Inflammatory cells in ischemic acute renal failure

Role of miRNAs in macrophage-mediated kidney injury

Macrophages, crucial components of the human immune system, can be polarized into M1/M2 phenotypes, each with distinct functions and roles. Macrophage polarization has been reported to be significantly involved in the inflammation and fibrosis observed in kidney injury. MicroRNA (miRNA), a type of short RNA lacking protein-coding function, can inhibit specific mRNA by partially binding to its target mRNA. The intricate association between miRNAs and macrophages has been attracting increasing interest in recent years. This review discusses the role of miRNAs in regulating macrophage-mediated kidney injury. It shows how miRNAs can influence macrophage polarization, thereby altering the biological function of macrophages in the kidney. Furthermore, this review highlights the significance of miRNAs derived from exosomes and extracellular vesicles as a crucial mediator in the crosstalk between macrophages and kidney cells. The potential of miRNAs as treatment applications and biomarkers for macrophage-mediated kidney injury is also discussed.

Assessment of biological organ age using molecular pathology in pre-transplant kidney biopsies

Organ shortage is a major challenge in kidney transplantation but the use of older donors, often with co-morbidities, is hampered by inconsistent outcomes. Methods of accurately stratifying marginal donor organs by clinical and histological assessment are lacking. To better understand organ variability, we profiled the transcriptomes of 271 kidneys from deceased donors at retrieval. Following correction for biopsy composition, we assessed molecular pathways that associated with delayed, and sub-optimal one-year graft function. Analysis of cortical biopsies identified an adaptive immune gene-rich module that significantly associated with increasing age and worse outcomes. Cellular deconvolution using human kidney reference single cell transcriptomes confirmed an increase in kidney-specific B and T cell signatures, as well as kidney macrophage, myofibroblast and fibroblast gene sets in this module. Surprisingly, innate immune pathway and neutrophil gene signature enrichment was associated with better outcomes. Thus, our work uncovers cellular molecular features of pathological organ ageing, identifiable at kidney retrieval, with translational potential.

Advance in Iron Metabolism, Oxidative Stress and Cellular Dysfunction in Experimental and Human Kidney Diseases

Kidney diseases pose a significant global health issue, frequently resulting in the gradual decline of renal function and eventually leading to end-stage renal failure. Abnormal iron metabolism and oxidative stress-mediated cellular dysfunction facilitates the advancement of kidney diseases. Iron homeostasis is strictly regulated in the body, and disturbance in this regulatory system results in abnormal iron accumulation or deficiency, both of which are associated with the pathogenesis of kidney diseases. Iron overload promotes the production of reactive oxygen species (ROS) through the Fenton reaction, resulting in oxidative damage to cellular molecules and impaired cellular function. Increased oxidative stress can also influence iron metabolism through upregulation of iron regulatory proteins and altering the expression and activity of key iron transport and storage proteins. This creates a harmful cycle in which abnormal iron metabolism and oxidative stress perpetuate each other, ultimately contributing to the advancement of kidney diseases. The crosstalk of iron metabolism and oxidative stress involves multiple signaling pathways, such as hypoxia-inducible factor (HIF) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways. This review delves into the functions and mechanisms of iron metabolism and oxidative stress, along with the intricate relationship between these two factors in the context of kidney diseases. Understanding the underlying mechanisms should help to identify potential therapeutic targets and develop novel and effective therapeutic strategies to combat the burden of kidney diseases.

Neutrophil depletion attenuates acute renal injury after exhaustive exercise in mice

Prolonged intense exercise induces acute renal injury; however, the precise mechanism remains unclear. We investigated the effects of neutrophil depletion in male C57BL/6J mice. Male C57BL/6J mice were divided into four groups: sedentary with control antibody; sedentary with antineutrophil antibody; exhaustive exercise with control antibody; and exhaustive exercise with antineutrophil antibody. Antineutrophil (1A8) or control antibody was administered i.p. to the mice before they ran on a treadmill. Plasma levels of creatinine and blood urea nitrogen (BUN) were measured. Renal histology was assessed 24 h after exhaustive exercise, and the concentration of kidney injury molecule (KIM)-1 was measured using an enzyme-linked immunosorbent assay. The expression levels of inflammatory cytokines were measured using qRT-PCR. Furthermore, NADPH oxidase activity and the hydrogen peroxide concentration in the kidney were measured. Immediately after exhaustive exercise, plasma BUN was significantly increased, but creatinine was not. The increase in BUN after exercise was suppressed by 1A8 treatment. The pathological changes manifested as congested and swollen glomeruli and nuclear infiltration after exhaustive exercise. These changes were suppressed by treatment with the 1A8 antibodies. The KIM-1 concentration increased after exhaustive exercise but was reduced by the 1A8 antibodies. Treatment with the 1A8 antibody also decreased exhaustive exercise-induced inflammation and reactive oxygen species levels in the kidney. These results suggest that neutrophils contribute to exercise-induced acute renal injury by regulating inflammation and oxidative stress.

Advances in understanding of dendritic cell in the pathogenesis of acute kidney injury

Acute kidney injury (AKI) is characterized by a rapid decline in renal function and is associated with a high morbidity and mortality rate. At present, the underlying mechanisms of AKI remain incompletely understood. Immune disorder is a prominent feature of AKI, and dendritic cells (DCs) play a pivotal role in orchestrating both innate and adaptive immune responses, including the induction of protective proinflammatory and tolerogenic immune reactions. Emerging evidence suggests that DCs play a critical role in the initiation and development of AKI. This paper aimed to conduct a comprehensive review and analysis of the role of DCs in the progression of AKI and elucidate the underlying molecular mechanism. The ultimate objective was to offer valuable insights and guidance for the treatment of AKI.

The role of non-protein-coding RNAs in ischemic acute kidney injury

Acute kidney injury (AKI) is a condition characterized by a rapid decline in kidney function within a span of 48 hours. It is influenced by various factors including inflammation, oxidative stress, excessive calcium levels within cells, activation of the renin-angiotensin system, and dysfunction in microcirculation. Ischemia-reperfusion injury (IRI) is recognized as a major cause of AKI; however, the precise mechanisms behind this process are not yet fully understood and effective treatments are still needed. To enhance the accuracy of diagnosing AKI during its early stages, the utilization of innovative markers is crucial. Numerous studies suggest that certain noncoding RNAs (ncRNAs), such as long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), play a central role in regulating gene expression and protein synthesis. These ncRNAs are closely associated with the development and recovery of AKI and have been detected in both kidney tissue and bodily fluids. Furthermore, specific ncRNAs may serve as diagnostic markers and potential targets for therapeutic interventions in AKI. This review aims to summarize the functional roles and changes observed in noncoding RNAs during ischemic AKI, as well as explore their therapeutic potential.

Association of preoperative neutrophil-lymphocyte ratio with acute kidney injury in patients with non-cardiac surgery: difference among surgical types

PURPOSE

To examine the relationship between Neutrophil-Lymphocyte Ratio (NLR) and Acute Kidney Injury (AKI) in patients undergoing noncardiac surgery, and subgroup analysis was performed for different types of non-cardiac surgery.

METHODS

The present retrospective cohort study included 10,159 adult patients who underwent major noncardiac surgery at Nanfang Hospital, Southern Medical University, between 2008 and 2018. Postoperative AKI was defined as an increase in serum creatinine level of at least 0.3 mg/dl within 48 h, or 1.5 times higher than baseline within 7 days postoperatively according to the Kidney Disease Improving Global Outcome. The correlation between preoperative NLR and postoperative AKI was determined by stepwise multivariate logistic regression analysis, and the predictive value of NLR was evaluated by the receiver operating characteristics curve (ROC) analysis.

RESULTS

Four hundred and eighty-five (4.77%) patients developed AKI postoperatively. Preoperative NLR was independently associated with postoperative AKI in all patients undergoing non-cardiac surgery (Odds ratio [OR], 1.03; 95% confidence interval [CI], 1.00-1.06). The optimal cut-off value of NLR was 2.12 according ROC analysis. The OR and 95% CI of AKI for NLR > 2.12 was 1.48 (1.21-1.81) compared with NLR ≤ 2.12. In addition, the positive association was mainly shown in patients undergone digestive system surgery with a cut-off value of 2.12 but not in neurological and musculoskeletal system surgeries.

CONCLUSION

The present study confirmed the association of preoperative NLR with postoperative AKI in digestive system surgical patients. A NLR value of 2.12 may be a useful cut-off to evaluate the risk of AKI.

