Molecular Mechanisms of the Acute Kidney Injury to Chronic Kidney Disease Transition: An Updated View

The role of lncRNAs in AKI and CKD: Molecular mechanisms, biomarkers, and potential therapeutic targets

Exosomes, a type of extracellular vesicle, are commonly found in different body fluids and are rich in nucleic acids (circRNA, lncRNAs, miRNAs, mRNAs, tRNAs, etc.), proteins, and lipids. They are involved in intercellular communication. lncRNAs are responsible for the modulation of gene expression, thus affecting the pathological process of kidney injury. This review summarizes the latest knowledge on the roles of exosome lncRNAs and circulating lncRNAs in the pathogenesis, biomarker discovery, and treatment of chronic kidney disease, renal fibrosis, and acute kidney injury, providing an overview of novel regulatory approaches and lncRNA delivery systems.

From Liver to Kidney: The Overlooked Burden of Nonalcoholic Fatty Liver Disease in Chronic Kidney Disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a contributor to chronic kidney disease (CKD), yet its impact remains underappreciated in clinical practice. Recent studies reveal a strong association between NAFLD and CKD progression, with evidence linking hepatic dysfunction to renal impairment through metabolic and inflammatory pathways. NAFLD not only increases the risk of CKD but also accelerates its progression, leading to worse cardiovascular outcomes and higher mortality, particularly in patients with advanced fibrosis. Despite this growing evidence, NAFLD often goes undiagnosed in CKD patients and routine hepatic evaluation is rarely integrated into nephrology care. Emerging diagnostic tools, including noninvasive biomarkers and imaging techniques, offer potential for earlier detection, yet their clinical implementation remains inconsistent. Although lifestyle modifications remain the foundation of treatment, pharmacotherapeutic strategies, including SGLT2 inhibitors and GLP-1 receptor agonists, have demonstrated potential in mitigating both hepatic and renal impairment. Recognizing the interplay between NAFLD and CKD is essential for improving patient outcomes. A multidisciplinary approach, integrating hepatology and nephrology expertise, is crucial to refining screening strategies, optimizing treatment, and reducing the long-term burden of these coexisting conditions.

Synthetic Bilirubin-Based Nanomedicine Protects Against Renal Ischemia/Reperfusion Injury Through Antioxidant and Immune-Modulating Activity

Renal ischemia/reperfusion injury (IRI) is a common form of acute kidney injury. The basic mechanism underlying renal IRI is acute inflammation, where oxidative stress plays an important role. Although bilirubin exhibits potent reactive oxygen species (ROS)-scavenging properties, its clinical application is hindered by problems associated with solubility, stability, and toxicity. In this study, BX-001N, a synthetic polyethylene glycol-conjugated bilirubin 3α nanoparticle is developed and assessed its renoprotective effects in renal IRI. Intravenous administration of BX-001N led to increase uptake in the kidneys with minimal migration to the brain after IRI. Peri-IRI BX-001N administration improves renal function and attenuates renal tissue injury and tubular apoptosis to a greater extent than free bilirubin on day 1 after IRI. BX-001N suppressed renal infiltration of inflammatory cells and reduced expression of TNF-α and MCP-1. Furthermore, BX-001N increases renal tubular regeneration on day 3 and suppresses renal fibrosis on day 28. BX-001N decreases the renal expressions of dihydroethidium, malondialdehyde, and nitrotyrosine after IRI. In conclusion, BX-001N, the first Good Manufacturing Practice-grade synthetic bilirubin-based nanomedicine attenuates acute renal injury and chronic fibrosis by suppressing ROS generation and inflammation after IRI. It shows adequate safety profiles and holds promise as a new therapy for renal IRI.

Aromadendrin alleviates LPS-induced kidney apoptosis and inflammation by inhibiting phosphorylation of MAPK and NF-κB signaling pathways

BACKGROUND

Excessive inflammation and apoptosis in kidneys are critical players in the pathogenesis of acute kidney injury (AKI). Aromadendrin is a natural flavonoid characterized by anti-inflammatory, anti-apoptotic, and antioxidant actions. Thus, we investigated the roles and mechanisms of aromadendrin in the development of AKI.

METHODS

Lipopolysaccharide (LPS) was used to induce AKI mice, and one hour after LPS challenge, the mice received oral administration of aromadendrin or vehicle. Renal functions were assessed by measuring blood urea nitrogen and creatinine in serum. Histological changes were determined by hematoxylin and eosin staining. Apoptotic cells of renal tissues were detected by TUNEL staining. Gene expression was measured by western blotting and RT-qPCR.

RESULTS

Aromadendrin alleviated LPS-induced renal dysfunctions and histological defects in mice. Additionally, aromadendrin suppressed excessive inflammation and tissue apoptosis in the kidneys of LPS-induced AKI mice. Mechanistically, aromadendrin blocked the activation of NF-κB and MAPK pathways in LPS-induced AKI mice.

CONCLUSION

Aromadendrin alleviates LPS-stimulated inflammation and tissue cell apoptosis in kidneys by inactivating the NF-κB and MAPK pathways.

Intermittent Fasting Protects Against the Progression from Acute Kidney Injury to Chronic Kidney Disease

Acute kidney injury (AKI) is a major but often underestimated risk factor for the development of chronic kidney disease (CKD). Exploring innovative approaches to prevent this progression is critical. Intermittent fasting (IF), recognized for its metabolic and anti-inflammatory benefits, may offer protective effects in this context. Using a unilateral ischemia-reperfusion injury (UIRI) model in male C57BL/6 mice, we evaluated the impact of IF on tubulointerstitial fibrosis and tubular epithelial-mesenchymal transition (EMT) over 8 weeks. Mice in the IF group followed a 5:2 regimen, fasting for 24 h twice weekly. Four groups were studied: control, IF, UIRI, and IF + UIRI. The UIRI group exhibited increased fibrosis and EMT, both of which were significantly attenuated in the IF + UIRI group. IF also reduced levels of TGF-β1, phosphorylated NF-κB p65, inflammatory cytokines, and F4/80-positive macrophages, along with markers of oxidative stress. These findings highlight IF's ability to mitigate fibrosis and EMT through reductions in inflammation and oxidative stress during AKI-to-CKD progression. Our study suggests that IF may serve as a promising dietary strategy to prevent AKI from advancing into CKD.

PSTK exerts protective role in cisplatin-tubular cell injury via BAX/BCL2/Caspase3 pathway

Cisplatin is a widely used anticancer drug, but its accumulation in renal tubular epithelial cells (TECs) can cause acute kidney injury. Phosphoseryl-tRNA kinase (PSTK) is an intermediate product produced under oxidative stress conditions. This study aimed to elucidate whether PSTK could protect TECs and its possible mechanisms. We found that PSTK levels decreased after cisplatin treatment, but PSTK overexpression using lentivirus vectors protected TEC viability. Overexpression of PSTK increased selenoprotein concentrations and reduced intracellular ROS levels. Additionally, PSTK overexpression inhibited the BAX/BCL2/Caspase 3 pathway after cisplatin stimulation, suggesting its potential role in preventing cell apoptosis. Taken together, this study suggests that PSTK could protect TEC viability from cisplatin-induced injury, possibly by inhibiting mitochondrial apoptosis. The study is significant for developing therapeutic strategies that could manipulate PSTK to delay AKI progression.

Propionate and butyrate counteract renal damage and progression to chronic kidney disease

BACKGROUND

Short-chain fatty acids (SCFAs), mainly acetate, propionate and butyrate, are produced by gut microbiota through fermentation of complex carbohydrates that cannot be digested by the human host. They affect gut health and can contribute at the distal level to the pathophysiology of several diseases, including renal pathologies.

METHODS

SCFA levels were measured in chronic kidney disease (CKD) patients (n = 54) at different stages of the disease, and associations with renal function and inflammation parameters were examined. The impact of propionate and butyrate in pathways triggered in tubular cells under inflammatory conditions was analysed using genome-wide expression assays. Finally, a pre-clinical mouse model of folic acid-induced transition from acute kidney injury to CKD was used to analyse the preventive and therapeutic potential of these microbial metabolites in the development of CKD.

RESULTS

Faecal levels of propionate and butyrate in CKD patients gradually reduce as the disease progresses, and do so in close association with established clinical parameters for serum creatinine, blood urea nitrogen and the estimated glomerular filtration rate. Propionate and butyrate jointly downregulated the expression of 103 genes related to inflammatory processes and immune system activation triggered by tumour necrosis factor-α in tubular cells. In vivo, the administration of propionate and butyrate, either before or soon after injury, respectively, prevented and slowed the progression of damage. This was indicated by a decrease in renal injury markers, the expression of pro-inflammatory and pro-fibrotic markers, and recovery of renal function over the long term.

