Unilateral Ureteral Obstruction Research Articles

Contribution of ECT2 to Tubulointerstitial Fibrosis in the Progression of Chronic Kidney Disease.

Chronic kidney disease (CKD) is a complex disorder resulting from a combination of various environmental and genetic factors. Considerable efforts have been dedicated to elucidating its etiological mechanisms. Nevertheless, the pathogenic mechanism of CKD remains poorly understood, which hinders the development of effective therapeutic strategies. In this study, we aimed to identify novel mediators that could contribute to the development of CKD. The ClinVar, STRING, MEME Suite, TRRUST, bedtools, GEO, and R Studio databases and software were used to analyze their common features and investigate potential CKD disease genes. Transcriptomic analysis, immunohistochemistry, qRT-PCR, and Western blotting were utilized to further validate the role of ECT2 in kidney fibrosis. In total, 26 CKD disease genes were obtained from the ClinVar database, and the STRING, MEME Suite, TRRUST, bedtools, and GEO databases and software were used to analyze their common properties and explore potential CKD disease genes. Epithelial cell transforming sequence 2 (ECT2), cyclin B 1, caspase 7 and collagen alpha-1 (IV) were identified as potential candidates for CKD progression. Weighted correlation network analysis (WGCNA) subsequently revealed the relationships between potential genes and CKD. The results of the transcriptomic analysis further confirmed that ECT2 expression was greater in the kidney tissue of CKD patients than in that of healthy controls. Next, immunohistochemistry and Western blotting demonstrated that ECT2 was predominantly expressed in the renal tubules of a unilateral ureteral obstruction (UUO) mouse model. Consistently, in vitro experiments revealed that ECT2 was upregulated in TGF-β1-treated HK-2 cells. Moreover, ECT2 overexpression or knockdown in HK-2 cells altered the intensity of fibrosis markers. ECT2 significantly affects the development and progression of CKD, particularly in association with tubulointerstitial fibrosis.

Propolis Extract Attenuates NF-κB Activation and Chronic Kidney Disease Progression in a Rat Model: Potential Surgical Adjuvant?

Background: Chronic kidney disease (CKD) is a global health concern often complicated by cardiovascular diseases like atherosclerosis. Both conditions share an inflammatory pathogenesis, with nuclear factor kappa B (NF-κB) playing a central role. Propolis, a natural bee product with anti-inflammatory properties, has shown potential in mitigating CKD progression. This study aimed to investigate the effects of propolis extract on NF-κB activation in a rat model of CKD, exploring its potential benefits as a surgical adjuvant. Methods: Male white rats (Rattus norvegicus) were divided into three groups: a control group, a CKD group, and a CKD+Propolis group receiving propolis extract (200 mg/kg body weight) daily for 20 days. CKD was induced using the unilateral ureteral obstruction (UUO) method. NF-κB levels were measured weekly using ELISA. Results: Propolis extract significantly reduced NF-κB levels in the CKD+Propolis group compared to the CKD group (p<0.05). This effect was consistently observed across all time points, indicating a sustained reduction in NF-κB activation with propolis treatment. Conclusion: Propolis extract effectively attenuates NF-κB activation in a rat model of CKD, suggesting its potential as an adjunctive therapy for CKD management, particularly in the context of surgical interventions. Further research is needed to elucidate the underlying mechanisms and evaluate its efficacy in human subjects.

Nuclear receptor 4A1 ameliorates UUO-induced renal fibrosis by inhibiting the PI3K/AKT pathway.

As an ultra-early response gene, Nuclear receptor 4A1 (NR4A1) has been reported to be involved in the development of various diseases through various pathological pathways, but its specific mechanism in chronic kidney disease (CKD) is unknown currently. Our study showed that the expression of NR4A1 was reduced in unilateral ureteral obstruction (UUO) mice and it could exacerbate UUO-induced renal pathological injury when knocked down NR4A1 in UUO mice. We found that the knockdown of NR4A1 could promote angiogenesis, renal inflammation, and cell apoptosis to aggravate renal fibrosis induced by UUO. As an agonist of NR4A1, Cytosporone B (Csn-B) could inhibit the renal fibrosis by attenuating angiogenesis, renal inflammation and cell apoptosis. In addition, the PI3K/AKT pathway was activated with NR4A1 knockdown in vivo and in vitro experiments. In conclusion, our study demonstrates that NR4A1 can ameliorate renal fibrosis. Furthermore, we speculate that its underlying mechanism may be related to the activation of PI3K/AKT pathway according to our present results.

