Tubular Epithelial Cells Research Articles

In renal proximal tubular epithelial cells of the hibernator Syrian hamster, anoxia-reoxygenation-induced reactive oxygen species bursts do not trigger a DNA damage response and cellular senescence.

Ischemia-reperfusion (I-R) injury represents a predominant etiology of acute kidney injury (AKI), for which effective treatments remain unavailable. In contrast, hibernating mammals exhibit notable resistance to cell death induced by I-R injury. However, the impact of I-R injury on cellular senescence-an important factor in AKI-has not been extensively studied in these species. Comparative biology may offer novel therapeutic insights. Renal proximal tubular epithelial cells (RPTECs) from the native hibernator Syrian hamster or mouse RPTECs were subjected to anoxia-reoxygenation. Proteins involved in DNA damage response (DDR) and cellular senescence were assessed using western blotting, reactive oxygen species (ROS) levels and cell death were quantified colorimetrically, and IL-6 with ELISA. Anoxia-reoxygenation induced oxidative stress in both mouse and hamster RPTECs; however, cell death was observed exclusively in mouse cells. While anoxia-reoxygenation elicited a DDR and subsequent senescence in mouse RPTECs, such responses were not detected in hamster RPTECs. Thus, RPTECs from the Syrian hamster exhibited increased ROS production upon reoxygenation but did not show DDR or cellular senescence. Further research is required to elucidate the specific protective molecular mechanisms in hibernators, which could potentially lead to the development of novel therapeutic approaches for I-R injury in non-hibernating species, including humans.

Enhanced therapeutic effects of hypoxia-preconditioned mesenchymal stromal cell-derived extracellular vesicles in renal ischemic injury

BackgroundExtracellular vesicles (EVs) secreted by mesenchymal stromal cells (MSCs) have been shown to provide significant protection against renal ischemia–reperfusion injury (IRI). Hypoxia has emerged as a promising strategy to enhance the tissue repair capabilities of MSCs. However, the specific effects of hypoxia on MSCs and MSC-EVs, as well as their therapeutic potential in renal IRI, remain unclear. In this study, we investigated the alterations occurring in MSCs and the production of MSC-EVs following hypoxia pre-treatment, and further explored the key intrinsic mechanisms underlying the therapeutic effects of hypoxic MSC-EVs in the treatment of renal IRI.MethodsHuman umbilical cord MSCs were cultured under normoxic and hypoxic conditions. Proliferation and related pathways were measured, and RNA sequencing was used to detect changes in the transcriptional profile. MSC-EVs from both normoxic and hypoxic conditions were isolated and characterized. In vivo, the localization and therapeutic effects of MSC-EVs were assessed in a rat renal IRI model. Histological examinations were conducted to evaluate the structure, proliferation, and apoptosis of IRI kidney tissue respectively. Renal function was assessed by measuring serum creatinine and blood urea nitrogen levels. In vitro, the therapeutic potential of MSC-EVs were measured in renal tubular epithelial cells injured by antimycin A. Protein sequencing analysis of hypoxic MSC-EVs was performed, and the depletion of Glutathione S-Transferase Omega 1 (GSTO1) in hypoxic MSC-EVs was carried out to verify its key role in alleviating renal injury.ResultsHypoxia alters MSCs transcriptional profile, promotes their proliferation, and increases the production of EVs. Hypoxia-pretreated MSC-EVs demonstrated a superior ability to mitigate renal IRI, enhancing proliferation and reducing apoptosis of renal tubular epithelial cells both in vivo and in vitro. Protein profiling of the EVs revealed an accumulation of numerous anti-oxidative stress proteins, with GSTO1 being particularly prominent. Knockdown of GSTO1 significantly reduced the antioxidant and therapeutic effects on renal IRI of hypoxic MSC-EVs.ConclusionsHypoxia significantly promotes the generation of MSC-EVs and enhances their therapeutic effects on renal IRI. The antioxidant stress effect induced by GSTO1 is identified as one of the most critical underlying mechanisms. Our findings highlight that hypoxia-pretreated MSC-EVs represent a novel and promising therapeutic strategy for renal IRI.Graphical

IgG expressed by renal tubular epithelial cells in epithelial mesenchymal transformation and interstitial fibrosis in diabetic kidney disease.

