Fig. 5.

APC-induced endothelial barrier protection is mediated by β-arrestins. (A and B) Serum-deprived endothelial cells (EC) transfected with 100 nM nonspecific (ns) or β-arrestin siRNAs were preincubated with or without 20 nM APC for 3 h at 37 °C. Cells were washed and then were stimulated with 10 nM thrombin (Th) or 20 nM APC for 10 min at 37 °C, and endothelial barrier permeability was assessed. Data (mean ± SEM) are expressed as the fraction of response compared with thrombin-induced permeability determined at 10 min from three separate experiments. The differences in thrombin-stimulated endothelial barrier permeability observed in APC-pretreated cells versus untreated control cells were significant (**P < 0.01; ***P < 0.001).