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. The lipid sphingosine-1-phosphate (S1P) is known to mediate leukocyte recruitment in inflammation. Here, Nussbaum et al. show that S1P, via its receptor S1P3, also regulates leukocyte rolling on endothelium by promoting the presentation of the adhesion molecule P-selectin on the endothelial surface.