Redox regulation of reactive oxygen species-induced p38 MAP kinase activation and barrier dysfunction in lung microvascular endothelial cells

Reactive oxygen species (ROS)-mediated compromise of endothelial barrier integrity has been implicated in a number of pulmonary disorders, including adult respiratory distress syndrome, pulmonary edema, and vasculitis. The mechanisms by which ROS increase endothelial permeability are unclear. We hypothesized that ROS-induced changes in cellular redox status (thiols) may contribute to endothelial barrier dysfunction. To test this hypothesis, we used N-acetylcysteine (NAC) and diamide to modulate intracellular levels of cellular glutathione (GSH) and investigated hydrogen peroxide (H2O2)-mediated mitogen-activated protein kinase (MAPK) activation and transendothelial electrical resistance (TER). Exposure of bovine lung microvascular endothelial cells (BLMVECs) to H2O2 in a dose- and time-dependent fashion, increased endothelial permeability. Pretreatment of BLMVECs with NAC (5 mM) for 1 h resulted in partial attenuation of H2O2-induced TER (a measure of increase in permeability) and GSH. Furthermore, treatment of BLMVECs with diamide, which is known to reduce the intracellular GSH, resulted in significant reduction in TER, which was prevented by NAC. To understand further the role of MAPKs in ROS-induced barrier dysfunction, we examined the role of extracellular signal-regulated kinase (ERK) and p38 MAPK on H2O2- and diamide-mediated permeability changes. Both H2O2 and diamide, in a dose-dependent manner, activated ERK and p38 MAPK in BLMVECs. However, SB203580, an inhibitor of p38 MAPK, but not PD98059, blocked H2O2- and diamide-induced TER. Also, NAC prevented H2O2- and diamide-induced p38 MAPK, but not ERK activation. These results suggest a role for redox regulation of p38 MAPK in ROS-dependent endothelial barrier dysfunction.