Acute kidney injury: Epidemiology, outcomes, complications, and therapeutic strategies

Acute kidney injury in hospitalized children in 20 hospitals of China's Hunan Province: a cross-sectional survey

OBJECTIVE

The incidence of acute kidney injury (AKI) in pediatric patients has been increasing over the years, and AKI significantly impacts children's health and quality of life. This article reviews the current epidemiological research on pediatric AKI.

METHODS

The clinical data of hospitalized children aged 0 to 14 years from 20 different hospitals in Hunan Province, China, collected from December 2017 to February 2018, were analyzed. The incidence rate, misdiagnosis rate, main causes, and medical costs of AKI in hospitalized children were examined.

RESULTS

A total of 29,639 patients were included, with an AKI incidence rate of 4.34% (1286/29,639). Among the 1286 AKI patients, 863 (67.11%) were classified as AKI stage 1324 (25.19%) as AKI stage 2, and 99 (7.7%) as AKI stage 3. AKI patients had significantly longer hospital stays [6.0 (4.0, 10) days vs. 6.0 (4.0, 8.0) days, p < 0.001] and higher hospitalization costs [3375.22 (1600, 6083.83) yuan vs. 2729.4 (1659.45, 8216.65) yuan, p = 0.003] than non-AKI patients. The mortality rate (1.2% vs. 0.1%, p < 0.001), intensive care unit (ICU) transfer rate (8.7% vs. 5.97%, p < 0.001), and use of invasive mechanical ventilation (3.6% vs. 1%, p < 0.001) were significantly greater in patients with AKI than in those without AKI patients. The etiology of AKI varied among different age groups, and dehydration, diarrhea, and shock were the main causes of pre-renal AKI.

CONCLUSION

The incidence and missed diagnosis rates of AKI in hospitalized children were high. AKI prolongs hospital stays, increases hospitalization costs, and increases the risk of mortality in children.

Predictive models of sepsis-associated acute kidney injury based on machine learning: a scoping review

BACKGROUND

With the development of artificial intelligence, the application of machine learning to develop predictive models for sepsis-associated acute kidney injury has made potential breakthroughs in early identification, grading, diagnosis, and prognosis determination.

METHODS

Here, we conducted a systematic search of the PubMed, Cochrane Library, Embase (Ovid), Web of Science, and Scopus databases on April 28, 2023, and screened relevant literature. Then, we comprehensively extracted relevant data related to machine learning algorithms, predictors, and predicted objectives. We subsequently performed a critical evaluation of research quality, data aggregation, and analyses.

RESULTS

We screened 25 studies on predictive models for sepsis-associated acute kidney injury from a total of originally identified 2898 studies. The most commonly used machine learning algorithm is traditional logistic regression, followed by eXtreme gradient boosting. We categorized these predictive models into early identification models (60%), prognostic prediction models (32%), and subtype identification models (8%) according to their predictive purpose. The five most commonly used predictors were serum creatinine levels, lactate levels, age, blood urea nitrogen concentration, and diabetes mellitus. In addition, a single data source, insufficient assessment of clinical utility, lack of model bias assessment, and hyperparameter adjustment may be the main reasons for the low quality of the current research.

CONCLUSIONS

However, studies on the nondeath prognostic outcomes, the long-term clinical outcomes, and the subtype identification models are insufficient. Additionally, the poor quality of the research and the insufficient practicality of the model are problems that need to be addressed urgently.

Neferine alleviates acute kidney injury by regulating the PPAR-α/NF-κB pathway

Acute kidney injury (AKI) is a cluster of clinical syndromes with diverse etiologies that ultimately result in a swift decline in kidney function. Regrettably, AKI lacks effective therapeutic agents at present. Neferine, a bioactive alkaloid derived from Lotus Plumule, has been reported to alleviate AKI triggered by cisplatin, ischemia/reperfusion (I/R), and sepsis by inhibiting inflammatory pathways. However, the precise molecular mechanisms underpinning its renoprotective effects remain elusive. Peroxisome proliferator-activated receptor alpha (PPAR-α), a regulator of lipid metabolism with anti-inflammatory properties, was investigated in this study to examine its role in neferine's renoprotective effects in cellular and mouse models of AKI. We found that neferine pretreatment in both I/R- or lipopolysaccharide (LPS)-induced AKI models inhibited the activation of the NF-κB inflammatory pathway and reversed PPAR-α deficiency. In NRK-52E cells exposed to hypoxia/reoxygenation (H/R) or LPS, overexpression of PPAR-α resulted in inhibition of the NF-κB pathway and TNF-α production, while PPAR-α silencing via siRNA transfection negated neferine's anti-inflammatory effects. Furthermore, pretreatment with neferine not only reduced lipid accumulation but also reversed the downregulation of FAO-related enzymes induced by LPS. Our findings suggest that neferine's renoprotective effects against AKI are partially mediated through the reversal of renal PPAR-α deficiency and subsequent inhibition of the inflammatory NF-κB pathway. Therefore, regulating renal PPAR-α expression by neferine could represent a promising therapeutic strategy for AKI.

Transitions and Long-Term Clinical Outcomes in Patients Admitted in Intensive Care Units Receiving Continuous Renal Replacement Therapy

Introduction: Acute kidney injury (AKI) significantly disrupts vital renal functions and is a common and serious condition in intensive care units (ICUs). AKI leads to extended hospital stays, increases mortality rates, and often necessitates nephrology consultations. Continuous renal replacement therapy (CRRT) plays a central role in managing AKI, requiring a multidisciplinary approach involving nephrologists, intensivists, and anesthesiologists. This study examines the clinical profile and progression of AKI in ICU patients requiring CRRT, with a focus on CRRT indications and modalities. Materials and Methods: We conducted a single-center retrospective observational study on ICU patients with AKI requiring CRRT from January to December 2019. AKI diagnosis followed the RIFLE criteria, and patients who received CRRT for less than 36 h were excluded. Data collected included demographics, hemodynamic parameters, and renal function parameters, with follow-ups at 1 week, 1 month, 6 months, and 12 months. Statistical analyses evaluated outcomes and transitions between CRRT and other renal replacement therapies. Results: Among 123 evaluated patients, 95 met inclusion criteria. Fifteen patients received CRRT for less than 36 h, with an early mortality rate of 80%. The final cohort comprised 80 patients who underwent CRRT for over 36 h, with a mean age of 65.3 years (SD = 13.6) and a Charlson index of 6.4. Patients were categorized based on primary diagnosis into heart failure, cardiac surgery, sepsis, other surgeries, and miscellanea groups. Mortality rates were highest in the heart failure and miscellanea groups. Significant variability was observed in therapy transitions and long-term outcomes. Continuous venovenous hemodiafiltration (CVVHDF) was the most frequently used CRRT modality. Conclusions: This study highlights the variability in CRRT practices and the poor prognosis for critically ill patients with AKI requiring CRRT. Timely nephrology consultation and tailored treatment plans may improve patient outcomes and optimize CRRT utilization. Future research should focus on refining CRRT protocols and exploring preventive strategies for AKI.

NLRP3 Inflammasome: A central player in renal pathologies and nephropathy

The cytoplasmic oligomer NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome has been implicated in most inflammatory and autoimmune diseases. Here, we highlight the significance of NLRP3 in diverse renal disorders, demonstrating its activation in macrophages and non-immune tubular epithelial and mesangial cells in response to various stimuli. This activation leads to the release of pro-inflammatory cytokines, contributing to the development of acute kidney injury (AKI), chronic renal injury, or fibrosis. In AKI, NLRP3 inflammasome activation and pyroptotic renal tubular cell death is driven by contrast and chemotherapeutic agents, sepsis, and rhabdomyolysis. Nevertheless, inflammasome is provoked in disorders such as crystal and diabetic nephropathy, obesity-related renal fibrosis, lupus nephritis, and hypertension-induced renal damage that induce chronic kidney injury and/or fibrosis. The mechanisms by which the inflammatory NLRP3/ Apoptosis-associated Speck-like protein containing a Caspase recruitment domain (ASC)/caspase-1/interleukin (IL)-1β & IL-18 pathway can turn on renal fibrosis is also comprehended. This review further outlines the involvement of dopamine and its associated G protein-coupled receptors (GPCRs), including D1-like (D1, D5) and D2-like (D2-D4) subtypes, in regulating this inflammation-linked renal dysfunction pathway. Hence, we identify D-related receptors as promising targets for renal disease management by inhibiting the functionality of the NLRP3 inflammasome.

