Pharmacological targets in the renal peritubular microenvironment: implications for therapy for sepsis-induced acute kidney injury

Sepsis-associated endothelial glycocalyx damage: a review of animal models, clinical evidence, and molecular mechanisms

In the mammalian cardiovascular system, endothelial glycocalyx is a gel-like layer that covers the luminal surface of endothelial cells (ECs) and plays crucial roles in vascular homeostasis, permeability and leukocyte adhesion. Degradation of this structure occurs early in sepsis and becomes accordingly dysfunctional. In severe cases, it is not self-regulated by the organism. However, the relationship between the glycocalyx and the occurrence and development of sepsis remains poorly understood. One possibility is that thinned glycocalyx promotes leukocyte recognition and adhesion, thereby facilitating the elimination of pathogens from infected areas. This may represent a protective mechanism developed by the organism during through evolutionary processes. However, if the damage persists and disrupts the dynamic balance of the microcirculation, interstitial edema or organ failure can occur. Thus, we asked the questions, what is the precise composition and structure of the glycocalyx? How is it degraded? What animal models are available to study the relationship between the glycocalyx and sepsis? What glycocalyx biomarkers are found in the blood of patients with sepsis? To determine whether sepsis can be treated by interfering with the glycocalyx, this study provides a systematic summary and discussion of the latest progress in addressing these questions.

Acute liver failure

Acute liver failure (ALF) is a life-threatening disorder characterised by rapid deterioration of liver function, coagulopathy, and hepatic encephalopathy in the absence of pre-existing liver disease. The cause of ALF varies across the world. Common causes of ALF in adults include drug toxicity, hepatotropic and non-hepatotropic viruses, herbal and dietary supplements, antituberculosis drugs, and autoimmune hepatitis. The cause of liver failure affects the management and prognosis, and therefore extensive investigation for cause is strongly suggested. Sepsis with multiorgan failure and cerebral oedema remain the leading causes of death in patients with ALF and early identification and appropriate management can alter the course of ALF. Liver transplantation is the best current therapy, although the role of artificial liver support systems, particularly therapeutic plasma exchange, can be useful for patients with ALF, especially in non-transplant centres. In this Seminar, we discuss the cause, prognostic models, and management of ALF.

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

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

Determination of trace elements and electrolyte levels in kidney tissue of simvastatin-treated septic rats

Trace elements are cofactors in various enzymes in the antioxidant defense and cell homeostasis required in the tissue during inflammation. In acute kidney injury induced by lipopolysaccharide (LPS), renal cells are affected by cytotoxicity. Renal evacuation and gastrointestinal absorption rates are important in regulating plasma levels of trace elements. Simvastatin is a widely used anti-lipidemic drug with known anti-inflammatory effects. This study aimed to examine the effect of simvastatin on trace elements and electrolyte levels in kidney tissue in rats with LPS-induced sepsis. Adult male Wistar albino rats were divided into four groups: control, LPS (20 mg/kg, i.p., single dose), simvastatin (20 mg/kg, o.p., 5 days), and LPS + Simvastatin (LPS + Sim). Sodium, potassium, calcium, magnesium, selenium, zinc, copper, and histological structural changes were examined in kidney tissue samples 4 h after LPS execution. The inductively coupled plasma optical emission spectroscopy technique (ICP-OES) was used to determine the tissue trace element levels. In rats with sepsis-induced LPS, selenium, calcium, sodium, and magnesium levels significantly decreased while copper, potassium, and zinc levels significantly increased compared to other experimental groups. In sepsis treated with the simvastatin (LPS + Simvastatin) group, trace elements and electrolyte levels are like the control groups, apart from selenium levels. Selenium levels were significantly decreased in the LPS + Simvastatin group compared to the controls. As a result of examining the kidney tissues under a light microscope, simvastatin improved tissue damage caused by LPS-induced acute kidney injury. LPS-induced renal injury and simvastatin caused significant changes in the oxidant/antioxidant system. In septic rats, simvastatin was shown to balance some trace element levels, and it may improve damage in the kidney tissue.

Acute kidney injury in acute liver failure: A narrative review

Acute kidney injury (AKI) is a frequent complication of acute liver failure (ALF) and it worsens the already worse prognoses of ALF. ALF is an uncommon disease, with varying etiologies and varying definitions in different parts of the world. There is limited literature on the impact of AKI on the outcome of ALF with or without transplantation. The multifaceted etiology of AKI in ALF encompasses factors such as hemodynamic instability, systemic inflammation, sepsis and direct nephrotoxicity. Indications of renal replacement therapy (RRT) for AKI in ALF patients extend beyond the conventional criteria for dialysis and continuous renal replacement therapy (CRRT) may have a role in transplant-free survival or bridge to liver transplantation (LT). LT is a life-saving option for ALF, so despite somewhat lower survival rates of LT in ALF patients with AKI, LT is not usually deferred. In this review, we will discuss the guidelines' recommended definition and classification of AKI in ALF, the impact of AKI in ALF, the pathophysiology of AKI and the role of CRRT and LT in ALF patients with AKI.

Anemonin inhibits sepsis-induced acute kidney injury via mitigating inflammation and oxidative stress

Elevated inflammation and oxidative stress (OS) are the main pathologic features of acute kidney injury (AKI)-caused by sepsis. Here, we made an investigation into the protective effects of the natural compound Anemonin (ANE) on sepsis-induced AKI both in vitro and in vivo. Lipopolysaccharide (LPS) was applied to construct an in vitro AKI model in renal tubular epithelial cells, and the septic C57BL/6J mouse model was constructed via cecal ligation and puncture (CLP). Cell viability and apoptosis were detected. The levels of p53, Bax, Bcl2, Caspase3, Caspase8, Caspase9, AMP-activated protein kinase (AMPK), Sirt-1, and forkhead box O3 were determined by Western Blot or RT-PCR. The reactive oxygen species level and OS markers were measured. Furthermore, the pathological changes of kidneys were evaluated by hematoxylin-eosin staining and immunohistochemistry. As per the information presented, ANE improved LPS-elicited apoptosis, inflammatory response, and OS in a dose-dependent pattern in renal tubular epithelial cells. Besides, ANE activated the AMPK/Sirt-1 pathway, and the AMPK inhibitor (Compound C) and Sirt-1 inhibitor (EX-527) significantly attenuated ANE-mediated protection on renal tubular epithelial cells. In vivo, ANE mitigated the levels of serum creatinine and urea nitrogen in the CLP-induced mouse sepsis model, reduced the renal tissue injury score, and attenuated OS, inflammation, and apoptosis levels in the kidney. Taken together, this study suggested that ANE has protective effects in sepsis-triggered AKI through repressing inflammation, OS, and cell apoptosis by activating the AMPK/Sirt-1 pathway.

Role of heparanase in sepsis‑related acute kidney injury (Review)

Sepsis-related acute kidney injury (S-AKI) is a common and significant complication of sepsis in critically ill patients, which can often only be treated with antibiotics and medications that reduce S-AKI symptoms. The precise mechanism underlying the onset of S-AKI is still unclear, thus hindering the development of new strategies for its treatment. Therefore, it is necessary to explore the pathogenesis of S-AKI to identify biomarkers and therapeutic targets for its early diagnosis and treatment. Heparanase (HPA), the only known enzyme that cleaves the side chain of heparan sulfate, has been widely studied in relation to tumor metabolism, procoagulant activity, angiogenesis, inflammation and sepsis. It has been reported that HPA plays an important role in the progression of S-AKI. The aim of the present review was to provide an overview of the function of HPA in S-AKI and to summarize its underlying molecular mechanisms, including mediating inflammatory response, immune response, autophagy and exosome biogenesis. It is anticipated that emerging discoveries about HPA in S-AKI will support HPA as a potential biomarker and therapeutic target to combat S-AKI.

Contrast-Enhanced Ultrasonography for Acute Kidney Injury: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of the work described here was to provide an evidence-based evaluation of contrast-enhanced ultrasonography (CEUS) in acute kidney injury (AKI) and assess variations in renal microperfusion with CEUS quantitative parameters in patients at a high risk of developing AKI.

METHODS

A meta-analysis and systematic review were conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the Embase, MEDLINE, Web of Science and the Cochrane Library databases were used to search the relevant articles systematically (2000-2022). Studies using CEUS to assess renal cortical microcirculation in AKI were included.

