Tumor necrosis factor-alpha induces cyclooxygenase-2 expression and prostaglandin release in brain microvessel endothelial cells.

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-alpha (TNF-alpha). Compared with control monolayers, BBMECs exposed to TNF-alpha formed actin filament tangles and extracellular gaps with a resultant increase in permeability. Both the permeability and cytoskeletal changes observed with TNF-alpha were significantly reduced following pretreatment with NS-398 or indomethacin, inhibitors of cyclooxygenase (COX). Western blot analysis showed that TNF-alpha 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-alpha exposure) as the permeability increases observed with the cytokine. Consistent with the increased expression of COX-2, BBMEC monolayers exposed to TNF-alpha had significantly greater secretion and release of prostaglandin E(2) (PGE(2)) and prostaglandin F(2alpha) (PGF(2alpha)). Furthermore, BBMEC monolayers treated with PGE(2) or PGF(2alpha) showed significant increases in permeability and cytoskeletal structural changes when compared with control monolayers. Together, these results suggest that the TNF-alpha-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.