p38 MAPK and Ca2+ contribute to hydrogen peroxide-induced increase of permeability in vascular endothelial cells but ERK does not

To examine the involvement of p38 mitogen-activated protein kinase (p38 MAPK) and extra-cellular signal-regulated kinase (ERK) in the oxidative stress-induced increase of permeability in endothelial cells, the effects of a p38 MAPK inhibitor (SB203580) and ERK inhibitor (PD90859) on the H₂O₂-induced increase of permeability in bovine pulmonary artery endothelial cells (BPAEC) were investigated using a two-compartment system partitioned by a semi-permeable filter. H₂O₂ at 1 mM caused an increase of the permeation rate of fluorescein isothiocyanate (FITC)-labeled dextran 40 through BPAEC monolayers. SB203580 inhibited the H₂O₂-induced increase of permeability but PD98059 did not, though activation (phosphorylation) of both p38 MAPK and ERK was observed in H₂O₂-treated cells in Western blot analysis. An H₂O₂-induced increase of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) was also observed and an intracellular Ca²⁺ chelator (BAPTA-AM) significantly inhibited the H₂O₂-induced increase of permeability. However, it showed no inhibitory effects on the H₂O₂-induced phosphorylation of p38 MAPK and ERK. The H₂O₂-induced increase of [Ca²⁺]_i was not influenced by SB203580 and PD98059. These results indicate that the activation of p38 MAPK and the increase of [Ca²⁺]_i are essential for the H₂O₂-induced increase of endothelial permeability and that ERK is not.