Pyrylium-Based Derivatization for Rapid Labeling and Enhanced Detection of Cholesterol in Mass Spectrometry Imaging

Abstract

Cholesterol in the central nervous system has been increasingly found to be closely related to neurodegenerative diseases. Defects in cholesterol metabolism can cause structural and functional disorders of the central nervous system. The detection of abnormal cholesterol is of great significance for the cognition of physiological and pathological states of organisms, and the spatial distribution of cholesterol can also provide more clues for our understanding of the complex mechanism of disease. Here, we developed a novel pyrylium-based derivatization reagent combined with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to visualize cholesterol in biological tissues. A new class of charged hydroxyl derivatization reagents was designed and synthesized, and finally 1-(carboxymethyl)-2,4,6-trimethylpyridinium (CTMP) was screened for tissue derivatization of cholesterol. Different from the shortcomings of traditional hydroxyl labeling methods such as harsh reaction conditions and long reaction time, in our study, we combined the advantages of CTMP itself and the EDCl/HOBt reaction system to achieve instant labeling of cholesterol on tissues through two-step activation. In addition, we also reported changes in cholesterol content in different stages and different brain regions during disease development in SOD1 mutant mouse model. The cholesterol derivatization method we developed provides an efficient way to explore the distribution and spatial metabolic network of cholesterol in biological tissues.

Mass Spectrometry Imaging of Cholesterol and Oxysterols

“…Although primarily used to enable gas-chromatography -MS of sterols/steroids, derivatisation has also been employed to improve the sensitivity of LC-MS and MALDI-MS analysis (28). More recently derivatisation methods have been used to enhance MSI of sterols/steroids (29,30). Many steroids possess a keto (oxo) group, this function is readily derivatised by hydrazine reagents to give a hydrazone, and this form of derivatisation has been widely exploited in steroid biochemistry for decades to enhance substrate polarity (Figure 4) (31,32).…”