Urinary Neutrophil Gelatinase-Associated Lipocalin: A Useful Biomarker for Tacrolimus-Induced Acute Kidney Injury in Liver Transplant Patients

Tacrolimus is widely used as an immunosuppressant in liver transplantation, and tacrolimus-induced acute kidney injury (AKI) is a serious complication of liver transplantation. For early detection of AKI, various urinary biomarkers such as monocyte chemotactic protein-1, liver-type fatty acid-binding protein, interleukin-18, osteopontin, cystatin C, clusterin and neutrophil gelatinase-associated lipocalin (NGAL) have been identified. Here, we attempt to identify urinary biomarkers for the early detection of tacrolimus-induced AKI in liver transplant patients. Urine samples were collected from 31 patients after living-donor liver transplantation (LDLT). Twenty recipients developed tacrolimus-induced AKI. After the initiation of tacrolimus therapy, urine samples were collected on postoperative days 7, 14, and 21. In patients who experienced AKI during postoperative day 21, additional spot urine samples were collected on postoperative days 28, 35, 42, 49, and 58. The 8 healthy volunteers, whose renal and liver functions were normal, were asked to collect their blood and spot urine samples. The urinary levels of NGAL, monocyte chemotactic protein-1 and liver-type fatty acid-binding protein were significantly higher in patients with AKI than in those without, while those of interleukin-18, osteopontin, cystatin C and clusterin did not differ between the 2 groups. The area under the receiver operating characteristics curve of urinary NGAL was 0.876 (95% confidence interval, 0.800–0.951; P<0.0001), which was better than those of the other six urinary biomarkers. In addition, the urinary levels of NGAL at postoperative day 1 (p = 0.0446) and day 7 (p = 0.0006) can be a good predictive marker for tacrolimus-induced AKI within next 6 days, respectively. In conclusion, urinary NGAL is a sensitive biomarker for tacrolimus-induced AKI, and may help predict renal event caused by tacrolimus therapy in liver transplant patients.     

Comparison of Plasma and Urine Biomarker Performance in Acute Kidney Injury

Background

New renal biomarkers measured in urine promise to increase specificity for risk stratification and early diagnosis of acute kidney injury (AKI) but concomitantly may be altered by urine concentration effects and chronic renal insufficiency. This study therefore directly compared the performance of AKI biomarkers in urine and plasma.

Methods

This single-center, prospective cohort study included 110 unselected adults undergoing cardiac surgery with cardiopulmonary bypass between 2009 and 2010. Plasma and/or urine concentrations of creatinine, cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), liver fatty acid-binding protein (L-FABP), kidney injury molecule 1 (KIM1), and albumin as well as 15 additional biomarkers in plasma and urine were measured during the perioperative period. The primary outcome was AKI defined by AKIN serum creatinine criteria within 72 hours after surgery.

Results

Biomarkers in plasma showed markedly better discriminative performance for preoperative risk stratification and early postoperative (within 24h after surgery) detection of AKI than urine biomarkers. Discriminative power of urine biomarkers improved when concentrations were normalized to urinary creatinine, but urine biomarkers had still lower AUC values than plasma biomarkers. Best diagnostic performance 4h after surgery had plasma NGAL (AUC 0.83), cystatin C (0.76), MIG (0.74), and L-FAPB (0.73). Combinations of multiple biomarkers did not improve their diagnostic power. Preoperative clinical scoring systems (EuroSCORE and Cleveland Clinic Foundation Score) predicted the risk for AKI (AUC 0.76 and 0.71) and were not inferior to biomarkers. Preexisting chronic kidney disease limited the diagnostic performance of both plasma and urine biomarkers.

Conclusions

In our cohort plasma biomarkers had higher discriminative power for risk stratification and early diagnosis of AKI than urine biomarkers. For preoperative risk stratification of AKI clinical models showed similar discriminative performance to biomarkers. The discriminative performance of both plasma and urine biomarkers was reduced by preexisting chronic kidney disease.     

