The phosphatidylinositol 3-kinase inhibitor wortmannin markedly reduces chemotactic peptide-induced locomotion and increases in cytoskeletal actin in human neutrophils

Abstract

To define a possible role of the enzyme phosphatidylinositol 3-kinase (PI 3-kinase) in motile functions of neutrophils, we have used a potent inhibitor of this enzyme, [1 S-(1 α,6 b α,9 a β,11 α,11 b β)]-11-(acetyloxy)-1,6 b,7,8,9 a,10,11,11 b-octahydro-1-(methoxymethyl)-9 a,11 b-dimethyl-3 H-furo[4,3,2-de]indeno[4,5- h]-2-benzopyran-3,6,9-trione (wortmannin). Wortmannin markedly attenuated chemotactic peptide-induced development of polarity, locomotion and increases in cytoskeletal actin and α-actinin in human neutrophils at low, nM, concentrations (ED 50=4–40 nM; 0.4–3 pmol/10 6 cells). The increase in cytoskeletal actin induced by phorbol-12-myristate-13-acetate in contrast was not affected by wortmannin (18 pmol/10 6 cells). Moreover, the increase in total F-actin induced by an incubation for 1 min with chemotactic peptide was much less sensitive to wortmannin than increases in cytoskeletal actin; 80 pmol/10 6 cells were necessary for half-maximal inhibition. Wortmannin thus appears to primarily affect F-actin organization, rather than polymerization. Inhibition of development of polarity by wortmannin correlated with inhibition of production of phosphatidylinositol 3,4,5-trisphosphate. According to our findings, activation of a wortmannin-sensitive target, very likely PI 3-kinase, is required for optimal chemotactic peptide-induced neutrophil motility.