Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury

Diagnostic Utility of Serum Neutrophil Gelatinase-Associated Lipocalin in Polytraumatized Patients Suffering Acute Kidney Injury: A Prospective Study

Introduction

The incidence of acute kidney injury (AKI) considerably increases the mortality rate in polytrauma victims. Undoubtedly, early identification of patients at risk is crucial for timely implementation of preventive strategies in order to improve their prognosis. Therefore, we aimed to investigate if serum neutrophil gelatinase-associated lipocalin (sNGAL) may serve as a diagnostic biomarker of early AKI in polytrauma victims, especially considering patients needing renal replacement theory (RRT).

Material and Methods

Forty consecutive polytrauma victims (ISS ≥ 16, AIS_Thorax ≥ 1, age ≥ 18 years, survival time ≥ 48 hours), directly admitted to our level I trauma center within one posttraumatic hour, were enrolled in our prospective study. sNGAL-levels were assessed at admission (initial) and on day 2 after trauma. AKI was diagnosed by an increase of serum creatinine (sCr) level of at least 0.3 mg/dl within 48 hours.

Results

Out of 30 men and 10 women (mean age, 43 years; mean ISS, 29), seven patients developed AKI, four of them needing RRT. AKI was diagnosed in 86% of the affected individuals until day 2. Day2-sNGAL-levels were higher in the AKI-group, compared to the no-AKI-group (p=0.049), and in patients treated with RRT than in individuals not needing RRT (p=0.037). Noteworthy, in patients not needing RRT sNGAL-levels significantly decreased from initial to day2-measurement (p=0.040). Furthermore, at any time point during our observation period polytraumatized patients with AKI and day2-sNGAL-levels of at least 181.0 ng/mL presented with higher sCr-levels compared to polytraumatized patients without AKI and day2-sNGAL-levels lower than 181.0 ng/mL (p≤0.029).

Conclusion

In polytrauma victims suffering AKI an increase in sNGAL-level from initial to day2-assessment may signalize deterioration in kidney function and thus indicate AKI progression. Unlike initial sNGAL-levels day2-sNGAL-levels might be an appropriate tool to define AKI and to signify the need of RRT in polytraumatized patients.

Effects of General Anesthesia on 2 Urinary Biomarkers of Kidney Injury-Hepatitis A Virus Cellular Receptor 1 and Lipocalin 2-in Male C57BL/6J Mice

Urinary biomarkers are used increasingly for sensitive prediction of kidney injury in preclinical and clinical studies. Given the frequent requirement of anesthesia in various animal models of disease, it is important to define the effects of anesthesia on kidney injury biomarkers to guide the appropriate selection of anesthetic agents and to avoid potential confounders in the interpretation of data. Therefore, we performed a prospective study using male C57BL/6J mice (n = 45) exposed to a single anesthetic episode to determine the effects several common anesthesia regimens on the urinary excretion of 2 commonly used kidney injury biomarkers: hepatitis A virus cellular receptor 1 (HAVCR1, also known as KIM1) and lipocalin 2 (LCN2, also known as NGAL). We evaluated 3 injectable regimens (ketamine-xylazine, tiletamine-zolazepam, and pentobarbital) and 2 inhalational agents (isoflurane and sevoflurane). Concentrations of HAVCR1 and LCN2 in urine collected at various time points after anesthesia were measured by using ELISA. Administration of ketamine-xylazine resulted in a significant increase in HAVCR1 levels at 6 h after anesthesia but a decrease in LCN2 levels compared with baseline. LCN2 levels steadily increased over the first 24 h after inhalant anesthesia, with a significant increase at 24 h after sevoflurane. These results suggest that injectable anesthesia had early effects on HAVCR1 and LCN2 levels, whereas inhalational agents increased these biomarkers over prolonged time.

Improving clinical prediction rules in acute kidney injury with the use of biomarkers of cell cycle arrest: a pilot study

INTRODUCTION

Early recognition of patients developing acute kidney injury (AKI) is of considerable interest, we report the first use of a combination of a clinical prediction rule with a biomarker in emergent adult medical patients to improve AKI recognition.

METHODS

Single-centre prospective pilot study of medical admissions without AKI identified as high risk by a clinical prediction rule. Urine samples were obtained and tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) - biomarkers associated with cell cycle arrest, were measured.

OUTCOME

Creatinine-based KDIGO hospital-acquired AKI (HA-AKI).

RESULTS

Of 69 patients recruited, HA-AKI developed in 13% (n = 9), in whom biomarker values were higher (median 0.43 (interquartile range (IQR) 0.21-1.25) vs. 0.07 (0.03-0.16) in cases without (p = 0.008). Peak rise in creatinine was higher in biomarker positive cases (median 30 μmol/L (7-72) vs. 1 μmol/L (0-16), p = 0.002). AUROC was 0.78 (95% CI 0.57-0.98). At the suggested cut-off (0.3) sensitivity for predicting AKI was 78% (95% CI 40-97%), specificity 89% (78-95%), positive predictive value 50% (31-69%) and negative predictive value 96% (89-99%).

DISCUSSION

Addition of a urinary biomarker allows exclusion of a significant number of patients identified to be at higher risk of AKI by a clinical prediction rule.

Iron in the Tumor Microenvironment-Connecting the Dots

Iron metabolism and tumor biology are intimately linked. Iron facilitates the production of oxygen radicals, which may either result in iron-induced cell death, ferroptosis, or contribute to mutagenicity and malignant transformation. Once transformed, malignant cells require high amounts of iron for proliferation. In addition, iron has multiple regulatory effects on the immune system, thus affecting tumor surveillance by immune cells. For these reasons, inconsiderate iron supplementation in cancer patients has the potential of worsening disease course and outcome. On the other hand, chronic immune activation in the setting of malignancy alters systemic iron homeostasis and directs iron fluxes into myeloid cells. While this response aims at withdrawing iron from tumor cells, it may impair the effector functions of tumor-associated macrophages and will result in iron-restricted erythropoiesis and the development of anemia, subsequently. This review summarizes our current knowledge of the interconnections of iron homeostasis with cancer biology, discusses current clinical controversies in the treatment of anemia of cancer and focuses on the potential roles of iron in the solid tumor microenvironment, also speculating on yet unknown molecular mechanisms.

Exploring macrophage cell therapy on Diabetic Kidney Disease

Alternatively activated macrophages (M2) have regenerative properties and shown promise as cell therapy in chronic kidney disease. However, M2 plasticity is one of the major hurdles to overcome. Our previous studies showed that genetically modified macrophages stabilized by neutrophil gelatinase‐associated lipocalin (NGAL) were able to preserve their M2 phenotype. Nowadays, little is known about M2 macrophage effects in diabetic kidney disease (DKD). The aim of the study was to investigate the therapeutic effect of both bone marrow‐derived M2 (BM‐фM2) and ф‐NGAL macrophages in the db/db mice. Seventeen‐week‐old mice with established DKD were divided into five treatment groups with their controls: D+BM‐фM2; D+ф‐BM; D+ф‐NGAL; D+ф‐RAW; D+SHAM and non‐diabetic (ND) (db/‐ and C57bl/6J) animals. We infused 1 × 10⁶ macrophages twice, at baseline and 2 weeks thereafter. BM‐фM2 did not show any therapeutic effect whereas ф‐NGAL significantly reduced albuminuria and renal fibrosis. The ф‐NGAL therapy increased the anti‐inflammatory IL‐10 and reduced some pro‐inflammatory cytokines, reduced the proportion of M1 glomerular macrophages and podocyte loss and was associated with a significant decrease of renal TGF‐β1. Overall, our study provides evidence that ф‐NGAL macrophage cell therapy has a therapeutic effect on DKD probably by modulation of the renal inflammatory response caused by the diabetic milieu.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Evaluation of cystatin C and neutrophil gelatinase-associated lipocalin as predictors of mortality in patients undergoing percutaneous mitral valve repair (MitraClip)

BACKGROUND

Compromised renal function is a major risk factor that is strongly associated with poor outcome in patients with mitral regurgitation (MR) and heart failure. Cystatin C, a cysteine protease inhibitor, has been used as a specific and sensitive biomarker of renal function. Neutrophil gelatinase-associated lipocalin (NGAL) is another sensitive biomarker that specifically indicates functional and structural kidney damage. The aim of the present study was to determine the predictive value of serum cystatin C and urinary NGAL as indicators of mortality in patients undergoing percutaneous mitral valve repair (PMVR).

METHODS

A total of 120 consecutive patients (age: 77.3 years [±11.2]) undergoing PMVR using the MitraClip system were included in this study. Venous blood and urinary samples were collected for biomarker analysis prior to PMVR. Physiological parameters, medication use, safety events, and all-cause mortality were assessed 12 months after the procedure.