Studies have reported that immunoglobulin G (IgG) "deposited" in the basement membrane of renal tubules is associated with tubulointerstitial damage in patients with diabetic kidney disease (DKD). Our previous study found that renal tubular epithelial cells (RTECs) can express and secrete IgG (RTEC-IgG) which may be associated with fibrosis. The present study aimed to explore the role of RTEC-IgG in renal tubulointerstitial fibrosis (TIF) in DKD. The results showed that RTEC-IgG expression was up-regulated in the renal tubulointerstitium of DKD patients and was associated with worse kidney function, more severe anemia, and higher interstitial fibrosis and tubular atrophy (IFTA) scores, and positively correlated with tubular epithelial mesenchymal transition (EMT) and TIF. IgG expression was also enhanced in the renal tubulointerstitium of DKD mice, which was positively correlated with TIF. High glucose induced an over expression of IgG in human renal tubular epithelial cells, and knockdown of IgG with siRNA relieved the expression of α-smooth muscle actin (SMA), collagen IV, fibronectin, and transforming growth factor (TGF)-β1 under high glucose conditions. In conclusion, our study suggests that RTEC-IgG is involved in the development of DKD by promoting EMT and interstitial fibrosis via TGF-β1.

UHRF1 promotes calcium oxalate-induced renal fibrosis by renal lipid deposition via bridging AMPK dephosphorylation.

Nephrolithiasis, a common urinary system disorder, exhibits high morbidity and recurrence rates, correlating with renal dysfunction and the increased risk of chronic kidney disease. Nonetheless, the precise role of disrupted cellular metabolism in renal injury induced by calcium oxalate (CaOx) crystal deposition is unclear. The purpose of this study is to investigate the involvement of the ubiquitin-like protein containing PHD and RING finger structural domain 1 (UHRF1) in CaOx-induced renal fibrosis and its impacts on cellular lipid metabolism. Various approaches, including snRNA-seq, transcriptome RNA-seq, immunohistochemistry, and western blot analyses, were employed to assess UHRF1 expression in kidneys of nephrolithiasis patients, hyperoxaluric mice, and CaOx-induced renal tubular epithelial cells. Subsequently, knockdown of UHRF1 in mice and cells corroborated its effect of UHRF1 on fibrosis, ectopic lipid deposition (ELD) and fatty acid oxidation (FAO). Rescue experiments using AICAR, ND-630 and Compound-C were performed in UHRF1-knockdown cells to explore the involvement of the AMPK pathway. Then we confirmed the bridging molecule and its regulatory pathway in vitro. Experimental results were finally confirmed using AICAR and chemically modified si-UHRF1 in vivo of hyperoxaluria mice model. Mechanistically, UHRF1 was found to hinder the activation of the AMPK/ACC1 pathway during CaOx-induced renal fibrosis, which was mitigated by employing AICAR, an AMPK agonist. As a nuclear protein, UHRF1 facilitates nuclear translocation of AMPK and act as a molecular link targeting the protein phosphatase PP2A to dephosphorylate AMPK and inhibit its activity. This study revealed that UHRF1 promotes CaOx -induced renal fibrosis by enhancing lipid accumulation and suppressing FAO via inhibiting the AMPK pathway. These findings underscore the feasible therapeutic implications of targeting UHRF1 to prevent renal fibrosis due to stones.

Proteinuria and tubular cells: Plasticity and toxicity.

Proteinuria is the most robust predictive factors for the progression of chronic kidney disease (CKD), and interventions targeting proteinuria reduction have shown to be the most effective nephroprotective treatments to date. While glomerular dysfunction is the primary source of proteinuria, its consequences extend beyond the glomerulus and have a profound impact on tubular epithelial cells. Indeed, proteinuria induces notable phenotypic changes in tubular epithelial cells and plays a crucial role in driving CKD progression. This comprehensive review aims to elucidate the mechanisms involved in the tubular handling of proteins and explore the potential effects of proteinuria on the function of tubular epithelial cells. This paper is a narrative review. Litterature review was performed on PubMed from its inception until 2024, focusing on the effects of proteinuria on tubular cells. The review highlights the toxic effects of plasma proteins on tubular epithelial cells through signal transduction pathways, as well as endoplasmic reticulum stress activation, oxidative stress, and metabolic alterations. Additionally, it provides an updated understanding of the dynamic phenotypic changes occurring within the nephron in response to proteinuria. By examining the intricate interplay between proteinuria and tubular epithelial cells, this review sheds light on key factors contributing to CKD progression and unveils potential targets for therapeutic interventions.

