Evaluation of Novel Biomarkers of Acute Kidney Injury: The Possibilities and Limitations

Is renal dysfunction amplified in an arginine vasopressin induced rat model of preeclampsia?

Renal dysfunction is important in preeclampsia (PE) pathophysiology and has not been fully explored in the arginine vasopressin (AVP) rat model of PE. This study aimed to determine kidney toxicity associated with this model. Female Sprague Dawley rats (n = 24) were subcutaneously infused with AVP or saline for 18 days. Urine samples (GD8, 14 and 18) were used to determine the levels of albumin, VEGF-A, clusterin, NGAL/Lipocalin-2, KIM-1, cystatin C, TIMP-1, β2M and OPN via Multiplex ELISAs. Albumin, and NGAL/lipocalin-2 were significantly elevated in the PAVP vs PS group on GD14 and GD18 (p < 0.001) respectively. VEGF-A significantly decreased in the pregnant vs non-pregnant groups on GD14 and 18 (p < 0.001). Clusterin (p < 0.001) and OPN (p < 0.05) were significantly higher in the PAVP vs PS group on GD18. Cystatin C and KIM-1 are significantly upregulated in the PAVP vs PS groups throughout gestation (p < 0.05). β2M is significantly elevated in the PAVP vs PS group on GD14 and 18 (p < 0.05). AVP elevated the urinary levels of the kidney injury biomarkers and replicated the renal dysfunction associated with PE development. Our findings confirm the potential applications of this model in studying the mechanisms underlying renal damage in PE.

Berberine alleviated contrast-induced acute kidney injury by mitophagy-mediated NLRP3 inflammasome inactivation in a mice model

The incidence of contrast-induced acute kidney injury (CI-AKI) has escalated to become the third most prevalent cause of hospital-acquired AKI, with a lack of efficacious interventions. Berberine (BBR) possesses diverse pharmacological effects and exhibits renoprotective properties; however, limited knowledge exists regarding its impact on CI-AKI. Therefore, our study aimed to investigate the protective effects and underlying mechanisms of BBR on CI-AKI in a mice model, focusing on the nucleotide-binding oligomerization domain-like pyrin domain-containing protein 3 (NLRP3) inflammasome and mitophagy. The CI-AKI mice model was established by administering NG-nitro-L-arginine methyl ester (L-NAME) (10 mg/kg), indomethacin (10 mg/kg), and iohexol (11 g/kg) following water deprivation. A pretreatment of 100 mg/kg of BBR was orally administered to the mice for two weeks. Renal injury markers, damage-associated molecular patterns (DAMPs), renal histopathology, mitochondrial morphology, autophagosomes, and potential mechanisms were investigated. BBR effectively reduced levels of renal injury biomarkers such as serum cystatin C, urea nitrogen, and creatinine, downregulated the protein level of kidney injury molecule 1 (KIM1), and mitigated renal histomorphological damage. Moreover, BBR reduced DAMPs, including high mobility group box-1 (HMGB1), heat shock protein 70 (HSP70), and uric acid (UA). It also alleviated oxidative stress and inflammatory factors such as monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β). Furthermore, the activation of NLRP3 inflammasome was attenuated in the BBR pretreatment group, as evidenced by both mRNA and protein levels. Electron microscopy and western blotting examination revealed that BBR mitigated mitochondrial damage and enhanced mitophagy. Additionally, BBR increased the P-AMPK/AMPK ratio. These findings indicated that BBR exerted a protective effect against CI-AKI by suppressing NLRP3 inflammasome activation and modulating mitophagy, providing a potential therapeutic strategy for its prevention.

Lack of mitochondrial Cyp2E1 drives acetaminophen-induced ER stress-mediated apoptosis in mouse and human kidneys: Inhibition by 4-methylpyrazole but not N-acetylcysteine

Acetaminophen (APAP) overdose causes liver injury and acute liver failure, as well as acute kidney injury, which is not prevented by the clinical antidote N-acetyl-L-cysteine (NAC). The absence of therapeutics targeting APAP-induced nephrotoxicity is due to gaps in understanding the mechanisms of renal injury. APAP metabolism through Cyp2E1 drives cell death in both the liver and kidney. We demonstrate that Cyp2E1 is localized to the proximal tubular cells in mouse and human kidneys. Virtually all the Cyp2E1 in kidney cells is in the endoplasmic reticulum (ER), not in mitochondria. By contrast, hepatic Cyp2E1 is in both the ER and mitochondria of hepatocytes. Consistent with this subcellular localization, a dose of 600 mg/kg APAP in fasted C57BL/6J mice induced the formation of APAP protein adducts predominantly in mitochondria of hepatocytes, but the ER of the proximal tubular cells of the kidney. We found that reactive metabolite formation triggered ER stress-mediated activation of caspase-12 and apoptotic cell death in the kidney. While co-treatment with 4-methylpyrazole (4MP; fomepizole) or the caspase inhibitor Ac-DEVD-CHO prevented APAP-induced cleavage of procaspase-12 and apoptosis in the kidney, treatment with NAC had no effect. These mechanisms are clinically relevant because 4MP but not NAC also significantly attenuated APAP-induced apoptotic cell death in primary human kidney cells. We conclude that reactive metabolite formation by Cyp2E1 in the ER results in sustained ER stress that causes activation of procaspase-12, triggering apoptosis of proximal tubular cells, and that 4MP but not NAC may be an effective antidote against APAP-induced kidney injury.

Kidney injury molecule-1 and podocalyxin dysregulation in an arginine vasopressin induced rodent model of preeclampsia

OBJECTIVE

To assess renal injury in an arginine vasopressin (AVP) rodent model of preeclampsia.

STUDY DESIGN

Urinary expression of kidney injury molecule-1 (KIM-1), urinary protein and creatinine was determined in rodents (n = 24; pregnant AVP, pregnant saline, non-pregnant AVP and non-pregnant saline), which received a continuous dose of either AVP or saline via subcutaneous mini osmotic pumps for 18 days, using a Multiplex kidney toxicity immunoassay. Renal morphology was assessed using haematoxylin and eosin staining and transmission electron microscopy. The immunolocalization of KIM-1 and podocalyxin was qualitatively evaluated using immunohistochemistry.