RESULTS

Six prospective studies (374 patients) were included. The overall quality of included studies was moderate to high. CEUS measures, maximum intensity (standard mean difference [SMD]: -1.37, 95% confidence interval [CI]: -1.64 to -1.09) and wash-in rate (SMD: -0.77, 95% CI: -1.09 to -0.45) were lower in the AKI+ group than in the AKI- group, and mean transit time (SMD: 0.76, 95% CI: 0.11-1.40) and time to peak (SMD: 1.63, 95% CI: 0.99-2.27) were higher in the AKI+ group. Moreover, maximum intensity and wash-in rate values changed before creatinine changed in the AKI+ group.

CONCLUSION

Patients with AKI had reduced microcirculatory perfusion, prolonged perfusion time and a reduced rising slope in the renal cortex, which occurred before serum creatinine changes. And they could be measured using CEUS, indicating that CEUS could help in the diagnosis of AKI.

Immunoregulatory mechanism of acute kidney injury in sepsis: A Narrative Review

Sepsis acute kidney injury (SAKI) is a common complication of sepsis, accounting for 26-50 % of all acute kidney injury (AKI). AKI is an independent risk factor for increased mortality risk in patients with sepsis. The excessive inflammatory cascade reaction in SAKI is one of the main causes of kidney damage. Both the innate immune system and the adaptive immune system are involved in the inflammation process of SAKI. Under the action of endotoxin, neutrophils, monocytes, macrophages, T cells and other complex immune network reactions occur, and a large number of endogenous inflammatory mediators are released, resulting in the amplification and loss of control of the inflammatory response. The study of immune cells in SAKI will help improve the understanding of the immune mechanisms of SAKI, and will lay a foundation for the development of new diagnostic and therapeutic targets. This article reviews the role of known immune mechanisms in the occurrence and development of SAKI, with a view to finding new targets for SAKI treatment.

Intrarenal 1-methoxypyrene, an aryl hydrocarbon receptor agonist, mediates progressive tubulointerstitial fibrosis in mice

Recent studies have shown that endogenous metabolites act via aryl hydrocarbon receptor (AhR) signalling pathway in tubulointerstitial fibrosis (TIF) pathogenesis. However, the mechanisms underlying endogenous metabolite-mediated AhR activation are poorly characterised. In this study, we conducted untargeted metabolomics analysis to identify the significantly altered intrarenal metabolites in a mouse model of unilateral ureteral obstruction (UUO). We found that the levels of the metabolite 1-methoxypyrene (MP) and the mRNA expression of AhR and its target genes CYP1A1, CYP1A2, CYP1B1 and COX-2 were progressively increased in the obstructed kidney at Weeks 1, 2 and 3. Furthermore, these changes were positively correlated with progressive TIF in UUO mice. In NRK-52E, RAW 264.7 and NRK-49F cells, MP dose-dependently upregulated the mRNA expression of AhR and its four target genes and the protein expression of nuclear AhR, accompanied by the upregulated protein expression of collagen I, α-SMA and fibronectin, as well as downregulated E-cadherin expression. Consistently, oral administration of MP in mice progressively enhanced AhR activity and upregulated profibrotic protein expression in the kidneys; these effects were partially inhibited by AhR knockdown in MP-treated mice and cell lines. In addition, we screened and identified erythro-guaiacylglycerol-β-ferulic acid ether (GFA), which was isolated from Semen plantaginis, as a new AhR antagonist. GFA significantly attenuated TIF in MP-treated NRK-52E cells and mice by partially antagonising AhR activity. Our results suggest that MP activates AhR signalling, thus mediating TIF through epithelial-mesenchymal transition and macrophage-myofibroblast transition. MP is a crucial metabolite that contributes to TIF via AhR signalling pathway.

Ginsenoside Rg1 ameliorates sepsis-induced acute kidney injury by inhibiting ferroptosis in renal tubular epithelial cells

Acute kidney injury (AKI) represents a prevailing complication of sepsis, and its onset involves ferroptosis. Ginsenoside Rg1 exerts a positive effect on kidney diseases. This study explored the action of ginsenoside Rg1 in sepsis-induced AKI (SI-AKI) by regulating ferroptosis in renal tubular epithelial cells (TECs). Sepsis rat models were established using cecal ligation and puncture (CLP) and cell models were established by treating human renal TECs (HK-2) with LPS to induce ferroptosis. Serum creatinine (SCr) and blood urea nitrogen (BUN) and urine KIM1 contents in rats were determined by ELISA kits. Kidney tissues were subjected to immunohistochemical and H&E stainings. Iron concentration, malondialdehyde (MDA), glutathione (GSH), and ferroptosis-related protein (ferritin light chain [FTL], ferritin heavy chain [FTH], GSH peroxidase 4 [GPX4], and Ferroptosis suppressor protein 1 [FSP1]) levels in kidney tissues and HK-2 cells were measured using ELISA kits and Western blotting. HK-2 cell viability was detected by cell counting kit-8, and cell death was observed via propidium iodide staining. Reactive oxygen species accumulation in cells was detected using C11 BODIPY 581/591 as a molecular probe. In CLP rats, ginsenoside Rg1 reduced SCr, BUN, KIM1, and NGAL levels, thus palliating SI-AKI. Additionally, ginsenoside Rg1 decreased iron content, FTL, FTH, and MDA levels, and elevated GPX4, FSP1, and GSH levels, thereby inhibiting lipid peroxidation and ferroptosis. Moreover, FSP1 knockdown annulled the inhibition of ginsenoside Rg1 on ferroptosis. In vitro experiments, ginsenoside Rg1 raised HK-2 cell viability and lowered iron accumulation and lipid peroxidation during ferroptosis, and its antiferroptosis activity was dependent on FSP1. Ginsenoside Rg1 alleviates SI-AKI, possibly resulting from inhibition of ferroptosis in renal TECs through FSP1.

Theacrine alleviates sepsis-induced acute kidney injury by repressing the activation of NLRP3/Caspase-1 inflammasome

Acute kidney injury (AKI) is a frequent and serious complication of sepsis, which results in a rapid decline of kidney function. Currently, there are no curative therapies for AKI. Theacrine is a purine alkaloid and exerts significant role in regulating inflammation, oxidative stress, and mood elevation. The study aims to evaluate the biological role and potential mechanism of theacrine in septic AKI. The murine and cellular models of septic AKI were established in lipopolysaccharide (LPS)-treated C57BL/6 mice and HK-2 cells, respectively. The effect of theacrine on alleviating septic AKI was assessed after pretreatment with theacrine in vivo and in vitro. We found that theacrine treatment significantly alleviated LPS-induced kidney injury, as evidenced by decreased levels of kidney injury markers (blood urea nitrogen and creatinine), inflammatory factors (IL-1β and IL-18), and cell apoptosis in vivo and in vitro. Mechanistically, theacrine markedly repressed the activation of NOD-like receptor (NLR) pyrin domain-containing protein 3 (NLRP3)inflammasome. As expected, MCC950 (a specific inhibitor of NLRP3) treatment also decreased LPS-induced production of IL-18 and IL-1β and cell apoptosis in HK-2 cells. More important, Nigericin sodiumsalt (a NLRP3 agonist) damaged the effect of theacrine on repressing kidney injury markers (blood urea nitrogen and creatinine), pro-inflammatory cytokines (IL-18 and IL-1β), and cell apoptosis. Taken together, these results demonstrate that theacrine alleviates septic AKI, at least in part by repressing the activation of NLRP3 inflammasome.

Chemokine CCL2 from proximal tubular epithelial cells contributes to sepsis-induced acute kidney injury

Damage-associated molecular patterns secreted from activated kidney cells initiate inflammatory response, a critical step in the development of sepsis-induced acute kidney injury (AKI). However, the underlying mechanism remains to be clarified. Here, we established a mouse model of sepsis-induced AKI through intraperitoneal injection of lipopolysaccharide (LPS), and demonstrated that LPS induced dramatical upregulation of C-C motif chemokine ligand 2 (CCL2) at both the mRNA and the protein levels in kidney, which was mainly expressed by tubular epithelial cells (TECs), especially by proximal TECs. Proximal tubule-specific ablation of CCL2 reduced LPS-induced macrophage infiltration, proinflammatory cytokine expression, and attenuated AKI. In vitro, using transwell migration assay, we found that deficiency of CCL2 in TECs decreased macrophage migration ability. However, myeloid-specific depletion of CCL2 could not protect the kidneys from the aforementioned effects. Mechanistically, LPS activated toll like receptor (TLR) 2 signaling in TECs, which induced activation of its downstream effector nuclear factor (NF)-κB. Blockade of TLR2 signaling or inhibition of NF-κB activation in TECs significantly suppressed LPS-induced CCL2 expression. Furthermore, ChIP analyses confirmed a direct binding of NF-κB p65 in the CCL2 promoter regein, and LPS increased the binding of NF-κB p65 to CCL2 promoter, suggesting that TLR2/NF-κB p65 regulates CCL2 expression in TECs. Together, these results demonstrate that endogenous CCL2 released from PTECs, not from myeloid cells was responsible for sepsis-induced kidney inflammation and AKI. Specificly targeting tubular TLR2/NF-κB/CCL2 signaling may be a potential therapeutic strategy for prevention or attenuation of septic AKI.