Hypoxia Promotes the Expression of ADAM9 by Tubular Epithelial Cells, Which Enhances Transforming Growth Factor β1 Activation and Promotes Tissue Fibrosis in Patients With Lupus Nephritis.

Enhanced expression of transforming growth factor (TGF) β in the kidneys of patients with lupus nephritis (LN) can lead to progressive fibrosis, resulting in end-organ damage. ADAM9 activates TGFβ1 by cleaving the latency-associated peptide (LAP). We hypothesized that ADAM9 in the kidney may accelerate fibrogenesis by activating TGFβ1. We assessed the expression of ADAM9 in the kidneys of mice and humans who were lupus prone. In vitro experiments were conducted using tubular epithelial cells (TECs) isolated from mice and explored the mechanisms responsible for the up-regulation of ADAM9 and the subsequent activation of TGFβ1. To assess the role of ADAM9 in the development of tubular-intestinal fibrosis in individuals with LN, we generated MRL/lpr mice who were Adam9 deficient. ADAM9 was highly expressed in tubules from MRL/lpr mice. The transcription factor hypoxia-inducible factor-1α was found to promote the transcription of ADAM9 in TECs. TECs from mice who were Adam9 deficient and exposed to the hypoxia mimetic agent dimethyloxalylglycine failed to cleave the LAP to produce bioactive TGFβ1 from latent TGFβ1. Coculture of TECs from mice who were Adam9 deficient with fibroblasts in the presence of dimethyloxalylglycine and latent TGFβ1 produced decreased amounts of type I collagen and α-smooth muscle actin (SMA) by fibroblasts. MRL/lpr mice who were Adam9 deficient showed reduced interstitial fibrosis. At the translational level, ADAM9 expression in tissues and urine of patients with LN was found to increase. Hypoxia promotes the expression of ADAM9 by TECs, which is responsible for the development of interstitial fibrosis in patients with LN by enhancing the TGFβ1 activation, which promotes fibroblasts to produce collagen and α-SMA.

Interferon regulatory factor 5 attenuates kidney fibrosis through transcriptional suppression of Tgfbr1.

Tubulointerstitial fibrosis is a common pathway of the progressive development of chronic kidney diseases (CKD) with different etiologies. The transcription factor interferon regulatory factor 5 (IRF5) can induce anti-type I interferons and proinflammatory cytokine genes and has been implicated as a therapeutic target for various inflammatory and autoimmune diseases. Currently, no experimental evidence has confirmed the role of IRF5 in CKD. Our results showed that IRF5 was aberrantly upregulated in fibrotic kidneys of CKD patients and was colocalized with tubular epithelial cells, peritubular endothelial cells and kidney interstitial fibroblasts. Up-regulation of IRF5 was also seen in unilateral ureteral obstruction (UUO), unilateral ischemia reperfusion and repeated low-dose cisplatin induced mice models, as well as TGF-β1-stimulated tubular epithelial cells and interstitial fibroblasts. Knockdown of Irf5 aggravated the degree of renal fibrosis in UUO mice. Consistently, overexpression of Irf5 attenuated TGF-β1-induced partial epithelial-to-mesenchymal transition and endothelial mesenchymal transition, as well as renal interstitial fibroblast activation and proliferation. Mechanistically, IRF5 can bind to the promoter region of Tgfbr1 and inhibit its transcription, thus inhibiting pro-fibrosis TGF-β1/Smad3 signal transduction. In summary, this research revealed an anti-fibrotic effect of exogenous IRF5 in tubular epithelial cells, endothelial cells and intestinal fibroblasts via transcriptionally repressing Tgfbr1. Activating IRF5 could therefore be a novel therapeutic strategy in the prevention of renal fibrosis.

VDAC1 Cleavage Promotes Autophagy in Renal Tubular Epithelial Cells With Hypoxia/Reoxygenation Injury.

