Cynaropicrin Suppresses Cell Proliferation by Inducing Mitophagy through p38 MAPK-Mediated Mitochondrial ROS Generation in Human Hepatocellular Carcinoma Cells

Abstract

Cynaropicrin, a sesquiterpene lactone, has diverse pharmacological activities. However, its anticancer activity against hepatocellular carcinoma (HCC) has not been fully elucidated. Here, we investigated the cytotoxic effects of cynaropicrin and examined its mechanism of action in human HCC cells. The results demonstrated that cynaropicrin significantly induced cytotoxicity and autophagy in HCC cells, but not in immortalized non-cancerous hepatocytes, which was related to the generation of mitochondrial reactive oxygen species (mtROS) and induction of mitochondrial membrane potential loss. Under cynaropicrin treatment, the expression of microtubule-associated protein light chain 3, which is involved in the elongation of the phagophore membrane, was upregulated, whereas the expression of Beclin-1 and p62, which are essential for the formation of autophagosomes, was downregulated. In addition, the expression of mitophagy regulators PTEN-induced kinase 1 (PINK1) and Parkin in the mitochondria increased, suggesting the induction of autophagic flux in the mitochondria. However, N-acetyl-l-cysteine, a ROS scavenger, counteracted cynaropicrin-induced effects. Moreover, cynaropicrin increased the phosphorylation of p38 mitogen-activated protein kinase (MAPK), and the p38 MAPK inhibitor, SB203580, specifically attenuated cynaropicrin-induced cytotoxicity and mtROS production. Importantly, SB203580 reversed cynaropicrin-induced expression of PINK1 and Parkin in the mitochondria. Collectively, our findings demonstrate that cynaropicrin exerts cytotoxic effects against HCC cells by inducing mitochondrial autophagy through the activation of the p38 MAPK-ROS pathway, indicating that cynaropicrin could be a potential therapeutic agent for liver cancer treatment.