Ischemic AKI Research Articles

Mechanisms of Injury and Protection in Ischemic AKI

Mechanisms of Injury and Protection in Ischemic AKI

Metabolomics Assessment Reveals Amino Acid Depletion in Skeletal Muscle after Ischemic AKI in Mice

Metabolomics Assessment Reveals Amino Acid Depletion in Skeletal Muscle after Ischemic AKI in Mice

Role of Sulfotransferase 1C2 in Vitamin D Signaling in Ischemic AKI Associated with Vitamin D Deficiency in Rats

Role of Sulfotransferase 1C2 in Vitamin D Signaling in Ischemic AKI Associated with Vitamin D Deficiency in Rats

Ischemic AKI Modifies Expression of Immune Checkpoint Inhibitor TIGIT Ligands and Co-signaling Partners

Ischemic AKI Modifies Expression of Immune Checkpoint Inhibitor TIGIT Ligands and Co-signaling Partners

Reno-Protective Effect of Haptoglobin and Hemopexin by Inhibiting Ferroptosis in Ischemic Reperfusion AKI

Reno-Protective Effect of Haptoglobin and Hemopexin by Inhibiting Ferroptosis in Ischemic Reperfusion AKI

Long Noncoding RNA GSTM3P1 Induces mir-668 Degradation to Promote Ischemic AKI

Long Noncoding RNA GSTM3P1 Induces mir-668 Degradation to Promote Ischemic AKI

Aging and Immune Response to the Late Recovery Phase of Ischemic AKI

Aging and Immune Response to the Late Recovery Phase of Ischemic AKI

Tubular Epithelial Cell HMGB1 Promotes AKI-CKD Transition by Sensitizing Cycling Tubular Cells to Oxidative Stress: A Rationale for Targeting HMGB1 during AKI Recovery.

Cells undergoing necrosis release extracellular high mobility group box (HMGB)-1, which triggers sterile inflammation upon AKI in mice. Neither deletion of HMGB1 from tubular epithelial cells, nor HMGB1 antagonism with small molecules, affects initial ischemic tubular necrosis and immediate GFR loss upon unilateral ischemia/reperfusion injury (IRI). On the contrary, tubular cell-specific HMGB1 deficiency, and even late-onset pharmacological HMGB1 inhibition, increased functional and structural recovery from AKI, indicating that intracellular HMGB1 partially counters the effects of extracellular HMGB1. In vitro studies indicate that intracellular HMGB1 decreases resilience of tubular cells from prolonged ischemic stress, as in unilateral IRI. Intracellular HMGB1 is a potential target to enhance kidney regeneration and to improve long-term prognosis in AKI. Late diagnosis is a hurdle for treatment of AKI, but targeting AKI-CKD transition may improve outcomes. High mobility group box-1 (HMGB1) is a nuclear regulator of transcription and a driver of necroinflammation in AKI. We hypothesized that HMGB1 would also modulate AKI-CKD transition in other ways. We conducted single-cell transcriptome analysis of human and mouse AKI and mouse in vivo and in vitro studies with tubular cell-specific depletion of Hmgb1 and HMGB1 antagonists. HMGB1 was ubiquitously expressed in kidney cells. Preemptive HMGB1 antagonism with glycyrrhizic acid (Gly) and ethyl pyruvate (EP) did not affect postischemic AKI but attenuated AKI-CKD transition in a model of persistent kidney hypoxia. Consistently, tubular Hmgb1 depletion in Pax8 rtTA, TetO Cre, Hmgb1fl/fl mice did not protect from AKI, but from AKI-CKD transition. In vitro studies confirmed that absence of HMGB1 or HMGB1 inhibition with Gly and EP does not affect ischemic necrosis of growth-arrested differentiated tubular cells but increased the resilience of cycling tubular cells that survived the acute injury to oxidative stress. This effect persisted when neutralizing extracellular HMGB1 with 2G7. Consistently, late-onset HMGB1 blockade with EP started after the peak of ischemic AKI in mice prevented AKI-CKD transition, even when 2G7 blocked extracellular HMGB1. Treatment of AKI could become feasible when ( 1 ) focusing on long-term outcomes of AKI; ( 2 ) targeting AKI-CKD transition with drugs initiated after the AKI peak; and ( 3 ) targeting with drugs that block HMGB1 in intracellular and extracellular compartments.

