TUMOR-NECROSIS-FACTOR REDUCES PROTEOGLYCAN SYNTHESIS IN CULTURED ENDOTHELIAL-CELLS

Tumor necrosis factor (TNF)-induced disruption of vascular endothelial barrier function may be due in part to alterations in proteoglycan me tabolism. To test this hypothesis, confluent endothelial cell monolaye rs were exposed for 24 h to 500 or 1,000 U of TNF per milliliter of cu lture medium together with 20 mu Ci (Na2SO4)-S-35. HPLC anion-exchange separation of proteoglycans secreted into media of control as well as TN F-treated cultures revealed one major peak (representing 95% of to tal radioactivity) and one minor peak (representing 5% of total radioa ctivity), which eluted at 0.6 and 0.9 M NaCl, respectively. One single peak was obtained from control as well as TNF-treated endothelial cel l monolayers and eluted at 1.2 M NaCl. TNF treatment did not change th e total quantity of radioactive proteoglycans secreted into the media but significantly decreased the amount of proteoglycans in endothelial cell monolayers. However, TNF treatment did not alter the size or gly cosaminoglycan (GAG) composition oi the proteoglycans either in the me dia or in the cell monolayers. In addition, mRNA levels of specific pr oteoglycans, perlecan and biglycan, were measured upon TNF treatment, using Northern analysis. TNF treatment caused a dose-dependent decreas e in mRNA levels for the core proteins of perlecan, a major heparan su lfate proteoglycan (HSPG), and biglycan in endothelial cultures. These results suggest that TNF decreases production of proteoglycans and al ters normal endothelial cell proteoglycan metabolism which may be suff icient to impair endothelial barrier function. (C) 1995 Wiley-Liss, In c.