NFAT inhibitor 11R-VIVIT ameliorates mouse renal fibrosis after ischemia-reperfusion-induced acute kidney injury.

Acute kidney injury (AKI) with maladaptive tubular repair leads to renal fibrosis and progresses to chronic kidney disease (CKD). At present, there is no curative drug to interrupt AKI-to-CKD progression. The nuclear factor of the activated T cell (NFAT) family was initially identified as a transcription factor expressed in most immune cells and involved in the transcription of cytokine genes and other genes critical for the immune response. NFAT2 is also expressed in renal tubular epithelial cells (RTECs) and podocytes and plays an important regulatory role in the kidney. In this study, we investigated the renoprotective effect of 11R-VIVIT, a peptide inhibitor of NFAT, on renal fibrosis in the AKI-to-CKD transition and the underlying mechanisms. We first examined human renal biopsy tissues and found that the expression of NFAT2 was significantly increased in RTECs in patients with severe renal fibrosis. We then established a mouse model of AKI-to-CKD transition using bilateral ischemia-reperfusion injury (Bi-IRI). The mice were treated with 11R-VIVIT (5 mg/kg, i.p.) on Days 1, 3, 10, 17 and 24 after Bi-IRI. We showed that the expression of NFAT2 was markedly increased in RTECs in the AKI-to-CKD transition. 11R-VIVIT administration significantly inhibited the nuclear translocation of NFAT2 in RTECs, decreased the levels of serum creatinine and blood urea nitrogen, and attenuated renal tubulointerstitial fibrosis but had no toxic side effects on the heart and liver. In addition, we showed that 11R-VIVIT administration alleviated RTEC apoptosis after Bi-IRI. Consistently, preapplication of 11R-VIVIT (100 nM) and transfection with NFAT2-targeted siRNA markedly suppressed TGFß-induced HK-2 cell apoptosis in vitro. In conclusion, 11R-VIVIT administration inhibits IRI-induced NFAT2 activation and prevents AKI-to-CKD progression. Inhibiting NFAT2 may be a promising new therapeutic strategy for preventing renal fibrosis after IR-AKI.

Hospital-Acquired Acute Kidney Injury in Older Patients: Clinical Characteristics and Drug Analysis.

BACKGROUND: Information on older patients with hospital-acquired acute kidney injury (HA-AKI) and use of drugs is limited. AIM: This study aimed to assess the clinical characteristics, drug uses, and in-hospital outcomes of hospitalized older patients with HA-AKI. METHODS: Patients aged ≥65 years who were hospitalized in medical wards were retrospectively analyzed. The study patients were divided into the HA-AKI and non-AKI groups based on the changes in serum creatinine. Disease incidence, risk factors, drug uses, and in-hospital outcomes were compared between the groups. RESULTS: Of 26,710 older patients in medical wards, 4,491 (16.8%) developed HA-AKI. Older patients with HA-AKI had higher rates of multiple comorbidities and Charlson Comorbidity Index score than those without AKI (p < 0.001). In the HA-AKI group, the proportion of patients with prior use of drugs with possible nephrotoxicity was higher than that of patients with prior use of drugs with identified nephrotoxicity (p < 0.05). The proportions of patients with critical illness, use of nephrotoxic drugs, and the requirements of intensive care unit treatment, cardiopulmonary resuscitation, and dialysis as well as in-hospital mortality and hospitalization duration and costs were higher in the HA-AKI than the non-AKI group; these increased with HA-AKI severity (all p for trend <0.001). With the increase in the number of patients with continued use of drugs with possible nephrotoxicity after HA-AKI, the clinical outcomes showed a tendency to worsen (p < 0.001). Moreover, HA-AKI incidence (adjusted odds ratio [OR], 10.26; 95% confidence interval (CI), 8.27-12.74; p < 0.001), and nephrotoxic drugs exposure (adjusted OR, 1.76; 95% CI, 1.63-1.91; p < 0.001) had an association with an increased in-hospital mortality risk. CONCLUSION: AKI incidence was high among hospitalized older patients. Older patients with HA-AKI had worse in-hospital outcomes and higher resource utilization. Nephrotoxic drug exposure and HA-AKI incidence were associated with an increased in-hospital mortality risk.

The second coordination sphere of FIH controls hydroxylation.