Exosomal let-7b-5p deriving from parietal epithelial cells attenuate renal fibrosis through suppression of TGFβR1 and ARID3a in obstructive kidney disease.

As renal progenitor cells, parietal epithelial cells (PECs) have demonstrated multilineage differentiation potential in response to kidney injury. However, the function of exosomes derived from PECs has not been extensively explored. Immunofluorescent staining of Claudin-1 was used to identify primary PECs isolated from mouse glomeruli. Transmission electron microscopy, nanoparticle tracking analysis, and western blotting were used to characterize the properties of PECs-derived exosomes (PEC-Exo). The therapeutic role of PEC-Exo in tubulointerstitial fibrosis was investigated in the unilateral ureteral obstruction (UUO) mouse model and TGF-β1-stimulated HK-2 cells. High-throughput miRNA sequencing was employed to profile PEC-Exo miRNAs. One of the most enriched miRNAs in PEC-Exo was knocked down by transfecting miRNA inhibitor, and then we investigated whether this candidate miRNA was involved in PEC-Exo-mediated tubular repair. The primary PECs expressed Claudin-1, PEC-Exo was homing to obstructed kidney, and TGF-β1 induced HK-2 cells. PEC-Exo significantly alleviated renal inflammation and ameliorated tubular fibrosis both invivo and invitro. Mechanistically, let-7b-5p, highly enriched in PEC-Exo, downregulated the protein levels of transforming growth factor beta receptor 1(TGFβR1) and AT-Rich Interaction Domain 3A(ARID3a) in tubular epithelial cells (TECs), leading to the inhibition of p21 and p27 to restoring cell cycle. Furthermore, administration of let-7b-5p agomir mitigated renal fibrosis invivo. Our findings demonstrated that PEC-derived exosomes significantly repressed the expression of TGFβR1 and ARID3a by delivering let-7b-5p, thereby alleviating renal fibrosis. This study provides novel insights into the role of PEC-Exo in the repair of kidney injury and new ideas for renal fibrosis intervention.

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.

β-Mangostin Alleviates Renal Tubulointerstitial Fibrosis via the TGF-β1/JNK Signaling Pathway.

The epithelial-to-mesenchymal transition (EMT) plays a key role in the pathogenesis of kidney fibrosis, and kidney fibrosis is associated with an adverse renal prognosis. Beta-mangostin (β-Mag) is a xanthone derivative obtained from mangosteens that is involved in the generation of antifibrotic and anti-oxidation effects. The purpose of this study was to examine the effects of β-Mag on renal tubulointerstitial fibrosis both in vivo and in vitro and the corresponding mechanisms involved. As shown through an in vivo study conducted on a unilateral ureteral obstruction mouse model, oral β-Mag administration, in a dose-dependent manner, caused a lesser degree of tubulointerstitial damage, diminished collagen I fiber deposition, and the depressed expression of fibrotic markers (collagen I, α-SMA) and EMT markers (N-cadherin, Vimentin, Snail, and Slug) in the UUO kidney tissues. The in vitro part of this research revealed that β-Mag, when co-treated with transforming growth factor-β1 (TGF-β1), decreased cell motility and downregulated the EMT (in relation to Vimentin, Snail, and N-cadherin) and phosphoryl-JNK1/2/Smad2/Smad3 expression. Furthermore, β-Mag co-treated with SB (Smad2/3 kinase inhibitor) or SP600125 (JNK kinase inhibitor) significantly inhibited the TGF-β1-associated downstream phosphorylation and activation of JNK1/2-mediated Smad2 targeting the Snail/Vimentin axis. To conclude, β-Mag protects against EMT and kidney fibrotic processes by mediating the TGF-β1/JNK/Smad2 targeting Snail-mediated Vimentin expression and may have therapeutic implications for renal tubulointerstitial fibrosis.

