Meng Aimin, Luberto Chiara, Meier Patrick, Bai Aiping, Yang Xiaofeng, Hannun Yusuf A, Zhou Daohong
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.
Exp Cell Res. 2004 Jan 15;292(2):385-92. doi: 10.1016/j.yexcr.2003.10.001.
Tricyclodecan-9-yl-xanthogenate (D609) is a selective tumor cytotoxic agent. However, the mechanisms of action of D609 against tumor cells have not been well established. Using U937 human monocytic leukemia cells, we examined the ability of D609 to inhibit sphingomyelin synthase (SMS), since inhibition of SMS may contribute to D609-induced tumor cell cytotoxicity via modulating the cellular levels of ceramide and diacylglycerol (DAG). The results showed that D609 is capable of inducing U937 cell death by apoptosis in a dose- and time-dependent manner. The induction of U937 cell apoptosis was associated with an inhibition of SMS activity and a significant increase in the intracellular level of ceramide and decrease in that of sphingomyelin (SM) and DAG, which resulted in an elevation of the ratio between ceramide and DAG favoring the induction of apoptosis. In addition, incubation of U937 cells with C(6)-ceramide and/or H7 (a selective PKC inhibitor) reduced U937 cell viability; whereas pretreatment of the cells with a PKC activator, PMA or 1-oleoyl-2-acetylglycerol (OAG), attenuated D609-induced U937 cell apoptosis. These results suggest that SMS is a potential target of D609 and inhibition of SMS may contribute to D609-induced tumor cell death via modulation of the cellular levels of ceramide and DAG.
三环癸烷-9-基-黄原酸酯（D609）是一种选择性肿瘤细胞毒性剂。然而，D609对肿瘤细胞的作用机制尚未完全明确。我们使用U937人单核细胞白血病细胞，研究了D609抑制鞘磷脂合酶（SMS）的能力，因为抑制SMS可能通过调节神经酰胺和二酰基甘油（DAG）的细胞水平，导致D609诱导的肿瘤细胞毒性。结果表明，D609能够以剂量和时间依赖性方式诱导U937细胞凋亡。U937细胞凋亡的诱导与SMS活性的抑制以及神经酰胺细胞内水平的显著增加、鞘磷脂（SM）和DAG水平的降低有关，这导致神经酰胺与DAG的比例升高，有利于凋亡的诱导。此外，用C(6)-神经酰胺和/或H7（一种选择性PKC抑制剂）孵育U937细胞会降低U937细胞活力；而用PKC激活剂PMA或1-油酰-2-乙酰甘油（OAG）预处理细胞，则会减弱D609诱导的U937细胞凋亡。这些结果表明，SMS是D609的潜在靶点，抑制SMS可能通过调节神经酰胺和DAG的细胞水平，导致D609诱导的肿瘤细胞死亡。
