Kidney functional reserve and damage biomarkers in subclinical chronic kidney disease and acute kidney injury.

Significant loss of kidney function is not easily identified by serum creatinine (sCr)-based measurements. In the presence of normal sCr, decreased kidney functional reserve (KFR) may identify a significant loss of function. We evaluated KFR in experimental subclinical chronic kidney disease (sCKD) before and after brief ischemia-reperfusion injury (IRI). Using fluorescein isothiocyanate-labeled sinistrin, glomerular filtration rate (GFR) was measured transcutaneously before and after adenine-induced sCKD, and 1 and 2 wk after brief IRI, and compared with urinary kidney damage biomarkers. sCKD reduced stimulated and unstimulated GFR by ∼20% while reducing KFR by 50%. IRI reduced unstimulated GFR for 14 days, but KFR remained relatively unchanged in sCKD and transiently increased in control kidneys at 7 days. sCr increased and creatinine clearance (CrCl) decreased only immediately after IRI; sCr and CrCl correlated poorly with measured GFR except on day 1 after IRI. Heterogeneity in sCr and CrCl resulted from variation in tubular creatinine secretion. The increase in damage biomarker concentrations persisted for up to 14 days after IRI, allowing retrospective detection of sCKD before AKI by urine clusterin/urine kidney injury molecule-1 with an area under the curve of 1.0. sCr and CrCl are unreliable unless sCr is acutely elevated. Measurement of KFR and urine damage biomarker excretion detected sCKD despite normal sCr and CrCl. After IRI, the urine clusterin-to-urine kidney injury molecule-1 ratio may identify prior sCKD.NEW & NOTEWORTHY Early kidney function loss is poorly identified by serum creatinine (sCr)-based measurements. Direct kidney functional reserve (KFR) measurement before kidney injury and elevated urinary biomarkers clusterin and kidney injury molecule-1 detect subclinical chronic kidney disease (sCKD) after kidney injury despite normal range sCr and creatinine clearance. Reliance on sCr masks underlying sCKD. Acute kidney injury risk evaluation requires direct glomerular filtration rate measurement and KFR, whereas kidney damage biomarkers facilitate identification of prior subclinical injury.

Targeted protection of proximal tubular cells by nanoparticle-enhanced delivery of a TLR9-antagonist.

The kidney target site for injury that leads to acute kidney injury (AKI) is the proximal tubule. Nanoparticle-encapsulation enhanced delivery of a selective Toll-like receptor 9 antagonist to mouse proximal tubules and attenuated experimental ischemia-reperfusion injury in a mouse model of AKI.

Acute kidney injury following intravenous acyclovir in children.

OBJECTIVE: The objective of this study was to describe the incidence of acute kidney injury (AKI) in children receiving intravenous acyclovir and determine risk factors that may be associated with it. DESIGN: This was a retrospective cohort study, conducted by chart review. SETTING: The study was conducted across two paediatric hospitals. PATIENTS: All inpatients that received intravenous acyclovir in records from January 2015 to December 2015 were reviewed. Only patients with creatinine measurements taken before and after starting acyclovir were included in the study. MAIN OUTCOME MEASURES: The main outcome measure was the development of AKI following intravenous acyclovir administration, with AKI defined according to change in serum creatinine. RESULTS: 150 patients were included in the analysis. Patients' ages ranged from 2 days to 18.6 years. 27 children (18%) developed at least stage 1 AKI. Children receiving cancer treatment developed AKI more frequently than children with other diagnoses; 29.3% vs 10.9% (OR 3.4, 95% CI 1.5 to 8.2, p=0.008). The baseline estimated glomerular filtration rate (eGFR) was higher in those children who developed AKI. 34% of children had an eGFR >120 mL/min/1.73 m2 prior to acyclovir use. 31% of these children developed AKI compared with only 11% of those with a normal baseline eGFR (OR 3.6, 95 CI 1.3 to 10.1, p=0.02). Baseline eGFR was a significant predictor of AKI in a multivariable analysis that included cumulative dose and treatment duration (OR 1.02, p=0.013). CONCLUSION: AKI following intravenous acyclovir exposure is common in children. This study raises the possibility that glomerular hyperfiltration is a previously unrecognised risk factor for acyclovir-induced AKI.

