Murine Kidney Research Articles

Beyond hemoglobin: Critical role of 2,3-bisphosphoglycerate mutase in kidney function and injury.

2,3-bisphosphoglycerate mutase (BPGM) is traditionally recognized for its role in modulating oxygen affinity to hemoglobin in erythrocytes. Recent transcriptomic analyses, however, have indicated a significant upregulation of BPGM in acutely injured murine and human kidneys, suggesting a potential renal function for this enzyme. Here we aim to explore the physiological role of BPGM in the kidney. A tubular-specific, doxycycline-inducible Bpgm-knockout mouse model was generated. Histological, immunofluorescence, and proteomic analyses were conducted to examine the localization of BPGM expression and the impact of its knockout on kidney structure and function. Invitro studies were performed to investigate the metabolic consequences of Bpgm knockdown under osmotic stress. BPGM expression was localized to the distal nephron and was absent in proximal tubules. Inducible knockout of Bpgm resulted in rapid kidney injury within 4 days, characterized by proximal tubular damage and tubulointerstitial fibrosis. Proteomic analyses revealed involvement of BPGM in key metabolic pathways, including glycolysis, oxidative stress response, and inflammation. Invitro, Bpgm knockdown led to enhanced glycolysis, decreased reactive oxygen species elimination capacity under osmotic stress, and increased apoptosis. Furthermore, interactions between nephron segments and immune cells in the kidney suggested a mechanism for propagating stress signals from distal to proximal tubules. BPGM fulfills critical functions beyond the erythrocyte in maintaining glucose metabolism in the distal nephron. Its absence leads to metabolic imbalances, increased oxidative stress, inflammation, and ultimately kidney injury.

Heterozygous variants in the teashirt zinc finger homeobox 3 (TSHZ3) gene in human congenital anomalies of the kidney and urinary tract.

Around 180 genes have been associated with congenital anomalies of the kidney and urinary tract (CAKUT) in mice, and represent promising novel candidate genes for human CAKUT. In whole-exome sequencing data of two siblings with genetically unresolved multicystic dysplastic kidneys (MCDK), prioritizing variants in murine CAKUT-associated genes yielded a rare variant in the teashirt zinc finger homeobox 3 (TSHZ3) gene. Therefore, the role of TSHZ3 in human CAKUT was assessed. Twelve CAKUT patients from 9/301 (3%) families carried five different rare heterozygous TSHZ3 missense variants predicted to be deleterious. CAKUT patients with versus without TSHZ3 variants were more likely to present with hydronephrosis, hydroureter, ureteropelvic junction obstruction, MCDK, and with genital anomalies, developmental delay, overlapping with the previously described phenotypes in Tshz3-mutant mice and patients with heterozygous 19q12-q13.11 deletions encompassing the TSHZ3 locus. Comparable with Tshz3-mutant mice, the smooth muscle layer was disorganized in the renal pelvis and thinner in the proximal ureter of the nephrectomy specimen of a TSHZ3 variant carrier compared to controls. TSHZ3 was expressed in the human fetal kidney, and strongly at embryonic day 11.5-14.5 in mesenchymal compartments of the murine ureter, kidney, and bladder. TSHZ3 variants in a 5' region were more frequent in CAKUT patients than in gnomAD samples (p < 0.001). Mutant TSHZ3 harboring N-terminal variants showed significantly altered SOX9 and/or myocardin binding, possibly adversely affecting smooth muscle differentiation. Our results provide evidence that heterozygous TSHZ3 variants are associated with human CAKUT, particularly MCDK, hydronephrosis, and hydroureter, and, inconsistently, with specific extrarenal features, including genital anomalies.

