Mechanisms and therapeutic targets of ischemic acute kidney injury

Co-treatment with Esculin and erythropoietin protects against renal ischemia-reperfusion injury via P2X7 receptor inhibition and PI3K/Akt activation

Renal ischemia/reperfusion (RI/R) is a critical clinical outcome with slightly reported improvement in mortality and morbidity. Effective therapies are still crucially required. Accordingly, the therapeutic effects of esculin (ESC, LCESI-MS/MS-isolated compound from Vachellia farnesiana flowers extract, with reported P2X7 receptor inhibitor activity) alone and in combination with erythropoietin (EPO) were investigated against RI/R injury and the possible underlying mechanisms were delineated. ESC and EPO were administered for 7 days and 30 min prior to RI, respectively. Twenty-four hour following reperfusion, blood and kidney samples were collected. Results revealed that pretreatment with either ESC or EPO reduced serum nephrotoxicity indices, renal oxidative stress, inflammatory, and apoptosis markers. They also ameliorated the renal histopathological injury on both endothelial and tubular epithelial levels. Notably, ESC markedly inhibited P2X7 receptors and NLRP3 inflammasome signaling (downregulated NLRP3 and Caspase-1 gene expressions), whereas EPO significantly upregulated PI3K and Akt gene expressions, also p-PI3K and p-Akt levels in renal tissues. ESC, for the first time, demonstrated effective protection against RI/R-injury and its combination with EPO exerted maximal renoprotection when compared to each monotherapy, thereby representing an effective therapeutic approach via inhibiting oxidative stress, inflammation, renal tubular and endothelial injury, apoptosis, and P2X7 receptors expression, and activating PI3K/Akt pathway.

Prazosin Treatment Protects Brain and Heart by Diminishing Oxidative Stress and Apoptotic Pathways After Renal Ischemia Reperfusion

Acute kidney injury (AKI) is a major medical challenge caused from renal ischemia-reperfusion (IR) injury connected with different cellular events in other distant organs. Renal IR-related oxidative stress and inflammation followed by cell apoptosis play a crucial role in IR-induced distant organ pathological damages. Prazosin has shown protective effects against IR-injuries. Thus, the current study intended to investigate the possible protective role of prazosin against the consequents of renal IR in the heart and brain tissues. To reach this goal, rats were randomly divided into 3 groups (n=7): Sham, IR and prazosin pretreatment-IR animals (1 mg/kg intraperitoneally injection of prazosin 45 min before IR induction). After 6 h reperfusion, lipid peroxidation and antioxidant markers levels were evaluated in the both, brain and heart tissue. Moreover, apoptotic pathway in the heart and brain tissues were assessed by western blotting. Accordingly, prazosin pretreatment in IR model rats could significantly increase the antioxidant capacity and attenuate apoptotic pathways by increasing the bcl-2 levels and decreasing the expression of Bax and caspase 3 enzymes (P<0.05). Thus, prazosin suppressed cellular damages of heart and brain tissues post kidney IR by anti-oxidative and anti-apoptotic effects, which suggests the plausible use of prazosin in improving the clinical outcomes during AKI after further investigations.

Maslinic Acid Attenuates Ischemia/Reperfusion-Induced Acute Kidney Injury by Suppressing Inflammation and Apoptosis Through Inhibiting NF-κB and MAPK Signaling Pathway

Inflammation and apoptosis are the major contributors to the mechanisms of acute kidney injury (AKI) due to renal ischemia-reperfusion injury (IRI). Maslinic acid (MA), a pentacyclic triterpene acid mostly found in dietary plants, the current study was to demonstrate the renoprotective effect of MA on IRI-induced AKI, and to investigate the role of inflammation and apoptosis-related signaling pathways as a molecular mechanism. C57BL/6J mice were subjected to IRI for 72 h, and MA was daily administered by intraperitoneal injection during this period. In parallel, rat renal proximal tubule cells (NRK52E) were prophylactically treated with MA and then exposed to hydrogen peroxide (H₂O₂). MA treatment significantly inhibited the mRNA expression of interleukin (IL-1β), tumor necrosis factor-α (TGF-α), monocyte chemoattractant protein-1 (MCP-1), and intercellular adhesion molecule-1(ICAM-1). Also, MA reduced the expression of Bax/Bcl2 ratio and cleaved caspase-3. In NRK52 cells, MA inhibited the IκBα degradation, blocked NF-κB/p65 phosphorylation, and nuclear translocation. The phosphorylation of ERK, JNK, and p38 was attenuated by MA in IRI-induced kidney injury and H₂O₂-stimulated NRK52 cells. The expression levels of IL-1β, MCP-1, and ICAM-1 were upregulated in H₂O₂-stimulated NRK52E cells, which was attenuated by NF-κB inhibitor. H₂O₂ treatment increased the Bax/Bcl2 ratio and cleaved caspase-3 in NRK52E cells, which was counteracted by MAPK inhibitors. Together, our data demonstrate that MA suppresses IR-induced AKI injury through NF-κB and MAPK signaling pathways and that MA is a promising agent in the treatment of kidney diseases.

Extracellular Vesicles and Acute Kidney Injury: Potential Therapeutic Avenue for Renal Repair and Regeneration

Acute kidney injury (AKI) is a sudden decline of renal function and represents a global clinical problem due to an elevated morbidity and mortality. Despite many efforts, currently there are no treatments to halt this devastating condition. Extracellular vesicles (EVs) are nanoparticles secreted by various cell types in both physiological and pathological conditions. EVs can arise from distinct parts of the kidney and can mediate intercellular communication between various cell types along the nephron. Besides their potential as diagnostic tools, EVs have been proposed as powerful new tools for regenerative medicine and have been broadly studied as therapeutic mediators in different models of experimental AKI. In this review, we present an overview of the basic features and biological relevance of EVs, with an emphasis on their functional role in cell-to-cell communication in the kidney. We explore versatile roles of EVs in crucial pathophysiological mechanisms contributing to AKI and give a detailed description of the renoprotective effects of EVs from different origins in AKI. Finally, we explain known mechanisms of action of EVs in AKI and provide an outlook on the potential clinical translation of EVs in the setting of AKI.

Efficacy and Safety of Chuan Huang Fang Combining Reduced Glutathione in Treating Acute Kidney Injury (Grades 1-2) on Chronic Kidney Disease (Stages 2-4): Study Protocol for a Multicenter Randomized Controlled Clinical Trial

Background

Acute kidney injury (AKI) is a global public health challenge resulting in considerable morbidity and mortality. AKI on chronic kidney disease (CKD) (AKI on CKD, A on C) accounts for about a third of total AKI. For severe AKI grade 3, renal replacement therapy (RRT) should be implemented in time. However, the lack of recognized drug treatment method for AKI grades 1-2 is a crucial problem in clinic. Chuan Huang Fang (CHF) is a Chinese herbal formulation developed for the treatment of A on C from the Shanghai Municipal Hospital of Traditional Chinese Medicine. Our previous studies suggested that CHF might effectively protect renal functions of A on C patients. As a widely used antioxidant in clinic, reduced glutathione (RG) is reported to improve the clinical efficacy of high-flux hemodialysis (HFHD) in severe AKI patients recently. To address the crucial problem mentioned above, thus we design a new clinical protocol of CHF combining RG and try to evaluate the efficacy and safety of this protocol in treating patients diagnosed with CKD stages 2-4 complicated with AKI grades 1-2.

Methods

This is a multicenter randomized controlled clinical trial. We intend to enroll 162 participants, and these participants will be divided into the RG group, the CHF group, and the RG + CHF group randomly assigning 1 : 1 : 1 principle. The RG group will be general treatments combining RG, the CHF group will be general treatments combining CHF, and the RG + CHF group will be general treatments combining RG and CHF. The duration of treatment will last two weeks. The primary evaluation outcome will be the change in the slope of serum creatinine (Scr) over 2 weeks. Secondary evaluation outcomes include changes in blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), urinary AKI biomarkers (neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), gamma-glutamyl transpeptidase (γ-GT), etc.), traditional Chinese medicine (TCM) symptoms, inflammatory indicators, and oxidative stress indicators. Meanwhile, the vital sign indicators and adverse events (AEs) will be closely observed. These dates will be meticulously recorded and properly handled by investigators throughout the study. Discussion. This study will provide convictive research-derived data to evaluate clinical efficacy and safety of CHF combing RG for CKD stages 2-4 complicated with AKI grades 1-2 and provide an evidence-based recommendation for clinicians. The timely completion of this trial will provide a novel drug treatment method for A on C. This trial is registered with ChiCTR2100043311 and registered on February 9, 2021.

Blockade of STAT3 signaling alleviates progression of acute kidney injury-to-chronic kidney disease through anti-apoptosis

Signal transducer and activator of transcription 3 (STAT3) is a pivotal mediator of IL-6-type cytokine signaling. However, the roles of its full-length and truncated isoforms in acute kidney injury (AKI) and its transition to chronic kidney disease (CKD) remain elusive. Herein, the role of STAT3 isoforms in AKI-to-CKD transition was characterized using an ischemia-reperfusion injury (IRI) mouse model. IRI was induced in C57BL/6 mice. Stattic^®, a STAT3 inhibitor, was administered to the mice 3 h prior to IRI. Intrarenal cytokine expression was quantified using real-time PCR, and FACS analysis was performed. The effect of Stattic^® on human tubular epithelial cells (TECs) cultured under hypoxic conditions was also evaluated. Phosphorylated STAT3 isoforms were detected by western blotting. Stattic^® treatment attenuated IRI-induced tubular damage and inflammatory cytokine/chemokine expression, while decreasing macrophage infiltration and fibrosis in mouse unilateral IRI and UUO models. Similarly, in vitro STAT3 inhibition downregulated fibrosis and apoptosis in 72-h hypoxia-induced human TECs and reduced pSTAT3α-mediated inflammation. Moreover, pSTAT3 expression was increased in human acute tubular necrosis and CKD tissues. STAT3 activation is associated with IRI progression, and STAT3-α may be a significant contributor. Hence, STAT3 may affect AKI-to-CKD transition, suggesting a novel strategy for AKI management with STAT3 inhibitors.

