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BACKGROUND:Autophagy and ferroptosis play important roles in the development of chronic kidney disease, but the molecular mechanisms and gene targets related to autophagy and ferroptosis in renal tissue of chronic kidney disease are still unclear. OBJECTIVE:To screen differentially expressed genes in chronic kidney disease-related datasets based on bioinformatics, and to explore potential key biomarkers suitable for screening renal function progression in patients with chronic kidney disease. METHODS: The GSE137570 dataset was obtained from GEO database to screen the differentially expressed genes by Networkanalyst database analysis. Ferroptosis and autophagy related targets were obtained by OMIM, GENECARD, FerrDb and HAMdb databases. The respective data were intersected to obtain autophagy-ferroptosis related differentially expressed genes in chronic kidney disease for parallel enrichment analysis. The STRING website was used to construct the protein-protein interaction network of differentially expressed genes, which was imported into Cytoscape software and analyzed by MCODEand Cytohubba plug-in to screen potential core targets. Enrichment analysis was performed to obtain the functions of these potential core targets. In the in vitro experiment, mouse renal tubular epithelial cells were divided into two groups:the control group received no intervention, while the model group was stimulated with 5 ng/mL transforming growth factor β1 for 24 hours to induce mesenchymal transformation of renal tubular epithelial cells. Flow cytometry was used to measure the levels of reactive oxygen species and changes in mitochondrial membrane potential in the cells. RT-PCR was employed to assess ferroptosis, autophagy-related markers, and the mRNA expression of potential core targets in the cells. RESULTS AND CONCLUSION:After screening the GSE137570 dataset, a total of 480 differentially expressed genes were obtained, including 104 upregulated genes and 376 downregulated genes (log2| (FC)|＞1, P＜0. 05). There were 562 ferroptosis-related targets and 1 266 autophagy-related targets obtained from the OMIM, GENECARD, FerrDb, and HAMdb databases. Intersection of differentially expressed genes with ferroptosis-and autophagy-related targets yielded15 ferroptosis-related targets and 18 autophagy-related targets, respectively. The enrichment analysis results indicate that ferroptosis-related differentially expressed genes are primarily involved in biological processes such as sulfur amino acid metabolism, neutrophil degranulation, and ferroptosis signaling pathways. Autophagy-related differentially expressed genes are mainly enriched in biological processes such as platelet degranulation, extracellular matrix degradation, and receptor tyrosine kinase signaling. After screened by MCODE and CytoHubba, key genes were identified in the protein-protein interaction network, including CD44, ALB, TIMP1, PLG, CCL2, and DPP4. Immune infiltration analysis results indicate that immune cells such as B cells, CD4+T cells, NK cells, and monocytes show significant differential expression in renal tissue after chronic kidney disease, and the core targets are also significantly correlated with these immune cells (P＜0. 05). The results of receiver operator characteristic curve analysis further demonstrate that the pathological progression of chronic kidney disease can be effectively diagnosed by CD44, ALB, TIMP1, PLG, CCL2, and DPP4. Single-cell sequencing results show that, except for PLG, the expression of target genes in the renal tissue of mice in each model group is generally consistent with the results of this experiment. RT-PCR results demonstrate that, for the validation of autophagy and ferroptosis phenotypes, compared with the control group, the model group shows a significant decrease in mRNA expression of LC3B, Nrf2, and SLC7A11 (P＜0. 05), and a significant increase in P62 mRNA expression (P＜0. 05). Regarding the validation of potential core targets, compared with the control group, the model group exhibits a significant decrease in mRNA expression of ALB and PLG (P＜0. 05), and a significant increase in TIMP1 and CCL2 mRNA expression (P＜0. 05). Overall, these findings indicate that, through bioinformatics analysis and experimental validation, CD44, ALB, TIMP1, PLG, and CCL2 are abnormally expressed in the renal tissue of patients with chronic kidney disease, closely correlated with estimated glomerular filtration rate and tubulointerstitial fibrosis, and maybe play a predictive role in the progression of chronic kidney disease [ABSTRACT FROM AUTHOR]

Background and Purpose: Activation of the renin‐angiotensin system, as a hallmark of hypertension and chronic kidney diseases (CKD) is the key pathophysiological factor contributing to the progression of tubulointerstitial fibrosis. LIM and senescent cell antigen‐like domains protein 1 (LIMS1) plays an essential role in controlling of cell behaviour through the formation of complexes with other proteins. Here, the function and regulation of LIMS1 in angiotensin II (Ang II)‐induced hypertension and tubulointerstitial fibrosis was investigated. Experimental Approach: C57BL/6 mice were treated with Ang II to induce tubulointerstitial fibrosis. Hypoxia‐inducible factor‐1α (HIF‐1α) renal tubular‐specific knockout mice or LIMS1 knockdown AAV was used to investigate their effects on Ang II‐induced renal interstitial fibrosis. In vitro, HIF‐1α or LIMS1 was knocked down or overexpressed in HK2 cells after exposure to Ang II. Key Results: Increased expression of tubular LIMS1 was observed in human kidney with hypertensive nephropathy and in murine kidney from Ang II‐induced hypertension model. Tubular‐specific knockdown of LIMS1 ameliorated Ang II‐induced tubulointerstitial fibrosis in mice. Furthermore, we demonstrated that LIMS1 was transcriptionally regulated by HIF‐1α in tubular cells and that tubular HIF‐1α knockout ameliorates LIMS1‐mediated tubulointerstitial fibrosis. In addition, LIMS1 promotes Ang II‐induced tubulointerstitial fibrosis by interacting with vimentin. Conclusion and Implications: We conclude that HIF‐1α transcriptionally regulated LIMS1 plays a central role in Ang II‐induced tubulointerstitial fibrosis through interacting with vimentin. Our finding represents a new insight into the mechanism of Ang II‐induced tubulointerstitial fibrosis and provides a novel therapeutic target for progression of CKD. [ABSTRACT FROM AUTHOR]

The role of microRNAs in regulating tubulointerstitial fibrosis, a key feature of progressive chronic kidney disease, is of significant importance. LIN28A has been reported to attenuate renal fibrosis in obstructive nephropathy. Here, our objective was to investigate the precise biological function of the miR-92a-3p/LIN28A axis in tubulointerstitial fibrosis. The human renal proximal tubular epithelial (HK-2) cell line was exposed to transforming growth factor (TGF)-β1, establishing an in vitro model mimicking tubulointerstitial fibrosis. Luciferase reporter assay was utilized to investigate the relationship between miR-92a-3p and LIN28A. Cell transfection techniques were employed to modify the expression of miR-92a-3p and LIN28A. An in vivo model of tubulointerstitial fibrosis was created by inducing unilateral ureteral obstruction (UUO) in C57BL/6N mice. Our initial observations showed that TGF-β1 treatment of HK-2 cells and the UUO mice model led to an increase in miR-92a-3p expression and a decrease in LIN28A expression. We confirmed that miR-92a-3p directly targeted LIN28A in HK-2 cells. In TGF-β1-stimulated HK-2 cells, knocking down miR-92a-3p notably reduced the levels of alpha smooth muscle actin and vimentin and concurrently enhanced the expression of E-cadherin. These changes were counteracted upon transfection with si-LIN28A. Thus, directing interventions toward miR-92a-3p holds the potential to emerge as a viable therapeutic approach for addressing tubulointerstitial fibrosis.

