HMGB1 Is a Prognostic Factor for Mortality in Acute Kidney Injury Requiring Renal Replacement Therapy.

INSTRUCTION: High mobility group box 1 (HMGB1) is a pro-inflammatory cytokine that reportedly causes kidney injury and other organ damage in rodent acute kidney injury (AKI) models. However, it remains unclear whether HMGB1 is associated with clinical AKI and related outcomes. This study aimed to evaluate the association with HMGB1 and prognosis of AKI requiring continuous renal replacement therapy (CRRT). METHODS: AKI patients treated with CRRT in our intensive care unit were enrolled consecutively during 2013-2016. Plasma HMGB1 was measured on initiation. Classic initiation was defined as presenting at least one of the following conventional indications: hyperkalemia (K ≥6.5 mEq/L), severe acidosis (pH <7.15), uremia (UN >100 mg/dL), and diuretics-resistant pulmonary edema. Early initiation was defined as presenting no conventional indications. The primary outcome was defined as 90-day mortality. RESULTS: A total of 177 AKI patients were enrolled in this study. HMGB1 was significantly associated with the primary outcome (hazard ratio, 1.06; 95% CI, 1.04-1.08). When the patients were divided into two-by-two groups by the timing of CRRT initiation and the HMBG1 cutoff value obtained by receiver operating curve (ROC) analysis, the high HMGB1 group (>10 ng/mL) with classic initiation was significantly associated with the primary outcome compared with the others, even after adjusting for other factors including the nonrenal serial organ failure assessment (SOFA) score. CONCLUSION: HMGB1 was associated with 90-day mortality in AKI patients requiring CRRT. Notably, the highest mortality was observed in the high HMGB1 group with classic initiation. These findings suggest that CRRT should be considered for AKI patients with high HMGB1, regardless of the conventional indications.

Different Roles of Functional and Structural Renal Markers Measured at Discontinuation of Renal Replacement Therapy for Acute Kidney Injury.

INTRODUCTION: Severe acute kidney injury (AKI) requiring renal replacement therapy (RRT) has been associated with an unacceptably high mortality of 50% or more. Successful discontinuation of RRT is thought to be linked to better outcomes. Although functional and structural renal markers have been evaluated in AKI, little is known about their roles in predicting outcomes at the time of RRT discontinuation. METHODS: In this prospective single-center cohort study, we analyzed patients who received continuous RRT (CRRT) for AKI between August 2016 and March 2018 in the intensive care unit of the University of Tokyo Hospital (Tokyo, Japan). Clinical parameters and urine samples were obtained at CRRT discontinuation. Successful CRRT discontinuation was defined as neither resuming CRRT for 48 h nor receiving intermittent hemodialysis for 7 days from the CRRT termination. Major adverse kidney events (MAKEs) were defined as death, requirement for dialysis, or a decrease in the estimated glomerular filtration rate (eGFR) of more than 25% from the baseline at day 90. RESULTS: Of 73 patients, who received CRRT for AKI, 59 successfully discontinued CRRT and 14 could not. Kinetic eGFR, urine volume, urinary neutrophil gelatinase-associated lipocalin (NGAL), and urinary L-type fatty acid binding protein were predictive for CRRT discontinuation. Of these factors, urine volume had the highest area under the curve (AUC) 0.91 with 95% confidence interval [0.80-0.96] for successful CRRT discontinuation. For predicting MAKEs at day 90, the urinary NGAL showed the highest AUC 0.76 [0.62-0.86], whereas kinetic eGFR and urine volume failed to show statistical significance (AUC 0.49 [0.35-0.63] and AUC 0.59 [0.44-0.73], respectively). CONCLUSIONS: Our prospective study confirmed that urine volume, a functional renal marker, predicted successful discontinuation of RRT and that urinary NGAL, a structural renal marker, predicted long-term renal outcomes. These observations suggest that the functional and structural renal makers play different roles in predicting the outcomes of severe AKI requiring RRT.

Plasma xanthine oxidoreductase is associated with carotid atherosclerosis in stable kidney transplant recipients.

