Unilateral Ureteral Obstruction Research Articles

Modulation of Stem Cell Factor by Forskolin Inhibits the Progression of Tubule Interstitial Fibrosis

Purpose: Forskolin is primarily found in the roots of the Coleus forskohlii plant, historically employed in Southeast Asian and Indian Ayurvedic medicine. Mast cells play a crucial role in fibrosis progression, yet their activation and inhibition in animal models are understudied; thus, we explored forskolin’s impact on kidney fibrosis. Materials and Methods: Forskolin was evaluated in a mouse model for stem cell factor-induced histamine release, and plasma histamine levels were measured using the enzyme-linked immunosorbent assay. Kidney fibrosis was developed by unilateral ureteral obstruction (UUO). Renal function was assessed by spectrophotometric measurements of serum blood urea nitrogen (BUN) and creatinine. The gene expression of collagen, transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA), interleukin-1 beta (IL-1β), and mast cell protease-5 (MCPT-5) in the kidney was analyzed by reverse transcription polymerase chain reaction (RT-PCR). Histopathological changes in the renal tissues were examined by hematoxylin and eosin (H&E) and Masson’s trichome stain. Results: Our results showed that 3 mg/kg forskolin inhibited SCF-induced plasma histamine release in a mouse model. In the 7-day UUO model, forskolin significantly showed inhibition of serum creatinine and blood urea nitrogen compared with the disease group. Forskolin significantly inhibited elevated expression of collagen, TGF-β, α-SMA, IL-1β, and MCPT-5 in the kidneys. Histopathological observation of H&E and Masson trichome-stained kidney forskolin demonstrated a reduction in inflammatory cells, pelvic and tubular dilation, and fibrosis. Conclusion: Forskolin showed an anti-fibrotic effect in UUO-induced renal fibrotic mice. Most significantly, forskolin administration showed a decrease in the expression of the mast cell protease MCPT5 in the kidneys. These results imply that forskolin, through modifying SCF activity, may be a viable potential treatment for the attenuation of tubule-interstitial fibrosis.

Renoprotective effect of diacerein in rats with partial unilateral ureteral obstruction model

Abstract Objectives We aimed to analyze the effects of diacerein in a rat model of partial unilateral ureteral obstruction (PUUO). Methods We randomly divided 24 female rats into three groups. Control group, PUUO group and PUUO + diacerein group. The PUUO group was subjected to the PUUO model for seven days. The PUUO + diacerein group received oral diacerein (80 mg/kg) for seven days. Spectrophotometric methods were employed to measure oxidative stress parameters, including malondialdehyde (MDA), protein carbonyl (PC) and antioxidant enzyme levels, including glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD), while indicators of renal function, such as kidney injury molecule-1 (KIM-1) and neutrophil gelatinous-associated lipocalin (NGAL), along with inflammatory parameters interleukin-1 beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6), were assessed using the ELISA method. Inflammatory parameters were measured in blood samples, and other parameters were analyzed in kidney tissue. Hematoxylin-eosin method examinations were used for histological analyses. Results IL-1beta, TNF-alpha, and IL-6 levels were found to be significantly decreased in the PUUO + diacerein group compared to the PUUO group (p=0.006, p=0.002 and p=0.001, respectively). In the PUUO + diacerein group, GSH-Px and SOD activities increased compared with the PUUO group (p=0.031 and p=0.037, respectively). We also observed a significant improvement in renal function parameters, such as KIM-1 and NGAL levels in the PUUO + diacerein group compared to PUUO (p=0.002 and p=0.012, respectively). The PC and MDA levels were highest in the PUUO group (p<0.001). Similarly, the histopathologic tissue damage was the most prominent PUUO group (p<0.001). Conclusions Our study found that diacerein is a highly effective pharmacologic agent in alleviating oxidative damage in PUUO model rats.

