Objective: To evaluate the effect of bear bile powder (BBP) on angiogenesis, and investigate the underlying molecular mechanisms.
Methods: A chick embryo chorioallantoic membrane (CAM) assay was used to evaluate the angiogensis in vivo. Human umbilical vein endothelial cells (HUVECs) were treated with 0, 0.25, 0.5, 0.75, and 1.0 mg/mL of BBP for 24, 48 and 72 h, respectively. The 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to determine the viability of HUVECs. Cell cycle progression of HUVECs was examined by fluorescence-activated cell sorting (FACS) analysis with propidium iodide staining. HUVEC migration was determined by wound healing method. An ECMatrix gel system was used to evaluate the tube formation of HUVECs. The mRNA and protein expression of vascular endothelial growth factor (VEGF)-A in both HUVECs and HepG2 human cells were examined by reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay, respectively.
Results: Compared with the untreated group, BBP inhibited angiogenesis in vivo in the CAM model (P< 0.01). In addition, treatment with 0.25-1 mg/mL of BBP for 24, 48, or 72 h respectively reduced cell viability by 14%-27%, 29%-69% and 33%-91%, compared with the untreated control cells (P< 0.01). Additionally, BBP inhibited the proliferation of HUVECs via blocking the cell cycle G to S progression, compared with the S phase of untreated cells 48.05%± 5.00%, 0.25-0.75 mg/mL BBP reduced S phase to 40.38%± 5.30%, 36.54± 4.50% and 32.13± 3.50%, respectively (Pglt; 0.05). Moreover, BBP inhibited the migration and tube formation of HUVECs, compared with the tube length of untreated cells 100%± 12%, 0.25-0.75 mg/mL BBP reduced the tube length to 62%± 9%, 43%± 5% and 17%± 3%, respectively (p< 0.01). Furthermore, BBP treatment down-regulated the mRNA and protein expression levels of VEGF-A in both HepG2 cells and HUVECs.
Conclusion: BBP could inhibit the angiogenesis by reducing VEGF-A expression, which may, in part, explain its anti-tumor activity.