The predictive value of hematological inflammatory markers for acute kidney injury and mortality in adults with hemophagocytic Lymphohistiocytosis: A retrospective analysis of 585 patients

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a rare immunological hyperactivation-related disease with a high mortality rate. The purpose of this study was to examine the relationship between complete blood count parameters and the occurrence of acute kidney injury (AKI) and mortality in patients with HLH.

METHODS

We included 585 adult patients with HLH. Logistic regression models for AKI and 28-day mortality were developed.

RESULTS

Multivariate logistic regression models revealed that hemoglobin (HB) ≤ 7.3 g/dl (adjusted OR, 1.651; 95% CI, 1.044-2.612), hemoglobin-to-red blood cell distribution width ratio (HRR) < 0.49 (adjusted OR, 1.692), neutrophil-to-lymphocyte ratio (NLR) ≥ 3.15 (adjusted OR, 1.697), and neutrophil-to-lymphocyte-platelet ratio (NLPR) ≥ 11.0 (adjusted OR, 1.608) were independent risk factors for the development of AKI. Moreover, lower platelet levels (31 × 109/L < platelets < 84 × 109/L, adjusted OR, 2.133; platelets ≤ 31 × 109/L, adjusted OR, 3.545) and higher red blood cell distribution width-to-platelet ratio (RPR) levels (0.20 < RPR < 0.54, adjusted OR, 2.595; RPR ≥ 0.54, adjusted OR, 4.307), lymphocytes ≤ 0.34 × 109/L (adjusted OR, 1.793), NLPR ≥ 11.0 (adjusted OR, 2.898), and the aggregate index of systemic inflammation (AISI) ≤ 7 (adjusted OR,1.778) were also independent risk factors for 28-day mortality. Furthermore, patients with AKI had a worse prognosis than those without AKI (P < 0.05).

CONCLUSION

In patients with HLH, hematological parameters are of great value for the early identification of patients at high risk of AKI and 28-day mortality.

Neutrophil diversity and plasticity: Implications for organ transplantation

Neutrophils, as the first defenders against external microbes and stimuli, are highly active and finely regulated innate immune cells. Emerging evidence has challenged the conventional dogma that neutrophils are a homogeneous population with a short lifespan that promotes tissue damage. Recent findings on neutrophil diversity and plasticity in homeostatic and disease states have centered on neutrophils in the circulation. In contrast, a comprehensive understanding of tissue-specialized neutrophils in health and disease is still lacking. This article will first discuss how multiomics advances have contributed to our understanding of neutrophil heterogeneity and diversification in resting and pathological settings. This discussion will be followed by a focus on the heterogeneity and role of neutrophils in solid organ transplantation and how neutrophils may contribute to transplant-related complications. The goal of this article is to provide an overview of the research on the involvement of neutrophils in transplantation, with the aim that this may draw attention to an underappreciated area of neutrophil research.

Heatstroke-induced acute kidney injury and the innate immune system

Heatstroke can cause multiple organ failure and systemic inflammatory response syndrome as the body temperature rises beyond the body's ability to regulate temperature in a hot environment. Previous studies have indicated that heatstroke-induced acute kidney injury (AKI) can lead to chronic kidney disease. Therefore, there is an urgent need to elucidate the mechanism of heatstroke-induced AKI and to establish methods for its prevention and treatment. Recent reports have revealed that innate immunity, including neutrophils, macrophages, lymphocytes, and mast cells, is deeply involved in heat-induced AKI. In this review, we will discuss the roles of each immune cell in heat-induced renal injury and their potential therapeutic use.

Acute kidney injury in diabetic patients: A narrative review

Diabetes mellitus (DM) is the most common cause of chronic kidney disease, which leads to end-stage renal failure worldwide. Glomerular damage, renal arteriosclerosis, and atherosclerosis are the contributing factors in diabetic patients, leading to the progression of kidney damage. Diabetes is a distinct risk factor for acute kidney injury (AKI) and AKI is associated with faster advancement of renal disease in patients with diabetes. The long-term consequences of AKI include the development of end-stage renal disease, higher cardiovascular and cerebral events, poor quality of life, and high morbidity and mortality. In general, not many studies discussed extensively "AKI in DM." Moreover, articles addressing this topic are scarce. It is also important to know the cause of AKI in diabetic patients so that timely intervention and preventive strategies can be implemented to decrease kidney injury. Aim of this review article is to address the epidemiology of AKI, its risk factors, different pathophysiological mechanisms, how AKI differs between diabetic and nondiabetic patients and its preventive and therapeutic implications in diabetics. The increasing occurrence and prevalence of AKI and DM, as well as other pertinent issues, motivated us to address this topic.

PPARγ Regulates Macrophage Polarization by Inhibiting the JAK/STAT Pathway and Attenuates Myocardial Ischemia/Reperfusion Injury In Vivo

This study aimed to investigate the role of PPARγ and underlying mechanisms in myocardial ischemia/reperfusion injury (IRI). IRI was surgically induced in mice and neonatal rat cardiomyocytes (NRCM) were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R). Quantitative genetic analysis and western blotting were performed to assess mRNA and protein levels, respectively, of PPARγ, as well as of different inflammatory, fibrosis, and apoptosis markers in cells and tissues. PPARγ was overexpressed in the heart of mice and NRCMs by viral transfection. Apoptosis and fibrosis were detected by TUNEL and Masson's trichrome staining, respectively. Enzyme-linked immunosorbent assay was performed to detect M1 and M2 macrophage-related inflammatory factors present in mouse sera. PPARγ overexpression significantly inhibited OGD/R- and IRI-induced cardiomyocyte apoptosis and fibrosis in vitro and in vivo. Moreover, PPARγ overexpression inhibited IRI-induced secretion of M1-related proinflammatory factors, whereas it supported the secretion of M2-related anti-inflammatory factors. Notably, these events were found to be mediated by the JAK/STAT pathway. In conclusion, PPARγ regulates macrophage polarization upon IRI via the JAK/STAT pathway, which will in turn prevent myocardial apoptosis and fibrosis. Hence, PPARγ may represent a valuable target for myocardial IRI treatment.

Incidence, predictors, and short-term outcomes of acute kidney injury in children with diabetic ketoacidosis: a systematic review

BACKGROUND

One-third of children with type 1 diabetes mellitus manifest with diabetic ketoacidosis (DKA). Most children presenting with DKA are in a volume-depleted state, leading to acute kidney injury (AKI). Besides volume depletion, hyperglycemia can induce tubular injury and kidney inflammation. Therefore, a thorough knowledge of incidence of AKI, risk factors, and outcomes in pediatric DKA is desirable to improve its management and outcomes.

OBJECTIVE

To synthesize currently available evidence on the incidence, risk factors, and outcomes of AKI in children with DKA.

DATA SOURCES

We searched three electronic databases (EMBASE, PubMed, and Web of Science) from inception to September 2022 for original studies reporting AKI in children with DKA. Search strategies for the individual databases were drafted using free text words and MeSH incorporating "acute kidney injury" and "diabetic ketoacidosis."

STUDY ELIGIBILITY CRITERIA

Cohort and cross-sectional studies reporting AKI in children with type 1 DM and DKA were included.

PARTICIPANTS AND INTERVENTIONS

Children (aged less than 18 years) with type 1 DM and DKA.

STUDY APPRAISAL AND SYNTHESIS METHODS

The critical appraisal tool of NHLBI for cohort studies was used to assess the quality of the studies. We estimated the pooled incidence of AKI with 95% CI in children with DKA using a random effects model. The primary outcome was the pooled incidence of AKI during the DKA episodes.

RESULTS

Twenty-one studies assessing 4087 children (4500 DKA episodes) reported AKI during DKA episodes. The pooled incidence of any stage of AKI during the DKA episode was 47% (95% CI: 40 to 55). Severe AKI was observed in 28% (21 to 35) of DKA episodes; however, only 4% (1 to 11%) of children with AKI received dialysis. Low serum bicarbonate, low corrected sodium, higher blood sugar, and high blood urea nitrogen at presentation have been reported to be associated with the development of AKI.

CONCLUSION

AKI developed in almost half of the DKA episodes, and every fourth DKA episode was associated with severe AKI. The recovery rate from DKA-associated AKI appears to be high; however, further studies are needed to assess the exact impact of AKI on long-term outcomes.