AIM: Xanthine oxidoreductase (XOR) is known as an enzyme related to purine metabolism, catalysing the oxidation of hypoxanthine to xanthine and of xanthine to uric acid. We investigated the relationship between plasma XOR activity in stable kidney transplantation (KT) recipients and carotid artery lesions. METHODS: A total of 42 KT patients visiting our outpatient clinic on regular basis were recruited. Associations between plasma XOR activity and the existence of plaque in the common carotid artery (CCA) or internal carotid artery (ICA) and maximum intima-medial thickness (IMT) of CCA (max-CIMT) > 0.9 mm were examined using univariate and multivariate analyses. RESULTS: At blood sampling, the mean and SD patient age was 52.7 ± 13.8 years old. Plasma XOR(pmol/h/ml) activity was significantly higher in patients with CCA/ICA plaque or max-CIMT >0.9 mm than those without. [23.9 (11.8, 38.3) vs. 8.29 (6.67, 17.5), p < .01, 23.9 (16.9, 71.2) vs. 9.16 (6.67, 28.2), p = .01] Univariate and multivariate logistic regression analyses revealed age and plasma XOR activity as independent predictors of CCA/ICA plaque or max-CIMT >0.9 mm. Receiver operator characteristic curve analyses revealed that the cutoff value of plasma XOR activity for the diagnosis of CCA/ICA plaque or CCA-IMT > 0.9 mm was 16.3 pmol/h/ml. CONCLUSION: Plasma XOR activity is associated independently with atherosclerotic changes in the carotid artery of stable post-KT patients.

Prognostic significance of concentric left ventricular hypertrophy at peritoneal dialysis initiation.

BACKGROUND: Concentric left ventricular hypertrophy (cLVH) is a common left ventricular geometric pattern in patients undergoing maintenance dialysis, including peritoneal dialysis (PD). The relationship between cLVH at PD initiation and the prognosis of patients remains unclear, however. This study aimed to investigate the impact of cLVH at PD initiation on patient survival and major adverse cardiovascular events (MACE). METHODS: The retrospective cohort study included 131 patients who underwent echocardiography during the PD initiation period. Based on echocardiographic measurements, cLVH was defined as a condition with increased LV mass index and increased relative wall thickness. The relationship between cLVH and the prognosis was assessed. RESULTS: Concentric LVH was identified in 29 patients (22%) at PD initiation, and patient survival, MACE-free survival and PD continuation were significantly reduced in the cLVH group compared with the non-cLVH group. In the Cox regression analysis, cLVH was demonstrated as an independent risk factor of mortality (HR [95%CI]: 3.32 [1.13-9.70]) for all patients. For patients over 65 years old, cLVH was significantly associated with mortality and MACE (HR [95%CI]: 3.51 [1.06-11.58] and 2.97 [1.26-7.01], respectively). Serum albumin at PD initiation was independently correlated with cLVH. CONCLUSIONS: In our study, cLVH at PD initiation was independently associated with survival in all patients and with both survival and MACE in elderly patients. Evaluation of LV geometry at PD initiation might therefore help identify high-risk patients. Further studies involving larger numbers of patients are needed to confirm the findings from this study and clarify whether treatment interventions for factors such as nutrition status could ameliorate cLVH and improve patient outcomes.

Association Between IV Thiamine and Mortality in Patients With Septic Shock: A Nationwide Observational Study.

OBJECTIVES: To examine the effect of thiamine administration on mortality in patients with septic shock requiring norepinephrine. DESIGN: Retrospective observational cohort study from July 2010 to March 2017. SETTING: More than 1,000 acute care hospitals covering approximately 90% of all tertiary care emergency hospitals in Japan. PATIENTS: Patients with septic shock requiring norepinephrine within 2 days of admission were retrospectively reviewed. INTERVENTIONS: Patients who received greater than or equal to 100 mg of thiamine within 2 days of admission were included in the thiamine group and those who did not were included in the control group. MEASUREMENTS AND MAIN RESULTS: We identified a total of 68,571 eligible patients, including 18,780 and 49,791 patients in the thiamine and control groups, respectively. In the thiamine group, 100 and 200 mg of thiamine per day were administered to 10,143 (54.0%) and 7,679 (40.9%) patients, respectively. The 28-day mortality were 19.2% (3,609/18,780) and 17.8% (8,845/49,791) in the thiamine and control groups, respectively. After adjusting for confounders by inverse probability of treatment weighting, no significant differences were observed between the two groups (risk difference, 0.2%; 95% CI, -0.5% to 0.9%). There were also no significant differences between the 100-mg thiamine group and the control group (risk difference, 0.6%; 95% CI, -0.3% to 1.4%) or between the 200-mg thiamine group and the control group (risk difference, -0.3%; 95% CI, -1.3% to 0.8%). CONCLUSIONS: The findings of this nationwide database-based observational study did not support an association between thiamine administration early after admission and the 28-day mortality in patients with septic shock.