To study the effect and elucidate the underlying mechanisms of VDAC1-ΔC on autophagy in renal tubular epithelial cells injured by hypoxia/reoxygenation. C57/BL6 mice were randomly divided into groups: sham operation group, IRI 1d group and IRI 2d group. The inner canthal blood of mice was collected to detect the levels of serum creatinine and urea nitrogen and kidney tissues were sampled, and sections were stained with Periodic acid-Schiff for morphological evaluation. The expression of VDAC1 in kidney tissue was detected by Western blot. An immortalised human proximal tubular epithelial cell line, HK-2 cells, were subjected to hypoxia/reoxygenation treatment. HK-2 cells were incubated under hypoxia for 6 h, followed by 6 and 24 h of reoxygenation, cells were divided into four groups: H6/R0 group, H6/R6 group, H6/R24 group and control group. The release of LDH and cytosolic ROS were assessed, the expression of autophagy-related proteins LC3 and p62 was detected by Western blot, autophagy flux was monitored by transfecting mRFP-GFP-LC3 lentivirus in HK2 cells, and cells were pretreated with bafilomycin A1 to further monitor the autophagy flux. VDAC1-cleavage-defective mutant in HK-2 cells silencing VDAC1 was established to examine the effect of VDAC1 cleavage on autophagy and hypoxia/reoxygenation injury. In vivo, IRI 1d/2d promoted the disorder of renal tubular structure and the cleavage of VDAC1 in kidney tissue; invitro, hypoxia/reoxygenation promoted cytosolic ROS accumulation, LDH release, VDAC1 cleavage and induced autophagy and autophagic flux; reduced VDAC1 cleavage inhibited autophagy; and decreased cytosolic ROS accumulation and LDH release, thus alleviated cell injury. In renal tubular epithelial cells injured by H/R, VDAC1 cleavage was increased, triggering an autophagic response, and VDAC1 cleavage promoted autophagy to regulate cell injury.

Crucial roles of asprosin in cisplatin-induced ferroptosis and acute kidney injury.

Ferroptosis is a type of non-apoptotic regulated cell death characterized by iron accumulation and lipid peroxidation. Cisplatin is an effective chemotherapy drug with several serious side effects including acute kidney injury (AKI). Asprosin is a peptide contributing to metabolism regulation and metabolic disorders. This study aimed to determine the role and mechanism of asprosin in AKI. Cisplatin was used to induce cell damage in mouse renal tubular epithelial (TCMK-1) cells and AKI in C57BL/6 mice. Cisplatin caused asprosin upregulation in cisplatin-treated TCMK-1cells and mice. In TCMK-1cells, asprosin overexpression led to iron overload and lipid peroxidation, while asprosin knockdown attenuated cisplatin-induced iron overload, lipid peroxidation and ferroptosis. Exogenous asprosin promoted cell damage and ferroptosis, which were attenuated by ferroptosis inhibitors. Asprosin-induced iron overload, lipid peroxidation, cell damage and SMAD1/5/8 phosphorylation were prevented by bone morphogenetic protein (BMP) type I receptor inhibitor. Integrin antagonist prevented asprosin-induced SMAD1/5/8 phosphorylation, and asprosin can specifically bind to integrin β3. Inhibition of integrin β3 reduced the asprosin-induced increases in Fe2+ and MDA levels. Asprosin knockdown relieved cisplatin-induced hepcidin upregulation, while hepcidin knockdown attenuated asprosin-induced iron overload, lipid peroxidation and ferroptosis. In cisplatin-induced AKI mice, specific knockdown of asprosin in the kidney not only attenuated renal dysfunction and damage, but also alleviated iron overload, lipid peroxidation and ferroptosis. These results indicated that excessively increased asprosin promotes TCMK-1cells ferroptosis and damage via integrin β3/BMP/hepcidin-mediated iron overload and lipid peroxidation. Silencing of asprosin attenuates renal injury and dysfunction in cisplatin-induced AKI by inhibiting ferroptosis.

Overexpression Bcl-2 alleviated ferroptosis induced by molybdenum and cadmium co-exposure through inhibiting mitochondrial ROS in duck kidneys.

