Early Tubular Injury Research Articles

Empagliflozin’s role in early tubular protection for type 2 diabetes patients

BackgroundPatients with type 2 diabetes often face early tubular injury, necessitating effective treatment strategies. This study aimed to evaluate the impact of the SGLT2 inhibitor empagliflozin on early tubular injury biomarkers in type 2 diabetes patients with normoalbuminuria.MethodsA randomized controlled clinical study comprising 54 patients selected based on specific criteria was conducted. Patients were divided into an intervention group (empagliflozin, n = 27) and a control group (n = 27) and treated for 6 weeks. Tubular injury biomarkers KIM-1 and NGAL were assessed pre- and post-treatment.ResultsBoth groups demonstrated comparable baseline characteristics. Post-treatment, fasting and postprandial blood glucose levels decreased similarly in both groups. The intervention group exhibited better improvements in total cholesterol, low-density lipoprotein, and blood uric acid levels. Renal function indicators, including UACR and eGFR, showed greater enhancements in the intervention group. Significant reductions in KIM-1 and NGAL were observed in the intervention group.ConclusionTreatment with empagliflozin in type 2 diabetes patients with normoalbuminuria led to a notable decrease in tubular injury biomarkers KIM-1 and NGAL. These findings highlight the potential of SGLT2 inhibitors in early tubular protection, offering a new therapeutic approach.

B-289 Acute Kidney Injury Urinary Biomarker, Neutrophil Gelatinase-Associated Lipocalin (NGAL) Analytical Performance Evaluation on Roche Cobas c502 Chemistry Platform

Abstract Background Acute kidney injury (AKI) is a sudden and serious kidney damage condition that affects more than 1.2 million people every year. KDIGO guidelines suggest serum creatinine increase as a diagnostic marker for AKI but elevation of serum creatinine levels can take up to seven days. Neutrophil gelatinase-associated lipocalin (NGAL) has been identified as an early tubular injury biomarker for AKI that is detected within three hours of AKI patients’ urine. In this study, we evaluated technical performance of BioPorto NGAL assay on Roche cobas c502 chemistry analyzer. Methods BioPorto’s (Hellerup, Denmark) particle enhanced turbidimetry immunoassay (PETIA) NGAL assay was installed on cobas c502 chemistry analyzer (Roche, Indianapolis, U.S.A) following vendor-specific application parameters with few modifications. Linearity was determined with BioPorto’s linearity material and verified by serial dilutions of a high NGAL patient urine sample. Limit of quantitation was determined in urine samples with values 20, 25 and 35 ng/mL, run in duplicate for 10 days. Precisions were determined by running urine samples containing 100 ng/mL and 400 ng/ml NGAL 20 times for within-run precision and twice a day × 10 days for between-run precision, respectively. To determine the accuracy of the NGAL method on cobas 502, 40 sample results (provided by the vendor) were compared with those measured on Siemens Atellica using BioPorto’s NGAL assay. Reference interval verification was carried out in 40 urine samples collected from healthy adult volunteer-donors. Results The linearity was found to be excellent from 0–3000 ng/mL. Limit of quantification was found at 26 ng/mL. Precision results are in the table below. Method comparison showed a slope of 0.90 and intercept of 32.9. The reference interval was verified to be <50 ng/mL (in accordance with current NGAL reference cut­off for AKI diagnosis). Conclusion Performance of BioPorto’s NGAL PETIA assay was validated in urine on cobas c502 chemistry analyzer.

The effect of standard percutaneous nephrolithotomy, miniaturized percutaneous nephrolithotomy and retrograde intrarenal surgery on biomarkers of renal injury: a randomized clinical trial.

