The link between acute kidney injury and chronic kidney disease

Latent space representation of electronic health records for clustering dialysis-associated kidney failure subtypes

OBJECTIVE

Kidney failure manifests in various forms, from sudden occurrences such as Acute Kidney Injury (AKI) to progressive like Chronic Kidney Disease (CKD). Given its intricate nature, marked by overlapping comorbidities and clinical similarities-including treatment modalities like dialysis-we sought to design and validate an end-to-end framework for clustering kidney failure subtypes.

MATERIALS AND METHODS

Our emphasis was on dialysis, utilizing a comprehensive dataset from the UK Biobank (UKB). We transformed raw Electronic Health Record (EHR) data into standardized matrices that incorporate patient demographics, clinical visit data, and the innovative feature of visit time-gaps. This matrix structure was achieved using a unique data cutting method. Latent space transformation was facilitated using a convolution autoencoder (ConvAE) model, which was then subjected to clustering using Principal Component Analysis (PCA) and K-means algorithms.

RESULTS

Our transformation model effectively reduced data dimensionality, thereby accelerating computational processes. The derived latent space demonstrated remarkable clustering capacities. Through cluster analysis, two distinct groups were identified: CKD-majority (cluster 1) and a mixed group of non-CKD and some CKD subtypes (cluster 0). Cluster 1 exhibited notably low survival probability, suggesting it predominantly represented severe CKD. In contrast, cluster 0, with substantially higher survival probability, likely to include milder CKD forms and severe AKI. Our end-to-end framework effectively differentiates kidney failure subtypes using the UKB dataset, offering potential for nuanced therapeutic interventions.

CONCLUSIONS

This innovative approach integrates diverse data sources, providing a holistic understanding of kidney failure, which is imperative for patient management and targeted therapeutic interventions.

Multiparametric MRI based assessment of kidney injury in a mouse model of ischemia reperfusion injury

Kidney diseases pose a global healthcare burden, with millions requiring renal replacement therapy. Ischemia/reperfusion injury (IRI) is a common pathology of acute kidney injury, causing hypoxia and subsequent inflammation-induced kidney damage. Accurate detection of acute kidney injury due to IRI is crucial for timely intervention. We used longitudinal, multi-parametric magnetic resonance imaging (MRI) employing arterial spin labelling (ASL), diffusion weighted imaging (DWI), and dynamic contrast enhanced (DCE)-MRI to assess IRI induced changes in both the injured and healthy contralateral kidney, in a unilateral IRI mouse model (n = 9). Multi-parametric MRI demonstrated significant differences in kidney volume (p = 0.001), blood flow (p = 0.002), filtration coefficient (p = 0.038), glomerular filtration rate (p = 0.005) and apparent diffusion coefficient (p = 0.048) between the injured kidney and contralateral kidney on day 1 post-IRI surgery. Identification of the injured kidney using principal component analysis including most of the imaging parameters demonstrated an area under the curve (AUC) of 0.97. These results point to the utility of multi-parametric MRI in early detection of IRI-induced kidney damage suggesting that the combination of various MRI parameters may be suitable for monitoring the extent of injury in this model.

The Role of Mitochondrial Sirtuins (SIRT3, SIRT4 and SIRT5) in Renal Cell Metabolism: Implication for Kidney Diseases

Kidney diseases, including chronic kidney disease (CKD), diabetic nephropathy, and acute kidney injury (AKI), represent a significant global health burden. The kidneys are metabolically very active organs demanding a large amount of ATP. They are composed of highly specialized cell types in the glomerulus and subsequent tubular compartments which fine-tune metabolism to meet their numerous and diverse functions. Defective renal cell metabolism, including altered fatty acid oxidation or glycolysis, has been linked to both AKI and CKD. Mitochondria play a vital role in renal metabolism, and emerging research has identified mitochondrial sirtuins (SIRT3, SIRT4 and SIRT5) as key regulators of renal cell metabolic adaptation, especially SIRT3. Sirtuins belong to an evolutionarily conserved family of mainly NAD+-dependent deacetylases, deacylases, and ADP-ribosyl transferases. Their dependence on NAD+, used as a co-substrate, directly links their enzymatic activity to the metabolic status of the cell. In the kidney, SIRT3 has been described to play crucial roles in the regulation of mitochondrial function, and the antioxidative and antifibrotic response. SIRT3 has been found to be constantly downregulated in renal diseases. Genetic or pharmacologic upregulation of SIRT3 has also been associated with beneficial renal outcomes. Importantly, experimental pieces of evidence suggest that SIRT3 may act as an important energy sensor in renal cells by regulating the activity of key enzymes involved in metabolic adaptation. Activation of SIRT3 may thus represent an interesting strategy to ameliorate renal cell energetics. In this review, we discuss the roles of SIRT3 in lipid and glucose metabolism and in mediating a metabolic switch in a physiological and pathological context. Moreover, we highlight the emerging significance of other mitochondrial sirtuins, SIRT4 and SIRT5, in renal metabolism. Understanding the role of mitochondrial sirtuins in kidney diseases may also open new avenues for innovative and efficient therapeutic interventions and ultimately improve the management of renal injuries.

Acute Kidney Injury and Subsequent Kidney Failure With Replacement Therapy Incidence in Older Adults With Advanced CKD: A Cohort Study of US Veterans

Rationale & Objective

Advanced age is a major risk factor for chronic kidney disease (CKD) development, which has high heterogeneity in disease progression. Acute kidney injury (AKI) hospitalization rates are increasing, especially among older adults. Previous AKI epidemiologic analyses have focused on hospitalized populations, which may bias results toward sicker populations. This study examined the association between AKI and incident kidney failure with replacement therapy (KFRT) while evaluating age as an effect modifier of this relationship.

Study Design

Retrospective cohort study.

Setting & Participants

24,133 Veterans at least 65 years old with incident CKD stage 4 from 2011 to 2013.

Exposures

AKI, AKI severity, and age.

Outcomes

KFRT and death.

Analytical Approach

The Fine-Gray competing risk regression was used to model AKI and incident KFRT with death as a competing risk. A Cox regression was used to model AKI severity and death.

Results

Despite a nonsignificant age interaction between AKI and KFRT, a clinically relevant combined effect of AKI and age on incident KFRT was observed. Compared with our oldest age group without AKI, those aged 65-74 years with AKI had the highest risk of KFRT (subdistribution HR [sHR], 14.9; 95% CI, 12.7-17.4), whereas those at least 85 years old with AKI had the lowest (sHR, 1.71; 95% CI, 1.22-2.39). Once Veterans underwent KFRT, their risk of death increased by 44%. A 2-fold increased risk of KFRT was observed across all AKI severity stages. However, the risk of death increased with worsening AKI severity.

Limitations

Our study lacked generalizability, was restricted to ever use of medications, and used inpatient serum creatinine laboratory results to define AKI and AKI severity.

Conclusions

In this national cohort, advanced age was protective against incident KFRT but not death. This is likely explained by the high frequency of deaths observed in this population (51.1%). Nonetheless, AKI and younger age are substantial risk factors for incident KFRT.

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

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

Determination of the reference interval for urine kidney injury molecule-1 in 50 healthy cats

OBJECTIVES

The aim of the present study was to establish a reference interval (RI) for urine kidney injury molecule-1 (KIM-1) in healthy cats.

METHODS

History, physical examination, blood pressure, and feline immunodeficiency virus and feline leukemia virus serology status were determined. A complete blood cell count, serum biochemical profile, urinalysis and kidney ultrasound were performed, and N-terminal pro-brain natriuretic peptide, total thyroxine (TT4) and urine KIM-1 were measured. An RI was calculated and the effect of age, sex, body condition score (BCS), blood pressure, symmetric dimethylarginine (SDMA), serum creatinine concentration (SCr), phosphorus, TT4, urine specific gravity (USG) and mid-sagittal kidney length on urine KIM-1 was evaluated using a general linear model.