CONCLUSIONS

Propionate and butyrate levels are associated with a progressive loss of renal function in CKD patients. Early administration of these SCFAs prevents disease advancement in a pre-clinical model of acute renal damage, demonstrating their therapeutic potential independently of the gut microbiota.

Endothelial-specific deletion of connexin 43 improves renal function and structure after acute kidney injury

BACKGROUND

We have previously reported that the gap junction protein connexin 43 (Cx43) was upregulated in chronic renal disease in humans and rodents and plays a crucial role in the progression of experimental nephropathy. In this study, we investigated its role after renal ischemia/reperfusion (rIR), which is a major mechanism of injury in acute renal injury (AKI) and renal transplant graft dysfunction.

METHODS

Wild-type mice (WT) and mice in which Cx43 expression was genetically reduced by half (Cx43 ±) were unilaterally nephrectomized. The left renal artery was subsequently clamped, with reperfusion of varying duration. Mice with tubular- or endothelial-specific deletion of Cx43 were also used to assess the effect of this connexin in each cell type after rIR. Kidneys were assessed for histological evaluation, immunohistochemistry, and RT-PCR.

RESULTS

Blood urea nitrogen and creatininemia were progressively elevated in WT mice and picked up 48 h after rIR. At the same time point, severe tubular necrosis and dilation occurred in the cortico-medullary junction of the injured kidneys with accompanying massive neutrophil infiltration. Interestingly, Cx43 expression was progressively increased within the tubulointerstitial compartment during kidney damage progression and was paralleled closely by that of markers of renal dysfunction. Cx43 ± mice showed fewer tubular lesions, less inflammation, and further improved renal function. Similar results were observed in mice where Cx43 was specifically deleted within the vascular endothelium. In contrast, Cx43 deletion in renal tubules did not significantly improve renal structure and function after rIR.

CONCLUSION

Our findings suggest that endothelial Cx43 plays a crucial role in AKI.

Cell therapy in kidney diseases: advancing treatments for renal regeneration

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), pose a significant global health challenge, with high morbidity and mortality rates driven by rising prevalence of risk factors such as diabetes and hypertension. Current therapeutic strategies are often limited, prompting the exploration of advanced cell therapies as potential solutions. This review provides a comprehensive overview of the state of cell therapies in kidney disease, tracing the progression from preclinical studies to clinical applications. Recent studies highlited that cell-based interventions offer kidney-protective properties through mechanisms such as paracrine signaling, immune modulation, and direct tissue integration, demonstrating potential in both AKI and CKD settings. Despite promising results, challenges remain in optimizing cell therapy protocols, including cell sourcing, delivery methods, and long-term outcomes. Finally, the review addresses on efforts to enhance cell function, optimize dosing, and refine delivery techniques to improve clinical outcomes in kidney disease management.

Wnt/beta-catenin modulation: A promising frontier in chronic kidney disease management

BACKGROUND

Being amongst the leading factors of death and distress, chronic kidney disease (CKD) has affected around 850 million people globally. The Wnt/β-catenin axis is vital for maintaining kidney homeostasis, from nephron generation to overall management. The β-catenin growth factor is typically not expressed in the adult kidney; however, its expression is found to increase under stress and injury conditions. It is categorised as canonical and non-canonical based on β-catenin availability, which mounts promising targets for ameliorating CKD. Hence, modulation of the Wnt/β-catenin signalling for CKD management is of utmost relevance.

OBJECTIVES

The primary aim of this review is to highlight the significance of targeting Wnt/β-catenin signalling for CKD management.

METHODS

The literature review regarding the role of Wnt/β-catenin signalling and therapies modulating it in CKD was conducted using PubMed, Scopus, Science Direct and Google Scholar.

RESULTS

The current review summarises the pharmacological therapies modulating the Wnt/β-catenin axis in CKD, building upon promising preclinical studies to establish a foundation for clinical studies in the future.

CONCLUSION

Wnt/β-catenin signalling is the evolution's most conserved pathway, which plays a pivotal role in CKD progression. Therapies modulating Wnt/β-catenin signalling have emerged as effective means for alleviating CKD.

Acute kidney disease in mice is associated with early cardiovascular dysfunction

Acute kidney injury (AKI) and chronic kidney disease (CKD) are major health concerns due to their increasing incidence and high mortality. They are interconnected syndromes; AKI without recovery evolves into acute kidney disease (AKD), which can indicate an AKI-to-CKD transition. Both AKI and CKD are associated with a risk of long-term cardiovascular complications, but whether vascular and cardiac dysfunctions can occur as early as the AKD period has not been studied extensively. In a mouse model of kidney injury (KI) with non-recovery, we performed vasoreactivity and echocardiography analyses on days 15 (D15) and 45 (D45) after KI. We determined the concentrations of two major gut-derived protein-bound uremic toxins known to induce cardiovascular toxicity-indoxyl sulfate (IS) and para-cresyl sulfate (PCS)-and the levels of inflammation and contraction markers on D7, D15, and D45. Mice with KI showed acute tubular and interstitial kidney lesions on D7 and D15 and chronic glomerulosclerosis on D45. They showed significant impairment of aorta relaxation and systolic-diastolic heart function, both on D15 and D45. Such dysfunction was associated with downregulation of the expression of two contractile proteins, αSMA and SERCA2a, with a more pronounced effect on D15 than on D45. KI was also followed by a rapid increase in IS and PCS serum concentrations and the expression induction of pro-inflammatory cytokines and endothelial adhesion molecules in serum and cardiovascular tissues. Therefore, these results highlight that AKD leads to early cardiac and vascular dysfunctions. How these dysfunctions could be managed to prevent cardiovascular events deserves further study.

Novel dysregulated long non-coding RNAs in the acute kidney injury-to-chronic kidney diseases transition unraveled by transcriptomic analysis

Acute kidney injury (AKI)-to-chronic kidney disease (CKD) transition involves a complex pathomechanism, including inflammation, apoptosis, and fibrosis where long non-coding RNAs (lncRNAs) play a crucial role in their regulation. However, to date, only a few lncRNAs have been discovered to be involved in the AKI-to-CKD transition. Therefore, this study aims to investigate the dysregulated lncRNAs in the AKI-to-CKD transition in vitro and in vivo. To mimic AKI-to-CKD transition both in vivo and in vitro, bilateral ischemia-reperfusion (IR) kidney injury was performed in Wistar rats (male), and normal rat kidney epithelial cell (NRK52E) cells were treated with exogenous transforming growth factor-β1 (TGF-β1). Further processing and analysis of samples collected from these studies (e.g., biochemical, histopathology, immunofluorescence, and RNA isolation) were also performed, and transcriptomic analysis was performed to identify the dysregulated lncRNAs. Rats subjected to IR showed a significant increase in kidney injury markers (creatinine, blood urea nitrogen (BUN), kidney injury molecule-1(KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) along with altered cell morphology). Apoptosis, inflammation, and fibrosis markers were markedly increased during the AKI-to-CKD transition. Furthermore, transcriptomic analysis revealed 62 and 84 unregulated and 95 and 92 downregulated lncRNAs in vivo and in vitro, respectively. Additionally, functional enrichment analysis revealed their involvement in various pathways, including the tumor necrosis factor (TNF), wingless-related integration site (Wnt), and hypoxia-inducible factor-1 (HIF-1) signaling pathways. These identified dysregulated lncRNAs significantly contribute to AKI-to-CKD transition, and their knockin/out can aid in developing targeted therapeutic interventions against AKI-to-CKD transition.

Transition from acute kidney injury to chronic kidney disease: mechanisms, models, and biomarkers

Acute kidney injury (AKI) and chronic kidney disease (CKD) are increasingly recognized as interconnected conditions with overlapping pathophysiological mechanisms. This review examines the transition from AKI to CKD, focusing on the molecular mechanisms, animal models, and biomarkers essential for understanding and managing this progression. AKI often progresses to CKD due to maladaptive repair processes, persistent inflammation, and fibrosis, with both conditions sharing common pathways involving cell death, inflammation, and extracellular matrix (ECM) deposition. Current animal models, including ischemia-reperfusion injury (IRI) and nephrotoxic damage, help elucidate these mechanisms but have limitations in replicating the complexity of human disease. Emerging biomarkers such as kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and soluble tumor necrosis factor receptors (TNFRs) show promise in early detection and monitoring of disease progression. This review highlights the need for improved animal models and biomarker validation to better mimic human disease and enhance clinical translation. Advancing our understanding of the AKI-to-CKD transition through targeted therapies and refined research approaches holds the potential to significantly improve patient outcomes.

