Ischemic acute renal failure: An inflammatory disease?

The effect of zinc acexamate on oxidative stress, inflammation and mitochondria induced apoptosis in rat model of renal warm ischemia

AIM

Zinc has proved its efficacy in many models of ischemia reperfusion (I/R) injury. In this study, we used zinc acexamate (ZAC) as an exogenous source of zinc against renal I/R injury and we investigated whether its protective effects are mediated by the decrease of oxidative stress, inflammation, and mitochondria induced-apoptosis.

METHODS

Rats were orally pretreated with vehicle or ZAC (10 or 100 mg/kg) 24 h and 30 min prior to 1 h of bilateral renal warm ischemia and 2 h of reperfusion.

RESULTS

Our data showed that 10 mg/kg of ZAC, but not 100 mg/kg, improved renal architecture and function. Also, the low dose of ZAC up-regulated antioxidant enzymes activities and glutathione level and decreased lipids and proteins oxidation. Interestingly, the use of ZAC resulted in a significant reduce of pro-inflammatory cytokines (IL-1ß, IL-6 and MCP-1), enhanced mitochondria integrity and decreased expression of the pro-apoptotic protein caspase-9.

CONCLUSION

We conclude that renal I/R induced oxidative stress, inflammation and apoptosis and that the use of ZAC at 10 mg/kg, but not 100 mg/kg, protects rat kidneys from I/R injury by down-regulating these processes.

Cutaneous exposure to lewisite causes acute kidney injury by invoking DNA damage and autophagic response

Lewisite (2-chlorovinyldichloroarsine) is an organic arsenical chemical warfare agent that was developed and weaponized during World Wars I/II. Stockpiles of lewisite still exist in many parts of the world and pose potential environmental and human health threat. Exposure to lewisite and similar chemicals causes intense cutaneous inflammatory response. However, morbidity and mortality in the exposed population is not only the result of cutaneous damage but is also a result of systemic injury. Here, we provide data delineating the pathogenesis of acute kidney injury (AKI) following cutaneous exposure to lewisite and its analog phenylarsine oxide (PAO) in a murine model. Both agents caused renal tubular injury, characterized by loss of brush border in proximal tubules and tubular cell apoptosis accompanied by increases in serum creatinine, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1. Interestingly, lewisite exposure enhanced production of reactive oxygen species (ROS) in the kidney and resulted in the activation of autophagic and DNA damage response (DDR) signaling pathways with increased expression of beclin-1, autophagy-related gene 7, and LC-3A/B-II and increased phosphorylation of γ-H2A.X and checkpoint kinase 1/2, respectively. Terminal deoxyribonucleotide-transferase-mediated dUTP nick-end labeling-positive cells were detected in renal tubules along with enhanced proapoptotic BAX/cleaved caspase-3 and reduced antiapoptotic BCL2. Scavenging ROS by cutaneous postexposure application of the antioxidant N-acetyl-l-cysteine reduced lewisite-induced autophagy and DNA damage. In summary, we provide evidence that topical exposure to lewisite causes AKI. The molecular mechanism underlying these changes involves ROS-dependent activation of autophagy and DDR pathway associated with the induction of apoptosis.

Persistent expression of neutrophil gelatinase-associated lipocalin and M2 macrophage markers and chronic fibrosis after acute kidney injury

Recent epidemiologic studies revealed a correlation between acute kidney injury (AKI) episodes and the progression to chronic kidney disease (CKD). Although the severity and duration of the initial insult likely predict the development of CKD, information regarding tissue markers predictive of early development of renal fibrosis is limited. We investigated key markers in fibrotic kidney in rats and mice. Seven- to eight-week-old male Sprague-Dawley rats underwent bilateral ischemia-reperfusion injury (IRI). Kidney tissues were collected to determine the markers correlated with the severity of kidney fibrosis. In a separate set, a specific chemokine (C-C motif) receptor 2 (CCR2) inhibitor, RS-102895, was administered to 9-week-old male C57BL/6J mice that underwent unilateral IRI (9.2 mg/kg/day in drinking water for 17 days) to investigate whether blockade of the monocyte chemotactic protein-1 (MCP-1) signaling was sufficient to prevent fibrosis. Among candidate tissue markers, neutrophil gelatinase-associated lipocalin (NGAL) and MCP-1 mRNA expressions were correlated with kidney fibrosis. Studies on macrophage polarity showed that mRNA expression of M2, but not M1 macrophage markers, were correlated with acute-phase serum creatinine and fibrosis. Pharmacological blockade of the MCP-1-CCR2 signaling downregulated CCR2, which was insufficient to improve fibrosis in mouse unilateral IRI model, suggesting that additional, redundant pathways contribute to fibrosis. These findings suggested that tissue NGAL expression and M2 macrophage markers are promising markers that show severity of kidney fibrosis. Mechanistic involvement of these markers in CKD pathogenesis warrant additional investigation.

The Fibrin Cleavage Product Bβ15-42 Channels Endothelial and Tubular Regeneration in the Post-acute Course During Murine Renal Ischemia Reperfusion Injury

Early and adequate restoration of endothelial and tubular renal function is a substantial step during regeneration after ischemia reperfusion (IR) injury, occurring, e.g., in kidney transplantation, renal surgery, and sepsis. While tubular epithelial cell injury has long been of central importance, recent perception includes the renal vascular endothelium. In this regard, the fibrin cleavage product fibrinopeptide Bβ_15-42 mitigate IR injury by stabilizing interendothelial junctions through its affinity to VE-cadherin. Therefore, this study focused on the effect of Bβ_15-42 on post-acute physiological renal regeneration. For this, adult male C57BL/6 mice were exposed to a 30 min bilateral renal ischemia and reperfusion for 24 h or 48 h. Animals were randomized in a non-operative control group, two operative groups each treated with i.v. administration of either saline or Bβ_15-42 (2.4 mg/kg) immediately prior to reperfusion. Endothelial activation and inflammatory response was attenuated in renal tissue homogenates by single application of Bβ_15-42. Meanwhile, Bβ_15-42 did not affect acute kidney injury markers. Regarding the angiogenetic players VEGF-A, Angiopoietin-1, Angiopoietin-2, however, we observed significant higher expressions at mRNA and trend to higher protein level in Bβ_15-42 treated mice, compared to saline treated mice after 48 h of IR, thus pointing toward an increased angiogenetic activity. Similar dynamics were observed for the intermediate filament vimentin, the cytoprotective protein klotho, stathmin and the proliferation cellular nuclear antigen, which were significantly up-regulated at the same points in time. These results suggest a beneficial effect of anatomical contiguously located endothelial cells on tubular regeneration through stabilization of endothelial integrity. Therefore, it seems that Bβ_15-42 represents a novel pharmacological approach in the targeted therapy of acute renal failure in everyday clinical practice.

Prediction of acute kidney injury in cirrhotic patients: a new score combining renal, liver and inflammatory markers

Introduction

Acute kidney injury (AKI) is common in hospitalized patients with cirrhosis and is associated with poor prognosis. A risk prediction score combining values easily measured at admission could be valuable to stratify patients for prevention, monitoring and early intervention, ultimately improving patient care and outcomes. The aim of this study was to develop a risk score for AKI in a cohort of cirrhotic patients.

Patients and methods

We cross-examined the data from a retrospective analysis of 186 patients with cirrhosis admitted to the Gastroenterology and Hepatology Service of Centro Hospitalar Lisboa Norte from January 2003 to December 2005. AKI was defined as an increase in serum creatinine (SCr)≥0.3 mg/dL within 48 hours or a percentage increase in SCr≥50% from baseline. Neutrophil-to-lymphocyte ratio (NLR) was used as a marker for inflammation. A receiver operating characteristic (ROC) curve was produced to assess the discriminative ability of the variables. Cutoff values were defined as those with highest validity. The final AKI risk score model was assessed using the ROC curve.

Results

A total of 52 patients (28%) developed AKI. Higher baseline SCr (p<0.001), more severe liver disease as evaluated by the modified Model of End-stage Liver Disease (MELD)-Na score (p<0.001) and higher NLR (p=0.028) were independently associated with AKI. The area under the ROC (AUROC) curve for the prediction of AKI was 0.791 (95% CI 0.726–0.847) for SCr, 0.771 (95% CI 0.704–0.829) for modified MELD-Na and 0.757 (95% CI 0.689–0.817) for NLR. Cutoff values with the highest validity for predicting AKI were determined and defined as 0.9 for the SCr, 21.7 for the modified MELD-Na and 6 for the NLR. The risk score was created allowing 3 points if the SCr is higher than 0.9, 1 point if the modified MELD-Na is higher than 21.7 and 1 point if the NLR is higher than 6. The AUROC curve of the risk prediction score for AKI was 0.861. A risk score of ≥2 points predicts AKI in cirrhotic patients with a sensitivity of 88.5% and specificity of 72.4%.