Developing poly(ethylene glycol)-b-poly(β-hydroxybutyrate)-based self-assembling prodrug for the management of cisplatin-induced acute kidney injury

Although β-hydroxybutyrate (BHB), one of the endogenous body ketones, possesses high bioactivities, it is rapidly consumed, metabolized, and eliminated from the body. In this study, we designed new self-assembling nanoparticles that sustainably released BHB to improve bioavailability and evaluated their efficacy in in vivo experiments using rodent animal models. Since poly(β-hydroxybutyrate) [poly(BHB)] is regarded as a polymeric prodrug that is hydrolyzed by endogenous enzymes and releases BHB in a sustained manner, our idea was to engineer hydrophobic poly(BHB) in one of the segments in the amphiphilic block copolymer, of which self-assembles in water to form nanoparticles of tens of nanometers in size (abbreviated as NanoBHB). Here, methoxy-poly(ethylene glycol) was employed as the hydrophilic segment of the block copolymer to stabilize the nanoparticles in aqueous environments, thus enabling NanoBHBs to be administrable both orally and through injection. Experimental results showed that NanoBHB has low toxicity and releases free BHB for an extended period in vitro and in vivo. Moreover, NanoBHB exhibits superior nephroprotective effects in cisplatin-induced acute kidney injury mouse models compared to low-molecular-weight (LMW) sodium BHB, suggesting the potential of NanoBHB as a sustainable release formulation to supply BHB for medicinal applications.

The AMPK activator ATX-304 alters cellular metabolism to protect against cisplatin-induced acute kidney injury

Acute kidney injury (AKI) disrupts energy metabolism. Targeting metabolism through AMP-activated protein kinase (AMPK) may alleviate AKI. ATX-304, a pan-AMPK activator, was evaluated in C57Bl/6 mice and tubular epithelial cell (TEC) cultures. Mice received ATX-304 (1 mg/g) or control chow for 7 days before cisplatin-induced AKI (CI-AKI). Primary cultures of tubular epithelial cells (TECs) were pre-treated with ATX-304 (20 µM, 4 h) prior to exposure to cisplatin (20 µM, 23 h). ATX-304 increased acetyl-CoA carboxylase phosphorylation, indicating AMPK activation. It protected against CI-AKI measured by serum creatinine (control 0.05 + 0.03 mM vs ATX-304 0.02 + 0.01 mM, P = 0.03), western blot for neutrophil gelatinase-associated lipocalin (NGAL) (control 3.3 + 1.8-fold vs ATX-304 1.2 + 0.55-fold, P = 0.002), and histological injury (control 3.5 + 0.59 vs ATX-304 2.7 + 0.74, P = 0.03). In TECs, pre-treatment with ATX-304 protected against cisplatin-mediated injury, as measured by lactate dehydrogenase release, MTS cell viability, and cleaved caspase 3 expression. ATX-304 protection against cisplatin was lost in AMPK-null murine embryonic fibroblasts. Metabolomic analysis in TECs revealed that ATX-304 (20 µM, 4 h) altered 66/126 metabolites, including fatty acids, tricarboxylic acid cycle metabolites, and amino acids. Metabolic studies of live cells using the XFe96 Seahorse analyzer revealed that ATX-304 increased the basal TEC oxygen consumption rate by 38%, whereas maximal respiration was unchanged. Thus, ATX-304 protects against cisplatin-mediated kidney injury via AMPK-dependent metabolic reprogramming, revealing a promising therapeutic strategy for AKI.

Urinary oxygen tension and its role in predicting acute kidney injury: A narrative review

Acute kidney injury occurs frequently in the perioperative setting. The renal medulla often endures hypoxia or hypoperfusion and is susceptible to the imbalance between oxygen supply and demand due to the nature of renal blood flow distribution and metabolic rate in the kidney. The current available evidence demonstrated that the urine oxygen pressure is proportional to the variations of renal medullary tissue oxygen pressure. Thus, urine oxygenation can be a candidate for reflecting the change of oxygen in the renal medulla. In this review, we discuss the basic physiology of acute kidney injury, as well as techniques for monitoring urine oxygen tension, confounding factors affecting the reliable measurement of urine oxygen tension, and its clinical use, highlighting its potential role in early detection and prevention of acute kidney injury.

Ensemble Machine Learning for Predicting 90-Day Outcomes and Analyzing Risk Factors in Acute Kidney Injury Requiring Dialysis

Purpose

Our objectives were to (1) employ ensemble machine learning algorithms utilizing real-world clinical data to predict 90-day prognosis, including dialysis dependence and mortality, following the first hospitalized dialysis and (2) identify the significant factors associated with overall outcomes.

Patients and Methods

We identified hospitalized patients with Acute kidney injury requiring dialysis (AKI-D) from a dataset of the Taipei Medical University Clinical Research Database (TMUCRD) from January 2008 to December 2020. The extracted data comprise demographics, comorbidities, medications, and laboratory parameters. Ensemble machine learning models were developed utilizing real-world clinical data through the Google Cloud Platform.

Results

The Study Analyzed 1080 Patients in the Dialysis-Dependent Module, Out of Which 616 Received Regular Dialysis After 90 Days. Our Ensemble Model, Consisting of 25 Feedforward Neural Network Models, Demonstrated the Best Performance with an Auroc of 0.846. We Identified the Baseline Creatinine Value, Assessed at Least 90 Days Before the Initial Dialysis, as the Most Crucial Factor. We selected 2358 patients, 984 of whom were deceased after 90 days, for the survival module. The ensemble model, comprising 15 feedforward neural network models and 10 gradient-boosted decision tree models, achieved superior performance with an AUROC of 0.865. The pre-dialysis creatinine value, tested within 90 days prior to the initial dialysis, was identified as the most significant factor.

Conclusion

Ensemble machine learning models outperform logistic regression models in predicting outcomes of AKI-D, compared to existing literature. Our study, which includes a large sample size from three different hospitals, supports the significance of the creatinine value tested before the first hospitalized dialysis in determining overall prognosis. Healthcare providers could benefit from utilizing our validated prediction model to improve clinical decision-making and enhance patient care for the high-risk population.

Protein and peptide-based renal targeted drug delivery systems

Renal diseases have become an increasingly concerned public health problem in the world. Kidney-targeted drug delivery has profound transformative potential on increasing renal efficacy and reducing extra-renal toxicity. Protein and peptide-based kidney targeted drug delivery systems have garnered more and more attention due to its controllable synthesis, high biocompatibility and low immunogenicity. At the same time, the targeting methods based on protein/peptide are also abundant, including passive renal targeting based on macromolecular protein and active targeting mediated by renal targeting peptide. Here, we review the application and the drug loading strategy of different proteins or peptides in targeted drug delivery, including the ferritin family, albumin, low molecular weight protein (LMWP), different peptide sequence and antibodies. In addition, we summarized the factors influencing passive and active targeting in drug delivery system, the main receptors related to active targeting in different kidney diseases, and a variety of nano forms of proteins based on the controllable synthesis of proteins.

The effects of antibiotic therapy on neonatal sepsis-associated acute kidney injury

AIM

Neonatal sepsis remains one of the most dangerous conditions in the neonatal intensive care units. One of the organs affected by sepsis is the kidney, making acute kidney injury (AKI) a common complication of sepsis. Treatment of sepsis almost always involves antibiotic therapy, which by itself may cause some adverse effects, including nephrotoxicity. We analyzed the mutual effect of antibiotic therapy and sepsis on AKI in an experimental and clinical study in infants and neonatal rats.

MATERIALS AND METHODS

We evaluated the influence of therapy with different antibiotics on the appearance of AKI markers (blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL), clusterin, interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), calbindin, glutation-S-transferase subtype π (GST-π)) and liver injury markers in newborns with or without clinical signs of sepsis in the intensive care unit. In parallel, we analyzed the development of AKI in experimental lipopolysaccharide (LPS)-induced systemic inflammation in newborn rats accompanied by antibiotic therapy.

KEY FINDINGS

We showed that therapy with metronidazole or ampicillin in combination with sulbactam had a beneficial effect in children with suspected sepsis, resulting in a decrease in AKI markers levels. However, treatment of newborns with netilmicin, cefepime, linezolid, or imipenem in combination with cilastatin worsened kidney function in these patients.

SIGNIFICANCE

This prospective study indicates which antibiotics are preferable in neonatal sepsis and which should be used with caution in view of the risk of AKI development.

The secretory leukocyte protease inhibitor (SLPI) in pathophysiology of non-communicable diseases: Evidence from experimental studies to clinical applications

Non-communicable diseases (NCDs) are a worldwide health issue because of their prevalence, negative impacts on human welfare, and economic costs. Protease enzymes play important roles in viral and NCD diseases. Slowing disease progression by inhibiting proteases using small-molecule inhibitors or endogenous inhibitory peptides appears to be crucial. Secretory leukocyte protease inhibitor (SLPI), an inflammatory serine protease inhibitor, maintains protease/antiprotease balance. SLPI is produced by host defense effector cells during inflammation to prevent proteolytic enzyme-induced tissue damage. The etiology of noncommunicable illnesses is linked to SLPI's immunomodulatory and tissue regeneration roles. Disease phases are associated with SLPI levels and activity changes in regional tissue and circulation. SLPI has been extensively evaluated in inflammation, but rarely in NCDs. Unfortunately, the thorough evaluation of SLPI's pathophysiological functions in NCDs in multiple research models has not been published elsewhere. In this review, data from PubMed from 2014 to 2023 was collected, analysed, and categorized into in vitro, in vivo, and clinical studies. According to the review, serine protease inhibitor (SLPI) activity control is linked to non-communicable diseases (NCDs) and other illnesses. Overexpression of the SLPI gene and protein may be a viable diagnostic and therapeutic target for non-communicable diseases (NCDs). SLPI is also cytoprotective, making it a unique treatment. These findings suggest that future research should focus on these pathways using advanced methods, reliable biomarkers, and therapy approaches to assess susceptibility and illness progression. Implications from this review will help pave the way for a new therapeutic target and diagnosis marker for non-communicable diseases.