Atg5 deficiency in macrophages protects against kidney fibrosis via the CCR6-CCL20 axis

BackgroundAutophagy is a lysosome-dependent degradation pathway that regulates macrophage activation, differentiation, and polarization. Autophagy related 5 (Atg5) is a key protein involved in phagocytic membrane elongation in autophagic vesicles that forms a complex with Atg12 and Atg16L1. Alterations in Atg5 are related to both acute and chronic kidney diseases in experimental models. However, the role of macrophage-expressed Atg5 in acute kidney injury remains unclear.MethodsUsing a myeloid cell-specific Atg5 knockout (MΦ atg5−/−) mouse, we established renal ischemia/reperfusion and unilateral ureteral obstruction models to evaluate the role of macrophage Atg5 in renal macrophage migration and fibrosis.ResultsBased on changes in the serum urea nitrogen and creatinine levels, Atg5 deletion had a minimal effect on renal function in the early stages after mild injury; however, MΦ atg5−/− mice had reduced renal fibrosis and reduced macrophage recruitment after 4 weeks of ischemia/reperfusion injury and 2 weeks of unilateral ureteral obstruction injury. Atg5 deficiency impaired the CCL20-CCR6 axis after severe ischemic kidneys. Chemotactic responses of bone marrow-derived monocytes (BMDMs) from MΦ atg5−/− mice to CCL20 were significantly attenuated compared with those of wild-type BMDMs, and this might be caused by the inhibition of PI3K, AKT, and ERK1/2 activation.ConclusionsOur data indicate that Atg5 deficiency decreased macrophage migration by impairing the CCL20-CCR6 axis and inhibited M2 polarization, thereby improving kidney fibrosis.

557 Dual TGFβR1/MAP4K4 inhibitor reduces kidney injury in a mouse model of renal fibrosis.

OBJECTIVES/GOALS: Renal fibrosis is a critical pathophysiological event in chronic kidney diseases. Our goal is to determine the ability of dual-inhibitor of transforming growth factor beta receptor 1 (TGFα²R1) and mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4), TK850, on reducing kidney fibrosis. METHODS/STUDY POPULATION: To test the renal anti-fibrotic action ofdual TK850,8-10-week-old male and female C57BL/6mice with unilateral ureteral obstruction (UUO) induced kidney fibrosis were used. Mice were separated into 3 groups: group 1 contained mice that had UUO surgery (UUO control), group 2 contained mice prophylactically treated with TK850 thatstarted 7 days prior to UUO(UUO-P,20 mpk/d/ip), and group 3 contained mice interventionally treated with TK850 that started3 days after UUO(UUO-I,20 mpk/d/ip). Ten days following UUO the kidneys and blood were collected for analysis. Renal fibrosis was assessed from hydroxyproline content (measure of collagen)and histological collagen analysis using Picrosirius red stain. RESULTS/ANTICIPATED RESULTS: Renal hydroxyproline was increased equally in the UUO kidney of male (5.4 ± 0.41 µg/10mg, n=5) and female mice (5.5 ± 0.50 µg/10mg, n=5) compared to the contralateral control kidney (2.9 ± 0.14 µg/10mg, n=10). TK850 treatment in UUO-P mice (n=10, 3.4 ± 0.24 µg/10mg) and UUO-I mice (4.30 ± 0.20 µg/10mg, n=10) had significantly reduced hydroxyproline levels. Histopathological evaluation revealed that kidney injury increased collagen deposition in the UUO kidney (17.1 ± 0.43% collagen positive area, n=10) compared to the control kidney (2.0 ± 0.23%, n=10). TK850 treatment in UUO-P mice significantly attenuated collagen deposition (10.5 ± 0.38%, n=10), while UUO-I had significantly reduced collagen deposition as well (13.1 ± 0.25%, n=10). DISCUSSION/SIGNIFICANCE: Taken together, these results validate the dual TGFβR1/MAP4K4 inhibitor, TK850 as a potential therapeutic to mitigate renal fibrosis and supports the emergence of a combinational pharmacotherapeutic approach for multi-factorial kidney diseases.

Icariin alleviates renal inflammation and tubulointerstitial fibrosis via Nrf2-mediated attenuation of mitochondrial damage.