Conclusion

A new score combining SCr, MELD-Na and NLR demonstrated a strong discriminative ability to predict AKI in cirrhotic patients.

Urinary IL-8 is a marker of early and long-term graft function after renal transplantation

In this study, we examined whether the IL-8 content of urine sampled on day 1 and day 14 after renal transplantation is a marker of early and long-term renal function. Moreover, we assessed whether its concentration is positively correlated with the matrix metalloproteinase-9 (MMP-9) content of urine sampled on day 1 and day 30 and 12 months after renal transplantation. Our analysis covered 87 patients who underwent a kidney transplant. The patients were observed for an average of 30 months (12-60 months). The IL-8 concentration determined on day 1 was significantly negatively correlated with creatinine clearance early after renal transplantation (on days 1, 7, 14 and 30), as well as during long-term observations. IL-8 concentration in urine sampled on day 1 and day 14 was higher in patients demonstrating DGF than in those without DGF. No relationship was found between IL-8 content and cold ischaemia time. MMP-9 activity determined on day 1 and month 3 after renal transplantation was positively correlated with the IL-8 content determined in urine sampled on day 1, Rs = +0.32, p < .05 and Rs = +0.31, p < .05, respectively. The results of this study suggest that a high IL-8 content in urine sampled on day 1 after renal transplantation is an unfavourable marker of early and long-term (years-long) graft function. A high IL-8 content in urine sampled on day 1 after renal transplantation was positively correlated with the activity of metalloproteinase-9 in urine. This proves that both of these chemokines cooperate in ischaemia-reperfusion injuries in transplanted kidneys.

MicroRNA-30b promotes lipopolysaccharide-induced inflammatory injury and alleviates autophagy through JNK and NF-κB pathways in HK-2 cells

BACKGROUND

Acute kidney injury (AKI) is an abrupt loss of kidney function. MicroRNA-30b (miR-30b) has been reported to be involved in the inflammatory reaction of a variety of diseases. However, the role of miR-30b in AKI remains unknown. In this research, we aimed to investigate the role of miR-30b in lipopolysaccharide (LPS)-induced kindey inflammatory injury in vitro and in vivo.

METHODS

In vitro, after miR-30b mimic/inhibitor transfection and/or LPS treatment, the viability, apoptosis, autophagy and inflammatory cytokines releases, as well as activation of c-Jun-N-terminal kinase (JNK) and nuclear factor-kappa B (NF-κB) pathways were detected by cell counting kit-8 (CCK-8) assay, flow cytometry, qRT-PCR, enzyme-linked immunosorbent assay (ELISA) and western blot, respectively. In vivo, after LPS treatment and/or anti-miR-30b administration, the levels of creatinine, the activities of alanine aminotransferase (ALT) and histologic scores, as well as concentrations of inflammatory cytokines were assessed by creatinine assay kit, ALT assay kit and ELISA, respectively.

RESULTS

LPS inhibited HK-2 cell viability and induced HK-2 cell apoptosis, autophagy and the releases of inflammatory cytokines. Overexpression of miR-30b promoted LPS-induced HK-2 cell viability inhibition, cell inflammatory cytokines releases, cell apoptosis induction and activation of JNK and NF-κB signaling pathways, but inhibited LPS-induced HK-2 cell autophagy. Suppression of miR-30b had opposite effects. Moreover, suppression of miR-30b alleviated the LPS-induced kidney injury in mice model by decreasing creatinine level, ALT activity and histologic scores, as well as concentrations of inflammatory cytokines.

CONCLUSION

miR-30b participated in the LPS-induced kindey inflammatory injury in vitro and in vivo.

Effects of a Single Dose of Parecoxib on Inflammatory Response and Ischemic Tubular Injury Caused by Hemorrhagic Shock in Rats

Parecoxib, a selective COX-2 inhibitor, is used to improve analgesia in postoperative procedures. Here we evaluated whether pretreatment with a single dose of parecoxib affects the function, cell injury, and inflammatory response of the kidney of rats subjected to acute hemorrhage. Inflammatory response was determined according to serum and renal tissue cytokine levels (IL-1α, IL-1β, IL-6, IL-10, and TNF-α). Forty-four adult Wistar rats anesthetized with sevoflurane were randomized into four groups: placebo/no hemorrhage (Plc/NH); parecoxib/no hemorrhage (Pcx/NH); placebo/hemorrhage (Plc/H); and parecoxib/hemorrhage (Pcx/H). Pcx groups received a single dose of intravenous parecoxib while Plc groups received a single dose of placebo (isotonic saline). Animals in hemorrhage groups underwent bleeding of 30% of blood volume. Renal function and renal histology were then evaluated. Plc/H showed the highest serum levels of cytokines, suggesting that pretreatment with parecoxib reduced the inflammatory response in rats subjected to hemorrhage. No difference in tissue cytokine levels between groups was observed. Plc/H showed higher percentage of tubular dilation and degeneration, indicating that parecoxib inhibited tubular injury resulting from renal hypoperfusion. Our findings indicate that pretreatment with a single dose of parecoxib reduced the inflammatory response and tubular renal injury without altering renal function in rats undergoing acute hemorrhage.

17β-Estradiol Accelerated Renal Tubule Regeneration in Male Rats After Ischemia/Reperfusion-Induced Acute Kidney Injury

Ischemic/reperfusion injury (IRI) is the most common cause of acute kidney injury (AKI). Murine studies report that pretreatment with 17β-estradiol protects against AKI using multiple mechanisms, but how 17β-estradiol is involved in regenerating tubular cells is unknown. To visualize the kidney injury and repair, we used 17β-estradiol to treat rats with postischemic acute kidney injury. AKI was induced by clamping the renal pedicle for 90 minutes 2 weeks after a unilateral nephrectomy. Rats were treated with an intravenous injection of 17β-estradiol or vehicle immediately after reperfusion. Kidney injury was assessed by measuring biochemical and histopathological changes. Immunohistochemical staining of vimentin, proliferating cell nuclear antigen (PCNA), and E-cadherin were used to assess dedifferentiation, proliferation, and redifferentiation. Rats treated with 17β-estradiol had less kidney injury than did vehicle-treated rats post-IRI day 1. The number of PCNA-positive (PCNA) cells was significantly higher in post-IRI kidneys on day 1 in 17β-estradiol-treated rats. Moreover, vimentin and E-cadherin cells, which were interpreted as regeneration markers, were expressed earlier and significantly more copiously in 17β-estradiol-treated rats. We hypothesize that 17β-estradiol attenuates IRI-induced AKI by reducing inflammation and accelerating injured tubular cell regeneration.

Just Look! Intravital Microscopy as the Best Means to Study Kidney Cell Death Dynamics

Kidney cell death plays a key role in the progression of life-threatening renal diseases, such as acute kidney injury and chronic kidney disease. Injured and dying epithelial and endothelial cells take part in complex communication with the innate immune system, which drives the progression of cell death and the decrease in renal function. To improve our understanding of kidney cell death dynamics and its impact on renal disease, a study approach is needed that facilitates the visualization of renal function and morphology in real time. Intravital multiphoton microscopy of the kidney has been used for more than a decade and made substantial contributions to our understanding of kidney physiology and pathophysiology. It is a unique tool that relates renal structure and function in a time- and spatial-dependent manner. Basic renal function, such as microvascular blood flow regulation and glomerular filtration, can be determined in real time and homeostatic alterations, which are linked inevitably to cell death and can be depicted down to the subcellular level. This review provides an overview of the available techniques to study kidney dysfunction and inflammation in terms of cell death in vivo, and addresses how this novel approach can be used to improve our understanding of cell death dynamics in renal disease.

Real-Time and Non-invasive Monitoring of the Activation of the IRE1α-XBP1 Pathway in Individuals with Hemodynamic Impairment

Many stressors that are encountered upon kidney injury are likely to trigger endoplasmic reticulum (ER) stress, subsequently activating transcriptional, translational and metabolic reprogramming. Monitoring early cellular adaptive responses engaged after hemodynamic impairment yields may represent a clinically relevant approach. However, a non-invasive method for detecting the ER stress response has not been developed. We combined a metabolomic approach with genetic marker analyses using urine from individuals undergoing scheduled cardiac surgery under cardiopulmonary bypass to investigate the feasibility and significance of monitoring the ER stress response in the kidney. We developed an original method based on fragment analysis that measures urinary levels of the spliced X-box binding protein 1 (sXBP1) mRNA as a proxy of inositol-requiring enzyme 1α (IRE1α) activity because sXBP1 is absolutely sensitive and specific for ER stress. The early engagement of the ER stress response after ischemic stress is critical for protecting against tissue damage, and individuals who mount a robust adaptive response are protected against AKI. The clinical consequences of our findings are of considerable importance because ER stress is involved in numerous conditions that lead to AKI and chronic kidney disease; in addition, the detection of ER stress is straightforward and immediately available in routine practice.

