Urinary kidney injury molecule-1: a sensitive quantitative biomarker for early detection of kidney tubular injury

Regression of microalbuminuria in type 1 diabetes is associated with lower levels of urinary tubular injury biomarkers, kidney injury molecule-1, and N-acetyl-β-D-glucosaminidase

Elevated urinary albumin excretion in patients with type 1 diabetes reverts to normoalbuminuria in a majority of patients but advances toward proteinuria in some. In order to gain valuable insights into the early pathophysiology of diabetic nephropathy we evaluated the association of kidney tubular injury biomarkers with changes in albuminuria in patients with type 1 diabetes mellitus. Urine levels of kidney injury molecule-1 (KIM-1), N-acetyl-β-D-glucosaminidase (NAG), and some inflammatory markers were determined in 38 healthy individuals and 659 patients with type 1 diabetes mellitus having varying degrees of albuminuria. Urinary interleukin-6, CXCL10/IP-10, NAG, and KIM-1 levels were very low in healthy individuals, increased in type 1 patients with normoalbuminuria, and were highest in diabetic patients that had microalbuminuria. Low baseline concentrations of urinary KIM-1 and NAG both individually and collectively were significantly associated with the regression of microalbuminuria over the subsequent 2 years; an effect independent of clinical characteristics. Progression and regression of microalbuminuria were unrelated to urinary levels of interleukins 6 and 8, CXCL10/IP-10, and monocyte chemoattractant protein-1. Thus our results show that lower urinary KIM-1 and NAG levels were associated with the regression of microalbuminuria in type 1 diabetes mellitus. Hence, tubular dysfunction is a critical component of the early course of diabetic nephropathy.

Update on the diagnosis and management of acute kidney injury

Acute kidney injury (AKI) is an independent risk factor for morbidity and mortality. This review provides essential information for the diagnosis and management of AKI. Blood urea nitrogen and serum creatinine are used for the diagnosis of AKI. The review also focuses on recent studies on the diagnosis of AKI using the RIFLE (R-renal risk, I-injury, F-failure, L-loss of kidney function, E-end stage kidney disease) and Acute Kidney Injury Network criteria, and serum and urine AKI biomarkers. Dialysis is the only Food and Drug Administration-approved therapy for AKI. Recent studies on the dose of dialysis in AKI are reviewed.

The suffocating kidney: tubulointerstitial hypoxia in end-stage renal disease

Chronic kidney disease (CKD) is characterized by irreversible pathological processes that result in the development of end-stage renal disease (ESRD). Accumulating evidence has emphasized the important role of chronic hypoxia in the tubulointerstitium in the final common pathway that leads to development of ESRD. The causes of chronic hypoxia in the tubulointerstitium are multifactorial and include mechanisms such as hemodynamic changes and disturbed oxygen metabolism of resident kidney cells. Epidemiological studies have revealed an association between CKD and systemically hypoxic conditions, such as chronic obstructive pulmonary disease and sleep apnea syndrome. In addition to tubulointerstitial hypoxia, glomerular hypoxia can occur and is a crucial factor in the development of glomerular disorders. Chemical compounds, polarographic sensors, and radiographical methods can be used to detect hypoxia. Therapeutic approaches that target chronic hypoxia in the kidney should be effective against a broad range of kidney diseases. Amelioration of hypoxia is one mechanism of inhibiting the renin-angiotensin system, the current gold standard of CKD therapy. Future therapeutic approaches include protection of the vascular endothelium and appropriate activation of hypoxia-inducible factor, a key transcription factor involved in adaptive responses against hypoxia.

Molecular biomarker candidates of acute kidney injury in zero-hour renal transplant needle biopsies

The aim of this study was to assess gene expression levels of four biomarker candidates [lipocalin 2 (LCN2), the kidney injury molecule 1 (HAVCR1), netrin 1, and the cysteine-rich, angiogenic inducer, 61] in the tubulointerstitial and the glomerular compartment of zero-hour kidney biopsies in order to predict developing delayed graft function (DGF). Thirty-four needle kidney biopsy samples of deceased donors were manually microdissected. Relative gene expression levels were determined by real-time RT-PCR. For the validation of the biomarker candidates, we calculated a mixed model comparing kidneys with DGF, primary function and control samples from the healthy parts of tumor nephrectomies. Significant biomarker candidates were analyzed together with donor age in multivariable regression models to determine the prognostic value. Expression levels of LCN2 and HAVCR1 in the tubulointerstitium were significantly upregulated in the DGF group (LCN2: fold change = 3.78, P = 0.031 and HAVCR1: fold change = 3.44, P = 0.010). Odds ratios of both genes could not reach significance in the multivariable model together with donor age. The area under the curve of the receiver operating characteristic ranges between 0.75 and 0.83. LCN2 and HAVCR1 gene expression levels in zero-hour biopsies show potential to act as early biomarkers for DGF.

A panel of urinary biomarkers to monitor reversibility of renal injury and a serum marker with improved potential to assess renal function

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Tubular damage in chronic systolic heart failure is associated with reduced survival independent of glomerular filtration rate

BACKGROUND

The prognostic impact of reduced glomerular filtration rate (GFR) in chronic heart failure (CHF) is increasingly recognised, but little is known about tubular damage in these patients.

OBJECTIVE

To investigate the prevalence of tubular damage, and its association with GFR, and prognosis in patients with CHF.

METHODS AND RESULTS

In 90 patients with CHF, GFR and effective renal plasma flow (ERPF) were measured ([(125)I]iothalamate and [(131)I]hippuran clearances). The tubular markers neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-beta-D-glucosaminidase (NAG) and kidney injury molecule 1 (KIM-1) as well as urinary albumin excretion were determined in 24 h urine collections. Mean GFR was 78+/-26 ml/min/1.73 m(2). Urinary NGAL (175 (70-346) microg/g creatinine (gCr)), NAG (12 (6-17) U/gCr) and KIM-1 (277 (188-537) ng/gCr) levels were increased compared with 20 healthy controls (all p<0.001). Urinary NAG, but not NGAL or KIM-1 correlated with GFR (r=-0.34, p=0.001) and ERPF (r=-0.29, p=0.006). Both NAG (r=0.21, p=0.048) and KIM-1 (r=0.23, p=0.033) correlated with plasma N-terminal pro-brain natriuretic peptide levels. Both urinary KIM-1 (HR=1.15 (95% CI 1.02 to 1.30) per 100 ng/gCr increase, p=0.025) and NAG (HR=1.42 (95% CI 1.02 to 1.94) per 5 U/gCr increase, p=0.039), were associated with an increased risk of death or heart failure hospitalisations, independent of GFR.

