Paeoniflorin inhibits function of synoviocytes pretreated by rIL-1α and regulates EP4 receptor expression

Ethnopharmacological relevance: To investigate the effect of the Paeoniflorin (Pae), a main active component of total glucosides of paeony (TGP) extracted from the root of Paeonia lactiflora, on regulation of synoviocytes cultured from rats collagen-induced arthritis (CIA) in vitro. Materials and methods: CIA was induced in male Sprague-Dawley rats immunized with chicken type II collagen (CCII) in Freund's complete adjuvant. The levels of interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-alpha), prostaglandin E-2 (PGE(2)) and cyclic adenosine monophosphate (cAMP) were measured by radioimmunoassay. The proliferation responses was determined by the 3-(4,5-2dimethylthiazal-2yl) 2,5-diphenyltetrazoliumbromide (MTT) assay. Expression of E-prostanoid (EP4) receptor was detected by Western blotting technique. Results: Treatment of Pae (2.5, 12.5, 62.5 mu g/ml) significantly decreased the production of IL-1 and TNF-alpha. Recombinant interleukin-1 (rIL-1 alpha) (10 ng/ml) apparently stimulated synoviocyte, thymocyte and splenocyte proliferation, and Pae (12.5, 62.5 mu g/ml) inhibited abnormal proliferation responses stimulated by rIL-1 alpha. Moreover, rIL-1 alpha time- and concentration-dependently increased production of PGE(2). The production of PGE(2) produced by synoviocytes from CIA rats significantly inhibited by administration of Pae (12.5, 62.5 mu g/ml). rIL-1a (10 ng/ml) decreased cAMP of synoviocytes cells treated for 24 h. Similarly rIL-1 alpha (0.1, 1, 10 ng/ml) induced a concentration-dependent decrease in the production of cAMP at 24 h. Pae (12.5, 62.5 mu g/ml) increased the production of cAMP in synoviocytes. The immunoblot, Pae (12.5, 62.5 mu g/ml) apparently increased the expression of EP4 receptor in synoviocytes stimulated by rIL-1 alpha (10 ng/ml). Conclusions: The present study indicates that Pae might exert its anti-inflammatory effects through suppressing synoviocytes function and regulating immune cells responses in CIA rats, which might be associated with its ability to up-regulate the E-prostanoid (EP4) receptor protein expression and modulate intracellular cAMP level. (C) 2011 Elsevier Ireland Ltd. All rights reserved.