Natural Drug Silybin And Evodiamine Induced Human Fibrosarcoma Ht1080 Cells Death Mechanism

Silibinin, also known as silybin, is a major active constituent of silymarin, which is a mixture of flavonolignans extracted from milk thistle (Silybum marianum). Silibinin has hepatoprotective properties and anti-cancer effects. We found that silibinin induced HT1080 cell autophagy and apoptosis both in medium containing 10%fetal bovine serum (FBS) and serum free medium (SFM), and that autophagy enhanced apoptosis. Silibinin induced cell death by increasing generation of reactive oxygen species (ROS), of which H2O2 and O2 were the major forms. ROS activated p38 (a member of MAPK (mitogen-activated protein kinase) family) and subsequently induced transposition of NF-kB (nuclear transcription factor kappa B) from cytoplasm to nucleus; meanwhile, p38 and NF-kB promoted generation of ROS, indicating that ROS-p38-NF-kB might operate in a way of positive feedback mechanism. Tumor suppressor p53 and JNK (c-Jun NH2-terminal kinase, another member of MAPK family) were also found to enhance silibinin-induced autophagic cell death. Both p38 and JNK regulated the function of p53, and p53 augmented silibinin's cytotoxicity by inhibition of MEK/ERK (extracellular signal-regulated kinase) and PI3K/Akt (PKB) (phosphatidylinositol 3-OH kinase/protein kinase B) survival pathways.Evodiamine was investigated to demonstrate relation of autophagy and apoptosis under effects of different drugs. Evodiamine is an active constituent isolated from the dry unripe fruit of Evodia rutaecarpa. Our results suggested that evodiamine induced HT1080 cell autophagy and apoptosis both in medium containing 10%FBS and SFM, and autophagy inhibited apoptosis, which was opposite to silibinin's effect on autophagy-apoptosis relationship. Silibinin upregulated expressions of JNK/p-JNK while evodiamine downregulated them, suggesting that these two drugs might regulate different functions of autophagy through JNK activity. Additionally, evodiamine induced mitochondria-mediated apoptosis and regulated cell death by modulation of MAPK family members. PI3K/Akt pathway protected cells, while NF-kB augmented evodiamine'cytotoxicity. Meanwhile, low dose of evodiamine induced significant G2/M cell-cycle arrest.