Tubule dysfunction and injury and future risk of sepsis-associated acute kidney injury.

BACKGROUND: Novel biomarkers can quantify both kidney tubule function, including proximal tubule reabsorptive (urine α-1 microglobulin (uα1m)) and tubule protein synthesis capacities (urine uromodulin (uUMOD)), and tubular injury (urine neutrophil gelatinase-associated lipocalin (uNGAL)). In a blood pressure trial, we reported that lower reabsorptive and synthetic protein capacity at times of health predicted future risk of acute kidney injury (AKI), but most AKI was related to hemodynamic causes in this trial. Associations between tubular function and injury and future AKI related to other causes is unknown. MATERIALS AND METHODS: We performed a case-control study in REGARDS, a population-based cohort study, among participants who provided urine at the baseline visit. We matched each septic AKI case by age, sex, race, and time from baseline to hospital admission 1 : 1 to a participant with sepsis who did not develop AKI (controls). Using conditional logistic regression, we evaluated the associations of uα1m, uUMOD, urine ammonium, and uNGAL with septic AKI. RESULTS: Mean age was 69 ± 8 years, 44% were female, and 39% were Black participants. Median baseline eGFR among cases and controls was 73 (55, 90) and 82 (65, 92) mL/min/1.73m2, and median albuminuria was 19 (8, 87) vs. 9 (5, 22) mg/g, respectively. No independent associations were observed between the tubule function or injury markers and subsequent risk of septic AKI once models were adjusted for baseline albuminuria, estimated glomerular filtration rate, and other risk factors. CONCLUSION: Among community participants, tubule function and injury markers at times of health were not independently associated with future risk of septic AKI.

The Relationship of Kidney Tubule Biomarkers with Brain Imaging in CKD Patients in SPRINT.

Urine biomarker concentrations reflecting kidney tubule injury and dysfunction were not associated with brain MRI measures.Higher eGFR was associated with lower total brain cerebral blood flow.This is the first evaluation of the relationship of kidney tubule biomarkers with brain imaging by MRI in patients with CKD.

Long Non-Coding RNA Small Nucleolar RNA Host Gene 5 (SNHG5) Regulates Renal Tubular Damage in Diabetic Nephropathy via Targeting MiR-26a-5p.

The study explored the diagnostic value of SNHG5 in diabetic nephropathy (DN) and investigated the role and mechanism on DN via establishing the in vitro HK2 cell model. This study recruited 62 types 2 diabetes mellitus (T2DM) patients, 58 DN patients and 60 healthy controls (HC). The expressions of serum SNHG5 and miR-26a-5p were measured by RT-qPCR analysis. The diagnostic value of SNHG5 in DN was assessed by ROC curve. The in vitro cell model was built to estimate the effects of SNHG5 on cell viability, cell apoptosis, inflammation response and oxidative stress. Serum SNHG5 was increased in DN patients (relative expression: 2.04±0.34) and had the diagnostic value in DN. After HK2 cells were treated with high glucose, the cell viability decreased and apoptosis increased, and the production of inflammatory cytokines and ROS enhanced significantly. It was noticed that inhibition of SNHG5 could reverse the above phenomenon caused by high glucose. Besides, serum miR-26a-5p was diminished in DN patients, and luciferase reporter gene revealed that miR-26a-5p is direct target of SNHG5. These results indicated that inhibition of SNHG5 may mitigate HG-induced renal tubular damage via targeting miR-26a-5p, which providing a new insight into the mechanism of renal tubule damage in DN patients.

Urine Biomarkers of Kidney Tubule Health, Injury, and Inflammation are Associated with Progression of CKD in Children.

