Stable Isotope-Assisted Metabolomics for Deciphering Xenobiotic Metabolism in Mammalian Cell Culture

Xenobiotics are ubiquitous in the environment and modified abundantly in the human body by phase I and II metabolism. Liquid chromatography coupled to high resolution mass spectrometry is a powerful tool to investigate these biotransformation products. Here, we present a workflow based on stable isotope-assisted metabolomics and the bioinformatics tool MetExtract II for deciphering all measureable xenobiotic metabolites produced by human cells in vitro in an untargeted manner. The value of this workflow is demonstrated by the detailed investigation of the metabolism of deoxynivalenol (DON), an abundant food contaminant, in two cell models (HepG2, HT29). Detected known metabolites included DON-3-sulfate, DON-10-sulfonate, and DON-10-glutathione as well as DON-cysteine. Conjugation with amino acids and antibiotics was observed and confirmed for the first time. The approach allows for the generic and untargeted elucidation of human xenobiotic products in tissue culture. It may be easily applied to other fields of research including drug metabolism, personalized medicine and systems biology and serves to better understand the relevance of in vitro experiments.