The factor inhibiting HIF (FIH) is a proximate oxygen sensor for human cells, hydroxylating Asn(803) within the α-subunit of the hypoxia inducible factor (HIF). FIH is an α-ketoglutatrate (αKG)-dependent, non-heme Fe(II) dioxygenase, in which Fe(II) is coordinated by a (His(2)Asp) facial triad, αKG, and H(2)O. Hydrogen bonding among the facial triad, the HIF-Asn(803) side chain, and various second-sphere residues suggests a functional role for the second coordination sphere in tuning the chemistry of the Fe(II) center. Point mutants of FIH were prepared to test the functional role of the αKG-centered (Asn(205) and Asn(294)) or HIF-Asn(803)-centered (Arg(238) and Gln(239)) second-sphere residues. The second sphere was tested for local effects on priming Fe(II) to react with O(2), oxidative decarboxylation, and substrate positioning. Steady-sate kinetics were used to test for overall catalytic effects; autohydroxylation rates were used to test for priming and positioning, and electronic spectroscopy was used to assess the primary coordination sphere and the electrophilicity of αKG. Asn(205) → Ala and Asn(294) → Ala mutants exhibited diminished rates of steady-state turnover, while minimally affecting autohydroxylation, consistent with impaired oxidative decarboxylation. Blue-shifted metal to ligand charge transfer transitions for (Fe+αKG)FIH indicated that these point mutations destabilized the π* orbitals of αKG, further supporting a slowed rate of oxidative decarboxylation. The Arg(238) → Met mutant exhibited steady-state rates too low to measure and diminished product yields, suggesting impaired substrate positioning or priming; the Arg(238) → Met mutant was capable of O(2) activation for the autohydroxylation reaction. The Gln(239) → Asn mutant exhibited significantly slowed steady-state kinetics and diminished product yields, suggesting impaired substrate positioning or priming. As HIF binding to the Gln(239) → Asn mutant stimulated autohydroxylation, it is more likely that this point mutant simply mispositions the HIF-Asn(803) side chain. This work combines kinetics and spectroscopy to show that these second-sphere hydrogen bonds play roles in promoting oxidative decarboxylation, priming Fe(II) to bind O(2), and positioning HIF-Asn(803).

Effect of blood sample type on the measurement of advanced oxidation protein products as a biomarker of inflammation and oxidative stress in hemodialysis patients.

Advanced oxidation protein products (AOPP) is widely used as a uremic biomarker, especially for cardiovascular disease. However, it has not been determined whether it is better to measure AOPP in plasma or serum. In this cross-sectional study, which included 102 patients undergoing maintenance hemodialysis, fibrinogen-free serum and defibrinated plasma samples were prepared. AOPP levels from fibrinogen-free samples displayed a stronger correlation with myeloperoxidase activity and levels of C-reactive protein, interleukin-6 and tumor necrosis factor-alpha, as well as prevalent cardiovascular disease, than AOPP levels obtained from plasma samples. These results demonstrated that fibrinogen interferes with the measurement of AOPP.

[The sensitivity and accuracy of RIFLE and AKIN criteria for acute kidney injury diagnosis in intensive care unit patients].

OBJECTIVE: To evaluate the sensitivity/accuracy of 2 different acute kidney injury (AKI) diagnosis/classification criteria, the RIFLE (risk, injury, failure, loss of kidney function, end-stage kidney disease) and the acute kidney injury network (AKIN), for patients in intensive care unit (ICU). METHODS: Clinical data were collected from all adult patients admitted to the Department of Intensive Medicine in Guangdong General Hospital between October 2009 and July 2010, and AKI cases were identified/classified using RIFLE and AKIN criteria separately, for statistical evaluation of their diagnostic sensitivity, and accuracy in hospital mortality prediction. RESULTS: In all 524 patients evaluated, AKI were identified by RIFLE criteria in 95 of them, while by AKIN, 135. The AKI incidence by RIFLE (18.1%), and AKIN (25.8%) were significantly different (P < 0.05). Meanwhile, AKI incidence was found independent from the mortality, either by RIFLE or AKIN (both P < 0.001). In all patients, the area under the receiver operator characteristic curve (ROC curve), the index for hospital mortality prediction, was 0.7293 for RIFLE [with 95% confidence interval (95%CI) ranging from 0.6005 to 0.8581, P < 0.001], and for AKIN, 0.7777 (95%CI: 0.6664 - 0.8890, P < 0.001). No significant difference was found between the total hospital mortality by the two criteria (37.9% vs. 34.1%, P > 0.05). CONCLUSION: Although AKIN criteria has higher sensitivity in AKI diagnosis, it is not different from the RIFLE criteria in predicting hospital mortality in critically ill patients.

How to carry out monthly blood flow surveillance of fistula in large-scale hemodialysis units: A cross-sectional study.