BACKGROUND: Novel urine biomarkers may improve identification of children at greater risk of rapid kidney function decline, and elucidate the pathophysiology of CKD progression. METHODS: We investigated the relationship between urine biomarkers of kidney tubular health (EGF and α-1 microglobulin), tubular injury (kidney injury molecule-1; KIM-1), and inflammation (monocyte chemoattractant protein-1 [MCP-1] and YKL-40) and CKD progression. The prospective CKD in Children Study enrolled children aged 6 months to 16 years with an eGFR of 30-90ml/min per 1.73m2. Urine biomarkers were assayed a median of 5 months [IQR: 4-7] after study enrollment. We indexed the biomarker to urine creatinine by dividing the urine biomarker concentration by the urine creatinine concentration to account for the concentration of the urine. The primary outcome was CKD progression (a composite of a 50% decline in eGFR or kidney failure) during the follow-up period. RESULTS: Overall, 252 of 665 children (38%) reached the composite outcome over a median follow-up of 6.5 years. After adjustment for covariates, children with urine EGF concentrations in the lowest quartile were at a seven-fold higher risk of CKD progression versus those with concentrations in the highest quartile (fully adjusted hazard ratio [aHR], 7.1; 95% confidence interval [95% CI], 3.9 to 20.0). Children with urine KIM-1, MCP-1, and α-1 microglobulin concentrations in the highest quartile were also at significantly higher risk of CKD progression versus those with biomarker concentrations in the lowest quartile. Addition of the five biomarkers to a clinical model increased the discrimination and reclassification for CKD progression. CONCLUSIONS: After multivariable adjustment, a lower urine EGF concentration and higher urine KIM-1, MCP-1, and α-1 microglobulin concentrations were each associated with CKD progression in children.

CPT1α maintains phenotype of tubules via mitochondrial respiration during kidney injury and repair.

Impaired energy metabolism in proximal tubular epithelial cells (PTECs) is strongly associated with various kidney diseases. Here, we characterized proximal tubular phenotype alternations during kidney injury and repair in a mouse model of folic acid nephropathy, in parallel, identified carnitine palmitoyltransferase 1α (CPT1α) as an energy stress response accompanied by renal tubular dedifferentiation. Genetic ablation of Cpt1α aggravated the tubular injury and interstitial fibrosis and hampered kidney repair indicate that CPT1α is vital for the preservation and recovery of tubular phenotype. Our data showed that the lipid accumulation and mitochondrial mass reduction induced by folic acid were persistent and became progressively more severe in PTECs without CPT1α. Interference of CPT1α reduced capacities of mitochondrial respiration and ATP production in PTECs, and further sensitized cells to folic acid-induced phenotypic changes. On the contrary, overexpression of CPT1α protected mitochondrial respiration and prevented against folic acid-induced tubular cell damage. These findings link CPT1α to intrinsic mechanisms regulating the mitochondrial respiration and phenotype of kidney tubules that may contribute to renal pathology during injury and repair.

Exenatide Attenuates Obesity-Induced Mitochondrial Dysfunction by Activating SIRT1 in Renal Tubular Cells.

Saturated free fatty acid (FFA)-induced lipotoxicity plays an important role in obesity-induced kidney injury. Exenatide, a Glucagon-like peptide-1 receptor agonist(GLP-1RA), protects against high-fat diet (HFD)-induced kidney injury. The precise mechanism needs to be further explored. This study investigated whether exenatide protects against FFA-induced tubular epithelial cells (TECs) lipotoxicity and elucidated its underlying mechanisms. Here, we show that exenatide treatment reversed HFD induced TECs injuries, including TECs apoptosis and SIRT1 downregulation. The efficacy of exenatide was better than simvastatin. In palmitate (PA)-stimulated HK2 cells, exenatide treatment reversed the downregulation of SIRT1 and prevented an increase in reactive oxygen species (ROS) production, a decrease in mitochondrial membrane potential, and mitochondrial apoptosis. The renal-protective effects of exenatide on the generation of mitochondrial ROS and mitochondrial apoptosis were blocked by inhibiting SIRT1 activation. Collectively, these findings show that exenatide was superior to simvastatin in the treatment of obesity-TECs injuries, the mechanism is partially through SIRT1 restoration, which directly reverses mitochondrial dysfunction and apoptosis.

Associations of CKD risk factors and longitudinal changes in urine biomarkers of kidney tubules among women living with HIV.

