Mediators of inflammation in acute kidney injury. Mediators Inflamm. 2009;2009:137072. [PMID: 20182538 PMCID: PMC2825552 DOI: 10.1155/2009/137072]

MicroRNA-21 in the pathogenesis of acute kidney injury

Acute kidney injury (AKI), associated with significant morbidity and mortality, is widely known to involve epithelial apoptosis, excessive inflammation, and fibrosis in response to ischemia or reperfusion injury, which results in either chronic pathological changes or death. Therefore, it is imperative that investigations are conducted in order to find effective, early diagnoses, and therapeutic targets needed to help prevent and treat AKI. However, the mechanisms modulating the pathogenesis of AKI still remain largely undetermined. MicroRNAs (miRNAs), small non-coding RNA molecules, play an important role in several fundamental biological and pathological processes by a post transcriptional regulatory function of gene expression. MicroRNA-21 (miR-21) is a recently identified, typical miRNA that is functional as a regulator known to be involved in apoptosis as well as inflammatory and fibrotic signaling pathways in AKI. As a result, miR-21 is now considered a novel biomarker when diagnosing and treating AKI. This article reviews the correlative literature and research progress regarding the roles of miR-21 in AKI.

A novel experimental model of orthopedic trauma with acute kidney injury in obese Zucker rats

Obesity is associated with an increased risk of acute kidney injury (AKI) after blunt traumatic injury in humans. Because limitations exist in studying trauma in human patients, animal models are necessary to elucidate mechanisms of remote organ injury after trauma. We developed a model of severe orthopedic trauma in lean (LZ) and obese (OZ) Zucker rats, in which OZ develop greater kidney dysfunction after trauma than LZ. Orthopedic trauma was inflicted via bilateral hindlimb soft tissue injury, fibula fracture, and injection of homogenized bone components. Mean arterial pressure (MAP) and heart rate (HR) were measured for 6 h after trauma, and again at 24 h after trauma. Urine was collected for 24 h before and after trauma to measure urine albumin excretion. Glomerular filtration rate (GFR), renal plasma flow (RPF), plasma interleukin-6 (IL-6), and renal macrophage infiltration (ED-1 [CD68 Antibody] immunostaining) were measured in animals with and without trauma. MAP and HR were similar between LZ and OZ throughout the study, with the exception that OZ had a 18 mmHg lower pressure 24 h posttrauma. GFR and RPF were decreased significantly (∼50%), while urine albumin excretion, plasma IL-6, and renal ED-1-positive cells were increased in OZ 24 h after trauma compared to both OZ without trauma and LZ after trauma. In conclusion, these data are consistent with studies in humans that show that AKI develops more frequently in obese than in lean individuals. This model will be an important experimental tool to better understand the underlying mechanisms of poor outcomes after trauma in obese patients.

Citral is renoprotective for focal segmental glomerulosclerosis by inhibiting oxidative stress and apoptosis and activating Nrf2 pathway in mice

The pathogenesis of focal segmental glomerulosclerosis (FSGS) is considered to be associated with oxidative stress, mononuclear leukocyte recruitment and infiltration, and matrix production and/or matrix degradation, although the exact etiology and pathogenic pathways remain to be determined. Establishment of a pathogenesis-based therapeutic strategy for the disease is clinically warranted. Citral (3,7-dimethyl-2,6-octadienal), a major active compound in Litseacubeba, a traditional Chinese herbal medicine, can inhibit oxidant activity, macrophage and NF-κB activation. In the present study, first, we used a mouse model of FSGS with the features of glomerular epithelial hyperplasia lesions (EPHLs), a key histopathology index of progression of FSGS, peri-glomerular inflammation, and progressive glomerular hyalinosis/sclerosis. When treated with citral for 28 consecutive days at a daily dose of 200 mg/kg of body weight by gavage, the FSGS mice showed greatly reduced EPHLs, glomerular hyalinosis/sclerosis and peri-glomerular mononuclear leukocyte infiltration, suggesting that citral may be renoprotective for FSGS and act by inhibiting oxidative stress and apoptosis and early activating the Nrf2 pathway. Meanwhile, a macrophage model involved in anti-oxidative and anti-inflammatory activities was employed and confirmed the beneficial effects of citral on the FSGS model.

A screen for apoptotic synergism between clinical relevant nephrotoxicant and the cytokine TNF-α

Nephrotoxicity remains one of the main reasons for post-market drug withdrawal. Tumour necrosis factor α (TNF-α) secretion has been shown to underlie the nephrotoxicity induced by some of these drugs. Yet, there is currently no reliable and sensitive in vitro assay available to screen for nephrotoxicants of which toxicity largely depends on TNF-α secretion. Therefore, we developed and applied a sensitive fluorescence-based in vitro assay for TNF-α-mediated nephrotoxicity screening using mouse immortalized proximal tubular epithelial cells (IM-PTECs). Our assay allows rapid evaluation of TNF-α-mediated toxicant-induced apoptosis and necrosis using fixed endpoint and live cell measurements. To evaluate our assay, sixteen nephrotoxicants and two control non-nephrotoxicants were used. Out of the sixteen nephrotoxicants, eight induced cell death, of which five induced apoptosis as well as necrosis. Moreover, TNF-α significantly enhanced apoptotic cell death induced by cisplatin, cyclosporine A, tacrolimus and azidothymidine. These nephrotoxicants are known to induce inflammation in vivo which has been linked to an enhancement of nephrotoxicity for cisplatin, cyclosporine A and tacrolimus, confirming the functionality of our assay. Overall, our assay allows rapid and sensitive measurement of apoptosis and necrosis induced by a combination of nephrotoxicants and inflammatory components such as TNF-α and can be used as an alternative assay for nephrotoxicity prediction in vitro.

Anti-inflammatory strategies to reduce acute kidney injury in cardiac surgery patients: a meta-analysis of randomized controlled trials

Acute kidney injury (AKI) after cardiac operations is a serious complication associated with postoperative mortality. Multiple factors contribute to AKI development, principally ischemia-reperfusion injury and inflammatory response. It is well proven that glucocorticoid administration, leukocyte filter application, and miniaturized extracorporeal circuits (MECC) modulate inflammatory response. We conducted a systematic review of randomized controlled trials (RCTs) in which one of these inflammatory system modulation strategies was used, with the aim to evaluate the effects on postoperative AKI. MEDLINE and Cochrane Library were screened through November 2011 for RCTs in which an inflammatory system modulation strategy was adopted. Included were trials that reported data about postoperative renal outcomes. Because AKI was defined by different criteria, including biochemical determinations, urine output, or dialysis requirement, we unified renal outcome as worsening renal function (WRF). We identified 14 trials for steroids administration (931 patients, WRF incidence [treatment vs. placebo]: 2.7% vs. 2.4%; OR: 1.13; 95% CI: 0.53-2.43; P = 0.79), 9 trials for MECC (947 patients, WRF incidence: 2.4% vs. 0.9%; OR: 0.47; 95% CI: 0.18-1.25; P = 0.13), 6 trials for leukocyte filters (374 patients, WRF incidence: 1.1% vs. 7.5%; OR: 0.18; 95% CI: 0.05-0.64; P = 0.008). Only leukocyte filters effectively reduced WRF incidence. Not all cardiopulmonary bypass-related anti-inflammatory strategies analyzed reduced renal damage after cardiac operations. In adult patients, probably other factors are predominant on inflammation in determining AKI, and only leukocyte filters were effective. Large multicenter RCTs are needed in order to better evaluate the role of inflammation in AKI development after cardiac operations.

