title: P53 dependent mitochondrial permeability transition pore opening is required for dexamethasone-induced death of osteoblasts.
abstract: Prolonged or overdose glucocorticoids (GCs) usage is the common cause of osteoporosis. In the present study, we studied the cellular mechanism of dexamethasone (Dex)-induce osteoblast cell death by focusing on the role of mitochondrial permeability transition pore (mPTP). In cultured osteoblastic MC3T3-E1 cells, Dex-induced mPTP opening, which was demonstrated by mitochondrial membrane potential (MPP) decrease, cyclophilin-D (CyPD)-adenine nucleotide translocator 1 (ANT-1) mitochondrial complexation and cytochrome C (cyto-C) release. The mPTP inhibitor sanglifehrin A (SfA) dramatically inhibited Dex-induced MPP loss, cyto-C release and MC3T3-E1 cell death. Dex-induced cell death requires mPTP composing protein CyPD, as CyPD inhibitor cyclosporin A (CsA) and CyPD siRNA knockdown inhibited Dex-induced MC3T3-E1 cell death, while CyPD overexpression aggravated Dex's cytotoxic effect. We found that Dex induced P53 phosphorylation and translocation to mitochondria, where it formed a complex with CyPD. Glucocorticoid receptor (GR) siRNA knockdown, or P53 inhibition (by its inhibitor pifithrin-α or shRNA silencing) suppressed Dex-induced CyPD-P53 mitochondrial association and subsequent MC3T3-E1 cell death. Finally, in primary cultured osteoblasts, Dex-induced cell death was inhibited by CsA, SfA or pifithrin-α. Together, our data suggest that Dex-induced osteoblast cell death is associated with GR-P53-regulated mPTP opening.
authors.affiliation: The Center of Diagnosis and Treatment for Children's Bone Diseases, the Children's Hospital Affiliated to Soochow University, Suzhou, Jiangsu, 215000, China.
authors.forename: Yun-Fang
authors.initials: YF
authors.lastname: Zhen
authors.forename: Guo-Dong
authors.initials: GD
authors.lastname: Wang
authors.forename: Lun-Qing
authors.initials: LQ
authors.lastname: Zhu
authors.forename: Shi-Ping
authors.initials: SP
authors.lastname: Tan
authors.forename: Fu-Yong
authors.initials: FY
authors.lastname: Zhang
authors.forename: Xiao-Zhong
authors.initials: XZ
authors.lastname: Zhou
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Wang
mesh_terms: D016475:3T3 Cells; D033741:Adenine Nucleotide Translocator 1 / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003907:Dexamethasone / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010024:Osteoporosis / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D021381:Protein Transport; D034622:RNA Interference; D011965:Receptors, Glucocorticoid / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D033741:Adenine Nucleotide Translocator 1; D000081406:Peptidyl-Prolyl Isomerase F; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C000631446:PPIF protein, mouse; D011965:Receptors, Glucocorticoid; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C411470:glucocorticoid receptor alpha; D003907:Dexamethasone; D045304:Cytochromes c; D021983:Cyclophilins