Abstract

Primary cultured bovine brain microvessel endothelial cells (BBMECs), were used as an in vitro model of the blood-brain barrier to examine the involvement of eicosanoids in the permeability and cytoskeletal structural changes observed following exposure to tumor necrosis factor-α (TNF-α). Compared with control monolayers, BBMECs exposed to TNF-α formed actin filament tangles and extracellular gaps with a resultant increase in permeability. Both the permeability and cytoskeletal changes observed with TNF-α were significantly reduced following pretreatment with NS-398 or indomethacin, inhibitors of cyclooxygenase (COX). Western blot analysis showed that TNF-α had no apparent effect on the expression of COX-1, but did induce the expression of COX-2 in the BBMECs. The induction of COX-2 expression occurred within the same time frame (2–4 h following TNF-α exposure) as the permeability increases observed with the cytokine. Consistent with the increased expression of COX-2, BBMEC monolayers exposed to TNF-α had significantly greater secretion and release of prostaglandin E₂ (PGE₂) and prostaglandin F_2α (PGF_2α). Furthermore, BBMEC monolayers treated with PGE₂ or PGF_2α showed significant increases in permeability and cytoskeletal structural changes when compared with control monolayers. Together, these results suggest that the TNF-α-induced permeability and cytoskeletal structural effects are due, in part, to an induction of the COX-2 system and increased release of prostaglandins in the cerebral microvasculature.