Cytosolic phospholipase A2{alpha} activation induced by S1P is mediated by the S1P3 receptor in lung epithelial cells

• Published in: American journal of physiology. Lung cellular and molecular physiology Vol. 295; no. 2; p. L326
• Main Authors: Chen, Li-Yuan, Woszczek, Grzegorz, Nagineni, Sahrudaya, Logun, Carolea, Shelhamer, James H
• Format: Journal Article
• Language: English
• Published: 01.08.2008
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00393.2007

Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland Submitted 20 September 2007 ; accepted in final form 19 May 2008 Cytosolic phospholipase A 2 (cPLA 2 ) 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 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 inhibitors methyl arachidonyl fluorophosphonate (MAFP) and pyrrolidine derivative, by small interfering RNA-mediated downregulation of cPLA 2 , and by inhibition of S1P-induced calcium flux, suggesting a significant role of cPLA 2 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 activation. Our data suggest that S1P acting through S1P3, calcium flux, and Rho kinase activates cPLA 2 and releases AA in lung epithelial cells. An understanding of S1P-induced cPLA 2 activation mechanisms in epithelial cells may provide potential targets to control inflammatory processes in the lung. eicosanoid; calcium flux; airway inflammation Address for reprint requests and other correspondence: J. H. Shelhamer, Critical Care Medicine Dept., National Institutes of Health, Warren Grant Magnuson Clinical Center, Bldg. 10, Rm. 2C145, 9000 Rockville Pike, Bethesda, MD 20892 (e-mail: jshelhamer{at}cc.nih.gov )