A promising application of kidney-specific cell-free DNA methylation markers in real-time monitoring sepsis-induced acute kidney injury.

Sepsis-induced acute kidney injury (SI-AKI) is a common clinical syndrome that is associated with high mortality and morbidity. Effective timely detection may improve the outcome of SI-AKI. Kidney-derived cell-free DNA (cfDNA) may provide new insight into understanding and identifying SI-AKI. Plasma cfDNA from 82 healthy individuals, 7 patients with sepsis non-acute kidney injury (SN-AKI), and 9 patients with SI-AKI was subjected to genomic methylation sequencing. We deconstructed the relative contribution of cfDNA from different cell types based on cell-specific methylation markers and focused on exploring the association between kidney-derived cfDNA and SI-AKI.Based on the deconvolution of the cfDNA methylome: SI-AKI patients displayed the elevated cfDNA concentrations with an increased contribution of kidney epithelial cells (kidney-Ep) DNA; kidney-Ep derived cfDNA achieved high accuracy in distinguishing SI-AKI from SN-AKI (AUC = 0.92, 95% CI 0.7801-1); the higher kidney-ep cfDNA concentrations tended to correlate with more advanced stages of SI-AKI; strikingly, SN-AKI patients with potential kidney damage unmet by SI-AKI criteria showed higher levels of kidney-Ep derived cfDNA than healthy individuals. The autonomous screening of kidney-Ep (n = 24) and kidney endothelial (kidney-Endo, n = 12) specific methylation markers indicated the unique identity of kidney-Ep/kidney-Endo compared with other cell types, and its targeted assessment reproduced the main findings of the deconvolution of the cfDNA methylome. Our study first demonstrates that kidney-Ep- and kidney-Endo-specific methylation markers can serve as a novel marker for SI-AKI emergence, supporting further exploration of the utility of kidney-specific cfDNA methylation markers in the study of SI-AKI.

EP300-mediated H3 acetylation elevates MTHFD2 expression to reduce mitochondrial dysfunction in lipopolysaccharide-induced tubular epithelial cells.

Sepsis represents an organ dysfunction resulting from the host's maladjusted response to infection, and can give rise to acute kidney injury (AKI), which significantly increase the morbidity and mortality of septic patients. This study strived for identifying a novel therapeutic strategy for patients with sepsis-induced AKI (SI-AKI). Rat tubular epithelial NRK-52E cells were subjected to lipopolysaccharide (LPS) exposure for induction of in-vitro SI-AKI. The expressions of E1A binding protein p300 (EP300) and methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) in NRK-52E cells were assessed by western blot and qRT-PCR, and their interaction was explored by chromatin immunoprecipitation performed with antibody for H3K27 acetylation (H3K27ac). The effect of them on SI-AKI-associated mitochondrial dysfunction of tubular epithelial cells was investigated using transfection, MTT assay, TUNEL staining, 2',7'-Dichlorodihydrofluorescein diacetate probe assay, Mitosox assay, and JC-1 staining. MTHFD2 and EP300 were upregulated by LPS exposure in NRK-52E cells. LPS increased the acetylation of H3 histone in the MTHFD2 promoter region, and EP300 suppressed the effect of LPS. EP300 ablation inhibited the expression of MTHFD2. MTHFD2 overexpression antagonized LPS-induced viability reduction, apoptosis promotion, reactive oxygen species overproduction, and mitochondrial membrane potential collapse of NRK-52E cells. By contrast, MTHFD2 knockdown and EP300 ablation brought about opposite consequences. Furthermore, MTHFD2 overexpress and EP300 ablation counteracted each other's effect in LPS-exposed NRK-52E cells. EP300-mediated H3 acetylation elevates MTHFD2 expression to reduce mitochondrial dysfunction of tubular epithelial cells in SI-AKI.

Morin attenuates sepsis-induced acute kidney injury by regulating inflammatory responses, oxidative stress and tubular regeneration (morin and sepsis-induced acute kidney injury).

Sepsis-associated acute kidney injury (AKI) is a health complication, encompassing excessive inflammatory response, oxidative stress, and tubular necrosis; leading to kidney failure and death. Sepsis treatments are nonspecific and palliative. In this study, we evaluated the effect of morin, a flavonoid with known nephroprotective capabilities, on sepsis-induced AKI by dividing eighty male mice into: normal, morin-treated, septic, and septic mice treated with morin. Half of the groups were sacrified 3 days post sepsis induction, while the rest was sacrified on the 7th day. Treating septic mice with morin resulted in the amelioration of sepsis-associated pathophysiological renal alterations and the increase of the survival and recovery rates compared with those of septic control group. These findings indicate that morin has a therapeutic effect against sepsis-associated AKI via its anti-inflammatory, antioxidant and regenerative effects. Thus, it could be used as potential pharmacological intervention for preventing renal complications of sepsis.

