Acute kidney injury and lung dysfunction: a paradigm for remote organ effects of kidney disease?

Renalase Challenges the Oxidative Stress and Fibroproliferative Response in COVID-19

The hallmark of the coronavirus disease 2019 (COVID-19) pathophysiology was reported to be an inappropriate and uncontrolled immune response, evidenced by activated macrophages, and a robust surge of proinflammatory cytokines, followed by the release of reactive oxygen species, that synergistically result in acute respiratory distress syndrome, fibroproliferative lung response, and possibly even death. For these reasons, all identified risk factors and pathophysiological processes of COVID-19, which are feasible for the prevention and treatment, should be addressed in a timely manner. Accordingly, the evolving anti-inflammatory and antifibrotic therapy for severe COVID-19 and hindering post-COVID-19 fibrosis development should be comprehensively investigated. Experimental evidence indicates that renalase, a novel amino-oxidase, derived from the kidneys, exhibits remarkable organ protection, robustly addressing the most powerful pathways of cell trauma: inflammation and oxidative stress, necrosis, and apoptosis. As demonstrated, systemic renalase administration also significantly alleviates experimentally induced organ fibrosis and prevents adverse remodeling. The recognition that renalase exerts cytoprotection via sirtuins activation, by raising their NAD⁺ levels, provides a “proof of principle” for renalase being a biologically impressive molecule that favors cell protection and survival and maybe involved in the pathogenesis of COVID-19. This premise supports the rationale that renalase's timely supplementation may prove valuable for pathologic conditions, such as cytokine storm and related acute respiratory distress syndrome. Therefore, the aim for this review is to acknowledge the scientific rationale for renalase employment in the experimental model of COVID-19, targeting the acute phase mechanisms and halting fibrosis progression, based on its proposed molecular pathways. Novel therapies for COVID-19 seek to exploit renalase's multiple and distinctive cytoprotective mechanisms; therefore, this review should be acknowledged as the thorough groundwork for subsequent research of renalase's employment in the experimental models of COVID-19.

Urinary metabolomics to develop predictors for pediatric acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is characterized by an abrupt decline in glomerular filtration rate (GFR). We sought to identify separate early urinary metabolomic signatures at AKI onset (with-AKI) and prior to onset of functional impairment (pre-AKI).

METHODS

Pre-AKI (n=15), AKI (n=22), and respective controls (n=30) from two prospective PICU cohort studies provided urine samples which were analyzed by GC-MS and DI-MS mass spectrometry (193 metabolites). The cohort (n=58) was 8.7±6.4 years old and 66% male. AKI patients had longer PICU stays, higher PRISM scores, vasopressors requirement, and respiratory diagnosis and less commonly had trauma or post-operative diagnosis. Urine was collected within 2-3 days after admission and daily until day 5 or 14.

RESULTS

The metabolite classifiers for pre-AKI samples (1.5±1.1 days prior to AKI onset) had a cross-validated area under receiver operator curve (AUC)=0.93 (95%CI 0.85-1.0); with-AKI samples had an AUC=0.94 (95%CI 0.87-1.0). A parsimonious pre-AKI classifier with 13 metabolites was similarly robust (AUC=0.96, 95%CI 0.89-1.0). Both classifiers were similar and showed modest correlation of high-ranking metabolites (tau=0.47, p<0.001).

CONCLUSIONS

This exploratory study demonstrates the potential of a urine metabolite classifier to detect AKI-risk in pediatric populations earlier than the current standard of diagnosis with the need for external validation. A higher resolution version of the Graphical abstract is available as Supplementary information with inner reference to ESM for GA.

Lung-kidney interactions and their role in chronic kidney disease-associated pulmonary diseases

Chronic illnesses rarely present in a vacuum, devoid of other complications, and chronic kidney disease is hardly an exception. Comorbidities associated with chronic kidney disease lead to faster disease progression, expedited dialysis dependency, and a higher mortality rate. Although chronic kidney disease is most commonly accompanied by cardiovascular diseases and diabetes, there is clear cross talk between the lungs and kidneys pH balance, phosphate metabolism, and immune system regulation. Our present understanding of the exact underlying mechanisms that contribute to chronic kidney disease-related pulmonary disease is poor. This review summarizes the current research on kidney-pulmonary interorgan cross talk in the context of chronic kidney disease, highlighting various acute and chronic pulmonary diseases that lead to further complications in patient care. Treatment options for patients presenting with chronic kidney disease and lung disease are explored by assessing activated molecular pathways and the body's compensatory response mechanisms following homeostatic imbalance. Understanding the link between the lungs and kidneys will potentially improve health outcomes for patients and guide healthcare professionals to better understand how and when to treat each of the pulmonary comorbidities that can present with chronic kidney disease.

Ameliorative Effects of Oleuropein on Lipopolysaccharide-Induced Acute Lung Injury Model in Rats

Acute lung injury (ALI) is one of the most common causes of death in diseases with septic shock. Oleuropein, one of the important components of olive leaf, has antioxidant and anti-inflammatory effects. The objective of this study was to investigate the effects of oleuropein on lipopolysaccharide (LPS)-induced ALI in rats. Oleuropein was administered to rats at a dose of 200 mg/kg for 20 days and LPS was given through intratracheal administration to induce ALI. The study was terminated after 12 h. The results showed that in the group treated with oleuropein, inflammatory cytokines and oxidative stress decreased in serum, bronchoalveolar lavage fluid (BALF), and lung tissue, and there were significant improvements in the picture of acute interstitial pneumonia (AIP) caused by LPS in histopathological examination. Based on the findings of the present study, oleuropein showed protective effects against LPS-induced ALI.

The influence of renal ischemia-reperfusion injury on remote organs: The histological brain changes in male and female rats

INTRODUCTION:

Brain tissue was adversely affected by renal ischemia-reperfusion injury (renal IRI) in several studies. Moreover, we are awareness that kidney diseases are gender dependent, but there is not enough evidence of the impact of gender on renal IRI-induced brain injury. Hence, this study was designed to investigate gender differences in renal IRI-induced brain tissue injury in adult rats.

MATERIALS AND METHODS:

Forty Wistar rats (four groups) include two main groups (20 male and 20 female). Each of them was divided into two subgroups including 1 and 2: male and female sham-operated groups and 3and 4: male and female ischemia (ISC) groups were exposed to renal ischemia for 45 min and then 24 h reperfusion (male and female ISC 24 h). Sham groups were exposed to surgery without ischemia process. After reperfusion time, blood samples were obtained for the renal function measurements. The kidney and brain were removed and were fixed in a 10% formalin solution for pathological assessment. The left kidney was used to measure malondialdehyde (MDA) and nitrite.

RESULTS:

Renal IRI increased significantly levels of creatinine, blood urea nitrogen, kidney weight, and damage score in both genders (P < 0.05). Furthermore, brain injuries were significantly higher following 24 h of reperfusion in male and female groups. Serum nitrite level and MDA concentration of female rats decreased significantly in ISC 24 h group (P < 0.05) but not in male rats.

CONCLUSION:

The brain tissue of both genders, male and female, is affected by renal IRI as a remote organ. Female sex hormones may indicate a protective role against IR by the nitric oxide pathway and antioxidant signaling.

