Mechanisms of tubulointerstitial fibrosis

Confrontation with kidney inflammation through a HMGB1-targeted peptide augments anti-fibrosis therapy

Damage to the renal tubular epithelial cells (TEC) is a key cellular event in kidney inflammation and subsequent fibrosis. However, drugs targeting renal TEC (RTEC) are limited to the alleviation of kidney fibrosis. Lethal giant larvae 1 (Lgl1) plays a key role in epithelial cell polarity and proliferation. Here, we report that the renal tubule epithelial-specific deletion of Lgl1 significantly ameliorated intrarenal inflammation and kidney fibrosis. Mechanistically, Lgl1 suppressed the activity of the deacetylase sirtuin 1 (SIRT1) and augmented the acetylation of high-mobility group box 1 (HMGB1) at the lysine 90 (K90) site. Consequently, HMGB1 migrated from the nucleus to the cytoplasm, activating an inflammatory cascade. Our renoprotective strategy was to construct a mimic peptide, TAT-K90WT, that targets HMGB1 K90 acetylation. Administration of this peptide significantly ameliorated inflammation and fibrosis in the kidneys. In summary, the Lgl1-HMGB1 axis plays an important role in renal fibrosis, and targeting HMGB1 acetylation by mimicking peptides is a potential strategy to prevent fibrosis.

Renal Angptl4 is a key fibrogenic molecule in progressive diabetic kidney disease

Angiopoietin-like 4 (ANGPTL4), a key protein involved in lipoprotein metabolism, has diverse effects. There is an association between Angptl4 and diabetic kidney disease; however, this association has not been well investigated. We show that both podocyte- and tubule-specific ANGPTL4 are crucial fibrogenic molecules in diabetes. Diabetes accelerates the fibrogenic phenotype in control mice but not in ANGPTL4 mutant mice. The protective effect observed in ANGPTL4 mutant mice is correlated with a reduction in stimulator of interferon genes pathway activation, expression of pro-inflammatory cytokines, reduced epithelial-to-mesenchymal transition and endothelial-to-mesenchymal transition, lessened mitochondrial damage, and increased fatty acid oxidation. Mechanistically, we demonstrate that podocyte- or tubule-secreted Angptl4 interacts with Integrin β1 and influences the association between dipeptidyl-4 with Integrin β1. We demonstrate the utility of a targeted pharmacologic therapy that specifically inhibits Angptl4 gene expression in the kidneys and protects diabetic kidneys from proteinuria and fibrosis. Together, these data demonstrate that podocyte- and tubule-derived Angptl4 is fibrogenic in diabetic kidneys.

Oridonin ameliorates renal fibrosis in diabetic nephropathy by inhibiting the Wnt/β-catenin signaling pathway

Diabetic nephropathy (DN) is one of the most serious and frequent complications among diabetes patients and presently constitutes vast the cases of end-stage renal disease worldwide. Tubulointerstitial fibrosis is a crucial factor related to the occurrence and progression of DN. Oridonin (Ori) is a diterpenoid derived from rubescens that has diverse pharmacological properties. Our previous study showed that Ori can protect against DN by decreasing the inflammatory response. However, whether Ori can alleviate renal fibrosis in DN remains unknown. Here, we investigated the mechanism through which Ori affects the Wnt/β-catenin signaling pathway in diabetic rats and human proximal tubular epithelial cells (HK-2) exposed to high glucose (HG) levels. Our results revealed that Ori treatment markedly decreased urinary protein excretion levels, improved renal function and alleviated renal fibrosis in diabetic rats. In vitro, HG treatment increased the migration of HK-2 cells while reducing their viability and proliferation rate, and treatment with Ori reversed these changes. Additionally, the knockdown of β-catenin arrested cell migration and reduced the expression levels of Wnt/β-catenin signaling-related molecules (Wnt4, p-GSK3β and β-catenin) and fibrosis-related molecules (α-smooth muscle actin, collagen I and fibronectin), and Ori treatment exerted an effect similar to that observed after the knockdown of β-catenin. Furthermore, the combination of Ori treatment and β-catenin downregulation exerted more pronounced biological effects than treatment alone. These findings may provide the first line of evidence showing that Ori alleviates fibrosis in DN by inhibiting the Wnt/β-catenin signaling pathway and thereby reveal a novel therapeutic avenue for treating tubulointerstitial fibrosis.

Global trends and prospects related to macrophage in chronic kidney disease: a bibliometric analysis

BACKGROUND AND AIMS

Macrophages play a variety of widely concerned roles in the process of chronic kidney disease (CKD). To further understand the research hotspots and development trends regarding the relationship between macrophages and CKD, the role of macrophages in the occurrence and progression of CKD was summarized by bibliometrics in this study.

MATERIAL AND METHODS

We collected the studies relevant the role of macrophages in CKD from the Web of Science Core Collection, which included 1332 relevant studies from Jan 1st, 2004 to Jul 6th, 2023 in WoSCC. CiteSpace, biblioshiny in R, VOSviewer and SCImago Graphica Beta were used for bibliometric analysis and visualization.

RESULTS

Monash University from Australia is the most productive institution, while China and the USA are most productive countries. Anders HJ is the most cited author. In terms of the number of co-citations, the top one was "Macrophages: versatile players in renal inflammation and fibrosis" by Patrick Ming-Kuen Tang, published in Nature Reviews Nephrology in 2019. Important keywords of this research topic include inflammation, dendritic cell, oxidative stress, NF-κB, tgf-beta, interstitial fibrosis, glomerulonephritis, diabetic nephropathy. Future research hotspots may include molecular mechanism, acute kidney injury, macrophage polarization, kidney fibrosis.

CONCLUSION

This study provides a systematic review of the role of macrophages in CKD and speculates that future research hotspots. Previous studies have focused on the immune function of macrophages and atypia, and metabolic factors (especially iron metabolism within macrophages) have attracted the attention of researchers in recent years and are the forefront of recent research.

ACVR1 mediates renal tubular EMT in kidney fibrosis via AKT activation

Tubulointerstitial fibrosis in the kidneys is a chronic and progressive process. Although studies suggested that tubular epithelial-mesenchymal transition (EMT) plays a key role in the development of kidney fibrosis, whether ACVR1, a member of the TGFβ superfamily, is involved in the EMT needs to be illustrated. Using bioinformatics analysis of bulk-seq data (GSE23338 and GSE168876), we found that TGF-β1 perhaps activated the PI3K/AKT signaling pathway and induced the mRNA expression of ACVR1, fibronectin, and Collagen I in HK-2 cells (human renal tubular epithelial cell line). Furthermore, qPCR and western blotting results confirmed the high expressions of ACVR1 and EMT markers in TGFβ-induced HK-2 cells. Similar results were also found in the UUO mouse model. Besides, different time-point immunofluorescent staining indicated a positive correlation between the expression of the ACVR1 and EMT marker vimentin in TGF-β1-induced HK-2 cells. Consequently, knockdown ACVR1 effectively inhibited the expression of TGF-β1-induced EMT markers and AKT phosphorylation in HK-2 cells. Moreover, treatment of HK-2 cells with MK2206 (an allosteric inhibitor of AKT) decreased the activation of AKT and the expression of α-SMA while treatment of cells with SC79 (a AKT activator) enhanced the expression of α-SMA. These findings suggest that ACVR1 regulated the EMT of renal tubular epithelial cells through activation of the AKT signaling pathway and that ACVR1 could be considered novel therapeutic targets for renal fibrosis.

Renal Epithelial Complement C3 Expression Affects Kidney Fibrosis Progression

Kidney fibrosis is a hallmark of chronic kidney diseases. Evidence shows that genetic variability and complement component 3 (C3) might influence tubulointerstitial fibrosis. Still, the role of renal C3 production in the epithelial-to-mesenchymal transition (EMT) and genetically determined fibrosis progression remains undiscovered. The kidneys of fibrosis-resistant C57Bl/6J (B6) and fibrosis-prone CBA/J (CBA) and BALB/cJ (BalbC) mice (n = 4-8/group) were subjected to unilateral ureteral obstruction (UUO) and analyzed after 1, 3, and 7 days, along with human focal glomerular sclerotic (FSGS) and healthy kidneys. Mouse primary tubular epithelial cells (PTECs) were investigated after 24 h of treatment with transforming growth factor β (TGFβ) or complement anaphylatoxin 3a (C3a) agonist (n = 4/group). UUO resulted in delayed kidney injury in fibrosis-resistant B6 mice, but very early renal C3 messenger RNA (mRNA) induction in fibrosis-prone CBA and BalbC mice, along with collagen I (Col1a1) and collagen III (Col3a1). CBA depicted the fastest fibrosis progression with the highest C3, lipocalin-2 (Lcn2), Tgfb1, and chemokine (C-C motif) ligand 2 (Ccl2) expression. Human FSGS kidneys depicted C3 mRNA over-expression and strong tubular C3 immunostaining. In PTECs, C3a agonist treatment induced pro-fibrotic early growth response protein 1 (EGR1) expression and the EMT, independent of TGFβ signaling. We conclude that de novo renal tubular C3 synthesis is associated with the genetically determined kidney fibrosis progression rate in mice and the pathogenesis of FSGS in humans. This tubular C3 overproduction can, through local pro-fibrotic effects, influence the progression of chronic kidney disease.

