Inhibition of Human Eosinophil Functions by Ketotifen in vitro

Abstract

Abstract: : Purpose: To investigate the effects of ketotifen, a drug with multiple mechanisms of action used for the treatment of allergic conjunctivitis, on human eosinophil chemotaxis, oxidative metabolism, and mediator release induced after activation. Methods: Eosinophils from hypereosinophilic patients or normal donors were purified by Percoll gradient and isolated by immunomagnetic separation using the MACS system. Chemotaxis was studied in a Boyden chamber using three potent chemoattractants, fMLP, IL-5 and eotaxin. Oxidative metabolism was determined by a luminol-dependent chemiluminescence assay after activation with eotaxin or secretory IgA (sIgA). Release of eosinophil cationic protein (ECP) and eosinophil derived neurotoxin (EDN) was measured by radioimmunoassay after activation with sIgA. Results: At therapeutically relevant concentrations (10^-4–10^-8 Mol/L), ketotifen inhibited chemotaxis of eosinophils to fMLP, IL-5 and eotaxin in a dose-dependent manner. Production of reactive oxygen species (ROS) induced by eotaxin and sIgA was significantly decreased by ketotifen, the effect being more pronounced when cells were activated by eotaxin. Activation by sIgA resulted in ECP and EDN release, which was partially inhibited by ketotifen. Conclusions: Through inhibition of chemotaxis, ketotifen has the potential to limit the number of eosinophils at the site of inflammation during the allergic reaction. Furthermore, inhibition of release of main inflammatory mediators suggests a possible role of ketotifen in limiting the pathological potential of eosinophils.

Keywords: conjunctivitis • cytokines/chemokines • pharmacology