Norepinephrine released by intestinal Paneth cells exacerbates ischemic AKI

Small intestinal Paneth cells play a critical role in acute kidney injury (AKI) and remote organ dysfunction by synthesizing and releasing IL-17A. In addition, intestine-derived norepinephrine is a major mediator of hepatic injury and systemic inflammation in sepsis. We tested the hypothesis that small intestinal Paneth cells synthesize and release norepinephrine to exacerbate ischemic AKI. After ischemic AKI, we demonstrated larger increases in portal venous norepinephrine levels compared with plasma norepinephrine in mice, consistent with an intestinal source of norepinephrine release after renal ischemia and reperfusion. We demonstrated that murine small intestinal Paneth cells express tyrosine hydroxylase mRNA and protein, a critical rate-limiting enzyme for the synthesis of norepinephrine. We also demonstrated mRNA expression for tyrosine hydroxylase in human small intestinal Paneth cells. Moreover, freshly isolated small intestinal crypts expressed significantly higher norepinephrine levels after ischemic AKI compared with sham-operated mice. Suggesting a critical role of IL-17A in Paneth cell-mediated release of norepinephrine, recombinant IL-17A induced norepinephrine release in the small intestine of mice. Furthermore, mice deficient in Paneth cells (SOX9 villin Cre mice) have reduced plasma norepinephrine levels after ischemic AKI. Finally, supporting a critical role for norepinephrine in generating ischemic AKI, treatment with the selective α-adrenergic antagonists yohimbine and phentolamine protected against murine ischemic AKI with significantly reduced renal tubular necrosis, inflammation, and apoptosis and less hepatic dysfunction. Taken together, we identify Paneth cells as a critical source of norepinephrine release that may lead to intestinal and liver injury and systemic inflammation after AKI.

Lung ultrasound to detect and monitor pulmonary congestion in patients with acute kidney injury in nephrology wards: a pilot study

INTRODUCTION

Lung congestion and frank pulmonary edema are established complications of acute kidney injury (AKI) and early detection and monitoring of lung congestion may be useful for the clinical management of AKI patients.

METHODS

We compared standardized clinical criteria (including lung crackles and peripheral edema grading) and simultaneous chest ultrasound (US) to detect lung congestion in a series of 39 inpatients with AKI.

RESULTS

At baseline, twelve patients (31%) were clinically euvolemic and twelve presented clear-cur cardiovascular congestion (31%) by clinical criteria. Fifteen patients (38%) were hypovolemic. The median number of US-B lines in patients with cardiovascular congestion was much higher (50, inter-quartile range 27-99) than in euvolemic (14, IQR 11-37) and hypovolemic patients (7, IQR 3-16, P < 0.001). Remarkably, a substantial proportion of asymptomatic euvolemic (66%) and hypovolemic (46%) patients had lung congestion of moderate to severe degree (> 15 US-B lines) by lung US. Crackles severity and the number of US-B lines over time were inter-related (Spearman's ρ = 0.38, P < 0.01) but the agreement (Cohen k statistics) between the two metrics was unsatisfactory. Forty-eight percent of patients had lung congestion of moderate to severe degree by lung US and this estimate by far exceeded that by clinical criteria (32%).

CONCLUSIONS

This pilot study shows that chest US has potential for the detection of lung congestion at a pre-clinical stage in AKI. The results of this pilot study form the basis for a clinical trial testing the usefulness of this technique for guiding lung congestion treatment in patients with AKI.

Treatment with toll-like receptor 2 inhibitor ortho-vanillin alleviates lipopolysaccharide-induced acute kidney injury in mice

Reducing inflammation is a promising approach for the prevention and treatment of septic acute kidney injury (AKI), since AKI is characterized by excessive inflammation in the kidney. Previous studies have demonstrated that toll-like receptor 2 (TLR2) is overstimulated, which promotes inflammation by activating the NF-κB signaling pathway, in a lipopolysaccharide (LPS)-induced model of AKI mice. For the present study, it was hypothesized that TLR2 inhibition could reduce inflammation and consequently prevent septic AKI. Therefore, the potential renal protective effects of ortho-vanillin (OV), an inhibitor of TLR2, were investigated in the present study in vitro and in vivo. In vitro treatment with OV on LPS-stimulated mouse podocyte cell line MPC5 did not affect TLR2 expression but interrupted the interaction between TLR2 and its downstream adaptor MyD88, resulting in the reduction of inflammatory cytokines IL-6 and TNF-α expression. In vivo OV treatment in an LPS-challenged mouse model effectively alleviated LPS-induced kidney injury as indicated by histology analysis and the significantly reduced blood urea nitrogen and serum creatinine levels. Additionally, inflammatory cytokines TNF-α, IL-6 and IL-1β expression were also significantly reduced in mice with OV treatment. Signaling pathway analysis further demonstrated that OV treatment did not affect the expression of TLR2 and p65 but suppressed p65 phosphorylation. Taken together, data from the present study demonstrated that OV was effective in protecting renal function against LPS-induced AKI through the inhibition of TLR2/NF-κB signaling and subsequent inflammatory cytokine production. These findings indicated that OV or targeting TLR2 signaling in general, represents a novel therapeutic approach for use in the prevention and treatment of AKI.

Angiopoietin-2 as a predictor of acute kidney injury in critically ill patients and association with ARDS

BACKGROUND AND OBJECTIVE

Angiopoietin-2 (AGPT2) has been proposed as a key mediator of organ dysfunction, mainly in acute respiratory distress syndrome (ARDS). It has also been associated with acute kidney injury (AKI). We aimed to investigate the role of AGPT2 in patients with and without ARDS.

METHODS

In a cohort study with critically ill patients, AGPT1 and AGPT2 were assayed in plasma collected within the first 24 h after admission to intensive care unit (ICU). Severe AKI and the need for dialysis were outcome measures from comparative analysis with clinical characteristics useful for AKI risk stratification.

RESULTS

Among 283 patients (50.2% males), 109 (38.5%) had ARDS. AGPT2 levels at admission were higher in patients with ARDS. Although overall AGPT2 and AGPT2/AGPT1 levels were associated with severe AKI, this association was not significant in patients without ARDS; however, it remained strongly significant in ARDS patients. In patients without ARDS, AGPT2 showed only a weak discriminatory capacity to predict severe AKI (area under the curve (AUC): 0.64 vs 0.81 in the ARDS group). The continuous net reclassification improvement (NRI) in the ARDS group resulting from AGPT2 inclusion was 64.1% (P < 0.001) and the integrated discrimination improvement (IDI) index was 0.057 (P = 0.003). There was no significant difference in NRI in the no-ARDS group.

CONCLUSION

AGPT2 and AGPT2/AGPT1 ratio are associated with severe AKI and there was only a need of renal replacement therapy (RRT) in patients with or at risk of ARDS, not in other critically ill patients. Adding AGPT2 to a clinical model resulted in a significant improvement in the capacity to predict severe AKI specifically in ARDS patients.

The aquaporin 5 -1364A/C promoter polymorphism impacts on resolution of acute kidney injury in pneumonia evoked ARDS

Background

Aquaporin 5 (AQP5) expression impacts on cellular water transport, renal function but also on key mechanisms of inflammation and immune cell migration that prevail in sepsis and ARDS. Thus, the functionally relevant AQP5 -1364A/C promoter single nucleotide polymorphism could impact on the development and resolution of acute kidney injury (AKI). Accordingly, we tested the hypothesis that the AQP5 promoter -1364A/C polymorphism is associated with AKI in patients suffering from pneumonia evoked ARDS.

Methods

This prospective study included 136 adult patients of Caucasian ethnicity with bacterially evoked pneumonia resulting in ARDS. Blood sampling was performed within 24 hours of ICU admission and patients were genotyped for the AQP5 promoter -1364A/C single nucleotide polymorphism. The development of an AKI and the cumulative net fluid balance was described over a 30-day observation period and compared between the AA and AC/CC genotypes, and between survivors and non-survivors.

