title: MHY1485 activates mTOR and protects osteoblasts from dexamethasone.
abstract: Dexamethasone (Dex) exerts cytotoxic effects to cultured osteoblasts. The potential effect of MHY1485, a small-molecular mammalian target of rapamycin (mTOR) activator, against the process was studied here. In both osteoblastic MC3T3-E1 cells and primary murine osteoblasts, treatment with MHY1485 significantly ameliorated Dex-induced cell death and apoptosis. mTOR inhibition, through mTOR kinase inhibitor OSI-027 or mTOR shRNAs, abolished MHY1485-mediated osteoblast cytoprotection against Dex. Intriguingly, activation of mTOR complex (mTORC1), but not mTORC2, is required for MHY1485's anti-Dex activity. mTORC1 inhibitors (rapamycin and RAD001) or Raptor knockdown almost reversed MHY1485-induced osteoblast cytoprotection. mTORC2 inhibition, via shRNA knockdown of Rictor, failed to affect MHY1485's activity in MC3T3-E1 cells. Further studies showed that MHY1485 treatment in MC3T3-E1 cells and primary murine osteoblasts significantly inhibited Dex-induced mitochondrial death pathway activation, the latter was tested by mitochondrial depolarization, cyclophilin D-ANT-1 association and cytochrome C cytosol release. Together, these results suggest that MHY1485 activates mTORC1 signaling to protect osteoblasts from Dex.
authors.affiliation: Department of Paediatrics, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China.
authors.forename: Sai
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Clinical Laboratory, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China.
authors.forename: Caiyun
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Orthopedics, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China. Electronic address: shouguoha126@126.com.
authors.forename: Shouguo
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Ji
authors.affiliation: Department of Orthopedics, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Xie
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D019610:Cytoprotection / Q000187:drug effects*; D003907:Dexamethasone / Q000633:toxicity*; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology*; D046912:Multiprotein Complexes / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014227:Triazines / Q000494:pharmacology*
chemical_list: C577756:4,6-dimorpholino-N-(4-nitrophenyl)-1,3,5-triazin-2-amine; D009025:Morpholines; D046912:Multiprotein Complexes; D014227:Triazines; D003907:Dexamethasone; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases
keywords: Dexamethasone; MHY1485; Mitochondrial death pathway; Osteoblasts; mTOR