YB-1 is an early and central mediator of bacterial and sterile inflammation in vivo

In vitro studies identified Y-box-binding protein (YB)-1 as a key regulator of inflammatory mediators. In this study, we observed increased levels of secreted YB-1 in sera from sepsis patients. This led us to investigate the in vivo role of YB-1 in murine models of acute peritonitis following LPS injection, in sterile renal inflammation following unilateral ureteral obstruction, and in experimental pyelonephritis. LPS injection enhanced de novo secretion of YB-1 into the urine and the peritoneal fluid of LPS-treated mice. Furthermore, we could demonstrate a significant, transient upregulation and posttranslational modification (phosphorylation at serine 102) of YB-1 in renal and inflammatory cells. Increased renal cytoplasmic YB-1 amounts conferred enhanced expression of proinflammatory chemokines CCL2 and CCL5. Along these lines, heterozygous YB-1 knockout mice (YB-1(+/d)) that display 50% reduced YB-1 levels developed significantly lower responses to both LPS and sterile inflammation induced by unilateral ureteral obstruction. This included diminished immune cell numbers due to impaired migration propensities and reduced chemokine expression. YB-1(+/d) mice were protected from LPS-associated mortality (20% mortality on day 3 versus 80% in wild-type controls); however, immunosuppression in YB-1(+/d) animals resulted in 50% mortality. In conclusion, our findings identify YB-1 as a major, nonredundant mediator in both systemic and local inflammatory responses.

Association between serum cystatin C, monocytes and other inflammatory markers

BACKGROUND

Cystatin C is a marker of renal function that appears to be associated with inflammation. The aim of the present study was to investigate whether there is any relationship between cystatin C, total and differential leukocyte count and other inflammatory markers.

METHODS

Cystatin C, creatinine, high sensitivity C-reactive protein (hs-CRP), haptoglobin, ferritin, serum albumin, glucose, total cholesterol, HDL and triglycerides together with total and differential leukocyte count were determined in 490 adults (46 ± 16 years, 40% men) who underwent a typical health examination. Glomerular filtration rate was estimated by the simplified Modification of Diet in Renal Disease formula. Anthropometric and lifestyle characteristics were also recorded.

RESULTS

After adjustment for demographic risk factors, comorbid health conditions and renal function, a positive and independent relationship of serum cystatin C levels with peripheral monocyte blood count (regression coefficient ± SE: 12 ± 3.38, P < 0.001) and white blood count (0.616 ± 0.278, P= 0.027) was evident. In this multiple linear regression analysis, other inflammatory markers (i.e. hs-CRP, haptoglobin, ferritin, albumin) did not seem to affect cystatin C blood levels.

CONCLUSION

The results of this study demonstrated that monocytes, which play an important role in chronic inflammation and atherosclerosis, were independently related with cystatin C concentrations. This finding may provide a plausible link for the usefulness of cystatin C in predicting increased cardiovascular risk.

Tumor necrosis factor alpha promoter polymorphism and severity of acute kidney injury

BACKGROUND

Tumor necrosis factor-alpha is a proinflammatory cytokine that has been implicated in the pathobiology of acute kidney injury (AKI).

METHODS

We explored the association of a functional polymorphism in the promoter region (rs1800629) of the TNFA gene with severity of AKI, as defined by level of glomerular filtration (serum cystatin C and creatinine) and tubular injury (urinary NAG, KIM-1, α-GST, and π-GST) markers, in 262 hospitalized adults.

RESULTS

In unadjusted analyses, compared with the GG genotype, the TNFA GA and AA genotype groups tended to have higher enrollment (p = 0.08), peak (p = 0.004), and discharge (p = 0.004) serum creatinine levels, and the AA genotype tended to have a higher enrollment serum cystatin C level (p = 0.04). Compared with the GG genotype, the TNFA GA and AA genotype groups tended to have a higher urinary KIM-1 level (p = 0.03), and the AA genotype group tended to have a higher urinary π-GST level (p = 0.03). After adjustment for sex, race, age, baseline estimated glomerular filtration rate, sepsis, and dialysis requirement, compared with the GG genotype, the TNFA minor A-allele group had a higher peak serum creatinine of 1.03 mg/dl (0.43, 1.63; p = 0.001) and a higher urinary KIM-1 (relative ratio: 1.73; 95% CI: 1.16, 2.59; p = 0.008). The TNFA minor A-allele group also had a higher Multiple Organ Failure score of 0.26 (95% CI: 0.03, 0.49; p = 0.024) after adjustment for sex, race, age, and sepsis.

CONCLUSIONS

The TNFA rs1800629 gene polymorphism is associated with markers of kidney disease severity and distant organ dysfunction among patients with AKI. Larger studies are needed to confirm these relationships.

C-reactive protein exacerbates renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI), occurring with hypotension and cardiovascular surgery and inevitably during kidney transplantation. Mortality from AKI is high due to incomplete knowledge of the pathogenesis of IRI and the lack of an effective therapy. Inflammation accompanies IRI and increases the blood level of C-reactive protein (CRP), a biomarker of worsened outcomes in AKI. To test if CRP is causal in AKI we subjected wild-type mice (WT) and human CRP transgenic mice (CRPtg) to bilateral renal IRI (both pedicles clamped for 30 min at 37°C then reperfused for 24 h). Serum human CRP level was increased approximately sixfold after IRI in CRPtg (10.62 ± 1.31 μg/ml at baseline vs. 72.01 ± 9.41 μg/ml at 24 h) but was not elevated by sham surgery wherein kidneys were manipulated but not clamped. Compared with WT, serum creatinine, urine albumin, and histological evidence of kidney damage were increased after IRI in CRPtg mice. RT-PCR analysis of mRNA isolated from whole kidneys of CRPtg and WT subjected to IRI revealed that in CRPtg kidneys 1) upregulation of markers of macrophage classical activation (M1 markers) was blunted, 2) downregulation of markers of macrophage alternative activation (M2 markers) was more robust, and 3) expression of the activating receptor FcγRI was increased. Our finding that CRP exacerbates IRI-induced AKI, perhaps by shifting the balance of macrophage activation and FcγR expression towards a detrimental portfolio, might make CRP a promising therapeutic target for the treatment of AKI.

Kidney transplants with progressing chronic diseases express high levels of acute kidney injury transcripts

We previously reported that kidney transplants with early acute injury express transcripts indicating injury repair--the acute kidney injury signal. This study investigated the significance of this signal in transplants with other conditions, including rejection and recurrent disease. The injury signal was elevated in biopsies in many different conditions, including T cell-mediated rejection and potentially progressive diseases such as antibody-mediated rejection and glomerulonephritis. A high injury signal correlated with poor function and with inflammation in areas of fibrosis, but not with fibrosis without inflammation. In multivariate survival analysis, the injury signal in late kidney transplant biopsies strongly predicted future graft loss, similar to a published molecular risk score derived in late kidneys. Indeed, the injury signal shared many individual transcripts with the risk score, e.g. ITGB6, VCAN, NNMT. The injury signal was a better predictor of future graft loss than fibrosis, inflammation or expression of collagen genes. Thus the acute injury signal, first defined in early reversible injury, is present in many diseases as a reflection of parenchymal distress, where its significance is dictated by the inducing insult, i.e. treatable/self-limited versus untreatable and sustained. Progression in troubled transplants is primarily a function of ongoing parenchymal injury by disease, not fibrogenesis.