Excessive molybdenum (Mo) and cadmium (Cd) are environmental pollutants with serious nephrotoxicity. B-cell lymphoma 2 (Bcl-2) plays a critical role in modulating mitochondrial ROS (Mito-ROS). Ferroptosis is a form of cell death dependent on lipid peroxidation. However, the impacts of Mo and Cd co-exposure on ferroptosis in duck kidneys and the function of Bcl-2 in the process are still unclear. Ducks and duck primary renal tubular epithelial cells exposed to different doses of Mo and/or Cd were used as the research target. Our work suggested that Mo and/or Cd significantly decreased Bcl-2 protein level and induced ferroptosis with the increase of ferrous ion, lipid peroxidation, TF protein level and the decrease of GPX4, FT protein levels. The Bcl-2 inhibitor HA14-1 exacerbated the changes of these indexes, but Bcl-2 overexpression had the opposite effect. Mito-ROS inhibitor ROS-IN-1 alleviated ferroptosis induced by Mo and Cd. Besides, Bcl-2 was involved in mitochondrial dysfunction induced by Mo and Cd, accompanied by disturbing Mito-ROS, ATP level, mitochondrial complex IV activity, Bcl-2 and COX-2 co-localization, lipid peroxidation, mitochondrial membrane potential (MMP) and mitochondrial structure. These findings substantiated that overexpression Bcl-2 alleviated ferroptosis co-induced by Mo and Cd through reducing Mito-ROS level in duck kidneys.

Transcriptomic changes and mitochondrial toxicity in response to acute and repeat dose treatment with brequinar in human liver and kidney in vitro models.

The potent dihydroorotate dehydrogenase (DHODH) inhibitor brequinar has been investigated as an anticancer, immunosuppressive, and antiviral pharmaceutical agent. However, its toxicity is still poorly understood. We investigated the cellular responses of primary human hepatocytes (PHH) and telomerase-immortalised human renal proximal tubular epithelial cells (RPTEC/TERT1) after a single 24-h exposure up to 100 μM brequinar. Additionally, RPTEC/TERT1 cells underwent repeated daily exposure for five consecutive days at 0.3, 3, and 20 μM. Transcriptomic analysis revealed that PHH were less sensitive to brequinar treatment than RPTEC/TERT1 cells. Upregulation of various phase I and II drug-metabolising enzymes, particularly Cytochrome P450 (CYP) 1 A and 3 A enzymes, in PHH suggests potential detoxification. Furthermore, brequinar exposure led to a significant upregulation of several stress response pathways in PHH and RPTEC/TERT1 cells, including the unfolded protein response, Nrf2, p53, and inflammatory responses. RPTEC/TERT1 cells exhibited greater sensitivity to brequinar at 0.3 μM with repeated exposure compared to a single exposure. Furthermore, brequinar could impair the mitochondrial respiration of RPTEC/TERT1 cells after 24 h. This study provides new insights into the differential responses of PHH and RPTEC/TERT1 cells in response to brequinar exposure and highlights the biological relevance of implementing repeated dosing regimens in in vitro studies.

Epigenetic regulation of macrophage function in kidney disease: New perspective on the interaction between epigenetics and immune modulation.

The interaction between renal intrinsic cells and macrophages plays a crucial role in the onset and progression of kidney diseases. In recent years, epigenetic mechanisms such as DNA methylation, histone modification, and non-coding RNA regulation have become essential windows for understanding these processes. This review focuses on how renal intrinsic cells (including tubular epithelial cells, podocytes, and endothelial cells), renal cancer cells, and mesenchymal stem cells influence the function and polarization status of macrophages through their own epigenetic alterations, and how the epigenetic regulation of macrophages themselves responds to kidney damage, thus participating in renal inflammation, fibrosis, and repair. Moreover, therapeutic studies targeting these epigenetic interaction mechanisms have found that the application of histone deacetylase inhibitors, histone methyltransferase inhibitors, various nanomaterials, and locked nucleic acids against non-coding RNA have positive effects on the treatment of multiple kidney diseases. This review summarizes the latest research advancements in these epigenetic regulatory mechanisms and therapies, providing a theoretical foundation for further elucidating the pathogenesis of kidney diseases and the development of novel therapeutic strategies.

Characterizing Chemokine Signaling Pathways and Hub Genes in Calcium Oxalate-Induced Kidney Stone Formation: Insights from Rodent Models.