Paternal High Fat Diet in Rats Leads to Renal Accumulation of Lipid and Tubular Changes in Adult Offspring.

Along with diabetes and obesity, chronic kidney disease (CKD) is increasing across the globe. Although some data support an effect of maternal obesity on offspring kidney, the impact of paternal obesity is unknown; thus, we have studied the effect of paternal obesity prior to conception. Male Sprague Dawley rats were fed chow diet or high fat diet (HFD) for 13-14 weeks before mating with chow-fed females. Male offspring were weaned onto chow and killed at 27 weeks for renal gene expression and histology. Fathers on HFD were 30% heavier than Controls at mating. At 27 weeks of age offspring of obese fathers weighed 10% less; kidney triglyceride content was significantly increased (5.35 ± 0.84 vs. 2.99 ± 0.47 µg/mg, p < 0.05, n = 8 litters per group. Histological analysis of the kidney demonstrated signs of tubule damage, with significantly greater loss of brush border, and increased cell sloughing in offspring of obese compared to Control fathers. Acat1, involved in entry of fatty acid for beta-oxidation, was significantly upregulated, possibly to counteract increased triglyceride storage. However other genes involved in lipid metabolism, inflammation and kidney injury showed no changes. Paternal obesity was associated with renal triglyceride accumulation and histological changes in tubules, suggesting a mild renal insult in offspring, who may be at risk of developing CKD.

TRAIL deficiency contributes to diabetic nephropathy in fat-fed ApoE-/- mice.

BACKGROUND: We recently demonstrated that TNF-related apoptosis-inducing ligand (TRAIL) is protective of diet-induced diabetes in mice. While TRAIL has been implicated in chronic kidney disease, its role in vivo in diabetic nephropathy is not clear. The present study investigated the role of TRAIL in the pathogenesis of diabetic nephropathy using TRAIL(-/-)ApoE(-/-) mice. METHODS: TRAIL(-/-)ApoE(-/-) and ApoE(-/-) mice were fed a high fat diet for 20 w. Plasma glucose and insulin levels were assessed over 0, 5, 8 and 20 w. At 20 w, markers of kidney function including creatinine, phosphate, calcium and cystatin C were measured. Changes in mRNA expression of MMPs, TIMP-1, IL-1ß and IL-18 were assessed in the kidney. Functional and histological changes in kidneys were examined. Glucose and insulin tolerance tests were performed. RESULTS: TRAIL(-/-)ApoE(-/-) mice had significantly increased urine protein, urine protein:creatinine ratio, plasma phosphorous, and plasma cystatin C, with accelerated nephropathy. Histologically, increased extracellular matrix, mesangial expansion and mesangial cell proliferation in the glomeruli were observed. Moreover, TRAIL(-/-)ApoE(-/-) kidneys displayed loss of the brush border and disorganisation of tubular epithelium, with increased fibrosis. TRAIL-deficient kidneys also had increased expression of MMPs, TIMP-1, PAI-1, IL-1ß and IL-18, markers of renal injury and inflammation. Compared with ApoE(-/-) mice, TRAIL-/-ApoE-/- mice displayed insulin resistance and type-2 diabetic features with reduced renal insulin-receptor expression. CONCLUSIONS: Here, we show that TRAIL-deficiency in ApoE(-/-) mice exacerbates nephropathy and insulin resistance. Understanding TRAIL signalling in kidney disease and diabetes, may therefore lead to novel strategies for the treatment of diabetic nephropathy.

Murine renal ischaemia-reperfusion injury.

Ischaemia/reperfusion is a major cause of acute kidney injury in native and transplant kidneys and is associated with significant morbidity and mortality. Murine models of renal ischaemia/reperfusion injury have great potential to improve understanding of the underlying processes and are an important focus of ongoing research into therapeutic and preventative strategies. Like all experimental models, murine models of renal ischaemia/reperfusion are prone to significant variability and results may be influenced by a number of technical and design factors. In this article we review the factors that may influence experimental results and provide a guide to conducting reproducible experiments in murine renal ischaemia/reperfusion.

