Time-series proteomic analysis of body fluid extracellular vesicles in amyotrophic lateral sclerosis

Extracellular vesicles (EVs) hold the potential for elucidating the pathogenesis and serving as biomarkers of amyotrophic lateral sclerosis (ALS). Notably, the comparative and longitudinal alterations in the protein profiles of EVs in serum (sEVs) and CSF (cEVs) of sporadic ALS (SALS) patients remain unexplored. This study sought to reveal such changes by collecting serum and CSF at fixed intervals from 10 controls and 20 SALS patients participating in the Ropinirole Hydrochloride Remedy for Amyotrophic Lateral Sclerosis trial. We also aimed to reveal longitudinal changes with disease progression and the effects of ropinirole hydrochloride (ROPI, a dopamine D2 receptor agonist identified as an anti-ALS drug candidate using induced pluripotent stem cell drug discovery) on protein profiles of EVs. Comprehensive proteomic analyses of EVs extracted from these samples were conducted using liquid chromatography-mass spectrometry to trace longitudinal shifts linked to disease progression and the influence of ROPI on EV protein profiles. The findings revealed notable disparities but high congruity in sEV and cEV protein profiles concerning disease status, time, and ROPI administration. Moreover, the sEV and cEV protein profiles converged over time in SALS patients, at least in part, suggestive of a loosening of the blood–brain barrier. In SALS patients, both sEVs and cEVs presented elevated inflammation-related protein levels but reduced levels of proteins associated with the unfolded protein response. These results mirrored the longitudinal changes after disease onset and correlated with the revised ALS Functional Rating Scale at sampling time, suggesting a link to the onset and progression of SALS. ROPI appeared to counteract these changes, attenuating inflammation-related protein levels and boosting those tied to the unfolded protein response in SALS, suggesting an anti-ALS effect on EV protein profiles. Reverse translational research using induced pluripotent stem cell-derived astrocytes indicated that these changes may partly reflect the DRD2-dependent neuroinflammatory inhibitory effects of ROPI. Baseline levels of OGN in sEVs and FRMPD1 in cEVs correlated with subsequent disease progression, indicating their potential as prognostic biomarkers for SALS. Machine learning-driven biomarker searches and diagnostic classification yielded an accuracy of 90.4% for sEVs and 80.3% for cEVs. Despite the limited sample size, this study is the first to report time-series proteomic alterations in sEVs and cEVs from SALS patients, offering comprehensive insights into SALS pathogenesis, ROPI-induced changes, and potential prognostic and diagnostic biomarkers.