Dichloroacetate reduces cisplatin-induced apoptosis by inhibiting the JNK/14-3-3/Bax/caspase-9 pathway and suppressing caspase-8 activation via cFLIP in murine tubular cells

Cisplatin-induced injury to renal proximal tubular cells stems from mitochondrial damage-induced apoptosis and inflammation. Dichloroacetate (DCA), a pyruvate dehydrogenase kinase (PDK) inhibitor, a potential generator of ROS and ATP, protects against cisplatin-induced nephrotoxicity by promoting the TCA cycle. However, its effects on apoptotic pathways and ROS production in renal tubular cells remain unclear. Here, we investigated the detailed molecular mechanisms of the DCA’s effects by immunoblot, RT-PCR, RNA-sequencing, and RNA-silencing in a murine renal proximal tubular (mProx) cell line and mouse kidneys. In mProx cells, DCA suppressed cisplatin-induced apoptosis by attenuating the JNK/14-3-3/Bax/caspase-9 and death receptor/ligand/caspase-8 pathways without impeding inflammatory signaling. RNA-sequencing demonstrated that DCA increased the cisplatin-reduced expression of cFLIP, a caspase-8 inactivator, and decreased the expression of almost all oxidative phosphorylation (OXPHOS) genes. DCA also increased NF-kB activation and ROS production, probably enhancing the cFLIP induction and OXPHOS gene reduction, respectively. Furthermore, cFLIP silencing weakened the DCA’s anti-apoptotic effects. Finally, in mouse kidneys, DCA attenuated cisplatin-caused injuries such as functional and histological damages, caspase activation, JNK/14-3-3 activation, and cFLIP reduction. Conclusively, DCA mitigates cisplatin-induced nephrotoxicity by attenuating the JNK/14-3-3/Bax/caspase-9 pathway and inhibiting the caspase-8 pathways via cFLIP induction, probably outweighing the cisplatin plus DCA-derived cytotoxic effects including ROS.

Overcoming amphotericin B resistance in Candida auris using the antiemetic drug rolapitant.

The emergence of Candida auris poses a significant health challenge that has led to a new era of multidrug-resistant fungal infections. Invasive infections caused by C. auris are usually associated with remarkable morbidity and mortality. For many years, amphotericin B (AmB) remained the most efficient and the last line of treatment against most hard-to-treat fungal infections. However, strains of C. auris possess extraordinary resistance to most antifungal agents, including AmB. In this study, we screened ~2,600 FDA-approved drugs and clinical compounds to identify the antiemetic drug rolapitant as a promising enhancer to AmB against C. auris. Rolapitant exhibited potent synergistic interactions with AmB against all tested (29/29) C. auris isolates. In a time-kill assay, rolapitant restored the fungicidal activity of AmB within 4 h. Additionally, the synergistic relationship between rolapitant and AmB was observed against other medically crucial Candida, Cryptococcus, and Aspergillus species. A transcriptomic study revealed that exposure to rolapitant affects oxidation reduction processes, ion transporters, and ATP production. Rolapitant triggers an elevation in cytosolic and mitochondrial calcium levels and induces oxidative stress within fungal cells. An ATP luminescence assay confirmed that rolapitant, at sub-inhibitory concentrations, significantly interfered with ATP production in C. auris. Moreover, rolapitant enhanced the in vivo activity of AmB in a mouse model of disseminated C. auris infection, as the combination reduced the fungal burden in murine kidneys by ~1 log (~90%) colony forming units. Our findings warrant further investigation of using rolapitant to overcome AmB resistance in C. auris and other fungal species.

Understanding the role of ten-eleven translocation family proteins in kidney diseases.

Epigenetic mechanisms play a critical role in the pathogenesis of human diseases including kidney disorders. As the erasers of DNA methylation, Ten-eleven translocation (TET) family proteins can oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), thus leading to passive or active DNA demethylation. Similarly, TET family proteins can also catalyze the same reaction on RNA. In addition, TET family proteins can also regulate chromatin structure and gene expression in a catalytic activity-independent manner through recruiting the SIN3A/HDAC co-repressor complex. In 2012, we reported for the first time that the genomic 5-hydroxymethylcytosine level and the mRNA levels of Tet1 and Tet2 were significantly downregulated in murine kidneys upon ischemia and reperfusion injury. Since then, accumulating evidences have eventually established an indispensable role of TET family proteins in not only acute kidney injury but also chronic kidney disease. In this review, we summarize the upstream regulatory mechanisms and the pathophysiological role of TET family proteins in major types of kidney diseases and discuss their potential values in clinical diagnosis and treatment.

