Imaging bioactive lipid isomers in acetaminophen-induced liver injury using nano-DESI tandem MS.

Acetaminophen (APAP) overdose is a leading cause of acute liver failure, resulting from the production of a reactive metabolite that induces hepatocyte necrosis. Current clinical treatments for APAP overdose offer limited therapeutic efficacy, highlighting the need for alternative strategies. 4-Methylpyrazole (4-MP, fomepizole) has emerged as a potential intervention to mitigate APAP toxicity in both mouse models and humans. Bioactive lipids, including eicosanoids and specialized proresolving mediators (SPMs), play essential roles in the inflammatory and resolution phases of APAP-induced liver injury. However, the impact of APAP overdose and 4-MP intervention on their distribution in liver tissue is poorly understood. Their low abundance and structural isomerism present challenges for MS imaging (MSI). In this study, we use nanospray desorption electrospray ionization MSI in tandem MS mode for the spatial mapping of eicosanoids and SPMs in liver tissues of mice subjected to moderate APAP overdose with and without 4-MP treatment. Using ammonium fluoride as a solvent dopant, known to enhance analyte signals, and leveraging MS/MS mode for isomer-specific analysis, we effectively detected low-abundance isomeric bioactive species. Our results reveal the localization of eicosanoids and SPMs in centrilobular hepatocytes following APAP overdose, correlating with APAP metabolism and hepatocyte necrosis. Notably, 4-MP treatment restores the spatial distributions of these lipids, supporting its therapeutic potential in modulating lipid-mediated inflammatory processes in APAP overdose. This study provides new insights into the localization of bioactive lipids in APAP-induced liver injury and highlights the power of nanospray desorption electrospray ionization MSI for investigating lipid-driven pathology.