RESULTS

Of 69 recruited cats, 50 met the inclusion criteria. There were 35 male cats and 15 female cats, with a median age of 4.3 years (range 1.0-12.3), median weight of 5.11 kg (range 2.52-8.45) and median BCS of 6/9 (range 3-8). The median serum concentrations were SDMA 11.0 µg/dl (range 2-14), SCr 88.5 µmol/l (range 47-136), phosphorus 1.41 mmol/l (range 0.8-2.2) and TT4 32.0 nmol/l (range 17-51). Median USG was 1.057 (range 1.035-1.076), mid-sagittal left kidney length was 3.50 cm (range 2.94-4.45) and mid-sagittal right kidney length was 3.70 cm (range 3.06-4.55). The derived RI for urine KIM-1 was 0.02-0.68. USG was a significant (P <0.001) predictor of urine KIM-1. Individually, age, sex, blood pressure, BCS, SDMA, SCr, phosphorus, TT4 and mid-sagittal kidney length were not significant predictors of urine KIM-1. In a multivariate model, if combined with USG, SDMA concentration was predictive (P = 0.030) of urine KIM-1.

CONCLUSIONS AND RELEVANCE

Urine concentration was significantly correlated with urine KIM-1, which will be an important consideration when interpreting findings in cats with potential kidney injury.

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

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

Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates

Chronic kidney disease (CKD) is caused by hypoxia in the renal tissue, leading to inflammation and increased migration of pathogenic cells. Studies showed that leukocytes directly sense hypoxia and respond by initiating gene transcription, encoding the 2-integrin adhesion molecules. Moreover, other mechanisms participate in hypoxia, including anemia. CKD-associated anemia is common, which induces and worsens hypoxia, contributing to CKD progression. Anemia correction can slow CKD progression, but it should be cautiously approached. In this comprehensive review, the underlying pathophysiology mechanisms and the impact of renal tissue hypoxia and anemia in CKD onset and progression will be reviewed and discussed in detail. Searching for the latest updates in PubMed Central, Medline, PubMed database, Google Scholar, and Google search engines were conducted for original studies, including cross-sectional studies, cohort studies, clinical trials, and review articles using different keywords, phrases, and texts such as "CKD progression, anemia in CKD, CKD, anemia effect on CKD progression, anemia effect on CKD progression, and hypoxia and CKD progression". Kidney tissue hypoxia and anemia have an impact on CKD onset and progression. Hypoxia causes nephron cell death, enhancing fibrosis by increasing interstitium protein deposition, inflammatory cell activation, and apoptosis. Severe anemia correction improves life quality and may delay CKD progression. Detection and avoidance of the risk factors of hypoxia prevent recurrent acute kidney injury (AKI) and reduce the CKD rate. A better understanding of kidney hypoxia would prevent AKI and CKD and lead to new therapeutic strategies.

Incidence of Chronic Kidney Disease Following Acute Coronavirus Disease 2019 Based on South Carolina Statewide Data

BACKGROUND

Coronavirus disease 2019 (COVID-19) was associated with severe acute illness including multiple organ failure. Acute kidney injury (AKI) was a common finding, often requiring dialysis support.

OBJECTIVE

Define the incidence of new clinically identified chronic kidney disease (CKD) among patients with COVID-19 and no pre-existing kidney disease.

DESIGN PARTICIPANTS

The South Carolina (SC) Department of Health and Environmental Control (DHEC) COVID-19 mandatory reporting registry of SC residents testing for COVID-19 between March 2020 and October 2021 was included.

DESIGN MAIN MEASURES

The primary outcome was a new incidence of a CKD diagnosis (N18.x) in those without a pre-existing diagnosis of CKD during the follow-up period of March 2020 to January 14, 2022. Patients were stratified by severity of illness (hospitalized or not, intensive care unit needed or not). The new incidence of CKD diagnosis was examined using logistic regression and cox proportional hazards analyses.

KEY RESULTS

Among patients with COVID-19 (N = 683,958) without a pre-existing CKD diagnosis, 8322 (1.2 %) were found to have a new diagnosis of CKD. The strongest predictors for subsequent CKD diagnosis were age ≥ 60 years hazard ratio (HR) 31.5 (95% confidence interval [95%CI] 25.5-38.8), and intervening (between COVID-19 and CKD diagnoses) AKI diagnosis HR 20.7 (95%CI 19.7-21.7). The presence of AKI was associated with an HR of 23.6, 95% CI 22.3-25.0, among those not hospitalized, and HR of 6.2, 95% CI 5.7-6.8 among those hospitalized, for subsequent CKD. COVID-19 was not significantly associated with subsequent CKD after accounting for the severity of illness and comorbidities.

CONCLUSION

Among SC residents, COVID-19 was not associated with CKD independent from indicators of the severity of illness, especially AKI diagnosis. Kidney-specific follow-up testing may be reserved for those high-risk for CKD development. Further prospective registries should examine the long-term kidney consequences to confirm these findings.

Roles of NAD+ in Acute and Chronic Kidney Diseases

Nicotinamide adenine dinucleotide (oxidized form, NAD⁺) is a critical coenzyme, with functions ranging from redox reactions and energy metabolism in mitochondrial respiration and oxidative phosphorylation to being a central player in multiple cellular signaling pathways, organ resilience, health, and longevity. Many of its cellular functions are executed via serving as a co-substrate for sirtuins (SIRTs), poly (ADP-ribose) polymerases (PARPs), and CD38. Kidney damage and diseases are common in the general population, especially in elderly persons and diabetic patients. While NAD⁺ is reduced in acute kidney injury (AKI) and chronic kidney disease (CKD), mounting evidence indicates that NAD⁺ augmentation is beneficial to AKI, although conflicting results exist for cases of CKD. Here, we review recent progress in the field of NAD⁺, mainly focusing on compromised NAD⁺ levels in AKI and its effect on essential cellular pathways, such as mitochondrial dysfunction, compromised autophagy, and low expression of the aging biomarker αKlotho (Klotho) in the kidney. We also review the compromised NAD⁺ levels in renal fibrosis and senescence cells in the case of CKD. As there is an urgent need for more effective treatments for patients with injured kidneys, further studies on NAD⁺ in relation to AKI/CKD may shed light on novel therapeutics.

Pregnancy-related acute kidney injury in the African continent: where do we stand? A systematic review

BACKGROUND

Pregnancy-Related Acute kidney injury (PR-AKI) is a global health problem with substantial maternal and fetal morbidity and mortality. However, little is known about the current situation in the developing world including African countries. Africa is the poorest continent per capita, and women from Sub-Saharan Africa alone account for 66% of the estimated global maternal deaths from preventable obstetric causes.

METHODS

OBJECTIVE: To review the literature on the clinical profile, maternal and renal outcomes of women with PR-AKI in the African continent.

SEARCH STRATEGY

Medline, ISI Web of Science, Scopus, and Cochrane library were searched in February 2022, using the MeSH terms and text key words: "pregnancy", "pregnant", "acute kidney injury", "acute renal insufficiency", "acute renal injury", "acute renal failure", and "Africa".

SELECTION CRITERIA AND DATA COLLECTION

Studies from African countries which reported maternal and renal outcomes in women with PR-AKI during pregnancy or postpartum were included. Editorials, short communications, and case reports were excluded. The study quality was assessed using the NHLBI tool. Data extraction was done using predefined data fields.

RESULTS

A total of 167 studies were evaluated, of which 14 studies from seven African countries met the inclusion criteria. Preeclampsia, obstetric hemorrhage, and sepsis represented the main causes of PR-AKI. Maternal mortality ranged between 0 and 34.4%. Although the majority of women needed ICU admission and hemodialysis, renal recovery occurred in 53.1-90% of patients. Perinatal mortality has been reported to be 1.5-60.5% in the included studies.

AUTHORS' CONCLUSIONS

PR-AKI in Africa represents the second leading cause of AKI. Limited access to obstetric care, late referral, and late diagnosis of women with risks for PR-AKI hinder the curtailment of the problem. Provision of health care facilities with adequately trained personnel and implementation of preventive strategies will be of great value in decreasing the magnitude of the problem.

Impact of decreasing vancomycin exposure on acute kidney injury in stem cell transplant recipients

OBJECTIVE

To evaluate the change in vancomycin days of therapy (DOT) and vancomycin-associated acute kidney injury (AKI) after an antimicrobial stewardship program (ASP) intervention to decrease vancomycin use in stable patients after hematopoietic stem cell transplantation (HSCT).

DESIGN

Retrospective cohort study and quasi-experimental interrupted time series analysis. Change in unit-level vancomycin DOT per 1,000 inpatient days after the intervention was assessed using segmented Poisson regression. Subject-specific risk of vancomycin-associated AKI was evaluated using a random intercept logistic regression model with mediation analysis.