Observational studies on the association of endourological procedures with renal parenchymal damage are lacking. This randomized trial examined the effect of standard percutaneous nephrolithotomy (sPCNL) in comparison with miniaturized-PCNL (mini-PCNL) and retrograde intrarenal surgery (RIRS) for nephrolithiasis treatment on novel biomarkers of renal injury. Seventy-five patients were randomized in a 1:1:1 ratio to receive sPCNL, mini-PCNL and RIRS for nephrolithiasis. The ratios of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1) and interleukin-18 (IL-18) normalized for urinary creatinine (Cr) were calculated from urine samples collected at baseline (2-h preoperatively) and at 2-, 6-, 24- and 48-h postoperatively. Two-way mixed analysis of variance (ANOVA) for repeated measurements was used to evaluate the effects of type of procedure and time on studied biomarkers. Between baseline and 2-h postoperatively, no significant differences were observed in NGAL/Cr changes between sPCNL [median (interquartile range) 9.46 (4.82-14.9)], mini-PCNL [12.78 (1.69-25.24)] and RIRS [6.42 (2.61-23.90)] (P=.902). Similarly, no between-group differences were observed for KIM-1/Cr (P=.853) and IL-18 (P=.980) at 2 h, and all biomarkers at any time-point postoperatively. Within-groups, significant increases from baseline were noted for NGAL/Cr (sPCNL, P<.001; mini-PCNL, P<.001; RIRS, P=.001), KIM-1/Cr and IL-18/Cr at 2 h; progressively lower increases from baseline were noted in all groups for KIM-1/Cr and IL-18/Cr at 6-, 24- and 48-h postoperatively. As such, a significant effect of time but not of type of procedure was evidenced with two-way mixed ANOVA. No significant between-group differences were observed in acute kidney injury incidence and complications. The endourological procedures under study are associated with similar patterns of early tubular injury, detected by novel biomarkers, which is largely reduced within 48h and no changes in glomerular function.

Inhaled silica nanoparticles cause chronic kidney disease in rats.

Silica nanoparticles (SiNPs) released during the burning of sugarcane have been postulated to have a role in chronic kidney disease of unknown etiology. We tested the hypothesis that pristine SiNPs of the size present in sugarcane might cause chronic kidney injury when administered through the lung in rats. We administered 200- or 300-nm amorphous SiNPs twice weekly (4 mg/dose), or vehicle by oropharyngeal aspiration for 13 wk to rats followed by euthanasia after an additional 13 wk (26 wk total). Tissues were evaluated for the presence of SiNPs and evidence of histological injury. Both sizes of SiNPs caused kidney damage, with early tubular injury and inflammation (at week 13) that continued to inflammation and chronic fibrosis at week 26 despite discontinuation of the SiNP administration. Both sizes of SiNPs caused local inflammation in the lung and kidney and were detected in the serum and urine at week 13, and the 200-nm particles were also localized to the kidney with no evidence of retention of the 300-nm particles. At week 26, there was some clearance of the 200-nm silica from the kidneys, and urinary levels of SiNPs were reduced but still significant in both 200- and 300 nm-exposed rats. In conclusion, inhaled SiNPs cause chronic kidney injury that progresses despite stopping the SiNP administration. These findings support the hypothesis that human exposure to amorphous silica nanoparticles found in burned sugarcane fields could have a participatory role in chronic kidney disease of unknown etiology.NEW & NOTEWORTHY Inhalation of silica nanoparticles (SiNPs) released during the burning of sugarcane has been postulated to have a role in chronic kidney disease of unknown etiology (CKDu). We administered 200- and 300-nm amorphous SiNPs to rats by aspiration and observed kidney damage with tubular injury and inflammation that persisted even after stopping the SiNP exposure. These findings support the hypothesis that human exposure to SiNPs found in sugarcane ash could have a participatory role CKDu.

MO1019: Sigma-1 Receptor Agonists are Protective in a Rat Model of Kidney Transplantation

Abstract BACKGROUND AND AIMS End-stage renal disease affects nearly 2 million people worldwide. The disease is associated with an irreversible deterioration in renal function and can only be treated by dialysis or kidney transplantation (KTx). KTx is associated with better long-term outcomes and quality of life compared with dialysis, but the shortage of donor organs is a serious and unsolved problem. Graft survival is highly dependent on the extent of cold and warm ischemic injury during Tx. We recently described the renoprotective effects of Sigma-1 receptor (S1R) agonist treatment in IRI. Thus, our aim was to develop a novel preservation solution that, with the addition of S1R agonist compounds, minimizes ischemic damage in order to improve the condition of grafts and so increase the number of organs suitable for Tx. METHOD Kidneys of male Wistar rats were perfused and placed in ice cold (i) custodiol preservation solution; custodiol containing S1R agonists, (ii) fluvoxamine or (iii) SA-4503 for 2 h, then autotransplanted and sacrificed 24 h after reperfusion. Sham-operated rats served as controls. In a second experiment, kidneys of wild-type and S1R knockout mice were perfused and placed in an ice-cold preservation solution containing an original, selective S1R agonist compound (VCC) for 24 h of cold ischemia and tissue samples were collected. Renal function parameters were determined. Renal expression of tubular injury markers (Kim-1, Ngal) and inflammatory cytokines (Il-1α, Il-6, Tnf-α, Mcp-1) were measured. Periodic acid-Schiff staining was performed on kidney tissue sections to evaluate structural changes. CD45 immunostaining was performed on kidney sections to determine the extent of leukocyte infiltration. DNA fragmentation resulted by apoptotic events in the kidney was evaluated by TUNEL-assay. RESULTS S1R agonists mitigated renal functional impairment and tubular dilatation following Tx. Expression of early and sensitive tubular injury markers was markedly less elevated in S1R agonist-treated kidneys. S1R agonists alleviated renal apoptosis as shown on TUNEL-stained kidney sections. Decreased numbers of CD45 + leukocytes and decreased inflammatory cytokine expressions confirmed the anti-inflammatory effect of S1R agonists. The S1R agonist VCC compound mitigated cold ischemic structural kidney damage in wild-type but not in S1R KO mice, which confirms the protective role of the receptor. CONCLUSION The addition of S1R agonists to the preservation solution during Tx improves graft function and alleviates structural damage, thus improving long-term outcomes. S1R agonists reduce graft injury during cold storage, therefore the number of transplantable donor organs can be increased. FUNDING OTKA PD-131 637; FK-124 491; 2020–4.1.1.-TKP2020-6 183 069 269; 2020–4.1.1.-TKP2020-6 183 169 273; KDP-2020/1 019 145.