BACKGROUND: Novel urine biomarkers have enabled the characterization of kidney tubular dysfunction and injury among persons living with HIV, a population at an increased risk of kidney disease. Even though several urine biomarkers predict progressive kidney function decline, antiretroviral toxicity, and mortality in the setting of HIV infection, the relationships among the risk factors for chronic kidney disease (CKD) and urine biomarkers are unclear. METHODS: We assessed traditional and infection-related CKD risk factors and measured 14 urine biomarkers at baseline and at follow-up among women living with HIV in the Women's Interagency Health Study (WIHS). We then used simultaneously adjusted multivariable linear regression models to evaluate the associations of CKD risk factors with longitudinal changes in biomarker levels. RESULTS: Of the 647 women living with HIV in this analysis, the majority (67%) were Black, the median age was 45 years and median follow-up time was 2.5 years. Each traditional and infection-related CKD risk factor was associated with a unique set of changes in urine biomarkers. For example, baseline hemoglobin a1c was associated with worse tubular injury (higher interleukin [IL]-18), proximal tubular reabsorptive dysfunction (higher α1-microglobulin), tubular reserve (lower uromodulin) and immune response to injury (higher chitinase-3-like protein-1 [YKL-40]). Furthermore, increasing hemoglobin a1c at follow-up was associated with further worsening of tubular injury (higher kidney injury molecule-1 [KIM-1] and IL-18), as well as higher YKL-40. HCV co-infection was associated with worsening proximal tubular reabsorptive dysfunction (higher ß2-microglobulin [ß2m]), and higher YKL-40, whereas HIV viremia was associated with worsening markers of tubular and glomerular injury (higher KIM-1 and albuminuria, respectively). CONCLUSIONS: CKD risk factors are associated with unique patterns of biomarker changes among women living with HIV, suggesting that serial measurements of multiple biomarkers may help in detecting and monitoring kidney disease in this setting.

Ginkgo Biloba Extract EGB761 Ameliorates the Extracellular Matrix Accumulation and Mesenchymal Transformation of Renal Tubules in Diabetic Kidney Disease by Inhibiting Endoplasmic Reticulum Stress.

The study is aimed at investigating the effects of Ginkgo biloba extract EGB761 on renal tubular damage and endoplasmic reticulum stress (ERS) in diabetic kidney disease (DKD). A total of 50 C57BL/6 N mice were randomly divided into the normal group, DKD group, DKD+EGB761 group (36 mg/kg), and DKD+4-phenylbutyrate (4-PBA) group (1 g/kg). The DKD model was replicated by high-fat diet combined with intraperitoneal injection of streptozotocin (STZ). Renal tubular epithelial cells (HK-2) were divided into the control group, high-glucose group (30 mmol/L), EGB761 group (40 mg/L, 20 mg/L, 10 mg/L), TM group, and TM+4-PBA group. After 8 weeks of administration, expressions of serum creatinine (Scr), blood urea nitrogen (BUN), 24 h urinary protein (24 h Pro), fasting blood glucose (FBG), ß 2-microglobulin (ß 2-MG), and retinol binding protein 4 (RBP4) of mice were tested. The pathological changes of renal tissue were observed. The expressions of extracellular matrix (ECM) accumulation and epithelial-mesenchymal transition (EMT) markers α-smooth muscle actin (α-SMA), E-cadherin, fibronectin, and collagen IV, as well as the ERS markers GRP78 and ATF6, were tested by Western blot, qPCR, immunohistochemistry, or immunofluorescence. EGB761 could decrease the Scr, BUN, 24 h Pro, and FBG levels in the DKD group, alleviate renal pathological injury, decrease urine ß 2-MG, RBP4 levels, and decrease the expression of α-SMA, collagen IV, fibronectin, and GRP78, as well as ATF6, while increase the expression of E-cadherin. These findings demonstrate that EGB761 can improve renal function, reduce tubular injury, and ameliorate ECM accumulation and EMT in DKD kidney tubules, and the mechanism may be related to the inhibition of ERS.

Kidney tubule health scores and their associations with incident CKD in women living with HIV.

