[Molecular mechanism of zoledronic acid inhibiting angiogenesis by semi flexible binding with vascular endothelial growth factor conformation].

Objective: To study the relationship between zoledronic acid (ZOL) and vascular endothelial growth factor (VEGF) conformation so as to reveal the mechanism of bisphosphonates inhibiting angiogenesis. Methods: The binding structures of ZOL and VEGF were preprocessed and the molecular dockings were simulated through AutoDockTools, Discovery studio4 and AutoDockVina. The best binding conformation was accurately screened. The effects of various concentrations of ZOL (group A was 0 µmol/L, groups B, C and D were 25, 50 and 100 µmol/L, respectively) on human umbilical vein endothelial cell (HUVEC) proliferation, angiogenesis and angiogenic molecules were detected by using cell counting kit-8 (CCK-8) in vivo and in vitro angiogenesis, immunofluorescence and Western blotting. Results: There was a ZOL binding site on the target protein VEGF conformation. The affinity was -5.2 kcal/mol. This binding site consisted of the hydrophobic region composed of amino acids Cys26, 51, 57, etc. and the hydrogen bond binding region of the A chain (ASP34, SER50) and B chain (CYS61, 68, LEU66, GLY59). The results of CCK-8 showed that the levels of value A in groups B, C and D were significantly lower than that in group A at each time point from 3 to 6 days (P<0.05). In vitro vascular experiments demonstrated that the numbers of budding in groups B, C and D [(208±28), (151±21) and (62±9), respectively] were significantly lower than that in group A (276±30) (P<0.05). In vivo vascular experiments displayed that the ratio of Matrigel gel/plasma fluorescence in group A (0.003 1±0.000 3) was significantly higher than those in group B (0.002 1±0.000 2), group C (0.001 6±0.000 2) and group D (0.000 6±0.000 1) (P<0.05). The results of Western blotting revealed that the expression of VEGF in groups B, C and D [(0.72±0.11), (0.41±0.07) and (0.24±0.04), respectively] were significantly lower than that in group A (1.01±0.02) (P<0.05), and the expression levels of hypoxia-inducible factor-1α (HIF-1α) in groups B, C and D [(0.68±0.09), (0.55±0.06) and (0.43±0.08), respectively] were significantly lower than that in group A (0.96±0.04) (P<0.05). Conclusions: ZOL could inhibit cell proliferation, in vivo and in vitro vascularization and expression of VEGF/HIF-1α. The binding site of ZOL with the conformation of VEGF was located in the hydrophobic region and hydrogen-bonding region of amino acids. Designing an antagonist targeting this site might potentially alleviate the effect of ZOL in inhibiting angiogenesis.