Genistein-induced LKB1-AMPK activation inhibits senescence of VSMC through autophagy induction.

Genistein, the primary isoflavone from soy products, enhances antioxidant enzyme activities and inhibits tyrosine kinase. However, the mechanisms underlying genistein-induced autophagy are not yet completely understood. Autophagy refers to a regulated cellular process for the lysosomal-dependent turnover of organelles and proteins. During starvation or nutrient deficiency, autophagy provides an endogenous mechanism for prolonging survival. Here, we investigated whether genistein exerts autophagic effects through the activation of LKB1-AMPK signaling in VSMCs. Genistein dose- and time-dependently increased the phosphorylation of LKB1 and AMPK in VSMCs. LKB1 and AMPK induced autophagy through the downregulation of mTOR in VSMCs. Genistein-induced autophagy was inhibited in dominant-negative AMPK-transfected cells, whereas it was accelerated in cells transfected with the constitutively active form of AMPK. Increased autophagosome activity was confirmed by a concentration-dependent increase in LC3-II formation on Western blots and by increased perinuclear LC3-II puncta in genistein-treated VSMCs. Furthermore, genistein-induced autophagy attenuated adriamycin-induced SA-b-gal staining. These results suggest that genistein-dependent autophagy diminishes VSMC senescence and genistein may attenuate the VSMC senescence via an LKB1-AMPK-dependent mechanism.