Organic washes of tissue sections for comprehensive analysis of small molecule metabolites by MALDI MS imaging of rat brain following status epilepticus
In-situ detection and in particular comprehensive analysis of small molecule metabolites (SMMs, m/z < 500) using matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) remain a challenge, mainly due to ion suppression effects from more abundant molecules in tissue section like lipids.
A strategy based on organic washes to remove most ionization-suppressing lipids from tissue section was firstly explored for improved analysis of SMMs by MALDI MSI.
The tissue sections after rinse with different organic solvents were analyzed by MALDI MSI, and the results were compared for the optimized washing conditions.
The rinse with chloroform for 15 s at − 20 °C significantly removed most glycerophospholipids and glycerolipids from tissue section. Consequentially, ATP-related energy metabolites, amino acids and derivatives, glucose derivatives, glycolysis pathway metabolites and other SMMs were able to be well-visualized with enhanced ion intensity and good reproducibility. The organic washes-based MALDI MSI was applied to the metabolic pathway analysis in rat brain following status epilepticus (SE) model, which was, as far as we know, the first report about in-situ detection of a broad range of metabolites in the model of SE by MALDI MSI technique. The alterations of cyclic adenosine monophosphate (cyclic AMP), inosine, glutamine, glutathione, taurine and spermine during SE were observed.
A simple organic washing protocol enables comprehensive analysis of tissue SMMs in MALDI MSI by removing ionization-suppressing lipids. The application in the SE model indicates that MALDI MSI analysis potentially provides new insight for understanding the disease mechanism.
KeywordsMALDI MSI Metabolites Organic wash Status epilepticus
This work was supported by National Natural Science Foundation of China (Grant Nos. 21575146, 21635008 and 21621062).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest and no conflict of financial interest.
The animal experiments were performed according to “the Guide for the Care and Use of Laboratory Animals” from the Association for Assessment and Accreditation of Laboratory Animal Care and ethical approval of the present study was obtained from the Animal Care and Use Committee at National Center for Nanoscience and Technology of China.
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