RESULTS

Urinary KIM-1 and urinary protein levels were significantly increased in treated vs. untreated rats on gestational days 8 (p < 0.05), 14 (p < 0.001) and 18 (p < 0.001). The pregnant rats displayed a lower trend of creatinine compared to the non-pregnant groups, albeit non-significantly. KIM-1 was immunolocalized in the proximal convoluted tubules in AVP treated vs. untreated groups. In contrast, podocalyxin was weakly immunostained within glomeruli of pregnant AVP treated vs. pregnant untreated rats. Histological evaluation revealed reduced Bowman's space, with some tubular and blood vessel necrosis in the pregnant treated group. Ultrastructural observations included effacement and fusion of podocyte foot processes, glomerular basement membrane abnormalities, podocyte nuclear crenations, mitochondrial oedema and cristae degeneration with cytoplasmic lysis within treated tissue.

CONCLUSION

Our findings demonstrate region-specific kidney injury particularly glomerular impairment and endothelial injury in AVP-treated rats. The findings highlight the utility of this model in studying the mechanisms driving renal damage in a rodent model of preeclampsia.

New Insight in Cardiorenal Syndrome: From Biomarkers to Therapy

Cardiorenal syndrome consists in the coexistence of acute or chronic dysfunction of heart and kidneys resulting in a cascade of feedback mechanisms and causing damage to both organs associated with high morbidity and mortality. In the last few years, different biomarkers have been investigated with the aim to achieve an early and accurate diagnosis of cardiorenal syndrome, to provide a prognostic role and to guide the development of targeted pharmacological and non-pharmacological therapies. In such a context, sodium-glucose cotransporter 2 (SGLT2) inhibitors, recommended as the first-line choice in the management of heart failure, might represent a promising strategy in the management of cardiorenal syndrome due to their efficacy in reducing both cardiac and renal outcomes. In this review, we will discuss the current knowledge on the pathophysiology of cardiorenal syndrome in adults, as well as the utility of biomarkers in cardiac and kidney dysfunction and potential insights into novel therapeutics.

Insulin-like growth factors and their carrier proteins in kidneys of rats with experimental diabetes, malignant tumor, and their combination

Persistent hyperglycemia resulting from diabetes mellitus causes microvascular lesions and long-term diabetic complications, such as nephropathy.

The aim of the study was to analyze the levels of insulin-like growth factors (IGFs), their carrier proteins (IGFBP), and markers of kidney tissue damage (IL-18, L-FABP, cystatin C, NGAL, and KIM-1) in male rats with diabetes mellitus, tumor growth, and their combination.

Materials and methods. The study included white outbred male rats (n = 32) weighing 180–220 g. The animals were divided into four groups (n = 8 each): group 1 – intact animals; controls (2) – animals with diabetes mellitus; controls (3) – animals with Guerin carcinoma; experimental group (4) – animals with Guerin carcinoma against the background of diabetes mellitus. Levels of IGF-1, IGF-2, IGFBP-1, IGFBP-2 and markers of acute kidney injury (IL-18, L-FABP, cystatin С, NGAL, and KIM-1) were determined in the kidney homogenates using enzyme-linked immunosorbent assay.

Results. Increased levels of acute kidney injury markers were found in the kidneys of male rats with diabetes mellitus alone and in combination with Guerin carcinoma. In the animals with diabetes mellitus, the levels of IGF-1, IGFBP-1, and IGFBP-2 were decreased on average by 1.3 times, and the level of IGF-2 was increased by 2.1 times compared with the values in the intact male rats. The elevation of IGF-2 / IGF-1 on average by 2.8 times indicated increasing hypoglycemia in the kidney tissue of the animals with diabetes mellitus and in the experimental group with diabetes mellitus and Guerin carcinoma. In the kidney tissues of the rats with Guerin carcinoma, IGF-1 and IGF-2 were elevated on average by 1.5 times, and IGFBP-2 was decreased by 1.7 times. In the animals with malignant tumors growing against the background of diabetes mellitus, IGF-2 and IGFBP-1 were increased by 2.3 and 1.7 times, respectively, and the levels of IGF-1 and IGFBP-2 were similar to those in the intact animals.

Conclusion. The study demonstrated abnormalities in the metabolic profile of the kidneys in male rats with experimental diabetes mellitus, Guerin carcinoma, and their combination.

miR-23a-3p inhibits sepsis-induced kidney epithelial cell injury by suppressing Wnt/β-catenin signaling by targeting wnt5a

The present study was designed to investigate the involvement of miR-23a-3p in the progression of sepsis-induced acute kidney injury (AKI). The expression levels of miR-23a-3p and wnt5a in sepsis-induced AKI patients and lipopolysaccharide (LPS)-treated HK-2 cells were detected by real-time PCR and western blotting. Then, the effects of miR-23a-3p overexpression on cell viability, apoptosis, and inflammatory cytokines secretion in LPS-stimulated HK-2 cells were investigated. Moreover, luciferase reporter assay was performed to confirm the regulatory relationship between miR-23a-3p and wnt5a. Whether miR-23a-3p regulated the activation of Wnt/β-catenin signaling was also explored. mR-23a-3p was lowly expressed in the serum of patients with sepsis-associated AKI and in LPS-treated HK-2 cells. In addition, the overexpression of miR-23a-3p restrained LPS-induced proliferation inhibition and promotion of apoptosis and cytokine production in HK-2 cells. Moreover, wnt5a was identified as a target of miR-23a-3p, which could be negatively regulated by miR-23a-3p. Overexpression of miR-23a-3p suppressed the activation of Wnt/β-catenin signaling in LPS-treated HK-2 cells, which was markedly reversed by wnt5a upregulation. Upregulation of miR-23a-3p may alleviate LPS-induced cell injury by targeting wnt5a and inactivating Wnt/β-catenin pathway, which may serve as a novel therapeutic target for sepsis-associated AKI.

