Rodent models of AKI-CKD transition

Pyruvate kinase M2 regulates kidney fibrosis through pericyte glycolysis during the progression from acute kidney injury to chronic kidney disease

We aimed to investigate the role of renal pericyte pyruvate kinase M2 (PKM2) in the progression of acute kidney injury (AKI) to chronic kidney disease (CKD). The role of PKM2 in renal pericyte-myofibroblast transdifferentiation was investigated in an AKI-CKD mouse model. Platelet growth factor receptor beta (PDGFRβ)-iCreERT2; tdTomato mice were used for renal pericyte tracing. Western blotting and immunofluorescence staining were used to examine protein expression. An 5-ethynyl-2'-deoxyuridine assay was used to measure renal pericyte proliferation. A scratch cell migration assay was used to analyse cell migration. Seahorse experiments were used to examine glycolytic rates. Enzyme-linked immunoassay was used to measure pyruvate kinase enzymatic activity and lactate concentrations. The PKM2 nuclear translocation inhibitors Shikonin and TEPP-46 were used to alter pericyte transdifferentiation. In AKI-CKD, renal pericytes proliferated and transdifferentiated into myofibroblasts and PKM2 is highly expressed in renal pericytes. Shikonin and TEPP-46 inhibited pericyte proliferation, migration, and pericyte-myofibroblast transdifferentiation by reducing nuclear PKM2 entry. In the nucleus, PKM2 promoted downstream lactate dehydrogenase A (LDHA) and glucose transporter 1 (GLUT1) transcription, which are critical for glycolysis. Therefore, PKM2 regulates pericyte glycolytic and lactate production, which regulates renal pericyte-myofibroblast transdifferentiation. PKM2-regulated renal pericyte-myofibroblast transdifferentiation by regulating downstream LDHA and GLUT1 transcription and lactate production. Reducing nuclear PKM2 import can reduce renal pericytes-myofibroblasts transdifferentiation, providing new ideas for AKI-CKD treatment.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8 and Vcam1, while the surviving proximal tubules (PTs) showed restored transcriptional signature. We also found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

The Expression and Molecular Mechanisms of Matrix Metalloproteinase- 9 and Vascular Endothelial Growth Factor in Renal Interstitial Fibrosis in Rats

OBJECTIVE

To explore a new approach for the treatment of renal interstitial fibrosis (RIF), we detected the expression of matrix metalloproteinase-9 (MMP9) and vascular endothelial growth factor (VEGF).

METHODS

Twenty-four male Sprague Dawley (SD) rats were randomly divided into 2- week normal control (2NC) group, 4-week NC (4NC) group, 2-week unilateral ureteral obstruction (2UUO) group, and 4-week UUO (4UUO) group. We performed left ureteral ligation on UUO groups. Then, we sacrificed the rats of the 2NC group and 2UUO group at 2 weeks and the other groups at 4 weeks after the surgery. Immunohistochemistry and western blot were applied to detect the expression of MMP9, VEGF, fibronectin (FN), type IV collagen (Col-IV), and transforming growth factor-β1 (TGF-β1). MMP9 levels reduced after UUO surgery. Its expression was less in the 4UUO group than in the 2UUO group (P<0.05). The expression of VEGF, TGF- β1, FN, and Col-IV was higher in UUO groups than in NC groups (P<0.05). The expression of these indicators was higher in the 4UUO group than in the 2UUO group (P<0.05).

RESULTS

In the correlation analysis, MMP9 levels in UUO groups had a negative correlation with the expression of TGF-β1, VEGF, Col-IV, FN, and RIF index (all P<0.05). In UUO groups, VEGF levels had a positive correlation with the expression of TGF-β1, Col-IV, FN, and RIF index (all P<0.05).

CONCLUSION

In conclusion, with the aggravation of RIF lesions, MMP9 levels decreased, and VEGF levels increased. Whether there is a mutual inhibition relationship between them remains to be confirmed by further experiments.

Glomerular injury after trauma, burn, and sepsis

Acute kidney injury development after trauma, burn, or sepsis occurs frequently but remains a scientific and clinical challenge. Whereas the pathophysiological focus has mainly been on hemodynamics and the downstream renal tubular system, little is known about alterations upstream within the glomerulus post trauma or during sepsis. Particularly for the glomerular endothelial cells, mesangial cells, basal membrane, and podocytes, all of which form the glomerular filter, there are numerous in vitro studies on the molecular and functional consequences upon exposure of single cell types to specific damage- or microbial-associated molecular patterns. By contrast, a lack of knowledge exists in the real world regarding the orchestrated inflammatory response of the glomerulus post trauma or burn or during sepsis. Therefore, we aim to provide an overview on the glomerulus as an immune target but also as a perpetrator of the danger response to traumatic and septic conditions, and present major players involved in the context of critical illness. Finally, we highlight research gaps of this rather neglected but worthwhile area to define future molecular targets and therapeutic strategies to prevent or improve the course of AKI after trauma, burn, or sepsis.

Measured GFR in murine animal models: review on methods, techniques, and procedures

Chronic kidney disease (CKD) is one of the most common chronic diseases worldwide, with increasing rates of morbidity and mortality. Thus, early detection is essential to prevent severe adverse events and the progression of kidney disease to an end stage. Glomerular filtration rate (GFR) is the most appropriate index to evaluate renal function in both clinical practice and basic medical research. Several animal models have been developed to understand renal disease induction and progression. Specifically, murine models are useful to study the pathogenesis of renal damage, so a reliable determination of GFR is essential to evaluate the progression of CKD. However, as in clinical practise, the estimation of GFR in murine by levels of serum/urine creatinine or cystatin-C could not be accurate and needed other more reliable methods. As an alternative, the measurement of GFR by the clearance of exogenous markers like inulin, sinistrin, 51Cr-EDTA, 99mTc-DTPA, 125I-iothalamate, or iohexol could be performed. Nevertheless, both approaches-estimation or measurement of GFR-have their limitations and a standard method for the GFR determination has not been defined. Altogether, in this review, we aim to give an overview of the current methods for GFR assessment in murine models, describing each methodology and focusing on their advantages and limitations.

Serum Cys C predicts acute kidney injury in patients with acute pancreatitis: A retrospective study

BACKGROUND AND STUDY AIMS

We investigated the value of the serum cystatin C level as a potential predictor of acute kidney injury (AKI) in patients with acute pancreatitis (AP).

PATIENTS AND METHODS

We retrospectively examined patients diagnosed with AP between January 2013 and December 2018. Patients were categorized into two groups based on their serum cystatin C levels after admission: the normal (n-Cys C group) and high serum cystatin C levels groups (h-Cys C group). Patients in the h-Cys C group demonstrated serum cystatin C levels ≥1.05 mg/L. Demographic parameters, laboratory data, and AP severity were compared between the two groups. Receiver operating curve (ROC) analysis was used to evaluate the efficacy of serum cystatin C in predicting persistent AKI.

RESULTS

A total of 379 patients with AP were enrolled: 319 in the n-Cys C group and 60 in the h-Cys C group. Serum cystatin C levels were significantly higher in patients with severe acute pancreatitis (SAP) compared to moderate acute pancreatitis (MAP) (P< 0.05). The h-Cys C group had a higher BISAP score (P < 0.001). Incidences of organ failure and SAP were significantly higher in the h-Cys C group (P < 0.05). ROC analysis indicated that a serum cystatin C cutoff point of 1.055 mg/L optimally predicted persistent AKI (AUC = 0.711). For internal validation, we selected 545 AP patients, treated at our center from 2019 to 2022, including 54 AKI patients. ROC analysis in this validation group yielded a sensitivity of 100% and specificity of 90.9% (AUC = 0.916, 95% CI: 0.894-0.937).

CONCLUSION

Elevated serum cystatin C levels are sensitive indicators of adverse AKI prognosis in AP patients. The cystatin C level at admission can reflect a patient's initial renal function status.

SMN haploinsufficiency promotes ischemia/ reperfusion-induced AKI-to-CKD transition by endoplasmic reticulum stress activation

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected syndromes that represent a global public health challenge. Here, we identified a specific role of survival of motor neuron (SMN) in ischemia/reperfusion (I/R)-induced kidney injury and progression of CKD. SMN was an essential protein in all cell type and was reported to play important roles in multiple fundamental cellular homeostatic pathways. However, the function of SMN in experimental models of I/R-induced kidney fibrosis has not extensively studied. Genetic ablation of SMN or small interfering RNA-base knockdown of SMN expression aggravated the tubular injury and interstitial fibrosis. Administration of scAAV9-CB-SMN or epithelial cell overexpression of SMN reduced I/R-induced kidney dysfunction and attenuated AKI-to-CKD transition, indicating that SMN is vital for the preservation and recovery of tubular phenotype. Our data showed that the endoplasmic reticulum stress (ERS) induced by I/R was persistent and became progressively more severe in the kidney without SMN. On the contrary, overexpression of SMN prevented against I/R-induced ERS and tubular cell damage. In summary, our data collectively substantiate a critical role of SMN in regulating the ERS activation and phenotype of AKI-to-CKD transition that may contribute to renal pathology during injury and repair.

