Paeoniflorin inhibits function and down-regulates HLA-DR and CD80 expression of human peripheral blood monocytes stimulated by rhIL-1β.

Paeoniflorin has been demonstrated to exert anti-inflammatory and immunomodulatory effects in the animal study. The purpose of the present study was to investigate the effect of paeoniflorin on the recombinant human interleukin-1β (rhIL-1β)-stimulated monocytes from the peripheral blood of healthy adults in vitro. Monocytes, collected from the peripheral blood of healthy adults by the Ficoll density gradient centrifugation, were co-cultured with rhIL-1β to imitate inflammatory circumstance in vitro. After exposure of rhIL-1β (0.01, 0.1, 1, 10 μg·l(-1)) for 24h or rhIL-1β (1 μg·l(-1)) for different time periods (3, 6, 12, 24h), we observed that the phagocytic function and the production of TNF-α and PGE(2) with monocytes were promoted significantly by rhIL-1β. MTT assay demonstrated that paeoniflorin (concentrations ranged from 10(-4)mol·l(-1) to 10(-9)mol·l(-1)) showed low cytotoxicity with rhIL-1β-stimulated monocytes. Paeoniflorin (10(-9), 10(-8), 10(-7), 10(-6), 10(-5)mol·l(-1)) significantly suppressed phagocytic function of rhIL-1β-induced monocytes (P<0.05), and decreased the levels of TNF-α and PGE(2) production in a concentration-dependent manner (r=-0.820 and r=-0.836, respectively). The flow cytometry analysis showed that the stimulation of rhIL-1β significantly increased the mean fluorescence rates of HLA-DR in a time-dependent manner (r=0.977). Administration of paeoniflorin (10(-9), 10(-8), 10(-7), 10(-6), 10(-5)mol·l(-1)) significantly inhibited the mean fluorescence rates of HLA-DR and CD80 with rhIL-1β-stimulated monocytes (P<0.05). These results indicated that paeoniflorin might inhibit activation of human peripheral blood monocytes stimulated by rhIL-1β, suppress function of monocytes, and down-regulate expression of HLA-DR and CD80, suggesting that paeoniflorin might alleviate the chronic inflammation by inhibiting human monocytes.