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Endoplasmic Reticulum (ER) stress is involved in the pathophysiology of numerous kidney diseases.

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We developed a method based on fragment analysis that measures urinary levels of XBP1 mRNA to detect renal ER stress.

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ER stress occurs early after cardiopulmonary bypass, a procedure leading to acute kidney injury.

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The detection of renal ER stress in this context can predict the occurrence of acute kidney injury.

The better care of patients with kidney disease requires the identification of biomarkers of ongoing tissue injury to provide therapies to slow disease progression. In this study, we have developed for the first time a non-invasive (urinary) biomarker of a protective cellular process called Endoplasmic Reticulum stress that occurs early in the kidney after ischemic injury. Renal ischemic injury follows cardiac surgery and could lead to acute kidney injury. Our results indicate that the early detection of individuals who do not activate Endoplasmic Reticulum stress could help to identify individuals who will develop acute kidney injury.

Angiotensinogen as a biomarker of acute kidney injury

Early recognition of acute kidney injury (AKI) is critical to prevent its associated complications as well as its progression to long term adverse outcomes like chronic kidney disease. A growing body of evidence from both laboratory and clinical studies suggests that inflammation is a key factor contributing to the progression of AKI regardless of the initiating event. Biomarkers of inflammation are therefore of interest in the evaluation of AKI pathogenesis and prognosis. There is evidence that the renin angiotensin aldosterone system is activated in AKI, which leads to an increase in angiotensin II (Ang II) formation within the kidney. Ang II activates pro-inflammatory and pro-fibrotic pathways that likely contribute to the progression of AKI. Angiotensinogen is the parent polypeptide from which angiotensin peptides are formed and its stability in urine makes it a more convenient marker of renin angiotensin system activity than direct measurement of Ang II in urine specimens, which would provide more direct information. The potential utility of urinary angiotensinogen as a biomarker of AKI is discussed in light of emerging data showing a strong predictive value of AKI progression, particularly in the setting of decompensated heart failure. The prognostic significance of urinary angiotensinogen as an AKI biomarker strongly suggests a role for renin-angiotensin system activation in modulating the severity of AKI and its outcomes.

Comparison of acute kidney injury between open and laparoscopic liver resection: Propensity score analysis

The inflammatory response has been shown to be a major contributor to acute kidney injury. Considering that laparoscopic surgery is beneficial in reducing the inflammatory response, we compared the incidence of postoperative acute kidney injury between laparoscopic liver resection and open liver resection. Among 1173 patients who underwent liver resection surgery, 222 of 926 patients who underwent open liver resection were matched with 222 of 247 patients who underwent laparoscopic liver resection, by using propensity score analysis. The incidence of postoperative acute kidney injury assessed according to the creatinine criteria of the Kidney Disease: Improving Global Outcomes definition was compared between those 1:1 matched groups. A total 77 (6.6%) cases of postoperative acute kidney injury occurred. Before matching, the incidence of acute kidney injury after laparoscopic liver resection was significantly lower than that after open liver resection [1.6% (4/247) vs. 7.9% (73/926), P < 0.001]. After 1:1 matching, the incidence of postoperative acute kidney injury was still significantly lower after laparoscopic liver resection than after open liver resection [1.8% (4/222) vs. 6.3% (14/222), P = 0.008; odds ratio 0.273, 95% confidence interval 0.088-0.842, P = 0.024]. The postoperative inflammatory marker was also lower in laparoscopic liver resection than in open liver resection in matched set data (white blood cell count 12.7 ± 4.0 × 103/μL vs. 14.9 ± 3.9 × 103/μL, P < 0.001). Our findings suggest that the laparoscopic technique, by decreasing the inflammatory response, may reduce the occurrence of postoperative acute kidney injury during liver resection surgery.

Independent Risk Factors and 2-Year Outcomes of Acute Kidney Injury after Surgery for Congenital Heart Disease

BACKGROUND

Data are limited regarding risk factors for acute kidney injury (AKI) following cardiac surgery in children with congenital heart disease (CHD). This observational study was performed to examine temporal trends in AKI incidence according to the Pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease (pRIFLE) criteria, identify independent risk factors for AKI after cardiac surgery, and examine associations between AKI and long-term mortality.

METHODS

We retrospectively evaluated 418 patients (259 males, 159 females; median age, 5 months) who underwent cardiac surgery for CHD between April 2007 and August 2013. Patients were followed up for 2 years. AKI was defined according to the pRIFLE criteria as ≥25% decrease in estimated creatinine clearance.

RESULTS

AKI developed postoperatively in 104 cases (24.9%). Approximately 80% belonged to the "Risk" category according to the pRIFLE criteria, and only 21 cases (5%) required renal replacement therapy (peritoneal dialysis in all cases). Multivariate analysis revealed 3 independent risk factors for onset of AKI: young age (<1 year), surgery in Risk Adjustment in Congenital Heart Surgery (RACHS-1) category ≥4, and long cardiopulmonary bypass (CPB) time (≥90 min). Twenty-three patients (22%) with AKI died during the 2-year follow-up. In multivariate cox hazard regression analysis, the most significant contributor to risk of mortality was AKI.

CONCLUSIONS

Postoperative AKI was strongly associated with young age, high RACHS-1 category, and prolonged CPB time. In addition, mortality rate was higher in patients who survived after recovery from AKI than in those without AKI, even among the lower pRIFLE categories.

Complement inhibition attenuates acute kidney injury after ischemia-reperfusion and limits progression to renal fibrosis in mice

The complement system is an essential component of innate immunity and plays a major role in the pathogenesis of ischemia-reperfusion injury (IRI). In this study, we investigated the impact of human C1-inhibitor (C1INH) on the early inflammatory response to IRI and the subsequent progression to fibrosis in mice. We evaluated structural damage, renal function, acute inflammatory response, progression to fibrosis and overall survival at 90-days post-injury. Animals receiving C1INH prior to reperfusion had a significant improvement in survival rate along with superior renal function when compared to vehicle (PBS) treated counterparts. Pre-treatment with C1INH also prevented acute IL-6, CXCL1 and MCP-1 up-regulation, C5a release, C3b deposition and infiltration by neutrophils and macrophages into renal tissue. This anti-inflammatory effect correlated with a significant reduction in the expression of markers of fibrosis alpha smooth muscle actin, desmin and picrosirius red at 30 and 90 days post-IRI and reduced renal levels of TGF-β1 when compared to untreated controls. Our findings indicate that intravenous delivery of C1INH prior to ischemic injury protects kidneys from inflammatory injury and subsequent progression to fibrosis. We conclude that early complement blockade in the context of IRI constitutes an effective strategy in the prevention of fibrosis after ischemic acute kidney injury.

Dexmedetomidine ameliorates the inflammatory immune response in rats with acute kidney damage

It has been demonstrated that dexmedetomidine (Dex) can protect patients with acute kidney injury from experiencing further tissue damage, however its mechanism of action remains unclear. The present study investigated the immune modulatory functions of Dex in rats with acute kidney injury (AKI) induced via injection of lipopolysaccharide into the tail vein. ELISA analysis showed that Dex reduced the levels of inflammatory cytokines in rats with AKI in a dose dependent manner. Furthermore, the regulatory effects of Dex on cytokine production disappeared when the α-2 adrenergic receptor antagonist Yohimbine (YOH) was added. For a detailed investigation on how Dex regulates the immune response in rats with AKI, the impact of Dex on the viability of splenocytes and lymphocytes was determined and it was determined that Dex did not influence splenocyte and lymphocyte viability. In addition, ELISA tests showed that Dex regulated the production of the T-helper (Th) 17 cytokines interleukin (IL)-17 and IL-23, but not the Th1 cytokine tumor necrosis factor α, in splenocytes and lymphocytes. To confirm whether Dex functioned as an α-2-adrenergic receptor in these immune regulations, YOH was administered together with Dex. When Dex and YOH were administered together, the regulatory functions of Dex were reduced, confirming that Dex acted as an agonist on the α-2-adrenergic receptor. Thus the results of the current study may provide novel insights regarding how Dex modulates immune functions in AKI.

Dose and timing of injections for effective cyclosporine A pretreatment before renal ischemia reperfusion in mice

Background

There is experimental evidence that lethal ischemia-reperfusion injury (IRI) is largely due to mitochondrial permeability transition pore (mPTP) opening, which can be prevented by cyclosporine A (CsA). The aim of our study is to show that a higher dose of CsA (10 mg/kg) injected just before ischemia or a lower dose of CsA (3 mg/kg) injected further in advance of ischemia (1 h) protects the kidneys and improves mitochondrial function.

