Cytosolic phospholipase A2alpha activation induced by S1P is mediated by the S1P3 receptor in lung epithelial cells.
Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) activation is a regulatory step in the control of arachidonic acid (AA) liberation for eicosanoid formation. Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator involved in the regulation of many important proinflammatory processes and has been found in the airways of asthmatic subjects. We investigated the mechanism of S1P-induced AA release and determined the involvement of cPLA(2)alpha in these events in A549 human lung epithelial cells. S1P induced AA release rapidly within 5 min in a dose- and time-dependent manner. S1P-induced AA release was inhibited by the cPLA(2)alpha inhibitors methyl arachidonyl fluorophosphonate (MAFP) and pyrrolidine derivative, by small interfering RNA-mediated downregulation of cPLA(2)alpha, and by inhibition of S1P-induced calcium flux, suggesting a significant role of cPLA(2)alpha in S1P-mediated AA release. Knockdown of the S1P3 receptor, the major S1P receptor expressed on A549 cells, inhibited S1P-induced calcium flux and AA release. The S1P-induced calcium flux and AA release was associated with sphingosine kinase 1 (Sphk1) expression and activity. Furthermore, Rho-associated kinase, downstream of S1P3, was crucial for S1P-induced cPLA(2)alpha activation. Our data suggest that S1P acting through S1P3, calcium flux, and Rho kinase activates cPLA(2)alpha and releases AA in lung epithelial cells. An understanding of S1P-induced cPLA(2)alpha activation mechanisms in epithelial cells may provide potential targets to control inflammatory processes in the lung.
Chen
Li-Yuan
LY
Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA.
Woszczek
Grzegorz
G
Nagineni
Sahrudaya
S
Logun
Carolea
C
Shelhamer
James H
JH
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001095:Arachidonic Acids / Q000494:pharmacology; D001249:Asthma / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D015777:Eicosanoids / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000201:enzymology*; D008246:Lysophospholipids / Q000378:metabolism*; D063065:Organophosphonates / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor); D034741:RNA, Small Interfering / Q000494:pharmacology; D049349:Receptors, Lysosphingolipid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000201:enzymology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism; D000099157:Sphingosine Kinase
D016718:Arachidonic Acid; D001095:Arachidonic Acids; D002118:Calcium; D015777:Eicosanoids; D004791:Enzyme Inhibitors; D054513:Group IV Phospholipases A2; D008246:Lysophospholipids; D063065:Organophosphonates; D017853:Phosphotransferases (Alcohol Group Acceptor); D034741:RNA, Small Interfering; D049349:Receptors, Lysosphingolipid; D013110:Sphingosine; D054460:rho-Associated Kinases; D000099157:Sphingosine Kinase; C104810:methyl arachidonylfluorophosphonate; C060506:sphingosine 1-phosphate; C516389:PLA2G4A protein, human