Spice Up Your Kidney: A Review on the Effects of Capsaicin in Renal Physiology and Disease

Capsaicin, the organic compound which attributes the spicy flavor and taste of red peppers and chili peppers, has been extensively studied for centuries as a potential natural remedy for the treatment of several illnesses. Indeed, this compound exerts well-known systemic pleiotropic effects and may thus bring important benefits against various pathological conditions like neuropathic pain, rhinitis, itching, or chronic inflammation. Yet, little is known about the possible biological activity of capsaicin at the kidney level, as this aspect has only been addressed by sparse experimental investigations. In this paper, we aimed to review the available evidence focusing specifically on the effects of capsaicin on renal physiology, as well as its potential benefits for the treatment of various kidney disorders. Capsaicin may indeed modulate various aspects of renal function and renal nervous activity. On the other hand, the observed experimental benefits in preventing acute kidney injury, slowing down the progression of diabetic and chronic kidney disease, ameliorating hypertension, and even delaying renal cancer growth may set the stage for future human trials of capsaicin administration as an adjuvant or preventive therapy for different, difficult-to-treat renal diseases.

Risk of chronic kidney disease in patients with acute kidney injury following a major surgery: a US claims database analysis

Background

Acute kidney injury (AKI) is a common complication after major surgery. This study assessed the risk of developing or worsening of chronic kidney disease (CKD) and other clinical outcomes in patients experiencing AKI after major surgery.

Methods

This retrospective observational study used Optum's de-identified Clinformatics Data Mart Database to investigate cardiorenal outcomes in adult patients at the first AKI event following major surgery. The primary outcome was CKD stage ≥3; secondary outcomes included myocardial infarction (MI), stroke, heart failure, all-cause hospitalization, end-stage kidney disease, need for dialysis or kidney transplant and composite measures. Follow-up was up to 3 years. Additionally, the effect of intercurrent events on the risk of clinical outcomes was assessed.

Results

Of the included patients (N = 31 252), most were male (61.9%) and White (68.9%), with a median age of 72 years (interquartile range 64-79). The event rates were 25.5 events/100 patient-years (PY) for CKD stage ≥3, 3.1 events/100 PY for end-stage kidney disease, 3.0 events/100 PY for dialysis and 0.1 events/100 PY for kidney transplants. Additionally, there were 6.9 events/100 PY for MI, 8.7 events/100 PY for stroke and 49.8 events/100 PY for all-cause hospitalization during follow-up. Patients with AKI relapses as intercurrent events were more likely to develop CKD stage ≥3 than those with just one AKI event after major surgery.

Conclusion

This analysis demonstrated that patients experiencing AKI following major surgery are at high risk of developing severe CKD or worsening of pre-existing CKD and other cardiorenal clinical outcomes such as MI and stroke.

Acute kidney injury associated with nephrotoxic drugs in critically ill patients: a multicenter cohort study using electronic health record data

Background

Nephrotoxic drugs frequently cause acute kidney injury (AKI) in adult intensive care unit (ICU) patients. However, there is a lack of large pharmaco-epidemiological studies investigating the associations between drugs and AKI. Importantly, AKI risk factors may also be indications or contraindications for drugs and thereby confound the associations. Here, we aimed to estimate the associations between commonly administered (potentially) nephrotoxic drug groups and AKI in adult ICU patients whilst adjusting for confounding.

Methods

In this multicenter retrospective observational study, we included adult ICU admissions to 13 Dutch ICUs. We measured exposure to 44 predefined (potentially) nephrotoxic drug groups. The outcome was AKI during ICU admission. The association between each drug group and AKI was estimated using etiological cause-specific Cox proportional hazard models and adjusted for confounding. To facilitate an (independent) informed assessment of residual confounding, we manually identified drug group-specific confounders using a large drug knowledge database and existing literature.

Results

We included 92 616 ICU admissions, of which 13 492 developed AKI (15%). We found 14 drug groups to be associated with a higher hazard of AKI after adjustment for confounding. These groups included established (e.g. aminoglycosides), less well established (e.g. opioids) and controversial (e.g. sympathomimetics with α- and β-effect) drugs.

Conclusions

The results confirm existing insights and provide new ones regarding drug associated AKI in adult ICU patients. These insights warrant caution and extra monitoring when prescribing nephrotoxic drugs in the ICU and indicate which drug groups require further investigation.

Regulatory roles of SP-A and exosomes in pneumonia-induced acute lung and kidney injuries

Introduction

Pneumonia-induced sepsis can cause multiple organ dysfunction including acute lung and kidney injury (ALI and AKI). Surfactant protein A (SP-A), a critical innate immune molecule, is expressed in the lung and kidney. Extracellular vesicles like exosomes are involved in the processes of pathophysiology. Here we tested one hypothesis that SP-A regulates pneumonia-induced AKI through the modulation of exosomes and cell death.

Methods

Wild-type (WT), SP-A knockout (KO), and humanized SP-A transgenic (hTG, lung-specific SP-A expression) mice were used in this study.

Results

After intratracheal infection with Pseudomonas aeruginosa, KO mice showed increased mortality, higher injury scores, more severe inflammation in the lung and kidney, and increased serum TNF-α, IL-1β, and IL-6 levels compared to WT and hTG mice. Infected hTG mice exhibited similar lung injury but more severe kidney injury than infected WT mice. Increased renal tubular apoptosis and pyroptosis in the kidney of KO mice were found when compared with WT and hTG mice. We found that serum exosomes from septic mice cause ALI and AKI through mediating apoptosis and proptosis when mice were injected intravenously. Furthermore, primary proximal tubular epithelial cells isolated from KO mice showed more sensitivity than those from WT mice after exposure to septic serum exosomes.

Discussion

Collectively, SP-A attenuates pneumonia-induced ALI and AKI by regulating inflammation, apoptosis and pyroptosis; serum exosomes are important mediators in the pathogenesis of AKI.

[Association of neutrophil, lymphocyte, platelet ratio with acute kidney injury in sepsis]

Background

Acute kidney injury (AKI) is frequent in sepsis (25 to 51%), with high mortality (40 to 80%) and long-term complications. Despite its importance we do not have accessible markers in intensive care. In other entities (post-surgical and COVID-19) the neutrophil/lymphocyte and platelet (N/LP) ratio has been associated with acute kidney injury; however, this relationship has not been studied in a pathology with a severe inflammatory response such as sepsis.

Objective

To demonstrate the association between N/LP with AKI secondary to sepsis in intensive care.

Material and methods

Ambispective cohort study in patients over 18 years who were admitted to intensive care with a diagnosis of sepsis. The N/LP ratio was calculated from admission up to the seventh day and up to the diagnosis of AKI and outcome. Statistical analysis was performed with chi squared test, Cramer's V and multivariate logistic regression.

Results

Out of the 239 patients studied, the incidence of AKI developed in 70%. 80.9% of patients with N/LP ratio > 3 had AKI (p < 0.0001, Cramer's V 0.458, OR 3.05, 95% CI 1.602-5.8) and increased renal replacement therapy (21.1 vs. 11.1%, p = 0.043).

Conclusion

N/LP ratio > 3 has a moderate association with AKI secondary to sepsis in the intensive care unit.

Learning Curve for Temporary Hemodialysis Catheter Placement

BACKGROUND

Training is essential for the safe and uncomplicated placement of hemodialysis catheters. This study explores the learning curve of this procedure.

METHODS

In this prospective study, 60 patients who needed emergency hemodialysis without vascular access were included. All catheters were placed under ultrasound guidance. One nephrologist was included in each two groups, one to be consisted of a junior, and one to be consisted of a senior. Learning curves were created using the cumulative total methodology and receiver operating characteristic curve analyses.

RESULTS

The patients' mean age was 67.92 ± 14.23 years. The mean catheter insertion time of the senior nephrologist was significantly shorter than that of the junior. According to cumulative total analysis, the junior group's maximum learning point overlaps with patient 22. When the confidence intervals of the study durations of both groups were examined, they overlapped in the 95% confidence interval starting from the 19th patient. When the mean catheter insertion time of the senior and the mean of the last 12 patients of the junior were compared, there was no significant difference between them (F = 15.827, P = .092). The receiver operating characteristic curve analysis showed a cutoff value of 320 seconds for the junior group compared with the senior group, indicating an overlap in case 22 for the junior nephrologist.

