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. 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 microg/ml), (iii) propofol alone (20 microg/ml), (iv) intralipid (a solvent of propofol) alone (20 microg/ml), (v) LPS (10 microg/ml) combination with propofol (4 and 20 microg/ml) and (vi) LPS (10 microg/ml) combination with intralipid (20 microg/ml). Changes of cell permeability and filamentous actin (F-actin) were determined. Expression of nitrotyrosine proteins and activity of nuclear factor kappaB (NF-kappaB) 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. 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-kappaB and decreased mRNA of eNOS (P < 0.05). Propofol at both concentrations (4 and 20 microg/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-kappaB protein levels whilst it increased eNOS mRNA expression (P < 0.05). This study demonstrated that propofol, both at therapeutic concentrations and 5 times therapeutic concentrations, inhibited NF-kappaB activation in LPS-stimulated endothelial cells and was found to protect endothelial cells against LPS-induced barrier dysfunction.