BACKGROUND: The important effect of regular blood flow surveillance on arteriovenous fistula maintenance is emphasized. The ultrasonic dilution technique for blood flow surveillance can be performed during hemodialysis, but there are some limitations. Blood flow is traditionally measured by duplex Doppler ultrasound during the nondialysis period. However, the surveillance workload for arteriovenous fistula has increased with the rapid increase in the hemodialysis population size. Efficient methods for blood flow surveillance during hemodialysis are needed. METHODS: Eighty-four hemodialysis patients with a forearm radiocephalic arteriovenous fistula were enrolled in this cross-sectional study. Each received blood flow measurements using ultrasonic dilution technique and duplex Doppler ultrasound during hemodialysis. Duplex Doppler ultrasound measurements included the blood flow of the brachial artery and radial artery. The correlations between these variables were analyzed. RESULTS: The correlation coefficients (r) between flow measured by ultrasonic dilution technique and brachial artery flow measured by duplex Doppler ultrasound, between flow measured by ultrasonic dilution technique and radial artery flow measured by duplex Doppler ultrasound, and between brachial artery flow and radial artery flow measured by duplex Doppler ultrasound were 0.724, 0.784, and 0.749, respectively (all p < 0.001). CONCLUSION: Blood flow measured by ultrasonic dilution technique was positively correlated with blood flow measured by duplex Doppler ultrasound during hemodialysis, suggesting that duplex Doppler ultrasound can be used to monitor the trends in the blood flow of the brachial artery and radial artery for timely intervention to improve patency during hemodialysis.

Combination of urinary kidney injury molecule-1 and interleukin-18 as early biomarker for the diagnosis and progressive assessment of acute kidney injury following cardiopulmonary bypass surgery: a prospective nested case-control study.

The aim of this nested case-control study was to assess the combined use of urinary kidney injury molecule (KIM)-1 and interleukin (IL)-18 for acute kidney injury (AKI) after cardiopulmonary bypass surgery (CPB). From a cohort of 122 subjects who underwent CPB, serial urinary KIM-1 and IL-18 concentrations were determined in 30 AKI and 92 non-AKI patients. An increased level of urinary KIM-1 was associated with the occurrence of AKI, whereas an increased level of IL-18 was related to progressive AKI. The combination of these two biomarkers facilitates the early diagnosis and assessment of the likely progression of AKI after CPB.

Can the fistula arm be used to lift heavy items? Six-pound dumbbells versus handgrip exercise in a 6-month follow-up secondary analysis of a randomized controlled trial.

INTRODUCTION: Patients with arteriovenous fistulas are advised to avoid carrying heavy objects draped over the fistula arm. Awareness gradually leads to overprotection and a reduction in the use of the fistula arm. However, restricting motion in the fistula arm leads to decreased quality of life and diminished muscle strength. The current safety recommendations regarding lifting heavy items with the fistula arm are primarily based on experience. Few studies have provided evidence clarifying the scope of safe activity and the influence of load bearing on the continued patency of arteriovenous fistulas. METHODS: This prospective observation was based on a long-term follow-up study in which 86 hemodialysis recipients with arteriovenous fistulas were randomized into either a dumbbell group or a handgrip group. The dumbbell group exercised with 6-lb dumbbells, while the handgrip group squeezed rubber balls. Postintervention primary patency and adverse events at the 6-month follow-up were analyzed. RESULTS: No significant difference in postintervention primary patency was observed between the dumbbell group and the handgrip group at 6 months (97.4% vs 95.0%). There were two participants with high-flow fistulas in the dumbbell group and three in the handgrip group, with no significant difference between the two groups (5.3% vs 7.5%). In both groups, there were no other adverse events reported regarding cardiac failure, aneurysm, puncture site hematoma, or hemorrhage. CONCLUSION: Hemodialysis patients can safely use their fistula arm to lift objects weighing less than 6 lb, which encourages increased motion and helps preserve the functionality of the fistula arm.

Auto-hydroxylation of FIH-1: an Fe(ii), alpha-ketoglutarate-dependent human hypoxia sensor.

HIF-asparaginyl hydroxylase (FIH-1) normally couples O(2)-activation to hydroxylation of Asn(803) on the alpha-subunit of the hypoxia-inducible factor (HIFalpha), a key step in pO(2) sensing; in the absence of HIFalpha, O(2)-activation becomes uncoupled, leading to self-hydroxylation at Trp(296) and a purple Fe(iii)-O-Trp chromophore-this alternative reactivity may affect human hypoxia sensing.

[Association of heart valve calcification with cardiovascular outcomes in patients on maintenance hemodialysis].