Crosstalk between E-Cadherin/β-Catenin and NF-κB Signaling Pathways: The Regulation of Host-Pathogen Interaction during Leptospirosis

Approximately 1 million cases of leptospirosis, an emerging infectious zoonotic disease, are reported each year. Pathogenic Leptospira species express leucine-rich repeat (LRR) proteins that are rarely expressed in non-pathogenic Leptospira species. The LRR domain-containing protein family is vital for the virulence of pathogenic Leptospira species. In this study, the biological mechanisms of an essential LRR domain protein from pathogenic Leptospira were examined. The effects of Leptospira and recombinant LRR20 (rLRR20) on the expression levels of factors involved in signal transduction were examined using microarray, quantitative real-time polymerase chain reaction, and western blotting. The secreted biomarkers were measured using an enzyme-linked immunosorbent assay. rLRR20 colocalized with E-cadherin on the cell surface and activated the downstream transcription factor β-catenin, which subsequently promoted the expression of MMP7, a kidney injury biomarker. Additionally, MMP7 inhibitors were used to demonstrate that the secreted MMP7 degrades surface E-cadherin. This feedback inhibition mechanism downregulated surface E-cadherin expression and inhibited the colonization of Leptospira. The degradation of surface E-cadherin activated the NF-κB signal transduction pathway. Leptospirosis-associated acute kidney injury is associated with the secretion of NGAL, a downstream upregulated biomarker of the NF-κB signal transduction pathway. A working model was proposed to illustrate the crosstalk between E-cadherin/β-catenin and NF-κB signal transduction pathways during Leptospira infection. Thus, rLRR20 of Leptospira induces kidney injury in host cells and inhibits the adhesion and invasion of Leptospira through the upregulation of MMP7 and NGAL.

Systems analysis of miRNA biomarkers to inform drug safety

microRNAs (miRNAs or miRs) are short non-coding RNA molecules which have been shown to be dysregulated and released into the extracellular milieu as a result of many drug and non-drug-induced pathologies in different organ systems. Consequently, circulating miRs have been proposed as useful biomarkers of many disease states, including drug-induced tissue injury. miRs have shown potential to support or even replace the existing traditional biomarkers of drug-induced toxicity in terms of sensitivity and specificity, and there is some evidence for their improved diagnostic and prognostic value. However, several pre-analytical and analytical challenges, mainly associated with assay standardization, require solutions before circulating miRs can be successfully translated into the clinic. This review will consider the value and potential for the use of circulating miRs in drug-safety assessment and describe a systems approach to the analysis of the miRNAome in the discovery setting, as well as highlighting standardization issues that at this stage prevent their clinical use as biomarkers. Highlighting these challenges will hopefully drive future research into finding appropriate solutions, and eventually circulating miRs may be translated to the clinic where their undoubted biomarker potential can be used to benefit patients in rapid, easy to use, point-of-care test systems.

The protective effects of sinapic acid on acute renal ischemia/reperfusion injury

Objectives

The aim of this research was to investigate whether sinapic acid (SA) can alleviate oxidative damage, apoptosis, and inflammation in I/R induced renal injury.

Methods

A total of 24 male rats were randomly separated into four groups as six rats in each group. Group 1 (Sham), Group 2 (I/R), Group 3 (I/R + SA, 10 mg/kg), Group 4 (I/R + SA, 20 mg/kg). In order to evaluate kidney function serum BUN, Cr, and AST were measured in an autoanalyzer. SOD, GSH-Px, MDA, PC and NO oxidative stress parameters were measured with spectrophotometric methods and TNF-α, IL-1β, IL-6, KIM-1 and NGAL parameters were measured with the ELISA method. In addition, H&E method and immunohistochemical examinations were performed for histological evaluations of kidney tissue.

Results

SA significantly decreases the increase in kidney damage, inflammation, oxidative stress, cell death and restore the decrease in antioxidant enzyme activities (p<0.05). Pre-treatment of the rats with SA reduces kidney dysfunction and morphological changes.

Conclusions

The development of oxidative stress and lipid peroxidation seems to be the leading factors that accelerate inflammation and cell death during renal IRI. The antioxidant, anti-inflammatory, and anti-apoptotic features of SA displayed a renoprotective effect.

Early kidney injury in immunoglobulin A vasculitis: Role of renal biomarkers

BACKGROUND

We aimed to determine whether urine kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) can be used as early noninvasive biomarkers of kidney injury in immunoglobulin A vasculitis.

METHODS

Patients who were diagnosed with immunoglobulin A vasculitis were included in the study. Urine samples were collected for determination of urine KIM-1 and NGAL levels. The control group consisted of age-matched healthy children.

RESULTS

Sixty-one patients who were diagnosed with immunoglobulin A vasculitis were included in the study; 37.7% of these patients were determined to have renal involvement. Median KIM-1 was found to be significantly higher in the patient group (69.59 pg/mL) than the control group (40.84 pg/mL) (P = 0.001). Median NGAL was determined to be statistically significantly higher in the patient group (59.87 ng/mL) compared with the control group (44.87 ng/mL) (P = 0.013). In 23.6% of the patients without renal involvement at admission renal involvement developed within the following 6 months. When median KIM-1 and NGAL at admission of these patients were compared with the control group, they were determined to be statistically significantly higher (P = 0.001, P = 0.003).

CONCLUSIONS

The fact that our patients with late-term nephropathy had no hematuria and / or proteinuria and that KIM-1 and NGAL levels were determined to be high indicates that these biomarkers might be potentially reliable, noninvasive and early determinants of kidney injury.

Cardionephrology from the point of view of the cardiologist: no more agree to disagree-getting to 'yes' for every patient

Whether one wants to or not, interactions between the heart and the kidneys exist and manifest nevertheless. Both from theoretical and clinical perspectives, it seems the need for a subspecialty of cardionephrology seems justified. Our editorial is a cardiologist perspective on the article by Diez and Ortiz published in Clinical Kidney Journal related to the 'need for a cardionephrology subspecialty'. We analysed the historical similarities of the emergence of already ingrained clinical fields with the current needs in the cardionephrology sector. We motivated our approach based on novel cardiovascular diagnostic and therapeutic developments and significant pathophysiological differences from a cardiological perspective, accounting for the foundation of a novel sustainable medical field. One of the sensitive issues we also addressed was the operationality and applicability of the principles. We answered with some examples from high-risk debatable contexts the question of where a cardionephrologist should be integrated. Clarifying the operationality aspects would be a positive shift towards improving guidelines adherence in managing complex patients. In conclusion, we underline that the necessity of a cardionephrologist must be addressed from an operational and scientific perspective, with the ultimate goal of reducing mortality and complications in cardiorenal patients.