REGISTRATION

PROSPERO (CRD42022303200). A higher resolution version of the Graphical abstract is available as Supplementary information.

Acute kidney injury post-abdominal surgery in infants: implications for prevention and management

Acute kidney injury (AKI) is common in critically ill infants and is associated with long-term sequelae including hypertension and chronic kidney disease. The etiology of AKI in infants is multifactorial. There is robust literature highlighting the risk of AKI after cardiothoracic surgery in infants. However, risk factors and outcomes for AKI in infants after abdominal surgery remains limited. This article reviews the epidemiology and association of abdominal surgery with postoperative AKI and suggests methods for AKI management and prevention. Postoperative AKI may result from hemodynamic shifts, hypoxia, exposure to nephrotoxic medications, and inflammation. Infants in the intensive care unit after intraabdominal surgeries have a unique set of risk factors that predispose them to AKI development. Prematurity, sepsis, prolonged operation time, emergent nature of the procedure, and diagnosis of necrotizing enterocolitis increase risk of AKI after intrabdominal surgeries. Prevention, early diagnosis, and management of AKI post-abdominal surgery is imperative to clinical practice. Close monitoring of urine output, serum creatinine, and fluid status is necessary in infants after abdominal surgery. A recent study suggests elevated levels of a urinary biomarker, neutrophil gelatinase-associated lipocalin (NGAL), 24 h after an abdominal procedure may improve early prediction of AKI. Identification of risk factors, avoidance of nephrotoxic medications, careful fluid balance, early detection of AKI, and maintenance of hemodynamic stability is imperative to potentially prevent and/or mitigate AKI.

microRNA-338-3p suppresses lipopolysaccharide-induced inflammatory response in HK-2 cells

BACKGROUND

Inflammation is the most common cause of kidney damage, and inflammatory responses in a number of diseases are mediated by microRNA-338-3p (miR-338-3p). However, there are only a few reports which described the regulation of miR-338-3p in human proximal tubular cells. The goal of this study was to see how miR-338-3p affected lipopolysaccharide (LPS)-caused inflammatory response in HK-2 cells.

METHODS

LPS was used to construct an inflammatory model in HK-2 cells. miR-338-3p mimic was used to increase the levels of miR-338-3p in HK-2 cells. MTT, JC-1 staining, and apoptosis assays were used to detect cell viability, mitochondrial membrane potential (MMP), and apoptosis, respectively. The production of inflammatory factors and the levels of p38, p65, phospho-p65, phospho-p38, Bax, Bcl-2, cleaved caspase-9, and cleaved caspase-3 were investigated using real-time polymerase chain reaction, western blotting, or enzyme-linked immunosorbent assay.

RESULTS

The levels of miR-338-3p were significantly lower in serum from patients with sepsis-induced kidney injury compared to the serum from healthy volunteers (P < 0.05). LPS reduced the level of miR-338-3p in HK-2 cells (P < 0.05). HK-2 cell viability, mitochondrial membrane potential, and Bcl-2 mRNA and protein levels were decreased by LPS (all P < 0.05). Apoptosis, the mRNA and protein levels of inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α) and Bax, and the levels of cleaved caspase-9 and caspase-3 were increased by LPS (all P < 0.05). Raising the level of miR-338-3p mitigated these effects of LPS (all P < 0.05).

CONCLUSION

LPS-induced inflammation in HK-2 cells is reduced by miR-338-3p.

Transcriptional profile changes after treatment of ischemia reperfusion injury-induced kidney fibrosis with 18β-glycyrrhetinic acid

Introduction

Chronic kidney disease (CKD) is characterized by renal fibrosis without effective therapy. 18β-Glycyrrhetinic acid (GA) is reported to have detoxification and anti-inflammatory functions and promotes tissue repair. However, the role of GA in CKD remains unclear. In this study, we investigated whether GA has a potential therapeutic effect in kidney fibrosis.

Methods

A renal fibrosis mouse model was established by ischemia/reperfusion (I/R) injury via clamping unilateral left renal pedicle for 45 min; then, the mice were treated with vehicle or GA. Kidney tissues and blood samples were extracted 14 days after reperfusion and renal function, histopathological staining, quantitative PCR, and western blotting were performed. RNA-seq was performed to explore the changes in the transcriptional profile after GA treatment.

Results

Renal function, pathological and molecular analysis displayed that fibrosis was successfully induced in the I/R model. In the GA treatment group, the severity of fibrosis gradually reduced with the best effect seen at a concentration of 25 mg kg ⁻¹. A total of 970 differentially expressed genes were identified. Pathway enrichment showed that reduced activation and migration of inflammatory cells and decreased chemokine interaction in significant pathways. Protein–protein interaction networks were constructed and 15 hub genes were selected by degree rank, including chemokines, such as C3, Ccl6, Ccr2, Ptafr, Timp1, and Pf4.

Conclusions

GA may alleviate renal fibrosis by inhibiting the inflammatory response. GA is a promising therapy that may perhaps be used in treating renal fibrosis and CKD.

The complement system in pediatric acute kidney injury

The complement cascade is an important part of the innate immune system. In addition to helping the body to eliminate pathogens, however, complement activation also contributes to the pathogenesis of a wide range of kidney diseases. Recent work has revealed that uncontrolled complement activation is the key driver of several rare kidney diseases in children, including atypical hemolytic uremic syndrome and C3 glomerulopathy. In addition, a growing body of literature has implicated complement in the pathogenesis of more common kidney diseases, including acute kidney injury (AKI). Complement-targeted therapeutics are in use for a variety of diseases, and an increasing number of therapeutic agents are under development. With the implication of complement in the pathogenesis of AKI, complement-targeted therapeutics could be trialed to prevent or treat this condition. In this review, we discuss the evidence that the complement system is activated in pediatric patients with AKI, and we review the role of complement proteins as biomarkers and therapeutic targets in patients with AKI.

Inflammation in kidney repair: Mechanism and therapeutic potential

The kidney has a remarkable ability of repair after acute kidney injury (AKI). However, when injury is severe or persistent, the repair is incomplete or maladaptive and may lead to chronic kidney disease (CKD). Maladaptive kidney repair involves multiple cell types and multifactorial processes, of which inflammation is a key component. In the process of inflammation, there is a bidirectional interplay between kidney parenchymal cells and the immune system. The extensive and complex crosstalk between renal tubular epithelial cells and interstitial cells, including immune cells, fibroblasts, and endothelial cells, governs the repair and recovery of the injured kidney. Further research in this field is imperative for the discovery of biomarkers and promising therapeutic targets for kidney repair. In this review, we summarize the latest progress in the immune response and inflammation during maladaptive kidney repair, analyzing the interaction between immune cells and intrinsic kidney cells, pointing out the potentialities of inflammation-related pathways as therapeutic targets, and discussing the challenges and future research prospects in this field.

Protective Effects of PPARγ on Renal Ischemia-Reperfusion Injury by Regulating miR-21

Renal ischemia-reperfusion injury (RIRI) is a common pathological process that causes kidney injury. Previous studies have indicated that both peroxisome proliferator-activated receptor γ (PPARγ) and microRNA-21 (miR-21) exert protective effects against RIRI. However, their relationship is not well understood. In the present study, we investigated the role of the PPARγ/miR-21/programmed cell death 4 (PDCD4) axis in IRI, both in vivo and in vitro. In vitro cell hypoxia/reoxygenation (H/R) and in vivo RIRI models were established, and cell viability, cell apoptosis, and key molecule expression profiles were analyzed. Our results showed that both PPARγ and miR-21 had protective effects against RIRI to varying degrees, and there was an interaction between PPARγ and miR-21. PPARγ could promote the expression of miR-21 and partially protect against RIRI by reducing the level of the miR-21 target protein (PDCD4). Our findings underscore the potential utility of future clinical investigations of PPARγ activation and targeting of the underlying miR-21/PDCD4/caspase-3 pathway, which may participate in the pathogenesis of human IRI.

Urinary interleukin-6 is a potentially useful diagnostic and prognostic marker of acute kidney injury in dogs

BACKGROUND

Interleukin-6 (IL6) is a pro-inflammatory cytokine implicated in the pathophysiology of urinary tract diseases. The objective of this study was to evaluate the diagnostic and prognostic utilities of urinary IL6 (uIL6) in dogs with acute kidney injury (AKI) and other urinary tract diseases.

METHODS

Eighty client-owned dogs were included and divided into four groups: AKI, chronic kidney disease (CKD), urinary tract infection and healthy controls. Urine samples were analysed for uIL6 and normalised to urinary creatinine (uIL6/uCr).

