Sphingosine-1-Phosphate Receptor-1 Controls Venous Endothelial Barrier Integrity in Zebrafish

Objective—Endothelial sphingosine-1-phosphate (S1P) receptor-1 (S1P1) affects different vascular functions, including blood vessel maturation and permeability. Here, we characterized the role of the zS1P1 ortholog in vascular development in zebrafish. Methods and Results—zS1P1 is expressed in dorsal aorta and posterior cardinal vein of zebrafish embryos at 24 to 30 hours postfertilization. zS1P1 downregulation by antisense morpholino oligonucleotide injection causes early pericardial edema, lack of blood circulation, alterations of posterior cardinal vein structure, and late generalized edema. Also, zS1P1 morphants are characterized by downregulation of vascular endothelial cadherin (VE-cadherin) and Eph receptor EphB4a expression and by disorganization of zonula occludens 1 junctions in posterior cardinal vein endothelium, with no alterations of dorsal aorta endothelium. VE-cadherin knockdown results in similar vascular alterations, whereas VE-cadherin overexpression is sufficient to rescue venous vascular integrity defects and EphB4a downregulation in zS1P1 morphants. Finally, S1P1 small interfering RNA transfection and the S1P1 antagonist W146 cause EPHB4 receptor down-modulation in human umbilical vein endothelial cells and the assembly of zonula occludens 1 intercellular contacts is prevented by the EPHB4 antagonist TNYL-RAW peptide in these cells. Conclusion—The data demonstrate a nonredundant role of zS1P1 in the regulation of venous endothelial barrier in zebrafish and identify a S1P1/VE-cadherin/EphB4a genetic pathway that controls venous vascular integrity.