Tubulointerstitial fibrosis is an inevitable consequence of all progressive chronic kidney disease (CKD) and contributes to a substantial health burden worldwide. Icariin, an active flavonoid glycoside obtained from Epimedium species, exerts potential antifibrotic effect. The study aimed to explore the protective effects of icariin against tubulointerstitial fibrosis in unilateral ureteral obstruction (UUO)-induced CKD mice and TGF-β1-treated HK-2 cells, and furthermore, to elucidate the underlying mechanisms. The results demonstrated that icariin significantly improved renal function, alleviated tubular injuries, and reduced fibrotic lesions in UUO mice. Furthermore, icariin suppressed renal inflammation, reduced oxidative stress as evidenced by elevated superoxide dismutase activity and decreased malondialdehyde level. Additionally, TOMM20 immunofluorescence staining and transmission electron microscope revealed that mitochondrial mass and morphology of tubular epithelial cells in UUO mice was restored by icariin. In HK-2 cells treated with TGF-β1, icariin markedly decreased profibrotic proteins expression, inhibited inflammatory factors, and protected mitochondria along with preserving mitochondrial morphology, reducing reactive oxygen species (ROS) and mitochondrial ROS (mtROS) overproduction, and preserving membrane potential. Further investigations demonstrated that icariin could activate nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway both in vivo and in vitro, whereas inhibition of Nrf2 by ML385 counteracted the protective effects of icariin on TGF-β1-induced HK-2 cells. In conclusion, icariin protects against renal inflammation and tubulointerstitial fibrosis at least partly through Nrf2-mediated attenuation of mitochondrial dysfunction, which suggests that icariin could be developed as a promising therapeutic candidate for the treatment of CKD.

Secreted frizzled-related protein 5 protects against renal fibrosis by inhibiting Wnt/β-catenin pathway.

Renal fibrosis (RF) is an important pathogenesis for renal function deterioration in chronic kidney disease. Secreted frizzled-related protein 5 (SFRP5) is an anti-fibrotic adipokine but its direct role on RF remains unknown. It was aimed to study the protective effect of SFRP5 against RF and interference with Wnt/β-catenin signaling pathway for the first time. First, the therapeutic efficacy of SFRP5 was evaluated by adenovirus overexpression in rats with unilateral ureteral obstruction (UUO) in vivo. Thirty-six rats were randomly divided into the sham, UUO, and SFRP5 (UUO + Ad-SFRP5) groups. Half rats in each group were selected at random for euthanasia at 7 days and the others until 14 days. Then, the transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) was established in HK-2 cells in vitro. The cells were divided into four groups: the control group, the TGF-β1 group, the TGF-β1 + SFRP5 group, and the TGF-β1 + SFRP5 + anti-SFRP5 group. The makers of EMT and Wnt/β-catenin pathway proteins were investigated. In the UUO model, expression of SFRP5 showed compensatory upregulation, and adenoviral-mediated SFRP5 over-expression remarkably attenuated RF, as demonstrated by maintenance of E-cadherin and suppression of α-smooth muscle actin (SMA). In vitro, SFRP5 was shown to inhibit TGF-β1-mediated positive regulation of α-SMA, fibronectin, collagen I but negative regulation of E-cadherin. Furthermore, SFRP5 abrogated activation of Wnt/β-catenin, which was the essential pathway in EMT and RF pathogenesis. The changes after a neutralizing antibody to SFRP5 confirmed the specificity of SFRP5 for inhibition. These findings suggest that SFRP5 can directly ameliorate EMT and protect against RF by inhibiting Wnt/β-catenin pathway.

RfxCas13d-mediated inhibition of Circ1647 alleviates renal fibrosis via PI3K/AKT signaling pathway

Background Circular RNAs (CircRNAs) have been shown to be involved in the development of chronic kidney disease (CKD). This study aimed to investigate the role of Circ1647 in renal fibrosis, which is a hallmark of CKD. Methods In this study, we established a unilateral ureteral obstruction (UUO) model and delivered Circ1647 RfxCas13d knockdown plasmid into renal parenchymal cells via retrograde injection through the ureter followed by electroporation. After that, the pathological changes were determined by Hematoxylin and Eosin. Meanwhile, Immunohistochemistry, qRT-PCR and Western blot were conducted to assess the degree of fibrosis. In addition, overexpressing of Circ1647 in renal tubular epithelial cells (TCMK1) was performed to investigate the underlying mechanisms of Circ1647. Results Our results displayed that electroporation-mediated knockdown of Circ1647 by RfxCas13d knockdown plasmid significantly inhibited renal fibrosis in UUO mice as evidenced by reduced expression of fibronectin and α-SMA (alpha-smooth muscle actin). Conversely, overexpression of Circ1647 in TCMK1 cells promoted the fibrosis. In terms of mechanism, Circ1647 may mediate the PI3K/AKT Signaling Pathway as demonstrated by the balance of the phosphorylation of PI3K and AKT in vivo and the aggravated phosphorylation of PI3K and AKT in vitro. These observations were corroborated by the effects of the PI3K inhibitor LY294002, which mitigated fibrosis post Circ1647 overexpression. Conclusion Our study suggests that Circ1647 plays a significant role in renal fibrosis by mediating the PI3K/AKT signaling pathway. RfxCas13d-mediated inhibition of Circ1647 may serve as a therapeutic target for renal fibrosis in CKD.