Correlation between the Incidence and Attributable Mortality Fraction of Acute Kidney Injury: A Systematic Review.

INTRODUCTION: The incidence of acute kidney injury (AKI) as diagnosed by international standardized criteria as well as its mortality has undergone extreme variations. Although AKI is a significant worsening mortality factor, a higher prevalence may lead to better patient management, thereby lowering mortality. We investigated the correlation between AKI incidence and its associated mortality. METHODS: We conducted a systematic review of studies on AKI reporting its incidence and mortality. Literature searches were performed in -MEDLINE, EMBASE, and Cochrane Library, within the time frame of 2004-2018. Studies with small number of participants (<500 for adult cohorts, 50 for pediatric cohorts) were excluded. The correlation among AKI incidence, mortality, and AKI-attributable fraction of mortality was evaluated using a regression model. The trend test was used to analyze the effect of publication year and country gross domestic product (GDP). RESULTS: A total of 4,694 manuscripts were screened, from which 287 cohorts were eligible (adults: 203 cohorts comprising 7,076,459 patients; children: 84 comprising 69,677 patients). Within adult cohorts, AKI patients' mortality increased (R2 = 0.023, ß = 0.12, p = 0.03) but the attributable fraction of mortality decreased (R2 = 0.27, ß = -0.43, p < 0.001) with the increasing AKI incidence. Both more recent publications and higher GDP countries had a lower crude AKI patients' mortality, although AKI-attributable fraction did not decrease. CONCLUSIONS: Cohorts with high AKI incidence had a relatively low AKI-attributable mortality fraction, which suggests an advantage of more experienced AKI management. Further study is needed, however, to address the heterogeneity of included cohorts and to confirm the causality. (Registered in prospective register of systematic reviews database; CRD 42019129322.).

Expanded Indication for Recombinant Tissue Plasminogen Activator from 3 to 4.5 h after Onset of Stroke in Japan.

OBJECTIVE: We examined the impact of expansion of the time window (from 3 to 4.5 hours) in the labeled indication for recombinant tissue-plasminogen activator (rt-PA) in August 2012 on the use of rt-PA for patients with acute ischemic stroke (AIS) and the outcomes of patients treated with rt-PA. MATERIALS AND METHODS: Using a Japanese nationwide inpatient claims database, we identified patients with AIS who admitted to hospitals that consecutively participated in the database from 2010 to 2014. We defined the pre-expansion period as before August 2012 and the post-expansion period as after August 2012. We conducted an interrupted time-series analysis using patient-level data to examine the association between the expansion and use of rt-PA. We also assessed the association of the expansion with outcomes in patients treated with rt-PA. RESULTS: Among 257,778 patients with AIS, 4.5% patients (5,796/129,326) were treated with rt-PA in the pre-expansion period and 5.8% patients (7,483/128,452) were treated with rt-PA in the post-expansion period. The expansion was associated with greater use of rt-PA (adjusted odds ratio [aOR], 1.35; 95% confidence interval [CI], 1.24-1.48). Among patients treated with rt-PA, the expansion was associated with functional independence (modified Rankin scale of ≤2) at discharge (aOR, 1.26; 95% CI, 1.03-1.54), but not with in-hospital mortality (aOR, 0.92; 95% CI, 0.68-1.24). CONCLUSIONS: This study showed that expansion of the time window for rt-PA was associated with increased use of rt-PA in patients with AIS, while the functional outcome at discharge was improved after the expansion in patients treated with rt-PA.

Recombinant Thrombomodulin on Neutrophil Extracellular Traps in Murine Intestinal Ischemia-Reperfusion.