Renal cortical albumin gene induction and urinary albumin excretion in response to acute kidney injury

This study evaluated the potential utility of albuminuria as a "biomarker" of acute kidney injury (AKI) and tested whether AKI induces renal expression of the normally silent albumin gene. Urine albumin concentrations were measured in mice with five different AKI models (maleate, ischemia-reperfusion, rhabdomyolysis, endotoxemia, ureteral obstruction). Albumin gene induction in renal cortex, and in antimycin A-injured cultured proximal tubular cells, was assessed (mRNA levels; RNA polymerase II binding to the albumin gene). Albumin's clinical performance as an AKI biomarker was also tested (29 APACHE II-matched intensive care unit patients with and without AKI). Results were contrasted to those obtained for neutrophil gelatinase-associated lipocalin (NGAL), an established "AKI biomarker" gene. The experimental and clinical assessments indicated albumin's equivalence to NGAL as an AKI biomarker (greater specificity in experimental AKI; slightly better receiver-operating curve in humans). Furthermore, experimental AKI markedly induced the albumin gene (mRNA/RNA polymerase II binding increases; comparable to those seen for NGAL). Albumin gene activation in patients with AKI was suggested by fivefold increases in RNA polymerase II binding to urinary fragments of the albumin gene (vs. AKI controls). Experimental AKI also increased renal cortical mRNA levels for α-fetoprotein (albumin's embryonic equivalent). A correlate in patients was increased urinary α-fetoprotein excretion. We conclude that AKI can unmask, in the kidney, the normally silent renal albumin and α-fetoprotein genes. In addition, the urinary protein data independently indicate that albuminuria, and perhaps α-fetoprotein, have substantial utility as biomarkers of acute tubular injury.     

Update on biomarkers of acute kidney injury: moving closer to clinical impact?

Acute kidney injury (AKI) represents a common disorder in hospitalized patients, and its incidence is rising at an alarming rate. Despite significant improvements in critical care and renal replacement therapies (RRT), the outcome of critically ill patients with AKI necessitating RRT remains unacceptably dismal. In current clinical practice, the diagnosis and severity classification of AKI is based on a rise in serum creatinine levels, which may occur 2-3 days after the initiating renal insult and delay potentially effective therapies that are limited to the early stage. The emergence of numerous renal tubular damage-specific biomarkers offers an opportunity to diagnose AKI at an early timepoint, to facilitate differential diagnosis of structural and functional AKI, and to predict the outcome of established AKI. The purposes of this review are to summarize and to discuss the performance of these novel AKI biomarkers in various clinical settings. The most promising AKI biomarkers include plasma and urinary neutrophil gelatinase-associated lipocalin (NGAL), urinary interleukin (IL)-18, urinary liver-type fatty acid binding protein (L-FABP), urinary cystatin C, and urinary kidney injury molecule (KIM)-1. However, enthusiasm about their usefulness in the emergency department seems unwarranted at present. There is little doubt that urinary biomarkers of nephron damage may enable prospective diagnostic and prognostic stratification in the emergency department. However, comparison of the areas under the receiver-operating characteristic curves of these biomarkers with clinical and/or routine biochemical outcome parameters reveals that none of these biomarkers has a clear advantage beyond the traditional approach in clinical decision making in patients with AKI. The performance of various biomarkers for predicting AKI in patients with sepsis or with acute-on-chronic kidney disease is poor. The inability of biomarkers to improve classification of 'unclassifiable' (structural or functional) AKI, in which accurate differential diagnosis of pre-renal versus intrinsic renal AKI has the most value, illustrates another problem. Future research is necessary to clarify whether serial measurements of a specific biomarker or the use of a panel of biomarkers may be more useful in critically ill patients at risk of AKI. Whether or not the use of AKI biomarkers revolutionizes critical care medicine by early diagnosis of severe AKI and individualizes the management of AKI patients remains to be shown. Currently, the place of biomarkers in this decision-making process is still uncertain. Indiscriminate use of various biomarkers may distract clinicians from adequate clinical evaluation, may result in worse instead of better patient outcomes, and may waste money. Future large randomized studies are necessary to demonstrate the association between biomarker levels and clinical outcomes, such as dialysis, clinical events, or death. It needs to be shown whether assignment to earlier treatment for AKI on the basis of generally accepted biomarker cut-off levels results in a reduction in mortality and an improvement in recovery of renal function.     