CONCLUSION

Tubular damage, as indicated by increased urinary concentrations of NGAL, NAG and KIM-1 is common in patients with CHF and mildly reduced GFR. Both urinary KIM-1 and NAG showed prognostic information additional to GFR. These findings suggest an important role for tubular damage and tubular markers in cardiorenal interaction in heart failure.

TIM2 gene deletion results in susceptibility to cisplatin-induced kidney toxicity

T-cell Immunoglobulin and Mucin domain 2 (TIM2) belongs to the receptor family of cell surface molecules expressed on kidney, liver, and T cells. Previous studies have revealed that TIM2-deficient mice (TIM2(-/-)) are more susceptible to the Th2-mediated immune response in an airway inflammation model. Here, we investigated the phenotypic response of TIM2(-/-) mice to cisplatin-induced kidney toxicity. A lethality study in male BALB/c wild-type (TIM2(+/+)) and TIM2(-/-) mice, administered with 20 mg/kg cisplatin ip, resulted in 80% mortality of TIM2(-/-) mice as compared with 30% mortality in the TIM2(+/+) group by day 5. The TIM2(-/-) mice showed approximately fivefold higher injury as estimated by blood urea nitrogen and serum creatinine at 48 h that was confirmed by significantly increased proximal tubular damage assessed histologically (H & E staining). A significantly higher expression of Th2-associated cytokines, TNF-α, IL-1β, IL-6, and TGFβ, with a significant reduction of Th1-associated cytokines, RANTES and MCP-1, by 72 h was observed in the TIM2(-/-) mice as compared with TIM2(+/+) mice. A higher baseline protein expression of caspase-3 (approximately twofold) coupled with an early onset of p53 protein activation by 48 h resulted in an increased apoptosis by 48-72 h in TIM2(-/-) compared with TIM2(+/+). In conclusion, the increased expression of the proinflammatory and proapoptotic genes, with a higher number of apoptotic cells, and a pronounced increase in injury and mortality of the TIM2-deficient mice collectively suggest a protective role of TIM2 in cisplatin-induced nephrotoxicity.

Urinary biomarkers for sensitive and specific detection of acute kidney injury in humans

Acute kidney injury (AKI) is associated with high morbidity and mortality. The lack of sensitive and specific injury biomarkers has greatly impeded the development of therapeutic strategies to improve outcomes of AKI.The unique objective of this study was to evaluate the diagnostic performance of nine urinary biomarkers of AKI-kidney injury molecule-1 (KIM-1), neutrophil gelatinase associated lipocalin (NGAL), interleukin-18 (IL-18), hepatocyte growth factor (HGF), cystatin C (Cys), N-acetyl-beta-D-glucosaminidase (NAG), vascular endothelial growth factor (VEGF), chemokine interferon-inducible protein 10 (IP-10; CXCL10), and total protein-in a cross-sectional comparison of 204 patients with or without AKI.Median urinary concentrations of each biomarker were significantly higher in patients with AKI than in those without AKI (p < 0.001). The area under the receiver operating characteristics curve (AUC-ROC) for the combination of biomarkers using a logic regression model [risk score of 2.93*(NGAL > 5.72 and HGF > 0.17) + 2.93*(PROTEIN > 0.22) -2*(KIM < 0.58)] was greater (0.94) than individual biomarker AUC-ROCs. Age-adjusted levels of urinary KIM-1, NAG, HGF, VEGF, and total protein were significantly higher in patients who died or required renal replacement therapy (RRT) when compared to those who survived and did not require RRT.Our results demonstrate the comparative value of multiple biomarkers in the diagnosis and prognosis of AKI.

Influence of Oct1/Oct2-deficiency on cisplatin-induced changes in urinary N-acetyl-beta-D-glucosaminidase

PURPOSE

This study aimed to test the influence of functional renal organic cation transporters (OCT2 in humans, Oct1 and Oct2 in mice) on biomarkers of cisplatin nephrotoxicity, such as urinary activity of N-acetyl-beta-D-glucosaminidase (NAG).

EXPERIMENTAL DESIGN

Temporal cisplatin-induced nephrotoxicity was assessed by histopathology and biomarkers. Cisplatin-mediated NAG changes and survival were determined in wild-type and Oct1/2(-/-) mice. Identification of OCT2 inhibitors was done in transfected 293Flp-In cells, and the NCI(60) cell line panel was used to assess contribution of OCT2 to cisplatin uptake in cancer cells.

RESULTS

Classical biomarkers such as blood urea nitrogen and serum creatinine were not elevated until 72 hours after cisplatin administration and substantial kidney damage had occurred. Oct1/2(-/-) mice had 2.9-fold lower NAG by 4 hours (P < 0.0001) and 2.3-fold increased survival (P = 0.0097). Among 16 agents, cimetidine strongly inhibited uptake of tetraethylammonium bromide (P = 0.0006) and cisplatin (P < 0.0001), but did not have an influence on cisplatin uptake in SK-OV-3 cells, the cancer line with the highest OCT2 mRNA levels. In wild-type mice, cimetidine inhibited cisplatin-induced NAG changes (P = 0.016 versus cisplatin alone) to a degree similar to that seen in Oct1/2(-/-) mice receiving cisplatin (P = 0.91). Cumulative NAG activity of >0.4 absorbance units (AU) was associated with 21-fold increased odds for severe nephrotoxicity (P = 0.0017), which was linked with overall survival (hazard ratio, 8.1; 95% confidence interval, 2.1-31; P = 0.0078).

CONCLUSIONS

Cimetidine is able to inhibit OCT2-mediated uptake of cisplatin in the kidney, and subsequently ameliorate nephrotoxicity likely with minimal effect on uptake in tumor cells.

