Yatomi Y, Ruan F, Hakomori S, Igarashi Y
Biomembrane Institute, University of Washington, Seattle 98119, USA.
Blood. 1995 Jul 1;86(1):193-202.
Sphingosine-1-phosphate (Sph-1-P) is the initial product of catabolism of sphingosine by sphingosine kinase and is cleaved by Sph-1-P lyase to a fatty aldehyde and ethanolamine phosphate. This phosphorylated sphingoid base is not only an intermediary catabolite, but also a bioactive lipid with important functions, including stimulation of cell proliferation in Swiss 3T3 fibroblasts and inhibition of tumor cell motility. In the present study, we examined functional roles of Sph-1-P in human platelets. Sph-1-P induced platelet shape change and aggregation reactions, although it failed to elicit secretion. Sphingosine, ceramide, sphingomyelin, and N,N-dimethylsphingosine did not mimic the positive effects of Sph-1-P on platelets. Subthreshold concentrations of Sph-1-P and weak platelet agonists such as adenosine diphosphate (ADP) and epinephrine synergistically elicited aggregation, which may be important for efficient amplification of platelet activation. Sph-1-P induced intracellular Ca2+ mobilization and the dose-response for Ca2+ release correlated closely with the concentration required for induction of shape change. On addition of [3H]sphingosine to intact platelets, the label was rapidly converted to Sph-1-P, and subsequently to ceramide and sphingomyelin. Interestingly, the Sph-1-P formed was specifically released into medium on stimulation of platelets with physiologic agonists. The amount of Sph-1-P in platelets, as measured by its conversion into radiolabeled N-acetyl-Sph-1-P, was 1.4 nmol/10(9) cells and was about four times higher than the mass of Sph present. When compared by mole percent Sph-1-P/phospholipid, the value for platelets is over 10 times higher than that for neutrophils. Our results suggest that Sph-1-P, rapidly converted from sphingosine, abundantly stored in platelets, and released on the cell activation, may play a physiologic role in thrombosis, hemostasis, and the natural wound-healing processes.
1-磷酸鞘氨醇（Sph-1-P）是鞘氨醇激酶分解鞘氨醇的初始产物，经1-磷酸鞘氨醇裂解酶作用后可裂解为脂肪醛和磷酸乙醇胺。这种磷酸化的鞘氨醇碱基不仅是一种中间分解代谢产物，还是一种具有重要功能的生物活性脂质，包括刺激瑞士3T3成纤维细胞的细胞增殖以及抑制肿瘤细胞的运动。在本研究中，我们检测了Sph-1-P在人血小板中的功能作用。Sph-1-P可诱导血小板形态改变和聚集反应，尽管它未能引发分泌。鞘氨醇、神经酰胺、鞘磷脂和N,N-二甲基鞘氨醇均无法模拟Sph-1-P对血小板的积极作用。低于阈值浓度的Sph-1-P与弱血小板激动剂如二磷酸腺苷（ADP）和肾上腺素协同引发聚集，这可能对血小板激活的有效放大很重要。Sph-1-P可诱导细胞内Ca2+动员，且Ca2+释放的剂量反应与诱导形态改变所需的浓度密切相关。向完整血小板中添加[3H]鞘氨醇后，该标记物迅速转化为Sph-1-P，随后转化为神经酰胺和鞘磷脂。有趣的是，形成的Sph-1-P在生理激动剂刺激血小板时会特异性释放到培养基中。通过将其转化为放射性标记的N-乙酰-Sph-1-P来测量，血小板中Sph-1-P的含量为1.4 nmol/10(9)个细胞，约为鞘氨醇质量的四倍。当按Sph-1-P/磷脂的摩尔百分比进行比较时，血小板的值比中性粒细胞的值高10倍以上。我们的结果表明，Sph-1-P由鞘氨醇快速转化而来，大量储存在血小板中，并在细胞激活时释放，可能在血栓形成、止血和自然伤口愈合过程中发挥生理作用。
