Hydrogen peroxide inhibits mTOR signaling by activation of AMPKα leading to apoptosis of neuronal cells

Oxidative stress results in apoptosis of neuronal cells, leading to neurodegenerative disorders. However, the underlying molecular mechanism remains to be elucidated. Here, we show that hydrogen peroxide (H2O2), a major oxidant generated when oxidative stress occurs, induced apoptosis of neuronal cells (PC12 cells and primary murine neurons), by inhibiting the mammalian target of rapamycin (mTOR)-mediated phosphorylation of ribosomal p70 S6 kinase (S6K1) and eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1). N-acetyl-L-cysteine (NAC), a scavenger of reactive oxygen species (ROS), blocked H2O2 inhibition of mTOR signaling. Ectopic expression of wild-type (wt) mTOR, constitutively active S6K1 or downregulation of 4E-BP1 partially prevented H2O2 induction of apoptosis. Furthermore, we identified that H2O2 induction of ROS inhibited the upstream kinases, Akt and phosphoinositide-dependent kinase 1 (PDK1), but not the type I insulin-like growth factor receptor (IGFR), and activated the negative regulator, AMP-activated protein kinase alpha (AMPK alpha), but not the phosphatase and tensin homolog (PTEN) in the cells. Expression of a dominant negative AMPK alpha or downregulation of AMPK alpha 1 conferred partial resistance to H2O2 inhibition of phosphorylation of S6K1 and 4E-BP1, as well as cell viability, indicating that H2O2 inhibition of mTOR signaling is at least in part through activation of AMPK. Our findings suggest that AMPK inhibitors may be exploited for prevention of H2O2-induced neurodegenerative diseases. Laboratory Investigation (2010) 90, 762-773; doi:10.1038/labinvest.2010.36; published online 8 February 2010