Age-related differences in susceptibility to cisplatin-induced renal toxicity

Limited experimental models exist to assess drug toxicity in pediatric populations. We recently reported how a multi-age rat model could be used for pre-clinical studies of comparative drug toxicity in pediatric populations. The objective of this study was to expand the utility of this animal model, which previously demonstrated an age-dependent sensitivity to the classic nephrotoxic compound, gentamicin, to another nephrotoxicant, namely cisplatin (Cis). Sprague-Dawley rats (10, 25, 40 and 80 days old) were injected with a single dose of Cis (0, 1, 3 or 6 mg kg(-1) i.p.). Urine samples were collected prior and up to 72 h after treatment in animals that were >or= 25 days old. Several serum, urinary and 'omic' injury biomarkers as well as renal histopathology lesions were evaluated. Statistically significant changes were noted with different injury biomarkers in different age groups. The order of age-related Cis-induced nephrotoxicity was different than our previous study with gentamicin: 80 > 40 > 10 > 25 day-old vs 10 >or= 80 > 40 > 25-day-old rats, respectively. The increased levels of kidney injury molecule-1 (Kim-1: urinary protein/tissue mRNA) provided evidence of early Cis-induced nephrotoxicity in the most sensitive age group (80 days old). Levels of Kim-1 tissue mRNA and urinary protein were significantly correlated to each other and to the severity of renal histopathology lesions. These data indicate that the multi-age rat model can be used to demonstrate different age-related sensitivities to renal injury using mechanistically distinct nephrotoxicants, which is reflected in measurements of a variety of metabolite, gene transcript and protein biomarkers.

Kidney injury molecule-1 outperforms traditional biomarkers of kidney injury in preclinical biomarker qualification studies

Kidney toxicity accounts both for the failure of many drug candidates as well as considerable patient morbidity. Whereas histopathology remains the gold standard for nephrotoxicity in animal systems, serum creatinine (SCr) and blood urea nitrogen (BUN) are the primary options for monitoring kidney dysfunction in humans. The transmembrane tubular protein kidney injury molecule-1 (Kim-1) was previously reported to be markedly induced in response to renal injury. Owing to the poor sensitivity and specificity of SCr and BUN, we used rat toxicology studies to compare the diagnostic performance of urinary Kim-1 to BUN, SCr and urinary N-acetyl-beta-D-glucosaminidase (NAG) as predictors of kidney tubular damage scored by histopathology. Kim-1 outperforms SCr, BUN and urinary NAG in multiple rat models of kidney injury. Urinary Kim-1 measurements may facilitate sensitive, specific and accurate prediction of human nephrotoxicity in preclinical drug screens. This should enable early identification and elimination of compounds that are potentially nephrotoxic.

JNK signalling in human and experimental renal ischaemia/reperfusion injury

BACKGROUND

Ischaemia/reperfusion (I/R) is an important factor in delayed graft function in renal transplantation and is a determinant of long-term graft outcome. This study examined the role of c-Jun N-terminal kinase (JNK) signalling in human and experimental renal I/R injury.

METHODS

Biopsies obtained 15-20 min after reperfusion of human renal allografts were examined for JNK signalling by immunostaining for phospho-c-Jun. To examine the pathologic role of JNK signalling, a selective JNK inhibitor (CC-401) was administered to rats before or after the induction of a 30-min period of bilateral renal ischaemia followed by reperfusion. Renal function and tubular damage were analysed.

RESULTS

Substantial JNK activation was evident in tubular epithelial cells in kidneys from deceased donors (n = 30) which was less prominent in kidneys from live donors (n = 7) (44.6 +/- 24.8% vs 29.1 +/- 20% p-c-Jun+, respectively; P < 0.05), whereas biopsies of thin basement membrane disease exhibited little, or no, p-c-Jun staining. The degree of p-c-Jun staining correlated with ischaemic time in deceased donor allografts, but not with graft function. Administration of CC-401 to rats prior to bilateral renal I/R prevented acute renal failure and largely prevented tubular damage, leucocyte infiltration and upregulation of pro-inflammatory molecules. However, delaying CC-401 treatment until 1 h after reperfusion (after the peak of JNK activation) had no protective effect.

CONCLUSIONS

We have identified acute activation of the JNK signalling pathway following I/R in human kidney allografts. Experimental studies indicate that blockade of JNK signalling, commenced prior to this activation, can prevent acute tubular necrosis and renal dysfunction secondary to I/R injury.

Polymerized type I collagen reduces chronic cyclosporine nephrotoxicity

BACKGROUND

Polymerized type I collagen (P-collagen) has been successfully used to reduce human hypertrophic scars due to its anti-fibrotic and anti-inflammatory properties. We therefore carried out a study to determine if P-collagen reduces functional and structural injury in chronic cyclosporine [cyclosporine A (CsA)] nephropathy.

METHODS

Four groups of six male Wistar rats fed with a low sodium diet were treated with vehicle, P-collagen (0.8 mg/day, i.p.), CsA (15 mg/kg) or CsA + P-collagen for 15 days. Mean arterial pressure, renal blood flow and glomerular filtration rate were measured in all groups. Structural injury such as arteriolopathy, tubulo-interstitial fibrosis (TI-fibrosis) and positive apoptotic cells were quantified. The mRNA expression levels of transforming growth factor-beta (TGF-beta), kidney injury molecule (Kim-1), alpha-smooth muscle actin (alpha-SMA), glutathione peroxidase, catalase and Cu/Zn superoxide dismutase (SOD) as well as MnSOD were assessed. Antioxidant enzyme activity, renal lipoperoxidation and urinary excretion of oxygen peroxide (UH(2)O(2)V) were determined.

RESULTS

Cyclosporine produced renal dysfunction and induced the development of arteriolopathy, TI-fibrosis and tubular apoptosis. These alterations were associated with increases in TGF-beta, Kim-1 and alpha-SMA mRNA levels as well as with a significant increase of oxidative stress and a reduction of SOD activity. P-Collagen partially ameliorated CsA-induced renal dysfunction and structural injury and prevented both tubular apoptosis and increased oxidative stress. This renoprotective effect was found to be associated with a reduction of TGF-beta, Kim-1 and alpha-SMA mRNA levels.