Interleukin-19 mediates tissue damage in murine ischemic acute kidney injury

Inflammation and renal tubular injury are major features of acute kidney injury (AKI). Many cytokines and chemokines are released from injured tubular cells and acts as proinflammatory mediators. However, the role of IL-19 in the pathogenesis of AKI is not defined yet. In bilateral renal ischemia/reperfusion injury (IRI)-induced and HgCl2-induced AKI animal models, real-time quantitative (RTQ)-PCR showed that the kidneys, livers, and lungs of AKI mice expressed significantly higher IL-19 and its receptors than did sham control mice. Immunohistochemical staining showed that IL-19 and its receptors were strongly stained in the kidney, liver, and lung tissue of AKI mice. In vitro, IL-19 upregulated MCP-1, TGF-β1, and IL-19, and induced mitochondria-dependent apoptosis in murine renal tubular epithelial M-1 cells. IL-19 upregulated TNF-α and IL-10 in cultured HepG2 cells, and it increased IL-1β and TNF-α expression in cultured A549 cells. In vivo, after renal IRI or a nephrotoxic dose of HgCl2 treatment, IL-20R1-deficient mice (the deficiency blocks IL-19 signaling) showed lower levels of blood urea nitrogen (BUN) in serum and less tubular damage than did wild-type mice. Therefore, we conclude that IL-19 mediates kidney, liver, and lung tissue damage in murine AKI and that blocking IL-19 signaling may provide a potent therapeutic strategy for treating AKI.

Gene polymorphisms of interleukin-10 and tumor necrosis factor-α are associated with contrast-induced nephropathy

BACKGROUND/AIMS

Contrast-induced nephropathy (CIN) is the third most common cause of hospital-acquired acute renal failure. However, the pathogenesis of CIN remains unclear. This study evaluated the role of anti-inflammatory cytokine interleukin-10 (IL-10) and pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) gene polymorphisms as CIN susceptibility markers after percutaneous coronary intervention (PCI).

METHODS

Four IL-10 tag SNPs (rs1554286, rs3021094, rs3790622, rs1800896) and three TNF-α tag SNPs (rs1799964, rs1800630, rs1800629) were analyzed by MALDI-TOF mass spectrometry in 53 CIN patients and 455 control subjects. Serum IL-10 and TNF-α were detected using ELISA.

RESULTS

When compared to controls, the CIN patients showed increased frequencies of CC (rs1554286) and AG+GG (rs1800896) genotypes in IL-10 and GA+AA (rs1800629) genotype in TNF-α (OR = 2.24 (1.13-4.44), p = 0.018; OR = 2.61 (1.30-5.26), p = 0.005, and OR = 2.11 (1.08-4.09), p = 0.025, respectively). Baseline serum IL-10 levels in CIN patients were significantly lower (1.02 ± 1.14 vs. 2.78 ± 4.73 pg/ml, p = 0.008). Patients with CIN had a higher rate of decline in renal function than those without CIN (0.89 ± 1.67 vs. 0.30 ± 0.95 ml/min/1.73 m(2) per month, p = 0.002). Significantly higher rates of decline in creatinine clearance were noted in patients with TNF-α (rs1800629) GA+AA than GG genotype (0.88 ± 1.83 vs. 0.36 ± 0.70, p = 0.03), and with IL-10 (rs1800896) AG+GG than AA genotype (1.28 ± 2.14 vs. 0.33 ± 0.90, p < 0.001).

CONCLUSIONS

Gene polymorphisms of IL-10 and TNF-α are associated with CIN risk and long-term renal outcome after PCI. More prospective studies are needed to confirm our results.

Kidney protection and regeneration following acute injury: progress through stem cell therapy

Acute kidney injury (AKI) is a common clinical entity with high morbidity and mortality rates and ever increasing medical costs. A large number of patients who are hospitalized with morbidities such as diabetes, vascular disease, or chronic kidney disease are at high risk to develop AKI due to ischemic and nephrotoxic insults. The pathophysiology of ischemic and toxic forms of AKI is complex and includes tubular and vascular cell damage and inflammation. Given the seriousness of this essentially therapy-resistant complication, treatment beyond supportive measures and renal replacement therapy is urgently needed. Recent stem cell research has shown promising results, and cell therapy-based interventions are advancing into clinical trials. An example is our phase 1 clinical trial (NCT00733876) in which cardiac surgery patients at high risk of postoperative AKI were treated safely with allogeneic mesenchymal stem cells. Together with the introduction of biomarkers for an earlier and specific AKI diagnosis, currently tested stem cell-based therapies are expected to provide an entirely new class of diagnostic and therapeutic tools.

Diagnostic value of urine sCD163 levels for sepsis and relevant acute kidney injury: a prospective study

BACKGROUND

Sepsis is a common syndrome in critically ill patients and easily leads to the occurrence of acute kidney injury (AKI), with high mortality rates. This study aimed to investigate the diagnostic value of urine soluble CD163 (sCD163) for identification of sepsis, severity of sepsis, and for secondary AKI, and to assess the patients' prognosis.

METHODS

We enrolled 20 cases with systemic inflammatory response syndrome (SIRS), 40 cases with sepsis (further divided into 17 sepsis cases and 23 severe sepsis cases) admitted to the intensive care unit (ICU), and 20 control cases. Results for urine sCD163 were recorded on the day of admission to the ICU, and AKI occurrence was noted.

RESULTS

On the day of ICU admission, the sepsis group exhibited higher levels of urine sCD163 (74.8 ng/ml; range: 47.9-148.3 ng/ml) compared with those in the SIRS group (31.9 ng/ml; 16.8-48.0, P < 0.001). The area under the curve (AUC) was 0.83 (95% confidence interval [CI]: 0.72-0.94, P < 0.001) the sensitivity was 0.83, and the specificity was 0.75 (based on a cut-off point of 43.0 ng/ml). Moreover, the severe sepsis group appeared to have a higher level of sCD163 compared with that in the sepsis group (76.2; 47.2-167.5 ng/ml vs. 74.2; 46.2-131.6 ng/ml), but this was not significant. For 15 patients with AKI, urine sCD163 levels at AKI diagnosis were significantly higher than those of the remaining 35 sepsis patients upon ICU admission (121.0; 74.6-299.1 ng/ml vs. 61.8; 42.8-128.3 ng/ml, P = 0.049). The AUC for urine sCD163 was 0.688 (95% CI: 0.51-0.87, P = 0.049). Sepsis patients with a poor prognosis showed a higher urine sCD163 level at ICU admission (98.6; 50.3-275.6 ng/ml vs. 68.0; 44.8-114.5 ng/ml), but this was not significant. Patients with AKI with a poor prognosis had higher sCD163 levels than those in patients with a better prognosis (205.9; 38.6-766.0 ng/ml vs. 80.9; 74.9-141.0 ng/ml), but this was not significant.

CONCLUSIONS

This study shows, for the first time, the potential value of urine sCD163 levels for identifying sepsis and diagnosing AKI, as well as for assessment of patients' prognosis.

TRIAL REGISTRATION

ChiCTR-ONC-10000812.