Epithelial Transport in Disease: An Overview of Pathophysiology and Treatment

Epithelial transport is a multifaceted process crucial for maintaining normal physiological functions in the human body. This comprehensive review delves into the pathophysiological mechanisms underlying epithelial transport and its significance in disease pathogenesis. Beginning with an introduction to epithelial transport, it covers various forms, including ion, water, and nutrient transfer, followed by an exploration of the processes governing ion transport and hormonal regulation. The review then addresses genetic disorders, like cystic fibrosis and Bartter syndrome, that affect epithelial transport. Furthermore, it investigates the involvement of epithelial transport in the pathophysiology of conditions such as diarrhea, hypertension, and edema. Finally, the review analyzes the impact of renal disease on epithelial transport and highlights the potential for future research to uncover novel therapeutic interventions for conditions like cystic fibrosis, hypertension, and renal failure.

Acute kidney injury decreases pulmonary vascular growth and alveolarization in neonatal rat pups

BACKGROUND

Acute kidney injury (AKI) is common in sick neonates and associated with poor pulmonary outcomes, however, the mechanisms responsible remain unknown. We present two novel neonatal rodent models of AKI to investigate the pulmonary effects of AKI.

METHODS

In rat pups, AKI was induced surgically via bilateral ischemia-reperfusion injury (bIRI) or pharmacologically using aristolochic acid (AA). AKI was confirmed with plasma blood urea nitrogen and creatinine measurements and kidney injury molecule-1 staining on renal immunohistochemistry. Lung morphometrics were quantified with radial alveolar count and mean linear intercept, and angiogenesis investigated by pulmonary vessel density (PVD) and vascular endothelial growth factor (VEGF) protein expression. For the surgical model, bIRI, sham, and non-surgical pups were compared. For the pharmacologic model, AA pups were compared to vehicle controls.

RESULTS

AKI occurred in bIRI and AA pups, and they demonstrated decreased alveolarization, PVD, and VEGF protein expression compared controls. Sham pups did not experience AKI, however, demonstrated decreased alveolarization, PVD, and VEGF protein expression compared to controls.

CONCLUSION

Pharmacologic AKI and surgery in neonatal rat pups, with or without AKI, decreased alveolarization and angiogenesis, producing a bronchopulmonary dysplasia phenotype. These models provide a framework for elucidating the relationship between AKI and adverse pulmonary outcomes.

IMPACT

There are no published neonatal rodent models investigating the pulmonary effects after neonatal acute kidney injury, despite known clinical associations. We present two novel neonatal rodent models of acute kidney injury to study the impact of acute kidney injury on the developing lung. We demonstrate the pulmonary effects of both ischemia-reperfusion injury and nephrotoxin-induced AKI on the developing lung, with decreased alveolarization and angiogenesis, mimicking the lung phenotype of bronchopulmonary dysplasia. Neonatal rodent models of acute kidney injury provide opportunities to study mechanisms of kidney-lung crosstalk and novel therapeutics in the context of acute kidney injury in a premature infant.

Animal Models of Kidney Disease: Challenges and Perspectives

Kidney disease is highly prevalent and affects approximately 850 million people worldwide. It is also associated with high morbidity and mortality, and current therapies are incurable and often ineffective. Animal models are indispensable for understanding the pathophysiology of various kidney diseases and for preclinically testing novel remedies. In the last two decades, rodents continue to be the most used models for imitating human kidney diseases, largely because of the increasing availability of many unique genetically modified mice. Despite many limitations and pitfalls, animal models play an essential and irreplaceable role in gaining novel insights into the mechanisms, pathologies, and therapeutic targets of kidney disease. In this review, we highlight commonly used animal models of kidney diseases by focusing on experimental AKI, CKD, and diabetic kidney disease. We briefly summarize the pathological characteristics, advantages, and drawbacks of some widely used models. Emerging animal models such as mini pig, salamander, zebrafish, and drosophila, as well as human-derived kidney organoids and kidney-on-a-chip are also discussed. Undoubtedly, careful selection and utilization of appropriate animal models is of vital importance in deciphering the mechanisms underlying nephropathies and evaluating the efficacy of new treatment options. Such studies will provide a solid foundation for future diagnosis, prevention, and treatment of human kidney diseases.

Pre-clinical Evaluation of Biomarkers for Early Detection of Nephrotoxicity Following Alpha-particle Radioligand Therapy

Purpose

Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLTs nephrotoxicity.

Methods

A bifunctional cyclic peptide, melanocortin ligand-1(MC1L), labeled with [ 203 Pb]Pb-MC1L, was used for [ 212 Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [ 212 Pb]Pb-MC1L in a dose escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers.

Results

Biodistribution analysis identified [ 212 Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [ 212 Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary Neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [ 212 Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings.

Conclusion

urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.

Insights into Repeated Renal Injury Using RNA-Seq with Two New RPTEC Cell Lines

Renal proximal tubule epithelial cells (RPTECs) are a primary site for kidney injury. We created two RPTEC lines from CD-1 mice immortalized with hTERT (human telomerase reverse transcriptase) or SV40 LgT antigen (Simian Virus 40 Large T antigen). Our hypothesis was that low-level, repeated exposure to subcytotoxic levels of 0.25-2.5 μM cisplatin (CisPt) or 12.5-100 μM aflatoxin B1 (AFB1) would activate distinctive genes and pathways in these two differently immortalized cell lines. RNA-seq showed only LgT cells responded to AFB1 with 1139 differentially expressed genes (DEGs) at 72 h. The data suggested that AFB1 had direct nephrotoxic properties on the LgT cells. However, both the cell lines responded to 2.5 μM CisPt from 3 to 96 h expressing 2000-5000 total DEGs. For CisPt, the findings indicated a coordinated transcriptional program of injury signals and repair from the expression of immune receptors with cytokine and chemokine secretion for leukocyte recruitment; robust expression of synaptic and substrate adhesion molecules (SAMs) facilitating the expression of neural and hormonal receptors, ion channels/transporters, and trophic factors; and the expression of nephrogenesis transcription factors. Pathway analysis supported the concept of a renal repair transcriptome. In summary, these cell lines provide in vitro models for the improved understanding of repeated renal injury and repair mechanisms. High-throughput screening against toxicant libraries should provide a wider perspective of their capabilities in nephrotoxicity.

Acute Kidney Injury-Induced Circulating TNFR1/2 Elevations Correlate with Persistent Kidney Injury and Progression to Fibrosis

Elevated levels of circulating tumor necrosis factor receptors 1 and 2 (cTNFR1/2) predict chronic kidney disease (CKD) progression; however, the mechanisms of their release remain unknown. Whether acute kidney injury (AKI) drives cTNFR1/2 elevations and whether they predict disease outcomes after AKI remain unknown. In this study, we used AKI patient serum and urine samples, mouse models of kidney injury (ischemic, obstructive, and toxic), and progression to fibrosis, nephrectomy, and related single-cell RNA-sequencing datasets to experimentally test the role of kidney injury on cTNFR1/2 levels. We show that TNFR1/2 serum and urine levels are highly elevated in all of the mouse models of kidney injury tested, beginning within one hour post injury, and correlate with its severity. Consistent with this, serum and urine TNFR1/2 levels are increased in AKI patients and correlate with the severity of kidney failure. Kidney tissue expression of TNFR1/2 after AKI is only slightly increased and bilateral nephrectomies lead to strong cTNFR1/2 elevations, suggesting the release of these receptors by extrarenal sources. The injection of the uremic toxin indoxyl sulfate in healthy mice induces moderate cTNFR1/2 elevations. Moreover, TNF neutralization does not affect early cTNFR1/2 elevations after AKI. These data suggest that cTNFR1/2 levels in AKI do not reflect injury-induced TNF activity, but rather a rapid response to loss of kidney function and uremia. In contrast to traditional disease biomarkers, such as serum creatinine or BUN, cTNFR1/2 levels remain elevated for weeks after severe kidney injury. At these later timepoints, cTNFR1/2 levels positively correlate with remaining kidney injury. During the AKI-to-CKD transition, elevations of TNFR1/2 kidney expression and of cTNFR2 levels correlate with kidney fibrosis levels. In conclusion, our data demonstrate that kidney injury drives acute increases in cTNFR1/2 serum levels, which negatively correlate with kidney function. Sustained TNFR1/2 elevations after kidney injury during AKI-to-CKD transition reflect persistent tissue injury and progression to kidney fibrosis.

