MECHANISMS OF PERTUSSIS TOXIN-INDUCED BARRIER DYSFUNCTION IN BOVINE PULMONARY-ARTERY ENDOTHELIAL-CELL MONOLAYERS

We have previously characterized several G proteins in endothielial ce lls (EC) as substrates for the ADP-ribosyltransferase activity of both pertussis (PT) and cholera toxin and described the modulation of key EC physiological responses, including gap formation and barrier functi on, by these toxins. In this study, we investigated the mechanisms inv olved in PT-mediated regulation of bovine pulmonary artery endothelial cells barrier function. PT caused a dose-dependent increase in albumi n transfer, dependent upon action of the holotoxin, since neither the heat-inactivated PT, the isolated oligomer, nor the protomer induced E C permeability. PT-induced gap formation and barrier dysfunction were additive to either thrombin- or thrombin receptor-activating peptide-i nduced permeability, suggesting that thrombin and PT utilize distinct mechanisms. PT did not result in Ca2+ mobilization or alter either bas al or thrombin-induced myosin light chain phosphorylation. However, PT stimulated protein kinase C (PKC) activation, and both PKC downregula tion and PKC inhibition attenuated PT-induced permeability, indicating that PKC activity is involved in PT-induced barrier dysfunction. Like thrombin-induced permeability, the PT effect was blocked by prior inc reases in adenosine 3',5'-cyclic monophosphate. Thus PT-catalyzed ADP- ribosylation of a G protein (possibly other than G(i)) may regulate cy toskeletal protein interactions, leading to EC barrier dysfunction.