Pyxinol Fatty Acid Ester Derivatives J16 against AKI by Selectively Promoting M1 Transition to M2c Macrophages.

Acute kidney injury (AKI) is a common, multicause clinical condition that, if ignored, often progresses to chronic kidney disease (CKD) and end-stage kidney disease, with a mortality rate of 40-50%. However, there is a lack of universal treatment for AKI. Inflammation is the basic pathological change of early kidney injury, and inflammation can exacerbate AKI. Macrophages are the primary immune cells involved in the inflammatory microenvironment of kidney disease. Therefore, regulating the function of macrophages is a crucial breakthrough for the AKI intervention. Our team chemically modified pyxinol, an ocotillol-type ginsenoside, to prepare PJ16 with higher solubility and bioavailability. In vitro, using a model of macrophages stimulated by LPS, it was found that PJ16 could regulate macrophage function, including inhibiting the secretion of inflammatory factors, promoting phagocytosis, inhibiting M1 macrophages, and promoting M1 transition to the M2c macrophage. Further investigation revealed that PJ16 may shield renal tubular epithelial cells (HK-2) damaged by LPS in vitro. Based on this, PJ16 was validated in the animal model of unilateral ureteral obstruction, which showed that it improves renal function and inhibits renal tissue fibrosis by decreasing inflammatory responses, reducing macrophage inflammatory infiltration, and preferentially upregulating M2c macrophages. In conclusion, our study is the first to show that PJ16 resists AKI and fibrosis by mechanistically regulating macrophage function by modulating the phenotypic transition from M1 to M2 macrophages, mainly M2c macrophages.

Abstract 2969: Targeting novel senescence markers by conditionally active biologics eliminates senescence-associated secretory phenotype in in vitro and in vivo models

Abstract Clearing senescent cells has been shown to have promising effects against cancer and age-related pathologies in preclinical models as well as early human clinical trials. However, current senescent cell elimination strategies are focused on targets that do not distinguish between hyper-inflamed or SASP senescent cells versus relatively non-inflamed senescent cells. The use of senolytics in the clinic is still limited due to their cytotoxicity to either normal cells or potentially beneficial senescent cells. A more effective senescence cell targeted approach is needed to reduce side effects and increase the efficiency of senescence cell removal or reduction. Conditionally Active Biologics (CAB) technology is a proprietary platform unique in its ability to be selectively active in the context of diseased tissues, but not normal tissues. The aberrant accumulation of senescent cells in aged and cancerous tissue triggers inflammatory signaling through a senescence-associated secretory phenotype (SASP), promoting aging and tumor progression. Since our CAB technology is currently being tested as a cancer therapy by targeting cell surface markers such as AXL, ROR2, and CTLA4 in clinical studies, we explored whether CAB technology allows selective removal of senescent cells in SASP-associated microenvironments. In our previous report, we demonstrated several novel senescence-specific surface antigens upregulated in senescent cells (1). CAB antibodies targeting these senescence markers have no or very low binding to the target antigen on senescence cells in physiological, alkaline conditions, but have strong binding in glycolytic, acidic SASP conditions in in vitro binding assays. In in vitro antibody-dependent cell-mediated cytotoxicity assays, CAB antibodies were more potent against senescent cells compared to proliferating cells and displayed high selectivity for the glycolytic, acidic condition. To study whether CAB antibody reduces senescent cell occurrence in vivo, we developed a unilateral ureteral obstruction (UUO) mouse model to induce senescent cells, fibrosis, and inflammation in mouse kidney. The mice treated with CAB antibodies had a significant reduction of senescent cells and inflammatory cells infiltrated in the renal cortex, compared to the mice treated with benchmark and isotype antibodies in UUO kidneys. Thus, the CAB antibody-based therapeutic is a promising strategy for senescent cell removal in an inflammatory microenvironment. In conclusion, CAB technology provides a new generation of biologics with an increased safety margin and therapeutic index targeting SASP, acidic senescence cells in cancer and age-related diseases. (1). Chen J, Wang J, Liu H, Chang C, Boyle WJ, and Short JM. Abstract 4795: Conditionally active biologics eliminates senescence cells in cancer and aging. Cancer Res (2023) 83. Citation Format: Jian Chen, Jian Wang, Haizheng Liu, Cathy Chang, William J. Boyle, Jay M. Short. Targeting novel senescence markers by conditionally active biologics eliminates senescence-associated secretory phenotype in in vitro and in vivo models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2969.

