Induction of Endothelial-Leukocyte Interaction by Interferon-γ Requires Coactivation of Nuclear Factor-κB

Abstract

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