Early Effects of Extracellular Vesicles Secreted by Adipose Tissue Mesenchymal Cells in Renal Ischemia Followed by Reperfusion: Mechanisms Rely on a Decrease in Mitochondrial Anion Superoxide Production

Acute kidney injury (AKI) caused by ischemia followed by reperfusion (I/R) is characterized by intense anion superoxide (O₂^•−) production and oxidative damage. We investigated whether extracellular vesicles secreted by adipose tissue mesenchymal cells (EVs) administered during reperfusion can suppress the exacerbated mitochondrial O₂^•− formation after I/R. We used Wistar rats subjected to bilateral renal arterial clamping (30 min) followed by 24 h of reperfusion. The animals received EVs (I/R + EVs group) or saline (I/R group) in the kidney subcapsular space. The third group consisted of false-operated rats (SHAM). Mitochondria were isolated from proximal tubule cells and used immediately. Amplex Red™ was used to measure mitochondrial O₂^•− formation and MitoTracker™ Orange to evaluate inner mitochondrial membrane potential (Δψ). In vitro studies were carried out on human renal proximal tubular cells (HK-2) co-cultured or not with EVs under hypoxic conditions. Administration of EVs restored O₂^•− formation to SHAM levels in all mitochondrial functional conditions. The gene expression of catalase and superoxide dismutase-1 remained unmodified; transcription of heme oxygenase-1 (HO-1) was upregulated. The co-cultures of HK-2 cells with EVs revealed an intense decrease in apoptosis. We conclude that the mechanisms by which EVs favor long-term recovery of renal structures and functions after I/R rely on a decrease of mitochondrial O₂^•− formation with the aid of the upregulated antioxidant HO-1/Nuclear factor erythroid 2-related factor 2 system, thus opening new vistas for the treatment of AKI.

Alleviation of renal ischemia/reperfusion injury by exosomes from induced pluripotent stem cell-derived mesenchymal stem cells

BACKGROUND/AIMS

Renal ischemia followed by reperfusion (I/R) is a leading cause of acute kidney injury (AKI), which is closely associated with high morbidity and mortality. Studies have shown that induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) exert powerful therapeutic effects in renal ischemia. However, the efficacy of iMSC-derived exosomes (iExo) on I/R injuries remains largely unknown.

METHODS

Human iPSCs were differentiated into iMSCs using a modified one-step method. Ultrafiltration, combined with purification, was used to isolate iExo from iMSCs. iExo was administered following I/R injury in a mouse model. The effect of iExo on I/R injury was assessed through changes in renal function, histology, and expression of oxidative stress, inflammation, and apoptosis markers. Further, we evaluated its association with the extracellular signal-regulated kinase (ERK) 1/2 signaling pathway.

RESULTS

Mice subjected to I/R injury exhibited typical AKI patterns; serum creatinine level, tubular necrosis, apoptosis, inflammatory cytokine production, and oxidative stress were markedly increased compared to sham mice. However, treatment with iExo attenuated these changes, significantly improving renal function and tissue damage, similar to the renoprotective effects of iMSCs on I/R injury. Significant induction of activated ERK 1/2 signaling molecules was observed in mice treated with iExo compared to those in the I/R injury group.

CONCLUSION

The present study demonstrates that iExo administration ameliorated renal damage following I/R, suggesting that iMSC-derived exosomes may provide a novel therapeutic approach for AKI treatment.

Sevoflurane preconditioning prevents acute renal injury caused by ischemia‑reperfusion in mice via activation of the Nrf2 signaling pathway

Oxidative stress, caused by renal ischemia reperfusion (IR)/hypoperfusion, is one of the main causes of acute kidney injury (AKI). Previous studies have demonstrated that sevoflurane (SEV) protects organs from the damage caused by oxidative stress. In the present study, mice were randomly assigned to a sham operation group (Sham), IR-vehicle group (IR+ vehicle), IR + SEV low-dose preconditioning group and an IR + SEV high-dose preconditioning group. The effect of SEV on nuclear factor E2-related factor 2 (Nrf2), a key regulatory protein of the endogenous antioxidant defense system and, consequently oxidative stress, inflammation and apoptosis-related factors, were all quantified using commercial kits or by western blotting. SEV preconditioning was demonstrated to ameliorate kidney injury as a result of decreased blood urine nitrogen and serum creatinine levels, activated Nrf2 expression in the kidney and decreased oxidative stress and inflammatory index levels an AKI mouse model. SEV preconditioning also protected injured kidney via the downregulation of caspase-3 protein expression levels. In addition, using the Nrf2 inhibitor, Brusatol, significantly abolished the SEV preconditioning renal protective effect. Using an in vitro HK-2 cell model of hypoxia/reoxygenation, it was also demonstrated that Nrf2 pathway activation was necessary for SEV to exert its beneficial effect for tubular cell injury caused by hypoxia/reoxygenation. These results indicated that SEV may protect against renal injury caused by IR via Nrf2 upregulation.

Calpain Inhibitor Calpeptin Alleviates Ischemia/Reperfusion-Induced Acute Kidney Injury via Suppressing AIM2 Inflammasome and Upregulating Klotho Protein

Renal ischemia/reperfusion injury is a major contributor of acute kidney injury (AKI), leading to renal cell necrosis, apoptosis, and inflammation. Calpains, a family of Ca²⁺-dependent cysteine proteases, play a pivotal role in the pathogenesis of renal diseases. Several studies have reported calpain inhibitors showing remarkable reno-protective effects against proteinuria and α-klotho deficiency-induced renal aging symptoms, particularly against glomerulus injury. However, little is known about the role of the calpain inhibitor calpeptin in acute kidney injury. The present study aims to investigate the potential mechanism of downregulation of Calpain 1 and 2 activity by calpeptin in the ischemia/reperfusion (IR)-induced AKI model. Firstly, we observed that the contents of Calpain 1 and 2 were significantly increased in the renal biopsy of clinical AKI patients, especially in the diseased tubules space. To investigate the impacts of calpain activity inhibition, we further pretreated with calpeptin in both the IR mouse model and in the HK-2 cells hypoxia model. We found that the calpain inhibitor calpeptin improved renal functional deterioration, attenuated pathological structure damage, and decreased tubular cell apoptosis in the IR injury-induced AKI mice model. Mechanistically, calpeptin significantly suppressed the AIM2 (absent in melanoma 2) and NLRP3 (NOD-like receptor protein 3) inflammasome signaling pathways and increased Klotho protein levels. Furthermore, immunofluorescence assays demonstrated that the application of calpeptin effectively inhibited Calpain 1 activation and gasdermin D (GSDMD) cleavage in the renal tubules of IR mice. Taken together, our both in vivo and in vitro experiments suggest that calpeptin conveyed reno-protection in AKI might be mediated by the inhibition of AIM2 inflammasome activation and upregulation of Klotho protein. As such, we provide new evidence that Calpain 1 and 2 activation may be closely associated with the pathogenesis of clinical AKI. The calpain-mediated AIM2 inflammasome signaling pathway and distinct interaction between calpain and Klotho may provide a potential novel preventative and therapeutic target for acute kidney injury.

A ketogenic diet attenuates acute and chronic ischemic kidney injury and reduces markers of oxidative stress and inflammation

BACKGROUND

Ischemic kidney injury is a common clinical condition resulting from transient interruption of the kidney's normal blood flow, leading to oxidative stress, inflammation, and kidney dysfunction. The ketogenic diet (KD), a low-carbohydrate, high-fat diet that stimulates endogenous ketone body production, has potent antioxidant and anti-inflammatory effects in distinct tissues and might thus protect the kidney against ischemia and reperfusion (IR) injury.

MAIN METHODS

Male Wistar rats were fed a KD or a control diet (CD) for three days before analyzing metabolic parameters or testing nephroprotection. We used two different models of kidney IR injury and conducted biochemical, histological, and Western blot analyses at 24 h and two weeks after surgery.

KEY FINDINGS

Acute KD feeding caused protein acetylation, liver AMPK activation, and increased resistance to IR-induced kidney injury. At 24 h after IR, rats on KD presented reduced tubular damage and improved kidney functioning compared to rats fed with a CD. KD attenuated oxidative damage (protein nitration, 4-HNE adducts, and 8-OHdG), increased antioxidant defenses (GPx and SOD activity), and reduced inflammatory intermediates (IL6, TNFα, MCP1), p50 NF-κB expression, and cellular infiltration. Also, KD prevented interstitial fibrosis development at two weeks, up-regulation of HSP70, and chronic Klotho deficiency.

SIGNIFICANCE

Our findings demonstrate for the first time that short-term KD increases tolerance to experimental kidney ischemia, opening the opportunity for future therapeutic exploration of a dietary preconditioning strategy to convey kidney protection in the clinic.