Sensitivity to Iron‐Mediated Pro‐Inflammatory Signaling in NZBWF1 Mice, a Model of Systemic Lupus Erythematosus

IntroductionThe autoimmune disease systemic lupus erythematosus predominantly affects women and can lead to lupus nephritis (LN) as a common and severe complication in approximately 50% of patients. The F1 hybrid of New Zealand Black (NZB) X New Zealand White (NZW) mice (NZBWF1) is a well‐established mouse model to study LN. Our previous data indicated that the onset of albuminuria in female 34‐week NZBWF1 mice was associated with renal iron accumulation, and iron may contribute to renal injury. This study tests the hypothesis that 34‐week NZBWF1 lupus mice are sensitized to iron's injurious and pro‐inflammatory effects compared to 8‐week normal NZBWF1 mice. As a means to differentiate effects of age as opposed to development of lupus, parallel experiments were performed in 8 and 34‐week‐old NZW mice as healthy controls.Methods and ResultsFemale 8‐week (pre‐autoimmune) and 34‐week NZBWF1 (autoimmune, pre‐albuminuric) mice together with age‐matched healthy control NZW mice underwent 24 h urine collection to confirm non‐albuminuric status. Mice were then were injected i.v. with a single dose of iron‐sucrose (2 mg elemental iron) or vehicle (saline) and sacrificed 24 h later. Plasma blood urea nitrogen (BUN) was measured to determine renal health, SRY‐Box Transcription Factor 9 (SOX‐9)‐ positive cells were quantified in kidney sections as an early tubular injury marker, and plasma monocyte chemoattractant protein‐1 (MCP‐1) was measured by ELISA as an inflammatory marker. Lupus (NZBWF1) and control mice (NZW) were compared within strains by age (8‐week vs. 34‐week) and treatment (Vehicle vs. Treatment). All statistical analyses were done by 2‐way ANOVA (n=7‐12/group), and post‐hoc testing was done using Bonferroni. Iron‐sucrose treatment significantly increased plasma MCP‐1 concentrations in the NZBWF1 and the control NZW mice (PTreatment &lt; 0.01). There was no significant effect of age on this effect for NZW mice (PTreatment*Age = 0.2); however, in NZBWF1 mice, the iron‐sucrose induced increase in MCP‐1 was significantly greater in 34‐week compared to 8‐week mice (PTreatment*Age &lt; 0.05; P&lt;0.05 by posthoc test). BUN was significantly increased with age in both strains (PAge&lt;0.05), but there was no significant effect of iron‐sucrose (PTreatment&gt;0.05). The numbers of SOX‐9+ tubular cells increased in the 34‐week NZBWF1 mice compared to 8‐week mice (Page&lt;0.05), consistent with early stages of renal injury, but iron sucrose treatment did not show any significant effect (PTreatment= 0.9).ConclusionOur data suggest that at the autoimmune but pre‐albuminuric stage, 34‐week NZBWF1 mice show increased pro‐inflammatory responsiveness to iron‐mediated stress. Further studies to determine whether the enhanced pro‐inflammatory effects of iron contribute to pathology in lupus nephritis are ongoing.