Methods

All mice underwent a right unilateral nephrectomy followed by 30 min clamping of the left renal artery. Mice in the control group did not receive any pharmacological treatment. Mice in the three groups treated by CsA were injected at different times and with different doses, namely 3 mg/kg 1 h or 10 min before ischemia or 10 mg/kg 10 min before ischemia. After 24 h of reperfusion, the plasma creatinine level were measured, the histological score was assessed and mitochondria were isolated to calculate the calcium retention capacity (CRC) and level of oxidative phosphorylation.

Results

Mortality and renal function was significantly higher in the CsA 10 mg/kg-10 min and CsA 3mg/kg-1 h groups than in the CsA 3mg/kg-10 min group. Likewise, the CRC was significantly higher in the former two groups than in the latter, suggesting that the improved renal function was due to a longer delay in the opening of the mPTP. Oxidative phosphorylation levels were also higher 24 h after reperfusion in the protected groups.

Conclusions

Our results suggest that the protection afforded by CsA is likely limited by its availability. The dose and timing of the injections are therefore crucial to ensure that the treatment is effective, but these findings may prove challenging to apply in practice.

Kidney Injury and Repair Biomarkers in Marathon Runners

BACKGROUND

Investigation into strenuous activity and kidney function has gained interest given increasing marathon participation.

STUDY DESIGN

Prospective observational study.

SETTING & PARTICIPANTS

Runners participating in the 2015 Hartford Marathon.

PREDICTOR

Completing a marathon.

OUTCOMES

Acute kidney injury (AKI) as defined by AKI Network (AKIN) criteria. Stage 1 AKI was defined as 1.5- to 2-fold or 0.3-mg/dL increase in serum creatinine level within 48 hours of day 0 and stage 2 was defined as a more than 2- to 3-fold increase in creatinine level. Microscopy score was defined by the number of granular casts and renal tubular epithelial cells.

MEASUREMENTS

Samples were collected 24 hours premarathon (day 0), immediately postmarathon (day 1), and 24 hours postmarathon (day 2). Measurements of serum creatinine, creatine kinase, and urine albumin were completed, as well as urine microscopy analysis. 6 injury urine biomarkers (IL-6, IL-8, IL-18, kidney injury molecule 1, neutrophil gelatinase-associated lipocalin, and tumor necrosis factor α) and 2 repair urine biomarkers (YKL-40 and monocyte chemoattractant protein 1) were measured.

RESULTS

22 marathon runners were included. Mean age was 44 years and 41% were men. 82% of runners developed an increase in creatinine level equivalent to AKIN-defined AKI stages 1 and 2. 73% had microscopy diagnoses of tubular injury. Serum creatinine, urine albumin, and injury and repair biomarker levels peaked on day 1 and were significantly elevated compared to day 0 and day 2. Serum creatine kinase levels continued to significantly increase from day 0 to day 2.

LIMITATIONS

Small sample size and limited clinical data available at all time points.

CONCLUSIONS

Marathon runners developed AKI and urine sediment diagnostic of tubular injury. An increase in injury and repair biomarker levels suggests structural damage to renal tubules occurring after marathon. The results of our study should be validated in larger cohorts with longer follow-up of kidney function.

Aripiprazole prevents renal ischemia/reperfusion injury in rats, probably through nitric oxide involvement

Renal ischemia/reperfusion (I/R) injury is strongly related to morbidity and mortality. Oxidative stress, inflammation, and apoptosis play key roles in renal dysfunction following renal I/R. Aripiprazole is an atypical antipsychotic which used for the treatment of schizophrenia and bipolar disorder. Recent studies have reported aripiprazole as displaying certain anti-inflammatory effects. Regarding the underlying mechanisms of renal ischemia-reperfusion, therefore, nephroprotective effects might be predicted to be seen with aripiprazole. I/R injury was induced by bilateral clamping of the renal pedicles (45min) followed by reperfusion (24h). The mechanism of aripiprazole-mediated nephroprotection was explored by a combined use of aripiprazole and L-NAME (non-selective nitric oxide synthase inhibitor). Animals were given aripiprazole (2.5, 5, 10 and 20mg/kg) intraperitoneally, 30min before ischemia. L-NAME was administered before the aripiprazole injection. Serum creatinine and blood urea nitrogen were assessed after 24h of reperfusion. Serum levels of malondialdehyde (MDA), TNF-α and IL-1β were measured for rats treated with aripiprazole. The extent of necrosis was measured by the stereology method. Ischemia/reperfusion caused significant renal dysfunction and marked renal injury. Aripiprazole reduced creatinine and blood urea nitrogen. Serum levels of MDA, IL-1β and TNF-α were significantly lower in the aripiprazole group. Aripiprazole treatment also decreased the volume of kidney necrosis. The administration of L-NAME reversed the renoprotective effect of aripiprazole on BUN and creatinine, but enhanced the anti-necrotic effect of aripiprazole. The results show that a single dose of aripiprazole significantly improved renal function following ischemia/reperfusion injury - probably through the involvement of nitric oxide.

Diagnostic value of plasma NGAL and intraoperative diuresis for AKI after major gynecological surgery in patients treated within an intraoperative goal-directed hemodynamic algorithm: A substudy of a randomized controlled trial

Data on early markers for acute kidney injury (AKI) after noncardiovascular surgery are still limited. This study aimed to determine the diagnostic value of plasma neutrophil-gelatinase-associated lipocalin (pNGAL) and intraoperative diuresis for AKI in patients undergoing major abdominal surgery treated within a goal-directed hemodynamic algorithm.This study is a post-hoc analysis of a randomized controlled pilot trial comparing intravenous solutions within a hemodynamic goal-directed algorithm based on the esophageal Doppler in patients undergoing epithelial ovarian cancer surgery. The diagnostic value of plasma NGAL obtained at ICU admission and intraoperative diuresis was determined with respect to patients already meeting AKI criteria 6 hours after surgery (AKI6h) and to all patients meeting AKI criteria at least once during the postoperative course (AKItotal). AKI was diagnosed by the definition of the Kidney Disease Improving Global Outcome (KDIGO) group creatinine criteria and was screened up to postoperative day 3. Receiver operating characteristic curves including a gray zone approach were performed.A total of 48 patients were analyzed. None of the patients had increased creatinine levels before surgery and 14 patients (29.2%) developed AKI after surgery. Plasma NGAL was predictive for AKI6h (AUCAKI6h 0.832 (95% confidence interval [CI], 0.629-0.976), P = .001) and AKItotal (AUCAKItotal 0.710 (CI 0.511-0.878), P = .023). The gray zones of pNGAL calculated for AKI6h and AKItotal were 210 to 245 and 207 to 274 ng mL, respectively. The lower cutoffs of the gray zone at 207 and 210 ng mL had a negative predictive value (NPV) (i.e., no AKI during the postoperative course) of 96.8% (CI 90-100) and 87.1% (CI 78-97), respectively. Intraoperative diuresis was also predictive for AKI6h (AUCAKI6h 0.742 (CI 0.581-0.871), P = .019) with a gray zone of 0.5 to 2.0 mL kg h. At the lower cutoff of the gray zone at 0.5 mL kg h, corresponding to the oliguric threshold, the NPV was 84.2% (78-92).This study indicates that pNGAL can be used as an early marker to rule out AKI occurring within 3 days after major abdominal surgery. Intraoperative diuresis can be used to rule out AKI occurring up to 6 hours after surgery.

TRIAL REGISTRATION

ISRCTN 53154834.

Identification of a sensitive urinary biomarker, selenium-binding protein 1, for early detection of acute kidney injury

Acute kidney injury (AKI) is associated with increased mortality rate in patients but clinically available biomarkers for disease detection are currently not available. Recently, a new biomarker, selenium-binding protein 1 (SBP1), was identified for detection of nephrotoxicity using proteomic analysis. The aim of this study was to assess the sensitivity of urinary SBP1 levels as an early detection of AKI using animal models such as cisplatin or ischemia/reperfusion (I/R). Sprague-Dawley rats were injected with cisplatin (6 mg/kg, once i.p.) and sacrificed at 1, 3, or 5 days after treatment. Ischemia was achieved by bilaterally occluding both kidneys with a microvascular clamp for 45 min and verified visually by a change in tissue color. After post-reperfusion, urine samples were collected at 9, 24, and 48 hr intervals. Urinary excretion of protein-based biomarkers was measured by Western blot analysis. In cisplatin-treated rats, mild histopathologic alterations were noted at day 1 which became severe at day 3. Blood urea nitrogen (BUN) and serum creatinine (SCr) levels were significantly increased at day 3. Levels of urinary excretion of SBP1, neutrophil gelatinase-associated lipocalin (NGAL), and a tissue inhibitor of metalloproteinase-1 (TIMP-1) were markedly elevated at day 3 and 5 following drug treatment. In the vehicle-treated I/R group, serum levels of BUN and SCr and AST activity were significantly increased compared to sham. Urinary excretion of SBP1 and NGAL rose markedly following I/R. The urinary levels of SBP1, NGAL, TIMP-1, and KIM-1 proteins excreted by AKI patients and normal subjects were compared. Among these proteins, a marked rise in SBP1 was observed in urine of patients with AKI compared to normal subjects. Based upon receiver-operator curves (ROC), SBP1 displayed a higher area under the curve (AUC) scores than levels of SCr, BUN, total protein, and glucose. In particular, SBP1 protein was readily detected in small amounts of urine without purification. Data thus indicate that urinary excretion of SBP1 may be useful as a reliable biomarker for early diagnosis of AKI in patients.

