Mechanisms and therapeutic targets of ischemic acute kidney injury

Hinokitiol Prevents Diabetic Acute Kidney Injury by Mitigating ER Stress

Acute kidney injury (AKI) in diabetic conditions often advances to chronic kidney disease (CKD), exacerbated by ischemia-reperfusion injury (IRI) through pathomechanisms such as endoplasmic reticulum (ER) stress and inflammation. Currently, available treatment options for diabetic AKI are not uniformly effective, highlighting the need for novel interventions. This study aimed to examine the renoprotective effects of hinokitiol, a natural tropolone compound, against diabetic AKI with its capability to decrease ER stress and inflammation, along with apoptosis. This study involved NRK-52E cells grown in-vitro under high-glucose conditions subjected to 10 mM sodium azide to elicit hypoxia/reperfusion injury (HRI). The expression of key ER stress markers like binding immunoglobulin binding protein (BiP), R/PKR-like ER kinase (PERK), and eukaryotic initiation factor-2 (eIF2α) as well as inflammatory proteins was markedly diminished by hinokitiol pretreatment (50 μM). Hinokitiol further reduced apoptosis in the NRK-52E cells. Similarly, in the in-vivo study, male Wistar rats with STZ-induced Type 1 diabetes (55 mg/kg, i.p.) were treated with hinokitiol 50 and 100 mg/kg/day i.p. for 5 days, followed by AKI induction via bilateral IRI. Hinokitiol pretreatment significantly reduced the elevated plasma blood urea nitrogen (BUN), creatinine, and urinary kidney injury molecule-1 (KIM-1) levels and tubular damage in diabetic AKI rats. Hinokitiol also reduced the respective ER stress protein expressions in diabetic AKI rats, as demonstrated by immunohistochemical analysis and immunoblotting. These findings suggest that hinokitiol alleviates diabetic AKI by modulating the PERK/CHOP/NF-κB axis, highlighting the likeliness of hinokitiol as a viable therapeutic technique for alleviating diabetic AKI.

A phase 3 study of ravulizumab to protect patients with chronic kidney disease from cardiac surgery-associated acute kidney injury and major adverse kidney events (ARTEMIS)

BACKGROUND

Cardiac procedures, particularly those requiring cardiopulmonary bypass (CPB), are associated with the development of cardiac surgery-associated acute kidney injury (CSA-AKI). Development of CSA-AKI occurs as a result of inflammation, uncontrolled complement activation, and kidney cell damage. In patients with preoperative renal impairment, such as those with chronic kidney disease (CKD), there is an increased risk of both CSA-AKI and poorer clinical outcomes. Currently, there are limited effective, targeted pharmacological interventions for the prevention or treatment of CSA-AKI, although emerging therapies are being investigated, particularly in patients with existing CKD. The ARTEMIS (RAvulizumab to PRotect PaTients with Chronic Kidney DisEase froM CSA-AKI and Subsequent Major Adverse Kidney Events) trial will assess the efficacy and safety of ravulizumab (a complement C5 inhibitor) in reducing the risk of major adverse kidney events (MAKE) in patients with preoperative CKD undergoing non-emergent cardiac surgery with CPB.

METHODS

This trial is currently recruiting patients with CKD who have planned cardiac surgery requiring CPB including coronary artery bypass grafting, valve replacement or repair, or combined procedures. This is a phase 3, randomized, double-blind, placebo-controlled, global study assessing the efficacy and safety of a single preoperative dose of ravulizumab. These outcomes will be assessed using the occurrence of MAKE and its components, as well as the occurrence and severity of CSA-AKI throughout the study period.

DISCUSSION

Complement activation is known to occur during and after cardiac procedures as a result of CPB and ischemia-reperfusion injury, leading to a cycle of cell damage and death. Therefore, it is hypothesized that preoperative administration of ravulizumab will provide immediate and complete complement inhibition, which will be sustained throughout the surgical period, preventing the uncontrolled complement activation associated with the development of CSA-AKI, thus minimizing poor outcomes for patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05746559. Registered on February 27, 2023.

Advances in Nano-Immunomodulatory Systems for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) occurs when there is an imbalance in the immune microenvironment, leading to ongoing and excessive inflammation. Numerous immunomodulatory therapies have been suggested for the treatment of AKI, the current immunomodulatory treatment delivery systems are suboptimal and lack efficiency. Given the lack of effective treatment, AKI can result in multi-organ dysfunction and even death, imposing a significant healthcare burden on both the family and society. This underscores the necessity for innovative treatment delivery systems, such as nanomaterials, to better control pathological inflammation, and ultimately enhance AKI treatment outcomes. Despite the modification of numerous immunomodulatory nanomaterials to target the AKI immune microenvironment with promising therapeutic results, the literature concerning their intersection is scarce. In this article, the pathophysiological processes of AKI are outlined, focusing on the immune microenvironment, discuss significant advances in the comprehension of AKI recovery, and describe the multifunctionality and suitability of nanomaterial-based immunomodulatory treatments in managing AKI. The main obstacles and potential opportunities in the swiftly advancing research field are also clarified.

Kidney Injury Following Cardiac Surgery: A Review of Our Current Understanding

Around one-quarter of all patients undergoing cardiac procedures, particularly those on cardiopulmonary bypass, develop cardiac surgery-associated acute kidney injury (CSA-AKI). This complication increases the risk of several serious morbidities and of mortality, representing a significant burden for both patients and the healthcare system. Patients with diminished kidney function before surgery, such as those with chronic kidney disease, are at heightened risk of developing CSA-AKI and have poorer outcomes than patients without preexisting kidney injury who develop CSA-AKI. Several mechanisms are involved in the development of CSA-AKI; injury is primarily thought to result from an amplification loop of inflammation and cell death, with complement and immune system activation, cardiopulmonary bypass, and ischemia-reperfusion injury all contributing to pathogenesis. At present there are no effective, targeted pharmacological therapies for the prevention or treatment of CSA-AKI, although several preclinical trials have shown promise, and clinical trials are under way. Progress in the understanding of the complex pathophysiology of CSA-AKI is needed to improve the development of successful strategies for its prevention, management, and treatment. In this review, we outline our current understanding of CSA-AKI development and management strategies and discuss potential future therapeutic targets under investigation.

Inhibiting the Translocation of HMGB1 Alleviates Renal Ischemia-Reperfusion Injury by Cutting Down Inflammatory Cascade

BACKGROUND

Ischemia and reperfusion does damage to tissues and causes the decline of organ function though the inflammatory cascade. Noteworthy, HMGB1 possess a crucial role in promoting progression of these effects in kidney. The study aimed at ascertaining the concrete mechanism of HMGB1 triggering inflammatory cascade in renal ischemia-reperfusion injury (IRI).

METHODS

IRI was induced in mice by clamping left renal arteries for 60 minutes followed by 24 hours of reperfusion with the removal of right kidney. The effects of HMGB1on IRI were evaluated by targeting creatinine, blood urea nitrogen, survival rates, renal morphology, and the translocation and secretion of HMGB1. In addition, the expression of Toll-like receptor 4, phosphorylated nuclear factor κB p65, nuclear factor κB p65, and inflammatory cascade molecules (interleukin [IL]-1β, and IL-6, and tumor necrosis factor-α) were carried out.

RESULTS

Our results demonstrated that antibody against HMGB1 (anti-HMGB1) can improve the survival rate; decrease the expression of creatinine, blood urea nitrogen, Toll-like receptor 4, phosphorylated nuclear factor κB p65, IL-1β, IL-6, and tumor necrosis factor-α; reduce renal pathological injury; alleviate the secretion of HMGB1; and suppress the translocation of HMGB1 from nucleus into cytoplasm in IRI. Notably, recombinant HMGB1, the agonist of HMGB1, can alleviate the noted effects of anti-HMGB1 in IRI.

CONCLUSION

HMGB1 can aggravate renal IRI by triggering the inflammatory cascade, the mechanism of which is associated with activating the Toll-like receptor 4-nuclear factor κB p65 signal pathway.

Extracellular Vesicles in Renal Inflammatory Diseases: Revealing Mechanisms of Extracellular Vesicle-Mediated Macrophage Regulation

Renal inflammatory diseases are a group of severe conditions marked by significant morbidity and mortality. Extracellular vesicles (EVs), as facilitators of intercellular communication, have been recognized as pivotal regulators of renal inflammatory diseases, significantly contributing to these conditions by modulating immune responses among other mechanisms. This review highlights the intricate mechanisms through which EVs modulate macrophage-kidney cell interactions by regulating macrophages, the principal immune cells within the renal milieu. This regulation subsequently influences the pathophysiology of renal inflammatory diseases such as acute kidney injury and chronic kidney disease. Furthermore, understanding these mechanisms offers novel opportunities to alleviate the severe consequences associated with renal inflammatory diseases. In addition, we summarize the therapeutic landscape based on EV-mediated macrophage regulatory mechanisms, highlighting the potential of EVs as biomarkers and therapeutic targets as well as the challenges and limitations of translating therapies into clinical practice.

