Objective    To observe the effect of sinomenine (SN) in vitro on nuclear factor-κB (NF-κB) DNA binding activity and nuclear translocation of synoviocytes in collagen-induced arthritis (CIA) rats and explore its antiinflammatory mechanisms.     Methods    The experimental model of CIA rats was used and synoviocytes were collected. Cells were divided into five groups: normal control

CIA

CIA+10  μmol/L methotrexate (MTX)

CIA+50  μmol/L SN

CIA+500  μmol/L SN. Nuclear translocation of NF-κB p65 subunit and NF-κB DNA binding activity of synoviocytes were investigated by fluorescence labelling laser confocal scanning microscopy and electrophoretic mobility shift assay (EMSA) respectively.     Results    Compared to normal control

significant nuclear translocation of NF-κB p65 subunit was observed and NF-κB DNA binding activity was increased in synoviocytes of CIA rats (P0.01). SN (50

500  μmol/L) attenuated nuclear translocation of NF-κB p65 subunit and the DNA binding activity of NF-κB in a concentration-dependent manner. MTX (10  μmol/L) inhibited NF-κB DNA binding activity but had no effect on nuclear translocation of NF-κB p65 subunit.      Conclusion    SN inhibits nuclear translocation of NF-κB p65 subunit and NF-κB DNA binding activity of synoviocytes

which might be one of antiinflammatory mechanisms.