Hypoxia-Treated Adipose Mesenchymal Stem Cells Derived Exosomes Enhance the Therapeutic Effects on Unilateral Ureteral Obstruction Mice

INTRODUCTION

The exosomes from adipose-derived mesenchymal stem cells (AMSCs) had therapeutic effects. However, whether the exosomes derived from hypoxia-treated AMSCs could improve renal functions in unilateral ureteral obstruction (UUO) mice remains unclear.

METHODS

The exosomes were characterized using a transmission electron microscope and Western blot. Its size distribution was determined using the Zetasizer Nano ZS analysis system. The differentiation ability was assessed by alkaline phosphatase and oil red staining. Consequently, the function of exosomes in inhibiting inflammatory factors was evaluated using an enzyme-linked immunosorbent assay, and apoptosis inhibition was evaluated by Western blot. Finally, the function of exosomes to ameliorate kidney fibrosis was evaluated using quantitative reverse transcription polymerase chain reaction, Western blot, hematoxylin-eosin staining, and Masson staining.

RESULTS

The cultured AMSCs could differentiate into osteoblast and adipocyte. Meanwhile, the cultured AMSCs could effectively secrete the exosomes, which were characterized by around 110 nm diameter and surface marker expression. Exosomes derived from hypoxia-treated AMSCs improved renal functions in UUO mice. The mechanism exploration revealed that exosomes could decrease the TNF-α and IL-6 and inhibit cell apoptosis. Finally, the fibrosis-associated protein was reversed, and the renal dysfunctions were ameliorated in UUO mice.

CONCLUSION

The exosomes derived from the hypoxia-treated AMSCs have a better effect than those from normal AMSCs in ameliorating renal dysfunctions in UUO mice.

Epigenetics of Hypertensive Nephropathy

Hypertensive nephropathy (HN) is a leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD), contributing to significant morbidity, mortality, and rising healthcare costs. In this review article, we explore the role of epigenetic mechanisms in HN progression and their potential therapeutic implications. We begin by examining key epigenetic modifications-DNA methylation, histone modifications, and non-coding RNAs-observed in kidney disease. Next, we discuss the underlying pathophysiology of HN and highlight current in vitro and in vivo models used to study the condition. Finally, we compare various types of HN-induced renal injury and their associated epigenetic mechanisms with those observed in other kidney injury models, drawing inferences on potential epigenetic therapies for HN. The information gathered in this work indicate that epigenetic mechanisms can drive the progression of HN by regulating key molecular signaling pathways involved in renal damage and fibrosis. The limitations of Renin-Angiotensin-Aldosterone System (RAAS) inhibitors underscore the need for alternative treatments targeting epigenetic pathways. This review emphasizes the importance of further research into the epigenetic regulation of HN to develop more effective therapies and preventive strategies. Identifying novel epigenetic markers could provide new therapeutic opportunities for managing CKD and reducing the burden of ESRD.

Impact of immunosuppressive drugs on efficacy of mesenchymal stem cell therapy for suppressing renal fibrosis

Preemptive regenerative medicine using mesenchymal stem cells (MSCs) may provide a novel therapeutic approach to prevent the progression from organ damage to organ failure. Although immunosuppressive drugs are often used in patients with organ disorder, their impact on MSC therapy remains unclear. We investigated the effects of immunosuppressive drugs on the therapeutic efficacy of MSCs. We created unilateral ureteral obstruction models, as a well-established model of renal fibrosis, a preliminary stage of organ failure. Three immunosuppressive drugs (methylprednisolone, cyclosporine, and cyclophosphamide) were intraperitoneally administered 3 days after surgery, and MSCs were injected via tail vein the following day. Preadministration of methylprednisolone or cyclophosphamide interfered with MSC activation by reducing expression of interferon-gamma (IFN-γ) and high-mobility group box-1 protein, thus significantly attenuating the therapeutic efficacy of MSCs. Preadministration of cyclophosphamide downregulated the expression of stromal cell-derived factor-1/C-X-C motif ligand 12, which is a potent migration factor for MSCs, resulting in reduced MSC engraftment in the renal cortex. IFN-γ-preconditioned activated MSCs were unaffected by these drugs and maintained their beneficial therapeutic effects. Cyclosporine preadministration had no effect on the therapeutic efficacy of MSCs. Our study demonstrated that the administration of certain immunosuppressive drugs interfered with MSC activation and engraftment at the site of injury, resulting in a significant attenuation of their therapeutic efficacy. These findings provide crucial information for selecting patients suitable for MSC therapy. Use of MSCs preactivated with IFN-γ or other means is preferred for patients on methylprednisolone or cyclophosphamide.

Eucommiae cortex extract alleviates renal fibrosis in CKD mice induced by adenine through the TGF-β1/Smad signaling pathway

Research into the potential therapeutic benefits of herbal remedies for treating chronic kidney disease (CKD), a condition marked by renal fibrosis and persistent inflammation, has become popular. Eucommiae cortex (EC) is a vital herb for strengthening bones and muscles and tonifying the kidneys and liver. In the study, C57 BL/6 mice were given a diet containing 0.2% adenine to create a CKD model. The findings demonstrated that exogenous EC supplementation successfully decreased the levels of creatinine and urea nitrogen, down-regulated the TGF-β1/Smad signaling pathway's expression levels of TGF-β1, α-SMA, Smad3, and phospho-Smad3, and prevented renal fibrosis. Consequently, it was determined that EC might have a nephroprotective impact.

Collecting Duct Pro(Renin) Receptor Contributes to Unilateral Ureteral Obstruction-Induced Kidney Injury via Activation of the Intrarenal RAS

BACKGROUND

Although the concept of the intrarenal renin-angiotensin system (RAS) in renal disease is well-described in the literature, the precise pathogenic role and mechanism of this local system have not been directly assessed in the absence of confounding influence from the systemic RAS. The present study used novel mouse models of collecting duct (CD)-specific deletion of (pro)renin receptor (PRR) or renin together with pharmacological inhibition of soluble PRR production to unravel the precise contribution of the intrarenal RAS to renal injury induced by unilateral ureteral obstruction.

METHODS

We examined the impact of CD-specific deletion of PRR, CD-specific deletion of renin, and S1P (site-1 protease) inhibitor PF429242 treatment on renal fibrosis and inflammation and the indices of the intrarenal RAS in a mouse model of unilateral ureteral obstruction.

RESULTS

After 3 days of unilateral ureteral obstruction, the indices of the intrarenal RAS including the renal medullary renin content, activity and mRNA expression, and Ang (angiotensin) II content in obstructed kidneys of floxed mice were all increased. That effect was reversed with CD-specific deletion of PRR, CD-specific deletion of renin, and PF429242 treatment, accompanied by consistent improvement in renal fibrosis and inflammation. On the other hand, renal cortical renin levels were unaffected by unilateral ureteral obstruction, irrespective of the genotype. Similar results were obtained via pharmacological inhibition of S1P, the key protease for the generation of soluble PRR.

CONCLUSIONS

Our results reveal that PRR-dependent/soluble PRR-dependent activation of CD renin represents a key determinant of the intrarenal RAS and, thus, obstruction-induced renal inflammation and fibrosis.

