Deltonin inhibits angiogenesis by regulating VEGFR2 and subsequent signaling pathways in endothelial cells

Deltonin enhances gastric carcinoma cell apoptosis and chemosensitivity to cisplatin via inhibiting PI3K/AKT/mTOR and MAPK signaling

BACKGROUND

As an active ingredient derived from Dioscorea zingiberensis C.H. Wright, deltonin has been reported to show anti-cancer effects in a variety of malignancies.

AIM

To investigate the role and mechanism of action of deltonin in promoting gastric carcinoma (GC) cell apoptosis and chemosensitivity to cisplatin.

METHODS

The GC cell lines AGS, HGC-27, and MKN-45 were treated with deltonin and then subjected to flow cytometry and 3-(4,5-dimethylthiazol-2-yl)-3,5-diphenyltetrazolium bromide assays for cell apoptosis and viability determination. Western blot analysis was conducted to examine alterations in the expression of apoptosis-related proteins (Bax, Bid, Bad, and Fas), DNA repair-associated proteins (Rad51 and MDM2), and phosphatidylinositol 3-kinase/protein kinase B/mammalian target of the rapamycin (PI3K/AKT/mTOR) and p38-mitogen-activated protein kinase (MAPK) axis proteins. Additionally, the influence of deltonin on GC cell chemosensitivity to cisplatin was evaluated both in vitro and in vivo.

RESULTS

Deltonin treatment weakened viability, enhanced apoptosis, and dampened DNA repair in GC cell lines in a dose-dependent pattern. Furthermore, deltonin mitigated PI3K, AKT, mTOR, and p38-MAPK phosphorylation. HS-173, an inhibitor of PI3K, attenuated GC cell viability and abolished deltonin inhibition of GC cell viability and PI3K/AKT/mTOR and p38-MAPK pathway activation. Deltonin also promoted the chemosensitivity of GC cells to cisplatin via repressing GC cell proliferation and growth and accelerating apoptosis.

CONCLUSION

Deltonin can boost the chemosensitivity of GC cells to cisplatin via inactivating p38-MAPK and PI3K/AKT/mTOR signaling.

Inhibiting Angiogenesis by Anti-Cancer Saponins: From Phytochemistry to Cellular Signaling Pathways

Saponins are one of the broadest classes of high-molecular-weight natural compounds, consisting mainly of a non-polar moiety with 27 to 30 carbons and a polar moiety containing sugars attached to the sapogenin structure. Saponins are found in more than 100 plant families as well as found in marine organisms. Saponins have several therapeutic effects, including their administration in the treatment of various cancers. These compounds also reveal noteworthy anti-angiogenesis effects as one of the critical strategies for inhibiting cancer growth and metastasis. In this study, a comprehensive review is performed on electronic databases, including PubMed, Scopus, ScienceDirect, and ProQuest. Accordingly, the structural characteristics of triterpenoid/steroid saponins and their anti-cancer effects were highlighted, focusing on their anti-angiogenic effects and related mechanisms. Consequently, the anti-angiogenic effects of saponins, inhibiting the expression of genes related to vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-α (HIF-1α) are two main anti-angiogenic mechanisms of triterpenoid and steroidal saponins. The inhibition of inflammatory signaling pathways that stimulate angiogenesis, such as pro-inflammatory cytokines, mitogen-activated protein kinase (MAPKs), and phosphoinositide 3-kinases/protein kinase B (PI3K/Akt), are other anti-angiogenic mechanisms of saponins. Furthermore, the anti-angiogenic and anti-cancer activity of saponins was closely related to the binding site of the sugar moiety, the type and number of their monosaccharide units, as well as the presence of some functional groups in their aglycone structure. Therefore, saponins are suitable candidates for cancer treatment by inhibiting angiogenesis, for which extensive pre-clinical and comprehensive clinical trial studies are recommended.

Ginsenoside Rb1 prevents homocysteine-induced EPC dysfunction via VEGF/p38MAPK and SDF-1/CXCR4 activation

Hyperhomocystinemia (HHcy) is known as an independent risk factor for cardiovascular disease. Our previous study showed that ginsenoside Rb1, the major active constituent of ginseng, prevents homocysteine (Hcy)-induced endothelial damage. However, the role of ginsenoside Rb1 in Hcy-induced dysfunction in endothelial progenitor cells (EPCs) remains unknown. In the study, we found that ginsenoside Rb1 reversed the Hcy-induced impairment of adhesive and migratory ability in EPCs which were significantly abolished by CXCR4 antagonist AMD3100 and VEGFR2 inhibitor SU5416. Ginsenoside Rb1 significantly reversed Hcy-induced SDF-1 reduction in the supernatant and in the serum. Ginsenoside Rb1 reversed downregulation of SDF-1 and VEGFR2 protein expression, inhibition of p38MAPK phosphorylation induced by Hcy. Re-endothelialization in balloon-injured carotid arteries significantly increased with EPCs transplant, and was even better with Rb1 treatment. This effect was significantly abolished by AMD3100. AMD3100 also decreased the number of CM-DiI labeled EPCs in injured arteries. Here we show for the first time that Rb1 prevents Hcy-induced EPC dysfunction via VEGF/p38MAPK and SDF-1/CXCR4 activation. These findings demonstrate a novel mechanism of the action of Rb1 that may have value in prevention of HHcy associated cardiovascular disease.

Structural Determinant and Its Underlying Molecular Mechanism of STPC2 Related to Anti-Angiogenic Activity

In this study, we aimed to use different strategies to further uncover the anti-angiogenic molecular mechanism of a fucoidan-like polysaccharide STPC2, isolated from brown alga Sargassum thunbergii. A desulfated derivative, STPC2-DeS, was successfully prepared and identified. The native polysaccharide and desulfated product were subjected to evaluate their anti-angiogenic effects. In the tube formation assay, STPC2 showed dose-dependent inhibition. In addition, STPC2 could distinctly inhibit the permeation of HUVEC cells into the lower chamber. Moreover, a significant reduction of microvessel density was observed in chick chorioallantoic membrane assay treated with STPC2. Meanwhile, STPC2 was found to repress the VEGF-induced neovessel formation in the matrigel plug assay in vivo. However, STPC2-DeS failed to suppress the anti-angiogenic activity via these in vitro and in vivo strategies. In addition, we demonstrated that STPC2 could significantly downregulate the phosphorylation of VEGFR2 and its related downstream Src family kinase, focal adhesion kinase, and AKT kinase. Furthermore, surface plasmon resonance assay revealed that STPC2 bound strongly to VEGF to interfere with VEGF-VEGFR2 interaction. Taken together, these results evidently demonstrated that STPC2 exhibited a potent anti-angiogenic activity through binding to VEGF via sulfated groups to impede VEGF-VEGFR2 interaction, thus affected the downstream signaling molecules.