Overexpression of Sirt6 promotes M2 macrophage transformation, alleviating renal injury in diabetic nephropathy

Sirt6 overexpression relieves ferroptosis and delays the progression of diabetic nephropathy via Nrf2/GPX4 pathway

OBJECTIVE

Sirt6, reactive oxygen species and ferroptosis may participate in the pathogenesis of Diabetic Nephropathy (DN). Exploring the relationship between Sirt6, oxidative stress, and ferroptosis provides new scientific ideas to DN.

METHODS

Human podocytes were stimulated with 30 mM glucose and 5.5 mM glucose. The mice of db/db group were randomly divided into two groups:12 weeks and 16 weeks. Collect mouse blood and urine specimens and renal cortices for investigations. HE, Masson, PAS and immunohistochemical staining were used to observe pathological changes. Western blot, RT-qPCR and immunofluorescence staining were used to evaluate expression of relevant molecules. CCK8 method was introduced to observe cell viability. The changes of podocyte mitochondrial membrane potential and mitochondrial morphology in each group were determined by JC-1 staining and Mito-Tracker.

RESULTS

The expression level of Sirt6, Nrf2, SLC7A11, HO1, SOD2 and GPX4 were reduced, while ACSL4 was increased in DN. Blood glucose, BUN, Scr, TG, T-CHO and 24h urine protein were upregulated, while ALB was reduced in diabetic group. The treatment of Ferrostatin-1 significantly improved these changes, which proved ferroptosis was involved in the development of DN. Overexpression of Sirt6 might ameliorate the oxidation irritable reaction and ferroptosis. Sirt6 plasmid transfection increased mitochondrial membrane potential and protected morphology and structure of mitochondria. The application of Sirt6 siRNA could aggravated the damage manifestations.

CONCLUSION

High glucose stimulation could decrease the antioxidant capacity and increase formation of ROS and lipid peroxidation. Sirt6 might alleviate HG-induced mitochondrial dysfunction, podocyte injury and ferroptosis through regulating Nrf2/GPX4 pathway.

Sirtuins in kidney health and disease

Sirtuins (SIRTs) are putative regulators of lifespan in model organisms. Since the initial discovery that SIRTs could promote longevity in nematodes and flies, the identification of additional properties of these proteins has led to understanding of their roles as exquisite sensors that link metabolic activity to oxidative states. SIRTs have major roles in biological processes that are important in kidney development and physiological functions, including mitochondrial metabolism, oxidative stress, autophagy, DNA repair and inflammation. Furthermore, altered SIRT activity has been implicated in the pathophysiology and progression of acute and chronic kidney diseases, including acute kidney injury, diabetic kidney disease, chronic kidney disease, polycystic kidney disease, autoimmune diseases and renal ageing. The renoprotective roles of SIRTs in these diseases make them attractive therapeutic targets. A number of SIRT-activating compounds have shown beneficial effects in kidney disease models; however, further research is needed to identify novel SIRT-targeting strategies with the potential to treat and/or prevent the progression of kidney diseases and increase the average human healthspan.

The Role of Immune Cells in DKD: Mechanisms and Targeted Therapies

Diabetic kidney disease (DKD), is a common microvascular complication and a major cause of death in patients with diabetes. Disorders of immune cells and immune cytokines can accelerate DKD development of in a number of ways. As the kidney is composed of complex and highly differentiated cells, the interactions among different cell types and immune cells play important regulatory roles in disease development. Here, we summarize the latest research into the molecular mechanisms underlying the interactions among various immune and renal cells in DKD. In addition, we discuss the most recent studies related to single cell technology and bioinformatics analysis in the field of DKD. The aims of our review were to explore immune cells as potential therapeutic targets in DKD and provide some guidance for future clinical treatments.

Downregulating lncRNA MIAT attenuates apoptosis of podocytes exposed to high glucose

AIMS

Diabetic nephropathy (DN), a destructive complication of diabetes mellitus (DM), is one of the leading causes of end-stage renal disease (ESRD). This study aimed to investigate the role of long non-coding RNA (lncRNA) MIAT in high-glucose (HG)-induced podocyte injury associated with DN.

METHODS

Three human kidney podocyte (HKP) cultures were treated with HG to mimic DN. Expression of lncRNA MIAT, podocyte-specific and injury-related proteins, and apoptosis were assessed before and after MIAT knockdown using MIAT shRNAs.

RESULTS

MIAT expression was upregulated in HKPs in response to glucose stress. HG treatment resulted in a significant increase in the apoptotic rate, Bax level, and levels of injury-related proteins desmin, fibroblast-specific protein 1 (FSP-1), and smooth muscle α-actin (α-SMA), and a significant reduction in Bcl-2 levels and the levels of podocyte-specific proteins synaptopodin and podocin. Transfection of HKPs with shRNAs significantly reduced MIAT levels (p < 0.05) and attenuated apoptosis in HG-medium. Correspondingly, the levels of synaptopodin and podocin were upregulated, and desmin, FSP-1, and α-SMA were reduced (p < 0.05). Western blot analysis also showed that anti-apoptotic active caspase-3 and Bax and proapoptotic Bcl-2 were elevated and decreased, respectively, after MIAT knockdown, suggesting that apoptosis pathways are deactivated after MIAT downregulation.

CONCLUSIONS

High glucose upregulates MIAT level in HKPs and induces cellular injury. Knockdown of MIAT alleviates the injury likely via deactivating apoptosis pathways.

Macrophage polarization and signaling in diabetic kidney disease: a catalyst for disease progression

Diabetic kidney disease (DKD) is a serious complication of diabetes affecting millions of people worldwide. Macrophages, a critical immune cell type, are central players in the development and progression of DKD. In this comprehensive review, we delve into the intricate role of macrophages in DKD, examining how they can become polarized into proinflammatory M1 or anti-inflammatory M2 phenotypes. We explore the signaling pathways involved in macrophage recruitment and polarization in the kidneys, including the key cytokines and transcription factors that promote M1 and M2 polarization. In addition, we discuss the latest clinical studies investigating macrophages in DKD and explore the potential of hypoglycemic drugs for modulating macrophage polarization. By gaining a deeper understanding of the mechanisms that regulate macrophage polarization in DKD, we may identify novel therapeutic targets for this debilitating complication of diabetes. This review provides valuable insights into the complex interplay between macrophages and DKD, shedding light on the latest developments in this important area of research. This review aims to enhance understanding of the role that macrophages play in the pathogenesis of DKD.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Sirtuin 6 protects against podocyte injury by blocking the renin-angiotensin system by inhibiting the Wnt1/β-catenin pathway