Does the Composition of Gut Microbiota Affect Chronic Kidney Disease? Molecular Mechanisms Contributed to Decreasing Glomerular Filtration Rate

Chronic kidney disease (CKD) is a very prevalent and insidious disease, particularly with initially poorly manifested symptoms that progressively culminate in the manifestation of an advanced stage of the condition. The gradual impairment of kidney function, particularly decreased filtration capacity, results in the retention of uremic toxins and affects numerous molecular mechanisms within the body. The dysbiotic intestinal microbiome plays a crucial role in the accumulation of protein-bound uremic toxins such as p-cresol (pC), indoxyl sulfate (IS), and p-cresyl sulfate (p-CS) through the ongoing fermentation process. The described phenomenon leads to an elevated level of oxidative stress and inflammation, subsequently resulting in tissue damage and complications, particularly an increase in cardiovascular risk, representing the predominant cause of mortality in chronic kidney disease (CKD). Therefore, exploring methods to reduce uremic toxins is currently a pivotal therapeutic strategy aimed at reducing the risk of organ damage in patients with chronic kidney disease (CKD). This review aims to summarize recent discoveries on modifying the composition of the intestinal microbiota through the introduction of special probiotic and synbiotic supplements for CKD therapy. The potential to connect the gut microbiota with CKD opens the possibility for further extensive research in this area, which could lead to the incorporation of synbiotics and probiotics into the fundamental treatment and prevention of CKD.

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

Resveratrol reinforces the therapeutic effect of mesenchymal stem cell (MSC)-derived exosomes against renal ischemia‒reperfusion injury (RIRI)-associated fibrosis by suppressing TGF-β-induced epithelial-mesenchymal transition

Resveratrol (RSV) has been shown to prevent epithelial-mesenchymal transition (EMT) in different diseases by modulating several signaling pathways, and RSV can prevent EMT by modulating the signaling of the TGF-β/Smad axis. In the development of renal ischemia‒reperfusion injury (RIRI), RSV and MSC-derived exosomes could ameliorate RIRI via different signaling pathways. In this study, we aimed to investigate the effect of RSV plus MSC-derived exosomes on the prognosis of RIRI. Quantitative real-time polymerase chain reaction (PCR) was performed to measure the expression of E-CAD, SMA, COL10A1, VMT and MMP-7 mRNA in TCMK-1 cells and mice under various conditions. HE and Masson staining were used to evaluate kidney injury and fibrosis in mice under various conditions. RSV effectively maintained the TGF-β- and AA-induced upregulation of E-CAD, SMA, COL10A1, VMT and MMP-7 mRNA expression in TCMK-1 cells. Moreover, MSC-derived exosomes effectively reinforced the effect of RSV on reducing the TGF-β- and AA-induced upregulation of E-CAD, SMA, COL10A1, VMT and MMP-7 mRNA expression in TCMK-1 cells. Furthermore, MSC-derived exosomes enhanced the capability of RSV to maintain the RIRI-induced increases in Cr and BUN, as well as the upregulation of E-CAD, SMA, COL10A1, VMT and MMP-7 mRNA expression in mice. In addition, MSC-derived exosomes enhanced the capability of RSV to decrease RIRI-induced kidney injury and fibrosis in mice. Our findings showed that the administration of MSC-derived exosomes and RSV could suppress the TGF-β-induced epithelial-mesenchymal transition. This suppressive effect was promoted by the coadministration of MSC-derived exosomes and RSV.

Lactate drives epithelial-mesenchymal transition in diabetic kidney disease via the H3K14la/KLF5 pathway

High levels of urinary lactate are an increased risk of progression in patients with diabetic kidney disease (DKD). However, it is still unveiled how lactate drive DKD. Epithelial-mesenchymal transition (EMT), which is characterized by the loss of epithelial cells polarity and cell-cell adhesion, and the acquisition of mesenchymal-like phenotypes, is widely recognized a critical contributor to DKD. Here, we found a switch from oxidative phosphorylation (OXPHOS) toward glycolysis in AGEs-induced renal tubular epithelial cells, thus leading to elevated levels of renal lactic acid. We demonstrated that reducing the lactate levels markedly delayed EMT progression and improved renal tubular fibrosis in DKD. Mechanically, we observed lactate increased the levels of histone H3 lysine 14 lactylation (H3K14la) in DKD. ChIP-seq & RNA-seq results showed histone lactylation contributed to EMT process by facilitating KLF5 expression. Moreover, KLF5 recognized the promotor of cdh1 and inhibited its transcription, which accelerated EMT of DKD. Additionally, nephro-specific knockdown and pharmacological inhibition of KLF5 diminished EMT development and attenuated DKD fibrosis. Thus, our study provides better understanding of epigenetic regulation of DKD pathogenesis, and new therapeutic strategy for DKD by disruption of the lactate-drived H3K14la/KLF5 pathway.

Macrophage-Induced Pro-Fibrotic Gene Expression in Tubular Cells after Ischemia/Reperfusion Is Paralleled but Not Directly Mediated by C5a/C5aR1 Signaling

Ischemia/reperfusion (I/R) is inevitable during kidney transplantation and causes acute kidney injury (AKI), which affects immediate outcome and leads to chronic changes such as fibrotic remodeling of the graft. We investigated pro-fibrotic signaling after I/R, focusing on the complement component and receptor C5a/C5aR1 and macrophage/tubule crosstalk. Male Dark Agouti rats were subjected to I/R and their kidneys were harvested 10 min, 6 h, 24 h, 3 days, 5 days and 8 weeks after reperfusion. The development of renal fibrosis was assessed by the detection of Vimentin (VIM), α-smooth muscle actin (α-SMA) and collagen by immunohistochemistry and Sirius Red staining, respectively. The characterization of C5a/C5aR1 activity and C5aR1+ cells was performed by multiplex mRNA analysis, ELISA, immunofluorescence flow cytometry and in situ hybridization in animal models and cell culture analyses. In the cell culture experiments, we focused on macrophage/tubule cell crosstalk in co-culture experiments and mimicked in vivo conditions by hypoxia/reoxygenation and supplementation with C5a. Already 6-24 h after the induction of I/R in the rat model, C5a concentration in the plasma was significantly increased compared to the control. The matrix components VIM and α-SMA peaked on day 5 and declined after 8 weeks, when an increase in collagen was detected using Sirius Red. In contrast to early I/R-induced C5a activation, renal C5ar1 expression was maximal at day 5 and C5 expression increased until week 8, indicating that the renal upregulation of expression is not required for early complement activation. C5aR1 mRNA was detected in neutrophils and macrophages, but not in proximal tubular cells in the injured kidneys. The macrophage/tubular cell co-culture experiments showed that macrophages were mainly responsible for the increased expression of fibrosis-associated genes in tubule cells (ACTA2, VIM, SNAI1, TGFB1 and FGF-2), and hypoxia/reoxygenation had a partially enhancing effect. A direct pro-fibrotic effect of C5a was not observed. Increased TGF-ß levels were dependent on the differentiation of macrophages to the M2 subtype. In conclusion, the early activation of mesenchymal markers in tubular epithelial cells leads to long-term fibrotic remodeling characterized by VIM expression and driven by TGF-ß-dependent macrophage/tubular crosstalk. The chemoattractive properties of complement C5a may contribute to the recruitment of pro-fibrotic macrophages.

Targeting SIRT2 in Aging-Associated Fibrosis Pathophysiology

Aging is a complex biological process that involves multi-level structural and physiological changes. Aging is a major risk factor for many chronic diseases. The accumulation of senescent cells changes the tissue microenvironment and is closely associated with the occurrence and development of tissue and organ fibrosis. Fibrosis is the result of dysregulated tissue repair response in the development of chronic inflammatory diseases. Recent studies have clearly indicated that SIRT2 is involved in regulating the progression of fibrosis, making it a potential target for anti-fibrotic drugs. SIRT2 is a NAD+ dependent histone deacetylase, shuttling between nucleus and cytoplasm, and is highly expressed in liver, kidney and heart, playing an important role in the occurrence and development of aging and fibrosis. Therefore, we summarized the role of SIRT2 in liver, kidney and cardiac fibrosis during aging.

Assessment of biological organ age using molecular pathology in pre-transplant kidney biopsies

Organ shortage is a major challenge in kidney transplantation but the use of older donors, often with co-morbidities, is hampered by inconsistent outcomes. Methods of accurately stratifying marginal donor organs by clinical and histological assessment are lacking. To better understand organ variability, we profiled the transcriptomes of 271 kidneys from deceased donors at retrieval. Following correction for biopsy composition, we assessed molecular pathways that associated with delayed, and sub-optimal one-year graft function. Analysis of cortical biopsies identified an adaptive immune gene-rich module that significantly associated with increasing age and worse outcomes. Cellular deconvolution using human kidney reference single cell transcriptomes confirmed an increase in kidney-specific B and T cell signatures, as well as kidney macrophage, myofibroblast and fibroblast gene sets in this module. Surprisingly, innate immune pathway and neutrophil gene signature enrichment was associated with better outcomes. Thus, our work uncovers cellular molecular features of pathological organ ageing, identifiable at kidney retrieval, with translational potential.

