Effects of wortmannin on human neutrophil respiratory burst and phagocytosis.

Modulation of neutrophil response to naturally occurring stimuli is important to avoid host tissue injure. Both soluble and particulate stimuli may induce superoxide anion generation in human polymorphonuclear leukocytes. Recently wortannin has been shown to inhibit the N-formyl-methionyl-leucyl-phenylalanine (fMLP) induced activation of respiratory burst via phosphatidylinositol 3-kinase. However no data are available about the effect of the inhibitor on the respiratory burst induced by a particulate stimulus. In this paper we studied the effect of wortmannin on E. coli induced respiratory burst and phagocytosis by flow cytometry, which allows the quantitation of both H2O2 production and ingested bacteria in whole blood samples without the need of purification and concomitant manipulation of the cells. The effects of worthmannin on fMLP-induced chemotaxis was also examined by the under agarose method. Neither the E. coli nor the fMLP-induced responses were blocked by wortmannin, suggesting that PI 3-kinase activity is not required to activate these neutrophil functions. Since it is known that the respiratory burst elicited by fMLP is blocked by wortmannin, our results suggest that the generation of oxygen radicals is controlled via different signal transduction pathways, depending on the agonist used.