Chronic epithelial kidney injury molecule-1 expression causes murine kidney fibrosis

Comparison of Effect Sevoflurane-Based Anesthesia and Propofol-Based Anesthesia on the Early Postoperative Renal Function of Living Kidney Transplant Donors: A Randomized Controlled Trial

Purpose

Living kidney transplantation is a common treatment for end-stage renal disease. The impact of anaesthetics on postoperative biomarkers of renal injury in living kidney transplant donors is not well understood.

Patients and Methods

70 transplant donors who underwent kidney extraction were randomly assigned to following two groups: sevoflurane (S group) and propofol (P group). Urine and blood were collected before induction and 1, 2, 6 days after operation. Kidney injury marker-1 (KIM-1), interleukin-18 (IL-18) and tissue inhibitor of metalloproteinase-2 (TIMP-2) were measured by enzyme-linked immunosorbent assay. Record the cystatin C, glomerular filtration rate, urine output during perioperative period.

Results

There were both increases in biomarkers of kidney injury before and 1, 2 and 6 days after the anaesthetic surgery in donors, However, no statistical differences in KIM-1 (P (0.42 pg/mL (95% CI 0.21 to 0.63 pg/mL)) vs S (0.26 pg/mL (95% CI 0.02 to 0.49 pg/mL)), -0.16 pg/mL (95% CI -0.48 to 0.16 pg/mL)), IL-18 (P (178.54 pg/mL (95% CI 110.15 to 24693 pg/mL)) vs S (175.86 pg/mL (95% CI 100.35 to 251.38 pg/mL)), -2.68 pg/mL (95% CI -105.61 to 100.25 pg/mL)), and TIMP-2 (P (12.88 ng/mL (95% CI 8.69 to 17.07 ng/mL)) vs S (14.85 ng/mL (95% CI 10.23 to 19.46 ng/mL)), 1.97 ng/mL (95% CI -4.30 to 8.23 ng/mL)) concentration changes between the two types of anaesthesia.

Conclusion

There was no difference between sevoflurane and propofol anaesthesia on postoperative changes in biomarkers of renal injury in living kidney transplant donors.

Leucine-rich alpha-2-glycoprotein 1 deficiency suppresses ischemia-reperfusion injury-induced renal fibrosis

Ischemia reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and ultimately leads to renal fibrosis, primarily via the transforming growth factor-β (TGF-β) pathway. Leucine-rich alpha-2-glycoprotein 1 (LRG1), a novel modulator of the TGF-β pathway, has been implicated in the modulation of renal fibrosis by affecting the TGF-β/Smad3 signaling axis. However, the role of LRG1 in the transition from AKI to chronic kidney disease (CKD) remains unclear. This study aimed to investigate the functional role of LRG1 during the remodeling phase post-IRI. Unilateral IRI was induced in C57BL/6J wild-type (WT) mice and systemic LRG1 knockout (KO) mice. In C57BL/6J WT mice, renal LRG1 mRNA expression was significantly elevated on the ischemia/reperfusion side compared to the sham side over a 28-day period. In contrast, LRG1 KO mice demonstrated significantly reduced renal fibrosis compared to WT mice on postoperative day 28. Additionally, renal mRNA expression of TGF-β and associated pro-fibrotic genes was diminished in LRG1 KO mice compared to WT mice. Consequently, LRG1 KO mice exhibited attenuated IRI-induced chronic fibrosis. These findings indicate that LRG1 is involved in the pathogenesis of the transition from AKI to CKD and may be a potential therapeutic target.

Dysregulation of lipid metabolism in chronic kidney disease and the role of natural products

Dysregulation of lipid metabolism plays a key role in the onset and progression of CKD, and a thorough understanding of its regulatory mechanisms is essential for the development of effective treatments. In recent years, an increasing number of studies have focused on the pharmacological activities of natural products and their application in the treatment of chronic diseases. Natural products, including plant extracts and bioactive compounds, have been shown to exert anti-inflammatory, antioxidant, antifibrosis, and anti-apoptotic effects through various signaling pathways in the treatment of CKD. Many natural products have been shown to target dysregulated lipid metabolism through various signaling pathways. This review summarizes the key regulatory factors and signaling pathways involved in the dysregulation of lipid metabolism in chronic kidney disease (CKD), highlighting their importance as potential therapeutic targets. Recently published research on the potential therapeutic benefits of natural products for the treatment of CKD was described. These studies have revealed the multi-target role of natural products in the regulation of lipid metabolism. Natural products show great potential in targeting lipid metabolism-related pathways, offering a novel research direction for the treatment of CKD while providing a scientific basis and experimental support for the development of new treatment strategies.

Beyond hemoglobin: Critical role of 2,3-bisphosphoglycerate mutase in kidney function and injury

AIM

2,3-bisphosphoglycerate mutase (BPGM) is traditionally recognized for its role in modulating oxygen affinity to hemoglobin in erythrocytes. Recent transcriptomic analyses, however, have indicated a significant upregulation of BPGM in acutely injured murine and human kidneys, suggesting a potential renal function for this enzyme. Here we aim to explore the physiological role of BPGM in the kidney.

METHODS

A tubular-specific, doxycycline-inducible Bpgm-knockout mouse model was generated. Histological, immunofluorescence, and proteomic analyses were conducted to examine the localization of BPGM expression and the impact of its knockout on kidney structure and function. In vitro studies were performed to investigate the metabolic consequences of Bpgm knockdown under osmotic stress.

RESULTS

BPGM expression was localized to the distal nephron and was absent in proximal tubules. Inducible knockout of Bpgm resulted in rapid kidney injury within 4 days, characterized by proximal tubular damage and tubulointerstitial fibrosis. Proteomic analyses revealed involvement of BPGM in key metabolic pathways, including glycolysis, oxidative stress response, and inflammation. In vitro, Bpgm knockdown led to enhanced glycolysis, decreased reactive oxygen species elimination capacity under osmotic stress, and increased apoptosis. Furthermore, interactions between nephron segments and immune cells in the kidney suggested a mechanism for propagating stress signals from distal to proximal tubules.

CONCLUSION

BPGM fulfills critical functions beyond the erythrocyte in maintaining glucose metabolism in the distal nephron. Its absence leads to metabolic imbalances, increased oxidative stress, inflammation, and ultimately kidney injury.

Dynamic regulation of proximal tubular autophagy from injury to repair after ischemic kidney damage

BACKGROUND

The role of proximal tubular autophagy in repairing kidney injury following ischemia remains unclear.

METHODS

In this study, we utilized mice with conditional deletion of the Atg5 gene in proximal tubules and monitored the long-term dynamic regulation of autophagy following ischemic acute kidney injury (AKI).

RESULTS

The results showed that Atg5-deficient proximal tubule epithelial cells exhibited damaged mitochondria, concentric membranes, and lysosomal accumulation 24 h after ischemia/reperfusion. However, 28 days after ischemia/reperfusion, concentric membrane bodies remained, but lysosomal accumulation was no longer observed. Notably, the absence of Atg5 in renal tubular epithelial cells impaired renal function and led to increased tubular cell proliferation and oxidative stress in the early stage of injury. However, during the repair period following AKI, Atg5 deficiency exhibited no significant difference in the expression of proliferating cell nuclear antigen (PCNA) and 4-hydoxynonenal (4HNE), suggesting that the improvement in renal fibrosis associated with Atg5 deficiency is unlikely to result from its effect on cell proliferation or reactive oxygen species levels. Additionally, Atg5 deficiency inhibits the secretion of profibrotic factor fibroblast growth factor 2 (FGF2) from the early stage of renal injury to the recovery stage of AKI, indicating that autophagy-specific regulation of FGF2 secretion is a dynamic process overlapping with other stages of injury. Furthermore, increased co-localization of ATG5 with 4HNE and FGF2 was observed in patient samples.

CONCLUSION

In summary, our results suggest that the dynamic regulation of autophagy on key molecules involved in kidney injury and repair varies with the stage of kidney injury.

Integration of spatial multiplexed protein imaging and transcriptomics in the human kidney tracks the regenerative potential timeline of proximal tubules

The organizational principles of nephronal segments are based on longstanding anatomical and physiological attributes that are closely linked to the homeostatic functions of the kidney. Novel molecular approaches have recently uncovered layers of deeper signatures and states in tubular cells that arise at various timepoints on the spectrum between health and disease. For example, a dedifferentiated state of proximal tubular cells with mesenchymal stemness markers is frequently seen after injury. The persistence of such a state is associated with failed repair. Here, we introduce a novel analytical pipeline applied to highly multiplexed spatial protein imaging to characterize proximal tubular subpopulations and neighborhoods in reference and disease human kidney tissue. The results were validated and extended through integration with spatial and single cell transcriptomics. We demonstrate that, in reference tissue, a large proportion of S1 and S2 proximal tubular epithelial cells express THY1, a mesenchymal stromal and stem cell marker that regulates differentiation. Kidney disease is associated with loss of THY1 and transition towards expression of PROM1, another stem cell marker shown recently to be linked to failed repair. We demonstrate that the trajectory of proximal tubular cells to THY1 expression is clearly distinct from that of PROM1, and that a state with PROM1 expression is associated with niches of inflammation. Our data support a model in which the interplay between THY1 and PROM1 expression in proximal tubules associates with their regenerative potential and marks the timeline of disease progression.