SETTING

HSCT unit at a single quaternary-care pediatric hospital.

PARTICIPANTS

Inpatients aged 3 months and older who underwent HSCT between January 1, 2015, and March 31, 2019 (27 months before and after the intervention) who received any dose of vancomycin.

INTERVENTION

An ASP intervention in April 2017 creating a new practice guideline to decrease prolonged (>72 hours) vancomycin courses for stable HSCT patients with febrile neutropenia.

RESULTS

Overall, 439 vancomycin exposures (234 before the intervention and 205 after the intervention) occurring across 300 transplants and 259 subjects were included. The mean vancomycin DOT was 307 per 1,000 inpatient days (95% confidence interval [CI], 272-342) and decreased after the intervention to 207 per 1,000 inpatient days (95% CI, 173-240). In multivariable analyses, the odds of AKI in the postintervention period were 37% lower than in the preintervention period (adjusted OR, 0.63; 95% CI, 0.42-0.95; P = .0268); 56% of the excess risk was mediated by vancomycin DOT.

CONCLUSIONS

An ASP intervention successfully decreased vancomycin use after HSCT and resulted in a decrease in AKI. Reducing empiric antibiotic exposure for stable patients after HSCT can improve clinical outcomes.

TCRαβ+ CD4-/CD8- "double negative" T cells in health and disease-implications for the kidney

Double negative (DN) T cells, one of the least studied T lymphocyte subgroups, express T cell receptor αβ but lack CD4 and CD8 coreceptors. DN T cells are found in multiple organs including kidney, lung, heart, gastrointestinal tract, liver, genital tract, and central nervous system. DN T cells suppress inflammatory responses in different disease models including experimental acute kidney injury, and significant evidence supports an important role in the pathogenesis of systemic lupus erythematosus. However, little is known about these cells in other kidney diseases. Therefore, it is important to better understand different functions of DN T cells and their signaling pathways as promising therapeutic targets, particularly with the increasing application of T cell-directed therapy in humans. In this review, we aim to summarize studies performed on DN T cells in normal and diseased organs in the setting of different disease models with a focus on kidney.

The renoprotective effects of gallic acid on cisplatin-induced nephrotoxicity through anti-apoptosis, anti-inflammatory effects, and downregulation of lncRNA TUG1

Cisplatin, an antineoplastic drug used in cancer therapy, -induced nephrotoxicity mediated by the production of reactive oxygen species (ROS). Gallic acid (GA) is identified as an antioxidant substance with free radical scavenging properties. This research was designed to examine the ameliorative impact of GA caused by cisplatin-induced nephrotoxicity through apoptosis and long non-coding RNA (lncRNA) Taurine-upregulated gene 1 (TUG1) expression. Thirty-two male Sprague Dawley rats (200 - 220 g) were randomly allocated to four groups: (1) control group; (2) rats treated with cisplatin (7.5 mg/kg, i.p.) on the fourth day; and the two other groups include rats pretreated with GA (20 and 40 mg/kg by gavage) for s7 days and cisplatin (7.5 mg/kg, i.p.) at the fourth day. The rats were anesthetized and sacrificed for collecting samples, 72 h after cisplatin administration. The blood samples were used to investigate biochemical factors and kidney tissue was evaluated for measuring oxidative stress and inflammatory factors and the gene expression of molecular parameters. The results indicated that GA administration increased the B-cell lymphoma-2 (Bcl-2) mRNA and lncRNA TUG1 expression, and reduced Bcl-2-associated x protein (Bax), and caspase-3 expression. Likewise, the TAC level increased, and kidney MDA content decreased by administration of GA. GA also decreased the inflammatory factor levels, including IL-1β and TNF-α. Moreover, GA led to the improvement of kidney dysfunction as evidenced by reducing plasma BUN (blood urea nitrogen) and Cr (creatinine). Taken together, GA could protect the kidney against cisplatin-induced nephrotoxicity through antioxidant, anti-inflammatory, and anti-apoptosis properties and reduction of lncRNA TUG1 expression.

Kidney-Targeted Redox Scavenger Therapy Prevents Cisplatin-Induced Acute Kidney Injury

Cisplatin-induced acute kidney injury (CI-AKI) is a significant co-morbidity of chemotherapeutic regimens. While this condition is associated with substantially lower survival and increased economic burden, there is no pharmacological agent to effectively treat CI-AKI. The disease is hallmarked by acute tubular necrosis of the proximal tubular epithelial cells primarily due to increased oxidative stress. We investigated a drug delivery strategy to improve the pharmacokinetics of an approved therapy that does not normally demonstrate appreciable efficacy in CI-AKI, as a preventive intervention. In prior work, we developed a kidney-selective mesoscale nanoparticle (MNP) that targets the renal proximal tubular epithelium. Here, we found that the nanoparticles target the kidneys in a mouse model of CI-AKI with significant damage. We evaluated MNPs loaded with the reactive oxygen species scavenger edaravone, currently used to treat stroke and ALS. We found a marked and significant therapeutic benefit with edaravone-loaded MNPs, including improved renal function, which we demonstrated was likely due to a decrease in tubular epithelial cell damage and death imparted by the specific delivery of edaravone. The results suggest that renal-selective edaravone delivery holds potential for the prevention of acute kidney injury among patients undergoing cisplatin-based chemotherapy.

Exogenous Wnt1 Prevents Acute Kidney Injury and Its Subsequent Progression to Chronic Kidney Disease

Studies suggest that Wnt/β-catenin agonists are beneficial in the treatment of acute kidney injury (AKI); however, it remains elusive about its role in the prevention of AKI and its progression to chronic kidney disease (CKD). In this study, renal Wnt/β-catenin signaling was either activated by overexpression of exogenous Wnt1 or inhibited by administration with ICG-001, a small molecule inhibitor of β-catenin signaling, before mice were subjected to ischemia/reperfusion injury (IRI) to induce AKI and subsequent CKD. Our results showed that in vivo expression of exogenous Wnt1 before IR protected mice against AKI, and impeded the progression of AKI to CKD in mice, as evidenced by both blood biochemical and kidney histological analyses. In contrast, pre-treatment of ICG-001 before IR had no effect on renal Wnt/β-catenin signaling or the progression of AKI to CKD. Mechanistically, in vivo expression of exogenous Wnt1 before IR suppressed the expression of proapoptotic proteins in AKI mice, and reduced inflammatory responses in both AKI and CKD mice. Additionally, exogenous Wnt1 inhibited apoptosis of tubular cells induced by hypoxia-reoxygenation (H/R) treatment in vitro. To conclude, the present study provides evidences to support the preventive effect of Wnt/β-catenin activation on IR-related AKI and its subsequent progression to CKD.

The sympathies of the body: functional organization and neuronal differentiation in the peripheral sympathetic nervous system

During the last 30 years, our understanding of the development and diversification of postganglionic sympathetic neurons has dramatically increased. In parallel, the list of target structures has been critically extended from the cardiovascular system and selected glandular structures to metabolically relevant tissues such as white and brown adipose tissue, lymphoid tissues, bone, and bone marrow. A critical question now emerges for the integration of the diverse sympathetic neuron classes into neural circuits specific for these different target tissues to achieve the homeostatic regulation of the physiological ends affected.

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.

Osteocrin, a bone-derived humoral factor, exerts a renoprotective role in ischemia-reperfusion injury in mice

Background

Osteocrin (OSTN), a bone-derived humoral factor, was reported to act on heart and bone by potentiating the natriuretic peptide (NP) system. Ostn gene polymorphisms have been associated with renal function decline, but its pathophysiological role in the kidney remains unclear.

Methods

The role of endogenous OSTN was investigated using systemic Ostn-knockout (KO) mice. As a model for OSTN administration, liver-specific Ostn-overexpressing mice crossed with KO (KO-Tg) were generated. These mice were subjected to unilateral ischemia–reperfusion injury (IRI) and renal lesions after 21 days of insult were evaluated. A comprehensive analysis of the Wnt/β-catenin pathway was performed using a polymerase chain reaction (PCR) array. Reporter plasmid-transfected proximal tubular cells (NRK52E) were used to investigate the mechanism by which OSTN affects the pathway.