Objective To investigate the role and mechanism of zinc finger protein 281 (ZNF281) in high glucose (HG)-induced epithelial-mesenchymal transition (EMT) and extracellular matrix (ECM) synthesis in renal tubular epithelial cells (RTECs). Methods HG induced RTECs were used to construct a diabetic kidney disease cell model, and cells were divided into the control group, the HG group and the mannitol group. Cell proliferation viability was detected by CCK-8. The expression of ZNF281 was knocked down in HG-treated RTECs using small interfering RNA (siRNA). HG-induced RTECs after knockdown of ZNF281 were divided into the control group, the HG group, the HG+ZNF281 siRNA group and the HG+ ZNF281 vector group. Adenosine monophosphate-activated protein kinase (AMPK) was activated using AMPK agonist, acadexin (AICAR), and then cells were divided into the control group, the HG group, the HG+AICAR group and the HG+ dimethyl sulfoxide group. The expression levels of ZNF281, EMT and ECM synthesis-related indexes were detected by qPCR and Western blot assay. Results Compared with the control group, the protein and mRNA expression levels of vimentin, α-smooth muscle actin (α-SMA), fibronectin (FN) and collagen Ⅰ (Col Ⅰ) were significantly higher, and the expression of E-cadherin was significantly lower in the HG group. Compared with the HG group, the protein and mRNA expression levels of EMT and ECM synthesis-related indexes were significantly changed in the HG+ZNF281 siRNA group and the HG+AICAR group. The protein and mRNA expression levels of ZNF281 were significantly reduced in the HG+ AICAR group compared with the HG group. In cells co-treated with AICAR and transfected with ZNF281 plasmid, the expression levels of vimentin, α -SMA, FN and Col Ⅰ were significantly higher in the AICAR+ZNF281 group, and E-cadherin was significantly lower compared with that of the vector group. Conclusion AMPK inhibits EMT and ECM synthesis in HG-treated RTECs by negatively regulating the expression level of ZNF281. [ABSTRACT FROM AUTHOR]

The role of microRNAs in regulating tubulointerstitial fibrosis, a key feature of progressive chronic kidney disease, is of significant importance. LIN28A has been reported to attenuate renal fibrosis in obstructive nephropathy. Here, our objective was to investigate the precise biological function of the miR-92a-3p/LIN28A axis in tubulointerstitial fibrosis. The human renal proximal tubular epithelial (HK-2) cell line was exposed to transforming growth factor (TGF)-β1, establishing an in vitro model mimicking tubulointerstitial fibrosis. Luciferase reporter assay was utilized to investigate the relationship between miR-92a-3p and LIN28A. Cell transfection techniques were employed to modify the expression of miR-92a-3p and LIN28A. An in vivo model of tubulointerstitial fibrosis was created by inducing unilateral ureteral obstruction (UUO) in C57BL/6N mice. Our initial observations showed that TGF-β1 treatment of HK-2 cells and the UUO mice model led to an increase in miR-92a-3p expression and a decrease in LIN28A expression. We confirmed that miR-92a-3p directly targeted LIN28A in HK-2 cells. In TGF-β1-stimulated HK-2 cells, knocking down miR-92a-3p notably reduced the levels of alpha smooth muscle actin and vimentin and concurrently enhanced the expression of E-cadherin. These changes were counteracted upon transfection with si-LIN28A. Thus, directing interventions toward miR-92a-3p holds the potential to emerge as a viable therapeutic approach for addressing tubulointerstitial fibrosis. [ABSTRACT FROM AUTHOR]

Glomerulosclerosis and tubulointerstitial fibrosis (TIF) are closely involved in the development of diabetic nephropathy (DN). Moreover, the development of TIF is closely related to epithelial-to-mesenchymal transition (EMT). Tanshinone IIA (Tan) has various pharmacological effects, especially the anti-fibrotic effect. And it is mainly used in the clinical treatment of cardiovascular diseases. Currently, the protective effect of Tan on DN and its possible mechanism have not been clearly elucidated. Our previous studies illustrated that Tan could improve the EMT of HK-2 cells induced by high glucose by regulating the vitamin D receptor (VDR)/Wnt/β-catenin pathway. Here, we collected demographic information and laboratory results from the National Health and Nutrition Examination Survey (NHANES) database in order to investigate the relationship between VD and DN. Then, we established a DN model and treated DN rats with Tan and paricalcitol (Par) for 6 weeks. We subsequently compared the changes in general condition, renal function, pathological changes, and TIF-related protein expression levels of control rats, DN rats induced by STZ, DN rats with Tan at 5.4 mg/kg, DN rats with Tan at 10.8 mg/kg, and DN rats with Par at 0.054 µg/kg, to explore the effect and mechanism of Tan and Par on DN rats. The results showed that VD had a protective effect against DN in diabetic patients. And we found that Tan had a protective effect on renal fibrosis in DN rats, which was superior to Par in improving the symptoms of "three more and one less," reducing fasting blood glucose level, improving renal index, BUN/SCr, and UACR, reducing histopathological damage of kidney, and improving the expression of fibrosis-related proteins in kidney tissue by regulating VDR/Wnt/β-catenin pathway. Tan was superior to Par in ameliorating tubulointerstitial fibrosis by regulating VDR/Wnt/β-catenin pathway in rats with diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Diabetic nephropathy(DN) is the primary factor leading to the advancement of end-stage renal disease.Tubulointerstitial fibrosis(TIF) is a crucial element that impacts renal function in DN.When exposed to high levels of glucose,the activation of inflammasomes can trigger cell death pathways,including pyroptosis.This can potentially lead to TIF,which in turn causes the decline of renal function.This article focuses on the pathogenic mechanisms of TIF resulting from DN.This study reviews the potential of blocking pyroptosis to slow down the course of DN,providing a new and promising target for therapeutic intervention in the treatment of DN.

Metabolic acidosis is a frequent complication of chronic kidney disease and is associated with a number of adverse outcomes, including worsening kidney function, poor musculoskeletal health, cardiovascular events, and death. Mechanisms that prevent metabolic acidosis detrimentally promote further kidney damage, creating a cycle between acid accumulation and acid-mediated kidney injury. Disrupting this cycle through the provision of alkali, most commonly using sodium bicarbonate, is hypothesized to preserve kidney function while also mitigating adverse effects of excess acid on bone and muscle. However, results from clinical trials have been conflicting. There is also significant interest to determine whether sodium bicarbonate might improve patient outcomes for those who do not have overt metabolic acidosis. Such individuals are hypothesized to be experiencing acid-mediated organ damage despite having a normal serum bicarbonate concentration, a state often referred to as subclinical metabolic acidosis. Results from small- to medium-sized trials in individuals with subclinical metabolic acidosis have also been inconclusive. Well-powered clinical trials to determine the efficacy and safety of sodium bicarbonate are necessary to determine if this intervention improves patient outcomes. [ABSTRACT FROM AUTHOR]

