miR-16-5p aggravates sepsis-associated acute kidney injury by inducing apoptosis

Sepsis-associated acute kidney injury (S-AKI) is a common disease in pediatric intensive care units (ICU) with high morbidity and mortality. The newly discovered results indicate that microRNAs (miRNAs) play an important role in the diagnosis and treatment of S-AKI and can be used as markers for early diagnosis. In this study, the expression level of miR-16-5p was found to be significantly upregulated about 20-fold in S-AKI patients, and it also increased by 1.9 times in the renal tissue of S-AKI mice. Receiver operating characteristic (ROC) curve analysis showed that miR-16-5p had the highest predictive accuracy in the diagnosis of S-AKI (AUC = 0.9188). In vitro, the expression level of miR-16-5p in HK-2 cells treated with 10 μg/mL lipopolysaccharide (LPS) increased by more than 2 times. In addition, LPS-exposed renal tissue and HK-2 cells lead to upregulation of inflammatory cytokines IL-6, IL-1β, TNF-a, and kidney damage molecules kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL). However, inhibition of miR-16-5p significantly mitigated LPS expose-mediated kidney injury and inflammation. Furthermore, LPS-exposed HK-2 cells increased more than 1.7-fold the expression levels of Bax and caspase-3, decreased 3.2-fold the expression level of B-cell lymphoma-2 (Bcl-2), and significantly promoted the occurrence of apoptosis. MiR-16-5p mimic further increased LPS-induced apoptosis in HK-2 cells. Nevertheless, inhibition of miR-16-5p significantly attenuated this effect. In summary, up-regulation of miR-16-5p expression can significantly aggravate renal injury and apoptosis in S-AKI, which also proves that miR-16-5p can be used as a potential biomarker to promote early identification of S-AKI.

Nanoparticles transfected with plasmid-encoded lncRNA-OIP5-AS1 inhibit renal ischemia-reperfusion injury in mice via the miR-410-3p/Nrf2 axis

Nanostructures composed of liposomes and polydopamine (PDA) have demonstrated efficacy as carriers for delivering plasmids, effectively alleviating renal cell carcinoma. However, their role in acute kidney injury (AKI) remains unclear. This study aimed to investigate the effects of the plasmid-encoded lncRNA-OIP5-AS1@PDA nanoparticles (POP-NPs) on renal ischemia/reperfusion (RI/R) injury and explore the underlying mechanisms. RI/R or OGD/R models were established in mice and HK-2 cells, respectively. In vivo, vector or POP-NPs were administered (10 nmol, IV) 48 h after RI/R treatment. In the RI/R mouse model, the OIP5-AS1 and Nrf2/HO-1 expressions were down-regulated, while miR-410-3p expression was upregulated. POP-NPs treatment effectively reversed RI/R-induced renal tissue injury, restoring altered levels of blood urea nitrogen, creatinine, malondialdehyde, inflammatory factors (IL-8, IL-6, TNF-α), ROS, apoptosis, miR-410-3p, as well as the suppressed expression of SOD and Nrf2/HO-1 in the model mice. Similar results were obtained in cell models treated with POP-NPs. Additionally, miR-410-3p mimics could reverse the effects of POP-NPs on cellular models, partially counteracted by Nrf2 agonists. The binding relationship between OIP5-AS1 and miR-410-3p, alongside miR-410-3p and Nrf2, has been substantiated by dual-luciferase reporter and RNA pull-down assays. The study revealed that POP-NPs can attenuate RI/R-induced injury through miR-410-3p/Nrf2 axis. These findings lay the groundwork for future targeted therapeutic approaches utilizing nanoparticles for RI/R-induced AKI.

Krüppel-like factor 4 modulates the miR-101/COL10A1 axis to inhibit renal fibrosis after AKI by regulating epithelial-mesenchymal transition

Acute kidney injury (AKI) can progress to renal fibrosis and chronic kidney disease (CKD), which reduces quality of life and increases the economic burden on patients. However, the molecular mechanisms underlying renal fibrosis following AKI remain unclear. This study tested the hypothesis that the Krüppel-like factor 4 (KLF4)/miR-101/Collagen alpha-1X (COL10A1) axis could inhibit epithelial-mesenchymal transition (EMT) and renal fibrosis after AKI in a mouse model of ischemia-reperfusion (I/R)-induced renal fibrosis and HK-2 cells by gene silencing, overexpression, immunofluorescence, immunohistochemistry, real-time quantitative PCR, Western blotting, dual-luciferase reporter assay, fluorescence in situ hybridization (FISH) and ELISA. Compared with the Sham group, I/R induced renal tubular and glomerular injury and fibrosis, and increased the levels of BUN, serum Scr and neutrophil gelatinase-associated lipocalin (NGAL), Col10a1 and Vimentin expression, but decreased E-cadherin expression in the kidney tissues of mice at 42 days post-I/R. Similarly, hypoxia promoted fibroblastic morphological changes in HK-2 cells and enhanced NGAL, COL10A1, Vimentin, and α-SMA expression, but reduced E-cadherin expression in HK-2 cells. These pathological changes were significantly mitigated in COL10A1-silenced renal tissues and HK-2 cells. KLF4 induces miR-101 transcription. More importantly, hypoxia upregulated Vimentin and COL10A1 expression, but decreased miR-101, KLF4, and E-cadherin expression in HK-2 cells. These hypoxic effects were significantly mitigated or abrogated by KLF4 over-expression in the HK-2 cells. Our data indicate that KLF4 up-regulates miR-101 expression, leading to the downregulation of COL10A1 expression, inhibition of EMT and renal fibrosis during the pathogenic process of I/R-related renal fibrosis.

Molecular mechanism of circHIPK3 in mitochondrial function in septic acute kidney injury

Cell senescence, glycolysis, and mitochondrial deficit jointly regulate the development of septic acute kidney injury (SAKI). This study aimed to explore the role of circular RNA HIPK3 (circHIPK3) in mitochondrial function in SAKI. The SAKI mouse model was established by Candida albicans infection, followed by Western blot assay, measurements of serum lactate, and adenosine triphosphate (ATP), 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazolylcarbocyanine iodide (JC-1) staining and flow cytometry. Human renal tubular epithelial cells were treated with lipopolysaccharide to establish the SAKI cell model, followed by cell counting kit-8 assay, tests of hexokinase activity, lactate production, oxygen consumption rate, extracellular acidification rate, ATP, and JC-1 staining, and Western blot assay. The roles of mitochondrial pyruvate carrier 1 (MPC1) were validated by kidney function tests, hematoxylin and eosin staining, periodic acid-Schiff staining, and SA-β-gal staining. circHIPK3 downregulation reduced glycolysis and mitochondrial dysfunction both in vivo and in vitro through the microRNA (miR)-148b-3p/DNMT1/3a/Klotho axis. Inhibition of miR-148b-3p or Klotho increased glycolysis and mitochondrial dysfunction. Knockdown of MPC1 increased lactate content and decreased ATP levels and MMP both in vivo and in vitro. Collectively, circHIPK3, in concert with the miR-148b-3p/DNMT1/3a/Klotho axis, increased glycolysis, and inhibited the negative regulation of lactate production by MPC1, and aggravated mitochondrial dysfunction and cell senescence in SAKI.

Uromodulin in sepsis and severe pneumonia: a two-sample Mendelian randomization study

The outcome for patients with sepsis-associated acute kidney injury in the intensive care unit (ICU) remains poor. Low serum uromodulin (sUMOD) protein levels have been proposed as a causal mediator of this effect. We investigated the effect of different levels of sUMOD on the risk of sepsis and severe pneumonia and outcomes in these conditions. A two-sample Mendelian randomization (MR) study was performed. Single-nucleotide polymorphisms (SNPs) associated with increased levels of sUMOD were identified and used as instrumental variables for association with outcomes. Data from different cohorts were combined based on disease severity and meta-analyzed. Five SNPs associated with increased sUMOD levels were identified and tested in six datasets from two biobanks. There was no protective effect of increased levels of sUMOD on the risk of sepsis [two cohorts, odds ratio (OR) 0.99 (95% confidence interval 0.95-1.03), P = 0.698, and OR 0.95 (0.91-1.00), P = 0.060, respectively], risk of sepsis requiring ICU admission [OR 1.04 (0.93-1.16), P = 0.467], ICU mortality in sepsis [OR 1.00 (0.74-1.37), P = 0.987], risk of pneumonia requiring ICU admission [OR 1.05 (0.98-1.14), P = 0.181], or ICU mortality in pneumonia [OR 1.17 (0.98-1.39), P = 0.079]. Meta-analysis of hospital-admitted and ICU-admitted patients separately yielded similar results [OR 0.98 (0.95-1.01), P = 0.23, and OR 1.05 (0.99-1.12), P = 0.86, respectively]. Among patients with sepsis and severe pneumonia, there was no protective effect of different levels of sUMOD. Results were consistent regardless of geographic origins and not modified by disease severity. NEW & NOTEWORTHY The presence of acute kidney injury in severe infections increases the likelihood of poor outcome severalfold. A decrease in serum uromodulin (sUMOD), synthetized in the kidney, has been proposed as a mediator of this effect. Using the Mendelian randomization technique, we tested the hypothesis that increased sUMOD is protective in severe infections. Analyses, however, showed no evidence of a protective effect of higher levels of sUMOD in sepsis or severe pneumonia.

FOXA1-Driven pathways exacerbate Radiotherapy-Induced kidney injury in colorectal cancer

OBJECTIVE

This study aimed to investigate the role of FOXA1 in acute kidney injury (AKI) induced by radiotherapy in colorectal cancer. Although FOXA1 is known to be aberrantly expressed in malignant tumors, its contribution to AKI remains unclear. This study aimed to explore the involvement of FOXA1 in AKI induced by radiotherapy in colorectal cancer and its influence on the regulation of downstream target genes.