9210 Nephron specific ATP6AP2 knockout reduces renal fat accumulation in mice consuming high fat diet

Abstract Disclosure: S.A. Culver: None. J. Balugo: None. M. Jansen: None. T. Harris: None. H.M. Siragy: None. Diet induced obesity causes increased renal fat accumulation in both humans and mice which contributes to obesity related kidney injury. We have previously shown that mice with nephron specific ATP6AP2 knockout (KO) consuming high fat diet (HFD) are resistant to weight gain due to increased urinary excretion of glucose, albumin, and fatty acids. Magnetic resonance imaging (MRI) is a useful imaging modality for quantifying organ fat content in live animals though there are few reports of its use quantifying fat in murine kidney. We hypothesized that nephron specific ATP6AP2 knockout inhibits renal fat accumulation with HFD and that we would be able to detect this using MRI. Eight-week-old male wild type (WT) or inducible nephron specific ATP6AP2 KO mice underwent either induction with oral doxycycline or received sucrose water as controls before being placed on either normal diet (ND) (12% fat) or HFD (45% fat) for 3 months. Mice were then imaged using a 9.4 Tesla Bruker BioSpin MRI to determine both liver and kidney cortex fat content. The mean weight of WT HFD mice was 36.03 g compared to 29.03 g in WT ND controls. ND fed and HFD fed KO mice weighed 22.74 g and 23.03 g respectively. MRI showed significant 67% (p&amp;lt;0.05) increase in liver fat content in WT HFD compared to WT ND fed controls, confirming the ability of our MRI technique to detect expected differences in organ fat content. In renal cortex, MRI detected a 54% (p&amp;lt;0.05) increase in lipid content for WT HFD mice compared to WT ND controls. Nephron specific ATP6AP2 KO on HFD demonstrated reduced renal cortical lipid content by 36% (p&amp;lt;0.05) compared to WT HFD controls. These results indicate that ATP6AP2 KO is associated with reduced renal fat accumulation that is measurable with in vivo MRI. MRI therefore represents a valuable tool for studying renal sequelae of obesity in live murine models. Future investigation should examine whether ATP6AP2 KO prevents renal lipotoxicity and kidney injury in the setting of obesity. Presentation: 6/3/2024

Localization of albumin with correlative super resolution light- and electron microscopy in the kidney

The functioning of vertebrate life relies on renal filtration of surplus fluid and elimination of low-molecular-weight waste products, while keeping serum proteins in the blood. In disease, however, there is leak of serum proteins and tracing them to identify the leaking position within tissue with a nanometer resolution poses a significant challenge. Correlative microscopy integrates the specificity of fluorescent protein labeling into high-resolution electron micrographs. Using chemical tagging of albumin with synthetic fluorophores we achieve protein-specific labeling that preserve their post-embedding fluorescence after high-pressure freezing and freeze-substitution of murine kidney tissue. Using advanced registration techniques for super-resolution correlative light and electron microscopy, we can localize the labeled albumin with a high precision in the x-y plane of electron micrographs and cartograph its distribution. Thereby we can quantify the albumin concentration and measure a linear reduction gradient across the kidney filtration barrier. Our study shows the feasibility of combining different microscopy contrasts for tracing fluorescently labeled protein markers with super resolution in various tissue samples and opens new perspectives for correlative imaging in volume electron microscopy.

SETD2 regulates SLC family transporter-mediated sodium and glucose reabsorptions in renal tubule

A regulatory mechanism for SLC family transporters, critical transporters for sodium and glucose reabsorptions in renal tubule, is incompletely understood. Here, we report an important regulation of SLC family transporter by SETD2, a chromatin remodeling gene whose alterations have been found in a subset of kidney cancers. Kidney-specific inactivation of Setd2 resulted in hypovolemia with excessive urine excretion in mouse and interestingly, RNA-sequencing analysis of Setd2-deficient murine kidney exhibited decreased expressions of SLC family transporters, critical transporters for sodium and glucose reabsorptions in renal tubule. Importantly, inactivation of Setd2 in murine kidney displayed attenuated dapagliflozin-induced diuresis and glucose excretion, further supporting that SETD2 might regulate SLCfamily transporter-mediated sodium and glucose reabsorptions in renal tubule. These data uncover an important regulation of SLC family transporter by SETD2, which may illuminate a crosstalk between metabolism and epigenome in renal tubule.