Inhibition of proinflammatory cytokines by SCH79797, a selective protease-activated receptor 1 antagonist, protects rat kidney against ischemia-reperfusion injury

Renal ischemia-reperfusion injury (I/R) is the most common cause of acute renal failure. It is partially mediated by thrombin as it is attenuated by thrombin inhibition or deletion of its receptor protease-activated receptor 1 (PAR1). However, the role of PAR1 in renal I/R injury needs to be further elucidated. The present study investigated the effect of PAR1 antagonist, SCH79797 (SCH), on renal protection and downstream effectors involved. Male Wistar rats were pretreated with SCH (25 μg/kg i.p.) or vehicle, 15 min before 45 min of clamping of left renal pedicle after right nephrectomy. To investigate the involvement of phosphatidylinositol 3-kinase (PI3K)/Akt, a group of rats was subjected to pretreatment with an inhibitor of PI3K/Akt (LY 29004, 3 mg/kg i.p.) before renal ischemia and SCH treatment. A sham-operated group served as control and received saline. All rats were killed 24 h after reperfusion or sham operation, and blood samples collected and kidney tissues processed either for immunostaining and histological assessment or for biochemical analysis. SCH79797 markedly attenuated kidney damage histologically and by improving serum creatinine. Both plasma and protein expression of P selectin were markedly reduced as well as neutrophil infiltration, cytokine-induced neutrophil chemoattractant 1, and tumor necrosis factor α. These protective effects of blocking PAR1 receptor were abolished by preadministration of LY29004. These results suggest that PAR1 mediates renal I/R injury and that blocking PAR1 using SCH limits renal injury by an anti-inflammatory effect possibly signaling via PI3K/Akt.

Mild electrical stimulation and heat shock ameliorates progressive proteinuria and renal inflammation in mouse model of Alport syndrome

Alport syndrome is a hereditary glomerulopathy with proteinuria and nephritis caused by defects in genes encoding type IV collagen in the glomerular basement membrane. All male and most female patients develop end-stage renal disease. Effective treatment to stop or decelerate the progression of proteinuria and nephritis is still under investigation. Here we showed that combination treatment of mild electrical stress (MES) and heat stress (HS) ameliorated progressive proteinuria and renal injury in mouse model of Alport syndrome. The expressions of kidney injury marker neutrophil gelatinase-associated lipocalin and pro-inflammatory cytokines interleukin-6, tumor necrosis factor-α and interleukin-1β were suppressed by MES+HS treatment. The anti-proteinuric effect of MES+HS treatment is mediated by podocytic activation of phosphatidylinositol 3-OH kinase (PI3K)-Akt and heat shock protein 72 (Hsp72)-dependent pathways in vitro and in vivo. The anti-inflammatory effect of MES+HS was mediated by glomerular activation of c-jun NH₂-terminal kinase 1/2 (JNK1/2) and p38-dependent pathways ex vivo. Collectively, our studies show that combination treatment of MES and HS confers anti-proteinuric and anti-inflammatory effects on Alport mice likely through the activation of multiple signaling pathways including PI3K-Akt, Hsp72, JNK1/2, and p38 pathways, providing a novel candidate therapeutic strategy to decelerate the progression of patho-phenotypes in Alport syndrome.

N-octanoyl-dopamine is an agonist at the capsaicin receptor TRPV1 and mitigates ischemia-induced [corrected] acute kidney injury in rat

Since stimulation of transient receptor potential channels of the vanilloid receptor subtype 1 (TRPV1) mitigates acute kidney injury (AKI) and endogenous N-acyl dopamine derivatives are able to activate TRPV1, we tested if synthetic N-octanoyl-dopamine (NOD) activates TRPV1 and if it improves AKI. These properties of NOD and its intrinsic anti-inflammatory character were compared with those of dopamine (DA). TRPV1 activation and anti-inflammatory properties of NOD and DA were tested using primary cell cultures in vitro. The influence of NOD and DA on AKI was tested in a prospective, randomized, controlled animal study with 42 inbred male Lewis rats (LEW, RT1), treated intravenously with equimolar concentrations of DA or NOD one hour before the onset of warm ischemia and immediately before clamp release. NOD, but not DA, activates TRPV1 channels in isolated dorsal root ganglion neurons (DRG) that innervate several tissues including kidney. In TNFα stimulated proximal tubular epithelial cells, inhibition of NFκB and subsequent inhibition of VCAM1 expression by NOD was significantly stronger than by DA. NOD improved renal function compared to DA and saline controls. Histology revealed protective effects of NOD on tubular epithelium at day 5 and a reduced number of monocytes in renal tissue of DA and NOD treated rats. Our data demonstrate that NOD but not DA activates TRPV1 and that NOD has superior anti-inflammatory properties in vitro. Although NOD mitigates deterioration in renal function after AKI, further studies are required to assess to what extend this is causally related to TRPV1 activation and/or desensitization.

Mammalian target of rapamycin complex 2 regulates inflammatory response to stress

OBJECTIVE AND DESIGN

To explore the role of mammalian target of rapamycin 2 (mTORC2) in the activation of inflammatory and oxidative responses in rodent models of acute injury and metabolic stress.

MATERIAL

The impact of nephrilin, an inhibitor of mTORC2 complex, was assessed in three CD-1 mouse models of acute xenobiotic stress and in a hypertensive Dahl rat model of metabolic stress.

METHODS

Animals received daily subcutaneous bolus injections of saline or 4 mg/kg nephrilin. Tissues were assayed by ELISA, gene arrays and immunohistochemical staining.

RESULTS

Nephrilin significantly inhibited elevations in plasma tumor necrosis factor-alpha, kidney substance P, and CX3CR1, and urinary lipocalin-2 [urinary neutrophil gelatinase-associated lipocalin (uNGAL)] in models of acute xenobiotic stress. UCHL1 gene expression levels dropped and plasma HMGB1 levels rose in the rhabdomyolysis model. Both effects were reversed by nephrilin. The inhibitor also blocked diet-induced elevations of uNGAL and albumin-creatinine ratio (UACR) as well as kidney tissue phosphorylation of PKC-beta-2-T641 and p66shc-S36, and reduced dark ring-like staining of nuclei by anti-phos-p66shc-S36 antibody in frozen sections of diseased kidneys from hypertensive Dahl rats fed an 8 % NaCl diet for 4 weeks.

CONCLUSIONS

Taken together, our results suggest a role for mTORC2 in the inflammatory-oxidative responses to stress.

Type I interferons promote fatal immunopathology by regulating inflammatory monocytes and neutrophils during Candida infections

Invasive fungal infections by Candida albicans (Ca) are a frequent cause of lethal sepsis in intensive care unit patients. While a contribution of type I interferons (IFNs-I) in fungal sepsis remains unknown, these immunostimulatory cytokines mediate the lethal effects of endotoxemia and bacterial sepsis. Using a mouse model lacking a functional IFN-I receptor (Ifnar1^−/−), we demonstrate a remarkable protection against invasive Ca infections. We discover a mechanism whereby IFN-I signaling controls the recruitment of inflammatory myeloid cells, including Ly6C^hi monocytes and neutrophils, to infected kidneys by driving expression of the chemokines CCL2 and KC. Within kidneys, monocytes differentiate into inflammatory DCs but fail to functionally mature in Ifnar1^−/− mice, as demonstrated by the impaired upregulation of the key activation markers PDCA1 and iNOS. The increased activity of inflammatory monocytes and neutrophils results in hyper-inflammation and lethal kidney pathology. Pharmacological diminution of monocytes and neutrophils by treating mice with pioglitazone, a synthetic agonist of the nuclear receptor peroxisome proliferator-activated receptor-γ (PPAR-γ), strongly reduces renal immunopathology during Ca infection and improves mouse survival. Taken together, our data connect for the first time the sepsis-promoting functions of IFNs-I to the CCL2-mediated recruitment and the activation of inflammatory monocytes/DCs with high host-destructing potency. Moreover, our data demonstrate a therapeutic relevance of PPAR-γ agonists for microbial infectious diseases where inflammatory myeloid cells may contribute to fatal tissue damage.