METHODS

Firstly, a transcriptome analysis was performed on mice to establish a radiation-induced AKI model, and qPCR was used to determine the expression of FOXA1 in renal cell injury models induced by X-ray irradiation. Additionally, FOXA1 was silenced using lentiviral vectors to investigate its effects on the apoptosis of mice with radiation-induced AKI and HK-2 cells. Next, bioinformatics analysis and various experimental validation methods such as ChIP assays, co-immunoprecipitation, and dual-luciferase reporter assays were employed to explore the relationship between FOXA1 and the downstream regulatory factors ITCH promoter and the ubiquitin ligase-degradable TXNIP. Finally, lentiviral overexpression or knockout techniques were used to investigate the impact of the FOXA1/ITCH/TXNIP axis on oxidative stress and the activation of inflammatory body NLRP3.

RESULTS

This study revealed that FOXA1 was significantly upregulated in the renal tissues of mice with radiation-induced AKI and in the injured HK-2 cells. Furthermore, in vitro cell experiments and animal experiments demonstrated that FOXA1 suppressed the transcription of the E3 ubiquitin ligase ITCH, thereby promoting apoptosis of renal tubular cells and causing renal tissue damage. Further in vivo animal experiments confirmed that TXNIP, a protein degraded by ITCH ubiquitination, could inhibit oxidative stress and the activation of NLRP3 inflammasome in the AKI mouse model.

CONCLUSION

FOXA1 enhances oxidative stress, cell apoptosis, and NLRP3 inflammasome activation by regulating the ITCH/TXNIP axis, thereby exacerbating radiotherapy-induced AKI.

PRMT4 interacts with NCOA4 to inhibit ferritinophagy in cisplatin-induced acute kidney injury

Cisplatin-induced acute kidney injury (AKI) is commonly seen in the clinical practice, and ferroptosis, a type of non-apoptotic cell death, plays a pivotal role in it. Previous studies suggested that protein arginine methyltransferase 4 (PRMT4) was incorporated in various bioprocesses, but its role in renal injuries has not been investigated. Our present study showed that PRMT4 was highly expressed in renal proximal tubular cells, and it was downregulated in cisplatin-induced AKI. Besides, genetic disruption of PRMT4 exacerbated, while its overexpression attenuated, cisplatin-induced redox injuries in renal proximal epithelia. Mechanistically, our work showed that PRMT4 interacted with NCOA4 to inhibit ferritinophagy, a type of selective autophagy favoring lipid peroxidation to accelerate ferroptosis. Taken together, our study demonstrated that PRMT4 interacted with NCOA4 to attenuate ferroptosis in cisplatin-induced AKI, suggesting that PRMT4 might present as a new therapeutic target for cisplatin-related nephropathy.

JMJD3 activation contributes to renal protection and regeneration following acute kidney injury in mice

We have recently demonstrated that Jumonji domain-containing protein D3 (JMJD3), a histone demethylase of histone H3 on lysine 27 (H3K27me3), is protective against renal fibrosis, but its role in acute kidney injury (AKI) remains unexplored. Here, we report that JMJD3 activity is required for renal protection and regeneration in murine models of AKI induced by ischemia/reperfusion (I/R) and folic acid (FA). Injury to the kidney upregulated JMJD3 expression and induced expression of H3K27me3, which was coincident with renal dysfunction, renal tubular cell injury/apoptosis, and proliferation. Blocking JMJD3 activity by GSKJ4 led to worsening renal dysfunction and pathological changes by aggravating tubular epithelial cell injury and apoptosis in both murine models of AKI. JMJD3 inhibition by GSKJ4 also reduced renal tubular cell proliferation and suppressed expression of cyclin E and phosphorylation of CDK2, but increased p21 expression in the injured kidney. Furthermore, inactivation of JMJD3 enhanced I/R- or FA-induced expression of TGF-β1, vimentin, and Snail, phosphorylation of Smad3, STAT3, and NF-κB, and increased renal infiltration by F4/80 (+) macrophages. Finally, GSKJ4 treatment caused further downregulation of Klotho, BMP-7, Smad7, and E-cadherin, all of which are associated with renal protection and have anti-fibrotic effects. Therefore, these data provide strong evidence that JMJD3 activation contributes to renal tubular epithelial cell survival and regeneration after AKI.

Proximal tubular MBD2 promotes autophagy to drive the progression of AKI caused by vancomycin via regulation of miR-597-5p/S1PR1 axis

Our recent investigation has indicated that the global deletion of MBD2 can mitigate the progression of AKI induced by VAN. Nevertheless, the role and regulatory mechanisms of proximal tubular MBD2 in this pathophysiological process have yet to be elucidated. Our preceding investigation revealed that autophagy played a crucial role in advancing AKI induced by VAN. Consequently, we postulated that MBD2 present in the proximal tubule could upregulate the autophagic process to expedite the onset of AKI. In the present study, we found for the first time that MBD2 mediated the autophagy production induced by VAN. Through the utilization of miRNA chip analysis, we have mechanistically demonstrated that MBD2 initiates the activation of miR-597-5p through promoter demethylation. This process leads to the suppression of S1PR1, which results in the induction of autophagy and apoptosis in renal tubular cells. Besides, PT-MBD2-KO reduced autophagy to attenuate VAN-induced AKI via regulation of the miR-597-5p/S1PR1 axis, which was reversed by rapamycin. Finally, the overexpression of MBD2 aggravated the diminished VAN-induced AKI in autophagy-deficient mice (PT-Atg7-KO). These data demonstrate that proximal tubular MBD2 facilitated the process of autophagy via the miR-597-5p/S1PR1 axis and subsequently instigated VAN-induced AKI through the induction of apoptosis. The potentiality of MBD2 being a target for AKI was established.

Apoptosis-related prognostic biomarkers and potential targets for acute kidney injury based on machine learning algorithm and in vivo experiments

Acute kidney injury (AKI) is a common critical illness in hospitalized patients, characterized by a rapid decline in kidney function over a short period, which can seriously endanger the patient's life. Currently, there is a lack of precise and universal AKI diagnostic biomarkers in clinical practice. In this study, weighted gene coexpression network analysis (WGCNA), differential expression analysis, univariate and multivariate logistic regression analyses, receiver operating characteristic (ROC) curves, and immune cell infiltration were performed to identify apoptosis-related biomarkers that can be used for AKI diagnosis. Three core apoptosis-related genes (ARGs), CBFB, EGF and COL1A1, were identified as AKI biomarkers. More importantly, an apoptosis-related signature containing three hub ARGs was validated as a diagnostic model. The hub genes exhibited good correlations with glomerular filtration rate (GFR) and serum creatinine (SCr) in the Nephroseq kidney disease database. Additionally, CIBERSORT immune infiltration analysis indicated that these core ARGs may affect immune cell recruitment and infiltration in AKI patients. Subsequently, we investigated the alteration of the expression levels of three core ARGs in AKI samples using single-cell RNA sequencing analysis and analyzed the cell types that mainly expressed these ARGs. More importantly, the expression of core ARGs was validated in folic acid- and cisplatin-induced AKI mouse models. In summary, our study identified three diagnostic biomarkers for AKI, explored the roles of ARGs in AKI progression and provided new ideas for the clinical diagnosis and treatment of AKI.

Significance of LncRNAs in AKI-to-CKD transition: A therapeutic and diagnostic viewpoint

Acute kidney injury to chronic kidney disease (AKI-to-CKD) transition is a complex intermingling of characteristics of both AKI and CKD. Pathophysiologically, the transition lasts seven days after the AKI episode and thereafter silently progresses towards CKD. Growing reports confirm that the AKI-to-CKD transition is heavily regulated by epigenetic modifiers. Long non-coding RNAs (lncRNAs) share a diverse role in gene regulation at transcriptional and translational levels and have been reported to be involved in the regulation and progression of AKI-to-CKD transition. Several lncRNAs have been considered potential biomarkers for diagnosing kidney disease, including AKI and CKD. Targeting lncRNAs gives a promising therapeutic strategy against kidney diseases. The primitive role of lncRNA in the progression of the AKI-to-CKD transition is yet to be fully understood. As known, the lncRNAs could be used as a biomarker and a therapeutic target to halt the CKD development and progression after AKI. This review aims to deepen our understanding of the current knowledge regarding the involvement of lncRNAs in the AKI-to-CKD transition. This review primarily discusses the role of lncRNAs and the change in their mechanisms during different stages of kidney disease, such as in AKI, AKI-to-CKD transition, and CKD. Further, we have discussed the potential diagnostic and pharmacological outcomes of targeting lncRNAs to prevent or slow the progression of AKI-to-CKD transition.

Induction of p16Ink4a Gene Expression in Heme Protein-Induced AKI and by Heme: Pathophysiologic Implications

Key Points

Background

Understanding the pathogenetic basis for AKI involves the study of ischemic and nephrotoxic models of AKI, the latter including heme protein–mediated AKI (HP-AKI). Recently, interest has grown regarding the role of senescence as a mechanism of kidney injury, including AKI. We examined whether senescence occurs in HP-AKI and potential inducers of and the role of a key driver of senescence, namely, p16Ink4a, in HP-AKI.

Methods

The long-established murine glycerol model of HP-AKI was used, and indices of senescence were examined. To evaluate the interaction of heme and p16Ink4a expression, murine models of genetic deficiency of hemopexin (HPX) and heme oxygenase-1 (HO-1) were used. To determine the involvement of p16Ink4a in HP-AKI, the population of p16Ink4a-expressing cells was reduced using the INK-ATTAC model.

