Regulation of eosinophil function by phosphatidylinositol-specific PLC and cytosolic PLA(2).
We examined the regulatory role of cytosolic phospholipase A(2) (cPLA(2)) and phosphatidylinositol (PI)-specific phospholipase C (PLC) in the degranulation of human eosinophils and leukotriene (LT) C(4) synthesis. Activation with formyl-Met-Leu-Phe + cytochalasin B (fMLP/B) caused a time-dependent release of eosinophil peroxidase (EPO) and LTC(4), which was inhibited by pertussis toxin. By immunoblotting, eosinophil PLC-beta2 and -gamma2 isoforms were identified, and PLC activation was measured as a function of inositol 1,4,5-trisphosphate concentration. Stimulated release of EPO and intracellular Ca(2+) concentration was inhibited by ET-18-OCH(3), a PI-PLC inhibitor, whereas trifluoromethylketone (TFMK), a cPLA(2) blocker, had no inhibitory effect. Both TFMK and ET-18-OCH(3) attenuated stimulated arachidonate release and LTC(4) secretion, suggesting that activation of both PLC and cPLA(2) is essential for LTC(4) synthesis caused by fMLP/B. The structurally unrelated protein kinase C inhibitors bisindolylmaleimide, Ro-31-8220, and Go-6976 all blocked fMLP/B-induced EPO release but not LTC(4) secretion. 1,2-bis(2-Aminophenoxy)ethane-N,N,N',N'- tetraacetic acid acetoxymethyl ester, an intracellular Ca(2+) chelator, suppressed both EPO release and LTC(4) secretion. We found that fMLP/B-induced LTC(4) secretion from human eosinophils is regulated by PI-PLC through calcium-mediated activation of cPLA(2). However, cPLA(2) does not regulate eosinophil degranulation.
Sano
A
A
Section of Pulmonary and Critical Care Medicine, Department of Medicine, The University of Chicago, Illinois 60637, USA.
Zhu
X
X
Sano
H
H
Muñoz
N M
NM
Boetticher
E
E
Leff
A R
AR
D016718:Arachidonic Acid / Q000378:metabolism; D015415:Biomarkers; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D047209:Eosinophil Peroxidase; D004804:Eosinophils / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D007659:Ketones / Q000494:pharmacology; D017997:Leukotriene C4 / Q000096:biosynthesis / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D037342:Pertussis Toxin; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D054801:Phosphoinositide Phospholipase C; D054799:Phospholipase C beta; D051966:Phospholipase C gamma; D010741:Phospholipases A / Q000378:metabolism*; D010742:Phospholipid Ethers / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015415:Biomarkers; D002614:Chelating Agents; D007527:Isoenzymes; D007659:Ketones; D010726:Phosphodiesterase Inhibitors; D010742:Phospholipid Ethers; D010566:Virulence Factors, Bordetella; C026659:edelfosine; D016718:Arachidonic Acid; D017997:Leukotriene C4; D004533:Egtazic Acid; D015544:Inositol 1,4,5-Trisphosphate; D047209:Eosinophil Peroxidase; D010544:Peroxidases; D037342:Pertussis Toxin; D011493:Protein Kinase C; D010741:Phospholipases A; D010738:Type C Phospholipases; C518036:PLCB2 protein, human; D054801:Phosphoinositide Phospholipase C; D054799:Phospholipase C beta; D051966:Phospholipase C gamma; D043265:Phosphatidylinositol Diacylglycerol-Lyase; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium