Distribution of GABA with Mass Spectrometry Imaging
Based on litterature, we developed a protocol to investigate distribution and quantification of GABA. We used the 4-hydroxy-3-methoxycinnamaldehyde (CA) as a derivatisation reagent to specifically identify GABA on brain tissue and enhance its sensitivity. Thanks to this derivatization strategy, we are able to detect and precisely locate GABA on brain tissue using MALDI-FTICR analysis. For this purpose, it is important to differentiate GABA from endogenous isoforms that have the same exact mass in the literature. Therefore, specific identification of GABA was developed at the same time as the derivati-sation strategy. Indeed, out of 6 isoforms, 2 of them could be confused with GABA aer derivatisation: the 3-aminobutyric acid (BABA) and the 3-amino-isobutyric acid (BAIBA).
GABA (-aminobutyric acid) is one of the major inhibitory neurotransmitter in the Central Nervous System and is involved in neural and mood disorders such as bipolar disorder, schizophrenia, Huntington, and Parkinson diseases. The ability to achieve precise distribution and concentration of this endogenous molecule on tissue may allow a better understanding of disease and drug eicacy. However, to know the localisation of the compounds, it depends on their specificity and sensibility: 2 challenging tasks of Mass Spectrometry Imaging (MSI) based studies. MSI developments are subsequently steered towards enhancement of detection and spatial resolu-tion to enable the analysis of more and more compounds. Endogenous molecule such as neurotrans-mitters, amino acids, and metabolites are known to be diicult to detect by MALDI-MSI; and new approaches are being investigated. Therefore, ImaBiotech has decided to embark on developing strategies for GABA analysis.
To detect GABA on brain tissue, the derivatisation strategy has been used. The reaction between GABA and the derivatisation reagent has increased the signal due to additional charge. Moreover, the dierentiation between isoforms and GABA was, therefore, made though specific fragmentation analysis of derivatisated GABA with the 4-hydroxy-3-methoxycinna-maldehyde. Images of GABA distribution were successfully obtained with MALDI-FTICR-MS analyses to performed locali-sation of GABA on the grey matter. Moreover, distinction between grey and white matter allow visualising the arbor vitae in cerebellum with only slight delocalisation induce by the derivatization method. This strategy allow the localisation on brain tissue of the major inhibitory neurotransmitter in the Central Nervous System and could provide a better unders-tanding of its involvement in neural and mood disorders as bipolar disorder, schizophrenia, Huntington and Parkinson diseases.