Klotho and S100A8/A9 as Discriminative Markers between Pre-Renal and Intrinsic Acute Kidney Injury

Early detection and accurate differentiation of the cause of AKI may improve the prognosis of the patient. However, to date, there are few reliable biomarkers that can discriminate between pre-renal and intrinsic AKI. In this study, we determined whether AKI is associated with altered serum and urinary levels of Klotho, S100A8/A9 (an endogenous ligand of toll-like receptor 4), and neutrophil gelatinase-associated lipocalin (NGAL), which may allow differentiation between pre-renal and intrinsic AKI. A volume-depleted pre-renal AKI model was induced in male Sprague Dawley rats fed a low-salt diet (0.03%) without water 96 h before two intraperitoneal (IP) injections of furosemide (20 mg/kg) at a 24 h interval. In contrast, in the cisplatin-induced intrinsic AKI model, animals were given a single IP injection of cisplatin (5 mg/kg). All of the animals were euthanized 72 h after the first IP injection. Serum and urinary levels of Klotho, S100A8/A9, and NGAL were measured using an enzyme-linked immunosorbent assay. We also performed a proof-of-concept cross-sectional study to measure serum and urinary biomarkers in 61 hospitalized patients with established AKI. Compared to the intrinsic AKI group, the pre-renal AKI group showed a marked depression in urinary Klotho levels (13.21±17.32 vs. 72.97±17.96 pg/mL; P = 0.002). In addition, the intrinsic AKI group showed marked elevation of S100A8/A9 levels compared to the pre-renal AKI group (2629.97±598.05 ng/mL vs. 685.09±111.65 ng/mL; P = 0.002 in serum; 3361.11±250.86 ng/mL vs. 741.72±101.96 ng/mL; P = 0.003 in urine). There was no difference in serum and urinary NGAL levels between the pre-renal and intrinsic AKI groups. The proof-of-concept study with the hospitalized AKI patients also demonstrated decreased urinary Klotho in pre-renal AKI patients and increased urinary S100A8/A9 concentrations in intrinsic AKI patients. The attenuation of urinary Klotho and increase in urinary S100A8/A9 may allow differentiation between pre-renal and intrinsic AKI.     

Urinary neutrophil gelatinase-associated lipocalin and L-type fatty acid binding protein as diagnostic markers of early acute kidney injury after liver transplantation

Objective: We examined the value of two potential novel urinary biomarkers, neutrophil gelatinase-associated lipocalin (NGAL) and L-type fatty acid binding protein (L-FABP), in diagnosing acute kidney injury (AKI) in liver transplant recipients.

Methods: NGAL and L-FABP in urinary sample from Twenty-five patients before surgery and at 2, 4, 6, 12, 24, 48, 72 and 120 h after the anhepatic phase were tested. Standard statistics were used along with receiver-operating characteristic (ROC) analysis to evaluate the diagnostic value of selected markers.

Results: Urinary NGAL was only slightly elevated at 2 h in the non-AKI group while rose and stayed high from 2–6 h in the AKI group. However, urinary L-FABP rose transiently in both groups 2–120 h following surgery. The level of urinary NGAL presented differences at 2–6 h (p < 0.05) and urinary L-FABP at 4 h (p < 0.05) between AKI and non-AKI groups. ROC analysis showed that area under the curves (AUCs) of NGAL were 0.766, 0.773, and 0.773 at 2, 4 and 6 h respectively while 0.760 of L-FABP at 4 h.

Conclusion: Urinary NGAL rather than L-FABP appeared to be a sensitive and specific marker of AKI in liver transplant recipients.     

