Down-regulation of Lyn kinase does not inhibit the LPS-induced increase in endothelial permeability. (A-B) Transfection of Lyn siRNA did not inhibit the LPS-induced TER decline. Confluent HUVECs grown on gold microelectrodes were transfected with control or Lyn siRNA for 48 hours and used for TER measurements. (A) Cells were stimulated with LPS (1 mg/mL) in the presence of FBS (2.5%). (B) Bar graph indicated normalized TER relative to non–LPS-treated groups at 15 hours after LPS stimulation.