Sirtuins (Sirts) are a family of nicotinamide adenine dinucleotide-dependent protein deacetylases that share diverse cellular functions. Increasing evidence shows that Sirts play a critical role in podocyte injury, which is a major determinant of proteinuria-associated renal disease. Membranous nephropathy (MN) is a typical glomerular disease in which podocyte damage mediates proteinuria development. In this study we investigated the molecular mechanisms underlying the regulatory roles of Sirt in podocyte injury in MN patients, rats with cationic bovine serum albumin (CBSA)-induced MN and zymosan activation serum (ZAS)-stimulated podocytes. Compared with healthy controls, MN patients showed significant reduction in intrarenal Sirt1 and Sirt6 protein expression. In CBSA-induced MN rats, significant reduction in intrarenal Sirt1, Sirt3 and Sirt6 protein expression was observed. However, only significant decrease in Sirt6 protein expression was found in ZAS-stimulated podocytes. MN patients showed significantly upregulated protein expression of Wnt1 and β-catenin and renin-angiotensin system (RAS) components in glomeruli. CBSA-induced MN rats exhibited significantly upregulated protein expression of intrarenal Wnt1 and β-catenin and their downstream gene products as well as RAS components. Similar results were observed in ZAS-stimulated podocytes. In ZAS-stimulated podocytes, treatment with a specific Sirt6 activator UBCS039 preserved the protein expression of podocin, nephrin and podocalyxin, accompanied by significant inhibition of the protein expression of β-catenin and its downstream gene products, including Snail1 and Twist; treatment with a β-catenin inhibitor ICG-001 significantly preserved the expression of podocyte-specific proteins and inhibited the upregulation of downstream β-catenin gene products accompanied by significant suppression of the protein expression of RAS components. Thus, we demonstrate that Sirt6 ameliorates podocyte injury by blocking RAS signalling via the Wnt1/β-catenin pathway. Sirt6 is a specific therapeutic target for the treatment of podocyte damage-associated renal disease.

Protein acetylation and related potential therapeutic strategies in kidney disease

Kidney disease can be caused by various internal and external factors that have led to a continual increase in global deaths. Current treatment methods can alleviate but do not markedly prevent disease development. Further research on kidney disease has revealed the crucial function of epigenetics, especially acetylation, in the pathology and physiology of the kidney. Histone acetyltransferases (HATs), histone deacetylases (HDACs), and acetyllysine readers jointly regulate acetylation, thus affecting kidney physiological homoeostasis. Recent studies have shown that acetylation improves mechanisms and pathways involved in various types of nephropathy. The discovery and application of novel inhibitors and activators have further confirmed the important role of acetylation. In this review, we provide insights into the physiological process of acetylation and summarise its specific mechanisms and potential therapeutic effects on renal pathology.

SIRT6's function in controlling the metabolism of lipids and glucose in diabetic nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus (DM) and the main cause of excess mortality in patients with type 2 DM. The pathogenesis and progression of DN are closely associated with disorders of glucose and lipid metabolism. As a member of the sirtuin family, SIRT6 has deacetylation, defatty-acylation, and adenosine diphosphate-ribosylation enzyme activities as well as anti-aging and anticancer activities. SIRT6 plays an important role in glucose and lipid metabolism and signaling, especially in DN. SIRT6 improves glucose and lipid metabolism by controlling glycolysis and gluconeogenesis, affecting insulin secretion and transmission and regulating lipid decomposition, transport, and synthesis. Targeting SIRT6 may provide a new therapeutic strategy for DN by improving glucose and lipid metabolism. This review elaborates on the important role of SIRT6 in glucose and lipid metabolism, discusses the potential of SIRT6 as a therapeutic target to improve glucose and lipid metabolism and alleviate DN occurrence and progression of DN, and describes the prospects for future research.

Downregulation of SIRT6 and NMNAT2 is associated with proliferative diabetic retinopathy

Purpose

To determine the expression levels of SIRT6 and NMNAT2 in diabetic retinopathy (DR).

Methods

We obtained peripheral blood mononuclear cells (PBMCs) and vitreous samples from 77 patients with type 2 diabetes mellitus: 52 with DR and 25 without DR, and 27 healthy control subjects. Western blot analysis and qRT-PCR were performed to evaluate the expression of SIRT6 and NMNAT2 in their PBMCs. The levels of IL-1β, IL-6, and TNF-α in the vitreous fluid were determined by ELISA. Immunohistochemistry was performed to detect the expression of SIRT6 and NMNAT2 in proliferative DR (PDR) and the control subjects.

Results

The expression of SIRT6 and NMNAT2 was markedly downregulated in DR patients, which was negatively correlated with the increased expression of IL-1β, IL-6 and TNF-α. Additionally, we observed decreased expression of SIRT6 and NMNAT2 in the fibrovascular membranes of PDR patients.

Conclusions

The downregulated expression of SIRT6 and NMNAT2 in PDR patients reveals a potential pathogenic association; more extended studies could verify them as potential therapeutic targets.

Regulation of autophagy by natural polyphenols in the treatment of diabetic kidney disease: therapeutic potential and mechanism

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes and a leading cause of end-stage renal disease worldwide. Autophagy plays an important role in maintaining cellular homeostasis in renal physiology. In DKD, the accumulation of advanced glycation end products induces decreased renal autophagy-related protein expression and transcription factor EB (TFEB) nuclear transfer, leading to impaired autophagy and lysosomal function and blockage of autophagic flux. This accelerates renal resident cell injury and apoptosis, mediates macrophage infiltration and phenotypic changes, ultimately leading to aggravated proteinuria and fibrosis in DKD. Natural polyphenols show promise in treating DKD by regulating autophagy and promoting nuclear transfer of TFEB and lysosomal repair. This review summarizes the characteristics of autophagy in DKD, and the potential application and mechanisms of some known natural polyphenols as autophagy regulators in DKD, with the goal of contributing to a deeper understanding of natural polyphenol mechanisms in the treatment of DKD and promoting the development of their applications. Finally, we point out the limitations of polyphenols in current DKD research and provide an outlook for their future research.

Visualizing temporal dynamics and research trends of macrophage-related diabetes studies between 2000 and 2022: a bibliometric analysis

Background

Macrophages are considered an essential source of inflammatory cytokines, which play a pivotal role in the development of diabetes and its sequent complications. Therefore, a better understanding of the intersection between the development of diabetes and macrophage is of massive importance.

Objectives

In this study, we performed an informative bibliometric analysis to enlighten relevant research directions, provide valuable metrics for financing decisions, and help academics to gain a quick understanding of the current macrophage-related diabetes studies knowledge domain.

Methods

The Web of Science Core Collection database was used for literature retrieval and dataset export. Bibliometrix R-package was performed to conduct raw data screening, calculating, and visualizing.

Results

Between 2000 and 2022, the annual publication and citation trends steadily increased. Wu Yonggui was the scholar with the most published papers in this field. The institute with the highest number of published papers was the University of Michigan. The most robust academic collaboration was observed between China and the United States of America. Diabetologia was the journal that published the most relevant publications. The author's keywords with the highest occurrences were "inflammation", "diabetic nephropathy", and "obesity". In addition, "Macrophage polarization" was the current motor topic with potential research prospects.

Conclusions

These comprehensive and visualized bibliometric results summarized the significant findings in macrophage-related diabetes studies over the past 20 years. It would enlighten subsequent studies from a macro viewpoint and is also expected to strengthen investment policies in future macrophage-related diabetes studies.

