title: Protection against glucocorticoid-induced damage in human tenocytes by modulation of ERK, Akt, and forkhead signaling.
abstract: Antiinflammatory glucocorticoid (GC) injections are extensively used to treat painful tendons. However, GC cause severe tissue wasting in other collagen-producing tissues such as skin and bone. The objective of this study was to determine the effects of GC on tenocytes and to explore strategies to protect against unwanted side effects of GC treatment. Cell survival, collagen production, and the induction of signaling pathways in primary human tenocytes treated with dexamethasone (Dex) were assessed. Antioxidant and growth factor approaches to protection were tested. Dex treatment resulted in reduced viable cell number, cell proliferation, and collagen production. Dex induced reactive oxygen species generation in tenocytes and strongly up-regulated the stress-response transcription factors FOXO1 and FOXO3A. Phosphorylation of ERK and protein kinase B/Akt, which regulate cell proliferation and also inhibit forkhead activity, was decreased. Chemical inhibition of ERK or Akt activity significantly reduced tenocyte cell number. Ameliorating the Dex-induced reduction in ERK or Akt activity by cotreatment with vitamin C or insulin protected against the Dex-induced reduction in cell number. Silencing FOXO1 prevented the Dex-induced reduction in collagen 1α1 expression. Cotreatment with vitamin C or insulin protected against the Dex-induced increase in FOXO and the Dex-induced inhibition of collagen 1α1 expression. Reduced ERK and Akt activation and increased forkhead signaling contribute to the negative effects of GC on tenocytes. Cotreatment therapies that target these signaling pathways are protective. Vitamin C in particular may be a clinically useable co-therapy to reduce connective tissue side effects associated with GC therapy.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Science, Botnar Research Centre, University of Oxford, Oxford OX3 7LD, United Kingdom. raewyn.poulsen@ndorms.ox.ac.uk
authors.forename: Raewyn C
authors.initials: RC
authors.lastname: Poulsen
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Carr
authors.forename: Philippa A
authors.initials: PA
authors.lastname: Hulley
mesh_terms: D000328:Adult; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D001205:Ascorbic Acid / Q000494:pharmacology; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology*; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D000893:Anti-Inflammatory Agents; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D005938:Glucocorticoids; D006025:Glycosaminoglycans; D007328:Insulin; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D003907:Dexamethasone; D003094:Collagen; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D001205:Ascorbic Acid