FOXQ1, deubiquitinated by USP10, alleviates sepsis-induced acute kidney injury by targeting the CREB5/NF-κB signaling axis.

Sepsis-induced acute kidney injury (S-AKI) is a severe and frequent complication that occurs during sepsis. This study aimed to understand the role of FOXQ1 in S-AKI and its potential upstream and downstream regulatory mechanisms. A cecal ligation and puncture induced S-AKI mouse model in vivo and an LPS-induced HK-2 cell model in vitro were used. FOXQ1 was significantly upregulated in CLP mice and downregulated in the LPS-induced HK-2 cells. Upregulation of FOXQ1 improved kidney injury and dysfunction in CLP mice. Overexpression of FOXQ1 remarkably suppressed the apoptosis and inflammatory response via down-regulating oxidative stress indicators and pro-inflammatory factors (IL-1ß, IL-6, and TNF-α), both in vivo and in vitro. From online analysis, the CREB5/NF-κB axis was identified as the downstream target of FOXQ1. FOXQ1 transcriptionally activated CREB5, upregulating its expression. Overexpression of FOXQ1 suppressed the phosphorylation level and nucleus transport of p65. Rescue experiments showed that CREB5 mediates the protective role of FOXQ1 on S-AKI. Furthermore, FOXQ1 was identified as a substrate of USP10, a deubiquitinating enzyme. Ectopic expression of USP10 reduced the ubiquitination of FOXQ1, promoting its protein stability. USP10 upregulation alleviated LPS-induced cell apoptosis and inflammatory response, while suppression of FOXQ1 augmented these trends. Collectively, our results suggest that FOXQ1, deubiquitinated by USP10, plays a protective role in S-AKI induced inflammation and apoptosis by targeting CREB5/NF-κB axis.

Usp9x contributes to the development of sepsis-induced acute kidney injury by promoting inflammation and apoptosis in renal tubular epithelial cells via activation of the TLR4/nf-κb pathway.

As a pattern recognition receptor, Toll-like receptor 4 (TLR4) is crucial for the development and progression of acute kidney injury (AKI). This study aims to explore whether the deubiquitinase Usp9x influences the TLR4/NF-B pathway to cause sepsis-induced acute kidney injury (S-AKI). The model of AKI was established in Sprague-Dawley rats using the cecal ligation and puncture (CLP) method, while renal tubular epithelial cell NRK-52E was stimulated with lipopolysaccharide (LPS) in vitro. All plasmids were transfected into NRK-52E cells according to the indicated group. The deubiquitinase of TLR4 was predicted by the online prediction software Ubibrowser. Subsequently, Western blot and Pearson correlation analysis identified Usp9x protein as a potential candidate. Co-IP analysis verified the interaction between TLR4 and Usp9x. Further research revealed that overexpression of Usp9x inhibited degradation of TLR4 protein by downregulating its ubiquitination modification levels. Both in vivo and in vitro experiments observed that interference with Usp9x effectively alleviated the inflammatory response and apoptosis of renal tubular epithelial cells (RTECs) induced by CLP or LPS, whereas overexpression of TLR4 reversed this situation. Transfection with sh-Usp9x in NRK-52E cells suppressed the expression of proteins associated with the TLR4/NF-κB pathway induced by LPS. Moreover, the overexpression of TLR4 reversed the effect of sh-Usp9x transfection. Therefore, the deubiquitinase Usp9x interacts with TLR4, leading to the upregulation of its expression through deubiquitination modification, and the activation of the TLR4/NF-κB signaling pathway, thereby promoting inflammation and apoptosis in renal tubular epithelial cells and contributing to sepsis-induced acute kidney injury.

MicroRNA­17­5p alleviates sepsis­related acute kidney injury in mice by modulating inflammation and apoptosis.