Immune Checkpoint Molecule TIGIT Regulates Kidney T Cell Functions and Contributes to AKI.

T cells mediate pathogenic and reparative processes during AKI, but the exact mechanisms regulating kidney T cell functions are unclear. This study identified upregulation of the novel immune checkpoint molecule, TIGIT, on mouse and human kidney T cells after AKI. TIGIT-expressing kidney T cells produced proinflammatory cytokines and had effector (EM) and central memory (CM) phenotypes. TIGIT-deficient mice had protection from both ischemic and nephrotoxic AKI. Single-cell RNA sequencing led to the discovery of possible downstream targets of TIGIT. TIGIT mediates AKI pathophysiology, is a promising novel target for AKI therapy, and is being increasingly studied in human cancer therapy trials. T cells play pathogenic and reparative roles during AKI. However, mechanisms regulating T cell responses are relatively unknown. We investigated the roles of the novel immune checkpoint molecule T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) in kidney T cells and AKI outcomes. TIGIT expression and functional effects were evaluated in mouse kidney T cells using RNA sequencing (RNA-Seq) and flow cytometry. TIGIT effect on AKI outcomes was studied with TIGIT knockout (TIGIT-KO) mice in ischemia reperfusion (IR) and cisplatin AKI models. Human kidney T cells from nephrectomy samples and single cell RNA sequencing (scRNA-Seq) data from the Kidney Precision Medicine Project were used to assess TIGIT's role in humans. RNA-Seq and flow cytometry analysis of mouse kidney CD4+ T cells revealed increased expression of TIGIT after IR injury. Ischemic injury also increased TIGIT expression in human kidney T cells, and TIGIT expression was restricted to T/natural killer cell subsets in patients with AKI. TIGIT-expressing kidney T cells in wild type (WT) mice had an effector/central memory phenotype and proinflammatory profile at baseline and post-IR. Kidney regulatory T cells were predominantly TIGIT+ and significantly reduced post-IR. TIGIT-KO mice had significantly reduced kidney injury after IR and nephrotoxic injury compared with WT mice. scRNA-Seq analysis showed enrichment of genes related to oxidative phosphorylation and mTORC1 signaling in Th17 cells from TIGIT-KO mice. TIGIT expression increases in mouse and human kidney T cells during AKI, worsens AKI outcomes, and is a novel therapeutic target for AKI.

Evaluation of Plasma Oxidative Stress Levels in New Zealand White Rabbits Undergoing Ischemic Acute Kidney Injury

Oxidative stresses are particularly important in biomedical studies of ischemic AKI because these animals are very sensitive to stress. This study aims to evaluate serum oxidative stress levels in New Zealand white rabbits following ischemic AKI. On clinical histological examination and autopsy, some rabbits demonstrated severe organ dysfunctions such as gastrointestinal stasis or acute kidney or small intestine inflammation. Twenty-four hours following surgery, serum oxidative stress levels were significantly more increased in all rabbits than they had been prior to surgery. Compared to 24 hours after surgery, most rabbits had lower levels of oxidative stress at one week, but those with symptoms of organ dysfunction had higher levels. Elevated oxidative stress levels prior to kidney surgery were associated with severe organ dysfunction, more pronounced inflammatory and pathological changes to organs, and shorter survival times. Assessment of oxidative stress levels may be a useful indicator for predicting the risk of death from severe organ dysfunction in New Zealand white rabbits.

TIGIT Modulates Kidney T Cell Memory Phenotype and Metabolic Profile and Mediates Both Ischemic and Nephrotoxic AKI in Mice

TIGIT Modulates Kidney T Cell Memory Phenotype and Metabolic Profile and Mediates Both Ischemic and Nephrotoxic AKI in Mice

Dietary Modification of Fat and Protein Composition and Its Effects on the Repair of Ischemic AKI

Dietary Modification of Fat and Protein Composition and Its Effects on the Repair of Ischemic AKI

TNF or EGFR inhibition equally block AKI-to-CKD transition: opportunities for etanercept treatment.