Identification of Differentially Expressed Genes in Cold Storage-associated Kidney Transplantation.

Although it is acknowledged that ischemia-reperfusion injury is the primary pathology of cold storage-associated kidney transplantation, its underlying mechanism is not well elucidated. To extend the understanding of molecular events and mine hub genes posttransplantation, we performed bulk RNA sequencing at different time points (24 h, day 7, and day 14) on a murine kidney transplantation model with prolonged cold storage (10 h). In the present study, we showed that genes related to the regulation of apoptotic process, DNA damage response, cell cycle/proliferation, and inflammatory response were steadily elevated at 24 h and day 7. The upregulated gene profiling delicately transformed to extracellular matrix organization and fibrosis at day 14. It is prominent that metabolism-associated genes persistently took the first place among downregulated genes. The gene ontology terms of particular note to enrich are fatty acid oxidation and mitochondria energy metabolism. Correspondingly, the key enzymes of the above processes were the products of hub genes as recognized. Moreover, we highlighted the proximal tubular cell-specific increased genes at 24 h by combining the data with public RNA-Seq performed on proximal tubules. We also focused on ferroptosis-related genes and fatty acid oxidation genes to show profound gene dysregulation in kidney transplantation. The comprehensive characterization of transcriptomic analysis may help provide diagnostic biomarkers and therapeutic targets in kidney transplantation.

Insoluble HIFa protein aggregates by cadmium disrupt hypoxia-prolyl hydroxylase (PHD)-hypoxia inducible factor (HIFa) signaling in renal epithelial (NRK-52E) and interstitial (FAIK3-5) cells.

The kidney is the main organ that senses changes in systemic O2 pressure by hypoxia-PHD-HIFa (HPH) signaling, resulting in adaptive target gene activation, including erythropoietin (EPO). The non-essential transition metal cadmium (Cd) is nephrotoxic and disrupts the renal HPH pathway, which may promote Cd-associated chronic renal disease (CKD). A deeper molecular understanding of Cd interference with renal HPH signaling is missing, and no data with renal cell lines are available. In rat kidney NRK-52E cells, which model the proximal tubule, and murine fibroblastoid atypical interstitial kidney (FAIK3-5) cells, which mimic renal EPO-producing cells, the chemical hypoxia mimetic dimethyloxalylglycine (DMOG; 1 mmol/l) or hypoxia (1% O2) activated HPH signaling. Cd2+ (2.5-20 µmol/l for ≤ 24h) preferentially induced necrosis (trypan blue uptake) of FAIK3-5 cells at high Cd whereas NRK-52E cells specially developed apoptosis (PARP-1 cleavage) at all Cd concentrations. Cd (12.5 µmol/l) abolished HIFa stabilization and prevented upregulation of target genes (quantitative real-time polymerase chain reaction and immunoblotting) induced by DMOG or hypoxia in both cell lines, which was caused by the formation of insoluble HIFa aggregates. Strikingly, hypoxic preconditioning (1% O2 for 18h) reduced apoptosis of FAIK3-5 and NRK-52E cells at low Cd concentrations and decreased insoluble HIFa proteins. Hence, drugs mimicking hypoxic preconditioning could reduce CKD induced by chronic low Cd exposure.

Inflammation primes the murine kidney for recovery by activating AZIN1 adenosine-to-inosine editing.