Dietary nitrate attenuates renal ischemia-reperfusion injuries by modulation of immune responses and reduction of oxidative stress

Ischemia-reperfusion (IR) injury involves complex pathological processes in which reduction of nitric oxide (NO) bioavailability is suggested as a key factor. Inorganic nitrate can form NO in vivo via NO synthase-independent pathways and may thus provide beneficial effects during IR. Herein we evaluated the effects of dietary nitrate supplementation in a renal IR model. Male mice (C57BL/6J) were fed nitrate-supplemented chow (1.0mmol/kg/day) or standard chow for two weeks prior to 30min ischemia and during the reperfusion period. Unilateral renal IR caused profound tubular and glomerular damage in the ischemic kidney. Renal function, assessed by plasma creatinine levels, glomerular filtration rate and renal plasma flow, was also impaired after IR. All these pathologies were significantly improved by nitrate. Mechanistically, nitrate treatment reduced renal superoxide generation, pro-inflammatory cytokines (IL-1β, IL-6 and IL-12 p70) and macrophage infiltration in the kidney. Moreover, nitrate reduced mRNA expression of pro-inflammatory cytokines and chemo attractors, while increasing anti-inflammatory cytokines in the injured kidney. In another cohort of mice, two weeks of nitrate supplementation lowered superoxide generation and IL-6 expression in bone marrow-derived macrophages. Our study demonstrates protective effect of dietary nitrate in renal IR injury that may be mediated via modulation of oxidative stress and inflammatory responses. These novel findings suggest that nitrate supplementation deserve further exploration as a potential treatment in patients at high risk of renal IR injury.

TAK1 as the mediator in the protective effect of propofol on renal interstitial fibrosis induced by ischemia/reperfusion injury

Ischemia-reperfusion injury (IRI), which is a major cause of acute and chronic renal dysfunction, induces both apoptosis and fibrotic processes. The mitogen-activated protein kinase kinase kinase transforming growth factor-β-activated kinase 1 (TAK1) was implicated in the processes of inflammation and fibrosis. The protective effect of propofol on renal functionality after acute kidney injury (AKI) in mice has been identified, whereas the mechanisms underlying fibrosis induced by kidney injury remain obscure. Herein, we investigated whether the protective effect of propofol on renal interstitial fibrosis induced by ischemia/reperfusion injury was modulated by TAK1 in renal ischemia /reperfusion (I/R) mouse models. The results of immunohistochemistry and western blotting revealed that TAK1 was significantly upregulated in IR group versus the control group, which was reversed by propofol administration. In addition, fibronectin (FN), α-smooth muscle actin (α-SMA) and type I collagen (COL1) were significantly downregulated and Tunnel staining revealed the number of tubular apoptotic cells was markedly reduced in IRP group versus IR group. Collectively, our results validated that propofol could ameliorate the IRI-induced renal interstitial fibrosis in mice by downregulation of TAK1 and inhibition of apoptosis at the early stage.

Innate Immune Response in Kidney Ischemia/Reperfusion Injury: Potential Target for Therapy

Acute kidney injury caused by ischemia and subsequent reperfusion is associated with a high rate of mortality and morbidity. Ischemia/reperfusion injury in kidney transplantation causes delayed graft function and is associated with more frequent episodes of acute rejection and progression to chronic allograft nephropathy. Alloantigen-independent inflammation is an important process, participating in pathogenesis of injurious response, caused by ischemia and reperfusion. This innate immune response is characterized by the activity of classical cells belonging to the immune system, such as neutrophils, macrophages, dendritic cells, lymphocytes, and also tubular epithelial cells and endothelial cells. These immune cells not only participate in inflammation after ischemia exerting detrimental influence but also play a protective role in the healing response from ischemia/reperfusion injury. Delineating of complex mechanisms of their actions could be fruitful in future prevention and treatment of ischemia/reperfusion injury. Among numerous so far conducted experiments, observed immunomodulatory role of adenosine and adenosine receptor agonists in complex interactions of dendritic cells, natural killer T cells, and T regulatory cells is emphasized as promising in the treatment of kidney ischemia/reperfusion injury. Potential pharmacological approaches which decrease NF-κB activity and antagonize mechanisms downstream of activated Toll-like receptors are discussed.

ELABELA and an ELABELA Fragment Protect against AKI

Renal ischemia-reperfusion (I/R) injury is the most common cause of AKI, which associates with high mortality and has no effective therapy. ELABELA (ELA) is a newly identified 32-residue hormone peptide highly expressed in adult kidney. To investigate whether ELA has protective effects on renal I/R injury, we administered the mature peptide (ELA32) or the 11-residue furin-cleaved fragment (ELA11) to hypoxia-reperfusion (H/R)-injured or adriamycin-treated renal tubular cells in vitro ELA32 and ELA11 significantly inhibited the elevation of the DNA damage response, apoptosis, and inflammation in H/R-injured renal tubular cells and suppressed adriamycin-induced DNA damage response. Similarly, overexpression of ELA32 or ELA11 significantly inhibited H/R-induced cell death, DNA damage response, and inflammation. Notably, treatment of mice with ELA32 or ELA11 but not an ELA11 mutant with a cysteine to alanine substitution at the N terminus (AE11C) inhibited I/R injury-induced renal fibrosis, inflammation, apoptosis, and the DNA damage response and markedly reduced the renal tubular lesions and renal dysfunction. Together, our results suggest that ELA32 and ELA11 may be therapeutic candidates for treating AKI.

Preoperative aspirin use and acute kidney injury after cardiac surgery: A propensity-score matched observational study

BACKGROUND

The association between preoperative aspirin use and postoperative acute kidney injury (AKI) in cardiovascular surgery is unclear. We sought to evaluate the effect of preoperative aspirin use on postoperative AKI in cardiac surgery.

METHODS

A total of 770 patients who underwent cardiovascular surgery under cardiopulmonary bypass were reviewed. Perioperative clinical parameters including preoperative aspirin administration were retrieved. We matched 108 patients who took preoperative aspirin continuously with patients who stopped aspirin more than 7 days or did not take aspirin for the month before surgery. The parameters used in the matching included variables related to surgery type, patient's demographics, underlying medical conditions and preoperative medications.

RESULTS

In the first seven postoperative days, 399 patients (51.8%) developed AKI, as defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria and 128 patients (16.6%) required hemodialysis. Most patients took aspirin 100 mg once daily (n = 195, 96.5%) and the remaining 75 mg once daily. Multivariable analysis showed that preoperative maintenance of aspirin was independently associated with decreased incidence of postoperative AKI (odds ratio [OR] 0.46, 95% confidence interval [CI] 0.21-0.98, P = 0.048; after propensity score matching: OR 0.39, 95% CI 0.22-0.67, P = 0.001). Preoperative maintenance of aspirin was associated with less incidence of AKI defined by KDIGO both in the entire and matched cohort (n = 44 [40.7%] vs. 69 [63.9%] in aspirin and non-aspirin group, respectively in matched sample, relative risk [RR] 0.64, 95% CI 0.49, 0.83, P = 0.001). Preoperative aspirin was associated with decreased postoperative hospital stay after matching (12 [9-18] days vs. 16 [10-25] in aspirin and non-aspirin group, respectively, P = 0.038). Intraoperative estimated or calculated blood loss using hematocrit difference and estimated total blood volume showed no difference according to aspirin administration in both entire and matched cohort.

CONCLUSIONS

Preoperative low dose aspirin administration without discontinuation was protective against postoperative AKI defined by KDIGO criteria independently in both entire and matched cohort. Preoperative aspirin was also associated with decreased hemodialysis requirements and decreased postoperative hospital stay without increasing bleeding. However, differences in AKI and hospital stay were not associated with in-hospital mortality.