Inflammation is a key driver of the transition of acute kidney injury to progressive fibrosis and chronic kidney disease (AKI-to-CKD transition). Blocking a-disintegrin-and-metalloprotease-17 (ADAM17)-dependent ectodomain shedding, in particular of epidermal growth factor receptor (EGFR) ligands and of the type 1 inflammatory cytokine tumor necrosis factor (TNF), reduces pro-inflammatory and pro-fibrotic responses after ischemic AKI or unilateral ureteral obstruction (UUO), a classical fibrosis model. Metalloprotease or EGFR inhibition show significant undesirable side effects in humans. In retrospective studies anti-TNF biologics reduce the incidence and progression of CKD in humans. Whether TNF has a role in AKI-to-CKD transition and how TNF inhibition compares to EGFR inhibition is largely unknown. Mice were subjected to bilateral renal ischemia-reperfusion injury or unilateral ureteral obstruction. Kidneys were analyzed by histology, immunohistochemistry, qPCR, western blot, mass cytometry, scRNA sequencing, and cytokine profiling. Here we show that TNF or EGFR inhibition reduce AKI-to-CKD transition and fibrosis equally by about 25%, while combination has no additional effect. EGFR inhibition reduced kidney TNF expression by about 50% largely by reducing accumulation of TNF expressing immune cells in the kidney early after AKI, while TNF inhibition did not affect EGFR activation or immune cell accumulation. Using scRNAseq data we show that TNF is predominantly expressed by immune cells in AKI but not in proximal tubule cells (PTC), and PTC-TNF knockout did not affect AKI-to-CKD transition in UUO. Thus, the anti-inflammatory and anti-fibrotic effects of the anti-TNF biologic etanercept in AKI-to-CKD transition rely on blocking TNF that is released from immune cells recruited or accumulating in response to PTC-EGFR signals. Short-term anti-TNF biologics during or after AKI could be helpful in the prevention of AKI-to-CKD transition.

Tubular epithelial progenitors are excreted in urine during recovery from severe acute kidney injury and are able to expand and differentiate in vitro.

BackgroundAcute kidney injury (AKI) is a serious condition associated with chronic kidney disease, dialysis requirement and a high risk of death. However, there are specialized repair mechanisms for the nephron, and migrated committed progenitor cells are the key players. Previous work has described a positive association between renal recovery and the excretion of tubular progenitor cells in the urine of kidney transplant recipients. The aim of this work was to describe such structures in non-transplanted AKI patients and to focus on their differentiation.MethodsMorning urine was obtained from four patients with AKI stage 3 and need for RRT on a consecutive basis. Urine sediment gene expression was performed to assess which part of the tubular or glomerular segment was affected by injury, along with measurement of neprilysin. Urine output and sediment morphology were monitored, viable hyperplastic tubular epithelial clusters were isolated and characterized by antibody or cultured in vitro. These cells were monitored by phase contrast microscopy, gene, and protein expression over 9 days by qPCR and confocal immunofluorescence. Furthermore, UMOD secretion into the supernatant was quantitatively measured.ResultsUrinary neprilysin decreased rapidly with increasing urinary volume in ischemic, toxic, nephritic, and infection-associated AKI, whereas the decrease in sCr required at least 2 weeks. While urine output increased, dead cells were present in the sediment along with debris followed by hyperplastic agglomerates. Monitoring of urine sediment for tubular cell-specific gene transcript levels NPHS2 (podocyte), AQP1 and AQP6 (proximal tubule), and SLC12A1 (distal tubule) by qPCR revealed different components depending on the cause of AKI. Confocal immunofluorescence staining confirmed the presence of intact nephron-specific epithelial cells, some of which appeared in clusters expressing AQP1 and PAX8 and were 53% positive for the stem cell marker PROM1. Isolated tubule epithelial progenitor cells were grown in vitro, expanded, and reached confluence within 5–7 days, while the expression of AQP1 and UMOD increased, whereas PROM1 and Ki67 decreased. This was accompanied by a change in cell morphology from a disproportionately high nuclear/cytoplasmic ratio at day 2–7 with mitotic figures. In contrast, an apoptotic morphology of approximately 30% was found at day 9 with the appearance of multinucleated cells that were associable with different regions of the nephron tubule by marker proteins. At the same time, UMOD was detected in the culture supernatant.ConclusionDuring renal recovery, a high replicatory potential of tubular epithelial progenitor cells is found in urine. In vitro expansion and gene expression show differentiation into tubular cells with marker proteins specific for different nephron regions.