Renal impairment assessment on adults living nearby a landfill: Early kidney dysfunction biomarkers linked to the environmental exposure to heavy metals

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Health risk of the neighboring population of the Mbeubeuss landfill (Senegal).

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Assessment of the impact of Cd/Pb exposure through dysfunction renal biomarkers.

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Specific increases of a set of early dysfunction renal biomarkers in exposed subjects.

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Glomerular and tubular dysfunction in exposed subjects.

The aim of this study was to assess the integrity and kidney overall functional capacity of subjects exposed to landfill emissions. Urine and blood levels of Pb and Cd, and several of the newly biomarkers of nephrotoxicity (Kim Injury Molecule 1 (KIM-1), alpha-1 Microglobulin (α1 M), beta-2 Microglobulin (β2 M), Cystatin-C (Cyst C), Clusterin, alpha-glutathione S-transferase (GSTα), pi-glutathione S-transferase (GSTπ), Tissue Inhibitor of Metalloproteinase-1 (TIMP1), Calbindin, Neutrophil Gelatinase-Associated Lipocalin (NGAL), Osteopontin (OPN), (Retinol Binding Protein(RBP), Liver-type Fatty Acid-Binding Protein (FABP-1), Trefoil Factor 3 (TFF3), Collagen VI) were measured in order to assess glomerular and tubule damage in adults living near a landfill.

Our results indicate glomerular dysfunction in exposed subjects, and supported evidence of necrosis of proximal and distal tubule epithelial cells as specific biomarkers began to appear in the urine.

Positive correlation by Pearson test were obtained between : blood Pb and B-OPN, B-Cyst C, Calbindin, U-KIM-1, TIMP1, U-OPN, and U-Clusterin; and also, between urinary Cd and TIMP1, B-Clusterin, U-OPN, FABP-1, Albumin, and U-Clusterin. The relation between biomarkers of Cd/Pb exposure and early effect biomarkers in this study clearly predicts the future risk of severe kidney injury in subjects living close to the landfill.

Crystal structure of Leptospira leucine-rich repeat 20 reveals a novel E-cadherin binding protein to induce NGAL expression in HK2 cells

Leptospirosis is the most common zoonotic disease caused by pathogenic Leptospira, which is classified into three groups according to virulence. Its pathogenic and intermediate species contain leucine-rich repeat (LRR) proteins that are rarely expressed in non-pathogenic strains. In this study, we presented the crystal structure of LSS_11580 (rLRR20) from pathogenic L. santarosai serovar Shermani. X-ray diffraction at a resolution of 1.99 Å revealed a horseshoe-shaped structure containing seven α-helices and five β-sheets. Affinity assays indicated that rLRR20 interacts with E-cadherin on the cell surface. Interestingly, its binds to the extracellular (EC) 1 domain in human epithelial (E)-cadherin, which is responsible for binding to another E-cadherin molecule in neighboring cells. Several charged residues on the concave face of LRR20 were predicted to interact with EC1 domain. In the affinity assays, these charged residues were replaced by alanine, and their affinities to E-cadherin were measured. Three vital residues and mutation variants of LRR20, namely D56A, E59A, and E123A, demonstrated significantly reduced affinity to E-cadherin compared with the control. Besides, we also demonstrated that rLRR20 induced the expression of neutrophil gelatinase-associated lipocalin (NGAL) in HK2 cells. The low ability of the three mutation variants to induce NGAL expression further demonstrates this induction. The present findings indicate that LRR20 from pathogenic Leptospira binds to E-cadherin and interacts with its EC1 domain. In addition, its induction of NGAL expression in HK2 cells is associated with acute kidney injury in human.

A long journey for acute kidney injury biomarkers

Acute kidney injury (AKI) is a life-threatening illness that continues to have an in-hospital mortality rate of patients with AKI ranges from 20% to 50% or greater, depending on underlying conditions. However, it has only marginally declined over the past 25 years. Previous authoritative publications have been pointed out that the lack of useful biomarkers for AKI has limited progress in improving the outcomes of this disorder. The purpose of this paper is to review the recent biomarkers involved in the early detection of AKI and main reasons for the failure to identify new AKI biomarkers. So far, several new AKI biomarkers have been discovered and validated to improve early diagnosis, degree of severity, pathophysiology, differential diagnosis, prediction for major kidney adverse events (MAKE, risk groups for progressive renal failure, need for renal replacement therapy [RRT], or death). These biomarkers can be classified into functional, damage and pre-injury phase biomarkers. However, the clinical use of the studied biomarkers in AKI prediction remains unclear because large prospective multicenter trials have failed to demonstrate troponin-like diagnostic performance. Reasons for the failure to identify AKI biomarkers are the heterogeneity of AKI itself, biomarker limitations and long roads to the validation of candidates for new AKI biomarkers. In an effort to overcome these barriers to identifying new AKI biomarkers, kidney biopsy specimens should be obtained and assessed in human AKI populations. Research in this field should be carried out in a pan-social approach rather than conducted by just a few medical institutions.

Impact of Pneumoperitoneum on the Development of Acute Kidney Injury: Comparison Between Normal and Diabetic Rats

BACKGROUND

Minimally invasive surgery is considered the gold-standard approach for many surgical procedures. However, it requires CO2 insufflation and elevated intra-abdominal pressure (IAP), which may result in adverse pulmonary, cardiovascular, gastrointestinal, and renal changes. The kidneys are highly sensitive to pressure changes, where risk factors such as severe infection, dehydration, older age, and chronic kidney disease may aggravate the likelihood for the development of acute kidney injury (AKI). Unfortunately, the impact of diabetes mellitus on the deleterious effects of elevated IAP-induced AKI was not fully studied so far. The present study was designed to examine the effect of pneumoperitoneum on renal function and the development of AKI in diabetic rats.

MATERIALS AND METHODS

Sprague Dawley rats were divided into 2 groups: control (nondiabetic) rats (n=7) and diabetic rats (n=10). A Veress needle was introduced through the supravesical incision where inflating CO2 allowing the IAP to be increased to the desired pressures 7, 10, and 14 mm Hg for 45 minutes each and at the end of the experiment, the pressure was deflated to zero. During each pressure point, hemodynamic parameters were recorded and urine and blood samples were collected for analysis.