Proteinuria is a well-established biomarker of chronic kidney disease (CKD) and a risk predictor of associated disease outcomes. Proteinuria is also a driver of CKD progression toward end-stage kidney disease. Toxic effects of filtered proteins on proximal tubular epithelial cells enhance tubular atrophy and interstitial fibrosis. The extent of protein toxicity and the underlying molecular mechanisms responsible for tubular injury during proteinuria remain unclear. Nevertheless, albumin elicits its toxic effects when degraded and reabsorbed by proximal tubular epithelial cells. Overall, healthy kidneys excrete over 1000 individual proteins, which may be potentially harmful to proximal tubular epithelial cells when filtered and/or reabsorbed in excess. Proteinuria can cause kidney damage, inflammation and fibrosis by increasing reactive oxygen species, autophagy dysfunction, lysosomal membrane permeabilization, endoplasmic reticulum stress and complement activation. Here we summarize toxic proteins reported in proteinuria and the current understanding of molecular mechanisms of toxicity of proteins on proximal tubular epithelial cells leading to CKD progression. [ABSTRACT FROM AUTHOR]

Purpose: To elucidate the role of cordycepin in modulating autophagy and mitigating renal tubular interstitial fibrosis in a rat model of unilateral ureteral obstruction (UUO). Methods: Forty male Sprague-Dawley (SD) rats were assigned to four groups: control, sham, UUO and cordyceps-treated groups (10 rats per group). The UUO and cordyceps groups underwent surgery to induce unilateral ureteral obstruction. The cordyceps group received intravenous cordycepin (10 mg/kg) daily for 14 days, while the control and UUO groups received normal saline. Histopathological examination, assessment of fibrosis markers (a-SMA, collagen III) and autophagy markers (Atg5, LC3II/I) were conducted. Results: The UUO group exhibited significant tubular damage and interstitial fibrosis, with elevated serum levels of pro-inflammatory and oxidative markers (p < 0.05). Cordycepin treatment attenuated these pathological changes, evidenced by reduced fibrosis, inflammation and oxidative stress. Enhanced autophagic activity was observed in the cordycepin group, suggesting a potential mechanism of its renoprotective effect. Conclusion: Cordyceps is effective in inhibiting renal tubulointerstitial fibrosis, potentially through the activation of autophagy and reduction of inflammation and oxidative stress. Future studies should focus on unraveling the specific molecular mechanisms of cordycepin's action and assessing its applicability in CKD treatment. [ABSTRACT FROM AUTHOR]

Recent studies have shown that endogenous metabolites act via aryl hydrocarbon receptor (AhR) signalling pathway in tubulointerstitial fibrosis (TIF) pathogenesis. However, the mechanisms underlying endogenous metabolite-mediated AhR activation are poorly characterised. In this study, we conducted untargeted metabolomics analysis to identify the significantly altered intrarenal metabolites in a mouse model of unilateral ureteral obstruction (UUO). We found that the levels of the metabolite 1-methoxypyrene (MP) and the mRNA expression of AhR and its target genes CYP1A1, CYP1A2, CYP1B1 and COX-2 were progressively increased in the obstructed kidney at Weeks 1, 2 and 3. Furthermore, these changes were positively correlated with progressive TIF in UUO mice. In NRK-52E, RAW 264.7 and NRK-49F cells, MP dose-dependently upregulated the mRNA expression of AhR and its four target genes and the protein expression of nuclear AhR, accompanied by the upregulated protein expression of collagen I, α-SMA and fibronectin, as well as downregulated E-cadherin expression. Consistently, oral administration of MP in mice progressively enhanced AhR activity and upregulated profibrotic protein expression in the kidneys; these effects were partially inhibited by AhR knockdown in MP-treated mice and cell lines. In addition, we screened and identified erythro-guaiacylglycerol-β-ferulic acid ether (GFA), which was isolated from Semen plantaginis, as a new AhR antagonist. GFA significantly attenuated TIF in MP-treated NRK-52E cells and mice by partially antagonising AhR activity. Our results suggest that MP activates AhR signalling, thus mediating TIF through epithelial-mesenchymal transition and macrophage-myofibroblast transition. MP is a crucial metabolite that contributes to TIF via AhR signalling pathway.

Abstract Background Tubulointerstitial fibrosis plays an important role in the progression of diabetic kidney disease (DKD). Sacubitril/valsartan (Sac/Val) exerts a robust beneficial effect in DKD. However, the potential functional effect of Sac/Val on tubulointerstitial fibrosis in DKD is still largely unclear. Methods Streptozotocin-induced diabetic mice were given Sac/Val or Val by intragastric administration once a day for 12 weeks. The renal function, the pathological changes of tubule injury and tubulointerstitial fibrosis, as well as mitochondrial morphology of renal tubules in mice, were evaluated. Genome-wide gene expression analysis was performed to identify the potential mechanisms. Meanwhile, human tubular epithelial cells (HK-2) were cultured in high glucose condition containing LBQ657/valsartan (LBQ/Val). Further, mitochondrial functions and Sirt1/PGC1α pathway of tubular epithelial cells were assessed by Western blot, Real-time-PCR, JC-1, MitoSOX or MitoTracker. Finally, the Sirt1 specific inhibitor, EX527, was used to explore the potential effects of Sirt1 signaling in vivo and in vitro. Results We found that Sac/Val significantly ameliorated the decline of renal function and tubulointerstitial fibrosis in DKD mice. The enrichment analysis of gene expression indicated metabolism as an important modulator in DKD mice with Sac/Val administration, in which mitochondrial homeostasis plays a pivotal role. Then, the decreased expression of Tfam and Cox IV;, as well as changes of mitochondrial function and morphology, demonstrated the disruption of mitochondrial homeostasis under DKD conditions. Interestingly, Sac/Val administration was found to restore mitochondrial homeostasis in DKD mice and in vitro model of HK-2 cells. Further, we demonstrated that Sirt1/PGC1α, a crucial pathway in mitochondrial homeostasis, was activated by Sac/Val both in vivo and in vitro. Finally, the beneficial effects of Sac/Val on mitochondrial homeostasis and tubulointerstitial fibrosis was partially abolished in the presence of Sirt1 specific inhibitor. Conclusions Taken together, we demonstrate that Sac/Val ameliorates tubulointerstitial fibrosis by restoring Sirt1/PGC1α pathway-mediated mitochondrial homeostasis in DKD, providing a theoretical basis for delaying the progression of DKD in clinical practice.

Background: Tubulointerstitial fibrosis plays an important role in the progression of diabetic kidney disease (DKD). Sacubitril/valsartan (Sac/Val) exerts a robust beneficial effect in DKD. However, the potential functional effect of Sac/Val on tubulointerstitial fibrosis in DKD is still largely unclear. Methods: Streptozotocin-induced diabetic mice were given Sac/Val or Val by intragastric administration once a day for 12 weeks. The renal function, the pathological changes of tubule injury and tubulointerstitial fibrosis, as well as mitochondrial morphology of renal tubules in mice, were evaluated. Genome-wide gene expression analysis was performed to identify the potential mechanisms. Meanwhile, human tubular epithelial cells (HK-2) were cultured in high glucose condition containing LBQ657/valsartan (LBQ/Val). Further, mitochondrial functions and Sirt1/PGC1α pathway of tubular epithelial cells were assessed by Western blot, Real-time-PCR, JC-1, MitoSOX or MitoTracker. Finally, the Sirt1 specific inhibitor, EX527, was used to explore the potential effects of Sirt1 signaling in vivo and in vitro. Results: We found that Sac/Val significantly ameliorated the decline of renal function and tubulointerstitial fibrosis in DKD mice. The enrichment analysis of gene expression indicated metabolism as an important modulator in DKD mice with Sac/Val administration, in which mitochondrial homeostasis plays a pivotal role. Then, the decreased expression of Tfam and Cox IV;, as well as changes of mitochondrial function and morphology, demonstrated the disruption of mitochondrial homeostasis under DKD conditions. Interestingly, Sac/Val administration was found to restore mitochondrial homeostasis in DKD mice and in vitro model of HK-2 cells. Further, we demonstrated that Sirt1/PGC1α, a crucial pathway in mitochondrial homeostasis, was activated by Sac/Val both in vivo and in vitro. Finally, the beneficial effects of Sac/Val on mitochondrial homeostasis and tubulointerstitial fibrosis was partially abolished in the presence of Sirt1 specific inhibitor. Conclusions: Taken together, we demonstrate that Sac/Val ameliorates tubulointerstitial fibrosis by restoring Sirt1/PGC1α pathway-mediated mitochondrial homeostasis in DKD, providing a theoretical basis for delaying the progression of DKD in clinical practice. [ABSTRACT FROM AUTHOR]

