Superoxide production by human eosinophils can be inhibited in an agonist-selective manner

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Abstract
This paper focuses on eosinophil activation and its selective inhibition. Superoxide anion (O 2 − ) production by human eosinophils, an indicator of their activation, was induced by a variety of activators. Several compounds which are known to inhibit protein kinase C (staurosporine, K252a, sphingosine) inhibited O 2 − production induced by phorbol ester (PMA) but failed to inhibit O 2 − production induced by IgG coupled to Sepharose beads. Inhibition of O 2 − production by other agents (plasma-activated zymosan, fMLP, and leukotriene B4 (LTB4), was intermediate. By contrast, wortmannin, a compound which has been previously reported to inhibit O 2 − production in neutrophils via a protein kinase-independent pathway, potently inhibited O 2 − production in eosinophils which had been activated by IgG and by Platelet-Activating Factor but was virtually inactive against PMA-induced O 2 − production. Taken together, the results indicate that, as a minimum, there must be two pathways of induction of O 2 − production in eosinophils. Moreover, the intermediate levels of inhibition in cells which had been activated with serum-activated zymosan, FMLP, and LTB4 suggest that these agents may either be acting via both of these pathways or that yet other pathways may exist.

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