Inflammation constitutes a major host response in many microbial infections. Innate immune cells orchestrate the inflammatory response to kill pathogens and clear infections. However, invasive infections by pathogenic microbes including the fungus Candida albicans, can result in an uncontrolled hyper-inflammatory response, leading to severe host damage and sepsis. Type I interferons constitute a hallmark of protective innate immunity in viral and bacterial infections, but at the same time have been notoriously known for their sepsis-promoting effects in numerous experimental inflammation models. Here, we show that type I interferon-signaling mediates the lethal hyper-inflammatory response during systemic mouse infections with C. albicans. Following fungal infections, type I interferons promote the recruitment and activation of inflammatory monocytes and neutrophils to infected organs. The high abundance and activity of inflammatory phagocytes lead to fatal tissue damage. Remarkably, we show that the pharmacological suppression of these inflammatory cells with the drug pioglitazone reduces immunopathology and sepsis-related lethality, suggesting a novel therapeutic option to combat fungal sepsis. In conclusion, our data couple the sepsis-promoting role of type I interferons to the host-destructive activity of inflammatory monocytes and neutrophils. We propose that therapeutic approaches dampening hyper-inflammation might be of general importance in microbial diseases where deleterious immunopathology occurs.

Protective effects of propofol on endotoxemia-induced acute kidney injury in rats

1. Animal studies suggest that propofol protects against endotoxaemia-induced lung and kidney injury. Upregulation of aquaporin expression in lung tissue mediates these effects, but the mechanism of action in the kidney is unclear. The present study examined the protective effects of propofol on endotoxaemia-induced acute kidney injury in rats. 2. A rat model of endotoxaemia was established using lipopolysaccharide (LPS). We determined the effects of 10% propofol administration 1 h before, during and 1 h after LPS-induced endotoxaemia on expression of aquaporin (AQP)-2, tumour necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1, caspase 3, Bcl-2 and Bax using reverse transcription-polymerase chain reaction, western blotting and immunocytochemistry. Renal morphology, superstructure, apoptosis and function were also assessed. 3. Normal renal tubular structure was seen in the propofol pretreated group, but LPS treatment resulted in changes to renal tissue morphology. Propofol treatment improved renal function in LPS-treated rats. Pretreatment with propofol 1 h before LPS normalized urine and serum osmolality, serum creatinine and blood urea nitrogen to control levels. Lipopolysaccharide downregulated expression of AQP-2 and downregulated the expression of ICAM-1 and TNF-α. These effects were reversed by propofol treatment. Lipopolysaccharide reduced the Bcl2 : Bax ratio and induced renal cell apoptosis and these effects were reduced by propofol treatment. Overall, propofol pretreatment had greater effects than concurrent treatment or propofol administration after LPS induction of endotoxaemia. 4. In conclusion, propofol pretreatment protected renal function in a rat model of endotoxaemia. Further studies are necessary to confirm this effect in other experimental models and in humans.

Increased immunogenicity is an integral part of the heat shock response following renal ischemia

Renal ischemia increases tubular immunogenicity predisposing to increased risk of kidney allograft rejection. Ischemia-reperfusion not only disrupts cellular homeostasis but also induces the cytoprotective heat shock response that also plays a major role in cellular immune and defense processes. This study therefore tested the hypothesis that upregulation of renal tubular immunogenicity is an integral part of the heat shock response after renal ischemia. Expressions of 70 kDa heat shock protein (Hsp70), major histocompatibility complex (MHC) class II, and intercellular adhesion molecule-1 (ICAM-1) were assessed in normal rat kidney (NRK) cells following ATP depletion (antimycin A for 3 h) and heat (42°C for 24 h). In vitro, transient Hsp70 transfection and heat shock factor-1 (HSF-1) transcription factor decoy treatment were performed. In vivo, ischemic renal cortex was investigated in Sprague-Dawley rats following unilateral renal artery clamping for 45 min and 24 h recovery. Upregulation of Hsp70 was closely and significantly correlated with upregulation of MHC class II and/or ICAM-1 following ATP depletion and heat injury. Bioinformatics analysis searching the TRANSFAC database predicted HSF-1 binding sites in these genes. HSF-1 decoy significantly reduced the expression of immunogenicity markers in stressed NRK cells. In the in vivo rat model of renal ischemia, concordant upregulation of MHC class II molecules and Hsp70 suggests biological relevance of this link. The results demonstrate that upregulation of renal tubular immunogenicity is an integral part of the heat shock response after renal ischemia. Bioinformatic analysis predicted a molecular link to tubular immunogenicity at the level of the transcription factor HSF-1 that was experimentally verified by HSF-1 decoy treatment. Future studies in HSF-1 knockout mice are needed.

Sulforaphane, a natural constituent of broccoli, prevents cell death and inflammation in nephropathy

Cisplatin (cis-diamminedichloroplatinum II, CIS) is a potent and widely used chemotherapeutic agent to treat various malignancies, but its therapeutic use is limited because of dose-dependent nephrotoxicity. Cell death and inflammation play a key role in the development and progression of CIS-induced nephropathy. Sulforaphane (SFN), a natural constituent of cruciferous vegetables such as broccoli, Brussels sprouts, etc., has been shown to exert various protective effects in models of tissue injury and cancer. In this study, we have investigated the role of prosurvival, cell death and inflammatory signaling pathways using a rodent model of CIS-induced nephropathy, and explored the effects of SFN on these processes. Cisplatin triggered marked activation of stress signaling pathways [p53, Jun N-terminal kinase (JNK), and p38-α mitogen-activated protein kinase (MAPK)] and promoted cell death in the kidneys (increased DNA fragmentation, caspases-3/7 activity, terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick-end labeling), associated with attenuation of various prosurvival signaling pathways [e.g., extracellular signal-regulated kinase (ERK) and p38-β MAPK]. Cisplatin also markedly enhanced inflammation in the kidneys [promoted NF-κB activation, increased expression of adhesion molecules ICAM and VCAM, enhanced tumor necrosis factor-α (TNF-α) levels and inflammatory cell infiltration]. These effects were significantly attenuated by pretreatment of rodents with SFN. Thus, the cisplatin-induced nephropathy is associated with activation of various cell death and proinflammatory pathways (p53, JNK, p38-α, TNF-α and NF-κB) and impairments of key prosurvival signaling mechanisms (ERK and p38-β). SFN is able to prevent the CIS-induced renal injury by modulating these pathways, providing a novel approach for preventing this devastating complication of chemotherapy.