CONCLUSIONS

This study has therefore demonstrated that P-collagen appears to have anti-fibrotic and anti-apoptotic properties and highlights the possibility that the compound might be useful in a strategy to reduce chronic CsA nephrotoxicity.

Performance of novel kidney biomarkers in preclinical toxicity studies

The kidney is one of the main targets of drug toxicity, but early detection of renal damage is often difficult. As part of the InnoMed PredTox project, a collaborative effort aimed at assessing the value of combining omics technologies with conventional toxicology methods for improved preclinical safety assessment, we evaluated the performance of a panel of novel kidney biomarkers in preclinical toxicity studies. Rats were treated with a reference nephrotoxin or one of several proprietary compounds that were dropped from drug development in part due to renal toxicity. Animals were dosed at two dose levels for 1, 3, and 14 days. Putative kidney markers, including kidney injury molecule-1 (Kim-1), lipocalin-2 (Lcn2), clusterin, and tissue inhibitor of metalloproteinases-1, were analyzed in kidney and urine using quantitative real-time PCR, ELISA, and immunohistochemistry. Changes in gene/protein expression generally correlated well with renal histopathological alterations and were frequently detected at earlier time points or at lower doses than the traditional clinical parameters blood urea nitrogen and serum creatinine. Urinary Kim-1 and clusterin reflected changes in gene/protein expression and histopathological alterations in the target organ in the absence of functional changes. This confirms clusterin and Kim-1 as early and sensitive, noninvasive markers of renal injury. Although Lcn2 did not appear to be specific for kidney toxicity, its rapid response to inflammation and tissue damage in general may suggest its utility in routine toxicity testing.

Biomarkers in renal transplantation ischemia reperfusion injury

Ischemia reperfusion injury (IRI) is a choreographed process leading to delayed graft function (DGF) and reduced long-term patency of the transplanted organ. Early identification of recipients of grafts at risk would allow modification of the posttransplant management, and thereby potentially improve short- and long-term outcomes. The recently emerged "omics" technologies together with bioinformatics workup have allowed the integration and analysis of IRI-associated molecular profiles in the context of DGF. Such a systems biological approach promises qualitative information about interdependencies of complex processes such as IRI regulation, rather than offering descriptive tables of differentially regulated features on a transcriptome, proteome, or metabolome level leaking the functional, biological framework. In deceased-donor kidney transplantation as the primary causative factor resulting in IRI and DGF, a distinct signature and choreography of molecular events in the graft before harvesting seems to be associated with subsequent DGF. A systems biological assessment of these molecular changes suggests that processes along inflammation are of pivotal importance for the early stage of IRI. The causal proof of this association has been tested by a double-blinded, randomized, controlled trial of steroid or placebo infusion into deceased donors before the organs were harvested. Thorough systems biological analysis revealed a panel of biomarkers with excellent discrimination. In summary, integrated analysis of omics data has brought forward biomarker candidates and candidate panels that promise early assessment of IRI. However, the clinical utility of these markers still needs to be established in prospective trials in independent patient populations.

Cardio-renal syndromes: report from the consensus conference of the acute dialysis quality initiative

A consensus conference on cardio-renal syndromes (CRS) was held in Venice Italy, in September 2008 under the auspices of the Acute Dialysis Quality Initiative (ADQI). The following topics were matter of discussion after a systematic literature review and the appraisal of the best available evidence: definition/classification system; epidemiology; diagnostic criteria and biomarkers; prevention/protection strategies; management and therapy. The umbrella term CRS was used to identify a disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other organ. Different syndromes were identified and classified into five subtypes. Acute CRS (type 1): acute worsening of heart function (AHF–ACS) leading to kidney injury and/or dysfunction. Chronic cardio-renal syndrome (type 2): chronic abnormalities in heart function (CHF-CHD) leading to kidney injury and/or dysfunction. Acute reno-cardiac syndrome (type 3): acute worsening of kidney function (AKI) leading to heart injury and/or dysfunction. Chronic reno-cardiac syndrome (type 4): chronic kidney disease leading to heart injury, disease, and/or dysfunction. Secondary CRS (type 5): systemic conditions leading to simultaneous injury and/or dysfunction of heart and kidney. Consensus statements concerning epidemiology, diagnosis, prevention, and management strategies are discussed in the paper for each of the syndromes.

Urinary biomarkers for the detection of renal injury

Despite the well-known limitations, currently the most widely used biomarkers for the early detection of chronic kidney disease or acute kidney injury are proteinuria, serum creatinine, and blood urea nitrogen. All of these are less than optimal and tend to focus attention on later stages of injury when therapies may be less effective. Recently, there has been a great surge of interest in identifying novel biomarkers that can be easily detected in the urine that can diagnose renal injury at the earliest stages. A variety of methods have been employed to identify these biomarkers including transcriptomics, proteomics, metabolomics, lipidomics, and gene arrays. Currently, several candidate biomarkers have been identified and studied in different renal injury states. These include kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, and fatty-acid binding proteins (FABPs). This review will highlight the current state of knowledge of these biomarkers as well as the limitation of these biomarkers in the early diagnosis of renal injury.

Urinary liver-type fatty acid-binding protein predicts adverse outcomes in acute kidney injury

Acute kidney injury (AKI) is a common condition with significant associated morbidity and mortality. The insensitivity and non-specificity of traditional markers of renal dysfunction prevent timely diagnosis, estimation of the severity of renal injury, and the administration of possible therapeutic agents. Here, we determine the prognostic ability of urinary liver-type fatty acid-binding protein (L-FABP), and further characterize its sensitivity and specificity as a biomarker of AKI. Initial western blot studies found increased urinary L-FABP in patients with confirmed AKI. A more extensive cross-sectional study found significant increases in urinary L-FABP, normalized to urinary creatinine, in 92 patients with established AKI compared with 62 patients without clinical evidence of AKI. In hospitalized patients, the diagnostic performance of urinary L-FABP for AKI, assessed by the area under the receiver operating characteristic curve, was 0.93. This compares favorably with other established biomarkers of AKI such as kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, N-acetyl-beta-glucosaminidase, and interleukin-18. Our study shows that age-adjusted urinary L-FABP levels were significantly higher in patients with poor outcome, defined as the requirement for renal replacement therapy or the composite end point of death or renal replacement therapy.