Cardiac tissue factor: roles in physiology and fibrosis.

1. The aim of the present review is to discuss: (i) the role of tissue factor (TF) in the heart and focus on its potential role in maintaining normal extracellular cardiac homeostasis; (ii) the means by which TF may be contributing to extracellular matrix regulation and vascular maintenance; and (iii) potential mechanisms whereby reduced TF expression leads to cardiac fibrosis. 2. Tissue factor is the main initiator of the coagulation cascade in response to tissue injury, but it is also involved in numerous other biological processes, including angiogenesis, cell migration, apoptosis, metastasis and inflammation. 3. Tissue factor is implicated in cardiovascular disease and its localization and level of expression in cardiomyocytes suggests a unique role in maintaining the structure and function of cardiac muscle. 4. It has been shown that TF(-/-) mice die in utero as a result of disrupted yolk sac vasculature. Low-TF mice, which have transgenic expression of TF at less than 1% of normal levels, are rescued from lethality. 5. Low-TF mice develop cardiac fibrosis in a gender-dependent manner that may be dependent on differential expression of urokinase plasminogen activator. 6. Intracardiac bleeding in low-TF mice may occur as a result of a primary haemostasis defect and/or as a result of disrupted vascular maintenance. The mechanism, when elucidated, will have important therapeutic implications and may provide novel strategies for the treatment of cardiac fibrosis.

The development of cardiac fibrosis in low tissue factor mice is gender-dependent and is associated with differential regulation of urokinase plasminogen activator.

Tissue factor (TF) initiates the protease coagulation cascade in response to tissue injury. Homozygous deficiency of murine TF results in embryonic lethality, which is rescued by low-level expression of human TF. These low-TF mice have been shown to develop cardiac fibrosis. We tested the hypothesis that the development of cardiac fibrosis in low-TF mice results from dysregulated protease expression and is affected by gender. Mice were divided into the age groups 2-5, 6-12, 13-18 and 19+ weeks. Fibrosis was assessed by trichrome staining. Protease expression was measured in male and female mice by RT-PCR for mRNA and zymography, ELISA or immunoblot for protein. Urokinase plasminogen activator (uPA) activity was determined by zymography and chromogenic substrate assay. A marked gender effect was noted for the development of fibrosis, with interstitial collagen deposition occurring from 9 weeks in male low-TF mice, but not until 19 weeks in low-TF females. This delayed onset in females was accompanied by delayed up-regulation of molecular markers of injury. Matrix metalloproteinase (MMP)-3 and tissue inhibitor of metalloproteinase (TIMP)-1 expression were up-regulated in the hearts of male low-TF mice from 6 to 12 weeks and in females from 19 weeks. MMP/TIMP dysregulation was not seen prior to cardiac fibrosis and did not appear to explain the gender differences. However, uPA expression and activity were down-regulated prior to cardiac fibrosis in low-TF females, but were up-regulated in age-matched males. This suggests that the down-regulation of uPA in female low-TF mice protects them from more severe cardiac fibrosis.

Tissue factor deficiency and PAR-1 deficiency are protective against renal ischemia reperfusion injury.

Ischemia/reperfusion (IR) injury is a leading cause of acute renal failure and an important contributor to allograft damage. Tissue factor (TF) is up-regulated during IR, and TF inhibition reduces renal injury. However, the underlying mechanisms by which TF contributes to injury have not been elucidated. We postulated that TF contributes to IR injury by production of coagulation proteases and subsequent signaling by protease activated receptor (PARs). We compared renal injury after 25 minutes of bilateral renal ischemia and varying periods of reperfusion in C57BL/6 mice, those expressing low levels of TF (low-TF), hirudin-treated C57BL/6, and mice lacking either PAR-1 or PAR-2. C57BL/6 mice developed severe renal failure and died within 48 hours of reperfusion. In contrast, low-TF, hirudin-treated C57BL/6, and PAR-1-/- mice were protected from renal failure and had reduced mortality, tubular injury, neutrophil accumulation, and lower levels of the chemokines KC and MIP-2. Importantly, PAR-1-/- mice had lower chemokine levels despite up-regulation of TF and fibrin deposition. In addition, treating PAR-1-/- mice with hirudin conferred no additional benefit. Somewhat surprisingly, PAR-2 deficiency did not protect from renal failure. These experiments indicate that increased TF activity after renal IR leads to increased CXC chemokine expression and subsequent neutrophil-mediated injury predominantly by thrombin-dependent PAR-1 signaling.