BACKGROUND: In multiple-organ dysfunction, an injury affecting one organ remotely impacts others, and the injured organs synergistically worsen outcomes. Recently, several mediators, including extracellular histones and neutrophil extracellular traps, were identified as contributors to distant organ damage. This study aimed to elucidate whether these mediators play a crucial role in remote organ damage induced by intestinal ischemia-reperfusion. This study also aimed to evaluate the protective effects of recombinant thrombomodulin, which has been reported to neutralize extracellular histones, on multiple-organ dysfunction after intestinal ischemia-reperfusion. METHODS: Intestinal ischemia was induced in male C57BL/6J mice via clamping of the superior mesenteric artery. Recombinant thrombomodulin (10 mg/kg) was administered intraperitoneally with the initiation of reperfusion. The mice were subjected to a survival analysis, histologic injury scoring, quantitative polymerase chain reaction analysis of tumor necrosis factor-α and keratinocyte-derived chemokine expression, Evans blue dye vascular permeability assay, and enzyme-linked immunosorbent assay analysis of histones in the jejunum, liver, lung, and kidney after 30- or 45-min ischemia. Neutrophil extracellular trap formation was evaluated by immunofluorescence staining. RESULTS: Recombinant thrombomodulin yielded statistically significant improvements in survival after 45-min ischemia (ischemia-reperfusion without vs. with 10 mg/kg recombinant thrombomodulin: 0% vs. 33%, n = 21 per group, P = 0.001). Recombinant thrombomodulin reduced the histologic injury score, expression of tumor necrosis factor-α and keratinocyte-derived chemokine, and extravasation of Evans blue dye, which were augmented by 30-min ischemia-reperfusion, in the liver, but not in the intestine. Accumulated histones and neutrophil extracellular traps were found in the livers and intestines of 30-min ischemia-reperfusion-injured mice. Recombinant thrombomodulin reduced these accumulations only in the liver. CONCLUSIONS: Recombinant thrombomodulin improved the survival of male mice with intestinal ischemia-reperfusion injury. These findings suggest that histone and neutrophil extracellular trap accumulation exacerbate remote liver injury after intestinal ischemia-reperfusion. Recombinant thrombomodulin may suppress these accumulations and attenuate liver injury.

Temporal change in characteristics and outcomes of acute kidney injury on renal replacement therapy in intensive care units: analysis of a nationwide administrative database in Japan, 2007-2016.

BACKGROUND: We aimed to examine recent trends in patient characteristics and mortality in patients with acute kidney injury (AKI) receiving renal replacement therapy (RRT), including continuous RRT (CRRT) and intermittent RRT (IRRT), in intensive care units (ICUs). METHODS: From the Diagnosis Procedure Combination database in Japan during 6 months (July-December) from 2007 to 2016, we identified patients with AKI who received RRT in ICUs. We restricted the study participants to those admitted to hospitals (in which both CRRT and IRRT were available) that participated in the Diagnosis Procedure Combination database for all 10 years. We examined the trends in patient characteristics and mortality overall, by RRT modality, and by main diagnosis category subgroup. Logistic regression was used to adjust for patient characteristics. RESULTS: We identified 51,758 patients starting RRT in 287 hospitals, including 39,471 (76.3%) and 12,287 (23.7%) patients starting CRRT and IRRT. The crude in-hospital mortality declined from 44.9 to 36.1% (P for trend < 0.001). Compared with 2007, the adjusted odds ratio (aOR) for in-hospital mortality was 0.66 (95% confidence interval (CI) 0.60-0.72) in 2016, and the decreasing trend was observed in both patients starting CRRT (aOR 0.67, 95% CI 0.61-0.75) and IRRT (0.58, 0.45-0.74), and in all subgroups except for coronary artery disease: sepsis aOR 0.68 (95% CI 0.57-0.81); cardiovascular surgery 0.58 (0.45-0.76); coronary artery disease 0.84 (0.60-1.19); non-coronary heart disease 0.78 (0.64-0.94); central nervous system disorders 0.42 (0.28-0.62); trauma 0.39 (0.21-0.72); and other 0.64 (0.50-0.82). CONCLUSIONS: This nationwide study confirmed a consistent decline in mortality among patients with AKI on RRT in ICUs. The adjusted mortality also declined during the study period; however, physiological variables were not measured in this study and it is possible that RRT may have been indicated for patients with less severe AKI in more recent years.

Kinetic estimated glomerular filtration rate as a predictor of successful continuous renal replacement therapy discontinuation.