Cul4a attenuates LPS-induced acute kidney injury via blocking NF-kB signaling pathway in sepsis

Background

Acute kidney injury (AKI) is a common disease that can develop into end-stage kidney disease. Sepsis is one of the main causes of AKI. Currently, there is no satisfactory way to treat septic AKI. Therefore, we have shown the protective function of Cul4a in septic AKI and its molecular mechanism.

Methods

The cellular and animal models of septic AKI were established by using lipopolysaccharide (LPS). Western blot (WB) was employed to analyze Cul4a expression. RT-qPCR was employed to test the expression of Cul4a, SOD1, SOD2, GPX1, CAT, IL-6, TNF-a, Bcl-2, IL1b, Bax and KIM-1 mRNA. ELISA was performed to detect the contents of inflammatory factors and LDH. CCK-8 was utilized to detect cell viability. Flow cytometry was utilized to analyze the apoptosis. DHE-ROS kit was used to detect the content of ROS.

Results

Cul4a was down-regulated in cellular and animal models of septic AKI. Oxidative stress is obviously induced by LPS, as well as apoptosis and inflammation. However, these can be significantly inhibited by up-regulating Cul4a. Moreover, LPS induced the activation of the NF-kB pathway, which could also be inhibited by overexpression of Cul4a.

Conclusions

Cul4awas found to be a protective factor in septic AKI, which could inhibit LPS-induced oxidative stress, apoptosis and inflammation of HK-2 cells by inhibiting the NF-kB pathway.

Renal microvascular endothelial cell responses in sepsis-induced acute kidney injury

Microvascular endothelial cells in the kidney have been a neglected cell type in sepsis-induced acute kidney injury (sepsis-AKI) research; yet, they offer tremendous potential as pharmacological targets. As endothelial cells in distinct cortical microvascular segments are highly heterogeneous, this Review focuses on endothelial cells in their anatomical niche. In animal models of sepsis-AKI, reduced glomerular blood flow has been attributed to inhibition of endothelial nitric oxide synthase activation in arterioles and glomeruli, whereas decreased cortex peritubular capillary perfusion is associated with epithelial redox stress. Elevated systemic levels of vascular endothelial growth factor, reduced levels of circulating sphingosine 1-phosphate and loss of components of the glycocalyx from glomerular endothelial cells lead to increased microvascular permeability. Although coagulation disbalance occurs in all microvascular segments, the molecules involved differ between segments. Induction of the expression of adhesion molecules and leukocyte recruitment also occurs in a heterogeneous manner. Evidence of similar endothelial cell responses has been found in kidney and blood samples from patients with sepsis. Comprehensive studies are needed to investigate the relationships between segment-specific changes in the microvasculature and kidney function loss in sepsis-AKI. The application of omics technologies to kidney tissues from animals and patients will be key in identifying these relationships and in developing novel therapeutics for sepsis.

ZLN005 protects against ischemia-reperfusion-induced kidney injury by mitigating oxidative stress through the restoration of mitochondrial fatty acid oxidation

To date, the treatment of acute kidney injury (AKI) remains a difficult problem for clinicians. In the present study, we assessed whether ZLN005, a novel peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) agonist, can protect against ischemic AKI in vivo and in vitro. Notably, ZLN005 treatment significantly alleviated Ischemia-reperfusion (I/R)-induced tubular injury and reversed the decrease in hypoxia-reoxygenation-induced cell viability by restoring PGC-1α expression in a dose-dependent manner. This beneficial effect of ZLN005 was associated with the preservation of mitochondrial fatty acid oxidation (MitoFAO) and the alleviation of oxidative stress. Cotreatment with etomoxir, a specific inhibitor of carnitine palmitoyltransferase-1α (CPT-1α) activity, or CPT-1α siRNA abrogated ZLN005-induced antistress responses by mitigating reactive oxygen species production and decreasing apoptosis under ischemia-hypoxia conditions by suppressing MitoFAO. Further studies revealed that activation of endoplasmic reticulum (ER) stress may be involved in the effect of CPT-1α inhibition observed in vivo and in vitro. Collectively, our results suggest that ZLN005 confers a protective effect on I/R-induced kidney injury by mitigating ER stress through the restoration of MitoFAO by targeting PGC-1α.

Circ_RASGEF1B Promotes LPS-Induced Apoptosis and Inflammatory Response by Targeting MicroRNA-146a-5p/Pdk1 Axis in Septic Acute Kidney Injury Cell Model

BACKGROUND

We intended to investigate the function of circular RNA RasGEF domain family member 1B (circ_RASGEF1B) in lipopolysaccharide (LPS)-induced septic acute kidney injury (AKI) cell model and its associated mechanism.

METHODS

TCMK-1 cells were exposed to 10 μg/mL LPS for 24 h to establish a septic AKI cell model. Mice were intraperitoneally injected with 10 mg/kg LPS to establish a septic AKI mice model. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were used to measure RNA and protein expression, respectively. Cell viability and apoptosis were assessed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry. Cell inflammatory response was analyzed using enzyme-linked immunosorbent assay. Dual-luciferase reporter assay was conducted to confirm the predicted target relationship between microRNA-146a-5p (miR-146a-5p) and circ_RASGEF1B or pyruvate dehydrogenase kinase 1 (Pdk1).

RESULTS

The circ_RASGEF1B level was upregulated in LPS-induced TCMK-1 cells and septic AKI mice models. LPS exposure reduced cell viability and promoted cell apoptosis and inflammatory response partly by upregulating circ_RASGEF1B. Circ_RASGEF1B bound to miR-146a-5p and miR-146a-5p interference partly overturned circ_RASGEF1B silencing-mediated effects in LPS-induced TCMK-1 cells. Pdk1 was a target of miR-146a-5p, and Pdk1 accumulation partly counteracted miR-146a-5p-induced influences in TCMK-1 cells upon LPS stimulation.

CONCLUSION

Circ_RASGEF1B promoted LPS-induced apoptosis and inflammatory response in renal tubular epithelial cells partly by upregulating Pdk1 via acting as miR-146a-5p sponge.

MiR-22-3p suppresses sepsis-induced acute kidney injury by targeting PTEN

Background: Septic acute kidney injury is considered as a severe and frequent complication that occurs during sepsis. The present study was performed to understand the role of miR-22-3p and its underlying mechanism in sepsis-induced acute kidney injury.

Methods: Rats were injected with adenovirus carrying miR-22-3p or miR-NC in the caudal vein before cecal ligation. Meanwhile, HK-2 cells were transfected with the above adenovirus following LPS stimulation. We measured the markers of renal injury (blood urea nitrogen (BUN), serum creatinine (SCR)). Histological changes in kidney tissues were examined by hematoxylin and eosin (H&E), Masson staining, periodic acid Schiff staining and TUNEL staining. The levels of IL-1β, IL-6, TNF-α and NO were determined by ELISA assay. Using TargetScan prediction and luciferase reporter assay, we predicted and validated the association between PTEN and miR-22-3p.

Results: Our data showed that miR-22-3p was significantly down-regulated in a rat model of sepsis-induced acute kidney injury, in vivo and LPS-induced sepsis model in HK-2 cells, in vitro. Overexpression of miR-22-3p remarkably suppressed the inflammatory response and apoptosis via down-regulating HMGB1, p-p65, TLR4 and pro-inflammatory factors (IL-1β, IL-6, TNF-α and NO), both in vivo and in vitro. Moreover, PTEN was identified as a target of miR-22-3p. Furthermore, PTEN knockdown augmented, while overexpression reversed the suppressive role of miR-22-3p in LPS-induced inflammatory response.

Conclusions: Our results showed that miR-22-3p induced protective role in sepsis-induced acute kidney injury may rely on the repression of PTEN.