RESULTS

The baseline values of renal hemodynamic were significantly lower in diabetic rats. There were no major statistically significant changes from baseline in urinary flow, urinary sodium excretion (UNaV), glomerular filtration rate, and renal plasma flow during 7 mm Hg pressure in both groups. When the IAP was further elevated, a significant deterioration of these parameters was recorded. This trend was more pronounced among diabetic rats. When examining urinary neutrophil gelatinase-associated lipocalin, a linear correlation was observed between the IAP and the biomarker level. This correlation was more significant in the diabetic group.

CONCLUSION

The present study demonstrated a direct correlation between IAP elevation and the development of AKI. Diabetic rats were more sensitive to the deleterious effect of pneumoperitoneum, where urinary neutrophil gelatinase-associated lipocalin levels may be used as a future biomarker to predict postoperative AKI, especially in patients with diabetes.

Acute Kidney Injury After Esophageal Cancer Surgery: Incidence, Risk Factors, and Impact on Oncologic Outcomes

OBJECTIVE

To determine the incidence, risk factors, and consequences of AKI in patients undergoing surgery for esophageal cancer.

SUMMARY OF BACKGROUND DATA

Esophageal cancer surgery is an exemplar of major operative trauma, with well-defined risks of respiratory, cardiac, anastomotic, and septic complications. However, there is a paucity of literature regarding AKI.

METHODS

Consecutive patients undergoing curative-intent surgery for esophageal cancer from 2011 to 2017 in 3 high-volume centers were studied. AKI was defined according to the AKI Network criteria. AKI occurred if, within 48 hours postoperatively, serum creatinine rose by 50% or by 0.3 mg/dL (26.5 μmol/L) from preoperative baseline. Complications were recorded prospectively. Multivariable logistic regression determined factors independently predictive of AKI.

RESULTS

A total of 1135 patients (24.7%:75.3% female:male, with a mean age of 64, a baseline BMI of 27 kg m, and dyslipidemia in 10.2%), underwent esophageal cancer surgery, 85% having an open thoracotomy. Overall in-hospital mortality was 2.1%. Postoperative AKI was observed in 208 (18.3%) patients, with AKI Network 1, 2, and 3 in 173 (15.2%), 28 (2.5%), and 7 (0.6%), respectively. Of these, 70.3% experienced improved renal function within 48 hours. Preoperative factors independently predictive of AKI were age [P = 0.027, odds ratio (OR) 1.02 (1.00-1.04)], male sex [P = 0.015, OR 1.77 (1.10-2.81)], BMI at diagnosis [P < 0.001, OR 1.10 (1.07-1.14)], and dyslipidemia [P = 0.002, OR 2.14 (1.34-3.44)]. Postoperatively, AKI was associated with atrial fibrillation (P = 0.013) and pneumonia (P = 0.005). Postoperative AKI did not impact survival outcomes.

CONCLUSION

AKI is common but mostly self-limiting after esophageal cancer surgery. It is associated with age, male sex, increased BMI, dyslipidemia, and postoperative morbidity.

Acute toxic kidney injury

Substances toxic to the kidney are legion in the modern world. The sheer number and variety, their mutual interactions and, metabolism within the body are a challenge to research. Moreover, the kidney is especially prone to injury owing to its physiology. Acute kidney injury (AKI) induced by poisonous or primarily nephrotoxic substances, may be community acquired with ingestion or inhalation or nosocomial. Many nephrotoxic plants, animal poisons, medications, chemicals and illicit drugs can induce AKI by varying pathophysiological pathways. Moreover, the epidemiology of toxic AKI varies depending on country, regions within countries, socioeconomic status and health care facilities. In this review, we have selected nephrotoxic insults due to medication, plants, animal including snake venom toxicity, environmental, (agri)chemicals and also illicit drugs. We conclude with a section on diagnosis, clinical presentation and management of poisoning accompanied by various organ dysfunction and AKI.

Kidney injury molecule-1 expression predicts structural damage and outcome in histological acute tubular injury

Background: A few studies have shown that urinary kidney injury molecule-1 (uKIM-1) levels are increased in acute kidney injury (AKI); however, the correlation between uKIM-1 and histological tubular injury, which is considered to be the gold standard for evaluating renal damage and predicting prognosis, is still unclear. We performed this study to determine whether the predicted value of uKIM-1 is correlated with renal KIM-1 (tKIM-1) expression and tissue damage in AKI patients.

Methods: This retrospective study recruited 14 healthy individuals and 27 biopsy-proven acute tubular injury (ATI) patients. uKIM-1 and plasma KIM-1 (sKIM-1) levels were measured by ELISA, and tKIM-1 expression was evaluated by immunohistochemistry.

Results: Elevated levels of urinary, plasma, and renal KIM-1 were found in ATI patients. The uKIM-1 concentration was positively correlated with tKIM-1 expression and reflected the severity of renal histological injury. The outcome of ATI was associated with uKIM-1 expression: the ATI patients with higher uKIM-1 levels had an increased potential for an incomplete recovery of renal function during follow-up. Additionally, the level of KIM-1, regardless of source, was negatively related to the eGFR, and ROC curve analysis revealed that the ROC-AUC was 0.923 (p = 0.000) for the diagnosis of ATI based on a combination of high uKIM-1 and sKIM-1 levels.

Conclusion: The uKIM-1 level corresponds with the severity of renal histological damage and can be a potential reliable predictor of adverse renal outcomes in ATI patients. Moreover, combining uKIM-1 and sKIM-1 can increase the sensitivity and specificity of the diagnosis of severe ATI.

