Sphingosine-1-phosphate and lysophosphatidic acid stimulate endothelial cell migration

Endothelial cell migration is necessary for the formation of new blood vess els. We investigated the effects of 2 lysophospholipid mediators, sphingosi ne-l -phosphate (S1P) and lysophosphatidic acid (LPA), on endothelial cell migration. S1P and LPA stimulated migration of fetal bovine heart endotheli al cells (FBHEs) in a SD-modified Boyden chamber assay with concentrations as low as 15 nmol/L stimulating a 2-fold change and concentrations in the 1 - to 2-mu mol/L range stimulating 14- to 20-fold changes. S1P specifically stimulated the migration of several endothelial cell strains but did not st imulate the migration of tumor cells or smooth muscle cells. LPA stimulated some endothelial and nonendothelial cell types to migrate. For FBHEs, S1P and LPA were mostly chemokinetic in checkerboard assays. S1P and LPA stimul ated extracellular signal-regulated kinase 1/2 phosphorylation and enhanced paxillin localization to focal contacts, with no discernible change in the actin cytoskeleton in FBHEs. To characterize responsible receptor-dependen t signaling pathways, we investigated the involvement of Gi, Rho, and phosp hoinositide 3-OH kinase in S1P- and LPA-stimulated migration. Although pert urbation of all 3 signaling molecules resulted in decreased migration, the mechanisms underlying the decreased migration were different. Pertussis tox in treatment, to target Gi, caused endothelial cells to develop dense bundl es of F-actin and distribute paxillin staining to the cell periphery in res ponse to S1P or LPA. Modification of Rho with C3 toxin disrupted the actin cytoskeleton. Inhibition of phosphoinositide 3-OH kinase decreased S1P- or LPA-induced endothelial cell migration with only minor disruption of the ac tin cytoskeleton. Inhibition of extracellular signal-regulated kinase kinas e with PD98059 caused a loss of phosphorylation of extracellular signal-reg ulated kinase 1/2, similar to pertussis toxin, but only a minimal decrease in migration. These results indicate that S1P and, for some cells, LPA stim ulate migration of endothelial cells through a mechanism that likely requir es a balance between G(i) and Rho signaling to achieve the cytoskeletal rem odeling necessary for cell migration.