Curcumin inhibits angiogenesis in endothelial cells using downregulation of the PI3K/Akt signaling pathway

Curcumin, a major yellow pigment and active component of turmeric, has anti-angiogenesis properties. However, its molecular targets and mechanisms of curcumin effects on angiogenesis of endothelial cells are not known. The effect of curcumin on angiogenesis activity of endothelial cells in vitro was studied. Human umbilical vein endothelial cells (HUVEC) were mixed with various concentrations of curcumin for 72 h. Cell viability was measured using the WST-1 test. The in vitro tubulogenesis assay was used to determine the potency of curcumin in inhibiting capillary-like formation. HUVEC migration capacity was evaluated using the scratch and transwell insert assays. Lipoprotein lipase activity of curcumin-treated HUVEC was measured. Vascular endothelial growth factor-1 (VEGFR-1) and −2 levels, and the phospo-endothelial nitric oxide synthase (p-eNOS)/eNOS ratio were measured using an ELISA test. The metalloproteinase activity was evaluated using gelatin zymography. The ratio of p-Akt/Akt was followed using western blotting. The WST-1 assay indicated a suppressed proliferation of HUVEC after exposure to curcumin in a dose- and time-dependent manner. Curcumin was able to diminish tube area and length values in HUVEC on Matrigel substrate. A significant reduction in migration rate of curcumin-treated cells coincided with diminished MMP-2 and MMP-9 activities. Lipoprotein lipase activity of HUVEC was reduced following treatment with curcumin indicated by a diminished fluorescence activity. The ELISA test showed a down-regulation of VEGFR-2. Western blotting confirmed the reduced p-Akt/Akt ratio after HUVEC being exposed to curcumin. Curcumin is able to inhibit angiogenesis through the modulation of VEGFR and PI3K/Akt signaling pathway.