance of excess sFlt-1 in kidney disease was first shown in preeclampsia, a major renal complication of pregnancy. However, circulating sFlt-1 levels appear to be increased in various diseases with varying degrees of renal impairment. Relevant clinical associations between circulating sFlt-1 and severe outcomes (e.g., endothelial dysfunction, renal impairment, cardiovascular disease, and all-cause mortality) have been observed in patients with CKD and after kidney transplantation. However, sFlt-1 appears to be protective against renal dysfunction-associated aggravation of atherosclerosis and diabetic nephropathy. Therefore, in this study, we provide an update on sFlt-1 in several kidney diseases other than preeclampsia, discuss clinical findings and experimental studies, and briefly consider its use in clinical practice.

Study of the Active Components and Molecular Mechanism of Tripterygium wilfordii in the Treatment of Diabetic Nephropathy

We aimed to explore the active ingredients and molecular mechanism of Tripterygium wilfordii (TW) in the treatment of diabetic nephropathy (DN) through network pharmacology and molecular biology. First, the active ingredients and potential targets of TW were obtained through the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and related literature materials, and Cytoscape 3.7.2 software was used to construct the active ingredient-target network diagram of TW. Second, the target set of DN was obtained through the disease database, and the potential targets of TW in the treatment of DN were screened through a Venn diagram. A protein interaction network diagram (PPI) was constructed with the help of the String platform and Cytoscape 3.7.2. Third, the ClueGO plug-in tool was used to enrich the GO biological process and the KEGG metabolic pathway. Finally, molecular docking experiments and cell pathway analyses were performed. As a result, a total of 52 active ingredients of TW were screened, and 141 predicted targets and 49 target genes related to DN were identified. The biological process of GO is mediated mainly through the regulation of oxygen metabolism, endothelial cell proliferation, acute inflammation, apoptotic signal transduction pathway, fibroblast proliferation, positive regulation of cyclase activity, adipocyte differentiation and other biological processes. KEGG enrichment analysis showed that the main pathways involved were AGE-RAGE, vascular endothelial growth factor, HIF-1, IL-17, relaxin signalling pathway, TNF, Fc epsilon RI, insulin resistance and other signaling pathways. It can be concluded that TW may treat DN by reducing inflammation, reducing antioxidative stress, regulating immunity, improving vascular disease, reducing insulin resistance, delaying renal fibrosis, repairing podocytes, and reducing cell apoptosis, among others, with multicomponent, multitarget and multisystem characteristics.

Reduced Glomerular Endothelial Thrombomodulin Is Associated with Glomerular Macrophage Infiltration in Diabetic Nephropathy

The endothelial glycoprotein thrombomodulin regulates coagulation, inflammation, and apoptosis. In diabetic mice, reduced thrombomodulin function results in diabetic nephropathy (DN). Furthermore, thrombomodulin treatment reduces renal inflammation and fibrosis. Herein, thrombomodulin expression was examined in human kidney samples to investigate the possibility of targeting thrombomodulin in patients with DN. Glomerular thrombomodulin was analyzed together with the number of glomerular macrophages in 90 autopsied diabetic cases with DN, 55 autopsied diabetic cases without DN, and 37 autopsied cases without diabetes or kidney disease. Thrombomodulin mRNA was measured in glomeruli microdissected from renal biopsies from patients with DN and nondiabetic controls. Finally, glomerular thrombomodulin was measured in diabetic mice following treatment with the selective endothelin A receptor (ET_AR) blocker, atrasentan. In diabetic patients, glomerular thrombomodulin expression was increased at the mRNA level, but decreased at the protein level, compared with nondiabetic controls. Reduced glomerular thrombomodulin was associated with an increased glomerular influx of macrophages. Blocking the ET_AR with atrasentan restored glomerular thrombomodulin protein levels in diabetic mice to normal levels. The reduction in glomerular thrombomodulin in diabetes likely serves as an early proinflammatory step in the pathogenesis of DN. Thrombomodulin protein may be cleaved under diabetic conditions, leading to a compensatory increase in transcription. The nephroprotective effects of ET_AR antagonists in diabetic patients may be attributed to the restoration of glomerular thrombomodulin.