RESULTS

Dogs in the AKI group had higher uIL6/uCr compared with the control and CKD groups (p < 0.001 and 0.012, respectively). Receiver operator characteristic (ROC) curve analysis of uIL6/uCr as a diagnostic marker for AKI had an area under the curve (AUC) of 0.91 (95% confidence interval [CI], 0.81-1.0) with 82% sensitivity and 90% specificity (cutoff point 4.5 pg/mg) when including the AKI and control groups. ROC analysis including AKI compared with all other groups had an AUC of 0.77 (95% CI, 0.67-0.87) for the diagnosis of AKI with sensitivity and specificity of 71% and 78%, respectively (cutoff point 10.4 pg/mg). The 30-day mortality of the AKI group was 34%, and there was no difference in uIL6/uCr between survivors and non-survivors of AKI.

CONCLUSIONS

uIL6/uCr is a potentially sensitive and specific diagnostic marker for AKI in dogs.

Prognostic Value of Systemic Immune-Inflammation Index among Critically Ill Patients with Acute Kidney Injury: A Retrospective Cohort Study

Inflammation plays a significant role in the occurrence and development of acute kidney injury (AKI). Evidence regarding the prognostic effect of the systemic immune-inflammation index (SII) in critically ill patients with AKI is scarce. The aim of this study was to assess the association between SII and all-cause mortality in these patients. Detailed clinical data were extracted from the Medical Information Mart for Intensive Care Database (MIMIC)-IV. The primary outcome was set as the in-hospital mortality. A total of 10,764 AKI patients were enrolled in this study. The restricted cubic splines analyses showed a J-shaped curve between SII and the risk of in-hospital and ICU mortality. After adjusting for relevant confounders, multivariate Cox regression analysis showed that both lower and higher SII levels were associated with an elevated risk of in-hospital all-cause mortality. A similar trend was observed for ICU mortality. In summary, we found that the SII was associated in a J-shaped pattern with all-cause mortality among critically ill patients with AKI. SII appears to be have potential applications in the clinical setting as a novel and easily accessible biomarker for predicting the prognosis of AKI patients.

Renal Injuries after Cardiac Arrest: A Morphological Ultrastructural Study

BACKGROUND

This study aims to investigate the probable lesions and injuries induced in the renal tissue after a cardiac arrest. The renal ischemia-reperfusion model in cardiac arrest describes the effects of ischemia in the kidneys, alongside a whole-body ischemia-reperfusion injury. This protocol excludes ischemic conditions caused by surgical vascular manipulation, venous injury or venous congestion.

METHODS

For the experimental study, 24 swine were subjected to cardiac arrest. Seven minutes later, the cardiopulmonary resuscitation technique was performed for 5 min. Afterwards, advanced life support was provided. The resuscitated swine consisted one group and the non-resuscitated the other. Tissue samples were obtained from both groups for light and electron microscopy evaluation.

RESULTS

Tissue lesions were observed in the tubules, parallel to destruction of the microvilli, reduction in the basal membrane invaginations, enlarged mitochondria, cellular vacuolization, cellular apoptosis and disorganization. In addition, fusion of the podocytes, destruction of the Bowman's capsule parietal epithelium and abnormal peripheral urinary space was observed. The damage appeared more extensive in the non-resuscitated swine group.

CONCLUSIONS

Acute kidney injury is not the leading cause of death after cardiac arrest. However, evidence suggests that the kidney damage after a cardiac arrest should be highly considered in the prognosis of the patients' health outcome.

Macrophage depletion attenuates acute renal damage after exhaustive exercise in mice

Exhaustive exercise is known to induce acute renal damage. However, the precise mechanisms remain unclear. We investigated the effects of macrophage depletion on exhaustive exercise-induced acute renal damage. Male C57BL/6 J mice were divided into four groups: sedentary with control liposome (n=8), sedentary with clodronate liposome (n=8), exhaustive exercise with control liposome (n=8), and exhaustive exercise with clodronate liposome (n=8). Mice were treated with clodronate liposomes or control liposomes intraperitoneally for 48 h before undergoing exhaustive exercise. Renal function and renal histology were tested at 24 h. The expression levels of kidney injury molecule (KIM)-1 and inflammatory cytokines in kidney tissues were measured by quantitative RT-PCR, and KIM-1 concentration was semi-quantified by immunostaining. As a result, exhaustive exercise increased macrophage infiltration into the kidney. However, clodronate reduced it. Although exhaustive exercise resulted in an increase in KIM-1 mRNA expression levels and concentration, injection of clodronate liposome reduced it. In addition, TUNEL positive apoptotic cells were increased after exercise, but significantly reduced by clodronate. Clodronate liposome treatment also decreased the mRNA expression levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the kidney after exhaustive exercise. These results suggest that macrophages play a critical role in increasing renal damage by regulating inflammation.

Bryostatin-1 Attenuates Ischemia-Elicited Neutrophil Transmigration and Ameliorates Graft Injury after Kidney Transplantation

Ischemia reperfusion injury (IRI) is a form of sterile inflammation whose severity determines short- and long-term graft fates in kidney transplantation. Neutrophils are now recognized as a key cell type mediating early graft injury, which activates further innate immune responses and intensifies acquired immunity and alloimmunity. Since the macrolide Bryostatin-1 has been shown to block neutrophil transmigration, we aimed to determine whether these findings could be translated to the field of kidney transplantation. To study the effects of Bryostatin-1 on ischemia-elicited neutrophil transmigration, an in vitro model of hypoxia and normoxia was equipped with human endothelial cells and neutrophils. To translate these findings, a porcine renal autotransplantation model with eight hours of reperfusion was used to study neutrophil infiltration in vivo. Graft-specific treatment using Bryostatin-1 (100 nM) was applied during static cold storage. Bryostatin-1 dose-dependently blocked neutrophil activation and transmigration over ischemically challenged endothelial cell monolayers. When applied to porcine renal autografts, Bryostatin-1 reduced neutrophil graft infiltration, attenuated histological and ultrastructural damage, and improved renal function. Our novel findings demonstrate that Bryostatin-1 is a promising pharmacological candidate for graft-specific treatment in kidney transplantation, as it provides protection by blocking neutrophil infiltration and attenuating functional graft injury.

Transcriptional analysis identifies potential novel biomarkers associated with successful ex-vivo perfusion of human donor lungs

Background

Transplantation is an effective treatment for end‐stage lung disease, but the donor organ shortage is a major problem. Ex‐vivo lung perfusion (EVLP) of extended criteria organs enables functional assessment to facilitate clinical decision‐making around utilization, but the molecular processes occurring during EVLP, and how they differ between more or less viable lungs, remain to be determined.

Methods

We used RNA sequencing of lung tissue to delineate changes in gene expression occurring in 10 donor lungs undergoing EVLP and compare lungs that were deemed non‐transplantable (n = 4) to those deemed transplantable (n = 6) following perfusion.

Results

We found that lungs deemed unsuitable for transplantation had increased induction of innate immune pathways and lower expression of oxidative phosphorylation related genes. Furthermore, the expression of SCGB1A1, a gene encoding an anti‐inflammatory secretoglobin CC10, and other club cell genes was significantly decreased in non‐transplantable lungs, while CHIT‐1 was increased. Using a larger validation cohort (n = 17), we confirmed that the ratio of CHIT1 and SCGB1A1 protein levels in lung perfusate have potential utility to distinguish transplantable from non‐transplantable lungs (AUC .81).

Conclusions

Together, our data identify novel biomarkers that may assist with pre‐transplant lung assessment, as well as pathways that may be amenable to therapeutic intervention during EVLPAQ6.

Inflammation: improving understanding to prevent or ameliorate kidney diseases

Inflammatory processes are believed to play an important role in immune response to maintain tissue homeostasis by activating cellular signaling pathways and releasing inflammatory mediators in the injured tissue. Although acute inflammation can be considered protective, an uncontrolled inflammation may evolve to tissue damage, leading to chronic inflammatory diseases. Inflammation can be considered the major factor involved in the pathological progression of acute and chronic kidney diseases. Functional characteristics of this organ increase its vulnerability to developing various forms of injuries, including acute kidney injury (AKI) and chronic kidney disease (CKD). In view of translational research, several discoveries should be considered regarding the pathogenesis of the inflammatory process, which results in the validation of biomarkers for early detection of kidney diseases. Biomarkers enable the identification of proinflammatory mediators in kidney affections, based on laboratory research applied to clinical practice. Some inflammatory molecules can be useful biomarkers for the detection and diagnosis of kidney diseases, such as neutrophil gelatinase-associated lipocalin, kidney injury molecule-1 and interleukin 18.