Lipopolysaccharide Pretreatment Prevents Medullary Vascular Congestion following Renal Ischemia by Limiting Early Reperfusion of the Medullary Circulation.

Vascular congestion of the renal medulla-trapped red blood cells in the medullary microvasculature-is a hallmark finding at autopsy in patients with ischemic acute tubular necrosis. Despite this, the pathogenesis of vascular congestion is not well defined. In this study, to investigate the pathogenesis of vascular congestion and its role in promoting renal injury, we assessed renal vascular congestion and tubular injury after ischemia reperfusion in rats pretreated with low-dose LPS or saline (control). We used laser Doppler flowmetry to determine whether pretreatment with low-dose LPS prevented vascular congestion by altering renal hemodynamics during reperfusion. We found that vascular congestion originated during the ischemic period in the renal venous circulation. In control animals, the return of blood flow was followed by the development of congestion in the capillary plexus of the outer medulla and severe tubular injury early in reperfusion. Laser Doppler flowmetry indicated that blood flow returned rapidly to the medulla, several minutes before recovery of full cortical perfusion. In contrast, LPS pretreatment prevented both the formation of medullary congestion and its associated tubular injury. Laser Doppler flowmetry in LPS-pretreated rats suggested that limiting early reperfusion of the medulla facilitated this protective effect, because it allowed cortical perfusion to recover and clear congestion from the large cortical veins, which also drain the medulla. Blockage of the renal venous vessels and a mismatch in the timing of cortical and medullary reperfusion results in congestion of the outer medulla's capillary plexus and promotes early tubular injury after renal ischemia. These findings indicate that hemodynamics during reperfusion contribute to the renal medulla's susceptibility to ischemic injury.

NLRP3 inflammasome in rosmarinic acid-afforded attenuation of acute kidney injury in mice

Cisplatin (CP) is a well-known anticancer drug used to effectively treat various kinds of solid tumors. CP causes acute kidney injury (AKI) and unfortunately, there is no therapeutic approach in hand to prevent AKI. Several signaling pathways are responsible for inducing AKI which leads to inflammation in proximal convoluted tubule cells in the kidney. Furthermore, the nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome is involved in the CP-induced AKI. In this study, we investigated therapeutic effects of rosmarinic acid (RA) against inflammation-induced AKI. RA was orally administered at the dose of 100 mg/kg for two consecutive days after 24 h of a single injection of CP at the dose of 20 mg/kg administered intraperitoneally in Swiss albino male mice. Treatment of RA inhibited the activation of NLRP3 signaling pathway by blocking the activated caspase-1 and downstream signal molecules such as IL-1β and IL18. CP activated HMGB1-TLR4/MyD88 axis was also found to be downregulated with the RA treatment. Activation of nuclear factor-κB and elevated protein expression of cyclooxygenase-2 (COX-2) were also found to be downregulated in RA-treated animals. Alteration of early tubular injury biomarker, kidney injury molecule-1 (KIM-1), was found to be subsided in RA-treated mice. RA has been earlier reported for antioxidant and anti-inflammatory properties. Our findings show that blocking a critical step of inflammasome signaling pathway by RA treatment can be a novel and beneficial approach to prevent the CP-induced AKI.

Microalbuminuria and Urinary Neutrophil Gelatinase-associated Lipocalin (uNGAL) in Human Immunodeficiency Virus Infected Children.

Introduction:Renal dysfunction and progression to end stage renal disease is well known in human immunodeficiency virus (HIV) infection. We studied the role of microalbuminuria and urinary NGAL levels in children with HIV infection for the prediction of renal dysfunction.Design and Methods:A cross-sectional study was carried out and 60 HIV infected children, aged (18 months to 15 years) were screened for microalbuminuria by nephelometry and for uNGAL by ELISA. Thirty healthy children were screened for uNGAL for normative data in Indian children.Results:The prevalence of microalbuminuria in studied population was 3.3%. The mean uNGAL and uNGAL/creatinine in study population was higher than controls (26.94 ± 93.12 ng/ml vs. 88.94 ± 345.20 mcg/g, and 15.53 ± 37.52 ng/ml vs. 30.12 ± 78.66 ng/ml; P = 0.003, P = 0.002). Children with lower CD4 counts had significant higher mean Albumin Creatinine Ratio (ACR) and mean uNGAL; P = 0.03, P = 0.01.Conclusions:uNGAL and urine microalbumin are useful biomarkers of early tubular and glomerular injury in children with HIV infection.