Results

After injury, KO mice showed marginal worsening of renal fibrosis compared with wild-type mice, with comparable renal atrophy. KO-Tg mice showed significantly ameliorated renal atrophy, fibrosis and tubular injury, together with reduced expressions of fibrosis- and inflammation-related genes. The PCR array showed that the activation of the Wnt/β-catenin pathway was attenuated in KO-Tg mice. The downstream targets Mmp7, Myc and Axin2 showed similar results. MMP7 and Wnt2 were induced in corticomedullary proximal tubules after injury, but not in KO-Tg. In NRK52E, OSTN significantly potentiated the inhibitory effects of NP on transforming growth factor β1–induced activation of the Wnt/β-catenin pathway, which was reproduced by a cyclic guanosine monophosphate analog.

Conclusions

Ectopic Ostn overexpression ameliorated subsequent renal injury following ischemia–reperfusion. OSTN could represent possible renoprotection in acute to chronic kidney disease transition, thus serving as a potential therapeutic strategy.

Urinary Plasminogen Activator Inhibitor-1: A Biomarker of Acute Tubular Injury

INTRODUCTION

Acute kidney injury (AKI) is a threatening, multiaetiological syndrome encompassing a variety of forms and damage patterns. AKI lacks sufficiently specific diagnostic tools to evaluate the distinct combination of pathophysiological events underlying each case, which limits personalized and optimized handling. Therefore, a pathophysiological diagnosis based on new urinary biomarkers is sought for practical (readiness and noninvasiveness) and conceptual reasons, as the urine is a direct product of the kidneys. However, biomarkers found in the urine may also have extrarenal origin, thus conveying pathophysiological information from other organs or tissues. Urinary plasminogen activator inhibitor-1 (PAI-1) has been associated to AKI, although its origin and traffic to the urine are not known.

METHODS

Herein, we studied the blood or renal origin of urinary PAI-1 (uPAI-1) in experimental AKI in Wistar rats, by means of the in situ renal perfusion method. For this purpose, urine was collected while the kidneys of rats with AKI showing increased uPAI-1 excretion, and controls, were in situ perfused with a saline solution.

RESULTS

Our results show that during perfusion, PAI-1 remained in the urine of AKI rats, suggesting that renal cells shed this protein directly to the urine. PAI-1 is also significantly increased in the urine of AKI patients. Its low correlation with other urinary markers such as NGAL or NAG suggests that PAI-1 provides complementary and distinct phenotypical information.

CONCLUSION

In conclusion, uPAI-1 is a biomarker produced by damaged kidneys following AKI, whose precise pathophysiological meaning in AKI needs to be further investigated.

The protective mechanism of Klotho gene-modified bone marrow mesenchymal stem cells on acute kidney injury induced by rhabdomyolysis

Background

Studies have shown that the Klotho gene has tremendous potential for future therapeutic purposes in both acute and chronic kidney diseases (CKD). This study aimed to investigate the possible protective mechanisms of the Klotho gene against acute kidney injury (AKI) induced by rhabdomyolysis (RM).

Methods

In this study, bone marrow mesenchymal stem cells (BMSCs) were transfected with recombinant adenoviruses expressing the Klotho gene (BMSCs-Klotho) and by those expressing empty vector (BMSCs-EV). After successful transfection, we tested the proliferation, secretion and migration abilities of the BMSCs-Klotho compared with those of the BMSCs-EV and BMSCs. Then, 30 male C57BL/6 mice were examined, with 6 mice randomly assigned to the control group (PBS injected into the tail vein, CON) or one of the four treatment groups treated with either BMSCs-Klotho (AKI+BMSCs-Klotho), BMSCs-EV (AKI+BMSCs-EV), BMSCs (AKI+BMSCs) or PBS (AKI+PBS) after induction of RM. Seventy-two h after treatment, serum creatinine (SCr) and blood urea nitrogen (BUN) levels were obtained to assess renal function, and renal tissue was obtained to measure kidney tissue damage. Additionally, kidney protective mechanism-related indexes, such as EPO, IGF-1, KIM-1 and HIF-1, were analysed using Western blot analysis and immunohistochemistry.

Results

The results obtained showed that the proliferation, secretory and migration abilities of the BMSCs were significantly increased after transfection with the Klotho gene. Treatment with BMSCs-Klotho, BMSCs-EV or BMSCs improved renal function compared to treatment with PBS. However, the improvement observed in renal function in the BMSCs-Klotho group was better than that of the other groups. Histological analysis demonstrated that tissue damage was significantly decreased in the mice in the AKI+BMSCs-Klotho, AKI+BMSCs-EV or AKI+BMSCs groups compared to that in the mice in the AKI+PBS group. However, the best recovery was observed in the mice treated with BMSCs-Klotho concomitantly. Furthermore, the expression of protective factors erythropoietin (EPO) and insulin-like growth factor 1 (IGF-1) increased obviously, and the injury biomarkers kidney injury molecule 1 (KIM-1) and hypoxia inducible factor 1 (HIF-1) decreased notably in the group of BMSCs-Klotho, BMSCs-EV and BMSCs. Additionally, the levels of the aforementioned protein indicators in the AKI+BMSCs-Klotho group were not different from those in the CON group.

Conclusion

Klotho overexpression exerted positive effects on BMSCs and markedly promoted recovery from RM-induced AKI. These findings suggest that the overexpression of the Klotho gene might be a good candidate for further therapy for AKI in clinical trials.

Urinary TCP1-eta: A Cortical Damage Marker for the Pathophysiological Diagnosis and Prognosis of Acute Kidney Injury

Acute kidney injury (AKI) is a serious syndrome with increasing incidence and health consequences, and high mortality rate among critically ill patients. Acute kidney injury lacks a unified definition, has ambiguous semantic boundaries, and relies on defective diagnosis. This, in part, is due to the absence of biomarkers substratifying AKI patients into pathophysiological categories based on which prognosis can be assigned and clinical treatment differentiated. For instance, AKI involving acute tubular necrosis (ATN) is expected to have a worse prognosis than prerenal, purely hemodynamic AKI. However, no biomarker has been unambiguously associated with tubular cell death or is able to provide etiological distinction. We used a cell-based system to identify TCP1-eta in the culture medium as a noninvasive marker of damaged renal tubular cells. In rat models of AKI, TCP1-eta was increased in the urine co-relating with renal cortical tubule damage. When kidneys from ATN rats were perfused in situ with Krebs-dextran solution, a portion of the urinary TCP1-eta protein content excreted into urine disappeared, and another portion remained within the urine. These results indicated that TCP1-eta was secreted by tubule cells and was not fully reabsorbed by the damaged tubules, both effects contributing to the increased urinary excretion. Urinary TCP1-eta is found in many etiologically heterogeneous AKI patients, and is statistically higher in patients partially recovered from severe AKI. In conclusion, urinary TCP1-eta poses a potential, substratifying biomarker of renal cortical damage associated with bad prognosis.

Effect of NAD+ boosting on kidney ischemia-reperfusion injury

Acute kidney injury (AKI) is associated with a very high mortality and an increased risk for progression to chronic kidney disease (CKD). Ischemia-reperfusion injury (IRI) is a model for AKI, which results in tubular damage, dysfunction of the mitochondria and autophagy, and in decreased cellular nicotinamide adenine dinucleotide (NAD⁺) with progressing fibrosis resulting in CKD. NAD⁺ is a co-enzyme for several proteins, including the NAD⁺ dependent sirtuins. NAD⁺ augmentation, e.g. by use of its precursor nicotinamide riboside (NR), improves mitochondrial homeostasis and organismal metabolism in many species. In the present investigation the effects of prophylactic administration of NR on IRI-induced AKI were studied in the rat. Bilateral IRI reduced kidney tissue NAD⁺, caused tubular damage, reduced α-Klotho (klotho), and altered autophagy flux. AKI initiated progression to CKD, as shown by induced profibrotic Periostin (postn) and Inhibin subunit beta-A, (activin A / Inhba), both 24 hours and 14 days after surgery. NR restored tissue NAD⁺ to that of the sham group, increased autophagy (reduced p62) and sirtuin1 (Sirt1) but did not ameliorate renal tubular damage and profibrotic genes in the 24 hours and 14 days IRI models. AKI induced NAD⁺ depletion and impaired autophagy, while augmentation of NAD⁺ by NR restored tissue NAD⁺ and increased autophagy, possibly serving as a protective response. However, prophylactic administration of NR did not ameliorate tubular damage of the IRI rats nor rescued the initiation of fibrosis in the long-term AKI to CKD model, which is a pivotal event in CKD pathogenesis.