Our previous study found that miR‐26a alleviates aldosterone‐induced tubulointerstitial fibrosis (TIF). However, the effect of miR‐26a on TIF in diabetic kidney disease (DKD) remains unclear. This study clarifies the role and possible mechanism of exogenous miR‐26a in controlling the progression of TIF in DKD models. Firstly, we showed that miR‐26a was markedly decreased in type 2 diabetic db/db mice and mouse tubular epithelial cells (mTECs) treated with high glucose (HG, 30 mM) using RT‐qPCR. We then used adeno‐associated virus carrying miR‐26a and adenovirus miR‐26a to enhance the expression of miR‐26a in vivo and in vitro. Overexpressing miR‐26a alleviated the TIF in db/db mice and the extracellular matrix (ECM) deposition in HG‐stimulated mTECs. These protective effects were caused by reducing expression of protease‐activated receptor 4 (PAR4), which involved in multiple pro‐fibrotic pathways. The rescue of PAR4 expression reversed the anti‐fibrosis activity of miR‐26a. We conclude that miR‐26a alleviates TIF in DKD models by directly targeting PAR4, which may provide a novel molecular strategy for DKD therapy. [ABSTRACT FROM AUTHOR]

The energy needs of tubular epithelial components, especially proximal tubular epithelial cells (PTECs), are high and they heavily depend on aerobic metabolism. As a result, they are particularly vulnerable to various injuries caused by factors such as ischemia, proteinuria, toxins, and elevated glucose levels. Initial metabolic and phenotypic changes in PTECs after injury are likely an attempt at survival and repair. Nevertheless, in cases of recurrent or prolonged injury, PTECs have the potential to undergo a transition to a secretory state, leading to the generation and discharge of diverse bioactive substances, including transforming growth factor-b, Wnt ligands, hepatocyte growth factor, interleukin (IL)-1b, lactic acid, exosomes, and extracellular vesicles. By promoting fibroblast activation, macrophage recruitment, and endothelial cell loss, these bioactive compounds stimulate communication between epithelial cells and other interstitial cells, ultimately worsening renal damage. This review provides a summary of the latest findings on bioactive compounds that facilitate the communication between these cellular categories, ultimately leading to the advancement of tubulointerstitial fibrosis (TIF). [ABSTRACT FROM AUTHOR]

Tubulointerstitial fibrosis (TIF) plays a crucial role in the progression of diabetic kidney disease (DKD). However, the underlying molecular mechanisms remain obscure. The present study aimed to examine whether transmembrane member 16A (TMEM16A), a Ca2+-activated chloride channel, contributes to the development of TIF in DKD. Interestingly, we found that TMEM16A expression was significantly up-regulated in tubule of murine model of DKD, which was associated with development of TIF. In vivo inhibition of TMEM16A channel activity with specific inhibitors Ani9 effectively protects against TIF. Then, we found that TMEM16A activation induces tubular mitochondrial dysfunction in in vivo and in vitro models, with the evidence of the TMEM16A inhibition with specific inhibitor. Mechanically, TMEM16A mediated tubular mitochondrial dysfunction through inhibiting PGC-1α, whereas overexpression of PGC-1α could rescue the changes. In addition, TMEM16A-induced fibrogenesis was dependent on increased intracellular Cl−, and reducing intracellular Cl− significantly blunted high glucose-induced PGC-1α and profibrotic factors expression. Taken together, our studies demonstrated that tubular TMEM16A promotes TIF by suppressing PGC-1α-mediated mitochondrial homeostasis in DKD. Blockade of TMEM16A may serve as a novel therapeutic approach to ameliorate TIF. [ABSTRACT FROM AUTHOR]

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which has a close relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) plays an important role not only in regulating the fibrosis process but also in maintaining the mitochondrial function of pancreatic β-cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG up-regulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose-cultured HK-2 cells and 8-weeks-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF. [ABSTRACT FROM AUTHOR]

Zhaohua Yang,1,&ast; Jinying Wei,1,&ast; Yashu Wang,1 Yunxia Du,1 Shan Song,1 Jiawei Li,2 Ziyuan Su,2 Yonghong Shi,1 Haijiang Wu1 1Department of Pathology, Hebei Medical University, Shijiazhuang, 050017, People’s Republic of China; 2Basic Medical College, Hebei Medical University, Shijiazhuang, 050017, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Haijiang Wu, Email haijianglaoqi@163.comBackground: The primary pathophysiology of diabetic kidney disease (DKD) is tubulointerstitial fibrosis (TIF), and an essential contributing element is excessive extracellular matrix deposition. Irisin is a polypeptide formed by splitting fibronectin type III domain containing 5 (FNDC5), which participates in a number of physiological and pathological processes.Methods: The purpose of this article is to examine irisin’s function in DKD and analyze both its in vitro and in vivo effects. The Gene Expression Omnibus (GEO) database was used to download GSE30122, GSE104954, and GSE99325. Analysis of renal tubule samples from nondiabetic and diabetic mice identified 94 differentially expressed genes (DEGs). The transforming growth factor beta receptor 2 (TGFBR2), irisin, and TGF-β 1 were utilized as DEGs to examine the impact of irisin on TIF in diabetic kidney tissue, according to the datasets retrieved from the GEO database and Nephroseq database. Additionally, the therapeutic impact of irisin was also examined using Western blot, RT-qPCR, immunofluorescence, immunohistochemistry, and kits for detecting mouse biochemical indices.Results: In vitro, the findings demonstrated that irisin not only down-regulated the expression of Smad4 and β-catenin but also reduced the expression of proteins linked to fibrosis, the epithelial-mesenchymal transition (EMT), and mitochondrial dysfunction in HK-2 cells maintained in high glucose (HG) environment. In vivo, overexpressed FNDC5 plasmid was injected into diabetic mice to enhance its expression. Our studies found that overexpressed FNDC5 plasmid not only reversed the biochemical parameters and renal morphological characteristics of diabetic mice but also alleviated EMT and TIF by inhibiting Smad4/β-catenin signaling pathway.Conclusion: The above experimental results revealed that irisin could reduce TIF in diabetic mice via regulating the Smad4/β-catenin pathway.Keywords: irisin, diabetic kidney disease, tubulointerstitial fibrosis, Smad4, β-catenin

