Visualizing Cholesterol in the Brain by On-Tissue Derivatization and Quantitative Mass Spectrometry Imaging.

Roberto Angelini,Thu T A Nguyen,Wei Rao,Luke B Allen,Rathnayake A C Rathnayake,Gilles Frache,Fowzi A Yusuf,Lauren Griffiths,Yuqin Wang,Zeljka Korade,Stephanie M Cologna,Eylan Yutuc,Dana El Assad,William J Griffiths,Benjamin J Cooze,Malcolm R Clench,Jillian Newton,Owain W Howell,Mark F Wyatt

doi:10.1021/acs.analchem.0c05399

Abstract

Despite being a critical molecule in the brain, mass spectrometry imaging (MSI) of cholesterol has been under-reported compared to other lipids due to the difficulty in ionizing the sterol molecule. In the present work, we have employed an on-tissue enzyme-assisted derivatization strategy to improve detection of cholesterol in brain tissue sections. We report distribution and levels of cholesterol across specific structures of the mouse brain, in a model of Niemann-Pick type C1 disease, and during brain development. MSI revealed that in the adult mouse, cholesterol is the highest in the pons and medulla and how its distribution changes during development. Cholesterol was significantly reduced in the corpus callosum and other brain regions in the Npc1 null mouse, confirming hypomyelination at the molecular level. Our study demonstrates the potential of MSI to the study of sterols in neuroscience.

Highlights

Despite being a critical molecule in the brain, mass spectrometry imaging (MSI) of cholesterol has been underreported compared to other lipids due to the difficulty in ionizing the sterol molecule
The enzyme-assisted derivatization for sterol analysis (EADSA)-MSI method presented provides a tool for the quantitative imaging of cholesterol in mouse brain tissue sections
On-tissue EADSA was successfully employed to improve the analytical power of MSI toward sterols, allowing quantitative mapping of cholesterol at pixel sizes down to 30 μm

Summary

Introduction

Despite being a critical molecule in the brain, mass spectrometry imaging (MSI) of cholesterol has been underreported compared to other lipids due to the difficulty in ionizing the sterol molecule. To better understand sterol biochemical and physiological roles, there is a need to match molecular abundance with the exact location To this end, brain dissection can be coupled to gas chromatography (GC) mass spectrometry (MS) or to liquid chromatography (LC) MS.[8,11,12] An alternative method to map sterol concentrations in the brain is by exploiting mass spectrometry imaging (MSI), for example, time-of-flight (ToF) secondary-ion MS (SIMS) MSI, where cholesterol has been detected with high intensities, even at subcellular resolutions. Others have exploited a Girard-T hydrazine to derivatize and visualize by MSI steroid molecules, already possessing an oxo function.[25,26]

Objectives

Methods

Results

Conclusion