Septic acute kidney injury (AKI) is considered as a severe and frequent complication that occurs during sepsis. Mounting evidence has confirmed the pivotal pathogenetic roles of microRNA (miRNA or miR) in sepsis­induced AKI; however, the role of miRNAs and their underlying mechanisms in sepsis­induced AKI have not been entirely understood. The present study aimed to elucidate the functions of special miRNAs during sepsis­induced AKI and its underlying mechanism. First, a number of differently expressed miRNAs was identified based on the microarray dataset GSE172044. Subsequently, lipopolysaccharide (LPS) was used to induce AKI in mice, and the role of miR­17­5p on AKI was clarified. Finally, the related molecular mechanisms were further examined by western blotting and immunohistochemical analysis. MiR­17­5p was found to be continuously decreased and reached the bottom at h 24 after AKI in mice. Functionally, injection of agomiR­17­5p could observably improve renal injury and survival rate, as well as inhibit inflammatory cytokine production and renal cell apoptosis in mice after AKI. On the contrary, injection of antagomiR­17­5p aggravated LPS­induced renal injury, inflammation and apoptosis in mice after AKI. Moreover, transforming growth factor ß receptor 2 (TGFßR2) was identified as a direct target of miR­17­5p, and its downstream phosphorylated Smad3 was also suppressed by miR­17­5p upregulation. Taken together, these results demonstrated that miR­17­5p overexpression may exhibit a beneficial effect by attenuating LPS­induced inflammation and apoptosis via regulating the TGFßR2/TGF­ß/Smad3 signaling pathway, indicating that miR­17­5p could act as a potential target for sepsis treatment.

Acute Kidney Injury in Sepsis.

Sepsis-associated kidney injury is common in critically ill patients and significantly increases morbidity and mortality rates. Several complex pathophysiological factors contribute to its presentation and perpetuation, including macrocirculatory and microcirculatory changes, mitochondrial dysfunction, and metabolic reprogramming. Recovery from acute kidney injury (AKI) relies on the evolution towards adaptive mechanisms such as endothelial repair and tubular cell regeneration, while maladaptive repair increases the risk of progression to chronic kidney disease. Fundamental management strategies include early sepsis recognition and prompt treatment, through the administration of adequate antimicrobial agents, fluid resuscitation, and vasoactive agents as needed. In septic patients, organ-specific support is often required, particularly renal replacement therapy (RRT) in the setting of severe AKI, although ongoing debates persist regarding the ideal timing of initiation and dosing of RRT. A comprehensive approach integrating early recognition, targeted interventions, and close monitoring is essential to mitigate the burden of SA-AKI and improve patient outcomes in critical care settings.

Zn2+ improves sepsis-induced acute kidney injury by upregulating SIRT7-mediated Parkin acetylation.

Zn2+ levels are reported to be correlated with kidney function. We explored the significance of Zn2+ in sepsis-induced acute kidney injury (SI-AKI) through the regulation of sirtuin 7 (SIRT7) activity. The sepsis rat model was established by cecal ligation and perforation (CLP) and intraperitoneally injected with ZnSO4 or SIRT7 inhibitor 97491 (SIRT7i), with renal tubular injury assessed by hematoxylin and eosin staining. In vitro, human renal tubular epithelial cells (HK-2) were induced with lipopolysaccharide to obtain a renal injury cell model, followed by ZnSO4 or SIRT7i and autophagy inhibitor (3-methyladenine) treatment. Interleukin (IL)-1ß, IL-18, reactive oxygen species (ROS), Parkin acetylation level, kidney injury molecule-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) expression levels were determined. The renal tubule injury, inflammation condition, and pyroptosis-related and autophagy-related protein levels were assessed. The pyroptosis in kidney tissues and autophagosome formation were observed by transmission electron microscopy. Zn2+ alleviated renal injury in CLP rats and inhibited pyroptosis and its related protein levels by inhibiting SIRT7 activity in septic rat renal tissues. In vitro, Zn2+ increased HK-2 cell viability and reduced KIM-1, NGAL, IL-1ß, IL-18, NLRP3 inflammasome, cleaved caspase-1, gasdermin D-N levels, and pyroptotic cell number. Zn2+ increased autophagosome number and LC3BII/LC3BI ratio and decreased TOM20, TIM23, P62, and mitochondrial ROS levels. Zn2+ increased Parkin acetylation by repressing SIRT7 activity. Inhibiting mitophagy partially averted Zn2+-inhibited NLRP3 inflammasome activation and apoptosis in HK-2 cells. Zn2+ upregulated Parkin acetylation by repressing SIRT7 activity to promote mitophagy and inhibit NLRP3 inflammasome activation and pyroptosis, thus improving SI-AKI.NEW & NOTEWORTHY Zn2+ upregulated Parkin acetylation by repressing sirtuin 7 activity to promote mitophagy and inhibit NLRP3 inflammasome activation and pyroptosis, thus improving sepsis-induced acute kidney injury.