Results

Incidence of an AKI upon admission did not differ in AA (58%) and AC/CC genotype carriers (60%; p = 0.791). However, on day 30, homozygous AA genotypes (57%) showed an increased prevalence of AKI compared to AC/CC genotypes (24%; p = 0.001). Furthermore, the AA genotype proved to be a strong, independent risk factor for predicting AKI persistence (odds-ratio: 3.35; 95%-CI: 1.2–9.0; p = 0.017). While a negative cumulative fluid balance was associated with increased survival (p = 0.001) the AQP5 promoter polymorphism had no impact on net fluid balance (p = 0.96).

Conclusions

In pneumonia evoked ARDS, the AA genotype of the AQP5 promoter polymorphism is associated with a decreased recovery rate from AKI and this is independent of fluid balance. Consequently, the role of AQP5 in influencing AKI likely rests in factors other than fluid balance.

IL-35 Pretreatment Alleviates Lipopolysaccharide-Induced Acute Kidney Injury in Mice by Inhibiting NF-κB Activation

Septic acute kidney injury (AKI) is a public health problem with high mortality. Suppression of over-active inflammation is considered as a promising strategy for septic AKI. In this study, we evaluated the prophylactic effect of interleukin (IL)-35, the unique immune-suppressive member of IL-12 cytokine family, on lipopolysaccharide (LPS)-induced AKI in mice, and found that compared with control mice given empty vector, mice pretreated with plasmid encoding IL-35 (pIL-35) significantly improved renal function indicated by reduced blood urea nitrogen (BUN) and serum creatinine (SCr), and obviously alleviated renal pathological changes. To explore the underlying protective mechanisms, we found that pIL-35 treatment could robustly reduce the production of renal pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β), with no significant impact on IL-10, an anti-inflammatory cytokine. Furthermore, our results revealed that IL-35 pretreatment could potentially inhibit the activation of renal NF-κB signaling pathway in LPS-induced AKI mice. Taken together, our study indicated that IL-35 pretreatment could efficiently prevent LPS-induced AKI via inhibiting NF-κB activation and reducing pro-inflammatory cytokine production, and it might represent a novel therapeutic strategy against septic AKI and other inflammatory renal diseases.

Nephrogenic acute respiratory distress syndrome: A narrative review on pathophysiology and treatment

The kidneys have a close functional relationship with other organs especially the lungs. This connection makes the kidney and the lungs as the most organs involved in the multi-organ failure syndrome. The combination of acute lung injury (ALI) and renal failure results a great clinical significance of 80% mortality rate. Acute kidney injury (AKI) leads to an increase in circulating cytokines, chemokines, activated innate immune cells and diffuse of these agents to other organs such as the lungs. These factors initiate pathological cascade that ultimately leads to ALI and acute respiratory distress syndrome (ARDS). We comprehensively searched the English medical literature focusing on AKI, ALI, organs cross talk, renal failure, multi organ failure and ARDS using the databases of PubMed, Embase, Scopus and directory of open access journals. In this narrative review, we summarized the pathophysiology and treatment of respiratory distress syndrome following AKI. This review promotes knowledge of the link between kidney and lung with mechanisms, diagnostic biomarkers, and treatment involved ARDS induced by AKI.

Acute lung injury complicating acute kidney injury: A model of endogenous αKlotho deficiency and distant organ dysfunction

The lung interfaces with atmospheric oxygen via a large surface area and is perfused by the entire venous return bearing waste products collected from the whole body. It is logical that the lung is endowed with generous anti-oxidative capacity derived both locally and from the circulation. The single-pass pleiotropic alpha-Klotho (αKlotho) protein was discovered when its genetic disruption led to premature multi-organ degeneration and early death. The extracellular domain of αKlotho is cleaved by secretases and released into circulation as endocrine soluble αKlotho protein, exerting wide-ranging cytoprotective effects including anti-oxidation on distant organs including the lung, which exhibits high sensitivity to circulating αKlotho insufficiency. Because circulating αKlotho is derived mainly from the kidney, acute kidney injury (AKI) leads to systemic αKlotho deficiency that in turn increases the risks of pulmonary complications, i.e., edema and inflammation, culminating in the acute respiratory distress syndrome. Exogenous αKlotho increases endogenous anti-oxidative capacity partly via activation of the Nrf2 pathway to protect lungs against injury caused by direct hyperoxia exposure or AKI. This article reviews the current knowledge of αKlotho antioxidation in the lung in the setting of AKI as a model of circulating αKlotho deficiency, an under-recognized condition that weakens innate cytoprotective defenses and contributes to the dysfunction in distant organs.

Peptidyl arginine deiminase-4-deficient mice are protected against kidney and liver injury after renal ischemia and reperfusion

We previously demonstrated that renal peptidyl arginine deiminase-4 (PAD4) is induced after renal ischemia and reperfusion (I/R) injury and exacerbates acute kidney injury (AKI) by increasing the renal tubular inflammatory response. Here, we tested whether genetic ablation of PAD4 attenuates renal injury and inflammation after I/R in mice. After renal I/R, PAD4 wild-type mice develop severe AKI with large increases in plasma creatinine, neutrophil infiltration, as well as significant renal tubular necrosis, apoptosis, and proinflammatory cytokine generation. In contrast, PAD4-deficient mice are protected against ischemic AKI with reduced real tubular neutrophil infiltration, renal tubular necrosis, and apoptosis. In addition, hepatic injury and inflammation observed in PAD4 wild-type mice after renal I/R are significantly attenuated in PAD4-deficient mice. We also show that increased renal tubular PAD4 expression after renal I/R is associated with translocation of PAD4 from the nucleus to the cytosol. Consistent with PAD4 cytosolic translocation, we show increased renal tubular cytosolic peptidyl-citrullination after ischemic AKI. Mechanistically, recombinant PAD4 treatment increased nuclear translocation of NF-κB in cultured human as well as murine proximal tubule cells that is inhibited by a PAD4 inhibitor (2-chloroamidine). Taken together, our studies further support the hypothesis that renal tubular PAD4 plays a critical role in renal I/R injury by increasing the renal tubular inflammatory response and neutrophil infiltration after renal I/R perhaps by interacting with the proinflammatory transcription factor NF-κB in the cytosol and promoting its nuclear translocation.

Acute Kidney Injury: Definition, Pathophysiology and Clinical Phenotypes

Acute kidney injury (AKI) is a clinical syndrome that complicates the course and worsens the outcome in a significant number of hospitalised patients. Recent advances in clinical and basic research will help with a more accurate definition of this syndrome and in the elucidation of its pathogenesis. With this knowledge we will be able to conduct more accurate epidemiologic studies in an effort to gain a better understanding of the impact of this syndrome. AKI is a syndrome that rarely has a sole and distinct pathophysiology. Recent evidence, in both basic science and clinical research, is beginning to change our view for AKI from a single organ failure syndrome to a syndrome where the kidney plays an active role in the progress of multi-organ dysfunction. Accurate and prompt recognition of AKI and better understanding of the pathophysiologic mechanisms underlying the various clinical phenotypes are of great importance to research for effective therapeutic interventions. In this review we provide the most recent updates in the definition, epidemiology and pathophysiology of AKI.