Asiatic acid alleviates cisplatin-induced renal fibrosis in tumor-bearing mice by improving the TFEB-mediated autophagy-lysosome pathway

Nephrotoxicity is a major side effect of cisplatin treatment of solid tumors in the clinical setting. Long-term low-dose cisplatin administration causes renal fibrosis and inflammation. However, few specific medicines with clinical application value have been developed to reduce or treat the nephrotoxic side effects of cisplatin without affecting its tumor-killing effect. The present study analyzed the potential reno-protective effect and mechanism of asiatic acid (AA) in long-term cisplatin-treated nude mice suffering from tumors. AA treatment significantly attenuated renal injury, inflammation, and fibrosis induced by long-term cisplatin injection in tumor-bearing mice. AA administration notably suppressed tubular necroptosis and improved the autophagy-lysosome pathway disruption caused by chronic cisplatin treatment in tumor-transplanted nude mice and HK-2 cells. AA promoted transcription factor EB (TFEB)-mediated lysosome biogenesis and reduced the accumulation of damaged lysosomes, resulting in enhanced autophagy flux. Mechanistically, AA increased TFEB expression by rebalancing Smad7/Smad3, whereas siRNA inhibition of Smad7 or TFEB abolished the effect of AA on autophagy flux in HK-2 cells. In addition, AA treatment did not weaken, but actually enhanced the anti-tumor effect of cisplatin, as evidenced by the promoted tumor apoptosis and inhibited proliferation in nude mice. In summary, AA alleviates cisplatin-induced renal fibrosis in tumor-bearing mice by improving the TFEB-mediated autophagy-lysosome pathway.

HCK induces macrophage activation to promote renal inflammation and fibrosis via suppression of autophagy

Renal inflammation and fibrosis are the common pathways leading to progressive chronic kidney disease (CKD). We previously identified hematopoietic cell kinase (HCK) as upregulated in human chronic allograft injury promoting kidney fibrosis; however, the cellular source and molecular mechanisms are unclear. Here, using immunostaining and single cell sequencing data, we show that HCK expression is highly enriched in pro-inflammatory macrophages in diseased kidneys. HCK-knockout (KO) or HCK-inhibitor decreases macrophage M1-like pro-inflammatory polarization, proliferation, and migration in RAW264.7 cells and bone marrow-derived macrophages (BMDM). We identify an interaction between HCK and ATG2A and CBL, two autophagy-related proteins, inhibiting autophagy flux in macrophages. In vivo, both global or myeloid cell specific HCK-KO attenuates renal inflammation and fibrosis with reduces macrophage numbers, pro-inflammatory polarization and migration into unilateral ureteral obstruction (UUO) kidneys and unilateral ischemia reperfusion injury (IRI) models. Finally, we developed a selective boron containing HCK inhibitor which can reduce macrophage pro-inflammatory activity, proliferation, and migration in vitro, and attenuate kidney fibrosis in the UUO mice. The current study elucidates mechanisms downstream of HCK regulating macrophage activation and polarization via autophagy in CKD and identifies that selective HCK inhibitors could be potentially developed as a new therapy for renal fibrosis.

Proteomics reveals defective peroxisomal fatty acid oxidation during the progression of acute kidney injury and repair

Acute kidney injury (AKI) is characterized by a rapid decrease in renal function with high mortality and risk of progression to chronic kidney disease (CKD). Ischemia and reperfusion injury (IRI) is one of the major causes of AKI. However, the cellular and molecular responses of the kidney to IRI are complex and not fully understood. Herein, we conducted unbiased proteomics and bioinformatics analyses in an IRI mouse model on days 3, 7, and 21, and validated the results using IRI, unilateral ureteral obstruction (UUO), and biopsies from patients with AKI or CKD. The results indicated an obvious temporal expression profile of differentially expressed proteins and highlighted impaired lipid metabolism during the progression of AKI to CKD. Acyl-coenzyme A oxidase 1 (Acox1), the first rate-limiting enzyme of peroxisomal fatty acid beta-oxidation, was then selected, and its disturbed expression in the two murine models validated the proteomic findings. Accordingly, Acox1 expression was significantly downregulated in renal biopsies from patients with AKI or CKD, and its expression was negatively correlated with kidney injury score. Furthermore, in contrast to the decreased Acox1 expression, lipid droplet accumulation was remarkably increased in these renal tissues, suggesting dysregulation of fatty acid oxidation. In conclusion, our results suggest that defective peroxisomal fatty acid oxidation might be a common pathological feature in the transition from AKI to CKD, and that Acox1 is a promising intervention target for kidney injury and repair.

The role of the SGK3/TOPK signaling pathway in the transition from acute kidney injury to chronic kidney disease

Introduction: Profibrotic phenotype of renal tubular epithelial cells (TECs) featured with epithelial to mesenchymal transition (EMT) and profibrotic factors secretion, and aberrant accumulation of CD206⁺ M2 macrophages are the key points in the transition from acute kidney injury (AKI) to chronic kidney disease (CKD). Nevertheless, the underlying mechanisms involved remain incompletely understood. Serum and glucocorticoid-inducible kinase (SGK) is a serine/threonine protein kinase, required for intestinal nutrient transport and ion channels modulation. T-LAK-cell-originated protein kinase (TOPK) is a member of the mitogen activated protein kinase family, linked to cell cycle regulation. However, little is known about their roles in AKI-CKD transition. Methods: In this study, three models were constructed in C57BL/6 mice: low dose and multiple intraperitoneal injection of cisplatin, 5/6 nephrectomy and unilateral ureteral obstruction model. Rat renal tubular epithelial cells (NRK-52E) were dealt with cisplatin to induce profibrotic phenotype, while a mouse monocytic cell line (RAW264.7) were cultured with cisplatin or TGF-β1 to induce M1 or M2 macrophage polarization respectively. And co-cultured NRK-52E and RAW264.7 through transwell plate to explore the interaction between them. The expression of SGK3 and TOPK phosphorylation were detected by immunohistochemistry, immunofluorescence and western blot analysis. Results: In vivo, the expression of SGK3 and p-TOPK were gradually inhibited in TECs, but enhanced in CD206⁺ M2 macrophages. In vitro, SGK3 inhibition aggravated epithelial to mesenchymal transition through reducing the phosphorylation state of TOPK, and controlling TGF-β1 synthesis and secretion in TECs. However, SGK3/TOPK axis activation promoted CD206⁺ M2 macrophage polarization, which caused kidney fibrosis by mediating macrophage to myofibroblast transition (MMT). When co-cultured, the TGF-β1 from profibrotic TECs evoked CD206⁺ M2 macrophage polarization and MMT, which could be attenuated by SGK3/TOPK axis inhibition in macrophages. Conversely, SGK3/TOPK signaling pathway activation in TECs could reverse CD206⁺ M2 macrophages aggravated EMT. Discussion: We revealed for the first time that SGK3 regulated TOPK phosphorylation to mediate TECs profibrotic phenotype, macrophage plasticity and the crosstalk between TECs and macrophages during AKI-CKD transition. Our results demonstrated the inverse effect of SGK3/TOPK signaling pathway in profibrotic TECs and CD206⁺ M2 macrophages polarization during the AKI-CKD transition.

Tubular Elabela-APJ axis attenuates ischemia-reperfusion induced acute kidney injury and the following AKI-CKD transition by protecting renal microcirculation

Rationale: Ischemia-reperfusion injury (I/R) is a common cause of acute kidney injury (AKI). Post-ischemic recovery of renal blood supply plays an important role in attenuating injury. Exogenous application of elabela (ELA) peptides has been demonstrated by us and others to alleviate AKI, partly through its receptor APJ. However, the endogenous role of ELA in renal I/R remains unclear. Methods: Renal tubule specific ELA knockout (ApelaKsp KO) mice challenged with bilateral or unilateral I/R were used to investigate the role of endogenous ELA in renal I/R. RNA-sequencing analysis was performed to unbiasedly investigate altered genes in kidneys of ApelaKsp KO mice. Injured mice were treated with ELA32 peptide, Nω-hydroxy-nor-L-arginine (nor-NOHA), prostaglandin E2 (PGE2), Paricalcitol, ML221 or respective vehicles, individually or in combination. Results: ELA is mostly expressed in renal tubules. Aggravated pathological injury and further reduction of renal microvascular blood flow were observed in ApelaKsp KO mice during AKI and the following transition to chronic kidney disease (AKI-CKD). RNA-seq analysis suggested that two blood flow regulators, arginine metabolizing enzyme arginase 2 (ARG2) and PGE2 metabolizing enzyme carbonyl reductases 1 and 3 (CBR1/3), were altered in injured ApelaKsp KO mice. Notably, combination application of an ARG2 inhibitor nor-NOHA, and Paricalcitol, a clinically used activator for PGE2 synthesis, alleviated injury-induced AKI/AKI-CKD stages and eliminated the worst outcomes observed in ApelaKsp KO mice. Moreover, while the APJ inhibitor ML221 blocked the beneficial effects of ELA32 peptide on AKI, it showed no effect on combination treatment of nor-NOHA and Paricalcitol. Conclusions: An endogenous tubular ELA-APJ axis regulates renal microvascular blood flow that plays a pivotal role in I/R-induced AKI. Furthermore, improving renal blood flow by inhibiting ARG2 and activating PGE2 is an effective treatment for AKI and prevents the subsequent AKI-CKD transition.

Regulation of pericyte metabolic reprogramming restricts the AKI to CKD transition

BACKGROUND AND AIMS

Acute kidney injury (AKI) is associated with high morbidity and mortality and is recognized as a long-term risk factor for progression to chronic kidney disease (CKD). The AKI to CKD transition is characterized by interstitial fibrosis and the proliferation of collagen-secreting myofibroblasts. Pericytes are the major source of myofibroblasts in kidney fibrosis. However, the underlying mechanism of pericyte-myofibroblast transition (PMT) is still unclear. Here we investigated the role of metabolic reprogramming in PMT.