Levels of Protein C and Soluble Thrombomodulin in Critically Ill Patients with Acute Kidney Injury: A Multicenter Prospective Observational Study

Endothelial dysfunction contributes to the development of acute kidney injury (AKI) in animal models of ischemia reperfusion injury and sepsis. There are limited data on markers of endothelial dysfunction in human AKI. We hypothesized that Protein C (PC) and soluble thrombomodulin (sTM) levels could predict AKI. We conducted a multicenter prospective study in 80 patients to assess the relationship of PC and sTM levels to AKI, defined by the AKIN creatinine (AKI Scr) and urine output criteria (AKI UO). We measured marker levels for up to 10 days from intensive care unit admission. We used area under the curve (AUC) and time-dependent multivariable Cox proportional hazard model to predict AKI and logistic regression to predict mortality/non-renal recovery. Protein C and sTM were not different in patients with AKI UO only versus no AKI. On intensive care unit admission, as PC levels are usually lower with AKI Scr, the AUC to predict the absence of AKI was 0.63 (95%CI 0.44-0.78). The AUC using log10 sTM levels to predict AKI was 0.77 (95%CI 0.62-0.89), which predicted AKI Scr better than serum and urine neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C, urine kidney injury molecule-1 and liver-fatty acid-binding protein. In multivariable models, PC and urine NGAL levels independently predicted AKI (p=0.04 and 0.02) and PC levels independently predicted mortality/non-renal recovery (p=0.04). In our study, PC and sTM levels can predict AKI Scr but are not modified during AKI UO alone. PC levels could independently predict mortality/non-renal recovery. Additional larger studies are needed to define the relationship between markers of endothelial dysfunction and AKI.     

Balanced Hydroxyethylstarch (HES 130/0.4) Impairs Kidney Function In-Vivo without Inflammation

Volume therapy is a standard procedure in daily perioperative care, and there is an ongoing discussion about the benefits of colloid resuscitation with hydroxyethylstarch (HES). In sepsis HES should be avoided due to a higher risk for acute kidney injury (AKI). Results of the usage of HES in patients without sepsis are controversial. Therefore we conducted an animal study to evaluate the impact of 6% HES 130/0.4 on kidney integrity with sepsis or under healthy conditions Sepsis was induced by standardized Colon Ascendens Stent Peritonitis (sCASP). sCASP-group as well as control group (C) remained untreated for 24 h. After 18 h sCASP+HES group (sCASP+VOL) and control+HES (C+VOL) received 50 ml/KG balanced 6% HES (VOL) 130/0.4 over 6h. After 24h kidney function was measured via Inulin- and PAH-Clearance in re-anesthetized rats, and serum urea, creatinine (crea), cystatin C and Neutrophil gelatinase-associated lipocalin (NGAL) as well as histopathology were analysed. In vitro human proximal tubule cells (PTC) were cultured +/- lipopolysaccharid (LPS) and with 0.1–4.0% VOL. Cell viability was measured with XTT-, cell toxicity with LDH-test. sCASP induced severe septic AKI demonstrated divergent results regarding renal function by clearance or creatinine measure focusing on VOL. Soleley HES (C+VOL) deteriorated renal function without sCASP. Histopathology revealed significantly derangements in all HES groups compared to control. In vitro LPS did not worsen the HES induced reduction of cell viability in PTC cells. For the first time, we demonstrated, that application of 50 ml/KG 6% HES 130/0.4 over 6 hours induced AKI without inflammation in vivo. Severity of sCASP induced septic AKI might be no longer susceptible to the way of volume expansion.     

Comparative analysis of urinary biomarkers for early detection of acute kidney injury following cardiopulmonary bypass

The purpose of this study was to compare the performance of six candidate urinary biomarkers, kidney injury molecule (KIM)-1, N-acetyl-β-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, cystatin C and α-1 microglobulin, measured 2?h following cardiopulmonary bypass (CPB) for the early detection of acute kidney injury (AKI) in a prospective cohort of patients undergoing cardiac surgery. A total of 103 subjects were enrolled; AKI developed in 13%. Urinary KIM-1 achieved the highest area under-the-receiver-operator-characteristic curve (AUC 0.78, 95% confidence interval 0.64–0.91), followed by IL-18 and NAG. Only urinary KIM-1 remained independently associated with AKI after adjustment for a preoperative AKI prediction score (Cleveland Clinic Foundation score; p?=?0.02), or CPB perfusion time (p?=?0.006). In this small pilot cohort, KIM-1 performed best as an early biomarker for AKI. Larger studies are needed to explore further the role of biomarkers for early detection of AKI following cardiac surgery.     