Matrix metalloproteinase-7 protects against acute kidney injury by priming renal tubules for survival and regeneration

Matrix metalloproteinase-7 (MMP-7) is a secreted endopeptidase that degrades a broad range of substrates. Recent studies have identified MMP-7 as an early biomarker to predict severe acute kidney injury (AKI) and poor outcomes after cardiac surgery; however, the role of MMP-7 in the pathogenesis of AKI is unknown. In this study, we investigated the expression of MMP-7 and the impact of MMP-7 deficiency in several models of AKI. MMP-7 was induced in renal tubules following ischemia/ reperfusion injury or cisplatin administration, and in folic acid-induced AKI. MMP-7 knockout mice experienced higher mortality, elevated serum creatinine, and more severe histologic lesions after ischemic or toxic insults. Tubular apoptosis and interstitial inflammation were more prominent in MMP-7 knockout kidneys. These histologic changes were accompanied by increased expression of FasL and other components of the extrinsic apoptotic pathway, as well as increased expression of pro-inflammatory chemokines. In a rescue experiment, exogenous MMP-7 ameliorated kidney injury in MMP-7 knockout mice after ischemia/reperfusion. In vitro, MMP-7 protected tubular epithelial cells against apoptosis by directly degrading FasL. In isolated tubules ex vivo, MMP-7 promoted cell proliferation by degrading E-cadherin and thereby liberating β-catenin, priming renal tubules for regeneration. Taken together, these results suggest that induction of MMP-7 is protective in AKI by degrading FasL and mobilizing β-catenin, thereby priming kidney tubules for survival and regeneration.

Elevated Serum Markers of Acute Kidney Injury in Patients With Obstructive Sleep Apnea

STUDY OBJECTIVES

Previous research revealed a positive correlation between endothelial cell injury (indicated by albuminuria) and obstructive sleep apnea (OSA). However, little else has been revealed about acute kidney injury (AKI) in patients with OSA.

METHODS

This prospective study recruited consecutive patients undergoing overnight polysomnography for evaluation of sleep apnea. Patients in whom any major disease or recent infection had been previously diagnosed were excluded. Ultimately, data from 75 patients with apnea-hypopnea indices of 5 or more were analyzed. Baseline values for the urinary albumin-creatinine ratio (UACR), serum levels for three markers of AKI (cystatin C, neutrophil gelatinase-associated lipocalin [NGAL], interleukin-18 [IL-18]), and polysomnography data were recorded and analyzed. Patients then were followed for 6 months of continuous positive airway pressure (CPAP) treatment.

RESULTS

At baseline, UACRs were greater in patients with more severe OSA (P = .005, r = .329). All three serum markers of AKI (cystatin C, NGAL, and IL-18) studied were positively correlated with OSA severity, and two (cystatin C and IL-18) were positively correlated with the frequency of oxygen desaturation during sleep. However, none of the AKI markers had positive correlations with UACR. After 6 months of CPAP treatment, UACR and IL-18 were decreased significantly in patients with good adherence.

CONCLUSIONS

Albuminuria and levels of three serum markers of AKI (cystatin C, NGAL, IL-18) were positively correlated with OSA severity, and good adherence with CPAP treatment decreased albuminuria and interleukin-18 levels. These results may provide additional tools for assessing early renal injury in patients with OSA.

Purification and characterization of two cysteine proteinase inhibitors from silkworm, Bombyx mori

Cysteine proteinase inhibitors from silkworm are selective inhibitors with low molecular weight and regulate cathepsin L-like cysteine proteinase activity, thus, affecting silkworm metamorphosis. In a previous study, two cysteine proteinase inhibitors, BCPI and BmCPI, were identified in the silkworm genome. To characterize these inhibitors, we expressed and purified them in an Escherichia coli system and analyzed their structure and inhibitory activity in vitro. Both inhibitors showed strong tolerance to high temperature. Their CD spectra revealed that their secondary structures could be recovered by a gradual decrease in temperature. Compared to BCPI, BmCPI exhibited weak inhibitory activity toward cathepsin L. BCPI activity was significantly decreased when its C-terminus was truncated, whereas BmCPI activity increased considerably when the C-terminus tail of BCPI was attached to BmCPI. Additionally, the inhibitory activity of BCPI was strongly reduced if R31 was mutated to A31. In summary, two cysteine proteinase inhibitors from silkworm were characterized in the present study, which facilitates an understanding of the interaction mechanism between cysteine proteinase and its inhibitors in the silkworm.

Urinary kidney injury molecule-1 in renal disease

Kidney injury molecule-1 (KIM-1), a type l transmembrane glycoprotein, is recognized as a potential biomarker for detection of tubular injury in the main renal diseases. Urinary KIM-1 increases rapidly upon the tubular injury, and its levels are associated with the degree of tubular injury, interstitial fibrosis, and inflammation in the injured kidney. Currently, the investigation of kidney diseases is usually performed through the assessment of serum creatinine and urinary albumin. However, these biomarkers are limited for the early detection of changes in renal function. Besides, the tubular injury appears to precede glomerular damage in the pathophysiology of renal diseases. For these reasons, the search for sensitive, specific and non-invasive biomarkers is of interest. Therefore, the purpose of this article is to review the physiological mechanisms of KIM-1, as well to present clinical evidence about the association between elevated urinary KIM-1 levels and the main renal diseases such as chronic kidney disease, diabetic kidney disease, acute kidney injury, and IgA nephropathy.

Biomarkers in Cardiorenal Syndromes

There is a consensus that cardiorenal syndromes (CRS) are defined as the disorders of heart and kidney where acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in another. Patients with CRS have increased hospitalization and mortality rates, and thus their identification is of great implication. Biomarkers are not only predictive in heart failure or renal diseases, but also useful in identifying cardiac dysfunction in renal diseases and renal injury in heart failure. Thus, they may be applied in order to identify patients with CRS and even assess prognosis and guide therapy in these patients. However, studies on biomarkers have just begun in CRS. Future studies are essential to observe current biomarkers and find novel biomarkers in CRS so as to improve diagnosis, therapy, and prognosis of CRS.

Pyruvate as a novel carrier of hydroxyethyl starch 130/0.4 may protect kidney in rats subjected to severe burns

BACKGROUND

The carrier of hydroxyethyl starch (HES) may play a critical role in kidney injury in fluid resuscitation. This study aimed mainly to compare effects of pyruvate-enriched saline with normal saline (NS) and acetate Ringer's (AR) solution as a carrier in HES130/0.4 on kidney function in rats subjected to severe burns.

