title: BCP crystals increase prostacyclin production and upregulate the prostacyclin receptor in OA synovial fibroblasts: potential effects on mPGES1 and MMP-13.
abstract: OBJECTIVE
  To investigate the potential involvement of prostacyclin in basic calcium phosphate (BCP) crystal-induced responses in osteoarthritic synovial fibroblasts (OASF).
  
  
  METHODS
  OASF grown in culture were stimulated with BCP crystals. Prostacyclin production was measured by enzyme immunoassay. Expression of messenger RNA (mRNA) transcripts was assessed by real-time polymerase chain reaction (PCR). Expression of prostacyclin synthase (PGIS) and the prostacyclin (IP) receptor was measured. The effects of iloprost, a prostacyclin analogue, on expression of genes implicated in osteoarthritis such as microsomal prostaglandin E2 synthase 1 (mPGES1) and matrix metalloproteinases (MMPs) were also studied. FPT inhibitor II, a farnesyl transferase inhibitor, was used to antagonize iloprost-induced responses.
  
  
  RESULTS
  BCP crystal stimulation led to a five-fold increase in prostacyclin production in OASF compared to untreated cells. This induction was attenuated by cyclooxygenase (COX)-2 and COX-1 inhibition at 4 and 32h, respectively. PGIS and IP receptor transcripts were constitutively expressed in OASF. BCP crystals upregulated IP receptor expression two-fold. While iloprost diminished BCP crystal-stimulated IP receptor upregulation, the inhibitory effect of iloprost was blocked by the farnesyl transferase inhibitor. In addition, iloprost upregulated mPGES1 and downregulated MMP-13 expression in BCP crystal-stimulated OASF, effects that were not influenced by the farnesyl transferase inhibitor.
  
  
  CONCLUSIONS
  These data showed for the first time that BCP crystals can increase prostacyclin production and upregulate expression of the IP receptor in OASF. The potential of prostacyclin to influence BCP crystal-stimulated responses was supported by the effects of iloprost on the expression of the IP receptor, mPGES1 and MMP-13. These data demonstrate the potential involvement of prostacyclin in BCP crystal-associated osteoarthritis (OA) and suggest that inhibition of PG synthesis with non-steroidal anti-inflammatory drugs may have both deleterious and beneficial effects in BCP crystal-associated OA.
authors.affiliation: Department of Molecular and Cellular Therapeutics, Royal College of Surgeons of Ireland, and National Orthopaedic Hospital, Dublin, Ireland. eamonn.molloy@ireland.com
authors.forename: E S
authors.initials: ES
authors.lastname: Molloy
authors.forename: M P
authors.initials: MP
authors.lastname: Morgan
authors.forename: B
authors.initials: B
authors.lastname: McDonnell
authors.forename: J
authors.initials: J
authors.lastname: O'Byrne
authors.forename: G M
authors.initials: GM
authors.lastname: McCarthy
mesh_terms: D002130:Calcium Phosphates / Q000494:pharmacology*; D011464:Epoprostenol / Q000502:physiology*; D005347:Fibroblasts / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000187:drug effects* / Q000502:physiology; D053509:Matrix Metalloproteinase 13 / Q000187:drug effects* / Q000502:physiology; D000071876:Prostaglandin-E Synthases; D044006:Receptors, Epoprostenol; D013582:Synovial Fluid / Q000187:drug effects* / Q000502:physiology
chemical_list: D002130:Calcium Phosphates; D044006:Receptors, Epoprostenol; C020243:calcium phosphate; D011464:Epoprostenol; D053509:Matrix Metalloproteinase 13; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases