anti-angiogenesis activity in a rabbit cornea model and inhibition of the swelling of mouse feet in an anti-type II collagen antibody-induced arthritis

lipid which affects cell proliferation and migration, etc., through 5 receptors: sphingosine-1-phosphate receptors 1 (S1P1) to 5 (S1P5). 1) Among these receptors, S1P1 is the most studied and attractive pharmacological target because the S1P1 agonism provokes lymphopeina 2) and immunosuppression in vivo. Meanwhile, S1P1 antagonism is supposed to inhibit angiogenesis. In the case of agonist compounds, the non-selective Sph-1-P receptor agonist FTY720 (fingolimod, Novartis International AG, Basel, Switzerland) is pre-registered as a drug of multiple sclerosis. Additionally, the S1P1 specific agonist R-3477 (Actelion Pharmaceuticals Ltd., Basel, Switzerland) is being evaluated in Phase II and I studies as an immunosuppressant for autoimmune disease and organ transplantation, respectively. In the case of antagonist compounds, a preclinical report showed that the small interfering RNA for S1P1 inhibited tumor growth ; nevertheless, there have been no clinical reports on a chemical compound for the treatment of angiogenic diseases, such as diabetic retinopathy and solid tumors. This is presumably because there are few S1P1 antagonists that are potent and selective in vivo. Both S1P1 and S1P3 also play a role in cardiovascular regulation. The intravenous (i.v.) administration of Sph-1-P at high doses of 100—200 mg/kg caused bradycardia in anesthetized rats. Moreover, the heart rate of S1P3 homozygous knockout mice was unchanged by Sph-1-P administration. These results indicate that Sph-1-P caused bradycardia via S1P3 in the heart, at least in the case of mice. On the other hand, i.v. administration of Sph-1-P at a low dose of 10 mg/kg provoked transient hypotension without affecting the heart rate in anesthetized rats. In this case, it is expected that Sph1-P caused vasodilation on the vascular endothelial cells via S1P1 and S1P3, followed by activation of the endothelial isoform of nitric oxide synthase and NO production. We previously reported that a S1P1 antagonist, designated as chemical lead 2, showed anti-angiogenesis activity in a rabbit cornea model and inhibition of the swelling of mouse feet in an anti-type II collagen antibody-induced arthritis model. Afterwards, we synthesized derivatives of chemical lead 2 to obtain more effective S1P1 antagonists and determined the representatives, named as compounds 1 to 5. The aim of this study is to elucidate whether the derivatives inhibit the effect of Sph-1-P both in vitro and in vivo. Therefore, here we describe the Sph-1-P antagonistic activity of the representative derivatives, compounds 1 to 5, through several in vitro and in vivo assays focusing on the proliferation, migration, tube formation, and relaxation of vascular endothelial cells.