αKlotho deficiency in acute kidney injury contributes to lung damage

αKlotho is a circulating protein that originates predominantly from the kidney and exerts cytoprotective effects in distant sites. We previously showed in rodents that the lung is particularly vulnerable to αKlotho deficiency. Because acute lung injury is a common and serious complication of acute kidney injury (AKI), we hypothesized that αKlotho deficiency in AKI contributes to lung injury. To test the hypothesis, we created AKI by renal artery ischemia-reperfusion in rats and observed the development of alveolar interstitial edema and increased pulmonary oxidative damage to DNA, protein, and lipids. Administration of αKlotho-containing conditioned media 6 h post-AKI did not alter plasma creatinine but improved recovery of endogenous αKlotho production 3 days post-AKI, reduced lung edema and oxidative damage, and increased endogenous antioxidative capacity in the lung. Intravenously injected αKlotho rapidly exits alveolar capillaries as a macromolecule, suggesting transcytosis and direct access to the epithelium. To explore the epithelial action of αKlotho, we simulated oxidative stress in vitro by adding hydrogen peroxide to cultured A549 lung epithelial cells. Purified recombinant αKlotho directly protected cells at 20 pM with half-maximal effects at 40-50 pM, which is compatible with circulating αKlotho levels. Addition of recombinant αKlotho activated an antioxidant response element reporter and increased the levels of target proteins of the nuclear factor erythroid-derived 2 related factor system. In summary, αKlotho deficiency in AKI contributes to acute lung injury by reducing endogenous antioxidative capacity and increasing oxidative damage in the lung. αKlotho replacement partially reversed these abnormalities and mitigated pulmonary complications in AKI.

Remote effects of acute kidney injury in a porcine model

Acute kidney injury (AKI) is a common and serious condition with no specific treatment. An episode of AKI may affect organs distant from the kidney, further increasing the morbidity associated with AKI. The mechanism of organ cross talk after AKI is unclear. The renal and immune systems of pigs and humans are alike. Using a preclinical animal (porcine) model, we tested the hypothesis that early effects of AKI on distant organs is by immune cell infiltration, leading to inflammatory cytokine production, extravasation, and edema. In 29 pigs exposed to either sham surgery or renal ischemia-reperfusion (control, n = 12; AKI, n = 17), we assessed remote organ (liver, lung, brain) effects in the short (from 2- to 48-h reperfusion) and longer term (5 wk later) using immunofluorescence (for leukocyte infiltration, apoptosis), a cytokine array, tissue elemental analysis (e.g., electrolytes), blood hematology and chemistry (e.g., liver enzymes), and PCR (for inflammatory markers). AKI elicited significant, short-term (∼24 h) increments in enzymes indicative of acute liver damage (e.g. , AST: ALT ratio; P = 0.02) and influenced tissue biochemistry in some remote organs (e.g., lung tissue [Ca(2+)] increased; P = 0.04). These effects largely resolved after 48 h, and no further histopathology, edema, apoptosis, or immune cell infiltration was noted in the liver, lung, or hippocampus in the short and longer term. AKI has subtle biochemical effects on remote organs in the short term, including a transient increment in markers of acute liver damage. These effects resolved by 48 h, and no further remote organ histopathology, apoptosis, edema, or immune cell infiltration was noted.

Remifentanil attenuates lipopolysaccharide-induced acute lung injury by downregulating the NF-κB signaling pathway

Remifentanil significantly represses cell immune responses and influences neutrophil migration through endothelial cell monolayers. The present study determines the beneficial effects of remifentanil and the mechanisms by which it attenuates lipopolysaccharide (LPS)-induced acute lung injury (ALI). Rats were intratracheally instilled with 2 mg/kg LPS to induce ALI. Results showed that remifentanil could resolve lung injury, as evidenced by remarkable decreases in lung edema (wet-to-dry weight ratio), neutrophil infiltration (myeloperoxidase activity), and pulmonary permeability [total number of cells and protein concentrations in bronchoalveolar lavage fluid (BALF)]. Remifentanil also attenuated the concentrations of proinflammatory cytokines tumor necrosis factor alpha, interleukin-1β, and interleukin-6 in BALF, as well as effectively repressed the activation of nuclear factor-kappaB (NF-κB), which has been associated with the inhibition of IκBα degradation.These results suggest that remifentanil may be a suitable treatment for LPS-induced ALI. Remifentanil exerts beneficial effects on the inhibition of proinflammatory cytokine production by downregulating the NF-κB pathway.

Peptidyl arginine deiminase-4 activation exacerbates kidney ischemia-reperfusion injury

Peptidyl arginine deiminase (PAD)4 is a nuclear enzyme that catalyzes the posttranslational conversion of arginine residues to citrulline. Posttranslational protein citrullination has been implicated in several inflammatory autoimmune diseases, including rheumatoid arthritis, colitis, and multiple sclerosis. Here, we tested the hypothesis that PAD4 contributes to ischemic acute kidney injury (AKI) by exacerbating the inflammatory response after renal ischemia-reperfusion (I/R). Renal I/R injury in mice increased PAD4 activity as well as PAD4 expression in the mouse kidney. After 30 min of renal I/R, vehicle-treated mice developed severe AKI with large increases in plasma creatinine. In contrast, mice pretreated with PAD4 inhibitors (2-chloroamidine or streptonigrin) had significantly reduced renal I/R injury. Further supporting a critical role for PAD4 in generating ischemic AKI, mice pretreated with recombinant human PAD4 (rPAD4) protein and subjected to mild (20 min) renal I/R developed exacerbated ischemic AKI. Consistent with the hypothesis that PAD4 regulates renal tubular inflammation after I/R, mice treated with a PAD4 inhibitor had significantly reduced renal neutrophil chemotactic cytokine (macrophage inflammatory protein-2 and keratinocyte-derived cytokine) expression and had decreased neutrophil infiltration. Furthermore, mice treated with rPAD4 had significantly increased renal tubular macrophage inflammatory protein-2 and keratinocyte-derived cytokine expression as well as increased neutrophil infiltration and necrosis. Finally, cultured mouse kidney proximal tubules treated with rPAD4 had significantly increased proinflammatory chemokine expression compared with vehicle-treated cells. Taken together, our results suggest that PAD4 plays a critical role in renal I/R injury by increasing renal tubular inflammatory responses and neutrophil infiltration after renal I/R.

Vagal efferent fiber stimulation ameliorates pulmonary microvascular endothelial cell injury by downregulating inflammatory responses

Electrical stimulation of the vagus nerve may have positive effects on many inflammatory diseases. This study determined the beneficial effects of vagus nerve stimulation and the mechanisms by which it attenuates lipopolysaccharide (LPS)-induced acute lung injury (ALI). Rats were intraperitoneally injected with 10 mg/kg LPS to induce ALI. The results showed that vagus nerve stimulation could improve lung injury, as evidenced by remarkable reductions in lung edema (wet-to-dry weight ratio), neutrophil infiltration (myeloperoxidase activity), and pulmonary permeability [total number of cells and protein concentrations in bronchoalveolar lavage fluid (BALF)]. In addition, vagus nerve stimulation not only decreased the expressions of Src-suppressed C kinase substrate and E-selectin proteins in lung tissue but also effectively attenuated the concentrations of the proinflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 in BALF. These suggest that vagus nerve stimulation is a suitable treatment for LPS-induced ALI and indicate that it helps ameliorate pulmonary microvascular endothelial cell injury by downregulating inflammatory responses.