Transition from acute kidney injury to chronic kidney disease in a long-term murine model of Shiga toxin-induced hemolytic-uremic syndrome

Introduction

Up to 40% of patients with typical hemolytic-uremic syndrome (HUS), characterized by microangiopathic hemolytic anemia and acute kidney injury (AKI), develop long-term consequences, most prominently chronic kidney disease (CKD). The transition from AKI to CKD, particularly in the context of HUS, is not yet fully understood. The objective of this study was to establish and characterize a Shiga toxin (Stx)-induced long-term HUS model to facilitate the study of mechanisms underlying the AKI-to-CKD transition.

Methods

C57BL/6J mice were subjected to 5, 10, 15, or 20 ng/kg Stx on days 0, 3, and 6 of the experiment and were sacrificed on day 14 or day 21 to identify the critical time of turnover from the acute to the chronic state of HUS disease.

Results

Acute disease, indicated by weight loss, plasma neutrophil gelatinase-associated lipocalin (NGAL) and urea, and renal neutrophils, diminished after 14 days and returned to sham level after 21 days. HUS-associated hemolytic anemia transitioned to non-hemolytic microcytic anemia along with unchanged erythropoietin levels after 21 days. Renal cytokine levels indicated a shift towards pro-fibrotic signaling, and interstitial fibrosis developed concentration-dependently after 21 days. While Stx induced the intrarenal invasion of pro-inflammatory M1 and pro-fibrotic M2 macrophages after 14 days, pro-fibrotic M2 macrophages were the dominant phenotype after 21 days.

Conclusion

In conclusion, we established and characterized the first Stx-induced long-term model of HUS. This tool facilitates the study of underlying mechanisms in the early AKI-to-CKD transition following HUS and allows the testing of compounds that may protect patients with AKI from developing subsequent CKD.

The significance of ferroptosis in renal diseases and its therapeutic potential

Kidney diseases are significant global public health concern, with increasing prevalence and substantial economic impact. Developing novel therapeutic approaches are essential for delaying disease progression and improving patient quality of life. Cell death signifying the termination of cellular life, could facilitate appropriate bodily development and internal homeostasis. Recently, regulated cell death (RCD) forms such as ferroptosis, characterized by iron-dependent lipid peroxidation, has garnered attention in diverse renal diseases and other pathological conditions. This review offers a comprehensive examination of ferroptosis, encompassing an analysis of the involvement of iron and lipid metabolism, the System Xc - /glutathione/glutathione peroxidase 4 signaling, and additional associated pathways. Meanwhile, the review delves into the potential of targeting ferroptosis as a therapeutic approach in the management of acute kidney injury (AKI), chronic kidney disease (CKD), diabetic nephropathy, and renal tumors. Furthermore, it emphasizes the significance of ferroptosis in the transition from AKI to CKD and further accentuates the potential for repurposing drug and utilizing traditional medicine in targeting ferroptosis-related pathways for clinical applications. The integrated review provides valuable insights into the role of ferroptosis in kidney diseases and highlights the potential for targeting ferroptosis as a therapeutic strategy.

Removal of the catalytic subunit of DNA-protein kinase in the proximal tubules promotes DNA and tubular damage during kidney injury

Tubular epithelial cell damage can be repaired through a series of complex signaling pathways. An early event in many forms of tubular damage is the observation of DNA damage, which can be repaired by specific pathways depending upon the type of genomic alteration.. In this study, we report that the catalytic subunit of DNA protein kinase (DNA-PKcs), a central DNA repair enzyme involved in sensing DNA damage and performing double stranded DNA break repair, plays an important role in the extent of tubular epithelial cell damage following exposure to injurious acute and chronic stimuli. Selective loss of DNA-PKcs in the proximal tubules led to increased markers of kidney dysfunction, DNA damage, and tubular epithelial cell injury in multiple models of acute kidney injury, specifically bilateral renal ischemia-reperfusion injury and single dose of cisplatin (15 mg/kg IP). In contrast, in a mouse model of kidney fibrosis and chronic kidney disease (UUO),the protective effects of DNA-PKcs was not as obvious histologically from the tissue sections. In the absence of proximal tubular DNA-PKcs, there was reduced levels of fibrotic markers, α-SMA and fibronectin, which suggests that there may be a biphasic role of DNA-PKcs depending upon the conditions exerted upon the kidney. In conclusion, this study demonstrates that the catalytic subunit of DNA-PKcs plays a context-dependent role in the kidney to reduce DNA damage during exposure to various types of acute, but not chronic forms of injurious stimuli.

The Impact of Acute Kidney Injury on Chronic Kidney Disease After Cardiac Surgery: A Systematic Review and Meta-analysis

OBJECTIVES

To evaluate the impact of acute kidney injury on transition to chronic kidney disease (CKD) after cardiac surgery and to determine frequency of incident CKD in these patients.

DESIGN

A systematic review and meta-analysis of observational studies.

SETTING

Electronic databases Medline and Embase were systematically searched from 1974 to February 6, 2023.

PARTICIPANTS

Eligible studies were original observational studies on adult cardiac surgery patients, written in the English language, and with clear kidney disease definitions. Exclusion criteria were studies with previously transplanted populations, populations with preoperative kidney impairment, ventricular assist device procedures, endovascular procedures, a kidney follow-up period of <90 days, and studies not presenting necessary data for effect size calculations.

INTERVENTIONS

Patients developing postoperative acute kidney injury after cardiac surgery were compared with patients who did not develop acute kidney injury.

MEASUREMENTS AND MAIN RESULTS

The search identified 4,329 unique studies, 87 underwent full-text review, and 12 were included for analysis. Mean acute kidney injury occurrence across studies was 16% (minimum-maximum: 8-50), while mean occurrence of CKD was 24% (minimum-maximum: 3-35), with high variability depending on definitions and follow-up time. Acute kidney injury was associated with increased odds of CKD in all individual studies. The pooled odds ratio across studies was 5.67 (95% confidence interval, 3.34-9.64; p < 0.0001).

CONCLUSIONS

Acute kidney injury after cardiac surgery was associated with a more than 5-fold increased odds of developing CKD. New-onset CKD occurred in almost 1 in 4 patients in the years after surgery.

Epithelial cell states associated with kidney and allograft injury

The kidney epithelium, with its intricate arrangement of highly specialized cell types, constitutes the functional core of the organ. Loss of kidney epithelium is linked to the loss of functional nephrons and a subsequent decline in kidney function. In kidney transplantation, epithelial injury signatures observed during post-transplantation surveillance are strong predictors of adverse kidney allograft outcomes. However, epithelial injury is currently neither monitored clinically nor addressed therapeutically after kidney transplantation. Several factors can contribute to allograft epithelial injury, including allograft rejection, drug toxicity, recurrent infections and postrenal obstruction. The injury mechanisms that underlie allograft injury overlap partially with those associated with acute kidney injury (AKI) and chronic kidney disease (CKD) in the native kidney. Studies using advanced transcriptomic analyses of single cells from kidney or urine have identified a role for kidney injury-induced epithelial cell states in exacerbating and sustaining damage in AKI and CKD. These epithelial cell states and their associated expression signatures are also observed in transplanted kidney allografts, suggesting that the identification and characterization of transcriptomic epithelial cell states in kidney allografts may have potential clinical implications for diagnosis and therapy.

Mesenchymal stem cells pretreated with interferon-gamma attenuate renal fibrosis by enhancing regulatory T cell induction

Mesenchymal stem cells (MSCs) exert their anti-inflammatory and anti-fibrotic effects by secreting various humoral factors. Interferon-gamma (IFN-γ) can enhance these effects of MSCs, and enhancement of regulatory T (Treg) cell induction is thought to be an underlying mechanism. However, the extent to which Treg cell induction by MSCs pretreated with IFN-γ (IFN-γ MSCs) ameliorates renal fibrosis remains unknown. In this study, we investigated the effects of Treg cell induction by IFN-γ MSCs on renal inflammation and fibrosis using an siRNA knockdown system. Administration of IFN-γ MSCs induced Treg cells and inhibited infiltration of inflammatory cells in ischemia reperfusion injury (IRI) rats more drastically than control MSCs without IFN-γ pretreatment. In addition, administration of IFN-γ MSCs more significantly attenuated renal fibrosis compared with control MSCs. Indoleamine 2,3-dioxygenase (IDO) expression levels in conditioned medium from MSCs were enhanced by IFN-γ pretreatment. Moreover, IDO1 knockdown in IFN-γ MSCs reduced their anti-inflammatory and anti-fibrotic effects in IRI rats by reducing Treg cell induction. Our findings suggest that the increase of Treg cells induced by enhanced secretion of IDO by IFN-γ MSCs played a pivotal role in their anti-fibrotic effects. Administration of IFN-γ MSCs may potentially be a useful therapy to prevent renal fibrosis progression.