The predominant component of kidney stone is calcium oxalate monohydrate (COM), a fact widely acknowledged. Although rodent models are frequently used to induce calcium oxalate (CaOx) crystallization, further exploration of Randall's plaques (RPs) in these models is still needed. We first selected the GSE89028 and GSE75542 datasets from the Gene Expression Omnibus (GEO) database to identify commonly differentially expressed genes (co-DEGs). Based on co-DEGs, we conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to identify significantly enriched pathways. Additionally, we performed Gene Set Enrichment Analysis (GSEA) to validate the enriched pathways. In order to identify hub genes, we established a network of protein-protein interactions (PPI). Finally, we conducted real-time PCR and Western blot to validate the findings from the bioinformatics analysis. We selected 28 co-DEGs from two datasets. The enrichment analysis using GO, KEGG, and GSEA revealed significant enrichment of chemokine-related signaling pathways. The histogram analysis showed that three chemokine factor-related genes were involved in multiple pathways. We used Cytohubba to confirm the presence of three hub genes. Subsequently, analysis of external datasets and quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot demonstrated significant upregulation of CCL2, CXCL1, and CXCL2 in HK-2 cells following CaOx treatment compared to the control group (p < 0.05).Our study demonstrated that upon stimulation by CaOx, renal tubular epithelial cells release chemokines, including CCL2, CXCL1, and CXCL2. This release of chemokines is accompanied by the activation of signaling pathways such as TNF and IL-17. These findings may provide new directions for future research on Kidney Stone Disease.

When two signals cross paths: cGAS-STING and ER stress in kidney disease progression.

Previous reports have suggested that both the endoplasmic reticulum (ER) stress and cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathways contribute to the progression of chronic kidney disease; however, the relationship between these 2 pathways in kidney injury has not been fully elucidated. Andrade-Silva etal. revealed that the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathway can enhance ER stress through the protein kinase R-like ER kinase (PERK)-mediated signaling cascade in kidney tubular epithelial cells and sequentially augment fibrosis during kidney injury. Further studies are needed to elucidate the precise mechanisms by which the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathway activates PERK-dependent ER stress in kidney tubular epithelial cells post injury.

Involvement of mitochondrial dysfunction and oxidative stress in the nephrotoxicity induced by high-fat diet in Sprague-Dawley rats.

The prevalence of obesity-associated kidney injury has increased, yet the precise extent of the injury and its underlying mechanisms remain unclear. This study used a Sprague-Dawley (SD) rat model to simulate human exposure scenarios, with the objective of investigating the involvement of mitochondria in obesity-induced renal toxicity. Biochemical analysis revealed significant increases in serum creatinine, cystatin C, urinary protein, urinary microalbumin, and urinary α1-microglobulin levels in rats fed a high-fat diet, indicating a notable decline in glomerular filtration function. Histopathological examination showed mild to moderate degeneration in renal tubular epithelial cells, slight glomerular enlargement, fusion and disappearance of pedunculated cell, and decreased electron density of mitochondrial matrix and cristae, indicating the impaired filtration function of kidney. Furthermore, the study found reduced mitochondrial membrane potential and superoxide dismutase (SOD) levels, along with increased malondialdehyde (MDA) levels, signifying elevated mitochondrial oxidative stress in the kidneys of high-fat diet-fed rats. Additionally, a decrease in the number of mitochondrial proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and uncoupling protein-2 (UCP-2)-positive cells, as well as reduced protein expression levels in the mitochondria, suggests a reduced renal mitochondrial resistance to oxidative stress. Collectively, these findings indicate that a high-fat diet triggers abnormalities in both renal filtration and structural functionality in SD rats. The observed reduction in renal mitochondrial density and the elevation in oxidative stress levels could potentially serve as underlying mechanisms.

Impacts of live and artificial feed on histology, biochemical indicators, gene expression, and bacterial resistance in mandarin fish (Siniperca chuatsi).