Doxycycline treatment reestablishes renal function of Wistar rats in experimental envenomation with Bothrops jararacussu venom

Acute kidney injury is one of the main complications of ophidian accidents and the leading cause of death in patients who survive the initial damage effects of venom. The hypothesis proposed in this investigation is that the pharmacological repositioning of doxycycline (doxy) attenuates renal injury provoked by Bothrops jararacussu (Bj) venom. Male Wistar rats were subjected or not (control) to experimental envenomation with Bj venom (3.5 mg/kg, im). Doxy (3 mg/kg, ip) was administered 2 h after envenoming. Envenomation with Bj venom promoted tissue damage in the renal cortex (moderate degree, score 3) in 24 h associated with decreased glomerular and tubular function, which promoted proteinuria and polyuria. Doxy treatment prevented the increase in urinary volume in 3 times, the increase in plasma creatinine in 33%, the increase in blood urea-nitrogen accumulation in 65%, the increase in urinary Na⁺ excretion in 2 times, marked proteinuria and kidney cortex injury induced by Bj envenomation. Bj venom promoted increase in protein content (66%) and reduction of 45% (Na⁺+K⁺)-ATPase activity in the renal cortex. The enzyme was detected mainly in the luminal membrane. Doxy treatment was effective in preventing the mentioned alterations, maintaining (Na⁺+K⁺)-ATPase in the basolateral membranes.

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.

Chronic Kidney Disease as a Systemic Inflammatory Syndrome: Update on Mechanisms Involved and Potential Treatment

Chronic kidney disease (CKD) is characterized by manifestations and symptoms involving systemic organs and apparatus, associated with elevated cardiovascular morbidity and mortality, bone disease, and other tissue involvement. Arterial hypertension (AH), diabetes mellitus (DM), and dyslipidemia, with glomerular or congenital diseases, are the traditional risk factors recognized as the main causes of progressive kidney dysfunction evolving into uremia. Acute kidney injury (AKI) has recently been considered an additional risk factor for the worsening of CKD or the development of CKD de novo. Evidence underlies the role of systemic inflammation as a linking factor between AKI and CKD, recognizing the role of inflammation in AKI evolution to CKD. Moreover, abnormal increases in oxidative stress (OS) and inflammatory status in CKD seem to exert an important pathogenetic role, with significant involvement in the clinical management of this condition. With our revision, we want to focus on and update the inflammatory mechanisms responsible for the pathologic conditions associated with CKD, with particular attention on the development of AKI and AKI-CKD de novo, the alteration of calcium-phosphorus metabolism with bone disease and CKD-MBD syndrome, the status of malnutrition and malnutrition-inflammation complex syndrome (MICS) and protein-energy wasting (PEW), uremic sarcopenia, the status of OS, and the different inflammatory pathways, highlighting a new approach to CKD. The depth comprehension of the mechanisms underlying the development of inflammation in CKD may present new possible therapeutic approaches in CKD and hopefully improve the management of correlated morbidities and provide a reduction in associated mortality.

Factors associated with acute kidney injury during delivery or the postpartum period: A case control study

INTRODUCTION

To investigate the incidence of risk factors associated with acute kidney injury(AKI) occurring during the intrapartum or the immediate postpartum period.

MATERIAL AND METHODS

A retrospective case control study in a tertiary UK hospital of pregnant women identified with AKI in labour or in the postpartum period between July 2019 and June 2020 was carried out. Women identified with pregnancy related AKI (pr-AKI) in labour or postpartum were compared with a matched cohort of women with no evidence of pr-AKI, using multiple regression analysis.

RESULTS

In 4600 births, 71 women with pr-AKI and 142 control women were identified. The antenatal and intrapartum risk factors strongly associated with pr-AKI were pre-eclampsia, prolonged ruptured membranes, delivery by emergency caesarean section and greater blood loss at delivery (all p < 0.001 in multivariable regression).

CONCLUSION

Pr-AKI is relatively common, occurring in 1.5 % of our cohort. Women who are overweight, have prolonged rupture of the membranes, an emergency caesarean section and/or a postpartum haemorrhage are at greatest risk. Clinicians should be check renal function before prescribing non-steroidal medication for postpartum pain relief if there are risk factors for AKI.

Risk Factors for Acute Kidney Injury in COVID-19 Patients: A Systematic Review

BACKGROUND: Acute kidney injury (AKI) in coronavirus disease-19 (COVID-19) has high incidence and mortality. Risk factors for AKI in COVID-19 patients are not well explored. This systematic review provides a combination of available evidence regarding risk factors of AKI in COVID-19 patients. METHODS: A systematic research was performed in Medline, Cochrane Central Register of Controlled Trials, and ScienceDirect journal databases from 2019 to August 2020. The study selection process was plotted using a Preferred Reporting Items for Systematic Review and Meta-Analyses flow diagram. RESULTS: Out of 553 studies found, four full-text studies met the inclusion criteria and were included in qualitative analysis. There are 2205 COVID-19 patients with AKI (36.44%) from 6051 COVID-19 patients. Age was a risk factors for AKI in two studies (odds ratio [OR] 1.03 [p < 0.001], OR 1.03 [p < 0.007]). Critical condition of patient is risk factors for AKI (OR 8.155 [p = 0.006]). Hirsch et al. stated that diabetes mellitus (OR 1.74 [p < 0.001]), cardiovascular disease (OR 1.48 [p < 0.001]), and hypertension (OR 1.25 [p = 0.02]) are also risk factors. Laboratory results such as elevated procalcitonin (PCT) and estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 showed positive association to AKI in COVID-19 patients (OR 4.822 [p = 0.037]; OR 13.451 [p = 0.016]). A higher sequential organ failure assessment (SOFA) score at admission is one of the risk factors (OR 1.498 [p = 0.027]). CONCLUSION: Demographics, clinical classification of COVID-19, comorbidities, SOFA score, PCT, and eGFR can help clinicians predict AKI in COVID-19 patients.

Cancer, Mortality, and Acute Kidney Injury among Hospitalized Patients with SARS-CoV-2 Infection

Background:

To evaluate Coronavirus Disease 2019-(COVID19) patients treated within our academic medical system to determine if history of malignancy, both in general and specifically in genitourinary oncology patients, is associated with adverse clinical outcomes, including acute kidney injury (AKI) and mortality.

Methods:

We conducted a retrospective cohort study among patients with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a multi-hospital, academic medical institution in New York City. Outcomes included mortality, intensive care unit (ICU) admission and AKI among hospitalized patients. We also evaluated risk of hospitalization among all patients with SARS-CoV-2 infection. Multilevel logistic regression models were used for analysis.

Results:

We identified 6,893 patients who met inclusion criteria, of which 4,018 were hospitalized. Among hospitalized patients 374 (9%) had a history of cancer, 281 (7%) experienced AKI, and 1,045 (26%) died. In adjusted analyses, patients with a history of cancer had 1.33 (95% CI = 1.05, 1.69) times the odds of death compared to those without cancer and this appeared to be driven by lung cancer (odds ratio (OR) = 2.44, 95% CI= 1.05, 4.39). Patients with a history of genitourinary cancer were not at higher risk of mortality compared to those without cancer (OR=0.99, 95% CI= 0.61, 1.62). History of cancer was not associated with ICU admission or AKI in overall and subgroup analyses.

Conclusions:

Patients with a history of cancer who are hospitalized with SARS-CoV-2 infection are not at greater risk for AKI, though they are at higher risk for mortality as compared to patients without a history of cancer. The increased risk in mortality appears driven by patients with pulmonary neoplasms. Patients with a history of genitourinary malignancies do not appear to be at higher risk for AKI or for mortality compared to the general population.