Background Thromboembolic events are prevalent in chronic kidney disease (CKD) patients due to increased thrombin generation leading to a hypercoagulable state. We previously demonstrated that inhibition of protease-activated receptor-1 (PAR-1) by vorapaxar reduces kidney fibrosis. Methods We used an animal model of unilateral ischemia–reperfusion injury-induced CKD to explore the tubulovascular crosstalk mechanisms of PAR-1 in acute kidney injury (AKI)-to-CKD transition. Results During the early phase of AKI, PAR-1-deficient mice exhibited reduced kidney inflammation, vascular injury, and preserved endothelial integrity and capillary permeability. During the transition phase to CKD, PAR-1 deficiency preserved kidney function and diminished tubulointerstitial fibrosis via downregulated transforming growth factor-β/Smad signaling. Maladaptive repair in the microvasculature after AKI further exacerbated focal hypoxia with capillary rarefaction, which was rescued by stabilization of hypoxia-inducible factor and increased tubular vascular endothelial growth factor A in PAR-1-deficient mice. Chronic inflammation was also prevented with reduced kidney infiltration by both M1- and M2-polarized macrophages. In thrombin-induced human dermal microvascular endothelial cells (HDMECs), PAR-1 mediated vascular injury through activation of NF-κB and ERK MAPK pathways. Gene silencing of PAR-1 exerted microvascular protection via a tubulovascular crosstalk mechanism during hypoxia in HDMECs. Finally, pharmacologic blockade of PAR-1 with vorapaxar improved kidney morphology, promoted vascular regenerative capacity, and reduced inflammation and fibrosis depending on the time of initiation. Conclusions Our findings elucidate a detrimental role of PAR-1 in vascular dysfunction and profibrotic responses upon tissue injury during AKI-to-CKD transition and provide an attractive therapeutic strategy for post-injury repair in AKI. [ABSTRACT FROM AUTHOR]

Introduction: Inflammatory cell infiltration is a novel hallmark of diabetic kidney disease (DKD), in part, by activated macrophages. Macrophage-to-tubular epithelial cell communication may play an important role in renal fibrosis. Circular RNAs (circRNAs) have been reported in the pathogenesis of various human diseases involving macrophages activation, including DKD. However, the exact mechanism of circRNAs in macrophage infiltration and renal fibrosis of DKD remains obscure. Methods: In our study, a novel circRNA circUBXN7 was identified in DKD patients using microarray. The function of circUBXN7 in vitro and in vivo was investigated by qRT-PCR, western blot, and immunofluorescence. Finally, a dual-luciferase reporter assay, ChIP, RNA pull-down, RNA immunoprecipitation and rescue experiments were performed to investigate the mechanism of circUBXN7. Results: We demonstrated that the expression of circUBXN7 was significantly upregulated in the plasma of DKD patients and correlated with renal function, which might serve as an independent biomarker for DKD patients. According to investigations, ectopic expression of circUBXN7 promoted macrophage activation, EMT and fibrosis in vitro, and increased macrophage infiltration, EMT, fibrosis and proteinuria in vivo. Mechanistically, circUBXN7 was transcriptionally upregulated by transcription factor SP1 and could reciprocally promote SP1 mRNA stability and activation via directly binding to the m6A-reader IGF2BP2 in DKD. Conclusion: CircUBXN7 is highly expressed in DKD patients may provide the potential biomarker and therapeutic target for DKD. [ABSTRACT FROM AUTHOR]

Tubulointerstitial fibrosis is an important pathological feature of diabetic nephropathy that is associated with impaired renal function. However, the mechanism by which fibrosis occurs in diabetic nephropathy is unclear. Differentially expressed genes were identified from transcriptome profiles of renal tissue from diabetic patients and unilateral ureteral obstruction mice and intersected to obtain genes that may be involved in diabetic fibrosis. Biological function analysis and protein–protein interaction network analysis were performed. ROC curve and Pearson correlation analysis between hub genes were performed and glomerular filtration rate estimated. Finally, the RNA levels of hub genes were measured using real-time PCR. A total of 283 genes were identified as potentially involved in diabetic nephropathy fibrosis. TYROBP, CTSS, LCP2, LUM and TLR7 were identified as aberrantly expressed hub genes. Immune cell infiltration analysis demonstrated higher numbers of cytotoxic lymphocytes, B lineage cells, monocyte lineage cells, myeloid dendritic cells, neutrophils, and fibroblasts in the diabetic nephropathy group. The areas under ROC curves for TYROBP, CTSS, LCP2, LUM and TLR7 were 0.9167, 0.9583, 0.9917, 0.93333, and 0.9583, respectively (P < 0.001), and their correlation coefficients with estimated glomerular filtration rate were − 0.8332, − 0.752, − 0.7875, − 0.7567, and − 0.7136, respectively (P < 0.001). The RNA levels of TYROBP, CTSS, LUM and TLR7 were upregulated in high-glucose-treated human renal tubular epithelial cells (P < 0.005). Our study identified TYROBP, CTSS, LCP2, LUM and TLR7 as potentially involved in diabetic nephropathy fibrosis. Furthermore, TYROBP, CTSS, LUM and TLR7 may be associated with epithelial–mesenchymal transition of tubular epithelial cells. [ABSTRACT FROM AUTHOR]

Renal fibrosis is the final common pathophysiological pathway in chronic kidney disease (CKD) regardless of the underlying cause of kidney injury. Tubulointerstitial fibrosis (TIF) is considered to be the key pathological predictor of CKD progression. Currently, the gold‐standard tool to identify TIF is kidney biopsy, an invasive method that carries risks. Non‐invasive diagnostics rely on an estimation of glomerular filtration rate and albuminuria to assess kidney function, but these fail to diagnose early CKD accurately or to predict progressive decline in kidney function. In this review, we summarize the current and emerging molecular biomarkers that have been studied in various clinical settings and in animal models of kidney disease and that are correlated with the degree of TIF. We examine the potential of these biomarkers to diagnose TIF non‐invasively and to predict disease progression. We also examine the potential of new technologies and non‐invasive diagnostic approaches in assessing TIF. Limitations of current and potential biomarkers are discussed and knowledge gaps identified. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease continues to be the leading cause of chronic kidney disease, often advancing to end stage kidney disease. In addition to the well characterized glomerular alterations including mesangial expansion, podocyte injury, and glomerulosclerosis, tubulointerstitial fibrosis is also an important component of diabetic kidney injury. Similarly, tubulointerstitial fibrosis is a critical component of any chronic kidney injury. Therefore, sensitive and quantitative identification of tubulointerstitial fibrosis is critical for the assessment of long-term prognosis of kidney disease. Here, we employed phasor approach to fluorescence lifetime imaging, commonly known as FLIM, to understand tissue heterogeneity and calculate changes in the tissue autofluorescence lifetime signatures due to diabetic kidney disease. FLIM imaging was performed on cryostat sections of snap-frozen biopsy material of patients with diabetic nephropathy. There was an overall increase in phase lifetime (τphase) with increased disease severity. Multicomponent phasor analysis shows the distinctive differences between the different disease states. Thus, phasor autofluorescence lifetime imaging, which does not involve any staining, can be used to understand and evaluate the severity of kidney disease.