Results

Using multiple indices, a senescence phenotype appears in the kidney within hours after the induction of HP-AKI. This phenotype includes significant upregulation of p16Ink4a. p16Ink4a is upregulated in the kidney after the individual administration of myoglobin, hemoglobin, and heme, as well as in renal epithelial cells exposed to heme in vitro. Genetic deficiencies of HPX and HO-1, which, independently, are expected to increase heme content in the kidney, exaggerate induction of p16Ink4a in the kidney and exacerbate HP-AKI, the latter shown in the present studies involving HPX −/− mice and in previous studies involving HO-1 −/− mice. Finally, reduction in the population of p16Ink4a-expressing cells in the kidney improves renal function in HP-AKI even within 24 hours.

Conclusions

The pathogenesis of HP-AKI involves senescence and the induction of p16Ink4a, the latter driven, in part, by hemoglobin, myoglobin, and heme.

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.

KNOCKDOWN OF CIRC_0114428 ALLEVIATES LPS-INDUCED HK2 CELL APOPTOSIS AND INFLAMMATION INJURY VIA TARGETING MIR-215-5P/TRAF6/NF-ΚB AXIS IN SEPTIC ACUTE KIDNEY INJURY

ABSTRACT

Background: Sepsis is a systemic inflammatory disease that can cause multiple organ damage. Circular RNAs (circRNAs) have been reported to play a regulatory role in sepsis-induced acute kidney injury (AKI); however, the role of circ_0114428 has not been studied. Methods: In this study, HK2 cells were treated with different concentrations of LPS to induce cell damage, and then the expressions of circ_0114428, microRNA-215-5p (miR-215-5p), and tumor necrosis factor receptor-associated factor 6 (TRAF6) were detected by quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot examined the Bax and cleaved-Caspase-3 proteins. Cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and thymidine analog 5-ethynyl-2'-deoxyuridine (EdU) assay. In addition, cell apoptosis was detected by flow cytometry, and the levels of inflammatory factors were detected by enzyme-linked immunosorbent assay. Results: After LPS treatment with different concentrations, we found that LPS at 10 μg/mL had the best effect on HK2 cells. Circ_0114428 was highly expressed in sepsis-AKI patients and LPS-treated HK2 cells. Knockdown of circ_0114428 restored the effects of LPS treatment on proliferation, apoptosis, and inflammatory response of HK2 cells. MiR-215-5p was a target of circ_0114428, and TRAF6 was a downstream target of miR-215-5p. Circ_0114428 regulated TRAF6 expression by sponging miR-215-5p in LPS-treated HK2 cells. Circ_0114428 regulated LPS-induced NF-κB signaling in HK2 cells by targeting miR-215-5p/TRAF6 axis. Conclusion: Circ_0114428 knockdown abolished the cell proliferation, apoptosis, and inflammatory damage in LPS-induced HK2 cells by targeting miR-215-5p/TRAF6/NF-κB.

DRD4 alleviates acute kidney injury by suppressing ISG15/NOX4 axis-associated oxidative stress

Acute kidney injury (AKI) is a life-threatening health condition associated with increasing morbidity and mortality. Despite extensive research on the mechanisms underlying AKI, effective clinical tools for prediction and treatment remain scarce. Oxidative stress and mitochondrial damage play a critical role in AKI and dopamine D4 receptor (DRD4) has been confirmed to be associated with oxidative stress. In this study, we hypothesized that DRD4 could attenuate AKI through its antioxidative and antiapoptotic effects. In vivo, DRD4 was remarkably decreased in the kidneys of mice subjected to ischemia/reperfusion injury (IRI) or cisplatin treatment. Notably, DRD4 significantly attenuated nephrotoxicity by suppressing oxidative stress and enhancing mitochondrial bioenergetics through the downregulation of reactive oxygen species (ROS) generation and NADPH oxidase 4 (NOX4) expression. In vitro, DRD4 demonstrated the ability to ameliorate oxidative stress-induced apoptosis in HK-2 cells subjected to hypoxia/reoxygenation- or cisplatin treatment. Transcriptome sequencing revealed that, mechanistically, DRD4 reduced the expression of its downstream target, interferon-stimulated gene 15 (ISG15), suppressing NOX4 ISGylation, enhancing the ubiquitination of NOX4, leading to its degradation, and ultimately counteracting oxidative stress-induced AKI. Altogether, these findings underscore the significance of DRD4 in AKI and elucidate DRD4 as a potential protectant against IRI or cisplatin-induced nephrotoxicity.

Characterization of macrophages in ischemia-reperfusion injury-induced acute kidney injury based on single-cell RNA-Seq and bulk RNA-Seq analysis

Acute kidney injury (AKI) is a complex disease, with macrophages playing a vital role in its progression. However, the mechanism of macrophage function remains unclear and strategies targeting macrophages in AKI are controversial. To address this issue, we used single-cell RNA-seq analysis to identify macrophage sub-types involved in ischemia-reperfusion-induced AKI, and then screened for associated hub genes using intersecting bulk RNA-seq data. The single-cell and bulk RNA-seq datasets were obtained from the Gene Expression Omnibus (GEO) database. Screening of differentially-expressed genes (DEGs) and pseudo-bulk DEG analyses were used to identify common hub genes. Pseudotime and trajectory analyses were performed to investigate the progression of cell differentiation. CellChat analysis was performed to reveal the crosstalk between cell clusters. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were used to identify enriched pathways in the cell clusters. Immunofluorescence and RT-PCR were preformed to validate the expression of the identified hub genes. Four hub genes, Vim, S100a6, Ier3, and Ccr1, were identified in the infiltrated macrophages between normal samples and those 3 days after ischemia-reperfusion renal injury (IRI); all were associated with the progression of IRI-induced AKI. Increased expression of Vim, S100a6, Ier3, and Ccr1 in infiltrated macrophages may be associated with inflammatory responses and may mediate crosstalk between macrophages and renal tubular epithelial cells under IRI conditions. Our results reveal that Ier3 may be critical in AKI, and that Vim, S100a6, Ier3, and Ccr1 may act as novel biomarkers and potential therapeutic targets for IRI-induced AKI.

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

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

Identification and validation of ferroptosis-related gene SLC2A1 as a novel prognostic biomarker in AKI

BACKGROUND

Emerging evidence reveals the key role of ferroptosis in the pathophysiological process of acute kidney injury (AKI). Our study aimed to investigate the potential ferroptosis-related gene in AKI through bioinformatics and experimental validation.

METHODS

The AKI single-cell sequencing dataset was retrieved from the GEO database and ferroptosis-related genes were extracted from the GENECARD website. The potential differentially expressed ferroptosis-related genes of AKI were selected. Functional enrichment analysis was performed. Machine learning algorithms were used to identify key ferroptosis-related genes associated with AKI. A multi-factor Cox regression analysis was used to construct a risk score model. The accuracy of the risk score model was validated using receiver operating characteristic (ROC) curve analysis. We extensively explored the immune landscape of AKI using CIBERSORT tool. Finally, expressions of ferroptosis DEGs were validated in vivo and in vitro by Western blot, ICH and transfection experiments.

RESULTS

Three hub genes (BAP1, MDM4, SLC2A1) were identified and validated by constructing drug regulatory network and subsequent screening using experimentally determined interactions. The risk mode showed the low-risk group had significantly better prognosis compared to high-risk group. The risk score was independently associated with overall survival. The ROC curve analysis showed that the prognosis model had good predictive ability. Additionally, CIBERSORT immune infiltration analysis suggest that the hub gene may influence cell recruitment and infiltration in AKI. Validation experiments revealed that SLC2A1 functions by regulating ferroptosis.

CONCLUSIONS

In summary, our study not only identifies SLC2A1 as diagnostic biomarker for AKI, but also sheds light on the role of it in AKI progression, providing novel insights for the clinical diagnosis and treatment of AKI.

Circular RNA hsa_circ_0005519 contributes to acute kidney injury via sponging microRNA-98-5p

BACKGROUND

This study intends to explore the role and molecular mechanism of hsa_circ_0005519 in acute kidney injury (AKI).

METHODS

We conducted reverse transcription-qPCR for human serum to determine levels of hsa_circ_0005519 in AKI patients and healthy controls. Hsa_circ_0005519 was inhibited for expression in HK-2 cells using specific siRNAs. A number of techniques, MTT and ELISA assays, were used to analyze the potential role of hsa_circ_0005519 in cell viability, oxidative stress, and inflammation of LPS-induced HK-2 cells.

RESULTS

The serum of patients with AKI exhibited a significant increase in hsa_circ_0005519 expression, compared with healthy controls. Hsa_circ_0005519 was knockdown by siRNA, and its knockdown led to cell viability increase in LPS-induced HK-2 cells. Inhibition of hsa_circ_0005519 can reverse the TNF-α, IL-6 and IL-1β increase in LPS-induced HK-2 cells. Inhibiting hsa_circ_0005519 led to downregulation of MPO and MDA levels. MiR-98-5p was a downstream miRNA for hsa_circ_0005519. MiR-98-5p can offset the effects of hsa_circ_0005519 on LPS-induced HK-2 cells. IFG1R was a target gene for miR-98-5p.

CONCLUSIONS

These findings indicate that the highly expressed hsa_circ_0005519 plays a promoting role in AKI.

Knockdown of circ-Gatad1 alleviates LPS induced HK2 cell injury via targeting miR-22-3p/TRPM7 axis in septic acute kidney

BACKGROUND

Sepsis is a life-threatening, systemic inflammatory disease that can lead to a variety of conditions, including septic acute kidney injury (AKI). Recently, multiple circular Rnas (circRNAs) have been implicated in the development of this disease.

