Received for publication January 10, 2006.
Revised May 19, 2006.
Accepted for publication May 22, 2006.

Evaluation of original dual thromboxane A₂ modulators as anti-angiogenic agents

Abstract

Angiogenesis is a promising target for the therapy of several diseases including cancer. This study was undertaken to characterize the anti-angiogenic properties of a series of original dual thromboxane A₂ (TXA₂) inhibitors derived from torasemide, a marketed loop diuretic with TXA₂ antagonistic properties, by evaluating their effects on human endothelial cell migration, adhesion and viability in vitro, as well as in the ex vivo rat aortic ring assay. All drugs tested exhibited a marked affinity toward human platelet TXA₂ receptor, significantly prevented platelet aggregation induced by U-46,619, a stable TXA₂ receptor agonist, and inhibited platelet TXA₂ synthase without affecting COX-1 or COX-2 enzymatic activities. These dual TXA₂ inhibitors dose-dependently inhibited endothelial cell migration in chemotaxis assays using VEGF as chemoattractant but failed to affect cell adhesion and viability. Highest rates of cell migration inhibition were obtained with original compounds BM-567 and BM-573 (50.3% and 59.4% inhibition, respectively) when used at the final concentration of 10 µM. In addition, pretreatment of endothelial cells with these 2 drugs significantly prevented U-46,619-induced intracellular Ca²⁺ pool mobilization, thus suggesting a mechanistic link between inhibition of the TXA₂ pathway and reduced endothelial cell migration. Treatment of rat aortic explants with U-46,619 significantly enhanced vessel sprouting while aortic rings treated with some of the compounds, including BM-567 and BM-573, showed a significant decrease in vessel sprouting, which was not reversed by the addition of VEGF. These data suggest that our original dual TXA₂ inhibitors bear anti-angiogenic properties, mainly by inhibiting endothelial cell migration.

Key words: HUVECs adhesion, HUVECs migration, Thromboxane A2, angiogenesis, rat aortic ring assay, tumor angiogenesis