An InSitu Sustained-Release Chitosan Hydrogel to Attenuate Renal Fibrosis by Retaining Klotho Expression.

Klotho (KLO) is an anti-fibrotic protein expressed in the kidneys and has been decreasing in the development of renal fibrosis (RF). However, restoring the decline in KLO levels remains a great challenge during RF treatment. Herein, an injectable KLO-loaded chitosan (CS) hydrogel (KLO-Gel) is designed to achieve localized and prolonged release of KLO in the RF treatment. KLO-Gel was prepared by cross-linking CS with β-glycerophosphate (β-GP), followed by rapid (within 3 min) thermosensitive gelation at 37 °C. Furthermore, KLO-Gel exhibited a slow and sustained release (over 14 d) of KLO both in PBS and in the kidneys of mice with unilateral ureter obstruction (UUO). A single local injection of KLO-Gel into the renal capsule of UUO mice was more effective at reducing RF (i.e., maintaining renal function and tissue structure, alleviating extracellular matrix accumulation, and inhibiting the TGF-β1/Smad2/3 signaling pathway) over a 14-d period than daily intraperitoneal injections of free KLO or captopril. Crucially, CS was found to induce endogenous KLO secretion, highlighting the added value of using CS in RF treatment. Overall, this study demonstrated that KLO-Gel enhanced the anti-fibrotic efficacy of KLO while minimizing its off-target toxicity, and its clinical potential awaits further validation.

The LncRNA6524/miR-92a-2-5p/Dvl1/Wnt/β-catenin axis promotes renal fibrosis in the UUO mouse model

LncRNAs are reported to participate in multiple biological and pathological processes, including renal fibrosis due to obstructive nephropathy. However, the function and mechanisms of each lncRNA in this context differ. In this study, we created a fibrosis model in vitro using TGF-β1 treatment and in vivo through unilateral ureteral obstruction. We demonstrated that lncRNA6524 expression increased in both models, as confirmed by qPCR. Additionally, we discovered that lncRNA6524 mediates the TGF-β1-induced accumulation of extracellular matrix (ECM) proteins in BUMPT cells. We investigated the mechanism using dual luciferase reporter assays, immunofluorescence, and qPCR. Our results indicate that lncRNA6524 acts as a sponge for miR-92a-2-5p, promoting renal fibrosis by upregulating the Dvl1/Wnt/β-catenin signaling pathway. In summary, our findings demonstrate a linear regulatory relationship among lncRNA6524, miR-92a-2-5p, and the Dvl1/Wnt/β-catenin axis in renal epithelial cells during kidney obstruction. This highlights a new potential target for treating obstruction-related renal fibrosis.

Lack of Cannabinoid Type 2 Promoter Activity in Normal or Injured Kidneys Using a Cnr2-GFP Reporter Mouse.

Introduction: Although cannabinoid type 2 (CB2) receptor activity is known to promote diverse biological functions in the kidney, published data regarding CB2 receptor protein levels and cellular distribution within the kidney is inconsistent. The goal of the present study was to investigate the changes of CB2 in the kidney obtained from mice exposed to various forms of kidney injury using a genetic mouse model expressing green fluorescent protein (GFP) driven by the endogenous cannabinoid receptor 2 (Cnr2) promoter. Materials and Methods: Kidney injury was established in a genetic mouse model expressing green fluorescent protein (GFP) driven by the endogenous Cnr2 promoter. Kidney injury was initiated by either treatment with different chemicals [cisplatin or lipopolysaccharide (LPS)] or by unilateral ureteral obstruction (UUO). Changes in the detection of GFP were used as a proxy for CB2 levels and localization. Histological changes due to the injury stimuli were observed by time-related, morphological changes in kidney cytoarchitecture and blood parameters, such as serum creatinine levels. Cnr2 mRNA levels were detected by reverse transcription coupled to polymerase chain reaction (RT-PCR) while protein changes in the tissue lysates were measured by Western blot analysis. Cellular localization of GFP was detected by fluorescent microscopy. Results: Our data demonstrated that there was no band or a minimally detectable band for GFP using kidney lysates from vehicle- or cisplatin-treated mice. A similar lack of GFP was detected in the UUO kidney versus the contralateral control kidney. This is consistent with the low, albeit detectable levels of Cnr2 mRNA in the kidney samples from control or cisplatin treatment. In frozen kidney sections from vehicle and cisplatin-treated mice, GFP fluorescence was not detectable in tubular epithelia, glomeruli or blood vessels in the cortex. Instead, GFP was detected in rare cells within the interstitial space. A second chemical injury model using LPS found a similar lack of GFP protein levels and an absence of legitimate GFP fluorescence in the main cell types within the kidney. Conclusion: These findings suggest that Cnr2 promoter activity is minimally active in normal or injured kidneys, and that pharmacological manipulation of CB2 receptors may be associated with receptors being expressed in cells recruited to the kidney.