Age-Dependent Risk of Long-Term All-Cause Mortality in Patients Post-Myocardial Infarction and Acute Kidney Injury

OBJECTIVES

We aimed to investigate the association between acute kidney injury (AKI) and the risk for long-term (up to 10 years) all-cause mortality among elderly compared with younger patients following an acute myocardial infarction (AMI).

METHODS

This study was a retrospective analysis of the Soroka Acute Myocardial Infarction registry and covered the years 2002 to 2017. It included patients diagnosed with an AMI who had a baseline estimated glomerular filtration rate (eGFR) greater than 60 mL/min/1.73 m2 and serum creatinine measurements available during hospitalization. The patients were stratified by age: elderly (aged 65 years or older at admission) and younger. In each stratum, two groups were defined based on the presence of an AKI. The survival approach (Kaplan-Meier survival curves, log-rank test and Cox regressions) was utilized to estimate and compare the probability of long-term (up to 10 years) all-cause mortality in each group.

RESULTS

Among the 10,511 eligible patients, which consisted of 6132 younger patients (58.3%) and 4379 elderly (41.7%), an AKI occurred in 15.2% of cases, where the elderly patients experienced a higher incidence than the younger patients (20.9% vs. 11.2%, p < 0.001). The presence of an AKI significantly increased the risk of death in both age groups, with the association being stronger among the younger patients (AdjHR = 1.634, 95% CI: 1.363-1.959, p < 0.001) than among the elderly (AdjHR = 1.278, 95% CI: 1.154-1.415, p < 0.001, p-for-interaction = 0.020).

CONCLUSIONS

An AKI following an AMI was associated with a high risk for long-term all-cause mortality in both age groups, with a stronger association among younger patients.

Enhanced renal ischemia/reperfusion injury repair potential of exosomes derived from B7-H1high mesenchymal stem cells

Two subgroups with high expression of B7-H1 and low expression of B7-H1 were successfully isolated from primitive human umbilical cord mesenchymal stem cells. And exosomes with high B7-H1 expression and low B7-H1 expression were successfully isolated. In comparison to the sham-operated group, mice in the IRI group demonstrated elevated serum levels of blood urea nitrogen (BUN) and serum creatinine (Scr), accompanied by a more pronounced degree of renal tissue damage. The administration of exosomes via the tail vein markedly accelerated the recovery of renal function in IRI mice, with the therapeutic effect beingmore pronounced in those treated with B7-H1high-Exo. Moreover RNA sequencing of mouse kidney treated with B7-H1high-Exo and B7-H1low-Exo showed that eight genes (C3, IRF7, AREG, CXCL10, Aldh1l2, Fnip2, Vcam1, St6galnac3) were involved in the pathophysiological process of ischemia-reperfusion injury. The in vitro and in vivo experiments showed that the expression level of C3 protein was significantly decreased, which indicated that B7-H1high-Exo played a therapeutic role by down-regulating C3.

Sex differences in kidney and lung status in an animal model of brain death

BACKGROUND

In transplantation, sex-mismatched procedures correlate with poorer outcomes. Previous research has indicated that females respond worst to Brain Death (BD) and that organ damage varies with the speed of BD induction. The authors aimed to investigate the effects of slow BD-induction on lung and kidney responses in male and female rats.

METHODS

Males and female rats were subjected to slow induction of BD and kept for 4h. Blood gas samples were taken at 0 h and 4h. At 4 h, blood, urine and tissue samples were collected. IL-1β was measured in plasma, lung homogenate and lung culture. IL-6 was quantified in plasma, lung culture, and kidney homogenate. Leukocyte infiltration/activation was evaluated. Biochemical analyses of creatinine were performed in the plasma. Naïve animals were used as controls.

RESULTS

Males presented reduced testosterone levels after 4h. Females presented reduced progesterone, whereas estradiol remained similar at 0 h and 4h. Compared with Naive, BD-groups presented increased plasma IL-1β and IL-6. Males and females presented reduced pO2 after BD, with females presenting even lower values at 4h. In lung tissue, males presented increased expression of IL-1β, whereas IL-1β was elevated in females in lung culture. Females presented increased cell infiltration/activation. In the kidney, males presented increased plasma creatinine, increased expression of caspase-3, and increased leukocyte migration to renal tissue than females.

CONCLUSIONS

The authors observed an organ and sex-dependent response to the slow-induction of BD. These results suggest that management strategies should consider the sex of the donor to achieve the best treatment, improving graft quality.

Effects and Mechanisms of Extracellular Vesicles in Different Models of Acute Kidney Injury

Acute kidney injury (AKI) is a rapid decline in renal function caused by ischemia/reperfusion (I/R), renal toxic injury, and sepsis. While the precise molecular mechanisms underlying AKI are still under investigation, current therapeutic approaches remain insufficient. In recent years, there has been growing evidence that mesenchymal stem cells (MSCs) have great potential in accelerating renal repair after AKI in various preclinical models, while there has been extensive research on extracellular vesicles (EVs) as therapeutic mediators in AKI models, and they are considered to be superior to MSCs as new regenerative therapies. EVs are nanoparticles secreted by various types of cells under physiological and pathological conditions. EVs derived from various sources possess biomarker potential and play crucial roles in mediating cellular communication between kidney cells and other tissue cells by transmitting signal molecules. These vesicles play a direct and indirect role in regulating the pathophysiological mechanisms of AKI and contribute to the occurrence, development, treatment, and repair of AKI. In this review, we briefly outline the essential characteristics of EVs, focus on the multiple molecular mechanisms currently involved in the protection of EVs against different types of AKI, and further discuss the potential targets of EVs from different sources in the treatment of AKI. Finally, we summarized the deficiencies in the production and treatment of EVs and the current strategies for improvement.

Molecular mechanisms and therapeutic interventions in acute kidney injury: a literature review

Acute kidney injury (AKI) is a clinical challenge characterized by elevated morbidity and a substantial impact on individual health and socioeconomic factors. A comprehensive examination of the molecular pathways behind AKI is essential for its prevention and management. In recent years, vigorous research in the domain of AKI has concentrated on pathophysiological characteristics, early identification, and therapeutic approaches across many aetiologies and highlighted the principal themes of oxidative stress, inflammatory response, apoptosis, necrosis, and immunological response. This review comprehensively reviewed the molecular mechanisms underlying AKI, including oxidative stress, inflammatory pathways, immune cell-mediated injury, activation of the renin-angiotensin-aldosterone (RAAS) system, mitochondrial damage and autophagy, apoptosis, necrosis, etc. Inflammatory pathways are involved in the injuries in all four structural components of the kidney. We also summarized therapeutic techniques and pharmacological agents associated with the aforementioned molecular pathways. This work aims to clarify the molecular mechanisms of AKI thoroughly, offer novel insights for further investigations of AKI, and facilitate the formulation of efficient therapeutic methods to avert the progression of AKI.

Insights into the effects of apelin-13 on renal function and NHE3 activity following ischemia/reperfusion-induced acute kidney injury

Introduction

Acute kidney injury (AKI) is a clinical syndrome characterized by rapid decline in renal function with varying severity. In this context, tubular function is impaired in ischemia-induced AKI. Although there are no effective therapies for AKI, many compounds have been reported to reduce kidney injury, such as apelin-13. Considering the relevance of proximal tubular cells in maintaining fluid and electrolyte homeostasis, the effects of apelin-13 on tubular injury or sodium proximal transport remain unclear. Thus, the present study aims to evaluate the effects of exogenous administration of apelin-13 in the renal ischemia/reperfusion (I/R) model, with particular focus on renal function, injury markers, and tubular proliferation.

Methods

Male C57BL/6 mice were initially treated with a vehicle or high dose of apelin-13 (200 μg/kg/day) and subjected to kidney bilateral ischemia procedure for 30 min or a sham surgery. The mice were euthanized by exsanguination 2 d after the ischemic procedure. Then, the renal function was assessed through the plasma urea level and creatinine clearance. Tubular injury was evaluated by hematoxylin and eosin staining. Kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), megalin, Ki67, and phospho ERK 1/2 (Thr202/Tyr204) were evaluated through immunohistochemical or immunoblotting experiments. Moreover, the murine proximal tubular cells (TKPTS) were treated with apelin-13 (100 nM) to evaluate the activity of the Na+/H+ exchanger isoform 3 (NHE3) via intracellular pH measurements.

Results

Initial administration of apelin-13 did not improve tubular injury, creatinine clearance, or plasma urea level after renal I/R. Moreover, KIM-1 and NGAL markers were markedly increased after renal I/R and were not reduced in the apelin-13 + I/R group. Furthermore, megalin downregulation by renal I/R was not prevented by apelin-13. Interestingly, apelin-13 worsened the renal responses to tubular proliferation after renal I/R as Ki67 and phosphorylation of ERK/1/2 (Thr202/Tyr204) were sharply reduced in the apelin-13 + I/R group. In vitro experiments also demonstrated that apelin-13 inhibited NHE3 activity in murine proximal tubular cells.