Hyperuricemia (HUA)-induced oxidative stress is a crucial contributor to hyperuricemic nephropathy (HN), but the molecular mechanisms underlying the disturbed redox homeostasis in kidneys remain elusive. Using RNA sequencing, together with biochemical analyses, we found that nuclear factor erythroid 2-related factor 2 (NRF2) expression and nuclear localization levels were increased in early HN progression and then gradually declined below the baseline level. We identified the impaired activity of the NRF2-activated antioxidant pathway as a driver of oxidative damage in HN progression. Through nrf2 deletion, we further confirmed aggravated kidney damage in nrf2 knockout HN mice compared with HN mice. In contrast, the pharmacological agonist of NRF2 improved kidney function and alleviated renal fibrosis in mice. Mechanistically, the activation of NRF2 signaling reduced oxidative stress by restoring mitochondrial homeostasis and reducing NADPH oxidase 4 (NOX4) expression in vivo or in vitro. Moreover, the activation of NRF2 promoted the expression levels of heme oxygenase 1 (HO-1) and quinone oxidoreductase 1 (NQO1) and enhanced the antioxidant capacity of cells. Furthermore, the activation of NRF2 ameliorated renal fibrosis in HN mice through the downregulation of the transforming growth factor-beta 1 (TGF-β1) signaling pathway and ultimately delayed the progression of HN. Collectively, these results suggested NRF2 as a key regulator in improving mitochondrial homeostasis and fibrosis in renal tubular cells by reducing oxidative stress, upregulating the antioxidant signaling pathway, and downregulating the TGF-β1 signaling pathway. The activation of NRF2 represents a promising strategy to restore redox homeostasis and combat HN. [ABSTRACT FROM AUTHOR]

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which had a closely relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) played an important role not only in regulating fibrosis process, but also in maintaining mitochondrial function of pancreatic β cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG upregulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose cultured HK-2 cells and 8-week-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF. [ABSTRACT FROM AUTHOR]

Objectives Fibrocytes, the extracellular matrix-producing cells derived from bone marrow progenitors, contribute to organ fibrosis. We investigated the presence and characteristics of fibrocytes in the peripheral blood and kidney of patients with lupus nephritis (LN), and the association of the abundance of fibrocytes with renal tubular epithelial cells (RTECs) in LN fibrogenesis. Methods Fibrocytes were identified with type I collagen (colI), α-smooth muscle actin (α-SMA), CD34 and CD45 using flow cytometry and confocal imaging. The associations between the levels of fibrocytes and pathological features of patients with LN were analysed. The contribution of RTECs to fibrocyte generation was determined using LN sera-treated HK-2 cells. Results Spindle-shaped fibrocytes (colI+α-SMA+CD34+CD45+ cells) were present in the peripheral blood and their abundance was especially high in LN patients with interstitial fibrosis compared with healthy control. Renal fibrocytes (colI+α-SMA+CD45+ cells) were found in the tubulointerstitium in patients with LN, and their numbers were significantly associated with the degrees of chronicity indices including interstitial fibrosis and renal dysfunction. Stimulation of peripheral blood mononuclear cells with supernatants from LN serum-treated HK-2 cells led to a significant generation of fibrocytes, which was abrogated by the addition of IL-6 neutralizing antibody. Conclusion Fibrocytes were significantly increased in the blood and kidney tissue of patients with LN, especially those with interstitial fibrosis. Fibrocytes could be differentiated from blood cells, with an active contribution from RTECs. Our results show a possible link between fibrocytes and tubulointerstitial fibrosis, which may serve as a novel therapeutic target for LN fibrogenesis. [ABSTRACT FROM AUTHOR]

Renal fibrosis, a common pathological manifestation of virtually all types of chronic kidney disease (CKD), ultimately predisposes patients to end‐stage renal disease. However, there is no effective therapy for renal fibrosis. Our earlier studies proved that RIP3‐mediated necroptosis might be an important mode of renal tubular cell death in rats with chronic renal injury. Under transmission electron microscopy (TEM), we found morphological changes in the necrosis of human renal tissue, and the percentage of necrotic cells increased significantly in patients with stages 2 and 3a CKD. Immunofluorescence analyses showed that the percentages of TUNEL+/RIP3+ double‐positive and TUNEL+/MLKL+ double‐positive tubular epithelial cells in renal tubules of patients with stages 2 and 3a CKD were significantly increased compared to those in control patients without renal disease. Immunohistochemistry analyses of renal biopsy specimens from patients with CKD revealed RIP3, MLKL, and p‐MLKL upregulation in patients with stages 2 and 3a CKD, suggesting that necroptosis of renal tubular epithelial cells in CKD patients occurs, and the peak of necroptosis was in stages 2 and 3a CKD. We showed that profibrotic factor proteins (TGF‐β1, Smad2 and Smad3) and fibroblast activation markers (α‐SMA and Vimentin) were specifically upregulated in stage 2 and 3a CKD patients. In addition, Pearson correlation analysis showed that the percentage of necroptotic renal tubular epithelial cells was positively correlated with TGF‐β1 and collagen‐I. We also showed that RIP1/3 or MLKL inhibitors decreased the expression of RIP3, MLKL, TGF‐β1, and Smad3 in HK‐2 cells treated with TNF‐α. FGF‐2, α‐SMA, Vimentin and FN were overexpressed in the hRIFs cultured with the supernatant of necroptotic HK‐2 cells, whereas necroptosis blockers (Nec‐1s, GSK'872 and NSA) and TGF‐β1/Smad3 pathway antagonists (LY364947 and SIS3) reduced FGF‐2, α‐SMA, Vimentin and FN levels. Collectively, necroptosis of renal tubular epithelial cells in CKD patients occurs, and the peak of necroptosis was in stages 2 and 3a CKD. Renal tubular epithelial cell necroptosis mediates renal tubulointerstitial fibrosis in patients with chronic kidney disease, which is related to the TGF‐β1/Smad3 signaling pathway. [ABSTRACT FROM AUTHOR]

Chronic kidney disease (CKD) is a significant health burden, with rising incidence and prevalence, attributed in part to increasing obesity and diabetes rates. Lipid accumulation in the kidney parenchyma and chronic, low-grade inflammation are believed to significantly contribute to the development and progression of CKD. The effect of dysregulated kidney lipid metabolism in CKD progression, including altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury through the activation of oxidative stress and inflammatory signalling cascades. In contrast, classes of endogenous specialized pro-resolving lipid mediators (SPMs) have been described that act to limit the inflammatory response and promote the resolution of inflammation. This review highlights our current understanding of how lipids can cause damage within the kidney, and classes of protective lipid metabolites that offer therapeutic benefits. [Display omitted] • Endogenous specialized pro-resolving lipid mediators (SPMs) can attenuate the inflammatory response. • SPMs are derived from omega-3 and -6 PUFAs. • SPMs have demonstrated protective effects in models of kidney injury. • Synthetic mimics of SPMs can be exploited as novel therapies in chronic kidney disease. [ABSTRACT FROM AUTHOR]

Tubulointerstitial fibrosis (TIF), a common end result of almost all progressive chronic kidney diseases (CKD), is also the best predictor of kidney survival. Almost all cells in the kidney are involved in the progression of TIF. Myofibroblasts, the primary producers of extracellular matrix, have previously received a great deal of attention; however, a large body of emerging evidence reveals that proximal tubule (PT) plays a central role in TIF progression. In response to injury, renal tubular epithelial cells (TECs) transform into inflammatory and fibroblastic cells, producing various bioactive molecules that drive interstitial inflammation and fibrosis. Here we reviewed the increasing evidence for the key role of the PT in promoting TIF in tubulointerstitial and glomerular injury and discussed the therapeutic targets and carrier systems involving the PT that holds particular promise for treating patients with fibrotic nephropathy.