Urinary Biomarkers Indicative of Apoptosis and Acute Kidney Injury in the Critically Ill

Background

Apoptosis is a key mechanism involved in ischemic acute kidney injury (AKI), but its role in septic AKI is controversial. Biomarkers indicative of apoptosis could potentially detect developing AKI prior to its clinical diagnosis.

Methods

As a part of the multicenter, observational FINNAKI study, we performed a pilot study among critically ill patients who developed AKI (n = 30) matched to critically ill patients without AKI (n = 30). We explored the urine and plasma levels of cytokeratin-18 neoepitope M30 (CK-18 M30), cell-free DNA, and heat shock protein 70 (HSP70) at intensive care unit (ICU) admission and 24h thereafter, before the clinical diagnosis of AKI defined by the Kidney Disease: Improving Global Outcomes -creatinine and urine output criteria. Furthermore, we performed a validation study in 197 consecutive patients in the FINNAKI cohort and analyzed the urine sample at ICU admission for CK-18 M30 levels.

Results

In the pilot study, the urine or plasma levels of measured biomarkers at ICU admission, at 24h, or their maximum value did not differ significantly between AKI and non-AKI patients. Among 20 AKI patients without severe sepsis, the urine CK-18 M30 levels were significantly higher at 24h (median 116.0, IQR [32.3–233.0] U/L) than among those 20 patients who did not develop AKI (46.0 [0.0–54.0] U/L), P = 0.020. Neither urine cell-free DNA nor HSP70 levels significantly differed between AKI and non-AKI patients regardless of the presence of severe sepsis. In the validation study, urine CK-18 M30 level at ICU admission was not significantly higher among patients developing AKI compared to non-AKI patients regardless of the presence of severe sepsis or CKD.

Conclusions

Our findings do not support that apoptosis detected with CK-18 M30 level would be useful in assessing the development of AKI in the critically ill. Urine HSP or cell-free DNA levels did not differ between AKI and non-AKI patients.     

Human Urinary Composition Controls Antibacterial Activity of Siderocalin

During Escherichia coli urinary tract infections, cells in the human urinary tract release the antimicrobial protein siderocalin (SCN; also known as lipocalin 2, neutrophil gelatinase-associated lipocalin/NGAL, or 24p3). SCN can interfere with E. coli iron acquisition by sequestering ferric iron complexes with enterobactin, the conserved E. coli siderophore. Here, we find that human urinary constituents can reverse this relationship, instead making enterobactin critical for overcoming SCN-mediated growth restriction. Urinary control of SCN activity exhibits wide ranging individual differences. We used these differences to identify elevated urinary pH and aryl metabolites as key biochemical host factors controlling urinary SCN activity. These aryl metabolites are well known products of intestinal microbial metabolism. Together, these results identify an innate antibacterial immune interaction that is critically dependent upon individualistic chemical features of human urine.     

NGAL、KIM-1和PCT在脓毒症AKI中的标志物作用

探讨NGAL与KIM-1联合检测和PCT在重症监护病房重症患者中急性肾损伤(AKI)发生中的作用。选取2018年1月至2019年6月我院101例重症患者,其中脓毒症AKI组61例,非AKI组40例,通过分析NGAL、KIM-1和PCT在2组患者中表达水平变化情况,结合与ACR指标对比分析,评价NGAL、KIM-1和PCT在脓毒症急性肾损伤早期诊断中的价值。结果显示,所有脓毒症AKI患者均检测出明显更高的尿NGAL生物标志物水平(67.32μg/g Cr)。尿KIM-1和尿NGAL水平升高与患者ACR升高均呈正相关(p<0.001),而在脓毒症AKI患者中PCT和ACR之间观察到显著的负相关(r_s=-0.102 5, p=0.307)。通过Kruskal-Wallis检验发现,NGAL和KIM-1值显示出与脓毒症严重程度具有显著统计学意义,且直接成比例的关系(p≤0.01)。进一步检查NGAL、KIM-1和PCT标志物与病情发展的相关性表明,PCT值似乎与临床结果没有很强的相关性。尿KIM-1联合NGAL在早期检测脓毒症AKI中具有较大的预测价值;PCT是有希望的脓毒症标志物之一,但不足以提供可靠诊断依据,在肾功能下降的患者中通过PCT进行脓毒症的临床诊断需要更加谨慎。     