RESULTS

Twelve months after PMVR, there was a significant reduction in the severity of MR (P < 0.001), and an improvement in the New York Heart Association class (P < 0.01) was documented. Baseline levels of serum cystatin C (nonsurvivors: 2.4 mg/L [interquartile, IQR: 1.7;3.1] vs survivors: 1.7 mg/L [IQR: 1,3;2.1], P < 0.001) and urinary NGAL (nonsurvivors: 242.0 ng/mL [IQR: 154.5;281.5] vs survivors: 132.0 ng/mL [IQR:107.0;177.3], P < 0.001) were significantly higher in patients who died during the 12-month follow-up period.

CONCLUSION

Cystatin C and urinary NGAL were found to be predictors of long-term mortality in high-risk patients undergoing PMVR. Thus, cystatin C and NGAL assessment may be helpful in risk stratification in patients undergoing PMVR.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) in predicting acute kidney injury following orthotopic liver transplantation: A systematic review

BACKGROUND

Acute kidney injury (AKI) is common after orthotopic liver transplantation (OLT) usually occurring early post-transplant. Multiple causes include graft preservation injury, blood loss, hypotension but also severity of recipient liver disease. Early intervention in AKI has both short and long term patient benefits. Unfortunately there are no current clinical biomarkers of early AKI.

AIM

To assess the value of NGAL in predicting AKI following OLT.

METHODS

Ovid MEDLINE and EMBASE were searched between the years of 2000 and 2017 for studies using keywords: Neutrophil Gelatinase Associated Lipocalin or NGAL variants combined with synonyms for liver transplantation.

RESULTS

96 studies were identified. 11 studies including 563 patients were considered suitable for analysis. Both urinary (uNGAL) and plasma NGAL (pNGAL) measurement were found to predict AKI after liver transplantation. Optimal reported area under the receiver-operator characteristics curve (AUROC) values of 0.5-0.83 and 0.54-0.86 respectively.

CONCLUSIONS

NGAL is a good predictor of early AKI post OLT although there is considerable variation in the published results. Further studies with prospectively defined cut-off values, standardized definitions of AKI and rigorous data reporting should be conducted to establish its clinical usefulness and limitations.

Beclin-1 regulates cigarette smoke-induced kidney injury in a murine model of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), associated with cigarette smoke-induced (CS-induced) emphysema, contributes significantly to the global health care burden of disease. Although chronic kidney disease (CKD) may occur in patients with COPD, the relationship between COPD and CKD remains unclear. Using a murine model of experimental COPD, we show that chronic CS exposure resulted in marked kidney injury and fibrosis, as evidenced by histological and ultrastructural changes, altered macrophage subpopulations, and expression of tissue injury, fibrosis, and oxidative stress markers. CS induced mitochondrial dysfunction, and increased autophagic flux in kidney tissues and in kidney tubular epithelial (HK-2) cells, as determined by LC3B turnover assays. Mice heterozygous for Beclin-1 (Becn1+/-) were protected from the development of kidney tissue injury and renal fibrosis in response to CS exposure, and displayed impaired basal and inducible mitochondrial turnover by mitophagy. Interestingly, CS caused a reduction of Beclin-1 expression in mouse kidneys and kidney tubular epithelial cells, attributed to increased autophagy-dependent turnover of Beclin-1. These results suggest that Beclin-1 is required for CS-induced kidney injury and that reduced levels of Beclin-1 may confer renoprotection. These results identify the kidney as a target for CS-induced injury in COPD and the Beclin-1-dependent autophagy pathway as a potential therapeutic target in CKD.

Activity-Based Protein Profiling of Intraoperative Serine Hydrolase Activities during Cardiac Surgery

The processes involved in the initiation of acute kidney injury (AKI) following cardiopulmonary bypass (CPB) are thought to occur during the intraoperative period. Such a rapid development might indicate that some of the inductive events are not dependent on de novo protein synthesis, raising the possibility that changes in activities of pre-existing enzymes could contribute to the development of AKI. Activity-based protein profiling (ABPP) was used to compare the serine hydrolase enzyme activities present in the urines of CPB patients who subsequently developed AKI versus those who did not (non-AKI) during the intra- and immediate postoperative periods. Sequential urines collected from a nested case-control cohort of AKI and non-AKI patients were reacted with a serine hydrolase activity probe, fluorophosphonate-TAMRA, and separated by SDS-PAGE. The patterns and levels of probe-labeled proteins in the two groups were initially comparable. However, within 1 h of CPB there were significant pattern changes in the AKI group. Affinity purification and mass spectrometry-based analysis of probe-labeled enzymes in AKI urines at 1 h CPB and arrival to the intensive care unit (ICU) identified 28 enzymes. Quantitative analysis of the activity of one of the identified enzymes, kallikrein-1, revealed some trends suggesting differences in the levels and temporal patterns of enzyme activity between a subset of patients who developed AKI and those who did not. A comparative analysis of affinity-purified probe reacted urinary proteins from these patient groups during the intraoperative period suggested the presence of both shared and unique enzyme patterns. These results indicate that there are intraoperative changes in the levels and types of serine hydrolase activities in patients who subsequently develop AKI. However, the role of these activity differences in the development of AKI remains to be determined.

Preoperative risk assessment improves biomarker detection for predicting acute kidney injury after cardiac surgery

Background

Although urinary neutrophil gelatinase-associated lipocalin (NGAL) has emerged as a promising biomarker for the early detection of kidney injury, previous studies of adult patients who underwent cardiac surgery have reported only moderate discrimination. The age, creatinine, and ejection fraction (ACEF) score is a preoperative validated risk model with satisfactory accuracy for predicting AKI following cardiac surgery. It remains unknown whether combining preoperative risk assessment through ACEF scores followed by urinary NGAL test in a population of high-risk individuals is an optimal approach with improved predictive performance.

Material and methods

A total of 177 consecutive patients who underwent cardiac surgery were enrolled. Clinical characteristics, prognostic model scores, and outcomes were assessed. Urinary NGAL were examined within 6 hours after cardiac surgery. Patients were stratified according to preoperative ACEF scores, and comparisons were made using the area under the receiver operator characteristic curve (AUROC) for the prediction of AKI.

Results

A total of 45.8% (81/177) of the patients had AKI. As expected, patients with ACEF scores ≥ 1.1 were older and more likely to have class III or IV heart failure. They were also more likely to have diabetes mellitus, myocardial infarction, and peripheral arterial disease. Urinary NGAL alone moderately predicted AKI, with an AUROC of 0.732. Risk stratification by ACEF scores ≥ 1.1 substantially improved the AUROC of urinary NGAL to 0.873 (95% confidence interval, 0.784–0.961; P < .001).

Conclusions

Risk stratification by preoperative ACEF scores ≥ 1.1, followed by postoperative urinary NGAL, provides more satisfactory risk discrimination than does urinary NGAL alone for the early detection of AKI after cardiac surgery. Future studies should investigate whether this strategy could improve the outcomes and cost-effectiveness of care in patients undergoing cardiac surgery.

Telluric Acid Ameliorates Endotoxemic Kidney Injury in Mice: Involvement of TLR4, Nrf2, and PI3K/Akt Signaling Pathways

Being one of the most abundant trace elements in the human body, the therapeutic potential of tellurium-based compounds has been a target of interest. Recent reports denoted their redox-modulating and anti-inflammatory activities in experimental endotoxemia. However, their potential nephroprotective effect against endotoxemic kidney injury is yet to be elucidated. This study investigated the possible renoprotective effect of telluric acid (TEL) against lipopolysaccharide (LPS)-induced acute kidney injury (AKI) in mice, targeting toll-like receptor 4 (TLR4), phosphoinositide 3-kinase (PI3K)/Akt, and nuclear factor-erythroid 2-related factor-2 (Nrf2) pathways as possible mechanistic contributors to TEL's effect. AKI was induced by LPS (2 mg/kg). TEL (60 μg/kg; i.p.) was administered once daily for seven consecutive days before LPS injection. Pretreatment with TEL alleviated LPS-induced AKI as evidenced by the hampered serum levels of creatinine and cystatin C. TEL also opposed LPS-induced elevation in renal kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, nuclear factor-kappa B p65, interleukin-1β, and thiobarbituric acid-reactive substance contents. This was accompanied by a replenishment of renal glutathione, transcriptional upregulation of Nrf2, enhancement of heme oxygenase-1 activity, and a marked upregulation of phospho-PI3K and phospho-Akt protein expressions. Histopathological findings corroborated with the amendment of biochemical parameters. In view of these findings, we may conclude that TEL pretreatment purveyed novel nephroprotective effects against endotoxemic kidney injury, which might be partly attributed to the modulation of TLR4, PI3K/Akt, and Nrf2 signaling pathways and may hence provide a valuable asset for the management of endotoxemic renal complications.