Exosomes: Biomarkers and Therapeutic Targets of Diabetic Vascular Complications

Diabetic vascular complications (DVC) including macrovascular and microvascular lesions, have a significant impact on public health, and lead to increased patient mortality. Disordered intercellular cascades play a vital role in diabetic systemic vasculopathy. Exosomes participate in the abnormal signal transduction of local vascular cells and mediate the transmission of metabolic disorder signal molecules in distant organs and cells through the blood circulation. They can store different signaling molecules in the membrane structure and release them into the blood, urine, and tears. In recent years, the carrier value and therapeutic effect of exosomes derived from stem cells have garnered attention. Exosomes are not only a promising biomarker but also a potential target and tool for the treatment of DVC. This review explored changes in the production process of exosomes in the diabetic microenvironment and exosomes' early warning role in DVC from different systems and their pathological processes. On the basis of these findings, we discussed the future direction of exosomes in the treatment of DVC, and the current limitations of exosomes in DVC research.

Glomerular clusterin expression is increased in diabetic nephropathy and protects against oxidative stress-induced apoptosis in podocytes

Clusterin, a glycoprotein encoded by the CLU gene, is expressed in many tissues, including the kidney, and clusterin expression is upregulated in the glomeruli of patients with various forms of kidney disease. Here, we investigated the role of clusterin in diabetic nephropathy (DN). In this study, we found that glomerular clusterin expression was increased in both patients with DN and streptozotocin-induced diabetic mice and that it co-localised with the podocyte marker WT1, indicating clusterin is expressed in podocytes. In our in vitro analysis, we found no significant change in CLU mRNA expression in podocytes following stimulation with high glucose and angiotensin II; in contrast, CLU mRNA expression was significantly upregulated following methylglyoxal stimulation. Methylglyoxal treatment also significantly decreased the mRNA expression of the slit diaphragm markers ZO-1 and NEPH1 and significantly increased the mRNA expression of the oxidative stress marker HO-1. Lastly, we showed that pre-incubating podocytes with recombinant human clusterin protein increased podocyte survival, prevented slit diaphragm damage, and reduced oxidative stress‒induced apoptosis following methylglyoxal stimulation. Taken together, our results indicate that glomerular clusterin is upregulated in DN, and this increase in clusterin expression may protect against oxidative stress-induced apoptosis in podocytes, providing a possible new therapeutic target for DN and other kidney diseases.

Role of VEGF-A and LRG1 in Abnormal Angiogenesis Associated With Diabetic Nephropathy

Diabetic nephropathy (DN) is an important public health concern of increasing proportions and the leading cause of end-stage renal disease (ESRD) in diabetic patients. It is one of the most common long-term microvascular complications of diabetes mellitus that is characterized by proteinuria and glomerular structural changes. Angiogenesis has long been considered to contribute to the pathogenesis of DN, whereas the molecular mechanisms of which are barely known. Angiogenic factors associated with angiogenesis are the major candidates to explain the microvascular and pathologic finds of DN. Vascular endothelial growth factor A (VEGF-A), leucine-rich α-2-glycoprotein 1, angiopoietins and vasohibin family signal between the podocytes, endothelium, and mesangium have important roles in the maintenance of renal functions. An appropriate amount of VEGF-A is beneficial to maintaining glomerular structure, while excessive VEGF-A can lead to abnormal angiogenesis. LRG1 is a novel pro-angiogenic factors involved in the abnormal angiogenesis and renal fibrosis in DN. The imbalance of Ang1/Ang2 ratio has a role in leading to glomerular disease. Vasohibin-2 is recently shown to be in diabetes-induced glomerular alterations. This review will focus on current understanding of these angiogenic factors in angiogenesis and pathogenesis associated with the development of DN, with the aim of evaluating the potential of anti-angiogenesis therapy in patients with DN.