AIM: No standardized criteria for continuous renal replacement therapy (CRRT) discontinuation have been established. Kinetic estimated glomerular filtration rate (eGFR) is a newly developed estimation method based on dynamic changes of serum creatinine expected to reflect the true GFR. This study aimed to evaluate the predictive role of kinetic eGFR for CRRT discontinuation. METHODS: A retrospective single-centre cohort study was conducted. Acute kidney injury (AKI) patients who received CRRT between May 2015 and April 2016 were enrolled. Successful CRRT discontinuation was defined as neither resuming CRRT for the next 48 h nor receiving intermittent haemodialysis 7 days from the CRRT discontinuation. Clinical factors associated with CRRT discontinuation were evaluated by receiver operating characteristic (ROC) curve analysis. RESULTS: Of 52 AKI patients treated with CRRT, 38 could discontinue CRRT while 14 could not. Urine volume, regular and kinetic eGFR of days 0 (day of CRRT discontinuation) and 1 were all good predictive parameters (area under the ROC curve (AUC) > 0.7). Kinetic eGFR of day 1 showed the AUC of 0.87 [95% confidence interval 0.73-0.94]). Combining kinetic eGFR of day 1 and urine volume of day 0 gave a high AUC of 0.93 [95% confidence interval 0.82-0.97]. The combination was significantly greater than urine volume of day 0 (P = 0.008). CONCLUSION: Kinetic eGFR combined with urine volume was a better predictor for CRRT discontinuation. Evaluation of kinetic eGFR utility in other clinical settings will be necessary.

Complete solubilization of cartilage using the heat-stable protease thermolysin for comprehensive GAG analysis.

Articular cartilage comprises collagens, proteoglycans, and glycosaminoglycans (GAGs) together with water, in hyaline matrixes. Articular cartilage is resistant to proteolytic solubilization for comprehensive GAG analyses partly because of assemblies of collagen fibers with thermolabile hydrogen bonds. In this study, we used the heat-stable protease thermolysin to digest collagen in solid articular cartilage at 70 °C and compared the efficiencies of collagen digestion and GAG extraction to those with collagenase digestion at 50 °C. Overnight digestion with thermolysin completely solubilized cartilage, whereas collagenase with >10-times higher proteolytic activity digested <20% of collagen. Following thermolysin treatments, almost all GAGs were extracted from the cartilage, whereas only 56% of GAGs were extracted after collagenase digestion. Disaccharide analyses of extracted GAG chains revealed >98% extraction efficiencies of several GAG classes from thermolysin-treated cartilage, compared with <60% extraction efficiencies using collagenase, depending on GAG classes. These results indicate that thermolysin allows complete GAG extraction from solid articular cartilage and that complete solubilization is required for accurate and reproducible analyses of cartilage GAGs. Hence, thermolysin offers a tool for complete solubilization of cartilage prior to comprehensive GAGomic analysis, and is likely applicable to other collagen-rich tissues such as ligaments, skin, and blood vessels.

Prediction of immunoglobulin M reduction via therapeutic dose of simple plasma exchange and double filtration plasmapheresis using membrane separation in patients with hyperviscosity syndrome caused by Waldenstrom macroglobulinemia.

BACKGROUND: Plasma exchange (PE) and double filtration plasmapheresis (DFPP) are known as effective treatment options for hyperviscosity syndrome (HVS) caused by Waldenstrom macroglobulinemia. Nonetheless, few data are available for the relation between the prescribed dose of apheresis and the reduction rate of target molecule immunoglobulin M (IgM), especially in the modality using membrane separation. OBJECTIVES: This study was conducted to establish a model to predict the IgM reduction rate by the dose of simple PE and DFPP using membrane separation in patients with HVS and to compare the consumption of albumin between PE and DFPP. METHODS: We retrospectively analyzed data of total 17 sessions of PE and DFPP with various therapeutic doses performed for five patients at our institution. We used linear regression analysis to examine the relation between the ratio of processed plasma volume to estimated circulating plasma volume (X) and the reduction rate of IgM (Y). RESULTS: Regression analysis revealed that Y is expressed by X as the following equation: Y = 0.35X + 0.095. The total usage of albumin for replacement fluid was lower in DFPP than in PE (21.5 g vs 150 g per session), although the treatment efficacies of both modalities are similar. CONCLUSION: The dose of PE and DFPP using membrane separation can predict IgM reduction rate in the HVS patients. Predicted IgM reduction rates based on our model are lower than those calculated using a known theoretical model. In terms of the amount of use of albumin, DFPP is preferred to PE.

Interstitial renal fibrosis due to multiple cisplatin treatments is ameliorated by semicarbazide-sensitive amine oxidase inhibition.

