Reactive oxygen species (ROS) are strong inducers of the angiogenic hormone vascular endothelial growth factor (VEGF). Although, rutin (R) in combination with vitamin E (VE) has been shown to synergistically inhibit oxidative damage, it is unclear whether the combination of R and VE (R+VE) inhibits VEGF secretion in tumor cells. Using a human promyelocytic leukemia (HL-60) cell line, we showed that R in combination with VE synergistically decreased the expressions of VEGF protein and mRNA. We also demonstrated that R+VE significantly decreased the binding capacity of nuclear factor-activator protein-1 (AP-1) to the VEGF gene promoter and decreased the expression of c-Jun protein. Furthermore, we demonstrated that R+VE synergistically reduced insulin receptor substrate-1 (IRS-1) protein expression in HL-60 cells. The decrease of ROS was only partially associated with the decrease of VEGF secreted (r(2)=0.12, P=0.083). Thus, the present results indicate that R in combination with VE attenuates VEGF expression in HL-60 cells and that this effect is mediated by a decreased binding activity of AP-1 through down-regulation of protein expression of insulin-like growth factor 1 receptor (IGF1-R)/IRS-1, while the antioxidant activity of R+VE appears to play a minor role.
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