Endothelial barrier function: Regulation by shear stress and protein kinase C

Using endothelial cells (EC) cultured on porous microcarrier beads, we have measured the permeability of bovine pulmonary artery EC monolayers exposed to shear stress in a column chromatography system. We previously demonstrated that EC monolayer permeability was dependent upon the level of fluid shear stress to which the cells were exposed (J. Cell. Physiol., 1996). Since EC barrier function is in part regulated by bonds between junctional proteins and cytoskeletal components, we hypothesized that the maintenance of the EC barrier under shear stress may be a dynamic process which involves protein kinase C (PKC). We investigated the effect of PKC inhibition on endothelial permeability under static conditions and under 4.7 dynes/cm² of shear stress using the PKC inhibitor calphostin C (calC). In the static (Transwell) system, the permeability to sodium fluorescein (NaFlsc, M.W. =342) was not affected by calC (control: 2.5 ± 0.3; calC: 23 ± 06; mean ± SEM × 10^-5 cm/s, n=10). However, when EC's on microcarrier beads were exposed to shear stress, inhibition of PKC stimulated a steady increase in permeability which was significantly different (p<.05) from baseline approximately 1 hr after exposure to calC (14.0 ± 3.9 to 30.3 ± 8.4 × 10^-5 cm/s; n=5). Inhibition of PKC may affect the ability of the cell cytoskeleton to remodel and adjust to shear stress.