METHODS

In this study, we aimed to elucidate the role of circ-Gatad1 in sepsis induced AKI and its potential mechanism of action. High-throughput sequencing was used to investigate abnormal expression of circRNA in AKI and healthy volunteer. Bioinformatics analysis and luciferase reporting analysis were used to clarify the interacted relationship among circRNA, miRNA and mRNA. HK2 cells were treated with lipopolysaccharide (LPS) to establish septic AKI cell model. HK2 cells were employ to analysis the ROS, inflammatory cytokines expression, proliferation and apoptosis under LPS condition.

RESULTS

The result show that the expression of circ-Gatad1 was increased in septic acute kidney patients. Downregulation circ-Gatad1 suppressed LPS-treated induced HK2 cells injury including apoptosis, proliferation ability, ROS and inflammatory cytokines level. Bioinformatics and luciferase report analysis confirmed that both miR-22-3p and TRPM7 were downstream targets of circ-Gatad1. Overexpression of TRPM7 or downregulation of miR-22-3p reversed the protective effect of si-circ-Gatad1 to HK2 after exposure to LPS (5 µg/ml) microenvironment.

CONCLUSION

In conclusion, knockdown of circ-Gatad1 alleviates LPS induced HK2 cell injury via targeting miR-22-3p/TRPM7 axis in septic acute kidney.

P16INK4a deletion alleviates contrast-induced acute kidney injury by ameliorating renal cell apoptosis and suppressing inflammation and oxidative stress

Contrast-induced acute kidney injury (CI-AKI) is the third leading cause of hospital-acquired acute kidney injury. Cellular senescence is associated with CI-AKI. P16INK4a (p16) is a cell cycle regulator and link to aging and senescence. We found that the expression of p16 was elevated in CI-AKI renal tissues, however its role in CI-AKI remains insufficiently understood. In this study, we used p16 knockout (p16KO) mice and wild-type (WT) littermates to establish CI-AKI mice model to elucidate the impact of p16 on CI-AKI. The results showed that serum creatinine (SCr), blood urea nitrogen (BUN), and serum neutrophil gelatinase-associated lipocalin (NGAL) levels were markedly reduced in p16KO CI-AKI mice. Both immunohistochemistry and western blot analyses confirmed that p16 knockout alleviated renal cell apoptosis. Furthermore, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were attenuated by downregulating NLRP3 and NF-κB inflammasomes. Additionally, ROS levels were diminished via activating Nrf2/Keap-1 pathway in p16KO CI-AKI mice. Collectively, our findings suggest that p16 deletion exerts protective effects against apoptosis, inflammation, and oxidative stress in CI-AKI mice model, p16 deletion might be a potential therapeutic strategy for ameliorating CI-AKI.

Energy depletion by cell proliferation sensitizes the kidney epithelial cells to injury

Acute kidney injury activates both proliferative and antiproliferative pathways, the consequences of which are not fully elucidated. If an initial proliferation of the renal epithelium is necessary for the successful repair, the persistence of proliferation markers is associated with the occurrence of chronic kidney disease. We hypothesized that proliferation in stress conditions impacts cell viability and renal outcomes. We found that proliferation is associated with cell death after various stresses in kidney cells. In vitro, the ATP/ADP ratio oscillates reproducibly throughout the cell cycle, and cell proliferation is associated with a decreased intracellular ATP/ADP ratio. In vivo, transcriptomic data from transplanted kidneys revealed that proliferation was strongly associated with a decrease in the expression of the mitochondria-encoded genes of the oxidative phosphorylation pathway, but not of the nucleus-encoded ones. These observations suggest that mitochondrial function is a limiting factor for energy production in proliferative kidney cells after injury. The association of increased proliferation and decreased mitochondrial function was indeed associated with poor renal outcomes. In summary, proliferation is an energy-demanding process impairing the cellular ability to cope with an injury, highlighting proliferative repair and metabolic recovery as indispensable and interdependent features for successful kidney repair.NEW & NOTEWORTHY ATP depletion is a hallmark of acute kidney injury. Proliferation is instrumental to kidney repair. We show that ATP levels vary during the cell cycle and that proliferation sensitizes renal epithelial cells to superimposed injuries in vitro. More proliferation and less energy production by the mitochondria are associated with adverse outcomes in injured kidney allografts. This suggests that controlling the timing of kidney repair might be beneficial to mitigate the extent of acute kidney injury.

Cisplatin induces acute kidney injury by downregulating miR-30e-5p that targets Galnt3 to activate the AMPK signaling pathway

Cisplatin nephrotoxicity is an etiological factor for acute kidney injury (AKI). MicroRNA (miRNA) expression is dysregulated in cisplatin-induced AKI (cAKI) although the underlying mechanisms are unclear. A cAKI model was established by intraperitoneally injecting cisplatin, and key miRNAs were screened using high-throughput miRNA sequencing. The functions of key miRNAs were determined using the cell viability, live/dead, reactive oxygen species (ROS), and 5-ethynyl-2'-deoxyuridine (EdU) proliferation assays. Additionally, the macrophage membrane was wrapped around a metal-organic framework (MOF) loaded with miRNA agomir to develop a novel composite material, macrophage/MOF/miRNA agomir nanoparticles (MMA NPs). High-throughput miRNA sequencing revealed that miR-30e-5p is a key miRNA that is downregulated in cAKI. The results of in vitro experiments demonstrated that miR-30e-5p overexpression partially suppressed the cisplatin-induced or lipopolysaccharide (LPS)-induced downregulation of cell viability, proliferation, upregulation of ROS production, and cell death. Meanwhile, the results of in vivo and in vitro experiments demonstrated that MMA NPs alleviated cAKI by exerting anti-inflammatory effects. Mechanistically, cisplatin downregulates the expression of miR-30e-5p, and the downregulated miR-30e-5p can target Galnt3 to activate the adenosine 5'-monophosphate activated protein kinase (AMPK) signaling pathway, which promotes the progression of AKI. Our study found that miR-30e-5p is a key downregulated miRNA in cAKI. The downregulated miR-30e-5p promotes AKI progression by targeting Galnt3 to activate the AMPK signaling pathway. The newly developed MMA NPs were found to have protective effects on cAKI, suggesting a potential novel strategy for preventing cAKI.

Clonal hematopoiesis of indeterminate potential is associated with acute kidney injury

Age is a predominant risk factor for acute kidney injury (AKI), yet the biological mechanisms underlying this risk are largely unknown. Clonal hematopoiesis of indeterminate potential (CHIP) confers increased risk for several chronic diseases associated with aging. Here we sought to test whether CHIP increases the risk of AKI. In three population-based epidemiology cohorts, we found that CHIP was associated with a greater risk of incident AKI, which was more pronounced in patients with AKI requiring dialysis and in individuals with somatic mutations in genes other than DNMT3A, including mutations in TET2 and JAK2. Mendelian randomization analyses supported a causal role for CHIP in promoting AKI. Non-DNMT3A-CHIP was also associated with a nonresolving pattern of injury in patients with AKI. To gain mechanistic insight, we evaluated the role of Tet2-CHIP and Jak2V617F-CHIP in two mouse models of AKI. In both models, CHIP was associated with more severe AKI, greater renal proinflammatory macrophage infiltration and greater post-AKI kidney fibrosis. In summary, this work establishes CHIP as a genetic mechanism conferring impaired kidney function recovery after AKI via an aberrant inflammatory response mediated by renal macrophages.

Macrophage Ontogeny, Phenotype, and Function in Ischemia Reperfusion-Induced Injury and Repair

AKI is characterized by a sudden, and usually reversible, decline in kidney function. In mice, ischemia-reperfusion injury (IRI) is commonly used to model the pathophysiologic features of clinical AKI. Macrophages are a unifying feature of IRI as they regulate both the initial injury response as well as the long-term outcome following resolution of injury. Initially, macrophages in the kidney take on a proinflammatory phenotype characterized by the production of inflammatory cytokines, such as CCL2 (monocyte chemoattractant protein 1), IL-6, IL-1 β , and TNF- α . Release of these proinflammatory cytokines leads to tissue damage. After resolution of the initial injury, macrophages take on a reparative role, aiding in tissue repair and restoration of kidney function. By contrast, failure to resolve the initial injury results in prolonged inflammatory macrophage accumulation and increased kidney damage, fibrosis, and the eventual development of CKD. Despite the extensive amount of literature that has ascribed these functions to M1/M2 macrophages, a recent paradigm shift in the macrophage field now defines macrophages on the basis of their ontological origin, namely monocyte-derived and tissue-resident macrophages. In this review, we focus on macrophage phenotype and function during IRI-induced injury, repair, and transition to CKD using both the classic (M1/M2) and novel (ontological origin) definition of kidney macrophages.

Exploration of potential biomarkers and therapeutic targets for trauma-related acute kidney injury

PURPOSE

Acute kidney injury (AKI) is one of the most common functional injuries observed in trauma patients. However, certain trauma medications may exacerbate renal injury. Therefore, the early detection of trauma-related AKI holds paramount importance in improving trauma prognosis.

METHODS

Qualified datasets were selected from public databases, and common differentially expressed genes related to trauma-induced AKI and hub genes were identified through enrichment analysis and the establishment of protein-protein interaction (PPI) networks. Additionally, the specificity of these hub genes was investigated using the sepsis dataset and conducted a comprehensive literature review to assess their plausibility. The raw data from both datasets were downloaded using R software (version 4.2.1) and processed with the "affy" package19 for correction and normalization.

RESULTS

Our analysis revealed 585 upregulated and 629 downregulated differentially expressed genes in the AKI dataset, along with 586 upregulated and 948 downregulated differentially expressed genes in the trauma dataset. Concurrently, the establishment of the PPI network and subsequent topological analysis highlighted key hub genes, including CD44, CD163, TIMP metallopeptidase inhibitor 1, cytochrome b-245 beta chain, versican, membrane spanning 4-domains A4A, mitogen-activated protein kinase 14, and early growth response 1. Notably, their receiver operating characteristic curves displayed areas exceeding 75%, indicating good diagnostic performance. Moreover, our findings postulated a unique molecular mechanism underlying trauma-related AKI.

