A Novel Sphingosine-1-Phosphate Receptor 1 Antagonist Prevents the Proliferation and Relaxation of Vascular Endothelial Cells by Sphingosine-1-Phosphate

A sphingosine-1-phosphate receptor 1 (S1P(1)) antagonist is expected to be an anti-angiogenic compound; however, there are few reports that demonstrated that a S1P(1) inhibitor improved the disease state in an angiogenic animal model. Since we determined that a prototype S1P(1) antagonist was an in vivo angiogenesis inhibitor, we developed the derivatives to acquire more effective compounds. In this report, we show the S1P(1) antagonistic activity of some representatives, especially compound 5 {sodium 4-[(4-butoxyphenyl)thio]-2'-[{4-[(heptylthio)methyl]-2-hydroxyphenyl}(hydroxy)methyl]biphenyl-3-sulfonate}. The IC50 values calculated from an intracellular cyclic AMP measurement assay and a [P-33]sphingosine-1-phosphate (Sph-1-P)/S1P(1) binding assay were 38 and 200 nm, respectively. A subtype specificity test for the other Sph-1-P receptors showed that compound 5 was the S1P(1)-directional antagonist. It also inhibited the proliferation, migration, and tube formation of human umbilical vein endothelial cells stimulated by Sph-1-P with the IC50 values of 18, 650, and 230 nm, respectively. A cytotoxicity assay concurrently performed with a tube formation assay supported the hypothesis that these biological effects were not due to its cytotoxicity. Furthermore, administration (10 mg/kg, intravenously) to anesthetized Sprague-Dawley rats inhibited Sph-1-P-induced hypotension by 100-90% for 30 min. This is presumably through the inhibition of Sph-1-P-induced vasorelaxation, mainly by the blocking of S1P(1) and/or S1P(3). Taken together, these results show that compound 5 is an inhibitor of in vitro and in vivo Sph-1-P signaling, and that it will be useful to elucidate the in vivo effect of Sph-1-P on vascular endothelial cells.