CONCLUSION

This study suggests that 22 catheter insertions under the supervision of a senior nephrologist are needed to complete the learning curve for a junior nephrologist. If the number of nephrologists at the center is limited, safe catheter insertion may be allowed after 19 insertions.

The combined effect of zinc oxide nanoparticles and milrinone on acute renal ischemia/reperfusion injury in rats: Potential underlying mechanisms

AIM

To investigate the efficacy of zinc oxide nanoparticles (ZnO-NPs) and/or milrinone (MIL) on renal ischemia/reperfusion injury (I/RI) in rats and their possible underlying mechanisms.

MATERIALS AND METHODS

Forty-eight adult male Sprague-Dawley albino rats were randomly assigned into six equal-sized groups (n = 8): normal control, sham-operated, I/R group (45 min/24 h), ZnO-NPs group (10 mg/Kg i.p.), MIL group (0.5 mg/Kg i.p.), and ZnO-NPs + MIL group in the same previous doses.

KEY FINDINGS

In comparison to the I/R-operated group, administration of either ZnO-NPs or MIL significantly decreased serum creatinine and urea concentrations, and renal vascular permeability (p < 0.05). The oxidative stress was significantly declined, as evidenced by increased GPx, CAT, and SOD activities and decreased MDA and NO concentrations. Renal expressions of TNF-α, NF-κB, KIM-1, NGAL, and caspase-3 decreased significantly, while Nrf2 increased significantly. Histopathology investigation revealed improvement with minimal renal lesions and fibrosis after ZnO-NPs or MIL treatments. The combined treatments synergistically improved the studied parameters more than either treatment alone. These findings were validated by molecular modeling, which revealed that MIL inhibited TNF-α, NF-kB, caspase-3, KIM-1 and NGAL.

SIGNIFICANCE

Both ZnO-NPs and MIL exerted cytoprotective effects against acute renal I/RI, and a combination of both was found to be even more effective. This renoprotective effect is suggested to be mediated through activation of Nrf2 and the prevention of the NF-κB activation-induced oxidative stress and inflammation, which may strengthen the potential role of ZnO-NPs or MIL in renal I/RI protection during surgical procedures.

Drug-related causes attributed to acute kidney injury and their documentation in intensive care patients

PURPOSE

To investigate drug-related causes attributed to acute kidney injury (DAKI) and their documentation in patients admitted to the Intensive Care Unit (ICU).

METHODS

This study was conducted in an academic hospital in the Netherlands by reusing electronic health record (EHR) data of adult ICU admissions between November 2015 to January 2020. First, ICU admissions with acute kidney injury (AKI) stage 2 or 3 were identified. Subsequently, three modes of DAKI documentation in EHR were examined: diagnosis codes (structured data), allergy module (semi-structured data), and clinical notes (unstructured data).

RESULTS

n total 8124 ICU admissions were included, with 542 (6.7%) ICU admissions experiencing AKI stage 2 or 3. The ICU physicians deemed 102 of these AKI cases (18.8%) to be drug-related. These DAKI cases were all documented in the clinical notes (100%), one in allergy module (1%) and none via diagnosis codes. The clinical notes required the highest time investment to analyze.

CONCLUSIONS

Drug-related causes comprise a substantial part of AKI in the ICU patients. However, current unstructured DAKI documentation practice via clinical notes hampers our ability to gain better insights about DAKI occurrence. Therefore, both automating DAKI identification from the clinical notes and increasing structured DAKI documentation should be encouraged.

Associations of cold exposure with hospital admission and mortality due to acute kidney injury: A nationwide time-series study in Korea

BACKGROUND

Emerging evidence supports an association between heat exposure and acute kidney injury (AKI). However, there is a paucity of studies on the association between cold exposure and AKI.

OBJECTIVE

We aimed to investigate the associations of cold exposure with hospital admission and mortality due to AKI and to explore whether these associations were influenced by age and sex.

METHODS

Information on daily counts of hospital admission and mortality due to AKI in 16 regions of Korea during the cold seasons (2010-2019) was obtained from the National Health Insurance Service (a single national insurer providing universal health coverage) and Statistics Korea. Daily mean temperature and relative humidity were calculated from hourly data obtained from 94 monitoring systems operated by the Korean Meteorological Administration. Associations of low temperatures (<10th percentile of daily mean temperature) and cold spells (≥2 consecutive days with <5th percentile of daily mean temperature) up to 21 days with AKI were estimated using quasi-Poisson regression models adjusted for potential confounders (e.g., relative humidity and air pollutants) with distributed lag models and univariate meta-regression models.

RESULTS

Low temperatures were associated with hospital admission due to AKI [relative risk (RR) = 1.12, 95 % confidence interval (CI): 1.09, 1.16]. Cold spells were associated with hospital admission (RR = 1.87, 95 % CI: 1.46, 2.39) and mortality due to AKI (RR = 4.84, 95 % CI: 1.30, 17.98). These associations were stronger among individuals aged ≥65 years than among those aged <65 years.

CONCLUSION

Our results underscore the need for the general population, particularly the elderly, physicians, and other healthcare providers to be more vigilant to cold exposure, given the risk of AKI. Government agencies need to develop specific strategies for the prevention and early detection of cold exposure-related AKI.

New experimental model of kidney injury: Photothrombosis-induced kidney ischemia

Acute kidney injury (AKI) is a frequent pathology with a high mortality rate after even a single AKI episode and a great risk of chronic kidney disease (CKD) development. To get insight into mechanisms of the AKI pathogenesis, there is a need to develop diverse experimental models of the disease. Photothrombosis is a widely used method for inducing ischemia in the brain. In this study, for the first time, we described photothrombosis-induced kidney ischemia as an appropriate model of AKI and obtained comprehensive characteristics of the photothrombotic lesion using micro-computed tomography (micro-CT) and histological techniques. In the ischemic area, we observed destruction of tubules, the loss of brush border and nuclei, connective tissue fibers disorganization, leukocyte infiltration, and hyaline casts formation. In kidney tissue and urine, we revealed increased levels in markers of proliferation and injury. The explicit long-term consequence of photothrombosis-induced kidney ischemia was renal fibrosis. Thus, we establish a new low invasive experimental model of AKI, which provides a reproducible local ischemic injury lesion. We propose our model of photothrombosis-induced kidney ischemia as a useful approach for investigating AKI pathogenesis, studying the mechanisms of kidney regeneration, and development of therapy against AKI and CKD.

Twenty-Three-Year Trends in the Use of Potentially Nephrotoxic Drugs in Denmark

Background

The occurrence of acute and chronic kidney diseases has been rising in the last decades. Although drug use is a common risk factor for impaired kidney function, changes in utilization of potential nephrotoxic drugs have received little attention.

Purpose

To describe temporal trends in the utilization of potentially nephrotoxic drugs in Denmark between 1999 and 2021.

Methods

Specific drugs known or suspected to be nephrotoxic were identified in the literature. Data on the sold defined daily doses (DDDs) of potentially nephrotoxic drugs between 1999 and 2021 were retrieved using the Danish Register of Medical Product Statistics. Trends in sales of DDDs per 1000 inhabitants per day were tabulated and illustrated graphically.

Results

From 1999 to 2021, the total sale of all selected drugs increased from 286 to 457 DDDs per 1000 inhabitants per day. The overall sale reached a preliminary peak in 2012 with 449 DDDs per 1000 inhabitants per day and remained relatively stable thereafter until reaching an all-time high in 2021 with 457 DDDs per 1000 inhabitants per day. Contributing with the majority in volume, sales of drugs inhibiting the renin-angiotensin-aldosterone system (RAAS) increased dramatically throughout the period. The same was observed for acetaminophen, methotrexate, tacrolimus, and iodinated contrast dye. In contrast, the sales of diuretics, acetylsalicylic acid, and ciclosporin decreased during the last decade of the study period.

Conclusion

From 1999-2021 considerable changes in sales of potentially nephrotoxic drugs were observed. In general, the sales increased, in volume predominated by RAAS inhibiting drugs. This increase in sales of potential nephrotoxins could contribute to an increasing occurrence of kidney diseases.

Assessment of Burden in Family Caregivers of Chronic Hemodialysis and Peritoneal Dialysis Patients During the Pandemic Period of COVID-19

INTRODUCTION

In Greece, patients undergoing hemodialysis (HD) usually go to dialysis centers two or three times a week for three/four hours per session because the treatment for home is unavailable; therefore, caregivers should perform supportive transportation and care functions.

PURPOSE

This study was designed to assess the burden and quality of life in caregivers of patients undergoing hemodialysis and peritoneal dialysis (PD) and to record their attitude toward Coronavirus Disease-2019 (COVID-19).

METHODOLOGY

We studied caregivers of patients undergoing hemodialysis and peritoneal dialysis. A total of 80 caregivers took part (30 caregivers of patients of PD and 50 caregivers of patients of HD). The final form of the questionnaire was based on the Quality-of-Life Scale (SF-12) and the Zarit Scale, in order to record the scale of burden and the effect on them throughout the process. The Fear Due to COVID-19 Scale (FCV-19S) contributed to recording the caregivers' fear toward the pandemic of COVID-19.