Lipid isolated from a Leishmania donovani strain reduces Escherichia coli induced sepsis in mice through inhibition of inflammatory responses

Sepsis is the reflection of systemic immune response that manifests in the sequential inflammatory process in presence of infection. This may occur as a result of gram-negative bacterial sepsis including Escherichia coli infection that gives rise to excessive production of inflammatory mediators and causes severe tissue injuries. We have reported earlier that the lipid of attenuated Leishmania donovani suppresses the inflammatory responses in arthritis patients. Using heat killed E. coli stimulated macrophages, we have now investigated the effect of leishmanial total lipid (LTL) isolated from Leishmania donovani (MHO/IN/1978/UR6) for amelioration of the inflammatory mediators and transcriptional factor with suppression of TLR4-CD14 expression. To evaluate the in vivo effect, E. coli induced murine sepsis model was used focusing on the changes in different parameter(s) of lung injury caused by sepsis, namely, edema, vascular permeability, and pathophysiology, and the status of different cytokine-chemokine(s) and adhesion molecule(s). Due to the effect of LTL, E. coli induced inflammatory cytokine-chemokine(s) levels were significantly reduced in serum and bronchoalveolar lavage fluid simultaneously. LTL also improved the lung injury and suppressed the cell adhesion molecules in lung tissue. These findings indicate that LTL may prove to be a potential anti-inflammatory agent and provide protection against gram-negative bacterial sepsis with pulmonary impairment.

Heart-kidney crosstalk and role of humoral signaling in critical illness

Organ failure in the heart or kidney can initiate various complex metabolic, cell-mediated and humoral pathways affecting distant organs, contributing to the high therapeutic costs and significantly higher morbidity and mortality. The universal outreach of cells in an injured state has myriad consequences to distant organ cells and their milieu. Heart performance and kidney function are closely interconnected and communication between these organs occurs through a variety of bidirectional pathways. The term cardiorenal syndrome (CRS) is often used to describe this condition and represents an important model for exploring the pathophysiology of cardiac and renal dysfunction. Clinical evidence suggests that tissue injury in both acute kidney injury and heart failure has immune-mediated inflammatory consequences that can initiate remote organ dysfunction. Acute cardiorenal syndrome (CRS type 1) and acute renocardiac syndrome (CRS type 3) are particularly relevant in high-acuity medical units. This review briefly summarizes relevant research and focuses on the role of signaling in heart-kidney crosstalk in the critical care setting.

N-acetylcysteine Prevents Kidney and Lung Disturbances in Renal Ischemia/Reperfusion Injury in Rat

BACKGROUND

One of the most common causes of acute kidney injury (AKI) is kidney ischemia/reperfusion injury (IRI). The distant organ injury such as acute lung injury is one of the side effects of AKI or kidney IRI. In this study, we performed bilateral renal IRI in rats and the protective role of N-acetylcysteine (NAC) in kidney and lung was investigated.

METHODS

Rats (n = 30) were randomly assigned to four experiment groups. The group 1 was assigned as sham-operated group. Before kidney IRI performance, the others groups were treated with saline (group 2), 150 mg/kg (group 3) or 500 mg/kg (group 4) of NAC, and the treatment were continued daily after IRI for next 3 days. At day 3, the all groups' animals were subjected for the measurements.

RESULTS

The serum level of blood urea nitrogen (BUN) and creatinine (Cr) in the control group increased significantly (P < 0.05), and administration of NAC (150 mg/kg) decreased the serum levels of Cr and BUN. However, only the serum level of Cr decreased significantly (P < 0.05). NAC did not improve kidney weight and damage; however, its low dose (150 mg/kg) attenuated the lung injury score (P < 0.05) when compared with the control group. No significant differences were observed in lung water content and endothelial permeability, serum levels of malondialdehyde and nitrite between the groups.

CONCLUSIONS

Low dose of NAC as a protectant agent may protect the kidney function and lung tissue damage after kidney IRI.

Selective deletion of the endothelial sphingosine-1-phosphate 1 receptor exacerbates kidney ischemia-reperfusion injury

The role for the endothelial sphingosine-1-phosphate 1 receptor (S1P1R) in acute kidney injury (AKI) remains unclear as germline endothelial S1P1R deletion is embryonically lethal. Here, we generated conditional endothelial S1P1R deficiency by crossing mice with floxed S1P1R with mice expressing a tamoxifen-inducible form of Cre recombinase under the transcriptional control of the platelet-derived growth factor-β gene. Mice with tamoxifen-induced deletion of endothelial S1P1R had increased renal tubular necrosis, inflammation, impaired vascular permeability as well as exacerbated renal tubular apoptosis after ischemic AKI compared to tamoxifen-treated wild type mice. Moreover, endothelial S1P1R deletion resulted in increased hepatic injury after ischemic AKI. As a potential mechanism for exacerbated renal injury, conditional endothelial S1P1R null mice had markedly reduced endothelial HSP27 expression compared to wild type mice. Cultured glomerular endothelial cells treated with a specific S1P1R antagonist (W146) for 3 days also showed reduced HSP27 expression compared to vehicle treated cells. Finally, mice treated with W146 for 3 days also showed reduced endothelial HSP27 expression as well as exacerbated renal and hepatic injury after ischemic AKI. Thus, our studies demonstrate a protective role for endothelial S1P1R against ischemic AKI most likely by regulating endothelial barrier integrity and endothelial HSP27 expression.

Protective role of recombinant human erythropoietin in kidney and lung injury following renal bilateral ischemia-reperfusion in rat model

BACKGROUND

Acute kidney injury (AKI) has been recognized as one of the most complex clinical complications in modern medicine, and ischemia/reperfusion (I/R) injury is well-known as a main reason of AKI. In addition, AKI leads to important systemic consequences such as acute lung injury. This study was designed to investigate the role of erythropoietin (EPO) on kidney function makers and tissue damage; and lung endothelial permeability and lung water content (LWC) in bilateral renal I/R injury model in rats.

METHODS

Male Wistar rats were randomly divided into three groups of sham, I/R, and I/R treated with EPO (I/R + EPO) groups. The I/R and I/R + EPO groups were subjected to bilateral renal I/R injury; however, only the I/R + EPO group received EPO (500 IU/kg, i.p.) 2 h before ischemia surgery, and the same dose was continued once a day for 3 days after ischemia. The sham group underwent a surgical procedure without ischemia process.

RESULTS

The blood urea nitrogen (BUN) and serum creatinine (Cr) levels, kidney tissue damage score (KTDS), and kidney weight (KW) per 100 g body weight significantly increased in I/R group (P < 0.05). EPO administration decreased levels of BUN and Cr significantly (P < 0.05), and KTDS and KW insignificantly (P = 0.1). No significant differences in kidney and serum levels of malondialdehyde, and lung vascular permeability and LWC were observed between the groups. The serum and kidney levels of nitrite were not significantly different between I/R and sham groups; however, administration of EPO increased the renal level of nitrite (P < 0.05).

CONCLUSIONS

EPO protected the kidney against I/R injury; however, it may not protect the lung tissue from the damage induced by renal I/R injury in rats.

