Induction of endothelial-cell permeability by RNA is mediated via VEGF. Confluent BMEC cultures were preincubated for 2 days with (A) antisense oligonucleotide to VEGF-R2 (as-VEGF-R2; 2 μM) or the scrambled nonsense oligonucleotide (scr-VEGF-R2; 2 μM). Permeability changes were analyzed in the absence of additives (−) or following treatment with RNA (50 μg/mL), poly-I:C (25 μg/mL), ssRNA (0.25 μg/mL), or heparin (10 μg/mL), and additionally in the presence of anti-VEGF antibody (10 μg/mL). Values represent the mean (± SEM; n = 24). *P < .05 compared with the corresponding control. (B) Alternatively, BMEC cultures were preincubated for 2 days with the antisense oligonucleotide to VEGF-R1 (as-VEGF-R1; 2 μM) or the scrambled nonsense oligonucleotide (scr-VEGF-R2; 2 μM) and treated as before. Flux determined after 3 hours in the absence of any added compound was set to 100%, and values represent the mean (± SEM; n = 9) for each condition. *P < .05 compared with the corresponding control value.