Atherosclerosis in mice is not affected by a reduction in tissue factor expression.

OBJECTIVE: To determine whether tissue factor (TF) contributes to the progression of atherosclerotic lesions in mice. METHODS AND RESULTS: We determined the effect of a 50% reduction of TF levels in all cells on atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice. No differences were observed in the extent of atherosclerosis in apoE(-/-)/TF(+/+) and apoE(-/-)/TF(+/-) mice fed regular chow for 34 weeks. Atherosclerosis could not be analyzed in apoE(-/-) mice expressing low levels of TF because of premature death of these mice. Macrophages are a major source of TF in atherosclerotic plaques. Therefore, in a second series of experiments, we investigated the effect on atherosclerosis of selectively reducing hematopoietic cell-derived TF by transplanting bone marrow from mice expressing low levels of TF into low-density lipoprotein receptor deficient (LDLR(-/-)) mice. Atherosclerosis within the arterial tree and aortic root were similar in LDLR(-/-) mice with low-TF bone marrow compared with control bone marrow (TF(+/+) or TF(+/-)) after 4 and 16 weeks on an atherogenic diet. Furthermore, the cellular composition of the aortic root lesions was similar between the 2 groups. CONCLUSIONS: Our data indicate that either a 50% reduction of TF in all cells or a selective reduction in hematopoietic cell-derived TF does not affect the development of atherosclerotic lesions in mice.

Insulin resistance and postprandial triglyceride levels in primary renal disease.

BACKGROUND: Renal failure is associated with a range of metabolic abnormalities including insulin resistance and dyslipidemia. We examined the role of creatinine clearance (CrCl) and body composition in the development of insulin resistance in patients with primary renal disease and a variable degree of renal failure. We also determined the effect of a high-fat meal on postprandial triglyceride levels in a subgroup of these patients. METHODS: Forty-four patients with primary renal disease (men, 25; women, 19; age, 21-75 years) were compared to 44 controls matched for age, sex, and body composition. Renal biochemistry, plasma glucose, insulin, lipids, and nonesterified fatty acids were measured in the fasting state. Insulin sensitivity was calculated using the Homeostasis Model Assessment for Insulin Resistance (HOMA-R), and pancreatic beta-cell secretory capacity by HOMA- beta . Fourteen normotriglyceridemic subjects from each group consumed an 80-g fat meal to examine their postprandial metabolic response. RESULTS: Although there was no significant difference between HOMA-R for the controls and the entire patient group ( P = .06), HOMA-R was significantly higher in patients with CrCl less than 60 mL/min than those with CrCl greater than 60 mL/min or control subjects ( P < .01 for each pair). Exponential analysis of the relationship between CrCl and HOMA-R and - beta showed a line of best fit that was superior to that obtained by linear regression analysis ( P < .01 and P < .005, respectively). HOMA-R in renal patients was correlated with several parameters of body composition, including central fat (kilogram) ( P < .005). There was no difference in body fat parameters or HOMA-R for the patient and control subgroups undergoing a fat meal challenge. However, the patient subgroup showed a greater postprandial incremental rise in plasma triglycerides compared to controls ( P < .02). CONCLUSION: Patients with renal disease exhibit metabolic features typically associated with the metabolic syndrome. Insulin resistance increased with decline in renal function and was significantly higher in patients with CrCl less than 60 mL/min compared to subjects with CrCl greater than 60 mL/min or carefully matched controls. Renal patients also showed significant postprandial hypertriglyceridemia.