Sphingosine-1-phosphate: characterization of its inhibition of platelet aggregation

In this study, the ability of sphingosine-1-phosphate (S1P) to modulate pla telet aggregation induced by other agents in platelet-rich plasma (PRP) was investigated. S1P alone did not stimulate platelet aggregation in PRP. S1P inhibited the platelet aggregation induced by the TRAP peptide (6.75 mu M) , noradrenaline (NA; 12.5 mu M) and the Ca2+ ionophore (5.0-9.5 mu M). S1P also increased the response time of platelets to arachidonic acid (AA), but decreased the response time to PMA, S1P displayed a dual effect on sodium fluoride (NaF)-induced platelet aggregation and had no effect on the aggreg ation induced by ADP or lysophosphatidic acid (LPA). Furthermore, S1P block ed the synergistic interaction of oleyol-lysophosphatidic acid (O-LPA) with the TRAP peptide or noradrenaline, while the synergistic interaction of O- LPA with ADP remained largely unaffected.