The key mediator of diabetic kidney disease: Potassium channel dysfunction

Diabetic kidney disease is a leading cause of end-stage renal disease, making it a global public health concern. The molecular mechanisms underlying diabetic kidney disease have not been elucidated due to its complex pathogenesis. Thus, exploring these mechanisms from new perspectives is the current focus of research concerning diabetic kidney disease. Ion channels are important proteins that maintain the physiological functions of cells and organs. Among ion channels, potassium channels stand out, because they are the most common and important channels on eukaryotic cell surfaces and function as the basis for cell excitability. Certain potassium channel abnormalities have been found to be closely related to diabetic kidney disease progression and genetic susceptibility, such as KATP, KCa, Kir, and KV. In this review, we summarized the roles of different types of potassium channels in the occurrence and development of diabetic kidney disease to discuss whether the development of DKD is due to potassium channel dysfunction and present new ideas for the treatment of DKD.

Tubular insulin-induced gene 1 deficiency promotes NAD+ consumption and exacerbates kidney fibrosis

Profibrotic proximal tubules (PT) were identified as a unique phenotype of proximal tubule cells (PTCs) in renal fibrosis by single-cell RNA sequencing (scRNA-seq). Controlling the process of renal fibrosis requires understanding how to manage the S1 subset's branch to the S3 subset rather than to the profibrotic PT subset. Insulin-induced gene 1 (Insig1) is one of the branch-dependent genes involved in controlling this process, although its role in renal fibrosis is unknown. Here, we discovered that tubular Insig1 deficiency, rather than fibroblast Insig1 deficiency, plays a detrimental role in the pathogenesis of renal fibrosis in vivo and in vitro. Overexpression of Insig1 profoundly inhibited renal fibrosis. Mechanistically, Insig1 deletion in PTCs boosted SREBP1 nuclear localization, increasing Aldh1a1 transcriptional activity, causing excessive NAD+ consumption and ER enlargement, as well as accelerating renal fibrosis. We also identified nicardipine as a selective inhibitor of Aldh1a1, which could restore NAD+ and maintain ER homeostasis, as well as improve renal fibrosis. Together, our findings support tubular Insig1 as a new therapeutic target for chronic kidney disease (CKD).

CD226 promotes renal fibrosis by regulating macrophage activation and migration

It has been found that CD226 plays an important role in regulating macrophage function, but its expression and function in macrophages during renal fibrogenesis have not been studied. Our data demonstrated that CD226 expression in macrophages was obviously upregulated in the unilateral ureteral obstruction model, while CD226 deficiency attenuated collagen deposition in renal interstitium along with fewer M1 within renal cortex and renal medulla and a lower level of proinflammatory factors compared to that of control littermates. Further studies demonstrated that Cd226-/- bone marrow-derived macrophages transferring could significantly reduce the tubular injury, collagen deposition, and proinflammatory cytokine secretion compared with that of Cd226+/+ bone marrow-derived macrophages transferring in the unilateral ureteral obstruction model. Mechanistic investigations revealed that CD226 promoted proinflammatory M1 macrophage accumulation in the kidney via suppressing KLF4 expression in macrophages. Therefore, our results uncovered a pathogenic role of CD226 during the development of chronic kidney disease by promoting monocyte infiltration from peripheral blood into the kidney and enhancing macrophage activation toward the inflammatory phenotype by suppressing KLF4 expression.

Role of Uremic Toxins, Oxidative Stress, and Renal Fibrosis in Chronic Kidney Disease

Affecting millions of people worldwide, chronic kidney disease is a serious medical problem. It results in a decrease in glomerular filtration rate below 60 mL/min/1.73 m, albuminuria, abnormalities in urine sediment and pathologies detected by imaging studies lasting a minimum of 3 months. Patients with CKD develop uremia, and as a result of the accumulation of uremic toxins in the body, patients can be expected to suffer from a number of medical consequences such as progression of CKD with renal fibrosis, development of atherosclerosis or increased incidence of cardiovascular events. Another key element in the pathogenesis of CKD is oxidative stress, resulting from an imbalance between the production of antioxidants and the production of reactive oxygen species. Oxidative stress contributes to damage to cellular proteins, lipids and DNA and increases inflammation, perpetuating kidney dysfunction. Additionally, renal fibrogenesis involving the accumulation of fibrous tissue in the kidneys occurs. In our review, we also included examples of forms of therapy for CKD. To improve the condition of CKD patients, pharmacotherapy can be used, as described in our review. Among the drugs that improve the prognosis of patients with CKD, we can include: GLP-1 analogues, SGLT2 inhibitors, Finerenone monoclonal antibody-Canakinumab and Sacubitril/Valsartan.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Role of mitochondria in pathogenesis and therapy of renal fibrosis

Renal fibrosis, specifically tubulointerstitial fibrosis, represents the predominant pathological consequence observed in the context of progressive chronic kidney conditions. The pathogenesis of renal fibrosis encompasses a multifaceted interplay of mechanisms, including but not limited to interstitial fibroblast proliferation, activation, augmented production of extracellular matrix (ECM) components, and impaired ECM degradation. Notably, mitochondria, the intracellular organelles responsible for orchestrating biological oxidation processes in mammalian cells, assume a pivotal role within this intricate milieu. Mitochondrial dysfunction, when manifest, can incite a cascade of events, including inflammatory responses, perturbed mitochondrial autophagy, and associated processes, ultimately culminating in the genesis of renal fibrosis. This comprehensive review endeavors to furnish an exegesis of mitochondrial pathophysiology and biogenesis, elucidating the precise mechanisms through which mitochondrial aberrations contribute to the onset and progression of renal fibrosis. We explored how mitochondrial dysfunction, mitochondrial cytopathy and mitochondrial autophagy mediate ECM deposition and renal fibrosis from a multicellular perspective of mesangial cells, endothelial cells, podocytes, macrophages and fibroblasts. Furthermore, it succinctly encapsulates the most recent advancements in the realm of mitochondrial-targeted therapeutic strategies aimed at mitigating renal fibrosis.

Improvement effects of transplanting pancreatic islet that previously incubated with biomaterials on the diabetic nephropathy in STZ- diabetic rats

BACKGROUND

Islet transplantation is an effective treatment for diabetes or even its complications. Aim of this study is to investigate efficacy of biomaterial treated islet transplantation on treating diabetic nephropathy.

METHODS

Male rats were randomly divided into 6 groups; Control, diabetic control, diabetic transplanted with untreated islets, with platelet rich plasma treated islets, with pancreatic islets homogenate treated islets, or with these biomaterials combination treated islets. Islets cultured with biomaterials and transplanted to diabetic rats. After 60 days, biochemical, oxidative stress, and stereological parameters were assessed.

RESULTS

Serum albumin and BUN concentration, decreased and increased respectively, Oxidative stress of kidney impaired, kidney weight, volume of kidney, cortex, medulla, glomerulus, proximal and distal tubules, collecting ducts, vessels, inflammatory, necrotic and fibrotic tissue in diabetic group increased compared to control group (p < 0.001). In treated groups, especially pancreatic islets homogenate treated islets transplanting animals, there was significant changes in kidney weight, and volume of kidney, proximal and distal tubules, Henle's loop and collecting ducts compared with diabetic group (p = 0.013 to p < 0.001). Combination treated islets animals showed significant increase in vessel volume compared to diabetic group (p < 0.001). Necrotic and fibrotic tissue significantly decreased in islets treated than untreated islet animals, it was higher in pancreatic islets homogenate, and combination treated islets groups (p = 0.001).

CONCLUSIONS

Biomaterials treated islets transplanting could improve diabetic nephropathy. Improvement of oxidative stress followed by controlling glucose level, and effects of growth factors presenting in biomaterials can be considered as capable underlying mechanism of ameliorating inflammatory, necrotic and fibrotic tissue volume.

Associations of Kidney Functional Magnetic Resonance Imaging Biomarkers with Markers of Inflammation in Individuals with CKD

Key Points

Lower baseline apparent diffusion coefficient, indicative of greater cortical fibrosis, correlated with higher baseline concentrations of serum markers of inflammation. No association between baseline cortical R2* and baseline serum markers of inflammation were found. Baseline kidney functional magnetic resonance imaging biomarkers of fibrosis and oxygenation were not associated with changes in inflammatory markers over time, which may be due to small changes in kidney function in the study.