Changes of expression levels of serum cystatin C and soluble vascular endothelial growth factor receptor 1 in the treatment of patients with glomerulus nephritis

Expression levels and changes of serum cystatin C (C's C) and soluble vascular endothelial growth factor receptor 1 (sVEGFR1) in treatment of patients with glomerulus nephritis (GN) were investigated. The medical records of 88 patients with GN who were diagnosed in Weifang People's Hospital from March 2014 to June 2017 were collected, and their medical records were considered as a study group. The study group was divided into secondary glomerulonephritis (SGN) group (52 cases) and primary glomerulonephritis (PGN) group (36 cases). Physical examination data of 50 healthy volunteers who were examined in the same hospital during the same period were considered as a control group. The correlation between expression of serum C's C and expression of sVEGFR1 of patients with GN was compared. Expression levels of serum C's C and sVEGFR1 of patients before treatment in the study group were higher than those in the control group (P<0.05). With the extension of the treatment cycle, C's C and sVEGFR1 expression levels in PGN and SGN groups reduced gradually (P<0.05). With the extension of the treatment cycle, the renal function indexes of the study group patients showed a downward trend (P<0.05). Expression of C's C was positively correlated with urea nitrogen and creatinine (P<0.05). In conclusion, C's C and sVEGFR1 are highly expressed in the serum of patients with GN. Expression of C's C and sVEGFR1 decrease as patients are treated. C's C and sVEGFR1 can be used as indicators for monitoring the condition of patients with GN. It is worthwhile to promote C's C and sVEGFR1 in clinical practice.

Development of a long acting FGF21 analogue-albumin fusion protein and its anti-diabetic effects

Fibroblast growth factor 21 (FGF21) is a hormone-like protein that improves blood glucose and lipid metabolism. However, its short half-life and instability are bottlenecks to its clinical applications. In this study, to extend its pharmacological action, we created a stabilized mutant FGF21 (mFGF21:ΔHPIP, P171G, A180E, L118C-A134C, S167A) and then genetically fused it with human albumin (HSA-mFGF21) via a polypeptide linker. Physicochemical analyses suggested that HSA-mFGF21 was formed from both intact HSA and mFGF21. Pharmacokinetic findings indicated the half-life of HSA-mFGF21 was 20 times longer than that of FGF21. In addition, HSA-mFGF21 was persistently distributed in adipose tissue as a target tissue. The in vivo hypoglycemic activity of HSA-mFGF21 using streptozotocin (STZ)-induced type I diabetes model mice, in which insulin secretion was suppressed, showed that a single intravenous administration of HSA-mFGF21 rapidly alleviated hyperglycemia. At that time, HSA-mFGF21 increased GLUT1 mRNA expression in adipose tissue without having any effect on insulin secretion. A twice weekly administration of HSA-mFGF21 continuously suppressed blood glucose levels and ameliorated the abnormalities of adipose tissue induced by STZ treatment. Interestingly, HSA-mFGF21 showed no hypoglycemic effects in healthy mice. Together, HSA-mFGF21 could be a novel biotherapeutic for the treatment of metabolic disorders including diabetes mellitus.

A Network Pharmacology-Based Strategy for Unveiling the Mechanisms of Tripterygium Wilfordii Hook F against Diabetic Kidney Disease

BACKGROUND

Diabetic kidney disease (DKD) poses a major public-health burden globally. Tripterygium wilfordii Hook F (TwHF) is a widely employed herbal medicine in decreasing albuminuria among diabetic patients. However, a holistic network pharmacology strategy to investigate the active components and therapeutic mechanism underlying DKD is still unavailable.

METHODS

We collected TwHF ingredients and their targets by traditional Chinese Medicine databases (TCMSP). Then, we obtained DKD targets from GeneCards and OMIM and collected and analyzed TwHF-DKD common targets using the STRING database. Protein-protein interaction (PPI) network was established by Cytoscape and analyzed by MCODE plugin to get clusters. In addition, the cytoHubba software was used to identify hub genes. Finally, all the targets of clusters were subjected for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses via DAVID.

RESULTS

A total of 51 active ingredients in TwHF were identified and hit by 88 potential targets related to DKD. Compounds correspond to more targets include kaempferol, beta-sitosterol, stigmasterol, and Triptoditerpenic acid B, which appeared to be high-potential compounds. Genes with higher degree including VEGFA, PTGS2, JUN, MAPK8, and HSP90AA1 are hub genes of TwHF against DKD, which are involved in inflammation, insulin resistance, and lipid homeostasis. Kaempferol and VEGFA were represented as the uppermost active ingredient and core gene of TwHF in treating DKD, respectively. DAVID results indicated that TwHF may play a role in treating DKD through AGE-RAGE signaling pathway, IL-17 signaling pathway, TNF signaling pathway, insulin resistance, and calcium signaling pathway (P < 0.05).