RESULTS

Most of the caregivers were women with an average age of about 60 years and 6-10 were the patient's wife or partners. The prevalence of the moderate or severe burden of the patients was found at 18.7%, and the few or no burden at all at 33.8%. The prevalence of fear toward COVID-19 was at very high levels, reaching 82.5% in all caregivers.

CONCLUSIONS

During the pandemic period of COVID-19, the role of the caregivers of the patients, both who follow the PD method and those who have joined the HD, is particularly important. Their quality of life has been partially affected in all dimensions.

NEPHROPROTECTIVE EFFECT OF OLMESARTAN ON RENAL ISCHEMIA REPERFUSION INJURY IN MALE RATS: THE ROLE OF NRF2/HO-1 SIGNALING PATHWAY

OBJECTIVE

The aim: To investigate the Nephroprotective potential of Olmesartan in RIRI via modulation of the Nrf2/OH-1 signaling pathway.

PATIENTS AND METHODS

Materials and methods: Thirty male rats were equally divided into four groups. The sham group was exposed to surgical conditions without induction of RIRI. The control group was exposed to ischemia by clamping the renal pedicles for 30 min, followed by 2h of blood restoration. The vehicle-treated group was received dimethyl sulfoxide (DMSO) by intraperitoneal injection (IP) 30 min before clamping.

RESULTS

Results: Olmesartan-treated group was pretreated with Olmesartan a dose of 10 mg/kg IP; 30 min prior to induction of ischemia. Following 30 min of ischemia, the clamps were released and allowed to the reperfusion for 2 h. Blood samples were collected to examine the levels of serum urea and creatinine. Kidney tissue was used to measure the levels of cytokines (TNFα, IL6, MCP, BAX, BCL2 and isoprostane F2. Immunohistochemistry was used to assess the levels of Nrf2 and HO-1. Histological analyses were used to detect the tubular damage in the kidney.

CONCLUSION

Conclusions: The results showed that Olmesartan alleviates renal tissue damage through activating the antioxidant effect mediated by Nrf2 signaling.

SGLT2i reduces renal injury by improving mitochondrial metabolism and biogenesis

OBJECTIVES

Despite advances in treatment, an effective therapeutic strategy for acute kidney injury (AKI) is still lacking. Considering the widely reported clinical benefits of canagliflozin in the kidneys, we assessed the effects of canagliflozin on AKI.

METHODS

Lipopolysaccharide was used to induce AKI in the presence of canagliflozin.

RESULTS

Canagliflozin treatment reduced blood urea nitrogen and serum creatinine levels and improved the renal tubular structure in mice with lipopolysaccharide-induced septic AKI. Canagliflozin also suppressed the inflammatory response, oxidative stress and tubular cell death in the kidneys during septic AKI. In vitro, canagliflozin supplementation maintained mitochondrial function in lipopolysaccharide-treated HK-2 cells by restoring the mitochondrial membrane potential, inhibiting mitochondrial reactive oxygen species production and normalizing mitochondrial respiratory complex activity. In HK-2 cells, canagliflozin stimulated the adenosine monophosphate-activated protein kinase catalytic subunit alpha 1 (AMPKα1)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)/nuclear respiratory factor 1 (NRF1) pathway, thus elevating the number of live and healthy mitochondria following lipopolysaccharide treatment. Inhibition of the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway abolished the protective effects of canagliflozin on renal cell mitochondria and tubular viability. Similarly, the protective effects of canagliflozin on kidney function and tubular structure were abrogated in AMPKα1-knockout mice.

CONCLUSIONS

Canagliflozin could be used to treat septic AKI by activating the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway.

What do we actually know about exosomal microRNAs in kidney diseases?

There are several types of kidney diseases with complex causes. If left untreated, these diseases irreversibly progress to end-stage renal disease. Thus, their early diagnosis and targeted treatment are important. Exosomes-extracellular vesicles released by a variety of cells-are ideal carriers for DNA, RNA, proteins, and other metabolites owing to their bilayer membranes. Studies have shown that almost all renal cells can secrete exosomes. While research on exosomal microRNAs in the context of renal diseases begun only recently, rapid progress has been achieved. This review summarizes the changes in exosomal microRNA expression in different kidney diseases. Thus, it highlights the diagnostic and prognostic value of these exosomal microRNAs. Further, this review analyzes their roles in the development of different kidney diseases, guiding research on molecular mechanisms and therapeutic strategies.

Expression of MicroRNAs in Sepsis-Related Organ Dysfunction: A Systematic Review

Sepsis is a critical condition characterized by increased levels of pro-inflammatory cytokines and proliferating cells such as neutrophils and macrophages in response to microbial pathogens. Such processes lead to an abnormal inflammatory response and multi-organ failure. MicroRNAs (miRNA) are single-stranded non-coding RNAs with the function of gene regulation. This means that miRNAs are involved in multiple intracellular pathways and thus contribute to or inhibit inflammation. As a result, their variable expression in different tissues and organs may play a key role in regulating the pathophysiological events of sepsis. Thanks to this property, miRNAs may serve as potential diagnostic and prognostic biomarkers in such life-threatening events. In this narrative review, we collect the results of recent studies on the expression of miRNAs in heart, blood, lung, liver, brain, and kidney during sepsis and the molecular processes in which they are involved. In reviewing the literature, we find at least 122 miRNAs and signaling pathways involved in sepsis-related organ dysfunction. This may help clinicians to detect, prevent, and treat sepsis-related organ failures early, although further studies are needed to deepen the knowledge of their potential contribution.

Development and validation of outcome prediction models for acute kidney injury patients undergoing continuous renal replacement therapy

Object

This study aimed to develop and validate a set of practical predictive tools that reliably estimate the 28-day prognosis of acute kidney injury patients undergoing continuous renal replacement therapy.

Methods

The clinical data of acute kidney injury patients undergoing continuous renal replacement therapy were extracted from the Medical Information Mart for Intensive Care IV database with structured query language and used as the development cohort. An all-subset regression was used for the model screening. Predictive models were constructed via a logistic regression, and external validation of the models was performed using independent external data.

Results

Clinical prediction models were developed with clinical data from 1,148 patients and validated with data from 121 patients. The predictive model based on seven predictors (age, vasopressor use, red cell volume distribution width, lactate, white blood cell count, platelet count, and phosphate) exhibited good predictive performance, as indicated by a C-index of 0.812 in the development cohort, 0.811 in the internal validation cohort and 0.768 in the external validation cohort.

Conclusions

The model reliably predicted the 28-day prognosis of acute kidney injury patients undergoing continuous renal replacement therapy. The predictive items are readily available, and the web-based prognostic calculator (https://libo220284.shinyapps.io/DynNomapp/) can be used as an adjunctive tool to support the management of patients.

The Role of Histone H3 Methylation in Acute Kidney Injury

Acute kidney injury (AKI) is a clinical syndrome in which kidney function declines sharply due to various reasons. Although the morbidity and mortality of AKI are high, the mechanism of occurrence and development of AKI has not been fully elucidated, and precise prevention and treatment measures are lacking. Epigenetics is a branch of genetics that provides a new perspective to explore the pathophysiology of AKI and renal repair. A large amount of literature shows that the methylation mechanism of H3 in histones is closely related to the development of kidney diseases. The sorting out of histone H3 methylation mechanism in AKI and kidney repair can help understand the pathophysiological process of the disease more deeply. It may also provide new ideas for diagnosing and treating of the disease.

Inhibition of Homeobox D10 Alleviates Acute Kidney Injury by Upregulating PI3K/AKT Signaling Proteins

Purpose. To observe the protective effect of homeobox D10 (HOXD10) on acute kidney injury (AKI) by regulating PI3K/AKT signaling pathway is the purpose of this study.Methods. 30 rats were randomly divided into three groups: blank control group, model group, and HOXD10 interference group. The kidney function indexes, HOXD10 protein expression, histopathological features, tubulointerstitial injury, and PI3K and AKT protein expression levels of the three groups were analyzed. Results. Compared with the blank control group, the kidney weight, BUN and SCr in model group increased significantly, and TIL score was higher ( $P>0.05$ ). The expression of HOXD10 in model group and HOXD10 interference group were higher than blank control group, and the expression of HOXD10 in HOXD10 interference group was lower than model group ( $P<0.05$ ). After we administered HOXD10 blocker to AKI rats, pathological sections by HE staining showed that the kidney tissue damage was significantly reduced compared with the model group, and the expression levels of BUN and SCr in kidney tissue decreased, and the TIL score decreased. The expression of p-PI3K and p-AKT decreased after kidney injury. Compared with the model group, the phosphorylation levels of PI3K and AKT in HOXD10 interference group were significantly increased ( $P<0.05$ ). Conclusion. Downregulation of HOXD10 can play a protective role on AKI by activating PI3K/AKT signaling pathway, which can reduce tubulointerstitial injury and improve kidney function.