SGLT2 Inhibitors in Kidney Diseases-A Narrative Review

Some of the most common conditions affecting people are kidney diseases. Among them, we distinguish chronic kidney disease and acute kidney injury. Both entities pose serious health risks, so new drugs are still being sought to treat and prevent them. In recent years, such a role has begun to be assigned to sodium-glucose cotransporter-2 (SGLT2) inhibitors. They increase the amount of glucose excreted in the urine. For this reason, they are currently used as a first-line drug in type 2 diabetes mellitus. Due to their demonstrated cardioprotective effect, they are also used in heart failure treatment. As for the renal effects of SGLT2 inhibitors, they reduce intraglomerular pressure and decrease albuminuria. This results in a slower decline in glomelular filtration rate (GFR) in patients with kidney disease. In addition, these drugs have anti-inflammatory and antifibrotic effects. In the following article, we review the evidence for the effectiveness of this group of drugs in kidney disease and their nephroprotective effect. Further research is still needed, but meta-analyses indicate SGLT2 inhibitors' efficacy in kidney disease, especially the one caused by diabetes. Development of new drugs and clinical trials on specific patient subgroups will further refine their nephroprotective effects.

Recent Update on Acute Kidney Injury-to-Chronic Kidney Disease Transition

Acute kidney injury (AKI) is characterized by an abrupt decline of excretory kidney function. The incidence of AKI has increased in the past decades. Patients diagnosed with AKI often undergo diverse clinical trajectories, such as early or late recovery, relapses, and even a potential transition from AKI to chronic kidney disease (CKD). Although recent clinical studies have demonstrated a strong association between AKI and progression of CKD, our understanding of the complex relationship between AKI and CKD is still evolving. No cohort study has succeeded in painting a comprehensive picture of these multi-faceted pathways. To address this lack of understanding, the idea of acute kidney disease (AKD) has recently been proposed. This presents a new perspective to pinpoint a period of heightened vulnerability following AKI, during which a patient could witness a substantial decline in glomerular filtration rate, ultimately leading to CKD transition. Although AKI is included in a range of kidney conditions collectively known as AKD, spanning from mild and self-limiting to severe and persistent, AKD can also occur without a rapid onset usually seen in AKI, such as when kidney dysfunction slowly evolves. In the present review, we summarize the most recent findings about AKD, explore the current state of biomarker discovery related to AKD, discuss the latest insights into pathophysiological underpinnings of AKI to CKD transition, and reflect on therapeutic challenges and opportunities that lie ahead.

Pyroptosis: The Determinator of Cell Death and Fate in Acute Kidney Injury

Background

Acute kidney injury (AKI) is kidney damage that leads to a rapid decline in function. AKI primarily occurs when the tubular epithelium is damaged, causing swelling, loss of brush margin, and eventual apoptosis. Research has shown that tubular epithelial cell damage in AKI is linked to cell cycle arrest, autophagy, and regulation of cell death.

Summary

Pyroptosis, a type of programmed cell death triggered by inflammation, is believed to play a role in the pathophysiology of AKI. Cumulative evidence has shown that pyroptosis is the main cause of tubular cell death in AKI. Thus, targeted intervention of pyroptosis may be a promising therapeutic approach for AKI. This review delves deep into the cutting-edge research surrounding pyroptosis in the context of AKI, shedding light on its intricate mechanisms and potential implications for clinical practice. Additionally, we explore the exciting realm of potential preclinical treatment options for AKI, aiming to pave the way for future therapeutic advancements.

Key Messages

Pyroptosis, a highly regulated form of cell death, plays a crucial role in determining the fate of cells during the development of AKI. This intricate process involves the activation of inflammasomes, which are multi-protein complexes that initiate pyroptotic cell death. By understanding the mechanisms underlying pyroptosis, researchers aim to gain insights into the pathogenesis of AKI and potentially identify new therapeutic targets for this condition.

Impaired TFEB-mediated autophagy-lysosome fusion promotes tubular cell cycle G2/M arrest and renal fibrosis by suppressing ATP6V0C expression and interacting with SNAREs

Increasing evidence suggests that autophagy plays a major role during renal fibrosis. Transcription factor EB (TFEB) is a critical regulator of autophagy- and lysosome-related gene transcription. However, the pathophysiological roles of TFEB in renal fibrosis and fine-tuned mechanisms by which TFEB regulates fibrosis remain largely unknown. Here, we found that TFEB was downregulated in unilateral ureteral obstruction (UUO)-induced human and mouse fibrotic kidneys, and kidney-specific TFEB overexpression using recombinant AAV serotype 9 (rAAV9)-TFEB in UUO mice alleviated renal fibrosis pathogenesis. Mechanically, we found that TFEB's prevention of extracellular matrix (ECM) deposition depended on autophagic flux integrity and its subsequent blockade of G2/M arrest in tubular cells, rather than the autophagosome synthesis. In addition, we together RNA-seq with CUT&Tag analysis to determine the TFEB targeted gene ATP6V0C, and revealed that TFEB was directly bound to the ATP6V0C promoter only at specific site to promote its expression through CUT&Run-qPCR and luciferase reporter assay. Interestingly, TFEB induced autophagic flux integrity, mainly dependent on scaffold protein ATP6V0C-mediated autophagosome-lysosome fusion by bridging with STX17 and VAMP8 (major SNARE complex) by co-immunoprecipitation analysis, rather than its mediated lysosomal acidification and degradation function. Moreover, we further investigated the underlying mechanism behind the low expression of TEFB in UUO-induced renal fibrosis, and clearly revealed that TFEB suppression in fibrotic kidney was due to DNMT3a-associated TFEB promoter hypermethylation by utilizing methylation specific PCR (MSP) and bisulfite-sequencing PCR (BSP), which could be effectively recovered by 5-Aza-2'-deoxycytidine (5A-za) to alleviate renal fibrosis pathogenesis. These findings reveal for the first time that impaired TFEB-mediated autophagosome-lysosome fusion disorder, tubular cell G2/M arrest and renal fibrosis appear to be sequentially linked in UUO-induced renal fibrosis and suggest that DNMT3a/TFEB/ATP6V0C may serve as potential therapeutic targets to prevent renal fibrosis.

[Role of Histone Modifications in Acute Kidney Injury Progressing to Chronic Kidney Disease]

Acute kidney injury (AKI), a clinical syndrome caused by various factors, is characterized by a rapid decline in kidney function in a short period of time. AKI affects the short-term prognosis of patients and may also induce chronic kidney disease (CKD). However, the current treatment options for AKI mainly focus on symptom management. Specific therapeutic measures available for the prevention of transition from AKI to CKD are very limited in number. Histones are basic proteins that intricately bind the DNA in chromosomes. After translation, histones undergo various modifications on their amino-terminal tails, such as methylation, acetylation, phosphorylation, ubiquitination, and lactylation, collectively forming the "histone code", which affects the expression of genes mainly by regulating the elastic structure of chromatin or recruiting specific proteins. Extensive research conducted in recent years on histone post-translational modifications (PTMs) has also sparked continuous interest in their association with the AKI-to-CKD transition. Therefore, this paper highlights the significant role of PTMs in the process of AKI developing and progressing to CKD, with a view to finding new approaches to preventing the progression of AKI to CKD.

The AKI-to-CKD Transition: The Role of Uremic Toxins

After acute kidney injury (AKI), renal function continues to deteriorate in some patients. In a pro-inflammatory and profibrotic environment, the proximal tubules are subject to maladaptive repair. In the AKI-to-CKD transition, impaired recovery from AKI reduces tubular and glomerular filtration and leads to chronic kidney disease (CKD). Reduced kidney secretion capacity is characterized by the plasma accumulation of biologically active molecules, referred to as uremic toxins (UTs). These toxins have a role in the development of neurological, cardiovascular, bone, and renal complications of CKD. However, UTs might also cause CKD as well as be the consequence. Recent studies have shown that these molecules accumulate early in AKI and contribute to the establishment of this pro-inflammatory and profibrotic environment in the kidney. The objective of the present work was to review the mechanisms of UT toxicity that potentially contribute to the AKI-to-CKD transition in each renal compartment.

Pediatric chronic kidney disease: blood cell count indexes as inflammation markers

INTRODUCTION

Chronic kidney disease (CKD) is defined as a progressive decline of kidney functions. In childhood, the main triggering factors are congenital anomalies of the kidneys and urinary tract (CAKUT) and glomerulopathies. Inflammatory responses present challenges for diagnosis and staging, which justifies studies on biomarkers/indexes.

