Background: Aminoglycoside antibiotics are commonly used in paediatric clinical practice, especially for the treatment of neonatal sepsis and pulmonary exacerbations in cystic fibrosis (CF). However, megalin-mediated endocytosis of the aminoglycosides by renal proximal tubule epithelial cells leads to toxicity, and may result in acute kidney injury and chronic kidney disease. Current approaches to identify and prevent toxicity are limited. Several novel biomarkers have shown utility in preclinical studies for the identification of aminoglycoside-induced nephrotoxicity, but clinical data and an understanding of their clinical utility is lacking. The potential of statins to prevent aminoglycoside-induced nephrotoxicity by inhibition of megalin-mediated endocytosis has been previously demonstrated in vitro and in a rat model, but its potential in man is unclear. Aims: Firstly, to investigate the utility of novel urinary biomarkers for the early identification of aminoglycoside-induced nephrotoxicity in children. Secondly, to develop a novel intervention using statins to prevent aminoglycoside-induced nephrotoxicity in children with CF. Methods and Results: Urine samples were collected from 41 premature neonates at least once per week, and daily during courses of gentamicin. Three urinary biomarkers were measured using Luminex-based (Kidney Injury Molecule-1 (KIM-1) and Neutrophil Gelatinase-associated Lipocalin (NGAL)) and colorimetric assays (N-acetyl-β-D-glucosaminidase (NAG)). All three biomarkers were elevated during treatment with gentamicin, but when adjusted for potential confounders, only the elevation in KIM-1 remained significant (mean difference from not treated, 1.35ng/mg urinary creatinine; 95% CI 0.05-2.65). Electrochemiluminescent assays for both KIM-1 and NGAL were validated, and were compared to Luminex-based assays by analysing samples from healthy children in the UK (n=120) and the US (n=171). 95% reference intervals for both biomarkers were derived using quantile regression. Urine samples were collected from a cohort of children with cystic fibrosis (n=158) at outpatient clinic appointments and during exposure to tobramycin. Biomarkers were measured using the validated electrochemiluminescent assays. Elevations in both KIM-1 and NGAL (median peak fold-change was 2.28 (IQR 2.69) and 4.02 (IQR 7.29) respectively) were observed during exposure to tobramycin. In a multiple regression model, baseline KIM-1 was associated with the number of previous courses of IV aminoglycoside (p < 0.0001; R2=0.11). An in vitro model of aminoglycoside-induced nephrotoxicity was developed using a conditionally immortalized proximal tubule epithelial cell line (ciPTECs). Dose and time-dependent toxicity was demonstrated with neomycin, gentamicin, and tobramycin (from most to least potent). In rats, the addition of rosuvastatin significantly reduced nephrotoxicity compared to gentamicin alone (p < 0.01). In guinea pigs, dose-dependent inhibition of gentamicin-induced nephrotoxicity was seen with rosuvastatin (at a minimum concentration of 0.94mg/kg/day, p < 0.0001), but not with simvastatin. In vitro models demonstrated that neither rosuvastatin nor atorvastatin had any effect on the minimum inhibitory concentration of tobramycin for Pseudomonas aeruginosa. Conclusion: Urinary KIM-1 has shown potential as a biomarker of both acute and chronic proximal tubular injury associated with exposure to aminoglycosides in children. Inhibition of aminoglycoside-induced nephrotoxicity by statins was demonstrated in further animal models, allowing the selection of a statin and dose (rosuvastatin 10mg) which have been taken forward into a clinical trial which will test this hypothesis in children with CF, utilising urinary KIM-1 as the primary outcome measure.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:706631 |
| Date | January 2015 |
| Creators | McWilliam, Stephen |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/2049479/ |
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