METHODS

Unilateral ischemia/reperfusion-induced AKI to CKD mouse model and TGF-β-treated pericyte-like cells were used to detect the levels of fatty acid oxidation (FAO) and glycolysis, and the critical signaling pathways during PMT under the treatment of drugs regulating metabolic reprogramming.

RESULTS

PMT is characterized by a decrease in FAO and an increase in glycolysis. Enhancement of FAO by the peroxisome proliferator-activated receptor gamma coactivator-1α (PGC1α) activator ZLN-005 or suppression of glycolysis by the hexokinase 2 (HK2) inhibitor 2-DG can inhibit PMT, preventing the transition of AKI to CKD. Mechanistically, AMPK modulates various pathways involved in the metabolic switch from glycolysis to FAO. Specifically, the PGC1α-CPT1A pathway activates FAO, while inhibition of the HIF1α-HK2 pathway drives glycolysis inhibition. The modulations of these pathways by AMPK contribute to inhibiting PMT.

CONCLUSIONS

Metabolic reprogramming controls the fate of pericyte transdifferentiation and targets the abnormal metabolism of pericytes can effectively prevent AKI to CKD transition.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8, while the surviving proximal tubules (PTs) showed restored transcriptional signature. Furthermore, we found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Single-cell sequencing reveals homogeneity and heterogeneity of the cytopathological mechanisms in different etiology-induced AKI

Homogeneity and heterogeneity of the cytopathological mechanisms in different etiology-induced acute kidney injury (AKI) are poorly understood. Here, we performed single-cell sequencing (scRNA) on mouse kidneys with five common AKI etiologies (CP-Cisplatin, IRI-Ischemia-reperfusion injury, UUO-Unilateral ureteral obstruction, FA-Folic acid, and SO-Sodium oxalate). We constructed a potent multi-model AKI scRNA atlas containing 20 celltypes with 80,689 high-quality cells. The data suggest that compared to IRI and CP-AKI, FA- and SO-AKI exhibit injury characteristics more similar to UUO-AKI, which may due to tiny crystal-induced intrarenal obstruction. Through scRNA atlas, 7 different functional proximal tubular cell (PTC) subtypes were identified, we found that Maladaptive PTCs and classical Havcr1 PTCs but not novel Krt20 PTCs affect the pro-inflammatory and pro-fibrotic levels in different AKI models. And cell death and cytoskeletal remodeling events are widespread patterns of injury in PTCs. Moreover, we found that programmed cell death predominated in PTCs, whereas apoptosis and autophagy prevailed in the remaining renal tubules. We also identified S100a6 as a novel AKI-endothelial injury biomarker. Furthermore, we revealed that the dynamic and active immune (especially Arg1 Macro_2 cells) -parenchymal cell interactions are important features of AKI. Taken together, our study provides a potent resource for understanding the pathogenesis of AKI and early intervention in AKI progression at single-cell resolution.

Longitudinal biomarkers and kidney disease progression after acute kidney injury

BACKGROUNDLongitudinal investigations of murine acute kidney injury (AKI) suggest that injury and inflammation may persist long after the initial insult. However, the evolution of these processes and their prognostic values are unknown in patients with AKI.METHODSIn a prospective cohort of 656 participants hospitalized with AKI, we measured 7 urine and 2 plasma biomarkers of kidney injury, inflammation, and tubular health at multiple time points from the diagnosis to 12 months after AKI. We used linear mixed-effect models to estimate biomarker changes over time, and we used Cox proportional hazard regressions to determine their associations with a composite outcome of chronic kidney disease (CKD) incidence and progression. We compared the gene expression kinetics of biomarkers in murine models of repair and atrophy after ischemic reperfusion injury (IRI).RESULTSAfter 4.3 years, 106 and 52 participants developed incident CKD and CKD progression, respectively. Each SD increase in the change of urine KIM-1, MCP-1, and plasma TNFR1 from baseline to 12 months was associated with 2- to 3-fold increased risk for CKD, while the increase in urine uromodulin was associated with 40% reduced risk for CKD. The trajectories of these biological processes were associated with progression to kidney atrophy in mice after IRI.CONCLUSIONSustained tissue injury and inflammation, and slower restoration of tubular health, are associated with higher risk of kidney disease progression. Further investigation into these ongoing biological processes may help researchers understand and prevent the AKI-to-CKD transition.FUNDINGNIH and NIDDK (grants U01DK082223, U01DK082185, U01DK082192, U01DK082183, R01DK098233, R01DK101507, R01DK114014, K23DK100468, R03DK111881, K01DK120783, and R01DK093771).

Pretreatment with a novel Toll-like receptor 4 agonist attenuates renal ischemia-reperfusion injury

Acute kidney injury (AKI) is common in surgical and critically ill patients. This study examined whether pretreatment with a novel Toll-like receptor 4 agonist attenuated ischemia-reperfusion injury (IRI)-induced AKI (IRI-AKI). We performed a blinded, randomized-controlled study in mice pretreated with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide (PHAD), a synthetic Toll-like receptor 4 agonist. Two cohorts of male BALB/c mice received intravenous vehicle or PHAD (2, 20, or 200 µg) at 48 and 24 h before unilateral renal pedicle clamping and simultaneous contralateral nephrectomy. A separate cohort of mice received intravenous vehicle or 200 µg PHAD followed by bilateral IRI-AKI. Mice were monitored for evidence of kidney injury for 3 days postreperfusion. Kidney function was assessed by serum blood urea nitrogen and creatinine measurements. Kidney tubular injury was assessed by semiquantitative analysis of tubular morphology on periodic acid-Schiff (PAS)-stained kidney sections and by kidney mRNA quantification of injury [neutrophil gelatinase-associated lipocalin (Ngal), kidney injury molecule-1 (Kim-1), and heme oxygenase-1 (Ho-1)] and inflammation [interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (Tnf-α)] using quantitative RT-PCR. Immunohistochemistry was used to quantify proximal tubular cell injury and renal macrophages by quantifying the areas stained with Kim-1 and F4/80 antibodies, respectively, and TUNEL staining to detect the apoptotic nuclei. PHAD pretreatment yielded dose-dependent kidney function preservation after unilateral IRI-AKI. Histological injury, apoptosis, Kim-1 staining, and Ngal mRNA were lower in PHAD-treated mice and IL-1β mRNA was higher in PHAD-treated mice. Similar pretreatment protection was noted with 200 mg PHAD after bilateral IRI-AKI, with significantly reduced Kim-1 immunostaining in the outer medulla of mice treated with PHAD after bilateral IRI-AKI. In conclusion, PHAD pretreatment leads to dose-dependent protection from renal injury after unilateral and bilateral IRI-AKI in mice.NEW & NOTEWORTHY Pretreatment with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide; a novel synthetic Toll-like receptor 4 agonist, preserves kidney function during ischemia-reperfusion injury-induced acute kidney injury.

The Mineralocorticoid Receptor on Smooth Muscle Cells Promotes Tacrolimus-Induced Renal Injury in Mice

Tacrolimus (Tac) is a calcineurin inhibitor commonly used as an immunosuppressor after solid organ transplantation. However, Tac may induce hypertension, nephrotoxicity, and an increase in aldosterone levels. The activation of the mineralocorticoid receptor (MR) is related to the proinflammatory status at the renal level. It modulates the vasoactive response as they are expressed on vascular smooth muscle cells (SMC). In this study, we investigated whether MR is involved in the renal damage generated by Tac and if the MR expressed in SMC is involved. Littermate control mice and mice with targeted deletion of the MR in SMC (SMC-MR-KO) were administered Tac (10 mg/Kg/d) for 10 days. Tac increased the blood pressure, plasma creatinine, expression of the renal induction of the interleukin (IL)-6 mRNA, and expression of neutrophil gelatinase-associated lipocalin (NGAL) protein, a marker of tubular damage (p < 0.05). Our study revealed that co-administration of spironolactone, an MR antagonist, or the absence of MR in SMC-MR-KO mice mitigated most of the unwanted effects of Tac. These results enhance our understanding of the involvement of MR in SMC during the adverse reactions of Tac treatment. Our findings provided an opportunity to design future studies considering the MR antagonism in transplanted subjects.