A bifunctional fusion protein protected against diabetic nephropathy by suppressing NLRP3 activation

Diabetic nephropathy (DN), the principal pathogeny of end-stage renal disease (ESRD), is related to metabolic disorders, chronic inflammation, and oxidative stress. It was reported that high expression of interleukin-17A (IL-17A) was intimately related to the progression of DN, and targeting IL-17A exhibited regulating effects on inflammation and autoimmunity but had only limited impact on the oxidative stress damage in DN. Recent studies showed that interleukin-22 (IL-22) could inhibit mitochondrial damage and inflammatory response. Thus, the cytokine IL-22 was first fused to anti-IL-17A antibody for endowing the antibody with the anti-hyperglycemia and anti-inflammation activity. Our study demonstrated that the fusion molecule, anti-IL17A/IL22 fusion protein, could not only lead to the increase of M1 macrophages and the decrease of M2 macrophages, further improving the immune microenvironment, but also prevent the loss of mitochondrial membrane potential by reducing the production of ROS in murine DN model. In addition, the fusion protein could block TRAF6/NF-κB and AKT/ROS/TXNIP signaling pathways, further synergistically restraining the production of NLRP3, thus suppressing the inflammatory response and playing beneficial effect on slowing down the progression of DN. In conclusion, our findings demonstrated that the bifunctional IL-17A antibody and IL-22 fusion protein were of great benefit to DN, which highlighted a potential therapeutic strategy. KEY POINTS: • Anti-IL17A/IL22 fusion protein could improve the immune microenvironment and reduce the production of ROS. • Anti-IL17A/IL22 fusion protein could block TRAF6/NF-κB and AKT/ROS/TXNIP signaling pathways and then restrain the activation of NLRP3.

Single-cell RNA and transcriptome sequencing profiles identify immune-associated key genes in the development of diabetic kidney disease

Background

There is a growing public concern about diabetic kidney disease (DKD), which poses a severe threat to human health and life. It is important to discover noninvasive and sensitive immune-associated biomarkers that can be used to predict DKD development. ScRNA-seq and transcriptome sequencing were performed here to identify cell types and key genes associated with DKD.

Methods

Here, this study conducted the analysis through five microarray datasets of DKD (GSE131882, GSE1009, GSE30528, GSE96804, and GSE104948) from gene expression omnibus (GEO). We performed single-cell RNA sequencing analysis (GSE131882) by using CellMarker and CellPhoneDB on public datasets to identify the specific cell types and cell-cell interaction networks related to DKD. DEGs were identified from four datasets (GSE1009, GSE30528, GSE96804, and GSE104948). The regulatory relationship between DKD-related characters and genes was evaluated by using WGCNA analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) datasets were applied to define the enrichment of each term. Subsequently, immune cell infiltration between DKD and the control group was identified by using the “pheatmap” package, and the connection Matrix between the core genes and immune cell or function was illuminated through the “corrplot” package. Furthermore, RcisTarget and GSEA were conducted on public datasets for the analysis of the regulation relationship of key genes and it revealed the correlation between 3 key genes and top the 20 genetic factors involved in DKD. Finally, the expression of key genes between patients with 35 DKD and 35 healthy controls were examined by ELISA, and the relationship between the development of DKD rate and hub gene plasma levels was assessed in a cohort of 35 DKD patients. In addition, we carried out immunohistochemistry and western blot to verify the expression of three key genes in the kidney tissue samples we obtained.

Results

There were 8 cell types between DKD and the control group, and the number of connections between macrophages and other cells was higher than that of the other seven cell groups. We identified 356 different expression genes (DEGs) from the RNA-seq, which are enriched in urogenital system development, kidney development, platelet alpha granule, and glycosaminoglycan binding pathways. And WGCNA was conducted to construct 13 gene modules. The highest correlations module is related to the regulation of cell adhesion, positive regulation of locomotion, PI3K-Akt, gamma response, epithelial-mesenchymal transition, and E2F target signaling pathway. Then we overlapped the DEGs, WGCNA, and scRNA-seq, SLIT3, PDE1A and CFH were screened as the closely related genes to DKD. In addition, the findings of immunological infiltration revealed a remarkable positive link between T cells gamma delta, Macrophages M2, resting mast cells, and the three critical genes SLIT3, PDE1A, and CFH. Neutrophils were considerably negatively connected with the three key genes. Comparatively to healthy controls, DKD patients showed high levels of SLIT3, PDE1A, and CFH. Despite this, higher SLIT3, PDE1A, and CFH were associated with an end point rate based on a median follow-up of 2.6 years. And with the gradual deterioration of DKD, the expression of SLIT3, PDE1A, and CFH gradually increased.

Conclusions

The 3 immune-associated genes could be used as diagnostic markers and therapeutic targets of DKD. Additionally, we found new pathogenic mechanisms associated with immune cells in DKD, which might lead to therapeutic targets against these cells.

Yi-Shen-Hua-Shi granules inhibit diabetic nephropathy by ameliorating podocyte injury induced by macrophage-derived exosomes

Objective: To observe the therapeutic effect of Yi-Shen-Hua-Shi (YSHS) granule in podocyte damage and diabetic nephropathy (DN) proteinuria and to explore the corresponding mechanism. Methods: The db/db mice were used to establish the DN model. Serum creatinine (SCr), blood urea nitrogen (BUN), and 24 h urinary proteinuria were detected with specific kits. Glomerular structural lesions and podocyte apoptosis were detected through HE staining, TUNEL assay, and immunofluorescence. The medicated serum of YSHS granule (YSHS-serum) or control serum was prepared. Macrophage-derived exosomes were extracted using an exosome extraction kit. Morphology and the protein concentration of exosomes were evaluated by a transmission electron microscope (TEM) and BCA kit. The activity and apoptosis of podocyte MPC5 cells, the M1 macrophage polarization, and the protein expression of an exosome marker and cleaved caspase were detected by the CCK8 experiment, flow cytometry, and Western blot, respectively. The miR-21a-5p expression in podocytes and the exosomes from macrophages were measured by qRT-PCR. The effect of YSHS granule on the infiltration of M1 macrophages in the kidney tissue in db/db mice was measured by immunofluorescence. Results: The YSHS granule could improve renal function, reduce proteinuria, and inhibit glomerular structural lesions and podocyte apoptosis in db/db mice. High-glucose (HG) stimulation and YSHS granule treatment did not affect the protein concentration in macrophage-derived exosomes. Macrophage-derived exosomes could inhibit the cell viability and increase apoptosis of podocytes, especially the exosomes from macrophages treated with HG and control serum. Compared with the exosomes secreted by macrophages after an HG treatment, the exosome from macrophages treated with HG and YSHS granule showed lower inhibitory effects on podocyte activity, accompanied by the decreased upregulating effects of macrophage-derived exosomes on the miR-21a-5p in podocytes. miR-21a-5p mimics could reduce podocyte activity and promote caspase-3 shearing. M1 polarization of macrophages could change the content of miR-21a-5p in macrophage-derived exosomes. In addition, YSHS granule could inhibit HG-induced M1 polarization of macrophages and M1 macrophage infiltration in renal tissues. Conclusion: The YSHS granule could improve the podocyte injury induced by macrophage-derived exosomes and alleviate the progression of DN. This regulation might be related to the inhibition of M1 macrophage polarization by YSHS granule and the reduction of the miR-21a-5p content in macrophage-derived exosomes.