MO352: The Effect and Mechanism of Renal Targeted Delivery of MSC Exosomes in the Treatment of AKI

Abstract BACKGROUND AND AIMS AKI occurs in ∼15% hospitalized patients and over 50% intensive care unit patients. However, effective therapeutic strategies for AKI are urgently needed. The exosomes derived from mesenchymal stem cells (MSC-exos) have achieved great focus as a cell-free therapy. As foremost metabolic organs, MSC-exos mainly collect in the liver and spleen. More attention should be considered how to induce more exosomes targeted to the injured kidney. In addition, the potential role of MSC-exos in injured kidney and the underlying mechanisms still need further research. METHOD Transmission electron microscopy, western blotting and nanoparticle tracking analysis were used to identify the properties of human umbilical cord mesenchymal stem cells (hucMSCs) derived exosomes. Kidney targeting peptide was chosen by the IVIS spectrum imaging system. Moreover, kidney targeting peptide (peptide-CGA) and CD63 targeting peptide were loaded to the MSC-exos by co-incubated (CGA-exos). Flow cytometry and immunofluorescence staining were utilized to confirm this. IVIS spectrum imaging system was used to assess MSC-exos distribution in vivo. RESULTS In vivo imaging showed that Peptide-CGA was efficiently homing to the ischemic kidney and predominantly accumulated in proximal tubules. Further Immunoprecipitation study showed that Peptide- CGA treatment group produced a specific stripe in silver staining compared with other groups. CGA-exos was successfully constructed. MSC-exos could alleviate murine ischemic kidney injury and reduced the renal tubules injury. Furthermore, in vivo imaging showed CGA-exos treatment group could attract more MSC-exos into the injured kidney, and its therapeutic effect was significantly better than that of the MSC-exos treatment group. without causing significant organ side effects. CONCLUSION Novel kidney targeting MSC-exos was constructed. It exhibited a preferential tendency to injured kidney and was localized to proximal tubules in AKI. We demonstrate that MSC-exos ameliorate ischemic AKI. But its further mechanisms need more insight. All in all, this highlights the potential of MSC-exos as a promising therapeutic strategy for AKI.

Abstract 135: A case of acquired Gitelman syndrome presenting as hypokalemic paralysis and AKI

Introduction: Gitelman syndrome is usually an inherited disorder, it is induced by defect in the thiazide sensitive Na –Cl co-transporter in distal tubules. Case reports on hypokalemia, AKI secondary to GS has been discussed in present case report.Clinical Case: A 18 year old female referred from department of General Medicine as a case of AKI having recurrent hypokalemia. She gave history of hypokalemic paralysis. There was no potential cause of dehydration such as diarrhoea, vomiting, nephrotoxic agent intake or contrast exposure. Family history was negative. During current hospitalization, she was normotensive with normal renal function test. Other electrolyte levels including calcium and routine laboratory parameters were determined to be normal. Kidney dimensions and echogenicity were determined to be normal without hydronephrosis in the urinary system as oer USG finding. Further workup for hypokalemia revealed urine potassium creatinine ratio (17 mmol/g), ABG (pH 7.44, bicarbonate 26.5 mmol/l), urine chloride (111.3 mmol/l) and urine calcium creatinine ratio (0.05 mmol/mmol) respectively with serum Mg (1.7 mg/dl) on lower range. Based on above findings, a diagnosis of Gitelman syndrome has been made. Autoimmune etiology were ruled out. These finding suggested that patient had AKI secondary to hypokalemia. She was started on oral potassium supplementation and magnesium supplementation.Conclusion: GS is a rare tubulopathy transmitted as an autosomal recessive trait. It is caused by mutation in thiazide sensitive Na Cl co-transporter coding gene, SLC12A3. Patients may be referred with hypokalemia, hypomagnesemia and metabolic alkalosis associated muscular weakness and cramping. By contrast, worsening hypokalemia and profound volume depletion as the predisposing factors for ischemic AKI appears to coexist.