Function of the p38MAPK-HSP27 pathway in rat lung injury induced by acute ischemic kidney injury

This study aims to observe the changes and the function of p38MAPK-HSP27 signaling pathways in acute lung injury (ALI) induced by acute ischemic kidney injury in rats. Wistar rats were randomly divided into Group A (control group), Group B (acute kidney injury group), and Group C (acute kidney injury +SB203580). The concentration of protein in BALF, neutrophil counts, PI, W/D; the concentration of TNF- α , IL-6, and IL-1 β in plasma and BALF; and the concentrations of MDA and NO in the lung tissue started to increase 2 h after the experiment in Group B, which showed a significant difference compared with those in Groups A and C. The expressions of p-p38MAPK and p-HSP27 in the lung tissue began to increase 2 h after the experiment in Group B, which was different from those in Groups A and C. A significant increase was observed in the F-actin expression in Group B than that in Group A. In Group B, the correlation of cytokine TNF- α , IL-6, and p-p38MAPK in BALF was positive. Acute kidney injury (AKI) induced by bilateral renal arteriovenous clamp closure could activate p38MAPK-HSP27 signaling pathways and induce lung injury, which blocks the p38MAPK-HSP27 signal pathway to reduce the risk of lung injury.

Renalase protects against ischemic AKI

Elevated levels of plasma catecholamines accompany ischemic AKI, possibly contributing the inflammatory response. Renalase, an amine oxidase secreted by the proximal tubule, degrades circulating catecholamines and reduces myocardial necrosis, suggesting that it may protect against renal ischemia reperfusion injury. Here, mice subjected to renal ischemia reperfusion injury had significantly lower levels of renalase in the plasma and kidney compared with sham-operated mice. Consistent with this, plasma NE levels increased significantly after renal ischemia reperfusion injury. Furthermore, renal tubular inflammation, necrosis, and apoptosis were more severe and plasma catecholamine levels were higher in renalase-deficient mice subjected to renal ischemia reperfusion compared with wild-type mice. Administration of recombinant human renalase reduced plasma catecholamine levels and ameliorated ischemic AKI in wild-type mice. Taken together, these data suggest that renalase protects against ischemic AKI by reducing renal tubular necrosis, apoptosis, and inflammation, and that plasma renalase might be a biomarker for AKI. Recombinant renalase therapy may have potential for the prevention and treatment of AKI.

Paneth cell-mediated multiorgan dysfunction after acute kidney injury

Acute kidney injury (AKI) is frequently complicated by extrarenal multiorgan injury, including intestinal and hepatic dysfunction. In this study, we hypothesized that a discrete intestinal source of proinflammatory mediators drives multiorgan injury in response to AKI. After induction of AKI in mice by renal ischemia-reperfusion or bilateral nephrectomy, small intestinal Paneth cells increased the synthesis and release of IL-17A in conjunction with severe intestinal apoptosis and inflammation. We also detected significantly increased IL-17A in portal and systemic circulation after AKI. Intestinal macrophages appear to transport released Paneth cell granule constituents induced by AKI, away from the base of the crypts into the liver. Genetic or pharmacologic depletion of Paneth cells decreased small intestinal IL-17A secretion and plasma IL-17A levels significantly and attenuated intestinal, hepatic, and renal injury after AKI. Similarly, portal delivery of IL-17A in macrophage-depleted mice decreased markedly. In addition, intestinal, hepatic, and renal injury following AKI was attenuated without affecting intestinal IL-17A generation. In conclusion, AKI induces IL-17A synthesis and secretion by Paneth cells to initiate intestinal and hepatic injury by hepatic and systemic delivery of IL-17A by macrophages. Modulation of Paneth cell dysregulation may have therapeutic implications by reducing systemic complications arising from AKI.

Deciphering the mechanisms of the Na+/H+ exchanger-3 regulation in organ dysfunction

The Na+/H+ exchanger-3 (NHE3) belongs to the mammalian NHE protein family and catalyzes the electro-neutral exchange of extracellular sodium for intracellular proton across cellular membranes. Its transport function is of essential importance for the maintenance of the body's salt and water homeostasis as well as acid-base balance. Indeed, NHE3 activity is finely regulated by a variety of stimuli, both acutely and chronically, and its transport function is fundamental for a multiplicity of severe and world-wide infection-pathological conditions. This review aims to provide a concise overview of NHE3 physiology and discusses the role of NHE3 in clinical conditions of prominent importance, specifically in hypertension, diabetic nephropathy, heart failure, acute kidney injury, and diarrhea. Study of NHE3 function in models of these diseases has contributed to the deciphering of mechanisms that control the delicate ion balance disrupted in these disorders. The majority of the findings indicate that NHE3 transport function is activated before the onset of hypertension and inhibited thereafter; NHE3 transport function is also upregulated in diabetic nephropathy and heart failure, while it is reported to be downregulated in acute kidney injury and in diarrhea. The molecular mechanisms activated during these pathological conditions to regulate NHE3 transport function are examined with the aim of linking NHE3 dysfunction to the analyzed clinical disorders.

Adenosine and protection from acute kidney injury

PURPOSE OF REVIEW

Acute kidney injury (AKI) is a major clinical problem without effective therapy. Development of AKI among hospitalized patients drastically increases mortality and morbidity. With increases in complex surgical procedures together with a growing elderly population, the incidence of AKI is rising. Renal adenosine receptor manipulation may have great therapeutic potential in mitigating AKI. In this review, we discuss renal adenosine receptor biology and potential clinical therapies for AKI.

RECENT FINDINGS

The four adenosine receptor subtypes (A(1)AR, A(2A)AR, A(2B)AR, and A(3)AR) have diverse effects on the kidney. The pathophysiology of AKI may dictate the specific adenosine receptor subtype activation needed to produce renal protection. The A(1)AR activation in renal tubules and endothelial cells produces beneficial effects against ischemia and reperfusion injury by modulating metabolic demand, decreasing necrosis, apoptosis, and inflammation. The A(2A)AR protects against AKI by modulating leukocyte-mediated renal and systemic inflammation, whereas the A(2B)AR activation protects by direct activation of renal parenchymal adenosine receptors. In contrast, the A(1)AR antagonism may play a protective role in nephrotoxic AKI and radiocontrast induced nephropathy by reversing vascular constriction and inducing naturesis and diuresis. Furthermore, as the A(3)AR activation exacerbates apoptosis and tissue damage due to renal ischemia and reperfusion, selective A(3)AR antagonism may hold promise to attenuate renal ischemia and reperfusion injury. Finally, renal A(1)AR activation also protects against renal endothelial dysfunction caused by hepatic ischemia and reperfusion injury.

SUMMARY

Despite the current lack of therapies for the treatment and prevention of AKI, recent research suggests that modulation of renal adenosine receptors holds promise in treating AKI and extrarenal injury.

Effects of adipose-derived mesenchymal cells on ischemia-reperfusion injury in kidney

BACKGROUND

Acute kidney injury (AKI) is a critical condition for kidney and other remote organs, including the lung. However, available treatments for AKI are limited. In this study, we explored the effect of adipose-derived mesenchymal cells on a mouse model of AKI.

METHODS

Adipose-derived mesenchymal cells were isolated from mouse subcutaneous and peritoneal adipose tissue by digestion with collagenase type I. The left renal artery and vein of C57BL/6 mice were clamped for 45 min to induce ischemia and were injected with the adipose-derived mesenchymal cells [1 × 10(5) cells/0.2 ml phosphate-buffered saline (PBS)] or 0.2 ml PBS via the tail vein on days 0, 1, and 2.

RESULTS

The adipose-derived mesenchymal cells had stem-cell surface markers and multilineage differentiating potentials. Administered adipose-derived mesenchymal cells homed primarily into lung. Interestingly, repeated administration of adipose-derived mesenchymal cells reduced acute tubular necrosis and interstitial macrophage infiltration in the injured kidney, accompanied with reduced cytokine and chemokine expression.

CONCLUSION

Adipose-derived mesenchymal cells can be used as cell-based therapy for ischemic kidney injury.