AIM

To define blood cell count indexes and verify their association with pediatric CKD etiology and staging. The included indexes were: Neutrophil-Lymphocyte Ratio (NLR), Derived Neutrophil-Lymphocyte Ratio (dNLR), Lymphocyte-Monocyte Ratio (LMR), Systemic Inflammation Response Index (SIRI), Aggregate Index of Systemic Inflammation (AISI), and Systemic Immune-Inflammation Index (SII).

METHODS

We determined the indexes in 52 pediatric CKD patients and 33 healthy controls by mathematical calculation. CKD patients were separated in five groups based on the etiology and staging: Group IA: glomerulopathies at stage 1 or 2; IB: glomerulopathies at stage 3 or 4; IIA: CAKUT at stage 1 or 2; IIB: CAKUT at stage 3 or 4; and III: stages 3 or 4 of other etiologies. In addition, we combined all patients with CKD in one group (IV). Group V was a healthy control group.

RESULTS

Lower values of LMR were observed for groups IB and IIB compared to group V (p = 0.047, p = 0.031, respectively). Increased values of SIRI were found for group III versus group V (p = 0.030). There was no difference for other indexes when the groups were compared two by two.

CONCLUSION

The LMR and SIRI indexes showed promising results in the evaluation of inflammation, as they correlated with CKD etiologies and specially staging in these patients.

Geriatric Nutritional Risk Index and Risk of Mortality in Critically Ill Patients With Acute Kidney Injury: A Multicenter Cohort Study

OBJECTIVES

Malnutrition is associated with adverse outcomes in acute or chronic diseases. However, the prediction value of the Geriatric Nutritional Risk Index (GNRI) in critically ill patients with acute kidney injury (AKI) has not been well studied.

METHODS

Data was extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) and the electronic intensive care unit database. We used two nutritional indicators, the GNRI and the modified Nutrition Risk in Critically ill (NUTRIC) score, to evaluate the relationship between the nutritional status of patients with AKI and prognosis. The outcome is in-hospital mortality and 90-day mortality. The prediction accuracy of GNRI was compared with the NUTRIC score.

RESULTS

A total of 4,575 participants with AKI were enrolled in this study. The median age of 68 (interquartile range, 56-79) years, and 1,142 (25.0%) patients experienced in-hospital mortality, and 1,238 (27.1%) patients experienced 90-day mortality. Kaplan-Meier survival analysis indicated that lower GNRI levels and high NUTRIC score are associated with lower in-hospital and 90-day survival of patients with AKI (P < .001 by log-rank test). After multivariate adjustment, Cox regression analysis demonstrated a 2-fold increased risk of in-hospital (hazard ratio = 2.019, 95% confidence interval: 1.699-2.400, P < .001) and 90-day (hazard ratio = 2.023, 95% confidence interval: 1.715-2.387, P < .001) mortality in the low GNRI group. Moreover, the multivariate-adjusted Cox model containing GNRI had higher prediction accuracy for the prognosis of patients with AKI than that with NUTRIC score (AUCGNRI model vs. AUCNUTRIC model for in-hospital mortality = 0.738 vs. 0.726, AUCGNRI model vs. AUCNUTRIC model for 90-day mortality = 0.748 vs. 0.726). In addition, the prediction value of GNRI was validated by the electronic intensive care unit database (7,881 patients with AKI) with satisfying performance (AUCGNRI model = 0.680).

CONCLUSIONS

Our results demonstrated that GNRI is strongly associated with survival in patients in the intensive care unit coexisting with AKI, and the GNRI has a superior predictive value than the NUTRIC score.

The Therapeutic Potential of CDK4/6 Inhibitors, Novel Cancer Drugs, in Kidney Diseases

Inflammation is a crucial pathological feature in cancers and kidney diseases, playing a significant role in disease progression. Cyclin-dependent kinases CDK4 and CDK6 not only contribute to cell cycle progression but also participate in cell metabolism, immunogenicity and anti-tumor immune responses. Recently, CDK4/6 inhibitors have gained approval for investigational treatment of breast cancer and various other tumors. Kidney diseases and cancers commonly exhibit characteristic pathological features, such as the involvement of inflammatory cells and persistent chronic inflammation. Remarkably, CDK4/6 inhibitors have demonstrated impressive efficacy in treating non-cancerous conditions, including certain kidney diseases. Current studies have identified the renoprotective effect of CDK4/6 inhibitors, presenting a novel idea and potential direction for treating kidney diseases in the future. In this review, we briefly reviewed the cell cycle in mammals and the role of CDK4/6 in regulating it. We then provided an introduction to CDK4/6 inhibitors and their use in cancer treatment. Additionally, we emphasized the importance of these inhibitors in the treatment of kidney diseases. Collectively, growing evidence demonstrates that targeting CDK4 and CDK6 through CDK4/6 inhibitors might have therapeutic benefits in various cancers and kidney diseases and should be further explored in the future.

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.

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.

Mesenchymal Stem Cells Delivered Locally to Ischemia-Reperfused Kidneys via Injectable Hyaluronic Acid Hydrogels Decrease Extracellular Matrix Remodeling 1 Month after Injury in Male Mice

The translation of stem cell therapies has been hindered by low cell survival and retention rates. Injectable hydrogels enable the site-specific delivery of therapeutic cargo, including cells, to overcome these challenges. We hypothesized that delivery of mesenchymal stem cells (MSC) via shear-thinning and injectable hyaluronic acid (HA) hydrogels would mitigate renal damage following ischemia-reperfusion acute kidney injury. Acute kidney injury (AKI) was induced in mice by bilateral or unilateral ischemia-reperfusion kidney injury. Three days later, mice were treated with MSCs either suspended in media injected intravenously via the tail vein, or injected under the capsule of the left kidney, or MSCs suspended in HA injected under the capsule of the left kidney. Serial measurements of serum and urine biomarkers of renal function and injury, as well as transcutaneous glomerular filtration rate (tGFR) were performed. In vivo optical imaging showed that MSCs localized to both kidneys in a sustained manner after bilateral ischemia and remained within the ipsilateral treated kidney after unilateral ischemic AKI. One month after injury, MSC/HA treatment significantly reduced urinary NGAL compared to controls; it did not significantly reduce markers of fibrosis compared to untreated controls. An analysis of kidney proteomes revealed decreased extracellular matrix remodeling and high overlap with sham proteomes in MSC/HA-treated animals. Hydrogel-assisted MSC delivery shows promise as a therapeutic treatment following acute kidney injury.

LTBP4 Protects Against Renal Fibrosis via Mitochondrial and Vascular Impacts

BACKGROUND

As a part of natural disease progression, acute kidney injury (AKI) can develop into chronic kidney disease via renal fibrosis and inflammation. LTBP4 (latent transforming growth factor beta binding protein 4) regulates transforming growth factor beta, which plays a role in renal fibrosis pathogenesis. We previously investigated the role of LTBP4 in chronic kidney disease. Here, we examined the role of LTBP4 in AKI.

METHODS

LTBP4 expression was evaluated in human renal tissues, obtained from healthy individuals and patients with AKI, using immunohistochemistry. LTBP4 was knocked down in both C57BL/6 mice and human renal proximal tubular cell line HK-2. AKI was induced in mice and HK-2 cells using ischemia-reperfusion injury and hypoxia, respectively. Mitochondrial division inhibitor 1, an inhibitor of DRP1 (dynamin-related protein 1), was used to reduce mitochondrial fragmentation. Gene and protein expression were then examined to assess inflammation and fibrosis. The results of bioenergetic studies for mitochondrial function, oxidative stress, and angiogenesis were assessed.

RESULTS

LTBP4 expression was upregulated in the renal tissues of patients with AKI. Ltbp4-knockdown mice showed increased renal tissue injury and mitochondrial fragmentation after ischemia-reperfusion injury, as well as increased inflammation, oxidative stress, and fibrosis, and decreased angiogenesis. in vitro studies using HK-2 cells revealed similar results. The energy profiles of Ltbp4-deficient mice and LTBP4-deficient HK-2 cells indicated decreased ATP production. LTBP4-deficient HK-2 cells exhibited decreased mitochondrial respiration and glycolysis. Human aortic endothelial cells and human umbilical vein endothelial cells exhibited decreased angiogenesis when treated with LTBP4-knockdown conditioned media. Mitochondrial division inhibitor 1 treatment ameliorated inflammation, oxidative stress, and fibrosis in mice and decreased inflammation and oxidative stress in HK-2 cells.