Enhancer of zeste homolog 2 promotes renal fibrosis after acute kidney injury by inducing epithelial-mesenchymal transition and activation of M2 macrophage polarization

Long-term follow-up data indicates that 1/4 patients with acute kidney injury (AKI) will develop to chronic kidney disease (CKD). Our previous studies have demonstrated that enhancer of zeste homolog 2 (EZH2) played an important role in AKI and CKD. However, the role and mechanisms of EZH2 in AKI-to-CKD transition are still unclear. Here, we demonstrated EZH2 and H3K27me3 highly upregulated in kidney from patients with ANCA-associated glomerulonephritis, and expressed positively with fibrotic lesion and negatively with renal function. Conditional EZH2 deletion or pharmacological inhibition with 3-DZNeP significantly improved renal function and attenuated pathological lesion in ischemia/reperfusion (I/R) or folic acid (FA) mice models (two models of AKI-to-CKD transition). Mechanistically, we used CUT & Tag technology to verify that EZH2 binding to the PTEN promoter and regulating its transcription, thus regulating its downstream signaling pathways. Genetic or pharmacological depletion of EZH2 upregulated PTEN expression and suppressed the phosphorylation of EGFR and its downstream signaling ERK1/2 and STAT3, consequently alleviating the partial epithelial-mesenchymal transition (EMT), G2/M arrest, and the aberrant secretion of profibrogenic and proinflammatory factors in vivo and vitro experiments. In addition, EZH2 promoted the EMT program induced loss of renal tubular epithelial cell transporters (OAT1, ATPase, and AQP1), and blockade of EZH2 prevented it. We further co-cultured macrophages with the medium of human renal tubular epithelial cells treated with H₂O₂ and found macrophages transferred to M2 phenotype, and EZH2 could regulate M2 macrophage polarization through STAT6 and PI3K/AKT pathways. These results were further verified in two mice models. Thus, targeted inhibition of EZH2 might be a novel therapy for ameliorating renal fibrosis after acute kidney injury by counteracting partial EMT and blockade of M2 macrophage polarization.

S100-A8/A9 activated TLR4 in renal tubular cells to promote ischemia-reperfusion injury and fibrosis

Renal ischemia/reperfusion injury (IRI) is a significant clinical problem without effective therapy. Unbiased omics approaches may reveal key renal mediators to initiate IRI. S100-A8/A9 was identified as the most significantly upregulated gene and protein base on proteomic analysis and RNA sequencing during the early reperfusion stage. S100-A8/A9 levels were significantly increased 1 day after transplantation in patients with donation after brain death (DBD). S100-A8/A9 production was associated with CD11b⁺Ly6G⁺ CXCR2⁺ immunocytes infiltration. Administration of S100-A8/A9 blocker ABR238901 significantly alleviates renal tubular injury, inflammatory cell infiltration, and renal fibrosis after renal IRI. Mechanistically, S100-A8/A9 could promote renal tubular cell injury and profibrotic cytokine production via TLR4. In conclusion, our findings found that early activation of S100-A8/A9 in renal IRI and targeting S100-A8/A9 signaling alleviates tubular injury and inhibits inflammatory response and renal fibrosis, which may provide a novel target for the prevention and treatment of acute kidney injury.

Identifying disease progression in chronic kidney disease using proton magnetic resonance spectroscopy

Chronic kidney disease (CKD) affects approximately 10% of the world population, higher still in some developing countries, and can cause irreversible kidney damage eventually leading to kidney failure requiring dialysis or kidney transplantation. However, not all patients with CKD will progress to this stage, and it is difficult to distinguish between progressors and non-progressors at the time of diagnosis. Current clinical practice involves monitoring estimated glomerular filtration rate and proteinuria to assess CKD trajectory over time; however, there remains a need for novel, validated methods that differentiate CKD progressors and non-progressors. Nuclear magnetic resonance techniques, including magnetic resonance spectroscopy and magnetic resonance imaging, have the potential to improve our understanding of CKD progression. Herein, we review the application of magnetic resonance spectroscopy both in preclinical and clinical settings to improve the diagnosis and surveillance of patients with CKD.

Gray level co-occurrence matrix and wavelet analyses reveal discrete changes in proximal tubule cell nuclei after mild acute kidney injury

Acute kidney injury (AKI) relates to an abrupt reduction in renal function resulting from numerous conditions. Morbidity, mortality, and treatment costs related to AKI are relatively high. This condition is strongly associated with damage to proximal tubule cells (PTCs), generating distinct patterns of transcriptional and epigenetic alterations that result in structural changes in the nuclei of this epithelium. To this date, AKI-related nuclear chromatin redistribution in PTCs is poorly understood, and it is unclear whether changes in PTC chromatin patterns can be detected using conventional microscopy during mild AKI, which can progress to more debilitating forms of injury. In recent years, gray level co-occurrence matrix (GLCM) analysis and discrete wavelet transform (DWT) have emerged as potentially valuable methods for identifying discrete structural changes in nuclear chromatin architecture that are not visible during the conventional histopathological exam. Here we present findings indicating that GLCM and DWT methods can be successfully used in nephrology to detect subtle nuclear morphological alterations associated with mild tissue injury demonstrated in rodents by inducing a mild form of AKI through ischemia-reperfusion injury. Our results show that mild ischemic AKI is associated with the reduction of local textural homogeneity of PTC nuclei quantified by GLCM and the increase of nuclear structural heterogeneity indirectly assessed with DWT energy coefficients. This rodent model allowed us to show that mild ischemic AKI is associated with the significant reduction of textural homogeneity of PTC nuclei, indirectly assessed by GLCM indicators and DWT energy coefficients.

SARS-CoV-2 viral protein ORF3A injures renal tubules by interacting with TRIM59 to induce STAT3 activation

Acute kidney injury occurs frequently in COVID-19 patients infected by the coronavirus SARS-CoV-2, and infection of kidney cells by this virus has been reported. However, little is known about the direct impact of the SARS-CoV-2 infection upon the renal tubular cells. We report that SARS-CoV-2 activated signal transducer and activator of transcription 3 (STAT3) signaling and caused cellular injury in the human renal tubular cell line. Mechanistically, the viral protein ORF3A of SARS-CoV-2 augmented both NF-κB and STAT3 signaling and increased the expression of kidney injury molecule 1. SARS-CoV-2 infection or expression of ORF3A alone elevated the protein level of tripartite motif-containing protein 59 (TRIM59), an E3 ubiquitin ligase, which interacts with both ORF3A and STAT3. The excessive TRIM59 in turn dissociated the phosphatase TCPTP from binding to STAT3 and hence inhibited the dephosphorylation of STAT3, leading to persistent STAT3 activation. Consistently, ORF3A induced renal injury in zebrafish and mice. In addition, expression of TRIM59 was elevated in the kidney autopsies of COVID-19 patients with acute kidney injury. Thus, the aberrant activation of STAT3 signaling by TRIM59 plays a significant role in the renal tubular cell injury caused by SARS-CoV-2, which suggests a potential targeted therapy for the renal complications of COVID-19.

Tubular Epithelial Cell HMGB1 Promotes AKI-CKD Transition by Sensitizing Cycling Tubular Cells to Oxidative Stress: A Rationale for Targeting HMGB1 during AKI Recovery

SIGNIFICANCE STATEMENT

Cells undergoing necrosis release extracellular high mobility group box (HMGB)-1, which triggers sterile inflammation upon AKI in mice. Neither deletion of HMGB1 from tubular epithelial cells, nor HMGB1 antagonism with small molecules, affects initial ischemic tubular necrosis and immediate GFR loss upon unilateral ischemia/reperfusion injury (IRI). On the contrary, tubular cell-specific HMGB1 deficiency, and even late-onset pharmacological HMGB1 inhibition, increased functional and structural recovery from AKI, indicating that intracellular HMGB1 partially counters the effects of extracellular HMGB1. In vitro studies indicate that intracellular HMGB1 decreases resilience of tubular cells from prolonged ischemic stress, as in unilateral IRI. Intracellular HMGB1 is a potential target to enhance kidney regeneration and to improve long-term prognosis in AKI.

BACKGROUND

Late diagnosis is a hurdle for treatment of AKI, but targeting AKI-CKD transition may improve outcomes. High mobility group box-1 (HMGB1) is a nuclear regulator of transcription and a driver of necroinflammation in AKI. We hypothesized that HMGB1 would also modulate AKI-CKD transition in other ways.

METHODS

We conducted single-cell transcriptome analysis of human and mouse AKI and mouse in vivo and in vitro studies with tubular cell-specific depletion of Hmgb1 and HMGB1 antagonists.

RESULTS

HMGB1 was ubiquitously expressed in kidney cells. Preemptive HMGB1 antagonism with glycyrrhizic acid (Gly) and ethyl pyruvate (EP) did not affect postischemic AKI but attenuated AKI-CKD transition in a model of persistent kidney hypoxia. Consistently, tubular Hmgb1 depletion in Pax8 rtTA, TetO Cre, Hmgb1fl/fl mice did not protect from AKI, but from AKI-CKD transition. In vitro studies confirmed that absence of HMGB1 or HMGB1 inhibition with Gly and EP does not affect ischemic necrosis of growth-arrested differentiated tubular cells but increased the resilience of cycling tubular cells that survived the acute injury to oxidative stress. This effect persisted when neutralizing extracellular HMGB1 with 2G7. Consistently, late-onset HMGB1 blockade with EP started after the peak of ischemic AKI in mice prevented AKI-CKD transition, even when 2G7 blocked extracellular HMGB1.

CONCLUSION

Treatment of AKI could become feasible when ( 1 ) focusing on long-term outcomes of AKI; ( 2 ) targeting AKI-CKD transition with drugs initiated after the AKI peak; and ( 3 ) targeting with drugs that block HMGB1 in intracellular and extracellular compartments.