Elucidation of acute kidney diseases and disorders (AKD), including acute kidney injury (AKI), is important to prevent their progression to chronic kidney disease. Current animal AKI models are often too severe for use in evaluating human AKI. Therefore, new animal models of mild kidney injury are needed. Here a new clinically relevant animal model using multiple low doses of cisplatin (CP) was used to evaluate AKD. When 10 mg/kg CP was administered intraperitoneally once weekly for three times to L-type fatty acid-binding protein (L-FABP) transgenic mice, moderate renal interstitial fibrosis and tubule dilatation occurred, accompanied by brush-border loss. Urinary L-FABP, a promising biomarker of AKI, changed more drastically than blood urea nitrogen or creatinine. Preventing fibrosis in organs was also studied. Oral administration of a recently reported selective semicarbazide-sensitive amine oxidase inhibitor, PXS-4728A, for 1 week attenuated kidney injury and interstitial fibrosis compared with vehicle. Inhibition of renal lipid accumulation in semicarbazide-sensitive amine oxidase inhibitor-treated mice, together with reduced oxidative stress and L-FABP suppression in proximal tubules, suggested an antifibrotic effect of semicarbazide-sensitive amine oxidase inhibition in this CP-AKD model, a representative onco-nephrology. Thus, semicarbazide-sensitive amine oxidase inhibitors may be promising candidates for the prevention of chronic kidney disease in patients using CP to treat malignancy.

Erythropoietin concentration in acute kidney injury is associated with insulin-like growth factor-binding protein-1.

AIM: Erythropoietin (EPO) production is stimulated by hypoxia in the kidney. Ischaemic injury plays a crucial role in the pathogenesis of acute kidney injury (AKI). However, EPO concentrations in critically ill patients complicated with AKI have not been evaluated sufficiently. This study was conducted to clarify the factors associated with plasma EPO concentrations in AKI. METHODS: This study prospectively enrolled 98 critically ill adult patients treated at the adult mixed ICU. Plasma EPO, insulin-like growth factor-binding protein-1 (IGFBP-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin-6 (IL-6) and urinary N-acetyl-ß-D-glucosaminidase (NAG) were measured on ICU admission. RESULTS: Acute kidney injury occurred in 42 (42.9%) patients. Significantly higher plasma EPO in the AKI group was detected than in the non-AKI group (16.13 (9.87-28.47) mIU/mL versus 27.81 (10.16-106.02) mIU/mL, P < 0.05). Plasma IGFBP-1 in the AKI group was also significantly higher than in the non-AKI group (19 208 (8820-50 780) pg/mL versus 63 199 (25 289-147 489) pg/mL, P < 0.05). Plasma EPO concentration was negatively correlated with haemoglobin in the non-AKI group with statistical significance, but not in the AKI group. Multiple logistic regression analysis revealed that plasma EPO in the AKI group was associated significantly with plasma IGFBP-1 and complication of diabetes mellitus, but not the haemoglobin concentration, partial pressure of arterial oxygen (PaO2 ), and IL-6. CONCLUSIONS: Not low arterial oxygen tension, haemoglobin concentration, and inflammation evaluated by IL-6 but plasma IGFBP-1 was significantly associated with plasma EPO concentration in AKI, suggesting an unknown mechanism related to systemic stress conditions for EPO regulation in AKI.

Regulation of Mitochondrial Dynamics by Dynamin-Related Protein-1 in Acute Cardiorenal Syndrome.

Experimental evidence has clarified distant organ dysfunctions induced by AKI. Crosstalk between the kidney and heart, which has been recognized recently as cardiorenal syndrome, appears to have an important role in clinical settings, but the mechanisms by which AKI causes cardiac injury remain poorly understood. Both the kidney and heart are highly energy-demanding organs that are rich in mitochondria. Therefore, we investigated the role of mitochondrial dynamics in kidney-heart organ crosstalk. Renal ischemia reperfusion (IR) injury was induced by bilateral renal artery clamping for 30 min in 8-week-old male C57BL/6 mice. Electron microscopy showed a significant increase of mitochondrial fragmentation in the heart at 24 h. Cardiomyocyte apoptosis and cardiac dysfunction, evaluated by echocardiography, were observed at 72 h. Among the mitochondrial dynamics regulating molecules, dynamin-related protein 1 (Drp1), which regulates fission, and mitofusin 1, mitofusin 2, and optic atrophy 1, which regulate fusion, only Drp1 was increased in the mitochondrial fraction of the heart. A Drp1 inhibitor, mdivi-1, administered before IR decreased mitochondrial fragmentation and cardiomyocyte apoptosis significantly and improved cardiac dysfunction induced by renal IR. This study showed that renal IR injury induced fragmentation of mitochondria in a fission-dominant manner with Drp1 activation and subsequent cardiomyocyte apoptosis in the heart. Furthermore, cardiac dysfunction induced by renal IR was improved by Drp1 inhibition. These data suggest that mitochondrial fragmentation by fission machinery may be a new therapeutic target in cardiac dysfunction induced by AKI.