HIPK2 C-terminal domain inhibits NF-κB signaling and renal inflammation in kidney injury.

HIPK2 is a multifunctional kinase that acts as a key pathogenic mediator of chronic kidney disease and fibrosis. It acts as a central effector of multiple signaling pathways implicated in kidney injury, such as TGF-β/Smad3-mediated extracellular matrix accumulation, NF-κB-mediated inflammation, and p53-mediated apoptosis. Thus, a better understanding of the specific HIPK2 regions necessary for distinct downstream pathway activation is critical for optimal drug development for CKD. Our study now shows that Caspase 6-mediated removal of the C-terminal region of HIPK2 (HIPK2-CT) leads to hyperactive p65 NF-κB transcriptional response in kidney cells. In contrast, the expression of cleaved HIPK2-CT fragment can restrain p65 NF-κB transcriptional activity by cytoplasmic sequestration NF-κB signaling component, p65 NF-κB, and attenuation of IκBα degradation. Therefore, we examined whether HIPK2-CT expression can be exploited to restrain renal inflammation in vivo. The induction of HIPK2-CT overexpression in kidney tubular cells attenuated p65 nuclear translocation, expression of inflammatory cytokines, and macrophage infiltration in the kidney of mice with unilateral ureteral obstruction and lipopolysaccharide-induced acute kidney injury. Collectively, our findings indicate that the C-terminal region of HIPK2 is involved in the regulation of nuclear NF-κB transcriptional activity and that HIPK2-CT or its analogs could be further exploited as potential anti-inflammatory agents to treat kidney disease.

Kaempferitrin attenuates unilateral ureteral obstruction-induced renal inflammation and fibrosis in mice by inhibiting NOX4-mediated tubular ferroptosis.

Tubular ferroptosis significantly contributes to renal inflammation and fibrosis, critical factors in chronic kidney disease (CKD). This study aims to investigate Kaempferitrin, a potent flavonoid glycoside from Bauhinia forficata leaves, renowned for its anti-inflammatory and antitumor effects, and to elucidate its potential mechanisms in mitigating inflammation and fibrosis induced by tubular ferroptosis. The study investigated Kaempferitrin's impact on tubular ferroptosis using a unilateral ureteral obstruction (UUO) model-induced renal inflammation and fibrosis. In vitro, erastin-induced ferroptosis in primary tubular epithelial cells (TECs) was utilized to further explore Kaempferitrin's effects. Additionally, NADPH oxidase 4 (NOX4) transfection in TECs and cellular thermal shift assay (CETSA) were conducted to identify Kaempferitrin's target protein. Kaempferitrin effectively improved renal function, indicated by reduced serum creatinine and blood urea nitrogen levels. In the UUO model, it significantly reduced tubular necrosis, inflammation, and fibrosis. Its renoprotective effects were linked to ferroptosis inhibition, evidenced by decreased iron, 4-hydroxynonenal (4-HNE), and malondialdehyde (MDA) levels, and increased glutathione (GSH). Kaempferitrin also normalized glutathione peroxidase 4 (GPX4) and Solute Carrier Family 7 Member 11(SLC7A11) expression, critical ferroptosis mediators. In vitro, it protected TECs from ferroptosis and consistently suppressed NOX4 expression. NOX4 transfection negated Kaempferitrin's antiferroptosis effects, while CETSA confirmed Kaempferitrin-NOX4 interaction. Kaempferitrin shows promise as a nephroprotective agent by inhibiting NOX4-mediated ferroptosis in tubular cells, offering potential therapeutic value for CKD.