Discovery of novel Ketamine-inspired derivatives as a protective agent against renal ischemic/reperfusion injury in Wistar rats

Renal ischemia-reperfusion (I/R) injury is a limiting factor for the success of renal grafts and is deemed greatly responsible for the mortality. A novel series of Ketamine inspired compounds were synthesized and subjected to NF-ĸB transcriptional inhibitory activity in LPS-stimulated RAW264.7 cells, where entire set of compounds showed mild to significant NF-ĸB transcriptional inhibitory activity (IC₅₀ 6.53 - 67.52 µM). Compound 6d showed highest inhibitory activity among the tested series (IC₅₀ 2.62 µM), and found more potent as compared to Ketamine as standard. The effect of compound 6d was further quantified in I/R injury in Wistar rats, where it dose-dependently improves kidney function of rats with significant amelioration of kidney injury as suggested by histopathological examination of renal tissues. It further showed reduction in the generation of pro-inflammatory cytokines and improves the anti-oxidant status of experimental rats. Compound 6d inhibited apoptosis and increases the expression of Bcl2 and decreases Bax, and cleaved caspase-3 level. It further reduces TLR-4 and NF-κB expression in renal cells of rats, with increases in IκB-α level in western blot analysis as compared to I/R group. In summary, our current study showed the development of a novel class of Ketamine-inspired derivatives against renal ischemia/reperfusion injury.

Knockdown of TRIM8 Protects HK-2 Cells Against Hypoxia/Reoxygenation-Induced Injury by Inhibiting Oxidative Stress-Mediated Apoptosis and Pyroptosis via PI3K/Akt Signal Pathway

Background

Acute kidney injury (AKI) emerges as an acute and critical disease. Tripartite motif 8 (TRIM8), one number of the TRIM protein family, is proved to participate in ischemia/reperfusion (I/R) injury. However, whether TRIM8 is involved in renal I/R injury and the associated mechanisms are currently unclear.

Purpose

This study aimed to investigate the precise role of TRIM8 and relevant mechanisms in renal I/R injury.

Materials and Methods

In this study, human renal proximal tubular epithelial cells (HK-2 cells) underwent 12 hours of hypoxia and 2 h, 3 h or 4 h of reoxygenation to establish an in vitro hypoxia/reoxygenation (H/R) model. The siRNAs specific to TRIM8 (si-TRIM8) were transfected into HK-2 cells to knockdown TRIM8. The cell H/R model included various groups including Control, H/R, H/R+DMSO, H/R+NAC, si-NC+H/R, si-TRIM8+H/R and si-TRIM8+LY294002+H/R. The cell viability and levels of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂), mRNA, apoptotic proteins, pyroptosis-related proteins and PI3K/AKT pathway-associated proteins were assessed.

Results

In vitro, realtime-quantitative PCR and western-blot analysis showed that the mRNA and protein expression of TRIM8 were obviously upregulated after H/R treatment in HK-2 cells. Compared with the H/R model group, knockdown of TRIM8 significantly increased cell viability and reduced the levels of ROS, H₂O₂, apoptotic proteins (Cleaved caspasebase-3 and BAX) and pyroptosis-related proteins (NLRP3, ASC, Caspase-1, Caspase-11, IL-1β and GSDMD-N). Western-blot analysis also authenticated that PI3K/AKT pathway was activated after TRIM8 inhibition. The application of 5 mM N-acetyl-cysteine, one highly efficient ROS inhibitor, significantly suppressed the expression of apoptotic proteins and pyroptosis-related proteins. Moreover, the combined treatment of TRIM8 knockdown and LY294002 reversed the effects of inhibiting oxidative stress.

Conclusion

Knockdown of TRIM8 can alleviate H/R-induced oxidative stress by triggering the PI3K/AKT pathway, thus attenuating pyropyosis and apoptosis in vitro.

Pomegranate extract ameliorates renal ischemia/reperfusion injury in rats via suppressing NF-κB pathway

Inflammation and oxidative stress are the major pathways involved in ischemia-reperfusion (I/R)-induced renal injury. This study was designed to evaluate the potential effect of pomegranate against I/R-induced renal injury. I/R injury was induced in nephrectomized rats by unilateral occlusion of the left renal pedicle for 45 min followed by 24 h of perfusion. Pomegranate succeeded to decrease serum levels of creatinine, potassium, and urea nitrogen, along with increasing creatinine clearance. Pomegranate also decreased I/R-induced changes in histopathological examination. Pomegranate attenuated the renal inflammatory response reflected by the suppression of nuclear factor κB p65 DNA binding activity, the upregulation of inhibitory protein kappa B-alpha mRNA expression, the downregulation of mRNA and protein expression of tumor necrosis factor α, in addition to the reduced myeloperoxidase activity and mRNA expression. Additionally, pomegranate attenuated oxidative stress likely through the modulation of lipid peroxidation and antioxidant levels reflected by the decreased MDA content and the increased glutathione level and superoxide dismutase activity. Results confirm the potential protective effect of pomegranate against I/R-induced renal injury through its anti-inflammatory and anti-oxidant effects mediated through the upregulation of inhibitory protein kappa B-alpha, the inhibition of NF-κB activity, and the associated TNF-α release, neutrophil infiltration, and oxidative stress.

SIRT3 mediates mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury

Ischemia reperfusion-induced acute kidney injury (IR-induced AKI) is a life-threatening disease with many complications. Mitofusin 2 (Mfn2) ubiquitination is related to AKI. But the underlying molecular mechanisms remain unknown. This study aimed to probe the mechanism of Mfn2 ubiquitination in IR-induced AKI development. In IR-induced AKI mouse models, orbital blood and urine were collected for assessing kidney function. The kidney injury, ultrastructure of mitochondria, and histopathology in mice were evaluated after injection of G5, an ubiquitination inhibitor. Oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HK-2 cells, and the mitochondria were extracted. Cell viability, apoptosis, oxidative stress, inflammatory reaction, mitochondrial membrane potential, and ATP production were measured. Mfn2 ubiquitination in mouse and cell models was evaluated. si-SIRT3 and pcDNA3.1-SIRT3 were transfected into cell models. Consequently, kidney function in mice was impaired by IR-induced AKI. Mfn2 ubiquitination and degradation promoted IR-induced AKI. OGD/R induced renal tubular epithelial cell injury and disrupted mitochondrial dynamics and functions through promoting Mfn2 ubiquitination. SIRT3 knockdown led to Mfn2 ubiquitination by binding to UBC; while its overexpression alleviated tubular epithelial cell injury. Briefly, SIRT3 mediates Mfn2 ubiquitination to relieve IR-induced AKI. This investigation may offer new insights for the treatment of IR-induced AKI injury.

A naturally occurring FXR agonist, alisol B 23-acetate, protects against renal ischemia-reperfusion injury

The ligand-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating renal function. Activation of FXR by its specific agonists exerts renoprotective action in animals with acute kidney injury (AKI). In the present study, we aimed to identify naturally occurring agonists of FXR with potential as therapeutic agents in renal ischemia-reperfusion injury. In vitro and in vivo FXR activation was determined by a dual-luciferase assay, docking analysis, site-directed mutagenesis, and whole kidney transcriptome analysis. Wild-type (WT) and FXR knockout (FXR-/-) mice were used to determine the effect of potential FXR agonist on renal ischemia-reperfusion injury (IRI). We found that alisol B 23-acetate (ABA), a major active triterpenoid extracted from Alismatis rhizoma, a well-known traditional Chinese medicine, can activate renal FXR and induce FXR downstream gene expression in mouse kidney. ABA treatment significantly attenuated renal ischemia-reperfusion-induced AKI in WT mice but not in FXR-/- mice. Our results demonstrate that ABA can activate renal FXR to exert renoprotection against ischemia-reperfusion injury-induced AKI. Therefore, ABA may represent a potential therapeutic agent in the treatment of ischemic AKI.NEW & NOTEWORTHY In the present study, we found that alisol B 23-acetate (ABA), an identified natural farnesoid X receptor (FXR) agonist from the well-known traditional Chinese medicine Alismatis rhizoma, protects against ischemic acute kidney injury (AKI) in an FXR-dependent manner, as reflected by improved renal function, reduced renal tubular apoptosis, ameliorated oxidative stress, and suppressed inflammatory factor expression. Therefore, ABA may have great potential as a novel therapeutic agent in the treatment of AKI in the future.

A DNA Nanoraft-Based Cytokine Delivery Platform for Alleviation of Acute Kidney Injury

Cytokine immunotherapy represents an attractive strategy to stimulate robust immune responses for renal injury repair in ischemic acute kidney injury (AKI). However, its clinical application is hindered by its nonspecificity to kidney, short circulation half-life, and severe side effects. An ideal cytokine immunotherapy for AKI requires preferential delivery of cytokines with accurate dosage to the kidney and sustained-release of cytokines to stimulate the immune responses. Herein, we developed a DNA nanoraft cytokine by precisely arranging interleukin-33 (IL-33) nanoarray on rectangle DNA origami, through which IL-33 can be preferentially delivered to the kidney for alleviation of AKI. A nanoraft carrying precisely quantified IL-33 predominantly accumulated in the kidney for up to 48 h. Long-term sustained-release of IL-33 from nanoraft induced rapid expansion of type 2 innate lymphoid cells (ILC 2s) and regulatory T cells (Tregs) and achieved better treatment efficiency compared to free IL-33 treatment. Thus, our study demonstrates that a nanoraft can serve as a structurally well-defined delivery platform for cytokine immunotherapy in ischemic AKI and other renal diseases.

