title: miR-135b expression downregulates Ppm1e to activate AMPK signaling and protect osteoblastic cells from dexamethasone.
abstract: Activation of AMP-activated protein kinase (AMPK) could potently protect osteoblasts/osteoblastic cells from dexamethasone (Dex). We aim to induce AMPK activation via microRNA ("miRNA") downregulation of its phosphatase Ppm1e. We discovered that microRNA-135b ("miR-135b") targets the 3' untranslated regions (UTRs) of Ppm1e. In human osteoblasticOB-6 cells and hFOB1.19 cells, forced-expression of miR-135b downregulated Ppm1e and activated AMPK signaling. miR-135b also protected osteoblastic cells from Dex. shRNA-induced knockdown of Ppm1e similarly activated AMPK and inhibited Dex-induced damages. Intriguingly, in the Ppm1e-silenced osteoblastic cells, miR-135b expression failed to offer further cytoprotection against Dex. Notably, AMPK knockdown (via shRNA) or dominant negative mutation abolished miR-135b-induced AMPK activation and cytoprotection against Dex. Molecularly, miR-135b, via activating AMPK, increased nicotinamide adenine dinucleotide phosphate (NADPH) activity and inhibited Dex-induced oxidative stress. At last, we found that miR-135b level was increased in human necrotic femoral head tissues, which was correlated with Ppm1e downregulation and AMPK activation. There results suggest that miR-135b expression downregulates Ppm1e to activate AMPK signaling, which protects osteoblastic cells from Dex.
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.|Department of Orthopaedics, Jinling Hospital, Nanjing Medical University, Nanjing 210008, Jiangsu, PR China.
authors.forename: Jian-Bo
authors.initials: JB
authors.lastname: Fan
authors.affiliation: The Department of Orthopedics, the Second Affiliated Hospital of Soochow University, Suzhou 215000, China.
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Ruan
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: The Center of Diagnosis and Treatment for Childrens' Bone Disease, Childrens' Hospital Affiliated to Soochow University, Suzhou 215000, Jiangsu, PR China.
authors.forename: Lun-Qing
authors.initials: LQ
authors.lastname: Zhu
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.
authors.forename: Xin-Hui
authors.initials: XH
authors.lastname: Zhu
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.
authors.forename: Sheng-Yu
authors.initials: SY
authors.lastname: Cui
authors.affiliation: Department of Orthopaedics, Jinling Hospital, Nanjing Medical University, Nanjing 210008, Jiangsu, PR China.
authors.forename: Jian-Ning
authors.initials: JN
authors.lastname: Zhao
authors.affiliation: The Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, PR China.
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Cui
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D055372:AMP-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D019610:Cytoprotection / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D010020:Osteonecrosis / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D005938:Glucocorticoids; C544965:MIRN135 microRNA, human; D035683:MicroRNAs; D003907:Dexamethasone; D055372:AMP-Activated Protein Kinases; C000607459:PPM1E protein, human; D000071636:Protein Phosphatase 2C
keywords: AMP-activated protein kinase (AMPK); dexamethasone (Dex); microRNA-135b; osteoblastic cells; phosphatase 1E (Ppm1e)