Preserved Na/HCO3 cotransporter sensitivity to insulin may promote hypertension in metabolic syndrome.

Hyperinsulinemia can contribute to hypertension through effects on sodium transport. To test whether the stimulatory effect of insulin on renal proximal tubule sodium transport is preserved in insulin resistance, we compared the effects of insulin on abdominal adipocytes and proximal tubules in rats and humans. Insulin markedly stimulated the sodium-bicarbonate cotransporter (NBCe1) activity in isolated proximal tubules through the phosphoinositide 3-kinase (PI3-K) pathway. Gene silencing in rats showed that while insulin receptor substrate (IRS)1 mediates the insulin effect on glucose uptake into adipocytes, IRS2 mediates the insulin effect on proximal tubule transport. The stimulatory effect of insulin on glucose uptake into adipocytes was severely reduced, but its stimulatory effect on NBCe1 activity was completely preserved in insulin-resistant Otsuka Long-Evans Tokushima Fatty (OLETF) rats and patients with insulin resistance. Despite widespread reduction of IRS1 and IRS2 expression in insulin-sensitive tissues, IRS2 expression in the kidney cortex was exceptionally preserved in both OLETF rats and patients with insulin resistance. Unlike liver, acute insulin injection failed to change the expression levels of IRS2 and sterol regulatory element-binding protein 1 in rat kidney cortex, indicating that regulatory mechanisms of IRS2 expression are distinct in liver and kidney. Thus, preserved stimulation of proximal tubule transport through the insulin/IRS2/PI3-K pathway may play an important role in the pathogenesis of hypertension associated with metabolic syndrome.

Phospholipase A2 receptor positive membranous nephropathy long after living donor kidney transplantation between identical twins.

Although membranous nephropathy (MN) is a commonly observed cause of post-transplant glomerulonephritis, distinguishing de novo from recurrent MN in kidney allograft is often difficult. Phospholipase A2 receptor (PLA2R) staining is useful for diagnosing recurrent MN in allografts similarly to idiopathic MN in native kidney. No specific treatment strategy has been established for MN, especially when accompanied with HCV infection in kidney transplant recipients. This report describes a 66-year-old man who was diagnosed as having PLA2R positive membranous nephropathy accompanied with already-known IgA nephropathy and HCV infection 26 years after kidney transplantation conducted between identical twins. PLA2R was detected along capillary loops, implying that this patient is affected by the same pathogenic mechanism as idiopathic MN, not secondary MN associated with other disorders such as HCV infection. The patient successfully achieved clinical remission after steroid therapy.

The high-mobility group protein B1-Toll-like receptor 4 pathway contributes to the acute lung injury induced by bilateral nephrectomy.

Acute lung injury and acute kidney injury are severe complications in critically ill patients and synergistically increase mortality in intensive care units. Organ cross-talk between the kidney and the lung has been implicated recently as amplifying injury in each organ. Here we sought to identify a possible mechanism of acute kidney injury-induced acute lung injury using a mouse bilateral nephrectomy model. Toll-like receptor 4 (TLR4)-mutant C3H/HeJ mice were more resistant to lung injury including neutrophil infiltration, increased neutrophil elastase activity, and vascular permeability caused by bilateral nephrectomy compared with TLR4-wild-type C3H/HeN mice 6 h after surgery. High-mobility group protein B1 (HMGB1) is one agonist for TLR4. Its blood concentrations were increased significantly by bilateral nephrectomy. Blockade of HMGB1 by neutralizing antibody reduced neutrophil infiltration in TLR4-wild-type C3H/HeN but not in TLR4-mutant C3H/HeJ mice. However, HMGB1 blockade in a renal ischemia reperfusion model reduced pulmonary neutrophil infiltration independent from TLR4. Thus, an enhanced HMGB1-TLR4 pathway contributes to lung injury induced by bilateral nephrectomy and the other HMGB1-dependent pathway exists in pulmonary neutrophil infiltration caused by renal ischemia reperfusion. Targeting the HMGB1-TLR4 pathway might enable development of a new therapeutic strategy to improve the outcomes of severely ill patients with both acute lung and acute kidney injury.

