CCR3-active chemokines promote rapid detachment of eosinophils from VCAM-1in vitro

Selective eosinophil recruitment is the result of orchestrated events invol ving cell adhesion molecules, chemokines, and their receptors, The mechanis ms by which chemokines regulate eosinophil adhesion and migration via integ rins are not fully understood. In our study, we examined the effect of CCR3 -active chemokines on eosinophil adhesion to VCAM-1 and BSA under both stat ic and flow conditions. When eotaxin-2 or other CCR3-active chemokines were added to adherent eosinophils, it induced rapid and sustained eosinophil d etachment from VCAM-1 in a concentration-dependent manner. Adhesion was det ectably reduced within 3 min and was further reduced at 10-60 min. Simultan eously, eotaxin-2 enhanced eosinophil adhesion to BSA, Preincubation of eos inophils with the CCR3-blocking mAb 7B11 completely prevented chemokine-ind uced changes in adhesion to VCAM-1 and BSA, Using a different protocol, pre treatment of eosinophils with chemokines for 0-30 min before their use in a dhesion assays resulted in inhibition of VCAM-1 adhesion and enhancement of BSA adhesion. By flow cytometry, expression of alpha (4) integrins and a b eta (1) integrin activation epitope on eosinophils was decreased by eotaxin -2. In a how-based adhesion assay, eotaxin-2 reduced eosinophil accumulatio n and the strength of attachment to VCAM-1. These results show that eotaxin -2 rapidly reduced alpha (4) integrin function while increasing beta (2) in tegrin function, These findings suggest that chemokines facilitate migratio n of eosinophils by shifting usage away from beta (1) integrins toward beta (2) integrins.