Investigating the cause of cardiovascular dysfunction in chronic kidney disease: capillary rarefaction and inflammation may contribute to detrimental cardiovascular outcomes

Myocardial ischemia-reperfusion (IR) injury is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD). The most frequently used and representative experimental model is the rat dietary adenine-induced CKD, which leads to CKD-associated CVD. However, the continued intake of adenine is a potential confounding factor. This study investigated cardiovascular dysfunction following brief adenine exposure, CKD development and return to a normal diet. Male Wistar rats received a 0.3% adenine diet for 10 weeks and normal chow for an additional 8 weeks. Kidney function was assessed by urinalysis and histology. Heart function was assessed by echocardiography. Sensitivity to myocardial IR injury was assessed using the isolated perfused rat heart (Langendorff) model. The inflammation profile of rats with CKD was assessed via cytokine ELISA, tissue histology and RNA sequencing. Induction of CKD was confirmed by a significant increase in plasma creatinine and albuminuria. Histology revealed extensive glomerular and tubular damage. Diastolic dysfunction, measured by the reduction of the E/A ratio, was apparent in rats with CKD even following a normal diet. Hearts from rats with CKD had significantly larger infarcts after IR injury. The CKD rats also had statistically higher levels of markers of inflammation including myeloperoxidase, KIM-1 and interleukin-33. RNA sequencing revealed several changes including an increase in inflammatory signaling pathways. In addition, we noted that CKD induced significant cardiac capillary rarefaction. We have established a modified model of adenine-induced CKD, which leads to cardiovascular dysfunction in the absence of adenine. Our observations of capillary rarefaction and inflammation suggest that these may contribute to detrimental cardiovascular outcomes.

Association between exposure to arsenic, cadmium, and lead and chronic kidney disease: evidence from four practical statistical models

BACKGROUND

Environmental exposure to arsenic (As), lead (Pb) and cadmium (Cd) may cause chronic kidney disease (CKD), with varying independent effects and unclear combined impact. This study aimed to evaluate these effects on CKD.

METHODS

1,398 individuals were included. Urine arsenic (UAs) was determined by atomic fluorescence method. Urinary cadmium (UCd) and blood lead (BPb) levels were determined by graphite-furnace atomic absorption spectrometry. CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2 or proteinuria. Generalized linear models (GLM), restricted cubic spline (RCS) models, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models were employed to study the independent and combined effects of exposure to As, Pb and Cd on CKD risk.

RESULTS

Compared with non-CKD subjects, UAs, UCd, BPb, and creatinine adjusted urinary cadmium (UCdCr) were all significantly higher in CKD subjects. Compared with the lowest quartiles, the ORs (95%CIs) of CKD risk in the highest quartiles were 2.09 (1.16-3.74) for UAs, 2.84(1.56-5.18) for UCd, and 1.79 (1.05-3.06) for UCdCr, respectively. UAs, UCd, and UCdCr were all significantly positively associated with CKD risk in p-trend tests. RCS models revealed non-linear links between UAs, UCd, UCdCr and CKD risk, while a linear dose-response existed for BPb and CKD risk. The OR (95%CI) in WQS models were 1.72 (1.25-2.36) with UAs being the highest weighing metal(loid). BKMR models showed co-exposure mixture linked to higher CKD risk when the ln-transformed metal(loid)s above their 55th percentile. The ln-transformed UAs and UCdCr was significantly positively associated with CKD risk when the other two ln-transformed metals levels were all fixed at their different percentile levels. Synergism between Cd and Pb was also apparent.

CONCLUSIONS

Single As, and Cd exposure were positively associated with an increased CKD risk. Co-exposure to As, Pb and Cd was positively associated with CKD risk, with As playing a dominant role.

The association between novel urinary kidney damage biomarkers and coronary atherosclerosis in an apparently healthy population

Several novel urinary kidney damage biomarkers predict the progression of kidney disease. However, the relations of these biomarkers to atherosclerosis, a major consequence of kidney disease, are less studied. Urinary levels of several biomarkers, including kidney injury molecule-1 (KIM-1), osteopontin, epidermal growth factor, and Dickkopf-3, were assessed in participants enrolled in the Swedish CArdioPulmonary BioImage Study. The study included 9,628 individuals with a mean age of 57.5 years, of which 52.4% were women. The presence of coronary artery stenosis and the coronary artery calcium score (CACS) were determined using coronary computed tomography angiography. To analyze the associations between coronary atherosclerosis and urinary biomarker levels, an ordered logistic regression model adusting for confounding factors was employed. KIM-1 was the only biomarker associated with both coronary stenosis and CACS after adjusting for established cardiovascular risk factors (odds ratio [95% confidence intervals], 1.23[1.05-1.44] and 1.25[1.07-1.47]). These results were consistent in sensitivity analyses of individuals without hypertension, diabetes, or known cardiovascular disease and with normal kidney function. Urinary KIM-1, a specific marker of proximal tubular damage, was robustly linked to coronary atherosclerosis even in apparently healthy individuals, which suggests that the detrimental interplay between the kidney and cardiovascular system begins before clinically overt kidney disease. Additional studies are warranted to evaluate the urinary KIM-1 to predict kidney and cardiovascular disease.

Proteomic Correlates and Prognostic Significance of Kidney Injury in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Kidney disease is common in heart failure with preserved ejection fraction (HFpEF). However, the biologic correlates and prognostic significance of kidney injury (KI), in HFpEF, beyond the estimated glomerular filtration rate (eGFR), are unclear.

METHODS AND RESULTS

Using baseline plasma samples from the TOPCAT (Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist) trial, we measured the following KI biomarkers: cystatin-C, fatty acid-binding protein-3, Beta-2 microglobulin, neutrophil gelatinase-associated lipocalin, and kidney-injury molecule-1. Factor analysis was used to extract the common variability underlying these biomarkers. We assessed the relationship between the KI-factor score and the risk of death or HF-related hospital admission in models adjusted for the Meta-Analysis Global Group in Chronic Heart Failure risk score and eGFR. We also assessed the relationship between the KI factor score and ~5000 plasma proteins, followed by pathway analysis. We validated our findings among HFpEF participants in the Penn Heart Failure Study. KI was associated with the risk of death or HF-related hospital admission independent of the Meta-Analysis Global Group in Chronic Heart Failure risk score and eGFR. Both the risk score and eGFR were no longer associated with death or HF-related hospital admission after adjusting for the KI factor score. KI was predominantly associated with proteins and biologic pathways related to complement activation, inflammation, fibrosis, and cholesterol homeostasis. KI was associated with 140 proteins, which reproduced across cohorts. Findings regarding biologic associations and the prognostic significance of KI were also reproduced in the validation cohort.

CONCLUSIONS

KI is associated with adverse outcomes in HFpEF independent of baseline eGFR. Patients with HFpEF and KI exhibit a plasma proteomic signature indicative of complement activation, inflammation, fibrosis, and impaired cholesterol homeostasis.

Renal ischemia/reperfusion induces prominent progressive kidney disease in diabetic mice

Acute kidney injury (AKI) is a public health concern associated with high rates of mortality, even in milder cases. One of the reasons for the difficulty in managing AKI in patients is due to its association with pre-existing comorbidities, such as diabetes. In fact, diabetes increases the susceptibility to develop more severe AKI after renal ischemia. However, the long-term effects of this association are not known. Thus, an experimental model was designed to evaluate the chronic effects of renal ischemia/reperfusion (IR) in streptozotocin (STZ)-treated mice. We focused on the glomerular and tubulointerstitial damage, as well as kidney function and metabolic profile. It was found that pre-existing diabetes may potentiate progressive kidney disease after AKI, mainly by exacerbating proinflammatory and sustaining fibrotic responses and altering renal glucose metabolism. To our knowledge, this is the first report that highlights the long-term effects of renal IR on diabetes. The findings of this study can support the management of AKI in clinical practice.NEW & NOTEWORTHY This study demonstrated that early diabetes potentiates progressive kidney disease after ischemia/reperfusion (IR)-induced acute kidney injury, mainly by exacerbating pro-inflammatory and sustaining fibrotic responses and altering renal glucose metabolism. Thus, these findings will contribute to the therapeutic support of patients with type 1 diabetes with eventual renal IR intervention in clinical practice.

Renal protective and immunoregulatory effects of Lactobacillus casei strain Shirota in nephropathy-prone mice

Introduction

The incidence of severe acute kidney injury (AKI) is considerably high worldwide. A previous study showed that gut microbial dysbiosis was a hallmark of AKI in mice. Whether the probiotic Lactobacillus casei strain Shirota (LcS) plays a role in kidney disease, particularly AKI, remains unclear.

Methods

To investigate the effects of LcS on kidney injury, tubule-specific conditional von Hippel-Lindau gene-knockout C57BL/6 mice (Vhlhdel/del mice) were supplemented without (Ctrl) or with probiotics (LcS) in Experiment 1, and their lifespan was monitored. Additionally, the Vhlhdel/+ mice were supplemented without (Ctrl and AA) or with probiotics (LcS and LcS + AA) in Experiment 2. Probiotic LcS (1 × 109 colony-forming units) was supplemented once daily. After 4 weeks of LcS supplementation, AA and LcS + AA mice were administered aristolochic acid (AA; 4 mg/kg body weight/day)-containing purified diet for 2 weeks to induce AA nephropathy before sacrifice.

Results

Supplementation of LcS significantly prolonged the lifespan of Vhlhdel/del mice, suggesting a potential renal protective effect. AA induced-nephropathy increased not only the indicators of renal dysfunction and injury, including urinary protein and kidney injury molecule (KIM)-1, serum blood urea nitrogen (BUN) and creatinine, but also serum interleukin (IL)-6 levels, renal macrophage infiltrations, and pathological lesions in Vhlhdel/+ mice. LcS supplementation significantly reduced urinary protein and KIM-1 levels, serum BUN and IL-6 levels, and renal M1 macrophages, tissue lesions, and injury scores. We also found that LcS maintained gut integrity under AA induction and increased intestinal lamina propria dendritic cells. Furthermore, LcS significantly reduced pro-inflammatory IL-17A and upregulated anti-inflammatory IL-10 production by immune cells from intestinal Peyer's patches (PP) or mesenteric lymph nodes (MLN), and significantly increased IL-10 and reduced IL-6 production by splenocytes.

