PDE2 inhibition reduced TNF-α and thrombin-induced F-actin and VE-cadherin redistribution. HUVECs were grown to confluency on gelatin-coated Thermanox slides, stained for F-actin and VE-cadherin, and visualized by double immunofluorescence (630-fold magnification). Cells treated with vehicle (A) or PDP 1 μM (B) did not show stress fibers or intercellular gap formation as visualized with F-actin–specific phalloidin Alexa 546 (red) and VE-cadherin (green). TNF-α (10 ng/mL, 2 hours) (C) or thrombin stimulation (0.75 U/mL, 15 minutes) (E) caused a massive increase of stress fibers, redistribution of VE-cadherin, and gap formation. Pretreatment with 1 μM PDP for 30 minutes before TNF-α (D) or thrombin (F) stimulation prevented VE-cadherin redistribution and gap formation, reduced stress fibers, and maintained the peripheral dense band. Representative fields of HUVEC monolayers of 3 experiments are shown. Bars = 20 μm.