Acyl Peptide Enzyme Hydrolase (APEH) activity is inhibited by lipid metabolites and peroxidation products

Acyl Peptide Enzyme Hydrolase (APEH) activity is decreased in certain diseases but the mechanism and impact behind this loss in activity is not well understood. We hypothesized that lipid metabolites and lipid peroxidation products produced in inflammatory diseases may bind to and inhibit APEH activity. In vitro studies carried out in mammalian cell lysates, as well as with purified APEH protein, support our hypothesis that cellular lipid metabolites and lipid peroxidation products significantly decrease APEH activity. Enzymatic assays and molecular docking in silico analysis suggest that larger lipid metabolites are the best APEH inhibitors. APEH activity was measured in vivo in mice exposed to chronic e-cigarette vapor, as e-cigarettes are known to increase reactive oxygen species and lipid peroxidation products. In support of our in vitro findings, APEH activity in our mouse model demonstrates decreased APEH activity in the brains of mice exposed to e-cigarette vapor. These results provide a novel mechanism by which APEH activity may be inhibited in disease states. Furthermore, APEH inhibition may contribute to disease development and progression in pathologies associated with redox imbalances and can potentially act as biomarker for oxidative stress in disease.