Predictive ability of NGAL in identifying urinary tract infection in children with neurogenic bladders

BACKGROUND

Distinguishing between urinary tract infection (UTI) and colonization (UTC) in patients with neurogenic bladders who require clean intermittent catheterization (CIC) is difficult. Urinary neutrophil gelatinase-associated lipocalin concentrations (uNGAL) are increased in UTIs. Our objective was to determine the predictive accuracy of uNGAL for UTI in CIC-dependent children.

METHODS

Cross-sectional study of CIC-dependent patients from August, 2015 to November, 2016. UTI was defined as (1) growth of ≥ 50,000 cfu/mL of a uropathogen, (2) > 10 urinary white blood cells/hpf, and (3) ≥ 2 of the following: temperature > 38 °C, abdominal pain, back pain, worsened incontinence, pain with catheterization, or malodorous/cloudy urine. Positive urine cultures that did not meet these criteria were grouped as UTC, and negative cultures were grouped as no growth.

RESULTS

Two hundred one patients were included (no growth = 100, UTC = 77, UTI = 24). Median (interquartile range) uNGAL was higher in the UTI group (UTI 1361 (931, 2516) μg/g creatinine, UTC 246 (106, 548) μg/g creatinine, no growth 36 (11, 179) μg/g creatinine, p < 0.01 for all comparisons). The area under the ROC curve for uNGAL for UTI versus no UTI was 0.89, 95% CI (0.80-0.98).

CONCLUSION

uNGAL is elevated in CIC-dependent children with UTI compared to those with negative cultures and those with UTC.

Tempol, a superoxide dismutase mimetic agent, reduces cisplatin-induced nephrotoxicity in rats

Cisplatin (CP) is one of the most potent anti-cancer drugs used against different types of cancer. Its use is limited due to its nephrotoxicity. This study is aimed to evaluate the role of a super oxide dismutase (SOD) mimetic agent, tempol, in protection against CP nephrotoxicity in rats. Animals were divided into four groups: Group-1: Normal control group, Group-2: CP group (single dose of CP 6 mg/kg, i.p.), Group-3 and Group-4: Tempol-treated groups (50 mg/kg p.o. and 100 mg/kg p.o. respectively) daily for a week before CP injection and continued for an additional four days after CP injection. Urine and blood samples were collected for the evaluation of kidney function including serum creatinine, BUN, cystatin-c, and creatinine clearance. In addition, western blotting was used to determine urine lipocalin-2 content. Furthermore, kidney tissue was collected for the determination of oxidative stress markers, caspase-3 expression, and histopathological examination. We noticed that both doses of tempol significantly improved kidney function, which was deteriorated by CP injection. Tempol significantly elevated kidney glutathione (GSH) content and SOD activity, and decreased kidney lipid peroxidation and NOx production. Tempol also significantly decreased kidney caspase-3 expression which was elevated by CP toxicity. Thus, we conclude that tempol can protect against CP nephrotoxicity. We noticed that both doses of tempol are effective in ameliorating CP-nephrotoxicity.

Early intraoperative iron-binding proteins are associated with acute kidney injury after cardiac surgery

OBJECTIVES

Iron regulation is an important modifier of renal ischemia-reperfusion injury, but the role of iron-binding proteins during cardiopulmonary bypass remains unclear. The goal was to characterize iron-binding proteins throughout ischemia-reperfusion injury to determine their association with acute kidney injury development.

METHODS

A prospective observational cohort of adult patients who underwent cardiac surgery (n = 301) was obtained, and acute kidney injury was defined by Kidney Disease Improving Global Outcomes. Serum ferritin, transferrin saturation, and urine hepcidin-25 were measured.

RESULTS

Intraoperative serum ferritin was lower at the start of cardiopulmonary bypass (P = .005) and 1-hour cardiopulmonary bypass (P = .001) in patients with acute kidney injury versus patients without acute kidney injury. Lower serum ferritin and higher transferrin saturation at 1-hour cardiopulmonary bypass were independent predictors of acute kidney injury (serum ferritin odds ratio, 0.66; 95% confidence interval [CI], 0.48-0.91; transferrin saturation odds ratio, 1.26; 95% CI, 1.02-1.55) and improved model discrimination (area under the curve [AUC], 0.76; 95% CI, 0.67-0.85) compared with clinical prediction alone (AUC, 0.72; 95% CI, 0.62-0.81; ΔAUC and net reclassification index, P = .01). Lower ferritin, higher transferrin saturation at 1-hour cardiopulmonary bypass, and lower urine hepcidin-25 at postoperative day 1 were also independent predictors for acute kidney injury development, and this model demonstrated an AUC of 0.80 (0.72-0.87), which was superior to clinical prediction (ΔAUC P = .002, integrated discrimination improvement and net reclassification index P = .003).

CONCLUSIONS

Our findings suggest that lower levels of intraoperative iron-binding proteins may reflect an impaired capacity to rapidly handle catalytic iron released during cardiopulmonary bypass, leading to kidney injury. These data highlight the importance of iron homeostasis in human ischemia-reperfusion injury and suggest it is a potentially modifiable risk during cardiac surgery. Intraoperative detection of incipient acute kidney injury may be feasible and could be used as an enrichment strategy for clinical trials.

Biomarkers in acute kidney injury (AKI)

Acute kidney injury is common in critically ill patients and portends a significant impact on mortality, progressive chronic kidney disease, and cardiovascular disease and mortality. Though most physicians alter therapy depending on changes in serum creatinine, this often represents delayed intervention. Various AKI biomarkers have been discovered and validated to improve timely detection, differentiation and stratification into risk groups for progressive renal decline, need for renal replacement therapy or death. This chapter will review AKI biomarkers validated over the past decade. We also describe the clinical performance of the biomarkers. We suggest that using AKI biomarkers to complement serum creatinine (or cystatin C) and urine output will better integrate patient care through earlier recognition and clinical outcome prediction after AKI.

NGAL protects against endotoxin-induced renal tubular cell damage by suppressing apoptosis

Background

We sought to confirm that neutrophil gelatinase-associated lipocalin (NGAL) protects against apoptosis during endotoxemia.

Methods

Endotoxemia was induced in rats with lipopolysaccharide (LPS; 3.5 mg/kg) and serum creatinine (SCr), urinary NGAL (uNGAL), renal histopathology confirmed acute kidney injury (AKI). Renal caspase 3 and NGAL were assayed with immunohistochemistry 6 h later. A HK-2 cell model was used in which NGAL and caspase 3 mRNA were evaluated by qRT-PCR within 6 h after LPS (50 μM) treatment, and correlations were studied. NGAL and caspase 3 mRNA expression were measured after delivering NGAL siRNA in HK-2 cells and apoptosis was measured with TUNEL and flow cytometry.

Results

SCr and uNGAL were significantly increased after LPS treatment and renal morphology data indicated AKI and renal tubular epithelial cell apoptosis. Caspase 3 and NGAL were predominantly expressed in the tubular epithelial cells and there was a correlation between caspase 3 and NGAL protein (r = 0.663, p = 0.01). In vitro, there was a strong correlation between caspase 3 and NGAL mRNA in LPS-injured HK-2 cells within 24 h (r = 0.448, p < 0.05). Suppressing the NGAL gene in HK-2 cells increased caspase 3 mRNA 4.5-fold and apoptosis increased 1.5-fold after LPS treatment.

Conclusions

NGAL is associated with caspase 3 in renal tubular cells with endotoxin-induced kidney injury, and may regulate its expression and inhibit apoptosis.

Kidney injury molecule-1 staining in renal allograft biopsies 10 days after transplantation is inversely correlated with functioning proximal tubular epithelial cells

Background

Kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are promising biomarkers for monitoring delayed graft function (DGF) after kidney transplantation. Here we investigated localization and distribution of KIM-1 and NGAL staining in renal allograft biopsies and studied their association with histological features, functional DGF (fDGF) and the tubular function slope (TFS), a functioning proximal tubular epithelial cell (PTEC) marker.

Methods

Day 10 protocol biopsies of 64 donation after circulatory death recipients were stained for KIM-1 and NGAL and the positive area was quantified using ImageJ software. Biopsies were scored according to Banff and acute tubular necrosis (ATN) criteria. A 99mtechnetium-mercaptoacetyltriglycine (99mTc-MAG3)-renography was performed to calculate TFS.