Therapeutic potential of mesenchymal stem cells in acute kidney injury is affected by administration timing

Mesenchymal stem cell (MSC) transplantation is a promising therapy for acute kidney injury; however, the efficacy is limited due to poor survival after transplantation. In this study, we investigated how MSC transplantation timing affected the survival and therapeutic potential of MSCs in the kidney ischemia-reperfusion (I/R) injury model. After kidney I/R injury, the inflammatory process and tissue damage were characterized over 1 week post-I/R, we found that inflammation peaked at 12-24 h post-I/R (h.p.i.), and urine  neutrophil gelatinase-associated lipocalin (NGAL) measurements correlated highly with measures of inflammation. We cultured MSCs with supernatants from I/R injured kidney tissue homogenates collected at different time points and found that kidney homogenates from 12 and 24 h.p.i. were most toxic to MSCs, whereas homogenates from 1 h.p.i. were not as cytotoxic as those from 12 and 24 h.p.i. Compared with MSCs administered at 12, or 24 h.p.i., cells administered immediately after ischemia or 1 h.p.i. yielded the highest renoprotective and anti-inflammatory effects. Our findings indicate that MSC treatment for acute kidney injury is most effective when applied prior to the development of a potent inflammatory microenvironment, and urine NGAL may be helpful for detecting inflammation and selecting MSC transplantation timing in I/R kidney injury.

Vitamin C Attenuates Hemorrhagic Shock-induced Dendritic Cell-specific Intercellular Adhesion Molecule 3-grabbing Nonintegrin Expression in Tubular Epithelial Cells and Renal Injury in Rats

BACKGROUND

The expression of dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) in renal tubular epithelial cells has been thought to be highly correlated with the occurrence of several kidney diseases, but whether it takes place in renal tissues during hemorrhagic shock (HS) is unknown. The present study aimed to investigate this phenomenon and the inhibitory effect of Vitamin C (VitC).

METHODS

A Sprague-Dawley rat HS model was established in vivo in this study. The expression level and location of DC-SIGN were observed in kidneys. Also, the degree of histological damage, the concentrations of tumor necrosis factor-μ and interleukin-6 in the renal tissues, and the serum concentration of blood urea nitrogen and creatinine at different times (2-24 h) after HS (six rats in each group), with or without VitC treatment before resuscitation, were evaluated.

RESULTS

HS induced DC-SIGN expression in rat tubular epithelial cells. The proinflammatory cytokine concentration, histological damage scores, and functional injury of kidneys had increased. All these phenomena induced by HS were relieved when the rats were treated with VitC before resuscitation.

CONCLUSIONS

The results of the present study illustrated that HS could induce tubular epithelial cells expressing DC-SIGN, and the levels of proinflammatory cytokines in the kidney tissues improved correspondingly. The results also indicated that VitC could suppress the DC-SIGN expression in the tubular epithelial cells induced by HS and alleviate the inflammation and functional injury in the kidney.

Expression of Kidney Injury Molecule-1 in Healthy and Diseased Feline Kidney Tissue

Sensitive markers to detect acute kidney injury (AKI) in cats are lacking. Kidney injury molecule-1 (KIM-1) is a promising marker of acute tubular injury in humans, and sequence and structure of feline KIM-1 have been determined. KIM-1 is shed into urine of cats with natural AKI. The objectives of this study were to characterize temporal and cellular expression of KIM-1 in kidneys from cats without and with experimental and natural AKI using histopathology and immunohistochemistry. Tissue sections from 8 cats without kidney disease, 3 to 4 cats with experimentally induced AKI on each day 1, 3, 6, and 12 after unilateral ischemia/reperfusion, and 9 cats with natural AKI were assessed. In sections from cats without kidney disease, patterns of periodic acid–Schiff and aquaporin-1 staining allowed identification of 3 distinct segments of the proximal tubule. KIM-1 staining was absent in segments 1 (S1) and S2, and faint in S3. Injury of S3 in cats with experimental and natural AKI was characterized by cell loss and necrosis, and remaining intact cells had cytoplasmic blebs and reduced brush borders. In experimental AKI, intensity of KIM-1 expression increased in proportion to the severity of injury and was consistently present in S3 but only transiently in other segments. Vimentin was absent in proximal tubules of healthy cats but expressed in injured S3. These findings indicate that S3 is the proximal tubular segment most susceptible to ischemic injury and that KIM-1 is a sensitive tissue indicator of AKI in cats.

Targeting Inflammation in So-Called Acute Kidney Injury

The clinical category of acute kidney injury includes a wide range of completely different disorders, many with their own pathomechanisms and treatment targets. In this review we focus on the role of inflammation in the pathogenesis of acute tubular necrosis (ATN). We approach this topic by first discussing the role of the immune system in the different phases of ATN (ie, early and late injury phase, recovery phase, and the long-term outcome phase of an ATN episode). A more detailed discussion focuses on putative therapeutic targets among the following mechanisms and mediators: oxidative stress and reactive oxygen species-related necroinflammation, regulated cell death-related necroinflammation, immunoregulatory lipid mediators, cytokines and cytokine signaling, chemokines and chemokine signaling, neutrophils and neutrophils extracellular traps (NETs) associated neutrophil cell death, called NETosis, extracellular histones, proinflammatory mononuclear phagocytes, humoral mediators such as complement, pentraxins, and natural antibodies. Any prioritization of these targets has to take into account the intrinsic differences between rodent models and human ATN, the current acute kidney injury definitions, and the timing of clinical decision making. Several conceptual problems need to be solved before anti-inflammatory drugs that are efficacious in rodent ATN may become useful therapeutics for human ATN.

Association of Preoperative Urinary Uromodulin with AKI after Cardiac Surgery

BACKGROUND AND OBJECTIVES

AKI is a serious complication after cardiac surgery. Although high urinary concentrations of the tubular protein uromodulin, a marker of tubular health, are associated with less AKI in animal models, its relationship in humans is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A post hoc analysis of a prospective cohort study of 218 adults undergoing on-pump cardiac surgery between 2004 and 2011 was conducted. Multivariable logistic and linear regression analyses were used to evaluate the associations of preoperative urinary uromodulin-to-creatinine ratio with postoperative AKI (defined as a rise in serum creatinine of >0.3 mg/dl or >1.5 times baseline); severe AKI (doubling of creatinine or need for dialysis) and peak postoperative serum creatinine over the first 72 hours.

RESULTS

Mean age was 68 years, 27% were women, 95% were white, and the median uromodulin-to-creatinine ratio was 10.0 μg/g. AKI developed in 64 (29%) patients. Lower urinary uromodulin-to-creatinine ratio was associated with higher odds for AKI (odds ratio, 1.49 per 1-SD lower uromodulin; 95% confidence interval, 1.04 to 2.13), which was marginally attenuated after multivariable adjustment (odds ratio, 1.43; 95% confidence interval, 0.99 to 2.07). The lowest uromodulin-to-creatinine ratio quartile was also associated with higher odds for AKI relative to the highest quartile (odds ratio, 2.94; 95% confidence interval, 1.19 to 7.26), which was slightly attenuated after multivariable adjustment (odds ratio, 2.43; 95% confidence interval, 0.91 to 6.48). A uromodulin-to-creatinine ratio below the median was associated with higher adjusted odds for severe AKI, although this did not reach statistical significance (odds ratio, 4.03; 95% confidence interval, 0.87 to 18.70). Each 1-SD lower uromodulin-to-creatinine ratio was associated with a higher adjusted mean peak serum creatinine (0.07 mg/dl per SD; 95% confidence interval, 0.02 to 0.13).

CONCLUSIONS

Lower uromodulin-to-creatinine ratio is associated with higher odds of AKI and higher peak serum creatinine after cardiac surgery. Additional studies are needed to confirm these preliminary results.

Impact of Steroids on the Inflammatory Response after Ischemic Acute Kidney Injury in Rats

Inflammation plays a crucial role in acute kidney injury (AKI). The current study was designed to analyze the influence of prednisolone treatment on the inflammatory reaction during the first 96 h after AKI induction in a rat model. AKI was induced by unilateral clipping of the renal vessels. The treatment group received prednisolone 5 mg/kg s.c. daily. Infiltration rates of macrophages, leukocytes, and T-cells (24, 96 h) as well as plasma concentrations of the inflammatory markers intercellular adhesion molecule, interleukin-1 beta (IL-1β), IL-18, IL-6, and tumor necrosis factor-alpha (0, 6, 24, 96 h) were determined by fluorescence-activated cell sorting (FACS) analysis only. Ninety-six hours after AKI induction, the prednisolone group demonstrated significantly lower creatinine concentrations compared to the control group (P < 0.05). Twenty-four hours after induction of AKI, a significantly higher rate of infiltrating leukocytes was detectable with FACS analysis in the control group (P < 0.01) with a corresponding significantly higher rate of macrophages after 96 h (P < 0.01). IL-6 and IL-1β demonstrated a peak after 6 h with a significantly higher release in the control group (IL-6: P < 0.01; IL-1β: P < 0.05). In contrast to the control group, the prednisolone group demonstrated no further incline of IL-18 after 24 h. The results demonstrate the importance of stretching the observation period in an ischemia-reperfusion-induced AKI setting beyond the first 24 h. Despite the demonstrated protective effects of a continuous prednisolone application, it seems that this single anti-inflammatory agent will not be able to completely suppress the inflammatory response after an ischemia-reperfusion-induced AKI.