Non-Albumin Proteinuria (NAP) as a Complementary Marker for Diabetic Kidney Disease (DKD).

Diabetic kidney disease (DKD) is one of the most common forms of chronic kidney disease. Its pathogenic mechanism is complex, and it can affect entire structures of the kidney. However, conventional approaches to early stage DKD have focused on changes to the glomerulus. Current standard screening tools for DKD, albuminuria, and estimated glomerular filtration rate are insufficient to reflect early tubular injury. Therefore, many tubular biomarkers have been suggested. Non-albumin proteinuria (NAP) contains a wide range of tubular biomarkers and is convenient to measure. We reviewed the clinical meanings of NAP and its significance as a marker for early stage DKD.

Blocking Connexin-43 mediated hemichannel activity protects against early tubular injury in experimental chronic kidney disease

BackgroundTubulointerstitial fibrosis represents the key underlying pathology of Chronic Kidney Disease (CKD), yet treatment options remain limited. In this study, we investigated the role of connexin43 (Cx43) hemichannel-mediated adenosine triphosphate (ATP) release in purinergic-mediated disassembly of adherens and tight junction complexes in early tubular injury.MethodsHuman primary proximal tubule epithelial cells (hPTECs) and clonal tubular epithelial cells (HK2) were treated with Transforming Growth Factor Beta1 (TGF-β1) ± apyrase, or ATPγS for 48 h. For inhibitor studies, cells were co-incubated with Cx43 mimetic Peptide 5, or purinergic receptor antagonists Suramin, A438079 or A804598. Immunoblotting, single-cell force spectroscopy and trans-epithelial electrical resistance assessed protein expression, cell-cell adhesion and paracellular permeability. Carboxyfluorescein uptake and biosensing measured hemichannel activity and real-time ATP release, whilst a heterozygous Cx43+/− mouse model with unilateral ureteral obstruction (UUO) assessed the role of Cx43 in vivo.ResultsImmunohistochemistry of biopsy material from patients with diabetic nephropathy confirmed increased expression of purinergic receptor P2X7. TGF-β1 increased Cx43 mediated hemichannel activity and ATP release in hPTECs and HK2 cells. The cytokine reduced maximum unbinding forces and reduced cell-cell adhesion, which translated to increased paracellular permeability. Changes were reversed when cells were co-incubated with either Peptide 5 or P2-purinoceptor inhibitors. Cx43+/− mice did not exhibit protein changes associated with early tubular injury in a UUO model of fibrosis.ConclusionData suggest that Cx43 mediated ATP release represents an initial trigger in early tubular injury via its actions on the adherens and tight junction complex. Since Cx43 is highly expressed in nephropathy, it represents a novel target for intervention of tubulointerstitial fibrosis in CKD.-4b_UPmq1WosguM_gnU3qmVideo Graphical abstractIn proximal tubular epithelial cells (PTECs), tight junction proteins, including zona occuludens-1 (ZO-1), contribute to epithelial integrity, whilst the adherens junction protein epithelial (E)-cadherin (ECAD) maintains cell-cell coupling, facilitating connexin 43 (Cx43) gap junction-mediated intercellular communication (GJIC) and the direct transfer of small molecules and ions between cells. In disease, such as diabetic nephropathy, the pro-fibrotic cytokine transforming growth factor beta1 (TGF-β1) binds to its receptor and recruits SMAD2/3 signalling ahead of changes in gene transcription and up-regulation of Cx43-mediated hemichannels (HC). Uncoupled hemichannels permit the release of adenosine triphosphate (ATP) in to the extracellular space (↑[ATP]e), where ATP binds to the P2X7 purinoreceptor and activates the nucleotide-binding domain and leucine-rich repeat containing (NLR) protein-3 (NLRP3) inflammasome. Inflammation results in epithelial-to-mesenchymal transition (EMT), fibrosis and tubular injury. A major consequence is further loss of ECAD and reduced stickiness between cells, which can be functionally measured as a decrease in the maximum unbinding force needed to uncouple two adherent cells (Fmax). Loss of ECAD feeds forward to further lessen cell-cell coupling exacerbating the switch from GJIC to HC-mediated release of ATP. Reduction in ZO-1 impedes tight junction effectiveness and decreases trans-epithelial resistance (↓TER), resulting in increased paracellular permeability.

Examining Cell-Cell Interactions in the Kidney Using AFM Single-Cell Force Spectroscopy.