CONCLUSION

This study presents an alternative strategy for the early diagnosis and treatment of trauma-related AKI, based on the identification of potential biomarkers and therapeutic targets. Additionally, this study provides theoretical references for elucidating the mechanisms of trauma-related AKI.

SOX9 switch links regeneration to fibrosis at the single-cell level in mammalian kidneys

The steps governing healing with or without fibrosis within the same microenvironment are unclear. After acute kidney injury (AKI), injured proximal tubular epithelial cells activate SOX9 for self-restoration. Using a multimodal approach for a head-to-head comparison of injury-induced SOX9 lineages, we identified a dynamic SOX9 switch in repairing epithelia. Lineages that regenerated epithelia silenced SOX9 and healed without fibrosis (SOX9on-off). By contrast, lineages with unrestored apicobasal polarity maintained SOX9 activity in sustained efforts to regenerate, which were identified as a SOX9on-on Cadherin6pos cell state. These reprogrammed cells generated substantial single-cell WNT activity to provoke a fibroproliferative response in adjacent fibroblasts, driving AKI to chronic kidney disease. Transplanted human kidneys displayed similar SOX9/CDH6/WNT2B responses. Thus, we have uncovered a sensor of epithelial repair status, the activity of which determines regeneration with or without fibrosis.

CHOP-mediated Gasdermin E expression promotes pyroptosis, inflammation, and mitochondrial damage in renal ischemia-reperfusion injury

In clinical practice, renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI), often leading to acute renal failure or end-stage renal disease (ESRD). The current understanding of renal IRI mechanisms remains unclear, and effective therapeutic strategies and clear targets are lacking. Therefore, the need to find explicit and effective ways to reduce renal IRI remains a scientific challenge. The current study explored pyroptosis, a type of inflammation-regulated programmed cell death, and the role of Gasdermins E (GSDME)-mediated pyroptosis, mitochondrial damage, and inflammation in renal IRI. The analysis of human samples showed that the expression levels of GSDME in normal human renal tissues were higher than those of GSDMD. Moreover, our study demonstrated that GSDME played an important role in mediating pyroptosis, inflammation, and mitochondrial damage in renal IRI. Subsequently, GSDME-N accumulated in the mitochondrial membrane, leading to mitochondrial damage and activation of caspase3, which generated a feed-forward loop of self-amplification injury. However, GSDME knockout resulted in the amelioration of renal IRI. Moreover, the current study found that the transcription factor CHOP was activated much earlier in renal IRI. Inhibition of BCL-2 by CHOP leaded to casapse3 activation, resulting in mitochondrial damage and apoptosis; not only that, but CHOP positively regulated GSDME thereby causing pyroptosis. Therefore, this study explored the transcriptional mechanisms of GSDME during IRI development and the important role of CHOP/Caspase3/GSDME mechanistic axis in regulating pyroptosis in renal IRI. This axis might serve as a potential therapeutic target.

FTO attenuates LPS-induced acute kidney injury by inhibiting autophagy via regulating SNHG14/miR-373-3p/ATG7 axis

N6-methyladenosine (m6A) is a master driver of RNA function and implicates in the pathogenesis of renal injury. LncRNA SNHG14 is highly expressed in sepsis patients with acute kidney injury (AKI) and aggravates kidney cell dysfunction. This study aimed to explore whether demethylase FTO affect m6A methylation of SNHG14 in AKI injury and its underlying mechanism. The expression level of FTO was obviously downregulated in sepsis-associated AKI patients compared with normal controls. Mechanistically, FTO overexpression impeded SNHG14 expression by decreasing the stability of SNHG14 in an m6A-dependent manner in LPS-induced HK-2 cells. Additionally, FTO overexpression inhibited cell autophagy and apoptosis while promoting cell viability of LPS-induced HK-2 cells. Moreover, overexpression of FTO inhibited SNHG14 expression and autophagy in LPS-induced AKI mice. Functionally, SNHG14 acts as a competing endogenous RNA (ceRNA) via directly sponging miR-373-3p in LPS induced HK-2 cells. Additionally, miR-373-3p directly targets ATG7. Inhibition of SNHG14 suppresses NF-κB signaling pathway and production of inflammatory cytokines (TNF-α, IL-6, and IL-1β) via miR-373-3p/ATG7 in LPS-induced HK-2 cells. Furthermore, the SNHG14/miR-373-3p/ATG7 interaction network contributes to the regulatory effect of FTO on LPS-induced HK-2 cell viability, apoptosis and autophagy. These results suggested demethylase FTO suppressed the m6A modification of lncRNA SNHG14 and inhibits autophagy in LPS-induced AKI via regulating miR-373-3p/ATG7, which provided an important novel perspective for understanding sepsis-associated AKI and is conducive for developing new therapeutic targets and strategies.

Connexin32 gap junction channels deliver miR155-3p to mediate pyroptosis in renal ischemia-reperfusion injury

OBJECTIVES

To explore whether the gap junction (GJ) composed by connexin32(Cx32) mediated pyroptosis in renal ischemia-reperfusion(I/R) injury via transmitting miR155-3p, with aim to provide new strategies for the prevention and treatment of acute kidney injury (AKI) after renal I/R.

METHODS

8-10 weeks of male C57BL/ 6 wild-type mice and Cx32 knockdown mice were divided into two groups respectively: control group and renal I/R group. MCC950 (50 mg/kg. ip.) was used to inhibit NLRP3 in vivo. Human kidney tubular epithelial cells (HK - 2) and rat kidney tubular epithelial cells (NRK-52E) were divided into high-density group and low-density group, and treated with hypoxia reoxygenation (H/R) to mimic I/R. The siRNA and plasmid of Cx32, mimic and inhibitor of miR155-3p were transfected into HK - 2 cells respectively. Kidney pathological and functional injuries were measured. Western Blot and immunofluorescent staining were used to observe the expression of NLRP3, GSDMD, GSDMD-N, IL - 18, and mature IL-18. The secretion of IL-18 and IL-1β in serum, kidney tissue and cells supernatant were detected by enzyme-linked immuno sorbent assay (ELISA) kit, and the expression of NLPR3 and miR155-3p were detected by RT-qPCR and fluorescence in situ hybridization (FISH).

RESULTS

Tubular pyroptosis were found to promote AKI after I/R in vivo and Cx32-GJ regulated pyroptosis by affecting the expression of miR155-3p after renal I/R injury. In vitro, H/R could lead to pyroptosis in HK-2 and NRK-52E cells. When the GJ channels were not formed, and Cx32 was inhibited or knockdown, the expression of miR155-3p was significantly reduced and the pyroptosis was obviously inhibited, leading to the reduction of injury and the increase of survival rate. Moreover, regulating the level of miR155-3p could affect survival rate and pyroptosis in vitro after H/R.

CONCLUSIONS

The GJ channels composed of Cx32 regulated tubular pyroptosis in renal I/R injury by transmitting miR155-3p. Inhibition of Cx32 could reduce the level of miR155-3p further to inhibit pyroptosis, leading to alleviation of renal I/R injury which provided a new strategy for preventing the occurrence of AKI. Video Abstract.

The role of non-protein-coding RNAs in ischemic acute kidney injury

Acute kidney injury (AKI) is a condition characterized by a rapid decline in kidney function within a span of 48 hours. It is influenced by various factors including inflammation, oxidative stress, excessive calcium levels within cells, activation of the renin-angiotensin system, and dysfunction in microcirculation. Ischemia-reperfusion injury (IRI) is recognized as a major cause of AKI; however, the precise mechanisms behind this process are not yet fully understood and effective treatments are still needed. To enhance the accuracy of diagnosing AKI during its early stages, the utilization of innovative markers is crucial. Numerous studies suggest that certain noncoding RNAs (ncRNAs), such as long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), play a central role in regulating gene expression and protein synthesis. These ncRNAs are closely associated with the development and recovery of AKI and have been detected in both kidney tissue and bodily fluids. Furthermore, specific ncRNAs may serve as diagnostic markers and potential targets for therapeutic interventions in AKI. This review aims to summarize the functional roles and changes observed in noncoding RNAs during ischemic AKI, as well as explore their therapeutic potential.

Prophylactic vitamin C supplementation regulates DNA demethylation to protect against cisplatin-induced acute kidney injury in mice

Cisplatin-induced acute kidney injury (AKI) restricts the use of cisplatin as a first-line chemotherapeutic agent. Our previous study showed that prophylactic vitamin C supplementation may act as an epigenetic modulator in alleviating cisplatin-induced AKI in mice. However, the targets of vitamin C and the mechanisms underlying the epigenetics changes remain largely unknown. Herein, whole-genome bisulfite sequencing and bulk RNA sequencing were performed on the kidney tissues of mice treated with cisplatin with prophylactic vitamin C supplementation (treatment mice) or phosphate-buffered saline (control mice) at 24 h after cisplatin treatment. Ascorbyl phosphate magnesium (APM), an oxidation-resistant vitamin C derivative, was found that led to global hypomethylation in the kidney tissue and regulated different functional genes in the promoter region and gene body region. Integrated evidence suggested that APM enhanced renal ion transport and metabolism, and reduced apoptosis and inflammation in the kidney tissues. Strikingly, Mapk15, Slc22a6, Cxcl5, and Cd44 were the potential targets of APM that conferred protection against cisplatin-induced AKI. Moreover, APM was found to be difficult to rescue cell proliferation and apoptosis caused by cisplatin in the Slc22a6 knockdown cell line. These results elucidate the mechanism by which vitamin C as an epigenetic regulator to protects against cisplatin-induced AKI and provides a new perspective and evidence support for controlling the disease process through regulating DNA methylation.