Effect of Lipopolysaccharide from Rhodobacter sphaeroides on Inflammatory Pathway and Oxidative Stress in Renal Ischemia/Reperfusion Injury in Male Rats

Ischemia/reperfusion injury (IRI) is caused by a sudden temporary impairment of the blood flow to the particular organ. The IRI of the kidneys is one of the main causes of acute kidney injury. A vigorous inflammatory and oxidative stress response to hypoxia and reperfusion usually happens as IRI consequences that disturb the organ function. The current study aimed to investigate the effect of antagonizing toll-like receptors (TLRs) effects by lipopolysaccharide obtained from Rhodobacter sphaeroides (LPS-RS) on this critical condition. In total, 28 adult male Wistar rats were divided into four groups (n=7) as follows: the sham group which underwent only laparotomy; control group that underwent laparotomy and IRI induction; vehicle group which was similar to the control group plus vehicle treatment, LPS-RS group that was similar to the control group but was pretreated with 0.5 mg/kg of LPS-RS. The results of the current research showed that LPS-RS reduced interleukin-1β, interleukin-6, tumor necrosis factor α, and 8-isoprostane levels, compared to the control IRI group. However, LPS-RS did not ameliorate the kidney injury as manifested by the elevated levels of urea, creatinine, and neutrophil gelatinase-associated lipocalin. Taken together, the present study demonstrated that LPS-RS at the tested dose failed to offer a renoprotective effect against the IRI in rats.

Rhodomeroterpene alleviates macrophage infiltration and the inflammatory response in renal tissue to improve acute kidney injury

Inflammation is broadly recognized as an important factor in the pathogenesis of acute kidney injury (AKI), but pharmacological approaches to alleviate inflammation in AKI have not been proved successful in clinical trials. Macrophage infiltration into renal tissue promotes inflammatory responses that contribute to the pathogenesis of AKI. Suppression of renal tissue inflammatory responses is postulated to improve renal injury of patients and animals. Rhodomeroterpene (RMT) is a novel meroterpenoid isolated from the Rhododendron genus that was shown to exert anti-inflammatory action in vivo or in vitro in this study. We investigated the treatment effects of RMT on LPS-induced sepsis and two different AKI models. The results showed that pretreatment with RMT (30 mg kg^-1  d^-1 , ip, for 3 days) significantly inhibited acute inflammatory responses in LPS-induced septic mice. In both renal ischemia-reperfusion injury (I/R) and sepsis-induced AKI models, RMT (30 mg kg^-1  d^-1 , ip, for 3 days) ameliorated renal function and injury and alleviated inflammation by reducing the infiltration of immune cells, including macrophages and neutrophils. Furthermore, our study demonstrated that RMT inhibits inflammatory responses in macrophages. The anti-inflammatory effects of RMT may be due to the inactivation of the IKK/NF-κB and PI3K/PDK1/Akt inflammatory signaling pathways in macrophages. Collectively, our findings indicate that RMT ameliorates renal injury and alleviates the renal inflammatory state in different AKI models, suggesting that RMT may be a potential agent for the treatment of AKI.

Deletion of the Gamma Subunit of ENaC in Endothelial Cells Does Not Protect against Renal Ischemia Reperfusion Injury

Acute kidney injury due to renal ischemia-reperfusion injury (IRI) may lead to chronic or end stage kidney disease. A greater understanding of the cellular mechanisms underlying IRI are required to develop therapeutic options aimed at limiting or reversing damage from IRI. Prior work has shown that deletion of the α subunit of the epithelial Na+ channel (ENaC) in endothelial cells protects from IRI by increasing the availability of nitric oxide. While canonical ENaCs consist of an α, β, and γ subunit, there is evidence of non-canonical ENaC expression in endothelial cells involving the α subunit. We therefore tested whether the deletion of the γ subunit of ENaC also protects mice from IRI to differentiate between these channel configurations. Mice with endothelial-specific deletion of the γ subunit and control littermates were subjected to unilateral renal artery occlusion followed by 48 h of reperfusion. No significant difference was noted in injury between the two groups as assessed by serum creatinine and blood urea nitrogen, levels of specific kidney injury markers, and histological examination. While deletion of the γ subunit did not alter infiltration of immune cells or cytokine message, it was associated with an increase in levels of total and phosphorylated endothelial nitric oxide synthase (eNOS) in the injured kidneys. Our studies demonstrate that even though deletion of the γ subunit of ENaC may allow for greater activation of eNOS, this is not sufficient to prevent IRI, suggesting the protective effects of α subunit deletion may be due, in part, to other mechanisms.

High-Fat Diet Increased Oxidative Stress and Mitochondrial Dysfunction Induced by Renal Ischemia-Reperfusion Injury in Rat

Renal ischemia-reperfusion (IR) injury is one of the major causes of acute kidney injury influenced by the ischemic duration and the presence of comorbidities. Studies have reported that high-fat diet consumption can induce renal lipotoxicity and metabolic dyshomeostasis that can compromise the vital functions of kidney. This study aimed to evaluate the impact of a high-fat diet in the recovery of renal tissue from IR and explored the cellular pathology. In this study, 24 male Wistar rats were divided into two groups: normal diet (ND; n = 12) and high-fat diet (HD; n = 12), which were further subdivided into sham and IR groups at the end of the dietary regimen. The high-fat diet was introduced in 4-week-old rats and continued for 16 weeks. IR was induced by bilateral clamping of the renal peduncle for 45 min, followed by 24 h of reperfusion. Blood chemistry, estimated glomerular filtration rate (eGFR), mitochondrial function, and oxidative stress analysis were carried out to study the pathological changes. The rats fed with HD showed a decreased eGFR and elevated plasma creatinine, thereby compromised kidney function. Subcellular level changes in HD rats are deceased mitochondrial copy number, low PGC-1α gene expression, and declined electron transport chain (ETC) enzymes and adenosine triphosphate (ATP) level. Upon IR induction, HD rats exhibited severely impaired renal function (eGFR-0.09 ml/min) and elevated injury markers compared with ND rats. A histological analysis displayed increased tubular necrosis and cast formation in HD-IR in comparison to ND-IR. The oxidative stress and mitochondrial dysfunction were more prominent in HD-IR. In vitro protein translation assessment revealed impaired translational capacity in HD-IR mitochondria, which suggests mitochondrial changes with diet that may adversely affect the outcome of IR injury. High-fat diet consumption alters the normal renal function by modifying the cellular mitochondria. The renal changes compromise the ability of the kidney to recover from ischemia during reperfusion.

The Predictive Role of Lymphocyte-to-Monocyte Ratio in Acute Kidney Injury in Acute Debakey Type I Aortic Dissection

Background: The post-operative acute kidney injury (AKI) represents a common complication in the Acute Debakey Type I Aortic Dissection (ADTIAD) and predicts a poorer prognosis. The clinical evidence is scarce supporting the predictive value of the pre-operative lymphocyte-to-monocyte ratio (LMR) in post-operative AKI in ADTIAD.

Methods: In this retrospective cohort study, 190 consecutive patients with ADTIAD enrolled for surgical treatment between January 1, 2013, and December 31, 2018. The diagnosis of AKI followed the Kidney Disease: Improving Global Outcomes guidelines (KDIGO). Pre-operative LMR and other possible risk factors were analyzed for their prognostic value in the post-operative AKI in ADTIAD.

Results: The subjects were assigned to the low-LMR and high-LMR groups according to the median value of pre-operative LMR. For post-operative AKI, the incidence and the severity in the low-LMR group were statistically different from that of the high-LMR group. Besides, the lower LMR was statistically associated with the more extended ICU stay and intubation time and higher incidences of ischemic stroke and in-hospital mortality. Additionally, in the multivariable analysis, the pre-operative LMR was an independent predictor for post-operative AKI in ADTIAD. A predictive model for post-operative AKI in ADTIAD was established incorporating LMR.

Conclusions: LMR is an independent prognostic indicator incorporated into the predictive model with other risk factors to predict the post-operative AKI in ADTIAD.

A novel caffeic acid derivative prevents renal remodeling after ischemia/reperfusion injury

Acute kidney disease due to renal ischemia/reperfusion (I/R) is a major clinical problem without effective therapies. The injured tubular epithelial cells may undergo epithelial-mesenchymal transition (EMT). It will loss epithelial phenotypes and express the mesenchymal characteristics. The formation of scar tissue in the interstitial space during renal remodeling is caused by the excessive accumulation of extracellular matrix components and induced fibrosis. This study investigated the effect of caffeic acid ethanolamide (CAEA), a novel caffeic acid derivative, on renal remodeling after injury. The inhibitory role of CAEA on EMT was determined by western blotting, real-time PCR, and immunohistochemistry staining. Treating renal epithelial cells with CAEA in TGF-β exposed cell culture successfully maintained the content of E-cadherin and inhibited the expression of mesenchymal marker, indicating that CAEA prevented renal epithelial cells undergo EMT after TGF-β exposure. Unilateral renal I/R were performed in mice to induce renal remodeling models. CAEA can protect against I/R-induced renal remodeling by inhibiting inflammatory reactions and consecutively inhibiting TGF-β-induced EMT, characterized by the preserved E-cadherin expression and alleviated α-SMA and collagen expression, as well as the alleviated of renal fibrosis. We also revealed that CAEA may exhibits biological activity by targeting TGFBRI. CAEA may antagonize TGF-β signaling by interacting with TGFBR1, thereby blocking binding between TGF-β and TGFBR1 and reducing downstream signaling, such as Smad3 phosphorylation. Our data support the administration of CAEA after I/R as a viable method for preventing the progression of acute renal injury to renal fibrosis.