Incidence and Perioperative Risk Factors of Acute Kidney Injury Among Lung Transplant Recipients

BACKGROUND

Acute kidney injury (AKI) is a significant burden in an early postoperative period after lung transplantation (LT). The development of severe AKI, including a need for continuous renal replacement therapy (CRRT), is associated with increased mortality among lung transplant recipients. Evaluation of AKI incidence and predictive factors related to the development of severe AKI and with the use of CRRT in the early postoperative period after LT.

METHODS

Retrospective study of 73 consecutive patients after LT operated between 2015 and 2018 in our center. We noted the stage of AKI according to KDIGO guidelines in the 7 postoperative days.

RESULTS

We noted AKI among 62 lung transplant recipients (84.9%). We recognized the first and second stages of AKI in 21 patients (28.8%) and 19 patients 26%, respectively (group A). We identified severe AKI (group C) in 22 recipients (30.1%), 9 of whom needed CRRT postoperatively. There was a nonsignificant difference between groups in baseline serum creatinine (0.69 ± 0.22 mg/dL vs 0.84 ± 0.34; P = .073). Group C subjects statistically more often suffered from pulmonary hypertension (P < .001) and diabetes (P < .001). In both groups, the duration of the procedure was comparable, but, among patients with severe AKI, procedures were performed more often with the use of extracorporeal circulation (50% vs 68%; P = .194) CONCLUSIONS: Pulmonary hypertension and diabetes could be significant risk factors of high-grade AKI development after LT. Identification of factors modifying renal insufficiency development in lung transplant recipients needs further investigations.

Therapeutic effect of quercetin polymeric nanoparticles on ischemia/reperfusion-induced acute kidney injury in mice

Acute kidney injury (AKI) is known as a sudden episode of kidney injury, which happens suddenly within a few hours or a few days. Quercetin (3,3',4',5,7-pentahydroxyflavone) is a flavonoid found in plants. Quercetin is known to have several biological activities, such as anti-oxidant, anti-inflammatory, and anti-carcinogenic effects. However, low water solubility and bioavailability are the limitations of quercetin for its clinical applications. Moreover, ischemia/reperfusion (I/R) injury is a common cause of AKI. There are no satisfactory strategies for I/R-induced AKI. Developing suitable preventive or therapeutic intervention for AKI is an important and urgent issue. We investigated the benefit effect of synthesized polyethylene glycol (PEG) conjugated polyethyleneimine (PEI) nanoparticles for targeted delivery of quercetin on AKI in a mouse model. An I/R-induced AKI mouse model was used to evaluate the therapeutic effect of quercetin polymeric nanoparticles by intravenous injection. Biochemical changes for renal function in blood samples were analyzed. Histological and immunohistochemical changes were also analyzed. The biochemical changes of blood urea nitrogen (BUN), creatinine, and cystatin C were significantly increased in I/R-induced AKI mice, which could be significantly reversed by quercetin polymeric nanoparticles. Quercetin polymeric nanoparticles could also significantly decrease the histological lesions, positive staining for 3-nitrotyrosine and cyclooxygenase-2, and lipid peroxidation in the kidneys of I/R-induced AKI mice. These results demonstrate for the first time that quercetin polymeric nanoparticles possess therapeutic potential for the treatment of I/R-induced AKI in vivo.

Prognostic Factors for Stage 3 Acute Kidney Injury in Isolated Serious Traumatic Brain Injury

BACKGROUND

Stage 3 acute kidney injury (AKI) has been observed to develop following serious traumatic brain injury (TBI) and is associated with worse outcomes, though its incidence is not consistently established. This study aims to report the incidence of stage 3 AKI in serious isolated TBI in a large, national trauma database, and explore associated predictive factors.

METHODS

This was a retrospective cohort study using 2015-2018 data from the American College of Surgeons Trauma Quality Improvement Program (ACS-TQIP), a national database of trauma patients. Adult trauma patients admitted to the hospital with isolated serious TBI were included. Variables relating to demographics, comorbidities, vitals, hospital presentation, and course of stay were assessed. Imputed multivariable logistic regression assessed factors predictive of stage 3 AKI development.

RESULTS

A total of 342,675 patients with isolated serious TBI were included, 1,585 (0.5%) of whom developed stage 3 AKI. Variables associated with stage 3 AKI in multivariable analysis were older age, male sex, Black race, higher BMI, history of hypertension, diabetes, peripheral artery disease, chronic kidney disease, higher injury severity score, higher heart rate on arrival, lower oxygen saturation and motor Glasgow coma scale (GCS), admission to the intensive care unit (ICU) or operating room, development of catheter-associated urinary tract infections (CAUTI) or acute respiratory distress syndrome (ARDS), longer ICU stay and ventilation duration.

CONCLUSIONS

Stage 3 AKI occurred in 0.5% of serious TBI cases. Complications of ARDS and CAUTI are more likely to co-occur with stage 3 AKI in serious TBI patients.

Neutral ceramidase deficiency protects against cisplatin-induced acute kidney injury

Cisplatin is a commonly used chemotherapeutic for the treatment of many solid organ cancers; however, its effectiveness is limited by the development of acute kidney injury (AKI) in 30% of patients. AKI is driven by proximal tubule cell death, leading to rapid decline in renal function. It has previously been shown that sphingolipid metabolism plays a role in regulating many of the biological processes involved in cisplatin-induced AKI. For example, neutral ceramidase (nCDase) is an enzyme responsible for converting ceramide into sphingosine, which is then phosphorylated to become sphingosine-1-phosphate, and our lab previously demonstrated that nCDase knockout (nCDase-/-) in mouse embryonic fibroblasts led to resistance to nutrient and energy deprivation-induced cell death via upregulation of autophagic flux. In this study, we further characterized the role of nCDase in AKI by demonstrating that nCDase-/- mice are resistant to cisplatin-induced AKI. nCDase-/- mice display improved kidney function, reduced injury and structural damage, lower rates of apoptosis, and less ER stress compared to wild-type mice following cisplatin treatment. Although the mechanism of protection is still unknown, we propose that it could be mediated by increased autophagy, as chloroquine treatment resensitized nCDase-/- mice to AKI development. Taken together, we conclude that nCDase may represent a novel target to prevent cisplatin-induced nephrotoxicity.

The Human Microbiome in Chronic Kidney Disease: A Double-Edged Sword

Chronic kidney disease (CKD) is an increasing global health burden. Current treatments for CKD include therapeutics to target factors that contribute to CKD progression, including renin–angiotensin–aldosterone system inhibitors, and drugs to control blood pressure and proteinuria control. Recently, associations between chronic disease processes and the human microbiota and its metabolites have been demonstrated. Dysbiosis—a change in the microbial diversity—has been observed in patients with CKD. The relationship between CKD and dysbiosis is bidirectional; gut-derived metabolites and toxins affect the progression of CKD, and the uremic milieu affects the microbiota. The accumulation of microbial metabolites and toxins is linked to the loss of kidney functions and increased mortality risk, yet renoprotective metabolites such as short-chain fatty acids and bile acids help restore kidney functions and increase the survival rate in CKD patients. Specific dietary interventions to alter the gut microbiome could improve clinical outcomes in patients with CKD. Low-protein and high-fiber diets increase the abundance of bacteria that produce short-chain fatty acids and anti-inflammatory bacteria. Fluctuations in the urinary microbiome are linked to increased susceptibility to infection and antibiotic resistance. In this review, we describe the potential role of the gut, urinary and blood microbiome in CKD pathophysiology and assess the feasibility of modulating the gut microbiota as a therapeutic tool for treating CKD.

The urinary exosomes derived from premature infants attenuate cisplatin-induced acute kidney injury in mice via microRNA-30a-5p/ mitogen-activated protein kinase 8 (MAPK8)

Acute kidney injury (AKI) is a susceptible factor for chronic kidney disease (CKD). There is still a lack of effective prevention methods in clinical practice. This study investigated the protective effect of the urinary exosomes from premature infants on cisplatin-induced acute kidney injury. Here we isolated exosomes from the fresh urine of premature infants. A C57BL/6 mice model of cisplatin-induced acute kidney injury was given 100 ug urinary exosomes 24 hours after model establishment. The kidneys were collected for pathological examination and the evaluation of renal tubular damage and apoptosis. In the in vitro experiment, human renal cortex/proximal tubular cells (HK-2) were induced by cisplatin to assess the effect of the urine exosomes from premature infants. Exosome microRNA (miRNA) sequencing technology was applied to investigate the miRNAs enriched in exosomes and the dual-luciferase gene reporter system to examine the targeting relationship of the miRNA with target genes. The results indicated that the urinary exosomes could decrease the serum creatinine level and the apoptosis of renal tubular cells, and reduce mice mortality. In addition, miR-30a-5p was the most abundant miRNA in the exosomes. It protected HK-2 cells from cisplatin-induced apoptosis by targeting and down-regulating the mitogen-activated protein kinase 8 (MAPK8). Together, our findings identified that the urinary exosomes derived from premature infants alleviated cisplatin-induced acute kidney injury and inhibited the apoptosis of HK-2 via miR-30a-5p, which could target MAPK8. These findings implied that urinary exosomes from premature infants riched in miR-30a-5p might become a potential treatment for AKI.