Bone marrow stromal cell antigen-1 deficiency protects from acute kidney injury

This study aimed to investigate the role of bone marrow stromal cell antigen-1 (Bst1; also known as CD157) in acute kidney injury (AKI). Bst1 is a cell surface molecule with various enzymatic activities and downstream intracellular signaling pathways that modulate the immune response. Previous research has linked Bst1 to diseases such as ovarian cancer, Parkinson's disease, and rheumatoid arthritis. We used bilateral ischemia-reperfusion injury (IRI) as an AKI model and created bone marrow chimeric mice to evaluate the role of Bst1 in bone marrow-derived cells. We also used flow cytometry to identify Bst1/CD157 expression in hematopoietic cells and evaluate immune cell dynamics in the kidney. The findings showed that Bst1-deficient (Bst1-/-) mice were protected against renal bilateral IRI. Bone marrow chimera experiments revealed that Bst1 expression on hematopoietic cells, but not parenchymal cells, induced renal IRI. Bst1 was mainly found in B cells and neutrophils by flow cytometry of the spleen and bone marrow. In vitro, migration of neutrophils from Bst1-/- mice was suppressed, and adoptive transfer of neutrophils from wild-type Bst1+/+ mice abolished the renal protective effect in Bst1 knockout mice. In conclusion, the study demonstrated that Bst1-/- mice are protected against renal IRI and that Bst1 expression in neutrophils plays a crucial role in inducing renal IRI. These findings suggest that targeting Bst1 in neutrophils could be a potential therapeutic strategy for AKI.NEW & NOTEWORTHY Acute kidney injury (AKI), a serious disease for which there is no effective Federal Drug Administration-approved treatment, is associated with high mortality rates. Bone marrow stromal cell antigen-1 (Bst1) is a cell surface molecule that can cause kidney fibrosis, but its role in AKI is largely unknown. Our study showed that Bst1-/- mice revealed a protective effect against renal bilateral ischemia-reperfusion injury (IRI). Adoptive transfer studies confirmed that Bst1 expression in hematopoietic cells, especially neutrophils, contributed to renal bilateral IRI.

Role of protease-activated receptor 4 in mouse models of acute and chronic kidney injury

Protease-activated receptor 4 (PAR4) is a G protein-coupled receptor activated by thrombin. In the platelet, response to thrombin PAR4 contributes to the predominant procoagulant microparticle formation, increased fibrin deposition, and initiation of platelet-stimulated inflammation. In addition, PAR4 is expressed in other cell types, including endothelial cells. Under inflammatory conditions, PAR4 is overexpressed via epigenetic demethylation of the PAR4 gene, F2RL3. PAR4 knockout (KO) studies have determined a role for PAR4 in ischemia-reperfusion injury in the brain, and PAR4 KO mice display normal cardiac function but present less myocyte death and cardiac dysfunction in response to acute myocardial infarction. Although PAR4 has been reported to be expressed within the kidney, the contribution of PAR4 to acute kidney injury (AKI) and chronic kidney disease (CKD) is not well understood. Here we report that PAR4 KO mice are protected against kidney injury in two mouse models. First, PAR4 KO mice are protected against induction of markers of both fibrosis and inflammation in two different models of kidney injury: 1) 7 days following unilateral ureter obstruction (UUO) and 2) an AKI-CKD model of ischemia-reperfusion followed by 8 days of contralateral nephrectomy. We further show that PAR4 expression in the kidney is low in the control mouse kidney but induced over time following UUO. PAR4 KO mice are protected against blood urea nitrogen (BUN) and glomerular filtration rate (GFR) kidney function pathologies in the AKI-CKD model. Following the AKI-CKD model, PAR4 is expressed in the collecting duct colocalizing with Dolichos biflorus agglutinin (DBA), but not in the proximal tubule with Lotus tetragonolobus lectin (LTL). Collectively, the results reported in this study implicate PAR4 as contributing to the pathology in mouse models of acute and chronic kidney injury.NEW & NOTEWORTHY The contribution of the thrombin receptor protease-activated receptor 4 (PAR4) to acute kidney injury (AKI) and chronic kidney disease (CKD) is not well understood. Here we report that PAR4 expression is upregulated after kidney injury and PAR4 knockout (KO) mice are protected against fibrosis following kidney injury in two mouse models. First, PAR4 KO mice are protected against unilateral ureter obstruction. Second, PAR4 KO mice are protected against an AKI-CKD model of ischemia-reperfusion followed by contralateral nephrectomy.

Mitochondrial genetic variation and risk of chronic kidney disease and acute kidney injury in UK Biobank participants

Experimental models suggest an important role for mitochondrial dysfunction in the pathogenesis of chronic kidney disease (CKD) and acute kidney injury (AKI), but little is known regarding the impact of common mitochondrial genetic variation on kidney health. We sought to evaluate associations of inherited mitochondrial DNA (mtDNA) variation with risk of CKD and AKI in a large population-based cohort. We categorized UK Biobank participants who self-identified as white into eight distinct mtDNA haplotypes, which were previously identified based on their associations with phenotypes associated with mitochondrial DNA copy number, a measure of mitochondrial function. We used linear and logistic regression models to evaluate associations of these mtDNA haplotypes with estimated glomerular filtration rate by serum creatinine and cystatin C (eGFRCr-CysC, N = 362,802), prevalent (N = 416 cases) and incident (N = 405 cases) end-stage kidney disease (ESKD), AKI defined by diagnostic codes (N = 14,170 cases), and urine albumin/creatinine ratio (ACR, N = 114,662). The mean age was 57 ± 8 years and the mean eGFR was 90 ± 14 ml/min/1.73 m2. MtDNA haplotype was significantly associated with eGFR (p = 2.8E-12), but not with prevalent ESKD (p = 5.9E-2), incident ESKD (p = 0.93), AKI (p = 0.26), or urine ACR (p = 0.54). The association of mtDNA haplotype with eGFR remained significant after adjustment for diabetes mellitus and hypertension (p = 1.2E-10). When compared to the reference haplotype, mtDNA haplotypes I (β = 0.402, standard error (SE) = 0.111; p = 2.7E-4), IV (β = 0.430, SE = 0.073; p = 4.2E-9), and V (β = 0.233, SE = 0.050; p = 2.7E-6) were each associated with higher eGFR. Among self-identified white UK Biobank participants, mtDNA haplotype was associated with eGFR, but not with ESKD, AKI or albuminuria.

Pax protein depletion in proximal tubules triggers conserved mechanisms of resistance to acute ischemic kidney injury preventing transition to chronic kidney disease

Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part, this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Identifying the molecular and genetic regulators unique to nephron segments that dictate vulnerability to injury and regenerative potential could lead to new therapeutic targets to treat ischemic kidney injury. Pax2 and Pax8 are homologous transcription factors with overlapping functions that are critical for kidney development and are re-activated in AKI. Here, we examined the role of Pax2 and Pax8 in recovery from ischemic AKI and found them upregulated after severe AKI and correlated with chronic injury. Surprisingly, proximal-tubule-selective deletion of Pax2 and Pax8 resulted in a less severe chronic injury phenotype. This effect was mediated by protection against the acute insult, similar to pre-conditioning. Prior to injury, Pax2 and Pax8 mutant mice develop a unique subpopulation of proximal tubule cells in the S3 segment that displayed features usually seen only in acute or chronic injury. The expression signature of these cells was strongly enriched with genes associated with other mechanisms of protection against ischemic AKI including caloric restriction, hypoxic pre-conditioning, and female sex. Thus, our results identified a novel role for Pax2 and Pax8 in mature proximal tubules that regulates critical genes and pathways involved in both the injury response and protection from ischemic AKI.

Renal-specific loss of ferroportin disrupts iron homeostasis and attenuates recovery from acute kidney injury

Chronic kidney disease is increasing at an alarming rate and correlates with the increase in diabetes, obesity, and hypertension that disproportionately impact socioeconomically disadvantaged communities. Iron plays essential roles in many biological processes including oxygen transport, mitochondrial function, cell proliferation, and regeneration. However, excess iron induces the generation and propagation of reactive oxygen species, which lead to oxidative stress, cellular damage, and ferroptosis. Iron homeostasis is regulated in part by the kidney through iron resorption from the glomerular filtrate and exports into the plasma by ferroportin (FPN). Yet, the impact of iron overload in the kidney has not been addressed. To test more directly whether excess iron accumulation is toxic to kidneys, we generated a kidney proximal tubule-specific knockout of FPN. Despite significant intracellular iron accumulation in FPN mutant tubules, basal kidney function was not measurably different from wild type kidneys. However, upon induction of acute kidney injury (AKI), FPN mutant kidneys exhibited significantly more damage and failed recovery, evidence for ferroptosis, and increased fibrosis. Thus, disruption of iron export in proximal tubules, leading to iron overload, can significantly impair recovery from AKI and can contribute to progressive renal damage indicative of chronic kidney disease. Understanding the mechanisms that regulate iron homeostasis in the kidney may provide new therapeutic strategies for progressive kidney disease and other ferroptosis-associated disorders.NEW & NOTEWORTHY Physiological iron homeostasis depends in part on renal resorption and export into the plasma. We show that specific deletion of iron exporters in the proximal tubules sensitizes cells to injury and inhibits recovery. This can promote a chronic kidney disease phenotype. Our paper demonstrates the need for iron balance in the proximal tubules to maintain and promote healthy recovery after acute kidney injury.

Integrative analysis of transcriptome and metabolome provide new insights into mechanisms of Capilliposide A against cisplatin-induced nephrotoxicity

OBJECTIVE

Cisplatin (CDDP) has been widely used for chemotherapy against tumours. However，the nephrotoxicity has limited its clinical use. Here, we reported a novel compound, Capilliposide A (CPS-A), to exhibit therapeutic effects on CDDP-induced acute kidney injury (AKI) and explored its potential mechanisms via transcriptome and metabolome.