Novel lncRNA XLOC_032768 protects against renal tubular epithelial cells apoptosis in renal ischemia-reperfusion injury by regulating FNDC3B/TGF-β1

Renal ischemia–reperfusion injury is a leading cause of acute kidney injury, but its underlying mechanism remains poorly understood and effective therapies are still lacking. Here, we identified lncRNA XLOC_032768 as a novel target in renal ischemia–reperfusion injury by analyzing differentially expressed genes of the transcriptome data. PCR results show that XLOC_032768 was markedly downregulated in the kidney during renal ischemia–reperfusion in mice and in cultured kidney cells during hypoxia. Upon induction in vitro, XLOC_032768 overexpression repressed the expression of fibronectin type III domain containing 3B (FNDC3B) and tubular epithelial cells apoptosis. Administration of XLOC_032768 preserved FNDC3B expression and attenuated renal tubular epithelial cells apoptosis, resulting in protection against kidney injury in mice. Knockdown of FNDC3B markedly reduced the expression of TGF-β1 and apoptosis of renal tubular cells. Thus, XLOC_032768/FNDC3B/TGF-β1signaling pathway in ischemia–reperfusion injury may be targeted for therapy.

Sestrin2 in hypoxia and hypoxia-related diseases

Objectives: Sestrin2 is a stress-inducible protein and play an important role in adapting stress states of cells. This article reviewed the role of Sestrin2 in hypoxia and hypoxia-related diseases to provide new perspectives for future research and new therapeutic targets for hypoxia-related diseases.

Methods: A review was conducted through an electronic search of PubMed and Medline databases. Keywords included Sestrin2, ROS, hypoxia, and hypoxia-related disease. Articles from 2008 to 2021 were mostly included and older ones were not excluded.

Results: Sestrin2 is upregulated under various stress conditions, especially hypoxia. Under hypoxic condition, Sestrin2 plays a protective role by reducing the generation of ROS through various pathways, such as adenosine monophosphatea-ctivated protein kinase (AMPK) / mammalian target of rapamycin (mTOR) pathway and nuclear factor-E2-related factor2 (Nrf2) pathway. In addition, Sestrin2 is involved in various hypoxia-related diseases, such as cerebral hypoxic disease, myocardial hypoxic disease, hypoxia-related respiratory disease, and diabetes.

Discussion: Sestrin2 is involved in various hypoxia-related diseases and maybe a therapeutic target. Furthermore, most studies focus on cerebral and myocardial ischemia reperfusion. More researches on hypoxia-related respiratory diseases, kidney injury, and diabetes are needed in future.

Meta-analysis of AKI to CKD transition in perioperative patients

Background

Recent research shows AKI increases the risk of incident CKD. We hypothesized that perioperative AKI may confer increased risk of subsequent CKD compared to nonperioperative AKI.

Methods

A MEDLINE search was performed for “AKI, CKD, chronic renal insufficiency, surgery, and perioperative” and related terms yielded 5209 articles. One thousand sixty-five relevant studies were reviewed. One thousand six were excluded because they were review, animal, or pediatric studies. Fifty-nine studies underwent full manuscript review by two independent evaluators. Seventeen met all inclusion criteria and underwent analysis. Two-by-two tables were constructed from AKI +/− and CKD +/− data. The R package metafor was employed to determine odds ratio (OR), and a random-effects model was used to calculate weighted ORs. Leave-1-out, funnel analysis, and structured analysis were used to estimate effects of study heterogeneity and bias.

Results

Nonperioperative studies included studies of oncology, percutaneous coronary intervention, and myocardial infarction patients. Perioperative studies comprised patients from cardiac surgery, vascular surgery, and burns. There was significant heterogeneity, but risk of bias was overall assessed as low. The OR for AKI versus non-AKI patients developing CKD in all studies was 4.31 (95% CI 3.01–6.17; p < 0.01). Nonperioperative subjects demonstrated OR 3.32 for developing CKD compared to non-AKI patients (95% CI 2.06–5.34; p < 0.01) while perioperative patients demonstrated OR 5.20 (95% CI 3.12–8.66; p < 0.01) for the same event.

Conclusions

We conclude that studies conducted in perioperative and nonperioperative patient populations suggest similar risk of development of CKD after AKI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13741-021-00192-6.

The Role and Mechanism of Histone Deacetylases in Acute Kidney Injury

Acute kidney injury (AKI) is a common clinical complication with an incidence of up to 8-18% in hospitalized patients. AKI is also a complication of COVID-19 patients and is associated with an increased risk of death. In recent years, numerous studies have suggested that epigenetic regulation is critically involved in the pathophysiological process and prognosis of AKI. Histone acetylation, one of the epigenetic regulations, is negatively regulated by histone deacetylases (HDACs). Increasing evidence indicates that HDACs play an important role in the pathophysiological development of AKI by regulation of apoptosis, inflammation, oxidative stress, fibrosis, cell survival, autophagy, ATP production, and mitochondrial biogenesis (MB). In this review, we summarize and discuss the role and mechanism of HDACs in the pathogenesis of AKI.

cMet agonistic antibody prevents acute kidney injury to chronic kidney disease transition by suppressing Smurf1 and activating Smad7

We aimed to investigate the role of cMet agonistic antibody (cMet Ab) in preventing kidney fibrosis during acute kidney injury (AKI) to chronic kidney disease (CKD) transition. Additionally, we explored the effect of cMet Ab on TGF-β1/Smad pathway during the pathogenesis of kidney fibrosis. A unilateral ischemia-reperfusion injury (UIRI) mouse model was established to induce AKI-to-CKD transition. Furthermore, we incubated human proximal tubular epithelial cells (hPTECs) under hypoxic conditions as in vitro model of kidney fibrosis. We analyzed the soluble plasma cMet level in patients with AKI requiring dialysis. Patients who did not recover kidney function and progressed to CKD presented a higher increase in the cMet level. The kidneys of mice treated with cMet Ab showed fewer contractions and weighed more than the controls. The mice in the cMet Ab-treated group showed reduced fibrosis and significantly decreased expression of fibronectin and α-smooth muscle actin. cMet Ab treatment decreased inflammatory markers (MCP-1, TNF-α, and IL-1β) expression, reduced Smurf1 and Smad2/3 level, and increased Smad7 expressions. cMet Ab treatment increased cMet expression and reduced the hypoxia-induced increase in collagen-1 and ICAM-1 expression, thereby reducing apoptosis in the in vitro cell model. After cMet Ab treatment, hypoxia-induced expression of Smurf1, Smad2/3, and TGF-β1 was reduced, and suppressed Smad7 was activated. Down-regulation of Smurf1 resulted in suppression of hypoxia-induced fibronectin expression, whereas treatment with cMet Ab showed synergistic effects. cMet Ab can successfully prevent fibrosis response in UIRI models of kidney fibrosis by decreasing inflammatory response and inhibiting the TGF-β1/Smad pathway.

Immunomodulatory Effects of Mesenchymal Stem Cells on Drug-Induced Acute Kidney Injury

Drug-induced nephrotoxicity is an important and increasing cause of acute kidney injury (AKI), which accounts for approximately 20% of hospitalized patients. Previous reviews studies on immunity and AKI focused mainly on ischemia-reperfusion (IR), whereas no systematic review addressing drug-induced AKI and its related immune mechanisms is available. Recent studies have provided a deeper understanding on the mechanisms of drug-induced AKI, among which acute tubular interstitial injury induced by the breakdown of innate immunity was reported to play an important role. Emerging research on mesenchymal stem cell (MSC) therapy has revealed its potential as treatment for drug-induced AKI. MSCs can inhibit kidney damage by regulating the innate immune balance, promoting kidney repair, and preventing kidney fibrosis. However, it is important to note that there are various sources of MSCs, which impacts on the immunomodulatory ability of the cells. This review aims to address the immune pathogenesis of drug-induced AKI versus that of IR-induced AKI, and to explore the immunomodulatory effects and therapeutic potential of MSCs for drug-induced AKI.

miR-211 alleviates ischaemia/reperfusion-induced kidney injury by targeting TGFβR2/TGF-β/SMAD3 pathway

MicroRNA-211 (miR-211) is closely related to apoptosis and plays an important role in ischemia/reperfusion (I/R) injury. Whether miR-211 is involved in the protective effects in renal I/R injury is unknown. In this study, we evaluated the role of miR-211 in human tubular epithelial cells in response to hypoxia-reoxygenation (H/R) stimulation and I/R injury in vitro and in vivo. The results revealed that miR-211 was down-regulated and TGFβR2 was up-regulated in human kidney (HK-2) cells subjected to H/R. Luciferase reporter assay showed that TGFβR2 was a direct target of miR-211. Enforced miR-211 expression decreased H/R-induced HK-2 cell apoptosis and increased cell viability, and targeting miR-211 further increased H/R-induced HK-2 cell apoptosis and decreased cell viability. However, the effect of miR-211 was reversed by targeting TGFβR2 or enforced TGFβR2 expression in miR-211 overexpressing cells or miR-211 downexpressing cells. Moreover, we confirmed that miR-211 interacted with TGFβR2, and regulating TGF-β/SMAD3 signal. In vivo in mice, miR-211 overexpression ameliorates biochemical and histological kidney injury, reduces apoptosis in mice following I/R. On the contrary, miR-211 downexpressing promoted histological kidney injury and increased apoptosis in mice following I/R. Inhibition of miR-211 or miR-211 overexpression inhibited TGF-β/SMAD3 pathways or activated TGF-β/SMAD3 signal pathways in vitro and in vivo, which are critical for cell survival. Our findings suggested that miR-211 suppress apoptosis and relieve kidney injury following H/R or I/R via targeting TGFβR2/TGF-β/SMAD3 signals. Therefore, miR-211 may be as therapeutic potential for I/R- induced kidney injury.