Cardiorenal syndrome: biomarkers linking kidney damage with heart failure

All the vital organs of the body share information by virtue of various biological mediators. Primary pathology of a major organ can lead to dysfunction of the other. Cardiorenal syndrome is an important example of such organ crosstalk. Primary dysfunction of the heart or kidney can lead to injury of the other organ. As molecular injury occurs prior to clinical dysfunction, effective interventions can be planned if one can detect this organ dysfunction at an earlier stage by virtue of some biological markers. Such biomarkers can be substances in urine, serum, imaging maneuvers or any other quantifiable parameters. Some currently available biomarkers are not sensitive enough to provide timely diagnosis of the disorder. An important research priority is the development of newer biomarkers or a panel of biomarkers for the early diagnosis of organ dysfunction, as well as nature of injury, guidance for therapeutic interventions and prognosis. Many newer biomarkers have been studied for both heart and kidney dysfunction. This article focuses on newer biomarkers for the cardiorenal syndrome.

Adrenalectomy prevents renal ischemia-reperfusion injury

Spironolactone treatment prevents renal damage induced by ischemia-reperfusion (I/R), suggesting that renoprotection conferred by spironolactone is mediated by mineralocorticoid receptor (MR) blockade. It is possible, however, that this effect is due to other mechanisms. Therefore, this study evaluated whether adrenalectomy prevented renal damage induced by I/R. Three groups of Wistar rats were studied: 1) a group subjected to a sham surgery, 2) a group subjected to bilateral I/R, and 3) a group of rats in which adrenal glands were removed 3 days before induction of I/R. As expected, I/R resulted in renal dysfunction and severe tubular injury that was associated with a significant increase in tubular damage markers. In contrast, there was no renal dysfunction or tubular injury in rats that were adrenalectomized before I/R. These effects were demonstrated by normalization of glomerular filtration rate, markers of oxidative stress, and tubular injury markers in adrenalectomized rats. The renoprotection observed was associated with the reestablishment of nitric oxide metabolites, increased endothelial nitric oxide synthase expression and its activating phosphorylation, as well as normalization of Rho-kinase expression and ETA mRNA levels. Our results show that aldosterone plays a central role in the pathogenesis of renal damage induced by I/R and that MR blockade may be a promising strategy that opens a new therapeutic option for preventing acute renal injury.

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-beta-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, cystatin C and alpha-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.

Kidney injury molecule-1 is an early noninvasive indicator for donor brain death-induced injury prior to kidney transplantation

With more marginal deceased donors affecting graft viability, there is a need for specific parameters to assess kidney graft quality at the time of organ procurement in the deceased donor. Recently, kidney injury molecule-1 (Kim-1) was described as an early biomarker of renal proximal tubular damage. We assessed Kim-1 in a small animal brain death model as an early and noninvasive marker for donor-derived injury related to brain death and its sequelae, with subsequent confirmation in human donors. In rat kidney, real-time PCR revealed a 46-fold Kim-1 gene upregulation after 4 h of brain death. In situ hybridization showed proximal tubular Kim-1 localization, which was confirmed by immunohistochemistry. Also, Luminex assay showed a 6.6-fold Kim-1 rise in urine after 4 h of brain death. In human donors, 2.5-fold kidney injury molecule-1 (KIM-1) gene upregulation and 2-fold higher urine levels were found in donation after brain death (DBD) donors compared to living kidney donors. Multiple regression analysis showed that urinary KIM-1 at brain death diagnosis was a positive predictor of recipient serum creatinine, 14 days (p < 0.001) and 1 year (p < 0.05) after kidney transplantation. In conclusion, we think that Kim-1 is a promising novel marker for the early, organ specific and noninvasive detection of brain death-induced donor kidney damage.

Differences in immunolocalization of Kim-1, RPA-1, and RPA-2 in kidneys of gentamicin-, cisplatin-, and valproic acid-treated rats: potential role of iNOS and nitrotyrosine

The present study compared the immunolocalization of Kim-1, renal papillary antigen (RPA)-1, and RPA-2 with that of inducible nitric oxide synthase (iNOS) and nitrotyrosine in kidneys of gentamicin sulfate (Gen)- and cisplatin (Cis)-treated rats. The specificity of acute kidney injury (AKI) biomarkers, iNOS, and nitrotyrosine was evaluated by dosing rats with valproic acid (VPA). Sprague-Dawley (SD) rats were injected subcutaneously (sc) with 100 mg/kg/day of Gen for six or fourteen days; a single intraperitoneal (ip) dose of 1, 3, or 6 mg/kg of Cis; or 650 mg/kg/day of VPA (ip) for four days. In Gen-treated rats, Kim-1 was expressed in the epithelial cells, mainly in the S1/S2 segments but less so in the S3 segment, and RPA-1 was increased in the epithelial cells of collecting ducts (CD) in the cortex. Spatial expression of iNOS or nitrotyrosine with Kim-1 or RPA-1 was detected. In Cis-treated rats, Kim-1 was expressed only in the S3 segment cells, and RPA-1 and RPA-2 were increased in the epithelial cells of medullary CD or medullary loop of Henle (LH), respectively. Spatial expression of iNOS or nitrotyrosine with RPA-1 or RPA-2 was also identified. These findings suggest that peroxynitrite formation may be involved in the pathogenesis of Gen and Cis nephrotoxicity and that Kim-1, RPA-1, and RPA-2 have the potential to serve as site-specific biomarkers for Gen or Cis AKI.

Pharmacologic management of the cardiorenal syndrome in heart failure

Cardiorenal syndrome describes the impairment of renal function and associated diuretic resistance in patients with heart failure and clinically manifest volume overload. The pathophysiology of this syndrome is poorly understood, but appears to be caused by impairment of tubuloglomerular feedback, neurohormonal activation, and other factors and therapies used in the management of heart failure. Early diagnosis of the cardiorenal syndrome by way of markers of renal injury and function is critical for timely interventions that may attenuate progression. Many novel therapies have been evaluated in the cardiorenal syndrome setting, including agents that block key local factors (eg, adenosine A(I) receptor antagonists), improve diuresis, aquaresis, and natriuresis, and augment natural vasodilator mechanisms to improve renal perfusion. Furthermore, device-based approaches such as ultrafiltration may also play an important therapeutic role.

