白花蛇舌草激发肿瘤细胞产生超氧化物和激活半胱氨酸天冬氨酸蛋白酶诱导肿瘤细胞凋亡

背景与目的:白花蛇舌草是常用于抗肿瘤的中药之一。实验研究和临床使用表明该药有明显的抗肿瘤作用,但是该药抗癌作用的原理尚不清楚。本文研究了白花蛇舌草的乙醇和水的提取物对人急性髓样白血病细胞HL60生存和死亡的影响及其机制。方法:我们用白花蛇舌草的提取物处理细胞,在处理后2h开始测量细胞内的超氧化物及各种半胱氨酸天冬氨酸蛋白酶(caspase)的水平,并于24h测量细胞的生存及凋亡情况。结果:我们发现乙醇和水的提取物对HL60细胞的生存有较强的抑制作用。对乙醇提取物的进一步研究则表明该提取物能有效地激活caspase-2和caspase-3并诱发癌细胞凋亡。乙醇提取物在较短的时间(2h)内诱导细胞产生超氧化物。结论:白花蛇舌草乙醇提取物能有效地激发肿瘤细胞产生超氧化物并诱导肿瘤细胞凋亡。由于细胞内产生超氧化物能诱导细胞凋亡,我们认为白花蛇舌草的抗癌机制是通过激发肿瘤细胞产生大量超氧化物,致使癌细胞内氧爆破,最终激活凋亡信号网络而使癌细胞凋亡。

Evidence for Oldenlandia diffusa-evoked cancer cell apoptosis through superoxide burst and caspase activation

BACKGROUND & OBJECTIVE: Oldenlandia diffusa (Bai Hua She She Cao) is one of the herbs most commonly used in traditional Chinese medicine for treating cancer. Various studies using the herb alone or in combination with other therapy plans have evidenced the effectiveness of the herb in the management of cancers of different tissue origin. However, the mechanisms underlying its anti-cancer activity are unknown. In the present study, we attempted to investigate the apoptotic activity of crude extracts of the herb as well as the possible molecular pathways. METHODS: We incubated human promyelocytic leukemia cell line HL60 cells with ethanol or aqueous extracts of the herb, and determined the levels of intracellular superoxide at 2 and 4 hours as well as caspase activity at 3, 6 and 8 hours using photospectrometry. Cancer cell survival and apoptosis were quantified at 24 hours by using MTT and flow cytometry analyses respectively. RESULTS: We found that it dose-dependently inhibited the cancer cell growth in MTT assay. Flow cytometry analysis revealed that it elicited significant production of sub-G(1) population of the cells, indicating the extract-evoked cell apoptotic death. The LD(50) of the ethanol extract was estimated to be approximately 320 microg/ml. Moreover, treatment of the cancer cells with the ethanol component markedly increased the production of superoxide within few hours. Significant elevation in the protease activities of caspases-2 and -3 were detected at as early as 3 and 6 hours respectively. CONCLUSION: Our results show that the ethanol extract of the herb effectively evokes cancer cell apoptosis, possibly through burst-mediated caspase activation.