Hepatocyte growth factor preferentially activates the anti-inflammatory arm of NF-κB signaling to induce A20 and protect renal proximal tubular epithelial cells from inflammation

Inflammation induces the NF-κB dependent protein A20 in human renal proximal tubular epithelial cells (RPTEC), which secondarily contains inflammation by shutting down NF-κB activation. We surmised that inducing A20 without engaging the pro-inflammatory arm of NF-κB could improve outcomes in kidney disease. We showed that hepatocyte growth factor (HGF) increases A20 mRNA and protein levels in RPTEC without causing inflammation. Upregulation of A20 by HGF was NF-κB/RelA dependent as it was abolished by overexpressing IκBα or silencing p65/RelA. Unlike TNFα, HGF caused minimal IκBα and p65/RelA phosphorylation, with moderate IκBα degradation. Upstream, HGF led to robust and sustained AKT activation, which was required for p65 phosphorylation and A20 upregulation. While HGF treatment of RPTEC significantly increased A20 mRNA, it failed to induce NF-κB dependent, pro-inflammatory MCP-1, VCAM-1, and ICAM-1 mRNA. This indicates that HGF preferentially upregulates protective (A20) over pro-inflammatory NF-κB dependent genes. Upregulation of A20 supported the anti-inflammatory effects of HGF in RPTEC. HGF pretreatment significantly attenuated TNFα-mediated increase of ICAM-1, a finding partially reversed by silencing A20. In conclusion, this is the first demonstration that HGF activates an AKT-p65/RelA pathway to preferentially induce A20 but not inflammatory molecules. This could be highly desirable in acute and chronic renal injury where A20-based anti-inflammatory therapies are beneficial.

Effects of electroacupuncture pretreatment on inflammatory response and acute kidney injury in endotoxaemic rats

This study investigated the effect of electroacupuncture pretreatment on the lipopolysaccharide (LPS)-induced inflammatory response and on acute kidney injury in adult male pathogen-free Wistar rats. Rats received electroacupuncture at the Zusanli (ST36) and Neiguan (PC6) acupoints, or electrical stimulation at sham points, for 30 min before stimulation with either 5 mg/kg LPS intravenously or normal saline. Plasma cytokines, plasma nitrite, renal inducible nitric oxide synthase (iNOS) and nuclear factor κB (NF-κB) activity were assessed 240 min after LPS or normal saline injection. Blood urea nitrogen (BUN), creatinine (Cr) and histopathological score for renal tubular damage were also measured. Electroacupuncture pretreatment significantly decreased LPS-induced plasma tumour necrosis factor-α and interleukin (IL)-1β, increased plasma IL-10, and decreased plasma nitrite, renal iNOS and NF-κB activity. It also significantly decreased LPS-induced BUN, Cr and the renal histopathological score. These findings suggest that electroacupuncture pretreatment at the ST36 and PC6 acupoints attenuated the LPS-induced inflammatory response and mitigated acute kidney injury.

Regional citrate anticoagulation reduces polymorphonuclear cell degranulation in critically ill patients treated with continuous venovenous hemofiltration

Citrate which chelates ionized calcium can be used as regional anticoagulation in continuous venovenous hemofiltration (CVVH). This is the first study conducted to examine the potentially additive benefit effect of regional citrate anticoagulation (RCA) on polymorphonuclear (PMN) cell degranulation of myeloperoxidase (MPO) and cytokines production in patients with critically acute kidney injury (AKI) undergoing CVVH treatment. This prospective randomized controlled trial was conducted in 20 critically ill patients with AKI who underwent CVVH. The patients were randomized into regional citrate group (n=10) and heparin group (n=10). The pre-dilution CVVH with polyethersulfone dialyzers were utilized in both groups. The levels of pre-filter and post-filter MPO as well as inflammatory and anti-inflammatory cytokines were measured at baseline, 6h, and 24 h after initiating CVVH. In the heparin group, the post-filter serum MPO levels were significantly higher than the pre-filter (median 49.0 vs. 60.5 ng/mL, P<0.05) at 6 h. There were no significant differences between pre- and post-dialyzer MPO levels in the citrate group. Citrate could significantly decrease systemic pre-filter serum MPO levels from baseline at 6 h (median 43.5 vs. 17.3 ng/mL, P<0.01) as well as IL-8 levels (P<0.05) whereas heparin provided only significant TNF-α reduction (P<0.05). The CVVH circuit survival in the citrate group was longer than the heparin group. In conclusion, citrate, utilized as a regional anticoagulant in CVVH, can reduce both membrane bioincompatibility-induced and systemic oxidative stress and inflammation, and can prolong CVVH circuit survival time.

Role of circulating fibroblast growth factor-2 in lipopolysaccharide-induced acute kidney injury in mice

Fibroblast growth factor-2 (FGF-2) is an angiogenic growth factor involved in renal growth and regeneration. Previous studies in rodents revealed that single intrarenal injections of FGF-2 improved the outcome of acute kidney injury (AKI). Septic children usually show elevated plasma levels of FGF-2, and are at risk of developing AKI. However, the role of circulating FGF-2 in the pathogenesis of AKI is not well understood. We have developed a mouse model to determine how FGF-2 released into the circulation modulates the outcome of AKI induced by lipopolysaccharide (LPS). Young FVB/N mice were infected with adenoviruses carrying a secreted form of human FGF-2 or control LacZ vectors. Subsequently, when the circulating levels of FGF-2 were similar to those seen in septic children, mice were injected with a non-lethal dose of LPS or control buffer. All mice injected with LPS developed hypotension and AKI, from which they recovered after 5 days. FGF-2 did not improve the outcome of AKI, and induced more significant renal proliferative and apoptotic changes during the recovery phase. These findings suggest that circulating FGF-2 may not necessarily prevent the development or improve the outcome of AKI. Moreover, the renal accumulation of FGF-2 might cause further renal damage.

Diagnostic value of urine sTREM-1 for sepsis and relevant acute kidney injuries: a prospective study

Introduction

We explored the diagnostic value of a urine soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) for early sepsis identification, severity and prognosis assessment, and for secondary acute kidney injury (AKI). We compared this with white blood cell (WBC) counts, serum C-reactive protein (CRP), serum procalcitonin (PCT), urine output, creatinine clearance (CCr), serum creatinine (SCr), and blood urea nitrogen (BUN).

Methods

We enrolled 104 subjects admitted to the ICU: 16 cases with systemic inflammatory response syndrome (SIRS); 35 with sepsis and 53 with severe sepsis. Results for urine sTREM-1, WBC, serum CRP and serum PCT were recorded on days 1, 3, 5, 7, 10, and 14. For 17 sepsis cases diagnosed with secondary AKI, comparisons between their urine sTREM-1, urine output, CCr, SCr and BUN at diagnosis and 48 h before diagnosis were made.

Results

On the day of admission to the ICU, and compared with the SIRS group, the sepsis group exhibited higher levels of urine sTREM-1 and Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE II) scores (P < 0.05). Areas under the curve (AUC) shaped by the scores were 0.797 (95% CI 0.711 to 0.884) and 0.722 (95% CI 0.586 to 0.858), respectively. On days 1, 3, 5, 7, 10, and 14, urine sTREM-1, serum PCT and WBC levels registered higher in the severe sepsis group in contrast to the sepsis group (P < 0.05). Urine sTREM-1 and serum PCT levels continuously increased among non-survivors, while WBC and serum CRP levels in both groups declined. For 17 patients with AKI, urine sTREM-1, SCr and BUN levels at 48 h before AKI diagnosis were higher, and CCr level was lower than those for non-AKI subjects (P < 0.05). AUC for urine sTREM-1 was 0.922 (95% CI 0.850 to 0.995), the sensitivity was 0.941, and the specificity was 0.76 (based on a cut-off point of 69.04 pg/ml). Logistic regression analysis showed that urine sTREM-1 and severity were risk factors related to AKI occurrence.

