Novel Isotope-Coded Photochemical Derivatization Coupled with LC-MS and MS Imaging Platform Enables Sensitive Quantification and Accurate Localization of Amine Submetabolome in Pancreatic Disease

Alterations in amine metabolite levels are closely associated with the poor progression of pancreatic disease, including acute pancreatitis (AP) and pancreatic cancer (PC). However, effectively quantifying and visualizing these metabolites through mass spectrometry (MS) has proven to be challenging. Here, we have designed a novel and rapid strategy for analyzing the amine submetabolome within liquid chromatography-mass spectrometry (LC-MS) and air-flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) platforms by inducing a pair of isotope-labeling-based photochemical derivatization reagents. The simultaneous introduction of a 4-amino-1-methylpyridinium moiety renders a 160- to 1037-fold higher response in MS. Coupled with full MS-ddMS2 and precursor ion scan modes, this labeling strategy allows for straightforward detection of 423 peaks for indazolone derivatives and identification of 82 amine metabolites in biological samples. The semiquantitation of the 82 amines in plasma from AP patients and healthy controls resulted in the discovery of unreported aromatic amines and aminoaldehydes with significant changes in AP and employing ethanolamine for distinguishing the severities of AP in the early stage. In the MSI platform, the photochemical reagent can efficiently derivatize primary amine metabolites avoiding spatial deviation and significantly enhancing imaging sensitivity in rat brain and kidney. Further joint analysis of amine submetabolome in plasma and pancreas from PC patients by use of these two platforms allowed for identifying the significant metabolite, methylamine. These results together enhance the role of amine-driven biomarker discovery in the diagnosis of pancreatic disease and accelerate the application of on-tissue photochemical derivation in MSI.