Roles and crosstalks of macrophages in diabetic nephropathy

Diabetic nephropathy (DN) is the most common chronic kidney disease. Accumulation of glucose and metabolites activates resident macrophages in kidneys. Resident macrophages play diverse roles on diabetic kidney injuries by releasing cytokines/chemokines, recruiting peripheral monocytes/macrophages, enhancing renal cell injuries (podocytes, mesangial cells, endothelial cells and tubular epithelial cells), and macrophage-myofibroblast transition. The differentiation and cross-talks of macrophages ultimately result renal inflammation and fibrosis in DN. Emerging evidence shows that targeting macrophages by suppressing macrophage activation/transition, and macrophages-cell interactions may be a promising approach to attenuate DN. In the review, we summarized the diverse roles of macrophages and the cross-talks to other cells in DN, and highlighted the therapeutic potentials by targeting macrophages.

Protective effects of budesonide on LPS‑induced podocyte injury by modulating macrophage M1/M2 polarization: Evidence from in vitro and in silico studies

Budesonide (Bud), one of the most widely used lung medicines, is currently used as a repurposing medicine for immunoglobulin A nephropathy (IgAN) treatment. The progression of IgAN is related to inflammation involving macrophages and podocytes. The present study aimed to explore the effects of Bud on classically activated (M1)/alternatively activated (M2) macrophage polarization and podocyte injury under lipopolysaccharide (LPS)-induced inflammatory stress in vitro. Anti-inflammatory bioinformation of Bud was identified based on the Gene Expression Omnibus database. RAW264.7 cells were treated with normal medium, LPS, curcumin (Cur, positive control), or Bud 5, 10, or 20 µM. The expression levels of inducible nitric oxide synthase (iNOS), TNF-α, mannose receptor (CD206) and arginase (Arg)-1 were quantified by western blotting. The collected supernatants from macrophages were termed (Nor)MS, (LPS)MS, (Cur)MS and (Bud)MS. The TNF-α, IL-1β and nitric oxide (NO) levels in the supernatants were evaluated by ELISA and Griess assay. The podocytes were cultured in different supernatants and their survival rates were assessed by bromodeoxyuridine assay. TNF signaling is an important pathway by which Bud exerts anti-inflammatory activities. Compared with the LPS group, 5, 10 and 20 µM Bud significantly increased Arg-1 and decreased iNOS expression (Six: P<0.05) and 20 µM Bud significantly increased Arg-1 and CD206 and decreased iNOS and TNF-α expression (Four: P<0.05). Cur significantly decreased iNOS and TNF-α expression (Two: P<0.05). Compared with LPS, 5, 10 and 20 µM Bud and Cur significantly decreased TNF-α, IL-1β and NO levels (All: P<0.05). The podocyte survival rates of (Bud)MS and (Cur)MS were significantly higher than those of (LPS)MS (Four: P<0.05). The protective effect of Bud on podocyte injury is related to its modulation of M1/M2 polarization.

CircRNA ITCH: Insight Into Its Role and Clinical Application Prospect in Tumor and Non-Tumor Diseases

CircRNA E3 ubiquitin protein ligase (ITCH) (circRNA ITCH, circ-ITCH), a stable closed-loop RNA derived from the 20q11.22 region of chromosome 20, is a new circRNA discovered in the cytoplasm in recent decades. Studies have shown that it does not encode proteins, but regulates proteins expression at different levels. It is down-regulated in tumor diseases and is involved in a number of biological activities, including inhibiting cell proliferation, migration, invasion, and promoting apoptosis. It can also alter disease progression in non-tumor disease by affecting the cell cycle, inflammatory response, and critical proteins. Circ-ITCH also holds a lot of promise in terms of tumor and non-tumor clinical diagnosis, prognosis, and targeted therapy. As a result, in order to aid clinical research in the hunt for a new strategy for diagnosing and treating human diseases, this study describes the mechanism of circ-ITCH as well as its clinical implications.

Screening and Identification of Hub Genes in the Development of Early Diabetic Kidney Disease Based on Weighted Gene Co-Expression Network Analysis

Objective

The study aimed to screen key genes in early diabetic kidney disease (DKD) and predict their biological functions and signaling pathways using bioinformatics analysis of gene chips interrelated to early DKD in the Gene Expression Omnibus database.

Methods

Gene chip data for early DKD was obtained from the Gene Expression Omnibus expression profile database. We analyzed differentially expressed genes (DEGs) between patients with early DKD and healthy controls using the R language. For the screened DEGs, we predicted the biological functions and relevant signaling pathways by enrichment analysis of Gene Ontology (GO) biological functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways. Using the STRING database and Cytoscape software, we constructed a protein interaction network to screen hub pathogenic genes. Finally, we performed immunohistochemistry on kidney specimens from the Beijing Hospital to verify the above findings.

Results

A total of 267 differential genes were obtained using GSE142025, namely, 176 upregulated and 91 downregulated genes. GO functional annotation enrichment analysis indicated that the DEGs were mainly involved in immune inflammatory response and cytokine effects. KEGG pathway analysis indicated that C-C receptor interactions and the IL-17 signaling pathway are essential for early DKD. We identified FOS, EGR1, ATF3, and JUN as hub sites of protein interactions using a protein-protein interaction network and module analysis. We performed immunohistochemistry (IHC) on five samples of early DKD and three normal samples from the Beijing Hospital to label the proteins. This demonstrated that FOS, EGR1, ATF3, and JUN in the early DKD group were significantly downregulated.

Conclusion

The four hub genes FOS, EGR1, ATF3, and JUN were strongly associated with the infiltration of monocytes, M2 macrophages, and T regulatory cells in early DKD samples. We revealed that the expression of immune response or inflammatory genes was suppressed in early DKD. Meanwhile, the FOS group of low-expression genes showed that the activated biological functions included mRNA methylation, insulin receptor binding, and protein kinase A binding. These genes and pathways may serve as potential targets for treating early DKD.

SIRT6 Widely Regulates Aging, Immunity, and Cancer

SIRT6 is a member of the Sir2-like family in mammals. Recent structural and biochemical studies have characterized SIRT6 as having deacetylation, defatty-acylation, and mono-ADP-ribosylation activities, which determine its important regulatory roles during physiological and pathological processes. This review focuses mainly on the regulatory functions of SIRT6 in aging, cancer, and, especially, immunity. Particular attention is paid to studies illustrating the critical role of SIRT6 in the regulation of immune cells from the viewpoints of immunesenescence, immunometabolism, and tumor immunology. Owing to its role in regulating the function of the immune system, SIRT6 can be considered to be a potential therapeutic target for the treatment of diseases.

Circular RNA ITCH: An Emerging Multifunctional Regulator

In the last decade, numerous circRNAs were discovered by virtue of the RNA-Seq technique. With the deepening of experimental research, circRNAs have brought to light the key biological functions and progression of human diseases. CircRNA ITCH has been demonstrated to be a tumor suppressor in numerous cancers, and recently it was found to play an important role in bone diseases, diabetes mellitus, and cardiovascular diseases. However, the functions of circ-ITCH have not been completely understood. In this review, we comprehensively provide a conceptual framework to elucidate circ-ITCH biological functions of cell proliferation, apoptosis and differentiation, and the pathological mechanisms of inflammation, drug resistance/toxicity, and tumorigenesis. Finally, we summarize its clinical applications in various diseases. This research aimed at clarifying the role of circ-ITCH, which could be a promising therapeutic target.

