Picropodophyllotoxin (PPT), an epimer of podophyllotoxin, is derived from the roots of Podophyllum hexandrum and it exerts various biological effects, such as anti- proliferation activity. However, the effect of PPT on colorectal cancer cells and the cellular mechanisms have not been studied. In the present study, we explored the anticancer activity and its underlying mechanisms of PPT in HCT116 cells. The MTT assay was used to monitor the cell viability. The flow cytometry was used to evaluate cell cycle distribution, induction of apoptosis, level of reactive oxygen species (ROS), assessment of the mitochondrial membrane potential (Δψm) and multi-caspase activity. western blotting assay was performed to detect the expression of cell cycle regulatory proteins, apoptosis-related proteins, and p38MAPK. We found that PPT induced apoptosis, cell cycle arrest at the G1-phase, and reactive oxygen species production in HCT116 cell line. In addition, PPT enhanced phosphorylation of p38 MAPK that regulates apoptosis and PPT induced apoptosis. The phosphorylation of p38 MAPK was inhibited by antioxidant agent (N-acetyl-L-cysteine, NAC) and the p38 inhibitor (SB203580). PPT induced depolarization of the mitochondrial inner membrane and caspase dependent apoptosis, which was attenuated by exposure to Z VAD FMK. Overall, these data indicate that PPT induces G1/S arrest and apoptosis via the ROS generation and activation of p38 MAPK signaling pathway.

中文翻译：

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鬼臼苦毒素通过 ROS 的产生和 p38 MAPK 信号通路的激活，诱导人结直肠癌细胞的 G1/S 细胞周期停滞和细胞凋亡。

Picropodophyllotoxin (PPT) 是鬼臼毒素的差向异构体，来源于Podophyllum hexandrum的根并发挥多种生物学效应，如抗增殖活性。然而，PPT对结直肠癌细胞的作用及其细胞机制尚未研究。在本研究中，我们探讨了 PPT 在 HCT116 细胞中的抗癌活性及其潜在机制。MTT测定用于监测细胞活力。流式细胞术用于评估细胞周期分布、细胞凋亡的诱导、活性氧 (ROS) 水平、线粒体膜电位 (Δψm) 和多半胱天冬酶活性的评估。免疫印迹法检测细胞周期调节蛋白、凋亡相关蛋白和p38MAPK的表达。我们发现 PPT 在 HCT116 细胞系中诱导细胞凋亡、G1 期细胞周期停滞和活性氧产生。此外，PPT 增强了调节细胞凋亡和 PPT 诱导细胞凋亡的 p38 MAPK 的磷酸化。p38 MAPK的磷酸化被抗氧化剂抑制（N -乙酰基-L-半胱氨酸，NAC) 和 p38 抑制剂 (SB203580)。PPT 诱导线粒体内膜去极化和 caspase 依赖性细胞凋亡，这通过暴露于 Z VAD FMK 而减弱。总的来说，这些数据表明 PPT 通过 ROS 的产生和 p38 MAPK 信号通路的激活诱导 G1/S 阻滞和细胞凋亡。