Comorbidities and the COVID-19 pandemic dynamics in Africa

The debate around the COVID‐19 response in Africa has mostly focused on effects and implications of public health measures, in light of the socio‐economic peculiarities of the continent. However, there has been limited exploration of the impact of differences in epidemiology of key comorbidities, and related healthcare factors, on the course and parameters of the pandemic. We summarise what is known about (a) the pathophysiological processes underlying the interaction of coinfections and comorbidities in shaping prognosis of COVID‐19 patients, (b) the epidemiology of key coinfections and comorbidities, and the state of related healthcare infrastructure that might shape the course of the pandemic, and (c) implications of (a) and (b) for pandemic management and post‐pandemic priorities. There is a critical need to generate empirical data on clinical profiles and the predictors of morbidity and mortality from COVID‐19. Improved protocols for acute febrile illness and access to diagnostic facilities, not just for SARS‐CoV‐2 but also other viral infections, are of urgent importance. The role of malaria, HIV/TB and chronic malnutrition on pandemic dynamics should be further investigated. Although chronic non‐communicable diseases account for a relatively lighter burden, they have a significant effect on COVID‐19 prognosis, and the fragility of care delivery systems implies that adjustments to clinical procedures and re‐organisation of care delivery that have been useful in other regions are unlikely to be feasible. Africa is a large region with local variations in factors that can shape pandemic dynamics. A one‐size‐fits‐all response is not optimal, but there are broad lessons relating to differences in epidemiology and healthcare delivery factors, that should be considered as part of a regional COVID‐19 response framework.

Sequential Wnt Agonist Then Antagonist Treatment Accelerates Tissue Repair and Minimizes Fibrosis

Tissue fibrosis compromises organ function and occurs as a potential long-term outcome in response to acute tissue injuries. Currently, lack of mechanistic understanding prevents effective prevention and treatment of the progression from acute injury to fibrosis. Here, we combined quantitative experimental studies with a mouse kidney injury model and a computational approach to determine how the physiological consequences are determined by the severity of ischemia injury and to identify how to manipulate Wnt signaling to accelerate repair of ischemic tissue damage while minimizing fibrosis. The study reveals that memory of prior injury contributes to fibrosis progression and ischemic preconditioning reduces the risk of death but increases the risk of fibrosis. Furthermore, we validated the prediction that sequential combination therapy of initial treatment with a Wnt agonist followed by treatment with a Wnt antagonist can reduce both the risk of death and fibrosis in response to acute injuries.

Non-steroidal anti-inflammatory drug (NSAID) therapy in patients with hypertension, cardiovascular, renal or gastrointestinal comorbidities: joint APAGE/APLAR/APSDE/APSH/APSN/PoA recommendations

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly prescribed medications, but they are associated with a number of serious adverse effects, including hypertension, cardiovascular disease, kidney injury and GI complications.

OBJECTIVE

To develop a set of multidisciplinary recommendations for the safe prescription of NSAIDs.

METHODS

Randomised control trials and observational studies published before January 2018 were reviewed, with 329 papers included for the synthesis of evidence-based recommendations.

RESULTS

Whenever possible, a NSAID should be avoided in patients with treatment-resistant hypertension, high risk of cardiovascular disease and severe chronic kidney disease (CKD). Before treatment with a NSAID is started, blood pressure should be measured, unrecognised CKD should be screened in high risk cases, and unexplained iron-deficiency anaemia should be investigated. For patients with high cardiovascular risk, and if NSAID treatment cannot be avoided, naproxen or celecoxib are preferred. For patients with a moderate risk of peptic ulcer disease, monotherapy with a non-selective NSAID plus a proton pump inhibitor (PPI), or a selective cyclo-oxygenase-2 (COX-2) inhibitor should be used; for those with a high risk of peptic ulcer disease, a selective COX-2 inhibitor plus PPI are needed. For patients with pre-existing hypertension receiving renin-angiotensin system blockers, empirical addition (or increase in the dose) of an antihypertensive agent of a different class should be considered. Blood pressure and renal function should be monitored in most cases.

CONCLUSION

NSAIDs are a valuable armamentarium in clinical medicine, but appropriate recognition of high-risk cases, selection of a specific agent, choice of ulcer prophylaxis and monitoring after therapy are necessary to minimise the risk of adverse events.

Gene knockout of the Na+-glucose cotransporter SGLT2 in a murine model of acute kidney injury induced by ischemia-reperfusion

In the early proximal tubule, Na⁺-glucose cotransporter 2 (SGLT2) mediates the bulk of renal glucose reabsorption. Gene deletion in mice (Sglt2^-/-) was used to determine the role of SGLT2 in acute kidney injury induced by bilateral ischemia-reperfusion (IR). In Sglt2^-/- and littermate wild-type mice, plasma creatinine increased similarly on day 1 after IR. This was associated with an equal increase in both genotypes in the urinary kidney injury molecule-1-to-creatinine ratio, a tubular injury marker, and similarly reduced urine osmolality and increased plasma osmolality, indicating impaired urine concentration. In both IR groups, FITC-sinistrin glomerular filtration rate was equally reduced on day 14, and plasma creatinine was similarly and incompletely restored on day 23. In Sglt2^-/- mice subjected to IR, fractional urinary glucose excretion was increased on day 1 but reduced and associated with normal renal Na⁺-glucose cotransporter 1 (Sglt1) mRNA expression on day 23, suggesting temporary SGLT1 suppression. In wild-type mice subjected to IR, renal Sglt1 mRNA was likewise normal on day 23, whereas Sglt2 mRNA was reduced by 57%. In both genotypes, IR equally reduced urine osmolality and renal mRNA expression of the Na⁺-K⁺-2Cl^- cotransporter and renin on day 23, suggesting thick ascending limb dysfunction, and similarly increased renal mRNA expression of markers of injury, inflammation, oxidative stress, and fibrosis (kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, transforming growth factor-β1, NADPH oxidase-2, and collagen type 1). This was associated with equal increases in kidney histological damage scores and similar degree of capillary loss in both genotypes. The data indicate that genetic deletion of SGLT2 did not protect the kidneys in the initial injury phase or the subsequent recovery phase in a mouse model of IR-induced acute kidney injury.

Renal Sympathetic Nerve-Derived Signaling in Acute and Chronic kidney Diseases

The kidney is innervated by afferent sensory and efferent sympathetic nerve fibers. Norepinephrine (NE) is the primary neurotransmitter for post-ganglionic sympathetic adrenergic nerves, and its signaling, regulated through adrenergic receptors (AR), modulates renal function and pathophysiology under disease conditions. Renal sympathetic overactivity and increased NE level are commonly seen in chronic kidney disease (CKD) and are critical factors in the progression of renal disease. Blockade of sympathetic nerve-derived signaling by renal denervation or AR blockade in clinical and experimental studies demonstrates that renal nerves and its downstream signaling contribute to progression of acute kidney injury (AKI) to CKD and fibrogenesis. This review summarizes our current knowledge of the role of renal sympathetic nerve and adrenergic receptors in AKI, AKI to CKD transition and CKDand provides new insights into the therapeutic potential of intervening in its signaling pathways.

Autophagy Function and Regulation in Kidney Disease

Autophagy is a dynamic process by which intracellular damaged macromolecules and organelles are degraded and recycled for the synthesis of new cellular components. Basal autophagy in the kidney acts as a quality control system and is vital for cellular metabolic and organelle homeostasis. Under pathological conditions, autophagy facilitates cellular adaptation; however, activation of autophagy in response to renal injury may be insufficient to provide protection, especially under dysregulated conditions. Kidney-specific deletion of Atg genes in mice has consistently demonstrated worsened acute kidney injury (AKI) outcomes supporting the notion of a pro-survival role of autophagy. Recent studies have also begun to unfold the role of autophagy in progressive renal disease and subsequent fibrosis. Autophagy also influences tubular cell death in renal injury. In this review, we reported the current understanding of autophagy regulation and its role in the pathogenesis of renal injury. In particular, the classic mammalian target of rapamycin (mTOR)-dependent signaling pathway and other mTOR-independent alternative signaling pathways of autophagy regulation were described. Finally, we summarized the impact of autophagy activation on different forms of cell death, including apoptosis and regulated necrosis, associated with the pathophysiology of renal injury. Understanding the regulatory mechanisms of autophagy would identify important targets for therapeutic approaches.