Conclusion

The overall findings suggest that apelin-13 suppresses tubular proliferation and potentially impairs the adaptive response to renal I/R injury, thereby highlighting its relevance in ischemia-induced AKI.

microRNA-30c attenuates contrast-induced acute kidney injury by reducing renal tubular epithelial cell apoptosis via targeting SOCS1

Contrast-induced acute kidney injury (CIAKI) is a common complication after contrast media administration. Growing evidences implicate microRNA (miR)-30c has a key role in renal diseases. This study aimed to investigate the role and mechanism of miR-30c in CIAKI. CIAKI rat models were established using tail vein injection of omnipaque. MiR-30c was significantly downregulated in CIAKI models both in vivo and in vitro, concomitant with increased cell apoptosis and deteriorated renal injury. Meanwhile, the cell apoptosis, renal dysfunction and renal injury under contrast exposure were alleviated after overexpression of miR-30c. Mechanistically, we demonstrated that miR-30c directly targeted SOCS1, whose downregulation reduced contrast-induced HK-2 cell apoptosis. Furthermore, the upregulation of SOCS1 abolish the protective effect of the overexpression of miR-30c on contrast-induced cell apoptosis. In summary, overexpression of miR-30c inhibited renal tubular epithelial cell apoptosis and mitigated CIAKI via inhibiting the gene of SOCS1.

Muse Cells Orchestrating Renal Repair via Macrophage M2 Polarization in Ischemia-Reperfusion Injury

Acute renal ischemia-reperfusion injury (IRI) poses significant challenges in clinical management, necessitating the exploration of novel therapeutic strategies. This study investigates the therapeutic potential and underlying mechanisms of multilineage-differentiating stress-enduring (Muse) cells in alleviating renal IRI. In recent years, stem cell research has advanced significantly, providing promising prospects for clinical treatment. Mesenchymal stromal cells (MSCs), from which Muse cells are derived, are a heterogeneous population of cells that include stem cells with varying degrees of multipotency, committed progenitors, and differentiated cells. Muse cells, a subpopulation of MSCs, were isolated from adipose tissue obtained through liposuction in this study. In vivo studies revealed the effective recruitment of Muse cells to injured kidneys and their ability to ameliorate renal pathological damage and improve renal function in a rat model of acute kidney IRI. Mechanistically, Muse cells modulated the polarization of macrophages toward an anti-inflammatory M2 phenotype, as evidenced by decreased M1/M2 ratios. In vitro experiments further elucidated the interaction between Muse cells and macrophages, demonstrating Muse cell-mediated promotion of M2 polarization. Co-culture with M2 macrophages during reoxygenation phases enhanced the survival of renal tubular epithelial cells following hypoxia-reoxygenation injury, highlighting the therapeutic potential of Muse cells in mitigating renal IRI through modulation of macrophage polarization. These findings provide insights into the therapeutic mechanisms of Muse cells and offer promising avenues for the development of innovative renal injury treatments.

Mitochondrial DNA (mtDNA) accelerates oxygen-glucose deprivation-induced injury of proximal tubule epithelia cell via inhibiting NLRC5

The high morbidity and mortality associated with acute kidney injury (AKI) are global health concerns. AKI is commonly attributed to ischemia/reperfusion injury (IRI), a condition characterized by activation of inflammatory responses and mitochondrial dysfunction. Nonetheless, mitochondrial DNA (mtDNA) has the potential to induce renal IRI. This study aimed to elucidate the mechanism and function of mtDNA in HK-2 cells that had been exposed to oxygen-glucose deprivation/reperfusion (OGD/R) and in renal IRI mice. OGD/R was discovered to induce an increase in the amount of mtDNA in HK-2 cells. Moreover, our study demonstrated that mtDNA facilitated cellular apoptosis and inflammation in vivo and in vitro. Given the potential role of inflammation in OGD/R, we investigated the effect of mtDNA on various signaling pathways associated with inflammation. Western blot analysis demonstrated that mtDNA significantly upregulated NLRC5/TAP1 signaling. Furthermore, the upregulation of NLRC5 and TAP1 expression induced by mtDNA was reversed when NLRC5 was inhibited. It is worth mentioning that the loss of NLRC5 effectively nullified the beneficial effects of mtDNA on inflammation and cell apoptosis induced by OGD/R. In addition, in renal IRI mice, mtDNA treatment also aggravated inflammation and kidney damage, and increased the NLRC5 levels in kidney tissues. These results suggested that NLRC5 acts as an intermediary between mtDNA and the pathogenicity of renal IRI. In summary, this study provides evidence that mtDNA promotes apoptosis and inflammation in OGD/R treated HK-2 cells and renal IRI mice through upregulating NLRC5 levels.

Vagus nerve stimulation: A targeted approach for reducing tissue-specific ischemic reperfusion injury

Vagus Nerve Stimulation (VNS), a neuromodulation technique of applying controlled electrical impulses to the vagus nerve, has now emerged as a potential therapeutic approach for ischemia-reperfusion insults. It provides a pivotal link in improving functional outcomes for the central nervous system and multiple target organs affected by ischemia-reperfusion injury (I/RI). Reduced blood flow during ischemia and subsequent resumption of blood supply during reperfusion to the tissue compromises cellular health because of the combination of mitochondrial dysfunction, oxidative stress, cytokine release, inflammation, apoptosis, intracellular calcium overload, and endoplasmic reticulum stress, which ultimately leads to cell death and irreversible tissue damage. Furthermore, inflammation and apoptosis also play critical roles in the acute progression of ischemic injury pathology. Emerging evidence indicates that VNS in I/RI may act in an anti-inflammatory capacity, reducing oxidative stress and apoptosis, while also improving endothelial and mitochondrial function leading to reduced infarct sizes and cytoprotection in skeletal muscle, gastrointestinal tract, liver, kidney, lung, heart, and brain tissue. In this review, we attempt to shed light on the mechanistic links between tissue-specific damage following I/RI and the therapeutic approach of VNS in attenuating damage, considering both direct and remote I/RI scenarios. Thus, we want to advance the understanding of VNS that could further warrant its clinical implementation, especially as a treatment for I/RI.

Remote Ischemic Preconditioning Attenuates Mitochondrial Dysfunction and Ferroptosis of Tubular Epithelial Cells by Inhibiting NOX4-ROS Signaling in Acute Kidney Injury

Acute kidney injury (AKI) is a worldwide clinical burden associated with high morbidity and mortality. Remote ischemic preconditioning (rIPC), a brief nonlethal ischemia and reperfusion (IR) in remote tissues or limbs, has been used in an attempt to protect against AKI, but its underlying signaling pathways has not been elucidated. In the present study, rIPC protected kidney function and pathological injury and mitigated NADPH oxidase 4 (NOX4) upregulation in different AKI models (cisplatin, LPS and IRI). Furthermore, rIPC significantly attenuated mitochondrial dysfunction and ameliorated tubular epithelial ferroptosis during AKI. Mechanistically, in wild-type AKI mice and TCMK-1 cells, rIPC effectively decreased kidney ROS production, preserved mitochondrial dynamics and mitophagy, and ameliorated tubular epithelial ferroptosis. Notably, these protective effects of rIPC were further enhanced by NOX4 knockout or silencing and mitigated by NOX4 overexpression. Our study showed that rIPC may attenuate mitochondrial dysfunction and ferroptosis in tubular epithelial cells in AKI by inhibiting NOX4-ROS signaling. NOX4 might be used as a biomarker for monitoring the biological effects of rIPC to optimize the rIPC protocol and facilitate future translational studies.

Ankrd1 as a potential biomarker for the transition from acute kidney injury to chronic kidney disease

Ischemia-reperfusion injury (IRI) is one of the leading causes of acute kidney injury (AKI), predisposing patients to chronic kidney disease (CKD) due to maladaptive renal repair. Nevertheless, the molecular mechanisms and biomarkers that cause maladaptive repair remain unclear. In this study, we used single-nucleus RNA sequencing data from GEO database (GSE139107) to identify molecular markers during the transition from AKI to CKD caused by IRI. Analysis of intercellular crosstalk, trajectory and machine learning algorithms revealed hub cell clusters and genes. Proximal tubule (PT) cells, especially a new cluster (New PT2), significantly interacted with fibroblasts during the transition. The expression levels of hub genes were validated using the bulk RNA-seq data (GSE98622) and further confirmed through RT-qPCR and immunohistochemical analysis in ischemia-reperfusion injury (uIRI) mice. Ankrd1, a hub gene in New PT2, showed sustained upregulation in the proximal tubule in AKI. Compared to the sham-operated group, the expression of Ankrd1 in mice increased at 0.5 days post-reperfusion, peaked at day 1, and remained significantly elevated up to 60 days. This study indicated that the upregulation of Ankrd1 was positively associated with the progression from AKI to CKD and may potentially serve as a valuable biomarker for this transitional process.

Research progress on the pathogenesis of AKI complicated by ECMO

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) stands as a pivotal intervention for patients grappling with cardiopulmonary insufficiency. However, alongside its therapeutic benefits, ECMO carries the risk of complications, with acute kidney injury (AKI) emerging as a significant concern. The precise pathophysiological underpinnings of AKI in the context of ECMO remain incompletely elucidated.