OBJECTIVES: Individual kidney tubule biomarkers are associated with chronic kidney disease (CKD) risk in people living with HIV (PLWH). Whether a combination of kidney biomarkers can be integrated into informative summary scores for PLWH is unknown. METHODS: We measured eight urine biomarkers of kidney tubule health at two visits over a 3-year period in 647 women living with HIV in the Women's Interagency Health Study. We integrated biomarkers into factor scores using exploratory factor analysis. We evaluated associations between CKD risk factors and factor scores, and used generalized estimating equations to determine associations between factor scores and risk of incident CKD. RESULTS: Factor analysis identified two unique factor scores: a tubule reabsorption score comprising alpha-1-microglobulin, beta-2-microglobulin and trefoil factor-3; and a tubule injury score comprising interleukin-18 and kidney injury molecule-1. We modelled the two factor scores in combination with urine epidermal growth factor (EGF) and urine albumin. Predominantly HIV-related CKD risk factors were independently associated with worsening tubule reabsorption scores and tubule injury scores. During a median follow-up of 7 years, 9.7% (63/647) developed CKD. In multivariable time-updated models that adjusted for other factor scores and biomarkers simultaneously, higher tubule reabsorption scores [risk ratio (RR) = 1.27, 95% confidence interval (CI): 1.01-1.59 per 1 SD higher time-updated score], higher tubule injury scores (RR = 1.36, 95% CI: 1.05-1.76), lower urine EGF (RR = 0.75, 95% CI: 0.64-0.87), and higher urine albumin (RR = 1.20, 95% CI: 1.02-1.40) were jointly associated with risk of incident CKD. CONCLUSIONS: We identified two novel and distinct dimensions of kidney tubule health that appear to quantify informative metrics of CKD risk in PLWH.

Netrin-1 and clusterin: Innovative potential diagnostic biomarkers for early renal damage in ß-thalassemia major children.

BACKGROUND: Children with ß-thalassemia major (ß-TM) suffer from tubular dysfunction even before the onset of any renal impairment symptoms and/or clinical signs. Therefore, identifying innovative biomarkers allowing early renal damage detection has focused attention. AIM: This study aims to preliminary assess Netrin-1(NTN-1) and clusterin (CLU) in ß-TM children and explore their possible roles as surrogate noninvasive biomarkers of renal tubular dysfunction. SUBJECTS AND METHODS: In this study, 40 ß-TM children and 30 healthy children were enrolled. Routine serum and urinary biochemical variables were determined. Urinary NTN-1 and CLU levels were measured using ELISA and their mRNA expression in PBMCs were assayed using real-time PCR. Serum TNF-α, MDA levels and GST activity were measured. RESULTS: Urinary NTN-1 and CLU concentrations and mRNA relative expression levels in PBMCs were significantly increased in ß-TM children relative to controls. Oxidative stress and inflammatory markers revealed significant elevation in ß-TM children compared to controls. The change in these parameters correlated significantly with other renal parameters. ROC curves analysis showed that urinary NTN-1 and CLU levels are of promising diagnostic performance. CONCLUSION: Our results suggest that NTN-1 and CLU are qualified as new noninvasive biomarker panels for early detection of renal injury in ß-TM children. Moreover, urinary NTN-1 is recommended as a precise one during the clinical practices.

Association of Urine Biomarkers of Kidney Tubule Injury and Dysfunction With Frailty Index and Cognitive Function in Persons With CKD in SPRINT.

