β2-Integrin blockade driven by E-selectin promoter prevents neutrophil sequestration and lung injury in mice

Abstract

Interaction of CD11/CD18 β2 integrins on polymorphonuclear leukocytes (PMNs) with their counterreceptor, intercellular adhesion molecule-1, on the surface of vascular endothelial cells is a critical event mediating stable PMN adhesion and migration across the pulmonary vascular endothelial barrier. Neutrophil inhibitory factor (NIF), a 41-kDa glycoprotein isolated from the canine hookworm (Ancylostoma caninum), binds to the I domain of CD11a and CD11b and inhibits β2 integrin-dependent PMN adhesion. We describe a novel strategy using the endothelial cell-specific E-selectin promoter to induce NIF expression in an inflammation-specific manner in pulmonary vascular endothelial cells. A construct containing NIF cDNA driven by the inducible endothelial cell-specific E-selectin promoter (pESNIF) was transfected into human pulmonary artery endothelial cells (HPAECs). Lipopolysaccharide challenge (known to activate E-selectin) resulted in NIF mRNA and protein expression in transfected HPAECs. NIF expression induced by the E-selectin promoter prevented PMN adhesion to the activated HPAECs, whereas PMNs adhered avidly to activated HPAECs in the absence of NIF expression. To address the utility of this approach in conditionally preventing in vivo PMN sequestration, we injected mice intravenously with cationic liposomes containing the pESNIF construct. Analysis of lung tissue showed that intraperitoneal challenge of Escherichia coli resulted in NIF expression. Inflammation-specific NIF expression induced by the E-selectin promoter prevented lung PMN sequestration and vascular injury induced by E coli challenge. These studies suggest the feasibility of conditionally blocking β2 integrin function at sites where the endothelium is activated and thereby of locally preventing PMN activation and migration responses that lead to tissue inflammation.