Conclusion

Prior supplementation with probiotic LcS significantly alleviated the severity of renal injury. This renal protective effect was partially associated with the enhancements of intestinal and systemic anti-inflammatory immune responses, suggesting that LcS-induced immunoregulation might contribute to its renal protective effects.

Early Detection of Chronic Kidney Disease Using Plasma Neutrophil Gelatinase-Associated Lipocalin and Kidney Injury Molecule-1 in Small-Breed Dogs: A Retrospective Pilot Study

Multiple diagnostic modalities are urgently needed to identify early-stage kidney diseases. Various molecules have been investigated; however, most studies have focused on identifying specific biomarkers in urine. Considering that assessing the symmetrical dimethylarginine (SDMA) plasma concentration is more suitable as an early diagnostic test for chronic kidney disease (CKD) in routine veterinary practice, we aimed to investigate the clinical usefulness of plasma neutrophil gelatinase-associated lipocalin (pNGAL) and plasma kidney injury molecule-1 (pKIM-1) concentrations for CKD detection in small-breed dogs. Through a retrospective analysis, we found that numerous clinicopathological data showed a log-normal distribution, even when they satisfied normality tests. Moreover, the log-transformed pNGAL and pKIM-1 concentrations successfully identified CKD International Renal Interest Society (IRIS) stages 1-4 and the risk group with underlying CKD risk factors. Correlation analysis and group comparison of other factors confirmed the possibility of using these two biomarkers for detecting the CKD risk group and IRIS stage 1. Receiver operating characteristic curve analysis revealed that the diagnostic accuracy for discriminating the risk group was superior in the order of pKIM-1, pNGAL, SDMA, and serum creatinine levels. In conclusion, these results suggest that pKIM-1 and pNGAL are possible early or quantifiable markers of insignificant CKD or can be at least used as an adjunct with traditional indicators.

Association of urinary excretion rates of uric acid with biomarkers of kidney injury in patients with advanced chronic kidney disease

BACKGROUND

The potential influence of hyperuricemia on the genesis and progression of chronic kidney disease (CKD) remains controversial. In general, the correlation between blood levels of uric acid (UA) and the rate of progression of CKD is considered to be modest, if any, and the results of relevant trials oriented to disclose the effect of urate-lowering therapies on this outcome have been disappointing. Urinary excretion rates of UA could reflect more accurately the potential consequences of urate-related kidney injury.

METHOD

Using a cross-sectional design, we investigated the correlation between different estimators of the rates of urinary excretion of UA (total 24-hour excretion, mean urinary concentration, renal clearance and fractional excretion)(main study variables), on one side, and urinary levels of selected biomarkers of kidney injury and CKD progression (DKK3, KIM1, NGAL, interleukin 1b and MCP)(main outcome variables), in 120 patients with advanced CKD (mean glomerular filtration rate 21.5 mL/minute). We took into consideration essential demographic, clinical and analytic variables with a potential confounding effect on the explored correlations (control variables). Spearman's rho correlation and nonlinear generalized additive regression models (GAM) with p-splines smoothers were used for statistical analysis.

MAIN RESULTS

Multivariate analysis disclosed independent correlations between urinary UA concentrations, clearances and fractional excretion rates (but not plasma UA or total 24-hour excretion rates of UA), on one side, and the scrutinized markers. These correlations were more consistent for DKK3 and NGAL than for the other biomarkers. Glomerular filtration rate, proteinuria and treatment with statins or RAA axis antagonists were other independent correlates of the main outcome variables.

CONCLUSIONS

Our results support the hypothesis that urinary excretion rates of UA may represent a more accurate marker of UA-related kidney injury than plasma levels of this metabolite, in patients with advanced stages of CKD. Further, longitudinal studies will be necessary, to disclose the clinical significance of these findings.

Systematic Review of Kidney Injury Biomarkers for the Evaluation of CKD of Uncertain Etiology

Introduction

Chronic kidney disease of uncertain etiology (CKDu) is an incompletely defined phenotype of chronic kidney disease (CKD) affecting young individuals mostly in agricultural communities in Central America and South Asia. CKDu is a diagnosis of exclusion made in individuals from endemic regions.

Methods

We conducted a systematic review of the primary literature on urinary and plasma kidney injury biomarkers measured in the setting of CKDu (through February 2023). The literature was identified via a Web of Science search and hand search of the references of previously identified literature. Search terms included "CKDu," "Mesoamerican Nephropathy," "CKD of unknown etiology," "Chronic Interstitial Nephritis in Agricultural Communities," "biomarker," "urin∗," and/or "plasma."

Results

A total of 25 papers were included. The 2 most frequently measured biomarkers were urinary kidney injury molecule-1 (KIM-1) and urinary neutrophil gelatinase-associated lipocalin (NGAL). There was substantial variability in study design, laboratory assay methods, and statistical methodology, which prohibited meta-analysis.

Conclusion

Biomarkers that identify tubulointerstitial disease early and accurately may substantially accelerate progress in the study of CKDu and facilitate public health approaches that eventually lead to its prevention and elimination. To date, the literature is limited by relatively small sample sizes and methodological limitations which should be addressed in future studies.

Sensing Dying Cells in Health and Disease: The Importance of Kidney Injury Molecule-1

Kidney injury molecule-1 (KIM-1), also known as T-cell Ig and mucin domain-1 (TIM-1), is a widely recognized biomarker for AKI, but its biological function is less appreciated. KIM-1/TIM-1 belongs to the T-cell Ig and mucin domain family of conserved transmembrane proteins, which bear the characteristic six-cysteine Ig-like variable domain. The latter enables binding of KIM-1/TIM-1 to its natural ligand, phosphatidylserine, expressed on the surface of apoptotic cells and necrotic cells. KIM-1/TIM-1 is expressed in a variety of tissues and plays fundamental roles in regulating sterile inflammation and adaptive immune responses. In the kidney, KIM-1 is upregulated on injured renal proximal tubule cells, which transforms them into phagocytes for clearance of dying cells and helps to dampen sterile inflammation. TIM-1, expressed in T cells, B cells, and natural killer T cells, is essential for cell activation and immune regulatory functions in the host. Functional polymorphisms in the gene for KIM-1/TIM-1, HAVCR1 , have been associated with susceptibility to immunoinflammatory conditions and hepatitis A virus-induced liver failure, which is thought to be due to a differential ability of KIM-1/TIM-1 variants to bind phosphatidylserine. This review will summarize the role of KIM-1/TIM-1 in health and disease and its potential clinical applications as a biomarker and therapeutic target in humans.

Autophagy activates EGR1 via MAPK/ERK to induce FGF2 in renal tubular cells for fibroblast activation and fibrosis during maladaptive kidney repair

Macroautophagy/autophagy contributes to maladaptive kidney repair by inducing pro-fibrotic factors such as FGF2 (fibroblast growth factor 2), but the underlying mechanism remains elusive. Here, we show that EGR1 (early growth response 1) was induced in injured proximal tubules after ischemic acute kidney injury (AKI) and this induction was suppressed by autophagy deficiency in inducible, renal tubule-specific atg7 (autophagy related 7) knockout (iRT-atg7 KO) mice. In cultured proximal tubular cells, TGFB1 (transforming growth factor beta 1) induced EGR1 and this induction was also autophagy dependent. Egr1 knockdown in tubular cells reduced FGF2 expression during TGFB1 treatment, leading to less FGF2 secretion and decreased paracrine effects on fibroblasts. ChIP assay detected an increased binding of EGR1 to the Fgf2 gene promoter in TGFB1-treated tubular cells. Both Fgf2 and Egr1 transcription was inhibited by FGF2 neutralizing antibody, suggesting a positive feedback for EGR1-mediated FGF2 autoregulation. This feedback was confirmed using fgf2-deficient tubular cells and fgf2-deficient mice. Upstream of EGR1, autophagy deficiency in mice suppressed MAPK/ERK (mitogen-activated protein kinase) activation in post-ischemic renal tubules. This inhibition correlated with SQSTM1/p62 (sequestosome 1) aggregation and its sequestration of MAPK/ERK. SQSTM1/p62 interacted with MAPK/ERK and blocked its activation during TGFB1 treatment in autophagy-deficient tubular cells. Inhibition of MAPK/ERK suppressed EGR1 and FGF2 expression in maladaptive tubules, leading to the amelioration of renal fibrosis and improvement of renal function. These results suggest that autophagy activates MAPK/ERK in renal tubular cells, which induces EGR1 to transactivate FGF2. FGF2 is then secreted into the interstitium to stimulate fibroblasts for fibrogenesis.Abbreviation: 3-MA: 3-methyladenine; ACTA2/α-SMA: actin alpha 2, smooth muscle, aorta; ACTB/β-actin: actin, beta; AKI: acute kidney injury; aa: amino acid; ATG/Atg: autophagy related; BUN: blood urea nitrogen; ChIP: chromatin immunoprecipitation; CKD: chronic kidney disease; CM: conditioned medium; COL1A1: collagen, type I, alpha 1; COL4A1: collagen, type IV, alpha 1; CQ: chloroquine; DBA: dolichos biflorus agglutinin; EGR1: early growth response 1; ELK1: ELK1, member of ETS oncogene family; FGF2: fibroblast growth factor 2; FN1: fibronectin 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HAVCR1/KIM-1: hepatitis A virus cellular receptor 1; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2K/MEK: mitogen-activated protein kinase kinase; MAPK: mitogen-activated protein kinase; NFKB: nuclear factor kappa B; PB1: Phox and Bem1; PFT: pifithrin α; PPIB/cyclophilin B: peptidylprolyl isomerase B; RT-qPCR: real time-quantitative PCR; SQSTM1/p62: sequestosome 1; TGFB1/TGF-β1: transforming growth factor beta 1; VIM: vimentin.