Interleukin-10 enhances recruitment of immune cells in the neonatal mouse model of obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, leukocyte infiltration, tubular cell death, and interstitial fibrosis. Interleukin-10 (IL-10) is an anti-inflammatory cytokine, produced mainly by monocytes/macrophages and regulatory T-cells. IL-10 inhibits innate and adaptive immune responses. IL-10 has a protective role in the adult model of obstructive uropathy. However, its role in neonatal obstructive uropathy is still unclear which led us to study the role of IL-10 in neonatal mice with unilateral ureteral obstruction (UUO). UUO serves as a model for congenital obstructive nephropathies, a leading cause of kidney failure in children. Newborn Il-10−/− and C57BL/6 wildtype-mice (WT) were subjected to complete UUO or sham-operation on the 2nd day of life. Neonatal kidneys were harvested at day 3, 7, and 14 of life and analyzed for different leukocyte subpopulations by FACS, for cytokines and chemokines by Luminex assay and ELISA, and for inflammation, programmed cell death, and fibrosis by immunohistochemistry and western blot. Compared to WT mice, Il-10−/− mice showed reduced infiltration of neutrophils, CD11bhi cells, conventional type 1 dendritic cells, and T-cells following UUO. Il-10−/− mice with UUO also showed a reduction in pro-inflammatory cytokine and chemokine release compared to WT with UUO, mainly of IP-10, IL-1α, MIP-2α and IL-17A. In addition, Il-10−/− mice showed less necroptosis after UUO while the rate of apoptosis was not different. Finally, α-SMA and collagen abundance as readout for fibrosis were similar in Il-10−/− and WT with UUO. Surprisingly and in contrast to adult Il-10−/− mice undergoing UUO, neonatal Il-10−/− mice with UUO showed a reduced inflammatory response compared to respective WT control mice with UUO. Notably, long term changes such as renal fibrosis were not different between neonatal Il-10−/− and neonatal WT mice with UUO suggesting that IL-10 signaling is different in neonates and adults with UUO.

FTO-mediated m6A mRNA demethylation aggravates renal fibrosis by targeting RUNX1 and further enhancing PI3K/AKT pathway.

Chronic kidney disease (CKD) is a global health burden, with ineffective therapies leading to increasing morbidity and mortality. Renal interstitial fibrosis is a common pathway in advanced CKD, resulting in kidney function and structure deterioration. In this study, we investigate the role of FTO-mediated N6-methyladenosine (m6A) and its downstream targets in the pathogenesis of renal fibrosis. M6A modification, a prevalent mRNA internal modification, has been implicated in various organ fibrosis processes. We use a mouse model of unilateral ureteral obstruction (UUO) as an invivo model and treated tubular epithelial cells (TECs) with transforming growth factor (TGF)-β1 as invitro models. Our findings revealed increased FTO expression in UUO mouse model and TGF-β1-treated TECs. By modulating FTO expression through FTO heterozygous mutation mice (FTO+/- ) invivo and small interfering RNA (siRNA) invitro, we observed attenuation of UUO and TGF-β1-induced epithelial-mesenchymal transition (EMT), as evidenced by decreased fibronectin and N-cadherin accumulation and increased E-cadherin levels. Silencing FTO significantly improved UUO and TGF-β1-induced inflammation, apoptosis, and inhibition of autophagy. Further transcriptomic assays identified RUNX1 as a downstream candidate target of FTO. Inhibiting FTO was shown to counteract UUO/TGF-β1-induced RUNX1 elevation invivo and invitro. We demonstrated that FTO signaling contributes to the elevation of RUNX1 by demethylating RUNX1 mRNA and improving its stability. Finally, we revealed that the PI3K/AKT pathway may be activated downstream of the FTO/RUNX1 axis in the pathogenesis of renal fibrosis. In conclusion, identifying small-molecule compounds that target this axis could offer promising therapeutic strategies for treating renal fibrosis.

Uncovering the Nephroprotective Mechanism of Caffeic Acid in Renal Tubulointerstitial Fibrosis through Network Pharmacology Analysis

