Regulation of prostaglandin E_2 synthesis by sphingolipids in human gingival fibroblasts

神经酰胺是鞘脂信号通路的重要组成部分，在许多细胞类型的炎症、细胞增殖和凋亡等细胞过程中作为第二信使发挥作用。本研究以人牙龈成纤维细胞为研究对象，观察了细胞渗透性神经酰胺（一系列酰基链长度分别为2、6、8和16的神经酰胺类似物）对人牙龈成纤维细胞前列腺素E_2合成及花生四烯酸转化为前列腺素类化合物的限速酶COX-2 mRNA表达的影响。前列腺素E_2释放用酶免疫法测定。结果：神经酰胺本身不能诱导细胞合成E_2。C_2-神经酰胺可抑制IL-1β诱导的E_2释放，并呈剂量和时间依赖性; C_2-神经酰胺可促进IL-1β诱导的COX-2 mRNA表达。C_2-脱氢神经酰胺（C_2-dehydroceramide）是一种无生物活性的C2-神经酰胺类似物，它不影响IL-1β诱导的E_2释放和COX-2 mRNA表达。而另一种长链神经酰胺则能增强IL-1β刺激的E_2产生。最有效的C_<16>-神经酰胺可使E_2产量提高60%。控制力这些结果表明，N-酰基链的长度对神经酰胺类似物的细胞渗透性的影响取决于E_2的产生。C_2-神经酰胺抑制IL-1β诱导的E_2合成，但这种抑制作用可能不是通过降低COX-2 mRNA表达而实现的。这些结果提示，通过调控C_2-神经酰胺信号通路，可能为抑制环氧化酶-2活性，如牙周病等提供一种新的治疗途径。

Ceramide is an integral component of sphingolipids signaling pathway, which acts as second messenger in cellular process such as inflammation, cell proliferation, and apoptosis in number of cell types. In this study, we investigated the effects of the cell permeable ceramide (a series of ceramide analog with acyl chain length of 2, 6, 8 and 16 on the) on prostaglandin E_2 synthesis and cyclooxgenas&2mRNA expression, a rate-limiting enzyme for the conversion of arachidonic acid to prostanoids in human gingival fibroblasts.Methods : Human gingival fibroblasts was obtained from explants of human gingival tissue. Prostaglan-dinE_2 release was determined by an enzyme-immunoassay. Cyclooxgenase-2mRNA levels was detected by RT-PCR.Results : Cell permeable ceramide by itself did not induced prostaglandinE_2 synthesis. The only treated with C_2-ceramide, IL-1β-induced prostaglandinE_2 release was inhibited in a dose-and time-dependent manner, whereas C_2-ceramide enhanced IL-1β-stimulated cyclooxgenase-2mRNA expression. C_2-dehydroceramide, a biologically inactive C2-ceramide analog, did not affect both IL-1β-induced prostaglandinE_2 release and cyclooxgenase-2mRNA expression. In contrast, the other long chain ceramide potentiated IL-1β-stimulated prostaglandinE_2 production. The most effective C_<16>-ceramide enhanced prostaglandinE_2 production by 60%. of control. These results indicate that effect of cell permeable ceramide analog on prostaglandinE_2 production depends on N-acyl chain length. C_2-ceramide inhibits the IL-1β-induced prostaglandinE_2 synthesis, but which appears not to be due to the decrease of Cyclooxgenase-2mRNA expression. These results suggest that the modulation on the C_2-ceramide signaling pathway may offer a therapeutic approach for inhibiting cyclooxgenase-2 activity, such as periodontal diseases.