CONCLUSION

Kaempferol and VEGFA were represented as the uppermost active ingredient and core gene of TwHF in treating DKD, respectively. The key mechanisms of TwHF against DKD might be involved in the reduction of renal inflammation by downregulating VEGFA.

Exosomal microRNA-16-5p from human urine-derived stem cells ameliorates diabetic nephropathy through protection of podocyte

Diabetic nephropathy (DN) remains one of the severe complications associated with diabetes mellitus. It is worthwhile to uncover the underlying mechanisms of clinical benefits of human urine‐derived stem cells (hUSCs) in the treatment of DN. At present, the clinical benefits associated with hUSCs in the treatment of DN remains unclear. Hence, our study aims to investigate protective effect of hUSC exosome along with microRNA‐16‐5p (miR‐16‐5p) on podocytes in DN via vascular endothelial growth factor A (VEGFA). Initially, miR‐16‐5p was predicated to target VEGFA based on data retrieved from several bioinformatics databases. Notably, dual‐luciferase report gene assay provided further verification confirming the prediction. Moreover, our results demonstrated that high glucose (HG) stimulation could inhibit miR‐16‐5p and promote VEGFA in human podocytes (HPDCs). miR‐16‐5p in hUSCs was transferred through the exosome pathway to HG‐treated HPDCs. The viability and apoptosis rate of podocytes after HG treatment together with expression of the related factors were subsequently determined. The results indicated that miR‐16‐5p secreted by hUSCs could improve podocyte injury induced by HG. In addition, VEGA silencing could also ameliorate HG‐induced podocyte injury. Finally, hUSC exosomes containing overexpressed miR‐16‐5p were injected into diabetic rats via tail vein, followed by qualification of miR‐16‐5p and observation on the changes of podocytes, which revealed that overexpressed miR‐16‐5p in hUSCs conferred protective effects on HPDCs in diabetic rats. Taken together, the present study revealed that overexpressed miR‐16‐5p in hUSC exosomes could protect HPDCs induced by HG and suppress VEGFA expression and podocytic apoptosis, providing fresh insights for novel treatment of DN.

PTPN2 improved renal injury and fibrosis by suppressing STAT-induced inflammation in early diabetic nephropathy

Diabetic nephropathy (DN) is a chronic inflammatory disease triggered by disordered metabolism. Recent studies suggested that protein tyrosine phosphatase non‐receptor type 2 (PTPN2) could ameliorate metabolic disorders and suppress inflammatory responses. This study investigated PTPN2's role in modulating DN and the possible cellular mechanisms involved. In a mouse model combining hyperglycaemia and hypercholesterolaemia (streptozotocin diabetic, ApoE^‐/‐ mice), mice showed severe insulin resistance, renal dysfunction, micro‐inflammation, subsequent extracellular matrix expansion and decreased expression of PTPN2. We found that mice treated with PTPN2 displayed reduced serum creatinine, serum BUN and proteinuria. PTPN2 gene therapy markedly attenuated metabolic disorders and hyperglycaemia. In addition, PTPN2 gene transfer significantly suppressed renal activation of signal transducers and activators of transcription (STAT), STAT‐dependent pro‐inflammatory and pro‐fibrotic genes expression, and influx of lymphocytes in DN, indicating anti‐inflammatory effects of PTPN2 by inhibiting the activation of STAT signalling pathway in vivo. Furthermore, PTPN2 overexpression inhibited the high‐glucose induced phosphorylation of STAT, target genes expression and proliferation in mouse mesangial and tubuloepithelial cells, suggesting that the roles of PTPN2 on STAT activation was independent of glycaemic changes. Our results demonstrated that PTPN2 gene therapy could exert protective effects on DN via ameliorating metabolic disorders and inhibiting renal STAT‐dependent micro‐inflammation, suggesting its potential role for treatment of human DN.