Prolonged exposure to mercuric chloride induces oxidative stress-mediated nephrotoxicity in freshwater food fish Channa punctatus

Mercury (Hg) is regarded as a serious hazard to aquatic life and is particularly prevalent in aquatic ecosystems. However, there is little evidence available regarding the toxicity of mercury chloride (HgCl2) in vital organs of fish. This study was conducted to assess the effects of HgCl2 (0.039 mg/L and 0.078 mg/L) on oxidative stress-mediated genotoxicity, poikilocytosis, apoptosis, and renal fibrosis after 15, 30, and 45 days of the exposure period. According to the findings, HgCl2 intoxication in fish resulted in a significantly (P < 0.05) elevated lipid peroxidation (LPO), protein carbonyls (PC), lactate dehydrogenase (LDH) activity levels in kidney tissues and significantly (P < 0.05) increased reactive oxygen species (ROS), poikilocytosis, DNA tail length, and the frequency of apoptotic cells (AC%) in blood cells. Kidney's ultra-structure and histopathology revealed its fibrosis, which was evident by mRNA expression of targeted genes KIM1, NOX4, TGFβ, and NFϏβ. Different indicators of oxidative stress, apoptosis, and genotoxicity were altered in a dose and time-dependent manner, according to a two-way ANOVA analysis. There was a considerable positive link between oxidative stress and kidney fibrosis in the fish Channa punctatus, and it is evident from regression correlation and PCA data analysis. The kidney's ultra-structure evaluation and histopathology both revealed a noticeable fibrosis state. Additionally, a significant (P < 0.05) downregulation in PPARδ reveals that fish body was unable to combat diseases such as kidney fibrosis induced by HgCl2. This study shed fresh light on the mechanisms underlying nephrotoxicity caused by HgCl2 exposure.

Amiloride Reduces Urokinase/Plasminogen-Driven Intratubular Complement Activation in Glomerular Proteinuria

SIGNIFICANCE STATEMENT

Proteinuria predicts accelerated decline in kidney function in CKD. The pathologic mechanisms are not well known, but aberrantly filtered proteins with enzymatic activity might be involved. The urokinase-type plasminogen activator (uPA)-plasminogen cascade activates complement and generates C3a and C5a in vitro / ex vivo in urine from healthy persons when exogenous, inactive, plasminogen, and complement factors are added. Amiloride inhibits uPA and attenuates complement activation in vitro and in vivo . In conditional podocin knockout (KO) mice with severe proteinuria, blocking of uPA with monoclonal antibodies significantly reduces the urine excretion of C3a and C5a and lowers tissue NLRP3-inflammasome protein without major changes in early fibrosis markers. This mechanism provides a link to proinflammatory signaling in proteinuria with possible long-term consequences for kidney function.

BACKGROUND

Persistent proteinuria is associated with tubular interstitial inflammation and predicts progressive kidney injury. In proteinuria, plasminogen is aberrantly filtered and activated by urokinase-type plasminogen activator (uPA), which promotes kidney fibrosis. We hypothesized that plasmin activates filtered complement factors C3 and C5 directly in tubular fluid, generating anaphylatoxins, and that this is attenuated by amiloride, an off-target uPA inhibitor.

METHODS

Purified C3, C5, plasminogen, urokinase, and urine from healthy humans were used for in vitro / ex vivo studies. Complement activation was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and ELISA. Urine and plasma from patients with diabetic nephropathy treated with high-dose amiloride and from mice with proteinuria (podocin knockout [KO]) treated with amiloride or inhibitory anti-uPA antibodies were analyzed.

RESULTS

The combination of uPA and plasminogen generated anaphylatoxins C3a and C5a from intact C3 and C5 and was inhibited by amiloride. Addition of exogenous plasminogen was sufficient for urine from healthy humans to activate complement. Conditional podocin KO in mice led to severe proteinuria and C3a and C5a urine excretion, which was attenuated reversibly by amiloride treatment for 4 days and reduced by >50% by inhibitory anti-uPA antibodies without altering proteinuria. NOD-, LRR- and pyrin domain-containing protein 3-inflammasome protein was reduced with no concomitant effect on fibrosis. In patients with diabetic nephropathy, amiloride reduced urinary excretion of C3dg and sC5b-9 significantly.

CONCLUSIONS

In conditions with proteinuria, uPA-plasmin generates anaphylatoxins in tubular fluid and promotes downstream complement activation sensitive to amiloride. This mechanism links proteinuria to intratubular proinflammatory signaling. In perspective, amiloride could exert reno-protective effects beyond natriuresis and BP reduction.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Increased Activity of a Renal Salt Transporter (ENaC) in Diabetic Kidney Disease, NCT01918488 and Increased Activity of ENaC in Proteinuric Kidney Transplant Recipients, NCT03036748 .

Lineage tracing reveals transient phenotypic adaptation of tubular cells during acute kidney injury

Tubular injury is the hallmark of acute kidney injury (AKI) with a tremendous impact on patients and health-care systems. During injury, any differentiated proximal tubular cell (PT) may transition into a specific injured phenotype, so-called "scattered tubular cell" (STC)-phenotype. To understand the fate of this specific phenotype, we generated transgenic mice allowing inducible, reversible, and irreversible tagging of these cells in a murine AKI model, the unilateral ischemia-reperfusion injury (IRI). For lineage tracing, we analyzed the kidneys using single-cell profiling during disease development at various time points. Labeled cells, which we defined by established endogenous markers, already appeared 8 h after injury and showed a distinct expression set of genes. We show that STCs re-differentiate back into fully differentiated PTs upon the resolution of the injury. In summary, we show the dynamics of the phenotypic transition of PTs during injury, revealing a reversible transcriptional program as an adaptive response during disease.

Bi-functional KIT-PR1P peptides combine with VEGF to protect ischemic kidney in rats by targeting to Kim-1

Introduction

Acute kidney injury (AKI) was a disease with a high mortality mainly caused by renal ischemia/reperfusion injury (I/R). Although the current non-targeted administration of vascular endothelial growth factor (VEGF) for AKI had been revealed to facilitate the recovery of renal I/R, how to targeted deliver VEGF and to retain it efficiently in the ischemic kidney was critical for its clinical application.

Methods

In present study, bi-functional KIT-PR1P peptides were constructed which bond VEGF through PR1P domain, and targeted ischemic kidney through KIT domain to interact with biomarker of AKI-kidney injury molecule-1 (Kim-1). Then the targeted and therapeutic effects of KIT-PR1P/VEGF in AKI was explored in vitro and in vivo.

Results

The results showed KIT-PR1P exhibited better angiogenic capacity and targeting ability to hypoxia HK-2 cells with up-regulated Kim-1 in vitro. When KIT-PR1P/VEGF was used for the treatment of renal I/R through intravenous administration in vivo, KIT-PR1P could guide VEGF and retain its effective concentration in ischemic kidney. In addition, KIT-PR1P/VEGF promoted angiogenesis, alleviated renal tubular injury and fibrosis, and finally promoted functional recovery of renal I/R.

Conclusion

These results indicated that the bi-functional KIT-PR1P peptides combined with VEGF would be a promising strategy for the treatment of AKI by targeting to Kim-1.

Novel Perspectives in Chronic Kidney Disease-Specific Cardiovascular Disease

Chronic kidney disease (CKD) affects > 10% of the global adult population and significantly increases the risk of cardiovascular disease (CVD), which remains the leading cause of death in this population. The development and progression of CVD-compared to the general population-is premature and accelerated, manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. CKD and CV disease combine to cause multimorbid cardiorenal syndrome (CRS) due to contributions from shared risk factors, including systolic hypertension, diabetes mellitus, obesity, and dyslipidemia. Additional neurohormonal activation, innate immunity, and inflammation contribute to progressive cardiac and renal deterioration, reflecting the strong bidirectional interaction between these organ systems. A shared molecular pathophysiology-including inflammation, oxidative stress, senescence, and hemodynamic fluctuations characterise all types of CRS. This review highlights the evolving paradigm and recent advances in our understanding of the molecular biology of CRS, outlining the potential for disease-specific therapies and biomarker disease detection.

Potential Alternative Receptors for SARS-CoV-2-Induced Kidney Damage: TLR-4, KIM-1/TIM-1, and CD147

Kidney damage in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can occur even in patients with no underlying kidney disease. Signs of kidney problems can progress to a state that demands dialysis and hampering recovery. Although not without controversy, emerging evidence implicates direct infectivity of SARS-CoV-2 in the kidney. At the early stage of the pandemic, consideration was mainly on the well-recognized angiotensin-converting enzyme 2 (ACE2) receptor as being the site for viral interaction and subsequent cellular internalization. Despite the abundance of ACE2 receptors in the kidneys, researchers have expanded beyond ACE2 and identified novel viral entry pathways that could be advantageously explored as therapeutic targets. This review presents the potential involvement of toll-like receptor 4 (TLR-4), kidney injury molecule-1/T cell immunoglobulin mucin domain 1 (KIM-1/TIM-1), and cluster of differentiation 147 (CD147) in SARS-CoV-2-associated renal damage. In this context, we address the unresolved issues surrounding SARS-CoV-2 renal infectivity.

