Accurate quantification of sphingosine-1-phosphate in normal and Fabry disease plasma, cells and tissues by LC-MS/MS with ¹³C-encoded natural S1P as internal standard

We developed a mass spectrometric procedure to quantify sphingosine-1-phosphate (S1P) in biological materials. The use of newly synthesized ¹³C₅ C18-S1P and commercial C17-S1P as internal standards rendered very similar results with respect to linearity, limit of detection and limit of quantitation. Caution is warranted with determination of plasma S1P levels. Earlier it was reported that S1P is elevated in plasma of Fabry disease patients. We investigated this with the improved quantification. No clear conclusion could be drawn for patient plasma samples given the lack of uniformity of blood collection and plasma preparation. To still obtain insight, plasma and tissues were identically collected from α-galactosidase A deficient Fabry mice and matched control animals. No significant difference was observed in plasma S1P levels. A significant 2.3 fold increase was observed in kidney of Fabry mice, but not in liver and heart. Comparative analysis of S1P in cultured fibroblasts from normal subjects and classically affected Fabry disease males revealed no significant difference. In conclusion, accurate quantification of S1P in biological materials is feasible by mass spectrometry using the internal standards ¹³C₅ C18-S1P or C17-S1P. Significant local increases of S1P in the kidney might occur in Fabry disease as suggested by the mouse model.