Tubular Epithelial Cell Death Research Articles

Mitochondrial dysfunction in acute kidney injury.

Acute kidney injury (AKI) is a systemic clinical syndrome increasing morbidity and mortality worldwide in recent years. Renal tubular epithelial cells (TECs) death caused by mitochondrial dysfunction is one of the pathogeneses. The imbalance of mitochondrial quality control is the main cause of mitochondrial dysfunction. Mitochondrial quality control plays a crucial role in AKI. Mitochondrial quality control mechanisms are involved in regulating mitochondrial integrity and function, including antioxidant defense, mitochondrial quality control, mitochondrial DNA (mtDNA) repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Currently, many studies have used mitochondrial dysfunction as a targeted therapeutic strategy for AKI. Therefore, this review aims to present the latest research advancements on mitochondrial dysfunction in AKI, providing a valuable reference and theoretical foundation for clinical prevention and treatment of this condition, ultimately enhancing patient prognosis.

DNA damage-induced AIM2 pyroptosis in high glucose-induced proximal tubular epithelial cell

Pyroptosis is one of the ways to cause proximal tubular epithelial cell death in diabetic nephropathy (DN), but the exact mechanism remains unclear. Absent in melanoma 2 (AIM2), a sensor for double-stranded DNA, creates an inflammasome that triggers the cleavage of gasdermin D (GSDMD), leading to a type of inflammatory cell death called pyroptosis. This study investigated the role of AIM2 in pyroptosis within proximal tubular epithelial cells in DN. We observed significantly elevated AIM2 expression in renal tubules from DN patients and db/db mice, as well as in high glucose (HG)-induced Human Kidney-2 (HK2) cells. Besides, increased AIM2 expression was accompanied by activation of the pyroptosis pathway (cleaved-caspase-1, GSDMD-FL, GSDMD-NT) in the renal cortex of db/db mice and HG-induced HK2 cells in vitro. Knocking down GSDMD can reduce HG-induced HK2 cell death, indicating that HG triggers pyroptosis in HK2 cells. Furthermore, HG-induced pyroptosis was mitigated in HK2 cells with AIM2 knockdown using siRNA. Additionally, reducing ROS levels using NAC was able to attenuate HG-induced HK2 cells DNA damage, AIM2 activation, and pyroptosis. Notably, AIM2 upregulation was observed in renal biopsies from DN patients, with expression levels positively correlating with serum creatinine and inversely with estimated glomerular filtration rate (eGFR). Collectively, DNA damage caused by HG could result in the activation of the AIM2 inflammasome, leading to the pyroptosis of proximal tubular epithelial cells, indicating that targeting AIM2 could be a potential novel approach for treating DN.

Mesenchymal Stem Cell-conditioned Medium Protecting Renal Tubular Epithelial Cells by Inhibiting Hypoxia-inducible Factor-1α and Nuclear Receptor Coactivator-1.

Acute kidney injury (AKI) is characterized by inflammatory infiltration and damage and death of renal tubular epithelial cells (RTECs), in which hypoxia plays an important role. Deferoxamine (DFO) is a well-accepted chemical hypoxia-mimetic agent. Mesenchymal stem cell-conditioned medium (MSC-CM) can reduce local inflammation and repair tissue. In this study, we explored the effect and molecular mechanism of MSC-CM-mediated protection of RTECs under DFO-induced hypoxia. Rat renal proximal tubule NRK-52E cells were treated with different concentrations of DFO for 24 hours, followed by evaluation of RTEC injury, using a Cell Counting Kit-8 (CCK-8) to detect cell viability and western blotting to evaluate the expression of transforming growth factor- beta 1 (TGF-β1), α-smooth muscle actin (α-SMA), and hypoxia-inducible factor-1 alpha (HIF-1α) in NRK-52E cells. Then, three groups of NRK-52E cells were used in experiments, including normal control (NC), 25 μM DFO, and 25 μM DFO + MSC-CM. MSC-CM was obtained from the human umbilical cord. MSC-CM was used to culture cells for 12 hours before DFO treatment, then fresh MSC-CM and 25 μM DFO were added, and cells were cultured for another 24 hours before analysis. Western blotting and cellular immunofluorescence staining showed culture of NRK-52E cells in 25 μM DFO for 24 hours induced HIF-1α and nuclear receptor coactivator-1 (NCoA-1), simulating hypoxia. MSC-CM could inhibit the DFO-induced up-regulation of α-SMA, TGF-β1, HIF-1α and NCoA-1. Our results suggest that MSC-CM has a protective effect on RTECs by down-regulating HIF-1α and NCoA-1, which may be the harmful factors in renal injury.

NINJ1-mediated Macrophage Plasma Membrane Rupture and Neutrophil Extracellular Trap Formation Contribute to Oxalate Nephropathy.

