Human group V phospholipase A2 induces group IVA phospholipase A2-independent cysteinyl leukotriene synthesis in human eosinophils.
We previously reported that exogenously added human group V phospholipase A2 (hVPLA2) could elicit leukotriene B4 biosynthesis in human neutrophils through the activation of group IVA phospholipase A2 (cPLA2) (Kim, Y. J., Kim, K. P., Han, S. K., Munoz, N. M., Zhu, X., Sano, H., Leff, A. R., and Cho, W. (2002) J. Biol. Chem. 277, 36479-36488). In this study, we determined the functional significance and mechanism of the exogenous hVPLA2-induced arachidonic acid (AA) release and leukotriene C4 (LTC4) synthesis in isolated human peripheral blood eosinophils. As low a concentration as 10 nm exogenous hVPLA2 was able to elicit the significant release of AA and LTC4 from unstimulated eosinophils, which depended on its ability to act on phosphatidylcholine membranes. hVPLA2 also augmented the release of AA and LTC4 from eosinophils activated with formyl-Met-Leu-Phe + cytochalasin B. A cellular fluorescent PLA2 assay showed that hVPLA2 had a lipolytic action first on the outer plasma membrane and then on the perinuclear region. hVPLA2 also caused the translocation of 5-lipoxygenase from the cytosol to the nuclear membrane and a 2-fold increase in 5-lipoxygenase activity. However, hVPLA2 induced neither the increase in intracellular calcium concentration nor cPLA2 phosphorylation; consequently, cPLA2 activity was not affected by hVPLA2. Pharmacological inhibition of cPLA2 and the hVPLA2-induced activation of eosinophils derived from the cPLA2-deficient mouse corroborated that hVPLA2 mediates the release of AA and leukotriene in a cPLA2-independent manner. As such, this study represents a unique example in which a secretory phospholipase induces the eicosanoid formation in inflammatory cells, completely independent of cPLA2 activation.
Muñoz
Nilda M
NM
Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA.
Kim
Young Jun
YJ
Meliton
Angelo Y
AY
Kim
Kwang Pyo
KP
Han
Sang-Kyou
SK
Boetticher
Evan
E
O'Leary
Eileen
E
Myou
Shigeharu
S
Zhu
Xiangdong
X
Bonventre
Joseph V
JV
Leff
Alan R
AR
Cho
Wonhwa
W
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D015153:Blotting, Western; D001854:Bone Marrow Cells; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry*; D003571:Cytochalasin B / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D004804:Eosinophils / Q000378:metabolism*; D054513:Group IV Phospholipases A2; D054505:Group V Phospholipases A2; D006801:Humans; D006868:Hydrolysis; D007150:Immunohistochemistry; D017997:Leukotriene C4 / Q000378:metabolism; D015289:Leukotrienes / Q000096:biosynthesis*; D051379:Mice; D008856:Microscopy, Fluorescence; D009504:Neutrophils / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism* / Q000502:physiology*; D054467:Phospholipases A2; D010766:Phosphorylation; D020033:Protein Isoforms; D013997:Time Factors
D015289:Leukotrienes; D010713:Phosphatidylcholines; C516390:Pla2g4a protein, mouse; D020033:Protein Isoforms; D016718:Arachidonic Acid; D017997:Leukotriene C4; D003571:Cytochalasin B; D001094:Arachidonate 5-Lipoxygenase; D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054505:Group V Phospholipases A2; C516389:PLA2G4A protein, human; D054467:Phospholipases A2; C101424:phospholipase A2-V, Trimeresurus; D003545:Cysteine; D002118:Calcium