Induction of Endothelial-Leukocyte Interaction by Interferon-\(\gamma\) Requires Coactivation of Nuclear Factor-\(\kappa\)B

Abstract

To determine whether nuclear factor (NF)-(\kappa) B is necessary to confer endothelial cell responsiveness to interferon (INF)-(\gamma) in terms of vascular cell adhesion molecule (VCAM)-1 expression and leukocyte adhesion, human endothelial cells were treated with IFN-(\gamma) in the presence of low concentrations (LCs) of interleukin (IL)-1(\alpha) (≤100 pg/mL), which activates (NF-\kappa B) but does not induce VCAM-1 expression. Although IFN-(\gamma) induced major histocompatibility complex class II antigen expression and although a high concentration of IL-1(\alpha) (10 ng/mL) induced leukocyte adhesion and VCAM-1 expression, neither IFN-(\gamma) nor LC IL-1(\alpha) was able to induce VCAM-1 expression or leukocyte adhesion. However, the combination of IFN-(\gamma) and LC IL-1(\alpha) induced VCAM-1 expression and increased leukocyte adhesion (67% and 49% of high-concentration IL-1(\alpha), respectively). Electrophoretic mobility shift assays and immunoblotting of nuclear extracts showed that IFN-(\gamma) activated signal transducers and activators of transcription (STAT)-1(\alpha) and interferon regulatory factor (IRF)-1 but not (NF-\kappa B), whereas LC IL-1(\alpha) activated (NF-\kappa B) but not STAT-1(\alpha) or IRF-1. Nuclear run-on studies showed that LC IL-1(\alpha) is necessary but not sufficient for inducing VCAM-1 gene transcription and that the combination of IFN-(\gamma) and LC IL-1(\alpha) is required for full VCAM-1 gene transcription. These findings suggest that factors that activate (NF-\kappa B) can synergize with IFN-(\gamma) in promoting endothelial-leukocyte interaction.