OBJECTIVETo explore the effect of combination therapy of tetramethylpyrazine (TMP) with methotrexate (MTX) on collagen induced arthritis (CIA) rats.

METHODSTotally 55 male SD rats were stratified by body weight. Nine of them were randomly recruited as the normal control group. The rest 46 were immunized with type II bovine collagen (C II) for establishing rheumatoid arthritis (RA) model. Forty successfully modeled rats were randomly divided into 4 groups according to swollen toe degree, i.e., the CIA group, the TMP group, the MTX group, and the TMP plus MTX group, 10 in each group. Rats in the MTX group were administered with MTX (1. 2 mg/kg) , once per week for 4 continuous weeks. Those in the TMP group were administered with 40 mg/kg TMP, once per day for 10 continuous days, and then discontinued for 7 successive days, and continued for another 10 successive days. Rats in the TMP plus MTX group were administered with a mixture of equal dose MTX and TMP, and when MTX was discontinue, TMP was administered according to the way in the TMP group. Equal volume of saline solution was given to rats in the normal control group and the CIA group. Clinical parameters including ankle width (mediolateral diameter) and hindpaw swelling were measured at day 0, 4, 11, 18, and 26 after treatment. Rats were sacrificed 28 days after treatment, their knee joints and ankle joints were collected for pathological analyses. Serum levels of IL-1β, IL-6, and IL-17A were detected by ELISA. Changes of fibrinogen (FIB) and platelet aggregation rate (PAg) were detected.

RESULTSCompared with the normal control group, the ankle width and hindpaw swelling increased significantly (P < 0.01), contents of FIB and PAg increased obviously (P < 0.05, P < 0.01), serum levels of IL-1β, IL-6, and IL-17 increased remarkably (P <0. 01) in the CIA group. Obvious cell proliferation, inflammatory cell infiltration, hyperemia and edema of synovial tissues could be seen. Pannus formed and immerged in cartilages, resulting in necrosis. Compared with the model group, changes of ankle width and hindpaw swelling were all alleviated in each medicated group (P <0. 05, P <0. 01). Of them, the effect was superior in the MTX group to that of the TMP group and the MTX plus TMP group (P < 0.05, P < 0.01). Contents of FIB, serum levels of IL-1β and IL-6 decreased significantly in the MTX group (P < 0.05). Contents of FIB, serum levels of IL-1β and IL-6 decreased significantly in the TMP group and the MTX plus TMP group (P < 0.05). Besides, serum levels of FIB and IL-6 were obviously lower in the MTX plus TMP group than in the TMP group and the MTX group (P < 0.01). Levels of PAg and IL-17A were more significantly lowered in the TMP group than in the MTX plus TMP group and the MTX group. Pathological changes could be alleviated in each medicated group, with the optimal effect obtained in the MTX plus TMP group.

CONCLUSIONCombination of TMP with MTX could significantly ameliorate inflammatory reactions and FIB contents of CIA rats.