Sweeney E A, Sakakura C, Shirahama T, Masamune A, Ohta H, Hakomori S, Igarashi Y
The Biomembrane Institute, University of Washington, Seattle, 98119, USA.
Int J Cancer. 1996 May 3;66(3):358-66. doi: 10.1002/(SICI)1097-0215(19960503)66:3<358::AID-IJC16>3.0.CO;2-7.
In the study of apoptosis initiated by various signals including ligands binding to cell membrane receptors such as Fas and TNFRI, the sphingomyelin pathway and its resulting metabolites, the sphingolipids, have been suggested to be involved in the signaling pathway. In earlier studies we presented data which indicated that sphingosine (Sph) itself was increased during apoptosis induced by phorbol myristate acetate (PMA) in HL60 cells and tumor necrosis factor (TNF) in neutrophils, and when added exogenously was able to induce apoptosis. We report here that Sph and its methylated derivative N,N,-dimethylsphingosine (DMS) are able to induce apoptosis in cancer cells of both hematopoietic and carcinoma origin. In human leukemic cell lines CMK-7, HL60 and U937, treatment with 20 microM Sph for 6 hr caused apoptosis in up to 90% of cells. Human colonic carcinoma cells HT29, HRT18, MKN74 and COLO205 were shown to be more susceptible to apoptosis upon addition of DMS (>50%) than of Sph (<50%), yet were weakly or not sensitive to N,N,N-trimethylsphingosine (TMS). Under the same conditions, in the presence of serum, neither Sph-1-phosphate nor ceramide analogues C2-, C6- or C8-ceramide were able to induce apoptosis in any cell lines. However, in the absence of serum, ceramide analogues induced apoptosis in leukemia cell lines after 18 hr, yet much less so than Sph or DMS. Furthermore, apoptosis induced by Sph or DMS could not be inhibited by the ceramide synthase inhibitor fumonisin B1. Apoptosis was not induced by sphingolipids in primary culture cells, such as HUVEC or rat mesangial cells, but was apparent in transformed rat mesangial cells. Additionally, apoptosis induced by Sph, DMS or C2Cer was inhibited by protease inhibitors. Our data further support the evidence that the catabolic pathway of sphingomyelin involving Sph and other metabolites is an integral part of the apoptosis pathway.
在对包括与Fas和TNFRI等细胞膜受体结合的配体在内的各种信号引发的细胞凋亡研究中，鞘磷脂途径及其产生的代谢产物鞘脂类物质被认为参与了信号通路。在早期研究中，我们提供的数据表明，在佛波酯（PMA）诱导HL60细胞凋亡以及肿瘤坏死因子（TNF）诱导中性粒细胞凋亡的过程中，鞘氨醇（Sph）自身含量增加，并且外源性添加时能够诱导细胞凋亡。我们在此报告，Sph及其甲基化衍生物N,N,-二甲基鞘氨醇（DMS）能够诱导造血来源和癌来源的癌细胞发生凋亡。在人白血病细胞系CMK-7、HL60和U937中，用20微摩尔/升的Sph处理6小时，高达90%的细胞发生凋亡。人结肠癌细胞HT29、HRT18、MKN74和COLO205在添加DMS（>50%）时比添加Sph（<50%）时对凋亡更敏感，但对N,N,N-三甲基鞘氨醇（TMS）反应较弱或不敏感。在相同条件下，有血清存在时，鞘氨醇-1-磷酸以及神经酰胺类似物C2-、C6-或C8-神经酰胺均不能在任何细胞系中诱导凋亡。然而，无血清时，神经酰胺类似物在18小时后可诱导白血病细胞系发生凋亡，但程度远低于Sph或DMS。此外, 鞘氨醇合酶抑制剂伏马菌素B1不能抑制Sph或DMS诱导的凋亡。鞘脂类物质在原代培养细胞如人脐静脉内皮细胞（HUVEC）或大鼠系膜细胞中不诱导凋亡，但在转化的大鼠系膜细胞中则明显诱导凋亡。另外，Sph、DMS或C2神经酰胺诱导的凋亡可被蛋白酶抑制剂抑制。我们的数据进一步支持了以下证据，即涉及Sph和其他代谢产物的鞘磷脂分解代谢途径是细胞凋亡途径的一个组成部分。
