title: Oxidative damage to osteoblasts can be alleviated by early autophagy through the endoplasmic reticulum stress pathway--implications for the treatment of osteoporosis.
abstract: Oxidative stress can damage various cellular components of osteoblasts, and is regarded as a pivotal pathogenic factor for bone loss. Increasing evidence indicates a significant role of cell autophagy in response to oxidative stress. However, the role of autophagy in the osteoblasts under oxidative stress remains to be clarified. In this study, we verified that hydrogen peroxide induced autophagy and apoptosis in a dose- and time-dependent manner in osteoblastic Mc3T3-E1 cells. Both 3-methyladenine (the early steps of autophagy inhibitor) and bafilomycin A1 (the last steps of autophagy inhibitor) enhanced the cell apoptosis and reactive oxygen species level in the osteoblasts insulted by hydrogen peroxide. However, promotion of autophagy with either a pharmacologic inducer (rapamycin) or the Beclin-1 overexpressing technique rescued the cell apoptosis and reduced the reactive oxygen species level in the cells. Treatment with H2O2 significantly increased the levels of carbonylated proteins, malondialdehyde and 8-hydroxy-2'-deoxyguanosine, decreased the mitochondrial membrane potential, and increased the mitochondria-mediated apoptosis markers. The damaged mitochondria were cleared by autophagy. Furthermore, the molecular levels of the endoplasmic reticula stress signaling pathway changed in hydrogen peroxide-treated Mc3T3-E1 cells, and blocking this stress signaling pathway by RNA interference against candidates of glucose-regulated protein 78 and protein kinase-like endoplasmic reticulum kinase decreased autophagy while increasing apoptosis in the cells. In conclusion, oxidative damage to osteoblasts could be alleviated by early autophagy through the endoplasmic reticulum stress pathway. Our findings suggested that modulation of osteoblast autophagy could have a potentially therapeutic value for osteoporosis.
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Yue-Hua
authors.initials: YH
authors.lastname: Yang
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Xin-Feng
authors.initials: XF
authors.lastname: Zheng
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Jiang-Wei
authors.initials: JW
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Sheng-Dan
authors.initials: SD
authors.lastname: Jiang
authors.affiliation: Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China. Electronic address: jiangleisheng@126.com.
authors.forename: Lei-Sheng
authors.initials: LS
authors.lastname: Jiang
mesh_terms: D000818:Animals; D017209:Apoptosis; D001343:Autophagy; D002460:Cell Line; D002470:Cell Survival; D059865:Endoplasmic Reticulum Stress; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D010006:Osteoblasts / Q000502:physiology*; D010024:Osteoporosis / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species
keywords: Apoptosis; Autophagy; Endoplasmic reticulum stress; Osteoblast; Oxidative stress