The progression of kidney disease varies among individuals, but a general methodology to quantify disease timelines is lacking. Particularly challenging is the task of determining the potential for recovery from acute kidney injury following various insults. Here, we report that quantitation of post-transcriptional adenosine-to-inosine (A-to-I) RNA editing offers a distinct genome-wide signature, enabling the delineation of disease trajectories in the kidney. A well-defined murine model of endotoxemia permitted the identification of the origin and extent of A-to-I editing, along with temporally discrete signatures of double-stranded RNA stress and adenosine deaminase isoform switching. We found that A-to-I editing of antizyme inhibitor 1 (AZIN1), a positive regulator of polyamine biosynthesis, serves as a particularly useful temporal landmark during endotoxemia. Our data indicate that AZIN1 A-to-I editing, triggered by preceding inflammation, primes the kidney and activates endogenous recovery mechanisms. By comparing genetically modified human cell lines and mice locked in either A-to-I-edited or uneditable states, we uncovered that AZIN1 A-to-I editing not only enhances polyamine biosynthesis but also engages glycolysis and nicotinamide biosynthesis to drive the recovery phenotype. Our findings implicate that quantifying AZIN1 A-to-I editing could potentially identify individuals who have transitioned to an endogenous recovery phase. This phase would reflect their past inflammation and indicate their potential for future recovery.

ST2 + T-Regulatory Cells in Renal Inflammation and Fibrosis after Ischemic Kidney Injury.

Inflammation is a major cause of kidney injury. The Interleukin (IL)-1 family cytokine IL-33 is released from damaged cells and modulates the immune response through its receptor ST2 expressed on many cell types, including regulatory T-cells (Tregs). While a proinflammatory role of IL-33 has been proposed, exogenous IL-33 expanded Tregs and suppressed renal inflammation. However, the contribution of endogenous IL-33/ST2 for the role of Tregs in the resolution of kidney injury has not been investigated. We used murine renal ischemia-reperfusion injury and kidney organoids to delineate the role of the ST2 and amphiregulin (AREG) specifically in Treg cells using targeted deletion. Bulk and single-cell RNA sequencing was performed on flow-sorted Tregs from spleen and CD4 T-cells from post-ischemic kidneys respectively. The protective role of ST2-sufficient Tregs was analyzed using a novel co-culture system of syngeneic kidney organoids and Treg cells under hypoxic conditions. Bulk RNA-sequencing of splenic and single-cell-RNA-sequencing of kidney T-cells showed that ST2+ Tregs are enriched for genes related to Treg proliferation and function. Genes for reparative factors such as AREG were also enriched in ST2+ Tregs. Treg-specific deletion of ST2 or AREG exacerbated kidney injury and fibrosis in the unilateral ischemia reperfusion injury model. In co-culture studies, WT but not ST2-deficient Tregs preserved the hypoxia-induced loss of kidney-organoid viability, which was restored by AREG supplementation. Our study identified the role of the IL-33/ST2 pathway in Tregs for resolution of kidney injury. The transcriptome of ST2+ Tregs was enriched for reparative factors including AREG. Lack of ST2 or AREG in Tregs worsened kidney injury. Tregs protected kidney organoids from hypoxia in ST2 and AREG-dependent manner. Thus Treg-based approaches could be of benefit for resolution of renal injury.

SET8 inhibition preserves PTEN to attenuate kidney cell apoptosis in cisplatin nephrotoxicity.

The aberrant expression of SET8, a histone methyltransferase that mediates H4 lysine 20 mono-methylation (H4K20me1), is implicated in the pathogenesis of various tumors, however, its role in acute kidney injury (AKI) is unknown. Here we showed that SET8 and H4K20me1 were upregulated in the murine kidney with AKI induced by cisplatin, along with increased renal tubular cell injury and apoptosis and decreased expression of E-cadherin and Phosphatase and Tensin Homolog (PTEN). Suppression of SET8 by UNC0379 improved renal function, attenuated tubule damage, and restored expression of PTEN, but not E-cadherin. UNC0379 was also effective in lessening cisplatin-induced DNA damage response (DDR) as indicated by reduced expression of γ-H2AX, p53, p21, and alleviating cisplatin-impaired autophagy as shown by retained expression of Atg5, Beclin-1, and CHMP2A and enhanced levels of LC3-II in the kidney. Consistently, inhibition of SET8 with either UNC0379 or siRNA mitigated apoptosis and DDR, and restored autophagy, along with PTEN preservation in cultured renal proximal tubular epithelial cell (TKPTs) exposed to cisplatin. Further studies showed that inhibition of PTEN with Bpv or siRNA potentiated cisplatin-induced apoptosis, DDR, and hindered autophagy, and conversely, alleviated by overexpression of PTEN in TKPTs. Finally, blocking PTEN largely abolished the inhibitory effect of UNC0379 on apoptosis. Taken together, these results suggest that SET8 inhibition protects against cisplatin-induced AKI and renal cell apoptosis through a mechanism associated with the preservation of PTEN, which in turn inhibits DDR and restores autophagy.

