Modulation of cell adhesion molecules on human endothelial cells by eosinophil-derived mediators

Mechanisms that allow a selective eosinophil emigration in different eosinophilic lung diseases remain poorly understood. In this study, we tested the hypothesis that eosinophils might participate in their own recruitment, particularly through adhesion molecule expression on human endothelial cells (EC). Blood eosinophils from donors with blood eosinophilia were purified and maintained in culture medium for 1 and 18 h. The expression of ICAM-1, E-selectin, and VCAM-1 on human umbilical vein endothelial cells (HUVEC) was evaluated by ELISA and flow cytometry analysis after addition of eosinophil supernatants. Eosinophil supernatants collected after 1 h induced a weak increase of CAM expression on HUVEC. In contrast, supernatants from eosinophils cultured for 18 h considerably amplified ICAM-1, E-selectin, and VCAM-1 expression on the surface of EC. These levels of CAM expression (in optical density determined by ELISA) were about two- or threefold more important than those obtained with eosinophil supernatants collected after a 1-h culture. The characterization of the implicated molecules showed that anti-IL-1beta antibodies significantly inhibited ICAM-1, E-selectin, and VCAM-1 expression, whereas anti-TNF-alpha antibodies only induced a moderate inhibition. Our data support the hypothesis that eosinophils, through the release of at least IL-1beta and TNF-alpha, might participate in the amplification of the inflammatory reaction by activating the vascular endothelium.