Eriocitrin prevents Sepsis-induced acute kidney injury through anti-inflammation and anti-oxidation via modulating Nrf2/DRP1/OPA1 signaling pathway.

BACKGROUND: Severe inflammation and oxidative stress are characteristics of sepsis-associated kidney injury with high morbidity and mortality. Eriocitrin (ERI) has shown promise in suppressing sepsis-associated kidney injury and LPS-induced periodontal disease, however, its efficacy in alleviating SAKI remains unexplored. This study aimed to investigate the therapeutic potential of ERI on SAKI through in vivo and in vitro experiments, elucidating its underlying mechanism. METHODS: The therapeutic effects of ERI against SAKI were evaluated by survival rate, changes of serum creatinine (Scr) and blood urea nitrogen (BUN) and statistic of renal histological score in a Cecal ligation and puncture (CLP)-induced septic mice. Impactions about anti-coagulation, anti-inflammation, anti-oxidative stress and improvement of mitochondrial damage and mitochondrial morphology were further assayed. In vitro, HUVECs upon stimulation of LPS with or without different dosage of ERI, followed by evaluating changes in inflammation, mitochondrial dynamic equilibrium and signaling pathways. RESULTS: ERI demonstrated ameliorative effects on SAKI by attenuating inflammation, oxidative stress and coagulation evidenced by the improved survival rate, alleviated kidney histological injury, declined BUN and Scr in serum and diminished levels of inflammation cytokines, and coagulation factors. Mechanistically, ERI suppressed DRP1-regulated mitochondrial fission and promoted OPA1-modulated mitochondrial fusion by activating Nrf2 in septic mice and LPS-stimulated HUVECs, which maintained mitochondrial dynamic equilibrium, improved mitochondrial morphology, assured integrity of mitochondrial function, decreased oxidative stress, impeded overwhelming inflammation, and thus, played a pivotal role in ERI's protection against SAKI. CONCLUSION: Our data confirmed the therapeutic potential of ERI in mitigating SAKI，suggesting its viability as a pharmacological agent in clinic settings.

Fibroblastic reticular cell-derived exosomes are a promising therapeutic approach for septic acute kidney injury.

Sepsis-induced acute kidney injury (S-AKI) is highly lethal, and effective drugs for treatment are scarce. Previously, we reported the robust therapeutic efficacy of fibroblastic reticular cells (FRCs) in sepsis. Here, we demonstrate the ability of FRC-derived exosomes (FRC-Exos) to improve C57BL/6 mouse kidney function following cecal ligation and puncture-induced sepsis. In vivo imaging confirmed that FRC-Exos homed to injured kidneys. RNA-Seq analysis of FRC-Exo-treated primary kidney tubular cells (PKTCs) revealed that FRC-Exos influenced PKTC fate in the presence of lipopolysaccharide (LPS). FRC-Exos promoted kinase PINK1-dependent mitophagy and inhibited NLRP3 inflammasome activation in LPS-stimulated PKTCs. To dissect the mechanism underlying the protective role of Exos in S-AKI, we examined the proteins within Exos by mass spectrometry and found that CD5L was the most upregulated protein in FRC-Exos compared to macrophage-derived Exos. Recombinant CD5L treatment in vitro attenuated kidney cell swelling and surface bubble formation after LPS stimulation. FRCs were infected with a CD5L lentivirus to increase CD5L levels in FRC-Exos, which were then modified in vitro with the kidney tubular cell targeting peptide LTH, a peptide that binds to the biomarker protein kidney injury molecule-1 expressed on injured tubule cells, to enhance binding specificity. Compared with an equivalent dose of recombinant CD5L, the modified CD5L-enriched FRC-Exos selectively bound PKTCs, promoted kinase PINK-ubiquitin ligase Parkin-mediated mitophagy, inhibiting pyroptosis and improved kidney function by hindering NLRP3 inflammasome activation, thereby improving the sepsis survival rate. Thus, strategies to modify FRC-Exos could be a new avenue in developing therapeutics against kidney injury.

CircRNA itchy E3 ubiquitin protein ligase improves mitochondrial dysfunction in sepsis-induced acute kidney injury by targeting microRNA-214-3p/ATP-binding cassette A1 axis.