Murine kidney transplant outcome is best measured by transdermal glomerular filtration rate

Mouse kidney transplantation provides a powerful preclinical model for the study of kidney transplant alloimmunity. However, accurate measurement of graft function is difficult because of the inaccuracy of traditional surrogate markers serum creatinine and urea. We report the use of transdermal glomerular filtration rate measurement under the experimental conditions of unilateral nephrectomy and allogeneic kidney transplantation. Our findings demonstrate that transdermal glomerular filtration rate measurement is easy to perform, reproducible, and has more interexperimental consistency than serum creatinine or urea measurements. Most importantly, it significantly reduces the numbers of experimental animals required to detect subtle and yet clinically relevant differences in kidney function as often is the case in experimental murine kidney transplantation models.

Structural and molecular alterations in murine tissue due to far-field radiofrequency exposure

Public concern over exposure to radiofrequency electromagnetic fields has prompted several studies to determine possible health outcomes. However, studies on low level far-field radiofrequency (RF) exposure remain inconclusive on whether it can alter biological systems. Our study's aim was to evaluate structural and molecular modifications such as apoptosis and gene expression in murine brain, liver and kidney tissues exposed to a far-field RF of 915 MHz at a whole-body specific absorption rate of 1.17 W/kg. Forty (40) Swiss male mice were equally and randomly divided into 2 groups: a control group and an RF-exposed group. Each were further equally subdivided (n=5 per subgroup) based on different time points: baseline or no exposure, 3-day exposure, 6-day-exposure and 9-day exposure subgroups. Biometric parameters such as body temperature, body weight, and organ weight were obtained. Tissue samples were collected and analyzed using light and electron microscopy, followed by qPCR assay for both the p53 and Hsp-70 genes. Statistical analysis was performed using ANOVA. There was evidence of both structural and molecular modification beginning Day 3 from continuous-wave far-field RF exposure. The study established multi-level alterations in the murine system due to far field RF exposure providing a glimpse of possible biological effects, and therefore, a need for further studies to translate such evidence in a larger biological perspective.

Insulin receptor orchestrates kidney antibacterial defenses

Urinary tract infection (UTI) commonly afflicts people with diabetes. This augmented infection risk is partly due to deregulated insulin receptor (IR) signaling in the kidney collecting duct. The collecting duct is composed of intercalated cells (ICs) and principal cells (PCs). Evidence suggests that ICs contribute to UTI defenses. Here, we interrogate how IR deletion in ICs impacts antibacterial defenses against uropathogenic Escherichia coli. We also explore how IR deletion affects immune responses in neighboring PCs with intact IR expression. To accomplish this objective, we profile the transcriptomes of IC and PC populations enriched from kidneys of wild-type and IC-specific IR knock-out mice that have increased UTI susceptibility. Transcriptomic analysis demonstrates that IR deletion suppresses IC-integrated stress responses and innate immune defenses. To define how IR shapes these immune defenses, we employ murine and human kidney cultures. When challenged with bacteria, murine ICs and human kidney cells with deregulated IR signaling cannot engage central components of the integrated stress response-including activating transcriptional factor 4 (ATF4). Silencing ATF4 impairs NFkB activation and promotes infection. In turn, NFkB silencing augments infection and suppresses antimicrobial peptide expression. In diabetic mice and people with diabetes, collecting duct cells show reduced IR expression, impaired integrated stress response engagement, and compromised immunity. Collectively, these translational data illustrate how IR orchestrates collecting duct antibacterial responses and the communication between ICs and PCs.

