title: Increased permeability of primary cultured brain microvessel endothelial cell monolayers following TNF-alpha exposure.
abstract: TNF-alpha is a cytokine that produces increased permeability in the peripheral vasculature; however, little is known about the effects of TNF-alpha on the blood-brain barrier (BBB). Using primary cultured bovine brain microvessel endothelial cells (BBMEC) as an in vitro model of the BBB, this study shows that TNF-alpha produces a reversible increase in the permeability of the brain microvessel endothelial cells. The BBMEC monolayers were pre-treated with 100 ng/ml of TNF-alpha for periods ranging from 2 to 12 hours. Permeability was assessed using three molecular weight markers, fluorescein (376 MW), fluorescein-dextran (FDX-4400; 4400 MW), and FDX-70000 (MW 70000). The permeability of BBMEC monolayers to all three fluorescent markers was increased two-fold or greater in the TNF-alpha treatment group compared to control monolayers receiving no TNF-alpha. Significant changes in permeability were also observed with TNF-alpha concentrations as low as 1 ng/ml. These results suggest that TNF-alpha acts directly on the brain microvessel endothelial cells in a dynamic manner to produce a reversible increase in permeability. Exposure of either the lumenal or ablumenal side of BBMEC monolayers to TNF-alpha resulted in similar increases in permeability to small macromolecules, e.g. fluorescein. However, when a higher molecular weight marker was used (e.g. FDX-3000), there was a greater response following lumenal exposure to TNF-alpha. Together, these studies demonstrate a reversible and time dependent increase in brain microvessel endothelial cell permeability following exposure to TNF-alpha. Such results appear to be due to TNF's direct interaction with the brain microvessel endothelial cell.
authors.affiliation: Department of Pharmaceutical Science, College of Pharmacy, University of Nebraska Medical Center, Omaha 68198-6025, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Mark
authors.forename: D W
authors.initials: DW
authors.lastname: Miller
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply*; D002199:Capillary Permeability / Q000187:drug effects*; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D014409:Tumor Necrosis Factor-alpha