SIRT1 attenuates sepsis-induced acute kidney injury via Beclin1 deacetylation-mediated autophagy activation

Our previous studies showed that silent mating-type information regulation 2 homologue-1 (SIRT1, a deacetylase) upregulation could attenuate sepsis-induced acute kidney injury (SAKI). Upregulated SIRT1 can deacetylate certain autophagy-related proteins (Beclin1, Atg5, Atg7 and LC3) in vitro. However, it remains unclear whether the beneficial effect of SIRT1 is related to autophagy induction and the underlying mechanism of this effect is also unknown. In the present study, caecal ligation and puncture (CLP)-induced mice, and an LPS-challenged HK-2 cell line were established to mimic a SAKI animal model and a SAKI cell model, respectively. Our results demonstrated that SIRT1 activation promoted autophagy and attenuated SAKI. SIRT1 deacetylated only Beclin1 but not the other autophagy-related proteins in SAKI. SIRT1-induced autophagy and its protective effect against SAKI were mediated by the deacetylation of Beclin1 at K430 and K437. Moreover, two SIRT1 activators, resveratrol and polydatin, attenuated SAKI in CLP-induced septic mice. Our study was the first to demonstrate the important role of SIRT1-induced Beclin1 deacetylation in autophagy and its protective effect against SAKI. These findings suggest that pharmacologic induction of autophagy via SIRT1-mediated Beclin1 deacetylation may be a promising therapeutic approach for future SAKI treatment.

LINC00261 relieves the progression of sepsis-induced acute kidney injury by inhibiting NF-κB activation through targeting the miR-654-5p/SOCS3 axis

Sepsis is a life-threatening disease, which can cause the dysfunction of multiple organs, including kidney. Recently, a number of studies found that the long non-coding RNA (lncRNA) is closely associated with the development and progression of sepsis; however, the role of long intergenic non-protein coding RNA 261 (LINC00261) in sepsis-induced acute kidney injury is poorly understood. In this study, we found the expression of LINC00261 was significantly decreased in the serum of patients with sepsis than healthy controls. A similar result was also observed in the mouse model of sepsis induced by lipopolysaccharide (LPS). Further investigations revealed that overexpression of LINC00261 improved the viability, suppressed the apoptosis and reduced the generation of inflammatory cytokines in LPS-treated HK-2 cells. Mechanistically, we confirmed that LINC00261 could function as a sponge to combine with microRNA-654-5p (miR-654-5p) which inhibits nuclear factor-κB (NF-κB) activity by targeting suppressor of cytokine signaling 3 (SOCS3). In conclusion, our results demonstrate that LINC00261 may regulate the progression of sepsis-induced acute kidney injury via the miR-654-5p/SOCS3/NF-κB pathway and therefore provides a new insight into the treatment of this disease.

miR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury

Exosomes have been shown to effectively regulate the biological functions of target cells. Here, we investigated the protective effect and mechanism of hypoxia-induced renal tubular epithelial cells (TECs)-derived exosomes on acute tubular injury. We found that in vitro hypoxia-induced tubular exosomes (Hy-EXOs) were protective in acute tubular injury by promoting TECs proliferation and improving mitochondrial functions. By using exosome miRNA sequencing, we identified miR-20a-5p was abundant and was a key mechanism for the protective effect of Hy-EXOs on tubular injury as up-regulation of miR-20a-5p enhanced but down-regulation of miR-20a-5p inhibited the protective effect of Hy-EXOs on tubular injury under hypoxia conditions. Further study in a mouse model of ischemia–reperfusion-induced acute kidney injury (IRI-AKI) also confirmed this notion as pre-treating mice with the miR-20a-5p agomir 48 h prior to AKI induction was capable of inhibiting IRI-AKI by lowering serum levels of creatinine and urea nitrogen, and attenuating the severity of tubular necrosis, F4/80(+) macrophages infiltration and vascular rarefaction. Mechanistically, the protective effect of miR-20a-5p on acute kidney injury (AKI) was associated with inhibition of TECs mitochondrial injury and apoptosis in vitro and in vivo. In conclusion, miR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury. Results from the present study also reveal that miR-20a-5p may represent as a novel therapy for AKI.

Role of Nrf2 in Lipopolysaccharide-Induced Acute Kidney Injury: Protection by Human Umbilical Cord Blood Mononuclear Cells

Background

Acute kidney injury (AKI) is one of the common complications of sepsis. Heretofore, there is no effective treatment for septic AKI. Recent studies have revealed that besides treating hematological malignancies, human umbilical cord blood mononuclear cells (hUCBMNCs) show good therapeutic effects on other diseases. But whether hUCBMNCs can protect against septic AKI and its underlying mechanism are unknown.

Methods

The rat model of lipopolysaccharide- (LPS-) induced AKI was developed, and the injection of hUCBMNCs was executed to prevent and treat AKI. ML385, a specific nuclear factor E2-related factor 2 (Nrf2) inhibitor, was used to silence Nrf2. The cell experiments were conducted to elaborate the protective mechanism of Nrf2 pathway.

Results

An effective model of LPS-induced AKI was established. Compared to the rats only with LPS injection, the levels of inflammation, reactive oxygen species (ROS), and apoptosis in renal tissues after hUCBMNC injection were markedly attenuated. Pathological examination also indicated significant remission of renal tissue injury in the LPS+MNCs group, compared to rats in the LPS group. Transmission electron microscopy (TEM) showed that the damage of the mitochondria in the LPS+MNCs group was lighter than that in the LPS group. Noteworthily, the renal Nrf2/HO-1 pathway was activated and autophagy was enhanced after hUCBMNC injection. ML385 could partly reverse the renoprotective effect of hUCBMNCs, which could demonstrate that Nrf2 participated in the protection of hUCBMNCs. Cell experiments showed that increasing the expression level of Nrf2 could alleviate LPS-induced cell injury by increasing the autophagy level and decreasing the injury of the mitochondria in HK-2 cells.

Conclusion

All results suggest that hUCBMNCs can protect against LPS-induced AKI via the Nrf2 pathway. Activating Nrf2 can upregulate autophagy to protect LPS-induced cell injury.

Endothelial progenitor cells-secreted extracellular vesicles containing microRNA-93-5p confer protection against sepsis-induced acute kidney injury via the KDM6B/H3K27me3/TNF-α axis

The pivotal pathogenetic role of microRNAs (miRs) in sepsis-induced acute kidney injury (AKI) has been demonstrated in mounting evidence. The functions of the target cells are regulated through the release of cells-encapsulated extracellular vesicles (Evs) into the extracellular space. The present study aims to elucidate the clinical significance as well as biological function of the endothelial progenitor cell (EPC)-derived Evs containing miR-93-5p in sepsis-induced AKI. We first established a cellular sepsis-induced AKI mouse model by treatment with lipopolysaccharide (LPS), and tested ectopic expression and depletion experiments in the model. Evs derived from miR-93-5p inhibitor-transfected EPCs (Evs/miR-93-5p inhibitor) were isolated, and co-cultured with HK2 cells to explore the effects of EPC-derived Evs overexpressing miR-93-5p on LPS-induced HK2 cell injury. The interaction between miR-93-5p and lysine (K)-specific demethylase 6B (KDM6B) was identified using dual-luciferase reporter assay, and ChIP was used to validate the relationship between KDM6B and tumor necrosis factor-α (TNF-α). Mice were made septic by cecal ligation and puncture (CLP), and then injected with Ev/miR-93-5p inhibitor to explore its functions in vivo. The results found that miR-93-5p and histone H3 Lys27 trimethylation (H3K27me3) were downregulated while KDM6B was upregulated in LPS-treated HK2 cells. EPC-derived Evs alleviated LPS-induced HK2 cell injury, while Ev/miR-93-5p inhibitor potentiated the cell injury in vitro. miR-93-5p was found to directly target KDM6B. Silencing KDM6B induced H3K27me3, inhibiting the activation of TNF-α, thereby weakening LPS-induced HK2 cell injury. EPC-derived Evs containing miR-93-5p attenuated multiple organ injury, vascular leakage, inflammation, and apoptosis in septic mice. In conclusion, the present study demonstrated that endothelial protection from EPC-derived Evs carrying miR-93-5p in sepsis-induced AKI, which was mediated by regulation KDM6BH/3K27me3/TNF-α axis.

