Department of Medicinal Chemistry, School of Pharmacy, Taipei Medical University, Taipei, Taiwan.
Chem Biol Interact. 2011 Aug 15;193(1):3-11. doi: 10.1016/j.cbi.2011.03.008. Epub 2011 Mar 29.
2-Methyl-1,4-naphthoquinone (menadione or vitamin K3; EPO) and K3-2,3-epoxide (EPO1), but not vitamin K3-3-OH (EPO2), exhibited cytotoxicity that caused DNA fragmentation and chromatin condensation in U87 and C6 cells. EPO1 showed more-potent cytotoxicity than EPO, and the IC(50) values of EPO and EPO1 in U87 cells were 37.5 and 15.7μM, respectively. Activation of caspase 3 enzyme activity with cleavage of caspase 3 protein was detected in EPO1-treated U87 and C6 cells, and the addition of the caspase 3 peptidyl inhibitor, DEVD-FMK, reduced the cytotoxic effect of EPO1. An increase in the intracellular ROS level by EPO1 was observed in the DCHF-DA analysis, and EPO1-induced apoptosis and caspase 3 protein cleavage were prevented by adding the antioxidant, N-acetyl-cysteine (NAC), with decreased ROS production elicited by EPO1. Activation of ERK and JNK, but not p38, via phosphorylation induction was identified in EPO1- but not EPO- or EPO2-treated U87 and C6 cells, and this was blocked by adding NAC. However, the ERK inhibitor, PD98059, and the JNK inhibitor, SP600125, showed no effect on EPO1-induced cytotoxicity in either cell type. Our findings demonstrate that 2,3-epoxide substitution significantly potentiates the apoptotic effect of vitamin K3 via stimulating ROS production, which may be useful in the chemotherapy of glioblastoma cells.
2-甲基-1,4-萘醌（甲萘醌或维生素 K3；EPO）和 K3-2,3-环氧化物（EPO1），但维生素 K3-3-OH（EPO2）没有，表现出细胞毒性，导致 U87 和 C6 细胞的 DNA 片段化和染色质凝聚。EPO1 比 EPO 表现出更强的细胞毒性，EPO 和 EPO1 在 U87 细胞中的 IC50 值分别为 37.5 和 15.7μM。EPO1 处理的 U87 和 C6 细胞中检测到 caspase 3 酶活性的激活和 caspase 3 蛋白的切割，添加 caspase 3 肽抑制剂 DEVD-FMK 可降低 EPO1 的细胞毒性作用。在 DCHF-DA 分析中观察到 EPO1 引起的细胞内 ROS 水平增加，添加抗氧化剂 N-乙酰半胱氨酸（NAC）可减少 EPO1 引起的 ROS 产生，从而防止 EPO1 诱导的细胞凋亡和 caspase 3 蛋白切割。在 EPO1 处理的 U87 和 C6 细胞中，通过磷酸化诱导鉴定出 ERK 和 JNK 的激活，而不是 p38，但在 EPO 或 EPO2 处理的细胞中没有，添加 NAC 可阻断这种激活。然而，ERK 抑制剂 PD98059 和 JNK 抑制剂 SP600125 对两种细胞类型中 EPO1 诱导的细胞毒性均无影响。我们的研究结果表明，2,3-环氧化物取代物通过刺激 ROS 产生显著增强了维生素 K3 的促凋亡作用，这可能对胶质母细胞瘤细胞的化学治疗有用。
