Endothelial P2Y2 receptor regulates LPS-induced neutrophil transendothelial migration in vitro

Previous studies showed that P2 receptors are involved in neutrophil migration via stimulation of chemokine release and by facilitating chemoattractant gradient sensing. Here, we have investigated whether these receptors are involved in LPS-induced neutrophil transendothelial migration (TEM) using a Boyden chamber where neutrophils migrated through a layer of lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cells (HUVECs). In line with a role of P2 receptors, neutrophil TEM was inhibited by the P2 receptor antagonists suramin and reactive blue 2 (RB-2) acting on the basolateral, but not luminal, HUVECs' P2 receptors. HUVECs express P2Y1, P2Y2, P2Y4, P2Y6 and P2Y11. The involvement of P2Y4 was unlikely as this receptor is insensitive to suramin while P2Y1, P2Y6 and P2Y11 were excluded with available selective antagonists, leaving P2Y2 as the only candidate. Indeed, the P2Y2 knockdown in HUVECs inhibited neutrophil TEM compared to control HUVECs transfected with scrambled siRNA. Moreover, UTP, a P2Y2 ligand, markedly potentiated LPS-induced TEM. Interestingly, IL-8 and ICAM-1 had a modest effect on neutrophil TEM in this 3 h assay which was significantly diminished by the inhibition of Rho kinase in HUVECs with Y27632. In summary, endothelial P2Y2 receptors control the early LPS-induced neutrophil TEM in vitro via Rho kinase activation.