MATERIALS AND METHODS

HK-2 cells were treated with CPS-A, after which cell viability, apoptosis and inflammation were investigated. A mouse model of AKI was constructed by single injection of CDDP in vivo. The renal function and morphology and mitochondrial function were assessed by pathological section and transmission electron microscope (TEM). Transcriptomics and metabolomics are used to explore possible mechanisms which was later verified in vitro.

RESULTS

CPS-A administration improved the survival rates of HK-2 cells with a significant decrease in the expression of KIM-1, NGAL, IL-6, IL-8 and IL-1β. In vivo results also suggested that CPS-A attenuates CDDP-induced kidney injury by reducing serum creatinine (Cr) and blood urea nitrogen (BUN) levels. Furthermore, TEM also showed the improvement of mitochondrial ultrastructure both in vivo and vitro. Transcriptomics analysis of the mice's renal cortex indicated the expression of ATF4 and CHOP were upregulated, which was further validated by qPCR and Western blotting in vitro. Integrative analysis of transcriptome and metabolome indicated that L-Leucine enriched in Valine, leucine and isoleucine degradation might be potential targets.

CONCLUSIONS

CPS-A can effectively regulate endogenous metabolites associated with amino acid metabolism and ameliorate apoptosis and oxidative stress in CDDP-induced AKI by reducing endoplasmic reticulum stress.

Cutaneous Arsenical Exposure Induces Distinct Metabolic Transcriptional Alterations of Kidney Cells

Arsenicals are deadly chemical warfare agents that primarily cause death through systemic capillary fluid leakage and hypovolemic shock. Arsenical exposure is also known to cause acute kidney injury, a condition that contributes to arsenical-associated death due to the necessity of the kidney in maintaining whole-body fluid homeostasis. Because of the global health risk that arsenicals pose, a nuanced understanding of how arsenical exposure can lead to kidney injury is needed. We used a nontargeted transcriptional approach to evaluate the effects of cutaneous exposure to phenylarsine oxide, a common arsenical, in a murine model. Here we identified an upregulation of metabolic pathways such as fatty acid oxidation, fatty acid biosynthesis, and peroxisome proliferator-activated receptor (PPAR)-α signaling in proximal tubule epithelial cell and endothelial cell clusters. We also revealed highly upregulated genes such as Zbtb16, Cyp4a14, and Pdk4, which are involved in metabolism and metabolic switching and may serve as future therapeutic targets. The ability of arsenicals to inhibit enzymes such as pyruvate dehydrogenase has been previously described in vitro. This, along with our own data, led us to conclude that arsenical-induced acute kidney injury may be due to a metabolic impairment in proximal tubule and endothelial cells and that ameliorating these metabolic effects may lead to the development of life-saving therapies. SIGNIFICANCE STATEMENT: In this study, we demonstrate that cutaneous arsenical exposure leads to a transcriptional shift enhancing fatty acid metabolism in kidney cells, indicating that metabolic alterations might mechanistically link topical arsenical exposure to acute kidney injury. Targeting metabolic pathways may generate promising novel therapeutic approaches in combating arsenical-induced acute kidney injury.

Bioinformatics analysis and experimental validation reveal the anti-ferroptosis effect of FZD7 in acute kidney injury

BACKGROUND

Ferroptosis plays an important role in acute kidney injury (AKI), but the specific regulatory mechanism of ferroptosis in AKI remains unclear. This study is expected to analyze ferroptosis-related genes (FRGs) in AKI and explore their underlying mechanisms.

RESULTS

A total of 479 differentially expressed genes (DEGs), including 196 up-regulated genes and 283 down-regulated genes were identified in the AKI chip GSE30718. 341 FRGs were obtained from the Genecard, OMIM and NCBI database. Totally 11 ferroptosis-related DEGs in AKI were found, in which 7 genes (CD44, TIGAR, RB1, LCN2, JUN, ARNTL, ACSL4) were up-regulated and 4 genes (FZD7, EP300, FOXC1, DLST) were down-regulated. Three core genes (FZD7, JUN, EP300) were obtained by PPI and KEGG analysis, among which the function of FZD7 in AKI is unclear. The WGCNA analysis found that FZD7 belongs to a module that was negatively correlated with AKI. Further basic experiments confirmed that FZD7 is down-regulated in mouse model of ischemia-reperfusion-AKI and cellular model of hypoxia-reoxygenation(H/R). In addition, knockdown of FZD7 could further aggravate the down-regulation of cell viability induced by H/R and Erastin, while overexpression of FZD7 can rescue its down-regulation to some extent. Furthermore, we verified that knockdown of FZD7 decreased the expression of GPX4 and overexpression of FZD7 increased the expression of GPX4, suggesting that FZD7 may inhibit ferroptosis by regulating the expression of GPX4 and plays a vital role in the onset and development of AKI.

CONCLUSIONS

This article revealed the anti-ferroptosis effect of FZD7 in acute kidney injury through bioinformatics analysis and experimental validation, suggesting that FZD7 is a promising target for AKI and provided more evidence about the vital role of ferroptosis in AKI.

CIRCUSP42 AMELIORATES LPS-INDUCED HUMAN RENAL EPITHELIAL CELLS IN VITRO BY REGULATING THE MIR-182-5P/DUSP1 AXIS

ABSTRACT

Background: Sepsis is a life-threatening systemic inflammatory disease that can cause many diseases, including acute kidney injury (AKI). Increasing evidence showed that a variety of circular RNAs were considered to be involved in the development of the disease. In this study, we aimed to elucidate the role and potential mechanism of circUSP42 in sepsis-induced AKI. Methods: HK2 cells were treated with lipopolysaccharide (LPS) to establish septic AKI cell model. The expression levels of circUSP42, microRNA-182-5p (miR-182-5p), and DUSP1 in LPS-treated HK2 cells were measured by quantitative real-time polymerase chain reaction or Western blot. Functional experiments were performed by using Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine staining, flow cytometry, oxidative stress assay, and enzyme-linked immunosorbent assay. The potential target binding site between miR-182-5p and CircUSP42 or DUSP1 was verified by dual-luciferase reporter and RNA immunoprecipitation assays. Results: CircUSP42 and DUSP1 were downregulated in serum samples from patients with AKI and LPS-treated HK2 cells, while miR-182-5p was upregulated. Functionally, overexpression of CircUSP42 promoted cell proliferation and inhibited apoptosis, inflammation, and oxidative stress in LPS-triggered HK2 cells. Further mechanism analysis showed that miR-182-5p had potential binding sites with circUSP42 and DUSP1, and circUSP42 regulated LPS-induced cell damage by targeting miR-182-5p. At the same time, miR-182-5p knockdown inhibited LPS-treated HK2 cell damage by regulating DUSP1. In addition, circUSP42 induced DUSP1 expression via sponging miR-182-5p to ameliorate LPS-induced HK2 cell damage. Conclusion : Our results showed that circUSP42 overexpression might attenuate LPS-induced HK2 cell injury by regulating miR-182-5p/DUSP1 axis. This might provide therapeutic strategy for the treatment of sepsis.

Raised CK and acute kidney injury following intense exercise in three patients with a history of exercise intolerance due to homozygous mutations in SLC2A9

Acute rhabdomyolysis (AR) leading to acute kidney injury has many underlying etiologies, however, when the primary trigger is exercise, the most usual underlying cause is either a genetic muscle disorder or unaccustomed intense exercise in a healthy individual. Three adult men presented with a history of exercise intolerance and episodes of acute renal impairment following intense exercise, thought to be due to AR in the case of two, and dehydration in one. The baseline serum CK was mildly raised between attacks in all three patients and acutely raised during attacks in two of the three patients. Following referral to a specialized neuromuscular centre, further investigation identified very low serum urate (<12 umol/L). In all three men, genetic studies confirmed homozygous mutations in SLC2A9, which encodes for facilitated glucose transporter member 9 (GLUT9), a major regulator of urate homeostasis. Hereditary hypouricaemia should be considered in people presenting with acute kidney injury related to intense exercise. Serum urate evaluation is a useful screening test best undertaken after recovery.

[Effect and mechanism of Jiedu Huoxue Decoction in regulating YAP/ACSL4 pathway to inhibit ferroptosis in treatment of acute kidney injury]