Increased soluble fms-like tyrosine kinase 1 after ischemia reperfusion contributes to adverse clinical outcomes following kidney transplantation

Renal ischemia reperfusion injury (IRI) adversely affects clinical outcomes following kidney transplantation. Understanding the cellular mechanisms and the changes in gene/protein expression following IRI may help to improve these outcomes. Serum soluble fms-like tyrosine kinase 1 (sFlt-1), a circulating antiangiogenic protein, is increased in the first week following kidney transplantation. We evaluated the casual relationship of elevated sFlt-1 levels with renal microvascular dysfunction following IRI in a longitudinal study of 93 kidney transplant recipients and in several animal models. Transplant recipients with higher sFlt-1 levels had higher odds of delayed graft function, graft rejection, impaired graft function, and death. In a subgroup of 25 participants who underwent kidney biopsy within 4 months of kidney transplantation, peritubular capillary area was lower in those with elevated serum sFtl-1 levels. The administration of recombinant sFlt-1 into rodents resulted in significant structural and functional changes of the renal microvasculature, including reduced peritubular capillary density and intracapillary blood volume, and lead to increased expression of inflammatory genes and increased fibrosis. In a murine model of IRI, the kidney was a site of sFlt-1 production, and systemic neutralization of sFlt-1 preserved peritubular capillary density and alleviated renal fibrosis. Our data indicate that high sFlt-1 levels after IRI play an important role in the pathogenesis of microvascular dysfunction, thereby contributing to adverse clinical outcomes following kidney transplantation.

A signal-on nanobiosensor for VEGF165 detection based on supraparticle copper nanoclusters formed on bivalent aptamer

In this study, a signal-on nanobiosensor based on bivalent aptamer-Cu nanocluster was designed and optimized for specific and sensitive detection of VEGF₁₆₅. The VEGF₁₆₅ is known as a promising biomarker in different diseases such as cancer in the angiogenic stage. Detection and quantification of VEGF₁₆₅ is a crucial step in diagnosis and monitoring the treatment plan. The represented nanostructure consists of multimerized VEGF₁₆₅ aptamer joint with ssDNA based linker in the middle and poly thymine sequences on both 3' and 5' ends as a template for Cu-nanocluster supraparticle formation. This self-assembled structure leads to accurate controlling of aggregation in the presence of VEGF₁₆₅. This study is the first report for Cu nanocluster nucleation on ploy thymine tails of ssDNA which performed in two reduction steps to form stable CuNC supraparticle. The sensing strategy was designed based on the target-induced structure switching mode of the aptamer. In the presence of VEGF₁₆₅, due to self-assembly induced emission and aggregation-induced emission phenomena this nanostructure depicted the visible wavelength shift and enhancement in the fluorescence emission intensity. Also, the results of the analytical performance of this nanobiosensor indicated the LOD of 12 pM which revealed high rate sensitivity. This aptasensor exhibited stability and decent response linearity range (10-800 pM, R² = 0.9943). The selectivity and specificity assessment showed high discriminant capability in the real serum sample. In conclusion, this signal-on nanobiosensor provides a facile, sensitive and reliable assay for clinical monitoring of the VEGF₁₆₅ concentration in serum without further sample preparation.

Chemerin/ChemR23 axis promotes inflammation of glomerular endothelial cells in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by inflammation of renal tissue. Glomerular endothelial cells (GEnCs) play an important role in inflammation and protein leakage in urine in DN patients. Chemerin and its receptor ChemR23 are inducers of inflammation. The aim of this study was to investigate the function of chemerin/ChemR23 in GEnCs of DN patients. Immunohistochemical staining and qRT‐PCR were used to measure the expression of chemerin, ChemR23 and inflammatory factors in renal tissues of DN patients. Db/db mice were used as animal model. ChemR23 of DN mice was knocked down by injecting LV3‐shRNA into tail vein. Inflammation, physiological and pathological changes in each group was measured. GEnCs were cultured as an in vitro model to study potential signalling pathways. Results showed that expression of chemerin, ChemR23 and inflammatory factors increased in DN patients and mice. LV3‐shRNA alleviated renal damage and inflammation in DN mice. GEnCs stimulated by glucose showed increased chemerin, ChemR23 and inflammatory factors and decreased endothelial marker CD31. Both LV3‐shRNA and SB203580 (p38 MAPK inhibitor) attenuated chemerin‐induced inflammation and injury in GEnCs. Taken together, chemerin/ChemR23 axis played an important role in endothelial injury and inflammation in DN via the p38 MAPK signalling pathway. Suppression of ChemR23 alleviated DN damage.

