鞘氨醇
鞘脂
鞘氨醇激酶1
1-磷酸鞘氨醇
神经酰胺
前列腺素E2
鞘氨醇激酶
肿瘤坏死因子α
化学
小干扰RNA
脂质信号
药理学
生物
细胞生物学
生物化学
内分泌学
转染
酶
受体
细胞凋亡
基因
作者
Benjamin J. Pettus,Jacek Bielawski,Anna Maria Porcelli,Davis L. Reames,Korey R. Johnson,Jason D. Morrow,Charles E. Chalfant,Lina M. Obeid,Yusuf A. Hannun
标识
DOI:10.1096/fj.02-1038com
摘要
In this study we addressed the role of sphingolipid metabolism in the inflammatory response. In a L929 fibroblast model, tumor necrosis factor-alpha (TNF) induced prostaglandin E2 (PGE2) production by 4 h and cyclooxygenase-2 (COX-2) induction as early as 2 h. This TNF-induced PGE2 production was inhibited by NS398, a COX-2 selective inhibitor. GC-MS analysis revealed that only COX-2-generated prostanoids were produced in response to TNF, thus providing further evidence of COX-2 selectivity. As sphingolipids have been implicated in mediating several actions of TNF, their role in COX-2 induction and PGE2 production was evaluated. Sphingosine-1-phosphate (S1P) induced both COX-2 and PGE2 in a dose-responsive manner with an apparent ED50 of 100-300 nM. The related sphingolipid sphingosine also induced PGE2, though with much less efficacy. TNF induced a 3.5-fold increase in sphingosine-1-phosphate levels at 10 min that rapidly returned to baseline by 40 min. Small interfering RNAs (siRNAs) directed against mouse SK1 decreased (typically by 80%) SK1 protein and inhibited TNF-induced SK activity. Treatment of cells with RNAi to SK1 but not SK2 almost completely abolished the ability of TNF to induce COX-2 or generate PGE2. By contrast, cells treated with RNAi to S1P lyase or S1P phosphatase enhanced COX-2 induction leading to enhanced generation of PGE2. Treatment with SK1 RNAi also abolished the effects of exogenous sphingosine and ceramide on PGE2, revealing that the action of sphingosine and ceramide are due to intracellular metabolism into S1P. Collectively, these results provide novel evidence that SK1 and S1P are necessary for TNF to induce COX-2 and PGE2 production. Based on these findings, this study indicates that SK1 and S1P could be implicated in pathological inflammatory disorders and cancer.
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