Results

KIM-1 staining was located on the brush border of tubular epithelial cells (TECs) and correlated with denudation, while NGAL was present more focally in a cytoplasmic distribution. KIM-1 and NGAL staining were not correlated and no co-localization was observed. Quantitative stainings were not associated with fDGF, but KIM-1 tended to be higher in patients with prolonged fDGF (≥21 days; P = 0.062). No correlation was observed between the quantitative tissue stainings and urinary KIM-1 or NGAL. Quantitative KIM-1 staining was inversely correlated with the TFS (Spearman's ρ = -0.53; P < 0.001), whereas NGAL was not. The latter finding might be because cortical NGAL staining is dependent on filtration and subsequent reabsorption by functioning PTECs. Staining of NGAL was indeed restricted to PTECs, as shown by co-localization with a PTEC-specific lectin.

Conclusions

KIM-1 and NGAL staining showed different localization and distribution. Quantitative KIM-1 staining was inversely correlated with functioning PTECs.

Elevated Neutrophil Gelatinase Lipocalin Levels Are Associated With Increased Oxidative Stress in Hemodialysis Patients

BACKGROUND

Administration of intravenous iron is an essential treatment of anemia in hemodialysis patients, but it may lead to oxidative stress and increased morbidity and mortality. There is evidence that neutrophil gelatinase-associated lipocalin (NGAL) is protective against oxidative stress and thus the aim of the present study was to investigate the relationship between plasma NGAL and advanced oxidative protein products (AOPP) in hemodialysis patients treated with intravenous iron.

METHODS

In a prospective study, 47 hemodialysis patients (mean age 63 years, SD = 13.6; 40% women) were enrolled from two separate hospitals. Oxidative stress was induced by an intravenous administration of 100 mg iron saccharate 0.5 h after the start of dialysis. Blood samples were drawn at the beginning of the dialysis, 0.5 h after iron administration and at the end of dialysis. NGAL levels were measured from the first blood sample, AOPP levels were measured from all blood samples.

RESULTS

Our results showed that higher NGAL and AOPP levels at the beginning of the dialysis, prior to iron administration, significantly predicted higher levels of AOPP toward the end of dialysis, (β = 0.355, SE = 0.054, P = 0.035; β = 0.297, SE = 0.159, P = 0.043, respectively).

CONCLUSIONS

Our results suggest that higher level of NGAL is a risk factor for oxidative stress, as measured by AOPP levels, in dialysis patients receiving intravenous iron. Our findings could identify dialysis patients who are at higher risk from iron supplementation via measurement of NGAL levels.

Early prediction of contrast-induced acute kidney injury by a "bedside" assessment of Neutrophil Gelatinase-Associated Lipocalin during elective percutaneous coronary interventions

Contrast-induced acute kidney injury (CI-AKI) is a serious complication during percutaneous coronary interventions (PCI). Currently, the diagnosis of CI-AKI relies on serum creatinine (SCr) that is however affected by several limitations potentially leading to delayed or missed diagnoses. In this study we examined the diagnostic accuracy of a “bedside” measurement of plasma Neutrophil Gelatinase-Associated Lipocalin (NGAL) in the early detection of CI-AKI in 97 patients undergoing elective PCI. The overall incidence of CI-AKI was 3%. A significant positive correlation was observed between 6-hours NGAL and post-PCI SCr (r = 0.339, p = 0.004) and a significant negative correlation between 6-hours NGAL and post-PCI CrCl (r = -0.303, p = 0.010). In patients with post-PCI SCr increase > 0.24 mg/dl (median SCr absolute increase), delta NGAL 0–6 hours and 6-hours NGAL values were higher compared with patients with SCr elevation below the defined threshold (p = 0.049 and p = 0.056). The ROC analysis showed that a 6 hours NGAL value > 96 ng/ml significantly predicted an absolute SCr increase > 0.24 mg/dl after contrast exposure with sensitivity of 53% and specificity of 74% (AUC 0.819, 95% CI: 0.656 to 0.983, p = 0.005). The use of bedside NGAL assessment may significantly hasten diagnosis and treatment of CI-AKI, with remarkable clinical prognostic consequences.

More than a simple biomarker: the role of NGAL in cardiovascular and renal diseases

Neutrophil gelatinase-associated lipocalin (NGAL) is a small circulating protein that is highly modulated in a wide variety of pathological situations, making it a useful biomarker of various disease states. It is one of the best markers of acute kidney injury, as it is rapidly released after tubular damage. However, a growing body of evidence highlights an important role for NGAL beyond that of a biomarker of renal dysfunction. Indeed, numerous studies have demonstrated a role for NGAL in both cardiovascular and renal diseases. In the present review, we summarize current knowledge concerning the involvement of NGAL in cardiovascular and renal diseases and discuss the various mechanisms underlying its pathological implications.

Ameliorative effect of ursolic acid on renal fibrosis in adenine-induced chronic kidney disease in rats

Ursolic acid (UA), an ursane-type pentacyclic triterpenoid commonly found in apple peels and holy basil has been shown to possess many beneficial effects. Renal fibrosis is a complication of kidney injury and associated with increased risk of morbidity and mortality. In our previous investigation, a lupane-type pentacyclic triterpenoid, betulinic acid (BA) was found to have protective effect on chronic kidney disease (CKD) and renal fibrosis. This prompted us to explore the therapeutic value of UA, a chemically related compound to BA in CKD. CKD was induced by feeding adenine with the feed at a concentration of 0.75% for 28 days. UA at the dose rate of 30 mg/kg in 0.5% carboxy methyl cellulose (CMC) was administered by oral route, simultaneously with adenine feeding for 28 days. Adenine feeding increased the kidney weight to body weight index, decreased the kidney function due to injury as indicated by increased markers like serum urea, uric acid, creatinine, cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) and initiated the fibrotic response in kidney by increasing the profibrotic proteins viz. transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), fibronectin and collagen. However, treatment with UA reversed the damage induced by adenine as shown by reduced kidney injury and fibrosis markers which was further clearly evident in histological picture indicating the suitability of UA for use in CKD.

Biomarkers of Sepsis-Induced Acute Kidney Injury

Sepsis, an infection-induced systemic disease, leads to pathological, physiological, and biochemical abnormalities in the body. Organ dysfunction is caused by a dysregulated host response to infection during sepsis which is a major contributing factor to acute kidney injury (AKI) and the mortality rate for sepsis doubles due to coincidence of AKI. Sepsis-induced AKI is strongly associated with increased mortality and other adverse outcomes. More timely diagnosis would allow for earlier intervention and could improve patient outcomes. Sepsis-induced AKI is characterized by a distinct pathophysiology compared with other diseases and may also have unique patterns of plasma and urinary biomarkers. This concise review summarizes properties and perspectives of the biomarkers for their individual clinical utilization.

Urinary Neutrophil Gelatinase-Associated Lipocalin Is Excellent Predictor of Acute Kidney Injury in Septic Elderly Patients

Elderly is the main age group affected by acute kidney injury (AKI). There are no studies that investigated the predictive properties of urinary (u) NGAL as an AKI marker in septic elderly population. This study aimed to evaluate the efficacy of uNGAL as predictor of AKI diagnosis and prognosis in elderly septic patients admitted to ICUs. We prospectively studied elderly patients with sepsis admitted to ICUs from October 2014 to November 2015. Assessment of renal function was performed daily by serum creatinine and urine output. The level of uNGAL was performed within the first 48 hours of the diagnosis of sepsis (NGAL1) and between 48 and 96 hours (NGAL2). The results were presented using descriptive statistics and area under the receiver operating characteristic curve (AUC-ROC) and p value was 5%. Seventy-five patients were included, 47 (62.7%) developed AKI. At logistic regression, chronic kidney disease and low mean blood pressure at admission were identified as factors associated with AKI (OR=0.05, CI=0.01-0.60, p=0.045 and OR=0.81, CI=0,13-0.47; p=0.047). The uNGAL was excellent predictor of AKI diagnosis (AUC-ROC >0.95, and sensitivity and specificity>0.89), anticipating the AKI diagnosis in 2.1±0.3 days. Factors associated with mortality in the logistic regression were presence of AKI (OR=2.14, CI=1.42-3.98, p=0.04), chronic obstructive pulmonary disease (OR = 9.37, CI =1.79-49.1, p=0.008) and vasoactive drugs (OR=2.06, CI=0.98-1.02, p=0.04). The accuracy of NGALu 1 and 2 as predictors of death was intermediate, with AUC-ROC of 0.61 and 0.62; sensitivity between 0.65 and 0.77 and specificity lower than 0.6. The uNGAL was excellent predictor of AKI in septic elderly patients in ICUs and can anticipate the diagnosis of AKI in 2.1 days.