Oxalate nephropathy is characterized by calcium oxalate crystals deposition, which triggers necrosis of renal tubular epithelial cells, initiates an inflammatory cascade characterized by neutrophil and macrophage activation within the renal microenvironment. Despite the close association of immune cells with acute oxalate nephropathy, the underlying mechanisms still remain unclear. Nerve injury-induced protein 1 (NINJ1) plays an essential role in the induction of plasma membrane rupture (PMR), leading to damage-associated molecular patterns (DAMPs) release and triggering inflammation. We hypothesize that NINJ1-mediated high mobility group box 1 (HMGB1) release from macrophage PMR and neutrophil extracellular traps (NETs) formation synergistically contribute to the progression of acute oxalate nephropathy. Using a murine model of acute oxalate nephropathy, myeloid cell-specific deletion of Ninj1 mice (Ninj1fl/flvavcre) and their wild-type littermate control mice (Ninj1wt/wtvavcre) were administered intraperitoneal injection of 100 mg/kg sodium oxalate followed by drinking water with 3% sodium oxalate. Evaluation was conducted on tubular injury and inflammatory cell infiltration. In vitro studies involved isolation and culture of renal proximal tubular epithelial cells (RTECs), bone marrow-derived macrophages, and neutrophils to investigate NETs formation and HMGB1 release. Targeted deletion of Ninj1 in myeloid cells significantly mitigated oxalate-induced acute kidney injury by suppressing both HMGB1 release and NETs formation in vivo. In vitro investigations demonstrated that HMGB1 release from macrophage PMR and NETs formation in neutrophils mediated by NINJ1 oligomerization, which consequently coordinated to enhance renal tubular epithelial cell death. Our findings elucidate the pivotal role of NINJ1-dependent macrophage PMR and NETs formation in the progression of acute oxalate nephropathy, providing novel insights for its prevention and therapeutic targets.

The IDH1-R132H mutation aggravates cisplatin-induced acute kidney injury by promoting ferroptosis through disrupting NDUFA1 and FSP1 interaction

AbstractThe IDH1-R132H mutation is implicated in the development of various tumors. Whether cisplatin, a common chemotherapeutic agent, induces more significant renal toxicity in individuals with the IDH1-R132H mutation remains unclear. In this study, we observed that the IDH1-R132H mutation exacerbates mitochondrial lipid peroxidation and dysfunction in renal tubules, rendering the kidneys more susceptible to cisplatin-induced ferroptosis. The IDH1-R132H mutation increases methylation of the Ndufa1 promoter, thereby suppressing NDUFA1 transcription and translation. This suppression disrupts NDUFA1’s interaction with FSP1, reducing its resistance to cisplatin-induced tubular epithelial cell death. As a consequence, ROS accumulates, lipid peroxidation occurs, and ferroptosis is triggered, thereby promoting acute kidney injury. In summary, this study elucidates a novel mechanism underlying cisplatin-induced nephrotoxicity and provides valuable insights for the development of personalized treatment strategies for tumor patients carrying the IDH1-R132H mutation.

Mesoporous zinc-polyphenol nanozyme for attenuating renal ischemia-reperfusion injury.

Aim: To target the reactive oxygen species (ROS) accumulation and renal tubular epithelial cell (rTEC) death in renal ischemia-reperfusion injury (IRI), we constructed a nanoparticle that offers ROS scavenging and rTEC-death inhibition: mesoporous zinc-tannic acid nanozyme (ZnTA).Materials & methods: After successfully constructing ZnTA, we proceeded to examine its effect on ROS accumulation, cellular ferroptosisand apoptosis, as well as injury severity.Results: Malondialdehyde, Fe2+ amounts and 4-HNE staining demonstrated that ZnTA effectively attenuated rTEC ferroptosis. TUNEL staining confirmed that Zn2+ carried by ZnTA could effectively inhibit caspase 3 and caspase 9, mitigating apoptosis. Finally, it reduced renal IRI through the synergistic effect of ROSscavenging and cell-death inhibition.Conclusion: This study is expected to provide a paradigm for a combined therapeutic strategy for renal IRI.

