title: Dexamethasone decreases substance P expression in human tendon cells: an in vitro study.
abstract: OBJECTIVE
  Glucocorticoid injections are used by rheumatologists to treat chronic tendinopathy. Surprisingly, the mechanisms by which corticosteroids induce pain relief in this condition have not been investigated. Previous studies have shown local substance P (SP) levels to be correlated with tendon pain and tissue pathology. The objective of this study was to determine whether SP production in human tenocytes is modulated by exposure to dexamethasone.
  
  
  METHODS
  Human tendon fibroblasts were cultured in the presence or absence of dexamethasone (1-400 nM), an inhibitor of the glucocorticoid receptor, RU486, recombinant TGF-β (2.5 or 5.0 ng/ml) or an inhibitor of the TGF-β receptor (A83.01), recombinant human IL-1β and IL-6. Expression levels of the genes encoding for SP (TAC1) and its preferred receptor (NK1R), IL-1α, IL-1β and IL-6 were determined with quantitative PCR and protein levels of SP were examined by EIA and western blot.
  
  
  RESULTS
  Exposure of human tendon cells to dexamethasone resulted in a time-dependent reduction of mRNA for SP in both hamstrings and Achilles tenocytes, whereas NK1R was unaffected. The reduction of SP mRNA was dependent on signalling through the glucocorticoid receptor. SP protein was substantially decreased by dexamethasone. Dexamethasone also prevented induction of SP by IL-1β and by cyclic mechanical loading.
  
  
  CONCLUSIONS
  This study demonstrates that dexamethasone treatment of human tendon fibroblasts reduces the expression of SP through a glucocorticoid receptor-dependent pathway. Drugs interfering with SP signalling could be a future target in the treatment of tendinopathy.
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada, Umeå University, Institute for Integrative Medical Biology, Section for Anatomy, Umeå, Sweden, Department of Orthopedic Surgery and Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Rouhollah
authors.initials: R
authors.lastname: Mousavizadeh
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada, Umeå University, Institute for Integrative Medical Biology, Section for Anatomy, Umeå, Sweden, Department of Orthopedic Surgery and Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Ludvig
authors.initials: L
authors.lastname: Backman
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada, Umeå University, Institute for Integrative Medical Biology, Section for Anatomy, Umeå, Sweden, Department of Orthopedic Surgery and Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Robert G
authors.initials: RG
authors.lastname: McCormack
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada, Umeå University, Institute for Integrative Medical Biology, Section for Anatomy, Umeå, Sweden, Department of Orthopedic Surgery and Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, BC, Canada. ascott@interchange.ubc.ca.
authors.forename: Alex
authors.initials: A
authors.lastname: Scott
mesh_terms: D000125:Achilles Tendon / Q000378:metabolism; D000328:Adult; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D015536:Down-Regulation; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D005938:Glucocorticoids / Q000494:pharmacology*; D064368:Healthy Volunteers; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D013710:Tendons / Q000378:metabolism*; D055815:Young Adult
chemical_list: D005938:Glucocorticoids; D018040:Receptors, Neurokinin-1; D013373:Substance P; D003907:Dexamethasone
keywords: corticosteroids; inflammation; soft tissue rheumatology; tendinopathy