Urinary L-FABP and its combination with urinary NGAL in early diagnosis of acute kidney injury after cardiac surgery in adult patients

Background/Aim: The early detection of acute kidney injury (AKI) may be become possible by several promising early biomarkers which may facilitate the early detection, differentiation and prognosis prediction of AKI. In this study, we investigated the value of urinary liver-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL) and their combination in predicting the occurrence and the severity of AKI following cardiac surgery.

Methods: We prospectively followed 109 patients undergoing open heart surgery and identified 26 that developed AKI, defined as an increase in serum creatinine of ≥0.3?mg/dl or ≥150% of baseline creatinine. Serum creatinine (SCr), urinary L-FABP, and NGAL corrected by urine creatinine were tested pre-operation, at 0 hour and 2 hours post-operation. Each marker was assessed at each time point between patients with and without AKI. Receiver operating characteristic (ROC) curves and area under curves (AUC) were used to evaluate the diagnostic accuracy of urinary L-FABP, NGAL and their combination for predicting AKI.

Results: Patients were aged 63.0?±?11.3 years, 66.1% were male and baseline SCr was 70.5?±?19.1 umol/L. Of 109 patients, 26(23.9%) developed AKI (AKIN stage I, II and III were 46.2%, 34.6% and 19.2% separately). The levels of urinary L-FABP and NGAL were significantly higher in AKI patients than non-AKI patients at 0 hour and 2 hours postoperative. AUCs for L-FABP was 0.844 (sensitivity (ST) 0.846, specificity (SP) 0.819, cut-off (CO) 2226.50 μg/g Ucr) at 0 hours and 0.832 at 2 hours (ST 0.808, SP 0.747, CO 673.09 μg/g Ucr) while 0.866 for NGAL at 0 hours (ST 0.769, SP 0.819, CO 131.12 μg/g Ucr) and 0.871 at 2 hours (ST 0.808, SP 0.831, CO 33.73 μg/g Ucr) to predict AKI occurrence. Using a combination of L-FABP and NGAL analyzed at the same timepoint as above, we were able to obtain an AUC of 0.911–0.927, p < 0.001. Similar AUCs of 0.81–0.87 were found to predict AKI stage II–III.

Conclusions: Urinary L-FABP and NGAL increased at an early stage after cardiac surgery. The combination of the two biomarkers enhanced the accuracy of the early detection of postoperative AKI after cardiac surgery before a rise in SCr.     

Circulating mitochondrial dysfunction as an early biomarker for contrast media-induced acute kidney injury in chronic kidney disease patients

Contrast-induced acute kidney injury (CI-AKI) is the common hospitalized acute kidney injury (AKI). However, the diagnosis by serum creatinine might not be early enough. Currently, the roles of circulating mitochondria in CI-AKI are still unclear. Since early detection is crucial for treatment, the association between circulating mitochondrial function and CI-AKI was tested as a potential biomarker for detection of CI-AKI. Twenty patients with chronic kidney disease (CKD) undergoing percutaneous coronary intervention (PCI) were enrolled. Blood and urine samples were obtained at the time of PCI, and 6, 24, 48 and 72 h after PCI. Plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) were measured. Oxidative stress, inflammation, mitochondrial function, mitochondrial dynamics and cell death were determined from peripheral blood mononuclear cells. Forty percent of patients developed AKI. Plasma NGAL levels increased after 24 h after receiving contrast media. Cellular and mitochondrial oxidative stress, mitochondrial dysfunction and decreased mitochondrial fusion occurred at 6 h following contrast media exposure. Subgroup of AKI had higher %necroptosis cells and TNF-α mRNA expression than subgroup without AKI. Collectively, circulating mitochondrial dysfunction could be an early predictive biomarker for CI-AKI in CKD patients receiving contrast media. These findings provide novel strategies to prevent CI-AKI according to its pathophysiology.     

