Cytotoxic activities of Telectadium dongnaiense and its constituents by inhibition of the Wnt/ß-catenin signaling pathway.

BACKGROUND: Wnt/ß-catenin signaling pathway is a potential target for the treatment of human colon cancer. Thus, the inhibitory effects of various plant extracts on cell proliferation and Wnt signal transduction were evaluated to discover a Wnt signaling inhibitor. PURPOSE: The present study aimed to investigate the cytotoxicity involved in Wnt pathway of the MeOH extract from Telectadium dongnaiense bark (TDB) and to identify its bioactive constituents by bioassay-guided fractionation. METHODS: The sulforhodamine B-based proliferation assay and the ß-catenin/TCF-responsive reporter gene assay were employed as screening systems. The isolation and identification of compounds were elucidated on the basis of spectroscopic methods. Inhibitory effects on the expression levels of Wnt target genes were determined by real-time PCR and western blotting. RESULTS: The extract of TDB most strongly inhibited cell proliferation and TOPflash activity (IC50 = 1.5 and 2.0 µg/ml), which was correlated with its inhibitory effects on the expression of Wnt target genes. Three major compounds were isolated from bioactive fractions and were identified as 1,4-dicaffeoylquinic acid (1), quercetin 3-rutinoside (2), and periplocin (3). Only compound 3 showed anti-proliferative activity (IC50 = 0.06 µM) and exhibited Wnt signaling inhibitory effects in HCT116 colon cancer cells. CONCLUSIONS: This study contributes to understanding the cytotoxic properties of TDB extract and its constituents and provides a potent strategy for its further application.

Magnolol inhibits angiogenesis by regulating ROS-mediated apoptosis and the PI3K/AKT/mTOR signaling pathway in mES/EB-derived endothelial-like cells.

Magnolol, a neolignan from the traditional medicinal plant Magnolia obovata, has been shown to possess neuroprotective, anti-inflammatory, anticancer and anti-angiogenic activities. However, the precise mechanism of the anti-angiogenic activity of magnolol remains to be elucidated. In the present study, the anti-angiogenic effect of magnolol was evaluated in mouse embryonic stem (mES)/embryoid body (EB)-derived endothelial-like cells. The endothelial-like cells were obtained by differentiation from mES/EB cells. Magnolol (20 µM) significantly suppressed the transcriptional and translational expression of platelet endothelial cell adhesion molecule (PECAM), an endothelial biomarker, in mES/EB-derived endothelial-like cells. To further understand the molecular mechanism of the suppression of PECAM expression, signaling pathways were analyzed in the mES/EB-derived endothelial-like cells. Magnolol induced the generation of reactive oxygen species (ROS) by mitochondria, a process that was associated with the induction of apoptosis as determined by positive Annexin V staining and the activation of cleaved caspase-3. The involvement of ROS generation by magnolol was confirmed by treatment with an antioxidant, N-acetyl-cysteine (NAC). NAC inhibited the magnolol-mediated induction of ROS generation and suppression of PECAM expression. In addition, magnolol suppressed the activation of MAPKs (ERK, JNK and p38) and the PI3K/AKT/mTOR signaling pathway in mES/EB-derived endothelial-like cells. Taken together, these findings demonstrate for the first time that the anti-angiogenic activity of magnolol may be associated with ROS-mediated apoptosis and the suppression of the PI3K/AKT/mTOR signaling pathway in mES/EB-derived endothelial-like cells.