Figure 6. (A–C) Effects of Sirt1 knock-down in HepG2 cells after 3-5 passages. (A) Sirt1 knock-down decreased ATP, mitochondria membrane potential, and NAD+ levels (n=6, *p<0.05). (B, C) Sirt1 knock-down increased pAMPK levels and AMPK α2. It decreased LKB1 specific activity (pMARK1/LKB1) and CaMKKβ. (n=4, *p<0.05). (D, E) Effects of LKB1 epitopic expression by lentivirus on cellular senescence of cultured primary human aortic endothelial cells. LKB1 or null lentivirus was infected to the endothelial cells at passage 5 and passaged up 9. SA-β-Gal activity by X-gal staining and LKB1 immunostaining (DAB as substrate) were performed at passages 8 and 9. A significant increase in the percentage of SA-β-Gal positive cells was observed between passages 8 and 9 in null-lentivirus infected cells (n=6, *p<0.05). LKB1 expressed cells showed a significantly less percentage of positive cells at both passages and had no increase between passages 8 and 9.