Astragalin attenuates lipopolysaccharide-induced inflammatory responses by down-regulating NF-κB signaling pathway

Astragalin (AG), a flavonoid from many traditional herbs and medicinal plants, has been described to exhibit in vitro anti-inflammatory activity. The present study aimed to determine the protective effects and the underlying mechanisms of astragalin on lipopolysaccharide-induced endotoxemia and lung injury in mice. Mice were injected intraperitoneally (i.p.) with lipopolysaccharide (LPS) (dose range: 5-40 mg/kg). We observed mice on mortality for 7 days twice a day and recorded survival rates. In drug testing, we examined the therapeutic effects of astragalin (25, 50 or 75 mg/kg) on LPS- induced endotoxemia by dosing orally astragalin 1 hour before LPS challenge. Using an experimental model of LPS-induced acute lung injury (ALI), we examined the effect of astragalin in resolving lung injury. The investigations revealed that pretreatment with astragalin can improve survival during lethal endotoxemia and attenuate inflammatory responses in a murine model of lipopolysaccharide-induced acute lung injury. The mechanisms by which Astragalin exerts its anti-inflammatory effect are correlated with inhibition of tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6) production via inactivation of NF-κB.

Costs and outcomes of acute kidney injury in critically ill patients with cancer

BACKGROUND

Acute kidney injury (AKI) is a common complication in critically ill patients with cancer. The RIFLE criteria define three levels of AKI based on the percent increase in serum creatinine (Scr) from baseline: risk (> or = 50%), injury (> or = 100%), and failure (> or = 200% or requiring dialysis). The utility of the RIFLE criteria in critically ill patients with cancer is not known.

OBJECTIVE

To examine the incidence, outcomes, and costs associated with AKI in critically ill patients with cancer.

METHODS

We retrospectively analyzed all patients admitted to a single-center ICU over a 13-month period with a baseline Scr < or = 1.5 mg/dL (n = 2,398). Kaplan-Meier estimates for survival by RIFLE category were calculated. Logistic regression was used to determine the association of AKI on 60-day mortality. A log-linear regression model was used for economic analysis. Costs were assessed by hospital charges from the provider's perspective.

RESULTS

For the risk, injury, and failure categories of AKI, incidence rates were 6%, 2.8%, and 3.7%; 60-day survival estimates were 62%, 45%, and 14%; and adjusted odds ratios for 60-day mortality were 2.3, 3, and 14.3, respectively (P < or = 0.001 compared to patients without AKI). Hematologic malignancy and hematopoietic cell transplant were not associated with mortality in the adjusted analysis. Hospital cost increased by 0.16% per 1% increase in creatinine and by 21% for patients requiring dialysis.

LIMITATIONS

Retrospective analysis. Single-center study. No adjustment by cost-to-charge ratios.

CONCLUSIONS

AKI is associated with higher mortality and costs in critically ill patients with cancer.

Clearance and beyond: the complementary roles of GFR measurement and injury biomarkers in acute kidney injury (AKI)

Acute kidney injury (AKI) is a common and frequently fatal illness in critically ill patients. The reliance on daily measurements of serum creatinine as a surrogate of glomerular filtration rate (GFR) not only delays diagnosis and development of successful therapies but also hinders insight into the pathophysiology of human AKI. Measurement of GFR under non-steady-state conditions remains an elusive gold standard against which biomarkers of renal injury need to be judged. Approaches to the rapid (near real-time) measurement of GFR are explored. Even if real-time GFR was available, absent baseline information will always limit diagnosis of AKI based on GFR or serum creatinine to a detection of change. Biomarkers of renal cellular injury have provided new strategies to facilitate detection and early intervention in AKI. However, the diagnostic and predictive performance of urinary biomarkers of injury vary, depending on both the time after renal injury and on the preinjury GFR. Progress in understanding the role of each novel biomarker in the causal pathways of AKI promises to enhance their diagnostic potential. We predict that combining rapid measures of GFR with biomarkers of renal injury will yield substantive progress in the treatment of AKI.

Evaluation and management of critically ill children with acute kidney injury

PURPOSE OF REVIEW

This review will highlight recent studies on the diagnosis of acute kidney injury (AKI), review the differential diagnosis, highlight the importance of cumulative fluid overload and provide key management strategies for the pediatric patient with AKI.

RECENT FINDINGS

Over the last decade, serum creatinine-based categorical definitions of AKI have been accepted, which allow detection earlier in the disease process. Evidence-based modifications of these definitions have occurred. Fluid overload portends poor outcomes in critically ill patients. Significant improvements in our understanding of the pathophysiology of glomerular/vascular causes of AKI have occurred.

SUMMARY

Categorical definitions of AKI have shown that higher AKI portends poor outcomes even with adjustment for severity of illness and other confounders. Cumulative fluid overload independently predicts poor outcomes. Strategies to prevent and/or treat fluid overload are likely to improve outcomes.

Cytokines induce small intestine and liver injury after renal ischemia or nephrectomy

Patients with acute kidney injury (AKI) frequently suffer from extra-renal complications including hepatic dysfunction and systemic inflammation. We aimed to determine the mechanisms of AKI-induced hepatic dysfunction and systemic inflammation. Mice subjected to AKI (renal ischemia reperfusion (IR) or nephrectomy) rapidly developed acute hepatic dysfunction and suffered significantly worse hepatic IR injury. After AKI, rapid peri-portal hepatocyte necrosis, vacuolization, neutrophil infiltration and pro-inflammatory mRNA upregulation were observed suggesting an intestinal source of hepatic injury. Small intestine histology after AKI showed profound villous lacteal capillary endothelial apoptosis, disruption of vascular permeability and epithelial necrosis. After ischemic or non-ischemic AKI, plasma TNF-α, IL-17A and IL-6 increased significantly. Small intestine appears to be the source of IL-17A, as IL-17A levels were higher in the portal circulation and small intestine compared with the levels measured from the systemic circulation and liver. Wild-type mice treated with neutralizing antibodies against TNF-α, IL-17A or IL-6 or mice deficient in TNF-α, IL-17A, IL-17A receptor or IL-6 were protected against hepatic and small intestine injury because of ischemic or non-ischemic AKI. For the first time, we implicate the increased release of IL-17A from small intestine together with induction of TNF-α and IL-6 as a cause of small intestine and liver injury after ischemic or non-ischemic AKI. Modulation of the inflammatory response and cytokine release in the small intestine after AKI may have important therapeutic implications in reducing complications arising from AKI.

Predictors and outcome of acute kidney injury in patients with acute myelogenous leukemia or high-risk myelodysplastic syndrome

BACKGROUND

: Acute kidney injury (AKIis a common complication in the treatment of patients with acute myelogenous leukemia (AML) or high-risk myelodysplastic syndrome (HR-MDS), but, to the authors' knowledge, its clinical relevance has not been detailed to date. The objective of the current study was to identify the incidence, predictors, and outcome for AKI in patients with AML and HR-MDS.

METHODS

: Data were analyzed from 537 patients with AML or HR-MDS undergoing induction chemotherapy from 1999 to 2007. Predictors for AKI were identified by logistic regression. Eight-week mortality of patients was estimated by the Kaplan-Meier method stratified by the RIFLE criteria, a novel multilevel classification system for AKI based on the percent rise in serum creatinine from baseline (Risk, >50%; Injury, >100%; and Failure, >200% or requiring dialysis).