Galectin-8 counteracts folic acid-induced acute kidney injury and prevents its transition to fibrosis

Acute kidney injury (AKI), characterized by a sudden decline in kidney function involving tubular damage and epithelial cell death, can lead to progressive tissue fibrosis and chronic kidney disease due to interstitial fibroblast activation and tissue repair failures that lack direct treatments. After an AKI episode, surviving renal tubular cells undergo cycles of dedifferentiation, proliferation and redifferentiation while fibroblast activity increases and then declines to avoid an exaggerated extracellular matrix deposition. Appropriate tissue recovery versus pathogenic fibrotic progression depends on fine-tuning all these processes. Identifying endogenous factors able to affect any of them may offer new therapeutic opportunities to improve AKI outcomes. Galectin-8 (Gal-8) is an endogenous carbohydrate-binding protein that is secreted through an unconventional mechanism, binds to glycosylated proteins at the cell surface and modifies various cellular activities, including cell proliferation and survival against stress conditions. Here, using a mouse model of AKI induced by folic acid, we show that pre-treatment with Gal-8 protects against cell death, promotes epithelial cell redifferentiation and improves renal function. In addition, Gal-8 decreases fibroblast activation, resulting in less expression of fibrotic genes. Gal-8 added after AKI induction is also effective in maintaining renal function against damage, improving epithelial cell survival. The ability to protect kidneys from injury during both pre- and post-treatments, coupled with its anti-fibrotic effect, highlights Gal-8 as an endogenous factor to be considered in therapeutic strategies aimed at improving renal function and mitigating chronic pathogenic progression.

Rosmarinic acid plus deferasirox inhibits ferroptosis to alleviate crush syndrome-related AKI via Nrf2/Keap1 pathway

BackgroundMyoglobin (Mb) induced death of renal tubular epithelial cells (RTECs) is a major pathological factor in crush syndrome-related acute kidney injury (CS-AKI). It is unclear whether ferroptosis is involved and could be a target for treatment. PurposeThis study aimed to evaluate the potential therapeutic effects of combining the natural small molecule rosemarinic acid (RA) and the iron chelator deferasirox (Dfe) on CS-AKI through inhibition of ferroptosis. MethodsSequencing data were downloaded from the GEO database, and differential expression analysis was performed using the R software limma package. The CS-AKI mouse model was constructed by squeezing the bilateral thighs of mice for 16 h with 1.5 kg weight. TCMK1 and NRK-52E cells were induced with 200 μM Mb and then treated with RA combined with Dfe (Dfe + RA, both were 10 μM). Functional and pathological changes in mouse kidney were evaluated by glomerular filtration rate (GFR) and HE pathology. Immunofluorescence assay was used to detect Mb levels in kidney tissues. The expression levels of ACSL4, GPX4, Keap1, and Nrf2 were analyzed by WB. ResultsWe found that AKI mice in the GSE44925 cohort highly expressed the ferroptosis markers ACSL4 and PTGS2. CS-AKI mice showed a rapid decrease in GFR, up-regulation of ACSL4 expression in kidney tissue, and down-regulation of GPX4 expression, indicating activation of the ferroptosis pathway. Mb was found to deposit in renal tubules, and it has been proven to cause ferroptosis in TCMK1 and NRK-52E cells in vitro. We found that Dfe had a strong iron ion scavenging effect and inhibited ACSL4 expression. RA could disrupt the interaction between Keap1 andNrf2, stabilize Nrf2, and promote its nuclear translocation, thereby exerting antioxidant effects. The combination of Dfe and RA effectively reversed Mb induced ferroptosis in RTECs. ConclusionIn conclusion, we found that RA combined with Dfe attenuated CS-AKI by inhibiting Mb-induced ferroptosis in RTECs via activating the Nrf2/Keap1 pathway.

A novel ESIPT fluorescent probe for early detection and assessment of ferroptosis-mediated acute kidney injury via peroxynitrite fluctuation

BackgroundAcute kidney injury (AKI) poses a severe risk to public health, mostly manifested by damage and death of renal tubular epithelial cells. However, routine blood examination, a conventional approach for clinical detection of AKI, is not available for identifying early-stage AKI. Plenty of reported methods were lack of early biomarkers and real time evaluation tools, which resulted in a vital challenge for early diagnosis of AKI. Therefore, developing novel probes for early detection and assessment of AKI is exceedingly crucial. ResultsBased on ESIPT mechanism, a new fluorescent probe (MEO-NO) with 2-(2′-hydroxyphenyl) benzothiazole (HBT) derivatives as fluorophore has been synthesized for dynamic imaging peroxynitrite (ONOO−) levels in ferroptosis-mediated AKI. Upon the addition of ONOO−, MEO-NO exhibited obvious fluorescence changes, a significant Stokes shift (130 nm) and rapid response (approximately 45 s), and featured exceptional sensitivity (LOD = 7.28 nM) as well as high selectivity from the competitive species at physiological pH. In addition, MEO-NO was conducive to the biological depth imaging ONOO− in cells, zebrafish, and mice. Importantly, MEO-NO could monitor ONOO− levels during sorafenib-induced ferroptosis and CP-induced AKI. With the assistance of MEO-NO, we successfully visualized and tracked ONOO− variations for early detection and assessment of ferroptosis-mediated AKI in cells, zebrafish and mice models. Significance and noveltyBenefiting from the superior performance of MEO-NO, experimental results further demonstrated that the levels of ONOO− was overexpressed during ferroptosis-mediated AKI in cells, zebrafish, and mice models. The developed novel probe MEO-NO provided a strong visualization tool for imagining ONOO−, which might be a potential method for the prevention, diagnosis, and treatment of ferroptosis-mediated AKI.