Acute Kidney Injury Associated With Urinary Stone Disease in Children and Young Adults Presenting to a Pediatric Emergency Department

Background: Acute kidney injury (AKI) due to urinary stone disease (USD) is rare in adults; AKI rates in children with USD may be higher, and emerging data links stones to chronic kidney disease (CKD) development in adults. Methods: This study is a retrospective analysis of USD patients at a single pediatric hospital system's emergency department (ED). Patients were initially identified by USD ICD codes; USD was then confirmed by imaging or physician documentation; patients had to have baseline creatinine (Cr) and Cr in the ED for comparison to be included. AKI was defined by Kidney Disease: Improving Global Outcomes (KDIGO), Acute Kidney Injury Network (AKIN), and Pediatric Risk, Injury, Failure, Loss, End Stage (pRIFLE). Results: Of the 589 total visits, 264/589 (45%) had data to evaluate for AKI, 23% were AKI(+) and 77% were AKI(-). pRIFLE was most common (82%) and 18% were only positive by AKIN/KDIGO. AKI(+) were more likely to be younger (16.7 vs. 17.4 years, p = 0.046) and more likely to present with vomiting {odds ratio [OR] [95% confidence interval (CI)]: 2.4 [1.4-4.3], p = 0.002}; also, the proportion of AKI(+) was significantly higher in <18 vs. ≥18 years [26.9 vs. 15.5%, p = 0.032, OR (95% CI): 2.0 (1.1-3.9)]. Urinary tract infection (UTI) and obstruction rates were similar between groups. AKI(+) patients had a significant OR <1 suggesting less risk of receiving non-steroidal anti-inflammatory drugs (NSAIDs); however, 51% of them did receive NSAIDs during their ED encounter. AKI(+) patients were more likely to require admission to the hospital (53 vs. 32%, p = 0.001). Conclusion: We have demonstrated a novel association between USD-induced renal colic and AKI in a group of young adults and children. AKI(+) patients were younger and were more likely to present with vomiting. AKI(+) patients did not have higher rates of obstruction or UTI, and 51% of AKI(+) received NSAIDs.

Acute Kidney Injury in Patients Undergoing Cardiac Transplantation: A Meta-Analysis

Background: Acute kidney injury (AKI) is a common complication following solid-organ transplantation. However, the epidemiology of AKI and mortality risk of AKI among patients undergoing cardiac transplantation is not uniformly described. We conducted this study to assess the incidence of AKI and mortality risk of AKI in adult patients after cardiac transplantation. Methods: A systematic review of EMBASE, MEDLINE, and Cochrane Databases was performed until June 2019 to identify studies evaluating the incidence of AKI (by standard AKI definitions), AKI requiring renal replacement therapy (RRT), and mortality risk of AKI in patients undergoing cardiac transplantation. Pooled AKI incidence and mortality risk from the included studies were consolidated by random-effects model. The protocol for this study is registered with PROSPERO (no. CRD42019134577). Results: 27 cohort studies with 137,201 patients undergoing cardiac transplantation were identified. Pooled estimated incidence of AKI and AKI requiring RRT was 47.1% (95% CI: 37.6-56.7%) and 11.8% (95% CI: 7.2-18.8%), respectively. The pooled ORs of hospital mortality and/or 90-day mortality among patients undergoing cardiac transplantation with AKI and AKI requiring RRT were 3.46 (95% CI, 2.40-4.97) and 13.05 (95% CI, 6.89-24.70), respectively. The pooled ORs of 1-year mortality among patients with AKI and AKI requiring RRT were 2.26 (95% CI, 1.56-3.26) and 3.89 (95% CI, 2.49-6.08), respectively. Conclusion: Among patients undergoing cardiac transplantation, the incidence of AKI and severe AKI requiring RRT are 47.1% and 11.8%, respectively. AKI post cardiac transplantation is associated with reduced short term and 1-year patient survival.

The Potential for Renal Injury Elicited by Physical Work in the Heat

An epidemic of chronic kidney disease (CKD) is occurring in laborers who undertake physical work in hot conditions. Rodent data indicate that heat exposure causes kidney injury, and when this injury is regularly repeated it can elicit CKD. Studies in humans demonstrate that a single bout of exercise in the heat increases biomarkers of acute kidney injury (AKI). Elevations in AKI biomarkers in this context likely reflect an increased susceptibility of the kidneys to AKI. Data largely derived from animal models indicate that the mechanism(s) by which exercise in the heat may increase the risk of AKI is multifactorial. For instance, heat-related reductions in renal blood flow may provoke heterogenous intrarenal blood flow. This can promote localized ischemia, hypoxemia and ATP depletion in renal tubular cells, which could be exacerbated by increased sodium reabsorption. Heightened fructokinase pathway activity likely exacerbates ATP depletion occurring secondary to intrarenal fructose production and hyperuricemia. Collectively, these responses can promote inflammation and oxidative stress, thereby increasing the risk of AKI. Equivalent mechanistic evidence in humans is lacking. Such an understanding could inform the development of countermeasures to safeguard the renal health of laborers who regularly engage in physical work in hot environments.

Exercise-Induced Acute Kidney Injury in a Police Officer with Hereditary Renal Hypouricemia

Hereditary renal hypouricemia is characterized by hypouricemia with hyper-uric acid clearance due to a defect in renal tubular transport. Patients with hereditary renal hypouricemia have a higher risk of exercise-induced acute kidney injury (EAKI) and reduced kidney function. Although the best preventive measure is avoiding exercise, there are many kinds of jobs that require occupational exercise. A 27-year-old male police officer suffered from stage 3 AKI after performing a 20-m multistage shuttle run test. His mother had previously been diagnosed as having renal hypouricemia at another facility. The patient had reported having hypouricemia during a health check at a previous police station, but his serum uric acid concentration was within the normal range at our hospital. After treatment, he recovered from EAKI and exhibited low serum uric acid and hyper-uric acid clearance. Since the patient desired to continue his career requiring strenuous exercise, it was difficult to establish a preventive plan against the recurrence of EAKI. Patients with hereditary renal hypouricemia who must undergo strenuous occupational anaerobic exercise are at higher risk of developing EAKI than other workers. The risks of EAKI among patients with hypouricemia should be considered when undergoing physical occupational training.

Metabolomic and biochemical characterization of a new model of the transition of acute kidney injury to chronic kidney disease induced by folic acid

Background

Renal diseases represent a major public health problem. The demonstration that maladaptive repair of acute kidney injury (AKI) can lead to the development of chronic kidney disease (CKD) and end-stage renal disease has generated interest in studying the pathophysiological pathways involved. Animal models of AKI–CKD transition represent important tools to study this pathology. We hypothesized that the administration of multiple doses of folic acid (FA) would lead to a progressive loss of renal function that could be characterized through biochemical parameters, histological classification and nuclear magnetic resonance (NMR) profiling.

Methods

Wistar rats were divided into groups: the control group received a daily intraperitoneal (I.P.) injection of double-distilled water, the experimental group received a daily I.P. injection of FA (250 mg kg body weight⁻¹). Disease was classified according to blood urea nitrogen level: mild (40–80 mg dL⁻¹), moderate (100–200 mg dL⁻¹) and severe (>200 mg dL⁻¹). We analyzed through biochemical parameters, histological classification and NMR profiling.

Results

Biochemical markers, pro-inflammatory cytokines and kidney injury biomarkers differed significantly (P < 0.05) between control and experimental groups. Histology revealed that as damage progressed, the degree of tubular injury increased, and the inflammatory infiltrate was more evident. NMR metabolomics and chemometrics revealed differences in urinary metabolites associated with CKD progression. The main physiological pathways affected were those involved in energy production and amino-acid metabolism, together with organic osmolytes. These data suggest that multiple administrations of FA induce a reproducible model of the induction of CKD. This model could help to evaluate new strategies for nephroprotection that could be applied in the clinic.

Pioglitazone Improves the Function of Human Mesenchymal Stem Cells in Chronic Kidney Disease Patients

Mesenchymal stem cells (MSCs) are optimal sources of autologous stem cells for cell-based therapy in chronic kidney disease (CKD). However, CKD-associated pathophysiological conditions, such as endoplasmic reticulum (ER) stress and oxidative stress, decrease MSC function. In this work, we study the protective effect of pioglitazone on MSCs isolated from CKD patients (CKD-MSCs) against CKD-induced ER stress. In CKD-MSCs, ER stress is found to induce mitochondrial reactive oxygen species generation and mitochondrial dysfunction. Treatment with pioglitazone reduces the expression of ER stress markers and mitochondrial fusion proteins. Pioglitazone increases the expression of cellular prion protein (PrP^C) in CKD-MSCs, which is dependent on the expression levels of proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Treatment with pioglitazone is found to protect CKD-MSCs against reactive oxygen species generation, aberrant mitochondrial oxidative phosphorylation of complexes I and IV, and aberrant proliferation capacity through the PGC-1α-PrP^C axis. These results indicate that pioglitazone protects the mitochondria of MSCs from CKD-induced ER stress. Pioglitazone treatment of CKD-MSCs may be a potential therapeutic strategy for CKD patients.