Foodborne toxin aflatoxin B1 induced glomerular podocyte inflammation through proteolysis of RelA, downregulation of miR-9 and CXCR4/TXNIP/NLRP3 pathway

Aflatoxin B1 (AFB1) is a naturally-occurring mycotoxin and recognized as the most toxic foodborne toxin, particularly causing damages to kidney. Glomerular podocytes are terminally differentiated epithelial cells. AFB1 induces podocyte inflammation, proteinuria and renal dysfunction. Studying the mechanism of AFB1-induced podocyte inflammation and murine kidney dysfunction, we detected that AFB1 increased ubiquitin-dependent degradation of the transcription factor RelA through enhanced interaction of RelA with E3 ubiquitin ligase tripartite motif containing 7 (TRIM7) in mouse podocyte clone-5 (MPC-5) and mouse glomeruli. Reduction of RelA resulted in decreasing microRNA-9 (miR-9) and activating the chemokine receptor 4 (CXCR4), thioredoxin interacting protein (TXNIP), and NOD-like receptor pyrin domain-containing 3 (NLRP3) signaling axis (CXCR4/TXNIP/NLRP3 pathway), leading to podocyte inflammation. We also determined that downregulation of miR-9 led to CXCR4 expression and the downstream TXNIP/NLRP3 pathway activation. Overexpression of miR-9 or deletion of CXCR4 suppressed AFB1-induced CXCR4/TXNIP/NLRP3 pathway, resulting in alleviating podocyte inflammation and kidney dysfunction. Our findings indicated that ubiquitin-dependent proteolysis of RelA, downregulation of miR-9, and activation of CXCR4/TXNIP/NLRP3 pathway played an essential role in AFB1-induced glomerular podocyte inflammation. Our study revealed a novel mechanism, via RelA, for the control of AFB1’s nephrotoxicity, leading to an effective protection of food safety and public health.

Sex-Related Differences in Oxidant and Antioxidant Profiles of Murine Kidney and Brain: A Focus on Sirt3-Mediated Regulation

Background: Sirt3 is a mitochondrial deacetylase with an important role in maintainance of cellular redox and metabolic homeostasis and mitochondrial function. As growing evidence support the existence of sex-specific responses to metabolic and oxidative stress, we aimed to investigate sex- and organ-specific effects of Sirt3 loss. Materials and methods: Expression of Sirt3, PGC-1a, CuZnSOD, MnSOD and Cat proteins in kidneys and brains of Sirt3-wild type (Sirt3 WT) and Sirt3-knockout (Sirt3 KO) mice was assessed by Western blotting. Protein carbonylation and lipid peroxidation levels were measured using ELISA and fluorometric assays, respectively. SOD and Cat activities were determined using standard enzymatic assays. Results: Significant sex- and organ- specific differences in response to Sirt3 loss were detected. Sirt3 knockout affected kidneys more than brain tissue, with females showing lower levels PC and LPO. In kidneys, female KO showed higher MnSOD, but lower CuZnSOD and Cat activity compared to males. In brains, WT females show higher activities of these enzymes than males, suggesting a sex-specific protection mechanism, but female KO brains show a larger decrease in these parameters. Conclusion: Our study provides comprehensive insights into the complex interplay of Sirt3, oxidative stress, and antioxidant defenses in murine kidney and brain. The observed differences between the two organs and the impact of sex highlight the need for studying Sirt3 function in diverse physiological contexts. The tissue-specific responses and sex-related variations underscore the importance of considering these factors in the development of therapeutic strategies targeting mitochondrial function and redox homeostasis.

Dysfunction of infiltrating cytotoxic CD8+ T cells within the graft promotes murine kidney allotransplant tolerance.

Tolerance of mouse kidney allografts arises in grafts that develop regulatory tertiary lymphoid organs (rTLOs). Single-cell RNA-seq (scRNA-seq) data and adoptive transfer of alloreactive T cells after transplantation showed that cytotoxic CD8+ T cells are reprogrammed within the accepted graft to an exhausted/regulatory-like phenotype mediated by IFN-γ. Establishment of rTLOs was required because adoptive transfer of alloreactive T cells prior to transplantation results in kidney allograft rejection. Despite the presence of intragraft CD8+ cells with a regulatory phenotype, they were not essential for the induction and maintenance of kidney allograft tolerance since renal allotransplantation into CD8-KO recipients resulted in acceptance and not rejection. Analysis of scRNA-seq data from allograft kidneys and malignant tumors identified similar regulatory-like cell types within the T cell clusters and trajectory analysis showed that cytotoxic CD8+ T cells are reprogrammed into an exhausted/regulatory-like phenotype intratumorally. Induction of cytotoxic CD8+ T cell dysfunction of infiltrating cells appears to be a beneficial mechanistic pathway that protects the kidney allotransplant from rejection through a process we call "defensive tolerance." This pathway has implications for our understanding of allotransplant tolerance and tumor resistance to host immunity.