BACKGROUND: Circular RNAs (circRNAs) are promising biomarkers and therapeutic targets for acute kidney injury (AKI). In this study, we investigated the mechanism by which circRNA itchy E3 ubiquitin protein ligase (circ-ITCH) regulates sepsis-induced AKI. METHODS: A sepsis-induced AKI mouse model was created using LPS induction and circ-ITCH overexpression. Circ-ITCH levels were confirmed via RT-qPCR. Kidney tissue changes were examined through various stains and TUNEL. Enzyme-linked immunosorbent assay (ELISA) gauged oxidative stress and inflammation. Mitochondrial features were studied with electron microscopy. RT-qPCR and western blotting assessed mitochondrial function parameters. Using starBase, binding sites between circ-ITCH and miR-214-3p, as well as miR-214-3p and ABCA1, were predicted. Regulatory connections were proven by dual-luciferase assay, RT-qPCR, and western blotting. RESULTS: Circ-ITCH expression was downregulated in LPS-induced sepsis mice. Overexpression of circ-ITCH ameliorates indicators of renal function (serum creatinine [SCr], blood urea nitrogen [BUN], neutrophil gelatinase-associated lipocalin [NGAL], and kidney injury molecule-1 [Kim-1]), reduces renal cell apoptosis, mitigates oxidative stress markers (reactive oxygen species [ROS] and malondialdehyde [MDA]), and diminishes inflammatory markers (interleukin [IL]-1ß, IL-6, and tumor necrosis factor [TNF-α]). Moreover, circ-ITCH overexpression alleviated mitochondrial damage and dysfunction. Furthermore, circ-ITCH acts as a sponge for miR-214-3p, thereby upregulating ABCA1 expression. In addition, the miR-214-3p inhibitor repressed oxidative stress, inflammation, and mitochondrial dysfunction, which was reversed by circ-ITCH knockdown. Further cellular analysis in HK-2 cells supported these findings, highlighting the protective role of circ-ITCH against sepsis-induced AKI, particularly through the miR-214-3p/ABCA1 axis. CONCLUSION: The novel circ-ITCH/miR-214-3p/ABCA1 pathway plays an essential role in the regulation of oxidative stress and mitochondrial dysfunction in sepsis-induced AKI.

Red blood cell distribution width improves the prediction of 28-day mortality for patients with sepsis-induced acute kidney injury: A retrospective analysis from MIMIC-IV database using propensity score matching.

Background: The predictive value of red blood cell distribution width (RDW) for mortality in patients with sepsis-induced acute kidney injury (SI-AKI) remains unclear. The present study aimed to investigate the potential association between RDW at admission and outcomes in patients with SI-AKI. Methods: The Medical Information Mart for Intensive Care (MIMIC)-IV (version 2.0) database, released in June of 2022, provides medical data of SI-AKI patients to conduct our related research. Based on propensity score matching (PSM) method, the main risk factors associated with mortality in SI-AKI were evaluated using Cox proportional hazards regression analysis to construct a predictive nomogram. The concordance index (C-index) and decision curve analysis were used to validate the predictive ability and clinical utility of this model. Patients with SI-AKI were classified into the high- and low-RDW groups according to the best cut-off value obtained by calculating the maximum value of the Youden index. Results: A total of 7574 patients with SI-AKI were identified according to the filter criteria. Compared with the low-RDW group, the high-RDW group had higher 28-day (9.49% vs. 31.40%, respectively, P <0.001) and 7-day (3.96% vs. 13.93%, respectively, P <0.001) mortality rates. Patients in the high-RDW group were more prone to AKI progression than those in the low-RDW group (20.80% vs. 13.60%, respectively, P <0.001). Based on matched patients, we developed a nomogram model that included age, white blood cells, RDW, combined hypertension and presence of a malignant tumor, treatment with vasopressor, dialysis, and invasive ventilation, sequential organ failure assessment, and AKI stages. The C-index for predicting the probability of 28-day survival was 0.799. Decision curve analysis revealed that the model with RDW offered greater net benefit than that without RDW. Conclusion: The present findings demonstrated the importance of RDW, which improved the predictive ability of the nomogram model for the probability of survival in patients with SI-AKI.

The potential biomarker TIFA regulates pyroptosis in sepsis-induced acute kidney injury.

