NEUTROPHIL INHIBITORY FACTOR PREVENTS NEUTROPHIL-DEPENDENT LUNG INJURY

Neutrophil inhibitory factor (NIF) is a recently cloned 41-kDa protein from the canine hookworm that binds CD11b/CD18 and inhibits CD11b/CD1 8-dependent neutrophil adhesion. We evaluated NIF's effects on neutrop hil-dependent lung injury in guinea pigs. Pulmonary vascular endotheli al CD54 (ICAM-1) was induced in buffer-perfused lungs by 90-min exposu re to 1000 U/ml TNF-alpha. Human neutrophils (2 x 10(7)) were added to the perfusate and activated by 5 x 10(-9) PMA; in some lungs, the neu trophils were pretreated with NIF (100 nM) before their addition to th e perfusate. Lung injury was assessed by wet:dry weight ratio, and neu trophil uptake by lung myeloperoxidase (MPO) activity. HUVEC exposed t o TNF-alpha for 90 min were assayed for neutrophil adhesion, and we co mpared PMA-stimulated neutrophil adhesion to endothelial cells and fib rinogen-coated plates, PMA-induced pulmonary edema (lung wet:dry ratio increased from 8.8 +/- 0.7 to 18.8 +/- 4.4) was inhibited by NIF (10. 0 +/- 1.0), Lung MPO activity concomitantly decreased from 17.1 +/- 6. 1 to 8.7 +/- 1.8 U/mg dry lung tissue in the NIF-treated group, simila r to controls (6.9 +/- 2.0). Endothelial monolayer experiments confirm ed that NIF reduced neutrophil adherence (basal adhesion of 11 +/- 3% increased to 30 +/- 5% with TNF-alpha pretreatment of endothelial cell s, an increase that was reduced to 10 +/- 4% with NIF). Moreover, NIF prevented PMA-induced neutrophil adhesion to fibrinogen, a CD11b/CD18- dependent event, but produced a smaller decrease in adherence to endot helial cells, which also involves CD11a/CD18 integrins. These studies indicate that NIF prevents neutrophil-dependent lung vascular injury b y inhibiting neutrophil adhesion to the TNF-alpha-activated endotheliu m.