METHODS

A comprehensive literature review was conducted to explore the epidemiology and pathophysiological mechanisms underlying the utilization of ECMO in the management of AKI.

RESULTS

ECMO initiates a multifaceted cascade of inflammatory reactions, encompassing complement activation, endothelial dysfunction, white blood cell activation, and cytokine release. Furthermore, factors such as renal hypoperfusion, ischemia-reperfusion injury, hemolysis, and fluid overload exacerbate AKI. Specifically, veno-arterial ECMO (VA-ECMO) may directly induce renal hypoperfusion, whereas veno-venous ECMO (VV-ECMO) predominantly impacts pulmonary function, indirectly influencing renal function.

CONCLUSION

While ECMO offers significant therapeutic advantages, AKI persists as a potentially fatal complication. A thorough comprehension of the pathogenesis underlying ECMO-associated AKI is imperative for effective prevention and management strategies. Moreover, additional research is warranted to delineate the incidence of AKI secondary to ECMO and to refine clinical approaches accordingly.

Ferroptosis in organ ischemia-reperfusion injuries: recent advancements and strategies

Ferroptosis is a newly discovered type of regulated cell death participated in multiple diseases. Different from other classical cell death programs such as necrosis and apoptosis, ferroptosis involving iron-catalyzed lipid peroxidation is characterized by Fe2+ accumulation and mitochondria alterations. The phenomenon of oxidative stress following organ ischemia-reperfusion (I/R) has recently garnered attention for its connection to the onset of ferroptosis and subsequent reperfusion injuries. This article provides a comprehensive overview underlying the mechanisms of ferroptosis, with a further focus on the latest research progress regarding interference with ferroptotic pathways in organ I/R injuries, such as intestine, lung, heart, kidney, liver, and brain. Understanding the links between ferroptosis and I/R injury may inform potential therapeutic strategies and targeted agents.

Special Issue "New Molecular Insights into Ischemia/Reperfusion"

Ischemia/reperfusion (IR) injury is a complex pathophysiological process in which the restoration of blood flow to ischemic tissue paradoxically exacerbates tissue damage and death [...].

Deletion of lymphotoxin-β receptor (LTβR) protects against acute kidney injury by PPARα pathway

BACKGROUND

Recent data has shown a considerable advancement in understanding the role of lymphotoxin-β receptor (LTβR) in inflammation. However, the functions and underlying mechanisms of LTβR in acute kidney injury (AKI) remain largely unknown.

METHODS

AKI was induced in mice by renal ischemia-reperfusion (I/R). HK-2 cells and primary renal tubular epithelial cells (RTECs) were subjected to hypoxia/reoxygenation (H/R) injury. The effects of LTβR depletion were examined in mice, as well as primary RTECs. Bone marrow chimeric mice was generated to determine whether the involvement of LTβR expression by parenchymal cells or bone marrow derived cells contributes to renal injury during AKI. RNA sequencing techniques were employed to investigate the mechanism via which LTβR signaling provides protection against I/R-induced AKI RESULTS: LTβR expression was downregulated both in vivo and in vitro models of AKI. Moreover, depletion of LTβR decreased renal damage and inflammation in I/R-induced AKI. We also found that LTβR deficient mice engrafted with wild type bone marrow had significantly less tubular damage, implying that LTβR in renal parenchymal cells may play dominant role in I/R-induced AKI. RNA sequencing indicated that the protective effect of LTβR deletion was associated with activation of PPARα signaling. Furthermore, upregulation of PPARα was observed upon depletion of LTβR. PPARα inhibitor, GW6471, aggravated the tubular damage and inflammation in LTβR-/- mice following I/R injury. Then we further demonstrated that LTβR depletion down-regulated non-canonical NF-κB and Bax/Bcl-2 apoptosis pathway through PPARα.

CONCLUSIONS

Our results suggested that the LTβR/PPARα axis may be a potential therapeutic target for the treatment of AKI.

Bioprospecting hydroxylated chalcones in in vitro model of ischemia-reoxygenation and probing NOX4 interactions via molecular docking

Ischemia/reperfusion injury (I/R) is a leading cause of acute kidney injury (AKI) in conditions like kidney transplants, cardiac surgeries, and nephrectomy, contributing to high global mortality and morbidity. This study aimed to analyze the protective effects of 2'-hydroxychalcones in treating I/R-induced AKI by targeting key pathological pathways. Considering strong antioxidant action along with other pharmacological roles of chalcone derivatives, six 2'-hydroxychalcones were synthesized via Claisen-Schmidt condensation and analyzed for their protective effects in an I/R induced AKI model using HK-2 cells. Among six 2'-hydroxychalcones, chalcone A4 significantly increased the HK-2 cells viability compared to I/R group. Chalcone A4 reduced the cell death events by reducing generation of cytoplasmic ROS and mitochondrial transmembrane potential. It also increased GSH and SOD activity while reducing TBARS levels, indicating strong antioxidant action. Scanning electron microscope images showed that chalcone A4 reversed I/R-induced morphological changes in HK-2 cells, including apoptotic blebbing and cytoplasmic fragmentation. Furthermore, in silico studies revealed interactions with NADPH oxidase 4, further supporting its protective role in I/R-induced AKI. These results showed that chalcone A4 possess potential protective action against I/R induced cellular damage possibly due to its strong antioxidant action and potential interaction with NOX4 subunit of NADPH oxidase.

Shikonin Inhibits Endoplasmic Reticulum Stress-Induced Apoptosis to Attenuate Renal Ischemia/Reperfusion Injury by Activating the Sirt1/Nrf2/HO-1 Pathway

INTRODUCTION

Shikonin is the major bioactive compound abundant in Lithospermum erythrorhizon and possesses diverse pharmacological properties. This study aimed to examine shikonin roles in experimental renal ischemia/reperfusion (I/R) injury.

METHODS

Renal tissues and blood were collected from experimental renal I/R injury models. Kidney functions, structural injuries, and cellular death were assessed. Markers of endoplasmic reticulum (ER) stress were evaluated by RT-qPCR and Western blotting. The effect of shikonin on Sirt1/Nrf2/HO-1 signaling was detected by Western blotting and immunofluorescence staining. HK-2 cells that underwent hypoxia/reoxygenation (H/R) process were used to perform CCK-8 and flow cytometry.

RESULTS

For in vivo analysis, renal dysfunctions and tissue structural damage induced by I/R were relieved by shikonin. Additionally, shikonin alleviated ER stress-induced apoptosis in I/R mice. For in vitro analysis, shikonin inhibited ER stress-stimulated apoptosis of H/R cells. Mechanistically, shikonin activated Sirt1/Nrf2/HO-1 signaling post-I/R, and inhibition of Sirt1 limited shikonin-mediated protection against ER stress-stimulated apoptosis in both animal and cellular models.

CONCLUSION

By activating Sirt1/Nrf2/HO-1 signaling, shikonin inhibits apoptosis caused by ER stress and relieves renal I/R injury.

Advances in macrophage-derived exosomes as immunomodulators in disease progression and therapy

Most somatic cells secrete vesicles called exosomes, which contain a variety of biomolecules. Recent research indicates that macrophage-derived exosomes are strongly correlated with tumors, infectious diseases, chronic inflammation, and tissue fibrosis. Therefore, the purpose of this review is to delve into the mechanisms of pathological states and how macrophage-derived exosomes react to them. We also discuss the biological effects of exosomes and how they affect disease. In addition, we have examined the possible uses of exosomes in illness treatment, highlighting both the benefits and drawbacks of these applications.

Implication of endoplasmic reticulum stress and mitochondrial perturbations in remote liver injury after renal ischemia/reperfusion in rats: potential protective role of azilsartan

Objectives: Distant liver injury is a complication of renal ischemia-reperfusion (I/R) injury, which imposes mortality and economic burden. This study aimed to elucidate the cross-talk of endoplasmic reticulum (ER) stress and mitochondrial perturbations in renal I/R-induced liver injury, and the potential hepatoprotective effect of azilsartan (AZL).Methods: Male albino Wister rats were pre-treated with AZL (3 mg/kg/day, PO) for 7 days then a bilateral renal I/R or sham procedure was performed. Activities of liver enzymes were assessed in plasma. The structure and ultra-structure of hepatocytes were assessed by light and electron microscopy. Markers of ER stress, mitochondrial biogenesis and apoptosis were analyzed in livers of rats.Results: Renal ischemic rats showed higher plasma levels of liver enzymes than sham-operated rats, coupled with histological and ultra-structural alterations in hepatocytes. Mechanistically, there was up-regulation of ER stress markers and suppression of mitochondrial biogenesis-related proteins and enhanced apoptosis in livers of renal ischemic rats. These abnormalities were almost abrogated by AZL pretreatment.Discussion: Our findings uncovered the involvement of mitochondrial perturbations, ER stress and apoptosis in liver injury following renal I/R, and suggested AZL as a preconditioning strategy to ameliorate remote liver injury in patients susceptible to renal I/R after adequate clinical testing.