Indian National Association for the Study of the Liver Consensus Statement on Acute Liver Failure (Part 1): Epidemiology, Pathogenesis, Presentation and Prognosis

Acute liver failure (ALF) is an infrequent, unpredictable, potentially fatal complication of acute liver injury (ALI) consequent to varied etiologies. Etiologies of ALF as reported in the literature have regional differences, which affects the clinical presentation and natural course. In this part of the consensus article designed to reflect the clinical practices in India, disease burden, epidemiology, clinical presentation, monitoring, and prognostication have been discussed. In India, viral hepatitis is the most frequent cause of ALF, with drug-induced hepatitis due to antituberculosis drugs being the second most frequent cause. The clinical presentation of ALF is characterized by jaundice, coagulopathy, and encephalopathy. It is important to differentiate ALF from other causes of liver failure, including acute on chronic liver failure, subacute liver failure, as well as certain tropical infections which can mimic this presentation. The disease often has a fulminant clinical course with high short-term mortality. Death is usually attributable to cerebral complications, infections, and resultant multiorgan failure. Timely liver transplantation (LT) can change the outcome, and hence, it is vital to provide intensive care to patients until LT can be arranged. It is equally important to assess prognosis to select patients who are suitable for LT. Several prognostic scores have been proposed, and their comparisons show that indigenously developed dynamic scores have an edge over scores described from the Western world. Management of ALF will be described in part 2 of this document.

Down-regulation of LncRNA CRNDE aggravates kidney injury via increasing MiR-181a-5p in sepsis

Long non-coding RNA (lncRNA) colorectal neoplasia differentially expressed (CRNDE) is reported to be linked to inflammation and cell apoptosis. However its role in sepsis induced kidney injury remains unclear. This study aims to explore the possible mechanism of CRNDE in kidney injury induced by sepsis. In vivo urine-derived sepsis (US) rat model and in vitro LPS-induced HK-2 and HEK293 cells were established. Kidney function was measured in rats from different groups. Relative levels of tumor necrosis factor-α (TNF-α) and interleukin-1β(IL-1β) in kidney tissue were detected via Enzyme-linked immune sorbent assay (ELISA). Then we up- or down-regulated CRNDE and miRNA-181a-5p expression in the cells. The biological influence of CRNDE and miR-181a-5p on cells was studied using CCK-8 assay and Annexin V assay. Interaction between CRNDE and miR-181a-5p was determined by bioinformatics analysis, RT-PCR, and dual luciferase reporter assay. Peroxisome proliferator-activated receptor-α (PPARα) and cell apoptosis related molecules were detected by western blot. We demonstrated that CRNDE was markedly down-regulated while miR-181a-5p was significantly up-regulated in sepsis models. CRNDE interacted with miR-181a-5p, and negatively regulated its expression level. CRNDE knockdown in rats increased the urea nitrogen and serum creatinine in plasma. Knockdown of CRNDE or transfection of miR-181a-5p significantly inhibited proliferation and promoted apoptosis of HK-2 and HEK293 cells, while overexpression of CRNDE and transfection of miR-181a-5p inhibitors had opposite effects. For mechanism, miR-181a-5p directly targeted the 3' untranslated region of PPARα, and depressed its protein level, and PPARα was regulated indirectly by CRNDE. We concluded that CRNDE protected renal cell from sepsis-induced injury via miR-181a-5p/PPARα pathway.

Overexpressed CD39 mitigates sepsis‑induced kidney epithelial cell injury via suppressing the activation of NLR family pyrin domain containing 3

Unfettered inflammation is a leading cause of multiple organ failures in sepsis. The anti-inflammatory role of cluster of differentiation (CD)39 has been previously reported. The present study aimed to investigate the role of unfettered inflammation in sepsis-induced acute kidney injury (AKI). Lipopolysaccharide (LPS) was introduced to construct a sepsis mouse model. Kidney function and pathological changes in mice were measured at 12, 24 and 48 h. CD39 overexpression and inhibition vectors were transfected into renal tubular epithelial (HK-2) cells, followed by LPS treatment (10 μg/ml), and the cell viability changes at 24 h after treatment were assessed and the expression of NLR family pyrin domain containing 3 (NLRP3), cleaved caspase-1 and CD39 were determined by performing ELISAs. Cell apoptosis and reactive oxygen species (ROS) levels were determined by flow cytometry. It was found that after LPS administration, kidney injury was the most serious at 24 h in mice. CD39 overexpression could suppress the upregulation of pro-inflammatory cytokines induced by LPS treatment. In addition, the cell apoptosis and ROS level exhibited an obvious decrease, while cell viability increased. The NLRP3 expression and activity also showed a great inhibition in CD39-overexpressed cells. By contrast to CD39 overexpression, CD39 inhibition promoted the activation of the NLRP3 inflammasome. These data indicate the protective role of CD39 in LPS-induced renal tubular epithelial cell damage through inhibiting NLRP3 inflammasome activation and that CD39 might be a potential therapeutic target in sepsis-induced AKI.

MicroRNA-191-5p diminished sepsis-induced acute kidney injury through targeting oxidative stress responsive 1 in rat models

There is no effective treatment for septic acute kidney injury (AKI), which is considered a major public health concern in today’s world. Here, we studied the functions of miR-191-5p in septic AKI. MiR-191-5p mimic or mimic control was injected into rats from caudal vein before cecal ligation and puncture (CLP) surgery. Part of kidney tissues was stained by Hematoxylin and Eosin (H&E) for histological examination. The levels of serum cytokines were evaluated using enzyme-linked immunosorbent assay (ELISA). For cell transfection, renal cells were isolated from the kidneys of CLP rat model injected with mimic control and miR-191-5p mimic. With TargetScan prediction, serine/threonine-protein kinase OSR1 was identified as a target of miR-191-5p. Oxidative stress responsive 1 (OXSR1) overexpression vector was transfected into renal cells. Cell viability and apoptosis rate were determined by Cell Counting Kit-8 (CCK-8) and flow cytometry, respectively. We additionally measured the phosphorylation levels of p38 and p65. We found that the injection of miR-191-5p mimic could observably inhibit renal injury scores, and inhibit inflammatory cytokine productions and apoptotic protein levels in septic rats. After being transfected with OXSR1, the apoptosis rates and expressions of B-cell lymphoma-2 (Bcl-2), down-regulated Bax and Cleaved caspase-3 (C caspase-3) indicated overexpressed OXSR1 contributed to cell apoptosis. The up-regulated protein levels of p-p38 and p-p65 may suggest the involvement of p38 MAPK/NF-κB signaling pathway in the functions of OXSR1. Our results showed that the protective effects of miR-191-5p on kidney tissues of septic rats may rely on the repression of OXSR1.

Inhibition of neddylation plays protective role in lipopolysaccharide-induced kidney damage through CRL-mediated NF-κB pathways

It has been shown that NF-κB signaling path is very effective pharmacological target for the treatment of various inflammatory diseases, including bacterial infection-associated acute kidney injury (AKI), which remains a main cause of disability and death in patients. Notably, IκB, the upstream molecular of NF-κB, plays an important role by inhibiting NF-κB activity, and IκB is regulated by cullin-RING E3 ligases (CRLs)-mediated proteasomal degradation. Therefore inhibition of CRLs-mediated neddylation and degradation of IκB would prevent NF-κB-mediated inflammation. MLN4924, a potent neddylation-inhibiting pharmacological agent, has been shown to have significant protective effects against lipopolysaccharide (LPS)-induced pro-inflammatory cytokine production through restriction of the CRL-mediated NF-κB pathway. However, it is still unclear whether MLN4924 plays a protective role through its anti-inflammatory properties in sepsis-induced AKI. In the current research, we explored whether MLN4924 have anti-inflammatory action in LPS-induced AKI mice. Our results show that MLN4924 dramatically decreased the cytotoxicity of LPS and inhibited LPS-induced synthesis and release of pro-inflammatory cytokines, such as TNF-α, IL-6 and IL-1β, in HK2 cells, a renal tubular cell line. In addition, MLN4924 inhibited Nedd8-activating enzymes, which broke the process of cullin proteins neddylation and subsequent CRL target proteins degradation. The MLN4924-induced degradation of CRL attenuated the phosphorylation modification of IκB and IKK-α/β and blocked the nuclear translocation of P50-NF-κB and P65-NF-κB in HK2 cells under LPS stimulation. Finally, our in vivo results show that MLN4924 protected against LPS-induced AKI at relatively low doses. Collectively, these results suggest that pharmacologically blocking neddylation by MLN4924 results in the suppression of pro-inflammatory cytokines generation through the CRL/NF-κB pathway in LPS-stimulated HK2 cells, and attenuated renal inflammation in LPS-induced AKI.

