Effects and mechanisms of total glucosides of paeony on synoviocytes activities in rat collagen-induced arthritis

The aim of the study was to investigate the effects of TGP, an active compound extracted from the roots of Paeonia lactiflora Pall, on the activities of synoviocytes in rats with collageninduced arthritis (CIA) and its possible mechanisms. CIA was induced in male Sprague–Dawley (SD) rats immunized with chicken type II collagen (CII) in Freund's complete adjuvant (FCA). Synoviocytes proliferation was determined by 3-(4, 5-2dimethylthiazal-2yl) 2, 5-diphenyltetrazoliumbromide (MTT) assay. Tumor necrosis factor alpha (TNF-α), interleukin-1 (IL-1), prostaglandin E2 (PGE2) and cyclic adenosine monophosphate (cAMP) levels in synoviocytes were measured by radioimmunoassay (RIA). E-prostanoid (EP)2 and EP4 receptors were analyzed by Western blot analysis. The results showed that TGP significantly inhibited the proliferation of synoviocytes, decreased the production of IL-1, TNF-α and PGE2 and elevated the levels of cAMP. Further study showed that TGP could up-regulate the expression of EP2 and EP4. These results indicated that TGP might exert its anti-inflammatory effects through inhibiting the production of pro-inflammatory mediators in synoviocytes of CIA rats, which might be associated with its ability to regulate cAMP-dependent EP2/EP4-mediated pathway.