Cep120 is essential for kidney stromal progenitor cell growth and differentiation

Mutations in genes that disrupt centrosome structure or function can cause congenital kidney developmental defects and lead to fibrocystic pathologies. Yet, it is unclear how defective centrosome biogenesis impacts renal progenitor cell physiology. Here, we examined the consequences of impaired centrosome duplication on kidney stromal progenitor cell growth, differentiation, and fate. Conditional deletion of the ciliopathy gene Cep120, which is essential for centrosome duplication, in the stromal mesenchyme resulted in reduced abundance of interstitial lineages including pericytes, fibroblasts and mesangial cells. These phenotypes were caused by a combination of delayed mitosis, activation of the mitotic surveillance pathway leading to apoptosis, and changes in both Wnt and Hedgehog signaling that are key for differentiation of stromal cells. Cep120 ablation resulted in small hypoplastic kidneys with medullary atrophy and delayed nephron maturation. Finally, Cep120 and centrosome loss in the interstitium sensitized kidneys of adult mice, causing rapid fibrosis after renal injury via enhanced TGF-β/Smad3-Gli2 signaling. Our study defines the cellular and developmental defects caused by loss of Cep120 and aberrant centrosome biogenesis in the embryonic kidney stroma.

Potential Biomarkers for the Earlier Diagnosis of Kidney and Liver Damage in Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is an inherited metabolic disorder associated with complications including kidney failure and hepatocellular carcinoma, probably caused by elevations in the porphyrin precursors porphobilinogen (PBG) and delta-aminolevulinic acid (ALA). This study explored differences in modern biomarkers for renal and hepatic damage between AIP patients and controls. Urine PBG testing, kidney injury panels, and liver injury panels, including both routine and modern biomarkers, were performed on plasma and urine samples from AIP cases and matched controls (50 and 48 matched pairs, respectively). Regarding the participants' plasma, the AIP cases had elevated kidney injury marker-1 (KIM-1, p = 0.0002), fatty acid-binding protein-1 (FABP-1, p = 0.04), and α-glutathione S-transferase (α-GST, p = 0.001) compared to the matched controls. The AIP cases with high PBG had increased FABP-1 levels in their plasma and urine compared to those with low PBG. In the AIP cases, KIM-1 correlated positively with PBG, CXCL10, CCL2, and TCC, and the liver marker α-GST correlated positively with IL-13, CCL2, and CCL4 (all p < 0.05). In conclusion, KIM-1, FABP-1, and α-GST could represent potential early indicators of renal and hepatic damage in AIP, demonstrating associations with porphyrin precursors and inflammatory markers.

An analysis of the relationship between donor and recipient biomarkers and kidney graft function, dysfunction, and rejection

BACKGROUND

The study aimed to find predictive biomarkers to evaluate donor kidney function to predict graft dysfunction as well as to assess an early signs of acute graft rejection.

METHOD

Twenty-seven deceased donors and 54 recipients who underwent a successful kidney transplantation were enrolled in the study. An assessment was made in serum and urine from donors and recipients to measure the following biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), tissue inhibitor of metalloproteinase 2 (TIMP-2) and urinary N-acetyl-b-D-glucosaminidase (uNAG). These biomarkers were used to establish a model for predicting a reduced graft function (RGF) classified as either a delayed or slow graft function.

RESULT

Our analysis suggest that out of four tested biomarkers, the serum TIMP-2 and uNAG levels of the donors had a predictive value for RGF; the area under the receiver operating characteristic curves (AUROC) of serum TIMP-2 and uNAG were 0.714 and 0.779, respectively. The combined best fitting prediction model of serum TIMP-2, uNAG, and creatinine levels was better in predicting RGF than the serum creatinine level alone. In addition, the recipient serum TIMP-2 level on the third day post-transplantation (D3) was associated with the estimated glomerular filtration rate (eGFR) on the seventh day post-transplantation (D7; OR 1.119, 95% CI 1.016-1.233, p = 0.022). Furthermore, the ROC curve value revealed that the AUROC of TIMP-2 on D3 was 0.99 (95% CI 0.97-1, p < 0.001), and this was the best predictive value of the renal function on D7.

CONCLUSIONS

Donor serum TIMP-2 and uNAG levels are useful predictive biomarkers because they can provide the donor-based prediction for RGF.

Biotherapy of experimental acute kidney injury: emerging novel therapeutic strategies

Acute kidney injury (AKI) is a complex and heterogeneous disease with high incidence and mortality, posing a serious threat to human life and health. Usually, in clinical practice, AKI is caused by crush injury, nephrotoxin exposure, ischemia-reperfusion injury, or sepsis. Therefore, most AKI models for pharmacological experimentation are based on this. The current research promises to develop new biological therapies, including antibody therapy, non-antibody protein therapy, cell therapy, and RNA therapy, that could help mitigate the development of AKI. These approaches can promote renal repair and improve systemic hemodynamics after renal injury by reducing oxidative stress, inflammatory response, organelles damage, and cell death, or activating cytoprotective mechanisms. However, no candidate drugs for AKI prevention or treatment have been successfully translated from bench to bedside. This article summarizes the latest progress in AKI biotherapy, focusing on potential clinical targets and novel treatment strategies that merit further investigation in future pre-clinical and clinical studies.

A Brief Review of Diagnostic Techniques and Clinical Management in Chronic Kidney Disease

Given its increasing incidence and detrimental effects on life expectancy and quality of life, chronic kidney disease (CKD) is a significant worldwide health concern. This review article provides a complete summary of current information on the diagnosis and management of CKD, focusing on recent advances and innovative approaches. The article discusses the most current findings on CKD risk assessment, emphasizing the need for early diagnosis utilizing better biomarkers and predictive models. A rigorous examination of diagnostic tools such as albumin-to-creatinine ratio (ACR) in urine and glomerular filtration rate (GFR) highlights their importance in determining CKD phases and etiologies. In terms of therapy, the study explores evidence-based techniques to reduce the development of CKD, such as enhanced blood pressure control, glycemic management in diabetic patients, dietary changes, and renin-angiotensin-aldosterone system (RAAS) blocking. Novel therapeutic approaches, including antifibrotic and precision medicine, are evaluated regarding their potential to revolutionize CKD treatment. The study also underlines the need for multidisciplinary therapy and patient education to achieve the best possible CKD patient outcomes. It also highlights the financial and social effects of CKD, highlighting the importance of early treatment to lower medical expenses and enhance the patient's standard of living. Finally, this review article provides a comprehensive update on CKD diagnosis and treatment, highlighting present successes alongside future potential. It is a valuable resource for healthcare professionals, academics, and policymakers who want to improve CKD treatment methods and patient outcomes.

Inhibition of retinoic acid signaling in proximal tubular epithelial cells protects against acute kidney injury

Retinoic acid receptor (RAR) signaling is essential for mammalian kidney development but, in the adult kidney, is restricted to occasional collecting duct epithelial cells. We now show that there is widespread reactivation of RAR signaling in proximal tubular epithelial cells (PTECs) in human sepsis-associated acute kidney injury (AKI) and in mouse models of AKI. Genetic inhibition of RAR signaling in PTECs protected against experimental AKI but was unexpectedly associated with increased expression of the PTEC injury marker Kim1. However, the protective effects of inhibiting PTEC RAR signaling were associated with increased Kim1-dependent apoptotic cell clearance, or efferocytosis, and this was associated with dedifferentiation, proliferation, and metabolic reprogramming of PTECs. These data demonstrate the functional role that reactivation of RAR signaling plays in regulating PTEC differentiation and function in human and experimental AKI.

Role of MCP-1/CCR2 axis in renal fibrosis: Mechanisms and therapeutic targeting

Renal fibrosis is a common pathological manifestation in various chronic kidney diseases. Inflammation plays a central role in renal fibrosis development. Owing to their significant participation in inflammation and autoimmunity, chemokines have always been the hot spot and focus of scientific research and clinical intervention. Among the chemokines, monocyte chemoattractant protein-1 (MCP-1), also known as C-C motif chemokine ligand 2, together with its main receptor C-C chemokine receptor type 2 (CCR2) are important chemokines in renal fibrosis. The MCP-1/CCR2 axis is activated when MCP-1 binds to CCR2. Activation of MCP-1/CCR2 axis can induce chemotaxis and activation of inflammatory cells, and initiate a series of signaling cascades in renal fibrosis. It mediates and promotes renal fibrosis by recruiting monocyte, promoting the activation and transdifferentiation of macrophages. This review summarizes the complex physical processes of MCP-1/CCR2 axis in renal fibrosis and addresses its general mechanism in renal fibrosis by using specific examples, together with the progress of targeting MCP-1/CCR2 in renal fibrosis with a view to providing a new direction for renal fibrosis treatment.

The Fatty Kidney and Beyond: A Silent Epidemic

As the prevalence of obesity rises in the United States, so does the incidence of obesity-related kidney disease. Obesity itself is an independent risk factor for chronic kidney disease where the pathophysiology is complex, involving altered hemodynamics, renin-angiotensin-aldosterone system overactivation, and adipokines leading to inflammation and fibrosis. Obesity-related kidney disease comprises both obesity-related glomerulopathy and fatty kidney disease. Obesity-related glomerulopathy is a consequence of glomerular hyperfiltration and often presents clinically with subnephrotic proteinuria and pathologically with glomerulomegaly with or without focal glomerulosclerosis. Fatty kidney disease is the effect of renal ectopic fat contributing to chronic kidney disease. Whether the renal ectopic fat is a distinct clinical entity or a pathologic mechanism contributing to obesity-related glomerulopathy, the treatment paradigm of weight and proteinuria reduction remains the same. We present the pathophysiology behind obesity-related kidney disease, clinical outcomes, and treatment strategies, which include lifestyle interventions, use of renin-angiotensin-aldosterone system inhibitors, glucagon-like peptide 1 receptor agonists, sodium-glucose co-transporter-2 inhibitors, and bariatric surgery. With old and novel therapeutics, we are attempting to stave off the silent epidemic that obesity-related kidney disease is becoming.

Radiation nephropathy: Mechanisms of injury and recovery in a murine model

BACKGROUND

Radiation nephropathy (RN) can be a severe late complication for patients treated with radiotherapy (RT) targeting abdominal and paraspinal tumors. Recent studies investigating the mechanisms of RT-mediated injury in the kidney have demonstrated that RT disrupts the cellular integrity of renal podocytes leading to cell death and loss of renal function.

