Eotaxin-2 activates chemotaxis-related events and release of reactive oxygen species via pertussis toxin-sensitive G proteins in human eosinophils.

Eosinophils play an important role in allergic and autoimmune diseases. They are activated by distinct chemokines, leading to the immigration into the inflamed tissue, and mediate tissue damage by releasing reactive oxygen species. Recently, eotaxin was found to have the broadest spectrum of activities of all eosinophil-activating CC chemokines. In this study we investigated the effect of the novel CC chemokine, eotaxin-2, on eosinophil effector functions and compared its activity with eotaxin. Using nitrobenzoxadiazole-phallacidin staining and flow cytometry, we show that eotaxin-2 induced rapid and transient actin polymerization, a prerequisite for cell migration and modulation of the respiratory burst, in eosinophils in the same range of efficacy as observed for eotaxin. Eotaxin-2 induced the release of reactive oxygen species in a dose-dependent manner; half maximal and maximal release were found at 50 ng/ml and 500 ng/ml, respectively. Surprisingly, the efficacy of eotaxin-2 was comparable to that of eotaxin and C5a. Release of reactive oxygen species was inhibited by pertussis toxin, indicating the involvement of Gi proteins in the signaling of eotaxin-2. Moreover, the anti-CC chemokine receptor 3 (CCR3) monoclonal antibody, 7B11, was able to inhibit transient rise in the cytosolic Ca2+ concentration and the release of reactive oxygen species following stimulation with eotaxin-2. Therefore, eotaxin-2 represents a potent CC chemokine for human eosinophils activating chemotaxis-related events, such as actin polymerization, and the respiratory burst via the CCR3. Moreover, the efficacy of eotaxin-2 seems to be in the same range as that of eotaxin which might re-evaluate the recent profile of activity of CC chemokines in the activation of human eosinophils.