Human type II phospholipase A2-induced Mac-1 expression on human neutrophils

Abstract

To investigate the effect of type II phospholipase A2 (PLA2-II) on neutrophil function, we assessed the Mac-1 (CD11b/CD18) expression on human neutrophils by flow cytometry after incubation of the cells with human PLA2-II. PLA2-II at a concentration of 10 microg/mL increased the Mac-1 expression by 150% compared with unstimulated cells at 30 min and after. Under these conditions PLA2-II increased the exocytosis from secretory vesicles but not from azurophilic, specific, or gelatinase granules. The results suggest that PLA2-II induces translocation of Mac-1 from the secretory vesicles to the plasma membrane. The Mac-1 induction mediated by PLA2-II was inhibited by an anti-PLA2-II antibody, which was able to inhibit the catalytic activity. However, the Mac-1 induction by PLA2-II was not inhibited by a 5-lipoxygenase, cyclooxygenase inhibitor, or a platelet-activating factor antagonist. Thus, we examined the effects of fatty acids and lysophospholipids on Mac-1 expression. Only arachidonic acid induced Mac-1 expression. These results imply that PLA2-II induces Mac-1 expression on neutrophils via production of arachidonic acid.

Induction of the activation-related antigen CD69 on human eosinophils by type IIA phospholipase A 2

“…Activation of other cell types by PLA 2 -IIA has been reported to be promoted by generation of lysophospholipids [28,33]. On the other hand, PLA 2 -IIA induced Mac-1 expression on human neutrophils at least partly via the generation of arachidonic acid [13]. From these findings, PLA 2 -IIA may induce diverse cell functions on many cell types via the liberation of various fatty acids and lysophospholipids.…”

“…In addition, several cytokines including IL-3, IL-4, IL-5, IL-13, and GM-CSF are believed to promote survival and eosinophil activation such as CD69 expression over 2-4 h after in vitro stimulation [1,[16][17][18] We demonstrated in the present study that catalytic activity of PLA 2 -IIA was essential for induction of CD69 expression on human eosinophils. Mac-1 expression and degranulation by PLA 2 -IIA in neutrophils and T lymphocyte activation by PLA 2 -IIA are also mediated by catalytic activity of PLA 2 -IIA [13,28]. On the other hand, Murakami et al found that PLA 2 -IIA caused mast cells to release histamine without generation of prostaglandin D 2 and this effect was not blocked at all by EDTA which completely inhibited the catalytic activity [29].…”

“…The PLA 2 activities were measured using [ 3 H]oleic acid-labeled, autoclaved Escherichia coli [13]. Briefly, the assay mixture contained 100 mM Tris/HCl (pH 8.0), 10 …”

“…3). To confirm the inhibitory effect of p-BPB on the enzymatic activity of PLA 2 -IIA, parts of reaction mixtures in each experiment were picked up and their PLA 2 activities were measured by using [ 3 H]oleic acidlabeled autoclaved E. coli [13]. Treatment with p-BPB inhibited PLA 2 -IIA activity almost completely (relative PLA 2 activity (%): buffer control, 0; 5 mg/ml PLA 2 -IIA, 100; 5 mg/ml p-BPB-treated PLA 2 -IIA, 5.25 ± 1.1 (mean ± SEM, n = 4)).…”

“…In addition, levels of PLA 2 -IIA in plasma increase in inflammatory diseases such as septic shock and pancreatitis [11]. Although the effects of PLA 2 -IIA on the functions of many cell types, including neutrophils, have been reported [12][13][14], few have been on the function of eosinophils.…”