Background: Renal tubulointerstitial fibrosis (RTF) is a progressive kidney condition characterized by the formation of fibrotic tissue. Caffeic acid (CA), a key component of the medicinal plant Antirhea borbonica, shows promise as a potential treatment for renal fibrosis. Here, we investigated the nephroprotective effect of CA in RTF and its underlying mechanisms. Methods: RTF was induced in rats through unilateral ureteral obstruction (UUO), followed by intraperitoneal administration of CA for 5 days. We assessed kidney weight/body weight (KW/BW) ratio, serum creatinine (Scr), blood urea nitrogen (BUN), 24-h urine protein (UP), and performed histological examinations. We also analyzed the expression of fibrosis-related proteins. Genes associated with RTF and CA were identified using public databases. A protein-protein interaction (PPI) network and molecular docking studies were conducted. Results: CA treatment significantly reduced the KW/BW ratio, levels of Scr, BUN, and 24-h UP, indicating improved kidney function in UUO-induced RTF rats. Histological examination revealed reduced fibrotic changes. CA administration also led to decreased collagen deposition and downregulation of fibrosis-related protein expression. CA administration also led to decreased collagen deposition and downregulation of fibrosis-related protein expression. The PPI network analysis showed significant differential expression of 13 genes between the fibrosis and normal groups. Notably, EGFR and MAPK14 were strongly associated with CA, and CA treatment downregulated EGFR and MAPK14 protein expression in UUO rats. Conclusion: CA exhibits substantial nephroprotective effects in UUO-induced RTF rats by modulating key genes EGFR and MAPK14, and MAPK signaling pathway.

Cardiac transcriptomic changes induced by early CKD in mice reveal novel pathways involved in the pathogenesis of Cardiorenal syndrome type 4

BackgroundCardiorenal syndrome (CRS) type 4 is prevalent among the chronic kidney disease (CKD) population, with many patients dying from cardiovascular complications. However, limited data regarding cardiac transcriptional changes induced early by CKD is available. MethodsWe used a murine unilateral ureteral obstruction (UUO) model to evaluate renal damage, cardiac remodeling, and transcriptional regulation at 21 days post-surgery through histological analysis, RT-qPCR, RNA-seq, and bioinformatics. ResultsUUO leads to significant kidney injury, low uremia, and pathological cardiac remodeling, evidenced by increased collagen deposition and smooth muscle alpha-actin 2 expression. RNA-seq analysis identified 76 differentially expressed genes (DEGs) in UUO hearts. Upregulated DEGs were significantly enriched in cell cycle and cell division pathways, immune responses, cardiac repair, inflammation, proliferation, oxidative stress, and apoptosis. Gene Set Enrichment Analysis further revealed mitochondrial oxidative bioenergetic pathways, autophagy, and peroxisomal pathways are downregulated in UUO hearts. Vimentin was also identified as an UUO-upregulated transcript. ConclusionsOur results emphasize the relevance of extensive transcriptional changes, mitochondrial dysfunction, homeostasis deregulation, fatty-acid metabolism alterations, and vimentin upregulation in CRS type 4 development.

Hypermethylation leads to the loss of HOXA5, resulting in JAG1 expression and NOTCH signaling contributing to kidney fibrosis

Epigenetic regulations, including DNA methylation, are critical to the development and progression of kidney fibrosis, but the underlying mechanisms remain elusive. Here, we show that fibrosis of the mouse kidney was associated with the induction of DNA methyltransferases and increases in global DNA methylation and was alleviated by the DNA methyltransferase inhibitor 5-Aza-2’-deoxycytidine (5-Aza). Genome wide analysis demonstrated the hypermethylation of 94 genes in mouse unilateral ureteral obstruction kidneys, which was markedly reduced by 5-Aza. Among these genes, Hoxa5 was hypermethylated at its gene promoter and this hypermethylation was associated with reduced HOXA5 expression in fibrotic mouse kidneys after ureteral obstruction or unilateral ischemia-reperfusion injury. 5-Aza prevented Hoxa5 hypermethylation, restored HOXA5 expression, and suppressed kidney fibrosis. Down-regulation of HOXA5 was verified in human kidney biopsies from patients with chronic kidney disease and correlated with the increased kidney fibrosis and DNA methylation. Kidney fibrosis was aggravated by conditional knockout of Hoxa5 and alleviated by conditional knockin of Hoxa5 in kidney proximal tubules of mice. Mechanistically, we found that HOXA5 repressed Jag1 transcription by directly binding to its gene promoter, resulting in the suppression of JAG1-NOTCH signaling during kidney fibrosis. Thus, our results indicate that loss of HOXA5 via DNA methylation contributes to fibrogenesis in kidney diseases by inducing JAG1 and consequent activation of the NOTCH signaling pathway.

HIF-1 contributes to autophagy activation via BNIP3 to facilitate renal fibrosis in hypoxia in vitro and UUO in vivo.

