EXPOSURE OF TUMOR-NECROSIS-FACTOR-ALPHA TO LUMINAL MEMBRANE OF BOVINE BRAIN CAPILLARY ENDOTHELIAL-CELLS COCULTURED WITH ASTROCYTES INDUCES A DELAYED INCREASE OF PERMEABILITY AND CYTOPLASMIC STRESS FIBER FORMATION OF ACTIN

Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, has long been known to be involved in the pathogenesis of central nervous system infections and of certain neurodegenerative diseases. However, the possible role of the blood-brain barrier (BBB), the active interface between the blood circulation and brain tissue, remained unknown during these pathological conditions. In our in vitro reconstructed BBB model, 1-hr exposure of recombinant human TNF-alpha (in concentrations of 50, 250, and 500 U/ml, respectively) to the luminal membrane of bovine brain capillary endothelial cells (BBCEC) did not change significantly the transendothelial flux of either sucrose (m.w. 342 Da), or inulin (m.w. 5 kDa) up to 4 hr (early phase), except for a slight decrease (P < 0.05) in sucrose permeation at 2-4 hr with the highest dose of TNF-alpha. On the other hand, at 16 hr after the 1-hr challenge with TNF-alpha (delayed phase) at all 3 concentrations, significant increase was induced in the permeability of BBCEC monolayers for both markers. These changes of permeability were accompanied by a selective reorganization of F-actin filaments into stress fibers, while the intracellular distribution of vimentin remained similar to the control. These results suggest that BBCEC can respond directly to TNF-alpha by a delayed increase of permeability and reorganization of actin filaments. (C) 1995 Wiley-Liss, Inc.