RATIONALE & OBJECTIVE: The associations of the glomerular markers of kidney disease, estimated glomerular filtration rate (eGFR) and albuminuria, with frailty and cognition are well established. However, the relationship of kidney tubule injury and dysfunction with frailty and cognition is unknown. STUDY DESIGN: Observational cross-sectional study. SETTING & PARTICIPANTS: 2,253 participants with eGFR<60mL/min/1.73m2 in the Systolic Blood Pressure Intervention Trial (SPRINT). EXPOSURE: Eight urine biomarkers: interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), chitinase-3-like protein 1 (YKL-40), monocyte chemoattractant protein 1 (MCP-1), α1-microglobulin (A1M), ß2-microglobulin (B2M), and uromodulin (Umod). OUTCOME: Frailty was measured using a previously validated frailty index (FI), categorized as fit (FI≤0.10), less fit (0.100.21). Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA). ANALYTICAL APPROACH: Associations between kidney tubule biomarkers with categorical FI were evaluated using multinomial logistic regression with the fit group as the reference. Cognitive function was evaluated using linear regression. Models were adjusted for demographic, behavioral, and clinical variables including eGFR and urine albumin. RESULTS: Three of the 8 urine biomarkers of tubule injury and dysfunction were independently associated with FI. Each 2-fold higher level of urine KIM-1, a marker of tubule injury, was associated with a 1.22 (95% CI, 1.01-1.49) greater odds of being in the frail group. MCP-1, a marker of tubulointerstitial fibrosis, was associated with a 1.30 (95% CI, 1.04-1.64) greater odds of being in the frail group, and A1M, a marker of tubule reabsorptive capacity, was associated with a 1.48 (95% CI, 1.11-1.96) greater odds of being in the frail group. These associations were independent of confounders including eGFR and urine albumin, and were stronger than those of urine albumin with FI (1.15 [95% CI, 0.99-1.34]). Higher urine B2M, another marker of tubule reabsorptive capacity, was associated with worse cognitive scores at baseline (ß: -0.09 [95% CI, -0.17 to-0.01]). Urine albumin was not associated with cognitive function. LIMITATIONS: Cross-sectional design, and FI may not be generalizable in other populations. CONCLUSIONS: Urine biomarkers of tubule injury, fibrosis, and proximal tubule reabsorptive capacity are variably associated with FI and worse cognition, independent of glomerular markers of kidney health. Future studies are needed to validate these results among other patient populations.

Uromodulin aggravates renal tubulointerstitial injury through activation of the complement pathway in rats.

Uromodulin (Umod) is the most abundant constituent of urine in humans and exclusively found in the kidney tubular epithelium. However, the specific role of Umod in renal tubulointerstitial injury is yet to be understood. The present study was conducted with aim of investigating the potential therapeutic mechanism of Umod in the regulation of renal tubulointerstitial injury. Protein expression of Umod in renal tubular epithelial cells was measured with the conduction of Western blot analysis. Enzyme-linked immunosorbent assay and immunofluorescence assay were performed to detect the complement activation products and the activation products of surface deposition. The expression of C1q, C2, C4, B factor, C3, C5, H factor, CD46, CD55, C3aR, and C5aR were determined with the use of reverse-transcription quantitative polymerase chain reaction and Western blot analyses. Subsequently, the unilateral ureteral obstruction (UUO) rat model was established. Renal tubulointerstitial injury was assessed with the application of hematoxylin-eosin staining and Masson staining in rats. UUO rats and normal rats were injected with si-NC or si-Umod and complement inhibitor. UUO rats were observed to have serious impairment of kidney tubule, renal tubular dilation, and epithelial atrophy, with downregulated Umod and activated complement pathway. Silencing of Umod resulted in the activation of complement system while promoting interstitial fibrosis in renal tubules. Moreover, addition of complement inhibitor significantly alleviated the renal tubule injury and fibrosis. Collectively, our study suggests that silencing of Umod mediates the complement pathway, exacerbating renal tubulointerstitial injury in rats, which provides insight into the development of novel therapeutic agents for renal tubulointerstitial injury.

Fructose-Rich Diet Is a Risk Factor for Metabolic Syndrome, Proximal Tubule Injury and Urolithiasis in Rats.