Immunohistochemical Analysis of 4-HNE, NGAL, and HO-1 Tissue Expression after Apocynin Treatment and HBO Preconditioning in Postischemic Acute Kidney Injury Induced in Spontaneously Hypertensive Rats

Oxidative stress has been considered as a central aggravating factor in the development of postischemic acute kidney injury (AKI). The aim of this study was to perform the immunohistochemical analysis of 4-hydroxynonenal (4-HNE), neutrophil gelatinase-associated lipocalin (NGAL), and heme oxygenase-1 (HO-1) tissue expression after apocynin (APO) treatment and hyperbaric oxygenation (HBO) preconditioning, applied as single or combined protocol, in postischemic acute kidney injury induced in spontaneously hypertensive rats (SHR). Twenty-four hours before AKI induction, HBO preconditioning was carried out by exposing to pure oxygen (2.026 bar) twice a day, for 60 min in two consecutive days. Acute kidney injury was induced by removal of the right kidney while the left renal artery was occluded for 45 min by atraumatic clamp. Apocynin was applied in a dose of 40 mg/kg body weight, intravenously, 5 min before reperfusion. We showed increased 4-HNE renal expression in postischemic AKI compared to Sham-operated (SHAM) group. Apocynin treatment, with or without HBO preconditioning, improved creatinine and phosphate clearances, in postischemic AKI. This improvement in renal function was accompanied with decreased 4-HNE, while HO-1 kidney expression restored close to the control group level. NGAL renal expression was also decreased after apocynin treatment, and HBO preconditioning, with or without APO treatment. Considering our results, we can say that 4-HNE tissue expression can be used as a marker of oxidative stress in postischemic AKI. On the other hand, apocynin treatment and HBO preconditioning reduced oxidative damage, and this protective effect might be expected even in experimental hypertensive condition.

Dynamics in perioperative neutrophil-to-lymphocyte*platelet ratio as a predictor of early acute kidney injury following cardiovascular surgery

BACKGROUND

In this study, we applied a composite index of neutrophil-lymphocyte * platelet ratio (NLPR), and explore the significance of the dynamics of perioperative NLPR in predicting cardiac surgery-associated acute kidney injury (CSA-AKI).

METHODS

During July 1^st and December 31^th 2019, participants were prospectively derived from the 'Zhongshan Cardiovascular Surgery Cohort'. NLPR was determined using neutrophil counts, lymphocyte and platelet count at the two-time points. Dose-response relationship analyses were applied to delineate the non-linear odds ratio (OR) of CSA-AKI in different NLPR levels. Then NLPRs were integrated into the generalized estimating equation (GEE) to predict the risk of AKI.

RESULTS

Of 2449 patients receiving cardiovascular surgery, 838 (34.2%) cases developed CSA-AKI with stage 1 (n = 658, 26.9%), stage 2-3 (n = 180, 7.3%). Compared with non-AKI patients, both preoperative and postoperative NLPR were higher in AKI patients (1.1[0.8, 1.8] vs. 0.9[0.7,1.4], p < 0.001; 12.4[7.5, 20.0] vs. 10.1[6.4,16.7], p < 0.001). Such an effect was a 'J'-shaped relationship: CSA-AKI's risk was relatively flat until 1.0 of preoperative NLPR and increased rapidly afterward, with an odds ratio of 1.13 (1.06-1.19) per 1 unit. Similarly, patients whose postoperative NLPR value >11.0 were more likely to develop AKI with an OR of 1.02. Integrating the dynamic NLPRs into the GEE model, we found that the AUC was 0.806(95% CI 0.793-0.819), which was significantly higher than the AUC without NLPR (0.799, p < 0.001).

CONCLUSION

Dynamics of perioperative NPLR is a promising marker for predicting acute kidney injury. It will facilitate AKI risk management and allow clinicians to intervene early so as to reverse renal damage.

Cytokine absorption during human kidney perfusion reduces delayed graft function-associated inflammatory gene signature

Transplantation is the optimal treatment for most patients with end-stage kidney disease but organ shortage is a major challenge. Normothermic machine perfusion (NMP) has been used to recondition marginal organs; however, mechanisms by which NMP might benefit organs are not well understood. Using pairs of human kidneys obtained from the same donor, we compared the effect of NMP with that of cold storage on the global kidney transcriptome. We found that cold storage led to a global reduction in gene expression, including inflammatory pathway genes and those required for energy generation processes, such as oxidative phosphorylation (OXPHOS). In contrast, during NMP, there was marked upregulation OXPHOS genes, but also of a number of immune and inflammatory pathway genes. Using biopsies from kidneys undergoing NMP that were subsequently transplanted, we found that higher inflammatory gene expression occurred in organs with prolonged delayed graft function (DGF). Therefore, we used a hemoadsorber (HA) to remove pro-inflammatory cytokines. This attenuated inflammatory gene expression increased OXPHOS pathway genes and had potentially clinically important effects in reducing the expression of a DGF-associated gene signature. Together, our data suggest that adsorption of pro-inflammatory mediators from the perfusate represents a potential intervention which may improve organ viability.

Dexmedetomidine Exerts Renal Protective Effect by Regulating the PGC-1α/STAT1/IRF-1 Axis

BACKGROUND

Ischemia-reperfusion (I/R) injury is the main cause of acute kidney injury (AKI), and its incidence and mortality increase year by year in the population. Dexmedetomidine (DEX) can improve AKI by regulating inflammation and oxidative stress, but its mechanism is still unclear.

METHODS

A hypoxia/reoxygenation (H/R) model of HK-2 cells and a kidney I/R model of C57BL/6J mice were established. In the experiment, cells were transfected with sh-PGC-1α to inhibit PGC-1α expression. The changes of ROS level and mitochondrial membrane potential (MMP) were analyzed. HE staining was used to assess kidney damage in mice. Concentration of kidney injury markers serum creatinine and blood urea nitrogen and expression of inflammatory factors were detected by ELISA. qPCR analysis was used to detect mRNA levels of related proteins in cells and mouse kidney tissues. The protein intracellular content and phosphorylation levels were determined by Western blotting.

RESULT

The production of inflammatory factors and ROS was increased in HK-2 cells treated with H/R, while MMP, cell viability, and mitochondrial-related protein levels were decreased. DEX attenuated pathological changes induced by H/R, while knockdown of PGC-1α eliminated the mitigation effect. DEX inhibited the damage of I/R to the kidneys of mice and increased the expression of mitochondrial-related proteins and PGC-1α in the kidneys, while inhibiting the phosphorylation of STAT1 and the expression of IRF-1.

CONCLUSIONS

DEX appears to inhibit mitochondrial damage and cellular inflammation by upregulating PGC-1α to affect STAT1 phosphorylation level and IRF-1 expression, thereby preventing AKI.

PPARγ in Ischemia-Reperfusion Injury: Overview of the Biology and Therapy

Ischemia-reperfusion injury (IRI) is a complex pathophysiological process that is often characterized as a blood circulation disorder caused due to various factors (such as traumatic shock, surgery, organ transplantation, burn, and thrombus). Severe metabolic dysregulation and tissue structure destruction are observed upon restoration of blood flow to the ischemic tissue. Theoretically, IRI can occur in various tissues and organs, including the kidney, liver, myocardium, and brain, among others. The advances made in research regarding restoring tissue perfusion in ischemic areas have been inadequate with regard to decreasing the mortality and infarct size associated with IRI. Hence, the clinical treatment of patients with severe IRI remains a thorny issue. Peroxisome proliferator-activated receptor γ (PPARγ) is a member of a superfamily of nuclear transcription factors activated by agonists and is a promising therapeutic target for ameliorating IRI. Therefore, this review focuses on the role of PPARγ in IRI. The protective effects of PPARγ, such as attenuating oxidative stress, inhibiting inflammatory responses, and antagonizing apoptosis, are described, envisaging certain therapeutic perspectives.