SIRT1 regulates lipopolysaccharide-induced CD40 expression in renal medullary collecting duct cells by suppressing the TLR4-NF-κB signaling pathway

AIMS

Recent evidence indicates that sirtuin1 (SIRT1), an NAD⁺-dependent deacetylase, exerts a protective effect against inflammatory kidney injury by suppressing pro-inflammatory cytokines production. The co-stimulatory molecule, CD40, is expressed in a variety of inflammatory diseases in the kidney. Here, we aimed to investigate the potential effect of SIRT1 on CD40 expression induced by lipopolysaccharide (LPS) and to disclose the underlying mechanisms in renal inner medullary collecting duct (IMCD) cells.

MAIN METHODS

mRNA and protein expressions were identified by quantitative real-time PCR and Western blot respectively. Subcellular localization of SIRT1 and CD40 were respectively detected by immunofluorescence and immunohistochemical staining. Small-interfering RNA (siRNA) was carried out for mechanism study.

KEY FINDINGS

LPS reduced SIRT1 expression and up-regulated the expression of CD40, Toll-like receptor 4 (TLR4) and phospho-NF-κBp65 (p-NF-κBp65) in time- and concentration-dependent manners. Moreover, SIRT1 overexpression or activation by SRT1720 diminished the expression of CD40, TLR4 and p-NF-κBp65, which was reversed by SIRT1 siRNA or inhibitors Ex527 and sirtinol in LPS-stimulated IMCD cells. In addition, knockdown of TLR4 decreased the expression of CD40 and p-NF-κBp65 in IMCD cells exposed to LPS. Knockdown of NF-κBp65 or NF-κBp65 inhibition by pyrrolidine dithiocarbamate (PDTC) reduced LPS-induced CD40 expression in IMCD cells. Importantly, the inhibitory effect of SIRT1 on the expression of CD40 and p-NF-κBp65 was augmented by pre-treating with TLR4 siRNA.

SIGNIFICANCE

Our data indicate that SIRT1 inhibits LPS-induced CD40 expression in IMCD cells by suppressing the TLR4-NF-κB signaling pathway, which might provide novel insight into understanding the protective effect of SIRT1 in kidney.

Sodium Pentosan Polysulfate Reduced Renal Ischemia-Reperfusion-Induced Oxidative Stress and Inflammatory Responses in an Experimental Animal Model

Acute kidney injury (AKI) remains an independent risk factor for mortality and morbidity after vascular surgery (affecting the renal arteries) or aortic surgery (requiring suprarenal aortic clamping). These types of vascular surgery produce renal ischemia/reperfusion (I/R) injury, a common cause of AKI. The present studies aimed at monitoring the course of renal I/R injury at the cellular level and investigating the efficacy of long-term preoperative and single-shot intraoperative administration of sodium pentosan polysulfate (PPS) to protect renal tissue from acute I/R injury both in native and diabetic kidneys in rats. Western blot analyses of the proapoptotic (bax) and antiapoptotic (bcl-2) signaling pathways, as well as the extent of DNA damage (phospho-p53), were performed. Oxidative stress followed upon the termination of malondialdehyde, reduced glutathione, thiol group, and superoxide dismutase plasma levels. Inflammatory changes were measured by the determination of serum tumor necrosis factor-α and interleukin-1 levels. Morphological changes were detected by histological examinations. Our results showed that the long-term administration of PPS has an advantage in reducing I/R kidney injury in diabetic rats, while high-dose, single-shot parenteral administration of PPS prior to revascularization might be useful in nondiabetic rats.

Risk Assessment of Patients Undergoing Transfemoral Aortic Valve Implantation upon Admission for Post-Interventional Intensive Care and Surveillance: Implications on Short- and Midterm Outcomes

Background

Several studies have found that standard risk scores inaccurately reflect risk in TAVI cohorts. The assessment of mortality risk upon post-interventional ICU admission is important to optimizing clinical management. This study sought to determine outcomes and factors affecting mortality in patients admitted to the intensive care unit (ICU) after transcatheter aortic valve implantation (TAVI), and to analyze and compare the predictive values of SAPS II and EuroSCORE.

Methods and Findings

214 consecutive patients treated with transfemoral TAVI (2006–2012) admitted to the ICU in an academic tertiary-care university hospital, were included in this retrospective data analysis. The overall 30-day mortality rate was 7%. Non-survivors at 30-days and survivors showed differences in the rates of catecholamine therapy upon ICU admission (93 vs. 29%; p<0.001), stroke (20 vs. 1%;p<0.001), sepsis (27 vs. 2%;p<0.001), kidney injury (83 vs. 56%; log-rank p<0.001), catecholamine therapy (88 vs. 61%;log-rank p<0.001) and vascular complications (60 vs. 17%; p<0.001). Mean SAPS II score and predicted mortality were higher in non-survivors (38.1±7.0 vs. 29.9±6.2;p<0.001 and 23.1±11.7 vs. 10.5±8.2;p<0.001, retrospectively), whereas the logistic EuroSCORE could not discriminate between the groups (p = 0.555). Among the biochemical parameters, the maximum values of creatinine, procalcitonin, and troponin I during the first 48 h after ICU admission were significantly higher in non-survivors. Multivariate analysis of baseline characteristics and complications associated with two-year mortality showed no significant results.

Conclusions

The SAPS II is a good tool for estimating ICU mortality immediately after performing the TAVI procedure and provides valuable information for other known predictors of mortality.

Acute Kidney Injury

Acute kidney injury (AKI) is a global public health concern associated with high morbidity, mortality, and healthcare costs. Other than dialysis, no therapeutic interventions reliably improve survival, limit injury, or speed recovery. Despite recognized shortcomings of in vivo animal models, the underlying pathophysiology of AKI and its consequence, chronic kidney disease (CKD), is rich with biological targets. We review recent findings relating to the renal vasculature and cellular stress responses, primarily the intersection of the unfolded protein response, mitochondrial dysfunction, autophagy, and the innate immune response. Maladaptive repair mechanisms that persist following the acute phase promote inflammation and fibrosis in the chronic phase. Here macrophages, growth-arrested tubular epithelial cells, the endothelium, and surrounding pericytes are key players in the progression to chronic disease. Better understanding of these complex interacting pathophysiological mechanisms, their relative importance in humans, and the utility of biomarkers will lead to therapeutic strategies to prevent and treat AKI or impede progression to CKD or end-stage renal disease (ESRD).

Analyzing gene expression profiles in dilated cardiomyopathy via bioinformatics methods

Dilated cardiomyopathy (DCM) is characterized by ventricular dilatation, and it is a common cause of heart failure and cardiac transplantation. This study aimed to explore potential DCM-related genes and their underlying regulatory mechanism using methods of bioinformatics. The gene expression profiles of GSE3586 were downloaded from Gene Expression Omnibus database, including 15 normal samples and 13 DCM samples. The differentially expressed genes (DEGs) were identified between normal and DCM samples using Limma package in R language. Pathway enrichment analysis of DEGs was then performed. Meanwhile, the potential transcription factors (TFs) and microRNAs (miRNAs) of these DEGs were predicted based on their binding sequences. In addition, DEGs were mapped to the cMap database to find the potential small molecule drugs. A total of 4777 genes were identified as DEGs by comparing gene expression profiles between DCM and control samples. DEGs were significantly enriched in 26 pathways, such as lymphocyte TarBase pathway and androgen receptor signaling pathway. Furthermore, potential TFs (SP1, LEF1, and NFAT) were identified, as well as potential miRNAs (miR-9, miR-200 family, and miR-30 family). Additionally, small molecules like isoflupredone and trihexyphenidyl were found to be potential therapeutic drugs for DCM. The identified DEGs (PRSS12 and FOXG1), potential TFs, as well as potential miRNAs, might be involved in DCM.

Involvement of peroxisome proliferator activated receptor-γ in the anti-inflammatory effects of atorvastatin in oxygen-glucose deprivation/reperfusion-stimulated RAW264.7 murine macrophages

Ischemia-reperfusion (I/R) injury is important in the pathogenesis and/or progression of various diseases, including stroke, cardiovascular disease and acute renal injury. Increasing evidence indicates that atorvastatin exerts protective effects in I/R injury-associated diseases; however, the underlying mechanisms remain to be fully elucidated. In the present study, oxygen-glucose deprivation (OGD)/reperfusion-stimulated. RAW264.7 murine macrophages served as a model of I/R injury. The knockdown of peroxisome proliferator activated receptor-γ (PPARγ) expression in these cells increased OGD/reperfusion-induced expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), and enhanced OGD/reperfusion-induced downregulation of the expression of cluster of differentiation (CD) 206, at the mRNA and protein levels. Conversely, overexpression of PPARγ significantly attenuated OGD/reperfusion-induced alterations in the expression of iNOS, TNF-α, IFN-γ and CD206 at the mRNA and protein levels. Notably, atorvastatin inhibited OGD/reperfusion-induced iNOS expression and reversed OGD/reperfusion-induced downregulation of the expression of CD206 and PPARγ at the mRNA and protein levels. The results of the present study indicate that atorvastatin exhibits significant anti-inflammatory effects in OGD/reperfusion-stimulated RAW264.7 cells, possibly via PPARγ regulation. The findings of the present study may reveal a novel mechanism underlying the protective effects of atorvastatin in I/R injury-associated diseases.

