Targeted proteomic analysis of dry blood spot samples collected during long-term spaceflights

Abstract The molecular mechanisms of organismal adaptation to spaceflight (SF) conditions are not fully investigated and remain relevant for study. Newly emerging multi-omics technologies may provide information at the molecular level regarding physiological changes caused by SF factors. The aim of the study was to apply blood proteome analysis using dried blood spots (DBS) micro-sampling technique to study at the molecular level the physiological response to SF conditions for 7 cosmonauts during 169–199 days long-duration missions (one of the cosmonauts participated in a year-long mission). The level of 119 blood proteins was quantified in DBS samples by targeted mass spectrometry based proteomics with a validated MRM assay using stable isotope-labeled peptide standards (SIS). To identify proteins whose concentrations are sensitive to the high physiological stress of landing and takeoff the Mann-Whitney and Cohen's d-size effect tests were used. As a result, 10 proteins (p-value < 0.05 and Cohen's d size > 0.8) were found to be significant. In order to determine additional stress marker proteins, the dynamic changes in protein concentration during SF were analyzed to find proteins whose concentrations change monotonously after stress exposure (takeoff or landing). A simple exponential decay model for protein concentration relaxation was proposed which allows to reveal additional 14 proteins. Intersections of both protein panels mentioned above resulted in a final list of 19 blood proteins that are related to SF factors such as takeoff and landing. The panel includes 2 plasma proteins (Lumican and Insulin-like protein binding growth factor 3) that were previously mentioned in other studies to be related with SF. As far as we know this is the first DBS proteomic study for monitoring adaptive reactions of the organism to long-term SF.