The mandarin fish (Siniperca chuatsi) is a significant freshwater carnivorous species in Chinese aquaculture industry, and its farming scale is continuously expanding. The use of feed in aquaculture has become an increasingly common practice. However, the impacts of substituting artificial feed for live bait on fish's biochemical and immune responses are poorly understood. In this study, two hundred forty mandarin fish (weight: 5.60 ± 0.41 g) were divided into two groups and fed live bait or artificial feed (LB and AF groups) over a 63-day aquaculture experiment. We compared the differences between the two groups in terms of histology, biochemical indicators, gene expression, and bacterial resistance. The results showed that artificial feed promoted enhanced growth, evidenced by higher weight (p < 0.05). The AF group exhibited higher liver and intestinal somatic indices (p < 0.05), and histological examination revealed denser cytoplasmic content in liver cells, less fragmentation of renal tubular epithelial cells, and less detachment of intestinal epithelial cells in the AF group. Regarding biochemical indicators and gene expression, the AF group showed better performance in glucose regulation and lipid metabolism. The AF group maintained glucose balance (p < 0.05) and effectively regulated cholesterol transport (p < 0.05), promoting lipolysis (p < 0.05) while inhibiting lipogenesis (p < 0.05). In contrast, live bait consumption resulted in reduced lipolysis (p < 0.05), increased lipogenesis (p < 0.05), impaired endoplasmic reticulum function (p < 0.05), heightened inflammation (p < 0.05), and diminished antioxidant capacity (p < 0.05). Additionally, the LB group exhibited lower survival rates and lysozyme levels during bacterial challenges. Overall, artificial feed was more beneficial for the growth, regulate physiology and enhance disease resistance of S. chuatsi, highlighting its potential to improve fish health and increase aquaculture yield.

Senolytic procyanidin C1 alleviates renal fibrosis by promoting apoptosis of senescent renal tubular epithelial cells.

Renal fibrosis is a common pathological process in various chronic kidney diseases. The accumulation of senescent renal tubular epithelial cells (TECs) in renal tissues plays an important role in the development of renal fibrosis. Eliminating senescent TECs has been proven to effectively reduce renal fibrosis. Procyanidin C1 (PCC1) plays a senolytic role by specifically eliminating senescent cells and extending its overall lifespan. However, whether PCC1 can alleviate unilateral ureteral obstruction (UUO)-induced renal fibrosis and the associated therapeutic mechanisms remains unclear. Here, we observed a marked increase in senescent TECs within obstructed human renal tissue and demonstrated the positive correlation between the accumulation of senescent TECs and renal fibrosis in UUO-induced renal fibrosis in mice. We found that PCC1 reduced the number of senescent TECs, restored the regenerative phenotype in kidneys with reduced fibrosis, and improved tubular repair after UUO-induced injury. Invitro, PCC1 effectively cleared senescent HK2 cells by inducing apoptosis via ANGPTL4/NOX4 signaling. Incubation with culture medium from senescent HK2 cells promoted fibroblast activation, whereas PCC1 impeded profibrotic effects by downregulating senescence-associated secretory phenotype (SASP) factors from senescent HK2 cells. Therefore, PCC1 alleviated interstitial renal fibrosis not only by clearing senescent TECs and improving tubular repair but also by indirectly attenuating myofibroblast activation by reducing the level of SASP. In summary, PCC1 may be a novel therapeutic senolytic agent for treating renal fibrosis.

Human proximal tubular epithelial cell interleukin-1 receptor signalling triggers G2/M arrest and cellular senescence during hypoxic kidney injury

Hypoxia and interleukin (IL)-1β are independent mediators of tubulointerstitial fibrosis, the histological hallmark of chronic kidney disease (CKD). Here, we examine how hypoxia and IL-1β act in synergy to augment maladaptive proximal tubular epithelial cell (PTEC) repair in human CKD. Ex vivo patient-derived PTECs were cultured under normoxic (21% O2) or hypoxic (1% O2) conditions in the absence or presence of IL-1β and examined for maladaptive repair signatures. Hypoxic PTECs incubated with IL-1β displayed a discrete transcriptomic profile distinct from PTECs cultured under hypoxia alone, IL-1β alone or under normoxia. Hypoxia+IL-1β-treated PTECs had 692 ‘unique’ differentially expressed genes (DEGs) compared to normoxic PTECs, with ‘cell cycle’ the most significantly enriched KEGG pathway based on ‘unique’ down-regulated DEGs (including CCNA2, CCNB1 and CCNB2). Hypoxia+IL-1β-treated PTECs displayed signatures of cellular senescence, with reduced proliferation, G2/M cell cycle arrest, increased p21 expression, elevated senescence-associated β-galactosidase (SA-β-gal) activity and increased production of pro-inflammatory/fibrotic senescence-associated secretory phenotype (SASP) factors compared to normoxic conditions. Treatment of Hypoxia+IL-1β-treated PTECs with either a type I IL-1 receptor (IL-1RI) neutralizing antibody or a senolytic drug combination, quercetin+dasatinib, attenuated senescent cell burden. In vitro findings were validated in human CKD bio-specimens (kidney tissue, urine), with elevated PTEC IL-1RI expression and senescence (SA-β-gal activity) detected in fibrotic kidneys and numbers of senescent (SA-β-gal+) urinary PTECs correlating with urinary IL-1β levels and severity of interstitial fibrosis. Our data identify a mechanism whereby hypoxia in combination with IL-1β/IL-1RI signalling trigger PTEC senescence, providing novel therapeutic and diagnostic check-points for restoring tubular regeneration in human CKD.