Background

Greater fibrosis and decreased oxygenation may amplify systemic inflammation, but data on the associations of kidney functional magnetic resonance imaging (fMRI) measurements of fibrosis (apparent diffusion coefficient [ADC]) and oxygenation (relaxation rate [R2*]) with systemic markers of inflammation are limited.

Methods

We evaluated associations of baseline kidney fMRI-derived ADC and R2* with baseline and follow-up serum IL-6 and C-reactive protein (CRP) in 127 participants from the CKD Optimal Management with Binders and NicotinamidE trial, a randomized, 12-month trial of nicotinamide and lanthanum carbonate versus placebo in individuals with CKD stages 3–4. Cross-sectional analyses of baseline kidney fMRI biomarkers and markers of inflammation used multivariable linear regression. Longitudinal analyses of baseline kidney fMRI biomarkers and change in markers of inflammation over time used linear mixed-effects models.

Results

Mean±SD eGFR, ADC, and R2* were 32.2±8.7 ml/min per 1.73 m2, 1.46±0.17×10−3 mm2/s, and 20.3±3.1 s−1, respectively. Median (interquartile range) IL-6 and CRP were 3.7 (2.4–4.9) pg/ml and 2.8 (1.2–6.3) mg/L, respectively. After multivariable adjustment, IL-6 and CRP were 13.1% and 27.3% higher per 1 SD decrease in baseline cortical ADC, respectively. Baseline cortical R2* did not have a significant association with IL-6 or CRP. Mean annual IL-6 and CRP slopes were 0.98 pg/ml per year and 0.91 mg/L per year, respectively. Baseline cortical ADC and R2* did not have significant associations with change in IL-6 or CRP over time.

Conclusions

Lower cortical ADC, suggestive of greater fibrosis, was associated with higher systemic inflammation. Baseline kidney fMRI biomarkers did not associate with changes in systemic markers of inflammation over time.

ELABELA-derived peptide ELA13 attenuates kidney fibrosis by inhibiting the Smad and ERK signaling pathways

Kidney fibrosis is an inevitable result of various chronic kidney diseases (CKDs) and significantly contributes to end-stage renal failure. Currently, there is no specific treatment available for renal fibrosis. ELA13 (amino acid sequence: RRCMPLHSRVPFP) is a conserved region of ELABELA in all vertebrates; however, its biological activity has been very little studied. In the present study, we evaluated the therapeutic effect of ELA13 on transforming growth factor-β1 (TGF-β1)-treated NRK-52E cells and unilateral ureteral occlusion (UUO) mice. Our results demonstrated that ELA13 could improve renal function by reducing creatinine and urea nitrogen content in serum, and reduce the expression of fibrosis biomarkers confirmed by Masson staining, immunohistochemistry, real-time polymerase chain reaction (RT-PCR), and western blot. Inflammation biomarkers were increased after UUO and decreased by administration of ELA13. Furthermore, we found that the levels of essential molecules in the mothers against decapentaplegic (Smad) and extracellular signal-regulated kinase (ERK) pathways were reduced by ELA13 treatment in vivo and in vitro. In conclusion, ELA13 protected against kidney fibrosis through inhibiting the Smad and ERK signaling pathways and could thus be a promising candidate for anti-renal fibrosis treatment.

The role of tubular cells in the pathogenesis of Fabry nephropathy

The pathophysiology of Fabry nephropathy (FN) is induced by galactosidase A deficiency with a chronic exposure of glycolipids to every lineage of renal cells. Tissue damage is attributed to the activation of molecular pathways, resulting in tissue fibrosis and chronic kidney disease. Podocytes have been the primary focus in clinical pathophysiological research because of the striking accumulation of large glycolipid deposits observable in histology. Yet, the tubular interstitium makes up a large portion of the whole organ, and therefore, its role must be further considered in pathogenic processes. In this review, we would like to propose Fabry tubulopathy and its ensuing functional effects as the first pathological signs and contributing factors to the development of FN. We will summarize and discuss the current literature regarding the role of tubular cells in Fabry kidney pathophysiology. Starting from clinical and histological evidence, we will highlight the data from animal models and cell cultures outlining the pathophysiological pathways associated with tubular interstitial injury causing renal fibrosis in Fabry nephropathy.

Continuous genetic monitoring of transient mesenchymal gene activities in distal tubule and collecting duct epithelial cells during renal fibrosis

Epithelial cells (ECs) have been proposed to contribute to myofibroblasts or fibroblasts through epithelial-mesenchymal transition (EMT) during renal fibrosis. However, since EMT may occur dynamically, transiently, and reversibly during kidney fibrosis, conventional lineage tracing based on Cre-loxP recombination in renal ECs could hardly capture the transient EMT activity, yielding inconsistent results. Moreover, previous EMT research has primarily focused on renal proximal tubule ECs, with few reports of distal tubules and collecting ducts. Here, we generated dual recombinases-mediated genetic lineage tracing systems for continuous monitoring of transient mesenchymal gene expression in E-cadherin+ and EpCAM+ ECs of distal tubules and collecting ducts during renal fibrosis. Activation of key EMT-inducing transcription factor (EMT-TF) Zeb1 and mesenchymal markers αSMA, vimentin, and N-cadherin, were investigated following unilateral ureteral obstruction (UUO). Our data revealed that E-cadherin+ and EpCAM+ ECs did not transdifferentiate into myofibroblasts, nor transiently expressed these mesenchymal genes during renal fibrosis. In contrast, in vitro a large amount of cultured renal ECs upregulated mesenchymal genes in response to TGF-β, a major inducer of EMT.

Critical Role of histone deacetylase 3 in the regulation of kidney inflammation and fibrosis

Chronic kidney disease (CKD) is characterized by kidney inflammation and fibrosis. However, the precise mechanisms leading to kidney inflammation and fibrosis are poorly understood. Since histone deacetylase is involved in inflammation and fibrosis in other tissues, we examined the role of histone deacetylase 3 (HDAC3) in the regulation of inflammation and kidney fibrosis. HDAC3 is induced in the kidneys of animal models of CKD but mice with conditional HDAC3 deletion exhibit significantly reduced fibrosis in the kidneys compared with control mice. The expression of proinflammatory and profibrotic genes was significantly increased in the fibrotic kidneys of control mice, which was impaired in mice with HDAC3 deletion. Genetic deletion or pharmacological inhibition of HDAC3 reduced the expression of proinflammatory genes in cultured monocytes/macrophages. Mechanistically, HDAC3 deacetylates Lys122 of NF-κB p65 subunit turning on transcription. RGFP966, a selective HDAC3 inhibitor, reduced fibrosis in cells and in animal models by blocking NF-κB p65 binding to κB-containing DNA sequences. Thus, our study identified HDAC3 as a critical regulator of inflammation and fibrosis of the kidney through deacetylation of NF-κB unlocking its transcriptional activity. Hence, targeting HDAC3 could serve as a novel therapeutic strategy for CKD.

Exercise for patients with chronic kidney disease: from cells to systems to function

Chronic kidney disease (CKD) is among the leading causes of death and disability, affecting an estimated 800 million adults globally. The underlying pathophysiology of CKD is complex creating challenges to its management. Primary risk factors for the development and progression of CKD include diabetes mellitus, hypertension, age, obesity, diet, inflammation, and physical inactivity. The high prevalence of diabetes and hypertension in patients with CKD increases the risk for secondary consequences such as cardiovascular disease and peripheral neuropathy. Moreover, the increased prevalence of obesity and chronic levels of systemic inflammation in CKD have downstream effects on critical cellular functions regulating homeostasis. The combination of these factors results in the deterioration of health and functional capacity in those living with CKD. Exercise offers protective benefits for the maintenance of health and function with age, even in the presence of CKD. Despite accumulating data supporting the implementation of exercise for the promotion of health and function in patients with CKD, a thorough description of the responses and adaptations to exercise at the cellular, system, and whole body levels is currently lacking. Therefore, the purpose of this review is to provide an up-to-date comprehensive review of the effects of exercise training on vascular endothelial progenitor cells at the cellular level; cardiovascular, musculoskeletal, and neural factors at the system level; and physical function, frailty, and fatigability at the whole body level in patients with CKD.