Conclusions

Besides being non-invasive, urine sTREM-1 testing is more sensitive than testing WBC, serum CRP, and serum PCT for the early diagnosis of sepsis, as well as for dynamic assessments of severity and prognosis. It can also provide an early warning of possible secondary AKI in sepsis patients.

Trial Registration

ClinicalTrial.gov identifier NCT01333657

Preconditioning with physiological levels of ethanol protect kidney against ischemia/reperfusion injury by modulating oxidative stress

Background

Oxidative stress due to excessive production of reactive oxygen species (ROS) and subsequent lipid peroxidation plays a critical role in renal ischemia/reperfusion (IR) injury. The purpose of current study is to demonstrate the effect of antecedent ethanol exposure on IR-induced renal injury by modulation of oxidative stress.

Materials and Methods

Bilateral renal warm IR was induced in male C57BL/6 mice after ethanol or saline administration. Blood ethanol concentration, kidney function, histological damage, inflammatory infiltration, cytokine production, oxidative stress, antioxidant capacity and Aldehyde dehydrogenase (ALDH) enzymatic activity were assessed to evaluate the impact of antecedent ethanol exposure on IR-induced renal injury.

Results

After bilateral kidney ischemia, mice preconditioned with physiological levels of ethanol displayed significantly preserved renal function along with less histological tubular damage as manifested by the reduced inflammatory infiltration and cytokine production. Mechanistic studies revealed that precondition of mice with physiological levels of ethanol 3 h before IR induction enhanced antioxidant capacity characterized by significantly higher superoxidase dismutase (SOD) activities. Our studies further demonstrated that ethanol pretreatment specifically increased ALDH2 activity, which then suppressed lipid peroxidation by promoting the detoxification of Malondialdehyde (MDA) and 4-hydroxynonenal (HNE).

Conclusions

Our results provide first line of evidence indicating that antecedent ethanol exposure can provide protection for kidneys against IR-induced injury by enhancing antioxidant capacity and preventing lipid peroxidation. Therefore, ethanol precondition and ectopic ALDH2 activation could be potential therapeutic approaches to prevent renal IR injury relevant to various clinical conditions.

14S,21R-dihydroxy-docosahexaenoic acid treatment enhances mesenchymal stem cell amelioration of renal ischemia/reperfusion injury

Bone marrow mesenchymal stem cells (MSCs) have shown potential to improve treatment of renal failure. The prohealing functions of MSCs have been found to be enhanced by treatment with the lipid mediator, 14S,21R-dihydroxy-docosa4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid (14S,21R-diHDHA). In this article, using a murine model of renal ischemia/reperfusion (I/R) injury, we found that treatment with 14S,21R-diHDHA enhanced MSC amelioration of renal I/R injury. Treated MSCs more efficiently inhibited I/R-induced elevation of serum creatinine levels, reduced renal tubular cell death, and inhibited infiltration of neutrophils, macrophages, and dendritic cells in kidneys. Conditioned medium from treated MSCs reduced the generation of tumor necrosis factor-α and reactive oxygen species by macrophages under I/R conditions. Infusion of treated MSCs more efficiently reduced I/R-damage to renal histological structures compared with untreated MSCs (injury score: 7.9±0.4 vs. 10.5±0.5). Treated MSCs were resistant to apoptosis in vivo when transplanted under capsules of I/R-injured kidneys (active caspase-3+ MSCs: 4.2%±2.8% vs. 11.7%±2.4% of control) and in vitro when cultured under I/R conditions. Treatment with 14S,21R-diHDHA promoted viability of MSCs through a mechanism involving activation of the phosphoinositide 3-kinase -Akt signaling pathway. Additionally, treatment of MSCs with 14S,21R-diHDHA promoted secretion of renotrophic hepatocyte growth factor and insulin growth factor-1. Similar results were obtained when 14S,21RdiHDHA was used to inhibit apoptosis of human MSCs (hMSCs) and to increase the generation of renotrophic cytokines from hMSCs. These findings provide a lead for new strategies in the treatment of acute kidney injury with MSCs.

IL-33 exacerbates acute kidney injury

Inflammation contributes to the pathogenesis of acute kidney injury (AKI). IL-33 is a proinflammatory cytokine, but its role in AKI is unknown. Here we observed increased protein expression of full-length IL-33 in the kidney following induction of AKI with cisplatin. To determine whether IL-33 promotes injury, we administered soluble ST2 (sST2), a fusion protein that neutralizes IL-33 activity by acting as a decoy receptor. Compared with cisplatin-induced AKI in untreated mice, mice treated with sST2 had fewer CD4 T cells infiltrate the kidney, lower serum creatinine, and reduced acute tubular necrosis (ATN) and apoptosis. In contrast, administration of recombinant IL-33 (rIL-33) exacerbated cisplatin-induced AKI, measured by an increase in CD4 T cell infiltration, serum creatinine, ATN, and apoptosis; this did not occur in CD4-deficient mice, suggesting that CD4 T cells mediate the injurious effect of IL-33. Wildtype mice that received cisplatin and rIL-33 also had higher levels of the proinflammatory chemokine CXCL1, which CD T cells produce, in the kidney compared with CD4-deficient mice. Mice deficient in the CXCL1 receptor also had lower serum creatinine, ATN, and apoptosis than wildtype mice following cisplatin-induced AKI. Taken together, IL-33 promotes AKI through CD4 T cell-mediated production of CXCL1. These data suggest that inhibiting IL-33 or CXCL1 may have therapeutic potential in AKI.

Use of a hanging-weight system for isolated renal artery occlusion

In hospitalized patients, over 50% of cases of acute kidney injury (AKI) are caused by renal ischemia. A recent study of hospitalized patients revealed that only a mild increase in serum creatinine levels (0.3 to 0.4 mg/dl) is associated with a 70% greater risk of death than in persons without any increase. Along these lines, surgical procedures requiring cross-clamping of the aorta and renal vessels are associated with a renal failure rates of up to 30%. Similarly, AKI after cardiac surgery occurs in over 10% of patients under normal circumstances and is associated with dramatic increases in mortality. AKI are also common complications after liver transplantation. At least 8-17% of patients end up requiring renal replacement therapy. Moreover, delayed graft function due to tubule cell injury during kidney transplantation is frequently related to ischemia-associated AKI. Moreover, AKI occurs in approximately 20% of patients suffering from sepsis. The occurrence of AKI is associated with dramatic increases of morbidity and mortality. Therapeutic approaches are very limited and the majority of interventional trials in AKI have failed in humans. Therefore, additional therapeutic modalities to prevent renal injury from ischemia are urgently needed. To elucidate mechanisms of renal injury due to ischemia and possible therapeutic strategies murine models are intensively required. Mouse models provide the possibility of utilizing different genetic models including gene-targeted mice and tissue specific gene-targeted mice (cre-flox system). However, murine renal ischemia is technically challenging and experimental details significantly influence results. We performed a systematic evaluation of a novel model for isolated renal artery occlusion in mice, which specifically avoids the use of clamping or suturing the renal pedicle. This model requires a nephrectomy of the right kidney since ischemia can be only performed in one kidney due to the experimental setting. In fact, by using a hanging-weight system, the renal artery is only instrumented once throughout the surgical procedure. In addition, no venous or urethral obstruction occurs with this technique. We could demonstrate time-dose-dependent and highly reproducible renal injury with ischemia by measuring serum creatinine. Moreover, when comparing this new model with conventional clamping of the whole pedicle, renal protection by ischemic preconditioning is more profound and more reliable. Therefore his new technique might be useful for other researchers who are working in the field of acute kidney injury.

