Human type II phospholipase A(2)-induced Mac-1 expression on human neutrophils

To investigate the effect of type II phospholipase A(2) (PLA(2)-II) on neutrophil function, we assessed the Mac-1 (CD11b/CD18) expression on human neutrophils by flaw cytometry after incubation of the cells with human PLA(2)-II, PLA(2)-II at a concentration of 10 mu g/mL increased the Mac-1 expression by 150% compared wit unstimulated cells at 30 min and after. Under these conditions PLA(2)-II increased the exocytosis from secretory vesicles but not from azurophilic, specific, or gelatinase granules. The results suggest that PLA(2)-II induces translocation of Mac-1 from the secretory vesicles to the plasma membrane. The Mac-1 induction mediated by PLA(2)-II was inhibited by an anti-PLA(2)-II antibody, which was able to inhibit the catalytic activity. However, the Mac-1 induction by PLA(2)-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 oil Mac-1 expression, Only arachidonic acid induced Mac-1 expression. These results imply that PLA(2)-II induces Mac-1 expression oil neutrophils via production of arachidonic acid.