Nanotechnology-Based Drug Delivery Systems for Treating Acute Kidney Injury

Acute kidney injury (AKI) is a disease that is characterized by a rapid decline in renal function and has a relatively high incidence in hospitalized patients. Sepsis, renal hypoperfusion, and nephrotoxic drug exposure are the main causes of AKI. The major therapy measures currently include supportive treatment, symptomatic treatment, and kidney transplantation. These methods are supportive treatments, and their results are not satisfactory. Fortunately, many new treatments that markedly improve the AKI therapy efficiency are emerging. These include antioxidant therapy, ferroptosis therapy, anti-inflammatory therapy, autophagy therapy, and antiapoptotic therapy. In addition, the development of nanotechnology has further promoted therapeutic effects on AKI. In this review, we highlight recent advances in the development of nanocarriers for AKI drug delivery. Emphasis has been placed on the latest developments in nanocarrier modification and design. We also summarize the applications of different nanocarriers in AKI treatment. Finally, the advantages and challenges of nanocarrier applications in AKI are summarized, and several nanomedicines that have been approved for clinical trials to treat diverse kidney diseases are listed.

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.

Sivelestat Sodium Alleviates Ischemia-Reperfusion-Induced Acute Kidney Injury via Suppressing TLR4/Myd88/NF-κB Signaling Pathway in Mice

Purpose

We aim to detect the effects of sivelestat on renal ischemia-reperfusion associated with AKI and also explore the underlying mechanism.

Materials and Methods

Mice, aged between 8 and 12 weeks, were randomly allocated among four distinct groups, respectively normal saline sham group(C), normal saline surgery group(I), sivelestat (50 mg/kg) sham group(S), sivelestat (50 mg/kg) surgery group(SI) (n=6, each group). In the surgical groups, the renal pedicles of mice were clamped with non-traumatic micro-aneurysm clamps, resulting in ischemia of the kidneys for 45 minutes. This was followed by a period of reperfusion lasting 24 hours. Sham group mice underwent the identical surgery produced without clamping renal pedicles. Mice blood was obtained from eyeballs, and Serum creatinine and blood urea nitrogen levels were measured. After a 24-hour period of reperfusion, the mice were euthanized, and their kidneys were gathered for various analyses, including Western Blot (WB) analysis, RT-PCR, immunofluorescence (IF), hematoxylin and eosin (H&E) staining, and Tunel assay.

Results

Pretreatments with sivelestat decreased renal Neutrophil elastase (NE), serum creatinine, and blood urea nitrogen levels after renal ischemia-reperfusion. Sivelestat also reduced histological damage and cell apoptosis in kidneys following ischemia-reperfusion injury (IRI). In addition, the sivelestat administration diminished the levels of mRNA expression of interleukin 6 (IL-6), Macrophage inflammatory protein-2 (MIP-2), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor (TNF)-α in the kidneys during IRI. The kidney tissues of the SI group had significantly mitigated TLR4, Myd88, and NF-κB p-p65 protein expression levels compared to the I group (all P<0.05).

Conclusion

We demonstrated a previously unidentified mechanism that sivelestat effectively attenuates AKI-induced renal dysfunction, possibly through suppressing the TLR4/Myd88/ NF-κB pathway.

Impact of ciprofloxacin with autophagy on renal tubular injury

BACKGROUNDS

Renal tubular injury caused by oxidative stress and inflammation results in acute kidney injury. Recent research reported that antibiotics may protect renal tubules from progressive deterioration, but the underlying mechanism remains unclear. Therefore, we investigated the efficacy and mechanism of action of antibiotics against renal tubular injury.

METHODS

We screened ciprofloxacin, ceftizoxime, minocycline, and netilmicin and selected ciprofloxacin to examine further because of its low toxicity towards renal tubular cells. We evaluated the effect of ciprofloxacin on cell survival by analyzing apoptosis and autophagy.

RESULTS

Terminal deoxynucleotidyl transferase-mediated d-UTP nick end labeling (TUNEL) assay results showed that the ciprofloxacin group had less apoptotic cells than the control group. The ratio of cleaved caspase 3 to caspase 3, the final effector in the apoptosis process, was decreased, but the ratio of B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) to Bcl-2 located upstream of caspase 3 was not decreased in the ciprofloxacin group. Therefore, apoptosis inhibition does not occur via Bax/Bcl-2. Conversely, the levels of phosphorylated Bcl-2, and Beclin-1, an autophagy marker, were increased, and that of caspase-3 was decreased in the ciprofloxacin group.

CONCLUSION

This indicates that ciprofloxacin enhances autophagy, increasing the amount of free Beclin-1 via phosphorylated Bcl-2, and inhibits caspase activity. Therefore, ciprofloxacin might protect against renal tubular injury through the activation of autophagy in the setting of acute kidney injury.

RIPK3 causes mitochondrial dysfunction and albuminuria in diabetic podocytopathy through PGAM5-Drp1 signaling

BACKGROUND

Receptor-interacting protein kinase (RIPK)3 is an essential molecule for necroptosis and its role in kidney fibrosis has been investigated using various kidney injury models. However, the relevance and the underlying mechanisms of RIPK3 to podocyte injury in albuminuric diabetic kidney disease (DKD) remain unclear. Here, we investigated the role of RIPK3 in glomerular injury of DKD.

METHODS

We analyzed RIPK3 expression levels in the kidneys of patients with biopsy-proven DKD and animal models of DKD. Additionally, to confirm the clinical significance of circulating RIPK3, RIPK3 was measured by ELISA in plasma obtained from a prospective observational cohort of patients with type 2 diabetes, and estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR), which are indicators of renal function, were followed up during the observation period. To investigate the role of RIPK3 in glomerular damage in DKD, we induced a DKD model using a high-fat diet in Ripk3 knockout and wild-type mice. To assess whether mitochondrial dysfunction and albuminuria in DKD take a Ripk3-dependent pathway, we used single-cell RNA sequencing of kidney cortex and immortalized podocytes treated with high glucose or overexpressing RIPK3.

RESULTS

RIPK3 expression was increased in podocytes of diabetic glomeruli with increased albuminuria and decreased podocyte numbers. Plasma RIPK3 levels were significantly elevated in albuminuric diabetic patients than in non-diabetic controls (p = 0.002) and non-albuminuric diabetic patients (p = 0.046). The participants in the highest tertile of plasma RIPK3 had a higher incidence of renal progression (hazard ratio [HR] 2.29 [1.05-4.98]) and incident chronic kidney disease (HR 4.08 [1.10-15.13]). Ripk3 knockout improved albuminuria, podocyte loss, and renal ultrastructure in DKD mice. Increased mitochondrial fragmentation, upregulated mitochondrial fission-related proteins such as phosphoglycerate mutase family member 5 (PGAM5) and dynamin-related protein 1 (Drp1), and mitochondrial ROS were decreased in podocytes of Ripk3 knockout DKD mice. In cultured podocytes, RIPK3 inhibition attenuated mitochondrial fission and mitochondrial dysfunction by decreasing p-mixed lineage kinase domain-like protein (MLKL), PGAM5, and p-Drp1 S616 and mitochondrial translocation of Drp1.

CONCLUSIONS

The study demonstrates that RIPK3 reflects deterioration of renal function of DKD. In addition, RIPK3 induces diabetic podocytopathy by regulating mitochondrial fission via PGAM5-Drp1 signaling through MLKL. Inhibition of RIPK3 might be a promising therapeutic option for treating DKD.

Pseudogene GSTM3P1 derived long non-coding RNA promotes ischemic acute kidney injury by target directed microRNA degradation of kidney-protective mir-668

Long non-coding RNAs (lncRNAs) are a group of epigenetic regulators that have been implicated in kidney diseases including acute kidney injury (AKI). However, very little is known about the specific lncRNAs involved in AKI and the mechanisms underlying their pathologic roles. Here, we report a new lncRNA derived from the pseudogene GSTM3P1, which mediates ischemic AKI by interacting with and promoting the degradation of mir-668, a kidney-protective microRNA. GSTM3P1 and its mouse orthologue Gstm2-ps1 were induced by hypoxia in cultured kidney proximal tubular cells. In mouse kidneys, Gstm2-ps1 was significantly upregulated in proximal tubules at an early stage of ischemic AKI. This transient induction of Gstm2-ps1 depends on G3BP1, a key component in stress granules. GSTM3P1 overexpression increased kidney proximal tubular apoptosis after ATP depletion, which was rescued by mir-668. Notably, kidney proximal tubule-specific knockout of Gstm2-ps1 protected mice from ischemic AKI, as evidenced by improved kidney function, diminished tubular damage and apoptosis, and reduced kidney injury biomarker (NGAL) induction. To test the therapeutic potential, Gstm2-ps1 siRNAs were introduced into cultured mouse proximal tubular cells or administered to mice. In cultured cells, Gstm2-ps1 knockdown suppressed ATP depletion-associated apoptosis. In mice, Gstm2-ps1 knockdown ameliorated ischemic AKI. Mechanistically, both GSTM3P1 and Gstm2-ps1 possessed mir-668 binding sites and downregulated the mature form of mir-668. Specifically, GSTM3P1 directly bound to mature mir-668 to induce its decay via target-directed microRNA degradation. Thus, our results identify GSTM3P1 as a novel lncRNA that promotes kidney tubular cell death in AKI by binding mir-668 to inducing its degradation.