Lung cancer-kidney cross talk induces kidney injury, interstitial fibrosis, and enhances cisplatin-induced nephrotoxicity

Patients with cancer represent a unique patient population with increased susceptibility to kidney disease. Drug-induced acute kidney injury (AKI) in patients with cancer is a common problem. Cisplatin is a highly effective treatment used in many solid-organ cancers and causes AKI in 30% of patients, increasing the risk of chronic kidney disease development. Most preclinical cisplatin toxicity studies have been completed in mice without cancer. We believe that the physiology of patients with cancer is not adequately represented in preclinical models, and the objective of this study was to determine how lung cancer will alter the nephrotoxicity of cisplatin. A genetically engineered mouse model and a syngeneic xenograft model of lung cancer were used. Mice were divided into the following four groups: 1) noncancer/vehicle, 2) noncancer/cisplatin, 3) cancer/vehicle, and 4) cancer/cisplatin. Mice were administered cisplatin via intraperitoneal injection once a week for 4 wk. Animals were euthanized 72 h following their final cisplatin injection. Mice with lung cancer had increased renal toxicity, injury, and fibrosis following repeated low doses of cisplatin. In addition, lung cancer alone induced kidney injury and fibrosis in the kidney before cisplatin treatment. In conclusion, this is the first study that we are aware of that assesses the impact of cancer on the kidney in conjunction with the nephrotoxicity of cisplatin. We believe that cancer is providing the first hit to the kidney and the subsequent damage from repeated doses of cisplatin becomes unsurmountable, leading to AKI and progression to chronic kidney disease.NEW & NOTEWORTHY Patients with cancer have impaired kidney function and increased susceptibility to nephrotoxic agents. Cisplatin is a commonly used chemotherapeutic with nephrotoxicity as the dose-limiting side effect. Cisplatin nephrotoxicity is almost exclusively studied in mice without cancer. Our current preclinical models do not adequately represent the complexity of patients with cancer. This study demonstrates increased renal toxicity, injury, and fibrosis in mice with lung cancer, which is exacerbated with cisplatin treatment. These results highlight the necessity of using preclinical models that more accurately capture the altered physiology of patients with cancer treated with cisplatin.

Single-cell transcriptome analysis of a rat model of bilateral renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) causes massive tissue damage. Renal IRI is the most common type of acute renal injury, and the defects caused by it may progress to chronic kidney disease (CKD). Rodent models of renal IRI, with various patterns, have been used to study the treatment of human kidney injury. A rat model of bilateral IRI, in which the bilateral kidney blood vessels are clamped for 60 min, is widely used, inducing both acute and chronic kidney disease. However, the molecular mechanisms underlying the effects of bilateral IRI on kidney cells have not yet been fully elucidated. This study aimed to perform a whole-transcriptome analysis of the IRI kidney using single-cell RNA sequencing. We found renal parenchymal cells, including those from the proximal tubule, the loop of Henle, and distal tubules, to be damaged by IRI. In addition, we observed significant changes in macrophage population. Our study delineated the detailed cellular and molecular changes that occur in the rat model of bilateral IRI. Collectively, our data and analyses provided a foundation for understanding IRI-related kidney diseases in rat models.

Autophagy in acute kidney injury and maladaptive kidney repair

Acute kidney injury (AKI) is a major renal disease characterized by a sudden decrease in kidney function. After AKI, the kidney has the ability to repair, but if the initial injury is severe the repair may be incomplete or maladaptive and result in chronic kidney problems. Autophagy is a highly conserved pathway to deliver intracellular contents to lysosomes for degradation. Autophagy plays an important role in maintaining renal function and is involved in the pathogenesis of renal diseases. Autophagy is activated in various forms of AKI and acts as a defense mechanism against kidney cell injury and death. After AKI, autophagy is maintained at a relatively high level in kidney tubule cells during maladaptive kidney repair but the role of autophagy in maladaptive kidney repair has been controversial. Nonetheless, recent studies have demonstrated that autophagy may contribute to maladaptive kidney repair after AKI by inducing tubular degeneration and promoting a profibrotic phenotype in renal tubule cells. In this review, we analyze the role and regulation of autophagy in kidney injury and repair and discuss the therapeutic strategies by targeting autophagy.

Tubular aryl hydratocarbon receptor upregulates EZH2 to promote cellular senescence in cisplatin-induced acute kidney injury

Acute kidney injury (AKI) is one of the serious clinical syndromes with high morbidity and mortality. Despite substantial progress in understanding the mechanism of AKI, no effective drug is available for treatment or prevention. In this study, we identified that a ligand-activated transcription factor aryl hydrocarbon receptor (AhR) was abnormally increased in the kidneys of cisplatin-induced AKI mice or tubular epithelial TCMK-1 cells. The AhR inhibition by BAY2416964 and tubular conditional deletion both alleviated cisplatin-induced kidney dysfunction and tubular injury. Notably, inhibition of AhR could improve cellular senescence of injured kidneys, which was indicated by senescence-associated β-galactosidase (SA-β-gal) activity, biomarker p53, p21, p16 expression, and secretory-associated secretory phenotype IL-1β, IL-6 and TNFα level. Mechanistically, the abnormal AhR expression was positively correlated with the increase of a methyltransferase EZH2, and AhR inhibition suppressed the EZH2 expression in cisplatin-injured kidneys. Furthermore, the result of ChIP assay displayed that EZH2 might indirectly interact with AhR promoter region by affecting H3K27me3. The direct recruitment between H3K27me3 and AhR promoter is higher in the kidneys of control than that of cisplatin-treated mice, suggesting EZH2 reversely influenced AhR expression through weakening H3K27me3 transcriptional inhibition on AhR promoter. The present study implicated that AhR and EZH2 have mutual regulation, which further accelerated tubular senescence in cisplatin-induced AKI. Notably, the crucial role of AhR is potential to become a promising target for AKI.

Costunolide prevents renal ischemia-reperfusion injury in rats by reducing autophagy, apoptosis, inflammation, and DNA damage

Objectives

Renal ischemia-reperfusion (I/R) is a vital health condition leading to acute kidney injury. Costunolide (COST) is an actively used molecule clinically for its anti-inflammatory, antioxidant, and immunomodulatory properties. In the present study, we searched for the possible protective effects of COST against renal ischemia/reperfusion (I/R) injury in rats.

Materials and Methods

We established a renal I/R rat model. We divided forty rats into four groups: group I (sham), group II (I/R), group III (I/R+COST 5 mg/kg), and group IV (I/R+COST 10 mg/kg). We collected blood, kidney, and lung samples for analysis.

Results

COST administration performed anti-oxidant and anti-inflammatory activity by reducing oxidant parameters and proinflammatory cytokine levels. COST alleviated DNA damage through declining 8-hydroxydeoxyguanosine (8-OHdG) levels. In addition, COST diminished tubular damage and inflammation by reducing kidney injury molecule-1 (KIM-1) production. COST administration also ameliorated apoptosis and autophagy by decreasing caspase-3 and microtubule-associated protein light chain 3B (MAPLC3, LC3B) expression.

Conclusion

COST demonstrated protective effects against renal I/R-induced injury.

Melatonin Attenuates Mitochondrial Damage in Aristolochic Acid-Induced Acute Kidney Injury

Aristolochic acid (AA), extracted from Aristolochiaceae plants, plays an essential role in traditional herbal medicines and is used for different diseases. However, AA has been found to be nephrotoxic and is known to cause aristolochic acid nephropathy (AAN). AA-induced acute kidney injury (AKI) is a syndrome in AAN with a high morbidity that manifests mitochondrial damage as a key part of its pathological progression. Melatonin primarily serves as a mitochondria-targeted antioxidant. However, its mitochondrial protective role in AA-induced AKI is barely reported. In this study, mice were administrated 2.5 mg/kg AA to induce AKI. Melatonin reduced the increase in Upro and Scr and attenuated the necrosis and atrophy of renal proximal tubules in mice exposed to AA. Melatonin suppressed ROS generation, MDA levels and iNOS expression and increased SOD activities in vivo and in vitro. Intriguingly, the in vivo study revealed that melatonin decreased mitochondrial fragmentation in renal proximal tubular cells and increased ATP levels in kidney tissues in response to AA. In vitro, melatonin restored the mitochondrial membrane potential (MMP) in NRK-52E and HK-2 cells and led to an elevation in ATP levels. Confocal immunofluorescence data showed that puncta containing Mito-tracker and GFP-LC3A/B were reduced, thereby impeding the mitophagy of tubular epithelial cells. Furthermore, melatonin decreased LC3A/B-II expression and increased p62 expression. The apoptosis of tubular epithelial cells induced by AA was decreased. Therefore, our findings revealed that melatonin could prevent AA-induced AKI by attenuating mitochondrial damage, which may provide a potential therapeutic method for renal AA toxicity.

