Cyclooxygenase 2-derived prostaglandin E2 production by corticotropin-releasing hormone contributes to the activated cAMP response element binding protein content in rheumatoid arthritis synovial tissue

Objective. To determine a mechanism by which corticotropin-releasing hormone (CRH) promotes human inflammatory joint disease progression. Methods. An ex vivo synovial tissue culture system was established to investigate the functional properties of CRH at peripheral sites of inflammation. CRH- and interleukin-1β (IL-1β)-induced prostaglandin E₂ (PGE ₂) production from 10 fresh rheumatoid arthritis (RA) synovial tissue (ST) explants was quantified using a competitive enzyme-linked immunosorbent assay. Modulation of PGE₂ levels was further examined following selective and nonselective cyclooxygenase 2 (COX-2) inhibition. Nuclear extracts were analyzed by electrophoretic mobility shift assays to determine functional cAMP response element binding protein (CREB) activity in response to CRH and PGE₂ in isolated primary synovial cell populations. Western blot analysis measured levels of total and activated (phosphospecific) CREB/activating transcription factor (ATF) family members prior to and following stimulation. Results. CRH, in a time- and dose-dependent manner, significantly (P = 0.022) up-regulated PGE₂ production from 10 fresh RA ST explants. Costimulation of RA ST with CRH and IL-1β significantly augmented (P = 0.036) the effects on PGE₂ production additively over 24 hours. We demonstrated that selective COX-2 inhibitors prevent the induction of PGE₂ by both CRH and IL-1β. Further, we provided evidence that CRH and PGE₂ signal through the induction of CREB and phosphorylated CREB/ATF family members in RA ST and in isolated primary RA cell populations. Conclusion. Our findings underscore the pathogenic role that CRH may play in modulating inflammatory joint disease and establish the CREB/ATF family of transcription factors as principal effector molecules of proinflammatory mediator action in RA.