Exosome-based delivery of super-repressor IκBα ameliorates kidney ischemia-reperfusion injury

Ischemia-reperfusion injury is a major cause of acute kidney injury. Recent studies on the pathophysiology of ischemia-reperfusion-induced acute kidney injury showed that immunologic responses significantly affect kidney ischemia-reperfusion injury and repair. Nuclear factor (NF)-ĸB signaling, which controls cytokine production and cell survival, is significantly involved in ischemia-reperfusion-induced acute kidney injury, and its inhibition can ameliorate ischemic acute kidney injury. Using EXPLOR, a novel, optogenetically engineered exosome technology, we successfully delivered the exosomal super-repressor inhibitor of NF-ĸB (Exo-srIĸB) into B6 wild type mice before/after kidney ischemia-reperfusion surgery, and compared outcomes with those of a control exosome (Exo-Naïve)-injected group. Exo-srIĸB treatment resulted in lower levels of serum blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin in post-ischemic mice than in the Exo-Naïve treatment group. Systemic delivery of Exo-srIĸB decreased NF-ĸB activity in post-ischemic kidneys and reduced apoptosis. Post-ischemic kidneys showed decreased gene expression of pro-inflammatory cytokines and adhesion molecules with Exo-srIĸB treatment as compared with the control. Intravital imaging confirmed the uptake of exosomes in neutrophils and macrophages. Exo-srIĸB treatment also significantly affected post-ischemic kidney immune cell populations, lowering neutrophil, monocyte/macrophage, and T cell frequencies than those in the control. Thus, modulation of NF-ĸB signaling through exosomal delivery can be used as a novel therapeutic method for ischemia-reperfusion-induced acute kidney injury.

Pathophysiology of Cardiorenal Syndrome and Use of Diuretics and Ultrafiltration as Volume Control

Acute deterioration in kidney function in the setting of decompensated heart failure, known as cardiorenal syndrome, results from venous congestion. Although diuretics or ultrafiltration are effective measures in decreasing venous congestion and improving symptoms in patients with cardiorenal syndrome, the impact of decongestive therapy on kidney function or mortality remains uncertain. A precise assessment of venous congestion is required to assess the adequacy of patients' response to decongestive therapy and to guide therapeutic decision making.

Acute or chronic dysfunction of the heart or kidneys can cause dysfunction of other organs. This interaction between the heart and kidneys is characterized as cardiorenal syndrome (CRS). Recently, a preponderance of data indicated that venous congestion plays an important role in the combination of renal and cardiac diseases. This review aims to focus on the pathophysiology of venous congestion that leads to renal impairment in heart failure and the use of diuretics or ultrafiltration as decongestive therapy in CRS. We found that although clinical studies have confirmed that decongestive therapy has a definite role in decreasing volume overload and the consequent symptom improvement in patients with CRS, the impact of diuretics or ultrafiltration on the improvement of kidney function or mortality remains uncertain. A precise assessment of volume status is required to determine the adequacy of decongestion. Objective measures of renal venous congestion may be a future metric to assess the adequacy of the diuretic response in patients and guide therapeutic decision making.

Genetically modified cell sheets in regenerative medicine and tissue engineering

Genetically modified cell sheet technology is emerging as a promising biomedical tool to deliver therapeutic genes for regenerative medicine and tissue engineering. Virus-based gene transfection and non-viral gene transfection have been used to fabricate genetically modified cell sheets. Preclinical and clinical studies have shown various beneficial effects of genetically modified cell sheets in the regeneration of bone, periodontal tissue, cartilage and nerves, as well as the amelioration of dental implant osseointegration, myocardial infarction, skeletal muscle ischemia and kidney injury. Furthermore, this technology provides a potential treatment option for various hereditary diseases. However, the method has several limitations, such as safety concerns and difficulties in controlling transgene expression. Therefore, recent studies explored efficient and safe gene transfection methods, prolonged and controllable transgene expression and their potential application in personalized and precision medicine. This review summarizes various types of genetically modified cell sheets, preparation procedures, therapeutic applications and possible improvements.

Impact of nutritional index on contrast-associated acute kidney injury and mortality after percutaneous coronary intervention

The risk of malnutrition in acute kidney injury and mortality in coronary artery disease patients has not been studied. This study aimed to evaluate whether nutritional status assessed by Onodera's prognostic nutritional index (PNI) was related to percutaneous coronary intervention (PCI) outcomes. A total of 3731 patients who received PCI between January 2010 and December 2018 were included. The relationship between PNI at the time of PCI and the occurrence of contrast-associated acute kidney injury (AKI) and all-cause death was evaluated using logistic regression and Cox proportional hazards models, respectively. AKI occurred in 271 patients (7.3%). A low PNI was independently associated with an increased risk of AKI on multivariate logistic regression analysis (OR 0.96, 95% CI 0.94-0.98, P = 0.001). During the median follow-up of 4.3 years, Kaplan-Meier analysis showed that patients with AKI/low PNI < 47.8 had a higher death rate. After adjusting for various risk factors, a low PNI was a significant risk factor for mortality (HR 0.98, CI 0.96-0.99, P = 0.003). A low level of PNI was associated with increased mortality, especially in the group aged over 70 years and female sex. PNI was closely associated with acute kidney outcomes and patient mortality after PCI.

Tubular epithelial cells derived-exosomes containing CD26 protects mice against renal ischemia/reperfusion injury by maintaining proliferation and dissipating inflammation

Ischemia-reperfusion injury (IR) is the leading cause of acute kidney injury (AKI). No effective drugs to treat IR-related AKI are currently available. Recent pre-clinical trials have evaluated the therapeutic potential of extracellular vesicles-exosomes to chronic kidney disease. Here, we found exosomes derived from the tubular epithelial cell in IR condition (Exo^IR) enriched CD26, compared with control (Exo^Normal). Tracking exosomes in vivo certified tubular epithelial cell uptake exosomes. We have isolated exosomes with overexpression of CD26 (Exo^CD26+) from culture media from tubular epithelial cell line transferred by adenovirus vectors. After administration of exosomes (100 mg) or bovine serum albumin (BSA, equivalent protein control) in IR or sham operation mice after 72 h via tail vein injection, the renal function impairment and histology injury were relived in mice receiving Exo^CD26+. Immunofluorescence staining with proliferating cell nuclear antigen revealed Exo^CD26+ recovered proliferation of cells partly after IR injury. Cell cycle modulator, p53 and p21 were upregulated in IR mice receiving BSA control, Exo^Normal, and Exo^IR. Exo^CD26+ significantly blunt this protein upregulation. Inflammatory cell infiltration and chemokine receptor (CXCR4) were dissipated in IR mice receiving Exo^CD26+. Downstream chemokine of CXCR4, stromal derived factor-1 (SDF1) also decreased after administration of Exo^CD26+ in IR mice. Finally, Exo^CD26+ suppressed inundant collagenⅠ expression in IR kidney. In conclusion, Tubular epithelial cells derived-exosomes containing CD26 might be one of the therapy modes for IR-AKI by maintaining proliferation and dissipating inflammation.

A Cell-Penetrating Peptide That Blocks Toll-Like Receptor Signaling Protects Kidneys against Ischemia-Reperfusion Injury

Renal ischemia-reperfusion injury (IRI) is involved in the majority of clinical conditions that manifest as renal function deterioration; however, specific treatment for this type of injury is still far from clinical use. Since Toll-like receptor (TLR)-mediated signaling is a key mediator of IRI, we examined the effect of a multiple-TLR-blocking peptide named TLR-inhibitory peptide 1 (TIP1), which exerts the strongest action on TLR4, on renal IRI. We subjected C57BL/6 mice to 23 min of renal pedicle clamping preceded by intraperitoneal injection with a vehicle or TIP1. Sham control mice underwent flank incision only. Mouse kidneys were harvested after 24 h of reperfusion for histology, western blot, RT-PCR, and flow cytometry analysis. Pretreatment with TIP1 lowered the magnitude of elevated plasma creatinine levels and attenuated tubular injury. TIP1 treatment also reduced mRNA expression of inflammatory cytokines and decreased apoptotic cells and oxidative stress in post-ischemic kidneys. In kidneys pretreated with TIP1, the infiltration of macrophages and T helper 17 cells was less abundant than those in the IRI only group. These results suggest that TIP1 has a potential beneficial effect in attenuating the degree of kidney damage induced by IRI.

Comparative study of gavage and intraperitoneal administration of gamma-oryzanol in alleviation/attenuation in a rat animal model of renal ischemia/reperfusion-induced injury

OBJECTIVES

Ischemia/reperfusion (I/R) is the leading cause of acute kidney injury. This study aimed to elucidate the reno-protective effect of gamma-oryzanol (GO) by comparing gavage and intraperitoneal (IP) administration methods on renal I/R injury in a rat model.

MATERIALS AND METHODS

Rats were divided into four groups including (group 1) sham, (group 2) I/R-control, (group 3) I/R+GO gavage-treated, and (group 4) I/R+ GO IP-treated. A single dose of GO was administrated to groups 3 and 4 (100 mg/kg body weight), 60 min before induction of I/R. After anesthesia, I/R was created by 45 min of ischemia, followed by 6 hr of reperfusion. Then, blood and tissue samples were subjected to evaluation of renal function, anti-oxidant capacity, inflammation, apoptotic proteins, and IKB/NF-kB pathway.

RESULTS

The two GO administration methods showed improvement of renal function along with attenuation of histological abnormalities. An increase in antioxidant capacity along with a decrease in pro-inflammatory markers, decline in the expression levels of BAX, Bax/Bcl-2, and caspase-3, and up-regulation of Bcl-2 expression were recorded. Moreover, a significant decrease in NF-Kb, p-IKBα, and MMP-2/9 with an increase in IKBα levels were also observed. Overall, in a comparative evaluation between the two gavage and IP administration methods, we did not find any differences in all examined parameters, except IL-6 which had a better result via gavage.

