Mechanisms involved in human eosinophil chemotaxis induced by the newly cloned C-C chemokine eotaxin

Abstract

The present study was performed in order to investigate the mechanism(s) involved in eotaxin-induced normal human eosinophil chemotaxis using a 48-well microchemotaxis chamber assay. Eotaxin, at a wide range of doses, induced eosinophil chemotaxis with optimal activity at 100 ng/mL. To elucidate the role of Ca²⁺ as a second messenger, eosinophils were depleted of intracellular Ca²⁺ which, per se, did not modify eosinophil chemotaxis. To gain insight of the possible intracellular signal transduction, we blocked pertussis toxin (PTX)-sensitive G_i proteins as well as several protein kinases. It was found that the inhibition of tyrosine kinase with herbimycin A and the inhibition of mitogen-activated protein kinase (MAPK) with MEK-1 inhibitor (PD98059) significantly blocked chemotaxis; however, inhibition of protein kinase C with staurosporine, protein kinase A with H-89 and G_i proteins with PTX did not affect chemotaxis. These results suggest a signal transduction pathway(s) involving Ca²⁺-independent tyrosine kinase and MAPK activities.