Puromycin-induced kidney injury and subsequent regeneration in adult zebrafish

Puromycin treatment can cause glomerular injury to the kidney, leading to proteinuria. However, the pathogenesis of acute kidney injury and subsequent regeneration after puromycin administration in animal models remain unclear. In this work, we examined the characteristics of kidney injury and subsequent regeneration following puromycin treatment in adult zebrafish. We intraperitoneally injected 100 μg of puromycin into zebrafish; sacrificed them at 1, 3, 5, 7, or 14 days post-injection (dpi); and examined the morphological, functional, and molecular changes in the kidney. Puromycin-treated zebrafish presented more rapid clearance of rhodamine dextran than control animals. Morphological changes were observed immediately after the puromycin injection (1-7 dpi) and had recovered by 14 dpi. The mRNA production of lhx1a, a renal progenitor marker, increased during recovery from kidney injury. Levels of NFκB, TNFα, Nampt, and p-ERK increased significantly during nephron injury and regeneration, and Sirt1, FOXO1, pax2, and wt1b showed an increasing tendency. However, TGF-β1 and smad5 production did not show any changes after puromycin treatment. This study provides evidence that puromycin-induced injury in adult zebrafish kidneys is a potential tool for evaluating the mechanism of nephron injury and subsequent regeneration.

LncRNA 148400 Promotes the Apoptosis of Renal Tubular Epithelial Cells in Ischemic AKI by Targeting the miR-10b-3p/GRK4 Axis

Although recent studies have reported that long non-coding RNA (lncRNA) is involved in the development of ischemic acute kidney injury (AKI), the exact function and regulatory mechanism of lncRNAs in ischemic AKI remain largely unknown. Herein, we found that ischemic injury promoted the expression of lncRNA 148400 in mouse proximal tubule-derived cell line (BUMPT) and C57BL/6J mice. Furthermore, the lncRNA148400 mediates ischemic injury-induced apoptosis of BUMPT cells. Mechanistically, lncRNA 148400 sponged miR-10b-3p to promote apoptosis via GRK4 upregulation. Finally, knockdown of lncRNA 148400 alleviated the I/R-induced deterioration of renal function, renal tubular injury, and cell apoptosis. In addition, cleaved caspase-3 is increased via targeting the miR-10b-3p/GRK4 axis. Collectively, these results showed that lncRNA 148400/miR-10b-3p/GRK4 axis mediated the development of ischemic AKI.

miR-122-5p Regulates Renal Fibrosis In Vivo

The role of exogenous microRNAs (miRNAs) in renal fibrosis is poorly understood. Here, the effect of exogenous miRNAs on renal fibrosis was investigated using a renal fibrosis mouse model generated by unilateral ureteral obstruction (UUO). miRNA microarray analysis and quantitative reverse-transcription polymerase chain reaction showed that miR-122-5p was the most downregulated (0.28-fold) miRNA in the kidneys of UUO mice. The injection of an miR-122-5p mimic promoted renal fibrosis and upregulated COL1A2 and FN1, whereas an miR-122-5p inhibitor suppressed renal fibrosis and downregulated COL1A2 and FN1. The expression levels of fibrosis-related mRNAs, which were predicted targets of miR-122-5p, were evaluated. The expression level of TGFBR2, a pro-fibrotic mRNA, was upregulated by the miR-122-5p mimic, and the expression level of FOXO3, an anti-fibrotic mRNA, was upregulated by the miR-122-5p inhibitor. The protein expressions of TGFBR2 and FOXO3 were confirmed by immunohistochemistry. Additionally, the expression levels of LC3, downstream anti-fibrotic mRNAs of FOXO3, were upregulated by the miR-122-5p inhibitor. These results suggest that miR-122-5p has critical roles in renal fibrosis.

Effect of M2-like macrophages of the injured-kidney cortex on kidney cancer progression

Chronic kidney disease (CKD) affects kidney cancer patients' mortality. However, the underlying mechanism remains unknown. M2-like macrophages have pro-tumor functions, also exist in injured kidney, and promote kidney fibrosis. Thus, it is suspected that M2-like macrophages in injured kidney induce the pro-tumor microenvironment leading to kidney cancer progression. We found that M2-like macrophages present in the injured kidney promoted kidney cancer progression and induced resistance to anti-PD1 antibody through its pro-tumor function and inhibition of CD8⁺ T cell infiltration. RNA-seq revealed Slc7a11 was upregulated in M2-like macrophages. Inhibition of Slc7a11 with sulfasalazine inhibited the pro-tumor function of M2-like macrophages and synergized with anti-PD1 antibody. Moreover, SLC7A11-positive macrophages were associated with poor prognosis among kidney cancer patients. Collectively, this study dissects the characteristic microenvironment in the injured kidney that contributed to kidney cancer progression and anti-PD1 antibody resistance. This insight offers promising combination therapy with anti-PD1 antibody and macrophage targeted therapy.

Effects of contralateral nephrectomy timing and ischemic conditions on kidney fibrosis after unilateral kidney ischemia-reperfusion injury

Acute kidney injury (AKI) is an important cause of chronic kidney disease (CKD), but the underlying mechanisms are unclear. Animal models are tools for studying the AKI-CKD progression. Kidney ischemia-reperfusion injury (IRI) models, especially the unilateral IRI (uIRI) model with delayed contralateral kidney resection, are commonly used to induce fibrotic progression to CKD after AKI. However, in previous studies, we found that details of the operation had a significant impact on the long-term outcomes of the kidney in this uIRI model. In this study, we investigated the effects of resection timing of the contralateral intact kidney, core body temperatures during ischemia, and time length of kidney ischemia on kidney function, histological injury and kidney fibrosis after AKI, using a mouse uIRI model with delayed contralateral nephrectomy. The results showed that all these parameters significantly affected the AKI-CKD transition. The post-AKI fibrosis worsened and the survival rate declined with a longer interval between contralateral nephrectomy and uIRI, higher ischemic body temperature, or longer ischemic duration when the other two variables were fixed. In conclusion, in the uIRI model with delayed contralateral nephrectomy, kidney fibrosis after AKI is influenced by many factors. Strictly controlling the experimental conditions is very important for the stability and consistency of the model.

LncRNA ENSMUST00000171502 Induced by HIF-1α Ameliorates Ischemic Acute Kidney Injury via Targeting the miR-130b-3p/Mybl-1 Axis

Background: Numerous studies have suggested that long non-coding RNA (lncRNA) affects the progression of ischemic acute kidney injury (IAKI). However, little information is currently available concerning the mechanisms of lncRNA171502 involved in IAKI. Methods: We applied an RT-qPCR assay for the expression of lncRNA171502 and miRNA-130b-3p, immunoblotting for the detection of Mybl-1-myeloblastosis oncogene-like 1 (Mybl-1) and cleaved caspase-3 (CC3) expression, and flow cytometry (FCM) for the evaluation of apoptosis. Result: Initially, lncRNA171502 was induced by HIF-1α in the mouse proximal tubular (BUMPT) cell line and C57BL/6J mice during ischemic injury. Secondly, ischemic injury-induced BUMPT cell apoptosis was markedly relieved following the overexpression of lncRNA171502. However, this effect was enhanced by the knockdown of lncRNA171502. Mechanistically, lncRNA171502 could sponge miRNA-130b-3p and would subsequently upregulate the expression of Mybl-1 to drive the apoptotic process. Lastly, the overexpression of lncRNA171502 alleviated the development of IAKI by targeting miRNA-130b-3p/Mybl-1 pathways. Conclusions: In summary, the HIF-1α/lncRNA171502/miRNA-130b-3p/Mybl-1 axis prevented the progression of IAKI and might serve as a potential therapeutic target.

No safe renal warm ischemia time-The molecular network characteristics and pathological features of mild to severe ischemia reperfusion kidney injury

Ischemic acute kidney injury (AKI) has always been a hot and difficult research topic in the field of renal diseases. This study aims to illustrate the safe warm ischemia time of kidney and the molecular network characteristics and pathological features of mild to severe ischemia reperfusion kidney injury. We established varying degrees of renal injury due to different ischemia time (0 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, and 30 min) on unilateral (left kidney) ischemia-reperfusion injury and contralateral (right kidney) resection (uIRIx) mouse model. Mice were sacrificed 24 h after uIRIx, blood samples were harvested to detect serum creatinine (Scr), and kidney tissue samples were harvested to perform Periodic Acid-Schiff (PAS) staining and RNA-Seq. Differentially expressed genes (DEGs) were identificated, time-dependent gene expression patterns and functional enrichment analysis were further performed. Finally, qPCR was performed to validated RNA-Seq results. Our results indicated that there was no absolute safe renal warm ischemia time, and every minute of ischemia increases kidney damage. Warm ischemia 26min or above in mice makes severe kidney injury, renal pathology and SCr were both significantly changed. Warm ischemia between 18 and 26 min makes mild kidney injury, with changes in pathology and renal molecular expression, while SCr did not change. No obvious pathological changes but significant differences in molecular expression were found less than 16min warm ischemia. There are two key time intervals in the process of renal ischemia injury, 0 min-16 min (short-term) and 26 min-28 min (long-term). Gene expression of immune-related pathways were most significantly down-regulated in short-term ischemia, while metabolism-related pathways were the mainly enriched pathway in long-term ischemia. Taken together, this study provides novel insights into safe renal artery occlusion time in partial nephrectomy, and is of great value for elucidating molecular network characteristics and pathological features of mild to severe ischemia reperfusion kidney injury, and key genes related to metabolism and immune found in this study also provide potential diagnostic and therapeutic biomarkers for AKI.