Jiedu Huoxue Decoction(JDHX), first recorded in the Correction on Errors in Medical Works by WANG Qing-ren, is an effective formula screened out from ancient formulas by the traditional Chinese medicine(TCM) master ZHANG Qi to treat acute kidney injury(AKI) caused by heat, toxicity, stasis, and stagnation. This paper elucidated the therapeutic effect of JDHX on AKI and probed into the potential mechanism from ferroptosis. Thirty-two male C57BL/6 mice were randomized into four groups(n=8): normal, model, and low-and high-dose JDHX. Since the clinical treatment of AKI depends on supportive or alternative therapies and there is no specific drug, this study did not include a positive drug group. The low dose of JDHX corresponded to half of clinically equivalent dose, while the high dose corresponded to the clinically equivalent dose. Mice were administrated with JDHX by gavage daily for 7 consecutive days, while those in the normal group and the model group were administered with the corresponding volume of distilled water. On day 5 of drug administration, mice in other groups except the normal group were injected intraperitoneally with cisplatin solution at a dose of 20 mg·kg~(-1) to induce AKI, and the normal group was injected with saline. All of the mice were sacrificed 72 h after modeling, blood and kidney samples were collected for subsequent analysis. The levels of serum creatine(Scr) and blood urea nitrogen(BUN) were measured by the commercial kits. The expression level of kidney injury molecule 1(KIM-1) in the serum was measured by enzyme-linked immunosorbent assay. Hematoxylin-eosin(HE) staining, periodic acid-Schiff(PAS) staining, and Prussian blue staining were employed to observe the pathological changes, glycogen deposition, and iron deposition, respectively, in the renal tissue. In addition, the levels of glutathione(GSH), superoxide dismutase(SOD), and catalase(CAT) in the renal tissue were examined by biochemical colorimetry. Western blot was performed to determine the protein levels of acyl-CoA synthetase long chain family member 4(ACSL4), lysophosphatidylcholine acyltransferase 3(LPCAT3), and Yes-associated protein(YAP, a key molecule in the Hippo pathway) in the renal tissue. Immunohistochemistry was then employed to detect the location and expression of YAP in the renal tissue. Real-time fluorescence quantitative polymerase chain reaction(qRT-PCR) was performed to measure the mRNA levels of ACSL4 and glutathione peroxidase 4(GPX4). Compared with the normal group, the model group showed elevated serum levels of Scr, BUN, and KIM-1. In the AKI model group, the tubular epithelial cells underwent atrophy and necrotic detachment, disappearance of brush border, and some tubules became protein tubules or experienced vacuole-like degeneration. In addition, this group presented widening of the interstitium or even edema, increased renal tubule injury score, and obvious glycogen and iron deposition in parts of the renal tissue. Moreover, the model group had lower GSH, SOD, and CAT levels, higher ASCL4 and LPCAT3 levels, and lower GPX4 expression and higher YAP expression than the normal group. Compared with the model group, high dose of JDHX effectively protected renal function, lowered the levels of Scr, BUN and KIM-1, alleviated renal pathological injury, reduced glycogen and iron deposition, and elevated the GSH, SOD, and CAT levels in the renal tissue. Furthermore, JDHX down-regulated the protein levels of ACSL4, LPCAT3, and YAP and up-regulated the level of GPX4, compared with the model group. In conclusion, JDHX can protect mice from cisplatin-induced AKI by inhibiting ferroptosis via regulating the YAP/ACSL4 signaling pathway.

Sex and Gender Differences in AKI

Sex differences in AKI continue to be identified. Generally, women are protected from AKI when compared to men. Much of the protection exhibited in women is diminished after menopause. These sex and age effects have also been noted in animal models of AKI. Gonadal hormones, as modifiers of incidence, severity, and progression of AKI, have been offered as likely contributors to this sex and age effect. In animal models of AKI, estrogen and testosterone seem to modulate susceptibility. Questions remain however regarding cellular and molecular changes that are initiated by modulation of these hormones because both estrogen and testosterone have effects across cell types that play a role in AKI. Although findings have largely been informed by studies in males, molecular pathways that are involved in the initiation and progression of AKI may be modulated by gonadal hormones. Compounding the hormone-receptor effects are developmental effects of sex chromosomal complement and epigenetic influences that may confer sex-based baseline differences in gene and protein expression, and gene dosage effects of X inactivation and escape on molecular pathways. Elucidation of sex-based protection may afford a more complete view of AKI and potential therapeutic interventions. Furthermore, the effect on susceptibility to AKI in transgender patients, who receive life-altering and essential gender-affirming hormone therapy, requires greater attention. In this review, several potential contributors to the sex differences observed in humans and animal models are discussed.

Arginine-methylated c-Myc affects mitochondrial mitophagy in mouse acute kidney injury via Slc25a24

The transcription factor methylated c-Myc heterodimerizes with MAX to modulate gene expression, and plays an important role in energy metabolism in kidney injury but the exact mechanism remains unclear. Mitochondrial solute transporter Slc25a24 imports ATP into mitochondria and is central to energy metabolism. Gene Expression Omnibus data analysis reveals Slc25a24 and c-Myc are consistently upregulated in all the acute kidney injury (AKI) cells. Pearson correlation analysis also shows that Slc25a24 and c-Myc are strongly correlated (⍴ > 0.9). Mutant arginine methylated c-Myc (R299A and R346A) reduced its combination with MAX when compared with the wild type of c-Myc. On the other hand, the Slc25a24 levels were also correspondingly reduced, which induced the downregulation of ATP production. The results promoted reactive oxygen species (ROS) production and mitophagy generation. The study revealed that the c-Myc overexpression manifested the most pronounced mitochondrial DNA depletion. Additionally, the varied levels of mitochondrial proteins like TIM23, TOM20, and PINK1 in each group, particularly the elevated levels of PINK1 in AKI model groups and lower levels of TIM23 and TOM20 in the c-Myc overexpression group, suggest potential disruptions in mitochondrial dynamics and homeostasis, indicating enhanced mitophagy or mitochondrial loss. Therefore, arginine-methylated c-Myc affects mouse kidney injury by regulating mitochondrial ATP and ROS, and mitophagy via Slc25a24.

APOBEC-1 deletion enhances cisplatin-induced acute kidney injury

Cisplatin (CP) induces acute kidney injury (AKI) whereby proximal tubules undergo regulated necrosis. Repair is almost complete after a single dose. We now demonstrate a role for Apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (Apobec-1) that is prominently expressed at the interface between acute and chronic kidney injury (CKD), in the recovery from AKI. Apobec-1 knockout (KO) mice exhibited greater mortality than in wild type (WT) and more severe AKI in both CP- and unilateral ischemia reperfusion (IR) with nephrectomy. Specifically, plasma creatinine (pCr) 2.6 ± 0.70 mg/dL for KO, n = 10 and 0.16 ± 0.02 for WT, n = 6, p < 0.0001 in CP model and 1.34 ± 0.22 mg/dL vs 0.75 ± 0.06, n = 5, p < 0.05 in IR model. The kidneys of Apobec-1 KO mice showed increased necrosis, increased expression of KIM-1, NGAL, RIPK1, ASCL4 and increased lipid accumulation compared to WT kidneys (p < 0.01). Neutrophils and activated T cells were both increased, while macrophages were reduced in kidneys of Apobec-1 KO animals. Overexpression of Apobec-1 in mouse proximal tubule cells protected against CP-induced cytotoxicity. These findings suggest that Apobec-1 mediates critical pro-survival responses to renal injury and increasing Apobec-1 expression could be an effective strategy to mitigate AKI.

Analysis of the human kidney transcriptome and plasma proteome identifies markers of proximal tubule maladaptation to injury

Acute kidney injury (AKI) is a major risk factor for long-term adverse outcomes, including chronic kidney disease. In mouse models of AKI, maladaptive repair of the injured proximal tubule (PT) prevents complete tissue recovery. However, evidence for PT maladaptation and its etiological relationship with complications of AKI is lacking in humans. We performed single-nucleus RNA sequencing of 120,985 nuclei in kidneys from 17 participants with AKI and seven healthy controls from the Kidney Precision Medicine Project. Maladaptive PT cells, which exhibited transcriptomic features of dedifferentiation and enrichment in pro-inflammatory and profibrotic pathways, were present in participants with AKI of diverse etiologies. To develop plasma markers of PT maladaptation, we analyzed the plasma proteome in two independent cohorts of patients undergoing cardiac surgery and a cohort of marathon runners, linked it to the transcriptomic signatures associated with maladaptive PT, and identified nine proteins whose genes were specifically up- or down-regulated by maladaptive PT. After cardiac surgery, both cohorts of patients had increased transforming growth factor-β2 (TGFB2), collagen type XXIII-α1 (COL23A1), and X-linked neuroligin 4 (NLGN4X) and had decreased plasminogen (PLG), ectonucleotide pyrophosphatase/phosphodiesterase 6 (ENPP6), and protein C (PROC). Similar changes were observed in marathon runners with exercise-associated kidney injury. Postoperative changes in these markers were associated with AKI progression in adults after cardiac surgery and post-AKI kidney atrophy in mouse models of ischemia-reperfusion injury and toxic injury. Our results demonstrate the feasibility of a multiomics approach to discovering noninvasive markers and associating PT maladaptation with adverse clinical outcomes.

Acute kidney injury interacts with VKORC1 genotype on initiative warfarin dose among heart surgery recipients: a real-world research

Patients who receive heart valve surgery need anticoagulation prophylaxis to reduce the risk of thrombosis. Warfarin often is a choice but its dosage varies due to gene and clinical factors. We aim to study, among them, if there is an interaction between acute kidney injury and two gene polymorphisms from this study. We extracted data of heart valve surgery recipients from the electronic health record (EHR) system of a medical center. The primary outcome is about the average daily dose of warfarin, measured as an additive interaction effect (INTadd) between acute kidney injury (AKI) and warfarin-related gene polymorphisms. The confounders, including age, sex, body surface area (BSA), comorbidities (i.e., atrial fibrillation [AF], hypertension [HTN], congestive heart failure [CHF]), serum albumin level, warfarin-relevant gene polymorphism (i.e., CYP2C9, VKORC1), prosthetic valve type (i.e., metal, bio), and warfarin history were controlled via a multivariate-linear regression model. The study included 200 patients, among whom 108 (54.00%) are female. Further, the mean age is 54.45 years, 31 (15.50%) have CHF, and 40 (20.00%) patients were prescribed concomitant amiodarone, which potentially overlays with the warfarin prophylaxis period. During the follow-up, AKI occurred in 30 (15.00%) patients. VKORC1 mutation (1639G>A) occurred in 25 (12.50%) patients and CYPC29 *2 or *3 mutations presented in 20 patients (10.00%). We found a significant additive interaction effect between AKI and VKORC1 (- 1.17, 95% CI - 1.82 to - 0.53, p = 0.0004). This result suggests it is probable that there is an interaction between acute kidney injury and the VKORC1 polymorphism for the warfarin dose during the initial period of anticoagulation prophylaxis.