Peroxynitrite causes endothelial cell monolayer barrier dysfunction

Nitric oxide (·NO) attenuates hydrogen peroxide (H2O2)-mediated barrier dysfunction in cultured porcine pulmonary artery endothelial cells (PAEC) (Gupta MP, Ober MD, Patterson C, Al-Hassani M, Natarajan V, and Hart, CM. Am J Physiol Lung Cell Mol Physiol 280: L116–L126, 2001). However, ·NO rapidly combines with superoxide (O 2 − ) to form the powerful oxidant peroxynitrite (ONOO−), which we hypothesized would cause PAEC monolayer barrier dysfunction. To test this hypothesis, we treated PAEC with ONOO− (500 μM) or 3-morpholinosydnonimine hydrochloride (SIN-1; 1–500 μM). SIN-1-mediated ONOO− formation was confirmed by monitoring the oxidation of dihydrorhodamine 123 to rhodamine. Both ONOO− and SIN-1 increased albumin clearance (P < 0.05) in the absence of cytotoxicity and altered the architecture of the cytoskeletal proteins actin and β-catenin as detected by immunofluorescent confocal imaging. ONOO−-induced barrier dysfunction was partially reversible and was attenuated by cysteine. Both ONOO− and SIN-1 n...