Activation of AMPK protects against hydrogen peroxide-induced osteoblast apoptosis through autophagy induction and NADPH maintenance: New implications for osteonecrosis treatment?

• Published in: Cellular signalling 2014-01, Vol.26 (1), p.1-8
• Main Authors: She, Chang, Zhu, Lun-qing, Zhen, Yun-fang, Wang, Xiao-dong, Dong, Qi-rong
• Format: Article
• Language: English
• Subjects: AMP-Activated Protein Kinases - metabolism; AMPK; Animals; Apoptosis - drug effects; Autophagy; Autophagy - drug effects; Cell Line, Transformed; Cytoprotection - drug effects; Enzyme Activation - drug effects; HEK293 Cells; Humans; Hydrogen peroxide; Hydrogen Peroxide - pharmacology; Mice; NADP - metabolism; NADPH and osteonecrosis; Osteoblasts - drug effects; Osteoblasts - enzymology; Osteoblasts - pathology; Osteonecrosis - enzymology; Osteonecrosis - pathology; Osteonecrosis - therapy; Oxidative Stress - drug effects; Protein Kinase Inhibitors - pharmacology
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2013.08.046

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. •A high level of AMPK activation is seen in surgery isolated osteonecrosis tissues.•H2O2 induces AMPK activation, oxidative stress and apoptosis in osteoblasts.•Activation of AMPK protects against H2O2-induced osteoblasts death and apoptosis.•H2O2 activates autophagy through AMPK-Ulk1 activation and mTORC1 inhibition.•Activation of AMPK by H2O2 inhibits oxidative stress by inhibiting NADPH depletion.