Comparing the potential renal protective activity of desferrioxamine B and the novel chelator desferrioxamine B-N-(3-hydroxyadamant-1-yl)carboxamide in a cell model of myoglobinuria

Accumulating Mb (myoglobin) in the kidney following severe burns promotes oxidative damage and inflammation, which leads to acute renal failure. The potential for haem-iron to induce oxidative damage has prompted testing of iron chelators [e.g. DFOB (desferrioxamine B)] as renal protective agents. We compared the ability of DFOB and a DFOB-derivative {DFOB-AdAOH [DFOB-N-(3-hydroxyadamant-1-yl)carboxamide]} to protect renal epithelial cells from Mb insult. Loading kidney-tubule epithelial cells with dihydrorhodamine-123 before exposure to 100 μM Mb increased rhodamine-123 fluorescence relative to controls (absence of Mb), indicating increased oxidative stress. Extracellular Mb elicited a reorganization of the transferrin receptor as assessed by monitoring labelled transferrin uptake with flow cytometry and inverted fluorescence microscopy. Mb stimulated HO-1 (haem oxygenase-1), TNFα (tumour necrosis factor α), and both ICAM (intercellular adhesion molecule) and VCAM (vascular cell adhesion molecule) gene expression and inhibited epithelial monolayer permeability. Pre-treatment with DFOB or DFOB-AdAOH decreased Mb-mediated rhodamine-123 fluorescence, HO-1, ICAM and TNFα gene expression and restored monolayer permeability. MCP-1 (monocyte chemotactic protein 1) secretion increased in cells exposed to Mb-insult and this was abrogated by DFOB or DFOB-AdAOH. Cells treated with DFOB or DFOB-AdAOH alone showed no change in permeability, MCP-1 secretion or HO-1, TNFα, ICAM or VCAM gene expression. Similarly to DFOB, incubation of DFOB-AdAOH with Mb plus H2O2 yielded nitroxide radicals as detected by EPR spectroscopy, indicating a potential antioxidant activity in addition to metal chelation; Fe(III)-loaded DFOB-AdAOH showed no nitroxide radical formation. Overall, the chelators inhibited Mb-induced oxidative stress and inflammation and improved epithelial cell function. DFOB-AdAOH showed similar activity to DFOB, indicating that this novel low-toxicity chelator may protect the kidney after severe burns.

Metabolic stress promotes renal tubular inflammation by triggering the unfolded protein response

The renal epithelium contributes to the development of inflammation during ischemic injury. Ischemia induces endoplasmic reticulum (ER) stress and activates the unfolded protein response (UPR). Ischemic tissues generate distress signals and inflammation that activates fibrogenesis and may promote adaptive immunity. Interestingly, the UPR may activate inflammation pathways. Our aim was to test whether the UPR is activated during metabolic stress and mediates a tubular inflammatory response. Glucose deprivation, not hypoxia and amino acids deprivation, activated the UPR in human renal cortical tubular cells in culture. This stress activated NF-κB and promoted the transcription of proinflammatory cytokines and chemokines, including IL-6, IL-8, TNF-α, RANTES and MCP-1. The protein kinase RNA (PKR)-like ER kinase signaling pathway was not required for the induction of inflammation but amplified cytokine. Inositol-requiring enzyme 1 activated NF-κB signaling and was required for the transcription of proinflammatory cytokines and chemokines following metabolic stress. Moreover, acute ischemia activated ER stress and inflammation in rat kidneys. Finally, the ER stress marker GRP78 and NF-κB p65/RelA were coexpressed in human kidney transplants biopsies performed before implantation, suggesting that ER stress activates tubular inflammation in human renal allografts. In conclusion, this study establishes a link between ischemic stress, the activation of the UPR and the generation of a tubular inflammatory response.

Klotho in acute kidney injury: biomarker, therapy, or a bit of both?

Acute kidney injury (AKI) diagnosis is based on an increase in serum creatinine or a decrease in urine output. To be effective, treatment of AKI should be started very early after the insult and well before the rise of serum creatinine. Thus, sensitive biologic markers of renal tubular injury in AKI are strongly needed. Hu et al. suggest that Klotho could be a novel biomarker and therapeutic target of ischemia-induced AKI.

Pathophysiology of ischemic acute kidney injury

Acute kidney injury (AKI) as a consequence of ischemia is a common clinical event leading to unacceptably high morbidity and mortality, development of chronic kidney disease (CKD), and transition from pre-existing CKD to end-stage renal disease. Data indicate a close interaction between the many cell types involved in the pathophysiology of ischemic AKI, which has critical implications for the treatment of this condition. Inflammation seems to be the common factor that links the various cell types involved in this process. In this Review, we describe the interactions between these cells and their response to injury following ischemia. We relate these events to patients who are at high risk of AKI, and highlight the characteristics that might predispose these patients to injury. We also discuss how therapy targeting specific cell types can minimize the initial and subsequent injury following ischemia, thereby limiting the extent of acute changes and, hopefully, long-term structural and functional alterations to the kidney.

Acute kidney injury in dogs and cats

The term acute kidney injury (AKI) has replaced the historical term acute renal failure for renal damage occurring over a short period of time (hours to days) because it is thought to better describe the pathophysiologic changes and duration of the different phases of injury. There are many potential causes of AKI in dogs and cats, and the prognosis has been shown to vary with the cause as well as with therapy. This article reviews current concepts of the pathophysiology, causes, clinical presentation, approach to diagnosis, and medical management of AKI in dogs and cats.

Association of clinic vascular access monitoring practices with clinical outcomes in hemodialysis patients

BACKGROUND

Early identification of access dysfunctions may be associated with improved patient outcomes. We examined whether patient outcomes were associated with vascular access monitoring practices in an incident dialysis cohort.

METHODS

We conducted a national prospective cohort study and analyzed 363 hemodialysis patients who had a first permanent vascular access (arteriovenous fistula or graft) by 6 months after the start of dialysis. Multivariate methods were used to examine associations between monitoring practices and 6-month Kt/V (reaching Kt/V >/=1.2), access intervention, access failure, and 2-year septicemia and all-cause hospitalization and mortality.

RESULTS

Patients who received monitoring weekly or more often (49%) were more likely to have an access intervention (adjusted RH = 1.40, 95% CI, 1.07-1.84) than those who received monitoring less frequently. Additionally, patients treated at clinics that reported performing regular access monitoring (80% of patients) were less likely to be hospitalized for septicemia (IRR = 0.35, 95% CI, 0.21-0.61) or for any cause (IRR = 0.77, 95% CI, 0.60-0.99). There were no statistically significant differences between patients exposed to different vascular access monitoring practices in access failure, achievement of Kt/V, or survival.

CONCLUSION

Frequent monitoring of dialysis access may initially increase the number of interventions but is beneficial to longer-term outcomes, including septicemia-related and all-cause hospitalization.