Advances in genomics have revealed many of the genetic underpinnings of human disease, but exposomics methods are currently inadequate to obtain a similar level of understanding of environmental contributions to human disease. Exposomics methods are limited by low abundance of xenobiotic metabolites and lack of authentic standards, which precludes identification using solely mass spectrometry-based criteria. Here, we develop and validate a method for enzymatic generation of xenobiotic metabolites for use with high-resolution mass spectrometry (HRMS) for chemical identification. Generated xenobiotic metabolites were used to confirm identities of respective metabolites in mice and human samples based upon accurate mass, retention time and co-occurrence with related xenobiotic metabolites. The results establish a generally applicable enzyme-based identification (EBI) for mass spectrometry identification of xenobiotic metabolites.

Beyond the well-defined role of Eph receptor tyrosine kinases in biological processes, cell migration, adhesion, nothing is known about their implication in liver pathologies. During blood-stage rodent malaria infection, EphB2 mRNA and proteins are upregulated in the liver, a result likely driven by elevated surface expression on macrophages. This is significant for malaria pathogenesis because EphB2-/- mice are protected from malaria-induced liver fibrosis despite having a similar liver parasite burden compared with littermate mice. This protection is correlated with a defect in inflammatory potential of hepatocytes from EphB2-/- mice resulting in a reduction in adhesion molecules, chemokine/chemokine receptors RNA levels and infiltration of leukocytes including Kupffer cells which mediate liver fibrosis during malaria. These observations are recapitulated in the well-established carbon tetrachloride (CCL4) model of liver fibrosis in which EphB2-/- CCL4-treated mice showed a significant reduction of liver fibrosis compared to CCL4-treated littermate mice. EphB2 is predominantly expressed by Kupffer cells and depletion of macrophages abrogates liver EphB2 mRNA and protein increase in malaria infected mice, as well as fibrosis. Altogether these results reinforce the critical role played by EphB2 in promoting liver inflammation and fibrosis. To our knowledge, this work is the first to reveal the potential profibrotic nature of EphB receptor tyrosine kinases in liver injury.