Urine and serum biomarkers for acetaminophen hepatotoxicity in rats
markers of liver toxicity are relatively insensitive to the effects of APAP and have limited value in predicting outcomes for patients who have overdosed with the drug. Biochemical profiling (metabolomics) is a zero-based diagnostic approach (i.e. requiring no prior assumptions) that has the potential to simultaneously map changes in multiple biochemical processes that serve as novel biomarkers of liver disease. APAP was administered to groups of 6 rats in a single oral dose of either 50 or 1500 mg/kg. Urine was collected during various periods up to 48h and a single serum sample was also obtained at 48h. Biochemical profiles were determined in urine and serum by LC/MS (ToF) with an ESI source in either positive or negative
mode. Mass spectra at each retention time were matched to a library of around 500 known standards using proprietary software. Data were reduced and visualized by principle component analysis (PCA). Results from urine showed separation of the 1500 mg/kg group from the control and low dose groups within the first 6h collection period. Progressively greater separation occurred from 6-24h and 24-48h. PCA analysis of serum showed similar classifications at 48h. The mechanisms underlying the changes in urine included decreases in homocysteine and cystathione, reflecting
protection against oxidative stress. Amongst the other changes observed, some were representative of effects on phospholipid and nucleic acid turnover. Others mainly involved various pathways of amino acid metabolism. The most striking alteration in urine was a large, rapid increase in cAMP at the high dose and a smaller, transient increase at the low dose. A large increase in cAMP was also observed with the high dose in serum. These results suggest a basis for development of a novel panel of biomarkers for early detection and monitoring of liver toxicity. Samples for this study were kindly provided by NIEHS.