ABT-719 for the Prevention of Acute Kidney Injury in Patients Undergoing High-Risk Cardiac Surgery: A Randomized Phase 2b Clinical Trial

Background

Patients undergoing cardiac surgeries with cardiopulmonary bypass (on‐pump) have a high risk for acute kidney injury (AKI). We tested ABT‐719, a novel α‐melanocyte‐stimulating hormone analog, for prevention of AKI in postoperative cardiac surgery patients.

Methods and Results

This phase 2b randomized, double‐blind, placebo‐controlled trial included adult patients with stable renal function undergoing high‐risk on‐pump cardiac surgery in the United States and Denmark. Participants received placebo (n=61) or cumulative ABT‐719 doses of 800 (n=59), 1600 (n=61), or 2100 μg/kg (n=59). Primary outcome was development of AKI based on Acute Kidney Injury Network (AKIN) criteria, measured utilizing preoperative creatinine value and maximum value within 48 hours and urine output within the first 42 hours postsurgery. Secondary outcomes included incidence of AKI based on maximal changes from baseline in novel AKI biomarkers over a 72‐hour period after clamp release and length of intensive care unit stays through 90 days postsurgery. A total of 65.5%, 62.7%, and 69.6% of patients in the 800‐, 1600‐, and 2100‐μg/kg groups, respectively, developed AKI (stages 1, 2, and 3 combined) versus 65.5% in the placebo group (for each pair‐wise comparison with placebo, P=0.966, 0.815, and 0.605, respectively). Adverse events occurred at a similar rate in all treatment groups.

Conclusions

ABT‐719 treatment did not lower AKI incidence using AKIN criteria, influence the elevations of novel biomarkers, or change 90‐day outcomes in patients after cardiac surgery.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01777165.

Renoprotective effect of a combination of garlic and telmisartan against ischemia/reperfusion-induced kidney injury in obese rats

Obesity enhances the frequency and severity of acute kidney injury (AKI). Telmisartan pre-treatment was used experimentally in the amelioration of ischemia/reperfusion (IR)-induced AKI. However, there is a lack of evidence regarding its beneficial effects on AKI in obese animals. The present study, therefore, aimed to explore the protective effects of garlic and/or telmisartan against renal damage induced by unilateral IR in obese rats. Meloxicam was used as a standard anti-inflammatory agent. Prophylactic oral administration of meloxicam (3 mg kg(-1)), garlic (500 mg kg(-1)) and/or telmisartan (5 and 10 mg kg(-1)) for 4 wk protected against renal function deterioration induced by IR in obese rats. Both doses of telmisartan significantly reduced serum total cholesterol and triacyglycerol levels as well as peri-renal adipocytes size and renal fibrosis. Renal nuclear factor-kappa B immunoreactivity, tumor necrosis factor-alpha content as well as interleukin-10, adiponectin receptor 1 and macrophages (M1, M2) polarization markers (CD11c, CD206) mRNA expressions were down-regulated in ischemic kidney tissues and white adipose tissues around them by all treatments. Moreover, garlic, telmisartan and their combinations significantly suppressed oxidative stress in renal ischemic tissues. Histological picture was also improved by these treatments. Interestingly, the combinations provided a greater protection than their monotherapy in a dose-dependent manner. We suppose that this combination may be a promising prophylactic regimen for managing AKI in case of obesity. Thus, future experimental and clinical large-scale studies are necessary.

The multifaceted role of the renal microvasculature during acute kidney injury

Pediatric acute kidney injury (AKI) represents a complex disease process for clinicians as it is multifactorial in cause and only limited treatment or preventatives are available. The renal microvasculature has recently been implicated in AKI as a strong therapeutic candidate involved in both injury and recovery. Significant progress has been made in the ability to study the renal microvasculature following ischemic AKI and its role in repair. Advances have also been made in elucidating cell-cell interactions and the molecular mechanisms involved in these interactions. The ability of the kidney to repair post AKI is closely linked to alterations in hypoxia, and these studies are elucidated in this review. Injury to the microvasculature following AKI plays an integral role in mediating the inflammatory response, thereby complicating potential therapeutics. However, recent work with experimental animal models suggests that the endothelium and its cellular and molecular interactions are attractive targets to prevent injury or hasten repair following AKI. Here, we review the cellular and molecular mechanisms of the renal endothelium in AKI, as well as repair and recovery, and potential therapeutics to prevent or ameliorate injury and hasten repair.

Heyman S, Lupo A, Vlodavsky I, Abassi Z. Heparanase: A Potential New Factor Involved in the Renal Epithelial Mesenchymal Transition (EMT) Induced by Ischemia/Reperfusion (I/R) Injury

BACKGROUND

Ischemia/reperfusion (I/R) is an important cause of acute renal failure and delayed graft function, and it may induce chronic renal damage by activating epithelial to mesenchymal transition (EMT) of renal tubular cells. Heparanase (HPSE), an endoglycosidase that regulates FGF-2 and TGFβ-induced EMT, may have an important role. Therefore, aim of this study was to evaluate its role in the I/R-induced renal pro-fibrotic machinery by employing in vitro and in vivo models.

METHODS

Wild type (WT) and HPSE-silenced renal tubular cells were subjected to hypoxia and reoxygenation in the presence or absence of SST0001, an inhibitor of HPSE. In vivo, I/R injury was induced by bilateral clamping of renal arteries for 30 min in transgenic mice over-expressing HPSE (HPA-tg) and in their WT littermates. Mice were sacrificed 48 and 72 h after I/R. Gene and protein EMT markers (α-SMA, VIM and FN) were evaluated by bio-molecular and histological methodologies.

RESULTS

In vitro: hypoxia/reoxygenation (H/R) significantly increased the expression of EMT-markers in WT, but not in HPSE-silenced tubular cells. Notably, EMT was prevented in WT cells by SST0001 treatment. In vivo: I/R induced a remarkable up-regulation of EMT markers in HPA-tg mice after 48-72 h. Noteworthy, these effects were absent in WT animals.

CONCLUSIONS

In conclusion, our results add new insights towards understanding the renal biological mechanisms activated by I/R and they demonstrate, for the first time, that HPSE is a pivotal factor involved in the onset and development of I/R-induced EMT. It is plausible that in future the inhibition of this endoglycosidase may represent a new therapeutic approach to minimize/prevent fibrosis and slow down chronic renal disease progression in native and transplanted kidneys.

C-reactive protein promotes acute kidney injury via Smad3-dependent inhibition of CDK2/cyclin E

Acute kidney injury (AKI) is exacerbated in C-reactive protein transgenic mice but alleviated in Smad3 knockout mice. Here we used C-reactive protein transgenic/Smad3 wild-type and C-reactive protein transgenic/Smad3 knockout mice to investigate the signaling mechanisms by which C-reactive protein promotes AKI. Serum creatinine was elevated, and the extent of tubular epithelial cell necrosis following ischemia/reperfusion-induced AKI was greater in C-reactive protein transgenics but was blunted when Smad3 was deleted. Exacerbation of AKI in C-reactive protein transgenics was associated with increased TGF-β/Smad3 signaling and expression of the cyclin kinase inhibitor p27, but decreased phosphorylated CDK2 and expression of cyclin E. Concomitantly, tubular epithelial cell proliferation was arrested at the G1 phase in C-reactive protein transgenics with fewer cells entering the S-phase cell cycle as evidenced by fewer bromodeoxyuridine-positive cells. In contrast, the protection from AKI in C-reactive protein transgenic/Smad3 knockout mice was associated with decreased expression of p27 and promotion of CDK2/cyclin E-dependent G1/S transition of tubular epithelial cells. In vitro studies using tubular epithelial cells showed that C-reactive protein activates Smad3 via both TGF-β-dependent and ERK/MAPK cross talk mechanisms, Smad3 bound directly to p27, and blockade of Smad3 or the Fc receptor CD32 prevented C-reactive protein-induced p27-dependent G1 cell cycle arrest. In vivo, treatment of C-reactive protein transgenics with a Smad3 inhibitor largely improved AKI outcomes. Thus, C-reactive protein may promote AKI by impairing tubular epithelial cell regeneration via the CD32-Smad3-p27-driven inhibition of the CDK2/cyclin E complex. Targeting Smad3 may offer a new treatment approach for AKI.