ABSTRACT
We investigated the effect of casticin on apoptosis induced by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). We found that casticin potentiated TRAIL-induced apoptosis in human colon cancer cells. Casticin downregulated cell survival proteins including Bcl-xL, Bcl-2, survivin, XIAP and cFLIP, and induced death receptor 5 (DR5), but had no effect on DR4 and decoy receptors (DcR1 or DcR2). Deletion of DR5 by siRNA significantly reduced the apoptosis induced by TRAIL and casticin. In addition, casticin induced reactive oxygen species (ROS) generation in a dose-dependent manner. Collectively, the present study showed that casticin potentiates TRAIL-induced apoptosis through downregulation of cell survival proteins and induction of DR5 mediated by ROS.
Subject(s)
Apoptosis Regulatory Proteins/metabolism , Apoptosis/drug effects , Colonic Neoplasms/metabolism , Flavonoids/pharmacology , Receptors, TNF-Related Apoptosis-Inducing Ligand/biosynthesis , TNF-Related Apoptosis-Inducing Ligand/pharmacology , Analysis of Variance , Down-Regulation/drug effects , GPI-Linked Proteins/metabolism , Gene Silencing , HCT116 Cells , HT29 Cells , Humans , Inhibitor of Apoptosis Proteins/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Reactive Oxygen Species/metabolism , Receptors, TNF-Related Apoptosis-Inducing Ligand/genetics , Receptors, TNF-Related Apoptosis-Inducing Ligand/metabolism , Receptors, Tumor Necrosis Factor, Member 10c , Survivin , Tumor Necrosis Factor Decoy Receptors/metabolism , Up-Regulation/drug effects , X-Linked Inhibitor of Apoptosis Protein/metabolism , bcl-X Protein/metabolismABSTRACT
Carvacrol is one of the members of monoterpene phenol and is present in the volatile oils of Thymus vulgaris, Carum copticum, origanum and oregano. It is a safe food additive commonly used in our daily life, and few studies have indicated that carvacrol has anti-hepatocarcinogenic activities. The rationale of the study was to examine whether carvacrol affects apoptosis of human hepatoma HepG2 cells. In this study, we showed that carvacrol inhibited HepG2 cell growth by inducing apoptosis as evidenced by Hoechst 33258 stain and Flow cytometric (FCM) analysis. Incubation of HepG2 cells with carvacrol for 24 h induced apoptosis by the activation of caspase-3, cleavage of PARP and decreased Bcl-2 gene expression. These results demonstrated that a significant fraction of carvacrol treated cells died by an apoptotic pathway in HepG2 cells. Moreover, carvacrol selectively altered the phosphorylation state of members of the MAPK superfamily, decreasing phosphorylation of ERK1/2 significantly in a dose-dependent manner, and activated phosphorylation of p38 but not affecting JNK MAPK phosphorylation. These results suggest that carvacrol may induce apoptosis by direct activation of the mitochondrial pathway, and the mitogen-activated protein kinase pathway may play an important role in the antitumor effect of carvacrol. These results have identified, for the first time, the biological activity of carvacrol in HepG2 cells and should lead to further development of carvacrol for liver disease therapy.
