Tumor necrosis factor inhibits a polymorphonuclear leukocyte-dependent airway edema in guinea pigs

Intravenously administered endotoxin inhibits the polymorphonuclear leukocyte (PMN)-dependent airway edema produced in guinea pigs exposed to toluene diisocyanate (TDI). Tumor necrosis factor (TNF) is produced in vivo by peripheral blood monocytes and tissue macrophages stimulated with endotoxin and has been shown to activate PMN's and vascular endothelial cells. To determine whether the inhibition of airway edema is mediated by TNF, guinea pigs were treated with intravenous saline or 75,000 U/kg recombinant human TNF 1.5 h before exposure to air or 3 ppm TDI for 1 h. Animals were then injected intravenously with 50 mg/kg Evans blue dye as a marker of protein extravasation. Saline-treated animals exposed to TDI had a significant increase in tracheal Evans blue dye extravasation (85 +/- 6.5 micrograms dye/g trachea, mean +/- SE) compared with saline-treated animals exposed to air (31.3 +/- 2.5, P less than 0.001). The tracheal extravasation of Evans blue dye was significantly inhibited (P less than 0.05) in TDI-exposed animals treated with TNF (64.7 +/- 7.5). Neither heat-inactivated TNF (104.9 +/- 9.5) nor TNF neutralized with a monoclonal antibody against TNF (99.7 +/- 17.9) inhibited TDI-induced airway edema. In addition, treatment with 15,000 U/kg (99.9 +/- 21.3) or 150,000 U/kg (103.2 +/- 17.6) interleukin 1, a monokine also produced in response to endotoxin, did not prevent airway edema. These results suggest that TNF released in response to endotoxin mediates endotoxin's inhibition of a PMN-dependent airway edema.