OBJECTIVE: To investigate the impact of heart valve calcification (HVC) on cardiovascular outcomes in patients on maintenance hemodialysis (MHD). METHODS: We enrolled 302 Chinese patients on MHD between 2009 and 2011 including 99 with HVC identified by echocardiography screening. All the patients were followed up for 2 years and survival analysis was performed with all-cause mortality, cardiovascular mortality and new onset cardiovascular events as the endpoints. Cox regression analysis was used for analyzing the impact of heart valve calcification on the cardiovascular outcomes of the patients. RESULTS: The mean age of the total patients was 58.2∓15.0 years when receiving the initial MHD, and 53.6% were male patients. The overall mortality, cardiovascular mortality and new on-set cardiovascular events in HVC and non-HVC groups were 30.3% vs 16.3%, 22.2% vs 6.9%, and 48.5% vs 25.6%, respectively (P<0.05). Kaplan-Meier survival analysis showed a significant difference in all-cause mortality (P=0.006), cardiovascular mortality (P<0.001) and new-onset cardiovascular events (P<0.001) between HVC and non-HVC groups. After adjustment, Cox regression analysis identified HVC as a risk factor for increased all-cause mortality (HR=1.88; 95%CI: 1.11-3.19), cardiovascular mortality (HR=3.47, 95%CI: 1.76-6.84) and cardiovascular events (HR=1.64, 95% CI: 1.09-2.47). CONCLUSIONS: HVC is an independent risk factor for increased cardiovascular mortality and new cardiovascular events in patients on MHD.

[Effect of early postoperative use of ACEI/ARB or diuretics on the incidence of acute kidney injury after cardiac surgery in elderly patients].

OBJECTIVE: To explore the influence of early postoperative use of angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB) or diuretics on acute kidney injury (AKI) after cardiac surgery in elderly patients. METHODS: Data from elderly patients (age≥60 years old) who underwent cardiac surgery with extracorporeal circulation in Guangdong General Hospital between January 2007 and December 2010 were analyzed in this retrospective research. The primary endpoint was AKI as diagnosed according to the serum creatinine criteria of RIFLE (risk, injury, failure, loss, end stage renal disease). The baseline serum creatinine was defined as the latest serum creatinine level before cardiac surgery. Multivariate analysis by logistic regression was used to obtain the independent risk factors for AKI. RESULTS: Among 618 elderly patients, 76 (12.3%) patients received ACEI/ARB during early postoperative period, 491 (79.4%) patients were given diuretics during early postoperative period, and postoperative AKI occurred in 394 (63.8%) patients. The incidence of AKI was 46.1% in patients who received early postoperative ACEI/ARB, and 66.2% in patients who did not (P<0.001). Patients who received diuretics postoperatively were less likely to suffer from AKI compared with patients who did not (57.0% vs. 89.8%, P<0.001). After adjustment of other potential factors of postoperative AKI, logistic regression analysis showed that early postoperative use of ACEI/ARB [odds ratio (OR)=0.131, 95% confidence interval (95%CI) 0.033-0.517, P=0.004], and early postoperative use of diuretics (OR=0.149, 95%CI 0.076-0.291, P<0.001) independently predicted the occurrence of AKI. CONCLUSIONS: Early postoperative use of ACEI/ARB or diuretics is associated with a lower incidence of AKI after cardiac surgery with extracorporeal circulation in elderly patients.

Coordination changes and auto-hydroxylation of FIH-1: uncoupled O2-activation in a human hypoxia sensor.

Hypoxia sensing is the generic term for pO2-sensing in humans and other higher organisms. These cellular responses to pO2 are largely controlled by enzymes that belong to the Fe(II) alpha-ketoglutarate (alphaKG) dependent dioxygenase superfamily, including the human enzyme called the factor inhibiting HIF (FIH-1), which couples O2-activation to the hydroxylation of the hypoxia inducible factor alpha (HIFalpha). Uncoupled O2-activation by human FIH-1 was studied by exposing the resting form of FIH-1 (alphaKG + Fe)FIH-1, to air in the absence of HIFalpha. Uncoupling lead to two distinct enzyme oxidations, one a purple chromophore (lambda(max) = 583 nm) arising from enzyme auto-hydroxylation of Trp296, forming an Fe(III)-O-Trp296 chromophore [Y.-H. Chen, L.M. Comeaux, S.J. Eyles, M.J. Knapp, Chem. Commun. (2008), doi:10.1039/B809099H]; the other a yellow chromophore due to Fe(III) in the active site, which under some conditions also contained variable levels of an oxygenated surface residue (oxo)Met275. The kinetics of purple FIH-1 formation were independent of Fe(II) and alphaKG concentrations, however, product yield was saturable with increasing [alphaKG] and required excess Fe(II). Yellow FIH-1 was formed from (succinate+Fe)FIH-1, or by glycerol addition to (alphaKG+Fe)FIH-1, suggesting that glycerol could intercept the active oxidant from the FIH-1 active site and prevent hydroxylation. Both purple and yellow FIH-1 contained high-spin, rhombic Fe(III) centers, as shown by low temperature EPR. XAS indicated distorted octahedral Fe(III) geometries, with subtle differences in inner-shell ligands for yellow and purple FIH-1. EPR of Co(II)-substituted FIH-1 (alphaKG + Co)FIH-1, indicated a mixture of 5-coordinate and 6-coordinate enzyme forms, suggesting that resting FIH-1 can readily undergo uncoupled O2-activation by loss of an H2O ligand from the metal center.