Sepsis is the leading cause of acute kidney injury (AKI), and specific treatment options for septic AKI are very limited. Here, we used bulk RNA sequencing of a septic model of AKI to characterize the mRNA profile during AKI. The differentially expressed genes (DEGs) mainly participate in the inflammatory response and metabolic processes. Analysis of comprehensive mRNA-seq datasets revealed sepsis-induced AKI-specific cohorts of expressed genes, and six DEGs were tested in urine from septic patients with/without AKI. TRAF-interacting protein with forkhead-associated domain (TIFA) and fatty acid synthase (FASN) were differentially expressed in the urine from the sepsis-induced AKI group. Furthermore, we found that TIFA expression was significantly upregulated in mouse kidney tissue following cecal ligation and puncture (CLP). We sought to investigate its role in lipopolysaccharide (LPS) (TLR4 ligand)- and oligodeoxynucleotides (ODN) (TLR9 ligand)-treated human kidney cells and mouse. TIFA was located in Lotus tetragonolobus lectin (LTL) positive renal cells in kidney tissue, which was stained by immunofluorescence. Exposure of HK-2 cells to LPS and ODN caused disruption of the mitochondrial transmembrane potential. The results of transmission electron microscope (TEM) showed that mitochondrial damages were improved in TIFA-knockdown group. Moreover, knockdown of TIFA resulted in a decrease in the percentage of annexin V-positive and PI-negative cells after ODN treatment. The protein of NLRP3, Caspase-1 and GSDMD were also decreased when si-TIFA was transferred into HK-2 cells following LPS and ODN treatment. Activation of TIFA enhanced the expression of IL-1ß and IL18. These results indicated that TIFA induced pyroptosis by activating the mitochondrial damage. Our study provides a detailed transcriptomic description of the renal cellular responses after sepsis. Our study suggest that TIFA is involved in pyroptosis by activating the mitochondrial damage and may be a therapeutic target to treat sepsis-induced kidney injury.

Resolvin D1 attenuates sepsis induced acute kidney injury targeting mitochondria and NF-κB signaling pathway.

Background: Acute kidney injury is a highly common and multifactorial renal disease resulting in significant morbidity and mortality, especially sepsis-induced acute kidney injury. There is no effective therapy available to treat or prevent sepsis-induced acute kidney injury. One of the specialized pro-resolving mediators, Resolvin D1 exhibits special anti-inflammatory effects in several inflammatory disease models, but there is little evidence about the effect and mechanism of Resolvin D1 in sepsis-induced acute kidney injury. Methods: We conducted experiments to explore the effect and mechanism of Resolvin D1 in sepsis-induced acute kidney injury. In vitro, human proximal tubular epithelial cells were used to test the apoptosis ratio, cell viability and reactive oxygen species level. In vivo, C57BL/6 mice were injected with lipopolysaccharide to establish a sepsis-induced acute kidney injury model. Renal function and structure, apoptosis ratio of kidney cells, mitochondrial structure and function and related protein and gene levels were assessed. Results: In vitro, the resolvin D1-treated group showed higher cell viability and lower reactive oxygen species levels and apoptosis ratios than the LPS group. In vivo, Resolvin D1 can not only improve renal function and mitochondrial function but also reduce the apoptosis ratio, while mediating mitochondrial dynamics and inhibiting NF-κB pathway. Conclusions: Resolvin D1 has a good renoprotective effect by maintaining mitochondrial dynamics and inhibiting the NF-κB pathway.

Kynurenine Pathway-An Underestimated Factor Modulating Innate Immunity in Sepsis-Induced Acute Kidney Injury?

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and it accounts for about half of the cases of acute kidney injury (AKI). Although sepsis is the most frequent cause of AKI in critically ill patients, its pathophysiological mechanisms are not well understood. Sepsis has the ability to modulate the function of cells belonging to the innate immune system. Increased activity of indoleamine 2,3-dioxygenase 1 (IDO1) and production of kynurenines are the major metabolic pathways utilized by innate immunity cells to maintain immunological tolerance. The activation of the kynurenine pathway (KP) plays a dual role in sepsis-in the early stage, the induction of IDO1 elicits strong proinflammatory effects that may lead to tissue damage and septic shock. Afterwards, depletion of tryptophan and production of kynurenines contribute to the development of immunosuppression that may cause the inability to overpower opportunistic infections. The presented review provides available data on the various interdependencies between elements of innate immunity and sepsis-induced AKI (SAKI) with particular emphasis on the immunomodulatory significance of KP in the above processes. We believe that KP activation may be one of the crucial, though underestimated, components of a deregulated host response to infection during SAKI.

USF2 knockdown downregulates THBS1 to inhibit the TGF-ß signaling pathway and reduce pyroptosis in sepsis-induced acute kidney injury.