The Link between Autosomal Dominant Polycystic Kidney Disease and Chromosomal Instability: Exploring the Relationship.

In autosomal dominant polycystic kidney disease (ADPKD) with germline mutations in a PKD1 or PKD2 gene, innumerable cysts develop from tubules, and renal function deteriorates. Second-hit somatic mutations and renal tubular epithelial (RTE) cell death are crucial features of cyst initiation and disease progression. Here, we use established RTE lines and primary ADPKD cells with disease-associated PKD1 mutations to investigate genomic instability and DNA damage responses. We found that ADPKD cells suffer severe chromosome breakage, aneuploidy, heightened susceptibility to DNA damage, and delayed checkpoint activation. Immunohistochemical analyses of human kidneys corroborated observations in cultured cells. DNA damage sensors (ATM/ATR) were activated but did not localize at nuclear sites of damaged DNA and did not properly activate downstream transducers (CHK1/CHK2). ADPKD cells also had the ability to transform, as they achieved high saturation density and formed colonies in soft agar. Our studies indicate that defective DNA damage repair pathways and the somatic mutagenesis they cause contribute fundamentally to the pathogenesis of ADPKD. Acquired mutations may alternatively confer proliferative advantages to the clonally expanded cell populations or lead to apoptosis. Further understanding of the molecular details of aberrant DNA damage responses in ADPKD is ongoing and holds promise for targeted therapies.

Site 1 protease aggravates acute kidney injury by promoting tubular epithelial cell ferroptosis through SIRT3-SOD2-mtROS signaling.

Ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) is a common clinical syndrome with high morbidity and mortality. Ferroptosis, a newly discovered form of oxidative cell death, is involved in the pathogenesis of renal I/R injury; however, the underlying mechanism remains to be explored. Here, we reported that site 1 protease (S1P) promotes ischemic kidney injury by regulating ferroptotic cell death of tubular epithelial cells. S1P abundance was measured in hypoxia/reoxygenation (H/R)-treated Boston University mouse proximal tubular (BUMPT) cells and I/R-induced murine kidney tissue. S1P expression in BUMPT cells and kidneys was initially activated by hypoxic stimulation, accompanied by the ferroptotic response. Blocking S1P blunted H/R-induced ferroptotic cell death, which also restored sirtuin 3 (SIRT3) expression and superoxide dismutase 2 (SOD2) activity in BUMPT cells. Next, inhibition of S1P expression restored I/R-suppressed SIRT3 abundance, SOD2 activity and reduced the elevated level of mitochondria reactive oxygen species (mtROS), which attenuated tubular cell ferroptosis and renal I/R injury. In conclusion, S1P promoted renal tubular epithelial cell ferroptosis under I/R status by activating SIRT3-SOD2-mtROS signaling, thereby accelerating kidney injury. Thus, targeting S1P signaling may serve as a promising strategy for I/R kidney injury.

Astragaloside Ⅳ negatively regulates Gpr97-TPL2 signaling to protect against hyperhomocysteine-exacerbated sepsis associated acute kidney injury

BackgroundHyperhomocysteine (HHcy) plays an important role in promoting inflammation and cell death of tubular epithelial cells. However, the role of HHcy and Astragaloside IV (AS-IV) in sepsis associated acute kidney injury (S-AKI) remain unclear. PurposeA significant aspect of this study aimed to elucidate the effect of AS-Ⅳ treatment on HHcy-exacerbated S-AKI and reveal its potential mechanism. MethodsMale C57BL/6 J mice fed with specific diet containing 2% methionine were established as in vivo models, and AS-Ⅳ was orally administrated continuously for 3 weeks, and then LPS (10 mg·kg−1 bodyweight) was given by a single intraperitoneal injection. The renal morphological changes were evaluated by HE and PAS staining. RNA-sequencing analysis was applied to select key signaling. The NRK-52E cells exposed to Hcy or combined with LPS were used as in vitro models. The mRNA and protein expression levels of Gpr97-TPL2 signaling were examined by qRT-PCR and western blotting assays. ResultsIn vivo, HHcy mice developed more severe renal injury and prevalent tubular inflammation after LPS injection. In vitro, the levels of NGAL, Gpr97 and TPL2 were significantly increased in NRK-52E cells induced by Hcy (1.6 mM) or in combination with LPS. Notably, the effects of Hcy on TPL2 signaling was abolished by transfecting TPL2 siRNA or treating TPL2 inhibitor, without alterations in Gpr97. However, the enhancement of Gpr97-TPL2 signaling induced by Hcy was counteracted by Gpr97 siRNA. Subsequently, our findings demonstrated that AS-Ⅳ treatment can improve renal function in HHcy-exacerbated S-AKI mice. Mechanistically, AS-Ⅳ alleviated renal tubular damage characterized by abnormal increases in KIM-1, NGAL, TPL2, Gpr97, Sema3A and TNF-α, and decreases in survivin in vivo and in vitro mainly through suppressing the activation of Gpr97-TPL2 signaling. ConclusionThe present study suggested that HHcy-exacerbated S-AKI was mediated mechanically by activation of Gpr97-TPL2 signaling for the first time. Furthermore, our research also illustrated that AS-Ⅳ protected against HHcy-exacerbated S-AKI by attenuating renal tubular epithelial cells damage through negatively regulating Gpr97-TPL2 signaling, proposing a natural product treatment strategy for HHcy-exacerbated S-AKI.

