ABSTRACT
Tubeimoside-1 is a triterpenoid saponin extracted from the traditional Chinese herb Bolbostemma paniculatum (Maxim.) Franquet (Cucurbitaceae). We investigated the cytotoxic effect and apoptosis mechanism of tubeimoside-1. Tubeimoside-1 was cytotoxic in seven human cancer cell lines, with HepG2 the most sensitive. Tubeimoside-1 induced apoptosis of HepG2 cells dose and time dependently. Both the extrinsic and intrinsic pathways were triggered by tubeimoside-1. Caspase-3, -8 and -9 were activated and the expression of Fas, Fas ligand, Bcl-2, Bak and Bax was regulated. Moreover, tubeimoside-1 induced accumulation of reactive oxygen species and arrested cell cycle at the G(2)/M phase, thus contributing to apoptosis, through signaling regulation by tumor necrosis factor α, nuclear factor κB (NF-κB), Jun N-terminal kinase (JNK) and p53. We provide further insight into the tubeimoside-1 cytotoxic effect for antitumor chemotherapeutic treatment.
Subject(s)
Apoptosis/drug effects , G2 Phase Cell Cycle Checkpoints/drug effects , JNK Mitogen-Activated Protein Kinases/metabolism , NF-kappa B/metabolism , Oxidative Stress/drug effects , Saponins/pharmacology , Triterpenes/pharmacology , Tumor Suppressor Protein p53/metabolism , Caspase 3/genetics , Caspase 3/metabolism , Caspase 8/genetics , Caspase 8/metabolism , Caspase 9/genetics , Caspase 9/metabolism , Cucurbitaceae/chemistry , Drugs, Chinese Herbal/pharmacology , Fas Ligand Protein/genetics , Fas Ligand Protein/metabolism , Gene Expression Regulation , Hep G2 Cells , Humans , JNK Mitogen-Activated Protein Kinases/genetics , NF-kappa B/genetics , Reactive Oxygen Species/metabolism , Signal Transduction , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/metabolism , Tumor Suppressor Protein p53/genetics , bcl-2-Associated X Protein/genetics , bcl-2-Associated X Protein/metabolismABSTRACT
Pharmaceutical interactions with human serum albumin (HSA) are of great interest, because HSA is a pharmacokinetic determinant and a good model for exploring the protein-ligand interactions. Due to their hydrophobic nature, naturally occurring flavones, which possess various pharmacological activities, bind to HSA in human plasma. Here, we have identified the binding modes of two representative flavones--baicalin (BLI) and its aglycon, baicalein (BLE)--to HSA using a combination of experimental and computational approaches. The association properties were measured by applying spectroscopic methods, and a higher affinity was found for BLE. As evidenced by displacement and chemical unfolding assays, both ligands bind at Sudlow site I. Furthermore, molecular docking was utilized to characterize the models of HSA-flavone complexes, and molecular dynamics (MD) simulations as well as free energy calculations were undertaken to examine the energy contributions and the roles of various amino acid residues of HSA in flavones binding; the mechanism whereby glycosylation affects the association was also discussed. The present work provides reasonable binding models for both flavones to HSA.
Subject(s)
Flavanones/chemistry , Flavonoids/chemistry , Serum Albumin/chemistry , Binding Sites , Glycosylation , Humans , Molecular Dynamics Simulation , Protein Binding , Protein Structure, Tertiary , Spectrometry, Fluorescence , ThermodynamicsABSTRACT
In this study, the apoptotic effect of alpha-bisabolol, a sesquiterpene, against human liver carcinoma cell line HepG2 was investigated. MTT assay showed alpha-bisabolol could effectively induce cytotoxicity in several human cancer cell lines (PC-3, Hela, ECA-109 and HepG2). The results of nuclei morphology examination, DNA fragmentation detection, flow cytometry analysis and cleavage of poly(ADP-ribose) polymerase and caspases indicated alpha-bisabolol might induce dose- and time-dependent apoptosis in HepG2 cells. Western blot data also showed a cascade activation of caspases-8,-9,-3 and promoted expression of Fas, implying caspase-8 might function as an upstream regulator, and the Fas-related pathway might be involved in this process. Preparation of mitochondrial/cytosol fraction followed with immunoblot analysis showed the release of chromosome c from mitochondria, down-regulated expression of Bcl-2 and translocation of Bax, Bak and Bid, suggesting the mitochondrial-related pathway might be involved in alpha-bisabolol-induced apoptosis either. Detection of accumulation of nuclear wild-type p53 and up-regulated expression of NFkappaB indicated these two key regulator with transcriptional decision-making function in various signaling pathways might also play a role in alpha-bisabolol-induced apoptosis in HepG2 cells.
