Abstract.
Objective: This study was designed to demonstrate the presence of adenosine A3 receptors on human peripheral blood eosinophils, and to investigate the effect of A3 receptor stimulation on eosinophil function.¶Material: Eosinophils from either non-asthmatic or asthmatic donors.¶Methods: Eosinophils were isolated from peripheral venous blood by discontinuous gradient centrifugation and negative immunoselection. Receptor localisation was investigated by immunoblotting and by immunocytochemistry using a novel antibody specific for the human A3 receptor. Two pharmacological responses were studied: elevation of intracellular calcium in single eosinophils, measured by microfluorimetry, and hydrogen peroxide generation in cell suspensions.¶Results: The expression of A3 receptors by eosinophils was confirmed using the selective antibody. Addition of the A3 receptor selective agonist, IB-MECA (100 nM), produced increases in intracellular calcium in less than 10% of the eosinophils isolated from non-asthmatic donors. These responses were only partially attenuated with the A3 receptor antagonist, I-ABOPX. IB-MECA (0.001-1000 nM) did not stimulate hydrogen peroxide (H2O2) generation, nor did it enhance fMLP- or C5a-stimulated generation of H2O2. In fact high concentrations of IB-MECA inhibited the generation of H2O2 (when stimulated by fMLP or C5a), an effect probably mediated by A2 receptors. Similar results were obtained using eosinophils from asthmatic donors.¶Conclusions: Stimulation of adenosine A3 receptors does not appear to be a prime mechanism for free radical generation by human peripheral blood eosinophils.
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Received 18 November 1999; returned for revision 10 April 2000; accepted by C.J. Whelan 2 May 2000
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Reeves, J., Harris, C., Hayes, B. et al. Studies on the effects of adenosine A3 receptor stimulation on human eosinophils isolated from non-asthmatic or asthmatic donors. Inflamm. res. 49, 666–672 (2000). https://doi.org/10.1007/s000110050644
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DOI: https://doi.org/10.1007/s000110050644