Lipocalin 2 Plays an Important Role in Regulating Inflammation in Retinal Degeneration

It has become increasingly important to understand how retinal inflammation is regulated because inflammation plays a role in retinal degenerative diseases. Lipocalin 2 (LCN2), an acute stress response protein with multiple innate immune functions, is increased in ATP-binding cassette subfamily A member 4 (Abca4) ^-/- retinol dehydrogenase 8 (Rdh8) ^-/- double-knockout mice, an animal model for Stargardt disease and age-related macular degeneration (AMD). To examine roles of LCN2 in retinal inflammation and degeneration, Lcn2^-/-Abca4^-/-Rdh8^-/- triple-knockout mice were generated. Exacerbated inflammation following light exposure was observed in Lcn2^-/-Abca4^-/-Rdh8^-/- mice as compared with Abca4^-/-Rdh8^-/- mice, with upregulation of proinflammatory genes and microglial activation. RNA array analyses revealed an increase in immune response molecules such as Ccl8, Ccl2, and Cxcl10 To further probe a possible regulatory role for LCN2 in retinal inflammation, we examined the in vitro effects of LCN2 on NF-κB signaling in human retinal pigmented epithelial (RPE) cells differentiated from induced pluripotent stem cells derived from healthy donors. We found that LCN2 induced expression of antioxidant enzymes heme oxygenase 1 and superoxide dismutase 2 in these RPE cells and could inhibit the cytotoxic effects of H₂O₂ and LPS. ELISA revealed increased LCN2 levels in plasma of patients with Stargardt disease, retinitis pigmentosa, and age-related macular degeneration as compared with healthy controls. Finally, overexpression of LCN2 in RPE cells displayed protection from cell death. Overall these results suggest that LCN2 is involved in prosurvival responses during cell stress and plays an important role in regulating inflammation during retinal degeneration.

Lipocalin-2 protects the brain during inflammatory conditions

Sepsis is a prevalent health issue that can lead to central nervous system (CNS) inflammation with long-term behavioral and cognitive alterations. Using unbiased proteomic profiling of over 100 different cytokines, we found that Lipocalin-2 (LCN2) was the most substantially elevated protein in the CNS after peripheral administration of lipopolysaccharide (LPS). To determine whether the high level of LCN2 in the CNS is protective or deleterious, we challenged Lcn2^-/- mice with peripheral LPS and determined effects on behavior and neuroinflammation. At a time corresponding to peak LCN2 induction in wild-type (WT) mice injected with LPS, Lcn2^-/- mice challenged with LPS had exacerbated levels of pro-inflammatory cytokines and exhibited significantly worsened behavioral phenotypes. To determine the extent of global inflammatory changes dependent upon LCN2, we performed an RNAseq transcriptomic analysis. Compared with WT mice injected with LPS, Lcn2^-/- mice injected with LPS had unique transcriptional profiles and significantly elevated levels of multiple pro-inflammatory molecules. Several LCN2-dependent pathways were revealed with this analysis including, cytokine and chemokine signaling, nucleotide-binding oligomerization domain-like receptor signaling and Janus kinase-signal transducer and activator of transcription signaling. These findings demonstrate that LCN2 serves as a potent protective factor in the CNS in response to systemic inflammation and may be a potential candidate for limiting sepsis-related CNS sequelae.

Hemojuvelin Predicts Acute Kidney Injury and Poor Outcomes Following Cardiac Surgery

Acute kidney injury (AKI) is detrimental after cardiac surgery. In this multicenter study, the novel biomarker hemojuvelin (HJV) was evaluated for AKI prediction following cardiac surgery. Urinary HJV, neutrophil gelatinase-associated lipocalin (NGAL), and urinary creatinine were measured in 151 patients after surgery. The outcomes of advanced AKI (KDIGO stages 2 and 3) and all causes of in-hospital mortality as the composite outcome were recorded. Areas under the receiver operator characteristic curves (AUC) and a multivariate generalized additive model (GAM) were applied to predict these outcomes of interest. Urinary HJV differentiated patients with/without AKI, advanced AKI or composite outcome after surgery (p < 0.001, by a generalized estimating equation) in this study. At three hours post-surgery, urinary HJV predicted advanced AKI (p < 0.001) and composite outcome (p < 0.001) with corresponding AUC values of 0.768 and 0.828, respectively. The performance of creatinine-adjusted HJV was also superior to NGAL in predicting advanced AKI (AUC = 0.784 and 0.694; p = 0.037) and composite outcome (AUC = 0.842 and 0.676; p = 0.002). The integration of HJV into the Cleveland Clinic score for advanced AKI led to a significant increase in risk stratification (net reclassification improvement [NRI] = 0.598; p < 0.001).

Neutrophil Gelatinase-Associated Lipocalin Attenuates Ischemia/Reperfusion Injury in an In Vitro Model via Autophagy Activation

Background

The aim of this study was to investigate the protective effects of neutrophil gelatinase-associated lipocalin (NGAL) on hypoxia/reoxygenation (H/R) induced acute kidney injury (AKI) in vitro.

Material/Methods

We used NRK-52E cells and H/R treatments to mimic ischemia/reperfusion injury (IRI) in vitro. Experimental groups were: the control group, the H/R group, the 3-methyladenine (3-MA)+H/R group, the NGAL (0.25, 0.5, and 1 ug/mL)+H/R group, and the NGAL (0.25, 0.5, 1 ug/mL)+3-MA+H/R group. After 24 hours of culture, cell proliferation was analyzed by CCK-8 assay. Expression of LC3-II was detected by immunoblot assay. Autophagy was detected by electron microscopy.

Results

The expression of LC3-II was increased in the H/R group compared with normoxic condition (p<0.05) and proliferation also improved. Autophagy was significantly inhibited by 3-MA, with downregulated of LC3-II, followed by decreased cell viability (p<0.05). We further detected the effect of different doses of NGAL in H/R induced injury, and found that low doses of NGAL alone slightly increased LC3-II protein accumulation, and autophagy was further induced with higher dose of NGAL treatment. Meanwhile, cell viability assays showed induced cell survival. We found that in the NGAL+3-MA group, cell viability assays revealed reduced cell damage, followed concomitantly with depressed autophagy. The formulation of autophagosomes were correlated with LC3-II protein expression in each group.

Conclusions

Autophagy plays a renoprotective role in H/R injury, as well in AKI. NGAL might be related to attenuated tubular epithelial cell damage via adjusting autophagy.

Immunological consequences of kidney cell death

Death of renal cells is central to the pathophysiology of acute tubular necrosis, autoimmunity, necrotizing glomerulonephritis, cystic kidney disease, urosepsis, delayed graft function and transplant rejection. By means of regulated necrosis, immunogenic damage-associated molecular patterns (DAMPs) and highly reactive organelles such as lysosomes, peroxisomes and mitochondria are released from the dying cells, thereby causing an overwhelming immunologic response. The rupture of the plasma membrane exhibits the "point of no return" for the immunogenicity of regulated cell death, explaining why apoptosis, a highly organized cell death subroutine with long-lasting plasma membrane integrity, elicits hardly any immune response. Ferroptosis, an iron-dependent necrotic type cell death, results in the release of DAMPs and large amounts of lipid peroxides. In contrast, anti-inflammatory cytokines are actively released from cells that die by necroptosis, limiting the DAMP-induced immune response to a surrounding microenvironment, whereas at the same time, inflammasome-associated caspases drive maturation of intracellularly expressed interleukin-1β (IL-1β). In a distinct setting, additionally interleukin-18 (IL-18) is expressed during pyroptosis, initiated by gasdermin-mediated plasma membrane rupture. As all of these pathways are druggable, we provide an overview of regulated necrosis in kidney diseases with a focus on immunogenicity and potential therapeutic interventions.

Urinary Hepcidin-25 Is Elevated in Patients That Avoid Acute Kidney Injury Following Cardiac Surgery

Background:

Acute kidney injury (AKI) following cardiac surgery leads to increased morbidity and mortality. Characterization and validation of early biomarkers of AKI may ultimately facilitate early therapeutic intervention. We have previously identified that elevated urinary hepcidin-25 is inversely and independently associated with the development of AKI in adult cardiac surgery patients. Hepcidin-25 is an antimicrobial peptide that sequesters iron intracellularly, and its elevation following human ischemia reperfusion injury may represent a renoprotective response to minimize renal injury.

Objective:

Our goal was to validate urinary hepcidin-25 as a non-invasive biomarker in an independent cardiac surgery cohort, within the context of clinical AKI predictors.

Design:

Prospective observational cohort study.

Setting:

Adult cardiac surgery program at St. Boniface Hospital, Winnipeg, Manitoba, Canada.

Patients:

Adult cardiac surgery patients undergoing cardiopulmonary bypass (CPB), n = 306.

Measurements:

Urine hepcidin-25, measured on post-operative day (POD) 1.

Methods:

A prospective, observational cohort of adult CPB patients (n = 306) was collected with serial perioperative urine samples. Urine hepcidin-25 at POD 1 was measured by competitive ELISA. Its diagnostic performance was evaluated in conjunction with clinical parameters and the Thakar clinical prediction score, using multivariate logistic regression.