Energy metabolic reprogramming regulates programmed cell death of renal tubular epithelial cells and might serve as a new therapeutic target for acute kidney injury.

Acute kidney injury (AKI) induces significant energy metabolic reprogramming in renal tubular epithelial cells (TECs), thereby altering lipid, glucose, and amino acid metabolism. The changes in lipid metabolism encompass not only the downregulation of fatty acid oxidation (FAO) but also changes in cell membrane lipids and triglycerides metabolism. Regarding glucose metabolism, AKI leads to increased glycolysis, activation of the pentose phosphate pathway (PPP), inhibition of gluconeogenesis, and upregulation of the polyol pathway. Research indicates that inhibiting glycolysis, promoting the PPP, and blocking the polyol pathway exhibit a protective effect on AKI-affected kidneys. Additionally, changes in amino acid metabolism, including branched-chain amino acids, glutamine, arginine, and tryptophan, play an important role in AKI progression. These metabolic changes are closely related to the programmed cell death of renal TECs, involving autophagy, apoptosis, necroptosis, pyroptosis, and ferroptosis. Notably, abnormal intracellular lipid accumulation can impede autophagic clearance, further exacerbating lipid accumulation and compromising autophagic function, forming a vicious cycle. Recent studies have demonstrated the potential of ameliorating AKI-induced kidney damage through calorie and dietary restriction. Consequently, modifying the energy metabolism of renal TECs and dietary patterns may be an effective strategy for AKI treatment.

#4976 DIFFERENTIAL ROLES OF REGNASE3 IN RESIDENT MACROPHAGE VERSUS TUBULAR EPITHELIAL CELLS IN THE HEALTHY OR POSTISCHEMIC KIDNEY

Abstract Background and Aims Acute kidney injury (AKI) is a prevalent yet severe condition that occurs in clinical settings. The prognosis for AKI is poor, with many patients progressing to AKD, CKD, and even ESKD especially in those who were admitted to the ICU. RNA-binding proteins (RBPs) are a class of proteins that play a vital role in regulating gene expression and have been implicated in a wide range of diseases. Regnase3 is a member of the Regnase RBPs family and has been shown to promote inflammation by increasing TNF in macrophages. Despite this knowledge, the full extent of the role played by Regnase3 in AKI remains unknown. Therefore, we hypothesized that Regnase3 plays a role in both macrophages and tubular epithelial cells, influencing inflammation and tubular repair in AKI. Method In order to investigate the role of Regnase3 in kidney injury, a series of genetically-modified mice were developed on the C57BL/6J genetic background. These mice included the paired box gene 8 (Pax8)-reverse tetracycline transactivator (rTtA, Pax8rTtA), tetracycline resistance protein (TetO)-Cre (TetOCre), transgenic receptor activator of nuclear factor kappa-Β (Rank)-Cre (RankCre), and Regnase3 floxed (Regnase-3fl/fl) mice. Using these genetically modified mice, we applied a range of experimental animal models to study the effects of Regnase3 on kidney injury, including unilateral kidney ischemia-reperfusion surgery with or without nephrectomy and nephrocalcinosis-related kidney injury. Additionally, we employed in vitro models utilizing primary cells to study Regnase3 on the cellular level. Furthermore, we utilized scRNA-seq and RNA-seq to investigate the underlying mechanisms of Regnase3’s function. Results We conducted a thorough investigation and discovered that the Regnase3 is highly expressed in macrophages located within the kidney after AKI. The scRNA-seq showed the expression Regnase3 positively correlated with the phagocytosis, chemokines, and monocyte maturation. Furthermore, Rank-Regnase3 mice suffered from more inflammation and kidney injury after AKI, characterized by an increase in CCR2 positive leukocyte infiltration. Additionally, in vitro experiments revealed that Regnase3 is involved in modulating macrophage behavior, acting as a regulator of macrophage polarization towards an M1 and M2 phenotype and influencing the capacity of cell migration. These findings indicate that Regnase3 is essential in the migration of macrophages after AKI, which contribute to both early phase inflammation and progression towards AKI- CKD. Next, we aimed to examine the role of Regnase3 in the context of renal tubule injury. We observed that Regnase3 is highly expressed in healthy renal tubules, but its expression is reduced following injury. Through in silico, in vivo and in vitro experiments, we found that Regnase3 controls early apoptosis, cell death, proliferation, and wound healing capability of tubular epithelial cells. These effects contribute to kidney injury in postischemic kidneys. Additionally, we discovered that the deletion of Regnase3 provides protection against ischemic AKI (Figure 1). Mechanistically, Regnase3 targets pre-RNA and modulates alternative splicing by increasing the proportion of targeted skipped exon events and decreasing the probability of targeted retained intron events. Overall, our findings indicate that Regnase3 plays a vital role in tubular epithelial cells in the response to kidney injury by regulating alternative splicing. Conclusion In summary, our findings indicate that Regnase3 contributes to kidney injury in postischemic kidneys. However, the impact of Regnase3 is contingent upon the specific cell lineage in question. The Rank-Regnase3 leads to an exacerbation of kidney injury by increasing macrophage recruitment, whereas the Pax8-Regnase3 leads to an improvement in kidney injury through its effects on cell death and wound healing capability of tubular epithelial cells. Therefore, the role of Regnase3 in kidney injury is dependent on the cell lineage, which ultimately determines the detrimental or beneficial impact on kidney injury.