Sniffing chronic renal failure in rat model by an array of random networks of single-walled carbon nanotubes

In this study, we use an experimental model of bilateral nephrectomy in rats to identify an advanced, yet simple nanoscale-based approach to discriminate between exhaled breath of healthy states and of chronic renal failure (CRF) states. Gas chromatography/mass spectroscopy (GC-MS) in conjugation with solid-phase microextraction (SPME) of healthy and CRF breath, collected directly from the trachea of the rats, identified 15 common volatile organic compounds (VOCs) in all samples of healthy and CRF states and 27 VOCs that appear in CRF but not in healthy states. Online breath analysis via an array of chemiresistive random network of single-walled carbon nanotubes (SWCNTs) coated with organic materials showed excellent discrimination between the various breath states. Stepwise discriminate analysis showed that enhanced discrimination capacity could be achieved by decreasing the humidity prior to their analysis with the sensors' array. Furthermore, the analysis showed the adequacy of using representative simulated VOCs to imitate the breath of healthy and CRF states and, therefore, to train the sensors' array the pertinent breath signatures. The excellent discrimination between the various breath states obtained in this study provides expectations for future capabilities for diagnosis, detection, and screening various stages of kidney disease, especially in the early stages of the disease, where it is possible to control blood pressure and protein intake to slow the progression.

A rapid urine test for early detection of kidney injury

Kidney injury molecule-1 (Kim-1) has been qualified by the Food and Drug Administration and European Medicines Agency as a highly sensitive and specific urinary biomarker to monitor drug-induced kidney injury in preclinical studies and on a case-by-case basis in clinical trials. Here we report the development and evaluation of a rapid direct immunochromatographic lateral flow 15-min assay for detection of urinary Kim-1 (rat) or KIM-1 (human). The urinary Kim-1 band intensity using the rat Kim-1 dipstick significantly correlated with levels of Kim-1 as measured by a microbead-based assay, histopathological damage, and immunohistochemical assessment of renal Kim-1 in a dose- and time-dependent manner. Kim-1 was detected following kidney injury induced in rats by cadmium, gentamicin, or bilateral renal ischemia/reperfusion. In humans, the urinary KIM-1 band intensity was significantly greater in urine from patients with acute kidney injury than in urine from healthy volunteers. The KIM-1 dipstick also enabled temporal evaluation of kidney injury and recovery in two patients who developed postoperative acute kidney injury following cytoreductive surgery for malignant mesothelioma with intraoperative local cisplatin administration. We hope that future, more extensive studies will confirm the utility of these results, which show that the Kim-1/KIM-1 dipsticks can provide a sensitive and accurate detection of Kim-1/KIM-1, thereby providing a rapid diagnostic assay for kidney damage and facilitating the rapid and early detection of kidney injury in preclinical and clinical studies.

Chordin-like 1 and twisted gastrulation 1 regulate BMP signaling following kidney injury

Stimulation of the bone morphogenetic protein (BMP) pathway protects the kidney from acute and chronic injury. Numerous regulators in the kidney control BMP signaling, offering many targets for therapeutic manipulation. Here, we screened for modulators of BMP signaling in the ischemia-sensitive S3 segment and found that Chordin-like 1 is expressed in this segment of both the mouse and human nephron. Chordin-like 1 specifically antagonizes BMP7, which is expressed in the neighboring distal nephron, and this depends on the presence of the protein Twisted gastrulation. Upon ischemia-induced degeneration of the S3 segment, we observed a reduction in Chordin-like 1 expression coincident with intense BMP signaling in tubules of the recovering kidney. Restored expression accompanied proximal tubule epithelia redifferentiation, again coincident with decreased BMP signaling. We propose that Chordin-like 1 reduces BMP7 signaling in healthy proximal tubules, and the loss of this activity upon sloughing of injured epithelia promotes BMP7 signaling in repopulating, dedifferentiated epithelia. As regenerating epithelia differentiate, Chordin-like 1 is again expressed, antagonizing BMP7. These data suggest a mechanism for dynamic regulation of renoprotective BMP7 signaling in the S3 segment of the proximal tubule.

Therapeutic and predictive targets of AKI

Acute kidney injury (AKI) is a very common condition encountered in a hospital setting. AKI is an independent risk factor for in-hospital mortality. In this review, we discuss in detail about the tubular, inflammatory and vascular molecular targets of AKI which may result in therapies to improve mortality and biomarkers for earlier diagnosis of AKI.

Reduction of proteinuria in adriamycin-induced nephropathy is associated with reduction of renal kidney injury molecule (Kim-1) over time

Tubulointerstitial lesions are important in the progression of proteinuric renal disease. Tubular kidney injury molecule-1 (Kim-1) is induced in acute renal injury and reversible as a natural course. Kim-1 is also present in chronic renal damage; however, the dynamics of Kim-1 in chronic renal damage and effects of antiproteinuric treatment on Kim-1 are unknown. We studied Kim-1 in adriamycin nephrosis (AN) before and after renin-angiotensin system blockade. A renal biopsy was taken 6 wk after adriamycin injection to study renal damage and Kim-1 expression. Subsequently, ACE inhibition (ACEi; n = 23), angiotensin II antagonist (AT(1A); n = 23), or vehicle (n = 10) was given for 6 wk; healthy rats served as controls (CON; n = 8). In AN, renal Kim-1 mRNA was induced 26-fold vs. CON at week 6, with further increase in vehicle to week 12 (40-fold) but was reduced by ACEi and AT(1A) to 10- and 12-fold vs. CON (P < 0.05 vs. week 6). Kim-1 protein was undetectable in CON; in AN, it was present in brush border of dilated tubules in areas with adjacent interstitial lesions. Renal Kim-1 protein levels increased from weeks 6-12 in vehicle and decreased in ACEi- and AT(1A)-treated groups (P < 0.05). In vehicle, urinary Kim-1 was increased (P < 0.05 vs. CON), with a reduction by ACEi and AT(1A) (P < 0.05 vs. vehicle). Renal and urinary Kim-1 correlated with proteinuria and interstitial damage cross-sectionally. Reductions in proteinuria and renal Kim-1 correlated, which was not associated by corresponding changes in tubulointerstitial fibrosis. In conclusion, on longitudinal follow-up during antiproteinuric treatment increased renal Kim-1 expression is reversible in proportion to proteinuria reduction, likely reflecting reversibility of early tubular injury, supporting its potential as a biomarker for tubulointerstitial processes of damage and repair.

