Chen Li-Yuan, Woszczek Grzegorz, Nagineni Sahrudaya, Logun Carolea, Shelhamer James H
Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA.
Am J Physiol Lung Cell Mol Physiol. 2008 Aug;295(2):L326-35. doi: 10.1152/ajplung.00393.2007. Epub 2008 May 23.
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.
胞质型磷脂酶A2α（cPLA2α）的激活是控制花生四烯酸（AA）释放以形成类花生酸的一个调节步骤。1-磷酸鞘氨醇（S1P）是一种生物活性脂质介质，参与许多重要促炎过程的调节，且已在哮喘患者的气道中发现。我们研究了S1P诱导AA释放的机制，并确定了cPLA2α在A549人肺上皮细胞这些事件中的作用。S1P在5分钟内迅速以剂量和时间依赖性方式诱导AA释放。cPLA2α抑制剂甲基花生四烯酰氟磷酸酯（MAFP）和吡咯烷衍生物、通过小干扰RNA介导下调cPLA2α以及抑制S1P诱导的钙内流，均可抑制S1P诱导的AA释放，提示cPLA2α在S1P介导的AA释放中起重要作用。敲低A549细胞上表达的主要S1P受体S1P3受体，可抑制S1P诱导的钙内流和AA释放。S1P诱导的钙内流和AA释放与鞘氨醇激酶1（Sphk1）的表达和活性有关。此外，S1P3下游的Rho相关激酶对S1P诱导的cPLA2α激活至关重要。我们的数据表明，S1P通过S1P3、钙内流和Rho激酶发挥作用，激活cPLA2α并在肺上皮细胞中释放AA。了解上皮细胞中S1P诱导的cPLA2α激活机制可能为控制肺部炎症过程提供潜在靶点。