Silencing Long Non-coding RNA Kcnq1ot1 Limits Acute Kidney Injury by Promoting miR-204-5p and Blocking the Activation of NLRP3 Inflammasome

Acute kidney injury (AKI) is a critical clinical disease characterized by an acute decrease in renal function. Long non-coding RNAs (LncRNAs) are important in AKI. This study aimed to explore the mechanism of lncRNA Kcnq1ot1 in AKI by sponging microRNA (miR)-204-5p as a competitive endogenous RNA (ceRNA). AKI mouse model and hypoxia/reoxygenation (H/R) model of human kidney (HK) cells were established. Kcnq1ot1 expression, cell proliferation, and apoptosis were measured. Binding relations among Kcnq1ot1, miR-204-5p, and NLRP3 were verified. Pathological changes and cell apoptosis were detected. The results showed that Kcnq1ot1 was highly expressed in the AKI model in vivo and in vitro. Kcnq1ot1 knockdown promoted cell proliferation and prevented apoptosis and inflammation. Furthermore, Kcnq1ot1 inhibited miR-204-5p expression by competitively binding to miR-204-5p in HK-2 cells. miR-204-5p targeted NLRP3 and NLRP3 overexpression averted the inhibiting effect of miR-204-5p on apoptosis and inflammation in HK-2 cells in vitro. Kcnq1ot1 knockdown in vivo promoted miR-204-5p expression, inhibited NLRP3 inflammasome activation, reduced levels of SCr, BUN, and KIM-1, and thus alleviated AKI and reduced apoptosis. In summary, silencing lncRNA Kcnq1ot1 inhibited AKI by promoting miR-204-5p and inhibiting NLRP3 inflammasome activation.

Utility of bedside ultrasound derived hepatic and renal parenchymal flow patterns to guide management of acute kidney injury

PURPOSE OF REVIEW

Ideal fluid management of critically ill patients is maintaining an adequate perfusion pressure but avoiding venous congestion. Venous excess ultrasound score (VExUS) quantifies venous congestion to guide the management of fluid balance.

RECENT FINDINGS

VExUS of abdominal veins measures fluid tolerance and helps clinicians avoid congestion. VExUS scoring predicts the development of acute kidney injury (AKI) that is a common hospital problem resulting in higher mortality and morbidity. VExUS can predict patients at risk of developing AKI post cardiac surgery. VExUS has been associated with an increase in adverse outcomes in a general intensive care population. Hepatic vein ultrasound can manifest as a sequela of right heart failure and pulmonary hypertension. Intrarenal congestion suggests poorer prognosis in heart failure patients. VExUS score has been used in decision-making to remove fluid in patients with cardiorenal syndrome. VExUS scoring may help curtail overly aggressive fluid resuscitation for patients with septic shock and help avoid iatrogenic 'salt water drowning'.

SUMMARY

We summarize the technique and clinical practice of VExUS to help guide fluid balance across different populations of critically ill patients.

Biomarkers of persistent renal vulnerability after acute kidney injury recovery

Acute kidney injury (AKI) is a risk factor for new AKI episodes, chronic kidney disease, cardiovascular events and death, as renal repair may be deficient and maladaptive, and activate proinflammatory and profibrotic signals. AKI and AKI recovery definitions are based on changes in plasma creatinine, a parameter mostly associated to glomerular filtration, but largely uncoupled from renal tissue damage. The evolution of structural and functional repair has been incompletely described. We thus aimed at identifying subclinical sequelae persisting after recovery from cisplatin-induced AKI in rats. Compared to controls, after plasma creatinine recovery, post-AKI kidneys showed histological alterations and attendant susceptibility to new AKI episodes. Tubular function (assessed by the furosemide stress test, FST) also remained affected. Lingering parenchymal and functional subclinical alterations were paralleled by tapering, but abnormally high levels of urinary albumin, transferrin, insulin-like growth factor-binding protein 7 (IGFBP7), tissue inhibitor of metalloproteinases-2 (TIMP-2) and, especially, the [TIMP-2]*[IGFBP7] product. As subclinical surrogates of incomplete renal recovery, the FST and the urinary [TIMP-2]*[IGFBP7] product provide two potential diagnostic tools to monitor the sequelae and kidney vulnerability after the apparent recovery from AKI.

Gremlin1 and TGF-β1 protect kidney tubular epithelial cells from ischemia-reperfusion injury through different pathways

BACKGROUND

Gremlin1 belongs to the superfamily members of transforming growth factor (TGF)-β1, playing a profibrotic role in chronic kidney diseases (CKD) and the transition from the late stage of acute kidney injury (AKI) to CKD, but the effect it plays in the early stage of AKI is unclear. This study aimed to investigate the role of Gremlin1on apoptosis in renal tubular epithelial cells under ischemia-reperfusion (I/R) induction.

METHODS

We detected Gremlin1 and TGF-β1 expression in the kidneys of mice undergoing renal ischemia-reperfusion injury bilaterally. We induced apoptosis through depletion and reperfusion of oxygen and serum in human kidney tubular epithelial cells (HKCs), mimicking I/R injury in vivo, and detected the role and pathways of Gremlin1 and TGF-β1on HKCs injury.

RESULTS

Mice undergoing bilateral I/R surgery presented AKI with a significant increase in serum creatinine, obvious renal tubular injuries, and increased macrophage cell and T-cell infiltration in interstitial areas. Gremlin1 expression was significantly increased along with TGF-β1 in the kidneys of AKI mice compared to sham mice. Exogenous Gremlin1 inhibited I/R-induced caspase3 expression in HKCs, which was blocked by a VEGFR2 kinase inhibitor III (SU5416). TGF-β1 also inhibited I/R-induced cell apoptosis in HKCs but had no synergic effect with Gremlin1. The TGF-β1's inhibitory effect could be blocked by the TGF-β1 type I receptor (activin receptor-like kinase 5, and ALK5)-specific inhibitor SB431542.

CONCLUSIONS

Gremlin1 and TGF- β1 protect kidney tubular epithelial cells from ischemia-reperfusion-induced apoptosis through VEGFR2 and Smad2 signaling pathways.

Mortality Prediction in Patients with Severe Acute Kidney Injury Requiring Renal Replacement Therapy

Background and Objective: Acute kidney injury (AKI) remains a serious health condition around the world, and is related to high morbidity, mortality, longer hospitalization duration and worse long-term outcomes. The aim of our study was to estimate the significant related factors for poor outcomes of patients with severe AKI requiring renal replacement therapy (RRT). Materials and Methods: We retrospectively analyzed data from patients (n = 573) with severe AKI requiring RRT within a 5-year period and analyzed the outcomes on discharge from the hospital. We also compared the clinical data of the surviving and non-surviving patients and examined possible related factors for poor patient outcomes. Logistic regression was used to analyze the odds ratio for patient mortality and its related factors. Results: In 32.5% (n = 186) of the patients, the renal function improved and RRT was stopped, 51.7% (n = 296) of the patients died, and 15.9% (n = 91) of the patients remained dialysis-dependent on the day of discharge from the hospital. During the period of 5 years, the outcomes of the investigated patients did not change statistically significantly. Administration of vasopressors, aminoglycosides, sepsis, pulmonary edema, oliguria, artificial pulmonary ventilation (APV), patient age ≥ 65 y, renal cause of AKI, AKI after cardiac surgery, a combination of two or more RRT methods, dysfunction of three or more organs, systolic blood pressure (BP) ≤ 120 mmHg, diastolic BP ≤ 65 mmHg, and Sequential Organ Failure Assessment (SOFA) score on the day of the first RRT procedure ≥ 7.5 were related factors for lethal patient outcome. Conclusions: The mortality rate among patients with severe AKI requiring RRT is very high—52%. Patient death was significantly predicted by the causes of AKI (sepsis, cardiac surgery), clinical course (oliguria, pulmonary edema, hypotension, acidosis, lesion of other organs) and the need for a continuous renal replacement therapy.

Development and External Verification of a Nomogram for Patients with Persistent Acute Kidney Injury in the Intensive Care Unit

Background

We aimed to identify the affecting features of persistent acute kidney injury (pAKI) for patients in intensive care units (ICU).

Methods

The Medical Information Mart for Intensive Care IV (MIMIC-IV) database and eICU Collaborative Research Database (eICU-CRD) were used to identify AKI patients with and without duration of more than 48 hours. Least absolute shrinkage and selection operator (LASSO) regression and support vector machine (SVM-RFE) were utilized to screen for the significant clinical indexes associated with pAKI. Predictive nomogram was created based on the above informative parameters to predict the probability of pAKI.