Diosgenin Reduces Acute Kidney Injury and Ameliorates the Progression to Chronic Kidney Disease by Modifying the NOX4/p65 Signaling Pathways

Acute kidney injury (AKI), if not well controlled, may progress to chronic kidney disease (CKD). Diosgenin is a natural phytosteroid sapogenin from plants. This study aimed to investigate the mechanistic effects of diosgenin on AKI and AKI related development of CKD. The mouse model of ischemia/reperfusion (I/R)-induced AKI was used, and its progressive changes were followed. Human renal proximal tubular epithelial cells were used, and hypoxia stimulation was applied to mimic the in vivo I/R. Diosgenin, given after renal injury, preserved kidney function, as evidenced by a reduction in serum levels of BUN, creatinine, and UACR in both acute and chronic phases of AKI. Diosgenin alleviated I/R-induced tubular injury and prevented macrophage infiltration and renal fibrosis in AKI mice. Furthermore, diosgenin also mitigated the development of CKD from AKI with reduced renal expression of inflammatory, fibrotic, and epithelial-mesenchymal transition markers. In human renal tubular epithelial cells, diosgenin downregulated the hypoxia-induced oxidative stress and cellular damages that were dependent on the NOX4/p65 signaling pathways. Taken together, diosgenin treatment reduced I/R-induced AKI and ameliorated the progression to CKD from AKI probably by modifying the NOX4/p65 signaling pathways.

Inhibition of Usp14 ameliorates renal ischemia-reperfusion injury by reducing Tfap2a stabilization and facilitating mitophagy

Mitochondrial dysfunction is recognized as a pivotal contributor to the pathogenesis of renal ischemia-reperfusion (IR) injury. Mitophagy, the process responsible for removing damaged protein aggregates, stands as a critical mechanism safeguarding cells against IR injury. Currently, the role of deubiquitination in regulating mitophagy still needs to be completely elucidated. This study aimed to evaluate the impact of ubiquitin-specific peptidase 14 (Usp14), a deubiquitinase, in IR injury by influencing mitophagy. Utilizing a murine model of renal IR injury, Usp14 silencing was found to ameliorate kidney injury, leading to decreased levels of serum creatinine and blood urea nitrogen, alongside diminished oxidative stress and inflammation. In renal epithelial cells subjected to hypoxia/reoxygenation (H/R), Usp14 knockdown increased cell viability and reduced apoptosis. Further mechanistic studies revealed that Usp14 interacted with and deubiquitinated transcription factor AP-2 alpha (Tfap2a), thereby suppressing its downstream target gene, TANK binding kinase 1 (Tbk1), to influence mitophagy. Tfap2a overexpression or Tbk1 inhibition reversed the protective effects of Usp14 silencing on renal tubular cell injury and its facilitation of mitophagy. In summary, our study demonstrated the renoprotective role of Usp14 knockdown in mitigating renal IR injury by promoting Tfap2a-mediated Tbk1 upregulation and mitophagy. These findings advocate for exploring Usp14 inhibition as a promising therapeutic avenue for mitigating IR injury, primarily by enhancing the clearance of damaged mitochondria through augmented mitophagy.

Time-Restricted Feeding Protects against Renal Ischemia-Reperfusion Injury in Mice

Ischemia-reperfusion injury (IRI) in the kidneys is a major cause of acute kidney injury (AKI). Time-restricted feeding (TRF), known for its metabolic health benefits and alleviation of various chronic diseases without calorie restriction, was investigated for its potential protective effects against IRI-induced AKI. Male C57BL/6 mice underwent unilateral IRI, with their kidneys collected after two days. For two weeks before IRI induction, the TRF group had unlimited access to standard chow but within an 8-hour feeding window during the dark cycle. The study groups were Control, TRF, IRI, and TRF + IRI. In the TRF + IRI group, tubular damage scores significantly decreased compared to the IRI group. Furthermore, the TRF + IRI mice had lower levels of phosphorylated NF-κB and fewer F4/80-positive macrophages than the IRI group. Oxidative stress markers for lipids and proteins were also notably lower in the TRF + IRI group. Additionally, TUNEL-positive tubular cells and cleaved caspase-3 expression were reduced in the TRF + IRI group. Without calorie restriction, TRF mitigated renal damage by reducing inflammation, oxidative stress, and tubular apoptosis in renal IRI. This suggests that TRF could be a promising dietary strategy to prevent IRI-induced AKI.

The novel potential therapeutic target PSMP/MSMP promotes acute kidney injury via CCR2

Acute kidney injury (AKI) is a major worldwide health concern that currently lacks effective medical treatments. PSMP is a damage-induced chemotactic cytokine that acts as a ligand of CCR2 and has an unknown role in AKI. We have observed a significant increase in PSMP levels in the renal tissue, urine, and plasma of patients with AKI. PSMP deficiency improved kidney function and decreased tubular damage and inflammation in AKI mouse models induced by kidney ischemia-reperfusion injury, glycerol, and cisplatin. Single-cell RNA sequencing analysis revealed that Ly6Chi or F4/80lo infiltrated macrophages (IMs) were a major group of proinflammatory macrophages with strong CCR2 expression in AKI. We observed that PSMP deficiency decreased CCR2+Ly6Chi or F4/80lo IMs and inhibited M1 polarization in the AKI mouse model. Moreover, overexpressed human PSMP in the mouse kidney could reverse the attenuation of kidney injury in a CCR2-dependent manner, and this effect could be achieved without CCL2 involvement. Extracellular PSMP played a crucial role, and treatment with a PSMP-neutralizing antibody significantly reduced kidney injury in vivo. Therefore, PSMP might be a therapeutic target for AKI, and its antibody is a promising therapeutic drug for the treatment of AKI.

Time-restricted feeding protects against cisplatin-induced acute kidney injury in mice

BACKGROUND

Time-restricted feeding (TRF), devoid of calorie restriction, is acknowledged for promoting metabolic health and mitigating various chronic metabolic diseases. While TRF exhibits widespread benefits across multiple tissues, there is limited exploration into its impact on kidney function. In this study, our aim was to investigate the potential ameliorative effects of TRF on kidney damage in a mouse model of cisplatin-induced acute kidney injury (AKI).

METHODS

Cisplatin-induced AKI was induced through intraperitoneal injection of cisplatin into C57BL/6 male mice. Mice undergoing TRF were provided unrestricted access to standard chow daily but were confined to an 8-hour feeding window during the dark cycle for 2 weeks before cisplatin injection. The mice were categorized into four groups: control, TRF, cisplatin, and TRF + cisplatin.

RESULTS

The tubular damage score and serum creatinine levels were significantly lower in the TRF + cisplatin group compared to the cisplatin group. The TRF + cisplatin group exhibited reduced expression of phosphorylated nuclear factor kappa B, inflammatory cytokines, and F4/80-positive macrophages compared to the cisplatin group. Furthermore, oxidative stress markers for DNA, protein, and lipid were markedly decreased in the TRF + cisplatin group compared to the cisplatin group. TUNEL-positive tubular cells, cleaved caspase-3 expression, and the Bax/Bcl-2 ratio in the TRF + cisplatin group were lower than those in the cisplatin group.

CONCLUSION

TRF, without calorie restriction, effectively mitigated kidney damage by suppressing inflammatory reactions, oxidative stress, and tubular apoptosis in a mouse model of cisplatin-induced AKI. TRF holds promise as a novel dietary intervention for preventing cisplatin-induced AKI.

A novel marine-derived anti-acute kidney injury agent targeting peroxiredoxin 1 and its nanodelivery strategy based on ADME optimization

Insufficient therapeutic strategies for acute kidney injury (AKI) necessitate precision therapy targeting its pathogenesis. This study reveals the new mechanism of the marine-derived anti-AKI agent, piericidin glycoside S14, targeting peroxiredoxin 1 (PRDX1). By binding to Cys83 of PRDX1 and augmenting its peroxidase activity, S14 alleviates kidney injury efficiently in Prdx1-overexpression (Prdx1-OE) mice. Besides, S14 also increases PRDX1 nuclear translocation and directly activates the Nrf2/HO-1/NQO1 pathway to inhibit ROS production. Due to the limited druggability of S14 with low bioavailability (2.6%) and poor renal distribution, a pH-sensitive kidney-targeting dodecanamine-chitosan nanoparticle system is constructed to load S14 for precise treatment of AKI. l-Serine conjugation to chitosan imparts specificity to kidney injury molecule-1 (Kim-1)-overexpressed cells. The developed S14-nanodrug exhibits higher therapeutic efficiency by improving the in vivo behavior of S14 significantly. By encapsulation with micelles, the AUC0‒t , half-life time, and renal distribution of S14 increase 2.5-, 1.8-, and 3.1-fold, respectively. The main factors contributing to the improved druggability of S14 nanodrugs include the lower metabolic elimination rate and UDP-glycosyltransferase (UGT)-mediated biotransformation. In summary, this study identifies a new therapeutic target for the marine-derived anti-AKI agent while enhancing its ADME properties and druggability through nanotechnology, thereby driving advancements in marine drug development for AKI.

