Adenosine triphosphate-induced oxygen radical production and CD11b up-regulation: Ca++ mobilization and actin reorganization in human eosinophils

Eosinophils are major effector cells in cellular inflammatory conditions su ch as parasitic infections, atopic diseases, bullous dermatoses, and vascul itis, Biological activities of adenosine triphosphate (ATP) were characteri zed in human eosinophils and compared with those of other eosinophil activa tors such as complement fragment product C5a, platelet-activating factor (P AF), and eotaxin, ATP initiated production of reactive oxygen metabolites, as demonstrated by lucigenin-dependent chemiluminescence. Furthermore, ATP caused up-regulation of the integrin CD11b, In addition, fluorescence micro scope measurements labeled with fura-2 (1-[2-(5-carboxy-oxazol-2-yl)-6-amin obenzofuran-5-oxy]-2-(2'-amino-5'-methyl-phenoxy)ethaneN, N, N, N'-tetraace tic acid, pentaacetoxymethyl ester) eosinophils in the presence or absence of ethyleneglycotetraacetic acid (EGTA) indicated that there was Ca++ mobil ization from intracellular stores by ATP, Flow cytometric studies showed tr ansient actin polymerization upon stimulation with ATP and its stable analo gues adenosine 5'-0-(3-thiotriphosphate) and 2-methylthioadenosine triphosp hate tetrasodium (met-ATP), The reactions induced by ATP were comparable to those obtained by C5a, PAF and eotaxin, Production of reactive oxygen meta bolites and actin polymerization after stimulation with ATP was inhibited b y pertussis toxin, which indicated involvement of receptor-coupled guanine nucleotide-binding proteins (G(i) proteins). In addition, experiments with oxidized ATP also suggest involvement of P2X receptors in this activation p rocess, The results show that ATP is a strong activator of eosinophils and has biological activity comparable to those of the eosinophil chemotaxins C 5a, PAF, and eotaxin, The findings strongly suggest a role of ATP in the pa thogenesis of eosinophilic inflammation as an activator of proinflammatory effector functions. (C) 2000 by The American Society of Hematology.