Results:

Urinary hepcidin-25 is elevated following cardiac surgery in AKI and non-AKI patients. Elevated urinary hepcidin-25 concentration was inversely associated with AKI on both univariate (odds ratio [OR]: 0.61, 95% confidence interval [CI]: 0.45-0.83, P = .002) and multivariate analysis (OR: 0.67, 95% CI: 0.50-0.95, P = .02). A combined model with clinical risk factors demonstrated that baseline estimated glomerular filtration rate (eGFR), diabetes mellitus, and urinary hepcidin-25 concentration had an overall area under the curve (AUC) of 0.82 (0.75-0.88) for predicting subsequent AKI development, which was superior to clinical prediction alone as determined by the Thakar score.

Limitations:

(1) A single-center observational study. (2) Polyclonal antibody–based competitive ELISA.

Conclusion:

Hepcidin-25 is inversely associated with AKI in a multivariate model when combined with eGFR and diabetes mellitus, with an overall AUC of 0.82. Notably, urinary hepcidin-25 improves on clinical AKI prediction compared to the Thakar score alone.

Spleen contributes significantly to increased circulating levels of fibroblast growth factor 23 in response to lipopolysaccharide-induced inflammation

Background

Circulating levels of fibroblast growth factor 23 (FGF23) increase progressively and correlate with systemic inflammation in chronic kidney disease (CKD). The aim of this study was to identify and characterize the causal relationship between FGF23 and inflammation in CKD.

Methods

Circulating FGF23 and inflammatory cytokines were correlated in healthy subjects and patients with varying levels of CKD. In addition, FGF23 expression in blood and solid organs was measured in normal mice that were exposed acutely (one time) or chronically (2-week) to low-dose lipopolysaccharide (LPS); chronic exposure being either sustained (subcutaneous pellets), intermittent (daily injections) or combined sustained plus acute (subcutaneous pellets plus acute injection on the day of sacrifice). Blood was analyzed for both terminal (cFGF23) and intact (iFGF23) FGF23 levels. Solid tissues were investigated with immunohistochemistry, enzyme-linked immunosorbent assay and reverse transcription polymerase chain reaction.

Results

FGF23 levels correlated significantly with neutrophil gelatinase-associated lipocalin ( r = 0.72, P < 0.001), C-reactive protein ( r = 0.38, P < 0.001), tumor necrosis factor-α ( r = 0.32, P = 0.001) and interleukin-6 ( r = 0.48, P < 0.001). Acute LPS administration increased tissue FGF23 mRNA and plasma levels of cFGF23 but not iFGF23. Neither chronic sustained nor chronic pulsatile LPS increased the tissue or circulating levels of FGF23. However, acute on chronic LPS raised tissue FGF23 mRNA and both circulating cFG23 and iFGF23. Interestingly, the spleen was the major source of FGF23.

Conclusion

Acute on chronic exposure to LPS stimulates FGF23 production in a normal mouse model of inflammation. We provide the first evidence that the spleen, under these conditions, contributes substantially to elevated circulating FGF23 levels.

Neutrophil gelatinase-associated lipocalin in patients with sarcoidosis

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a glycoprotein that is involved in the innate immune system and increased expression has been detected in diverse diseases. Sarcoidosis is a systemic granulomatous disorder and its clinical course and prognosis are changeable and highly divergent. This study aimed to examine the expression of NGAL in patients with sarcoidosis. In addition, we examined whether NGAL could serve as a marker of disease activity and prognosis.

METHODS

Ninety-six sarcoidosis patients were studied. Serum samples collected at the time of diagnosis were examined for NGAL by cellular enzyme-linked immunosorbent assay. The level of NGAL was compared with clinical, radiological and laboratory data.

RESULTS

Patients with sarcoidosis had significantly higher levels of NGAL (the median [interquartile range] was 35.1 ng/mL [23.5-60.8] in sarcoidosis patients versus 17.2 ng/mL [13.0-27.0] in the reference population, p < .0001). NGAL levels were not correlated with markers for disease activity. During the follow-up period, 26 patients (27.1%) deteriorated and received systemic corticosteroid therapy for organ dysfunction. In those patients, NGAL levels were significantly higher than in those who did not receive corticosteroid therapy (56.5 ng/mL [27.3-92.3] versus 34.3 ng/mL [23.0-53.0], p = .0201). Upon multivariate logistic regression analysis, elevated NGAL levels at diagnosis were associated with subsequent use of systemic corticosteroid therapy (hazard ratio, 1.20; 95% confidence interval, 1.09-1.31; p = .0004).

CONCLUSION

NGAL may be a useful marker to predict the disease course of sarcoidosis.

Phenotyping of Acute Kidney Injury: Beyond Serum Creatinine

Acute kidney injury (AKI) is a common complication in hospitalized patients and is associated with adverse short- and long-term outcomes. AKI is diagnosed by serum creatinine (SCr)-based consensus definitions that capture an abrupt decrease in glomerular filtration rate associated with AKI. However, SCr-based AKI definitions lack sensitivity and specificity for diagnosing structural kidney injury. Moreover, AKI is a heterogeneous condition consisting of distinct phenotypes based on its etiology, prognosis, and molecular pathways, and that may potentially require different therapies. SCr-based AKI definitions provide no information on these AKI phenotypes. This review highlights traditional and novel tools that overcome the limitations of SCr-based AKI definitions to improve AKI phenotyping.

Subclinical First Trimester Renal Abnormalities Are Associated With Preeclampsia in Normoalbuminuric Women With Type 1 Diabetes

OBJECTIVE

This study was conducted to determine the utility of tubular (urinary/plasma neutrophil gelatinase-associated lipocalin [NGAL] and urinary kidney injury molecule 1 [KIM-1]) and glomerular (estimated glomerular filtration rate [eGFR]) biomarkers in predicting preeclampsia (PE) in pregnant women with type 1 diabetes mellitus (T1DM) who were free of microalbuminuria and hypertension at the first trimester.

RESEARCH DESIGN AND METHODS

This was a prospective study of T1DM pregnancy. Maternal urinary and plasma NGAL, urinary KIM-1 (ELISA of frozen samples), and eGFR (Chronic Kidney Disease Epidemiology Collaboration equation) were determined at three study visits (V1: 12.4 ± 1.8; V2: 21.7 ± 1.4; V3: 31.4 ± 1.5 weeks' gestation [mean ± SD]) in 23 women with T1DM with subsequent PE (DM+PE+), 24 who remained normotensive (DM+PE-), and, for reference, in 19 normotensive pregnant women without diabetes (DM-). The groups with diabetes were matched for age, diabetes duration, and parity. All subjects were normotensive and free of microalbuminuria or albuminuria at V1. All study visits preceded the onset of PE.

RESULTS

Urinary creatinine-corrected NGAL (uNGALcc, ng/mg) was significantly elevated at V1 in DM+PE+ vs. DM+PE- women (P = 0.01); this remained significant after exclusion of leukocyte-positive samples (5 DM+PE+ and 2 DM+PE-) (P = 0.02). Accounting for BMI, HbA_1c, and total daily insulin dose, a doubling of uNGALcc at V1 conferred a sevenfold increase in risk for PE (P = 0.026). In contrast, neither plasma NGAL nor urinary KIM-1 predicted PE. Also at V1, eGFR was elevated in DM+PE+ vs. DM+PE- (P = 0.04).

CONCLUSIONS

Early tubular and glomerular dysfunction may predict PE in first trimester women with T1DM, even if free of microalbuminuria. These data suggest that subclinical renal tubular and glomerular injury, if present early in pregnancy, may predispose women with T1DM to PE.

Neutrophil Gelatinase-Associated Lipocalin from immune cells is mandatory for aldosterone-induced cardiac remodeling and inflammation

Immune system activation is involved in cardiovascular (CV) inflammation and fibrosis, following activation of the mineralocorticoid receptor (MR). We previously showed that Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a novel target of MR signaling in CV tissue and plays a critical role in aldosterone/MR-dependent hypertension and fibrosis. We hypothesized that the production of NGAL by immune cells may play an important part in the mediation of these deleterious mineralocorticoid-induced effects. We analyzed the effect of aldosterone on immune cell recruitment and NGAL expression in vivo. We then studied the role of NGAL produced by immune cells in aldosterone-mediated cardiac inflammation and remodeling using mice depleted for NGAL in their immune cells by bone marrow transplantation and subjected to mineralocorticoid challenge NAS (Nephrectomy, Aldosterone 200μg/kg/day, Salt 1%). NAS treatment induced the recruitment of various immune cell populations to lymph nodes (granulocytes, B lymphocytes, activated CD8⁺ T lymphocytes) and the induction of NGAL expression in macrophages, dendritic cells, and PBMCs. Mice depleted for NGAL in their immune cells were protected against NAS-induced cardiac remodeling and inflammation. We conclude that NGAL produced by immune cells plays a pivotal role in cardiac damage under mineralocorticoid excess. Our data further stressed a pathogenic role of NGAL in cardiac damages, besides its relevance as a biomarker of renal injury.