Recombinant apoptosis inhibitor of macrophage protein reduces delayed graft function in a murine model of kidney transplantation

Reperfusion injury following cold and warm ischemia (IRI) is unavoidable during kidney transplantation and contributes to delayed graft function (DGF) and premature graft loss. Death of tubular epithelial cells (TECs) by necrosis during IRI releases pro-inflammatory mediators (e.g. HMGB1), propagating further inflammation (necroinflammation) and tissue damage. Kidney Injury Molecule-1 (KIM-1) is a phagocytic receptor upregulated on proximal TECs during acute kidney injury. We have previously shown that renal KIM-1 protects the graft against transplant associated IRI by enabling TECs to clear apoptotic and necrotic cells, and that recognition of necrotic cells by KIM-1 is augmented in the presence of the opsonin, apoptosis inhibitor of macrophages (AIM). Here, we tested whether recombinant AIM (rAIM) could be used to mitigate transplant associated IRI. We administered rAIM or vehicle control to nephrectomised B6 mice transplanted with a single B6 donor kidney. Compared to grafts in vehicle-treated recipients, grafts from rAIM-treated mice exhibited significantly less renal dysfunction, tubular cell death, tissue damage, tubular obstruction, as well as local and systemic inflammation. Both mouse and human rAIM enhanced the clearance of necrotic cells by murine and human TECs, respectively in vitro. These data support testing of rAIM as a potential therapeutic agent to reduce DGF following kidney transplantation.

Protective Effect of Hydroalcoholic Extract of Stachys pilifera on Oxidant-Antioxidant Status in Renal Ischemia/Reperfusion Injuries in Male Rats

Background

Renal ischemia-reperfusion (I/R) has a pivotal role in the progression of acute renal failure. Reactive oxygen species are considered the major constituents involved in the biochemical and pathophysiological changes that were shown during kidney I/R. The purpose of this study was to examine the renoprotective effects of Stachys pilifera ethanolic extract on oxidant-antioxidant status in renal I/R-injuries in male rats. Material and methods. Twenty-one male Wistar rats were arbitrarily distributed into 3 groups: sham control (SC), I/R, and I/R + Stachys pilifera ethanolic extract (500 mg/kg). The artery and vein of the right kidney were completely blocked, and the right kidney was completely removed in all groups. Then, the left kidney artery was blocked with suture thread for 30 minutes in only I/R and I/R + SP extract groups. Kidney function indices, oxidative stress markers, and hematoxylin and eosin staining were investigated in the plasma and kidney tissues.

Results

It was shown that the urine Na and K, fractional excretion of Na and K, and protein carbonyl content markedly increased in the merely I/R group as compared to SC rats, while the administration of SP extract markedly reduced these indices (P < 0.05). Also, glomerular filtration rate and total thiol meaningfully reduced in the I/R rats in contrast to the SC group, while the treatment with SP extract markedly augmented these indices (P < 0.05). However, in agreement with renal function tests, SP extract had no significant effects on histopathological examinations.

Conclusion

It seems that SP extract employs renoprotective effects on renal damage induced by I/R, possibly by improving of oxidant-antioxidant status in favor of the antioxidant system.

[Therapeutics for acute tubular necrosis in 2020]

Acute kidney injury is a major cause of in-hospital morbidity and mortality because of the serious nature of the underlying illnesses and the high incidence of complications. The two major causes of acute kidney injury that occur in the hospital are prerenal disease and acute tubular necrosis. Acute tubular necrosis has a histological definition, even if a kidney biopsy is rarely performed. Kidney injuries occurring during acute tubular necrosis are underlined by different pathophysiological mechanisms that emphasize the role of hypoxia on the tubular cells such as apoptosis, cytoskeleton disruption, mitochondrial function and the inflammation mediated by innate immune cells. The microcirculation and the endothelial cells are also the targets of hypoxia-mediated impairment. Repair mechanisms are sometimes inadequate because of pro-fibrotic factors that will lead to chronic kidney disease. Despite all the potential therapeutic targets highlighted by the pathophysiological knowledge, further works remain necessary to find a way to prevent these injuries.

Acute Kidney Injury in Pediatric Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common complication of type 1 and 2 diabetes and often presents during adolescence and young adulthood. Given the growing incidence of both type 1 and type 2 diabetes in children and adolescents, DKD represents a significant public health problem. Acute kidney injury (AKI) in youth with diabetes is strongly associated with risk of DKD development. This review will summarize the epidemiology and pathophysiology of AKI in children with diabetes, the relationship between AKI and DKD, and the potential therapeutic interventions. Finally, we will appraise the impact of the recent COVID-19 infection pandemic on AKI in children with diabetes.

Acute Kidney Injury in Pediatric Inflammatory Multisystem Syndrome Temporally Associated With Severe Acute Respiratory Syndrome Coronavirus-2 Pandemic: Experience From PICUs Across United Kingdom

OBJECTIVES

To study the prevalence, evolution, and clinical factors associated with acute kidney injury in children admitted to PICUs with pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2.

DESIGN

Multicenter observational study.

SETTING

Fifteen PICUs across the United Kingdom.

PATIENTS

Patients admitted to United Kingdom PICUs with pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2 between March 14, 2020, and May 20, 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Deidentified data collected as part of routine clinical care were analyzed. All children were diagnosed and staged for acute kidney injury based on the level of serum creatinine above the upper limit of reference interval values according to published guidance. Severe acute kidney injury was defined as stage 2/3 acute kidney injury. Uni- and multivariable analyses were performed to study the association between demographic data, clinical features, markers of inflammation and cardiac injury, and severe acute kidney injury. Over the study period, 116 patients with pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2 were admitted to 15 United Kingdom PICUs. Any-stage acute kidney injury occurred in 48 of 116 patients (41.4%) and severe acute kidney injury in 32 of 116 (27.6%) patients, which was mostly evident at admission (24/32, 75%). In univariable analysis, body mass index, hyperferritinemia, high C-reactive protein, Pediatric Index of Mortality 3 score, vasoactive medication, and invasive mechanical ventilation were associated with severe acute kidney injury. In multivariable logistic regression, hyperferritinemia was associated with severe acute kidney injury (compared with nonsevere acute kidney injury; adjusted odds ratio 1.04; 95% CI, 1.01-1.08; p = 0.04). Severe acute kidney injury was associated with longer PICU stay (median 5 days [interquartile range, 4-7 d] vs 3 days [interquartile range, 1.5-5 d]; p < 0.001) and increased duration of invasive mechanical ventilation (median 4 days [interquartile range, 2-6 d] vs 2 days [interquartile range, 1-3 d]; p = 0.04).

CONCLUSIONS

Severe acute kidney injury occurred in just over a quarter of children admitted to United Kingdom PICUs with pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2. Hyperferritinemia was significantly associated with severe acute kidney injury. Severe acute kidney injury was associated with increased duration of stay and ventilation. Although short-term outcomes for acute kidney injury in pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2 appear good, long-term outcomes are unknown.

Ellagic Acid Ameliorates Renal Ischemic-Reperfusion Injury Through NOX4/JAK/STAT Signaling Pathway

Ellagic acid (EA), a natural polyphenolic compound, has been proved to possess multiple biological activities including alleviating ischemic-reperfusion (I/R) injury. The aim of this current study was to investigate whether EA alleviates I/R injury via regulating inflammatory signaling pathway. Rats were subjected to ischemic-reperfusion (I/R) injury and given orally with different doses of EA before surgery. H&E staining, ELISA assay, and biochemical index analysis were performed to evaluate renal injury and inflammatory factors. Oxidative stress level was detected by DCFH-DA staining and corresponding assay kits. In addition, TUNEL assay and flow cytometric assay were applied for exploring the apoptosis of tissue and cells, respectively. Western blot assay was used to assess protein expressions in tissue and cells. The results showed that EA attenuated the renal I/R injury and reserved renal cell function in vivo. The levels of TNF-a, IL-1β, IL-6, and MCP-1, oxidative stress level, and apoptosis were suppressed in EA-treated rats. Mechanistic studies showed that EA suppressed the phosphorylation of JAK1, JAK2, and STAT1 and reduced the NOX4 level. EA reduced apoptosis, hypoxia-induced inflammatory response, and ROS levels. Moreover, overexpression of NOX4 reversed the protective function with NOX4 inhibition, indicating that the effect of EA against renal IRI or cell hypoxia/reoxygenation might mainly depend on NOX4. The results suggest that EA exerts the renoprotective effect via suppressing NOX4/JAK/STAT signaling pathway, which may be a novel potential therapy for the treatment of acute kidney injury in clinic.