SIRT1-SIRT7 in Diabetic Kidney Disease: Biological Functions and Molecular Mechanisms

Diabetic kidney disease (DKD) is a severe microvascular complication in patients with diabetes and is one of the main causes of renal failure. The current clinical treatment methods for DKD are not completely effective, and further exploration of the molecular mechanisms underlying the pathology of DKD is necessary to improve and promote the treatment strategy. Sirtuins are class III histone deacetylases, which play an important role in many biological functions, including DNA repair, apoptosis, cell cycle, oxidative stress, mitochondrial function, energy metabolism, lifespan, and aging. In the last decade, research on sirtuins and DKD has gained increasing attention, and it is important to summarize the relationship between DKD and sirtuins to increase the awareness of DKD and improve the cure rates. We have found that miRNAs, lncRNAs, compounds, or drugs that up-regulate the activity and expression of sirtuins play protective roles in renal function. Therefore, in this review, we summarize the biological functions, molecular targets, mechanisms, and signaling pathways of SIRT1-SIRT7 in DKD models. Existing research has shown that sirtuins have the potential as effective targets for the clinical treatment of DKD. This review aims to lay a solid foundation for clinical research and provide a theoretical basis to slow the development of DKD in patients.

Sirtuin Family and Diabetic Kidney Disease

Diabetes mellitus (DM) is gradually attacking the health and life of people all over the world. Diabetic kidney disease (DKD) is one of the most common chronic microvascular complications of DM, whose mechanism is complex and still lacks research. Sirtuin family is a class III histone deacetylase with highly conserved NAD⁺ binding domain and catalytic functional domain, while different N-terminal and C-terminal structures enable them to bind different deacetylated substrates to participate in the cellular NAD⁺ metabolism. The kidney is an organ rich in NAD⁺ and database exploration of literature shows that the Sirtuin family has different expression localization in renal, cellular, and subcellular structures. With the progress of modern technology, a variety of animal models and reagents for the Sirtuin family and DKD emerged. Machine learning in the literature shows that the Sirtuin family can regulate pathophysiological injury mainly in the glomerular filtration membrane, renal tubular absorption, and immune inflammation through various mechanisms such as epigenetics, multiple signaling pathways, and mitochondrial function. These mechanisms are the key nodes participating in DKD. Thus, it is of great significance for target therapy to study biological functions of the Sirtuin family and DKD regulation mechanism in-depth.

Identification of copper-related biomarkers and potential molecule mechanism in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a chronic microvascular complication in patients with diabetes mellitus, which is the leading cause of end-stage renal disease. However, the role of copper-related genes (CRGs) in DN development remains unclear.

MATERIALS AND METHODS

CRGs were acquired from the GeneCards and NCBI databases. Based on the GSE96804 and GSE111154 datasets from the GEO repository, we identified hub CRGs for DN progression by taking the intersection of differentially expressed CRGs (DECRGs) and genes in the key module from Weighted Gene Co-expression Network Analysis. The Maximal Clique Centrality algorithm was used to identify the key CRGs from hub CRGs. Transcriptional factors (TFs) and microRNAs (miRNAs) targeting hub CRGs were acquired from publicly available databases. The CIBERSORT algorithm was used to perform comparative immune cell infiltration analysis between normal and DN samples.

RESULTS

Eighty-two DECRGs were identified between normal and DN samples, as were 10 hub CRGs, namely PTGS2, DUSP1, JUN, FOS, S100A8, S100A12, NAIP, CLEC4E, CXCR1, and CXCR2. Thirty-nine TFs and 165 miRNAs potentially targeted these 10 hub CRGs. PTGS2 was identified as the key CRG and FOS as the most significant gene among all of DECRGs. RELA was identified as the hub TF interacting with PTGS2 by taking the intersection of potential TFs from the ChEA and JASPAR public databases. let-7b-5p was identified as the hub miRNA targeting PTGS2 by taking the intersection of miRNAs from the miRwalk, RNA22, RNAInter, TargetMiner, miRTarBase, and ENCORI databases. Similarly, CREB1, E2F1, and RELA were revealed as hub TFs for FOS, and miR-338-3p as the hub miRNA. Finally, compared with those in healthy samples, there are more infiltrating memory B cells, M1 macrophages, M2 macrophages, and resting mast cells and fewer infiltrating activated mast cells and neutrophils in DN samples (all p< 0.05).

CONCLUSION

The 10 identified hub copper-related genes provide insight into the mechanisms of DN development. It is beneficial to examine and understand the interaction between hub CRGs and potential regulatory molecules in DN. This knowledge may provide a novel theoretical foundation for the development of diagnostic biomarkers and copper-related therapy targets in DN.

Roles of SIRT6 in kidney disease: a novel therapeutic target

SIRT6 is an NAD+ dependent deacetylase that belongs to the mammalian sirtuin family. SIRT6 is mainly located in the nucleus and regulates chromatin remodeling, genome stability, and gene transcription. SIRT6 extensively participates in various physiological activities such as DNA repair, energy metabolism, oxidative stress, inflammation, and fibrosis. In recent years, the role of epigenetics such as acetylation modification in renal disease has gradually received widespread attention. SIRT6 reduces oxidative stress, inflammation, and renal fibrosis, which is of great importance in maintaining cellular homeostasis and delaying the chronic progression of kidney disease. Here, we review the structure and biological function of SIRT6 and summarize the regulatory mechanisms of SIRT6 in kidney disease. Moreover, the role of SIRT6 as a potential therapeutic target for the progression of kidney disease will be discussed. SIRT6 plays an important role in kidney disease. SIRT6 regulates mitochondrial dynamics and mitochondrial biogenesis, induces G2/M cycle arrest, and plays an antioxidant role in nephrotoxicity, IR, obstructive nephropathy, and sepsis-induced AKI. SIRT6 prevents and delays progressive CKD induced by hyperglycemia, kidney senescence, hypertension, and lipid accumulation by regulating mitochondrial biogenesis, and has antioxidant, anti-inflammatory, and antifibrosis effects. Additionally, hypoxia, inflammation, and fibrosis are the main mechanisms of the AKI-to-CKD transition. SIRT6 plays a critical role in the AKI-to-CKD transition and kidney repair through anti-inflammatory, antifibrotic, and mitochondrial quality control mechanisms. AKI Acute kidney injury, CKD Chronic kidney disease.

Hyperoside Suppresses Renal Inflammation by Regulating Macrophage Polarization in Mice With Type 2 Diabetes Mellitus

Accumulating evidence reveals that both inflammation and lymphocyte dysfunction play a vital role in the development of diabetic nephropathy (DN). Hyperoside (HPS) or quercetin-3-O-galactoside is an active flavonoid glycoside mainly found in the Chinese herbal medicine Tu-Si-Zi. Although HPS has a variety of pharmacological effects, including anti-oxidative and anti-apoptotic activities as well as podocyte-protective effects, its underlying anti-inflammatory mechanisms remain unclear. Herein, we investigated the therapeutic effects of HPS on murine DN and the potential mechanisms responsible for its efficacy. We used C57BLKS/6J ^Lepdb/db mice and a high glucose (HG)-induced bone marrow-derived macrophage (BMDM) polarization system to investigate the potentially protective effects of HPS on DN. Our results showed that HPS markedly reduced diabetes-induced albuminuria and glomerular mesangial matrix expansion, accompanied with a significant improvement of fasting blood glucose level, hyperlipidaemia and body weight. Mechanistically, pretreatment with HPS effectively regulated macrophage polarization by shifting proinflammatory M1 macrophages (F4/80⁺CD11b⁺CD86⁺) to anti-inflammatory M2 ones (F4/80⁺CD11b⁺CD206⁺) in vivo and in bone marrow-derived macrophages (BMDMs) in vitro, resulting in the inhibition of renal proinflammatory macrophage infiltration and the reduction in expression of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor (TNF-α) and inducible nitric oxide synthase (iNOS) while increasing expression of anti-inflammatory cytokine Arg-1 and CD163/CD206 surface molecules. Unexpectedly, pretreatment with HPS suppressed CD4⁺ T cell proliferation in a coculture model of IL-4-induced M2 macrophages and splenic CD4⁺ T cells while promoting their differentiation into CD4⁺IL-4⁺ Th2 and CD4⁺Foxp3⁺ Treg cells. Taken together, we demonstrate that HPS ameliorates murine DN via promoting macrophage polarization from an M1 to M2 phenotype and CD4⁺ T cell differentiation into Th2 and Treg populations. Our findings may be implicated for the treatment of DN in clinic.