CONCLUSIONS

Our study is the first to demonstrate that LTBP4 deficiency increases AKI severity, consequently leading to chronic kidney disease. Potential therapies focusing on LTBP4-associated angiogenesis and LTBP4-regulated DRP1-dependent mitochondrial division are relevant to renal injury.

Inflammatory mediators act at renal pericytes to elicit contraction of vasa recta and reduce pericyte density along the kidney medullary vascular network

Introduction: Regardless of initiating cause, renal injury promotes a potent pro-inflammatory environment in the outer medulla and a concomitant sustained decrease in medullary blood flow (MBF). This decline in MBF is believed to be one of the critical events in the pathogenesis of acute kidney injury (AKI), yet the precise cellular mechanism underlying this are still to be fully elucidated. MBF is regulated by contractile pericyte cells that reside on the descending vasa recta (DVR) capillaries, which are the primary source of blood flow to the medulla. Methods: Using the rat and murine live kidney slice models, we investigated the acute effects of key medullary inflammatory mediators TNF-α, IL-1β, IL-33, IL-18, C3a and C5a on vasa recta pericytes, the effect of AT1-R blocker Losartan on pro-inflammatory mediator activity at vasa recta pericytes, and the effect of 4-hour sustained exposure on immunolabelled NG2+ pericytes. Results and discussion: Exposure of rat and mouse kidney slices to TNF-α, IL-18, IL-33, and C5a demonstrated a real-time pericyte-mediated constriction of DVR. When pro-inflammatory mediators were applied in the presence of Losartan the inflammatory mediator-mediated constriction that had previously been observed was significantly attenuated. When live kidney slices were exposed to inflammatory mediators for 4-h, we noted a significant reduction in the number of NG2+ positive pericytes along vasa recta capillaries in both rat and murine kidney slices. Data collected in this study demonstrate that inflammatory mediators can dysregulate pericytes to constrict DVR diameter and reduce the density of pericytes along vasa recta vessels, further diminishing the regulatory capacity of the capillary network. We postulate that preliminary findings here suggest pericytes play a role in AKI.

Hippo signaling in acute kidney injury to chronic kidney disease transition: current understandings and future targets

Acute kidney injury (AKI)-to-chronic kidney disease (CKD) transition is a slow but persistent progression toward end-stage kidney disease. Earlier reports have shown that Hippo components, such as Yes-associated protein (YAP) and its homolog TAZ (Transcriptional coactivator with PDZ-binding motif), regulate inflammation and fibrogenesis during the AKI-to-CKD transition. Notably, the roles and mechanisms of Hippo components vary during AKI, AKI-to-CKD transition, and CKD. Hence, it is important to understand these roles in detail. This review addresses the potential of Hippo regulators or components as future therapeutic targets for halting the AKI-to-CKD transition.

Gut microbiota dysbiosis in AKI to CKD transition

BACKGROUND AND AIM

The symptoms of acute kidney injury (AKI) include a sudden drop-in glomerular filtration rate (GFR), a rise in serum creatinine (sCr), blood urea nitrogen (BUN), and electrolytes, which leads to a rapid loss of kidney function. Chronic kidney disease progresses when AKI symptoms persist for over three months or 90 days. Numerous prevalent secondary risk factors, including diabetes, hypertension, obesity, and heart illness, are directly or indirectly linked to the development of AKI and the switch from AKI to CKD. Recently, the change of intestinal bacteria known as "gut dysbiosis" has been linked to distant organ dysfunction, including the heart, lungs, kidneys, and brain. Indirectly or directly, gut dysbiosis contributes to the progression of CKD and AKI. However, the effects of gut dysbiosis and the mechanism of action in the progression from AKI to CKD are unknown or need further investigation. The mechanism by which gut dysbiosis initiates AKI's progression to CKD should be explicitly concerned. The review primarily focuses on the action of gut dysbiosis in kidney disease, the effects of dysbiosis, the characterisation of dysbiosis and its pathogenic products, the various pathogenic routes and mechanism involved in expediting the transition from AKI to CKD.

CONCLUSION

We identified and briefly reviewed the impacts of dysbiosis in various situations such as hypoxia, mitochondrial induced reactive oxygen species (mtROS), aryl hydrocarbon receptor (AhR) activation and microbiota derived uremic toxemic substances profoundly to push AKI to CKD conditions.

Long-Term Effects of Severe Burns on the Kidneys: Research Advances and Potential Therapeutic Approaches

Burns are a seriously underestimated form of trauma that not only damage the skin system but also cause various complications, such as acute kidney injury (AKI). Recent clinical studies have shown that the proportion of chronic kidney diseases (CKD) in burn patients after discharge is significantly higher than that in the general population, but the mechanism behind this is controversial. The traditional view is that CKD is associated with hypoperfusion, AKI, sepsis, and drugs administered in the early stages of burns. However, recent studies have shown that burns can cause long-term immune dysfunction, which is a high-risk factor for CKD. This suggests that burns affect the kidneys more than previously recognized. In other words, severe burns are not only an acute injury but also a chronic disease. Neglecting to study long-term kidney function in burn patients also results in a lack of preventive and therapeutic methods being developed. Furthermore, stem cells and their exosomes have shown excellent comprehensive therapeutic properties in the prevention and treatment of CKD, making them increasingly the focus of research attention. Their engineering strategy further improved the therapeutic performance. This review will focus on the research advances in burns on the development of CKD, illustrating the possible mechanism of burn-induced CKD and introducing potential biological treatment options and their engineering strategies.

Roles of DNA damage in renal tubular epithelial cells injury

The prevalence of renal diseases including acute kidney injury (AKI) and chronic kidney disease (CKD) is increasing worldwide. However, the pathogenesis of most renal diseases is still unclear and effective treatments are still lacking. DNA damage and the related DNA damage response (DDR) have been confirmed as common pathogenesis of acute kidney injury and chronic kidney disease. Reactive oxygen species (ROS) induced DNA damage is one of the most common types of DNA damage involved in the pathogenesis of acute kidney injury and chronic kidney disease. In recent years, several developments have been made in the field of DNA damage. Herein, we review the roles and developments of DNA damage and DNA damage response in renal tubular epithelial cell injury in acute kidney injury and chronic kidney disease. In this review, we conclude that focusing on DNA damage and DNA damage response may provide valuable diagnostic biomarkers and treatment strategies for renal diseases including acute kidney injury and chronic kidney disease.

Revisiting the Role of NAG across the Continuum of Kidney Disease

Acute and chronic kidney diseases are an evolving continuum for which reliable biomarkers of early disease are lacking. The potential use of glycosidases, enzymes involved in carbohydrate metabolism, in kidney disease detection has been under investigation since the 1960s. N-acetyl-beta-D-glucosaminidase (NAG) is a glycosidase commonly found in proximal tubule epithelial cells (PTECs). Due to its large molecular weight, plasma-soluble NAG cannot pass the glomerular filtration barrier; thus, increased urinary concentration of NAG (uNAG) may suggest injury to the proximal tubule. As the PTECs are the workhorses of the kidney that perform much of the filtration and reabsorption, they are a common starting point in acute and chronic kidney disease. NAG has previously been researched, and it is widely used as a valuable biomarker in both acute and chronic kidney disease, as well as in patients suffering from diabetes mellitus, heart failure, and other chronic diseases leading to kidney failure. Here, we present an overview of the research pertaining to uNAG’s biomarker potential across the spectrum of kidney disease, with an additional emphasis on environmental nephrotoxic substance exposure. In spite of a large body of evidence strongly suggesting connections between uNAG levels and multiple kidney pathologies, focused clinical validation tests and knowledge on underlining molecular mechanisms are largely lacking.

Akt1 is involved in renal fibrosis and tubular apoptosis in a murine model of acute kidney injury-to-chronic kidney disease transition

Maladaptive repair after acute kidney injury (AKI) can predispose patients to chronic kidney disease (CKD). However, the molecular mechanism underlying the AKI-to-CKD transition remains unclear. The Akt signaling pathway has been reported to be involved in the pathological processes of both AKI and CKD. In this study, we investigated the role of Akt1 in a murine model of the AKI-to-CKD transition. Wild-type (WT) and Akt1^-/- mice were subjected to unilateral ischemia-reperfusion injury (UIRI), with their kidneys harvested after two days and two, four, and six weeks after UIRI. The dynamic changes in tubulointerstitial fibrosis, markers of tubular epithelial-mesenchymal transition (EMT), and tubular apoptosis were investigated. Akt1 of the three Akt isoforms was activated during the AKI-to-CKD transition. After UIRI, tubulointerstitial fibrosis and tubular EMT were significantly increased in WT mice, but were attenuated in Akt1^-/- mice. The expression of the transforming growth factor (TGF)-β1/Smad was increased in both WT and Akt1^-/- mice, but was not different between the two groups. The levels of phosphorylated glycogen synthase kinase (GSK)-3β, Snail, and β-catenin in the Akt1^-/- mice were lower than those in the WT mice. The number of apoptotic tubular cells and the expression of cleaved caspase-3/Bax were both lower in Akt1^-/- mice than in WT mice. Genetic deletion of Akt1 was associated with attenuation of tubulointerstitial fibrosis, tubular EMT, and tubular apoptosis during the AKI-to-CKD transition. These findings were associated with TGF-β1/Akt1/GSK-3β/(Snail and β-catenin) signaling independent of TGF-β1/Smad signaling. Thus, Akt1 signaling could serve as a potential therapeutic target for inhibiting the AKI-to-CKD transition.