#3666 THE PROTECTIVE ROLE OF BUTYRATE IN KIDNEY INJURY

Abstract Background and Aims Butyrate is a well-known short-chain fatty acid (SCFAs) produced by the microbial fermentation of indigestible fibers. It contributes to colon homeostasis and controls inflammatory responses and homeostasis in other tissues. It is thought to play an important role in the pathogenesis of kidney disease and contributes to the connections between diet, gut microbiota, and kidney disease. However, a detailed characterization of its function in kidney injury is required. TWEAK is involved in tissue injury, driving inflammation, proliferation, fibrosis and inducing death of renal tubular epithelial cells under certain microenvironmental conditions, such a proinflammatory milieu composed of TNFα and INFγ. It downregulates nephroprotector factors and upregulate the expression of inflammatory markers. Method A dose-response curve evaluated cell viability in murine tubular cells (MCT) at different butyrate concentrations using MTT assay. For this, cells were pre-treated with butyrate 0.5, 1 or 5 mM for one hour. After that, they were treated either with TWEAK (tumor necrosis factor-like weak inducer of apoptosis), a member of the TNF superfamily or TTI (TWEAK 100 ng/mL, TNfα 30 ng/mL and INFΓ 30 UI/mL). Through RT-PCR and Western blotting, mRNA and protein levels of various markers were quantified at 3, 6 and 24 h. Results were validated in a kidney-on-a-chip, a microphysiological system that intends to recapitulate key functional characteristics of the kidney, among them, the dynamic conditions in which cells are cultured, mimicking the fluid flows that occurs in the body and with the benefit of representing an alternative to animal testing. It is composed of a hollow fiber membrane, precoated with L-DOPA (2 mg/mL) and collagen IV (1 mg/mL) seeded with human conditionally immortalized proximal tubule epithelial cells (cipTEC-OAT1). After ten days, cells were exposed to butyrate (1 mM) in the basolateral compartment and TWEAK (100 ng/mL) in the apical compartment for 24 h. Cell toxicity, cell viability and cell permeability were measured at 24 h through LDH release, and PrestoBlue and FITC-Inulin assays, respectively. Cells and supernatant were collected to perform RT-PCR and ELISA for relevant markers. Results When MCT cells were pre-treated with butyrate and then injured either with TWEAK or TTI (TWEAK, TNF-α, IFN-Γ), the expression of klotho, a nephroprotector and anti-aging gene, and peroxisome proliferator-activated receptor Γ coactivator-1α (PGC-1α), a transcription factor that promotes mitochondrial biogenesis, were preserved, as opposed to decreased by cytokines only. Moreover, cells pre-treated with butyrate had decreased expression of inflammatory markers such as MCP1 as compared to increased expression upon cytokine stimulation. In the kidney-on-a-chip, cell viability was reduced after exposure to TWEAK compared to the cells treated only with butyrate, while cells treated with butyrate and TWEAK had lower toxicity as assessed by LDH release. Furthermore, results for Klotho, PGC-1α and the inflammation markers MCP1 and IL6 were aligned with those in MCT cells. Conclusion In summary, in-vitro, butyrate prevents injury caused by TWEAK, preserves protective factors such as the anti-aging factor Klotho and the master regulator of mitochondrial biogenesis PGC-1α and decreases inflammation. Furthermore, these results were validated in a kidney-on-a-chip microphysiological system. Characterization of the mechanism behind the protection of butyrate for kidney injury is ongoing.