Persistent disruption of mitochondrial homeostasis after acute kidney injury

While mitochondrial dysfunction is a pathological process that occurs after acute kidney injury (AKI), the state of mitochondrial homeostasis during the injury and recovery phases of AKI remains unclear. We examined markers of mitochondrial homeostasis in two nonlethal rodent AKI models. Myoglobinuric AKI was induced by glycerol injection into rats, and mice were subjected to ischemic AKI. Animals in both models had elevated serum creatinine, indicative of renal dysfunction, 24 h after injury which partially recovered over 144 h postinjury. Markers of proximal tubule function/injury, including neutrophil gelatinase-associated lipocalin and urine glucose, did not recover during this same period. The persistent pathological state was confirmed by sustained caspase 3 cleavage and evidence of tubule dilation and brush-border damage. Respiratory proteins NDUFB8, ATP synthase β, cytochrome c oxidase subunit I (COX I), and COX IV were decreased in both injury models and did not recover by 144 h. Immunohistochemical analysis confirmed that COX IV protein was progressively lost in proximal tubules of the kidney cortex after ischemia-reperfusion (I/R). Expression of mitochondrial fission protein Drp1 was elevated after injury in both models, whereas the fusion protein Mfn2 was elevated after glycerol injury but decreased after I/R AKI. LC3-I/II expression revealed that autophagy increased in both injury models at the later time points. Markers of mitochondrial biogenesis, such as PGC-1α and PRC, were elevated in both models. These findings reveal that there is persistent disruption of mitochondrial homeostasis and sustained tubular damage after AKI, even in the presence of mitochondrial recovery signals and improved glomerular filtration.     

Proximal tubule haptoglobin gene activation is an integral component of the acute kidney injury "stress response"

Haptoglobin (Hp) synthesis occurs almost exclusively in liver, and it is rapidly upregulated in response to stress. Because many of the pathways that initiate hepatic Hp synthesis are also operative during acute kidney injury (AKI), we tested whether AKI activates the renal cortical Hp gene. CD-1 mice were subjected to six diverse AKI models: ischemia-reperfusion, glycerol injection, cisplatin nephrotoxicity, myoglobinuria, endotoxemia, and bilateral ureteral obstruction. Renal cortical Hp gene induction was determined either 4-72 h or 1-3 wk later by measuring Hp mRNA and protein levels. Relative renal vs. hepatic Hp gene induction during endotoxemia was also assessed. Each form of AKI induced striking and sustained Hp mRNA increases, leading to ～10- to 100-fold renal Hp protein elevations (ELISA; Western blot). Immunohistochemistry, and isolated proximal tubule assessments, indicated that the proximal tubule was the dominant (if not only) site of the renal Hp increases. Corresponding urinary and plasma Hp elevations were surrogate markers of this response. Endotoxemia evoked 25-fold greater Hp mRNA increases in kidney vs. liver, indicating marked renal Hp gene reactivity. Clinical relevance of these findings was suggested by observations that urine samples from 16 patients with established AKI had statistically higher (～12×) urinary Hp levels than urine samples from either normal subjects or from 15 patients with chronic kidney disease. These AKI-associated urinary Hp increases mirrored those seen for urinary neutrophil gelatinase-associated lipoprotein, a well accepted AKI biomarker gene. In summary, these studies provide the first evidence that AKI evokes rapid, marked, and sustained induction of the proximal tubule Hp gene. Hp's known antioxidant, as well as its protean pro- and anti-inflammatory, actions imply potentially diverse effects on the evolution of acute tubular injury.     

