| 11557588 |
Sano A, Zhu X, Sano H, Munoz NM, Boetticher E, Leff AR: Regulation of eosinophil function by phosphatidylinositol-specific PLC and cytosolic PLA (2). Am J Physiol Lung Cell Mol Physiol. 2001 Oct;281(4):L844-51.
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. |
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