Endoglin Mediates Vascular Endothelial Growth Factor-A-Induced Endothelial Cell Activation by Regulating Akt Signaling

In diabetic nephropathy, differential expression of growth factors leads to vascular changes, including endothelial cell activation, monocyte infiltration, and inflammation. Endoglin plays an important role in endothelial function and is also associated with inflammation. In the kidney, vascular endoglin expression is increased in animal models of renal injury, where it contributes to disease severity, possibly by promoting endothelial cell activation and inflammation. Herein, we investigated whether endoglin expression is associated with diabetic nephropathy. In addition, we examined whether reducing endothelial endoglin expression in vitro affects endothelial cell activation and monocyte adhesion and, if so, which intracellular pathways are involved. Finally, we analyzed whether glomerular endoglin expression is correlated with endothelial cell activation in patients with diabetic nephropathy. Endoglin levels were significantly increased in mice with type 1 diabetes compared with control mice. Reducing endoglin expression in cultured endothelial cells significantly impaired the vascular endothelial growth factor-A-induced up-regulation of activation markers and monocyte adhesion. This was mediated by increased phosphorylation of Akt, thereby inhibiting activating transcription factor 2 phosphorylation, which regulates vascular cell adhesion molecule-1 (VCAM1) gene transcription in these cells. Last, endoglin colocalized with VCAM-1 in the glomeruli of diabetic patients, glomerular VCAM-1 expression was significantly increased in these patients, and this increase in VCAM-1 expression was correlated with increased glomerular endoglin expression. Thus, targeting endoglin function may have therapeutic value in patients at risk for diabetic nephropathy.

Endogenous Antiangiogenic Factors in Chronic Kidney Disease: Potential Biomarkers of Progression

Chronic kidney disease (CKD) is a major global health problem. Unless intensive intervention is initiated, some patients can rapidly progress to end-stage kidney disease. However, it is often difficult to predict renal outcomes using conventional laboratory tests in individuals with CKD. Therefore, many researchers have been searching for novel biomarkers to predict the progression of CKD. Angiogenesis is involved in physiological and pathological processes in the kidney and is regulated by the balance between a proangiogenic factor, vascular endothelial growth factor (VEGF)-A, and various endogenous antiangiogenic factors. In recent reports using genetically engineered mice, the roles of these antiangiogenic factors in the pathogenesis of kidney disease have become increasingly clear. In addition, recent clinical studies have demonstrated associations between circulating levels of antiangiogenic factors and renal dysfunction in CKD patients. In this review, we summarize recent advances in the study of representative endogenous antiangiogenic factors, including soluble fms-related tyrosine kinase 1, soluble endoglin, pigment epithelium-derived factor, VEGF-A₁₆₅b, endostatin, and vasohibin-1, in associations with kidney diseases and discuss their predictive potentials as biomarkers of progression of CKD.

[Correlation between expressions of VEGF and TRPC6 and their roles in podocyte injury in rats with diabetic nephropathy]

OBJECTIVE

To analyze the correlation between the expressions of vascular endothelial growth factor (VEGF) and transient receptor potential canonical 6 (TRPC6) and their role in podocyte injury in rats with diabetic nephropathy.

METHODS

Forty SD rats with diabetic nephropathy induced by intraperitoneal injection of 65 mg/kg streptozotocin were randomized equally into 5 groups, including a diabetic nephropathy model group and 4 treatment groups, with 8 normal SD rats as the normal control group. In the 4 treatment groups, the rats received intraperitoneal injections with SU5416 at 5 mg/kg or 10 mg/kg twice a week or with LY294002 at 1 mg/kg or 2 mg/kg once daily for 8 weeks. Blood glucose, serum creatinine, blood urea nitrogen, and 24-h urinary protein levels of the rats were detected at different time points, and the pathologies in the renal tissue were observed using HE staining, PAS staining and immunohistochemistry. The expressions of VEGF, nephrin, and TRPC6 at mRNA and protein levels were detected using RT-PCR and Western blotting.