OBJECTIVE: Acute kidney injury (AKI) is a serious complication of sepsis. This study was performed to explore the mechanism that THBS1 mediated pyroptosis by regulating the TGF-ß signaling pathway in sepsis-induced AKI. METHODS: Gene expression microarray related to sepsis-induced AKI was obtained from the GEO database, and the mechanism in sepsis-induced AKI was predicted by bioinformatics analysis. qRT-PCR and ELISA were performed to detect expressions of THBS1, USF2, TNF-α, IL-1ß, and IL-18 in sepsis-induced AKI patients and healthy volunteers. The mouse model of sepsis-induced AKI was established, with serum creatinine, urea nitrogen, 24-h urine output measured, and renal tissue lesions observed by HE staining. The cell model of sepsis-induced AKI was cultured in vitro, with expressions of TNF-α, IL-1ß, and IL-18, pyroptosis, Caspase-1 and GSDMD-N, and activation of TGF-ß/Smad3 pathway detected. The upstream transcription factor USF2 was knocked down in cells to explore its effect on sepsis-induced AKI. RESULTS: THBS1 and USF2 were highly expressed in patients with sepsis-induced AKI. Silencing THBS1 protected mice against sepsis-induced AKI, and significantly decreased the expressions of NLRP3, Caspase-1, GSDMD-N, IL-1ß, and IL-18, increased cell viability, and decreased LDH activity, thus partially reversing the changes in cell morphology. Mechanistically, USF2 promoted oxidative stress responses by transcriptionally activating THBS1 to activate the TGF-ß/Smad3/NLRP3/Caspase-1 signaling pathway and stimulate pyroptosis, and finally exacerbated sepsis-induced AKI. CONCLUSION: USF2 knockdown downregulates THBS1 to inhibit the TGF-ß/Smad3 signaling pathway and reduce pyroptosis and further ameliorate sepsis-induced AKI.

Roflumilast improves resolution of sepsis-induced acute kidney injury by retarding late phase renal interstitial immune cells infiltration and leakage in urinary sediments.

Some evidence has demonstrated that both inflammation and immune cell dysregulation are coincident at late phase (post 24 h) of sepsis. The present study was designed to determine the pathological role of hyperinflammation and renal immune cells mobilization during late phase of sepsis induced acute kidney injury (S-AKI) and tests the pharmacological effects of PDE-4 inhibitor on these events. Sepsis was induced by cecal ligation puncture and renal function, oxidative-inflammatory stress biomarkers were assessed after 24 h. PDE-4 inhibitor was administered for 7 days prior to induction of S-AKI. Renal immune cells infiltration during sepsis was analyzed by H&E staining and papanicolaou staining method was used for detecting leukocytes and cast in urinary sediments, periodic acid schiff (PAS) staining was used for detection of brush border loss. AKI developed 24 h post sepsis insult as depicted by increase in serum creatinine, blood urea nitrogen (BUN), renal oxidative stress, and elevated inflammatory biomarkers levels. Moreover, septic rats displayed increased bacterial load, renal expression of phosphodiesterase-4B, 4D isoforms, enhanced vascular permeability, caspase-3 and myeloperoxidase activity, electrolyte imbalance, reduced Na+ K+ ATPase activity, declined cAMP levels, increased interstitial leukocyte infiltration, and leakage in urinary sediments along with histological alterations. Pre-treatment with roflumilast at high dose completely prevented the various AKI associated manifestations in septic rats. Renal hyper-inflammation and leukocyte infiltration was detected in late phase of S-AKI. Roflumilast pre-treatment resolved sepsis induced renal dysfunction and histological damage by suppressing late phase renal immune cells invasion and anti-inflammatory effects mediated by up-regulation of renal cAMP levels.

Effect of miR-132-3p on sepsis-induced acute kidney injury in mice via regulating HAVCR1/KIM-1.

OBJECTIVE: To investigate the effect of miR-132-3p and HAVCR1/kidney injury molecule (KIM)-1 on sepsis-induced acute kidney injury (AKI) in mice. METHODS: One hundred C57BL/6 mice were divided into five groups with 20 mice in each group: the normal group (normal mice), the model group (mice with sepsis), the miR-132-3p mimic group (miR-132-3p overexpression), the oe-HAVCR1/KIM-1 group (HAVCR1/KIM-1 overexpression), and the miR-132-3p mimic + oe-HAVCR1/KIM-1 group. Dual-luciferase reporter assay was performed to verify the targeting relationship between miR-132-3p and HAVCR1/KIM-1. The expressions of miR-132-3p and HAVCR1/KIM-1 in mice' kidneys, the levels of renal function markers, the expressions of apoptosis-associated proteins, the renal cell apoptosis rate, and the inflammatory factors in serum were all examined. RESULTS: We found that miR-132-3p can target HAVCR1/KIM-1 and regulate its expression. Compared with the normal mice, the septic mice exhibited lower miR-132-3p level and higher HAVCR1/KIM-1 level (both P<0.05). Moreover, the septic mice had higher levels of cleaved caspase-3, Bax, blood urea nitrogen, creatinine, tumor necrosis factor-α, interleukin-1ß, and interleukin-6, higher renal cell apoptosis rate, and lower Bcl-2 level than the normal mice (all P<0.05). MiR-132-3p overexpression could improve the renal function of the mice with sepsis and inhibit renal cell apoptosis and inflammatory progression, whereas HAVCR1/KIM1 overexpression exhibited an opposite effect and could block the renal protective effects of miR-132-3p overexpression on the septic mice. CONCLUSION: MiR-132-3p overexpression can inhibit renal cell apoptosis and inflammatory progression via suppressing HAVCR1/KIM-1 expression, thereby exert renal protective effects on mice with sepsis.