Excessive consumption of fructose (FR) leads to obesity, metabolic syndrome (MS) and insulin resistance, which are known risk factors for kidney stones. The epidemiological study has suggested the association between fructose consumption and urolithiasis, but the precise mechanism is still not well understood. Male Wistar rats were assigned for 8 weeks to three groups with different FR content in diet: RD (n = 5)-regular diet with a FR < 3%; F10 (n = 6)-regular diet with an addition of 10% Fr in drinking water; F60 (n = 5)-60% FR as a solid food. Serum concentration of FR, creatinine (Cr), insulin (Ins), triglycerides (Tg), homocysteine (HCS), uric acid (UA), calcium (Ca), phosphate (Pi), magnesium (Mg) and sodium (Na) were measured. Based on 24 h urine collection the following tests were performed: urine pH, proteinuria (PCR), excretion of N-Acetyl-(D)-Glucosaminidase (NAG), monocyte chemoattractant protein (MCP-1), uric acid (uUAEx), phosphate (uPiEx), calcium (uCaEx), magnesium (uMgEx) and sodium (uNaEx). The creatinine clearance (CrCl) was calculated. Calcium deposits in kidney sections were examined using hematoxylin and eosin (HE) and von Kossa stains. The rats on F10 and F60, as compared to the RD diet, showed a tendency for lower CrCl, higher HCS level and some features of MS as higher Ins and TG levels. Interestingly, F10 (fluid) versus F60 (solid) diet led to higher serum Ins levels. F10 and F60 versus RD demonstrated higher urinary excretion of MCP-1 and NAG which were suggestive for inflammatory injury of the proximal tubule. F10 and F60 as compared to RD showed significantly lower uUAEx, although there were no differences in clearance and fractional excretion of UA. F60 versus RD induced severe phosphaturia (>30×) and natriuria (4×) and mild calciuria. F10 versus RD induced calciuria (3×), phosphaturia (2×) and mild natriuria. Calcium phosphate stones within the tubules and interstitium were found only in rats on FR diet, respectively, in two rats from the F10 group and another two in the F60 group. The rats which developed stones were characterized by significantly higher serum insulin concentration and urinary excretion of calcium and magnesium. A fructose-rich diet may promote development of calcium stones due to proximal tubule injury and metabolic syndrome.

PEGylated and Acylated Elabela Analogues Show Enhanced Receptor Binding, Prolonged Stability, and Remedy of Acute Kidney Injury.

Acute kidney injury (AKI), mostly caused by renal ischemia-reperfusion (I/R) injury and nephrotoxins, is characterized by rapid deterioration in renal-functions without effective drug treatment available. Through activation of a G protein-coupled receptor APJ, a furin-cleaved fragment of Elabela (ELA[22-32], E11), an endogenous APJ ligand, protects against renal I/R injury. However, the poor plasma stability and relatively weak APJ-binding ability of E11 limit its application. To address these issues, we rationally designed and synthesized a set of E11 analogues modified by palmitic acid (Pal) or polyethylene glycol; improved plasma stability and APJ-binding capacity of these analogues were achieved. In cultured renal tubular cells, these analogues protected against hypoxia-reperfusion or cisplatin-caused injury. For renal I/R-injured mice, these analogues showed improved reno-protective effects than E11; notably, Pal-E11 showed therapeutic effects at 24 h post I/R injury. These results present ELA analogues as potential therapeutic options in managing AKI.

TRPV1 Hyperfunction Involved in Uremic Toxin Indoxyl Sulfate-Mediated Renal Tubular Damage.

Indoxyl sulfate (IS) is accumulated during severe renal insufficiency and known for its nephrotoxic properties. Transient receptor potential vanilloid 1 (TRPV1) is present in the kidney and acts as a renal sensor. However, the mechanism underlying IS-mediated renal tubular damage in view of TRPV1 is lacking. Here, we demonstrated that TRPV1 was expressed in tubular cells of Lilly Laboratories cell-porcine kidney 1 (LLC-PK1) and Madin-Darby canine kidney cells (MDCK). IS treatment in both cells exhibited tubular damage with increased LDH release and reduced cell viability in dose- and time-dependent manners. MDCK, however, was more vulnerable to IS. We, therefore, investigated MDCK cells to explore a more detailed mechanism. Interestingly, IS-induced tubular damage was markedly attenuated in the presence of selective TRPV1 blockers. IS showed no effect on TRPV1 expression but significantly increased arachidonate 12-lipoxygenase (ALOX12) protein, mRNA expression, and 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) amounts in a dose-dependent manner, indicating that the ALOX12/12(S)-HETE pathway induced TRPV1 hyperfunction in IS-mediated tubulotoxicity. Blockade of ALOX12 by cinnamyl-3,4-dihydroxy-α-cyanocinnamate or baicalein attenuated the effects of IS. Since aryl hydrocarbon receptor (AhR) activation after IS binding is crucial in mediating cell death, here, we found that the AhR blockade not only ameliorated tubular damage but also attenuated ALOX12 expression and 12(S)-HETE production caused by IS. The uremic toxic adsorbent AST-120, however, showed little effect on ALOX12 and 12(S)-HETE, as well as IS-induced cell damage. These results clearly indicated that IS activated AhR and then upregulated ALOX12, and this induced endovanilloid 12(S)-HETE synthesis and contributed to TRPV1 hyperfunction in IS-treated tubular cells. Further study on TRPV1 may attenuate kidney susceptibility to the functional loss of end-stage kidney disease via IS.