CONCLUSION

A single dose of GO administration has a reno-protective effect against renal I/R injury. Gavage and IP administration exhibit similar efficiency in alleviation of I/R injury.

The protective effect of 1-methyltryptophan isomers in renal ischemia-reperfusion injury is not exclusively dependent on indolamine 2,3-dioxygenase inhibition

BACKGROUND AND PURPOSE

Indolamine 2,3-dioxygenase (IDO), an enzyme that catalyses the metabolism of tryptophan, may play a detrimental role in ischemia-reperfusion injury (IRI). IDO can be inhibited by 1-methyl-tryptophan, which exists in a D (D-MT) or L (L-MT) isomer. These forms show different pharmacological effects besides IDO inhibition. Therefore, we sought to investigate whether these isomers can play a protective role in renal IRI, either IDO-dependent or independent.

EXPERIMENTAL APPROACH

We studied the effect of both isomers in a rat renal IRI model with a focus on IDO-dependent and independent effects.

KEY RESULTS

Both MT isomers reduced creatinine and BUN levels, with D-MT having a faster onset of action but shorter duration and L-MT a slower onset but longer duration (24 h and 48 h vs 48 h and 96 h reperfusion time). Interestingly, this effect was not exclusively dependent on IDO inhibition, but rather from decreased TLR4 signalling, mimicking changes in renal function. Additionally, L-MT increased the overall survival of rats. Moreover, both MT isomers interfered with TGF-β signalling and epithelial-mesenchymal transition. In order to study the effect of isomers in all mechanisms involved in IRI, a series of in vitro experiments was performed. The isomers affected signalling pathways in NK cells and tubular epithelial cells, as well as in dendritic cells and T cells.

CONCLUSION AND IMPLICATIONS

This study shows that both MT isomers have a renoprotective effect after ischemia-reperfusion injury, mostly independent of IDO inhibition, involving mutually different mechanisms. We bring novel findings in the pharmacological properties and mechanism of action of MT isomers, which could become a novel therapeutic target of renal IRI.

Renoprotective effect of carbamylated darbepoetin and udenafil in ischemia-reperfusion of rat kidney due to the effect of preconditioning and inhibition of nuclear factor kappa B

Introduction: Acute kidney injury is a widespread complication in hospitalized patients, with a high mortality rate and long-term complications affecting prognosis and quality of life and with high human and financial costs. In addition, to date, no clear algorithm for the prevention of this type of damage has been developed.

Materials and methods: The research was carried out on male Wistar rats. A 40-minute renal ischemia-reperfusion model was used to model acute kidney injury. Further, the renoprotective properties of carbamylated darbepoetin, udenafil and their combination were assessed based on the analysis of the biochemical studies’ results, dynamics of the renal status and the renal microvasculature, and the pathomorphological picture. A series of experiments was also carried out to assess the contribution of adenosine triphosphate-dependent potassium channels and nuclear factor kappa B to the renoprotective properties of the said agents.

Results and discussion: Prophylactic administration of carbamylated darbepoetin at a dose of 50 µg/kg and udenafil at a dose of 8.7 mg/kg led to a statistically significant decrease in creatinine and blood urea nitrogen, an increase in glomerular filtration rate with a simultaneous decrease in fractional excretion of sodium, as well as an increase in the level of microcirculation in the kidneys and a decrease in the severity of damage according to the data of a pathomorphological examination at all time points of the experiment. A higher efficiency of correcting ischemic and reperfusion renal injuries was observed when using a combination of the said pharmacological agents. A series of experiments with glibenclamide demonstrated that its preliminary administration levels the renoprotective properties of carbamylated darbepoetin and udenafil. The ability of the studied pharmacological agents to reduce lipopolysaccharide-induced expression of nuclear factor kappa B in mononuclear cells was also demonstrated. The results of the research suggest that the renoprotective effects of carbamylated darbepoetin, udenafil, and their combination are realized through ATP-dependent potassium channels and nuclear factor kappa B.

Conclusion: Pharmacological preconditioning with carbamylated darbepoetin and udenafil reduces the severity of acute kidney injury induced by ischemia-reperfusion.

Graphical abstract:

PI3K/AKT activation attenuates acute kidney injury following liver transplantation by inducing FoxO3a nuclear export and deacetylation

AIMS

Acute kidney injury (AKI) is a severe complication of autologous orthotopic liver transplantation (AOLT). Apoptosis has been shown to be involved in renal ischemia/reperfusion, and the PI3K/AKT signaling pathway is involved in numerous cell processes, including promoting cell survival and inhibiting apoptosis. We aimed to verify whether the PI3K/AKT signaling pathway participates in the development of post-AOLT AKI.

METHODS

Male Sprague-Dawley rats underwent AOLT with or without treatment with insulin-like growth factor-1 (IGF-1, a PI3K/AKT activator) and LY294002 (a PI3K/AKT inhibitor; n = 8/group). NRK-52E cells (rat renal tubular epithelial cell line) were subjected to hypoxia-re-oxygenation to mimic renal cell I/R injury in vitro, and confirm whether silencing information regulator 1 (SIRT1) mediated the protective effects of PI3K/AKT by deacetylating forkhead protein O3a (FoxO3a).

KEY FINDINGS

During the reperfusion stage, kidney injury peaked at 8 h after reperfusion, then gradually recovered, which was consistent with the dynamic changes in apoptosis and the protein expressions of Bcl-2 interacting mediator of cell death (Bim), Fas ligand (FasL), and nuclear FoxO3a AKT phosphorylation and nuclear SIRT1 protein expression were also upregulated. IGF-1 application decreased Bim, FasL, and nuclear FoxO3a protein expressions, and protected against apoptosis and AKI. In NRK-52E cells, IGF-1 upregulated nuclear SIRT1 expression, reduced FoxO3a acetylation, downregulated Bim and FasL protein expressions, and attenuated apoptosis and AKI; these effects were reversed by SIRT1 blocking.

CONCLUSION

The activation of the PI3K/AKT signaling pathway not only induced FoxO3a nuclear export but also deacetylation through upregulating nuclear SIRT1 expression to attenuate post-AOLT AKI.

Identification of MicroRNA-92a-3p as an Essential Regulator of Tubular Epithelial Cell Pyroptosis by Targeting Nrf1 via HO-1

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and has no effective treatment. Exploring the molecular mechanisms of renal IRI is critical for the prevention of AKI and its evolution to chronic kidney disease and end-stage renal disease. The aim of the present study was to determine the biological function and molecular mechanism of action of miR-92a-3p in tubular epithelial cell (TEC) pyroptosis. We investigated the relationship between nuclear factor-erythroid 2-related factor 1 (Nrf1) and TEC pyroptosis induced by ischemia-reperfusion in vivo and oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. MicroRNAs (miRNAs) are regulators of gene expression and play a role in the progression of renal IRI. Nrf1 was confirmed as a potential target for miRNA miR-92a-3p. In addition, the inhibition of miR-92a-3p alleviated oxidative stress in vitro and decreased the expression levels of NLRP3, caspase-1, GSDMD-N, IL-1β, and IL-18 in vitro and in vivo. Moreover, Zn-protoporphyrin-IX, an inhibitor of heme oxygenase-1, reduced the protective effect of Nrf1 overexpression on OGD/R-induced TEC oxidative stress and pyroptosis. The results of this study suggest that the inhibition of miR-92a-3p can alleviate TEC oxidative stress and pyroptosis by targeting Nrf1 in renal IRI.

A nonbiodegradable scaffold-free cell sheet of genome-engineered mesenchymal stem cells inhibits development of acute kidney injury

Cell therapy using genome-engineered stem cells has emerged as a novel strategy for the treatment of kidney diseases. By exploiting genome editing technology, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) secreting an angiogenic factors or an anti-inflammatory factor were generated for therapeutic application in acute kidney injury. Junction polymerase chain reaction analysis verified zinc finger nucleases-assisted integration of the desired gene into the hUC-MSCs. Flow cytometry and differentiation assays indicated that genome editing did not affect the differentiation potential of these mesenchymal stem cells. Protein measurement in conditioned media with the use of ELISA and immunoblotting revealed the production and secretion of each integrated gene product. For cell therapy in the bilateral ischemia-reperfusion mouse model of acute kidney injury, our innovative scaffold-free cell sheets were established using a non-biodegradable temperature-responsive polymer. One of each type of scaffold-free cell sheets of either the angiogenic factor vascular endothelial grown factor or angiopoietin-1, or the anti-inflammatory factor erythropoietin, or α-melanocyte-stimulating hormone-secreting hUC-MSCs was applied to the decapsulated kidney surface. This resulted in significant amelioration of kidney dysfunction in the mice with acute kidney injury, effects that were superior to intravenous administration of the same genome-engineered hUC-MSCs. Thus, our scaffold-free cell sheets of genome-engineered mesenchymal stem cells provides therapeutic effects by inhibiting acute kidney injury via angiogenesis or anti-inflammation.

Mechanistic Aspects and Therapeutic Potential of Quercetin against COVID-19-Associated Acute Kidney Injury

The inflammatory mediator and oxidant agent storm caused by the SARS-CoV-2 infection has been strongly associated with the failure of vital organs observed in critically ill patients with coronavirus disease 2019 (COVID-19) and the death of thousands of infected people around the world. Acute kidney injury (AKI) is a common renal disorder characterized by a sudden and sustained decrease in renal function with a critical influence on poor prognosis and lethal clinical outcomes of various etiologies, including some viral infection diseases. It is known that oxidative stress and inflammation play key roles in the pathogenesis and development of AKI. Quercetin is a natural substance that has multiple pharmacological properties, such as anti-inflammatory action, and is used as a dietary supplement. There is evidence of the anti-coronavirus activities of this compound, including against the target SARS-CoV-2 3CLpro. The ability to inhibit coronavirus and its inflammatory processes is strongly desired in a new drug for the treatment of COVID-19. Therefore, in this review, the dual effect of quercetin is discussed from a mechanistic perspective in relation to AKI kidney injury and its nephroprotective potential to SARS-CoV-2 patients.

