Background: Propofol has been widely used in intravenous anesthesia. It possesses antioxidant and immunomodulating effects. This study aimed to investigate whether propofol may attenuate lipopolysaccharide (LPS)-induced endothelial cell barrier dysfunction and the possible mechanisms of such modulation. Methods: Cultured human umbilical vein endothelial cells (HUVECs) were used to assess the following treatments: (i) no additives (negative control), (ii) LPS alone (1 and 10 mu g/ ml), (iii) propofol alone (20 mu g/ml), (iv) intralipid (a solvent of propofol) alone (20 mu g/ml), (v) LPS (10 mu g/ml) combination with propofol (4 and 20 mu g/ml) and (vi) LPS (10 mu g/ml) combination with intralipid (20 mu g/ml). Changes of cell permeability and filamentous actin (F-actin) were determined. Expression of nitrotyrosine proteins and activity of nuclear factor kappa B (NF-kappa B) were analyzed by Western blot and immunocytochemistry. Expression of endothelial nitric-oxide synthase (eNOS) and inducible nitric-oxide synthase (iNOS) were analyzed by reverse transcriptase-polymerase chain reaction. Results: LPS markedly increased the permeability of endothelial cells, the formation of peroxynitrite and depolymerization of F-actin in HUVECs. LPS also significantly increased mRNA of iNOS, protein level of NF-kappa B and decreased mRNA of eNOS (P < 0.05). Propofol at both concentrations (4 and 20 mu g/ml) significantly inhibited the LPS-induced increase in cell permeability and alteration in F-actin organization. Propofol also reduced the LPS-enhanced iNOS mRNA and NF-kappa B protein levels whilst it increased eNOS mRNA expression (P < 0.05). Conclusion: This study demonstrated that propofol, both at therapeutic concentrations and 5 times therapeutic concentrations, inhibited NF-kappa B activation in LPS-stimulated endothelial cells and was found to protect endothelial cells against LPS-induced barrier dysfunction.