Curcumin inhibits lipopolysaccharide-induced proximal renal tubular epithelial cell death by regulating ADAMTS18 methylation and AKT/Notch pathways.

This study aimed to explore the effect of curcumin on the activity of lipopolysaccharide (LPS)-induced proximal renal tubular epithelial cells (PRTECs) and to analyze the molecular mechanism by which curcumin regulates their occurrence. LPS-induced PRTECs were used to construct an inflammatory cell model. RT-qPCR and western blot (WB) were used to detect ADAMTS18 expression. Methylation-specific PCR was used to detect ADAMTS18 methylation levels. After curcumin treatment, MTT assay was used to analyze cell viability, flow cytometry was used to analyze apoptosis, and ADAMTS18 expression and methylation levels were detected again. After transfection with siADAMTS18, cell viability and apoptosis were analyzed again. The levels of inflammatory factors were measured by enzyme-linked immunosorbent assay, and the expression levels of AKT, Notch-1 and Notch-2 were analyzed by WB. Curcumin strongly inhibited LPS-induced PRTEC inflammatory lesions, restored normal cell proliferation, and reduced the apoptosis rate by downregulating ADAMTS18 methylation and restoring ADAMTS18 expression. After siADAMTS18, the ability of curcumin to improve cell viability was reduced, and the ability of curcumin to downregulate inflammatory factors was significantly reduced. Curcumin could also inhibit the expression of AKT, Notch-1 and Notch-2 simultaneously. siADAMTS18 attenuated the abovementioned effects of curcumin. Curcumin inhibits LPS-induced PRTEC death by regulating ADAMTS18 methylation and AKT/Notch pathways.

Human umbilical cord mesenchymal stem cell exosome-derived miR-874-3p targeting RIPK1/PGAM5 attenuates kidney tubular epithelial cell damage

BackgroundKidney insults due to various pathogenic factors, such as trauma, infection, and inflammation, can cause tubular epithelial cell injury and death, leading to acute kidney injury and the transformation of acute kidney injury to chronic kidney disease. There is no definitive treatment available. In previous studies, human umbilical cord mesenchymal stem cells have been shown to promote kidney injury. In this preclinical study, we investigate the role and mechanism of human umbilical cord mesenchymal stem cell exosomes (HucMSC-Exos) on the repair of renal tubular epithelial cells after injury.MethodsC57BL/6 mice underwent unilateral ureteral obstruction, and epithelial cell injury was induced in HK-2 cells by cisplatin. HucMSC-Exos were assessed in vivo and in vitro. The extent of renal cell injury, activation of necroptosis pathway, and mitochondrial quality-control-related factors were determined in different groups. We also analyzed the possible regulatory effector molecules in HucMSC-Exos by transcriptomics.ResultsHucMSC-Exo inhibited necroptosis after renal tubular epithelial cell injury and promoted the dephosphorylation of the S637 site of the Drp1 gene by reducing the expression of PGAM5. This subsequently inhibited mitochondrial fission and maintained mitochondrial functional homeostasis, mitigating renal injury and promoting repair. In addition, HucMSC-Exo displayed a regulatory role by targeting RIPK1 through miR-874-3p.ConclusionThe collective findings of the present study demonstrate that HucMSC-Exos can regulate necroptosis through miR-874-3p to attenuate renal tubular epithelial cell injury and enhance repair, providing new therapeutic modalities and ideas for the treatment of AKI and the process of AKI to CKD transformation to mitigate renal damage.

