Characterization of plasmacytoid dendritic cells in inflammatory arthritis synovial fluid

OBJECTIVE

To examine the phenotype of dendritic cell subsets in synovial fluid and peripheral blood from patients with rheumatoid arthritis (RA) or spondyloarthropathy (SpA).

METHODS

Multiparameter flow cytometry was used to identify and characterize dendritic cells in mononuclear cell populations isolated from synovial fluid and peripheral blood.

RESULTS

Synovial fluid contained two subsets of dendritic cells (DC), myeloid and plasmacytoid. These subsets could also be identified in peripheral blood, but there were lower numbers of DC in peripheral blood compared with synovial fluid. Plasmacytoid DC were distinguished from the myeloid subset by high expression of CD123 and lack of expression of CD11c. In comparison with myeloid dendritic cells, the plasmacytoid subset were less mature, similar to those in peripheral blood. They failed to express CD83 and DC-LAMP, and had relatively low levels of CD40 and CD86. Comparison of dendritic cells in synovial fluid from RA and SpA patients showed increased numbers of the plasmacytoid subset in SpA.

CONCLUSIONS

This is the first demonstration of the plasmacytoid subset of dendritic cells in synovial fluid. Since these cells are major producers of type I interferons, their increased numbers in SpA might be relevant to pathogenesis, but the immature phenotype in SpA synovial fluid may also indicate that conditions for maturation of this subset do not pertain in SpA synovium.

Antagonists of retinoic acid receptors (RARs) are potent growth inhibitors of prostate carcinoma cells

Novel synthetic antagonists of retinoic acid receptors (RARs) have been developed. To avoid interference by serum retinoids when testing these compounds, we established serum-free grown sub-lines (>3 years) of the prostate carcinoma lines LNCaP, PC3 and DU145. A high affinity pan-RAR antagonist (AGN194310, K(d) for binding to RARs = 2-5 nM) inhibited colony formation (by 50%) by all three lines at 16-34 nM, and led to a transient accumulation of flask-cultured cells in G1 followed by apoptosis. AGN194310 is 12-22 fold more potent than all-trans retinoic acid (ATRA) against cell lines and also more potent in inhibiting the growth of primary prostate carcinoma cells. PC3 and DU145 cells do not express RARbeta, and an antagonist with predominant activity at RARbeta and RARgamma (AGN194431) inhibited colony formation at concentrations (approximately 100 nM) commensurate with a K(d)value of 70 nM at RARgamma. An RARalpha antagonist (AGN194301) was less potent (IC(50) approximately 200 nM), but was more active than specific agonists of RARalpha and of betagamma. A component(s) of serum and of LNCaP-conditioned medium diminishes the activity of antagonists: this factor is not the most likely candidates IGF-1 and EGF. In vitro studies of RAR antagonists together with data from RAR-null mice lead to the hypothesis that RARgamma-regulated gene transcription is necessary for the survival and maintenance of prostate epithelium. The increased potencies of RAR antagonists, as compared with agonists, suggest that antagonists may be useful in the treatment of prostate carcinoma.