Assays of urine levels of HNL/NGAL in patients undergoing cardiac surgery and the impact of antibody configuration on their clinical performances

BACKGROUND

Acute kidney injury (AKI) is one of the most serious postoperative complications of cardiac surgery. The lack of early and powerful markers for AKI makes the morbidity and mortality still very high. HNL (Human neutrophil lipocalin)/NGAL (Neutrophil gelatinase-associated lipocalin) was recently shown as a novel biomarker for AKI after cardiac surgery.

METHODS

Serial urine samples from 59 patients undergoing cardiac surgery were analyzed by polyclonal antibody based radioimmunoassay (RIA), monoclonal-polyclonal antibody based enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found 10 to 100-fold increases in urine HNL/NGAL levels in about half of the patients 2 h after termination of the operation and elevated levels in all patients 72 h post operation. The urine levels of HNL/NGAL showed a weak, but significant relation with kidney function as measured by plasma levels of cystatin C or creatinine. The 2 h-HNL/NGAL levels were positively correlated to extracorporeal circulation time (p<0001). The assays were well correlated, but had different clinical performances.

CONCLUSIONS

We confirmed that urine HNL/NGAL may be a useful early biomarker of postoperative kidney injury. The results indicate that the antibody configuration of the assay has an impact on the clinical performance of the assay.

Preclinical evaluation of novel urinary biomarkers of cadmium nephrotoxicity

As a result of the widespread use of Cd in industry and its extensive dissemination in the environment, there has been considerable interest in the identification of early biomarkers of Cd-induced kidney injury. Kim-1 is a transmembrane glycoprotein that is not detectable in normal kidney, but is up-regulated and shed into the urine following ischemic or nephrotoxic injury. Recent studies utilizing a sub-chronic model of Cd exposure in the rat have shown that Kim-1 is an early urinary marker of Cd-induced kidney injury. Kim-1 was detected in the urine 4-5 weeks before the onset of proteinuria and 1-3 weeks before the appearance of urinary metallothionein and Clara cell protein 16, which are standard markers of Cd nephrotoxicity. In the present study, we have compared the time course for the appearance of Kim-1 in the urine with the time course for the appearance of alpha glutathione-S-transferase (alpha-GST), N-acetyl-beta-D-glucose amidase (NAG) and Cd, each of which have been used or proposed as urinary markers of Cd nephrotoxicity. Adult male Sprague-Dawley rats were given daily subcutaneous injections of 0.6 mg (5.36 micromoles)/kg Cd, 5 days per week for up to 12 weeks. One day each week, 24 h urine samples were collected and analyzed for protein, creatinine and the various markers. The results showed that significant levels of Kim-1 appeared in the urine as early as 6 weeks into the treatment protocol and then continued to rise for the remainder of the 12 week treatment period. By contrast, significant levels of alpha-GST and NAG did not appear in the urine until 8 and 12 weeks, respectively, while proteinuria was not evident until 10 weeks. The urinary excretion of Cd was below the level of detection until week 4 and then showed a slow, linear increase over the next 6 weeks before increasing markedly between weeks 10 and 12. These results provide additional evidence that Kim-1 is a sensitive biomarker of the early stages of Cd-induced proximal tubule injury.

Expression of kidney injury molecule-1 (Kim-1) in relation to necrosis and apoptosis during the early stages of Cd-induced proximal tubule injury

Cadmium (Cd) is a nephrotoxic industrial and environmental pollutant that causes a generalized dysfunction of the proximal tubule. Kim-1 is a transmembrane glycoprotein that is normally not detectable in non-injured kidney, but is up-regulated and shed into the urine during the early stages of Cd-induced proximal tubule injury. The objective of the present study was to examine the relationship between the Cd-induced increase in Kim-1 expression and the onset of necrotic and apoptotic cell death in the proximal tubule. Adult male Sprague-Dawley rats were treated with 0.6 mg (5.36 micromol) Cd/kg, subcutaneously, 5 days per week for up to 12 weeks. Urine samples were analyzed for levels of Kim-1 and the enzymatic markers of cell death, lactate dehydrogenase (LDH) and alpha-glutathione-S-transferase (alpha-GST). In addition, necrotic cells were specifically labeled by perfusing the kidneys in situ with ethidium homodimer using a procedure that has been recently developed and validated in the Prozialeck laboratory. Cryosections of the kidneys were also processed for the immunofluorescent visualization of Kim-1 and the identification of apoptotic cells by TUNEL labeling. Results showed that significant levels of Kim-1 began to appear in the urine after 6 weeks of Cd treatment, whereas the levels of total protein, alpha-GST and LDH were not increased until 8-12 weeks. Results of immunofluorescence labeling studies showed that after 6 weeks and 12 weeks, Kim-1 was expressed in the epithelial cells of the proximal tubule, but that there was no increase in the number of necrotic cells, and only a modest increase in the number of apoptotic cells at 12 weeks. These results indicate that the Cd-induced increase in Kim-1 expression occurs before the onset of necrosis and at a point where there is only a modest level of apoptosis in the proximal tubule.

Assay validation for KIM-1: human urinary renal dysfunction biomarker

Urinary kidney injury molecule (KIM-1) is a sensitive quantitative biomarker for early detection of kidney tubular injury. The objective of the present work was to analytically validate this urinary renal injury biomarker. Duo-set reagents from R&D were used to develop the ELISA and validate the assay's linearity, intra-run precision, inter-run precision, lower limit of quantification, recovery, dilutional verification, reference range, stability, and length of run. The reference range data suggests that the healthy population falls within the assay range (59 - 2146 pg/mL) and upper limit of quantitation for this assay is 17168 pg/mL for the patient population. This is a robust assay to detect urinary levels of KIM-1, which serves as a non-invasive sensitive, reproducible, and potentially high-throughput method to detect early kidney injury in drug development studies.