AIM

To determine if RT-induced renal dysfunction is associated with alterations in podocyte and glomerular function, and whether RT-induced podocyte alterations were associated with changes in the glomerular basement membrane (GBM).

METHODS

C57BL/6 mice were treated with focal bilateral X-irradiation using a single dose (SD) of 4 Gy, 10 Gy, or 14 Gy or fractionated dosing (FD) of 5x6Gy or 24x2Gy. Then, 10-40 weeks after RT parameters of renal function were measured, along with glomerular filtration rate (GFR) and glomerular histology, as well as ultrastructural changes in GBM by transmission electron microscopy.

RESULTS

RT treatment resulted in persistent changes in renal function beginning at 10 weeks with little recovery up to 40 weeks post RT. Dose dependent changes were seen with increasing SD but no functional sparing was evident after FD. RT-induced loss of renal function was associated with expansion of the GBM and significant increases in foot process width, and associated with significant reduction in GFR, podocyte loss, and renal fibrosis.

CONCLUSION

For the first time, these data show that expansion of the GBM is one consequence of radiation injury, and disarrangement of the GBM might be associated with the death of podocytes. These data shed new light on the role podocyte injury and GBM in RT-induced renal dysfunction.

Transcriptome analysis of renal ischemia/reperfusion (I/R) injury in BAFF and BAFF-R deficient mice

Acute kidney injury (AKI) accompanies with high morbidity and mortality. Incomplete renal recovery can lead to chronic and finally end-stage kidney disease, which results in the requirement of lifelong dialysis or kidney transplantation. Consequently, finding predictive biomarker and therefore developing preventive therapeutic approaches is an urgent need. For this purpose, a better understanding of the mechanism underlying AKI is necessary. The cytokine BAFF (B cell activating factor) is related to AKI by supporting B cells, which in turn play an important role in inflammatory processes and the production of antibodies. In our study, we investigated the role of BAFF and its receptor BAFF-R in the early phase of AKI. Therefore, we performed the well-established ischemia/reperfusion (I/R) model in BAFF (B6.129S2-Tnfsf13btm1Msc/J) and BAFF-R (B6(Cg)-Tnfrsf13ctm1Mass/J) deficient mice. Transcriptome of ischemic and contralateral control kidneys was analyzed and compared to wildtype littermates. We detected the upregulation of Lcn2, Lyz2, Cd44, Fn1 and Il1rn in ischemic kidneys as well as the downregulation of Kl. Furthermore, we revealed different expression patterns in BAFF and BAFF-R knockout mice. Compared to wildtype littermates, up- and downregulation of each investigated gene were higher in BAFF-R knockout and lower in BAFF knockout. Our findings indicate a positive impact of BAFF knockout in early phase of AKI, while BAFF-R knockout seems to worsen I/R injury. In addition, our study shows for the first time a remarkable renal upregulation of Lyz2 in a murine I/R model. Therefore, we consider Lyz2 as conceivable predictive or early biomarker in case of I/R and AKI.

Kidney injury molecule 1 (KIM-1): a potential biomarker of acute kidney injury and tubulointerstitial injury in patients with ANCA-glomerulonephritis

Background

Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein expressed by proximal tubular cells, recognized as an early, sensitive and specific urinary biomarker for kidney injury. Blood KIM-1 was recently associated with the severity of acute and chronic kidney damage but its value in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis with glomerulonephritis (ANCA-GN) has not been studied. Thus, we analyzed its expression at ANCA-GN diagnosis and its relationship with clinical presentation, kidney histopathology and early outcomes.

Methods

We assessed KIM-1 levels and other pro-inflammatory molecules (C-reactive protein, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1 and pentraxin 3) at ANCA-GN diagnosis and after 6 months in patients included in the Maine-Anjou registry, which gathers data patients from four French Nephrology Centers diagnosed since January 2000.

Results

Blood KIM-1 levels were assessed in 54 patients. Levels were elevated at diagnosis and decreased after induction remission therapy. KIM-1 was associated with the severity of renal injury at diagnosis and the need for kidney replacement therapy. In opposition to other pro-inflammatory molecules, KIM-1 correlated with the amount of acute tubular necrosis and interstitial fibrosis/tubular atrophy (IF/TA) on kidney biopsy, but not with interstitial infiltrate or with glomerular involvement. In multivariable analysis, elevated KIM-1 predicted initial estimated glomerular filtration rate (β = -19, 95% CI -31, -7.6, P = .002).

Conclusion

KIM-1 appears as a potential biomarker for acute kidney injury and for tubulointerstitial injury in ANCA-GN. Whether KIM-1 is only a surrogate marker or is a key immune player in ANCA-GN pathogenesis remain to be determined.

Dnajb11-Kidney Disease Develops from Reduced Polycystin-1 Dosage but not Unfolded Protein Response in Mice

SIGNIFICANCE STATEMENT

Heterozygous DNAJB11 mutation carriers manifest with small cystic kidneys and renal failure in adulthood. Recessive cases with prenatal cystic kidney dysplasia were recently described. Our in vitro and mouse model studies investigate the proposed disease mechanism as an overlap of autosomal-dominant polycystic kidney disease and autosomal-dominant tubulointerstitial kidney disease pathogenesis. We find that DNAJB11 loss impairs cleavage and maturation of the autosomal-dominant polycystic kidney disease protein polycystin-1 (PC1) and results in dosage-dependent cyst formation in mice. We find that Dnajb11 loss does not activate the unfolded protein response, drawing a fundamental contrast with the pathogenesis of autosomal-dominant tubulointerstitial kidney disease. We instead propose that fibrosis in DNAJB11 -kidney disease may represent an exaggerated response to polycystin-dependent cysts.

BACKGROUND

Patients with heterozygous inactivating mutations in DNAJB11 manifest with cystic but not enlarged kidneys and renal failure in adulthood. Pathogenesis is proposed to resemble an overlap of autosomal-dominant polycystic kidney disease (ADPKD) and autosomal-dominant tubulointerstitial kidney disease (ADTKD), but this phenotype has never been modeled in vivo . DNAJB11 encodes an Hsp40 cochaperone in the endoplasmic reticulum: the site of maturation of the ADPKD polycystin-1 (PC1) protein and of unfolded protein response (UPR) activation in ADTKD. We hypothesized that investigation of DNAJB11 would shed light on mechanisms for both diseases.

METHODS

We used germline and conditional alleles to model Dnajb11 -kidney disease in mice. In complementary experiments, we generated two novel Dnajb11-/- cell lines that allow assessment of PC1 C-terminal fragment and its ratio to the immature full-length protein.

RESULTS

Dnajb11 loss results in a profound defect in PC1 cleavage but with no effect on other cystoproteins assayed. Dnajb11-/- mice are live-born at below the expected Mendelian ratio and die at a weaning age with cystic kidneys. Conditional loss of Dnajb11 in renal tubular epithelium results in PC1 dosage-dependent kidney cysts, thus defining a shared mechanism with ADPKD. Dnajb11 mouse models show no evidence of UPR activation or cyst-independent fibrosis, which is a fundamental distinction from typical ADTKD pathogenesis.

CONCLUSIONS

DNAJB11 -kidney disease is on the spectrum of ADPKD phenotypes with a PC1-dependent pathomechanism. The absence of UPR across multiple models suggests that alternative mechanisms, which may be cyst-dependent, explain the renal failure in the absence of kidney enlargement.

Vitamin A and retinoid signaling in the kidneys

Vitamin A (VA, retinol) and its metabolites (commonly called retinoids) are required for the proper development of the kidney during embryogenesis, but retinoids also play key roles in the function and repair of the kidney in adults. Kidneys filter 180-200 liters of blood per day and each kidney contains approximately 1 million nephrons, which are often referred to as the 'functional units' of the kidney. Each nephron consists of a glomerulus and a series of tubules (proximal tubule, loop of Henle, distal tubule, and collecting duct) surrounded by a network of capillaries. VA is stored in the liver and converted to active metabolites, most notably retinoic acid (RA), which acts as an agonist for the retinoic acid receptors ((RARs α, β, and γ) to regulate gene transcription. In this review we discuss some of the actions of retinoids in the kidney after injury. For example, in an ischemia-reperfusion model in mice, injury-associated loss of proximal tubule (PT) differentiation markers occurs, followed by re-expression of these differentiation markers during PT repair. Notably, healthy proximal tubules express ALDH1a2, the enzyme that metabolizes retinaldehyde to RA, but transiently lose ALDH1a2 expression after injury, while nearby myofibroblasts transiently acquire RA-producing capabilities after injury. These results indicate that RA is important for renal tubular injury repair and that compensatory mechanisms exist for the generation of endogenous RA by other cell types upon proximal tubule injury. ALDH1a2 levels also increase in podocytes, epithelial cells of the glomeruli, after injury, and RA promotes podocyte differentiation. We also review the ability of exogenous, pharmacological doses of RA and receptor selective retinoids to treat numerous kidney diseases, including kidney cancer and diabetic kidney disease, and the emerging genetic evidence for the importance of retinoids and their receptors in maintaining or restoring kidney function after injury. In general, RA has a protective effect on the kidney after various types of injuries (eg. ischemia, cytotoxic actions of chemicals, hyperglycemia related to diabetes). As more research into the actions of each of the three RARs in the kidney is carried out, a greater understanding of the actions of vitamin A is likely to lead to new insights into the pathology of kidney disorders and the development of new therapies for kidney diseases.