Impact of acute versus repetitive moderate intensity endurance exercise on kidney injury markers

Exercise may lead to kidney injury through several mechanisms. Urinary Kidney Injury Molecule-1 (uKIM1) and Neutrophil Gelatinase-Associated Lipocalin (uNGAL) are known biomarkers for acute kidney injury, but their response to repetitive exercise remains unknown. We examined the effects of a single versus repetitive bouts of exercise on markers for kidney injury in a middle-aged population. Sixty subjects (aged 29-78 years, 50% male) were included and walked 30, 40 or 50 km for three consecutive days. At baseline and after exercise day 1 and 3, a urine sample was collected to determine uNGAL and uKIM1. Furthermore, urinary cystatin C, creatinine, and osmolality were used to correct for dehydration-related changes in urinary concentration. Baseline uNGAL was 9.2 (5.2-14.7) ng/mL and increased to 20.7 (11.0-37.2) ng/mL and 14.2(8.0-26.3) ng/mL after day 1 and day 3, respectively, (P ≤ 0.001). Baseline uKIM1 concentration was 2.6 (1.4-6.0) ng/mL and increased to 5.2 (2.4-9.1) ng/mL (P = 0.002) after day 1, whereas uKIM1 was not different from baseline at day 3 (2.9 [1.4-6.4] ng/mL (P = 0.52)). Furthermore, both uNGAL and uKIM1 levels were higher after day 1 compared to day 3 (P < 0.01). When corrected for urinary cystatin C, creatinine, and osmolality, uNGAL demonstrated a similar response compared to the uncorrected data, whereas differences in uKIM1 between baseline, day 1 and day 3 (Ptime = 0.63) were no longer observed for cystatin C and creatinine corrected data. A single bout of prolonged exercise significantly increased uNGAL concentration, whereas no changes in uKIM1 were found. Repetitive bouts of exercise show that there is no cumulative effect of kidney injury markers.

Obesity-promoting and anti-thermogenic effects of neutrophil gelatinase-associated lipocalin in mice

Neutrophil gelatinase-associated lipocalin (NGAL, lipocalin 2 or LCN2) is an iron carrier protein whose circulating level is increased by kidney injury, bacterial infection and obesity, but its metabolic consequence remains elusive. To study physiological role of LCN2 in energy homeostasis, we challenged female Lcn2 knockout (KO) and wild-type (WT) mice with high fat diet (HFD) or cold exposure. Under normal diet, physical constitutions of Lcn2 KO and WT mice were indistinguishable. During HFD treatment, Lcn2 KO mice exhibited larger brown adipose tissues (BAT), consumed more oxygen, ate more food and gained less body weights as compared to WT mice. When exposed to 4 °C, KO mice showed higher body temperature and more intense ¹⁸F-fluorodeoxyglucose uptake in BAT, which were cancelled by β3 adrenergic receptor blocker or iron-loaded (but not iron-free) LCN2 administration. These findings suggest that circulating LCN2 possesses obesity-promoting and anti-thermogenic effects through inhibition of BAT activity in an iron-dependent manner.

Insights into cellular and molecular basis for urinary tract infection in autosomal-dominant polycystic kidney disease

Urinary tract infection (UTI) is a broad term referring to an infection of the kidneys, ureters, bladder, and/or urethra. Because of its prevalence, frequent recurrence, and rising resistance to antibiotics, UTI has become a challenge in clinical practice. Autosomal-dominant polycystic kidney disease (ADPKD) is the most common monogenic disorder of the kidney and is characterized by the growth of fluid-filled cysts in both kidneys. Progressive cystic enlargement, inflammation, and interstitial fibrosis result in nephron loss with subsequent decline in kidney function. ADPKD patients frequently develop UTI; however, the cellular and molecular mechanisms responsible for the high UTI incidence in ADPKD patients remain virtually unaddressed. Emerging evidence suggests that α-intercalated cells (α-ICs) of the collecting ducts function in the innate immune defense against UTI. α-ICs inhibit bacterial growth by acidifying urine and secreting neutrophil gelatinase-associated lipocalin (NGAL) that chelates siderophore-containing iron. It is necessary to determine, therefore, if ADPKD patients with recurrent UTI have a reduced number and/or impaired function of α-ICs. Identification of the underlying cellular and molecular mechanisms may lead to the development of novel strategies to reduce UTI in ADPKD.

Neutrophil gelatinase-associated lipocalin level is a prognostic factor for survival in rat and human chronic liver diseases

Chronic liver disease patients often have complications, such as hepatocellular carcinoma (HCC) and acute bacterial infection. Model for end‐stage liver disease and Child‐Pugh scores are useful prognostic factors for chronic liver diseases but not for all chronic conditions, such as HCC. Our investigative aim targeted the prognostic abilities of neutrophil gelatinase‐associated lipocalin (NGAL) in rat and human chronic liver diseases. Blood NGAL levels were measured by enzyme‐linked immunosorbent assay in rats with cirrhosis and 96 patients with chronic liver disease and HCC. We examined the correlation between blood NGAL levels and liver functions as well as survival. In our rat model, liver NGAL expression was assessed by immunostaining, real‐time quantitative polymerase chain reaction, and immunoblot. In rats with cirrhosis, blood NGAL levels were continuously and significantly elevated in the deceased group and were significantly correlated with liver functions. Liver NGAL, toll‐like receptor 4, and interleukin‐6 levels were increased in the deceased group compared to the survival group. Blood NGAL levels were significantly correlated with liver NGAL levels, indicating blood NGAL was derived from the liver. In patients with chronic liver disease, blood NGAL levels were associated with liver function and renal function. Blood NGAL levels were significantly increased in patients with chronic liver disease with HCC compared to without HCC. For the survival group, 38 out of 96 patients were dead in the average follow‐up period of 9.9 months. The patients with blood NGAL ≤119 ng/mL had significantly longer rates of survival compared to patients with blood NGAL >119 ng/mL. Conclusion: Blood NGAL predicts the survival rate in rat and human chronic liver diseases. Our findings suggest blood NGAL may be prognostic of survival in chronic liver diseases complicated by HCC. (Hepatology Communications 2017;1:946–956)

AKI after pediatric cardiac surgery for congenital heart diseases-recent developments in diagnostic criteria and early diagnosis by biomarkers

Background

Acute kidney injury (AKI) after cardiac surgery in children with congenital heart disease is a common complication. AKI is also associated with high morbidity and mortality. The Kidney Diseases Improving Global Outcomes (KDIGO) criteria for AKI classification are now widely used for the definition of AKI. It is noteworthy that a statement about children was added to the criteria. Many studies aimed at finding useful biomarkers are now being performed by using these criteria. Clinicians should be aware of the recent progress in understanding AKI in children.

Main contents

Unlike adult patients, young age is one of the major risk factors for AKI in pediatric cardiac surgery. The mechanism of the development of AKI in children might be different from that in adults because the surgical procedure and CPB technique in pediatric patients are greatly different from those in adult patients.

There are many biomarkers for early detection of AKI, and some of them are widely used in hospitals. One of the major benefits of such biomarkers is the rapidness of expression for detecting increases in their expression levels. Neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, cystatin C, and albumin have been investigated in some studies, and the usefulness of these biomarkers for detection of AKI and diagnosis of disease severity has been shown.

Although there are many interventions for preventing and treating AKI after cardiac surgery in children, there is still no specific effective treatment. Peritoneal dialysis is effective for only maintaining a negative fluid balance early after cardiac surgery. The long-term prognosis of AKI is an issue of interest. Although mortality and morbidity of AKI in the acute phase of disease remain high, the long-term condition in pediatric patients is relatively acceptable unlike in adults.

Conclusions

KDIGO criteria are advocated as a diagnostic tool for common perception. Early recognition and intervention for AKI can be achieved by using several biomarkers. Further studies are needed to establish effective treatment for AKI.

Urine Interleukin 18 and Lipocalin 2 Are Biomarkers of Acute Tubular Necrosis in Patients With Cirrhosis: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Acute kidney injury (AKI) is a common complication in patients with cirrhosis that increases mortality. The most common causes of AKI in these patients are prerenal azotemia, acute tubular necrosis (ATN), and hepatorenal syndrome; it is important to determine the etiology of AKI to select the proper treatment and predict patient outcome. Urine biomarkers could be used to differentiate between patients with ATN and functional causes of AKI. We performed a systematic review and meta-analysis of published studies to determine whether urine levels of interleukin (IL)18 and lipocalin 2 or neutrophil gelatinase-associated lipocalin (NGAL) are associated with the development of ATN in patients with cirrhosis.