CAV1 Exacerbates Renal Tubular Epithelial Cell Senescence by Suppressing CaMKK2/AMPK-Mediated Autophagy.

Renal proximal tubular epithelial cell (PTEC) senescence and defective autophagy contribute to kidney aging, but the mechanisms remain unclear. Caveolin-1 (CAV1), a crucial component of cell membrane caveolae, regulates autophagy and is associated with cellular senescence. However, its specific role in kidney aging is poorly understood. In this study, we generated Cav1 gene knockout mice and induced kidney aging using D-galactose (D-gal). The results showed that CAV1 expression increased in the renal cortex of the aging mice, which was accompanied by exacerbated renal interstitial fibrosis, elevated levels of senescence-associated proteins γH2AX and p16INK4a, and increased β-galactosidase activity. Moreover, autophagy and AMPK phosphorylation in PTECs were reduced. These phenotypes were partially reversed in D-gal-induced Cav1 knockout mice. Similar results were observed in D-gal-induced human proximal tubular epithelial (HK-2) cells, but these effects were blocked when AMPK activation was inhibited. Additionally, in CaMKK2 knockdown HK-2 cells, siCAV1 failed to promote AMPK phosphorylation, whereas this effect persisted when STK11 was knocked down. Besides, we examined the phosphorylation of CaMKK2 and found that siCAV1 increased its activity. Given that CaMKK2 activity is affected by intracellular Ca2+, we examined Ca2+ levels in HK-2 cells and found that D-gal treatment reduced intracellular Ca2+ concentration, but CAV1 knockdown did not alter these levels. Through GST pull-down assays, we demonstrated a direct interaction between CAV1 and CaMKK2. In conclusion, these findings suggest that CAV1 exacerbates renal tubular epithelial cell senescence by directly interacting with CaMKK2, suppressing its activity and AMPK-mediated autophagy via a Ca2+-independent pathway.

Toxicological effects and mechanisms of renal injury induced by inhalation exposure to airborne nanoplastics.

Micro-nanoplastics (MNPs) are ubiquitously present in various natural habitats, and the kidney plays a critical role in eliminating metabolic waste from the body. Therefore, nephrotoxicity studies of MNPs are necessary. Consequently, we conducted a study utilizing a mouse model that underwent autonomous inhalation of polystyrene nanoplastics (PS-NPs) to investigate the impact of airborne nanoplastics (NPs) on kidney. The results demonstrated that airborne NPs could accumulate within the kidney subsequent to pulmonary entry. Transcriptome analysis showed that exposure to airborne NPs persistently interfered with important signaling pathways including oxidative stress, inflammation, and coagulation, which activated the NR4A1/CASP3 and TF/F12 signaling pathways. In vitro studies have shown that NPs were internalized by human kidney proximal tubular epithelial (HK-2) cells, leading to a range of pathological responses, and ultimately affecting cell fate. Furthermore, we pioneered the exposure of NPs to human kidney organoids. Our findings revealed a heightened sensitivity in kidney organoids towards NPs as compared to immortalized cell lines. This suggested that exposure to NPs could potentially inflict a more substantial toxic effect on the development of embryonic kidneys. In conclusion, this study has revealed the deleterious effects of exposure to airborne NPs on the mouse kidney.