METHODS

Using a lethal burn model, 140 rats were randomly allocated in seven groups (n = 20): sham group (group S); no fluid after burn (group N); burn resuscitated with NS (group NS); burn resuscitated with pyruvate saline (group PS); burn resuscitated with AR plus pyruvate-HES (group SP); burn resuscitated with AR plus acetate-HES (group SA), and burn resuscitated with AR plus NS-HES (group SN). A low volume (18.75 mL·kg^-1 during 12 h) of HES130/0.4 was infused with the ratio of 1:1 to crystalloids. Renal surface blood flow, blood creatinine and blood urea nitrogen, early sensitive indicators of kidney function: alpha-1 microglobulin, cystatin-C, and neutrophil gelatinase-associated lipocalin in blood and urine, and kidney tissue water contents were determined. Renal histopathological alterations with Paller scores were also measured at 8 h and 24 h after burn (n = 10), respectively.

RESULTS

The results showed in a comparable manner that group SP was the best in three HES groups and group PS was superior to group NS in renal preservation; group SP appeared significantly beneficial compared with group PS in renal surface blood flow, cystatin-C, neutrophil gelatinase-associated lipocalin, water contents, and Paller scores at 8-h or both time points after burn, respectively (all P < 0.05).

CONCLUSIONS

The carrier of HES130/0.4 played a crucial role in kidney injury in fluid resuscitation of rats subjected to severe burns. Pyruvate-enriched HES130/0.4 was superior and HES130/0.4, per se, might be not renocytotoxic, but renoprotective. Further studies are warranted.

Effect of perinatal risk factors on neutrophil gelatinase-associated lipocalin (NGAL) level in umbilical and peripheral blood in neonates

Introduction

Acute kidney injury biomarkers are opening a new era in diagnosing kidney failure. The requirement for a specific and sensitive marker of kidney function is highly desirable in neonates because the diagnostic possibilities in this age group are not sufficient. Recent research show that neutrophil gelatinase-associated lipocalin (NGAL) can have a great potential but there is a wide range of medical conditions, that may influence their expression.

The aim of the study

was to evaluate the impact of perinatal risk factors on NGAL level in neonates.

Material and methods

NGAL was measured in umbilical cord blood and peripheral blood in full term neonates with perinatal risk factors during the first days of life.

Results

We found significantly higher umbilical cord blood NGAL levels in neonates with perinatal risk factors (117.69 ng/ml) compared to the control group (64.37 ng/ml). No significant difference in peripheral blood NGAL level was shown between the two groups. Umbilical cord blood NGAL level correlated positively with peripheral blood NGAL level (r = 0.36, p < 0.01). Umbilical cord blood NGAL level was significantly higher in neonates with fetal distress and infection compared to neonates with other perinatal risk factors. Peripheral blood NGAL level was significantly higher in neonates with infection compared to neonates with other perinatal risk factors. Significantly higher umbilical cord blood NGAL levels were seen in neonates born by operative delivery compared to born by natural delivery.

Angiotensinogen as a biomarker of acute kidney injury

Early recognition of acute kidney injury (AKI) is critical to prevent its associated complications as well as its progression to long term adverse outcomes like chronic kidney disease. A growing body of evidence from both laboratory and clinical studies suggests that inflammation is a key factor contributing to the progression of AKI regardless of the initiating event. Biomarkers of inflammation are therefore of interest in the evaluation of AKI pathogenesis and prognosis. There is evidence that the renin angiotensin aldosterone system is activated in AKI, which leads to an increase in angiotensin II (Ang II) formation within the kidney. Ang II activates pro-inflammatory and pro-fibrotic pathways that likely contribute to the progression of AKI. Angiotensinogen is the parent polypeptide from which angiotensin peptides are formed and its stability in urine makes it a more convenient marker of renin angiotensin system activity than direct measurement of Ang II in urine specimens, which would provide more direct information. The potential utility of urinary angiotensinogen as a biomarker of AKI is discussed in light of emerging data showing a strong predictive value of AKI progression, particularly in the setting of decompensated heart failure. The prognostic significance of urinary angiotensinogen as an AKI biomarker strongly suggests a role for renin-angiotensin system activation in modulating the severity of AKI and its outcomes.

Biomarkers of acute kidney injury: the pathway from discovery to clinical adoption

Acute kidney injury (AKI) is a common complication of critical illnesses and has a significant impact on outcomes, including mortality and morbidities. Unfortunately, apart from prophylactic measures, no effective treatment for this syndrome is known. Therefore, early recognition of AKI not only can provide better opportunities for preventive interventions, but also opens many gates for research and development of effective therapeutic options. Over the last few years, several new AKI biomarkers have been discovered and validated to improve early detection, differential diagnosis, and differentiation of patients into risk groups for progressive renal failure, need for renal replacement therapy (RRT), or death. These novel AKI biomarkers complement serum creatinine (SCr) and urine output, which are the standard diagnostic tools for AKI detection. In this article, we review the available literature on characteristics of promising AKI biomarkers that are currently the focus of preclinical and clinical investigations. These biomarkers include neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein, interleukin 18 (lL-18), insulin-like growth factor-binding protein 7, tissue inhibitor of metalloproteinase 2 (TIMP-2), calprotectin, urine angiotensinogen (AGT), and urine microRNA. We then describe the clinical performance of these biomarkers for diagnosis and prognostication. We also appraise each AKI biomarker's advantages and limitations as a tool for early AKI recognition and prediction of clinical outcomes after AKI. Finally, we review the current and future states of implementation of biomarkers in the clinical practice.

