Figure 6.

Effects of prolonged exposure to FTY720-P and SEW2871 on endothelial cell cytoskeletal rearrangements induced by thrombin. HUVEC actin filaments were visualized with FITC-labeled phalloidin staining. Baseline cortical arrangement of the actin cytoskeleton was unaffected by 24 hours of exposure to FTY720 or SEW2871 (top row). Stimulation with thrombin (1 U/ml) for 1 hour induced stress fiber formation with cellular distortion and paracellular gap formation, a process inhibited by costimulation with S1P. Pretreating HUVEC monolayers with FTY720 or SEW2871 for 24 hours eliminated the ability of S1P to attenuate thrombin-induced cytoskeletal changes. Images are representative of two independent experiments. Scale bar = 50 μm.