Lee Jang-Chang, Tsai Chih-Yen, Kao Jung-Yie, Kao Ming-Ching, Tsai Shih-Chang, Chang Chih-Shiang, Huang Li-Jiau, Kuo Sheng-Chu, Lin Jen-Kun, Way Tzong-Der
Graduate institute of Pharmaceutical Chemistry, College of Pharmacy, China Medical University, Taichung, Taiwan.
Mol Nutr Food Res. 2008 Jun;52(6):655-63. doi: 10.1002/mnfr.200700381.
Geraniin, a form of tannin separated from geranium, causes cell death through induction of apoptosis; however, cell death characteristics for geraniin have not yet been elucidated. Here, we investigated the mechanism of geraniin-induced apoptosis in human melanoma cells and demonstrated that geraniin was able to induce cell apoptosis in a concentration- and time-dependent manner. We also examined the signaling pathway related to geraniin-induced apoptosis. To clarify the relationship between focal adhesion kinase (FAK) and geraniin-induced apoptosis, we treated human melanoma cells with geraniin and found that this resulted dose- and time-dependent degradation in FAK. However, FAK cleavage was significantly inhibited when cells were pretreated with a selective inhibitor of caspase-3 (Ac-Asp-Glu-Val-Asp-CHO). Here, we demonstrated for the first time that geraniin triggered cell death by caspase-3-mediated cleavage of FAK. There were two possible mechanisms for activating caspase-3, mitochondria-mediated and receptor-mediated apoptosis. To confirm the geraniin-relevant signaling pathway, using immunoblot analysis we found that geraniin-induced apoptosis was associated with the up-regulation of Fas ligand expression, the activation of caspase-8, the cleavage of Bid, and the induction of cytochrome c release from mitochondria to the cytosol. Treatment with geraniin caused induction of caspase-3 activity in a dose- and time-dependent manner followed by proteolytic cleavage of poly-(ADP-ribose) polymerase, and DNA fragmentation factor 45. The geraniin-induced apoptosis may provide a pivotal mechanism for its cancer-chemopreventive action.
老鹳草素是从老鹳草中分离出的一种单宁形式，可通过诱导细胞凋亡导致细胞死亡；然而，老鹳草素的细胞死亡特征尚未阐明。在此，我们研究了老鹳草素诱导人黑色素瘤细胞凋亡的机制，并证明老鹳草素能够以浓度和时间依赖性方式诱导细胞凋亡。我们还研究了与老鹳草素诱导凋亡相关的信号通路。为了阐明粘着斑激酶（FAK）与老鹳草素诱导凋亡之间的关系，我们用老鹳草素处理人黑色素瘤细胞，发现这导致FAK呈剂量和时间依赖性降解。然而，当细胞用半胱天冬酶-3的选择性抑制剂（Ac-Asp-Glu-Val-Asp-CHO）预处理时，FAK的裂解受到显著抑制。在此，我们首次证明老鹳草素通过半胱天冬酶-3介导的FAK裂解触发细胞死亡。激活半胱天冬酶-3有两种可能的机制，即线粒体介导的凋亡和受体介导的凋亡。为了确定与老鹳草素相关的信号通路，我们通过免疫印迹分析发现，老鹳草素诱导的凋亡与Fas配体表达上调、半胱天冬酶-8激活、Bid裂解以及细胞色素c从线粒体释放到细胞质中有关。用老鹳草素处理导致半胱天冬酶-3活性呈剂量和时间依赖性诱导，随后多聚（ADP-核糖）聚合酶和DNA片段化因子45发生蛋白水解裂解。老鹳草素诱导的凋亡可能为其癌症化学预防作用提供关键机制。