The ability of individual cells to synchronize activity is a basic feature of efficient and appropriate tissue function. Central to this is the physicochemical binding between cells through multiprotein complexes that functionally mediate adhesion. Importantly, the direct connection of physical properties and intercellular signaling is of great importance to certain pathologies including diabetes. Atomic force microscopy (AFM) single-cell force spectroscopy (SCFS) is a high-resolution technique that provides a statistically reliable measurement of the minute forces involved in cell tethering and membrane dynamics. Detection of altered nanoscale forces underlying the loss of adhesion in early tubular injury is pivotal for the development of novel therapeutic strategies for diabetic nephropathy. Here we describe the step-by-step use of an integrated AFM-SCFS system designed to measure functional force-displacement in separating renal tubular epithelial cells. Parameters such as unbinding forces, detachment energy, and distance to complete separation can be obtained from force-displacement (F-d) curves and are critical in assessing how physical changes of cellular adhesion contribute to cell contact, coupling, and communication in the diabetic kidney.

Baseline tubular biomarkers in young adults with congenital heart disease as compared to healthy young adults: Detecting subclinical kidney injury.

There are significant implications for kidney disease in young adults with congenital heart disease. Prior investigations have not focused on the use of urinary tubular biomarkers for the early identification of kidney disease in this growing patient group. Determine if young adults with congenital heart disease have differences in the baseline concentration of urinary tubular biomarkers when compared to healthy young adults. In a pilot case control study, 30 patients from 18 to 35 years of age with congenital heart disease and a normal serum creatinine were recruited during a routine follow-up visit. In the same age group, 30 control subjects without history of heart or kidney disease were recruited. Urine samples were obtained to measure beta 2-microglobin, alpha 1-microglobin, N-acetyl-B-D-glucosaminidase, liver fatty acid binding protein, kidney injury molecule-1, insulin-like growth factor binding protein 7, and tissue inhibitor of metalloproteinases-2. Comparisons were done using Wilcoxon rank-sum or Fisher's exact test. No study participants had proteinuria on urine dipstick. Median concentrations of kidney injury molecule-1 were higher (P=.01) and concentrations of insulin-like growth factor binding protein 7 (P=.001) and tissue inhibitor of metalloproteinases-2 (P=.009) were lower in the subjects with congenital heart disease when compared to the control subjects. There were no significant differences between the groups with respect to the other biomarkers. Our data suggest that young adults with congenital heart disease may have subclinical kidney dysfunction. Lower levels of insulin-like growth factor binding protein 7 and tissue inhibitor of metalloproteinases-2 may indicate an impaired ability to respond to injury, while higher levels of kidney injury molecule-1 may reflect early tubular injury.

Hyperfiltration predicts long-term renal outcomes in humanized sickle cell mice

AbstractWe previously reported that humanized sickle cell (HbSS) mice develop spontaneous nephropathy, a major cause of morbidity and mortality in sickle cell disease (SCD). Because sex-dependent protective mechanisms in SCD have been reported, we examined the course of nephropathy in male and female HbSS mice to determine contributors and/or predictors of disease severity. In male HbSS mice, glomerular filtration rate was characterized by a rapid onset of hyperfiltration and subsequent progressive decline of renal function over 20 weeks. Early tubular injury presented with increased excretion of kidney injury marker 1 (KIM-1), progressive loss of tubular brush border, and interstitial fibrosis that preceded the onset of glomerular damage, suggesting a tubuloglomerular mechanism of kidney injury in these mice. Additionally, we observed a strong association between the magnitude of hyperfiltration and the degree of long-term kidney injury in male HbSS mice. Unlike males, female HbSS mice did not demonstrate a significant loss of renal function or severe kidney damage during the time course of the study. These results suggest that magnitude of hyperfiltration predicts the onset of chronic kidney damage in male HbSS mice, whereas protective mechanisms in female HbSS mice delay the onset of SCD nephropathy.

Effect of intraoperative dexmedetomidine on renal function after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy: a randomized, placebo-controlled trial

