CYTOSKELETAL REARRANGEMENT MEDIATES HUMAN MICROVASCULAR ENDOTHELIAL TIGHT JUNCTION MODULATION BY CYTOKINES

The tight junction (TJ) is a specialized intercellular structure respo nsible for the regulation of ionic and macromolecular Aux across cell monolayers. Because plasma leakage is believed to occur mainly across the microvasculature, we hypothesized that microvascular endothelial c ells (MVEC) may form more intact, regulatable TJ than other endothelia l cell (EC) types, allowing further insight; into the control of EC pe rmeability. Primary cultures of MVEC monolayers produced transmonolaye r electrical resistances (TER) of 120-155 Omega.cm(2), similar to 10 t imes that of large-vessel EC. Treatment with tumor necrosis factor and interferon-gamma caused a 50% decrease in the TER and a striking frag mentation of the basal, continuous interendothelial cell zonula occlud ens-1 protein (ZO-1) distribution determined by immunofluorescence. Fr agmentation was inhibited by cytochalasin D, and confocal microscopy d emonstrated a colocalization between F actin and ZO-1. These findings suggest that the F actin cytoskeleton plays a central role in endothel ial TJ barrier regulation and that dynamic cytoskeletal alterations ma y primarily control vascular permeability.