急性肾损伤患者血清胱抑素-C及尿NGAL 水平的变化及其临床意义

目的:观察急性肾损伤(Acute kidney injury,AKI)患者血清胱抑素-C(Cystatin-C,CysC)及尿中性粒细胞明胶酶相关脂质运载蛋白(Neutrophil gelatinase-associated lipocalin,NGAL)水平的变化及其临床意义。方法:选择60例AKI患者为实验组,50例正常健康人作为对照组,应用酶联免疫吸附法测定两组人群血清胱抑素-C和尿NGAL水平。结果:实验组与对照组相比血清胱抑素-C和尿NGAL水平显著升高,差异有统计学意义(P<0.05)。实验组尿NGAL检出率高于血清胱抑素-C、血肌酐,差异有统计学意义(P<0.05)。结论:急性肾损伤患者血清胱抑素-C和尿NGAL均升高,其中尿NGAL是反映AKI较敏感的生物学标志物,值得临床进一步研究。     

Invariant Natural Killer T Cells Play a Role in Chemotaxis,Complement Activation and Mucus Production in a Mouse Model of Airway Hyperreactivity and Inflammation

CD1d-restricted invariant natural killer T (iNKT) cells play a critical role in the induction of airway hyperreactivity (AHR). After intranasal alpha-galactosylceramide (α-GalCer) administration, bronchoalveolar lavage fluid (BALF) proteins from mouse lung were resolved by two-dimensional differential gel electrophoresis (2D-DIGE), and identified by tandem mass spectroscopy. A lack of iNKT cells prevented the development of airway responses including AHR, neutrophilia and the production of the proinflammatory cytokines in lungs. Differentially abundant proteins in the BALF proteome of α-GalCer-treated wild type mice included lungkine (CXCL15), pulmonary surfactant-associated protein D (SFTPD), calcium-activated chloride channel regulator 1 (CLCA1), fragments of complement 3, chitinase 3-like proteins 1 (CH3LI) and 3 (CH3L3) and neutrophil gelatinase-associated lipocalin (NGAL). These proteins may contribute to iNKT regulated AHR via several mechanisms: altering leukocyte chemotaxis, increasing airway mucus production and possibly via complement activation.     

先天性心脏病患儿术后急性肾损伤的影响因素及尿NGAL、KIM-1的诊断价值分析

摘要 目的：探讨影响先天性心脏病患儿术后急性肾损伤（AKI）的影响因素及尿中性粒细胞明胶酶相关脂质运载蛋白（NGAL）、肾损伤分子1（KIM-1）的诊断价值。方法：选择2018年1月至2019年12月我院心胸外科收治的60例先天性心脏病术后并发AKI患儿（AKI组）和同期收治的172例先天性心脏病术后未发生AKI患儿（NAKI组）作为研究对象。收集患儿临床基线资料,检测尿NGAL、KIM-1水平,采用Logistic回归分析先天性心脏病患儿术后发生AKI的影响因素,受试者工作特征曲线（ROC）分析尿NGAL、KIM-1诊断先天性心脏病患儿术后发生AKI的价值。结果：AKI组年龄、体重低于NAKI组（P＜0.05）,手术时间、心肺转流（CPB）时间、主动脉阻断（ACT）时间、机械通气时间、重症监护室（ICU）住院时间长于NAKI组（P＜0.05）,术后平均动脉压（MAP）、尿素氮（BUN）、血肌酐（Scr）、NGAL、KIM-1高于NAKI组（P＜0.05）。Logistic回归分析结果显示低龄、低体重、CPB时间长、高NGAL、KIM-1水平是先天性心脏病患儿术后发生AKI的危险因素（P＜0.05）。ROC分析显示尿NGAL、KIM-1诊断先天性心脏病患儿术后发生AKI的灵敏度分别为81.67%,83.33%,特异度分别为84.30%,87.79%。结论：低龄、低体重、CPB时间长、高NGAL、KIM-1水平是先天性心脏病患儿术后发生AKI的危险因素,尿NGAL、KIM-1诊断先天性心脏病术后AKI具有较高价值。