Association of SIRT6 circulating levels with urinary and glycometabolic markers in pre-diabetes and diabetes

AIM

The study is aimed to detect the expression of serum Sirtuin 6 (SIRT6) with different severities and urinary albumin creatinine ratios (UACR) in type 2 diabetes mellitus (T2DM) patients, thus exploring the association of SIRT6 together with glycolipid metabolism and urinary protein in the cross-sectional study.

METHODS

T2DM patients (313 cases), pre-diabetic patients (102 cases), and healthy volunteers (100 cases) were selected. T2DM patients were divided into the normal albuminuria (103 cases, UACR < 30 mg/g), micro-albuminuria (106 cases, UACR 30-300 mg/g), and large amount of albuminuria group (104 cases, UACR > 300 mg/g) based on different UACR levels. The medical history was asked, biochemical indicators were detected, hematuria samples were taken, serum SIRT6 levels were detected, and detailed statistical analysis was conducted.

RESULTS

FPG, 2 h-PG, HOMA-IR, HbA1c, and LDL-C increased, while ISI and HDL-C decreased with the aggravation of diabetic status (P < 0.05). HbA1c, UACR, TNFα, HIF1α, and SIRT6 increased with UACR in T2DM patients (P < 0.05). Correlation analysis demonstrated that SIRT6 was significantly positively correlated with glycolipid metabolism in the whole samples, and correlated with UACR, TNFα, and HIF1α in T2DM patients (P < 0.05). Ridge regression analysis showed that SIRT6 was a risk factor for both glycolipid metabolism and urinary protein (P < 0.05).

CONCLUSION

SIRT6 increases with biomarkers in glycolipid metabolism and urinary protein in different severities of diabetes and UACR, which is expected to be a potential biomarker for early prediction and diagnosis related to glycolipid metabolism disorders and related nephropathy. Trial number: ChiCTR2000039808.

The Pathogenesis of End-Stage Renal Disease from the Standpoint of the Theory of General Pathological Processes of Inflammation

Chronic kidney disease can progress to end-stage chronic renal disease (ESRD), which requires the use of replacement therapy (dialysis or kidney transplant) in life-threatening conditions. In ESRD, irreversible changes in the kidneys are associated with systemic changes of proinflammatory nature and dysfunctions of internal organs, skeletal muscles, and integumentary tissues. The common components of ESRD pathogenesis, regardless of the initial nosology, are (1) local (in the kidneys) and systemic chronic low-grade inflammation (ChLGI) as a risk factor for diabetic kidney disease and its progression to ESRD, (2) inflammation of the classical type characteristic of primary and secondary autoimmune glomerulonephritis and infectious recurrent pyelonephritis, as well as immune reactions in kidney allograft rejection, and (3) chronic systemic inflammation (ChSI), pathogenetically characterized by latent microcirculatory disorders and manifestations of paracoagulation. The development of ChSI is closely associated with programmed hemodialysis in ESRD, as well as with the systemic autoimmune process. Consideration of ESRD pathogenesis from the standpoint of the theory of general pathological processes opens up the scope not only for particular but also for universal approaches to conducting pathogenetic therapies and diagnosing and predicting systemic complications in severe nephropathies.

Development of Biomarkers and Molecular Therapy Based on Inflammatory Genes in Diabetic Nephropathy

Diabetic Nephropathy (DN) is a debilitating consequence of both Type 1 and Type 2 diabetes affecting the kidney and renal tubules leading to End Stage Renal Disease (ESRD). As diabetes is a world epidemic and almost half of diabetic patients develop DN in their lifetime, a large group of people is affected. Due to the complex nature of the disease, current diagnosis and treatment are not adequate to halt disease progression or provide an effective cure. DN is now considered a manifestation of inflammation where inflammatory molecules regulate most of the renal physiology. Recent advances in genetics and genomic technology have identified numerous susceptibility genes that are associated with DN, many of which have inflammatory functions. Based on their role in DN, we will discuss the current aspects of developing biomarkers and molecular therapy for advancing precision medicine.

Role of Histone Deacetylases in Monocyte Function in Health and Chronic Inflammatory Diseases

Histone deacetylases (HDACs) are a family of 18 members that participate in the epigenetic regulation of gene expression. In addition to histones, some HDACs also deacetylate transcription factors and specific cytoplasmic proteins.Monocytes, as part of the innate immune system, maintain tissue homeostasis and help fight infections and cancer. In these cells, HDACs are involved in multiple processes including proliferation, migration, differentiation, inflammatory response, infections, and tumorigenesis. Here, a systematic description of the role that most HDACs play in these functions is reviewed. Specifically, some HDACs induce a pro-inflammatory response and play major roles in host defense. Conversely, other HDACs reprogram monocytes and macrophages towards an immunosuppressive phenotype. The right balance between both types helps monocytes to respond correctly to the different physiological/pathological stimuli. However, aberrant expressions or activities of specific HDACs are associated with autoimmune diseases along with other chronic inflammatory diseases, infections, or cancer.This paper critically reviews the interesting and extensive knowledge regarding the role of some HDACs in these pathologies. It also shows that as yet, very little progress has been made toward the goal of finding effective HDAC-targeted therapies. However, given their obvious potential, we conclude that it is worth the effort to develop monocyte-specific drugs that selectively target HDAC subtypes with the aim of finding effective treatments for diseases in which our innate immune system is involved.

NAD+ Homeostasis in Diabetic Kidney Disease

The redox reaction and energy metabolism status in mitochondria is involved in the pathogenesis of metabolic related disorder in kidney including diabetic kidney disease (DKD). Nicotinamide adenine dinucleotide (NAD+) is a cofactor for redox reactions and energy metabolism in mitochondria. NAD+ can be synthesized from four precursors through three pathways. The accumulation of NAD+ may ameliorate oxidative stress, inflammation and improve mitochondrial biosynthesis via supplementation of precursors and intermediates of NAD+ and activation of sirtuins activity. Conversely, the depletion of NAD+ via NAD+ consuming enzymes including Poly (ADP-ribose) polymerases (PARPs), cADPR synthases may contribute to oxidative stress, inflammation, impaired mitochondrial biosynthesis, which leads to the pathogenesis of DKD. Therefore, homeostasis of NAD+ may be a potential target for the prevention and treatment of kidney diseases including DKD. In this review, we focus on the regulation of the metabolic balance of NAD+ on the pathogenesis of kidney diseases, especially DKD, highlight benefits of the potential interventions targeting NAD+-boosting in the treatment of these diseases.

