Sphingosine-1-phosphate receptor 3 promotes leukocyte rolling by mobilizing endothelial P-selectin

Sphingosine-1-phosphate (S1P) participates in inflammation; however, its role in leukocyte rolling is still unclear. Here we use intravital microscopy in inflamed mouse cremaster muscle venules and human endothelial cells to show that S1P contributes to P-selectin-dependent leukocyte rolling through endothelial S1P receptor 3 (S1P(3)) and Gα(q), PLCβ and Ca(2+). Intra-arterial S1P administration increases leukocyte rolling, while S1P(3) deficiency or inhibition dramatically reduces it. Mast cells involved in triggering rolling also release S1P that mobilizes P-selectin through S1P(3). Histamine and epinephrine require S1P(3) for full-scale effect accomplishing it by stimulating sphingosine kinase 1 (Sphk1). In a counter-regulatory manner, S1P(1) inhibits cAMP-stimulated Sphk1 and blocks rolling as observed in endothelial-specific S1P(1)(−/−) mice. In agreement with a dominant pro-rolling effect of S1P(3), FTY720 inhibits rolling in control and S1P(1)(−/−) but not in S1P(3)(−/−) mice. Our findings identify S1P as a direct and indirect contributor to leukocyte rolling and characterize the receptors mediating its action.