METHODS

We searched MEDLINE, Scopus, ISI Web of Knowledge, and conference abstracts through December 31, 2015, for studies that assessed urine biomarkers for detection of acute kidney injury in patients with cirrhosis or reported an association between urine biomarkers and all-cause mortality in these patients. We included only biomarkers assessed in 3 or more independent studies, searching for terms that included urine biomarkers, cirrhosis, NGAL, and IL18. We calculated the pooled sensitivities and specificities for detection and calculated the area under the receiver operating characteristic curve (AUC) values using a bivariate logistic mixed-effects model. We used the χ² test to assess heterogeneity among studies.

RESULTS

We analyzed data from 8 prospective studies, comprising 1129 patients with cirrhosis. We found urine levels of the markers discriminated between patients with ATN and other types of kidney impairments, with AUC values of 0.88 for IL18 (95% confidence interval [CI], 0.79-0.97) and 0.89 for NGAL (95% CI, 0.84-0.94). Urine levels of IL18 identified patients who would die in the hospital or within 90 days (short-term mortality) with an AUC value of 0.76 (95% CI, 0.68-0.85); NGAL identified these patients with the same AUC (0.76; 95% CI, 0.71-0.82).

CONCLUSIONS

In a systematic review and meta-analysis, we found that urine levels of IL18 and NGAL from patients with cirrhosis discriminate between those with ATN and other types of kidney impairments, with AUC values of 0.88 and 0.89, respectively. Urine levels of IL18 and NGAL identified patients with short-term mortality with an AUC value of 0.76. These biomarkers might be used to determine prognosis and select treatments for patients with cirrhosis.

Measuring non-polyaminated lipocalin-2 for cardiometabolic risk assessment

Aims

Lipocalin‐2 is a pro‐inflammatory molecule characterized by a highly diversified pattern of expression and structure–functional relationships. In vivo, this molecule exists as multiple variants due to post‐translational modifications and/or protein–protein interactions. Lipocalin‐2 is modified by polyamination, which enhances the clearance of this protein from the circulation and prevents its excessive accumulation in tissues. On the other hand, animal studies suggest that non‐polyaminated lipocalin‐2 (npLcn2) plays a causal role in the pathogenesis of obesity‐associated medical complications. The present study examined the presence of npLcn2 in samples from healthy volunteers or patients with cardiac abnormalities and evaluated npLcn2 as a biomarker for cardiometabolic risk assessment.

Methods and results

Immunoassays were developed to quantify npLcn2 in blood and urine samples collected from 100 volunteers (59 men and 41 women), or venous plasma and pericardial fluid samples obtained from 37 cardiothoracic surgery patients. In healthy volunteers, npLcn2 levels in serum are significantly higher in obese and overweight than in lean subjects. After adjustment for age, gender, smoking, and body mass index (BMI), serum npLcn2 levels are positively correlated with heart rate, circulating triglycerides, high‐sensitivity C‐reactive protein (hsCRP), and creatinine in plasma. The npLcn2 levels in urine are significantly increased in subjects with metabolic syndrome and positively correlated with BMI, heart rate, circulating triglycerides, and urinary aldosterone. In cardiothoracic surgery patients, the circulating concentrations of npLcn2 are higher (more than two‐fold) than those of healthy volunteers and positively correlated with the accumulation of this protein in the pericardial fluid. Heart failure patients exhibit excessive expression and distribution of npLcn2 in mesothelial cells and adipocytes of the parietal pericardium, which are significantly correlated with the elevated plasma levels of npLcn2, total cholesterol, and creatinine.

Conclusions

Quantitative and qualitative evaluation of npLcn2 in human biofluid samples and tissue samples can be applied for risk assessment of healthy individuals and disease management of patients with obesity‐related cardiometabolic and renal complications.

Effect of a single intravenous zoledronic acid administration on biomarkers of acute kidney injury (AKI) in patients with osteoporosis: a pilot study

AIMS

The pilot study was designed to evaluate the early effect of intravenous (i.v.) zoledronic acid (ZA) on renal function.

METHODS

Five mg i.v. ZA was administered to 23 patients with osteoporosis (17 women and 6 men, mean age 73 ± 7 SD years). Urinary NGAL, KIM-1, and MCP-1, plasma (p) MCP-1 and serum (s) IL-18, serum calcium (sCa), Creatinine clearance (CrCl), parathyroid hormone (PTH), plasma C-terminal FGF23 (pFGF23), serum (s) Klotho, calcium excretion (CaEx) and renal threshold phosphate concentration/GFR (TmPO₄ /GFR) were assessed at baseline, 24 h and Day 30 after administration.

RESULTS

There was a significant decrease in sCa and CaEx at 24 h (-4.1 ± 2.8%, P < 0.01 and -28 ± 59%, P < 0.05, respectively) and Day 30 (-3.9 ± 4%, P < 0.001 and -26 ± 43%, P < 0.01) and a significant increase in PTH (79.8 ± 95.8%) at Day 30 (P < 0.001) compared to baseline. TmPO₄ /GFR decreased significantly at 24 h and Day 30 (-8.6 ± 15.9%, P < 0.05 and -11.3 ± 13.5%, P < 0.001) compared to baseline. We observed no difference in the concentration of pFGF23, sKlotho and urinary AKI biomarkers at any time points. Mean levels of sIL-18 and pMCP-1 increased significantly at 24 h (44 ± 88%; P < 0.01 and 198 ± 237%; P < 0.001) and returned to baseline at Day 30.

CONCLUSIONS

Our pilot study suggests that there is no direct acute effect of ZA on kidney function. The increase in plasma MCP-1 and serum IL-18 concentration could be associated with the stimulation of immunity mechanisms occurring soon after the administration of the drug. Secondary hyperparathyroidism develops shortly after the infusion of ZA and is maintained even after 1 month.

Lipocalin 2: An Emerging Player in Iron Homeostasis and Inflammation

Lipocalin 2 (Lcn2), an innate immune protein, has emerged as a critical iron regulatory protein during physiological and inflammatory conditions. As a bacteriostatic factor, Lcn2 obstructs the siderophore iron-acquiring strategy of bacteria and thus inhibits bacterial growth. As part of host nutritional immunity, Lcn2 facilitates systemic, cellular, and mucosal hypoferremia during inflammation, in addition to stabilizing the siderophore-bound labile iron pool. In this review, we summarize recent advances in understanding the interaction between Lcn2 and iron, and its effects in various inflammatory diseases. Lcn2 exerts mostly a protective role in infectious and inflammatory bowel diseases, whereas both beneficial and detrimental functions have been documented in neurodegenerative diseases, metabolic syndrome, renal disorders, skin disorders, and cancer. Further animal and clinical studies are necessary to unveil the multifaceted roles of Lcn2 in iron dysregulation during inflammation and to explore its therapeutic potential for treating inflammatory diseases.

Predicting acute kidney injury: current status and future challenges

Acute kidney injury (AKI) is characterized by an acute decline in renal function and is associated to increased mortality rate, hospitalization time, and total health-related costs. The severity of this ‘fearsome’ clinical complication might depend on, or even be worsened by, the late detection of AKI, when the diagnosis is based on the elevation of serum creatinine (SCr). For these reasons, in recent years a great number of new tools, biomarkers and predictive models have been proposed to clinicians in order to improve diagnosis and prevent the development of AKI. The purpose of this narrative paper is to review the current state of the art in prediction and early detection of AKI and outline future challenges.

Novel bone metabolism-associated hormones: the importance of the pre-analytical phase for understanding their physiological roles

The endocrine function of bone is now a recognized feature of this tissue. Bone-derived hormones that modulate whole-body homeostasis, are being discovered as for the effects on bone of novel and classic hormones produced by other tissues become known. Often, however, the data regarding these last generation bone-derived or bone-targeting hormones do not give about a clear picture of their physiological roles or concentration ranges. A certain degree of uncertainty could stem from differences in the pre-analytical management of biological samples. The pre-analytical phase comprises a series of decisions and actions (i.e., choice of sample matrix, methods of collection, transportation, treatment and storage) preceding analysis. Errors arising in this phase will inevitably be carried over to the analytical phase where they can reduce the measurement accuracy, ultimately, leading discrepant results. While the pre-analytical phase is all important, in routine laboratory medicine, it is often not given due consideration in research and clinical trials. This is particularly true for novel molecules, such as the hormones regulating the endocrine function of bone. In this review we discuss the importance of the pre-analytical variables affecting the measurement of last generation bone-associated hormones and describe their, often debated and rarely clear physiological roles.