Introduction: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) predispose to postoperative renal dysfunction. Dexmedetomidine is an α2 adrenoreceptor agonist, which has renoprotective effects after cardiac surgery.Objective: To assess the effect of dexmedetomidine on renal function after CRS and HIPEC.Materials: Thirty-eight patients undergoing CRS and HIPEC were randomized to receive dexmedetomidine (dexmedetomidine group, n = 19, loading 1 μg/kg over 20 min followed by infusion at 0.5 μg/kg/h) or 0.9% sodium chloride (control group, n = 19) during surgery. Creatinine clearance (CrCl) was assessed daily until postoperative day 7. Urine neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule (KIM)-1 were measured for 24 h after surgery.Results: There was no difference in the lowest CrCl value during the first 7 days postoperatively, but the % change from baseline to the lowest value was lower in the dexmedetomidine group than in the control group (p = .037). Urine NGAL and KIM-1 levels were increased over time in both groups, but the increases were significantly less in the dexmedetomidine group (p = .018 and 0.038, respectively). In the dexmedetomidine group, the length of intensive care unit stay was shorter (p = .034).Conclusions: Intraoperative dexmedetomidine infusion did not improve renal function in terms of serum Cr-related indices following CRS and HIPEC. However, as the decrease in CrCl was attenuated and early tubular-injury markers were lower in the dexmedetomidine group, dexmedetomidine may have protective effects against early tubular injury in CRS and HIPEC.Clinical Trials Registry: http://clinicaltrials.gov (NCT02641938).

Wnt4 is significantly upregulated during the early phases of cisplatin-induced acute kidney injury

Wnt4 is a secreted growth factor associated with renal tubulogenesis. Our previous studies identified that renal and urinary Wnt4 are upregulated following ischemia-reperfusion injury in mice, but the roles of Wnt4 in other forms of acute kidney injury (AKI) remain unclear. Here, we investigated the changes in Wnt4 expression using a cisplatin-induced AKI model. We found that renal and urinary Wnt4 expression increased as early as 12 hours, peaked at day 4 following cisplatin-induced AKI and was closely correlated with histopathological alterations. By contrast, the serum creatinine level was significantly elevated until day 3, indicating that Wnt4 is more sensitive to early tubular injury than serum creatinine. In addition, renal Wnt4 was co-stained with aquaporin-1 and thiazide-sensitive NaCl cotransporter, suggesting that Wnt4 can detect both proximal and distal tubular injuries. These data were further confirmed in a clinical study. Increased urinary Wnt4 expression was detected earlier than serum creatinine and eGFR in patients with contrast-induced AKI after vascular intervention. This study is the first to demonstrate that increased expression of renal and urinary Wnt4 can be detected earlier than serum creatinine after drug-induced AKI. In particular, urinary Wnt4 can potentially serve as a noninvasive biomarker for monitoring patients with tubular injury.

Endogenous IL-33 Contributes to Kidney Ischemia-Reperfusion Injury as an Alarmin.

Inflammation is a prominent feature of ischemia-reperfusion injury (IRI), which is characterized by leukocyte infiltration and renal tubular injury. However, signals that initiate these events remain poorly understood. We examined the role of the nuclear alarmin IL-33 in tissue injury and innate immune response triggered by experimental kidney ischemia-reperfusion. In wild-type mice, we found that IL-33 was constitutively expressed throughout the kidney in peritubular and periglomerular spaces, mainly by microvascular endothelial cells, from which it was released immediately during IRI. Compared with wild-type mice, mice lacking IL-33 (IL-33Gt/Gt) exhibited reductions in early tubular cell injury and subsequent renal infiltration of IFN-γ/IL-17A-producing neutrophils, with preservation of renal functions. This protection associated with decreased renal recruitment of myeloid dendritic cells, natural killer (NK) cells, and invariant natural killer T (iNKT) cells, the latter of which were reported as deleterious in IRI. Increases in the level of circulating IL-12, a key IL-33 cofactor, and the expression of ST2, an IL-33-specific receptor, on the surface of iNKT cells preceded the IL-33- and iNKT cell-dependent phase of neutrophil infiltration. Furthermore, IL-33 directly targeted iNKT cells in vitro, inducing IFN-γ and IL-17A production. We propose that endogenous IL-33 is released as an alarmin and contributes to kidney IRI by promoting iNKT cell recruitment and cytokine production, resulting in neutrophil infiltration and activation at the injury site. Our findings show a novel molecular mediator contributing to innate immune cell recruitment induced by renal ischemia-reperfusion and may provide therapeutic insights into AKI associated with renal transplantation.

Urinary Netrin-1: A New Biomarker for the Early Diagnosis of Renal Damage in Obese Children.