Perioperative Acute Renal Injury: Revisiting Pathophysiology

BACKGROUND

Acute renal dysfunction and subsequent acute renal failure after cardiac surgery are associated with high mortality and morbidity. Early therapeutic or preventive intervention is hampered by the lack of an early biomarker for acute renal injury. Recent studies showed that urinary neutrophil gelatinase-associated lipocalin (NGAL or lipocalin 2) is upregulated early (within 1 to 3 h) after murine renal injury and in pediatric acute renal dysfunction after cardiac surgery. The authors hypothesized that postoperative urinary NGAL concentrations are increased in adult patients developing acute renal dysfunction after cardiac surgery compared with patients without acute renal dysfunction.

METHODS

After institutional review board approval, 81 cardiac surgical patients were prospectively studied. Urine samples were collected immediately before incision and at various time intervals after surgery for NGAL analysis by quantitative immunoblotting. Acute renal dysfunction was defined as peak postoperative serum creatinine increase by 50% or greater compared with preoperative serum creatinine.

RESULTS

Sixteen of 81 patients (20%) developed postoperative acute renal dysfunction, and the mean urinary NGAL concentrations in patients who developed acute renal dysfunction were significantly higher early after surgery (after 1 h, mean ± SD, 4,195 ± 6,520 vs. 1,068 ± 2,129 ng/ml; P < 0.01) compared with patients who did not develop acute renal dysfunction. Mean urinary NGAL concentrations continued to increase and remained significantly higher at 3 and 18 h after cardiac surgery in patients with acute renal dysfunction. In contrast, urinary NGAL in patients without acute renal dysfunction decreased rapidly after cardiac surgery.

CONCLUSIONS

Patients developing postoperative acute renal dysfunction had significantly higher urinary NGAL concentrations early after cardiac surgery. Urinary NGAL may therefore be a useful early biomarker of acute renal dysfunction after cardiac surgery. These findings may facilitate the early detection of acute renal injury and potentially prevent progression to acute renal failure.

Cardiac Surgery-Associated Acute Kidney Injury

AKI is a common and serious complication of cardiac surgery that has a significant impact on patient morbidity and mortality. The Kidney Disease Improving Global Outcomes definition of AKI is widely used to classify and identify AKI associated with cardiac surgery (cardiac surgery-associated AKI [CSA-AKI]) on the basis of changes in serum creatinine and/or urine output. There are various preoperative, intraoperative, and postoperative risk factors for the development of CSA-AKI which should be recognized and addressed as early as possible to expedite its diagnosis, reduce its occurrence, and prevent or ameliorate its devastating complications. Crucial issues are the inaccuracy of serum creatinine as a surrogate parameter of kidney function in the perioperative setting of cardiothoracic surgery and the necessity to discover more representative markers of the pathophysiology of AKI. However, except for the tissue inhibitor of metalloproteinase-2 and insulin-like growth factor binding protein 7 ratio, other diagnostic biomarkers with an acceptable sensitivity and specificity are still lacking. This article provides a comprehensive review of various aspects of CSA-AKI, including pathogenesis, risk factors, diagnosis, biomarkers, classification, prevention, and treatment management.

Neutrophil-derived nanovesicles deliver IL-37 to mitigate renal ischemia-reperfusion injury via endothelial cell targeting

Renal ischemia-reperfusion injury (IRI) is one of the most important causes of acute kidney injury (AKI). Interleukin (IL)-37 has been suggested as a novel anti-inflammatory factor for the treatment of IRI, but its application is still limited by its low stability and delivery efficiency. In this study, we reported a novel engineered method to efficiently and easily prepare neutrophil membrane-derived vesicles (N-MVs), which could be utilized as a promising vehicle to deliver IL-37 and avoid the potential side effects of neutrophil-derived natural extracellular vesicles. N-MVs could enhance the stability of IL-37 and targetedly deliver IL-37 to damaged endothelial cells of IRI kidneys via P-selectin glycoprotein ligand-1 (PSGL-1). In vitro and in vivo evidence revealed that N-MVs encapsulated with IL-37 (N-MV@IL-37) could inhibit endothelial cell apoptosis, promote endothelial cell proliferation and angiogenesis, and decrease inflammatory factor production and leukocyte infiltration, thereby ameliorating renal IRI. Our study establishes a promising delivery vehicle for the treatment of renal IRI and other endothelial damage-related diseases.

Trends and predictors of changes in renal function after radical nephrectomy for renal tumours

BACKGROUND

Chronic kidney disease (CKD) is a common postoperative complication in patients who undergo radical nephrectomy for renal tumours. However, the factors influencing long-term renal function require further investigation.

OBJECTIVE

This study was designed to investigate the trends in renal function changes and risk factors for renal function deterioration in renal tumour patients after radical nephrectomy.

METHODS

We monitored changes in renal function before and after surgery for 3 years. The progression of renal function was determined by the progression and degradation of CKD stages. Univariate and multivariate logistic regression analyses were used to analyse the causes of renal function progression.

RESULTS

We analysed the data of 329 patients with renal tumours who underwent radical nephrectomies between January 2013 and December 2018. In this study, 43.7% of patients had postoperative acute kidney injury (AKI), and 48.3% had CKD at advanced stages. Further research revealed that patients' renal function stabilized 3 months after surgery. Additionally, renal function changes during these 3 months have a substantial impact on the progression of long-term renal function changes in patients.

CONCLUSION

AKI may be an indicator of short-term postoperative changes in renal function. Renal function tests should be performed in patients with AKI after radical nephrectomy to monitor the progression of functional impairment, particularly within the first 3 months after radical nephrectomy.

Metabolomic and lipidomic landscape of porcine kidney associated with kidney perfusion in heart beating donors and donors after cardiac death

Transplant centers are currently facing a lack of tools to ensure adequate evaluation of the quality of the available organs, as well as a significant shortage of kidney donors. Therefore, efforts are being made to facilitate the effective use of available organs and expand the donor pool, particularly with expanded criteria donors. Fulfilling a need, we aim to present an innovative analytical method based on solid-phase microextraction (SPME) - chemical biopsy. In order to track changes affecting the organ throughout the entire transplant procedure, porcine kidneys were subjected to multiple samplings at various time points. The application of small-diameter SPME probes assured the minimal invasiveness of the procedure. Porcine model kidney autotransplantation was executed for the purpose of simulating two types of donor scenarios: donors with a beating heart (HBD) and donors after cardiac death (DCD). All renal grafts were exposed to continuous normothermic ex vivo perfusion. Following metabolomic and lipidomic profiling using high-performance liquid chromatography coupled to a mass spectrometer, we observed differences in the profiles of HBD and DCD kidneys. The alterations were predominantly related to energy and glucose metabolism, and differences in the levels of essential amino acids, purine nucleosides, lysophosphocholines, phosphoethanolamines, and triacylglycerols were noticed. Our results indicate the potential of implementing chemical biopsy in the evaluation of graft quality and monitoring of renal function during perfusion.

Potential therapeutic applications of circular RNA in acute kidney injury

Acute kidney injury (AKI) is a common clinical syndrome characterized by a rapid deterioration in renal function, manifested by a significant increase in creatinine and a sharp decrease in urine output. The incidence of morbidity and mortality associated with AKI is on the rise, with most patients progressing to chronic kidney disease or end-stage renal disease. Treatment options for patients with AKI remain limited. Circular RNA (circRNA) is a wide and diverse class of non-coding RNAs that are present in a variety of organisms and are involved in gene expression regulation. Studies have shown that circRNA acts as a competing RNA, is involved in disease occurrence and development, and has potential as a disease diagnostic and prognostic marker. CircRNA is involved in the regulation of important biological processes, including apoptosis, oxidative stress, and inflammation. This study reviews the current status and progress of circRNA research in the context of AKI.

Allogeneic bone marrow mesenchymal stem cell-derived exosomes alleviate human hypoxic AKI-on-a-Chip within a tight treatment window

BACKGROUND

Acute hypoxic proximal tubule (PT) injury and subsequent maladaptive repair present high mortality and increased risk of acute kidney injury (AKI) - chronic kidney disease (CKD) transition. Human bone marrow mesenchymal stem cell-derived exosomes (hBMMSC-Exos) as potential cell therapeutics can be translated into clinics if drawbacks on safety and efficacy are clarified. Here, we determined the real-time effective dose and treatment window of allogeneic hBMMSC-Exos, evaluated their performance on the structural and functional integrity of 3D microfluidic acute hypoxic PT injury platform.

METHODS

hBMMSC-Exos were isolated and characterized. Real-time impedance-based cell proliferation analysis (RTCA) determined the effective dose and treatment window for acute hypoxic PT injury. A 2-lane 3D gravity-driven microfluidic platform was set to mimic PT in vitro. ZO-1, acetylated α-tubulin immunolabelling, and permeability index assessed structural; cell proliferation by WST-1 measured functional integrity of PT.

