OBJECTIVETo observe the effect of Tetramethyl pyrazine (TMP) on the cytokines and inflammatory mediators in the serum and the synovial fluid of collagen-induced arthritis (CIA)rats, and further to investigate its possible mechanisms for treating rheumatoid arthritis (RA).

METHODSType II CIA rat model was established. Rats in the TMP group were administered with TMP at 50 mg/kg and 100 mg/kg, once daily. Dexamethasone at 2.0 mg/kg was intramuscularly injected to those in the Dexamethasone treated group, once daily. Normal saline at 2 mL/kg was given to those in the normal control group and the model group, once daily. All medication was started from the 7th day, lasting to the 35th day. CIA rats' foot swelling degree was observed. Contents of serum IL-1, IL-6, IL-2, NO and PGE2in the synovial fluid were detected by radioimmunoassay and nitrate reduction method.

RESULTSCompared with the normal group, the foot swelling obviously increased, contents of NO and PGE2 in the synovial fluid were obviously elevated in the model group (P < 0.01). Compared with the model group, the foot swelling could be obviously inhibited by 100 mg/kg TMP and Dexamethasone; serum levels of IL-1 and IL-6 obviously decreased, serum IL-2 level obviously increased, contents of NO and PGE, decreased (P < 0.01). TMP 50 mg/kg could obviously inhibit the foot swelling of CIA rats (P < 0.01). There was no statistical difference in other indices (P > 0.05).

CONCLUSIONSTMP at 100 mg/kg showed obvious inhibition on CIA rats. Its inhibitory effect might be correlated to inhibiting activities of endogenous cytokines and the generation of inflammatory mediators in inflammation local regions, improving contents of anti-inflammation cytokines, and inducing the balance of the inflammatory cytokine network.