Eosinophil cysteinyl leukotriene synthesis mediated by exogenous secreted phospholipase A2 group X.
Secreted phospholipase A(2) group X (sPLA(2)-X) has recently been identified in the airways of patients with asthma and may participate in cysteinyl leukotriene (CysLT; C(4), D(4), and E(4)) synthesis. We examined CysLT synthesis and arachidonic acid (AA) and lysophospholipid release by eosinophils mediated by recombinant human sPLA(2)-X. We found that recombinant sPLA(2)-X caused marked AA release and a rapid onset of CysLT synthesis in human eosinophils that was blocked by a selective sPLA(2)-X inhibitor. Exogenous sPLA(2)-X released lysophospholipid species that arise from phospholipids enriched in AA in eosinophils, including phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine as well as plasmenyl phosphatidylcholine and phosphatidylethanolamine. CysLT synthesis mediated by sPLA(2)-X but not AA release could be suppressed by inhibition of cPLA(2)α. Exogenous sPLA(2)-X initiated Ser(505) phosphorylation of cPLA(2)α, an intracellular Ca(2+) flux, and translocation of cPLA(2)α and 5-lipoxygenase in eosinophils. Synthesis of CysLTs in response to sPLA(2)-X or lysophosphatidylcholine was inhibited by p38 or JNK inhibitors but not by a MEK 1/2 inhibitor. A further increase in CysLT synthesis was induced by the addition of sPLA(2)-X to eosinophils under conditions of N-formyl-methionyl-leucyl-phenylalanine-mediated cPLA(2)α activation. These results indicate that sPLA(2)-X participates in AA and lysophospholipid release, resulting in CysLT synthesis in eosinophils through a mechanism involving p38 and JNK MAPK, cPLA(2)α, and 5-lipoxygenase activation and resulting in the amplification of CysLT synthesis during cPLA(2)α activation. Transactivation of eosinophils by sPLA(2)-X may be an important mechanism leading to CysLT formation in the airways of patients with asthma.
Lai
Ying
Y
Division of Pulmonary and Critical Care, University of Washington, Seattle, Washington 98195, USA.
Oslund
Rob C
RC
Bollinger
James G
JG
Henderson
William R
WR
Santana
Luis F
LF
Altemeier
William A
WA
Gelb
Michael H
MH
Hallstrand
Teal S
TS
D001249:Asthma / Q000188:drug therapy; D002118:Calcium / Q000737:chemistry; D003545:Cysteine / Q000096:biosynthesis*; D015777:Eicosanoids / Q000737:chemistry; D004804:Eosinophils / Q000201:enzymology* / Q000378:metabolism; D054509:Group X Phospholipases A2 / Q000737:chemistry; D006801:Humans; D015289:Leukotrienes / Q000096:biosynthesis* / Q000737:chemistry; D008246:Lysophospholipids / Q000737:chemistry; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D054467:Phospholipases A2 / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D015777:Eicosanoids; D015289:Leukotrienes; D008246:Lysophospholipids; D011994:Recombinant Proteins; C112381:cysteinyl-leukotriene; D012694:Serine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D048051:p38 Mitogen-Activated Protein Kinases; D054509:Group X Phospholipases A2; C516365:PLA2G10 protein, human; D054467:Phospholipases A2; D003545:Cysteine; D002118:Calcium