Endotoxaemia differentially regulates the expression of renal Ca2+ transport proteins in mice

AIM

Alterations in parathyroid hormone (PTH) and/or vitamin D signalling are frequently reported in patients with sepsis. The consequences on renal and intestinal Ca²⁺ and P_i regulatory mechanisms are still unclear. We hypothesized that endotoxaemia alters the expression of important renal and intestinal Ca²⁺ and P_i transport proteins.

METHODS

Male C57BL/6 mice were treated with lipopolysaccharide (LPS; 3 mg/kg; i.p.). The mRNA and protein levels of renal and intestinal Ca²⁺ and P_i transport proteins were measured by RT-qPCR, immunohistochemistry and western blot analysis.

RESULTS

Lipopolysaccharide-induced hypocalcaemia and hyperphosphataemia was paralleled by a decrease in glomerular filtration rate and urinary excretion of Ca²⁺ and P_i . Endotoxaemia augmented plasma levels of PTH and affected the fibroblast growth factor 23 (FGF23)-klotho-vitamin D axis by increasing plasma levels of FGF23 and downregulation of renal klotho expression. Renal expression of CYP27b1 and plasma levels of 1,25-dihydroxyvitamin D₃ were increased in response to LPS. Endotoxaemia augmented the renal expression of TRPV5, TRPV6 and PiT1, whereas the renal expression of calbindin-D_28K , NCX1, NaP_i -2a and NaP_i -2c were decreased. Incubation of primary distal tubule cells with LPS increased TRPV6 mRNA levels. Furthermore, LPS decreased the intestinal expression of TRPV6, calbindin-D_9K and of NaP_i -2b.

CONCLUSION

Our findings indicate that endotoxaemia is associated with hypocalcaemia and hyperphosphataemia and a disturbed FGF23-klotho-vitamin D signaling. Further, LPS-induced acute kidney injury was accompanied by an increased or decreased expression of specific renal and intestinal Ca²⁺ and P_i transporters respectively. It seems unlikely that LPS-induced hypocalcaemia is due to renal loss of Ca²⁺ .

Renal autoregulation in experimental septic shock and its response to vasopressin and norepinephrine administration

Evidence suggests that septic shock patients with chronic arterial hypertension may benefit from resuscitation targeted to achieve higher blood pressure values than other patients, possibly as a result of altered renal autoregulation. The effects of different vasopressor agents on renal autoregulation may be important in this context. We investigated the effects of arginine vasopressin (AVP) and norepinephrine (NE) on renal autoregulation in ovine septic shock. Sepsis was induced by fecal peritonitis. When shock developed (decrease in mean arterial pressure to <65 mmHg and no fluid-responsiveness), animals were randomized to receive NE or AVP in a crossover design. Before the switch to the second vasopressor, the first vasopressor was discontinued for 30 minutes to ensure complete washout of the first vasopressor. Renal autoregulation was evaluated by recording the change in renal blood flow (RBF) in response to manual, stepwise reductions in renal inflow pressure. In this model, the lower limit of renal autoregulation was not significantly altered 6 hours after sepsis induction (59±9 vs. 64±7 mmHg at baseline, p=0.096). After development of shock, the autoregulatory threshold was lower with AVP than with NE (59±5 vs. 65±7 mmHg, p=0.010). However, RBF was higher with NE both at the start of autoregulatory measurements (206±58 vs. 170±52 mL/min; p=0.050) and at the autoregulatory threshold (191±53 vs. 150±47 mL/min; p=0.008). As vasopressors may have different effects on renal autoregulation, blood pressure management in patients with septic shock should be individualized and take into account drug-specific effects.

Comparison of ultrasound shear wave elastography with magnetic resonance elastography and renal microvascular flow in the assessment of chronic renal allograft dysfunction

Background Monitoring of renal allograft function is essential for early identification of dysfunction and improvement of kidney transplant (KTX) outcome. Purpose To non-invasively assess renal stiffness in KTX recipients using ultrasound shear wave elastography (USE) in correlation with multifrequency magnetic resonance elastography (MRE), renal allograft function, and renal microvascular flow determined using a novel ultrasound microvascular imaging technique. Material and Methods This prospective study investigated 25 KTXs (functional KTX [FCT], n = 14; chronic KTX insufficiency [DYS], n = 11) in 20 KTX recipients (mean age = 43 ± 14 years). USE was performed using a high-frequency broadband linear transducer and compared with MRE. Shear wave velocity (SWV) was correlated with the estimated glomerular filtration rate (eGFR). Qualitative differences in renal microvascular flow were obtained using SMI. Results FCT had higher SWV than DYS in both cortex and pyramids (cortex, FCT: 3.75 ± 0.82 m/s vs. DYS: 2.79 ± 0.73 m/s, P = 0.0002; pyramid, FCT: 2.89 ± 0.46 m/s vs. DYS: 2.39 ± 0.34 m/s, P = 0.044). Cutoff values of 3.265 m/s for cortex, 2.535 m/s for pyramids, and 2.985 m/s for combined non-hilar parenchyma provided sensitivities of 72.7%, 77.8%, and 90.9% and specificities of 71.4%, 78.6%, and 85.7% for detecting renal allograft dysfunction with area under the receiver operating characteristic curve (AUC) values of 0.831, 0.841, 0.925 (95% confidence interval [CI] = 0.67-0.99, 0.66-1.02, 0.83-1.03). USE correlated positively with eGFR ( r = 0.741, P = 0.0004) and with MRE-derived SWV ( r = 0.562, P = 0.004). Renal microvascular flow was decreased in DYS. Conclusion USE is sensitive to renal allograft dysfunction, which is characterized by reduced SWV and renal perfusion. USE has higher image resolution than MRE, while MRE has slightly better diagnostic accuracy.

The role of adenosine 1a receptor signaling on GFR early after the induction of sepsis

Sepsis and acute kidney injury (AKI) synergistically increase morbidity and mortality in the ICU. How sepsis reduces glomerular filtration rate (GFR) and causes AKI is poorly understood; one proposed mechanism includes tubuloglomerular feedback (TGF). When sodium reabsorption by the proximal tubules is reduced in normal animals, the macula densa senses increased luminal sodium chloride, and then adenosine-1a receptor (A1aR) signaling triggers tubuloglomerular feedback, reducing GFR through afferent arteriole vasoconstriction. We measured GFR and systemic hemodynamics early during cecal ligation and puncture-induced sepsis in wild-type and A1aR-knockout mice. A miniaturized fluorometer was attached to the back of each mouse and recorded the clearance of FITC-sinistrin via transcutaneous fluorescence to monitor GFR. Clinical organ injury markers and cytokines were measured and hemodynamics monitored using implantable transducer telemetry devices. In wild-type mice, GFR was stable within 1 h after surgery, declined by 43% in the next hour, and then fell to less than 10% of baseline after 2 h and 45 min. In contrast, in A1aR-knockout mice GFR was 37% below baseline immediately after surgery and then gradually declined over 4 h. A1aR-knockout mice had similar organ injury and inflammatory responses, albeit with lower heart rate. We conclude that transcutaneous fluorescence can accurately monitor GFR and detect changes rapidly during sepsis. Tubuloglomerular feedback plays a complex role in sepsis; initially, TGF helps maintain GFR in the 1st hour, and over the subsequent 3 h, TGF causes GFR to plummet. By 18 h, TGF has no cumulative effect on renal or extrarenal organ damage.

Transplantation of Human Umbilical Cord Blood Mononuclear Cells Attenuated Ischemic Injury in MCAO Rats via Inhibition of NF-κB and NLRP3 Inflammasome

Accumulated evidence displayed that transplantation of stem cells may be a promising approach for the treatment of neurological disorders. However, the underlying mechanisms remain to be well elucidated. Moreover, some investigators cannot reproduce similar results as the previous. The present results showed that transplantation of fresh human umbilical cord blood mononuclear cells (cbMNCs) attenuated ischemic damage in middle cerebral artery occlusion (MCAO) rats, accompanied with improvement of neurologic deficits, learning and memory function. The increase in neovascularization and related molecules such as vascular endothelial growth factor (VEGF), Angiopoietin-1 (Ang-1) and endothelium-specific receptor tyrosine kinase 2 (Tie-2) in the injured brain was observed in cbMNCs-treated rats. Moreover, nuclear factor-κB (NF-κB) activation and nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome were also inhibited by the cells graft, resulting in reduction in cleaved caspase-1 and mature interleukin-1β (IL-1β) content. These results suggested that the protective actions of the cells on the cerebral ischemia may be related to inhibition of NF-κB pathway and NLRP3 inflammasome.