Objective:Urinary netrin-1 is a new marker to demonstrate early tubular damage. The aim of this study was to determine whether urinary netrin-1 is increased in obese children.Methods:A total of 68 normoalbuminuric and normotensive obese patients and 65 controls were included in the study. Urine samples were collected for assessment of urinary phosphorus, sodium, potassium, creatinine, albumin, and netrin-1. Blood samples were collected for measurements of fasting glucose, insulin, lipid, phosphorus, sodium, potassium, and creatinine levels. Homeostatic model assessment insulin resistance index was calculated.Results:Gender and age were similar between obese and control groups (12.01±3.03 vs. 11.7±3.2 years, p=0.568 and 33 vs. 35 girls, p=0.543, respectively). Obese patients had significantly higher netrin-1 excretion than the controls (841.68±673.17 vs. 228.94±137.25 pg/mg creatinine, p=0.000). Urinary netrin-1 level was significantly higher in obese subjects with insulin resistance compared to those without insulin resistance (1142±1181 vs. 604.9±589.91 pg/mg creatinine, p=0.001).Conclusion:In normotensive and normoalbuminuric obese children, urinary netrin-1 level can increase before onset of albuminuria. Urinary netrin-1 excretion appears to be affected predominantly by insulin resistance and hyperinsulinemia. Urinary netrin-1 may be a new biomarker for determining early tubular injury in obese children.

Urine Liver-Type Fatty Acid-Binding Protein Predicts Graft Outcome up to 2 Years After Kidney Transplantation

BackgroundSeveral new biomarkers for the detection of early tubular injury have been investigated in kidney transplant recipients. We recently identified day 2 urinary neutrophil gelatinase-associated lipocalin (NGAL) as a predictor of slow graft function and adverse 1-year outcome. In the present study, we further investigated the value of urinary NGAL and liver-type fatty acid binding protein (L-FABP) for predicting long-term graft outcomes up to 2 years. MethodsThis study was a single-center, prospective observational study. Serial urinary NGAL and L-FABP levels at 0 hours, 2 days, and 6 days after kidney transplantation (KT) were measured, and the clinical data were assessed during the 2-year period after KT. ResultsDuring the 2-year follow-up period, 13 (18.8%), 5 (7.2%), and 4 (5.8%) patients were diagnosed with acute T-cell–mediated rejection, acute antibody-mediated rejection (AMR) and chronic AMR, respectively. In addition, 10 patients (14.3%) developed calcineurin inhibitor toxicity and 6 (8.7%) developed BK viremia. The mean estimated glomerular filtration rates (eGFR) at 1 and 2 years after KT were 65.1 ± 19.1 and 58.5 ± 22.6 mL/min/1.73 m2, respectively, When poor long-term graft function was defined as eGFR of less than 50 mL/min/1.73 m2 at 2 years, elderly donors, acute rejection, and high 0-hour urinary L-FABP levels were significant risk factors. Furthermore, in rejection-free patients, L-FABP was strongly associated with poor long-term graft function (P = .006). Multivariate logistic regression analysis showed that high 0-hour L-FABP (P = .015) and acute rejection (P = .006) were independent factors predicting poor long-term graft function. Receiver operating characteristic analysis showed that the area under the curve for urinary L-FABP was 0.692 (P = .036). ConclusionsOur results suggest that urinary L-FABP may be a useful predictor of adverse long-term outcomes in KT patients.

Nlrp3 Prevents Early Renal Interstitial Edema and Vascular Permeability in Unilateral Ureteral Obstruction

Progressive renal disease is characterized by tubulo-interstitial injury with ongoing inflammation and fibrosis. The Nlrp3 inflammasome contributes to these pathophysiological processes through its canonical effects in cytokine maturation. Nlrp3 may additionally exert inflammasome-independent effects following tissue injury. Hence, in this study we investigated potential non-canonical effects of Nlrp3 following progressive renal injury by subjecting WT and Nlrp3-deficient (−/−) mice to unilateral ureter obstruction (UUO).Our results revealed a progressive increase of renal Nlrp3 mRNA in WT mice following UUO. The absence of Nlrp3 resulted in enhanced tubular injury and dilatation and an elevated expression of injury biomarker NGAL after UUO. Moreover, interstitial edema was significantly elevated in Nlrp3−/− mice. This could be explained by increased intratubular pressure and an enhanced tubular and vascular permeability. In accordance, renal vascular leakage was elevated in Nlrp3−/− mice that associated with reduced mRNA expression of intercellular junction components. The decreased epithelial barrier function in Nlrp3−/− mice was not associated with increased apoptosis and/or proliferation of renal epithelial cells. Nlrp3 deficiency did not affect renal fibrosis or inflammation.Together, our data reveal a novel non-canonical effect of Nlrp3 in preserving renal integrity and protection against early tubular injury and interstitial edema following progressive renal injury.