title: Protein Phosphatase 2A Mediates Oxidative Stress Induced Apoptosis in Osteoblasts.
abstract: Osteoporosis is one of the most common bone diseases, which is characterized by a systemic impairment of bone mass and fragility fractures. Age-related oxidative stress is highly associated with impaired osteoblastic dysfunctions and subsequent osteoporosis. In osteoblasts (bone formation cells), reactive oxygen species (ROS) are continuously generated and further cause lipid peroxidation, protein damage, and DNA lesions, leading to osteoblastic dysfunctions, dysdifferentiations, and apoptosis. Although much progress has been made, the mechanism responsible for oxidative stress induced cellular alternations and osteoblastic toxicity is still not fully elucidated. Here, we demonstrate that protein phosphatase 2A (PP2A), a major protein phosphatase in mammalian cells, mediates oxidative stress induced apoptosis in osteoblasts. Our results showed that lipid peroxidation products (4-HNE) may induce dramatic oxidative stress, inflammatory reactions, and apoptosis in osteoblasts. These oxidative stress responses may ectopically activate PP2A phosphatase activity, which may be mediated by inactivation of AKT/mTOR pathway. Moreover, inhibition of PP2A activity by okadaic acid might partly prevent osteoblastic apoptosis under oxidative conditions. These findings may reveal a novel mechanism to clarify the role of oxidative stress for osteoblastic apoptosis and provide new possibilities for the treatment of related bone diseases, such as osteoporosis.
authors.affiliation: Department of Orthopaedics, Sichuan Provincial People's Hospital, No. 32 West Second Section, First Ring Road, Chengdu 610072, China.
authors.forename: Chong-xin
authors.initials: CX
authors.lastname: Huang
authors.affiliation: Department of Orthopaedics, Sichuan Provincial People's Hospital, No. 32 West Second Section, First Ring Road, Chengdu 610072, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Lv
authors.affiliation: Department of Orthopaedics, Sichuan Provincial People's Hospital, No. 32 West Second Section, First Ring Road, Chengdu 610072, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D016723:Bone Remodeling; D007249:Inflammation; D015227:Lipid Peroxidation; D051379:Mice; D019319:Okadaic Acid / Q000737:chemistry; D010006:Osteoblasts / Q000378:metabolism* / Q000473:pathology; D010024:Osteoporosis; D018384:Oxidative Stress; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D000447:Aldehydes; D017382:Reactive Oxygen Species; D019319:Okadaic Acid; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D054648:Protein Phosphatase 2; C027576:4-hydroxy-2-nonenal