Macrophage-derived exosomes mediate glomerular endothelial cell dysfunction in sepsis-associated acute kidney injury

BACKGROUND

Sepsis-associated AKI has been shown to be related to sepsis mortality. Macrophage activation and endothelial cell damage are involved in the progression of sepsis-associated AKI, but the specific mechanisms are still unclear.

METHODS

In vitro experiments, exosomes extracted from lipopolysaccharide (LPS) -stimulated macrophages were co-incubated with rat glomerular endothelial cells (RGECs) and then detected the injury markers of RGECs. Acid sphingomyelinase (ASM) inhibitor amitriptyline were used to investigate the role of ASM. In vivo experiment, exosomes produced by LPS-stimulated macrophages were injected into mice through tail vein to further explore the role of macrophage-derived exosomes. Moreover, ASM knockout mice were used to verify the mechanism.

RESULT

In vitro, the secretion of macrophage exosomes increased upon the stimulation with LPS. Notably, macrophage-derived exosomes can cause glomerular endothelial cell dysfunction. In vivo, macrophage infiltration and exosome secretion in glomeruli of the LPS-induced AKI group increased. The exosomes produced by LPS-stimulated macrophages were injected into mice, which also led to the injury of renal endothelial cells. In addition, in the LPS-induced AKI mouse model, compared with wild-type mice, the secretion of exosomes in glomeruli of ASM gene knockout mice and the injury of endothelial cells were reduced.

CONCLUSION

Our study shows that ASM regulates the secretion of macrophage exosomes, leading to endothelial cell injury, which may be a therapeutic target in sepsis-associated AKI.

Mitochondrial and NAD+ metabolism predict recovery from acute kidney injury in a diverse mouse population

Acute kidney failure and chronic kidney disease are global health issues steadily rising in incidence and prevalence. Animal models on a single genetic background have so far failed to recapitulate the clinical presentation of human nephropathies. Here, we used a simple model of folic acid-induced kidney injury in 7 highly diverse mouse strains. We measured plasma and urine parameters, as well as renal histopathology and mRNA expression data, at 1, 2, and 6 weeks after injury, covering the early recovery and long-term remission. We observed an extensive strain-specific response ranging from complete resistance of the CAST/EiJ to high sensitivity of the C57BL/6J, DBA/2J, and PWK/PhJ strains. In susceptible strains, the severe early kidney injury was accompanied by the induction of mitochondrial stress response (MSR) genes and the attenuation of NAD+ synthesis pathways. This is associated with delayed healing and a prolonged inflammatory and adaptive immune response 6 weeks after insult, heralding a transition to chronic kidney disease. Through a thorough comparison of the transcriptomic response in mouse and human disease, we show that critical metabolic gene alterations were shared across species, and we highlight the PWK/PhJ strain as an emergent model of transition from acute kidney injury to chronic disease.

New Frontiers in Sepsis-Induced Acute Kidney Injury and Blood Purification Therapies: The Role of Polymethylmethacrylate Membrane Hemofilter

Acute kidney injury (AKI) is a common consequence of sepsis with a mortality rate of up to 40%. The pathogenesis of septic AKI is complex and involves several mechanisms leading to exacerbated inflammatory response associated with renal injury. A large body of evidence suggests that inflammation is tightly linked to AKI through bidirectional interaction between renal and immune cells. Preclinical data from our and other laboratories have identified in complement system activation a crucial mediator of AKI. Partial recovery following AKI could lead to long-term consequences that predispose to chronic dysfunction and may also accelerate the progression of preexisting chronic kidney disease. Recent findings have revealed striking morphological and functional changes in renal parenchymal cells induced by mitochondrial dysfunction, cell cycle arrest via the activation of signaling pathways involved in aging process, microvascular rarefaction, and early fibrosis. Although major advances have been made in our understanding of the pathophysiology of AKI, there are no available preventive and therapeutic strategies in this field. The identification of ideal clinical biomarkers for AKI enables prompt and effective therapeutic strategy that could prevent the progression of renal injury and promote repair process. Therefore, the use of novel biomarkers associated with clinical and functional criteria could provide early interventions and better outcome. Several new drugs for AKI are currently being investigated; however, the complexity of this disease might explain the failure of pharmacological intervention targeting just one of the many systems involved. The hypothesis that blood purification could improve the outcome of septic AKI has attracted much attention. New relevant findings on the role of polymethylmethacrylate-based continuous veno-venous hemofiltration in septic AKI have been reported. Herein, we provide a comprehensive literature review on advances in the pathophysiology of septic AKI and potential therapeutic approaches in this field.

Lasmiditan promotes recovery from acute kidney injury through induction of mitochondrial biogenesis

Acute kidney injury (AKI) involves rapid loss of renal function and occurs in 8-16% of hospitalized patients. AKI can be induced by drugs, sepsis, and ischemia-reperfusion (I/R). Hallmarks of AKI include mitochondrial and microvasculature dysfunction as well as renal tubular injury. There is currently no available therapeutic for AKI. Previously, our group identified that serotonin (5-HT)1F receptor agonism with lasmiditan accelerated endothelial cell recovery and induced mitochondrial biogenesis (MB) in vitro. We hypothesized that lasmiditan, a Federal Drug Administration-approved drug, would induce MB and improve microvascular and renal function in a mouse model of AKI. Male mice were subjected to renal I/R and treated with lasmiditan (0.3 mg/kg) or vehicle beginning 24 h after injury and then daily until euthanasia at 6 or 12 days. Serum creatinine was measured to estimate glomerular filtration rate. The renal cortex was assessed for mitochondrial density, vascular permeability and integrity, tubular damage, and interstitial fibrosis. Lasmiditan increased mitochondrial number (1.4-fold) in renal cortices. At 6 days, serum creatinine decreased 41% in the I/R group and 72% with lasmiditan. At 6 or 12 days, kidney injury molecule-1 increased in the I/R group and decreased 50% with lasmiditan. At 12 days, interstitial fibrosis decreased with lasmiditan by 50% and collagen type 1 by 38%. Evan's blue dye leakage increased 2.5-fold in the I/R group and was restored with lasmiditan. The tight junction proteins zonula occludens-1, claudin-2, and claudin-5 decreased in the I/R group and recovered with lasmiditan. At 6 or 12 days, peroxisome proliferator-activated receptor-γ coactivator-1α and electron transport chain complexes increased only with lasmiditan. In conclusion, lasmiditan treatment beginning AKI induces MB, attenuated vascular and tubular injury, decreased interstitial fibrosis, and lowered serum creatinine. Given that lasmiditan is a Federal Drug Administration-approved drug, these preclinical data support repurposing lasmiditan as a therapeutic for AKI.NEW & NOTEWORTHY AKI pathology involves a rapid decline in kidney function and occurs in 8-16% of hospitalized patients. There is currently no therapeutic for AKI. AKI results in mitochondria dysfunction, microvasculature injury, and loss of renal tubular function. In an I/R-induced AKI mouse model, treatment with the FDA-approved 5-HT1F receptor-selective agonist lasmiditan induced mitochondrial biogenesis, improved vascular integrity, reduced fibrosis, and reduced proximal tubule damage. These data support repurposing lasmiditan for the treatment of AKI.

KCNQ1OT1 Influences HK-2 Apoptosis and Inflammation in LPS-Induced Acute Renal Injury via Modulating miR-30a-5p/NLRP3 Axis

Objective

To investigate the influence of KCNQ1OT1 on HK-2 apoptosis and inflammation in ARI and its molecular mechanism.