Scutellarein relieves the death and inflammation of tubular epithelial cells in ischemic kidney injury by degradation of COX-2 protein

ObjectivesAcute kidney injury (AKI) is a clinical syndrome that usually caused by ischemia/reperfusion (I/R). Previous studies have revealed the protection of scutellarein against ischemia in nervous system. This study aimed to demonstrate the potential of scutellarein in ischemic AKI. MethodsAnimal model of ischemic AKI was established by clamping bilateral kidney pedicles in Sprague-Dawley rats. HK-2 cells were exposed to oxygen glucose deprivation/reoxygenation (OGD/R) to induce a cell model of AKI. The effects of scutellarein pre-treatment were detected by H&E staining, TUNEL, ELISA, CCK-8, LDH activity assay, ROS generation, flow cytometry, qRT-PCR and western blotting. Bioinformatic analysis was performed to probe the targets of scutellarein. ResultsThe blood urea nitrogen (BUN) and serum creatinine (SCr) levels in rats treated with scutellarein were lower than that in model groups. Scutellarein suppressed the pathological injury of kidney, and dose-dependently inhibited the apoptosis and pro-inflammatory cytokines release (IL-1β, IL-6 and IL-18). Scutellarein prevented OGD/R-induced HK-2 cell loss and cytotoxicity. ROS generation, apoptosis, and inflammation induced by OGD/R were all inhibited by scutellarein. By searching on the TCMSP and Symmap databases, COX-2 was screened out as a target of scutellarein. Scutellarein has no significant impacts on COX-2 mRNA expression, but could inhibit its protein level. Scutellarein promoted COX-2 protein degradation via enhancing autophagy. Furthermore, overexpression of COX-2 partly eliminated the renal protection of scutellarein in HK-2 cells. ConclusionsScutellarein was suggested as a renal protective agent against ischemia-induced damage in AKI. The protective properties of scutellarein may be through inhibition of COX-2.

T Cell Metabolic Reprogramming and Effect of Glutamine Blockade in Ischemic AKI

T Cell Metabolic Reprogramming and Effect of Glutamine Blockade in Ischemic AKI

The Long Noncoding RNA GSTM3P1 Is Induced to Exacerbate Ischemic AKI by Antagonizing MicroRNA-668

The Long Noncoding RNA GSTM3P1 Is Induced to Exacerbate Ischemic AKI by Antagonizing MicroRNA-668

RvD1 Attenuated Susceptibility to Ischemic AKI in Diabetes by Downregulating Nuclear Factor-κ B Signal and Inhibiting Apoptosis.

BackgroundAcute kidney injury (AKI), when occurring in diabetic kidney disease (DKD), is known to be more severe and difficult to recover from. Inflammation and apoptosis may contribute to the heightened sensitivity of, and non-recovery from, AKI in patients with DKD. Resolvin D1 (RvD1) is a potent lipid mediator which can inhibit the inflammatory response and apoptosis in many diseases. However, it has been reported that the RvD1 levels were decreased in diabetes, which may explain why DKD is more susceptible to AKI.MethodsFor animal experiments, diabetic nephropathy (DN) mice were induced by streptozotocin (STZ) injection intraperitoneally. Renal ischemia–reperfusion was used to induce AKI. Blood urea nitrogen (BUN) and serum creatinine were determined using commercial kits to indicate renal function. Renal apoptosis was examined by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Real-time polymerase chain reaction (PCR) was used to detect the marker of inflammatory response. Western blot was used to detect the expression of nuclear factor-κB (NF-κB)-related proteins. For clinical study, 12 cases diagnosed with DKD were enrolled in this study, and an equal number of non-diabetic renal disease patients (NDKD) were recruited as a control group. The serum RvD1 in DKD or NDKD patients were detected through an ELISA kit.ResultsIn clinical study, we found that the serum RvD1 levels were decreased in DKD patients compared to those in NDKD patients. Decreased serum RvD1 levels were responsible for the susceptibility to ischemic AKI in DKD patients. In animal experiments, both the serum RvD1 and renal ALX levels were downregulated. RvD1 treatment could ameliorate renal function and histological damage after ischemic injury in DN mice. RvD1 treatment also could inhibit the inflammatory response. Di-tert-butyl dicarbonate (BOC-2) treatment could deteriorate renal function and histological damage after ischemic injury in non-diabetic mice. RvD1 could inhibit the NF-κB activation and suppress inflammatory response mainly by inhibiting NF-κB signaling.ConclusionRvD1 attenuated susceptibility to ischemic AKI in diabetes by downregulating NF-κB signaling and inhibiting apoptosis. Downregulated serum RvD1 levels could be the crucial factor for susceptibility to ischemic AKI in diabetes.