Elevated serum levels of lipoprotein‑associated phospholipase A2 predict mortality rates in patients with sepsis

Sepsis remains one of the leading contributors to mortality rates in the intensive care unit (ICU) and emergency intensive care unit (EICU). Therefore, any treatments against the agents which produce sepsis in a medical emergency, are welcome. Elevated serum levels of lipoprotein‑associated phospholipase A2 (Lp‑PLA2) have been reported in a small cohort of patients with inflammation. The present study evaluated serum levels of Lp‑PLA2 in patients with sepsis and investigated the role of Lp‑PLA2 in sepsis. The investigation involved the selection of 151 patients with sepsis admitted to the emergency department of the Affiliated Hospital of Nantong University (Nantong, China) and 30 healthy controls. All patients (39 with sepsis, 55 with severe sepsis and 57 with septic shock) were examined on admission to the EICU. A complete blood count was performed, and serum levels of Lp‑PLA2, C‑reactive protein, procalcitonin, and interleukin 6, sequential organ failure (SOFA) scores and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were determined on hospital admission. The EICU and overall mortality rates were evaluated at baseline. The present study also assessed various laboratory parameters, clinical data and inflammatory cytokines. The patient follow up duration was 90 days. The data suggested that the serum levels of Lp‑PLA2 on admission to the EICU in patients with sepsis were elevated, compared with those in healthy controls. The concentrations of Lp‑PLA2 were correlated with the severity of disease, and were significantly associated with experimental markers of inflammation and established prognostic scores. In the total cohort, persistently elevated levels of Lp‑PLA2 on admission for EICU treatment was a predictor of poor prognosis, and provided superior diagnostic use, compared with the prognostic scoring systems, including SOFA or APACHE II scores. Taken together, the results suggested that Lp‑PLA2, with respect to other markers of inflammation, may have a role as a prognostic marker in sepsis, and provide background evidence for further trials to evaluate the clinical and pathophysiologic roles of Lp‑PLA2 in sepsis. Persistently elevated serum concentrations of Lp‑PLA2 indicated an unfavorable outcome in patients with sepsis. In addition, the results indicated the potential role of Lp‑PLA2 as a prognostic biomarker in patients with sepsis during the early course of EICU treatment.

SIRT1/3 Activation by Resveratrol Attenuates Acute Kidney Injury in a Septic Rat Model

Sepsis often results in damage to multiple organ systems, possibly due to severe mitochondrial dysfunction. Two members of the sirtuin family, SIRT1 and SIRT3, have been implicated in the reversal of mitochondrial damage. The aim of this study was to determine the role of SIRT1/3 in acute kidney injury (AKI) following sepsis in a septic rat model. After drug pretreatment and cecal ligation and puncture (CLP) model reproduction in the rats, we performed survival time evaluation and kidney tissue extraction and renal tubular epithelial cell (RTEC) isolation. We observed reduced SIRT1/3 activity, elevated acetylated SOD2 (ac-SOD2) levels and oxidative stress, and damaged mitochondria in RTECs following sepsis. Treatment with resveratrol (RSV), a chemical SIRT1 activator, effectively restored SIRT1/3 activity, reduced acetylated SOD2 levels, ameliorated oxidative stress and mitochondrial function of RTECs, and prolonged survival time. However, the beneficial effects of RSV were greatly abrogated by Ex527, a selective inhibitor of SIRT1. These results suggest a therapeutic role for SIRT1 in the reversal of AKI in septic rat, which may rely on SIRT3-mediated deacetylation of SOD2. SIRT1/3 activation could therefore be a promising therapeutic strategy to treat sepsis-associated AKI.

THE ENDOTHELIUM IN SEPSIS

Sepsis affects practically all aspects of endothelial cell (EC) function and is thought to be the key factor in the progression from sepsis to organ failure. Endothelial functions affected by sepsis include vasoregulation, barrier function, inflammation, and hemostasis. These are among other mechanisms often mediated by glycocalyx shedding, such as abnormal nitric oxide metabolism, up-regulation of reactive oxygen species generation due to down-regulation of endothelial-associated antioxidant defenses, transcellular communication, proteases, exposure of adhesion molecules, and activation of tissue factor. This review covers current insight in EC-associated hemostatic responses to sepsis and the EC response to inflammation. The endothelial cell lining is highly heterogeneous between different organ systems and consequently also in its response to sepsis. In this context, we discuss the response of the endothelial cell lining to sepsis in the kidney, liver, and lung. Finally, we discuss evidence as to whether the EC response to sepsis is adaptive or maladaptive. This study is a result of an Acute Dialysis Quality Initiative XIV Sepsis Workgroup meeting held in Bogota, Columbia, between October 12 and 15, 2014.

Protection of resveratrol on acute kidney injury in septic rats

AIM

The aim of the study is to investigate protective effect of resveratrol (Res) on acute kidney injury (AKI) in sepsis.

METHODS

Rats in sham group received sham operation; in sham + Res received sham operation and Res (3 mg/kg); in cecal ligation and puncture (CLP) established as sepsis; in CLP + Res (3 mg/kg) with sepsis and Res (3 mg/kg); and in CLP + Res (10 mg/kg) with sepsis and Res (10 mg/kg). Survival rate, serum indexes, inflammatory factors, NF-κB-P65, and SIRT1 were detected. Lipopolysaccharide (LPS) mesangial cell was with Res and SIRT1 silencing.

RESULTS

(1) Res intervention improved survival rate of CLP rat. (2) Compared to sham, serum creatinine, blood urine nitrogen, serum cystatin C, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, tumor necrosis factor-α, interleukin-1β, IL-6, and renal injury index increased in CLP group, while decreased in CLP + Res (3 mg/kg) and CLP + Res (10 mg/kg), significantly, as dose-dependent ( p < 0.05). (3) With Res, NF-κB-P65 and de-acetylated SIRT1 decreased, while SIRT1 and de-acetylated Nuclear factor kB-p65 9 NF-κB-P65) increased, significantly ( p < 0.05). (4) SIRT1 and de-acetylated NF-κB-P65 decreased in LPS cells, while SIRT1 increased after Res intervention, significantly ( p < 0.05). After silencing SIRT1, de-acetylated NF-κB-P65 increased, significantly ( p < 0.05).

CONCLUSIONS

Res increases the survival rate of septic rats by inhibiting inflammatory factors to ease AKI and promotes NF-κB-P65 de-acetylation by upregulating SIRT1.

Could Biomarkers Direct Therapy for the Septic Patient?

Sepsis is a serious medical condition caused by a severe systemic inflammatory response to a bacterial, fungal, or viral infection that most commonly affects neonates and the elderly. Advances in understanding the pathophysiology of sepsis have resulted in guidelines for care that have helped reduce the risk of dying from sepsis for both children and older adults. Still, over the past three decades, a large number of clinical trials have been undertaken to evaluate pharmacological agents for sepsis. Unfortunately, all of these trials have failed, with the use of some agents even shown to be harmful. One key issue in these trials was the heterogeneity of the patient population that participated. What has emerged is the need to target therapeutic interventions to the specific patient's underlying pathophysiological processes, rather than looking for a universal therapy that would be effective in a "typical" septic patient, who does not exist. This review supports the concept that identification of the right biomarkers that can direct therapy and provide timely feedback on its effectiveness will enable critical care physicians to decrease mortality of patients with sepsis and improve the quality of life of survivors.

A low toxicity synthetic cinnamaldehyde derivative ameliorates renal inflammation in mice by inhibiting NLRP3 inflammasome and its related signaling pathways

Uncontrolled inflammation is a leading cause of various chronic diseases. Cinnamaldehyde (CA) is a major bioactive compound isolated from the essential oil of the leaves of Cinnamomum osmophloeum kaneh that exhibits anti-inflammatory activity; however, the use of CA is limited by its cytotoxicity. Here, we synthesized three CA derivatives and identified 4-hydroxycinnamaldehyde-galactosamine (HCAG) as a low toxicity anti-inflammatory compound in vitro (HCAG IC50 ≫ 1600 µM; CA IC50=40 µM) and in vivo. HCAG reduced pro-inflammatory mediator expression in LPS-activated macrophages by inhibiting MAPK and PKC-α/δ phosphorylation, decreasing ROS generation and reducing NF-κB activation. HCAG also reduced NLRP3 inflammasome-derived IL-1β secretion by inhibiting the ATP-mediated phosphorylation of AKT and PKC-α/δ. In a mouse model of LPS-induced renal inflammation, we observed reduced albuminuria and a mild degree of glomerular proliferation, glomerular sclerosis and periglomerular inflammation in the HCAG-treated mice compared with the vehicle-treated mice. The underlying mechanisms for these renoprotective effects involved: (1) inhibited NLRP3 inflammasome activation; (2) decreased superoxide anion levels and apoptosis; and (3) suppressed activation of NF-κB and related downstream inflammatory mediators.