Methods

Normal cultivated HK-2 cells were used as negative control (NC) group. Three different concentrations of lipopolysaccharide (LPS) were used to treat the cells (5 μg/mL, 10 μg/mL, and 20 μg/mL). The groups included si-KCN1OT1+ LPS, si-NC + LPS, miR-30a-5p + LPS, pcDNA-NLRP3+si-KCNQ1OT1 + LPS group, miR-NC + LPS group, and pcDNA + si-KCNQ1OT1 + LPS group. CCK-8 and flow cytometry are used to measure cell viability and apoptosis, while RT-qPCR and Western blotting are used to detect KCNQ1OT1, miR-30a-5p, and NLRP3 mRNA. ELISA was used to detect the levels of TNF-α, IL-6, and IL-1β in HK-2 cells. The targeting relationship among KCNQ1OT1, miR-30a-5p, and NLRP3 was verified.

Results

After the intervention of LPS, the viability of HK-2 cells was decreased, while the apoptosis rates were increased. The mRNA and protein expressions of NLRP3 and KCNQ1OT1 were increased, while the mRNA and protein levels of miR-30a-5p were decreased (P < 0.05). The expressions of Bax and Cleaved-caspase-3 were downregulated after silencing KCNQ1OT1 and overexpressed miR-30a-5p. In addition, the viability of HK-2 cells was improved, and the apoptosis was reduced by inhibiting KCNQ1OT1 and overexpressed miR-30a-5p. Thus, KCNQ1OT1 modulated NLRP3 via targeting miR-30a-5p. Overexpression of NLRP3 reverses KCNQ1OT1 inhibition of LPS-induced apoptosis, activity, and inflammation in HK-2 cells.

Conclusions

Through modulating the miR-30a-5p/NLRP3 axis, inhibition of KCNQ1OT1 may reduce HK-2 apoptosis and inflammation in LPS-induced ARI.

dsDNA-induced AIM2 pyroptosis halts aberrant inflammation during rhabdomyolysis-induced acute kidney injury

Rhabdomyolysis is a severe condition that commonly leads to acute kidney injury (AKI). While double-stranded DNA (dsDNA) released from injured muscle can be involved in its pathogenesis, the exact mechanism of how dsDNA contributes to rhabdomyolysis-induced AKI (RIAKI) remains obscure. A dsDNA sensor, absent in melanoma 2 (AIM2), forms an inflammasome and induces gasdermin D (GSDMD) cleavage resulting in inflammatory cell death known as pyroptosis. In this study using a mouse model of RIAKI, we found that Aim2-deficiency led to massive macrophage accumulation resulting in delayed functional recovery and perpetuating fibrosis in the kidney. While Aim2-deficiency compromised RIAKI-induced kidney macrophage pyroptosis, it unexpectedly accelerated aberrant inflammation as demonstrated by CXCR3+CD206+ macrophage accumulation and activation of TBK1-IRF3/NF-κB. Kidney macrophages with intact AIM2 underwent swift pyroptosis without IL-1β release in response to dsDNA. On the other hand, dsDNA-induced Aim2-deficient macrophages escaped from swift pyroptotic elimination and instead engaged STING-TBK1-IRF3/NF-κB signalling, leading to aggravated inflammatory phenotypes. Collectively, these findings shed light on a hitherto unknown immunoregulatory function of macrophage pyroptosis. dsDNA-induced rapid macrophage cell death potentially serves as an anti-inflammatory program and determines the healing process of RIAKI.

Gender and Renal Insufficiency: Opportunities for Their Therapeutic Management?

Acute kidney injury (AKI) is a major clinical problem associated with increased morbidity and mortality. Despite intensive research, the clinical outcome remains poor, and apart from supportive therapy, no other specific therapy exists. Furthermore, acute kidney injury increases the risk of developing chronic kidney disease (CKD) and end-stage renal disease. Acute tubular injury accounts for the most common intrinsic cause of AKI. The main site of injury is the proximal tubule due to its high workload and energy demand. Upon injury, an intratubular subpopulation of proximal epithelial cells proliferates and restores the tubular integrity. Nevertheless, despite its strong regenerative capacity, the kidney does not always achieve its former integrity and function and incomplete recovery leads to persistent and progressive CKD. Clinical and experimental data demonstrate sexual differences in renal anatomy, physiology, and susceptibility to renal diseases including but not limited to ischemia-reperfusion injury. Some data suggest the protective role of female sex hormones, whereas others highlight the detrimental effect of male hormones in renal ischemia-reperfusion injury. Although the important role of sex hormones is evident, the exact underlying mechanisms remain to be elucidated. This review focuses on collecting the current knowledge about sexual dimorphism in renal injury and opportunities for therapeutic manipulation, with a focus on resident renal progenitor stem cells as potential novel therapeutic strategies.

Mechanism study of Cordyceps sinensis alleviates renal ischemia–reperfusion injury

Cordyceps sinensis (C. sinensis) is a kind of traditional Chinese medicine commonly used to protect renal function and relieve kidney injury. This study aimed to reveal the renal protective mechanism of C. sinensis in renal ischemia–reperfusion injury (RIRI). First, we obtained 8 active components and 99 common targets of C. sinensis against RIRI from public databases. Second, we have retrieved 38 core targets through STRING database analysis. Third, Gene Ontology analysis of 38 core targets is indicated that C. sinensis treatment RIRI may related hormone regulation, oxidative stress, cell proliferation, and immune regulation. Kyoto Encyclopedia of Genes and Genomes enrichment analysis of 38 core targets is indicated that C. sinensis treatment RIRI may involve in PI3K–Akt, HIF-1, and MAPK signaling pathways, as well as advanced glycation end product (AGE)–receptor for AGE (RAGE) signaling pathway in diabetic complications. Lastly, molecular docking was used to detect the binding activity and properties of active components and core target using molecular docking. And the results showed that eight active components of C. sinensis had low affinity with core targets. In conclusion, C. sinensis may improve RIRI by regulating oxidative stress and immunity through PI3K–Akt, HIF-1, and MAPK pathways.

Activation of EP4 alleviates AKI-to-CKD transition through inducing CPT2-mediated lipophagy in renal macrophages

Acute kidney injury (AKI) is a common clinical syndrome with complex pathogenesis, characterized by a rapid decline in kidney function in the short term. Worse still, the incomplete recovery from AKI increases the risk of progression to chronic kidney disease (CKD). However, the pathogenesis and underlying mechanism remain largely unknown. Macrophages play an important role during kidney injury and tissue repair, but its role in AKI-to-CKD transition remains elusive. Herein, single nucleus RNA sequencing (snRNA-Seq) and flow cytometry validations showed that E-type prostaglandin receptor 4 (EP4) was selectively activated in renal macrophages, rather than proximal tubules, in ischemia-reperfusion injury (IRI)-induced AKI-to-CKD transition mouse model. EP4 inhibition aggravated AKI-to-CKD transition, while EP4 activation impeded the progression of AKI to CKD though regulating macrophage polarization. Mechanistically, network pharmacological analysis and subsequent experimental verifications revealed that the activated EP4 inhibited macrophage polarization through inducing Carnitine palmitoyltransferase 2 (CPT2)-mediated lipophagy in macrophages. Further, CPT2 inhibition abrogated the protective effect of EP4 on AKI-to-CKD transition. Taken together, our findings demonstrate that EP4-CPT2 signaling-mediated lipophagy in macrophages plays a pivotal role in the transition of AKI to CKD and targeting EP4-CPT2 axis could serve as a promising therapeutic approach for retarding AKI and its progression to CKD.

Kidney targeting of formoterol containing polymeric nanoparticles improves recovery from ischemia reperfusion-induced acute kidney injury in mice

The β₂ adrenergic receptor agonist, formoterol, is an inducer of mitochondrial biogenesis and restorer of mitochondrial and kidney function in acute and chronic models of kidney injury. Unfortunately, systemic administration of formoterol has the potential for adverse cardiovascular effects, increased heart rate, and decreased blood pressure. To minimize these effects, we developed biodegradable and biocompatible polymeric nanoparticles containing formoterol that target the kidney, thereby decreasing the effective dose, and lessen cardiovascular effects while restoring kidney function after injury. Male C57Bl/6 mice, treated with these nanoparticles daily, had reduced ischemia-reperfusion-induced serum creatinine and kidney cortex kidney injury molecule-1 levels by 78% and 73% respectively, compared to control mice six days after injury. With nanoparticle therapy, kidney cortical mitochondrial number and proteins reduced by ischemic injury, recovered to levels of sham-operated mice. Tubular necrosis was reduced 69% with nanoparticles treatment. Nanoparticles improved kidney recovery even when the dosing frequency was reduced from daily to two days per week. Finally, compared to treatment with formoterol-free drug alone, these nanoparticles did not increase heart rate nor decrease blood pressure. Thus, targeted kidney delivery of formoterol-containing nanoparticles is an improvement in standard formoterol therapy for ischemia-reperfusion-induced acute kidney injuries by decreasing the dose, dosing frequency, and cardiac side effects.