Polyphyllin I induces G2/M phase arrest and apoptosis in U251 human glioma cells via mitochondrial dysfunction and the JNK signaling pathway

• Published in: Acta biochimica et biophysica Sinica Vol. 49; no. 6; pp. 479 - 486
• Main Authors: Liu, Jiaxin, Zhang, Yueting, Chen, Li, Yu, Fei, Li, Xiaojin, Dan Tao, Zhao, Jianhua, Zhou, Shuai
• Format: Journal Article
• Language: English
• Published: China 01.06.2017
• Subjects: Apoptosis - drug effects; Brain Neoplasms - metabolism; Brain Neoplasms - pathology; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Survival - drug effects; Diosgenin - analogs & derivatives; Diosgenin - chemistry; Diosgenin - pharmacology; Dose-Response Relationship, Drug; G2 Phase Cell Cycle Checkpoints - drug effects; Glioma - metabolism; Glioma - pathology; Humans; MAP Kinase Signaling System - drug effects; Membrane Potential, Mitochondrial - drug effects; Mitochondria - drug effects; Mitochondria - metabolism; Molecular Structure; Proto-Oncogene Proteins c-bcl-2 - metabolism; JNK pathway; apoptosis; U251 cell; cell cycle; polyphyllin I
• ISSN: 1672-9145; 1745-7270
• DOI: 10.1093/abbs/gmx033

Glioblastoma is the most aggressive brain tumor, and its prognosis remains poor. Therefore, novel therapeutic strategies are needed for glioma therapy. Polyphyllin I （PPI）, a bioactive constitu- ent extracted from Paris polyphylla, was reported to have anti-tumor activity. However, the detailed mechanism for this activity remains unclear. Here, we investigated the inhibitory effects of PPI on glioma cells and its mechanisms in vitro. U251 cells were treated with various concentra- tions of PPI （2-9 μM） for 24 to 72 h. The inhibition of U251 cell proliferation by PPI was assessed by MTT assay. The effects on cell cycle and apoptosis were examined by flow cytometry with PI and annexin V-FITC/PI dual staining, and the cell mitochondrial membrane potential level was evalu- ated by fluorescence microscopy with JC-1 staining. The expression levels of apoptosis-related proteins and JNK signal pathway proteins were evaluated by western blot analysis. Results showed that PPI significantly inhibited the proliferation of U251 cells in a concentration-dependent manner. PPI induced G2/M phase arrest and apoptosis, and it upregulated the expressions of Bax, cytochrome c, and p-JNK, but downregulated the expression of the anti-apoptotic protein Bcl-2 in U251 cells. Moreover, PPI provoked the depolarization of the mitochondrial membrane potential. In addition, apoptosis induced by the PPI was remarkably suppressed by the JNK inhibitor SP600125. Our data provide evidence that PPI inhibits proliferation and induces apoptotic cell death in U251 cells. This effect may be associated with the JNK pathway. These results suggest that PPI is an activator of the JNK signaling pathway with a potential anti-glioma effect.