IL-18 deficiency ameliorates the progression from AKI to CKD

Inflammation is an important factor in the progression from acute kidney injury (AKI) to chronic kidney disease (CKD). The role of interleukin (IL)-18 in this progression has not been examined. We aimed to clarify whether and how IL-18 limits this progression. In a folic acid induced renal injury mouse model, we studied the time course of kidney injury and renal IL-18 expression. In wild-type mice following injection, renal IL-18 expression increased. In parallel, we characterized other processes, including at day 2, renal tubular necroptosis assessed by receptor-interacting serine/threonine-protein kinase1 (RIPK1) and RIPK3; at day 14, transdifferentiation (assessed by transforming growth factor β1, vimentin and E-cadherin); and at day 30, fibrosis (assessed by collagen 1). In IL-18 knockout mice given folate, compared to wild-type mice, tubular damage and necroptosis, transdifferentiation, and renal fibrosis were attenuated. Importantly, IL-18 deletion decreased numbers of renal M1 macrophages and M1 macrophage cytokine levels at day 14, and reduced M2 macrophages numbers and macrophage cytokine expression at day 30. In HK-2 cells, IL-18 knockdown attenuated necroptosis, transdifferentiating and fibrosis.In patients with tubulointerstitial nephritis, IL-18 protein expression was increased on renal biopsies using immunohistochemistry. We conclude that genetic IL-18 deficiency ameliorates renal tubular damage, necroptosis, cell transdifferentiation, and fibrosis. The renoprotective role of IL-18 deletion in the progression from AKI to fibrosis may be mediated by reducing a switch in predominance from M1 to profibrotic M2 macrophages during the process of kidney repair.

Renoprotective Effects of Luteolin: Therapeutic Potential for COVID-19-Associated Acute Kidney Injuries

Acute kidney injury (AKI) has been increasingly reported in critically-ill COVID-19 patients. Moreover, there was significant positive correlation between COVID-19 deaths and renal disorders in hospitalized COVID-19 patients with underlying comorbidities who required renal replacement therapy. It has suggested that death in COVID-19 patients with AKI is 3-fold higher than in COVID-19 patients without AKI. The pathophysiology of COVID-19-associated AKI could be attributed to unspecific mechanisms, as well as COVID-19-specific mechanisms such as direct cellular injury, an imbalanced renin-angiotensin-aldosterone system, pro-inflammatory cytokines elicited by the viral infection and thrombotic events. To date, there is no specific treatment for COVID-19 and its associated AKI. Luteolin is a natural compound with multiple pharmacological activities, including anticoronavirus, as well as renoprotective activities against kidney injury induced by sepsis, renal ischemia and diverse nephrotoxic agents. Therefore, in this review, we mechanistically discuss the anti-SARS-CoV-2 and renoprotective activities of luteolin, which highlight its therapeutic potential in COVID-19-AKI patients.

A new LKB1 activator, piericidin analogue S14, retards renal fibrosis through promoting autophagy and mitochondrial homeostasis in renal tubular epithelial cells

Background: Liver kinase B1 (LKB1) is the key regulator of energy metabolism and cell homeostasis. LKB1 dysfunction plays a key role in renal fibrosis. However, LKB1 activators are scarce in commercial nowadays. This study aims to discover a new drug molecule, piericidin analogue S14 (PA-S14), preventing renal fibrosis as a novel activator to LKB1. Methods: Our group isolated PA-S14 from the broth culture of a marine-derived Streptomyces strain and identified its binding site. We adopted various CKD models or AKI-CKD model (5/6 nephrectomy, UUO, UIRI and adriamycin nephropathy models). TGF-β-stimulated renal tubular cell culture was also tested. Results: We identified that PA-S14 binds with residue D176 in the kinase domain of LKB1, and then induces the activation of LKB1 through its phosphorylation and complex formation with MO25 and STRAD. As a result, PA-S14 promotes AMPK activation, triggers autophagosome maturation, and increases autophagic flux. PA-S14 inhibited tubular cell senescence and retarded fibrogenesis through activation of LKB1/AMPK signaling. Transcriptomics sequencing and mutation analysis further demonstrated our results. Conclusion: PA-S14 is a novel leading compound of LKB1 activator. PA-S14 is a therapeutic potential to renal fibrosis through LKB1/AMPK-mediated autophagy and mitochondrial homeostasis pathways.

Multiparametric magnetic resonance imaging in diagnosis of long-term renal atrophy and fibrosis after ischemia reperfusion induced acute kidney injury in mice

Tubular atrophy and fibrosis are pathological changes that determine the prognosis of kidney disease induced by acute kidney injury (AKI). We aimed to evaluate multiple magnetic resonance imaging (MRI) parameters, including pool size ratio (PSR) from quantitative magnetization transfer, relaxation rates, and measures from spin-lock imaging ( R 1 ρ and S ρ ), for assessing the pathological changes associated with AKI-induced kidney disease. Eight-week-old male C57BL/6 J mice first underwent unilateral ischemia reperfusion injury (IRI) induced by reperfusion after 45 min of ischemia. They were imaged using a 7T MRI system 56 days after the injury. Paraffin tissue sections were stained using Masson trichrome and picrosirius red to identify histopathological changes such as tubular atrophy and fibrosis. Histology detected extensive tubular atrophy and moderate fibrosis in the cortex and outer stripe of the outer medulla (CR + OSOM) and more prominent fibrosis in the inner stripe of the outer medulla (ISOM) of IRI kidneys. In the CR + OSOM region, evident decreases in PSR, R 1 , R 2 , R 1 ρ , and S ρ showed in IRI compared with contralateral kidneys, with PSR and S ρ exhibiting the most significant changes. In addition, the exchange parameter S ρ dropped by the largest degree among all the MRI parameters, whileR 2 * increased significantly. In the ISOM of IRI kidneys, PSR increased while S ρ kept decreasing. R 2 , R 1 ρ , andR 2 * all increased due to more severe fibrosis in this region. Among MRI measures, PSR and R 1 ρ showed the highest detectability of renal changes no matter whether tubular atrophy or fibrosis dominated.R 2 * and S ρ could be more specific to a single pathological event than other MRI measures because onlyR 2 * increased and S ρ decreased consistently when either fibrosis or tubular atrophy dominated, and their correlations with fibrosis scores were higher than other MRI measures. Multiparametric MRI may enable a more comprehensive analysis of histopathological changes following AKI.

Protein arginine methyltransferase 3 inhibits renal tubulointerstitial fibrosis through asymmetric dimethylarginine

Mammalian protein arginine methyltransferase 3 (PRMT3) catalyzes the monomethylation and dimethylation of the arginine residues of proteins. The role of PRMT3 in renal fibrosis is currently unknown. We aimed to study the role of PRMT3 in renal fibrosis and explored its underlying mechanisms. Quantitative PCR analysis and Western blotting analysis showed that the expression of PRMT3 was up-regulated in unilateral ureteral obstruction (UUO) mouse kidneys. Knockout of Prmt3 gene enhanced interstitial fibrosis in UUO kidneys as shown by Masson staining and Western blotting analysis the expression of pro-fibrotic markers. The production of asymmetric dimethylarginine (ADMA) was increased in wide type UUO kidneys but not further increased in Prmt3 knockout UUO kidneys. Administration of exogeneous ADMA in UUO kidneys blocked the enhanced renal interstitial fibrosis in Prmt3 mutant mice. Moreover, genetic deletion of Prmt3 gene increased blood urea nitrogen levels and renal deposition of collagen in folic acid injected mice. We conclude that PRMT3 inhibits renal tubulointerstitial fibrosis through elevating renal ADMA levels.

Cpd-0225 attenuates renal fibrosis via inhibiting ALK5

Chronic kidney disease (CKD) is an increasing public health concern, characterized by a reduced glomerular filtration rate and increased urinary albumin excretion. Renal fibrosis is an important pathological condition in patients with CKD. In this study, we evaluated the anti-fibrotic effect of Cpd-0225, a novel transforming growth factor-β (TGF-β) type I receptor (also known as ALK5) inhibitor, in vitro and in vivo, by comparing its effect with that of SB431542, a classic ALK5 inhibitor, which has not entered the clinical trial stage owing to multiple side effects. Our data showed that Cpd-0225 attenuated fibrotic response in TGF-β1-stimulated human kidney tubular epithelial cells and repeated hypoxia/reoxygenation-treated mouse tubular epithelial cells. We further confirmed that Cpd-0225 improved renal tubular injury and ameliorated collagen deposition in unilateral ureteral obstruction-, ischemia/reperfusion-, and aristolochic acid-induced mouse models of renal fibrosis. In addition, molecular docking and site-directed mutagenesis showed that Cpd-0225 exerted a higher reno-protective effect than SB431542, by physically binding to the key amino acid residues, Lys232 and Lys335 of ALK5, thereby suppressing the phosphorylation of Smad3 and ERK1/2. Taken together, these findings suggest that Cpd-0225 administration attenuates renal fibrosis via ALK5-dependent mechanisms and displays a more effective therapeutic effect than SB431542. Thus, Cpd-0225 may serve as a potential therapeutic agent for the treatment of CKD.