IDENTIFYING MARKERS OF MICROGLIA ACTIVATION IN CSF FROM PATIENTS WITH ALZHEIMER'S DISEASE USING A NOVEL MASS SPECTROMETRY APPROACH

Abstract

The aim of the study was to apply the TMTcalibrator+ MS approach to explore the possibility of detecting markers of microglial activation in the CSF, and comparing the levels of such proteins in the CSF of AD patients compared to non-AD controls. We hypothesise that an early event in neurodegenerative pathology involves activation of microglial cells that will secrete distinct proteins into the brain and subsequently into CSF and ultimately plasma. The challenge is how to find these molecules in a readily available biofluid. Traditional unbiased proteomic approaches have struggled to detect low abundance markers due to the high dynamic range of plasma and CSF proteins, and the predominance of plasma albumin and other hyper-abundant proteins. To improve biomarker discovery in peripheral fluids, we developed TMTcalibrator+; a novel MS workflow. Here the use of isobaric Tandem Mass Tags (TMT) allows reference tissue or cell line samples to be labelled and mixed into equivalently labelled samples of peripheral biofluids at a concentration sufficient to ensure the vast majority of MS/MS acquisitions are made on reference-derived peptides. In this study, we analysed the peptides present in the CSF from AD and non-AD patients that are common to activated microglia cells to determine which activated microglial proteins are also found in CSF and which, if any, are differentially expressed in AD compared to individuals with normal cognitive function.