XJB-5-131 inhibited ferroptosis in tubular epithelial cells after ischemia-reperfusion injury.

Regulated necrosis has been reported to exert an important role in the pathogenesis of various diseases, including renal ischemia-reperfusion (I/R) injury. Damage to renal tubular epithelial cells and subsequent cell death initiate the progression of acute kidney injury (AKI) and subsequent chronic kidney disease (CKD). We found that ferroptosis appeared in tubular epithelial cells (TECs) of various human kidney diseases and the upregulation of tubular proferroptotic gene ACSL4 was correlated with renal function in patients with acute kidney tubular injury. XJB-5-131, which showed high affinity for TECs, attenuated I/R-induced renal injury and inflammation in mice by specifically inhibiting ferroptosis rather than necroptosis and pyroptosis. Single-cell RNA sequencing (scRNA-seq) indicated that ferroptosis-related genes were mainly expressed in tubular epithelial cells after I/R injury, while few necroptosis- and pyroptosis-associated genes were identified to express in this cluster of cell. Taken together, ferroptosis plays an important role in renal tubular injury and the inhibition of ferroptosis by XJB-5-131 is a promising therapeutic strategy for protection against renal tubular cell injury in kidney diseases.

Tubular injury and cell-cycle arrest biomarkers to predict acute kidney injury in noncritically ill children receiving aminoglycosides.

Aim: NGAL, IL-18, KIM-1 as well as urinary TIMP2 and IGFBP7 and their mathematical product (TIMP2*IGFBP7) were evaluated for detecting pediatric aminoglycoside acute kidney injury (AG-AKI). Methods: In a prospective study, noncritically ill children received aminoglycosides (AG) ≥3 days. The area under the curve (AUC) for biomarkers to detect AKI was calculated by a) days before AKI onset; b) treatment days. Results: There were 113 AG episodes (68% febrile neutropenia). The AKI group had a higher proportion with febrile neutropenia. The AKI group had significantly lower NGAL 3 days before AKI, as patients with febrile neutropenia had a lower NGAL during AG treatment (p < 0.05). NGAL, IL-18 and TIMP2*IGFBP7 had AUC ≥0.73 at 3, 2 and 2 days before AKI onset. Conclusion: NGAL, IL-18 and TIMP2*IGFBP7 were modest early biomarkers of AG-AKI. Febrile neutropenia was associated with lower NGAL.

Role of DNA damage in the progress of chronic tubule­interstitial injury.

Tubulointerstitial fibrosis (TIF) is a common final endpoint of chronic allograft nephropathy. Over the years, several hypotheses have been developed to explain the progression of TIF, including mechanisms such as inflammation, epithelial­mesenchymal transition, senescence, chronic hypoxia and reactive oxygen species. Furthermore, TIF is reportedly induced by the 'damage­proliferation­death' cycle. In the present study, an AA renal fibrosis model was established in vitro to investigate whether the vicious proliferation­death cycle is a pathophysiological process of TIF following chronic injury to the kidneys. Results from the present study revealed that cell death was associated with the entrance of cells into the cell cycle. Genetic knockdown of p21 was observed to increase cell cycle progression and the proliferative rate of cells, which overall promoted increased rates of cell death. In addition, the activation of the DNA damage response (DDR) signaling pathway was demonstrated to be crucial to the initiation of the vicious cycle of 'proliferation­death'. Ataxia telangiectasia mutated (ATM) is an important molecule of the DDR and the genetic knockdown of ATM induced apoptosis, increased cell proliferation and promoted cell death. The increase in apoptosis was suggested to be due to the decreased expression levels of p21 observed following the genetic knockdown of ATM. In conclusion, the present study suggested that the crosstalk between the ATM and p21 protein may serve an important role in the regulation of the 'proliferation­death' cycle in the progress of chronic tubulointerstitial injury.