Oleoylethanolamide attenuates acute-to-chronic kidney injury: in vivo and in vitro evidence of PPAR-α involvement

Chronic kidney disease (CKD) development after acute kidney injury (AKI) involves multiple mechanisms, including inflammation, epithelial-mesenchymal transition (EMT), and extracellular matrix deposition, leading to progressive tubulointerstitial fibrosis. Recently, a central role for peroxisome-proliferator activated receptor (PPAR)-α has been addressed in preserving kidney function during AKI. Among endogenous lipid mediators, oleoylethanolamide (OEA), a PPAR-α agonist, has been studied for its metabolic and anti-inflammatory effects. Here, we have investigated OEA effects on folic acid (FA)-induced kidney injury in mice and the underlying mechanisms. OEA improved kidney function, normalized urine output, and reduced serum BUN, creatinine, and albuminuria. Moreover, OEA attenuated tubular epithelial injury, as shown by histological analysis, and decreased expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1. Gene expression analysis of kidney tissue indicated that OEA limited immune cell infiltration and inflammation. Moreover, OEA significantly inhibited Wnt7b and Catnb1 gene transcription and α-smooth muscle actin expression, indicating suppression of EMT. Accordingly, OEA exhibited an anti-fibrotic effect, as shown by Masson staining and the reduced levels of transforming growth factor (TGF)-β1, fibronectin, and collagen IV. Mechanistically, the nephroprotective effect of OEA was related to PPAR-α activation since OEA failed to exert its beneficial activity in FA-insulted PPAR-α-/- mice. PPAR-α involvement was also confirmed in HK2 cells where GW6471, a PPAR-α antagonist, blunted OEA activity on the TGF-β1 signalling pathway and associated pro-inflammatory and fibrotic patterns. Our findings revealed that OEA counteracts kidney injury by controlling inflammation and fibrosis, making it an effective therapeutic tool for limiting AKI to CKD progression.

Great potential of renal progenitor cells in kidney: From the development to clinic

The mammalian renal organ represents a pinnacle of complexity, housing functional filtering units known as nephrons. During embryogenesis, the depletion of niches containing renal progenitor cells (RPCs) and the subsequent incapacity of adult kidneys to generate new nephrons have prompted the formulation of protocols aimed at isolating residual RPCs from mature kidneys and inducing their generation from diverse cell sources, notably pluripotent stem cells. Recent strides in the realm of regenerative medicine and the repair of tissues using stem cells have unveiled critical signaling pathways essential for the maintenance and generation of human RPCs in vitro. These findings have ushered in a new era for exploring novel strategies for renal protection. The present investigation delves into potential transcription factors and signaling cascades implicated in the realm of renal progenitor cells, focusing on their protection and differentiation. The discourse herein elucidates contemporary research endeavors dedicated to the acquisition of progenitor cells, offering crucial insights into the developmental mechanisms of these cells within the renal milieu and paving the way for the formulation of innovative treatment modalities.

Serum human epididymis protein 4 is associated with disease severity in patients with IgA nephropathy

BACKGROUND

Human epididymis protein 4 (HE4) is a promising tumor biomarker primarily utilized for the detection of ovarian cancer. However, its potential as a novel diagnostic indicator for immunoglobulin A nephropathy (IgAN) remains unknown. The objective of this study was to investigate the feasibility of serum HE4 as a novel biomarker for patients with IgAN.

METHODS

This study enrolled a total of 89 hospitalized patients with IgAN at Peking University Shenzhen Hospital between July 2020 and December 2022, along with 60 healthy control subjects matched for sex and age without evidence of comorbidities. Serum HE4 levels were measured using the Abbott Alinity automated immune analyzer, and the correlation between serum HE4 levels and biochemical markers of renal damage as well as clinicopathologic features in IgAN patients were analyzed.

RESULTS

In this study, serum HE4 levels were significantly elevated in patients with IgAN compared to healthy controls (116.43 ± 103.61 pmol/L vs. 35.57 ± 9.33 pmol/L, p < 0.001). There was a positive correlation between serum HE4 levels and blood urea nitrogen (r = 0.58, p < 0.001), creatinine (r = 0.73, p < 0.001), cystatin C (r = 0.82, p < 0.001), β2-microglobulin (r = 0.77, p < 0.001), α1-microglobulin (r = 0.75, p < 0.001), and glomerulosclerosis ratio (r = 0.56, p < 0.001). Conversely, a negative correlation was observed between serum HE4 levels and hemoglobin (r = -0.42, p < 0.001), albumin (r = -0.44, p < 0.001) and estimated glomerular filtration rate (eGFR) (r = -0.83, p < 0.001). In HE4+ IgAN patients, a higher glomerulosclerosis ratio (p < 0.01) and lower eGFR levels (p < 0.001) were observed compared to HE4- patients. Furthermore, patients with higher pathological classification grade also had higher serum HE4 levels.

CONCLUSIONS

Serum HE4 levels were significantly associated with both renal function and the pathological classification of patients with IgAN, indicating that HE4 may serve as a promising biomarker for assessing the severity of IgAN.

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

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

Alantolactone Attenuates Renal Fibrosis via Inhibition of Transforming Growth Factor β/Smad3 Signaling Pathway

BACKGRUOUND

Renal fibrosis is characterized by the accumulation of extracellular matrix proteins and interstitial fibrosis. Alantolactone is known to exert anticancer, anti-inflammatory, antimicrobial and antifungal effects; however, its effects on renal fibrosis remains unknown. Here, we investigated whether alantolactone attenuates renal fibrosis in mice unilateral ureteral obstruction (UUO) and evaluated the effect of alantolactone on transforming growth factor (TGF) signaling pathway in renal cells.

METHODS

To evaluate the therapeutic effect of alantolactone, cell counting kit-8 (CCK-8) assay, histological staining, Western blot analysis, and real-time quantitative polymerase chain reaction were performed in UUO kidneys in vivo and in TGF-β-treated renal cells in vitro.

RESULTS

Alantolactone (0.25 to 4 µM) did not affect the viability of renal cells. Mice orally administered 5 mg/kg of alantolactone daily for 15 days did not show mortality or liver toxicity. Alantolactone decreased UUO-induced blood urea nitrogen and serum creatinine levels. In addition, it significantly alleviated renal tubulointerstitial damage and fibrosis and decreased collagen type I, fibronectin, and α-smooth muscle actin (α-SMA) expression in UUO kidneys. In NRK-49F cells, alantolactone inhibited TGF-βstimulated expression of fibronectin, collagen type I, plasminogen activator inhibitor-1 (PAI-1), and α-SMA. In HK-2 cells, alantolactone inhibited TGF-β-stimulated expression of collagen type I and PAI-1. Alantolactone inhibited UUO-induced phosphorylation of Smad3 in UUO kidneys. In addition, it not only decreased TGF-β secretion but also Smad3 phosphorylation and translocation to nucleus in both kidney cell lines.

CONCLUSION

Alantolactone improves renal fibrosis by inhibiting the TGF-β/Smad3 signaling pathway in obstructive nephropathy. Thus, alantolactone is a potential therapeutic agent for chronic kidney disease.

Low intensity pulsed ultrasound ameliorates Adriamycin-induced chronic renal injury by inhibiting ferroptosis

OBJECTIVE

It is very important to develop a new therapeutic strategy to cope with the increasing morbidity and mortality of chronic kidney disease (CKD). As a kind of physical therapy, low intensity pulsed ultrasound (LIPUS) has remarkable anti-inflammatory and repair-promoting effects and is expected to become a new therapeutic method for CKD. This study aims to clarify the treatment effect of LIPUS on CKD-related renal inflammation and fibrosis, and to further explore the potential signal network of LIPUS treatment for ameliorating chronic renal injury.

METHODS

A rat model simulating the progress of CKD was established by twice tail-vein injection of Adriamycin (ADR). Under anesthesia, bilateral kidneys of CKD rats were continuously stimulated by LIPUS for four weeks. The parameters of LIPUS were 1.0 MHz, 60 mW/cm2, 50% duty cycle and 20 min/d.

RESULTS

LIPUS treatment effectively inhibited ADR-induced renal inflammation and fibrosis, and improved CKD-related to oxidative stress and ferroptosis. In addition, the therapeutic effect of LIPUS is closely related to the regulation of TGF-β1/Smad and Nrf2/keap1/HO-1 signalling pathways.

DISCUSSION

This study provides a new direction for further mechanism research and lays an important foundation for clinical trials.

BMAL1 inhibits renal fibrosis and renal interstitial inflammation by targeting the ERK1/2/ELK-1/Egr-1 axis

RATIONALE

Renal fibrosis and renal interstitial inflammation due to hydronephrosis are associated with progressive chronic kidney disease (CKD). The clock gene BMAL1 is thought to be involved in various diseases, including hypertension, diabetes, etc. However, little is known about how BMAL1 regulates renal fibrosis and renal interstitial inflammation in obstructed kidneys.