Akt1 is involved in tubular apoptosis and inflammatory response during renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI). Although Akt is involved in renal IRI, it is unclear as to which Akt isoform plays an important role in renal IRI. In this study, we investigated the role of Akt1 in renal IRI. We subjected the C57BL/6 male mice to unilateral IRI with contralateral nephrectomy. Two days after IRI, IRI-kidneys were harvested. The mice were divided into four groups: wild type (WT) IRI, Akt1^-/- IRI, WT sham, and Akt1^-/- sham. We found that Akt1, not Akt2 or Akt3, was markedly activated in WT IRI than in WT sham mice. The histologic damage score and serum creatinine level significantly increased in WT IRI mice, the increase being the highest in Akt1^-/- IRI mice. The number of TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells and expression of cleaved caspase-3/Bax were higher in Akt1^-/- IRI mice than in WT IRI mice. The expression of Bcl-2 was lower in Akt1^-/- IRI mice than in WT IRI mice. The expression of tumor necrosis factor-α/interleukin-6/interleukin-1β and number of F4/80-positive macrophages were markedly higher in Akt1^-/- IRI than in WT IRI mice. The expression of phosphorylated nuclear factor-κB p65 was also higher in Akt1^-/- IRI mice than in WT IRI mice. Our results show that Akt1 deletion exacerbates kidney damage as it increases tubular apoptosis and inflammatory response during renal IRI. Akt1 could be a potential therapeutic target for developing treatments against IRI-induced AKI.

Effects and molecular mechanism of pachymic acid on ferroptosis in renal ischemia reperfusion injury

Acute kidney injury (AKI) is a common clinical disease. Ferropotosis, a new type of regulatory cell death, serves an important regulatory role in AKI. Pachymic acid (PA), a lanostane‑type triterpenoid from Poria cocos, has been reported to be protective against AKI. However, the protective mechanism of PA in AKI is not yet fully understood. The present study aimed to investigate the effect and molecular mechanism of PA on ferroptosis in renal ischemia reperfusion injury in vivo. A total of 30 mice were intraperitoneally injected with 5, 10 and 20 mg/kg PA for 3 days. A bilateral renal pedicle clip was used for 40 min to induce renal ischemia‑reperfusion injury and establish the model. The results demonstrated that treatment with PA decreased serum creatinine and blood urea nitrogen, and ameliorated renal pathological damage. Transmission electron microscopy revealed no characteristic changes in ferroptosis in the mitochondria of the renal tissue in the high‑dose PA group, and only mild edema. Furthermore, treatment with PA increased glutathione expression, and decreased the expression levels of malondialdehyde and cyclooxygenase 2. Treatment with PA enhanced the protein and mRNA expression levels of the ferroptosis related proteins, glutathione peroxidase 4 (GPX4), solute carrier family 7 (cationic amino acid transporter, y+ system) member 11 (SLC7A11) and heme oxygenase 1 (HO‑1) in the kidney, and increased the expression levels of nuclear factor erythroid derived 2 like 2 (NRF2) signaling pathway members. Taken together, the results of the present study suggest that PA has a protective effect on ischemia‑reperfusion induced acute kidney injury in mice, which may be associated with the inhibition of ferroptosis in the kidneys through direct or indirect activation of NRF2, and upregulation of the expression of the downstream ferroptosis related proteins, GPX4, SLC7A11 and HO‑1.

ROS-responsive chitosan-SS31 prodrug for AKI therapy via rapid distribution in the kidney and long-term retention in the renal tubule

The development of drugs with rapid distribution in the kidney and long-term retention in the renal tubule is a breakthrough for enhanced treatment of acute kidney injury (AKI). Here, l-serine-modified chitosan (SC) was synthesized as a potential AKI kidney-targeting agent due to the native cationic property of chitosan and specific interaction between kidney injury molecule-1 (Kim-1) and serine. Results indicated that SC was rapidly accumulated and long-term retained in ischemia-reperfusion-induced AKI kidneys, especially in renal tubules, which was possibly due to the specific interactions between SC and Kim-1. SC-TK-SS31 was then prepared by conjugating SS31, a mitochondria-targeted antioxidant, to SC via reactive oxygen species (ROS)-sensitive thioketal linker. Because of the effective renal distribution combined with ROS-responsive drug release behavior, the administration of SC-TK-SS31 led to an enhanced therapeutic effect of SS31 by protecting mitochondria from damage and reducing the oxidative stress, inflammation, and cell apoptosis.

Mitochondrial dysfunction in kidney injury, inflammation, and disease: Potential therapeutic approaches

Mitochondria are energy-producing organelles that not only satisfy the high metabolic demands of the kidney but sense and respond to kidney injury-induced oxidative stress and inflammation. Kidneys are rich in mitochondria. Mitochondrial dysfunction plays a critical role in the progression of acute kidney injury and chronic kidney disease. Mitochondrial responses to specific stimuli are highly regulated and synergistically modulated by tightly interconnected processes, including mitochondrial dynamics (fission, fusion) and mitophagy. The counterbalance between these processes is essential in maintaining a healthy network of mitochondria. Recent literature suggests that alterations in mitochondrial dynamics are implicated in kidney injury and the progression of kidney diseases. A decrease in mitochondrial fusion promotes fission-induced mitochondrial fragmentation, but a reduction in mitochondrial fission produces excessive mitochondrial elongation. The removal of dysfunctional mitochondria by mitophagy is crucial for their quality control. Defective mitochondrial function disrupts cellular redox potential and can cause cell death. Mitochondrial DNA derived from damaged cells also act as damage-associated molecular patterns to recruit immune cells and the inflammatory response can further exaggerate kidney injury. This review provides a comprehensive overview of the role of mitochondrial dysfunction in acute kidney injury and chronic kidney disease. We discuss the processes that control mitochondrial stress responses to kidney injury and review recent advances in understanding the role of mitochondrial dysfunction in inflammation and tissue damage through the use of different experimental models of kidney disease. We also describe potential mitochondria-targeted therapeutic approaches.

NOX1 Inhibition Attenuates Kidney Ischemia-Reperfusion Injury via Inhibition of ROS-Mediated ERK Signaling

The protective effects of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) 1 inhibition against kidney ischemia-reperfusion injury (IRI) remain uncertain. The bilateral kidney pedicles of C57BL/6 mice were clamped for 30 min to induce IRI. Madin–Darby Canine Kidney (MDCK) cells were incubated with H₂O₂ (1.4 mM) for 1 h to induce oxidative stress. ML171, a selective NOX1 inhibitor, and siRNA against NOX1 were treated to inhibit NOX1. NOX expression, oxidative stress, apoptosis assay, and mitogen-activated protein kinase (MAPK) pathway were evaluated. The kidney function deteriorated and the production of reactive oxygen species (ROS), including intracellular H₂O₂ production, increased due to IRI, whereas IRI-mediated kidney dysfunction and ROS generation were significantly attenuated by ML171. H₂O₂ evoked the changes in oxidative stress enzymes such as SOD2 and GPX in MDCK cells, which was mitigated by ML171. Treatment with ML171 and transfection with siRNA against NOX1 decreased the upregulation of NOX1 and NOX4 induced by H₂O₂ in MDCK cells. ML171 decreased caspase-3 activity, the Bcl-2/Bax ratio, and TUNEL-positive tubule cells in IRI mice and H₂O₂-treated MDCK cells. Among the MAPK pathways, ML171 affected ERK signaling by ERK phosphorylation in kidney tissues and tubular cells. NOX1-selective inhibition attenuated kidney IRI via inhibition of ROS-mediated ERK signaling.

Comparison of ischemic and ischemic/reperfused kidney injury via clamping renal artery, vein, or pedicle in anesthetized rats

PURPOSE

We recently observed that 30 min of bilateral renal arterial, venous, or pedicle occlusion with 2-h reperfusion differentially induced acute kidney injury (AKI), which was suggested to be probably resulted from their directly exerting dissimilar impacts on kidney during the ischemic period. The present study was further designed to evaluate and prove this suggestion.

METHODS

Anesthetized male Sprague-Dawley rats were divided in two distinct supragroups with 30-min bilateral renal ischemia alone (BI) or followed by 30-min reperfusion (BIR), which each had four different groups (n = 8) of subjecting to renal artery, vein, or pedicle clamping and also sham operation.

RESULTS

In the BI groups, artery clamping caused lower renal tissue injury than pedicle clamping but vein occlusion caused the highest levels of kidney histological damages along with the widespread hemorrhagic congestion. In the BIR groups, renal vascular congestion, intratubular cast, and edema decreased, but tubular epithelial injury did not significantly change in comparison to their equivalents BI groups. However, the orders of total renal tissue damages in the BIR groups were still as clamping renal veins >  > pedicles > arteries and in association with their proportionally developed renal hemodynamic, excretory, and urine-concentrating dysfunctions.

CONCLUSION

The transmission of high arterial pressure into renal microvessels and rupturing of their walls during venous-clamping augment, but the retrograde blood flow from veins into kidney during artery clamping attenuates induction of renal tissue injury with respect to pedicle clamping not only at the ischemic period but also at the early reperfusion period and along with the proportional development of renal dysfunctions.