The future of pediatric acute kidney injury management--biomarkers

Acute kidney injury (AKI) represents a common and devastating problem in clinical medicine. A major reason is the lack of early biomarkers for AKI, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies has uncovered several novel biomarkers. The most promising of these are included in a putative AKI biomarker panel, consisting of neutrophil gelatinase-associated lipocalin, interleukin-18, and kidney injury molecule-1. These biomarkers have completed initial validation, and have entered the prospective screening stage in the biomarker development process, facilitated by the development of commercial tools for their reproducible measurement across laboratories. The availability of a panel of validated biomarkers will revolutionize renal and critical care, and enable the practice of personalized and predictive medicine at an unprecedented level.

Cardiorenal syndrome

The term cardiorenal syndrome (CRS) increasingly has been used without a consistent or well-accepted definition. To include the vast array of interrelated derangements, and to stress the bidirectional nature of heart-kidney interactions, we present a new classification of the CRS with 5 subtypes that reflect the pathophysiology, the time-frame, and the nature of concomitant cardiac and renal dysfunction. CRS can be generally defined as a pathophysiologic disorder of the heart and kidneys whereby acute or chronic dysfunction of 1 organ may induce acute or chronic dysfunction of the other. Type 1 CRS reflects an abrupt worsening of cardiac function (e.g., acute cardiogenic shock or decompensated congestive heart failure) leading to acute kidney injury. Type 2 CRS comprises chronic abnormalities in cardiac function (e.g., chronic congestive heart failure) causing progressive chronic kidney disease. Type 3 CRS consists of an abrupt worsening of renal function (e.g., acute kidney ischemia or glomerulonephritis) causing acute cardiac dysfunction (e.g., heart failure, arrhythmia, ischemia). Type 4 CRS describes a state of chronic kidney disease (e.g., chronic glomerular disease) contributing to decreased cardiac function, cardiac hypertrophy, and/or increased risk of adverse cardiovascular events. Type 5 CRS reflects a systemic condition (e.g., sepsis) causing both cardiac and renal dysfunction. Biomarkers can contribute to an early diagnosis of CRS and to a timely therapeutic intervention. The use of this classification can help physicians characterize groups of patients, provides the rationale for specific management strategies, and allows the design of future clinical trials with more accurate selection and stratification of the population under investigation.

Enzymuria determination in children treated with aminoglycosides drugs

Although aminoglycosides antibiotics are used in children and adult commonly, they have serious side effects such as nephrotoxicity and ototoxicity. In clinical practice, for renal function, the levels of serum creatinine and blood urea nitrogen routinely are measured. Since these parameters have limitations such as unreliability, insensitivity, and nonspecificity, the rapid assessment of renal function based on these patients is very important. Increase in N-acetyl-β-D-glucosaminidase (NAG), a hydrolytic lysosomal enzyme, suggests proximal tubular cell damage. In this study, 32 children aged 2 months through 2 years, treated with gentamicin and amikacin for suspected infections at the pediatric ward of Alborz hospital from September 2006 to February 2007, were enrolled. Serum and fresh urine before and after drug infusion were obtained on the 1st, 3rd, and 5th days of antibiotic treatment. Serum urea and creatinine with urinary creatinine, albumin, NAG, lactate dehydrogenase (LDH) and alkaline phosphatase (AP) activity were then determined. A statistically significant increase in urinary NAG, LDH, and AP on 5th day was found compared with before gentamicin administration ( P < 0.001, P < 0.01, P < 0.05, respectively). The urinary NAG activity may be a useful indicator of renal injury in children treated with aminoglycosides drugs compared with other routine clinical indicators.

Modulation of aquaporin-2/vasopressin2 receptor kidney expression and tubular injury after endotoxin (lipopolysaccharide) challenge

OBJECTIVE

Sepsis-induced organ dysfunctions remain prevalent and account for >50% of intensive care unit admissions for acute renal failure with a mortality rate nearing 75%. In addition to the fact that the mechanisms underlying the pathophysiology of sepsis-related acute renal failure are unclear, the impact on septic-induced acute renal failure of either norepinephrine, a gold-standard vasopressor, and arginine vasopressin, a candidate alternative, are not well understood.

DESIGN

Randomized and controlled in vivo study.

SETTING

Research laboratory and animal facilities.

SUBJECTS

Adult rats treated with endotoxin (lipopolysaccharide) and/or vasopressors.

INTERVENTIONS

Rats were intraperitoneally injected with lipopolysaccharide (12 mg/kg) or saline and then infused with either saline, 0.375 microg/microL arginine vasopressin, or 32.5 microg/microL norepinephrine for 18 hrs. These vasopressor rates yielded respective targeted blood levels observed in human septic shock.

MEASUREMENTS AND MAIN RESULTS

Renal function, including glomerular filtration rate and fraction, renal blood flow, aquaporin-2, and arginine vasopressin-2 (V2 receptor) networking, water and salt handling, and urinary protein excretion, were evaluated. After lipopolysaccharide challenge arginine vasopressin infusion: 1) impaired creatinine clearance without affecting renal blood flow, glomerular filtration rate, and fraction but reduced free-water clearance, both of which being partially restored by the V2 receptor antagonist SR-121463B; 2) decreased the recognized ability of arginine vasopressin alone to recruit aquaporin-2 to the apical membrane increase its mRNA expression and urinary release; 3) increased urinary protein content but decreased specific kidney injury molecule-1, and Clara cell protein-16 release (p < 0.05 vs. lipopolysaccharide alone). Conversely, norepinephrine infusion did not add to lipopolysaccharide-induced alteration of urine biochemistry, except for improved creatinine clearance and increased microalbuminuria.

CONCLUSION

In this endotoxic model, dose-targeted arginine vasopressin infusion increased lipopolysaccharide-induced renal dysfunction without affecting renal blood flow and glomerular function, but with particular disruption of aquaporin-2/V2 receptor networking, consecutive decreased salt and water handling ability. This is in clear contrast with norepinephrine infusion and suggests specific arginine vasopressin-induced "tubular epithelial dysfunction."