CAP37, a neutrophil-derived inflammatory mediator, augments leukocyte adhesion to endothelial monolayers

Cationic antimicrobial protein of molecular weight 37 kDa (CAP37) is a multifunctional inflammatory mediator that was originally isolated from human neutrophils and described to possess bactericidal and monocyte-activating functions. More recently its expression in endothelial and epithelial cells in response to inflammatory mediators and its ability to activate endothelial cells and alter permeability has been demonstrated. We hypothesize that CAP37 facilitates the process of transendothelial migration not only because of its potential to act as a chemoattractant but also through its ability to promote leukocyte adhesion to the endothelium by modulating adhesion molecule expression on the endothelium. Here we describe its ability to mediate neutrophil and monocyte adherence to endothelial monolayers in vitro. Using reverse transcriptase-polymerase chain reaction and flow cytometry, we demonstrate its ability to upregulate the adhesion molecules, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin in human umbilical vein and lung microvessel endothelial cells. The identity and kinetics of upregulation of the specific adhesion molecule was dependent on the endothelial cell type, suggesting that adhesion molecules on endothelial cells from different vascular beds are differentially regulated by CAP37. The cell-specific kinetics of adhesion molecule upregulation by CAP37 may influence selective leukocyte migration in certain inflammatory situations.