Perioperative plasma neutrophil gelatinase-associated lipocalin measurement in patients who undergo left ventricular assist device implantation surgery.

BACKGROUND: Perioperative complication of end-organ injury including acute kidney injury (AKI) is a frequent and severe problem for patients undergoing left ventricular assist device (LVAD) implantation. This study evaluated an emerging AKI biomarker, plasma neutrophil gelatinase-associated lipocalin (NGAL), in a LVAD implantation cohort. METHODS AND RESULTS: Of 31 LVAD implantation patients enrolled to this study, 17 (55%) patients were diagnosed as having AKI. Six AKI patients showed severe AKI requiring renal replacement therapy (RRT). Plasma NGAL values in the AKI-with-RRT group (n=6) were significantly higher than that in other patients, although the AKI-without-RRT (n=11) group showed a similar level of plasma NGAL to that of the non-AKI group (n=14). Multiple logistic regression analysis revealed that plasma NGAL measured at pre-operation and central venous pressure at pre-operation and 12 h after surgery independently discriminated against postoperative RRT requirement. In the AKI-with-RRT group, plasma NGAL decreased before termination of RRT in 4 patients who eventually showed renal recovery, although no decline of plasma NGAL was observed in 2 patients who showed no recovery of renal function. Removal of blood NGAL by continuous hemodiafiltration was shown to be 70-75% lower than that of creatinine. CONCLUSIONS: Measurement of perioperative plasma NGAL is useful for predicting severe AKI requiring RRT and renal recovery in patients who have had LVAD implantation surgery. Further investigation is necessary to confirm these findings because this study examined a low number of patients.

Evaluation of urinary tissue inhibitor of metalloproteinase-2 in acute kidney injury: a prospective observational study.

INTRODUCTION: Tissue inhibitor of metalloproteinase-2 (TIMP-2) is an emerging acute kidney injury (AKI) biomarker. We evaluated the performance of urinary TIMP-2 in an adult mixed ICU by comparison with other biomarkers that reflect several different pathways of AKI. METHODS: In this study, we prospectively enrolled 98 adult critically ill patients who had been admitted to the adult mixed ICU. Urinary TIMP-2 and N-acetyl-ß-D-glucosaminidase (NAG) and plasma neutrophil gelatinase-associated lipocalin (NGAL), interleukin-6 (IL-6) and erythropoietin (EPO) were measured on ICU admission. We evaluated these biomarkers' capability of detecting AKI and its severity as determined by using the Kidney Disease Improving Global Outcomes serum creatinine criteria, as well as its capacity to predict in-hospital mortality. The impact of sepsis, the leading cause of AKI in ICUs, was also evaluated. RESULTS: We found AKI in 42 patients (42.9%). All biomarkers were significantly higher in AKI than in non-AKI. In total, 27 patients (27.6%) developed severe AKI. Urinary TIMP-2 was able to distinguish severe AKI from non-severe AKI with an area under the receiver operating characteristic curve (AUC-ROC) of 0.80 (95% confidence interval, 0.66 to 0.90). A total of 41 cases (41.8%) were complicated with sepsis. Although plasma NGAL and IL-6 were increased by sepsis, urinary TIMP-2 and NAG were increased not by sepsis, but by the presence of severe AKI. Plasma EPO was increased only by septic AKI. In-hospital mortality was 15.3% in this cohort. Urinary TIMP-2 and NAG, and plasma NGAL, were significantly higher in non-survivors than in survivors, although plasma IL-6 and EPO were not. Among the biomarkers, only urinary TIMP-2 was able to predict in-hospital mortality significantly better than serum creatinine. CONCLUSION: Urinary TIMP-2 can detect severe AKI with performance equivalent to plasma NGAL and urinary NAG, with an AUC-ROC value higher than 0.80. Furthermore, urinary TIMP-2 was associated with mortality. Sepsis appeared to have only a limited impact on urinary TIMP-2, in contrast to plasma NGAL.