The molecular basis of renal interstitial fibrosis, a major pathological feature of progressive kidney diseases, remains poorly understood. Autophagy has been implicated in renal fibrosis, but whether it promotes or inhibits fibrosis remains controversial. Moreover, it is unclear how autophagy is activated and sustained in renal fibrosis. The present study was designed to address these questions using the in vivo mouse model of unilateral ureteral obstruction and the in vitro model of hypoxia in renal tubular cells. Both models showed the activation of hypoxia-inducible factor-1 (HIF-1) and autophagy along with fibrotic changes. Inhibition of autophagy with chloroquine reduced renal fibrosis in unilateral ureteral obstruction model, whereas chloroquine and autophagy-related gene 7 knockdown decreased fibrotic changes in cultured renal proximal tubular cells, supporting a profibrotic role of autophagy. Notably, pharmacological and genetic inhibition of HIF-1 led to the suppression of autophagy and renal fibrosis in these models. Mechanistically, knock down of BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3), a downstream target gene of HIF, decreased autophagy and fibrotic changes during hypoxia in BUMPT cells. Together, these results suggest that HIF-1 may activate autophagy via BNIP3 in renal tubular cells to facilitate the development of renal interstitial fibrosis.NEW & NOTEWORTHY Autophagy has been reported to participate in renal fibrosis, but its role and underlying activation mechanism is unclear. In this study, we report the role of HIF-1 in autophagy activation in models of renal fibrosis and further investigate the underlying mechanism.

Tubular CPT1A deletion minimally affects aging and chronic kidney injury.

Kidney tubules use fatty acid oxidation (FAO) to support their high energetic requirements. Carnitine palmitoyltransferase 1A (CPT1A) is the rate-limiting enzyme for FAO, and it is necessary to transport long-chain fatty acids into mitochondria. To define the role of tubular CPT1A in aging and injury, we generated mice with tubule-specific deletion of Cpt1a (Cpt1aCKO mice), and the mice were either aged for 2 years or injured by aristolochic acid or unilateral ureteral obstruction. Surprisingly, Cpt1aCKO mice had no significant differences in kidney function or fibrosis compared with wild-type mice after aging or chronic injury. Primary tubule cells from aged Cpt1aCKO mice had a modest decrease in palmitate oxidation but retained the ability to metabolize long-chain fatty acids. Very-long-chain fatty acids, exclusively oxidized by peroxisomes, were reduced in kidneys lacking tubular CPT1A, consistent with increased peroxisomal activity. Single-nuclear RNA-Seq showed significantly increased expression of peroxisomal FAO enzymes in proximal tubules of mice lacking tubular CPT1A. These data suggest that peroxisomal FAO may compensate in the absence of CPT1A, and future genetic studies are needed to confirm the role of peroxisomal β-oxidation when mitochondrial FAO is impaired.

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.

Delayed treatment with erythropoietin attenuates renal fibrosis in mouse model of unilateral ureteral obstruction.

Erythropoietin (EPO) exerts tissue-protective effects on various organs including the kidney. However, the effects of EPO on established renal fibrosis remain unclear. In this study, we aimed to examine the therapeutic potential of EPO against established renal fibrosis. Renal fibrosis was induced in mice by unilateral ureteral obstruction (UUO) and the mice were treated with recombinant human EPO (rhEPO) daily during 7 and 13 days after UUO. The degrees of renal fibrosis, myofibroblast accumulation, and macrophage infiltration; the mRNA expression levels of transforming growth factor (TGF)-β1 and α1(I) collagen; and the protein levels of Kelch-like ECH-associated protein 1 (Keap1) and nuclear NF-E2-related factor 2 (Nrf2) in the kidneys were assessed on day 14 after UUO. Treatment with rhEPO significantly decreased fibrosis, myofibroblast accumulation, and α1(I) collagen mRNA expression, but it did not significantly affect TGF-β1 mRNA expression. Although treatment with rhEPO did not significantly affect the total number of interstitial macrophages, it significantly decreased the number of CD86-positive cells (M1 macrophages), while significantly increased the number of CD206-positive cells (M2 macrophages) in the interstitium. Treatment with rhEPO did not affect the Keap1/Nrf2 protein level or the peripheral blood hematocrit value. These results indicate for the first time that EPO exerts antifibrotic effects against the evolution of established renal fibrosis, possibly by influencing the polarization of infiltrating macrophages.