Tumor necrosis factor causes microvascular protein leakage independently of neutrophils or mast cells

Tumor necrosis factor-alpha (TNF-alpha) has been implicated as an important mediator in the development of multiple system organ failure after either severe injury or infection. Using the rat cremaster muscle, we previously showed that systemically administered TNF-alpha caused hypotension, tachypnea, and microvascular protein leakage in association with leukocyte-endothelial adherence. In the current study, we hypothesized that topical administration of TNF-alpha to the cremaster muscle would cause microvascular protein leakage independent of changes in hemodynamic parameters. In addition, histological methods were used to study the role of neutrophils and mast cells in the TNF-alpha-induced microvascular protein leakage. Topically applied low-dose (1 ng/ml) TNF-alpha caused microvascular leakage in the cremaster, without changes in central hemodynamic parameters, but high-dose TNF-alpha (10 ng/ml) did not cause protein leakage. Histological studies did not demonstrate evidence of either neutrophil adhesion or mast cell degranulation in topically applied TNF-alpha-treated cremasters compared to controls. These data suggest that TNF-alpha-induced macromolecular leakage is a dose-dependent phenomenon which can occur independently of neutrophils or mast cell degranulation.