Comparison of therapeutic efficacy and mechanism of paclitaxel alone or in combination with methotrexate in a collagen-induced arthritis rat model

Objective To compare the therapeutic efficacy of paclitaxel (PTX) alone to its combination with methotrexate (MTX) on rheumatoid arthritis. Methods A collagen-induced arthritis (CIA) rat model was established by induction of type II collagen. Rats were divided into blank control group, CIA model group, MTX group 1 mg/kg, PTX 1.5 mg/kg, PTX 2.5 mg/kg, PTX 3.5 mg/kg, and MTX 1 mg/kg + PTX 3.5 mg/kg, with 10 rats per group. The inflammation of the ankle joint was analyzed by H&E staining and interleukin (IL)-1β and IL‑6 expression was detected by immunohistochemistry. TUNEL assay was performed to detect synovial tissue cell apoptosis after administration of PTX and MTX either alone or in combination. TLR4 and p‑NF-κBp65 protein expression in synovial tissue and the changes of serum IL‑1β, IL‑6, IL‑12, MMP‑3, and TNFα protein factors were detected by western blot and ELISA, respectively. Results PTX and MTX improved histopathological changes in CIA rats. Besides, the apoptosis rate of synovial tissue cells in the PTX 3.5 mg/kg group was more than that of the PTX + MTX group. Immunohistochemistry and western blot results indicated that PTX and MTX reduce the expression rate of IL‑6 and IL‑1β and downregulate TLR4 and p‑NF-κBp65 protein expression. Furthermore, TLR4 and p‑NF-κBp65 reduced the concentration of MMP‑3, IL‑12, IL‑6, IL1‑β, and TNFα. Conclusion Both PTX and MTX exert significant suppression on rheumatoid arthritis, and the combined effect of the two drugs is weaker than that of PTX alone. Moreover, intraperitoneal injection of PTX 3.5 mg/kg every other day was the optimal dose observed in this study.