S100A2 activation promotes interstitial fibrosis in kidneys by FoxO1-mediated epithelial-mesenchymal transition

BackgroundRenal interstitial fibrosis (RIF) is a common feature of chronic kidney diseases (CKD), with epithelial-mesenchymal transition (EMT) being one of its important mechanisms. S100A2 is a protein associated with cell proliferation and differentiation, but its specific functions and molecular mechanisms in RIF remain to be determined.MethodsS100A2 levels were evaluated in three mouse models, including unilateral ureteral obstruction (UUO), ischemia-reperfusion injury (IRI), and aristolochic acid nephropathy (AAN), as well as in TGF-β1- treated HK-2 cells and in kidney tissue samples. Furthermore, the role of S100A2 and its interaction with FoxO1 was investigated using RT-qPCR, immunoblotting, immunofluorescence staining, co-immunoprecipitation (Co-IP), transcriptome sequencing, and gain- or loss-of-function approaches in vitro.ResultsElevated expression levels of S100A2 were observed in three mouse models and TGF-β1-treated HK2 cells, as well as in kidney tissue samples. Following siRNA silencing of S100A2, exposure to TGF-β1 in cultured HK-2 cells suppressed EMT process and extracellular matrix (ECM) accumulation. Conversely, Overexpression of S100A2 induced EMT and ECM deposition. Notably, we identified that S100A2-mediated EMT depends on FoxO1. Immunofluorescence staining indicated that S100A2 and FoxO1 colocalized in the nucleus and cytoplasm, and their interaction was verified in Co-IP assay. S100A2 knockdown decreased TGF-β1-induced phosphorylation of FoxO1 and increased its protein expression, whereas S100A2 overexpression hampered FoxO1 activation. Furthermore, pharmacological blockade of FoxO1 rescued the induction of TGF-β1 on EMT and ECM deposition in S100A2 siRNA-treated cells.ConclusionS100A2 activation exacerbates interstitial fibrosis in kidneys by facilitating FoxO1-mediated EMT.Graphical abstractA schematic diagram of the underlying mechanisms by which S100A2 regulates EMT and renal fibrosis. Following injury, the cytoplasmic expression of S100A2 in renal tubular epithelial cells is markedly elevated. This increase promotes the phosphorylation of FoxO1, preventing its translocation into the nucleus and enhances EMT and extracellular matrix ECM deposition, thereby exacerbating renal interstitial fibrosis.

CH6824025, potent and selective DDR1 inhibitor, reduces kidney fibrosis in UUO mice.

