TNF-ALPHA RELEASE IN ENDOTOXEMIA CONTRIBUTES TO NEUTROPHIL-DEPENDENT PULMONARY-EDEMA

We examined whether the generation of tumor necrosis factor (TNF-alpha) after lipopolysaccharide (LPS) challenge contributes to increases in lung vascular permeability and water content. Guinea pig lungs perfused at constant flow with Ringer-albumin solution (0.5 g/100 ml) were challenged for 120 min with LPS (Escherichia coli; final concentration 33 ng/ml; n = 5). Lung effluent samples were assayed for TNF-alpha activity using the modified L-929 fibroblast cytolytic assay. TNF-alpha concentrations increased in a time-dependent manner with a peak value of 100 +/- 20 pg/ml noted 90-120 min after LPS. Human neutrophils [polymorphonuclear leukocytes (PMN; 2 x 10(7)] added to the perfusion solution after endotoxin challenge (n = 5) produced a threefold increase in lung tissue myeloperoxidase (MPO) activity over control values. PMN, added after LPS and activated using phorbol 12-myristate 13-acetate (PMA; 5 x 10(-9) M; n = 6), produced three- to sixfold increases in mean pulmonary arterial pressure (P(pa)) and pulmonary capillary pressure (P(cap)), wet weight-to-dry weight ratio (W/D), and the pulmonary capillary filtration coefficient (K(f,c)), over control values (P < 0.05). Activation of PMN with PMA in non-LPS-challenged lungs produced only threefold increases in P(pa) and P(cap) and did not change W/D and K(f,c). Infusion of an anti-TNF-alpha antibody before the LPS challenge reduced by approximately 50% the increases in P(pa), P(cap), MPO content, K(f,c), and lung wet weight gain (P < 0.05). Therefore, endotoxin-induced TNF-alpha generation in lungs significantly contributes to pulmonary sequestration of PMN. Activation of the sequestered PMN increases pulmonary vascular permeability and tissue water content.