Leptospirosis kidney disease: Evolution from acute to chronic kidney disease

Leptospirosis is a neglected bacterial disease caused by leptospiral infection that carries a substantial mortality risk in severe cases. Research has shown that acute, chronic, and asymptomatic leptospiral infections are closely linked to acute and chronic kidney disease (CKD) and renal fibrosis. Leptospires affect renal function by infiltrating kidney cells via the renal tubules and interstitium and surviving in the kidney by circumventing the immune system. The most well-known pathogenic molecular mechanism of renal tubular damage caused by leptospiral infection is the direct binding of the bacterial outer membrane protein LipL32 to toll-like receptor-2 expressed in renal tubular epithelial cells (TECs) to induce intracellular inflammatory signaling pathways. These pathways include the production of tumor necrosis factor (TNF)-α and nuclear factor kappa activation, resulting in acute and chronic leptospirosis-related kidney injury. Few studies have investigated the relationship between acute and chronic renal diseases and leptospirosis and further evidence is necessary. In this review, we intend to discuss the roles of acute kidney injury (AKI) to/on CKD in leptospirosis. This study reviews the molecular pathways underlying the pathogenesis of leptospirosis kidney disease, which will assist in concentrating on potential future research directions.

Renoprotective impact of Dapagliflozin and Mulberry extracts toward Fr-STZ induced diabetic nephropathy in rats: Biochemical and Molecular aspects.. [DOI: 10.21203/rs.3.rs-3186379/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Among the most typical reasons of end-stage renal disease (ESRD) is diabetic nephropathy (DN), which is also rated as a major microvascular complication of diabetes mellitus. The existent study looked at the impact of dapagliflozin, mulberry fruit and leaves extracts and their combination on the kidney of diabetic rats. To induce diabetic nephropathy, experimental rats were supplied with 10% fructose (Fr) in drinking water for the first two weeks. Each Fr-fed animal received an intraperitoneal injection of a low single dose of STZ (40 mg/kg) after being fasted for the whole night. Sixty albino rats were separated into six equivalent groups. Group I control rats, group II untreated diabetic rats, group III–VI are diabetic groups; received dapagliflozin for 4 weeks, mulberry fruit extract, mulberry leaves extract and combination of DAPA, MFE and MLE, respectively for 6 weeks. Untreated diabetic rats exhibited considerable rise in serum glucose, urea, creatinine, KIM-1, β2-MG, TNF-α, and TGβ1 levels compared to control rats, while treated diabetic ones manifested significant decrease in these measures in contrast to the untreated diabetic rats. Also, renal tissue IL-6, NF-κB and NADPH oxidase manifested significant increase in untreated diabetic rats, while treated groups revealed significant decline in comparison to the untreated one. DAPA and mulberry fruit and leaves extracts optimized IL-10 and renin expression in renal tissue. Histopathological picture of kidney, revealed significant improvement in rats received DAPA and mulberry extracts compared to untreated diabetic rats. It could be concluded that, DAPA, mulberry fruits and leaves extracts alleviated diabetic nephropathy complications. Therefore, combining these ingredients in a supplement may be promising for modulating diabetic nephropathy.

Longitudinal tracking of acute kidney injury reveals injury propagation along the nephron

Acute kidney injury (AKI) is an important risk factor for chronic kidney disease (CKD), but the underlying mechanisms of failed tubule repair and AKI-CKD transition are incompletely understood. In this study, we aimed for dynamic tracking of tubule injury and remodeling to understand if focal injury upon AKI may spread over time. Here, we present a model of AKI, in which we rendered only half of the kidney ischemic. Using serial intravital 2-photon microscopy and genetic identification of cycling cells, we tracked dynamic tissue remodeling in post- and non-ischemic kidney regions simultaneously and over 3 weeks. Spatial and temporal analysis of cycling cells relative to initial necrotic cell death demonstrated pronounced injury propagation and expansion into non-necrotic tissue regions, which predicted tubule atrophy with epithelial VCAM1 expression. In summary, our longitudinal analyses of tubule injury, remodeling, and fate provide important insights into AKI pathology.

Inhibition of Retinoic Acid Signaling in Proximal Tubular Epithelial cells Protects against Acute Kidney Injury by Enhancing Kim-1-dependent Efferocytosis

Retinoic acid receptor (RAR) signaling is essential for mammalian kidney development, but in the adult kidney is restricted to occasional collecting duct epithelial cells. We now show there is widespread reactivation of RAR signaling in proximal tubular epithelial cells (PTECs) in human sepsis-associated acute kidney injury (AKI), and in mouse models of AKI. Genetic inhibition of RAR signaling in PTECs protects against experimental AKI but is associated with increased expression of the PTEC injury marker, Kim-1. However, Kim-1 is also expressed by de-differentiated, proliferating PTECs, and protects against injury by increasing apoptotic cell clearance, or efferocytosis. We show that the protective effect of inhibiting PTEC RAR signaling is mediated by increased Kim-1 dependent efferocytosis, and that this is associated with de-differentiation, proliferation, and metabolic reprogramming of PTECs. These data demonstrate a novel functional role that reactivation of RAR signaling plays in regulating PTEC differentiation and function in human and experimental AKI.

Graphical abstract

Elucidating environmental factors and their combined effects on CKDu in Sri Lanka using zebrafish

Chronic kidney disease with uncertain etiology (CKDu) in Sri Lanka has attracted much attention as a global health issue. However, how environmental factors in local drinking water induce kidney damage in organisms is still elusive. We investigated multiple environmental factors including water hardness and fluoride (HF), heavy metals (HM), microcystin-LR (MC-LR), and their combined exposure (HFMM) to elucidate their toxic effects on CKDu risk in zebrafish. Acute exposure affected renal development and inhibited the fluorescence of Na, K-ATPase alpha1A4:GFP zebrafish kidney. Chronic exposure influenced the body weight of both genders of adult fish and induced kidney damage by histopathological analyses. Furthermore, the exposure significantly disturbed differential expression genes (DEGs), diversity and richness of gut microbiota, and critical metabolites related to renal functions. The transcriptomic analysis revealed that kidney-related DEGs were linked with renal cell carcinoma, proximal tubule bicarbonate reclamation, calcium signaling pathway, and HIF-1 signaling pathway. The significantly disrupted intestinal microbiota was closely related to the environmental factors and H&E score, which demonstrated the mechanisms of kidney risks. Notably, the Spearman correlation analysis indicated that the changed bacteria such as Pseudomonas, Paracoccus, and ZOR0006, etc were significantly connected to the DEGs and metabolites. Therefore, the assessment of multiple environmental factors provided new insights on "bio-markers" as potential therapies of the target signaling pathways, metabolites, and gut bacteria to monitor or protect residents from CKDu.

Intrinsic TGF-β signaling attenuates proximal tubule mitochondrial injury and inflammation in chronic kidney disease

Excessive TGF-β signaling and mitochondrial dysfunction fuel chronic kidney disease (CKD) progression. However, inhibiting TGF-β failed to impede CKD in humans. The proximal tubule (PT), the most vulnerable renal segment, is packed with giant mitochondria and injured PT is pivotal in CKD progression. How TGF-β signaling affects PT mitochondria in CKD remained unknown. Here, we combine spatial transcriptomics and bulk RNAseq with biochemical analyses to depict the role of TGF-β signaling on PT mitochondrial homeostasis and tubulo-interstitial interactions in CKD. Male mice carrying specific deletion of Tgfbr2 in the PT have increased mitochondrial injury and exacerbated Th1 immune response in the aristolochic acid model of CKD, partly, through impaired complex I expression and mitochondrial quality control associated with a metabolic rewiring toward aerobic glycolysis in the PT cells. Injured S3T2 PT cells are identified as the main mediators of the maladaptive macrophage/dendritic cell activation in the absence of Tgfbr2. snRNAseq database analyses confirm decreased TGF-β receptors and a metabolic deregulation in the PT of CKD patients. This study describes the role of TGF-β signaling in PT mitochondrial homeostasis and inflammation in CKD, suggesting potential therapeutic targets that might be used to mitigate CKD progression.

Low Level Mancozeb Exposure Causes Copper Bioaccumulation in the Renal Cortex of Rats Leading to Tubular Injury

Mancozeb is a widely-used, broad-spectrum contact dithiocarbamate fungicide. Dithiocarbamates are known to trans-chelate metals. This study was designed to evaluate the potential of Mancozeb to mobilize and bioaccumulate essential trace metals in various tissues. Long-Evans rats were orally gavaged with 0, 50, or 100mg/kg/day of Mancozeb for 28 days. Mancozeb caused a significant increase in copper and manganese in the hippocampus and manganese in the liver. Exceedingly higher level of copper was detected in the renal cortex using ICP-OES in both dose groups. This was confirmed histologically in the tubular epithelial cells. In addition, copper-associated protein levels were also increased. Copper bioaccumulation in the renal cortex was accompanied by oxidative damage and tubular insult indicated by increased 4-HNE, KIM-1, and NGAL immunoreactivity. These findings demonstrate that low-dose Mancozeb exposure is a potential risk for kidney injury due to copper overload and warrants further in vivo and human population-based investigations.

KIM-1 augments hypoxia-induced tubulointerstitial inflammation through uptake of small extracellular vesicles by tubular epithelial cells

Tubular epithelial cells (TECs) exposed to hypoxia incite tubulointerstitial inflammation (TII), while the exact mechanism is unclear. In this study, we identified that hypoxia evoked tubule injury as evidenced by tubular hypoxia-inducible factor-1α and kidney injury molecule-1 (KIM-1) expression and that renal small extracellular vesicle (sEV) production was increased with the development of TII after ischemia-reperfusion injury (IRI). Intriguingly, KIM-1-positive tubules were surrounded by macrophages and co-localized with sEVs. In vitro, KIM-1 expression and sEV release were increased in hypoxic TECs and the hypoxia-induced inflammatory response was ameliorated when KIM-1 or Rab27a, a master regulator of sEV secretion, was silenced. Furthermore, KIM-1 was identified to mediate hypoxic TEC-derived sEV (Hypo-sEV) uptake by TECs. Phosphatidylserine (PS), a ligand of KIM-1, was present in Hypo-sEVs as detected by nanoflow cytometry. Correspondingly, the inflammatory response induced by exogenous Hypo-sEVs was attenuated when KIM-1 was knocked down. In vivo, exogenous-applied Hypo-sEVs localized to KIM-1-positive tubules and exacerbated TII in IRI mice. Our study demonstrated that KIM-1 expressed by injured tubules mediated sEV uptake via recognizing PS, which participated in the amplification of tubule inflammation induced by hypoxia, leading to the development of TII in ischemic acute kidney injury.