RESULTS

Compared with normal control rats, the diabetic rats showed significantly increased fasting blood glucose, serum creatinine, blood urea nitrogen and 24-h urinary protein levels with decreased expressions of nephrin mRNA and protein (P<0.05) and increased expressions of VEGF and TRPC6 (P<0.05). Compared with the untreated diabetic rats, the rats with SU5416 treatment showed increased 24-h urinary protein, urea nitrogen, and nephrin expression and decreased TRPC6 expression without significant changes in fasting blood glucose, serum creatinine, or VEGF expression. The rats treated with LY294002 showed decreased 24-h urinary protein and TRPC6 expression without significant changes in fasting blood glucose, serum creatinine, urea nitrogen, or expressions of nephrin and VEGF.

CONCLUSION

The regulatory effect of VEGF on TRPC6 can be blocked by inhibiting VEGFR-2 or blocking PI3K/Akt signaling pathway.

COMP-angiopoietin-1 mitigates changes in lipid droplet size, macrophage infiltration of adipose tissue and renal inflammation in streptozotocin-induced diabetic mice

Adipose tissue is considered to be an endocrine organ, and adipocyte size correlates with insulin resistance and metabolic parameters in obesity. There is little data on the effects of angiopoietin-1 in adipose tissue and kidney in streptozotocin (STZ)-induced diabetes. In this study, we investigated the protective effect of COMP-angiopoietin-1 (COMP-Ang1), a potent variant of angiopoietin-1, on vascular endothelial cells in epididymal adipose tissue and its regulatory effect on other metabolic parameters, such as lipid droplet diameter, macrophage infiltration, and renal inflammation in STZ-treated mice. Our data showed that COMP-Ang1 increased the density of platelet endothelial cell adhesion molecule-1 (PECAM-1)-1-positive vascular endothelial cells in adipose tissue, which were significantly decreased by treatment with STZ. COMP-Ang1 ameliorated the STZ–induced decrease in lipid droplet diameter and increase in macrophage infiltration in adipose tissue. Serum free fatty acid and triglyceride levels were decreased after administration of COMP-Ang1. There was a beneficial effect on serum insulin levels after treatment with COMP-Ang1 in STZ-induced diabetic mice. Fasting blood glucose levels in COMP-Ang1-treated mice were significantly lower than those of LacZ-treated mice. Cotreatment with COMP-Ang1 and STZ also had similar effects on the above parameters. Administration of soluble Tie2, an inhibitor of angiopoietin-1, reversed the effects of COMP-Ang1. COMP-Ang1 was found to ameliorate the up-regulation of proinflammatory molecules and F4/80-positive macrophage infiltration in the kidneys of STZ-treated mice. COMP-Ang1 increased the phosphorylation of Akt in epididymal adipose tissue and kidneys of STZ-induced diabetic mice. These data indicate that COMP-Ang1 regulates lipogenic effects in adipose tissue and renal inflammation in STZ-induced diabetic mice.

GYY4137, a Hydrogen Sulfide Donor Modulates miR194-Dependent Collagen Realignment in Diabetic Kidney

The relationship between hydrogen sulfide (H₂S), microRNAs (miRs), matrix metalloproteinases (MMPs) and poly-ADP-ribose-polymerase-1 (PARP-1) in diabetic kidney remodeling remains mostly obscured. We aimed at investigating whether alteration of miR-194-dependent MMPs and PARP-1 causes renal fibrosis in diabetes kidney, and whether H₂S ameliorates fibrosis. Wild type, diabetic Akita mice as well as mouse glomerular endothelial cells (MGECs) were used as experimental models, and GYY4137 as H₂S donor. In diabetic mice, plasma H₂S levels were decreased while ROS and expression of its modulator (ROMO1) were increased. In addition, alteration of MMPs-9, −13 and −14 expression, PARP-1, HIF1α, and increased collagen biosynthesis as well as collagen cross-linking protein, P4HA1 and PLOD2 were observed along with diminished vascular density in diabetic kidney. These changes were ameliorated by GYY4137. Further, downregulated miRNA-194 was normalized by GYY4137 in diabetic kidney. Similar results were obtained in in vitro condition. Interestingly, miR-194 mimic also diminished ROS production, and normalized ROMO1, MMPs-9, −13 and −14, and PARP-1 along with collagen biosynthesis and cross-linking protein in HG condition. We conclude that decrease H₂S diminishes miR-194, induces collagen deposition and realignment leading to fibrosis and renovascular constriction in diabetes. GYY4137 mitigates renal fibrosis in diabetes through miR-194-dependent pathway.