Discoidin domain receptor 1 (DDR1) is a collagen receptor with tyrosine kinase activity, and its expression is enhanced in various disease conditions. Although previous research suggests that DDR1 contributes to renal disease progression, DDR1 inhibitors for renal fibrosis have yet to be developed. In this study, we used unilateral ureteral obstruction (UUO) mice to investigate whether CH6824025, a strong and selective DDR1 phosphorylation inhibitor, can improve renal fibrosis. Furthermore, we performed 10x Visium spatial transcriptomics (ST) analysis on the kidney. CH6824025 suppressed the phosphorylation of DDR1 in the kidney, and the amount of hydroxyproline, the Sirius red- and the F4/80-positive area, and the mRNA expression of fibrosis and inflammation-related genes in the kidney were significantly decreased. 10x Visium ST analysis suggested that DDR1 is mainly expressed in distal nephrons under normal conditions, but that its expression appears to increase in the injured proximal tubules in UUO mice. Comparing mRNA expression in DDR1 positive spots in the Vehicle and the CH6824025 group, oxidative phosphorylation and mitochondrial dysfunction might be improved, and pathways involved in fibrosis tended to be inhibited in the CH6824025 administration group. Downstream analysis would suggest that mRNA expression changes in the CH6824025 group contribute to the inhibition of cell movement. Taken together, our findings suggest that CH6824025 inhibited kidney fibrosis in UUO mice, which might be due to the inhibition of the migration of inflammatory cells to the injury site and the reduction of inflammation. DDR1 inhibitors are expected to be a promising treatment for renal fibrosis. Significance Statement The novel DDR1 inhibitor CH6824025 could ameliorate fibrosis and inflammation in UUO mice. CH6824025 would inhibit cell motility (e.g., migration) that prevents the progression of fibrosis and improves mitochondrial function in UUO mice. CH6824025 could provide a significant benefit to patients with kidney fibrosis.

Aldehyde dehydrogenase 2 preserves kidney function by countering acrolein-induced metabolic and mitochondrial dysfunction.

The prevalence of chronic kidney disease (CKD) varies by race because of genetic and environmental factors. The Glu504Lys polymorphism in aldehyde dehydrogenase 2 (ALDH2), commonly observed among East Asian people, alters the enzyme's function in detoxifying alcohol-derived aldehydes, affecting kidney function. This study investigated the association between variations in ALDH2 levels within the kidney and the progression of kidney fibrosis. Our clinical data indicate that diminished ALDH2 levels are linked to worse CKD outcomes, with correlations between ALDH2 expression, estimated glomerular filtration rate, urinary levels of acrolein - an aldehyde metabolized by ALDH2 - and fibrosis severity. In mouse models of unilateral ureteral obstruction and folic acid nephropathy, reduced ALDH2 levels and elevated acrolein were observed in kidneys, especially in ALDH2 Glu504Lys-knockin mice. Mechanistically, acrolein modifies pyruvate kinase M2, leading to its nuclear translocation and coactivation of HIF-1α, shifting cellular metabolism to glycolysis, disrupting mitochondrial function, and contributing to tubular damage and the progression of kidney fibrosis. Enhancing ALDH2 expression through adeno-associated virus vectors reduced acrolein and mitigated fibrosis in both WT and Glu504Lys-knockin mice. These findings underscore the potential therapeutic significance of targeting the dynamic interaction between ALDH2 and acrolein in CKD.

Unveiling the role of transgelin as a prognostic and therapeutic target in kidney fibrosis via a proteomic approach.

Chronic kidney disease (CKD) progression involves tubulointerstitial fibrosis, a process characterized by excessive extracellular matrix accumulation. To identify potential biomarkers for kidney fibrosis, we performed mass spectrometry-based proteomic profiling of human kidney tubular epithelial cells and kidney tissue from a 5/6 nephrectomy rat model. Multidisciplinary analysis across kidney fibrosis models revealed 351 differentially expressed proteins associated with kidney fibrosis, and they were enriched in processes related to the extracellular matrix, kidney aging, and mitochondrial functions. Network analysis of the selected proteins revealed five crucial proteins, of which transgelin emerged as a candidate protein that interacts with known fibrosis-related proteins. Concordantly, the gene expression of transgelin in the kidney tissue from the 5/6 nephrectomy model was elevated. Transgelin expression in kidney tissue gradually increased from intermediate to advanced fibrosis stages in 5/6 Nx rats and mice with unilateral ureteral obstruction. Subsequent validation in kidney tissue and urine samples from patients with CKD confirmed the upregulation of transgelin, particularly under advanced disease stages. Moreover, we investigated whether blocking TAGLN ameliorated kidney fibrosis and reduced reactive oxygen species levels in cellular models. In conclusion, our proteomic approach identified TAGLN as a potential noninvasive biomarker and therapeutic target for CKD-associated kidney fibrosis, suggesting its role in modulating mitochondrial dysfunction and oxidative stress responses.

