Blockage of the PI3K/Akt/eNOS signaling pathway abrogated SIRT1-induced phosphorylation of PI3K, Akt, and eNOS. (A) Western blot demonstrating that blockade by the PI3K inhibitor LY294002, the Akt-specific inhibitor sc-221226, and the NOS inhibitor L-NAME, reduced p-PI3K, p-Akt, and p-eNOS in EPCs transfected with Ad-SIRT1. Ad-SIRT1-induced phospho-PI3K (B), phospho-Akt (C), and phospho-eNOS (D) were normalized to total PI3K, Akt, or eNOS, respectively (*P < 0.05 vs. control, #P < 0.05 vs. Ad-SIRT1).