Weight-gain induced changes in renal perfusion assessed by contrast-enhanced ultrasound precede increases in urinary protein excretion suggestive of glomerular and tubular injury and normalize after weight-loss in dogs.

Early detection of obesity-related glomerulopathy in humans is challenging as it might not be detected by routine biomarkers of kidney function. This study's aim was to use novel kidney biomarkers and contrast-enhanced ultrasound (CEUS) to evaluate the effect of obesity development and weight-loss on kidney function, perfusion, and injury in dogs. Sixteen healthy lean adult beagles were assigned randomly but age-matched to a control group (CG) (n = 8) fed to maintain a lean body weight (BW) for 83 weeks; or to a weight-change group (WCG) (n = 8) fed the same diet to induce obesity (week 0-47), to maintain stable obese weight (week 47-56) and to lose BW (week 56-83). At 8 time points, values of systolic blood pressure (sBP); serum creatinine (sCr); blood urea nitrogen (BUN); serum cystatin C (sCysC); urine protein-to-creatinine ratio (UPC); and urinary biomarkers of glomerular and tubular injury were measured. Glomerular filtration rate (GFR) and renal perfusion using CEUS were assayed (except for week 68). For CEUS, intensity- and time-related parameters representing blood volume and velocity were derived from imaging data, respectively. At 12-22% weight-gain, cortical time-to-peak, representing blood velocity, was shorter in the WCG vs. the CG. After 37% weight-gain, sCysC, UPC, glomerular and tubular biomarkers of injury, urinary immunoglobulin G and urinary neutrophil gelatinase-associated lipocalin, respectively, were higher in the WCG. sBP, sCr, BUN and GFR were not significantly different. After 23% weight-loss, all alterations were attenuated. Early weight-gain in dogs induced renal perfusion changes measured with CEUS, without hyperfiltration, preceding increased urinary protein excretion with potential glomerular and tubular injury. The combined use of routine biomarkers of kidney function, CEUS and site-specific urinary biomarkers might be valuable in assessing kidney health of individuals at risk for obesity-related glomerulopathy in a non-invasive manner.

Injured tubular epithelial cells activate fibroblasts to promote kidney fibrosis through miR-150-containing exosomes.

The kidney injury induced by ischemia-reperfusion (IR) usually comes with irreversible renal fibrosis, a process that develops into chronic kidney disease (CKD), but the underlying cellular mechanism has yet to be determined. To test our hypothesis that exosomes are tightly connected with kidney fibrosis following AKI, we studied the role of exosomes and the transfer of specific miRNA among other genetic components in injured tubular epithelial cells (TECs). We utilized an experimental IR mice model to simulate the fibrotic environment in injured tissue and detect the production of exosomes, and found that exosome deficiency could significantly alleviate the degree of kidney fibrosis following IR administration. MiRNA profiling of exosomes extracted from renal tissue samples with or without ischemia-reperfusion injury (IRI) revealed that miR-150 was markedly increased as a compelling profibrotic molecule, as evidenced by the fact that overexpression of miR-150 facilitated renal fibrosis. Exosomes isolated from hypoxia TECs also induced the increased production of miR-150. In cocultured fibroblasts with TECs-derived exosomes, we confirmed a direct uptake of exosomal miR-150 by fibroblasts. Finally, we verified that in vivo ischemia mice pretreated with exosomes enriched in miR-150 developed more profibrotic manifestations. Thus, our current study indicated that TECs have the ability to employ exosomes to initiate the activation and proliferation of fibroblasts via direct shuttling of miR-150-containing exosomes during reparative responses, and that exosome/miR-150 provides the groundwork for research to develop more personalized therapeutic approaches for controlling tissue fibrosis.