CircRNA circ-ITCH improves renal inflammation and fibrosis in streptozotocin-induced diabetic mice by regulating the miR-33a-5p/SIRT6 axis

Diabetic nephropathy (DN) seriously affects the people's life and health in China. This study aimed to investigate the effect of circRNA circ-ITCH on improving DN by regulating the miR-33a-5p/SIRT6 axis and the possible mechanism of action. High glucose (HG)-induced rat mesangial cells (RMCs) were used to simulate the DN in vitro. Reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis were conducted to detect the gene or protein expression. Cell Counting Kit-8 (CCK-8) and wound healing assays were performed to estimate the cell viability and migration capability. Immunofluorescence and enzyme-linked immunosorbent assay (ELISA) were used to detect the α-Smooth Muscle Actin (α-SMA) expression and levels of inflammatory factors. The potential associations between circ-ITCH and miR-33a-5p, miR-33a-5p and SIRT6 in RMCs were measured via dual-luciferase reporter assay. Streptozotocin (STZ) was used to induce the diabetic mice. Blood glucose and serum insulin of mice were determined by corresponding kits, and blood urea nitrogen (BUN) and serum creatinine (SCr) were measured using an automatic biochemical analyzer. Hematoxylin and eosin (H&E) staining and periodic acid-Schiff (PAS) staining were applied to observe the degree of pathological injury and fibrosis of renal tissues. The results of the present study revealed that circ-ITCH expression was obviously decreased in HG-induced RMCs. In addition, circ-ITCH overexpression inhibited the viability, migration, fibrosis and inflammatory response of HG-induced RMCs. Further experiments confirmed that miR-33a-5p may be a direct target of circ-ITCH and SIRT6 may be a direct target of miR-33a-5p. Notably, the miR-33a-5p mimic or shRNA-SIRT6 were discovered to reverse the inhibitory effects of circ-ITCH on the proliferation, migration, fibrosis and inflammatory response of HG-induced RMCs. Furthermore, circ-ITCH overexpression ameliorated renal inflammation and fibrosis in STZ-induced diabetic mice. In conclusion, circ-ITCH alleviated renal inflammation and fibrosis in STZ-induced diabetic mice by regulating the miR-33a-5p/SIRT6 axis.Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Author 1 Given name: [ChunYang] Last name [Xu]. Author 2 Given name: [DingBo] Last name [Xu]. Author 3 Given name: [YongHua] Last name [Liu]. Author 4 Given name: [Juanjuan] Last name [Jiang]. Also, kindly confirm the details in the metadata are correct.ok.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

Emerging roles of SIRT6 in human diseases and its modulators

The biological functions of sirtuin 6 (SIRT6; e.g., deacetylation, defatty-acylation, and mono-ADP-ribosylation) play a pivotal role in regulating lifespan and several fundamental processes controlling aging such as DNA repair, gene expression, and telomeric maintenance. Over the past decades, the aberration of SIRT6 has been extensively observed in diverse life-threatening human diseases. In this comprehensive review, we summarize the critical roles of SIRT6 in the onset and progression of human diseases including cancer, inflammation, diabetes, steatohepatitis, arthritis, cardiovascular diseases, neurodegenerative diseases, viral infections, renal and corneal injuries, as well as the elucidation of the related signaling pathways. Moreover, we discuss the advances in the development of small molecule SIRT6 modulators including activators and inhibitors as well as their pharmacological profiles toward potential therapeutics for SIRT6-mediated diseases.

Uncovering the Key miRNAs and Targets of the Liuwei Dihuang Pill in Diabetic Nephropathy-Related Osteoporosis based on Weighted Gene Co-Expression Network and Network Pharmacology Analysis

BACKGROUND

Diabetic nephropathy-related osteoporosis (DNOP) is the most common comorbid bone metabolic disorder associated with diabetes mellitus (DM). The Liuwei Dihuang Pill (LWD) is a traditional Chinese herbal medicine widely used to treat diabetic complications, including diabetic nephropathy (DN). This study aimed to identify the biomarkers of the mechanisms of DNOP in LWD with systems biology approaches.

METHODS

Herein, we performed an integrated analysis of the GSE51674 and GSE63446 datasets from the GEO database via weighted gene co-expression network and network pharmacology (WGCNA) analysis. In addition, a network pharmacology approach, including bioactive compounds, was used with oral bioavailability (OB) and drug-likeness (DL) evaluation. Next, target prediction, functional enrichment analysis, network analysis, and virtual docking were used to investigate the mechanisms of LWD in DNOP.

RESULTS

WGCNA successfully identified 63 DNOP-related miRNAs. Among them, miR-574 was significantly upregulated in DN and OP samples. A total of 117 targets of 22 components associated with LWD in DNOP were obtained. The cellular response to nitrogen compounds, the AGE-RAGE signaling pathway in diabetic complications, and the MAPK signaling pathway were related to the main targets. Network analysis showed that kaempferol and quercetin were the most significant components. MAPK1 was identified as a potential target of miR-574 and the hub genes in the protein-protein interaction (PPI) network. The docking models demonstrated that kaempferol and quercetin had a strong binding affinity for Asp 167 of MAPK1.

CONCLUSION

This study demonstrated that miR-574 may play important roles in DNOP, and the therapeutic effects of kaempferol and quercetin on LWD in DNOP might be mediated by miR-574 by targeting MAPK1. Our results provide new perspectives for further studies on the anti-DNOP mechanism of LWD.

Recovery of Renal Function following Kidney-Specific VEGF Therapy in Experimental Renovascular Disease

BACKGROUND

Chronic renovascular disease (RVD) can lead to a progressive loss of renal function, and current treatments are inefficient. We designed a fusion of vascular endothelial growth factor (VEGF) conjugated to an elastin-like polypeptide (ELP) carrier protein with an N-terminal kidney-targeting peptide (KTP). We tested the hypothesis that KTP-ELP-VEGF therapy will effectively recover renal function with an improved targeting profile. Further, we aimed to elucidate potential mechanisms driving renal recovery.

METHODS

Unilateral RVD was induced in 14 pigs. Six weeks later, renal blood flow (RBF) and glomerular filtration rate (GFR) were quantified by multidetector CT imaging. Pigs then received a single intrarenal injection of KTP-ELP-VEGF or vehicle. CT quantification of renal hemodynamics was repeated 4 weeks later, and then pigs were euthanized. Ex vivo renal microvascular (MV) density and media-to-lumen ratio, macrophage infiltration, and fibrosis were quantified. In parallel, THP-1 human monocytes were differentiated into naïve macrophages (M0) or inflammatory macrophages (M1) and incubated with VEGF, KTP-ELP, KTP-ELP-VEGF, or control media. The mRNA expression of macrophage polarization and angiogenic markers was quantified (qPCR).

RESULTS

Intrarenal KTP-ELP-VEGF improved RBF, GFR, and MV density and attenuated MV media-to-lumen ratio and renal fibrosis compared to placebo, accompanied by augmented renal M2 macrophages. In vitro, exposure to VEGF/KTP-ELP-VEGF shifted M0 macrophages to a proangiogenic M2 phenotype while M1s were nonresponsive to VEGF treatment.