Hyperhomocysteinemia Accelerates Acute Kidney Injury to Chronic Kidney Disease Progression by Downregulating Heme Oxygenase-1 Expression

AIMS

The risk factors promoting acute kidney injury (AKI) to chronic kidney disease (CKD) progression remain largely unknown. The aim of the present study was to investigate whether hyperhomocysteinemia (Hhcy) accelerates the development of renal fibrosis after AKI.

RESULTS

Hhcy aggravated ischemia-reperfusion-induced AKI and the subsequent development of renal fibrotic lesions characterized by excessive extracellular matrix deposition. Mechanistically, the RNA binding protein human antigen R (HuR) bound to the 3'-untranslated region (3'-UTR) of heme oxygenase-1 (HO-1) messenger RNA (mRNA). Homocysteine (Hcy) downregulated HuR expression, reduced the binding of HuR to the 3'-UTR of HO-1, and thereafter decreased HO-1 expression. Administration of the HO-1 inducer cobalt protoporphyrin-IX significantly hindered Hhcy-augmented reactive oxygen species production and renal fibrotic lesions. Innovation and Conclusion: These data indicate that Hhcy might be a novel risk factor that promotes AKI to CKD progression. Lowering Hcy level or HO-1 induction might be a potential therapeutic strategy to improve the outcome of AKI.

EGFR drives the progression of AKI to CKD through HIPK2 overexpression

The molecular mechanism underlying the transition of acute kidney injury (AKI) to chronic kidney disease (CKD) induced by vancomycin (VAN) remains largely unknown. Methods: The mice model of VAN drives AKI to CKD was developed to investigate the role and molecular mechanism of epidermal growth factor receptor (EGFR). The EGF receptor mutant (Wa-2) mice and gefitinib were used to inactivation of EGFR. The homeodomain interacting protein kinase 2 (HIPK2) siRNA was applied to silence of HIPK2. Human proximal tubular epithelial cells (HK-2) were used to explore the molecular regulation methanism of EGFR. ChIp analysis was used to investigate if STAT3 interaction with the promoter of HIPK2. Results: A novel VAN-induced AKI mouse model was established for the first time. Moreover, the expression levels collagen I&IV, α-SMA, p-EGFR and the expression of HIPK2 proteins were upregulated in this model. Interestingly, AKI caused by VAN was markedly attenuated in waved-2 mice at the early stage, as evidenced by the suppression of renal dysfunction, renal cell apoptosis and caspase3 activation. In the latter stage, renal fibrosis and inflammation were significantly ameliorated in Wa-2 mice, accompanied by the downregulation of profibrotic molecules and F4/80. Besides, the expression levels of HIPK2 and p-STAT3 were suppressed in Wa-2 mice during VAN-induced transition of AKI to CKD. In addition, renal fibrosis and inflammation, profibrotic molecules, and EGFR/STAT3/HIPK2 signaling were ameliorated by gefitinib treatment after VAN-induced AKI. These results were consistent with the findings of Wa-2 mice. EGFR/STAT3 signaling mediated VAN-induced HIPK2 expression in HK-2 cells. ChIp analysis revealed that STAT3 directly bound to the promoter region of HIPK2. Finally, inhibition of HIPK2 attenuated the VAN drove the progression of AKI to CKD. Conclusion: These data suggest that EGFR plays an important role in VAN-driven progression of AKI to CKD.

Mitochondrial mechanisms and therapeutics in ischaemia reperfusion injury

Acute kidney injury (AKI) remains a major problem in critically unwell children and young adults. Ischaemia reperfusion (IR) injury is a major contributor to the development of AKI in a significant proportion of these cases and mitochondria are increasingly recognised as being central to this process through generation of a burst of reactive oxygen species early in reperfusion. Mitochondria have additionally been shown to have key roles in downstream processes including activation of the immune response, immunomodulation, and apoptosis and necrosis. The recognition of the central role of mitochondria in IR injury and an increased understanding of the pathophysiology that undermines these processes has resulted in identification of novel therapeutic targets and potential biomarkers. This review summarises a variety of therapeutic approaches that are currently under exploration and may have potential in ameliorating AKI in children in the future.

A Single-Center Retrospective Study of Acute Kidney Injury Incidence in Patients With Advanced Malignancies Treated With Antimitochondrial Targeted Drug

Introduction

Mitochondrial dysfunction plays an important role in the pathophysiology of kidney disease. Inhibitors of mitochondrial metabolism are being developed for the treatment of solid organ and hematologic malignancies. We describe the incidence and clinical features of acute kidney injury (AKI) in patients treated with the antimitochondrial drug CPI-613.

Methods

We identified 33 patients with relapsed or refractory malignancy, previously enrolled in 3 open-label phase II studies, who received single-agent CPI-613 chemotherapy. AKI was defined by the Kidney Disease Improving Global Outcomes serum creatinine criteria. Participants were followed for a median (25th–75th percentile) of 120.0 (74.0–301.0) days. Risk factors for AKI were assessed by proportional hazards regression using univariate and multivariate analyses.

Results

Participants had baseline mean (SD) age of 63.8 (11.6) years and serum creatinine 0.9 (0.3) mg/dl. AKI developed in 9 (27%) patients; chart review failed to identify a potential cause of AKI other than CPI-613 administration in 5 (15%) patients, of whom 1 had AKI stage 1, 1 had AKI stage 2, and 3 experienced AKI stage 3. Time from initiation of CPI-613 treatment to AKI was 51.0 (16.0–58.0) days. Age, per 5-year increase, was associated with higher risk of AKI (adjusted hazard ratio 2.01, 95% confidence interval 1.06–3.79, P = 0.03). Follow-up serum creatinine was available in 4 participants 174.8 (139.6) days after the episode of AKI; 3 patients had complete recovery in kidney function and 1 had partial recovery.

Conclusion

AKI is a possible complication during treatment with mitochondria-targeted chemotherapy.

Pro-resolving lipid mediators: Agents of anti-ageing?

Inflammation is an essential response to injury and its timely and adequate resolution permits tissue repair and avoidance of chronic inflammation. Ageing is associated with increased inflammation, sub-optimal resolution and these act as drivers for a number of ageing-associated pathologies. We describe the role played by specialised proresolving lipid mediators (SPMs) in the resolution of inflammation and how insufficient levels of these mediators, or compromised responsiveness may play a role in the pathogenesis of many ageing-associated pathologies, e.g. Alzheimer's Disease, atherosclerosis, obesity, diabetes and kidney disease. Detailed examination of the resolution phase of inflammation highlights the potential to harness these lipid mediators and or mimetics of their bioactions, in particular, their synthetic analogues to promote effective resolution of inflammation, without compromising the host immune system.

Points of Concern in Post Acute Kidney Injury Management

The incidence of acute kidney injury (AKI) will in the future remain high, partly due to an increase in comorbidities and other AKI favoring factors such as the rise in high-risk diagnostic and therapeutic interventions. AKI has emerged as a major public health concern with high human and financial costs. It has recently been demonstrated that patients surviving an AKI episode show increased all-cause mortality, chronic kidney disease (CKD), ESRD, cardiovascular events, and reduced quality of life. Although it is important to acknowledge that, after an AKI episode, the risk of dying by far exceeds the risk of developing incident or progressive CKD and/or entering a maintenance renal replacement therapy (RRT) program, currently only a minority of patients are referred for renal follow-up, even after AKI-requiring RRT. On the other hand, renal follow-up for all AKI survivors might not be necessary and would represent an overwhelming work load for the health care system. There are at present no clear guidelines on which patients should be referred and on the elements of post AKI care that may improve non-renal and renal outcomes. In this review, we discuss several points of concern in post-AKI management and propose an algorithm on post-AKI care, mainly based on the renal recovery pattern at discharge from the hospital. Potential opportunities to improve care include appropriate risk stratification, close monitoring of kidney function, management of CKD complications, blood pressure control, medication reconciliation, and education of patients and non-nephrologists on AKI and its downstream complications.