Renoprotective Effects of Origanum majorana Methanolic L and Carvacrol on Ischemia/Reperfusion-Induced Kidney Injury in Male Rats

Background. The most important cause of acute renal failure in normal kidneys is ischemia-reperfusion (I/R) injury. The aim of the current study was to investigate the protective effects of Origanum majorana (OM) methanolic extract, carvacrol, and vitamin E on I/R-induced kidney injury in male rats. Material and Method. Thirty Wistar male rats were randomly allocated into 5 groups; sham, I/R, I/R + OM (300 mg/kg), I/R + carvacrol (75 mg/kg), and I/R + vitamin E (100 mg/kg). Renal function markers, oxidant-antioxidant parameters, and histopathological examination were evaluated. Results. It was exhibited that the urea, creatinine, protein carbonyl, glomerular filtration rate, total thiol, ferric reducing antioxidant power, and histopathological changes markedly reversed in the treatment groups with OM or carvacrol in comparison to the I/R merely group. Conclusion. We conclude that OM extract or its ingredient, carvacrol, exerts renoprotective impacts in I/R-induced kidney injury possibly by scavenging free radicals and increasing antioxidant power.

Inhibition of 15-PGDH prevents ischemic renal injury by the PGE2/EP4 signaling pathway mediating vasodilation, increased renal blood flow, and increased adenosine/A2A receptors

In the present study, we demonstrated the marked activity of SW033291, an inhibitor of 15-hydoxyprostaglandin dehydrogenase (15-PGDH), in preventing acute kidney injury (AKI) in a murine model of ischemia-reperfusion injury. AKI due to ischemic injury represents a significant clinical problem. PGE₂ is vasodilatory in the kidney, but it is rapidly degraded in vivo due to catabolism by 15-PGDH. We investigated the potential of SW033291, a potent and specific 15-PGDH inhibitor, as prophylactic treatment for ischemic AKI. Prophylactic administration of SW033291 significantly increased renal tissue PGE₂ levels and increased post-AKI renal blood flow and renal arteriole area. In parallel, prophylactic SW033291 decreased post-AKI renal morphology injury scores and tubular apoptosis and markedly reduced biomarkers of renal injury that included blood urea nitrogen, creatinine, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1. Prophylactic SW033291 also reduced post-AKI induction of proinflammatory cytokines, high-mobility group box 1, and malondialdehyde. Protective effects of SW033291 were mediated by PGE₂ signaling, as they could be blocked by pharmacological inhibition of PGE₂ synthesis. Consistent with activation of PGE₂ signaling, SW033291 induced renal levels of both EP₄ receptors and cAMP, along with other vasodilatory effectors, including AMP, adenosine, and the adenosine A_2A receptor. The protective effects of SW0333291 could largely be achieved with a single prophylactic dose of the drug. Inhibition of 15-PGDH may thus represent a novel strategy for prophylaxis of ischemic AKI in multiple clinical settings, including renal transplantation and cardiovascular surgery.

Long Non-coding RNA LRNA9884 Promotes Acute Kidney Injury via Regulating NF-kB-Mediated Transcriptional Activation of MIF

Acute kidney injury (AKI) is one of the most common complications affecting hospitalized patients associated with an extremely high mortality rate. However, the underlying pathogenesis of AKI remains unclear that largely limits its effective management in clinic. Increasing evidence demonstrated the importance of long non-coding RNAs (lncRNAs) in the pathogenesis of AKI, because of their regulatory roles in transcription, translation, chromatin modification, and cellular organization. Here, we reported a new role of LRNA9884 in AKI. Using experimental cisplatin-induced AKI model, we found that LRNA9884 was markedly up-regulated in the nucleus of renal tubular epithelium in mice with AKI. We found that silencing of LRNA9884 effectively inhibited the production of inflammatory cytokines MCP-1, IL-6, and TNF-α in the mouse renal tubular epithelial cells (mTECs) under IL-1β stimulation in vitro. Mechanistically, LRNA9884 was involved into NF-κB-mediated inflammatory cytokines production especially on macrophage migration inhibitory factor (MIF). Collectedly, our study suggested LRNA9884 promoted MIF-triggered the production of inflammatory cytokines via NF-κB pathway after AKI injury. This study uncovered LRNA9884 has an adverse impact in AKI, and targeting LRNA9884 might represent a potential therapeutic target for AKI.

Exercise as a therapeutic option for acute kidney injury: mechanisms and considerations for the design of future clinical studies

Acute kidney injury (AKI) is a known risk factor for chronic kidney disease (CKD) and end stage kidney disease (ESKD). The progression from AKI to CKD, despite being well recognised, is not completely understood, although sustained inflammation and fibrosis are implicated. A therapeutic intervention targeting the post AKI stage could reduce the progression to CKD, which has high levels of associated morbidity and mortality. Exercise has known anti-inflammatory effects with animal AKI models demonstrating its use as a therapeutic agent in abrogating renal injury. This suggests the use of an exercise rehabilitation programme in AKI patients following discharge could attenuate renal damage and improve long term patient outcomes. In this review article we outline considerations for future clinical studies of exercise in the AKI population.

The adaptive immune response in cardiac arrest resuscitation induced ischemia reperfusion renal injury

Background

The present study aims to investigate, immunohistochemically, the role of the adaptive immune response in cardiac arrest/resuscitation-induced ischemia–reperfusion renal injury (IRI), namely to assess the presence of lymphocytes in renal tissue samples and the connection between the extent of the damage and the concentration of the lymphocytes by comparing the kidneys of non resuscitated swine with the kidneys of resuscitated swine.

Methods

Twenty four swine underwent cardiac arrest (CA) via a pacemaker wire. After 7 min, without any intervention, Cardiopulmonary Resuscitation, CPR, was commenced. Five min after CPR was commenced advanced life-support, ALS. Animals were divided into resuscitated animals and non resuscitated animals. Tissue samples obtained from the two groups for immunohistological study aiming to detect T-cells, B-cells and plasma cells using CD3 + , CD20 + , and CD138 + antibodies.

Results

There seems to be a strong concentration of T lymphocytes in the kidney tissues after ischemia of both non-resuscitated and resuscitated swine. B lymphocytes, also, appear to have infiltrated the ischemic kidneys of both animal groups; nevertheless, the contribution of T lymphocytes to the induction of injury remains greater. There is no strong evidence of correlation between the plasma cells and the damage.

Conclusion

The adaptive immune response seems to have a strong association with kidney injury and acute tubular necrosis after cardiac arrest/ resuscitation-induced ischemia–reperfusion. However, the extent to which the adaptive immune cells are involved in the induction of renal injury remains uncertain and there are many questions about the mechanism of function of these cells, the answers of which require further studies.

ArhGAP15, a RacGAP, Acts as a Temporal Signaling Regulator of Mac-1 Affinity in Sterile Inflammation

During inflammation, leukocyte recruitment has to be tightly controlled to prevent overwhelming leukocyte infiltration, activation, and, consequently, organ damage. A central regulator of leukocyte recruitment is Rac1. In this study, we analyzed the effects of the RacGAP ArhGAP15 on leukocyte recruitment. Using ArhGAP15-deficient mice, reduced neutrophil adhesion and transmigration in the TNF-α-inflamed cremaster muscle and a prolongation of chemokine-dependent leukocyte adhesion could be observed. In a murine model of sterile kidney injury, reduced neutrophil infiltration, and serum creatinine levels were apparent. Further in vitro and in vivo analyses revealed a defective intravascular crawling capacity, resulting from increased affinity of the β₂-integrin Mac-1 after prolonged chemokine stimulation of neutrophils. LFA-1 activity regulation was not affected. Summarizing, ArhGAP15 specifically regulates Mac-1, but not LFA-1, and affects leukocyte recruitment by controlling postadhesion strengthening and intravascular crawling in a Mac-1-dependent manner. In conclusion, ArhGAP15 is involved in the time-dependent regulation of leukocyte postadhesion in sterile inflammation.

Role of promoting inflammation of Krüppel-like factor 6 in acute kidney injury

Background

Krüppel-like factor 6 (KLF6) is a transcription factor that participate in various pathophysiological processes, but its contribution in ischemia acute kidney injury (AKI) is lacking so far. The study aimed to investigate the expression and the role of KLF6 in kidney ischemia–reperfusion (IR) injury.

Method

Microarray data were collected from GSE58438 and GSE52004. The rat IR model was established to evaluate the mRNA and protein expression of KLF6 and inflammatory cytokines in serum and kidney tissues. SiRNA-KLF6 was transfected with HK-2 cells, and then a cell-based hypoxia-reoxygenation (HR) model was established.