Pharmacological modulation of transglutaminase 2 in the unilateral ureteral obstruction mouse model

BackgroundTransglutaminase 2 (TG2) is a multifunctional enzyme involved in fibrosis by promoting transforming-growth-factor-β1 and crosslinking of extracellular matrix proteins. These functions are dependent on the open conformation, while the closed state of TG2 can induce vasodilation. We explored the putative protective role of TG2 in its closed state on development of renal fibrosis and blood pressure (BP) regulation. MethodsWe studied the unilateral ureteral obstruction (UUO) mouse model treated with LDN27219, which promotes the closed conformation of TG2. Mice were subjected to 7 days UUO or sham operation and treated with vehicle (n = 10), LDN27219 (15 mg/kg/12 h, n = 9) or candesartan (5 mg/kg/day, n = 10) as a clinically comparator. Renal expression of TG2 and pro-fibrotic mediators were evaluated by Western blotting, qPCR and histology, and BP by tail-cuff measurements. ResultsObstructed kidneys showed increased mRNA and protein expression of fibronectin, collagen 3α1 (Col3α1), α-smooth muscle actin and collagen staining. Despite increased renal TG2 mRNA, protein expression was reduced in all UUO groups, but with increased transamidase activity in the vehicle and candesartan groups. LDN27219 reduced mRNA expression of fibronectin and Col3α1, but their protein expression remained unchanged. In contrast to LDN27219, candesartan lowered BP without affecting expression of pro-fibrotic biomarkers. ConclusionRenal TG2 mRNA and protein expression levels seem dissociated, with transamidase activity being increased. LDN27219 influences kidney pro-fibrotic markers at the mRNA level and attenuates transamidase activity but without affecting collagen content or BP. Our findings suggest that TG2 in its closed conformation has anti-fibrotic effects at the molecular level.

Spatiotemporal delivery of multiple components of rhubarb-astragalus formula for the sysnergistic treatment of renal fibrosis.

Rhubarb (Rheum palmatum L.) and astragalus (Radix astragali) find widespread used in clinical formulations for treating chronic kidney disease (CKD). Notably, the key active components, total rhubarb anthraquinone (TRA) and total astragalus saponin (TAS), exhibit superiority over rhubarb and astragalus in terms of their clear composition, stability, quality control, small dosage, and efficacy for disease treatment. Additionally, astragalus polysaccharides (APS) significantly contribute to the treatment of renal fibrosis by modulating the gut microbiota. However, due to differences in the biopharmaceutical properties of these components, achieving synergistic effects remains challenging. This study aims to develop combined pellets (CPs) and evaluate the potential effect on unilateral ureteral obstruction (UUO)-induced renal fibrosis. The CPs pellets were obtained by combining TRA/TAS-loaded SNEDDS pellets and APS-loaded pellets, prepared using the fluidized bed coating process. The prepared pellets underwent evaluation for morphology, bulk density, hardness, and flowing property. Moreover, the in vitro release of the payloads was evaluated with the CHP Type I method. Furthermore, the unilateral ureteral obstruction (UUO) model was utilized to investigate the potential effects of CPs pellets on renal fibrosis and their contribution to gut microbiota modulation. The ex-vivo study demonstrated that the developed CPs pellets not only improved the dissolution of TRA and TAS but also delivered TRA/TAS and APS spatiotemporally to the appropriate site along the gastrointestinal tract. In an animal model of renal fibrosis (UUO rats), oral administration of the CPs ameliorated kidney histological pathology, reduced collagen deposition, and decreased the levels of inflammatory cytokines. The CPs also restored the disturbed gut microbiota induced by UUO surgery and protected the intestinal barrier. The developed CPs pellets represent a promising strategy for efficiently delivering active components in traditional Chinese medicine formulas, offering an effective approach for treating CKD.

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

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. 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. 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. 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.