Bone Marrow-Derived Mesenchymal Stem Cells Ameliorate Sepsis-Induced Acute Kidney Injury by Promoting Mitophagy of Renal Tubular Epithelial Cells via the SIRT1/Parkin Axis.

Sepsis is a common risk factor for acute kidney injury (AKI). Bone marrow-derived mesenchymal stem cells (BMSCs) bear multi-directional differentiation potential. This study explored the role of BMSCs in sepsis-induced AKI (SI-AKI). A rat model of SI-AKI was established through cecal ligation and perforation. The SI-AKI rats were injected with CM-DiL-labeled BMSCs, followed by evaluation of pathological injury of kidney tissues and kidney injury-related indicators and inflammatory factors. HK-2 cells were treated with lipopolysaccharide (LPS) to establish SI-SKI model in vitro. Levels of mitochondrial proteins, autophagy-related proteins, NLRP3 inflammasome-related protein, and expressions of Parkin and SIRT1 in renal tubular epithelial cells (RTECs) of kidney tissues and HK-2 cells were detected. The results showed that BMSCs could reach rat kidney tissues and alleviate pathological injury of SI-SKI rats. BMSCs inhibited inflammation and promoted mitophagy of RTECs and HK-2 cells in rats with SI-AKI. BMSCs upregulated expressions of Parkin and SIRT1 in HK-2 cells. Parkin silencing or SIRT1 inhibitor reversed the promoting effect of BMSCs on mitophagy. BMSCs inhibited apoptosis and pyroptosis of RTECs in kidney tissues by upregulating SIRT1/Parkin. In conclusion, BMSCs promoted mitophagy and inhibited apoptosis and pyroptosis of RTECs in kidney tissues by upregulating SIRT1/Parkin, thereby ameliorating SI-AKI.

Efficacy and prognosis of continuous renal replacement therapy at different times in the treatment of patients with sepsis-induced acute kidney injury.

OBJECTIVE: To investigate the efficacy and prognosis of CRRT at different times in the treatment of sepsis-induced acute kidney injury (SAKI). METHODS: A total of 156 patients with SAKI were grouped into two groups in accordance with a random number table, with 78 patients in each group. Patients in the observation group (OG) were treated with early CRRT, and in the control group (CG), patients were treated with delayed CRRT. According to whether the patients died, there were 51 cases in the death group and 105 in the survival group. Renal function and inflammatory factors were compared before and after treatment; univariate and multilateral comparison were conducted to analyze the survival status of the patients. RESULTS: After treatment, the blood urea nitrogen (BUN) and serum creatinine (Scr) in both groups fell below those prior to treatment, while the estimated glomerular filtration rate (eGFR) was elevated (P<0.01); the decrease of BUN and Scr in the OG was greater than that of the other group, while increase eGFR was more than that the other group (P<0.01). After treatment, C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in both groups decreased compared to that prior to treatment (P<0.001); the decrease of the three factors in the OG was greater than that in the CG (P<0.05). The 60-day survival rate of patients in the OG was 76.92%, which was higher that of 57.69% in the CG (P<0.05). The age, acute physiology and chronic health enquiry (APACHE-II) score and proportion of chronic obstructive pulmonary disease (COPD) in the death group was elevated compared to those in the survival group, while the number of patients with early CRRT and eGFR level before treatment were lower than those in the survival group (P<0.05). Age was an independent risk factor for the prognosis of SAKI, and early CRRT was a protective factor for the prognosis (P<0.05). CONCLUSION: Early CRRT for SAKI can improve the renal function and inflammatory state effectively, and reduce the mortality of patients. Age is an independent risk factor affecting the prognosis of patients with SAKI, and early CRRT is a protective factor for the prognosis.