IN-VIVO EXPRESSION OF NEUTROPHIL INHIBITORY FACTOR VIA GENE-TRANSFER PREVENTS LIPOPOLYSACCHARIDE-INDUCED LUNG NEUTROPHIL INFILTRATION AND INJURY BY A BETA(2) INTEGRIN-DEPENDENT MECHANISM

The binding of beta(2) (CD18) integrins on PMN cell membrane to interc ellular adhesion molecule (ICAM) counter-receptors on the surface of v ascular endothelial cells mediates PMN adhesion to endothelial cells. Neutrophil inhibitory factor (NIF), a 41-kD glycoprotein isolated from the canine hookworm (Ancylostoma caninum), is a beta(2) integrin anta gonist that inhibits PMN adhesion to endothelial cells. We transferred the NIF gene into CD1 mouse lungs by intravenous injection of cationi c liposomes to study the effects of in vivo NIF expression on LPS-indu ced lung PMN sequestration and the development of lung injury. RT-PCR and Northern blot analysis indicated the lung-selective expression of the NIF transgene, and immunocytochemistry showed prominent NIF expres sion in pulmonary microvessel endothelial cells. NIF staining was also observed in intraluminal leukocytes present in pulmonary microvessels . This may be the result of NIF binding to leukocytes after its secret ion from the transduced lung cells, since there was no evidence of NIF gene expression in circulating leukocytes. Pulmonary vascular NIF exp ression abrogated the lung tissue PMN uptake and airspace migration of PMN and prevented lung vascular injury (as measured by the lung tissu e uptake of [I-125]labeled albumin) after the intraperitoneal LPS chal lenge (200 mu g/mouse). Expression of a control protein, chloramphenic ol acetyltransferase (CAT), by the same strategy, had no effect on the se responses. In vitro studies showed that NIF prevented mouse PMN adh esion consistent with the inhibition of lung uptake after LPS challeng e in NIF transgene-expressing mice. We conclude that pulmonary vascula r expression of NIF, a specific beta(2) integrinbinding protein, is a potentially useful gene transfer strategy in modulating the infiltrati on of PMN across the alveolar-capillary epithelial barrier and in prev enting lung vascular endothelial injury.