Attenuation of renal fibrosis in mice due to lack of bombesin receptor-activated protein homologue.

Bombesin receptor-activated protein (BRAP), encoded by the C6orf89 gene in humans, is expressed in various cells with undefined functions. BC004004, the mouse homologue of C6orf89, has been shown to play a role in bleomycin-induced pulmonary fibrosis through the use of a BC004004 gene knockout mouse (BC004004-/-). In this study, we investigated the potential involvement of BRAP in renal fibrosis using two mouse models: unilateral ureteral obstruction (UUO) and type 2 diabetes mellitus induced by combination of a high-fat diet (HFD) and streptozocin (STZ). BRAP or its homologue was expressed in tubular epithelial cells (TECs) in the kidneys of patients with chronic kidney disease (CKD) and in BC004004+/+ mice. Compared to control mice, BC004004-/- mice exhibited attenuated renal injury and renal fibrosis after UUO or after HFD/STZ treatment. Immunohistochemistry and immunoblot analyses of the kidneys of BC004004+/+ mice after UUO surgery showed a more significant decrease in E-cadherin expression and a more significant increase in both α smooth muscle actin (α-SMA) and vimentin expression compared to BC004004-/- mice. Additionally, stimulation with transforming growth factor-β1 (TGF-β1) led to a more significant decrease in E-cadherin expression and a more significant increase in α-SMA and vimentin expression in isolated TECs from BC004004+/+ than in those from BC004004-/- mice. These results suggest that an enhanced epithelial-mesenchymal transition (EMT) process occurred in TECs in BC004004+/+ mice during renal injury, which might contribute to renal fibrosis. The loss of the BRAP homologue in BC004004-/- mice suppressed EMT activation in kidneys and contributed to the suppression of fibrosis during renal injury.

Dose-Dependent Nephroprotective Effects of an ALK5 Inhibitor in the Unilateral Ureteral Obstruction (UUO) Mouse Model of Kidney Fibrosis

Dose-Dependent Nephroprotective Effects of an ALK5 Inhibitor in the Unilateral Ureteral Obstruction (UUO) Mouse Model of Kidney Fibrosis

Global but Not Tubule Cell-Specific Knockout of STING Attenuates Kidney Injury in Mice with Unilateral Ureteral Obstruction

Global but Not Tubule Cell-Specific Knockout of STING Attenuates Kidney Injury in Mice with Unilateral Ureteral Obstruction

Elevated serum GDF15 level as an early indicator of proximal tubular cell injury in acute kidney injury

Acute kidney injury (AKI) is a high-burden medical condition, and current diagnostic criteria can only assess AKI after full manifestation. Stress marker growth differentiation factor 15 (GDF15) was reported to have a role in kidney injury of critical patients. Herein, we evaluated dynamic changes in GDF15 across diverse AKI scenarios and explored the underlying mechanisms of its induction. Serum parameters and renal lesions were analyzed in mouse models of unilateral ischemia-reperfusion injury (uni-IRI) and unilateral ureteral obstruction (UUO). The human proximal tubular (HK−2) cell line was stimulated with various conditions, and induction of GDF15 expression was determined. Serum GDF15 levels were rapidly induced within hours after injury in both animal models and declined thereafter. Renal GDF15 expression exhibited a temporary and early increased induction and was mainly located in aquaporin 1-positive proximal tubules in both unilateral AKI model tissues. In cell experiments, rapid GDF15 production was highly induced by t-BHP and CoCl2. Treatment with either an antioxidant or mitogen-activated protein kinase inhibitors abolished t-BHP- and CoCl2-mediated GDF15 expression. In addition, silencing nuclear factor erythroid 2-related factor 2 expression also reduced the basal and t-BHP- or CoCl2-mediated GDF15 expression level in HK-2 cells. Our data showed that elevated serum GDF15 levels could be detected early in unilateral AKI models without notable alterations in kidney function parameters. GDF15 expression was associated with oxidative stress- and hypoxia-mediated proximal tubular cell injury. These data document that elevated serum GDF15 can possibly serve as an early biomarker for proximal tubular cell injury in AKI.