Impaired centrosome biogenesis in kidney stromal progenitors reduces abundance of interstitial lineages and accelerates injury-induced fibrosis

Defective centrosome function can disrupt embryonic kidney development, by causing changes to the renal interstitium that leads to fibrocystic disease pathologies. Yet, it remains unknown how mutations in centrosome genes impact kidney interstitial cells. Here, we examined the consequences of defective centrosome biogenesis on stromal progenitor cell growth, differentiation and fate. Conditional deletion of Cep120 , a ciliopathy gene essential for centrosome duplication, in the stromal mesenchyme resulted in reduced abundance of pericytes, interstitial fibroblasts and mesangial cells. This was due to delayed mitosis, increased apoptosis, and changes in Wnt and Hedgehog signaling essential for differentiation of stromal lineages. Cep120 ablation resulted in hypoplastic kidneys with medullary atrophy and delayed nephron maturation. Finally, centrosome loss in the interstitium sensitized kidneys of adult mice, causing rapid fibrosis via enhanced TGF-β/Smad3-Gli2 signaling after renal injury. Our study defines the cellular and developmental defects caused by centrosome dysfunction in embryonic kidney stroma.

Highlights

Defective centrosome biogenesis in kidney stroma causes:Reduced abundance of stromal progenitors, interstitial and mesangial cell populationsDefects in cell-autonomous and paracrine signalingAbnormal/delayed nephrogenesis and tubular dilationsAccelerates injury-induced fibrosis via defective TGF-β/Smad3-Gli2 signaling axis.

Neuraminidase 1 promotes renal fibrosis development in male mice

The functions of the influenza virus neuraminidase has been well documented but those of the mammalian neuraminidases remain less explored. Here, we characterize the role of neuraminidase 1 (NEU1) in unilateral ureteral obstruction (UUO) and folic acid (FA)-induced renal fibrosis mouse models. We find that NEU1 is significantly upregulated in the fibrotic kidneys of patients and mice. Functionally, tubular epithelial cell-specific NEU1 knockout inhibits epithelial-to-mesenchymal transition, inflammatory cytokines production, and collagen deposition in mice. Conversely, NEU1 overexpression exacerbates progressive renal fibrosis. Mechanistically, NEU1 interacts with TGFβ type I receptor ALK5 at the 160-200aa region and stabilizes ALK5 leading to SMAD2/3 activation. Salvianolic acid B, a component of Salvia miltiorrhiza, is found to strongly bind to NEU1 and effectively protect mice from renal fibrosis in a NEU1-dependent manner. Collectively, this study characterizes a promotor role for NEU1 in renal fibrosis and suggests a potential avenue of targeting NEU1 to treat kidney diseases.

Urinary KIM-1 is not correlated with gestational age among 5-year-old children born prematurely

Background

Preterm birth is associated with decreased nephron endowment. Currently, there is no reliable non-invasive biomarker to identify or monitor decreased nephron number in at-risk patients. Urinary Kidney Injury Molecule-1 (KIM-1) is a biomarker of acute and chronic renal injury. We measured urinary KIM-1 among a wide array of other potential biomarkers.

Methods

We conducted an ambispective cohort study of 5-years-old children born prematurely and healthy controls identified from city schools. Detailed anthropometrics, renal ultrasound dimensions, and biochemical parameters were measured. Urinary KIM-1 was measured using Luminex® technology. Age independent z-scores were calculated and compared. Spearman correlations were used for estimating the association between measures and KIM-1.

Results

We enrolled 129 children, 97 (75.2%) born pre-term and 32 (24.8%) healthy controls born at full-term. Pre-term patients had significantly lower weight and body surface area than controls. Pre-term patients and controls did not differ in current age, sex, race, height, blood pressure, urinary sodium, fractional sodium excretion, serum creatinine and estimated GFR. All spearman correlation between KIM-1 and gestational age, renal and serum measurements were weak without statistical significance.

Conclusion

In 5-year-old children born prematurely, KIM-1 was not correlated with gestational age. Further prospective studies need to confirm this finding.

Urinary Biomarkers in a Living Donor Kidney Transplantation Cohort—Predictive Value on Graft Function

Early non-invasive detection and prediction of graft function after kidney transplantation is essential since interventions might prevent further deterioration. The aim of this study was to analyze the dynamics and predictive value of four urinary biomarkers: kidney injury molecule-1 (KIM-1), heart-type fatty acid binding protein (H-FABP), N-acetyl-β-D-glucosaminidase (NAG), and neutrophil gelatinase-associated lipocalin (NGAL) in a living donor kidney transplantation (LDKT) cohort. Biomarkers were measured up to 9 days after the transplantation of 57 recipients participating in the VAPOR-1 trial. Dynamics of KIM-1, NAG, NGAL, and H-FABP significantly changed over the course of 9 days after transplantation. KIM-1 at day 1 and NAG at day 2 after transplantation were significant predictors for the estimated glomerular filtration rate (eGFR) at various timepoints after transplantation with a positive estimate (p < 0.05), whereas NGAL and NAG at day 1 after transplantation were negative significant predictors (p < 0.05). Multivariable analysis models for eGFR outcome improved after the addition of these biomarker levels. Several donor, recipient and transplantation factors significantly affected the baseline of urinary biomarkers. In conclusion, urinary biomarkers are of added value for the prediction of graft outcome, but influencing factors such as the timing of measurement and transplantation factors need to be considered.

Localization and characterization of proenkephalin-A as a potential biomarker for kidney disease in murine and human kidneys

INTRODUCTION

Exact measurement of renal function is essential for the treatment of patients. Elevated serum-creatinine levels, while established, are influenced by other parameters and show a significant time-lag. This drives the search for novel biomarkers of renal function and injury. Beside Lipocalin-2 and kidney-injury-molecule-1 (KIM-1), the endogenous opioid precursor proenkephalin-A (Penk) has recently emerged as a promising marker for renal function. But the cellular origin and regulation of Penk outside the brain has not yet been investigated in depth.

MATERIALS AND METHODS

This study characterizes the cellular origin of Penk expression with high-resolution in situ hybridization in two models of renal fibrosis in mice and human tissue.

RESULTS

Interstitial cells are the main expression site for renal Penk. This classifies Penk as biomarker for interstitial damage as opposed to tubular damage markers like Lipocalin-2 and KIM-1. Furthermore, our data indicate that renal Penk expression is not regulated by classical profibrotic pathways.

DISCUSSION

This study characterizes changing Penk expression in the kidneys. The similarity of Penk expression across species gives rise to further investigations into the function of Penk in healthy and injured kidneys.

CONCLUSION

Penk is a promising biomarker for interstitial renal damage that warrants further studies to utilize its predictive potential.Clinical significanceKnowledge of real-time renal function is essential for proper treatment of critically ill patients and in early diagnosis of acute kidney injury (AKI). Proenkephalin-A has been measured in a number of patient cohorts as a highly accurate and predictive biomarker of renal damage.The present study identifies Penk as a biomarker for interstitial damage in contrast to the tubular biomarkers such as Lipocalin-2 or KIM-1.Our data show that Penk is regulated independently of classical profibrotic or proinflammatory pathways, indicating it might be more robust against extra-renal influences.Data presented in this study provide fundamental information about cell type-specific localization and regulation of the potential new biomarker Penk across species as foundation for further research.

Autophagy as a Therapeutic Target for Chronic Kidney Disease and the Roles of TGF-β1 in Autophagy and Kidney Fibrosis

Autophagy is a lysosomal protein degradation system that eliminates cytoplasmic components such as protein aggregates, damaged organelles, and even invading pathogens. Autophagy is an evolutionarily conserved homoeostatic strategy for cell survival in stressful conditions and has been linked to a variety of biological processes and disorders. It is vital for the homeostasis and survival of renal cells such as podocytes and tubular epithelial cells, as well as immune cells in the healthy kidney. Autophagy activation protects renal cells under stressed conditions, whereas autophagy deficiency increases the vulnerability of the kidney to injury, resulting in several aberrant processes that ultimately lead to renal failure. Renal fibrosis is a condition that, if chronic, will progress to end-stage kidney disease, which at this point is incurable. Chronic Kidney Disease (CKD) is linked to significant alterations in cell signaling such as the activation of the pleiotropic cytokine transforming growth factor-β1 (TGF-β1). While the expression of TGF-β1 can promote fibrogenesis, it can also activate autophagy, which suppresses renal tubulointerstitial fibrosis. Autophagy has a complex variety of impacts depending on the context, cell types, and pathological circumstances, and can be profibrotic or antifibrotic. Induction of autophagy in tubular cells, particularly in the proximal tubular epithelial cells (PTECs) protects cells against stresses such as proteinuria-induced apoptosis and ischemia-induced acute kidney injury (AKI), whereas the loss of autophagy in renal cells scores a significant increase in sensitivity to several renal diseases. In this review, we discuss new findings that emphasize the various functions of TGF-β1 in producing not just renal fibrosis but also the beneficial TGF-β1 signaling mechanisms in autophagy.