Identification of a sensitive urinary biomarker, selenium-binding protein 1, for early detection of acute kidney injury

Acute kidney injury (AKI) is associated with increased mortality rate in patients but clinically available biomarkers for disease detection are currently not available. Recently, a new biomarker, selenium-binding protein 1 (SBP1), was identified for detection of nephrotoxicity using proteomic analysis. The aim of this study was to assess the sensitivity of urinary SBP1 levels as an early detection of AKI using animal models such as cisplatin or ischemia/reperfusion (I/R). Sprague-Dawley rats were injected with cisplatin (6 mg/kg, once i.p.) and sacrificed at 1, 3, or 5 days after treatment. Ischemia was achieved by bilaterally occluding both kidneys with a microvascular clamp for 45 min and verified visually by a change in tissue color. After post-reperfusion, urine samples were collected at 9, 24, and 48 hr intervals. Urinary excretion of protein-based biomarkers was measured by Western blot analysis. In cisplatin-treated rats, mild histopathologic alterations were noted at day 1 which became severe at day 3. Blood urea nitrogen (BUN) and serum creatinine (SCr) levels were significantly increased at day 3. Levels of urinary excretion of SBP1, neutrophil gelatinase-associated lipocalin (NGAL), and a tissue inhibitor of metalloproteinase-1 (TIMP-1) were markedly elevated at day 3 and 5 following drug treatment. In the vehicle-treated I/R group, serum levels of BUN and SCr and AST activity were significantly increased compared to sham. Urinary excretion of SBP1 and NGAL rose markedly following I/R. The urinary levels of SBP1, NGAL, TIMP-1, and KIM-1 proteins excreted by AKI patients and normal subjects were compared. Among these proteins, a marked rise in SBP1 was observed in urine of patients with AKI compared to normal subjects. Based upon receiver-operator curves (ROC), SBP1 displayed a higher area under the curve (AUC) scores than levels of SCr, BUN, total protein, and glucose. In particular, SBP1 protein was readily detected in small amounts of urine without purification. Data thus indicate that urinary excretion of SBP1 may be useful as a reliable biomarker for early diagnosis of AKI in patients.

Does remifentanil attenuate renal ischemia-reperfusion injury better than dexmedetomidine in rat kidney?

Background

Ischemia–reperfusion (I/R) injury is a common cause of patient morbidity and mortality in the perioperative period. Patients undergoing long-lasting, abdominal, and urogenital surgeries with risk factors such as advanced age, peripheral artery disease, diabetes mellitus, renovascular disease, and congestive heart failure are candidates for acute kidney injury (AKI) due to impaired renal perfusion and decreased functional renal reserve. Pharmacological agents with multiple functions and anti-oxidative and anti-inflammation properties may be promising preventative strategies for AKI. Recently, dexmedetomidine (dex) has been postulated to have renoprotective effects.

Objectives

We aimed to investigate the protective effects of an intravenous anesthetic remifentanil in renal I/R injury in the rat in comparison with dex.

Materials and methods

A total of 30 Sprague Dawley adult rats were randomly assigned into five groups: the control group (group C, n=6), the sham group (group Sh, n=6, saline-infused rats without I/R injury), the saline group (group S, n=6, saline-infused rats with I/R injury), the remifentanil-treated group (group REM, n=6), and the dexmedetomidine-treated group (group DEX, n=6). The infusions (saline, remifentanil, and dex) were started after anesthesia induction and right nephrectomy and continued until the end of the surgical procedure. In I/R injury groups, the left renal artery and vein were occluded together by a clamp for 30 minutes and reperfusion lasted for 30 minutes. The rats were sacrificed after reperfusion, and the left kidney tissue was harvested. Blood samples were drawn from all animals to evaluate plasma neutrophil gelatinase-associated lipocalin (NGAL) at the beginning, 15 minutes after ischemia, 15 minutes after reperfusion, and 6 hours after the surgical procedure (T0, T1, T2, and T3, respectively).

Results

The plasma NGAL levels exhibited increase at T1, T2, and T3 compared to the levels at T0 in group S (P<0.05). In group REM, there was a significant increase in plasma NGAL levels at T3 in comparison to those at T0, T1, and T2. The plasma NGAL levels at T2 in group S were significantly higher than those at T2 in group DEX (P<0.05). The groups S and REM showed significantly higher plasma NGAL levels at T3 compared to those at T0 (P<0.05). Upon histological examination, there was no difference among the study groups when left kidneys were evaluated (P>0.05).

Conclusion

The NGAL levels and histopathological findings reflected protection by dex against renal I/R injury. However, the same exact results could not be mentioned for remifentanil depending on our study results.

Diallyl disulfide attenuates acetaminophen-induced renal injury in rats

This study investigated the protective effects of diallyl disulfide (DADS) against acetaminophen (AAP)-induced acute renal injury in male rats. We also investigated the effects of DADS on kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), which are novel biomarkers of nephrotoxicity in renal tissues, in response to AAP treatment. The following four experimental groups were evaluated: (1) vehicle control, (2) AAP (1,000 mg/kg), (3) AAP&DADS, and (4) DADS (50 mg/kg/day). AAP treatment caused acute kidney injury evidenced by increased serum blood urea nitrogen (BUN) levels and histopathological alterations. Additionally, Western blot and immunohistochemistry analysis showed increased expression of KIM-1 and NGAL proteins in renal tissues of AAP-treated rats. In contrast, DADS pretreatment significantly attenuated the AAP-induced nephrotoxic effects, including serum BUN level and expression of KIM-1 and NGAL proteins. Histopathological studies confirmed the renoprotective effect of DADS. The results suggest that DADS prevents AAP-induced acute nephrotoxicity, and that KIM-1 and NGAL may be useful biomarkers for the detection and monitoring of acute kidney injury associated with AAP exposure.

The emerging threat of superwarfarins: history, detection, mechanisms, and countermeasures

Superwarfarins were developed following the emergence of warfarin resistance in rodents. Compared to warfarin, superwarfarins have much longer half-lives and stronger affinity to vitamin K epoxide reductase and therefore can cause death in warfarin-resistant rodents. By the mid-1970s, the superwarfarins brodifacoum and difenacoum were the most widely used rodenticides throughout the world. Unfortunately, increased use was accompanied by a rise in accidental poisonings, reaching >16,000 per year in the United States. Risk of exposure has become a concern since large quantities, up to hundreds of kilograms of rodent bait, are applied by aerial dispersion over regions with rodent infestations. Reports of intentional use of superwarfarins in civilian and military scenarios raise the specter of larger incidents or mass casualties. Unlike warfarin overdose, for which 1-2 days of treatment with vitamin K is effective, treatment of superwarfarin poisoning with vitamin K is limited by extremely high cost and can require daily treatment for a year or longer. Furthermore, superwarfarins have actions that are independent of their anticoagulant effects, including both vitamin K-dependent and -independent effects, which are not mitigated by vitamin K therapy. In this review, we summarize superwarfarin development, biology and pathophysiology, their threat as weapons, and possible therapeutic approaches.