Silibinin activated ROS–p38–NF-κB positive feedback and induced autophagic death in human fibrosarcoma HT1080 cells

Abstract

Our previous results demonstrated that silibinin induced autophagic and apoptotic cell death dependent on reactive oxygen species (ROS especially H₂O₂ and ) in HT1080 cells. In this study, we further show that p38–NF-κB pathway is involved in silibinin-induced ROS-mediated autophagy. Cells were pretreated with serum-free media for 24 h before being treated with silibinin. Generation of ROS and autophagy was detected in 15 min and 1 h, respectively. Development of autophagy was supported by an upregulated expression of Beclin-1 and conversion of light chain (LC3-I–LC3-II). Expression of p38/p-p38 and transposition of NF-κB from cytoplasm to nuclei were also increased. Inhibitors of p38 and NF-κB and scavengers of H₂O₂ and reduced both generation of ROS and simultaneous occurrence of silibinin-induced autophagy. Besides, expression of p38/p-p38 and transposition of NF-κB from cytoplasm to nuclei were decreased by these two ROS scavengers. ROS and p38–NF-κB pathway were possibly cooperated in a positive feedback mechanism. Inhibition of p38, NF-κB, H₂O₂, or rescued cells from silibinin-induced death in a long-term (12 h) manner. According to the previous study that silibinin-induced autophagy was a positive regulator of apoptotic cell death, it was possible that ROS and p38–NF-κB mediated silibinin-induced autophagy and eventually led to cell death.

Keywords:

• silibinin
• autophagy
• p38
• NF-κB
• H₂O₂
• O₂ ^.−