Genetic augmentation of nitric oxide synthase increases the vascular generation of VEGF

Objective: Vascular endothelial growth factor (VEGF) induces the release of nitric oxide (NO) from endothelial cells. There is also limited data sugge sting that NO may enhance VEGF generation. Methods: To further investigate this interaction, we examined the effect of exogenous and endogenous NO on the synthesis of VEGF by rat and human vascular smooth muscle cells (VSMC) by exposing cells to exogenous NO donors, or to genetic augmentation of eNO S or iNOS. Results: NO-donors potentiated by 2-fold the generation of VEGF protein by rat or human VSMC. Similarly, rat or human VSMC transiently tran sfected with plasmid DNA encoding eNOS or iNOS, synthesized up to 3-fold mo re VEGF than those transfected with control plasmid DNA, an effect which wa s reversed after treatment with the NOS antagonist L-NAME. Rat VSMC stably transfected with pKeNOS plasmid, constitutively produced NO and released hi gh concentrations of VEGF, In these cells, L-NAME significantly reduced NO synthesis and decreased VEGF generation. The VEGF protein produced by NOS-t ransfected VSMC was biologically active, as conditioned media harvested fro m these cells increased endothelial cell proliferation. Conclusion: These s tudies reveal that NO derived from NO-donors or generated by NOS within the cells, upregulates the synthesis of VEGF in vascular smooth muscle cells. Administration of NO donors, or augmentation of endogenous NO synthesis, ma y be an alternative approach in therapeutic angiogenesis. (C) 2001 Elsevier Science B.V. All rights reserved.