METHODS

The expression level of BMAL1 in UUO was examined using the GEO database. Lentivirus, siRNA and adeno-associated virus were used to modulate BMAL1 levels in HK-2 cells and mouse kidney. qRT-PCR, immunofluorescence staining, histological analysis, ELISA and Western blot were used to determine the level of fibrin deposition and the release of inflammatory factors. Immunofluorescence staining and western blotting were used to examine the interaction between BMAL1 and the ERK1/2/ELK-1/Egr-1 axis.

RESULTS

Bioinformatics analysis and in vivo experiments in this study showed that the expression level of BMAL1 in UUO model kidneys was higher than that in normal kidneys. We then found that downregulation of BMAL1 promoted the production of extracellular matrix (ECM) proteins and proinflammatory factors in vivo and in vitro, whereas upregulation inhibited this process. In addition, we demonstrated that the ERK1/2/ELK-1/Egr-1 axis is an important pathway for BMAL1 to play a regulatory role, and the use of PD98059 abolished the promoting effect of down-regulation of BMAL1 on fibrosis and inflammation.

CONCLUSIONS

Our findings suggest that BAML1 can target the ERK1/2/ELK-1/Egr-1 axis to suppress fibrotic progression and inflammatory events in obstructed kidneys, thereby inhibiting the development of CKD.

Artificial intelligence-assisted repurposing of lubiprostone alleviates tubulointerstitial fibrosis

Tubulointerstitial fibrosis (TIF) is the most prominent cause which leads to chronic kidney disease (CKD) and end-stage renal failure. Despite extensive research, there have been many clinical trial failures, and there is currently no effective treatment to cure renal fibrosis. This demonstrates the necessity of more effective therapies and better preclinical models to screen potential drugs for TIF. In this study, we investigated the antifibrotic effect of the machine learning-based repurposed drug, lubiprostone, validated through an advanced proximal tubule on a chip system and in vivo UUO mice model. Lubiprostone significantly downregulated TIF biomarkers including connective tissue growth factor (CTGF), extracellular matrix deposition (Fibronectin and collagen), transforming growth factor (TGF-β) downstream signaling markers especially, Smad-2/3, matrix metalloproteinase (MMP2/9), plasminogen activator inhibitor-1 (PAI-1), EMT and JAK/STAT-3 pathway expression in the proximal tubule on a chip model and UUO model compared to the conventional 2D culture. These findings suggest that the proximal tubule on a chip model is a more physiologically relevant model for studying and identifying potential biomarkers for fibrosis compared to conventional in vitro 2D culture and alternative of an animal model. In conclusion, the high throughput Proximal tubule-on-chip system shows improved in vivo-like function and indicates the potential utility for renal fibrosis drug screening. Additionally, repurposed Lubiprostone shows an effective potency to treat TIF via inhibiting 3 major profibrotic signaling pathways such as TGFβ/Smad, JAK/STAT, and epithelial-mesenchymal transition (EMT), and restores kidney function.

Identification of the key immune-related genes and immune cell infiltration changes in renal interstitial fibrosis

Background

Chronic kidney disease (CKD) is the third-leading cause of premature mortality worldwide. It is characterized by rapid deterioration due to renal interstitial fibrosis (RIF) via excessive inflammatory infiltration. The aim of this study was to discover key immune-related genes (IRGs) to provide valuable insights and therapeutic targets for RIF in CKD.

Materials and methods

We screened differentially expressed genes (DEGs) between RIF samples from CKD patients and healthy controls from a public database. Least absolute shrinkage and selection operator regression analysis and receiver operating characteristic curve analysis were applied to identify significant key biomarkers. The single-sample Gene Set Enrichment Analysis (ssGSEA) algorithm was used to analyze the infiltration of immune cells between the RIF and control samples. The correlation between biomarkers and immune cell composition was assessed.

Results

A total of 928 DEGs between CKD and control samples from six microarray datasets were found, 17 overlapping immune-correlated DEGs were identified by integration with the ImmPort database, and six IRGs were finally identified in the model: apolipoprotein H (APOH), epidermal growth factor (EGF), lactotransferrin (LTF), lysozyme (LYZ), phospholipid transfer protein (PLTP), and secretory leukocyte peptidase inhibitor (SLPI). Two additional datasets and in vivo experiments indicated that the expression levels of APOH and EGF in the fibrosis group were significantly lower than those in the control group, while the expression levels of LTF, LYZ, PLTP, and SLPI were higher (all P < 0.05). These IRGs also showed a significant correlation with renal function impairment. Moreover, four upregulated IRGs were positively associated with various T cell populations, which were enriched in RIF tissues, whereas two downregulated IRGs had opposite results. Several signaling pathways, such as the "T cell receptor signaling pathway" and "positive regulation of NF-κB signaling pathway", were discovered to be associated not only with immune cell infiltration, but also with the expression levels of six IRGs.

Conclusion

In summary, six IRGs were identified as key biomarkers for RIF, and exhibited a strong correlation with various T cells and with the NF-κB signaling pathway. All these IRGs and their signaling pathways may evolve as valuable therapeutic targets for RIF in CKD.

Dioscorea nipponica Makino: A comprehensive review of its chemical composition and pharmacology on chronic kidney disease

Chronic kidney disease (CKD) is a widespread ailment that significantly impacts global health. It is characterized by high prevalence, poor prognosis, and substantial healthcare costs, making it a major public health concern. The current clinical treatments for CKD are not entirely satisfactory, leading to a high demand for alternative therapeutic options. Chinese herbal medicine, with its long history, diverse varieties, and proven efficacy, offers a promising avenue for exploration. One such Chinese herbal medicine, Dioscorea nipponica Makino (DNM), is frequently used to treat kidney diseases. In this review, we have compiled studies examining the mechanisms of action of DNM in the context of CKD, focusing on five primary areas: improvement of oxidative stress, inhibition of renal fibrosis, regulation of metabolism, reduction of inflammatory response, and regulation of autophagy.

Single cell G-protein coupled receptor profiling of activated kidney fibroblasts expressing transcription factor 21

BACKGROUND AND PURPOSE

Activated fibroblasts deposit fibrotic matrix in chronic kidney disease (CKD) and G-protein coupled receptors (GPCRs) are the most druggable therapeutic targets. Here, we set out to establish a transcriptional profile that identifies activated kidney fibroblasts and the GPCRs that they express.

EXPERIMENTAL APPROACH

RNA sequencing and single cell qRT-PCR were performed on mouse kidneys after unilateral ureteral obstruction (UUO). Candidate expression was evaluated in mice with UUO or diabetes or injected with adriamycin or folic acid. Intervention studies were conducted in mice with diabetes or UUO. Correlative histology was performed in human kidney tissue.

KEY RESULTS

Transcription factor 21 (Tcf21)+ cells that expressed 2 or 3 of Postn, Acta2 and Pdgfra were highly enriched for fibrogenic genes and were defined as activated kidney fibroblasts. Tcf21+ α-smooth muscle actin (α-SMA)+ interstitial cells accumulated in kidneys of mice with UUO or diabetes or injected with adriamycin or folic acid, whereas renin-angiotensin system blockade attenuated increases in Tcf21 in diabetic mice. Fifty-six GPCRs were up-regulated in single Tcf21+ kidney fibroblasts, the most up-regulated being Adgra2 and S1pr3. Adenosine receptors, Adora2a/2b, were up-regulated in Tcf21+ fibroblasts and the adenosine receptor antagonist, caffeine decreased Tcf21 upregulation and kidney fibrosis in UUO mice. TCF21, ADGRA2, S1PR3 and ADORA2A/2B were each detectable in α-SMA+ interstitial cells in human kidney samples.

CONCLUSION AND IMPLICATIONS

Tcf21 is a marker of kidney fibroblasts that are enriched for fibrogenic genes in CKD. Further analysis of the GPCRs expressed by these cells may identify new targets for treating CKD.

