Activation of AMPK protects against hydrogen peroxide-induced osteoblast apoptosis through autophagy induction and NADPH maintenance: new implications for osteonecrosis treatment?
Elevated hydrogen peroxide (H2O2) causes osteoblast dysfunction and apoptosis, serving as an important contributor to the development of osteonecrosis. Here we aimed to understand the role of AMP-activated protein kinase (AMPK) in the process. We observed a high level of AMPK activation in surgery isolated patients' osteonecrosis tissues. In cultured osteoblastoma MG63 cells, H2O2 stimulation induced significant AMPK activation, oxidative stress, cell death and apoptosis. Inhibition of AMPK by its inhibitor (compound C) or by shRNA-mediated knockdown dramatically enhanced H2O2-induced MG63 cell apoptosis, while over-expression of AMPK in HEK-293 cells alleviated H2O2-induced cell damage. These results confirmed that H2O2-activated AMPK is pro-cell survival. We observed that H2O2 induced protective autophagy in MG63 cells, and AMPK-dependent Ulk1 activation and mTORC1 (mTOR complex 1) inactivation might involve autophagy activation. Further, AMPK activation inhibited H2O2-induced oxidative stress, probably through inhibiting NADPH (nicotinamide adenine dinucleotide phosphate) depletion, since more NADPH depletion and oxidative stress were induced by H2O2 in AMPK deficient MG63 cells. Finally, we observed a significant AMPK activation in H2O2-treated primary cultured and transformed (MC3T3-E1) osteoblasts, and AMPK inhibitor compound C enhanced death by H2O2 in these cells. Based on these results, we concluded that H2O2-induced AMPK activation is pro-survival and anti-apoptosis in osteoblasts. Autophagy induction and NADPH maintenance are involved in AMPK-mediated pro-survival effects. AMPK might represent a novel molecular target for osteonecrosis treatment.
Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215000, China.
Chang
C
She
Lun-qing
LQ
Zhu
Yun-fang
YF
Zhen
Xiao-dong
XD
Wang
Qi-rong
QR
Dong
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D002461:Cell Line, Transformed; D019610:Cytoprotection / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051379:Mice; D009249:NADP / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology / Q000473:pathology*; D010020:Osteonecrosis / Q000201:enzymology / Q000473:pathology / Q000628:therapy*; D018384:Oxidative Stress / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology
D047428:Protein Kinase Inhibitors; D009249:NADP; D006861:Hydrogen Peroxide; D055372:AMP-Activated Protein Kinases
3-MA; 3-methyladenine; ACC; ALP; AMP-activated protein kinase; AMPK; Autophagy; H(2)O(2); Hydrogen peroxide; LC3B; NADPH; NADPH and osteonecrosis; ROS; acetyl-CoA carboxylase; alkaline phosphotase; hydrogen peroxide; light chain 3B; nicotinamide adenine dinucleotide phosphate; reactive oxygen species