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus, which is characterized in renal tubulointerstitial fibrosis (TIF). The current study was designed to investigate the protective effect of Jujuboside A (Ju A) on TIF in type 2 diabetes (T2DM) mice, and explore its underlying anti-fibrosis mechanism. A mouse T2DM model was established using high fat diet (HFD) feeding combined with intraperitoneal injection of streptozotocin (STZ). Then, diabetic mice were treated with Ju A (10, 20 and 40 mg·kg−1·d−1, i.g.) for 12 weeks. Results showed that administration of Ju A not only down-regulated fasting blood glucose (FBG) levels, but also improved hyperlipidemia and renal function in diabetic mice. Moreover, the reduced ECM accumulation was observed in the renal cortex of Ju A treated diabetic mice, while the TIF progression was also attenuated by Ju A through blocking the epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells (RTECs). Further mechanism studies showed that Ju A treatment effectively down-regulated the protein expression and subsequent nuclear translocation of Yin Yang 1 (YY1) in the renal cortex of diabetic mice, and reduced the levels of transforming growth factor- β 1 (TGF- β 1) in the serum and renal cortex of Ju A treated mice. According to in vitro studies, the up-regulated YY1/TGF- β 1 signaling pathway was restored by Ju A in high glucose (HG) cultured HK-2 cells. Taken together, these findings demonstrated that Ju A can ameliorate the TIF of DN through down-regulating the YY1/TGF- β 1 signaling pathway. [ABSTRACT FROM AUTHOR]

Canonical transient receptor potential-6 (TRPC6) channels have been implicated in familial and acquired forms of focal and segmental glomerulosclerosis (FSGS), and in renal fibrosis following ureteral obstruction in mice. TRPC6 channels also appear to play a role in driving glomerular disease in aging and in autoimmune glomerulonephritis. In the present study, we examine the role of TRPC6 in the proteinuric state caused by prolonged albumin overload (AO) in Sprague Dawley rats induced by daily injections of exogenous albumin. This was assessed in rats with a global and constitutive inactivation of TRPC6 channels (Trpc6del/del rats) and in wild-type littermates (Trpc6wt/wt rats). AO for 14 and 28 days caused increased urine albumin excretion that was significantly attenuated in Trpc6del/del rats compared to Trpc6wt/wt controls. AO overload did not induce significant glomerulosclerosis or azotemia in either genotype. AO induced mild tubulointerstitial disease characterized by fibrosis, hypercellularity and increased expression of markers of fibrosis and inflammation. Those changes were equally severe in Trpc6wt/wt and Trpc6del/del rats. Immunoblot analysis of renal cortex indicated that AO increased the abundances of TRPC3 and TRPC6, and caused a nearly complete loss of TRPC5 in Trpc6wt/wt rats. The increase in TRPC3 and the loss of TRPC5 occurred to the same extent in Trpc6del/del rats. These data also suggest that TRPC6 plays a role in the normal function of the glomerular filtration barrier. However, whether TRPC6 inactivation protects the tubulointerstitial compartments in Sprague Dawley rats depends on the disease model examined. [ABSTRACT FROM AUTHOR]

Renal tubulointerstitial fibrosis (TIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, is the typical pathological alteration in diabetic nephropathy. Gentiopicroside (GPS), a natural compound with anti-inflammatory activity, has been demonstrated to alleviate glomerulosclerosis, whereas whether GPS inhibits TIF via regulating inflammation remains unclear. In this study, diabetic db/db mice and high glucose (HG)-stimulated renal tubular epithelial cells (NRK-52E) were applied to explore the effects and mechanisms of GPS on TIF. The results in vivo showed that GPS effectively improves glycolipid metabolism disorder, renal dysfunction, and TIF. In particular, GPS treatment reversed the abnormal expressions of EMT marker proteins including elevated α-smooth muscle actin and vimentin and decreased E-cadherin in the kidney of db/db mice. Moreover, GPS treatment also inhibited protein expressions of angiotensinⅡ type 1 receptor (AT1R) and CK2α and the activation of the NF-κB pathway. Importantly, the aforementioned effects of GPS acted in vivo were further observed in vitro in HG-stimulated NRK-52E cells, which were independent of its effects on glucose and lipid-lowering activity but were reversed by AT1R over-expression. Together, our results indicate that GPS that directly inhibits the CK2/NF-κB inflammatory signaling pathway via AT1R may also contribute to the amelioration of TIF in diabetes. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease is one of the most serious microvascular complications of diabetes. It progresses irreversibly to end-stage renal disease if left untreated. Bone morphogenetic protein (BMP)-7 is a negative regulator of organ fibrosis and may also play an essential role in tubulointerstitial fibrosis. This study aimed to investigate the precise role and potential molecular mechanisms of BMP-7 in the progression of diabetic nephropathy. In this study, BMP-7 was overexpressed in vivo after the replication of the diabetic rat model using streptozotocin. The results showed that BMP-7 inhibited the phosphorylation of related mitogen-activated protein kinase (MAPK) pathways while upregulating the inhibitor of differentiation (Id2) expression and effectively ameliorated pathological renal injury. Further in vitro validation showed that the inhibition of the phosphorylation of MAPKs at a high glucose concentration in renal tubular epithelial cells was followed by the upregulation of Id2 protein expression, suggesting that BMP-7 could improve diabetic nephropathy by upregulating Id2 protein levels through the BMP-7–MAPK signaling pathway. Previous laboratory studies found that oxymatrine improved renal fibrotic lesions. However, the exact mechanism is unclear. The present study showed that oxymatrine treatment in a diabetic rat model upregulated BMP-7 protein expression and inhibited MAPK pathway protein phosphorylation levels. These results suggested that oxymatrine improved the epithelial-to-mesenchymal transition process in the early stage of diabetic kidney disease by regulating the BMP-7–MAPK pathway and ameliorated renal tubulointerstitial fibrosis. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease is one of the most serious microvascular complications of diabetes. It progresses irreversibly to end-stage renal disease if left untreated. Bone morphogenetic protein (BMP)-7 is a negative regulator of organ fibrosis and may also play an essential role in tubulointerstitial fibrosis. This study aimed to investigate the precise role and potential molecular mechanisms of BMP-7 in the progression of diabetic nephropathy. In this study, BMP-7 was overexpressed in vivo after the replication of the diabetic rat model using streptozotocin. The results showed that BMP-7 inhibited the phosphorylation of related mitogen-activated protein kinase (MAPK) pathways while upregulating the inhibitor of differentiation (Id2) expression and effectively ameliorated pathological renal injury. Further in vitro validation showed that the inhibition of the phosphorylation of MAPKs at a high glucose concentration in renal tubular epithelial cells was followed by the upregulation of Id2 protein expression, suggesting that BMP-7 could improve diabetic nephropathy by upregulating Id2 protein levels through the BMP-7–MAPK signaling pathway. Previous laboratory studies found that oxymatrine improved renal fibrotic lesions. However, the exact mechanism is unclear. The present study showed that oxymatrine treatment in a diabetic rat model upregulated BMP-7 protein expression and inhibited MAPK pathway protein phosphorylation levels. These results suggested that oxymatrine improved the epithelial-to-mesenchymal transition process in the early stage of diabetic kidney disease by regulating the BMP-7–MAPK pathway and ameliorated renal tubulointerstitial fibrosis.

