title: Glucocorticoids induce senescence in primary human tenocytes by inhibition of sirtuin 1 and activation of the p53/p21 pathway: in vivo and in vitro evidence.
abstract: Cellular senescence is an irreversible side effect of some pharmaceuticals which can contribute to tissue degeneration.
  
  
  OBJECTIVE
  To determine whether pharmaceutical glucocorticoids induce senescence in tenocytes.
  
  
  METHODS
  Features of senescence (β-galactosidase activity at pH 6 (SA-β-gal) and active mammalian/mechanistic target of rapamycin (mTOR) in cell cycle arrest) as well as the activity of the two main pathways leading to cell senescence were examined in glucocorticoid-treated primary human tenocytes. Evidence of senescence-inducing pathway induction in vivo was obtained using immunohistochemistry on tendon biopsy specimens taken before and 7 weeks after subacromial Depo-Medrone injection.
  
  
  RESULTS
  Dexamethasone treatment of tenocytes resulted in an increased percentage of SA-βgal-positive cells. Levels of phosphorylated p70S6K did not decrease with glucocorticoid treatment indicating mTOR remained active. Increased levels of acetylated p53 as well as increased RNA levels of its pro-senescence effector p21 were evident in dexamethasone-treated tenocytes. Levels of the p53 deacetylase sirtuin 1 were lower in dexamethasone-treated cells compared with controls. Knockdown of p53 or inhibition of p53 activity prevented dexamethasone-induced senescence. Activation of sirtuin 1 either by exogenous overexpression or by treatment with resveratrol or low glucose prevented dexamethasone-induced senescence. Immunohistochemical analysis of tendon biopsies taken before and after glucocorticoid injection revealed a significant increase in the percentage of p53-positive cells (p=0.03). The percentage of p21-positive cells also tended to be higher post-injection (p=0.06) suggesting glucocorticoids activate the p53/p21 senescence-inducing pathway in vivo as well as in vitro.
  
  
  CONCLUSIONS
  As cell senescence is irreversible in vivo, glucocorticoid-induced senescence may result in long-term degenerative changes in tendon tissue.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Raewyn C
authors.initials: RC
authors.lastname: Poulsen
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Watts
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Murphy
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Snelling
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Carr
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Philippa A
authors.initials: PA
authors.lastname: Hulley
mesh_terms: D000328:Adult; D000368:Aged; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000187:drug effects* / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D055785:Gene Knockdown Techniques; D005938:Glucocorticoids / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D017006:Rotator Cuff; D015398:Signal Transduction / Q000187:drug effects*; D056564:Sirtuin 1 / Q000187:drug effects* / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000187:drug effects* / Q000378:metabolism; D052256:Tendinopathy / Q000188:drug therapy; D013710:Tendons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000187:drug effects / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005938:Glucocorticoids; D016159:Tumor Suppressor Protein p53; D003907:Dexamethasone; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D001616:beta-Galactosidase; C447939:SIRT1 protein, human; D056564:Sirtuin 1
keywords: Chondrocytes; Corticosteroids; Fibroblasts; Inflammation; Tendinitis