Rapid determination of sphingosine 1-phosphate association with carrier molecules by flow-induced dispersion analysis...

Flow-induced dispersion analysis (FIDA) was used to investigate the association of fluorescein isothiocyanate-labeled signaling lipid sphingosine 1-phosphate (S1P) with its carrier molecules human serum albumin (HSA) and high-density lipoprotein (HDL). Associations were measured in plasma samples of patients after surgery, with sepsis or septic shock. All patients demonstrated a significant shift between the carrier binding: decrease of S1P bound to HSA with a concomitant increase of S1P bound to HDL. The molecular sizes of binding complexes correlated well with the relative amounts of S1P bound to HSA and HDL detected by liquid chromatography-tandem mass spectrometry. Very low complex formation of S1P with HDL was observed in several septic shock patients and correlated with the need for mechanical ventilation and intensive care unit (ICU) mortality. Determination of S1P binding to HSA and HDL by FIDA could therefore be useful in the clinical setting to predict disease progression, severity, and outcome.