Renal tubulointerstitial fibrosis (TIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, is the typical pathological alteration in diabetic nephropathy. Gentiopicroside (GPS), a natural compound with anti-inflammatory activity, has been demonstrated to alleviate glomerulosclerosis, whereas whether GPS inhibits TIF via regulating inflammation remains unclear. In this study, diabetic db/db mice and high glucose (HG)-stimulated renal tubular epithelial cells (NRK-52E) were applied to explore the effects and mechanisms of GPS on TIF. The results in vivo showed that GPS effectively improves glycolipid metabolism disorder, renal dysfunction, and TIF. In particular, GPS treatment reversed the abnormal expressions of EMT marker proteins including elevated α-smooth muscle actin and vimentin and decreased E-cadherin in the kidney of db/db mice. Moreover, GPS treatment also inhibited protein expressions of angiotensinⅡ type 1 receptor (AT1R) and CK2α and the activation of the NF-κB pathway. Importantly, the aforementioned effects of GPS acted in vivo were further observed in vitro in HG-stimulated NRK-52E cells, which were independent of its effects on glucose and lipid-lowering activity but were reversed by AT1R over-expression. Together, our results indicate that GPS that directly inhibits the CK2/NF-κB inflammatory signaling pathway via AT1R may also contribute to the amelioration of TIF in diabetes.

Kidney aging is a normal physiological process associates with various molecular, morphologic and functional changes in the kidney tissues. This work was designed to study microscopically the structural changes in the kidney tissue of aged rats compared to young rats. Male Sprague–Dawley rats were used 10 young rats (4 months) and 10 aged rats (24 months). Rats were transcardially perfused with 4% paraformaldehyde. The kidneys were post fixed for 24 hours in 4 % PFA then proceeded for normal histopathology and light microscopic examination. Kidney tissue of aged rats showed serious morphological changes such as segmental glomerulosclerosis, pericapsular fibrosis, tubulointerstitial fibrosis, perivascular fibrosis, inflammatory cell infiltration, tubular dilatation, intra-tubular cast formation and tubular atrophy. These changes were compared to the normal histological appearance of glomeruli, tubules, interstitium and blood vessels of young rat kidneys. In addition, the kidney tissue of the aged rats showed compensatory glomerular hypertrophy, tubular hyperplasia and endothelial proliferation. Renal aging involves several degenerative changes in kidney structure and these alterations interfere with the physiologic functions and end with chronic renal failure.

Anti-partial epithelial-mesenchymal transition (pEMT) treatment of renal tubular epithelial cells (TECs) represents a promising therapeutic approach. Hyperuricemia nephropathy (HN) arises as a consequence of hyperuricemia (HUA)-induced tubulointerstitial fibrosis (TIF). Studies have suggested that the Ras homolog member A (RhoA)/Rho-associated kinase (ROCK) pathway is a crucial signaling transduction system in renal fibrosis. Fasudil, a RhoA/ROCK inhibitor, has exhibited the potential to prevent fibrosis progress. However, its impact on the pEMT of TECs in HN remains unclear. Here, an HN rat model and an uric acid (UA)-stimulated human kidney 2 (HK2) cell model were established and treated with Fasudil to explore its effects. Furthermore, the underlying mechanism of action involved in the attenuation of pEMT in TECs by Fasudil during HN was probed by using multiple molecular approaches. The HN rat model exhibited significant renal dysfunction and histopathological damage, whereas in vitro and in vivo experiments further confirmed the pEMT status accompanied by RhoA/ROCK pathway activation and oxidative stress in tubular cells exposed to UA. Notably, Fasudil ameliorated these pathological changes, and this was consistent with the trend of ROCK silencing in vitro. Mechanistically, we identified the Neh2 domain of nuclear factor erythroid 2-related factor 2 (Nrf2) as a target of Fasudil for the first time. Fasudil targets Nrf2 activation and antagonizes oxidative stress to attenuate the pEMT of TECs in HN. Our findings suggest that Fasudil attenuates oxidative stress-induced pEMT of TECs in HN by targeting Nrf2 activation. Thus, Fasudil is a potential therapeutic agent for the treatment of HN. [Display omitted] • Fasudil relieved renal dysfunction and TIF in HN rats. • Fasudil attenuated UA-induced pEMT in tubular cells. • UA-induced oxidative stress led to TIF in HN by promoting pEMT in tubular cells. • Fasudil targeted activation of Nrf2 for suppressing oxidative stress to defend against HN. [ABSTRACT FROM AUTHOR]

Hyperuricemia (HUA)-induced oxidative stress is a crucial contributor to hyperuricemic nephropathy (HN), but the molecular mechanisms underlying the disturbed redox homeostasis in kidneys remain elusive. Using RNA sequencing, together with biochemical analyses, we found that nuclear factor erythroid 2-related factor 2 (NRF2) expression and nuclear localization levels were increased in early HN progression and then gradually declined below the baseline level. We identified the impaired activity of the NRF2-activated antioxidant pathway as a driver of oxidative damage in HN progression. Through nrf2 deletion, we further confirmed aggravated kidney damage in nrf2 knockout HN mice compared with HN mice. In contrast, the pharmacological agonist of NRF2 improved kidney function and alleviated renal fibrosis in mice. Mechanistically, the activation of NRF2 signaling reduced oxidative stress by restoring mitochondrial homeostasis and reducing NADPH oxidase 4 (NOX4) expression in vivo or in vitro. Moreover, the activation of NRF2 promoted the expression levels of heme oxygenase 1 (HO-1) and quinone oxidoreductase 1 (NQO1) and enhanced the antioxidant capacity of cells. Furthermore, the activation of NRF2 ameliorated renal fibrosis in HN mice through the downregulation of the transforming growth factor-beta 1 (TGF-β1) signaling pathway and ultimately delayed the progression of HN. Collectively, these results suggested NRF2 as a key regulator in improving mitochondrial homeostasis and fibrosis in renal tubular cells by reducing oxidative stress, upregulating the antioxidant signaling pathway, and downregulating the TGF-β1 signaling pathway. The activation of NRF2 represents a promising strategy to restore redox homeostasis and combat HN.

Chronic kidney disease (CKD) was a major public health problem worldwide. Renal fibrosis, especially tubulointerstitial fibrosis, is final manifestation of CKD. Many studies have demonstrated that TGF-β/Smad signaling pathway plays a crucial role in renal fibrosis. Therefore, targeted inhibition of TGF-β/Smad signaling pathway can be used as a potential therapeutic measure for tubulointerstitial fibrosis. At present, a variety of targeting TGF-β1 and its downstream Smad proteins have attracted attention. Natural products used as potential therapeutic strategies for tubulointerstitial fibrosis have the characteristics of acting on multiple targets by multiple components and few side effects. With the continuous research and technique development, more and more molecular mechanisms of natural products have been revealed, and there are many natural products that inhibited tubulointerstitial fibrosis via TGF-β/Smad signaling pathway. This review summarized the role of TGF-β/Smad signaling pathway in tubulointerstitial fibrosis and natural products against tubulointerstitial fibrosis by targeting TGF-β/Smad signaling pathway. Additionally, many challenges and opportunities are presented for inhibiting renal fibrosis in the future. [ABSTRACT FROM AUTHOR]