Absolute quantification of synuclein proteoforms in plasma in patients with Synucleinopathies by LC-MRM mass spectrometry

Abstract

AbstractBackgroundSynucleinopathies include Parkinson’s disease (PD), Lewy body dementia (LBD) and Multiple system atrophy (MSA). Most studies of synucleinopathies rely on immunoassays to quantify total or oligomeric alpha synuclein. Immunoassay results are variable due to the inconstant nature of antibodies and different studies found higher, lower or equal levels of alpha synuclein between PD and control patients in biological matrixes. Mass spectrometry, has less inherent variability.MethodsTherefore, we developed the first reliable and validated mass spectrometry method to quantify synuclein proteoforms in human plasma using liquid chromatography coupled to mass spectrometry with multiple reaction monitoring mode (LC-MRM) mass spectrometry,ResultsThe study followed European and International guidelines (Food and Drug administration and European Medicines Agency) and paves the way for precise multiplex quantitation of synucleinopathies. Using a cohort of 143 patients with synucleinopathies and controls we found a peptide ratio and combination between α-syn EQVTNVGGAVVTGVTAVAQK and α/β-syn EGVLYVGSK peptides that discriminated PD patients from the other diseases (LBD, MSA and controls). The sensitivity and specificity (Area Under ROC Curve) of the method to distinguish between patients with PD and control patients was 0.84 and 0.76 (0.787), for PD vs LBD the values were 0.7 and 0.68 (0.743), and 0.85 and 0.85 (0.831) for PD vs MSA.ConclusionsThe developed and validated LC-MRM method presented here could be used in clinical to discriminate PD from other synucleinopathies and control patient.