#1738 Renal endogenous hepcidin alleviates ferroptosis of collecting duct in ischemia/reperfusion induced AKI

Abstract Background and Aims Recent studies have demonstrated that urinary and serum hepcidin predicted the incidence of acute kidney injury (AKI) among critically ill patients. As an endogenous acute phase hormone, hepcidin is synthesized not only by the liver but also secreted by distal nephron. However, the autocrine impact of hepcidin secreted by distal nephron on collecting duct cells in AKI remains poorly understood. Method We determined the expression and location of hepcidin in murine kidney in different severity of bilateral ischemia/reperfusion (bIRI) induced AKI model with ischemic duration for 20 min and 32 min. The effect of renal endogenous hepcidin was explored in cultured M-1 (Murine Cortical collecting duct) exposed to hypoxia/reoxygenation (H/R), as well as in bIRI mice with collecting duct-specific overexpression of hepcidin. Transgenic mice were generated by genetic cross between Hepcidin floxed mice which knocked the gene fragment of CAG-LSL-mHamp-flag-WPRE-PolyA into H11 locus and Cdh16-cre mice. Mechanistically, RNA-seq was performed in M-1 cells under H/R condition. Results The expression of renal endogenous hepcidin was significantly elevated in bIRI32min mice compared to both bIRI20min and sham group, suggesting that augmented secretion of hepcidin was induced by more severe AKI. Interestingly, renal endogenous hepcidin was mainly localized to distal convoluted tubule and collecting tubule as indicated by its co-staining with AQP2 and Calbindin-D28k in the kidney. To investigate the role of hepcidin in collecting duct, M-1 cells were cultured under hypoxia condition. We observed remarkable ferroptosis in collecting duct cells other than apoptosis nor necroptosis. Subsequently, hepcidin knockdown further exacerbated ferroptosis under H/R condition, as evidenced by an upregulation of PTGS2 expression and downregulation of GXP4 expression, lower proportion of GSH/GSSG ratio as well as enhanced lipid peroxide accumulation and production of Fe2+. Then, RNA-seq data revealed that hepcidin knockdown promoted the enrichment of genes related to oxidative stress and glutathione metabolic pathway which may be responsible for the deterioration of ferroptosis. To investigate the role of hepcidin in vivo, bIRI induced AKI was established in Cdh16-cre+Hepcidinflox/+ mice. We observed remarkable overexpression of Hepcidin-Flag localized to collecting duct and interstium area. Impressively, Cdh16-cre+Hepcidinflox/+ mice showed ameliorated renal dysfunction adrenal tubule injury histologically. Ferroptosis of renal was alleviated in Cdh16-cre+Hepcidinflox/+ mice as confirmed by an upregulation of GPX4 expression and downregulation of PTGS2, ACSL4, FPN expression, higher proportion of GSH/GSSG ratio, as well as reduced lipid peroxide accumulation and production of Fe2+ by Lipofluo (lipid peroxides) and FerroOrange (Fe2+) staining on frozen section of kidney. Ferroptosis of the collecting duct was alleviated as indicated by downregulation of PTGS2 expression which co-staining with AQP2. To demonstrate the beneficial role of hepcidin, exogenous hepcidin was applied to bIRI induced AKI mice to strengthen the endogenous protective response. Conclusion Renal endogenous hepcidin is induced in the distal tubule and collecting duct after AKI as a protective response via alleviating ferroptosis of collecting duct. Hepcidin may represent a novel therapeutic approach to promote tubule repair by targeting ferroptosis for AKI.