LINKED ARTICLES

This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

A Brief Review of Diagnostic Techniques and Clinical Management in Chronic Kidney Disease

Given its increasing incidence and detrimental effects on life expectancy and quality of life, chronic kidney disease (CKD) is a significant worldwide health concern. This review article provides a complete summary of current information on the diagnosis and management of CKD, focusing on recent advances and innovative approaches. The article discusses the most current findings on CKD risk assessment, emphasizing the need for early diagnosis utilizing better biomarkers and predictive models. A rigorous examination of diagnostic tools such as albumin-to-creatinine ratio (ACR) in urine and glomerular filtration rate (GFR) highlights their importance in determining CKD phases and etiologies. In terms of therapy, the study explores evidence-based techniques to reduce the development of CKD, such as enhanced blood pressure control, glycemic management in diabetic patients, dietary changes, and renin-angiotensin-aldosterone system (RAAS) blocking. Novel therapeutic approaches, including antifibrotic and precision medicine, are evaluated regarding their potential to revolutionize CKD treatment. The study also underlines the need for multidisciplinary therapy and patient education to achieve the best possible CKD patient outcomes. It also highlights the financial and social effects of CKD, highlighting the importance of early treatment to lower medical expenses and enhance the patient's standard of living. Finally, this review article provides a comprehensive update on CKD diagnosis and treatment, highlighting present successes alongside future potential. It is a valuable resource for healthcare professionals, academics, and policymakers who want to improve CKD treatment methods and patient outcomes.

Knockdown of lncRNA MALAT1 attenuates renal interstitial fibrosis through miR-124-3p/ITGB1 axis

Renal interstitial fibrosis (RIF) considered the primary irreversible cause of chronic kidney disease. Recently, accumulating studies demonstrated that lncRNAs play an important role in the pathogenesis of RIF. However, the underlying exact mechanism of lncRNA MALAT1 in RIF remains barely known. Here, the aim of our study was to investigate the dysregulate expression of lncRNA MALAT1 in TGF-β1 treated HK2/NRK-49F cells and unilateral ureteral obstruction (UUO) mice model, defining its effects on HK2/NRK-49F cells and UUO mice fibrosis process through the miR-124-3p/ITGB1 signaling axis. It was found that lncRNA MALAT1 and ITGB1 was significantly overexpression, while miR-124-3p was downregulated in HK2/NRK-49F cells induced by TGF-β1 and in UUO mice model. Moreover, knockdown of lncRNA MALAT1 remarkably downregulated the proteins level of fibrosis-related markers, ITGB1, and upregulated the expression of epithelial marker E-cadherin. Consistently, mechanistic studies showed that miR-124-3p can directly binds to lncRNA MALAT1 and ITGB1. And the protect effect of Len-sh-MALAT1 on fibrosis related protein levels could be partially reversed by co-transfected with inhibitor-miR-124-3p. Moreover, the expression trend of LncRNA MALAT1/miR-124-3p/ITGB1 in renal tissues of patients with obstructive nephropathy (ON) was consistent with the results of cell and animal experiments. Taken together, these results indicated that lncRNA MALAT1 could promote RIF process in vitro and in vivo via the miR-124-3p/ITGB1 signaling pathway. These findings suggest a new regulatory pathway involving lncRNA MALAT1, which probably serves as a potential therapeutic target for RIF.

Novel Approaches in Chronic Renal Failure without Renal Replacement Therapy: A Review

Chronic kidney disease (CKD) is characterized by renal parenchymal damage leading to a reduction in the glomerular filtration rate. The inflammatory response plays a pivotal role in the tissue damage contributing to renal failure. Current therapeutic options encompass dietary control, mineral salt regulation, and management of blood pressure, blood glucose, and fatty acid levels. However, they do not effectively halt the progression of renal damage. This review critically examines novel therapeutic avenues aimed at ameliorating inflammation, mitigating extracellular matrix accumulation, and fostering renal tissue regeneration in the context of CKD. Understanding the mechanisms sustaining a proinflammatory and profibrotic state may offer the potential for targeted pharmacological interventions. This, in turn, could pave the way for combination therapies capable of reversing renal damage in CKD. The non-replacement phase of CKD currently faces a dearth of efficacious therapeutic options. Future directions encompass exploring vaptans as diuretics to inhibit water absorption, investigating antifibrotic agents, antioxidants, and exploring regenerative treatment modalities, such as stem cell therapy and novel probiotics. Moreover, this review identifies pharmaceutical agents capable of mitigating renal parenchymal damage attributed to CKD, targeting molecular-level signaling pathways (TGF-β, Smad, and Nrf2) that predominate in the inflammatory processes of renal fibrogenic cells.

A sub-10-nm, folic acid-conjugated gold nanoparticle as self-therapeutic treatment of tubulointerstitial fibrosis

Nanomedicines for treating chronic kidney disease (CKD) are on the horizon, yet their delivery to renal tubules where tubulointerstitial fibrosis occurs remains inefficient. We report a folic acid-conjugated gold nanoparticle that can transport into renal tubules and treat tubulointerstitial fibrosis in mice with unilateral ureteral obstruction. The 3-nm gold core allows for the dissection of bio-nano interactions in the fibrotic kidney, ensures the overall nanoparticle (~7 nm) to be small enough for glomerular filtration, and naturally inhibits the p38α mitogen-activated protein kinase in the absence of chemical or biological drugs. The folic acids support binding to selected tubule cells with overexpression of folate receptors and promote retention in the fibrotic kidney. Upon intravenous injection, this nanoparticle can selectively accumulate in the fibrotic kidney over the nonfibrotic contralateral kidney at ~3.6% of the injected dose. Delivery to the fibrotic kidney depends on nanoparticle size and disease stage. Notably, a single injection of this self-therapeutic nanoparticle reduces tissue degeneration, inhibits genes related to the extracellular matrix, and treats fibrosis more effectively than standard Captopril therapy. Our data underscore the importance of constructing CKD nanomedicines based on renal pathophysiology.

Secreted frizzled-related protein 5: A promising therapeutic target for metabolic diseases via regulation of Wnt signaling

Metabolic diseases pose a significant global health challenge, characterized by an imbalance in metabolism and resulting in various complications. Secreted frizzled-related protein 5 (SFRP5), an adipokine known for its anti-inflammatory properties, has gained attention as a promising therapeutic target for metabolic diseases. SFRP5 acts as a key regulator in the Wnt signaling pathway, exerting its influence on critical cellular functions including proliferation, differentiation, and migration. Its significance extends to the realm of adipose tissue biology, where it plays a central role in regulating inflammation, insulin resistance, adipogenesis, lipid metabolism, glucose homeostasis, and energy balance. By inhibiting Wnt signaling, SFRP5 facilitates adipocyte growth, promotes lipid accumulation, and contributes to a decrease in oxidative metabolism. Lifestyle interventions and pharmacological treatments have shown promise in increasing SFRP5 levels and protecting against metabolic abnormalities. SFRP5 is a pivotal player in metabolic diseases and presents itself as a promising therapeutic target. An overview of SFRP5 and its involvement in metabolic disorders and metabolism is provided in this comprehensive review. By elucidating these aspects, valuable insights can be gained to foster the development of effective strategies in combating metabolic diseases.

Ootheca mantidis mitigates renal fibrosis in mice by the suppression of apoptosis via increasing the gut microbe Akkermansia muciniphila and modulating glutamine metabolism

Renal interstitial fibrosis (RIF), a progressive process affecting the kidneys in chronic kidney disease (CKD), currently lacks an effective therapeutic intervention. Traditional Chinese medicine (TCM) has shown promise in reducing RIF and slowing CKD progression. In this study, we demonstrated the dose-dependent attenuation of RIF by Ootheca mantidis (SPX), a commonly prescribed TCM for CKD, in a mouse model of unilateral ureteral obstruction (UUO). RNA-sequencing analysis suggested that SPX treatment prominently downregulated apoptosis and inflammation-associated pathways, thereby inhibiting the fibrogenic signaling in the kidney. We further found that transplantation of fecal microbiota from SPX-treated mice conferred protection against renal injury and fibrosis through suppressing apoptosis in UUO mice, indicating that SPX ameliorated RIF via remodeling the gut microbiota and reducing apoptosis in the kidneys. Further functional exploration of the gut microbiota combined with fecal metabolomics revealed increased levels of some probiotics, including Akkermansia muciniphila (A. muciniphila), and modulations in glutamine-related amino acid metabolism in UUO mice treated with SPX. Subsequent colonization of A. muciniphila and supplementation with glutamine effectively mitigated cell apoptosis and RIF in UUO mice. Collectively, these findings unveil a functionally A. muciniphila- and glutamine-involved gut-renal axis that contributes to the action of SPX, and provide important clue for the therapeutic potential of SPX, A. muciniphila, and glutamine in combatting RIF.

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.