RESULTS

hBMMSC-Exos induced PT proliferation with ED50 of 172,582 µg/ml at the 26th hour. Hypoxia significantly decreased ZO-1, increased permeability index, and decreased cell proliferation rate on 24-48 h in the microfluidic platform. hBMMSC-Exos reinforced polarity by a 1.72-fold increase in ZO-1, restored permeability by 20/45-fold against 20/155 kDa dextran and increased epithelial proliferation 3-fold compared to control.

CONCLUSIONS

The real-time potency assay and 3D gravity-driven microfluidic acute hypoxic PT injury platform precisely demonstrated the therapeutic performance window of allogeneic hBMMSC-Exos on ischemic AKI based on structural and functional cellular data. The novel standardized, non-invasive two-step system validates the cell-based personalized theragnostic tool in a real-time physiological microenvironment prior to safe and efficient clinical usage in nephrology.

Transmission of high arterial pressure into renal microvessels during venous-clamping augments ischaemia/reperfusion-induced acute kidney injury in anaesthetized rats

AIM

In two recent studies, we observed that a 30-min renal vein clamping caused formation of interstitial haemorrhagic congestion in ischaemic and ischaemic/reperfused kidney along with the development of severer acute kidney injury (AKI) than renal artery or pedicle clamping. It was suggested that the transmission of high arterial pressure into renal microvessels during vein occlusion probably causes the occurrence of interstitial haemorrhagic congestion that augments AKI. The present investigation aimed to evaluate this suggestion by reducing renal perfusion pressure (RPP) during renal venous occlusion.

METHODS

Anaesthetized male Sprague-Dawley rats were divided into three groups (n = 8), which underwent a 2-h reperfusion period following 30-min bilateral renal venous clamping along with reduced RPP (VIR-rRPP group) or without reduced RPP (VIR group) and an equivalent period after sham-operation (Sham group).

RESULTS

The VIR-rRPP group compared with VIR group had lower levels of kidney malondialdehyde and tissue damages as epithelial injuries of proximal tubule and thick ascending limb, vascular congestion, intratubular cast and oedema, along with the less reductions in renal blood flow, creatinine clearance, Na+ -reabsorption, K+ and urea excretion, urine osmolality and free-water reabsorption. Importantly, the formation of intensive interstitial haemorrhagic congestion in the VIR group was not observed in the VIR-rRPP group.

CONCLUSION

These results indicate that the transmission of high arterial pressure into renal microvessels during venous occlusion leads to rupturing of their walls and the formation of interstitial haemorrhagic congestion, which has an augmenting impact on ischaemia/reperfusion-induced renal structural damages and haemodynamic, excretory and urine-concentrating dysfunctions.

CD44-targeted melanin-based nanoplatform for alleviation of ischemia/reperfusion-induced acute kidney injury

Ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) is a serious kidney disease with high morbidity and mortality. However, there is no effective clinical treatment strategy. Herein, we developed a CD44 targeting nanoplatform based on HA-assembled melanin NPs covalently coupled with dexamethasone for I/R-induced AKI therapy by alleviating oxidative/inflammatory- induced damage. The constructed HA-MNP-DXM NPs had good dispersion, stability, and broad-spectrum scavenging capabilities against multiple reactive free radicals. Moreover, the NPs could be efficiently internalized and exhibited antioxidative, anti-inflammatory, and antiapoptotic effects in CoCl2-stimulated renal tubular epithelial NRK-52E cells. Furthermore, the I/R-induced AKI murine model was established to evaluate the in vivo performance of NPs. The results suggested the NPs could specifically target impaired kidneys upon intravenous administration according to NIR-II fluorescence imaging and showed high biosafety. Importantly, the NPs could improve renal function, alleviate oxidative stress and inflammatory reactions, inhibit apoptosis of tubular cells, and restore mitochondrial structure and function, exhibiting excellent therapeutic effects. Further therapeutic mechanism indicated the NPs maintained the cellular/mitochondrial redox balance by modulating the Nrf2 and HO-1 expression. Therefore, the NPs can be a promising therapeutic candidate for the treatment of I/R-induced AKI.

Cyclohexylalanine-Containing α-Helical Amphipathic Peptide Targets Cardiolipin, Rescuing Mitochondrial Dysfunction in Kidney Injury

Mitochondrial dysfunction is linked to degenerative diseases, resulting from cardiolipin (CL)-induced disruption of cristae structure in the inner mitochondrial membrane (IMM); therefore, preserving cristae and preventing CL remodeling offer effective strategies to maintain mitochondrial function. To identify reactive oxygen species (ROS)-blocking agents against mitochondrial dysfunction, a library of cyclohexylamine-containing cell-penetrating α-helical amphipathic "bundle" peptides were screened. Among these, CMP3013 is selectively bound to abnormal mitochondria, preserving the cristae structure impaired by mitochondria-damaging agents. With a stronger affinity for CL compared with other IMM lipid components, CMP3013 exhibited high selectivity. Consequently, it protected cristae, reduced ROS production, and enhanced adenosine triphosphate (ATP) generation. In mouse models of acute kidney injury, a 1 mg/kg dose of CMP3013 demonstrated remarkable efficacy, highlighting its potential as a therapeutic agent for mitochondrial dysfunction-related disorders. Overall, CMP3013 represents a promising agent for mitigating mitochondrial dysfunction and associated diseases.

Protective Effects of Sesamol on Renal Ischemia-Reperfusion Injury Via Regulation of Nuclear Factor Erythroid 2-Related Factor 2 Pathway

BACKGROUND

Sesamol is a natural antioxidant known for its potent antioxidant and free radical scavenging properties. This study aimed to explore the therapeutic effects and underlying mechanisms of sesamol in the development of renal ischemia-reperfusion injury (IRI) in mice.

METHODS

C57BL/6J wild-type mice were divided into 3 groups: IR group, treated with normal saline after undergoing the IRI procedure; Sesamol + IR group, treated with 30 mg/kg/d of sesamol after the IRI procedure; and Sham group, treated with normal saline but not subjected to the IRI process. Renal IRI was induced by performing a right kidney nephrectomy and subjecting the left kidney to 30-minute ischemia, followed by 24-hour reperfusion. Kidney tissues and serum were collected 24 hours post-IRI to assess the impact of sesamol on renal function after IRI. Serum creatinine and blood urea nitrogen levels were assessed, and renal cell apoptosis was detected through terminal deoxynucleotidyl transferase dUTP nick-end labeling staining. The levels of interleukin 1β and interleukin 18 in kidney tissues, as well as indicators of oxidative stress, were also measured. Furthermore, Nrf2-deficient mice were used to examine the protective function of the nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) signaling pathways induced by sesamol, as determined by western blot assay.

RESULTS

Sesamol demonstrated significant improvement in renal function, along with reductions in renal tubular injury, cell necrosis, and apoptosis in mice. It also effectively lowered key inflammatory mediator levels. Sesamol exhibited antioxidant properties by reducing malondialdehyde levels and enhancing superoxide dismutase activities 24 hours after IRI. Western blot assay revealed increased Nrf2, HO-1, and NQO-1 protein levels with sesamol treatment. Notably, Nrf2-deficient mice did not exhibit the beneficial effects of sesamol.

CONCLUSIONS

This study demonstrates that sesamol effectively alleviates renal IRI by enhancing antioxidant defenses and reducing inflammation potentially through the Nrf2/HO-1 and NQO1 signaling pathways.

Pre-treatment with β-hydroxybutyrate mitigates cisplatin-induced acute kidney injury

β-Hydroxybutyrate (β-HB), the primary circulating ketone body, plays a dual role as both a metabolic fuel and an endogenous signaling molecule, offering diverse systemic benefits. Recent studies have highlighted the renoprotective effects of exogenous β-HB therapy in various animal models of kidney disease. In this investigation, our goal was to assess whether pre-treatment with exogenous β-HB could alleviate kidney damage in a mouse model of cisplatin-induced acute kidney injury (AKI). Prior to cisplatin administration, intraperitoneal administration of β-HB was carried out, and the groups were classified into four: Sham, β-HB, cisplatin, and β-HB + cisplatin. The tubular damage score and serum creatinine levels were significantly lower in the β-HB + cisplatin group compared to the cisplatin group. Furthermore, the expression of phosphorylated NF-κB, inflammatory cytokines, and the quantity of F4/80-positive macrophages in the β-HB + cisplatin group were reduced compared to those in the cisplatin group. Additionally, oxidative stress markers for DNA, protein, and lipid in the β-HB + cisplatin group were markedly diminished compared to those in the cisplatin group. The number of TUNEL-positive and cleaved caspase 3-positive tubular cells in the β-HB + cisplatin group was lower than in the cisplatin group. Pre-treating with exogenous β-HB effectively mitigated kidney damage by suppressing inflammation, oxidative stress, and tubular apoptosis in cisplatin-induced AKI. Therefore, exogenous β-HB as a pre-treatment emerges as a promising and novel strategy for preventing cisplatin-induced AKI.