CONCLUSIONS

Our results support the efficacy of a new renal-specific biologic construct in recovering renal function and suggest that VEGF may directly influence macrophage phenotype as a possible mechanism to improve MV integrity and function in the stenotic kidney.

Protective Effects of Two Safflower Derived Compounds, Kaempferol and Hydroxysafflor Yellow A, on Hyperglycaemic Stress-Induced Podocyte Apoptosis via Modulating of Macrophage M1/M2 Polarization

Objective

The primary initiating mechanism in diabetes nephropathy (DN) is hyperglycemia-induced inflammation in which macrophage and podocyte play important roles. The present research is aimed at exploring the effects of kaempferol (Ka) and hydroxysafflor yellow A (HSYA) on classically activated (M1)/alternatively activated (M2) macrophage polarization and podocyte apoptosis under hyperglycaemic conditions in vitro.

Methods

(1) RAW264.7 cells were treated with 11.1 mM glucose (NG), 33.3 mM glucose (HG), Ka 4-8 μM, and HSYA 100-200 μM separately. The expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor- (TNF-) α, mannose receptor (CD206), and arginase- (Arg-) 1 were quantified by Western blotting and real-time quantitative PCR. The collected supernatants from macrophage were named as (NG) MS, (HG) MS, (Ka) MS, and (HSYA) MS. (2) The podocyte survival rate was assessed by Bromodeoxyuridine assay, while TNF-α and interleukin- (IL-) 1β levels were evaluated by Elisa.

Results

(1) Compared to the HG group, the Ka and HSYA 100 μM groups decreased iNOS and TNF-α levels and increased Arg-1 and CD206 expressions significantly (protein and mRNA: p < 0.05, respectively). (2) The podocyte survival rate of Ka 8 μM was higher than that of HG, and the rates of (Ka) MS and (HSYA 100 μM) MS were higher than that of (HG) MS significantly (all: p < 0.05). (3) TNF-α and IL-1β levels of Ka and HSYA 100 μM were significantly lower than those of the HG group, and both levels in the (Ka) MS and (HSYA) MS were lower than those in the (HG) MS group significantly (p < 0.05, respectively).

Conclusion

The protective effects of Ka and HSYA on podocyte apoptosis under hyperglycemic stress are related to their modulation on M1/M2 polarization and the lowering effects on TNF-α and IL-1β levels.

The Role of Sirtuins in Kidney Diseases

Sirtuins (SIRTs) are class III histone deacetylases (HDACs) that play important roles in aging and a wide range of cellular functions. Sirtuins are crucial to numerous biological processes, including proliferation, DNA repair, mitochondrial energy homeostasis, and antioxidant activity. Mammals have seven different sirtuins, SIRT1–7, and the diverse biological functions of each sirtuin are due to differences in subcellular localization, expression profiles, and cellular substrates. In this review, we summarize research advances into the role of sirtuins in the pathogenesis of various kidney diseases including acute kidney injury, diabetic kidney disease, renal fibrosis, and kidney aging along with the possible underlying molecular mechanisms. The available evidence indicates that sirtuins have great potential as novel therapeutic targets for the prevention and treatment of kidney diseases.

Protective Effects of SIRT6 Overexpression against DSS-Induced Colitis in Mice

Sirtuin 6 (SIRT6), as a NAD + -dependent deacetylase, plays an indispensable role in the regulation of health and physiology. Loss of SIRT6 causes spontaneous colitis in mice and makes intestinal epithelial cells prone to stress. However, whether SIRT6 overexpression increases resistance to colitis remains unknown. Here, in vivo results demonstrated that SIRT6 overexpression attenuates DSS-induced colitis in terms of clinical manifestations, histopathological damage, loss of tight junction function and imbalanced intestinal microenvironment. Additionally, we also found that the activation of NF-κB and c-Jun induced by DSS is diminished by SIRT6 overexpression. Furthermore, SIRT6 may regulate TAK1 to inhibit NF-κB and c-Jun signaling. Thus, our findings highlight the protective effect of SIRT6 on colon, further supporting the perspective that SIRT6 may be a therapeutic target for intestine injury under stress.

Macrophage Phenotype and Fibrosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease globally. The primary initiating mechanism in DN is hyperglycemia-induced vascular dysfunction, but its progression is due to different pathological mechanisms, including oxidative stress, inflammatory cells infiltration, inflammation and fibrosis. Macrophages (Mφ) accumulation in kidneys correlates strongly with serum creatinine, interstitial myofibroblast accumulation and interstitial fibrosis scores. However, whether or not Mφ polarization is involved in the progression of DN has not been adequately defined. The prevalence of the different phenotypes during the course of DN, the existence of hybrid phenotypes and the plasticity of these cells depending of the environment have led to inconclusive results. In the same sense the role of the different macrophage phenotype in fibrosis associated or not to DN warrants additional investigation into Mφ polarization and its role in fibrosis. Due to the association between fibrosis and the progressive decline of renal function in DN, and the role of the different phenotypes of Mφ in fibrosis, in this review we examine the role of macrophage phenotype control in DN and highlight the potential factors contributing to phenotype change and injury or repair in DN.

Isoliquiritigenin Attenuates UUO-Induced Renal Inflammation and Fibrosis by Inhibiting Mincle/Syk/NF-Kappa B Signaling Pathway

Purpose

Chronic kidney disease (CKD) is a global nephrotic syndrome characterized by chronic inflammation, oxidative stress and fibrosis in the kidney. Isoliquiritigenin (ISL), a flavonoid from licorice, has historically been reported to inhibit innate immune responses to inflammation and fibrosis in vivo. However, the effect of ISL on CKD progression is largely unknown.

Materials and Methods

In this study, we employed the inflammatory and fibrotic models of LPS/TGF-β-induced bone marrow-derived macrophages (BMDM) in vitro and unilateral ureteral obstruction (UUO) model in vivo to explore the potential effects and mechanism of ISL on renal inflammation and fibrosis.

Results

Our results manifest that ISL improved UUO-induced renal dysfunction and reduced tubular damage with a significantly downregulated mRNA expression and secretion of IL-1β, IL-6, TNF-α and MCP-1 in vitro and in vivo. It is worth noting that ISL can strongly inhibit the mRNA and protein expression of Mincle (macrophage-induced c-type lectin) in BMDM and UUO. ISL inhibited the phosphorylation of Syk and NF-kappa B and simultaneously reduced the expression of α-SMA and Col III in vivo and in vitro. More interestingly, when dealing with TDB, a ligand of Mincle, it revealed significant reversal of protein expression levels as that observed with ISL. The expressions of IL-1β, IL-6, TNF-α, iNOS, p-Syk, p-NF-kappa B, α-SMA and FN in BMDM inflammatory model were significantly upregulated with TDB treatment. This confirms that ISL inhibits inflammation and fibrosis of macrophage by suppressing Mincle/Syk/NF-kappa B signaling pathway.

Conclusion

To conclude, ISL protects UUO-induced CKD by inhibiting Mincle-induced inflammation and suppressing renal fibrosis, which might be a specific renal protective mechanism of ISL, making it a novel drug to ameliorate CKD.