Results

LASSO regression and SVM-RFE revealed that serum albumin, chronic kidney disease, AKI stage, sequential organ failure assessment score, lactate and renal replacement therapy during the first day were significantly associated with pAKI in the training cohort. The predictive nomogram based on the six predictors exhibited good predictive performance as calculated by C-index 0.730 (95% CI 0.710-0.749) in the training group, 0.702 (95% CI 0.672-0.722) in the internal validation set and 0.704 (0.677-0.731) in the external validation cohort for the prediction of pAKI. Moreover, the predictive nomogram exhibited not only encouraging calibration ability, but also great clinical utility in the training group, in the internal validation group as well as in the external validation cohort.

Conclusion

Serum albumin, CKD, AKI stage, SOFA score, lactate, RRT during the first day were closely associated with pAKI in patients in ICU. The predictive nomogram for pAKI manifested good predictive ability for the identification of ICU patients with pAKI.

Artificial Intelligence Pulse Coupled Neural Network Algorithm in the Diagnosis and Treatment of Severe Sepsis Complicated with Acute Kidney Injury under Ultrasound Image

The objective of this study was to explore the diagnosis of severe sepsis complicated with acute kidney injury (AKI) by ultrasonic image information based on the artificial intelligence pulse coupled neural network (PCNN) algorithm. In this study, an algorithm of ultrasonic image information enhancement based on the artificial intelligence PCNN was constructed and compared with the histogram equalization algorithm and linear transformation algorithm. After that, it was applied to the ultrasonic image diagnosis of 20 cases of severe sepsis combined with AKI in hospital. The condition of each patient was diagnosed by ultrasound image performance, change of renal resistance index (RRI), ultrasound score, and receiver operator characteristic curve (ROC) analysis. It was found that the histogram distribution of this algorithm was relatively uniform, and the information of each gray level was obviously retained and enhanced, which had the best effect in this algorithm; there was a marked individual difference in the values of RRI. Overall, the values of RRI showed a slight upward trend after admission to the intensive care unit (ICU). The RRI was taken as the dependent variable, time as the fixed-effect model, and patients as the random effect; the parameter value of time was between 0.012 and 0.015, p=0.000 < 0.05. Besides, there was no huge difference in the ultrasonic score among different time measurements (t = 1.348 and p=0.128 > 0.05). The area under the ROC curve of the RRI for the diagnosis of AKI at the 2nd day, 4th day, and 6th day was 0.758, 0.841, and 0.856, respectively, which was all greater than 0.5 (p < 0.05). In conclusion, the proposed algorithm in this study could significantly enhance the amount of information in ultrasound images. In addition, the change of RRI values measured by ultrasound images based on the artificial intelligence PCNN was associated with AKI.

micro-RNA-486-5p protects against kidney ischemic injury and modifies the apoptotic transcriptome in proximal tubules

Acute kidney injury (AKI) carries high morbidity and mortality, and effective treatments are lacking. Preclinical models support involvement of micro-RNAs (miRs) in AKI pathogenesis, although effects on the kidney transcriptome are unclear. We previously showed that injection of cord blood endothelial colony forming cell-derived exosomes, enriched in miR-486-5p, prevented ischemic AKI in mice. To further define this, we studied direct effects of miR-486-5p in mice with kidney ischemia-reperfusion injury. RNA-Seq was used to compare the impact of miR-486-5p and exosomes on the transcriptome of proximal tubules and kidney endothelial cells 24 hours after ischemia-reperfusion. In mice with AKI, injection of miR-486-5p mimic increased its levels in proximal tubules and endothelial cells, and improved plasma creatinine, histological injury, neutrophil infiltration, and apoptosis. Additionally, miR-486-5p inhibited expression of its target phosphatase and tensin homolog, and activated protein kinase B. In proximal tubules, miR-486-5p or exosomes reduced expression of genes associated with ischemic injury and the tumor necrosis factor (TNF) pathway, and altered distinct apoptotic genes. In endothelial cells, genes associated with metabolic processes were altered by miR-486-5p or exosomes, although TNF pathway genes were not affected. Thus, our results suggest that miR-486-5p may have therapeutic potential in AKI.

Utilization of Echocardiography After Acute Kidney Injury Was Associated with Improved Outcomes in Patients in Intensive Care Unit

Background

We aimed to investigate the association between usage of transthoracic echocardiography (TTE) within 24 hours after acute kidney injury (AKI) and the prognosis of patients in intensive care unit (ICU).

Methods

The Medical Information Mart for Intensive Care III (MIMIC-III) database was used to identify AKI patients with and without TTE administration. The primary outcome was 28-day mortality. Multivariable regression was used to clarify the association between TTE and clinical outcomes and propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were utilized to validate our findings.

Results

Among 23,945 eligible AKI patients, 3361 patients who received TTE and 3361 who did not conduct TTE had similar propensity scores which were included in this study. After matching, the TTE group had a significantly lower 28-day mortality (OR 0.80, 95% CI 0.72–0.88, P<0.001). Patients in the TTE group received more fluid on day 1 and day 2 and had a more urine volume on day 1 and day 3, and the reduction in serum creatinine was greater than that in the no TTE group. The mediating effect of creatinine reduction was remarkable for the whole cohort (P=0.02 for the average causal mediation effect).

Conclusion

TTE utilization was associated with decreased risk-adjusted 28-day mortality for AKI patients in ICU and was proportionally mediated through creatinine reduction.

Acute Kidney Injury Requiring Dialysis and Incident Dialysis Patient Outcomes in US Outpatient Dialysis Facilities

BACKGROUND AND OBJECTIVES

About 30% of patients with AKI may require ongoing dialysis in the outpatient setting after hospital discharge. A 2017 Centers for Medicare & Medicaid Services policy change allows Medicare beneficiaries with AKI requiring dialysis to receive outpatient treatment in dialysis facilities. Outcomes for these patients have not been reported. We compare patient characteristics and mortality among patients with AKI requiring dialysis and patients without AKI requiring incident dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used a retrospective cohort design with 2017 Medicare claims to follow outpatients with AKI requiring dialysis and patients without AKI requiring incident dialysis up to 365 days. Outcomes are unadjusted and adjusted mortality using Kaplan-Meier estimation for unadjusted survival probability, Poisson regression for monthly mortality, and Cox proportional hazards modeling for adjusted mortality.

RESULTS

In total, 10,821 of 401,973 (3%) Medicare patients requiring dialysis had at least one AKI claim, and 52,626 patients were Medicare patients without AKI requiring incident dialysis. Patients with AKI requiring dialysis were more likely to be White (76% versus 70%), non-Hispanic (92% versus 87%), and age 60 or older (82% versus 72%) compared with patients without AKI requiring incident dialysis. Unadjusted mortality was markedly higher for patients with AKI requiring dialysis compared with patients without AKI requiring incident dialysis. Adjusted mortality differences between both cohorts persisted through month 4 of the follow-up period (all P=0.01), then, they declined and were no longer statistically significant. Adjusted monthly mortality stratified by Black and other race between patients with AKI requiring dialysis and patients without AKI requiring incident dialysis was lower throughout month 4 (1.5 versus 0.60, 1.20 versus 0.84, 1.00 versus 0.80, and 0.95 versus 0.74; all P<0.001), which persisted through month 7. Overall adjusted mortality risk was 22% higher for patients with AKI requiring dialysis (1.22; 95% confidence interval, 1.17 to 1.27).

CONCLUSIONS

In fully adjusted analyses, patients with AKI requiring dialysis had higher early mortality compared with patients without AKI requiring incident dialysis, but these differences declined after several months. Differences were also observed by age, race, and ethnicity within both patient cohorts.

Harnessing the Physiological Functions of Cellular Prion Protein in the Kidneys: Applications for Treating Renal Diseases

A cellular prion protein (PrP^C) is a ubiquitous cell surface glycoprotein, and its physiological functions have been receiving increased attention. Endogenous PrP^C is present in various kidney tissues and undergoes glomerular filtration. In prion diseases, abnormal prion proteins are found to accumulate in renal tissues and filtered into urine. Urinary prion protein could serve as a diagnostic biomarker. PrP^C plays a role in cellular signaling pathways, reno-protective effects, and kidney iron uptake. PrP^C signaling affects mitochondrial function via the ERK pathway and is affected by the regulatory influence of microRNAs, small molecules, and signaling proteins. Targeting PrP^C in acute and chronic kidney disease could help improve iron homeostasis, ameliorate damage from ischemia/reperfusion injury, and enhance the efficacy of mesenchymal stem/stromal cell or extracellular vesicle-based therapeutic strategies. PrP^C may also be under the influence of BMP/Smad signaling and affect the progression of TGF-β-related renal fibrosis. PrP^C conveys TNF-α resistance in some renal cancers, and therefore, the coadministration of anti-PrP^C antibodies improves chemotherapy. PrP^C can be used to design antibody-drug conjugates, aptamer-drug conjugates, and customized tissue inhibitors of metalloproteinases to suppress cancer. With preclinical studies demonstrating promising results, further research on PrP^C in the kidney may lead to innovative PrP^C-based therapeutic strategies for renal disease.