Panaxadiol Saponin and Dexamethasone Improve Renal Function in Lipopolysaccharide-Induced Mouse Model of Acute Kidney Injury

Background

Acute kidney injury (AKI) is a serious complication of systemic inflammatory response syndrome (SIRS), which has a high mortality rate. Previous studies showed that panaxadiol saponin (PDS) and Dexamethasone have similar anti-inflammatory properties and protect cardiopulmonary function in lipopolysaccharide (LPS)-induced septic shock rats. In the present study, we investigated whether PDS or Dexamethasone has a similar role in improving kidney function in LPS-induced AKI mice.

Methods and Results

Mice subjected to LPS (10 mg/kg) treatment exhibited AKI demonstrated by markedly increased blood urea nitrogen and creatinine levels compared with controls (P<0.01). However, PDS and Dexamethasone induce similar reverse effects on renal function, such as reduced serum creatinine and blood urea nitrogen levels compared with the LPS group (P<0.05). PDS decreased the production and release of tumor necrosis factor (TNF)-α and interleukin (IL)-6 by inhibiting the NF-κB signaling pathway, down-regulating inducible nitric oxide synthase protein expression levels and inhibiting oxidative stress. In most anti-AKI mechanisms, PDS and dexamethasone were similar, but PDS are better at inhibition of TNF production, promote SOD activity and inhibition of IKB phosphorylation. In addition, nuclear glucocorticoid receptor expression was markedly enhanced in PDS and Dexamethasone treatment groups. Further research is required to determine whether PDS can combine with the glucocorticoid receptor to enter the nucleus.

Conclusion

This study demonstrated that PDS and dexamethasone have similar reverse amelioration for renal functions, and have potential application prospects in the treatment of sepsis-induced AKI.

Tubular cross talk in acute kidney injury: a story of sense and sensibility

The mammalian kidney is an organ composed of numerous functional units or nephrons. Beyond the filtering glomerulus of each nephron, various tubular segments with distinct populations of epithelial cells sequentially span the kidney from cortex to medulla. The highly organized folding of the tubules results in a spatial distribution that allows intimate contact between various tubular subsegments. This unique arrangement can promote a newly recognized type of horizontal epithelial-to-epithelial cross talk. In this review, we discuss the importance of this tubular cross talk in shaping the response of the kidney to acute injury in a sense and sensibility model. We propose that injury-resistant tubules such as S1 proximal segments and thick ascending limbs (TAL) can act as "sensors" and thus modulate the responsiveness or "sensibility" of the S2-S3 proximal segments to injury. We also discuss new findings that highlight the importance of tubular cross talk in regulating homeostasis and inflammation not only in the kidney, but also systemically.

Resveratrol attenuates lipopolysaccharide-induced acute kidney injury by suppressing inflammation driven by macrophages

SCOPE

Acute kidney injury (AKI) is the most frequent and serious complication in sepsis, a potentially deadly inflammatory response induced by bacterial, viral, or fungal infection. LPS-induced AKI is associated with an abnormal inflammatory response, including renal endothelial dysfunction and renal inflammation. Resveratrol, a natural phytoalexin with low toxicity and anti-inflammatory properties, is known to protect endothelial cells and modulate the immune response in sepsis.

METHODS AND RESULTS

This study investigates the potential protective effects of resveratrol on AKI induced by LPS exposure of mice. Resveratrol was administered as a pre- and posttreatment, or as a posttreatment alone following LPS injection and compared to control groups. Resveratrol significantly improved kidney function and lowered serum and kidney tissue inflammatory cytokine levels. Consistently, resveratrol prevented endotoxin-induced disruption of endothelial cell permeability and inhibited inflammation of kidney tissue. Resveratrol treatment attenuated the effects of LPS on macrophages, with significant inhibition of activation, cytokine release, and Toll-like receptor 4 activation. Resveratrol treatment also resulted in decreased expression of iNOS, Bcl-2, and Bcl-xL in macrophages, which was linked with induction of apoptosis in macrophages.

CONCLUSION

Our studies suggest that resveratrol might represent a novel therapeutic agent to prevent and treat sepsis-induced AKI.

Microparticles: markers and mediators of sepsis-induced microvascular dysfunction, immunosuppression, and AKI

Sepsis is a severe and complex syndrome that lacks effective prevention or therapeutics. The effects of sepsis on the microvasculature have become an attractive area for possible new targets and therapeutics. Microparticles (MPs) are cell membrane-derived particles that can promote coagulation, inflammation, and angiogenesis, and they can participate in cell-to-cell communication. MPs retain cell membrane and cytoplasmic constituents of their parental cells, including two procoagulants: phosphatidylserine and tissue factor. We highlight the role of microparticles released by endothelial and circulating cells after sepsis-induced microvascular injury, and we discuss possible mechanisms by which microparticles can contribute to endothelial dysfunction, immunosuppression, and multiorgan dysfunction--including sepsis-AKI. Once viewed as cellular byproducts, microparticles are emerging as a new class of markers and mediators in the pathogenesis of sepsis.

Pharmacologic targeting of sphingosine-1-phosphate receptor 1 improves the renal microcirculation during sepsis in the mouse

Microvascular failure is hallmark of sepsis in humans and is recognized as a strong predictor of mortality. In the mouse subjected to cecal ligation and puncture (CLP) to induce a clinically relevant sepsis, renal microvascular permeability increases and peritubular capillary perfusion declines rapidly in the kidney leading to acute kidney injury (AKI). Sphingosine-1-phosphate (S1P) is a key regulator of microvascular endothelial function. To investigate the role of S1P in the development of microvascular permeability and peritubular capillary hypoperfusion in the kidney during CLP-induced AKI, we used a pharmacologic approach and a clinically relevant delayed dosing paradigm. Evans blue dye was used to measure renal microvascular permeability and intravital video microscopy was used to quantitate renal cortical capillary perfusion. The S1P receptor 1 (S1P1) agonist SEW2871 [5-[4-phenyl-5-(trifluoromethyl)-2-thienyl]-3-[3-(trifluoromethyl)phenyl]-1,2,4-oxadiazole] and S1P2 antagonist JTE-013 [N-(2,6-dichloro-4-pyridinyl)-2-[1,3-dimethyl-4-(1-methylethyl)-1H-pyrazolo[3,4-b]pyridin-6-yl]-hydrazinecarboxamide] were administered at the time of CLP and produced a dose-dependent but partial reduction in renal microvascular permeability at 6 hours after CLP. However, neither agent improved capillary perfusion at 6 hours. With delayed administration at 6 hours after CLP, only SEW2871 reversed microvascular permeability when measured at 18 hours. Importantly, SEW2871 also restored capillary perfusion and improved renal function. These data suggest that S1P1 and S1P2 do not regulate the early decline in renal capillary perfusion. However, later in the course of sepsis, pharmacologic stimulation of S1P1, even when delaying therapy until after injury has occurred, improves capillary and renal function, suggesting this approach should be evaluated as an adjunct therapy during sepsis.

Biology of sepsis: its relevance to pediatric nephrology

Because of its multi-organ involvement, the syndrome of sepsis provides clinical challenges to a wide variety of health care providers. While multi-organ dysfunction triggered by sepsis requires general supportive critical care provided by intensivists, the impact of sepsis on renal function and the ability of renal replacement therapies to modulate its biologic consequences provide a significant opportunity for pediatric nephrologists and related care providers to impact outcomes. In this review, we aim to highlight newer areas of understanding of the pathobiology of sepsis with special emphasis on those aspects of particular interest to pediatric nephrology. As such, we aim to: (1) review the definition of sepsis and discuss advances in our mechanistic understanding of sepsis; (2) review current hypotheses regarding sepsis-induced acute kidney injury (AKI) and describe its epidemiology based on evolving definitions of AKI; (3) review the impact of renal failure on the immune system, highlighting the sepsis risk in this cohort and strategies that might minimize this risk; (4) review how renal replacement therapeutic strategies may impact sepsis-induced AKI outcomes. By focusing the review on these specific areas, we have omitted other important areas of the biology of sepsis and additional interactions with renal function from this discussion; however, we have aimed to provide a comprehensive list of references that provide contemporary reviews of these additional areas.