ACTIVATION OF PHOSPHOLIPASE-D BY INTERLEUKIN-8 IN HUMAN NEUTROPHILS

Interleukin 8 (IL-8), a member of the C-X-C branch of the chemokine su perfamily, stimulated the breakdown of 1-O[H-3]alkyl-2-acyl-sn-glycero -3-phosphocholine ([H-3]EAPC) and the formation of 1-O-[H-3]alkyl-2-ac yl-phosphatidic acid ([H-3]EAPA) in human polymorphonuclear leukocytes (PMN) in the presence of cytochalasin B. In addition, the mass of dir adyl-PA was increased with similar kinetics. In the presence of ethano l, 1-O-[H-3]alkyl-2-acyl-phosphatidylethanol ([H-3]EAPEt) was formed a t the expense of [H-3]EAPA formation, indicating the activation of pho spholipase D by the cytokine. The effect was time- and concentration-d ependent, reaching a plateau at 30 seconds with the maximally activati ng concentration of 120 nmol/L IL-8. Preincubation of cells with 1 mu g/mL Bordetella pertussis toxin inhibited the breakdown of [H-3]EAPC a nd [H-3]EAPA formation, indicating a role for a pertussis toxin-sensit ive guanosine triphosphate-binding protein. Formation of phosphatidic acid (PA) correlated with activation of nicotinamide adenine dinucleot ide phosphate (NADPH) oxidase, the oxidative burst enzyme, with both e vents occurring in the same concentration range. Inhibition of PA form ation, by the presence of ethanol, also inhibited the oxidative burst stimulation by IL-8. Pretreatment of PMN with 10 nmol/L platelet-activ ating factor potentiated both [H-3]EAPA accumulation and activation of NADPH oxidase by IL-8. Collectively, these data show that IL-8 stimul ates the metabolism of choline-containing phosphoglycerides in human P MN and support a role for PA in the signaling mecha nisms used by IL-8 to stimulate PMN function. (C) 1994 by The American Society of Hemato logy.