Results

Bioinformatics showed KLF6 mRNA in kidney tissue is up-regulated in 3 h after IR in rat kidney, which involved in cell activation, leukocyte activation, and response to hydrogen peroxide after IR. The rat IR model results showed that KLF6 expression was peaking at 6 h, and the expression of pro-inflammatory cytokines MCP-1 and TNF-α was increased both in serum and kidney tissues, while anti-inflammatory cytokine IL-10 was decreased after IR. Furthermore, in vitro results showed that KLF6 knock-down reduced the pro-inflammatory cytokines expression.

Conclusion

These results suggest that (1) KLF6 might be a novel biomarker for early diagnosis of AKI and (2) KLF6 may play a role in promoting inflammation in AKI.

Curcumin and LOXblock-1 ameliorate ischemia-reperfusion induced inflammation and acute kidney injury by suppressing the semaphorin-plexin pathway

AIMS

Ischemia/reperfusion (I/R) is one of the most important causes of acute kidney injury (AKI), a clinical syndrome with kidney dysfunction and high mortality rates. New diagnostic biomarkers need to be defined to better illuminate the pathophysiology of AKI. For the first time, we aim to investigate the protective effects of Curcumin which is known for its antioxidant and anti-inflammatory properties and 12/15 lipoxygenase inhibitor LOXblock-1 on I/R induced AKI by modulating inflammatory processes, oxidative stress, apoptosis and semaphorin-plexin pathway.

MAIN METHODS

The rats were divided into five groups, with eight animals per group: Sham, I/R, I/R + DMSO (1%, i.p.), I/R + Curcumin (100 mg/kg, i.p.), I/R + LOXblock-1 (2 μg/kg, i.p.).

KEY FINDINGS

The renal function biomarkers (BUN, CREA and UA) in serum were significantly increased in the I/R group. The inflammatory (TNF-α, IL-6 and MCP-1), apoptotic (CYCS and CASP3) and oxidative stress parameters (MDA, MPO, TAS and TOS) measured by ELISA were significantly increased in the I/R group. In histopathological analysis, it was observed that I/R caused serious damage to kidney tissue. SEMA3A was found to increase both serum level and mRNA expression in I/R group. It was observed that curcumin and LOXblock-1 reduce inflammatory processes, oxidative stress and apoptosis via the semaphorin-plexin pathway by both measurements and histopathological analysis. Curcumin was proved more effective than LOXblock-1 with its antioxidant feature in I/R injury.

SIGNIFICANCE

The current study reveals the protective effects of Curcumin and LOXblock-1 on acute kidney injury by suppressing SEMA3A as a new biomarker.

Inhibiting pannexin-1 alleviates sepsis-induced acute kidney injury via decreasing NLRP3 inflammasome activation and cell apoptosis

AIMS

Sepsis-induced acute kidney injury (SI-AKI) is the fifth most common cause of hospital-acquired acute kidney injury. Pannexin1 (Panx1) triggers inflammation and apoptosis which act as crucial factors in the pathogenesis of SI-AKI. We aimed to investigate the expression of Panx1 and its role on the inflammation and apoptosis in SI-AKI.

MATERIALS AND METHODS

SI-AKI model was established by lipopolysaccharide (LPS) injection in mice and LPS-treated HK-2 cells in vitro. Panx1 was inhibited by pretreating with carbenoxolone (CBX) or small interfering RNA in vivo and vitro, respectively. The expression of Panx1 was determined by qPCR, western blot and immunohistochemistry (IHC). Kidney damage was evaluated by kidney function, histopathological examination and AKI biomarkers. Inflammatory cytokines were detected by qPCR and ELISA. Apoptosis was detected by TUNEL staining and the expression of apoptosis-related proteins. The activation of nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome was measured by western blot.

KEY FINDINGS

Panx1 increased in LPS-induced SI-AKI mice and HK-2 cells, as well as in SI-AKI patients. CBX alleviated the renal function and pathological damage, as well as decreased the mRNA of kidney injury molecule (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Inhibiting Panx1 decreased the production of IL-1β, IL-6 and TNF-α, as well as tubular cell apoptosis in SI-AKI. Inhibiting Panx1 suppressed inflammatory cytokines and apoptosis via inhibiting NLRP3 inflammasome activation and regulating apoptotic protein Bax and Bcl2 expression, respectively.

SIGNIFICANCE

These observations suggest that pharmacological inhibition of Panx1 might be a potential approach in the clinical therapy of SI-AKI.

The Role of Oxidative Stress, Renal Inflammation, and Apoptosis in Post Ischemic Reperfusion Injury of Kidney Tissue: the Protective Effect of Dose-Dependent Boric Acid Administration

Ischemia/reperfusion (I/R) injury is associated with a strong inflammatory and oxidative stress response to hypoxia and reperfusion that impair organ function. We aimed to investigate the role of oxidative stress, renal inflammation, and apoptosis in the injury of the kidney tissue after ischemic reperfusion, and the protective effect of dose-dependent boric acid administration. For this purpose, 35 Sprague Dawley albino rats were divided into five groups of seven animals in each group: Sham, I/R and I/R + boric acid (BA) (i.p at doses of 50, 100, and 200 mg/kg). All animals underwent nephrectomy (the right kidney was removed) and were expected to recover for 15 days. After recovery, each animal received 45 min of ischemia. BA was injected intraperitoneally 10 min before reperfusion and a 24-h reperfusion procedure was performed. Sham group only underwent surgical stress procedure. In order to investigate the oxidative stress induced by I/R injury and antioxidant effects of different BA doses in the kidney tissue, TAS, TOS, MDA, SOD, CAT, and GSH levels were measured. DNA fragmentation, cytochrome C levels, caspase 3 activity were measured to determine apoptotic index in tissue. IL-6 and TNF-α levels were measured in the evaluation of inflammation. Hematoxylin-eosin and TUNEL staining was performed for histopathological examinations. As a result, increased oxidative stress, inflammation, and apoptosis after I/R were decreased with different doses of BA treatment. The application of high-dose BA was found to be lower in anti-apoptotic, anti-inflammatory, and antioxidant effects than in the low-dose groups.

Role of chemokines, innate and adaptive immunity

Polycystic Kidney Disease (PKD) triggers a robust immune system response including changes in both innate and adaptive immunity. These changes involve immune cells (e.g., macrophages and T cells) as well as cytokines and chemokines (e.g., MCP-1) that regulate the production, differentiation, homing, and various functions of these cells. This review is focused on the role of the immune system and its associated factors in the pathogenesis of PKDs as evidenced by data from cell-based systems, animal models, and PKD patients. It also highlights relevant pre-clinical and clinical studies that point to specific immune system components as promising candidates for the development of prognostic biomarkers and therapeutic strategies to improve PKD outcomes.

WWP2 ameliorates acute kidney injury by mediating p53 ubiquitylation and degradation

E3 ubiquitin ligase gene, WWP2, is associated with acute kidney injury (AKI). This research was conducted to explore the role of WWP2 in AKI. AKI cell model was produced in human renal proximal tubular epithelial cell line (HK-2) by ischemia-reperfusion (IR) injury. CCK8 and flow cytometry assay were performed to explore the influence of WWP2 overexpression on cell proliferation and apoptosis of IR-induced HK-2 cells. Quantitative real-time PCR and immunoblotting (IB) were performed to assess the gene and protein expression. Then, the influence of WWP2 on p53 ubiquitylation and degradation was estimated by immunoprecipitation assay. Our data indicated that WWP2 was down-regulated and p53 was up-regulated in IR-induced HK-2 cells. WWP2 overexpression promoted proliferation and inhibited apoptosis of IR-induced HK-2 cells. And WWP2 interacted with p53 and regulated p53 ubiquitylation and degradation. Furthermore, the influence of WWP2 on cell proliferation and apoptosis was rescued by MG132 (proteasome inhibitor) treatment. In conclusion, our work described for the first time the role of WWP2 in AKI, showing that WWP2 ameliorated AKI by mediating p53 ubiquitylation and degradation. Moreover, the study offers some important insights into the occurrence of AKI and WWP2 may be a novel target of AKI treatment. SIGNIFICANCE OF THE STUDY: Our data elaborates that WWP2 has protective effect against AKI by mediating p53 ubiquitylation and degradation. Thus, WWP2 might be a therapeutic target for AKI.