Role of Cisplatin in Inducing Acute Kidney Injury and Pyroptosis in Mice via the Exosome miR-122/ELAVL1 Regulatory Axis

Although cisplatin is an effective chemotherapy drug for the treatment of various cancers, its clinical use is limited due to its side effects, especially nephrotoxicity. Unfortunately, acute kidney injury (AKI) caused by cisplatin remains one of the main challenges in effective cancer treatment. Evidence increasingly suggests that renal inflammation and pyroptotic inflammatory cell death of renal tubular epithelial cells (RTECs) mainly determine the progression and outcome of cisplatin-induced AKI. However, it is not clear how cisplatin regulates the pyroptosis of RTECs cells in AKI. The current study aimed to determine the regulation mechanism of AKI induced by cisplatin. We used cisplatin to induce AKI in vivo. We performed H&E staining of mouse kidney tissue sections and evaluated serological indicators of kidney injury (including blood urea nitrogen (BUN), serum creatinine, and tumor necrosis factor-alpha (TNF-α)). We used immunohistochemistry and western blot to detect the important substrate protein gasdermin D (GSDMD) and key target caspase-1 of pyroptosis, respectively. Cisplatin induced mouse AKI and RTECs pyroptosis. HK2 cell-derived exosomes treated with cisplatin influenced pyroptosis of the surrounding HK2 cells. Cisplatin-treated HK2 cells exosome-derived miR-122 regulated pyroptosis in the surrounding cells. Exosome-derived miR-122 affected cisplatin-induced AKI and HK2 cells pyroptosis by regulating the expression of embryonic lethal abnormal vision (ELAVL1). These results suggest that exosome miR-122 inhibited pyroptosis and AKI by targeting ELAVL1 under cisplatin treatment, and this offers a potential target for the treatment of AKI.

Cpd-42 protects against calcium oxalate nephrocalcinosis-induced renal injury and inflammation by targeting RIPK3-mediated necroptosis.

Calcium oxalate (CaOx) crystals, as the predominant component of human kidney stones, can trigger excessive cell death and inflammation of renal tubular epithelial cells, involved in the pathogenesis of nephrocalcinosis. Necroptosis mediated by receptor-interacting protein kinase 3 (RIPK3) serves a critical role in the cytotoxicity of CaOx crystals. Here, we assessed the therapeutic potential of a novel RIPK3 inhibitor, compound 42 (Cpd-42), for CaOx nephrocalcinosis by comparison with dabrafenib, a classic RIPK3 inhibitor. Our results demonstrated that Cpd-42 pretreatment attenuated CaOx crystals-induced renal tubular epithelial cell (TEC) injury by inhibiting necroptosis and inflammation in vitro and in vivo. Furthermore, in an established mouse model of CaOx nephrocalcinosis, Cpd-42 also reduced renal injury while improving the impaired kidney function and intrarenal crystal deposition. Consistent with this finding, Cpd-42 was confirmed to exhibit superior inhibition of necroptosis and protection against renal TEC injury compared to the classic RIPK3 inhibitor dabrafenib in vitro and in vivo. Mechanistically, RIPK3 knockout (KO) tubular epithelial cells pretreated with Cpd-42 did not show further enhancement of the protective effect on crystals-induced cell injury and inflammation. We confirmed that Cpd-42 exerted protective effects by specifically targeting and inhibiting RIPK3-mediated necroptosis to block the formation of the RIPK1-RIPK3 necrosome. Taken together, targeted inhibition of RIPK3-mediated necroptosis with Cpd-42 may provide a potential therapeutic approach for CaOx nephrocalcinosis.

RIPK3 inhibitor-AZD5423 alleviates acute kidney injury by inhibiting necroptosis and inflammation

Acute kidney injury (AKI) is a clinical syndrome that is defined as a sudden decline in renal function and characterized by inflammation and programmed cell death of renal tubular epithelial cells. Necroptosis is a form of regulated cell death that requires activation of receptor interacting protein kinase 3 (RIPK3) and its phosphorylation of the substrate MLKL. RIPK3 plays an important role in acute kidney injury, and hence developing its inhibitors is considered as one of the promising strategies aimed at prevention and treatment of AKI. Recently, we discovered AZD5423 as a novel potent RIPK3 inhibitor using a computer-aided hybrid virtual screening strategy according to three-dimensional structure of RIPK3. Our findings revealed that AZD5423 strongly inhibits activation of RIPK3, and MLKL phosphorylation upon cisplatin-, hypoxia/reoxygenation (H/R)- and TNF-α stimuli as compared with GSK872, which is a previously identified RIPK3 inhibitor. Importantly, AZD5423 exerts effective protection against cisplatin- and ischemia/reperfusion (I/R)-induced AKI mouse model. The results of cellular thermal shift assay and experiments in RIPK3 knockout cells indicated that AZD5423 could directly target RIPK3 to inhibit RIPK3 kinase activity. Mechanistically, the docking of AZD5423 and RIPK3 suggested that the kinase domain of RIPK3 for Lys50, Arg313, Lys29, Arg37 might form hydrogen bonds with AZD5423. Site-directed mutagenesis further revealed that AZD5423 reduces injury response via interacting with the key RIPK3 amino acid residues of Lys50 and Arg313. In conclusion, our study has demonstrated that AZD5423 may serve as a potent inhibitor of RIPK3 kinase and a promising clinical candidate for AKI treatment.