The suppressive effect of sphingosine 1-phosphate on monocyte-endothelium adhesion may be mediated by the rearrangement of the endothelial integrins alpha(5)beta(1) and alpha(v)beta(3).
BACKGROUND
Sphingosine 1-phosphate (S1P), known to play important roles in vascular biology, is a bioactive lysophospholipid mediator that maintains endothelial integrity via its cell-surface receptors (S1Ps). In this in vitro study, we aimed to examine the role of S1P in monocyte-endothelium adhesion, which is an important event in the pathophysiology of atherosclerosis.


RESULTS
S1P pretreatment of human umbilical vein endothelial cells (ECs), but not U937 cells, effectively suppressed U937-EC adhesion independently from the expression of adhesion molecules, namely ICAM-1, VCAM-1, and E-selectin. This S1P-induced suppressive effect was inhibited by the blockage of S1P(1) and S1P(3) receptors and the specific inhibitors of G(i) protein, Src family proteins, phosphatidylinositol 3-kinase, and Rac1, indicating involvement of these key downstream pathways. Moreover, the RGD peptide and antibodies, which neutralize adhesion via alpha(5)beta(1) and alpha(v)beta(3), effectively inhibited U937-EC adhesion with a degree similar to S1P pretreatment. Both an adhesion assay and flow-cytometric analysis demonstrated that U937 cells adhered through integrins alpha(5)beta(1) and alpha(v)beta(3) expressed on the apical surface of monolayer ECs, and S1P shifted the localization of these integrins from the apical surface to the basal surface.


CONCLUSIONS
From the present results, we propose that S1P may contribute to the maintenance of vascular integrity and the regulation of atherogenesis through the rearrangement of endothelial integrins.
Aoki
S
S
Department of Clinical Laboratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Yatomi
Y
Y
Shimosawa
T
T
Yamashita
H
H
Kitayama
J
J
Tsuno
N H
NH
Takahashi
K
K
Ozaki
Y
Y
D000328:Adult; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D039081:Integrin alpha5beta1 / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D019169:Jurkat Cells; D008246:Lysophospholipids / Q000494:pharmacology*; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020298:U937 Cells
D039081:Integrin alpha5beta1; D039302:Integrin alphaVbeta3; D008246:Lysophospholipids; C060506:sphingosine 1-phosphate; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D013110:Sphingosine