RESULTS

: A total of 187 patients (36%) developed AKI. Significant independent risk factors for AKI included the following: age >/=55 years (odds ratio [OR], 1.8), mechanical ventilation (OR, 16), use of vancomycin (OR, 2.3), diuretics (OR, 3.0), amphotericin B lipid formulation (OR, 2.7), vasopressors (OR, 4.9), leukopenia (OR, 1.9), hypoalbuminemia (OR, 1.4), and use of non-fludarabine-based chemotherapy (OR, 2.7). The 8-week mortality rates were 3.8%, 13.6%, 19.6%, and 61.7% for the non-RIFLE, Risk, Injury, and Failure categories, respectively. Patients requiring dialysis (8%) had a median survival of 33 days. Survival of patients who achieved complete remission was favorable, regardless of degree of AKI.

CONCLUSIONS

: The RIFLE classification for AKI appears to have prognostic utility in predicting mortality in patients with AML or HR-MDS. Relatively mild elevations in creatinine are associated with higher mortality. Strategies to avoid nephrotoxic drugs or fluid overload may be of benefit. Cancer 2010. (c) 2010 American Cancer Society.

Delayed graft function and the risk of death with graft function in living donor kidney transplant recipients

BACKGROUND

The link between delayed graft function (DGF) and death with graft function (DWGF) in living donor kidney transplant recipients presently is unknown.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

44,630 adult living donor kidney recipients (first transplants only) in the US Renal Data System from January 1, 1994, to December 31, 2004.

PREDICTOR

DGF, defined as the need for dialysis therapy in the first week after transplant.

OUTCOME

Time to DWGF.

MEASUREMENTS

Kaplan-Meier curves were constructed to assess the impact of DGF on DWGF. Recipients with DGF were 1:1 propensity score matched to those without DGF, and time-dependent Cox proportional hazards models were used to examine factors associated with DWGF. Subgroup and sensitivity analyses also were conducted.

RESULTS

DWGF occurred in 3,878 patients during 3.9 years' (median) follow-up. In patients with DGF, survival with graft function at 1, 3, 5, and 10 years was 91.9%, 86.8%, 81.6%, and 61.7%, respectively (in patients without DGF, these values were 98.0%, 95.2%, 91.6%, and 80.1%, respectively; P < 0.001 compared with the DGF group). In a fully adjusted time-dependent Cox model, HRs for DWGF in patients with DGF (vs without DGF) were 6.55 (95% CI, 4.78-8.97), 3.55 (95% CI, 2.46-5.11), 2.07 (95% CI, 1.53-2.81), and 1.48 (95% CI, 1.26-1.73) at 0-1, 1-3, 3-12, and longer than 12 months posttransplant, respectively. Propensity score analysis showed similar results. Inferences were unchanged after adjustment for kidney function and acute rejection at 6 months and 1 year posttransplant. Cardiovascular and infectious causes of DWGF were more prevalent in patients with DGF. The association was more marked in female recipients and robust to various sensitivity analyses.

LIMITATIONS

The impact of lesser decreases in early graft function could not be evaluated.

CONCLUSIONS

DGF is associated with an increased risk of DWGF in living donor kidney recipients. The mechanisms underlying this relation require further study.

Protection against acute kidney injury via A(1) adenosine receptor-mediated Akt activation reduces liver injury after liver ischemia and reperfusion in mice

Hepatic ischemia reperfusion (IR) injury causes acute kidney injury (AKI). However, the contribution of AKI to the pathogenesis of liver IR injury is unclear. Furthermore, controversy still exists regarding the role of A(1) adenosine receptors (A(1)ARs) in AKI. In this study, we determined whether exogenous and endogenous A(1)AR activation protects against AKI with subsequent liver protection after hepatic IR in mice. We found that after hepatic IR A(1) knockout (KO) mice and A(1)AR antagonist-treated A(1) wild-type (WT) mice developed worse AKI and liver injury compared with vehicle-treated A(1)WT mice. Moreover, a selective A(1)AR agonist protected against hepatic IR-induced AKI and liver injury in A(1)WT mice. Renal A(1)AR-mediated kidney protection plays a crucial role in protecting the liver after IR because: 1) selective unilateral renal lentiviral overexpression of human A(1)ARs [enhanced green fluorescent protein (EGFP)-huA(1)AR] in A(1)KO mice protected against both kidney and liver injury sustained after liver IR, 2) removal of the EGFP-huA(1)AR lentivirus-injected kidney from A(1)KO mice abolished both renal and hepatic protection after liver IR, and 3) bilateral nephrectomy before hepatic ischemia abolished the protective effects of A(1)AR activation in A(1)WT mice. Finally, inhibition of Akt, but not extracellular signal-regulated kinase mitogen-activated protein kinase, prevented the kidney and liver protection afforded by A(1)AR agonist treatment. Taken together, we show that endogenous and exogenous activation of renal A(1)ARs protect against liver and kidney injury after liver IR in vivo via pathways involving Akt activation.

Early and prominent alterations in hemodynamics, signaling, and gene expression following renal ischemia in sickle cell disease

Acute ischemic insults to the kidney are recognized complications of human sickle cell disease (SCD). The present study analyzed in a transgenic SCD murine model the early renal response to acute ischemia. Renal hemodynamics were profoundly impaired following ischemia in sickle mice compared with wild-type mice: glomerular filtration rate, along with renal plasma flow and blood flow rates, were markedly reduced, while renal vascular resistances were increased more than threefold in sickle mice following ischemia. In addition to these changes in renal hemodynamics, there were profound disturbances in renal signaling processes: phosphorylation of members of the MAPK and Akt signaling proteins occurred in the kidney in wild-type mice after ischemia, whereas such phosphorylation did not occur in the kidney in sickle mice after ischemia. ATP content in the postischemic kidney in sickle mice was less than half that observed in wild-type mice. Examination of the expression of candidate genes uncovered changes that may predispose to increased sensitivity of the kidney in sickle mice to ischemia: increased expression of inducible nitric oxide synthase and decreased expression of endothelial nitric oxide synthase, and increased expression of TNF-alpha. Inducibility of anti-inflammatory, cytoprotective genes, such as heme oxygenase-1 and IL-10, was not impaired in sickle mice after ischemia. We conclude that the kidney in SCD is remarkably vulnerable to acute ischemic insults. We speculate that such sensitivity of the kidney to ischemia in SCD may underlie the occurrence of acute kidney injury in patients with SCD and may set the stage for the emergence of chronic kidney disease in SCD.

Delayed graft function and the risk for death with a functioning graft

Delayed graft function (DGF) associates with an increased risk for graft failure, but its link with death with graft function (DWGF) is unknown. We used the US Renal Data System to assemble a cohort of all first, adult, deceased-donor kidney transplant recipients from January 1, 1998, through December 31, 2004. In total, 11,542 (23%) of 50,246 recipients required at least one dialysis session in the first week after transplantation. Compared with patients without DGF, patients with DGF were significantly more likely to die with a functioning graft (relative hazard 1.83 [95% confidence interval 1.73 to 1.93] and 1.53 [95% CI 1.45 to 1.63] for unadjusted and fully adjusted models, respectively). The risk for DWGF was slightly higher among women with DGF than among men. There was no significant heterogeneity among other subgroups, and the results were robust to sensitivity analyses. Acute rejection within the first year attenuated the DGF-DWGF association. Cardiovascular and infectious deaths were slightly more prevalent in the DGF group, but the relative hazards of cause-specific death were similar between DWGF and deaths during total follow-up. In summary, DGF associates with an increased risk for DWGF; the mechanisms underlying the negative impact of DGF require further study.